Involvement of Nox2 NADPH oxidase in adverse cardiac remodeling after myocardial infarction

Oxidative stress plays an important role in the development of cardiac remodeling after myocardial infarction (MI), but the sources of oxidative stress remain unclear. We investigated the role of Nox2-containing reduced nicotinamide-adenine dinucleotide phosphate oxidase in the development of cardiac remodeling after MI. Adult Nox2(-/-) and matched wild-type (WT) mice were subjected to coronary artery ligation and studied 4 weeks later. Infarct size after MI was similar in Nox2(-/-) and WT mice. Nox2(-/-) mice exhibited significantly less left ventricular (LV) cavity dilatation and dysfunction after MI than WT mice (eg, echocardiographic LV end-diastolic volume: 75.7+/-5.8 versus 112.4+/-12.3 microL; ejection fraction: 41.6+/-3.7 versus 32.9+/-3.2%; both P<0.05). Similarly, in vivo LV systolic and diastolic functions were better preserved in Nox2(-/-) than WT mice (eg, LV dP/dt(max): 7969+/-385 versus 5746+/-234 mm Hg/s; LV end-diastolic pressure: 12.2+/-1.3 versus 18.0+/-1.8 mm Hg; both P<0.05). Nox2(-/-) mice exhibited less cardiomyocyte hypertrophy, apoptosis, and interstitial fibrosis; reduced increases in expression of connective tissue growth factor and procollagen 1 mRNA; and smaller increases in myocardial matrix metalloproteinase-2 activity than WT mice. These data suggest that the Nox2-containing reduced nicotinamide-adenine dinucleotide phosphate oxidase contributes significantly to the processes underlying adverse cardiac remodeling and contractile dysfunction post-MI.

Peripheral augmentation index defines the relationship between central and peripheral pulse pressure

Peripheral systolic blood pressure is amplified above central aortic systolic pressure, but the late systolic shoulder of the peripheral pulse may approximate central systolic pressure. Because late systolic pressure also determines the peripheral augmentation index, a measure of pressure wave reflection within the systemic circulation, this implies a direct relationship between amplification and augmentation. We compared the late systolic shoulder of the peripheral pressure waveform with estimates of central systolic pressure obtained using a transfer function in 391 subjects undergoing diagnostic coronary angiography and/or elective angioplasty (30% with insignificant coronary artery disease). In a subset (n=12) we compared the late systolic shoulder of the peripheral pulse with central pressure obtained with a catheter placed in the aortic root. Measurements were made at baseline, during atrial pacing, and during administration of nitroglycerin. Late systolic shoulder pressure closely approximated transfer function estimates of central pressure (R=0.96; P<0.0001; mean difference+/-SD: 0.5+/-5.2 mm Hg). Despite changes in waveform morphology induced by pacing and nitroglycerin (reducing mean values+/-SE of the augmentation index from 76+/-3.8% to 66+/-4.6% and 60+/-3.3%, respectively), there was close agreement between the late systolic shoulder of the peripheral pulse and measured values of central pressure (R=0.96; P<0.001; mean difference: 1.7+/-4.8 mm Hg). In conclusion, the late systolic shoulder of the peripheral pulse closely approximates central systolic pressure and peripheral augmentation index, the ratio of central:peripheral pulse pressure. Interventions to lower augmentation index and peripheral vascular resistance will have multiplicative effects in lowering central blood pressure.

The immune responses to human and microbial heat shock proteins in periodontal disease with and without coronary heart disease

The human 60 kDa and microbial 65 kDa heat shock proteins (HSP) have been implicated in the pathogenesis of chronic periodontitis (P) and coronary heart disease (CHD). We have studied four male non-smoking cohorts of 81 subjects, matched for age. Group (a) consisted of a healthy group with minimal gingivitis (n = 18), group (b) were patients with P (n = 23), group (c) patients with CHD and minimal gingivitis (n = 20) and group (d) patients with CHD and P (n = 20). T cells separated from peripheral blood were found to be primed to both microbial HSP65 and human HSP60 but significant CD4, human leucocyte antigen (HLA) class II-restricted proliferative responses were found only with the human HSP60 in patients with P (P < 0.001) and CHD without (P < 0.001) or with (P < 0.00001) periodontitis. Dose-dependent inhibition of T cell proliferative responses was carried out to determine the receptors involved in recognition of HSP60 and HSP65. Monoclonal antibodies to CD14 showed inhibition of T cell proliferation stimulated by both HSP60 and HSP65, consistent with the role of CD14 as a receptor for these HSPs in P and CHD. The toll-like receptor 2 (TLR-) and TLR-4 were then studied and these showed that TLR-4 was recognized by microbial HSP65, whereas TLR-2 was recognised by human HSP60 in both P and CHD. However, a dissociation was found in the HSP60 and TLR4 interaction, as TLR4 appeared to have been recognized by HSP60 in P but not in CHD. The results suggest an autoimmune or cross-reactive CD4(+) class II-restricted T cell response to the human HSP60 in P and CHD. Further studies are required to determine if there is a common epitope within HSP60 that stimulates T cell proliferation in P and CHD.

