Differential expression of retinal pigment epithelium (RPE) IP-10 and interleukin-8

Anti‑inflammatory effects of the NF‑κB inhibitor dehydroxymethylepoxyquinomicin on ARPE‑19 cells

The retinal pigment epithelium (RPE) is a polarized, monolayer of pigmented cells that forms the outer retinal layer. A key function of the RPE is to maintain the integrity of the photoreceptors mainly via phagocytosis and recycling of the digested photoreceptor outer segments. Moreover, RPE cells are a major source of inflammatory cytokines and chemokines, which play important roles in the activation of other immune cells under inflammatory conditions in the posterior segment of the eye. Dehydroxymethylepoxyquinomicin (DHMEQ) is a NF‑κB inhibitor and its structure is related to that of epoxyquinomicin C, which is an antibiotic. The present study evaluated the anti‑inflammatory effects of DHMEQ on a human retinal pigment epithelial cell line (ARPE‑19). It was revealed that high concentrations of DHMEQ (100 µg/ml) induced apoptosis and necrosis of tumor necrosis factor (TNF)‑α‑stimulated ARPE‑19 cells. Furthermore, the percentage of intercellular adhesion molecule 1 (ICAM‑1)‑positive TNF‑α‑stimulated cells was significantly reduced in the presence of DHMEQ (10 µg/ml), as determined by flow cytometry. It was also demonstrated that DHMEQ exposure significantly decreased the levels of interleukin (IL)‑8 and monocyte chemoattractant protein‑1 (MCP‑1) in the supernatant of cultured ARPE‑19 cells as determined by ELISA. Moreover, the protein expression levels of IL‑8 and MCP‑1 were significantly reduced in ARPE‑19 cells exposed to DHMEQ compared with cells exposed to dexamethasone. PCR array analysis revealed that DHMEQ reduced the expression levels of MCP‑1, ICAM‑1, IL‑6, Toll‑like receptor (TLR)2, TLR3 and TLR4. Therefore, the present results indicated that DHMEQ has anti‑inflammatory effects on TNF‑α‑stimulated ARPE‑19 cells. Thus, DHMEQ may have therapeutic potential for TNF‑α‑mediated inflammatory disorders of the eye.

Aqueous humour cytokines profiles in eyes with Coats disease and the association with the severity of the disease

Background

To investigate aqueous humour (AH) cytokine profiles in eyes with Coats disease and analyze the association between cytokine concentrations and the severity of the disease.

Methods

The study included 36 patients (36 eyes) with Coats disease and 15 control patients (15 eyes) with congenital cataract. AH samples were obtained preoperatively and the concentrations of 22 different cytokines were measured through Cytometric Bead Array technology. Clinical characteristics of Coats disease, including the extent of retinal exudation and exudative retinal detachment (ERD), were recorded for analysis.

Results

The concentrations of 8 cytokines (VEGF, IL-6, IL-8, MCP-1, MIP-1α, IP-10, VCAM-1 and ICAM-1) were significantly higher in the Coats disease group than in the control group (all P < 0.002). Except for VCAM-1 and ICAM-1, the concentration of the other cytokines listed above showed a significant increase from stage 2 to stage 3 (all P < 0.05). Meanwhile, the concentrations of VEGF, IL-8, MCP-1 and MIP-1α showed a significant and positive association with the extent of retinal exudation and ERD (all r > 0.4, P < 0.05). Among these, IL-8 showed a strong association with the extent of retinal exudation and ERD (all r > 0.7, P < 0.001). The concentrations of IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-10, IL-12, Fractalkine, RANTES, G-CSF and GM-CSF were very low in both groups.

Conclusions

Various cytokines in the AH, including elevated VEGF, IL-6, IL-8, MCP-1, MIP-1α, IP-10, VCAM-1 and ICAM-1, may be involved in the pathogenesis and progression of Coats disease. Increasing severity of Coats disease is significantly associated with the AH concentrations of VEGF, IL-8, MCP-1 and MIP-1α. Further clinical treatment aimed to reduce vascular leakage and antagonize neovascularization and inflammation may be useful in preventing the progression of Coats disease.

