Therapeutic Targets in Allergic Conjunctivitis

Novel therapeutic receptor agonists and antagonists in allergic conjunctivitis

PURPOSE OF REVIEW

Allergic conjunctivitis is characterized by the development of pathophysiological changes to the ocular surface, which occurs when pro-allergic and pro-inflammatory mediators interact with their cognate receptors expressed on immune and nonimmune cells. Traditional treatments with antihistamines and corticosteroids provide relief, but there is a need for more efficacious and tolerable long-term therapy with a better safety profile. This article aims to provide an overview of the mode of action and clinical application of agonist therapies targeting glucocorticoid, melanocortin, and toll-like receptors, as well as antagonist therapies targeting cytokine, chemokine, integrin, and histamine receptors.

RECENT FINDINGS

There has been considerable advancement in immunology and pharmacology, as well as a greater understanding of the cellular and molecular mechanisms of allergic conjunctivitis. Recent research advancing therapy for allergic conjunctivitis has focused on developing synthetic molecules and biologics that can interfere with the process of the allergic immune reaction.

SUMMARY

This review discusses novel therapeutic receptors being explored agonistically or antagonistically to develop alternative treatment options for allergic conjunctivitis. These novel approaches hold promise for improving the management of allergic eye diseases, offering patients hope for more effective and safer treatment options in the future.

Impact of inflammasomes on the ocular surface

PURPOSE OF REVIEW

The ocular surface is prone to inflammation due to exposure to environmental irritants and pathogens. Inflammasomes are intracellular, multiprotein complexes that communicate potentially dangerous signals to the immune system. The identification of inflammasomes in various inflammatory ocular surface conditions can aid in the development of therapeutics to treat these chronic inflammatory conditions.

RECENT FINDINGS

Several inflammasomes have been associated with ocular surface disorders including dry eye disease, keratitis, and allergies. Mechanisms for activation of these inflammasomes with regards to specific disorders have been explored in models to aid in the development of targeted treatments.

SUMMARY

Research efforts continue to characterize the types of inflammasomes and activators of these in inflammatory ocular surface conditions. Various therapies targeting specific inflammasome types or pyroptosis are being tested preclinically to assess effects on decreasing the associated chronic inflammation.

Polymeric Mixed Micelle-Loaded Hydrogel for the Ocular Delivery of Fexofenadine for Treating Allergic Conjunctivitis

This study was designed to formulate a polymeric mixed micelle (PMM) formulation to sustainably release fexofenadine (FEX) to treat allergic conjunctivitis effectively. A 32 factorial design was employed where the studied factors were PL90G amount (X1) and Pluronic (F127 and P123) mixture ratio (X2), and the dependent variables were entrapment efficacy (EE, Y1, %), particle size (PS, Y2, nm), zeta potential (ZP, Y3, mV), and the percent of drug released after 6 h (Q6h, Y4, %). The optimized formula was blended with a hydrogel base to develop an FEX-PMM hydrogel, where the safety and efficiency of this hydrogel were evaluated using in vivo studies. The EE% of FEX-PMM ranged from 62.15 ± 2.75 to 90.25 ± 1.48%, the PS from 291.35 ± 6.43 to 467.95 ± 3.60 nm, the ZP from -5.41 ± 0.12 to -9.23 ± 0.23 mV, and the Q6h from 50.27 ± 1.11 to 95.38 ± 0.92%. The Draize test results confirmed the safety of the FEX-PMM hydrogel. Furthermore, the FEX-PMM hydrogel showed rapid recovery in animals with induced allergic conjunctivitis compared to the free drug hydrogel. These results assure PMM's capability to deliver FEX to the conjunctival surface in a sustained pattern, consequently achieving better therapeutic outcomes.

