Identification of Lauric Acid as a Potent Sodium Channel Na1.5 Blocker from Compound Chinese Medicine Wenxin Keli.

Purpose: The major cardiac voltage-gated sodium channel Na1.5 (I) is essential for cardiac action potential initiation and subsequent propagation. Compound Chinese medicine Wenxin Keli (WXKL) has been shown to suppress arrhythmias and heart failure. However, its active components have not been fully elucidated. This study focused on identifying the active inhibitor of I in WXKL and exploring their mode of action in electrophysiological conduction.

Methods: A chemical fraction library was constructed from an aqueous extract of WXKL and screened using an automated patch-clamping system in cells stably expressing the Na1.5 gene SCN5A. Candidate fractions with I-inhibition activity were analyzed by HPLC-ESI-IT-TOF-MS and GC-MS to identify the ingredients. Na1.5 blocker molecules identified by single-cell electrocardiogram were tested in hiPSC-derived cardiomyocytes. We evaluated the SCN5A inhibitory potential of Wenxin Keli effective monomer employing molecular docking and molecular dynamics simulation approaches.

Results: A primary screen of the WXKL chemical library identified five fractions that significantly inhibited the Na1.5 channel, with one of them rich in poly-saturated fatty acids. Molecular structural characterization revealed the presence of lauric acid, myristic acid, palmitic acid, and stearic acid in the active subfraction. Electrophysiological characterization demonstrated lauric acid (LA) as the most effective monomer for I-inhibition with an IC at 27.40 ± 12.78 μM. LA shifted the steady-state inactivation of I to more negative potentials and decreased the amplitude of extracellular field potential in hiPSC-derived cardiomyocytes. We demonstrate for the first time that naturally poly-saturated fatty acid, lauric acid, as a potential novel I blocker. Molecular docking and molecular dynamics simulation suggested that LA binds to the Na1.5 protein, with a significant binding affinity forming interactions with functionally essential residues and blocks the inward flow of Na. Mechanistically, lauric acid acts on the fast inactivation of Na1.5 alter electrophysiology conduction of hiPSC-derived cardiomyocytes and contribute to the antiarrhythmic effect of WXKL.

Conclusion: Lauric acid is a potent blocker for sodium channel Na1.5 and alleviates arrhythmia via inhibiting I.