It has been demonstrated that 15-lipoxygenase (15-LO) plays a role in atherogenesis, but the underlying mechanisms were unclear. Therefore, the purpose of the present study is to explore the mechanisms of 15-LO role in atherogenesis. 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE], the major 15-LO-dependent metabolite of arachidonic acid (AA), stimulated the production of reactive oxygen species (ROS) by monocytes through the xanthine oxidase–mediated activation of NADPH oxidase, which led to the Syk-, Pyk2-, mitogen-activated protein kinase (MAPK)–, and cyclic adenosine monophosphate response element–binding protein (CREB)–dependent production of the pro-inflammatory cytokine interleukin-17A (IL-17A). In addition, this pathway was required for the 15(S)-HETE–dependent migration and adhesion of monocytes to endothelial cells. Consistent with these observations, we found that peritoneal macrophages from ApoE−/− mice fed a high-fat diet (a mouse model of atherosclerosis) exhibited increased xanthine oxidase and NADPH oxidase activities, ROS production, phosphorylation of Syk, Pyk2, MAPK, and CREB, and enhanced IL-17A production compared to those from ApoE−/−:12/15-LO−/− mice. These events correlated with increased lipid deposits and numbers of monocytes and macrophages in the aortic arches of these mice, which resulted in atherosclerotic plaque formation. Together, these observations suggest that 15(S)-HETE exacerbates atherogenesis by enhancing CREB-dependent IL-17A production.

Conflict of interest: JT is a cofounder of Principia Biopharma, which has licensed the p90RSK inhibitor FMK-MEA.

In understanding the mechanisms of cholesterol in the pathogenesis of atherosclerosis, previous studies from other laboratories have demonstrated that cholesterol crystals (CC) induce scavenger receptor CD36 expression and NLRP3-mediated inflammasome formation. In elucidating the mechanisms by which CC could enhance CD36 expression and foam cell formation, here we report that CC via NADPH and xanthine oxidases-mediated ROS production activates BTK, a non-receptor tyrosine kinase. In addition, CC induce p300 tyrosine phosphorylation and activation in a BTK-dependent manner, which in turn, leads to STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation. Furthermore, p300, STAT1 and PPARγ bound to a STAT binding site at −107 nt in CD36 promoter and enhanced its activity in ROS and BTK-dependent manner. Disruption of this STAT binding site by site-directed mutagenesis abolished CC-induced CD36 promoter activity. Together these results reveal for the first time that CC via producing ROS and activating BTK causes p300-mediated STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation.

Background:The purpose of this study was to test the role of PKN1 in vascular wall remodeling. Results: PKN1 mediates MCP-1-induced HASMC migration/proliferation and balloon injury-induced neointima formation. Conclusion: PKN1 plays a role in vascular wall remodeling following balloon injury. Significance: PKN1 could be a promising target for the next generation of drugs for vascular diseases such as restenosis.

Background: The incidence of cardiovascular disease (CVD) is higher in HIV + patients than it is in the average population, and combination antiretroviral therapy (cART) is a recognized risk factor for CVD. However, the molecular mechanisms that link cART and CVD are currently unknown. Our study explores the role of the activation of p90RSK, a reactive oxygen species (ROS)-sensitive kinase, in engendering senescent phenotype in macrophages and accelerating atherogenesis in patients undergoing cART. Methods: Peripheral whole blood from cART-treated HIV + individuals and non-treated HIV − individuals was treated with H 2 O 2 (200 μM) for 4 minutes, and p90RSK activity in CD14 + monocytes was measured. Plaque formation in the carotids were also analyzed in these individuals. Macrophage senescence was determined by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. The involvement of p90RSK-NRF2 signaling in cART-induced senescence was assessed by p90RSK specific inhibitor (FMK-MEA) or dominant negative p90RSK (DN-p90RSK), and NRF2 activator (NRF2A). Further, the severity of atherosclerosis was determined in myeloid cell-specific wild type and DN-p90RSK transgenic mice. Results: Monocytes from HIV + patients exhibited higher levels of p90RSK activity and were also more sensitive to ROS than monocytes from HIV − individuals. A multiple linear regression analysis involving cART, Reynolds CV risk score, and basal p90RSK activity revealed that cART and basal p90RSK activity were the two significant determinants of plaque formation. Many of the antiretroviral drugs individually activated p90RSK, which simultaneously triggered all components of the macrophage senescent phenotype. cART inhibited antioxidant response element reporter activity via ERK5 S496 phosphorylation. NRF2A reversed the H 2 O 2-induced over-activation of p90RSK in cART-treated macrophages by countering the induction of senescent phenotype. Lastly, the data obtained from our gain-or loss-of-function mice conclusively showed the crucial role of p90RSK in inducing senescent phenotype in macrophages and atherogenesis. Conclusions: cART increased monocyte/macrophage sensitivity to ROS in HIV + individuals by suppressing NRF2-ARE activity via p90RSK-mediated ERK5 S496 phosphorylation, which coordinately elicited senescent phenotypes and pro-inflammatory responses. As such, our report underscores the importance of p90RSK regulation in monocytes/macrophages as a viable biomarker and therapeutic target for preventing CVD, especially in HIV + patients treated with cART.

