Induction of TGF-beta 1 synthesis in D-glucose primed human proximal tubular cells by IL-1 beta and TNF alpha.
The aim of the present study was to examine whether the induction of TGF-beta 1 synthesis by the pro-inflammatory macrophage derived cytokines, IL-1 beta or TNF alpha, was modified by alterations in D-glucose concentrations. Stimulation of growth arrested HPTC with IL-1 beta or TNF alpha resulted in increased expression of TGF-beta 1 mRNA. The transcript was demonstrable 60 minutes after the addition of IL-1 beta, and apparent steady-state mRNA levels were achieved after six hours. Following stimulation with TNF alpha, TGF-beta 1 mRNA was detectable after 15 minutes and reached steady state levels by two hours. Quantitative RT-PCR revealed that following six hours stimulation with either IL-1 beta or TNF alpha (both at 1 ng/ml), there was no difference in the absolute amount of TGF-beta 1 mRNA induced by these two stimuli (14.8 +/- 5.6 vs. 19.7 +/- 4.9 PM). Despite induction of TGF-beta 1 mRNA following stimulation with IL-1 beta or TNF alpha, neither stimulus increased TGF-beta 1 protein synthesis or release. Pre-exposure of HPTC to 25 mM D-glucose for 48 hours and subsequent stimulation with IL-1 beta resulted in the secretion of latent TGF-beta 1 in both a time and dose dependent manner. This effect was not apparent following TNF alpha stimulation of D-glucose primed HPTC. Stimulation of TGF-beta 1 synthesis by IL-1 beta in D-glucose primed cells was inhibited by cycloheximide but not by actinomycin-D. Examination of D-glucose induced TGF-beta 1 mRNA revealed that IL-1 beta, but not TNF alpha, increased the stability of the D-glucose induced transcript. These results demonstrate that the interaction of D-glucose and IL-1 beta lead to secretion of TGF-beta 1 by HPTC. In contrast, such an interaction was not demonstrable between D-glucose and TNF alpha. This may be explained by the ability of IL-1 beta to stabilize D-glucose-induced TGF-beta 1 mRNA.
Institute of Nephrology, University of Wales College of Medicine, Cardiff Royal Infirmary, United Kingdom.
A O
AO
Phillips
N
N
Topley
R
R
Steadman
K
K
Morrisey
J D
JD
Williams
D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D013268:Stimulation, Chemical; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D003513:Cycloheximide; D005947:Glucose