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Effect of angiotensin II type 1 receptor antagonist losartan on expression and activity of antioxidative enzymes, cell adhesion molecules and proinflammatory cytokines in cerebral blood vessels of Sprague-Dawley rats

INTRODUCTION:Present study has assessed the effects of losartan (angiotensin II type 1 (AT-1R) receptor antagonist) on gene expression of antioxidative enzymes (Cu/Zn SOD, MnSOD, EC-SOD, GPx1, GPx4, CAT) and NOX1, gene expression of endothelial cells adhesion molecules (ICAM- 1, VCAM-1, E-selectin, endocan), pro-inflammatory cytokines (IL-1, IL-6, TNF-α) and chemokine GRO-α (CXCL1) in cerebral vessels, and on systemic oxidative stress. METHODS:Healthy male Sprague-Dawley rats were fed low salt diet for 7 days (0.4%NaCl ; LS group) or LS diet+losartan (40 mg/day in water ad libidum). Following dietary protocol, rats were anesthetized with ketamine (75 mg/kg) and midazolam (2.5 mg/kg) and sacrificed by decapitation. Oxidative stress was assessed by measurement of 8-iso prostaglandin concentration and antioxidative enzymes activity assay in serum samples by spectrophotometry.mRNA levels were determined by quantitative real-time PCR in surface cerebral vessels. Data were analysed by t-test, presented as mean±SD. All experimental procedures are conformed to the European Guidelines for the Care and Use of Laboratory Animals (directive 86/609) and were approved by the local and national Ethical Committee (No.525-10/0255-15-6). RESULTS:8-iso prostaglandin concentration was significantly increased in LS+losartan group (0.31±0.08 ng/ml) compared to LS group (0.23±0.08 mg/ml). Expression of GPx1 and Cu/Zn SOD was significantly decreased in LS+losartan group (GPx1 0.63±0.24, Cu/Zn SOD 0.73±0.20) vs.LS group (GPx1 1.23±0.38, Cu/Zn SOD 1.09±0.18). Expression of MnSOD, ECSOD, CAT and NOX1 was significantly increased in LS+ losartan group (MnSOD 2.53±0.66, EC-SOD 1.22±0.34, CAT 4.89±1.55, NOX1 0.006±0.003) compared to LS (MnSOD 0.96±0.21, EC-SOD 0.61±0.20, CAT 0.87±0.11, NOX1 0.003±0.003). GPx4 expression in vessels and serum GPx activity was not different between groups. Serum enzymes’ activity (U/mgP) of SOD (1.97±0.53 vs.1.57±0.24) and CAT (0.85±0.25 vs.0.55±0.32) was significantly decreased in LS+ losartan group. Expression of chemokine GRO-α was significantly increased in LS+losartan group (1.29±0.53 vs.3.69±1.14) without significant change in expression of other cytokines (p>0.05). Expression of VCAM-1 was significantly increased in LS+losartan group (1.91±0.58) vs.LS group (1.12±0.34). CONCLUSIONS:Blockade of AT-1 receptor causes increased vascular and systemic oxidative stress, possible due to increased expression of NOX1 (a source of superoxide), and decreased activity of antioxidative enzymes despite their increased expression in vessels. In addition, blockade of AT1 receptor leads to endothelial cell activation as their phenotype changes to neutrophil-attractive (increased expression of VCAM-1 and GRO-α).

angiotensin II type 1 receptor ; oxidative stress ; proinflammatory cytokines ; cerebral blood vessels

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