ABSTRACT
In the lungs, endothelial nitric oxide synthase (eNOS) is usually expressed in endothelial cells and inducible nitric oxide synthase (iNOS) is mainly expressed in alveolar macrophages and epithelial cells. Both eNOS and iNOS are involved in lung inflammation. While they play several roles in lung inflammation formation and resolution, their expression and activity are also regulated by inflammatory factors. Their expression relationship in virus infection-induced lung injury is not well addressed. In this report, we analyzed expression of both eNOS and iNOS, the production of nitric oxide (NO) and reactive oxygen species (ROS), and expression of their associated regulatory proteins, heat shock protein 90 (HSP90) and caveolin-1 (Cav-1), in a swine lung injury model induced by porcine reproductive and respiratory syndrome virus (PRRSV) infection. The combination of upregulation of iNOS and downregulation of eNOS was observed in both natural and experimental PRRSV-infected lungs, while the combination is much enhanced in natural infected lungs. While NO production is much reduced in both infections, ROS was enhanced only in natural infected lungs. Moreover, HSP90 is increased in both natural and experimental infection and less Cav-1 expressed was observed only in the natural PRRSV-infected lungs. Therefore, the increased ROS generation is likely due to the increased iNOS and its unbalanced regulation by HSP90 and Cav-1, and it also likely causes higher endothelial dysfunction in clinical PRRSV-infected lungs.
Subject(s)
Lung Injury/virology , Nitric Oxide Synthase Type II/metabolism , Porcine respiratory and reproductive syndrome virus/metabolism , Animals , Caveolin 1/metabolism , Caveolin 1/physiology , HSP90 Heat-Shock Proteins/metabolism , HSP90 Heat-Shock Proteins/physiology , Lung Injury/enzymology , Lung Injury/metabolism , Nitric Oxide/metabolism , Nitric Oxide Synthase Type III/metabolism , Reactive Oxygen Species/metabolism , SwineABSTRACT
Neutrophils are innate immune cells that play a crucial role in the first line of host defense. It is also known that neutrophil lung recruitment and infiltration may cause lung injury. The roles of neutrophils in virus infection-induced lung injury are not clear. We explore the mechanisms of neutrophil lung infiltration and the potential biomarkers for lung injury in a swine model of lung injury caused by natural or experimental porcine reproductive and respiratory syndrome virus (PRRSV) infection. Neutrophil lung infiltration was determined by measurement of myeloperoxidase expression and enzyme activity of lung tissues. Myeloperoxidase expression and enzyme activity were dramatically increased in the naturally and experimentally infected lung tissues. Chemokine analysis by quantitative PCR and ELISA showed that IL-8 expression was increased in both infections, while monocyte chemoattractant protein-1 expression was increased only in experimentally infected lung tissues. Expression of the cell adhesion molecules VCAM-1 and ICAM-1 was measured by quantitative PCR and Western blotting. VCAM-1 expression was increased in experimentally and naturally infected lungs, whereas ICAM-1 expression was increased only in the naturally infected lung samples. Our results suggest that neutrophil lung infiltrations in the infected animals are both ICAM-1- and -independent and that combined expression of VCAM-1 and IL-8 may serve as the biomarker for lung injury induced by virus infection.
