Lipid-laden partially-activated plasmacytoid and CD4(-)CD8α(+) dendritic cells accumulate in tissues in elderly mice

BACKGROUND

Aging is associated with a decline in lymphocyte function however, little is known about dendritic cell (DC) subsets and aging. Aging is also associated with increasing circulating lipid levels and intracellular lipid accumulation modulates DC function. Whether age-associated increases in lipid levels influence DC biology is unknown. Thus, the effects of aging on DC subsets were assessed in vivo using young adult and elderly C57BL/6 J mice.

RESULTS

Major age-related changes included increased CD11c(+) DC numbers in lymph nodes, spleens and livers, but not lungs, and significantly increased proportions of plasmacytoid (pDC) and CD4(-)CD8α(+) DCs in lymph nodes and livers. Other changes included altered pDC activation status (decreased CD40, increased MHC class-I and MHC class-II), increased lipid content in pDCs and CD4(-)CD8α(+) DCs, and increased expression of key mediators of lipid uptake including lipoprotein lipase, scavenger receptors (CD36, CD68 and LRP-1) in most tissues.

CONCLUSIONS

Aging is associated with organ-specific numerical changes in DC subsets, and DC activation status, and increased lipid content in pDCs and CD4(-)CD8α(+) DCs. Up-regulation of lipoprotein lipase and scavenger receptors by lipid-rich pDCs and CD4(-)CD8α(+) DCs suggests these molecules contribute to DC lipid accumulation in the elderly. Lipid accumulation and modulated activation in pDCs and CD4(-)CD8α(+) DCs may contribute to the declining responses to vaccination and infection with age.

Lack of evidence for association between endothelial nitric oxide synthase gene polymorphisms and coronary artery disease in the Australian Caucasian population

BACKGROUND

Genetic polymorphism in the gene for endothelial nitric oxide synthase (eNOS) has been identified as a potential risk factor for the development of premature coronary artery disease (CAD). We determined whether the eNOS 4ab, G894T, and T-786C polymorphisms are associated with premature coronary artery disease.

DESIGN

A case-control study.

METHODS

PCR-based assays were used to compare the frequency of eNOS gene polymorphisms in 573 Caucasian subjects aged under 50 years presenting with symptomatic CAD and documented by coronary angiography, with or without myocardial infarction, to that of 624 similarly aged community controls without a history of symptomatic CAD.

RESULTS

We found no difference in the frequency of 4ab genotypes between cases and controls: in the CAD subjects, the 4aa, 4ab, and 4bb genotype frequencies were 1.9%, 24.3% and 73.8% respectively, compared to 2.2%, 25.5% and 72.3% respectively for the controls. There was also no significant difference between cases and controls in the frequency of any allele (4a/4b, 894G/894T, -786C/-786T), or genotype for any of the polymorphisms. Similarly, logistic regression analysis showed no evidence for an association of the polymorphisms with premature CAD or myocardial infarction or any indication of an interaction between the polymorphisms and other CAD risk factors, including smoking.

CONCLUSIONS

In a large case-control study, and in contrast to some earlier positive findings by others, we have found no evidence for an association between several eNOS gene polymorphisms and premature CAD in an Australian Caucasian population.

Angiotensin-converting enzyme gene polymorphism and premature coronary heart disease

Since the initial report of the association of the deletion/insertion (D/I) polymorphism in the gene for angiotensin-converting enzyme (ACE) with myocardial infarction (MI), there has been considerable controversy. Some have found the D allele to be associated with MI, coronary heart disease (CHD) or other cardiac pathology, while others have not. In the present study 713 consecutive patients, < 50 years of age, documented prospectively with angiographic CHD (> 50% diameter stenosis of at least one coronary artery), with or without MI, were studied, along with 688 community control subjects, also < 50 years of age, selected randomly from the electoral rolls and without a history of CHD or MI. Genotyping was done by standard methods. Most of the subjects in both groups were Anglo-Celtic Caucasians (547 in the CHD group and 642 in the community group), and the report concerns primarily these subjects. ACE genotype distributions were not different between the Caucasian community control group and the CHD or the MI subgroups; the odds ratios and 95% confidence limits for the CHD group were 0.96 (0.73-1.27) for the D allele and 1.02 (0.80-1.31) for D homozygotes; for the MI group these values were 1.00 (0.83-1.20) and 0.99 (0.74-1.32) respectively. This negative result was supported in multivariate analysis accounting for conventional risk factors. There was a significant racial difference in ACE genotypes between Caucasians, Asians and Australian Aborigines in the CHD group (P < 0.001); for example, in this group, 158 of 540 (29%) Caucasians had the DD genotype compared with eight of 84 (10%) Aboriginals (P < 0.001) and six of 59 (10%) Asians (P = 0.002). Failure to account for such racial differences would have led to erroneous conclusions. In conclusion, we found no evidence that the D/I ACE gene polymorphism plays a role in the development of CHD or MI at an early age in a Western Australian Caucasian population. While this result refers uniquely to premature CHD and MI, and could be population specific, it is in general agreement with recent meta-analysis of the larger previous studies.

Elite athletes and the gene for angiotensin-converting enzyme

The deletion (D) allele of the gene for angiotensin-converting enzyme (ACE) is associated with higher plasma and tissue levels of the enzyme and has also been related to a variety of cardiovascular complications, particularly myocardial infarction. On the basis of indirect evidence, we hypothesized that inheritance of the D allele would contribute to elite athletic ability. Over a period of 4 yr, 120 Caucasian athletes who were national (Australian) representatives in sports demanding a high level of aerobic fitness were recruited. Their ACE genotypes were compared with those of a community control group recruited randomly from the electoral roll. There was no difference in ACE genotype frequencies between the two groups. The DD genotype frequency was 30% in athletes and 29% in the control group, and the II genotype frequency was 22.5 and 22%, respectively. The results do not exclude the possibility that ACE genotype could be related to some attribute relating to a specific type of elite athletic ability or that there may be a difference between genders. Larger studies are desirable.

Butyrycholinesterase K variant and Alzheimer's disease

This study attempted to corroborate findings on the association between butyrylcholinesterase K variant and Alzheimer's disease. This was performed on an autopsy-confirmed series of patients with Alzheimer's disease and controls. The butyrylcholinesterase K variant was found to be of increased allele frequency in patients with sporadic Alzheimer's disease. When related to APOE epsilon4 typing the association was specific but not sensitive for the diagnosis of Alzheimer's disease.

Comparison of the LDL-receptor binding of VLDL and LDL from apoE4 and apoE3 homozygotes

Compared with apolipoprotein E3 (apoE3), apoE2 is less effective in mediating the binding of lipoproteins to the low-density lipoprotein (LDL) receptor. The influence of the E4 isoform, which is associated with adverse effects on plasma lipids and coronary heart disease, is less clear. We compared the ability of very low density lipoprotein (VLDL) and LDL from paired E4/4 and E3/3 subjects to compete against 125I-labeled LDL for binding with the LDL receptor on cultured fibroblasts and Hep G2 cells. The concentrations of VLDL or LDL required to inhibit binding of 125I-LDL by 50% (IC50, microgram apoB/ml) were determined, and results were assessed in terms of an IC50 ratio, E4/4 IC50 relative to E3/3 IC50, to reduce the influence of interassay variability. In Hep G2 cells, E4/4 VLDL was more effective than E3/3 VLDL in competing for the LDL receptor, the IC50 ratio being lower than unity (0.73 +/- 0.31, P < 0.05, two-tailed t-test). IC50 values themselves were marginally lower in E4/4 than E3/3 subjects (3.7 +/- 1.3 vs. 6.1 +/- 3.7, P < 0.08). However, there was no difference between E4/4 and E3/3 VLDL in competing for the LDL receptor on fibroblasts or between E4/4 and E3/3 LDL in competing for the LDL receptor on either cell type. These results suggest that inheritance of apoE4 is associated with an increased affinity of VLDL particles for LDL receptors on hepatocytes and may partly explain the influence of the E4 isoform on lipid metabolism.

