An imbalance between matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase-2 contributes to the development of early diabetic nephropathy.
BACKGROUND
High glucose and angiotensin-II (Ang-II) levels are the known important mediators of diabetic nephropathy. However, the effects of these mediators on matrix metalloproteinase-2 (MMP-2) and on tissue inhibitor of metalloproteinase-2 (TIMP-2) in proximal tubule cells have yet to be fully examined within the context of early stage diabetic nephropathy.


METHODS
In this study, we attempted to characterize changes in MMP-2 and TIMP-2 in streptozotocin-induced diabetic rats. To further examine the molecular mechanisms involved, we evaluated the effects of high glucose (30 mM) or Ang-II on MMP-2, TIMP-2 and collagen synthesis in proximal tubule cells, and investigated whether MMP-2 and TIMP-2 are regulated via the TGF-beta1 pathway.


RESULTS
In streptozotocin-induced diabetic rats, TIMP-2 mRNA and protein levels were significantly higher than in controls. Urinary protein excretion also showed a significant positive correlation with glomerular and tubular TIMP-2 protein expressions, and a negative correlation with MMP-2 expression. In cultured cells, both high glucose and Ang-II induced significant increases in TGF-beta1, TIMP-2, and in collagen synthesis, and significant decreases in MMP-2 gene expression and activity, and thus disrupted the balance between MMP-2 and TIMP-2. Moreover, treatment with a selective angiotensin type 1 (AT1) receptor antagonist significantly inhibited Ang-II mediated changes in TGF-beta1, MMP-2, TIMP-2, and in collagen production, suggesting the role of the AT1 receptor. The addition of exogenous TGF-beta1 produced an effect similar to those of high glucose and Ang-II. Furthermore, the inhibition of TGF-beta1 protein prevented Ang-II-induced MMP-2 and TIMP-2 alterations, suggesting the involvement of a TGF-beta1 pathway.


CONCLUSIONS
High glucose or Ang-II treatment induce alterations in MMP-2 and TIMP-2 balance, which favour TIMP-2 over-activity. Moreover, Ang-II-mediated changes in the productions of MMP-2 and TIMP-2 occur via AT1 receptors and a TGF-beta1-dependent mechanism. These results suggest that an imbalance between the MMP-2 and TIMP-2, caused primarily by an increase in TIMP-2 activity, contributes to the pathogenesis of diabetic nephropathy.
Han
Sang Youb
SY
Department of Internal Medicine, Korea University Ansan-Hospital, 516 Kojan-Dong, Ansan City, Kyungki-Do 425-020, Korea. cdragn@unitel.co.kr
Jee
Yi Hwa
YH
Han
Kum Hyun
KH
Kang
Young Sun
YS
Kim
Hyoung Kyu
HK
Han
Jee Young
JY
Kim
Young Sik
YS
Cha
Dae Ryong
DR
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D024141:Collagen Type IV / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003928:Diabetic Nephropathies / Q000201:enzymology* / Q000473:pathology; D015870:Gene Expression; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000201:enzymology / Q000473:pathology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1
D024141:Collagen Type IV; D012333:RNA, Messenger; C508960:TGFB1 protein, human; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000804:Angiotensin II; D019716:Tissue Inhibitor of Metalloproteinase-2; D020778:Matrix Metalloproteinase 2; D005947:Glucose