Effects of the histone deacetylase inhibitor valproic acid on human pericytes in vitro

Sirtinol, a SIRT1 inhibitor, inhibits the EMT and metastasis of 4T1 breast cancer cells and impacts the tumor microenvironment

INTRODUCTION

The impact of epigenetic drugs on metastasis and the immunological microenvironment is poorly understood. In this study, we looked at how sirtinol, a SIRT1 inhibitor, affected epithelial-mesenchymal transition (EMT), metastasis, and the immune cells.

MATERIALS AND METHODS

In vitro experiments were carried out using tumor conditioned medium (TCM). For in vivo experiments, sirtinol was administered i.p. in tumor bearing BALB/c mice at a dose of 2 mg/kg body weight either alone or in combination with cisplatin. Estimation of cytokines was carried out using ELISA or ELIspot. Estimation of different markers was done using flow cytometry or western blot.

RESULTS

Sirtinol, a SIRT1 inhibitor, was found to be cytotoxic to 4T1 breast cancer cells with no synergistic effects with cisplatin, both under in vitro and in vivo conditions (p < 0.05). Sirtinol significantly reduced cancer cell metastasis to the spleen which was supported by in vitro findings such as decreased vimentin expression and cell mobility in migration and wound healing assays (p < 0.01). Studies on the effects of 4T1 tumor-conditioned medium on spleen cells indicated changes in T cell proliferation as well as differentiation (p < 0.01). In tumor bearing mice, spleen cells showed elevated IFN-γ secretion, increased CD11b+ cells, and decreased T cells (p < 0.01). This was reversed by sirtinol as well as the combination treatment, which may also have contributed to metastasis inhibition (p < 0.01).

CONCLUSION

Sirtinol, a SIRT1 inhibitor inhibits EMT and metastasis of 4T1 breast cancer cells and also has an impact on the immune microenvironment.

Epigenetics in blood-brain barrier disruption

The vessels of the central nervous system (CNS) have unique barrier properties. The endothelial cells (ECs) which comprise the CNS vessels contribute to the barrier via strong tight junctions, specific transporters, and limited endocytosis which combine to protect the brain from toxins and maintains brain homeostasis. Blood-brain barrier (BBB) leakage is a serious secondary injury in various CNS disorders like stroke, brain tumors, and neurodegenerative disorders. Currently, there are no drugs or therapeutics available to treat specifically BBB damage after a brain injury. Growing knowledge in the field of epigenetics can enhance the understanding of gene level of the BBB and has great potential for the development of novel therapeutic strategies or targets to repair a disrupted BBB. In this brief review, we summarize the epigenetic mechanisms or regulators that have a protective or disruptive role for components of BBB, along with the promising approaches to regain the integrity of BBB.

Protein Kinase CK2 Regulates Nerve/Glial Antigen (NG)2-Mediated Angiogenic Activity of Human Pericytes

Protein kinase CK2 is a crucial regulator of endothelial cell proliferation, migration and sprouting during angiogenesis. However, it is still unknown whether this kinase additionally affects the angiogenic activity of other vessel-associated cells. In this study, we investigated the effect of CK2 inhibition on primary human pericytes. We found that CK2 inhibition reduces the expression of nerve/glial antigen (NG)2, a crucial factor which is involved in angiogenic processes. Reporter gene assays revealed a 114 bp transcriptional active region of the human NG2 promoter, whose activity was decreased after CK2 inhibition. Functional analyses demonstrated that the pharmacological inhibition of CK2 by CX-4945 suppresses pericyte proliferation, migration, spheroid sprouting and the stabilization of endothelial tubes. Moreover, aortic rings of NG2^−/− mice showed a significantly reduced vascular sprouting when compared to rings of NG2^+/+ mice, indicating that NG2 is an important regulator of the angiogenic activity of pericytes. In vivo, implanted Matrigel plugs containing CX-4945-treated pericytes exhibited a lower microvessel density when compared to controls. These findings demonstrate that CK2 regulates the angiogenic activity of pericytes through NG2 gene expression. Hence, the inhibition of CK2 represents a promising anti-angiogenic strategy, because it does not only target endothelial cells, but also vessel-associated pericytes.

