Background. Reperfusion injury is a major bottleneck in the treatment of ischemic stroke, and blood–brain barrier (BBB) disruption is a key event. Autophagy studies have focused on neurons; however, the expression profile of vascular autophagy at different stages of reperfusion, its relationship with BBB disruption and inflammation, and whether hypothermia protects by regulating vascular autophagy remain to be systematically elucidated.

Methods. Rats underwent middle cerebral artery occlusion, and samples were collected at 6 h, 24 h, 3 d, 5 d and 7 d after reperfusion. Cerebral microvessels were isolated; autophagy markers  and tight-junction proteins were detected by Western blot; BBB integrity was assessed by brain water content and Evans blue extravasation; and vascular inflammation by ELISA. The hypothermia group (chlorpromazine plus promethazine) and 3-MA-treated bEnd.3 OGD/R group were additionally established to assess these parameters.

Results. Compared with sham, vascular autophagy was activated as early as 6 h and peaked at 24 h, with LC3B-II/LC3B-I increasing to 6.1-fold and P62 decreasing to 0.16-fold; tight-junction proteins showed no significant change at 6 h but declined at 24 h to 0.28-fold (Claudin-5), 0.55-fold (Occludin) and 0.20-fold (ZO-1). Brain water content, Evans blue, IL-1β and IL-6 all peaked at 24 h and improved by 7 d. At 7 d, tight-junction proteins had partially recovered, whereas LC3B-II remained elevated at 3.9-fold. Hypothermia suppressed autophagy and alleviated BBB damage and inflammation, and 3-MA partially reversed OGD/R-induced barrier damage in vitro.

Conclusion. Vascular autophagy is activated in a time-dependent manner after reperfusion, preceding tight-junction degradation and peaking at 24 h with BBB disruption and inflammation, and may act as an injury-inducing factor in the acute phase; hypothermia attenuates BBB disruption by inhibiting vascular autophagy. The 24-h point may be a critical window for intervention, and vascular autophagy a promising target for cerebral protection.