Lysophosphatidylcholine induces taurine release from HeLa cells

The putative role of lysophospholipids in activation and regulation of the volume-sensitive taurine efflux was investigated in HeLa cells using tracer technique. Lysophosphatidylcholine (LPC, 10 mu M) with oleic acid increase d taurine efflux during hypotonic and isotonic conditions. Substituting pal mitic or stearic acid for oleic acid enhanced taurine release during isoton ic conditions, whereas ethanolamine, serine or inositol containing lysophos phslipids were ineffective. High concentrations of LPC (25 mu M) induced Ca 2+ influx, loss of adenosine nucleotides, taurine and the Ca2+-sensitive pr obe Fura-2, and thus reflected a general breakdown of the membrane permeabi lity barrier. Low concentrations of LPC (5-10 mu M) solely induced taurine efflux. The LPC-induced taurine release was unaffected by anion channel blo ckers (DIDS, MK196) and the 5-lipoxygenase inhibitor ETH 615-139, which all blocked the volume sensitive taurine efflux. Furthermore, LPC-induced taur ine release was reduced by antioxidants (NDGA, vitamin E) and the protein t yrosine kinase inhibitor genistein. The swelling-induced taurine efflux was in the absence of LPC unaffected by vitamin E, blocked by genistein, and i ncreased by H2O2 and the protein tyrosine phosphatase inhibitor vanadate. I t is suggested that low concentrations of LPC permeabilizes the plasma memb rane in a Ca2+-independent process that involves generation of reactive oxy gen species and tyrosine phosphorylation, and that LPC is not a second mess enger in activation of the volume sensitive taurine efflux in HeLa cells.