Tear Histamine and Histaminase during the Early (Epr) and Late (Lpr) Phases of the Allergic Reaction and the Effects of Lodoxamide

Resolvin D2 and Resolvin D1 Differentially Activate Protein Kinases to Counter-Regulate Histamine-Induced [Ca2+]i Increase and Mucin Secretion in Conjunctival Goblet Cells

Resolvin (Rv) D2 and RvD1 are biosynthesized from docosahexaenoic acid (DHA) and promote resolution of inflammation in multiple organs and tissues, including the conjunctiva. Histamine is a mediator produced by mast cells in the conjunctiva during the allergic response. We determined the interaction of RvD2 with histamine and its receptor subtypes in cultured conjunctival goblet cells and compared them with RvD1 by measuring intracellular [Ca²⁺] and mucous secretion. Treatment with RvD2 significantly blocked the histamine-induced [Ca²⁺]_i increase as well as secretion. RvD2 and RvD1 counter-regulate different histamine receptor subtypes. RvD2 inhibited the increase in [Ca²⁺]_i induced by the activation of H1, H3, or H4 receptors, whereas RvD1 inhibited H1 and H3 receptors. RvD2 and RvD1 also activate distinct receptor-specific protein kinases to counter-regulate the histamine receptors, probably by phosphorylation. Thus, our data suggest that the counter-regulation of H receptor subtypes by RvD2 and RvD1 to inhibit mucin secretion are separately regulated.

Acute keratoconjunctivitis due to contamination of contact lens care solution with histamine-producing Raoultella species: A case report

RATIONALE

Contact lens storage cases are known to be contaminated by a significant number of bacteria. However, histamine-producing Raoultella species has not been reported to contaminate contact lens storage case.

PATIENT CONCERNS

A 27-year-old woman with keratoconjunctivitis that developed in the left eye owing to a cosmetic contact lens and poor hygiene was referred to our hospital. The corrected visual acuity was hand motion.

DIAGNOSES

Corneal infection other than Acanthamoeba keratitis (AK) and corneal hypoxia were excluded.

INTERVENTIONS

We initiated empirical therapy for AK, although no cysts or trophozoites were detected in the cornea and in the lens care solution. Analysis of 16S rDNA sequences from the lens care solution yielded the highest homology with Raoultella species, which are histamine-producing bacteria. Histamine was estimated to be 492 ng/mL in the lens care solution.

OUTCOMES

Her clinical course was distinct from that of usual AK cases. The corrected visual acuity increased up to (1.2) only 5 days after initiating empirical therapy.

LESSONS

To our knowledge, this is the first report to indicate an association between histamine-producing bacteria and keratoconjunctivitis. We should pay an attention to the microbial contamination of contact lens storage cases by histamine producing bacteria.

Conjunctival allergen provocation test : guidelines for daily practice

Conjunctival allergen provocation test (CAPT) reproduces the events occurring by instilling an allergen on the ocular surface. This paper is the compilation of a task force focussed on practical aspects of this technique based on the analysis of 131 papers. Main mechanisms involved are reviewed. Indications are diagnosing the allergen(s)-triggering symptoms in IgE-mediated ocular allergy in seasonal, acute or perennial forms of allergic conjunctivitis, especially when the relevance of the allergen is not obvious or in polysensitized patients. Contraindications are limited to ongoing systemic severe pathology, asthma and eye diseases. CAPT should be delayed if receiving systemic steroids or antihistamines. Local treatment should be interrupted according to the half-life of each drug. Prerequisites are as follows: obtaining informed consent; evidencing of an allergen by skin prick tests and/or serum-specific IgE dosages; being able to deal with an unlikely event such as acute asthma exacerbation, urticaria or anaphylaxis, or an exacerbation of allergic conjunctivitis. Allergen extracts should be diluted locally prior to administration. Positive criteria are based on itching or quoted according to a composite score. An alternative scoring is based on itching. CAPT remains underused in daily practice, although it is a safe and simple procedure which can provide valuable clinical information.

