2002 Fiscal Year Final Research Report Summary
Direct influence of proteinuria on tubulointerstitial lesion -Autocrine action of TGF-β1
| Project/Area Number |
12671051
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Kidney internal medicine
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| Research Institution | Teikyo University |
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Principal Investigator |
UCHIDA Shunya Teikyo University, Medicine, Associate professor, 医学部, 助教授 (50151882)
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| Project Period (FY) |
2000 – 2002
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| Keywords | proteinuria / albumin / activation of tubules / TGF-β1 / lysozomal enzyme / NAG / Ok cell / polarity of secretion |
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| Research Abstract |
There is evidence to suggest that proteinuria per se may aggravate renal injuries through tubulointerstitial damages. The mechanism underlying this process is largely unknown. We have, therefore, attempted to elucidate the possible recruitment of some cytokines such as TGF-b 1 which likely induces interstitial fibrosis. OKP cells, proximal tubular cell line derived from opossum kidney, were grown to a confluence in serum-free defined media consisting of DMEM supplemented with insulin, transferrin and selenium. Cells were cultivated in the media containing respectively various concentrations of bovine albumin and bovine g-globulin up to 24 hr. Northern blot was performed with poly (A)+ RNA and cDNA from rat TGF-b 1. Signals (〜2.5 kb) were normalized with those of GAPDH as internal control. NAG, another candidate for tubulointerstitial injury, was also measured in the same conditions. After administration of albumin, TGF-b1 mRNA levels increased in dose-dependent (0-10 mg/ml) and time-dependent manners (0-24 hr). NAG release was also elicited upon addition of proteins in dose-and time-dependent manners whereas the increase by albumin was several folds greater than that by g-globulin. Moreover, using two' chamber system NAG was preferentially released to the apical side when albumin was applied in the apical not in the basolateral side of the cells, indicating that luminal proteinuria plays a pivotal role. We conclude that in cultured proximal tubular cells, albumin by itself induces TGF-b1 expression and NAG secretion, both of which may participate in tubulointerstitial lesions seen in vivo. The present in vitro system warrants the further elucidation of molecular mechanisms of proteinuria-induced renal injury.
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