Parkin Mediates Endothelial Inflammatory Responses In Acute Lung Injury

Introduction Acute lung injury (ALI) and its more severe form, the Acute Respiratory Distress Syndrome (ARDS), are serious conditions resulting from direct or indirect lung injury that occur in critically ill patients and are associated with an unacceptable mortality of up to 40%. A key biological event in the pathogenesis of ALI/ARDS is the dysfunction of the lung endothelium (EC), which is triggered by a variety of inflammatory insults leading to damaged EC, vascular leak, and excessive inflammation. Recently, we demonstrated that an Abl family tyrosine kinase inhibitor, imatinib, protects against LPS-induced endothelial dysfunction by inhibiting c-Abl kinase through mechanisms that remain largely unknown. In the present study, we identified parkin, a novel c-Abl substrate, as a critical mediator of endothelial dysfunction in ALI. Methods In vitro Human pulmonary artery endothelial cells (EC) were transfected with siRNA for parkin and then challenged with LPS (1 µg/ml, 3 hrs). Inflammatory mediators were determined in cell lysates and supernatants by Western blotting and ELISA respectively. In vivo C57BL/6 (WT) and parkin deficient (PARK2 KO) male mice (8–12 wks, n=5–8) were subjected to LPS (intratracheally, 1 mg/kg) or PBS (controls), and allowed to recover prior to harvest 18 hrs later. Leakage of proteins into the alveolar space was assessed by measuring the protein levels in the bronchoalveolar lavage (BAL). To assess lung inflammation, neutrophil cell counts, myeloperoxidase (MPO) activity, and IL-6 levels were determined in BAL. Results In human lung EC, down-regulation of parkin by siRNA reduces LPS-induced VCAM-1 expression (adhesion molecule involved in neutrophil adhesion to EC) (by 35%, p Conclusion These results suggest that endothelial parkin mediates EC activation and neutrophil adhesion/migration after LPS, and therefore it may represent a new potential therapeutic target in ALI/ARDS.