Neuronal nitric oxide synthase induction in the antitumorigenic and neurotoxic effects of 2-methoxyestradiol

Human neural stem cells promote mitochondrial genesis to alleviate neuronal damage in MPTP-induced cynomolgus monkey models

Currently, there is no effective treatment for Parkinson's disease (PD), and the regenerative treatment of neural stem cells (NSCs) is considered the most promising method. This study aimed to investigate the protective effect and mechanism of NSCs on neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced cynomolgus monkey (Macaca fascicularis) model of PD. We first found that injecting NSCs into the subarachnoid space relieved motor dysfunction in PD cynomolgus monkeys, as well as reduced dopaminergic neuron loss and neuronal damage in the substantia nigra (SN) and striatum. Besides, NSCs decreased 17-estradiol (E2) level, an estrogen, in the cerebrospinal fluid (CSF) of PD cynomolgus monkeys, which shows NSCs may provide neuro-protection by controlling estrogen levels in the CSF. Furthermore, NSCs elevated proliferator-activated receptor gamma coactivator-1 alpha (PGC-1a), mitofusin 2 (MFN2), and optic atrophy 1 (OPA1) expression, three genes mediating mitochondrial biogenesis, in the SN and striatum of PD monkeys. In addition, NSCs suppress reactive oxygen species (ROS) production caused by MPTP, as well as mitochondrial autophagy, therefore preserving dopaminergic neurons. In summary, our findings show that NSCs may preserve dopaminergic and neuronal cells in an MPTP-induced PD cynomolgus monkey model. These protective benefits might be attributed to NSCs' ability of modulating estrogen balance, increasing mitochondrial biogenesis, and limiting oxidative stress and mitochondrial autophagy. These findings add to our understanding of the mechanism of NSC treatment and shed light on further clinical treatment options.

Endogenous estrogen metabolites as oxidative stress mediators and endometrial cancer biomarkers

BACKGROUND

Endometrial cancer is the most common gynecologic malignancy found in developed countries. Because therapy can be curative at first, early detection and diagnosis are crucial for successful treatment. Early diagnosis allows patients to avoid radical therapies and offers conservative management options. There are currently no proven biomarkers that predict the risk of disease occurrence, enable early identification or support prognostic evaluation. Consequently, there is increasing interest in discovering sensitive and specific biomarkers for the detection of endometrial cancer using noninvasive approaches.

CONTENT

Hormonal imbalance caused by unopposed estrogen affects the expression of genes involved in cell proliferation and apoptosis, which can lead to uncontrolled cell growth and carcinogenesis. In addition, due to their ability to cause oxidative stress, estradiol metabolites have both carcinogenic and anticarcinogenic properties. Catechol estrogens are converted to reactive quinones, resulting in oxidative DNA damage that can initiate the carcinogenic process. The molecular anticancer mechanisms are still not fully understood, but it has been established that some estradiol metabolites generate reactive oxygen species and reactive nitrogen species, resulting in nitro-oxidative stress that causes cancer cell cycle arrest or cell death. Therefore, identifying biomarkers that reflect this hormonal imbalance and the presence of endometrial cancer in minimally invasive or noninvasive samples such as blood or urine could significantly improve early detection and treatment outcomes.

Adverse effects of 2-Methoxyestradiol on mouse oocytes during reproductive aging

2-Methoxyestradiol (2-ME2) is a metabolite of 17β-estradiol and is currently in clinical trials as an antitumor agent. Here we found 2-ME2 level remains stable in the local environment of ovaries but declines in serum in aging mice, and exogenous 2-ME2 impacts the meiotic maturation of mouse oocytes in dose-dependent manner. In vitro 2-ME2 application arrested oocytes at metaphase I (MI), with abnormal spindle structure and chromosome alignment. 2-ME2 exposure induced excessive production of reactive oxygen species (ROS) and malondialdehyde, as well as accelerated apoptosis progression. 2-ME2 unbalanced mitochondrial dynamics by increasing DRP1 and MFN1 while decreasing Opa1. Similar phenotypes were also observed in oocytes from mice injected intraperitoneally with 2-ME2. Taken together, this study indicates 2-ME2 exposure impairs oocyte meiotic maturation through inducing mitochondrial imbalance, oxidative stress and apoptosis. The gradual decline in oocyte quality and quantity may be associated with the stable 2-ME2 in ovaries during female reproductive aging.

