Impact of Adiponectin Deficiency on Pulmonary Responses to Acute Ozone Exposure in Mice

Abstract

Obese mice have increased responses to acute ozone (O₃) exposure. T-cadherin is a binding protein for the high–molecular weight isoforms of adiponectin, an anti-inflammatory hormone that declines in obesity. The objective of the present study was to determine whether adiponectin affects pulmonary responses to O₃, and whether these effects are mediated through T-cadherin. We performed bronchoalveolar lavage (BAL) and measured pulmonary responsiveness to methacholine after acute air or O₃ exposure (2 ppm for 3 h) in adiponectin-deficient (Adipo^−/−) or T-cadherin–deficient (T-Cad^−/−) mice. O₃ increased pulmonary responses to methacholine and increased BAL neutrophils and protein to a greater extent in wild-type than in Adipo^−/− mice, whereas T-cadherin deficiency had no effect. O₃-induced increases in BAL IL-6 and keratinocyte-derived chemokine (KC), which contribute to O₃-induced pulmonary neutrophilia, were also greater in wild-type than in Adipo^−/− mice. In contrast, responses to O₃ were not altered by transgenic overexpression of adiponectin. To determine which adiponectin isoforms are present in the lung, Western blotting was performed. The hexameric isoform of adiponectin dominated in serum, whereas BAL was dominated by the high–molecular weight isoform of adiponectin. Interestingly, serum adiponectin was greater in T-Cad^−/− versus wild-type mice, whereas BAL adiponectin was lower in T-Cad^−/− versus wild-type mice, suggesting that T-cadherin may be important for transit of high–molecular weight adiponectin from the blood to the lung. Our results indicate that adiponectin deficiency inhibits pulmonary inflammation induced by acute O₃ exposure, and that T-cadherin does not mediate the effects of adiponectin responsible for these events.