Thrombin regulates chemokine induction during human retinal pigment epithelial cell/monocyte interaction.

Thrombin, an important clotting factor, extravasates at sites of blood-retina barrier breakdown that is often associated with many retinal diseases. Here we investigated the effects of thrombin on human retinal pigment epithelial (HRPE) cells, monocytes, and HRPE cell/monocyte co-cultures. Thrombin induced secretion and mRNA expression of HRPE interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1). Thrombin also enhanced IL-8 and MCP-1 by HRPE cell/monocyte co-cultures, by apparently enhancing cell-cell contact mechanisms. The thrombin effects on IL-6 secretion were similar to those on chemokine secretion. Thrombin-induced chemokines by co-cultures were inhibited by anti-tumor necrosis factor-alpha (TNF-alpha) antibody, but not by anti-IL-1beta antibody. TNF-alpha was detected in cell lysates of monocytes detached from HRPE cells after co-culture stimulation with thrombin. HRPE cells mainly produced these chemokines. However, thrombin generally potentiated exogenous IL-1beta- and TNF-alpha-induced chemokine production by HRPE cells, monocytes, and co-cultures. Interferon-gamma potentiated chemokine secretion by co-cultures with or without thrombin. Our results indicate that thrombin may cause leukocyte recruitment by inducing HRPE cell and monocyte chemokine and by enhancing HRPE cell/monocyte interactions, in part because of monocyte TNF-alpha induction, suggesting important mechanisms for ocular inflammation during blood-retina barrier breakdown and intra-ocular hemorrhage.

Activation of p38, ERK1/2 and NIK pathways is required for IL-1beta and TNF-alpha-induced chemokine expression in human retinal pigment epithelial cells.

Chemokine secretion by human retinal pigment epithelium (hRPE) in response to IL-1beta and TNF-alpha occurs in infectious and noninfectious retinal diseases. In this study, the roles of p38 kinase and extracellular signal-regulated kinase (ERK) signaling pathways were investigated for IL-1beta- or TNF-alpha-induced IL-8 and MCP-1 secretion by hRPE cells. Treatment of hRPE cells with IL-1beta or TNF-alpha caused increased steady-state IL-8 and MCP-1 mRNA levels and protein secretion. Stimulation of hRPE with IL-1beta and TNF-alpha resulted in degradation of IkappaB-alpha, nuclear translocation of NF-kappaB, and prominent increases in p38 and ERK1/2 phosphorylation for as little as 3 min. The induced IL-8 and MCP-1 mRNA and proteins were partially suppressed by U0126, a specific MEK inhibitor, and by SB202190, a selective p38 inhibitor. This induction was completely blocked by simultaneous administration of the two drugs or by incubation with inhibitors for activation of NF-kappaB such as BAY11-7085, CAPE, and parthenolide. These results suggest that co-activation of MEK/ERK and p38 pathways as well as activation of NIK pathway are essential for IL-1beta- and TNF-alpha-stimulation of IL-8 and MCP-1 gene expression in hRPE cells. Furthermore, co-administration of U0126 and SB202190 did not affect the induced degradation of IkappaB-alpha and NF-kappaB nuclear translocation, indicating that NF-kappaB is activated by IL-1beta and TNF-alpha independently of activation of MEK/MAPK and p38 pathways in hRPE cells.

Induction of interleukin-8 in human retinal pigment epithelial cells after denuding injury.

AIM: To determine interleukin 8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) expression in response to mechanical injury in human retinal pigment epithelial (HRPE) cells. METHODS: Enzyme linked immunosorbent assay (ELISA) was performed to determine IL-8 and MCP-1 secretion by HRPE cells after mechanical denudation. IL-8 and MCP-1 mRNA expression by HRPE cells was assessed using semiquantitative RT-PCR. The effects of immunosuppressive drugs, dexamethasone (DEX) and cyclosporin A (CSA), as well as immunosuppressive cytokines, interleukin 4 (IL-4), interleukin 10 (IL-10), and interleukin 13 (IL-13), on chemokine expression in HRPE cells after denuding injury were analysed. RESULTS: Mechanical injury induced HRPE IL-8 mRNA and IL-8 secretion. Although MCP-1 mRNA was enhanced slightly after denuding injury, MCP-1 secretion was not increased. DEX and CSA inhibited HRPE chemokine expression after injury. IL-4 and IL-13 enhanced IL-8 and MCP-1 production by HRPE cells after injury while IL-10 had no effect. CONCLUSIONS: These results suggest that IL-8 may be involved in retinal inflammatory responses to injury and that DEX and/or CSA treatment may help control the inflammatory components of retinal diseases such as proliferative vitreoretinopathy.

Differential chemokine regulation by Th2 cytokines during human RPE-monocyte coculture.

