title: Distinct functions of activated protein C differentially attenuate acute kidney injury.
abstract: Administration of activated protein C (APC) protects from renal dysfunction, but the underlying mechanism is unknown. APC exerts both antithrombotic and cytoprotective properties, the latter via modulation of protease-activated receptor-1 (PAR-1) signaling. We generated APC variants to study the relative importance of the two functions of APC in a model of LPS-induced renal microvascular dysfunction. Compared with wild-type APC, the K193E variant exhibited impaired anticoagulant activity but retained the ability to mediate PAR-1-dependent signaling. In contrast, the L8W variant retained anticoagulant activity but lost its ability to modulate PAR-1. By administering wild-type APC or these mutants in a rat model of LPS-induced injury, we found that the PAR-1 agonism, but not the anticoagulant function of APC, reversed LPS-induced systemic hypotension. In contrast, both functions of APC played a role in reversing LPS-induced decreases in renal blood flow and volume, although the effects on PAR-1-dependent signaling were more potent. Regarding potential mechanisms for these findings, APC-mediated PAR-1 agonism suppressed LPS-induced increases in the vasoactive peptide adrenomedullin and infiltration of iNOS-positive leukocytes into renal tissue. However, the anticoagulant function of APC was responsible for suppressing LPS-induced stimulation of the proinflammatory mediators ACE-1, IL-6, and IL-18, perhaps accounting for its ability to modulate renal hemodynamics. Both variants reduced active caspase-3 and abrogated LPS-induced renal dysfunction and pathology. We conclude that although PAR-1 agonism is solely responsible for APC-mediated improvement in systemic hemodynamics, both functions of APC play distinct roles in attenuating the response to injury in the kidney.
authors.affiliation: Biotechnology Discovery Research, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285-0444, USA.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Gupta
authors.forename: Bruce
authors.initials: B
authors.lastname: Gerlitz
authors.forename: Mark A
authors.initials: MA
authors.lastname: Richardson
authors.forename: Christopher
authors.initials: C
authors.lastname: Bull
authors.forename: David T
authors.initials: DT
authors.lastname: Berg
authors.forename: Samreen
authors.initials: S
authors.lastname: Syed
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Galbreath
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Swanson
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Jones
authors.forename: Brian W
authors.initials: BW
authors.lastname: Grinnell
mesh_terms: D000818:Animals; D006801:Humans; D007249:Inflammation; D020382:Interleukin-18 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D007668:Kidney / Q000293:injuries* / Q000378:metabolism; D007674:Kidney Diseases / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism; D008297:Male; D008833:Microcirculation; D011486:Protein C / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044463:Receptor, PAR-1 / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D020382:Interleukin-18; D015850:Interleukin-6; D008070:Lipopolysaccharides; D011486:Protein C; D044463:Receptor, PAR-1