Effects of Harpagophytum procumbens extract on inflammation and nociceptive system in human primary synoviocytes

Osteoarthritis (OA) is a chronicaldegenerative and inflammatory disease affecting joints, where cartilage is degraded and bones friction each other, causing pain. At present date, there is no specific anti-OA therapy, so painkilling and antiinflammatory drugs are dispensed. The aim of this research is to study the possible analgesic and antiinflammatory properties of nutraceutical substances, in in vitro cell models. We studied the therapeutic properties of the Harpagophytum procumbens extract (HPE), commonly known as devil’s claw, a plant worldwide used as a traditional remedy for joint pain, on primary human synoviocytes (FLSs) from osteoarthritis patients. HPE powder has been dissolved in deionized water (HPEH2O), DMSO (HPEDMSO), 100% v/v EtOH (HPEEtOH100), and 50% v/v EtOH (HPEEtOH50). HPEH2O and HPEDMSO were able to increase gene and protein expression of CB2, a cannabinoid receptor involved in the modulation of the pain and inflammation in FLSs, and to inhibit the expression of phospholipases C β2 (PI-PLC β2), where the other two extracts did not produce the same effects. Moreover, we observed that PI-PLC β2 has low concentrations in healthy synovial membrane and high concentrations in osteoarthritic tissues, suggesting its direct involvement in the development of the inflammatory process in OA. On the other hand, only HPEH2O was able to decrease the gene expression of FAAH enzyme, involved in endocannabinoids degradation, while all the other extracts were ineffective. Nonetheless, all extracts used in these experiments were able to interfere with FAAH activity in a fluorescence assay. Since these preliminary results are very promising, a future perspective is to analyze some intracellular pathways, modulated by HPE, in order to better explain the antiinflammatory activity in addition to the antinociceptive one as described in this study. Mariano A. et al., Nutrients, 2020, doi: 10.3390/nu12092545.