T-lymphocytes and monocytes in atherogenesis

Impact of acute antioxidant supplementation on vascular function and autonomic nervous system modulation in young adults with PTSD

Posttraumatic stress disorder (PTSD) has been associated with an increase in risk of cardiovascular disease (CVD). The goal of this study was to determine if peripheral vascular dysfunction, a precursor to CVD, was present in young adults with PTSD, and if an acute antioxidant (AO) supplementation could modify this potential PTSD-induced vascular dysfunction. Thirteen individuals with PTSD were recruited for this investigation and were compared with 35 age- and sex-matched controls (CTRL). The PTSD group participated in two visits, consuming either a placebo (PTSD-PL) or antioxidants (PTSD-AO; vitamins C and E; α-lipoic acid) before their visits, whereas the CTRL subjects only participated in one visit. Upper and lower limb vascular functions were assessed via flow-mediated dilation and passive leg movement technique. Heart rate variability was utilized to assess autonomic nervous system modulation. The PTSD-PL condition, when compared with the CTRL group, reported lower arm and leg microvascular function as well as sympathetic nervous system (SNS) predominance. After acute AO supplementation, arm, but not leg, microvascular function was improved and SNS predominance was lowered to which the prior difference between PTSD group and CTRL was no longer significant. Young individuals with PTSD demonstrated lower arm and leg microvascular function as well as greater SNS predominance when compared with age- and sex-matched controls. Furthermore, this lower vascular/autonomic function was augmented by an acute AO supplementation to the level of the healthy controls, potentially implicating oxidative stress as a contributor to this blunted vascular/autonomic function.

Oxidative stress accelerates the carotid atherosclerosis process in patients with chronic kidney disease

INTRODUCTION

The atherosclerosis process is highly accelerated in patients with chronic kidney disease (CKD). Oxidative stress is considered as one of the pro-atherogenic factors involved in accelerating the atherosclerosis process of the carotid artery. The aim of the present study was to determine the relationship between oxidative stress markers and the progression of carotid atherosclerosis in CKD patients.

MATERIAL AND METHODS

The study was conducted on 162 patients with CKD and 40 controls, and the disease stage was scored between 2 and 5D. Blood samples were taken and advanced oxidative protein product, myeloperoxidases, malondialdehyde, nitric oxide, glutathione, and oxidised low-density lipoprotein were measured. Furthermore, we studied the correlations between these biomarkers and clinical and para-clinical cardiovascular complications.

RESULTS

The average age of patients was 56.5 years. The oxidative stress markers average ± SD levels in CKD groups compared to the control were as follows: advanced oxidation protein product (61.89 ±1.4 vs. 26.65 ±1.05 µmol/l), myeloperoxidase (59.89 ±1.98 vs. 38.45 ±1.98 UI/ml), malondialdehyde (6.1 ±0.12 vs. 3.26 ±0.03 µmol/l), nitric oxide (65.82 ±1.06 vs. 52.19 ±2.1 µmol/l), glutathione (52.21 ±1.3 vs. 89.4 ±2.6 IU/ml), and oxLDL (15.57 ±1.07 vs. 1.72 ±0.82 µmol/l). While the glutathione level decreased significantly in advanced CKD stage (p < 0.05), the concentrations of all the other biomarkers increased significantly in accordance with CKD score (p < 0.05).

CONCLUSIONS

Cardiovascular diseases, mainly atherosclerosis, can be diagnosed indirectly by measuring oxidative stress markers. Furthermore, theses markers can be used to predict the progression of CKD, for better management of the disease.

Effects of acute exercise on monocyte subpopulations in metabolic syndrome patients

OBJECTIVE

Acute exercise induces numerous changes in peripheral blood, e.g. counts of leukocytes. CD16^pos monocytes, which play a role in the pathogenesis of arteriosclerosis and the metabolic syndrome (MetS), are among the blood cells with the highest fold increase through exercise. So far no studies have investigated the effect of exercise on the blood cell composition of patients with MetS.

APPROACH AND RESULTS

Blood cell counts, a wide panel of laboratory tests, as well as lipid and protein content of monocytes and granulocytes were determined in healthy subjects, persons with metabolic risk and MetS patients before and after one minute of exercise at 400 W. Leukocyte counts increased significantly in all groups with CD14^pos CD16^pos monocytes showing the highest fold-change. In MetS patients the fold increase was smaller. They had a higher resting level of CD14^pos CD16^pos monocytes and a lower basal ratio of CD16^neg /CD16^pos monocytes. A similar ratio of these cells was induced in control and risk subjects after exercise. However, absolute counts of mobilized pro-inflammatory monocytes did not differ significantly. Furthermore, we detected a decrease in protein content of monocytes in controls, but not in MetS patients.

