An Allosteric Shift in CD11c Affinity Activates a Proatherogenic State in Arrested Intermediate Monocytes.

Intermediate monocytes (iMo; CD14+CD16+) increase in number in the circulation of patients with unstable coronary artery disease (CAD), and their recruitment to inflamed arteries is implicated in events leading to mortality following MI. Monocyte recruitment to inflamed coronary arteries is initiated by high affinity ß2-integrin (CD11c/CD18) that activates ß1-integrin (VLA-4) to bind endothelial VCAM-1. How integrin binding under shear stress mechanosignals a functional shift in iMo toward an inflammatory phenotype associated with CAD progression is unknown. Whole blood samples from patients treated for symptomatic CAD including non-ST elevation MI, along with healthy age-matched subjects, were collected to assess chemokine and integrin receptor levels on monocytes. Recruitment on inflamed human aortic endothelium or rVCAM-1 under fluid shear stress was assessed using a microfluidic-based artery on a chip (A-Chip). Membrane upregulation of high affinity CD11c correlated with concomitant activation of VLA-4 within focal adhesive contacts was required for arrest and diapedesis across inflamed arterial endothelium to a greater extent in non-ST elevation MI compared with stable CAD patients. The subsequent conversion of CD11c from a high to low affinity state under fluid shear activated phospho-Syk- and ADAM17-mediated proteolytic cleavage of CD16. This marked the conversion of iMo to an inflammatory phenotype associated with nuclear translocation of NF-κB and production of IL-1ß+ We conclude that CD11c functions as a mechanoregulator that activates an inflammatory state preferentially in a majority of iMo from cardiac patients but not healthy patients.

CagY-Dependent Regulation of Type IV Secretion in Helicobacter pylori Is Associated with Alterations in Integrin Binding.

Strains of Helicobacter pylori that cause ulcer or gastric cancer typically express a type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI). CagY is an ortholog of VirB10 that, unlike other VirB10 orthologs, has a large middle repeat region (MRR) with extensive repetitive sequence motifs, which undergo CD4+ T cell-dependent recombination during infection of mice. Recombination in the CagY MRR reduces T4SS function, diminishes the host inflammatory response, and enables the bacteria to colonize at a higher density. Since CagY is known to bind human α5ß1 integrin, we tested the hypothesis that recombination in the CagY MRR regulates T4SS function by modulating binding to α5ß1 integrin. Using a cell-free microfluidic assay, we found that H. pylori binding to α5ß1 integrin under shear flow is dependent on the CagY MRR, but independent of the presence of the T4SS pili, which are only formed when H. pylori is in contact with host cells. Similarly, expression of CagY in the absence of other T4SS genes was necessary and sufficient for whole bacterial cell binding to α5ß1 integrin. Bacteria with variant cagY alleles that reduced T4SS function showed comparable reduction in binding to α5ß1 integrin, although CagY was still expressed on the bacterial surface. We speculate that cagY-dependent modulation of H. pylori T4SS function is mediated by alterations in binding to α5ß1 integrin, which in turn regulates the host inflammatory response so as to maximize persistent infection.IMPORTANCE Infection with H. pylori can cause peptic ulcers and is the most important risk factor for gastric cancer, the third most common cause of cancer death worldwide. The major H. pylori virulence factor that determines whether infection causes disease or asymptomatic colonization is the type IV secretion system (T4SS), a sort of molecular syringe that injects bacterial products into gastric epithelial cells and alters host cell physiology. We previously showed that recombination in CagY, an essential T4SS component, modulates the function of the T4SS. Here we found that these recombination events produce parallel changes in specific binding to α5ß1 integrin, a host cell receptor that is essential for T4SS-dependent translocation of bacterial effectors. We propose that CagY-dependent binding to α5ß1 integrin acts like a molecular rheostat that alters T4SS function and modulates the host immune response to promote persistent infection.

Bio-synthetic materials for immunomodulation of islet transplants.

