Activated protein C protects against myocardial ischemic/reperfusion injury through AMP‐activated protein kinase signaling

Abstract

Summary Background Activated protein C (APC) is a vitamin K-dependent plasma serine protease that down-regulates clotting and inflammatory pathways. It is known that APC exerts a cardioprotective effect by decreasing apoptosis of cardiomyocytes and inhibiting expression of inflammatory mediators after myocardial ischemia. Objectives The objective of this study was to understand the mechanism of the APC-mediated cardioprotection against ischemic injury. Methods Cardioprotective activities of wild-type APC and two derivatives having either dramatically reduced anticoagulant activity or lacking signaling activity were monitored in an acute ischemia/reperfusion injury model in which the left anterior descending coronary artery (LAD) was occluded. Results APC reduced the myocardial infarct size by a mechanism that was largely independent of its anticoagulant activity. Thus, the non-anticoagulant APC-2Cys mutant, but not the non-signaling APC-E170A mutant attenuated myocardial infarct size by EPCR and PAR-1-dependent mechanisms. Further studies revealed that APC acts directly on cardiomyocytes to stimulate the AMP-activated protein kinase (AMPK) signaling pathway. The activation of AMPK by APC ameliorated the post-ischemic cardiac dysfunction in isolated perfused mouse hearts. Moreover, both APC and APC-2Cys inhibited production of TNFα and IL-6 in vivo by attenuating the ischemia/reperfusion-induced JNK and NF-κB signaling pathways. Conclusions APC exerts a cardioprotective function in ischemic/reperfusion injury through modulation of AMPK, NF-κB and JNK signaling pathways.

Cytoprotective activated protein C averts Nlrp3 inflammasome–induced ischemia-reperfusion injury via mTORC1 inhibition

“…Inhibition of mTORC1 by aPC is congruent with AMPK activation (an inhibitor of mTORC1 signaling) by aPC after myocardial infarction. 21 mTORC1 activation in IRI has frequently been observed, 58,59 corroborating a mechanistic relevance of mTORC1 inhibition by aPC. We acknowledge that the role of mTOR signaling in myocardial IRI is complex and depends on its temporal activation pattern, the cell type, the extent of mTOR activity, and the involvement of mTORC1 vs mTORC2.…”

“…Congruent with previous reports, aPC markedly reduced infarct size ( Figure 1B-C). [17][18][19][20][21][22] Reduction of infarct size by aPC was associated with reduced inflammasome activation within the heart. Cardiac expression of Nlrp3 and cl-Casp1 and cl-IL-1b were increased after myocardial IRI but reduced after aPC pretreatment ( Figure 1D-E).…”

“…Cardioprotection by aPC after IRI has been linked with 59 adenosine monophosphate-activated protein kinase (AMPK) activation. 21 Furthermore, mTOR complex 1 (mTORC1), which is negatively regulated by AMPK, was recently shown to activate Nlrp3 inflammasome in macrophages via hexokinase 1 (HK1). 40 Hence, we speculated that aPC restricts inflammasome activation by restricting mTORC1 signaling in the setting of myocardial IRI.…”

“…In regard to myocardial IRI, several studies have demonstrated cardioprotection by aPC, which has been linked with apoptosis inhibition. [17][18][19][20][21][22] However, apoptosis is an immunogenically silent cell-death form and is less likely to promote myocardial IRI than other cell-death forms associated with inflammation, such as pyroptosis. 23 Considering the close association of myocardial IRI, as well as other forms of IRI, with a strong sterile inflammatory response and the anti-inflammatory effect of aPC, we hypothesized that aPC restricts inflammasome activation in IRI.…”

Activated protein C: biased for translation

“…[59][60][61][62][63] PAR1 and EPCR were required for the in vivo beneficial effects of APC in murine coronary I/R injury. 63 Despite multiple studies showing reduction of coronary I/R injury, it remains to be established how long after ischemia onset APC may be beneficial or what receptors, in addition to PAR1, mediate APC's cardioprotection. Further studies on cardioprotection by wt-APC and APC variants may well lead to translation to the clinic.…”