Improvement of renal hemodynamics during hypertension-induced chronic renal disease: role of EGF receptor antagonism

Abstract

The present study investigated mechanisms of regression of renal disease after severe proteinuria by focusing on the interaction among EGF receptors, renal hemodynamics, and structural lesions. The nitric oxide (NO) inhibitor NG-nitro-l-arginine-methyl ester (l-NAME) was administered chronically in Sprague-Dawley rats. When proteinuria exceeded 2 g/mmol creatinine, animals were divided into three groups for an experimental period of therapy of 2 wk; in one group, l-NAME was removed to allow reactivation of endogenous NO synthesis; in the two other groups, l-NAME removal was combined with EGF or angiotensin receptor type 1 (AT1) antagonism. l-NAME removal partially reduced mean arterial pressure and proteinuria and increased renal blood flow (RBF), but not microvascular hypertrophy. Progression of structural damage was stopped, but not reversed. The administration of an EGF receptor antagonist did not have an additional effect on lowering blood pressure or on renal inflammation but did normalize RBF and afferent arteriole hypertrophy; the administration of an AT1antagonist normalized all measured functional and structural parameters. Staining with a specific marker of endothelial integrity indicated loss of functional endothelial cells in the l-NAME removal group; in contrast, in the animals treated with an EGF or AT1receptor antagonist, functional endothelial cells reappeared at levels equal to control animals. In addition, afferent arterioles freshly isolated from the l-NAME removal group showed an exaggerated constrictor response to endothelin; this response was blunted in the vessels isolated from the EGF or AT1receptor antagonist groups. The EGF receptor is an important mediator of endothelial dysfunction and contributes to the decline of RBF in the chronic kidney disease induced by NO deficiency. The EGF receptor antagonist-induced improvement of RBF is important but not sufficient for a complete reversal of renal disease, because it has little effect on renal inflammation. To achieve full recovery, it is necessary to apply AT1receptor antagonism.