Inflammation in macrophages is exacerbated under hyperglycemic conditions, contributing to chronic inflammation and impaired wound healing in diabetes. This study investigates the potential of mangiferin, a natural polyphenol, to alleviate this inflammatory response by targeting a redox-sensitive transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2). Mangiferin, a known Nrf2 activator, was evaluated for its ability to counteract the hyperglycemia-induced inhibition of Nrf2 and enhance antioxidant defenses. The protective effects of mangiferin on macrophages in a hyperglycemic environment were assessed by examining the expression of Nrf2, NF-κB, NLRP3, HO-1, CAT, COX-2, IL-6, and IL-10 through gene and protein expression analyses using qPCR and immunoblotting, respectively. The mangiferin-mediated nuclear translocation of Nrf2 was evidenced, leading to a robust antioxidant response in macrophages exposed to a hyperglycemic microenvironment. This activation suppressed NF-κB signaling, reducing the expression of pro-inflammatory mediators such as COX-2 and IL-6. Additionally, mangiferin decreased NLRP3 inflammasome activation and reactive oxygen species accumulation in hyperglycemia exposed macrophages. Our findings revealed that mangiferin alleviated hyperglycemia-induced reductions in AKT phosphorylation, highlighting its potential role in modulating key signaling pathways. Furthermore, mangiferin significantly enhanced the invasiveness and migration of macrophages in a hyperglycemic environment, indicating its potential to improve wound healing. In conclusion, this study suggests that mangiferin may offer a promising therapeutic approach for managing inflammation and promoting wound healing in diabetic patients by regulating Nrf2 activity in hyperglycemia-induced macrophages.

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a stress-activated transcription factor regulating antioxidant genes, and a deficiency thereof, slowing lymphangiogenesis, has been reported in diabetic foot ulcer (DFU). The mode of Nrf2 regulation in DFU has been less explored. Emerging studies on miRNA-mediated target regulation show miRNA to be the leading player in the pathogenesis of the disease. In the present study, we demonstrated the role of miR-27b in regulating Nrf2-mediated angiogenesis in DFU. A lower expression of mRNA targets, such as Nrf2, HO-1, SDF-1α, and VEGF, was observed in tissue biopsied from chronic DFU subjects, which was in line with miR-27b, signifying a positive correlation with Nrf2. Similarly, we found significantly reduced expression of miR-27b and target mRNAs Nrf2, HO-1, SDF-1α, and VEGF in endothelial cells under a hyperglycemic microenvironment (HGM). To confirm the association of miR-27b on regulating Nrf2-mediated angiogenesis, we inhibited its expression through RNA interference-mediated knockdown and observed disturbances in angiogenic signaling with reduced endothelial cell migration. In addition, to explore the role of miR-27b and angiogenesis in the activation of Nrf2, we pretreated the endothelial cells with two well-known pharmacological compounds—pterostilbene and resveratrol. We observed that activation of Nrf2 through these compounds ameliorates impaired angiogenesis on HGM-induced endothelial cells. This study suggests a positive role of miR-27b in regulating Nrf2, which seems to be decreased in DFU and improves on treatment with pterostilbene and resveratrol.

Non-healing lesions in diabetic foot ulcers are a significant effect of poor angiogenesis. Epigenetic regulators, mainly lncRNA and miRNA, are recognized for their important roles in disease progression. We deciphered the regulation of lncRNA NEAT1 through the miR-146a-5p/mafG axis in the progression of DFU. A lowered expression of lncRNA NEAT1 was associated with dysregulated angiogenesis through the reduced expression of mafG, SDF-1α, and VEGF in chronic ulcer subjects compared to acute DFU. This was validated by silencing NEAT1 by SiRNA in the endothelial cells which resulted in the transcriptional repression of target genes. Our in silico analysis identified miR-146a-5p as a potential target of lncRNA NEAT1. Further, silencing NEAT1 led to an increase in the levels of miR-146a-5p in chronic DFU subjects. This research presents the role of the lncRNA NEAT1/miR-146a-5p/mafG axis in enhancing angiogenesis in DFU.