PURPOSE: To determine the effects of the potent anti-inflammatory Th2 cytokines, interleukin (IL)-4, -10, and -13, on IL-8 and monocyte chemoattractant protein (MCP) 1 production by human retinal pigment epithelial (HRPE) cells, monocytes, and HRPE cell-monocyte cocultures. METHODS: Enzyme-linked immunosorbent assays were performed to determine IL-8 and MCP-1 secretion by HRPE cells, monocytes, and HRPE cell-monocyte cocultures stimulated with IL-1beta or TNF-alpha, either alone, or in combination with IL-4, -10, or -13, at various time points. RESULTS: IL-4 and -13, but not IL-10, enhanced constitutive and TNF-alpha-induced HRPE IL-8 and MCP-1 secretion. IL-4 also enhanced IL-1beta-induced HRPE IL-8. IL-4 and -13 reduced monocyte IL-8 and MCP-1, whereas IL-10 reduced monocyte IL-8 but enhanced MCP-1. Overlay of monocytes onto HRPE cell cultures resulted in increased IL-8 and MCP-1 secretion. IL-8 secretion by HRPE cell-monocyte cocultures was inhibited by IL-4, -10, and -13, whereas MCP-1 was inhibited only by IL-10. These cytokines also inhibited IL-1beta potentiation of IL-8, but not MCP-1 secretion by cocultures. IL-4 enhanced TNF-alpha potentiation of chemokine secretion by cocultures, whereas IL-10 had no effects. IL-13 potentiated TNF-alpha-induced MCP-1, but not IL-8 secretion by cocultures. CONCLUSIONS: IL-4, -10 and -13 have complex effects on chemokine secretion by HRPE cells, monocytes, and HRPE cell-monocyte cocultures. IL-10 appears to be the most consistently suppressive cytokine, suggesting potential therapeutic usefulness of IL-10 in the treatment of ocular inflammatory and proliferative diseases.

Signaling pathways for glycated human serum albumin-induced IL-8 and MCP-1 secretion in human RPE cells.

PURPOSE: To determine the signal mediators involved in glycated human serum albumin (GHSA) stimulation of interleukin (IL)-8 and monocyte chemotactic protein (MCP)-1 secretion in human retinal pigment epithelium (hRPE) cells. METHODS: hRPE cells were stimulated by GHSA in the presence or absence of a series of kinase inhibitors. The induced IL-8 and MCP-1 mRNA and proteins were determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Western blot analysis, electrophoretic mobility shift assay, and immunohistochemical staining were used to analyze activation of signaling mediators and transcription factors. RESULTS: Incubation of hRPE cells with GHSA resulted in rapid activation of Raf-1, extracellular signal-regulated protein kinases (ERK) 1/2, p38, and the transcription factor nuclear factor (NF)-kappaB. Coincubation of hRPE cells with the mitogen-activated protein (MAP) kinase (MEK) inhibitor U0126; NF-kappaB inhibitors BAY11-7085, caffeic acid phenethyl ester (CAPE), parthenolide, and curcumin; protein kinase (PK)C inhibitor Ro318220; and protein tyrosine kinase (PTK) inhibitor genistein largely eliminated most of the stimulated production of IL-8 and MCP-1. Combined inhibition of MEK by U0126, p38 by SB202190, and Janus kinase (jak) by AG490 revealed that GHSA stimulation of IL-8 production was predominately mediated by MEK and to a lesser extent by p38 pathways, whereas activation of MEK, p38, and jak was required for maximal MCP-1 induction. Moreover, GHSA-stimulated IL-8 secretion was more sensitive to U0126 (50% inhibitory concentration [IC(50)] = 0.5 microM) than MCP-1 (IC(50) = 10 microM). CONCLUSIONS: GHSA stimulates hRPE IL-8 and MCP-1 production through divergent and overlapping, but not identical, intracellular signaling cascades. GHSA induces activation of a series of kinases including PKC, PTK, MAPK, p38, and jak and the transcription factor NF-kappaB. The Raf/MAPK pathway plays an essential role in GHSA signaling.

Management of submacular hemorrhage with intravitreous tissue plasminogen activator injection and pneumatic displacement.

