SB203580 reverses adrenomedullin's effect on proliferation and apoptosis in cultured mesangial cells

Adrenomedullin is a potent vasodilatory peptide that has a variety of effec ts in a number of different systems including kidney. In cultured rat glome rular mesangial cells adrenomedullin increases cAMP, decreases proliferatio n and increases apoptosis. Associated with the anti-proliferative and apopt otic effects, adrenomedullin also causes a decrease in extracellular signal -regulated kinase2 (ERK2) and an increase in cJun N-terminal kinase1 (JNK1) and P38 mitogen-activated protein kinase (P38 MAPK) activities. The purpos e of the present study was to examine the role of P38 MAPK on adrenomedulin -mediated inhibition of [H-3]thymidine incorporation tan index of prolifera tion) and on adrenomedullin-stimulated nucleosome-associated cytoplasmic DN A fragmentation tan index of apoptosis) in mesangial cells, using a selecti ve inhibitor of P38 MAPK, SB203580 ([4-(4-fluorophenyl)-2-(4-methylsulfinyl phenyl)-5-(4-pyridyl)1 H-imidazole), and also to characterize the proximal signal transduction pathways of the three MAPKs in relation to [H-3]thymidi ne incorporation and cytoplasmic DNA fragmentation using a phosphotidyl ino sitol-3-kinase inhibitor, wortmannin {[1S-(1 alpha,6b alpha,9a beta, 11 alp ha,11b beta)]-11-(acetyloxy)-1,6b,7,8,9a,10,11,11 b-octahydro-1-(methoxymet hyl)-9a,11b-dimethyl-3H-furo[4,3,2-de]indeno[4,5-h]-2-benzopyran-3,6,9-trio ne), SB203580 significantly reversed the effects of adrenomedullin on [H-3] thymidine incorporation and cytoplasmic DNA fragmentation, and inhibited on ly P38 MAPK activity. It had no effect on]ERK2 and JNK1 activities. Wortman nin, on the other hand, inhibited only adrenomedullin-stimulated cytoplasmi c DNA fragmentation and did not affect adrenomedullin-mediated inhibition o f [H-3]thymidine incorporation. Wortmannin also inhibited adrenomedullin-st imulated P38 MAPK activity without affecting ERK2 and JNK1 activities. Thes e results indicate that: (a) In rat mesangial cells adrenomedullin-mediated inhibition of [H-3]thymidine incorporation and stimulation of nucleosome-a ssociated cytoplasmic DNA fragmentation are sensitive to SB203580, and (b) adrenomedullin activates a P38 MAPK through a wortmannin-sensitive kinase. The data using SB203580 suggest an important physiological role for P38 MAP K in rat mesangial cell proliferation and apoptosis. (C) 1999 Elsevier Scie nce B.V. All rights reserved.