2-Methoxyestradiol Damages DNA in Glioblastoma Cells by Regulating nNOS and Heat Shock Proteins

Gliomas are the most prevalent primary tumors of the central nervous system (CNS), accounting for over fifty percent of all primary intracranial neoplasms. Glioblastoma (GBM) is the most prevalent form of malignant glioma and is often incurable. The main distinguishing trait of GBM is the presence of hypoxic regions accompanied by enhanced angiogenesis. 2-Methoxyestradiol (2-ME) is a well-established antiangiogenic and antiproliferative drug. In current clinical studies, 2-ME, known as Panzem, was examined for breast, ovarian, prostate, and multiple myeloma. The SW1088 grade III glioma cell line was treated with pharmacological and physiological doses of 2-ME. The induction of apoptosis and necrosis, oxidative stress, cell cycle arrest, and mitochondrial membrane potential were established by flow cytometry. Confocal microscopy was used to detect DNA damage. The Western blot technique determined the level of nitric oxide synthase and heat shock proteins. Here, for the first time, 2-ME is shown to induce nitro-oxidative stress with the concomitant modulation of heat shock proteins (HSPs) in the SW1088 grade III glioma cell line. Crucial therapeutic strategies for GMB should address both cell proliferation and angiogenesis, and due to the above, 2-ME seems to be a perfect candidate for GBM therapy.

Induction of 2-hydroxycatecholestrogens O-methylation: A missing puzzle piece in diagnostics and treatment of lung cancer

Lung cancer is one of the most common cancers worldwide, causing nearly one million deaths each year. Herein, we present the effect of 2-methoxyestradiol (2-ME), the endogenous metabolite of 17β-estradiol (E2), on non-small cell lung cancer (NSCLC) cells. We observed that 2-ME reduced the viability of lung adenocarcinoma in two-dimensional (2D) and three-dimensional (3D) spheroidal A549 cell culture models. Molecular modeling was carried out aiming to visualize amino acid residues within binding pockets of the acyl-protein thioesterases, namely 1 (APT1) and 2 (APT2), and thus to identify which ones were more likely involved in the interaction with 2-ME. Our findings suggest that 2-ME acts as an APT1 inhibitor enhancing protein palmitoylation and oxidative stress phenomena in the lung cancer cell. In order to support our data, metabolomics of blood serum from NSCLC patients was also performed. Moreover, computational analysis suggests that 2-ME as compared to other estrogen metabolism intermediates is relatively safe in terms of its possible non-receptor bioactivity within healthy human cells due to a very low electrophilic potential and hence no substantial risk of spontaneous covalent modification of biologically protective nucleophiles. We propose that 2-ME can be used as a selective tumor biomarker in the course of certain types of lung cancers and possibly as a therapeutic adjuvant or neoadjuvant.

Regulation of Mitochondrial Dynamics in Parkinson's Disease-Is 2-Methoxyestradiol a Missing Piece?

Mitochondria, as "power house of the cell", are crucial players in cell pathophysiology. Beyond adenosine triphosphate (ATP) production, they take part in a generation of reactive oxygen species (ROS), regulation of cell signaling and cell death. Dysregulation of mitochondrial dynamics may lead to cancers and neurodegeneration; however, the fusion/fission cycle allows mitochondria to adapt to metabolic needs of the cell. There are multiple data suggesting that disturbed mitochondrial homeostasis can lead to Parkinson's disease (PD) development. 2-methoxyestradiol (2-ME), metabolite of 17β-estradiol (E2) and potential anticancer agent, was demonstrated to inhibit cell growth of hippocampal HT22 cells by means of nitric oxide synthase (NOS) production and oxidative stress at both pharmacologically and also physiologically relevant concentrations. Moreover, 2-ME was suggested to inhibit mitochondrial biogenesis and to be a dynamic regulator. This review is a comprehensive discussion, from both scientific and clinical point of view, about the influence of 2-ME on mitochondria and its plausible role as a modulator of neuron survival.

