Ocular inflammatory effects of intravitreally injected tumor necrosis factor-alpha and endotoxin

Tumor necrosis factor (TNF) inhibitors for juvenile idiopathic arthritis-associated uveitis

BACKGROUND

Uveitis is the most common extra-articular manifestation of juvenile idiopathic arthritis (JIA) and a potentially sight-threatening condition characterized by intraocular inflammation. Current treatment for JIA-associated uveitis (JIA-U) is largely based on physician experience, observational evidence and consensus guidelines, resulting in considerable variations in practice.  OBJECTIVES: To evaluate the effectiveness and safety of tumor necrosis factor (TNF) inhibitors used for treatment of JIA-U.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We last searched the electronic databases on 3 February 2022.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing TNF inhibitors with placebo in participants with a diagnosis of JIA and uveitis who were aged 2 to 18 years old.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology and graded the certainty of the body of evidence for seven outcomes using the GRADE classification.

MAIN RESULTS

We included three RCTs with 134 participants. One study conducted in the USA randomized participants to etanercept or placebo (N = 12). Two studies, one conducted in the UK (N = 90) and one in France (N = 32), randomized participants to adalimumab or placebo. All studies were at low risk of bias. Initial pooled estimates suggested that TNF-inhibitors may result in little to no difference on treatment success defined as 0 to trace cells on Standardization of Uveitis Nomenclature (SUN)-grading; or two-step decrease in activity based on SUN grading (estimated risk ratio (RR) 0.66; 95% confidence interval (CI) 0.21 to 2.10; 2 studies; 43 participants; low-certainty evidence) or treatment failure defined as a two-step increase in activity based on SUN grading (RR 0.31; 95% CI 0.01 to 7.15; 1 study; 31 participants; low-certainty evidence). Further analysis using the individual trial definitions of treatment response and failure suggested a positive treatment effect of TNF inhibitors; a RR of treatment success of 2.60 (95% CI 1.30 to 5.20; 3 studies; 124 participants; low-certainty evidence), and RR of treatment failure of 0.23 (95% CI 0.11 to 0.50; 3 studies; 133 participants). Almost all the evidence was on adalimumab and the evidence on etanercept was very limited.  For secondary outcomes, one study suggests that adalimumab may have little to no effect on risk of recurrence after induction of remission at three months (RR 2.50, 95% CI 0.31 to 20.45; 90 participants; very low-certainty evidence) and visual acuity, but the evidence is very uncertain; mean difference in longitudinal logMAR score change over six months was -0.01 (95% CI -0.06 to 0.03) and -0.02 (95% CI -0.07 to 0.03) using the best and worst logMAR measurement, respectively (low-certainty evidence). Low-certainty evidence from one study suggested that adalimumab treatment results in reduction of topical steroid doses at six months (hazard ratio 3.58; 95% CI 1.24 to 10.32; 74 participants who took one or more topical steroid per day at baseline). Adverse events, including injection site reactions and infections, were more common in the TNF inhibitor group. Serious adverse events were uncommon.

AUTHORS' CONCLUSIONS

Adalimumab appears to increase the likelihood of treatment success and decrease the likelihood of treatment failure when compared with placebo. The evidence was less conclusive about a positive treatment effect with etanercept. Adverse events from JIA-U trials are in keeping with the known side effect profile of TNF inhibitors. Standard validated JIA-U outcome measures are required to homogenize assessment and to allow for comparison and analysis of multiple datasets.

Ocular manifestations of inflammatory bowel diseases: an update for gastroenterologists

Inflammatory bowel diseases (IBD), that includes ulcerative colitis and Crohn's disease, can affect not only the gastrointestinal tract but a wide spectrum of organs. The extra-intestinal manifestations (EIMs) are one of the most challenging aspect of IBD, playing a significant role for the lifetime care and the quality of life of patients. Ocular manifestations are the third most frequent EIMs, preceded by articular and dermatological ones. The aim of this narrative review is to describe the different types of ocular involvements, focusing on their clinical management. Uveitis and episcleritis are the most common ocular EIMs, differing for many aspects. Uveitis are unrelated with IBD activity and they even precede the onset of the intestinal disease, while episcleritis are common defined as a good mark of IBD activity. Pain is uncommon in most cases of episcleritis, while severe eye pain and photophobia are the most frequent onset of anterior uveitis. Less common but even more severe, are orbital pseudotumor or posterior segment involvement. Most of the ocular EIMs can be successfully treated with topic and oral steroids and the underlying therapy for IBD can reduce or cut out at all the recurrence of these manifestations. Symptoms are commonly not specific, in some cases being unnoticed for years leading to permanent ocular consequences. Cooperation between different specialists is crucial to avoid all the possible consequences of a non-treated EIMs, especially for ocular ones.

Effectiveness and Safety of Anti-Tumor Necrosis Factor-Alpha Agents Treatment in Behcets' Disease-Associated Uveitis: A Systematic Review and Meta-Analysis

Purpose

We conducted a systematic review and meta-analysis to determine the effectiveness and safety of anti-tumor necrosis factor-alpha (TNF-α) agents in the treatment of Behcets’ disease (BD)-associated uveitis.

Method

Three electronic databases, Embase, MEDLINE, and the Cochrane Library, were searched for eligible papers focusing on the anti-TNF-α agents treatment in BD-associated uveitis with at least 6 months follow-up time. A systematic review and meta-analysis was conducted on selected papers with appropriate clinical and methodological homogeneity. The effectiveness outcomes included inflammation remission, visual acuity (VA) improvement, central macular thickness (CMT) decrease, corticosteroid (CS)-sparing effects, and the safety outcomes included minor and severe drug-related adverse events (AEs).

Result

From Jan 2010 to Dec 2019, there were 504 records produced in total, in which 18 clinical trials were selected for meta-analysis (15 trials were retrospective studies, and 3 were prospective studies). The number of patients in each study ranged from 11 to 163 and the mean follow-up time from 0.9 to 6.44 years. During the follow-up, the pooled inflammation remission rate was 68% with a 95% confidence interval (CI) of 0.59–0.79, VA improvement rate was 60% (95% CI 0.47–0.77), CMT decrease was 112.70 μm (95% CI 72.8–153.0 μm). The proportions of patients who had CS-suspended and CS-tapered reached 38% (95% CI 0.23–0.65) and 34% (95% CI 0.16–0.70), respectively. The severe AEs were reported but not common, which included severe infusion reactions, pneumonia, bacteremia, tuberculosis, melanoma, and lymphoma.

Conclusion

Anti-TNF-α agents treatment has high effectiveness including efficient inflammation remission, satisfactory VA improvement, obvious CMT reduction, and significant CS-sparing effects. Although some drug-related AEs were reported, the incidence of severe AEs was acceptable. Anti-TNF-α agents treatment is a promising option for controlling BD-associated uveitis.

