Folinic Acid Improves Healing of Diabetic Foot Ulcers

A novel folinic acid (FA) wound treatment (FAWT) significantly (p < 0.05) improved healing (re-epithelialization) of chronic diabetic foot ulcers (DFUs). In a double-blind RCT, 10 (n = 10) chronic DFU subjects received daily topical treatment in either the Control group [(n = 5); PluroGel] or the FAWT group [(n = 5); PluroGel with FA 2.5%]. After 12 weeks, FAWT subjects experienced significantly (p < 0.05) greater %-DFU area reduction (88% [SD: 16]) vs. Control (40% [SD: 39]), respectively. Proteomic analysis of keratinocytes (KCs) pre- and post-FAWT, using Reverse Phase Proteomic Array (RPPA), documented significantly decreased levels of HMGB1 (High Mobility Group Box1) protein and activated IL-1B protein at 12 weeks after FAWT as compared to Control. RPPA also documented significantly decreased activating phosphorylation of SAP/JNK3 (T183/Y185) and p38 MAPK (T180/Y182) levels after FAWT as compared to Control. These findings suggested decreased activation and possible reduction of NFKB/p65 and p38 MAPK following FAWT that could decrease proinflammatory gene expression. Genomic DNA-methylation analysis of KCs identified significantly decreased FAWT-induced methylation at gene expression regulatory sites for multiple microRNAs (MiRNA) associated with regulating proinflammatory responses. FAWT-induced decreased methylation levels in MiRNAs suggested increased expression and their potential to inhibit protein translation. These MiRNAs are predicted to target multiple mitogen-activated protein kinase (MAPK) pathways. These MAPK pathways mediate signalling from proinflammatory cell surface receptors (such as RAGE, TLRs and IL1R), altering gene expression. FAWT-induced inhibition of MAPK-signalling may lessen NFKB/p65 and p38 MAPK induction of proinflammatory gene expression, reflected in the significantly decreased protein levels of HMGB1 and IL-1B. The data suggest FAWT-induced coordinated expression of multiple anti-inflammatory MiRNAs associated with impaired MAPK-signalling that resulted in decreased expression of HMGB1 and IL1B and this process may facilitate DFUs' transition from an inflammatory state to wound repair, enabling KCs to regulate their proliferative phase, migration and the promotion of DFU re-epithelialization.