Allergic Conjunctivitis: Review of Current Types, Treatments, and Trends

Allergic conjunctivitis is an allergen-induced immune response secondary to the binding of immunoglobulin-E (IgE) to sensitized mast cells. Approximately 40% of North Americans and 20% of the world's population are impacted by some form of allergy and it continues to increase in prevalence, especially among children. Specified IgE antibodies can be found in almost all cases of exposure to seasonal or perennial allergens. Activation and degranulation of mast cells lead to increased tear levels of histamine, tryptase, leukotrienes, cytokines, and prostaglandins. The release of these factors initiates the recruitment of inflammatory cells in the conjunctival mucosa, which causes the late-phase reaction. Signs and symptoms of ocular allergies include itching, tearing, chemosis, and hyperemia, which can lead to decreased productivity and poor quality of life. Many treatment options are available to improve symptoms, including, mast cell stabilizers, antihistamines, dual-acting agents, steroids, nonsteroidal anti-inflammatory drugs (NSAIDS), and other off-label treatment modalities. This review article provides an overview of different types of allergic conjunctivitis, its pathology and immunology, and recommended methods of treatment.

Exploration of efficacy and mechanism of 0.05% cyclosporine eye drops (II) monotherapy in allergic conjunctivitis-associated dry eye

PURPOSE

To explore the efficacy and relevant mechanism of 0.05% cyclosporine A (CsA) eye drops (II) monotherapy in patients with allergic conjunctivitis-associated dry eye (ACDE).

METHODS

Prospective, randomized, controlled study. Fifty-three patients with mild-to-moderate ACDE were randomly assigned to two groups. The CsA group received 0.05% CsA eye drops (II) monotherapy four times daily. The control group received 0.1% olopatadine twice daily combined with 0.1% preservative-free artificial tears four times daily. Clinical symptoms and signs, tear total IgE, and lymphotoxin-α (LT-α) concentrations were assessed at pre- and post-treatment days 7, 30, and 60. And we further measured six tear cytokines levels using a microsphere-based immunoassay.

RESULTS

The CsA group showed significant improvement in symptoms (Ocular Surface Disease Index and itching scores) and signs (conjunctival hyperaemia, conjunctival oedema, conjunctival papillae, tear break-up time (TBUT), corneal fluorescein staining, and goblet cell density) at each follow-up period compared to pre-treatment (all P < 0.050). And its improvement in itching scores (P7th < 0.001, P30th = 0.039, and P60th = 0.031) and TBUT (P7th = 0.009, P30th = 0.003, and P60th = 0.005) was more significant than the control group at all follow-up periods. The tear total IgE, interleukin (IL)-5, IL-6, periostin, eotaxin-3, and MMP-9 levels significantly decreased in the CsA group at day 60 after treatment (all P < 0.050). And the changed values in tear total IgE were positively correlated with the change in itching scores.

CONCLUSIONS

0.05% CsA eye drops (II) monotherapy can rapidly improve the symptoms and signs, especially in ocular itching and TBUT, in patients with ACDE. And its efficacy is superior to 0.1% olopatadine combined with artificial tears. Moreover, CsA downregulates the expression levels of tear inflammatory cytokines, including tear total IgE, IL-5, IL-6, periostin, eotaxin-3, and MMP-9. Among that, the reduction in tear total IgE levels may reflect the improvement of ocular itching.

Evaluation of Allergic Conjunctivitis Prevalence and Attitude Toward Prevention and Control in Saudi Arabia

BACKGROUND

Allergic conjunctivitis (AC) is a prevalent ocular condition with a substantial impact on individuals' quality of life. This study aimed to explore the demographic patterns, prevalence, symptoms, awareness, and attitudes associated with AC, while also examining potential associations with gender, age, and region of residence in Saudi Arabia.

METHODS

A cross-sectional study was conducted involving 487 participants. Data was collected through a self-administered questionnaire that included demographic information about AC prevalence, symptoms, attitudes, and awareness levels. Statistical analyses, including chi-square tests, were employed to examine associations between variables.

RESULTS

The study revealed a prevalence of AC (89, 18.3%) with common symptoms being eye redness (73, 82%) and itching (73, 82%). Participants displayed diverse awareness levels, with (376, 77.2%) correctly defining AC. The majority demonstrated either a good (230, 47.2%) or insufficient (196, 40.2%) attitude, while 54 (11.1%) had a sufficient attitude, and 7 (1.4%) exhibited an excellent attitude and awareness. Significant regional disparities were observed, impacting both prevalence and attitudes. While no gender differences were noted, the age group of 31-40 displayed a higher prevalence.

