ALPHA-TOCOPHEROL PREVENTS CYCLOSPORINE A-MEDIATED ACTIVATION OF PHOSPHOLIPASE A(2) AND INHIBITION OF NA+,K+-ADENOSINE TRIPHOSPHATASE-ACTIVITY IN CULTURED HAMSTER RENAL TUBULAR CELLS

At concentrations of 0.5 mu M and upward, cyclosporin A (CsA) caused dose-related inhibition of the growth of a hamster renal tubular cell line (HAK ATCC; CCL15) in vitro. Inhibition of cell growth was due to the cytotoxic properties of CsA which were associated with enhancement of activity of phospholipase A(2) (PLA(2)) according to the increased generation of arachidonic acid and lysophosphatidylcholine (LPC). Arachidonate per se, at concentrations of up to 20 mu M, did not affect the growth of HAK cells, while cyclooxygenase and 5-lipoxygenase inhibitors failed to protect the cells against the antiproliferative effects of CsA. However, LPC caused dose-related inhibition of the growth of HAK cells. Moreover, coincubation with lysophospholipase or alpha-tocopherol (AT, vitamin E), a PLA(2) inhibitory and lysophospholipid-complexing agent, protected the HAK cells against both CsA and LPC. The Na+, K+-ATPase activity of HAK cells was also inhibited by CsA, with the enzyme being protected by inclusion of AT or lysophospholipase. Increased activity of PLA(2) and inhibition of Na+, K+(-)ATPase preceded cytotoxicity and cytolysis. Excessive production of lysophospholipids and consequent inhibition of Na+, K+-ATPase in renal tubular cells is a possible mechanism of CsA-induced nephrotoxicity. The protective effects of AT suggest that this agent may be clinically useful in preventing the renal side effects of CsA. (C) 1994 Academic Press, Inc.