Regulation of mitochondrial dynamics in 2-methoxyestradiol-mediated osteosarcoma cell death

Osteosarcoma (OS) is one of the most malignant tumors of childhood and adolescence. Research on mitochondrial dynamics (fusion/fission) and biogenesis has received much attention in last few years, as they are crucial for death of cancer cells. Specifically, it was shown that increased expression of the cytoplasmic dynamin-related protein 1 (Drp1) triggers mitochondrial fission (division), which activates BAX and downstream intrinsic apoptosis, effectively inhibiting OS growth. In the presented study, human OS cells (metastatic 143B OS cell line) were incubated with 2-methoxyestradiol (2-ME) at both physiologically and pharmacologically relevant concentrations. Cell viability was determined by the MTT assay. Confocal microscopy and western blot methods were applied to examine changes in Drp1 and BAX protein levels. Mitochondrial Division Inhibitor 1, MDIVI-1, was used in the study to further examine the role of Drp1 in 2-ME-mediated mechanism of action. To determine quantitative and qualitative changes in mitochondria, electron microscopy was used. 2-ME at all used concentrations increased mitochondrial fission and induced autophagy in OS cells. At the concentration of 1 µM 2-ME increased the area density of mitochondria in OS cells. Subsequent, upregulated expression of Drp1 and BAX proteins by 2-ME strongly suggests the activation of the intrinsic apoptosis pathway. We further observed 2-ME-mediated regulation of glycolytic state of OS cells. Therefore, we suggest that changes of mitochondrial dynamics may represent a novel mechanism of anticancer action of 2-ME. This finding may open new approaches to improve the efficacy of chemotherapy in the treatment of OS, however, it has to be confirmed by in vivo studies.

Modification of DNA structure by reactive nitrogen species as a result of 2-methoxyestradiol-induced neuronal nitric oxide synthase uncoupling in metastatic osteosarcoma cells

2-methoxyestradiol (2-ME) is a physiological anticancer compound, metabolite of 17β-estradiol. Previously, our group evidenced that from mechanistic point of view one of anticancer mechanisms of action of 2-ME is specific induction and nuclear hijacking of neuronal nitric oxide synthase (nNOS), resulting in local generation of nitro-oxidative stress and finally, cancer cell death.

The current study aims to establish the substantial mechanism of generation of reactive nitrogen species by 2-ME. We further achieved to identify the specific reactive nitrogen species involved in DNA-damaging mechanism of 2-ME.

The study was performed using metastatic osteosarcoma 143B cells. We detected the release of biologically active (free) nitric oxide (^•NO) with concurrent measurements of peroxynitrite (ONOO⁻) in real time in a single cell of 143B cell line by using ^•NO/ONOO⁻ sensitive microsensors after stimulation with calcium ionophore. Detection of nitrogen dioxide (^•NO₂) and determination of chemical rate constants were carried out by a stopped-flow technique. The affinity of reactive nitrogen species toward the guanine base of DNA was evaluated by density functional theory calculations. Expression and localization of nuclear factor NF-kB was determined using imaging cytometry, while cell viability assay was evaluated by MTT assay.

Herein, we presented that 2-ME triggers pro-apoptotic signalling cascade by increasing cellular reactive nitrogen species overproduction – a result of enzymatic uncoupling of increased nNOS protein levels. In particular, we proved that ONOO⁻ and ^•NO₂ directly formed from peroxynitrous acid (ONOOH) and/or by auto-oxidation of ^•NO, are inducers of DNA damage in anticancer mechanism of 2-ME. Specifically, the affinity of reactive nitrogen species toward the guanine base of DNA, evaluated by density functional theory calculations, decreased in the order: ONOOH > ONOO⁻ > ^•NO₂ > ^•NO.

Therefore, we propose to consider the specific inducers of nNOS as an effective tool in the field of chemotherapy.

The Major Heat Shock Proteins, Hsp70 and Hsp90, in 2-Methoxyestradiol-Mediated Osteosarcoma Cell Death Model

2-Methoxyestradiol is one of the natural 17β-estradiol derivatives and a potential novel anticancer agent currently being under evaluation in advanced phases of clinical trials. However, the mechanism of anticancer action of 2-methoxyestradiol has not been yet fully established. In our previous studies we have demonstrated that 2-methoxyestradiol selectively induces the expression and nuclear translocation of neuronal nitric oxide synthase in osteosarcoma 143B cells. Heat shock proteins (Hsps) are factors involved in the regulation of expression and activity of nitric oxide synthases. Herein, we chose osteosarcoma cell lines differed in metastatic potential, metastatic 143B and highly metastatic MG63.2 cells, in order to further investigate the anticancer mechanism of 2-methoxyestradiol. The current study aimed to determine the role of major heat shock proteins, Hsp90 and Hsp70 in 2-methoxyestradiol-induced osteosarcoma cell death. We focused on the implication of Hsp90 and Hsp70 in control under expression of neuronal nitric oxide synthase, localization of the enzyme, and further generation of nitro-oxidative stress. To give the insight into the role of Hsp90 in regulation of anticancer efficacy of 2-methoxyestradiol, we used geldanamycin as a potent Hsp90 inhibitor. Herein, we evidenced that inhibition of Hsp90 controls the protein expression of 2-methoxyestradiol-induced neuronal nitric oxide synthase and inhibits enzyme nuclear translocation. We propose that decreased level of neuronal nitric oxide synthase protein after a combined treatment with 2-methoxyestradiol and geldanamycin is directly associated with the accompanying upregulation of Hsp70 and downregulation of Hsp90. This interaction resulted in abrogation of anticancer efficacy of 2-methoxyestradiol by geldanamycin.

