A key role for matrix metalloproteinases and neutral sphingomyelinase-2 in transplant vasculopathy triggered by anti-HLA antibody.

Background: Outcomes for organ transplantation are constantly improving because of advances in organ preservation, surgical techniques, immune clinical monitoring, and immunosuppressive treatment preventing acute transplant rejection. However, chronic rejection including transplant vasculopathy still limits long-term patient survival. Transplant vasculopathy is characterized by progressive neointimal hyperplasia leading to arterial stenosis and ischemic failure of the allograft.

Lipid-induced peroxidation in the intestine is involved in glucose homeostasis imbalance in mice.

Background: Daily variations in lipid concentrations in both gut lumen and blood are detected by specific sensors located in the gastrointestinal tract and in specialized central areas. Deregulation of the lipid sensors could be partly involved in the dysfunction of glucose homeostasis. The study aimed at comparing the effect of Medialipid (ML) overload on insulin secretion and sensitivity when administered either through the intestine or the carotid artery in mice.

Stress-induced sphingolipid signaling: role of type-2 neutral sphingomyelinase in murine cell apoptosis and proliferation.

Background: Sphingomyelin hydrolysis in response to stress-inducing agents, and subsequent ceramide generation, are implicated in various cellular responses, including apoptosis, inflammation and proliferation, depending on the nature of the different acidic or neutral sphingomyelinases. This study was carried out to investigate whether the neutral Mg(2+)-dependent neutral sphingomyelinase-2 (nSMase2) plays a role in the cellular signaling evoked by TNFalpha and oxidized LDLs, two stress-inducing agents, which are mitogenic at low concentrations and proapoptotic at higher concentrations.

Methodology And Principal Findings: For this purpose, we used nSMase2-deficient cells from homozygous fro/fro (fragilitas ossium) mice and nSMase2-deficient cells reconstituted with a V5-tagged nSMase2.

HLA class I antibodies provoke graft arteriosclerosis in human arteries transplanted into SCID/beige mice.

Antibodies toward HLA class I and/or MICA are commonly observed in transplanted patients suffering from allograft arteriosclerosis, also called chronic vascular rejection (CVR). The relative importance of cellular versus humoral alloreactivity for CVR is still disputed. We demonstrate that antibodies toward HLA class I provoke lesions typical for CVR in human arteries in vivo in the absence of cellular immunity.

Integrin alpha(v)beta(3), metalloproteinases, and sphingomyelinase-2 mediate urokinase mitogenic effect.

Plasminogen activators are implicated in the pathogenesis of several diseases such as inflammatory diseases and cancer. Beside their serine-protease activity, these agents trigger signaling pathways involved in cell migration, adhesion and proliferation. We previously reported a role for the sphingolipid pathway in the mitogenic effect of plasminogen activators, but the signaling mechanisms involved in neutral sphingomyelinase-2 (NSMase-2) activation (the first step of the sphingolipid pathway) are poorly known.

Interleukin-6 deficiency fails to prevent chronic rejection after aortic allografts in apolipoprotein E-deficient mice.

Background: Chronic vascular rejection (CVR) is characterized by an intimal thickening in the arteries of allografts due to immunoinflammatory reactions and smooth muscle cell proliferation. Interleukin 6 (IL-6) levels are increased in patients with graft rejection, however the role of IL-6 in CVR is not known. We investigated if IL-6 deficiency in the recipient could prevent CVR after an aortic allograft.

Oxidized low-density lipoproteins trigger endoplasmic reticulum stress in vascular cells: prevention by oxygen-regulated protein 150 expression.

Oxidized low-density lipoproteins (oxLDLs) trigger various biological responses potentially involved in atherogenesis. Disturbing endoplasmic reticulum (ER) function results in ER stress and unfolded protein response, which tends to restore ER homeostasis but switches to apoptosis when ER stress is prolonged. We aimed to investigate whether ER stress is induced by oxLDLs and can be prevented by the ER-associated chaperone ORP150 (150-kDa oxygen-regulated protein).

Carbonyl scavenger and antiatherogenic effects of hydrazine derivatives.

Reactive carbonyl compounds (RCC) generated by polyunsaturated fatty acid oxidation alter progressively cellular and tissular proteins by forming adducts on free amino groups and thiol residues (carbonyl stress). Carbonyl scavengers may neutralize RCC, but their protective effect in atherosclerosis has not been extensively studied. We report the carbonyl scavenger and antiatherogenic properties of hydrazine derivatives, namely hydralazine, an antihypertensive drug, isoniazid, an antituberculosis agent, and two antidepressants, phenelzine and iproniazid.