CONCLUSIONS

As strenuous exercise is able to mobilize the same amount of pro-inflammatory monocytes in MetS patients as in healthy persons, the elevated basal level of these cells in MetS patients is likely to be caused by enhanced maturation rather than chronic mobilization. The removal of these monocytes from the endothelium might be part of the beneficial effect of exercise on vascular disease. © 2016 International Clinical Cytometry Society.

Norepinephrine-induced myeloid-derived suppressor cells block T-cell responses via generation of reactive oxygen species

Increased numbers of myeloid-derived suppressor cells (MDSCs) are often observed in various pathological and physiological conditions. However, the interactions between neurotransmitters and MDSCs have not been elucidated. In this study, we studied whether norepinephrine (NE), a neurotransmitter, could affect the differentiation of human MDSCs in vitro. Flow cytometric analysis showed that treatment with 20 μM NE significantly enhanced the expansion of MDSCs. The NE-generated MDSCs suppressed the T-cells proliferation, depending on the production of reactive oxygen species (ROS). Moreover, the expansion of MDSCs induced by NE resulted in a dramatic induction of nicotinamide adenine dinucleotide phosphate oxidase subunit P47(phox). Addition of the ROS inhibitor catalase into the MDSCs/T-cell co-culture system partly abrogated the suppressive effects of MDSCs on T-cell proliferation. In summary, our data have shown that NE enhanced the expansion of human MDSCs in vitro, providing important insights into the novel roles of neurotransmitters in the regulation of myeloid cell differentiation and function.

Systemic effects of polymethylmethycrylate in total knee replacement: A prospective case-control study

OBJECTIVE

Mortality rates reported by the National Joint Registry for England and Wales (NJR) were higher following cemented total knee replacement (TKR) compared with uncemented procedures. The aim of this study is to examine and compare the effects of cemented and uncemented TKR on the activation of selected markers of inflammation, endothelium, and coagulation, and on the activation of selected cytokines involved in the various aspects of the systemic response following surgery.

METHODS

This was a single centre, prospective, case-control study. Following enrolment, blood samples were taken pre-operatively, and further samples were collected at day one and day seven post-operatively. One patient in the cemented group developed a deep-vein thrombosis confirmed on ultrasonography and was excluded, leaving 19 patients in this cohort (mean age 67.4, (sd 10.62)), and one patient in the uncemented group developed a post-operative wound infection and was excluded, leaving 19 patients (mean age 66.5, (sd 7.82)).

RESULTS

Both groups had a similar response with regards to the levels of C-reactive protein (CRP), interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNFα). CD40 levels rose significantly on the cemented group over day one to day seven compared with that of the uncemented group, which occurred over the first 24 hours. The CD14/42a levels demonstrated a statistically significant increase in the cemented group (p < 0.001 first 24 hours and p = 0.02 between days one and seven).

CONCLUSIONS

The uncemented and cemented groups demonstrated significant changes in the various parameters measured at various time points but apart from CD14/42a levels, there was no significant difference in the serum markers of inflammation, coagulation and endothelial dysfunction following cemented TKR. Cite this article: Bone Joint Res 2014;3:108-16.

Norepinephrine increases NADPH oxidase-derived superoxide in human peripheral blood mononuclear cells via α-adrenergic receptors

Many diseases associated with sympathoexcitation also exhibit elevated reactive oxygen species (ROS). A recent animal study indicated that exogenous administration of the sympathetic neurotransmitter norepinephrine (NE) increased systemic ROS via circulating leukocytes. The mechanisms contributing to this effect of NE and whether these findings can be translated to humans is unknown. Thus we tested the hypothesis that NE increases superoxide production in human peripheral blood mononuclear cells (PBMCs) via NADPH oxidase. Primary human PBMCs were freshly isolated from healthy young men and placed in culture. After NE (50 pg/ml, 50 ng/ml, and 50 μg/ml concentrations) or control treatments, NADPH oxidase mRNA expression (gp91(phox), p22(phox), and p67(phox)) was assessed using real-time RT-PCR, and intracellular superoxide production was measured using dihydroethidium fluorescence. PBMCs were also treated with selective adrenergic agonists-antagonists to determine the receptor population involved. In addition, CD14(+) monocyte-endothelial cell adhesion was determined using a fluorescent-based assay. NE significantly increased NADPH oxidase gene expression and intracellular superoxide production in a time-dependent manner (superoxide: 0.9 ± 0.2 fold, 6 h vs. 3.0 ± 0.3 fold, 36 h; NE, 50 μg/ml; P < 0.05). The sustained increase in NE-induced superoxide production was primarily mediated via α-adrenergic receptors, preferentially α2-receptors. The NADPH oxidase blocker diphenylene iodonium and protein kinase C inhibitor Staurosporine significantly attenuated NE-induced increases in superoxide production. Importantly, NE treatment increased CD14(+) monocyte-endothelial cell adhesion. These findings indicate for the first time that NE increases superoxide production in freshly isolated primary human PBMCs via NADPH oxidase through α-adrenergic receptors, an effect facilitating monocyte adhesion to the endothelium.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