2-Methoxyestradiol and Its Combination with a Natural Compound, Ferulic Acid, Induces Melanoma Cell Death via Downregulation of Hsp60 and Hsp90

Melanoma is an aggressive type of skin cancer with one of the highest mortality rates. Notably, its incidence in the last few decades has increased faster than any other cancer. Therefore, searching for novel anticancer therapies is of great clinical importance. In the present study, we investigated the anticancer potential of 2-methoxyestradiol, potent chemotherapeutic, in the A375 melanoma cellular model. In order to furthermore evaluate the anticancer efficacy of 2-methoxyestradiol, we have additionally combined the treatment with a naturally occurring polyphenol, ferulic acid. The results were obtained using the melanoma A375 cellular model. In the study, we used MTT assay, flow cytometry, and western blot techniques. Herein, we have evidenced that the molecular mechanism of action of 2-methoxyestradiol and ferulic acid is partly related to the reduction of Hsp60 and Hsp90 levels and the induction of nitric oxide in the A375 melanoma cell model, while no changes were observed in Hsp70 expression after 2-methoxyestradiol and ferulic acid treatment separately or in combination. This is especially important in case of chemoresistance mechanisms because the accumulation of Hsp70 reduces induction of cancer cell death, thus decreasing antitumour efficacy.

Nitric oxide and its derivatives in the cancer battlefield

Elevated levels of reactive nitrogen species, alteration in redox balance and deregulated redox signaling are common hallmarks of cancer progression and chemoresistance. However, depending on the cellular context, distinct reactive nitrogen species are also hypothesized to mediate cytotoxic activity and are thus used in anticancer therapies. We present here the dual face of nitric oxide and its derivatives in cancer biology. Main derivatives of nitric oxide, such as nitrogen dioxide and peroxynitrite cause cell death by inducing protein and lipid peroxidation and/or DNA damage. Moreover, they control the activity of important protein players within the pro- and anti-apoptotic signaling pathways. Thus, the control of intracellular reactive nitrogen species may become a sophisticated tool in anticancer strategies.

Hypoxia increases chemoresistance in human medulloblastoma DAOY cells via hypoxia‑inducible factor 1α‑mediated downregulation of the CYP2B6, CYP3A4 and CYP3A5 enzymes and inhibition of cell proliferation

Medulloblastomas are among the most frequently diagnosed pediatric solid tumors, and drug resistance remains as the principal cause of treatment failure. Hypoxia and the subsequent activation of hypoxia-inducible factor 1α (HIF-1α) are considered key factors in modulating drug antitumor effectiveness, but the underlying mechanisms in medulloblastomas have not yet been clearly understood. The aim of the present study was to determine whether hypoxia induces resistance to cyclophosphamide (CPA) and ifosfamide (IFA) in DAOY medulloblastoma cells, whether the mechanism is dependent on HIF-1α, and whether involves the modulation of the expression of cytochromes P450 (CYP)2B6, 3A4 and 3A5 and the control of cell proliferation. Monolayer cultures of DAOY medulloblastoma cells were exposed for 24 h to moderate (1% O₂) or severe (0.1% O₂) hypoxia, and protein expression was evaluated by immunoblotting. Cytotoxicity was studied with the MTT assay and by Annexin V/PI staining and flow cytometry. Cell proliferation was determined by the trypan-blue exclusion assay and cell cycle by propidium iodide staining and flow cytometry. Hypoxia decreased CPA and IFA cytotoxicity in medulloblastoma cells, which correlated with a reduction in the protein levels of CYP2B6, CYP3A4 and CYP3A5 and inhibition of cell proliferation. These responses were dependent on hypoxia-induced HIF-1α activation, as evidenced by chemical inhibition of its transcriptional activity with 2-methoxyestradiol (2-ME), which enhanced the cytotoxic activity of CPA and IFA and increased apoptosis. Our results indicate that by stimulating HIF-1α activity, hypoxia downregulates the expression of CYP2B6, CYP3A4 and CYP3A5, that in turn leads to decreased conversion of CPA and IFA into their active forms and thus to diminished cytotoxicity. These results support that the combination of HIF-1α inhibitors and canonical antineoplastic agents provides a potential therapeutic alternative against medulloblastoma.

