Inhibition of the PKC-TRPV1-SP axis by propolis ameliorates chronic inflammatory pain in mice

Chronic inflammatory pain significantly affects patient quality of life; however, existing treatment methods have limitations. Propolis is rich in various bioactive ingredients, such as flavonoids and phenolic acids. This study aimed to explore the effects and action mechanisms of propolis against chronic inflammatory pain.

A mouse model of chronic inflammatory pain was established using Complete Freund's adjuvant, with the mice divided into normal control, model, and propolis-treated groups. Body weight, pain score, foot volume, thermal pain threshold, mechanical pain threshold, and pathological changes in the toe tissue were recorded before injection (day 0) and on days 1, 7, 14, 21, and 28 after injection.After the experiment, changes in inflammatory factors (TNF-α, IL-4, IL-6, and IL-10) were detected, and the expression and distribution of proteins associated with the PKC-TRPV1-SP signalling axis in the toe, spinal cord, and hippocampus were detected by Western blot and immunofluorescence.

Propolis treatment significantly inhibited foot swelling, alleviated tissue inflammatory lesions, relieved pain, and increased heat and mechanical pain thresholds in mice. In addition, propolis inhibited the secretion of pro-inflammatory cytokines TNF-α, IL-4, and IL-6, promoted the secretion of the anti-inflammatory cytokine IL-10, and inhibited the expression of proteins related to the PKC-TRPV1-SP signalling axis.

This study demonstrated that propolis exerts anti-inflammatory and analgesic effects by regulating the PKC-TRPV1-SP signalling axis. The findings offer new perspectives for the clinical treatment of chronic inflammatory pain and provide a reference for the development of new medications.