Hyperbaric Oxygen Reduces Oxidative Stress Impairment and DNA Damage and Simultaneously Increases HIF-1α in Ischemia-Reperfusion Acute Kidney Injury

The central exacerbating factor in the pathophysiology of ischemic-reperfusion acute kidney injury (AKI) is oxidative stress. Lipid peroxidation and DNA damage in ischemia are accompanied by the formation of 3-nitrotyrosine, a biomarker for oxidative damage. DNA double-strand breaks (DSBs) may also be a result of postischemic AKI. gamma H2AX(S139) histone has been identified as a potentially useful biomarker of DNA DSBs. On the other hand, hypoxia-inducible factor (HIF) is the "master switch" for hypoxic adaptation in cells and tissues. The aim of this research was to evaluate the influence of hyperbaric oxygen (HBO) preconditioning on antioxidant capacity estimated by FRAP (ferric reducing antioxidant power) and ABTS (2,2 '-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, as well as on oxidative stress parameter 3-nitrotyrosine, and to assess its effects on gamma H2AX(S139), HIF-1 alpha, and nuclear factor-kappa B (NF-kappa B) expression, in an experimental model of postischemic AKI induced in spontaneously hypertensive rats. The animals were divided randomly into three experimental groups: sham-operated rats (SHAM, n = 6), rats with induced postischemic AKI (AKI, n = 6), and group exposed to HBO preconditioning before AKI induction (AKI + HBO, n = 6). A significant improvement in the estimated glomerular filtration rate, eGFR, in AKI + HBO group (p < 0.05 vs. AKI group) was accompanied with a significant increase in plasma antioxidant capacity estimated by FRAP (p < 0.05 vs. SHAM group) and a reduced immunohistochemical expression of 3-nitrotyrosine and gamma H2AX(S139). Also, HBO pretreatment significantly increased HIF-1 alpha expression (p < 0.001 vs. AKI group), estimated by Western blot and immunohistochemical analysis in kidney tissue, and decreased immunohistochemical NF-kappa B renal expression (p < 0.01). Taking all of these results together, we may conclude that HBO preconditioning has beneficial effects on acute kidney injury induced in spontaneously hypertensive rats.