The peripheral blood mononuclear cell microRNA signature of coronary artery disease

BACKGROUND

MicroRNAs are being used in the oncology field to characterize tumors and predict the survival of cancer patients. Here, we explored the potential of microRNAs as biomarkers for coronary artery disease (CAD) and acute coronary syndromes.

METHODS AND RESULTS

Using real-time PCR-based profiling, we determined the microRNA signature of peripheral blood mononuclear cells (PBMCs) from stable and unstable CAD patients and unaffected controls. 129 of 157 microRNAs measured were expressed by PBMCs and low variability between separate PBMC pools was observed. The presence of CAD in general coincided with a marked 5-fold increase (P<0.001) in the relative expression level of miR-135a, while the expression of miR-147 was 4-fold decreased (P<0.05) in PBMCs from CAD patients as compared to controls, resulting in a 19-fold higher miR-135a/miR-147 ratio (P<0.001) in CAD. MicroRNA/target gene/biological function linkage analysis suggested that the change in PBMC microRNA signature in CAD patients is probably associated with a change in intracellular cadherin/Wnt signaling. Interestingly, unstable angina pectoris patients could be discriminated from stable patients based upon their relatively high expression level of a cluster of three microRNAs including miR-134, miR-198, and miR-370, suggesting that the microRNA signatures can be used to identify patients at risk for acute coronary syndromes.

CONCLUSIONS

The present study is the first to show that microRNA signatures can possibly be utilized to identify patients exhibiting atherosclerotic CAD in general and those at risk for acute coronary syndromes. Our findings highlight the importance of microRNAs signatures as novel tool to predict clinical disease outcomes.

Soluble but not platelet P-selectin correlates with spontaneous platelet aggregation: a pilot study

BACKGROUND

P-selectin (PS) is a marker of platelet activation measured on the platelet surface as platelet PS (pPS) or in serum as soluble PS (sPS). Controversy remains over the exact relationship between sPS, pPS, and other markers such as spontaneous platelet aggregation (SPA).

OBJECTIVE

To investigate correlations between pPS, sPS, and SPA in patients with peripheral arterial disease.

METHODS

SPA, pPS, and sPS levels were measured in venous blood sampled from patients following intermittent claudication (n = 18) or an acute stroke (n = 18).

RESULTS

SPA and sPS correlated significantly in the claudicants (Pearson correlation coefficient, r = 0.661; P = .0020) and stroke patients (r = 0.514; P = .020). No significant correlation was identified between pPS and SPA, or sPS and pPS.

CONCLUSIONS

The 2 methods of assessing PS are not comparable. Although pPS is accepted as a platelet activation marker, sPS may be a better indicator of aggregation represented by SPA.

Two different modes of costimulation predispose human T lymphocytes to differential responses in the presence of HDL or oxidized LDL

In addition to levels of high-density lipoprotein (HDL), oxidized (ox) low-density lipoprotein (LDL), the inflammatory process and certain genetic factors, T cells are crucial for expansion of atherosclerotic plaque. The interrelationships among these influences are still being defined. Here, we examined how HDL and oxLDL affect T cell function. T cells require two activation signals to achieve functional activity. The first signal is specific and is delivered by appropriately presented antigen. The second (costimulatory) signal can be received through any of several T cell surface proteins, the most widely studied of which are CD28 and LFA-1. We have identified ICAM-1, resident on T cells, as a costimulatory protein. Here, we describe differential effects when T cells were costimulated through either LFA-1 or ICAM-1 in the presence of HDL or oxLDL. In general, T cells costimulated through either LFA-1 or ICAM-1 in the presence of oxLDL were predisposed to a decrease in proliferation and increased apoptosis, although ICAM-1-costimulated cells were protected from apoptosis induced by lower levels of oxLDL. T cell subsets also were examined. In the presence of HDL, CD8(+) T cells increased proliferation when costimulated through LFA-1. HDL exerted no effect on proliferation of CD4(+) T cells whereas proliferation decreased in the presence of oxLDL. Naïve T cells proliferated better in response to costimulation through LFA-1 in the presence of HDL but proliferation of effector/memory cells was not altered in the presence of HDL. When T cells were costimulated through LFA-1, in the presence of either HDL or oxLDL synthesis of Th-1 but not Th-2 cytokines was increased. T cells costimulated through ICAM-1 increased Th-1 but not Th-2 cytokines but this was not altered in the presence of HDL or oxLDL. Thus, the nature of costimulation seems to influence T cell responses in the presence of the lipoproteins.

