Phosphatidylinositol 3-Kinase and Xanthine Oxidase Regulate Nitric Oxide and Reactive Oxygen Species Productions by Apoptotic Lymphocyte Microparticles in Endothelial Cells

Abstract

Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis. We have previously shown that MPs from apoptotic T cells induce endothelial dysfunction, but the mechanisms implicated are not completely elucidated. In this study, we dissect the pathways involved in endothelial cells with respect to both NO and reactive oxygen species (ROS). Incubation of endothelial cells with MPs decreased NO production that was associated with overexpression and phosphorylation of endothelial NO synthase (eNOS). Also, MPs enhanced expression of caveolin-1 and decreased its phosphorylation. Microparticles enhanced ROS by a mechanism sensitive to xanthine oxidase and P-IκBα inhibitors. PI3K inhibition reduced the effects of MPs on eNOS, but not on caveolin-1, whereas it enhanced the effects of MPs on ROS production. Microparticles stimulated ERK1/2 phosphorylation via a PI3K-depedent mechanism. Inhibition of MEK reversed eNOS phosphorylation but had no effect on ROS production induced by MPs. In vivo injection of MPs in mice impaired endothelial function. In summary, MPs activate pathways related to NO and ROS productions through PI3K, xanthine oxidase, and NF-κB pathways. These data underscore the pleiotropic effects of MPs on NO and ROS, leading to an increase oxidative stress that may account for the deleterious effects of MPs on endothelial function.

Evolving Role of Microparticles in the Pathophysiology of Endothelial Dysfunction

“…MPs from T lymphocytes decrease NO production and increase oxidative stress in endothelial cells (20 ). These effects are associated with reduced endothelial NO synthase (eNOS) activity, which depends on phosphatidylinositol-3-kinase (PI3K), extracellular signal-regulated kinase 1/2 (ERK1/2), and nuclear factor -light-chain-enhancer of activated B cell (NFB) pathways (20 ).…”

“…MPs from T lymphocytes decrease NO production and increase oxidative stress in endothelial cells (20 ). These effects are associated with reduced endothelial NO synthase (eNOS) activity, which depends on phosphatidylinositol-3-kinase (PI3K), extracellular signal-regulated kinase 1/2 (ERK1/2), and nuclear factor -light-chain-enhancer of activated B cell (NFB) pathways (20 ). Furthermore, aorta from mice injected with T-lymphocyte MPs shows an impaired acetylcholine-evoked endothelial relaxation due to a decline in NO and an increase in the production of reactive oxygen species (ROS) (20 ).…”

Heme oxygenase (HO)-1 induction prevents Endoplasmic Reticulum stress-mediated endothelial cell death and impaired angiogenic capacity

“…Culture medium samples were then centrifuged to remove dead cells and cell debris. The medium was subsequently processed to determine nitrate and nitrite concentrations according to the manufacturer's protocol [25].…”

Endothelial Dysfunction Caused by Circulating Microparticles from Patients with Metabolic Syndrome

“…21,24 Briefly, cells were treated with 250 l of colloid Fe(DETC) 2 and incubated at 37°C for 45 minutes. NO measurement was performed on a tabletop x-band spectrometer miniscope (MS200; Magnettech, Berlin, Germany).…”

“…Male Swiss mice (8 to 10 weeks old) were treated in vivo by intravenous injection into the tail vein of MPs at the circulating levels of MPs detected in the blood of each patient or healthy subject as previously performed. 21,24 After 24 hours, aortic rings were obtained from animals and mounted on a wire myograph as previously described. 21,24 Endothelium-dependent vasodilatation was studied by cumulative application of acetylcholine (1 nmol/L to 10 mol/L, Sigma-Aldrich) in aortas with functional endothelium precontracted with U46619 (Sigma-Aldrich).…”