Study On Overexpression Of GRK6 In Dorsal Root Ganglion Attenuates Bone Cancer Pain In Rats

Objective: Bone cancer pain(BCP)is one of the most severe types of chronic pain,whose clinical treatment remains challenging and the involved mechanisms were largely unknown.G protein coupled receptor kinase 6(GRK6)is an intracellular kinase that regulates the sensitivity of certain G-protein-coupled receptors,thus involving in a wide variety of processes including inflammation and nociception.However,the role of GRK6 in BCP is poorly understood and studied.The present study was designed to investigate the role of GRK6 in dorsal root ganglion(DRG)in the development of BCP.Method: BCP was established by injection of Walker 256 mammary gland tumor cells into the rat tibia canal.Behavior tests,the paw withdrawal latency(PWL)to radiant heat,the 50% paw withdrawal threshold(PWT)to a static mechanical stimulus and weight bearing difference tests were used to test the pain hyperalgesia induced by tumor cells.By intrathecal infection of Lentiviral-GRK6,GRK6 was overexpressed and the behavior tests were tested again.Western blotting and Real time-PCR were performed to detect the expression of GRK6.Immunohistochemical staining was performed to determine whether SOCS3 was expressed in neural cells or microglia cells.Results: Tumor cell intra-tibia injection produced pain hypersensitivity and GRK6 expression was significantly downregulated in rat DRGs at L2-5 segments both at Mrna and protein level.Overexpression of GRK6 using lentiviral-mediated production of GRK6 at spinal cord level,drastically attenuated mechanical allodynia ? thermal hyperalgesia and body-weight bearing difference.Immunohistochemical staining showed GRK6 were located in neurons,but not in glias or microglia cells in DRGs.Conclusions: Tumor cell intra-tibia injection could build animal models of cancer-induced pain,inducing pain hypersensitivity and decreased the expression of GRK6.And reversed the change in the expression of GRK6 relieved pain hypersensitivity.These results suggest that GRK6 might be a key molecular involved in the development of complicated bone cancer pain.Overexpression of GRK6 might be an important strategy for treatment for mechanical allodynia associated with bone cancer.