Inhaled flunisolide suppresses the hypothalamic-pituitary-adrenocortical axis, but has minimal systemic immune effects in healthy cats.

Feline bronchial disease is commonly treated with oral glucocorticoids (OGC), which might be contraindicated in cats with certain infectious, endocrine, renal, or cardiac diseases. Inhalant GC (IGC) maximize local efficacy and minimize systemic bioavailability. We evaluated systemic endocrine and immune effects of IGC (flunisolide, 250 microg/puff q12h) versus OGC (prednisone, 10 mg/d PO) and placebo. Six healthy cats received each drug for 2 weeks followed by a 1-month washout. Testing included determination of single early morning cortisol concentration, results of ACTH stimulation, the urine cortisol-to-creatinine ratio (UC: Cr), lymphocyte phenotype, lymphocyte blastogenesis, serum total IgA and IgM concentrations, and cytokine profiles. Significant differences between treatments were not apparent for serum immunoglobulin concentrations, or expression (mRNA) for the cytokines, interleukin (IL-) 2, IL-4, and IL-10, or gamma interferon. Single early morning cortisol concentration was lower for IGC (0.68 - 0.74 microg/dL), compared with that associated with placebo (2.82 +/- 1.94 microg/dL; P = .033). The ACTH-stimulated peak cortisol concentrations were lower after treatment in cats receiving IGC (before, 8.5 +/- 50.2 microg/dL; after, 2.9 +/- 3.3 microg/dL, P = .0004), but not OGC (before, 8.0 +/- 6.1 microg/dL; after, 6.0 +/- 4.5 microg/dL, P = .07). Similarly, UC: Cr (0.8 +/- 0.8) before IGC was lower than the value (5.02 +/- 3.62; P = .019) after IGC. Compared with placebo, cats given OGC, but not IGC, had significantly lower total percentages of T and B cells. Lymphocyte proliferation was decreased in cats receiving OGC, but not IGC, in comparison with placebo (6.9 +/- 3.3; 24.0 +/- 6.5; 18.8 +/- 14.0, respectively). Significantly more IL-10 mRNA transcription was detected in cats administered OGC or IGC, compared with placebo. Although IGC suppress the hypothalamic-pituitary-adrenocortical axis, IGC had minimal effects on the systemic adaptive immune system.

Effects of drug treatment on inflammation and hyperreactivity of airways and on immune variables in cats with experimentally induced asthma.

OBJECTIVE: To compare the effects of an orally administered corticosteroid (prednisone), an inhaled corticosteroid (flunisolide), a leukotriene-receptor antagonist (zafirlukast), an antiserotonergic drug (cyproheptadine), and a control substance on the asthmatic phenotype in cats with experimentally induced asthma. ANIMALS: 6 cats with asthma experimentally induced by the use of Bermuda grass allergen (BGA). PROCEDURES: A randomized, crossover design was used to assess changes in the percentage of eosinophils in bronchoalveolar lavage fluid (BALF); airway hyperresponsiveness; blood lymphocyte phenotype determined by use of flow cytometry; and serum and BALF content of BGA-specific IgE, IgG, and IgA determined by use of ELISAs. RESULTS: Mean +/- SE eosinophil percentages in BALF when cats were administered prednisone (5.0 +/- 2.3%) and flunisolide (2.5 +/- 1.7%) were significantly lower than for the control treatment (33.7 +/- 11.1%). We did not detect significant differences in airway hyperresponsiveness or lymphocyte surface markers among treatments. Content of BGA-specific IgE in serum was significantly lower when cats were treated with prednisone (25.5 +/- 5.4%), compared with values for the control treatment (63.6 +/- 12.9%); no other significant differences were observed in content of BGA-specific immunoglobulins among treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Orally administered and inhaled corticosteroids decreased eosinophilic inflammation in airways of cats with experimentally induced asthma. Only oral administration of prednisone decreased the content of BGA-specific IgE in serum; no other significant local or systemic immunologic effects were detected among treatments. Inhaled corticosteroids can be considered as an alternate method for decreasing airway inflammation in cats with asthma.

Concentrations of cysteinyl leukotrienes in urine and bronchoalveolar lavage fluid of cats with experimentally induced asthma.

