A novel signaling mechanism between gas and blood compartments of the lung.
Propagation of inflammatory signals from the airspace to the vascular space is pivotal in lung inflammation, but mechanisms of intercompartmental signaling are not understood. To define signaling mechanisms, we microinfused single alveoli of blood-perfused rat lung with TNF-alpha, and determined in situ cytosolic Ca(2+) concentration ([Ca(2+)](i)) by the fura-2 ratio method, cytosolic phospholipase A(2) (cPLA(2)) activation and P-selectin expression by indirect immunofluorescence. Alveolar TNF-alpha increased [Ca(2+)](i) and activated cPLA(2) in alveolar epithelial cells, and increased both endothelial [Ca(2+)](i) and P-selectin expression in adjoining perialveolar capillaries. All responses were blocked by pretreating alveoli with a mAb against TNF receptor 1 (TNFR1). Crosslinking alveolar TNFR1 also increased endothelial [Ca(2+)](i). However, the endothelial responses to alveolar TNF-alpha were blocked by alveolar preinjection of the intracellular Ca(2+) chelator BAPTA-AM, or the cPLA(2) blockers AACOCF(3) and MAFP. The gap-junction uncoupler heptanol had no effect. We conclude that TNF-alpha induces signaling between the alveolar and vascular compartments of the lung. The signaling is attributable to ligation of alveolar TNFR1 followed by receptor-mediated [Ca(2+)](i) increases and cPLA(2) activation in alveolar epithelium. These novel mechanisms may be relevant in the alveolar recruitment of leukocytes.
Kuebler
W M
WM
Departments of Medicine and Physiology & Cellular Biophysics, College of Physicians and Surgeons, Columbia University, St. Luke's-Roosevelt Hospital Center, New York, New York 10019, USA.
Parthasarathi
K
K
Wang
P M
PM
Bhattacharya
J
J
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002196:Capillaries / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D019007:P-Selectin / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000098:blood supply* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D014657:Vasculitis / Q000378:metabolism
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D002614:Chelating Agents; D019007:P-Selectin; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D010741:Phospholipases A; D002118:Calcium