A Localized Ischemic Preconditioning Regimen Increases Tumor Necrosis Factor α Expression in a Rat Model of Kidney Ischemia-Reperfusion Injury.

OBJECTIVES: We evaluated a continuous, immediate, localized ischemic preconditioning regimen in a rat model of ischemia-reperfusion injury and assessed whether it attenuated injury at the histologic and molecular levels. MATERIALS AND METHODS: Fifteen adult male Lewis rats received sham operation, left unilateral warm ischemia (45 minutes of cross-clamping of the renal pedicle; ischemia-reperfusion injury group), or 15 minutes of ischemia followed by a 20-minute reperfusion period, 45 minutes of ischemia-reperfusion injury, and subsequent reperfusion (ischemic preconditioning/ischemia-reperfusion injury group). Kidney tissue was retrieved 48 hours later, sectioned, stained with hematoxylin and eosin, and examined. We used RNA extraction and real-time quantitative polymerase chain reaction analysis to assess acute kidney injury markers, cytokines, and microRNA-21. RESULTS: Forty-five minutes of unilateral ischemia-reperfusion injury caused marked changes in histology at 48 hours, characterized by endothelial loss, tubulointerstitial damage (inflammation, cast formation), tubular cell necrosis, and glomerular capsule thickening. The ischemia-reperfusion injury and ischemic preconditioning/ischemia-reperfusion injury groups showed no measurable differences in histology. Expression of the acute kidney injury markers was significantly increased in the ischemia-reperfusion injury versus Sham group; however, no difference was found between the ischemia reperfusion injury and ischemic preconditioning/ischemia-reperfusion injury groups. Similarly, expression of interleukin 17, interleukin 18, and tumor necrosis factor ? was significantly increased in the ischemia-reperfusion injury versus Sham group. No significant difference was found between the ischemia-reperfusion injury and ischemic preconditioning/ischemia-reperfusion injury groups for interleukin 17 and interleukin 18; however, tumor necrosis factor ? expression was significantly increased in the ischemic preconditioning/ischemia-reperfusion injury versus ischemia-reperfusion injury group. CONCLUSIONS: In our ischemic preconditioning model, tumor necrosis factor α expression was increased without altering the sequelae of ischemia-reperfusion injury. The long-term consequences of this augmented early inflammatory response and whether these consequences are altered by variations in ischemic preconditioning or a subsequent injury require further study.