2-Methoxyestradiol Affects Mitochondrial Biogenesis Pathway and Succinate Dehydrogenase Complex Flavoprotein Subunit A in Osteosarcoma Cancer Cells

BACKGROUND/AIM

Dysregulation of mitochondrial pathways is implicated in several diseases, including cancer. Notably, mitochondrial respiration and mitochondrial biogenesis are favored in some invasive cancer cells, such as osteosarcoma. Hence, the aim of the current work was to investigate the effects of 2-methoxyestradiol (2-ME), a potent anticancer agent, on the mitochondrial biogenesis of osteosarcoma cells.

MATERIALS AND METHODS

Highly metastatic osteosarcoma 143B cells were treated with 2-ME separately or in combination with L-lactate, or with the solvent (non-treated control cells). Protein levels of α-syntrophin and peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α) were determined by western blotting. Impact of 2-ME on mitochondrial mass, regulation of cytochrome c oxidase I (COXI) expression, and succinate dehydrogenase complex flavoprotein subunit A (SDHA) was determined by immunofluorescence analyses. Inhibition of sirtuin 3 (SIRT3) activity by 2-ME was investigated by fluorescence assay and also, using molecular docking and molecular dynamics simulations.

RESULTS

L-lactate induced mitochondrial biogenesis pathway via up-regulation of COXI. 2-ME inhibited mitochondrial biogenesis via regulation of PGC-1α, COXI, and SIRT3 in a concentration-dependent manner as a consequence of nuclear recruitment of neuronal nitric oxide synthase and nitric oxide generation. It was also proved that 2-ME inhibited SIRT3 activity by binding to both the canonical and allosteric inhibitor binding sites. Moreover, regardless of the mitochondrial biogenesis pathway, 2-ME affected the expression of SDHA.

CONCLUSION

Herein, mitochondrial biogenesis pathway regulation and SDHA were presented as novel targets of 2-ME, and moreover, 2-ME was demonstrated as a potent inhibitor of SIRT3. L-lactate was confirmed to exert pro-carcinogenic effects on osteosarcoma cells via the induction of the mitochondrial biogenesis pathway. Thus, L-lactate level may be considered as a prognostic biomarker for osteosarcoma.

2-Methoxyestradiol Reverses the Pro-Carcinogenic Effect of L-Lactate in Osteosarcoma 143B Cells

BACKGROUND/AIM

According to the reverse Warburg effect, tumor cells may metabolize lactate as an energy source and shuttle L-lactate to neighboring cancer cells, adjacent stroma, and vascular endothelial cells, thus inducing metabolic reprogramming. An increased tumor L-lactate level strictly correlates with increased metastasis, tumor recurrence and a poor outcome. A potent anticancer agent that may act on L-lactate activated cells is 2-metoxyestradiol. Thus, the aim of the study was to evaluate whether a potent anticancer agent, 2-methoxyestradiol, is able to reverse L-lactate-induced metabolic reprogramming in osteosarcoma 143B cells.

MATERIALS AND METHODS

We used flow cytometry in order to determine cell death, autophagy, expression of KI-67, mitochondrial membrane depolarization. We performed cell proliferation assay in order to determine cell viability and cell migration assay to determine invasive potential of osteosarcoma cells. While, CalcuSyn software was used in order to evaluate the interaction between 2-methoxyestradiol and L-lactate.

RESULTS

We demonstrated that 2-methoxyestradiol abolished L-lactate-induced migration and proliferation of osteosarcoma cells. Moreover, we observed that this effect was associated with regulation of Ki-67 and induction of autophagy.

CONCLUSION

2-Methoxyestradiol is a potent anticancer agent also under metabolic reprogramming conditions.

