ABSTRACT
New classes of antibiotics with different mechanisms of action are urgently required for combating antimicrobial resistance. Blestriacin, a dihydro-biphenanthrene with significant antibacterial activity, was recently isolated from the fibrous roots of Bletilla striata. Here, we report the further characterization of the antimicrobial potential and mode of action of blestriacin. The phenanthrene compound inhibited the growth of all tested clinical isolates of Staphylococcus aureus including methicillin-resistant S. aureus (MRSA). The minimum inhibitory concentrations (MICs) of blestriacin against these pathogens ranged from 2 to 8 µg/mL. Minimum bactericidal concentration (MBC) tests were conducted, and the results demonstrated that blestriacin was bactericidal against S. aureus. This effect was confirmed by the time-kill assays. At bactericidal concentrations, blestriacin caused loss of membrane potential in B. subtilis and S. aureus and disrupted the bacterial membrane integrity of the two strains. The spontaneous mutation frequency of S. aureus to blestriacin was determined to be lower than 10-9. The selection and whole genome sequencing of the blestriacin -resistant mutants of S. aureus indicated that the development of blestriacin resistance in S. aureus involves mutations in multi-genes. All these observations can be rationalized by the suggestion that membrane is a biological target of blestriacin.
ABSTRACT
Ym1 and Ym2 (Ym1/2) are chitinase-like proteins and we reported previously that IL-4 induced Ym1/2 in mouse bone marrow-derived mast cells. In the present study, ovalbumin-induced asthmatic mice were used to investigate the effect of glucocorticoids on Ym1/2 expression. Ym1/2 were highly induced in bronchoalveolar lavage fluid (BALF) and the lung. Ym1/2 expression was completely inhibited by dexamethasone (Dex) in BALF and weakly inhibited in the lung. Primary cultured macrophages were used to investigate the inhibition of Ym1/2 expression at the cellular level. Although Dex pretreatment inhibited the Ym1/2 expression level in an animal model, it did not reduce IL-4 induction of Ym1/2 expression in vitro. Next, we tested whether Dex blocks IL-4 induced STAT6 signaling and found that it had no inhibitory effect on the phosphorylation level of STAT6 in macrophages. The luciferase reporter assay also revealed that Dex did not inhibit IL-4 induction of Ym1/2 promoter activity. These results indicate that the inhibitory effect of Dex on Ym1/2 protein expression in the murine model of asthma does not involve the STAT6 signaling pathway.
Subject(s)
Chitinases/metabolism , Dexamethasone/pharmacology , Lectins/metabolism , STAT6 Transcription Factor/physiology , beta-N-Acetylhexosaminidases/metabolism , Animals , Blotting, Northern , Blotting, Western , Bronchoalveolar Lavage Fluid/cytology , Cells, Cultured , Chitinases/biosynthesis , Electrophoresis, Polyacrylamide Gel , Female , Indicators and Reagents , Lectins/biosynthesis , Luciferases/genetics , Luciferases/metabolism , Macrophages/drug effects , Macrophages/metabolism , Mice , Mice, Inbred BALB C , Ovalbumin/metabolism , Phosphorylation , Plasmids/genetics , Reverse Transcriptase Polymerase Chain Reaction , Transfection , beta-N-Acetylhexosaminidases/biosynthesisABSTRACT
As part of an ongoing investigation to find bioactive medicinal herbs exerting anti-inflammation activity, the effect of an ethanol extract from the parts of Ailanthus altissima (Simaroubaceae) was evaluated in both in vitro and in in vivo system. The ethanol extract of A. altissima (EAa) inhibited generation of the cyclooxygenase-2 (COX-2) dependent phases of prostaglandin D2 in bone marrow-derived mast cells (BMMC) in a concentration-dependent manner with an IC50 value of 214.6 microg/ml. However, this compound did not inhibit COX-2 protein expression up to a concentration of 400 microg/ml in the BMMC, indicating that EAa directly inhibits COX-2 activity. In addition, EAa inhibited leukotriene C4 production with an IC50 value of 25.7 microg/ml. Furthermore, this compound inhibited degranulation reaction in a dose dependent manner, with an IC50 value of 27.3 microg/ml. Ovalbumin (OVA)-sensitized mice were orally pretreated with EAa before aerosol challenges. EAa reduced the eosinophil infiltration into the airway and the eotaxin, IL-4, and IL-13 mRNA expression levels. These results suggest that the anti-inflammation activity of A. altissima in OVA-induced lung inflammation may occur in part via the down regulation of T(H)2 cytokines and eotaxin transcripts as well as the inhibition of inflammatory mediators.
Subject(s)
Ailanthus/chemistry , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Ovalbumin , Pneumonia/chemically induced , Pneumonia/prevention & control , Animals , Arachidonate 5-Lipoxygenase/metabolism , Arachidonic Acid/metabolism , Blotting, Western , Bone Marrow Cells/enzymology , Bronchoalveolar Lavage Fluid/cytology , Cyclooxygenase 2/metabolism , Cyclooxygenase 2 Inhibitors/pharmacology , Cytokines/biosynthesis , DNA, Complementary/biosynthesis , Eosinophils/physiology , Female , Leukocyte Count , Mast Cells/enzymology , Mice , Mice, Inbred BALB C , Prostaglandin D2/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction , beta-N-Acetylhexosaminidases/metabolismABSTRACT
The effect of deoxypodophyllotoxin (DPT) isolated from Anthriscus sylvestris Hoffm. was evaluated in an IN VIVO animal model for antiasthmatic activity. DPT (1.0 to 5 mg/kg) was given orally to ovalbumin (OVA)/alum-induced asthmatic mice. DPT reduced the number of infiltrated eosinophils in bronchoalveolar lavage (BAL) fluid in a dose-dependent manner. Dexamethasone (5 mg/kg), which was used as a positive control, also strongly inhibited the number of infiltrated eosinophils. The effect of DPT on a transcript profile in a murine asthma model was determined by RT-PCR, which showed that DPT decreased the mRNA levels of the Th2 cytokines. Northern blot analysis showed that DPT also reduced both the eotaxin and arginase I mRNA levels in a dose-dependent manner.
