Hepatocytes Express the Antimicrobial Peptide HBD-2 After Multiple Trauma: An Experimental Study in Human and Mice

BMC Musculoskelet Disord. 2017 Mar 7;18(1):100. doi: 10.1186/s12891-017-1458-8.

Abstract

Background: Human-beta defensins (HBD) belong to the family of acute phase peptides and hold a broad antimicrobial spectrum that includes gram-positive and gram-negative bacteria. HBD are up-regulated after severe injuries but the source of posttraumatic HBD expression has not been focused on before. In the current study we analysed the role of liver tissue in expression of HBD after multiple trauma in human and mice.

Methods: HBD-2 expression has been detected in plasma samples of 32 multiple trauma patients (ISS > 16) over 14 days after trauma by ELISA. To investigate major sources of HBD-2, its expression and regulation in plasma samples, polymorphonuclear neutrophils (PMN) and human tissue samples of liver and skin were analysed by ELISA. As liver samples of trauma patients are hard to obtain we tried to review findings in an established trauma model. Plasma samples and liver samples of 56 male C57BL/6 N-mice with a thorax trauma and a femur fracture were analysed by ELISA, real-time PCR and immunohistochemistry for murine beta defensin 4 (MBD-4) and compared with the expression of control group without trauma. The induction of HBD-2 expression in cultured hepatocytes (Hep G2) was analysed after incubation with IL-6, supernatant of Staphylococcus aureus (SA) and Lipopolysaccharides (LPS). One possible signalling pathway was tested by blocking toll-like receptor 2 (TLR2) in hepatocytes.

Results: Compared to healthy control group, plasma of multiple traumatized patients and mice showed significantly higher defensin levels after trauma. Compared to skin cells, which are known for high beta defensin expression, liver tissue showed less HBD-2 expression, but higher HBD-2 expression compared to PMN. Immunhistochemical staining demonstrated upregulated MBD-4 in hepatocytes of traumatised mice. In HepG2 cells HBD-2 expression could be increased by stimulation with IL-6 and SA. Neutralization of HepG2 cells with αTLR2 showed reduced HBD-2 expression after stimulation with SA.

Conclusion: Plasma samples of multiple traumatized patients showed high expression of HBD-2, which may protect the severely injured patient from overwhelming bacterial infection. Our data support the hypothesis that liver is one possible source for HBD-2 in plasma while posttraumatic inflammatory response.

Keywords: Antimicrobial peptides; Hepatocytes; Human beta-defensin; Liver; MBD; Multiple trauma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Animals
  • Bacterial Infections / immunology
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Hep G2 Cells
  • Hepatocytes / metabolism*
  • Humans
  • Immunohistochemistry
  • Inflammation / metabolism
  • Interleukin-6 / metabolism
  • Lipopolysaccharides / metabolism
  • Liver / cytology
  • Liver / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • Multiple Trauma / blood*
  • Multiple Trauma / complications
  • Real-Time Polymerase Chain Reaction
  • Signal Transduction
  • Skin / cytology
  • Skin / metabolism*
  • Toll-Like Receptor 2 / antagonists & inhibitors*
  • Toll-Like Receptor 2 / metabolism
  • Up-Regulation
  • Young Adult
  • beta-Defensins / immunology
  • beta-Defensins / metabolism*

Substances

  • DEFB4A protein, human
  • Defb4 protein, mouse
  • IL6 protein, human
  • Interleukin-6
  • Lipopolysaccharides
  • Toll-Like Receptor 2
  • beta-Defensins