Bleomycin triggers chronic mechanical nociception by activating TRPV1 and glial reaction-mediated neuroinflammation via TSLP/TSLPR/pSTAT5 signals

Chronic pain is a universal public health problem with nearly one third of global human involved, which causes significant distressing personal burden. After painful stimulus, neurobiological changes occur not only in peripheral nervous system but also in central nervous system where somatosensory cortex is important for nociception. Being an ion channel, transient receptor potential vanilloid 1 (TRPV1) act as an inflammatory detector in the brain. Thymic stromal lymphopoietin (TSLP) is a potent neuroinflammation mediator after nerve injury. Bleomycin is applied to treat dermatologic diseases, and its administration elicits local painful sensation. However, whether bleomycin administration can cause chronic pain remains unknown. In the present study, we aimed to investigate how mice develop chronic pain after receiving repeated bleomycin administration. In addition, the relevant neurobiological brain changes after noxious stimuli were clarified. C57BL/6 mice aged five- to six-weeks were randomly classified into two group, PBS (normal) group and bleomycin group which bleomycin was intradermally administered to back five times a week over a three-week period. Calibrated forceps testing was used to measure mouse pain threshold. Western blots were used to assess neuroinflammatory response; immunofluorescence assay was used to measure the status of neuron apoptosis, glial reaction, and neuro-glial communication. Bleomycin administration induced mechanical nociception and activated both TRPV1 and TSLP/TSLPR/pSTAT5 signals in mouse somatosensory cortex. Through these pathways, bleomycin not only activates glial reaction but also causes neuronal apoptosis. TRPV1 and TSLP/TSLPR/pSTAT5 signaling had co-labeled each other by immunofluorescence assay. Taken together, our study provides a new chronic pain model by repeated intradermal bleomycin injection by activating TRPV1 and glial reaction-mediated neuroinflammation via TSLP/TSLPR/pSTAT5 signals.