Tempol, a membrane-permeable radical scavenger, reduces oxidant stress-mediated renal dysfunction and injury in the rat.
BACKGROUND
The generation of reactive oxygen species (ROS) contributes to the pathogenesis of renal ischemia-reperfusion injury. The aim of this study was to investigate the effects of tempol in (1) an in vivo rat model of renal ischemia/reperfusion injury and on (2) cellular injury and death of rat renal proximal tubular (PT) cells exposed to oxidant stress in the form of hydrogen peroxide (H2O2).


METHODS
Male Wistar rats underwent bilateral renal pedicle clamping for 45 minutes followed by reperfusion for six hours. Tempol (30 mg/kg/h), desferrioxamine (DEF; 40 mg/kg/h), or a combination of tempol (30 mg/kg/h) and DEF (40 mg/kg/h) were administered prior to and throughout reperfusion. Plasma concentrations of urea, creatinine, Na+, gamma-glutamyl transferase (gammaGT), aspartate aminotransferase (AST), and urinary Na+ and N-acetyl-beta-D-glucosaminidase (NAG) were measured for the assessment of renal function and reperfusion injury. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of nitrotyrosine and poly(ADP-ribose) synthetase (PARS). Primary cultures of rat PT cells were incubated with H2O2 (1 mmol/L for 4 h) either in the absence or presence of increasing concentrations of tempol (0.03 to 10 mmol/L), DEF (0.03 to 10 mmol/L), or a combination of tempol (3 mmol/L) or DEF (3 mmol/L). PT cell injury and death were determined by evaluating mitochondrial respiration and lactate dehydrogenase (LDH) release, respectively.


RESULTS
In vivo, tempol significantly reduced the increase in urea, creatinine, gammaGT, AST, NAG, and FENa produced by renal ischemia/reperfusion, suggesting an improvement in both renal function and injury. Tempol also significantly reduced kidney MPO activity and MDA levels, indicating a reduction in PMN infiltration and lipid peroxidation, respectively. Tempol reduced the histologic evidence of renal damage associated with ischemia/reperfusion and caused a substantial reduction in the staining for nitrotyrosine and PARS, suggesting reduced nitrosative and oxidative stress. In vitro, tempol significantly attenuated H2O2-mediated decrease in mitochondrial respiration and increase in LDH release from rat PT cells, indicating a reduction in cell injury and death. Both in vivo and in vitro, the beneficial actions of tempol were similar to those obtained using the Fe2+ chelator DEF. However, coadministration of DEF and tempol did not produce any additional beneficial actions against renal ischemia/reperfusion injury or against oxidative stress-mediated PT cell injury/death.


CONCLUSIONS
Our results suggest that the membrane-permeable radical scavenger, tempol, reduces the renal dysfunction and injury associated with ischemia/reperfusion of the kidney.
The William Harvey Research Institute, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Charterhouse Square, London, England, United Kingdom. p.k.chatterjee@mds.qmw.ac.uk
P K
PK
Chatterjee
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Cuzzocrea
P A
PA
Brown
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Zacharowski
K N
KN
Stewart
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Mota-Filipe
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Thiemermann
D058186:Acute Kidney Injury / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D002463:Cell Membrane Permeability; D002469:Cell Separation; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D003676:Deferoxamine / Q000494:pharmacology; D004195:Disease Models, Animal; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007678:Kidney Glomerulus / Q000098:blood supply / Q000201:enzymology / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000201:enzymology / Q000473:pathology; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009336:Necrosis; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D009195:Peroxidase / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D013113:Spin Labels; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D002614:Chelating Agents; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D016877:Oxidants; D013113:Spin Labels; C002744:3-nitrotyrosine; D014443:Tyrosine; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D009195:Peroxidase; D011065:Poly(ADP-ribose) Polymerases; D003676:Deferoxamine; C001803:tempol