Protective effect of melatonin on blood⁃brain barrier dysfunction in rats with chronic cerebral hypoperfusion

Abstract

Objective To investigate the mechanism of the effect of melatonin (MT) on permeability of blood-brainbarrier (BBB) in chronic cerebral hypoperfusion (CCH) rats. Methods Therat model of CCH was established by bilateral common carotid artery occlusion (BCCAO). A total of 72 male Sprague-Dawley rats were randomly divided into 4 groups:sham group(N=18),BCCAOgroup(N=18), the melatonin [5 mg/(kg·d)] treatment model group (MT1 group, N=18), and the melatonin [10 mg/(kg·d)] treatment model group(MT2 group,N=18). Evans blue staining and fluorescein-labeled glucoside(FITC-Dextran)staining marked by fluorescein isothiocyanate(FITC)were used to assess the permeability o fBBB in rats. Expression of matrix metalloproteinase-2(MMP-2) and MMP-9 mRNA levels in basal ganglia of the brain were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Expression of Occludin and Claudin-5 protein in rat basal ganglia were measured by Western blotting method. Results Compared with the sham group, the fluorescence density in basal ganglia was increased (P = 0.000), expression of MMP-2 and MMP-9 were increased(all P=0.000),and expression of Occludin and Claudin-5 were decreased (all P =0.000) of BCCAO group. Compared with the BCCAO group, the fluorescence density in basal ganglia was decreased (P=0.021),the expression of MMP-2 was decreased(P=0.000)and the expression of Claudin-5 was increased (P=0.000) in MT1 group, and the differences with sham group were statistically significant (P=0.000, 0.006, 0.000). Compared with the BCCAO group, in MT2 group,the fluorescence degree in basal ganglia was further decreased (P=0.000), the expression of MMP-2 and MMP-9 were decreased (all P=0.000),and were similar to the sham group (all P>0.05),while expression of Occludin and Claudin-5 were increased (all P=0.000) but lower than those of sham group (P=0.003, 0.000). Compared with the two melatonin treatment groups, the efficacy of the 10mg/(kg·d) group (MT2 group)was better thanthat of the 5mg/(kg·d ) group (MT1 group, all P<0.05). Conclusions Melatonin may protect the integrity of BBB by inhibiting the degradation of Occludin and Claudin-5 protein through inhibiting the expression of matrix metalloproteinases.

Keywords

• Cerebral small vessel diseases; Melatonin; Blood⁃brain barrier; Disease models
• animal