Role of TNFalpha in regulation of myeloperoxidase expression in irradiated HL60 promyelocytic cells

Improving the prognosis of renal patients: The effects of blood flow-restricted resistance training on redox balance and cardiac autonomic function

NEW FINDINGS

What is the central question of this study? Can resistance training with and without blood flow restriction improve redox balance and positively impact the autonomic cardiac modulation in chronic kidney disease patients? What is the main finding and its importance? Resistance training with and without blood flow restriction improved antioxidant defence (paraoxonase 1), decreased the pro-oxidative myeloperoxidase, improved cardiac autonomic function and slowed the decrease in renal function. We draw attention to the important clinical implications for the management of redox balance and autonomic cardiac function in chronic kidney disease patients.

ABSTRACT

Patients with chronic kidney disease (CKD) are prone to cardiovascular diseases secondary to abnormalities in both autonomic cardiac function and redox balance [myeloperoxidase (MPO) to paraoxonase 1 (PON1) ratio]. Although aerobic training improves both autonomic balance and redox balance in patients with CKD, the cardioprotective effects of resistance training (RT), with and without blood flow restriction (BFR), remain unknown. We aimed to compare the effects of RT and RT+BFR on antioxidant defence (PON1), pro-oxidative status (MPO), cardiac autonomic function (quantified by heart rate variability analysis) and renal function. Conservative CKD (stages 1 to 5 who do not need hemodialysis) patients (n = 105, 33 female) of both sexes were randomized into three groups: control (CTL; 57.6 ± 5.2 years; body mass index, 33.23 ± 1.62 kg/m² ), RT (58.09 ± 6.26 years; body mass index 33.63 ± 2.05 kg/m² ) and RT+BFR (58.06 ± 6.47 years; body mass index, 33.32 ± 1.87 kg/m² ). Patients completed 6 months of RT or RT+BFR on three non-consecutive days per week under the supervision of strength and conditioning professionals. Training loads were adjusted every 2 months. Heart rate variability was recorded with a Polar-RS800 and data were analysed for time and frequency domains using Kubios software. The redox balance markers were PON1 and MPO, which were analysed in plasma samples. Renal function was estimated as estimated glomerular filtration rate. The RT and RT+BFR decreased pro-oxidative MPO (RT, ∼34 ng/ml and RT+BFR, ∼27 ng/ml), improved both antioxidant defence (PON1: RT, ∼23 U/L and RT+BFR, ∼31 U/L) and cardiac autonomic function (R-R interval: RT, ∼120.4 ms and RT+BFR, ∼117.7 ms), and slowed the deterioration of renal function (P < 0.0001). Redox balance markers were inversely correlated with heart rate variability time-domain indices. Our data indicated that both training models were effective as non-pharmacological tools to increase the antioxidant defences, decrease oxidative stress and improve the cardiac autonomic function of CKD patients.

Targeting Myeloperoxidase Disrupts Mitochondrial Redox Balance and Overcomes Cytarabine Resistance in Human Acute Myeloid Leukemia

Chemotherapies alter cellular redox balance and reactive oxygen species (ROS) content. Recent studies have reported that chemoresistant cells have an increased oxidative state in hematologic malignancies. In this study, we demonstrated that chemoresistant acute myeloid leukemia (AML) cells had a lower level of mitochondrial and cytosolic ROS in response to cytarabine (AraC) and overexpressed myeloperoxidase (MPO), a heme protein that converts hydrogen peroxide to hypochlorous acid (HOCl), compared with sensitive AML cells. High MPO-expressing AML cells were less sensitive to AraC in vitro and in vivo. They also produced higher levels of HOCl and exhibited an increased rate of mitochondrial oxygen consumption when compared with low MPO-expressing AML cells. Targeting MPO expression or enzyme activity sensitized AML cells to AraC treatment by triggering oxidative damage and sustaining oxidative stress, particularly in high MPO-expressing AML cells. This sensitization stemmed from mitochondrial superoxide accumulation, which impaired oxidative phosphorylation and cellular energetic balance, driving apoptotic death and selective eradication of chemoresistant AML cells in vitro and in vivo. Altogether, this study uncovers a noncanonical function of MPO enzyme in maintaining redox balance and mitochondrial energetic metabolism, therefore affecting downstream pathways involved in AML chemoresistance. SIGNIFICANCE: These findings demonstrate the role of myeloperoxidase in the regulation of ROS levels and sensitivity of AML cells to cytarabine, an essential chemotherapeutic backbone in the therapy of AML.

