Activated protein C targets CD8+ dendritic cells to reduce the mortality of endotoxemia in mice
Edward Kerschen, Irene Hernandez, Mark Zogg, Shuang Jia, Martin J. Hessner, Jose A. Fernandez, John H. Griffin, Claudia S. Huettner, Francis J. Castellino, Hartmut Weiler
Edward Kerschen, Irene Hernandez, Mark Zogg, Shuang Jia, Martin J. Hessner, Jose A. Fernandez, John H. Griffin, Claudia S. Huettner, Francis J. Castellino, Hartmut Weiler
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Research Article

Activated protein C targets CD8+ dendritic cells to reduce the mortality of endotoxemia in mice

Abstract

Activated protein C (aPC) therapy reduces mortality in adult patients with severe sepsis. In mouse endotoxemia and sepsis models, mortality reduction requires the cell signaling function of aPC, mediated through protease-activated receptor–1 (PAR1) and endothelial protein C receptor (EPCR; also known as Procr). Candidate cellular targets of aPC include vascular endothelial cells and leukocytes. Here, we show that expression of EPCR and PAR1 on hematopoietic cells is required in mice for an aPC variant that mediates full cell signaling activity but only minimal anticoagulant function (5A-aPC) to reduce the mortality of endotoxemia. Expression of EPCR in mature murine immune cells was limited to a subset of CD8+ conventional dendritic cells. Adoptive transfer of splenic CD11chiPDCA-1– dendritic cells from wild-type mice into animals with hematopoietic EPCR deficiency restored the therapeutic efficacy of aPC, whereas transfer of EPCR-deficient CD11chi dendritic cells or wild-type CD11chi dendritic cells depleted of EPCR+ cells did not. In addition, 5A-aPC inhibited the inflammatory response of conventional dendritic cells independent of EPCR and suppressed IFN-γ production by natural killer–like dendritic cells. These data reveal an essential role for EPCR and PAR1 on hematopoietic cells, identify EPCR-expressing dendritic immune cells as a critical target of aPC therapy, and document EPCR-independent antiinflammatory effects of aPC on innate immune cells.

Authors

Edward Kerschen, Irene Hernandez, Mark Zogg, Shuang Jia, Martin J. Hessner, Jose A. Fernandez, John H. Griffin, Claudia S. Huettner, Francis J. Castellino, Hartmut Weiler

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Figure 1

Mortality reduction by aPC requires EPCR and PAR1 expression in BM-derived cells.

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Mortality reduction by aPC requires EPCR and PAR1 expression in BM-deriv...
BM chimeras were generated by reciprocal BM transfers between CD45 isotype–mismatched animals of the indicated genotypes (EPCRlo: reduced EPCR expression; Par1–/–: PAR1-knockout mice). Eight to 10 weeks after documented hematopoietic reconstitution, animals received a dose of LPS causing 50% mortality in wild-type mice, followed by intravenous infusion of a 10-μg bolus of murine recombinant 5A-aPC (aPC) in PBS or carrier alone. (A) BM transfer between wild-type mice does not alter the sensitivity to LPS and response to aPC therapy. Full efficacy of mortality reduction by 5A-aPC requires normal expression of EPCR and PAR1 in hematopoietic cells (B and D), as well as in non-hematopoietic cells (C and E). Significance of the aPC effect on 7-day survival was determined by Kaplan-Meier log-rank test.