Redox Balance In Cells Research Articles

Glutathione-Depleting Pro-Oxidant as a Selective Anticancer Therapeutic Agent.

A main challenge in the development of anticancer drugs that eradicate cancer cells specifically with minimal toxicity to normal cells is to identify the cancer-specific properties. Cancer cells sustain a higher level of reactive oxygen species, owing to metabolic and signaling aberrations and unrestrained growth. Cancer cells are also furnished with a powerful reducing environment, owing to the overproduction of antioxidants such as glutathione (GSH). Therefore, the altered redox balance is probably the most prevailing property of cancer cells distinct from normal cells, which could serve as a plausible therapeutic target. In this work, we developed a GSH-depleting pro-oxidant, benzoyloxy dibenzyl carbonate, termed B2C, which is capable of rapidly declining GSH and elevating oxidative stress to a threshold level above which cancer cells cannot survive. B2C was designed to release quinone methide (QM) that rapidly depletes GSH through esterase-mediated hydrolysis. B2C was able to rapidly deplete GSH and induce an overwhelming level of oxidative stress in cancer cells, leading to mitochondrial disruption, activation of procaspase-3 and PARP-1, and cleavage of Bcl-2. In the study of tumor xenograft models, intravenously injected B2C caused apoptotic cell death in tumors and significantly suppressed tumor growth. These findings provide a new insight into the design of more effective anticancer drugs, which exploit altered redox balance in cancer cells.

The role of thioredoxin system in cancer: strategy for cancer therapy.

Cancer, a major public health problem, exhibits significant redox alteration. Thioredoxin (Trx) system, including Trx and Trx reductase (TrxR), as well as Trx-interacting protein (TXNIP) play important roles in controlling the cellular redox balance in cancer cells. In most cancers, Trx and TrxR are usually overexpressed and TXNIP is underexpressed. In recent years, some agents targeting Trx, TrxR, and TXNIP were used to explore a therapy approach for cancer patients. A systematic search of PMC and the PubMed Database was conducted to summarize the potential of Trx system inhibitors for cancer treatment. In this article, we first summarize the functions of Trx, TrxR, and TXNIP in cancers. We also review some small moleculeinhibitors of Trx/TrxR and D-allose (TXNIP inducer) and discuss their antitumor mechanisms. We highlight the combined inhibition of Trx system and GSH system in cancer therapy. We expect that a highly specific and selective antitumor agent with no cytotoxicity on human normal cells could be developed in the future. In conclusion, Trx system may be very promising for clinical therapy of cancer in the future.

Triptolide suppresses human synoviocyte MH7A cells mobility and maintains redox balance by inhibiting autophagy

Triptolide (TPL), the main active ingredient in Tripterygium glycosides, has been reported to exert anti-inflammation and anti-tumor effects. The present study was designed to investigate the effects of TPL on rheumatoid arthritis (RA) and explore the underlying mechanisms. By using human synoviocyte MH7A cells, TPL was proven to significantly impede migration and invasion of MH7A cells, and also inhibited MMP-2 and MMP-9 expression. Moreover, TPL was found to increase SOD, CAT, GSH-Px activities while decrease MDA activity, indicating that TPL maintained redox balance in MH7A cells. TPL could down-regulate the number of LC3+ puncta, Beclin1 expression and LC3 II/I ratio in a concentration-dependent manner, indicating that TPL inhibited autophagy in MH7A cells. Activation of autophagy was found to counteract the effects of TPL on MH7A cells while inhibition of autophagy had the opposite effects. Our data demonstrated that TPL suppressed cell mobility and maintained redox balance through inhibiting autophagy in MH7A cells. Finally, our data revealed that TPL increased p-AKT/AKT ratio significantly and inhibition of PI3K/AKT signaling pathway activated autophagy in MH7A cells, suggesting that TPL suppressed autophagy through activating AKT signaling pathway in MH7A cells. Taken together, our present study revealed that TPL inhibited cell mobility and maintained redox balance in human synoviocyte MH7A cells through autophagy inhibition. Our findings suggested the potential clinical application of TPL on RA treatment.

Abnormal Ribosome Biogenesis Partly Induced p53-Dependent Aortic Medial Smooth Muscle Cell Apoptosis and Oxidative Stress.

