Carvedilol ameliorates endothelial dysfunction in streptozotocin-induced diabetic rats

Metabolic effects of carvedilol through β-arrestin proteins: investigations in a streptozotocin-induced diabetes rat model and in C2C12 myoblasts

BACKGROUND AND PURPOSE

Carvedilol is a third-generation β-adrenoceptor antagonist, which also stimulates β-arrestins. β-arrestins initiate intracellular signalling and are involved in insulin release and sensitivity. Carvedilol is superior in effectiveness to other drugs that are used for similar indications and does not cause insulin resistance or diabetes, which can occur with other β-antagonists. We have shown that carvedilol increased glucose usage in C2C12 cells. We investigate the biased agonist efficacy of carvedilol on β-arrestins.

EXPERIMENTAL APPROACH

Streptozotocin (STZ)-induced diabetes rat model was used to induce metabolic and cardiac disorders. After 8 weeks of diabetes, animals were treated with carvedilol or vehicle for another 4 weeks. In vitro heart function was evaluated at baseline as well as with increasing concentrations of isoprenaline. Effects of diabetes and carvedilol treatment on β-arrestins, ERK, PPARα, CD36 proteins and pyruvate kinase activity were evaluated. β-arrestins were silenced in C2C12 cells by using siRNA. Acute effects of carvedilol on ERK, CD36, mitochondrial transcription factor A, cardiolipin proteins and citrate synthase activity were investigated.

KEY RESULTS

Carvedilol reversed the deterioration of cardiac function in diabetes and diabetes-induced decrease in β-arrestins in rats. Carvedilol decreased the expression of CD36 in diabetes and increased mitochondrial transcription factor A and cardiolipin proteins. Silencing of β-arrestins in cells prevented the effects of carvedilol on these proteins.

CONCLUSION AND IMPLICATIONS

The metabolic effects of carvedilol seem to be related to biased activation of β-arrestins. Patients with cardiovascular and metabolic disorders may benefit from new compounds that selectively act on β-arrestins.

Mechanisms mediating the cardioprotective effect of carvedilol in cadmium induced cardiotoxicity. Role of eNOS and HO1/Nrf2 pathway

Cadmium (Cd) is a highly toxic heavy metal with several harmful effects including cardiotoxicity. For the first time, we aimed to evaluate the possible cardioprotective effect of carvedilol (CAR) in Cd induced cardiotoxicity and study the mechanisms involved in such protection including endothelial nitric oxide synthase (eNOS) and HO1/Nrf2 pathway. CAR (1,10 mg/kg/d) was administered orally for 4 weeks with Cd induced cardiac injury (3 mg/kg/d) orally for 4 weeks. We measured cardiac enzymes, mean arterial pressure changes, heme oxygenase-1 (HO1) and total antioxidant capacity (TAC). Moreover; cardiac tissue malondialdehyde (MDA), tumor necrosis factor alpha (TNFα), western blotting of caspase3 and eNOS levels and histopathology were evaluated. Immunoexpression of eNOS in cardiac tissue, gene expression changes of HO1, and nuclear factor erythroid 2-related factor 2 (Nrf2) using real time polymerase chain reactions (rtPCR) were detected. Our results showed that CAR could significantly decrease Cd induced cardiotoxicity.

Influence of chromium citrate on oxidative stress in the tissues of muscle and kidney of rats with experimentally induced diabetes

