Endothelin-1 inhibits cytokine-stimulated transcription of inducible nitric oxide synthase in glomerular mesangial cells

Abstract

Endothelin-1 (ET-1) is a potent vasoconstrictor while nitric oxide (NO) has strong vasodilatory effects. Recent studies have indicated that vasoconstrictors and NO may mutually modulate their production and/or activity, thus regulating each other in the context of microcirculatory maintenance. We examined the question whether ET-1 may affect NO formation by controlling the expression of the inducible isoform of the NO synthase (iNOS) in cultured rat glomerular mesangial cells (MCs), as induced by the inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) plus interleukin-1 beta (IL-1 beta). We found that ET-1 in MCs markedly reduced cytokine-induced NO production (measured as stable NO2-) and inhibited the expression of iNOS mRNA (Northern blot analysis) and of iNOS protein (Western blotting). Inhibition of cytokine-stimulated iNOS mRNA expression by ET-1 was almost complete at the level of gene transcription while post-transcriptional effects were not detected. The ETA receptor antagonist BQ-123 blocked the inhibitory effect of ET1. The ETA agonist sarafotoxin 6b (S6b) inhibited, while the ETB agonist-sarafotoxin 6c (S6c) did not inhibit cytokine-initiated iNOS transcription in MCs. The results demonstrate that ET-1 can strongly inhibit cytokine induction of iNOS and formation of NO in cultured MCs, and that this action is mediated via the ETA receptor. While the precise mechanism(s) and biological relevance of this ET-1 effect are presently unclear, it is conceivable that down-regulation of iNOS by the vasopressor ET-1 may serve in vivo to prevent massive NO build-up and subsequent vasomotor collapse in the glomerular capillary tuft. This could help to maintain glomerular ultrafiltration in states of endotoxin excess as well as during glomerular formation and action of TNF-alpha and IL-1 beta causing iNOS induction and subsequent overproduction of NO.

Cloning and sequencing of the proximal promoter of the rat iNOS gene: activation of NFκB is not sufficient for transcription of the iNOS gene in rat mesangial cells

“…This renders the elucidation of a universal signaling pathway for iNOS regulation more difficult. Cloning of murine [18], human [19,20] and rat iNOS promoters has enabled us to examine transcriptional effects with authentic promoter fragments.We have recently reported that ET-1 inhibits iNOS expression induced by TNF-c~ and IL-I[3 via the ETA receptor in rat MCs [17]. Our data indicated that the inhibition occurs at the transcriptional level.…”

Cytotoxic effect of autocrine and macrophage-derived nitric oxide on cultured rat mesangial cells

“…The ability of MC to enhance production of nitrite and expression of the iNOS in response to these proinflammatory cytokines have been reported by many groups, including ourselves [15][16][17]. Results of some of these studies [16,17], by indicating that co-stimulation of mesangium with IL-1 and TNF-acts synergistically to generate large amounts of nitrite, prompted us to utilize concurrently both cytokines in our experiments. MC stimulated to proliferate with bFGF did not in our hands respond as vigorously by production of nitrite to stimulation with IL-1 and TNF-as did quiescent cells, contrary to vascular smooth muscle cells, which more remarkably enhance generation of NO 2 -upon triggering with IL-1 and bFGF, as described by Scott-Burden et al [19].…”

“…We (Beck et al [16]) and others [17] have previously reported that co-stimulation of cultured mesangial cells with IL-1 and TNFresults in generation of greater quantities of nitrite than when cells are stimulated with either cytokine alone. In the present experiments triggering quiescent mesangial cells with IL-1 and TNFcaused a remarkable increase in nitrite production, inhibitable by L-NMMA as depicted in Fig.…”

Role of nitric oxide synthase in release of endothelin from cultured human endometrial cells

“…iNOS-like immunoreactivity was also demonstrated in glandular epithelial cells, but eNOS and iNOS could not be detected in human endometrial stromal cells by immunocytochemical methods (27). On the other hand, although several studies have focused on the effect of ET on NO production in glomerular mesangial cells (28,29) and vascular smooth muscle EUROPEAN JOURNAL OF ENDOCRINOLOGY (1998) 138 Figure 1 Effect of IL-1b and LNMMA on ET-1 release from cultured human endometrial stromal cells in the first (A), second (B) and third (C) 24 h culture. Cells were incubated with or without IL-1b in the absence or presence of LNMMA at 37 ЊC in RPMI 1640 medium without fetal bovine serum.…”