Ribosome biogenesis is a crucial biological process related to cell proliferation, redox balance, and muscle contractility. Aortic smooth muscle cells (ASMCs) show inhibition of proliferation and apoptosis, along with high levels of oxidative stress in aortic dissection (AD). Theoretically, ribosome biogenesis should be enhanced in the ASMCs at its proliferative state but suppressed during apoptosis and oxidative stress. However, the exact status and role of ribosome biogenesis in AD are unknown. We therefore analyzed the expression levels of BOP1, a component of the PeBoW complex which is crucial to ribosome biogenesis, in AD patients and a murine AD model and its influence on the ASMCs. BOP1 was downregulated in the aortic tissues of AD patients compared to healthy donors. In addition, overexpression of BOP1 in human aortic smooth muscle cells (HASMCs) inhibited apoptosis and accumulation of p53 under hypoxic conditions, while knockdown of BOP1 decreased the protein synthesis rate and motility of HASMCs. The RNA polymerase I inhibitor cx-5461 induced apoptosis, ROS production, and proliferative inhibition in the HASMCs, which was partly attenuated by p53 knockout. Furthermore, cx-5461 aggravated the severity of AD in vivo, but a p53-/- background extended the life-span and lowered AD incidence in the mice. Taken together, decreased ribosome biogenesis in ASMCs resulting in p53-dependent proliferative inhibition, oxidative stress, and apoptosis is one of the underlying mechanisms of AD.

Electrochemical monitoring of reactive oxygen/nitrogen species and redox balance in living cells.

Levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in cells and cell redox balance are of great interest in live cells as they are correlated to several pathological and physiological conditions of living cells. ROS and RNS detection is limited due to their spatially restricted abundance: they are usually located in sub-cellular areas (e.g., in specific organelles) at low concentration. In this work, we will review and highlight the electrochemical approach to this bio-analytical issue. Combining electrochemical methods and miniaturization strategies, specific, highly sensitive, time, and spatially resolved measurements of cellular oxidative stress and redox balance analysis are possible. Graphical abstract In this work, we highlight and review the use of electrochemistry for the highly spatial and temporal resolved detection of ROS/RNS levels and of redox balance in living cells. These levels are central in several pathological and physiological conditions and the electrochemical approach is a vibrant bio-analytical trend in this field.

A mini-review and perspective on ferroptosis-inducing strategies in cancer therapy

Ferroptosis, as a new type of cell death caused by lipid peroxidation, has attracted much attention since it was first identified in 2012. A lot of progress has been made in unraveling its mechanisms and therapeutic potential as a target for cancer therapy. Hitherto, there are mainly two strategies widely adopted for designing ferroptosis-inducing agents, which include increasing the intracellular reactive oxygen species (ROS) level by Fenton reaction, and inactivating the glutathione peroxidase 4 (GPX4). In this mini-review, we summarize the recent advances in ferroptosis-based anticancer treatments with a highlight on nanomaterials, and discuss the current challenges faced by those agents from the perspective of in vivo applications. Moreover, by generalizing ferroptosis induced by excess iron ions to cell death caused by the polyvalent metal-mediated oxidative burden, we introduce a new paradigm of cancer treatment by exploiting various polyvalent metals to disrupt the vulnerable redox balance in cancer cells, which may greatly diversify our arsenal to combat cancer.

Catalase activity of herbs in conditions of urban environment pollution

Pollutants entering plants cells are able to cause biochemical malfunction, including lipid peroxidation, which leads to the change in antioxidant system activity. Sustaining redox balance in cells is a required condition of plants survival in conditions of anthropogenic pollution. The goal of this research was the investigation of catalase activity in meadow grass, wild vetch, red clover, coltsfoot and chamomile near various factories of Tyumen. Plants were gathered near the highway as well as close to the metallurgical plant, engine factory, oil refinery and accumulator plants. The change in catalase activity in the cells of plants turned out to be species-specific. The decrease in catalase activity was observed in the meadow grass and wild vetch cells, while in coltsfoot, red clover and chamomile both decrease and increase in enzyme activity was obtained. Pollutants from all the examined factories affected more or less on the catalase activity, but the greatest effect was registered near the metallurgical factory, that probably related to high heavy metal concentration in plants. The lowest effect on catalase activity, compared to control, was observed near the highway.