OBJECTIVE: To investigate the efficacy and safety of treating thick submacular hemorrhages with intravitreous tissue plasminogen activator (tPA) and pneumatic displacement. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: From 5 participating centers, 15 eligible patients had acute (<3 weeks) thick subretinal hemorrhage involving the center of the macula in eyes with pre-existing good visual acuity. Hemorrhages were secondary to age-related macular degeneration in 13 eyes and macroaneurysm and trauma in 1 eye each. METHODS: The authors reviewed the medical records of 15 consecutive patients who received intravitreous injection of commercial tPA solution (25-100 microg in 0.1-0.2 ml) and expansile gas (0.3-0.4 ml of perfluoropropane or sulfur hexafluoride) for thrombolysis and displacement of submacular hemorrhage. After surgery, patients maintained prone positioning for 1 to 5 days (typically, 24 hours). MAIN OUTCOME MEASURES: Degree of blood displacement from under the fovea, best postoperative visual acuity, final postoperative visual acuity, and surgical complications. RESULTS: In 15 (100%) of 15 eyes, the procedure resulted in complete displacement of thick submacular hemorrhage out of the foveal area. Best postprocedure visual acuity improved by 2 lines or greater in 14 (93%) of 15 eyes. After a mean follow-up of 10.5 months (range, 4-19 months), final visual acuity improved by 2 lines or greater in 10 (67%) of 15 eyes and measured 20/80 or better in 6 (40%) of 15 eyes. Complications included breakthrough vitreous hemorrhage in three eyes and endophthalmitis in one eye. Four eyes developed recurrent hemorrhage 1 to 3 months after treatment, three of which were retreated with the same procedure. CONCLUSIONS: Intravitreous injection of tPA and gas followed by brief prone positioning is effective in displacing thick submacular blood and facilitating visual improvement in most patients. The rate of serious complications appears low. Final visual outcomes are limited by progression of the underlying macular disease in many patients.

Orbital fibroblast interleukin-6 gene expression and immunomodulation.

PURPOSE: Orbital inflammation is common, but the mechanisms underlying leukocytic infiltration of orbital tissue are poorly understood. We studied human orbital fibroblast (OF) interleukin-6 (IL-6) gene expression in response to proinflammatory stimuli and the effects of dexamethasone (DEX) and cyclosporin A (CSA) on cytokine-stimulated OF IL-6 gene expression. METHODS: Cultured OFs were left unstimulated or incubated with varying concentrations of lipopolysaccharide (LPS), or recombinant (r) interleukin-1-beta (rIL-1beta), tumor necrosis factor-alpha (rTNF-alpha), or interferon-gamma (rIFN-gamma) for 2, 4, 8, or 24 hours. OFs were also incubated with rIL-1beta (0.2, 2.0, 20 ng/ml) alone or in the presence of DEX (10(-8), 10(-7), 10(-6) mol/l) or CSA (3, 30, 300 ng/ml) for 8 hours to determine the effects of these immunomodulating drugs on IL-6 expression. Northern blot analyses were performed to determine OF IL-6 mRNA expression in response to varying concentrations of these agents. Experiments were repeated four times on different cell lines. RESULTS: OFs lacked constitutive IL-6 gene expression. Substantial time- and dose-dependent increases in steady-state IL-6 mRNA expression occurred by 4 hours of LPS or cytokine stimulation (rIL-1beta>rTNF-alpha(>LPS>rIFN-gamma), peaked at 8 hours, and were maintained at 24 hours. DEX caused dose-dependent inhibition of IL-1-induced IL-6 mRNA expression, while CSA potentiated IL-1-induced OF IL-6 mRNA expression. CONCLUSIONS: OFs express IL-6 mRNA in response to proinflammatory stimuli. DEX is a potent inhibitor of OF IL-6 mRNA while CSA increases IL-1-induced OF IL-6 gene expression. These observations may in part explain the lack of CSA effectiveness in human orbital diseases that respond to corticosteroids.

IL-4 potentiates IL-1beta- and TNF-alpha-stimulated IL-8 and MCP-1 protein production in human retinal pigment epithelial cells.

PURPOSE: Human retinal pigment epithelial (HRPE) cells are involved in ocular inflammation by secretion of chemokines such as IL-8 and MCP-1. It has been shown in this and other laboratories that interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) are potent inducers of HRPE IL-8 and MCP-1 secretion. The induced IL-8 and MCP-1 expression is often modulated by other proinflammatory factors in a synergistic manner. Modulation of IL-8 and MCP-1 production by interleukin-4 (IL-4), a important mediator in Th2-mediated immunity, and granulocyte/macrophage-colony-stimulating factor (GM-CSF), one of the cytokines secreted by HRPE has been reported in non-ocular cells. The aim of the present investigation was to study effects of these two cytokines alone or in combination with IL-1beta or TNF-alpha on HRPE IL-8 and MCP-1 generation. METHODS: The primary culture of HRPE cells was stimulated with various doses of IL-4, GM-CSF, IL-1beta and TNF-alpha alone or in combination for 8 or 24 hr. The supernatants were subjected to enzyme-linked immunosorbent assay (ELISA) for IL-8 and MCP-1. The mRNAs were isolated from the corresponding cells for Northern blot analysis. RESULTS: IL-1beta and TNF-alpha induced dose-dependent increases in HRPE IL-8 and MCP-1 secretion with maximal stimulation observed at 2-5 ng/ml. IL-4 alone (100 ng/ml) resulted in a slight increase of MCP-1 and IL-8 secretion. When IL-4 was co-administrated with IL-1beta or TNF-alpha, two to three-fold increases in IL-8 and MCP-1 were observed over the maximal levels induced by IL-1beta or TNF-alpha alone. Northern blot analyses revealed that IL-4 did not alter the steady-state MCP-1 mRNA stimulated by IL-1beta and TNF-alpha, or alter the IL-8 mRNA stimulated by TNF-alpha, although the IL-1beta-induced IL-8 mRNA was slightly enhanced by higher concentrations of IL-4 (100 ng/ml). CONCLUSION: The synergistic action by IL-4 occurs predominately at the post-transcriptional level. In contrast to IL-4, GM-CSF alone or in combination with IL-1beta or TNF-alpha did not generate additional secretion of HRPE IL-8 and MCP-1. HRPE IL-8 and MCP-1 gene expression and protein production are stimulated by IL-1beta or TNF-alpha through pathways differentially modulated by IL-4 and GM-CSF.

