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

Ameliorative role of rolipram, PDE-4 inhibitor, against sodium arsenite-induced vascular dementia in rats

Arsenic exposure to the population leads to serious health problems like neurotoxicity, nephrotoxicity, and cardiovascular abnormality. In the present study, the work has been commenced to discover the prospect of rolipram a phosphodiestrase-4 (PDE-4) inhibitor against sodium arsenite (SA)-induced vascular endothelial dysfunction (EnDF) leading to dementia in rats. Wistar rats were treated with SA (5 mg/kg body weight/day orally) for 44 days for induction of vascular EnDF and dementia. Learning and memory were evaluated using Morris water maze (MWM) test. Vascular EnDF was evaluated using aortic ring preparation. Various biochemical parameters were also evaluated like brain oxidative stress (viz. reduced glutathione and thiobarbituric acid reactive substances level), serum nitrite/nitrate activity, acetylcholinesterase activity, and inflammatory markers (viz. neutrophil infiltration in brain and myeloperoxidase). SA-treated rats showed poor performance in water maze trials indicating attenuated memory and ability to learn with significant rise (p < 0.05) in brain acetylcholinesterase activity, brain oxidative stress, neutrophil count, and significant decrease (p < 0.05) in serum nitrite/nitrate levels and vascular endothelial functions. Rolipram (PDE-4 inhibitor) treatment (0.03 mg/kg and 0.06 mg/kg body weight, intraperitoneally daily for 14 days) significantly improved memory and learning abilities, and restored various biochemical parameters and EnDF. It is concluded that PDE-4 modulator may be considered the prospective target for the treatment of SA-induced vascular EnDF and related dementia.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide "hot spots" where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide.

Thiazolidinediones improve flow-mediated dilation: a meta-analysis of randomized clinical trials

AIMS

Thiazolidinediones administration is assumed to be related with an improvement of endothelial dysfunction (ED); nevertheless, previous studies have been inconsistent. For this reason, the present meta-analysis was directed to estimate if thiazolidinediones were related to endothelial dysfunction improvement by using flow-mediated dilation (FMD) measurement.

METHODS

Literature search of the PubMed, the Cochrane Library, the Web of Science, and the Scopus databases was performed covering the period until July 01, 2015, for randomized clinical trials that investigated an influence of thiazolidinediones on FMD. For the calculation of the pooled overall effect, a random effect model was used. Meta-regression and subgroup analyses were performed to evaluate the impact of study characteristics on the effect of thiazolidinediones administration on FMD.

RESULTS

This meta-analysis included 16 studies with 812 subjects. The obtained results demonstrated an improvement of endothelial dysfunction measured with FMD (16 studies, 812 subjects; WMD: 2.4 %, 95 % CI = 1.1 to 3.69 %; p = 0.0003). The significant heterogeneity was noted (I (2) = 95 %, p < 0.00001). Subgroup analysis demonstrated that pioglitazone and rosiglitazone were able to improve FMD. Also, thiazolidinediones improved FMD if treatment was longer than 12 weeks and if patients were younger than 65 years. Additionally, a lipid profile was found to influence thiazolidinediones effect on FMD.

CONCLUSION

The results of this meta-analysis demonstrated that thiazolidinediones were able to improve FMD, which in clinical terms can be further translated to the improvement of an impaired endothelial function. Nevertheless, the link between FMD and its predictive clinical relevance still requires further clarification.

Catechin averts experimental diabetes mellitus-induced vascular endothelial structural and functional abnormalities

Diabetes mellitus is associated with an induction of vascular endothelial dysfunction (VED), an initial event that could lead to the pathogenesis of atherosclerosis and hypertension. Previous studies showed that catechin, a key component of green tea, possesses vascular beneficial effects. We investigated the effect of catechin hydrate in diabetes mellitus-induced experimental vascular endothelial abnormalities (VEA). Streptozotocin (50 mg/kg, i.p., once) administration to rats produced diabetes mellitus, which subsequently induced VEA in 8 weeks by markedly attenuating acetylcholine-induced endothelium-dependent relaxation in the isolated aortic ring preparation, decreasing aortic and serum nitrite/nitrate concentrations and impairing aortic endothelial integrity. These abnormalities in diabetic rats were accompanied with elevated aortic superoxide anion generation and serum lipid peroxidation in addition to hyperglycemia. Catechin hydrate treatment (50 mg/kg/day p.o., 3 weeks) markedly prevented diabetes mellitus-induced VEA and vascular oxidative stress. Intriguingly, in vitro incubation of L-NAME (100 μM), an inhibitor of nitric oxide synthase, or Wortmannin (100 nM), a selective inhibitor of phosphatidylinositol 3-kinase (PI3K), markedly prevented catechin hydrate-induced improvement in acetylcholine-provoked endothelium-dependent relaxation in the diabetic rat aorta. Moreover, catechin hydrate treatment considerably reduced the elevated level of serum glucose in diabetic rats. In conclusion, catechin hydrate treatment prevents diabetes mellitus-induced VED through the activation of endothelial PI3K signal and subsequent activation of eNOS and generation of nitric oxide. In addition, reduction in high glucose, vascular oxidative stress, and lipid peroxidation might additionally contribute to catechin hydrate-associated prevention of diabetic VEA.