Chromium is one of the important trace elements that is essential for carbohydrate, protein and lipid metabolism. Chromium improves glucose metabolism and reduces insulin resistance due to increased insulin sensitivity. Therefore, it is important to consider the use of chromium citrate as a nutritional supplement with potential hypoglycemic and hypolipidemic effects. In this research work, we investigated the activity of the antioxidant system and the level of lipid hydroperoxides in the tissues of skeletal muscles and kidneys of experimental diabetic rats and for rats which received in their daily diet chromium citrate in the amounts 0.1 and 0.2 μg/mL of water. We induced the experimental model of diabetes by intraperitoneal injection of alloxan in the amount 150 mg/kg of body weight of the animals. We monitored glucose levels by measuring daily glucose levels with a portable glucose meter. For research, we selected animals with a glucose level > 11.1 mmol/L. We monitored the body weight of rats. On the 40th day of the study, we withdrew the animals from the experiment by decapitation. We selected the tissue for research, namely skeletal muscles and kidneys. In samples of the tissue homogenates, we measured the activity of antioxidant enzymes and the content of lipid peroxide oxidation products. As a result of our research, we found that the products of lipid peroxide oxidation and glutathione peroxidase activity increased in skeletal muscle of animals with diabetes mellitus. The activity of glutathione reductase, catalase, superoxide dismutase, and the content of reduced glutathione decreased at the same time. In the kidneys of diabetic rats, the activity of glutathione peroxidase, glutathione reductase, catalase and content of lipid hydroperoxides increased but the activity of superoxide dismutase and the content of reduced glutathione decreased. The addition of chromium citrate to the diet of animals in amounts 0.1 and 0.2 μg/mL led to the suppression of oxidative stress. The activity of catalase, glutathione peroxidase and the content of lipid hydroperoxides, TBA-positive substances decreased. Also, the activity of superoxide dismutase increased with the addition of chromium citrate. These results indicate normalization of antioxidant defense in the skeletal muscle and kidneys of experimental rats with experimental diabetes given chromium citrate in the amount 0.1 mg/mL of water.

Carvedilol can attenuate histamine-induced paw edema and formaldehyde-induced arthritis in rats without risk of gastric irritation

BACKGROUND AND AIM

Rheumatoid arthritis treatment aims to control joint damage and any associated complications such as cardiovascular disease. Most anti-inflammatory drugs have a high tendency to cause gastro-intestinal irritation. The present study is designed to investigate the anti-inflammatory effect of carvedilol and to study its effect on gastric mucosa.

EXPERIMENTAL APPROACH

Lornoxicam (1.3mg/kg) or carvedilol (10mg/kg) was administrated orally 1h before histamine injection into animals of a histamine-induced paw edema model and orally daily for 11days into animals of a formaldehyde-induced arthritis model. Tumor necrosis factor-α and prostaglandin E₂ were measured in animals of the formaldehyde-induced arthritis model. The effect of lornoxicam and carvedilol on gastric mucosa was assessed in normal rats and after induction of cold stress ulcer.

RESULTS

Carvedilol succeeded in reducing hind paw edema in both histamine-induced paw edema and formaldehyde-induced arthritis and in reducing the elevated level of tumor necrosis factor-α and prostaglandin E₂ nearly with near equal efficacy compared with lornoxicam. Carvedilol did not show any ulcerative effect on the gastric mucosa of normal rats, and its use was associated with an improvement of both the gross and histopathological pictures of gastric ulcers in animals of the cold stress ulcer model compared with lornoxicam treated rats.

CONCLUSION

The current findings support the use of carvedilol both in the management of inflammation as well as the prevention of cardiovascular complications in rheumatoid arthritis patients. The use of carvedilol was not associated with any gastro-intestinal tract irritation.

Carvedilol and antioxidant proteins in a type I diabetes animal model

BACKGROUND

Patients with diabetes are at a high risk of developing both micro- and macrovascular disease. Hyperglycaemia seems to be the main factor in the pathogenesis of diabetic cardiomyopathy, often based on increased oxidative stress. Carvedilol, a β-adrenergic blocker, has intrinsic antioxidant properties and was previously described to be effective in the protection of cardiac mitochondria against oxidative stress. The objective of this study was to evaluate the effect of carvedilol on hyperglycaemia-induced oxidative damage and mitochondrial abnormalities in cardiac and skeletal muscle in streptozotocin-treated rats.

