Hyaluronan fragments contribute to the ozone-primed immune response to lipopolysaccharide

• Published in: The Journal of immunology (1950) 2010-12, Vol.185 (11), p.6891-6898
• Main Authors: Li, Zhuowei, Potts, Erin N, Piantadosi, Claude A, Foster, W Michael, Hollingsworth, John W
• Format: Article
• Language: English
• Subjects: Acute Lung Injury - chemically induced; Acute Lung Injury - immunology; Acute Lung Injury - pathology; Administration, Inhalation; Animals; Bone Marrow Cells - drug effects; Bone Marrow Cells - immunology; Bone Marrow Cells - metabolism; Bronchoalveolar Lavage Fluid - chemistry; Bronchoalveolar Lavage Fluid - cytology; Bronchoalveolar Lavage Fluid - immunology; Cells, Cultured; Dose-Response Relationship, Immunologic; Hyaluronan Receptors - metabolism; Hyaluronic Acid - biosynthesis; Hyaluronic Acid - chemistry; Hyaluronic Acid - toxicity; Lipopolysaccharides - administration & dosage; Lipopolysaccharides - chemistry; Lipopolysaccharides - pharmacology; Macrophages, Alveolar - drug effects; Macrophages, Alveolar - immunology; Macrophages, Alveolar - metabolism; Male; Mice; Mice, Inbred C57BL; Molecular Weight; Ozone - administration & dosage; Ozone - chemistry; Ozone - toxicity
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1000283

Hyaluronan is a high-molecular mass component of pulmonary extracelluar matrix, and lung injury can generate a low-molecular mass hyaluronan (HA) fragment that functions as endogenous ligand to cell surface receptors CD44 and TLR4. This leads to activation of intracellular NF-κB signaling and proinflammatory cytokine production. Based on previous information that ozone exposure causes increased HA in bronchial alveolar lavage fluid and ozone pre-exposure primes immune response to inhaled LPS, we hypothesized that HA production during ozone exposure augments the inflammatory response to LPS. We demonstrate that acute ozone exposure at 1 part per million for 3 h primes the immune response to low-dose aerosolized LPS in C57BL/6J mice, resulting in increased neutrophil recruitment into the airspaces, increased levels of protein and proinflammatory cytokines in the bronchoalveolar lavage fluid, and increased airway hyperresponsiveness. Intratracheal instillation of endotoxin-free HA (25 μg) enhances the biological response to inhaled LPS in a manner similar to ozone pre-exposure. In vitro studies using bone marrow-derived macrophages indicate that HA enhances LPS responses measured by TNF-α production, while immunofluorescence staining of murine alveolar macrophages demonstrates that HA induces TLR4 peripheralization and lipid raft colocalization. Collectively, our observations support that ozone primes macrophage responsiveness to low-dose LPS, in part, due to HA-induced TLR4 peripheralization in lung macrophages.