P2Y2 receptor modulates shear stress-induced cell alignment and actin stress fibers in human umbilical vein endothelial cells.

Endothelial cells release ATP in response to fluid shear stress, which activates purinergic (P2) receptor-mediated signaling molecules including endothelial nitric oxide (eNOS), a regulator of vascular tone. While P2 receptor-mediated signaling in the vasculature is well studied, the role of P2Y2 receptors in shear stress-associated endothelial cell alignment, cytoskeletal alterations, and wound repair remains ill defined. To address these aspects, human umbilical vein endothelial cell (HUVEC) monolayers were cultured on gelatin-coated dishes and subjected to a shear stress of 1 Pa. HUVECs exposed to either P2Y2 receptor antagonists or siRNA showed impaired fluid shear stress-induced cell alignment, and actin stress fiber formation as early as 6 h. Similarly, when compared to cells expressing the P2Y2 Arg-Gly-Asp (RGD) wild-type receptors, HUVECs transiently expressing the P2Y2 Arg-Gly-Glu (RGE) mutant receptors showed reduced cell alignment and actin stress fiber formation in response to shear stress as well as to P2Y2 receptor agonists in static cultures. Additionally, we observed reduced shear stress-induced phosphorylation of focal adhesion kinase (Y397), and cofilin-1 (S3) with receptor knockdown as well as in cells expressing the P2Y2 RGE mutant receptors. Consistent with the role of P2Y2 receptors in vasodilation, receptor knockdown and overexpression of P2Y2 RGE mutant receptors reduced shear stress-induced phosphorylation of AKT (S473), and eNOS (S1177). Furthermore, in a scratched wound assay, shear stress-induced cell migration was reduced by both pharmacological inhibition and receptor knockdown. Together, our results suggest a novel role for P2Y2 receptor in shear stress-induced cytoskeletal alterations in HUVECs.

CART is overexpressed in human type 2 diabetic islets and inhibits glucagon secretion and increases insulin secretion.

AIMS/HYPOTHESIS: Insufficient insulin release and hyperglucagonaemia are culprits in type 2 diabetes. Cocaine- and amphetamine-regulated transcript (CART, encoded by Cartpt) affects islet hormone secretion and beta cell survival in vitro in rats, and Cart (-/-) mice have diminished insulin secretion. We aimed to test if CART is differentially regulated in human type 2 diabetic islets and if CART affects insulin and glucagon secretion in vitro in humans and in vivo in mice. METHODS: CART expression was assessed in human type 2 diabetic and non-diabetic control pancreases and rodent models of diabetes. Insulin and glucagon secretion was examined in isolated islets and in vivo in mice. Ca(2+) oscillation patterns and exocytosis were studied in mouse islets. RESULTS: We report an important role of CART in human islet function and glucose homeostasis in mice. CART was found to be expressed in human alpha and beta cells and in a subpopulation of mouse beta cells. Notably, CART expression was several fold higher in islets of type 2 diabetic humans and rodents. CART increased insulin secretion in vivo in mice and in human and mouse islets. Furthermore, CART increased beta cell exocytosis, altered the glucose-induced Ca(2+) signalling pattern in mouse islets from fast to slow oscillations and improved synchronisation of the oscillations between different islet regions. Finally, CART reduced glucagon secretion in human and mouse islets, as well as in vivo in mice via diminished alpha cell exocytosis. CONCLUSIONS/INTERPRETATION: We conclude that CART is a regulator of glucose homeostasis and could play an important role in the pathophysiology of type 2 diabetes. Based on the ability of CART to increase insulin secretion and reduce glucagon secretion, CART-based agents could be a therapeutic modality in type 2 diabetes.

Comparative Proteomic Analysis of Extracellular Vesicles Isolated by Acoustic Trapping or Differential Centrifugation.

Extracellular vesicles (ECVs), including microparticles and exosomes, are submicrometer membrane vesicles released by diverse cell types upon activation or stress. Circulating ECVs are potential reservoirs of disease biomarkers, and the complexity of these vesicles is significantly lower compared to their source, blood plasma, which makes ECV-based biomarker studies more promising. Proteomic profiling of ECVs is important not only to discover new diagnostic or prognostic markers but also to understand their roles in biological function. In the current study, we investigated the protein composition of plasma-derived ECVs isolated by acoustic seed trapping. Additionally, the protein composition of ECVs isolated with acoustic trapping was compared to that isolated with a conventional differential centrifugation protocol. Finally, the proteome of ECVs originating from ST-elevation myocardial infarction patients was compared with that of healthy controls using label-free LC-MS quantification. The acoustic trapping platform allows rapid and automated preparation of ECVs from small sample volumes, which are therefore well-suited for biobank repositories. We found that the protein composition of trapped ECVs is very similar to that isolated by the conventional differential centrifugation method.

