Abstract
Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is characterized by pulmonary microvascular endothelial barrier dysfunction. Mesenchymal stem cell-secreted hepatocyte growth factor (HGF) has positive effects of lipopolysaccharide- (LPS-) induced pulmonary endothelial barrier. Studies have exhibited the mammalian TORC1 (mTORC1) signaling is of potent angiogenesis effects. The mTOR protein kinase has two distinct multiprotein complexes mTORC1 and mTORC2 that regulate different branches of the mTOR network. However, detailed mTORC2 mechanisms of HGF protective effects remain poorly defined. Therefore, the aim of this study was to determine whether mTORC2 mediated protective effects of MSC-secreted HGF against LPS-induced pulmonary microvascular endothelial barrier dysfunction activated like mTORC1 activation. We introduced MSC-PMVEC coculture transwell system and recombinant murine HGF on LPS-induced endothelial cell barrier dysfunction in vitro and then explored potential mechanisms by lentivirus vector-mediated HGF, mTORC1 (raptor), and mTORC2 (rictor) gene knockdown modification. Endothelial paracellular and transcellular permeability, adherent junction protein (VE-Cadherin), cell proliferation, apoptosis, and mTOR-associated proteins were tested. These revealed that HGF could promote quick reestablishment of adherent junction VE-cadherin and decrease endothelial paracellular and transcellular permeability during LSP-induced endothelial dysfunction with the involvement of mTORC2 (rictor) and mTORC1 (raptor) pathways. Raptor and rictor knockdown in LPS-induced PMEVECs with stimulation of HGF increased apoptosis ratio, activated Cleaved-Caspase-3 expression, and downregulated cell proliferation. Moreover, mTORC2/Akt but not mTORC2/PKC had significance on HGF endothelial protective effects. Taken together, these highlight activation mTORC2 pathway could also contribute to vascular endothelial barrier recovery by MSC-secreted HGF in LPS stimulation.
Highlights
Clinical manifestations of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are variable and complex
The aim of this study was to determine whether protective effects of Mesenchymal stem cells (MSC)-secreted hepatocyte growth factor (HGF) against LPS-induced pulmonary microvascular endothelial barrier dysfunction were activated by the mTOR complex 2 (mTORC2) pathway
We introduced MSCPMVEC coculture transwell system and recombinant murine HGF on endothelial cell barrier dysfunction stimulated by gram-negative bacterial pathogen lipopolysaccharide (LPS) in vitro and explored potential mechanisms by lentivirus vector-mediated HGF, mammalian TORC1 (mTORC1), and mTORC2 gene knockdown modification
Summary
Clinical manifestations of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are variable and complex. Pathology mechanisms are the magnitude injury to pulmonary microvascular endothelial barrier [1,2]. The possibility of attenuating lung endothelial barrier dysfunction at early stage is a critical determinant of endothelial recovery. Some researchers have devoted to investigate new approaches to lung endothelial barrier, such as endothelin-1 receptor antagonist, phosphodiesterase inhibitor, and prostaglandin [3]. The results of protective effect were not ideal due to complex physiological environments, drug doses, and administration time. Mesenchymal stem cells (MSC), which derived from the early development of mesoderm and ectoderm, have capacity with high self-renewal, multiple differentiation potential, reducing vascular endothelium permeability, and
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