Relationship of monocyte count and peripheral arterial disease: results from the National Health and Nutrition Examination Survey 1999-2002

BACKGROUND

Although white blood cell (WBC) count has been consistently associated with cardiovascular end points, little information is available on the independent contribution of specific white blood cell types. The objective of this study is to assess the independent association of WBC types and other inflammatory markers with the presence of reduced ankle-brachial blood pressure index (ABI), a marker of subclinical peripheral arterial disease (PAD).

METHODS & RESULTS

Cross-sectional study in 3949 individuals > or =40 years of age without known cardiovascular disease who participated in the 1999 to 2002 National Health and Nutrition Examination Survey (NHANES). PAD was defined as an ABI <0.9 in at least 1 leg. After adjustment for traditional cardiovascular risk factors, the odds ratios of PAD comparing the highest to the lowest quartiles were 2.24 (95% confidence interval 1.24 to 4.04) for monocytes, 1.74 (0.87 to 3.45) for neutrophils, 2.53 (1.62 to 3.96) for C-reactive protein, and 2.68 (1.03 to 6.94) for fibrinogen. When WBC types and inflammatory markers were simultaneously included in the full model, the corresponding odds ratios were 1.91 (95% confidence interval 1.06 to 3.42) for monocytes, 1.15 (0.49 to 2.69) for neutrophils, 1.37 (0.75 to 2.49) for C-reactive protein, and 2.21 (0.88 to 5.57) for fibrinogen.

CONCLUSIONS

Monocytes were the only WBC type significantly and independently associated with PAD in a representative sample of the U.S. population after adjustment for other inflammatory markers. These findings reflect the potential role of circulating monocyte counts as markers of atherosclerosis.

Cytomegalovirus infection aggravates atherogenesis in apoE knockout mice by both local and systemic immune activation

Since the 1970s, cytomegalovirus (CMV) infection has been associated with atherosclerotic disease. However, the exact contribution of the virus remains uncertain. In this article we describe both a direct and indirect immune-mediated effect of the virus on the disease process. Eight-week-old apolipoprotein E (apoE) knockout mice were infected with mouse CMV (MCMV) or mock injected, and they were sacrificed at 2 and 20 weeks post-injection (p.i.) to study atherosclerosis, vascular wall IFNgamma and TNFalpha expression and MCMV spread. To study plasma IFNgamma and TNFalpha levels, blood was collected at 1, 2, 4 and 6 days p.i. in addition to days of sacrifice. Plasma cytokine levels were increased after MCMV infection at early time points and decreased to mock levels at 2 and 20 weeks p.i. At 2 weeks p.i., more aortic arch samples showed local cytokine expression after MCMV infection. The number of early atherosclerotic lesions and the percentage of mice containing early lesions were increased at 2 weeks p.i., while at 20 weeks p.i., the MCMV-induced effect on atherogenesis was seen on the late lesions. In conclusion, MCMV infection induces a systemic immune response reflecting an indirect effect of MCMV infection on atherosclerosis in addition to a local aortic immune response reflecting a direct effect of the virus on the atherosclerotic process.

Method for large scale isolation, culture and cryopreservation of human monocytes suitable for chemotaxis, cellular adhesion assays, macrophage and dendritic cell differentiation

This paper presents an improved method of isolating, culturing and cryopreserving human monocytes in large quantity with high purity using standard laboratory centrifuges. Monocytes were isolated from 300 to 360 ml of heparinized human blood using a Double Density technique employing Ficoll Isopaque and 46% iso-osmotic Percoll. Yields of monocytes ranged from 75 to 205 million (from 300 to 360 ml of blood) with an average purity of 90.6%. The ability of fresh or frozen monocytes to adhere to endothelial cells in the presence of oxidized L-alpha-1-palmitoyl-2-arachidonosyl-sn-glycero-3-phosphocholine (oxPAPC) or lipopolysaccharide (LPS) did not differ and no significant difference in response to the chemotactic stimulant N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) was observed. We define a useful method for the culture and differentiation of fresh or frozen monocytes isolated by this method, into macrophages as judged by morphology, expression of the macrophage marker SRA-1 and induction of inflammatory genes TNF-alpha, IL-6 and COX-2. Also, fresh or frozen Double Density isolated cells can be successfully differentiated into dendritic cells in the presence of GM-CSF and IL-4 as judged by the expression of the hallmark surface proteins CD1a and DC-sign and the absence of CD14. This method also yields a pure population of lymphocytes.

