Expression of mRNA coding for TNF alpha, IL-1 beta and IL-6 by cells infiltrating retinal membranes

Methylglyoxal-induces multiple stable changes in human serum albumin before forming nephrotoxic advanced glycation end-products: Injury demonstration in human embryonic kidney cells

The minor fraction of methylglyoxal that is not metabolized in healthy humans reacts with macromolecules to form AGEs. In diabetics, the formation of MG is accelerated; its level may be enhanced multifold. The glyoxalase enzymes responsible for the regular and effective clearance of excess methylglyoxal may become defective in diabetes mellitus leading to its retention in cells and plasma. The methylglyoxal-modified-HSA was prepared, characterised by multiple biophysical techniques and biochemical (s) and its damaging effect was examined on embryonic kidney cell line HEK 293. The UV results showed hyperchromicity in MG-modified-HSA while nitroblue tetrazolium and fluorescence data suggested AGEs formation in comparison to control HSA. Upward shift of negative peaks in CD suggested reduction in α-helicity. Accelerated mobility and diffused broad bands observed in native and SDS polyacrylamide gel, respectively suggest neutralization of some of the positive charges on MG-modified-HSA as well as generation of cross-links. As observed by trypan blue assay, MTT, LDH activity assay, acridine orange, propidium iodide, ethidium bromide, 4',6-diamidino-2-phenylindole (DAPI) staining and ROS measurements, the MG-HSA AGEs caused damage to human embryonic kidney cells. The data suggest that MG-HSA AGEs may trigger powerful inflammatory responses at cellular level which might set the stage for nephrotoxicity in diabetics.

The angiogenic effects of exosomes secreted from retinal pigment epithelial cells on endothelial cells

Exosomes are informative microvesicles associated with intercellular communication via the transfer of many molecular constituents such as proteins, lipids, and nucleic acids; environmental changes and the cellular status around cells greatly affect exosome components. Cells of the retinal pigment epithelium (RPE) are key players in retinal homeostasis. Transforming growth factor (TGF)-β and tumour necrosis factor (TNF)-α are increased in the vitreous and retina in several retinal diseases and activate and undergo epithelial-mesenchymal transition (EMT) in RPE cells. EMT is closely associated with mechanisms of wound healing, including fibrosis and related angiogenesis; however, whether exosome components depend on the cell status, epithelium or mesenchyme and whether these exosomes have pro- or anti-angiogenic roles in the retina are unknown. We performed this study to investigate whether these EMT inducers affect the kinds of components in exosomes secreted from RPE cells and to assess their angiogenic effects. Exosomes were collected from culture media supernatants of a human RPE cell line (ARPE-19) stimulated with or without 10 ng/ml TNF-α and/or 5 ng/ml TGF-β2. NanoSight tracking analysis and immunoblot analysis using exosome markers were used to qualify harvested vesicles. Angiogenic factor microarray analysis revealed that exosomes derived from ARPE-19 cells cultured with TNF-α alone (Exo-TNF) and co-stimulated with TNF-α and TGF-β2 (Exo-CO) contained more angiogenic factors than exosomes derived from control cells (Exo-CTL) or ARPE-19 cells cultured with TGF-β2 alone (Exo-TGF). To assess the effect on angiogenesis, we performed chemotaxis, tube formation, and proliferation assays of human umbilical vein endothelial cells (HUVECs) stimulated with or without exosomes. HUVECs migrated to RPE-derived exosomes, and exosomes derived from ARPE-19 cells accelerated HUVEC tube formation. In contrast, Exo-TNF and Exo-CO reduced HUVEC proliferation. Our findings provide insight into the mechanisms underlying the relation between angiogenesis and exosomes derived from RPE cells.

Inflammatory mediators of proliferative vitreoretinopathy: hypothesis and review

Purpose

To review the role of inflammatory mediators in proliferative vitreoretinopathy (PVR) development and the current treatment for PVR prevention.

Methods

A PubMed search was carried out using these keywords “PVR,” “inflammatory mediators,” “growth factors,” “cytokines” and “treatment.” Studies regarding inflammatory mediators and PVR therapy were included and published up to December 2019.

Results

Inflammatory mediators, namely growth factors and cytokines, have been implicated in the occurrence and development of PVR. Among various inflammatory mediators, transforming growth factor-β, platelet-derived growth factor, interleukin-6, interleukin-8 and tumor necrosis factor-α are considered to be particularly important. In this review, we focus on the hypothesis that growth factors and cytokines are involved in the development of PVR, and current treatment for the prevention of PVR.

Conclusion

We support the hypothesis that growth factors and cytokines may participate in the complex process of PVR development. More importantly, the identification of inflammatory mediators provides novel and efficacious therapeutic targets for the treatment of PVR.

Retinal function and morphology in the rabbit eye after intravitreal injection of the TNF alpha inhibitor adalimumab

Aim

To study the effects of the tumor necrosis factor alpha inhibitor adalimumab on rabbit retina after injection into the vitreous body.

