Neoline, an active ingredient of the processed aconite root in Goshajinkigan formulation, targets Nav1.7 to ameliorate mechanical hyperalgesia in diabetic mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Goshajinkigan (GJG), a traditional Japanese Kampo formula, has been shown to exhibit several pharmacological actions, including antinociceptive effects. Processed aconite root (PA), which is considered to be an active ingredient of GJG, has also been demonstrated to have an ameliorative effect on pain, such as diabetic peripheral neuropathic pain. We recently identified neoline as the active ingredient of both GJG and PA that is responsible for its effects against oxaliplatin-induced neuropathic pain in mice. AIM OF THE STUDY: In the present study, we investigated whether GJG, PA, and neoline could inhibit Nav1.7 voltage-gated sodium channel (VGSC) current and whether neoline could ameliorate mechanical hyperalgesia in diabetic mice. MATERIALS AND METHODS: To assess the electrophysiological properties of GJG extract formulation, powdered PA, and neoline on Nav1.7 VGSCs, whole-cell patch clamp recording was performed using human HEK293 cells expressing Nav1.7 VGSCs. In addition, the ameliorative effects of neoline on diabetic peripheral neuropathic pain were evaluated using the von Frey test in streptozotocin (STZ)-induced diabetic model mice. RESULTS: GJG extract formulation significantly inhibited Nav1.7 VGSC peak current. Powdered PA also inhibited Nav1.7 VGSC peak current. Like GJG and PA, neoline could inhibit Nav1.7 VGSC current. When diabetic mice were treated with neoline by intraperitoneal acute administration, the mechanical threshold was increased in diabetic mice, but not in non-diabetic mice, in a behavioral study. CONCLUSION: These results suggest that neoline might be a novel active ingredient of GJG and PA that is one of responsible ingredients for ameliorating mechanical hyperalgesia in diabetes via the inhibition of Nav1.7 VGSC current at least.

Neuroprotective effect of liquiritin as an antioxidant via an increase in glucose-6-phosphate dehydrogenase expression on B65 neuroblastoma cells.

Glycyrrhiza (the roots and rhizomes of licorice) has been used worldwide as both an herbal nutraceutical and herbal medicine. In addition, it is well known that Glycyrrhiza contains various compounds with biological effects, such as anti-viral, anti-inflammatory, immunoregulatory, anti-tumor and neuroprotective effects. Among the various compounds in Glycyrrhiza, the active compounds that show biological activity are thought to include glycyrrhizin, glycyrrhetinic acid, glabridin, licochalcones and liquiritin. In the present study, we investigated the biological effects of three of these compounds (glycyrrhizin, liquiritin and isoliquiritin) on B65 neuroblastoma cells derived from serotonergic neurons. Among these three compounds, only liquiritin enhanced the proliferation of B65 neuroblastoma cells. In contrast, both glycyrrhizin and isoliquiritin, particularly at high concentrations had cytotoxic effects. Cells were treated with various cytotoxic agents and liquiritin could ameliorate the cytotoxicity induced by menadione sodium bisulfate in a dose-dependent manner. We also examined the effect of liquiritin on cell survival by evaluating the expression levels of phospho-p44/42 mitogen-activated protein kinase, cyclin-related proteins and glucose-6-phosphate dehydrogenase, which produces nicotinamide adenine dinucleotide phosphate. Under treatment with liquiritin, the protein expression level of glucose-6-phosphate dehydrogenase increased in a dose-dependent manner. In contrast, the protein expression level of cyclin-related proteins did not change at all under treatment with liquiritin. These results suggest that liquiritin, which is contained in Glycyrrhiza, may enhance cell survival by increasing the protein expression level of glucose-6 phosphate dehydrogenase.

Yokukansan enhances the proliferation of B65 neuroblastoma.

Yokukansan, a traditional Japanese herbal medicine, has been considered to be a novel alternative treatment for several neurological diseases such as neurodegenerative disorders, as well as neurosis, insomnia, and behavioral and psychological symptoms in Alzheimer's disease. Moreover, it has been shown that yokukansan has antidepressant-like and pain-relieving effects in animal models. Recently, several studies have shown that yokukansan has a neuroprotective effect. In this study, we focused on whether or no yokukansan influences cell proliferation related to cell-cycle progression by using B65 neuroblastoma cells derived from monoaminergic neurons. Under treatment with yokukansan, the proliferation rate of B65 neuroblastoma cells significantly increased in a dose-dependent manner. In particular, a proliferative effect was observed after treatment with yokukansan for 48 h and 72 h. Moreover, among seven medicinal herbs that comprise yokukansan, both Bupleuri Radix and Glycyrrhize Radix also enhanced the proliferation of B65 neuroblastoma cells. We assessed the effect of yokukansan on p44/42 mitogen-activated protein kinase (MAPK) phosphorylation in B65 neuroblastoma cells, and found that yokukansan increased p44/42 MAPK phosphorylation after treatment for 48 h. In contrast, neither Bupleuri Radix nor Glycyrrhize Radix altered the level of p44/42 MAPK phosphorylation, although they did increase cell proliferation. Our findings suggest that yokukansan has a cell-proliferative due to both Bupleuri Radix and Glycyrrhize Radix, and this is unrelated to the p44/42 MAPK signaling cascade.

Neuroprotective effect of yokukansan against cytotoxicity induced by corticosterone on mouse hippocampal neurons.

Yokukansan, a traditional Japanese herbal medicine, has been used for the management of neurodegenerative disorders and for the treatment of neurosis, insomnia, and behavioral and psychological symptoms of dementia. Recently, several studies have shown that yokukansan has a neuroprotective effect. The aim of this study was to examine the neuroprotective effect of yokukansan on hippocampal neurons from embryonic mouse brain against the effects of corticosterone, which is considered to be a stress hormone and to be cytotoxic toward neurons. The cell survival rates were measured by the WST-8 assay and LDH assay. Twenty-four hours after treatment with corticosterone, cell numbers were significantly decreased compared with the control or treatment with vehicle in a dose-dependent manner. When cells were treated with 30 µM corticosterone, the decrease in the number of cells was significantly recovered by treatment with yokukansan (100-1,000 µg/ml) in a dose-dependent manner. However, yokukansan did not suppress the decrease in cell numbers that was induced by treatment with 100 µM corticosterone. In the LDH assay, treatment with yokukansan at a high concentration (500-1,000 µg/ml) suppressed the LDH concentration induced by treatment with both 30 µM and 100 µM corticosterone compared to treatment with corticosterone alone, respectively. These results suggest that yokukansan protects against the cytotoxic effect of a low concentration of corticosterone on hippocampal neurons.