Background. Ischemia by itself can trigger cell killing, and reperfusion accelerates the process. Many studies have demonstrated that HIF-1Α play an important role in mitochondrial metabolism from I/R injury. However, the mechanism of its pleiotropic effect remains unclear. So we investigating mt-DNA encoded gene expression to evaluate relationships between HIF-1Α and mitochondrial in I/R injury.
Methods. An immortalized proximal tubule epithelial cell line (HK-2) cells were exposed to 1% O2 for 16hours before reoxygenation for 3hours. Experiment includes five groups:H/R+PHD2 siRNA group (I), H/R+ nontargeting siRNA control group(II), H/R+PHD2 siRNA+L-NIL [the selective iNOS inhibitor] group (III), H/R group(IV), untreated control group (V). The number of viable cells was used estimate the degree of necroptosis. Mitochondrial integrity (JC-1) and activated caspase 3 activities was used estimate the degree of apoptosis. The level of ATP and cytochrome-c oxidase (COX) activity was used estimate the mitochondrial function. Protein and mRNA levels of HIF-1Α, iNOS, PGC-1 alpha, mtDNA-encoded genes CytOxI, were analyzed separately by real-time PCR and western blot.
Results. We found in group(I), hypoxia 16h mediated inhibition of mitochondrial coded CytOxI mRNA, but it increase under reoxygenation for 3h, and the protein response is reversible, but the degree of necroptosis, apoptosis and the mitochondrial function statistically significant compared with group(IV),and closer to the normal group(V), these protective effects were abolished by L-NIL group(III). PHD2 siRNA increased HIF-1 alpha accumulation, and also mRNA and protein expressions of its downstream gene iNOS. Moreover, NO induces mitochondrial biogenesis by up-regulation of PGC-1Α (which was a key regulator of mitochondrial ATP production).
Conclusion. The result indicating a statistically significant correlation between decreased CytOxI protein expression and apoptosis resistance in H/R+PHD2 siRNA group, that means CytOxI which acts as a seed around which the full complex is assembled might present a mt-protein antigens in ischemia/reperfusion allograft injury. Taken together, Upregulation of HIF-1Α by PHD2 siRNA significantly protect mitochondrial survival mechanisms and tends to restore the original enzyme level, leading to reduced apoptosis and necroptosis from I/R-related stress simultaneously.
To cite this abstract in AMA style:Guo Y, Feng L, Zhou Y, Xia M, Sun G, Li S, Long D, Li Y. Protects Effect of HIF-1α in Ischemia/Reperfusion-Induced Mitochondrial Injury, The [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/protects-effect-of-hif-1-in-ischemiareperfusion-induced-mitochondrial-injury-the/. Accessed January 29, 2020.
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