Pathophysiology of InflammationPathophysiology of Inflammation

Miklós MolnárMiklós Molnár

Inflammation is a Inflammation is a complexcomplex defense defense reactionreaction in the vascularized connective in the vascularized connective tissue in response to tissue in response to endogenous or endogenous or exogenousexogenous stimuli in order to stimuli in order to destroy, destroy, eliminateeliminate the injurious agents or the injurious agents or microorganisms and initiate a series of microorganisms and initiate a series of events that events that heal and reconstituteheal and reconstitute the the damaged tissuedamaged tissue

Essentials of InflammationEssentials of Inflammation

Subsequent EventsSubsequent Events

Alteration (tissue injury)Alteration (tissue injury)Vascular reactionVascular reactionProliferation (reconstitution)Proliferation (reconstitution)

LocalizationLocalization

The connective tissue and its The connective tissue and its microcirculation including the microcirculation including the surrounding extracellular space.surrounding extracellular space.

PlaPlassmamaproteinsproteins– ProteolProteolytic cascadesytic cascades: :

coagulationcoagulation, kinin, , kinin, fibrinolfibrinolyticytic

Blood cellsBlood cells– NeutroNeutrophphililss, eo, eossinoinophphililss, ,

babassoophphililss, monoc, monocytesytes, , llyymmphphococyytteses, , plateletsplatelets

Cells of the connective tissueCells of the connective tissue– Mast cellsMast cells, fibroblast, fibroblastss, ,

mamaccrorophaphaggss, l, lyymmphphococytesytes Blood veselsBlood vesels

– Endothelium, baEndothelium, basement sement membranemembrane, s, smooth muscle mooth muscle cellscells

ParticipantsParticipants

ParticipantsParticipants

Extracellular matrixExtracellular matrix– FibroneFibronecctin, laminin, tin, laminin, ccollagollageen, n,

enactin, tenascin, proteoglikenactin, tenascin, proteoglikansans etcetc..

SpecifiSpecificc medi mediatorsators– Early Early medimediaatortorss positive, positive,

amplificationamplification

– LateLate medi mediaatortorss negative, negative, restiturestitutiotio

Restitution

Restitution

Proliferation(granuloma)

Restitution

ChronicInflammation

Acute Inflammation

Injury

or

or

Types of Inflammatory Types of Inflammatory reactionsreactions

TypeType AAccututee ChronicChronic

InflammationInflammation Inflammation Inflammation

Duration max. 1 week > 1 week

Characteristics exudation (edema) connective tissue emigration of leuko- proliferation

cytes lymphocytes and macrophages accumulation

InflammationInflammation

Local reactionsLocal reactions Systemic reactionsSystemic reactions

Classical (cardinal)

signs

Acute phase reaction, Acute phase reaction, fever, leukocytosis fever, leukocytosis etc.etc.

Celsus described the four famous signs of Celsus described the four famous signs of inflammation calor, rubor, tumor, and dolorinflammation calor, rubor, tumor, and dolor((A.D. 30)A.D. 30)

Systemic Effects of InflammationSystemic Effects of Inflammation

Acute-phase reactionAcute-phase reaction TNFTNF, IL-1 & IL-6, IL-1 & IL-6 feverfever leukocytosisleukocytosis Iron deficiency, anemiaIron deficiency, anemia proteolysisproteolysis activation of lymphocytesactivation of lymphocytes

Initiation ofInitiation ofAcute PhaseAcute PhaseReactionReaction

MACROPHAGES

TNFα

NEURO-PEPTIDES

ENDOTOXINEXOTOXIN

-INTERFERONIMMUNCOMPLEX

URATE SILICATECRISTALS

IL-1IL-6

Acute Phase proteinsAcute Phase proteins CeruloplasminCeruloplasmin

– Scavenges oxygen radicals generated by leukocytesScavenges oxygen radicals generated by leukocytes

Protease inhibitorsProtease inhibitors– αα11-protease inhibitor, -protease inhibitor, αα11-antichymotrypsin and -antichymotrypsin and αα22-macroglobulin-macroglobulin

