INHIBITION OF GLYCOGEN SYNTHASE KINASE 3BETA ACTIVITY WITH LITHIUM PREVENTS AND ATTENUATES PACLITAXEL-INDUCED NEUROPATHIC PAIN

Paclitaxel (taxol) is a first-line chemotherapydrug used to treat many types of cancers. Neuropathic pain and sensory dysfunction are the major toxicities, which are dose-limiting and significantly reduce the quality of life in patients. Two known critical spinal mechanisms underlying taxol-induced neuropathic pain are an increased production of pro-inflammatory cytokines including interleukin-1 beta (IL-1 beta) and suppressed glial glutamate transporter activities. In this study, we uncovered that increased activation of glycogen synthase kinase 3beta (GSK3 beta) in the spinal dorsal horn was concurrently associated with increased protein expressions of GFAP, IL-1 beta and a decreased protein expression of glial glutamate transporter 1 (GLT-1), as well as the development and maintenance of taxol-induced neuropathic pain. The enhanced GSK3 beta activities were supported by the concurrently decreased AKT and mTOR activities. The changes of all these biomarkers were basically prevented when animals received pre-emptive lithium (a GSK3 beta inhibitor) treatment, which also prevented the development of taxol-induced neuropathic pain. Further, chronic lithium treatment, which began on day 11 after the first taxol injection, reversed the existing mechanical and thermal allodynia induced by taxol. The taxol-induced increased GSK3 beta activities and decreased AKT and mTOR activities in the spinal dorsal horn were also reversed by lithium. Meanwhile, protein expressions of GLT-1, GFAP and IL-1 beta in the spinal dorsal horn were improved. Hence, suppression of spinal GSK3 beta activities is a key mechanism used by lithium to reduce taxol-induced neuropathic pain, and targeting spinal GSK3 beta is an effective approach to ameliorate GLT-1 expression and suppress the activation of astrocytes and IL-1 beta over-production in the spinal dorsal horn. Published by Elsevier Ltd. on behalf of IBRO.