Distinct functions of activated protein C differentially attenuate acute kidney injury

J Am Soc Nephrol. 2009 Feb;20(2):267-77. doi: 10.1681/ASN.2008030294. Epub 2008 Dec 17.

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.

MeSH terms

  • Animals
  • Humans
  • Inflammation
  • Interleukin-18 / metabolism
  • Interleukin-6 / metabolism
  • Kidney / injuries*
  • Kidney / metabolism
  • Kidney Diseases / metabolism*
  • Lipopolysaccharides / metabolism
  • Male
  • Microcirculation
  • Protein C / metabolism
  • Protein C / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, PAR-1 / metabolism
  • Signal Transduction

Substances

  • Interleukin-18
  • Interleukin-6
  • Lipopolysaccharides
  • Protein C
  • Receptor, PAR-1