Endothelial dysfunction: Mechanisms of development and therapeutic options

Nitrate Metabolism and Ischemic Cerebrovascular Disease: A Narrative Review

Inorganic and organic nitrates are present in vivo and in vitro. Inorganic nitrate is considered a pool of nitric oxide (NO), but it can be converted into nitrite and NO through various mechanisms. It plays an important role in the regulation of complex physiological and biochemical reactions, such as anti-inflammatory processes and the inhibition of platelet aggregation, which are closely related to the pathology and treatment of cerebrovascular disease. Ischemic cerebrovascular disease is characterized by high incidence, recurrence, and disability rates. Nitrate, nitrite, and NO were recently found to be involved in cerebrovascular disease. In this review, we describe the relationship between cerebrovascular disease and nitrate metabolism to provide a basis for further advances in laboratory and clinical medicine.

Comparative Effects of Preoperative Angiotensin-converting Enzyme In-hibitor, Statin and Beta-blocker Treatment on Human Internal Mammary Artery Reactivity in Patients with Coronary Artery Disease: A Pilot Study

PURPOSE

We investigated the effect of angiotensin-converting enzyme (ACE)- inhibitor, statin, and beta-blocker usage before coronary bypass surgery (CABG) on vascular reactivity of the internal mammary artery (IMA).

METHODS

Patients, who underwent elective CABG were evaluated. Samples of IMA obtained from 22 patients were divided into 4 groups in respect of drugs used by patients before bypass surgery (control group, ACE inhibitor + statin group, ACE inhibitor + statin + beta-blocker group, and ACE inhibitor + beta-blocker group). The discarded, distal end section of IMA was carefully removed, and the vasoreactivity of IMA rings was evaluated in vitro using an organ chamber. Smooth muscle contractile function was tested on artery segments exposed to 10-80 mM KCl and norepinephrine. The endothelial function of IMA rings was assessed with acetylcholine (ACh) and bradykinin, while endothelium-independent vasorelaxation was evaluated by sodium nitroprusside (SNP).

RESULTS

Both ACh and bradykinin caused concentration-dependent relaxation in endothelium-intact IMA rings. However, the maximal effect produced by endothelium-dependent agents in all treatment groups was more prominent when compared with the control group. There was no significant difference in the endothelium-dependent relaxation response of IMA between ACE inhibitor + statin, ACE inhibitor + beta-blocker and ACE inhibitor + statin + beta-blocker groups. The vasodilatory potency of SNP was similar in all groups. Similarly, contractile response to KCl or norepinephrine was not significantly different between groups.

CONCLUSION

Use of ACE inhibitors and statins before bypass surgery may influence IMA vasoreactivity by improving endothelial control of vascular tone.

[Individual renal hemodynamic response to chronic angiotensin II receptor blockade and the influence on the renin-angiotensin system gene polymorphisms]

INTRODUCTION

Our study was aimed at determining whether the polymorphism of genes for different components of the renin-angiotensin-aldosterone system could influence the renal hemodynamic response to losartan treatment.

MATERIAL AND METHOD

The study included 35 patients with type I diabetes mellitus and persistent albuminuria, genotyped for the 1166 A/C polymorphism gene for the angiotensin II type 1 receptor and I/D polymorphism of the angiotensin-converting enzyme gene. The participants were divided into groups according to the combinations of A or C allele: AA, AC, CC; and according to the combinations of I or D allele: II, ID and DD genotype. The patients received losartan therapy for 12 weeks. The renal hemodynamic measurements were determined at baseline and after the examination period.

RESULTS

Losartan therapy significantly reduced the filtration fraction from the baseline by 0.018 +/- 0.024 (p = 0.012) only in the AC genotype. The glomerular filtration rate remained unchanged in all genotype groups. A significant increase in the effective renal plasma flow was obtained only in AC genotype (544 +/- 88 vs 575 +/- 90 ml/min; p = 0.02), while significant reductions in the renal vascular resistance were found in AA group (115 +/- 25 vs 95 +/- 21 mmHg x l(-1) x min(-1), p = 0.001) and in AC group (118 +/- 30 vs 101 +/- 28 mmHg x l(-1) x min(-1); p = 0.001). A significant reduction of the glomerular filtration rate by 8 +/- 10 ml/min was obtained only in the DD genotype (p = 0.016), and only the DD genotype achieved a significant reduction of the filtration fraction by 0.019 +/- 0,022 (p = 0.008). The most pronounced increase of the effective renal plasma flow was found only in the ID genotype (536 +/- 75 vs 591 +/- 63 ml/min; p = 0.01). The reduction of the renal vascular resistance was independent of ACE gene polymorphism.

