Macropinocytosis inhibition attenuates pro-fibrotic responses in lung fibroblasts and pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a devastating chronic lung disorder with limited treatment options. Macropinocytosis is one of the key cellular processes involved in nutrient consumption from the extracellular environment under stress conditions. Here, we studied the role of macropinocytosis in lung fibroblast activation and experimental pulmonary fibrosis.

Osteoprotegerin is induced by transforming growth factor-beta 1 and regulates pro-fibrotic responses in human dermal fibroblasts.

Transforming growth factor-beta1 (TGF-β1) is known to play a key role in the progression of organ fibrosis. Here, we demonstrate that TGF-β1 induces osteoprotegerin (OPG) expression in human dermal fibroblasts (HDFs) at both protein and mRNA levels. OPG neutralization has led to attenuation of TGF-β1-mediated profibrotic effects in HDFs.

PIK-III exerts anti-fibrotic effects in activated fibroblasts by regulating p38 activation.

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune-driven connective tissue disorder that results in fibrosis of the skin and internal organs such as the lung. Fibroblasts are known as the main effector cells involved in the progression of SSc through the induction of extracellular matrix (ECM) proteins and myofibroblast differentiation. Here, we demonstrate that 4'-(cyclopropylmethyl)-N2-4-pyridinyl-[4,5'-bipyrimidine]-2,2'-diamine (PIK-III), known as class III phosphatidylinositol 3-kinase (PIK3C3/VPS34) inhibitor, exerts potent antifibrotic effects in human dermal fibroblasts (HDFs) by attenuating transforming growth factor-beta 1 (TGF-β1)-induced ECM expression, cell contraction and myofibroblast differentiation.