JAZ (Znf346), a SIRT1-interacting protein, protects neurons by stimulating p21 (WAF/CIP1) protein expression

Role of non-coding RNAs in neuroblastoma

Neuroblastoma is known as the most prevalent extracranial malignancy in childhood with a neural crest origin. It has been widely accepted that non-coding RNAs (ncRNAs) play important roles in many types of cancer, including glioma and gastrointestinal cancers. They may regulate the cancer gene network. According to recent sequencing and profiling studies, ncRNAs genes are deregulated in human cancers via deletion, amplification, abnormal epigenetic, or transcriptional regulation. Disturbances in the expression of ncRNAs may act either as oncogenes or as anti-tumor suppressor genes, and can lead to the induction of cancer hallmarks. ncRNAs can be secreted from tumor cells inside exosomes, where they can be transferred to other cells to affect their function. However, these topics still need more study to clarify their exact roles, so the present review addresses different roles and functions of ncRNAs in neuroblastoma.

Spinal motor neuron loss occurs through a p53-and-p21-independent mechanism in the Smn2B/- mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a pediatric neuromuscular disease caused by genetic deficiency of the survival motor neuron (SMN) protein. Pathological hallmarks of SMA are spinal motor neuron loss and skeletal muscle atrophy. The molecular mechanisms that elicit and drive preferential motor neuron degeneration and death in SMA remain unclear. Transcriptomic studies consistently report p53 pathway activation in motor neurons and spinal cord tissue of SMA mice. Recent work has identified p53 as an inducer of spinal motor neuron loss in severe Δ7 SMA mice. Additionally, the cyclin-dependent kinase inhibitor P21 (Cdkn1a), an inducer of cell cycle arrest and mediator of skeletal muscle atrophy, is consistently increased in motor neurons, spinal cords, and other tissues of various SMA models. p21 is a p53 transcriptional target but can be independently induced by cellular stressors. To ascertain whether p53 and p21 signaling pathways mediate spinal motor neuron death in milder SMA mice, and how they affect the overall SMA phenotype, we introduced Trp53 and P21 null alleles onto the Smn^2B/- background. We found that p53 and p21 depletion did not modulate the timing or degree of Smn^2B/- motor neuron loss as evaluated using electrophysiological and immunohistochemical methods. Moreover, we determined that Trp53 and P21 knockout differentially affected Smn^2B/- mouse lifespan: p53 ablation impaired survival while p21 ablation extended survival through Smn-independent mechanisms. These results demonstrate that p53 and p21 are not primary drivers of spinal motor neuron death in Smn^2B/- mice, a milder SMA mouse model, as motor neuron loss is not alleviated by their ablation.

MiR-542-3p Suppresses Neuroblastoma Cell Proliferation and Invasion by Downregulation of KDM1A and ZNF346

Neuroblastoma is one of the most common malignancies in infants and children. MicroRNAs (miRNAs) have been reported as significant regulators that play important roles in neuroblastoma development. This research aimed to analyze the functional mechanism of miR-542-3p in neuroblastoma. Here, we found that miR-542-3p was downregulated and KDM1A as well as ZNF346 were upregulated in neuroblastoma tissues and cells. Both overexpression of miR-542-3p and the knockdown of KDM1A suppressed cell proliferation and invasion in neuroblastomas. Moreover, miR-542-3p reduced the levels of KDM1A and ZNF346 through interaction. Both KDM1A overexpression and ZNF346 upregulation weakened the effect of miR-542-3p on neuroblastoma cells. Besides, miR-542-3p negatively regulated tumor growth in vivo. Our results suggested that miR-542-3p suppressed cell proliferation and invasion by targeting KDM1A and ZNF346 in neuroblastomas, providing a theoretical basis for the treatment of neuroblastoma.

Catalytic-independent neuroprotection by SIRT1 is mediated through interaction with HDAC1

SIRT1, a NAD+-dependent deacetylase, protects neurons in a variety of in vitro and in vivo models of neurodegenerative disease. We have previously described a neuroprotective effect by SIRT1 independent of its catalytic activity. To confirm this conclusion we tested a panel of SIRT1 deletion mutant constructs, designated Δ1–Δ10, in cerebellar granule neurons induced to undergo apoptosis by low potassium treatment. We find that deletions of its N-terminal, those lacking portions of the catalytic domain, as well as one that lacks the ESA (Essential for SIRT1 Activity) motif, are as protective as wild-type SIRT1. In contrast, deletion of the region spanning residues 542–609, construct Δ8, substantially reduced the neuroprotective activity of SIRT1. As observed with LK-induced apoptosis, all SIRT1 constructs except Δ8 protect neurons against mutant huntingtin toxicity. Although its own catalytic activity is not required, neuroprotection by SIRT1 is abolished by inhibitors of Class I HDACs as well as by knockdown of endogenous HDAC1. We find that SIRT1 interacts with HDAC1 and this interaction is greatly increased by deleting regions of SIRT1 necessary for its catalytic activity. However, SIRT1-mediated protection is not dependent on HDAC1 deacetylase activity. Although other studies have described that catalytic activity of SIRT1 mediates is neuroprotective effect, our study suggests that in cerebellar granule neurons its deacetylase activity is not important and that HDAC1 contributes to the neuroprotective effect of SIRT1.

