Protein phosphatase 2Cm-regulated branched-chain amino acid catabolic defect in dorsal root ganglion neurons drives pain sensitization

Abstract

Maladaptive changes of metabolic patterns in the lumbar dorsal root ganglion (DRG) are critical for nociceptive hypersensitivity genesis. The accumulation of branched-chain amino acids (BCAAs) in DRG has been implicated in mechanical allodynia and thermal hyperalgesia, but the exact mechanism is not fully understood. This study aimed to explore how BCAA catabolism in DRG modulates pain sensitization. Wildtype male mice were fed a high-fat diet (HFD) for 8 weeks. Adult PP2Cmfl/fl mice of both sexes were intrathecally injected with pAAV9-hSyn-Cre to delete the mitochondrial targeted 2 C-type serine/threonine protein phosphatase (PP2Cm) in DRG neurons. Here, we reported that BCAA catabolism was impaired in the lumbar 4–5 (L4-L5) DRGs of mice fed a high-fat diet (HFD). Conditional deletion of PP2Cm in DRG neurons led to mechanical allodynia, heat and cold hyperalgesia. Mechanistically, the genetic knockout of PP2Cm resulted in the upregulation of C-C chemokine ligand 5/C-C chemokine receptor 5 (CCL5/CCR5) axis and an increase in transient receptor potential ankyrin 1 (TRPA1) expression. Blocking the CCL5/CCR5 signaling or TRPA1 alleviated pain behaviors induced by PP2Cm deletion. Thus, targeting BCAA catabolism in DRG neurons may be a potential management strategy for pain sensitization.