Assembling systems biology, embryo development and teratogenesis: What do we know so far and where to go next?

The recognition of molecular mechanisms of a teratogen can provide insights to understand its embryopathy, and later to plan strategies for the prevention of new exposures. In this context, experimental research is the most invested approach. Despite its relevance, these assays require financial and time investment. Hence, the evaluation of such mechanisms through systems biology rise as an alternative for this conventional methodology. Systems biology is an integrative field that connects experimental and computational analyses, assembling interaction networks between genes, proteins, and even teratogens. It is a valid strategy to generate new hypotheses, that can later be confirmed in experimental assays. Here, we present a literature review of the application of systems biology in embryo development and teratogenesis studies. We provide a glance at the data available in public databases, and evaluate common mechanisms between different teratogens. Finally, we discuss the advantages of using this strategy in future teratogenesis researches.

Pharmacological modulation of cell functional activity with valproic acid and erythropoietin

Introduction: Valproic acid (VA) is carboxylic acid with a branched chain, which is used as an antiepileptic drug.

Valproic acid influence on cells in vivo: VA, which is an antiepileptic drug, is also a teratogen, which causes defects of a neural tube and an axial skeleton, although the mechanisms are not yet fully clear.

Valproic acid influence on mesenchymal stem cells (MSC) in vitro: It is shown that valproic acid reduces the intracellular level of oxygen active forms.

Valproic acid effect on tumor cells: VA inhibits tumor growth through several mechanisms, including the cell cycle stop, differentiation induction and inhibition of growth of tumor vessels.

Valproic acid influence on enzymes: It affects mainly GSK-3.

Valproic acid influence on animals’ cells: It is shown that VA can significantly improve an ability to develop in vitro and improve nuclear reprogramming of embryos.

Erythropoietin (EPO): Is an hypoxia-induced hormone and a cytokine, which is necessary for normal erythropoiesis. EPO is widely used in in vitro experiments.

Conclusion: Thus, the influence of VA and EPO on cells can be used in cell technologies.

Epigenetic Crosstalk between the Tumor Microenvironment and Ovarian Cancer Cells: A Therapeutic Road Less Traveled

Metastatic dissemination of epithelial ovarian cancer (EOC) predominantly occurs through direct cell shedding from the primary tumor into the intra-abdominal cavity that is filled with malignant ascitic effusions. Facilitated by the fluid flow, cells distribute throughout the cavity, broadly seed and invade through peritoneal lining, and resume secondary tumor growth in abdominal and pelvic organs. At all steps of this unique metastatic process, cancer cells exist within a multidimensional tumor microenvironment consisting of intraperitoneally residing cancer-reprogramed fibroblasts, adipose, immune, mesenchymal stem, mesothelial, and vascular cells that exert miscellaneous bioactive molecules into malignant ascites and contribute to EOC progression and metastasis via distinct molecular mechanisms and epigenetic dysregulation. This review outlines basic epigenetic mechanisms, including DNA methylation, histone modifications, chromatin remodeling, and non-coding RNA regulators, and summarizes current knowledge on reciprocal interactions between each participant of the EOC cellular milieu and tumor cells in the context of aberrant epigenetic crosstalk. Promising research directions and potential therapeutic strategies that may encompass epigenetic tailoring as a component of complex EOC treatment are discussed.

Valproic acid regulates Ang II-induced pericyte-myofibroblast trans-differentiation via MAPK/ERK pathway

