5
Treatment of Vascular Retinopathies with Pycnogenol 1 L. Spadea and E. Balestrazzi* Dipartimento di Discipline Chirurgiche, Cattedra di Clinica Oculistica, Facolta ` di Medicina e Chirurgia, Via Vetoio, Coppito 2, L’Aquila, Italy The aim of our study was to investigate the effects of Pycnogenol 1 on the progression of diabetic retino- pathy and other vascular retinal disorders. The study consisted of a double-blind phase in which 20 patients were recruited and randomly treated with placebo or Pycnogenol 1 (50 mg  3/day for 2 months) and an open phase in which another 20 patients were treated with Pycnogenol 1 at the same dose schedule. In total, 40 patients with diabetes, atherosclerosis and other vascular diseases involving the retina were enrolled; 30 of them were treated with Pycnogenol 1 and 10 with placebo. The results demonstrated a beneficial effect of Pycnogenol 1 on the progression of retinopathy. Without any treatment (placebo) the retinopathy progressively worsened during the trial and the visual acuity significantly decreased; on the contrary, the Pycnogenol 1 -treated patients showed no deterioration of retinal function and a significant recovery of visual acuity was also obtained. The fluorangiography showed an improvement of retinal vascularization and a reduced endothelial permeability and leakage in the Pycnogenol 1 , but not in the placebo-treated, patients. The ophthalmoscopy and the electroretinogram (ERG) also confirmed the beneficial effects of Pycnogenol 1 . The mechanism of action of Pycnogenol 1 may be related to its free radical (FR) scavenging, anti- inflammatory and capillary protective activities. It has been suggested that Pycnogenol 1 may bind to the blood vessel wall proteins and mucopolysaccharides and produce a capillary ‘sealing’ effect, leading to a reduced capillary permeability and oedema formation. Copyright # 2001 John Wiley & Sons, Ltd. Keywords: Pycnogenol 1 ; retinopathy; diabetes; atherosclerosis. INTRODUCTION Retinopathy frequently occurs as a consequence of a retinal localization of microangiopathy in the course of diseases, such as diabetes, hypertension and athero- sclerosis. The literature has widely described the role of free radicals in the pathogenesis of these retinopathies, as well as of other eye diseases, such as cataract, age-related macular degeneration and cystic macular oedema (Malenfant, 1995). Considerable evidence indicates that oxidative stress plays a role in retinal function deterioration. The oxidation of lipids, proteins and other macromolecules is also involved in the pathogenesis of diabetic retino- pathy. A significantly lower content of sulphydryl proteins was found in the lens and vitreous humor of the eyes of diabetic patients than in those of non-diabetic and control subjects. Moreover, an increased formation of protein-bound and free sulphydryls and carbonyl indices of oxidative damage to proteins was noted in diabetic patients (Altomare et al., 1997). All these parameters are mostly altered when diabetes is compli- cated with retinal alterations. Glutathione peroxidase activity and ascorbic acid levels, known to exert important antioxidant functions in the eye compartment, have been found significantly decreased in the lens of diabetic patients, especially in the presence of retinal damage (Bambolkar and Sainani, 1995; Rema et al., 1995). Evidence has been published supporting the use of antioxidants in the prevention and treatment of diabetic retinopathy and other eye vascular diseases (Kahler et al., 1993; Stahl and Sies, 1997). The antioxidants may play an important role in preventing the preretinal neovascu- larization and the chronic retinal oedema, which are two major sight-threatening complications of diabetic retino- pathy. Ocular neovascularization is strongly associated with retinal ischaemia, and growth factors have been implicated in its pathogenesis. The ischaemic retina is assumed to secrete growth factors that stimulate residual vessels to proliferate (Paques et al., 1997). To date, the growth factor correlating most closely with neovascularization is vascular endothelial cell growth factor (VEGF). Human retinal pigment epithelial cells exposed to FR (superoxide and hydrogen peroxide) rapidly increased the expression of VEGF, which is required for ocular angiogenesis during diabetic retino- pathy. Superoxide-associated VEGF-mRNA increase was completely prevented by antioxidant administration (Kuroki et al., 1996), thus suggesting that antioxidants, such as Pycnogenol 1 , may play a useful role in reducing retinal neovascularization in diabetic retinopathy. Pycnogenol 1 is a French maritime pine (Pinus PHYTOTHERAPY RESEARCH Phytother. Res. 15, 219–223 (2001) DOI: 10.1002/ptr.853 Copyright # 2001 John Wiley & Sons, Ltd. * Correspondence to: Prof. E. Balestrazzi, Dipartimento di Discipline Chirurgiche, Cattedra di Clinica Oculistica, Facolta ` di Medicina e Chirurgia, Via Vetoio, Coppito 2, L’Aquila, Italy. Received 14 April 2000 Accepted 11 January

