P2Y12 receptor in trigeminal ganglion contributes to CFA-induced mechanical allodynia in mice

Chronic orofacial inflammatory pain remains a major clinical challenge, and peripheral sensitization within the trigeminal ganglion (TG) is thought to contribute to its development. This study aimed to investigate whether P2Y12 Receptor signaling contributes to orofacial inflammatory pain, with particular focus on the TG as a potential peripheral site of action. A mouse model of orofacial pain was established through the subcutaneous injection of complete Freund's Adjuvant (CFA) into the right whisker pad. The expression and distribution of P2Y12 Receptor were characterized using single-cell RNA Sequencing, immunohistochemistry, and immunofluorescence. The functional role of P2Y12 signaling was examined by systemic clopidogrel treatment in vivo and by ADP stimulation with or without the selective antagonist PSB-0739 in primary satellite glial cells (SGCs) and macrophages in vitro. P2Y12 expression in the TG was significantly upregulated 7 days after CFA injection and was predominantly expressed on SGCs and macrophages. Systemic pharmacological inhibition of P2Y12 alleviated mechanical allodynia and was associated with reduced c-Fos expression in the spinal trigeminal nucleus caudalis (SpVc). In addition, the P2Y12 inhibition was accompanied by decreased SGC activation, fewer CD86-positive macrophages, and lower interleukin-6 (IL-6) expression in the TG. In vitro assays further showed that P2Y12 activation promoted pro-inflammatory cytokine expression in both SGCs and macrophages, and this effect was attenuated by PSB-0739. Collectively, these findings suggest that P2Y12 Receptor may contribute to the regulation of orofacial inflammatory pain, in part through neuroimmune alterations within the TG.