Cross-talk between p(38)MAPK and G(i)alpha in regulating cPLA(2) activity by ET-1 in pulmonary smooth muscle cells

摘要

Endothelin-1 (ET-1) is known as the most potent vasoconstrictor yet described. Infusion of ET-1 into isolated rabbit lung has been shown to cause pulmonary vasoconstriction with the involvement of arachidonic acid metabolites. Given the potency of arachidonic acid metabolites, the activity of phospholipase A(2) must be tightly regulated. Herein, we determined the mechanisms by which ET-1 stimulates cPLA(2) activity during ET-1 stimulation of bovine pulmonary artery smooth muscle cells. We demonstrated that (i) treatment of bovine pulmonary artery smooth muscle cells with ET-1 stimulates cPLA(2) activity in the cell membrane; (ii) ET-1 caused increase in O (2) (center dot-) production occurs via NADPH oxidase-dependent mechanism; (iii) ET-1-stimulated NADPH oxidase activity is markedly prevented upon pretreatment with PKC-zeta inhibitor, indicating that PKC-zeta plays a prominent role in this scenario; (iv) ET-1-induced NADPH oxidase-derived O (2) (center dot-) stimulates an aprotinin sensitive protease activity due to prominent increase in [Ca2+](i); (v) the aprotinin sensitive protease plays a pivotal role in activating PKC-alpha, which in turn phosphorylates p(38)MAPK and subsequently G(i)alpha leading to the activation of cPLA(2). Taken together, we suggest that cross-talk between p(38)MAPK and G(i)alpha with the involvement of PKC-zeta, NADPH oxidase-derived O (2) (center dot-) , [Ca2+](i), aprotinin-sensitive protease and PKC-alpha play a pivotal role for full activation of cPLA(2) during ET-1 stimulation of pulmonary artery smooth muscle cells.