Comparative analysis of inflammatory response in the BALB/c and C57BL/6 mouse strains in an endotoxin-induced uveitis model

Uveitis is an inflammatory disease associated with diverse systemic and autoimmune diseases, defined as the inflammation of any given segment of the uveal tract, uveitis contributes with 5-20% cases of blindness in the USA/Europe and >25% of cases in third-world countries. To understand its pathogenic mechanisms, BALB/c and C57BL/6 mice were induced to develop the condition by a single intraperitoneal injection of E. coli lipopolysaccharide, the aim of the present work is to determine leukocyte infiltration in an endotoxin-induced uveitis (EIU) in two non-related mouse strains. Histopathological findings and clinical analysis were conducted 24 and 48 h postinjection. Both strains presented conventional clinical signs of uveitis 24 h post LPS injection and the highest inflammatory leukocyte infiltration in the uveal tract was found in the BALB/c mouse strain. This article will give an insight on the difference of the inflammatory response in the EIU model in two different mouse strains and the relationship between the pathologic response.

Determination of a No Observable Effect Level for Endotoxin Following a Single Intravitreal Administration to Cynomolgus Monkeys

Purpose: To characterize the inflammatory response and determine the no-observable-effect level (NOEL) in cynomolgus monkey eyes after intravitreal (ITV) injection of endotoxin. Methods: The inflammatory response to endotoxin was assessed in a single-dose study in monkeys at doses of 0.01 to 0.51 endotoxin units (EU)/eye. Tolerability was assessed by clinical ophthalmic examinations, intraocular pressure measurements, fundus color photography, optical coherence tomography, and anatomic pathology. Results: ITV injection of endotoxin at ≥0.04 EU/eye resulted in a dose-related anterior segment inflammatory response. No aqueous flare or cell was noted in the 0.01 EU/eye dose group. A more delayed posterior segment response characterized by vitreous cell was observed beginning on day 5, peaking on day 15, and decreasing in some groups. Microscopic findings of mononuclear cell infiltrates in the vitreous were observed in eyes given ≥0.21 EU/eye. Conclusion: The NOEL for ITV endotoxin in cynomolgus monkeys was 0.01 EU/eye, suggesting that this species is as sensitive as rabbits to the effects of endotoxin. The vitreous cavity also appears more sensitive to endotoxin than the anterior segment/aqueous chamber. Overall, the magnitude of the inflammatory response at ≥0.04 EU/eye suggests that dose-response curve in monkeys is steeper than in rabbits. These data highlight the importance of assessing endotoxin level in ITV formulations, as levels as low as 0.04 EU/eye may confound the safety evaluations of ITV therapeutics in cynomolgus monkeys.

Psoriatic Eye Manifestations

The relationship between the eye and psoriasis has been recognized for decades, but the precise eye manifestations in patients with psoriasis and psoriatic arthritis are only recently coming to light. Psoriatic eye findings may include conjunctivitis, dry eye, episcleritis, and uveitis, all of which may precede articular changes. Uveitis, seen in 7% to 25% of psoriatic arthritis patients, may be recognized by the presence of conjunctival injection, photophobia, pain, lid swelling, or otherwise unexplained visual changes. Early recognition is paramount because its natural course may lead to vision loss. Immunopathogenesis has shown evidence for T-helper cell (Th) type 1 (Th1) and Th17 involvement in the pathogenesis of uveitis according to the murine experimental autoimmune uveitis model. Corticosteroids are the primary treatment modality; however, increasing emphasis has been placed on immunomodulators and biologics for more intractable cases. Referral to an ophthalmologist is essential for definitive diagnosis and treatment.

Immune Relevant Models for Ocular Inflammatory Diseases

Ocular inflammatory diseases, such as dry eye and uveitis, are common, painful, difficult to treat, and may result in vision loss or blindness. Ocular side effects from the use of antiinflammatory drugs (such as corticosteroids or nonsteroidal antiinflammatories) to treat ocular inflammation have prompted development of more specific and safer medications to treat inflammatory and immune-mediated diseases of the eye. To assess the efficacy and safety of these new therapeutics, appropriate immune-relevant animal models of ocular inflammation are needed. Both induced and naturally-occurring models have been described, but the most valuable for translating treatments to the human eye are the animal models of spontaneous, immunologic ocular disease, such as those with dry eye or uveitis. The purpose of this review is to describe common immune-relevant models of dry eye and uveitis with an overview of the immuno-pathogenesis of each disease and reported evaluation of models from small to large animals. We will also review a selected group of naturally-occurring large animal models, equine uveitis and canine dry eye, that have promise to translate into a better understanding and treatment of clinical immune-relevant ocular disease in man.

The Hierarchy of Proinflammatory Cytokines in Ocular Inflammation

PURPOSE

The concept of tissue-dependent cytokine hierarchy has been demonstrated in a number of diseases, but it has not been investigated in ophthalmic diseases. Here, we evaluated the functional hierarchy of interleukin-1β (IL-1β), IL-6, IL-17A, and tumor necrosis factor (TNF) in the induction of ocular inflammation.

MATERIALS AND METHODS

We delivered adeno-associated virus (AAV) vectors expressing IL-1β, IL-6, IL-17A, or TNF intravitreally in naïve C57/BL6 mice and compared and contrasted the inflammatory effects in the eye 5 weeks after AAV-mediated gene transfer. We also used an in vitro human system to test the effect of cytokines on barrier function.

RESULTS

We found that IL-1β had the highest ability to initiate ocular inflammation. The continuous overexpression of IL-1β resulted in a significant upregulation of additional proinflammatory mediators in the eye. Using scanning laser ophthalmoscope and optical coherence tomography imaging techniques, we showed that a low dose of AAVIL-1β was sufficient and was as pathogenic as a high dose of TNF in inducing vascular leakage, retinal degeneration, and cellular infiltration. Furthermore, only a marginal increase in IL-1β was enough to cause cellular infiltration, thus confirming the highly pathogenic nature of IL-1β in the eye. Contrary to our expectation, IL-6 or IL-17A had minimal or no effect in the eye. To examine the clinical relevance of our findings, we used an impedance assay to show that IL-1β alone or TNF alone was able to cause primary human retinal endothelial cell barrier dysfunction in vitro. Again, IL-6 alone or IL-17A alone had no effect on barrier function; however, in the presence of IL-1β or TNF, IL-17A but not IL-6 may provide additive proinflammatory effects.

CONCLUSIONS

Our studies demonstrate the existence of a functional hierarchy of proinflammatory cytokines in the eye, and we show that IL-1β is the most pathogenic when it is continuously expressed in the eye.

Infliximab exerts a dose-dependent effect on retinal safety in the albino rabbit

PURPOSE

To assess the retinal toxicity of an intravitreal injection of infliximab, a monoclonal antibody to tumor necrosis factor α, in a rabbit model.

MATERIALS AND METHODS

Two groups of adult albino rabbits (n = 5) received intravitreal injections of infliximab (0.1 ml) in the study eye and balanced salt solution (BSS, 0.1 ml) in the control eye at baseline. Group 1 was administered with 1.5 mg/0.1 ml, and group 2 was injected with 7.5 mg/0.1 ml of infliximab solution. Electroretinography (ERG) was performed at baseline and at 1, 7, 30, and 45 days after the injection. Visual evoked potentials (VEPs) were recorded at 7 and 45 days after the injection. After the last electrophysiological assessment, the rabbits were euthanized and retinal histopathology and immunhistochemistry for glial fibrillary acidic protein (GFAP) were performed.

RESULTS

ERG responses demonstrated no significant deficit in retinal function in eyes injected with infliximab. Mean dark-adapted a-wave and b-wave maximal amplitude and semi-saturation constant values at baseline and throughout the 45 days of follow-up after the injection indicated no remarkable difference in outer retinal function between the control and experimental eyes. VEP responses were similar at each time point (7 and 45 days). No difference was seen in retinal histopathology and immunocytochemistry sections in eyes receiving the 1.5 mg/0.1 ml dose compared to the control eyes. However, increased GFAP labeling in retinal Müller cells was detected in rabbit eyes treated with the 7.5 mg/0.1 ml dose.

CONCLUSIONS

Intravitreal injection of 1.5 mg/0.1 ml infliximab dose has no toxic effect on the integrity (functional or structural) of the retina in rabbits. A higher dose of 7.5 mg/0.1 ml may be slightly toxic as suggested by positive Müller cell GFAP expression. Additional studies of retinal toxicity at higher doses and after multiple injections are needed to establish the retinal safety of intravitreal infliximab therapy in humans.

Vitreous humor in the pathologic scope: insights from proteomic approaches

The vitreous humor (VH) is the largest component of the eye. It is a colorless, gelatinous, highly hydrated matrix that fills the posterior segment of the eye between the lens and retina in vertebrates. In VH, a diversity of proteins that can influence retinal physiology is present, including growth factors, hormones, proteins with transporter activity, and enzymes. More importantly, the protein composition of VH has been described as being altered in a number of disease states. Therefore, attempts aiming at establishing a map of VH proteins and detecting putative biomarkers for ocular illness or protein fluctuations with putative physiologic significance were conducted over the last two decades, using proteomic approaches. Proteomic strategies often involve gel-based or LC techniques as sample fractioning approaches, subsequently coupled with MS procedures. This set of studies resulted in the proteomic characterization of a range of ocular disease samples, with particular incidence on diabetic retinopathy. However, practical therapeutic applications arising from these studies are scarce at the moment. A pertinent example of therapeutic targets arising from VH proteomics has emerged concerning vasoproliferative factors present in the vitreous, which should be involved in neovascularization and subsequent fibrovascular proliferation of the retina, in ocular disease context. Therefore, this review attempts to sum up the information acquired from the proteomic approaches to ocular disease conducted in VH samples, highlighting its clinical potential for disclosing ocular disease mechanisms and engendering pharmacological therapeutic treatments.

Off-label uses of anti-TNF therapy in three frequent disorders: Behçet's disease, sarcoidosis, and noninfectious uveitis

Tumoral necrosis factor α plays a central role in both the inflammatory response and that of the immune system. Thus, its blockade with the so-called anti-TNF agents (infliximab, etanercept, adalimumab, certolizumab pegol, and golimumab) has turned into the most important tool in the management of a variety of disorders, such as rheumatoid arthritis, spondyloarthropatties, inflammatory bowel disease, and psoriasis. Nonetheless, theoretically, some other autoimmune disorders may benefit from these agents. Our aim is to review these off-label uses of anti-TNF blockers in three common conditions: Behçet's disease, sarcoidosis, and noninfectious uveitis. Due to the insufficient number of adequate clinical trials and consequently to their lower prevalence compared to other immune disorders, this review is mainly based on case reports and case series.

Rabbit intraocular reactivity to endotoxin measured by slit-lamp biomicroscopy and laser flare photometry

OBJECTIVE

To evaluate the ocular reactivity of the rabbit to an intracameral injection of a dispersive ophthalmic viscosurgical device (OVD) containing various levels of bacterial endotoxin using slit-lamp biomicroscopy and laser flare photometry.

DESIGN

Experimental, randomized, masked animal study.

PARTICIPANTS

Thirty Dutch-Belted rabbits.

METHODS

The rabbits were randomized into 6 groups to receive 0.05 ml of a hydroxypropyl methylcellulose-based dispersive OVD to which had been added one of 5 different doses of bacterial endotoxin ranging from 0.02 to 1.4 endotoxin units (EUs) or a vehicle control to both eyes. The eyes were evaluated for anterior segment inflammation at baseline and 3, 6, 9, 24, 48, and 72 hours after injection using slit-lamp biomicroscopy and laser flare photometry.

MAIN OUTCOME MEASURES

Corneal clarity and anterior chamber (AC) inflammation.

RESULTS

All the corneas remained clear throughout the study. Anterior chamber cells were seen at 6, 9, and 24 hours in 60% to 100% of the eyes intracamerally injected with endotoxin-containing OVD, and the response declined rapidly after 24 hours. A dose-response effect was seen between the concentration of endotoxin and the AC cell response. The aqueous flare response in eyes injected with the 2 highest doses of endotoxin was significantly greater (P<0.05) than that of controls. The amounts of fibrin observed in the AC were random, with no apparent dose-response effect seen. The flare values as obtained by laser flare photometry were consistent with the slit-lamp biomicroscopy flare findings up to grade 3+. However, the increase in laser flare value seemed to level off in eyes with more than 3+ flare. Neither measure of flare correlated with endotoxin level.

CONCLUSIONS

Among the parameters evaluated in this study, the AC cell response, evaluated by slit-lamp biomicroscopy and graded using a standard grading system, was found to be the most reliable indicator of the amount of endotoxin in the dispersive OVD. The use of laser flare photometry alone does not seem to be useful in detecting an ocular response to endotoxin contamination in OVDs.

Role of intravitreal inflammatory cytokines and angiogenic factors in proliferative diabetic retinopathy

OBJECTIVE

Inflammatory reaction has been shown to involve the progress of type 2 (non-insulin-dependent) diabetes. We, therefore, examined the effects of inflammatory cytokines and angiogenic factors in the pathogenesis of proliferative diabetic retinopathy (PDR) in type 2 diabetes.

PATIENTS AND METHODS

Vitreous fluid samples were obtained by vitrectomy from 62 eyes of PDR patients with type 2 diabetes and from 20 eyes of age-matched non-diabetic patients. The concentrations of interleukin 1 beta (IL1B), IL6, IL8, IL10, chemokine (C-C motif) ligand 2 (CCL2), endothelin 1 (EDN1), vascular endothelial growth factor (VEGF), and tumor necrosis factor (TNF) in the vitreous samples were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The concentrations of LI1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF in the vitreous samples were considerably higher in PDR patients in comparison with the controls. However, the level of IL10 in PDR patients was similar to that obtained in the controls. Analysis of the correlations of the studied factors revealed the correlation of VEGF and IL6, VEGF and EDN1, IL8 and CCL2, and EDN1 and TNF in PDR patients. In addition, a significant positive correlation was observed between vitreous TNF as well as EDN1 and serum HbA(1)c levels in PDR patients.