MicroRNA-1247 inhibits cell proliferation by directly targeting ZNF346 in childhood neuroblastoma

BACKGROUND

Neuroblastoma (NB) represents the most common extracranial solid tumor in children. Accumulating evidence shows that microRNAs (miRs) play an important role in the carcinogenesis of NB. Here, we investigated the biological function of miR-1247 in NB in vitro.

METHODS/RESULTS

We found miR-1247 was downregulated in NB tissues and cells using quantitative PCR analysis. Gain- and loss-of-function studies demonstrated that miR-1247 significantly suppressed cell proliferation and induced cell cycle G0/G1 phase arrest and cell apoptosis of NB cells in vitro by using MTT, colony formation assay and Flow cytometry analysis. Luciferase assay suggested ZNF346 was the target of miR-1247 and its expression could be downregulated by miR-1247 overexpression using Western blotting. Furthermore, downregulation of ZNF346 by siRNA performed similar effects with overexpression of miR-1247 in NB cells.

CONCLUSIONS

Our findings suggested miR-1247 directly targeted to repress ZNF346 expression, thus suppressing the progression of NB, which might be a novel therapeutic target against NB.

Complex neuroprotective and neurotoxic effects of histone deacetylases

By their ability to shatter quality of life for both patients and caregivers, neurodegenerative diseases are the most devastating of human disorders. Unfortunately, there are no effective or long-terms treatments capable of slowing down the relentless loss of neurons in any of these diseases. One impediment is the lack of detailed knowledge of the molecular mechanisms underlying the processes of neurodegeneration. While some neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, are mostly sporadic in nature, driven by both environment and genetic susceptibility, many others, including Huntington's disease, spinocerebellar ataxias, and spinal-bulbar muscular atrophy, are genetically inherited disorders. Surprisingly, given their different roots and etiologies, both sporadic and genetic neurodegenerative disorders have been linked to disease mechanisms involving histone deacetylase (HDAC) proteins, which consists of 18 family members with diverse functions. While most studies have implicated certain HDAC subtypes in promoting neurodegeneration, a substantial body of literature suggests that other HDAC proteins can preserve neuronal viability. Of particular interest, however, is the recent realization that a single HDAC subtype can have both neuroprotective and neurotoxic effects. Diverse mechanisms, beyond transcriptional regulation have been linked to these effects, including deacetylation of non-histone proteins, protein-protein interactions, post-translational modifications of the HDAC proteins themselves and direct interactions with disease proteins. The roles of these HDACs in both sporadic and genetic neurodegenerative diseases will be discussed in the current review.

Shared metabolic and immune-inflammatory, oxidative and nitrosative stress pathways in the metabolic syndrome and mood disorders

This review examines the shared immune-inflammatory, oxidative and nitrosative stress (IO&NS) and metabolic pathways underpinning metabolic syndrome (MetS), bipolar disorder (BD) and major depressive disorder (MDD). Shared pathways in both MetS and mood disorders are low grade inflammation, including increased levels of pro-inflammatory cytokines and acute phase proteins, increased lipid peroxidation with formation of malondialdehyde and oxidized low density lipoprotein cholesterol (LDL-c), hypernitrosylation, lowered levels of antioxidants, most importantly zinc and paraoxonase (PON1), increased bacterial translocation (leaky gut), increased atherogenic index of plasma and Castelli risk indices; and reduced levels of high-density lipoprotein (HDL-c) cholesterol. Insulin resistance is probably not a major factor associated with mood disorders. Given the high levels of IO&NS and metabolic dysregulation in BD and MDD and the high comorbidity with the atherogenic components of the MetS, mood disorders should be viewed as systemic neuro-IO&NS-metabolic disorders. The IO&NS-metabolic biomarkers may have prognostic value and may contribute to the development of novel treatments targeting neuro-immune, neuro-oxidative and neuro-nitrosative pathways.

