Hypoxic preconditioning reinforces HIF-alpha-dependent HSP70 signaling to reduce ischemic renal failure-induced renal tubular apoptosis and autophagy.
OBJECTIVE
Repetitive hypoxic preconditioning (RHP) may provide more efficient protection than single hypoxic preconditioning against renal ischemia/reperfusion-induced injury via hypoxia-induced factor 1alpha (HIF-1alpha)-dependent heat shock protein 70 (HSP70) pathways.


METHODS
Wistar rats were subjected to intermittent hypoxic exposure (15h/day), whereas controls were kept at sea level. We evaluated renal expression of HIF-1alpha, HSP70, the endoplasmic reticulum stress protein GRP78, caspase 12, Beclin-1, and poly-(ADP-ribose)-polymerase (PARP) with western blotting. Renal apoptosis determined by terminal transferase dUTP nick end labeling (TUNEL), Beclin-1-dependent autophagy, and monocyte/macrophage (ED-1) infiltration were evaluated by immunocytochemistry. Renal function was determined with blood urea nitrogen (BUN) and plasma creatinine levels. HIF-1alpha inhibitors and Deoxyribonucleotide (DNA) or Ribonucleotide (RNA) interference of HSP70 were used to evaluate their possible roles in this process.


RESULTS
Renal HIF-1alpha and HSP70 expression were enhanced by hypoxic preconditioning and inhibited by the HIF-1alpha inhibitor, YC-1, as well as phosphatidylinositol 3-kinase (PI3K)/Akt inhibitors. After the return to normoxia, renal HSP70 protein levels were maintained for one week in the RHP group, but they decayed after one day in the single hypoxic preconditioning group. Ischemia/reperfusion significantly increased renal TUNEL-apoptosis, Beclin-1-dependent autophagy, ED-1 infiltration, expression of GRP78, caspase 12, Beclin-1, PARP, and BUN and plasma creatinine levels in control rats. RHP significantly decreased all ischemia/reperfusion-enhanced parameters. Intraperitoneal pretreatment with YC-1 and quercetin (an inhibitor of HSP70 induction) eliminated RHP-induced protection. Anti-sense oligodeoxyribonucleotides or interference RNA targeting HSP70 abrogated the protection against hypoxia/reoxygenation-induced oxidative injury in RHP-treated proximal tubules.


CONCLUSIONS
We demonstrate that RHP promotes HIF-1alpha-dependent HSP70 signaling to reduce renal ischemia/reperfusion injury.
Yeh
Chung-Hsin
CH
Division of Urology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
Hsu
Shih-Ping
SP
Yang
Chih-Ching
CC
Chien
Chiang-Ting
CT
Wang
Nai-Phog
NP
D000818:Animals; D017209:Apoptosis; D001343:Autophagy; D015153:Blotting, Western; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis*; D015151:Immunoblotting; D007684:Kidney Tubules / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D051437:Renal Insufficiency / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015427:Reperfusion Injury / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction
D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; C497444:Hif1a protein, rat