Compound 48/80-induced conjunctivitis in the mouse: kinetics, susceptibility, and mechanism

Inhibitory effect of hydroalcoholic extract of Cunila spicata Benth. on phlogistic agents-induced cellular migration in the airways of mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cunila spicata Benth. Is a creeping and aromatic plant that has an ethnopharmacological indication in the southern region of Brazil, in the Araucaria Forest biome. It's used as an alternative therapy for respiratory diseases for men and animals since the "tropeirista" movement in colonial Brazil.

AIM OF THE STUDY

Investigate the influence of oral administration of hydroalcoholic extract of C. spicata (HECS) on cellular inflammatory processes in the airways of mice.

MATERIAL AND METHODS

The HECS was obtained by the ultrasound-assisted technique. Phytochemical analysis of the volatile compounds was performed using gas-chromatography with mass spectrometry. To investigate the biological activity of HECS, the animals were pre-treated with HECS orally 1 h before and the bronchoalveolar lavage (BAL) model was used, in which the animals were subjected to inhalation of different pro-inflammatory agents such as carrageenan (CAR), histamine (HIST), capsaicin (CAP), bradykinin (BK), and 48/80 compound (C48/80). After sacrifice, BAL sample was collected from the bronchi and was analyzed for total and differential white blood cell counts, compared with control groups.

RESULTS

Fourteen volatile phytocompounds were identified in the HECS, the main ones being 2-bornanone, menthofuran and camphene. Among the HECS treated animals, all showed significant maximal inhibition (MI) when challenged with pro-inflammatory agents by nebulization. In the group of animals that received CAR, the MI was 72.77 ± 3.88%, compared to the negative control (NC). There was a predominance of lymphocytes (59.18 ± 4.07%). For the HIST group, MI was 64.03 ± 4.33%, in relation to the NC, with predominance in macrophages number (76.53 ± 2.78%). In the CAP group, the MI obtained was 38.90 ± 11.31%, with greater macrophage migration occurring (80.98 ± 3.44%) in the higher dose. For animals subjected to BK inhalation, the MI was 48.63 ± 3.95% with macrophages predominance (64.33 ± 10.04%). In the group that received C48/80 inhalation, the MI was 40.25 ± 5.30% (100 mg kg^-1), with higher occurrence of macrophages (72.97 ± 4.23%).

CONCLUSION

Our results suggest that HECS had a non-specific inhibitory effect on cellular migration induced by different pro-inflammatory agents, reducing inflammation in airways of mice. These effects coincide and support its ethnopharmacological use as an alternative medicine for respiratory diseases in regions where the plant is prevalent.

IL-10 confers protection from mast cell degranulation in a mouse model of allergic conjunctivitis

IL-10 is a regulatory cytokine known to inhibit allergic and inflammatory events. Mast cells (MC) are effector cells which when stimulated release histamine, chemokines and cytokines that initiate the allergic inflammatory response. Recent studies have shown that IL-10 regulates MC function by affecting cytokine production and expression of FcvarepsilonR1 in in vitro assays. Using IL-10 knockout (IL10KO) mice, we examined the effect of its absence on MC susceptibility to degranulation by the basic secretagogue, Compound 48/80 (C48/80). C48/80 is a receptor mimetic that directly activates G proteins and stimulates vigorous MC degranulation. For these studies we stimulated conjunctival MC with C48/80 and found that conjunctival MC of IL10KO mice exhibit increased degranulation compared with wild type mice. Reconstitution of IL10KO mice by adding rIL-10 24h prior to challenge with C48/80 conferred increased resistance of MC to the degranulatory effects of C48/80. The protective effect therefore appears to be due to the presence of IL-10. This is the first in vivo rodent study which reports a novel role of IL-10 in stabilizing mast cells from degranulation by a secretagogue, by as of yet an unknown mechanism.

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.