CONCLUSION

In this study, among 487 participants, the prevalence of AC was found to be 89 (18.3%). Meanwhile, attitude levels varied, with the majority demonstrating either a good or insufficient attitude. This provides valuable insights into the prevalence, symptoms, and awareness of AC in our population. The regional disparities underscore the need for tailored interventions addressing specific geographical contexts. The findings contribute to the broader understanding of AC, emphasizing the importance of targeted education and regional considerations in managing and preventing this condition.

[New and future treatment approaches for allergic conjunctivitis]

BACKGROUND

In severe and recurrent ocular allergies conventional ophthalmic drugs can reach their limits, especially in chronic forms. The first novel immunomodulators and biologicals are already in clinical use and could provide relief.

OBJECTIVE

Based on the immunopathophysiological mechanisms of ocular allergies, possible targets for innovative treatment approaches are presented. An overview of promising new and future immunomodulators and biologicals and their modes of action is also given.

MATERIAL AND METHODS

Current reviews on ocular allergies and the treatment of systemic allergic diseases were screened. Case reports on the treatment of ocular allergy using immunomodulators and biologicals were analyzed. The clinical relevance and possible applications are presented.

RESULTS

In chronic forms of ocular allergies, complex ocular surface inflammatory responses mediated via immunoglobulin E (IgE), mast cells, CD4-positive type 2 T‑helper cells and eosinophilic granulocytes are predominant. Cyclosporine A 0.1% eyedrops have been approved in Europe since 2018 for children aged 4 years and older with severe vernal keratoconjunctivitis (VKC). In addition, case reports present promising data on the systemic off-label use of biologicals, such as dupilumab or omalizumab, in refractory VKC or atopic keratoconjunctivitis (AKC).

CONCLUSION

A profound understanding of the immunopathophysiology of ocular allergies is necessary to detect further targets for future immunomodulators and biologicals. Currently, immunomodulatory therapy remains limited to cyclosporine A eyedrops. Other immunomodulatory agents, such as tacrolimus and biologicals can only be used off-label. Further studies on the controlled clinical use of these substances in the treatment of VKC or AKC are underway.

Podcast on Cross-speciality Perspectives on Practical Management of Atopic Dermatitis-Associated Ocular Surface Diseases

There is a growing awareness among dermatology providers of ocular comorbidities in patients with the chronic inflammatory skin disease atopic dermatitis (AD). For example, the prevalence of ocular surface diseases (OSD) such as conjunctivitis is higher in patients with AD than in the general population, and the use of some AD treatments may be associated with OSD. In a recent review published in the Journal of the American Academy of Dermatology, dermatologists and ophthalmologists provided an overview of the different types, etiology, pathophysiology, and practical management of OSD associated with AD. This review included a suggested treatment algorithm that champions a partnership between dermatology providers and eye care providers for optimal screening, diagnosis, and care. In this podcast article, a dermatologist and ophthalmologist who were authors on this review are joined by a nurse practitioner moderator to discuss how these concepts can be adapted to clinical practice, inclusive of dermatologists, eye care providers, and relevant advanced practice providers. This podcast focuses on the authors' clinical experiences and highlights the key aspects of optimal care, including exploring additional questions to answer with future research.

Ocular surface itch and pain: key differences and similarities between the two sensations

PURPOSE OF REVIEW

To review the pathophysiology and treatment of ocular itch and pain, encompassing nociceptive and neuropathic categories.

RECENT FINDINGS

Ocular itch and pain are sensations that arise from activation of ocular surface polymodal nerves. Nociceptive itch, commonly comorbid with ocular pain complaints, is mainly driven by a histamine-mediated type 1 hypersensitivity reaction. Beyond topical therapy, novel drug delivery systems are being explored to improve ocular residence time of nonsteroidal anti-inflammatory drugs (NSAIDs) and antihistamines. Nociceptive ocular pain can be driven by a variety of factors. Treatment focuses on addressing the causative sources of pain. Neuropathic ocular itch and pain are driven by nerve damage and dysfunction and as such, topical and oral neuromodulation have been explored as treatments. Oral neuromodulators include alpha 2 delta ligands, tricyclic antidepressants (TCAs), and low dose naltrexone. Novel therapies are being evaluated for both modalities such as difelikefalin (κ-opioid receptor agonist) for neuropathic itch and libvatrep (transient receptor potential vanilloid 1 antagonist) for neuropathic pain.

