Ca 2+ communication through connexin 43 in lung capillaries

Abstract

The extent to which endothelial (EC) cells support gap junctional intercellular communication (GJIC) remains unknown. To determine GJIC, by fluorescence microscopy we viewed septal capillaries of isolated, blood-perfused lungs from wild type (WT) mice, and from mice with targeted deletion of the gap junctional protein, connexin 43 (Cx43) in EC (Cx43-/-) (Liao, et al., PNAS, 2001). Lung artery, left atrial and airway pressures were held at 10, 3 and 5 cm H2O, respectively. We co-loaded vessels with the Ca2+ cage, NP-EGTA and the cytosolic Ca2+ (Ca2+cyt) indicator, fluo 4. At baseline, EC Ca 2+cyt was 88±17 gray levels. To increase Ca2+cyt focally, we targeted high-intensity UV light to a single EC of a septal capillary, thereby uncaging Ca2+ from NP-EGTA. In WT mice, uncaging increased EC Ca2+cyt locally as well as at a site 100 μm distant by 33±2 and 29±2 gray levels, respectively (mean±SE, n=3, P<0.05). By contrast, in Cx43-/- mice uncaging increased Ca2+cyt locally (n=3, P<0.05), but not at a distant site. Thus, the uncaging-induced Ca2+ signal was conducted 100 μm from the uncaging site in WT, but not in Cx43-/- mice. We conclude, EC of lung capillaries rapidly communicate Ca2+ signals through Cx43-containing gap junctions. Such spatial communication may amplify Ca2+-dependent proinflammatory responses in the lung capillary bed (supported by HL75503, HL57556).