Activated autophagy pathway in experimental subarachnoid hemorrhage

Recent results have suggested a role for autophagy in acute brain injury but an involvement in subarachnoid hemorrhage (SAH) has not been investigated. Although, autophagy is a regulated process essential for cellular homeostasis, it may represent an additional type of cell death mechanism. This study employed a modified endovascular perforation rat model under guidance by intracranial pressure monitoring to investigate whether autophagy pathway is involved in the early brain injury following SAH. Sham-operated control rats underwent an identical procedure without vessel perforation. Electron microscopy was performed to examine the ultrastructural changes in neural cells after SAH. Additionally, microtubule-associated protein light chain-3 (LC3), cathepsin-D and beclin-1 were investigated by Western blot analysis and immunohistochemistry. Electron microscopically, there was a marked increase in autophagosomes and autolysosomes in neurons at Day 1 following SAH. Although LC3 could be detected in sham-operated control rats, the conversion of LC3-I to LC3-II was significantly increased at Day 1 (P < 0.01) and Day 3 (P < 0.05). The time-course of beclin-1 expression paralleled the LC3 conversion. Cathepsin-D expression was also elevated at Day 1 (P < 0.01). Immunohistochemical study with antibodies against cathepsin-D and beclin-1 showed numerous positive stained cells after SAH, especially in deep layers of the fronto-basal cortex. Double immunolabeling revealed beclin-1 expression predominantly in neurons. This present study showed that the autophagy pathway is activated in neurons in the acute phase after SAH.