Donghui Liu

High-density lipoprotein of patients with Type 2 Diabetes Mellitus upregulates cyclooxgenase-2 expression and prostacyclin I-2 release in endothelial cells: relationship with HDL-associated sphingosine-1-phosphate

BackgroundDysfunctional high-density lipoprotein (HDL) may have pro-inflammatory effects on the endothelial cells,which causes atherosclerosis in type 2 diabetes mellitus (T2DM). HDL is a major carrier of sphingosine-1-phosphate (S1P) in plasma while S1P exhibits multiple biological activities. However, potential role of HDL and S1P in T2DM remains unexplored. We hypothesized that diabetic HDL with higher contents of S1P exerts beneficial effects on the vascular system.MethodsSubjects with T2DM with or without proved large arteries atherosclerosis and normal controls (n=15 for each group) were recruited in the present study. HDL was isolated from the subjects by ultracentrifugation. The levels of HDL-associated S1P were determined by UPLC-MS/MS. The protective function of diabetic HDL and S1P was evaluated by measuring cyclooxygenase-2 (COX-2) expression and prostacyclin I-2 (PGI-2) release by human umbilical vein endothelial cells (HUVECs) using western blot and enzyme-linked immunosorbent assay (ELISA), respectively.ResultsThe S1P levels in isolated HDL were significantly increased in T2DM subjects compared with controls (235.6 ± 13.4 vs 195.0 ± 6.4 ng/mg, P< 0.05). The diabetic HDL exerted greater protective effects on inducing COX-2 expression and PGI-2 release by HUVECs than those of control HDL (p < 0.05, p < 0.01, respectively). Pertussis toxin, a common inhibitor of G-couple protein receptors, and VPC 23019, an antagonist of S1P receptor 1 and 3 significantly attenuated HDL-induced COX-2 expression and PGI-2 release.ConclusionsDiabetic HDL carries higher level of S1P compared with normal HDL, which has the potential to contribute to protective effects on endothelial cells by inducing COX-2 expression and PGI-2 release. These findings provide a new insight of S1P function in T2DM patients, possibly leading to a new therapeutic target.

High‐density lipoprotein of patients with type 2 diabetes mellitus elevates the capability of promoting migration and invasion of breast cancer cells

Epidemiological studies suggested complicated associations between type 2 diabetes mellitus and breast cancer. There is a significant inverse association between high‐density lipoprotein (HDL) and the risk and mortality of breast cancer. However, HDL could be modified in various ways in diabetes patients, and this may lead to the altered effects on many different types of cells. In our study, we found that glycation and oxidation levels are significantly higher in HDL from type 2 diabetes mellitus patients compared to that from healthy subjects. Diabetic HDL dramatically had a stronger capability to promote cell proliferation, migration and invasion of breast cancer (as examined both on hormone‐independent cells and on hormone‐dependent cells). In addition, glycated and oxidized HDL, which were produced in vitro, acted in similar way as diabetic HDL. Diabetic HDL, glycated HDL and oxidized HDL also induced higher synthesis and secretion of VEGF‐C, MMP‐2 and MMP‐9 from malondialdehyde (MDA)‐MB‐231 cells. It was indicated that diabetic, glycated and oxidized HDL promote MDA‐MB‐231 cell migration and invasion through ERK and p38 MAPK pathways, and Akt pathway plays an important role as well in MDA‐MB‐231 cell invasion. The Akt, ERK and p38 MAPK pathways are also involved in VEGF‐C and MMP‐9 secretion induced by diabetic, glycated and oxidized HDL. Our study demonstrated that glycation and oxidation of HDL in diabetic patients could lead to abnormal actions on MDA‐MB‐231 cell proliferation, migration and invasion, thereby promoting the progression of breast cancer. This will largely draw the attention of HDL‐based treatments in diabetic patients especially those with breast cancer.