Vernal keratoconjunctivitis: a severe allergic eye disease with remodeling changes

Vernal keratoconjunctivitis (VKC) is an unusually severe sight-threatening allergic eye disease, occurring mainly in children. Conventional therapy for allergic conjunctivitis is generally not adequate for VKC. Pediatricians and allergists are often not familiar with the severe clinical symptoms and signs of VKC. As untreated VKC can lead to permanent visual loss, pediatric allergists should be aware of the management and therapeutic options for this disease to allow patients to enter clinical remission with the least side effects and sequelae. Children with VKC present with severe ocular symptoms, that is, severe eye itching and irritation, constant tearing, red eye, eye discharge, and photophobia. On examination, giant papillae are frequently observed on the upper tarsal conjunctiva (cobblestoning appearance), with some developing gelatinous infiltrations around the limbus surrounding the cornea (Horner-Trantas dot). Conjunctival injections are mostly severe with thick mucus ropy discharge. Eosinophils are the predominant cells found in the tears and eye discharge. Common therapies include topical antihistamines and dual-acting agents, such as lodoxamide and olopatadine. These are infrequently sufficient and topical corticosteroids are often required for the treatment of flare ups. Ocular surface remodeling leads to severe suffering and complications, such as corneal ulcers/scars. Other complications include side effects from chronic topical steroids use, such as increased intraocular pressure, glaucoma, cataract and infections. Alternative therapies for VKC include immunomodulators, such as cyclosporine A and tacrolimus. Surgery is reserved for those with complications and should be handled by ophthalmologists with special expertise. Newer research on the pathogenesis of VKC is reviewed in this article. Vernal keratoconjunctivitis is a very important allergic eye disease in children. Complications and remodeling changes are unique and can lead to blindness. Understanding of pathogenesis of VKC may lead to better therapy for these unfortunate patients.

Histamine H4 receptors in normal conjunctiva and in vernal keratoconjunctivitis

BACKGROUND

While it is known that histamine is the primary mediator of ocular allergy, the presence and distribution of histamine receptors are not well documented in the human eye. Our aim was to evaluate histamine receptor expression in normal and vernal keratoconjunctivitis conjunctiva.

METHODS

Mucosal biopsies were obtained from conjunctiva of healthy donors and from tarsal conjunctiva of vernal patients. Immunostaining and semi-quantitative reverse-transcriptase polymerase chain reaction for H(1), H(2), H(3), and H(4) receptors were performed. Histamine receptor expression was also evaluated in conjunctival cell cultures exposed to histamine, interleukin-4, interleukin-5, interferon-γ and tumor necrosis factor-α.

RESULTS

Immunostaining for H(1) and H(2) receptors was slightly positive in normal and over-expressed in vernal tissues. H(3) receptors were rarely present in normal and inflamed conjunctiva. In striking contrast to control tissues, H(4) receptors were highly expressed in all inflamed tissues, particularly by stromal inflammatory cells. Semi-quantitative reverse-transcriptase polymerase chain reaction demonstrated an over-expression of H(1), H(2), and H(4) receptors in vernal vs control tissues. Notably, H(4) receptors were five times more expressed in vernal vs control tissues. In cell cultures, H(2) receptor expression was stimulated eight times the normal levels by interleukin-4 and three times by histamine, but the H(4) receptor was only slightly affected by stimulation with these mediators.

CONCLUSIONS

Increased expression of H1, and particularly of H(2) and H(4) receptors in vernal keratoconjunctival tissues indicate their important role in the pathogenesis of this disease. H(4) receptors may be a target in the treatment of allergic inflammation.

Effect of aminoguanidine on the conjunctival histamine and nitrite levels in experimental conjunctivitis

PURPOSE

Histamine and nitric oxide (NO) play pivotal roles in ocular surface hypersensitivity reactions, whereas the activity of their metabolic enzymes diamine oxidase (DAO) and NO synthase (NOS) may affect their function. This study aimed at investigating the effects of ocular administration of aminoguanidine (AMG), a multiple action DAO and NOS inhibitor, on the conjunctival histamine and nitrite levels in a model of experimental conjunctivitis.

