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1 DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA. INFLAMMATION-burning INFLAMMATION: It is the body’s local protective defense response to eliminate or limit spread of injurious agents and removal of consequent necrosis. AGENTS CAUSING INFLAMMATION: 1. PHYSICAL - heat burns, cold frost bite, radiation, mechanical trauma. 2. CHEMICAL - organic/inorganic poisons. 3. INFECTIVE - bacteria, fungi, virus etc... 4. IMMUNOLOGICAL – cell/antigen mediated. 5. TISSUE NECROSIS - ischemia. THE 4 CARDINAL SIGNS BY CELSUS BY (ROMAN WRITER) RUBOR - Redness. TUMOR - Swelling. CALOR - Heat. DOLOR - Pain. Loss of Function- FUNCTIO LAESA. CLASSIFICATION BASED ON: defense capacity of the host and duration of inflammatory response. TYPES: 1. ACUTE – of short duration (less than 2 weeks). Early body reaction to injury followed by repair and healing. FEATURES:- a) Accumulation of fluid. b) Intravascular activation of platelets. c) Polymorph nuclear neutrophil as inflammatory cells. 2. CHRONIC – of long duration. After acute inflammation or stimulus induced chronic inflammation.

INFLAMMATION PATHOPHYSIOLOGY

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Page 1: INFLAMMATION PATHOPHYSIOLOGY

1DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

INFLAMMATION-burningINFLAMMATION: It is the body’s local protective defense response to eliminate or limit spread of injurious agents and removal of consequent necrosis.

AGENTS CAUSING INFLAMMATION:

1. PHYSICAL - heat burns, cold frost bite, radiation, mechanical trauma.2. CHEMICAL - organic/inorganic poisons.3. INFECTIVE - bacteria, fungi, virus etc...4. IMMUNOLOGICAL – cell/antigen mediated.5. TISSUE NECROSIS - ischemia.

THE 4 CARDINAL SIGNS BY CELSUS BY (ROMAN WRITER)

RUBOR - Redness. TUMOR - Swelling. CALOR - Heat. DOLOR - Pain. Loss of Function- FUNCTIO LAESA.

CLASSIFICATION BASED ON: defense capacity of the host and duration of inflammatory response.

TYPES:

1. ACUTE – of short duration (less than 2 weeks). Early body reaction to injury followed by repair and healing.

FEATURES:-

a) Accumulation of fluid.b) Intravascular activation of platelets.c) Polymorph nuclear neutrophil as inflammatory cells.

2. CHRONIC – of long duration. After acute inflammation or stimulus induced chronic

inflammation.

FEATURES:-

Cells: lymphocytes, plasma cells, macrophages, granulation tissue formation.

3. SUBACUTE INFLAMMATION: - the type of inflammation in between the transition from acute to chronic.

EVENTS: - It is a continuous process consists of both vascular events and cellular events.

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2DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

VASCULAR EVENTS

1. HAEMODYNAMIC CHANGES - changes in the vascular flow.

Transient vasoconstriction – it is an immediate response in the arterioles and blood-flow re-establishes in 3-5 seconds (mild) to 5 minutes (severe).

Persistent progressive vasodilatation – it occurs mostly in arterioles and in venules to less extent. Capillaries also dilate within half hour resulting in increased blood volume in the microvascular bed and feeling of warmth and redness at the site.

Elevation of local hydrostatic pressure - vasodilatation cause increased local hydrostatic pressure results in transudation of fluid into extra cellular space results in swelling at the local site of acute inflammation.

Slowing or stasis of microcirculation causes accumulation of RBCs and raises blood viscosity.

Leukocyte margination: Peripheral orientation of leukocytes (neutrophils) along the vascular

endothelium. Leukocytes stick to endothelial cells and then move and migrate to gaps of

endothelium to extravascular space known as emigration.

Triple response: flush, flare and wheal.

Features of triple response:

Red line/Flush: due to local vasodilation of capillaries and venules. Flare: bright reddish appearance due to vasodilation of adjacent arterioles. Wheal: Swelling/edema of the surrounding skin due to transduction of fluid into

the extravascular space.

2. ALTERED VASCULAR PERMEABILITY - Vascular permeability is increased. Non permeable endothelial layer become leakier. At initial stage there is accumulation of edema fluid around inflamed tissue from plasma due to vasodilation and consequent elevation in hydrostatic pressure.

1st transudate – non inflammatory edema, less cells, less protein. Then exudate – inflammatory edema – more proteins, cells, pus etc. For balance of hydrostatic pressure and osmotic pressure as per starlings

hypothesis Endothelial cell contraction of venules – immediate transient response, post

capillary venules develop temporary gaps and vascular leakiness for short duration and reversible within 15–30 minutes.

Histamine, bradykinin, Leukotriene etc. are released.

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3DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

Endothelial cell retraction – structural reorganization of cytoskeleton of endothelial cells and causes reversible retraction of intercellular junctions of cells 4-6 hours - 24 hours Interleukins, TNF-alpha.

Increased permeability immediately after injury and lasts for several hours/days Cell injury by leukocytes – venules and capillaries, leukocyte adherence and

activation – release mediators. Non permeable endothelial layer become leakier.

Direct injury to endothelial cells – cell necrosis, appearance of physical gaps, and initiate process of thrombosis - all mediators affects arteries, capillaries and veins.

Neovascularization - VEGF stimulates angiogenesis - blood vessel remains leaky until maturation of endothelial cells in case of repair and tumor.

FLUID: transudate and exudate

Outward movement of fluid from microcirculation: Due to increased hydrostatic pressure and decreased colloidal osmotic pressure of interstitial fluid.

Inward movement of fluid into circulation: Due to increased intravascular colloidal osmotic pressure and decreased hydrostatic pressure of interstitial fluid.

Transudate: filtrate of blood plasma without changes in endothelial permeability. Found in non-inflammatory edema. It contains mainly albumin and traces of fibrinogen hence no tendency to coagulate along with few cells mainly mesothelial cells and cellular debris. E.g. in Congestive cardiac failure.

Exudate: Edema of inflamed tissue associated with increased vascular permeability. Found in inflammatory edema. Readily coagulate due to high content of fibrinogen and other coagulation factors with many cells mainly inflammatory as well as parenchymal. E.g. PUS.

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4DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

CELLULAR EVENTS

I. EXUDATION OF LEUKOCYTES.

Escape of leukocytes from blood vessel to interstitial space. The cells includes:o Polymorphonuclear Neutrophils (PMN)o Monocyteso Macrophages

This is the first line response in the case of acute inflammation.