C-reactive protein (CRP)C-reactive protein (CRP)– binds to bacteria and produce capsular swelling, precipitation and binds to bacteria and produce capsular swelling, precipitation and

agglutination; binding also fixes complement, thus causing the agglutination; binding also fixes complement, thus causing the production of C3b (an opsonin) and chemotactic factorsproduction of C3b (an opsonin) and chemotactic factors

FibrinogenFibrinogen– may serve as opsonin by clumping bacteria together; breakdown may serve as opsonin by clumping bacteria together; breakdown

products of fibrinogen has anti-inflammatory activityproducts of fibrinogen has anti-inflammatory activity

TransferrinTransferrin– decreases, thus limiting the amount of iron available to meet bacterial decreases, thus limiting the amount of iron available to meet bacterial

growth requirementgrowth requirement

INFECTION, TOXINS, IMMUNCOMPLEXES, NEOPLASIAINFECTION, TOXINS, IMMUNCOMPLEXES, NEOPLASIA

IL-1/TNF IL-6IL-1/TNF IL-6

HypothalamusHypothalamus

Prostaglandins (EProstaglandins (E22))

Vasomotor center ?Vasomotor center ?

Sympathetic nervesSympathetic nerves

Skin vasoconstrictionSkin vasoconstriction

↓ ↓ Heat dissipationHeat dissipation

FEVERFEVER

PPAATTHHOOMMEECCHHAANNIISSMM

OOFF

FFEEVVEERR

Local Effect of Acute Local Effect of Acute InflammationInflammation

Blood flow increasesBlood flow increases (alteration of vascular caliber)(alteration of vascular caliber)

Increased vascular permeabilityIncreased vascular permeability (plasma (plasma proteins and leukocytes leave the circulation, retraction of proteins and leukocytes leave the circulation, retraction of endothelial cells, fenestration)endothelial cells, fenestration)

Cellular eventsCellular events (emigration of leukocytes and (emigration of leukocytes and makrophages: makrophages: mmargination, rolling, adhesion, emigration, argination, rolling, adhesion, emigration,

chemotaxis, phagocytosis)chemotaxis, phagocytosis)

Advantages of exudationAdvantages of exudation

Fluid exudationFluid exudation((dilution of toxinsdilution of toxins))

Increased protein contentIncreased protein contentGlobulins Globulins ((antibodiesantibodies))

Fibrin precipitationFibrin precipitation ((Bacterial fixation, wound healingBacterial fixation, wound healing))

Acute-phase proteinsAcute-phase proteins

Mechanisms of Vascular LeakageMechanisms of Vascular Leakage

1. 1. Endothelial contractionEndothelial contraction widening of intercellular junctions (rapid , short-lived action, histamine, bradykinin, leukotrienes etc. effects only the small venules)

2. 2. Junctional retractionJunctional retractioninduced by IL-1, TNFα, IFN, delayed (4-6 hours) effect

3. 3. Leukocyte-dependent leakageLeukocyte-dependent leakage

free radicals and proteolytic enzymes

4. 4. Leakage from regenerating capillariesLeakage from regenerating capillaries

angiogenesis, intercellular junction developmentangiogenesis, intercellular junction development

Leukocyte extravasationLeukocyte extravasation

MMarginarginationation, rolling, rolling and and adh adhesionesion Transmigration across the endothelium Transmigration across the endothelium

(diapedesis)(diapedesis) Migration in interstitial tissues toward a Migration in interstitial tissues toward a

chemotactic stimuluschemotactic stimulus

Adhesion receptorsAdhesion receptors

ImmunoglobulinImmunoglobulinss endotheliendothelialal adh adhesionesion mole moleculescules::

intercellulintercellularar (ICAM-1), vascular cell ~ (VCAM-1) (ICAM-1), vascular cell ~ (VCAM-1) both both interact with integrins found on leukocytesinteract with integrins found on leukocytes