Treatment of vascular retinopathies with Pycnogenol®

Embed Size (px)

Citation preview

Page 1: Treatment of vascular retinopathies with Pycnogenol®

Treatment of Vascular Retinopathies withPycnogenol�

L. Spadea and E. Balestrazzi*Dipartimento di Discipline Chirurgiche, Cattedra di Clinica Oculistica, Facolta di Medicina e Chirurgia, Via Vetoio, Coppito 2, L’Aquila,Italy

The aim of our study was to investigate the effects of Pycnogenol� on the progression of diabetic retino-pathy and other vascular retinal disorders.

The study consisted of a double-blind phase in which 20 patients were recruited and randomly treatedwith placebo or Pycnogenol� (50 mg � 3/day for 2 months) and an open phase in which another 20 patientswere treated with Pycnogenol� at the same dose schedule. In total, 40 patients with diabetes, atherosclerosisand other vascular diseases involving the retina were enrolled; 30 of them were treated with Pycnogenol�

and 10 with placebo.The results demonstrated a beneficial effect of Pycnogenol� on the progression of retinopathy. Without

any treatment (placebo) the retinopathy progressively worsened during the trial and the visual acuitysignificantly decreased; on the contrary, the Pycnogenol�-treated patients showed no deterioration ofretinal function and a significant recovery of visual acuity was also obtained. The fluorangiography showedan improvement of retinal vascularization and a reduced endothelial permeability and leakage in thePycnogenol�, but not in the placebo-treated, patients. The ophthalmoscopy and the electroretinogram(ERG) also confirmed the beneficial effects of Pycnogenol�.

The mechanism of action of Pycnogenol� may be related to its free radical (FR) scavenging, anti-inflammatory and capillary protective activities. It has been suggested that Pycnogenol� may bind to theblood vessel wall proteins and mucopolysaccharides and produce a capillary ‘sealing’ effect, leading to areduced capillary permeability and oedema formation. Copyright � 2001 John Wiley & Sons, Ltd.

Keywords: Pycnogenol�; retinopathy; diabetes; atherosclerosis.

INTRODUCTION

Retinopathy frequently occurs as a consequence of aretinal localization of microangiopathy in the course ofdiseases, such as diabetes, hypertension and athero-sclerosis. The literature has widely described the role offree radicals in the pathogenesis of these retinopathies, aswell as of other eye diseases, such as cataract, age-relatedmacular degeneration and cystic macular oedema(Malenfant, 1995).

Considerable evidence indicates that oxidative stressplays a role in retinal function deterioration. Theoxidation of lipids, proteins and other macromoleculesis also involved in the pathogenesis of diabetic retino-pathy. A significantly lower content of sulphydrylproteins was found in the lens and vitreous humor ofthe eyes of diabetic patients than in those of non-diabeticand control subjects. Moreover, an increased formationof protein-bound and free sulphydryls and carbonylindices of oxidative damage to proteins was noted indiabetic patients (Altomare et al., 1997). All theseparameters are mostly altered when diabetes is compli-cated with retinal alterations. Glutathione peroxidaseactivity and ascorbic acid levels, known to exert

important antioxidant functions in the eye compartment,have been found significantly decreased in the lens ofdiabetic patients, especially in the presence of retinaldamage (Bambolkar and Sainani, 1995; Rema et al.,1995).

Evidence has been published supporting the use ofantioxidants in the prevention and treatment of diabeticretinopathy and other eye vascular diseases (Kahler et al.,1993; Stahl and Sies, 1997). The antioxidants may playan important role in preventing the preretinal neovascu-larization and the chronic retinal oedema, which are twomajor sight-threatening complications of diabetic retino-pathy. Ocular neovascularization is strongly associatedwith retinal ischaemia, and growth factors have beenimplicated in its pathogenesis. The ischaemic retina isassumed to secrete growth factors that stimulate residualvessels to proliferate (Paques et al., 1997).

To date, the growth factor correlating most closelywith neovascularization is vascular endothelial cellgrowth factor (VEGF). Human retinal pigment epithelialcells exposed to FR (superoxide and hydrogen peroxide)rapidly increased the expression of VEGF, which isrequired for ocular angiogenesis during diabetic retino-pathy. Superoxide-associated VEGF-mRNA increasewas completely prevented by antioxidant administration(Kuroki et al., 1996), thus suggesting that antioxidants,such as Pycnogenol�, may play a useful role in reducingretinal neovascularization in diabetic retinopathy.

Pycnogenol� is a French maritime pine (Pinus

PHYTOTHERAPY RESEARCHPhytother. Res. 15, 219–223 (2001)DOI: 10.1002/ptr.853

Copyright � 2001 John Wiley & Sons, Ltd.

* Correspondence to: Prof. E. Balestrazzi, Dipartimento di DisciplineChirurgiche, Cattedra di Clinica Oculistica, Facolta di Medicina e Chirurgia,Via Vetoio, Coppito 2, L’Aquila, Italy.

Received 14 April 2000Accepted 11 January

Page 2: Treatment of vascular retinopathies with Pycnogenol®

maritima) bark extract, produced by a validated waterextraction procedure. Its main constituents are mono-meric phenolic compounds (catechin, epicatechin andtaxifolin) and condensed flavanoids (procyanidins/proanthocyanidins). Pycnogenol� has antioxidant andfree radical scavenging activities (Packer et al., 1999),which are higher than those of green tea extracts, Ginkgobiloba and other vegetable extracts (Noda et al., 1997).

The activity of oligomeric procyanidins on eyecapillary and vascular disorders were reported byMagnard et al., (1970), who described the beneficialeffects of procyanidins extracted from P. maritima barkin patients with ocular lesions either primary orsecondary to diabetes: a significant improvement ofcapillary resistance and subjective parameters wasreported in all cases treated. Our study was aimed toinvestigate the activity of Pycnogenol� in vascularretinopathy in a randomized placebo-controlled double-blind trial.

PATIENTS AND METHODS

Our study was initially planned in a randomized, placebo-controlled, parallel group, double-blind design. Twentypatients were enrolled with vascular disorders of theretina secondary to atherosclerosis, diabetes, hyperten-sion or thrombosis of the central retinal vein. After a 2-week run-in period, they were randomly treated withplacebo or Pycnogenol� 50 mg � 3/day for 2 months.During both the run-in and treatment periods, the patientswere not allowed to take drugs active on the cardiovas-cular system, diuretics or NSAIDs. The therapeuticefficacy was evaluated by means of the followinginstrumental tests.

Visual acuity (visus). This was measured by means of aSnellen Chart, both with and without lens correction; thebest corrected visual acuity was taken into account.