The Oxidative Stress Agent Hypochlorite Stimulates c-di-GMP Synthesis and Biofilm Formation in Pseudomonas aeruginosa

The opportunistic human pathogen Pseudomonas aeruginosa is able to survive under a variety of often harmful environmental conditions due to a multitude of intrinsic and adaptive resistance mechanisms, including biofilm formation as one important survival strategy. Here, we investigated the adaptation of P. aeruginosa PAO1 to hypochlorite (HClO), a phagocyte-derived host defense compound and frequently used disinfectant. In static biofilm assays, we observed a significant enhancement in initial cell attachment in the presence of sublethal HClO concentrations. Subsequent LC-MS analyses revealed a strong increase in cyclic-di-GMP (c-di-GMP) levels suggesting a key role of this second messenger in HClO-induced biofilm development. Using DNA microarrays, we identified a 26-fold upregulation of ORF PA3177 coding for a putative diguanylate cyclase (DGC), which catalyzes the synthesis of the second messenger c-di-GMP – an important regulator of bacterial motility, sessility and persistence. This DGC PA3177 was further characterized in more detail demonstrating its impact on P. aeruginosa motility and biofilm formation. In addition, cell culture assays attested a role for PA3177 in the response of P. aeruginosa to human phagocytes. Using a subset of different mutants, we were able to show that both Pel and Psl exopolysaccharides are effectors in the PA3177-dependent c-di-GMP network.

In vivo validation of the bystander effect

The bystander effect post radionuclide decay describes the biologic response(s) of cells not directly targeted by the radiation insult. Recently, we demonstrated that the specific irradiation of human tumor cells in vivo leads to a bystander effect in subcutaneously growing tumors. These in vivo findings 1) call for the re-evaluation of approaches currently used for estimating the risks to individuals/populations inadvertently exposed internally to radioactivity (e.g., alpha particles) as well as to patients undergoing routine diagnostic nuclear medical procedures, and 2) impact significantly the current dogma for assessing the therapeutic potential of internally administered radionuclides.

Differentially expressed proteins in gill and skin mucus of Atlantic salmon (Salmo salar) affected by amoebic gill disease

The external surfaces of fish, such as gill and skin, are covered by mucus, which forms a thin interface between the organism and water. Amoebic gill disease (AGD) is a parasitic condition caused by Neoparamoeba perurans that affects salmonids worldwide. This disease induces excessive mucus production in the gills. The host immune response to AGD is not fully understood, and research tools such as genomics and proteomics could be useful in providing further insight. Gill and skin mucus samples were obtained from Atlantic salmon (Salmo salar) which were infected with N. perurans on four successive occasions. NanoLC tandem mass spectrometry (MS/MS) was used to identify proteins in gill and skin mucus of Atlantic salmon affected by AGD. A total of 186 and 322 non-redundant proteins were identified in gill and skin mucus respectively, based on stringent filtration criteria, and statistics demonstrated that 52 gill and 42 skin mucus proteins were differentially expressed in mucus samples from AGD-affected fish. By generating protein-protein interaction networks, some of these proteins formed part of cell to cell signalling and inflammation pathways, such as C-reactive protein, apolipoprotein 1, granulin, cathepsin, angiogenin-1. In addition to proteins that were entirely novel in the context in the host response to N. perurans, our results have confirmed the presence of protein markers in mucus that have been previously predicted on the basis of modified mRNA expression, such as anterior gradient-2 protein, annexin A-1 and complement C3 factor. This first proteomic analysis of AGD-affected salmon provides new information on the effect of AGD on protein composition of gill and skin mucus. Future research should focus on better understanding of the role these components play in the response against infection with N. perurans.