Scaffolds for retinal pigment epithelial cell transplantation in age-related macular degeneration

In several retinal degenerative diseases, including age-related macular degeneration, the retinal pigment epithelium, a highly functionalized cell monolayer, becomes dysfunctional. These retinal diseases are marked by early retinal pigment epithelium dysfunction reducing its ability to maintain a healthy retina, hence making the retinal pigment epithelium an attractive target for treatment. Cell therapies, including bolus cell injections, have been investigated with mixed results. Since bolus cell injection does not promote the proper monolayer architecture, scaffolds seeded with retinal pigment epithelium cells and then implanted have been increasingly investigated. Such cell-seeded scaffolds address both the dysfunction of the retinal pigment epithelium cells and age-related retinal changes that inhibit the efficacy of cell-only therapies. Currently, several groups are investigating retinal therapies using seeded cells from a number of cell sources on a variety of scaffolds, such as degradable, non-degradable, natural, and artificial substrates. This review describes the variety of scaffolds that have been developed for the implantation of retinal pigment epithelium cells.

Chemokine-mediated inflammation in the degenerating retina is coordinated by Müller cells, activated microglia, and retinal pigment epithelium

BACKGROUND

Monocyte infiltration is involved in the pathogenesis of many retinal degenerative conditions. This process traditionally depends on local expression of chemokines, though the roles of many of these in the degenerating retina are unclear. Here, we investigate expression and in situ localization of the broad chemokine response in a light-induced model of retinal degeneration.

METHODS

Sprague-Dawley (SD) rats were exposed to 1,000 lux light damage (LD) for up to 24 hrs. At time points during (1 to 24 hrs) and following (3 and 7 days) exposure, animals were euthanized and retinas processed. Microarray analysis assessed differential expression of chemokines. Some genes were further investigated using polymerase chain reaction (PCR) and in situ hybridization and contrasted with photoreceptor apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Recruitment of retinal CD45 (+) leukocytes was determined via fluorescence activated cell sorting (FACS), and expression of chemokine receptors determined using PCR.

RESULTS

Exposure to 24 hrs of LD resulted in differential expression of chemokines including Ccl3, Ccl4, Ccl7, Cxcl1, and Cxcl10. Their upregulation correlated strongly with peak photoreceptor death, at 24 hrs exposure. In situ hybridization revealed that the modulated chemokines were expressed by a combination of Müller cells, activated microglia, and retinal pigment epithelium (RPE). This preceded large increases in the number of CD45(+) cells at 3- and 7-days post exposure, which expressed a corresponding repertoire of chemokine receptors.

CONCLUSIONS

Our data indicate that retinal degeneration induces upregulation of a broad chemokine response whose expression is coordinated by Müller cells, microglia, and RPE. The findings inform our understanding of the processes govern the trafficking of leukocytes, which are contributors in the pathology of retinal degenerations.

Regulation of VEGF expression in human retinal cells by cytokines: implications for the role of inflammation in age-related macular degeneration

Chronic inflammation is implicated in the pathogenesis of age-related macular degeneration (AMD). Choroidal neovascularization (CNV) observed in exudative form of AMD results in vision loss. Human retinal pigment epithelial cell (HRPE) layer and choroidal tissue are the primary pathological sites in AMD. Pathological and therapeutic evidences have strongly indicated the vascular endothelial growth factor (VEGF) molecules as critical components in CNV pathogenesis. In these studies, we used human primary HRPE and choroidal fibroblast cells (HCHF) prepared from adult donor eyes. The effects of inflammatory cytokine (IFN-γ+ TNF-α+IL-1β) mix (ICM) on global gene expression profiles in HRPE cells, revealed 10- and 9-fold increase in VEGF-A and VEGF-C expression, respectively. The microarray results were validated by quantitative RT-PCR and secretion of VEGFs proteins. IL-1β is the most potent in inducing VEGFs secretion followed by IFN-γ and TNF-α, and the secretion was more effective in the presence of 2 and 3 cytokines. NF-κB and JAK-STAT pathway, but not HIF-1α, Sp-1, Sp-3, and STAT-3, transcription factors were upregulated and translocated to nucleus by ICM treatment. The mRNA levels of VEGF-A and VEGF-C and secretion of these proteins were also significantly enhanced by ICM in HCHF cells. The secretion of other angiogenic molecules, PEDF, SDF-1α, endostatin, and angiopoietins was not affected by ICM. Our results show that the inflammatory cytokines enhance secretion of VEGF-A and VEGF-C by HRPE and HCHF cells. These studies indicate that VEGFs secreted by these cells initiate and promote pathological choroidal and retinal noevascularization processes in AMD.

