Diabetic foot ulcers are characterized by hypoxia. For many patients, hyperbaric oxygen (HBO) therapy is the last recourse for saving the limb from amputation, for which the molecular basis is not understood. We previously identified the active form of matrix metalloproteinase-9 (MMP-9) as responsible for diabetic foot ulcer's recalcitrance to healing. Transcription of mmp-9 to the inactive zymogen is upregulated during hypoxia. Activation of the zymogen is promoted by proteases and reactive oxygen species (ROS). We hypothesized that the dynamics of these two events might lead to a lowering of active MMP-9 levels in the wounded tissue. We employed the full-thickness excisional db/db mouse model to study wound healing, and treated the mice to 3.0 atm of molecular oxygen for 90 minutes, 5 days per week for 10 days in an HBO research chamber. Treatment with HBO accelerated diabetic wound healing compared to untreated mice, with more completed and extended reepithelialization. We imaged the wounds for ROS in vivo with a luminol-based probe and found that HBO treatment actually decreases ROS levels. The levels of superoxide dismutase, catalase, and glutathione peroxidase—enzymes that turn over ROS—increased after HBO treatment, hence the observation of decreased ROS. Since ROS levels are lowered, we explored the effect that this would have on activation of MMP-9. Quantitative analysis with an affinity resin that binds and pulls down the active MMPs exclusively, coupled with proteomics, revealed that HBO treatment indeed reduces the active MMP-9 levels. This work for the first time demonstrates that diminution of active MMP-9 is a contributing factor and a mechanism for enhancement of diabetic wound healing by HBO therapy.
|Number of pages
|Wound Repair and Regeneration
|Published - Mar 1 2020
Bibliographical noteFunding Information:
Sources of Funding: This work was supported by the American Diabetes Association Pathway to Stop Diabetes (grant 1-15-ACN-06). TTN and JIJ are Ruth L. Kirschstein National Research Service Award Fellows of the Chemistry-Biochemistry-Biology Interface Program at the University of Notre Dame, supported by training grant T32 GM075762 from the National Institutes of Health. Conflicts of Interest: The authors declare no conflicts of interest relevant to the reported work.
Sources of Funding : This work was supported by the American Diabetes Association Pathway to Stop Diabetes (grant 1‐15‐ACN‐06). TTN and JIJ are Ruth L. Kirschstein National Research Service Award Fellows of the Chemistry‐Biochemistry‐Biology Interface Program at the University of Notre Dame, supported by training grant T32 GM075762 from the National Institutes of Health. Conflicts of Interest : The authors declare no conflicts of interest relevant to the reported work.
© 2019 by the Wound Healing Society
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