Ophthalmoscopy. The examination was done with anindirect binocular ophthalmoscope after mydriasis wasobtained by instilling few drops of a tropicamide 1%solution into the lower conjunctival fornix. The ophthal-moscopy allows the visualization of retinal vasculariza-tion and the presence of macular oedema, haemorrhagesand hard exudates. The severity of the retinal damage wasscored with a 4-point semiquantitative scale: 3 = severe,when a macular haemorrhage occurred; 2 = moderate, if amacular oedema is present with perimacular haemor-rhages and/or hard exudates; 1 = slight, if only fewscattered retinal haemorrhages with macular oedema notclinically significant were observed; 0 = normal, if noclinically evident signs were found.

Field of vision. Perimetry analyses the efficiency of theentire visual system, but it may reveal also thedeterioration of only one of its components, such as theretina. The examination of the visual field was carried outwith a manual Goldmann kinetic perimeter: it wasconsidered improved—when a greater isopter wasobtained with a stimulus of lower intensity or smallersize—or worsened—if the opposite occured.

Fluorangiography. Ophthalmic fluorescein angiography

is an important clinical procedure used to investigate thestatus of retinal and choroidal vessels. When adminis-tered intravenously and followed by rapid-sequenceserial photographs, the fluorescein produces an angio-graphic pattern which allows the checking of the retinalblood flow dynamics, the integrity of the blood–retinabarrier and the function of the retinal epithelium. Themicroangiopathy was scored with a semiquantitative 4-scale scale (severe = 3; moderate = 2; slight = 1; normal =0).

Electroretinogram. The amplitude of the patternelectroretinogram (PERG) is usually reduced in diabeticretinopathy (Prager et al., 1990). The PERG is a usefulmethod to assess the metabolic and physiologicalalterations of the retina. The PERG recordings wereobtained by eliciting the inner retinal layer (gangliarcells) by means ofa checkerboard generated from atelevision screen. The transient mode stimulus (1.96 Hz)was at high contrast and three spatial frequencies (3.1, 1.5and 0.7 c/d) were employed. The patient was kept inmesopic condition during the examination with normo-kinetic pupils and the correction of any refractive error.Gold foil corneal (Arden) and skin (on the orbital rim)Ag/AgCl electrodes were employed as explorer (positive)and reference electrode (negative) respectively. Thesignals filtered, amplified and averaged were analysedby the cursor to measure the amplitudes of N35 - P50 -N95 components of the wave. A difference of at least0.5 �V between the pre-treatment and the post-treatmentregistration was considered an improvement (in the caseof rising) or a worsening (in the case of decreasing).

The safety was evaluated by recording the side effectsand by means of haematology and blood chemistryparameters determined before and at the end of thetreatment. Finally, the physician was asked to judge thetreatments’ efficacy at the end of the trial, using a 4-pointsemiquantitative scale (very good = 4; good = 3;moderate = 2; poor = 1).

In the second part of the study, an additional 20patients with vascular disorders of the retina wereenrolled and treated with Pycnogenol� at a dose of50 mg � 3/day for 60 days in an open design. Thesepatients underwent the same clinical and instrumentalevaluation of efficacy and safety as described for thedouble-blind study.

The results of efficacy and safety were analysedseparately (double-blind and open parts) and pooledwherever appropriate. A descriptive analysis of data wasperformed using the SPSS software on an IBM personalcomputer. The statistical analysis included analysis ofvariance (ANOVA) and the Student’s t-test for para-metric data. Non-parametric data were analysed bymeans of Mann–Whitney and Wilcoxon tests; frequen-cies were analysed by means of the Kruskall–Wallis and�2 tests.

RESULTS

The demographic characteristics and patterns of retino-pathy of the patients enrolled are given in Table 1.