1. Changes in formed elements of blood are due to stasis, margination and pavementing.

Stasis – stoppage of flow of blood i.e. normal axial blood flow is disturbed. Margination i.e. central stream of blood cells widens and peripheral plasma zone

becomes narrower as plasma exudates (oozes out). Pavementing - neutrophils of central stream of blood cells comes close to vessel wall.

2. Rolling and adhesion

Peripherally marginated and pavemented neutrophils roll over the membrane which lines the walls of the blood vessels (endothelial cells).

Adhesion occurs by transient bond formation between leukocytes and endothelial cells by selectins, integrins and immunoglobulin super family adhesion molecules.

o Selectins. P selectins – preformed and stored in endothelial cells &

platelets. E selectins – from cytokine activated endothelial cells. L selectins – from lymphocytes and neutrophils.

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5DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

o Integrins. It activates receptors on endothelial cell wall and neutrophils, which

causes firm adhesion.o Immunoglobulin super family adhesion molecule. ICAM 1 and 2 locates the neutrophils.

3. Emigration

After sticking, neutrophils move along the cell, between endothelial cells of basement membrane using pseudopods and damaging basement membrane by collagenase through which, neutrophils cross basement membrane and escapes out to the extra vascular space. Damaged basement membrane repaired immediately.

For the 1st 24 hours of inflammation neutrophils are present at the site which then dies out.

For the next 24 - 48 hours monocytes and macrophages are present. Diapedsis: It is the escape of red blood cells through gaps in the endothelial cells. It is

a passive process and gives a haemorrhagic appearance to exudate.

4. Chemotaxis – chemical attraction.

The chemotactic factors mediated trans-migration of leukocytes crossing several barriers (endothelium, basement membrane, perivascular fibroblasts, and extracellular matrix) to reach interstitial tissues.

Chemotactic factors for neutrophils includes:o Leukotriene.o Cytokines.o Soluble bacterial product.o Component of complement system.

Other mediators + chemokines - (LT-B4, PF4, complement system components (C3, C5), cytokines (IL1, 5 & 6), soluble bacterial products, monocyte chemotactic protein, chemokine for CD4T cells, eotaxin for eosinophils etc.).

II. PHAGOCYTOSIS

Role of neutrophils in inflammation Cell eating, engulfing solid particles by cells named phagocytes Performed mainly by two phagocytic cell types - PMNs or called

microcytes/microphage. Circulating monocytes and fixed tissue monomolecular phagocytic macrophages. Neutrophils and macrophages on reaching tissue releases proteolytic enzymes

(lysozyme, gelatinase, acid hydrolase, protease, elastase, proteinases, collagenase and lipase) which degrades collagen and extracellular matrix.

Followed by phagocytosis by neutorphills. Occurs in 4 steps.

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6DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

1. Recognition and attachment Binding of opsonized particle to phagocytic cells. Surface receptors on macrophages (mannose and scavenger receptor) recognize

microorganisms and coat them with protein opsonin. Bacterial products also attract phagocytic cells and get coated with opsonins. Opsonins – establishes a bond between bacteria and cell membrane of phagocytic cell. Main opsonins includes:

o IgG opsonin – antibody.o C3b opsonin – from complementary system.

Lectins – Carbohydrate binding protein.2. Engulfment stage

Formation of cytoplasmic pseudopods around particles due to activation of actin filaments beneath cell wall enveloping it in a phagocytic vacuole.

3. Degranulation stage Formation of phagocytic vacuole and granules both outside and inside of the cells. Enzymes kill and one or more lysosomal granules from PMN fused with vacuoles

form phagosome or phagolysosome. It breaks of plasma membrane enclosing cell inclusions and they become free in cell cytoplasm.

4. Killing (by antibacterial substances) and degradation by hydrolytic enzymes. Mainly 3 ways.

A. O2 dependent bactericidal mechanism – reactive O2 species – O2-, H2O2, OH- ,

HOCl, HOBr, HOI.B. O2 independent bactericidal mechanism – lysosomal hydrolase, permeability

increasing factors, defensing, cationic proteases.C. Nitric oxide mechanism – can kill, it is formed from endothelial cells activated by

macrophages.

O2 - NADPH oxidases - 2O2. Myeloperoxidase dependent – HOCl. MPO independent – Haber weis reaction - OH- Fenton reaction Fe3+ - OH-.

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7DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

CHEMICAL MEDIATORS OF INFLAMMATION

Permeability factors or endogenous mediators of increased vascular permeability are large number of endogenous compounds which enhances vascular permeability. Many chemical mediators take part in processes of acute inflammation like vasodilatation, chemotaxis, fever, pain and tissue damage.

Chemical mediators of inflammation are released from the cells, the plasma, or damaged tissue.

They are classified into 2 groups:

1. Cell-derived Mediators; and2. Plasma-derived Mediators (Plasma Proteases).

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8DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

I. CELL-DERIVED MEDIATORS

1. Vasoactive Amines: The important pharmacologically active amines in the early inflammatory response (first one hour) are:

i. Histamineii. 5-hydroxytryptamine (5-HT) or serotonin and

iii. Recently added group of neuropeptides.

i. Histamine. It is stored in the granules of mast cells (it contains histamine, heparin, immunoglobulin-E), basophils and platelets. Histamine is released from these cells by various agents like:

a) Stimuli or substances inducing acute inflammation e.g.heat, cold, irradiation, trauma, irritant chemicals, immunologic reactions etc.

b) Anaphylatoxins like fragments of complement C3a, and C5a, which increase vascular permeability and cause oedema in tissues.

c) Histamine-releasing factors from neutrophils, monocytes and platelets.d) Interleukins: They are lymphokines – polypeptides produced by activated

lymphocytes.

Actions of histamine:

a) Vasodilatationb) Increased vascular (venular) permeability andc) Itching and pain.

Stimulation of mast cells and basophils also releases products of arachidonic acid metabolism. Releases slow reacting substances of anaphylaxis (SRS-As) which, consist of various leukotrienes (LTC4, LTD4 and LTE4).

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9DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

ii. 5-Hydroxytryptamine (5-HT or serotonin). It is present in tissues like chromaffin cells (affinity towards chromium salts) of GIT, spleen, nervous tissue, mast cells and platelets.

Actions of 5-HT are similar to histamine but is less potent.

iii. Neuropeptides: Recently added vasoactive amines include tachykinin neuropeptides, such as substance P, neurokinin-A, vasoactive intestinal polypeptide (VIP) and somatostatin. These small peptides are produced in the central and peripheral nervous systems.

