PHARMACOLOGICAL PROTECTION AGAINST THE CYTOTOXICITY INDUCED BY 6-HYDROXYDOPAMINE AND H2O2 IN CHROMAFFIN CELLS

We present in this report the characteristics of the damage induced by 6-hydroxydopamine and H2O2 on bovine chromaffin cells in primary cult ure. Cytotoxicity was quantified using catecholamine cell contents, la ctate dehydrogenase (LDH) release, trypan blue exclusion and morpholog ical appearance. An excellent correlation between these four parameter s was found. The cytotoxic effects of 6-hydroxydopamine were Ca2+-inde pendent. In spite of this, the Ca2+ channel antagonists R56865 tyl)]-4 -piperidinyl-N-methyl-2-benzo-thiazolamine) and lidoflazine exhibited marked cytoprotective effects against both 6-hydroxydopamine and H2O2. The selective dopamine uptake blocker, bupropion, increased the viabi lity of 6-hydroxydopamine and H2O2-treated cells from 20% to around 80 %. Catalase drastically protected against the cytotoxic effects of 6-h ydroxydopamine and H2O2. In contrast, desferrioxamine gave better prot ection against H2O2 cytotoxicity; glutathione and N-acetylcysteine onl y afforded substantial protection against 6-hydroxydopamine. Three mai n conclusions emerge from this study. (Ist) 6-Hydroxydopamine causes c hromaffin cell damage via a mechanism probably related to the producti on of free radicals, but unrelated to Ca2+ ions. Cytoprotection afford ed by R56865 and lidoflazine must be unrelated to their Ca2+ antagonis t properties. This suggests a novel component in the cytoprotective me chanism of action of these drugs. (2nd) The strong cytoprotective effe cts of bupropion seem to be unrelated to its ability to block the plas malemmal dopamine carrier. (3rd) Bovine adrenal chromaffin cells in pr imary cultures are a suitable model for adult neurons to study the bas ic mechanism of cell damage, and to screen new drugs with putative neu roprotective properties.