Diabetic HDL Is Dysfunctional in Stimulating Endothelial Cell Migration and Proliferation Due to Down Regulation of SR-BI Expression

Background Diabetic HDL had diminished capacity to stimulate endothelial cell (EC) proliferation, migration, and adhesion to extracellular matrix. The mechanism of such dysfunction is poorly understood and we therefore sought to determine the mechanistic features of diabetic HDL dysfunction. Methodology/Principal Findings We found that the dysfunction of diabetic HDL on human umbilical vein endothelial cells (HUVECs) was associated with the down regulation of the HDL receptor protein, SR-BI. Akt-phosphorylation in HUVECs was induced in a biphasic manner by normal HDL. While diabetic HDL induced Akt phosphorylation normally after 20 minutes, the phosphorylation observed 24 hours after diabetic HDL treatment was reduced. To determine the role of SR-BI down regulation on diminished EC responses of diabetic HDL, Mouse aortic endothelial cells (MAECs) were isolated from wild type and SR-BI (−/−) mice, and treated with normal and diabetic HDL. The proliferative and migratory effects of normal HDL on wild type MAECs were greatly diminished in SR-BI (−/−) cells. In contrast, response to diabetic HDL was impaired in both types suggesting diminished effectiveness of diabetic HDL on EC proliferation and migration might be due to the down regulation of SR-BI. Additionally, SR-BI down regulation diminishes diabetic HDL’s capacity to activate Akt chronically. Conclusions/Significance Diabetic HDL was dysfunctional in promoting EC proliferation, migration, and adhesion to matrix which was associated with the down-regulation of SR-BI. Additionally, SR-BI down regulation diminishes diabetic HDL’s capacity to activate Akt chronically.

Nonenzymatic glycation of high-density lipoprotein impairs its anti-inflammatory effects in innate immunity

In type 2 diabetes mellitus (T2DM), the abnormal protein and lipid composition of diabetic high‐density lipoprotein (HDL) could impair its anti‐inflammatory functions. Whether nonenzymatic glycation directly impaired the anti‐inflammatory effects of HDL in innate immunity remained unclear.

Cyclooxygenase-2 Expression, Prostacyclin Production and Endothelial Protection of High-density Lipoprotein

Atherosclerosis is a multi-factorial inflammatory disease with accumulation of lipids and recruitment of leukocytes into the subendothelial space. Due to the consistent inflammation in vessels, a subset of atherosclerotic plaques is even prone to physical disruption or producing thrombosis that triggers acute coronary syndromes (ACS). Cyclooxygenase (COX) and the downstream diverse prostanoids are involved in numerous physiological activities and inflammatory processes. Remarkably, prostanoids are a group of bioactive lipid mediators, and play a series of complicated and even contradictory roles during the progression of atherogenesis. Some, mainly prostacyclin (PGI2) have cardioprotective effects to inhibit the aggravation of atherosclerosis, however, others including prostaglandin E2 (PGE2) and thromboxane A2 (TXA2), increase the risk of cardiovascular thromboembolic events. Therefore, the controversial effects bring about a debate on the use of cyclooxygenase-2 (COX-2) specific and non-specific inhibitors in the prevention from cardiovascular diseases. In addition to reverse cholesterol transport (RCT), high-density lipoprotein (HDL) exerts several beneficial effects on endothelial protection. Moreover, HDL could also regulate the expression of COX-2 and the production of PGI2 in endothelial cells. While as a diverse complex of heterogeneous particle composed of various apolipoproteins, enzymes and lipids, the individual components of HDL, such as apolipoprotein A-I (apoA-I) and sphingosine-1-phosphate (S1P), have distinct effects on COX-2 expression and PGI2 production in endothelial cells. In the present review, we summarize the roles of COX-2 as well as PGI2 in atherosclerosis and atherothrombosis, the controversial vascular effects on prostanoid inhibition by COX-2 inhibitors, and the effects of HDL on the endothelial protection by the upregulation of COX-2 and the release of PGI2 during the progression of atherosclerosis.

