E and P selectins are not required for resistance to severe murine lyme arthritis

VAP-1-deficient mice display defects in mucosal immunity and antimicrobial responses: implications for antiadhesive applications

VAP-1, an ecto-enzyme expressed on the surface of endothelial cells, is involved in leukocyte trafficking between the blood and tissues under physiological and pathological conditions. In this study, we used VAP-1-deficient mice to elucidate whether absence of VAP-1 alters the immune system under normal conditions and upon immunization and microbial challenge. We found that VAP-1-deficient mice display age-dependent paucity of lymphocytes, in the Peyer's patches of the gut. IgA concentration in serum was also found to be lower in VAP-1(-/-) animals than in wild-type mice. Although there were slightly less CD11a on B and T cells isolated from VAP-1-deficient mice than on those from wild-type mice, there were no differences in the expression of gut-homing-associated adhesion molecules or chemokine receptors. Because anti-VAP-1 therapies are being developed for clinical use to treat inflammation, we determined the effect of VAP-1 deletion on useful immune responses. Oral immunization with OVA showed defective T and B cell responses in VAP-1-deficient mice. Antimicrobial immune responses against Staphylococcus aureus and coxsackie B4 virus were also affected by the absence of VAP-1. Importantly, when the function of VAP-1 was acutely neutralized using small molecule enzyme inhibitors and anti-VAP-1 Abs rather than by gene deletion, no significant impairment in antimicrobial control was detected. In conclusion, VAP-1-deficient mice have mild deviations in the mucosal immune system and therapeutic targeting of VAP-1 does not appear to cause a generalized increase in the risk of infection.

A small molecule alpha 4 beta 1 antagonist prevents development of murine Lyme arthritis without affecting protective immunity

After infection with Borrelia burgdorferi, humans and mice under certain conditions develop arthritis. Initiation of inflammation is dependent on the migration of innate immune cells to the site of infection, controlled by interactions of a variety of adhesion molecules. In this study, we used the newly synthesized compound S18407, which is a prodrug of the active drug S16197, to analyze the functional importance of alpha4beta1-dependent cell adhesion for the development of arthritis and for the antibacterial immune response. S16197 is shown to interfere specifically with the binding of alpha4beta(1 integrin to its ligands VCAM-1 and fibronectin in vitro. Treatment of B. burgdorferi-infected C3H/HeJ mice with the alpha4beta1 antagonist significantly ameliorated the outcome of clinical arthritis and the influx of neutrophilic granulocytes into ankle joints. Furthermore, local mRNA up-regulation of the proinflammatory mediators IL-1, IL-6, and cyclooxygenase-2 was largely abolished. Neither the synthesis of spirochete-specific Igs nor the development of a Th1-dominated immune response was altered by the treatment. Importantly, the drug also did not interfere with Ab-mediated control of spirochete load in the tissues. These findings demonstrate that the pathogenesis, but not the protective immune response, in Lyme arthritis is dependent on the alpha4beta1-mediated influx of inflammatory cells. The onset of inflammation can be successfully targeted by treatment with S18407.

Treatment of mice with the neutrophil-depleting antibody RB6-8C5 results in early development of experimental lyme arthritis via the recruitment of Gr-1- polymorphonuclear leukocyte-like cells

Recently, we demonstrated that blocking the entry of neutrophils into Borrelia burgdorferi-infected joints in mice deficient in the chemokine receptor CXCR2 prevented the development of experimental Lyme arthritis. Neutrophils were marginalized in blood vessels at the site of infection but could not enter the joint tissue. In the present study, we treated both genetically arthritis-resistant DBA/2J (DBA) and arthritis-susceptible C3H/HeJ (C3H) mice with the neutrophil-depleting monoclonal antibody RB6-8C5 (RB6) to determine the effect on arthritis development. Surprisingly, both DBA and C3H mice treated with RB6 developed arthritis at 1 week postinfection, approximately 1 week earlier than the control-treated C3H mice. The early development of arthritis in the RB6-treated mice was accompanied by an influx into the joints of cells with ring-shaped polymorphonuclear leukocyte (PMN) cell morphology that were negative for the Gr-1 neutrophil maturation marker. RB6 treatment of mice also resulted in increased numbers of B. burgdorferi cells in the joints at 7 days postinfection and earlier expression of the chemokines KC and monocyte chemoattractant protein 1 in the joints compared to control-treated animals. Together, these results suggest that recruitment of neutrophils or PMN-like cells into an infected joint is a key requirement for Lyme arthritis development and that altered recruitment of these cells into the joints of arthritis-resistant mice can exacerbate the development of pathology.

Endothelial cell activation in inflammation: lessons from mutant mouse models

Dysregulation of the inflammatory response is a causative or contributing factor in many cardiovascular pathologies. Molecular mechanisms involved in these processes indicate that the vascular endothelium is an important facet in the regulation of inflammation. Gene targeted mutational studies in the mouse have shown that adhesion and signaling molecule expression within the endothelium participate in the pathogenic process of cardiovascular disease. These studies provide insight into genetic pathways that may be therapeutically relevant in both treatment and diagnostic regimens. However, we have also learned that the role of these pathways in endothelium during inflammatory diseases is complex, requiring further study to better understand specific mechanisms involved in endothelial cell dysfunction during cardiovascular disease. Alternative gene targeting techniques, such as the Cre-loxP system, are beginning to allow tissue specific investigation of genetic pathways within the endothelium; however, extensive use of this technology is limited. This review discusses the role of the endothelium during inflammation and the insights that have been gained from the use of gene targeted mutant mice.

Mice genetically lacking endothelial selectins are resistant to the lethality in septic peritonitis

Leukocyte interactions with vascular endothelium are an initial step for leukocyte entry into infectious foci where endothelial selectins may play a key role. Infiltrating leukocyte is essential for bacterial clearance, suggesting that endothelial selectins would be important in host defense against microorganisms. To address this, E-, P-, and E/P-selectin-deficient mice (E(-/-), P(-/-), E/P(-/-)) and wild-type (WT) mice underwent cecal ligation and puncture (CLP). Neither leukocyte infiltration nor bacterial load in the peritoneum was altered in E(-/-), P(-/-), and E/P(-/-) mice compared to WT mice. However, E(-/-), P(-/-), and E/P(-/-) mice were resistant to the lethality induced by CLP. At the mechanistic level, E(-/-), P(-/-), and E/P(-/-) mice did not develop renal dysfunction, a possible cause of death during sepsis. The serum level of interleukin-13 in E(-/-), P(-/-), and E/P(-/-) mice that had undergone CLP was higher than that in WT mice, whereas levels of macrophage inflammatory protein-2, KC in serum, and KC in kidney were lower than those in WT mice. These experiments demonstrate that endothelial selectin-mediated leukocyte rolling is not required for leukocyte entry in septic peritonitis and that endothelial selectins may affect mice survival during sepsis by influencing the cytokine profiles.