Inhibition of protein kinase Cbeta prevents foam cell formation by reducing scavenger receptor A expression in human macrophages

BACKGROUND: Low-density lipoprotein (LDL) uptake by monocyte-derived macrophages is a crucial step in foam cell formation and early atherosclerotic lesion. Increasing evidence supports the theory that activation of protein kinase Cbeta (PKCbeta) is involved in many mechanisms promoting atherosclerosis. Thus, we investigated whether inhibition of PKCbeta prevents foam cell formation. METHODS AND RESULTS: The differentiation of human primary monocytes or the monocytic THP-1 cell line into monocyte-derived macrophages was induced by phorbol 12-myristate 13-acetate (PMA; 0.1 mmol/L), a potent activator of PKC. Incubation of monocyte-derived macrophages with DiI-modified LDL (acetylated LDL and oxidized LDL, 10 mug/mL) led to lipoprotein uptake. Interestingly enough, the nonselective inhibitor of PKCbeta(1) and PKCbeta(2), LY379196 (5x10(-7) to 10(-5) mol/L), blunted LDL uptake in monocyte-derived macrophages as shown by flow cytometry. Specific siRNA-mediated knockdown of PKCbeta exerted a similar effect. Furthermore, PMA alone and in the presence of modified LDL induced scavenger receptor A mRNA and protein expression, which was abolished by LY379196. CGP53353, a selective inhibitor of PKCbeta(2), did not affect LDL uptake, nor did it prevent scavenger receptor A upregulation. Incubation of monocyte-derived macrophages with PMA/LDL increased PKCbeta(1) phosphorylation at the Thr-642 residue, which was blunted by LY379196. However, the expression of CD68, a marker of activated macrophages, was not affected by LY379196. Moreover, LY379196 did not affect lipopolysaccharide-induced CD14 degradation, tumor necrosis factor-alpha release, or superoxide anion production, ruling out any effect of PKCbeta inhibition on innate immunity. CONCLUSIONS: Nonspecific inhibition of PKCbeta prevents LDL uptake in macrophages. These findings suggest that PKCbeta inhibitors may represent a novel class of antiatherosclerotic drugs

Vascular effects of eplerenone in coronary artery disease with preserved ejection fraction: a double-blind, randomized, placebo-controlled trial

BACKGROUND: Mineralocorticoid receptor antagonists (MRAs) reduce morbidity and mortality in heart failure with reduced ejection fraction (HFrEF). Their role in patients without heart failure, particularly in patients with coronary artery disease (CAD) and preserved EF, is still a matter of debate. HYPOTHESIS: The MRA eplerenone on top of standard medical therapy improves endothelial dysfunction and other markers of vascular health in CAD patients with preserved EF. METHODS: In this double-blind, randomized, placebo-controlled study, 42 patients (mean age: 63.5 ± 9.1 years; 37 males) were randomized to 4-week treatment with eplerenone 25 mg daily or placebo. The primary endpoint was difference in endothelial function as assessed by flow-mediated dilatation (FMD) of the brachial artery. Secondary endpoints included 24-hour blood pressure (BP), endothelial progenitor cells, and platelet adhesion. RESULTS: No difference in the primary endpoint FMD was noted after 4 weeks of treatment with eplerenone compared with placebo (FMD: 4.7% ± 2.0% and 4.9% ± 2.1%, respectively; P = 0.77). There were no significant differences between eplerenone and placebo in 24-hour BP (mean systolic BP: 126.9 ± 17.3 and 123.3 ± 9.7 mm Hg, P = 0.41; diastolic BP: 73.3 ± 12.9 and 72.0 ± 7.5 mm Hg, respectively, P = 0.69), number of endothelial progenitor cells, and platelet adhesion. CONCLUSIONS: Adding low-dose eplerenone to standard medical therapy did not improve important markers of vascular health in patients with CAD and preserved EF. Our results may help understand conflicting evidence from larger clinical trials on MRAs in patients with preserved EF