APOA-II DIRECTS MORPHOGENETIC MOVEMENTS OF ZEBRAFISH EMBRYO BY PREVENTING CHROMOSOME FUSION DURING NUCLEAR DIVISION IN YOLK SYNCYTIAL LAYER

The high density lipoprotein (HDL) represents a class of lipid- and protein-containing particles and consists of two major apolipoproteins apoA-I and apoA-II. ApoA-II has been shown to be involved in the pathogenesis of insulin resistance, adiposity, diabetes, and metabolic syndrome. In embryo, apoa2 mRNAs are abundant in the liver, brain, lung, placenta, and in fish yolk syncytial layer (YSL), suggesting that apoa2 may perform a function during embryonic development. Here we find out that apoa2 modulates zebrafish embryonic development by regulating the organization of YSL. Disruption of apoa2 function in zebrafish caused chromosome fusing, which strongly blocked YSL nuclear division, inducing disorders in YSL organization and finally disturbing the embryonic epiboly. Purified native human apoA-II was able specifically to rescue the defects and induced nuclear division in zebrafish embryos and in human HeLa cells. The C terminus of apoA-II was required for the proper chromosome separation during nuclear division of YSL in zebrafish embryos and in human HeLa cells. Our data indicate that organization of YSL is required for blastoderm patterning and morphogenesis and suggest that apolipoprotein apoA-II is a novel factor of nuclear division in YSL involved in the regulation of early zebrafish embryonic morphogenesis and in mammalian cells for proliferation.

The compensatory enrichment of sphingosine -1- phosphate harbored on glycated high-density lipoprotein restores endothelial protective function in type 2 diabetes mellitus

BackgroundGlycation of high-density lipoprotein (HDL) decreases its ability to induce cyclooxygenase-2 (COX-2) expression and prostacyclin I-2 (PGI-2) release in endothelial cells. Whether lipid content of HDL, especially sphingosine-1-phosphate (S1P), plays any specific role in restoring the protective function of HDL in type 2 diabetes mellitus (T2DM) is still unknown.Methods and resultsImmunochemical techniques demonstrated that glycated HDL loses its protective function of regulating COX-2 expression compared with diabetic HDL. We proved that the lipid content, especially phospholipid content differed between diabetic HDL and glycated HDL. Levels of HDL-c-bound S1P were increased in T2DM compared with control subjects as detected by UPLC-MS/MS (HDL-c-bound S1P in control subjects vs. T2DM: 309.1 ± 13.71 pmol/mg vs. 382.1 ± 24.45 pmol/mg, P < 0.05). Additionally, mRNA levels of S1P lyase enzymes and S1P phosphatase 1/2 were decreased in peripheral blood by real-time PCR. Antagonist of S1P receptor 1 and 3 (S1PR1/3) diminished the functional difference between apoHDL&PL (HDL containing the protein components and phospholipids) and diabetic apoHDL&PL (diabetic HDL containing the protein components and phospholipids). With different doses of S1P reconstituted on glycated HDL, its function in inducing the COX-2 expression was restored to the same level as diabetic HDL. The mechanism of S1P reconstituted HDL (rHDL) in the process of regulating COX-2 expression involved the phosphorylation of ERK/MAPK-CREB signal pathway.Conclusion/SignificanceS1P harbored on HDL is the main factor which restores its protective function in endothelial cells in T2DM. S1P and its receptors are potential therapeutic targets in ameliorating the vascular dysfunction in T2DM.

A novel anti-inflammatory mechanism of high density lipoprotein through up-regulating annexin A1 in vascular endothelial cells

