P-Cadherin is decreased in diabetic glomeruli and in glucose-stimulated podocytes in vivo and in vitro studies.
BACKGROUND
Proteinuria is a cardinal feature of glomerular disease, including diabetic nephropathy, and the glomerular filtration barrier acts as a filter, restricting protein excretion in urine. We tested whether the expression of P-cadherin, a molecule known to be located at the slit diaphragm, was altered by diabetes in vivo and by high glucose in vitro.


METHODS
In vivo, 24 Sprague-Dawley rats were injected with diluent [control (C), n=8] or streptozotocin intraperitoneally and the latter were left untreated (DM, n=8) or treated with insulin (DM+I, n=8) for 6 weeks. In vitro, immortalized mouse podocytes were cultured in media with 5.6 mM glucose (LG), LG+19.4 mM mannitol (LG+M) or 25 mM glucose (HG) with or without protein kinase C (PKC) inhibitor (10(-7) M calphostin C or 10(-6) M GF 109203X). Reverse transcription-polymerase chain reaction, western blotting for P-cadherin mRNA and protein expression, respectively, were performed with sieved glomeruli and cell lysates, and immunofluorescence staining was undertaken with renal tissue.


RESULTS
Twenty-four hour urinary albumin excretion was significantly higher in DM compared with C and DM+I rats (P<0.05). Glomerular P-cadherin mRNA expression was significantly lower in DM (1.36+/-0.20x10(-2) attm/ng RNA) than in C rats (2.61+/-0.33x10(-2) attm/ng RNA) (P<0.05). P-Cadherin protein expression, assessed by western blot and immunofluorescence staining, was also decreased in DM compared with C and DM+I glomeruli. HG significantly reduced P-cadherin mRNA and protein expression in cultured podocytes by 42% and 62%, respectively (P<0.05), and these decrements were ameliorated by PKC inhibitor.


CONCLUSIONS
Diabetes in vivo and exposure of podocytes to HG in vitro reduced P-cadherin mRNA and protein expression, and PKC was involved in the regulation of HG-induced down-regulation of P-cadherin. These findings suggest that the decrease in P-cadherin expression is connected with the early changes of diabetic nephropathy and, thus, may contribute to the development of proteinuria.
Xu
Zhong-Gao
ZG
Yonsei University College of Medicine, Department of Internal Medicine, 134 Shinchon-Dong, Seodaemoon-Gu, Seoul 120-752, Korea.
Ryu
Dong-Ryeol
DR
Yoo
Tae-Hyun
TH
Jung
Dong-Sub
DS
Kim
Jin-Ju
JJ
Kim
Hyung-Jong
HJ
Choi
Hoon-Young
HY
Kim
Joo-Seong
JS
Adler
Sharon G
SG
Natarajan
Rama
R
Han
Dae-Suk
DS
Kang
Shin-Wook
SW
D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D018929:Cell Culture Techniques; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage*; D007678:Kidney Glomerulus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008353:Mannitol / Q000008:administration & dosage; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013311:Streptozocin; D013549:Sweetening Agents / Q000008:administration & dosage*
D015820:Cadherins; D012333:RNA, Messenger; D013549:Sweetening Agents; D008353:Mannitol; D013311:Streptozocin; D005947:Glucose