Mitochondria-Derived Reactive Oxygen Species Play an Important Role in Doxorubicin-Induced Platelet Apoptosis

Doxorubicin (DOX) is an effective chemotherapeutic agent; however; its use is limited by some side effects; such as cardiotoxicity and thrombocytopenia. DOX-induced cardiotoxicity has been intensively investigated; however; DOX-induced thrombocytopenia has not been clearly elucidated. Here we show that DOX-induced mitochondria-mediated intrinsic apoptosis and glycoprotein (GP)Ibα shedding in platelets. DOX did not induce platelet activation; whereas; DOX obviously reduced adenosine diphosphate (ADP)- and thrombin-induced platelet aggregation; and impaired platelet adhesion on the von Willebrand factor (vWF) surface. In addition; we also show that DOX induced intracellular reactive oxygen species (ROS) production and mitochondrial ROS generation in a dose-dependent manner. The mitochondria-targeted ROS scavenger Mito-TEMPO blocked intracellular ROS and mitochondrial ROS generation. Furthermore; Mito-TEMPO reduced DOX-induced platelet apoptosis and GPIbα shedding. These data indicate that DOX induces platelet apoptosis; and impairs platelet function. Mitochondrial ROS play a pivotal role in DOX-induced platelet apoptosis and GPIbα shedding. Therefore; DOX-induced platelet apoptosis might contribute to DOX-triggered thrombocytopenia; and mitochondria-targeted ROS scavenger would have potential clinical utility in platelet-associated disorders involving mitochondrial oxidative damage.     

ROS-mediated TNF-alpha and MIP-2 gene expression in alveolar macrophages exposed to pine dust

BACKGROUND: Respiratory symptoms, impaired lung function, and asthma have been reported in workers exposed to wood dust in a number of epidemiological studies. The underlying pathomechanisms, however, are not well understood. Here, we studied the effects of dust from pine (PD) and heat-treated pine (HPD) on the release of reactive oxygen species (ROS) and inflammatory mediators in rat alveolar macrophages. METHODS: Tumour necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) protein release, TNF-alpha and MIP-2 mRNA expression, and generation of ROS were studied as end points after treatment of rat alveolar macrophages with PD or HPD. In a separate series of experiments, the antioxidants glutathione and N-acetyl-L-cysteine were included in combination with wood dust. To determine the endogenous oxidative and antioxidant capacity of wood dusts, electron spin resonance (ESR) spectroscopy was used. RESULTS: After 4 h incubation, both PD and HPD elicited a significantly (p < 0.05) increased mRNA expression of TNF-alpha and MIP-2 as well as a concentration-dependent release of TNF-alpha and MIP-2 protein. Interestingly, PD induced a significantly higher TNF-alpha and MIP-2 production than HPD. Moreover, a significantly increased ROS production was observed in alveolar macrophages exposed to both PD and HPD. In the presence of the antioxidants glutathione and N-acetyl-L-cysteine, the PD- and HPD-induced release of ROS, TNF-alpha, and MIP-2 was significantly reduced. Finally, electron spin resonance analyses demonstrated a higher endogenous antioxidant capacity of HPD compared to PD. Endotoxin was not present in either dust sample. CONCLUSION: These results indicate that pine dust is able to induce expression of TNF-alpha and MIP-2 in rat alveolar macrophages by a mechanism that is, at least in part, mediated by ROS.     

