title: Participation of autophagy in renal ischemia/reperfusion injury.
abstract: Renal ischemia-reperfusion (I/R) injury is inevitable in transplantation, and it results in renal tubular epithelial cells undergoing cell death. We observed an increase in autophagosomes in the tubular epithelial cells of I/R-injured mouse models, and in biopsy specimens from human transplanted kidney. However, it remains unclear whether autophagy functions as a protective pathway, or contributes to I/R-induced cell death. Here, we employed the human renal proximal tubular epithelial cell line HK-2 in order to explore the role of autophagy under hypoxia (1% O(2)) or activation of reactive oxygen species (500 microM H(2)O(2)). When compared to normoxic conditions, 48h of hypoxia slightly increased LC3-labeled autophagic vacuoles and markedly increased LAMP2-labeled lysosomes. We observed similar changes in the mouse IR-injury model. We then assessed autophagic generation and degradation by inhibiting the downstream lysosomal degradation of autophagic vacuoles using lysosomal protease inhibitor. We found that autophagosomes increased markedly under hypoxia in the presence of lysosomal protease inhibitors, thus suggesting that hypoxia induces high turnover of autophagic generation and degradation. Furthermore, inhibition of autophagy significantly inhibited H(2)O(2)-induced cell death. In conclusion, high turnover of autophagy may lead to autophagic cell death during I/R injury.
authors.affiliation: Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Chigure
authors.initials: C
authors.lastname: Suzuki
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Isaka
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Takabatake
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Tanaka
authors.forename: Masato
authors.initials: M
authors.lastname: Koike
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shibata
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Uchiyama
authors.forename: Shiro
authors.initials: S
authors.lastname: Takahara
authors.forename: Enyu
authors.initials: E
authors.lastname: Imai
mesh_terms: D000818:Animals; D001343:Autophagy; D015415:Biomarkers; D001706:Biopsy; D015687:Cell Hypoxia; D002460:Cell Line; D006801:Humans; D007425:Intracellular Membranes; D007668:Kidney / Q000293:injuries* / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology* / Q000601:surgery
chemical_list: D015415:Biomarkers