Atorvastatin restores arsenic-induced vascular dysfunction in rats: modulation of nitric oxide signaling and inflammatory mediators

We evaluated whether atorvastatin, an extensively prescribed statin for reducing the risks of cardiovascular diseases, can reduce the risk of arsenic-induced vascular dysfunction and inflammation in rats and whether the modulation could be linked to improvement in vascular NO signaling. Rats were exposed to sodium arsenite (100ppm) through drinking water for 90 consecutive days. Atorvastatin (10mg/kg bw, orally) was administered once daily during the last 30days of arsenic exposure. On the 91(st) day, blood was collected for measuring serum C-reactive protein. Thoracic aorta was isolated for assessing reactivity to phenylephrine, sodium nitroprusside and acetylcholine; evaluating eNOS and iNOS mRNA expression and measuring NO production, while abdominal aorta was used for ELISA of cytokines, chemokine and vascular cell adhesion molecules. Histopathology was done in aortic arches. Arsenic did not alter phenylephrine-elicited contraction. Atorvastatin inhibited Emax of phenylephrine, but it augmented the contractile response in aortic rings from arsenic-exposed animals. Sodium nitroprusside-induced relaxation was not altered with any treatment. However, arsenic reduced acetylcholine-induced relaxation and affected aortic eNOS at the levels of mRNA expression, protein concentration, phosphorylation and NO production. Further, it increased aortic iNOS mRNA expression, iNOS-derived NO synthesis, production of pro-inflammatory mediators (IL-1β, IL-6, MCP-1, VCAM, sICAM) and serum C-reactive protein and aortic vasculopathic lesions. Atorvastatin attenuated these arsenic-mediated functional, biochemical and structural alterations. Results show that atorvastatin has the potential to ameliorate arsenic-induced vascular dysfunction and inflammation by restoring endothelial function with improvement in NO signaling and attenuating production of pro-inflammatory mediators and cell adhesion molecules.

Fish oil blunted nicotine-induced vascular endothelial abnormalities possibly via activation of PPARγ-eNOS-NO signals

Nicotine exposure is associated with an induction of vascular endothelial dysfunction (VED), a hallmark of various cardiovascular disorders. The present study investigated the effect of fish oil in nicotine-induced experimental VED. VED was assessed by employing isolated aortic ring preparation, estimating aortic and serum nitrite/nitrate, aortic superoxide anion generation, and serum TBARS, and carrying out electron microscopic and histological studies of thoracic aorta. Nicotine (2 mg/kg/day, i.p., 4 weeks) administration produced VED in rats by attenuating acetylcholine-induced endothelium-dependent relaxation in the isolated aortic ring preparation, decreasing aortic and serum nitrite/nitrate concentration, impairing endothelial integrity, and inducing vascular oxidative stress. Treatment with fish oil (2 mL/kg/day p.o., 4 weeks) markedly prevented nicotine-induced endothelial functional and structural abnormalities and oxidative stress. However, administration of GW9662, a selective inhibitor of PPARγ, to a significant degree attenuated fish oil-associated anti-oxidant action and vascular endothelial functional and structural improvements. Intriguingly, in vitro incubation of L-NAME (100 μM), an inhibitor of nitric oxide synthase (NOS), markedly attenuated fish oil-induced improvement in endothelium-dependent relaxation in the aorta of nicotine-administered rats. Nicotine administration altered the lipid profile by increasing serum total cholesterol, which was significantly prevented by fish oil treatment. The vascular protective potential of fish oil in preventing nicotine-induced VED may pertain to its additional properties (besides its lipid-lowering effect) such as activation of PPARγ and subsequent possible activation of endothelial NOS and generation of nitric oxide, and consequent reduction in oxidative stress.

