Role of nitric oxide in lipopolysaccharide-induced hepatic injury in D-galactosamine-sensitized mice as an experimental endotoxic shock model

The role of nitric oxide (NO) in lipopolysaccharide (LPS)-induced hepatic injury was studied in D-galactosamine (D-GalN)-sensitized mice. The inducible isoform of NO synthase (iNOS) was immunohistochemically detected on hepatocytes around blood vessels in livers of mice injected with D-GalN and LPS not on hepatocytes in mice injected with D-GalN or LPS alone, although mRNA for iNOS was found in those mice. Nitrotyrosine (NT) was also found in livers of mice injected with D-GalN and LPS. The localization of NT was consistent with that of iNOS, and the time courses of NT and iNOS expression were almost the same. Expression of iNOS and NT was detected exclusively in the hepatic lesions of mice injected with D-GalN and LPS. Anti-tumor necrosis factor alpha neutralizing antibody inhibited iNOS and NT expression and hepatic injury. The results suggested that NO from iNOS may play a role in LPS-induced hepatic injury on D-GalN-sensitized mice as an experimental endotoxic shock model.     

Inhibition of caspase 3 abrogates lipopolysaccharide-induced nitric oxide production by preventing activation of NF-kappaB and c-Jun NH2-terminal kinase/stress-activated protein kinase in RAW 264.7 murine macrophage cells

The effect of caspase inhibitors on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 267.4 murine macrophage cells was investigated. Pretreatment of RAW cells with a broad caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), resulted in a striking reduction in LPS-induced NO production. Z-VAD-FMK inhibited LPS-induced NF-kappaB activation. Furthermore, it blocked phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) but not that of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinases. Similarly, a caspase 3-specific inhibitor, Z-Asp-Glu-Val-Asp-fluoromethylketone, inhibited NO production, NF-kappaB activation, and JNK/SAPK phosphorylation in LPS-stimulated RAW cells. The attenuated NO production was due to inhibition of the expression of an inducible-type NO synthase (iNOS). The overexpression of the dominant negative mutant of JNK/SAPK and the addition of a JNK/SAPK inhibitor blocked iNOS expression but did not block LPS-induced caspase 3 activation. It was therefore suggested that the inhibition of caspase 3 might abrogate LPS-induced NO production by preventing the activation of NF-kappaB and JNK/SAPK. The caspase family, especially caspase 3, is likely to play an important role in the signal transduction for iNOS-mediated NO production in LPS-stimulated mouse macrophages.     

Differential Modulation of Intracellular Survival of Cytosolic and Vacuolar Pathogens by Curcumin

Curcumin, a principal component of turmeric, acts as an immunomodulator regulating the host defenses in response to a diseased condition. The role of curcumin in controlling certain infectious diseases is highly controversial. It is known to alleviate symptoms of Helicobacter pylori infection and exacerbate that of Leishmania infection. We have evaluated the role of curcumin in modulating the fate of various intracellular bacterial pathogens. We show that pretreatment of macrophages with curcumin attenuates the infections caused by Shigella flexneri (clinical isolates) and Listeria monocytogenes and aggravates those caused by Salmonella enterica serovar Typhi CT18 (a clinical isolate), Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Yersinia enterocolitica. Thus, the antimicrobial nature of curcumin is not a general phenomenon. It modulated the intracellular survival of cytosolic (S. flexneri and L. monocytogenes) and vacuolar (Salmonella spp., Y. enterocolitica, and S. aureus) bacteria in distinct ways. Through colocalization experiments, we demonstrated that curcumin prevented the active phagosomal escape of cytosolic pathogens and enhanced the active inhibition of lysosomal fusion by vacuolar pathogens. A chloroquine resistance assay confirmed that curcumin retarded the escape of the cytosolic pathogens, thus reducing their inter- and intracellular spread. We have demonstrated that the membrane-stabilizing activity of curcumin is crucial for its differential effect on the virulence of the bacteria.     

sopB of Salmonella enterica serovar Typhimurium is a potential DNA vaccine candidate in conjugation with live attenuated bacteria

