Goshajinkigan, a Traditional Japanese Medicine, Suppresses Voltage-Gated Sodium Channel Nav1.4 Currents in C2C12 Cells

Functional effects of drugs and toxins interacting with NaV1.4

NaV1.4 is a voltage-gated sodium channel subtype that is predominantly expressed in skeletal muscle cells. It is essential for producing action potentials and stimulating muscle contraction, and mutations in NaV1.4 can cause various muscle disorders. The discovery of the cryo-EM structure of NaV1.4 in complex with β1 has opened new possibilities for designing drugs and toxins that target NaV1.4. In this review, we summarize the current understanding of channelopathies, the binding sites and functions of chemicals including medicine and toxins that interact with NaV1.4. These substances could be considered novel candidate compounds or tools to develop more potent and selective drugs targeting NaV1.4. Therefore, studying NaV1.4 pharmacology is both theoretically and practically meaningful.

Novel In Vitro Assay of the Effects of Kampo Medicines against Intra/Extracellular Advanced Glycation End-Products in Oral, Esophageal, and Gastric Epithelial Cells

Kampo medicines are Japanese traditional medicines developed from Chinese traditional medicines. The action mechanisms of the numerous known compounds have been studied for approximately 100 years; however, many remain unclear. While components are normally affected through digestion, absorption, and metabolism, in vitro oral, esophageal, and gastric epithelial cell models avoid these influences and, thus, represent superior assay systems for Kampo medicines. We focused on two areas of the strong performance of this assay system: intracellular and extracellular advanced glycation end-products (AGEs). AGEs are generated from glucose, fructose, and their metabolites, and promote lifestyle-related diseases such as diabetes and cancer. While current technology cannot analyze whole intracellular AGEs in cells in some organs, some AGEs can be generated for 1-2 days, and the turnover time of oral and gastric epithelial cells is 7-14 days. Therefore, we hypothesized that we could detect these rapidly generated intracellular AGEs in such cells. Extracellular AEGs (e.g., dietary or in the saliva) bind to the receptor for AGEs (RAGE) and the toll-like receptor 4 (TLR4) on the surface of the epithelial cells and can induce cytotoxicity such as inflammation. The analysis of Kampo medicine effects against intra/extracellular AGEs in vitro is a novel model.

Suppressive effects of processed aconite root on dexamethasone-induced muscle ring finger protein-1 expression and its active ingredients

Processed aconite root (PA), the tuberous root of Aconitum carmichaelii prepared by autoclaving, is a crude drug used in Japanese traditional Kampo medicine and traditional Chinese medicine for the symptoms of kidney deficiency, that is related to the muscle atrophy in modern medicine. The objective of the present study is to evaluate the effectiveness of PA on muscle atrophy and to find its active ingredients using dexamethasone-induced muscle ring finger protein-1 (MuRF1) mRNA expression in murine myoblast C2C12 cells. Dexamethasone-induced MuRF1 expression was significantly suppressed by methanol-soluble part of boiling water extract of PA in a concentration-dependent manner with its IC₅₀ value of 1.5 mg/ml. By the activity-guided fractionations of PA extract using the partition between organic solvents and its aqueous solution, the activity of PA did not transfer into the fraction containing aconitine-type diterpenoid alkaloids but into BuOH layer. Then, we found higenamine and salsolinol as the active ingredients in PA. Higenamine and salsolinol significantly suppressed dexamethasone-induced MuRF1 expression, and their IC₅₀ values were 0.49 and 50 µM, respectively. The contents of higenamine and salsolinol in the decoctions of commercially available fourteen PA products are 0.12 and 14 µg/ml as the average values, and varied with the coefficient of variation (CV) values of 97 and 63%, respectively. Higenamine also significantly suppressed dexamethasone-induced mRNA expressions of muscle atrophy F-box protein (MAFbx)/atrogin1, casitas B-lineage lymphoma-b (Cbl-b), troponin, branched-chain amino acid aminotransferase 2 (BCAT2), and Bcl-2 binding and pro-apoptotic protein3 (Bnip3). Although the quality control of PA is regulated by the contents of diterpene alkaloids, salsolinol and higenamine can be used as the marker compounds to certificate the pharmacological activities of PA.