Extracellular Uridine Triphosphate and Adenosine Triphosphate Attenuate Endothelial Inflammation through miR-22-Mediated ICAM-1 Inhibition.

Adenosine and uridine triphosphate (ATP and UTP) can act as extracellular signalling molecules, playing important roles in vascular biology and disease. ATP and UTP acting via the P2Y2-receptor have, for example, been shown to regulate endothelial dilatation, inflammation and angiogenesis. MicroRNAs (miRNAs), a class of regulatory, short, non-coding RNAs, have been shown to be important regulators of these biological processes. In this study, we used RNA deep-sequencing to explore changes in miRNA expression in the human microvascular endothelial cell line HMEC-1 upon UTP treatment. The expression of miR-22, which we have previously shown to target ICAM-1 mRNA in HMEC-1, increased significantly after stimulation. Up-regulation of miR-22 and down-regulation of cell surface ICAM-1 were confirmed with qRT-PCR and flow cytometry, respectively. siRNA-mediated knockdown of the P2Y2-receptor abolished the effect of UTP on miR-22 transcription. Leukocyte adhesion was significantly inhibited in HMEC-1 following miR-22 overexpression and treatment with UTP/ATP. In conclusion, extracellular UTP and ATP can attenuate ICAM-1 expression and leukocyte adhesion in endothelial cells through miR-22.

Cocaine- and amphetamine-regulated transcript (CART) protects beta cells against glucotoxicity and increases cell proliferation.

Cocaine- and amphetamine-regulated transcript (CART) is an islet peptide that promotes glucose-stimulated insulin secretion in beta cells via cAMP/PKA-dependent pathways. In addition, CART is a regulator of neuronal survival. In this study, we examined the effect of exogenous CART 55-102 on beta cell viability and dissected its signaling mechanisms. Evaluation of DNA fragmentation and chromatin condensation revealed that CART 55-102 reduced glucotoxicity-induced apoptosis in both INS-1 (832/13) cells and isolated rat islets. Glucotoxicity in INS-1 (832/13) cells also caused a 50% reduction of endogenous CART protein. We show that CART increased proliferation in INS-1 (832/13) cells, an effect that was blocked by PKA, PKB, and MEK1 inhibitors. In addition, CART induced phosphorylation of CREB, IRS, PKB, FoxO1, p44/42 MAPK, and p90RSK in INS-1 (832/13) cells and isolated rat islets, all key mediators of cell survival and proliferation. Thus, we demonstrate that CART 55-102 protects beta cells against glucotoxicity and promotes proliferation. Taken together our data point to the potential use of CART in therapeutic interventions targeted at enhancing functional beta cell mass and long-term insulin secretion in T2D.

Nesfatin-1 stimulates glucagon and insulin secretion and beta cell NUCB2 is reduced in human type 2 diabetic subjects.

Nesfatin-1 is a novel anorexigenic regulatory peptide. The peptide is the N-terminal part of nucleobindin 2 (NUCB2) and is expressed in brain areas regulating feeding. Outside the brain, nesfatin-1 expression has been reported in adipocytes, gastric endocrine cells and islet cells. We studied NUCB2 expression in human and rodent islets using immunocytochemistry, in situ hybridization and western blot. Furthermore, we investigated the potential influence of nesfatin-1 on secretion of insulin and glucagon in vitro and in vivo in mice and in INS-1 (832/13) cells. The impact of type 2 diabetes (T2D) and glucolipotoxicity on NUCB2 gene expression in human islets and its relationship to insulin secretory capacity and islet gene expression was studied using microarray. Nesfatin-1 immunoreactivity (IR) was abundant in human and rodent beta cells but absent in alpha, delta, PP and ghrelin cells. Importantly, in situ hybridization showed that NUCB2 mRNA is expressed in human and rat islets. Western blot analysis showed that nesfatin-1 IR represented full length NUCB2 in rodent islets. Human islet NUCB2 mRNA was reduced in T2D subjects but upregulated after culture in glucolipotoxic conditions. Furthermore, a positive correlation between NUCB2 and glucagon and insulin gene expression, as well as insulin secretory capacity, was evident. Nesfatin-1 enhanced glucagon secretion but had no effect on insulin secretion from mouse islets or INS-1 (832/13) cells. On the other hand, nesfatin-1 caused a small increase in insulin secretion and reduced glucose during IVGTT in mice. We conclude that nesfatin-1 is a novel glucagon-stimulatory peptide expressed in the beta cell and that its expression is decreased in T2D islets.

