7-Ketocholesterol enhances leukocyte adhesion to endothelial cells via p38MAPK pathway.

7-Ketocholesterol is a major dietary cholesterol oxidation product found in high concentrations in atherosclerotic plaques, which contribute to the development of atherosclerosis. This study aimed to investigate the effects of 7-ketocholesterol on endothelial inflammation, as well as the underlying mechanisms. Pretreatment of human umbilical vein endothelial cells (HUVEC) with 7-ketocholesterol significantly enhanced the total interactions between human monocytic cells (THP-1 cell line) and TNFα-activated HUVECs under physiological flow conditions, compared to pretreatment with cholesterol (TNFα+50 μM cholesterol: 13.1 ± 0.54 cells/CPF, TNFα+50 μM 7-ketocholesterol: 18.9 ± 0.35 cells/CPF, p < 0.01). 7-Ketocholesterol enhanced the expression of E-selectin, ICAM-1, and VCAM-1 proteins. It also activated p38 mitogen-activated protein kinase (MAPK), and treatment with a p38 MAPK inhibitor inhibited both E-selectin expression via ATF-2 activation and 7-ketocholesterol-induced THP-1 adhesion to HUVECs. These findings suggest that 7-ketocholesterol enhances leukocyte-endothelial interactions by upregulating the expression of adhesion molecules, presumably via the p38 MAPK-dependent pathway

Inhibitory Effect of Serotonin Antagonist on Leukocyte-Endothelial Interactions In Vivo and In Vitro.

Although 5-HT2A serotonergic antagonists have been used to treat vascular disease in patients with diabetes mellitus or obesity, their effects on leukocyte-endothelial interactions have not been fully investigated. In this study, we assessed the effects of sarpogrelate hydrochloride (SRPO), a 5-HT2A receptor inverse agonist, on leukocyte-endothelial cell interactions in obesity both in vivo and in vitro.In the in vivo experiment, C57BL/6 mice were fed a high-fat high-fructose diet (HFFD), comprising 20% fat and 30% fructose, with or without intraperitoneal injection of 5 mg/kg/day SRPO for 4 weeks. The body weight, visceral fat weight, and serum monocyte chemoattractant protein-1 levels in the mice increased significantly with the HFFD, but these effects were prevented by chronic injections of SRPO. Intravital microscopy of the femoral artery detected significant leukocyte-endothelial interactions after treatment with HFFD, but these leukocyte-endothelial interactions were reduced in the mice injected with SRPO. In the in vitro experiment, pre-incubation of activated human umbilical vein endothelial cells (HUVECs) with platelet-rich plasma (PRP) induced THP-1 cell adhesion under physiological flow conditions, but the adhesion was reduced by pretreatment of PRP with SRPO. A fluorescent immunobinding assay showed that PRP induced significant upregulation of E-selectin in HUVECs, but this upregulation was reduced by pretreatment of PRP with SRPO. In other in vitro conditions, pre-incubation of THP-1 cells with phorbol 12-myristate 13-acetate increased the adhesion of THP-1 cells to activated HUVECs under rotational conditions, but this adhesion was reduced by pretreatment with SRPO. Western blotting analysis showed that protein kinase C α activation in THP-1 cells was inhibited by SRPO.Our findings indicated that SRPO inhibits vascular inflammation in obesity via inactivation of platelets and leukocytes, and improvement of obese

7-Ketocholesterol increases the expression of adhesion molecules and cytokines in human umbilical vascular endothelial cells (HUVECs).

<p>(A) HUVECs were pretreated with 50 μM 7-ketocholesterol or cholesterol or ethanol alone for 18 h, followed by stimulation with or without 0.1 ng/ml tumor necrosis factor (TNF)-α for an additional 4 h. The levels of E-selectin, ICAM-1, and VCAM-1 protein expression were analyzed by western blotting. Representative blots from three independent experiments are shown. (B) HUVECs were pretreated with 50 μM 7-ketocholesterol or cholesterol or ethanol alone for 18 h, followed by stimulation with or without 0.1 ng/ml TNF-α for an additional 2 h. IL-8 and MCP-1 mRNA levels were analyzed by RT-qPCR. Data are shown as mean ± standard errors of the means. *p < 0.05, **p < 0.01 by one-way analysis of variance followed by Tukey’s test.</p

Schematic representation of the signaling pathways involved in the 7-ketocholesterol-induced leukocyte-endothelial interactions.

<p>7-ketocholesterol induces E-selectin expression mediated by ATF-2 and involves the p38MAPK activation pathway, which together increase the number of leukocyte interaction to endothelial cells.</p

Effects of 7-ketocholesterol on tumor necrosis factor (TNF)-α-induced mitogen-activated protein kinase (MAPK) activity in human umbilical vascular endothelial cells (HUVECs).

