Enhanced expression of naofen in kidney of streptozotocin-induced diabetic rats: possible correlation to apoptosis of tubular epithelial cells.
BACKGROUND
Hyperglycemia/high glucose may induce apoptosis in diabetic kidney, but the mechanism is not fully understood. Naofen was found as a Shiga toxin (Stx)-2-related protein. Based on renal dysfunction in infection with Stx-producing Escherichia coli and on participation of naofen in apoptosis of human embryonic kidney cells, the present study was undertaken to investigate the mechanism of renal dysfunction in diabetes mellitus with particular reference to naofen.


METHODS
In in vivo studies utilizing streptozotocin (STZ)-induced diabetic rats, and also in in vitro cultured rat kidney epithelial (NRK52E) cells, naofen messenger RNA (mRNA) and protein expressions were analyzed. Naofen mRNA location in diabetic kidney was studied by in situ hybridization. Apoptosis was assessed by caspase-3 activity assay.


RESULTS
Rat diabetic kidney showed significant increases in caspase-3 activities and naofen mRNA. Naofen was mainly observed at both proximal and distal urinary tubules. Incubation of NRK52E cells in high glucose medium resulted in elevated naofen mRNA expression, whereas neither interleukin-1, interleukin-6, nor tumor necrosis factor-alpha elicited such action. Moreover, treatment of NRK52E cells with naofen small interfering RNA (siRNA) inhibited naofen mRNA expression induced by high glucose and blocked the increase in caspase-3 activity.


CONCLUSIONS
These data suggest that naofen expression may be upregulated by hyperglycemia, with possible correlation to apoptosis of tubular epithelial cells and thereby to diabetic nephropathy.
Department of Anesthesiology, Aichi Medical University School of Medicine, Nagakute, Aichi-gun, Aichi, 480-1195, Japan.
Yuko
Y
Sato
Guo-Gang
GG
Feng
Lei
L
Huang
Jun-Hua
JH
Fan
Chang
C
Li
Jun
J
An
Koji
K
Tsunekawa
Shuji
S
Kurokawa
Yoshihiro
Y
Fujiwara
Toru
T
Komatsu
Fumio
F
Kondo
Naohisa
N
Ishikawa
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053148:Caspase 3 / Q000235:genetics; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D003928:Diabetic Nephropathies / Q000503:physiopathology; D004847:Epithelial Cells / Q000378:metabolism; D006943:Hyperglycemia / Q000378:metabolism; D007668:Kidney / Q000503:physiopathology; D007684:Kidney Tubules / Q000473:pathology; D008297:Male; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D011506:Proteins; D012333:RNA, Messenger; C582790:WDR35 protein, rat; D053148:Caspase 3