IntegrinIntegrinss (transmembr(transmembraanne-adhesive heterodimeric e-adhesive heterodimeric

glycoproteins, glycoproteins, αα and and ββ chains chains)) 22-in-inttegrinegrinss (LFA-1, MAC-1 (LFA-1, MAC-1 ICAM-1) ICAM-1) 11-in-inttegrin (VLA-4 egrin (VLA-4 VCAM-1) VCAM-1)

SelectinSelectinss– E-selectin (ELAM-1, endothelium)E-selectin (ELAM-1, endothelium)– P-selectin (GMP140, P-selectin (GMP140, plateletsplatelets))– L-selectin (LAM-1, L-selectin (LAM-1, leukocytes)leukocytes)

Cell Surface Adhesion ReceptorsCell Surface Adhesion Receptors

Roles and Mechanism of Adhesion Roles and Mechanism of Adhesion MoleculesMolecules

1.1. Redistribution of adhesion Redistribution of adhesion molecules to the cell surfacemolecules to the cell surface

P-selectin P-selectin (intracitopla(intracitoplassmatimatic granules of c granules of endothelendothelialial cellscells - - Weibel-Palabe granulWeibel-Palabe granuleses

histamin, thrombinhistamin, thrombin, PAF, PAF cell surfacecell surface adhesion and adhesion and rollingrolling of leukocytes of leukocytes

Roles and Mechanism of Adhesion Roles and Mechanism of Adhesion MoleculesMolecules

2.2. Induction of adhesion molecules on Induction of adhesion molecules on

endotheliumendothelium (IL-1, TNF) (IL-1, TNF) E-selectin, E-selectin, and and ICAM-1, VCAM-1ICAM-1, VCAM-1

3.3. Increased avidity of bindingIncreased avidity of binding LFA-1 LFA-1 on leukocytes dose not adhere to its ligand ICAM-on leukocytes dose not adhere to its ligand ICAM-1 on endothelium at resting condition. However, after 1 on endothelium at resting condition. However, after certain stimuli LFA-1 is converted from a state of low- to certain stimuli LFA-1 is converted from a state of low- to high-affinity binding toward ICAM-1high-affinity binding toward ICAM-1Strong bindingStrong binding Transmigration across endotheliumTransmigration across endothelium

Migration of LeukocytesMigration of Leukocytes

Selectins Integrins

Chemotaxis and Leukocyte ActivationChemotaxis and Leukocyte Activation

EExogxogenous substancesenous substances– babacctterial productserial products (N-formyl-methionin(N-formyl-methioninee containing containing

peptides, lipids)peptides, lipids)

EEndogndogenous substancesenous substances    Compounds of cCompounds of complementomplement system system ( C5a, C3a) ( C5a, C3a)

   Products of the Products of the LipoxygenaseLipoxygenase pathway pathway (LTB(LTB44))

CCyytokinetokiness (IL-8) (IL-8) receptor bindings PLC-Ca2+ actin-myosin active locomotion and activation of PLA2 AA, degranulation (lysosomal enzymes), modulation of

adhesion molecules

ChemotaxisChemotaxis

PhagocytosisPhagocytosis 1. 1.

Recognition and attachmentRecognition and attachment – opsoninopsonins mediateds mediated (Fc- (Fc-fragment of fragment of IgG, C3b) IgG, C3b)

((via via FcFcR receptorR receptorss))– nonopsoninonopsonic phagocytosisc phagocytosis recognition of recognition of LPS LPS

PhagocytosisPhagocytosis 2. 2. EngulfmentEngulfment

Binding to Binding to FcFcR R pseudopodspseudopods fusion of the fusion of the phagocytic vacules and the lysosomal granulesphagocytic vacules and the lysosomal granules

Killing or DegradationKilling or Degradation Oxygen dependent:

NADPH oxidNADPH oxidasease superoxide ion superoxide ion H H22OO22 MPO HMPO H

22OO22 + Cl + Cl-- HOCl HOClNO synthaseNO synthase NO NO peroxinitrite (CONO peroxinitrite (CONO

22-- ) )

Oxygen independent:

llysozymeysozyme, la, lacctofetoferrrin, MBPrin, MBP –major basic protein- –major basic protein-, , defendefenssininss, , acidacid h hyydroldrolasease

