P2Y6 receptor blockade promotes depression-like symptoms through oxidative stress and impaired autophagy

The P2Y6 receptor (P2Y6R) is implicated in neuroinflammation and synaptic plasticity, but its role in depression remains unclear. This study reveals a crucial role for the P2Y6 receptor (P2Y6R) in depression. Using a chronic restraint stress (CRS) mouse model, we found reduced hippocampal P2Y6R expression. Pharmacological inhibition of P2Y6R with MRS2578 (MRS) induced robust depressive-like behaviors in mice, including anhedonia and behavioral despair, accompanied by decreased hippocampal serotonin and norepinephrine. At the molecular level, MRS disrupted synaptic integrity, evidenced by reduced expression of key synaptic proteins (PSD95, synaptophysin, SNAP25, mature BDNF) and impaired associated signaling pathways. Our multi-omics analysis further showed that P2Y6R inhibition profoundly disrupted neuronal autophagic flux and metabolic homeostasis. The late-stage autophagy inhibitor chloroquine was more effective than the early-stage inhibitor 3-methyladenine in attenuating MRS-induced depressive symptoms and restoring synaptic protein expression. This suggests that lysosomal dysfunction is a key contributor to the pathology. We identified that MRS disrupts neuronal autophagy primarily through the P2Y6R-Oxidative stress axis, as evidenced by dysregulated antioxidant defences and increased oxidative damage markers, including protein carbonyls (PC), 3-nitrotyrosine (3-NT), and the lipid peroxidation product 4-hydroxynonenal (4-HNE). Crucially, antioxidant intervention with N-acetylcysteine (NAC) rescued MRS-induced depressive behaviors, synaptic deficits, and normalized oxidative stress and autophagy dynamics. Validation with P2Y6R agonists confirmed that the observed effects were specific to P2Y6R inhibition. These findings establish the P2Y6R-Oxidative stress-autophagy axis as a novel and promising therapeutic target for Major Depressive Disorder, offering new avenues for more effective treatments.