Nitro-Oleic Acid Reduces J774A.1 Macrophage Oxidative Status and Triglyceride Mass: Involvement of Paraoxonase2 and Triglyceride Metabolizing Enzymes

Nitro‐fatty acids possess anti‐atherogenic properties, but their effects on macrophage oxidative status and lipid metabolism that play important roles in atherosclerosis development are unclear. This study compared the effects of nitro‐oleic acid (OLA‐NO₂) with those of native oleic acid (OLA) on intracellular reactive oxygen species (ROS) generation, anti‐oxidants and metabolism of triglycerides and cholesterol in J774A.1 macrophages. Upon incubating the cells with physiological concentrations of OLA‐NO₂ (0–1 µM) or with equivalent levels of OLA, ROS levels measured by 2, 7‐dichlorofluorescein diacetate, decreased dose‐dependently, but the anti‐oxidative effects of OLA‐NO₂ were significantly augmented. Copper ion addition increased ROS generation in OLA treated macrophages without affecting OLA‐NO₂ treated cells. These effects could be attributed to elevated glutathione levels and to increased activity and expression of paraoxonase2 that were observed in OLA‐NO₂vs OLA treated cells. Beneficial effects on triglyceride metabolism were noted in OLA‐NO₂vs OLA treated macrophages in which cellular triglycerides were reduced due to attenuated biosynthesis and accelerated hydrolysis of triglycerides. Accordingly, OLA‐NO₂ treated cells demonstrated down‐regulation of diacylglycerol acyltransferase1, the key enzyme in triglyceride biosynthesis, and increased expression of hormone‐sensitive lipase and adipose triglyceride lipase that regulate triglyceride hydrolysis. Finally, OLA‐NO₂vs OLA treatment resulted in modest but significant beneficial effects on macrophage cholesterol metabolism, reducing cholesterol biosynthesis rate and low density lipoprotein influx into the cells, while increasing high density lipoprotein‐mediated cholesterol efflux from the macrophages. Collectively, compared with OLA, OLA‐NO₂ modestly but significantly reduces macrophage oxidative status and cellular triglyceride content via modulation of cellular anti‐oxidants and triglyceride metabolizing enzymes.     

Asbestos Induces Oxidative Stress and Activation of Nrf2 Signaling in Murine Macrophages: Chemopreventive Role of the Synthetic Lignan Secoisolariciresinol Diglucoside (LGM2605)

The interaction of asbestos fibers with macrophages generates harmful reactive oxygen species (ROS) and subsequent oxidative cell damage that are key processes linked to malignancy. Secoisolariciresinol diglucoside (SDG) is a non-toxic, flaxseed-derived pluripotent compound that has antioxidant properties and may thus function as a chemopreventive agent for asbestos-induced mesothelioma. We thus evaluated synthetic SDG (LGM2605) in asbestos-exposed, elicited murine peritoneal macrophages as an in vitro model of tissue phagocytic response to the presence of asbestos in the pleural space. Murine peritoneal macrophages (MFs) were exposed to crocidolite asbestos fibers (20 µg/cm²) and evaluated at various times post exposure for cytotoxicity, ROS generation, malondialdehyde (MDA), and levels of 8-iso Prostaglandin F2α (8-isoP). We then evaluated the ability of LGM2605 to mitigate asbestos-induced oxidative stress by administering LGM2605 (50 µM) 4-h prior to asbestos exposure. We observed a significant (p < 0.0001), time-dependent increase in asbestos-induced cytotoxicity, ROS generation, and the release of MDA and 8-iso Prostaglandin F2α, markers of lipid peroxidation, which increased linearly over time. LGM2605 treatment significantly (p < 0.0001) reduced asbestos-induced cytotoxicity and ROS generation, while decreasing levels of MDA and 8-isoP by 71%–88% and 41%–73%, respectively. Importantly, exposure to asbestos fibers induced cell protective defenses, such as cellular Nrf2 activation and the expression of phase II antioxidant enzymes, HO-1 and Nqo1 that were further enhanced by LGM2605 treatment. LGM2605 boosted antioxidant defenses, as well as reduced asbestos-induced ROS generation and markers of oxidative stress in murine peritoneal macrophages, supporting its possible use as a chemoprevention agent in the development of asbestos-induced malignant mesothelioma.     

