Protein/DNA arrays identify nitric oxide-regulated cis-element and trans-factor activities some of which govern neuroblastoma cell viability

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Sp1-regulated expression of p11 contributes to motor neuron degeneration by membrane insertion of TASK1

Disruption in membrane excitability contributes to malfunction and differential vulnerability of specific neuronal subpopulations in a number of neurological diseases. The adaptor protein p11, and background potassium channel TASK1, have overlapping distributions in the CNS. Here, we report that the transcription factor Sp1 controls p11 expression, which impacts on excitability by hampering functional expression of TASK1. In the SOD1-G93A mouse model of ALS, Sp1-p11-TASK1 dysregulation contributes to increased excitability and vulnerability of motor neurons. Interference with either Sp1 or p11 is neuroprotective, delaying neuron loss and prolonging lifespan in this model. Nitrosative stress, a potential factor in human neurodegeneration, stimulated Sp1 expression and human p11 promoter activity, at least in part, through a Sp1-binding site. Disruption of Sp1 or p11 also has neuroprotective effects in a traumatic model of motor neuron degeneration. Together our work suggests the Sp1-p11-TASK1 pathway is a potential target for treatment of degeneration of motor neurons.

The adaptor protein p11 and K+ channel TASK1 have overlapping distributions in the CNS. Here, the authors demonstrate that the transcription factor Sp1 regulates p11 levels, which in turn affects intrinsic membrane properties and can contribute to degeneration of motor neurons in disease and injury models.

Anticancer and Differentiation Properties of the Nitric Oxide Derivative of Lopinavir in Human Glioblastoma Cells

Glioblastoma (GBM) is the most frequent and deadly form of primary malignant brain tumor among adults. A promising emerging approach for GBM treatment may be offered from HIV protease inhibitors (HIV-PIs). In fact, in addition to their primary pharmacological activity in the treatment of HIV infection, they possess important anti-neoplastic effects. According to previous studies, the addition of a nitric oxide (NO) donating group to parental compounds can reduce their toxicity and enhance the anticancer action of various compounds, including HIV-PIs. In this study we compared the effects of the HIV-PI Lopinavir (Lopi) and of its NO-derivative Lopinavir-NO (Lopi-NO) on the in vitro growth of LN-229 and U-251 human GBM cell lines. Lopi-NO reduced the viability of LN-229 and U-251 cells at significantly lower concentrations than the parental drug. In particular, Lopi-NO inhibited tumor cell proliferation and induced the differentiation of U-251 cells toward an astrocyte-like phenotype without triggering significant cell death in both cell types. The anticancer effect of Lopi-NO was persistent even upon drug removal. Furthermore, Lopi-NO induced strong autophagy that did not appear to be related to its chemotherapeutic action. Overall, our results suggest that Lopi-NO could be a potential effective anticancer drug for GBM treatment.

Expression of BDNF and TrkB Phosphorylation in the Rat Frontal Cortex During Morphine Withdrawal are NO Dependent

Nitric oxide (NO) mediates pharmacological effects of opiates including dependence and abstinence. Modulation of NO synthesis during the induction phase of morphine dependence affects manifestations of morphine withdrawal syndrome, though little is known about mechanisms underlying this phenomenon. Neurotrophic and growth factors are involved in neuronal adaptation during opiate dependence. NO-dependent modulation of morphine dependence may be mediated by changes in expression and activity of neurotrophic and/or growth factors in the brain. Here, we studied the effects of NO synthesis inhibition during the induction phase of morphine dependence on the expression of brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF), and insulin-like growth factor 1 (IGF1) as well as their receptors in rat brain regions after spontaneous morphine withdrawal in dependent animals. Morphine dependence in rats was induced within 6 days by 12 injections of morphine in increasing doses (10-100 mg/kg), and NO synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) (10 mg/kg) was given 1 h before each morphine injection. The expression of the BDNF, GDNF, NGF, IGF1, and their receptors in the frontal cortex, striatum, hippocampus, and midbrain was assessed 40 h after morphine withdrawal. L-NAME treatment during morphine intoxication resulted in an aggravation of the spontaneous morphine withdrawal severity. Morphine withdrawal was accompanied by upregulation of BDNF, IGF1, and their receptors TrkB and IGF1R, respectively, on the mRNA level in the frontal cortex, and only BDNF in hippocampus and midbrain. L-NAME administration during morphine intoxication decreased abstinence-induced upregulation of these mRNAs in the frontal cortex, hippocampus and midbrain. L-NAME prevented from abstinence-induced elevation of mature but not pro-form of BDNF polypeptide in the frontal cortex. While morphine abstinence did not affect TrkB protein levels as well as its phosphorylation status, inhibition of NO synthesis decreased levels of phosphorylated TrkB after withdrawal. Thus, NO signaling during induction of dependence may be involved in the mechanisms of BDNF expression and processing at abstinence, thereby affecting signaling through TrkB in the frontal cortex.

