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Angiopoietin‐1 haploinsufficiency affects the endothelial barrier and causes hereditary angioedema
Author(s) -
d'Apolito Maria,
Santacroce Rosa,
Colia Anna Laura,
Cordisco Giorgia,
Maffione Angela Bruna,
Margaglione Maurizio
Publication year - 2019
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1111/cea.13349
Subject(s) - haploinsufficiency , endothelial stem cell , hereditary angioedema , endothelium , immunology , microbiology and biotechnology , medicine , biology , endocrinology , in vitro , biochemistry , gene , phenotype
Summary Background Different mutations of the angiopoietin‐1 gene ( ANGPT 1 ) have been associated with the occurrence of hereditary angioedema ( HAE ). Objective The purpose of the study is to clarify whether the ANGPT 1 A119S variant plays its role via haploinsufficiency or a dominant negative effect. Methods The ability of ANGPT 1 A119S variant to affect the endothelial barrier function was assessed by immunocytochemistry. Inter‐endothelial gap formation molecules primarily responsible for cell‐cell adhesions of HUVEC s, vascular endothelial ( VE )‐cadherin and β‐catenin, and reorganization of the F‐actin cytoskeletal were evaluated. Results In in vitro conditions mimicking the heterozygous state, the p.A119S variant significantly reduced the capability to bind its natural receptor (80.7% of normal), less than the homozygous condition (59.1%). After stimulation of VEGF or bradykinin, the addiction to equimolar amounts of wt ANGPT 1 and ANGPT 1 p.A119S clearly reduced the expression of VE ‐cadherin on the endothelial cell surface (31% and 24% respectively). Likewise, cell surface expression of β‐catenin was reduced and severe gap formation between adjacent HUVEC s developed. In cultured cells, β‐catenin expression was mostly observed along the cell surface. Treatment with equimolar amounts of wt ANGPT 1 and ANGPT 1 p.A119S failed to restore the reorganization of the F‐actin cytoskeletal elements. ANGPT 1 p.A119S variant in homozygous condition further diminished VE ‐cadherin and β‐catenin expression and failed to reduce stress fibre formation significantly affecting the endothelial barrier functionality. Conclusions and Clinical Relevance Present data show that in a heterozygous state the p.A119S substitution results in a pathogenic loss of function of the protein due to a mechanism of haploinsufficiency. The ANGPT 1 reduced ability to counteract the increment of endothelial permeability produced by inducers, such as VEGF and bradykinin, stimulate vascular leakage and reorganization of the F‐actin cytoskeletal elements. As a result, a partial impairment of the ANGPT 1 functionality, like when dominant mutations occur, represents a pathophysiological cause of HAE .