Protective effect of dietary azuki bean (Vigna angularis) seed coats against renal interstitial fibrosis of rats induced by cisplatin.
OBJECTIVE
We investigated the effects of azuki bean (Vigna angularis) seed coats (ABSCs), which mainly contain proanthocyanidins and dietary fibers, on the infiltration of macrophages and the progression of renal interstitial fibrosis induced by cisplatin (CDDP).


METHODS
Male rats were divided into two groups: controls received intraperitoneal injections of saline and the other rats were injected intraperitoneally with 3 mg of CDDP per kilogram once a week for 5 wk. The CDDP-injected animals received one of four diets: 1) control diet (commercial diet only), 2) 0.5% red ABSC (RABSC) diet, 3) 2.0% RABSC diet, and 4) 2.0% white ABSC (WABSC) diet. The saline-injected animals were given the commercial diet. Five weeks after the final CDDP injection, macrophage kinetics and interstitial fibrotic areas were examined.


RESULTS
The content of polyphenols in the RABSC (76.3 g/kg of plant material) was higher than that in the WABSC (18.1 g/kg). Proanthocyanidins were detected in the RABSC (20.4 g/kg) but not in the WABSC. Histologically, the fibrotic areas consisting of fibroblastic cells and mononuclear cells developed around the dilated or atrophic tubules in the corticomedullary junction in CDDP-treated rat kidney, whereas the extent and magnitude of damage were less in the WABSC- and RABSC-treated rats. In immunohistochemical analysis, ED1-positive macrophages in CDDP-treated rats showed a significant increase in number compared with the control. The number of macrophages in CDDP plus WABSC or RABSC groups was significantly smaller than that in CDDP-treated rats. In addition, the number of macrophages in the RABSC group was significantly smaller than in the WABSC group, indicating that ABSC, especially RABSC, prevented macrophages from infiltrating into areas of interstitial fibrosis.


CONCLUSIONS
These results suggest that ABSC, especially RABSC, suppress the increase of infiltrating macrophages in the damaged kidney and may lead to amelioration of interstitial fibrosis. Based on the composition of ABSC, molecules such as proanthocyanidins and/or dietary fibers may be associated with the amelioration of renal damage.
Sato
Shin
S
Department of Life Sciences, Graduate School of Health Sciences, Aomori University of Health and Welfare, Aomori, Japan. s_sato3@auhw.ac.jp
Hori
Yuuka
Y
Yamate
Jyoji
J
Saito
Takeshi
T
Kurasaki
Masaaki
M
Hatai
Asako
A
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000633:toxicity*; D001806:Blood Urea Nitrogen; D002945:Cisplatin / Q000008:administration & dosage / Q000633:toxicity*; D003404:Creatinine / Q000097:blood; D004032:Diet; D018450:Disease Progression; D007887:Fabaceae; D005355:Fibrosis / Q000097:blood / Q000139:chemically induced / Q000188:drug therapy; D007668:Kidney / Q000187:drug effects* / Q000473:pathology; D008264:Macrophages / Q000187:drug effects; D008297:Male; D009395:Nephritis, Interstitial / Q000097:blood / Q000139:chemically induced / Q000188:drug therapy*; D051381:Rats; D011916:Rats, Inbred F344; D012639:Seeds; D013997:Time Factors
D000970:Antineoplastic Agents; D003404:Creatinine; D002945:Cisplatin