Protective Effect Of Triptolide On White Matter Damage After Chronic Cerebral Hypoperfusion In Mice

Objective Subcortical Ischemic Vascular Dementia(SIVD)caused by chronic cerebral hypoperfusion is a common vascular dementia and there is no effective clinical treatment so far.The main pathological characteristic of SIVD is white matter damage,including the oligodencyte loss and demyelination,which may be due to the neuroinflammation.Triptolide has been found to inhibit the neuro inflammation in multiple cerebral disorders,therefore this research aims to study therapeutic effect of Triptolide(TP)on white matter damage caused by chronic cerebral hypoperfusion and explore its effect mechanism.Methods Animal experiments were carried out by 8-10 week-old C57BL/6J mice.They were divided into sham,right unilateral common carotid artery occlusion(rUCCAO),TP 5?g/kg/d,and TP 20 ?g/kg/d groups.TP groups were consecutively intraperitoneally injected with TP for 21 days after rUCCAO,and then all the mice were subjected to novel object recognition test and water maze test.Western blot,immunofluorescence staining,enzyme linked immunosorbent assay(ELISA),and biochemical examination were carried out after behavioral experiments.Cell experiments were carried out on BV2 microglial cells and oligodendrocytes,which were divided into control,oxygen-glucose deprivation(OGD),TP 0.001 nM,TP 0.01 nM,and TP 0.1 nM groups.Cells were subjected to immunofluorescence staining,ELISA,PI/Hoechst and lactate dehydrogenase(LDH)tests after OGD.Results After rUCCAO,TP 20 ?g/kg/d group showed significantly higher discrimination index than rUCCAO group(P<0.001)in novel object recognition test.In water maze test,the escape latency of TP 20 ?g/kg/d group was significantly shorter than that of rUCCAO group(P<0.05),and the exploring time in the target quadrant was significantly longer than that of rUCCAO group(P<0.001)in the probe trial.TP 5 ?g/kg/d group has no significant effect on cognitive abilities in above tests(P>0.05).Besides,immunofluorescence staining and western blot assay showed that the myelin basic protein(MBP)expression of TP 20 ?g/kg/d group significantly increased compared with rUCCAO group(P<0.01,P<0.001),and the number of CC-1+ oligodendrocytes significantly increased as well(P<0.001).In addition,TP 20?g/kg/d group significantly inhibited the microglia activation(P<0.001)and reduced TNF-a and IL-6 expression(P<0.05,P<0.05).TP 5 ?g/kg/d group only showed a tendency to improve in above pathological examination but without significance(P>0.05).TP 20 ?g/kg/d group had no effect on the hepatic and renal function by examining the alanine aminotransferase(ALT),aspartate transaminase(AST),albumin(ALB),creatinine(CRE),blood urea nitrogen(BUN)levels(P>0.05).In in vitro experiments,immunofluorescence staining,PI/Hoechst and LDH tests revealed that TP dose-dependently attenuated oligodendrocyte injury after OGD,and significantly reduced its TNF-a and IL-6 expression.Conclusion Triptolide alleviates cognitive dysfunction and white matter damage caused by chronic cerebral hypoperfusion,which may be due to its inhibition of microglia activation and expression of TNF-?,IL-6,alleviation of oligodendrocyte injury and then amelioration of the demyelination.It suggests that triptolide may have a potential therapeutic value for subcortical ischemic vascular dementia caused by chronic cerebral hypoperfusion.