Glycyrrhetinic acid prevents cutaneous scratching behavior in mice elicited by substance P or PAR-2 agonist

Use of 18β-glycyrrhetinic acid nanocrystals to enhance anti-inflammatory activity by improving topical delivery

18β-Glycyrrhetinic acid (GA) is often topically applied in clinical treatment of inflammatory skin diseases. However, GA has poor solubility in water, which results in poor skin permeability and low bioavailability. Nanocrystallization of drugs can enhance their permeability and improve bioavailability. We prepared GA nanocrystals (Nano GA) by high-pressure homogenization. These nanocrystals were characterized by photon correlation spectroscopy, scanning electron microscopy, thermogravimetric analysis, and X-ray diffractometry. The ability of Nano GA to improve dermal permeability was investigated ex vivo using Franz diffusion vertical cells and mouse skin. The topical anti-inflammatory activity of Nano GA was assessed in vivo by a 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced model in mouse ears. The average particle size of a GA nanocrystalline suspension was 288.6 ± 7.3 nm, with a narrow particle-size distribution (polydispersity index ∼0.13 ± 0.10), and the particle size of the lyophilized powder increased (552.0 ± 9.8 nm). After nanocrystallization, the thermal stability and crystallinity decreased but solubility increased significantly. Nano GA showed higher dermal permeability than Coarse GA. Macroscopic and staining-based observations of mouse ears and the levels of proinflammatory factors and myeloperoxidase revealed that the Nano GA hydrogel exhibited better anti-edema ability and more strongly inhibited inflammation development than the Coarse GA hydrogel and indomethacin hydrogel (positive drug). These results suggest that Nano GA could be an efficacious topical therapeutic agent for skin inflammation.

Grafting of 18β-Glycyrrhetinic Acid and Sialic Acid onto Chitosan to Produce a New Amphipathic Chitosan Derivative: Synthesis, Characterization, and Cytotoxicity

Chitosan is the only cationic polysaccharide found in nature. It has broad application prospects in biomaterials, but its application is limited due to its poor solubility in water. A novel chitosan derivative was synthesized by amidation of chitosan with 18β-glycyrrhetinic acid and sialic acid. The chitosan derivatives were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and measurement of the zeta potential. We also investigated the solubility, cytotoxicity, and blood compatibility of chitosan derivatives. 18β-glycyrrhetinic acid and sialic acid could be grafted onto chitosan molecular chains. The thermal stability of the synthesized chitosan derivatives was decreased and the surface was positively charged in water and phosphate-buffered saline. After chitosan had been modified by 18 β-glycyrrhetinic acid and sialic acid, the solubility of chitosan was improved greatly in water and phosphate-buffered saline, and percent hemolysis was <5%. Novel amphiphilic chitosan derivatives could be suitable polymers for biomedical purposes.

Functional recovery in human partial thickness skin wounds after application of multicomponent hydrolipidic film (MAS063DP): A prospective, open-label, comparative clinical trial

Acute and minor skin wounds are common in daily life. However, in clinical practice, after initial management in the acute phase, the wounds are managed mainly through observation, and the patients are usually lost to follow-up. Considering a multicomponent hydrolipidic dressing (MAS063DP) long-known for its safe application in eczema and recently in laser-induced wounds, we aimed to evaluate its ability in functional recovery of impaired skin integrity during wound healing. Sixteen patients (N = 16) were enrolled and completed (n = 8 vs n = 8) this prospective, open-label, vehicle-controlled clinical trial with 12-week follow-up. Transepidermal water, skin viscoelasticity and bioimpedance analysis were measured initially, at the 1st, 4th, 8th, and 12th weeks. Improvements in these parameters were greater in the MAS063DP group (from 31.4 ± 9.0 to 16.4 ± 4.3 g/m² h, P < .001; from 77 ± 16% to 88 ± 9%, P < .05; from 4182 ± 3823 to 2644 ± 1772 Ω) than in the white petrolatum group. No significant adverse events occurred, and all participants were more satisfied with the intervention. In this study, MAS063DP can restore skin integrity and reinstitute physiologic function as a feasible and safe intervention more markedly than management through observation during the healing process by providing protective hydrolipidic layer on the skin with simultaneous anti-inflammatory and antioxidant activities from its key ingredients such as glycyrrhetinic acid, Vitis vinifera, telmesteine, and vitamins C and E.

