Background: Ethanol exposure leads to changes of cell proliferation in a variety of cell types. However, how ethanol affects the proliferation of renal proximal tubule cells is not known. Methods: To examine the effect of ethanol on cell proliferation and its related signaling pathway, [H-3]thymidine incorporation, release of [H-3]arachidonic acid (AA), and Western blotting of protein kinase C (PKC)/mitogen-activated protein kinase (MAPK) were performed in primary cultured rabbit renal proximal tubule cells. Results: Ethanol inhibited [H-3]thymidine incorporation in a time- and dose-dependent manner. An inhibitory effect of ethanol on [3 H]thymidine incorporation was predominantly observed after 12 hr of treatment with 100 mM ethanol. Ethanol increased AA release and prostaglandin E-2 production. In addition, ethanol-induced inhibition of [H-3]thymidine incorporation was blocked by phospholipase A(2) inhibitors and was significantly blocked by PKC inhibitors. Indeed, ethanol induced a PKC translocation from the cytosolic to the membrane fraction. In addition, ethanol-induced inhibition of [3 H]thymidine incorporation was blocked by PD 98059 (a p44/42 MAPK inhibitor), but not by SB 203580 (a p38 MAPK inhibitor), and ethanol increased the phosphorylation of p44/42 MAPK. Results of phosphorylated p44/42 MAPK by ethanol were consistent with those of [H-3]thymidine incorporation and [H-3]AA-release experiments. Conclusions: Ethanol inhibited [H-3]thymidine incorporation via PKC, p44/42 MAPK, and phospholipase A2 signaling pathways in primary cultured renal proximal tubule cells.
