Toll-like receptor 4 activation promotes cardiac arrhythmias by decreasing the transient outward potassium current (I-to) through an. IRF3-dependent and MyD88-independent pathway

作者：Monnerat Cahli Gustavo; Alonso Hiart; Gallego Monica; Alarcon Micaela Lopez; Bassani Rosana A; Casis Oscar; Medei Emiliano^*

来源：Journal of Molecular and Cellular Cardiology, 2014, 76: 116-125.

DOI：10.1016/j.yjmcc.2014.08.012

• Cardiac electrophysiology
• TLR%26apos
• s
• Transient outward potassium current
• Signal transduction
• Calcium handling

Cardiac arrhythmias are one of the main causes of death worldwide. Several studies have shown that inflammation plays a key role in different cardiac diseases and Toll-like receptors (TLRs) seem to be involved in cardiac complications. In the present study, we investigated whether the activation of TLR4 induces cardiac electrical remodeling and arrhythmias, and the signaling pathway involved in these effects. Membrane potential was recorded in Wistar rat ventricle. Ca2+ transients, as well as the L-type Ca2+ current (I-cal) and the transient outward K+ current (I-to), were recorded in isolated myocytes after 24 h exposure to the TLR4 agonist, lipopolysaccharide (LPS, 1 mu g/ml).TLR4 stimulation in vitro promoted a cardiac electrical remodeling that leads to action potential prolongation associated with arrhythmic events, such as delayed afterdepolarization and triggered activity. After 24 h LPS incubation, I-to amplitude, as well as Kv4.3 and KChIP2 mRNA levels were reduced. The 6, decrease by LPS was prevented by inhibition of interferon regulatory factor B (IRF3), but not by inhibition of interleukin-1 receptor-associated kinase 4 (IRAK4) or nuclear factor kappa B (NF-kappa B). Extrasystolic activity was present in 25% of the cells, but apart from that, Ca2+ transients and Ica%26apos;, were not affected by LPS; however, Na+/Ca2+ exchanger (NCX) activity was apparently increased. We conclude that TLR4 activation decreased 6, which increased AP duration via a MyD88-independent, IRF3-dependent pathway. The longer action potential, associated with enhanced Ca2+ efflux via NCX, could explain the presence of arrhythmias in the LPS group.

• 出版日期2014-11