Protective effect of doxycycline use on coronary artery disease?

The effect of prolonged systemic doxycycline therapy on serum tissue degrading proteinases in coronary bypass patients: a randomized, double-masked, placebo-controlled clinical trial

OBJECTIVE

Serum matrix metalloproteinases (MMP-8, MMP-7) and their regulators may be associated with the risk of incident cardiovascular disease events. Doxycycline can be used as matrix metalloproteinase (MMP) inhibitor independent of its antimicrobial activity. We aimed to investigate serum inflammatory biomarkers during 4 months of doxycycline therapy in coronary bypass patients.

MATERIALS AND METHODS

Thirty-one non-smoking men who had previous coronary bypass surgery were randomly assigned to receive placebo or 100 mg doxycycline daily for 4 months. Serum samples were collected at baseline before the treatment, and at 2, 4, and 10 months. Serum levels of MMP-7, tissue inhibitor of matrix metalloproteinase (TIMP)-1, myeloperoxidase, and neutrophil elastase were analyzed with enzyme-linked immunosorbent assay, MMP-8 by immunofluorometric assay, and C-reactive protein by rate nephelometry.

RESULTS

At baseline, no significant differences existed between the two groups. Serum levels of MMP-8, MMP-7, and MMP-8/TIMP-1 were and remained lower (p = 0.034, p = 0.041, and NS) in the doxycycline group relative to the placebo group at 4 months of follow-up.

CONCLUSIONS

Doxycycline decreases the systemic inflammatory burden in patients with myocardial infarction and especially down-regulates MMP-7, MMP-8, and MMP-8/TIMP-1. Doxycycline might prevent or reduce the risk of secondary myocardial infarctions by providing a systemic anti-proteolytic and -inflammatory shield.

Activator protein-1 (AP-1) signalling in human atherosclerosis: results of a systematic evaluation and intervention study

Animal studies implicate the AP-1 (activator protein-1) pro-inflammatory pathway as a promising target in the treatment of atherosclerotic disease. It is, however, unclear whether these observations apply to human atherosclerosis. Therefore we evaluated the profile of AP-1 activation through histological analysis and tested the potential benefit of AP-1 inhibition in a clinical trial. AP-1 activation was quantified by phospho-c-Jun nuclear translocation (immunohistochemistry) on a biobank of aortic wall samples from organ donors. The effect of AP-1 inhibition on vascular parameters was tested through a double blind placebo-controlled cross-over study of 28 days doxycycline or placebo in patients with symptomatic peripheral artery disease. Vascular function was assessed by brachial dilation as well as by plasma samples analysed for hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-8, ICAM-1 (intercellular adhesion molecule-1), vWF (von Willebrand factor), MCP-1 (monocyte chemoattractant protein-1), PAI-1 (plasminogen activator inhibitor-1) and fibrinogen. Histological evaluation of human atherosclerosis showed minimal AP-1 activation in non-diseased arterial wall (i.e. vessel wall without any signs of atherosclerotic disease). A gradual increase of AP-1 activation was found in non-progressive and progressive phases of atherosclerosis respectively (P<0.044). No significant difference was found between progressive and vulnerable lesions. The expression of phospho-c-Jun diminished as the lesion stabilized (P<0.016) and does not significantly differ from the normal aortic wall (P<0.33). Evaluation of the doxycycline intervention only revealed a borderline-significant reduction of circulating hs-CRP levels (-0.51 μg/ml, P=0.05) and did not affect any of the other markers of systemic inflammation and vascular function. Our studies do not characterize AP-1 as a therapeutic target for progressive human atherosclerotic disease.

Potential implications of matrix metalloproteinase-9 in assessment and treatment of coronary artery disease

BACKGROUND

Matrix metalloproteinase (MMP)-9, a member of the MMP superfamily is consistently implicated in the pathophysiology of atherosclerosis and plaque rupture, the most common mechanism responsible for acute coronary syndrome (ACS).

AIM

To summarize the role of MMP-9 in atherosclerosis and its potential implications in assessment and treatment of coronary artery disease (CAD).

METHODS

We reviewed the PubMed database for relevant data regarding the role of MMP-9 in the pathophysiology of atherosclerosis. In the light of these data, we postulate potential implications of MMP-9 in the management and treatment of CAD.

RESULTS AND CONCLUSIONS

Existing data strongly support the role of MMP-9 in plaque destabilization and rupture. Based on the current knowledge, MMP-9 can potentially serve as a diagnostic biomarker in ACS and a prognostic biomarker in ACS and chronic CAD patients. MMP-9 is reduced by therapies that are associated with favourable outcome in atherosclerosis and thus may serve as a surrogate biomarker of treatment efficacy. However, large morbidity and mortality trials are still required to confirm that MMP-9 reduction is associated with improved outcome independent of the traditional risk factors (i.e. low-density lipoprotein cholesterol). Given its role in plaque rupture, inhibition of MMP-9 may promote plaque stabilization and consequently reduce cardiovascular events. Yet, the efficacy and safety of MMPs inhibitors should be first studied in preclinical models of atherosclerosis.