Interleukin-4 protects from chemotherapy-induced peripheral neuropathy in mice modal via the stimulation of IL-4/STAT6 signaling

Abstract Purpose: To investigate the possible role of IL-4 signaling pathway in vincristine-induced peripheral neuropathy. Methods: The mouse model of vincristine-induced peripheral neuropathy and interleukin (IL)-4 knockout mice were utilized to investigate the possible role of IL-4 signaling pathway in vincristine-induced peripheral neuropathy. Vincristine induced increased sensitivity to mechanical stimulation was measured by von Frey hair test 7 and 14 days after intraperitoneal administration of 0.1 mg/kg vincristine in mice. Relative expression levels of cytokines were detected by quantitative real-time PCR. STAT6 expression following vincristine treatment was assessed with western blotting. Results: We discovered that IL-4/STAT6 signaling was down-regulated in vincristine-treated mice. Deletion of IL-4 in mice increased the sensitivity to mechanical allodynia. IL-4 knockout mice also produced more pro-inflammatory cytokines, including IL-1β and TNF-α. Notably, co-administration of exogenous recombination IL-4 significantly prevented vincristine-induced mechanical allodynia. Conclusion: Anti-inflammatory cytokine IL-4 protects rodent model from vincristine-induced peripheral neuropathy via the stimulation of IL-4/STAT6 signaling and inhibition of the pro-inflammatory cytokines.

Studies on the changes of c-fos protein in spinal cord and neurotransmitter in dorsal root ganglion of the rat with an experimental peripheral neuropathy

Animal models for human chronic pain syndromes have been developed and widely used for pain research. One of these neuropathic pain models by Kim and Chung (1992) has many advantages for operation and pain elicitation. In this neuropathic model we have examined the c-fos protein, substance P, CGRP immunoreactivity in dorsal root ganglia and dorsal horn. 50 Sprague-Dawley rats were used for this study. L5 and L6 spinal nerves were ligated tightly to produce the neuropathic pain model. After 2, 4, 8, 16, and 24 hours and 1 week of surgery, rats were anesthetized and sacrificed by perfusion. After confirmation of the roots transected by the surgery, the L5 and L6 dorsal root ganglions and spinal cord were removed and processed for immunohistochemistry. All tissue sections were immunohistochemically stained for substance P, CGRP and c-fos using the peroxidase-antiperoxidase (PAP) method. The number of immunostained substance P and CGRP dorsal root ganglion cells and c-fos immunoreactive dorsal horn cells were counted and analyzed statistically with Mann-Whitney U test. The results are as follows. The number of c-fos protein immunoreactive neurons in the superficial layer of dorsal horn were increased markedly 2 hours after operation, and gradually decreased to normal level 1 week after operation. The number of c-fos protein immunoreactive neurons in the deep layer of the dorsal horn gradually increased to a peak 24 hours after operation, then decreased to the normal level 1 week after operation. The number of substance P and CGRP immunoreactive L5 and L6 dorsal root ganglion neurons were decreased markedly 1 week after the pain model operation. In conclusion, after neuropathic pain model operation, c-fos proteins were immediately expressed in the superficial layer of spinal dorsal horn, thereafter c-fos proteins in the deep layer of spinal dorsal horn were expressed. CGRP and substance P immunoreactive neurons in DRG were decreased markedly 1 week after neuropathic pain model operation. These decrements do not coincide with the other chronic pain models, which show great increases in these pain transmitting substances. Therefore, the relationship between pain and c-fos, SP and CGRP should be investigated further.