Expression of TGF-beta-induced matrix protein betaig-h3 is up-regulated in the diabetic rat kidney and human proximal tubular epithelial cells treated with high glucose.
BACKGROUND
betaig-h3 is an extracellular matrix protein whose expression in several cell types is greatly increased by transforming growth factor-beta (TGF-beta). TGF-beta is believed to be involved in the development of diabetic nephropathy and thus we have assessed the possibility that betaig-h3 may be a downstream molecule in this pathogenic process.


METHODS
Immunoblotting and immunohistochemistry were done using an antibody against mouse betaig-h3 protein. betaig-h3 and TGF-beta concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Cell adhesion and migration were assessed by measuring activity of N-acetyl-beta-d-glucosaminidase and using a transwell plate, respectively.


RESULTS
Immunohistochemistry revealed that betaig-h3 occurs mainly in the basement membrane of proximal tubules, particularly the S3 segment but also to lesser extents in the basement membranes of the cortical thick ascending limb cells and the parietal glomerular epithelial cells in Bowman's capsule. Immunoblotting revealed that approximately 68 kD bands were seen only in the cortex + the outer stripe of the outer medulla. Rats with streptozotocin (STZ)-induced diabetes exhibited a marked and sustained increase in renal betaig-h3 abundance. This was mirrored by urinary betaig-h3 levels. In vitro experiments with human primary renal proximal tubular epithelial cells revealed that their expression of betaig-h3 was greatly increased by either TGF-beta or glucose. High glucose levels also stimulated TGF-beta production by renal proximal tubular epithelial cells and the high glucose-induced betaig-h3 expression was almost completely blocked by anti-TGF-beta antibody. betaig-h3 mediated renal proximal tubular epithelial cells adhesion and migration.


CONCLUSIONS
betaig-h3 may be important in the development of diabetic nephropathy. Furthermore, the level of urinary betaig-h3 may be useful as an early marker reflecting disease onset and progression.
Lee
Suk-Hee
SH
Cell and Matrix Biology, National Research Laboratory, Kyungpook National University, Taegu, Korea.
Bae
Jong-Sup
JS
Park
Sun-Hee
SH
Lee
Byung-Heon
BH
Park
Rang-Woon
RW
Choi
Je-Yong
JY
Park
Jae Yong
JY
Ha
Sung-Woo
SW
Kim
Yong-Lim
YL
Kwon
Tae-Hwan
TH
Kim
In-San
IS
D000818:Animals; D002448:Cell Adhesion; D002465:Cell Movement; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000378:metabolism* / Q000652:urine; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D007158:Immunologic Techniques; D007668:Kidney / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000502:physiology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000502:physiology* / Q000652:urine; D015854:Up-Regulation; D000099222:betaIG-H3 Protein
D016326:Extracellular Matrix Proteins; D005947:Glucose; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein