First characterization of two C-type lectins of the tubeworm Alaysia sp. from a deep-sea hydrothermal vent.

C-type lectins (CTLs) play an important role in innate immune defense. In this study, we identified and characterized two CTLs (Lec1 and Lec2) from the tubeworm Alaysia sp. collected from a hydrothermal vent in Pacmanus. Lec1 and Lec2 possess the typical CTL domain but share low sequence identities (10.8%-20.4%) with known CTLs. Recombinant (r) of Lec1 and Lec2 bound to various PAMPs and a wide arrange of bacteria from neritic and deep-sea environments in a Ca2+-independent manner, but only rLec1 caused agglutination of the bound bacteria. The activities of rLec1 and rLec2 were most stable and highest at 4 °C, the ambient temperature of the hydrothermal vent, and decreased at higher temperatures. Both lectins inhibited bacterial growth in a highly selective manner and agglutinated the erythrocytes of fish, rabbit, and chicken in a Ca2+-dependent manner. These results provided the first insights into the functional properties of CTLs in deep-sea Alaysia sp.

Alteromonas oceani sp. nov., isolated from deep-sea sediment of a hydrothermal field.

A novel rod-shaped, Gram-stain-negative, aerobic bacterium, designated S35T, was isolated from deep-sea sediment collected from the Pacmanus hydrothermal field, Manus Basin, Papua New Guinea. Strain S35T grew optimally at 28 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. 16S rRNA gene sequence analysis indicated that strain S35T shared 97.38-98.55% similarity with the type strains of Alteromonas lipolytica, Alteromonas mediterranea and Aestuariibacterhalophilus. Phylogenetic analysis showed that strain S35T belonged to the genus Alteromonas. The strain contained ubiquinone-8 as the predominant respiratory lipoquinone. Summed feature 3 (C16 : 1ω7c and/or C16 : 1ω7c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0 were the major fatty acids. The DNA G+C content of strain S35T was 51.3 mol%. These results indicated that strain S35T represents a novel species of the genus Alteromonas, for which the name Alteromonas oceani sp. nov. (type strain S35T=KCTC 52449T=CGMCC 1.16029T) is proposed.

Placental growth factor silencing ameliorates liver fibrosis and angiogenesis and inhibits activation of hepatic stellate cells in a murine model of chronic liver disease.

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family and is involved in pathological angiogenesis associated with chronic liver diseases. However, the precise mechanisms underlying PlGF signalling contributing to liver fibrosis and angiogenesis remain largely unexplored. This study aimed to assess the effect of reducing PlGF expression using small interfering RNA (siRNA) on experimental liver fibrosis and angiogenesis, and to elucidate the underlying molecular mechanisms. Fibrosis was induced in mice by carbon tetrachloride (CCl4 ) for 8 weeks, and mice were treated with PlGF siRNA or non-targeting control siRNA starting two weeks after initiating CCl4 injections. The results showed that PlGF was highly expressed in cirrhotic human and mice livers; which mainly distributed in activated hepatic stellate cells (HSCs). PlGF silencing robustly reduced liver inflammation, fibrosis, intrahepatic macrophage recruitment, and inhibited the activation of HSCs in vivo. Moreover, PlGF siRNA-treated fibrotic mice showed diminished hepatic microvessel density and angiogenic factors, such as hypoxia-inducible factor-1α (HIF-1α), VEGF and VEGF receptor-1. Moreover, down-regulation of PlGF with siRNA in HSCs inhibited the activation and proliferation of HSCs. Mechanistically, overexpression of PlGF in activated HSCs was induced by hypoxia dependent on HIF-1α, and PlGF induces HSC activation and proliferation via activation the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathways. These findings indicate that PlGF plays an important role in liver fibrosis-associated angiogenesis and that blockage of PlGF could be an effective strategy for chronic liver disease.

The serine protease autotransporter Tsh contributes to the virulence of Edwardsiella tarda.

The temperature-sensitive hemagglutinin (Tsh), identified as serine protease autotransporters of the Enterobacteriaceae (SPATEs) proteins, is an important virulence factor for avian-pathogenic Escherichia coli (APEC) and uropathogenic E. coli. However, little is known about the role of Tsh as a virulence factor in Edwardsiella tarda, a severe fish pathogen. In this study, we characterized the Tsh of E. tarda (named TshEt) and examined its function and vaccine potential. TshEt is composed of 1224 residues and has three functional domains typical for autotransporters. Quantitative real-time reverse transcriptase-PCR analysis showed that expression of tshEt was upregulated under conditions of high temperature, increased cell density, high pH, and iron starvation and during the infection of host cells. A markerless tsh in-frame mutant strain, TX01Δtsh, was constructed to determine whether TshEt participates in the pathogenicity of E. tarda, Compared to the wild type TX01, TX01Δtsh exhibited (i) retarded biofilm growth, (ii) decreased resistance against serum killing, (iii) impaired ability to block the host immune response, (iv) attenuated tissue and cellular infectivity. Introduction of a trans-expressed tsh gene restored the lost virulence of TX01Δtsh. The passenger domain of TshEt contains a putative serine protease (PepS) that exhibits apparent proteolytic activity when expressed in and purified from E. coli as a recombinant protein (rPepS). When used as a subunit vaccine to immunize Japanese flounder, rPepS was able to induce effective immune protection. This is the first study of Tsh in a fish pathogen, and the results suggest that TshEt exerts pleiotropic effects on the pathogenesis of E. tarda.