Biomedical subjects

Janet Liversidge

Publications and source records attributed to Janet Liversidge.

22 records · Page 2Linked to original sources

PubMed2002

Nitric oxide mediates apoptosis through formation of peroxynitrite and Fas/Fas-ligand interactions in experimental autoimmune uveitis.

Conflicting reports have led to the description of nitric oxide as a "double-edged sword" in animal models of autoimmunity. In this study we show that tissue damage within the eye during experimental autoimmune uveoretinitis correlates with peroxynitrite formation in infiltrating monocytes/macrophages within the outer retina together with extensive photoreceptor apoptosis and apoptosis of Fas(+) T cells within the retina. Inducible nitric oxide synthase (NOS2) expression was primarily restricted to infiltrating monocytes/macrophages in the outer retina and photoreceptor rod outer segments (target tissue), but despite showing evidence of lipid peroxidation, myeloid cells remained resistant to apoptosis. The protective effect of the NOS inhibitor N(G)-nitro-L-arginine methyl ester could be attributed to dramatically reduced photoreceptor apoptosis, absence of nitrotyrosine formation, and reduced NOS2 protein expression. However, inhibition of NOS by N(G)-nitro-L-arginine methyl ester was accompanied by a sparing of CD3(+) and CD2(+) T cells despite continued expression of Fas and Fas ligand, thus compromising functional inactivation of T cells in the target tissue. These data suggests that in addition to contributing to tissue damage in the retina through generation of reactive oxygen species, nitric oxide also seems to be required for activation-induced cell death and elimination of T cells in the retina.

Animals↗

PubMed2002

Retinal microenvironment controls resident and infiltrating macrophage function during uveoretinitis.

PURPOSE: Macrophages infiltrating an inflamed or injured tissue undergo development of coordinated sets of properties that contribute to tissue damage, repair, and remodeling. The purpose of this study was to determine whether macrophages isolated from normal or inflamed retina are programmed to a distinct set of properties and to examine whether the development of experimental autoimmune uveoretinitis (EAU) affects macrophage function. METHODS: EAU was induced in Lewis rats, and a retina-derived macrophage-enriched population was generated by density centrifugation during the prepeak, peak, and resolution phases of the disease. Cell surface phenotype was assessed by two- and three-color flow cytometry, and function was determined in vitro by nitric oxide (NO) production, with or without further cytokine stimulation or by immunohistochemistry to determine expression of beta-glucuronidase, nitric oxide synthase (NOS)-2, and nitrotyrosine. RESULTS: Myeloid-derived cells from normal retina were programmed similar to TGF-beta-stimulated uncommitted bone-marrow-derived macrophages (BMDMs). Contrary to BMDM behavior, retina-isolated macrophages displayed distinct properties and phenotype at different phases of the disease course and remained resistant throughout, to further cytokine challenge in vitro. During peak disease, retina-isolated macrophages had characteristics of IFN-gamma/TNF-alpha primed cells (nitrotyrosine positive and NO producing). Despite equivalent numbers of macrophages during resolution, their function reverted to characteristics of TGF-beta primed cells (beta-glucuronidase positive). CONCLUSIONS: Resident retinal myeloid-derived cells are primed and are resistant to further cytokine stimulation, and, similar to macrophages derived during EAU recovery, behave operationally as though TGF-beta primed. During peak inflammation, infiltrating macrophages adapt to concurrent hierarchical Th1 T-cell response (IFN-gamma/TNF-alpha), generating NO. The results provide evidence of in vivo programming of macrophages within the retina.

Animals↗

PubMed2002

Secretion of interleukin-10 or interleukin-12 by LPS-activated dendritic cells is critically dependent on time of stimulus relative to initiation of purified DC culture.

Dendritic cells (DC) are key regulators of adaptive immunity with the potential to induce T cell activation/immunity or T cell suppression/tolerance. DC are themselves induced by "maturation" signals such as bacterial lipopolysaccharide (LPS). We demonstrate here that LPS can stimulate DC to display similar maturation phenotypes but to differentiate toward an interleukin (IL)-10(high)- or IL-12(high)-secretor profile depending on the timing of maturation signal induction. Immediate/early administration of LPS induced purified bone marrow-derived DC (BMDC) to differentiate as IL-10(high)IL-12(low)-secreting cells, termed early DC (eDC). Conversely, delayed administration of LPS altered the DC cytokine profile to IL-10(low)IL-12(high), termed later DC (lDC). The presence of IL-4 enhanced the yield and maturation of BMDC but inhibited LPS-induced IL-10 production by eDC. In contrast, interferon-gamma reduced the yield of DC but promoted the level of LPS-induced IL-10 production by lDC. Our data provide new evidence that ex vivo manipulation and the cytokine environment regulate DC maturation status and cytokine-secretor phenotype with implications for the control of T cell differentiation and function via DC-based immunotherapeutic strategies.

Animals↗

PubMed2002

Involvement of CD44 in leukocyte trafficking at the blood-retinal barrier.

In the present study, we investigated the involvement of CD44 in leukocyte trafficking in vivo at the blood-retinal barrier using experimental autoimmune uveoretinitis (EAU) as a model system. Leukocyte trafficking was evaluated using adoptive transfer of calcein-AM (C-AM)-labeled spleen cells harvested from syngeneic mice at prepeak severity of EAU to mice at a similar stage of disease. CD44 and its ligand hyaluronan were up-regulated in the eye during EAU. CD44-positive leukocytes were found sticking in the retinal venules and postcapillary venules but not in the retinal arterioles nor in mesenteric vessels. Preincubation of in vitro C-AM-labeled leukocytes with anti-CD44 monoclonal antibodies (mAb; IM7) or high molecular weight hyaluronic acid (HA) before transfer significantly suppressed leukocyte rolling but not sticking in retinal venules and also reduced cell infiltration in the retinal parenchyma. Administration of the HA-specific enzyme hyaluronidase to mice before cell transfer also reduced leukocyte infiltration, suggesting that CD44-HA interactions are involved in leukocyte recruitment in EAU. This was further supported by the observation that disease severity was reduced by administration of anti-CD44 mAb (IM7) at the early leukocyte-infiltration stage. Further studies also indicated that CD44 activation was associated with increased levels of apoptosis, and this may also be in part responsible for the reduction in disease severity. These findings demonstrate that CD44 is directly involved in leukocyte-endothelial interaction in vivo and influence the trafficking of primed leukocytes to the retina and their overall survival.

Animals↗