Insulin treatment prevents wounding associated changes in tissue and circulating neutrophil MMP-9 and NGAL in diabetic rats

PLoS One. 2017 Feb 9;12(2):e0170951. doi: 10.1371/journal.pone.0170951. eCollection 2017.

Abstract

Neutrophils are important for wound repair, but their persistence can impair the healing process. Neutrophils express matrix metalloproteinases including MMP-9 and its regulator neutrophil gelatinase associated lipocalin (NGAL). Whether wounding affects neutrophil MMP-9 and NGAL in diabetic animals is not known. Skin wound tissue MMP-9 and NGAL was examined by qRT-PCR and immunohistochemistry in control, diabetic and insulin treated diabetic rats. The temporal expression of MMP-9 and NGAL mRNA, MMP-9 activity and the NGAL/MMP-9 complex was also investigated in an implant model and their circulating neutrophils. The cellular localisation of MMP-9 and NGAL was confirmed by immunofluorescence and the ability of glucose to regulate these factors was examined in isolated neutrophils. In skin wound tissue compared with control, diabetes increased neutrophil infiltration, NGAL mRNA and MMP-9 protein (P<0.05). Diabetes significantly increased implant neutrophil NGAL and MMP-9 protein as well as NGAL mRNA, wound fluid NGAL/MMP-9 complex and MMP-9 activity (all <0.05). Circulating neutrophil MMP-9 and NGAL was also increased in these diabetic animals (P<0.05). These changes were prevented by insulin treatment. Ex vivo, high glucose (25mM) increased neutrophil NGAL and MMP-9 (both by 2 fold, P<0.05). NGAL and MMP-9 are increased in wound and circulating neutrophils in diabetic rodents. These changes and the association between higher NGAL and increased wound fluid MMP-9 activity suggest that increased neutrophil NGAL may contribute to increased MMP-9 in poorly healing diabetic wounds. Whether targeting neutrophil NGAL or MMP-9 can improve diabetic wound healing remains to be investigated.

MeSH terms

  • Acute-Phase Proteins / genetics
  • Acute-Phase Proteins / metabolism*
  • Animals
  • Diabetes Complications / drug therapy*
  • Diabetes Complications / metabolism
  • Insulin / pharmacology
  • Insulin / therapeutic use*
  • Lipocalin-2
  • Lipocalins / genetics
  • Lipocalins / metabolism*
  • Male
  • Matrix Metalloproteinase 9 / genetics
  • Matrix Metalloproteinase 9 / metabolism*
  • Neutrophils / drug effects
  • Neutrophils / metabolism*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Skin / drug effects
  • Skin / injuries*
  • Skin / metabolism
  • Wound Healing*

Substances

  • Acute-Phase Proteins
  • Insulin
  • Lcn2 protein, rat
  • Lipocalin-2
  • Lipocalins
  • Proto-Oncogene Proteins
  • Matrix Metalloproteinase 9
  • Mmp9 protein, rat

Grants and funding

This work was supported by the National Health and Medical Research Council of Australia (1009815) to DM, SMT, SVM, the Rebecca L Cooper Medical Research Foundation to SVM, the Diabetes Australia Research Trust to SVM, Australian Rotary Health to TN, the Sydney Medical Foundation to SVM, and by the Australian Postgraduate Association and International Postgraduate Research Scheme to MA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.