Clinical islet transplantation is an effective therapy in restoring physiological glycemic control in type 1 diabetics. However, allogeneic islets derived from cadaveric sources elicit immune responses that result in acute and chronic islet destruction. To prevent immune destruction of islets, transplant recipients require lifelong delivery of immunosuppressive drugs, which are associated with debilitating side effects. Biomaterial-based strategies to eliminate the need for immunosuppressive drugs are an emerging therapy for improving islet transplantation. In this context, two main approaches have been used: 1) encapsulation of islets to prevent infiltration and contact of immune cells, and 2) local release of immunomodulatory molecules from biomaterial systems that suppress local immunity. Synthetic biomaterials provide excellent control over material properties, molecule presentation, and therapeutic release, and thus, are an emerging platform for immunomodulation to facilitate islet transplantation. This review highlights various synthetic biomaterial-based strategies for preventing immune rejection of islet allografts.

Protease-degradable microgels for protein delivery for vascularization.

Degradable hydrogels to deliver bioactive proteins represent an emerging platform for promoting tissue repair and vascularization in various applications. However, implanting these biomaterials requires invasive surgery, which is associated with complications such as inflammation, scarring, and infection. To address these shortcomings, we applied microfluidics-based polymerization to engineer injectable poly(ethylene glycol) microgels of defined size and crosslinked with a protease degradable peptide to allow for triggered release of proteins. The release rate of proteins covalently tethered within the microgel network was tuned by modifying the ratio of degradable to non-degradable crosslinkers, and the released proteins retained full bioactivity. Microgels injected into the dorsum of mice were maintained in the subcutaneous space and degraded within 2 weeks in response to local proteases. Furthermore, controlled release of VEGF from degradable microgels promoted increased vascularization compared to empty microgels or bolus injection of VEGF. Collectively, this study motivates the use of microgels as a viable method for controlled protein delivery in regenerative medicine applications.

11,12-Epoxyecosatrienoic acids mitigate endothelial dysfunction associated with estrogen loss and aging: Role of membrane depolarization.

OBJECTIVE: Endothelial dysfunction, including upregulation of inflammatory adhesion molecules and impaired vasodilatation, is a key element in cardiovascular disease. Aging and estrogen withdrawal in women are associated with endothelial inflammation, vascular stiffness and increased cardiovascular disease. Epoxyecosatrienoic acids (EETs), the products of arachidonic acid metabolism mediated by cytochrome P450 (CYP) 2J, 2C and other isoforms, are regulated by soluble epoxide hydrolase (sEH)-catalyzed conversion into less active diols. We hypothesized that 11,12-EETs would reduce the endothelial dysfunction associated with aging and estrogen loss. APPROACH/RESULTS: When stabilized by an sEH inhibitor (seHi), 11,12-EET at a physiologically low dose (0.1nM) reduced cytokine-stimulated upregulation of adhesion molecules on human aorta endothelial cells (HAEC) and monocyte adhesion under shear flow through marked depolarization of the HAEC when combined with TNFα. Mechanistically, neither 11,12-EETs nor 17ß-estradiol (E2) at physiologic concentrations prevented activation of NFκB by TNFα. E2 at physiological concentrations reduced sEH expression in HAEC, but did not alter CYP expression, and when combined with TNFα depolarized the cell. We also examined vascular dysfunction in adult and aged ovariectomized Norway brown rats (with and without E2 replacement) using an ex-vivo model to analyze endothelial function in an intact segment of artery. sEHi and 11,12-EET with or without E2 attenuated phenylephrine induced constriction and increased endothelial-dependent dilation of aortic rings from ovariectomized rats. CONCLUSIONS: Increasing 11,12-EETs through sEH inhibition effectively attenuates inflammation and may provide an effective strategy to preserve endothelial function and prevent atherosclerotic heart disease in postmenopausal women.

CD11c/CD18 Signals Very Late Antigen-4 Activation To Initiate Foamy Monocyte Recruitment during the Onset of Hypercholesterolemia.

