Enhancement of oligodendrocyte autophagy alleviates white matter injury and cognitive impairment induced by chronic cerebral hypoperfusion in rats

Cognitive impairment caused by chronic cerebral hypoperfusion (CCH) is associated with white matter injury (WMI), possibly through the alteration of autophagy. Here, the autophagy-lysosomal pathway (ALP) dysfunction in white matter (WM) and its relationship with cognitive impairment were investigated in rats subjected to two vessel occlusion (2VO). The results showed that cognitive impairment occurred by the 28th day after 2VO. Injury and autophagy activation of mature oligodendrocytes and neuronal axons sequentially occurred in WM by the 3rd day. By the 14th day, abnormal accumulation of autophagy substrate, lysosomal dysfunction, and the activation of mechanistic target of rapamycin (MTOR) pathway were observed in WM, paralleled with mature oligodendrocyte death. This indicates autophagy activation was followed by ALP dysfunction caused by autophagy inhibition or lysosomal dysfunction. To target the ALP dysfunction, enhanced autophagy by systemic rapamycin treatment or overexpression of Beclin1 (BECN1) in oligodendrocytes reduced mature oligodendrocyte death, and subsequently alleviated the WMI and cognitive impairment after CCH. These results reveal that early autophagy activation was followed by ALP dysfunction in WM after 2VO, which was associated with the aggravation of WMI and cognitive impairment. This study highlights that alleviating ALP dysfunction by enhancing oligodendrocyte autophagy has benefits for cognitive recovery after CCH.

Experimental Study of Cerebral Protective Action with Dexamethasone in a Rat`s Forebrain Ischemic Model / 대한마취과학회지

This study examined the protective effect of dexamethansone following bilateral forebrain ischemia in a rat model of two-vessel occlusion. Twenty rats were subjected to dexamethasone (1 mg/kg intravenously) before bilateral common carotid artery occlusion for 10 minutes. Carotid artery blood flow was restored and the rats were terminated by a perfusion-fixation method after 7 days. Ten minutes of two-vessel occlusion produced cellular ischemic change in the cerebral hemispheres of most rats. This region was studied mainly with light microscope, and it was noticed that the CA 1 neuron in the hippocampus is the most vulnerable to ischemia. Ischemic neuronal damage was graded in accordance with conventional neuropathological criteria. The grade had no statistical significance.