An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

DDAH-1, via regulation of ADMA levels, protects against ischemia-induced blood-brain barrier leakage

Dimethylarginine dimethylamino hydrolase-1 (DDAH-1) is an important regulator of nitric oxide (NO) metabolism that has been implicated in the pathogenesis of cardiovascular diseases. Nevertheless, its role in cerebral ischemia still needs to be elucidated. Herein, we examined the expression of DDAH-1 in the brain of rat by double-label immunofluorescence staining. DDAH-1 knock-out (DDAH-1-/-) and wild-type rats underwent middle cerebral artery occlusion/reperfusion (MCAO/R). After 24 h, neurological scores, TTC staining and TUNEL assay were used to evaluate neurological damages. 3 and 7-days infarct outcomes were also shown. Blood-brain-barrier (BBB) permeability was examined via Evans blue extravasation and tight junction (TJ) proteins expression and mRNA levels by western blot and RT-qPCR. The levels of plasma asymmetric dimethylarginine (ADMA), NO and ADMA in brain tissue were also assessed. In addition, supplementation of L-arginine to DDAH-1-/- rats was used to explore its role in regulating NO. DDAH-1 was abundantly distributed in cerebral cortex and basal nuclei, and mainly expressed in neurons and endothelial cells. DDAH-1-/- rats showed aggravated neurological damage and BBB disruption, including decrease of TJ proteins expression but indistinguishable mRNA levels after MCAO/R. DDAH-1 depletion and neurological damages were accompanied with increased ADMA levels and decreased NO concentrations. The supplementation with L-arginine partly restored the neurological damages and BBB disruption. To sum up, DDAH-1 revealed to have a protective role in ischemia stroke (IS) and IS-induced leakage of BBB via decreasing ADMA level and possibly via preventing TJ proteins degradation.

Effects of β1-adrenergic receptor blockade on the cerebral microcirculation in the normal state and during global brain ischemia/reperfusion injury in rabbits

Background

Although recent studies using experimental models of ischemic brain injury indicate that systemically-administered β₁-blockers have potential protective effects on the cerebrovascular system, the precise mechanisms remain unclear. In addition to their cardiovascular effects, water-soluble β₁-blockers can pass the blood–brain barrier and may exert their vascular action on cerebral microvessels. The aim of this study was to investigate the direct effects of β₁-blockade on the cerebral microvasculature both in the normal state and ischemia/reperfusion state using the cranial window method.

Methods

The closed cranial window method was used to visualize the cerebral microcirculation and changes in the pial arteriole diameter in adult male rabbits. In the first experiment, various concentrations of the selective β₁-blocker landiolol were administered into the cranial window to evaluate the dose-response. In the second experiment, the effect of β₁-blockade on the brain during ischemic/reperfusion injury was investigated. Global brain ischemia/reperfusion was induced by clamping the brachiocephalic, left common carotid, and left subclavian arteries for 15 min. Either landiolol or artificial cerebrospinal fluid was infused 5 min after initiation of ischemia through 120 min after reperfusion. Pial arteriole diameter and hemodynamic and physiological parameters were recorded before ischemia, during ischemia, and 5, 10, 20, 40, 60, 80, 100, and 120 min after reperfusion.

Results

In the first experiment, topical administration of landiolol at higher concentrations produced slight pial arteriole dilation (10^− 8 mol/L: 4.3 ± 3.4%, 10^− 6 mol/L: 8.0 ± 5.8%, 10^− 4 mol/L: 7.3 ± 4.0%). In the second experiment, the topical administration of landiolol significantly dilated the pial arteriole diameters during ischemia/reperfusion injury (ischemia: 30.6 ± 38.6%, 5 min: 47.3 ± 42.2%, 10 min: 47.8 ± 34.2%, 20 min: 38.0 ± 39.0%). There were no statistical differences in hemodynamic and physiological parameters between the landiolol and control groups.

Conclusions

The blockade of β₁-adrenergic receptors induced significant vasodilation of pial arterioles during ischemia/reperfusion injury. By contrast, only a slight dilation of the arterioles was observed in the normal state, indicating that ischemic cerebral microvessels are more susceptible to the vasodilatory effect induced by selective blockade of β₁-adrenergic receptors than normal microvessels.

Nano-Curcumin Simultaneously Protects the Blood-Brain Barrier and Reduces M1 Microglial Activation During Cerebral Ischemia-Reperfusion Injury

Oxidative stress and inflammation are two important pathophysiological mechanisms that arouse neuronal apoptosis and cerebral damage after ischemia/reperfusion (I/R) injury. Here, we hypothesized that curcumin-encapsulated nanoparticles (NPcurcumin) could reduce oxidative stress and inflammation in the ischemic penumbra via protecting the blood-brain barrier (BBB) and inhibiting M1-microglial activation. Under oxidative stress conditions in vitro, we found that NPcurcumin protected microvascular endothelial cells against oxidative stress and reduced BBB permeability. In vivo, NPcurcumin could cross the BBB and accumulate in the ischemic penumbra. At 3 d after I/R injury, NPcurcumin inhibited the increase in MMP-9, attenuated the decrease in occludin and zona occluden-1, and maintained BBB integrity. NPcurcumin effectively reduced the number of activated M1 microglia and weakened the increase in TNF-α and IL-1β. Furthermore, NPcurcumin also reduced the infarct size and improved function recovery.