Intracellular Reactive Oxygen Species Homeostasis Research Articles

NaHS immersion alleviates the stress effect of chromium(III) on alfalfa seeds by affecting active oxygen metabolism

ABSTRACT Objective This study aimed to investigate the regulatory effects of exogenous hydrogen sulfide (H2S) on seed germination, seedling growth, and reactive oxygen species (ROS) homeostasis in alfalfa under chromium (Cr) ion (III) stress. Methods The effects of 0–4 mM Cr(III) on the germination and seedling growth of alfalfa were first assessed. Subsequently, following seed NaHS immersion, the influence of H2S on alfalfa seed germination and seedling growth under 2 mM Cr(III) stress was investigated, and the substance contents and enzyme activities associated with ROS metabolism were quantified. Results Compared to the control group, alfalfa plant germination was delayed under 2 mM Cr(III) stress for up to 48 h (p < 0.05). At 120 h, the total seedling length was approximately halved, and the root length was roughly one-third of the control. Treatment with 0.02–0.1 mM NaHS alleviated the delay in germination and root growth inhibition caused by 2 mM Cr(III) stress, resulting in an increased ratio of root length to hypocotyl length from 0.57 to 1 above. Additionally, immersion in 0.05 mM NaHS reduced hydrogen peroxide (H2O2) and oxygen-free radicals (O2 · –) levels (p < 0.05), boosted glutathione (GSH) levels (p < 0.05), and notably enhanced catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities (p < 0.05) compared to the 2 mM Cr(III) stress treatment group. Conclusion Seed immersion in NaHS mitigated the delay in germination and inhibition of root elongation under 2 mM Cr(III) stress. This effect is likely attributed to the regulation of intracellular ROS homeostasis and redox balance through enzymatic and non-enzymatic systems; thus, providing a potential mechanism for combating oxidative stress.

SYNTAXIN OF PLANTS81 regulates root meristem activity and stem cell niche maintenance via ROS signaling.

Root growth and development depend on continuous cell division and differentiation in root tips. In these processes, reactive oxygen species (ROS) play a critical role as signaling molecules. However, few ROS signaling regulators have been identified. In this study, we found knockdown of a syntaxin gene, SYNTAXIN OF PLANTS81 in Arabidopsis thaliana (AtSYP81) resulted in a severe reduction in root meristem activity and disruption of root stem cell niche (SCN) identity. Subsequently, we found AtSYP81 was highly expressed in roots and localized on the endoplasmic reticulum (ER). Interestingly, the reduced expression of AtSYP81 conferred a decreased number of peroxisomes in root meristem cells, raising a possibility that AtSYP81 regulates root development through peroxisome-mediated ROS production. Further transcriptome analysis revealed that class III peroxidases, which are responsible for intracellular ROS homeostasis, showed significantly changed expression in the atsyp81 mutants and AtSYP81 overexpression lines, adding evidence of the regulatory role of AtSYP81 in ROS signaling. Accordingly, rescuing the decreased ROS level via applying ROS donors effectively restored the defects in root meristem activity and SCN identity in the atsyp81 mutants. APETALA2 (AP2) transcription factors PLETHORA1 and 2 (PLT1 and PLT2) were then established as the downstream effectors in this pathway, while potential crosstalk between ROS signaling and auxin signaling was also indicated. Taken together, our findings suggest that AtSYP81 regulates root meristem activity and maintains root SCN identity by controlling peroxisome- and peroxidase-mediated ROS homeostasis, thus both broadening and deepening our understanding of the biological roles of SNARE proteins and ROS signaling.

Role of Reactive Oxygen Species in Aging and Age-Related Diseases: A Review.

Research on the role of reactive oxygen species (ROS) in the aging process has advanced significantly over the last two decades. In light of recent findings, ROS takes part in the aging process of cells along with contributing to various physiological signaling pathways. Antioxidants being cells' natural defense mechanism against ROS-mediated alteration, play an imperative role to maintain intracellular ROS homeostasis. Although the complete understanding of the ROS regulated aging process is yet to be fully comprehended, current insights into various sources of cellular ROS and their correlation with the aging process and age-related diseases are portrayed in this review. In addition, results on the effect of antioxidants on ROS homeostasis and the aging process as well as their advances in clinical trials are also discussed in detail. The future perspective in ROS-antioxidant dynamics on antiaging research is also marshaled to provide future directions for ROS-mediated antiaging research fields.

