Activation of membrane TGFβ1 on alveolar macrophages by co-cultured alcohol primed alveolar epithelial cells (111.1)

Abstract

Abstract Alcohol abuse impairs pulmonary innate immunity rendering individuals susceptible to pneumonia. We have previously shown that alcohol abuse causes oxidative stress in the lung and increases TGFβ1 expression. TGFβ1 downregulates GM-CSF receptors resulting in the alveolar macrophage and epithelial cell dysfunction. However, the exact mechanism of alcohol-mediated activation of TGFβ1 in vivo is still under investigation. We examined TGFβ1 expression on alveolar macrophages and epithelial cells from control- and alcohol-fed rats by real time PCR and flow cytometry. TGFβ1 gene expression was significantly higher in alcoholic macrophages and TGFβ1 protein was predominantly membrane bound in macrophages. In addition, as compared to control, alveolar epithelial cells from alcohol-fed rats had significantly higher expression of alpha5 integrin chain that is implicated in TGFβ1 activation. Therefore, we hypothesized that alcohol-induced increase in epithelial alpha5 would activate membrane TGFβ1 on macrophages. To examine this, macrophage (NR8383) and epithelial (L2) cell lines were co-cultured on transwell membranes to assess the changes in paracellular permeability. Only alcohol primed co-cultures showed a decrease in epithelial barrier function that was reversed by anti-TGFβ1 treatment. Taken together, these results suggest that cellular contact between alveolar macrophages and epithelial cells is essential for alcohol mediated activation of TGFβ1 in the lung.