Licochalcone E activates Nrf2/antioxidant response element signaling pathway in both neuronal and microglial cells: therapeutic relevance to neurodegenerative disease.

Oxidative stress and neuroinflammation are hallmarks of neurodegenerative diseases, which do not play independently but work synergistically through complex interactions exacerbating neurodegeneration. Therefore, the mechanism that is directly implicated in controlling oxidative stress and inflammatory response could be an attractive strategy to prevent the onset and/or delay the progression of neurodegenerative diseases. The transcription factor nuclear factor-E2-related factor-2 (Nrf2) is the guardian of redox homeostasis by regulating a battery of antioxidant and phase II detoxification genes, which are relevant to defense mechanism against oxidative stress and inflammatory responses. In this study, we show that a recently identified Glycyrrhiza-inflata-derived chalcone, licochalcone E (Lico-E), attenuates lipopolysaccharide-induced inflammatory responses in microglial BV2 cells and protects dopaminergic SH-SY5Y cells from 6-hydroxydopamine cytotoxicity. Lico-E activates Nrf2-antioxidant response element (ARE) system and up-regulates downstream NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Anti-inflammatory and cytoprotective effects of Lico-E are attenuated in siRNA-mediated Nrf2-silencing cells as well as in the presence with specific inhibitor of HO-1 or NQO1, respectively. Lico-E also has neuroprotective effect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced nigrostriatal dopaminergic neurodegeneration in mice, with up-regulation of HO-1 and NQO1 in the substantia nigra of the brain. This study demonstrates that Lico-E is a potential activator of the Nrf2/ARE-dependent pathway and is therapeutically relevant not only to oxidative-stress-related neurodegeneration but also inflammatory responses of microglial cells both in vitro and in vivo.

Licochalcone E has an antidiabetic effect.

Licochalcone E (lico E) is a retrochalcone isolated from the root of Glycyrrhiza inflata. Retrochalcone compounds evidence a variety of pharmacological profiles, including anticancer, antiparasitic, antibacterial, antioxidative and superoxide-scavenging properties. In this study, we evaluated the biological effects of lico E on adipocyte differentiation in vitro and obesity-related diabetes in vivo. We employed 3T3-L1 preadipocyte and C3H10T1/2 stem cells for in vitro adipocyte differentiation study and diet-induced diabetic mice for in vivo study. The presence of lico E during adipogenesis induced adipocyte differentiation to a significant degree, particularly at the early induction stage. Licochalcone E evidenced weak, but significant, peroxisome proliferator-activated receptor gamma (PPARγ) ligand-binding activity. Two weeks of lico E treatment lowered blood glucose levels and serum triglyceride levels in the diabetic mice. Additionally, treatment with lico E resulted in marked reductions in adipocyte size and increases in the mRNA expression levels of PPARγ in white adipose tissue (WAT). Licochalcone E was also shown to significantly stimulate Akt signaling in epididymal WAT. In conclusion, lico E increases the levels of PPARγ expression, at least in part, via the stimulation of Akt signals and functions as a PPARγ partial agonist, and this increased PPARγ expression enhances adipocyte differentiation and increases the population of small adipocytes, resulting in improvements in hyperglycemia and hyperlipidemia under diabetic conditions.

Licochalcone E reduces chronic allergic contact dermatitis and inhibits IL-12p40 production through down-regulation of NF-kappa B.

Licochalcone, a constituent of licorice, has antitumor, antimicrobial, and anti-inflammatory effects. Recently, licochalcone E was isolated from the roots of Glycyrrhiza inflata and its biological functions are not fully examined. In this study, we investigated its ability to modulate production of IL-12p40, a common subunit of IL-12 and IL-23. Licochalcone E dose-dependently inhibited IL-12p40 production from lipopolysaccharide-stimulated RAW264.7 macrophage cells. The repressive effect was mapped to a region in the IL-12 gene promoter containing a binding site for NF-kappaB. Furthermore, licochalcone E decreased binding to the NF-kappaB site in RAW264.7 macrophage cells. Using a chronic allergic contact dermatitis model induced by repeated application of oxazolone, we showed that licochalcone E inhibited the increased IL-12p40 expression and ear thickness induced by oxazolone. Taken together, licochalcone E inhibits IL-12p40 production and has therapeutic potential to reduce skin inflammation.

Inhibitory effect of chalcones and their derivatives from Glycyrrhiza inflata on protein tyrosine phosphatase 1B.

Compounds (1-6) isolated from the CH(2)Cl(2) extract of Glycyrrhiza inflata and semisynthetic licochalcone A derivatives (7-14) were evaluated for their protein tyrosine phosphatase 1B (PTP1B) inhibitory activities. Licochalcones A (4) and E (6), each with an allyl group at position 5 in the B ring exhibited significant inhibitory effects. Licochalcone A derivative 7, the most potent among the series, had an IC(50) value of 11.7+/-2.0 microM, ca. twofold better than that of licochalcone A (4).

Excavation of lead compounds that inhibit mast cell degranulation by combinatorial chemistry and activity-guided.

An allergic reaction ensues after antigen binds to mast cell or basophil high affinity IgE receptor, Fc epsilonRI, resulting in degranulation of various inflammatory mediators that produce various allergic symptoms. In this study, i) we isolated the active component for the inhibition of mast cell degranulation from the extract of leaves of Castanea crenata and identified it as quercetin; ii) we established the total synthesis procedure of quercetin; iii) using quercetin as positive control, we excavated some lead compounds that possess inhibitory activities for mast cell degranulation by screening the chemical libraries of 1,3-oxazolidine derivatives prepared by solid phase combinatorial chemistry. Some of 1,3-oxazolidine compounds possessing acetyl and 3',4'-dichlorophenyl group displayed strong inhibitory activities on Fc epsilonRI-mediated mast cell degranulation, suggesting that they can be used as lead compounds for the development of anti-allergic agents.