Protective Effect Of Losartan Research Articles

Antiapoptotic effect of angiotensin-II type-1 receptor blockade in renal tubular cells of hyperoxaluric rats

In this study, we investigated the protective effect of losartan as an AT1 receptor antagonist by evaluating the expression of apoptosis-regulatory genes that contribute to the progressive damage in the renal tubules of hyperoxaluric rats. Rats were divided into 4 groups of 10 each; control (C), ethylene glycol (EG), ethylene glycol + losartan (EG + L) and Losartan (L). For 4 weeks 0.8% EG, as a precursor for oxalate, was administered to EG and EG + L and losartan (300 mg/l) was administered to groups EG + L and L. Urine and blood samples were collected for biochemical determination. Bcl-2, bax, caspase-3 and TGF-beta 1 antibodies were used for immunohistochemistry. Apoptosis was determined by TUNEL method. A marked increase in urinary oxalate levels of the rats in EG and EG + L groups was found. In the EG group a diffuse amount of oxalate crystals into the tubular lumina and interstitium in the cortex was observed. In the EG group GBM thickening, interstitial fibrosis and tubular atrophy with infiltration of mononuclear cell findings reduced in the EG + L group were presented as well. In the EG group, immunoreactivity of TGF-beta 1 was increased in glomeruli and tubuli. In the EG + L group, immunoreactivity of TGF-beta 1 was decreased compared to the EG group. Bax expression increased in the renal tubules of EG group and reduced in the EG + L group comparing to the control. In the EG + L group, the immunoreactivity of bcl-2 was increased in glomeruli. In EG + L treated group, number of caspase-3 immunopositive cells were decreased compared to all groups (P < 0.01). Apoptotic cells were increased in the EG-treated group compared to the other groups. Decreased apoptotic cell number was observed in the EG + L compared to the EG group (P < 0.01). Our findings suggest that losartan may provide a beneficial effect against tubulointerstitial damage and decrease renal tubular apoptosis caused by hyperoxaluria.

N-Acetylcysteine Abolishes the Protective Effect of Losartan Against Left Ventricular Remodeling in Cardiomyopathy Hamster

Oxidative stress mediated by activation of angiotensin II type-1 receptor (AT(1)R) plays a crucial role in the progression of heart failure. We investigated the effect of N-acetylcysteine (NAC) and an AT(1)R blocker on oxidative stress and left ventricular (LV) remodeling in BIO14.6 cardiomyopathy hamsters. The cardiomyopathy hamsters were treated with NAC or the AT(1)R blocker losartan for 20 weeks. Although NAC and losartan inhibited oxidative stress and upregulation of iNOS in the cardiomyopathy hamster heart, only losartan inhibited LV chamber dilation, myocardial fibrosis, and LV dysfunction in the cardiomyopathy hamster. Co-treatment with NAC abolished the protective effect of losartan against LV remodeling associated with inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt and eNOS activation. An iNOS inhibitor 1400W or a nonselective NOS inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) exacerbated LV remodeling in the cardiomyopathy hamster. However, L-NAME but not 1400W abrogated losartan-mediated inhibition of LV remodeling. These results suggest that redox-sensitive upregulation of iNOS plays a crucial role in preventing LV remodeling in the BIO14.6 cardiomyopathy hamster. Losartan inhibits LV remodeling by switching the cardioprotective mechanism from iNOS- to eNOS-dependence, but NAC abolishes the protective effect of losartan by inhibiting redox-sensitive activation of PI3K/Akt and eNOS in the cardiomyopathy hamster.

Reduction of asymmetric dimethylarginine involved in the cardioprotective effect of losartan in spontaneously hypertensive rats

Previous studies have indicated that nitric oxide synthase (NOS) inhibitors can induce an increase of blood pressure and exacerbate myocardial injury induced by ischemia and reperfusion, whereas angiotensin II receptor antagonists protect the myocardium against injury induced by ischemia and reperfusion. Isolated hearts from male spontaneously hypertensive rats (SHR) or male Wistar-Kyoto rats (WKY) were subjected to 20 min global ischemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure, and its first derivatives (+/-dP/dt(max)) were recorded, and serum concentrations of asymmetric dimethylarginine (ADMA) and NO and the release of creatine kinase in coronary effluent were measured. The level of ADMA was significantly increased and the concentration of NO was decreased in SHR. Ischemia and reperfusion significantly inhibited the recovery of cardiac function and increased the release of creatine kinase, and ischemia and reperfusion-induced myocardial injury in SHR was aggravated compared with WKY. Vasodilation responses to acetylcholine of aortic rings were decreased in SHR. Treatment with losartan (30 mg/kg) for 14 days significantly lowered blood pressure, elevated the plasma level of NO, and decreased the plasma concentration of ADMA in SHR. Treatment with losartan significantly improved endothelium-dependent relaxation and cardiac function during ischemia and reperfusion in SHR. Exogenous ADMA also aggravated myocardial injury induced by ischemia and reperfusion in isolated perfused heart of WKY, as shown by increasing creatine kinase release and decreasing cardiac function. The present results suggest that the protective effect of losartan on myocardial injury induced by ischemia and reperfusion is related to the reduction of ADMA levels.

Protective effect of losartan on endothelial cells exposed to high glucose levels in vitro

To investigate the effect of losartan (an angiotensin II type I receptor antagonist) on endothelial cells exposed to high glucose in vitro and related mechanism. Vascular endothelial cells of human umbilical vein were cultured in media with high glucose levels. The activities of SOD and CAT, the level of MDA were measured by spectrophotometry in the conditioned media of endothelial cells, the VEGF mRNA expression was performed using semi-quantitative reverse transcription PCR (RT-PCR) in the cell lysates, and the protein expression of VEGF was examined by enzyme-linked immunosorbent assay (ELISA) in the supernatants of cultured cells. When endothelial cells were cultured in high glucose, the activities of SOD and CAT were significantly decreased, but the level of MDA was markedly increased. However, the high glucose-induced effects were inhibited by losartan. The application of high glucose upregulated the mRNA and protein expression of VEGF in endothelial cells, which was also attenuated by losartan. High glucose disrupts the oxidative equilibrium and increases the expression of VEGF in endothelial cells, which can be inhibited by losartan.