Abstract
RATIONALE: Atrial fibrillation is a critical health burden. Targeting calcium (Ca(2+)) dysregulation and oxidative stress are potential upstream therapeutic strategies. Fibroblast growth factor (FGF) 1 can modulate Ca(2+) homeostasis and has antioxidant activity. The aim of this study was to investigate whether FGF1 has anti-arrhythmic potential through modulating Ca(2+) homeostasis and antioxidant activity of pulmonary vein (PV) and left atrium (LA) myocytes. METHODS: Patch clamp, western blotting, confocal microscopy, cellular and mitochondrial oxidative stress studies were performed in isolated rabbit PV and LA myocytes treated with or without FGF1 (1 and 10 ng/mL). Conventional microelectrodes were used to record electrical activity in isolated rabbit PV and LA tissue preparations with and without FGF1 (3 μg/kg, i.v.). RESULTS: FGF1-treated rabbits had a slower heart rate than that observed in controls. PV and LA tissues in FGF1-treated rabbits had slower beating rates and longer action potential duration than those observed in controls. Isoproterenol (1 μM)-treated PV and LA tissues in the FGF1-treated rabbits showed less changes in the increased beating rate and a lower incidence of tachypacing (20 Hz)-induced burst firing than those observed in controls. FGF1 (10 ng/mL)-treated PV and LA myocytes had less oxidative stress and Ca(2+) transient than those observed in controls. Compared to controls, FGF1 (10 ng/mL) decreased I(Na-L) in PV myocytes and lowered I (to), I (Kr-tail) in LA myocytes. Protein kinase C (PKC)ε inhibition abolished the effects of FGF1 on the ionic currents of LA and PV myocytes. CONCLUSION: FGF1 changes PV and LA electrophysiological characteristics possibly via modulating oxidative stress, Na(+)/Ca(2+) homeostasis, and the PKCε pathway.