Inhibition of PARP1 improves cardiac function after myocardial infarction via up-regulated NLRC5.

The incidence and mortality rate of myocardial infarction are increasing per year in China. The polarization of macrophages towards the classically activated macrophages (M1) phenotype is of utmost importance in the progression of inflammatory stress subsequent to myocardial infarction. Poly (ADP-ribose) polymerase 1(PARP1) is the ubiquitous and best characterized member of the PARP family, which has been reported to support macrophage polarization towards the pro-inflammatory phenotype. Yet, the role of PARP1 in myocardial ischemic injury remains to be elucidated. Here, we demonstrated that a myocardial infarction mouse model induced cardiac damage characterized by cardiac dysfunction and increased PARP1 expression in cardiac macrophages. Inhibition of PARP1 by the PJ34 inhibitors could effectively alleviate M1 macrophage polarization, reduce infarction size, decrease inflammation and rescue the cardiac function post-MI in mice. Mechanistically, the suppression of PARP1 increase NLRC5 gene expression, and thus inhibits the NF-κB pathway, thereby decreasing the production of inflammatory cytokines such as IL-1ß and TNF-α. Inhibition of NLRC5 promote infection by effectively abolishing the influence of this mechanism discussed above. Interestingly, inhibition of NLRC5 promotes cardiac macrophage polarization toward an M1 phenotype but without having major effects on M2 macrophages. Our results demonstrate that inhibition of PARP1 increased NLRC5 gene expression, thereby suppressing M1 polarization, improving cardiac function, decreasing infarct area and attenuating inflammatory injury. The aforementioned findings provide new insights into the proinflammatory mechanisms that drive macrophage polarization following myocardial infarction, thereby introducing novel potential targets for future therapeutic interventions in individuals affected by myocardial infarction.

Macrophage-NLRP3 Inflammasome Activation Exacerbates Cardiac Dysfunction after Ischemic Stroke in a Mouse Model of Diabetes.

Ischemic stroke is one of the leading causes of death worldwide. In the post-stroke stage, cardiac dysfunction is common and is known as the brain-heart interaction. Diabetes mellitus worsens the post-stroke outcome. Stroke-induced systemic inflammation is the major causative factor for the sequential complications, but the mechanism underlying the brain-heart interaction in diabetes has not been clarified. The NLRP3 (NLR pyrin domain-containing 3) inflammasome, an important component of the inflammation after stroke, is mainly activated in M1-polarized macrophages. In this study, we found that the cardiac dysfunction induced by ischemic stroke is more severe in a mouse model of type 2 diabetes. Meanwhile, M1-polarized macrophage infiltration and NLRP3 inflammasome activation increased in the cardiac ventricle after diabetic stroke. Importantly, the NLRP3 inflammasome inhibitor CY-09 restored cardiac function, indicating that the M1-polarized macrophage-NLRP3 inflammasome activation is a pathway underlying the brain-heart interaction after diabetic stroke.