8-shogaol derived from dietary ginger alleviated acute and inflammatory pain by targeting TRPV1.

Ginger, a well-known spice plant, has been used widely in medicinal preparations for pain relief. However, little is known about its analgesic components and the underlying mechanism. Here, we ascertained, the efficacy of ginger ingredient 8-Shogaol (8S), on inflammatory pain and tolerance induced by morphine, and probed the role of TRPV1 in its analgesic action using genetic and electrophysiology approaches. Results showed that 8S effectively reduced nociceptive behaviors of mice elicited by chemical stimuli, noxious heat as well as inflammation, and antagonized morphine analgesic tolerance independent on opioid receptor function. Genetic deletion of TRPV1 significantly abolished 8S' analgesia action. Further calcium imaging and patch-clamp recording showed that 8S could specifically activate TRPV1 in TRPV1-expressing HEK293T cells and dorsal root ganglion (DRG) neurons. The increase of [Ca2+]i in DRG was primarily mediated through TRPV1. Mutational and computation studies revealed the key binding sites for the interactions between 8S and TRPV1 included Leu515, Leu670, Ile573, Phe587, Tyr511, and Phe591. Further studies showed that TRPV1 activation evoked by 8S resulted in channel desensitization both in vitro and in vivo, as may be attributed to TRPV1 degradation or TRPV1 withdrawal from the cell surface. Collectively, this work provides the first evidence for the attractive analgesia of 8S in inflammatory pain and morphine analgesic tolerance mediated by targeting pain-sensing TRPV1 channel. 8S from dietary ginger has potential as a candidate drug for the treatment of inflammatory pain.

Water extract of Notopterygium incisum alleviates cold allodynia in neuropathic pain by regulation of TRPA1.

ETHNOPHARMACOLOGICAL RELEVANCE: Neuropathic pain can be debilitating and drastically affects the quality of life of those patients suffering from this condition. The Chinese herb Notopterygium incisum Ting ex H.T. Chang has long been used to disperse "cold". One under examined clinical feature of neuropathic pain is sensitivity to cold. Patients with neuropathic pain or arthritis usually describe a worsening of symptoms during the winter. AIMS OF THIS STUDY: We proposed to test the hypothesis that Notopterygium incisum has a positive effect on the cold sensitivity found in neuropathic pain. MATERIALS AND METHODS: In this study, we established chronic constriction injury (CCI) and cisplatin induced neuropathic pain mice models. Behavioral experiments and physiological examination methods were employed to investigate the effect of water extract of Notopterygium incisum (WN) on cold pain. RESULTS: We found WN reduced cold pain and allyl isothiocyanate (AITC, Transient Receptor Potential A1 (TRPA1 agonist)) induced pain. WN inhibited AITC induced calcium response in HEK 293 cells transfected with TRPA1 and dorsal root ganglion (DRG) neurons. Moreover, we found that oral administration of WN reduced cold allodynia and mechanical allodynia caused by (CCI) and cisplatin induced neuropathic pain. We also observed that oral administration of WN decreased responses to AITC in DRG neurons as well as expression of TRPA1 in the WN treated neuropathic pain model. CONCLUSIONS: The present study provide evidence that Notopterygium incisum alleviates cold allodynia in CCI and cisplatin induced neuropathic pain mouse models. WN alleviated neuropathic pain induced cold allodynia via directly modulating TRPA1. Our findings identify WN as a promising candidate for treating neuropathic pain that highlights a new mechanism of Notopterygium incisum on 'disperse cold'.

Paeoniflorin alleviates CFA-induced inflammatory pain by inhibiting TRPV1 and succinate/SUCNR1-HIF-1α/NLPR3 pathway.

