title: TNF Regulates Essential Alternative Complement Pathway Components and Impairs Activation of Protein C in Human Glomerular Endothelial Cells.
abstract: Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy with severe renal injury secondary to an overactive alternative complement pathway (AP). aHUS episodes are often initiated or recur during inflammation. We investigated gene expression of the surface complement regulatory proteins (CD55, CD59, CD46, and CD141 [thrombomodulin]) and AP components in human glomerular microvascular endothelial cells (GMVECs) and in HUVECs, a frequently used investigational model of endothelial cells. Surface complement regulatory proteins were also quantified by flow cytometry. All experiments were done with and without exposure to IL-1β or TNF. Without cytokine stimulation, we found that GMVECs had greater AP activation than did HUVECs. With TNF stimulation, THBD gene expression and corresponding CD141 surface presence in HUVECs and GMVECs were reduced, and gene expression of complement components C3 (C3) and factor B (CFB) was increased. Consequently, AP activation, measured by Ba production, was increased, and conversion of protein C (PC) to activated PC by CD141-bound thrombin was decreased, in GMVECs and HUVECs exposed to TNF. IL-1β had similar, albeit lesser, effects on HUVEC gene expression, and it only slightly affected GMVEC gene expression. To our knowledge, this is the first detailed study of the expression/display of AP components and surface regulatory proteins in GMVECs with and without cytokine stimulation. In aHUS patients with an underlying overactive AP, additional stimulation of the AP and inhibition of activated PC-mediated anticoagulation in GMVECs by the inflammatory cytokine TNF are likely to provoke episodes of renal failure.
authors.affiliation: Section of Hematology-Oncology, Department of Pediatrics, Texas Children's Cancer and Hematology Centers, Houston, TX 77030; Baylor College of Medicine, Houston, TX 77030; and sesartai@txch.org.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Sartain
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005.
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Turner
authors.affiliation: Department of Bioengineering, Rice University, Houston, TX 77005.
authors.forename: Joel L
authors.initials: JL
authors.lastname: Moake
mesh_terms: D015703:Antigens, CD / Q000032:analysis / Q000096:biosynthesis; D065766:Atypical Hemolytic Uremic Syndrome / Q000276:immunology / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000276:immunology*; D042783:Endothelial Cells / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007118:Immunoassay; D007678:Kidney Glomerulus / Q000276:immunology* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D011486:Protein C / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D059467:Transcriptome; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D011486:Protein C; D014409:Tumor Necrosis Factor-alpha