Interleukin-1 inhibits the induction of insulin-like growth factor-I by growth hormone in CWSV-1 hepatocytes.
Sepsis results in hepatic "growth hormone (GH) resistance" with reductions in plasma IGF-I despite a two- to fourfold increase in circulating GH. In this study, we examine the effects of IL-1 on GH receptor (GHR) expression, GH signaling (via the JAK/STAT and MAPK pathways), and the induction of gene expression [IGF-I mRNA and serine protease inhibitor (Spi) 2.1] by GH in CWSV-1 hepatocytes. Incubation of cells with IL-1beta (10 ng/ml, 24 h) had no effect on the relative abundance of GHR or signaling proteins JAK2, STAT5b, and ERK1/2 in cell lysates. Baseline phosphorylation of GHR, JAK2, STAT5b, and ERK1/2 was minimal. After GH stimulation, tyrosine phosphorylation of GHR, JAK2, STAT5b, and ERK1/2 increased 2- to 10-fold. However, neither the time course nor the magnitude of GHR, JAK2, and ERK1/2 phosphorylation by GH were significantly altered by IL-1. The GH-induced translocation of STAT5b to the nucleus was not prevented by IL-1. Although phosphorylated STAT5 in nuclear extracts from GH + IL-1 cells was decreased by 24% (vs. controls) 15 min after GH stimulation, this did not result in reduced STAT5-DNA binding activity. Pretreatment with IL-1 did not significantly decrease IGF-I mRNA stability. We conclude that IL-1 only minimally affects the time course of JAK2/STAT5 and MAPK signaling by GH. Therefore, an inhibitory effect of IL-1 on IGF-I and Spi 2.1 mRNA synthesis by GH represents the most likely mechanism for IL-1-mediated GH resistance.
Shumate
Margaret L
ML
Dept. of Surgery, College of Medicine, Pennsylvania State University, Hershey, PA 17033, USA.
Yumet
Gladys
G
Ahmed
Tamer A
TA
Cooney
Robert N
RN
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007375:Interleukin-1 / Q000494:pharmacology*; D053614:Janus Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D008894:Milk Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics; D050799:STAT5 Transcription Factor; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics
D004268:DNA-Binding Proteins; D007375:Interleukin-1; C091103:LOC299282 protein, rat; D008894:Milk Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C106644:SOCS3 protein, human; D050799:STAT5 Transcription Factor; C494097:Stat5b protein, rat; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3