Maturation-dependent sequential expression of interferon regulatory factor-1 and inducible nitric oxide synthase in cultured human enterocytes.
We tested the hypothesis that inducible nitric oxide (NO) synthase (iNOS) and interferon regulatory factor 1 (IRF-1), a trans-acting factor in iNOS transcriptional activation, are maturation-dependently expressed in cytokine-stimulated human enterocytes. Caco-2BBe cells, at varying stages of maturation, were stimulated with IL-1beta and IFN-gamma. Cytokine stimulation of 3-day-old undifferentiated Caco-2BBe cells induced low levels of NO production, iNOS and IRF-1 immunoreactivity, iNOS and IRF-1 mRNA expression, and iNOS activity, whereas 24-day-old mature cells responded with a large and prolonged activation of iNOS and IRF-1 expression. The basis for this difference was accounted in part by the relatively greater iNOS transcription rate in 24- vs. 3-day-old cells. Sequential expression of IRF-1 followed by iNOS mRNA occurred in both 3- and 24-day-old cells. We conclude that enterocyte maturation profoundly alters the magnitude and duration of human iNOS and IRF-1 expression in response to cytokine stimulation. The differences in iNOS mRNA levels between the immature and mature cells are only partially explained by difference in transcriptional rates, implying that post-transcriptional regulation may also be influenced by the state of enterocyte maturation. Induction of IRF-1 expression precedes and parallels the level of iNOS expression at all stages of maturation. We propose that IRF-1 may modulate the expression of cytokine-induced iNOS activity in differentiating enterocytes.
Bernstein
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Division of Critical Care, Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA.
Szabó
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Salzman
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D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D020895:Enterocytes / Q000166:cytology / Q000502:physiology*; D006801:Humans; D050856:Interferon Regulatory Factor-1; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D010750:Phosphoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II