PIa1/a2 polymorphism of glycoprotein IIIa and risk of coronary artery disease and restenosis following coronary angioplasty

Glycoprotein IIIa (GpIIIa), a platelet protein that mediates platelet aggregation and thrombus formation, has attained recent widespread interest following a report that a common genetic variant of GpIIIa, known as Pla2, is an inherited risk factor for the development of premature coronary artery disease (CAD). We determined the frequency of the Pla2 allele in 589 prospectively recruited subjects aged <50 years presenting with symptomatic CAD with or without myocardial infarction and documented by coronary angiography (group I), 207 subjects investigated prospectively for restenosis 6 months after coronary balloon angioplasty (group II), and 570 control subjects without a history of angina or myocardial infarction, randomly selected from the community. Detection of the Pla2 allele was based on MspI digestion of polymerase chain reaction (PCR) amplified deoxyribonucleic acid (DNA) spanning the Pla1/a2 locus. The accuracy of genotyping was verified with a second independent method based on BstXI digestion of DNA amplified with mutagenic PCR primers. The frequency of the Pla2 allele was similar (p >0.1) in group I (170 of 1,178, 14%), group II (49 of 414, 12%), and control subjects (160 of 1,140, 14%). Among group I subjects, there was no relation (p >0.1) between the Pla2 allele frequency and the number of coronary vessels with >50% diameter obstruction, and current or previous myocardial infarction; among group II subjects, there was no difference between those with and without restenosis after angioplasty (26 of 242 and 23 of 172, respectively, p >0.1). We conclude that the Pla2 allele is not associated with a significantly elevated risk of premature CAD, myocardial infarction, or restenosis after coronary angioplasty.

The effect of homocysteine on DNA synthesis in cultured human vascular smooth muscle

Elevated plasma homocysteine is an established risk factor for vascular disease although the mechanisms are unclear. Homocysteine has been reported to stimulate DNA synthesis and proliferation in rat aortic smooth muscle cells. Human vascular smooth muscle cells (HVSMC) from saphenous veins (n = 8), internal mammary arteries (n = 6) and umbilical arteries (n = 2) were studied. To reflect DNA synthesis, 3H-thymidine incorporation, during 24 h exposure to homocysteine in concentrations from 0.0625 to 10 mM, was studied. Incorporation was significantly increased up to 0.5 or 1 mM and thence was progressively depressed, the maximum stimulation being 24 +/- 5(S.E.)% in vein (P < 0.005) and 34 +/- 4% in mammary artery (P < 0.001) while incorporation fell to approximately 25% of the control values at 10 mM (P < 0.001). Qualitatively similar results were obtained in umbilical arteries. Homocysteine had a biphasic effect on DNA synthesis in cultured HVSMC but the higher inhibitory concentrations are well above those commonly found in vivo. While the conditions of exposure to homocysteine render close analogy to the clinical situation impossible, homocysteine can stimulate HVSMC, offering one possible mechanism for the involvement of homocysteine in the pathogenesis of atherosclerosis.

Methylenetetrahydrofolate reductase gene and coronary artery disease

BACKGROUND

Hypermocysteinemia has been substantiated as a risk factor for occlusive vascular disease. A common mutation (nucleotide 677 C-->T) has been described recently in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, which results in a valine for alanine substitution, a thermolabile enzyme, and a tendency to elevate plasma homocysteine levels and which has been proposed to contribute importantly to coronary artery disease.

METHODS AND RESULTS

To study the potential influence of the mutation on ischemic heart disease, we screened 555 whites with angiographically documented coronary artery disease and 143 unrelated control subjects without a history of angina or myocardial infarction randomly selected from the community. The patients were in two groups: group 1 comprised 358 prospectively recruited individuals younger than 50 years, and group 2, 197 patients investigated prospectively for restenosis 6 months after coronary angioplasty. The frequency of homozygosity for the mutation was 10.5% in control subjects, 10.6% in group 1, and 9.1% in group 2 patients. There was no relationship between MTHFR genotype and number of coronary vessels with > 50% diameter obstruction, prior myocardial infarction, or restenosis after coronary angioplasty. Plasma folate concentrations in control subjects (n = 90) and patients (n = 208) showed closely similar distributions.

CONCLUSIONS

Although it is accepted that moderate hyperhomocysteinemia significantly increases the risk for coronary, cerebrovascular, and peripheral vascular diseases, our data suggest that a mutation of the MTHFR gene, which has been associated with a thermolabile form of the enzyme and with hyperhomocysteinemia in subjects with plasma folate below the median, does not appear to be significantly associated with risk for premature coronary artery disease or for restenosis after coronary angioplasty.