Actions of neuropeptides:

a) Increased vascular permeabilityb) Transmission of pain stimuli andc) Mast cell degranulation.

2. Arachidonic Acid Metabolites (Eicosanoids 20 ‘C’ atoms): It is the most potent mediators of inflammation. Arachidonic acid (a constituent of the phospholipid cell membrane) is released by the enzyme phospholipases during cell damage. It is activated to form arachidonic acid metabolites or eicosanoids by 2 pathways:

a) Cyclo-oxygenase pathway andb) Lipo-oxygenase pathway.

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10DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

a) Metabolites via cyclo-oxygenase pathway:

i. Prostaglandinsii. Thromboxane-A2

iii. Prostacyclin andiv. Resolvins.

Prostaglandins and related compounds are also called autocoids. Cyclo-oxygenase (COX), a fatty acid enzyme present as COX-1 and COX-2, acts on activated arachidonic acid to form prostaglandin endoperoxide (PGG2). PGG2 is enzymatically transformed into PGH2 with generation of free radical of oxygen. PGH2 is further acted upon by enzymes and results in formation of 3 metabolites:

a). Prostaglandins (PGD2, PGE2 and PGF2-α):

PGD2 and PGE2 act on blood vessels to cause increased venular permeability, vasodilatation and bronchodilatation and inhibit inflammatory cell function.

PGF2-α induces vasodilatation and bronchoconstriction.

b). Thromboxane A2 (TXA2):

Platelets contain the enzyme thromboxane synthetase.

TXA2 is active in platelet aggregation, vasoconstriction and bronchoconstriction.

c). Prostacyclin (PGI2):

PGI2 induces vasodilatation, Broncho-dilatation and inhibits platelet aggregation.

d). Resolvins:

These mediators act by inhibiting production of pro-inflammatory cytokines and are helpful. Drugs like aspirin act by inhibiting COX activity and stimulating production of resolvins.

The major anti-inflammatory drugs act by inhibiting activity of the enzyme COX; e.g. non-steroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors.

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11DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

b) Metabolites via lipo-oxygenase pathway: 5-HETE, leukotrienes and lipoxins. Lipo-oxygenase is a predominant enzyme in neutrophils, acts on activated arachidonic acid to form hydroperoxy eicosatetraenoic acid (5-HPETE) which on further peroxidation forms 2 metabolites:

a) 5-HETE (hydroxy compound), an intermediate product, is a potent chemotactic agent for neutrophils.

b) Leukotrienes (LT): First isolated from leucocytes. Unstable leukotriene A4 (LTA4) is acted upon by enzymes to form LTB4,which is chemotactic for phagocytic cells and stimulates phagocytic cell adherence. LTC4, LTD4 and LTE4 have common actions causing smooth muscle contraction, vasoconstriction, bronchoconstriction and increased vascular permeability. They are also called as slow reacting substances of anaphylaxis (SRS-As).

c) Lipoxins (LX) are recently described product of lipooxygenase pathway. Lipooxygenase-12 present in platelets acts on LTA4 derived from neutrophils and forms LXA4 and LXB4. Lipoxins regulate and counterbalance actions of leukotrienes.

3. LYSOSOMAL COMPONENTS. The inflammatory cells-neutrophils and monocytes, contain lysosomal granules which release a variety of mediators of inflammation.

i) Granules of neutrophils. Neutrophils have 3 types of granules: primary or azurophil, secondary or specific, and tertiary.

a) Primary or azurophil granules are large azurophil granules which contain functionally active enzymes. These are myeloperoxidase, acid hydrolases, acid phosphatase, lysozyme, defensin (cationic protein), phospholipase, cathepsin G, elastase, and protease.

b) Secondary or specific granules contain alkaline phosphatase, lactoferrin, gelatinase, collagenase, lysozyme, vitamin-B12 binding proteins, plasminogen activator.

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12DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

c) Tertiary granules or C particles contain gelatinase and acid hydrolases. Myeloperoxidase causes oxidative lysis by generation of oxygen free radicals, acid hydrolases act within the cell to cause destruction of bacteria in phagolysosome while proteases attack on the extracellular constituents such as basement membrane, collagen, elastin, cartilage etc.

ii) Granules of monocytes and tissue macrophages. These cells on degranulation also release mediators of inflammation like acid proteases, collagenase, elastase and plasminogen activator. They are more active in chronic inflammation.

4. PLATELET ACTIVATING FACTOR (PAF). It is released from IgE-sensitised basophils or mast cells, other leucocytes, endothelium and platelets. Platelet aggregation, release reaction and act as mediator of inflammation. They increase vascular permeability, results in vasodilatation in low concentration, vasoconstriction, bronchoconstriction, adhesion of leucocytes to endothelium; and chemotaxis.

5. CYTOKINES. Cytokines are polypeptide substances produced by activated lymphocytes (lymphokines) and monocytes (monokines). Cytokines, which act as mediators of inflammation are: interleukin-1 (IL-1), tumour necrosis factor (TNF)-α and β, interferon (IFN)-γ, and chemokines (IL-8, PF-4). IL-1 and TNF-α are formed by activated macrophages while TNF-β and IFN-γ are produced by activated T cells. The chemokines include interleukin 8 (released from activated macrophages) and platelet factor-4 from activated platelets, which are potent chemo-attractant for inflammatory cells.

i. IL-1 and TNF-α, TNF-β induce endothelial effects in the form of increased leucocyte adherence, thrombogenicity, elaboration of other cytokines, fibroblastic proliferation and acute phase reactions.

ii. IFN-γ causes activation of macrophages and neutrophils and is associated with synthesis of nitric acid synthase.

iii. Chemokines are a family of chemo-attractants for inflammatory cells and include: IL-8 chemotactic for neutrophils; platelet factor-4 chemotactic for neutrophils, monocytes and eosinophils; MCP-1 chemotactic for monocytes; and eotaxin chemotactic for eosinophils.

6. FREE RADICALS: OXYGEN METABOLITES AND NITRIC OXIDE.

Free radicals act as potent mediator of inflammation:

i. Oxygen-derived metabolites are released from activated neutrophils and macrophages and include superoxide oxygen (O’2), H2O2, OH’ and toxic NO products causes endothelial cell damage and increased vascular permeability. Activation of protease and inactivation of antiprotease causing tissue matrix damage.

ii. Nitric oxide (NO) is a vascular relaxation factor produced by endothelial cells. NO is formed by activated macrophages during the oxidation of arginine by the action

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13DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

of enzyme, NO synthase. NO plays role in mediating inflammation by Vasodilatation, Anti-platelet activating agent with microbicidal action.

