Lee Sun-Hye, Park Dae-Weon, Park Sung Chul, Park Yun-Ki, Hong Seong Yeon, Kim Jae-Ryong, Lee Chu-Hee, Baek Suk-Hwan
Aging-associated Vascular Disease Research Center, Department of Biochemistry and Molecular Biology, College of Medicine, Yeungnam University, Daegu, South Korea.
J Immunol. 2009 Dec 1;183(11):7497-504. doi: 10.4049/jimmunol.0900503. Epub 2009 Nov 16.
Foam cell formation is the most important process in atherosclerosis, and low density lipoprotein oxidation by reactive oxygen species (ROS) is the key step in the conversion of macrophages to foam cells. This study reveals the control mechanism of the gene for NADPH oxidase 1 (Nox1), which produces ROS in the formation of foam cells by stimulating TLR4. Treatment of macrophages by the TLR4 agonist LPS stimulated ROS production and ROS-mediated macrophage to foam cell conversion. This LPS-induced ROS production and foam cell formation could be abrogated by pretreatment of macrophages with N-acetyl cysteine or apocynin. LPS increased Nox1 promoter activity, and resultant expression of mRNA and protein. Small interfering RNA mediated inhibition of Nox1 expression decreased LPS-induced ROS production and foam cell formation. LPS-mediated Nox1 expression and the responses occurred in a calcium-independent phospholipase A(2) (iPLA(2))-dependent manner. The iPLA(2)beta-specific inhibitor S-BEL or iPLA(2)beta small interfering RNA attenuated LPS-induced Nox1 expression, ROS production, and foam cell formation. In addition, activation of iPLA(2)beta by LPS caused Akt phosphorylation and was followed by increased Nox1 expression. These results suggest that the binding of LPS and TLR4 increases Nox1 expression through the iPLA(2)beta-Akt signaling pathway, and control ROS production and foam cell formation.
泡沫细胞形成是动脉粥样硬化中最重要的过程，活性氧（ROS）介导的低密度脂蛋白氧化是巨噬细胞转化为泡沫细胞的关键步骤。本研究揭示了NADPH氧化酶1（Nox1）基因的调控机制，该酶通过刺激TLR4在泡沫细胞形成过程中产生ROS。用TLR4激动剂LPS处理巨噬细胞可刺激ROS产生以及ROS介导的巨噬细胞向泡沫细胞的转化。巨噬细胞用N-乙酰半胱氨酸或载脂蛋白预处理可消除这种LPS诱导的ROS产生和泡沫细胞形成。LPS增加了Nox1启动子活性，以及随后的mRNA和蛋白质表达。小干扰RNA介导的Nox1表达抑制降低了LPS诱导的ROS产生和泡沫细胞形成。LPS介导的Nox1表达及反应以不依赖钙的磷脂酶A2（iPLA2）依赖性方式发生。iPLA2β特异性抑制剂S-BEL或iPLA2β小干扰RNA减弱了LPS诱导的Nox1表达、ROS产生和泡沫细胞形成。此外，LPS激活iPLA2β导致Akt磷酸化，随后Nox1表达增加。这些结果表明，LPS与TLR4的结合通过iPLA2β-Akt信号通路增加Nox1表达，并控制ROS产生和泡沫细胞形成。
