Endotoxin induces fibrosis in vascular endothelial cells through a mechanism dependent on transient receptor protein melastatin 7 activity.
The pathogenesis of systemic inflammatory diseases, including endotoxemia-derived sepsis syndrome, is characterized by endothelial dysfunction. It has been demonstrated that the endotoxin lipopolysaccharide (LPS) induces the conversion of endothelial cells (ECs) into activated fibroblasts through endothelial-to-mesenchymal transition mechanism. Fibrogenesis is highly dependent on intracellular Ca2+ concentration increases through the participation of calcium channels. However, the specific molecular identity of the calcium channel that mediates the Ca2+ influx during endotoxin-induced endothelial fibrosis is still unknown. Transient receptor potential melastatin 7 (TRPM7) is a calcium channel that is expressed in many cell types, including ECs. TRPM7 is involved in a number of crucial processes such as the conversion of fibroblasts into activated fibroblasts, or myofibroblasts, being responsible for the development of several characteristics of them. However, the role of the TRPM7 ion channel in endotoxin-induced endothelial fibrosis is unknown. Thus, our aim was to study whether the TRPM7 calcium channel participates in endotoxin-induced endothelial fibrosis. Using primary cultures of ECs, we demonstrated that TRPM7 is a crucial protein involved in endotoxin-induced endothelial fibrosis. Suppression of TRPM7 expression protected ECs from the fibrogenic process stimulated by endotoxin. Downregulation of TRPM7 prevented the endotoxin-induced endothelial markers decrease and fibrotic genes increase in ECs. In addition, TRPM7 downregulation abolished the endotoxin-induced increase in ECM proteins in ECs. Furthermore, we showed that intracellular Ca2+ levels were greatly increased upon LPS challenge in a mechanism dependent on TRPM7 expression. These results demonstrate that TRPM7 is a key protein involved in the mechanism underlying endotoxin-induced endothelial fibrosis.
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.
Cesar
C
Echeverría
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.
Ignacio
I
Montorfano
Centro de Estudios Moleculares de la Celula, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Tamara
T
Hermosilla
Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Centro de Investigacion y Tratamiento del Cancer, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Ricardo
R
Armisén
Center for Integrative Medicine and Innovative Science (CIMIS), Facultad de Medicina, Universidad Andres Bello, Santiago, Chile; Centro para el Desarrollo de la Nanociencia y Nanotecnología, Universidad de Santiago de Chile, Santiago, Chile.
Luis A
LA
Velásquez
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.
Claudio
C
Cabello-Verrugio
Centro de Estudios Moleculares de la Celula, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Diego
D
Varela
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile; Millennium Institute on Immunology and Immunotherapy, Santiago, Chile.
Felipe
F
Simon
D015415:Biomarkers / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D004731:Endotoxins / Q000633:toxicity*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005355:Fibrosis; D005786:Gene Expression Regulation / Q000187:drug effects; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D050053:TRPM Cation Channels / Q000378:metabolism*
D015415:Biomarkers; D004731:Endotoxins; D016326:Extracellular Matrix Proteins; D008070:Lipopolysaccharides; D050053:TRPM Cation Channels; D017346:Protein Serine-Threonine Kinases; C486583:TRPM7 protein, human; D002118:Calcium