Clinical isolates of Staphylococcus aureus have osteolytic surface proteins and a proportion of the population have antibodies that block this activity: is this of prognostic significance?

Staphylococcus aureus is directly implicated in the bone destruction associated with infected orthopaedic implants and bacterial arthritis. The Oxford (laboratory) strain of this organism has surface-associated proteins (SAPs) which have potent osteolytic activity. In this study, we have examined the osteolytic activity of SAPs from clinical isolates and also investigated the role of the humoral immune response to such proteins. Nine patients with infected orthopaedic prostheses or infective arthritis, and six volunteers not suffering from overt S. aureus infection, were examined. The sera from 5/9 patients and 4/6 volunteers were able to neutralize the osteolytic activity of the SAPs. The SAPs were extracted from four clinical isolates and were found to have osteolytic activity, but with a wide range of efficacies and potencies. All four patients from whom the clinical isolates were obtained had serum IgG antibodies to the surface proteins from their autologous isolates as determined by ELISA. In conclusion, clinical isolates of S. aureus contain osteolytic SAPs which may be responsible for bone destruction. Apparently disease-free individuals and patients have antibodies able to block this activity. However, since the capacity of patients' sera to neutralize the activity of the SAPs derived from their own S. aureus isolate was not investigated, it is unclear whether these findings are of prognostic value.      

Enhanced co-stimulatory ability of synovial fluid accessory cells in rheumatoid arthritis

We have established in vitro assays that allow the examination of co- stimulatory function of rheumatoid arthritis (RA) antigen-presenting cells (APC). Synovial fluid (SF) and peripheral blood (PB) APC co- stimulatory ability was compared in the activation of peptide-specific human T-cell clones. T-cell receptor (TCR) stimulation by peptide or anti-CD3 antibody allowed the direct comparison of SF and PB APC co- stimulatory activity, separately from their ability to process antigen. SF APC from 15 RA patients consistently enhanced T-cell proliferation when compared to their PB counterparts. Moreover, increasing the numbers of PB APC present resulted in only a minor increase in T-cell proliferation, failing to achieve levels stimulated by SF APC. We propose that the enhanced co-stimulatory function of synovial APC may be a significant factor in the persistence of local immune responses in RA.      

博莱霉素致肺纤维化大鼠肺组织表面活性物质蛋白A B C mRNA的表达

目的观察博莱霉素致肺纤维化大鼠肺组织表面活性物质蛋白（ＳＰ）Ａ、Ｂ、ＣｍＲＮＡ的表达。方法气管内灌注博莱霉素Ａ５，复制肺纤维化模型，分别于３、７、１４和２８天处死动物，提取肺组织总ＲＮＡ，进行Ｎｏｒｔｈｅｒｎ杂交。结果肺纤维化大鼠肺泡Ⅱ型上皮细胞数量增加。灌注博莱霉素后第３天ＳＰＡ、ＳＰＢ及ＳＰＣｍＲＮＡ的表达即开始下降，７天时降至最低点，而后于１４天时开始回升，至２８天时上升最明显。但仍低于正常。结论博莱霉素致纤维化大鼠肺组织ＳＰＡ、ＳＰＢ及ＳＰＣｍＲＮＡ的表达减低。肺泡Ⅱ型上皮细胞功能的改变可能参与肺纤维化的发病过程。     

An essential role for lysophosphatidylcholine in the inhibition of platelet aggregation by secretory phospholipase A2

The release of secretory phospholipase A2 (sPLA2) into the mammalian circulation may contribute to the development of hemorrhagic and inflammatory diseases. sPLA2 has previously been shown to alter the behavior of platelets, leukocytes, and endothelial cells, although the molecular basis for these cellular effects has not been established. Our studies indicate that the inhibition of platelet aggregation by snake, bee venom, and pancreatic sPLA2 is dependent on a plasma cofactor. This cofactor resides within the lipoprotein fraction of plasma, with 54%, 31%, and 11% of the activity present in the high- density lipoprotein (HDL), low-density lipoprotein (LDL), and very low density lipoprotein (VLDL) fractions, respectively. Delipidation of HDL and LDL was associated with the complete loss of platelet-inhibitory activity. Incubation of purified sPLA2 with the HDL fraction of plasma resulted in the time-dependent generation of lysophosphatidylcholine (lysoPC). The formation of lysoPC correlated with the inhibition of platelet aggregation. Purified lysoPC (10 to 100 micrograms/mL) inhibited platelet aggregation and dense granule release induced by thrombin (0.05 U/mL), collagen (1 micrograms/mL), ionophore A23187 (2 mumol/L), ADP (12.5 mumol/L), and adrenaline (3.2 mumol/L). The inhibition of platelet aggregation by lysoPC was dose-dependent and correlated with decreased fibrinogen binding to glycoprotein IIb-IIIa. Our studies indicate that the enzymatic generation of lysoPC from plasma lipoproteins is essential for the sPLA2-mediated inhibition of platelet activation in the presence of albumin. These results raise the possibility that the toxic effects of circulating sPLA2 may be due in part to the generation of the bioactive lysophospholipid, lysoPC.     