2-methoxyestradiol impacts on amino acids-mediated metabolic reprogramming in osteosarcoma cells by its interaction with NMDA receptor

Deregulation of serine and glycine metabolism, have been identified to function as metabolic regulators in supporting tumor cell growth. The role of serine and glycine in regulation of cancer cell proliferation is complicated, dependent on concentrations of amino acids and tissue-specific. D-serine and glycine are coagonists of N-methyl-D-aspartate (NMDA) receptor subunit GRIN1. Importantly, NMDA receptors are widely expressed in cancer cells and play an important role in regulation of cell death, proliferation, and metabolism of numerous malignancies. The aim of the present work was to associate the metabolism of glycine and D-serine with the anticancer activity of 2-methoxyestradiol. 2-methoxyestradiol is a potent anticancer agent but also a physiological 17β- estradiol metabolite. In the study we have chosen two malignant cell lines expressing functional NMDA receptors, that is osteosarcoma 143B and breast cancer MCF7. We used MTS assay, migration assay, flow cytometric analyses, Western blotting and immunoprecipitation techniques as well as molecular modeling studies. We have demonstrated the extensive crosstalk between the deregulated metabolic network and cancer cell signaling. Herein, we observed an anticancer effect of high concentrations of glycine and D-serine in osteosarcoma cells. In contrast, the amino acids when used at low, physiological concentrations induced the proliferation and migration of osteosarcoma cells. Importantly, the pro-cancergogenic effects of both glycine and D-serine where abrogated by the usage of 2-methoxyestradiol at both physiological and pharmacological relevant concentrations. The obtained data confirmed that 2-methoxyestradiol may be a physiological anticancer molecule.

Neuronal Nitric Oxide Synthase-Mediated Genotoxicity of 2-Methoxyestradiol in Hippocampal HT22 Cell Line

2-methoxyestradiol, metabolite of 17β-estradiol, is considered a potential anticancer agent, currently investigated in several clinical trials. This natural compound was found to be effective towards great number of cancers, including colon, breast, lung, and osteosarcoma and has been reported to be relatively non-toxic towards non-malignant cells. The aim of the study was to determine the potential neurotoxicity and genotoxicity of 2-methoxyestradiol at physiological and pharmacological relevant concentrations in hippocampal HT22 cell line. Herein, we determined influence of 2-methoxyestradiol on proliferation, inhibition of cell cycle, induction of apoptosis, and DNA damage in the HT22 cells. The study was performed using imaging cytometry and comet assay techniques. Herein, we demonstrated that 2-methoxyestradiol, at pharmacologically and also physiologically relevant concentrations, increases nuclear localization of neuronal nitric oxide synthase. It potentially results in DNA strand breaks and increases in genomic instability in hippocampal HT22 cell line. Thus, we are postulating that naturally occurring 2-methoxyestradiol may be considered a physiological modulator of neuron survival.

Origin of endogenous nitric oxide released in the nucleus accumbens under real-time in vivo conditions

AIMS

Nitric oxide (NO), is a simple but multifarious molecule. It is implicated in physiological and pathological processes within the striatum, mainly in the nucleus accumbens (NAc). The aim of the present study was to determine the origin of NO in the NAc of anaesthetized rats by applying various compounds known to modulate the release of NO when applied either systemically or locally.

MAIN METHODS

Real-time monitoring of NO was carried out by introducing an amperometric NO sensor into the outer tubing of a push-pull cannula. For local application of substances, the push-pull superfusion technique was used.

KEY FINDINGS

An overdose of urethane (i.p.) or superfusion of the NAc with tetrodotoxin (TTX) led to a fall of NO release in the NAc. The NO synthase (NOS) inhibitors 7-nitroindazolmonosodiumsalt (7-NINA, neuronal NOS selective) and N-nitro-L-arginine (L-NNA, NOS selective) decreased release of NO when applied i.p. or locally. Superfusion of the NAc with N-methyl-D-aspartate (NMDA) elicited a dose dependent increase of NO release.

SIGNIFICANCE

Combination of an amperometric NO sensor for real-time monitoring of NO release with the push-pull superfusion technique showed that NO released in the NAc is, at least to a great extent, of neuronal origin. The enhanced release of NO elicited by locally applied NMDA demonstrates that activation of NMDA receptors facilitates NO synthesis, thus underlining the functionality of NO targets within the NAc.

DNA strand breaks induced by nuclear hijacking of neuronal NOS as an anti-cancer effect of 2-methoxyestradiol

2-Methoxyestradiol (2-ME) is a physiological metabolite of 17β-estradiol. At pharmacological concentrations, 2-ME inhibits colon, breast and lung cancer in tumor models. Here we investigated the effect of physiologically relevant concentrations of 2-ME in osteosarcoma cell model. We demonstrated that 2-ME increased nuclear localization of neuronal nitric oxide synthase, resulting in nitro-oxidative DNA damage. This in turn caused cell cycle arrest and apoptosis in osteosarcoma cells. We suggest that 2-ME is a naturally occurring hormone with potential anti-cancer properties.