Extensive Disturbances of Intracellular Components and Dysfunctions of Biological Pathways in the Brain Tissues During Prion Infection - China's Studies.

The study describes some of the major findings of changes in intracellular components and biological pathways in the brain during prion infection and hypothesizes some important physiological and pathological approaches mainly based on our studies. Omics techniques analysis of messenger RNA (mRNA) and proteins were carried out in the study. Meanwhile, Western blot, immunohistochemistry, and immunofluorescence were used for protein analysis in different signaling pathways. Statistical analyses were used to describe the protein differences in signaling pathways of infected and normal samples. This report reviewed and summarized our studies on the aberrant changes in intracellular components and biological functions in the brains of prion disease (PrD). Omics analyses proposed extensive abnormal alterations of brain mRNAs transcriptions, protein expressions, and post-translational modifications. The molecular disturbances for microtubule instability and depolymerization, the dysregulations of different signals related with neuron loss and synaptic plasticity, the abnormalities of mitochondrial and endoplasmic reticulum stress, and disturbance of intracellular reactive oxygen species homeostasis during prion infection were precisely analyzed and reviewed. Aberrant disturbances of numerous biological molecules and signals in brain tissues were found during prion infection.

Diffusional Interactions among Marine Phytoplankton and Bacterioplankton: Modelling H2O2 as a Case Study.

Marine phytoplankton vary widely in size across taxa, and in cell suspension densities across habitats and growth states. Cell suspension density and total biovolume determine the bulk influence of a phytoplankton community upon its environment. Cell suspension density also determines the intercellular spacings separating phytoplankton cells from each other, or from co-occurring bacterioplankton. Intercellular spacing then determines the mean diffusion paths for exchanges of solutes among co-occurring cells. Marine phytoplankton and bacterioplankton both produce and scavenge reactive oxygen species (ROS), to maintain intracellular ROS homeostasis to support their cellular processes, while limiting damaging reactions. Among ROS, hydrogen peroxide (H2O2) has relatively low reactivity, long intracellular and extracellular lifetimes, and readily crosses cell membranes. Our objective was to quantify how cells can influence other cells via diffusional interactions, using H2O2 as a case study. To visualize and constrain potentials for cell-to-cell exchanges of H2O2, we simulated the decrease of [H2O2] outwards from representative phytoplankton taxa maintaining internal [H2O2] above representative seawater [H2O2]. [H2O2] gradients outwards from static cell surfaces were dominated by volumetric dilution, with only a negligible influence from decay. The simulated [H2O2] fell to background [H2O2] within ~3.1 µm from a Prochlorococcus cell surface, but extended outwards 90 µm from a diatom cell surface. More rapid decays of other, less stable ROS, would lower these threshold distances. Bacterioplankton lowered simulated local [H2O2] below background only out to 1.2 µm from the surface of a static cell, even though bacterioplankton collectively act to influence seawater ROS. These small diffusional spheres around cells mean that direct cell-to-cell exchange of H2O2 is unlikely in oligotrophic habits with widely spaced, small cells; moderate in eutrophic habits with shorter cell-to-cell spacing; but extensive within phytoplankton colonies.

Cold plasma promotes Sertoli cell proliferation via AMPK–mTOR signaling pathway

This study investigated cold plasmas for multiple biological applications. Our previous work has found dielectric barrier discharge plasma improves chicken sperm quality. The number of Sertoli cells (SCs) decides spermatogenesis. However, whether cold plasma can regulate SC proliferation remains unclear. This study explored the effects of cold plasma on immature chicken SC proliferation and the regulation mechanism. Results showed that cold plasma exposure at 2.4 W for 30 s twice with an interval of 6 h produced (P<0.05) the maximum SC viability, cell growth, and cell cycle progression. SC proliferation-promoting effect of cold plasma treatment was regulated by increasing (P<0.05) the adenosine triphosphate production and the respiratory enzyme activity in the mitochondria. This process was potentially mediated by the adenosine monophosphate-activated protein kinase (AMPK)–mammalian target of rapamycin (mTOR) signaling pathway, which was regulated by the microRNA (miRNA) targeting regulation directly and by the intracellular reactive oxygen species homeostasis indirectly. The cold plasma treatment increased (P<0.01) the miR-7450-5p expression and led to a decreased (P<0.01) AMPKα1 level. On the other hand, miR-100-5p expression was reduced (P<0.05) and led to an increased (P<0.05) mTOR level in SCs. A single-stranded synthetic miR-7450-5p antagomir and a double-stranded synthetic miR-100-5p agomir reduced (P<0.05) the SC proliferation. However, this could be ameliorated (P<0.05) by the cold plasma treatment. Our findings suggest that appropriate cold plasma treatment provides a safe strategy to improve SC proliferation, which is beneficial to elevating male chicken reproductive capacity.

