Endothelin-1 receptor antagonist: Effects on endothelin- and cyclosporine-treated mesangial cells

Abstract

Endothelin-1 (Et) has profound effects on glomerular microcirculation and mesangial cell contraction. A parameter of mesangial cell contraction was examined by measuring myosin light chain phosphorylation (MLCP) in glomerular mesangial cells in the presence and absence of a newly developed endothelin-1 receptor antagonist (EtA). Addition of Et alone (10 nM) caused a marked increase in MLCP, which, on average, rose by 53 +/- 6% above the level in cells exposed to vehicle (P less than 0.0005). This effect was shown to continue for at least one hour; MLCP at 60 minutes was 64 +/- 12% higher than controls, (P less than 0.025), constituting a unique observation of an in vitro parameter which parallels the characteristic in vivo effect of Et. Treatment of cells with EtA virtually abolished this Et-induced increase in MLCP, which rose by only 2 +/- 3% and -1 +/- 4% for doses of EtA of 44 nM and 66 nM, respectively. Examination of the intracellular calcium concentration, [Ca2+]i, revealed that EtA almost completely abolished the transient increase in [Ca2+]i evoked by Et and also suppressed the early portions of the sustained increase in [Ca2+]i. EtA was ineffective in abolishing [Ca2+]i increase in response to arginine vasopressin. Finally, to evaluate EtA's efficacy in a pathophysiologic setting, we also studied mesangial cells exposed to cyclosporine (Cs). Exposure of mesangial cells to Cs (10(-5) M) for 60 minutes caused a significant increase in MLCP, on average, by 38 +/- 6% above control (P less than 0.0005), while cells exposed to Cs in the presence of EtA increased MLCP significantly less, by only 15 +/- 9%. These data provide further evidence for Et's long-lasting cellular actions, and demonstrate inhibitory effects of an Et receptor antagonist after direct cellular exposure to Et and also after Cs exposure, a pathophysiologic setting which likely involves Et.

Renal Damage in the SHR/N-cp Type 2 Diabetes Model: Comparison of an Angiotensin-Converting Enzyme Inhibitor and Endothelin Receptor Blocker

“…Of particular interest in this context are mesangial cells, because in rat (Takeda et al, 1992) and human (Goruppi et al, 2002;Orth et al, 2000) mesangial cell cultures, ET-1 is a potent stimulator of mesangial cell proliferation. In diabetic SHR/N-cp animals, glomerular ET-1 protein expression was also increased.…”

“…Renal cells produce ET-1 (Marsen et al, 1994), and cultured glomerular endothelial cells express ET B receptors (Hori et al, 1992). Furthermore ET A receptors are expressed in cultured mesangial cells (Takeda et al, 1992), and functional ET A receptors are also found on podocytes (Rebibou et al, 1992). This raises the issue of whether ET-receptor blockers (ET-RB) are beneficial, but the literature on their effects in diabetic nephropathy is controversial.…”

ATP-induced calcium mobilization in glomerular mesangial cells is mediated by P2U purinoceptor

“…Since proliferative response and contractile property are the most important functional characteristics in GMC, further studies concerning the effect of ATP on contractile property such as myosin light chain phosphorylation in GMC should be performed as we have done with endothelin (14) and arginine vasopressin (18). In conclusion, ATP induces calcium mobilization via P2u purinoceptor in GMC.…”

“…labeled mouse P2u cDNA and rat P2Y cDNA and sequencing. characterized not only pharmacologically, but also at molecular level (14,15,17,18). Nevertheless, P2 purinoceptor subtype in GMC has never been clearly defined yet.…”

“…All other chemicals were of the analytical grade from commercial sources. Mesangial cell culture: GMC were isolated from glomeruli of rat kidneys as previously described by us (14,15). GMC were maintained in RPMI-1640 supplemented with 20% FBS, 0.08 U/ml insulin, 100 U/ml penicillin, 100 gg/ml streptomycin, and 0.25 gg/ml fungizone at 37°C in 5% CO2 and 95% air.…”