1α,25-Dihydroxy-vitamin D3 in combination with 17β-estradiol lowers the cortical expression of heat shock protein-27 following experimentally induced focal cortical ischemia in rats

1α,25-(OH)2-vitamin-D3 (1,25-D3) and 17β-estradiol are both known to act neuroprotective in certain experimental in vitro and in vivo settings. We studied the effects of 1,25-D3 or 17β-estradiol or their combined application on heat shock protein-27 (HSP-27) distribution after focal cortical ischemia using the photothrombosis model. HSP-27 is a well-established marker of the cerebral oxidative stress response and a potent inhibitor of apoptosis. Lesioned rats were injected i.p. one hour after injury with either 1 μg 1,25-D3/kg or 7 μg 17β-estradiol/kg or a combination of both steroids. Groups of non-lesioned steroid-treated rats and lesioned, solvent-treated rats served as controls. Treatment with both steroids did not affect the size of the lesion. In addition, 17β-estradiol resulted in significant reduction of HSP-27 induction, whereas the combination of 1,25-D3 + 17β-estradiol resulted in a highly significant reduction of HSP-27 within the infracted cerebral cortex, indicating that both steroids act synergistically in a protective manner.