LRPPRC regulates redox homeostasis via the circANKHD1/FOXM1 axis to enhance bladder urothelial carcinoma tumorigenesis

Reactive oxygen species (ROS) which are continuously generated mainly by mitochondria, have been proved to play an important role in the stress signaling of cancer cells. Moreover, pentatricopeptide repeat (PPR) proteins have been suggested to take part in mitochondrial metabolism. However, the mechanisms integrating the actions of these distinct networks in urothelial carcinoma of the bladder (UCB) pathogenesis are elusive. In this study, we found that leucine rich pentatricopeptide repeat containing (LRPPRC) was frequently upregulated in UCB and that it was an independent prognostic factor in UCB. We further revealed that LRPPRC promoted UCB tumorigenesis by regulating the intracellular ROS homeostasis. Mechanistically, LRPPRC modulates ROS balance and protects UCB cells from oxidative stress via mt-mRNA metabolism and the circANKHD1/FOXM1 axis. In addition, the SRA stem-loop interacting RNA binding protein (SLIRP) directly interacted with LRPPRC to protect it from ubiquitination and proteasomal degradation. Notably, we showed that LRPPRC modulated the tumorigenesis of UCB cells in a circANKHD1-FOXM1-dependent manner. In conclusion, LRPPRC exerts critical roles in regulating UCB redox homeostasis and tumorigenesis, and is a prognostic factor for UCB; suggesting that LRPPRC may serve as an exploitable therapeutic target in UCB.

PRDX1 is essential for the viability and maintenance of reactive oxygen species in chicken DT40

BackgroundPeroxiredoxin 1 (PRDX1) is a member of a ubiquitous family of thiol peroxidases that catalyze the reduction of peroxides, including hydrogen peroxide. It functions as an antioxidant enzyme, similar to catalase and glutathione peroxidase. PRDX1 was recently shown act as a sensor of reactive oxygen species (ROS) and play a role in ROS-dependent intracellular signaling pathways. To investigate its physiological functions, PRDX1 was conditionally disrupted in chicken DT40 cells in the present study.ResultsThe depletion of PRDX1 resulted in cell death with increased levels of intracellular ROS. PRDX1-depleted cells did not show the accumulation of chromosomal breaks or sister chromatid exchange (SCE). These results suggest that cell death in PRDX1-depleted cells was not due to DNA damage. 2-Mercaptoethanol protected against cell death in PRDX1-depleted cells and also suppressed elevations in ROS.ConclusionsPRDX1 is essential in chicken DT40 cells and plays an important role in maintaining intracellular ROS homeostasis (or in the fine-tuning of cellular ROS levels). Cells deficient in PRDX1 may be used as an endogenously deregulated ROS model to elucidate the physiological roles of ROS in maintaining proper cell growth.

Illuminating the effect of beneficial blue light and ROS-modulating enzymes in Dupuytren's disease.

