Specific alterations of the HtrA2/HAX-1 ratio in the penumbra upon focal cerebral ischemia in mice.

HAX-1 is a mitochondrial protein which acts as an antiapoptotic protein in HeLa- and Jurkat cells after Fas-treatment, irradiation or serum deprivation. This underlines the evidence that HAX-1 might be involved in several apoptotic pathways. In this context, it is known that cell death executed by cerebral ischemia involves both receptor- and mitochondrial apoptotic mechanisms. In this study, we performed focal cerebral ischemia in mice and investigated principally the dynamic changes of HAX-1 expression and other apoptotic agents such as HtrA2, AIF and caspase-3. Western blot and immunohistochemistry analysis revealed that HAX-1 was expressed at very low levels under normal conditions. Focal cerebral ischemia significantly decreased cytosolic accumulation of HAX-1, induced an upregulation of HtrA2, an upregulation of AIF and activation of caspase-3. Taken together, these results suggested that HAX-1 is probably involved in the pathophysiology of cell death induced by focal ischemia.