Familial defective apolipoprotein B-100 (FDB): effect of simvastatin therapy on LDL-receptor binding

Heterozygotes for familial defective apolipoprotein B-100 (FDB) have two populations of low density lipoprotein (LDL), one bearing normal apolipoprotein B-100 (apo B) and the other bearing defective apo B which exhibits a much lower affinity for the LDL-receptor. If HMGCoA reductase inhibitors such as simvastatin lowered LDL mainly by up-regulating LDL-receptor mediated clearance, they should decrease the overall binding affinity of LDL from an FDB heterozygote by selectively decreasing LDL bearing normal apo B. We compared how LDL from FDB heterozygotes competed with normal 125I-labelled LDL for binding to LDL-receptors while on and off therapy with simvastatin. The LDL of FDB heterozygotes had 40% (n = 10) the affinity of normal LDL (n = 12) for the LDL receptor on cultured fibroblasts, and 55% (n = 6) of normal LDL (n = 6) for that on HepG2 cells. Treatment of FDB subjects with simvastatin (n = 10) decreased serum LDL by 22% but had no effect on its binding affinity for LDL receptors, indicative of lowering of LDL containing both normal and defective apo B. This is consistent with the major LDL lowering effect being associated with decreased synthesis of LDL, rather than enhanced LDL-receptor clearance.

Angiotensin-converting enzyme and apolipoprotein E genotypes and restenosis after coronary angioplasty

BACKGROUND

An insertion/deletion (I/D) polymorphism in the gene for angiotensin-converting enzyme (ACE) has been associated with myocardial infarction and other cardiac pathology. There is evidence for a role of the renin-angiotensin system in cell growth and in the repair of damaged arterial walls, so the ACE gene was postulated to be a candidate gene affecting the important clinical problem of restenosis after percutaneous transluminal balloon coronary angioplasty (PTCA). Because restenosis is influenced by the apolipoprotein E (apoE) genotype, the possibility of a relation between ACE and apoE genotypes and restenosis was also sought.

METHODS AND RESULTS

Subjects (< 70 years of age) were prospectively followed and had coronary angiography 6 months after PTCA to determine the presence or absence of restenosis. Those who had angiography earlier and did not have restenosis (> or = 50% loss of gain at PTCA plus > or = 50% luminal diameter stenosis) also had angiography at 6 months. The whole group (n = 207) had a higher DD genotype frequency than did 136 population control subjects (38% versus 26%, P < .02); in PTCA patients, the frequency was the same in those with and without prior myocardial infarction. The distribution of ACE genotypes was not different in the 88 patients with and 119 patients without restenosis, while the epsilon 4/4 genotype was more frequent in those with restenosis (8 of 88 versus 3 of 118, P < .05). There was no effect of the ACE genotype in noncarriers of the epsilon 4 allele, but there was a significant effect in epsilon 4 carriers (P < .005). The combined D and epsilon 4 carrier state showed a 16-fold increase in the odds ratio for restenosis (P < .02). Multiple linear regression examining the loss of lumen as a continuous variable showed significant independent effects of the ACE and apoE genotypes.

CONCLUSIONS

Overall, the ACE genotype had no clear influence on restenosis, but there was an interaction between ACE and apoE genotypes. The combined carrier state for the D and apoE epsilon 4 alleles substantially increased restenosis. For loss of lumen as a continuous variable, there were significant effects of both ACE and apoE genotypes. While the observations may not affect current management, they no doubt have implications in pathophysiology.

Apolipoprotein epsilon 4 homozygosity--a determinant of restenosis after coronary angioplasty

Conventional coronary risk factors have not consistently been found to be related to restenosis after coronary angioplasty. Apolipoprotein E (apo E) gene polymorphism and/or plasma apo(a) levels were determined in 195 subjects undergoing prospective follow up and angiographic study 6 months after elective balloon angioplasty of a previously untreated coronary obstruction. Restenosis (stenosis > or = 50% plus loss of > or = 50% of initial gain) had occurred in 59 of 150 subjects for whom E genotypes were available. The apo epsilon 4 allele frequency in those with restenosis was higher than those without (0.20 vs. 0.10, P < 0.01), attributable to an excess of epsilon 4 homozygotes in the restenosis group (5 of 59 vs. 1 of 91, P < 0.04). Restenosis was not related to plasma apo(a) and the apo epsilon 4 allele was not associated with elevated levels of apo(a) as has been reported elsewhere. No relationship was found between E genotype and serum lipid and lipoprotein levels; paradoxically, LDL cholesterol was significantly lower and HDL cholesterol higher in those with restenosis. In conclusion, homozygosity for apolipoprotein epsilon 4 appears to be an important determinant of restenosis after coronary angioplasty.

