Role of protein kinase C in NADPH oxidase derived O2•--mediated regulation of KV-LVOCC axis under U46619 induced increase in [Ca2+]i in pulmonary smooth muscle cells

Treatment of bovine pulmonary smooth muscle cells with the TxA(2) mimetic, U46619 stimulated [Ca2+](i), which was inhibited upon pretreatment with apocynin (NADPH oxidase inhibitor). Pretreatment with cromakalim (K-V channel opener) or nifedepine (L-VOCC inhibitor) inhibited U46619 induced increase in [Ca2+](i), indicating a role of K-V-LVOCC axis in this scenario. Neither cromakalim nor nifedepine inhibited U46619 induced increase in NADPH oxidase activity, suggesting that the NADPH oxidase activation is proximal to the K-V-LVOCC axis in the cells. Pretreatment with calphostin C (PKC inhibitor) markedly reduced U46619 induced increase in NADPH oxidase activity and [Ca2+](i) in the cells. Calphostin C pretreatment also markedly reduced p(47phox) phosphorylation and translocation to the membrane and association with p(22phox), a component of Cyt.b(558) of NADPH oxidase in the membrane. Overall, PI(C plays an important role in NADPH oxidase derived O-2(center dot-)-mediated regulation of K-V-LVOCC axis leading to an increase in [Ca2+](i) by U46619 in the cells. (C) 2009 Elsevier Inc. All rights reserved.