220 L. SPADEA AND E. BALESTRAZZI

Copyright � 2001 John Wiley & Sons, Ltd. Phytother. Res. 15, 219–223 (2001)

Page 3: Treatment of vascular retinopathies with Pycnogenol®

Visual acuity

The retinopathy progressively reduced the visual acuityin the placebo-treated patients; the mean value of righteye decreased from 9.20 (day 0) to 8.90 (day 60)(p � 0.05), and that of the left eye was reduced from 8.43(basal) to 7.80 (day 60) (p � 0.05) (Fig. 1). These datademonstrate that the retinopathy is a rapidly evolvingprocess which needs prompt treatment to be halted. The

treatment with Pycnogenol� slowed down the deteriora-tion of visual acuity and, in some cases, improved therecovery, by increasing the mean values from 7.57 to8.00 (p � 0.05) and from 8.10 to 8.67 (p � 0.01), for theright and left eyes, respectively. A statistically significantdifference between the treatments was found (p � 0.05for right eye; p � 0.01 for the left eye).

Ophthalmoscopy

The examination of the ocular fundus showed animprovement of pattern in the Pycnogenol�-treatedpatients: the difference was statistically significant bothfor the right (p � 0.01) and left (p � 0.05) eyes. Nodifference was found in the placebo-treated groupbetween day 0 and day 60 (Table 2).

Visual field

The visual field showed no significant change in eitherexperimental group, and no significant difference wasfound between the treatments (Table 2).

Fluorangiography

The fluoroangiography revealed no effect on the vascularpattern and endothelial permeability in the placebo-treated patients. On the contrary, a statistically significantreduction of vascular permeability and improvement ofblood–retina barrier was found in the Pycnogenol�-treated patients: the score decreased from 1.70 to 1.30 inthe right eye (p � 0.01), and from 1.63 to 1.37 in the lefteye (p � 0.01) (Table 2).

Electroretinogram

The PERG showed a clear improvement in the Pycno-genol�-treated patients, whose scores were reduced from1.17 to 0.73 in the right eye (p � 0.01) and from 1.03 to0.57 in the left eye (p � 0.001). On the contrary, no effectwas found in the placebo-treated patients. The resultsobtained from this objective functional test clearlydemonstrate the efficacy of Pycnogenol� (Table 2).

The physicians scored the efficacy ‘good’ to ‘very

Table 1. Demographic characteristics of the patients

������� ��������

�� ��� �� ������� �� ����� ����� ��� � ��!��� �� ������� "�#��� �#"� "$#%�� �#!�&������&������� �'�����������(���������)�

� ��

*��������(� ��������)� � ��+�)������������ ��������)� �,����� (�� �)�� ����� � �*��������(����)��������������������)�

- �

������ �� .����� ������ �� ��)� �/ ���� ���� 0��) �����'���)���1 ������/ 0��) �������� �� ������� �����������������2��� /�������� ���0�� ����� ���3 �� �#�" ��� ��)����4 �� �#�� ��� �)� ���� ����#

Table 2. Score of the instrumental tests

5�� ������������ ��������

5�� 6���� 5/ 6���� 5/

7�)�)�� ������ 8 �#"�� �# % �#"�� �# % �#��� �#�$ �#��� �#�"�

9 �# �� �# " �# �� �# " �#"%� �#�� �#��� �#���

.����� 2��/ 8 �#��� �# � �# �� �#�� �#%�� �#�" �#��� �#��9 �#%�� �#� �#"�� �#�� �#"�� �#�� �#�%� �#��

�����������)� 8 �#"�� �#�� �#��� �# � �#%�� �# � �#��� �#�!�

9 �#%�� �#�� �#��� �# �#��� �# �#�%� �#�!�

58: 8 �#!�� �# " �#%�� �# � �#�%� �# � �#%�� �#���

9 �#��� �#�� �#��� �# $ �#��� �#�" �#"%� �#� �

������������� ���2��� /��������� �� �#�"#� �� �#�� (� ����� � �)� ;������<� ����#

VASCULAR RETINOPATHIES AND PYCNOGENOL 221

Copyright � 2001 John Wiley & Sons, Ltd. Phytother. Res. 15, 219–223 (2001)

Page 4: Treatment of vascular retinopathies with Pycnogenol®

good’ in 53% of the Pycnogenol�-treated patients, whilein the placebo-treated group, the efficacy was scored‘good’ in only 30% of patients (p � 0.05). The efficacyscore was moderate in the remaining 47% of the patientstreated with Pycnogenol� (Table 3). Tolerability wasvery good in both the groups; no side effect was reportedduring the study. Although scattered significant differ-ences were found between the experimental groups in thehaematology and blood chemistry, no sign of systemictoxicity or poor tolerability was observed (Table 4).

