The role of LINGO-1 in regulating CB1R/TrkB signalling and GABAergic interneurons in Alzheimer's disease pathogenesis

Leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 1 (LINGO-1) is a neuronal system-specific transmembrane protein that is highly expressed in the brains of patients with Alzheimer's disease (AD), and our previous findings showed that LINGO-1 antagonism can improve cognitive function and protect hippocampal GABAergic interneurons in AD model mice. However, the specific mechanism underlying these effects is not clear. In this study, an adeno-associated virus (AAV) was used to directly interfere with hippocampal LINGO-1 in vivo, and LINGO-1 antagonists, cannabinoid type 1 receptor (CB1R) agonists, and CB1R antagonists were used to treat mouse hippocampal neurons (HT22 neurons) in vitro. We found that overexpressing hippocampal LINGO-1 in normal young mice impaired spatial learning and memory and reduced hippocampal CB1R protein levels, whereas silencing hippocampal LINGO-1 in AD model mice had the opposite effect. Additionally, antagonizing LINGO-1 increased CB1R/tyrosine kinase receptor B (TrkB) signalling and rescued CB1R- rich cholecystokinin-GABAergic (CCK-GABAergic) interneurons in HT22 neurons transduced with an APP/PS1-expressing virus. Competitive inhibition of LINGO-1 and CB1R was observed, and antagonizing LINGO-1 reversed the changes in HT22 neurons caused by the inhibition of CB1R, such as the decreases in the protein levels of doublecortin (DCX), TrkB, and phosphorylated TrkB (p-TrkB). These findings provide an important scientific basis for further exploration of the mechanism by which LINGO-1 regulates cognitive function and hippocampal GABAergic interneurons in AD model mice.