Antibacterial activity and cytotoxicity of a novel bacteriocin isolated from Pseudomonas sp. strain 166.

Pseudomonas sp. strain 166 was isolated from soil samples from Changbai Mountains. A novel bacteriocin PA166 from Pseudomonas sp. 166 was purified using ammonium sulfate, dextran gel chromatography column and Q-Sepharose column chromatography successively. The molecular mass of bacteriocin PA166 was found to be 49.38 kDa by SDS-PAGE and liquid chromatography-mass spectrometry (MS)/MS. Bacteriocin PA166 showed stability at a wide range of pH (2-10), and thermal stability (40, 60, 80 and 100°C). The bacteriocin PA166 antimicrobial activity was slightly inhibited by Ca2+ , K+ and Mg2+ . The minimum bactericidal concentrations of bacteriocin PA166 against five Pasteurella multocida strains ranged from 2 to 8 µg ml-1 . Bacteriocin PA166 showed low cytotoxicity and a higher treatment index (TI = 82.51). Fluorescence spectroscopy indicated that bacteriocin PA166 destroyed the cell membrane to exert antimicrobial activity. In summary, bacteriocin PA166 had strong antibacterial activity, high TI and low toxicity, and hence could serve as a potential clinical therapeutic drug.

Focal Adhesion Kinase Regulates Hepatic Stellate Cell Activation and Liver Fibrosis.

Understanding the underlying molecular mechanisms of liver fibrosis is important to develop effective therapy. Herein, we show that focal-adhesion-kinse (FAK) plays a key role in promoting hepatic stellate cells (HSCs) activation in vitro and liver fibrosis progression in vivo. FAK activation is associated with increased expression of α-smooth muscle actin (α-SMA) and collagen in fibrotic live tissues. Transforming growth factor beta-1 (TGF-ß1) induces FAK activation in a time and dose dependent manner. FAK activation precedes the α-SMA expression in HSCs. Inhibition of FAK activation blocks the α-SMA and collagen expression, and inhibits the formation of stress fibers in TGF-ß1 treated HSCs. Furthermore, inhibition of FAK activation significantly reduces HSC migration and small GTPase activation, and induces apoptotic signaling in TGF-ß1 treated HSCs. Importantly, FAK inhibitor attenuates liver fibrosis in vivo and significantly reduces collagen and α-SMA expression in an animal model of liver fibrosis. These data demonstrate that FAK plays an essential role in HSC activation and liver fibrosis progression, and FAK signaling pathway could be a potential target for liver fibrosis.

Tristetraprolin Down-Regulation Contributes to Persistent TNF-Alpha Expression Induced by Cigarette Smoke Extract through a Post-Transcriptional Mechanism.

RATIONALE: Tumor necrosis factor-alpha (TNF-α) is a potent pro-inflammatory mediator and its expression is up-regulated in chronic obstructive pulmonary disease (COPD). Tristetraprolin (TTP) is implicated in regulation of TNF-α expression; however, whether TTP is involved in cigarette smoke-induced TNF-α expression has not been determined. METHODS: TTP expression was examined by western blot analysis in murine alveolar macrophages and alveolar epithelial cells challenged without or with cigarette smoke extract (CSE). TNF-α mRNA stability, and the decay of TNF-α mRNA, were determined by real-time quantitative RT-PCR. TNF-α protein levels were examined at the same time in these cells. To identify the molecular mechanism involved, a construct expressing the human beta-globin reporter mRNA containing the TNF-α 3'-untranslated region was generated to characterize the TTP targeted site within TNF-α mRNA. RESULTS: CSE induced TTP down-regulation in alveolar macrophages and alveolar epithelial cells. Reduced TTP expression resulted in significantly increased TNF-α mRNA stability. Importantly, increased TNF-α mRNA stability due to impaired TTP function resulted in significantly increased TNF-α levels in these cells. Forced TTP expression abrogated the increased TNF-α mRNA stability and expression induced by CSE. By using the globin reporter construct containing TNF-α mRNA 3'-untranslated region, the data indicate that TTP directly targets the adenine- and uridine-rich region (ARE) of TNF-α mRNA and negatively regulates TNF-α expression at the post-transcriptional level. CONCLUSION: The data demonstrate that cigarette smoke exposure reduces TTP expression and impairs TTP function, resulting in significantly increased TNF-α mRNA stability and excessive TNF-α expression in alveolar macrophages and epithelial cells. The data suggest that TTP is a novel post-transcriptional regulator and limits excessive TNF-α expression and inflammatory response induced by cigarette smoke.

[Gene expression changes of regucalcin and prohibitin in cirrhotic rat liver and the related effects of compound glutathione inosine injection intervention].

OBJECTIVE: To study expression of regucalcin (RGN) and prohibitin (PHB) genes in cirrhotic rat liver and to investigate the related effects of compound glutathione inosine injection (CGII) intervention. METHODS: Forty male Wistar rats were randomly divided into a control group (n=12) and a model group (n=28).The model was established by injecting sterile porcine serum (0.5 mL) into the rat abdominal cavity, twice weekly for 8 consecutive weeks; the control group rats were treated with physiological saline injection (0.5 mL) into the abdominal cavity with the same frequency and time span. During the modeling period, four rats from the model group were randomly selected at different time points to examine changes in liver pathology. Upon pathology confirmation of liver cirrhosis, the porcine serum injection was terminated. The remaining 24 rats in the model group were randomly divided into a fibrosis group and a CGII treatment group.The CGII group received CGII (intramuscular injection of 0.018 mL 100g-1 body weight) once a day for 6 continuous weeks; the fibrosis rats were treated with the same dosage of physiological saline with the same frequency and time span.Liver tissue morphology was examined by both hematoxylin-eosin and Masson's staining. RGN and PHB expression at the mRNA and protein levels in liver tissues were detected by real time RT-PCR and immunohistochemical staining, respectively. RESULTS: Both the mRNA and protein expression levels of RGN and PHB were significantly lower in the liver tissues of the fibrosis group than in the control group.CGII intervention led to significant alleviation of the liver fibrosis severity; moreover, the mRNA and protein expression levels of RGN and PHB were significantly higher than those in the fibrosis group. CONCLUSION: Down-regulation of regucalcin and prohibitin gene expression might contribute to the pathogenesis of liver cirrhosis.