Fluorescence imaging of endothelial connexin43‐mediated proinflammatory signaling in lung

Spatially extensive inflammation is a major feature of acute lung injury. To determine mechanisms underlying the extensive inflammatory spread, we considered the role of intercellular communication. Fluorescence imaging of intact lung microvessels revealed that photolytic uncaging of caged Ca 2+ focally in alveolar capillaries increased endothelial Ca 2+ in the target vessel as well as in venules located 150 micron from the target. These data indicate that Ca 2+ was communicated from the capillary to adjacent vessels. Pretreatment of microvessels with a peptide inhibitor of the intercellular gap junction protein, connexin43 completely blocked the communicated Ca 2+ response. Moreover, Ca 2+ communication was not evident in lungs of mice lacking endothelial connexin43. These results show that interendothelial communication occurs in lung microvessels, and is mediated by connexin43. Connexin43‐dependent Ca 2+ communication from capillary to venule increased expression of the proinflammatory leukocyte adhesion receptor, P‐selectin in venules. Moreover, inhibition of connexin43 completely blocked thrombin‐induced increases in lung microvascular permeability. We interpret from these results that connexin43 gap junctions play a major role in the spread of proinflammatory responses in lung microvessels. Thus, the role of gap junctions in acute lung injury needs further elucidation. HL75503, HL57556