Nuclear RXRα and RXRβ receptors exert distinct and opposite effects on RA-mediated neuroblastoma differentiation

UNC-45A: A potential therapeutic target for malignant tumors

Uncoordinated mutant number-45 myosin chaperone A (UNC-45A), a protein highly conserved throughout evolution, is ubiquitously expressed in somatic cells. It is correlated with tumorigenesis, proliferation, metastasis, and invasion of multiple malignant tumors. The current understanding of the role of UNC-45A in tumor progression is mainly related to the regulation of non-muscle myosin II (NM-II). However, many studies have suggested that the mechanisms by which UNC-45A is involved in tumor progression are far greater than those of NM-II regulation. UNC-45A can also promote tumor cell proliferation by regulating checkpoint kinase 1 (ChK1) phosphorylation or the transcriptional activity of nuclear receptors, and induces chemoresistance to paclitaxel in tumor cells by destabilizing microtubule activity. In this review, we discuss the recent advances illuminating the role of UNC-45A in tumor progression. We also put forward therapeutic strategies targeting UNC-45A, in the hope of paving the way the development of UNC-45A-targeted therapies for patients with malignant tumors.

Effects of Anionic Liposome Delivery of All-Trans-Retinoic Acid on Neuroblastoma Cell Differentiation

All-trans-retinoic acid (ATRA) has long been known to affect cell growth and differentiation. To improve ATRA's therapeutic efficacy and pharmacodynamics, several delivery systems have been used. In this study, free ATRA and anionic-liposome-encapsulated ATRA were compared for their effects on SK-N-SH human neuroblastoma cell growth and differentiation. Anionic liposomes made of L-α-phosphatidylcholine (PC) and L-α-phosphatidic acid (PA), empty (PC-PA) and loaded with ATRA (PC-PA-ATRA), were characterized by dynamic light scattering (DLS) and electrophoretic mobility measurements, and drug entrapment efficiency (EE%) was measured to evaluate the applicability of the new colloidal formulation. The results of brightfield microscopy and cell growth curves indicated that ATRA, whether free or encapsulated, reduced growth and induced differentiation, resulting in SK-N-SH cells changing from epithelioid to neuronal-like morphologies, and producing a significant increase in neurite growth. To further characterize the neuro-differentiation of SK-N-SH cells, the expression of βIII-Tubulin and synaptophysin and mitochondria localization were analyzed via immunofluorescence. Increased expression of neuronal markers and a peculiar localization of mitochondria in the neuritic extensions were apparent both in ATRA- and PC-PA-ATRA-differentiated cells. As a whole, our results strongly indicate that ATRA treatment, by any means, can induce the differentiation of parent SK-N-SH, and they highlight that its encapsulation in anionic liposomes increases its differentiation ability in terms of the percentage of neurite-bearing cells. Interestingly, our data also suggest an unexpected differentiation capability of anionic liposomes per se. This work highlights the importance of developing and carefully testing novel delivery nanocarriers, which are a necessary first "step" in the development of new therapeutic settings.

[Different concentrations of adapalene induce differentiation and apoptosis of SH-SY5Y cells]

OBJECTIVES

To investigate the effects of different concentrations of adapalene on the morphology and functions of neuroblastoma cell line SH-SY5Y, as well as its role in inducing cell differentiation and apoptosis.

METHODS

SH-SY5Y cells were divided into control group, low concentration (0.1 μM and 1 μM) adapalene groups, and high concentration (10 μM) adapalene group. Time-lapse microscopy was used to observe the morphological changes of SH-SY5Y cells. Immunofluorescence staining was performed to detect the expression of neuronal specific marker βIII-tubulin and mature neuronal marker neurofilament heavy polypeptide (NFH). Multi-electrode array was used to record the electrophysiological features of SH-SY5Y cells. Cell apoptosis was evaluated using a cell apoptosis detection kit.