New Biocompatible β-Phosphorylated Linear Nitrones Targeting Mitochondria: Protective Effect in Apoptotic Cells

The mitochondrion, an essential organelle involved in cellular respiration, energy production, and cell death, is the main cellular source of reactive oxygen species (ROS), including superoxide. Mitochondrial diseases resulting from uncontrolled/excess ROS generation are an emerging public health concern and there is current interest in specific mitochondriotropic probes to get information on in-situ ROS production. As such, nitrones vectorized by the triphenylphosphonium (TPP) cation have recently drawn attention despite reported cytotoxicity. Herein, we describe the synthesis of 13 low-toxic derivatives of N-benzylidene-1-diethoxyphosphoryl-1-methylethylamine N-oxide (PPN) alkyl chain-grafted to a pyridinium, triethylammonium or berberinium lipophilic cation. These nitrones showed in-vitro superoxide quenching activity and EPR/spin-trapping efficiency towards biologically relevant free radicals, including superoxide and hydroxyl radicals. Their mitochondrial penetration was confirmed by ³¹P NMR spectroscopy, and their anti-apoptotic properties were assessed in Schwann cells treated with hydrogen peroxide. Two pyridinium-substituted PPNs were identified as potentially better alternatives to TPP nitrones conjugates for studying mitochondrial oxidative damage.     

The Effects of Cadmium at Low Environmental Concentrations on THP-1 Macrophage Apoptosis

Cadmium at environmental concentrations is a risk factor for many diseases, including cardiovascular and neurodegenerative diseases, in which macrophages play an important role. The aim of this study was to evaluate the effects of cadmium at low environmental (nanomolar) concentrations on apoptotic processes in THP-1(acute monocytic leukemia cells line)-derived macrophages, with special focus on mitochondrial events involved. Macrophages were incubated with various cadmium chloride (CdCl₂) solutions for 48 h at final concentrations of 5 nM, 20 nM, 200 nM and 2 µM CdCl₂. Cell viability was measured using flow cytometry. Flow cytometric measurement (annexin V/FITC (annexin V/fluorescein isothiocyanate) and PI (propidium iodide) double staining) was used to quantify the extent of apoptosis. Fluorescence and confocal microscopy were used for imaging of apoptosis process. Changes in mitochondrial membrane potential were monitored using cytofluorimetry after cell staining with JC-1(5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazol-carbocyane iodide) probe. Mitochondrial ROS (reactive oxygen species) levels were measured cytofluorimetrically after incubation of cells with mitochondrial superoxide indicator (MitoSOX) red fluorescent marker. The mRNA expression of Bcl-2 and Bax was analysed with qRT-PCR. Our study demonstrates that cadmium, even at low environmental concentrations, exerts mitochondrial toxicity in THP-1 macrophages. Forty-eight-hour exposure to very low concentrations reduces cell viability and results in cell death by apoptosis and necrosis. The decrease in mitochondrial membrane potential, increased ROS production, increased Bax and decreased Bcl-2 mRNA expression are mitochondrial events involved in cadmium-induced apoptosis.     

Copper Transfer from Cu–Aβ to Human Serum Albumin Inhibits Aggregation,Radical Production and Reduces Aβ Toxicity

Amyloid‐β peptides (Aβ) and the protein human serum albumin (HSA) interact in vivo. They are both localised in the blood plasma and in the cerebrospinal fluid. Among other functions, HSA is involved in the transport of the essential metal copper. Complexes between Aβ and copper ions have been proposed to be an aberrant interaction implicated in the development of Alzheimer's disease, where Cu is involved in Aβ aggregation and production of reactive oxygen species (ROS). In the present work, we studied copper‐exchange reaction between Aβ and HSA or the tetrapeptide DAHK (N‐terminal Cu‐binding domain of HSA) and the consequence of this exchange on Aβ‐induced ROS production and cell toxicity. The following results were obtained: 1) HSA and DAHK removed Cu^II from Aβ rapidly and stoichiometrically, 2) HSA and DAHK were able to decrease Cu‐induced aggregation of Aβ, 3) HSA and DAHK suppressed the catalytic HO^. production in vitro and ROS production in neuroblastoma cells generated by Cu–Aβ and ascorbate, 4) HSA and DAHK were able to rescue these cells from the toxicity of Cu–Aβ with ascorbate, 5) DAHK was more potent in ROS suppression and restoration of neuroblastoma cell viability than HSA, in correlation with an easier reduction of Cu^II–HSA than Cu–DAHK by ascorbate, in vitro. Our data suggest that HSA is able to decrease aberrant Cu^II–Aβ interaction. The repercussion of the competition between HSA and Aβ to bind Cu in the blood and brain and its relation to Alzheimer's disease are discussed.     