Methods

Forty-eight rabbits of mixed strain (9–12 months old, weighing ≈ 3.5 kg) were randomized into four groups. Adalimumab was injected at one of two concentrations (1.25 mg or 2.5 mg) into the eyes of two groups, and balanced salt solution into the eyes of the third group. The fourth group acted as controls. Full-field electroretinography (ffERG) was performed before injection and 1 and 6 weeks post-injection. At 6 weeks post-injection the rabbits were euthanized and the sectioned retinas were studied. Retinal histology was studied with hematoxylin–eosin staining. Immunohistochemical analysis was performed on rods, cones, rod bipolar cells, horizontal cells, amacrine cells and Müller cells.

Results

No significant difference in ffERG amplitudes or implicit times was observed between the four groups at any time point. Histological and immunohistochemical findings were similar in all groups.

Conclusions

Injection of adalimumab into the vitreous body of healthy rabbits, at doses up to 2.5 mg, does not appear to be toxic to the rabbit retina.

Interleukin-6 and matrix metalloproteinase expression in the subretinal fluid during proliferative vitreoretinopathy: correlation with extent, duration of RRD and PVR grade

PURPOSE

To investigate interleukin (IL)-6 protein levels in the subretinal fluid (SRF) of patients with rhegmatogenous retinal detachment (RRD) complicated by proliferative vitreoretinopathy (PVR); to correlate the IL-6 levels with matrix metalloproteinases (MMP)-1, -2, -3, -8, -9 and tissue inhibitor of metalloproteinases (TIMP)-1 with respect to RRD extent, duration and PVR grade.

METHODS

Thirty-one SRF samples from 31 eyes of 31 patients with RRD complicated with PVR and five SRF samples from five eyes of five patients suffering from RRD not complicated with PVR were collected during treatment by scleral buckling. Enzyme-Linked Immunosorbent Assay was employed for the measurement of IL-6, MMP-1, -3, -8 and TIMP-1 levels while the enzymatic activity of MMP-2 and MMP-9 was assessed by gelatin zymography.

RESULTS

Protein levels of IL-6 (p=0.050), MMP-1 (p=0.001), MMP-3 (p=0.005), MMP-8 (p=0.003), TIMP-1 (p=0.001) as well as enzymatic activity of proMMP-2 (p=0.001), MMP-2 (p=0.023) and MMP-9 (p=0.015), were significantly higher in the SRF of PVR patients compared to controls. IL-6 levels correlated significantly with TIMP-1 (r=0.528, p=0.035). Regarding clinical parameters of the detachment, IL-6 levels correlated with RRD extent (r=0.592, p=0.016), but not with RRD duration (p=0.857) and PVR grade (p=0.594). Regression analysis revealed positive correlations between IL-6 and MMP-2.

CONCLUSIONS

There was a significant correlation between IL-6 and TIMP-1 levels in the SRF of PVR patients. The findings of this study are in agreement with relevant studies concerning IL-6 involvement in the modulation of MMP expression and are indicative of IL-6 and MMP activity during PVR, mainly that of MMP-2 and TIMP-1.

Interleukin-6 and the matrix metalloproteinase response in the vitreous during proliferative vitreoretinopathy

PURPOSE

To investigate the levels of IL-6 in the vitreous of patients with RRD complicated with PVR and correlate the IL-6 levels with matrix metalloproteinase (MMP)-1,-2,-3,-8,-9 and tissue inhibitor of metalloproteinases (TIMP)-1 with respect to RRD extent, duration and PVR grade.

DESIGN

Cohort study.

PARTICIPANTS

Twenty-eight vitreous samples from 28 eyes of 28 patients with RRD complicated with PVR.

METHODS

Institutional study. Twenty-eight vitreous samples from 28 eyes of 28 patients with RRD complicated with PVR were collected during pars plana vitrectomy (PPV) and were compared to vitreous control samples. IL-6, MMP-1,-3,-8 and TIMP-1 levels were measured using ELISA while enzymatic activity of MMP-2, and -9 was determined employing gelatin zymography.

RESULTS

Protein IL-6 (p=0.030), MMP-1 (p=0.003), MMP-3 (p=0.003), TIMP-1 (p=0.001) levels as well as enzymatic activity of proMMP-9 (p=0.013), MMP-9 (p=0.017) and proMMP-2 (p=0.010), were significantly increased in PVR patients as compared to controls. IL-6 levels correlated with MMP-1 (p=0.002), proMMP-2 (p=0.006), MMP-3 (p=0.001) and TIMP-1 (p=0.006). Regression analysis revealed positive correlations between IL-6 and all MMPs and TIMP-1.

CONCLUSIONS

Taking into account the previously established effect of interleukins in MMP activity, the findings of this study suggest a role of IL-6 in MMP stimulation during PVR development.

