Loss of bag-1 immunoreactivity in rat brain after transient middle cerebral artery occlusion

Although bag-1 is a strong apoptosis repressor protein, its functions in no rmal or injured brains are not fully understood. In the present study, we i nvestigated expression of bag-1 protein in rat brain after transient middle cerebral artery (MCA) occlusion, and compared the results with that of ter minal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling (TUNEL ). Immunohistochemical analysis revealed that neuronal, choroid plexus, and ependymal cells were positively stained in the sham control brain. After 9 0 min of transient MCA occlusion, immunoreactivity for bag-1 progressively decreased from 3 to 48 h in the nuclei of neurons. Western blot analysis re vealed that immunoreactive bag-1 was markedly decreased in the nuclear frac tion. In contrast, cytosolic and mitochondrial fractions showed no or only slight change after the ischemia. TUNEL positive cells appeared at 48 h aft er the reperfusion, which was preceded by loss of bag-1 immunoreactivity. T he present results suggest that bag-1 plays some roles in normal neuronal f unction, and its loss may be involved in neuronal cell death after ischemia . (C) 2000 Elsevier Science B.V. All rights reserved.