MCMV infection increases early T-lymphocyte influx in atherosclerotic lesions in apoE knockout mice

BACKGROUND

Multiple epidemiological studies have suggested that cytomegalovirus (CMV) infection is associated with atherosclerotic disease. However, conclusive proof that the virus is directly related to the progression of the disease is still lacking.

OBJECTIVES

The goal of this study was to investigate whether MCMV is able to exacerbate the atherosclerotic process in atherosclerosis-susceptible mice.

STUDY DESIGN

apoE knockout mice kept on a chow diet were sacrificed at both 2 and 20 weeks post infection (p.i.). C57Bl/6J mice fed an atherogenic diet were sacrificed at 2 weeks p.i. Lesion area, lesion composition (endothelial cells and smooth muscle cells) and inflammatory influx (T-lymphocytes and macrophages) in lesions were determined. The former one was determined by means of a microscope coupled to a computer-assisted morphometry system. The latter ones were scored after immunohistochemical staining.

RESULTS

In the chronic phase of the infection mean lesion size was significantly increased after MCMV infection in the apoE knockout mice. This increase could to a large extent be attributed to a significant increase in type V lesion area after MCMV infection. Also, a significant increase in T-lymphocyte influx was observed in the acute phase of the infection in lesions from apoE knockout mice after MCMV infection while this effect was absent in C57Bl/6J mice. After MCMV infection no increase was observed in macrophage, smooth muscle cell and endothelial cell number in lesions from both mice strains.

CONCLUSIONS

MCMV infection may exacerbate the atherosclerotic process in apoE knockout mice by means of an acute lymphocytic inflammatory response. In contrast to the MCMV induced effect in apoE knockout mice, MCMV infection did not increase the influx of T-lymphocytes in atherosclerotic lesions of C57Bl/6J mice.

Atherogenic progression of carotid stenosis associates selectively with monocyte fraction in circulating leukocytes

Humoral biomarkers of inflammation appear to correlate with future cardiovascular events warranting investigation of more specific associations between phenotypic subclasses of circulating cellular immunity and atherogenic progression of carotid stenosis. Retrospective study of carotid stenosis progression based on archived serial carotid duplex ultrasonography examinations in 100 patients. Predictors of atherogenic progression of carotid stenosis were sought using univariate and multivariate analysis of age, gender, hypertension, diabetes mellitus, smoking, peripheral blood leukocyte count and leukocyte differential profile, platelets, diastolic and systolic and mean arterial blood pressure, pulse pressure, creatinine, glucose, total-, HDL-, and LDL-cholesterol, triglycerides, and body mass index. Atherogenic progression of carotid stenosis was limited to patients with carotid stenosis at baseline (41/100) and exhibited a sporadic episodic temporal course. Univariate predictors of stenosis progression were diabetes mellitus, smoking, percent monocytes, and absolute monocyte count. Logistic regression demonstrated that monocytes as a percentage of circulating leukocytes [odds ratio (OR) 1.25, 95% confidence interval (CI) 1.06-1.47, P=0.0093] and smoking (OR 7.09, 95% CI 1.97-25.43, P=0.0027) were independently associated with atherogenic epochs. A selective association between the fraction of monocytes among leukocytes in peripheral blood and atherogenic progression of carotid stenosis is described.

Increased level of advanced oxidation protein products in patients with coronary artery disease

Witko-Sarsat et al. previously reported that advanced oxidation protein products (AOPP), which were determined by measurements of optical density (OD) at 340 nm under acidic conditions, were present at high levels in the plasma of uremic patients. We measured AOPP in the plasma of 392 patients who underwent coronary angiography because of suspected coronary artery disease (CAD) and examined the association between plasma AOPP levels and CAD. We also collected plasma from hemodialysis patients and healthy volunteers for AOPP assay. Plasma fractionation by size-exclusion chromatography was performed to determine the weights of the molecules involved in the AOPP activity. The elution patterns obtained after plasma fractionation by size-exclusion chromatography were the similar in both CAD and hemodialysis patients, but differed from those of the healthy volunteers, whose AOPP levels were low. We also found that, the severity score of CAD obtained by the Gensini scoring system had good correlation with AOPP quartiles. Multivariable regression models revealed that the plasma AOPP level was significantly related to CAD status. This is the first report of an association between AOPP and CAD. AOPP was an independent risk factor for CAD. Oxidative stress is speculated to be associated with the pathogenesis of CAD.

Infiltrating CD14+ monocytes and expression of CD14 by activated parenchymal microglia/macrophages contribute to the pool of CD14+ cells in ischemic brain lesions

CD14, a key pattern recognition receptor of the innate immune system, is a surface molecule on monocytic cells involved in cellular activation. We investigated 18 autopsy cases of focal cerebral infarctions (FCI) by immunohistochemistry to examine CD14 expression following ischemia. Controls confirmed constitutive CD14 expression by few perivascular cells. In contrast to quiescent CD14- parenchymal microglial cells, following ischemia activated microglia/macrophages expressed abundant CD14. In FCI, CD14+ cells increased both in perivascular spaces and in brain parenchyma within 1-2.5 days and remained elevated until late stages. Early CD14 expression suggests an essential part of CD14 in the acute inflammatory response following stroke.

Tumor necrosis factor-dependent segmental control of MIG expression by high endothelial venules in inflamed lymph nodes regulates monocyte recruitment

Monocytes recruited from the blood are key contributors to the nature of an immune response. While monocyte recruitment in a subset of immunopathologies has been well studied and largely attributed to the chemokine monocyte chemoattractant protein (MCP)-1, mechanisms mediating such recruitment to other sites of inflammation remain elusive. Here, we showed that localized inflammation resulted in an increased binding of monocytes to perifollicular high endothelial venules (HEVs) of lymph nodes draining a local inflammatory site. Quantitative PCR analyses revealed the upregulation of many chemokines in the inflamed lymph node, including MCP-1 and MIG. HEVs did not express detectable levels of MCP-1; however, a subset of HEVs in inflamed lymph nodes in wild-type (but not tumor necrosis factor [TNF] null mice) expressed MIG and this subset of HEVs preferentially supported monocyte binding. Expression of CXCR3, the receptor for MIG, was detected on a small subset of peripheral blood monocytes and on a significant percentage of recruited monocytes. Most importantly, in both ex vivo and in vivo assays, neutralizing anti-MIG antibodies blocked monocyte binding to inflamed lymph node HEVs. Together, these results suggest that the lymph node microenvironment can dictate the nature of molecules expressed on HEV subsets in a TNF-dependent fashion and that inflammation-induced MIG expression by HEVs can mediate monocyte recruitment.

Reciprocal induction of IL-10 and IL-12 from macrophages by low-density lipoprotein and its oxidized forms

Atherosclerosis is a chronic inflammatory disease. Several lines of evidence indicate that altered or modified lipoproteins contribute to plaque formation and lesion progression in atherogenesis. In this study we examined if lipoproteins and their oxidized forms can exert an immunomodulatory effect, thereby potentially influencing atherogenesis. We demonstrate that LDL, upon binding to its receptor, induces interleukin (IL)-10 production from macrophages and biases naive T cells to become Th2-like. In contrast, oxLDL induces IL-12 from macrophages and accordingly favors differentiation of naive T cells along a Th1 pathway. IL-10 is a potent anti-inflammatory cytokine with a number of potential effects that could dampen inflammation at sites of vascular wall damage, including downregulation of MHC and adhesion molecules and biasing of adaptive immune responses toward the anti-inflammatory, humoral immune-promoting Th2 T cell subset. These studies assign a new immunomodulatory role to LDLs and offer a potential means to upregulate IL-10 production and prevent arterial inflammation.

Monocytes influence the fate of T cells challenged with oxidised low density lipoproteins towards apoptosis or MHC-restricted proliferation

Atherosclerosis has been implicated in myocardial infarction, stroke and a host of cardiovascular diseases. The presence of activated T lymphocytes and macrophages, and the increased expression of HLA-DR antigen are consistent with the notion of immune activity in the atherosclerotic plaque. The nature of the causative antigen has not been established although oxidised low density lipoproteins (oxLDL) that accumulate in atherosclerotic plaques could fulfil this role. Here, we report that monocytes play a key role in influencing the fate of purified peripheral human T lymphocytes from healthy donors when the cells are exposed to LDL oxidised under the controlled conditions of water radiolysis. Our data showed that oxLDL generated under these conditions were chemoattractants for T cells. However, they induced a state of apoptosis in T lymphocytes cultured in the absence of monocytes. The extent of apoptosis was related to the degree of oxidation of LDL and the time of T cell exposure to oxLDL. OxLDL-dependent apoptosis did not involve a scavenger-like receptor. CD4(+) cells were more sensitive to the apoptotic effect of oxLDL than CD8(+) cells. OxLDL-primed (12 h) autologous monocytes triggered a robust proliferation of T lymphocytes cultured in the absence of oxLDL. The strength of T cell stimulation was related to the degree of oxidation of the LDL used in priming. Heterologous monocytes exposed to oxLDL under similar conditions induced a response that was not different than monocytes exposed to untreated LDL (natLDL) which did not induce T cell proliferation. Fucoidan did not modify the oxLDL-, monocyte-dependent T cell response to proliferation, suggesting that a scavenger-like receptor was not involved. The expression of the HLA-DR marker and the B7.2 protein were up-regulated in monocytes exposed to oxLDL but not to natLDL. The levels of B7.1 were unchanged. Our data are consistent with the notion that monocytes are critical for T cell survival in the presence of oxLDL and MHC-restricted T cell proliferative response to oxLDL.