Obestatin-mediated proliferation of human retinal pigment epithelial cells: regulatory mechanisms

In this work, we have evaluated the effect of the new discovered peptide obestatin on cell proliferation in primary cultures of human retinal epithelial cells (hRPE cells). The results showed that this peptide induced, in a dose-dependent manner, cell proliferation by MEK/ERK 1/2 phosphorylation. A sequential analysis of the obestatin transmembrane signaling pathway showed that the ERK 1/2 activity is partially blocked after preincubation of the cells with pertussis toxin (PTX), as well as by wortmannin (an inhibitor of PI3K), claphostin C (an inhibitor of PKC), and PP2 (which inhibits the non receptor tyrosine kinase Src). Upon administration of obestatin, the intracellular levels of phospho-PKCepsilon-, theta-, and micro-isoenzymes rise with different time courses, from which PKCepsilon might be responsible for ERK 1/2 response. Based on the experimental data, a signaling pathway involving the consecutive activation of Gi, PI3K, novel PKC (probably PKCepsilon), and Src for ERK 1/2 activation is proposed. These results incorporate a new mitogenic factor to the group of factors that regulate proliferation of hRPE cells.

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.

Upregulation of RAGE and its ligands in proliferative retinal disease

We sought to study the presence of the receptor for advanced glycation endproducts (RAGE) and its ligands, advanced glycation endproducts (AGEs), S100/calgranulins and amphoterin (high mobility group box 1 protein; HMGB1), in the vitreous cavity and epiretinal membranes (ERMs) of eyes of patients with proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). Undiluted vitreous specimens were collected from 30 eyes of 30 patients undergoing pars plana vitrectomy for repair of retinal detachment (RD) secondary to PDR (n = 15) or PVR (n = 15). The vitreous samples obtained from 10 eyes undergoing macular hole repair were used as controls. Epiretinal membranes were obtained from eight eyes with PDR and from 10 eyes with PVR. The levels of AGEs in the vitreous were measured using ELISA. The vitreous levels of soluble RAGE (sRAGE), S100/calgranulins and amphoterin were measured using Western blot analyses. The localization of RAGE and its ligands in ERMs was determined with immunohistochemistry. The vitreous levels of sRAGE were significantly increased in both PDR and PVR (p < or = 0.05) compared to control vitreous. In both PDR and PVR, the vitreous levels of AGEs (p < or = 0.01), S100/calgranulins (p < or = 0.05), and amphoterin (p < or = 0.01) were also elevated compared to control eyes. Expression of RAGE was detected in six of eight ERMs from eyes with PDR and eight of 10 ERMs from eyes with PVR. Many cells expressing RAGE also expressed vimentin, suggesting a glial cell origin. Ligands for RAGE were also detected in ERMs, with AGEs detected in five eyes with PDR and eight eyes with PVR. Similarly, S100 and amphoterin ERM expression was observed in six eyes with PDR; these ligands were also expressed in ERMs from eyes with PVR (8 and 7 cases, respectively). We conclude that RAGE and its ligands are increased in the vitreous cavity of eyes with PDR and PVR and are present in ERMs of eyes with these proliferative retinal disorders. These findings suggest a role for the proinflammatory RAGE axis in the pathogenesis of proliferative retinal diseases.

The bovine vitreous-derived lipid factor (bVLF) is a powerful inhibitor of retinal pigmented epithelial (hRPE) cell proliferation

Human retinal pigmented epithelial cell (hRPE) proliferation plays a significant role in various proliferative diseases associated to the retina that leads to loss of vision, such as proliferative vitreoretinopathy. In the current study, the role of the bovine vitreous lipid factor (bVLF) in hRPE cell proliferation has been investigated. bVLF is a bioactive lipid isolated from the bovine vitreous body with strong Ca(2+)-mobilizing activity in fibroblast. In the first approach, the effects of bVLF on Ca(2+)-mobilizing activity were investigated in hRPE. The results showed that bVLF induced, in a dose-dependent manner, a Ca(2+) mobilization from PA-sensitive intracellular stores [non-Ins(1,4,5)P(3)-sensitive stores], in which extracellular Ca(2+) participated. The increase in intracellular Ca(2+) was associated with a dose-dependent inhibiting effect on cell proliferation. At a dose of 10 microg/mL, bVLF caused a 26% or a 44% inhibition in hRPE cell proliferation during the 3- or the 6-day culture periods, respectively. These effects appear to be specific in hRPE cells, since EFGR-T17 fibroblast cells treated with equivalent amounts of bVLF did not show any inhibiting effects. This inhibitory action was not associated to apoptotic/necrotic processes. Furthermore, bVLF inhibited EGF-, bFGF-, IGF-I-, PDGF-, HGF- and VEGF-induced proliferation of the hRPE cells. Moreover, this inhibitory response was also observed in FBS-induced hRPE cell proliferation. bVLF, at a concentration of 10 microg/mL, induced 16% inhibition of proliferation during a culture period of 3 days. This inhibitory action was greater during the 6-day culture period, exceeding 40%. With regard to this action, the results showed that bVLF has a potent inhibitory effect on ERK1/2 activation, and plays a key role in the control of hRPE cell proliferation. These observations contribute to the knowledge of inhibitory factors responsible for keeping antiproliferative environment that preserve the RPE-associated activities in normal states. It advances the interesting possibility that this factor or a factor with characteristics common to bVLF might be involved in the pathogenesis of abnormal proliferative eye processes.