High density lipoprotein (HDL) as well as annexin A1 have been reported to be associated with cardiovascular protection. However, the correlation between HDL and annexin A1 was still unknown. In this study, HDL increased endothelial annexin A1 and prevented the decrease of annexin A1 in TNF-α-activated endothelial cells in vitro and in vivo, and above effects were attenuated after knockdown of annexin A1. Annexin A1 modulation affected HDL-mediated inhibition of monocyte adhesion to TNF-α-activated endothelium (45.2±13.7% decrease for annexin A1 RNA interference; 78.7±16.3% decrease for anti-Annexin A1 antibody blocking; 11.2±6.9% increase for Ad-ANXA1 transfection). Additionally, HDL up-regulated annexin A1 through scavenger receptor class B type I, involving ERK, p38MAPK, Akt and PKC signaling pathways, and respective inhibitors of these pathways attenuated HDL-induced annexin A1 expression as well as impaired HDL-mediated inhibition of monocyte-endothelial cell adhesion. Apolipoprotein AI also increased annexin A1 and activated similar signaling pathways. Endothelial annexin A1 from apolipoprotein AI knockout mice was decreased in comparison to that from wild type mice. Finally, HDL-induced annexin A1 inhibited cell surface VCAM-1, ICAM-1 and E-selectin, and secretion of MCP-1, IL-8, VCAM-1 and E-selectin, thereby inhibiting monocyte adhesion.

The apolipoprotein A-I mimetic peptide, D-4F, alleviates ox-LDL-induced oxidative stress and promotes endothelial repair through the eNOS/HO-1 pathway

Apolipoprotein A-I (apoA-I) mimetic peptide exerts many anti-atherogenic properties. However, the underlying mechanisms related to the endothelial protective effects remain elusive. In this study, the apoA-I mimetic peptide, D-4F, was used. Proliferation assay, wound healing, and transwell migration experiments showed that D-4F improved the impaired endothelial proliferation and migration resulting from ox-LDL. Endothelial adhesion molecules expression and monocyte adhesion assay demonstrated that D-4F inhibited endothelial inflammation. Caspase-3 activation and TUNEL stain indicated that D-4F reduced endothelial cell apoptosis. A pivotal anti-oxidant enzyme, heme oxygenase-1 (HO-1) was upregulated by D-4F. The Akt/AMPK/eNOS pathways were involved in the expression of HO-1 induced by D-4F. Moreover, the anti-oxidation, pro-proliferation, and pro-migration capacities of D-4F were diminished by the inhibitors of both eNOS (L-NAME) and HO-1 (Znpp). Additionally, downregulation of ATP-binding cassette transporter A1 (ABCA1) by siRNA abolished the activation of Akt, AMPK and eNOS, and reduced the upregulation of HO-1 triggered by D-4F. Furthermore, D-4F promoted the reendothelialization of injured intima in carotid artery injury model of C57BL/6J mice in vivo. In summary, these findings suggested that D-4F might be a powerful candidate in the protection of endothelial cells and the prevention of cardiovascular disease (CVD).

The apolipoprotein A‐I mimetic peptide, D‐4F, restrains neointimal formation through heme oxygenase‐1 up‐regulation

D‐4F, an apolipoprotein A‐I (apoA‐I) mimetic peptide, possesses distinctly anti‐atherogenic effects. However, the biological functions and mechanisms of D‐4F on the hyperplasia of vascular smooth muscle cells (VSMCs) remain unclear. This study aimed to determine its roles in the proliferation and migration of VSMCs. In vitro, D‐4F inhibited VSMC proliferation and migration induced by ox‐LDL in a dose‐dependent manner. D‐4F up‐regulated heme oxygenase‐1 (HO‐1) expression in VSMCs, and the PI3K/Akt/AMP‐activated protein kinase (AMPK) pathway was involved in these processes. HO‐1 down‐regulation with siRNA or inhibition with zinc protoporphyrin (Znpp) impaired the protective effects of D‐4F on the oxidative stress and the proliferation and migration of VSMCs. Moreover, down‐regulation of ATP‐binding cassette transporter A1 (ABCA1) abolished the activation of Akt and AMPK, the up‐regulation of HO‐1 and the anti‐oxidative effects of D‐4F. In vivo, D‐4F restrained neointimal formation and oxidative stress of carotid arteries in balloon‐injured Sprague Dawley rats. And inhibition of HO‐1 with Znpp decreased the inhibitory effects of D‐4F on neointimal formation and ROS production in arteries. In conclusion, D‐4F inhibited VSMC proliferation and migration in vitro and neointimal formation in vivo through HO‐1 up‐regulation, which provided a novel prophylactic and therapeutic strategy for anti‐restenosis of arteries.