E-cadherin/beta-catenin/T-cell factor pathway is involved in smooth muscle cell proliferation elicited by oxidized low-density lipoprotein.

The E-cadherin/beta-catenin/T-cell factor (Tcf) signaling pathway plays a crucial role in embryogenesis and carcinogenesis and has recently emerged in atherosclerosis. The aim of this work was to investigate whether this signaling pathway is involved in smooth muscle cell proliferation induced by oxidized low-density lipoprotein (LDL). In human aortic smooth muscle cells, mitogenic concentration of mildly oxidized LDL induced the activation of beta-catenin, as assessed by the dissociation of the beta-catenin/cadherin complex, and the concomitant rise of active beta-catenin in the cytosol.

Oxygen-regulated protein-150 prevents calcium homeostasis deregulation and apoptosis induced by oxidized LDL in vascular cells.

Oxidized LDLs (oxLDLs) induce apoptosis, which contributes to the pathogenesis of atherosclerosis. The 150 kDa oxygen-regulated protein (ORP150), an endoplasmic reticulum (ER)-resident chaperone, is upregulated by hypoxia and prevents ischemia-induced cell death. The aim of this work was to investigate whether and how ORP150 can prevent apoptosis induced by oxLDLs in vascular cells.

Caveolin-1 sensitizes vascular smooth muscle cells to mildly oxidized LDL-induced apoptosis.

Oxidized low-density lipoprotein (oxLDL)-induced apoptosis of vascular cells may participate to plaque instability and rupture. Caveolin-1 has emerged as an important regulator of several signal transduction pathways and processes that play a role in atherosclerosis. In this study we examined the potential role of caveolin-1 in the regulation of oxLDL-induced Ca(2+) signaling and apoptosis in vascular smooth muscle cells (VSMC).

Effect of FTY720 on apoptosis of smooth muscle cells.

Background: Hyperproliferation of smooth muscle cells (SMCs) plays a key role in allograft arteriosclerosis. This prompted us to investigate the effect of the novel immune modulator and synthetic sphingolipid FTY720 on apoptosis of SMCs.

Methods: Rabbit SMC cultures were treated with FTY720 and apoptosis and necrosis were detected by fluorescence microscopy.

Methylglyoxal induces advanced glycation end product (AGEs) formation and dysfunction of PDGF receptor-beta: implications for diabetic atherosclerosis.

Purpose: Low molecular weight carbonyl compounds, such as the alpha-ketoaldehydes methylglyoxal (MGO) and glyoxal (GO), are formed under hyperglycemic conditions and behave as advanced glycation end product (AGE) precursors. They form adducts on proteins, thereby inducing cellular dysfunctions involved in chronic complications of diabetes.

Methods And Main Findings: Nontoxic concentrations of GO or MGO altered the PDGF-induced PDGFRbeta-phosphorylation, ERK1/2-activation, and nuclear translocation, and the subsequent proliferation of mesenchymal cells (smooth muscle cells and skin fibroblasts).

Multiple human mesenteric arterial grafts from the same donor to study human chronic vascular rejection in humanized SCID/beige mice.

Background: Chronic vascular rejection (CVR) is a major problem in clinical transplantation. Studies in experimental animals have been important to understand some of its mechanisms, but they are hampered by the difficulty of extrapolating the results into clinical practice.

Methods: We created a new experimental model for the study of human CVR by grafting multiple human mesenteric arteries from the same human donor into different SCID/beige mice in the infrarenal aortic position.

Engraftment of human T, B and NK cells in CB.17 SCID/beige mice by transfer of human spleen cells.

Models of severe combined immuno-deficient (SCID) mice reconstituted with a competent human immune system represent a valuable tool for the study of human immune responses in vivo. Reconstitution with human cells can be achieved using large numbers of peripheral blood lymphocytes, but levels of engraftment are poor and graft versus host disease (GVHD) frequently occurs. SCID/beige mice are at the same time deficient for adaptive and innate immunity and the objective of this study was to develop a safe and efficient way to achieve human lymphocyte engraftment in these mice using human spleen cells.

Human immune reconstitution with spleen cells in SCID/Beige mice.