Inhibitory effect of certain neuropeptides on the proliferation of human retinal pigment epithelial cells

AIMS

To define the effect of the neuropeptides substance P, calcitonin gene related peptide, vasoactive intestinal polypeptide, neuropeptide Y, and secretoneurin on the proliferation of human retinal pigment epithelial (RPE) cells.

METHODS

ARPE-19 cells were used. The cells were cultured in Dulbecco's modified Eagle's medium. 1000 and 2000 cells were incubated with the peptides for 3 and 5 days, and the effect of the peptides was evaluated by an ATP lite assay dose dependently. Furthermore, specific antagonists at 10(-6) M were used to find out whether the effect would be reversed.

RESULTS

In brief, each of the peptides tested had an inhibiting effect. This inhibiting effect was weak but highly significant, averaging 10% to 15%, and was most pronouncedly seen at concentrations between 10(-10) M and 10(-14) M. Each antagonist reversed the inhibiting effect fully.

CONCLUSIONS

These results clearly indicate that RPE cells are under neural control and the low effective concentration of the peptides may be the one physiologically acting on these cells. The results are of important relevance both physiologically and pathophysiologically: physiologically, the inhibitory effect may mean that these peptides cause the cells to remain in a differentiated condition. Pathophysiologically, the findings are relevant in proliferative vitreoretinopathy where RPE cells proliferate in excess. The authors hypothesise that the inhibiting effect diminishes when these cells are swept out and actively migrate from their physiological location and thus, dedifferentiate and begin to proliferate. This hypothesis improves the knowledge of the initial processes in the pathogenesis of the disease as there seems to be a discrepancy between facilitatory and inhibitory influences favouring the former in proliferative vitreoretinopathy. Furthermore, these neuropeptides constitute the first endogenous inhibitors of RPE cell proliferation.

Basic fibroblast growth factor, glutamine synthetase, and interleukin-6 in vitreous fluid from eyes with retinal detachment complicated by proliferative vitreoretinopathy

PURPOSE

To investigate the presence of basic fibroblast growth factor (bFGF), glutamine synthetase (GS), and interleukin-6 (IL-6) in vitreous fluid from eyes with retinal detachment complicated by proliferative vitreoretinopathy (PVR).

DESIGN

Comparative case series; experimental study.

METHODS

In a prospective study, we measured bFGF, GS, IL-6, and total protein in vitreous fluid samples from 53 eyes from 53 consecutive patients with PVR operated on in our hospital. As controls, vitreous fluid samples from eyes with a macular hole (n = 9) or pucker (n = 11) were used.

MAIN OUTCOME MEASURES

Laboratory data of the patient group were compared with the control group and correlated with various clinical data, especially with visual recovery and redetachment.

RESULTS

For IL-6, bFGF, and total protein we found significantly higher levels in PVR patients' eyes than in control eyes (P =.03, P =.046, and P <.0001, respectively). Within the PVR group, no significant correlation was found for IL-6, bFGF, GS, or total protein with the various tested clinical variables.

CONCLUSIONS

We found increased levels of IL-6, bFGF, and total protein in vitreous fluid from patients' eyes with PVR. Whether the increased levels of IL-6, bFGF, and total protein are the result of an injury-induced upregulation of these proteins as part of a self-protective mechanism of the retina to minimize photoreceptor damage after the mechanical injury induced by retinal detachment is, at present, not known.

Selective binding of nucleotide probes by eosinophilic cationic protein during in situ hybridisation

During in situ hybridisation on frozen and paraffin-embedded sections of bowel for IkappaB alpha, oligodeoxyribonucleotide probes were found to bind more avidly to eosinophils than target mRNA. This binding could not be obviated using strategies previously employed to block either binding of long DNA probes (200-mers) to eosinophils in bone marrow smears, or of riboprobes to eosinophils in sections of bowel, without removing specific hybridisation of probes. That this binding could arise through interaction of anionic oligodeoxyribonucleotides with eosinophil cationic protein, which has an unusually high pI, and is abundant in cytoplasmic granules of eosinophils, was demonstrated in vitro using real-time biomolecular interaction analysis with a BiacoreX instrument. Finally, a relationship between probe hydrophobicity, measured by reverse phase ion-pair high performance liquid chromatography, and in situ binding of individual probes to eosinophils was demonstrated. Effective tissue penetration by hydrophobic probes and subsequent strong probe-eosinophilic cationic protein interactions therefore may confound the interpretation of in situ hybridisation performed with oligonucleotide probes in eosinophil-containing tissues, such as bowel and nasal polyps.

