The
endothelins are a family of endothelium-derived
peptides that possess a variety of functions, including vasoconstriction.
Endothelin-1 (ET-1) is up-regulated during tissue repair and promotes myofibroblast contraction and migration, hence contributing to matrix remodeling during tissue repair. Here, we show that addition of ET-1 to normal lung fibroblasts induces expression of
proteins that contribute to a contractile phenotype, including alpha-smooth muscle actin (alpha-SMA),
ezrin,
moesin, and
paxillin. We confirm that ET-1 enhances the ability of lung fibroblasts to contract extracellular matrix, a function essential for tissue repair, through induction of de novo
protein synthesis. Blockade of the Akt/
phosphoinositide 3-kinase (PI3-kinase) pathway with
LY294002 and
wortmannin prevents the ability of ET-1 to induce alpha-SMA,
ezrin,
paxillin, and
moesin and to promote matrix contraction. Dominant negative rac and Akt blocked the ability of ET-1 to promote formation of alpha-SMA stress fibers. Using specific ET-1 receptor inhibitors, we show that ET-1 induces
collagen matrix contraction through the ETA, but not the ETB, receptor. Relative to normal pulmonary fibroblasts, fibroblasts cultured from
scars of patients with the fibrotic disease
systemic sclerosis (scleroderma) show enhanced ET-1 expression and binding.
Systemic sclerosis lung fibroblasts show increased ability to contract a
collagen matrix and elevated expression of the procontractile
proteins alpha-SMA,
ezrin,
paxillin, and
moesin, which are greatly reduced by antagonizing endogenous ET-1 signaling. Thus, blocking ET-1 or the
PI3-kinase/Akt cascades might be beneficial in reducing
scar formation in
pulmonary fibrosis.