Abstract 15718: Disruption of Natural Killer T Cells Ameliorates Myocardial Ischemia Reperfusion Injury in Mice
Background: Invariant natural killer T (iNKT) cells are involved in tissue inflammation via production of pro-inflammatory cytokines, such as interferon-γ (IFN-γ). It has been reported that IFN-γ has deleterious effects on myocardial ischemic reperfusion injury (I/R). However, no previous studies have examined the pathophysiological role of iNKT cells in myocardial I/R injury.
Methods and Results: A 45 min occlusion of the left coronary artery followed by 24 hour reperfusion (I/R) or sham operation was performed in wild-type (WT) and iNKT cell knockout (KO) mice (WT+sham, n=8, WT+I/R, n=11, KO+sham, n=8, KO+I/R, n=13). The number of iNKT cells, evaluated by flow cytometric analysis, was increased by 3-fold in ischemic myocardium from WT+I/R. As expected, iNKT cells were not detected in KO mice. Infarct size/area at risk was significantly smaller in KO+I/R than WT+I/R mice (33.9±1.8 vs 45.7±2.7 %, P<0.05), with no significant changes in area at risk. Consistent with the changes in infarct size, serum troponin-I was lower in KO+I/R than in WT+I/R mice (3.0±0.9 vs 7.4±1.0, P<0.05). The number of infiltrating myeloperoxidase and CD3 positive cells were also lower in KO+I/R than WT+I/R mice (MPO: 9.1±1.8 vs 17.6±3.3 cells/high power field (HPF), P<0.05 and CD3: 13.7±2.6 vs 36.3±7.6 cells/HPF, P<0.05). The number of TUNEL-positive myocyte and caspase-3 levels were significantly lower in the ischemic area from KO+I/R compared to WT+I/R. IFN-γ gene expression was significantly increased by 3-fold in WT+I/R compared to WT+sham , which was not observed in KO+I/R. To clarify the role of IFN-γ, iNKT cells were extracted from WT and IFN-γ-deficient mice, and reconstitution of these cells (1.0х106 in a volume of 200μL) to KO mice was performed by injection from caudal vein 1day before I/R. Adoptive transfer of iNKT cells extracted from WT mice to iNKT cells KO mice significantly increased infarct size/area at risk (31.2±2.3 vs 46.0±4.5%, P<0.05) whereas cells extracted from IFN-γ-deficient mice did not (31.2±2.3 vs 36.3±4.8%).
Conclusions: Disruption of iNKT cells ameliorated myocardial I/R injury in mice. iNKT cells have deleterious effects on the development of I/R injury in the heart, possibly through enhanced expression of IFN-γ and subsequent induction of apoptosis.
- © 2013 by American Heart Association, Inc.