METHODS

AMG, at 0.81, 81 or 81×10(3) μM, was instilled into the lower conjunctival fornix of normal and compound 48/80 (C48/80)-challenged eyes of male Wistar rats in the absence or presence of 40 mg/mL disodium cromoglycate. Histamine and nitrite were quantified in the conjunctival homogenate and lavage fluid 45 min and 6 h postchallenge, respectively.

RESULTS

AMG induced no significant alterations in basal histamine and nitrite levels in the normal rat eye. In experimental conjunctivitis, AMG failed to modify the reduction in histamine content and partially circumvented the increases in nitrite levels observed during the early and late phase reactions, respectively. In the presence of disodium cromoglycate, AMG significantly increased the levels of both proinflammatory mediators in the normal rat eye.

CONCLUSIONS

The data suggested that DAO may not be the main route of in situ histamine catabolism in the normal and C48/80-challenged rat conjunctiva, whereas NOS contributes to the phenotypic alterations observed in mast cell-dependent conjunctivitis. Mast cell stabilizing agents and AMG-modulated systems seem to interact through yet undefined mechanisms in the different phases of ocular hypersensitivity reactions.

Late-phase reaction in ocular allergy

PURPOSE OF REVIEW

To determine if the late-phase reaction, which commonly occurs in allergic rhinitis and asthma, is also found in ocular allergy.

RECENT FINDINGS

Using PubMed, 542 articles were found; 18 articles in the allergy and ophthalmology literature were specifically related to late-phase reaction. Ocular late-phase reaction is clinically seen in 50-100% of allergic rhinoconjunctivitis patients, is associated with progression to systemic atopic disorders that is allergic rhinoconjunctivitis and occurs in several forms including biphasic, multiphasic and a prolonged response.

SUMMARY

The existing literature demonstrates that an ocular late-phase reaction also exists and has implications in the development severity of disease, change of reactivity and progression of the atopic disease state from a localized target organ, such as the nose or eye, to a more systemic atopic disorder. The existence of the clinically relevant allergic late-phase response is not only limited to the nose, skin and lungs but also includes the eyes. The appreciation that the late-phase response may be clinically very important as there is a continuum of ocular mast-cell activation during the waking hours of the day, a better understanding of its clinical impact may be a more appropriate focus in the development of future treatments.

Les tests de provocation conjonctivaux

The conjunctival provocation test (CPT) is a human model of ocular allergy that has been used to study the ocular response to allergenic stimuli and to evaluate antiallergic therapy. Considerable useful information has been gained on the ocular allergic response and drug efficacy using the conjunctival provocation test and naturally occurring seasonal allergic conjunctivitis. The safety and the efficacy of these CPTs has resulted in many authors using this tool in the etiologic diagnosis of allergic conjunctivitis. This article summarizes the possibilities of these CPTs as a tool for the study, evaluation, diagnosis, and therapeutic follow-up of allergic conjunctivitis.

Allergic diseases of the eye

The prevalence of ocular allergy is clearly underappreciated; it has been an underdiagnosed and undertreated area in primary care medicine. The ocular symptoms associated with the most common ocular allergy conditions,such as seasonal and perennial AC, are twice as likely to affect the allergy sufferer as nasal symptoms alone. The emergence of new medications for the specific treatment of ocular symptoms over the course of the past 15 years offers a new field for improved patient care by the primary and sub-specialty health care providers.

The central role of conjunctival mast cells in the pathogenesis of ocular allergy

Ocular allergic diseases are characterized by specific activation of conjunctival mast cells with subsequent release of preformed and newly formed mediators. Mast-cell numbers on the ocular surface are increased in all forms of allergic conjunctivitis. Mast-cell activation plays a central role in the development of the ocular allergic reaction, which can be divided into an early and a late inflammatory phase. Mast-cell mediators have been measured in tears of patients suffering from various forms of allergic conjunctivitis, and in sensitized patients after specific ocular allergen challenge. Histamine and tryptase are the most studied mediators in tears of allergic patients. Several cytokines, such as IL-4 and TNF-a, are also produced and released by conjunctival mast cells, and probably play a role in the immunoregulation on the ocular surface. In vitro studies of the characteristics and biologic functions of conjunctival mast cells highlight their central role in the pathogenesis of ocular allergy, and have led to new opportunities to evaluate anti-allergic compounds. This review discusses the role of conjunctival mast cells in the development of ocular allergic diseases.