Distribution of melatonin receptors in murine pancreatic islets.

Melatonin has multiple receptor-dependent and receptor-independent functions. At the cell membrane, melatonin interacts with its receptors MT1 and MT2, which are expressed in numerous tissues. Genome-wide association studies have recently shown that the MTNR1B/MT2 receptor may be involved in the pathogenesis of type 2 diabetes mellitus. In line with these findings, expression of melatonin receptors has been shown in mouse, rat, and human pancreatic islets. MT1 and MT2 are G-protein-coupled receptors and are proposed to exert inhibitory effects on insulin secretion. Here, we show by immunocytochemistry that these membrane melatonin receptors have distinct locations in the mouse islet. MT1 is expressed in α-cells while MT2 is located to the ß-cells. These findings help to unravel the complex machinery underlying melatonin's role in the regulation of islet function.

Bilberry Supplementation after Myocardial Infarction Decreases Microvesicles in Blood and Affects Endothelial Vesiculation.

SCOPE: Diet rich in bilberries is considered cardioprotective, but the mechanisms of action are poorly understood. Cardiovascular disease is characterized by increased proatherogenic status and high levels of circulating microvesicles (MVs). In an open-label study patients with myocardial infarction receive an 8 week dietary supplementation with bilberry extract (BE). The effect of BE on patient MV levels and its influence on endothelial vesiculation in vitro is investigated. METHODS AND RESULTS: MVs are captured with acoustic trapping and platelet-derived MVs (PMVs), as well as endothelial-derived MVs (EMVs) are quantified with flow cytometry. The in vitro effect of BE on endothelial extracellular vesicle (EV) release is examined using endothelial cells and calcein staining. The mechanisms of BE influence on vesiculation pathways are studied by Western blot and qRT-PCR. Supplementation with BE decreased both PMVs and EMVs. Furthermore, BE reduced endothelial EV release, Akt phosphorylation, and vesiculation-related gene transcription. It also protects the cells from P2X7 -induced EV release and increase in vesiculation-related gene expression. CONCLUSION: BE supplementation improves the MV profile in patient blood and reduces endothelial vesiculation through several molecular mechanisms related to the P2X7 receptor. The findings provide new insight into the cardioprotective effects of bilberries.

Effect of exercise on the plasma vesicular proteome: a methodological study comparing acoustic trapping and centrifugation.

Extracellular vesicles (EVs) are a heterogeneous group of actively released vesicles originating from a wide range of cell types. Characterization of these EVs and their proteomes in the human plasma provides a novel approach in clinical diagnostics, as they reflect physiological and pathological states. However, EV isolation is technically challenging with the current methods having several disadvantages, requiring large sample volumes, and resulting in loss of sample and EV integrity. Here, we use an alternative, non-contact method based on a microscale acoustic standing wave technology. Improved coupling of the acoustic resonator increased the EV recovery from 30% in earlier reports to 80%, also displaying long term stability between experiment days. We report a pilot study, with 20 subjects who underwent physical exercise. Plasma samples were obtained before and 1 h after the workout. Acoustic trapping was compared to a standard high-speed centrifugation protocol, and the method was validated by flow cytometry (FCM). To monitor the device stability, the pooled frozen plasma from volunteers was used as an internal control. A key finding from the FCM analysis was a decrease in CD62E+ (E-selectin) EVs 1 h after exercise that was consistent for both methods. Furthermore, we report the first data that analyse differential EV protein expression before and after physical exercise. Olink-based proteomic analysis showed 54 significantly changed proteins in the EV fraction in response to physical exercise, whereas the EV-free plasma proteome only displayed four differentially regulated proteins, thus underlining an important role of these vesicles in cellular communication, and their potential as plasma derived biomarkers. We conclude that acoustic trapping offers a fast and efficient method comparable with high-speed centrifugation protocols. Further, it has the advantage of using smaller sample volumes (12.5 µL) and rapid contact-free separation with higher yield, and can thus pave the way for future clinical EV-based diagnostics.