Does a well developed collateral circulation predispose to restenosis after percutaneous coronary intervention? An intravascular ultrasound study

OBJECTIVE

To evaluate whether a well developed collateral circulation predisposes to restenosis after percutaneous coronary intervention (PCI).

DESIGN

Prospective observational study.

PATIENTS AND SETTING

58 patients undergoing elective single vessel PCI in a tertiary referral interventional cardiac unit in the UK.

METHODS

Collateral flow index (CFI) was calculated as (Pw-Pv)/(Pa-Pv), where Pa, Pw, and Pv are aortic, coronary wedge, and right atrial pressures during maximum hyperaemia. Collateral supply was considered poor (CFI < 0.25) or good (CFI > or = 0.25).

MAIN OUTCOME MEASURES

In-stent restenosis six months after PCI, classified as neointimal volume > or = 25% stent volume on intravascular ultrasound (IVUS), or minimum lumen area < or = 50% stent area on IVUS, or minimum lumen diameter < or = 50% reference vessel diameter on quantitative coronary angiography.

RESULTS

Patients with good collaterals had more severe coronary stenoses at baseline (90 (11)% v 75 (16)%, p < 0.001). Restenosis rates were similar in poor and good collateral groups (35% v 43%, p = 0.76 for diameter restenosis, 27% v 45%, p = 0.34 for area restenosis, and 23% v 24%, p = 0.84 for volumetric restenosis). CFI was not correlated with diameter, area, or volumetric restenosis (r2 < 0.1 for each). By multivariate analysis, stent diameter, stent length, > 10% residual stenosis, and smoking history were predictive of restenosis.

CONCLUSION

A well developed collateral circulation does not predict an increased risk of restenosis after PCI.

Progressive decrease in chaperone protein levels in a mouse model of Huntington's disease and induction of stress proteins as a therapeutic approach

The manipulation of chaperone levels has been shown to inhibit aggregation and/or rescue cell death in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster and cell culture models of Huntington's disease (HD) and other polyglutamine (polyQ) disorders. We show here that a progressive decrease in Hdj1, Hdj2, Hsp70, alphaSGT and betaSGT brain levels likely contributes to disease pathogenesis in the R6/2 mouse model of HD. Despite a predominantly extranuclear location, Hdj1, Hdj2, Hsc70, alphaSGT and betaSGT were found to co-localize with nuclear but not with extranuclear aggregates. Quantification of Hdj1 and alphaSGT mRNA levels showed that these do not change and therefore the decrease in protein levels may be a consequence of their sequestration to aggregates, or an increase in protein turnover, possibly as a consequence of their relocation to the nucleus. We have used genetic and pharmacological approaches to assess the therapeutic potential of chaperone manipulation. Ubiquitous overexpression of Hsp70 in the R6/2 mouse (as a result of crossing to Hsp70 transgenics) delays aggregate formation by 1 week, has no effect on the detergent solubility of aggregates and does not alter the course of the neurological phenotype. We used an organotypic slice culture assay to show that pharmacological induction of the heat shock response might be a more useful approach. Radicicol and geldanamycin could both maintain chaperone induction for at least 3 weeks and alter the detergent soluble properties of polyQ aggregates over this time course.

