title: HLA-B35 and dsRNA induce endothelin-1 via activation of ATF4 in human microvascular endothelial cells.
abstract: Endothelin 1 (ET-1) is a key regulator of vascular homeostasis. We have recently reported that the presence of Human antigen class I, HLA-B35, contributes to human dermal microvascular endothelial cell (HDMEC) dysfunction by upregulating ET-1 and proinflammatory genes. Likewise, a Toll-like receptor 3 (TLR3) ligand, Poly(I:C), was shown to induce ET-1 expression in HDMECs. The goal of this study was to determine the molecular mechanism of ET-1 induction by these two agonists. Because HLA-B35 expression correlated with induction of Binding Immunoglobulin Protein (BiP/GRP78) and several heat shock proteins, we first focused on ER stress and unfolded protein response (UPR) as possible mediators of this response. ER stress inducer, Thapsigargin (TG), HLA-B35, and Poly(I:C) induced ET-1 expression with similar potency in HDMECs. TG and HLA-B35 activated the PERK/eIF2α/ATF4 branch of the UPR and modestly increased the spliced variant of XBP1, but did not affect the ATF6 pathway. Poly(I:C) also activated eIF2α/ATF4 in a protein kinase R (PKR)-dependent manner. Depletion of ATF4 decreased basal expression levels of ET-1 mRNA and protein, and completely prevented upregulation of ET-1 by all three agonists. Additional experiments have demonstrated that the JNK and NF-κB pathways are also required for ET-1 upregulation by these agonists. Formation of the ATF4/c-JUN complex, but not the ATF4/NF-κB complex was increased in the agonist treated cells. The functional role of c-JUN in responses to HLA-B35 and Poly(I:C) was further confirmed in ET-1 promoter assays. This study identified ATF4 as a novel activator of the ET-1 gene. The ER stress/UPR and TLR3 pathways converge on eIF2α/ATF4 during activation of endothelial cells.
authors: Arthritis Center, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Stefania
authors: S
authors: Lenna
authors: Izabela
authors: I
authors: Chrobak
authors: G Alessandra
authors: GA
authors: Farina
authors: Fernando
authors: F
authors: Rodriguez-Pascual
authors: Santiago
authors: S
authors: Lamas
authors: Robert
authors: R
authors: Lafyatis
authors: Raffaella
authors: R
authors: Scorza
authors: Maria
authors: M
authors: Trojanowska
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D042783:Endothelial Cells / Q000378:metabolism*; D019332:Endothelin-1 / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D015797:HLA-B35 Antigen / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D051379:Mice; D055806:Microvessels; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D011070:Poly I-C / Q000008:administration & dosage; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects; D055815:Young Adult; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D019332:Endothelin-1; D015797:HLA-B35 Antigen; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D016328:NF-kappa B; D016755:Proto-Oncogene Proteins c-jun; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D051701:Activating Transcription Factor 4; D019892:eIF-2 Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D011070:Poly I-C