Effects and Interactions of Endothelin-1 and Angiotensin II on Matrix Protein Expression and Synthesis and Mesangial Cell Growth

Abstract Mesangial cell growth and accumulation of extracellular matrix proteins constitute key features of progressive glomerular injury. Endothelin-1 (ET-1) and angiotensin II (Ang II), two potent vasoconstrictor agents, evoke a number of similar responses in mesangial cells. In rat mesangial cells, we compared ET-1 and Ang II effects on matrix protein production and cell proliferation as well as the potential interaction between the two hormones. When cells in 0.5% fetal calf serum were incubated for 24 hours with various concentrations of ET-1 or Ang II, both peptides stimulated, in a dose-dependent manner, fibronectin and type IV collagen mRNA expression, fibronectin synthesis, and mitogenesis. Incubation with specific receptor antagonists of both hormones demonstrated that endothelin subtype A (ET A ) and angiotensin type 1 (AT 1 ) receptors were involved. Preincubation of cells with two different protein kinase C inhibitors or with a neutralizing anti–transforming growth factor-β antibody, but not an unrelated IgG, diminished the peptide-induced fibronectin synthesis. A dual interrelation seems to exist between ET-1 and Ang II. Thus, the AT 1 receptor antagonist losartan and the angiotensin-converting enzyme inhibitors quinaprilat and captopril diminished the ET-1–mediated effects, whereas the ET A receptor antagonist BQ-123 diminished the Ang II–induced fibronectin synthesis and mesangial cell proliferation. Our results suggest that ET-1 and Ang II stimulate matrix protein synthesis and mesangial cell mitogenesis through ET A and AT 1 receptors, respectively, by complicated mechanisms, implicating protein kinase C activation, synthesis of transforming growth factor-β, and release of one peptide by the other. These data could be important for a better understanding of the participation of vasoactive substances in the pathogenesis of glomerulosclerosis.