Angiotensin II induces human TGF-beta 1 promoter activation: similarity to hyperglycaemia.
OBJECTIVE
Activation of the renal renin-angiotensin system has been implicated in the pathogenesis of diabetic nephropathy. Because previous in vitro studies demonstrated the angiotensin II (ang II)-mediated up-regulation of the prosclerotic transforming growth factor beta 1 (TGF) we studied the molecular mechanism of ang II-induced TGF-beta 1 gene activation.


METHODS
Mesangial cells were stimulated with 100 nmol/l ang II with or without inhibitors of protein kinase C (PKC) and p38 MAPK and the TGF-beta 1 promoter activity was determined by promoter-reporter assays. The effect of ang II on the binding of nuclear proteins to the regulatory AP-1 site B, previously shown to mediate the high glucose-response of the TGF-beta 1 promoter, was studied by electrophoretic mobility shift assays.


RESULTS
Ang II enhanced the activity of the TGF-beta1 promoter fragment -453/+11 approximately 1.6-fold. Mutation of each of two AP-1 binding sites or inhibition of the PKC- and p38 MAPK-dependent pathways blocked the ang II-stimulated activity completely. Furthermore, ang II activated the binding of nuclear proteins to the AP-1 box B of the TGF-beta 1 promoter. These effects were similar to those previously observed with high glucose. Co-incubation with ang II and high glucose had no additive effect on TGF-beta 1 promoter activity, protein binding to the AP-1 box B or activation of p38 MAPK.


CONCLUSIONS
The findings indicate that ang II and hyperglycaemia stimulate the TGF-beta 1 gene activation through the same PKC- and p38 MAPK-dependent pathways by the same regulatory elements of the TGF-beta 1 promoter. Our data could also be relevant for e.g. hypertension-induced glomerulosclerosis.
Weigert
C
C
Department of Internal Medicine, Division of Endocrinology, Metabolism and Pathobiochemistry, University of Tübingen, Tübingen, Germany.
Brodbeck
K
K
Klopfer
K
K
Häring
H U
HU
Schleicher
E D
ED
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D005920:Glomerular Mesangium / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D006943:Hyperglycemia / Q000235:genetics / Q000503:physiopathology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D013552:Swine; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics*; D053773:Transforming Growth Factor beta1; D001616:beta-Galactosidase / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; C508960:TGFB1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000804:Angiotensin II; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D001616:beta-Galactosidase; D005947:Glucose