Objectives To clarify the role of granzyme B in acute coronary syndrome.
Design and Setting Granzyme B is a member of the serine esterase family released from cytotoxic lymphocytes and plays an important role in cellular apoptosis by activating intracellular caspases. We compared the granzyme B expression between patients with stable and unstable angina pectoris (UAP).
Patients We enrolled 173 patients with coronary artery disease (CAD). We found 84 patients with stable angina pectoris (SAP) and 89 patients with UAP.
Methods Peripheral blood was drawn from the patients. Peripheral blood mononuclear cells (PBMCs) isolated by gradient centrifugation were cultured at a density of 2 X 106 cells/mL for 24 hours. The supernatants were collected 24 hours after incubation and the granzyme B level was measured by enzyme-linked immunosorbent assay. Polychromic flow cytometric analysis was performed to evaluate the expression of granzyme B in the cells.
Results Granzyme B production from PBMCs of UAP patients was significantly higher than those in patients with SAP (39.1±6.6 versus 17.0±1.8 pg/mL, p<0.05). Granzyme B production from PBMCs increased with the increasing TIMI risk score in UAP patients. The percentage of granzyme B-positive lymphocytes to CD3-positive lymphocytes in UAP patients was significantly higher than in SAP (32.1±1.6% versus 18.4±0.9%, p<0.01).
Conclusions These results suggest that granzyme B might play an important role in triggering acute coronary events by inducing apoptosis and the degradation of atherosclerotic coronary plaques.
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Granzyme B expression in ruptured coronary plaques
Panel A: Figure shows the representative expression of granzyme B in ruptured coronary plaques obtained from a patient with unstable angina. Green fluorescence indicates granzyme B expression and blue fluorescence with 4,6-diamino-2-phenylindole (DAPI) demonstrates nuclear staining. Granular distribution of fluorescein isothiocyanate (FITC)-labeled granzyme B in mononuclear cells was observed.
Panel B: Positive control for granzyme B expression. Phorbol 12-myristate 13-acetate-stimulated peripheral blood mononuclear cells were stained with FITC-labeled anti-granzyme B antibody and DAPI.
Left panel: merged image stained with FITC-labeled granzyme B and DAPI. Right panel: the image stained with FITC-labeled granzyme B alone. Yellow arrows indicate FITC-labeled granzyme B in the cells.
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