NAAA-regulated lipid signaling in monocytes controls the induction of hyperalgesic priming in mice.

Circulating monocytes participate in pain chronification but the molecular events that cause their deployment are unclear. Using a mouse model of hyperalgesic priming (HP), we show that monocytes enable progression to pain chronicity through a mechanism that requires transient activation of the hydrolase, N-acylethanolamine acid amidase (NAAA), and the consequent suppression of NAAA-regulated lipid signaling at peroxisome proliferator-activated receptor-α (PPAR-α). Inhibiting NAAA in the 72 hours following administration of a priming stimulus prevented HP. This effect was phenocopied by NAAA deletion and depended on PPAR-α recruitment. Mice lacking NAAA in CD11b⁺ cells – monocytes, macrophages, and neutrophils – were resistant to HP induction. Conversely, mice overexpressing NAAA or lacking PPAR-α in the same cells were constitutively primed. Depletion of monocytes, but not resident macrophages, generated mice that were refractory to HP. The results identify NAAA-regulated signaling in monocytes as a control node in the induction of HP and, potentially, the transition to pain chronicity. Circulating monocytes contribute to the transition to pain chronicity but the molecular events that cause their deployment are still unclear. Using a mouse model of hyperalgesic priming, here the authors show that blood monocytes contribute to the emergence of chronic pain via a mechanism that requires a transient disruption of NAAA-regulated lipid signaling. [ABSTRACT FROM AUTHOR]