Background: We developed an original experimental model to study chronic vascular rejection (CVR) consisting of a graft of human mesenteric artery followed by human immune reconstitution into CB.17 SCID/Beige mice. Human immune reconstitution achieved after human PBMC injection has often been variable and incomplete.

Chronic vascular rejection: histologic comparison between two murine experimental models.

Background: We previously developed an experimental model to study chronic vascular rejection (CVR) in mice, the orthotopic aortic allograft. More recently we performed human arterial grafts into SCID/Beige mice reconstituted with human spleen cells. We report herein the differences in CVR lesions.

Use of human mesenteric arteries to study chronic vascular rejection in SCID/beige mice reconstituted with human spleen cells.

We wanted to establish a preclinical model of chronic vascular rejection (CVR) by transplanting small arteries from the mesentery of cadaveric organ donors by the rapid "sleeve" technique into SCID/beige mice reconstituted with human allogeneic spleen cells. After institutional authorization and with informed consent from relatives, we obtained tissues and cells from cadaveric organ donors. A piece of mesentery was recovered from the donor and kept in buffered solution at 4 degrees C until use.

Activation of the {beta}-catenin/T-cell-specific transcription factor/lymphoid enhancer factor-1 pathway by plasminogen activators in ECV304 carcinoma cells.

Besides its involvement in clot lysis, the plasminogen activator (PA) system elicits various cellular responses involved in cell migration, adhesion, and proliferation and plays a key role in the progression of cancers. beta-Catenin interacts with E-cadherins and functions as transcriptional coactivator of the Wnt-signaling pathway, which is implicated in tumor formation when aberrantly activated. We report that tissue-type plasminogen activator (tPA) elicited tyrosine phosphorylation and cytosolic accumulation of an active (non-serine-threonin phosphorylated, nonubiquitinated) form of beta-catenin in ECV304 carcinoma cells.

Two distinct calcium-dependent mitochondrial pathways are involved in oxidized LDL-induced apoptosis.

Objective: Oxidized low-density lipoprotein (oxLDL)-induced apoptosis of vascular endothelial cells may contribute to plaque erosion and rupture. We aimed to clarify the relationship between the oxLDL-induced calcium signal and induction of apoptotic pathways.

Methods And Results: Apoptosis was evaluated by biochemical methods, including studies of enzyme activities, protein processing, release of proapoptotic factors, chromatin cleavage, and especially by morphological methods that evaluate apoptosis/necrosis by SYTO-13/propidium iodide fluorescent labeling.

Role for matrix metalloproteinase-2 in oxidized low-density lipoprotein-induced activation of the sphingomyelin/ceramide pathway and smooth muscle cell proliferation.

Background: Oxidized LDLs (oxLDLs) and matrix metalloproteinases (MMPs) are present in atherosclerotic lesions. OxLDLs activate various signaling pathways potentially involved in atherogenesis. OxLDLs induce smooth muscle cell (SMC) proliferation mediated by the activation of the sphingomyelin/ceramide pathway and tyrosine kinase receptors.

Proliferation and wound healing of vascular cells trigger the generation of extracellular reactive oxygen species and LDL oxidation.

Cell proliferation of vascular cells is a key feature in vascular biology, wound healing, and pathophysiological processes such as atherosclerosis and restenosis. In atherosclerotic intima, cell proliferation colocalizes with oxidized LDL that indicate a local oxidative stress. This study aims to investigate whether cell proliferation is causally related with extracellular ROS generation and subsequent LDL oxidation.

Pancreatic bile salt-dependent lipase induces smooth muscle cells proliferation.

Background: Because bile salt-dependent lipase (BSDL), an enzyme secreted by the pancreatic acinar cells and associated with LDL in circulating blood, also locates with smooth muscle cells (SMCs) in atherosclerotic lesions, we aimed to investigate its effects on SMCs.

Methods And Results: Immunohistochemical experiments allowed us to detect an expression of BSDL in atherosclerotic lesions from hypercholesterolemic monkeys and from human arteries. BSDL was found to be associated with SMCs but not with macrophages.

Simultaneous orthotopic transplantation of carotid and aorta in the rat by the sleeve technique.

Graft vascular disease (GVD) remains the major limitation to long-term survival after solid organ transplantation. Aortic or carotid allografts in rats have been shown to be useful models because similar changes to those observed in man develop within weeks. Both immunological and non-immunological factors influence the process of GVD and a method that could permit rapid multiple arterial allotransplantation in the rat would be of great value.