II. Plasma-derived Mediators (Plasma Proteases):

These include activation and interaction of 4 interlinked systems: kinin, clotting, fibrinolytic and complement. Hageman factor (factor XII) of clotting system plays a key role in interactions of the four systems.

1. THE KININ SYSTEM. This system on activation by factor Xlla generates bradykinin (slow contraction of smooth muscle),. First, kallikrein is formed from plasma prekallikrein by the action of prekallikrein activator which is a fragment of factor Xlla. Kallikrein then acts on high molecular weight kininogen to form bradykinin. It acts in the early stage of inflammation and effects include: smooth muscle contraction; vasodilatation; increased vascular permeability; and pain.

2. THE CLOTTING SYSTEM. Factor Xlla initiates the cascade of the clotting system resulting in formation of fibrinogen which is acted upon by thrombin to form fibrin and fibrinopeptides. The actions of fibrinopeptides in inflammation are: increased vascular permeability; chemotaxis for leucocyte; and anticoagulant activity.

3. THE FIBRINOLYTIC SYSTEM. This system is activated by plasminogen activator, the sources of which include kallikrein of the kinin system, endothelial cells and leucocytes. Plasminogen activator acts on plasminogen present as component of plasma proteins to form plasmin. Further breakdown of fibrin by plasmin forms fibrinopeptides or fibrin split products. The actions of plasmin in inflammation are: activation of factor XII to form prekallikrein activator that stimulates the kinin system to generate bradykinin; splits off

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14DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

complement C3 to form C3a which is a permeability factor; and degrades fibrin to form fibrin split products which increase vascular permeability and are chemotactic to leucocytes.

4. THE COMPLEMENT SYSTEM. The activation of complement system can occur either:

i. By classic pathway through antigen-antibody complexes; orii. By alternate pathway via non-immunologic agents such as bacterial toxins, cobra

venoms and IgA.

Complement system on activation by either of these two pathways yields activated products which include anaphylatoxins (C3a, C4a and C5a), and membrane attack complexes (MAC) i.e. C5b, C6, 7, 8, 9. The actions of activated complement system in inflammation are: C3a, C5a, C4a (anaphylatoxins) activate mast cells and basophils to release of histamine, because increased vascular permeability causes oedema in tissues, augments phagocytosis. C3b is an opsonin. C5a is chemotactic for leucocytes. Membrane attack complexes (MAC) (C5b-C9) are lipid dissolving agents and form holes in the phospholipid membrane of the cells.

THE INFLAMMATORY CELLS

The cells participating in acute and chronic inflammation are circulating leucocytes, plasma cells and tissue macrophages.

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15DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

1. Polymorphonuclear Neutrophil (PMN).

Commonly called as neutrophils or polymorphs, these cells along with basophils and eosinophils are known as granulocytes due to the presence of granules in the cytoplasm. These granules contain many substances like proteases, myeloperoxidase, lysozyme, esterase, aryl sulfatase, acid and alkaline phosphatase and cationic proteins. These cells comprise 40-75% of circulating leucocytes and their number is increased in blood (neutrophilia) and tissues in acute bacterial infections. The functions of neutrophils in inflammation are:

i. Initial phagocytosis of microorganisms as they form the first line of body defense in bacterial infection. The steps involved are adhesion of neutrophils to vascular endothelium, emigration through the vessel wall, chemotaxis, engulfment, degranulation, killing and degradation of the foreign material.

ii. Engulfment of antigen-antibody complexes and nonmicrobial material.iii. Harmful effect of neutrophils in causing basement membrane destruction of the

glomeruli and small blood vessels.

2. Eosinophil.

These are larger than neutrophils but are fewer in number, comprising 1 to 6% of total blood leucocytes. Eosinophils share many structural and functional similarities with neutrophils like their production in the bone marrow, locomotion, phagocytosis, lobed nucleus and presence of granules in the cytoplasm containing a variety of enzymes, of which major basic protein and eosinophil cationic protein are the most important which have bactericidal and toxic action against helminthic parasites. However, granules of eosinophils are richer in myeloperoxidase than neutrophils and lack lysozyme. High level of steroid hormones leads to fall in number of eosinophils and even disappearance from blood. The absolute number of eosinophils is increased in inflammatory responses associated with these conditions:

i. Allergic conditions;ii. Parasitic infestations;

iii. Skin diseases; andiv. Certain malignant lymphomas.

3. Basophil (Mast Cells).

The basophils comprise about 1% of circulating leucocytes and are morphologically and pharmacologically similar to mast cells of tissue. These cells contain coarse basophilic granules in the cytoplasm and a polymorphonuclear nucleus. These granules are laden with heparin and histamine. Basophils and mast cells have receptors for IgE and degranulate when cross-linked with antigen. The roles of these cells in inflammation are:

i. In immediate and delayed type of hypersensitivity reactions; andii. Release of histamine by IgE-sensitised basophils.

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16DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

4. Lymphocyte.

Next to neutrophils, these cells are the most numerous of the circulating leucocytes (20-45%). Apart from blood, lymphocytes are present in large numbers in spleen, thymus, lymph nodes and mucosa-associated lymphoid tissue (MALT). They have scanty cytoplasm and consist almost entirely of nucleus. Their role in antibody formation (B lymphocytes) and in cell-mediated immunity in addition these cells participate in inflammatory responses:

i. In tissues, they are dominant cells in chronic inflammation and late stage of acute inflammation.

ii. In blood, their number is increased (lymphocytosis) in chronic infections like tuberculosis.

5. Plasma Cells

These cells are larger than lymphocytes with more abundant cytoplasm and an eccentric nucleus which has cart-wheel pattern of chromatin. Plasma cells are normally not seen in peripheral blood. They develop from B lymphocytes and are rich in RNA and γ-globulin in their cytoplasm. There is an interrelationship between plasmacytosis and hyperglobulinaemia. These cells are most active in antibody synthesis. Their number is increased in the following conditions: Prolonged infection with immunological responses e.g. in syphilis, rheumatoid arthritis, tuberculosis etc…

6. Mononuclear-Phagocyte System (Reticuloendothelial System).

This cell system includes cells derived from 2 sources with common morphology, function and origin. These are as under:

Blood monocytes. These comprise 4-8% of circulating leucocytes.

