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Dual targeting of MEK and PI3K pathways attenuates established and progressive pulmonary fibrosis.

ABSTRACT: Pulmonary fibrosis is often triggered by an epithelial injury resulting in the formation of fibrotic lesions in the lung, which progress to impair gas exchange and ultimately cause death. Recent clinical trials using drugs that target either inflammation or a specific molecule have failed, suggesting that multiple pathways and cellular processes need to be attenuated for effective reversal of established and progressive fibrosis. Although activation of MAPK and PI3K pathways have been detected in human fibrotic lung samples, the therapeutic benefits of in vivo modulation of the MAPK and PI3K pathways in combination are unknown. Overexpression of TGF? in the lung epithelium of transgenic mice results in the formation of fibrotic lesions similar to those found in human pulmonary fibrosis, and previous work from our group shows that inhibitors of either the MAPK or PI3K pathway can alter the progression of fibrosis. In this study, we sought to determine whether simultaneous inhibition of the MAPK and PI3K signaling pathways is a more effective therapeutic strategy for established and progressive pulmonary fibrosis. Our results showed that inhibiting both pathways had additive effects compared to inhibiting either pathway alone in reducing fibrotic burden, including reducing lung weight, pleural thickness, and total collagen in the lungs of TGF? mice. This study demonstrates that inhibiting MEK and PI3K in combination abolishes proliferative changes associated with fibrosis and myfibroblast accumulation and thus may serve as a therapeutic option in the treatment of human fibrotic lung disease where these pathways play a role.

SUBMITTER: Madala SK

PROVIDER: S-EPMC3903543 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Dual targeting of MEK and PI3K pathways attenuates established and progressive pulmonary fibrosis.

Madala Satish K SK Edukulla Ramakrishna R Phatak Mukta M Schmidt Stephanie S Davidson Cynthia C Acciani Thomas H TH Korfhagen Thomas R TR Medvedovic Mario M Lecras Timothy D TD Wagner Kimberly K Hardie William D WD

PloS one 20140127 1

Pulmonary fibrosis is often triggered by an epithelial injury resulting in the formation of fibrotic lesions in the lung, which progress to impair gas exchange and ultimately cause death. Recent clinical trials using drugs that target either inflammation or a specific molecule have failed, suggesting that multiple pathways and cellular processes need to be attenuated for effective reversal of established and progressive fibrosis. Although activation of MAPK and PI3K pathways have been detected i ...[more]

PMID: 24475138

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Project description:Patients with pulmonary graft-versus-host disease (pGVHD) have a poor prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Furthermore, pGVHD pathogenesis is not fully elucidated in humans, and currently available immunosuppressants are inadequately effective. We performed pathologic evaluation of lung specimens from 45 allo-HSCT recipients with pGVHD who underwent lung transplantation. Patient pathology was characterized by bronchiolitis and subpleural perivascular inflammation, with B-cell, monocyte, and T-cell accumulation around bronchioles. Bronchiolitis, perivascular inflammation, and peribronchial macrophage aggregation were also identified in a murine pGVHD model after transplant of bone marrow cells and splenocytes from C57BL/6 to B10.BR mice. Among mitogen-activated protein kinase kinase (MEK) inhibitors, cobimetinib, but not trametinib, improved survival rates. Cobimetinib attenuated bronchiolitis, improved airway resistance and lung compliance in the mice, and suppressed activation of B cells and tumor necrosis factor α production by monocytes in vitro; these features were not suppressed by trametinib or tacrolimus. Furthermore, cobimetinib suppressed activation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling, resulting in B-cell and monocyte suppression. Dual inhibition of the MEK/extracellular signal-regulated kinase (ERK) and PI3K/AKT pathways using a combination of trametinib and the PI3K inhibitor taselisib strongly suppressed B-cell activation in vitro and improved mouse survival rates compared with vehicle or monotherapy with trametinib or taselisib. Imaging mass cytometry of human pGVHD revealed that T cells around bronchioles were positive for phosphorylated ERK, whereas B cells were positive for phosphorylated AKT. Thus, perivascular inflammation and bronchiolitis mediated by activation of the MEK/ERK and PI3K/AKT pathways are essential for pGVHD and represent a potential novel therapeutic target in humans.

Project description:BACKGROUND:Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal disease. Histone deacetylase 6 (HDAC6) alters function and fate of various proteins via deacetylation of lysine residues, and is implicated in TGF-?1-induced EMT (epithelial-mesenchymal transition). However, the role of HDAC6 in pulmonary fibrosis is unknown. METHODS:HDAC6 expression in IPF and control lungs was assessed by quantitative real-time PCR (qRT-PCR) and immunoblots. Lung fibroblasts were treated with TGF-?1 ± HDAC6 inhibitors (Tubacin, Tubastatin, ACY1215, or MC1568), and fibrotic markers such as type I collagen were assessed using qRT-PCR and immunoblots. Mice were treated with bleomycin (oropharyngeal aspiration; single dose) ± Tubastatin (intraperitoneally injection; daily for 21 days), and lung collagen expression was gauged using immunoblots and trichrome staining. In a separate experiment, HDAC6 wild-type (WT) and knockout (KO) mice were administered bleomycin, and lungs were evaluated in the same manner. RESULTS:HDAC6 expression was deregulated in IPF lungs. Among the HDAC6 inhibitors tested, only Tubastatin significantly repressed TGF-?1-induced expression of type-1 collagen in lung fibroblasts, and this finding was coupled with decreased Akt phosphorylation and increased Akt-PHLPP (PH domain and Leucine rich repeat Protein Phosphatase) association. Tubastatin repressed TGF-?1-induced S6K phosphorylation, HIF-1? expression, and VEGF expression. Tubastatin also repressed TGF-?1-induced inhibition of LC3B-II (a marker of autophagosome formation). In bleomycin-treated mouse lungs, HDAC6 expression was increased, and Tubastatin repressed type-1 collagen expression. However, in HDAC6 KO mice, bleomycin-induced type-1 collagen expression was not repressed compared to WT mice. Knockdown of HDAC6, as well as HDAC10, another potential Tubastatin target, did not inhibit TGF-?1-induced collagen expression in lung fibroblasts. CONCLUSIONS:HDAC6 expression is altered during lung fibrogenesis. Tubastatin represses TGF-?1-induced collagen expression, by diminishing Akt phosphorylation and regulating downstream targets such as HIF-1?-VEGF axis and autophagy. Tubastatin-treated WT mice are protected against bleomycin-induced fibrosis, but HDAC6 KO mice are not. Our data suggest that Tubastatin ameliorates pulmonary fibrosis, by targeting the TGF?-PI3K-Akt pathway, likely via an HDAC6-independent mechanism.

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Dual targeting of MEK and PI3K pathways attenuates established and progressive pulmonary fibrosis.

Publications

Dual targeting of MEK and PI3K pathways attenuates established and progressive pulmonary fibrosis.

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