Interleukin-1beta expression after inhibition of protein phosphatases in endotoxin-tolerant cells.
Endotoxin (lipopolysaccharide [LPS]) is a potent activator of a number of inflammatory genes in blood leukocytes, including interleukin-1 (IL-1). Blood leukocytes isolated from patients with septic shock fail to produce IL-1 in response to LPS, a phenomenon known as endotoxin tolerance. To study the regulation of IL-1 expression in endotoxin-tolerant cells, the protein phosphatase inhibitor okadaic acid was used to examine the effects of protein phosphorylation on IL-1beta gene expression. We found that endotoxin-tolerant cells produced normal levels of IL-1beta when protein phosphatases were inhibited. In the human pro-monocytic cell line THP-1, okadaic acid increased mRNA accumulation and synthesis of IL-1beta protein. Normal and endotoxin-tolerant THP-1 cells accumulated IL-1beta mRNA and protein with similar delayed kinetics. Okadaic acid stabilization of IL-1beta mRNA appears to be the primary mechanism through which endotoxin-tolerant cells accumulate IL-1beta mRNA and protein. Endotoxin-tolerant cells were unable to activate transcription in response to okadaic acid. However, the transcription factor NF-kappaB, which is known to be involved in IL-1beta expression, was translocated to the nucleus in both normal and endotoxin-tolerant cells after treatment with okadaic acid. These studies revealed that protein phosphorylation can affect gene expression on at least two distinct levels, transcription factor activation and mRNA stability. Endotoxin-tolerant cells have decreased transcription activation potential, while IL-1beta mRNA stability remains responsive to protein phosphorylation.
Yoza
B K
BK
Department of Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA. byoza@wfubmc.edu
Wells
J D
JD
McCall
C E
CE
D002460:Cell Line; D004731:Endotoxins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis* / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D015533:Transcriptional Activation
D004731:Endotoxins; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases