Superoxide radical generation and Mn- and Cu-Zn superoxide dismutases activities in human leukemic cells

Mitochondrial metabolism as a target for acute myeloid leukemia treatment

Acute myeloid leukemias (AML) are a group of aggressive hematologic malignancies resulting from acquired genetic mutations in hematopoietic stem cells that affect patients of all ages. Despite decades of research, standard chemotherapy still remains ineffective for some AML subtypes and is often inappropriate for older patients or those with comorbidities. Recently, a number of studies have identified unique mitochondrial alterations that lead to metabolic vulnerabilities in AML cells that may present viable treatment targets. These include mtDNA, dependency on oxidative phosphorylation, mitochondrial metabolism, and pro-survival signaling, as well as reactive oxygen species generation and mitochondrial dynamics. Moreover, some mitochondria-targeting chemotherapeutics and their combinations with other compounds have been FDA-approved for AML treatment. Here, we review recent studies that illuminate the effects of drugs and synergistic drug combinations that target diverse biomolecules and metabolic pathways related to mitochondria and their promise in experimental studies, clinical trials, and existing chemotherapeutic regimens.

The Role of Reactive Oxygen Species in Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is an aggressive haematological malignancy with a poor overall survival. Reactive oxygen species (ROS) have been shown to be elevated in a wide range of cancers including AML. Whilst previously thought to be mere by-products of cellular metabolism, it is now clear that ROS modulate the function of signalling proteins through oxidation of critical cysteine residues. In this way, ROS have been shown to regulate normal haematopoiesis as well as promote leukaemogenesis in AML. In addition, ROS promote genomic instability by damaging DNA, which promotes chemotherapy resistance. The source of ROS in AML appears to be derived from members of the “NOX family” of NADPH oxidases. Most studies link NOX-derived ROS to activating mutations in the Fms-like tyrosine kinase 3 (FLT3) and Ras-related C3 botulinum toxin substrate (Ras). Targeting ROS through either ROS induction or ROS inhibition provides a novel therapeutic target in AML. In this review, we summarise the role of ROS in normal haematopoiesis and in AML. We also explore the current treatments that modulate ROS levels in AML and discuss emerging drug targets based on pre-clinical work.

Intersection of FOXO- and RUNX1-mediated gene expression programs in single breast epithelial cells during morphogenesis and tumor progression

Gene expression networks are complicated by the assortment of regulatory factors that bind DNA and modulate transcription combinatorially. Single-cell measurements can reveal biological mechanisms hidden by population averages, but their value has not been fully explored in the context of mRNA regulation. Here, we adapted a single-cell expression profiling technique to examine the gene expression program downstream of Forkhead box O (FOXO) transcription factors during 3D breast epithelial acinar morphogenesis. By analyzing patterns of mRNA fluctuations among individual matrix-attached epithelial cells, we found that a subset of FOXO target genes was jointly regulated by the transcription factor Runt-related transcription factor 1 (RUNX1). Knockdown of RUNX1 causes hyperproliferation and abnormal morphogenesis, both of which require normal FOXO function. Down-regulating RUNX1 and FOXOs simultaneously causes widespread oxidative stress, which arrests proliferation and restores normal acinar morphology. In hormone-negative breast cancers lacking human epidermal growth factor receptor 2 (HER2) amplification, we find that RUNX1 down-regulation is strongly associated with up-regulation of FOXO1, which may be required to support growth of RUNX1-negative tumors. The coordinate function of these two tumor suppressors may provide a failsafe mechanism that inhibits cancer progression.

Do reactive oxygen species play a role in myeloid leukemias?

Reactive oxygen species (ROS) are a heterogeneous group of molecules that are generated by mature myeloid cells during innate immune responses, and are also implicated in normal intracellular signaling. Excessive production of ROS (and/or a deficiency in antioxidant pathways) can lead to oxidative stress, a state that has been observed in several hematopoietic malignancies including acute and chronic myeloid leukemias (AML and CML). Currently it is unclear what the cause of oxidative stress might be and whether oxidative stress contributes to the development, progression, or maintenance of these diseases. This article reviews the current evidence suggesting a role for ROS both in normal hematopoiesis and in myeloid leukemogenesis, and discusses the usefulness of therapeutically targeting oxidative stress in myeloid malignancy.

Dysregulated calcium homeostasis and oxidative stress in chronic myeloid leukemia (CML) cells

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder caused by the oncogenic activity of the Bcr-Abl protein, a deregulated tyrosine kinase. Calcium may act directly on cellular enzymes and in conjunction with other cellular metabolites, such as cyclic nucleotides, to regulate cell functions. Alteration in the ionized calcium concentration in the cytosol has been implicated in the initiation of secretion, contraction, and cell proliferation as well as the production of reactive oxygen species (ROS) has been correlates with normal cell proliferation through activation of growth-related signaling pathways. In this study we evaluated in peripheral blood leukocytes from CML patients the role of the balance between intracellular calcium and oxidative stress in CML disease in order to identify possible therapeutic targets in patients affected by this pathology. Our results demonstrated that peripheral blood mononuclear cells derived from CML patients displayed decreased intracellular calcium [Ca(2+)](i) fluxes both after InsP(3) as well as ATP and ionomycin (IONO) administration. CML cells showed lower levels of superoxide dismutase (SOD) activity and significantly higher malondialdehyde levels (MDA) than peripheral blood mononuclear cells derived from control patients. Finally we showed that resveratrol is able to down-regulate InsP3 and ATP effects on intracellular calcium [Ca(2+)](i) fluxes as well as the effects of ATP and IONO on oxidative stress in CML cells.

The Sod2 mutant mouse as a model for oxidative stress: a functional proteomics perspective

Oxidative stress has been implicated in the pathogenesis of numerous human diseases and disorders, but the mechanistic basis often remains enigmatic. The Sod2 mutant mouse, which is sensitized to mitochondrial stress, is an ideal mutant model for studying the role of oxidative stress in a diverse range of complications arising from mitochondrial dysfunction and diminished antioxidant defense. To fully appreciate the widespread molecular consequences under increased oxidative stress, a systems approach utilizing proteomics is able to provide a global overview of the complex biological changes, which a targeted single biomolecular approach cannot address fully. This review focuses on the applications of mass spectrometry and functional proteomics in the Sod2 mouse. The combinatorial approach provides novel insights into the interplay of chemistry and biology, free radicals and proteins, thereby augmenting our understanding of how redox perturbations influence protein dynamics. Ultimately, this knowledge can lead to the development of free radical-targeted therapies.

Cell Activating Capacity of 50 Hz Magnetic Fields to Release Reactive Oxygen Intermediates in Human Umbilical Cord Blood-derived Monocytes and in Mono Mac 6 Cells

The aim of this study was to investigate the mechanism of cell activation induced by extremely low frequency magnetic fields (ELF-MF) (50 Hz) in human cells. We examined the production of free radicals in human umbilical cord blood-derived monocytes and in human Mono Mac 6 cells. The release of superoxide radical anions was analyzed using nitroblue tetrazolium chloride and the total of reactive oxygen species (ROS) was detected using dihydrorhodamine 123. Our results show a significant increase of superoxide radical anion production up-to 1.4 fold as well as an increase in ROS release up-to 1.2 fold upon exposure of monocytes to 1 mT ELF-MF (45 min). Mono Mac 6 cells exhibit higher superoxide radical anion and ROS production up-to 1.4 and 1.5 fold, respectively. These results indicate that Mono Mac 6 cells are more sensitive to ELF-MF than monocytes. Using diphenyleneiodonium chloride (DPI) a specific inhibitor for the NADPH oxidase, the MF-effect was not inhibited in Mono Mac 6 cells. Therefore, we suggest that ELF-MF exposure induces the activation of NADH oxidase in these cells. However, the MF-effect was inhibited by DPI in monocytes, indicating the activation of the NADPH oxidase after exposure to ELF-MF.

Serum and Ascitic Fluid Superoxide Dismutase and Malondialdehyde Levels in Patients with Cirrhosis

Summary

Serum and ascitic fluid superoxide dismutase (SOD) and malondialdehyde (MDA) levels were measured in 43 patients with cirrhosis and in a 10 healthy control group.

