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Kidney Week

Abstract: TH-PO110

Arginase 2 as a Mediator of Ischemia-Reperfusion Injury in the Kidney Through Regulation of Nitrosative Stress

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Hara, Masatoshi, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Fukuoka, Japan
  • Torisu, Kumiko, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Fukuoka, Japan
  • Kawai, Yasuhiro, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Fukuoka, Japan
  • Tsuruya, Kazuhiko, Nara Medical University, Kashihara, Japan
  • Nakano, Toshiaki, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Fukuoka, Japan
  • Kitazono, Takanari, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Fukuoka, Japan
Background

Arginase 2 (Arg2) is expressed exclusively in the kidney and catabolizes the hydrolysis of L-arginine, which is common substrate for nitric oxide synthase, to produce L- ornithine and urea. There were several reports that administration of arginase blockade protected hepatic and myocardial ischemia-reperfusion injury. However, the role of Arg2 for renal ischemia-reperfusion injury is still poorly unknown.

Methods

Human renal tubular epithelial cells, (HK-2 cells) were cultured under 6-hour hypoxic condition (1% O2) and subsequent 24-hour reoxygenation (21% O2) (H/R). To knockdown Arg2, cells were transfected with Arg2 siRNA. Eight to ten week-old wild type (WT) and Arg2 knockout (Arg2KO) male mice were subjected to clamping of bilateral renal pedicles for 28 minutes and euthanized 24 hours after reperfusion (I/R).

Results

The level of Arg2 mRNA and ARG2 protein was increased at 24 h after I/R in mouse kidney. Immunohistochemistry revealed that ARG2 was localized specifically in renal proximal tubules and increased after I/R. In HK-2 cells, the immunofluorescent signals of ARG2 were significantly elevated after H/R. ARG2 distributed in a punctate pattern throughout the cytoplasm and partly colocalized with mitochondrial marker. Arg2 knockdown in HK-2 cells resulted in attenuated 3-nitorotyrosine (3-NT) formation after H/R, though the extent of apoptosis was not changed. Arg2KO mice were markedly resistant to ischemic kidney injury as measured by serum urea nitrogen (WT 150 ± 23 vs Arg2KO 106 ± 34 mg/dL, p <0.05) and creatinine (WT 1.06 ± 0.65 vs Arg2KO 0.43 ± 0.45 mg/dL, p <0.05). The level of 3-NT in ARG2KO kidney was decreased as compared to WT at 24-h reperfusion.

Conclusion

Arg 2 was strongly induced after renal I/R injury particularly in tubular epithelial cells. Suppressing Arg2 by knockdown or knockout method resulted in reduced 3-NT in renal tubular cells. Deficiency of ARG2 significantly alleviated I/R injury in mouse kidney. Our results suggest that ARG2 is a cause of nitrosative stress and inhibition of ARG2 may be beneficial for treatment of renal I/R injury.