Amelioration of oxidative mitochondrial DNA damage and deletion after renal ischemic injury by the KATP channel opener diazoxide.
Renal ischemia was induced in the rat by constriction of the renal artery for 45 min, and the ability of the ATP-sensitive K(+) (K(ATP)) channel opener diazoxide (DZ) to ameliorate renal ischemia-reperfusion (I/R) injury was evaluated. In this model, blood urea nitrogen and creatinine were elevated 2 days after I/R injury but returned closer to normal levels by 7 days after reperfusion. Histological staining for reactive oxygen species (ROS) was clearly positive and oxidized DNA, detected by the presence of the stable adduct 8-hydroxy-2'-deoxyguanosine, was clearly present in the cytoplasm of tubular cells after 1 h of reperfusion and declined 7 days after reperfusion. This finding was confirmed by ELISA, which detected 8-hydroxy-2'-deoxyguanosine in the mitochondrial fraction of kidney homogenates. Despite evidence of improved function measured by blood urea nitrogen and creatinine 7 days after reperfusion, the early changes in tubules were alarming. Mitochondrial DNA showed the common deletion, and the number of TdT-mediated dUTP nick-end label-positive tubular cells increased. Activation of caspase-3 continued, and abnormal levels of ROS were found in the mitochondrial fraction of cellular homogenates. Treatment with DZ before ischemia reduced or prevented the acute and subacute deleterious effects associated with renal I/R injury. We conclude that excess production of ROS by mitochondria on reperfusion is a major upstream event in renal reperfusion injury and that DZ functioned by preventing ROS accumulation in the mitochondria after I/R injury, thereby reducing oxidative stress as measured by the presence of oxidized mitochondrial DNA and features of apoptosis.
Sun
Zhaoli
Z
Department of Surgery, Johns Hopkins University School of Medicine, 720 Rutland Ave., Ross 749, Baltimore, MD 21205, USA. zlsun@jhmi.edu
Zhang
Xiuying
X
Ito
Kazushige
K
Li
Yulin
Y
Montgomery
Robert A
RA
Tachibana
Shingo
S
Williams
George Melville
GM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D004272:DNA, Mitochondrial / Q000187:drug effects*; D003981:Diazoxide / Q000494:pharmacology / Q000627:therapeutic use*; D005609:Free Radicals / Q000378:metabolism; D007674:Kidney Diseases / Q000378:metabolism / Q000517:prevention & control*; D007677:Kidney Function Tests; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects*; D015221:Potassium Channels / Q000187:drug effects; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D017384:Sequence Deletion; D014665:Vasodilator Agents / Q000494:pharmacology / Q000627:therapeutic use*; D000099161:Kcnj11 Channel
D004272:DNA, Mitochondrial; D003981:Diazoxide; D005609:Free Radicals; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D014665:Vasodilator Agents; D000099161:Kcnj11 Channel; C117780:mitochondrial K(ATP) channel