β-carotene reverses the IL-1β-mediated reduction in paraoxonase-1 expression via induction of the CaMKKII pathway in human endothelial cells

Interleukin-1 beta (IL-1β) induces endothelial dysfunction and reduces nitric oxide (NO) production. IL-1β also enhances adhesion molecule expression and induces arteriosclerosis. Conversely, high-density lipoprotein (HDL) induces endothelial NO synthase (eNOS), paraoxonase-1 (PON-1) activity, and maintains vascular health. Diet-derived β-carotene prevents arteriosclerosis, but its mode of action is not understood. The purpose of this study was to examine the HDL-like mechanisms of β-carotene in endothelial cells. We added IL-1β and/or β-carotene to cultured human endothelial cells and examined its effects on the regulation of HDL signal transduction pathways using RT-PCR, real-time PCR, Western blot (WB), and endothelial-U937 adhesion analysis. IL-1β decreased the expression of Ca2+/calmodulin-dependent kinase II (CaMKII), eNOS, PON-1, phosphatidylinositol 3-kinase (PI3K), PSD-95/Dlg/ZO-1 (PZK1), and liver kinase B1 (LKB1). Conversely, it increased the expression of intercellular adhesion molecule-1 (ICAM-1), and monocyte chemoattractant protein 1 (MCP-1). In contrast, β-carotene increased the expression of CaMKKII, PI3K, PZK1, LKB1, eNOS, PON-1, and reduced the expression of ICAM-1 and MCP-1. β-carotene also induced phospho-AMP-activated protein kinase (p-AMPK), phospho-eNOS and PON-1 proteins. Importantly, β-carotene upregulated the IL-1β-mediated decrease of CaMKKII, PZK1, LKB1, eNOS and PON-1. β-carotene inhibited IL-1β-mediated cell adhesion of U937 to endothelial cells. The effect of β-carotene was reversed by a CaMKK inhibitor, STO-609. These findings indicate that β-carotene regulates the expression of PON-1, eNOS and adhesion molecules via CaMKK pathway activation. β-carotene may contribute to the functional maintenance of vascular endothelial cells in a manner similar to HDL, protecting them against stimuli such as IL-1β.