Sphingosine 1-phosphate, a potential target in neovascular retinal disease

Neovascular ocular diseases (such as age-related macular degeneration, diabetic retinopathy and retinal vein occlusion) are characterised by common pathological processes that contribute to disease progression. These include angiogenesis, oedema, inflammation, cell death and fibrosis. Currently available therapies target the effects of vascular endothelial growth factor (VEGF), the main mediator of pathological angiogenesis. Unfortunately, VEGF blockers are expensive biological therapeutics that necessitate frequent intravitreal administration and are associated with multiple adverse effects. Thus, alternative treatment options associated with fewer side effects are required for disease management. This review introduces sphingosine 1-phosphate (S1P) as a potential pharmacological target for the treatment of neovascular ocular pathologies. S1P is a sphingolipid mediator that controls cellular growth, differentiation, survival and death. S1P actions are mediated by five G protein-coupled receptors (S1P_1-5 receptors) which are abundantly expressed in all retinal and subretinal structures. The action of S1P on S1P₁ receptors can reduce angiogenesis, increase endothelium integrity, reduce photoreceptor apoptosis and protect the retina against neurodegeneration. Conversely, S1P₂ receptor signalling can increase neovascularisation, disrupt endothelial junctions, stimulate VEGF release, and induce retinal cell apoptosis and degeneration of neural retina. The aim of this review is to thoroughly discuss the role of S1P and its different receptor subtypes in angiogenesis, inflammation, apoptosis and fibrosis in order to determine which of these S1P-mediated processes may be targeted therapeutically.

Sphingolipids as critical players in retinal physiology and pathology

Sphingolipids have emerged as bioactive lipids involved in the regulation of many physiological and pathological processes. In the retina, they have been established to participate in numerous processes, such as neuronal survival and death, proliferation and migration of neuronal and vascular cells, inflammation, and neovascularization. Dysregulation of sphingolipids is therefore crucial in the onset and progression of retinal diseases. This review examines the involvement of sphingolipids in retinal physiology and diseases. Ceramide (Cer) has emerged as a common mediator of inflammation and death of neuronal and retinal pigment epithelium cells in animal models of retinopathies such as glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa. Sphingosine-1-phosphate (S1P) has opposite roles, preventing photoreceptor and ganglion cell degeneration but also promoting inflammation, fibrosis, and neovascularization in AMD, glaucoma, and pro-fibrotic disorders. Alterations in Cer, S1P, and ceramide 1-phosphate may also contribute to uveitis. Notably, use of inhibitors that either prevent Cer increase or modulate S1P signaling, such as Myriocin, desipramine, and Fingolimod (FTY720), preserves neuronal viability and retinal function. These findings underscore the relevance of alterations in the sphingolipid metabolic network in the etiology of multiple retinopathies and highlight the potential of modulating their metabolism for the design of novel therapeutic approaches.

Incidence of uveitis and macular edema among patients taking fingolimod 0.5 mg for multiple sclerosis

Background

Patients with multiple sclerosis (MS) have a higher incidence of uveitis compared with the general population. Fingolimod, a first line disease modifying drug used in multiple sclerosis, may cause macular edema and thus requires ophthalmic examination. However, murine models and anecdotal reports suggest fingolimod may reduce the incidence of uveitis.

Purpose

To report the incidence of uveitis and macular edema among those on fingolimod 0.5 mg (Gilenya®) therapy for multiple sclerosis (MS).

Methods

Retrospective review of patients on fingolimod who developed uveitis and/or macular edema.

Results

No patients had an occurrence or history of uveitis. Four of the 188 (2.13%) patients developed macular edema without ocular inflammation. One of the 188 (0.53%) patients developed Acute Macular Neuroretinopathy.

Conclusion

Patients taking fingolimod have a lower incidence of uveitis than expected in a population of MS patients.

Druggable Sphingolipid Pathways: Experimental Models and Clinical Opportunities

Intensive research in the field of sphingolipids has revealed diverse roles in cell biological responses and human health and disease. This immense molecular family is primarily represented by the bioactive molecules ceramide, sphingosine, and sphingosine 1-phosphate (S1P). The flux of sphingolipid metabolism at both the subcellular and extracellular levels provides multiple opportunities for pharmacological intervention. The caveat is that perturbation of any single node of this highly regulated flux may have effects that propagate throughout the metabolic network in a dramatic and sometimes unexpected manner. Beginning with S1P, the receptors for which have thus far been the most clinically tractable pharmacological targets, this review will describe recent advances in therapeutic modulators targeting sphingolipids, their chaperones, transporters, and metabolic enzymes.

[Intraocular inflammation in multiple sclerosis]

Multiple sclerosis (MS) is a chronic inflammatory disorder of the brain and the spinal cord occurring mostly in young adults and is associated with temporary or permanent neurological deficits. An association between uveitis and MS has been recognized for a long time. Current data indicate an approximately 10 times higher prevalence of uveitis in patients with MS compared to the general population. In particular, MS is associated with intermediate uveitis and typically with concomitant retinal vasculitis. The treatment of uveitis should not only take the severity of intraocular inflammation into account but a coordination of the active agents must also consider the neurological manifestations. Since uveitis and MS are pathogenetically based on an immune-mediated genesis, immunomodulatory treatment approaches are dominant but it is important to bear in mind that tumor necrosis factor(TNF)-alpha blocking agents may worsen MS.

Acid Ceramidase Deficiency in Mice Leads to Severe Ocular Pathology and Visual Impairment

Farber disease (FD) is a debilitating lysosomal storage disorder characterized by severe inflammation and neurodegeneration. FD is caused by mutations in the ASAH1 gene, resulting in deficient acid ceramidase (ACDase) activity. Patients with ACDase deficiency exhibit a broad clinical spectrum. In classic cases, patients develop hepatosplenomegaly, nervous system involvement, and childhood mortality. Ocular manifestations include decreased vision, a grayish appearance to the retina with a cherry red spot, and nystagmus. That said, the full effect of ACDase deficiency on the visual system has not been studied in detail. We previously developed a mouse model that is orthologous for a known patient mutation in Asah1 that recapitulates human FD. Herein, we report evidence of a severe ocular pathology in Asah1^P361R/P361R mice. Asah1^P361R/P361R mice exhibit progressive retinal and optic nerve pathology. Through noninvasive ocular imaging and histopathological analyses of these Asah1^P361R/P361R animals, we revealed progressive inflammation, the presence of retinal dysplasia, and significant storage pathology in various cell types in both the retina and optic nerves. Lipidomic analyses of retinal tissues revealed an abnormal accumulation of ceramides and other sphingolipids. Electroretinograms and behavioral tests showed decreased retinal and visual responses. Taken together, these data suggest that ACDase deficiency leads to sphingolipid imbalance, inflammation, dysmorphic retinal and optic nerve pathology, and severe visual impairment.

Re-programming immunosurveillance in persistent non-infectious ocular inflammation

Ocular function depends on a high level of anatomical integrity. This is threatened by inflammation, which alters the local tissue over short and long time-scales. Uveitis due to autoimmune disease, especially when it involves the retina, leads to persistent changes in how the eye interacts with the immune system. The normal pattern of immune surveillance, which for immune privileged tissues is limited, is re-programmed. Many cell types, that are not usually present in the eye, become detectable. There are changes in the tissue homeostasis and integrity. In both human disease and mouse models, in the most extreme cases, immunopathological findings consistent with development of ectopic lymphoid-like structures and disrupted angiogenesis accompany severely impaired eye function. Understanding how the ocular environment is shaped by persistent inflammation is crucial to developing novel approaches to treatment.

[Uveitis in multiple sclerosis : Overview and perspectives]

The association of uveitis and multiple sclerosis (MS) is less well known than the association between optic neuritis and MS even though MS patients suffer ten times more often from uveitis than the normal population. In this group of patients, intermediate uveitis presenting with periphlebitis and "snowbanks" or "snowballs", as well as granulomatous anterior uveitis play an important role. Simultaneous occurrence of MS and uveitis could be due to the fact that both neural and ocular tissues have the same embryological origin or could be the consequence of an immunological reaction following an Epstein-Barr virus infection. The aim is to find a drug for these patients that treats both MS and uveitis. Currently various studies with different drugs already used successfully in MS patients are under investigation for use in the treatment of uveitis. There is some evidence that interferon beta is effective in macular edema associated with uveitis. Other substances, such as daclizumab, natalizumab and fingolimod also seem to be promising.

Birdshot chorioretinopathy

PURPOSE OF REVIEW

Birdshot chorioretinopathy remains incompletely understood, but new insights into its pathogenesis have been reported recently, and treatment and monitoring options have also expanded. Central visual acuity may remain good until the late stages of the disease, but loss of visual field and peripheral retinal function is common.

RECENT FINDINGS

The underlying pathogenesis of the disease has long been believed to be T-cell driven, but examination of the IL-17 pathway has now further refined the potential underlying mechanism. New imaging techniques, including extended depth imaging of the choroid with optical coherence tomography, have demonstrated promise in detecting disease activity earlier, enabling targeted treatment to be given. Treatment options have expanded with the advent of the biological agents, and these may yet improve outcomes, particularly in refractory patients.

SUMMARY

Laboratory research continues to investigate the underlying mechanisms of disease, but our understanding remains frustratingly incomplete for a disease with such a clear HLA association. Clinical research is increasingly being driven to improve the phenotyping of affected patients so that those at risk of visual loss can be identified early and treated more aggressively with individually targeted therapies such as the newer biological agents, but how successful this approach will ultimately prove to be remains to be seen.

Pharmacotherapy for uveitis: current management and emerging therapy

Uveitis, a group of conditions characterized by intraocular inflammation, is a major cause of sight loss in the working population. Most uveitis seen in Western countries is noninfectious and appears to be autoimmune or autoinflammatory in nature, requiring treatment with immunosuppressive and/or anti-inflammatory drugs. In this educational review, we outline the ideal characteristics of drugs for uveitis and review the data to support the use of current and emerging therapies in this context. It is crucial that we continue to develop new therapies for use in uveitis that aim to suppress disease activity, prevent accumulation of damage, and preserve visual function for patients with the minimum possible side effects.

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of T_reg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8⁺ T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders.

Tissue-resident exhausted effector memory CD8+ T cells accumulate in the retina during chronic experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis is a model for noninfectious posterior segment intraocular inflammation in humans. Although this disease is CD4⁺ T cell dependent, in the persistent phase of disease CD8⁺ T cells accumulate. We show that these are effector memory CD8⁺ T cells that differ from their splenic counterparts with respect to surface expression of CD69, CD103, and Ly6C. These retinal effector memory CD8⁺ T cells have limited cytotoxic effector function, are impaired in their ability to proliferate in response to Ag-specific stimulation, and upregulate programmed death 1 receptor. Treatment with fingolimod (FTY720) during the late phase of disease revealed that retinal CD8⁺ T cells were tissue resident. Despite signs of exhaustion, these cells were functional, as their depletion resulted in an expansion of retinal CD4⁺ T cells and CD11b⁺ macrophages. These results demonstrate that, during chronic autoimmune inflammation, exhausted CD8⁺ T cells become established in the local tissue. They are phenotypically distinct from peripheral CD8⁺ T cells and provide local signals within the tissue by expression of inhibitory receptors such as programmed death 1 that limit persistent inflammation.

Sphingolipids in ocular inflammation

Sphingolipids are essential to cell membrane structure and the development and maintenance of neural tissues. The role of bioactive sphingolipids has been established in numerous cellular events, including cell survival, growth, and apoptosis. Ocular inflammatory and autoimmune diseases involve activation and migration of endothelial cells, neovascularization, and infiltration of immune cells into various tissues. Clinically, the impact and role of sphingolipid-mediated signaling is increasingly being appreciated in the pathogenesis and treatment of diseases ranging from multiple sclerosis to neovascularization in age-related macular degeneration and diabetic retinopathy. In this review, we discuss our current knowledge and understanding of sphingolipid metabolism and signaling associated with the pathogenesis of ocular diseases.

Birdshot uveitis: current and emerging treatment options

Birdshot chorioretinopathy is a relatively uncommon subtype of idiopathic posterior uveitis with distinct clinical characteristics and a strong genetic association with the Human Leukocyte Antigen (HLA)-A29 allele. The diagnosis remains clinical and is based on the presence of typical clinical features, including multiple, distinctive, hypopigmented choroidal lesions throughout the fundus. The long-term visual prognosis of this disorder, however, remains guarded – central visual acuity can be preserved until late in the disease and it is not uncommon for patients to receive inadequate immunosuppressive treatment, leading to a poor long-term outcome in which peripheral retinal damage eventually leads to visual deterioration. Birdshot chorioretinopathy has proven a particularly attractive area of study within the field of uveitis, as it is a relatively easily defined disease with an associated human leukocyte antigen haplotype. Despite this, however, the immune mechanisms involved in its pathogenesis remain unclear, and some patients continue to lose retinal function despite therapy with corticosteroids and conventional immunosuppressive agents. Laboratory research continues to investigate the underlying mechanisms of disease, and clinical research is now being driven to improve the phenotyping and monitoring of this condition as, in the era of so-called personalized medicine, it is becoming increasingly important to identify patients at risk of visual loss early so that they can be treated more aggressively with targeted therapies such as the newer biological agents. This approach requires the formation of collaborative groups, as the relative rarity of the condition makes it difficult for one center to accumulate enough patients for worthwhile studies. Nevertheless, results obtained with newer therapies, such as biological agents directed against particular cytokines or cell-surface receptors, demonstrate ever improving control of the inflammation in refractory cases, providing hope that the outlook for visual function in this condition can only improve.

Beyond the cherry-red spot: Ocular manifestations of sphingolipid-mediated neurodegenerative and inflammatory disorders

Sphingolipids are a ubiquitous membrane lipid present in every cell and found most abundantly in neural tissues. Disorders such as Tay-Sachs or Niemann-Pick disease are the most familiar examples of dysfunction in sphingolipid metabolism and are typically associated with neurodegeneration and ocular findings such as blindness. More recently, the role of bioactive sphingolipids has been established in a multitude of cellular events, including cell survival, growth, senescence and apoptosis, inflammation, and neovascularization. We discuss our current knowledge and understanding of sphingolipid metabolism and signaling in the pathogenesis of ocular diseases.

Sphingosine 1-phosphate receptors are essential mediators of eyelid closure during embryonic development

The fetal development of the mammalian eyelid involves the expansion of the epithelium over the developing cornea, fusion into a continuous sheet covering the eye, and a splitting event several weeks later that results in the formation of the upper and lower eyelids. Recent studies have revealed a significant number of molecular signaling components that are essential mediators of eyelid development. Receptor-mediated sphingosine 1-phosphate (S1P) signaling is known to influence diverse biological processes, but its involvement in eyelid development has not been reported. Here, we show that two S1P receptors, S1P2 and S1P3, are collectively essential mediators of eyelid closure during murine development. Homozygous deletion of the gene encoding either receptor has no apparent effect on eyelid development, but double-null embryos are born with an "eyes open at birth" defect due to a delay in epithelial sheet extension. Both receptors are expressed in the advancing epithelial sheet during the critical period of extension. Fibroblasts derived from double-null embryos have a deficient response to epidermal growth factor, suggesting that S1P2 and S1P3 modulate this essential signaling pathway during eyelid closure.

Local therapies for inflammatory eye disease in translation: past, present and future

Despite their side-effects and the advent of systemic immunosuppressives and biologics, the use of corticosteroids remains in the management of patients with uveitis, particularly when inflammation is associated with systemic disease or when bilateral ocular disease is present. The use of topical corticosteroids as local therapy for anterior uveitis is well-established, but periocular injections of corticosteroid can also be used to control mild or moderate intraocular inflammation. More recently, intraocular corticosteroids such as triamcinolone and steroid-loaded vitreal inserts and implants have been found to be effective, including in refractory cases. Additional benefits are noted when ocular inflammation is unilateral or asymmetric, when local therapy may preclude the need to increase the systemic medication.

Implants in particular have gained prominence with evidence of efficacy including both dexamethasone and fluocinolone loaded devices. However, an appealing avenue of research lies in the development of non-corticosteroid drugs in order to avoid the side-effects that limit the appeal of injected corticosteroids. Several existing drugs are being assessed, including anti-VEGF compounds such as ranibizumab and bevacizumab, anti-tumour necrosis factor alpha antibodies such as infliximab, as well as older cytotoxic medications such as methotrexate and cyclosporine, with varying degrees of success. Intravitreal sirolimus is currently undergoing phase 3 trials in uveitis and other inflammatory pathways have also been proposed as suitable therapeutic targets. Furthermore, the advent of biotechnology is seeing advances in generation of new therapeutic molecules such as high affinity binding peptides or modified high affinity or bivalent single chain Fab fragments, offering higher specificity and possibility of topical delivery.

Ophthalmic evaluations in clinical studies of fingolimod (FTY720) in multiple sclerosis

PURPOSE

To report outcomes of ophthalmic evaluations in clinical studies of patients receiving fingolimod (Gilenya; Novartis Pharma AG, Basel, Switzerland) for multiple sclerosis (MS).

DESIGN

Analysis done on pooled safety data (N = 2615, all studies group) from 3 double-masked, randomized, parallel-group clinical trials (phase 2 core and extension >5 years, and phase 3 FREEDOMS and TRANSFORMS core and extension studies).

PARTICIPANTS

Patients aged 18 to 55 years (18-60 years in phase 2 study) diagnosed with relapsing-remitting MS were included. Patients with diabetes mellitus or macular edema (ME) at screening were excluded.

INTERVENTION

Participants received fingolimod (0.5/1.25 mg), placebo, or interferon beta for the respective study durations. Ophthalmic examination included detailed eye history (at screening), visual acuity (VA) assessment, dilated ophthalmoscopy, optical coherence tomography (OCT), and fluorescein angiography (FA).

MAIN OUTCOME MEASURES

Extensive ophthalmic monitoring was performed for all patients. While being studied, patients with abnormal findings on dilated ophthalmoscopy and OCT compatible with ME were further studied by FA. All locally diagnosed ME cases were centrally reviewed by the retina specialist (M.A.Z.) on the Data and Safety Monitoring Board.

RESULTS

Among 2615 patients assessed, 19 confirmed ME cases were observed in fingolimod-treated groups (0.5 mg: n = 4, 0.3%; 1.25 mg: n = 15, 1.2%). Most patients (n = 13, 68%) presented with blurred vision, decreased VA, or eye pain. Macular edema was diagnosed within 3 to 4 months of treatment initiation in most cases (n = 13, 68%); 2 patients had late onset (>12 months) ME. Of the 19 patients with ME, 5 (26%), all treated with fingolimod 1.25 mg, had a history of uveitis compared with 26 (1%) in the all studies group. In most cases (n = 16, 84%), ME resolved after discontinuing the study drug. Eleven patients required topical anti-inflammatory medications. No patient had further vision deterioration.

CONCLUSIONS

Fingolimod 0.5 mg is associated with a low incidence of ME in MS studies. Patients with a history of uveitis may be at an increased risk of developing ME. An ophthalmic examination before initiating fingolimod therapy and regular follow-up eye examinations during fingolimod therapy are recommended.

Inhibition of de novo ceramide biosynthesis by FTY720 protects rat retina from light-induced degeneration

Light-induced retinal degeneration (LIRD) in albino rats causes apoptotic photoreceptor cell death. Ceramide is a second messenger for apoptosis. We tested whether increases in ceramide mediate photoreceptor apoptosis in LIRD and if inhibition of ceramide synthesis protects the retina. Sprague-Dawley rats were exposed to 2,700 lux white light for 6 h, and the retinal levels of ceramide and its intermediary metabolites were measured by GC-MS or electrospray ionization tandem mass spectrometry. Enzymes of the de novo biosynthetic and sphingomyelinase pathways of ceramide generation were assayed, and gene expression was measured. The dosage and temporal effect of the ceramide synthase inhibitor FTY720 on the LIRD retina were measured by histological and functional analyses. Retinal ceramide levels increased coincident with the increase of dihydroceramide at various time points after light stress. Light stress in retina induces ceramide generation predominantly through the de novo pathway, which was prevented by systemic administration of FTY720 (10 mg/kg) leading to the protection of retinal structure and function. The neuroprotection of FTY720 was independent of its immunosuppressive action. We conclude that ceramide increase by de novo biosynthesis mediates photoreceptor apoptosis in the LIRD model and that inhibition of ceramide production protects the retina against light stress.

Nuclear receptor NR4A2 orchestrates Th17 cell-mediated autoimmune inflammation via IL-21 signalling

IL-17-producing CD4⁺ T helper 17 (Th17) cells are pathogenic in a range of human autoimmune diseases and corresponding animal models. We now demonstrate that such T cells infiltrating the target organ during the induction of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune uveoretinitis (EAU) specifically express NR4A2. Further, we reveal a critical involvement of NR4A2 in Th17 cell functions and Th17 cell-driven autoimmune diseases. When NR4A2 expression was blocked with siRNA, full Th17 differentiation was prevented in vitro: although cells expressed the master Th17 regulator, RORγt, they expressed reduced levels of IL-23R and were unable to produce IL-17 and IL-21. Notably, Th17 differentiation in the absence of NR4A2 was restored by exogenous IL-21, indicating that NR4A2 controls full maturation of Th17 cells via autocrine IL-21 signalling. Preventing NR4A2 expression in vivo by systemic treatment with NR4A2-specific siRNA also reduced Th17 effector responses and furthermore protected mice from EAE induction. In addition, the lack of disease was associated with a reduction in autocrine IL-21 production and IL-23R expression. Similar modulation of NR4A2 expression was also effective as an intervention, reversing established autoimmune responses and ameliorating clinical disease symptoms. Thus, NR4A2 appears to control Th17 differentiation and so plays an essential role in the development of Th17-mediated autoimmune disease. As NR4A2 is also upregulated during human autoimmune disease, targeting NR4A2 may provide a new therapeutic approach in treating autoimmune disease.

Modelling experimental uveitis: barrier effects in autoimmune disease

OBJECTIVE AND DESIGN

A mathematical analysis of leukocytes accumulating in experimental autoimmune uveitis (EAU), using ordinary differential equations (ODEs) and incorporating a barrier to cell traffic.

MATERIALS AND SUBJECTS

Data from an analysis of the kinetics of cell accumulation within the eye during EAU.

METHODS

We applied a well-established mathematical approach that uses ODEs to describe the behaviour of cells on both sides of the blood-retinal barrier and compared data from the mathematical model with experimental data from animals with EAU.

RESULTS

The presence of the barrier is critical to the ability of the model to qualitatively reproduce the experimental data. However, barrier breakdown is not sufficient to produce a surge of cells into the eye, which depends also on asymmetry in the rates at which cells can penetrate the barrier. Antigen-presenting cell (APC) generation also plays a critical role and we can derive from the model the ratio for APC production under inflammatory conditions relative to production in the resting state, which has a value that agrees closely with that found by experiment.

CONCLUSIONS

Asymmetric trafficking and the dynamics of APC production play an important role in the dynamics of cell accumulation in EAU.

Therapeutic dosing of fingolimod (FTY720) prevents cell infiltration, rapidly suppresses ocular inflammation, and maintains the blood-ocular barrier

Fingolimod (FTY720) is an FDA-approved therapeutic drug with efficacy demonstrated in experimental models of multiple sclerosis and in phase III human multiple sclerosis trials. Fingolimod prevents T-cell migration to inflammatory sites by decreasing expression of the sphingosine-1 phosphate receptor normally required for egress from secondary lymphoid tissue. As a preclinical model of human uveitis, experimental autoimmune uveoretinitis permits assessment of immunotherapeutic efficacy. Murine experimental autoimmune uveoretinitis is induced by activation of retinal antigen-specific CD4(+) T cells that infiltrate the eye. High-dose fingolimod treatment administered before disease onset reduces ocular infiltration within hours of administration and suppresses clinicopathologic expression of experimental autoimmune uveoretinitis. In the present investigation of the efficacy of fingolimod treatment for established disease, single-dose treatment was effective and immunosuppressive ability was maintained through a dose range, demonstrating significant and rapid reduction in CD4(+) cell infiltration at clinically relevant therapeutic doses of fingolimod. A repeated-treatment regimen using a dose similar to that in current multiple sclerosis patient protocols significantly reduced infiltration within 24 hours of administration; importantly, repeated doses did not compromise the vascular integrity of the blood-ocular barrier. On withdrawal of fingolimod, drug-induced remission was lost and recrudescence of clinical disease was observed. These results support a strong therapeutic potential for fingolimod as an acute rescue therapy for the treatment of ocular immune-mediated inflammation.

Current concepts and future directions in the pathogenesis and treatment of non-infectious intraocular inflammation

The blockbuster drug paradigm is under increasing scrutiny across the biopharmaceutical industry. Intraocular inflammation poses particular challenges to this, given the heterogeneity of conditions in the uveitis spectrum, and the increasing acknowledgement of individual patient and disease variance in underlying immune responses. This need has triggered a drive towards personalised and stratified medicine, supported and enabled as a result of continued development of both experimental models and molecular biological techniques and improved clinical classification. As such we have the ability now to systematically appraise at a genomic, transcriptomic, and proteomic level individual immunophenotype, and the promise that in the eye this can be augmented by in vivo immune imaging to identify individual immunopathology. With such advances all running in parallel, we are entering an era of experimental medicine that will facilitate early diagnosis, generate biomarkers for accurate prognostication, and enable the development of individualised and targeted therapies, which can progress rapidly into clinical practice.

Autoimmune uveitis: study of treatment therapies

ABSTRACT Experimental autoimmune uveitis is an organ-specific T-cell mediated autoimmune disease characterized by inflammation and consequent destruction of the neural retina and adjacent tissues. Inflammation in experimental autoimmune uveitis may be induced in rodents by immunization with retinal antigens, such as interphotoreceptor retinoid-binding protein. We present a review of experimental studies that correlate primary immunobiological functions with this chronic disease and the possible use of molecules for the treatment of autoimmune uveitis.

TNFR1-dependent regulation of myeloid cell function in experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis is an autoimmune disease induced in mice, which involves the infiltration of CD11b(+) macrophages and CD4(+) T cells into the normally immune-privileged retina. Damage is produced in the target organ following the activation of Th1 and Th17 T cells and by the release of cytotoxic mediators such as NO by activated macrophages. The majority of immune cells infiltrating into the retina are CD11b(+) myeloid cells, but, despite the presence of these APCs, relatively limited numbers of T cells are observed in the retina during the disease course. These T cells do not proliferate when leukocytes are isolated from the retina and restimulated in vitro, although they do produce both IFN-gamma and IL-17. T cell proliferation was restored by depleting the myeloid cells from the cultures and furthermore those isolated myeloid cells were able to regulate the proliferation of other T cells. The ability of macrophages to regulate proliferation depends on activation by T cell-produced IFN-gamma and autocrine TNF-alpha signaling in the myeloid cells via TNFR1. In the absence of TNFR1 signaling, relative T cell expansion in the retina is increased, indicating that regulatory myeloid cells may also act in vivo. However, TNFR1 signaling is also required for macrophages, but not T cells, to migrate into the target organ. Thus, in TNFR1 knock out mice, the amplification of autoimmunity is limited, leading to resistance to experimental autoimmune uveoretinitis induction.