Gremlin gene expression in bovine retinal pericytes exposed to elevated glucose.
OBJECTIVE
To assess the influence of high extracellular glucose on the expression of the bone morphogenetic protein (BMP) antagonist, gremlin, in cultured bovine retinal pericytes (BRPC).


METHODS
BRPC were cultured under conditions of 5 mM and 30 mM d-glucose for 7 days and total RNA was isolated. Gremlin mRNA levels were correlated, by RT-PCR, with other genes implicated in the pathogenesis of diabetic retinopathy and the signalling pathways in high glucose induced gremlin expression were probed using physiological inhibitors. Gremlin expression was also examined in the retina of streptozotocin induced diabetic mice.


RESULTS
High glucose stimulated a striking increase in BRPC gremlin mRNA levels in parallel with increases in mRNA for the growth factors vascular endothelial growth factor (VEGF), transforming growth factor beta (TGFbeta), and connective tissue growth factor (CTGF) and changes in other genes including fibronectin and plasminogen activator inhibitor-1 (PAI-1). High glucose triggered gremlin expression was modulated by anti-TGFbeta antibody, by the uncoupler of oxidative phosphorylation, CCCP, and by inhibition of MAP-kinase (MAPK) activation. Striking gremlin expression was observed in the outer retina of diabetic mice and also at the level of the vascular wall.


CONCLUSIONS
Gremlin gene expression is induced in BRPC in response to elevated glucose and in the retina of the streptozotocin induced diabetic mouse. Its expression is modulated by hyperglycaemic induction of the MAPK, reactive oxygen species, and TGFbeta pathways, all of which are reported to have a role in diabetic fibrotic disease. This implicates a role for gremlin in the pathogenesis of diabetic retinopathy.
Kane
R
R
Institute of Ophthalmology, 60 Eccles Street, Dublin 7, Ireland. cobrien@mater.ie.
Stevenson
L
L
Godson
C
C
Stitt
A W
AW
O'Brien
C
C
D000818:Animals; D001483:Base Sequence; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors; D002417:Cattle; D002478:Cells, Cultured; D016207:Cytokines; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D003930:Diabetic Retinopathy / Q000378:metabolism; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020286:Pericytes / Q000187:drug effects* / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013045:Species Specificity
D019485:Bone Morphogenetic Proteins; D016207:Cytokines; D005947:Glucose; D036341:Intercellular Signaling Peptides and Proteins; C113178:Grem1 protein, mouse