Oxidant-induced alveolar epithelial cell (AEC) apoptosis is implicated in mediating lung injury, fibrosis, and malignant transformation by mechanisms that are not fully established. We previously reported that oxidative stress (eg, amosite asbestos or H2O2) induces mitochondria-regulated AEC apoptosis and that overexpression of a mitochondria-targeted DNA repair enzyme, human 8-oxoguanine-DNA glycosylase 1 (mt-hOgg-1), is protective. In this study, we explore the mechanism underlying the protective effects of mt-hOgg-1 (kind gift of Dr. M. Gillespie). We find that the protective effects are not due to redox activity of mt-hOgg-1 since, compared with empty vector controls, mt-hOgg-1 overexpressing A549 cells did not alter asbestos-induced ROS production as assessed by either DCF fluorescence or an adenovirally expressed redox sensor (ro-GFP) targeted to the mitochondria. As expected, mt-hOgg-1 enhanced DNA repair assessed by an 8-oxoG incision assay (1.7 ± 0.2-fold vs control; p < .05). Both asbestos and H2O2 reduced mitochondria (mt)-aconitase activity and protein expression, but, notably, these effects were completely blocked in mt-hOgg-1 over-expressing A549 cells. Immunoprecipitation studies show that hOgg-1, similar to frataxin, coprecipitates with mt-aconitase. We also found that hOgg-1 mutants that completely lack 8-oxoguanine DNA repair activity (V317, Long AB; kind gift of Dr. V. Bohr) blocked oxidant-induced caspase 9 activation and DNA fragmentation comparable to wild-type hOgg-1. We conclude that mt-hOgg-1 has a dual function as a DNA repair protein as well as a mt-aconitase chaperone. These data suggest a novel role of Mt-hOgg-1 preservation of AEC mitochondria aconitase in the pathogenesis of oxidant-induced lung toxicity.
Funding: VA Merit Award (DK), NIH-HL67835-01 (GRSB).
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.