Efficacy and safety of desonide phosphate for the treatment of allergic conjunctivitis

PURPOSE

To study the safety and efficacy of the topical corticosteroid, desonide 0.25% ophthalmic solution, for inhibition of the clinical allergic reaction induced by conjunctival provocation (CPT) and for the treatment of seasonal allergic conjunctivitis (SAC).

METHODS

For the CPT study, 12 allergic but inactive patients were exposed in both eyes to increasing doses of a specific allergen until a positive bilateral, symmetrical early- and late-phase reaction was obtained. After 2 weeks the last positive dose was readministrated and their positive response confirmed. After an additional 2 weeks, CPT was performed 30 minutes after topical administration of desonide in one eye and placebo in the contralateral eye (Group A) or after topical desonide or placebo four times a day for 2 days (Group B). Clinical signs and symptoms were recorded after 15, 30, and 60 minutes, and after 6 hours. Regarding the seasonal study, 96 patients with active SAC were treated bilaterally with either desonide or fluorometholone for 3 weeks, and allergic signs and symptoms evaluated at regular intervals. The safety of the drugs was assessed by identification of any side effects or adverse events of any kind.

RESULTS

For the CPT study: individual itching and redness, and the sum score for signs and symptoms were all statistically (p < 0.05) and clinically (greater than 1 change between treated eyes) significantly lower in desonide versus placebo eyes. Both early- and late-phase reactions were reduced by desonide pretreatment. Seasonal study: desonide and fluorometholone were both highly effective in reducing itching, tearing, and conjunctival hyperemia over time (p < 0.0001). Both drugs appeared safe, with no statistically significant changes in IOP observed with either treatment.

CONCLUSIONS

Desonide has a significant therapeutic effect on both the induced conjunctival early- and late-allergic reaction and in active SAC. It was also safe, with no side effects such as increases in intraocular pressure observed by physician or patient.

Update on ocular allergy treatment

Allergy affects > 15% of the world population with a higher prevalence of 30% in westernised industrialised countries, such as the US. Allergy commonly affects various target organs including the eyes, nose, sinuses, ears, lungs and skin. However, the ocular component may be the most common and initially the most prominent disabling feature. Some patients are affected for only a few weeks to months while others have symptoms that last throughout the year. The associated healthcare costs related to allergic conjunctivitis has been commonly nestled with allergic rhinitis and has been reported to be as high as US$5.9 billion in the US, with 25% (US$1.5 billion) of it related to medication use. The expenditures related to ocular prescription medication has only recently risen in the past decade from US$6 million in early 1990s to > US$200 million in the new millennium with a projected continuous expansion of 25% per year. This appears to be due to improved prescription medications and their clear benefit over the less efficacious over-the-counter products. The actual cost of the medications and their relative price increases over the past year have ranged from 0 - 49% with an average cost of < US$ day. The newer topical medications (multiple acting agents) are focusing on multiple actions that include an antihistaminic effect to provide an immediate relief and additional delayed effects to act on the mediators of the late phase reaction without steroid side effects (glaucoma, cataracts). The paradigm for the treatment of ocular allergy ranges from primary measures (avoidance measures, cold compresses and lubrication), to secondary measures (various combination of topical agents) and tertiary measures that would include topical steroids and immunotherapy. The increased interest in advancing ocular treatment will lead to the development of additional therapies, novel pharmacokinetic delivery systems and, thus, improved healthcare outcomes for patients with allergic conjunctivitis.

Comparison of the clinical efficacy and comfort of olopatadine hydrochloride 0.1% ophthalmic solution and nedocromil sodium 2% ophthalmic solution in the human conjunctival allergen challenge model

BACKGROUND

Mast cell stabilizers, such as the ocular antiallergic agent nedocromil sodium 2% ophthalmic solution, are not rapid acting and often require a loading period of > or =2 weeks for maximal efficacy. Olopatadine hydrochloride 0.1% ophthalmic solution is a member of a new class of topical antiallergic agents that have combined antihistaminic and mast cell-stabilizing properties.