Cystoid macular edema associated with latanoprost therapy in a case series of patients with glaucoma and ocular hypertension.

OBJECTIVE: To identify coexisting ocular diagnoses in a case series of eyes that developed cystoid macular edema (CME) associated with latanoprost therapy. DESIGN: Retrospective observational case series. PARTICIPANTS: Seven eyes of seven patients who developed CME possibly associated with latanoprost treatment were studied. INTERVENTION: When these patients, all of whom were treated with latanoprost in addition to other glaucoma medications, described blurred vision or eye irritation, ocular examination revealed CME, which was confirmed by fluorescein angiography. Latanoprost was discontinued, and in three cases topical corticosteroids and nonsteroidal anti-inflammatory agents were used to treat the CME. MAIN OUTCOME MEASURES: Visual acuity and intraocular pressure were determined before latanoprost use began, during therapy, and after latanoprost use ceased. In these cases, resolution of CME was documented clinically after discontinuing latanoprost. RESULTS: Clinically significant CME developed after 1 to 11 months of latanoprost treatment, with an average decrease of 3 lines in Snellen visual acuity. Intraocular pressure decreased an average of 27.9% during treatment. Cystoid macular edema was confirmed in all cases by fluorescein angiography. In these seven patients, the following coexisting ocular conditions may have placed these eyes at risk for prostaglandin-mediated blood-retinal barrier vascular insufficiency: history of dipivefrin-associated CME, epiretinal membrane, complicated cataract surgery, history of macular edema associated with branch retinal vein occlusion, history of anterior uveitis, and diabetes mellitus. In all cases, the macular edema resolved following discontinuation of latanoprost, in some instances with concomitant use of steroidal and nonsteroidal anti-inflammatory agents. CONCLUSIONS: In this case series of pseudophakic, aphakic, or phakic eyes, the temporal relationships between the use of latanoprost and developing CME, and the resolution of CME following cessation of the drug, suggest an association between latanoprost and CME. In all cases, coexisting ocular conditions associated with an altered blood-retinal barrier were present.

Gradual painless visual loss: retinal causes.

This article addresses retinal causes of gradual painless visual loss in older adults. The most common condition causing gradual vision loss is nonexudative age-related macular degeneration, for which no effective treatment exists. Diabetic retinopathy is another common cause of gradual visual loss in older adults, in which photocoagulation, as well as vitreous surgery, may be helpful in preserving or restoring vision. Macular hole and macular pucker, which may cause central visual loss, are treatable with intraocular surgery, and visual improvement may be achieved in the majority of patients. Inflammatory causes of gradual visual loss in older adults are less common, and may benefit from immunosuppressive therapy.

Interferon-induced protein 10 and interleukin 8. C-X-C chemokines present in proliferative diabetic retinopathy.

OBJECTIVE: To determine vitreous levels of interleukin 8 (IL-8) and interferon-induced protein 10 (IP-10), which are members of the C-X-C chemokine family that promote and inhibit neovascularization, respectively. METHODS: We measured the levels of IL-8 and IP-10 by specific enzyme-linked immunosorbent assays in the vitreous from 30 patients with proliferative diabetic retinopathy (PDR) and 10 control patients undergoing vitrectomy for idiopathic macular holes or idiopathic macular puckers. RESULTS: Detectable levels of IL-8 were found in 23 of 24 patients with active PDR, 4 of 6 patients with inactive PDR, and 6 of 10 controls. Levels of IL-8 were significantly increased in vitreous samples from the patients with active PDR (P = .02) when compared with vitreous samples from the controls. The IL-8 levels detected in vitreous samples from patients with inactive PDR were not significantly elevated over those found in the control samples. Interferon-induced protein 10 was detected in the vitreous samples from 23 of 24 patients with active PDR, all patients with inactive PDR, and 9 of 10 controls. Significant elevations of IP-10 were measured in samples from patients with active PDR (P = .004) and in those with inactive PDR (P = .00) over those from controls. In addition, levels of IP-10 were significantly elevated in vitreous samples from patients with inactive PDR compared with vitreous samples from patients with active PDR (P = .02). CONCLUSION: Both IL-8 and IP-10 participate in the pathogenesis of PDR.

Orbital fibroblast chemokine modulation: effects of dexamethasone and cyclosporin A.

