a Departments of Medicine and b Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, Japan
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Abstract |
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Introduction |
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Materials and methods |
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Study patients
The in vitro study was undertaken to determine the optimal dose of DOXY administration to suppress PMN activity in the ex vivo study (see below). Owing to the limited availability of blood samples from AMI patients for the in vitro study, we used blood samples obtained from 10 patients with coronary artery disease including angina pectoris and previous myocardial infarction (seven males; mean age 67 ± 8 years, range 5780 years). The freshly drawn sample (total volume 0.1 mL) containing 10 U/mL of heparin was diluted with 0.8 mL of Hank':s balanced salt solution (Gibco-BRL, Gaithersburg, MD, USA). The sample was then mixed with 0.1 mL of 0.9% saline containing various concentrations of DOXY, and assayed for PMN activity as described previously.3,4
For the ex vivo study, blood samples were obtained from 22 patients with AMI. In all 22 patients, direct percutaneous coronary intervention (PCI) was carried out, and procedural success, defined as residual stenosis of <50% without precipitating a major cardiac event, was achieved. Within 30 min after the PCI, intravenous administration of DOXY (100 mg) dissolved in 0.9% saline was carried out for 5 min (total volume of 20 mL; n = 10). The dose of 100 mg of DOXY was chosen because this is the recommended dose for clinical usage, and when 100 mg of DOXY is administered, a maximum blood concentration of 1520 mg/L can be expected, which is within the range that achieves significant reduction of PMN activity in vitro (see Results). Blood samples were obtained at 0, 15, 30 and 60 min after DOXY administration, heparinized, and then diluted as described above. In the control patients (n = 12), saline was administered instead of DOXY.
Measurements of PMN activity
The generation of ROS by PMNs is accompanied by a chemiluminescence (CL) response. Such a CL response can be used as a marker of PMN activation in a variety of pathological conditions including coronary artery diseases.3,4 The CL assay was carried out as described previously.3,4 The CL was monitored for 20 min, and the integrated CL count was calculated. PMN activity was expressed as the percentage of integrated CL count at each concentration (in vitro study) or time point (ex vivo study) divided by the integrated CL count at baseline.
Statistical analyses
All measurements were carried out in duplicate. Continuous variables were expressed as mean ± s.e. Statistical significance was assessed by the unpaired Student':s t-test for comparison of two means, and by ANOVA followed by Scheffe':s procedure for repeated measurements, using the StatView application (SAS Institute Inc., Cary, NC, USA). A value of P < 0.05 was considered to be statistically significant.
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Results |
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At a concentration of 10 mg/L, DOXY induced a significant reduction of PMN activity compared with the baseline level (10 mg/L: 89.2 ± 2.8%, P < 0.005; 15 mg/L: 82.4 ± 2.3%, P < 0.0001; 20 mg/L: 66.0 ± 2.5%, P < 0.0001). Higher concentrations of DOXY were not tested since such range is beyond clinical usage (Figure, a
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The clinical characteristics of the 22 patients with AMI are summarized in the Table. In the control group, PMN activity did not significantly change after saline administration compared with the baseline level (15 min: 106.8 ± 7.4%; 30 min: 112.7 ± 8.7%; 60 min: 113.1 ± 8.3%). In contrast, the patients treated with DOXY showed significant reduction in PMN activity at 30 and 60 min (15 min: 91.8 ± 2.9%, P = NS; 30 min: 87.4 ± 2.7%, P < 0.005; 60 min: 90.0 ± 3.8%, P < 0.05). The PMN activity of the control and DOXY groups differed significantly at 30 and 60 min (P < 0.05 for both) (Figure, b
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Discussion |
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The routine use of tetracyclines such as DOXY and minocycline hydrochloride in patients with coronary artery disease may also have an advantage over other classes of antibiotics in terms of management of Chlamydia pneumoniae infection.6 For example, Gupta et al.7 reported that a short course of azithromycin (3 or 6 days) significantly lowered the incidence of adverse cardiovascular events following AMI. Similarly, Gurfinkel et al.8 reported that 30 day treatment with roxithromycin (RXM) improved the clinical outcome of patients with acute non-Q-wave coronary syndrome. It must be noted that RXM directly inhibited oxidant production by PMNs in vitro.9 Whether similar beneficial effects on clinical outcome can be expected with DOXY remains to be determined.
In summary, the present study demonstrated that suppression of PMN activity could be achieved by a single intravenous administration of DOXY in patients with AMI. DOXY may thus serve as the first-line antibiotic regimen for patients with AMI. Future studies need to clarify whether the use of DOXY improves the clinical outcome of these patients.
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Notes |
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References |
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2 . Ono, Y. & Kunii, O. (1989). Influence of forty-two antimicrobial agents on the chemiluminescence response of human phagocytic cells. Chemotherapy 37, 5839.
3 . Takeshita, S., Isshiki, T., Ochiai, M., Ishikawa, T., Nishiyma, Y., Fusano, T. et al. (1997). Systemic inflammatory responses in acute coronary syndrome: increased activity observed in polymorphonuclear leukocytes but not T lymphocytes. Atherosclerosis 135, 18792.[ISI][Medline]
4 . Takeshita, S., Hashimoto, H., Ono, Y., Ochiai, M., Yokoyama, N., Terakura, M. et al. (2001). Increased leukocyte activity as a predictor for flow-limiting coronary lesions in patients with angina pectoris. Atherosclerosis 158, 47781.[ISI][Medline]
5 . Siegel, J. P. & Remington, J. S. (1982). Effect of antimicrobial agents on chemiluminescence of human polymorphonuclear leukocytes in response to phagocytosis. Journal of Antimicrobial Chemotherapy 10, 50515.[ISI][Medline]
6 . Danesh, J., Collins, R. & Peto, R. (1997). Chronic infections and coronary heart disease: is there a link? Lancet 350, 4306.[ISI][Medline]
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Gupta, S., Leatham, E. W., Carrington, D., Mendall, M. A., Kaski, J. C. & Camm, A. J. (1997). Elevated Chlamydia pneumoniae antibodies, cardiovascular events, and azithromycin in male survivors of myocardial infarction. Circulation 96, 4047.
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Gurfinkel, E., Bozovich, G., Beck, E., Testa, E., Livellara, B. & Maunter, B. (1999). Treatment with antibiotic roxithromycin in patients with acute non-Q-wave coronary syndromes: the final report of ROXIS study. European Heart Journal 20, 1217.
9 . Labro, M. T., el Benna, J. & Babin-Chevaye, C. (1989). Comparison of the in-vitro effect of several macrolides on the oxidative burst of human neutrophils. Journal of Antimicrobial Chemotherapy 24, 56172.[Abstract]
Received 28 August 2001; returned 18 October 2001; revised 20 November 2001; accepted 22 November 2001