Endotoxin Induces Fibrosis in Vascular Endothelial Cells through a Mechanism Dependent on Transient Receptor Protein Melastatin 7 Activity

Cesar Echeverría,Ricardo Armisén,Diego Varela,Claudio Cabello-Verrugio,Felipe Simon,Tamara Hermosilla,Luis A Velásquez,Ignacio Montorfano,Liwu Li

doi:10.1371/journal.pone.0094146

Cesar Echeverría, Ricardo Armisén + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0094146

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Journal: PLoS ONE	Publication Date: Apr 7, 2014
Citations: 95	License type: CC BY 4.0

Affiliation: University of Chile, Universidad Andrés Bello

Abstract

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 endothelialtomesenchymal 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.

Highlights

Sepsis syndrome is the most prevalent cause of mortality in critically ill patients admitted to intensive care units [1]
The results provided here contribute to our understanding of the molecular basis of endotoxin-induced endothelial fibrosis, revealing a novel target that could be useful in drug development for treating endothelial dysfunction during endotoxemia and other inflammatory diseases
To determine whether the Transient receptor potential melastatin 7 (TRPM7) channel is involved in the endotoxin-induced intracellular Ca2+ increase, we examined whether downregulation of TRPM7 expression via specific small interfering RNA (siRNA) treatment would modify the observed pattern of the increase in intracellular calcium levels

Summary

Introduction

Sepsis syndrome is the most prevalent cause of mortality in critically ill patients admitted to intensive care units [1]. The pathogenesis of sepsis syndrome develops through an overactivation of the immune system, which involves activation of immune cells, secretion of pro-inflammatory cytokines and generation of reactive oxygen species (ROS) [1,2]. Endotoxemia-derived sepsis syndrome is a important cause of sepsis syndrome. It is frequently characterized by deposition of large amounts of the Gram-negative bacterial endotoxin, lipopolysaccharide (LPS) [5,6,7,8]. The endotoxin circulating in the bloodstream interacts with the endothelial cells (ECs) located in the internal endothelial monolayer of blood vessels, inducing detrimental effects on endothelium function [9,10,11]

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