RESULTS

Low concentrations of adapalene promoted the formation of neurite outgrowth in SH-SY5Y cells, with the neurites interconnected to form a network. Spontaneous discharge activity was observed in SH-SY5Y cells treated with low concentrations of adapalene. Compared to the control group, the expression of βIII-tubulin and NFH increased in the 1 μM adapalene group, while the level of cell apoptosis increased in the high concentration adapalene group (P<0.05).

CONCLUSIONS

Low concentrations of adapalene can induce differentiation of SH-SY5Y cells into mature functional neurons, while high concentrations of adapalene can induce apoptosis in SH-SY5Y cells.

Identification of MicroRNA Profiles in Fetal Spina Bifida: The Role in Pathomechanism and Diagnostic Significance

Distinct miRNA expression patterns may reflect anomalies related to fetal congenital malformations such as spinal bifida (SB). The aim of this preliminary study was to determine the maternal miRNA expression profile of women carrying fetuses with SB. Therefore, six women carrying fetuses with SB and twenty women with euploid healthy fetuses were enrolled in this study. Using NanoString technology, we evaluated the expression level of 798 miRNAs in both plasma and amniotic fluid samples. A downregulation of miR-1253, miR-1290, miR-194-5p, miR-302d-3p, miR-3144-3p, miR-4536-5p, miR-548aa + miR-548t-3p, miR-548ar-5p, miR-548n, miR-590-5p, miR-612, miR-627-5p, miR-644a, and miR-122-5p, and an upregulation of miR-320e, let-7b-5p, miR-23a-3p, miR-873-3p, and miR-30d-5p were identified in maternal amniotic fluid samples in SB when compared to the control group. The target genes of these miRNAs play a predominant role in regulating the synthesis of several biological compounds related to signaling pathways such as those regulating the pluripotency of stem cells. Moreover, the maternal plasma expression of miR-320e was increased in pregnancies with SB, and this marker could serve as a valuable non-invasive screening tool. Our results highlight the SB-specific miRNA signature and the differentially expressed miRNAs that may be involved in SB pathogenesis. Our findings emphasize the role of miRNA as a predictive factor that could potentially be useful in prenatal genetic screening for SB.

DIRECTEUR: transcriptome-based prediction of small molecules that replace transcription factors for direct cell conversion

MOTIVATION

Direct reprogramming (DR) is a process that directly converts somatic cells to target cells. Although DR via small molecules is safer than using transcription factors (TFs) in terms of avoidance of tumorigenic risk, the determination of DR-inducing small molecules is challenging.

RESULTS

Here we present a novel in silico method, DIRECTEUR, to predict small molecules that replace TFs for DR. We extracted DR-characteristic genes using transcriptome profiles of cells in which DR was induced by TFs, and performed a variant of simulated annealing to explore small molecule combinations with similar gene expression patterns with DR-inducing TFs. We applied DIRECTEUR to predicting combinations of small molecules that convert fibroblasts into neurons or cardiomyocytes, and were able to reproduce experimentally verified and functionally related molecules inducing the corresponding conversions. The proposed method is expected to be useful for practical applications in regenerative medicine.

AVAILABILITY AND IMPLEMENTATION

The code and data are available at the following link: https://github.com/HamanoLaboratory/DIRECTEUR.git.

Retinoid Therapy for Neuroblastoma: Historical Overview, Regulatory Challenges, and Prospects

Retinoids are vitamin A derivatives and include trans-retinoic acid, isotretinoin, tamibarotene, and bexarotene, all of which are currently available for clinical use. The clinical development of retinoid therapy for neuroblastoma has a history spanning more than four decades. The most promising agent is isotretinoin, which can contribute to improving event-free survival in patients with high-risk neuroblastoma by approximately 10% when administered over six months as maintenance therapy. Although isotretinoin is regarded as an essential component in the standard clinical management of high-risk neuroblastoma, its use for this purpose in the US and EU is off-label. To promote isotretinoin use in Japan as a treatment for neuroblastoma, our clinical research team is planning to launch an investigator-initiated, registration-directed clinical trial. The present review article discusses the basic science behind retinoid therapy, pre-clinical/clinical evidence on neuroblastoma, the concept of the proposed clinical trial, and prospects for this therapy.

