David A. Zidar

Shared monocyte subset phenotypes in HIV-1 infection and in uninfected subjects with acute coronary syndrome

The mechanisms responsible for increased cardiovascular risk associated with HIV-1 infection are incompletely defined. Using flow cytometry, in the present study, we examined activation phenotypes of monocyte subpopulations in patients with HIV-1 infection or acute coronary syndrome to find common cellular profiles. Nonclassic (CD14(+)CD16(++)) and intermediate (CD14(++)CD16(+)) monocytes are proportionally increased and express high levels of tissue factor and CD62P in HIV-1 infection. These proportions are related to viremia, T-cell activation, and plasma levels of IL-6. In vitro exposure of whole blood samples from uninfected control donors to lipopolysaccharide increased surface tissue factor expression on all monocyte subsets, but exposure to HIV-1 resulted in activation only of nonclassic monocytes. Remarkably, the profile of monocyte activation in uncontrolled HIV-1 disease mirrors that of acute coronary syndrome in uninfected persons. Therefore, drivers of immune activation and inflammation in HIV-1 disease may alter monocyte subpopulations and activation phenotype, contributing to a pro-atherothrombotic state that may drive cardiovascular risk in HIV-1 infection.

Platelet-derived S100 family member myeloid-related protein-14 regulates thrombosis.

Expression of the gene encoding the S100 calcium-modulated protein family member MRP-14 (also known as S100A9) is elevated in platelets from patients presenting with acute myocardial infarction (MI) compared with those from patients with stable coronary artery disease; however, a causal role for MRP-14 in acute coronary syndromes has not been established. Here, using multiple models of vascular injury, we found that time to arterial thrombotic occlusion was markedly prolonged in Mrp14⁻/⁻ mice. We observed that MRP-14 and MRP-8/MRP-14 heterodimers (S100A8/A9) are expressed in and secreted by platelets from WT mice and that thrombus formation was reduced in whole blood from Mrp14⁻/⁻ mice. Infusion of WT platelets, purified MRP-14, or purified MRP-8/MRP-14 heterodimers into Mrp14⁻/⁻ mice decreased the time to carotid artery occlusion after injury, indicating that platelet-derived MRP-14 directly regulates thrombosis. In contrast, infusion of purified MRP-14 into mice deficient for both MRP-14 and CD36 failed to reduce carotid occlusion times, indicating that CD36 is required for MRP-14-dependent thrombosis. Our data identify a molecular pathway of thrombosis that involves platelet MRP-14 and CD36 and suggest that targeting MRP-14 has potential for treating atherothrombotic disorders, including MI and stroke.

Oxidized LDL levels are increased in HIV infection and may drive monocyte activation

Background: HIV infection is associated with increased cardiovascular risk, and this risk correlates with markers of monocyte activation. We have shown that HIV is associated with a prothrombotic monocyte phenotype, which can be partially mitigated by statin therapy. We therefore explored the relationship between oxidized low-density lipoprotein (oxLDL) particles and monocyte activation. Methods: We performed phenotypic analysis of monocytes using flow cytometry on fresh whole blood in 54 patients with HIV and 24 controls without HIV. Plasma levels of oxLDL, soluble CD14, IL-6, and soluble CD163 were measured by enzyme-linked immunosorbent assay. In vitro experiments were performed using flow cytometry. Results: Plasma levels of oxLDL were significantly increased in HIV infection compared with controls (60.1 units vs. 32.1 units, P < 0.001). Monocyte expression of the oxLDL receptors, CD36 and Toll-like receptor 4, was also increased in HIV. OxLDL levels correlated with markers of monocyte activation, including soluble CD14, tissue factor expression on inflammatory monocytes, and CD36. In vitro stimulation with oxLDL, but not to low-density lipoprotein, resulted in expansion of inflammatory monocytes and increased monocyte expression of tissue factor, recapitulating the monocyte profile we find in HIV disease. Conclusions: OxLDL may contribute to monocyte activation, and further study in the context of HIV disease is warranted.

SIV/SHIV Infection Triggers Vascular Inflammation, Diminished Expression of Krüppel-like Factor 2 and Endothelial Dysfunction

