An accumulation of reactive oxygen species (ROS) in cardiomyocytes can induce pro-arrhythmogenic late Na⁺ currents by removing the inactivation of voltage-gated Na⁺ channels including the tetrodotoxin (TTX)-resistant cardiac α-subunit Nav1.5 as well as TTX-sensitive α-subunits like Nav1.2 and Nav1.3. Here, we explored oxidant-induced late Na⁺ currents in mouse cardiomyocytes and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as well as in HEK 293 cells expressing Nav1.2, Nav1.3, or Nav1.5. Na⁺ currents in mouse cardiomyocytes and hiPSC-CMs treated with the oxidant chloramine T (ChT) developed a moderate reduction in peak current amplitudes accompanied by large late Na⁺ currents. While ChT induced a strong reduction in peak current amplitudes but only small persistent currents on Nav1.5, both Nav1.2 and Nav1.3 produced increased peak current amplitudes and large persistent currents following oxidation. TTX (300 nM) blocked ChT-induced late Na⁺ currents significantly stronger as compared to peak Na⁺ currents in both mouse cardiomyocytes and hiPSC-CMs. Similar differences between Nav1.2, Nav1.3, and Nav1.5 regarding ROS sensitivity were also evident when oxidation was induced with UVA-light (380 nm) or the cysteine-selective oxidant nitroxyl (HNO). To conclude, our data on TTX-sensitive Na⁺ channels expressed in cardiomyocytes may be relevant for the generation of late Na⁺ currents following oxidative stress.

Introduction: Chloroquine (CQ) and its derivate hydroxychloroquine (HCQ) are successfully deployed for different diseases beyond the prophylaxis and treatment of malaria. Both substances exhibit antiviral properties and have been proposed for prophylaxis and treatment of COVID-19 caused by SARS-CoV-2. CQ and HCQ cause similar adverse events including life-threatening cardiac arrhythmia generally based on QT-prolongation, which is one of the most reported adverse events for both agents associated with the treatment of COVID-19. Various drugs known to induce QT-prolongation have been proven to exert local anesthetic (LA)-like properties regarding their impact on the cardiac Na⁺ channel Nav1.5. Inhibition of Nav1.5 is considered as the primary mechanism of cardiotoxicity caused by LAs. However, the mechanism of the arrhythmogenic effects of CQ and HCQ related to Nav1.5 has not yet been fully investigated. Therefore, the exact mechanism of how CQ and HCQ affect the sodium currents generated by Nav1.5 need to be further elucidated. Objective: This in vitro study aims to investigate the effects of CQ and HCQ on Nav1.5-generated sodium currents to identify possible LA-like mechanisms that might contribute to their arrhythmogenic properties. Methods: The effects of CQ and HCQ on Nav1.5-generated sodium currents by HEK-293 cells expressing either wild-type human Nav1.5 or mutant Nav1.5 F1760A are measured using the whole-cell patch-clamp technique. Results: Both agents induce a state-dependent inhibition of Nav1.5. Furthermore, CQ and HCQ produce a use-dependent block of Nav1.5 and a shift of fast and slow inactivation. Results of experiments investigating the effect on the LA-insensitive mutant Nav1.5-F1760A indicate that both agents at least in part employ the proposed LA-binding site of Nav1.5 to induce inhibition. Conclusion: This study demonstrated that CQ and HCQ exert LA-typical effects on Nav1.5 involving the proposed LA binding site, thus contributing to their arrhythmogenic properties.

Article: Oropharyngeal leak pressure of the Ambu® AuraGain™ versus Flexicare® LarySeal™ Pro in ophthalmic surgery: a randomized controlled trial - Minerva Anestesiologica 2026 May;92(5):409-17 - Minerva Medica - Journals

Several transient receptor potential vanilloid (TRPV) ion channels are proton-sensitive, and recent structural studies have identified poorly conserved mechanisms for the proton sensitivity of TRPV1, TRPV2 and TRPV5. While such detailed studies are lacking for TRPV3, three distinct intracellular motifs were suggested to be required for a direct channel activation by cytosolic acidification. In this study, we investigated if these mechanisms are also relevant for the activation of TRPV3 by weak acids. Wildtype (WT) and several mutants of human TRPV3 transiently expressed in HEK 293T cells were investigated by whole-cell patch clamp electrophysiology. Cells expressing TRPV3-WT generated membrane currents induced by acetic acid (HOAc), formic acid and carbonic acid at pH 5.0. Activation induced by HOAc was concentration-dependent and increased with decreasing pH values. HOAc also strongly potentiated TRPV3-mediated responses to carvacrol and heat. Among the three suggested motifs for the binding of intracellular protons, only the mutant TRPV3-Asp512Ala exhibited an almost complete loss of HOAc sensitivity. The mutation of two C-terminal charged residues (Gln689/Asp727) even resulted in a clear gain of function for both HOAc and heat, and the mutation of the 2-APB-binding site His426 did not significantly abrogate HOAc sensitivity. Finally, insertion of the recently identified binding site in TRPV2 for the weak acid probenecid into TRPV3 (Glu216His) resulted in an increased HOAc sensitivity. To conclude, our data confirm that TRPV3 is sensitized and activated by several weak acids. While Asp512 appears to be a critical intracellular proton-modulating site, a more profound understanding of the mechanisms dictating the proton sensitivity of TRPV3 may require structural studies.

BACKGROUND: Cannabidiol (CBD) inhibits voltage-gated sodium channels (Na _v ). CBD is highly lipophilic and exhibits slow binding kinetics on Na _v s, a property that may enable CBD to enhance and prolong regional anesthesia. Here we explored the effects of CBD on lidocaine-induced Na _v -inhibition and neurotoxicity. METHODS: Patch clamp recordings were performed on tetrodotoxin (TTX)-sensitive Na _v s and the TTX-resistant Na _v 1.8 in ND7/23 cells or murine dorsal root ganglion neurons (DRG). Cytotoxicity was analyzed using flow cytometry. RESULTS: CBD induced a potent tonic inhibition of sodium currents with slow onset and offset kinetics. Na _v 1.8 exhibited a higher sensitivity to tonic block (IC ₅₀ 1.4 µM) as compared to TTX-sensitive sodium channels (IC ₅₀ 2.9 µM). Similar to local anesthetics, CBD also induced a shift of the steady-state inactivation and a modest use-dependent block at 10 Hz. In contrast to local anesthetics, inhibition of Na _v s by CBD is pH-independent. The co-application of CBD and lidocaine resulted in an additive tonic block of sodium currents in ND7/23 cells, but not in DRG neurons. While only high concentrations of CBD induced cytotoxicity, it potentiated lidocaine-induced cytotoxicity. CONCLUSIONS: CBD demonstrates promising characteristics as a long-lasting local anesthetic, or as an adjunct to local anesthetics used for regional or topical anesthesia.