Inhibition of protein tyrosine phosphatase 1B in spinal cord dorsal horn of rats attenuated diabetic neuropathic pain

Protein tyrosine phosphatase 1B (PTP1B) has been shown to dephosphorylate and inactivate insulin receptors, which contributes to the pathogenesis of diabetes. Neuropathic pain is one of the severe complications that results from diabetic neuropathy. However, whether PTP1B was involved in the development of diabetic neuropathic pain is largely unknown. The current study illustrated that PTP1B was located in spinal cord dorsal horn neurons of Sprague-Dawley rats. Western blot analysis demonstrated that the diabetic neuropathic pain induced by intraperitoneal injection of streptozotocin was associated with an increased protein expression and a dynamic redistribution of spinal PTP1B into excitatory glutamatergic synapses. We found that PTP1B operated to stimulate Src kinase and enhance the tyrosine phosphorylation of N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. The siRNA-mediated knockdown of PTP1B in streptozotocin-injected rats repressed Src activity, decreased NMDA receptor phosphorylation and alleviated the thermal hyperalgesia and mechanical allodynia. A similar analgesia against diabetic neuropathic pain was also achieved when PTP1B activity was manipulated by a chemical PTP Inhibitor or PTP1B(C215S) mutant. These data revealed a regulated expression of PTP1B in spinal cord dorsal horn of rats after diabetic neuropathy, and demonstrated that inhibition of PTP1B was beneficial for the treatment of pain hypersensitivity related to diabetes.