Comparative proteomic profiling of cerebrospinal fluid between living and post mortem ALS and control subjects.

Neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), lack definitive diagnostic tests or biomarkers of disease progression. Most studies that investigate protein abnormalities in ALS have used biofluids such as blood or cerebrospinal fluid (CSF), while some have used post mortem tissue or CSF samples. Since ALS disease progression and post mortem effects probably induce significant alterations to protein modifications or proteolysis, we directly examined the CSF proteome from ALS subjects at various lengths of time from symptom onset and at autopsy by mass spectrometry based proteomics. CSF was also obtained from both healthy age-matched control subjects and at autopsy from healthy and Alzheimer's disease (AD) controls. We identified significant differences in the CSF proteome between living and post mortem ALS subjects, as well as living and post mortem control subjects. We also noted differences in the CSF proteome of ALS subjects that have exhibited symptoms for varying lengths of time and between ALS and AD subjects at end-stage of disease. This is the first study describing differences in the CSF proteome from post mortem and living ALS subjects using a mass spectrometric approach. These differences highlight the importance of utilizing CSF from living ALS subjects near the time of symptom onset for the identification of early protein biomarkers, although some protein alterations that occur early in the disease process are maintained throughout the course of disease and in post mortem samples.

Plasmalemmal vesicle associated protein-1 is a novel marker implicated in brain tumor angiogenesis.

PURPOSE: Plasmalemmal vesicle associated protein-1 (PV-1) is up-regulated in the endothelium of human glioblastoma. We sought to further characterize the expression pattern of PV-1 in human brain tumors and interrogate its role in brain tumor angiogenesis. EXPERIMENTAL DESIGN: Quantitative reverse transcription-PCR and in situ hybridization were used to measure PV-1 expression in a panel of 46 human brain tumors and related pathologic states. Matrigel tubulogenesis assays and cell migration assays were used to show function of PV-1 in primary human endothelial cells (HMVEC) under gene knockdown conditions. RESULTS: PV-1 is selectively up-regulated in a variety of high-grade human brain tumors, including glioblastoma and metastatic carcinoma, as well as other cerebral disorders associated with blood-brain barrier disruption, such as acute ischemia. Expression levels were reduced in low-grade neoplasia; however, tumors associated with the ependyma and choroid plexus, known sites of PV-1 expression, also exhibited robust expression. Cerebral expression of PV-1 mRNA was confined to endothelial cells in all cases. PV-1 expression was induced in HMVEC cells in vitro by exposure to medium conditioned by U87MG and U251MG human brain tumor cell lines and by medium supplemented with exogenous vascular endothelial growth factor or scatter factor/hepatocyte growth factor. RNA interference-mediated inhibition of PV-1 induction in HMVEC cells blocked Matrigel-induced tubulogenesis and inhibited cell migration induced by conditioned medium or angiogenic growth factors. CONCLUSIONS: Our results confirm that PV-1 is preferentially induced in the endothelium of high-grade human brain tumors. Inhibition of PV-1 expression is associated with failure of endothelial differentiation in vitro. PV-1 represents a novel marker of brain tumor angiogenesis and integrity of the blood-brain barrier and is a potential therapeutic target.

The ATP Receptors P2X7 and P2X4 Modulate High Glucose and Palmitate-Induced Inflammatory Responses in Endothelial Cells.