Dopamine neuronal protection in the mouse Substantia nigra by GHSR is independent of electric activity

ObjectiveDopamine neurons in the Substantia nigra (SN) play crucial roles in control of voluntary movement. Extensive degeneration of this neuronal population is the cause of Parkinson's disease (PD). Many factors have been linked to SN DA neuronal survival, including neuronal pacemaker activity (responsible for maintaining basal firing and DA tone) and mitochondrial function. Dln-101, a naturally occurring splice variant of the human ghrelin gene, targets the ghrelin receptor (GHSR) present in the SN DA cells. Ghrelin activation of GHSR has been shown to protect SN DA neurons against 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) treatment. We decided to compare the actions of Dln-101 with ghrelin and identify the mechanisms associated with neuronal survival. MethodsHistologial, biochemical, and behavioral parameters were used to evaluate neuroprotection. Inflammation and redox balance of SN DA cells were evaluated using histologial and real-time PCR analysis. Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology was used to modulate SN DA neuron electrical activity and associated survival. Mitochondrial dynamics in SN DA cells was evaluated using electron microscopy data. ResultsHere, we report that the human isoform displays an equivalent neuroprotective factor. However, while exogenous administration of mouse ghrelin electrically activates SN DA neurons increasing dopamine output, as well as locomotion, the human isoform significantly suppressed dopamine output, with an associated decrease in animal motor behavior. Investigating the mechanisms by which GHSR mediates neuroprotection, we found that dopamine cell-selective control of electrical activity is neither sufficient nor necessary to promote SN DA neuron survival, including that associated with GHSR activation. We found that Dln101 pre-treatment diminished MPTP-induced mitochondrial aberrations in SN DA neurons and that the effect of Dln101 to protect dopamine cells was dependent on mitofusin 2, a protein involved in the process of mitochondrial fusion and tethering of the mitochondria to the endoplasmic reticulum. ConclusionsTaken together, these observations unmasked a complex role of GHSR in dopamine neuronal protection independent on electric activity of these cells and revealed a crucial role for mitochondrial dynamics in some aspects of this process.

Multi-omic and physiologic approach to understand Lotus japonicus response upon exposure to 3,4 dimethylpyrazole phosphate nitrification inhibitor

Nitrogen fertilization is a major force in global greenhouse gases emissions and causes environmental contamination through nitrate leaching. The use of nitrification inhibitors has been proven successful to mitigate these effects. However, there is an increasing concern about the undesired effects that their potential persistence in the soil or accumulation in plants may provoke. In this study, we first exposed Lotus japonicus plants to high amounts of 3,4 dimethylpyrazole phosphate (DMPP) and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) nitrification inhibitors. Exposure to doses higher than 1 mg·L−1 provoked DMPP accumulation mostly in the aerial part, while DMPSA was only detected from 10 mg·L−1 and nearly no translocation. To evaluate the effect that DMPP accumulation in leaves may provoke on plant performance we combined a transcriptome, proteome, and physiological analysis in plants treated with 10 mg/ L of DMPP. This treatment provoked changes in the expression of 229 genes and 59 proteins. Overall, we evidence that when DMPP accumulates in leaves it induces stress responses, notably provoking changes in cell redox balance, hormone signaling, protein synthesis and turnover and carbon and nitrogen metabolism.

Pro- and anti-oxidant properties of near-infrared (NIR) light responsive carbon nanoparticles

Elemental carbon nanomaterials (ECNMs) are redox active agents that can be exploited to purposely modify the redox balance of cells. Both pro- or antioxidant properties have been reported. However, to the best of our knowledge, there are not comprehensive studies exploring both properties on the same material in view of a potential application in medicine. At the same time, the effect of the bulk structure on the pro/antioxidant properties is poorly known. Here, carbon nanoparticles (CNPs) derived by glucose with definite size and shape have been prepared, and their redox properties evaluated in cell free systems in the dark or following activation with a Near Infrared (NIR) laser beam (945 nm, 1.3 W/cm2). We found that, when irradiated with NIR, CNPs efficiently generate heat and singlet oxygen (1O2), a property that can be exploited for dual photo-thermal (PT)/photodynamic (PD) therapy in cancer. On the other hand, in the absence of photo-activation, CNPs react with both oxidant (hydroxyl radicals) and antioxidant (glutathione) species. When tested on a murine macrophages cell line (RAW 264.7) CNPs were clearly antioxidant. Furthermore, albeit efficiently internalized, CNPs do not exert cytotoxic effect up to 80 µg/ml and do not exacerbate TNF-α-mediated inflammation. Overall, the results reported herein suggest that CNPs may represent a new class of safe nanomaterials with potential applications in medicine.

