Orexin A alleviates chronic cerebral hypoperfusion-induced neuroinflammation and cognitive dysfunction by inhibiting...

Chronic cerebral hypoperfusion (CCH)-induced neuroinflammation significantly impacts the functional prognosis of patients with vascular dementia (VaD). Microglial neuroinflammation is significantly aggravated by the chronic activation of the NLRP3 inflammasome, which has emerged as a major contributing factor. Our previous research indicated that Orexin A effectively alleviates acute inflammatory responses and neurological deficits following brain injury. However, its neuroprotective role in cognitive function recovery after CCH remains to be elucidated.

Adult male SD rats underwent permanent bilateral common carotid artery occlusion surgery for 8 weeks to establish a VaD model. Subsequently, the rats received 4 weeks of continuous intranasal Orexin A treatment (250 μg/kg). Additionally, in order to explore the potential mechanisms and neuroprotective roles of Orexin A, BV2 cells were subjected to hypoxia to simulate in vitro CCH stimulation, either with or without Orexin A pretreatment, and were then co-cultured with HT22 neurons.

After 8 weeks of modeling, we noted a significant decrease in Orexin A and OXR1 expression in the hippocampus of CCH rats, which was accompanied by pronounced cognitive impairments. Furthermore, CCH exposure resulted in prolonged activation of the NLRP3 inflammasome and M1-type microglia within the hippocampus, as well as blood-brain barrier disruption and neurodegenerative changes. Orexin A treatment effectively ameliorated these alterations. In vitro experiments demonstrated hypoxia exposure promoted NLRP3 inflammasome activation in microglia, along with the release of pore-forming Gasdermin-D-NT and NINJ1, ultimately causing "bystander" neuronal pyroptosis. Orexin A inhibited NLRP3 inflammasome activation in microglia, thereby promoting the transition of M1-type microglia to M2-type and mitigating neuronal pyroptosis. These effects were abolished by NEK7 overexpression.

Our findings indicate that Orexin A restores the M1/M2 microglial balance by inhibiting the NEK7/NLRP3 pathway. This, in turn, alleviates neuroinflammation and neuronal pyroptosis, ultimately improving cognitive dysfunction after CCH. This study enhances our understanding of the neuroprotective mechanisms of Orexin A, potentially offering a new therapeutic target for cognitive impairment following CCH.