Tissue macrophages. These include the following cells in different tissues:

i. Macrophages in inflammation.ii. Histiocytes which are macrophages present in connective tissues.

iii. Kupffer cells are macrophages of liver cells.iv. Alveolar macrophages (type II pneumocytes) in lungs.v. Macrophages/histiocytes of the bone marrow.

vi. Tingible body cells of germinal centres of lymph nodes.vii. Littoral cells of splenic sinusoids.

viii. Osteoclasts in the bones.ix. Microglial cells of the brain.x. Langerhans’ cells/dendritic histiocytes of the skin.

xi. Hoffbauer cells of the placenta.xii. Mesangial cells of glomerulus.

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17DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

Role of macrophages in inflammation. The functions of mononuclear-phagocyte cells are as under:

i. Phagocytosis (cell eating) and pinocytosis (cell drinking).ii. Macrophages on activation by lymphokines released by T lymphocytes or by non-

immunologic stimuli produces a variety of biologically active substances:a. Proteases like collagenase and elastase which degrade collagen and elastic

tissue.b. Plasminogen activator which activates the fibrinolytic system.c. Products of complement.d. Some coagulation factors (factor V and thromboplastin) which convert

fibrinogen to fibrin.e. Chemotactic agents for other leucocytes.f. Metabolites of arachidonic acid.g. Growth promoting factors for fibroblasts, blood vessels and granulocytes.h. Cytokines like interleukin-1 and TNF-α.i. Oxygen-derived free radicals.

7. Giant Cells.

Multinucleate giant cells exist in normal tissues (e.g. osteoclasts in the bones, trophoblasts in placenta and megakaryocytes in the bone marrow). In chronic inflammation when the macrophages fail they fuse together and form multinucleated giant cells.

FACTORS DETERMINING VARIATION IN INFLAMMATORY RESPONSE

Although acute inflammation is typically characterised by vascular and cellular events with emigration of neutrophilic leucocytes, not all examples of acute inflammation show infiltration by neutrophils. On the other hand, some chronic inflammatory conditions are characterised by neutrophilic infiltration. For example, typhoid fever is an example of acute inflammatory process but the cellular response in it is lymphocytic; osteomyelitis is an example of chronic inflammation but the cellular response in this condition is mainly neutrophilic. The variation in inflammatory response depends upon a number of factors and processes.

1. Factors Involving the Organisms

i. Type of injury and infection. For example, skin reacts to herpes simplex infection by formation of vesicle and to streptococcal infection by formation of boil; lung reacts to pneumococci by occurrence of lobar pneumonia while to tubercle bacilli it reacts by granulomatous inflammation.

ii. Virulence. Many species and strains of organisms may have varying virulence e.g. the three strains of C. diphtheria (gravis, intermedius and mitis) produce the same diphtheria exotoxin but in different amount.

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18DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

iii. Dose. The concentration of organism in small doses produces usually local lesions while larger dose results in more severe spreading infections.

iv. Portal of entry. Some organisms are infective only if administered by particular route e.g. Vibrio cholerae is not pathogenic if injected subcutaneously but causes cholera if swallowed.

v. Product of organisms. Some organisms produce enzymes that help in spread of infections e.g. hyaluronidase by Clostridium welchii, streptokinase by streptococci, staphylokinase and coagulase by staphylococci.

2. Factors Involving the Host

i. Systemic diseases. Certain acquired systemic diseases in the host are associated with impaired inflammatory response e.g. diabetes mellitus, chronic renal failure, cirrhosis of the liver, chronic alcoholism, bone marrow suppression from various causes (drugs, radiation, idiopathic). These conditions render the host more susceptible to infections.

ii. Immune status of host. Patients who are immunosuppressed from congenital or acquired immunodeficiency have lowered inflammatory response and spread of infections occurs rapidly e.g. in AIDS, congenital immunodeficiency diseases, protein calorie malnutrition, starvation.

iii. Congenital neutrophil defects. Congenital defects in neutrophil structure and functions result in reduced inflammatory response.

iv. Leukopenia. Patients with low WBC count with neutropenia or agranulocytosis develop spreading infection.

v. Site or type of tissue involved. For example, the lung has loose texture as compared to bone and, thus, both tissues react differently to acute inflammation.

vi. Local host factors. For instance, ischaemia, presence of foreign bodies and chemicals cause necrosis and are thus cause more harm.

3. Type of Exudation

The appearance of escaped plasma determines the morphologic type of inflammation as under:

i. Serous, when the fluid exudate resembles serum or is watery e.g. pleural effusion in tuberculosis, blister formation in burns.

ii. Fibrinous, when the fibrin content of the fluid exudate is high e.g. in pneumococcal and rheumatic pericarditis.

iii. Purulent or suppurative exudate is formation of creamy pus as seen in infection with pyogenic bacteria e.g. abscess, acute appendicitis.

iv. Haemorrhagic, when there is vascular damage e.g. acute haemorrhagic pneumonia in influenza.

v. Catarrhal, when the surface inflammation of epithelium produces increased secretion of mucous e.g. common cold.

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19DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

MORPHOLOGY OF ACUTE INFLAMMATION

Inflammation of an organ is usually named by adding the suffix-itis to its Latin name e.g. appendicitis, hepatitis, cholecystitis, meningitis etc. A few morphologic varieties of acute inflammation are described below:

1. PSEUDOMEMBRANOUS INFLAMMATION. It is inflammatory response of mucous surface (oral, respiratory, bowel) to toxins of diphtheria or irritant gases. As a result of denudation of epithelium, plasma exudes on the surface where it coagulates, and together with necrosed epithelium, forms false membrane.

2. ULCER. Ulcers are local defects on the surface of an organ produced by inflammation. Common sites for ulcerations are the stomach, duodenum, intestinal ulcers in typhoid fever, intestinal tuberculosis, bacillary and amoebic dysentery, ulcers of legs due to varicose veins etc.

3. SUPPURATION (ABSCESS FORMATION). When acute bacterial infection is accompanied by intense neutrophilic infiltrate in the inflamed tissue, it results in tissue necrosis. A cavity is formed which is called an abscess and contains pus and the process of abscess formation is known as suppuration. The bacteria which cause suppuration are called pyogenic.

Microscopically, pus is creamy or opaque in appearance and is composed of numerous dead as well as living neutrophils, some red cells, fragments of tissue debris and fibrin. An abscess may be discharged to the surface due to increased pressure inside or may require drainage by the surgeon. Due to tissue destruction, resolution does not occur but instead healing by fibrous scarring takes place. Some of the common examples of abscess formation are:

i. Boil or furruncle which is an acute inflammation via hair follicles in the dermal tissues.

ii. Carbuncle is seen in untreated diabetics and occurs as a loculated abscess in the dermis and soft tissues of the neck.