Thrombin stimulates RPE cell motility by PKC-zeta- and NF-kappaB-dependent gene expression of MCP-1 and CINC-1/GRO chemokines

Retinal pigment epithelial cells (RPE) are the major cell type involved in the pathogenesis of proliferative vitreoretinopathy (PVR), which involves the epithelial-mesenchymal transition, proliferation, and directional migration of transformed RPE cells to the vitreous upon RPE exposure to serum components, thrombin among them. Although the aqueous humor and vitreous of PVR patients contain high levels of chemokines, their possible involvement in PVR development has not been explored. We here analyzed the effect of thrombin on chemokine gene expression and its correlation with RPE cell migration using rat RPE cells in culture as a model system. We demonstrated that thrombin induces RPE cell migration through the dose-dependent stimulation of MCP1 and GRO expression/release, and the autocrine activation of CXCR-2 and CCR-2 chemokine receptors. Whereas inhibition of CXCR2 by Sb-225002 and of CCR2 by Rs-504393 partially prevented hirudin-sensitive cell migration, the joint inhibition of these receptors abolished thrombin effect, suggesting the contribution of distinct but coincident mechanisms. Thrombin effects were not modified by Ro-32-0432 inhibition of conventional/novel PKC isoenzymes or by the MAPkinase pathway inhibitor U0126. MCP1 and GRO expression/secretion, and cell migration were completely prevented by the inhibitory PKC-zeta pseudosubstrate and by the nuclear factor-kappa B (NF-kappaB) inhibitor BAY11-7082, but not by wortmannin inhibition of PI3K. Results show that signaling pathways leading to RPE cell migration differ from the MEK-ERK-PI3K-mediated promotion RPE of cell proliferation, both of which concur at the activation of PKC-zeta.

Pro-angiogenic effect of IFNgamma is dependent on the PI3K/mTOR/translational pathway in human retinal pigmented epithelial cells

Background

Mutations in COL8A2 gene which encodes the collagen alpha-2 (VIII) chain have been identified in both familial and sporadic cases of Fuchs endothelial corneal dystrophy (FECD). Heterozygous mutations in the SLC4A11 gene are also known to cause late-onset FECD. Therefore we screened for COL8A2, SLC4A11 gene variants in Indian FECD patients.

Methods

Eighty patients with clinically diagnosed FECD and 100 age matched normal individuals were recruited. Genomic DNA was isolated from peripheral blood leukocytes. Mutations in COL8A2, SLC4A11 coding regions were screened using bi-directional sequencing. Fischer's exact test or Pearson's chi squared test were used to predict the statistical association of genotypes with the phenotype.

Results

Screening of COL8A2 gene revealed 2 novel c.1610G>A, c.1643A>G and 3 reported variations c.112G>A, c.464G>A and c.1485G>A. In SLC4A11 gene, novel c.1659C>T, c.1974C>T and reported c.405G>A, c.481A>C and c.639G>A variants were identified. However all the variations in both the genes were also present in unaffected controls.

Conclusions

This is the first study analysing COL8A2 gene in Indian patients with FECD. No pathogenic mutations were identified in COL8A2. Merely silent changes, which showed statistically insignificant association with FECD, were identified in the screening of SLC4A11 gene. These results suggest that COL8A2, SLC4A11 genes may not be responsible for FECD in patients examined in this study.

