Pretreatment with valproic acid alleviates pulmonary fibrosis through epithelial–mesenchymal transition inhibition in vitro and in vivo

Abstract

Epithelial–mesenchymal transition (EMT) plays a crucial role in the development of pulmonary fibrosis. This study aims to investigate the effects of valproic acid (VPA) on EMT in vitro and in vivo. In vitro, EMT was induced by the administration of transforming growth factor-β1 (TGF-β1) in a human alveolar epithelial cell line (A549). The dose effects of VPA (0.1–3 mM) on EMT were subsequently evaluated at different timepoints. VPA (1 mM) was applied prior to the administration of TGF-β1 and the expression of E-cadherin, vimentin, p-Smad2/3 and p-Akt was assessed. In addition, the effects of a TGF-β type I receptor inhibitor (A8301) and PI3K-Akt inhibitor (LY294002) on EMT were evaluated. In vivo, the effects of VPA on bleomycin-induced lung fibrosis were evaluated by assessing variables such as survival rate, body weight and histopathological changes, whilst the expression of E-cadherin and vimentin in lung tissue was also evaluated. A8301 and LY294002 were used to ascertain the cellular signaling pathways involved in this model. The administration of VPA prior to TGF-β1 in A549 cells prevented EMT in both a time- and concentration-dependent manner. Pretreatment with VPA downregulated the expression of both p-Smad2/3 and p-Akt. A8301 administration increased the expression of E-cadherin and reduced the expression of vimentin. LY294002 inhibited Akt phosphorylation induced by TGF-β1 but failed to prevent EMT. Pretreatment with VPA both increased the survival rate and prevented the loss of body weight in mice with pulmonary fibrosis. Interestingly, both VPA and A8301 prevented EMT and facilitated an improvement in lung structure. Overall, pretreatment with VPA attenuated the development of pulmonary fibrosis by inhibiting EMT in mice, which was associated with Smad2/3 deactivation but without Akt cellular signal involvement.

State of the Art in Idiopathic Pulmonary Fibrosis

“…Interestingly, in contrast to in vitro studies, VPA was shown to significantly attenuate EMT and lung fibrosis in bleomycin-treated mice in vivo, which was associated with Smad2/3 deactivation but without Akt cellular signal involvement [170]. In bleomycintreated rats, it reduced oxidative stress and proinflammatory cytokines in injured lungs, together with significant improvement of the histopathological picture [254].…”

“…Interestingly, and vice versa, treatment of IPF fibroblasts with HDAC inhibitors resulted in the reduction of profibrotic genes, such as COL3A1, in association with marked chromatin alterations [164,165,167]. Further, many scientific groups have demonstrated that various HDAC inhibitors targeting global HDAC activity or single HDAC enzymes decreased lung fibrosis and ECM deposition in bleomycin-treated mice [164,[168][169][170][171]. Of note, HDAC inhibitors have been known for a long time as successful anticancer agents as they specifically induce cell cycle arrest and apoptosis in "abnormal" cancer cells, whereas normal healthy cells are relatively resistant to HDAC-inhibitor-induced cell death [172,173].…”

“…Increased activity and overexpression of histone deacetylases (HDACs) have been described for a long time in various pathological conditions such as cancer, cardiac hypertrophy and hypertension [166,193,241,242]. Upregulated HDAC activities are also observed in fibrotic diseases involving the heart, liver, kidneys and lungs; and experimental studies performed on animal models have shown that HDAC inhibitors can ameliorate various forms of fibrosis [164,[168][169][170][243][244][245].…”

β-Klotho Promotes the Development of Intrauterine Adhesions via the PI3K/AKT Signaling Pathway

“…However, the participation and roles of the Smad-independent pathways in ESC fibrosis mediated by TGF-β1 need to be deeply studied. The PI3K/AKT pathway has been found to play an important role in lung, liver, pancreas, and other organs’ fibrosis [ 40 , 41 , 42 ]. Our study found that the PI3K/AKT pathway can be activated by TGF-β1 and participate in endometrial fibrosis.…”

CS1, a controlled‐release formulation of valproic acid, for the treatment of patients with pulmonary arterial hypertension: Rationale and design of a Phase 2 clinical trial

“…At the cellular level, VPA induces apoptosis in PAAFs and PASMCs from patients with PAH 36 . VPA also has important anti‐inflammatory, anti‐fibrotic, and anti‐thrombotic properties, which may be advantageous in PAH 39–41 . Therefore, VPA exhibits a unique multitargeted mechanism of action that allows for pressure reduction, reverse vascular remodeling, and positive RV adaptation.…”