Impaired mitochondrial respiratory functions and oxidative stress in streptozotocin-induced diabetic rats

We have previously shown a tissue-specific increase in oxidative stress in the early stages of streptozotocin (STZ)-induced diabetic rats. In this study, we investigated oxidative stress-related long-term complications and mitochondrial dysfunctions in the different tissues of STZ-induced diabetic rats (>15 mM blood glucose for 8 weeks). These animals showed a persistent increase in reactive oxygen and nitrogen species (ROS and RNS, respectively) production. Oxidative protein carbonylation was also increased with the maximum effect observed in the pancreas of diabetic rats. The activities of mitochondrial respiratory enzymes ubiquinol: cytochrome c oxidoreductase (Complex III) and cytochrome c oxidase (Complex IV) were significantly decreased while that of NADH:ubiquinone oxidoreductase (Complex I) and succinate:ubiquinone oxidoreductase (Complex II) were moderately increased in diabetic rats, which was confirmed by the increased expression of the 70 kDa Complex II sub-unit. Mitochondrial matrix aconitase, a ROS sensitive enzyme, was markedly inhibited in the diabetic rat tissues. Increased expression of oxidative stress marker proteins Hsp-70 and HO-1 was also observed along with increased expression of nitric oxide synthase. These results suggest that mitochondrial respiratory complexes may play a critical role in ROS/RNS homeostasis and oxidative stress related changes in type 1 diabetes and may have implications in the etiology of diabetes and its complications.     

Extracellular Vesicles Released after Doxorubicin Treatment in Rats Protect Cardiomyocytes from Oxidative Damage and Induce Pro-Inflammatory Gene Expression in Macrophages

Doxorubicin (DOXO)-induced cardiomyopathy (DIC) is a lethal complication in cancer patients. Major mechanisms of DIC involve oxidative stress in cardiomyocytes and hyperactivated immune response. Extracellular vesicles (EVs) mediate cell–cell communication during oxidative stress. However, functions of circulating EVs released after chronic DOXO exposure on cardiomyocytes and immune cells are still obscured. Herein, we developed a DIC in vivo model using male Wistar rats injected with 3 mg/kg DOXO for 6 doses within 30 days (18 mg/kg cumulative dose). One month after the last injection, the rats developed cardiotoxicity evidenced by increased BCL2-associated X protein and cleaved caspase-3 in heart tissues, along with N-terminal pro B-type natriuretic peptide in sera. Serum EVs were isolated by size exclusion chromatography. EV functions on H9c2 cardiomyocytes and NR8383 macrophages were evaluated. EVs from DOXO-treated rats (DOXO_EVs) attenuated ROS production via increased glutathione peroxidase-1 and catalase gene expression, and reduced hydrogen peroxide-induced cell death in cardiomyocytes. In contrast, DOXO_EVs induced ROS production, interleukin-6, and tumor necrosis factor-alpha, while suppressing arginase-1 gene expression in macrophages. These results suggested the pleiotropic roles of EVs against DIC, which highlight the potential role of EV-based therapy for DIC with a concern of its adverse effect on immune response.     