<p>(A) HUVECs were treated with 50 μM cholesterol or 7-ketocholesterol for each indicated time interval, followed by stimulation with 0.1 ng/ml TNF-α for an additional 15 min. Western blotting was used to evaluate the levels of p38, phospho-p38, JNK and phospho-JNK proteins as described in the Materials and Methods. Representative blots from three independent experiments are shown. (B) HUVECs were pretreated with 50 μM of cholesterol or 7-ketocholesterol for 18 h, followed by incubation with 5 μM p38MAPK inhibitor (SB203580) for 30 min and stimulation with TNF-α for an additional 4 h. A non-static adhesion assay was performed. Fluorescently labeled THP-1 cells were added to the HUVECs and allowed to adhere for 10 min under rotating conditions. Data are shown as means ± standard errors of the means (SEM). *p < 0.05 by a one-way analysis of variance followed by Tukey’s test. (C) HUVECs were pretreated with 50 μM of cholesterol or 7-ketocholesterol for 18 h, incubated with 5 μM p38 MAPK inhibitor (SB203580) for 30 min and stimulated with TNF-α for an additional 4 h. Western blotting was used to evaluate the expression of E-selectin, ICAM-1, and VCAM-1 proteins as described in the Materials and Methods. Representative blots from three independent experiments are shown.</p

THP-1 cell adhesion to HUVECs (Non-static rotational assay) and expression of PKCα in THP-1 cells.

<p>(A) SRPO significantly reduced PMA-triggered THP-1 cell adhesion to the HUVECs. THP-1 cells were pretreated with SRPO (10 μM) for 1 h and stimulated with PMA (10 nM) for 10 min before the assay. Preliminary experiments with trypan blue staining demonstrated that THP-1 cells were not damaged by SRPO (10 μM, 1h) treatment (data not shown). Adhesion assays were performed as described in Materials and Methods. Data are the mean ± SD of three independent experiments in each group. (B) SRPO attenuated PMA-induced PKCα activation in THP-1 cells. THP-1 cells were incubated in the presence or absence of SRPO (10 μM) for 1 h and stimulated with PMA (10 nM) for 10 min before the assay, and membrane proteins and total PKCα protein were detected by immunoblotting. Data are representative of three independent experiments.</p

THP-1 cell adhesion to HUVECs (Flow chamber assay) and expression of E-selectin in HUVECs.

<p>(A) SRPO significantly reduced the number of PRP-induced THP-1 cell that adhered to HUVECs. HUVEC monolayers were stimulated with 3 ng/ml TNF-α for 3.5 h and exposed to PPP or PRP for 20 min. PRP was pretreated or not with SRPO (10 μM) just before addition to the HUVECs. THP-1 cells were perfused over activated HUVEC monolayers at a flow rate of 1.0 dyne/cm². Adhesion assays were performed as described in Materials and Methods. Data are the mean ± SD of three independent experiments in each group. (B) SRPO significantly reduced the expression of PRP-induced E-selectin in HUVECs. E-selectin expression was determined by FIA as described in Materials and Methods. Data are the mean ± SD of 6 independent experiments in each group.</p

Effects of SRPO on HFFD-induced obesity.

<p>(A) Body weight (n = 17, 28, 29). (B) Epididymal fat weight (n = 13, 18, 18). (C) Liver weight (n = 17, 23, 25). Values are the mean ± SE in each group. (Abbreviations: NC = normal chow; HFFD = high-fat high-fructose diet; VEH = vehicle; SRPO = Sarpogrelate hydrochloride.)</p

SRPO significantly decreased leukocyte-endothelial interactions and serum MCP-1 level.

<p>(A) Image of leukocyte-endothelial interactions in the femoral arteries of mice (with the margins of vessels indicated by dotted lines). Arrows indicate adhered or rolling leukocytes. (B) The numbers of rolling (left) and adherent cells (right) in all groups were calculated as described in Methods. Values are the mean ± SE (n = 10, 16, 18). (C) Effect of SRPO on serum MCP-1 levels in HFFD-induced obesity. Values are the mean ± SE (n = 13, 13, 11). Serum MCP-1 level of the HFFD + VEH group was higher than in the NC group, and SRPO prevented the increase in serum MCP-1 level on the HFFD + VEH group.</p

Roles for Cell-Cell Adhesion and Contact in Obesity-Induced Hepatic Myeloid Cell Accumulation and Glucose Intolerance

Obesity promotes infiltration of inflammatory cells into various tissues, leading to parenchymal and stromal cell interaction and development of cellular and organ dysfunction. Liver sinusoidal endothelial cells (LSECs) are the first cells that contact portal blood cells and substances in the liver, but their functions in the development of obesity-associated glucose metabolism remain unclear. Here, we find that LSECs are involved in obesity-associated accumulation of myeloid cells via VLA-4-dependent cell-cell adhesion. VLA-4 blockade in mice fed a high-fat diet attenuated myeloid cell accumulation in the liver to improve hepatic inflammation and systemic glucose intolerance. Ex vivo studies further show that cell-cell contact between intrahepatic leukocytes and parenchymal hepatocytes induces gluconeogenesis via a Notch-dependent pathway. These findings suggest that cell-cell interaction between parenchymal and stromal cells regulates hepatic glucose metabolism and offers potential strategies for treatment or prevention of obesity-associated glucose intolerance