SUMMARY

Both ocular itch and pain can be driven by nociceptive and/or neuropathic mechanisms. Identifying contributors to abnormal ocular sensations is vital for precise medical care. Novel therapeutics for these conditions aim to improve patient outcomes and quality of life.

Alleviation of allergic conjunctivitis by (±)5(6)-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid in mice

Background: Allergic conjunctivitis (AC) is a common ophthalmologic disorder that causes symptoms that often reduces a patient's quality of life (QOL). We investigated the effects of the eicosapentaenoic acid metabolite (±)5(6)-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid ((±)5(6)-DiHETE) on AC using a mouse model. Methods: BALB/c mice were sensitized with two injections of short ragweed pollen in alum, challenged fifth with pollen in eyedrops. The clinical signs and tear volume were evaluated at 15 min after the final challenge. Histamine-induced ocular inflammation model was prepared by instilling histamine onto the surface of the eye. Fifteen minutes after histamine application, tear volume was measured using the Schirmer tear test. Miles assay was performed to investigate vascular permeability. To cause scratching behavior 10 μg of serotonin was injected in the cheek. Results: Repeated topical application of pollen induced conjunctivitis, accompanied by eyelid edema and tearing in mice. Pollen application typically degranulates mast cells and recruits eosinophils to the conjunctiva. Intraperitoneal administration of 300 μg/kg of (±)5(6)-DiHETE significantly inhibited pollen-induced symptoms. The administration of (±)5(6)-DiHETE also attenuated mast cell degranulation and eosinophil infiltration into the conjunctiva. To assess the effects of (±)5(6)-DiHETE on the downstream pathway of mast cell activation in AC, we used a histamine-induced ocular inflammation model. Topical application of 4 μg/eye histamine caused eyelid edema and tearing and increased vascular permeability, as indicated by Evans blue dye extravasation. Intraperitoneal administration of 300 μg/kg or topical administration of 1 μg/eye (±)5(6)-DiHETE inhibited histamine-induced manifestations. Finally, we assessed the effects of (±)5(6)-DiHETE on itching. An intradermal injection of 10 μg serotonin in the cheek caused scratching behavior in mice. Intraperitoneal administration of 300 μg/kg (±)5(6)-DiHETE significantly inhibited serotonin-induced scratching. Conclusion: Thus, (±)5(6)-DiHETE treatment broadly suppressed AC pathology and could be a novel treatment option for AC.

Effects of Punctal Occlusion on Ocular Itching and Conjunctival Redness Associated with Allergic Conjunctivitis

PURPOSE

Punctal occlusion using punctal plugs has been successfully used to treat the signs and symptoms of dry eye disease. However, the effects of punctal occlusion on the symptoms of allergic conjunctivitis (AC) have been less well documented. There is some concern among clinicians that punctal occlusion may make signs/symptoms of allergic conjunctivitis worse by trapping allergens on the eye. The objective of this post hoc analysis was to address this question and thus assess the effect of punctal occlusion alone on ocular itching and conjunctival redness associated with AC.

METHODS

This was a pooled post hoc analysis of three randomized, double-blind, placebo insert-controlled clinical trials in subjects with AC. Enrolled subjects were generally healthy adults with ocular allergies and a positive skin test reaction to perennial and/or seasonal allergens. The study used a modified version of the traditional conjunctival allergen challenge (CAC) model, which included multiple, repeated allergen challenges following placement of the intracanalicular insert. Subjects were rechallenged on Days 6, 7 and 8; Days 13, 14 and 15; and Days 26, 27 and 28.

