Autoinduction of endothelin-1 (ET-1) has been suggested to be involved in the profound and long-lasting effects of ET-1. We examined mechanisms that underlie autoinduction of ET-1 in cultured rat glomerular mesangial cells. Incubation of mesangial cells with ET-1 resulted in an immediate and dose-dependent stimulation of preproET-1 mRNA expression as assessed by polymerase chain reaction coupled with reverse transcription. Within 1 h of exposure to ET-1 (10(-7) M), preproET-1 mRNA expression was increased to a maximal level of 465 +/- 43% of the control value (p < 0.01), which was accompanied by significant stimulation of production of the immunoreactive ET-1 peptide. Nuclear run-off analysis revealed increases in the transcriptional rate of preproET-1 mRNA to 239 and 175% above the control values at 1 and 3 h of ET-1 stimulation, respectively. ET-1 also increased the stability of preproET-1 mRNA, resulting in an mRNA half-life of 60 min from 20 min seen in non-stimulated cells. Addition of an ETB-specific antagonist, RES701-1, at > 10(-9) M abolished ET-1 stimulation of preproET-1 mRNA (p < 0.001), whereas an ETA-specific antagonist, BQ123, was without effects (up to 10(-5) M). The ETB agonist, sarafotoxin S6c (10(-7) M), significantly stimulated preproET-1 mRNA expression to 201 +/- 14% above controls (p < 0.01), and effect that was lessened significantly by RES701-1 (p < 0.05). RES701-1 abolished the ET-1-induced production of the ET-1 peptide (p < 0.001). Taken together, we demonstrates that in mesangial cells, autoinduction of ET-1 occurs through the ETB receptor subtype via increases in both preproET-1 transcription and mRNA stability.

The role of the endothelium is now known to encompass the generation of many potent cytokines which impact endothelial cells, adjacent tissue such as smooth muscle cells, and distant sites in an autocrine, paracrine, and endocrine manner, respectively. This review addresses two of these cytokines, nitric oxide and endothelin, and describes how each effects the functions of endothelial cells, including regulation of platelet aggregation and coagulation, regulation of vasomotor tone, modulation of inflammation, and the regulation of cellular proliferation. The emphasis is on the increasingly recognized importance of the autocrine and paracrine mechanisms by which nitric oxide and endothelin act. In particular, autoinduction of endothelin is proposed as a central mechanism underlying endothelin's renowned effects. Additionally, specific nitric oxide/endothelin interactions are discussed by which each cytokine modulates the production and actions of the other. The net effect observed in a variety of physiological and pathophysiological settings, therefore, reflects a balance of these opposing functions.

Endothelin (Et) has been suggested by us and others to play a role in glomerular dysfunction that characterizes cyclosporine (Cs)-associated nephrotoxicity. Since Et exerts its actions through at least two receptor subtypes, and because these receptor subtypes have particular distributions in the renal parenchyma, we investigated changes in mRNA expression for Et and its receptor subtypes in glomeruli and medulla of rats treated with Cs. Polymerase chain reaction coupled with reverse transcription (RT-PCR) method was used to assess prepro-Et-1, type A (EtA) and type B (EtB) receptor mRNA at 1, 3, 6, and 24 hours after Cs (20 mg/kg body wt i.v.). Results were normalized to the expression of beta-actin as an internal standard. Compared with control rats, glomerular mRNA expression for prepro-Et-1 was not affected by Cs. Similarly, Cs did not significantly change the glomerular mRNA expression of either EtA or EtB receptor subtypes. By contrast, in the medulla there was a marked and persistent increase in the expression for prepro-Et-1 and the EtB receptor subtype: prepro-Et-1 at 1, 3, 6, and 24 hours was 336 +/- 61, 295 +/- 65, 339 +/- 73, 440 +/- 123% of controls, respectively (P < 0.05 compared with controls at each time point). The EtB receptor mRNA at 1, 3, 6, 24 hours was 164 +/- 22, 157 +/- 15, 148 +/- 14, 116 +/- 18% (compared with controls, P < 0.01 at 3 hr and P < 0.05 at 1 and 6 hr), while the mRNA expression for EtA was not affected by Cs treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

We studied whether endothelin-1 (ET-1) and its receptor subtypes (ETAR, endothelin A type receptor; and ETBR, B type receptor) were up-regulated in the glomerulus of a rat model of mesangial proliferative glomerulonephritis induced by anti-thymocyte serum (anti-Thy-1 GN). A marked increase in preproET-1 mRNA could be demonstrated in glomerular RNA 3 and six days after disease induction (4.1- and 4.9-fold vs. day 0, respectively), corresponding to the time of mesangial cell proliferation, to the time of macrophage infiltration into glomeruli, and also to the time of increase in glomerular PDGF B-chain mRNA expression. The localization of ET-1 protein in the mesangial area and along the inner aspect of the glomerular capillary wall was also demonstrated by immunohistochemistry from day 3 and maximal at day 6. The major source of the cells expressing ET-1 in glomeruli appeared to be mesangial cells, glomerular endothelial cells and monocyte/macrophages. Furthermore, both gene and protein expression of ET-1 were associated with increased urinary excretion of ET-1. There was no increase in the plasma ET-1 immunoreactivity. Glomerular expression of ETBR mRNA increased in anti-Thy-1 GN (1.5-fold vs. day 0 at day 3 after disease induction, 3.6-fold at day 6 and 2.7-fold at day 10), but there was minimal change in ETAR mRNA expression. These results suggest that preproET-1 mRNA, which is induced in anti-Thy-1 GN, is linked primarily with ETBR mRNA expression.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract