Shirley Nakhla

Androgen Receptor Expression Is Greater in Macrophages From Male Than From Female Donors A Sex Difference With Implications for Atherogenesis

BACKGROUND Male sex is an independent risk factor for the extent and severity of atherosclerosis. The influence of androgens on foam cell formation, a key event in atherogenesis, has not yet been investigated. METHODS AND RESULTS Primary human monocytes were allowed to differentiate into macrophages. RNA was then extracted from healthy male-donor (n=8) and premenopausal female-donor (n=8) macrophages, and message for the androgen receptor (AR) was examined by RT-PCR. There was a significantly higher level of AR mRNA in macrophages isolated from men than in those from women (0.64+/-0.06 versus 0.15+/-0.02 amol/microgram total RNA; P<0.001). AR mRNA levels were similar in macrophages from postmenopausal and premenopausal women (P=0.16). The functional consequence of this sex difference was then explored. Lipid-loading studies were performed on male (n=9) macrophages treated with the androgen dihydrotestosterone (DHT) and/or the AR antagonist hydroxyflutamide. These showed that DHT caused a dose-dependent and receptor-mediated increase in macrophage cholesteryl ester content (109+/-10%, 117+/-3%, and 120+/-4% for 4, 40, and 400 nmol/L DHT, respectively, as a percentage of control, P=0.002; 95+/-8% for DHT with hydroxyflutamide, P=0.58 versus controls). By contrast, there was no significant effect of androgen on lipid loading in female-donor macrophages (P>0.2 versus controls). CONCLUSIONS Sex differences in androgen-mediated macrophage lipid loading may contribute to the greater prevalence and severity of atherosclerosis in men.

High-Density Lipoproteins Suppress Chemokines and Chemokine Receptors In Vitro and In Vivo

Objective—To investigate whether high-density lipoproteins (HDLs) suppress chemokine (CCL2, CCL5, and CX3CL1) and chemokine receptor (CCR2 and CX3CR1) expression, a mechanism for the atheroprotective properties of HDLs. Methods and Results—Apolipoprotein (apo) E−/− mice were fed a high-fat diet for 12 weeks. Before being euthanized, the mice received 5 consecutive daily injections of lipid-free apoA-I, 40 mg/kg, or saline (control). The injection of apoA-I reduced CCR2 and CX3CR1 expression in plaques compared with controls (P<0.05). ApoA-I–injected mice had lower plasma CCL2 and CCL5 levels. Hepatic CCL2, CCL5, and CX3CL1 levels were also reduced (P<0.05). In vitro studies found that reconstituted HDL (rHDL) reduced monocyte CCR2 and CX3CR1 expression and inhibited their migration toward CCL2 and CX3CL1 (P<0.05). Preincubation with rHDL reduced CCL2, CCL5, and CX3CL1 expression in monocytes and human coronary artery endothelial cells. The stimulation of CX3CR1 with peroxisome proliferator–activated receptor &ggr; agonist CAY10410 was suppressed by preincubation with rHDL but did not affect the peroxisome proliferator–activated receptor &ggr; antagonist (GW9664)–mediated increase in CCR2. In monocytes and human coronary artery endothelial cells, rHDL reduced the expression of the nuclear p65 subunit, I&kgr;B kinase activity, and the phosphorylation of I&kgr;B&agr; (P<0.05). Conclusion—Lipid-free apoA-I and rHDL reduce the expression of chemokines and chemokine receptors in vivo and in vitro via modulation of nuclear factor &kgr;B and peroxisome proliferator–activated receptor &ggr;.

Prospective Study of Effect of Androgens on Serum Inflammatory Markers in Men

Objective—Because male sex is an independent risk factor for the severity of atherosclerosis, it is possible that androgens may be proatherogenic. There is evidence that sex hormones, particularly estrogens, regulate (or modulate) inflammation, a process integral to atherogenesis. Because levels of serum inflammatory markers predict cardiovascular outcomes, we prospectively assessed the effects of androgen therapy on these markers in older men. Methods and Results—Levels of high-sensitivity C-reactive protein (CRP), soluble intracellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured from sera collected at baseline and at the end of 2 randomized double-blind placebo-controlled trials evaluating the effects of 3 months of androgen treatment with either dihydrotestosterone (DHT) or recombinant human chorionic gonadotropin (rhCG) in healthy men aged >60 years with partial androgen deficiency (serum testosterone levels <15 nmol/L). For the DHT study (70 mg transdermally daily), 33 men completed 3 months of treatment (16 men were treated with DHT, and there were 17 controls). For the rhCG (250 &mgr;g twice weekly) study, 20 men were treated with rhCG, and there were 20 controls. In both studies, groups were well matched for age and vascular risk factors. Androgen levels (DHT and testosterone) were consistently maintained at eugonadal levels throughout the trials, with estradiol markedly increased by rhCG but not DHT. Baseline CRP levels were 0.74 to 1.49 mg/L, sVCAM-1 levels were 847 to 950 ng/mL, and sICAM-1 levels were 256 to 292 ng/mL in all groups. Neither DHT nor rhCG resulted in significant changes in CRP, sVCAM-1, or sICAM-1 compared with placebo (P >0.3 in both studies). Conclusions—Exogenous androgen therapy with or without increased estradiol levels does not alter serum inflammatory markers in older men; this finding is in contrast to the effects of estrogens on inflammatory markers that have been found in postmenopausal women. These data provide a measure of reassurance concerning potential adverse cardiovascular effects of androgen therapy in older men.

Acute hypertriglyceridaemia in humans increases the triglyceride content and decreases the anti-inflammatory capacity of high density lipoproteins

INTRODUCTION Post-prandial hypertriglyceridaemia is a risk factor for cardiovascular disease, although the underlying mechanisms remain unclear. High density lipoproteins (HDL) have been shown to be atheroprotective, in part through attenuation of vascular inflammation. In this study, the influence of acute hypertriglyceridaemia on the composition and anti-inflammatory properties of HDL was investigated. METHODS Eight fasting healthy male subjects (34+/-2 years) received 20% Intralipid (15 mg/kg/h) or saline, on separate occasions in random order. At baseline and 60 min post-infusion, the total HDL fraction was isolated and its chemical composition determined. HDL were added to TNF-alpha stimulated human coronary artery endothelial cells and VCAM-1 and ICAM-1 expression was determined by flow cytometry. RESULTS Serum triglyceride (97.4+/-8.5mg/dL baseline, 283.2+/-35.4 mg/dL post-infusion, p<0.001) and HDL triglyceride content (3.8+/-0.5% HDL mass baseline, 5.3+/-0.9% HDL mass post-infusion, p<0.05) increased significantly after Intralipid infusion. HDL post-Intralipid were significantly less anti-inflammatory compared with control (e.g. at 8 microM apoA-I, %VCAM-1 expression 54+/-5 post-saline, 73+/-4 post-Intralipid, p=0.01; %ICAM-1 expression 94+/-1 post-saline, 99.4+/-0.6 post-Intralipid, p<0.01). There was also a significant correlation between HDL triglyceride content and VCAM-1 expression (R=0.70, p=0.005); as well as between plasma triglyceride levels and both VCAM-1 (R=0.71, p<0.005) and ICAM-1 expression (R=0.80, p<0.005). CONCLUSION Acute hypertriglyceridaemia, simulating the post-prandial state, results in triglyceride-rich HDL with impaired anti-inflammatory capacity.

Estrogen and Progesterone Reduce Lipid Accumulation in Human Monocyte-Derived Macrophages A Sex-Specific Effect

BACKGROUND Males have an earlier onset and greater prevalence of clinical atherosclerosis than age-matched females, which is consistent with an atheroprotective effect of the female sex steroids, estrogen and progesterone. We therefore examined the effects of estrogen and progesterone on human foam cell formation, a key early event in atherogenesis. METHODS AND RESULTS Monocytes from healthy female and male donors were obtained from white cell concentrates and allowed to differentiate into macrophages over 10 days. These human monocyte-derived macrophages (MDMs) were exposed to either control (0.1% vol/vol ethanol) or estrogen or progesterone treatment on days 3 through 10. Lipid loading was achieved on days 8 through 10 by incubation with acetylated LDL. Lipid from the MDMs was then extracted for analysis of cholesteryl ester (CE) content. 17beta-Estradiol at both physiological (2 nmol/L) and supraphysiological (20 and 200 nmol/L) concentrations produced a significant reduction in macrophage CE content (88+/-3%, 88+/-2%, and 85+/-4%, respectively; P<0.02 compared with control). Physiological and supraphysiological levels of progesterone (2, 10, and 200 nmol/L) produced an even more dramatic reduction in CE content (74+/-9%, 56+/-10%, and 65+/-8%, respectively; P<0.002 compared with control). This effect could be abrogated by coincubation with the progesterone receptor antagonist RU486. Neither estrogen nor progesterone produced a reduction in lipid loading in male-donor-derived MDMs. Detailed lipid trafficking studies demonstrated that both estrogen and progesterone altered macrophage uptake and/or processing of modified LDL. CONCLUSIONS Physiological levels of estrogen and progesterone are associated with a female-sex-specific reduction in human macrophage lipid loading, which is consistent with an atheroprotective effect.

