Up-regulation of heme oxygenase-1 as a resistance mechanism against MPP+ induced cytotoxicity in Raw 264.7 macrophages

To elucidate the effects of heme oxygenase-1 (HO-1) on a neurotoxic substance, 1-methyl-4-phenylpyridinium (MPP+), induced cytotoxicity in immune cells, cell death, and the production of reactive oxygen species (ROS) were studied using Raw 264.7 macrophages. HO-1 is induced by harmful stimuli including oxidative stress, and it exerts a protective effect against cytotoxicity in immune cells. Using Western blotting analysis, we have evaluated the expression of HO-1 in Raw 264.7 macrophages treated with MPP+. Via a WST assay and flow cytometric analysis, we have also evaluated the cytoprotective effect of HO-1 induction against the cytotoxicity induced by exposure to MPP+. In Raw 264.7 macrophage exposed MPP+ cells, HO-1 expression evidenced a rapid increase, peaking at 12 h. The increment of cell death and ROS production due to MPP+ exposure were aggravated further by treatment with Tin protoporphyrin-IX (SnPP-IX, HO-1 inhibitor). The increased cell death and ROS production induced by MPP+ exposure were recovered to a significant degree by treatment with Cobalt protoporphyrin-IX (CoPP-IX, HO-inducer). According to these results, HO-1 induction exerts a cytoprotective effect on MPP+-induced cytotoxicity, which is related to ROS production.