A role for NADPH oxidase 4 in the activation of vascular endothelial cells by oxidized phospholipids

Abstract

Previous studies from our group have demonstrated that oxidized 1-palmitoyl-2-arachidonyl-sn-glycerol-3-phosphocholine (Ox-PAPC) activates over 1000 genes in human aortic endothelial cell (HAEC). Prominent among these are genes regulating inflammation, cholesterol homeostasis, antioxidant enzymes, and the unfolded protein response. Previous studies from our lab and others suggested that transcriptional regulation by Ox-PAPC may be controlled, at least in part, by reactive oxygen species (ROS). We now present evidence that Ox-PAPC activation of NADPH oxidase 4 (NOX4) is responsible for the regulation of two of these important groups of genes: those controlling inflammation and sterol regulation. Our data demonstrate that Ox-PAPC increases reactive oxygen species formation in HAEC as seen by DCF fluorescence. NOX4 is the major molecule responsible for this increase since downregulation of NOX4 and its components (p22phox and rac1) blocked the Ox-PAPC effect. Our data show that Ox-PAPC did not change NOX4 transcription levels but did induce recruitment of rac1 to the membrane for NOX4 activation. We present evidence that vascular endothelial growth factor receptor 2 (VEGFR2) activation is responsible for rac1 recruitment to the membrane. Finally, we demonstrate that knockdown of NOX4 and its components rac1 and p22phox decrease Ox-PAPC induction of inflammatory and sterol regulatory genes, but do not affect Ox-PAPC transcriptional regulation of other gene of antioxidant and unfolded protein response. In summary, we have identified a VEGFR2/NOX4 regulatory pathway by which Ox-PAPC controls important endothelial functions.

Differential Regulation of Endothelial Cell Permeability by High and Low Doses of Oxidized 1-Palmitoyl-2-Arachidonyl-sn-Glycero-3-Phosphocholine

“…OxPAPC was shown to induce vascular endothelial peroxide production by activating the nicotinamide adenine dinucleotide phosphate-reduced (NADPH) oxidase complex. The knockdown of NADPH oxidase isoform-4 and its components Rac-1 and p22(phox) decreased the induction by OxPAPC of inflammatory and sterol regulatory genes, but did not affect OxPAPC's transcriptional regulation of antioxidant genes and the unfolded protein response (14,15). The Rac-1/NADPH-dependent generation of ROS may also promote EC permeability.…”

“…Oxidized phospholipids may induce various proinflammatory effects, including the stimulation of cytokines and chemokine production (10,11), the activation of cell adhesion molecules (12,13), the elevation of intracellular and extracellular levels of superoxide radicals in human ECs (14,15), the activation of coagulation cascades, and platelet activation (16,17). However, in addition to tissue-damaging and proinflammatory effects, oxidized phospholipid products may exhibit potent anti-inflammatory activities under certain conditions.…”

Treatment with n-3 polyunsaturated fatty acids reverses endothelial dysfunction and oxidative stress in experimental menopause

“…Caveolae-associated NADPH oxidase isoform 1 (NOX-1) is reportedly the major source of intracellular superoxide in coronaric smooth muscle cells in diabetic mice [26]. In addition, n-3 PUFA are direct modulators of superoxide anion production from the non caveolar NADPH oxidase isoform 4 (NOX-4) [27], highly expressed in the vasculature and localized in focal adhesion sites [25,28], and one of the primary sources of superoxide production together with its regulatory subunit p22 phox [29,30]. Finally, n-3 PUFA improve lipid profile by reducing free fatty acids and triglyceride levels [31].…”

Exercise tames the wild side of the Myc network: a hypothesis

“…NADPH is also substrate for NADPH oxidases (NOX) that are associated with coronary artery disease (5). NOX participates in signal transduction pathways in human endothelial cells (70,126,144,157,209) and possibly in cardiac (3,226) and skeletal myocytes (211). Silent information regulator type 1 (SIRT1) is implicated in the integration of energy metabolism with gene expression (225) and is subject to redox regulation by S-glutathiolation (223).…”