5-Hydroxytryptaime induces cyclooxygenase-2 in rat vascular smooth muscle cells: Mechanisms involving Src, PKC and MAPK activation

Considering the importance of 5-hydroxytryptamine (5-HT) and cyclooxygenase (COX) products in vascular pathology, we investigated the effects of 5-HT on COX expression in rat vascular smooth muscle cells (VSMCs), and to provide mechanistic insights into these effects. VSMCs were enzymatically isolated from aortic media of Wistar rats. Incubation of VSMCs with 5-HT for 24 h stimulated prostaglandin I2 production, but this stimulation was completely suppressed by NS-398, a selective COX-2 inhibitor. 5-HT induced transient COX-2, but not COX-1, protein and mRNA expression in concentration- and time-dependent manners. This effect of 5-HT was completely inhibited by sarpogrelate, a 5-HT2A receptor antagonist. 5-HT-induced COX-2 expression was markedly blunted by Ca2+ depletion; GF 109203X, a protein kinase C (PKC) inhibitor; PP2, an inhibitor of Src-family tyrosine kinase (Src); PD 98059, an inhibitor of extracellular signal-regulated kinase (ERK) activation; SB 203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK); and SP 600125, an inhibitor of c-Jun N-terminal kinase (JNK). 5-HT activated ERK and p38 MAPK, followed by JNK activation. PP2 inhibited these activations, while GF 109203X inhibited only JNK activation. Furthermore, PD 98059 inhibited JNK activation. These results suggest that 5-HT induces COX-2 expression in rat VSMCs, and that PKC, Src, and MAPK activation are each essential for the full expression of COX-2 pathways.