CONCLUSIONS

The inflammatory cytokines and angiogenic factors IL1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF are increased in the vitreous of PDR patients without an increase in IL-10. These results add support to the role of inflammatory cytokines and angiogenic factors in the genesis of PDR. Understanding the implication of these cytokines may provide diagnostic tools and therapeutic targets for treatment and prevention of PDR.

Adalimumab (humira™) in ophthalmology: a review of the literature

Tumor Necrosis Factor alpha (TNF-α) is a pleiotropic cytokine which plays a primary role in the induction of inflammation in autoimmune diseases. The newest anti-TNF-α agent is adalimumab (Humira, Abbott Pharmaceutical Inc.), a human-derived antibody. This review summarizes the characteristics of adalimumab, highlighting its clinical use in systemic and ocular inflammatory disorders, and the possible therapeutic strategies. Adalimumab has been successfully used for the treatment of rheumatoid arthritis, ankylosing spondylitis, and psoriasis arthritis. More recently, adalimumab has shown promising qualities in controlling intraocular inflammations, even though this has been used prevalently as a rescue therapy for unresponsive cases. This biologic agent was also used in pediatric cases, showing a good safety and efficacy profile. Albeit no direct comparison with other biologics has been done, and adalimumab seems to be equivalent to the other anti-TNF-α, the switching to adalimumab can offer a better uveitic control. Adalimumab is a promising drug for the treatment of uveitis, even though further studies are needed on its application as a primary therapy in uveitis.

Intravitreal infliximab in experimental endotoxin-induced uveitis

PURPOSE

Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the pathogenesis of ocular inflammation and the level of TNF-alpha is increased in ocular fluids of patients with uveitis. Intravenous infliximab, a monoclonal antibody against TNF-alpha, has been used for the treatment of uveitis with promising preliminary results. The aim of this study was to evaluate the effect of intravitreal injection of infliximab on experimental uveitis.

METHODS

Thirty-three white New Zealand rabbits were divided randomly into three groups. Group 1 (n=5) received intravitreal injection of 1 mg/0.1 cc infliximab plus 0.1 cc normal saline, group 2 (n=14) received intravitreal injection of 2 microg Salmonella typhimurium endotoxin plus 1 mg/0.1 cc infliximab, and group 3 (n=14) animals received intravitreal endotoxin 2 microg/0.1 cc plus normal saline 0.1 cc. Inflammation was evaluated by clinical examinations on days 1, 3, 5, and 7 after the injections; measuring the protein concentration and inflammatory cell content of the aqueous humor; and histopathologic examination.

RESULTS

No inflammation occurred in group 1 animals. There was a statistically significant difference between group 2 and 3 animals with regard to clinical examination on the third, fifth, and seventh postinjection days. The differences between groups 2 and 3 were significant with regard to aqueous cell counts and protein content at day 7 (p=0.02 and p=0.001, respectively). Histopathologic examination results showed less inflammation in group 2 animals compared to group 3 animals (p=0.009).

CONCLUSIONS

The results provide evidence that intravitreal injection of infliximab suppresses ocular inflammation in a rabbit model of severe endotoxin-induced uveitis.

Tumor necrosis factor antagonists: preliminary evidence for an emerging approach in the treatment of ocular inflammation

The anti-tumor necrosis factor (TNF) monoclonal antibody infliximab and the soluble TNF receptor etanercept inhibit the pleiotropic actions of TNF and are widely used for the treatment of rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), spondyloarthropathies (SpA), Crohn's disease, and psoriasis with an acceptable safety profile. A pathogenetic role of TNF in ocular inflammatory conditions has recently emerged from small trials reporting preliminary results on the efficacy of these agents in patients with noninfectious uveitis, regardless of the origin of the disease. The authors review the published experience, derived mostly from investigator-sponsored trials and uncontrolled case series, on the use of TNF antagonists in approximately 280 patients with various ocular conditions who were inadequately controlled on currently available therapy. These reports suggest that TNF antagonists, mainly infliximab, which may have better efficacy than etanercept, are useful in the treatment of ocular inflammation associated with Adamantiades-Behçet's disease, RA, JIA, SpA, Crohn's, sarcoidosis, and Graves' disease ophthalmopathy. Infliximab was also beneficial in small numbers of patients with idiopathic uveitis or scleritis, birdshot retinochoroiditis, uveitic and diabetic cystoid macular edema, and age-related macular degeneration. The currently available data are nonrandomized and thus preliminary, providing the foundation and justification for randomized trials to assess efficacy and safety. Until such results are available, knowledge regarding the use of anti-TNF regimens in ophthalmology is incomplete. However, the preliminary evidence points to a growing optimism for targeting TNF in patients with ocular inflammation.

Intravitreal bevacizumab for treatment of uveitic macular edema

PURPOSE

To evaluate the short-term safety and efficacy of intravitreal bevacizumab for the treatment of cystoid macular edema (CME) secondary to uveitis.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Thirteen patients undergoing treatment for recalcitrant uveitic macular edema at one referral center.

METHODS

Charts of patients who received one 2.5-mg intravitreal injection of bevacizumab in one eye were reviewed for clinical information including best-corrected Snellen visual acuity (VA), examination findings, optical coherence tomography (OCT) results, and fluorescein angiography results. Kaplan-Meier survival analysis was used to calculate probability success rates. The statistical significance of change in mean retinal thickness and VA was assessed using repeated-measures analysis of variance.

MAIN OUTCOME MEASURES

Assessments of changes in best-corrected Snellen VA and OCT retinal thickness were made.

RESULTS

Six (46.15%) patients had a decrease in foveal thickness at the end of the follow-up, whereas 5 (38.4%) patients had an improvement of VA by > or =2 lines 84 days or more after the injection. Mean retinal thickness showed a significant decrease over the follow-up (P<0.02). The change in mean logarithm of the minimum angle of resolution VA over the follow-up was not significant (P>0.05). Survival analysis showed that the probability of any improvement in VA increased progressively starting at 6 weeks and reached 81% at 14 weeks. No significant ocular or systemic adverse effects were observed.

CONCLUSIONS

These results suggest that a single intravitreal injection of bevacizumab is well tolerated and is associated with short-term improvement in VA and decreased OCT retinal thickness in a considerable proportion of patients with uveitic CME resistant to conventional therapy. Further evaluation of intravitreal bevacizumab for uveitic CME in controlled randomized studies is warranted.

Adalimumab in the therapy of uveitis in childhood

PURPOSE

Chronic anterior uveitis in children often takes a serious course. Despite various immunosuppressive drugs some children do not respond sufficiently and there is a high risk of them becoming seriously disabled. Anti-TNF alpha therapy has been shown by our group and others to be mostly ineffective (Etanercept) or partly effective (Infliximab) with the risk of anaphylactic reactions. Here we report on 18 young patients treated with Adalimumab (Humira), a complete humanised anti-TNF alpha antibody.