Levels of basic fibroblast growth factor, glutamine synthetase, and interleukin-6 in subretinal fluid from patients with retinal detachment

PURPOSE

To investigate the presence of basic fibroblast growth factor, glutamine synthetase activity, and interleukin-6 in subretinal fluid from patients with retinal detachment.

METHODS

In a prospective study we measured basic fibroblast growth factor, glutamine synthetase activity, interleukin-6, and total protein in subretinal fluid samples from 96 eyes from 94 consecutive patients with a retinal detachment corrected by a conventional scleral buckling operation in our clinical practice. As controls, vitreous fluid samples from eyes with a macular hole (n = 6) or pucker (n = 11) were used. Laboratory data of the patient group were compared with the control group and correlated with various clinical data.

RESULTS

Levels (median, range) of basic fibroblast growth factor, glutamine synthetase activity, interleukin-6, and total protein were significantly higher in patients than in controls (P <.0001). An increased level of glutamine synthetase and total protein correlated with a longer duration of the retinal detachment (r =.4, P =.002, and r =.34, P =.001, respectively). Interleukin-6 and basic fibroblast growth factor levels did not correlate with the duration of the detachment. After multivariate logistic regression analysis, no significant relation was found between any of the tested subretinal proteins and a low visual outcome or redetachment.

CONCLUSIONS

We found increased levels of basic fibroblast growth factor and glutamine synthetase in subretinal fluid from patients with retinal detachment. Basic fibroblast growth factor and glutamine synthetase may play a role in the pathogenesis and recovery after retinal detachment. The questions of whether the increased levels of basic fibroblast growth factor and glutamine synthetase result from leakage of dying glia cells (including Müller cells) and neurons and if basic fibroblast growth factor is actively produced to protect the photoreceptor cells need further research.

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.

Intravitreal invading cells contribute to vitreal cytokine milieu in proliferative vitreoretinopathy

AIM

To examine the contribution of infiltrating cells in the local production of cytokines within the vitreous of patients with proliferative vitreoretinopathy (PVR).

METHODS

The presence of mRNA coding for IL-6, IL-8, IL-1beta, IL-1alpha, TNFalpha, IFNgamma, IL-12, and HPRT was investigated in 25 vitreous samples from patients with PVR, 11 vitreous samples from patients with retinal detachment (RD) not complicated by PVR, and 10 vitreous samples from patients with macular hole (MH). A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) using an internal competitor was used to investigate these samples. From these samples, 15 PVR, 8 RD, and 8 MH were analysed for the protein levels of the same cytokines using enzyme linked immunosorbent assay (ELISA). Spearman correlation was used to test any association between mRNA and cytokine protein levels, as an indicator of the contribution these cells make to the intravitreal cytokine milieu.

RESULTS

A strong correlation was found between mRNA and their respective cytokine levels (protein products) for IL-6, IL-8, IL-1beta, IL-1alpha, TNFalpha, IFNgamma (Spearman r = 0.83, 0.73, 0.67, 0.91, 0.73, and 0.73 respectively), but not for IL-12. The median levels of IL-6, IL-8, IL-1beta, and IFNgamma mRNA and their respective cytokines were significantly higher (p <0.05) in patients with PVR than in those with macular hole. There was no statistically significant difference in the median levels of IL-1alpha mRNA between PVR and MH but the cytokine IL-1alpha was detected at a significantly higher level in PVR compared with MH patients. Between PVR and RD patients, there was no statistically significant difference in mRNA levels for all the investigated cytokines (p >0.05) except for IL-6 where there was a statistical significance (p= 0.038). In contrast, the median levels of IL-6, IL-8, and IL-1beta cytokines were significantly higher (p <0.05) in patients with PVR than in those with RD, whereas for IL-1alpha and IFNgamma no significant statistical difference was detected between PVR and RD patients (p >0.05). When results of RD and MH patients were compared, a statistical difference was only detected in mRNA levels of INFgamma (p = 0.008). However, no difference was detected for INFgamma (protein product) or for any of the other cytokines between RD and MH patients.

CONCLUSION

Levels of both protein and mRNA encoding IL-6, IL-8, IL-1beta, and IFNgamma is significantly increased in vitreous samples from patients with PVR. The strong correlation between ELISA detectable cytokines (protein products) and their respective mRNA levels suggest that intravitreal, invasive cells are the major source of these cytokines, with the exception of IL-12. Cells invading the vitreous do not appear to locally produce IL-12 mRNA. This would appear to implicate cells peripheral to the vitreal mass as the major source of this cytokine.

Detection of cytokine mRNA production in infiltrating cells in proliferative vitreoretinopathy using reverse transcription polymerase chain reaction

AIMS

To determine whether the infiltrating cells in the vitreous and subretinal fluid of patients with proliferative vitreoretinopathy (PVR) express messenger RNA for various cytokines found in this condition.