Anti-inflammatory effects of apolipoprotein A-I in the rabbit

OBJECTIVE Infusions of apoA-I in the lipid-free form or as a constituent of discoidal reconstituted high-density lipoproteins, (A-I)rHDL, markedly inhibit acute vascular inflammation in normocholesterolemic New Zealand White (NZW) rabbits. This effect is apparent even when apoA-I is administered 24h prior to the inflammatory insult. The present study asks if this benefit is related to an improved anti-inflammatory capacity of the high-density lipoprotein (HDL) fraction, or to increased arterial expression of genes that inhibit inflammation. METHODS AND RESULTS The ability of apoA-I to increase the anti-inflammatory capacity of HDL was assessed by infusing normocholesterolemic NZW rabbits with saline, lipid-free apoA-I or (A-I)rHDL. The infused apoA-I incorporated rapidly into the rabbit HDL fraction. The animals were sacrificed at 5 or 360 min post-infusion and plasma was collected. HDL were isolated by ultracentrifugation and incubated with cytokine-activated cultured human coronary artery endothelial cells. HDL from animals sacrificed at 5 min post-apoA-I infusion had a slightly enhanced anti-inflammatory capacity relative to HDL from the saline-infused animals. The anti-inflammatory capacity of HDL from the animals sacrificed at 360 min post-apoA-I infusion was comparable to that of HDL from the saline-infused animals. The effect of (A-I)rHDL infusions on arterial 3β-hydroxysteroid-Δ24 reductase (DHCR24) and endothelial adhesion molecule expression was investigated in cholesterol-fed NZW rabbits. Relative to animals infused with saline, (A-I)rHDL infusions decreased aortic VCAM-1 and ICAM-1 protein expression by 73 and 54%, respectively (p<0.05), and increased DHCR24 mRNA levels by 56% (p<0.0001). CONCLUSION ApoA-I inhibits vascular inflammation in NZW rabbits, at least in part, by increasing DHCR24 expression.

Nitroglycerin upregulates matrix metalloproteinase expression by human macrophages.

OBJECTIVES This study aimed to determine whether nitroglycerin (NTG) treatment affects matrix metalloproteinase (MMP) gene expression and activities in human macrophages. BACKGROUND Nitroglycerin is one of the most frequently used therapeutic agents for the symptomatic relief of stable or unstable coronary artery disease; however, its effects on vascular biology are poorly characterized. Despite its powerful vasodilator activity, NTG has not been shown to improve outcomes in coronary disease. We now describe evidence that NTG has potentially pro-inflammatory effects in human monocyte-derived macrophages (MDMs). METHODS Human monocytes were isolated from whole blood by elutriation and allowed to differentiate into macrophages over eight to 10 days. The MDMs were then treated for 4 or 24 h with control media, pharmacologically relevant doses of NTG or other nitric oxide donors. Matrix metalloproteinase activity was measured by zymography, protein levels measured by enzyme-linked immunosorbent assay and messenger ribonucleic acid (mRNA) levels were quantified by competitive reverse transcription-polymerase chain reaction. RESULTS The major MMP expressed by MDMs was MMP-9. Nitroglycerin treatment stimulated a dose-dependent increase in MMP-9 mRNA levels (NTG 200 pmol: 193 +/- 6% and NTG 2,000 pmol: 372 +/- 9% compared to controls, p < 0.005) and MMP-9 activity (NTG 200: 142 +/- 5.5% and NTG 2,000: 167 +/- 11% compared to controls, p < 0.005). Nitroglycerin 2,000 pmol also increased MMP-2 and MMP-7 mRNA levels to 187 +/- 8% and 183 +/- 21% of control values, respectively (p < 0.05). Furthermore, tissue inhibitor of metalloproteinase (TIMP)-1 (the major tissue inhibitor of MMPs) mRNA and protein levels were decreased in NTG 2,000 pmol-treated MDMs compared with control cells (mRNA: 67 +/- 7%, p < 0.005; protein: 45 +/- 5%, p < 0.005). CONCLUSIONS Nitroglycerin in pharmacologically relevant concentrations activates MMP but represses TIMP expression in human macrophages. The subsequent imbalance in MMP/TIMP expression associated with NTG treatment could promote matrix degradation, with potentially adverse effects on plaque stability.

Pathophysiological levels of the obesity related peptides resistin and ghrelin increase adhesion molecule expression on human vascular endothelial cells

1. In the present study, we sought to determine whether physiological or pathophysiological concentrations of obesity related peptides influence the key early atherogenic events of monocyte adhesion to endothelial cells and adhesion molecule expression using primary human cells.

The effects of obesity and non-pharmacological weight loss on vascular and ventricular function and structure.

Aims:  The mechanisms by which obesity confers increased cardiovascular risk and the effects of moderate weight loss on cardiovascular health are incompletely understood. We sought to characterize the preclinical changes in cardiac and vascular health that accompany obesity and the influence of lifestyle modification on these parameters.

REPERFUSION INJURY IN THE HUMAN FOREARM IS MILD AND NOT ATTENUATED BY SHORT-TERM ISCHAEMIC PRECONDITIONING

1. Ischaemia–reperfusion (IR) injury is an important contributor to tissue damage and has been shown to be attenuated by preconditioning (PC) in some animal models. A recent report has suggested that the forearm can be used for the study of this phenomenon in humans. We aimed to reproduce and further characterize this model.