DISCUSSION

The overall clinical improvement we observed withPycnogenol� in patients with diabetic retinopathy andother forms of retinal dysfunctions can be ascribed to itsfree radical scavenging properties.

The biochemical basis of diabetic retinopathy is stilluncertain. However, oxidative stress associated withoverproduction of reactive oxygen species is involved inmany age-related eye diseases, such as diabetic retino-pathy. The retina is a multilayer sheet of neural tissuevery rich in polyunsaturated fatty acids (PUFA), oxygen

and mitochondria, with the highest oxygen consumptionof all the body tissues. The retina is very sensitive tooxygenated free radicals (O2

�, OH�) (Droy-Lefaix et al.,1995): oxygen free radicals cause lipid peroxidation ofthe PUFA-rich membranes, and peroxy radicals (ROO�)released from membrane phospholipids peroxidation areresponsible for the induction of electrophysiologicaldisturbances leading to retinopathy (Stohs, 1995).

Pycnogenol� has free radical scavenging propertiestowards several free radicals derived both from oxygen(superoxide anion, hydroxyl radical, single oxygen, etc.)and nitrogen (nitric oxide and peroxynitrite radicals).Pycnogenol� also participates in the cellular antioxidantnetwork as indicated by its ability to regenerate theascorbyl radical and to protect endogenous vitamin E andglutathione from oxidative stress (Packer et al., 1999). Aprotective activity of Pycnogenol� towards the photo-oxidative stress of the eye has been reported at aconcentration of 2.5 �g/mL as well as protection of therod outer segments and retinal pigment epithelium fromlipid peroxidation induced in vitro by ferric ions (Ueda etal., 1996).

Our results are consistent with the beneficial effects onthe retina that have been reported in the literature forother antioxidants (Droy-Lefaix et al., 1995; Kowluru etal. 1996).

Other activities of Pycnogenol� may also be involvedin the beneficial effects on diabetic and vascularretinopathy. Gabor et al. (1993) reported the angiopro-tective effects of Pycnogenol� in spontaneously hyper-tensive rats (SHR) with a genetically induced abnormalcapillary permeability. Orally given Pycnogenol� dose-dependently enhanced the capillary resistance andreduced the capillary leakage in these animals; the effectlasted up to 8 h after administration, and it wascomparable to that of higher doses of O-(�-hydro-xyethyl)-rutosides and hesperidin-methyl-chalcone. It isworth mentioning that the morphological changes ofdiabetic retinopathy include basement membrane thick-ening and pericyte disappearance, and the functionalchanges include a strong increase in capillary perme-ability which may be attributable to endothelial cellinjury and basement membrane leaking. These defectsmay be related to the way in which endothelial cellsand pericytes synthesize and interact with the extra-cellular matrix (Mandarino, 1992). Recently, Arcangeli(2000) and Petrassi et al. (2000) have demonstratedthat treatment with Pycnogenol� 100 mg � 3/day for 2months in patients with chronic venous insufficiencyinduced a significant reduction of subcutaneous oedemaas a result of stabilization of the collagenous subendothe-lial basal membrane.

Oligomeric procyanidin extracts from French Mar-itime pine bark have proved their capacity to attachthemselves to specific proteins of blood vessel walls.These properties explain their protective effect oncollagen and elastin from enzyme degradation, and oncollagen from traumal degradation. In addition, Pycno-genol� has been shown to produce an increase in theperipheral capillary resistance and a decrease in capillarypermeability of venous disorders: these data werereviewed by Gulati (1999).