PhagocytosisPhagocytosis

Defects in Leukocyte FunctiomDefects in Leukocyte FunctiomGeneticGenetic

Leukocyte adhesion deficiency 1Leukocyte adhesion deficiency 1

Leukocyte adhesion deficiency 2Leukocyte adhesion deficiency 2

Neutrophil specific granule Neutrophil specific granule

deficiencydeficiency

Chronic granulomatosus diseaseChronic granulomatosus disease– X-linkedX-linked

– Autosomal recessiveAutosomal recessive

Myeloperoxidase deficiencyMyeloperoxidase deficiency

ChChéédiak-Higashi syndromediak-Higashi syndrome

ββ chain of CD11/ CD18 integrins chain of CD11/ CD18 integrins

Selectin receptors Selectin receptors (Sialyated oligosacharide)(Sialyated oligosacharide)

Absence of neutrophil specific Absence of neutrophil specific

granules, defective chemotaxisgranules, defective chemotaxis

Decreased oxidative burstDecreased oxidative burst– NADPH oxidase (membrane component)NADPH oxidase (membrane component)

– NADPH oxidase (cytoplasmic component)NADPH oxidase (cytoplasmic component)

Absent MPO-HAbsent MPO-H22OO22 system system

Multiple defectMultiple defect

DiseaseDisease DefectDefect

Defects in Leukocyte FunctiomDefects in Leukocyte FunctiomAcquiredAcquired

Thermal injury, diabetes, Thermal injury, diabetes, malignancy, sepsis, malignancy, sepsis, immunodeficienciesimmunodeficiencies

Hemodialysis, diabetesHemodialysis, diabetes Leukemia, anemia, sepsis, Leukemia, anemia, sepsis,

diabetes, neonates, diabetes, neonates, malnutritionmalnutrition

ChemotaxisChemotaxis

AdhesionAdhesion Phagocytosis and Phagocytosis and

microbicidal activitymicrobicidal activity

DiseaseDisease DefectDefect

Plasma Proteases Plasma Proteases

Kinin systemKinin systemFibrinolytic systemFibrinolytic systemComplement systemComplement system

The Kinin systemThe Kinin system

Bradykinin1. Inducing arteriolar dilatation

2. Increasing the permeability of venules

3. Causing pain

Kallinkrein1. Activation of plasminogen

2. Activation of C1q in the complement system

3. Found in plasma , tissues and secretions

The Fibrinolytic SystemThe Fibrinolytic System

Plasmin1. Produce vasodilatation by generating FDP

2. Can digest fibrin, removes fibrin deposit3. Can activate complement system by cleaving C3

Plasminogen Activating Factors

prourokinase urokinase

Kallikrein

Other Plasminogen ActivatorsOther Plasminogen Activators

Bacterial substances (eg. streptokinase)Bacterial substances (eg. streptokinase)Cell-derived activators (eg. trypsin)Cell-derived activators (eg. trypsin)Macrophage plasminogen activatorMacrophage plasminogen activatorHageman factorHageman factor

Note:

Plasmin was formerly known as fibrinolysin, this old name is still used for this system

The Complement SystemThe Complement System

Consist of 20 interactive plasma and cell Consist of 20 interactive plasma and cell membrane proteinsmembrane proteins

Activated complement:Activated complement:– Mediating vascular responses (histamine release)Mediating vascular responses (histamine release)– Requiting phagocytic leukocytes (chemotaxis)Requiting phagocytic leukocytes (chemotaxis)– Opsonizing target of phagocytic cellsOpsonizing target of phagocytic cells– Directly damaging target cells or tissueDirectly damaging target cells or tissue

Activation:Activation:– Classic pathwayClassic pathway– Alternative pathwayAlternative pathway

Classic PathwayClassic PathwayThis pathway is activated by antibody-coated targets or

antigen-antibody complexes

C1 inhibitor

Hageman Factor

Alternative PathwayAlternative PathwayActivated by: 1. LPS; 2. plasmin; 3. a factor from cobra venom;

