Risperidone enhances the vulnerability to stroke in hypertensive rats

Protective cerebrovascular effects of hydroxysafflor yellow A (HSYA) on ischemic stroke

The purpose of the present work was designed to explore protective cerebrovascular effects of hydroxysafflor yellow A (HSYA), and provide preclinical efficacy and mechanism data for its possible application in patients with cerebral ischemia. The protective effect of HSYA on ischemic stroke was evaluated by infarct sizes and neurological scores in Sprague-Dawley (SD) rats with middle cerebral artery occlusion (MCAO). Cerebrovascular permeability was detected by Evans blue dye leakage in MCAO rats. Cerebral blood flow, as well as blood pressure and heart rate were monitored using flow probes in Beagle dogs. Basilar artery tension isolated from Beagle dogs was evaluated with an MPA 2000 data-acquisition system. Coagulation-related function was also judged, including rabbit platelet aggregation by adenosine diphosphate (ADP) and platelet-aggregating factor (PAF), rabbit blood viscosity by a blood viscometer, and thrombus formation by rat arterial-venous shunts. Results showed that HSYA treatment significantly decreased the infarct sizes, neurological scores and cerebrovascular permeability in rats with MCAO. However, cerebral blood flow, blood pressure and heart rate were not affected by HSYA. In vitro, HSYA had a strong effect on cerebrovascular vasodilatation, and significantly decreased platelet aggregation, blood viscosity, and thrombogenesis. Besides well-known anti-coagulation effects, HSYA protects against ischemic stroke by dilating cerebral vessels and improving cerebrovascular permeability.

The γ-secretase blocker DAPT reduces the permeability of the blood-brain barrier by decreasing the ubiquitination and degradation of occludin during permanent brain ischemia

BACKGROUND

Tight junction protein degradation is a principal characteristic of the blood-brain barrier (BBB) damage that occurs during brain ischemia.

AIMS

We investigated the mechanisms of occludin degradation that underlie permanent middle cerebral artery occlusion (pMCAO) in rats.

METHODS AND RESULTS

Western blot and Co-immunoprecipitation data indicated ubiquitination and degradation of occludin in brain after pMCAO, which was consistent with ZO-1 degradation in penumbra regions as observed at 24 h after pMCAO. We further investigated candidate protease(s) responsible for the degradation of occludin during pMCAO. The intraventricular administration of γ-secretase blocker DAPT significantly inhibited the pMCAO-induced neurovascular damage, whereas ALLM and Batimastat, which are inhibitors of calpain and metalloproteinase proteases, respectively, were less effective. Notably, we found that DAPT significantly inhibited BBB disruption in comparison with vehicle treatment, as assessed by Evans blue excretion. Interestingly, the confocal immunostaining revealed that activation of the E3 ubiquitin ligase Itch is associated with degradation of occludin in brain microvessels following ischemia. Furthermore, our data demonstrate that the inhibition of γ-secretase signaling and the itch-mediated ubiquitination of occludin likely underlie the vasoprotective effect of DAPT after pMCAO.

CONCLUSION

The γ-secretase blocker DAPT reduces the permeability of the BBB by decreasing the ubiquitination and degradation of occludin during permanent brain ischemia, suggesting that γ-secretase may represent a novel therapeutic target for preventing neurovascular damage.