Ascorbic acid induced HepG2 cells' apoptosis via intracellular reductive stress.

Goals: Destruction of the redox balance in tumor cells is of great significance for triggering their apoptosis in clinical applications. We designed a pH sensitive multifunctional drug nanocarrier with controllable release of ascorbic acid under hypoxic environment to induce tumor cells' apoptosis via enhancing reductive stress, thereby dealing minimum damage to normal tissues.Methods: A core-shell nanostructure of CdTe quantum dots with mesoporous silica coating was developed and functionalized with poly(2-vinylpyridine)-polyethylene glycol-folic acid, which achieves cancer cells' targeting delivery and reversibly pH controlled release of ascorbic acid both in vitro and in vivo.Results: The result demonstrated that ascorbic acid can indeed lead liver cancer cells' death with the increase of nicotinamide adenine dinucleotide phosphate, while normal cells not being affected. The molecular mechanism of apoptosis induced by ascorbic acid was firstly elucidated at cellular levels, and further confirmed via in vivo investigations.Conclusion: For the first time we proposed the concept for applying reductive stress into cancer treatments, which brings great advantage of toxicity free and less damage to normal tissues. In general, this technique has taken an important step in the development of a targeted tumor treatment system, providing perspectives for the design of medicines via reductive stress, and offers new insights into future clinical mild-therapies.

Selenium compounds in redox regulation of inflammation and apoptosis

Monocytes and macrophages play a key role in the development of inflammation: under the action of lipopolysaccharides (LPS), absorbed from the intestine, monocytes and macrophages form reactive oxygen species (ROS) and cytokines, this leads to the development of oxidative stress, inflammation and/or apoptosis in all types of tissues. In the cells LPS induce an "internal" TLR4-mediated MAP-kinase inflammatory signaling pathway and cytokines through the superfamily of tumor necrosis factor receptor (TNFR) and the "death domain" (DD) initiate an "external" caspase apoptosis cascade or necrosis activation that causes necroptosis. Many of the proteins involved in intracellular signaling cascades (MYD88, ASK1, IKKa/b, NF-kB, AP-1) are redox-sensitive and their activity is regulated by antioxidants thioredoxin, glutaredoxin, nitroredoxin, and glutathione. Oxidation of these signaling proteins induced by ROS enhances the development of inflammation and apoptosis, and their reduction with antioxidants, on the contrary, stabilizes the signaling cascades speed, preventing the vicious circle of oxidative stress, inflammation and apoptosis that follows it. Antioxidant (AO) enzymes thioredoxin reductase (TRXR), glutaredoxin reductase (GLRXR), glutathione reductase (GR) are required for reduction of non-enzymatic antioxidants (thioredoxin, glutaredoxin, nitroredoxin, glutathione), and AO enzymes (SOD, catalase, GPX) are required for ROS deactivation. The key AO enzymes (TRXR and GPX) are selenium-dependent; therefore selenium deficiency leads to a decrease in the body's antioxidant defense, the development of oxidative stress, inflammation, and/or apoptosis in various cell types. Nrf2-Keap1 signaling pathway activated by selenium deficiency and/or oxidative stress is necessary to restore redox homeostasis in the cell. In addition, expression of some genes is changed with selenium deficiency. Consequently, growth and proliferation of cells, their movement, development, death, and survival, as well as the interaction between cells, the redox regulation of intracellular signaling cascades of inflammation and apoptosis, depend on the selenium status of the body. Prophylactic administration of selenium-containing preparations (natural and synthetic (organic and inorganic)) is able to normalize the activity of AO enzymes and the general status of the body. Organic selenium compounds have a high bioavailability and, depending on their concentration, can act both as selenium donors to prevent selenium deficiency and as antitumor drugs due to their toxicity and participation in the regulation of signaling pathways of apoptosis. Known selenorganic compounds diphenyldiselenide and ethaselen share similarity with the Russian organo selenium compound, diacetophenonylselenide (DAPS-25), which serves as a source of bioavailable selenium, exhibits a wide range of biological activity, including antioxidant activity, that governs cell redox balance, inflammation and apoptosis regulation.