4. aggregated IgM or IgG; 5. complexes of antigen with IgA

C3b inhibitor

The Role of Hageman FactorThe Role of Hageman Factor

C1 inhibitor

Chemical Mediators of Chemical Mediators of InflammationInflammation

VasodilatationVasodilatation Prostaglandins, histaminProstaglandins, histaminVascular permeabilityVascular permeability Vasoactiv amins Vasoactiv amins

CC3a3a and C and C5a5a

BradykininBradykinin Leukotrien CLeukotrien C44, D, D44, E, E44, PAF, PAF Chemotaxis Chemotaxis CC5a5a, Leukotrien B, Leukotrien B4 4 , lipids, bacterial products, lipids, bacterial products

Chemical Mediators of Chemical Mediators of InflammationInflammation

FeverFever IL-1; TNF, Prosztaglandin EIL-1; TNF, Prosztaglandin E22

PainPain Prosztaglandins, BradykininProsztaglandins, Bradykinin

Tissue injuryTissue injury Lysosomal enzymes (neutrophils, macrophages)Lysosomal enzymes (neutrophils, macrophages)oxygen metabolitesoxygen metabolites

Cyclo-oxygenase Hypothesis - 1990’sCyclo-oxygenase Hypothesis - 1990’smembrane phospholipidsmembrane phospholipids

arachidonic acidarachidonic acid

glucocorticoidsglucocorticoids(-)(-)

COX-1COX-1constitutiveconstitutive

COX-2COX-2inducibleinducible

selectiveCOX-2

inhibitors

selectiveCOX-2

inhibitors

ClassicalNSAIDSClassicalNSAIDS

INDUCTION:mitogens

endotoxinscytokines

(-)(-)

(-)(-)

StomachStomach KidneyKidney EndotheliumEndothelium PlateletsPlatelets

PGEPGE22/PGI/PGI22

gastricgastriccytoprotectioncytoprotection

PGEPGE22/PGI/PGI22

renal blood renal blood flowflow

PGIPGI22 TXATXA22

Inflammatory SitesInflammatory Sites

PGEPGE22

inflammatoryinflammatorymediatorsmediators

haemostasishaemostasis

Physiological EffectsPhysiological EffectsPhysiological EffectsPhysiological Effects InflammationInflammationInflammationInflammation

(-)(-)(-)(-)

Phospholipase APhospholipase A22

Hierarchies of cytokinesHierarchies of cytokines

TNF

IL-1

IL-6, IL-8, VEGF, GM-CSF

Stimulus

Effect of anti-TNFEffect of anti-TNF Treatment Treatment

Decreased synthesis of IL-1, IL-6 Decreased synthesis of IL-1, IL-6

Inhibition of the migration of leukocytesInhibition of the migration of leukocytes

Decreased number of endothelial adhesion Decreased number of endothelial adhesion moleculesmolecules (VCAM-1, ICAM-1, E-selectin)(VCAM-1, ICAM-1, E-selectin)

Decreased endothelial chemotactic chemokins (IL-8) Decreased endothelial chemotactic chemokins (IL-8)

Decreased T-cell infiltration (T CD4 sup+, CD45 Decreased T-cell infiltration (T CD4 sup+, CD45 RO sup+)RO sup+)

Chronic InflammationChronic Inflammation

Inflammation of prolonged duration (weeks, Inflammation of prolonged duration (weeks, months) in which active inflammation, tissue months) in which active inflammation, tissue destruction and attempts to healing are destruction and attempts to healing are proceeding simultaneouslyproceeding simultaneously– infiltration with mononuclear cellsinfiltration with mononuclear cells– tissue destructiontissue destruction– attempt to repair by connective tissue (fibrosis)attempt to repair by connective tissue (fibrosis)– angiogenesisangiogenesis

Causes of Chronic InflammationCauses of Chronic Inflammation

Persistent infectionPersistent infectionProlonged exposure to toxic agentsProlonged exposure to toxic agentsImmune reactions against own tissue Immune reactions against own tissue

autoimmune disease (SLE, RA)autoimmune disease (SLE, RA)