Chronic treatment with fibrates elevates superoxide dismutase in adult mouse brain microvessels

Fibrates are activators of peroxisome proliferator-activated receptor (PPAR) a. Pretreatment with fibrates has been shown to protect brain against ischemia in mice. We hypothesized that fibrates elevate superoxide dismutase (SOD) levels in the brain microvessels (BMVs). BMVs were isolated from male C57BL/6 and PPAR alpha null mice that had been treated with fenofibrate or gemfibrozil for 7 days. To examine the effect of discontinuation of fenofibrate, another animal group treated with fenofibrate was examined on post-discontinuation day 3 (D-3). To examine whether SOD elevations attenuate oxidative stress in the ischemic brain, separate animals treated with fenofibrate for 7 days were subjected to 60 minutes of focal ischemia on post-discontinuation day 0 (D-0) or D-3. Fenofibrate (30 mg/kg) increased mRNA levels of all three isoforms of SOD and activity level in BMV on D-0, but these effects were not detected on D-3. The elevations were not detected in PPARa null mice. SOD levels were also elevated by gemfibrozil (30 mg/kg). Fenofibrate significantly reduced superoxide production and protein oxidation in the ischemic brain at 30 minutes after reperfusion. Fenofibrate reduced infarct size measured at 24 hours after reperfusion on D-0; however, the infarct reduction was not seen when ischemia was induced on D-3. These findings suggest that fibrates elevate SOD in BMV through PPARa, which contributes to the infarct reduction, at least in part. Further studies are needed to establish the link between the SOD elevations and the brain protection by fibrates against ischemia. (C) 2010 Elsevier B.V. All rights reserved.