High glucose concentration inhibits the expression of membrane type metalloproteinase by mesangial cells: possible role in mesangium accumulation.
OBJECTIVE
High glucose concentration decreases the degradation of mesangium matrix, an action substantially mediated by a reduction in the activities of the matrix metalloproteinases (MMPs). Metalloproteinase-2 is unique in that it is activated on the cell surface by one of the membrane type metalloproteinases (MT1-MMP), a process involving complex interactions with tissue inhibitor of metalloproteinase-2. The aim of this study was investigate the effects of glucose concentration on mesangial cell gene expression of MT1-MMP and its ability to modulate the activation of metalloproteinase-2.


METHODS
Gene expression was determined using competitive RT-PCR, protein expression of MMP-2 was measured by western blot and its activation by zymography. Concanavalin A, known to increase MT1-MMP expression was added in some experiments.


RESULTS
High glucose concentration decreased MT1-MMP gene expression (11.52 +/- 1.63 and 4.84 +/- 0.72 amol/microg RNA, 5 vs 25 mmol/l glucose, respectively) and decreased activation of MMP-2 by 30% despite a twofold increase in gene expression of MMP-2. Concanavalin A increased expression of MT1-MMP and activation of MMP-2. Irrespective of whether MMP-2 was from endogenous or exogenous source there was an excellent correlation between the MT1-MMP expression and degree of MMP-2 activation, whereas the gene expression of TIMP-2 was not significantly altered by high glucose concentration or concanavalin A.


CONCLUSIONS
Our results indicate that in a high glucose milieu, suppression of MT1-MMP expression could explain the low MMP-2 activity in the presence of high MMP-2 expression. This process could contribute to the mesangium matrix accumulation in diabetic nephropathy.
McLennan
S V
SV
Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, Australia.
Martell
S Y
SY
Yue
D K
DK
D015153:Blotting, Western; D002462:Cell Membrane / Q000201:enzymology; D003208:Concanavalin A / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects*; D005920:Glomerular Mesangium / Q000201:enzymology*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000235:genetics* / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics / Q000502:physiology
D003208:Concanavalin A; D019716:Tissue Inhibitor of Metalloproteinase-2; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2; D005947:Glucose