FEATURES OF REDOX REGULATION IN TUMOR CELLS

Endogenous mechanisms of reactive oxygen (ROS) and nitrogen species production and of antioxidant defense systems in tumor cells are analyzed. Increased ROS production is an important regulator of metabolic changes in these cells: enhanced proliferation, apoptosis inhibition, resistance to hypoxia and to cytostatics (doxorubicin, carboplatin, cisplatin, etc.). The most active ROS sources in tumor cells are mitochondria, NAD(P)H oxidases and peroxisomes, which synthesize O2 • – and H2O2. In mitochondria, the superoxide anion radical is generated mainly by complexes I and III; membrane NAD(P)H oxidases Nox1, Nox2, Nox3, and Nox5 produce O2 • –, Nox4, and dual oxidases DUOX-1, DUOX-2 – mainly H2O2. Increasing ROS stationary concentration activates endogenous antioxidant defense mechanisms, such as redox-dependent antioxidant respons(iv)e element system Keap1/Nrf2/ARE and autophagy, which allows tumor cells to survive under oxidative stress and may underlie resistance to radio- and chemotherapy. The possibilities of tumor cell redox balance regulation by antioxidants with targeted action and by specific inhibitors of ROS enzymatic production are discussed.

LncRNA GAS5 regulates redox balance and dysregulates the cell cycle and apoptosis in malignant melanoma cells

PurposeClinical outcomes for advanced malignant melanoma (MM) are often poor due to tumor invasiveness, metastasis, recurrence, and multidrug resistance.MethodsWe investigated whether apoptosis, cell cycle regulation, oxidative status, and redox balance were altered by changes in the expression of the long noncoding RNA, growth arrest-specific transcript 5 (GAS5), in MM cells.ResultsAnalysis of clinical samples from MM patients showed that the rate of reduced GAS5 expression, relative to that in adjacent noncancerous tissues, was significantly lower for tumors from patients with advanced disease (76.6%, P < 0.001), as evidenced by larger tumor size, higher TNM stage, and higher incidences of ulceration and metastasis (P < 0.001 for all). Cell culture experiments showed that siRNA-mediated knockdown of GAS5 increased the viability of A375-GAS5si cells. Flow cytometry and western blotting showed that GAS5 knockdown increased MM cell proliferation by inducing G1/S cell cycle progression through increases in Cyclin D1, CDK4, and p27 expression (P < 0.05 for all) and by inhibiting apoptosis through an increase in Bcl-2 expression (P < 0.001). Knockdown of GAS5 also increased levels of superoxide anion (P < 0.01), NADP+(P < 0.001), and oxidized glutathiones (P < 0.01) through increases in NOX4 expression (P < 0.001), G6PD expression (P < 0.01), and NOX activity (P < 0.05), and RNA co-immunoprecipitation showed that GAS5 induced these changes through a physical interaction between GAS5 and the G6PD protein.ConclusionsOur findings show GAS5 contributes to regulation of the apoptosis, cell cycle, homeostasis of reactive oxygen species, and redox balance in MM cells, and suggest that reduced GAS5 expression contributes to disease progression in MM patients.

Moxifloxacin as an inducer of apoptosis in melanoma cells: A study at the cellular and molecular level

Fluoroquinolones were shown to be cytotoxic towards various cancer cell lines, thus representing a potentially important source of new anticancer agents. The aim of the present study was to examine the effect of moxifloxacin on cell viability, redox balance and apoptosis in both amelanotic – C32 and melanotic – COLO829 melanoma cells. Herein, we found that moxifloxacin decreases the viability of C32 and COLO829 cells in concentration- and time-dependent manner. The EC50 values were found to be as 0.16 mM, 0.12 mM and 0.11 mM for amelanotic C32 cells as well as 0.40 mM, 0.22 mM and 0.15 mM for COLO829 cells and 24, 48, 72 h incubation time, respectively. Moxifloxacin have also induced the intracellular disulphide imbalance and apoptosis as shown by externalization of phosphatidylserine, caspase-3/7 activation, G2/M cell cycle arrest and DNA fragmentation. The mechanism of apoptosis was related to the loss of mitochondrial membrane potential. This is the first study that characterized cellular and molecular mechanism underlying moxifloxacin cytotoxic and pro-apoptotic effect towards melanoma cells. Although further studies are required to establish efficacy of moxifloxacin against melanoma in clinical practice, the results of current study strongly suggest, that moxifloxacin is promising candidate as a repositioned drug for anti-melanoma treatment.

