Salmonella O48 Serum Resistance is Connected with the Elongation of the Lipopolysaccharide O-Antigen Containing Sialic Acid.

Complement is one of the most important parts of the innate immune system. Some bacteria can gain resistance against the bactericidal action of complement by decorating their outer cell surface with lipopolysaccharides (LPSs) containing a very long O-antigen or with specific outer membrane proteins. Additionally, the presence of sialic acid in the LPS molecules can provide a level of protection for bacteria, likening them to human cells, a phenomenon known as molecular mimicry. Salmonella O48, which contains sialic acid in the O-antigen, is the major cause of reptile-associated salmonellosis, a worldwide public health problem. In this study, we tested the effect of prolonged exposure to human serum on strains from Salmonella serogroup O48, specifically on the O-antigen length. After multiple passages in serum, three out of four tested strains became resistant to serum action. The gas-liquid chromatography/tandem mass spectrometry analysis showed that, for most of the strains, the average length of the LPS O-antigen increased. Thus, we have discovered a link between the resistance of bacterial cells to serum and the elongation of the LPS O-antigen.

Preliminary study on application of urine amino acids profiling for monitoring of renal tubular injury using GLC-MS.

BACKGROUND: The early diagnosis of the nephrotoxic effect of xenobiotics and drugs is still an unsolved problem. Recent studies suggest a correlation between the nephrotoxic activity of xenobiotics and increased concentration of amino acids in urine. The presented study was focused on the application of GLC-MS method for amino acids profiling in human urine as a noninvasive method for monitoring of kidney condition and tubular injury level. MATERIAL AND METHODS: The analytic method is based on the conversion of the amino acids present in the sample to tert-butyldimethylsilyl (TBDMS) derivatives and their analysis by gas-liquid chromatography-mass spectrometry (GLC-MS). The procedure of urine sample preparation for chromatographic analysis was optimized. RESULTS: The presence of 12 amino acids in most of the tested healthy human urine samples was detected. The significant differences in the levels of particular amino acids between patients with tubular injury and healthy controls were found, especially for lysine, valine, serine, alanine and leucine (on average 30.0, 7.5, 3.6, 2.9 and 0.5 fold respectively). CONCLUSIONS: We found that this approach based on GLC-MS detection can be used in nephrotoxicity studies for urine amino acids monitoring in exposure to xenobiotics and drugs.

H-Ras increases release of sphingosine resulting in down-regulation of TSP-1 in non-transformed cells.

Tumour progression is continuously driven by a sequence of genetic events. The presence of mutant or activated Ras proteins represents an interesting paradigm for the investigation of oncogene-dependent induction of tumour angiogenesis. These genes are widely distributed in human cancers. Previously we have shown that cells harbouring mutant H-Ras release soluble unidentified factor(s) associated with lowered expression of an angiogenesis inhibitor - Thrombospondin-1 - (TSP-1) in adjacent normal tissue. In this study, we have addressed the question as to whether or not introduction of the H-ras oncogene leads to increased production of sphingosine. To assess the amount of sphingosine in conditioned media, we developed a technique based on sphingolipid isolation and GC-MSMS detection of specific silylated sphingosine derivatives. Cells harbouring mutant H-Ras, release significant amounts of sphingosine in contrast to normal isogenic cells or premalignant cells. Increased concentration of sphingosine in conditioned media was correlated with their ability to down-regulate the expression of TSP-1. Moreover, medium collected in the presence of U0126, an inhibitor of MAPK kinase (MEK), contained undetectable amounts of sphingosine and had no ability to down-regulate TSP-1 expression. Overall, our studies suggest a H-Ras-dependent mechanism of changing the equilibrium of angiogenic factors in favour of induction of angiogenesis, where a central role is played by sphingosine, a low molecular entity. This represents an example of how a mechanism of translating genetic changes within transformed cells could be amplified into a much larger effect involving the tumour parenchyma and stroma, and this could greatly in turn accelerate local tumour growth and metastasis.