Cordycepin Inhibits Lipopolysaccharide (LPS)-Induced Tumor Necrosis Factor (TNF)-α Production via Activating AMP-Activated Protein Kinase (AMPK) Signaling

Tumor necrosis factor (TNF)-α is elevated during the acute phase of Kawasaki disease (KD), which damages vascular endothelial cells to cause systemic vasculitis. In the current study, we investigated the potential role of cordycepin on TNFα expression in both lipopolysaccharide (LPS)-stimulated macrophages and ex vivo cultured peripheral blood mononuclear cells (PBMCs) of KD patients. We found that cordycepin significantly suppressed LPS-induced TNFα expression and production in mouse macrophages (RAW 264.7 cells and bone marrow-derived macrophages (BMDMs)). Meanwhile, cordycepin alleviated TNFα production in KD patients’ PBMCs. PBMCs from healthy controls had a much lower level of basal TNF-α content than that of KD patients. LPS-induced TNF-α production in healthy controls’ PBMCs was also inhibited by cordycepin. For the mechanism study, we discovered that cordycepin activated AMP-activated protein kinase (AMPK) signaling in both KD patients’ PBMCs and LPS-stimulated macrophages, which mediated cordycepin-induced inhibition against TNFα production. AMPK inhibition by its inhibitor (compound C) or by siRNA depletion alleviated cordycepin’s effect on TNFα production. Further, we found that cordycepin inhibited reactive oxygen species (ROS) production and nuclear factor kappa B (NF-κB) activation in LPS-stimulate RAW 264.7 cells or healthy controls’ PBMCs. PBMCs of KD patients showed higher basal level of ROS and NF-κB activation, which was also inhibited by cordycepin co-treatment. In conclusion, our data showed that cordycepin inhibited TNFα production, which was associated with AMPK activation as well as ROS and NF-κB inhibition. The results of this study should have significant translational relevance in managing this devastating disease.     

Free Radical-Mediated Protein Radical Formation in Differentiating Monocytes

Free radical-mediated activation of inflammatory macrophages remains ambiguous with its limitation to study within biological systems. U-937 and HL-60 cell lines serve as a well-defined model system known to differentiate into either macrophages or dendritic cells in response to various chemical stimuli linked with reactive oxygen species (ROS) production. Our present work utilizes phorbol 12-myristate-13-acetate (PMA) as a stimulant, and factors such as concentration and incubation time were considered to achieve optimized differentiation conditions. ROS formation likely hydroxyl radical (HO^●) was confirmed by electron paramagnetic resonance (EPR) spectroscopy combined with confocal laser scanning microscopy (CLSM). In particular, U-937 cells were utilized further to identify proteins undergoing oxidation by ROS using anti-DMPO (5,5-dimethyl-1-pyrroline N-oxide) antibodies. Additionally, the expression pattern of NADPH Oxidase 4 (NOX4) in relation to induction with PMA was monitored to correlate the pattern of ROS generated. Utilizing macrophages as a model system, findings from the present study provide a valuable source for expanding the knowledge of differentiation and protein expression dynamics.     

Long-Chain and Very Long-Chain Ceramides Mediate Doxorubicin-Induced Toxicity and Fibrosis

Doxorubicin (Dox) is a chemotherapeutic agent with cardiotoxicity associated with profibrotic effects. Dox increases ceramide levels with pro-inflammatory effects, cell death, and fibrosis. The purpose of our study was to identify the underlying ceramide signaling pathways. We aimed to characterize the downstream effects on cell survival, metabolism, and fibrosis. Human fibroblasts (hFSF) were treated with 0.7 µM of Dox or transgenically overexpressed ceramide synthase 2 (FLAG-CerS2). Furthermore, cells were pre-treated with MitoTempo (MT) (2 h, 20 µM) or Fumonisin B1 (FuB) (4 h, 100 µM). Protein expression was measured by Western blot or immunofluorescence (IF). Ceramide levels were determined with mass spectroscopy (MS). Visualizations were conducted using laser scanning microscopy (LSM) or electron microscopy. Mitochondrial activity was measured using seahorse analysis. Dox and CerS2 overexpression increased CerS2 protein expression. Coherently, ceramides were elevated with the highest peak for C24:0. Ceramide- induced mitochondrial ROS production was reduced with MT or FuB preincubation. Mitochondrial homeostasis was reduced and accompanied by reduced ATP production. Our data show that the increase in pro-inflammatory ceramides is an essential contributor to Dox side-effects. The accumulation of ceramides resulted in a lipotoxic shift and subsequently mitochondrial structural and functional damage, which was partially reversible following inhibition of ceramide synthesis.     

