Bacterial cell wall components regulate adipokine secretion from visceral adipocytes

Recent studies suggest a relationship between intestinal microbiota and metabolic syndromes; however, the underlying mechanism remains unclear. To clarify this issue, we assessed the effects of bacterial cell wall components on adiponectin, leptin and resistin secretion from rat visceral adipocytes in vitro. We also measured the relative population of Firmicutes and Bacteroidetes in fecal microbiota and the amount of fecal mucin as an intestinal barrier function, when mice were fed a high-fat diet. In the present study, we demonstrated that bacterial cell wall components affect the secretion of adipokines, depending on the presence of antigens from gram-positive or gram-negative bacteria. Lipopolysaccharide markedly inhibited adiponectin, leptin, and resistin secretion, whereas peptidoglycan increased adiponectin secretion and decreased resistin secretion in vitro. In vivo experiments showed that the high-fat diet increased the population of Firmicutes and decreased that of Bacteroidetes. In contrast, the high-fat diet downregulated the stool output and fecal mucin content. These results demonstrate that bacterial cell wall components affect the onset of metabolic syndromes by mediating the secretion of adipokines from visceral adipose tissue. Furthermore, we believe that metabolic endotoxemia is not due to the increasing dominance of gram-negative bacteria, Bacteroidetes, but due to the depression of intestinal barrier function.     

满天星染料木黄酮对小鼠急性肝损伤的保护作用及机制

目的:研究满天星活性成分染料木黄酮对脂多糖(lipopolysaccharide,LPS)或D-氨基半乳糖(D-galactosamine,D-Gal N)诱导引起的小鼠急性肝损伤的保护作用及其机制。方法:雄性小鼠随机分为正常组、模型组、染料木黄酮低、中、高剂量组。正常组和模型组ip等容量生理盐水,染料木黄酮低、中、高剂量组分别腹腔注射0.5,1,2 mg·kg-1的染料木黄酮,每日1次。连续给药3 d后,除正常组外,其余各组小鼠ip LPS(50μg·kg-1)和D-Gal N(800 mg·kg-1),1.5 h后,眼眶血管丛取血,6 h后处死。采集肝脏组织,检测小鼠血清丙氨酸转氨酶(ALT),天冬氨酸转氨酶(AST),胆红素的水平;并检测各组小鼠肝组织中丙二醛(MDA),肿瘤坏死因子-α(TNF-α),一氧化氮(NO)含量及TNF-α,诱导型一氧化氮合酶(i NOS)mRNA,核因子(NF)-κB p65,半胱氨酸天冬氨酸蛋白酶-3(Caspase-3)和B细胞淋巴瘤/白血病2(Bcl-2)表达情况;同时做组织学检查,观察肝组织的病理变化。结果:与模型组比较,染料木黄酮显著降低小鼠血清中AST,ALT活性,明显减轻组织病理损伤;可抑制NF-κB的激活,继而减少炎症因子TNF-α,NO和i NOS的水平。此外,染料木黄酮明显抑制Caspase-3的表达,提高Bcl-2的水平,提升胆红素的含量。结论:满天星染料木黄酮对小鼠急性肝损伤具有明显的保护作用,其机制与抑制NF-κB信号通路、减轻炎症反应有关。     

Evidence for ProTα-TLR4/MD-2 binding: molecular dynamics and gravimetric assay studies

Objective: During preconditioning, lipopolysaccharide (LPS) selectively activates TLR4/MD-2/Toll/IL-1 receptor-domain-containing adaptor inducing IFN-β (TRIF) pathway instead of pro-inflammatory myeloid differentiation protein-88 (MyD88)/MyD88-adaptor-like protein (MAL) pathway. Extracellular prothymosin alpha (ProTα) is also known to selectively activate the TLR4/MD2/TRIF–IRF3 pathway in certain diseased conditions. In the current study, biophysical evidence for ProTα/TLR4/MD-2 complex formation and its interaction dynamics have been studied.

Research design and methods: Gravimetric assay was used to investigate ProTα/TLR4/MD-2 complex formation while molecular dynamics (MD) simulation was used to study its interaction dynamics.

Results: Through electrostatic interaction, full-length ProTα (F-ProTα) C-terminal peptide (aa 91 – 111) superficially interacts with similar TLR4/MD-2 (K_D = 273.36 nm vs 16.07 μg/ml [LPS]) conformation with LPS at an overlapping three-dimensional space while F-ProTα is hinged to the TLR4 scaffold by one-amino acid shift-Mosoian domain (aa-51 – 90). Comparatively, F-ProTα better stabilizes MD-2 metastable states transition and mediates higher TLR4/MD-2 interaction than LPS.

Conclusions: ProTα via its C-terminal peptide (aa 91 – 111) exhibits in vitro biophysical contact with TLR4/MD-2 complex conformation recognized by LPS at overlapping LPS-binding positions.     