Reduced Expression of Foxp1 as a Contributing Factor in Huntington's Disease

Huntington's disease (HD) is an inherited neurodegenerative disease caused by a polyglutamine expansion in the huntington protein (htt). The neuropathological hallmark of HD is the loss of neurons in the striatum and, to a lesser extent, in the cortex. Foxp1 is a member of the Forkhead family of transcription factors expressed selectively in the striatum and the cortex. In the brain, three major Foxp1 isoforms are expressed: isoform-A (∼90 kDa), isoform-D (∼70 kDa), and isoform-C (∼50 kDa). We find that expression of Foxp1 isoform-A and -D is selectively reduced in the striatum and cortex of R6/2 HD mice as well as in the striatum of HD patients. Furthermore, expression of mutant htt in neurons results in the downregulation of Foxp1 Elevating expression of isoform-A or -D protects cortical neurons from death caused by the expression of mutant htt On the other hand, knockdown of Foxp1 promotes death in otherwise healthy neurons. Neuroprotection by Foxp1 is likely to be mediated by the transcriptional stimulation of the cell-cycle inhibitory protein p21^Waf1/Cip1 Consistently, Foxp1 activates transcription of the p21^Waf1/Cip1 gene promoter, and overexpression of Foxp1 in neurons results in the elevation of p21 expression. Moreover, knocking down of p21^Waf1/Cip1 blocks the ability of Foxp1 to protect neurons from mut-Htt-induced neurotoxicity. We propose that the selective vulnerability of neurons of the striatum and cortex in HD is related to the loss of expression of Foxp1, a protein that is highly expressed in these neurons and required for their survival.SIGNIFICANCE STATEMENT Although the mutant huntingtin gene is expressed widely, neurons of the striatum and cortex are selectively affected in Huntington's disease (HD). Our results suggest that this selectivity is attributable to the reduced expression of Foxp1, a protein expressed selectively in striatal and cortical neurons that plays a neuroprotective role in these cells. We show that protection by Foxp1 involves stimulation of the p21^Waf1/Cip1 (Cdkn1a) gene. Although three major Foxp1 isoforms (A, C, and D) are expressed in the brain, only isoform-A has been studied in the nervous system. We show that isoform-D is also expressed selectively, neuroprotective and downregulated in HD mice and patients. Our results suggest that Foxp1 might be an attractive therapeutic target for HD.

miR-200a controls hepatic stellate cell activation and fibrosis via SIRT1/Notch1 signal pathway

OBJECTIVES

miR-200a has been established as a key regulator of HSC activation processes in liver fibrosis. Epigenetic silencing of miR-200a contributing to SIRT1 over-expression has been discussed in breast cancer; however, whether miR-200a controls SIRT1 gene expression in hepatic fibrosis is still unknown.

METHODS AND MATERIALS

We analyzed miR-200a regulation of SIRT1 expression in CCl₄-induced liver fibrosis and TGF-β1-mediated activation of HSC. miR-200a, SIRT1, α-SMA, Col1A1, Notch1 and NICD expression were estimated by Western blotting, qRT-PCR and Immunohistochemistry. HSCs were transfected with miR-200a mimic, miR-200a inhibitor and SIRT1-RNAi. Luciferase reporter assays further confirmed the interaction between miR-200a and the SIRT1 mRNA 3'-UTR. Cell proliferation ability was assessed by MTT and cell cycle.

RESULTS

We found that treatment activated HSC with miR-200a mimics, restored miR-200a expression and reduced SIRT1 levels. Conversely, treatment activated HSC with miR-200a inhibitors, decreased miR-200a expression and up-regulated SIRT1 levels. Restoration of miR-200a or the knockdown of SIRT1 prevented HSC activation and proliferation. We have established the SIRT1 transcript as subject to regulation by miR-200a, through miR-200a targeting of SIRT1 3'-UTR. Finally, HSC transfected with SIRT1-siRNA increased the levels of Notch1 protein and mRNA expression.

CONCLUSIONS

Our study demonstrated that miR-200a regulates SIRT1/Notch1 expression during HSC activation and fibrosis.

Regulation of Neuronal Survival by Nucleophosmin 1 (NPM1) Is Dependent on Its Expression Level, Subcellular Localization, and Oligomerization Status

NPM1 (nucleophosmin 1) is a nucleolar phosphoprotein that regulates many cellular processes, including ribosome biogenesis, proliferation, and genomic integrity. Although its role in proliferating cell types and tissues has been extensively investigated, little is known about its function in neurons and in the brain where it is highly expressed. We report that NPM1 protein expression is increased selectively in the striatum in both the R6/2 transgenic and 3-nitropropionic acid-injected mouse models of Huntington's disease. Examination of the effect of ectopic expression on cultured neurons revealed that increasing NPM1 is toxic to otherwise healthy cerebellar granule and cortical neurons. Toxicity is dependent on its cytoplasmic localization and oligomerization status. Forced retention of NPM1 in the nucleus, as well as inhibiting its ability to oligomerize, not only neutralizes NPM1 toxicity but also renders it protective against apoptosis. Although not blocked by pharmacological inhibition of the pro-apoptotic molecules, JNK, glycogen synthase kinase 3 beta, or caspases, toxicity is blocked by compounds targeting cyclin-dependent kinases (CDKs), as well as by dominant-negative forms of CDK1 and CDK2 and the pan-CDK inhibitor, p21(Cip1/Waf1) Although induced in in vivo Huntington's disease models, NPM1 protein levels are unchanged in cultured cerebellar granule and cortical neurons induced to die by low potassium or homocysteic acid treatment, respectively. Moreover, and counterintuitively, knockdown of its expression or inhibition of endogenous NPM1 oligomerization in these cultured neurons is toxic. Taken together, our study suggests that although neurons need NPM1 for survival, an increase in its expression beyond physiological levels and its translocation to the cytoplasm leads to death through abortive cell cycle induction.

