Involvement of the Lipopolysaccharides of Azospirilla in the Interaction with Wheat Seedling Roots

The present study was undertaken to comparatively investigate the attachment capacities of Azospirillum brasilenseSp245 and its lipopolysaccharide-defective Omegon-Km mutants KM018 and KM252, as well as their activities with respect to the alteration of the morphology of wheat seedling root hairs. The adsorption dynamics of the parent Sp245 and mutant KM252 strains of azospirilla on the seedling roots of the soft spring wheat cv. Saratovskaya 29 were similar; however, the attachment capacity of the mutant KM252 was lower than that of the parent strain throughout the incubation period (15 min to 48 h). The mutation led to a considerable decrease in the hydrophobicity of the Azospirillumcell surface. The lipopolysaccharides extracted from the outer membrane of A. brasilenseSp245 and mutant cells with hot phenol and purified by chromatographic methods were found to induce the deformation of the wheat seedling root hairs, the lipopolysaccharide of the parent strain being the most active in this respect. The role of the carbohydrate moiety of lipopolysaccharides in the interaction of Azospirillumcells with plants is discussed.     

Structural and immunochemical studies on the lipopolysaccharide of the ‘T-antigen’-containing mutant Proteus mirabilis R14/1959

Abstract In DOC-PAGE, lipopolysaccharide (LPS) of Proteus mirabilis R14/1959 (Rb-type) mutant showed a ladder-like migration pattern indicating the presence of a high molecular weight polysaccharide chain. The isolated polysaccharide, called T-antigen because of similarity with the T1 chain of Salmonella friedenau LPS, contained d -glucose, d -galacturonic acid ( d -GalA), and d -GlcNAc in molar ratios 2:1:1 and was structurally different from the O-antigen of the parental S-strain P. mirabilis S1959 but identical to the O-antigen of another S-strain Proteus penneri 42. The importance of a d -GalA( l -Lys)-containing epitope, most likely present in the core region of LPS, and of GalA present in the T-antigen chain in manifesting the serological specificity of P. mirabilis R14/1959 were revealed using rabbit polyclonal homologous and heterologous R- and O-specific antisera and the appropriate antigens, including synthetic antigens which represent partial structures of various Proteus LPS.     

Biochemical characterization of an ABC transporter LptBFGC complex required for the outer membrane sorting of lipopolysaccharides

Seven Lpt proteins (A through G) are thought to be involved in lipopolysaccharide transport from the inner to outer membrane of Escherichia coli. LptB belongs to the ATP-binding cassette transporter superfamily. Although the lptB gene lacks neighboring genes encoding membrane subunits, bioinformatic analyses recently indicated that two distantly located consecutive genes, lptF and lptG, could encode membrane subunits. To examine this possibility, LptB was expressed with LptF and LptG. We report here that both LptF and LptG formed a complex with LptB. Furthermore, an inner membrane protein, LptC, which had been implicated in lipopolysaccharide transport, was also included in this complex.

Structured summary

MINT-7137021: lptb (uniprotkb:P0A9V1) physically interacts (MI:0914) with lptc (uniprotkb:P0ADV9), lptg (uniprotkb:P0ADC6) and lptf (uniprotkb:P0AF98) by pull down (MI:0096)MINT-7137160: lptb (uniprotkb:P0A9V1) physically interacts (MI:0914) with lptf (uniprotkb:P0AF98) and lptg (uniprotkb:P0ADC6) by pull down (MI:0096)     

N-乙酰半胱氨酸抗脂多糖诱导的肺动脉损伤的研究

目的 :探讨N 乙酰半胱氨酸 (N acetylcysteine,NAC)减轻脂多糖 (lipopolysaccharide ,LPS)所致的肺损伤及其机制。方法 :应用血管环张力检测技术和扫描电镜方法 ,观察了NAC对LPS引起的肺动脉反应性及肺动脉内皮细胞超微结构变化的影响 ;并测定了肺动脉组织中丙二醛 (malondialhyde ,MDA)、超氧化物歧化酶 (superoxidedismutes ,SOD)及一氧化氮 (nitricoxide,NO)的变化。结果 :LPS(4μg/ml,7h)可降低肺动脉对乙酰胆碱 (ACh)介导的内皮依赖性舒张反应 ,NAC(0 .5mmol/L)可逆转此种反应降低而对正常肺动脉舒缩反应无明显影响 ;NAC可改善LPS引起的肺动脉内皮细胞超微结构损伤并可逆转LPS引起的肺动脉组织中MDA、NO含量增高和SOD活性降低。结论 :NAC可通过抗氧化作用保护肺动脉内皮细胞并增强肺动脉内皮依赖性舒张反应 ,提示此可能是其发挥抗肺动脉压增高从而改善内毒素所致肺损伤的机制之一。     

Aminothiazoles inhibit RANKL‐ and LPS‐mediated osteoclastogenesis and PGE2 production in RAW 264.7 cells