The inflamed plaque: cytokine production and cellular cholesterol balance in the vessel wall

Although the concept that inflammation plays a role in the biology of atherosclerosis is now well accepted, the basic feature of the arterial lesion remains the accumulation of clusters of foam cells. These clusters are the consequence of the enhanced recruitment of monocytes in the vessel wall induced by the hyperlipidemia and of the disproportionate accumulation of lipids in the cytoplasm of macrophages deriving from monocytes. Ultimately, every molecular force and pathway with modulating activity over the developing lesion will have to act on a convergence point with factors regulating cholesterol balance in the macrophage. Consistent with this view is the recent report that cytokines, such as tumor necrosis factor-alpha, can influence the expression of the scavenger receptor, whereas interferon-gamma can inhibit adenosine triphosphate-binding cassette transporter-1, the main effector of cholesterol efflux in the peripheral cell. Conversely, recent data have shown that primary alterations in macrophage cholesterol balance, such as those produced by the total absence of acylcoenzyme A:cholesterol acyltransferase-1, may determine local changes compatible with the activation of inflammatory pathways. In this brief review, we discuss some of the convergence points between inflammation and cholesterol balance, and we highlight the additional therapeutic targets suggested by these new developments in vascular biology.

Flow cytometric evaluation of apoptosis, necrosis and recovery when culturing monocytes

After developing and applying a method for cryopreserving monocytes, we found a substantial cell loss when culturing these cells. Monocytes were isolated from blood donors by density gradient centrifugation, purified by elutriation and cryopreserved. Thawed cells were cultured in ultra low attachment wells and studied with Annexin V, Propidium iodide, Dihexyloxacarbocyanine (DiOC(6)(3)), bromolated deoxyuridine triphosphate nucleotides (Br-dUTP), DNA ploidy and DNA ladder methodologies. The main cell loss was within the first 24 h and recovery on day 7 was 35-40%. The first 2-6 h of culture were found to be crucial for determining which cells survive. Initially (2-4 h), apoptosis was the main feature but after 6 h, necrosis dominated. Two populations of cells developed after 24 h: "A" consisting of larger cells with low levels of apoptosis and necrosis signals and population "B" comprising smaller cells with a high expression of necrotic but low levels of apoptotic signals. Signs of DNA fragmentation were slight. These early, dynamic changes may be important for the interpretation of experimental results when investigating monocytes in culture.

Mycophenolate mofetil treatment reduces atherosclerosis in the cholesterol-fed rabbit

Immune/inflammatory responses of arterial vessel wall constituents to lipid metabolic disturbances have been postulated to contribute to the pathogenesis of atherosclerosis. Mycophenolate mofetil (MMF), an antiproliferative agent used in clinical transplantation, has been shown to inhibit smooth muscle cell (SMC) proliferation and decrease the recruitment of monocytes into sites of chronic inflammation. This study was conducted to determine the effect of MMF on atherosclerotic plaque development after cholesterol-induced injury. New Zealand white rabbits were fed a high-cholesterol diet containing 0.5% cholesterol and 8% peanut oil. The experimental group (n = 10) was given MMF (80 mg/kg/day subcutaneously); the control group (n = 10) received placebo injections. The aortas were harvested at 12 weeks for immunohistochemical analyses. SMCs were identified by reactivity with a monoclonal antibody (mAb) to alpha smooth muscle actin. Monocytes/macrophages were detected with mAb RAM 11. Cross-sectional areas of the media and neointima were measured using computer-assisted image analysis. The density of SMCs and macrophage/foam cells within the neointima was calculated by dividing the number of cells by the area of the plaque. Total cholesterol, triglyceride, high density lipoprotein, and low density lipoprotein were significantly increased compared with levels before the initiation of a high-cholesterol diet, but there were no significant differences between the MMF-treated and untreated groups. Neointimal area in aortic tissue sections of the MMF-treated group (0.586 +/- 0.602 mm(2)) was significantly lower when compared with that in control animals (1.082 +/- 0.621 mm(2)) (P < 0.05). The densities of neointimal SMCs and monocytes/macrophages in the control group were 778 +/- 293 and 341 +/- 90 cells/mm(2), respectively. MMF treatment significantly reduced the number of neointimal SMCs (506 +/- 185 cells/mm(2)) (P < 0.05). The number of monocytes/macrophages was also reduced after MMF treatment (260 +/- 124 cells/mm(2)) but not significantly. Our results demonstrate that the administration of MMF significantly reduced neointimal SMC accumulation and plaque development in a hypercholesterolemic model of atherosclerosis.

