Bacterial mastitis is accompanied by a drastic increase in milk somatic cell count (SCC), with neutrophils being the predominant cell type found in the infected quarters. Accumulation and activation of neutrophils at the site of infection require local expression of many inflammatory genes encoding adhesion molecules, chemokines and cytokines. Most of the inflammatory genes contain binding sites for the nuclear factor kappaB (NF-kappaB) within their promoter and therefore partly depend on NF-kappaB for their expression. We thus hypothesized that an increase in NF-kappaB activity in the mammary gland could contribute to development of the neutrophilic inflammation that characterizes mastitis. In an attempt to verify this hypothesis, we first assessed milk cells from healthy and acute and chronic mastitis-affected cows for NF-kappaB activity using electrophoretic mobility shift assays. We next studied the relationships between the intensity of NF-kappaB activity in these cells and the degree of udder inflammation. Active NF-kappaB complexes were undetectable in milk cells from healthy cows, whereas high levels of NF-kappaB activity were always found in cells from cows with acute mastitis. In milk cells obtained from chronic mastitis-affected cows, NF-kappaB activity varied from low to high. Finally, the level of NF-kappaB activity measured in milk cells from chronic mastitis-affected cows was not correlated to SCC or to the proportion of neutrophils present in milk samples, but was highly correlated with the expression level of interleukin-8 and granulocyte/macrophage colony-stimulating factor, two NF-kappaB-dependent cytokines crucially involved in initiation and perpetuation of neutrophilic inflammation. These results suggest that NF-kappaB might play a role in mastitis pathogenesis.

Glucocorticoid (GC) therapy is recognized to be effective for the treatment of recurrent airway obstruction (RAO) in horses. Anti-inflammatory properties of GC are thought to be mediated by suppression of inflammatory gene expression via inhibition of transcription factors such as nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). The purpose of this study was to evaluate the effect of low-dose inhaled beclomethasone dipropionate and injectable dexamethasone 21-isonicotinate on clinical signs, pulmonary function, airway cytology, and activity of NF-kappaB and AP-1 in bronchial cells of RAO-affected horses. Seven horses with RAO were exposed to moldy hay until they developed airway obstruction on 3 separate occasions. In a crossover design, they were then treated with a placebo (injection on day 1), inhaled beclomethasone (500 microg q12h for 10 days), or dexamethasone (0.06 mg/kg, IM on day 1) and monitored for 10 days. Pulmonary function, bronchoalveolar lavage fluid cytology, and NF-kappaB and AP-1 activity in bronchial brushing cells were measured before (day 1) and after treatment (day 10). Treatment with beclomethasone resulted in significantly improved pulmonary function of RAO-affected horses compared with placebo and dexamethasone treatments. However, none of the treatments had an effect on bronchoalveolar lavage fluid cytology or NF-kappaB and AP-1 activity. These findings reveal that, in a model of severe RAO, the benefits of low-dose inhaled beclomethasone on pulmonary function are not accompanied by a decrease in airway inflammatory cells or a suppression of transcription factors NF-kappaB and AP-1 DNA-binding activity.

Glucocorticoid (GC) therapy is recognized to be effective for the treatment of recurrent airway obstruction (RAO) in horses. Anti-inflammatory properties of GC are thought to be mediated by suppression of inflammatory gene expression via inhibition of transcription factors such as nuclear factor-kB (NF-kB) and activator protein-1 (AP-1). The purpose of this study was to evaluate the effect of low-dose inhaled beclomethasone dipropionate and injectable dexamethasone 21-isonicotinate on clinical signs, pulmonary function, airway cytology, and activity of NF-kB and AP-1 in bronchial cells of RAO-affected horses. Seven horses with RAO were exposed to moldy hay until they developed airway obstruction on 3 separate occasions. In a crossover design, they were then treated with a placebo (injection on day 1), inhaled beclomethasone (500 mg q12h for 10 days), or dexamethasone (0.06 mg/kg, IM on day 1) and monitored for 10 days. Pulmonary function, bronchoalveolar lavage fluid cytology, and NF-kB and AP-1 activity in bronchial brushing cells were measured before (day 1) and after treatment (day 10). Treatment with beclomethasone resulted in significantly improved pulmonary function of RAOaffected horses compared with placebo and dexamethasone treatments. However, none of the treatments had an effect on bronchoalveolar lavage fluid cytology or NF-kB and AP-1 activity. These findings reveal that, in a model of severe RAO, the benefits of low-dose inhaled beclomethasone on pulmonary function are not accompanied by a decrease in airway inflammatory cells or a suppression of transcription factors NF-kB and AP-1 DNA-binding activity.