Functional coupling expression of COX-2 and cPLA2 induced by ATP in rat vascular smooth muscle cells: Role of ERK1/2, p38 MAPK, and NF-κB

Abstract

AimsVascular smooth muscle cells (VSMCs) that function as synthetic units play important roles in inflammatory diseases such as atherosclerosis and angiogenesis. As extracellular nucleotides such as ATP have been shown to act via activation of P2 purinoceptors implicated in various inflammatory diseases, we hypothesized that extracellular nucleotides contribute to vascular diseases via upregulated expression of inflammatory proteins, such as cyclooxygenase (COX-2) and cytosolic phospholipase A2 (cPLA2) in VSMCs.Methods and resultsWestern blotting, promoter assay, RT-PCR, and PGE2 immunoassay revealed that ATPγS induced expression of COX-2 and prostaglandin (PGE2) synthesis through the activation of p42/p44 MAPK (mitogen-activated protein kinase), p38 MAPK, and nuclear factor-κB (NF-κB). These responses were attenuated by inhibitors of MAPK/ERK kinase (MEK1/2; U0126), p38 MAPK (SB202190), and NF-κB (helenalin), or by tranfection with dominant negative mutants of p42, p38, IκB kinase (IKK)α, and IKKβ. Furthermore, the ATPγS-stimulated translocation of NF-κB into the nucleus and degradation of IκBα was blocked by U0126 and helenalin. In addition, the ATPγS-stimulated cPLA2 expression was inhibited by U0126, SB202190, helenalin, celecoxib (a selective COX-2 inhibitor), and PGE2 receptor antagonists (AH6809, GW627368X, and SC-19220). However, the inhibitory effect of celecoxib on cPLA2 expression was reversed by addition of exogenous PGE2.ConclusionOur results suggest that in VSMCs, activation of p42/p44 MAPK, p38 MAPK, and NF-κB is essential for ATPγS-induced COX-2 expression and PGE2 synthesis. Newly synthesized PGE2 was observed to act as an autocrine signal contributing to cPLA2 expression, which may be implicated in inflammatory responses. Collectively, our findings provide insights into the correlation between COX-2 and cPLA2 expression in ATPγS-stimulated VSMCs with similar molecular mechanisms and functional coupling to amplify the occurrence of vessel disease-related vascular inflammation.