OBJECTIVE

The purpose of this study was to compare the clinical efficacy and comfort of olopatadine with those of nedocromil in the conjunctival allergen challenge model.

METHODS

This was a single-center, 3-visit, randomized, double-masked, contralaterally controlled study. Seventy-five subjects with a history of allergic conjunctivitis were screened, and the 52 who responded to conjunctival allergen challenge at visits I and 2 were randomized by eye to receive olopatadine, nedocromil, or placebo (a "natural tears" lubricant eye drop). Because nedocromil may require a 2-week loading period for maximal efficacy, the eyes assigned to that agent received nedocromil for 14 days (between visits 2 and 3), whereas the eyes assigned to olopatadine or placebo received placebo during this period. Throughout the loading phase, subjects instilled 1 drop of the assigned masked medication in each eye twice daily. At the assessment visit (visit 3), subjects received I drop of masked olopatadine, nedocromil, or placebo in each eye and were asked to rate the comfort of each drop on a scale from 0 to 8. Fifteen minutes after instillation of medication, subjects were challenged with the allergen concentration that had elicited a positive conjunctival allergic response at the previous visits. Subjects then scored their itching on a scale from 0 to 4 at 3, 5, and 10 minutes after challenge. Mean itching scores for all eyes were compared by treatment. Paired t tests were performed on the mean itching and ocular comfort scores at each time point. At the end of the study, subjects were asked which treatment they preferred in terms of comfort and efficacy.

RESULTS

Forty-nine subjects completed the study. Forty eyes received olopatadine, 36 received nedocromil, and 22 received placebo. Olopatadine was clinically and statistically superior to nedocromil at reducing itching in the conjunctival allergen challenge model (mean unit difference: -1.60 at 3 minutes, -1.68 at 5 minutes, -1.19 at 10 minutes; P < 0.001). One drop of olopatadine was more efficacious than 29 drops of nedocromil. Olopatadine-treated eyes were rated as being significantly more comfortable than nedocromil-treated eyes (0.73 vs 1.55; P = 0.034). Of the 14 subjects treated with olopatadine and nedocromil who stated a preference, 10 (71%) were more satisfied with olopatadine than with nedocromil.

CONCLUSION

In the conjunctival allergen challenge model, olopatadine was more efficacious and comfortable than nedocromil in reducing the itching associated with allergic conjunctivitis.

Tear and serum soluble leukocyte activation markers in conjunctival allergic diseases

PURPOSE

To measure markers of leukocyte activation in patients with an exclusively ocular inflammatory or bacterial disease.

METHODS

Neutrophil myeloperoxidase, eosinophil cationic protein, eosinophil neurotoxin, and soluble interleukin-2 receptor were measured in serum and tears of 17 patients with allergic vernal keratoconjunctivitis, seven with atopic keratoconjunctivitis, 11 with seasonal allergic conjunctivitis, seven with giant papillary conjunctivitis, 13 with rosacea blepharokeratoconjunctivitis, seven with bacterial conjunctivitis, and 13 normal subjects as controls.

RESULTS

In serum of patients with vernal and atopic keratoconjunctivitis, levels of eosinophil cationic protein, eosinophil neurotoxin, and interleukin-2 receptor were significantly increased compared with control subjects but were not correlated with the severity of ocular symptoms. In tears of patients with vernal and atopic keratoconjunctivitis and seasonal allergic conjunctivitis, as well as in the nonallergic diseases, rosacea blepharokeratoconjunctivitis and bacterial conjunctivitis, levels of eosinophil cationic protein, neurotoxin, and interleukin-2 receptor were significantly increased compared with control subjects. The highest values of these markers were found in vernal keratoconjunctivitis samples. Neutrophil myeloperoxidase was significantly increased in vernal and atopic keratoconjunctivitis, rosacea blepharokeratoconjunctivitis, and bacterial conjunctivitis. In vernal keratoconjunctivitis, tear markers were correlated to the clinical score of the disease, but not with cytology.

CONCLUSIONS

Tear histamine was measured in 10 allergic patients after allergen challenge. Although none of the above markers can be considered specific to a single disease, their measurement may still be useful for the quantification of local cell activation in ocular inflammatory diseases.