Effects of rosiglitazone on serum paraoxonase activity and metabolic parameters in patients with type 2 diabetes mellitus

Human serum paraoxonase contributes to the anti-atherogenic effect of high-density lipoprotein cholesterol (HDL-C) and has been shown to protect both low-density lipoprotein cholesterol (LDL-C) and HDL-C against lipid peroxidation. We investigated the effects of rosiglitazone on paraoxonase activity and metabolic parameters in patients with type 2 diabetes mellitus [50 patients (30 males, 20 females); mean±SD age: 58.7±9.2 years, body mass index: 28.2±4.1'kg/m²], in whom glucose control could not be achieved despite treatment with metformin, sulphonylurea, and/or insulin. The patients were given 4'mg/day rosiglitazone for 3 months in addition to their usual treatment. Serum paraoxonase activity, malondialdehyde, homocysteine, and lipid profile were measured at the time of initiation and at the end of therapy with rosiglitazone. After rosiglitazone therapy, serum levels of HDL-C, apolipoprotein A-1, and paraoxonase activity increased significantly (P<0.05) and malondialdehyde, homocysteine, lipoprotein(a), and glucose levels decreased significantly (P<0.05), but no significant changes in levels of total cholesterol and apolipoprotein B were observed. Triglyceride levels also increased significantly (P<0.05). Rosiglitazone treatment led to an improvement in glycemic control and to an increase in paraoxonase activity and HDL-C levels. Although rosiglitazone showed favorable effects on oxidant/antioxidant balance and lipid profile, further studies are needed to determine the effect of rosiglitazone on cardiovascular risk factors and cardiovascular morbidity and mortality.

Possible involvement of PPARγ-associated eNOS signaling activation in rosuvastatin-mediated prevention of nicotine-induced experimental vascular endothelial abnormalities

Nicotine exposure via cigarette smoking and tobacco chewing is associated with vascular complications. The present study investigated the effect of rosuvastatin in nicotine (2 mg/kg/day, i.p., 4 weeks)-induced vascular endothelial dysfunction (VED) in rats. The development of VED was assessed by employing isolated aortic ring preparation and estimating aortic and serum nitrite/nitrate concentration. Further, scanning electron microscopy and hematoxylin-eosin staining of thoracic aorta were performed to assess the vascular endothelial integrity. Moreover, oxidative stress was assessed by estimating aortic superoxide anion generation and serum thiobarbituric acid-reactive substances. The nicotine administration produced VED by markedly reducing acetylcholine-induced endothelium-dependent relaxation, impairing the integrity of vascular endothelium, decreasing aortic and serum nitrite/nitrate concentration, increasing oxidative stress, and inducing lipid alteration. However, treatment with rosuvastatin (10 mg/kg/day, i.p., 4 weeks) markedly attenuated nicotine-induced vascular endothelial abnormalities, oxidative stress, and lipid alteration. Interestingly, the co-administration of peroxisome proliferator-activated receptor γ (PPARγ) antagonist, GW9662 (1 mg/kg/day, i.p., 2 weeks) submaximally, significantly prevented rosuvastatin-induced improvement in vascular endothelial integrity, endothelium-dependent relaxation, and nitrite/nitrate concentration in rats administered nicotine. However, GW9662 co-administration did not affect rosuvastatin-associated vascular anti-oxidant and lipid-lowering effects. The incubation of aortic ring, isolated from rosuvastatin-treated nicotine-administered rats, with L-NAME (100 μM), an inhibitor of nitric oxide synthase (NOS), significantly attenuated rosuvastatin-induced improvement in acetylcholine-induced endothelium-dependent relaxation. Rosuvastatin prevents nicotine-induced vascular endothelial abnormalities by activating PPARγ and endothelial NOS signaling pathways. Moreover, the PPARγ-independent anti-oxidant and lipid-lowering effects of rosuvastatin might additionally play a role in the improvement of vascular endothelial function.

Submaximal PPARγ activation and endothelial dysfunction: new perspectives for the management of cardiovascular disorders

PPARγ activation plays an important role in glucose metabolism by enhancing insulin sensitization. PPARγ is a primary target for thiazolidinedione-structured insulin sensitizers like pioglitazone and rosiglitazone employed for the treatment of type 2 diabetes mellitus. Additionally, PPARγ activation inhibits adhesion cascades and detrimental vascular inflammatory events. Importantly, activation of PPARγ plays a distinctive role in regulating the physiology and expression of endothelial nitric oxide synthase (eNOS) in the endothelium, resulting in enhanced generation of vascular nitric oxide. The PPARγ activation-mediated vascular anti-inflammatory and direct endothelial functional regulatory actions could, therefore, be beneficial in improving the vascular function in patients with atherosclerosis and hypertension with or without diabetes mellitus. Despite the disappointing cardiac side effect profile of rosiglitazone-like PPARγ full agonists, the therapeutic potential of novel pharmacological agents targeting PPARγ submaximally cannot be ruled out. This review discusses the potential regulatory role of PPARγ on eNOS expression and activation in improving the function of vascular endothelium. We argue that partial/submaximal activation of PPARγ could be a major target for vascular endothelial functional improvement. Interestingly, newly synthesized partial agonists of PPARγ such as balaglitazone, MBX-102, MK-0533, PAR-1622, PAM-1616, KR-62776 and SPPARγM5 are devoid of or have a reduced tendency to cause the adverse effects associated with full agonists of PPARγ. We propose that the vascular protective properties of pharmacological agents, which submaximally activate PPARγ, should be investigated. Moreover, the therapeutic opportunities of agents that submaximally activate PPARγ in preventing vascular endothelial dysfunction (VED) and VED-associated cardiovascular disorders are discussed.

