Rac2 deficiency attenuates CCl4-induced liver injury through suppressing inflammation and oxidative stress

Biomed Pharmacother. 2017 Oct:94:140-149. doi: 10.1016/j.biopha.2017.07.074. Epub 2017 Jul 28.

Abstract

Oxidative stress is a leading cause to liver injury. Rac2 is a Ras-associated guanosine triphosphatase, an important molecule modulating a large number of cells and involved in the regulation of reactive oxygen species (ROS). For the study described here, we supposed that Rac2 knockout protects mice against CCl4-induced acute liver injury. We found that Rac2 expressed highly in CCl4-induced liver tissues. CCl4-treated Rac2 knockout (Rac2-/-) mice had reduced CD24 levels and steatosis. In addition, CCl4-induced high expression of pro-inflammatory cytokines and chemokine were reversed by Rac2 deficiency compared to CCl4-treated wild type (WT) mice. We also found that fibrosis-related signals of MMP-9, MMP-2 and TGF-β1 were also down-regulated in Rac2 knockout mice induced by CCl4. Significantly, oxidative stress induced by CCl4 was also suppressed owing to the lack of Rac2, evidenced by enhanced superoxide dismutase (SOD) activity, and reduced malondialdehyde (MDA) levels, superoxide radical, H2O2, xanthine oxidase (XO), xanthine dehydrogenase (XDH) and XO/XDH ratio. Moreover, c-Jun N-terminal protein kinase mitogen-activated protein kinases (JNK MAPK) was activated by CCl4, which was reversed in the liver of Rac2-/- mice through western blot and immunohistochemical analysis. In vitro, endotoxin (LPS) was treated to hepatocytes isolated from WT mice and Rac2-/- mice. The data further confirmed the role of Rac2 deficiency suppressed pro-inflammatory cytokines and chemokine, as well as fibrosis-related signals. Of note, production of ROS induced by LPS was reduced in Rac2-/- cells, accompanied with enhanced SOD1, SOD2 and reduced XO and phosphorylated-JNK expressions. Our results indicated that Rac2 played an essential role in acute liver injury induced by CCl4, providing the compelling information of the effects of Rac2 on liver injury, and revealing a novel regulatory mechanism for acute liver injury.

Keywords: Acute liver injury; Inflammation; JNK; Oxidative stress; Rac2.

MeSH terms

  • Animals
  • Carbon Tetrachloride
  • Chemical and Drug Induced Liver Injury / blood
  • Chemical and Drug Induced Liver Injury / complications
  • Chemical and Drug Induced Liver Injury / metabolism*
  • Chemical and Drug Induced Liver Injury / pathology*
  • Chemokines / blood
  • Down-Regulation / drug effects
  • Enzyme Activation / drug effects
  • Gene Knockout Techniques
  • Inflammation / blood*
  • Inflammation / complications
  • Inflammation / pathology
  • Inflammation Mediators / metabolism
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Lipopolysaccharides / pharmacology
  • Liver / pathology
  • Male
  • Matrix Metalloproteinase 3 / blood
  • Matrix Metalloproteinase 9 / blood
  • Mice, Inbred C57BL
  • Oxidative Stress* / drug effects
  • RAC2 GTP-Binding Protein
  • Transforming Growth Factor beta1 / blood
  • Transforming Growth Factor beta1 / metabolism
  • rac GTP-Binding Proteins / deficiency*
  • rac GTP-Binding Proteins / metabolism

Substances

  • Chemokines
  • Inflammation Mediators
  • Lipopolysaccharides
  • Transforming Growth Factor beta1
  • Carbon Tetrachloride
  • JNK Mitogen-Activated Protein Kinases
  • Matrix Metalloproteinase 3
  • Matrix Metalloproteinase 9
  • rac GTP-Binding Proteins