The Acute Toxicity of Mineral Fibres: A Systematic In Vitro Study Using Different THP-1 Macrophage Phenotypes

Alveolar macrophages are the first line of defence against detrimental inhaled stimuli. To date, no comparative data have been obtained on the inflammatory response induced by different carcinogenic mineral fibres in the three main macrophage phenotypes: M0 (non-activated), M1 (pro-inflammatory) and M2 (alternatively activated). To gain new insights into the different toxicity mechanisms of carcinogenic mineral fibres, the acute effects of fibrous erionite, crocidolite and chrysotile in the three phenotypes obtained by THP-1 monocyte differentiation were investigated. The three mineral fibres apparently act by different toxicity mechanisms. Crocidolite seems to exert its toxic effects mostly as a result of its biodurability, ROS and cytokine production and DNA damage. Chrysotile, due to its low biodurability, displays toxic effects related to the release of toxic metals and the production of ROS and cytokines. Other mechanisms are involved in explaining the toxicity of biodurable fibrous erionite, which induces lower ROS and toxic metal release but exhibits a cation-exchange capacity able to alter the intracellular homeostasis of important cations. Concerning the differences among the three macrophage phenotypes, similar behaviour in the production of pro-inflammatory mediators was observed. The M2 phenotype, although known as a cell type recruited to mitigate the inflammatory state, in the case of asbestos fibres and erionite, serves to support the process by supplying pro-inflammatory mediators.     

Aerobic Exercise Improves Reverse Cholesterol Transport in Cholesteryl Ester Transfer Protein Transgenic Mice

We analyzed the effect of a 6-week aerobic exercise training program on the in vivo macrophage reverse cholesterol transport (RCT) in human cholesteryl ester transfer protein (CETP) transgenic (CETP-tg) mice. Male CETP-tg mice were randomly assigned to a sedentary group or a carefully supervised exercise training group (treadmill 15 m/min, 30 min sessions, five sessions per week). The levels of plasma lipids were determined by enzymatic methods, and the lipoprotein profile was determined by fast protein liquid chromatography (FPLC). CETP activity was determined by measuring the transfer rate of ¹⁴C-cholesterol from HDL to apo-B containing lipoproteins, using plasma from CETP-tg mice as a source of CETP. The reverse cholesterol transport was determined in vivo by measuring the [³H]-cholesterol recovery in plasma and feces (24 and 48 h) and in the liver (48 h) following a peritoneal injection of [³H]-cholesterol labeled J774-macrophages into both sedentary and exercise trained mice. The protein levels of liver receptors were determined by immunoblot, and the mRNA levels for liver enzymes were measured using RT-PCR. Exercise training did not significantly affect the levels of plasma lipids or CETP activity. The HDL fraction assessed by FPLC was higher in exercise-trained compared to sedentary mice. In comparison to the sedentary group, a greater recovery of [³H]-cholesterol from the injected macrophages was found in the plasma, liver and feces of exercise-trained animals. The latter occurred even with a reduction in the liver CYP7A1 mRNA level in exercised trained animals. Exercise training increased the liver LDL receptor and ABCA-1 protein levels, although the SR-BI protein content was unchanged. The RCT benefit in CETP-tg mice elicited by exercise training helps to elucidate the role of exercise in the prevention of atherosclerosis in humans.     

