Examination of the Staphylococcus aureus nitric oxide reductase (saNOR) reveals its contribution to modulating intracellular NO levels and cellular respiration.

Staphylococcus aureus nitrosative stress resistance is due in part to flavohemoprotein (Hmp). Although hmp is present in all sequenced S. aureus genomes, 37% of analyzed strains also contain nor, encoding a predicted quinol-type nitric oxide (NO) reductase (saNOR). DAF-FM staining of NO-challenged wild-type, nor, hmp and nor hmp mutant biofilms suggested that Hmp may have a greater contribution to intracellular NO detoxification relative to saNOR. However, saNOR still had a significant impact on intracellular NO levels and complemented NO detoxification in a nor hmp mutant. When grown as NO-challenged static (low-oxygen) cultures, hmp and nor hmp mutants both experienced a delay in growth initiation, whereas the nor mutant's ability to initiate growth was comparable with the wild-type strain. However, saNOR contributed to cell respiration in this assay once growth had resumed, as determined by membrane potential and respiratory activity assays. Expression of nor was upregulated during low-oxygen growth and dependent on SrrAB, a two-component system that regulates expression of respiration and nitrosative stress resistance genes. High-level nor promoter activity was also detectable in a cell subpopulation near the biofilm substratum. These results suggest that saNOR contributes to NO-dependent respiration during nitrosative stress, possibly conferring an advantage to nor+ strains in vivo.

Evidence for the expression of a second CD6 ligand by synovial fibroblasts.

OBJECTIVE: CD6, a cell surface glycoprotein expressed primarily on T cells, may function as a costimulatory molecule and may play a role in autoreactive immune responses. Recently, a CD6 ligand termed CD166 (previously known as activated leukocyte cell adhesion molecule [ALCAM]) has been identified and shown to be expressed on activated T cells, B cells, thymic epithelium, keratinocytes, and in rheumatoid arthritis synovial tissue. However, the results of functional studies have suggested the existence of a second CD6 ligand. The present study was undertaken to seek evidence for a second CD6 ligand on cultured synovial fibroblasts. METHODS: Flow cytometric and biochemical techniques were applied, using anti-CD166 monoclonal antibody (mAb) and a recombinant CD6 fusion protein, to determine whether cultured synovial fibroblasts and other cell types expressed a non-ALCAM CD6 ligand. RESULTS: CD14- fibroblastic synoviocytes showed greater binding of a recombinant CD6 fusion protein than of anti-ALCAM mAb. With interferon-gamma treatment of synovial fibroblasts, binding of both reagents increased, but this was more marked for binding of CD6 fusion protein. Exposure of synovial fibroblasts to other cytokines or to the superantigen staphylococcal enterotoxin A also regulated binding of CD6 fusion protein and anti-ALCAM mAb in a discordant manner. Immunoprecipitation of proteins from membrane extracts of synovial fibroblasts with a CD6-Ig fusion protein revealed a novel 130-kd band distinct from CD166; an identical molecule was also precipitated from membranes of HBL-100 tumor cells. CONCLUSION: Taken together with previous data regarding CD6 and CD166 function, the present findings strongly suggest the existence of a second CD6 ligand distinct from CD166, which can be expressed by synovial fibroblasts as well as other cells.

Contribution of the glycoprotein Ia 807TT, methylene tetrahydrofolate reductase 677TT and prothrombin 20210GA genotypes to prothrombotic risk among factor V 1691GA (Leiden) carriers.

The cooperative effects of the GPIa 807TT, MTHFR 677TT and prothrombin 20210GA genotypes with the FV Leiden 1691GA (FVL) genotype were evaluated by comparing these genotype frequencies in 77 asymptomatic and 156 symptomatic heterozygous FVL carriers. The GPIa 807TT and MTHFR 677TT genotypes did not segregate within the symptomatic FVL carrier group and did not contribute to venous thrombotic risk in this patient cohort. There was no difference in the prothrombin 20210GA genotype frequency between asymptomatic FVL carriers and a random Caucasian control group; however, the prothrombin 20210GA genotype was nearly 5 times as prevalent (19/156 v 2/77; P < 0.02) in the symptomatic FVL carriers (odds ratio 5.21; 95% confidence interval 1.20-47.62), demonstrating that this important prothrombotic risk factor acts synergistically with FVL.

Systemic toxicity following administration of sirolimus (formerly rapamycin) for psoriasis: association of capillary leak syndrome with apoptosis of lesional lymphocytes.

BACKGROUND: Sirolimus (formerly rapamycin) is an immunosuppressive agent that interferes with T-cell activation. After 2 individuals with psoriasis developed a capillary leak syndrome following treatment with oral sirolimus lesional skin cells and activated peripheral blood cells were analyzed for induction of apoptosis. OBSERVATIONS: A keratome skin specimen from 1 patient with sirolimus-induced capillary leak syndrome had a 2.3-fold increase in percentage of apoptotic cells (to 48%) compared with an unaffected sirolimus-treated patient with psoriasis (21%). Activated peripheral blood T cells from patients with psoriasis tended to exhibit greater spontaneous or dexamethasone-induced apoptosis than did normal T cells, particularly in the presence of sirolimus. CONCLUSIONS: Severe adverse effects of sirolimus include fever, anemia, and capillary leak syndrome. These symptoms may be the result of drug-induced apoptosis of lesional leukocytes, especially activated T lymphocytes, and possibly release of inflammatory mediators. Because patients with severe psoriasis may develop capillary leak from various systemic therapies, clinical monitoring is advisable for patients with inflammatory diseases who are treated with immune modulators.

EM changes and other toxic effects of firemaster BP-6 (polybrominated biphenyls) in the mouse.

Groups of Swiss ICR mice were fed 1000 ppm polybrominated biphenyls (FireMaster BP-6) in rodent chow for 4, 8, 11, and 14 days. Control groups were fed standard rodent chow without FireMaster BP-6. Animals were killed at the end of each feeding period and the livers examined by electron microscopy. EM changes noted were progressive increase in size of hepatocytes, a decrease in rough endoplasmic reticulum, a marked increase in smooth endoplasmic reticulum, mitochondrial degeneration, increased lysosomes, and a decrease in glycogen. In addition, there was increasing proliferation of microvilli in bile canaliculi with increasing feeding times. A group of mice fed 1000 ppm FireMaster BP-6 in rodent chow for 11 days had livers with a mean of 13.93% of total body weight as compared with 6.49% for the control group (P=0.02). Tissue distribution following ingestion of 100 ppm FireMaster BP-6 for 14 days was studied. Twelve weeks post-feeding, the tissue concentrations of hexabromobiphenyl in order of highest concentration to lowest were as follows: perithymic fat, perirenal fat, adrenal glands, thymus gland, liver and stomach.