Heparan sulfate-dependent ERK activation contributes to the overexpression of fibrotic proteins and enhanced contraction by scleroderma fibroblasts.
OBJECTIVE
To investigate the contribution of heparan sulfate proteoglycan and Ras/MEK/ERK to the overexpression of profibrotic proteins and the enhanced contractile ability of dermal fibroblasts from patients with systemic sclerosis (SSc; scleroderma).


METHODS
The effects of the MEK/ERK inhibitor U0126, the heparan sulfate side chain formation inhibitor beta-xyloside, and soluble heparin on the overexpression of profibrotic genes were compared in fibroblasts from lesional skin of patients with diffuse SSc and fibroblasts from healthy control subjects. Identified protein expressions were compared with the contractile abilities of fibroblasts while they resided within a collagen lattice. Forces generated were measured using a culture force monitor.


RESULTS
Inhibiting MEK/ERK with U0126 significantly reduced expression of a cohort of proadhesive and procontractile proteins that normally are overexpressed by scleroderma fibroblasts, including integrin alpha4 and integrin beta1. Antagonizing heparan sulfate side chain formation with beta-xyloside or the addition of soluble heparin prevented ERK activation, in addition to reducing the expression of these proadhesive/contractile proteins. Treatment with either U0126, beta-xyloside, or heparin resulted in a reduction in the overall peak contractile force generated by dermal fibroblasts. Blocking platelet-derived growth factor receptor with Gleevec (imatinib mesylate) reduced overall contractile ability and the elevated syndecan 4 expression and ERK activation in SSc fibroblasts.


CONCLUSIONS
The results of this study suggest that heparan sulfate-dependent ERK activation contributes to the enhanced contractile ability demonstrated by dermal fibroblasts from lesional skin of patients with scleroderma. These results are consistent with the notion that the MEK/ERK procontractile pathway is dysregulated in scleroderma dermal fibroblasts. Additionally, the results suggest that antagonizing the MEK/ERK pathway is likely to modulate heparan sulfate proteoglycan activity, which in turn may have a profound effect on the fibrotic response in SSc.
Chen
Yunliang
Y
University College London, London, UK.
Leask
Andrew
A
Abraham
David J
DJ
Pala
Daphne
D
Shiwen
Xu
X
Khan
Korsa
K
Liu
Shangxi
S
Carter
David E
DE
Wilcox-Adelman
Sarah
S
Goetinck
Paul
P
Denton
Christopher P
CP
Black
Carol M
CM
Pitsillides
Andrew A
AA
Sarraf
Catherine E
CE
Eastwood
Mark
M
D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D020405:Dermis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D005109:Extracellular Matrix / Q000473:pathology / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000473:pathology / Q000502:physiology*; D005355:Fibrosis; D015870:Gene Expression / Q000502:physiology; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D010641:Phenotype; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D053671:Syndecan-4 / Q000235:genetics
D048049:Extracellular Signal-Regulated MAP Kinases; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D053671:Syndecan-4; C508304:SDC4 protein, human