Urinary kallikrein reverses neuropathic pain by inhibiting ectopic neural discharges, neural inflammation and oxidative stress.

Background: Neuropathic pain is a refractory disease and badly impacts the lives of patients. Urinary kallikrein (UK) acted as a glycoprotein has been discovered to play a pivotal role in neuroprotection. However, the regulatory impacts and correlative pathways of UK in the progression of neuropathic pain remain dimness. Methods: The chronic constriction injury (CCI) rat model was firstly established to mimic neuropathic pain. The withdrawal threshold was measured through the Von Frey test. The levels of TNF-α, IL-1β and IL-6 were determined through ELISA. The levels of ROS, GSH, SOD and GSH-Px were examined through the commercial kits. The ectopic discharges were assessed. The protein expressions were inspected through western blot. Results: It was demonstrated that withdrawal threshold was reduced in CCI rat model, but this change was reversed after UK treatment, indicating that UK relieved mechanical allodynia. Moreover, UK alleviated the inflammatory response through reducing TNF-α, IL-1β and IL-6 levels. It was uncovered that oxidative stress was strengthened in CCI rat model, but this impact was restrained after UK treatment. Additionally, UK suppressed ectopic discharge. At last, it was proved that UK triggered the Nrf2/ARE signaling pathway in CCI rat model. Conclusion: This study manifested that UK reversed neuropathic pain by inhibiting ectopic neural pathways, neural pathways and oxidation via the Nrf2/ARE pathway. This study may offer useful proofs the regulatory functions of UK in the cure of neuropathic pain.