MATERIALS AND METHODS

Body mass, blood glucose, the level of protein carbonylation, caspase-9- and caspase-3-like activities, mitochondrial proteins, the status of antioxidant defence system and stress-related proteins were evaluated in streptozotocin vs streptozotocin + carvedilol (1 mg/kg/day)-treated rats.

RESULTS

The results showed that carvedilol decreased blood glucose in streptozotocin-treated animals. Content of catalase in the heart and SOD2, SOD1 and catalase in skeletal muscle were increased by carvedilol treatment in streptozotocin-treated animals. At this particular time point, streptozotocin-induced hyperglycaemia did not cause caspase activation or increase in protein carbonylation status. The data showed that carvedilol increased the level of antioxidant enzymes, what may contribute to preserve cell redox balance during hyperglycaemia. We also showed here for the first time that carvedilol effects on streptozotocin-treated rats are tissue dependent, with a more predominant effect on skeletal muscle.

CONCLUSIONS

Based on data showing modulation of the antioxidant network in the heart, carvedilol may be beneficial in diabetic patients without advanced disease complications, delaying their progression.

GPER inhibits diabetes-mediated RhoA activation to prevent vascular endothelial dysfunction

The effect of estrogen receptors on diabetes-induced vascular dysfunction is critical, but ambiguous. Individuals with diabetic vascular disease may require estrogen receptor-specific targeted therapy in the future. The G protein-coupled estrogen receptor (GPER) has beneficial effects on vascular function. However, its fundamental mechanisms are unclear. The RhoA/Rho-kinase pathway contributes to diabetic vascular complications, whereas estrogen can suppress Rho-kinase function. Thus, we assumed that GPER inhibits diabetes-mediated RhoA activation to prevent vascular dysfunction. We further investigated the underlying mechanisms involved in this process. Vascular endothelial cells and ex vivo cultured ovariectomized (OVX) C57BL/6 mouse aortae were treated with high glucose (HG) alone or in combination with GPER agonist (G1). G1 treatment was also administered to OVX db/db mice for 8 weeks. An ex-vivo isovolumic myograph was used to analyze the endothelium-dependent vasodilation and endothelium-independent contraction of mouse aortae. Apoptosis, oxidative stress, and inflammation were attenuated in G1-pretreated vascular endothelial cells. G1 significantly decreased the phosphorylation of inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495), inhibited RhoA expression, and increased NO production. Additionally, G1 rescued the impaired endothelium-dependent relaxation and inhibited RhoA activation in the thoracic aorta of OVX db/db mice and ex-vivo cultured OVX C57BL/6 mouse aortae treated with HG. Estrogens acting via GPER could protect vascular endothelium, and GPER activation might elicit ERα-independent effect to inhibit RhoA/Rho-kinase pathway. Additionally, GPER activation might reduce vascular smooth muscle contraction by inhibiting RhoA activation. Thus, the results of the present study suggest a new therapeutic paradigm for end-stage vascular dysfunction by inhibiting RhoA/Rho-kinase pathway via GPER activation.

Sex-specific vascular responses of the rat aorta: effects of moderate term (intermediate stage) streptozotocin-induced diabetes

Hyperglycemia affects male and female vascular beds differently. We have previously shown that 1 week after the induction of diabetes with streptozotocin (STZ), male and female rats exhibit differences in aortic endothelial function. To examine this phenomenon further, aortic responses were studied in male and female rats 8 weeks after the induction of diabetes (intermediate stage). Endothelium-dependent vasodilation (EDV) to acetylcholine (ACh) was measured in phenylephrine (PE) pre-contracted rat aortic rings. Concentration response curves to PE were generated before and after L-NAME, a nitric oxide synthase (NOS) inhibitor. Furthermore, mRNA expression of endothelial nitric oxide synthase (eNOS) and NADPH oxidase subunit (Nox1) were determined. At 8 weeks, diabetes impaired EDV to a greater extent in female than male aortae. Furthermore, the responsiveness to PE was significantly enhanced only in female diabetic rats, and basal NO, as indicated by the potentiation of the response to PE after L-NAME, was reduced in female diabetic rat aortae to the same levels as in males. In addition, eNOS mRNA expression was decreased, while the Nox1 expression was significantly enhanced in diabetic female rats. These results suggest that aortic function in female diabetic rats after 8 weeks exhibits a more prominent impairment and that NO may be involved.