AIM: Orbital inflammation is common, but the mechanisms underlying leucocytic infiltration of orbital tissue are poorly understood. Human orbital fibroblasts (OF) express chemokines, interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1), when exposed to proinflammatory cytokines. The effect of dexamethasone (DEX) and cyclosporin A (CSA) on OF IL-8 and MCP-1 were examined. METHODS: Cultured human OF were incubated with recombinant interleukin 1 beta (rIL-1 beta; 0.2, 2.0, 20 ng/ml) alone or incubated with rIL-1 beta and DEX (10(-8), 10(-7), 10(-6) M) or CSA (3, 30, 300 ng/ml) for 24 hours. ELISA and northern blot analyses were performed to determine OF IL-8 and MCP-1 protein secretion and mRNA expression, respectively. RESULTS: OF lacked constitutive IL-8 or MCP-1 expression, but secreted significant amounts of these chemokines and expressed substantial steady state mRNA for both chemokines upon rIL-1 beta stimulation. DEX caused dose dependent inhibition of IL-1 induced IL-8 (p < 0.001) and MCP-1 (p < 0.05) secretion and mRNA expression at all concentrations of rIL-1 beta. CSA enhanced IL-1 induced OF IL-8 (p < 0.001) and suppressed rIL-1 beta induced OF MCP-1 (p < 0.05) secretion when lower doses of rIL-1 beta were used. These effects on secreted chemokines at different concentrations of rIL-1 beta and immunomodulating agents were corroborated by steady state OF IL-8 and MCP-1 mRNA expression. CONCLUSIONS: DEX is a potent inhibitor of OF IL-8 and MCP-1. In contrast, CSA enhances IL-1 induced OF IL-8 and suppresses OF MCP-1. These observations may explain the relative lack of CSA effectiveness in human orbital diseases that respond to corticosteroids.

Synergy between glycated human serum albumin and tumor necrosis factor-alpha for interleukin-8 gene expression and protein secretion in human retinal pigment epithelial cells.

Chemokine production by human retinal pigment epithelium (HRPE) cells is believed to play an important role in ocular inflammation and immune responses. In our previous studies, we demonstrated that glycated human serum albumin (GHSA) strongly stimulates HRPE cells and human corneal keratocytes to produce chemokines. In the present study, we further examined the effects of GHSA on TNF-alpha- and IL-1 beta-induced HRPE IL-8 and monocyte chemoattractant protein (MCP)-1 gene expression and protein secretion in HRPE. At maximally effective concentrations, GHSA (2000 micrograms/ml) potentiated TNF-alpha (20 ng/ml)-stimulated HRPE IL-8 secretion approximately 7-fold. Consistent with the above observations were the time- and dose-dependent increases in the steady-state IL-8 mRNA after coadministration with these two factors, although the half-life of IL-8 mRNA (30 minutes) was not altered by GHSA. In contrast to IL-8, the TNF-alpha-induced HRPE MCP-1 gene expression was only slightly enhanced by GHSA. Moreover, potentiation of HRPE IL-8 generation by GHSA appeared to be selective for TNF-alpha because, under similar conditions, GHSA was unable to enhance the IL-1 beta-stimulated IL-8 gene expression and protein secretion. The IL-1 beta-stimulated HRPE MCP-1 production was also unchanged by GHSA. Collectively, these results suggest specific potentiation of TNF-alpha-induced HRPE IL-8 by human serum albumin that has been glycated either during circulation or locally within tissue. This interaction may be relevant to a variety of ocular diseases involving breakdown of the blood-retinal barrier.

Interleukin-8 and monocyte chemotactic protein-1 gene expression and protein production by human orbital fibroblasts.

Orbital inflammation is common, but the mechanisms underlying leukocytic infiltration of orbital tissue are poorly understood. We studied resident human orbital fibroblasts (OF) interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) mRNA expression and protein secretion in response to lipopolysaccharide (LPS) or recombinant human cytokines that are present during inflammation. Third-passaged cultured human OF were left unstimulated or incubated with varying concentrations of LPS, recombinant interleukin-1-beta (rIL-1 beta), recombinant tumor necrosis factor-alpha (rTNF-alpha), or recombinant interferon-gamma (rIFN-gamma) for 2, 4, 8, or 24 h. Northern blot analysis and ELISA were performed to determine OFIL-8 and MCP-1 mRNA expression and protein secretion, respectively. Experiments were performed in triplicate and repeated four times on different cell lines. OF lacked constitutive IL-8 or MCP-1 gene expression, but produced substantial dose-dependent increases in steady-state IL-8 and MCP-1 mRNA expression by 2 h of LPS or cytokine stimulation (rIL-1 beta > fTNF-alpha > LPS > rIFN-gamma), maintained at 24 h ELISA for IL-8 and MCP-1 proteins showed significant time- and dose-dependent OF secretion after exposure to recombinant cytokine or LPS (rIL-1 beta > rTNF-alpha > LPS), measured after 4 h of exposure (p < 0.01). This increased in the media over the next 20 h. rIFN-gamma was a potent stimulant of OF MCP-1, significant by 2 h (p < 0.05), but only a weak stimulant of IL-8 at 24 h. OF secreted IL-8 and MCP-1 in response to LPS and proinflammatory cytokines, indicating that these resident cells within the orbit have the capacity to actively participate in the initiation and propagation of orbital inflammation. Strategies aimed at modulating local mediators may be helpful in the management of orbital inflammatory disease.