Myocardial fibrosis (MF) plays an important part in cardiovascular diseases. The main cytological characteristics of MF is the increased number of myofibroblasts, which have multiple sources such as EMT, EndMT, myeloid progenitors, monocytes, and fibrocytes. Recent data showed that pericytes may represent a major source of myofibroblasts in kidney fibrosis. Valproic acid (VPA) is a kind of short-chain fatty acid. It was reported in recent studies that VPA regulates gene expression and influences various signal pathways. HDACs inhibitors can hinder the growth of tumor cells and differentiation of stem cells. And little is known about the effects of HDACs inhibitors on myofibroblasts transdiffererntiaton. This study focused on the role of HDACs in pericyte-myofibroblast trans-differentiation and how HDACs inhibitor VPA influenced proliferation, migration, viability and myofibroblast trans-differentiation of pericytes for the first time. Rat cardiac fibrosis model was induced by Ang II. Immunohistochemistry was employed to examine cardiac fibrosis and flow cytometry was used to analyze whether inflammatory cells involve VPA-induced trans-differentiation. Pericytes proliferation, migration and differentiation to myofibroblasts were performed to examine the role of VPA on pericyte trans-differentiation. Immunoblot and qPCR were applied to identify the signal transduction involving in VPA-induced trans-differentiation. In vivo study showed that HDAC inhibitor VPA blocks cardiac fibrosis, and inflammation inhibition was not involved in this process. VPA treatment inhibited Ang II pericyte proliferation, migration and transdifferentiation to myofibroblast. Furthermore, the inhibition of α-SMA expression by VPA was related to reduce phosphorylation of ERK, and a pharmacological inhibitor of MEK suppressed Ang II-induced α-SMA expression. HDAC4 knockdown resulted in inhibiting Ang II-mediated α-SMA expression as well as the phosphorylation of ERK. Moreover, the inhibitors of protein phosphatase 2A and 1 (PP2A and PP1) restored the Ang II-stimulated α-SMA expression from the inhibitory effect of VPA. Together, the current data indicate that the differentiation of pericytes to myofibroblasts is HDAC4 dependent and requires phosphorylation of ERK.

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

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.

Valproic acid inhibits glioblastoma multiforme cell growth via paraoxonase 2 expression

We studied the potential mechanisms of valproic acid (VPA) in the treatment of glioblastoma multiforme (GBM). Using the human U87, GBM8401, and DBTRG-05MG GBM-derived cell lines, VPA at concentrations of 5 to 20 mM induced G2/M cell cycle arrest and increased the production of reactive oxygen species (ROS). Stress-related molecules such as paraoxonase 2 (PON2), cyclin B1, cdc2, and Bcl-xL were downregulated, but p27, p21 and Bim were upregulated by VPA treatment. VPA response element on the PON2 promoter was localized at position -400/−1. PON2 protein expression was increased in GBM cells compared with normal brain tissue and there was a negative correlation between the expression of PON2 and Bim. These findings were confirmed by the public Bredel GBM microarray (Gene Expression Omnibus accession: GSE2223) and the Cancer Genome Atlas GBM microarray datasets. Overexpression of PON2 in GBM cells significantly decreased intracellular ROS levels, and PON2 expression was decreased after VPA stimulation compared with controls. Bim expression was significantly induced by VPA in GBM cells with PON2 silencing. These observations were further shown in the subcutaneous GBM8401 cell xenograft of BALB/c nude mice. Our results suggest that VPA reduces PON2 expression in GBM cells, which in turn increases ROS production and induces Bim production that inhibits cancer progression via the PON2–Bim cascade.

Pericyte-targeting drug delivery and tissue engineering

Pericytes are contractile mural cells that wrap around the endothelial cells of capillaries and venules. Depending on the triggers by cellular signals, pericytes have specific functionality in tumor microenvironments, properties of potent stem cells, and plasticity in cellular pathology. These features of pericytes can be activated for the promotion or reduction of angiogenesis. Frontier studies have exploited pericyte-targeting drug delivery, using pericyte-specific peptides, small molecules, and DNA in tumor therapy. Moreover, the communication between pericytes and endothelial cells has been applied to the induction of vessel neoformation in tissue engineering. Pericytes may prove to be a novel target for tumor therapy and tissue engineering. The present paper specifically reviews pericyte-specific drug delivery and tissue engineering, allowing insight into the emerging research targeting pericytes.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Histone deacetylase inhibitor treatment increases coronary t-PA release in a porcine ischemia model

Background

The expression of the tissue plasminogen activator gene can be affected by histone deacetylation inhibition and thus appears to be under epigenetic control.

Objectives

The study aimed to test if in vivo pharmacological intervention by valproic acid treatment would lead to increase in tissue plasminogen activator release capacity.

