VWF-mediated leukocyte recruitment with chromatin decondensation by PAD4 increases myocardial ischemia/reperfusion injury in mice

Innate immune cells play a major role in the early response to myocardial ischemia/reperfusion (MI/R) injury. Recombinant human ADAMTS13 (rhADAMTS13), cleaving von Willebrand factor (VWF), reduces leukocyte recruitment in mice. Death of cardiomyo-cytes and the possible formation of neutrophil extracellular traps (NETs) may result in chromatin release that is prothrombotic and cytotoxic. We investigated the pathophysi-ological role of extracellular chromatin during MI/R to evaluate the therapeutic potential of targeting extracellular DNA and VWF by using DNase I with/without rhADAMTS13. Finally, we examined the impact of histone citrullination and NETosis by peptidylarginine deiminase 4 (PAD4) on MI/R. We used a 24-hour MI/R mouse surgical model. MI/R injury caused an increase in plasma nucleosomes, abundant neutrophil infiltration, and the presence of citrullinated histone H3 at the site of injury. Both monotherapies and coadministration of DNase I and rhADAMTS13 revealed a cardioprotective effect, resulting in subsequent improvement of cardiac contractile function. PAD4^-/- mice, which do not produce NETs, were also significantly protected from MI/R and DNase I treatment had no further beneficial effect. We demonstrate that extra cellular chromatin released through NETosis exacerbates MI/R injury. Targeting both VWF-mediated leukocyte recruitment and chromatin removal may be a new therapeutic strategy to reduce ischemia-related cardiac damage.