Isoliquiritigenin exerts antioxidant activity in Caenorhabditis elegans via insulin-like signaling pathway and SKN-1.

BACKGROUND: Glycyrrhiza uralensis is a well-known medicinal plant. Different therapeutic effects have been reported for its secondary metabolites, including neuroprotective activity. Antioxidant properties have also been documented for some of its compounds and it could be a possible mechanism of neuroprotection. PURPOSE: The present study was conducted to investigate the antioxidant effect and underlying pathways of G. uralensis and its main compounds. METHODS: The experiments were conducted with Caenorhabditis elegans, a simple in vivo model, widely used in this context. The methanol extract of G. uralensis and its main compounds isoliquiritigenin, liquiritigenin, glycyrrhizic acid, and glycyrrhetinic acid were tested for their effects on heat shock protein expression under mild oxidative stress and survival rate under lethal oxidative stress. To clarify the underlying pathways, the effect on the transcription factors DAF-16, SKN-1, and HSF-1 was tested. RESULTS: Isoliquiritigenin was the most potent compound in both assays, leading to a 31% decrease in expression of the stress marker heat shock protein and an 87% increase in survival rate. It significantly activated DAF-16 and SKN-1, but not HSF-1. CONCLUSION: The present study identified isoliquiritigenin as the most active antioxidant compound in G. uralensis. It exerts its effect by activating the transcription factors DAF-16/FOXO and SKN-1/Nrf2 which regulate many genes, including those which code for proteins of antioxidative response. This implicates isoliquiritigenin as a possible supplement drug against oxidative stress especially in neurodegenerative diseases.

Carlina acaulis Exhibits Antioxidant Activity and Counteracts Aß Toxicity in Caenorhabditis elegans.

Carlina acaulis is a medicinal plant that has shown antioxidant activity in in vitro studies, but to date no corresponding in vivo data is available. Therefore, in the present study the antioxidant activity and its impact in counteracting Aß toxicity were studied in the Caenorhabditis elegans model. A dichloromethane extract of the roots of C. acaulis was prepared and characterised via gas-liquid-chromatography/mass-spectrometry (GLC-MS). The in vitro antioxidant activity was confirmed via 2,2-diphenyl-1-picrylhydracyl assay. The extract was further separated by thin layer chromatography into two fractions, one of which was a fraction of the dichloromethane extract of C. acaulis containing mostly Carlina oxide (CarOx). Different strains of C. elegans were employed to study the expression of hsp-16.2p::GFP as a marker for oxidative stress, delocalisation of the transcription factor DAF-16 as a possible mechanism of antioxidant activity, the effect of the drug under lethal oxidative stress, and the effect against beta-amyloid (Aß) toxicity in a paralysis assay. The C. acaulis extract and CarOx showed high antioxidant activity (stress reduction by 47% and 64%, respectively) in C. elegans and could activate the transcription factor DAF-16 which directs the expression of anti-stress genes. In paralysis assay, only the total extract was significantly active, delaying paralysis by 1.6 h. In conclusion, in vivo antioxidant activity was shown for C. acaulis for the first time in the C. elegans model. The active antioxidant compound is Carlina oxide. This activity, however, is not sufficient to counteract Aß toxicity. Other mechanisms and possibly other active compounds are involved in this effect.

Extracts of Glycyrrhiza uralensis and isoliquiritigenin counteract amyloid-ß toxicity in Caenorhabditis elegans.

Alzheimer's disease is a rising threat for modern societies as more and more people reach old age. To date, there is no effective treatment for this condition. In this study, we investigated the potential of Glycyrrhiza uralensis to counteract amyloid-ß toxicity, one of the key features of Alzheimer's disease. An LC-MS/MS analysis revealed glycyrrhizic acid and glycosylated forms of isoliquiritigenin and liquiritigenin as major constituents of water and methanol extracts of G. uralensis. These extracts and the pure compounds were tested for their activity in two Caenorhabditis elegans models of amyloid-ß aggregation and amyloid-ß toxicity, respectively. The number of amyloid-ß aggregates decreased by 30% after treatment with isoliquiritigenin, the methanol extract could reduce the number by 14%, liquiritigenin and glycyrrhizic acid by 15%, and the aglycon of glycyrrhizic acid, glycyrrhetinic acid, by 20%. Both extracts and isoliquiritigenin also showed significant activity against acute amyloid-ß toxicity in transgenic C. elegans that express human amyloid-ß peptides, delaying the paralysis in this model by 1.8 h and 1.1 h, respectively. We conclude that secondary compounds of G. uralensis may become interesting drug candidates for the treatment of Alzheimer's disease, which, however, need further analysis in other model systems.

Effects of methylphenidate: the cellular point of view.

The psychostimulant methylphenidate (MPH) is the first choice of treatment in attention-deficit hyperactivity disorder and is based mainly on inhibition of dopamine transporter (DAT). Nonetheless, the complete cellular effects of MPH are still unknown. We attempted to determine whether MPH influences neurotransmitter levels, synaptic gene expression, and cell proliferation in a dose-dependent manner in rat pheochromocytoma cells (PC12) lacking DAT. PC12 were treated in a dose-dependent manner with MPH. Gene expression level of synaptotagmin (Syt) 1 and 4, syntaxin 1a (Stx1a), and synaptic vesicle glycoprotein 2C (SV2C) was measured using quantitative real-time RT-PCR. Different Neurotransmitter release was measured using high-performance liquid chromatography (HPLC). Differences in cell proliferation were evaluated via BrdU incorporation. Treatment with low-dose MPH (1-100 nM) altered intra-/extracellular neurotransmitter levels, down-regulated all investigated genes as well as enhanced cell proliferation significantly. These data point to diverse effects of MPH on cell metabolism independent of inhibiting DAT.