RESULTS

The data set included 128 subjects that were administered placebo. Baseline mean (SD) ocular itching and conjunctival redness scores were 3.52 (0.44) and 2.97 (0.39), respectively. On post-insertion Days 7, 14 and 28, mean itching scores were 2.62, 2.26 and 1.91, respectively, representing 26%, 36% and 46% itching reductions, respectively (p < 0.001). On Days 7, 14 and 28, mean conjunctival redness scores were 1.98, 1.90, and 2.08, respectively, representing 33%, 36%, and 30% redness reductions, respectively (p < 0.001).

CONCLUSIONS

Based on this post hoc pooled analysis, punctal occlusion with a resorbable hydrogel intracanalicular insert did not worsen ocular itching or conjunctival redness in this patient population.

TLR7 Agonists Modulate the Activation of Human Conjunctival Epithelial Cells Induced by IL-1β via the ERK1/2 Signaling Pathway

Conjunctival epithelia cells play an important role in the development of allergic reactions. TLR7 agonists have been shown in studies to increase the body's immunological tolerance by controlling the proportion of Th1/Th2 cells, although it is still unknown what impact this has on conjunctival epithelial cells. In this study, we examined the effect of TLR7 agonists on the inflammatory-activation of conjunctival epithelial cells induced by IL-1β. Quantitative PCR and ELISA analysis confirmed that TLR7 agonists could impair the proinflammatory cytokines released by the epithelia cells, whereas pro-inflammatory cytokines led to subsequent reactive oxygen species and neutrophil chemotaxis. Phosphorylation analysis and nucleocytoplasmic separation further confirmed that TLR7 agonists inhibit IL-1β-induced epithelia cells activation and ATP depletion via modulating the cytoplasmic residence of ERK1/2. Our finding indicated that TLR7 of conjunctival epithelia cells could be as a potent anti-inflammatory target for the ocular surface. And TLR7 agonists may become potential new drug for the treatment of allergic conjunctivitis.

Drug Delivery for Ocular Allergy: Current Formulation Design Strategies and Future Perspectives

The incidences of ocular allergy have been growing with the increase in pollution. Because of challenges in new drug development, there have been efforts to maximize the efficacy of existing drugs through drug delivery approaches. The effectiveness of drugs in ophthalmic conditions is primarily determined by permeability across the barrier, corneal retention, and sustained release. Thus, there have been widespread efforts to optimize these parameters to enhance efficacy through novel formulations. This review aims to analyze the approaches to drug delivery systems to encourage further research to optimize effectiveness. With this objective, research on drug delivery aspects of anti-allergy therapeutics was included and analyzed based on formulation/drug delivery technique, Food and Drug Administration approval limits, residence time, compatibility, pre-clinical efficacy, and potential for translational application. Conventional eye drops have concerns such as poor residence time and ocular bioavailability. The novel formulations have the potential to improve residence and bioavailability. However, the use of preservatives and the lack of regulatory approval for polymers limit the translational application. The review may assist readers in identifying novel drug delivery strategies and their limitations for the development of effective ophthalmic formulations for the treatment of ocular allergy.

Ciprofloxacin-Loaded Zein/Hyaluronic Acid Nanoparticles for Ocular Mucosa Delivery

Bacterial conjunctivitis is a worldwide problem that, if untreated, can lead to severe complications, such as visual impairment and blindness. Topical administration of ciprofloxacin is one of the most common treatments for this infection; however, topical therapeutic delivery to the eye is quite challenging. To tackle this, nanomedicine presents several advantages compared to conventional ophthalmic dosage forms. Herein, the flash nanoprecipitation technique was applied to produce zein and hyaluronic acid nanoparticles loaded with ciprofloxacin (ZeinCPX_HA NPs). ZeinCPX_HA NPs exhibited a hydrodynamic diameter of <200 nm and polydispersity index of <0.3, suitable for ocular drug delivery. In addition, the freeze-drying of the nanoparticles was achieved by using mannitol as a cryoprotectant, allowing their resuspension in water without modifying the physicochemical properties. Moreover, the biocompatibility of nanoparticles was confirmed by in vitro assays. Furthermore, a high encapsulation efficiency was achieved, and a release profile with an initial burst was followed by a prolonged release of ciprofloxacin up to 24 h. Overall, the obtained results suggest ZeinCPX_HA NPs as an alternative to the common topical dosage forms available on the market to treat conjunctivitis.