The role of PKC/PKR in aging, Alzheimer's disease, and perioperative neurocognitive disorders

BackgroundThe incidence of perioperative neurocognitive disorders (PNDs) is reportedly higher in older patients. Mitochondrial and synaptic dysfunctions have consistently been demonstrated in models of aging and neurodegenerative diseases; nonetheless, their role in PND is not well understood. MethodsThe Morris water maze and elevated plus maze tests were used to assess the learning and memory abilities of both C57BL/6 and 3xTg-AD mice of different ages (8 and 18 months). PND was induced by laparotomy in C57BL/6 mice and 3xTg-AD mice (8 months old). Markers associated with neuroinflammation, mitochondrial function, synaptic function, and autophagy were assessed postoperatively. The roles of protein kinase C (PKC) and double-stranded RNA-dependent protein kinase (PKR) were further demonstrated by using PKC-sensitive inhibitor bisindolylmaleimide X (BIMX) or PKR-/- mice. ResultsSignificant cognitive impairment was accompanied by mitochondrial dysfunction and autophagy inactivation in both aged C57BL/6 and 3xTg-AD mice. Laparotomy induced a significant neuroinflammatory response and synaptic protein loss in the hippocampus. Cognitive and neuropathological changes induced by aging or laparotomy were further exacerbated in 3xTg-AD mice. Deficits in postoperative cognition, hippocampal mitochondria, autophagy, and synapse were significantly attenuated after pharmacological inhibition of PKC or genetic deletion of PKR. ConclusionsOur findings suggest similar pathogenic features in aging, Alzheimer's disease, and PND, including altered mitochondrial homeostasis and autophagy dysregulation. In addition, laparotomy may exacerbate cognitive deficits associated with distinct neuronal inflammation, mitochondrial dysfunction, and neuronal loss independent of genetic background. The dysregulation of PKC/PKR activity may participate in the pathogenesis of these neurodegenerative diseases.