Evaluation of CD14 in host defence

An extensive search for the cell membrane targets for lipopolysaccharide (LPS), the major causative agent of Gram-negative septic shock, resulted in the identification of CD14 as the major endotoxin 'receptor'. Besides recognition of LPS, several new aspects of its biological functions have been described recently. In this review the different CD14 forms, their most important biological and biochemical features, signalling properties, cellular and subcellular distribution and association with different diseases are discussed in detail, showing that these molecules posses several unique biological functions and further proving their central role in innate immunity.

Atherogenic properties of human monocytes induced by the carboxyl terminal proteolytic fragment of alpha-1-antitrypsin

Atherosclerotic plaques contain a significant number of macrophage foam cells and are associated with an inflammatory state. Inflammation induces the secretion from monocytes and other cells of cytokines, reactive oxygen species, proteinases and proteinase inhibitors among many other molecular species. AAT is prominent among the serine proteinase inhibitors and is an important regulator of leukocyte elastase and proteinase-3. It has been shown that the stable AAT-proteinase complex can upregulate AAT biosynthesis, and we have shown that the shorter, carboxyl terminal peptide (C-36) resulting from proteinase cleavage of AAT polymerizes, and in its fibrillar form alters cellular metabolism. To test for a possible link between the inflammation-generated C-36 peptide and cellular processes associated with atherogenesis, we have studied the effects of the fibrillar form of this peptide at varying concentrations on human monocytes in culture. We have found that fibrillar C-36 at concentrations of greater than or equal to 5 micromol/l in monocyte cultures for 24 h significantly increases LDL binding and uptake, upregulates LDL receptors, induces cytokine production and glutathione reductase activity, and upregulates AAT synthesis. The expression of CD36 protein, LDL Scavenger receptor, is also upregulated by fibrillar C-36 and native LDL in the presence of C-36-activated monocytes is more oxidized than with unactivated control monocytes. The majority of monocytes cultured for 24 h in the presence of C-36 fibrils were transformed morphologically into macrophages. These data establish a direct molecular link, mediated by C-36 peptide of AAT, between inflammation and the oxidation and accumulation of lipid in monocyte-derived macrophages. This may be important for an understanding of the events conducive to atherogenesis.

Human monocyte activation by cleaved form of alpha-1-antitrypsin involvement of the phagocytic pathway

Production of alpha-1-antitrypsin (AAT) by human monocytes is an important factor in controlling tissue damage by proteases in the microenvironment of inflammation. Increases, of four- to eightfold, in numbers of macrophages and levels of AAT and its cleavage fragments have been found in various inflammatory loci. We have found that the C-terminal peptide (C-36) of AAT, produced by specific proteinase cleavage when added in its fibrillar form at concentrations >/=5 microM to monocytes in culture for 24 h, significantly increases low density lipoprotein (LDL) binding and uptake, up-regulates levels of LDL receptors and also induces proinflammatory cytokine (interleukin-1, interleukin-6 and tumour necrosis factor alpha) production and glutathione reductase activity. Because it is known that various cells selectively internalize surface receptors and their ligands through receptor-mediated endocytosis via clathrin-coated pits, we tested whether antibodies raised against the clathrin heavy chain would block the effects of the fibrillar form of C-36 on human monocytes in culture. Addition of excess anti-(clathrin HC) with 10 microM fibrillar C-36 diminished the stimulatory effects of the latter on LDL binding, uptake and LDL receptor levels. In contrast, however, in the presence of anti-(clathrin HC), the potentially cytotoxic effects of fibrils, such as induction of cytokines, free radicals and cytosolic activity of cathepsin D, were much greater than those observed when cells were treated with fibrils alone. These results suggest that endocytosis is the pathway by which C-36 fibrils upregulate LDL receptors, and may be the natural mechanism for fibril clearance. We infer that human monocytes clear C-36 fibrils by a clathrin-dependent pathway, presumably endocytotic, and that loss of this pathway amplifies the cytotoxic effects of the fibrils by increasing their availability to other specific or nonspecific sites through which they exert their cytotoxic effects.

Lack of association of restenosis following coronary angioplasty with elevated C-reactive protein levels or seropositivity to Chlamydia pneumoniae

Seventy-five consecutive patients undergoing directional coronary atherectomy were evaluated by measuring anti-Chlamydia immunoglobulin G and anticytomegalovirus immunoglobulin G antibodies, and serum levels of C-reactive proteins (before atherectomy). The results showed that although both Chlamydia infection and elevated C-reactive protein levels are associated with coronary artery disease and coronary artery disease events, neither of these appears to play a role in the development of restenosis.