Melatonin prevents focal rat cerebellum injury as assessed by induction of heat shock protein (HO-1) following subarachnoid injections of lysed blood.

The present paper studies a marker of oxidative stress such as heme oxygenase-1 (HO-1), the main heat shock protein. HO-1 expression was induced in the focal region of the cerebellum following experimental subarachnoid hemorrhage (SAH). Lysed blood was injected into the subarachnoid space or cisterna magna region of adult rats. The experimental groups used were: (1) animals injected with lysed blood alone; (2) animals injected with saline alone; (3) lysed blood plus melatonin (10 mg/kg body weight(BW)); (4) lysed blood plus melatonin (10 mg/kg BW injected 1 h before SAH); (5) lysed blood plus melatonin (5 mg/kg BW injected 1 h before SAH); (6) lysed blood plus vitamin E (Trolox; 30 mg/kg BW injected simultaneously); (7) lysed blood plus vitamin E (30 mg/kg BW injected 1 h before SAH); and (8) lysed blood plus vitamin E (15 mg/kg BW injected 1 h before SAH). Animals were sacrificed 24 h later. Injection of lysed blood induced an overexpression of HO-1. Both, melatonin and vitamin E were able to prevent the expression of the heat shock protein. However, in terms of efficiency, the antioxidant capability of melatonin was clearly higher than that exhibited by vitamin E. The results presented in this study show that antioxidants, especially melatonin, prevent focal regions of injury as assessed by heat shock protein expression in a rat model of SAH.