Interleukin-1 induces insulin-like growth factor binding protein-3 gene expression and protein production by Leydig cells.
Interleukin-1 (IL-1) is a potent inhibitor of Leydig cell function. IL-1 blocks human CG-induced cAMP and testosterone formation, as well as cytochrome P450 side-chain cleavage messenger RNA (mRNA) expression. IL-1 also decreases insulin-like growth factor-I (IGF-I) mRNA levels in Leydig cells. The effects of IGF-I are modified by IGF binding proteins (IGFBPs). In the present study, we evaluated the effects of IL-1 on IGFBP expression. Purified Leydig cells from adult rats were cultured with 0.1% heat-inactivated fetal bovine serum in Dulbecco's modified Eagles' medium/F12. Culture medium was changed to serum-free Dulbecco's modified Eagles' medium/F12 after 24 h and IL-1 beta (0.1-10 ng/ml) was added. Treatment of Leydig cells with IL-1 beta (10 ng/ml) for 2, 4, and 6 h resulted in a progressive induction of IGFBP-3 expression without affecting IGFBP-2 or IGFBP-4 mRNA levels. IL-1 beta in concentrations of 0.1, 1, and 10 ng/ml caused a 1.5-, 4-, and 6.5-fold induction of IGFBP-3 expression, respectively, whereas IGF-I mRNA levels were decreased in a dose-dependent manner. IL-1 beta increased the average transcription rate of IGFBP-3 by 3.3-fold. The t1/2 for IGFBP-3 mRNA was 2.07 h and was not affected by the treatment with IL-1 beta (2.21 h). The immunoblot of cell-conditioned media showed that the basal level of IGFBP-3 protein was low and IL-1 beta caused a dose-dependent increase in the production of IGFBP-3. These results indicate that IL-1 beta increases IGFBP-3 levels by increasing the rate of transcription rather than by changing the stability of IGFBP-3 mRNA. The addition of cycloheximide markedly inhibited IL-1 beta-induced IGFBP-3 mRNA levels. However, IL-1 beta was able to induce IGFBP-3 mRNA levels even in the presence of cycloheximide. This suggests that de novo protein synthesis may not be required for induction of IGFBP-3 mRNA by IL-1 beta. In conclusion, IL-1 beta inhibits IGF-I but increases IGFBP-3 expression in Leydig cells, and this may contribute to the inhibitory effects of IL-1 beta on Leydig cell steroidogenesis.
Wang
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Medical Service, W.J.B. Dorn Veterans Hospital, Columbia, South Carolina 29201, USA.
Nagpal
M L
ML
Shimasaki
S
S
Ling
N
N
Lin
T
T
D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology*; D007985:Leydig Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000378:metabolism; D014158:Transcription, Genetic
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007375:Interleukin-1; D012333:RNA, Messenger; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D000242:Cyclic AMP