Effect of the monocyte chemoattractant protein-1/CC chemokine receptor 2 system on nephrin expression in streptozotocin-treated mice and human cultured podocytes.
OBJECTIVE
Monocyte chemoattractant protein-1 (MCP-1), a chemokine binding to the CC chemokine receptor 2 (CCR2) and promoting monocyte infiltration, has been implicated in the pathogenesis of diabetic nephropathy. To assess the potential relevance of the MCP-1/CCR2 system in the pathogenesis of diabetic proteinuria, we studied in vitro if MCP-1 binding to the CCR2 receptor modulates nephrin expression in cultured podocytes. Moreover, we investigated in vivo if glomerular CCR2 expression is altered in kidney biopsies from patients with diabetic nephropathy and whether lack of MCP-1 affects proteinuria and expression of nephrin in experimental diabetes.


METHODS
Expression of nephrin was assessed in human podocytes exposed to rh-MCP-1 by immunofluorescence and real-time PCR. Glomerular CCR2 expression was studied in 10 kidney sections from patients with overt nephropathy and eight control subjects by immunohistochemistry. Both wild-type and MCP-1 knockout mice were made diabetic with streptozotocin. Ten weeks after the onset of diabetes, albuminuria and expression of nephrin, synaptopodin, and zonula occludens-1 were examined by immunofluorescence and immunoblotting.


RESULTS
In human podocytes, MCP-1 binding to the CCR2 receptor induced a significant reduction in nephrin both mRNA and protein expression via a Rho-dependent mechanism. The MCP-1 receptor, CCR2, was overexpressed in the glomerular podocytes of patients with overt nephropathy. In experimental diabetes, MCP-1 was overexpressed within the glomeruli and the absence of MCP-1 reduced both albuminuria and downregulation of nephrin and synaptopodin.


CONCLUSIONS
These findings suggest that the MCP-1/CCR2 system may be relevant in the pathogenesis of proteinuria in diabetes.
Tarabra
Elena
E
Diabetic Nephropathy Laboratory, Department of Internal Medicine, University of Turin, Italy.
Giunti
Sara
S
Barutta
Federica
F
Salvidio
Gennaro
G
Burt
Davina
D
Deferrari
Giacomo
G
Gambino
Roberto
R
Vergola
Daniela
D
Pinach
Silvia
S
Perin
Paolo Cavallo
PC
Camussi
Giovanni
G
Gruden
Gabriella
G
D000818:Animals; D001706:Biopsy; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D015536:Down-Regulation / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D050199:Podocytes / Q000166:cytology / Q000502:physiology*; D011507:Proteinuria / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D062826:Zonula Occludens-1 Protein; D054460:rho-Associated Kinases / Q000378:metabolism
C111835:CCL2 protein, human; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D008565:Membrane Proteins; D008840:Microfilament Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C503967:SYNPO protein, human; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; C113267:nephrin; D054460:rho-Associated Kinases