advertisement
Abstract #6486 Published in IGR 3-2
Effects of prostaglandin F2α and carbachol on MAP kinases, cytosolic phospholipase A2 and arachidonic acid release in cat iris sphincter smooth muscle cells
Husain S; Abdel-Latif AAExperimental Eye Research 2001; 72: 581-590
The signal transduction pathways initiated by Ca2+-mobilizing agonists, such as prostaglandin F2α (PGF2α) and carbachol (CCh), leading to activation of cytosolic phospholipase A2 (cPLA2) and arachidonic acid (AA) release in a wide variety of tissue remain obscure. To further define the role of protein kinases in receptor mediated stimulation of cPLA2 and consequently AA release, the authors investigated the role of mitogen-activated protein (MAP) kinases and protein kinase C (PKC) in PGF2α- and CCh-induced cPLA2 phosphorylation and AA release in cat iris sphincter smooth muscle (CISM) cells. The cells were prelabelled with [3H]AA for 24 hours, and incubated in the absence or presence of the agonist for five to ten minutes as indicated. MAP kinases activities and cPLA2 phosphorylation were determined in immunoprecipitates obtained by using anti-p38 MAP kinase and anti-cPLA2 antibodies. The authors found that: (a) PGF2α and CCh increase p38 MAP kinase activity by 197 and 215%, respectively, and increased p42/p44 MAP kinase activity by 200 and 125%, respectively; (b) SB202190, a p38 MAP kinase specific inhibitor, inhibited PGF2α- and CCh-induced cPLA2 phosphorylation by 92 and 85%, respectively, and AA release by 62 and 78%, respectively; (c) PD98059, a p42/p44 MAP kinase inhibitor, inhibited CCh-induced cPLA2 phosphorylation by 70% and AA release by 71%, but had no effect on that of PGF2α; (d) inhibition of PKC activity by p31-8220 inhibited both PGF2α- and CCh-stimulation of p38 MAP kinase, p42/p44 MAP kinases and cPLA2 phosphorylation. The authors conclude from these results that, in CISM cells, PGF2α-induced cPLA2 phosphorylation and AA release is mediated through p 38 MAP kinase, but not through p42/p44 MAP kinases, whereas that of CCh is mediated through both p38 MAP kinase and p42/p44 MAP kinases. These effects of PGF2α and CCh are regulated by the MAP kinases in a PKC-dependent manner. Studies aimed at elucidating the role of protein kinases in the coupling mechanism between the activation of PGF2α and muscarinic receptors, and the stimulation of cPLA2 and AA release in the smooth muscles of the iris-ciliary body will provide important information about the role of protein kinases signalling pathways in smooth muscle function, as well as about the mechanism of the intraocular pressure-lowering effects of PGF2α and its analogue, latanoprost, in glaucoma therapy.
Dr S. Husain, Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA
Classification:
11.4 Prostaglandins (Part of: 11 Medical treatment)
