Influence of viral infection on expression of cell surface antigens in human retinal pigment epithelial cells

Green Tea Polyphenol Epigallocatechin-3-Gallate Attenuates TNF-α-Induced Intercellular Adhesion Molecule-1 Expression and Monocyte Adhesion to Retinal Pigment Epithelial Cells

Epigallocatechin-3-gallate (EGCG) is a major polyphenol component of green tea (Camellia sinensis) and demonstrates anti-oxidant, anticancer and anti-inflammatory properties. EGCG has been shown to protect retinal pigment epithelium (RPE) against oxidative stress-induced cell death. The pathogenesis of diseases in the retina is usually initiated by local inflammation at the RPE cell layer, and inflammation is mostly associated with leukocyte migration and the secretion of pro-inflammatory cytokines. Whether EGCG can modulate the cytokine-induced inflammatory response of RPE, particularly leukocyte migration, has not been clearly elucidated, and was therefore the objective of this study. ARPE-19 cells were cultured with different concentrations of TNF-α in the presence or absence of EGCG to different time points. Intracellular reactive oxygen species (ROS) levels were determined. Intercellular adhesion molecule (ICAM)-1 and phosphor-NF-κB and IκB expression were determined by Western blot analysis. Phosphor-NF-κB nuclear translocation and monocyte–RPE adhesion were investigated using immunofluorescence confocal laser scanning microscopy. Scanning electron microscopy (SEM) was carried out to further determine the ultrastructure of monocyte–RPE adhesion. The results demonstrated that TNF-α modulated inflammatory effects in ARPE-19 by induction of ROS and up-regulation of ICAM-1 expression. Moreover, TNF-α-induced phosphor-NF-κB nuclear translocation, increased phosphor-NF-κB expression and IκB degradation, and increased the degree of monocyte–RPE adhesion. Pretreating the cells with EGCG ameliorated the inflammatory effects of TNF-α. The results indicated that EGCG significantly exerts anti-inflammatory effects in ARPE-19 cells, partly as a suppressor of TNF-α signaling and that the inhibition was mediated via the NF-κB pathway.

Upregulation of human cytomegalovirus by HIV type 1 in human lymphoid tissue ex vivo

HIV-1 copathogens are believed to play a critical role in progression to AIDS. Human cytomegalovirus (HCMV) has a high prevalence in the general population and is a common copathogen in HIV-1-infected individuals. Important events in copathogen interactions with HIV-1 take place in lymphoid tissue where critical events in HIV-1 disease occur. Here, we used an experimental system of human lymphoid tissue ex vivo to investigate interactions of HCMV with HIV-1. We inoculated ex vivo blocks of human lymphoid tissue with a recombinant strain of HCMV, expressing the green fluorescent protein, and HIV-1 and monitored viral replication and the phenotype of productively infected cells. HCMV readily replicated in tissue blocks as revealed by the release of HCMV viral DNA and an increasing number of viral-positive cells. Immunophenotyping of HCMV-infected cells showed a preferential infection of activated lymphocytes. The number of these cells significantly increased in HIV-1-coinfected tissues. Accordingly, HCMV replication was enhanced 2- to-3 fold. This upregulation occurred in tissues infected with either CXCR4- or CCR5-utilizing HIV-1. Thus, HIV-1 creates new targets for HCMV, which may explain the strong association of HCMV with HIV-1 infection in vivo. Ex vivo-infected human lymphoid tissue constitutes a model to study the mechanisms of HCMV tissue pathogenesis and its interactions with HIV-1 and this model may provide new targets for anti-HIV-1 therapy.

Glucosamine sulfate inhibits leukocyte adhesion in response to cytokine stimulation of retinal pigment epithelial cells in vitro

Glucosamine is an amine-containing sugar that exhibits immunosuppressive effects in vitro and in vivo, although its mechanism of action is unknown. We investigated whether glucosamine sulfate (GS) modulates the proinflammatory cytokine interleukin (IL)-1beta-induced expression and production of intercellular adhesion molecule (ICAM)-1, the mechanism responsible for this effect, and whether GS inhibits leukocyte adhesion to the monolayer of retinal pigment epithelial (RPE) cells stimulated with various cytokines. We used flow cytometry and an ARPE-19 cell model to determine the effect of GS on the production of ICAM-1 in response to IL-1beta, IL-6, tumor necrosis factor (TNF)-alpha plus IL-1beta, TNF-alpha plus IL-6, and TNF-alpha plus interferon (IFN)-gamma. We also used semiquantitative RT-PCR to determine the effect of GS on IL-1beta-induced expression of the ICAM-1 gene, and immunocytochemistry and western blotting to measure the effect of GS on the activation and nuclear translocation of the nuclear factor NF-kappaB and the degradation of cytoplasmic IkappaB. The functionality of GS-modulated ICAM-1 on leukocyte adhesion was demonstrated in an RPE cell-neutrophil adherence assay. IL-1beta increased the expression of ICAM-1 at the mRNA and protein levels in ARPE-19 cells. GS downregulated the production of ICAM-1 induced by IL-1beta, IL-6, TNF-alpha, and IFN-gamma at the protein level in a dose-dependent manner. GS also inhibited the nuclear translocation of NF-kappaB subunit p65 and partially prevented the degradation of cytoplasmic IkappaB in IL-1beta-stimulated ARPE-19 cells. GS significantly decreased the number of neutrophils adhering to the RPE monolayer in response to cytokines IL-1beta, IL-6, TNF-alpha, and IFN-gamma. GS inhibits the expression of the ICAM-1 gene in ARPE-19 cells stimulated with IL-1beta by blocking NF-kappaB subunit p65 translocation and by partially preventing IkappaB degradation. GS also decreases leukocyte adhesion to the monolayer of ARPE-19 cells stimulated with various cytokines by decreasing ICAM-1 production. Our study demonstrates a potentially important property of GS in reducing ICAM-1-mediated inflammatory mechanisms in the eye.