Optogenetic activation of glutamatergic neu⁃rons in somatosensory cortex promotes remy⁃elination in ischemic vascular dementia

OBJECTIVE Chronic cerebral hy⁃poperfusion can lead to progressive demyelin⁃ation and ischemic vascular dementia,yet there are no effective treatments.METHODS Magnetic resonance imaging was employed in patients with white matter damage,and optogenetics and skin stroking were exerted to activate glutamater⁃gic neurons in the somatosensory cortex in a clas⁃sical mouse model of ischemia vascular dementia.RESULTS White matter damage was correlated with disrupted cortical structure from MRI results.In a mouse model,activating glutamatergic neu⁃rons in the somatosensory cortex promotes prolif⁃eration of OPCs and remyelination to rescue cog⁃nitive impairment after chronic cerebral hypoper⁃fusion.Such therapeutic action was limited to stimulation with moderate intensity at the upper layers of the cortex,but was achieved over a wide time window after ischemia.Mechanistically,enhanced glutamatergic neuron-OPC functional synaptic connections are required for protection from activation of cortical glutamatergic neurons.Finally,skin stroking activation of the somatosen⁃sory cortex,an easier approach for clinical trans⁃lation,promoted OPC proliferation and remyelin⁃ation as well as cognitive recovery after cerebral hypoperfusion.CONCLUSION Activation of gluta⁃matergic neurons in the somatosensory cortex may serve as novel approaches for treating isch⁃emic vascular dementia through precise modula⁃tion of glutamatergic neuron-OPC circuits.

Recommendation for and comparison of three types of dementia： Alzheimer’s disease, subcortical ischemic vascular dementia, and mixed dementia

With the progress in global demography of aging, dementia has become a great world health-care issue that require urgent attention and settlement. Demen-tia can arise from a variety of factors, such as neuronal degeneration for Alzheimer’s disease （AD）, vascular risk factors and multiple infarcts for vascular dementia （VaD）, and both degeneration and vascular factors for mixed de-mentia （MD）. Pathophysiology of AD includes the amy-loid and tau protein hypothesis, and infammation-related mechanisms are also widespread mentioned. Subcortical ischemic vascular dementia （SIVD）, a subtype of VaD, is commonly caused by complete or incomplete lacunar infarction of VaD pathology. MD involves both degenera-tion and vascular factors, and the interaction between the two results in the complication of the pathological mech-anism and clinical phenotype. The clinical manifestationsof AD are often divided into four stages according to the progress of the disease, while the phenotypes of SIVD usually has two categories. As for MD, the phenotypes are complex and diverse. Several clinical studies showedthat its symptoms and signs are more similar to SIVD than AD. This article aims to analyze and compare the differ-ent aspects of the three kinds of dementia.

Neuroprotective effects of tetrandrine against vascular dementia

Tetrandrine is one of the major active ingredients in Menispermaceae Stephania tetrandra S.Moore,and has specific therapeutic effects in ischemic cerebrovascular disease.Its use in vascular dementia has not been studied fully.Here,we investigated whether tetrandrine would improve behavioral and cellular impairments in a two-vessel occlusion rat model of chronic vascular dementia.Eight weeks after model establishment,rats were injected intraperitoneally with 10 or 30 mg/kg tetrandrine every other day for 4 weeks.Behavioral assessment in the Morris water maze showed that model rats had longer escape latencies in training trials,and spent less time swimming in the target quadrant in probe trials,than sham-operated rats.However,rats that had received tetrandrine showed shorter escape latencies and longer target quadrant swimming time than untreated model rats.Hematoxylin-eosin and Nissl staining revealed less neuronal necrosis and pathological damage,and more living cells,in the hippocampus of rats treated with tetrandrine than in untreated model rats.Western blot assay showed that interleukin-1β expression,and phosphorylation of the N-methyl-D-aspartate 2B receptor at tyrosine 1472,were lower in model rats that received tetrandrine than in those that did not.The present findings suggest that tetrandrine may be neuroprotective in chronic vascular dementia by reducing interleukin-1β expression,N-methyl-D-aspartate receptor 2B phosphorylation at tyrosine 1472,and neuronal necrosis.

Protective effects of carnosine on white matter damage induced by chronic cerebral hypoperfusion

Carnosine is a dipeptide that scavenges free radicals, inhibits infammation in the central nervous system, and protects against ischemic and hypoxic brain damage through its anti-oxidative and anti-apoptotic actions. Therefore, we hypothesized that carnosine would also protect against white matter damage caused by subcortical ischemic injury. White matter damage was induced by right unilateral common carotid artery occlusion in mice. The animals were treated with 200, 500 or 750 mg/kg carnosine by intraperitoneal injection 30 minutes before injury and every other day after injury. Then, 37 days later, Klfiver-Barrera staining, toluidine blue staining and immunofluorescence stain- ing were performed. Carnosine （200, 500 mg/kg） substantially reduced damage to the white matter in the corpus callosum, internal capsule and optic tract, and it rescued expression of myelin basic protein, and alleviated the loss of oligodendrocytes. However, carnosine at the higher dose of 750 mg/kg did not have the same effects as the 200 and 500 mg/kg doses. These findings show that carnosine, at a particular dose range, protects against white matter damage caused by chronic cerebral ischemia in mice, likely by reducing oligodendroglial cell loss.