Jiaofei Cao

Autophagy in idiopathic pulmonary fibrosis.

Background Autophagy is a basic cellular homeostatic process important to cell fate decisions under conditions of stress. Dysregulation of autophagy impacts numerous human diseases including cancer and chronic obstructive lung disease. This study investigates the role of autophagy in idiopathic pulmonary fibrosis. Methods Human lung tissues from patients with IPF were analyzed for autophagy markers and modulating proteins using western blotting, confocal microscopy and transmission electron microscopy. To study the effects of TGF-β1 on autophagy, human lung fibroblasts were monitored by fluorescence microscopy and western blotting. In vivo experiments were done using the bleomycin-induced fibrosis mouse model. Results Lung tissues from IPF patients demonstrate evidence of decreased autophagic activity as assessed by LC3, p62 protein expression and immunofluorescence, and numbers of autophagosomes. TGF-β1 inhibits autophagy in fibroblasts in vitro at least in part via activation of mTORC1; expression of TIGAR is also increased in response to TGF-β1. In the bleomycin model of pulmonary fibrosis, rapamycin treatment is antifibrotic, and rapamycin also decreases expression of á-smooth muscle actin and fibronectin by fibroblasts in vitro. Inhibition of key regulators of autophagy, LC3 and beclin-1, leads to the opposite effect on fibroblast expression of á-smooth muscle actin and fibronectin. Conclusion Autophagy is not induced in pulmonary fibrosis despite activation of pathways known to promote autophagy. Impairment of autophagy by TGF-β1 may represent a mechanism for the promotion of fibrogenesis in IPF.

Caveolin-1 regulates the secretion and cytoprotection of Cyr61 in hyperoxic cell death

Cysteine‐rich 61 (Cyr61) belongs to the CCN family and mediates cell proliferation, survival, and apoptosis. Our previous studies showed that Cyr61 protected against hyperoxia‐induced lung cell death via Akt phosphorylation. Caveolin‐1 (cav‐1), a 22‐kDa transmembrane scaffolding protein, is the principal structural component of caveolae. Emerging data show that cav‐1 regulates signal transduction‐associated proteins that reside in the caveolae. Numerous integrin‐related pathways, including PI3K/Akt‐induced cell survival are controlled by cav‐1‐mediated signaling. Our data showed that recombinant Cyr61 promoted cell proliferation and resistance to hyperoxia‐induced cell death in vitro. Neutralizing antibodies reversed the above effects, indicating functional role of secreted Cyr61 in response to hyperoxic stress. While deletion of cav‐1 protected cells from hyperoxia‐induced cell death, Cyr61‐neutralizing antibodies abolished this protective effect. Furthermore, Cyr61 and cav‐1 colocalized and physically interacted via integrins in bronchial epithelial cells. Deletion of cav‐1 increased extracellular and decreased cytosolic Cyr61, both in vitro and in vivo. Pretreatment with Brefeldin A increased intracellular Cyr61 in cav‐1−/− cells, while decreasing extracellular Cyr61. Taken together, Cav‐1/Cyr61 interaction via integrins represents a novel pathway of Cyr61 signaling involving cav‐1‐dependent processes, which play a critical role in regulating hyperoxia‐induced cell death.—Jin, Y., Kim, H. P., Cao, J., Zhang, M., Ifedigbo, E., Choi, A. M. K. Caveolin‐1 regulates the secretion and cytoprotection of Cyr61 in hyperoxic cell death. FASEB J. 23, 341–350 (2009)

Retinoic Acid–related Orphan Receptor-α Is Induced in the Setting of DNA Damage and Promotes Pulmonary Emphysema

RATIONALE The discovery that retinoic acid-related orphan receptor (Rora)-α is highly expressed in lungs of patients with COPD led us to hypothesize that Rora may contribute to the pathogenesis of emphysema. OBJECTIVES To determine the role of Rora in smoke-induced emphysema. METHODS Cigarette smoke extract in vitro and elastase or cigarette smoke exposure in vivo were used to model smoke-related cell stress and airspace enlargement. Lung tissue from patients undergoing lung transplantation was examined for markers of DNA damage and Rora expression. MEASUREMENTS AND MAIN RESULTS Rora expression was induced by cigarette smoke in mice and in cell culture. Gene expression profiling of Rora-null mice exposed to cigarette smoke demonstrated enrichment for genes involved in DNA repair. Rora expression increased and Rora translocated to the nucleus after DNA damage. Inhibition of ataxia telangiectasia mutated decreased the induction of Rora. Gene silencing of Rora attenuated apoptotic cell death in response to cigarette smoke extract, whereas overexpression of Rora enhanced apoptosis. Rora-deficient mice were protected from elastase and cigarette smoke induced airspace enlargement. Finally, lungs of patients with COPD showed evidence of increased DNA damage even in the absence of active smoking. CONCLUSIONS Taken together, these findings suggest that DNA damage may contribute to the pathogenesis of emphysema, and that Rora has a previously unrecognized role in cellular responses to genotoxicity. These findings provide a potential link between emphysema and features of premature ageing, including enhanced susceptibility to lung cancer.