Mechanism of testicular protection of carvedilol in streptozotocin-induced diabetic rats

Aims:

Male sub-fertility and infertility are major complications of diabetes mellitus. The non-selective β-blocker carvedilol has been reported to have favorable effects on some of the diabetic complications based on its antioxidant and anti-apoptotic effects. This study aims to evaluate the possible testicular protective effect of carvedilol in streptozotocin (STZ)-induced diabetic rat model and its possible mechanisms.

Materials and Methods:

Diabetes was induced by a single i.p. dose of 65 mg/kg of STZ. In parallel groups of diabetic rats, carvedilol in low and high doses (1 and 10 mg/kg/day orally) were administered for 4 weeks. Oxidative stress markers as reduced glutathione (GSH) and the product of lipid peroxidation; malondialdehyde (MDA) were evaluated in testicular homogenate. The level of expression of the apoptotic marker; caspase 3, was assessed using western blot, followed by densitometric analysis.

Results:

Induction of diabetes caused distortion of histological normal testicular structure, with decrease (P < 0.05) in GSH and increase (P < 0.05) in MDA, as well as induction of caspase 3 expression. Carvedilol in low or high doses reverted diabetes-induced histological damage, restored antioxidant activity and ameliorated caspase 3 expression.

Conclusion:

Carvedilol confers testicular protection against diabetes-induced damage through antioxidant and anti-apoptotic mechanisms.

Beta-blocker timolol alleviates hyperglycemia-induced cardiac damage via inhibition of endoplasmic reticulum stress

Current data support that pharmacological modulators of endoplasmic reticulum stress (ERS) have therapeutic potential for diabetic individuals. Therefore, we aimed to examine whether timolol, having free radical-scavenger action, besides being a β-blocker, exerts a cardioprotective effect via inhibition of ERS response in diabetic rats in a comparison with an antioxidant N-acetylcysteine (NAC). Histopathological data showed that either timolol- or NAC-treatment of diabetic rats prevented the changes in mitochondria and nucleus of the cardiac tissue while they enhanced the cellular redox-state in heart as well. The levels of ER-targeted cytoprotective chaperones GRP78 and calnexin, unfolded protein response signaling protein CHO/Gadd153 besides the levels of calpain, BCL-2, phospho-Akt, PUMA, and PML in the hearts from diabetic rats, treated with either timolol or NAC, are found to be similar among these groups, although all these parameters were markedly preserved in the untreated diabetics compared to those of the controls. Taken into consideration how important a balanced-ratio between anti-apoptotic and pro-apoptotic proteins for the maintenance mitochondria/ER function, our results suggest that ERS in diabetic rat heart is mediated by increased oxidative damage, which in turn triggers cardiac dysfunction. Moreover, we also demonstrated that timolol treatment of diabetic rats, similar to NAC treatment, induced a well-controlled redox-state and apoptosis in cardiac myocardium. We, thus for the first time, report that cardioprotective effect of timolol seems to be associated with normalization of ER function due to its antioxidant action in cardiomyocytes even under hyperglycemia.

Chronic treatment with qiliqiangxin ameliorates aortic endothelial cell dysfunction in diabetic rats

