Wound healing is characterized by a systemic and complex process of cellular and molecular activities. Dipotassium Glycyrrhizinate (DPG), a side product derived from glycyrrhizic acid, has several biological effects, such as being antiallergic, antioxidant, antibacterial, antiviral, gastroprotective, antitumoral, and anti-inflammatory. This study aimed to evaluate the anti-inflammatory effect of topical DPG on the healing of cutaneous wounds by secondary intention in an in vivo experimental model. Twenty-four male Wistar rats were used in the experiment, and were randomly divided into six groups of four. Circular excisions were performed and topically treated for 14 days after wound induction. Macroscopic and histopathological analyses were performed. Gene expression was evaluated by real-time qPCR. Our results showed that treatment with DPG caused a decrease in the inflammatory exudate as well as an absence of active hyperemia. Increases in granulation tissue, tissue reepithelization, and total collagen were also observed. Furthermore, DPG treatment reduced the expression of pro-inflammatory cytokines (Tnf-α, Cox-2, Il-8, Irak-2, Nf-kB, and Il-1) while increasing the expression of Il-10, demonstrating anti-inflammatory effects across all three treatment periods. Based on our results, we conclude that DPG attenuates the inflammatory process by promoting skin wound healing through the modulation of distinct mechanisms and signaling pathways, including anti-inflammatory ones. This involves modulation of the expression of pro- and anti-inflammatory cytokine expression; promotion of new granulation tissue; angiogenesis; and tissue re-epithelialization, all of which contribute to tissue remodeling.

The nuclear factor kappa B (NF-κB) pathway has been reported to be responsible for the aggressive disease phenomenon observed in glioblastoma (GBM). Dipotassium glycyrrhizinate (DPG), a dipotassium salt of glycyrrhizic acid isolated from licorice, has recently demonstrated an anti-tumoral effect on GBM cell lines U87MG and T98G through NF-κB suppression by IRAK2- and TRAF6-mediating microRNA (miR)-16 and miR-146a, respectively. Thus, the present study aimed to evaluate the expression profiles of miRNAs related to NF-κB suppression in T98G GBM cell line after DPG exposure using miRNA microarray (Affymetrix Human miRNA 4.0A), considering only predicted miRNAs as NF-κB regulator genes. Additional assays using U251 and U138MG cells were performed to validate the array results. DPG cytotoxicity was determined by (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and cellular apoptosis was quantified by DNA fragmentation and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. The anti-proliferative effect was observed by cell proliferation and wound-healing assays, and the sphere formation assay examined whether DPG reduced stem cell subpopulation formation. The most over-expressed miRNAs were miR-4443 and miR-3620. The cytotoxic effect of DPG in U251 and U138MG was observed with an IC50 of 32 and 20 mM for 48 h, respectively. The IC50 of each cell line was used in all further assays. DPG treatment-induced apoptosis is observed by DNA fragmentation and increased TUNEL-positive cells. Cell proliferation and wound-healing assays showed an anti-proliferative and anti-migratory effect by DPG on the evaluated cell lines. In addition, DPG treatment led to a 100% reduction in sphere formation. The qPCR results in U251 and U138MG cells showed that DPG increased miR-4443 (2.44 vs. 1.11, p-value = 0.11; 8.27 vs. 1.25, p-value = 0.04) and miR-3620 expression (1.66 vs. 1.00, p-value = 0.03; 8.47 vs. 1.01, p-value = 0.03) and decreased CD209 (0.44 vs. 1.10, p-value = 0.03; 0.49 vs. 1.07, p-value = 0.04) and TNC (0.20 vs. 1.03, p-value = 0.001; 0.39 vs. 1.06, p-value = 0.01) mRNA levels compared to controls. Our results suggest that DPG inhibits cell viability by activating apoptosis and inhibiting cell proliferation and stem cell subpopulation formation through miR-4443 and miR-3620 upregulation. Both miRNAs are responsible for the post-transcriptional inhibition of NF-κB by CD209 and TNC modulation.

Glycyrrhizic acid (GA), a natural compound isolated from licorice (Glycyrrhiza glabra), has exhibited anti-inflammatory and anti-tumor effects in vitro. Dipotassium glycyrrhizinate (DPG), a dipotassium salt of GA, also has shown an anti-tumor effect on glioblastoma cell lines, U87MG and T98G. The study investigated the DPG effects in the melanoma cell line (SK-MEL-28). MTT assay demonstrated that the viability of the cells was significantly decreased in a time- and dose-dependent manner after DPG (IC50 = 36 mM; 24 h). DNA fragmentation suggested that DPG (IC50) induced cellular apoptosis, which was confirmed by a significant number of TUNEL-positive cells (p-value = 0.048) and by PARP-1 [0.55 vs. 1.02 arbitrary units (AUs), p-value = 0.001], BAX (1.91 vs. 1.05 AUs, p-value = 0.09), and BCL-2 (0.51 vs. 1.07 AUs, p-value = 0.0018) mRNA compared to control cells. The proliferation and wound-healing assays showed an anti-proliferative effect on DPG-IC50-treated cells, also indicating an inhibitory effect on cell migration (p-values < 0.001). Moreover, it was observed that DPG promoted a 100% reduction in melanospheres formation (p-value = 0.008). Our previous microRNAs (miRs) global analysis has revealed that DPG might increase miR-4443 and miR-3620 expression levels. Thus, qPCR showed that after DPG treatment, SK-MEL-28 cells presented significantly high miR-4443 (1.77 vs. 1.04 AUs, p-value = 0.02) and miR-3620 (2.30 vs. 1.00 AUs, p-value = 0.01) expression compared to control cells, which are predicted to target the NF-kB, CD209 and TNC genes, respectively. Both genes are responsible for cell attachment and migration, and qPCR revealed significantly decreased CD209 (1.01 vs. 0.54 AUs, p-value = 0.018) and TNC (1.00 vs. 0.31 AUs, p-value = 2.38 × 10−6) mRNA expression levels after DPG compared to untreated cells. Furthermore, the migration of SK-MEL-28 cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) was attenuated by adding DPG by wound-healing assay (48 h: p-value = 0.004; 72 h: p-value = 7.0 × 10−4). In addition, the MMP-9 expression level was inhibited by DPG in melanoma cells stimulated by TPA and compared to TPA-treated cells (3.56 vs. 0.99 AUs, p-value = 0.0016) after 24 h of treatment. Our results suggested that DPG has an apoptotic, anti-proliferative, and anti-migratory effect on SK-MEL-28 cells. DPG was also able to inhibit cancer stem-like cells that may cause cerebral tumor formation.