Methods

In an anaesthetized pig model, a controlled transient coronary occlusion was used to stimulate coronary tissue plasminogen activator release in a valproic acid treated (one week) and a non-treated group. Coronary venous blood samples from the ischemic region were collected, great cardiac vein thermodilution flow measurements were performed, and trans-coronary tissue plasminogen activator fluxes were calculated. Plasminogen activator inhibitor-1 was also measured.

Results

Adequate sampling from the affected area after the 10 minute ischemic period was confirmed by lactate measurements. Fluxes for tissue plasminogen activator at minutes 1, 3, 5, 7 and 10 were measured and then used to present cumulative net tissue plasminogen activator release for the whole measurement period for both groups. Area under the curve was higher for the valproic acid treated group at 10 minutes; 932±173 nanograms (n = 12) compared to the non-treated group, 451±78 nanograms (n = 10, p = 0.023). There was no difference in levels of plasminogen activator inhibitor-1 between groups.

Conclusions

These findings support a proof of concept for histone deacetylation inhibition positive effect on tissue plasminogen activator expression in an in vivo setting. Further studies are needed to find an optimal way to implement histone deacetylation inhibition to achieve desired clinical changes in tissue plasminogen activator expression.

Potential roles of HDAC inhibitors in mitigating ischemia-induced brain damage and facilitating endogenous regeneration and recovery

Ischemic stroke is a leading cause of death and disability worldwide, with few available treatment options. The pathophysiology of cerebral ischemia involves both early phase tissue damage, characterized by neuronal death, inflammation, and blood-brain barrier breakdown, followed by late phase neurovascular recovery. It is becoming clear that any promising treatment strategy must target multiple points in the evolution of ischemic injury to provide substantial therapeutic benefit. Histone deacetylase (HDAC) inhibitors are a class of drugs that increase the acetylation of histone and non-histone proteins to activate transcription, enhance gene expression, and modify the function of target proteins. Acetylation homeostasis is often disrupted in neurological conditions, and accumulating evidence suggests that HDAC inhibitors have robust protective properties in many preclinical models of these disorders, including ischemic stroke. Specifically, HDAC inhibitors such as trichostatin A, valproic acid, sodium butyrate, sodium 4-phenylbutyrate, and suberoylanilide hydroxamic acid have been shown to provide robust protection against excitotoxicity, oxidative stress, ER stress, apoptosis, inflammation, and bloodbrain barrier breakdown. Concurrently, these agents can also promote angiogenesis, neurogenesis and stem cell migration to dramatically reduce infarct volume and improve functional recovery after experimental cerebral ischemia. In the following review, we discuss the mechanisms by which HDAC inhibitors exert these protective effects and provide evidence for their strong potential to ultimately improve stroke outcome in patients.

Histone deacetylase activity is required for embryonic posterior lateral line development

OBJECTIVES

The posterior lateral line (PLL) system in zebrafish has recently become a model for investigating tissue morphogenesis. PLL primordium periodically deposits neuromasts as it migrates along the horizontal myoseptum from head to tail of the embryonic fish, and this migration requires activity of various molecular mechanisms. Histone deacetylases (HDACs) have been implicated in numerous biological processes of development, by regulating gene transcription, but their roles in regulating PLL during embryonic development have up to now remained unexplored.

MATERIAL AND METHODS

In this study, we used HDAC inhibitors to investigate the role of HDACs in early development of the zebrafish PLL sensory system. We further investigated development of the PLL by cell-specific immunostaining and in situ hybridization.

RESULTS

Our analysis showed that HDACs were involved in zebrafish PLL development as pharmacological inhibition of HDACs resulted in its defective formation. We observed that migration of PLL primordium was altered and accompanied by disrupted development of PLL neuromasts in HDAC inhibitor-treated embryos. In these, positions of PLL neuromasts were affected. In particular, the first PLL neuromast was displaced posteriorly in a treatment dose-dependent manner. Primordium cell proliferation was reduced upon HDAC inhibition. Finally, we showed that inhibition of HDAC function reduced numbers of hair cells in PLL neuromasts of HDAC inhibitor-treated embryos.