Nadroparine inhibits the hypersensitivity response in the conjunctiva

This study sought to investigate the effects of nadroparine on an in vivo experimental model of type I hypersensitivity response in the rat conjunctiva. Following drug application onto the eye, either before or after challenge with the mast cell degranulator, basic polyamine compound 48/80, the conjunctival histamine content and the nitrite levels in the conjunctival lavage fluid were quantified fluorometrically and spectrophotometrically, respectively. Instillation into the eye of nadroparine inhibited the C48/80-induced decreases in conjunctival histamine and the delayed increases in nitrite levels, without influencing basal mediator levels. Protamine did not induce histamine release and only partially reversed the effects of nadroparine post-challenge, yet it had no effect on the protective action of the drug when administered prior to degranulation. The results showed that nadroparine was equally effective in attenuating the effects of compound 48/80 in the eye when administered topically either before or after challenge.

Animal models of ocular allergy

PURPOSE OF REVIEW

This review focuses on reports on animal models of ocular allergy published within the past year. A number of animal models are currently being used to clarify the pathophysiology of ocular allergy and to improve the therapeutic interventions for this disease.

RECENT FINDINGS

Published literature examined the role of cytokines and other effector molecules which drive the immunopathology of ocular allergies in several animal models. Animal models were also used to compare the safety and efficacy of currently available drugs, and were utilized in initial trials of novel therapeutic agents. Novel therapeutic options being studied include DNA immunizations and recombinant peptides that block enzymes involved in the inflammatory processes.

SUMMARY

Several animal models are currently being used in the study of ocular allergy. These include different strains within the mouse, rat, guinea pig, rabbit and dog species. Continuing investigations are needed to elucidate the complex molecular and cellular processes involved in the pathogenesis of ocular allergies. A better understanding of the interplay of effector cells, cytokines, adhesion molecules and a number of other inflammatory mediators will broaden our knowledge of the pathophysiology of ocular allergy and allow improved therapeutic options for this disease.

Mast-cell activation augments the late phase reaction in experimental immune-mediated blepharoconjunctivitis

BACKGROUND

How the early phase allergic reaction affects the late phase reaction remains unclear. We examined this issue with an experimental model of allergic conjunctivitis that permits the two reactions to be disconnected from each other.

METHODS

Experimental immune-mediated blepharoconjunctivitis (EC) was initiated in Brown Norway rats by transferring ovalbumin (OVA)-specific T cells and then challenging with OVA-containing eye drops. To induce early phase reaction, a mast-cell activator, C48/80, was challenged together with or without OVA. Rats were evaluated clinically and eyes were harvested for histologic examination and for evaluation of chemokine expression by reverse-transcriptase PCR.

RESULTS

The rats challenged with OVA alone developed the T-cell-mediated late phase reaction histologically, but not clinically, in the absence of early phase reaction. While rats challenged with C48/80 with or without OVA exhibited clinical signs of the early phase reaction, the clinical late phase reaction was observed only in the OVA+C48/80 group. Eosinophilic infiltration into the conjunctiva during the late phase reaction of the OVA+C48/80 group markedly exceeded that of rats challenged with either OVA or C48/80 alone. RANTES (regulated on activation, normal T-cell expressed and secreted), an eosinophil attractant, was expressed both in the OVA+C48/80 and OVA groups, while eotaxin was expressed at equivalent levels in all three groups.

CONCLUSION

The mast-cell-mediated early phase reaction potentiates the T-cell-mediated late phase reaction, and RANTES is involved in eosinophilic infiltration induced by antigen-specific T cells. Other molecules induced by allergen-specific T cells activated in an as yet unknown manner by the mast cells may be responsible for the infiltration of eosinophils.

Therapeutic applications of antiflammin peptides in experimental ocular inflammation

Antiflammins are synthetic peptides derived from the region of highest local similarity between uteroglobulin and lipocortin. These peptides have shown anti-inflammatory activity on carrageenan-induced rat footpad edema. They are potent inhibitors for phospholipase A2 activation both in vitro and in vivo. Previously, we have demonstrated the effectiveness of topical antiflammins in suppressing acute ocular inflammation and allergic response in rodent endotoxin-induced uveitis and murine allergic conjunctivitis. The mechanisms by which antiflammins protect against inflammation and allergy in these ocular models may involve inhibition of phospholipase A2 and inducible nitric oxide synthase (iNOS) as well as the production of proinflammatory cytokine, interleukin-6.