Design, Synthesis, Antibacterial Evaluation, and Induced Apoptotic Behaviors of Epimeric and Chiral 18β-Glycyrrhetinic Acid Ester Derivatives with an Isopropanolamine Bridge against Phytopathogens

Because only a handful of agrochemicals can manage bacterial infections, the discovery and development of innovative, inexpensive, and high-efficiency antibacterial agents targeting these infections are challenging. Herein, a series of novel epimeric and chiral 18β-glycyrrhetinic acid (GA) ester derivatives with various tertiary amine pendants were designed, synthesized, and screened for pharmacological activity. Results showed that some of the title compounds were conferred with significantly enhanced antibacterial activity toward phytopathogens Xanthomonas oryzae pv oryzae (A₂, B₁-B₃, and C₁, EC₅₀ values within 3.81-4.82 μg/mL) and Xanthomonas axonopodis pv citri (B₁, EC₅₀ = 3.18 μg/mL; B₂, EC₅₀ = 2.76 μg/mL). These activities are superior to those of GA (EC₅₀ > 400 μg/mL), thiodiazole copper, and bismerthiazol. Pharmacophore studies revealed that the synergistic combination of GA skeleton and tertiary amine scaffolds contributed to the biological actions. In vivo experiments displayed their promising applications in controlling bacterial infections. Antibacterial mechanism studies revealed that the title compounds could trigger apoptosis in the tested pathogens, evident by bacteria morphological changes observed in scanning electron microscopy images. This outcome should motivate the development of various apoptosis inducers against plant bacterial diseases by a novel mode of action compared to that of existing agricultural chemicals.

Glycyrrhetinic acid binds to the conserved P-loop region and interferes with the interaction of RAS-effector proteins

Members of the RAS proto-oncogene superfamily are indispensable molecular switches that play critical roles in cell proliferation, differentiation, and cell survival. Recent studies have attempted to prevent the interaction of RAS/GTP with RAS guanine nucleotide exchange factors (GEFs), impair RAS-effector interactions, and suppress RAS localization to prevent oncogenic signalling. The present study aimed to investigate the effect of the natural triterpenoic acid inhibitor glycyrrhetinic acid, which is isolated from the roots of Glycyrrhiza plant species, on RAS stability. We found that glycyrrhetinic acid may bind to the P-loop of RAS and alter its stability. Based on our biochemical tests and structural analysis results, glycyrrhetinic acid induced a conformational change in RAS. Meanwhile, glycyrrhetinic acid abolishes the function of RAS by interfering with the effector protein RAF kinase activation and RAS/MAPK signalling.

Glycyrrhetinic Acid Antagonizes Pressure-Induced Venous Remodeling in Mice

Development of spider veins is caused by the remodeling of veins located in the upper dermis and promoted by risk factors such as obesity or pregnancy that chronically increase venous pressure. We have repeatedly shown that the pressure-induced increase in biomechanical wall stress is sufficient to evoke the formation of enlarged corkscrew-like superficial veins in mice. Subsequent experimental approaches revealed that interference with endothelial- and/or smooth muscle cell (SMC) activation counteracts this remodeling process. Here, we investigate whether the herbal agent glycyrrhetinic acid (GA) is a suitable candidate for that purpose given its anti-proliferative as well as anti-oxidative properties. While basic abilities of cultured venous SMCs such as migration and proliferation were not influenced by GA, it inhibited proliferation but not angiogenic sprouting of human venous endothelial cells (ECs). Further analyses of biomechanically stimulated ECs revealed that GA inhibits the DNA binding capacity of the mechanosensitive transcription factor activator protein-1 (AP-1) which, however, had only a minor impact on the endothelial transcriptome. Nevertheless, by decreasing gelatinase activity in ECs or mouse veins exposed to biomechanical stress, GA diminished a crucial cellular response in the context of venous remodeling. In line with the observed inhibitory effects, local transdermal application of GA attenuated pressure-mediated enlargement of veins in the mouse auricle. In summary, our data identifies GA as an inhibitor of EC proliferation, gelatinase activity and venous remodeling. It may thus have the capacity to attenuate spider vein formation and remodeling in humans.

Fixing the skin barrier: past, present and future--man and dog compared

Skin barrier dysfunction exists in both human and canine atopic dermatitis, leading to increased water loss and potentially facilitating allergen penetration and sensitization. Both lipid (e.g. ceramides) and protein (e.g. filaggrin) abnormalities have been described. Some are genetically inherited (e.g. filaggrin mutations are one of the major risk factors in humans) and some are secondary and linked to inflammation. In humans, numerous studies have shown efficacy of emollients and moisturizers in barrier restoration, and this approach has been for years the mainstay of therapy. Recently, this strategy has shown promise as a preventative function. In veterinary medicine, evidence regarding skin barrier impairment is rapidly building. Decreased ceramides and filaggrin (in some subsets of dogs) have been described. Altered metabolism of ceramides has also been proposed. Despite these preliminary data and the availability of products marketed to improve the skin barrier, evidence regarding the clinical benefit of skin repair intervention is still limited. Preliminary studies have demonstrated that topical application of fatty acids and ceramides and systemic administration of fatty acids improve lipid deficiencies in the skin of dogs with atopic dermatitis, but limited clinical evidence exists. Disease remission in humans is paralleled by an improved skin barrier, both with calcineurin inhibitors and glucocorticoids. In veterinary medicine, a preliminary study on ciclosporin and prednisone failed to detect significant improvement of water loss, while successful immunotherapy correlated with an improved skin barrier. Controlled, large studies are needed to address the question of which skin repair approach is clinically most effective and whether this can be used as a preventative strategy.