Dose dependence and therapeutic window for the neuroprotective effects of curcumin in thromboembolic model of rat

Curcumin (diferuloylmethane), an active ingredient of turmeric, obtained from the powdered rhizomes of Curcuma longa Linn., has been traditionally recognized for treatment of several diseases. To evaluate the potential clinical use of curcumin, we determined the dose dependence of its effects in the therapeutic window and of the neuroprotective efficacy in a cerebral thromboembolic model of the rat. Rats were subjected to occlusion of the middle cerebral artery (MCAo) by a thrombus and treated with different doses of curcumin or the vehicle at 4 h after ischemia. The animals were assessed after 24 h for motor performance and neurological deficit. The rats were sacrificed immediately afterwards for evaluation of infarct, edema volume, estimation of nitrate and nitrite levels, neutrophil infiltration and levels of GSH and glutathione peroxidase (GSH-Px) in brain tissue. Curcumin reduced in a dose-dependent manner the ischemia-induced cerebral infarct and edema volume and attenuated neurological deficits observed after 24 h. Curcumin reduced post-ischemic brain neutrophil infiltration, nitrate and nitrite levels and ameliorated the loss of GSH-Px and tends to increase the GSH levels but not significantly in the brain tissue. Neuronal levels of reactive oxygen species, peroxynitrite, and nitric oxide were lowered and in brain cryosections inducible nitric oxide synthase expression were significantly inhibited after treatment with curcumin. The present study is the first evidence of effectiveness of curcumin when given 4 h post-ischemia in the rat thromboembolic stroke models, as it reduces infarct volume, ameliorates the sensory motor function and significantly attenuated the nitrosative stress.