Cell death and lipid peroxidation in isolated hepatocytes incubated in the presence of hydrogen peroxide and iron salts

Abstract

The incubation of isolated hepatocytes in the presence of glucose plus glucose oxidase, a H₂O₂-generating system, resulted in extensive loss of cell viability, as expressed by the release of lactate dehydrogenase (LDH). Disturbance of metabolic functions such as glycogen and protein synthesis was also caused by H₂O₂, but in no case was malondialdehyde (MDA)-like products detected. The lytic effect of H₂O₂ was significantly enhanced by incubating hepatocytes in the presence of iron salts. Under these conditions, MDA-like products were detected, but lipid peroxidation and cell injury did not correlate. Iron chelators modulated the cytotoxicity of H₂O₂ in different (and opposite) ways: when iron was complexed with ADP, increased cell lysis was observed compared to uncomplexed iron plus H₂O₂. Iron-DTPA, on the contrary, decreased such a lytic effect. The preincubation of hepatocytes with desferrioxamine mesylate (Desferal; a strong iron chelator) abolished the cytolytic effects produced by the association of iron salts and H₂O₂, as well as the membrane oxidative injury due to H₂O₂ alone, thus suggesting the existence of an intracellular source of iron. This kind of mechanism (metal chelation rather than radical scavenging) is supported by the absence of any protective effect by some free radical scavengers against the oxidative injury induced by the association iron H₂O₂. Nevertheless, the glycogenolytic effects observed in the presence of H₂O₂ were not modified by Desferal. In our opinion, the cytotoxicity of the association H₂O₂ plus iron salts involves at least two different and independent mechanisms.