Immunoreactive prostaglandin production by equine monocytes and alveolar macrophages and concentrations of PGE2 and PGF in bronchoalveolar lavage fluid

The equine mononuclear phagocyte system: The relevance of the horse as a model for understanding human innate immunity

The mononuclear phagocyte system (MPS) is a family of cells of related function that includes bone marrow progenitors, blood monocytes and resident tissue macrophages. Macrophages are effector cells in both innate and acquired immunity. They are a major resident cell population in every organ and their numbers increase in response to proinflammatory stimuli. Their function is highly regulated by a wide range of agonists, including lymphokines, cytokines and products of microorganisms. Macrophage biology has been studied most extensively in mice, yet direct comparisons of rodent and human macrophages have revealed many functional differences. In this review, we provide an overview of the equine MPS, describing the variation in the function and phenotype of macrophages depending on their location and the similarities and differences between the rodent, human and equine immune response. We discuss the use of the horse as a large animal model in which to study macrophage biology and pathological processes shared with humans. Finally, following the recent update to the horse genome, facilitating further comparative analysis of regulated gene expression between the species, we highlight the importance of future transcriptomic macrophage studies in the horse, the findings of which may also be applicable to human as well as veterinary research.

Cigarette smoke modulates PGE(2) and host defence against Moraxella catarrhalis infection in human airway epithelial cells

BACKGROUND AND OBJECTIVE

Airway bacterial infections pose a significant challenge to the management of COPD, a disease mainly caused by cigarette smoking. However, the mechanisms of impaired airway mucosal innate immunity against bacteria in COPD remain unclear. We examined the effect of cigarette smoke on prostaglandin E(2) (PGE(2)) and downstream epithelial host defence mechanisms including the antimicrobial substance human β-defensin-2 (hBD-2).

METHODS

Brushed bronchial epithelial cells were obtained from healthy smokers and individuals with COPD, and cultured under air-liquid interface conditions with or without exposure to whole cigarette smoke (WCS) or Moraxella catarrhalis (Mc) infection. Bacterial load, hBD-2 (a molecule known to kill Mc) and PGE(2) were measured.

RESULTS

WCS decreased Mc-induced hBD-2 expression and increased Mc load on bronchial epithelial cells from healthy smokers and COPD patients. Moreover, WCS inhibited PGE(2) induction following Mc. PGE(2) was shown to increase hBD-2 production in bronchial epithelial cells from healthy smokers, but not from COPD patients.

CONCLUSIONS

The results suggest that in well-differentiated human bronchial epithelial cells, WCS may impair host defence against Mc in part through inhibiting PGE(2) production.

Investigations on the ability of clenbuterol hydrochloride to reduce clinical signs and inflammation associated with equine influenza A infection

Twenty-four Quarter Horse and Quarter Horse-cross yearlings were experimentally infected with influenza A virus (Influenza A/equine/Saskatoon/90 [H3N8]) by nebulisation. In a double blind controlled trial the horses were randomly assigned to 3 groups of 8 animals. Group 1 received a placebo, (carrier syrup), Group 2 the labelled dose and Group 3 twice the labelled dose of clenbuterol hydrochloride. All treatments were given per os b.i.d. for 10 days and started on the day of infection. The horses were monitored for clinical signs of influenza infection for 14 days. Bronchoalveolar lavages were performed 4 days prior to, and 5 and 13 days after infection. Cell counts and concentrations of prostaglandin E2 and prostaglandin F2alpha in the lavage fluid were determined. Blood samples for haematology and serology were taken 4 days before, on the day of infection, 5, 9 and 13 days after infection. All horses experienced a typical influenza infection with fever, coughing and secondary bacterial infections with mainly Actinobacillus spp. and Streptococcus spp. There was no statistically or clinically significant effect of treatment with clenbuterol hydrochloride on measured clinical or laboratory parameters within 14 days of infection.

Inflammatory markers in bronchoalveolar lavage fluid of standardbred racehorses with inflammatory airway disease: response to interferon-alpha

Protein and eicosanoid concentrations and procoagulant activity were determined in bronchoalveolar lavage fluid (BALF) from 32 Standardbred racehorses with inflammatory airway disease (IAD) and 6 control horses. Total protein, albumin and immunoglobulin G (IgG) concentrations were high (P < 0.05) in the BALF from horses with IAD, a finding consistent with exudation of plasma protein into the airway. Immunoglobulin A (IgA) concentrations also were increased (P < 0.05) which may signify local immunoglobulin production. Difference was not detected in prostaglandin E2 and 6-ketoprostaglandin F1 alpha concentrations in BALF of IAD-affected and control horses. Procoagulant activity was identified in the majority (66%) of BALF samples from IAD-affected horses and was not detected in control horses. Natural human interferon-alpha (nHulFN alpha) (placebo, 50, 150, or 450 units) was administered orally for 5 days to IAD-affected horses in a double-blind, randomised block design. Total protein, IgG, and IgA concentrations in BALF were reduced (P < 0.05) 8 days after administration of 50 u and 150 u nHuIFN alpha, and 15 days after administration of 50 u nHuIFN alpha. Procoagulant activity and albumin concentrations in BALF were lower 8 days after administration of 50 u nHuIFN alpha. Oral administration of low-dose nHuIFN alpha appeared to ameliorate these parameters of lower respiratory tract inflammation in Standardbred racehorses with IAD.

Effect of stabling on bronchoalveolar cells obtained from normal and COPD horses

Bronchoalveolar lavages (BAL) were performed before and after 3 weeks of housing in 5 horses suffering from COPD and 5 normal horses. In the two groups, the total number of cells recovered remained unchanged after stabling. The most common cell populations in BAL fluid of control animals were alveolar macrophages (46.4%) and lymphocytes (44.9%). The percentage of neutrophils increased after stabling from 8.7% to 27.6%. In COPD horses, lymphocytes predominated (40.7%) in animals at pasture with neutrophils increasing from 29.4% to 71.6% after stabling. After fractionation by Percoll density gradient, alveolar macrophages and neutrophils from normal and COPD horses had a similar density distribution. After stabling, these cells from normal horses were increased in the low density layers, while those from COPD horses were predominantly in the hyperdense layers. Therefore, BAL cells obtained from COPD animals at pasture and after stabling differ from those of control horses in the same environment, not only in their populations but also in their buoyant densities. These differences could be related to different states of cellular activation and perhaps be responsible for disease activity in the COPD horses.

Arachidonate metabolites in bronchoalveolar lavage fluid from horses with and without COPD

Arachidonate metabolites were measured in bronchoalveolar lavage fluid (BALF) from horses with (N = 4) and without (N = 7) chronic obstructive pulmonary disease (COPD). Prostaglandin (PG) D2, leukotriene (LT) B4 and LTC4 were present in highest concentrations in BALF from clinically normal horses. Concentrations of PGE2 and PGF were significantly higher in BALF from horses with COPD than in BALF from normal horses, but no differences were detected in thromboxane B2, 6-keto-PGF1 alpha, PGD2, LTB4 or LTC4.