The immune response against Salmonella is multi-faceted involving both the innate and the adaptive immune system. The characterization of specific Salmonella antigens inducing immune response could critically contribute to the development of epitope based vaccines for Salmonella. We have tried to identify a protective T cell epitope(s) of Salmonella, as cell mediated immunity conferred by CD8+ T cells is the most crucial subset conferring protective immunity against Salmonella. It being a proven fact that secreted proteins are better in inducing cell mediated immunity than cell surface and cytosolic antigens, we have analyzed all the genbank annotated Salmonella pathogenicity island 1 and 2 secreted proteins of Salmonella enterica serovar Typhimurium (S. typhimurium) and S. enterica serovar Typhi (S. typhi). They were subjected to BIMAS and SYFPEITHI analysis to map MHC-I and MHC-II binding epitopes. The huge profile of possible T cell epitopes obtained from the two classes of secreted proteins were tabulated and using a scoring system that considers the binding affinity and promiscuity of binding to more than one allele, SopB and SifB were chosen for experimental confirmation in murine immunization model. The entire SopB and SifB genes were cloned into DNA vaccine vectors and were administered along with live attenuated Salmonella and it was found that SopB vaccination reduced the bacterial burden of organs by about 5-fold on day 4 and day 8 after challenge with virulent Salmonella and proved to be a more efficient vaccination strategy than live attenuated bacteria alone.     

Mouse B1 cell line responds to lipopolysaccharide via membrane-bound CD14

The role of membrane-bound CD14 in the response of mouse B1 cell lines to lipopolysaccharide (LPS) was studied. The surface profile of mouse TH2.52 B cells was positive for CD5, IgM, B220, CD11b and F4/80, suggesting that TH2.52 cells carried the typical phenotype of B1 cells. Furthermore, TH2.52 B1 cells were found to express membrane-bound CD14, which plays a critical role in LPS recognition. TH2.52 B1 cells responded to a very low concentration of LPS and exhibited: (i) augmentation of DNA synthesis; (ii) activation of nuclear factor (NF)-kappaB; and (iii) phosphorylation of extracellular signal regulated kinase 1/2 (Erk1/2). They were markedly inhibited by anti-CD14 antibody. Therefore, the expression of membrane-bound CD14 was suggested to provide high sensitivity to LPS for TH2.52 B1 cells.     

Production of experimental autoimmune sialadenitis in mice immunized with homologous salivary gland extract and Klebsiella O3 lipopolysaccharide

An experimental murine model for autoimmune sialadenitis was produced by repeated immunization of homologous salivary gland extract together with Klebsiella O3 lipopolysaccharides as an immunological adjuvant. The cell infiltration was observed in the salivary glands of mice immunized more than twice. Inflammatory cells consisting mainly of CD4+ T cells and CD8+ T cells accumulated at the perivascular regions. There was hyperplasia and enlargement of ductal epithelial cells in the secretory acinar units in salivary glands of repeatedly immunized mice. The repeated immunization developed delayed-type hypersensitivity and autoantibody production to the homologous salivary gland extract. The immunohistochemical analysis showed positive staining on the cuboidal cells in the intercalated ducts, and the columnar pseudostratified cells in the striated ducts. Organ-specific antigens with molecular weights ranging from 20 to 90 kDa were recognized by the sera from immunized mice. Therefore, it was suggested that the sialadenitis was produced by the autoimmune mechanism and might be a new experimental model for characterization of the pathogenesis of autoimmune sialadenitis.     

Expression of Fas and Fas Ligand on Mouse Renal Tubular Epithelial Cells in the Generalized Shwartzman Reaction and Its Relationship to Apoptosis

Previously we reported that the consecutive injection of lipopolysaccharide (LPS) into LPS-sensitized mice for the generalized Shwartzman reaction (GSR) appeared to induce the injury of renal tubular epithelial cells via apoptosis. The aim of this study was to characterize the mechanism of renal tubular epithelial cell injury in GSR. The expression of Fas and Fas ligand was immunohistochemically detected on renal tubular epithelial cells from GSR-induced mice, although neither Fas nor Fas ligand was found in cells from untreated control mice or in cells from mice receiving a single injection of LPS. GSR-induced renal tubular epithelial cell injury was produced in neither Fas-negative MRL-lpr/lpr mice nor Fas ligand-negative MRL-gld/gld mice. The administration of anti-gamma interferon antibody together with a preparative injection of LPS prevented the expression of Fas and Fas ligand and the apoptosis of renal tubular epithelial cells. A provocative injection of tumor necrosis factor alpha into LPS-sensitized mice augmented Fas and Fas ligand expression and the apoptosis of renal tubular epithelial cells. The administration of tumor necrosis factor alpha to interleukin-12-sensitized mice resulted in Fas and Fas ligand expression and the apoptosis. Sensitization with interleukin-12 together with anti-gamma interferon antibody did not cause the apoptosis of renal tubular epithelial cells. It was suggested that the Fas/Fas ligand system probably plays a critical role in the development of renal tubular epithelial cell injury through apoptotic cell death.