Schmetterer et al. (1997) hypothesized that either localendogenous nitric oxide (NO) synthesis or local reactiv-ity to endogenous NO might be impaired in diabeticpatients and that this may contribute to the development

Table 3. Judgement of efficacy reported by the physiciansat the end of a treatment with Pycnogenol� orplacebo (�2 = 3.1289; p = 0.074; Kruskall–Wallistest)

������� ��������

.��� ��/ � ��#��=� % � �# =�:��/ � ���#�=� $ ���#�=���/����� � ���#�=� �� ���#%=��� ������ � ���#�=� � ��#�=�

Table 4. Results of the haematology and blood chemistry

5�� ����� >� � ������� ��������

6?� 6���� �%#��� #$" �!#�%� �#�%5/ ��#$�� # � ��#�%� �#$��

:������ 6���� � #��� �#�� ��!#��� �#!�5/ ���#��� "#�% ���#�%� "#"��

6������� 6���� �#!�� �#�� �#$�� �#� 5/ �#!%� �#�� �#$�� �#�

:7> 6���� � #$�� �#�� ��#$�� �#"!5/ ��#��� �#$� ��#!�� �#"�

:�> 6���� ��#��� �#$� ��#$�� �#!"5/ �%#%�� �#! � �"#��� �#%

::> 6���� �"#"�� #�! �$#$%� �#!�5/ �"#$�� �#!" �$#��� �#%$

+� 6���� ���# � %#!$ ���#��� �#%�5/ ���#$� $#��� ��%#!%� �# !�

86, �@�1���� 6���� �!��� � " ����� �$5/ �!�"� $% ��%"� %�

;6, 6���� � "�� ��� �!%�� �� 5/ ����� ��� ����� �" �

*� 6���� ��# �� �#�� ��#! � �#��5/ ��#��� �# $ ��#�$� �#�"�

������������� ���2��� /��������3� �� �#�" (� ����� � �)� ���/��<� �'���� ��� �����/ /���#� �� �#��#

222 L. SPADEA AND E. BALESTRAZZI

Copyright � 2001 John Wiley & Sons, Ltd. Phytother. Res. 15, 219–223 (2001)

Page 5: Treatment of vascular retinopathies with Pycnogenol®

of diabetic retinopathy. The results of their study indicatethat systemic and ocular haemodynamic reactivity to NO-synthase inhibition is reduced in patients with long-standing diabetes, compared with healthy control sub-jects. Their findings indicate that either NO-synthaseactivity is increased or NO sensitivity is decreased indiabetic patients and supports the concept of an

involvement of the L-arginine–NO system in thepathophysiology of diabetic retinopathy. Like otherplant-derived antioxidants, Pycnogenol� significantlyaffects iNOS expression and activity in activatedmacrophages and may play an important role inpathologies characterized by an overproduction of NO,such as diabetic retinopathy (Packer et al., 1999).

REFERENCES

+��� ��� 51 :��������� A1 .�/� ���� :1 �������'������� >1������� +1 ,��/�� 9# �$$%# 7��/���(� ������ /� �� �)� � /������� ���3 �(�/��� �� � ������ ������������#��� � �� �� �� 3 ���B��%#

+������ �# ���# �������� � �)���� (���� ����2'�����# ���� ���� �3 ��B ��#

6� ���C�� �1 ����� :�# �$$"# 5(������� �� ���/���(� ������� /�������� 0��) �� 0��)��� (������� �� ���������# ������ ���� ��� ��3 ��B� #

&���'9����� �>1 ,��D�� E1 ������) E�1 6�)� � 61 &����# �$$"# +�����/�� ������ �� � ���� ����� ��������5:� %��� � �)� �����# �� � ���� � ��� �3 $�B���#