Kinetic modeling and sensitivity analysis for higher ethanol production in self-cloning xylose-using Saccharomyces cerevisiae

We constructed a xylose-utilizing Saccharomyces cerevisiae strain using endogenous xylose-assimilating genes (strain K7-XYL). Such self-cloning yeast is expected to make a great contribution to cost reduction of ethanol production processes. However, it is difficult to modify self-cloning yeast for optimal performance because the available gene source is limited. To improve the ethanol productivity of our self-cloning yeast, a kinetic model of ethanol production was constructed and sensitivity analysis was performed. Alcohol dehydrogenase (ADH1) was identified as a metabolic bottleneck reaction in the ethanol production pathway. An ADH1 overexpression strain (K7-XYL-ADH1) was constructed and evaluated in YP (yeast extract 10g/L, peptone 20g/L) medium containing 50g/L xylose as the sole carbon source. Strain K7-XYL-ADH1 showed higher ethanol productivity (13.8g/L) than strain K7-XYL (12.5g/L). Then, K7-XYL-ADH1 was evaluated in YP medium containing 80g/L glucose and 50g/L xylose; however, the ethanol productivity did not change relative to that of K7-XYL (K7-XYL 46.3g/L, K7-XYL-ADH1 45.9g/L). We presumed that due to the presence of glucose, the internal redox balance of the cells had changed. On culturing in an aerated 5-L jar fermentor to change the internal redox balance of cells, strain K7-XYL-ADH1 showed higher ethanol productivity than K7-XYL (K7-XYL 45.0g/L, K7-XYL-ADH1 49.4g/L). Our results confirmed that ADH1 was a metabolic bottleneck in the ethanol production pathway. By eliminating the bottleneck, self-cloning yeast showed almost the same ethanol productivity as genetically modified yeast.

Differentiation-Dependent Effects of a New Recombinant Manganese Superoxide Dismutase on Human SK-N-BE Neuron-Like Cells

We have recently isolated a new isoform of recombinant manganese superoxide dismutase (rMnSOD) which provides a potent antitumor activity and strongly counteracts the occurrence of oxidative stress and tissue inflammation. This isoform, in addition to the enzymatic action common to all SODs, also shows special functional and structural properties, essentially due to the presence of a first leader peptide that allows the protein to enter easily into cells. Among endogenous antioxidants, SOD constitutes the first line of natural defence against pathological effects induced by an excess of free radicals. Here, we firstly describe the effects of our rMnSOD administration on the proliferant and malignant undifferentiated human neuroblastoma SK-N-BE cell line. Moreover, we also test the effects of rMnSOD in the all trans retinoic-differentiated SK-N-BE neuron-like cells, a quiescent "not malignant" model. While rMnSOD showed an antitumor activity on proliferating cells, a poor sensitivity to rMnSOD overload in retinoid-differentiated neuron-like cells was observed. However, in the latter case, in presence of experimental-induced oxidative stress, overcharge of rMnSOD enhanced the oxidant effects, through an increase of H2O2 due to low activity of both catalase and glutathione peroxidase. In conclusion, our data show that rMnSOD treatment exerts differential effects, which depend upon both cell differentiation and redox balance, addressing attention to the potential use of the recombinant enzyme on differentiated neurons. These facts ultimately pave the way for further preclinical studies aimed at evaluation of rMnSOD effects in models of neurodegenerative diseases.

