Effect of alpha Ni3S2 on arachidonic acid metabolites in cultured human lung cells (L132 cell line).

Our previous investigations have shown evidence of an interaction between alpha Ni3S2 and membranous and cellular lipids of lung cells with a significant increase in the linoleic, linolenic and arachidonic acid pool. The present work is designed to follow the metabolic fate of arachidonic acid in alpha Ni3S2-exposed human embryonic pulmonary epithelial cells (L132) in culture (50 microM alpha Ni3S2 for 3 days). The metabolites of arachidonic acid were assessed by HPLC determination coupled with UV or electrochemical detection. We determined malondialdehyde (MDA), hydroxyeicosatetraenoic acid (HETE), leukotrienes (LT) and reduced glutathione (GSH). In exposed cells we observed a significant increase of MDA, which is a breakdown product of lipid peroxidation. In addition, we noted significant increases of 5-HETE and 15-HETE in L132 cells resulting from the enzymatic reduction of 5-HPETE and 15-HPETE respectively. There was also a simultaneous decrease of GSH--confirmed by a strong decrease of GSH in exposed cells with respect to controls. 5-HPETE is furthermore converted to epoxides such as leukotriene A4 and we also quantified in exposed cells a significant increase of its subsequent catabolites LTB4, LTC4 and LTE4. These investigations show clearly that exposure of L132 cells to alpha Ni3S2 enhances lipid peroxidation based upon direct measurements of MDA and other metabolites of arachidonic acid. This lipid peroxidation is an autocatalytic free-radical process and could be responsible for DNA damage.