Schisandrin B attenuates lipopolysaccharide-induced activation of hepatic stellate cells through Nrf-2-activating anti-oxidative activity.

Activated hepatic stellate cells (HSCs) are known to have a potential role in increasing the deposition of ECM and elevating proliferation in liver fibrosis, which can be driven by lipopolysaccharide (LPS). Schisandrin B (SB) is a dibenzocyclooctadiene derivative of Schisandra chinensis with anti-oxidative stress activity, but its effective target is unknown. Here, we have evaluated whether SB is protective against the LPS-induced activation of HSCs and have explored the underlying anti-oxidative stress mechanisms of SB. HSCs were treated with SB 1 h prior to LPS, and then incubated for indicated time. Nrf-2 in HSCs was inhibited genetically. The simultaneous effects on Nrf-2 activity, oxidative stress, cell proliferation, and ECM deposition were examined. SB decreased LPS-induced cell proliferation, fibrosis, and oxidative stress in HSCs. We further demonstrated that the protective effects of SB in LPS-induced HSCs activation involve the modulation of Nrf-2. SB, specifically targeting Nrf-2, attenuates the oxidative stress in HSCs. SB also reduces LPS-induced fibrosis and cell viability in HSCs. In addition, Nrf-2 may serve as a therapeutic target for infections or periods of chronic oxidative stress and may help with future drug discovery.

Catalytic and electrocatalytic oxidation of ethanol over palladium-based nanoalloy catalysts.

The control of the nanoscale composition and structure of alloy catalysts plays an important role in heterogeneous catalysis. This paper describes novel findings of an investigation for Pd-based nanoalloy catalysts (PdCo and PdCu) for ethanol oxidation reaction (EOR) in gas phase and alkaline electrolyte. Although the PdCo catalyst exhibits a mass activity similar to Pd, the PdCu catalyst is shown to display a much higher mass activity than Pd for the electrocatalytic EOR in alkaline electrolyte. This finding is consistent with the finding on the surface enrichment of Pd on the alloyed PdCu surface, in contrast to the surface enrichment of Co in the alloyed PdCo surface. The viability of C-C bond cleavage was also probed for the PdCu catalysts in both gas-phase and electrolyte-phase EOR. In the gas-phase reaction, although the catalytic conversion rate for CO2 product is higher over Pd than PdCu, the nanoalloy PdCu catalyst appears to suppress the formation of acetic acid, which is a significant portion of the product in the case of pure Pd catalyst. In the alkaline electrolyte, CO2 was detected from the gas phase above the electrolyte upon acid treatment following the electrolysis, along with traces of aldehyde and acetic acid. An analysis of the electrochemical properties indicates that the oxophilicity of the base metal alloyed with Pd, in addition to the surface enrichment of metals, may have played an important role in the observed difference of the catalytic and electrocatalytic activities. In comparison with Pd alloyed with Co, the results for Pd alloyed with Cu showed a more significant positive shift of the reduction potential of the oxygenated Pd species on the surface. These findings have important implications for further fine-tuning of the Pd nanoalloys in terms of base metal composition toward highly active and selective catalysts for EOR.

On resin amino acid side chain attachment strategy for the head to tail synthesis of new glutamine containing gramicidin-S analogs and their antimicrobial activity.

The alarming increase in infections caused by multiple drug resistant bacteria including methicillin-resistant Staphylococcus aureus has prompted a desperate search for new antimicrobials. Augmenting the discoveries of completely new scaffolds with antimicrobial activity are efforts aimed at modifying existing molecules to optimize activity or reduce toxicity. We report herein the parallel solid-phase synthesis of analogues of the cationic antimicrobial peptide gramicidin S (GS) using amino acid side chain attachment strategy. The ornithine (Orn) residues were replaced by glutamine (Gln) and the aromatic D-phenylalanine (Phe) were replaced by different aromatic D-amino acids. Additional Gln containing GS analogues with all the possible combinations of the hydrophobic amino acids valine and leucine were also synthesized. In this work we also report the antibacterial activity of these analogs against several clinically-important drug-resistant Gram-positive and Gram-negative pathogens.