title: Toll-like receptor 4 is involved in bacterial endotoxin-induced endothelial cell injury and SOC-mediated calcium regulation.
abstract: Bacterial endotoxins may lead to vascular endothelial cell injury. Our study explored the role of TLR4 (Toll-like receptor 4) and STIM1 (stromal interaction molecule 1) in bacterial endotoxin-induced calcium overload and inflammatory reactions in HUVECs (human umbilical vein endothelial cells). It showed that under LPS (lipopolysaccharide) stimulation, LBP (LPS-binding protein) mRNA levels peaked at 24 h, TLR4 levels at 12 h and NF-κB (nuclear factor κB) levels at 6 h (all P<0.01). LBP levels increased gradually and peaked at 24 h of LPS treatment. TLR4 protein levels increased significantly at 1 h and peaked at 12 h. NF-κB protein levels markedly increased at 1 h and peaked at 6 h. Knockdown of STIM1 alone, TLR4 alone or both STIM1 and TLR4 together, markedly abolished LPS-induced increase in calcium influx into cells (P<0.05, P<0.01 and P<0.01 respectively). LBP-TLR4 and STIM-NF-κB interactions were detected without LPS treatment, enhanced by LPS stimulation, and markedly reduced by knocking down TLR4 and STIM respectively. Both the NF-κB inhibitor, PDTC (pyrrolidine dithiocarbamate) and TLR4 knockdown could block LPS induction of NF-κB, STIM, TNFα (tumour necrosis factor α) and IL-6 (interleukin 6). The data indicate LPS-LBP may activate TLR4 signalling and downstream transcription factor NF-κB, which further can activate STIM1 and eventually lead to calcium influx and injury of HUVECs. Inhibition of TLR4 effectively reverses LPS induction of inflammatory mediator generation and extracellular calcium influx mediated by STIM1.
authors.affiliation: Department of Emergency, General Hospital of PLA, Beijing 100853, Peoples Republic of China.
authors.forename: Rongju
authors.initials: R
authors.lastname: Sun
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Zhu
authors.forename: Qin
authors.initials: Q
authors.lastname: Su
authors.forename: Tanshi
authors.initials: T
authors.lastname: Li
authors.forename: Qing
authors.initials: Q
authors.lastname: Song
mesh_terms: D000209:Acute-Phase Proteins / Q000235:genetics / Q000378:metabolism; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D011759:Pyrrolidines / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects; D000071737:Stromal Interaction Molecule 1; D013859:Thiocarbamates / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D000975:Antioxidants; D002118:Calcium; D002352:Carrier Proteins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D011759:Pyrrolidines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000071737:Stromal Interaction Molecule 1; D013859:Thiocarbamates; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D000099231:Lipopolysaccharide-Binding Protein; C103530:STIM1 protein, human; C020972:pyrrolidine dithiocarbamic acid