Control of chemokine gradients by the retinal pigment epithelium

PURPOSE

Proinflammatory cytokines in degenerative diseases can lead to the loss of normal physiology and the destruction of surrounding tissues. In the present study, the physiological responses of human fetal retinal pigment epithelia (hfRPE) were examined in vitro after polarized activation of proinflammatory cytokine receptors.

METHODS

Primary cultures of hfRPE were stimulated with an inflammatory cytokine mixture (ICM): interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. Western blot analysis and immunofluorescence were used to determine the expression/localization of the cytokine receptors on hfRPE. Polarized secretion of cytokines was measured. A capacitance probe technique was used to measure transepithelial fluid flow (J(V)) and resistance (R(T)).

RESULTS

IL-1R1 was mainly localized to the apical membrane and TNFR1 to the basal membrane, whereas IFN-gammaR1 was detected on both membranes. Activation by apical ICM induced a significant secretion of angiogenic and angiostatic chemokines, mainly across the hfRPE apical membrane. Addition of the ICM to the basal but not the apical bath significantly increased net fluid absorption (J(V)) across the hfRPE within 20 minutes. Similar increases in J(V) were produced by a 24-hour exposure to ICM, which significantly decreased total R(T).

CONCLUSIONS

Chemokine gradients across the RPE can be altered (1) through an ICM-induced change in polarized chemokine secretion and (2) through an increase in ICM-induced net fluid absorption. In vivo, both of these factors could contribute to the development of chemokine gradients that help mediate the progression of inflammation/angiogenesis at the retina/RPE/choroid complex.

Mechanisms of leukocyte migration across the blood-retina barrier

Immune-mediated inflammation in the retina is regulated by a combination of anatomical, physiological and immuno-regulatory mechanisms, referred to as the blood-retina barrier (BRB). The BRB is thought to be part of the specialised ocular microenvironment that confers protection or "immune privilege" by deviating or suppressing destructive inflammation. The barrier between the blood circulation and the retina is maintained at two separate anatomical sites. These are the endothelial cells of the inner retinal vasculature and the retinal pigment epithelial cells on Bruch's membrane between the fenestrated choroidal vessels and the outer retina. The structure and regulation of the tight junctions forming the physical barrier are described. For leukocyte migration across the BRB to occur, changes are needed in both the leukocytes themselves and the cells forming the barrier. We review how the blood-retina barrier is compromised in various inflammatory diseases and discuss the mechanisms controlling leukocyte subset migration into the retina in uveoretinitis in more detail. In particular, we examine the relative roles of selectins and integrins in leukocyte interactions with the vascular endothelium and the pivotal role of chemokines in selective recruitment of leukocyte subsets, triggering adhesion, diapedesis and migration of inflammatory cells into the retinal tissue.

Expression of IP-10 related to angiogenesis in uterine cervical cancers

Angiogenesis is essential for development, growth and advancement of solid tumours. Interferon-gamma-inducible protein 10 (IP-10) regulates lymphocyte chemotaxis, mediates vascular pericyte proliferation and acts as an angiostatic agent, thus inhibiting tumour growth. This prompted us to study the clinical implications of IP-10 expression related to angiogenesis in uterine cervical cancers. The levels of IP-10 decreased with advancement, and the prognosis of the 30 patients with low IP-10 expression in uterine cervical cancers was poor (66%), whereas the 24-month survival rate of the other patients with high IP-10 expression was 90%. Furthermore, IP-10 levels significantly reverse-correlated with vascular endothelial growth factor (VEGF) levels in uterine cervical cancers. Interferon-gamma-inducible protein 10 might work on suppression of angiogenesis associated with VEGF in advancement, and can be recognised as a prognostic indicator. Furthermore, IP-10 activation might be effective on the suppression of regrowth or recurrence after intensive treatment for advanced cervical cancers.