6-ketoprostaglandin-f1-alpha and phosphatidylethanol

Cardiac fibroblasts, as the source of extracellular matrix for the left ventricle, subserve important functions to cardiac remodeling and fibrotic development following myocardial infarction or with pressure-overload cardiac hypertrophy. The fibroblast may be the target cell for angiotensin-converting enzyme inhibitors (ACEI) that are cardioprotective and reverse collagen deposition and remodeling but whose mechanisms of action remain controversial. Because we previously documented phenotypic differences between cardiac fibroblasts from the spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) left ventricle, the present study evaluated whether phenotypic differences also exist in the release of endogenous arachidonic acid metabolites or in the activation of phospholipase D, and the importance of observed differences to the formation of collagen and the mechanism of action of ACEI. The experimental design compared endogenous sources of arachidonic acid with exogenous prelabeling of cells. Angiotensin II stimulated greater arachidonic acid release than bradykinin, and WKY cells were more responsive than SHR. The major prostanoid formed by cardiac fibroblasts was prostaglandin I2 (PGI2), with more prostacyclin production by WKY cells than SHR cells both under nonstimulated conditions and in response to angiotensin II or bradykinin. Beraprost, a PGI2 analogue, was shown to decrease growth rate and DNA synthesis of fibroblasts and to inhibit mRNA expression for collagen types I and III, with SHR cells being less responsive to beraprost than WKY cells. These results potentially implicate eicosanoid metabolism, particularly PGI2, in collagen formation, fibrotic development, and cardiac remodeling, and they imply that the SHR genetic hypertension model may be predisposed to excess cardiac fibrosis.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Arachidonic Acid; Cell Division; Chromatography, High Pressure Liquid; Collagen; Epoprostenol; Extracellular Matrix Proteins; Gene Expression; Glycerophospholipids; Male; Myocardium; Phosphatidic Acids; Rats; Rats, Inbred SHR; Rats, Inbred WKY

This study investigated the cellular mechanisms underlying the endothelin-1 (ET-1)-induced contraction of rat aorta with focus on the involvement of phospholipase D (PLD). Preincubating rat aorta in Ca(2+)-free solution reduced the contraction by 80%, whereas diltiazem (10 microM), a voltage-operated Ca2+ channel blocker, caused only a small reduction (27%, P less than 0.05) of the contraction. In myo-[3H]inositol-labeled aorta, ET-1 stimulated the formation of [3H]inositol bisphosphate and [3H]inositol trisphosphate, indicating the activation of phospholipase C (PLC). In aorta labeled with 32PO4, [3H] myristic acid or [32P]lyso-platelet-activating factor followed by exposure to ethanol (0.5%), ET-1 stimulated phosphatidylethanol (PEt) production, suggesting that ET-1 activates PLD. The PEt response was not attenuated by staurosporine (ST, 0.1 microM), an inhibitor of protein kinase C (PKC) but was inhibited by removal of Ca2+. The ET-1-induced PEt response was at least additive to that induced by phorbol 12-myristate 13-acetate (1 microM). ET-1 also stimulated the release of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) into the tissue medium. Unlike the PEt responses, the 6-keto-PGF1 alpha response could be inhibited by ST. Removal of Ca2+ abolished the response. These results suggest that 1) ET-1 activates multiple cellular mechanisms including PLC, PLD, and the arachidonate cascade; 2) PKC activation may not be essential for the ET-1 activation of PLD but may play an important role in the ET-1 stimulation of 6-keto-PGF1 alpha release; and 3) Ca2+ is an important factor in the ET-1-induced PLD activity and 6-keto-PGF1 alpha release.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Aorta; Calcium; Endothelins; Enzyme Activation; Glycerophospholipids; Hydrolysis; Male; Phosphatidic Acids; Phosphatidylinositols; Phospholipase D; Rats; Rats, Inbred Strains; Vasoconstriction