Recruitment of foamy monocytes to inflamed endothelium expressing VCAM-1 contributes to the development of plaque during atherogenesis. Foamy CD11c(+) monocytes arise in the circulation during the onset of hypercholesterolemia and recruit to nascent plaque, but the mechanism of CD11c/CD18 and very late Ag-4 (VLA-4) activation and cooperation in shear-resistant cell arrest on VCAM-1 are ill defined. Within 1 wk of the onset of a Western high-fat diet (WD) in apolipoprotein E-deficient mice, an inflammatory subset of foamy monocytes emerged that made up one fourth of the circulating population. These cells expressed ∼3-fold more CD11c/CD18 and 50% higher chemokine receptors than nonfoamy monocytes. Recruitment from blood to a VCAM-1 substrate under shear stress was assessed ex vivo using a unique artery-on-a-chip microfluidic assay. It revealed that foamy monocytes from mice on a WD increased their adhesiveness over 5 wk, rising to twice that of mice on a normal diet or CD11c(-/-) mice fed a WD. Shear-resistant capture of foamy human or mouse monocytes was initiated by high-affinity CD11c, which directly activated VLA-4 adhesion via phosphorylated spleen tyrosine kinase and paxillin within focal adhesion complexes. Lipid uptake and activation of CD11c are early and critical events in signaling VLA-4 adhesive function on foamy monocytes competent to recruit to VCAM-1 on inflamed arterial endothelium.

On-chip phenotypic analysis of inflammatory monocytes in atherogenesis and myocardial infarction.

Monocyte recruitment to inflamed arterial endothelium initiates plaque formation and drives progression of atherosclerosis. Three distinct monocyte subsets are detected in circulation (CD14(++)CD16(-), CD14(++)CD16(+), and CD14(+)CD16(++)), and each may play distinct roles during atherogenesis and myocardial infarction. We studied a range of subjects that included otherwise healthy patients with elevated serum triglyceride levels to patients presenting with acute myocardial infarction. Our objective was to correlate an individual's risk with the activation state of each monocyte subset as a function of changes in adhesion receptor expression using flow cytometric quantitation of integrins and l-selectin membrane expression. A microfluidic-based laboratory-on-a-chip was developed to quantify the adhesion efficiency of monocytes sheared in whole blood on vascular cell adhesion molecule-1, while characterizing adhesion receptor expression and topography on captured monocytes. CD14(++)CD16(+) monocytes adhered with sevenfold higher efficiency than other subsets, and in patients with myocardial infarction the capture efficiency of this subset was double that for healthy subjects. In patients with hypertriglyceridemia, this increase in monocyte adhesion was attributable to CD14(++)CD16(+) uptake of triglyceride-rich lipoproteins and subsequent signaling via a Phospholipase C-dependent mechanism to increase CD11c expression, very late antigen-4 function, and integrin coclustering within focal adhesive sites on vascular cell adhesion molecule-1. In summary, we introduce a unique laboratory-on-a-chip method for quantifying the activation state of monocyte subsets. These experiments reveal that CD11c/CD18 is an inducible integrin whose expression correlates with a monocyte inflammatory state in subjects at risk for atherogenesis and in patients with myocardial infarction.

On-chip endothelial inflammatory phenotyping.

Atherogenesis is potentiated by metabolic abnormalities that contribute to a heightened state of systemic inflammation resulting in endothelial dysfunction. However, early functional changes in endothelium that signify an individual's level of risk are not directly assessed clinically to help guide therapeutic strategy. Moreover, the regulation of inflammation by local hemodynamics contributes to the non-random spatial distribution of atherosclerosis, but the mechanisms are difficult to delineate in vivo. We describe a lab-on-a-chip based approach to quantitatively assay metabolic perturbation of inflammatory events in human endothelial cells (EC) and monocytes under precise flow conditions. Standard methods of soft lithography are used to microfabricate vascular mimetic microfluidic chambers (VMMC), which are bound directly to cultured EC monolayers. These devices have the advantage of using small volumes of reagents while providing a platform for directly imaging the inflammatory events at the membrane of EC exposed to a well-defined shear field. We have successfully applied these devices to investigate cytokine-, lipid- and RAGE-induced inflammation in human aortic EC (HAEC). Here we document the use of the VMMC to assay monocytic cell (THP-1) rolling and arrest on HAEC monolayers that are conditioned under differential shear characteristics and activated by the inflammatory cytokine TNF-α. Studies such as these are providing mechanistic insight into atherosusceptibility under metabolic risk factors.

