(P25-022-24) Topical Use of Arnica Ethanolic Extract Reduces Post-operative Pain via the Nrf2 Signaling Pathway

Objectives: Arnica Montana (Arnica) is an herbaceous perennial plant traditionally used to treat trauma, inflammation, or tissue injuries. However, the findings from previous studies on the analgesic effect of Arnica are inconsistent. This study aims to unravel the therapeutic potential of Arnica and elucidate the molecular mechanisms underlying its ability to alleviate postoperative pain.

Methods: In pursuit of this objective, we meticulously prepared various Arnica extracts and assessed their efficacy using a paw incision-induced postoperative pain model in CD-1 mice. The left hind paw underwent an incision, and mice were treated with a gel containing 1% Arnica extracts for one hour during the surgery and again 24 hours post-surgery, all while under anesthesia. The mechanical threshold was measured at 3, 5, 24, and 48 hours after the surgery using the von Frey filaments to evaluate the analgesic effect of Arnica extracts.

Results: We found that topical treatment with 1% Arnica extracts exhibited an analgesic effect in postoperative pain at different time points after surgery, demonstrating the most robust analgesic effect. Further, the analgesic effect of Arnica ethanolic extract was found to be mediated through the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. In contrast, naloxone, an opioid receptor antagonist, did not impact the observed analgesic effect.

Conclusions: These findings determine that Arnica reduces the postoperative pain via activating Nrf2 signaling pathway, which provides evidence to discover nonopioid drugs for pain management from Arnica.

Funding Sources: N/A