Allergic and immunologic disorders of the eye. Part I: immunology of the eye

Immuno-ophthalmology evolved during the 20th century as a subspecialty linking ophthalmologists and immunologists. This emerging subspecialty has focused on the use of immunology to better understand and treat ocular disorders. To help the allergist/clinical immunologist better appreciate the growing field of immuno-ophthalmology, this 2-part review series (Part II: Ocular Allergy will appear in the December issue of the Journal) will provide an overview of the impact that immunology has had on our understanding and treatment of allergic and immunologic eye diseases. The current review will focus on mechanisms by which mast cells, T cells, eosinophils, cytokines, and other inflammatory constituents contribute to the unique features of eye disease and their link to allergic responses that occur in other organs of the body.

Changes in histamine content following pharmacologically-induced mast cell degranulation in the rat conjunctiva

Compound 48/80 was applied into one eye of male Wistar rats and a drop of vehicle into the contralateral eye. Another group of rats received sodium cromoglycate in both eyes every 6 h for a period of 48 h. One eye was challenged with compound 48/80 30 min after the end of treatment with sodium cromoglycate. The eyes were monitored clinically and the histamine content of the conjunctiva was determined fluorometrically. The basal histamine levels in rat conjunctival homogenates were quantified. Pharmacologically-induced mast cell degranulation by a single application of 0.1 g ml(-1)of compound 48/80 resulted in significant decreases of conjunctival histamine levels 1, 12 and 24 h after challenge. Sodium cromoglycate prevented the effect of compound 48/80 when administered into the eye prior to the challenge with the non-immunogenic histamine releaser. Upon termination of the application, the membrane stabilizer was unable to reverse the reduced histamine levels in the conjunctival homogenates.

Establishment of T-helper type 2 clone-induced eosinophilia in mouse conjunctiva

Eosinophil infiltration is one of the aspects of the inflammatory response to an allergen. The aim of this study was to establish T-helper type-2 (Th2)-induced conjunctival eosinophilia in mice to evaluate the effect of anti-allergic drugs. Th2 clone, D10.G4.1. (D10) with its specific antigen, conalbumin was co-injected into conjunctival tissue in mice. At 3-6 hr after D10 injection, eosinophil and neutrophil recruitment into conjunctival tissue was observed. Cellular infiltration into conjunctival tissue reached a maximum level between 24-48 hr after D10 injection. The number of eosinophils which infiltrated after 24 hr was dose dependent on T cell injection titer from 1x10(4), 1x10(5)to 1x10(6)cells site-1. The ratio of eosinophils to neutrophils at 24 hr after D10 cell (1x10(5)cells site-1) injection was about 9 to 1. The eosinophil infiltration into conjunctival tissue was significantly reduced by the intraperitoneal administration of anti-IL-5 monoclonal antibody (100 micrograms animal-1). Anti-IL-4 monoclonal antibody (500 micrograms animal-1) partially inhibited eosinophilia. The combined inhibitory effect of anti-IL-4 and anti-IL-5 monoclonal antibodies was larger than the inhibitory effect of anti-IL-5 monoclonal antibody alone. In conclusion, a Th2-induced mouse conjunctival eosinophilia model was established in which D10 activation results in IL-4 and IL-5 release. These cytokines elicit eosiniophil infiltration. This response shows that the model will be effective for screening candidates of anti-allergic drugs.

A novel murine model of allergic conjunctivitis

Allergic conjunctivitis affects over 40 million patients per year in the United States. Here we present the first murine model that incorporates the clinical, cellular, and humoral parameters of allergic conjunctivitis, including a ragweed-induced Th2-type cytokine production by lymphocytes. SWR/J mice were immunized with short ragweed pollen in aluminum hydroxide. Ten days after immunization, allergic conjunctivitis was induced by one topical application of ragweed pollen onto the eye. Immediate response was characterized by chemosis, redness of the conjuctiva, and lid edema. Histopathology and immunohistochemistry showed dense conjunctival infiltration with polymorphonuclear leukocytes, macrophages, and CD4+ T lymphocytes. In addition, ragweed-specific IgG1 and IgE serum levels were significantly higher in immunized animals, and high levels of IL-4 and IL-5 were detected in supernatants from ragweed-activated lymphocytes. This reproducible model is a well-suited instrument for testing the pathophysiology and future therapies of allergic conjunctivitis.