Abstract
Neutrophils are not only involved in immune defense against infection but also contribute to the exacerbation of tissue damage after ischemia and reperfusion. We have previously shown that genetic ablation of regulatory Gα(i) proteins in mice has both protective and deleterious effects on myocardial ischemia reperfusion injury (mIRI), depending on which isoform is deleted. To deepen and analyze these findings in more detail the contribution of Gα(i2) proteins in resident cardiac vs circulating blood cells for mIRI was first studied in bone marrow chimeras. In fact, the absence of Gα(i2) in all blood cells reduced the extent of mIRI (22,9% infarct size of area at risk (AAR) Gnai2(-/-) → wt vs 44.0% wt → wt; p < 0.001) whereas the absence of Gα(i2) in non-hematopoietic cells increased the infarct damage (66.5% wt → Gnai2(-/-) vs 44.0% wt → wt; p < 0.001). Previously we have reported the impact of platelet Gα(i2) for mIRI. Here, we show that infarct size was substantially reduced when Gα(i2) signaling was either genetically ablated in neutrophils/macrophages using LysM-driven Cre recombinase (AAR: 17.9% Gnai2(fl/fl) LysM-Cre(+/tg) vs 42.0% Gnai2(fl/fl); p < 0.01) or selectively blocked with specific antibodies directed against Gα(i2) (AAR: 19.0% (anti-Gα(i2)) vs 49.0% (IgG); p < 0.001). In addition, the number of platelet-neutrophil complexes (PNCs) in the infarcted area were reduced in both, genetically modified (PNCs: 18 (Gnai2(fl/fl); LysM-Cre(+/tg)) vs 31 (Gnai2(fl/fl)); p < 0.001) and in anti-Gα(i2) antibody-treated (PNCs: 9 (anti-Gα(i2)) vs 33 (IgG); p < 0.001) mice. Of note, significant infarct-limiting effects were achieved with a single anti-Gα(i2) antibody challenge immediately prior to vessel reperfusion without affecting bleeding time, heart rate or cellular distribution of neutrophils. Finally, anti-Gα(i2) antibody treatment also inhibited transendothelial migration of human neutrophils (25,885 (IgG) vs 13,225 (anti-Gα(i2)) neutrophils; p < 0.001), collectively suggesting that a therapeutic concept of functional Gα(i2) inhibition during thrombolysis and reperfusion in patients with myocardial infarction should be further considered.