Perturbation of endothelial junction proteins by Staphylococcus aureus α-toxin: inhibition of endothelial gap formation by adrenomedullin
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Endothelial hyperpermeability is a hallmark of an inflammatory reaction and contributes to tissue damage in severe infections. Loss of endothelial cell–cell adhesion leads to intercellular gap formation allowing paracellular fluid flux. Although Staphylococcus aureus α-toxin significantly contributed to staphylococci disease, little is known about its mechanism of endothelial hyperpermeability induction. Here, we demonstrate that in a model of isolated perfused rat ileum discontinuation of capillary vascular-endothelial-cadherin (VE-cadherin) was observed after bolus application of S. aureus α-toxin being inhibited by the endogenous peptide adrenomedullin (ADM). In vitro, α-toxin exposure induced loss of immunoreactivity of VE-cadherin and occludin in human cultured umbilical vein endothelial cells. Likewise, ADM blocked α-toxin-related junctional protein disappearance from intercellular sites. Additionally, cyclic AMP elevation was shown to stabilize endothelial barrier function after α-toxin application. Although no RhoA activation was noted after endothelial α-toxin exposure, inhibition of Rho kinase and myosin light chain kinase blocked loss of immunoreactivity of VE-cadherin and occludin as well as intercellular gap formation. In summary, stabilization of endothelial junctional integrity as indicated by interendothelial immunostaining might be an interesting approach to stabilize endothelial barrier function in severe S. aureus infections.
KeywordsAdrenomedullin S. aureus α-toxin Junctions HUVECs Permeability
Contract grant sponsor: Deutsche Forschungsgemeinschaft (DFG). Contract grant number: SSP 1130; HI 789/5-1. Contract grant sponsor: Bundesministerium für Bildung und Forschung (BMBF), Competence Network CAPNETZ C14, C4. Contract grant sponsor: Charité—Universitätsmedizin Berlin, Rahel-Hirsch award. Parts of this work will be included in the M.D. thesis of K. Berger. We thank K. Moehr, S. Wagner and J. Hellwig for excellent technical assistance. We thank Jerrold R. Turner, M.D., Ph.D., Department of Pathology of the University of Chicago, South Maryland for the friendly gift of the MLCK inhibitor PIK.
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