Periodontitis is characterized by chronic inflammation and osteoclast‐mediated bone loss regulated by the receptor activator of nuclear factor‐κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG). The aim of this study was to investigate the effect of aminothiazoles targeting prostaglandin E synthase‐1 (mPGES‐1) on RANKL‐ and lipopolysaccharide (LPS)‐mediated osteoclastogenesis and prostaglandin E₂ (PGE₂) production in vitro using the osteoclast precursor RAW 264.7 cells. RAW 264.7 cells were treated with RANKL or LPS alone or in combination with the aminothiazoles 4‐([4‐(2‐naphthyl)‐1,3‐thiazol‐2‐yl]amino)phenol (TH‐848) or 4‐(3‐fluoro‐4‐methoxyphenyl)‐N‐(4‐phenoxyphenyl)‐1,3‐thiazol‐2‐amine (TH‐644). Aminothiazoles significantly decreased the number of multinucleated tartrate‐resistant acid phosphatase (TRAP)‐positive osteoclast‐like cells in cultures of RANKL‐ and LPS‐stimulated RAW 264.7 cells, as well as reduced the production of PGE₂ in culture supernatants. LPS‐treatment induced mPGES‐1 mRNA expression at 16 hrs and the subsequent PGE₂ production at 72 hrs. Conversely, RANKL did not affect PGE₂ secretion but markedly reduced mPGES‐1 at mRNA level. Furthermore, mRNA expression of TRAP and cathepsin K (CTSK) was reduced by aminothiazoles in RAW 264.7 cells activated by LPS, whereas RANK, OPG or tumour necrosis factor α mRNA expression was not significantly affected. In RANKL‐activated RAW 264.7 cells, TH‐848 and TH‐644 down‐regulated CTSK but not TRAP mRNA expression. Moreover, the inhibitory effect of aminothiazoles on PGE₂ production was also confirmed in LPS‐stimulated human peripheral blood mononuclear cell cultures. In conclusion, the aminothiazoles reduced both LPS‐ and RANKL‐mediated osteoclastogenesis and PGE₂ production in RAW 264.7 cells, suggesting these compounds as potential inhibitors for treatment of chronic inflammatory bone resorption, such as periodontitis.     

Emulsified lipids increase endotoxemia: possible role in early postprandial low-grade inflammation

Low-grade inflammation is a risk factor for the onset of atherosclerosis. Little is known about the involvement of endotoxin absorption from the gut during the digestion of lipids. In the present study, we first investigated in humans the impact of a mixed meal containing dispersed lipids on postprandial endotoxemia and inflammation. We then investigated the effect of (i) oil emulsification in vivo in rats and (ii) fatty acid amounts in vitro using Caco-2 cells on postprandial endotoxemia. In humans, postprandial endotoxemia increased early after the meal. Moreover, we evidenced that the endotoxin receptor sCD14 increased during digestion and that chylomicrons could contribute to absorbed endotoxin transport. This could explain the significant peak of inflammatory cytokine IL-6 that we observed 2 h after the mixed meal. Interestingly, in rats, the emulsion led to both higher endotoxemia and hypertriglyceridemia than oil and compared to a control saline load. In vitro, incubation of Caco-2 cells with increasing fatty acid concentrations enhanced epithelial absorption of endotoxin. To our knowledge, this is the first study evidencing in healthy humans that, following a mixed meal containing lipids, increased endotoxemia is associated with raised sCD14 and a peak of IL-6. On a repeated basis, this may thus be a triggering cascade for the onset of atherosclerosis. In this respect, optimizing both dietary fat amount and structure could be a possible strategy to limit such low-grade endotoxemia and inflammation by the control of postprandial lipemia.     

Steroids and triterpenoids from Eastern Nigeria mistletoe, Loranthus micranthus Linn. (Loranthaceae) parasitic on Kola acuminata with immunomodulatory potentials

In search of immunomodulatory constituents from the Eastern Nigeria mistletoe, Loranthus micranthus Linn, two new stigmastane steroids: stigmast-7,20 (21)-diene-3β-hydroxy-6-one (1) and 3β-hydroxy-stigmast-23-ene (2); three (two new and one known) lupeol-based triterpenoid esters: 7β,15α-dihydroxyl-lup-20(29)-ene-3β-palmitate (3), 7β,15α-dihydroxyl-lup-20(29)-ene-3β-stearate (4) and 7β,15α-dihydroxyl-lup-20(29)-ene-3β-eicosanoate (5) were isolated and characterized following bioactivity-guided fractionation. The new compounds, 1, 2, 4 and 5 at concentrations of 10, 25 and 100 μg/ml were subjected to cell proliferation and early activation marker (CD69) expression studies in C57Bl/6 mice splenocytes using flow cytometry techniques against Lipopolysaccharide (LPS; 10 μg/ml) and Concanavalin A (ConA; 2 μg/ml) standards. The stigmastane steroids (1 and 2) at the highest concentration of 100 μg/ml showed statistically significantly (p < 0.05) stimulatory activity on the C57B1/6 splenocytes compared to the controls with values of 46 ± 0.76% and 43 ± 0.46% compared to 7.69 ± 0.41% recorded for the negative control. The novel lupeol esters, 4 and 5 at same concentration of 100 μg/ml exhibited lower stimulations of 30 ± 0.41% and 29 ± 0.17% respectively compared to the controls above. The CD69 expression assay at the above doses showed that all the compounds have minimal stimulation. The present study supports the observed immunomodulatory property of the Eastern Nigeria mistletoe and thus confirms the efficacy of this plant in mitigating against wide array of disease conditions orchestrated by immunodeficiency.     

Over-expression of a RhoA-specific guanine nucleotide exchange factor, p190RhoGEF, in mouse dendritic cells negatively regulates cellular responses to bacterial lipopolysaccharide

We studied the role of a RhoA-specific guanine nucleotide exchange factor (p190RhoGEF) in dendritic cells (DCs), using transgenic (TG) mice that over-express a full gene of p190RhoGEF under the control of an invariant chain promoter. TG mice lacked localization of activated DCs to the T cell zone in the spleen and had reduced serum levels of IL-6 in response to lipopolysaccharide (LPS) injection. DCs from these mice also showed reduced surface expression of CD86, CD40, and CD205, but not MHCII, as well as a reduced capability to uptake antigen. Moreover, chemokine-driven migration and secretion of IL-6, but not of IL-12, were impaired after LPS-stimulation of TG DCs. Collectively, these results suggest that over-expressing p190RhoGEF negatively regulates conventional DC function in response to bacterial LPS infection.