Inflammation, apoptosis and autophagy as critical players in vascular dementia

X.-X. Wang, B. Zhang, R. Xia, Q.-Y. Jia

Medical Record Room, The Affiliated Hospital to Changchun University of Chinese Medicine, Changchun, China. qy_jia@yahoo.com

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• Neurology

Vascular dementia is the second-most cause of dementia, characterized by cerebral infarcts, white matter lesions, myelin loss and often amyloid angiopathy. Hence, vascular damage is a critical cause of neuronal loss and synaptic disintegration. Abnormal neuroinflammation, autophagy and apoptosis are the prerequisite factors for endothelial and neuronal cell damage. This leads to the onset and progression of cerebrovascular disorders and cognitive dysfunction. The innate immune cells, pattern recognition receptors, Toll-like receptor-4 and related inflammatory mechanisms disrupt cerebrovascular integrity via glial activation and increased pro-inflammatory interleukins and TNFα. Inflammasome polymorphisms and multi-faceted neuro-immune interactions further integrate systemic and central inflammatory pathways, which induce vascular tissue injury and neurodegeneration. Specifically, chronic cerebral hypoperfusion disrupts the self-cannibalization mechanism of autophagy via altered expression of autophagy-specific proteins, Beclin-1, LC3 and P62. The deregulated autophagy pathway causes neuronal loss, hippocampal shrinkage, and ultimate loss in synaptic plasticity. The vascular dementia models typically exhibit downregulated anti-apoptotic Bcl-2 and upregulated pro-apoptotic Bax, cleaved caspase-3, and cleaved-PARP levels in the brain, for which modulated p38 MAPK and JNK phosphorylation pathways play a vital role. Endoplasmic stress-induced apoptosis, calcium overload and glutamate excitotoxicity in combination with ASK1-MAPK signaling mechanism also contribute to the cerebrovascular pathology. Vascular injury reduces neurological scores and increases the infarct volume, DNA damage and neuronal apoptosis in ischemia/reperfusion injury. Additionally, synergistic and additive interactions between inflammasome, autophagy and apoptotic signaling pathways augment symptoms of vascular neurodegeneration. Overall, the current review enlightens the key risk factors and underlying mechanism triggering vascular dementia. The review additionally informs the challenges associated while treating vascular dysfunction, and highlights the need for targeted drugs for reducing cerebrovascular damage.

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