Targeting Gαi2 in neutrophils protects from myocardial ischemia reperfusion injury.

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.