Dupuytren's disease (DD) is a fibroproliferative disorder of the palmar aponeurosis, which is characterized by a compound myofibrogenesis and evidenced by an increased expression of α-smooth muscle actin (α-SMA). In Dupuytren's tissue, higher levels of reactive oxygen species (ROS) are documented, stimulating the proliferation and differentiation of myofibroblasts. Our preliminary study demonstrates that α-SMA-expression is significantly inhibited by blue light irradiation in DD. The objective of this study was to investigate the beneficial effect of blue light irradiation and to elucidate the influence of ROS on myofibrogenesis in the pathogenesis of DD. Therefore, an in-vitro model of human DD fibroblasts was used. DD fibroblasts and control fibroblasts isolated from carpal tunnel syndrome (CTS) were daily irradiated with 40 J/cm2 (λ = 453 nm, 38 mW/cm2). Protein expression of ROS-modulating enzymes (Catalase, NOX4, SOD1, MnSOD) and α-SMA were determined, and additionally analysed after a pharmacological inhibition of the TGF-β1-signaling with SB431542. Furthermore, the protein expression of α-SMA as surrogate parameter for myofibrogenesis was evaluated after applying different concentrations of long-lasting ROS. It could be determined that the beneficial blue light irradiation, which inhibited myofibrogenesis, is mediated by a significant inhibition of catalase protein expression. This effect should be accompanied with an increased intracellular ROS level. Proof of evidence was an H2O2-application on DD fibroblasts, also leading to a decreased myofibrogenesis. Furthermore, it could be demonstrated that endogenous MnSOD was significantly downregulated in resting DD fibroblasts. If DD fibroblasts were treated with the pharmacological inhibitor SB431542, myofibrogenesis was inhibited, but MnSOD expression was simultaneously elevated, which ought to affect ROS level by raising intracellular H2O2 amount. Blue light irradiation as well as the pharmacological action of SB431542 in consequence mediates their beneficial effect on disturbed myofibrogenesis in DD by further increasing ROS level. The present study demonstrates the importance of intracellular ROS homeostasis in DD and illuminates the beneficial effect of blue light as a promising therapy option for DD.

Tumor Microenvironment-Modulated Nanozymes for NIR-II-Triggered Hyperthermia-Enhanced Photo-Nanocatalytic Therapy via Disrupting ROS Homeostasis.

PurposeReactive oxygen species (ROS) are a group of signaling biomolecules that play important roles in the cell cycle. When intracellular ROS homeostasis is disrupted, it can induce cellular necrosis and apoptosis. It is desirable to effectively cascade-amplifying ROS generation and weaken antioxidant defense for disrupting ROS homeostasis in tumor microenvironment (TME), which has been recognized as a novel and ideal antitumor strategy. Multifunctional nanozymes are highly promising agents for ROS-mediated therapy.MethodsThis study constructed a novel theranostic nanoagent based on PEG@Cu2-xS@Ce6 nanozymes (PCCNs) through a facile one-step hydrothermal method. We systematically investigated the photodynamic therapy (PDT)/photothermal therapy (PTT) properties, catalytic therapy (CTT) and glutathione (GSH) depletion activities of PCCNs, antitumor efficacy induced by PCCNs in vitro and in vivo.ResultsPCCNs generate singlet oxygen (1O2) with laser (660 nm) irradiation and use catalytic reactions to produce hydroxyl radical (•OH). Moreover, PCCNs show the high photothermal performance under NIR II 1064-nm laser irradiation, which can enhance CTT/PDT efficiencies to increase ROS generation. The properties of O2 evolution and GSH consumption of PCCNs achieve hypoxia-relieved PDT and destroy cellular antioxidant defense system respectively. The excellent antitumor efficacy in 4T1 tumor-bearing mice of PCCNs is achieved through disrupting ROS homeostasis-involved therapy under the guidance of photothermal/photoacoustic imaging.ConclusionOur study provides a proof of concept of “all-in-one” nanozymes to eliminate tumors via disrupting ROS homeostasis.

Deficiency of Sirtuin 1 Impedes Endometrial Decidualization in Recurrent Implantation Failure Patients.

Decidualization is driven by differentiation of human endometrial stromal cells (ESCs), and is a prerequisite for successful implantation and establishment of pregnancy. The critical role of impaired decidualization in women suffered recurrent implantation failure (RIF) has been established, while the underlying mechanism is poorly understood. In the present study, we verified the essential role of Sirtuin1 (SIRT1) in regulating differentiation and maintaining reactive oxygen species (ROS) homeostasis of human ESCs during decidualization. The abundance of SIRT1 was decreased in RIF patients both in the endometria during window of implantation phase and in the decidualized ESCs. Downregulation of SIRT1 disrupted the intracellular ROS homeostasis during decidualization of ESC, manifested as the accumulation of intracellular ROS level and the reduction of antioxidant stress molecules. Elimination of ROS with N-acetyl-L-cysteine (NAC) could rescued the decidualization inhibition caused by SIRT1 knockdown. Further, we explored the insufficient expression of SIRT1 in ESC affected the deacetylation of forkhead box O1 (FOXO1), and thus inhibited the transcriptional activity of FOXO1. This could account for the dysregulation of intracellular ROS homeostasis during decidualization and decreased expression of decidual markers. Collectively, our findings provided insight into the role of down-regulated SIRT1 in the poor decidual response of ESCs in RIF patients.