Urine albumin excretion in healthy subjects

The relationship between cardiovascular risk factors and urine albumin excretion were studied in 474 healthy office workers. Albumin concentration was measured fresh in first morning midstream urines. Lifestyle details, oscillometric BP and lipids were assessed. Subjects with urine albumin concentration above the median (5.30 mg/l) were compared with those with albumin concentration below the median. Subjects with above median urinary albumin concentration had higher systolic blood pressure (mean 115.2 vs. 113.1 mm Hg for above median, respectively, P = 0.06), were more likely to be male (56.8 vs. 45.0%, respectively, P = 0.01) and to have lower levels of high density lipoprotein (HDL)-cholesterol (mean 1.34 vs. 1.41 mmol/l, P = 0.006). Multivariate analysis following adjustment for urine creatinine concentration to allow for urine volume confirmed the relationship with systolic blood pressure (P = 0.01) and sex (P = 0.02), and in addition revealed a relationship with alcohol intake approaching significance (mean intake 70.8 and 76.0 g/week, respectively, P = 0.06). The univariate finding of increased albuminuria with lower HDL-cholesterol appeared to be attributable to the associated relationships with male sex and lower alcohol intake. The relationships between albumin excretion and BP, male sex and alcohol intake may reflect the effects of asymptomatic developing arterial disease. The relationship with BP may also be a consequence of effects on glomerular hydrostatic or interstitial renal pressure on albumin filtration or resorption. Very low level urine albumin excretion in healthy subjects is associated with factors which predict arterial disease. Urine albumin excretion may prove to be a useful early marker of cardiovascular disease in population studies.

A robust strategy for screening and confirmation of familial defective apolipoprotein B-100

The diagnosis of familial defective apolipoprotein B-100 (FDB) has been facilitated by the use of mutagenic polymerase chain reaction (PCR) primers to introduce restriction sites at the FDB gene locus. We describe a two-test strategy for diagnosing FDB that overcomes the potential for error in single-test methods based on such techniques. We introduce an Sau96I restriction site for PCR products of the normal apolipoprotein B allele. Incomplete digestion of the PCR product with Sau96I suggests an FDB heterozygote, although a false-positive result due to nonideal digestion conditions remains a possibility. In such cases we use a second test that introduces an ScaI restriction site in PCR products of the FDB allele. The diagnosis is confirmed if half of this product can be digested with ScaI. Both tests use 0.25 units of Taq polymerase and are robust with respect to annealing temperature (31-58 degrees C) and to Mg2+ concentration (1.0-3.2 mmol/L).

A robust strategy for screening and confirmation of familial defective apolipoprotein B-100

The diagnosis of familial defective apolipoprotein B-100 (FDB) has been facilitated by the use of mutagenic polymerase chain reaction (PCR) primers to introduce restriction sites at the FDB gene locus. We describe a two-test strategy for diagnosing FDB that overcomes the potential for error in single-test methods based on such techniques. We introduce an Sau96I restriction site for PCR products of the normal apolipoprotein B allele. Incomplete digestion of the PCR product with Sau96I suggests an FDB heterozygote, although a false-positive result due to nonideal digestion conditions remains a possibility. In such cases we use a second test that introduces an ScaI restriction site in PCR products of the FDB allele. The diagnosis is confirmed if half of this product can be digested with ScaI. Both tests use 0.25 units of Taq polymerase and are robust with respect to annealing temperature (31-58 degrees C) and to Mg2+ concentration (1.0-3.2 mmol/L).

Apolipoprotein epsilon 4 homozygosity in young men with coronary heart disease

We have compared apolipoprotein E gene polymorphism in 91 Australian men aged 30-50 who had been referred for coronary angioplasty and in 172 healthy younger men. 5 of the 19 patients who were less than 40 years of age were homozygous for the epsilon 4 allele, representing a 16-fold increase in prevalence compared with controls. In patients aged 40-50 the epsilon 4 allele frequency was 60% higher than it was in controls. Inheritance of epsilon 4 seems to confer risk of premature ischaemic heart disease in males, homozygotes being especially at risk at a younger age.