Mohamed M. A. Khalifa

Adverse balance of nitric oxide/peroxynitrite in the dysfunctional endothelium can be reversed by statins.

Vascular endothelial dysfunction is a complex phenomenon that might be caused by a deficiency of nitric oxide (NO) and an overproduction of peroxynitrite (ONOO−). This study used a nanotechnological approach to monitor the in vitro effect of statins on the [NO]/[ONOO−] balance in normal and dysfunctional endothelial cells. NO and ONOO− were measured by electrochemical nanosensors in a single human umbilical vein endothelial cell (HUVEC) treated with atorvastatin or simvastatin for 24 hours in the presence or absence of 50 μg/mL oxidized-LDL. An imbalance between [NO]/[ONOO−] concentrations was used as an indicator of endothelial dysfunction and correlated with endothelial nitric oxide synthase (eNOS) expression. Ox-LDL induced dysfunction of the endothelium by uncoupling eNOS. NO concentration decreased from 300 ± 12 to 146 ± 8 nmol/L and ONOO− increased from 200 ± 9 to 360 ± 13 nmol/L. The [NO]/[ONOO−] balance decreased from 1.50 ± 0.04 (control) to 0.40 ± 0.03 for cells co-incubated with ox-LDL. Treatment with statins reversed eNOS uncoupling, induced by oxidized-LDL and significantly increased the [NO]/[ONOO−] balance to 1.2 ± 0.1. These results demonstrate that statins can restore endothelial function by increasing eNOS expression, decreasing eNOS uncoupling, reducing the ONOO− level (nitroxidative stress), and shifting the [NO]/[ONOO−] balance towards NO.

Comparative effects of Aliskiren and Telmisartan in high fructose diet-induced metabolic syndrome in rats

Fructose is a commonly used sweetener associated with diets that increase the prevalence of metabolic syndrome (MS). Inhibition of the renin-angiotensin system (RAS) has been consistently demonstrated to reduce MS. However, there has been no direct comparison among different pharmacological modes of inhibiting the RAS concerning their effects on MS. This study investigated the effect of aliskiren, a direct renin inhibitor, versus telmisartan, an angiotensin II-receptor blocker, in the treatment of fructose-induced MS in rats. MS was induced by high fructose (FRC) diet feeding for 12 weeks. Oral administrations of telmisartan (TEL, 5 mg/kg), aliskiren (ALS, 30 mg/kg) or vehicle were started in the last 4 weeks. Results showed that administration of either TEL or ALS with FRC diet equally ameliorated the metabolic parameters (glucose level, oral glucose tolerance test, insulin resistance and serum lipids profile), systolic blood pressure and oxidative stress markers (malondialdehyde, nitric oxide, reduced glutathione levels and catalase activity). Additionally, the effects of TEL and ALS were associated with a decrease in body composition index and attenuation of liver index, serum liver enzyme activities and hepatic expressions of inflammatory and fibrotic markers (tumor necrosis factor-α, nuclear factor kappa-B and transforming growth factor-β) with a significant increase in hepatic glucose transporter-2 and peroxisome proliferator-activated receptors-alpha and gamma expressions. The results suggested that, at indicated dosage, ALS has ameliorative effect equal to that of TEL against FRC-induced metabolic and hepatic disorders; implying that drugs which inhibit the RAS, by different mode of inhibition, profoundly affect fructose-induced MS in rats.

Sildenafil protects against nitric oxide deficiency-related nephrotoxicity in cyclosporine A treated rats

Cyclosporine A (CsA) is the most widely used immunosuppressant in organ transplant surgery and in treatment of autoimmune disease. Nevertheless, animal and clinical studies have demonstrated that nephrotoxicity is the major adverse effect limiting the prolonged CsA therapeutic use. The present study aimed to investigate possible protective effect of sildenafil, a phoshodiestrase-5 inhibitor, on CsA-induced nephrotoxicity and various mechanism(s) underlies this effect. Male Wistar rats were administered CsA (20 mg/kg/day, s.c.) for 21 days alone or in combination with sildenafil (5 mg/kg/day, p.o.). Sildenafil exhibited nephroprotective effects as evidenced by significant decrease in serum creatinine and urea levels, spot urine albumin-creatinine ratio, as well as renal level of malondialdehyde, with a concurrent increase in renal levels of reduced glutathione and nitric oxide along with catalase activity compared to CsA-treated rats. [corrected]. Additionally, immunohistochemical analysis demonstrated that sildenafil treatment markedly reduced inducible nitric oxide synthase, tumor necrosis factor-alpha, and caspase-3 expressions, while expression of endothelial nitric oxide synthase was prominently enhanced. The protective effects of sildenafil were confirmed by renal histopathological examination. Pretreatment with l-nitro-arginine methyl ester (10 mg/kg/day, i.p.), a non-selective nitric oxide synthase inhibitor, reversed the protection afforded by sildenafil. Taken together, the current study highlighted the renoprotective effects of sildenafil against CsA-induced nephrotoxicity in rats, which might be mediated, in part, through nitric oxide pathway as well as antioxidant, anti-inflammatory, and anti-apoptotic activities.

Protective effects of phloridzin against methotrexate-induced liver toxicity in rats

BACKGROUND Liver is the largest internal organ concerning with metabolism, hormonal balance and clarifying of the toxins. One of the main complications of methotrexate (MTX) therapy was the hepatic injury. OBJECTIVE This study was conducted to elucidate the possible protective effects of phloridzin (PHL) against MTX-induced hepatotoxicity as compared to standard agent N-acetylcysteine (NAC). MATERIALS AND METHODS Rats were randomly divided into a normal control group, a respective group (PHL 40mg/kg/day orally (p.o.) for 10 consecutive days), a hepatotoxicity control group (MTX 20mg/kg, i.p., once), and three treated groups received NAC (150mg/kg/day; a reference standard), PHL (40mg/kg/day) and PHL (80mg/kg/day) p.o. for 10 consecutive days, at the end of the day 3 of the experiment rats were administered MTX. Assessed biomarkers included serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) as liver function parameters, serum tumor necrosis factor-α (TNF-α) and cyclooxygenase-II (COX-II), as inflammatory biomarkers, hepatic total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS), glutathione reduced (GSH), nitrite (NO2-), catalase (CAT), glutathione-S-transferase (GST) and superoxide dismutase (SOD) as oxidative stress biomarkers. Furthermore, hepatic caspase-3 expression was assessed. Biochemical and molecular estimations reinforced by histopathological findings. RESULTS Rats pre-treated with PHL significantly reduced hepatic injury, evidenced by significant reductions in ALT, AST and LDH, TNF-α and COX-II levels, significant reductions in hepatic NO2- and TBARS levels, and significant elevations in hepatic TAC, GSH, GST, CAT and SOD levels. Additionally, downregulation of hepatic caspase-3 expression. Finally, histopathological results consistent with our previous findings. CONCLUSION PHL protects against hepatic injury in rats mainly through mitigation of oxidative stress, inflammation and apoptosis in hepatic tissues and may be promising to alleviate and early treatment of MTX-induced hepatoxicity in man.

Lixisenatide, a novel GLP-1 analog, protects against cerebral ischemia/reperfusion injury in diabetic rats

Type 2 diabetes mellitus (T2DM) is a major risk factor for ischemic stroke accompanied by vascular dysfunction and poor cerebrovascular outcome. Lixisenatide is a glucagon like peptide-1 (GLP-1) analog that is recently used for T2DM treatment with established neuroprotective properties. This study investigated and compared the neuroprotective effect of lixisenatide against glimepiride on diabetic rats subjected to global cerebral ischemia/reperfusion (I/R) injury. T2DM-induced adult male Wistar rats were administered lixisenatide or glimepiride prior to induction of global cerebral I/R-induced injury. Results showed a disturbance in oxidative stress parameters (catalase, reduced glutathione, and malondialdehyde) along with increasing in caspase-3 and tumor necrosis factor-alpha protein expressions in ischemic diabetic brain tissues. An upregulation of protein level of inducible nitric oxide (iNOS) synthase and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit, NOX2 gene expression associated with significant suppression of endothelial nitric oxide synthase (eNOS) protein expression are recorded in carotid arteries of diabetic I/R-injured rats. Apart from ameliorating glucose intolerance and insulin resistance, lixisenatide was found to be superior to glimepiride as protective treatment in terms of enhancing behavioral/neurological functions and suppressing cerebral oxidative stress, inflammation, and apoptosis in cerebral I/R-injured diabetic rats. Unlike glimepiride, lixisenatide relieved carotid endothelial dysfunction by increasing eNOS expression. It also dampened vascular nitrosative/oxidative stress via suppression of iNOS and NADPH oxidase expressions. This study supposed that lixisenatide represents a more suitable anti-diabetic therapy for patients who are at risk of ischemic stroke, and even so, the mechanisms of lixisenatide-mediated vascular protection warrant further experimental and clinical investigations.

Lixisenatide ameliorates cerebral ischemia-reperfusion injury via GLP-1 receptor dependent/independent pathways

Abstract Ischemic stroke is a major cause of neurological damage and brain dysfunction with consequent strong cerebral oxidative imbalance, inflammatory and apoptotic responses. Lixisenatide is a new potent glucagon‐like peptide −1 (GLP‐1) analogue that has been used clinically in the treatment of type II diabetes. Recent studies suggested the beneficial central effects of GLP‐1‐based therapies on different neurodegenerative diseases. This study aimed to investigate the ameliorative effect of lixisenatide in global cerebral ischemia‐reperfusion (I/R) rat model and elaborate the underline mechanisms that could mediate the proposed activity. Adult male Wistar rats were subjected to sham operation or global cerebral I/R injury. Rats were administered the following drugs in two scheduled doses at 1 h and 24 h after reperfusion: lixisenatide (1 and 10 nmole/kg), lixisenatide plus GLP‐1 receptor (GLP‐1R) antagonist (exendin(9−39)), and pentoxiphylline. Comparable to pentoxiphylline; both doses of lixisenatide produced a significant reduction in infarct volume and amelioration of neurobehavioural functions along with suppression of oxidative stress parameters (catalase, reduced glutathione, malondialdehyde and NO), inflammatory marker (tumor necrosis factor‐alpha) and apoptotic marker (caspase‐3) in ischemic rat brains. However, these effects weren’tinhibited by GLP‐1R antagonist, exendin(9−39), indicating that they are independent on GLP‐1R mediation. Also, lixisenatide upregulated protein expression of cerebral endothelial nitric oxide synthase and the angiogenic marker, vascular endothelial growth factor. Its worth noting that this effect was blocked by exendin(9−39). Overall, these data indicated that lixisenatide may offer a promising approach for alleviating cerebral I/R injury via different mechanisms that could be mediated, in part, through GLP‐1R.

Erratum to: Spironolactone improves endothelial dysfunction in streptozotocin-induced diabetic rats

Unfortunately, panel b in figures 4, 6 and 8 of our manuscript mistakenly replicated panel a (control rats) rather than showing data from control rats treated with spironolactone. The quantitative analysis of the data shown in panel e has not been affected by this. Corrected figures with their legends are provided below. We apologize for any confusion this may have caused for readers.