In order to identify active constituents and to gain some information regarding their mode of action, extracts from leaves of Epipremnum pinnatum were tested for their ability to inhibit inflammatory gene expression in endothelial- and monocyte-like cells (HUVECtert and THP-1, respectively). Bioactivity-guided fractionation using expression of PTGS2 (COX-2) mRNA as a readout resulted in the isolation of two C13 megastigmane glycosides, gusanlungionoside C (1) and citroside A (3), and the phenylalcohol glycoside phenylmethyl-2-O-(6-O-rhamnosyl)-ß-D-galactopyranoside (2). Further analysis identified six additional megastigmane glycosides and the aglycones β-damascenone (10), megastigmatrienone (11), 3-hydroxy-β-damascenone (12), and 3-oxo-7,8-dihydro-α-ionol (13). Pharmacological analysis demonstrated that 10 inhibits LPS-stimulated induction of mRNAs encoding for proinflammatory cytokines and leukocyte adhesion molecules, such as TNF-α, IL-1β, IL-8, COX-2, E-selectin, ICAM-1, and VCAM-1 in HUVECtert and THP-1 cells. 10 inhibited induction of inflammatory genes in HUVECtert and THP-1 cells treated with different agonists, such as TNF-α, IL-1β, and LPS. In addition to mRNA, also the upregulation of inflammatory proteins was inhibited by 10 as demonstrated by immune assays for cell surface E-selectin and secreted TNF-α. Finally, using a luciferase reporter construct, it was shown, that 10 inhibits NF-κB-dependent transcription. Therefore, we hypothesize that inhibition of NF-κB by β-damascenone (10) may represent one of the mechanisms underlying the in vitro anti-inflammatory activity of Epipremnum pinnatum extracts.
Murine 3T3-L1 adipocytes share many similarities with primary fat cells and represent a reliable in vitro model of adipogenesis. The aim of this study was to probe the effect of S-nitrosoglutathione (GSNO) on adipocyte differentiation. Adipogenesis was induced with a mixture of insulin, dexamethasone, and 3-isobutyl-1-methylxanthine in the absence and presence of increasing GSNO concentrations. Biochemical analysis after 7 days of differentiation showed a prominent anti-adipogenic effect of GSNO which was evident as reduced cellular triglycerides and total protein content as well as decreased mRNA and protein expression of late transcription factors (e.g. peroxisome proliferator activated receptor γ) and markers of terminal differentiation (e.g. leptin). By contrast, the nitrosothiol did not affect mRNA and protein expression of CCAAT/enhancer-binding protein β (C/EBPβ), which represents a pivotal early transcription factor of the adipogenic cascade. Differentiation was also inhibited by the NO donor (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate. Biotin switch experiments showed significantly increased S-nitrosation of C/EBPβ variants indicating that posttranslational S-nitrosative modification of this transcription factor accounts for the observed anti-adipogenic effect of NO. Our results suggest that S-nitrosation might represent an important physiological regulatory mechanism of fat cell maturation.
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