Treatment of rats with pioglitazone in the reperfusion phase of focal cerebral ischemia: a preclinical stroke trial

Abstract

Thiazolidinediones (TZDs), pioglitazone, rosiglitazone and troglitazone, the synthetic agonists for the PPARγ, administered prior or during ischemic insult improve stroke outcome in rodents, post-occlusion treatments yielded inconsistent results. In the present experiments carried out according to the Stroke Therapy Academic Industry Roundtable (STAIR) guidelines, we studied the effects of post-ischemic pioglitazone treatment on the outcome of focal cerebral ischemia, inflammatory and apoptotic processes, neuronal degeneration and regeneration, blood pressure, heart rate and physiological variables in blood. Male Wistar rats were subjected to a 90 min middle cerebral artery occlusion (MCAO). Subcutaneous (SC) treatment with vehicle or pioglitazone was initiated 90 min after MCAO, i.e. in the post-ischemic, reperfusion phase and continued on 2 (2 day-experiment, protocol 1) or 5 (5-day experiment, protocol 2) consecutive days. In the 2-day experiment, pioglitazone at a dose of 2.5 mg/kg body weight (bw) reduced infarct volume by 31% and oedema by 43% on day 2 after MCAO and attenuated the infiltration of ischemic cortical tissue with activated microglia and macrophages. The slight reduction in infarct volume by approximately 18%, detected in rats treated with 10 mg/kg bw pioglitazone did not reach statistical significance. The neurological scores of sham-operated rats treated with vehicle or 10 mg/kg bw pioglitazone were not significantly different. In rats subjected to cerebral ischemia, post-ischemic treatment with either dose of pioglitazone alleviated particular motor deficits and sensory impairments on day 2 after MCAO. A single injection of 10 mg/kg bw pioglitazone in the reperfusion phase (90 min after the onset of reperfusion) did not modify systolic and diastolic blood pressure, heart rate and physiological variables compared to vehicle-treated rats at any time point after MCAO. In the 5-day experiment, continuous post-occlusion treatment with 2.5 mg/kg body weight pioglitazone significantly reduced cerebral infarction by 29% and improved the partial paralysis of the forelimb and alleviated sensory deficits. In the peri-infarct cortex, pioglitazone effectively suppressed the accumulation of activated microglia/macrophages, inhibited neuronal degeneration and promoted neuroregeneration and formation of neuronal networks. The current results provide evidence that pioglitazone treatment in the post-ischemic, reperfusion phase improves the recovery from ischemic stroke. Neuroprotective effects of pioglitazone are mediated by inhibition of post-ischemic inflammation and neuronal degeneration, protection of neurones against ischemic injury and by promoting of neuronal regeneration. Our data together with previous findings favour the view that pioglitazone is a promising candidate for clinical stroke trials.