CXCL1-CXCR2 signaling mediates the activation of microglia in the nucleus tractus solitarii to promote pancreatic cancer-induced pain

Pancreatic cancer can cause severe abdominal pain. Its peripheral mechanisms have been studied, but the role of central nervous system in pancreatic cancer-induced pain remains unclear. The current study focused on the nucleus tractus solitarii (NTS), a primary center of visceral sensation located in medulla oblongata. Neurons in the NTS were activated and exhibited increased excitability among mice with pancreatic cancer-induced pain. Transcriptome analysis revealed that pancreatic cancer-induced pain was associated with neuroinflammation in the NTS, involving changes in chemokines expression. In mice with pancreatic cancer-induced pain, the microglia activation in the NTS was observed, characterized by increased cell density and decreased process number and length, while injection of microglia inhibitor minocycline in the NTS alleviated pancreatic cancer-induced pain. The cytokine CXCL1 and its receptor CXCR2 were upregulated in the NTS of mice with pancreatic cancer-induced pain. Blocking CXCL1-CXCR2 signaling by injection of CXCL1 neutralizing antibody or CXCR2 antagonist SB225002 in the NTS of mice with pancreatic cancer-induced pain alleviated abdominal hypersensitivity and hunching behavior, and also reversed the activation of neurons and microglia. Additionally, injection of recombinant CXCL1 in the NTS of sham-operated mice induced abdominal pain, and activated the neurons and microglia. In summary, our study highlights the critical role of NTS microglia activation mediated by CXCL1-CXCR2 signaling in pancreatic cancer-induced pain.