NO-β-catenin crosstalk modulates primitive streak formation prior to embryonic stem cell osteogenic differentiation

Nitric oxide (NO) has been shown to play a crucial role in bone formation in vivo. We sought to determine the temporal effect of NO on murine embryonic stem cells (ESCs) under culture conditions that promote osteogenesis. Expression profiles of NO pathway members and osteoblast-specific markers were analyzed using appropriate assays. We found that NO was supportive of osteogenesis specifically during an early phase of in vitro development (days 3-5). Furthermore, ESCs stably overexpressing the inducible NO synthase showed accelerated and enhanced osteogenesis in vitro and in bone explant cultures. To determine the role of NO in early lineage commitment, a stage in ESC differentiation equivalent to primitive streak formation in vivo, ESCs were transfected with a T-brachyury-GFP reporter. Expression levels of T-brachyury and one of its upstream regulators, β-catenin, the major effector in the canonical Wnt pathway, were responsive to NO levels in differentiating primitive streak-like cells. Our results indicate that NO may be involved in early differentiation through regulation of β-catenin and T-brachyury, controlling the specification of primitive-streak-like cells, which may continue through differentiation to later become osteoblasts.

Dynamic epigenetic regulation in neurons: enzymes, stimuli and signaling pathways

The development and function of neurons require the regulated expression of large numbers of very specific gene sets. Epigenetic modifications of both DNA and histone proteins are now emerging as fundamental mechanisms by which neurons adapt their transcriptional response to developmental and environmental cues. In the nervous system, the mechanisms by which extracellular signals regulate the activity of chromatin-modifying enzymes have just begun to be characterized. In this Review, I discuss how extracellular cues, including synaptic activity and neurotrophic factors, influence epigenetic modifications and regulate the neuronal transcriptional response. I also summarize additional mechanisms that induce chromatin remodeling events by combinatorial assembly of multiprotein complexes on neuronal gene promoters.

Impact of copy number of distinct SV40PolyA segments on expression of a GFP reporter gene

The presence of Alu repeats downregulates the expression of the green fluorescent protein (GFP) gene. We found that SV40PolyA (PolyA, 240 bp), in either orientation, eliminated the inhibition of GFP gene expression induced by Alu repeats when it was placed between the GFP gene and the Alu repeats. In this study, 4 different segments (each 60 bp) were amplified from antisense PolyA (PolyAas) by PCR, and inserted upstream of Alu14 in pAlu14 plasmid (14 Alu repeats inserted downstream of the GFP gene in vector pEGFP-C1 in a head-tail tandem manner). Segments 1F1R (the first 60 bp segment at the 5' end of PolyAas) and 4F4R (the fourth 60 bp segment from the 5' end of PolyAas) did not activate GFP gene expression, whereas 2F2R and 3F3R (the middle two segments) did (as detected by Northern blot analysis and fluorescent microscopy). Different copy numbers of 2F2R and 3F3R segments, in a head and tail tandem manner, were inserted downstream of the GFP gene in pAlu14. p2F2R*4-Alu28, p3F3R*4-Alu18 and p3F3R*4-Alu28 were used as length controls to verify that the decrease in the expression of GFP was not due to the increased length of the inserted segment in the expression vectors. We found that 2 and 4 copies of 2F2R or 3F3R activated the GFP gene more strongly than one copy of them. However, more than 8 copies of 2F2R or 3F3R reduced the activation of the GFP gene. We concluded that SV40PolyAas contained at least two gene-activating elements (2F2R and 3F3R) and 2-4 copies of 2F2R or 3F3R were optimal for the expression of the GFP gene.

