[Intrathecal injection of AG-490 reduces bone-cancer-induced spinal cord astrocyte reaction and thermal hyperalgesia in a mouse model].

OBJECTIVE: To investigate the role of spinal interleukin-6-Janus kinase 2 (IL-6-JAK2) signaling transduction pathway in regulating astrocytes activation during the maintenance of bone cancer pain (BCP).
 Methods: NCTC 2472 fibrosarcoma cells were injected into the femur marrow cavity in C3H/HeNCrlVr male mice to establish BCP model and they were replaced by the equal volume of α-MEM in the sham model. The paw withdrawal latency (PWL) was measured after inoculation of tumor cells. The lumbar enlargement of spinal cord (L3-L5) was isolated, and Real-time RT-PCR and Western blot were used to detect the expression of spinal glial fibrillary acidic protein (GFAP) and JAK2 mRNA and protein, respectively. The expression level of spinal GFAP mRNA indirectly reflect astrocytes activation level. Pain behaviors and spinal cord GFAP mRNA and protein expression were observed at the given time points after intrathecal administration of JAK2 antagonist AG-490.
 Results: The PWL at 10, 14, 21 d after operation in BCP model group were significantly shorter than that in the sham group (P<0.05); the spinal GFAP and JAK2 mRNA and protein levels were higher in the BCP model group in comparison to mice in the sham group (P<0.05); intrathecal injection of JAK2 agonist AG-490 (30 or 90 nmol) significantly alleviated PWL, and downregulated the expression of spinal GFAP mRNA and protein (P<0.05).
 Conclusion: The IL-6-JAK2 signaling pathway plays an important role in maintaining the BCP by regulating the expression of GFAP in the spinal cord. Intrathecal injection of AG-490 can reduce the BCP, and inhibit the activation of IL-6-JAK2 signaling pathway, which may be one of the mechanisms for spinal astrocyte activation.