Increased Generation of Reactive Oxygen Species (ROS) via Mechanosensing Requires PECAM in the Lung

Abstract

Endothelial cells sense mechanical forces and transduce them into biochemical signals; however the mechanisms are poorly understood. Based on previous studies (E. Tzima, Nature 437:426, 2005), we posited that the platelet endothelial cell adhesion molecule 1 (PECAM-1), by virtue of its junctional location and cytoskeletal linkage, could serve as a mechanosensor that senses loss of blood flow. ROS production by the pulmonary endothelium was evaluated by imaging of an isolated perfused lung in the presence of the fluorescent dye, 5-(and-6)-carboxy-2′,7′-difluorodihydrofluorescein diacetate (carboxy-H2DFFDA). PECAM-1 null mice produced ~two fold less reactive oxygen species (ROS) than wild type (WT) when subjected to ischemia (loss of shear). NADPH oxidase (NOX2) null lung failed to produce ROS indicating that this enzyme complex is the source of this ROS with ischemia. Pulmonary endothelial cells derived from WT and PECAM null lungs when activated by NOX2 agonist Angiotensin II showed comparable ROS generation, indicating that altered NOX2 status in PECAM null does not account for its reduced ROS production with ischemia. We conclude that with loss of shear, PECAM-1 is required for initiation of changes in pulmonary endothelium that result in cell signaling associated with ROS generation. NHLBI-T32-S54932