Concurrent regulation of AMP-activated protein kinase and SIRT1 in mammalian cells

We examined in HepG2 cells whether glucose-induced changes in AMP-activated protein kinase (AMPK) activity could be mediated by SIRT1, an NAD⁺-dependent histone/protein deacetylase that has been linked to the increase in longevity caused by caloric restriction. Incubation with 25 vs. 5 mM glucose for 6 h concurrently diminished the phosphorylation of AMPK (Thr 172) and ACC (Ser 79), increased lactate release, and decreased the abundance and activity of SIRT1. In contrast, incubation with pyruvate (0.1 and 1 mM) for 2 h increased AMPK phosphorylation and SIRT1 abundance and activity. The putative SIRT1 activators resveratrol and quercetin also increased AMPK phosphorylation. None of the tested compounds (low or high glucose, pyruvate, and resveratrol) significantly altered the AMP/ATP ratio. Collectively, these findings raise the possibility that glucose-induced changes in AMPK are linked to alterations in SIRT1 abundance and activity and possibly cellular redox state.     

Systemic administration of diarylpropionitrile (DPN) or phytoestrogens does not affect anxiety-related behaviors in gonadally intact male rats

The development of highly selective agonists for the two major subforms of the estrogen receptor (ERα and ERβ) has produced new experimental methodologies for delineating the distinct functional role each plays in neurobehavioral biology. It has also been suggested that these compounds might have the potential to treat estrogen influenced behavioral disorders, such as anxiety and depression. Prior work has established that the ERβ agonist, diarylpropionitrile (DPN) is anxiolytic in gonadectomized animals of both sexes, but whether or not this effect persists in gonadally intact individuals is unknown. Isoflavone phytoestrogens, also potent but less selective ERβ agonists, have also been shown to influence anxiety in multiple species and are becoming more readily available to humans as health supplements. Here we determined the effects of 0.5, 1 or 2 mg/kg DPN, 1 mg/kg of the ERα agonist propyl-pyrazole-triol (PPT), 3 or 20 mg/kg of the isoflavone equol (EQ) and 3 or 20 mg/kg of the isoflavone polyphenol resveratrol (RES) on anxiety behavior in the gonadally intact male rat using the light/dark box and the elevated plus maze. We first determined that DPN can be successfully administered either orally or by subcutaneous injection, although plasma DPN levels are significantly lower if given orally. Once injected, plasma levels peak rapidly and then decline to baseline levels within 3 h of administration. For the behavioral studies, all compounds were injected and the animals were tested within 3 h of treatment. None of the compounds, at any of the doses, significantly altered anxiety-related behavior. Plasma testosterone levels were also not significantly altered suggesting that these compounds do not interfere with endogenous androgen levels. The results suggest that the efficacy of ERβ agonists may depend on gonadal status. Therefore the therapeutic potential of ERβ selective agonists to treat mood disorders may be limited.     

Novel isolation of resveratrol dimer O-glucosides with enantiomeric aglycones from the leaves of Shorea cordifolia

Two O-glucosides of resveratrol dimers, ampelopsin F-11b-O-β-glucopyranosides with enantiomeric aglycones [cordifoloside A (1) and cordifoloside B (2)] and an enantiomer of the aglycone [(?)-ampelopsin F] were isolated from the leaves of Shorea cordifolia (Dipterocarpaceae). These structures were identified on the basis of spectroscopic evidence and their absolute configurations were elucidated using circular dichroism data. This is the first report on oligostilbenoids that demonstrates the co-occurrence of diastereomeric O-glucosides with enantiomeric aglycones in this family.     

The molecular basis for the inhibition of phosphodiesterase-4D by three natural resveratrol analogs. Isolation,molecular docking,molecular dynamics simulations,binding free energy,and bioassay

The phosphodiesterase-4 (PDE4) enzyme is a promising therapeutic target for several diseases. Our previous studies found resveratrol and moracin M to be natural PDE4 inhibitors. In the present study, three natural resveratrol analogs [pterostilbene, (E)-2′,3,5′,5-tetrahydroxystilbene (THSB), and oxyresveratrol] are structurally related to resveratrol and moracin M, but their inhibition and mechanism against PDE4 are still unclear. A combined method consisting of molecular docking, molecular dynamics (MD) simulations, binding free energy, and bioassay was performed to better understand their inhibitory mechanism. The binding pattern of pterostilbene demonstrates that it involves hydrophobic/aromatic interactions with Phe340 and Phe372, and forms hydrogen bond(s) with His160 and Gln369 in the active site pocket. The present work also reveals that oxyresveratrol and THSB can bind to PDE4D and exhibits less negative predicted binding free energies than pterostilbene, which was qualitatively validated by bioassay (IC₅₀ = 96.6, 36.1, and 27.0 μM, respectively). Additionally, a linear correlation (R² = 0.953) is achieved for five PDE4D/ligand complexes between the predicted binding free energies and the experimental counterparts approximately estimated from their IC₅₀ values (≈RT ln IC₅₀). Our results imply that hydrophobic/aromatic forces are the primary factors in explaining the mechanism of inhibition by the three products. Results of the study help to understand the inhibitory mechanism of the three natural products, and thus help the discovery of novel PDE4 inhibitors from resveratrol, moracin M, and other natural products.     

