Lipopolysaccharide induces the antiapoptotic molecules, A1 and A20, in microvascular endothelial cells.
The effect of lipopolysaccharide (LPS) on endothelial cells is a key component of the inflammatory response seen in Gram-negative sepsis. LPS does not cause death of cultured human endothelial cells. However, when the expression of new proteins is inhibited by cycloheximide, microvascular endothelial cells in culture undergo apoptosis. This finding suggests that LPS induces apoptotic and antiapoptotic pathways, with the antiapoptotic response being dependent on the synthesis of new proteins. Concurrent activation of apoptotic and antiapoptotic pathways has previously been documented for tumor necrosis factor (TNF). In the case of TNF, the antiapoptotic signal has been attributed to at least two cytoprotective proteins: the Bcl-2 homologue, A1, and the zinc-finger protein, A20. In this study, we demonstrate that both these molecules are induced in microvascular endothelial cells by LPS. Enforced overexpression of either A1 or A20 inhibits LPS and cycloheximide-initiated apoptosis. Induction of A1 and A20 does not require synthesis of intermediary proteins, but is dependent on the presence of soluble CD14. In addition, we show that inhibition of signaling by the transcription factor, NF-kappaB, blocks accumulation of A1 and A20 mRNA. Taken together, our findings suggest that LPS directly induces expression of the cytoprotective proteins, A1 and A20, via a CD14-dependent pathway requiring activation of NF-kappaB.
Department of Pathology and Laboratory Medicine, University of British Columbia and St Paul's Hospital, Vancouver, British Columbia, Canada.
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Hu
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Yee
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Harlan
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Wong
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Karsan
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002196:Capillaries; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D018398:Homeodomain Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D015778:Minor Histocompatibility Antigens; D016328:NF-kappa B / Q000502:physiology; D009687:Nuclear Proteins; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D051818:Replication Protein C; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3
C096816:BCL2-related protein A1; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D047908:Intracellular Signaling Peptides and Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; C096063:MATA1 protein, S cerevisiae; D015778:Minor Histocompatibility Antigens; D016328:NF-kappa B; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D003513:Cycloheximide; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D051818:Replication Protein C