TLR4 Is Necessary for Hyaluronan-mediated Airway Hyperresponsiveness after Ozone Inhalation

• Published in: American journal of respiratory and critical care medicine Vol. 181; no. 7; pp. 666 - 675
• Main Authors: GARANTZIOTIS, Stavros, ZHUOWEI LI, POTTS, Erin N, LINDSEY, James Y, STOBER, Vandy P, POLOSUKHIN, Vasiliy V, BLACKWELL, Timothy S, SCHWARTZ, David A, FOSTER, W. Michael, HOLLINGSWORTH, John W
• Format: Journal Article
• Language: English
• Published: New York, NY American Thoracic Society 01.04.2010
• Subjects: A. Airway Biology; Administration, Inhalation; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Animals; Biological and medical sciences; Bronchial Hyperreactivity - chemically induced; Bronchial Hyperreactivity - metabolism; Bronchial Hyperreactivity - pathology; Bronchoalveolar Lavage Fluid - chemistry; Cytokines; Cytokines - biosynthesis; Emergency and intensive respiratory care; Experiments; Hyaluronic acid; Hyaluronic Acid - administration & dosage; Hyaluronic Acid - metabolism; Inflammation Mediators - metabolism; Intensive care medicine; Lavage; Ligands; Macrophages, Alveolar - pathology; Male; Medical sciences; Mice; Mice, Inbred C57BL; Molecular weight; Ozone; Ozone - administration & dosage; Ozone - toxicity; Proteins; Pulmonary Alveoli - drug effects; Pulmonary Alveoli - metabolism; Pulmonary Alveoli - pathology; Toll-Like Receptor 4 - deficiency; Toll-Like Receptor 4 - metabolism; Tumor necrosis factor-TNF; Lung disease; environmental airways injury; Intensive care; Respiratory disease; Cytokine; Ozone; Asthma; Inhalation; TNF-α; Bronchus disease; toll-like receptor; Obstructive pulmonary disease; Tumor necrosis factor α; Resuscitation; Macrophage
• ISSN: 1073-449X; 1535-4970
• DOI: 10.1164/rccm.200903-0381OC

Ozone is a common environmental air pollutant that contributes to hospitalizations for respiratory illness. The mechanisms, which regulate ozone-induced airway hyperresponsiveness, remain poorly understood. We have previously reported that toll-like receptor 4 (TLR4)-deficient animals are protected against ozone-induced airway hyperresponsiveness (AHR) and that hyaluronan (HA) mediates ozone-induced AHR. However, the relation between TLR4 and hyaluronan in the airway response to ozone remains unexplored. We hypothesized that HA acts as an endogenous TLR4 ligand for the development of AHR after ozone-induced environmental airway injury. TLR4-deficient and wild-type C57BL/6 mice were exposed to either inhaled ozone or intratracheal HA and the inflammatory and AHR response was measured. TLR4-deficient mice have similar levels of cellular inflammation, lung injury, and soluble HA levels as those of C57BL/6 mice after inhaled ozone exposure. However, TLR4-deficient mice are partially protected from AHR after ozone exposure as well as after direct intratracheal instillation of endotoxin-free low molecular weight HA. Similar patterns of TLR4-dependent cytokines were observed in the bronchial alveolar lavage fluid after exposure to either ozone or HA. Exposure to ozone increased immunohistological staining of TLR4 on lung macrophages. Furthermore, in vitro HA exposure of bone marrow-derived macrophages induced NF-kappaB and production of a similar pattern of proinflammatory cytokines in a manner dependent on TLR4. Our observations support the observation that extracellular matrix HA contributes to ozone-induced airways disease. Furthermore, our results support that TLR4 contributes to the biological response to HA by mediating both the production of proinflammatory cytokines and the development of ozone-induced AHR.