CONCLUSION

Here, we have revealed a novel role for HDACs in orchestrating PLL morphogenesis. Our results suggest that HDAC activity is necessary for control of cell proliferation and migration of PLL primordium and hair cell differentiation during early stages of PLL development in zebrafish.

State-related alterations of gene expression in bipolar disorder: a systematic review

OBJECTIVE

Alterations in gene expression in bipolar disorder have been found in numerous studies. It is unclear whether such alterations are related to specific mood states. As a biphasic disorder, mood state-related alterations in gene expression have the potential to point to markers of disease activity, and trait-related alterations might indicate vulnerability pathways. This review therefore evaluated the evidence for whether gene expression in bipolar disorder is state or trait related.

METHODS

A systematic review, using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline for reporting systematic reviews, based on comprehensive database searches for studies on gene expression in patients with bipolar disorder in specific mood states, was conducted. We searched Medline, Embase, PsycINFO, and The Cochrane Library, supplemented by manually searching reference lists from retrieved publications.

RESULTS

A total of 17 studies were included, comprising 565 patients and 418 control individuals. Six studies evaluated intraindividual alterations in gene expression across mood states. Two of five studies found evidence of intraindividual alterations in gene expression between a depressed state and a euthymic state. No studies evaluated intraindividual differences in gene expression between a manic state and a euthymic state, while only one case study evaluated differences between a manic state and a depressed state, finding altered expression in seven genes. No study investigated intraindividual variations in gene expression between a euthymic state and multiple states of various polarities (depressive, manic, hypomanic). Intraindividual alterations in expression of the same genes were not investigated across studies. Only one gene (the brain-derived neurotrophic factor gene; BDNF) was investigated across multiple studies, showing no alteration between bipolar disorder patients and control individuals.

CONCLUSIONS

There is evidence of some genes exhibiting state-related alterations in expression in bipolar disorder; however, this finding is limited by the lack of replication across studies. Further prospective studies are warranted, measuring gene expression in various affective phases, allowing for assessment of intraindividual differences.

Chronic valproate treatment enhances postischemic angiogenesis and promotes functional recovery in a rat model of ischemic stroke

BACKGROUND AND PURPOSE

Enhanced angiogenesis facilitates neurovascular remodeling processes and promotes brain functional recovery after stroke. Previous studies from our laboratory demonstrated that valproate (VPA), a histone deacetylase inhibitor, protects against experimental brain ischemia. The present study investigated whether VPA could enhance angiogenesis and promote long-term functional recovery after ischemic stroke.

METHODS

Male rats underwent middle cerebral artery occlusion for 60 minutes followed by reperfusion for up to 14 days. Assessed parameters were: locomotor function through the Rotarod test; infarct volume through T2-weighted MRI; microvessel density through immunohistochemistry; relative cerebral blood flow through perfusion-weighted imaging; protein levels of proangiogenic factors through Western blotting; and matrix metalloproteinase-2/9 activities through gelatin zymography.

RESULTS

Postischemic VPA treatment robustly improved the Rotarod performance of middle cerebral artery occlusion rats on Days 7 and 14 after ischemia and significantly reduced brain infarction on Day 14. Concurrently, VPA markedly enhanced microvessel density, facilitated endothelial cell proliferation, and increased relative cerebral blood flow in the ipsilateral cortex. The transcription factor hypoxia-inducible factor-1α and its downstream proangiogenic factors, vascular endothelial growth factor and matrix metalloproteinase-2/9, were upregulated after middle cerebral artery occlusion and significantly potentiated by VPA in the ipsilateral cortex. Acetylation of histone-H3 and H4 was robustly increased by chronic VPA treatment. The beneficial effects of VPA on Rotarod performance and microvessel density were abolished by hypoxia-inducible factor-1α inhibition.

CONCLUSIONS

Chronic VPA treatment enhances angiogenesis and promotes functional recovery after brain ischemia. These effects may involve histone deacetylase inhibition and upregulation of hypoxia-inducible factor-1α and its downstream proangiogenic factors vascular endothelial growth factor and matrix metalloproteinase-2/9.