Bexarotene drives the self-renewing proliferation of adult neural stem cells, promotes neuron-glial fate shift, and regulates late neuronal differentiation

Treatment with bexarotene, a selective retinoid X receptor (RXR) agonist, significantly improves behavioral dysfunctions in various neurodegenerative animal models. Additionally, it activates neurodevelopmental and plasticity pathways in the brains of adult mice. Our objective was to investigate the impact of RXR activation by bexarotene on adult neural stem cells (aNSC) and their cell lineages. To achieve this, we treated NSCs isolated from the subventricular zone (SVZ) of adult rat brains from the proliferative stage to the differentiated status. The results showed that bexarotene-treated aNSC exhibited increased BrdU incorporation, SOX2+ dividing cell pairs, and cell migration from neurospheres, revealing that the treatment promotes self-renewing proliferation and cell motility in SVZ-aNCS. Furthermore, bexarotene induced a cell fate shift characterized by a significant increase in GFAP+/S100B+ differentiated astrocytes, which uncovers the participation of activated-RXR in astrogenesis. In the neuronal lineage, the fate shift was counteracted by bexarotene-induced enhancement of NeuN+ nuclei together with neurite network outgrowth, indicating that the RXR agonist stimulates SVZ-aNCS neuronal differentiation at later stages. These findings establish new connections between RXR activation, astro- and neurogenesis in the adult brain, and contribute to the development of therapeutic strategies targeting nuclear receptors for neural repair.

RXRγ attenuates cerebral ischemia-reperfusion induced ferroptosis in neurons in mice through transcriptionally promoting the expression of GPX4

Cerebral ischemia is a common cerebrovascular disease with high mortality and disability rate. Exploring its mechanism is essential for developing effective treatment for cerebral ischemia. Therefore, this study aims to explore the regulatory effect and mechanism of retinoid X receptor γ (RXRγ) on cerebral ischemia-reperfusion (I/R) injury. A mouse intraluminal middle cerebral artery occlusion model was established, and PC12 cells were exposed to anaerobic/reoxygenation (A/R) as an in vitro model in this study. Cerebral I/R surgery or A/R treatment induced ferroptosis, downregulated RXRγ and GPX4 (glutathione peroxidase 4) levels, upregulated cyclooxygenase-2 (COX-2) level and increased ROS (reactive oxygen species) level in A/R induced cells or I/R brain tissues in vivo or PC12 cells in vitro. Knockdown of RXRγ downregulated GPX4 and increased COX-2 and ROS levels in A/R induced cells. RXRγ overexpression has the opposite effect. GPX4 knockdown reversed the improvement of RXRγ overexpression on COX-2 downregulation, GPX4 upregulation and ferroptosis in PC12 cells. Furthermore, chromatin immunoprecipitation (ChIP) and luciferase reporter gene assays revealed that RXRγ bound to GPX4 promoter region and activated its transcription. Overexpression of RXRγ or GPX4 alleviated brain damage and inhibited ferroptosis in I/R mice. In conclusion, RXRγ-mediated transcriptional activation of GPX4 might inhibit ferroptosis during I/R-induced brain injury.

The histone deacetylase inhibitor OBP-801 has in vitro/in vivo anti-neuroblastoma activity

BACKGROUND

Patients with high-risk neuroblastoma have a poor prognosis; new therapeutic agents are therefore required. We investigated the antitumor effects of OBP-801, a novel histone deacetylase inhibitor, its underlying mechanism, and its potential as a therapeutic agent for patients with neuroblastoma.

METHODS

The study included five human neuroblastoma cell lines: IMR32, GOTO, KP-N-RTBM, SK-N-AS, and SH-SY5Y. We investigated cell proliferation, cell cycle status, protein expression patterns, and apoptosis in neuroblastoma cells after OBP-801 treatment in vitro. Cell survival rate and cell cycle were analyzed using the WST-8 assay and flow cytometry, respectively. Apoptosis was detected using annexin V staining, and the expression of apoptosis-related proteins was investigated by western blotting. The antitumor activity of OBP-801 was examined in an in vivo xenograft mouse model.