15(S)-Hydroxyeicosatetraenoic acid (15(S)-HETE), the major 15-lipoxygenase 1/2 (15-LO1/2) metabolite of arachidonic acid (AA), induces CD36 expression through xanthine oxidase and NADPH oxidase-dependent ROS production and Syk and Pyk2-dependent STAT1 activation. In line with these observations, 15(S)-HETE also induced foam cell formation involving ROS, Syk, Pyk2 and STAT1-mediated CD36 expression. In addition, peritoneal macrophages from Western diet-fed ApoE−/− mice exhibited elevated levels of xanthine oxidase and NADPH oxidase activities, ROS production, Syk, Pyk2, and STAT1 phosphorylation and CD36 expression compared to those from ApoE−/−:12/15-LO−/− mice and these events correlated with increased lipid deposits, macrophage content and lesion progression in the aortic roots. Human atherosclerotic arteries also showed increased 15-LO1 expression, STAT1 phosphorylation and CD36 levels as compared to normal arteries. Together, these findings suggest that 12/15-LO metabolites of AA, particularly 12/15(S)-HETE might play a crucial role in atherogenesis by enhancing foam cell formation.

This article is available online at http://www.jlr.org surface to the circulating blood, and releases vasoactive substances involved in the regulation of vascular tone ( 1, 2 ). Besides, it selectively permits the movement of molecules into and out of the bloodstream, and this semipermeable capacity of the endothelial monolayer depends majorly on cell-to-cell connections, namely adherens junctions (AJs), tight junctions (TJs), and gap junctions ( 3, 4 ). Disruption of these junctions leads to a leaky endothelial barrier, which allows the traffi cking of leukocytes through the blood vessels into the interstitial space and initiates infl ammation ( 2, 4 ). A large body of evidence indicates that TJs of endothelium play a pivotal role in modulating its barrier permeability, and dysfunctional endothelium often manifests increased barrier permeability ( 5, 6 ). Many studies suggest that oxidative stress is one of the underlying factors in endothelial dysfunction and atherosclerosis ( 7,8 ). NADPH oxidase, a major source of reactive oxygen species (ROS) production ( 9 ), has been reported to increase EC barrier permeability ( 10, 11 ). Xanthine oxidase (XO), a purine-catabolizing enzyme, was also found as another major source of cellular ROS production ( 12 ). XO results from sulfhydryl oxidation or proteolytic conversion of xanthine dehydrogenase (XDH) ( 13,14 ). Although both XDH and XO convert hypoxanthine and xanthine to uric acid, XO preferentially converts molecular oxygen to superoxide anion and hydrogen peroxide ( 12 ). However, under the reduced state, XDH can also react with molecular oxygen and generate ROS ( 15 ). Although the physiological signifi cance of XDH conversion to XO is not clear, XO was found to be abundantly present in several tissues, including in the luminal surface of the microvascular endothelium, and is thought to be involved in the pathogenesis of various diseases such as infl ammation and Endothelium, which is constituted by a monolayer of endothelial cells (ECs), is the inner most lining of the blood vessels, provides nonplatelet adherent nonthrombotic Abstract To understand the mechanisms of 15(S)-HETEinduced endothelial cell (EC) barrier dysfunction, we examined the role of xanthine oxidase (XO). 15(S)-HETE induced

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