METHODS

The presence of mRNA coding for HPRT, IL-6, IL-1beta, IL-8, and TNFalpha was investigated in 20 vitreous and subretinal fluid (SRF) samples from patients with PVR by reverse transcriptase polymerase chain reaction (RT-PCR). 16 samples from patients with retinal detachment and macular holes were used as controls.

RESULTS

HPRT was detected in all samples of PVR and in 11 (69%) control cases. Patients with PVR demonstrated mRNA for the cytokines tested more often than controls. The difference was statistically significant.

CONCLUSION

The presence of mRNA encoding for IL-6, IL-1beta, IL-8, and TNFalpha is significantly detected by RT-PCR in vitreous and SRF samples of patients with PVR, indicating local production of these cytokines by vitreous and SRF cells.

Effective chemokines and cytokines in the rejection of human retinal pigment epithelium (RPE) cell grafts

OBJECTIVE

In the rejection of transplanted retinal pigment epithelium (RPE) cells, an activation of allografts is probably the pivotal point for long-term success. The detailed immunological interactions involved in the rejection after RPE transplantation are still unknown. The aim of this study is to evaluate the interactions of pro-inflammatory cytokines and chemokines in this activation process in vitro.

METHODS

Human RPE cells (2 x 10(5)/ml) were therefore activated through a pre-treatment with different concentrations of interferon (IFN)-gamma (100 or 1000 U/ml), tumour necrosis factor (TNF)-alpha (1 or 10 ng/ml) or combinations of both, or employed in a nonactivated form. Afterwards, the RPE cells were tested by enzyme-linked immunosorbant assay (ELISA) and ribonuclease protection assays (RPA) for the secretion and mRNA content of the different chemokines (RANTES, MCP-1 and IL-8) and cytokines (IL-6) at various time points up to 48 h.

MAIN FINDINGS

HRPE cells secrete the investigated cytokines in response to pro-inflammatory activation. This could be demonstrated at both the mRNA (RPA) and the protein levels (ELISA). The secretion was time and dose dependent, and significantly upregulated in comparison to that observed with nonactivated cells.

CONCLUSIONS

This study demonstrates that RPE cells efficiently secrete such cytokines as RANTES, MCP-1, IL-6, and IL-8, and have an accountable neutrophil and monocyte chemotactic activity. Thus, it could be indicated that the investigated cytokines play a central role in the activation cascade of RPE and in RPE rejection as well.

Gelatinase B in proliferative vitreoretinal disorders

PURPOSE

To investigate whether gelatinases A and B are involved in the pathogenesis of proliferative vitreoretinal disorders.

METHODS

In a prospective study of 101 consecutive patients, vitreous and paired serum samples were obtained from 38 patients with rhegmatogenous retinal detachment complicated by proliferative vitreoretinopathy, 25 patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy, and 38 patients with proliferative diabetic retinopathy. Gelatinase activities were determined by quantitative zymography.

RESULTS

All vitreous samples contained comparable levels of the constitutive gelatinase A. Inducible gelatinase B was detected in eight (32%) of 25 vitreous samples from patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy (mean +/- SD, 319.5 +/- 521.0 scanning units), in 17 (44.7%) of 38 vitreous samples from patients with proliferative vitreoretinopathy (560.6 +/- 718.9 scanning units), and in 34 (89.5%) of 38 vitreous samples from patients with proliferative diabetic retinopathy (1,707.2 +/- 1,220.3 scanning units). The incidence of detection of gelatinase B in proliferative diabetic retinopathy cases was significantly higher than it was in rhegmatogenous retinal detachment with no proliferative vitreoretinopathy and proliferative vitreoretinopathy cases (P < .001). Gelatinase B levels in the vitreous samples of patients with proliferative diabetic retinopathy were higher than the levels found in patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy and in patients with proliferative vitreoretinopathy (P = .0152). Gelatinase A was detected in all the tested sera, whereas none of the tested paired serum samples contained detectable gelatinase B activity.

CONCLUSIONS

Gelatinase B may play an important role in extracellular matrix degradation associated with neovascularization in proliferative diabetic retinopathy.