The Histone Methyltransferase SETDB1 Modulates Survival of Spermatogonial Stem/Progenitor Cells Through NADPH Oxidase.

SETDB1, a histone H3 lysine 9 (H3K9) methyltransferase, is crucial in meiosis and embryo development. This study aimed to investigate whether SETDB1 was associated with spermatogonial stem cells (SSC) homeostasis. We found that knockdown of Setdb1 impaired cell proliferation, led to an increase in reactive oxygen species (ROS) level through NADPH oxidase, and Setdb1 deficiency activated ROS downstream signaling pathways, including JNK and p38 MAPK, which possibly contributed to SSC apoptosis. Melatonin scavenged ROS and rescued the phenotype of Setdb1 KD. In addition, we demonstrated that SETDB1 regulated NADPH oxidase 4 (Nox4) and E2F1. Therefore, this study uncovers the new roles of SETDB1 in mediating intracellular ROS homeostasis for the survival of SSC.

Arabidopsis BRCA1 represses RRTF1-mediated ROS production and ROS-responsive gene expression under dehydration stress.

Reactive oxygen species (ROS) act as important secondary messengers in abscisic acid (ABA) signaling and induce stomatal closure under dehydration stress. The breast cancer susceptibility gene 1 (BRCA1), an important tumor suppressor in animals, functions primarily in the maintenance of genome integrity in animals and plants. However, whether and how the plant BRCA1 regulates intracellular ROS homeostasis in guard cells under dehydration stress remains unknown. Here, we found that Arabidopsisatbrca1 loss-of-function mutants showed dehydration stress tolerance. This stress tolerant phenotype of atbrca1 was a result of ABA- and ROS-induced stomatal closure, which was enhanced in atbrca1 mutants compared with the wild-type. AtBRCA1 downregulated the expression of ROS-responsive and marker genes. Notably, these genes were also the targets of the AP2/ERF transcriptional activator RRTF1/ERF109. Under normal conditions, AtBRCA1 physically interacted with RRTF1 and inhibited its binding to the GCC-box-like sequence in target gene promoters. Under dehydration stress, the expression of AtBRCA1 was dramatically reduced and that of RRTF1 was activated, thus inducing the expression of ROS-responsive genes. Overall, our study reveals a novel molecular function of AtBRCA1 in the transcriptional regulation of intracellular ROS homeostasis under dehydration stress.

OsGSTU6 Contributes to Cadmium Stress Tolerance in Rice by Involving in Intracellular ROS Homeostasis

Glutathione S-transferases (GSTs) are multifunctional proteins that play important roles in cellular detoxification as well as in plant growth and development. Here, we cloned a new rice tau class GST gene, OsGSTU6, and evaluated its roles in regulating cadmium (Cd) stress tolerance of rice. OsGSTU6 is located both in the cytosol and nucleus of cells. The transcripts of OsGSTU6 were detected in the whole life cycle of rice with higher levels in the leaf blade and sheath at heading stage. The transcripts of OsGSTU6 were significantly stimulated by a number of environmental factors including several phytohormones, abiotic stresses, and heavy metals, suggesting its stress-responsive characteristics. Moreover, the overexpression (OE) of OsGSTU6 in rice reduced the accumulation of Cd in leaf and enhanced the tolerance of the plant to Cd stress, while knockdown (RNAi) of OsGSTU6 triggered Cd accumulation in rice leaves and decreased stress tolerance. Meanwhile, the expression levels of several candidate genes responsible for scavenging reactive oxygen species (ROS) were downregulated in OE of OsGSTU6 lines. In addition, the content of superoxide anions (O2−) and glutathione showed reduction in OE plants, but was augmented in RNAi plants under both normal growth and Cd stress, compared with wild type. Furthermore, both the yeast two-hybrid assay and firefly luciferase complementation imaging (LCI) assay demonstrated that OsGSTU6 might function with dimers in plant cells. All these results suggest that OsGSTU6 may play an important role in Cd stress tolerance of rice by involving in the intracellular ROS homeostasis.