METHODS

We retrospectively analysed 18 patients, who were treated with Adalimumab (20-40 mg, every 2 weeks, when ineffective every week); 17 had juvenile idiopathic arthritis, one was without detectable underlying disease. The age at onset of arthritis varied from 0.5-15 years and for uveitis from 2-19 years. Patients were included when the previous anti-inflammatory therapy had been ineffective. It consisted of systemic steroids (n = 18), Cyclosporin A (n = 18), Methotrexate (n = 18), Azathioprine (n = 12), Mycophenolate mofetil (n = 4), Cyclophosphamide (n = 2), Leflunomide (n = 3), Etanercept (n = 8) and Infliximab (n = 5). The grading for uveitis was: (a) effective: no relapse or more than two relapses less than before treatment, (b) mild: one relapse less than before treatment, (c) no response: no change in relapse rate and (d) worsening: more relapses under treatment than before. The grading for arthritis (depending on the clinical findings), using three out of six parameters of the ACR PED Criteria, was: effective, mild, no response, worsening.

RESULTS

For arthritis (n = 16) the response to Adalimumab was effective in 10 of 16 patients, mild in three patients, three did not respond. For uveitis (n = 18) Adalimumab was effective in 16, mild in one child, and one patient did not show any effect. After a very good response initially a shorter application time had to be used to maintain the good anti-inflammatory effect in one child. Additional immunosuppressive treatment was used in seven of the effectively treated children. Due to elevation of liver enzymes in one patient, who also took MTX, Adalimumab had to be discontinued. No anaphylactic reactions or increased frequency of infections since start of Adalimumab treatment was reported.

CONCLUSIONS

For our group of children with long lasting disease our results show that Adalimumab was effective or mildly effective against the arthritis in 81%, but in uveitis in 88%. While these results regarding arthritis are comparable with other TNF-alpha blocking drugs (Etanercept), Adalimumab seems to be much more effective against uveitis than Etanercept. Anaphylactic reactions, found in a previous study from our group after Infliximab treatment, were not seen with Adalimumab. The necessary dosage and the treatment period, which probably have to be defined individually for each patient, remain unclear.

Protein kinase C-zeta mediates retinal degeneration in response to TNF

Tumor necrosis factor-alpha (TNF) has been implicated in retinal ganglion cells (RGC) degeneration in glaucoma. Atypical protein kinase C (PKC) zeta is involved in cell protection against various stresses. The aim of this study was to investigate the potential proapoptotic effects of intravitreal injections of TNF with or without PKCzeta specific inhibitor on the rat retina. TNF was injected in the vitreous of rat eyes alone or in combination with specific PKCzeta inhibitor. PKCzeta and NF-kappaB were studied by immunohistochemistry and western-blotting analysis on retina, and apoptosis quantified by the TUNEL assay. While low basal PKCzeta was observed in the control eyes, TNF induced intense expression of PKCzeta mostly in bipolar cells processes. PKCzeta staining became nuclear when TNF was coinjected with PKCzeta inhibitor. TNF alone did not induce apoptosis in the retina. Coinjection of the PKCzeta-specific inhibitor and TNF, however, induced apoptosis in the inner nuclear and ganglion cell layers. The PKCzeta-specific inhibitor unmasks retinal cells to TNF cytotoxicity showing a link between the proapoptotic effects of TNF and the antiapoptotic PKCzeta signaling pathway.

Serum Cytokine Receptor Levels in Noninfectious Uveitis

PURPOSE

Understanding of the role of cytokines in uveitis may provide new clues to its treatment. Therefore, the purpose of our study was to evaluate systemic cytokine receptor expression in patients with noninfectious uveitis.

METHOD

Serum concentrations of soluble interleukin-2 receptor alpha (IL-2 s Ralpha) and soluble tumor necrosis factor receptor-1 (sTNF-R1) were measured in patients with intermediate uveitis (n = 26), posterior uveitis (n = 23) and healthy controls (n = 12) using ELISA. All patients were identified in a consecutive series of 996 uveitis patients who had been diagnosed between 1998 and 2002 and classified according to the recommendations of the International Uveitis Study Group. Inclusion criteria were idiopathic, active intraocular inflammation, uveitis as a primary process and no systemic anti-inflammatory treatment at the time of blood sampling. None of the patients had an underlying systemic disease.

RESULTS

Serum concentrations of IL-2 s Ralpha were significantly increased in patients with posterior (p < 0.005) and intermediate uveitis (p < 0.005) as compared to healthy controls. Similarly, concentrations of sTNF-R1 appeared to be increased in posterior (p < 0.005) and intermediate (p < 0.005) uveitis patients when compared to controls.

CONCLUSIONS

Our results may suggest that patients with noninfectious uveitis express systemic cytokine receptors such as TNF-R1 and IL-2 Ralpha, which may have an important role in the immune response of the eye and may lead to new immunomodulatory approaches.

Long-term treatment of refractory posterior uveitis with anti-TNFα (infliximab)

PURPOSE

To evaluate the long-term efficacy and safety of infliximab as treatment for noninfectious posterior uveitis.

METHODS

An open-label clinical trial including seven patients (12 eyes) with posterior uveitis refractory to conventional treatment regimens with corticosteroids and at least one immunosuppressive agent. Three intravenous doses of 5 mg/kg of infliximab were administered at weeks 0, 2, and 6. Infliximab infusion was repeated in patients undergoing a relapse of uveitis after initial remission. Improvement was defined as amelioration of visual acuity or disappearance of retinal exudates and/or haemorrhages, decreased macular oedema and/or vitreous opacities. All patients were followed up for at least 36 months.

RESULTS

Six of the seven patients (five diagnosed with Behçet's disease and one diagnosed with sarcoidosis) showed a significant improvement after the first infliximab dose. Only in one patient diagnosed with chronic idiopathic multifocal choroiditis did the drug have no effect, and this patient was withdrawn from the study. At the end of follow-up, one eye had lost one line of vision and three eyes showed improved vision. All eyes had improved in terms of signs of inflammation. No adverse effects of treatment were observed.

CONCLUSION

Infliximab is efficient and safe for the long-term management of refractory posterior uveitis, especially in patients with predominant retinal vasculitis and vitritis.