Glycated human serum albumin induces IL-8 and MCP-1 gene expression in human corneal keratocytes.

PURPOSE: The glycated human serum albumin (GHSA) has been demonstrated as effective chemokine inducer in human retinal pigment epithelial (hRPE) cells. Since little is known concerning endogenous chemokines induced by GHSA in corneal keratocytes, we investigated IL-8 and MCP-1 gene expression in human corneal keratocytes (HCK) as compared to human umbilical vein endothelial cells (HUVEC), a model for vascular endothelial cells, after stimulation by GHSA. METHODS: The HCK and HUVEC were incubated with GHSA, IL-1 beta and TNF-alpha. Secretion of IL-8 and MCP-1 was determined by enzyme-linked immunosorbent assay (ELISA). The total RNA was extracted from the corresponding cells and the mRNA levels were detected by Northern blot analysis. RESULTS: GHSA at 500 micrograms/ml concentration induced a significant increase in keratocyte IL-8 and MCP-1 protein secretion over the 24 h time course. The corresponding IL-8 mRNA levels reached a peak by 4 hr, while the MCP-1 mRNA increased steadily over this time period. The concentrations of GHSA for half-maximal stimulation of keratocyte IL-8 and MCP-1 secretion were 1,863 and 793 micrograms/ml, respectively. The levels of GHSA (500 micrograms/ml)-induced keratocyte IL-8 and MCP-1 expression were similar to that induced by IL-1 beta (0.02 ng/ml) and TNF-alpha (2.0 ng/ml). In contrast, the control HUVEC exposed to GHSA did not show sustained IL-8 and MCP-1 gene expression and protein secretion. CONCLUSIONS: This differential stimulation of keratocytes, not HUVEC, suggests that GHSA may be a plasma-borne inducer of chemokines acting on resident corneal cells at sites of inflammation where plasma leakage occurs.

Selective IL-10 inhibition of HLA-DR expression in IFN-gamma-stimulated human retinal pigment epithelial cells.

PURPOSE: Human RPE cells express HLA-DR antigens, bind leukocytes via ICAM-1, and secrete IL-8 and MCP-1, which attract and activate leukocytes. Since little is known concerning endogenous cytokines that may alter ocular immunologic and inflammatory mechanisms, we investigated whether IL-10, an immunosuppressive cytokine, modulates these HRPE features. METHODS: IL-10 effects on HLA-DR and ICAM-1 were examined by HRPE exposures to: (1) IFN-gamma (10-1000 U/ml) + IL-10 (1-100 U/ml) and (2) IL-10 pre-incubation followed by IFN-gamma + IL-10. Immunohistochemistry for HLA-DR and ICAM-1 was graded by masked observers. Flow cytometric analysis quantitated HRPE HLA-DR and ICAM-1. Effects of IL-10 on IL-1 beta (0.2 or 2 ng/ml)-, or TNF-alpha (0.2 or 2 ng/ml)-induced IL-8 and MCP-1 secretion and gene expression were assessed using enzyme-linked immunosorbent assay (ELISA) and Northern blot analysis. RESULTS: HLA-DR expression, detected by immunohistochemistry and flow cytometric analysis, showed dose-dependent increases to IFN-gamma. IL-10 pre-/co-incubation, but not co-incubation alone, markedly reduced HLA-DR expression, but did not modulate constitutive or IFN-gamma-induced ICAM-1. IL-10 alone did not induce MCP-1 or IL-8 secretion or steady-state mRNA expression, nor modulate IL-1 beta-, TNF-alpha- or IFN-gamma-induced IL-8 or MCP-1. CONCLUSIONS: This study suggests that HRPE HLA-DR antigens are selectively inhibited by IL-10, but the timing of IL-10 exposure may be crucial.

Human retinal pigment epithelial cell interleukin-8 and monocyte chemotactic protein-1 modulation by T-lymphocyte products.

