Abstract
Development of paclitaxel-induced neuropathic pain (PINP) during chemotherapy may lead to paclitaxel discontinuation, potentially compromising effective anticancer therapy. PINP can manifest as allodynia. One recently discovered key factor in paclitaxel-induced mechanical allodynia (PIMA) pathogenesis is the elevated activity of monoacylglycerol lipase (MAGL), an enzyme that metabolizes the endocannabinoid 2-arachidonoylglycerol (2-AG). Thus, inhibiting MAGL serves as a potential analgesic target. Notoginsenoside R1 (NGR1), a metabolite of Panax notoginseng, has shown promise in reducing oxidative stress and neuronal apoptosis in nerve injury models. However, its effects on PIMA and MAGL activity have not yet been explored. This study is a proof-of-concept preclinical study investigating the antiallodynic effects of NGR1 on PIMA in female BALB/c mice and also examining its effect on MAGL activity. The effect of treatment of mice with NGR1 intraperitoneally on the development of PIMA was evaluated. Molecular docking using CB-Dock2 compared the binding energies to MAGL of NGR1 and pristimerin, a triterpene MAGL inhibitor. The effects of NGR1 on human recombinant MAGL activity, as well as the MAGL activity in mice paw skin tissues, were assessed using MAGL inhibitor screening and MAGL activity assay kits, respectively. NGR1 prevented the development of PIMA in a dose-dependent manner. The docking scores showed that NGR1 has a good affinity for MAGL (-7.8 kcal/mol, binding energy) but less affinity than pristimerin (-10.3 kcal/mol). NGR1 inhibited the human recombinant MAGL activity in a reversible and concentration-dependent manner, although the inhibition was in a reverse order. Treatment of mice with NGR1 showed a non-significant trend in reducing the paclitaxel-induced increase in MAGL activity in the paw skin. This study shows for the first time that NGR1 prevents the development of PIMA and suggests that NGR1 has affinity for and inhibits human recombinant MAGL activity with a paradoxical inhibition pattern. More mechanistic studies are needed to fully elucidate the molecular mechanisms of NGR1 in preventing PIMA.