Tumour necrosis factor-alpha in conjunctivae affected by ocular cicatricial pemphigoid

Ocular mucous membrane pemphigoid: novel treatment strategies

PURPOSE OF REVIEW

To describe current treatments of ocular mucous membrane pemphigoid (OMMP), including conventional systemic immunosuppression (CIST) and novel biologic agents.

RECENT FINDINGS

CIST remains the main stay therapy for the management of OMMP. The choice of agents is tailored to disease severity - mild disease is treated with dapsone, whereas moderately severe cases are often treated with mycophenolate mofetil or sulfa-based drugs and severe cases are treated with cyclophosphamide. In recalcitrant disease newer biologics such as Rituximab, intravenous immunoglobins and tumour necrosis alpha antagonists have proven to be effective in disease control. Control of inflammation with topical therapy and halting conjunctival fibrosis remain as areas of unmet clinical needs.

SUMMARY

OMMP is largely treated with CIST. The recent introduction of new biologic agents could shape the way the disease is treated in the near future.

Endoplasmic reticulum stress promotes inflammation-mediated proteolytic activity at the ocular surface

A growing body of evidence implicates endoplasmic reticulum (ER) stress in the pathogenesis of chronic inflammatory and autoimmune disorders. Here, we demonstrate that the proinflammatory cytokine TNFα stimulates matrix metalloproteinase 9 (MMP9) at the ocular surface through a c-Fos-dependent mechanism of ER stress. We found positive reactivity of the molecular chaperone BiP/GRP78 in conjunctival epithelium of patients with ocular cicatricial pemphigoid and increased levels of BiP/GRP78, sXBP1 and GRP94 in human corneal epithelial cells treated with TNFα. Pharmacological blockade of ER stress in vitro using dexamethasone or the chemical chaperones TUDCA and 4PBA attenuated MMP9 expression and secretion in the presence of TNFα. Moreover, expression analysis of genes associated with inflammation and autoimmunity identified the c-Fos proto-oncogene as a mediator of ER stress responses in epithelial cells. Substantially less TNFα-induced MMP9 expression occurred when c-Fos signaling was suppressed with a function-blocking antibody. Taken together, these results indicate that activation of ER stress contributes to promote inflammation-mediated proteolytic activity and uncovers a target for restoring tissue homeostasis in ocular autoimmune disease.

Updates on diagnosis and management of autoimmune blistering diseases

Over the last several decades, advances in the understanding of the pathogenesis of autoimmune blistering diseases has resulted in significant improvements in diagnosis and management. These improvements include new diagnostic assays and therapies targeted at specific disease mediators. Furthermore, the abundance of new therapies in clinic trials for autoimmune blistering diseases will translate to an enhanced therapeutic armamentarium for clinicians. The aim of this article is to review new developments in the understanding of autoimmune blistering diseases and to summarize advancements in their diagnosis and management.

Inflammatory Stress Causes N-Glycan Processing Deficiency in Ocular Autoimmune Disease

High levels of proinflammatory cytokines have been associated with a loss of tissue function in ocular autoimmune diseases, but the basis for this relationship remains poorly understood. Here we investigate a new role for tumor necrosis factor α in promoting N-glycan-processing deficiency at the surface of the eye through inhibition of N-acetylglucosaminyltransferase expression in the Golgi. Using mass spectrometry, complex-type biantennary oligosaccharides were identified as major N-glycan structures in differentiated human corneal epithelial cells. Remarkably, significant differences were detected between the efficacies of cytokines in regulating the expression of glycogenes involved in the biosynthesis of N-glycans. Tumor necrosis factor α but not IL-1β had a profound effect in suppressing the expression of enzymes involved in the Golgi branching pathway, including N-acetylglucosaminyltransferases 1 and 2, which are required for the formation of biantennary structures. This decrease in gene expression was correlated with a reduction in enzymatic activity and impaired N-glycan branching. Moreover, patients with ocular mucous membrane pemphigoid were characterized by marginal N-acetylglucosaminyltransferase expression and decreased N-glycan branching in the conjunctiva. Together, these data indicate that proinflammatory cytokines differentially influence the expression of N-glycan-processing enzymes in the Golgi and set the stage for future studies to explore the pathophysiology of ocular autoimmune diseases.

