Chicken Cyclo-oxygenases Response in a Pulmonary Infection Disease

Abstract

Avian infectious bronchitis, associated coronavirus causes inflammation and damage to the lungs. To evaluate the molecular mechanisms behind this event, we investigated variations in the expression level of the proinflammatory factors, cyclo-oxygenase 1 (COX-1) and cyclo-oxygenases 2 (COX-2). In mammals, the increased generation of prostaglandins during the onset of inflammatory responses and activation of immune cell types has been attributed to the induction of COX-2. The recent sequencing of chicken genome and the identification of genes coding COX-1 and COX-2 allowed us to analyze their expression in lung inflammatory disease. The purpose of this study was to examine the relative expression and distribution of COX-1 and COX-2 in organs of normal hens and in hens with avian infection bronchitis. The expression levels of cyclo-oxygenase genes in several organs from uninfected chickens and infected ones were measured using a quantitative reverse transcription-PCR technique. Our results show that the expression level of COX-1 was highly up regulated in spleen, small intestine, lungs, and liver, but modestly up regulated in the pancreas. However, no significant change was observed in the expression levels of COX-2, in the small intestine, liver and spleen; suggesting a constitutive expression of this enzyme. Whereas, COX-2 mRNA expression was significantly decreased in the heart and lungs of infected chickens, ranging from 9-fold to 4-fold, respectively (p<0.05). Contrary to mammals, COX-2 is present constitutively in bird’s cells, while COX-1 is expressed primarily after inflammation.