Role of Sirtuins in Linking Metabolic Syndrome with Depression

Depression is now widely regarded as a common disabling disorder that affects negatively the social functioning all over the world. Depression is associated with diverse phenomenon in brain such as neuroinflammation, synaptic dysfunction, and cognitive deficit. Recent studies reported that depression occurs by various metabolic changes, leading to metabolic syndrome. Sirtuins (SIRTs) are NAD⁺-dependent class III histone deacetylases, known to regulate diverse biological mechanism such as longevity, genomic stability, and inflammation. The modulation of sirtuin activity has been highlighted as a promising approach to reduce neurodegenerative processes. In this review, we summarize the recent discoveries regarding the potential relationship between SIRTs and depression caused by metabolic disorders (Mets). Ultimately, we suggest the possibility that SIRTs will be novel targets to alleviate neuropathogenesis induced by depression.

Integrative Mouse and Human Studies Implicate ANGPT1 and ZBTB7C as Susceptibility Genes to Ischemic Injury

BACKGROUND AND PURPOSE

The extent of ischemic injury in response to cerebral ischemia is known to be affected by native vasculature. However, the nonvascular and dynamic vascular responses and their genetic basis are not well understood.

METHODS

We performed a genome-wide association study in 235 mice from 33 inbred strains using the middle cerebral artery occlusion model. Population structure and genetic relatedness were accounted for using the efficient mixed-model association method. Human orthologs to the genes associated with the significant and suggestive single-nucleotide polymorphisms from the mouse strain survey were examined in patients with M1 occlusions admitted with signs and symptoms of acute ischemic stroke.

RESULTS

We identified 4 genome-wide significant and suggestive single-nucleotide polymorphisms to be associated with infarct volume in mice (rs3694965, P=2.17×10(-7); rs31924033, P=5.61×10(-6); rs32249495, P=2.08×10(-7); and rs3677406, P=9.56×10(-6)). rs32249495, which corresponds to angiopoietin-1 (ANGPT1), was also significant in the recessive model in humans, whereas rs1944577, which corresponds to ZBTB7C, was nominally significant in both the additive and dominant genetic models in humans. ZBTB7C was shown to be upregulated in endothelial cells using both in vitro and in vivo models of ischemia.

CONCLUSIONS

Genetic variations of ANGPT1 and ZBTB7C are associated with increased infarct size in both mice and humans. ZBTB7C may modulate the ischemic response via neuronal apoptosis and dynamic collateralization and, in addition to ANGPT1, may serve as potential novel targets for treatments of cerebral ischemia.

Cell and Context-Dependent Effects of the Heat Shock Protein DNAJB6 on Neuronal Survival

Previous studies performed in cell lines have shown that the heat shock protein, DNAJB6, protects against the proteotoxic effects of mutant huntingtin (mut-Htt) via direct interaction with mut-Htt. However, these studies were performed primarily using in vitro models and cell lines. We report that when expressed in primary neurons, DNAJB6 induces cell death. Neurotoxicity is observed with both the DNAJB6a isoform, which is strictly nuclear, and the DNAJB6b isoform, which is predominantly cytoplasmic, suggesting that neurotoxicity is mediated in the nucleus. However, when co-expressed in primary neurons with mut-Htt, DNAJB6 protects against mut-Htt neurotoxicity. This suggests that the contrasting effect of DNAJB6 on neuronal viability depends on the presence or absence of proteotoxic stress. Neurotoxicity of DNAJB6 cannot be prevented by inhibition of glycogen synthase kinase 3 beta (GSK3β) or c-Jun N-terminal kinase (JNK) but is prevented by pharmacological inhibition of cyclin-dependent kinases (CDKs). Expression of dominant-negative forms of CDK2 or CDK4, or of p21(CIP1), the physiological inhibitor of CDKs, also inhibits DNAJB6 neurotoxicity. DNAJB6 neurotoxicity can also be inhibited by histone deacetylase-4 (HDAC4), which interacts with DNAJB6 and which has previously been described to inhibit cell cycle progression. These results conclude that neurotoxicity resulting from elevated DNAJB6 is cell cycle dependent.