Abstract 2668: Critical Role of Granzyme B in Left Ventricular Remodeling after Acute Myocardial Infarction

Abstract

Background: Granzyme B is a member of the serine esterase family produced by cytotoxic T lymphocytes (CTLs), and has an important role in cellular apoptosis and extracellular matrix degradation. We hypothesized that granzyme B is involved in left ventricular (LV) remodeling after acute myocardial infarction (AMI). Objectives: To elucidate the role of granzyme B in LV remodeling after AMI. Subjects and methods: We employed 41 patients with the first AMI (mean age: 61.9±8.9 years old). We obtained peripheral blood on day 1, day 7 and day 14 after onset. Plasma levels of apoptosis-related molecules, including tumor necrosis factor α (TNFα), a soluble form of the Fas ligand (sFasL) and granzyme B were measured. We checked the activation of CTLs by flow cytometry. Patients were treated by percutaneous coronary intervention within 12 hours after onset. Successful myocardial reperfusion (TIMI flow grade 2 or 3) was accomplished in all patients. LV end-diastolic volume index (LVEDVI) was calculated on day 1 and 6 months after onset. Results: Plasma levels of TNFα, sFasL and granzyme B increased significantly after the onset of AMI (TNFα; day 1: 1.6±0.47, day 7: 3.3±0.65, day14: 4.0±1.2 pg/ml, p<0.05, sFasL; day 1: 72±5.2, day 7: 86±6.7, day14: 95±7.3 pg/ml, p<0.05, granzyme B; day 1: 63±18.4, day 7: 283±57.8, day14: 210.9±46.3 pg/ml, p<0.001). The percentage of CD69± to CD3+ CD8+ lymphocytes was significantly increased (CD69+/CD3+ CD8+; day 1: 14.5±1.7, day 7: 15.8±1.2, day 14: 19.1±1.4%, p<0.05), suggesting that CTLs were activated after onset. Univariate regression analysis showed a significant positive correlation between plasma granzyme B level on day 14 and fold-increase in LVEDVI (r=+0.45, p<0.01). No significant correlation was observed between TNFα and changes in LVEDVI, or sFasL and changes in LVEDVI. Stepwise multivariate regression analysis showed that the plasma granzyme B level on day 14 is a significant explanatory variable for changes in LVEDVI (β = +0.53, p<0.001). Conclusions: These results first indicate that among proapoptic molecules, granzyme B has a critical role in the progression of LV remodeling after AMI.