Resveratrol Binding to Human Serum Albumin

Abstract

Resveratrol (Res), a polyphenolic compound found largely in the skin of red grape and wine, exhibits a wide range of pharmaceutical properties and plays a role in prevention of human cardiovascular diseases [Pendurthi et al., Arterioscler. Thromb. Vasc. Biol. 19, 419–426 (1999)]. It shows a strong affinity towards protein binding and used as inhibitor for cyclo- oxygenase and ribonuclease reductase. The aim of this study was to examine the interaction of resveratrol with human serum albumin (HSA) in aqueous solution at physiological conditions, using a constant protein concentration (0.3 mM) and various pigment contents μM to mM). FTIR, UV-Visible, CD, and fluorescence spectroscopic methods were used to determine the resveratrol binding mode, the binding constant and the effects of pigment complexation on protein secondary structure.

Structural analysis showed that resveratrol bind non-specifically (H-bonding) via polypeptide polar groups with overall binding constant of K_Res = 2.56× 10⁵ M^?1. The protein secondary structure, analysed by CD spectroscopy, showed no major alterations at low resveratrol concentrations (0.125 mM), whereas at high pigment content (1 mM), major increase of α-helix from 57% (free HSA) to 62% and a decrease of β-sheet from 10% (free HSA) to 7% occurred in the resveratrol-HSA complexes. The results indicate a partial stabilization of protein secondary structure at high resveratrol content.     

Inhibitory effect of resveratrol dimerized derivatives on nitric oxide production in lipopolysaccharide-induced RAW 264.7 cells

Four types of resveratrol dimerized analogues were synthesized and evaluated in vitro on LPS-induced NO production in RAW 264.7 cells. The results showed that several compounds, especially those containing 1,2-diphenyl-2,3-dihydro-1H-indene core (type I), exhibited good inhibitory activities. Among 25 analogues, 12b showed a significant inhibitory activity (49% NO production at 10 μM, IC₅₀ = 3.38 μM). Further study revealed that compound 12b could suppress LPS-induced iNOS expression, NO production, and IL-1β release in a concentration-dependently manner. The mechanism of action (MOA) involved for its anti-inflammatory responses was through signaling pathways of p38 MAPK and JNK1/2, but not ERK1/2.     

Resveratrol,an Ingredient of Wine,Acts Synergistically with Ara-C and Tiazofurin in HL-60 Human Promyelocytic Leukemia Cells

Resveratrol (RV), a naturally occurring stilbene derivative, is a potent free radical scavenger causing a number of biochemical and antineoplastic effects. It was shown to induce differentiation and apoptosis in leukemia cells and was also identified as an inhibitor of ribonucleotide reductase (RR), a key enzyme of DNA synthesis.

In this study, we report about the biochemical effects of RV in HL-60 human promyelocytic leukemia cells. RV effectively inhibited in situ RR activity. Furthermore, incubation of HL-60 cells with RV significantly decreased intracellular dCTP, dTTP, dATP and dGTP concentrations. In growth inhibition and clonogenic assays, RV acted synergistically with both Ara-C and tiazofurin in HL-60 cells. We conclude that RV could become a viable candidate as one compound in the combination chemotherapy of leukemia and therefore deserves further in vitro and in vivo testing.     

5,6-Dihydro-5-aza-2′-deoxycytidine potentiates the anti-HIV-1 activity of ribonucleotide reductase inhibitors

The nucleoside analog 5,6-dihydro-5-aza-2′-deoxycytidine (KP-1212) has been investigated as a first-in-class lethal mutagen of human immunodeficiency virus type-1 (HIV-1). Since a prodrug monotherapy did not reduce viral loads in Phase II clinical trials, we tested if ribonucleotide reductase inhibitors (RNRIs) combined with KP-1212 would improve antiviral activity. KP-1212 potentiated the activity of gemcitabine and resveratrol and simultaneously increased the viral mutant frequency. G-to-C mutations predominated with the KP-1212-resveratrol combination. These observations represent the first demonstration of a mild anti-HIV-1 mutagen potentiating the antiretroviral activity of RNRIs and encourage the clinical translation of enhanced viral mutagenesis in treating HIV-1 infection.