Hypoxia Inducible Factor (HIF)‐1 Accelerates Epithelial Wound Healing Through Regulation of Integrin‐α5β1
Authors: Goggins Bridie , Minahan Kyra , Mathe Andrea , Liu Gang , Walker Marjorie , Horvat Jay , Knight Darryl , Keely Simon 
Published: June 2021

The intestinal epithelium functions as a selective barrier and is critical for mucosal protection. Inflammation leads to a loss of epithelial barrier function and epithelial repair is critical to restore barrier integrity and gut homeostasis. Due to vascular damage and increased metabolic demands, epithelial wound healing occurs in an hypoxic environment. Previous work has shown that pharmacological stabilisation of the transcription factor Hypoxia inducible factor (HIF)‐1α by prolyl hydroxylase inhibitors (PHDi) accelerates wound healing. Importantly, our work has identified HIF‐1‐mediated induction of integrins at the mucosa as critical to this process. As integrins are key mediators of epithelial migration, we hypothesised that pharmacological HIF‐1α stabilisation accelerates epithelial restitution through integrin‐dependent pathways.

The aim of this study was to examine the functional role as well as the transcriptional and post‐translational activity of epithelial α5 integrins dimerizing with integrin‐β1 to promote HIF‐1‐mediated wound healing by PHDi.

Cell migration and functional scratch assays were performed on T84 monolayers treated with PHDi (AKB‐4924 100μM) or vehicle. Wound closure was monitored over 24 hours. Transcriptional and translational regulation of α‐integrins was analysed via PCR and Western blot respectively. Monolayers were stained by immunofluorescence to examine α5‐integrin cellular localisation. Biopsy‐wound models were used to study HIF‐mediated wound healing in vivo and TNBS colitis models were utilised to examine the role of HIF‐mediated epithelial integrin response during inflammatory hypoxia (PHDi AKB‐4924 5mg/kg or vehicle control).

PHDi treatments accelerated wound closure in T84 monolayers compared to vehicle (43% ±3.05%, p<0.0001, N=6), which was associated with increases in integrin‐α5 transcripts (32 ± 1.94 fold, p<0.0001 N=6) and protein (7.99 ± 1.108 fold, p<0.0003 N=3). PHDi‐mediated wound closure was inhibited by antibodies functionally targeting integrin‐α5, compared to isotype control antibodies (−4.63% ± 1.74%, p<0.0403, N=4). Immunofluorescent imaging of cell monolayers showed sub‐nuclear localisation in vehicle treated cells, and trafficking away from the nucleus during PHDi treatments. Immunohistochemical analysis of biopsy wounds and TNBS colon sections showed PHDi treatments accelerated mucosal wound closure (0.034 ± 0.012 mm2, p<0.0252, N=6 (day 4 wound area), and 0.040 ± 0.012 mm2, p<0.0079, N=6 (day 6 wound area)), and reduced disease pathology. Increased expression of integrin‐α5 was observed in the crypts and wound lesions of biopsy wounds as well as the crypts and inflammatory lesions in PHDi treated mice.

These data suggest that PHDi‐mediated HIF‐1α stabilisation promotes mucosal healing through regulation of epithelial integrin‐α5β1. Given the observed integrin‐α5 trafficking, PHDi compounds may be facilitating cell propulsion through up‐regulation of integrin‐α5 to promote wound closure in colonic epithelia.

Support or Funding Information

National Health and Medical Research Council Project Grant and Jennie Thomas Postgraduate Medical Research Scholarship

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.