Amiodarone inhibits the Toll-like receptor 3-mediated nuclear factor κB signaling pathway by blocking organelle acidification.

Toll-like receptor (TLR) agonists or pro-inflammatory cytokines converge to activate the nuclear factor κB (NF-κB) signaling pathway, which provokes inflammatory responses. In the present study, we identified amiodarone hydrochloride as a selective inhibitor of the TLR3-mediated NF-κB signaling pathway by screening the RIKEN NPDepo Chemical Library. In human umbilical vein endothelial cells (HUVEC), amiodarone selectively inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) induced by polyinosinic-polycytidylic acid (Poly(I:C)), but not tumor necrosis factor-α, interleukin-1α, or lipopolysaccharide. In response to a Poly(I:C) stimulation, amiodarone at 20 μM reduced the up-regulation of mRNA expression encoding ICAM-1, vascular cell adhesion molecule-1, and E-selectin. The nuclear translocation of the NF-κB subunit RelA was inhibited by amiodarone at 15-20 μM in Poly(I:C)-stimulated HUVEC. Amiodarone diminished the fluorescent dots of LysoTracker® Red DND-99 scattered over the cytoplasm of HUVEC. Therefore, the present study revealed that amiodarone selectively inhibited the TLR3-mediated NF-κB signaling pathway by blocking the acidification of intracellular organelles.