CONCLUSION

Our study shows that individual renal vascular response to losartan treatment in diabetic patients with persistent albuminuria, could be influenced by genetic polymorphisms.

Effect of rosiglitazone in sodium arsenite-induced experimental vascular endothelial dysfunction

The present study has been designed to investigate the effect of rosiglitazone, a peroxisome proliferator activated receptor gamma agonist in sodium arsenite-induced vascular endothelial dysfunction (VED) in rats. The rats were administered sodium arsenite (1.5 mg/kg/day, i.p., 2 weeks) to induce VED. The development of VED was assessed by employing isolated aortic ring preparation and estimating serum nitrite/nitrate concentration. Further, the integrity of the aortic endothelium was assessed histologically using haematoxylin-eosin staining. Moreover, the oxidative stress was assessed by estimating serum thiobarbituric acid reactive substances, aortic reactive oxygen species and reduced form of glutathione. The administration of sodium arsenite produced VED by impairing acetylcholine-induced endothelium dependent relaxation, diminishing the integrity of vascular endothelium and decreasing the serum nitrite/nitrate concentration. In addition, sodium arsenite was noted to produce oxidative stress as it increased serum thiobarbituric acid reactive substances and aortic reactive oxygen species and consequently decreased glutathione. Treatment with rosiglitazone (3 mg/kg/day, p.o., 2 weeks and 5 mg/kg/day, p.o., 2 weeks) significantly prevented sodium arsenite-induced VED by enhancing acetylcholine-induced endothelium dependent relaxation, improving the integrity of vascular endothelium, increasing the nitrite/nitrate concentration and decreasing the oxidative stress. However, the vascular protective effect of rosiglitazone was markedly abolished by co-administration of nitric oxide synthase inhibitor, N-Omega-Nitro-L-Arginine Methyl Ester (L-NAME) (25 mg/kg/day, i.p., 2 weeks). Thus, it may be concluded that rosiglitazone reduces oxidative stress, activates eNOS and enhances the generation of nitric oxide to prevent sodium arsenite-induced VED in rats.

Protective Effect of Quercetin on the Homocysteine-Injured Human Umbilical Vein Vascular Endothelial Cell Line (ECV304)

Homocysteine is responsible for the occurrence of many cardiovascular diseases for instance by injuring the vascular endothelial cells. Quercetin has many beneficial effects on the cardiovascular system, but it is unknown whether it provides protection against homocysteine-injured vascular endothelial cells. The aim of the present study was to investigate the protective effect and mechanism of quercetin on the homocysteine-injured human umbilical vein vascular endothelial cell line (ECV304) (i.e. morphology, viability and nuclear factor kappa B (NF-kappaB) expression of ECV304 injured with 1.0 mM homocysteine) by determination of lipid peroxidant and endothelium-derived factors in the cultural medium of homocysteine-injured ECV304. Quercetin at 6.25, 12.5, 25, 50 and 100 microM attenuated the morphological changes and increased viability of homocysteine-injured ECV304 in a dose-dependent manner (P < 0.05 or P < 0.01 versus the homocysteine-injured group). At the same time, quercetin at 12.5, 25 and 50 microM decreased malondialdehyde level, endothelin release and NF-kappaB expression, and increased superoxide dismutase activity, nitric oxide and 6-keto-prostaglandin F1alpha releases in homocysteine-injured ECV304 (P < 0.05 or P < 0.01 versus the homocysteine-injured group). These results suggest that quercetin has a protective effect on homocysteine-injured vascular endothelial cells by antioxidant and anti-inflammatory mechanisms.