Synthesis and secretion of tumour necrosis factor-alpha by human monocytic THP-1 cells and chemotaxis induced by human serum albumin derivatives modified with methylglyoxal and glucose-derived advanced glycation endproducts

Human serum albumin minimally-modified by methylglyoxal (MGmin-HSA) stimulated the synthesis and secretion of tumour necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells in vitro. Human serum albumin minimally-modified by glucose-derived advanced glycation endproducts (AGEmin-HSA) and human serum albumin highly-modified by glucose-derived advanced glycation endproducts (AGE-HSA) stimulated markedly lower synthesis and secretion of TNF-alpha from THP-1 cells than did MGmin-HSA. The median effective concentration EC50 value of MGmin-HSA for the secretion of TNF-alpha was 5.8 +/- 0.3 microM and the maximal secretion was 0.28 +/- 0.01 ng TNF-alpha/ml (n = 12) for incubations containing 5 x 10(5) cells/ml. MGmin-HSA (0.2-2.0 microM) also stimulated chemotaxis of THP-1 cells in vitro but AGE-HSA did not in this concentration range. The EC50 value of MGmin-HSA for the chemotactic response was 0.44 +/- 0.07 microM (n = 15). Similar induction of the synthesis and secretion of TNF-alpha and chemotaxis by monocytes in response to MGmin-HSA in vivo may contribute to atherosclerosis in macro- and micro-angiopathy, particularly in the development of chronic clinical complications of diabetes mellitus.

Monocyte chemotactic protein-1 in proliferative vitreoretinal disorders

PURPOSE

To investigate whether the chemokines monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) are involved in the pathogenesis of proliferative vitreoretinal disorders and to study their possible interaction with IL-6.

METHODS

In a prospective study of 125 consecutive patients (125 eyes), vitreous and paired serum samples were obtained and were assayed for MCP-1 and IL-8. Levels of IL-6 were determined by proliferation of the IL-6-dependent hybridoma cell line 7TD1.

RESULTS

Monocyte chemotactic protein-1 was detected in 13 (48%) of 27 vitreous samples from patients with retinal detachment, in five (63%) of eight samples from patients with macular pucker, in 31 (72%) of 43 samples from patients with proliferative vitreoretinopathy, and in 32 (76%) of 42 samples from patients with proliferative diabetic retinopathy, but not in samples from five patients with idiopathic epiretinal membrane. There was a significant (P = .049) correlation between the incidence of MCP-1 detection in retinal detachment, macular pucker, and proliferative vitreoretinopathy groups and the severity of proliferation. Interleukin-8 was detected in two vitreous samples from eyes with retinal detachment, in two samples from eyes with proliferative vitreoretinopathy, and in three samples from eyes with proliferative diabetic retinopathy. Monocyte chemotactic protein-1 levels in the vitreous samples were positively correlated with IL-6 levels (r = .31, P = .01). Interleukin-6 levels were significantly (P = .0097) greater in vitreous samples with than without detectable levels of MCP-1.

CONCLUSION

Monocyte chemotactic protein-1 is present in a substantial percent of vitreous samples from eyes with proliferative vitreoretinal disorders and may help in stimulating the infiltration of monocytes and macrophages into eyes with these disorders.

Synthesis and secretion of macrophage colony stimulating factor by mature human monocytes and human monocytic THP-1 cells induced by human serum albumin derivatives modified with methylglyoxal and glucose-derived advanced glycation endproducts

Human serum albumin minimally-modified by methylglyoxal (MGmin-HSA) stimulated the synthesis and secretion of macrophage-colony stimulating factor (M-CSF) by mature human monocytes in vitro. Human serum albumin minimally-modified by glucose-derived advanced glycation endproducts (AGEmin-HSA) and human serum albumin highly-modified by glucose-derived advanced glycation endproducts (AGE-HSA) stimulated much lower secretion of M-CSF from human monocytes than did MGmin-HSA. MGmin-HSA and AGE-HSA but not AGEmin-HSA also stimulated the growth of human monocytic THP-1 cells in vitro which was inhibited by polyclonal antibodies to human M-CSF. For MGmin-HSA, the median growth stimulatory concentration EC50 value was 0.24 +/- 0.07 microM and the maximal increase in cell growth was 36% of control cell growth (n = 24). Similar induction of secretion of M-CSF from monocytes in vivo may contribute to atherosclerosis in macro- and micro-angiopathy, particularly in the development of diabetic complications.

Schwann cells produce tumor necrosis factor alpha: expression in injured and non-injured nerves

We investigated the production of tumor necrosis factor alpha, a pleotropic cytokine, in the rat sciatic nerve using immunohistochemistry for the protein and in situ hybridization for specific messenger RNA sequences. Results demonstrated that in the uninjured sciatic nerve, few endothelial cells, fibroblasts, and Schwann cells were immunoreactive for tumor necrosis factor. In situ hybridization did not yield visible results in this control tissue. Following a compression injury, the number of immunoreactive cells in the nerve fascicle was increased. In situ hybridization showed positive staining in Schwann cells and endothelial cells at seven days. These observations are the first to demonstrate the production of this proinflammatory cytokine by peripheral nerve glia, and further support other studies from this laboratory suggesting that tumor necrosis factor has a pathogenic role in nerve injury. Because this cytokine is produced by Schwann cells in intimate contact with nerve fibers, tumor necrosis factor may also have a role in the hyperalgesia associated with neuropathic pain.

