Comparable study of whole cell patch clamp recording for hERG channel under physiological temperature using high-throughput automated patch clamp system QPatch II and Qube

Abstract

The activity of cardiac ion channels is crucial for generating action potentials with proper timing and duration. Drug-induced dysfunction of these channels can lead to adverse cardiac events such as QT prolongation, ventricular arrhythmias, and sudden death. These effects remain a major cause of drug withdrawal or failure to gain regulatory approval. To improve drug safety assessment, the Comprehensive in vitro Proarrhythmia Assay (CiPA) was developed, emphasizing the need to evaluate drug effects on ion channels under physiological temperature. We evaluated the inhibitory effects of a compound on hERG channels at physiological temperature (35 °C) using whole-cell patch clamp experiments with automated systems QPatch II and Qube. Temperature conditions during measurement were set to either 25 °C or 35 °C. After establishing whole-cell configuration, the CiPA voltage protocol was applied at 5-s intervals to measure hERG channel currents. Following vehicle application to record control currents, the compound was applied to assess inhibitory effects on the hERG channel. Previous studies using QPatch Compact showed that hERG channel behavior changes significantly when recordings are performed at 35 °C compared to 25 °C. Similar trends were observed with QPatch II and Qube, including reduced time constants to reach steady-state current, increased tail current amplitudes, and faster tail current rise times. We also investigated temperature-dependent drug effects using erythromycin. At room temperature, hERG current inhibition at 1000 μM was around 50–60%, whereas at 35 °C, the IC50 was significantly lower (60–90 μM), and nearly complete inhibition was seen at 1000 μM. This confirmed erythromycin's greater potency at physiological temperature. Tests with multiple compounds under both temperature conditions yielded results consistent with existing literature and previous QPatch Compact studies. These findings support the robustness of QPatch II and Qube in detecting temperature-dependent effects aligned with outcomes from manual patch clamp systems. Our results emphasize the importance of recording at physiological temperature to obtain accurate pharmacological data, supporting automated patch clamp systems in CiPA-compliant safety assessments. This enhances the predictive power and reliability of preclinical cardiotoxicity screening.