Arsenite promotes apoptosis and dysfunction in microvascular endothelial cells via an alteration of intracellular calcium homeostasis

Vascular endothelium has been considered as a target for arsenic-induced cardiovascular toxicity. The present study demonstrated that arsenite caused slow and sustained elevation of intracellular free calcium levels ([Ca2+]i) in HMEC-1, a human microvessel-derived endothelial cell line, in a concentration-dependent manner. Pretreatment with U-73122 (a specific PLC inhibitor) or 2-APB (a specific IP3 receptor antagonist) attenuated this effect, suggesting that PLC/IP3 signaling cascade is involved in arsenite-induced elevation of [Ca2+]i. Cytotoxic concentrations of arsenite (5 and 10 μM) significantly enhanced endothelial nitric oxide synthase (eNOS) phosphorylation, nitric oxide (NO) production and apoptosis after 24-h exposure. Additionally, 2-APB attenuated eNOS phosphorylation and apoptosis induced by arsenite, indicating that Ca2+ -mediated eNOS activation participates in arsenite-induced endothelial cell apoptosis. Moreover, we also found that non-apoptotic concentrations of arsenite (0.5 and 1 μM) dramatically mitigated thrombin-induced rapid transient rise of [Ca2+]i, eNOS phosphorylation and NO production, suggesting functional disruption of endothelial by arsenite, and these effects occurred without an alteration of PLC-β1 and thrombin receptor levels. Altogether, the results reveal that arsenite induces apoptotic cell death and endothelial dysfunction as indicated by the reduction of thrombin responses, particularly related to an alteration of intracellular Ca2+ homeostasis.

Mechanisms pertaining to arsenic toxicity

Arsenic is an environmental pollutant and its contamination in the drinking water is considered as a serious worldwide environmental health threat. The chronic arsenic exposure is a cause of immense health distress as it accounts for the increased risk of various disorders such as cardiovascular abnormalities, diabetes mellitus, neurotoxicity, and nephrotoxicity. In addition, the exposure to arsenic has been suggested to affect the liver function and to induce hepatotoxicity. Moreover, few studies demonstrated the induction of carcinogenicity especially cancer of the skin, bladder, and lungs after the chronic exposure to arsenic. The present review addresses diverse mechanisms involved in the pathogenesis of arsenic-induced toxicity and end-organ damage.

Pharmacological investigations on potential of peroxisome proliferator-activated receptor-gamma agonists in hyperhomocysteinemia-induced vascular dementia in rats

The present study has been designed to investigate the potential of peroxisome proliferator-activated receptor-gamma ([PPAR]-γ) agonists, pioglitazone, and rosiglitazone in hyperhomocysteinemia-induced vascular dementia of rats. l-methionine was administered for 8 weeks to induce hyperhomocysteinemia and associated vascular dementia. Pioglitazone and rosiglitazone were administered to l-methionine-treated rats for 4 weeks (starting from 5th to 8th weeks of methionine treatment). Donepezil served as a positive control in this study. On 52nd day onward, the animals were exposed to Morris water maze (MWM) for testing learning and memory abilities. Vascular endothelial function, serum nitrite/nitrate levels, brain thiobarbituric acid reactive species (TBARS), brain reduced glutathione (GSH) levels, and brain acetylcholinesterase (AChE) activity were also measured. l-methionine-treated animals have shown impairment of learning, memory, endothelial function, decrease in serum nitrite/nitrate levels, and brain GSH levels along with increase in brain TBARS levels and AChE activity. Pioglitazone, rosiglitazone, and donepezil significantly improved hyperhomocysteinemia-induced impairment of learning, memory, endothelial dysfunction, and changes in various biochemical parameters. It is concluded that pioglitazone and rosiglitazone may be considered as potential pharmacological agents for the management of hyperhomocysteinemia-induced vascular dementia.