Qiliqiangxin (QL), a traditional Chinese medicine, has been shown to be beneficial for chronic heart failure. However, whether QL can also improve endothelial cell function in diabetic rats remains unknown. Here, we investigated the effect of QL treatment on endothelial dysfunction by comparing the effect of QL to that of benazepril (Ben) in diabetic Sprague-Dawley rats for 8 weeks. Cardiac function was evaluated by echocardiography and catheterization. Assays for acetylcholine-induced, endothelium-dependent relaxation (EDR), sodium nitroprusside-induced endothelium-independent relaxation, serum nitric oxide (NO), and nitric oxide synthase (NOS) as well as histological analyses were performed to assess endothelial function. Diabetic rats showed significantly inhibited cardiac function and EDR, decreased expression of serum NO and phosphorylation at Ser(1177) on endothelial NOS (eNOS), and impaired endothelial integrity after 8 weeks. Chronic treatment for 8 weeks with either QL or Ben prevented the inhibition of cardiac function and EDR and the decrease in serum NO and eNOS phosphorylation caused by diabetes. Moreover, either QL or Ben suppressed inducible NOS (iNOS) protein levels as well as endothelial necrosis compared with the diabetic rats. Additionally, QL prevented the increase in angiotensin-converting enzyme 1 and angiotensin II receptor type 1 in diabetes. Thus, chronic administration of QL improved serum NO production, EDR, and endothelial integrity in diabetic rat aortas, possibly through balancing eNOS and iNOS activity and decreasing renin-angiotensin system expression.

Carvedilol ameliorates early diabetic nephropathy in streptozotocin-induced diabetic rats

Diabetic nephropathy results in end-stage renal disease. On the other hand, carvedilol has been reported to have various pharmacological properties. The aim of this study therefore is to evaluate the possible protective effect of carvedilol on streptozotocin-induced early diabetic nephropathy and various mechanisms underlie this effect in rats. Single i.p. injection of streptozotocin (65 mg/kg) was administered to induce early diabetic nephropathy in Wistar rats. Oral administration of carvedilol at a dose level of 1 and 10 mg/kg daily for 4 weeks resulted in nephroprotective effect as evident by significant decrease in serum creatinine level, urinary albumin/creatinine ratio, and kidney index as well as renal levels of malondialdehyde, nitric oxide, tumor necrosis factor- α , and cyclooxygenase-2 with a concurrent increase in creatinine clearance and renal reduced glutathione level compared to diabetic untreated rats. The protective effect of carvedilol was confirmed by renal histopathological examination. The electron microscopic examination indicated that carvedilol could effectively ameliorate glomerular basement membrane thickening and podocyte injury. In conclusion, carvedilol protects rats against streptozotocin-induced early diabetic nephropathy possibly, in part, through its antioxidant as well as anti-inflammatory activities, and ameliorating podocyte injury.

Sexual dimorphism in rat aortic endothelial function of streptozotocin-induced diabetes: possible involvement of superoxide and nitric oxide production

Little is known of the interactions between diabetes and sex hormones on vascular function. The objectives of this study were to investigate whether there were sex differences in rat aortic endothelial function one week after the induction of streptozotocin (STZ)-diabetes, and to examine the potential roles of superoxide and nitric oxide (NO) in this sex-specific effect. Endothelium-dependent vasodilatation to acetylcholine (ACh) was measured in rat aortic rings before and after treatment with MnTMPyP (25µM), a superoxide dismutase. Contractile responses to phenylephrine (PE) were generated before and after treatment with l-NAME (200μM), a nitric oxide synthase (NOS) inhibitor. The mRNA expression of NADPH oxidase (Nox) and endothelial nitric oxide synthase (eNOS) were also determined. We demonstrated that (1) STZ-diabetes impaired endothelium-dependent vasodilatation to ACh to a greater extent in female than male aortae, (2) inhibition of superoxide enhanced sensitivity to ACh only in diabetic females, and (3) Nox1 and Nox4 mRNA expression were significantly elevated only in aortic tissue of diabetic females. Furthermore, incubation of aortic rings with l-NAME potentiated PE responses in all groups, but aortae from control females showed a greater potentiation of the PE response after NOS inhibition compared with others. STZ-diabetes reduced the extent of PE potentiation after l-NAME and the aortic eNOS mRNA expression in females to the same levels as seen in males. These data suggest that a decrease in NO, resulting from either decreased eNOS or elevated superoxide, may partially contribute to the predisposition of the female aorta to injury early in diabetes.

