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Molecular Biology - Respiratory Medicine

Inhibition of PI3K Prevents the Proliferation and Differentiation of Human Lung Fibroblasts into Myofibroblasts: The Role of Class I P110 Isoforms
Published: Monday, October 03, 2011
Author: Enrico Conte et al.

by Enrico Conte, Mary Fruciano, Evelina Fagone, Elisa Gili, Filippo Caraci, Maria Iemmolo, Nunzio Crimi, Carlo Vancheri

Idiopathic pulmonary fibrosis (IPF) is a progressive fibroproliferative disease characterized by an accumulation of fibroblasts and myofibroblasts in the alveolar wall. Even though the pathogenesis of this fatal disorder remains unclear, transforming growth factor-ß (TGF-ß)-induced differentiation and proliferation of myofibroblasts is recognized as a primary event. The molecular pathways involved in TGF-ß signalling are generally Smad-dependent yet Smad-independent pathways, including phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), have been recently proposed. In this research we established ex-vivo cultures of human lung fibroblasts and we investigated the role of the PI3K/Akt pathway in two critical stages of the fibrotic process induced by TGF-ß: fibroblast proliferation and differentiation into myofibroblasts. Here we show that the pan-inhibitor of PI3Ks LY294002 is able to abrogate the TGF-ß-induced increase in cell proliferation, in a- smooth muscle actin expression and in collagen production besides inhibiting Akt phosphorylation, thus demonstrating the centrality of the PI3K/Akt pathway in lung fibroblast proliferation and differentiation. Moreover, for the first time we show that PI3K p110d and p110? are functionally expressed in human lung fibroblasts, in addition to the ubiquitously expressed p110a and ß. Finally, results obtained with both selective inhibitors and gene knocking-down experiments demonstrate a major role of p110? and p110a in both TGF-ß-induced fibroblast proliferation and differentiation. This finding suggests that specific PI3K isoforms can be pharmacological targets in IPF.