High glucose stimulates angiotensinogen gene expression and cell hypertrophy via activation of the hexosamine biosynthesis pathway in rat kidney proximal tubular cells.
The present study investigated whether activation of the hexosamine biosynthesis pathway might mediate at least in part the high glucose effect on angiotensinogen (ANG) gene expression and immortalized renal proximal tubular cell (IRPTC) hypertrophy. IRPTC were cultured in monolayer. ANG, renin, and beta-actin mRNA expression were determined by specific RT-PCR assays. Phosphorylation of p38 MAPK, activating transcription factor-2 (ATF-2), and cAMP-responsive element-binding protein (CREB) was determined by Western blot analysis. Cell hypertrophy was assessed by flow cytometry, intracellular p27kip1 protein levels, and [3H]leucine incorporation into proteins. Glucosamine stimulated ANG and renin mRNA expression and enhanced p38 MAPK, ATF-2, and CREB phosphorylation in normal glucose (5 mm) medium. Azaserine and 6-diazo-5-oxo-l-norleucine (inhibitors of glutamine: fructose-6-phosphate amino transferase enzyme) blocked the stimulatory effect of high glucose, but not that of glucosamine, on ANG gene expression in IRPTCs. SB 203580 (a specific p38 MAPK inhibitor) attenuated glucosamine action on ANG gene expression as well as p38 MAPK and ATF-2 phosphorylation, but not that of CREB. GF 109203X and calphostin C (inhibitors of protein kinase C) blocked the effect of glucosamine on ANG gene expression and CREB phosphorylation, but had no impact on p38 MAPK and ATF-2 phosphorylation. Finally, both glucosamine and high glucose induced IRPTC hypertrophy. The hypertrophic effect of glucosamine was blocked in the presence of GF 109203X, but not azaserine and SB 203580. In contrast, the hypertrophic effect of high glucose was blocked in the presence of azaserine and GF 109203X, but not SB203580. Our studies demonstrate that the stimulatory effect of high glucose on ANG gene expression and IRPTC hypertrophy may be mediated at least in part via activation of hexosamine biosynthesis pathway signaling.
Hsieh
Tusty-Jiuan
TJ
Université de Montréal Centre Hospitalier de l'Université de Montréal-Hôtel Dieu, Centre de Recherche Pavillon Masson, Montréal, Québec, Canada H2W 1T8.
Fustier
Pierre
P
Zhang
Shao-Ling
SL
Filep
Janos G
JG
Tang
Shiow-Shih
SS
Ingelfinger
Julie R
JR
Fantus
I George
IG
Hamet
Pavel
P
Chan
John S D
JS
D051698:Activating Transcription Factor 2; D000808:Angiotensinogen / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001377:Azaserine / Q000494:pharmacology; D002461:Cell Line, Transformed; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003980:Diazooxonorleucine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects*; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage*; D006595:Hexosamines / Q000096:biosynthesis*; D006984:Hypertrophy; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D051698:Activating Transcription Factor 2; C497107:Atf2 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D006595:Hexosamines; D012333:RNA, Messenger; D014157:Transcription Factors; D003980:Diazooxonorleucine; D000808:Angiotensinogen; D001377:Azaserine; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005947:Glucose; D005944:Glucosamine