ShcC proteins: Brain aging and beyond

To date, most studies of Shc family of signaling adaptor proteins have been focused on the near-ubiquitously expressed ShcA, indicating its relevance to age-related diseases and longevity. Although the role of the neuronal ShcC protein is much less investigated, accumulated evidence suggests its importance for neuroprotection against such aging-associated conditions as brain ischemia and oxidative stress. Here, we summarize more than decade of studies on the ShcC expression and function in normal brain, age-related brain pathologies and immune disorders with a focus on the interactions of ShcC with signaling proteins/pathways, and the possible implications of these interactions for changes associated with aging.     

心型脂肪酸结合蛋白对脂多糖所致心肌细胞损伤的保护作用

目的：探讨心型脂肪酸结合蛋白(heart-fatt y acid binding protein,H-FABP)对脂多糖(lipopolysaccharide,LPS) 所致心肌细胞损伤的保护作用。方法：以原代培养的新生大鼠心肌细胞为模型,通过基因转染方式改变H-FABP表 达水平,采用Western印迹、定量PCR检测原代培养中H-FABP的表达。分别检测心肌细胞培养液中TNF-α,IL-1β,乳 酸脱氢酶(lactate dehydrogenase,LDH)含量以及细胞存活率来反映LPS诱导的心肌细胞损伤与炎症反应。结果：LPS处 理24 h能增加H-FABP表达。SiRNA降低H-FABP后,显著促进LPS引起的心肌细胞存活率下降、LDH释放以及TNF-α和 IL-1β释放。相反,H-FABP过表达能显著抑制LPS引起的心肌细胞损伤与炎症反应。结论：H-FABP对LPS引起的心肌 细胞损伤具有保护作用。     

A new approach for therapeutic vaccination against chronic HBV infections

There are currently about 257 million people suffering from chronic HBV infection worldwide. In many cases, an insufficient T cell response is causative for establishment of a chronic infection. To ensure a robust cellular immune response and induction of neutralizing antibodies a novel vaccine platform based on modified cell–permeable HBV capsids was utilized. Cell permeability was achieved by fusion of the membrane–permeable TLM-peptide to HBV core monomers, assembling the capsids. Insertion of a Strep-tagIII into the spike tip domain that protrudes from the capsid surface enables flexible loading with antigens that are fused to streptavidin. In this study, HBV surface antigen-derived PreS1PreS2 domain, fused to monomeric streptavidin, served as cargo antigen. Binding between antigen and capsids was characterized by surface plasmon resonance spectroscopy, electron microscopy and density gradient centrifugation. Confocal immunofluorescence microscopy and in vivo imaging of immunized mice demonstrated membrane permeability of cargo-loaded carriers and spread of antigen over the whole organism. Immunization experiments of mice revealed a robust induction of a specific cellular immune response, leading to destruction of HBV-positive cells and induction of HBV-specific neutralizing antibodies. Membrane permeability of these carriers allows needle-free application of antigen-loaded capsids as evidenced by induction of an HBV-specific CTL response and HBV-specific B cell response after oral or transdermal vaccination.These data indicate that cell–permeable antigen carriers, based on HBV capsids and loaded with HBV antigen, have the capacity to induce a cellular and a neutralizing humoral immune response. In addition, cell permeability of the vaccine platform enables antigen transfer across several cell layers, that could allow oral or transdermal immunization.     

Diverse immune functions of hemocyanins

Substantial evidence gathered recently has revealed the multiple functionalities of hemocyanin. Contrary to previous claims that this ancient protein is involved solely in oxygen transport within the hemolymph of invertebrates, hemocyanin and hemocyanin-derived peptides have been linked to key aspects of innate immunity, in particular, antiviral and phenoloxidase-like activities. Both phenoloxidase and hemocyanin belong to the family of type-3 copper proteins and share a high degree of sequence homology. While the importance of phenoloxidase in immunity and development is well characterised, the contribution of hemocyanin to biological defence systems within invertebrates is not recognised widely.     

Human apolipoprotein A-I Gly26Arg stimulation of inflammatory responses via NF-kB activation: Potential roles in amyloidosis?

The cascade of molecular events leading to Human apolipoprotein A–I (apoA–I) amyloidosis is not completely understood, not even the pathways that determine clinical manifestations associated to systemic protein deposition in organs such as liver, kidney and heart. About twenty natural variants of apoA–I were described as inducing amyloidosis, but the mechanisms driving their aggregation and deposition are still unclear. We previously identified that the mutant Gly26Arg but not Lys107-0 induced the release of cytokines and reactive oxygen species from cultured RAW 264.7 murine macrophages, suggesting that part of the pathogenic pathway could elicit of an inflammatory signal. In this work we gained deep insight into this mechanism and determined that Gly26Arg induced a specific pro-inflammatory cascade involving activation of NF-κB and its translocation into the nucleus. These findings suggest that some but not all apoA–I natural variants might promote a pro-oxidant microenvironment which could in turn result in oxidative processing of the variants into a misfolded conformation.