Carvedilol alleviates adjuvant-induced arthritis and subcutaneous air pouch edema: modulation of oxidative stress and inflammatory mediators

Rheumatoid arthritis (RA) is a systemic inflammatory disease with cardiovascular complications as the leading cause of morbidity. Carvedilol is an adrenergic antagonist which has been safely used in treatment of several cardiovascular disorders. Given that carvedilol has powerful antioxidant/anti-inflammatory properties, we aimed to investigate its protective potential against arthritis that may add further benefits for its clinical usefulness especially in RA patients with concomitant cardiovascular disorders. Two models were studied in the same rat; adjuvant arthritis and subcutaneous air pouch edema. Carvedilol (10mg/kg/day p.o. for 21days) effectively suppressed inflammation in both models with comparable efficacy to the standard anti-inflammatory diclofenac (5mg/kg/day p.o.). Notably, carvedilol inhibited paw edema and abrogated the leukocyte invasion to air pouch exudates. The latter observation was confirmed by the histopathological assessment of the pouch lining that revealed mitigation of immuno-inflammatory cell influx. Carvedilol reduced/normalized oxidative stress markers (lipid peroxides, nitric oxide and protein thiols) and lowered the release of inflammatory cytokines (TNF-α & IL-6), and eicosanoids (PGE2 & LTB4) in sera and exudates of arthritic rats. Interestingly, carvedilol, per se, didn't present any effect on assessed biochemical parameters in normal rats. Together, the current study highlights evidences for the promising anti-arthritic effects of carvedilol that could be mediated through attenuation of leukocyte migration, alleviation of oxidative stress and suppression of proinflammatory cytokines and eicosanoids.

Nebivolol: impact on cardiac and endothelial function and clinical utility

Endothelial dysfunction is a systemic pathological state of the endothelium characterized by a reduction in the bioavailability of vasodilators, essentially nitric oxide, leading to impaired endothelium-dependent vasodilation, as well as disarrangement in vascular wall metabolism and function. One of the key factors in endothelial dysfunction is overproduction of reactive oxygen species which participate in the development of hypertension, atherosclerosis, diabetes, cardiac hypertrophy, heart failure, ischemia-reperfusion injury, and stroke. Because impaired endothelial activity is believed to have a major causal role in the pathophysiology of vascular disease, hypertension, and heart failure, therapeutic agents which modify this condition are of clinical interest. Nebivolol is a third-generation β-blocker with high selectivity for β1-adrenergic receptors and causes vasodilation by interaction with the endothelial L-arginine/ nitric oxide pathway. This dual mechanism of action underscores several hemodynamic qualities of nebivolol, which include reductions in heart rate and blood pressure and improvements in systolic and diastolic function. Although nebivolol reduces blood pressure to a degree similar to that of conventional β-blockers and other types of antihypertensive drugs, it may have advantages in populations with difficult-to-treat hypertension, such as patients with heart failure along with other comorbidities, like diabetes and obesity, and elderly patients in whom nitric oxide-mediated endothelial dysfunction may be more pronounced. Furthermore, recent data indicate that nebivolol appears to be a cost-effective treatment for elderly patients with heart failure compared with standard care. Thus, nebivolol is an effective and well tolerated agent with benefits above those of traditional β-blockers due to its influence on nitric oxide release, which give it singular hemodynamic effects, cardioprotective activity, and a good tolerability profile. This paper reviews the pharmacology structure and properties of nebivolol, focusing on endothelial dysfunction, clinical utility, comparative efficacy, side effects, and quality of life in general with respect to the other antihypertensive agents.

β-blockade: benefits beyond blood pressure reduction?