RESULTS

Dose-effect curve analysis showed that the mean half-maximal inhibitory concentration value was 5.5 ± 5.9 nM for the MYCN-amplified cell lines (IMR32, GOTO, and KP-N-RTBM) and 3.1 ± 0.7 nM for the MYCN-nonamplified cell lines (SK-N-AS and SH-SY5Y). OBP-801 inhibited cell proliferation and growth in all the cell lines. It induced G2/M phase arrest through the p21 (CDKN1A) pathway, increasing histone H3 levels and, subsequently, apoptosis in human neuroblastoma cells. OBP-801 suppressed the growth of neuroblastoma cells in the mouse xenograft model.

CONCLUSIONS

Overall, OBP-801 induces M-phase arrest and apoptosis in neuroblastoma cells via mitotic catastrophe. Our results indicate that OBP-801 is a promising therapeutic agent with fewer adverse effects for patients with neuroblastoma.

Hypoxia-Inducible Factor-1α (HIF-1α) Inhibition Impairs Retinoic Acid-Induced Differentiation in SH-SY5Y Neuroblastoma Cells, Leading to Reduced Neurite Length and Diminished Gene Expression Related to Cell Differentiation

Neuroblastoma is the most common extracranial solid tumour in childhood, originated from cells of the neural crest during the development of the Sympathetic Nervous System. Retinoids are vitamin-A derived differentiating agents utilised to avoid disease resurgence in high-risk neuroblastoma treatment. Several studies indicate that hypoxia—a common feature of the tumoural environment—is a key player in cell differentiation and proliferation. Hypoxia leads to the accumulation of the hypoxia-inducible factor-1α (HIF-1α). This work aims to investigate the effects of the selective inhibition of HIF-1α on the differentiation induced by retinoic acid in human neuroblastoma cells from the SH-SY5Y lineage to clarify its role in cell differentiation. Our results indicate that HIF-1α inhibition impairs RA-induced differentiation by reducing neuron-like phenotype and diminished immunolabeling and expression of differentiation markers.

Differential expression of retinoic acid alpha and beta receptors in neuronal progenitors generated from human embryonic stem cells in response to TTNPB (a retinoic acid mimetic)

Retinoic acid (RA), an active metabolite of vitamin A, plays a critical role in the morphogenesis and differentiation of various tissues, especially in the central nervous system. RA is the most commonly used morphogen for the differentiation of human embryonic stem cells (hESCs) into neuronal progenitor cells (NPCs), an abundant source of healthy neuronal tissues for regenerative therapy. During the differentiation process, the activity of RA is governed by the involvement of RA receptor subtypes (RAR α, β, and γ) and their isoforms in the nucleus. However, little is known about the involvement of specific RAR subtypes during neuronal differentiation in humans. It is essential to elucidate the dynamic function of different RAR subtypes and their influence on the phenotypic outcome. Here in this study, we used TTNPB, an analog and stabilized form of retinoic acid that potently and selectively activates retinoic acid receptors. Here we determined the optimum concentration of TTNPBfor the efficient generation of early NPCs from hESCs. Using the optimized concentration of -TTNPB, we found that RARα is the functionally dominant subtype and controls the RA-mediated neurogenesis of hESCs. Importantly, we also found that the RARγ subtype also played a role in neuronal differentiation. In contrast, the RARβ subtype negatively correlates with neuronal differentiation. Therefore, pharmacological inhibition of RARβ in the TTNPB-mediated differentiation process could be used as a strategy to generate a large number of NPCs in vitro. In summary, our results show that RARα and RARγ play a vital role in the TTNPB-mediated neuronal differentiation of hESCs, -whereas RARβ acts as a negative regulator.