PURPOSE: The purpose of the study was to examine the effect of T-lymphocyte products on human retinal pigment epithelial (HRPE) cell interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) secretion and gene expression. METHODS: HRPE cells were stimulated for 2, 4, 8, or 24 hours with 20% conditioned media (CM) from T-lymphocytes stimulated with CD3 or CD28 monoclonal antibodies (mAbs) or phorbol myristic acid. In some experiments, CM from CD3 mAb-stimulated T-lymphocytes was preincubated with neutralizing anti-(alpha)-tumor necrosis factor (TNF), alpha-interferon-gamma (IFN-gamma), or alpha-interleukin-1 (IL-1) mAb (control) to determine the contributions of each of these cytokines to HRPE chemokine induction by stimulated T-lymphocyte CM. HRPE cells were stimulated for 8 and 24 hours with IL-1 beta (0.2 to 20.0 ng/ml) (positive control), TNF-alpha (0.2 to 20.0 ng/ml) (positive control), IFN-gamma (1 to 1000 U/ml), IFN-gamma + IL-1 beta, IFN-gamma + TNF-alpha. Interleukin-2 (IL-2; 100 ng/ml) alone or in combination with IL-1 beta, TNF-alpha, or IFN-gamma also was tested. Enzyme-linked immunosorbent assay (ELISA) and Northern blot analyses were performed to determine secreted IL-8 and MCP-1 and their steady state mRNA expression, respectively. RESULTS: ELISA showed significant increases in HRPE IL-8 and MCP-1 secretion by CM from T-lymphocytes stimulated with CD3 or CD3 + CD28 mAb. Smaller, but significant, increases in IL-8 and MCP-1 resulted from CM phorbol myristic acid-stimulated T-lymphocytes. CM preincubated with neutralizing alpha-TNF or alpha-IFN-gamma mAb induced significantly less HRPE IL-8 and MCP-1, whereas preincubation of CM with neutralizing alpha-IL-1 mAb failed to inhibit CM-induced IL-8 or MCP-1. Northern blot analysis showed increased HRPE IL-8 and MCP-1 mRNA expression within 2 hours of stimulation and was maintained up to 24 hours. CM from T-lymphocytes stimulated with CD3 mAb or CD3 + CD28 mAb produced the greatest increases in IL-8 and MCP-1 mRNA. IFN-gamma induced dose-dependent increases in HRPE MCP-1, but not IL-8, IFN-gamma potentiated IL-1 beta and TNF-alpha-induced MCP-1 production, but showed little modulation of IL-1 beta and TNF-alpha-induced IL-8 production. IL-2 did not induce HRPE IL-8 or MCP-1, nor did it modulate the effects of the other cytokines. Northern blot analysis confirmed the ELISA results. CONCLUSIONS: T-lymphocyte secretions induce HRPE IL-8 and MCP-1 gene expression and secretion. TNF and IFN-gamma appear to be necessary components of T-lymphocyte CM for the induction of HRPE IL-8 and MCP-1. IFN-gamma alone induces HRPE MCP-1, albeit to a lesser extent than would IL-1 beta or TNF-alpha, and potentiates IL-1 beta- and TNF-alpha-induced HRPE MCP-1. IL-2 does not appear to modulate cytokine-induced HRPE IL-8 or MCP-1.

Dexamethasone and cyclosporin A modulation of human retinal pigment epithelial cell monocyte chemotactic protein-1 and interleukin-8.

PURPOSE: To examine the modulation of interleukin-1 beta (IL-1 beta)- and tumor necrosis factor-alpha (TNF-alpha)-stimulated monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) secretion and transcription in human retinal pigment epithelial (HRPE) cells by dexamethasone (DEX) and cyclosporin A (CSA). METHODS: Cultured HRPE cells were stimulated with IL-1 beta (0.2 to 20 ng/ml) or TNF-alpha (0.2 to 20 ng/ml) for 8 or 24 hours without (control) and with DEX (10(-8) to 10(-6) M) or with CSA (0.3 to 30 ng/ml). Secreted levels of HRPE MCP-1 and IL-8 were measured in the media using enzyme-linked immunosorbent assay (ELISA). Both MCP-1 and IL-8 mRNA were analyzed by Northern blot. RESULTS: Although DEX (10(-8) to 10(-6) M) inhibited IL-1 beta-stimulated MCP-1 and IL-8 production, it did not inhibit TNF-alpha-stimulated chemokine secretion. In contrast, CSA significantly inhibited TNF-alpha-stimulated, but not IL-1 beta-stimulated, HRPE MCP-1 and IL-8 secretion. Both DEX and CSA inhibitions showed dose dependence. Northern blot analysis of HRPE steady state MCP-1 and IL-8 mRNA corroborated the ELISA measurements of secreted MCP-1 and IL-8. CONCLUSIONS: Although DEX and CSA inhibit HRPE MCP-1 and IL-8 secretion, this is dependent on whether the inducing inflammatory mediator is IL-1 beta or TNF-alpha. IL-1 beta-induced chemokine secretion is sensitive to DEX, whereas MCP-1 and IL-8 induced by TNF-alpha are inhibited by CSA. This information may be useful in explaining in vivo observations and in suggesting targeted clinical treatments and combinations of immunosuppressive agents.

Cell-associated human retinal pigment epithelium interleukin-8 and monocyte chemotactic protein-1: immunochemical and in-situ hybridization analyses.