Ocular tissue distribution and pharmacokinetic study of a small 13kDa domain antibody after intravitreal, subconjuctival and eye drop administration in rabbits

Domain antibodies (dAb's) comprise the smallest functional unit of human IgG and can be targeted to a range of different soluble cytokine and receptor targets in the eye. In particular their small size may offer advantage for ocular tissue penetration and distribution. To investigate this we used a 13kDa tool molecule to undertake a preliminary short term ocular tissue distribution and pharmacokinetic study in the rabbit eye. The dAb was administered by the intravitreal or subconjunctival route or, as topical eye drops for up to five days and dAb concentrations measured in vitreous, aqueous, conjunctiva, choroid-RPE, retina, iris, sclera, and ciliary body. The observed elimination half-live of the dAb (~3 days) in vitreous showed a similar elimination rate to that of a much larger (∼50kDa) Fab fragment whilst the half-life following subconjunctival administration was ∼24 h and, after eye drop dosing the dAb was detectable in aqueous and conjunctiva. These preliminary data show that the intravitreal half-life of dAb's are similar to much larger antibody fragments, offering the potential to deliver significantly more drug to target on a molar basis with a single intravitreal injection potentially enabling dosing frequencies of once a month or less. Subconjunctival injection may provide short duration therapeutic levels of dAb to the anterior and posterior chamber whilst topical eye drop delivery of dAbs may be useful in front-of-eye disease. These data indicate that small domain antibodies may have utility in ophthalmology. Further studies are warranted.

Infliximab in the treatment of refractory ocular inflammatory diseases

PURPOSE

Infliximab is frequently used in the treatment of refractory rheumatic diseases. We report our initial local experience at a tertiary eye center in Hong Kong in using infliximab as treatment of various refractory ocular inflammatory diseases that have failed with conventional corticosteroid and immunosuppressant therapy.

DESIGN

This is a retrospective, interventional case series.

METHODS

We reviewed all the medical records of patients who had refractory ocular inflammatory diseases and received infliximab as part of their treatment. We collected data regarding the visual acuity, status of inflammation, and any complications arising from the treatment.

RESULTS

Seven eyes from 3 male and 2 female patients were recruited. Two patients had peripheral ulcerative keratitis, whereas the remaining patients had uveitis. Two patients had bilateral diseases, and the rest were unilateral. All patients achieved quiescence after 3 doses of infliximab infusions during the period of 3 months. Most of the patients retained a useful visual acuity of 20/70 or better at the end of the study. There were no serious adverse effects or complications encountered from the infliximab therapy.

CONCLUSIONS

Infliximab is a valuable and potent option that may be considered in the management of various refractory ocular inflammatory diseases. However, larger controlled studies are needed to evaluate the safety profile, optimal treatment schedule, and adverse effects of long-term infliximab therapy.

Collagen cross-linking of the Boston keratoprosthesis donor carrier to prevent corneal melting in high-risk patients

OBJECTIVE

To examine the clinical relevance and pathophysiology of Boston keratoprosthesis (B-KPro)-related corneal keratolysis (cornea melt) and to describe a novel method of preventing corneal melt using ex vivo crosslinked cornea tissue carrier.

METHODS

A review of B-KPro literature was performed to highlight cases of corneal melt. Studies examining the effect of corneal collagen cross-linking (CXL) on the biomechanical properties of corneal tissue are summarized. The use of crosslinked corneal tissue as a carrier to the B-KPro is illustrated with a case.

RESULTS

Corneal melting after B-KPro is a relatively rare event, occurring in 3% of eyes during the first 3 years of postoperative follow-up. The risk of post-KPro corneal melting is heightened in eyes with chronic ocular surface inflammation such as eyes with Stevens-Johnson syndrome and mucous membrane pemphigoid. This chronic inflammation results in high tear levels of matrix metalloproteinases, the enzymes responsible for collagenolysis and corneal melt. Crosslinked corneal tissue has been shown to have stiffer biomechanical properties and to be more resistant to degradation by collagenolytic enzymes. We have previously optimized the technique for ex vivo corneal CXL and are currently studying its impact on the prevention of corneal melting after B-KPro surgery in high-risk eyes. Crosslinked carrier tissue was used in a 52-year-old man with familial aniridia and severe post-KPro corneal melt. The patient maintained his visual acuity and showed no evidence of corneal thinning or melt in the first postoperative year.

CONCLUSION

Collagen crosslinking was previously shown to halt the enzymatic degradation of corneal buttons ex vivo. This study demonstrates the safety and potential benefit of using crosslinked corneal grafts as carriers for the B-KPro, especially in eyes at higher risk of postoperative melt.