4. CELLULITIS. It is a diffuse inflammation of soft tissues resulting from spreading effects of substances like hyaluronidase released by some bacteria.

5. BACTERIAL INFECTION OF THE BLOOD. This includes the 3 conditions:

i. Bacteraemia is defined as presence of small number of bacteria in the blood which do not multiply significantly. E.g. infection with Salmonella typhi, Escherichia coli, Streptococcus viridans.

ii. Septicaemia means presence of rapidly multiplying, highly pathogenic bacteria in the blood e.g. pyogenic cocci, bacilli of plague etc. Septicaemia is generally accompanied by systemic effects like toxaemia, multiple small haemorrhages, neutrophilic leucocytosis and disseminated intravascular coagulation (DIC).

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20DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

iii. Pyaemia is the dissemination of small septic thrombi in the blood which cause their effects at the site where they are lodged. This can result in pyaemic abscesses or septic infarcts.a. Pyaemic abscesses are multiple small abscesses in various organs such as in

cerebral cortex, myocardium, lungs and renal cortex, resulting from very small emboli fragmented from septic thrombus. Microscopy of pyaemic abscess shows a central zone of necrosis containing numerous bacteria, surrounded by a zone of suppuration and an outer zone of acute inflammatory cells.

b. Septic infarcts result from lodgement of larger fragments of septic thrombi in the arteries with relatively larger foci of necrosis, suppuration and acute inflammation e.g. septic infarcts of the lungs, liver, brain, and kidneys from septic thrombi of leg veins or from acute bacterial endocarditis.

SYSTEMIC EFFECTS OF ACUTE INFLAMMATION

Acute inflammation is associated with systemic effects which include fever, leucocytosis, lymphangitis and lymphadenitis.

1. Fever occurs due to bacteraemia. It is mediated through release of factors like prostaglandins, interleukin-1 and TNF-α in response to infection.

2. Leucocytosis commonly accompanies the acute inflammatory reactions, usually in the range of 15,000- 20,000/μl. In bacterial infections there is an abscess in the skin. It contains pus composed of necrotic tissue, debris, fibrin, RBCs and dead and living neutrophils. Some macrophages are seen at the periphery neutrophilia; in viral infections lymphocytosis; and in parasitic infestations, eosinophilia. Typhoid fever, an example of acute inflammation, induces leucopenia with relative lymphocytosis.

3. Lymphangitis-lymphadenitis is one of the important manifestations of localised inflammatory injury. The lymphatics and lymph nodes that drain the inflamed tissue show reactive inflammatory changes in the form of lymphangitis and lymphadenitis. The affected lymph nodes may show hyperplasia of lymphoid follicles (follicular hyperplasia) and proliferation of mononuclear phagocytic cells in the sinuses of lymph node (sinus histiocytosis).

4. Shock may occur in severe cases. Massive release of cytokine TNF-α, a mediator of inflammation, in response to severe tissue injury or infection results in profuse systemic vasodilatation, increased vascular permeability and intravascular volume loss. The net effect of these changes is hypotension and shock. Systemic activation of coagulation pathway may lead to microthrombi throughout the body. It results in disseminated intravascular coagulation (DIC), bleeding and death.

FATE OF ACUTE INFLAMMATION

The acute inflammatory process involves:

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21DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

1. Resolution. It means complete return to normal tissue following acute inflammation. This occurs when tissue changes are slight and the cellular changes are reversible e.g. resolution in lobar pneumonia.

2. Healing. Healing by fibrosis takes place when the tissue destruction in acute inflammation is extensive so that there is no tissue regeneration. But when tissue loss is superficial, it is restored by regeneration.

3. Suppuration. When the pyogenic bacteria causing acute inflammation result in severe tissue necrosis, the process progresses to suppuration. Initially, intense neutrophilic infiltration followed by mixture of neutrophils, bacteria, fragments of necrotic tissue, cell debris and fibrin comprise pus which is contained in a cavity to form an abscess. The abscess, get organised by dense fibrous tissue, and get calcified.

4. Chronic inflammation. Persisting or recurrent acute inflammation may progress to chronic inflammation in which the processes of inflammation and healing proceed side by side.

CHRONIC INFLAMMATION

Definition and causes. Chronic inflammation is defined as prolonged process in which tissue destruction and inflammation occur at the same time. Chronic inflammation can be caused by 3 ways:

1. Chronic inflammation following acute inflammation. When the tissue destruction is extensive, or the bacteria survive and persist in small numbers at the site of acute inflammation e.g. in osteomyelitis, pneumonia terminating in lung abscess.

2. Recurrent attacks of acute inflammation. Repeated occurring of acute inflammation increase chronicity of the process e.g. in recurrent urinary tract infection leading to chronic pyelonephritis, repeated acute infection of gallbladder leading to chronic cholecystitis.

3. Chronic inflammation starting de novo. When the infection with organisms of low pathogenicity is chronic from the beginning e.g. infection with Mycobacterium tuberculosis.

GENERAL FEATURES OF CHRONIC INFLAMMATION

1. MONONUCLEAR CELL INFILTRATION. Chronic inflammatory lesions are infiltrated by mononuclear inflammatory cells like phagocytes and lymphoid cells. Phagocytes are represented by circulating monocytes, tissue macrophages, epithelioid cells and sometimes, multinucleated giant cells. The macrophages comprise the most important cells in chronic inflammation. These may appear at the site of chronic inflammation from:

i. Chemotactic factors and adhesion molecules for continued infiltration of macrophages;

ii. Local proliferation of macrophages; andiii. Longer survival of macrophages at the site of inflammation.

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22DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

The blood monocytes on reaching the extravascular space transform into tissue macrophages. On activation, macrophages release several biologically active substances e.g. acid and neutral proteases, oxygen-derived reactive metabolites and cytokines which bring about tissue destruction, neovascularisation and fibrosis. Other chronic inflammatory cells include lymphocytes, plasma cells, eosinophils and mast cells.

2. TISSUE DESTRUCTION OR NECROSIS. Tissue destruction and necrosis are brought about by activated macrophages which release a variety of biologically active substances e.g. protease, elastase, collagenase, lipase, reactive oxygen radicals, cytokines (IL-1, IL-8, TNF-α), nitric oxide, angiogenesis growth factor etc.

3. PROLIFERATIVE CHANGES. As a result of necrosis, proliferation of small blood vessels and fibroblasts is stimulated resulting in formation of inflammatory granulation tissue. Eventually, healing by fibrosis and collagen laying takes place.

