Inhibitory Effects of Cyclopiazonic Acid on the Pacemaker Current in Sinoatrial Nodal Cells. (1st May 2020)

• Record Type: Journal Article
• Authors: Chen, Qian; Chen, Jian-Quan; Zhu, Peng-Li; Wu, Hong-Lin; Xie, Xiao-Ting; Dong, Ying; Xiang, Guo-Jian; Chen, Mei-Yan; Li, Yang; Zhang, Jian-Cheng
• Is Part Of: Neuroscience. Volume 433(2020)
• Page Start: 230
• Page End: 240
• Publication Date: 2020-05-01
• Subjects: CPA cyclopiazonic acid -- DD diastolic depolarization -- DMSO dimethyl sulfoxide -- EDTA ethylenediaminetetraacetic acid -- HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid -- SAN sinoatrial node -- SAPs spontaneous action potentials -- SERCA sarcoendoplasmic reticulum calcium transport ATPase -- SR sarcoplasmic reticulum; sinoatrial node cells -- cyclopiazonic acid -- pacemaker current -- spontaneous action potentials -- inhibitory effect; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2020.01.018
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: CPA show a reduction action on SAN automaticity and block I f directly at high concentration of 10 μM. A direct inhibitory effect of CPA on I f in SAN cells is concentration- and time-dependent. CPA slow down the steady-state activation current and downregulate the protein expression of I f . CPA may be a new potential agent to improve heart rate. Abstract: Objective: The spontaneous action potential of isolated sinoatrial node (SAN) cells is regulated by a coupled-clock system of two clocks: the calcium clock and membrane clock. However, it remains unclear whether calcium clock inhibitors have a direct effect on the membrane clock. The purpose of this study was to investigate the direct effect of cyclopiazonic acid (CPA), a selective calcium clock inhibitor, on the function of the membrane clock of SAN cells. Methods: at SAN cells were isolated by trypsinization and identified based on morphology and electrophysiology. I f and HCN currents were recorded via patch clamp technique. The expression of the HCN channel protein was determined by Western blotting analysis. Results: The diastolic depolarization rate of spontaneous action potentials and the current densities of I f were reduced by exposure to 10 μM CPA. The inhibitory effect of CPA was concentration-dependent with an IC50 value of 16.3 μM and a Hill coefficient of 0.98. The effect of CPA on I f current was also time-dependent, and the I f current amplitude was partially restored after washout. Furthermore, the steady-state activation curve of the I f current was shifted to a negative potential, indicating that channel activation slowed down. Finally, the protein expression of HCN4 in HEK293 cells was markedly downregulated by CPA. Conclusions: These results indicate that the direct inhibition effect of CPA on the I f current in SAN cells is both concentration- and time-dependent. The underlying mechanisms may involve slowing down steady-state activation and the downregulation of pacemaker channel protein expression.