Faculty Collaboration Database

Endotoxin Engages Mitochondrial Quality Control via an iNOS-Reactive Oxygen Species Signaling Pathway in Hepatocytes. Oxid Med Cell Longev 2019;2019:4745067

Date

11/28/2019

Pubmed ID

31772705

Pubmed Central ID

PMC6854992

DOI

10.1155/2019/4745067

Scopus ID

2-s2.0-85074757798 (requires institutional sign-in at Scopus site)   13 Citations

Abstract

BACKGROUND: Organ injury and dysfunction in sepsis accounts for significant morbidity and mortality. Adaptive cellular responses in the setting of sepsis prevent injury and allow for organ recovery. We and others have shown that part of the adaptive response includes regulation of cellular respiration and maintenance of a healthy mitochondrial population. Herein, we hypothesized that endotoxin-induced changes in hepatocyte mitochondrial respiration and homeostasis are regulated by an inducible nitric oxide synthase/nitric oxide (iNOS/NO)-mitochondrial reactive oxygen species (mtROS) signaling axis, involving activation of the NRF2 signaling pathway.

METHODS: Wild-type (C57Bl/6) or iNos^-/- male mice were subjected to intraperitoneal lipopolysaccharide (LPS) injections to simulate endotoxemia. Individual mice were randomized to treatment with NO-releasing agent DPTA-NONOate, mtROS scavenger MitoTEMPO, or vehicle controls. Other mice were treated with scramble or Nrf2-specific siRNA via tail vein injection. Primary murine hepatocytes were utilized for in vitro studies with or without LPS stimulation. Oxygen consumption rates were measured to establish mitochondrial respiratory parameters. Western blotting, confocal microscopy with immunocytochemistry, and rtPCR were performed for analysis of iNOS as well as markers of both autophagy and mitochondrial biogenesis.

RESULTS: LPS treatment inhibited aerobic respiration in vitro in wild-type but not iNos ^-/- cells. Experimental endotoxemia in vivo or in vitro induced iNOS protein and mtROS production. However, induction of mtROS was dependent on iNOS expression. Furthermore, LPS-induced hepatic autophagy/mitophagy and mitochondrial biogenesis were significantly attenuated in iNos ^-/- mice or cells with NO or mtROS scavenging. These responses were rescued in iNos ^-/- mice via delivery of NO both in vivo and in vitro. Conclusions. These data suggest that regulation of mitochondrial quality control following hepatocyte LPS exposure is dependent at least in part on a NO-mtROS signaling network. Further investigation to identify specific agents that modulate this process may facilitate the prevention of organ injury in sepsis.

Author List

Cyr A, Chambers L, Waltz PK, Whelan SP, Kohut L, Carchman E, Dyer M, Luciano J, Kautza B, Gomez HD, Otterbein LE, Rosengart MR, Shiva S, Zuckerbraun BS

Author

Mitchell R. Dyer MD Assistant Professor in the Surgery department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Endotoxins
Hepatocytes
Humans
Male
Mice
Mitochondria
Nitric Oxide Synthase Type II
Quality Control
Reactive Oxygen Species
Signal Transduction