IRF-1 and miRNA126 modulate VCAM-1 expression in response to a high-fat meal.

RATIONALE: A high-fat diet accompanied by hypertriglyceridemia increases an individual's risk for development of atherosclerosis. An early event in this process is monocyte recruitment through binding to vascular cell adhesion molecule 1 (VCAM-1) upregulated on inflamed arterial endothelium. Diets high in polyunsaturated fatty acids (PUFAs) may provide athero-protection by ameliorating this effect. OBJECTIVE: We investigated the acute regulation of VCAM-1 expression in human aortic endothelial cells (HAEC) in response to triglyceride-rich lipoproteins (TGRL) isolated from subjects after consumption of a high-fat meal. METHODS AND RESULTS: Postprandial TGRL isolated from 38 subjects were categorized as proatherogenic or antiatherogenic according to their capacity to alter the inflammatory response of HAEC. Proatherogenic TGRL increased expression of VCAM-1, intercellular adhesion molecule 1 (ICAM-1), and E-selectin by ≈20% compared with stimulation with tumor necrosis factor-α alone, whereas antiatherogenic TGRL decreased VCAM-1 expression by ≈20% while still upregulating ICAM-1. The relative atherogenicity of TGRL positively correlated with particle density of TG, apolipoprotein (Apo)CIII, ApoE, and cholesterol. Ω3-PUFA mimicked the effect of antiatherogenic TGRL by downregulating VCAM-1 expression. TGRL exerted this differential regulation of VCAM-1 by reciprocally modulating expression and activity of the transcription factor interferon regulatory factor 1 (IRF-1) and expression of microRNA 126 (miR-126). Overexpression or silencing of IRF-1 or miR-126 expression recapitulated the proatherogenic or antiatherogenic regulation of VCAM-1. CONCLUSIONS: In response to a high-fat meal, TGRL bias the inflammatory response of endothelium via transcriptional and posttranscriptional editing of VCAM-1. Subjects with an anti-inflammatory response to a meal produced TGRL that was enriched in nonesterified fatty acids, decreased IRF-1 expression, increased miR-126 activity, and diminished monocyte arrest.

CD11c/CD18 expression is upregulated on blood monocytes during hypertriglyceridemia and enhances adhesion to vascular cell adhesion molecule-1.

OBJECTIVE: Atherosclerosis is associated with monocyte adhesion to the arterial wall that involves integrin activation and emigration across inflamed endothelium. Involvement of ß(2)-integrin CD11c/CD18 in atherogenesis was recently shown in dyslipidemic mice, which motivates our study of its inflammatory function during hypertriglyceridemia in humans. METHODS AND RESULTS: Flow cytometry of blood from healthy subjects fed a standardized high-fat meal revealed that at 3.5 hours postprandial, monocyte CD11c surface expression was elevated, and the extent of upregulation correlated with blood triglycerides. Monocytes from postprandial blood exhibited an increased light scatter profile, which correlated with elevated CD11c expression and uptake of lipid particles. Purified monocytes internalized triglyceride-rich lipoproteins isolated from postprandial blood through low-density lipoprotein-receptor-related protein-1, and this also elicited CD11c upregulation. Laboratory-on-a-chip analysis of whole blood showed that monocyte arrest on a vascular cell adhesion molecule-1 (VCAM-1) substrate under shear flow was elevated at 3.5 hours and correlated with blood triglyceride and CD11c expression. At 7 hours postprandial, blood triglycerides decreased and monocyte CD11c expression and arrest on VCAM-1 returned to fasting levels. CONCLUSIONS: During hypertriglyceridemia, monocytes internalize lipids, upregulate CD11c, and increase adhesion to VCAM-1. These data suggest that analysis of monocyte inflammation may provide an additional framework for evaluating individual susceptibility to cardiovascular disease.

