CD14 as a mediator of the Mineralocorticoid Receptor - dependent anti-apolipoproteinA-1 IgG chronotropic effect on cardiomyocytes

In vitro and animal studies point to autoantibodies against apolipoproteinA-1 (anti-apoA-1 IgG) as possible mediators of cardiovascular disease involving several mechanisms, such as basal heart rate interference mediated by a mineralocorticoid receptor (MR)-dependent L-type calcium channel activation, and a direct pro-inflammatory effect through the engagement of the toll-like receptor (TLR) 2/CD14 complex. Nevertheless, the possible implication of these receptors in the pro-arrhythmogenic effect of anti-apoA-1 antibodies remains elusive. We aimed at determining whether CD14 and TLRs could mediate the anti-apoA-1 IgG chronotropic response in neonatal rat ventricular cardiomyocytes (NRVC). Blocking CD14 suppressed anti-apoA-1 IgG binding to NRVC and the related positive chronotropic response. Anti-apoA-1 IgG alone induced the formation of a TLR2/TLR4/CD14 complex, followed by the phosphorylation of Src, whereas aldosterone alone promoted the phosphorylation of Akt by phosphatidylinositol 3-kinase (PI3K), without affecting the chronotropic response. In the presence of both aldosterone and anti-apoA-1 IgG, the localization of TLR2/TLR4/CD14 was increased in membrane lipid rafts, followed by PI3K and Src activation, leading to a L-type calcium channel-dependent positive chronotropic response. Pharmacological inhibition of Src pathway led to the decrease of L-type calcium channel activity and abrogated the NRVC chronotropic response. Activation of CD14 appears as a key regulator of the MR-dependent anti-apoA-1 IgG positive chronotropic effect on NRVCs, involving relocation of the CD14/TLR2/TLR4 complex into lipid rafts followed by PI3K and Src-dependent L-type calcium channel activation.