Evidence supporting proteolytic cleavage of insulin-like growth factor binding protein-1 (IGFBP-1) protein in amniotic fluid.
OBJECTIVE
The purpose of this study was to determine if: 1) insulin-like growth factor binding protein-1 (IGFBP-1) in amniotic fluid (AF) exhibited proteolytic cleavage in cases of intra-amniotic inflammation; and 2) if the matrix metalloproteinases (MMP-3, MMP-8, MMP-9) in AF are associated with the degradation of IGFBP-1 in AF.


METHODS
AF samples (n=20) were obtained from preterm gestations with and without intra-amniotic inflammation. The form of IGFBP-1 in AF was assessed by Western blot analysis and AF MMP-8 concentration was measured by ELISA. Densitometric analysis of Western blot was performed and the fragmented/intact IGFBP-1 ratio was calculated. Proteolysis of AF IGFBP-1 by MMPs was evaluated by incubating AF with exogenous human MMP-3, MMP-8 or MMP-9, and by incubating recombinant human IGFBP-1 in AF with and without inflammation.


RESULTS
1) IGFBP-1 was present in AF without inflammation as an intact form; however, the fragmented form was dominant in AF with inflammation; 2) the ratio of fragmented/intact IGFBP-1 was significantly higher in AF with inflammation than in AF without inflammation; 3) a higher ratio of fragmented/intact IGFBP-1 was associated with a higher concentration of MMP-8; 4) in-vitro proteolysis experiments showed that AF IGFBP-1 was degraded by exogenous human MMP-3, MMP-8 and MMP-9; 5) recombinant human IGFBP-1 was fragmented in AF with inflammation, but not in AF without inflammation.


CONCLUSIONS
The fragmented form of AF IGFBP-1 was significantly increased in AF with intra-amniotic inflammation, and MMPs produced in AF with intra-amniotic inflammation were associated with the proteolytic change of AF IGFBP-1.
Lee
Si Eun
SE
Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Republic of Korea.
Han
Byoung-Don
BD
Park
In-Sook
IS
Romero
Roberto
R
Yoon
Bo Hyun
BH
D000328:Adult; D000653:Amniotic Fluid / Q000201:enzymology / Q000378:metabolism*; D015153:Blotting, Western; D002821:Chorioamnionitis / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000201:enzymology / Q000378:metabolism; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism*; D007527:Isoenzymes; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D011247:Pregnancy
C032231:IGFBP1 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D007527:Isoenzymes; D020782:Matrix Metalloproteinases