Compensated cirrhotic patients had no clinically detectable ascites, but decompensated patients had massive ascites. Cirrhotic patients were divided into three groups: patients with compensated cirrhosis (n = 16), patients with decompensated cirrhosis with Spontaneous bacterial peritonitis (SBP) (n = 14), and patients with decompensated cirrhosis without SBP (n = 13).

All cirrhotic patients in the experimental group had significantly higher serum SOD (p < 0.001) and MDA levels (p < 0.01) than those in the control group. There were no significant differences with respect to serum SOD and MDA levels among the three different groups of patients. There was no remarkable difference in ascitic fluid SOD and MDA levels between decompensated cirrhotic patients with and without SBP (p > 0.05).

These results suggest that the increase in serum SOD and MDA levels are not related to the presence of SBP and the status of liver cirrhosis. To sum up, clarifying the impact of increased serum SOD and MDA levels in cirrhotic patients needs further investigation.

Cardiovascular diseases: protective effects of melatonin

This brief review considers some of the cardiac diseases and conditions where free radicals and related reactants are believed to be causative. The report also describes the beneficial actions of melatonin against oxidative cardiovascular disorders. Based on the data available, melatonin seems to have cardioprotective properties via its direct free radical scavenger and its indirect antioxidant activity. Melatonin efficiently interacts with various reactive oxygen and reactive nitrogen species (receptor independent actions) and it also upregulates antioxidant enzymes and downregulates pro-oxidant enzymes (receptor-dependent actions). Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiologic barriers. These findings have implications for the protective effects of melatonin against cardiac diseases induced by oxidative stress. Melatonin attenuates molecular and cellular damages resulting from cardiac ischemia/reperfusion in which destructive free radicals are involved. Anti-inflammatory and antioxidative properties of melatonin are also involved in the protection against a chronic vascular disease, atherosclerosis. The administration of melatonin, as a result of its antioxidant features, has been reported to reduce hypertension and cardiotoxicity induced by clinically used drugs. The results described herein help to clarify the beneficial effects of melatonin against these conditions and define the potential clinical applicability of melatonin in cardiovascular diseases.

Antioxidant status and superoxide anion radical generation in acute myeloid leukemia

OBJECTIVES

This study was undertaken to investigate if there is a disparity in the antioxidant status and the ability of superoxide anion (O(2)(-)) generation in the patients with acute myeloid leukemia (AML).

DESIGN AND METHODS

The peripheral blood samples from thirty AML patients and thirty-six healthy subjects were collected and leukocytes, erythrocytes and plasma were separated for use in various parameter measurements.

RESULTS

The generation of O(2)(-), as reflected by lucigenin-based CL (LBCL), by the leukocytes of patients with AML was found to be significantly elevated either in resting or stimuli-elicited condition as compared with that of healthy controls (p<0.05). Coincidentally, these data were matched up with the suppressed SOD activities, notably in Cu/Zn SOD isoform found in AML patients (p<0.05). Conversely, SOD and GPx activities in erythrocytes of patients with AML were shown to be significantly higher than their normal counterparts (p<0.05).

CONCLUSIONS

These data suggest that altered expression of antioxidant enzymes and higher capability of O(2)(-) generation by leukocytes seem to be a distinct feature of AML.

Selenoureas and thioureas are effective superoxide radical scavengers in vitro

Oxygen radicals, such as superoxide radicals, embellishing DNA, protein, lipids, etc., and carrying out the obstacle of the function of a cell is known. It depends for the oxidant level in the living body on the balance of a generation system and an elimination system of oxygen radicals, and research which controls an oxidant level in the living body is briskly done by taking in the substance which eliminates an oxygen radical. We investigated scavenging effects of superoxide radicals by selenoureas and thioureas using a highly sensitive and quantitative chemiluminescence method. At 330 nM, five selenoureas and five thioureas scavenged fractions of superoxide radicals (O2-) ranging from 8.4% to 87.6%. Among five N,N-unsubstituted selenoureas and N,N-unsubstituted thioureas 1-selenocarbamoylpiperidine and 1-thiocarbamoylpyrrolidine were the most effective scavengers. A possibility that selenoureas could use it as a new superoxide anion-scavenging substance from the result of this research became clear.