Co-regulation of nuclear respiratory factor-1 by NFkappaB and CREB links LPS-induced inflammation to mitochondrial biogenesis

The nuclear respiratory factor-1 (NRF1) gene is activated by lipopolysaccharide (LPS), which might reflect TLR4-mediated mitigation of cellular inflammatory damage via initiation of mitochondrial biogenesis. To test this hypothesis, we examined NRF1 promoter regulation by NFκB, and identified interspecies-conserved κB-responsive promoter and intronic elements in the NRF1 locus. In mice, activation of Nrf1 and its downstream target, Tfam, by Escherichia coli was contingent on NFκB, and in LPS-treated hepatocytes, NFκB served as an NRF1 enhancer element in conjunction with NFκB promoter binding. Unexpectedly, optimal NRF1 promoter activity after LPS also required binding by the energy-state-dependent transcription factor CREB. EMSA and ChIP assays confirmed p65 and CREB binding to the NRF1 promoter and p65 binding to intron 1. Functionality for both transcription factors was validated by gene-knockdown studies. LPS regulation of NRF1 led to mtDNA-encoded gene expression and expansion of mtDNA copy number. In cells expressing plasmid constructs containing the NRF-1 promoter and GFP, LPS-dependent reporter activity was abolished by cis-acting κB-element mutations, and nuclear accumulation of NFκB and CREB demonstrated dependence on mitochondrial H(2)O(2). These findings indicate that TLR4-dependent NFκB and CREB activation co-regulate the NRF1 promoter with NFκB intronic enhancement and redox-regulated nuclear translocation, leading to downstream target-gene expression, and identify NRF-1 as an early-phase component of the host antibacterial defenses.

Computational identification of transcription frameworks of early committed spermatogenic cells

It is known that transcription factors (TFs) work in cooperation with each other to govern gene expression and thus single TF studies may not always reflect the underlying biology. Using microarray data obtained from two independent studies of the first wave of spermatogenesis, we tested the hypothesis that co-expressed spermatogenic genes in cells committed to differentiation are regulated by a set of distinct combinations of TF modules. A computational approach was designed to identify over-represented module combinations in the promoter regions of genes associated with transcripts that either increase or decrease in abundance between the first two major spermatogenic cell types: spermatogonia and spermatocytes. We identified five TFs constituting four module combinations that were correlated with expression and repression of similarly regulated genes. These modules were biologically assessed in the context that they represent the key transcriptional mediators in the developmental transition from the spermatogonia to spermatocyte.

Nitric oxide-induced nuclear GAPDH activates p300/CBP and mediates apoptosis

Besides its role in glycolysis, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) initiates a cell death cascade. Diverse apoptotic stimuli activate inducible nitric oxide synthase (iNOS) or neuronal NOS (nNOS), with the generated nitric oxide (NO) S-nitrosylating GAPDH, abolishing its catalytic activity and conferring on it the ability to bind to Siah1, an E3-ubiquitin-ligase with a nuclear localization signal (NLS). The GAPDH-Siah1 protein complex, in turn, translocates to the nucleus and mediates cell death; these processes are blocked by procedures that interfere with GAPDH-Siah1 binding. Nuclear events induced by GAPDH to kill cells have been obscure. Here we show that nuclear GAPDH is acetylated at Lys 160 by the acetyltransferase p300/CREB binding protein (CBP) through direct protein interaction, which in turn stimulates the acetylation and catalytic activity of p300/CBP. Consequently, downstream targets of p300/CBP, such as p53 (Refs 10,11,12,13,14,15), are activated and cause cell death. A dominant-negative mutant GAPDH with the substitution of Lys 160 to Arg (GAPDH-K160R) prevents activation of p300/CBP, blocks induction of apoptotic genes and decreases cell death. Our findings reveal a pathway in which NO-induced nuclear GAPDH mediates cell death through p300/CBP.

Secretogranin II: a key AP-1-regulated protein that mediates neuronal differentiation and protection from nitric oxide-induced apoptosis of neuroblastoma cells

Identification of AP-1 target genes in apoptosis and differentiation has proved elusive. Secretogranin II (SgII) is a protein widely distributed in nervous and endocrine tissues, and abundant in neuroendocrine granules. We addressed whether SgII is regulated by AP-1, and if SgII is involved in neuronal differentiation or the cellular response to nitrosative stress. Nitric oxide (NO) upregulated sgII mRNA dependent on a cyclic AMP response element (CRE) in the sgII promoter, and NO stimulated SgII protein secretion in neuroblastoma cells. Upregulation of sgII mRNA, sgII CRE-driven gene expression and SgII protein synthesis/export were attenuated in cells transformed with dominant-negative c-Jun (TAM67), which became sensitized to NO-induced apoptosis and failed to undergo nerve growth factor-dependent neuronal differentiation. Stable transformation of TAM67 cells with sgII restored neuronal differentiation and resistance to NO. RNAi knockdown of sgII in cells expressing functional c-Jun abolished neuronal differentiation and rendered the cells sensitive to NO-induced apoptosis. Therefore, SgII represents a key AP-1-regulated protein that counteracts NO toxicity and mediates neuronal differentiation of neuroblastoma cells.