A model of closed chest regional myocardial infarction in the rabbit: a clinically relevant in vivo assay system of post-infarction remodelling

Coronary artery ligation is the standard technique to induce regional myocardial infarction in small animal models. However, opening the chest and incising the pericardium independently influence post-MI remodelling. Our purpose was to develop and characterize a novel closed chest model of regional myocardial infarction (MI) in the rabbit of increased clinical relevance. Coronary angiography was performed percutaneously in New Zealand White Rabbits (NZW) using pre-formed catheters. A 0.36 mm thrombogenic coil was positioned in the circumflex artery to induce closed chest MI. Of rabbits undergoing coil deployment 40 % survived until day 100. Rabbits were classified as small MI (n = 5), moderate MI (n = 6) and large MI (n = 6) < 15 %, 15 - 30 %, > 30 % of LV myocardial volume respectively) or sham controls (n=11). Transthoracic echocardiographic images were obtained 0, 3, 5, 7, 14, 28, 60, 100 days post procedure. At day 100, LVEDP was measured before and after plasma substitute infusion. Hearts were subsequently excised and chamber stiffness (Kc) was derived from the passive pressure-volume relationship. Cardiac weight, dimensions and MI as a percentage of LV volume (MI%) were also recorded. Differences in percentage fractional shortening (%FS) were apparent from day 14. %FS was reduced in rabbits with large and moderate MI compared to controls (day 100, p < 0.005 and p < 0.05, respectively). LVEDP was increased in large and moderate MI compared to small MI and controls (26 mmHg +/- 6 and 21 mmHg +/- 5 vs. 9 mmHg +/- 1 and 7 mmHg +/- 3 p < 0.005); these differences were maintained during plasma substitute infusion. Kc in large MI was significantly less than moderate MI, small MI or control (all p < 0.05). Direct morphometric measurements distinguished between all groups.This study provides the first description of post-infarction remodelling after coronary artery occlusion where the pericardium remains intact in a small animal model. We believe it may provide a more physiologically and clinically relevant in vivo assay system of left ventricular dysfunction after myocardial infarction.

Glycoprotein IIb/IIIa antagonists: do they have a role in the management of unstable angina?

Plaque rupture, platelet aggregation and thrombosis have central roles in the pathogenesis of acute coronary syndromes. Despite several trials showing the benefit of aspirin and heparin in patients presenting with unstable angina and acute myocardial infarction, these patients are still at risk. This has prompted the development and evaluation of several new therapeutic agents including low molecular weight heparin, new antiplatelet drugs (e.g. ticlopidine and clopidogrel), direct thrombin inhibitors, and intravenous and oral glycoprotein IIb/IIIa antagonists. The IIb/IIIa receptor is the final common pathway involved in platelet aggregation. Thus, whatever the stimulus for platelet activation, subsequent aggregation is mediated by the IIb/IIIa receptor binding fibrinogen. A variety of antibody, peptide and non-peptide compounds that block the IIb/IIIa receptor have been developed, and several studies have investigated the role of these agents in patients with acute coronary syndromes both within and outside the setting of percutaneous intervention. This article summarises the studies to date using IIb/IIIa antagonists, and discusses their role in patients with non-ST segment elevation acute coronary syndromes.

Delay to invasive investigation and revascularisation for coronary heart disease in south west Thames region: a two tier system?

OBJECTIVES

To assess the accessibility of invasive investigation and revascularisation procedures in the management of coronary heart disease in a defined population in the South West Thames region over 10 years, and to audit the performance of both the NHS and the private sector.

DESIGN

Analysis of all patient referrals to the regional cardiothoracic centres for coronary heart disease during 1979-88.

SETTING

North West Surrey District Health Authority, which had a mean catchment population of 205,000 during the study period. The health district is one of the 13 in the South West Thames region.

PATIENTS

823 patients aged 34-80 years with suspected coronary heart disease, 204 of whom were referred for private investigation and 619 were referred within the NHS. The NHS referrals were mainly to St Thomas's Hospital during 1979-83 and to St George's Hospital during 1984-8.

MAIN OUTCOME MEASURES

Difference in time to investigation and intervention between the NHS and the private patients.

RESULTS

After some variation in earlier years the mean (SD, range) waiting times from referral to cardiac catheterisation and then revascularisation increased progressively in NHS patients, to 115.8 (126.5, 22-482) days and 305.9 (164.4, 22-620) days respectively in 1988. There was no significant change over the 10 years in waiting times within the private sector, with a mean of 17.2 (18.2, 1-62) days to angiography and 22.8 (14.5, 2-152) days to surgery. Fifteen people on the NHS waiting list died of probable cardiac causes. No people on the private waiting list died.

CONCLUSIONS

The performance of the NHS system in South West Thames region in response to emergency referral is adequate. The waiting time to routine investigation and revascularisation is prolonged and seems to be worsening despite increased investigative and surgical activity by the regional centre. The delays may subject NHS patients to unnecessary risk, which is not shared by private patients.