Eotaxin protein and gene expression in guinea-pig lungs: constitutive expression and upregulation after allergen challenge

Abstract

Eotaxin is an eosinophil-specific chemoattractant originally identified in bronchoalveolar lavage fluid after allergen challenge of sensitized guineapigs. We have determined and quantified for the first time the cellular sources of guinea-pig lung eotaxin and localized gene expression in structural cells of large and small airways and in alveolar macrophages.We used anti-guinea-pig eotaxin monoclonal and polyclonal antibodies and a complementary ribonucleic acid (cRNA) probe to detect eotaxin protein and cytoplasmic messenger ribonucleic acid (mRNA) transcripts by the techniques of immunohistochemistry and in situ hybridization in: 1) naive; 2) ovalbumin-sensitized/ saline-exposed; and 3) ovalbumin-sensitized/ovalbumin-challenged animals (n=5 for each group).Compared with the naive animals, there was a fivefold increase of eotaxin protein and a 25 fold upregulation of eotaxin gene expression in the airway epithelium 3 h after ovalbumin challenge of sensitized animals (p<0.001). The average percentages of alveolar macrophages staining for eotaxin protein and mRNA in the naive animals were approximately 30 and 10% respectively: both increased significantly in the sensitized/ovalbumin-challenged animals to 78 and 57%, respectively (p<0.0001). Compared with the naive animals, the procedure of sensitization and saline exposure significantly increased eotaxin gene expression in both bronchial epithelium and alveolar macrophages (p<0.01): the upregulation at these two sites showed a strong positive association (rcorr=0.95; p<0.0001).The results indicate that there are multiple cellular sources of guinea-pig lungderived eotaxin, including bronchial and bronchiolar epithelial cells, airway smooth muscle, bronchial vascular endothelium, and chondrocytes and alveolar macrophages, and that there are relatively rapid and marked increases of eotaxin protein and gene expression in airway epithelium and alveolar macrophages following allergen challenge.

Regulation of inflammation by airway smooth muscle

“…Further, a concomitant expression of CXCL10 in ASM cells and CXCR3 (CXCL10 receptor) in mast cells was also observed within ASM of subjects with asthma [20]. Studies in animal models of allergen-induced airway hyperresponsiveness detected eotaxin, an eosinophilspecific chemoattractant mediator, in bronchial ASM of guinea pigs [21].…”

Anti-inflammatory Effects of Thiazolidinediones in Human Airway Smooth Muscle Cells

“…Upon activation, cultured human ASM (HASM) cells secrete large amounts of eotaxin, regulated on activation, normal T expressed and secreted (RANTES), IL-6, vascular endothelial growth factor (VEGF), IL-8, monocyte chemoattractant protein-1 (MCP-1), MCP-2, and MCP-3 (4-7). In vivo, the expression of eotaxin is increased in guinea-pig ASM after allergen challenge (8), and both eotaxin and RANTES are highly expressed in the smooth muscle layer of the airways in patients with asthma (3,4,9). A recent study also showed that the mediators produced by human ASM promoted the differentiation of eosinophils from blood progenitor cells (10).…”

Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: Role of eosinophils, IL-5, eotaxin, and IL-13

“…Glucocorticoids potently inhibit airway eosinophilia by actions at all stages of the abovementioned processes. 1,[7][8][9] Eosinophilic inflammation is regulated to a major extent by activated T lymphocytes in the airways that secrete the T H 2 cytokine IL-5. This cytokine is a central mediator in the regulation of eosinophilic inflammation through effects on the proliferation, differentiation, and activation of eosinophils, 10,11 as well as providing a signal for the rapid mobilization of eosinophils from the bone marrow.…”