Nodakenetin Alleviates Inflammatory Pain Hypersensitivity by Suppressing NF-κB Signal Pathway.

BACKGROUND: Inflammatory pain mediated by nuclear factor kappa-B (NF-κB) signal pathway has become an increasingly important clinical issue in the last decade. As a potent antioxidant, Nodakenetin has been shown to have a prominent inhibitory effect on inflammation. However, the therapeutic effects and underlying pharmacological mechanisms of Nodakenetin for inflammatory pain remain unclear. METHODS: Intraplanar injection of complete Freund's adjuvant (CFA) was used to establish a model of chronic inflammation pain in C57BL/6 mice. The chronic neuropathic pain model was conducted by the sciatic nerve ligation surgery. QRT-PCR was performed to estimate the RNA levels of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6). Western blot was used to demonstrated the protein levels of phospho-IkappaBα (IκBα), p50, and p65 in HEK293T cells. RESULTS: The bioactive components of the traditional Chinese medicine Notopterygium forbesii boiss mainly include Nodakenetin, isoimperatorin, and pregnenolone. Nodakenetin significantly alleviated CFA-induced inflammatory pain but showed no significant therapeutic effect on surgically induced neuralgia in a mouse model. In contrast, isoimperatorin and pregnenolone did not relieve CFA-induced inflammatory pain. Mechanistically, Nodakenetin inhibited IL-1ß-induced activation of the NF-κB pathway and phosphorylation of IκBα in HEK293T cells. Furthermore, Nodakenetin treatment suppressed the expression of IL-6, TNF-α, and IL-1ß in mouse bone marrow-derived macrophages. CONCLUSION: Nodakenetin alleviates inflammatory pain induced by CFA injection in vivo and modulates NF-κB signal pathway in vitro.

TRPM3 is a nociceptor channel involved in the detection of noxious heat.

Transient receptor potential melastatin-3 (TRPM3) is a broadly expressed Ca(2+)-permeable nonselective cation channel. Previous work has demonstrated robust activation of TRPM3 by the neuroactive steroid pregnenolone sulfate (PS), but its in vivo gating mechanisms and functions remained poorly understood. Here, we provide evidence that TRPM3 functions as a chemo- and thermosensor in the somatosensory system. TRPM3 is molecularly and functionally expressed in a large subset of small-diameter sensory neurons from dorsal root and trigeminal ganglia, and mediates the aversive and nocifensive behavioral responses to PS. Moreover, we demonstrate that TRPM3 is steeply activated by heating and underlies heat sensitivity in a subset of sensory neurons. TRPM3-deficient mice exhibited clear deficits in their avoidance responses to noxious heat and in the development of inflammatory heat hyperalgesia. These experiments reveal an unanticipated role for TRPM3 as a thermosensitive nociceptor channel implicated in the detection of noxious heat.