Long-term activation of TLR3 by Poly(I:C) induces inflammation and impairs lung function in mice
1 Discovery Research, Centocor Research & Development, Inc, Radnor, Pennsylvania, USA
2 Department of Immunobiology, Yale University School of Medicine and Howard Hughes Medical Institute, New Haven, Connecticut, USA
3 Centre d'Immunologie de Marseille-Luminy, CNRS-INSERM-Universite de la Mediterranee, Campus de Luminy, Case 906, Marseille Cedex 13288, France
4 Genomics Institute of the Novartis Research Foundation, San Diego, California, USA
Respiratory Research 2009, 10:43 doi:10.1186/1465-9921-10-43Published: 1 June 2009
The immune mechanisms associated with infection-induced disease exacerbations in asthma and COPD are not fully understood. Toll-like receptor (TLR) 3 has an important role in recognition of double-stranded viral RNA, which leads to the production of various inflammatory mediators. Thus, an understanding of TLR3 activation should provide insight into the mechanisms underlying virus-induced exacerbations of pulmonary diseases.
TLR3 knock-out (KO) mice and C57B6 (WT) mice were intranasally administered repeated doses of the synthetic double stranded RNA analog poly(I:C).
There was a significant increase in total cells, especially neutrophils, in BALF samples from poly(I:C)-treated mice. In addition, IL-6, CXCL10, JE, KC, mGCSF, CCL3, CCL5, and TNFα were up regulated. Histological analyses of the lungs revealed a cellular infiltrate in the interstitium and epithelial cell hypertrophy in small bronchioles. Associated with the pro-inflammatory effects of poly(I:C), the mice exhibited significant impairment of lung function both at baseline and in response to methacholine challenge as measured by whole body plethysmography and an invasive measure of airway resistance. Importantly, TLR3 KO mice were protected from poly(I:C)-induced changes in lung function at baseline, which correlated with milder inflammation in the lung, and significantly reduced epithelial cell hypertrophy.
These findings demonstrate that TLR3 activation by poly(I:C) modulates the local inflammatory response in the lung and suggest a critical role of TLR3 activation in driving lung function impairment. Thus, TLR3 activation may be one mechanism through which viral infections contribute toward exacerbation of respiratory disease.