Cisplatin-induced macroautophagy occurs prior to apoptosis in proximal tubules in vivo.
BACKGROUND
Autophagy is an intracellular bulk degradation process induced by cell starvation. Autophagy was recently reported to be induced by various stresses such as hypoxia, ischemia/reperfusion, toxins, and denatured proteins, and to affect cell survival and death. Light chain 3-II (LC3-II) is specifically located on double membrane-bound autophagosomes that envelop disused proteins or organelles.


METHODS
Transgenic mice in which green fluorescent protein (GFP) was fused to LC3 (LC3-GFP) were administered cisplatin (20 mg/kg). After euthanasia at times between 0 and 72 h, kidneys were excised for immunohistochemical analyses. Microscopic examinations of the generated NRK-52E cell lines stably transfected with LC3-GFP, and Western blot analyses of NRK-52E cells, were undertaken after cisplatin treatment with or without autophagy inhibitors and beclin 1 small interfering RNA (siRNA).


RESULTS
Autophagosomes increased in the proximal tubular cells of transgenic mice from 12 h after cisplatin injection (20 mg/kg). The time course for this was faster than those for tubular necrosis and apoptosis. Autophagosomes also increased in NRK-52E cells after cisplatin treatment, with the time course for this being faster than that for apoptosis. When autophagy was suppressed by autophagy inhibitors or beclin 1 siRNA, the level of apoptosis was also suppressed.


CONCLUSIONS
Autophagy occurs in proximal tubular cells after cisplatin treatment and is involved in cell death in renal tubular injury. Our data suggest that autophagy is a kind of cell damage index and that cells with activated autophagy will be scavenged by apoptosis.
Inoue
Kosuke
K
The Department of Endocrinology, Metabolism and Nephrology, Kochi Medical School, Kochi University, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan.
Kuwana
Hitoshi
H
Shimamura
Yoshiko
Y
Ogata
Koji
K
Taniguchi
Yoshinori
Y
Kagawa
Toru
T
Horino
Taro
T
Takao
Toshihiro
T
Morita
Tatsuhito
T
Sasaki
Sei
S
Mizushima
Noboru
N
Terada
Yoshio
Y
D058186:Acute Kidney Injury / Q000503:physiopathology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D002945:Cisplatin / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic
D002945:Cisplatin