Different protective actions of losartan and tempol on the renal inflammatory response to acute sodium overload

Abstract

The aim of this work was to study the role of local intrarenal angiotensin II (Ang II) and the oxidative stress in the up-regulation of pro-inflammatory cytokines expression observed in rats submitted to an acute sodium overload. Sprague–Dawley rats were infused for 2 h with isotonic saline solution (Control group) and with hypertonic saline solution alone (Na group), plus the AT1 receptor antagonist losartan (10 mg kg 1 in bolus) (Na–Los group), or plus the superoxide dismutase mimetic tempol (0.5 mg min 1 kg 1 ) (Na–Temp group). Mean arterial pressure, glomerular filtration rate, and fractional sodium excretion (FENa) were measured. Ang II, NF-kB, hypoxia inducible factor-1a (HIF-1a), transforming growth factor b1 (TGF-b1), smooth muscle actin (a-SMA), endothelial nitric oxide synthase (eNOS), and RANTES renal expression was evaluated by immunohistochemistry. Ang II, NF-kB, and TGF-b1 and RANTES early inflammatory markers were overexpressed in Na group, accompanied by enhanced HIF-1a immunostaining, lower eNOS expression, and unmodified a-SMA. Losartan and tempol increased FENa in sodium overload group. Although losartan reduced Ang II and NF-kB staining and increased eNOS expression, it did not restore HIF-1a expression and did not prevent inflammation. Conversely, tempol increased eNOS and natriuresis, restored HIF-1a expression, and prevented inflammation. Early inflammatory markers observed in rats with acute sodium overload is associated with the imbalance between HIF-1a and eNOS expression. While both losartan and tempol increased natriuresis and eNOS expression, only tempol was effective in restoring HIF-1a expression and down-regulating TGF-b1 and RANTES expression. The protective role of tempol, but not of losartan, in the inflammatory response may be associated with its greater antioxidant effects.