Human retinal pigment epithelial (RPE) cells secrete chemokines, interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) in response to pro-inflammatory cytokines. In this study we (1) examined the efficiency of human RPE IL-8 and MCP-1 secretion, (2) determined the amount of neutrophil and monocyte chemotactic activity in human RPE cell conditioned media and cell extracts that is attributable to IL-8 and MCP-1, respectively, and (3) assessed the sensitivity of immunohistochemistry and in situ hybridization for detecting chemokine production by cytokine-stimulated human RPE cells. Conditioned media and extracts from human RPE cells stimulated with various physiologic concentrations of interleukin-1 beta (IL-1 beta) (0.2-20 ng ml-1), tumor necrosis factor (TNF-alpha) (0.2-20 ng ml-1) or interferon-gamma (IFN-gamma) (10-1000 U ml-1) were examined to compare secreted and cell associated levels of IL-8 and MCP-1 at various time points up to 24 hr. ELISA demonstrated that IL-8 and MCP-1 are both efficiently secreted by pro-inflammatory cytokine treated human RPE cells. Substantial dose- and time-dependent RPE secretion of IL-8 was observed following stimulation with IL-1 beta or TNF-alpha, but cell associated IL-8 was detectable only after high dose (20 ng ml-1) IL-1 beta stimulation and comprised less than 1% of the total IL-8 induced. Dose- and time-dependent RPE cell MCP-1 secretion was also observed following IL-1 beta > TNF-alpha > IFN-gamma stimulation, with an average of 4% of the total MCP-1 retained within RPE. Bioassays demonstrated neutrophil and monocyte chemotactic activity in conditioned media from stimulated RPE cells, but not in human RPE cell extracts. Inhibition of conditioned media-induced chemotaxis by specific anti-IL-8 or anti-MCP-1 antibodies demonstrated that IL-8 and MCP-1 were responsible for the majority of HRPE-derived neutrophil (> 60%) and monocyte (53-57%) chemotactic activity, respectively. Using in situ hybridization IL-8 mRNA was readily detected within IL-1 beta > TNF-alpha stimulated RPE cells and MCP-1 mRNA easily visualized within IL-1 beta > TNF-alpha > or IFN-gamma stimulated cells. Immunohistochemistry to detect IL-8 was positive only in RPE cells exposed to high dose IL-1 beta (20 ng ml-1) for 8 or 24 hr and was weak. Immunohistochemical staining for MCP-1 in RPE cells was more intense and was visualized within RPE cells stimulated with IL-beta, TNF-alpha, or IFN-gamma. This study demonstrates that: (1) RPE cells efficiently secrete IL-8 and MCP-1 upon stimulation with pro-inflammatory cytokines; (2) secreted IL-8 and MCP-1 account for the majority of human RPE neutrophil and monocyte chemotactic activity; (3) in situ hybridization readily detects IL-8 and MCP-1 mRNA in cytokine stimulated RPE cells; and (4) immunohistochemistry demonstrates cell-associated MCP-1 in cytokine stimulated RPE cells, but only minimal cell-associated IL-8.

Glycated serum albumin induces chemokine gene expression in human retinal pigment epithelial cells.

Chronic hyperglycemia is thought to be important in the development of diabetic neovascularization but the mechanisms involved remain poorly understood. Interleukin-8 (IL-8) is a leukocyte chemokine and activating agent with angiogenic properties that is present in diabetic vitreous and may play a role in diabetic vasculopathy. We studied IL-8 and monocyte chemotactic protein-1 (MCP-1) production by human retinal pigment epithelial (hRPE) cells exposed to glycated human serum albumin (GHSA). Enzyme-linked immunoassay GHSA (500 micrograms/mL)-treated hRPE cells secreted levels of IL-8 and MCP-1 detectable within 4 h and reached 26.0 +/- 1.3 and 42.2 0.4 ng/10(6) cells/mL after 24 h, respectively. Induction of IL-8 and MCP-1 by GHSA at concentrations ranging from 62.5 to 3,000 micrograms/mL exhibited dose-dependent kinetics. The GHSA-induced chemokine secretion by hRPE was almost completely inhibited by actinomycin D and cycloheximide, suggesting that de novo mRNA and protein synthesis are necessary for the GHSA-induced IL-8 and MCP-1 production. Northern blot analysis of GHSA-induced hRPE IL-8 and MCP-1 mRNA expression corresponded to the time- and dose-dependent increases measured by enzyme-linked immunosorbent assay. High concentrations of glucose (20 mM; 360 mg/dl) increased GHSA-induced hRPE IL-8 and MCP-1 secretion, whereas added insulin (0.5 ng/mL) inhibited IL-8 but not MCP-1 protein secretion and mRNA expression. GHSA also induced hRPE to secrete GRO-alpha, RANTES, and NAP-2 chemokines. GHSA induction of hRPE chemokines further suggests a role for the hRPE in leukocyte infiltration, vascular injury, and neovascularization.