BACKGROUND Human immunodeficiency virus (HIV) infection is associated with increased risk of thromboembolic and cardiovascular comorbid conditions. Although systemic inflammation is linked to cardiovascular risk, direct evidence of vascular inflammation and endothelial dysfunction is lacking. METHODS We examined by immunofluorescence microscopy thoracic aortas from 16 simian immunodeficiency virus (SIV)- or simian-human immunodeficiency virus (SHIV)-infected and 16 uninfected rhesus macaques. RESULTS Focal endothelial proliferation and subendothelial inflammatory cells were found in sections of all infected animals, compared with minimal changes in sections from the 16 uninfected controls. In the infected animals, we detected increased endothelial levels of bacterial 16s ribosomal DNA as well as increased subendothelial accumulation of CD68(+) monocytes/macrophages (P< .001) and CD8(+) T lymphocytes (P< .001). Endothelial dysfunction was manifested by decreased levels of endothelial nitric oxide synthase (P< .005) and Krüppel-like factor 2 (KLF2) (P< .005). KLF2 expression was decreased in primary human aortic endothelial cells exposed to bacterial lipopolysaccharide or to oxidized low-density lipoprotein in vitro, and this could be prevented by simvastatin. CONCLUSIONS SIV and SHIV infection lead to endothelial inflammation, dysfunction, and decreased KLF2 expression reflecting early atherosclerotic changes. Translocated bacterial components and lipid oxidation products may induce endothelial dysfunction in HIV infection that could be prevented by statin treatment.

Altered Monocyte Phenotype in HIV-1 Infection Tends to Normalize with Integrase-Inhibitor-Based Antiretroviral Therapy.

Background Monocytes are increasingly implicated in the inflammatory consequences of HIV-1 disease, yet their phenotype following antiretroviral therapy (ART) initiation is incompletely defined. Here, we define more completely monocyte phenotype both prior to ART initiation and during 48 weeks of ART. Methods Cryopreserved peripheral blood mononuclear cells (PBMCs) were obtained at baseline (prior to ART initiation) and at weeks 12, 24, and 48 of treatment from 29 patients participating in ACTG clinical trial A5248, an open label study of raltegravir/emtricitibine/tenofovir administration. For comparison, cryopreserved PBMCs were obtained from 15 HIV-1 uninfected donors, each of whom had at least two cardiovascular risk factors. Thawed samples were stained for monocyte subset markers (CD14 and CD16), HLA-DR, CCR2, CX3CR1, CD86, CD83, CD40, CD38, CD36, CD13, and CD163 and examined using flow cytometry. Results In untreated HIV-1 infection there were perturbations in monocyte subset phenotypes, chiefly a higher frequency and density (mean fluorescence intensity–MFI) of HLA-DR (%-p = 0.004, MFI-p = .0005) and CD86 (%-p = 0.012, MFI-p = 0.005) expression and lower frequency of CCR2 (p = 0.0002) expression on all monocytes, lower CCR2 density on inflammatory monocytes (p = 0.045) when compared to the expression and density of these markers in controls’ monocytes. We also report lower expression of CX3CR1 (p = 0.014) on patrolling monocytes at baseline, compared to levels seen in controls. After ART, these perturbations tended to improve, with decreasing expression and density of HLA-DR and CD86, increasing CCR2 density on inflammatory monocytes, and increasing expression and density of CX3CR1 on patrolling monocytes. Conclusions In HIV-1 infected patients, ART appears to attenuate the high levels of activation (HLA-DR, CD86) and to increase expression of the chemokine receptors CCR2 and CX3CR1 on monocyte populations. Circulating monocyte phenotypes are altered in untreated infection and tend to normalize with ART; the role of these cells in the inflammatory environment of HIV-1 infection warrants further study.

Neutrophils in Atherosclerosis Alarmin Evidence of a Hit and Run

Inflammation and activation of immune cells are key mechanisms in the development of atherosclerosis.1 Elegant experimental studies, typically performed in compound mutant mice susceptible to diet-induced atherosclerosis, indicate important roles for monocytes, T lymphocytes, and mast cells in lesion formation (Figure). Moreover, inflammatory pathways promote thrombosis, a late complication of atherosclerosis responsible for myocardial infarction and ischemic stroke. However, a direct contribution of neutrophils as the first line of immune offense (ie, acute inflammation) in atherosclerosis is controversial and uncertain. In this issue of Circulation Research , Doring and colleagues2 report that the neutrophil secondary granule protein cathelicidin (CRAMP in mice, LL37 in humans) directly promotes atherosclerosis by enhancement of the recruitment of inflammatory monocytes. Figure. The inflammatory basis of atherosclerosis. The progression of atherosclerosis is associated with multiple inter-related immune mechanisms. Proximate signals include a combination of endothelial injury, platelet adhesion, and stimulation of macrophage and T cell responses by modified LDL particles in the intima. The response of the innate immune system may also involve the transient recruitment of neutrophils expressing of alarmins, such as MRP-8/14 and CRAMP. The adaptive immune system includes proatherosclerotic responses such as IFN-γ production by CD4+ Th1 lymphocytes as well as protective mechanisms, such as the secretion of neutralizing antibodies by B lymphocytes and the anti-inflammatory activity of regulatory T cells. IL indicates interleukin; TNF, tumor necrosis factor; IFN, interferon. Article, see p 1052 Early histological studies of human atherosclerotic plaque identified a rich infiltrate of immune cells including monocyte/macrophages and T lymphocytes, but failed to identify significant neurophilic accumulation.3 The paradigm of atherosclerosis as a chronic inflammatory condition gained further traction as chemokines responsible for monocyte and lymphocyte trafficking were found to regulate atherosclerosis.1 Yet, tantalizing indirect evidence implicating neutrophils in the initiation, progression, and complications of atherosclerosis has …

Rate of Statin Prescription in Younger Patients With Severe Dyslipidemia.

