Endothelin-1 (ET-1) has been characterized as a potent vasoconstrictor secreted by the endothelium, and play a major role in the regulation of vascular tone. It has been also known to participate in inflammatory reactions. The production of ET-1 by macrophages during infection and inflammation is related to tissue perfusion and leukocyte extravasation. The aim of this study is to investigate the role of IL-8/CXCL8, as a major inflammatory chemokine, for ET-1 expression in macrophges. Expression of ET-1 mRNA in mouse peritoneal macrophages (PeM phi) was weaker than that in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). However, expression of IL-8/CXCL8-induced ET-1 mRNA in PeM phi was much more stronger than that in SHR and WKY VSMCs. Maximum expression of ET-1 mRNA was observed at 50 ng/ml dose of IL-8/CXCL8 and occurred at 2 h after addition of IL-8/CXCL8. Expression of ET-1 by IL-8/CXCL8 was dependent on NF-kappaB activation and ERK1/2 phosphorylation. Baicalein, a 12-lipoxygenase (LO) inhibitor, inhibited the expression of IL-8/CXCL8-induced ET-1 mRNA. This inhibitory action of baicalein was mediated via ERK1/2 inactivation. Induction of 12-LO mRNA by IL-8/CXCL8 and expression of ET-1 mRNA by 12-LO metabolite, 12(S)-HETE were also detected. The expression of IL-8/CXCL8-induced ET-1 mRNA was not detected in PeM phi transfected with 12-LO siRNA. These results suggest that IL-8/CXCL8 can act as one of main inducers of ET-1 in vascular inflammatory reactions, and ET-1 expression by IL-8/CXCL8 is related to 12-LO pathway in PeM phi.