Lith1, a major gene affecting cholesterol gallstone formation among inbred strains of mice.

The prevalence of cholesterol gallstones differs among inbred strains of mice fed a diet containing 15% (wt/wt) dairy fat, 1% (wt/wt) cholesterol, and 0.5% (wt/wt) cholic acid. Strains C57L, SWR, and A were notable for a high prevalence of cholelithiasis; strains C57BL/6, C3H, and SJL had an intermediate prevalence; and strains SM, AKR, and DBA/2 exhibited no cholelithiasis after consuming the diet for 18 weeks. Genetic analysis of the difference in gallstone prevalence rates between strains AKR and C57L was carried out by using the AKXL recombinant inbred strain set and (AKR x C57L)F1 x AKR backcross mice. Susceptibility to gallstone formation was found to be a dominant trait determined by at least two genes. A major gene, named Lith1, mapped to mouse chromosome 2. When examined after 6 weeks on the lithogenic diet, the activity of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.88) was downregulated as expected in the gallstone-resistant strains, AKR and SJL, but this enzyme failed to downregulate in C57L and SWR, the gallstone-susceptible strains. This suggests that regulation of the rate-limiting enzyme in cholesterol biosynthesis may be pivotal in determining the occurrence and severity of cholesterol hypersecretion and hence lithogenicity of gallbladder bile. These studies indicate that genetic factors are critical in determining gallstone formation and that the genetic resources of the mouse model may permit these factors to be identified.     

Preventive and curative effect of methanolic extract of Gardenia gummifera Linn. f. on thioacetamide induced oxidative stress in rats

ObjectiveTo evaluate the antioxidant and antihepatotoxic effect of methanolic extract of Gardenia gummifera Linn. f. root (MEGG) on thioacetamide (TAA) induced oxidative stress in male Wistar rats.MethodsIn the preventive study, rats were administered with 125 and 250 mg/kg of MEGG for 9 days prior to TAA administration (100 mg/kg s.c.). In post-treatment groups, rats were treated with MEGG at doses of 125 and 250 mg/kg, 2, 24 and 48 h after TAA intoxication. Silymarin was used as a standard drug control (100 mg/kg). Hepatotoxicity was assessed by quantifying the serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). The antioxidant potential of MEGG was evaluated by the estimation of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation [thiobarbituric acid reactive substances (TBARS)] in hepatic and renal tissues. Histopathological changes were also evaluated.ResultsMEGG significantly (P≤0.05) prevented the elevation of serum AST, ALT, ALP, LDH and tissue malondialdehyde levels in both experimental groups, when compared to the TAA alone treated groups. The rats receiving TAA plus MEGG exhibited significant (P≤0.05) increases in hepatic and renal antioxidant activities including GSH, GST, GR, GPx and CAT levels. Quantification of histopathological changes also supported the dose dependent protective effects of MEGG.ConclusionsThese observations suggest that MEGG has dose dependent hepatoprotective and antioxidant effect against TAA induced oxidative stress.     

Adriamycin and daunomycin generate reactive oxygen compounds in erythrocytes

Adriamycin and daunomycin produce dose-related cardiac toxicity that may be related to oxygen radicals. Addition of these compounds to human erythrocyte suspensions resulted in stimulation of hexose monophosphate shunt activity that was markedly impaired in the absence of oxyhemoglobin. Evidence for generation of hydrogen peroxide by these compounds was provided by oxidation of reduced glutathione, by 14C- formate oxidation, and by the catalase-aminotriazole trapping technique. These experiments indicate that Adriamycin and daunomycin interact with oxyhemoglobin to generate reactive oxygen metabolites. A similar interaction with oxymyoglobin may occur in the heart and produce oxygen radicals that injure cardiac myocytes.