Neuroprotective Mechanism of Taurine due to Up-regulating Calpastatin and Down-regulating Calpain and Caspase-3 during Focal Cerebral Ischemia

Abstract

Taurine as an endogenous substance possesses a number of cytoprotective properties. In the study, we have evaluated the neuroprotective effect of taurine and investigated whether taurine exerted neuroprotection through affecting calpain/calpastatin or caspase-3 actions during focal cerebral ischemia, since calpain and caspase-3 play central roles in ischemic neuronal death. Male Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion (MCAo), and 22 h of reperfusion. Taurine was administrated intravenously 1 h after MCAo. The dose-responses of taurine to MCAo were determined. Next, the effects of taurine on the activities of calpain, calpastatin and caspase-3, the levels of calpastatin, microtubule-associated protein-2 (MAP-2) and alphaII-spectrin, and the apoptotic cell death in penumbra were evaluated. Taurine reduced neurological deficits and decreased the infarct volume 24 h after MCAo in a dose-dependent manner. Treatment with 50 mg/kg of taurine significantly increased the calpastatin protein levels and activities, and markedly reduced the m-calpain and caspase-3 activities in penumbra 24 h after MCAo, however, it had no significant effect on mu-calpain activity. Moreover, taurine significantly increased the MAP-2 and alphaII-spectrin protein levels, and markedly reduced the ischemia-induced TUNEL staining positive score within penumbra 24 h after MCAo. Our data demonstrate the dose-dependent neuroprotection of taurine against transient focal cerebral ischemia, and suggest that one of protective mechanisms of taurine against ischemia may be blocking the m-calpain and caspase-3-mediated apoptotic cell death pathways.