BACKGROUND: Treatment of chronic inflammatory pain remains a major goal in the clinic. It is thus of prime importance to characterize inherent pathophysiological pathways to design new therapeutic strategies and analgesics for pain management. Paeoniflorin (PF), a monoterpenoid glycoside from Paeonia lactiflora Pallas plants, possesses promising anti-nociceptive property. However, therapeutic effect and underlying mechanism of action of PF on inflammatory pain have not yet been fully elucidated. In this study, we aim to investigate the analgesic effect further and clarify its mechanism of action of PF on complete freund's adjuvant (CFA)-evoked inflammatory pain. METHODS: Twenty-four male mice were divided into 3 groups: sham, CFA, and CFA + PF groups (n = 8/group). Mice were treated with normal saline or PF (30 mg/kg) for 11 days. Footpad swelling (n = 8/group), mechanical (n = 8/group) and thermal hypersensitivity (n = 8/group) were measured to evaluate the analgesic effect of PF on CFA-injected mice. At the end of the animal experiment, blood and L4-L6 dorsal root ganglion neurons were collected to assess the therapeutic effect of PF on CFA-induced inflammatory pain. Next, hematoxylin and eosin, quantitative realtime PCR, ELISA, capsaicin and dimethyl succinate induced pain test (n = 8/group), motor coordination test (n = 8/group), tail flicking test (n = 8/group), pyruvate and succinate dehydrogenase assay (n = 6/group), immunohistochemical staining, were performed to clarify the action mechanism of PF on CFA-evoked inflammatory pain. Besides, the effect of PF on TRPV1 was evaluated by whole-cell patch clamp recording on primary neurons (n = 7). Finally, molecular docking further performed to evaluate the binding ability of PF to TRPV1. RESULTS: PF significantly relieved inflammatory pain (P < 0.001) and paw edema (P < 0.001) on a complete Freund adjuvant (CFA)-induced peripheral inflammatory pain model. Furthermore, PF inhibited neutrophil infiltration (P < 0.01), IL-1ß increase (P < 0.01), and pain-related peptide substance P release (P < 0.001). Intriguingly, CFA-induced succinate aggregation was notably reversed by PF via modulating pyruvate and SDH activity (P < 0.01). In addition, PF dampened the high expression of subsequent succinate receptor SUCNR1 (P < 0.01), HIF-1α (P < 0.05), as well as the activation of NLPR3 inflammasome (P < 0.05) and TRPV1 (P < 0.05). More importantly, both capsaicin and dimethyl succinate supplementation obviously counteracted the pain-relieving effect of PF and TRPV1 (P < 0.01 or P < 0.001). CONCLUSION: Our findings suggest that PF can significantly relieve CFA-induced paw swelling, as well as mechanical and thermal hyperalgesia. PF alleviated inflammatory pain partly through inhibiting the activation of TRPV1 and succinate/SUCNR1-HIF-1α/NLPR3 pathway. Furthermore, we found that PF exerted its analgesic effect without affecting motor coordination and pain-related cold ion-channels. In summary, this study may provide valuable evidence for the potential application of PF as therapeutic strategy for inflammatory pain treatment.

Herbal formula Huangqi Guizhi Wuwu decoction attenuates paclitaxel-related neurotoxicity via inhibition of inflammation and oxidative stress.

BACKGROUND: Paclitaxel-induced peripheral neuropathy (PIPN) is a challenging clinical problem during chemotherapy. Our previous work found that herbal formula Huangqi Guizhi Wuwu decoction (HGWD) could reduce oxaliplatin-induced neurotoxicity. However, its effect on PIPN remains unknown. In this study, we aim to investigate the therapeutic effect and the underlying mechanisms of HGWD against PIPN with pharmacological experiment and network pharmacology. METHODS: Male Wistar rats were used to establish an animal model of PIPN and treated with different doses of HGWD for 3 weeks. Mechanical allodynia, thermal hyperalgesia and body weight were measured to evaluate the therapeutic effect of HGWD on PIPN rats. On the day of the sacrifice, blood, DRGs, sciatic nerve, and hind-paw intra-plantar skins were collected to assess neuroprotective effect of HGWD on PIPN. Next, network pharmacology was performed to decipher the potential active components and molecular mechanisms of HGWD, as were further verified by western blotting analyses in PIPN rats. Finally, the effect of HGWD on the chemotherapeutic activity of paclitaxel was evaluated in vitro and in vivo. RESULTS: In rats with PIPN, HGWD reversed mechanical allodynia, thermal hyperalgesia, and ameliorated neuronal damage. Moreover, HGWD significantly increased the level of nerve growth factor, dramatically reduced IL-1ß, IL-6, TNF-α levels and oxidative stress. Network pharmacology analysis revealed 30 active ingredients in HGWD and 158 candidate targets. Integrated pathway analysis identified PI3K/Akt and toll-like receptor as two main pathways responsible for the neuroprotective effect of HGWD. Further experimental validation demonstrated that HGWD expectedly inhibited the protein expression of TLR4, MyD88, IKKα, and p-NF-κB, and promoted PI3K, p-Akt, Nrf2, and HO-1 level in dorsal root ganglia. Last but not least, HGWD did not interfere with the antitumor activity of paclitaxel both in in vitro and in vivo models. CONCLUSION: These combined data showed that HGWD could inhibit paclitaxel-evoked inflammatory and oxidative responses in peripheral nervous system viaTLR4/NF-κB and PI3K/Akt-Nrf2 pathways involvement. The neuroprotective property of HGWD on PIPN provides fundamental support to the potential application of HGWD for counteracting the side effects of paclitaxel during chemotherapy.