Licochalcone A Attenuates Chronic Neuropathic Pain in Rats by Inhibiting Microglia Activation and Inflammation.

Immune response plays a vital role in the pathogenesis of neuropathic pain. Immune response-targeted therapy becomes an effective strategy for treating neuropathic pain. Licochalcone A (Lic-A) possesses anti-inflammatory and neuroprotective effects. However, the potential of Lic-A to attenuate neuropathic pain has not been well explored. To investigate the protective effect and evaluate the underlying mechanism of Lic-A against neuropathic pain in a rat model. Chronic constriction injury (CCI) surgery was employed in rats to establish neuropathic pain model. Rats were intraperitoneally administrated with Lic-A (1.25, 2.50 and 5.00 mg/kg) twice daily. Mechanical withdrawal threshold and thermal withdrawal latency were used to evaluate neuropathic pain. After administration, the lumbar spinal cord enlargement of rats was collected for ELISA, Western blot and immunofluorescence analysis. Mechanical withdrawal threshold and thermal withdrawal latency results showed that Lic-A significantly attenuated CCI-evoked neuropathic pain in dose-dependent manner. Lic-A administration also effectively blocked microglia activation. Moreover, Lic-A suppressed p38 phosphorylation and the release of inflammatory factors such as tumor necrosis factor-α, interleukin-1 and interleukin-6. Our findings provide evidence that Lic-A may have the potential to attenuate CCI-evoked neuropathic pain in rats by inhibiting microglia activation and inflammatory response.