Expanded evaluation of blood donors in the United States for human immunodeficiency virus type 1 non-B subtypes and antiretroviral drug-resistant strains: 2005 through 2007.

BACKGROUND: In a previous study of 66 human immunodeficiency virus (HIV)-infected US blood donors from 1999 to 2005, HIV-1 non-B and antiretroviral drug-resistant strains accounted for 4.7 and 6.5% of HIV infections, respectively. This study was expanded to include an additional 11 recently acquired infections and 197 established infections collected from January 2005 through December 2007. STUDY DESIGN AND METHODS: HIV-infected donors were detected using FDA-licensed assays. Drug resistance profiles for protease and reverse transcriptase (RT) genes were determined using a genotyping system (ViroSeq, Celera Diagnostics); genetic subtype was determined by phylogenetic analysis of these sequences. RESULTS: Drug resistance profiles were obtained for 203 of 208 specimens; 9.9% had mutations that confer drug resistance. Ten showed resistance to a single drug class: nine to nonnucleoside RT inhibitors (NNRTIs) and one to nucleoside RT inhibitors (NRTIs). Eight showed two drug class resistance: five NRTI plus NNRTI, two NRTI plus protease inhibitor (PI), and one NNRTI plus PI. Two showed three drug class resistance. Non-B strains were identified in 2.5% of donors and consisted of subtypes A1 and D, CRF02_AG, CRF43-02G, and URF_BF. CONCLUSIONS: Data from this and the previous study show that antiretroviral drug-resistant HIV-1 is present in 9.1% of HIV-infected donors from 1999 through 2007; 9.3% of established infections and 6.9% of recent infections. Diverse HIV-1 non-B strains presently account for 3.0% of HIV infections in US donors.

Identification of human immunodeficiency virus type 1 non-B subtypes and antiretroviral drug-resistant strains in United States blood donors.

BACKGROUND: In this study, human immunodeficiency virus type 1 (HIV-1)-infected blood donors were evaluated for genetic subtype and drug resistance to determine the prevalence of divergent HIV strains in the US donor population. STUDY DESIGN AND METHODS: Subtype was determined by phylogenetic analysis of viral sequences amplified by reverse transcription-polymerase chain reaction. The drug resistance profile of the protease and reverse transcriptase (RT) genes was determined using an HIV-1 genotyping system (ViroSeq). RESULTS: From 1999 through 2005, 26 recently infected donors, defined as HIV-1 RNA-positive, antibody-negative (RNA+/Ab-), were identified (yield, 1:1.61 million). Over the same period, the frequency of anti-HIV-positive donors was 1:34,700. Twenty RNA+/Ab- specimens were evaluated; all were infected with HIV-1 subtype B. Drug resistance profiles obtained for 18 donors identified one strain with protease mutation L90M that confers resistance to nelfinavir and one with RT mutation Y188H that confers resistance to nevirapine. Genetic subtype was determined for 44 of 46 HIV antibody-reactive and confirmed-positive (Ab+) specimens. Three infections (6.8%) were due to circulating recombinant forms: 2 CRF01_AE and 1 CRF02_AG. In the Ab+ group, one strain was resistant to all nucleoside RT inhibitors and one had mutations that confer resistance to protease inhibitors. CONCLUSION: The data show that antiretroviral drug-resistant HIV strains are being transmitted in the United States. Overall 6.5 percent (4 of 62) of HIV-1-infected donors harbored drug-resistant strains. HIV-1 non-B strains accounted for 4.7 percent (3 of 64) of the infections in donors. HIV-1 subtype B is still the predominant strain in the United States; however, non-B strains are increasing.