Endothelial cells lining the blood vessels are principal players in vascular inflammatory responses. Dysregulation of endothelial cell function caused by hyperglycemia, dyslipidemia, and hyperinsulinemia often result in impaired vasoregulation, oxidative stress, inflammation, and altered barrier function. Various stressors including high glucose stimulate the release of nucleotides thus initiating signaling via purinergic receptors. However, purinergic modulation of inflammatory responses in endothelial cells caused by high glucose and palmitate remains unclear. In the present study, we investigated whether the effect of high glucose and palmitate is mediated by P2X7 and P2X4 and if they play a role in endothelial cell dysfunction. Transcript and protein levels of inflammatory genes as well as reactive oxygen species production, endothelial-leukocyte adhesion, and cell permeability were investigated in human umbilical vein endothelial cells exposed to high glucose and palmitate. We report high glucose and palmitate to increase levels of extracellular ATP, expression of P2X7 and P2X4, and inflammatory markers. Both P2X7 and P2X4 antagonists inhibited high glucose and palmitate-induced interleukin-6 levels with the former having a significant effect on interleukin-8 and cyclooxygenase-2. The effect of the antagonists was confirmed with siRNA knockdown of the receptors. In addition, P2X7 mediated both high glucose and palmitate-induced increase in reactive oxygen species levels and decrease in endothelial nitric oxide synthase. Blocking P2X7 inhibited high glucose and palmitate-induced expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 as well as leukocyte-endothelial cell adhesion. Interestingly, high glucose and palmitate enhanced endothelial cell permeability that was dependent on both P2X7 and P2X4. Furthermore, antagonizing the P2X7 inhibited high glucose and palmitate-mediated activation of p38-mitogen activated protein kinase. These findings support a novel role for P2X7 and P2X4 coupled to induction of inflammatory molecules in modulating high glucose and palmitate-induced endothelial cell activation and dysfunction.

Vascular smooth muscle cell proliferation depends on caveolin-1-regulated polyamine uptake.

Much evidence highlights the importance of polyamines for VSMC (vascular smooth muscle cell) proliferation and migration. Cav-1 (caveolin-1) was recently reported to regulate polyamine uptake in intestinal epithelial cells. The aim of the present study was to assess the importance of Cav-1 for VSMC polyamine uptake and its impact on cell proliferation and migration. Cav-1 KO (knockout) mouse aortic cells showed increased polyamine uptake and elevated proliferation and migration compared with WT (wild-type) cells. Both Cav-1 KO and WT cells expressed the smooth muscle differentiation markers SM22 and calponin. Cell-cycle phase distribution analysis revealed a higher proportion of Cav-1 KO than WT cells in the S phase. Cav-1 KO cells were hyper-proliferative in the presence but not in the absence of extracellular polyamines, and, moreover, supplementation with exogenous polyamines promoted proliferation in Cav-1 KO but not in WT cells. Expression of the solute carrier transporters Slc7a1 and Slc43a1 was higher in Cav-1 KO than in WT cells. ODC (ornithine decarboxylase) protein and mRNA expression as well as ODC activity were similar in Cav-1 KO and WT cells showing unaltered synthesis of polyamines in Cav-1 KO cells. Cav-1 was reduced in migrating cells in vitro and in carotid lesions in vivo. Our data show that Cav-1 negatively regulates VSMC polyamine uptake and that the proliferative advantage of Cav-1 KO cells is critically dependent on polyamine uptake. We provide proof-of-principle for targeting Cav-1-regulated polyamine uptake as a strategy to fight unwanted VSMC proliferation as observed in restenosis.

Stimulated production of interleukin-8 covaries with psychosocial risk factors for inflammatory disease among middle-aged community volunteers.

A growing literature suggests that psychosocial factors, such as chronic stress and depression, are associated with increased vulnerability to inflammatory disease; however, the mechanisms of this effect remain unclear. One possibility is that these psychosocial characteristics are associated with activation of innate inflammatory pathways. Here, we explore relationships between a range of psychosocial risk factors for inflammatory disease and a measure of inflammatory potential, lipopolysaccharide-induced production of the monocyte-derived proinflammatory cytokines/chemokines interleukin (IL)-1beta, IL-6, TNF-alpha, and IL-8 among a community sample of 183 healthy adults aged 30-54 years. After controlling for demographic factors, health behavior practices, blood pressure, and white blood cell count, hierarchical regression analyses revealed a positive relationship between production of IL-8 and symptoms of depression, trait negative affect, and perceived stress. In contrast, there was an inverse relationship between IL-8 production and perceived social support. Relationships between IL-8 and symptoms of depression and perceived stress were attributable primarily to dispositional differences in NA. The relationship between negative affect measures and IL-8 was independent of social support. Although there were significant univariate associations between higher IL-6 production and symptoms of depression and less social support, these relationships did not withstand adjustment for demographic controls. There were no significant associations between IL-1beta or TNF-alpha and any of the psychosocial parameters. Our findings suggest that individuals at greater psychosocial risk for the development of inflammatory diseases, including cardiovascular disease, also show greater stimulated production of the proinflammatory chemokine, IL-8. Further exploration of this potential psychophysiological pathway is warranted.