1. Homocysteine induces calcium overload in neonatal rat atrial cells through activation of sodium current and CaMKⅡδ
Lu HAN ; Quanbin DONG ; Yichun WEI ; Ancai ZHENG ; Juxiang LI ; Kui HONG ; Yanqing WU ; Xiaoshu CHENG
Chinese Journal of Cardiology 2018;46(2):143-151
Objective:
To investigate the effect and related mechanism of homocysteine (Hcy) on calcium overload in neonatal rat atrial cells (NRICs).
Methods:
NRICs were assigned to 9 groups after culture for 3 days: (1) control group; (2) Hcy group (0, 50, 100, 200, 500 μmol/L for 48 hours); (3) antioxidant group (NAC, 10 μmol/L for 24 hours); (4) Hcy+NAC group (500 μmol/L Hcy for 48 hours, then treated with 10 μmol/L NAC for 24 hours); (5) calcium/calmodulin dependent protein kinase Ⅱδ (CaMKⅡδ) inhibitor group (KN-93, 3 μmol/L KN-93 for 5 hours); (6) specific sodium current inhibitor group (ELE, 1 μmol/L ELE for 5 hours); (7) Hcy+KN-93 group (500 μmol/L Hcy for 48 hours, then treated with 3 μmol/L KN-93 for 5 hours); (8) Hcy+ELE group (500 μmol/L Hcy for 48 hours, then treated with 1 μmol/L ELE for 5 hours; (9) Hcy+KN-93+ELE group (500 μmol/L Hcy for 48 hours, then treated with 3 μmol/L KN-93 and 1 μmol/L ELE for 5 hours). Moreover, NRICs were also treated with CaMKⅡδ-siRNA lentivirus, and Nav1.5-siRNA lentivirus, negative lentivirus carrier containing green fluorescent protein (GFP) for 24 hours. The MOI values of the three groups were 10. Infection efficiency of lentivirus was determined by observing the percentage of GFP fluorescence under inverted fluorescence microscope after transfection for 24 hours, and cultured regularly with simultaneous Puro screening, then cells were grouped as Hcy+CaMKⅡδ-siRNA group, Hcy+Nav1.5-siRNA group and Hcy+negative group. The concentration of Ca2+ in NRICs ([Ca2+]i) of various groups was detected through Fluo-4/AM fluorescence probe, then 2', 7'- two chlorofluorescein diacetate (DCFH-DA) was used as a probe to detect reactive oxygen species (ROS) in NRICs by flow cytometry. The malondialdehyde (MDA) was detected by the activity of superoxide dismutase (SOD) and xanthine oxidase was detected by thiobarbituric acid colorimetry. The protein and mRNA expression level of CaMKⅡδ and Nav1.5 in NRICs were detected by Western blot and quantitative real-time PCR.
Results:
(1) ROS, MDA and SOD were similar between NAC group and control group, ROS and MDA were significantly increased, while SOD was significantly reduced in Hcy group in a concentration-dependent manner. (2) [Ca2+]i: The level of [Ca2+]i was (155.57+7.25), (187.43+13.07), (248.98+27.22) and (307.36+15.09) nmol/L in 50, 100, 200 and 500 μmol/L Hcy groups, which was significantly higher than that in the control group ((123.18+7.24) nmol/L,