Coenzyme Q10 Attenuates Human Platelet Aggregation Induced by SARS-CoV-2 Spike Protein via Reducing Oxidative Stress In Vitro

Platelet hyperreactivity and oxidative stress are the important causes of thrombotic disorders in patients with COVID-19. Oxidative stress, induced by the excessive generation of reactive oxygen species (ROS), could increase platelet function and the risk of thrombus formation. Coenzyme Q10 (CoQ10), exhibits strong antioxidative activity and anti-platelet effect. However, the effects and mechanisms of CoQ10 on attenuating platelet aggregation induced by spike protein have never been studied. This study aims to investigate whether the SARS-CoV-2 spike protein potentiates human platelet function via ROS signaling and the protective effect of CoQ10 in vitro. Using a series of platelet function assays, we found that spike protein potentiated platelet aggregation and oxidative stress, such as ROS level, mitochondrial membrane potential depolarization, and lipid damage level (MDA and 8-iso-PGF2α) in vitro. Furthermore, CoQ10 attenuated platelet aggregation induced by spike protein. As an anti-platelet mechanism, we showed that CoQ10 significantly decreased the excess production of ROS induced by spike protein. Our findings show that the protective effect of CoQ10 on spike protein-potentiated platelet aggregation is probably associated with its strong antioxidative ability.     

Regulation of Neutrophil Functions by Hv1/VSOP Voltage-Gated Proton Channels

The voltage-gated proton channel, Hv1, also termed VSOP, was discovered in 2006. It has long been suggested that proton transport through voltage-gated proton channels regulate reactive oxygen species (ROS) production in phagocytes by counteracting the charge imbalance caused by the activation of NADPH oxidase. Discovery of Hv1/VSOP not only confirmed this process in phagocytes, but also led to the elucidation of novel functions in phagocytes. The compensation of charge by Hv1/VSOP sustains ROS production and is also crucial for promoting Ca²⁺ influx at the plasma membrane. In addition, proton extrusion into neutrophil phagosomes by Hv1/VSOP is necessary to maintain neutral phagosomal pH for the effective killing of bacteria. Contrary to the function of Hv1/VSOP as a positive regulator for ROS generation, it has been revealed that Hv1/VSOP also acts to inhibit ROS production in neutrophils. Hv1/VSOP inhibits hypochlorous acid production by regulating degranulation, leading to reduced inflammation upon fungal infection, and suppresses the activation of extracellular signal-regulated kinase (ERK) signaling by inhibiting ROS production. Thus, Hv1/VSOP is a two-way player regulating ROS production. Here, we review the functions of Hv1/VSOP in neutrophils and discuss future perspectives.     

Curcumin Induced Human Gastric Cancer BGC-823 Cells Apoptosis by ROS-Mediated ASK1-MKK4-JNK Stress Signaling Pathway

The signaling mediated by stress-activated MAP kinases (MAPK), c-Jun N-terminal kinase (JNK) has well-established importance in cancer. In the present report, we investigated the effects of curcumin on the signaling pathway in human gastric cancer BGC-823 cells. Curcumin induced reactive oxygen species (ROS) production and BGC-823 cells apoptosis. Inhibition of ROS generation by antioxidant (NAC or Trion) significantly prevented curcumin-mediated apoptosis. Notably, we observed that curcumin activated ASK1, a MAPKKK that is oxidative stress sensitive and responsible to phosphorylation of JNK via triggering cascades, up-regulated an upstream effector of the JNK, MKK4, and phosphorylated JNK protein expression in BGC-823 cells. However, curcumin induced ASK1-MKK4-JNK signaling was attenuated by NAC. All the findings confirm the possibility that oxidative stress-activated ASK1-MKK4-JNK signaling cascade promotes the apoptotic response in curcumin-treated BGC-823 cells.