The Role of Peroxiredoxin Family in Cancer Signaling.

Peroxiredoxins (Prxs) are antioxidant enzymes that protect cells from oxidative stress by reducing intracellular accumulation of reactive oxygen species (ROS). In mammalian cells, the six Prx isoforms are ubiquitously expressed in diverse intracellular locations. They are involved in the regulation of various physiological processes including cell growth, differentiation, apoptosis, immune response and metabolism as well as intracellular ROS homeostasis. Although there are increasing evidences that Prxs are involved in carcinogenesis of many cancers, their role in cancer is controversial. The ROS levels in cancer cells are increased compared to normal cells, thus promoting cancer development. Nevertheless, for various cancer types, an overexpression of Prxs has been found to be associated with poor patient prognosis, and an increasing number of studies have reported that tumorigenesis is either facilitated or inhibited by regulation of cancer-associated signaling pathways. This review summarizes Prx isoforms and their basic functions, the relationship between the expression level and the physiological role of Prxs in cancer cells, and their roles in regulating cancer-associated signaling pathways.

Nitric oxide and ROS mediate autophagy and regulate Alternaria alternata toxin-induced cell death in tobacco BY-2 cells

Synergistic interaction of nitric oxide (NO) and reactive oxygen species (ROS) is essential to initiate cell death mechanisms in plants. Though autophagy is salient in either restricting or promoting hypersensitivity response (HR)-related cell death, the crosstalk between the reactive intermediates and autophagy during hypersensitivity response is paradoxical. In this investigation, the consequences of Alternaria alternata toxin (AaT) in tobacco BY-2 cells were examined. At 3 h, AaT perturbed intracellular ROS homeostasis, altered antioxidant enzyme activities, triggered mitochondrial depolarization and induced autophagy. Suppression of autophagy by 3-Methyladenine caused a decline in cell viability in AaT treated cells, which indicated the vital role of autophagy in cell survival. After 24 h, AaT facilitated Ca2+ influx with an accumulation of reactive oxidant intermediates and NO, to manifest necrotic cell death. Inhibition of NO accumulation by 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) decreased the level of necrotic cell death, and induced autophagy, which suggests NO accumulation represses autophagy and facilitates necrotic cell death at 24 h. Application of N-acetyl-L-cysteine at 3 h, confirmed ROS to be the key initiator of autophagy, and together with cPTIO for 24 h, revealed the combined effects of NO and ROS is required for necrotic HR cell death.

A new function of copper zinc superoxide dismutase: as a regulatory DNA-binding protein in gene expression in response to intracellular hydrogen peroxide.

In microorganisms, a number of metalloproteins including PerR are found to regulate gene expression in response to environmental reactive oxygen species (ROS) changes. However, discovery of similar regulatory mechanisms remains elusive within mammalian cells. As an antioxidant metalloenzyme that maintains intracellular ROS homeostasis, copper zinc superoxide dismutase (SOD1) has high affinity for DNA in solution and in cells. Here, we explored the regulatory roles of SOD1 in the expression of genes in response to ROS changes within mammalian cells. SOD1-occupied DNA sites with distinct sequence preference were identified. Changing ROS levels both were found to impact DNA–SOD1 interactions in solution and within HeLa cells. GGA was one of the base triplets that had direct contact with SOD1. DNA–SOD1 interactions were observed to regulate the ROS-responsive expression of functional genes including oncogenes and amyotrophic lateral sclerosis-linked genes in transcriptional phases. Our results confirm another function of SOD1, acting as a H2O2-responsive regulatory protein in the expression of numerous mammalian genes.

NPGPx modulates CPEB2-controlled HIF-1α RNA translation in response to oxidative stress.