:���� �1 5� 51 ��C�/� �# �$$�# &�� F�������0�/�������D�/ �)�� 6���G����/���) 0�������H ����)� G�(�/��'�(��� ��� ����� )���������)� 8����# ��� ����� 3�%!B�! #

:����� 7�# �$$$# �������� � (���� /����/���3 � ��(��0#��� ���� ���� � � 3 !B��#

F�)��� ;1 F�C���C� 61 8�)� � ,1 ����D ,# �$$�# &������� �������3 � ���� ��/����'���������/ /������# 8������ ���/I�(�� ������/�� ������ ������# � � �! � � 3 �B � #

F�0���� 8+1 F�� >�1 5�� � 891 +� ���� &# �$$�#+��� ������� �� ������ �������� � /������� �������� ���� �������� ��# AAA# 5������ �� ������/���#��� � � ��3 � ��B� �%#

F���C� �1 .���� 551 + �� � � ��" �$$�# 8�����(� �������� �/����� ������� (������� �/��)����� ��0�) ���'��� ��������� ���� �/ ���# � �� �� �� � 3 ���%B��%"#

����/ :1 ����C E�1 &��� �+# �$%�# A��J ��� /� �����)�'/���� G�(�� /��� � ��)�)�� �����# #�� ! � �3 �B�!#

������� �# �$$"# &������� ��������)�3 ���)������1 ���C

�������1 ������� �������1 ������2�����# ���� $�� � �� %�����&�� ��3 ��B �#

��/���� 9E# �$$ # ,����� )����)���� ��� �)� ����)� ��������� �� /������� ��������)�# ��� � � ��� ��3 �!$ B�$��#

��/� K1 +D�� F1 ���� +1 F�)� �1 �)� �� �1 ���C�� 9#�$$%# *�/����� �/ ��������/� ��� ��/���� ���(������(����� �� ������ ������ ������/��� ��� �)� �� '������D�/ E5�'�8�� 5�8 ������� ���� ����� # ���� &!�� ��� �� � �3 �"B��#

���C�� 91 8� ���) :1 .����� �# �$$$# +�����/�� ����(��� �/������� ���������� �� � �������/�'���) ������� ��� ��� ���� &���&�� ���C1 ��������# �� ��� ���! � 3 %��B% �#

��L��� �1 ����� �1 :��/��� +# �$$%# :��0�) ������� �//������� ��������)�# ��� � � ! ��� �3 � "B���#

�������� ,1 ������ ���� +1 �������� ,# ���# ��������

� �)���� (���� ����2�����# �����& �� 3 �!�B�!!#

����� >,1 :����� ,+1 ���)�� ,+1 ���)�� E1 ,)� **# �$$�#>)� ������ �������������� � /�������# �& � %������'&�� ���3 %$B !�#

8� � �1 ��)� .1 6)��C�� +1 �)� ����/��� F8#�$$"# &��� ���/�� ������ ���� � ���� � /������� �����'���)�M ��� � %������&�� ��3 �%B �#

��) ������� 91 ��/� 71 ����)� � � ��" �$$%# ������ ���/��/ ������ ����/ G�0 � ������� 0��) A&&�# ��� � � ��3�"�B�"!#

���)� ;1 ���� *# �$$%# +�����/�� /�����3 (��� �� 5 �/ ,�/ ��������/�# ��� � � �� ������ �3 ��B�!#

���)� �E# �$$"# >)� ���� �� ���� ��/����� � �������� �//������# � ���� �� ������ ����&���� �3 �"B !#

?�/� >1 ?�/� >1 +� ���� &# �$$�# ���(���(� ������ �������� �/ ���)���� ������/��� � ����/ ������/����� �)� � ���� ���# %������& � � 3 �!�B�$ #

VASCULAR RETINOPATHIES AND PYCNOGENOL 223

Copyright � 2001 John Wiley & Sons, Ltd. Phytother. Res. 15, 219–223 (2001)