Comparison of Cognitive Performance and Cardiac Function Between Three Different Rat Models of Vascular Dementia

Dexmedetomidine Stereotaxic Injection Alleviates Neuronal Loss Following Bilateral Common Carotid Artery Occlusion via Up-Regulation of BDNF Expression

BACKGROUND/AIM

Neurogenesis is an important process in the recovery from neurological damage caused by ischemic lesions. Endogenous neurogenesis is insufficient to restore neuronal damage following cerebral ischemia. Dexmedetomidine (DEX) exerts neuroprotective effects against cerebral ischemia and ischemia/reperfusion injury. DEX promotes neurogenesis, including neuronal proliferation and maturation in the hippocampus. In a previous study, we showed that early neurogenesis increased 3 days after bilateral common carotid artery occlusion (BCCAO). In this study, we investigated the effect of DEX on neurogenesis 3 days after BCCAO.

MATERIALS AND METHODS

Male Sprague-Dawley (SD) rats (7-8 weeks old) were used as a BCCAO model. Right and left common carotid arteries of the rats were occluded using 4-0 silk sutures. Two hours after surgery, an intracranial DEX injection was administered to rats that underwent surgery using a stereotaxic injector. Brains were obtained from control and BCCAO rats 3 days after surgery. Immunohistochemistry was performed on the cortex and dentate gyrus of the hippocampus using a NeuN antibody. Western blot was performed with HIF1α and brain-derived neurotrophic factor (BDNF) antibodies.

RESULTS

The number of mature neurons decreased 3 days after BCCAO, but DEX treatment alleviated neural loss in the parietal cortex and hippocampus. Up-regulation of BDNF was also observed after dexmedetomidine treatment.

CONCLUSION

Stereotaxic injection of dexmedetomidine alleviates neural loss following BCCAO by up-regulating BDNF expression.

Associations of Lipids and Lipid-Lowering Drugs with Risk of Vascular Dementia: A Mendelian Randomization Study

Accumulating observational studies suggested that hypercholesterolemia is associated with vascular dementia (VaD); however, the causality between them remains unclear. Hence, the aim of this study is to infer causal associations of circulating lipid-related traits [including high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), apolipoprotein A-I (apoA-I), and apolipoprotein B (apoB)] with VaD jointly using univariable MR (uvMR), multivariable MR (mvMR) and bidirectional two-sample MR methods. Then, the summary-data-based MR (SMR) and two-sample MR analysis were conducted to investigate the association of lipid-lowering drugs target genes expression (including HMGCR, PCSK9, NPC1L1, and APOB) and LDL-C level mediated by these target genes with VaD. The results of forward MR analyses found that genetically predicted HDL-C, LDL-C, TG, apoA-I, and apoB concentrations were not significantly associated with the risk of VaD (all p > 0.05). Notably, there was suggestive evidence for a causal effect of genetically predicted VaD on HDL-C via reverse MR analysis [odds ratio (OR), 0.997; 95% confidence interval (CI), 0.994−0.999; p = 0.022]. On the contrary, the MR results showed no significant relationship between VaD with LDL-C, TG, apoA-I, and apoB. The results for the SMR method found that there was no evidence of association for expression of HMGCR, PCSK9, NPC1L1, and APOB gene with risk of VaD. Furthermore, the result of MR analysis provided evidence for the decreased LDL-C level mediated by gene HMGCR reduced the risk of VaD (OR, 18.381; 95% CI, 2.092−161.474; p = 0.009). Oppositely, none of the IVW methods indicated any causal effects for the other three genes. Using genetic data, this study provides evidence that the VaD risk may cause a reduction of HDL-C level. Additionally, the finding supports the hypothesis that lowering LDL-C levels using statins may be an effective prevention strategy for VaD risk, which requires clinical trials to confirm this result in the future.

Ameliorative Processes of Beta-Carotene in Streptozotocin-Induced Diabetic Vascular Dementia in Rats

Beta-carotene (BC) is a precursor of vitamin A and an excellent antioxidant. It protects the vascular system. Vascular dementia (VaD) is one of the aging disorders causing memory dysfunction. The available medicines for the management of VaD are limited. The present study aimed to evaluate the ameliorative effect of BC in streptozotocin (STZ)-induced diabetic VaD in rats. Diabetic VaD was induced through the administration of nicotinamide (NA, 50 mg/kg; i.p.) and STZ (50 mg/kg; i.p.). The test compound BC (50 and 100 mg/kg; p.o.) and reference compound donepezil (1 mg/kg; p.o.) were administered for 15 consecutive days. Cognitive changes were assessed by transfer latency (TL) using the elevated plus maze (EPM) test. The changes in acetylcholinesterase (AChE) activity were estimated in the septohippocampal system of rat brains. The administration of STZ caused significant changes in cognitive functions (increased TL) as compared to the normal group. BC ameliorated the anxiety-related cognitive behavior and neurotransmitter (elevated AChE) changes provoked by diabetic VaD. Therefore, BC could be a potential therapeutic candidate in the management of VaD.

Floralozone improves cognitive impairment in vascular dementia rats via regulation of TRPM2 and NMDAR signaling pathway

Vascular dementia (VD) is the second largest type of dementia after Alzheimer's disease. At present, the pathogenesis is complex and there is no effective treatment. Floralozone has been shown to reduce atherosclerosis in rats caused by a high-fat diet. However, whether it plays a role in VD remains elusive. In the present study, the protective activities and relevant mechanisms of Floralozone were evaluated in rats with cognitive impairment, which were induced by bilateral occlusion of the common carotid arteries (BCCAO) in rats. Cognitive function, pathological changes and oxidative stress condition in the brains of VD rats were assessed using Neurobehavioral tests, Morris water maze tests, hematoxylin-eosin staining, Neu N staining, TUNEL staining, Golgi staining, Western blot assay and antioxidant assays (MDA, SOD, GSH), respectively. The results indicated that VD model was established successfully and BCCAO caused a decline in spatial learning and memory and hippocampal histopathological abnormalities of rats. Floralozone (50, 100, 150 mg/kg) dose-dependently alleviated the pathological changes, decreased oxidative stress injury, which eventually reduced cognitive impairment in BCCAO rats. The same results were shown in further experiments with neurobehavioral tests. At the molecular biological level, Floralozone decreased the protein level of transient receptor potential melastatin-related 2 (TRPM2) in VD and normal rats, and increased the protein level of NR2B in hippocampus of N-methyl-D-aspartate receptor (NMDAR). Notably, Floralozone could markedly improved learning and memory function of BCCAO rats in Morris water maze (MWM) and improved neuronal cell loss, synaptic structural plasticity. In conclusion, Floralozone has therapeutic potential for VD, increased synaptic structural plasticity and alleviating neuronal cell apoptosis, which may be related to the TRPM2/NMDAR pathway.