SYSTEMIC EFFECTS OF CHRONIC INFLAMMATION

Chronic inflammation is associated with features like:

1. Fever. Invariably there is mild fever, often with loss of weight and weakness.2. Anaemia. Chronic inflammation is accompanied by anaemia of varying degree.3. Leucocytosis. As in acute inflammation, chronic inflammation also has leucocytosis

but generally there is relative lymphocytosis in these cases.4. ESR. ESR is elevated in all cases of chronic inflammation.5. Amyloidosis. Long-term cases of chronic suppurative inflammation may develop

secondary systemic (AA) amyloidosis.

TYPES OF CHRONIC INFLAMMATION

Chronic inflammation is subdivided into 2 types:

1. Non-specific, when the irritant substance produces a nonspecific chronic inflammatory reaction with formation of granulation tissue and healing by fibrosis e.g. chronic osteomyelitis, chronic ulcer.

2. Specific, when the injurious agent causes a characteristic histologic tissue response e.g. tuberculosis, leprosy, syphilis. Histological features classify chronic inflammation into 2 types:

i. Chronic non-specific inflammation. It is characterised by non-specific inflammatory cell infiltration e.g. chronic osteomyelitis, lung abscess. Chronic suppurative inflammation in which infiltration by polymorphs and abscess formation are additional features e.g. actinomycosis.

ii. Chronic granulomatous inflammation. It is characterised by formation of granulomas e.g. tuberculosis, leprosy, syphilis, actinomycosis, sarcoidosis etc.

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23DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

HEALINGHealing is the body response in injury to restore normal structure and function.

Healing involves 2 processes:

Regeneration: Healing takes place by proliferation of parenchymal cells and complete restoration of the original tissues.

Repair: Healing takes place by proliferation of connective tissue resulting in fibrosis and scarring.

At times, both the processes take place simultaneously.

REGENERATION:

To maintain proper structure of tissues, cells are under the regulatory control of their cell cycle. These include growth factors such as: epidermal growth factor, fibroblast growth factor, platelet derived growth factor, endothelial growth factor, transforming growth factor.

REPAIR:

It is the replacement of injured tissue by fibrous tissue. The processes involved in repair are:

1. Granulation tissue formation; and2. Contraction of wounds.

Repair response takes place by mesenchymal cells (consisting of connective tissue stem cells, fibrocytes and histiocytes), endothelial cells, macrophages, platelets, and the parenchymal cells of the injured organ.

Granulation Tissue Formation

Granulation tissue (granular and pink appearance of the tissue). Granule corresponds histologically to proliferation of new small blood vessels. The 3 phases observed in the formation of granulation tissue are:

1. PHASE OF INFLAMMATION. Following trauma, blood clots at the site of injury. There is acute inflammatory response with exudation of plasma, neutrophils and monocytes within 24 hours.

2. PHASE OF CLEARANCE. Combination of proteolytic enzymes liberated from neutrophils, autolytic enzymes from dead tissues cells, and phagocytic activity of macrophages clear off the necrotic tissue, debris and red blood cells.

3. PHASE OF INGROWTH OF GRANULATION TISSUE. This phase consists of 2 main processes: angiogenesis or neovascularisation, and fibrogenesis.

i) Angiogenesis (neovascularisation). Formation of new blood vessels at the site of injury takes place by proliferation of endothelial cells from the margins of blood vessels and within a few hours they develop lumen and start carrying blood. They are

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24DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

leaky. These blood vessels differentiate into muscular arterioles, thin-walled venules and true capillaries. Angiogenesis is stimulated with the proteolytic destruction of basement membrane and takes place under the influence of:a) Vascular endothelial growth factor (VEGF) its receptors are present in endothelial

cells only.b) Platelet-derived growth factor (PDGF), transforming growth factor-β(TGF-β),

basic fibroblast growth factor (bFGF) and surface integrins. Associated with cellular proliferation.

ii) Fibrogenesis. The newly formed blood vessels may also originate from fibrocytes by mitotic division of fibroblasts. These fibroblasts have combination of morphologic and functional characteristics of smooth muscle cells (myofibroblasts). Collagen fibrils begin to appear by about 6th day. As maturation proceeds, more and more of collagen is formed while the number of active fibroblasts and new blood vessels decreases. This results in formation of inactive looking scar known as cicatrisation.

Contraction of Wounds

The wound starts contracting after 2-3 days and the process is completed by the 14th day and the wound is reduced by 80% of its original size. Contracted wound results in rapid healing due to lesser surface area of the injured tissue. The mechanism of wound contraction and factors involved are:

1. Dehydration as a result of removal of fluid by drying of wound.2. Contraction of collagen was responsible for wound contraction.3. Myofibroblasts cells migration into the wound area and contraction decreases the size

of the defect.i. Fibrils present in the cytoplasm as seen in smooth muscle cells.

ii. These cells contain actin-myosin as found in non-striated muscle cells.iii. These cells have basement membrane and desmosomes which are not seen in

ordinary fibroblasts.iv. Drug response of granulation tissue is similar to that of smooth muscle.

WOUND HEALING

Healing of skin wounds is a combination of regeneration and repair Wound healing takes place by one of the two ways:

a. Healing by first intention (primary union)b. Healing by second intention (secondary union).

a. Healing by First Intention (Primary Union)

Healing of a wound with these characteristics occurs by Healing by First Intention (Primary Union):

i) Clean and uninfected;ii) Surgically incised;iii) Without much loss of cells and tissue;iv) Edges of wound are approximated by surgical sutures.

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25DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

1. Initial haemorrhage. Immediately after injury, the space between the approximated surfaces of incised wound is filled with blood which then clots and seals the wound against dehydration and infection.

2. Acute inflammatory response. This occurs within 24 hours with appearance of polymorphs from the margins of incision. By 3rd day, polymorphs are replaced by macrophages.

3. Epithelial changes. The basal cells of epidermis from both the cut margins start proliferating and migrating towards incisional space in the form of epithelial spurs. A well approximated wound is covered by a layer of epithelium in 48 hours. The migrated epidermal cells, necrotic material and clot, forming scab. The basal cells from the margins continue to divide and by 5th day, a multi-layered new epidermis is formed.

4. Organisation. By 3rd day, fibroblasts also invade the wound area. By 5th day, new collagen fibrils start forming which dominate till healing is completed. In 4 weeks, the scar tissue with scanty cellular and vascular elements, a few inflammatory cells and epithelialised surface is formed.

