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Abstract #15833 Published in IGR 2-3
Mitogen-activated protein kinase inhibitors suppress prostaglandin F(2α)-induced myosin-light chain phosphorylation and contraction in iris sphincter smooth muscle
Yousufzai SY; Gao G; Abdel-Latif AAEuropean Journal of Pharmacology 2000; 407: 17-26
The purpose of this study was to investigate the potential role of mitogen-activated protein (MAP) kinase in contraction by monitoring MAP kinase phosphorylation (activation) and contraction during agonist stimulation of cat iris sphincter smooth muscle. Changes in tension in response to prostaglandin F(2α), latanoprost, a prostaglandin F(2α) analogue used as an anti-glaucoma drug, and carbachol were recorded isometrically, and MAP kinase activation was monitored by Western blot using a phosphospecific p42/p44 MAP kinase antibody. The authors found that treatment of the muscle with 2'-amino-3'-methoxyflavone (PD98059) (10 &mgr;M), a specific inhibitor of MAP kinase (MEK), inhibited significantly prostaglandin F(2α)- and latanoprost-induced phosphorylation and contraction, but had little effect on those evoked by carbachol. Prostaglandin F(2α) increased MAP kinase phosphorylation in a concentration-dependent manner with EC(50) value of 1.1 x 10(-8) M and increased contraction with EC(50) of 0.92 x 10(-9) M. The MAP kinase inhibitors PD98059, apigenin and 1,4-diamino-2,3-dicyano-1, 4bis(2-aminophenylthio)butadiene (UO126) inhibited prostaglandin F(2α)-induced contraction in a concentration-dependent manner with IC(50) values of 2.4, 3.0 and 4.8 &mgr;M, respectively. PD98059 had no effect on prostaglandin F(2α)- or on carbachol-stimulated inositol-1,4,5-trisphosphate (IP(3)) production. In contrast, the MAP kinase inhibitor inhibited prostaglandin F(2α)-induced myosin-light chain (MLC) phosphorylation, but had no effect on that of carbachol. N-[2-(N-(4-Chloro-cinnamyl)-N-methylaminomethyl)phenyl]-N-[2-hydroxye thyl]-4-methoxybenzenesulfonamide (KN-93) (10 &mgr;M), a Ca(2+)-calmodulin-dependent protein kinase inhibitor, and Wortmannin (10 &mgr;M), an MLC kinase inhibitor, inhibited significantly (by 80%) prostaglandin F(2α)- and carbachol-induced contraction. It can be concluded that in this smooth muscle p42/p44 MAP kinases are involved in the mechanism of prostaglandin F(2α)-, but not in that of carbachol, induced contraction. In addition, these data clearly indicate that the stimulation of the iris sphincter with prostaglandin F(2α) and carbachol activate two distinct pathways, the MAP kinase pathway and the Ca(2+) mobilization pathway.
Dr. S.Y. Yousufzai, Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA
Classification:
11.4 Prostaglandins (Part of: 11 Medical treatment)