Pharmacology of methylglyoxal: formation, modification of proteins and nucleic acids, and enzymatic detoxification--a role in pathogenesis and antiproliferative chemotherapy

1. Methylglyoxal is a reactive alpha-oxoaldehyde and physiological metabolite formed by the fragmentation of triose-phosphates, and by the metabolism of acetone and aminoacetone. 2. Methylglyoxal modifies guanylate residues to form 6,7-dihydro-6,7-dihydroxy-6-methyl-imidazo[2,3-b]purine-9(8)one and N2-(1-carboxyethyl)guanylate residues and induces apoptosis. 3. Methylglyoxal modifies arginine residues in proteins to form N(delta)-(4,5-dihydroxy-4-methylimidazolidin-2-yl) ornithine, N(delta)-(5-hydro-5-methylimidazol-4-on-2-yl)ornithine and N(delta)-(5)methylimidazol-4-on-2-yl)ornithine residues. 4. Methylglyoxal-modified proteins undergo receptor-mediated endocytosis and lysosomal degradation in monocytes and macrophages, and induce cytokine synthesis and secretion. 5. Methylglyoxal is detoxified by the glyoxalase system. Decreased detoxification of methylglyoxal may be induced pharmacologically by glyoxalase I inhibitors which have anti-tumor and anti-malarial activities. 6. The modification of nucleic acids and protein by methylglyoxal is a signal for their degradation and may have a role in the development of diabetic complications, atherosclerosis, the immune response in starvation, aging and oxidative stress.

Evidence of chronic inflammation in retina excised after relaxing retinotomy for anterior proliferative vitreoretinopathy

BACKGROUND

Epiretinal membranes from eyes with proliferative vitreoretinopathy (PVR) frequently express molecules associated with chronic inflammation. To investigate the extent to which inflammation may compromise the detached retina, we determined the expression of inflammatory molecules in anterior retina removed after relaxing retinotomy for retinal detachment complicated by anterior PVR.

METHODS

Surgical retinal specimens were studied immunohistochemically for the distribution of the vascular cell adhesion molecules VCAM, E-selectin, P-selectin, ICAM and PECAM and for the presence of the cytokine TNF alpha and of T lymphocytes (CD3-positive cells), macrophages (CD68-positive cells) and HLA-DR molecules. The findings were compared with those in control cadaveric retina.

RESULTS

Aberrant expression of ICAM-1 was observed in four of nine retinal specimens from eyes with PVR, whereas its expression in control retinas was confined to the external limiting membrane and ganglion cell layers. PECAM was observed in seven of nine surgical retinal specimens and in four of five controls. E-selectin and P-selectin were expressed within the luminal aspects of four of nine retinal specimens from eyes with PVR, and VCAM was present in three of nine surgical specimens investigated. All cadaveric control retinas were negative for E-selectin and VCAM, whilst one was positive for P-selectin. Staining for TNF alpha was observed within luminal aspects and walls of retinal vessels from eight of nine surgical specimens, but was not seen in any of the cadaveric controls. T lymphocytes and cells expressing the macrophage marker CD68 were identified in two and seven of nine diseased retinas respectively, but not in any of the controls. Cells staining for HLA-DR were observed in eight of nine surgical retinal specimens and in three of five controls.

CONCLUSION

The present findings indicate that retina from eyes with advanced PVR may itself be subject to inflammatory changes, and indicate that the PVR process is not limited to retinal membranes, but involves a more widespread distribution of inflammation than is generally appreciated.

Induction of synthesis and secretion of interleukin 1 beta in the human monocytic THP-1 cells by human serum albumins modified with methylglyoxal and advanced glycation endproducts

Human serum albumin modified with 1-2 methylglyoxal residues per molecule of protein (MGmin-HSA) stimulated the synthesis and secretion of interleukin 1 beta (IL-1 beta) from human monocytic THP-1 cells in vitro. It was a more potent inducer of IL-1 beta synthesis than human serum albumin highly-modified with glucose-derived advanced glycation endproducts (AGE-HSA). With 20 microM ligand. IL-1 beta synthesis was (pg/10(6) cells): MGmin-HSA 484.5 +/- 50.3; AGE-HSA 30.6 +/- 2.0 (n = 3). IL-1 beta synthesis increased markedly with MGmin-HSA concentrations > 5 microM. IL-1 beta synthesis and secretion from monocytes in response to methylglyoxal-modified proteins in vivo may contribute to the development of macro- and micro-angiopathy, particularly in diabetes mellitus.

Non-vascular vitreoretinopathy: the cells and the cellular basis of contraction

BACKGROUND

We consider epiretinal membrane in terms of the two repair processes of gliosis and fibrosis and look at the cellular basis of contraction.

METHODS

Pathological material removed at surgery was examined by a range of morphological procedures. Cultures of fibroblasts, retinal pigment epithelium cells and retinal glia were subjected to bioassays which relate to behavioural activities in scar formation.

RESULTS AND CONCLUSIONS

Our findings highlight the importance of activities such as migration and adhesion in the formation of epiretinal membranes, and also show that these activities are central to our understanding of contraction.