5. Suture tracks. It is a separate wound due to suture. The suture track gets infected (stitch abscess), or the epithelial cells may persist in the track (implantation or epidermal cysts). Scar formed in a sutured wound is neat.

b. Healing by Second Intention (Secondary Union)

Healing of a wound with characteristics occurs by Healing by Second Intention (Secondary Union):

i) Open with a large tissue defect, at times infected;ii) Having extensive loss of cells and tissues;iii) The wound is not approximated by surgical sutures but is left open.

The basic events in secondary union are similar to primary union but differ in having a larger tissue defect which has to be bridged. Hence healing takes place from the base upwards as

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26DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

well as from the margins inwards. The healing by second intention is slow and results in a large, at times ugly scar.

1. Initial haemorrhage. As a result of injury, the wound space is filled with blood and fibrin clot which dries.

2. Inflammatory phase. There is an initial acute inflammatory response followed by appearance of macrophages which clear off the debris as in primary union.

3. Epithelial changes. As in primary healing, the epidermal cells from both the margins of wound proliferate and migrate into the wound in the form of epithelial spurs till they meet in the middle and re-epithelialise the gap completely. The regenerated epidermis becomes stratified and keratinised.

4. Granulation tissue. Granulation tissue is formed by proliferation of fibroblasts and neovascularisation. The newly-formed granulation tissue is deep red, granular and very fragile, the scar on maturation becomes pale and white due to increase in collagen and decrease in vascularity.

5. Wound contraction. Contraction of wound is an important feature of secondary healing, not seen in primary healing. Due to myofibroblasts present in granulation tissue, the wound contracts to one-third to one-fourth of its original size. Wound contraction occurs at a time when active granulation tissue is being formed.

6. Presence of infection. Bacterial contamination of an open wound delays the process of healing due to release of bacterial toxins that provoke necrosis, suppuration and thrombosis. Surgical removal of dead and necropsied tissue debridement helps in preventing the bacterial infection of open wounds.

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27DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

Complications of Wound Healing

Complications includes:

1. Infection of wound due to entry of bacteria delays the healing.2. Implantation (epidermal) cyst formation may occur due to persistence of epithelial

cells in the wound after healing.3. Pigmentation. Healed wounds may at times have rust-like colour due to staining with

haemosiderin. Some coloured particulate material left in the wound may persist and impart colour to the healed wound.

4. Deficient scar formation. This may occur due to inadequate formation of granulation tissue.

5. Incisional hernia. A weak scar, especially after a laparotomy, may be the site of bursting open of a wound (wound dehiscence) or an incisional hernia.

6. Hypertrophied scars and keloid formation. At times the scar formed is excessive, ugly and painful. Excessive formation of collagen in healing may result in keloid (claw-like) formation, seen more commonly in Blacks.

7. Excessive contraction. An exaggeration of wound contraction may result in formation of contractures or cicatrisation e.g. Dupuytren’s (palmar) contracture, plantar contracture and Peyronie’s disease (contraction of the cavernous tissues of penis).

8. Neoplasia. Rarely, scar may be the site for development of carcinoma later e.g. squamous cell carcinoma in Marjolin’s ulcer i.e. a scar following burns on the skin.

Extracellular Matrix—Wound Strength

The wound is strengthened by proliferation of fibroblasts and myofibroblasts which get structural support from the extracellular matrix (ECM). ECM can direct cell migration, attachment, differentiation and organisation. ECM has five main components: collagen, adhesive glycoproteins, basement membrane, elastic fibres, and proteoglycans.

1. COLLAGEN. The collagens are a family of proteins which provide structural support. It is the main component of tissues such as fibrous tissue, bone, cartilage, valves of heart, cornea, basement membrane etc. Defective regulation of collagen synthesis leads to hypertrophied scar, fibrosis, and organ dysfunction.

2. ADHESIVE GLYCOPROTEINS. Various adhesive glycoproteins acting as glue for the ECM and the cells consist of fibronectin, tenascin (cytotactin) and thrombospondin.

i) Fibronectin (nectere = to bind) is the best glycoprotein in ECM and It is of two types-plasma and tissue fibronectin.

Plasma fibronectin is synthesised by the liver cells and is trapped in basement membrane.

Tissue fibronectin is formed by fibroblasts, endothelial cells and other mesenchymal cells.

ii) Tenascin or cytotactin is the glycoprotein associated with fibroblasts and appears in wound about 48 hours after injury. It disappears from mature scar tissue.

iii) Thrombospondin is mainly synthesised by granules of platelets. It functions as adhesive protein for keratinocytes and platelets.

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28DAWN V TOMY M.Pharm., Asst.Professor, Dept. of Pharmacology, ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

3. BASEMENT MEMBRANE. Basement membranes are structures that lie underneath epithelia of different organs and endothelial cells.

4. ELASTIC FIBRES. Elastic fibres consist of 2 components—elastin glycoprotein and elastic microfibril. Elastases degrade the elastic tissue e.g. in inflammation, emphysema etc.

5. PROTEOGLYCANS. These have 2 components—an essential carbohydrate polymer (called polysaccharide or glycosaminoglycan), and a protein bound to it. Various proteoglycans are:

i) Chondroitin sulphate—abundant in cartilage, dermisii) Heparan sulphate—in basement membranesiii) Dermatan sulphate—in dermisiv) Keratan sulphate—in cartilagev) Hyaluronic acid—in cartilage, dermis.

Factors Influencing Healing

Two types of factors influence the wound healing: those acting locally, and those acting in general.

A. LOCAL FACTORS:

1. Infection is the most important factor acting locally which delays the process of healing.

2. Poor blood supply to wound slows healing e.g. injuries to face heal quickly due to rich blood supply while injury to leg with varicose ulcers having poor blood supply heals slowly.

3. Foreign bodies including sutures interfere with healing and cause intense inflammatory reaction and infection.

4. Movement delays wound healing.5. Exposure to ionising radiation delays granulation tissue formation.6. Exposure to ultraviolet light facilitates healing.7. Type, size and location of injury determine whether healing takes place by resolution

or organisation.

B. SYSTEMIC FACTORS:

1. Age. Wound healing is rapid in young and somewhat slow in aged and debilitated people due to poor blood supply to the injured area in the latter.

2. Nutrition. Deficiency of constituents like protein, vitamin C (scurvy) and zinc delays the wound healing.

3. Systemic infection delays wound healing.4. Administration of glucocorticoids has anti-inflammatory effect.5. Uncontrolled diabetics are more prone to develop infections and hence delay in

healing.6. Hematologic abnormalities like defect of neutrophil functions (chemotaxis and

phagocytosis), and neutropenia and bleeding disorders slow the process of wound healing.