Rho/ROCK acts downstream of lysophosphatidic acid receptor 1 in modulating P2X3 receptor-mediated bone cancer pain in rats.
BACKGROUND
Lysophosphatidic acid receptor 1 and Rho/ROCK signaling is implicated in bone cancer pain development. However, it remains unknown whether the two signaling pathways function together in P2X3 receptor-mediated bone cancer pain.


RESULTS
In this study, using a rat model of bone cancer, we examined the expression of P2X3 and lysophosphatidic acid receptor 1 in rat dorsal root ganglion neurons and further dissected whether lysophosphatidic acid receptor 1 and Rho/ROCK-mediated pathways interacted in modulating rat pain behavior. Bone cancer was established by inoculating Walker 256 cells into the left tibia of female Wistar rats. We observed a gradual and yet significant decline in mean paw withdrawal threshold in rats with bone cancer, but not in control rats. Our immunohistochemical staining revealed that the number of P2X3- and lysophosphatidic acid receptor 1-positive dorsal root ganglion neurons was significantly greater in rats with bone cancer than control rats. Lysophosphatidic acid receptor 1 blockade with VPC32183 significantly attenuated decline in mean paw withdrawal threshold. Flinching behavior test further showed that lysophosphatidic acid receptor 1 inhibition with VPC32183 transiently but significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Rho inhibition by intrathecal BoTXC3 caused a rapid reversal in decline in mean paw withdrawal threshold of rats with bone cancer. Flinching behavior test showed that BoTXC3 transiently and significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Similar findings were observed with ROCK inhibition by intrathecal Y27632. Furthermore, VPC32183 and BoTXC3 effectively aborted the appearance of lysophosphatidic acid-induced calcium influx peak.


CONCLUSIONS
Lysophosphatidic acid and its receptor LPAR1, acting through the Rho-ROCK pathway, regulate P2X3 receptor in the development of both mechanical and spontaneous pain in bone cancer.
Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China.
Jing-Xiang
JX
Wu
Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China.
Xiao-Min
XM
Yuan
Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China.
Qiong
Q
Wang
Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China.
Wang
W
Wei
Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China my_xu55@163.com.
Mei-Ying
MY
Xu
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives; D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D000072716:Cancer Pain / Q000378:metabolism*; D005260:Female; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D017208:Rats, Wistar; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism*; D058477:Receptors, Purinergic P2X3 / Q000378:metabolism*; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000378:metabolism*
D049368:Receptors, Lysophosphatidic Acid; D058477:Receptors, Purinergic P2X3; D000255:Adenosine Triphosphate; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium
Bone cancer pain; P2X3 receptor; Rho/ROCK; lysophosphatidic acid receptor