title: Air bubble contact with endothelial cells causes a calcium-independent loss in mitochondrial membrane potential.
abstract: OBJECTIVE
  Gas microembolism remains a serious risk associated with surgical procedures and decompression. Despite this, the signaling consequences of air bubbles in the vasculature are poorly understood and there is a lack of pharmacological therapies available. Here, we investigate the mitochondrial consequences of air bubble contact with endothelial cells.
  
  
  RESULTS
  Human umbilical vein endothelial cells were loaded with an intracellular calcium indicator (Fluo-4) and either a mitochondrial calcium indicator (X-Rhod-1) or mitochondrial membrane potential indicator (TMRM). Contact with 50-150 µm air bubbles induced concurrent rises in intracellular and mitochondrial calcium, followed by a loss of mitochondrial membrane potential. Pre-treating cells with 1 µmol/L ruthenium red, a TRPV family calcium channel blocker, did not protect cells from the mitochondrial depolarization, despite blocking the intracellular calcium response. Mitigating the interactions between the air-liquid interface and the endothelial surface layer with 5% BSA or 0.1% Pluronic F-127 prevented the loss of mitochondrial membrane potential. Finally, inhibiting protein kinase C-α (PKCα), with 5 µmol/L Gö6976, protected cells from mitochondrial depolarization, but did not affect the intracellular calcium response.
  
  
  CONCLUSIONS
  Our results indicate that air bubble contact with endothelial cells activates a novel, calcium-independent, PKCα-dependent signaling pathway, which results in mitochondrial depolarization. As a result, mitochondrial dysfunction is likely to be a key contributor to the pathophysiology of gas embolism injury. Further, this connection between the endothelial surface layer and endothelial mitochondria may also play an important role in vascular homeostasis and disease.
authors.affiliation: Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Sobolewski
authors.forename: Judith
authors.initials: J
authors.lastname: Kandel
authors.forename: David M
authors.initials: DM
authors.lastname: Eckmann
mesh_terms: D000388:Air; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004618:Embolism, Air / Q000209:etiology / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors; D013501:Surface-Active Agents / Q000494:pharmacology
chemical_list: D013501:Surface-Active Agents; D051571:Protein Kinase C-alpha; D002118:Calcium