Oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine induces vascular endothelial superoxide production: Implication of NADPH oxidase

Abstract

Modified low-density lipoprotein (LDL) induces reactive oxygen species (ROS) production by vascular cells. It is unknown if specific oxidized components in these LDL particles such as oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (ox-PAPC) can stimulate ROS production. Bovine aortic endothelial cells (BAEC) were incubated with ox-PAPC (50 μg/ml). At 4 h, ox-PAPC significantly enhanced the rate of O 2 −• production. Pretreatment of BAEC in glucose-free Dulbecco's modified Eagle's medium plus 10 mM 2-deoxyglucose (2-DOG), the latter being an antimetabolite that blocks NADPH production by the pentose shunt, significantly reduced the rate of O 2 −• production. The intensity of NAD(P)H autofluorescence decreased by 28 ± 12% in BAEC incubated with ox-PAPC compared to untreated cells, with a further decrease in the presence of 2-DOG. Ox-PAPC also increased Nox4 mRNA expression by 2.4-fold ± 0.1 while pretreatment of BAEC with the small interfering RNA (siNox4) attenuated Nox4 RNA expression. Ox-PAPC further reduced the level of glutathione while pretreatment with apocynin (100 μM) restored the GSH level (control = 22.54 ± 0.23, GSH = 18.06 ± 0.98, apocynin = 22.55 ± 0.60,.17 ± 0.36 nmol/10 6 cells). Treatment with ox-PAPC also increased MMP-2 mRNA expression accompanied by a 1.5-fold increase in MMP-2 activity. Ox-PAPC induced vascular endothelial O 2 −• production that appears to be mediated largely by NADPH oxidase activity.

Triglyceride-rich lipoprotein lipolysis releases neutral and oxidized FFAs that induce endothelial cell inflammation

“…Such oxidized lipids are generated by the interaction of unsaturated FAs with ROS either free in solution or coordinated by enzymes including the di-iron oxidases (e.g., lipoxygenase) and heme-monoxygenases (e.g., cytochrome P450s; CYP). Various oxidized lipids, including oxidized cholesterol (52) and oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (53), are reported to induce cellular responses that can promote the generation of ROS. Although LDLs are prominent targets for postprandial oxidative modification in humans, the balance of factors controlling LDL oxidation in vivo remains controversial.…”

OKL38 is an oxidative stress response gene stimulated by oxidized phospholipids

“…Several pieces of data reported here support the regulation of OKL38 by oxidative stress. First, OKL38 stimulation by OxPAPC requires the activity of Nox, which is a major source of cellular superoxide production in response to OxPAPC (13). Second, scavenging of superoxide by the antioxidant NAC blocks the stimulation of OKL38.…”

“…We and others have shown that OxPAPC induces superoxide production in endothelial cells and that superoxide induction by OxPAPC is mediated by NADPH oxidase (Nox) and uncoupled endothelial Nitric Oxide Synthase (eNOS) (13,14). In cells treated with OxPAPC, superoxide was shown to be involved in the expression of interleukin-8 in HAECs and of Matrix Metalloprotease-2 (MMP2) in bovine aortic endothelial cells (13,14).…”

“…In cells treated with OxPAPC, superoxide was shown to be involved in the expression of interleukin-8 in HAECs and of Matrix Metalloprotease-2 (MMP2) in bovine aortic endothelial cells (13,14).…”

Endothelial cell regulation by phospholipid oxidation products

“…Rouhanizadeh et al demonstrated that glutathione was depleted in response to Ox-PAPC treatment in bovine aortic endothelial cells and that NADPH oxidase was the source superoxide induction by Ox-PAPC, which led to glutathione depletion. 45 Therond et al observed a decrease in glutathione levels in response to short chain polar lipid derivatives in endothelial cells. 46 Gharavi et al demonstrated that superoxide produced by uncoupled e-NOS also is a source of ROS.…”