Valproic Acid Induces Endothelial-to-Mesenchymal Transition-Like Phenotypic Switching

Abstract

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, is a widely used anticonvulsant drug that is currently undergoing clinical evaluation for anticancer therapy due to its anti-angiogenic potential. Endothelial cells (ECs) can transition into mesenchymal cells and this form of EC plasticity is called endothelial-to-mesenchymal transition (EndMT), which is widely implicated in several pathologies including cancer and organ fibrosis. However, the effect of VPA on EC plasticity and EndMT remains completely unknown. We report herein that VPA-treatment significantly inhibits tube formation, migration, nitric oxide production, proliferation and migration in ECs. A microscopic evaluation revealed, and qPCR, immunofluorescence and immunoblotting data confirmed EndMT-like phenotypic switching as well as an increased expression of pro-fibrotic genes in VPA-treated ECs. Furthermore, our data confirmed important and regulatory role played by TGFβ-signaling in VPA-induced EndMT. Our qPCR array data performed for 84 endothelial genes further supported our findings and demonstrated 28 significantly and differentially regulated genes mainly implicated in angiogenesis, endothelial function, EndMT and fibrosis. We, for the first time report that VPA-treatment associated EndMT contributes to the VPA-associated loss of endothelial function. Our data also suggest that VPA based therapeutics may exacerbate endothelial dysfunction and EndMT-related phenotype in patients undergoing anticonvulsant or anticancer therapy, warranting further investigation.

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“…Accordingly, we plan to evaluate the potential role of the drug VPA on ACE-2 expression in ECs. We also discuss our findings in relation to other published articles [19], providing a plausible mechanism for the use of VPA for the prevention and treatment of COVID-19 ( Figure 2).…”

“…To test our hypothesis, we evaluated ACE-2 expression in cultured HUVECs that were treated with clinically relevant dose (5 mM) of VPA [19,21] for 24 hours. HUVECs represent the standard cellular model to study endothelial cells in vitro [19,20,22]. Our qPCR data demonstrated a significant ~70% reduction (p = 0.0079) in the expression level of ACE-2 in VPA-treated ECs in comparison to control ECs ( Figure 1A).…”

“…We have previously demonstrated that inhibition of endothelial autophagy via genetic deletion of autophagy-related gene 7 (ATG7) or by pharmacologic inhibition with bafilomycin induces EndMT-like phenotypic switching in ECs [18]. Interestingly, a similar effect of VPA was also observed, where VPA induced EndMT-like phenotypic switching in ECs [19]. Given that ACE-2 is expressed basally and widely on the endothelial cells [2,11], we hypothesized that VPA-induced EndMT-like phenotypic switching causes reduced expression of ACE-2 and thereby would inhibit the SARS-CoV-2 rate of infection.…”

Endothelial-specific Loss of IFT88 Promotes Endothelial-to-Mesenchymal Transition and Exacerbates Bleomycin-induced Pulmonary Fibrosis

“…Densitometry (ImageJ software) was performed to quantify the band intensities. Immunofluorescence experiments were carried out in 4-chamber microscopy slides performed as previously described 33,48,49 . Immunofluorescence signals from Acetyl-tubulin, CD31, VE-Cadherin, αSMA, Ift88 and α-actinin staining were visualized with standard protocols 24 hours post-treatment.…”

Endothelial-to-Mesenchymal Transition in Cancer

“…Responses to cancer treatment have important issues, leading to efficiency but often to resistance. Cancer therapies such as conventional radiotherapies (Mintet et al, 2015;Choi et al, 2018), high-dose radiation therapies (Banerjee et al, 2020) but also chemotherapies (Murugavel et al, 2018) are also currently identified as promoting EndMT in diverse type of tumors, with consequences in tumor response as described below.…”