Non-healing wounds in patients with Type 2 Diabetes (T2D) are a major cause of morbidity and mortality and are increasing at an alarming rate. Equally concerning, our current ?standard of care? leaves 70% of diabetic wounds unhealed. Given this substantial impact on patient outcomes and healthcare expenditure, a critical unmet need exists for improved understanding of the pathophysiology of diabetic wounds to develop effective treatments. Under normal wound healing conditions, the macrophage changes from an inflammatory phenotype, which is prone to tissue destruction, to a reparative cell. The factors controlling macrophage function and how these cells transition from an inflammatory to a reparative phenotype in wound tissues are not understood; leaving a large deficit in our ability to prevent and treat these wounds. Our laboratory is investigating novel epigenetic changes, induced via post-transitional modifications of histones, as mechanism(s) to regulate the macrophage phenotype during wound healing. We present data that the diabetic environment established in wounds induces the expression of specific epigenetic machinery in macrophages that control gene transcription, and hence, function. Using human cells and our experimental murine model of wound healing, we have identified that palmitate signaling induces JMJD3, a histone demethylase, that increases inflammatory gene expression. Palmitate has been previously shown to induce an inflammatory phenotype through stimulation of Toll-like receptor (TLR) 4. Growing evidence indicates that TLR4 is crucial for the promotion of an inflammatory phenotype following stimulation with non-microbial ligands such as saturated fatty acids and palmitate. We hypothesize that palmitate induces JMJD3 via TLR4 signaling which in turn leads to expression of inflammatory genes in macrophages. We further postulate that this process is enhanced in T2D resulting in chronic inflammation and impaired wound healing. This hypothesis will be investigated through the following specific aims: 1) Elucidate the palmitate/TLR4 mediated regulation of macrophage-specific JMJD3 expression in normal and diabetic wounds. 2) To quantify the in vivo effect of targeted JMJD3 inhibition on macrophage polarization and wound healing in a diabetic murine model.
Non-healing diabetic wounds represent the most common cause of amputation in the United States with a 5-year mortality rate of nearly 50% and costs the healthcare system over $19 billion annually. This study will examine the effect of the diabetic environment, specifically increased expression of palmitate fatty acid and toll-like receptor 4 (TLR4) signaling, on the chromatin modifying enzyme, JMJD3, and how the epigenetic changes driven by palmitate/TLR4 result in increased macrophage inflammation and poor wound healing. The success of the human and animal studies outlined in this proposal may lead to improved understanding of the pathophysiology for aberrant healing in diabetic wounds and novel therapeutic targets.
| Davis, Frank M; Gallagher, Katherine (2018) Time Heals All Wounds … But Wounds Heal Faster with Lactobacillus. Cell Host Microbe 23:432-434 |