Cardiovascular disease affects 1 in 3 patients and remains the leading cause of death in the United States.1 Severe elevation of low-density lipoprotein cholesterol (LDL-C) levels is a modifiable risk factor for developing premature cardiovascular disease, and elevation levels of 190 mg/dL or greater (to convert LDL-C values to millimoles per liter, multiply by 0.0259) may indicate a monogenic etiology such as familial hypercholesterolemia.2 Treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors or statins is recommended (class IA) for all adults 21 years or older with an LDL-C of 190 mg/dL or greater. Statin treatment appears to reduce mortality and result in cost savings for health systems.3,4 Therefore, we sought to examine rates of statin prescription in patients screened for dyslipidemia to identify treatment gaps in a real-world contemporary setting.

Altered Monocyte and Endothelial Cell Adhesion Molecule Expression Is Linked to Vascular Inflammation in Human Immunodeficiency Virus Infection

Background. Human immunodeficiency virus (HIV)-infected individuals have increased risk for vascular thrombosis, potentially driven by interactions between activated leukocytes and the endothelium. Methods. Monocyte subsets (CD14+CD16−, CD14+CD16+, CD14DimCD16+) from HIV negative (HIV−) and antiretroviral therapy-treated HIV positive (HIV+) participants (N = 19 and 49) were analyzed by flow cytometry for adhesion molecule expression (lymphocyte function-associated antigen 1 [LFA-1], macrophage-1 antigen [Mac-1], CD11c/CD18, very late antigen [VLA]-4) and the fractalkine receptor (CX3CR1); these receptors recognize ligands (intercellular adhesion molecules [ICAMs], vascular cell adhesion molecule [VCAM]-1, fractalkine) on activated endothelial cells (ECs) and promote vascular migration. Plasma markers of monocyte (soluble [s]CD14, sCD163) and EC (VCAM-1, ICAM-1,2, fractalkine) activation and systemic (tumor necrosis factor receptor [TNFR-I], TNFR-II) and vascular (lipoprotein-associated phospholipase A2 [Lp-PLA2]) inflammation were measured by enzyme-linked immunosorbent assay. Results. Proportions of CD16+ monocyte subsets were increased in HIV+ participants. Among all monocyte subsets, levels of LFA-1 were increased and CX3CR1 levels were decreased in HIV+ participants (P < .01). Levels of sCD163, sCD14, fractalkine, ICAM-1, VCAM-1, TNFR-II, and Lp-PLA2 were also increased in HIV+ participants (P < .05), and levels of sCD14, TNFR-I, and TNFR-II were directly related to ICAM-1 and VCAM-1 levels in HIV+ participants. Expression of CX3CR1 on monocyte subsets was inversely related to plasma Lp-PLA2 (P < .05 for all). Conclusions. Increased proportions of CD16+ monocytes, cells with altered adhesion molecule expression, combined with elevated levels of their ligands, may promote vascular inflammation in HIV infection.

Elevated Red Cell Distribution Width (RDW) Identifies Elevated Cardiovascular Disease Risk in Patients with HIV infection.

Abstract: Red cell distribution width (RDW) is linked to cardiovascular risk in the general population, an association that might be driven by inflammation. Whether this relationship holds for patients with HIV infection has not been previously studied. Using a large clinical registry, we show that elevated RDW (>14.5%) is independently associated with increased risk of coronary artery disease {odds ratio [OR] 1.39 [95% confidence interval (CI): 1.25 to 1.55]}, peripheral vascular disease [OR 1.41 (95% CI: 1.29 to 1.53)], myocardial infarction [1.43 (95% CI: 1.25 to 1.63)], heart failure [OR 2.23 (95% CI: 1.99 to 2.49)], and atrial fibrillation [OR 1.96 (95% CI: 1.64 to 2.33)]. In conclusion, in the context of the inflammatory milieu that accompanies HIV infection, RDW remains a powerful marker of cardiovascular disease.

Restenosis of the Coronary Arteries: Past, Present, Future Directions

Restenosis is a pathologic response to vascular injury, characterized by neointimal hyperplasia and progressive narrowing of a stented vessel segment. Although advances in stent design have led to a dramatic reduction in the incidence of restenosis, it continues to represent the most common cause of target lesion failure following percutaneous coronary intervention. Efforts to maximize restenosis prevention, through careful consideration of modifiable risk factors and an individualized approach, are critical, as restenosis, once established, can be particularly difficult to treat. Novel approaches are on the horizon that have the potential to alter the natural history of this stubborn disease.