Epigenetic regulation of the PGE2 pathway modulates macrophage phenotype in normal and pathologic wound repair

Abstract

Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E 2 (COX-2/PGE 2 ) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB–mediated inflammation in diabetic wounds and show increased COX-2/PGE 2 in diabetic macrophages. Further, we identify that COX-2/PGE 2 production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A 2 /COX-2/PGE 2 (cPLA 2 /COX-2/PGE 2 ) pathway. We demonstrate that TGF-β–induced miRNA29b increases COX-2/PGE 2 production via inhibition of DNA methyltransferase 3b–mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA 2 expression and drives COX-2/PGE 2 . Inhibition of the COX-2/PGE 2 pathway genetically ( Cox2 fl/fl Lyz2 Cre+ ) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE 2 pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.

Role of prostaglandin E2 in tissue repair and regeneration

“…COX-2/PGE2 pathway is increased in murine and human diabetic monocytes/macrophages. Unsuitable PGE2 activity might maintain the inflammatory phenotype of wound macrophages, which is not conducive to the repair of diabetic wounds 37 . The duality of PGE2 and the complexity of the body require us to explore more to find the better therapeutic effect.…”

Macrophages, Metabolites, and Nucleosomes: Chromatin at the Intersection between Aging and Inflammation

“…Signaling mediated by EP2 and EP4 activates adenylate cyclase, increasing cyclic AMP (cAMP) levels [ 58 ] ( Figure 3 , left). Work on human and murine macrophages has shown that the Cytosolic Phospholipase A 2 ( cPLA 2 ) and Cox-2 genes are activated in diabetic cells, and that the activation of these genes is dependent on H3K4me3 and the loss of DNA methylation at their respective promoters in a murine wound-healing model [ 16 ]. cPLA 2 acts at the first agonist-induced step in this pathway and was shown to require activation by the transcription factor Elk-1 and the p300 histone acetyltransferase in response to TNFα stimulation in human lung epithelial cells [ 57 ].…”

“…The methylation of these CpG islands may repress gene transcription by inhibiting transcription factor binding, preventing histone modifications that activate transcription, or by promoting the binding of transcriptional repressors [48]. The loss of DNA methylation of the Cox-2 gene promoter has been shown to affect macrophage function and promote inflammation in human/murine model studies (discussed below) [16]. Along with histone modification pattern changes, transcription factor binding patterns have been shown to be altered in aging in numerous species, including C. elegans and human cells [45].…”

“…High nutrient intake fuels chronic inflammation, and dietary restriction may improve markers of inflammation [ 15 ]. Even at the most fundamental level, the production of the vast array of molecules required to regulate inflammation uses a wide assortment of compounds derived from metabolites, such as the enzymatic digestion of cell membrane phospholipids to produce prostaglandins, or the use of S-adenosyl methionine (SAMe)/adenosine triphosphate (ATP) as a cofactor to influence cytokine production at the transcriptional level [ 16 , 17 ].…”

The Heritability of Behaviors Associated With the Host Gut Microbiota

“…The gastro-intestinal tract is home to microbes of an immense variety of genus ( 21 , 22 ) and enteric sensory neurons located next to the intestine ( 23 ) can detect changes in the composition of microbe’s metabolic byproducts ( 24 – 26 ). Diverse host’s physiological responses have shown to be modulated by microbial metabolites, like short-chain fatty acids, polysaccharides, bile acids, and others ( 27 ), in a bidirectional communication process between host and microbe that is evolutionary conserved across animals ( 28 ). Chemical information about the intestinal luminal environment is transmitted to the CNS through the vagus nerve in mammals ( 29 ), and through the recurrent nerve in insects, like Drosophila ( 30 ).…”