Kimiharu Hirose

In Vivo Synergy Between Green Tea Extract and Levofloxacin Against Enterohemorrhagic Escherichia coli O157 Infection

We studied the synergistic effects of Japanese green tea extract (JGTE) and levofloxacin (LVFX) against enterohemorrhagic Escherichia coli (EHEC) infection in a gnotobiotic mouse model. Mice fed on JGTE conferred a significant degree of protection against an oral challenge with EHEC. Complete elimination of the bacteria from the mice, was however, difficult. The combination of JGTE and LVFX increased the survival rate and reduced damage to target organs. Thus, dietary supplementation with JGTE improved the therapeutic effects of antibiotic treatment.

Porphyromonas gingivalis modulates the production of interleukin 8 and monocyte chemotactic protein 1 in human vascular endothelial cells.

Porphyromonas gingivalis seems to perturb the cytokine network to maintain periodontal disease. Although endothelial cells are a leading source of interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1), the effect of P. gingivalis on the cells remains unclear. We used reverse transcription-PCR (RT-PCR) to assess levels of IL-8 and MCP-1 mRNA and enzyme-linked immunosorbent assays (ELISA) to evaluate their protein production by human umbilical vein endothelial cells (HUVEC) challenged with P. gingivalis. IL-8 and MCP-1 protein levels decreased in response to challenge with P. gingivalis, and N-a-p-tosyl-L-lysine chloromethylketone (TLCK) prevented the degradation of these chemokines. Furthermore, the bacteria upregulated expression of the mRNAs of these chemokines. Our results indicate that P. gingivalis proteases degraded IL-8 and MCP-1. Degradation of chemokines secreted from endothelial cells may decrease the recruitment of leukocytes and their migration through the endothelium, thus contributing to a delay in the host immune defense mechanism.

Levels of Porphyromonas gingivalis Fimbriae and Inflammatory Cytokines in Gingival Crevicular Fluid from Adult Human Subjects

The Porphyromonas gingivalis fimbriae level was examined in the gingival crevicular fluid (GCF) from adult human subjects using an immunoblot assay with a monoclonal antibody. The cytokines, interleukin‐1α (IL‐1α), IL‐1β, IL‐6 and tumor necrosis factor‐a (TNF‐α) levels in the GCF were quantified by enzyme‐linked immunosorbent assay (ELISA). The reactivity of the GCF samples with the monoclonal antibody against P. gingivalis fimbriae was related to the IL‐1β, IL‐6 and TNF‐α levels. Moreover, the fimbriae content was associated with the gingival index (GI). In contrast, no significant correlation was seen between the fimbriae content and IL‐1α level. These results suggest that there are possible associations between P. gingivalis fimbriae and IL‐1β, IL‐6 and TNF‐α in the gingival crevicular fluid.

Therapeutic Effect of Anti-TNF-α Antibody and Levofloxacin(LVFX)in a Mouse Model of Enterohemorrhagic Escherichia coli O157 Infection

The ability of an anti-TNF-alpha antibody to confer protection against enterohaemorrhagic Escherichia coli (EHEC) O157 was investigated in germfree IQI mice. The use of an antibiotic levofloxacin (LVFX) alone or with the antibody was also studied. Protection included an increase in survival rate. Treatment with the anti-TNF-alpha antibody inhibited the histological signs associated with EHEC infection but did not prevent the colonization of EHEC or production of Shiga toxin (Stx). No clinical signs were observed and EHEC was completely eliminated in the mouse model receiving both anti-TNF-alpha antibody and LVFX. Anti-TNF-alpha antibody suppressed inflammatory cytokine response in the mouse kidney and brain by EHEC infection.

Porphyromonas gingivalis Fimbriae Induce Adhesion of Monocytic Cell Line U937 to Endothelial Cells

This study used the human monocytic cell line U937 to examine whether or not Porphyromonas gingivalis fimbriae could induce the adhesion of monocytes to endothelial cells. An in vitro adhesion assay was used to investigate the effects of the fimbriae on U937 cell adhesion to human umbilical vein endothelial cells (HUVEC). The fimbriae enhanced U937 cell adhesion to HUVEC in a dose‐dependent manner. U937 cells adhered better to HUVEC pretreated with the fimbriae for a minimum of 2 hr than to untreated HUVEC. The enhanced adhesion was inhibited by a monoclonal antibody against P. gingivalis 381 fimbriae. Pretreatment of U937 cells with the fimbriae for 24 hr enhanced U937 cell adhesion to HUVEC approximately 4‐fold. This phenomenon was inhibited by an anti‐CD11b antibody, suggesting the involvement of CD11b. These results indicate that P. gingivalis fimbriae can induce monocyte adhesion to the endothelial cell surface. They also suggest that the fimbriae may be involved in the initial event for infiltration of monocytes into the periodontal tissues of individuals with adult periodontitis.

Role of platelet-activating-factor (PAF) on cellular responses after stimulation with leptospire lipopolysaccharide

Leptospire lipopolysaccharide (LPS) stimulated the adherence of polymorphonuclear neutrophils (PMNs) to human umbilical vein endothelial cells (HUVEC). Enhanced PMN adherence in response to leptospire LPS can be mediated by platelet‐activator‐factor (PAF), because a PAF antagonist reduced adherence. Leptospire LPS also induced the adherence platelets or U937. The second experiment involved leptospire LPS elicited platelet aggregation in a PMN‐platelet mixture, because leptospire LPS stimulated human PMN but not the human platelets. The platelet response was observed only in the mixture system and was inhibited by a PAF antagonist. PAF could be an important pathogenic factor in human leptospirosis.