Therapeutic potential of the mitochondria-targeted antioxidant MitoQ in mitochondrial-ROS induced sensorineural hearing loss caused by Idh2 deficiency

Mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) is a major NADPH-producing enzyme which is essential for maintaining the mitochondrial redox balance in cells. We sought to determine whether IDH2 deficiency induces mitochondrial dysfunction and modulates auditory function, and investigated the protective potential of an antioxidant agent against reactive oxygen species (ROS)-induced cochlear damage in Idh2 knockout (Idh2−/−) mice. Idh2 deficiency leads to damages to hair cells and spiral ganglion neurons (SGNs) in the cochlea and ultimately to apoptotic cell death and progressive sensorineural hearing loss in Idh2−/− mice. Loss of IDH2 activity led to decreased levels of NADPH and glutathione causing abnormal ROS accumulation and oxidative damage, which might trigger apoptosis signal in hair cells and SGNs in Idh2−/− mice. We performed ex vivo experiments to determine whether administration of mitochondria-targeted antioxidants might protect or induce recovery of cells from ROS-induced apoptosis in Idh2-deficient mouse cochlea. MitoQ almost completely neutralized the H2O2-induced ototoxicity, as the survival rate of Idh2−/− hair cells were restored to normal levels. In addition, the lack of IDH2 led to the accumulation of mitochondrial ROS and the depolarization of ΔΨm, resulting in hair cell loss. In the present study, we identified that IDH2 is indispensable for the functional maintenance and survival of hair cells and SGNs. Moreover, the hair cell degeneration caused by IDH2 deficiency can be prevented by MitoQ, which suggests that Idh2−/− mice could be a valuable animal model for evaluating the therapeutic effects of various antioxidant candidates to overcome ROS-induced hearing loss.

86 - A new peroxisome-targeted two-photon fluorescent probe for imaging superoxide anion in mice with depression phenotypes

Depression is a devastating mental disease with high morbidity and mortality rates, intimately linked with oxidative stress. Peroxisomes can produce and scavenge reactive oxygen species (ROS), playing a pivotal role in maintaining redox balance in cells. Superoxide anion (O2•–), as the first produced reactive oxygen species in living systems, of whose level directly reflects the degree of oxidative stress. Thus, it is critical to identify the function of O2•− in peroxisomes for understanding the etiology of depression. Herein, we fabricate a new peroxisome-targetable fluorescent probe termed TCP for imaging O2•− in the living cells and brains of mice with depression-like behaviors. Upon excitation with 800 nm, TCP exhibits obvious fluorescence increased stepwise depend on the changes of O2•−. The imaging results demonstrate that the O2•− in peroxisomes of glutamate-stimulated PC12 cells significantly increased compared to that of normal cells. Importantly, utilizing TCP, we also explore the fluctuation of peroxisomes’ O2•− in brains of mice with depression phenotypes. Altogether, this work provides new ways to understand the the occurrence and development of depression.

Ibrutinib Resistance Is Reduced by an Inhibitor of Fatty Acid Oxidation in Primary CLL Lymphocytes.

Chronic Lymphocytic Leukemia (CLL) is an incurable disease, characterized by the accumulation of malignant B-lymphocytes in the blood stream (quiescent state) and homing tissues (where they can proliferate). In CLL, the targeting of B-cell receptor signaling through a Burton's tyrosine kinase inhibitor (ibrutinib) has rendered outstanding clinical results. However, complete remission is not guaranteed due to drug resistance or relapse, revealing the need for novel approaches for CLL treatment. The characterization of metabolic rewiring in proliferative cancer cells is already being applied for diagnostic and therapeutic purposes, but our knowledge of quiescent cell metabolism—relevant for CLL cells—is still fragmentary. Recently, we reported that glutamine metabolism in primary CLL cells bearing the del11q deletion is different from their del11q negative counterparts, making del11q cells especially sensitive to glutaminase and glycolysis inhibitors. In this work, we used our primary CLL lymphocyte bank and compounds interfering with central carbon metabolism to define metabolic traits associated with ibrutinib resistance. We observe a differential basal metabolite uptake linked to ibrutinib resistance, favoring glutamine uptake and catabolism. Upon ibrutinib treatment, the redox balance in ibrutinib resistant cells is shifted toward NADPH accumulation, without an increase in glutamine uptake, suggesting alternative metabolic rewiring such as the activation of fatty acid oxidation. In accordance to this idea, the curtailing of fatty acid oxidation by CPT1 inhibition (etomoxir) re-sensitized resistant cells to ibrutinib. Our results suggest that fatty acid oxidation could be explored as a target to overcome ibrutinib resistance.