Hypertension is a major cardiovascular (CV) risk factor, but several other common conditions, including chronic obstructive pulmonary disease (COPD), osteoporosis, and peripheral arterial disease (PAD), have been shown to independently increase the risk of CV events and death. The physiological basis for an increased CV risk in those conditions probably lies in the augmentations of oxidative stress, endothelial dysfunction, systemic inflammation, and arterial stiffness, which all are also hallmarks of hypertension. β-Blockers have been used for the treatment of hypertension for more than 40 years, but a number of meta-analyses have demonstrated that treatment with these agents may be associated with an increased risk of CV events and mortality. However, the majority of primary prevention β-blocker trials employed atenolol, an earlier-generation β(1) -selective blocker whose mechanism of action is based on a reduction of cardiac output. Available evidence suggests that vasodilatory β-blockers may be free of the deleterious effects of atenolol. The purpose of this review is to summarize pathophysiologic mechanisms thought to be responsible for the increased CV risk associated with COPD, osteoporosis, and PAD, and examine the possible benefits of vasodilatory β-blockade in those conditions. Our examination focused on nebivolol, a β(1) -selective agent with vasodilatory effects most likely mediated via β(3) activation.

Reactive oxygen-derived free radicals are key to the endothelial dysfunction of diabetes

Vascular complications are an important pathological issue in diabetes that lead to the further functional deterioration of several organs. The balance between endothelium-dependent relaxing factors and endothelium-dependent contracting factors (EDCFs) is crucial in controlling local vascular tone and function under normal conditions. Diabetic endothelial dysfunction is characterized by reduced endothelium-dependent relaxations and/or enhanced endothelium-dependent contractions. Elevated levels of oxygen-derived free radicals are the initial source of endothelial dysfunction in diabetes. Oxygen-derived free radicals not only reduce nitric oxide bioavailability, but also facilitate the production and/or action of EDCFs. Thus, the endothelial balance tips towards vasoconstrictor responses over the course of diabetes.

Rho kinase inhibition by fasudil ameliorates diabetes-induced microvascular damage

OBJECTIVE

Leukocyte adhesion in retinal microvasuculature substantially contributes to diabetic retinopathy. Involvement of the Rho/Rho kinase (ROCK) pathway in diabetic microvasculopathy and therapeutic potential of fasudil, a selective ROCK inhibitor, are investigated.

RESEARCH DESIGN AND METHODS

Localization of RhoA/ROCK and Rho activity were examined in retinal tissues of rats. Impact of intravitreal fasudil administration on retinal endothelial nitric oxide synthase (eNOS) and myosin phosphatase target protein (MYPT)-1 phosphorylation, intercellular adhesion molecule-1 (ICAM-1) expression, leukocyte adhesion, and endothelial damage in rat eyes were investigated. Adhesion of neutrophils from diabetic retinopathy patients or nondiabetic control subjects to cultured microvascular endothelial cells was quantified. The potential of fasudil for endothelial protection was investigated by measuring the number of adherent neutrophils and terminal transferase-mediated dUTP nick-end labeling-positive endothelial cells.

RESULTS

RhoA and ROCK colocalized predominantly in retinal microvessels. Significant Rho activation was observed in retinas of diabetic rats. Intravitreal fasudil significantly increased eNOS phosphorylation, whereas it reduced MYPT-1 phosphorylation, ICAM-1 expression, leukocyte adhesion, and the number of damaged endothelium in retinas of diabetic rats. Neutrophils from diabetic retinopathy patients showed significantly higher adhesion to cultured endothelium and caused endothelial apoptosis, which was significantly reduced by fasudil. Blockade of the Fas-FasL interaction prevented endothelial apoptosis. The protective effect of fasudil on endothelial apoptosis was significantly reversed by Nomega-nitro-l-arginine methyl ester, a NOS inhibitor, whereas neutrophil adhesion remained unaffected.

CONCLUSIONS

The Rho/ROCK pathway plays a critical role in diabetic retinal microvasculopathy. Fasudil protects the vascular endothelium by inhibiting neutrophil adhesion and reducing neutrophil-induced endothelial injury. ROCK inhibition may become a new strategy in the management of diabetic retinopathy, especially in its early stages.