DHA and Its Metabolites Have a Protective Role against Methylmercury-Induced Neurotoxicity in Mouse Primary Neuron and SH-SY5Y Cells

The consumption of fish now involves a risk of methylmercury (MeHg) exposure but also provides the benefit of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) such as docosahexaenoic acid (DHA). Some epidemiological studies have suggested that the intake of DHA can alleviate the neurotoxicity of MeHg, but the underlying mechanism is not known. Herein, we observed that pretreatment with 0.1–1 µM DHA suppressed MeHg-induced cytotoxicity in human neuroblastoma (SH-SY5Y) cells and mouse primary neuronal cells. These effects of DHA were canceled in the presence of the retinoid X receptor (RXR) antagonist UVI3003. An RXR agonist, bexarotene, suppressed the cytotoxicity of MeHg. DHA also suppressed the MeHg-induced production of reactive oxygen species (ROS) via an induction of antioxidant genes (catalase and SOD1). Pretreatment with DHA did not change the incorporation of MeHg. We showed previously that in the brain, the intake of DHA increased the level of 19,20-DHDP, which is the metabolite produced by cytochrome P450 and soluble epoxide hydrolase from DHA. In the present study, we observed that 19,20-DHDP also suppressed neurotoxicity from MeHg. These results indicate that DHA and its metabolites have a protective role in MeHg-induced neurotoxicity.

Genetic and pharmacological inhibition of the nuclear receptor RORα regulates TH17 driven inflammatory disorders

Full development of IL-17 producing CD4+ T helper cells (TH17 cells) requires the transcriptional activity of both orphan nuclear receptors RORα and RORγt. However, RORα is considered functionally redundant to RORγt; therefore, the function and therapeutic value of RORα in TH17 cells is unclear. Here, using mouse models of autoimmune and chronic inflammation, we show that expression of RORα is required for TH17 cell pathogenicity. T-cell-specific deletion of RORα reduces the development of experimental autoimmune encephalomyelitis (EAE) and colitis. Reduced inflammation is associated with decreased TH17 cell development, lower expression of tissue-homing chemokine receptors and integrins, and increased frequencies of Foxp3+ T regulatory cells. Importantly, inhibition of RORα with a selective small molecule antagonist mostly phenocopies our genetic data, showing potent suppression of the in vivo development of both chronic/progressive and relapsing/remitting EAE, but with no effect on overall thymic cellularity. Furthermore, use of the RORα antagonist effectively inhibits human TH17 cell differentiation and memory cytokine secretion. Together, these data suggest that RORα functions independent of RORγt in programming TH17 pathogenicity and identifies RORα as a safer and more selective therapeutic target for the treatment of TH17-mediated autoimmunity.

Involvement of non-coding RNAs and transcription factors in the induction of Transglutaminase isoforms by ATRA

The multifunctional protein Transglutaminase type 2, is associated with cancer epithelial mesenchymal transition, invasiveness, stemness and drugs resistance. Several variant isoforms and non-coding RNAs are present in cancer and this report explored the expression of these transcripts of the TGM2 gene in cancer cell lines after induction with all-trans retinoic acid. The expression of truncated variants along with two long non-coding RNAs, was demonstrated. One of these is coded from the first intron and the Last Exon Variant is constituted by a sequence corresponding to the last three exons and the 3'UTR. Analysis of ChIP-seq data, from ENCODE project, highlighted factors interacting with intronic sequences, which could interfere with the progression of RNApol II at checkpoints, during the elongation process. Some relevant transcription factors, bound in an ATRA-dependent way, were found by RNA immunoprecipitation, notably GATA3 mainly enriched to Last Exon Variant non-coding RNA. The involvement of NMD in the regulation of the ratio among these transcripts was observed, as the prevalent recovering of Last Exon Variant to phUPF1-complexes, with decrease of the binding towards other selective targets. This study contributes to identify molecular mechanisms regulating the ratio among the variants and improves the knowledge about regulatory roles of the non-coding RNAs of the TGM2 gene.