Effect of pyruvate on oxidant injury to isolated and cellular DNA

Abstract

Drawing upon the capacity of pyruvate to detoxify H2O2, we demonstrate that pyruvate (i) protects against H2O2-dependent, hydroxyl radical-mediated degradation of isolated DNA; (ii) reduces the amount of 8-hydroxy-2-deoxyguanosine detected following oxidative injury to isolated DNA and (iii) diminishes the amounts of detectable hydroxyl radical generated by a H2O2-dependent system. Compared to mannitol, pyruvate protects weakly against oxidative degradation of DNA induced by a H2O2-independent, hydroxyl radical-generating system. The protective effects of pyruvate against H2O2-instigated DNA damage were also evinced in cells in culture exposed to H2O2. In contrast to its protective effects against H2O2-dependent injury to DNA, pyruvate failed to offer convincing protection to another intracellular, H2O2-vulnerable target, glyceraldehyde-3-phosphate dehydrogenase. The protection conferred by pyruvate to intracellular H2O2-vulnerable targets is thus influenced by the nature of the target exposed to H2O2. Pyruvate was markedly protective in a model of cytotoxicity induced by the concomitant depletion of cellular glutathione and inhibition of catalase activity; pyruvate can thus function as an intracellular antioxidant and in this latter model, no evidence of DNA damage was observed. Pyruvate, in contrast to catalase, is a potent protector against cytotoxicity induced by organic peroxides, a finding that cannot be explained by the scavenging of organic peroxides, differences in glutathione content or attenuation in oxidative injury to DNA. We conclude that while DNA damage is a key pathogenetic event in oxidative stress induced by H2O2, such nuclear changes may not universally subserve a critical role in models of H2O2-dependent cell death. We also conclude that the antioxidant capabilities of pyruvate extend beyond scavenging of H2O2 to include potent protection against cytotoxicity induced by organic peroxides.

Oxidative Stress and Induction of Heme Oxygenase-1 in the Kidney in Sickle Cell Disease

“…To examine further the contribution of alterations in cellular redox to the complications of sickle cell disease, we decreased renal thiol content by administering BSO, an inhibitor of the synthesis of glutathione 26 ; glutathione represents the dominant thiol in tissues. Using this manipulation, we demonstrate marked effects in sickle but not control mice: the kidney in the sickle mouse, exposed to the glutathione-depleting agent, BSO, exhibited extension of vascular congestion from the inner medulla (where RBC congestion is normally exhibited in this unstressed transgenic sickle kidney) into the outer medulla, cortical capillaries, and glomerular capillaries.…”

“…Thiol content was determined by the method based on the reduction of the Ellman reagent, 5,5Ј-dithiobis (2-nitrobenzoic acid), as previously described. 26 …”

Renal Cortical Pyruvate as a Potentially Critical Mediator of Acute Kidney Injury

“…Seminal studies by Nath and colleagues pointed out that, as an α-ketoacid, pyruvate is capable of scavenging hydrogen peroxide by undergoing decarboxylation and yielding CO 2 and water [2,3]. The relevance of this pathway is that oxidative stress is a key determinant of most forms of acute as well as chronic kidney injury [4].…”

Renal Cortical Pyruvate Depletion during AKI

“…For example, studies by Salahudeen et al 1 and Nath et al 2 showed that pyruvate is a potent H 2 O 2 scavenger, which was assessed in an in vitro system. Furthermore, Salahudeen et al 1 and Nath et al 2 reported that pyruvate administration decreased renal injury after intrarenal H 2 O 2 injection and during the course of the glycerol model of rhabdomyolysisinduced ARF.…”