Upregulation of phagocytic clearance of apoptotic cells by autoimmune regulator

To investigate the effect of autoimmune regulator (AIRE) on phagocytic clearance of apoptotic cells, a recombinant expression vector containing full-length human AIRE cDNA was transfected into 16HBE cells. After incubation with transfected 16HBE cells, engulfment of apoptotic HL-60 cells induced by camptothecin was detected by myeloperoxidase (MPO) staining. The change in the expression of Rac 1 in transfected 16HBE cells was determined by RT-PCR and Western blotting. The results showed that the phagocytosis percentage of the experimental group, the mock transfection group and the negative control group (non-apoptotic cells) was (25.50 + or - 3.67)%, (6.25 + or - 1.58)% and (1.0 + or - 0.67)%, respectively. Moreover, the expressions of Rac 1 mRNA and protein were up-regulated in AIRE-transfected 16HBE cells, suggesting that AIRE may function as a regulator in the phagocytic clearance of apoptotic cells by promoting the expression of Rac 1.

Evidence for the involvement of carbon-centered radicals in the induction of apoptotic cell death by artemisinin compounds

Artemisinin and its derivatives are currently recommended as first-line antimalarials in regions where Plasmodium falciparum is resistant to traditional drugs. The cytotoxic activity of these endoperoxides toward rapidly dividing human carcinoma cells and cell lines has been reported, and it is hypothesized that activation of the endoperoxide bridge by an iron(II) species, to form C-centered radicals, is essential for cytotoxicity. The studies described here have utilized artemisinin derivatives, dihydroartemisinin, 10beta-(p-bromophenoxy)dihydroartemisinin, and 10beta-(p-fluorophenoxy)dihydroartemisinin, to determine the chemistry of endoperoxide bridge activation to reactive intermediates responsible for initiating cell death and to elucidate the molecular mechanism of cell death. These studies have demonstrated the selective cytotoxic activity of the endoperoxides toward leukemia cell lines (HL-60 and Jurkat) over quiescent peripheral blood mononuclear cells. Deoxy-10beta-(p-fluorophenoxy)dihydroartemisinin, which lacks the endoperoxide bridge, was 50- and 130-fold less active in HL-60 and Jurkat cells, respectively, confirming the importance of this functional group for cytotoxicity. We have shown that chemical activation is responsible for cytotoxicity by using liquid chromatography-mass spectrometry analysis to monitor endoperoxide activation by measurement of a stable rearrangement product of endoperoxide-derived radicals, which was formed in sensitive HL-60 cells but not in insensitive peripheral blood mononuclear cells. In HL-60 cells the endoperoxides induce caspase-dependent apoptotic cell death characterized by concentration- and time-dependent mitochondrial membrane depolarization, activation of caspases-3 and -7, sub-G(0)/G(1) DNA formation, and attenuation by benzyloxycarbonyl-VAD-fluoromethyl ketone, a caspase inhibitor. Overall, these results indicate that endoperoxide-induced cell death is a consequence of activation of the endoperoxide bridge to radical species, which triggers caspase-dependent apoptosis.

Catalase Regulates Cell Growth in HL60 Human Promyelocytic Cells: Evidence for Growth Regulation by H2O2

Reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)) are generated constitutively in mammalian cells. Because of its relatively long life and high permeability across membranes, H(2)O(2) is thought to be an important second messenger. Generation of H(2)O(2) is increased in response to external insults, including radiation. Catalase is located at the peroxisome and scavenges H(2)O(2). In this study, we investigated the role of catalase in cell growth using the H(2)O(2)-resistant variant HP100-1 of human promyelocytic HL60 cells. HP100-1 cells had an almost 10-fold higher activity of catalase than HL60 cells without differences in levels of glutathione peroxidase, manganese superoxide dismutase (MnSOD), and copper-zinc SOD (CuZnSOD). HP100-1 cells had higher proliferative activity than HL60 cells. Treatment with catalase or the introduction of catalase cDNA into HL60 cells stimulated cell growth. Exposure of HP100-1 cells to a catalase inhibitor resulted in suppression of cell growth with concomitant increased levels of intracellular H(2)O(2). Moreover, exogenously added H(2)O(2) or depletion of glutathione suppressed cell growth in HL60 cells. Extracellular signal regulated kinase 1/2 (ERK1/2) was constitutively phosphorylated in HP100-1 cells but not in HL60 cells. Inhibition of the ERK1/2 pathway suppressed the growth of HP100-1 cells, but inhibition of p38 mitogen-activated protein kinase (p38MAPK) did not affect growth. Moreover, inhibition of catalase blocked the phosphorylation of ERK1/2 but not of p38MAPK in HP100-1 cells. Thus our results suggest that catalase activates the growth of HL60 cells through dismutation of H(2)O(2), leading to activation of the ERK1/2 pathway; H(2)O(2) is an important regulator of growth in HL60 cells.

Phagocytosis and peroxidase release by seabream (Sparus aurata L.) leucocytes in response to yeast cells

A flow cytometric method was adapted to evaluate phagocytosis by gilthead seabream leucocytes after incubation with yeast cells (Saccharomyces cerevisiae). Head-kidney leucocytes were incubated in vitro for different times in different proportions with heat-killed fluorescein isothiocyanate (FITC)-labeled yeast cells to study the kinetics of phagocytosis. Attached and internalized yeast cells were differentiated by quenching FITC-labeled S. cerevisiae with trypan blue dye. Only internalized cells kept their FITC fluorescence after quenching. Monocyte-macrophages and acidophilic granulocytes showed phagocytic activity, as demonstrated by transmission electron microscopy (TEM). From the ultrastructural features of the phagocytic process, it was observed that cytoplasmic granule membranes fused with the phagocyte membrane at the point where the yeast cell was attached to the phagocyte surface. This observation led us to adapt a colorimetric method to study peroxidase (myeloperoxidase and eosinophil peroxidase) release, since both are considered to be markers of the degranulation that occurs in seabream head-kidney leucocytes in response to yeast cells. Head-kidney leucocytes were incubated with calcium ionophore (CaI), phorbol myristate acetate (PMA), or yeast cells for different periods of time (0-30 min) to study the kinetics of peroxidase release. The results obtained indicate that CaI and yeast cells, but not PMA, stimulate the degranulation (by about 44.51% and 21.04%, respectively, at 30 min) of seabream head-kidney leucocytes.

Bystander effect produced by radiolabeled tumor cells in vivo

The bystander effect, originating from cells irradiated in vitro, describes the biologic response(s) of surrounding cells not directly targeted by a radiation insult. To overcome the limitations of in vitro tissue culture models and determine whether a bystander effect that is initiated by the in vivo decay of a radionuclide can be demonstrated in an animal, the ability of 5-[(125)I]iodo-2'-deoxyuridine ((125)IUdR)-labeled tumor cells to exert a damaging effect on neighboring unlabeled tumor cells growing s.c. in nude mice has been investigated. When mice are injected with a mixture of human colon LS174T adenocarcinoma cells and LS174T cells prelabeled with lethal doses of DNA-incorporated (125)I, a distinct inhibitory effect on the growth of s.c. tumor (derived from unlabeled cells) is observed. Because (i) the (125)I present within the cells is DNA-bound, (ii) approximately 99% of the electrons emitted by the decaying (125)I atoms have a subcellular range (<0.5 microm), and (iii) the overall radiation dose deposited by radiolabeled cells in the unlabeled cells within the growing tumor is <10 cGy, we conclude that the results obtained are a consequence of a bystander effect that is generated in vivo by factor(s) present within and/or released from the (125)IUdR-labeled cells. These in vivo findings significantly impact the current dogma for assessing the therapeutic potential of internally administered radionuclides. They also call for reevaluation of the approaches currently used for estimating the risks to individuals and populations inadvertently exposed internally to radioactivity as well as to patients undergoing routine diagnostic nuclear medical procedures.