Anandamide Reduces the Capsaicin-Evoked Pain by Regulating TRPV1 Protein Levels

Background: Anandamide (AEA) is a lipid mediator of the endocannabinoid system that plays a key role in pain perception by regulating multiple molecular targets, including transient receptor potential vanilloid type 1 (TRPV1). This vanilloid receptor is abundantly expressed in nociceptive neurons (nociceptors) and plays a crucial role in mediating pain responses. Methods: We used mouse behavioral tests, cell culture, and Western blot assays to test whether AEA regulates acute pain induced by TRPV1 activation and TRPV1 total protein levels. Results: Our results demonstrate that AEA downregulates the capsaicin-evoked pain response and TRPV1 protein levels in nociceptors. Furthermore, in a transiently heterologous TRPV1 expression system, we found that AEA induces ubiquitination of TRPV1 and its degradation via the proteasome pathway, independent of calcium influx. We also found that AEA induced an upregulation of BiP protein levels, a key endoplasmic reticulum chaperone and stress sensor, without changes in other ER stress sensors. Finally, we explored whether the endocannabinoid 2-arachidonoylglycerol (2-AG) and the phytocannabinoid β-caryophyllene (BCP) modulate capsaicin-evoked pain, finding that 2-AG is less effective than AEA in reducing pain behavior, whereas BCP shows effects similar to AEA in reducing capsaicin-evoked pain. Conclusions: These results highlight AEA and BCP as regulators of TRPV1 protein levels and of the painful response mediated by this molecular pain target.