Nitration of manganese superoxide dismutase during ocular inflammation

Reactive nitrogen species, in particular, peroxynitrite (ONOO(-)) have been proposed to play an important role in the pathogenesis of endotoxin-induced uveitis (EIU). Tyrosine nitration by ONOO(-) has been shown in other model systems to inhibit the activity of the superoxide anion quenching enyzme, manganese superoxide dismutase (MnSOD), perhaps contributing to progression of disease. In this study, it is confirmed through immunoanalysis that nitrated proteins are produced during EIU, and furthermore, that MnSOD is a target of nitration during the inflammatory response. In addition, through microsequencing analyses, nitrated albumin--apparent in both control and EIU eyes--was identified. Positive immunostaining of nitrated proteins was seen in the ciliary epithelium, inflammatory cells, and protein exudate of eyes from rats injected with endotoxin. Incubation of nitrotyrosine immunoprecipitates from the iris and ciliary body (ICB) with a polyclonal antibody against MnSOD revealed that nitrated MnSOD was present only in the ICB of EIU rats. When the total activity of the enzyme was examined, it was observed that despite the presence of nitrated MnSOD, activity was increased relative to control. Analysis of MnSOD mRNA and protein from the ICB of both groups demonstrated an increase in mRNA expression and consequently a three- to five-fold increase in MnSOD protein in EIU rats as compared to control rats. Further examination of MnSOD protein expression through immunohistochemistry noted enhanced immunostaining in the ciliary epithelium of eyes of EIU rats. Additional investigation of a 70 kDa band apparent in nitrotyrosine immunoprecipitates from the ICB of control and EIU rats revealed that the plasma protein albumin is nitrated as well. This protein is present as a result of the breakdown of the blood-aqueous barrier during inflammation. In summary, two endogenous nitration targets, albumin and MnSOD, were identified. Nitrated MnSOD appears to be specifically targeted to the ICB during inflammation, underscoring the importance of the interface in EIU. Furthermore, the expression and activity of the enzyme is increased in the ICB during EIU, perhaps regulating reactive nitrogen species produced within the cells. This study implicates ONOO(-) in the pathogenesis of EIU and imparts the putative role MnSOD plays in disease resolution.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

Role of tumor necrosis factor receptors TNFR-I (P55) and TNFR-II (P75) in corneal transplantation

BACKGROUND

To determine the role of tumor necrosis factor-alpha (TNF-alpha) receptor (TNFR) function in corneal allograft immunology.

METHODS

Animals with gene-targeted deficiency in TNFR-I (p55-/-), TNFR-II (p75-/-), or combined TNFR-I/TNFR-II deficiency (p55-/-p75-/-) and their wild-type controls were used as recipients of fully-mismatched (BALB/c; n=88) or multiple minor alloantigen-mismatched (BALB.b; n=62) orthotopic corneal transplants to determine the effect of selective deficiency in one or both TNF-alpha receptors on corneal allograft survival. Grafted recipients were followed biomicroscopically for signs of rejection, and survival data were analyzed by the Kaplan-Meier method.

RESULTS

There was no discernible difference in survival of fully-mismatched BALB/c corneal grafts in p55-/- (n=12; P=0.76) or in double-knockout p55-/-p75-/- (n=13; P=0.41) as compared with wild-type C57BL/6.129 hosts. However, the survival of BALB/c allografts was lower in p75-/- (n=10; median survival 20 days) as compared with control C57BL/6 (n=30; median survival 30 days) hosts (P=0.02). In contrast, there was no discernible effect in survival of minor alloantigen-disparate BALB.b corneal grafts in p75-/- (n=13; P=0.95) or in combined p55-/-p75-/-(n=10; P=0.17) hosts as compared with C57BL/6 (n=9) and C57BL/6.129 (n=10) wild-type controls, respectively. However, there was a profound enhancement in the survival of BALB.b allografts in p55-/- recipients (n= 10; median survival 35 days) as compared to wild-type C57BL/6.129 (n=10; median survival 25 days) controls (P<0.01).

CONCLUSIONS

Our data suggest that the two TNF-alpha receptors largely play discrete roles in mediating rejection of murine corneal allografts. TNFR-I (p55) function seems to be integral to the rejection of minor-disparate grafts, and its selective suppression leads to enhancement of allograft survival. In contrast, TNFR-II (p75) function appears to be associated with enhanced survival of major histocompatibility complex-disparate allografts. The combined deletion of TNFR functionality in p55-/-p75-/- confers no net advantage or disadvantage to major histocompatibility complex or minor alloantigen-disparate grafts.

Involvement of TNF alpha, IL-1 beta and IL-1 receptor antagonist in LPS-induced rabbit uveitis

The objective of the study was to investigate involvement of TNF alpha, IL-1 beta and IL-1 receptor antagonist (IL-1Ra) in lipopolysaccharide (LPS)-induced uveitis. Intravitreal injection of LPS (100 ng) to rabbits induced a massive leukocyte infiltration and protein leakage into the aqueous humor. Aqueous leukocyte counts and protein levels reached a peak 24 hr after this injection. The peak concentrations of aqueous TNF alpha (230 +/- 37 pg ml-1, at 9 hr) and IL-1 beta (185 +/- 80 pg ml-1, at 18 hr) preceded peak levels of aqueous leukocyte counts and protein levels. In contrast, the levels of aqueous IL-1Ra peaked at 48 hr (12,239 +/- 1964 pg ml-1) and a fairly high concentration of IL-1Ra remained when the inflammatory reactions subsided. Immunohistochemistry and leukocyte-depletion studies showed that infiltrating leukocytes were the major cellular sources of aqueous TNF alpha, IL-1 beta and IL-1Ra. Intravitreal injection of homologous TNF alpha (0.1-1.5 micrograms) or IL-1 beta (0.5-5 ng) reproduced a rapid leukocyte infiltration and protein leakage. Administration of anti-TNF alpha mAb (10 micrograms) suppressed the number of LPS-induced infiltrating neutrophils by 50%, mononuclear cells by 58%, and protein leakage by 42%. Administration of rabbit IL-1Ra (10 micrograms) also suppressed neutrophil influx by 78%, however, neither mononuclear cell influx nor protein leakage was inhibited by rabbit IL-1Ra. Co-administration of the two inhibitors enhanced inhibition of neutrophil infiltration to 88%, and protein leakage to 64%. We conclude that TNF alpha and IL-1 beta are the principal mediators of LPS-induced uveitis. Our observations also suggest that endogenous IL-1Ra may down-regulate inflammatory reactions.

Human T-cell lymphotropic virus type 1 can infect primary rat retinal glial cells and induce gene expression of inflammatory cytokines

PURPOSE

To examine whether or not retinal glial cells can be infected by human T-cell lymphotropic virus type 1 (HTLV-1) and test the possibility that HTLV-1-infected retinal glial cells are involved in the pathogenesis of HTLV-1 uveitis (HU).

METHODS

We tested infection of HTLV-1 by a standard coculturing method using WKAH rat retinal glial cells and irradiated MT-2, a human T cell line that produces HTLV-1. Infection was confirmed by detecting the integrated HTLV-1 provirus, using polymerase chain reaction (PCR), viral gene expression, using reverse transcriptase-PCR (RT-PCR) and HTLV-1 p19 ELISA, and by identifying the HTLV-1-infected glial cells by immunofluorescence cytochemistry and in situ hybridization. Changes in cytokine gene expression were studied by RT-PCR.

RESULTS

Using a semiquantitative PCR of HTLV-1 provirus sequence, we found that 2.6% of the retinal glial cells were infected at 3 days after infection, followed by a gradual decrease in the percentage with an extended period of culture up to 4 weeks. This time course of infection was also verified by RT-PCR and ELISA studies that detect viral mRNA expression and protein production, respectively. Expression of HTLV-1 gag protein and tax mRNA was detected in a part of glial cells by indirect immunofluorescence cytochemistry and in situ hybridization, respectively. RT-PCR analysis of cytokine gene expression revealed that gene expression of IL-6, CINC-1 (Gro, KC), and TNF-alpha were induced in these cells, with a peak at 3 weeks after infection.

