Botch improves cognitive impairment after cerebral ischemia associated with microglia-induced A1-type astrocyte activation

Vascular cognitive impairment (VCI) is a clinical syndrome that arises from cerebrovascular issues and associated risk factors, resulting in difficulties in at least one area of cognitive function. VCI has emerged as the second most prevalent type of dementia following Alzheimer's disease, yet there is no effective clinical treatment. Botch, an endogenous Notch1 antagonist, demonstrates neuroprotective effects by inhibiting neuroinflammatory responses mediated through the Notch pathway. While its role in stroke-induced neuroinflammation is well-established, its involvement in VCI remains largely unexplored. This study investigates the role and potential mechanisms of Botch in a rat model of cognitive impairment caused by bilateral common carotid artery occlusion (BCCAO). Firstly, we observed that Botch levels were down-regulated in BCCAO rats, which correlated with increased release of inflammatory cytokines and neuronal damage. Microglia in BCCAO rats released interleukin-1 alpha (IL1 alpha), tumor necrosis factor-alpha (TNF-alpha), and complement component 1q (C1q), leading to the activation of neurotoxic C3+ A1 reactive astrocytes. Then, the down-regulation of Botch exacerbated microglia-mediated inflammation, activated C3+ A1 astrocytes, worsened neuronal damage, and led to a decline in cognitive function. Conversely, the re-expression of Botch alleviated C3+ astrocyte activation, inhibited neuronal damage, and improved mental function. In conclusion, Botch plays a crucial role in inhibiting neuroinflammation induced by type A1 reactive astrocytes. It achieves this by blocking the activation of microglia triggered by the Notch pathway. Ultimately, it inhibits neuronal damage to play a neuroprotective role. These findings suggest that Botch may represent a novel potential target for treating VCI.