Monocyte chemoattractant protein-1 has prosclerotic effects both in a mouse model of experimental diabetes and in vitro in human mesangial cells.
OBJECTIVE
Diabetic nephropathy is characterised by mesangial extracellular matrix accumulation. Monocyte chemoattractant protein-1 (MCP-1), a chemokine promoting monocyte infiltration, is upregulated in the diabetic glomerulus. We performed in vitro and in vivo studies to examine whether MCP-1 may have prosclerotic actions in the setting of diabetes, presumably via its receptor, chemokine (C-C motif) receptor 2 (CCR2), which has been described in mesangial cells.


METHODS
Human mesangial cells were exposed to recombinant human (rh)-MCP-1 (100 ng/ml) for 12, 24 and 48 h and to rh-MCP-1 (10, 100 and 200 ng/ml) for 24 h. Fibronectin, collagen IV and transforming growth factor, beta 1 (TGF-beta1) protein levels were measured by ELISA and pericellular polymeric fibronectin levels by western blotting. The intracellular mechanisms were investigated using specific inhibitors for CCR2, nuclear factor kappa B (NF-kappaB), p38 mitogen-activated protein kinase and protein kinase C, and an anti-TGF-beta1 blocking antibody. In both non-diabetic and streptozotocin-induced diabetic mice that were deficient or not in MCP-1, glomerular fibronectin accumulation was examined by immunohistochemistry, while cortical Tgf-beta1 (also known as Tgfb1) and fibronectin mRNA and protein levels were examined by real-time PCR and western blotting.


RESULTS
In mesangial cells, MCP-1 binding to CCR2 induced a 2.5-fold increase in fibronectin protein levels at 24 h followed by a rise in pericellular fibronectin, whereas no changes were seen in collagen IV production. MCP-1-induced fibronectin production was TGF-beta1- and NF-kappaB-dependent. In diabetic mice, loss of MCP-1 diminished glomerular fibronectin protein production and both renal cortical Tgf-beta1 and fibronectin mRNA and protein levels.


CONCLUSIONS
Our in vitro and in vivo findings indicate a role for the MCP-1/CCR2 system in fibronectin deposition in the diabetic glomerulus, providing a new therapeutic target for diabetic nephropathy.
Giunti
S
S
Department of Internal Medicine, University of Turin, C.so AM Dogliotti, 14, 10126, Turin, Italy. sara_giunti@katamail.com
Tesch
G H
GH
Pinach
S
S
Burt
D J
DJ
Cooper
M E
ME
Cavallo-Perin
P
P
Camussi
G
G
Gruden
G
G
D000818:Animals; D018932:Chemokine CCL2 / Q000235:genetics* / Q000502:physiology*; D024141:Collagen Type IV / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003928:Diabetic Nephropathies; D004797:Enzyme-Linked Immunosorbent Assay; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D050527:Mesangial Cells / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D018932:Chemokine CCL2; D024141:Collagen Type IV; D005353:Fibronectins; D016328:NF-kappa B; D053773:Transforming Growth Factor beta1; D048051:p38 Mitogen-Activated Protein Kinases