CONCLUSION

These results provided supportive evidence for the theory that the infection of retinal glial cells by HTLV-1 and subsequent production of inflammatory cytokines could be one contributing factor for the development of the unique clinical features of HU. A better understanding of the specific roles of the inflammatory cytokines in the pathogenesis of HU would be beneficial in the treatment and control of this disease.

Nitric oxide in the eye: multifaceted roles and diverse outcomes

Recent works have highlighted the role of nitric oxide in a wide array of disease entities, including septic shock, hypertension, cerebral ischemia, and chronic degenerative diseases of the nervous system. The functions of nitric oxide appear very diverse, having actions on vascular tone, neurotransmission, immune cytotoxicity, and many others. Nitric oxide is an important mediator of homeostatic processes in the eye, such as regulation of aqueous humor dynamics, retinal neurotransmission and phototransduction. Changes in its generation or actions could contribute to pathological states such as inflammatory diseases (uveitis, retinitis) or degenerative diseases (glaucoma, retinal degeneration). Localization in the eye and biochemical characteristics of nitric oxide will be reviewed. A better understanding of the nitric oxide pathway will be the key to the development of new approaches to the management and treatment of various ocular diseases.

Intravitreal transforming growth factor-beta 2 decreases cellular infiltration in endotoxin-induced ocular inflammation in rabbits

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine which has been identified in normal and inflamed ocular fluids, may play a role in the evolution of inflammatory ocular lesions. In this study we utilized a rabbit model of LPS-induced uveitis to determine if exogenous TGF-beta 2 could alter its course. Recombinant TGF-beta 2 (1-2000 ng), LPS (10 or 20 ng), or TGF-beta 2 (100 ng) plus LPS (10 ng) were injected intravitreally in one eye of a New Zealand white rabbit and the contralateral eye served as a paired control which received an equal volume of vehicle. The uveitic response was assessed by biomicroscopic examination of the anterior uvea and analysis of protein and cells in the aqueous humor. Ocular tissues were processed for histologic, immunohistochemical and in situ hybridization analyses. Rabbits injected with doses of TGF-beta 2 > or = 500 ng developed a mild uveitic response, compared to LPS alone, accompanied by expression of IL-1 beta mRNA and protein in the anterior uvea. Interestingly, rabbits coinjected with LPS (10 ng) and a nonuveitic dose (100 ng) of TGF-beta 2 exhibited a similar increase in ocular vascular permeability, but a decrease in inflammatory cell infiltration into the anterior uvea and aqueous humor (1185 +/- 117 versus 2465 +/- 176; p < 0.05). No evidence of inflammation was observed in eyes injected with 100 ng TGF-beta 2 alone. Similar to other models of inflammation, TGF-beta may interrupt the cascade of events leading to ocular inflammation, thereby suggesting therapeutic potential.

Systemic anti-tumor necrosis factor antibody treatment exacerbates endotoxin-induced uveitis in the rat

Tumor necrosis factor is released in the circulation and aqueous humor during endotoxin-induced uveitis, and induces acute uveitis when injected intraocularly in rats. To elucidate the role of tumor necrosis factor in the development of endotoxin-induced uveitis we analysed the effect of neutralizing anti-tumor necrosis factor antibodies and of pentoxifylline, a drug that inhibits tumor necrosis factor synthesis. Lewis rats were treated with: (a) a single intracardial injection of polyclonal rabbit anti-murine tumor necrosis factor antiserum prior to foot pad injection of 200 micrograms lipopolysaccharide; (b) an intraperitoneal injection of 10 mg pentoxifylline 1 hr before, at the time of, and 3 hr after foot pad injection of lipopolysaccharide; or (c) an intravitreal injection of 20 to 500 micrograms pentoxifylline together with 1 microgram lipopolysaccharide. The ocular inflammation was examined by slit-lamp and evaluated for the presence of hyperemia, flare, miosis, infiltrating cells or hypopyon. Levels of tumor necrosis factor in serum and aqueous samples were determined using a bioassay. Systemic treatment with either anti-tumor necrosis factor antibodies or pentoxifylline resulted in a significant inhibition, 90 and 70% respectively, of serum tumor necrosis factor activity at 3 to 4 hr after lipopolysaccharide injection. Systemic pentoxifylline treatment had no influence on the severity of uveitis. Anti-tumor necrosis factor antibody treatment, in contrast, caused an exacerbation of endotoxin-induced uveitis at t = 20 hr; mean uveitis score 3.9 vs. 1.4 in controls; P < 0.01. Intraocular administration of pentoxifylline together with lipopolysaccharide also had an aggravating effect on uveitis, that was associated with increased levels of intraocular tumor necrosis factor. The results show that inhibition of serum tumor necrosis factor activity does not block the development of endotoxin-induced uveitis. In fact, anti-tumor necrosis factor antibody treatment exacerbates the intraocular inflammation. These findings suggest that tumor necrosis factor may have other than proinflammatory properties in this uveitis model.

Mediators of the ocular inflammatory response to interleukin-1 beta plus tumor necrosis factor-alpha

BACKGROUND

Intravitreal injection of marginally inflammatory doses of interleukin-1 beta and tumor necrosis factor-alpha (IL-1 beta/TNF alpha) has been shown to produce intraocular inflammation distinctly different from that induced by higher intravitreal doses of either IL-1 or TNF alpha. Since cyclooxygenase inhibitors and platelet-activating factor (PAF)-receptor antagonists can reduce IL-1- or TNF alpha-induced uveitis, the present investigation was undertaken to determine whether cyclooxygenase metabolites of arachidonic acid and PAF are important mediators of IL-1 beta/TNF alpha-induced uveitis.

METHODS

The cyclooxygenase inhibitor indomethacin and two structurally dissimilar PAF-receptor antagonists, SRI 63-441 and WEB 2086, were used to investigate the importance of cyclooxygenase metabolites and PAF in IL-1 beta/TNF alpha-induced uveitis.

RESULTS

Based upon the effectiveness of indomethacin, the anterior uveitis induced by IL-1 beta/TNF alpha could be divided into two phases; a primary phase dependent upon generation of cyclooxygenase metabolites (the first 24 h) and a secondary phase largely independent of cyclooxygenase metabolite production (24-48 h). Posterior uveitis was also apparent at 48 h and was reduced by indomethacin. SRI 63-441 reduced the anterior uveitis at 24 h and to a lesser extent at 48 h; it also reduced the posterior uveitis at 48 h. However, although WEB 2086 was as effective as SRI 63-441 in reducing PAF-induced platelet aggregation, ex vivo, it did not significantly reduce IL-1 beta/TNF alpha-induced uveitis.

CONCLUSIONS

Although the findings do not support an important role for PAF in TNF alpha/IL-1 beta-induced uveitis, it cannot be ruled out that more intensive treatment with a specific and long-acting PAF-receptor antagonist might yield more positive results.

Tumour necrosis factor-induced uveitis in the Lewis rat is associated with intraocular interleukin 6 production

Lewis rats were injected with recombinant murine tumour necrosis factor-alpha either intravitreally (0.08-50 ng) or intracardially (1 microgram). The intraocular inflammatory response induced by tumour necrosis factor was examined by slit-lamp and protein extravasation into aqueous humor was determined. The phenotype of the inflammatory cells in the eye was analysed by immunohistochemistry. In addition, the kinetics of intraocular interleukin 6 production were determined. At 24 hr after intravitreal injection, a significant clinical uveitis was observed only in rats injected with 50 ng of tumour necrosis factor, when compared to saline-treated controls (P < 0.05). Maximal clinical uveitis and blood-aqueous barrier breakdown were already present at 4 hr after tumour necrosis factor injection. The uveitis was characterized by a massive cellular infiltrate in the anterior segment, consisting predominantly of polymorphonuclear cells and macrophages/monocytes, and to a lesser extent of T lymphocytes. Intraocular interleukin 6 mRNA expression and elevated levels of interleukin 6 in aqueous humor were detected 1 hr after tumor necrosis factor injection, reached a maximum at 3 to 4 hr after injection, and had declined again at 2 hr. Although intracardial injection of 1 microgram of tumour necrosis factor in Lewis rats induced a rise of circulating interleukin 6, it did not produce uveitis. The results obtained with intravitreally injected tumour necrosis factor indicate that intraocular TNF may play a pivotal role in the induction of uveitis in the rat. The transient intraocular production of interleukin 6 early during tumour necrosis factor-induced uveitis suggests that this cytokine may participate in the response induced by tumour necrosis factor.

Inflammation induced changes in adenosine 3',5'-cyclic monophosphate production by ciliary epithelial cell bilayers

Despite extensive evidence implicating the cytokines interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF alpha) in the intraocular inflammatory response, little is known about their effects on signal transduction in anterior uveal tissue. Since these cytokines have been shown to alter the adenylyl cyclase system in nonocular tissues, we tested the hypothesis that IL-1 beta and TNF alpha affect the anterior uvea by altering production of the intracellular second messenger adenosine 3',5'-cyclic monophosphate (cAMP) in ciliary epithelial bilayers. This was accomplished by measuring the levels of cAMP in bilayers ex vivo, following intraocular inflammation induced by intravitreal injection of IL-1 beta, TNF alpha or bacterial endotoxin, and in vitro, following exposure to IL-1 beta, TNF alpha or bacterial endotoxin. Although cAMP production was enhanced in bilayers from IL-1 beta-, TNF alpha- or endotoxin-inflamed eyes, ex vivo, exposure of normal bilayers to IL-1 beta (15 U ml-1), TNF alpha (20 U ml-1), or a low concentration of endotoxin (0.01 microgram ml-1) for 4 hr, in vitro, had no effect on cAMP production. The inability of IL-1 beta, TNF alpha, or the low concentration of endotoxin to increase cAMP production by bilayers, in vitro, suggests that the enhanced cAMP production observed with inflamed bilayers, ex vivo, was not due to a direct action of these inflammatory agonists on the ciliary epithelial bilayer. Although direct exposure to cytokines or endotoxin did not change cAMP production, treatment with IL-1 beta, TNF alpha, or a higher concentration of endotoxin (1 microgram ml-1) did affect signal transduction mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel production of interleukin-1 receptor antagonist peptides in normal human cornea

Interleukin-1 receptor antagonist (IL-1ra) is an important modulator of IL-1 activity in a variety of tissues. IL-1ra is differentially produced by different cell types as a 22-26-kD secreted peptide (sIL-1ra) and/or a smaller 16- or 18-kD intracellular peptide (icIL-1ra). This study was undertaken to evaluate the production of IL-1ra in the human cornea. IL-1ra mRNA can be detected in early passage human corneal epithelial cells and corneal stromal fibroblasts and is significantly enhanced by IL-1. Corneal endothelial cells do not express IL-1ra mRNA. Immunohistochemical studies of cultured corneal cells and whole human cornea demonstrate IL-1ra protein production by both the epithelial and stromal cells but not the endothelial cells. Reverse transcriptase polymerase chain reaction, ELISA, and immunoprecipitation studies indicate that corneal epithelial cells are capable of producing both icIL-1ra and sIL-1ra forms of IL-1ra whereas the corneal stromal cells produce only icIL-1ra. In addition to the larger 18-kD icIL-1ra, both corneal epithelial and stromal cells are also capable of producing a smaller recently described 16-kD icIL-1ra. Thus, the differential production of IL-1ra in the human cornea is unique; whereas both epithelial and stromal cells produce icIL-1ra (type 1 and type 2), the epithelial cells appear to also produce sIL-1ra. It is proposed that these IL-1ra proteins may play an important role in regulating IL-1-induced corneal inflammation.

Ocular inflammatory effects of intravitreally injected interleukin-2

The primary, known physiologic effect of interleukin-2 (IL-2) is to act as a T lymphocyte growth factor. We investigated the potential contribution of IL-2 to intraocular inflammation by studying the inflammation resulting from the intravitreal injection of recombinant, human IL-2 in New Zealand white rabbits. Serial slit lamp observations indicated that 40 microgram of intravitreally injected IL-2 induced an anterior uveitis which was maximal 5 days after the injection. Inflammation was less marked but still significant with amounts of IL-2 as low as 400 ng. Direct examination of aqueous humor confirmed elevations of protein, prostaglandin E2, and mononuclear cells which correlated with the clinical observations. The kinetics of the response to intravitreal IL-2 distinguished it from the responses to other intravitreally injected cytokines such as interleukins 1, 6, or 8 as well as tumor necrosis factor. Intramuscular injection of cyclosporine A significantly reduced the protein extravasation associated with IL-2 injection, but cyclosporine had no effect on inflammation secondary to an intravitreal injection of interleukin-1. These observations implicate IL-2 as a potential contributor to uveitis. In addition, the studies with cyclosporine indicate the heterogeneity of inflammation such that pharmacologic agents which affect one cause of uveitis are not necessarily efficacious in another model.

Cellular response to intravitreal injection of endotoxin and xanthine oxidase in rabbits

In the present study, the ocular inflammatory response to intravitreally injected endotoxin and xanthine oxidase was studied and the cellular response of the anterior and posterior segments was contrasted. There was a clear dose response relationship to both compounds in aqueous humor protein concentration and aqueous and vitreous humor white cell number. Xanthine oxidase and low doses of endotoxin (0.25 and 1.0 ng) produce a mainly mononuclear response in the anterior segment. Higher doses of endotoxin (10 and 100 ng) produced a predominantly neutrophilic response. Cellular infiltration into the posterior segment differed qualitatively and quantitatively from the anterior segment in response to the same stimuli. Myeloperoxidase (MPO) activity (a marker for neutrophils) of the iris-ciliary body was increased only in those eyes with a large neutrophilic response and thus is not recommended for use as a definitive index of the ocular inflammatory response, but may be a useful adjunct for such studies.