OBJECTIVE: To evaluate changes in cysteinyl leukotriene (LT) concentrations in urine and bronchoalveolar lavage fluid (BALF) in cats with experimentally induced asthma. ANIMALS: 19 cats with experimentally induced asthma and 5 control cats. PROCEDURE: Cats were sensitized to Bermuda grass or house dust mite allergen, and phenotypic features of asthma were confirmed with intradermal skin testing, evaluation of BALF eosinophil percentages, and pulmonary function testing. A competitive ELISA kit for LTC4, LTD4, and LTE4 was used for quantitative analysis of LTs. Urinary creatinine concentrations and BALF total protein (TP) concentrations were measured, and urinary LT-to-creatinine ratios and BALF LT-to-TP ratios were calculated. RESULTS: Mean urinary LT-to-creatinine ratios did not differ significantly between control cats and allergen-sensitized cats before or after sensitization and challenge exposure with saline (0.9% NaCl) solution or allergen, respectively. In BALF the mean LT-to-TP ratio of control cats did not differ significantly before or after sensitization and challenge exposure with saline. Asthmatic cats had BALF LT-to-TP ratios that were significantly lower than control cats at all time points, whereas ratios for asthmatic cats did not differ significantly among the various time points. CONCLUSIONS AND CLINICAL RELEVANCE: Although LTs were readily detectable in urine, no significant increases in urinary LT concentrations were detected after challenge in allergen-sensitized cats. Spot testing of urinary LT concentrations appears to have no clinical benefit for use in monitoring the inflammatory asthmatic state in cats. The possibility that cysteinyl LTs bind effectively to their target receptors in BALF and, thus, decrease free LT concentrations deserves further study.

Influence of pirfenidone on airway hyperresponsiveness and inflammation in a Brown-Norway rat model of asthma.

Pirfenidone was administered to sensitized Brown Norway rats prior to a series of ovalbumin challenges. Airway hyperresponsiveness, inflammatory cell infiltration, mucin and collagen content, and the degree of epithelium and smooth muscle staining for TGF-beta were examined in control, sensitized, and sensitized/challenged rats fed a normal diet or pirfenidone diet. Pirfenidone had no effect on airway hyperresponsiveness, but reduced distal bronchiolar cell infiltration and proximal and distal mucin content. Statistical analysis showed that the control group and sensitized/challenged pirfenidone diet group TGF-beta staining intensity scores were not significantly different from isotype controls, but that the staining intensity scores for the sensitized/challenged normal diet group was significantly different from isotype controls. These results suggest that pirfenidone treatment is effective in reducing some of the components of acute inflammation induced by allergen challenge.

Proximal airway mucous cells of ovalbumin-sensitized and -challenged Brown Norway rats accumulate the neuropeptide calcitonin gene-related peptide.

Mucous cell hypersecretion and increased neuropeptide production play a role in the exacerbation of symptoms associated with asthma. The source of these neuropeptides have been confined to the contributions of small afferent nerves or possibly neuroendocrine cells. We tested the hypothesis that repeated exposure to allergen would alter the sources and abundance of neuropeptides in airways. Right middle lobes from rats (8 wk old) exposed to 2.5% ovalbumin (OVA) for five episodes (30 min each) or filtered air were inflation fixed with paraformaldehyde. The lobes were dissected to expose the airway tree, permeabilized with DMSO, and incubated in antibody to rat calcitonin gene-related peptide (CGRP), followed with a fluorochrome-labeled second antibody. CGRP-positive structures were imaged via confocal microscopy. Airways were later embedded in plastic and sectioned for cell identification. In animals challenged with OVA, CGRP-positive cells, not neuroendocrine or neuronal in origin (confirmed by a lack of protein gene product 9.5 signal), were recorded along the axial path. In section, this fluorescent signal was localized to granules within epithelial cells. Alcian blue/periodic acid-Schiff staining of these same sections positively identify these cells as mucous cells. Mucous cells of animals not challenged with OVA were not positive for CGRP. We conclude that episodic allergen exposure results in the accumulation of CGRP within mucous cells, creating a new source for the release of this neuropeptide within the airway.

An experimental model of allergic asthma in cats sensitized to house dust mite or bermuda grass allergen.

BACKGROUND: Animal models are used to mimic human asthma, however, not all models replicate the major characteristics of the human disease. Spontaneous development of asthma with hallmark features similar to humans has been documented to occur with relative frequency in only one animal species, the cat. We hypothesized that we could develop an experimental model of feline asthma using clinically relevant aeroallergens identified from cases of naturally developing feline asthma, and characterize immunologic, physiologic, and pathologic changes over 1 year. METHODS: House dust mite (HDMA) and Bermuda grass (BGA) allergen were selected by screening 10 privately owned pet cats with spontaneous asthma using a serum allergen-specific IgE ELISA. Parenteral sensitization and aerosol challenges were used to replicate the naturally developing disease in research cats. The asthmatic phenotype was characterized using intradermal skin testing, serum allergen-specific IgE ELISA, serum and bronchoalveolar lavage fluid (BALF) IgG and IgA ELISAs, airway hyperresponsiveness testing, BALF cytology, cytokine profiles using TaqMan PCR, and histopathologic evaluation. RESULTS: Sensitization with HDMA or BGA in cats led to allergen-specific IgE production, allergen-specific serum and BALF IgG and IgA production, airway hyperreactivity, airway eosinophilia, an acute T helper 2 cytokine profile in peripheral blood mononuclear cells and BALF cells, and histologic evidence of airway remodeling. CONCLUSIONS: Using clinically relevant aeroallergens to sensitize and challenge the cat provides an additional animal model to study the immunopathophysiologic mechanisms of allergic asthma. Chronic exposure to allergen in the cat leads to a variety of immunologic, physiologic, and pathologic changes that mimic the features seen in human asthma.