Non-selenocysteine-containing phospholipid hydroperoxide glutathione peroxidase (NPGPx or GPx7) is an oxidative stress sensor that modulates the antioxidative activity of its target proteins through intermolecular disulfide bond formation. Given NPGPx's role in protecting cells from oxidative damage, identification of the oxidative stress-induced protein complexes, which forms with key stress factors, may offer novel insight into intracellular reactive oxygen species homeostasis. Here, we show that NPGPx forms a disulfide bond with the translational regulator cytoplasmic polyadenylation element-binding protein 2 (CPEB2) that results in negative regulation of hypoxia-inducible factor 1-alpha (HIF-1α) RNA translation. In NPGPx-proficient cells, high oxidative stress that disrupts this bonding compromises the association of CPEB2 with HIF-1α RNA, leading to elevated HIF-1α RNA translation. NPGPx-deficient cells, in contrast, demonstrate increased HIF-1α RNA translation under normoxia with both impaired induction of HIF-1α synthesis and blunted HIF-1α-programmed transcription following oxidative stress. Together, these results reveal a molecular mechanism for how NPGPx mediates CPEB2-controlled HIF-1α RNA translation in a redox-sensitive manner.

Acetylation at lysine 71 inactivates superoxide dismutase 1 and sensitizes cancer cells to genotoxic agents.

Cancer cells are characterized by a high dependency on antioxidant enzymes to cope with the elevated rates of reactive oxygen species (ROS). Impairing antioxidant capacity in cancer cells disturbs the ROS homeostasis and exposes cancer cells to massive oxidative stress. In this study, we have discovered that superoxide dismutase 1 (SOD1), a major player in maintaining the cellular redox status, was acetylated at lysine 71. This acetylation, which was primarily deacetylated by Sirtuin 1 (SIRT1), suppressed the enzymatic activity of SOD1 via disrupting its association with copper chaperone for SOD1 (CCS). More importantly, genotoxic agents, such as camptothecin (CPT), induced SOD1 acetylation by disrupting its binding with SIRT1. CPT-induced SOD1 acetylation was stimulated by its provoked ROS, suggesting a positive feedback loop, in which ROS per se impairs the antioxidative defence of cancer cells and reinforces oxidative stress stimulated by anticancer agents. The intrinsic abundance of SOD1 acetylation varied among cancer cells, and high level of SOD1 acetylation was correlated with elevated sensitivity to CPT. Together, our findings gained mechanistic insights into how cytotoxic agents fine tune the intracellular ROS homeostasis to strengthen their anticancer effects, and suggested SOD1 acetylation as a candidate biomarker for predicting response to CPT-based chemotherapy.

A Critical Role of Fas-Associated Protein with Death Domain Phosphorylation in Intracellular Reactive Oxygen Species Homeostasis and Aging

Reactive oxygen species (ROS) plays important roles in aging. However, the specific mechanisms for intracellular ROS accumulation, especially during aging, remain elusive. We have reported that Fas-associated protein with death domain (FADD) phosphorylation abolishes the recruitment of phosphatase type 2A C subunit (PP2Ac) to protein kinase C (PKC)βII, which specifically regulates mitochondrial ROS generation by p66shc. Here, we have studied the role of FADD phosphorylation in an FADD constitutive-phosphorylation mutation (FADD-D) mouse model. In FADD-D mice, the constitutive FADD phosphorylation led to ROS accumulation (hydrogen peroxide [H₂O₂]), in a process that was dependent on PKCβ and accompanied by increased PKCβ and p66shc phosphorylation, impaired mitochondrial integrity, and enhanced sensitivity to oxidative stress-mediated apoptosis. Moreover, FADD-D mice exhibited premature aging-like phenotypes, including DNA damage, cellular senescence, and shortened lifespan. In addition, we demonstrate that FADD phosphorylation and the recruitment of PP2A and FADD to PKCβ are induced responses to oxidative stress, and that the extent of FADD phosphorylation in wild-type mice was augmented during aging, accompanied by impairment of the interaction between PKCβ and PP2A. The present study first addresses the role of FADD phosphorylation in aging through controlling mitochondrial ROS specifically generated by PKCβ. These data identify that FADD phosphorylation is critical for the PKCβ-p66shc signaling route to generate H₂O₂ and to implicate enhanced FADD phosphorylation as a primary cause of ROS accumulation during aging.