Endogenous Reactive Oxygen Species Levels Research Articles

HFR1 antagonizes ABI4 to coordinate cytosolic redox status for seed germination under high-temperature stress.

Seed germination and dormancy represent critical phases in the life cycle of plants, tightly regulated by endogenous phytochrome levels and environment signals. High temperatures (HT) induce the overaccumulation of reactive oxygen species (ROS) and increase abscisic acid (ABA), thereby inhibiting seed germination. Our previous findings showed that HT induced the burst of reactive nitrogen species (RNS), increasing the S-nitrosylation modification of HFR1, which effectively blocks seed germination. Importantly, stabilizing HFR1 has been shown to significantly mitigate the inhibitory effect of HT on seed germination. In this study, we reported that HT increased the protein abundance of ABI4, a crucial component in ABA signaling, which in turn activates the expression of RbohD while suppressing the expression of VTC2. This leads to the rapid generation of ROS, thereby inhibiting seed germination. Consistently, the seed germination of abi4 mutant showed insensitivity to HT with lower ROS level during seed germination, whereas transgenic lines overexpressing ABI4 showed reduced germination rates accompanied by elevated ROS levels. Furthermore, we noted that HFR1 interacts with ABI4 to sequester its activity under normal conditions. However, HT-induced ROS triggered the degradation of HFR1, consequently releasing ABI4 activity. This activation of ABI4 promotes RbohD expression, culminating in a ROS burst that suppresses seed germination. Thus, our study unveils a novel function for ABI4 in regulating ROS level and seed germination under HT stress. Throughout this process, HFR1 plays a critical role in restraining ABI4 activity to maintain an optimal endogenous ROS level, thereby ensuring seed germination under favorable environmental conditions.

Identification of the Major Facilitator Superfamily Efflux Pump KpsrMFS in Klebsiella pneumoniae That Is Down-Regulated in the Presence of Multi-Stress Factors.

Efflux pumps play important roles in bacterial detoxification and some of them are stress-response elements that are up-regulated when the host is treated with antibiotics. However, efflux pumps that are down-regulated by stimulations are rarely discovered. Herein, we analyzed multiple transcriptome data and discovered a special (Major Facilitator Superfamily) MFS efflux pump, KpsrMFS, from Klebsiella pneumoniae, which was down-regulated when treated with antibiotics or extra carbon sources. Interestingly, overexpression of kpsrmfs resulted in halted cell growth in normal conditions, while the viable cells were rarely affected. The function of KpsrMFS was further analyzed and this efflux pump was determined to be a proton-driven transporter that can reduce the intracellular tetracycline concentration. In normal conditions, the expression of kpsrmfs was at a low level, while artificial overexpression of it led to increased endogenous reactive oxygen species (ROS) production. Moreover, by comparing the functions of adjacent genes of kpsrmfs, we further discovered another four genes that can confer similar phenotypes, indicating a special regulon that regulates cell growth. Our work provides new insights into the roles of efflux pumps and suggests a possible regulon that may regulate cell growth and endogenous ROS levels.

The master antioxidant defense is activated during EBV latent infection.

To our knowledge, this is the first report delineating the activation of the master antioxidant defense during EBV latency. We show that EBV-triggered reactive oxygen species production activates the Keap1-NRF2 pathway in EBV-transformed cells, and LMP1 plays a major role in this event, and the stress-related kinase TBK1 is required for NRF2 activation. Moreover, we show that the Keap1-NRF2 pathway is important for cell proliferation and EBV latency maintenance. Our findings disclose how EBV controls the balance between oxidative stress and antioxidant defense, which greatly improve our understanding of EBV latency and pathogenesis and may be leveraged to opportunities toward the improvement of therapeutic outcomes in EBV-associated diseases.

Regulation of reactive oxygen species and phytohormones in osmotic stress tolerance during seed germination in indica rice.

Climate change due to global warming is now affecting agricultural production worldwide. In rice, one of the most important crops, water limitation due to irregular rainfall in rainfed lowlands during crop growth limits yield. Dry direct-sowing has been proposed as a water-efficient approach to cope with water stress during rice growth, but poor seedling establishment due to drought during germination and emergence is a problem. Here, we germinated indica rice cultivars Rc348 (drought tolerant) and Rc10 (drought sensitive) under osmotic stress induced by PEG to elucidate mechanisms of germination under drought. Rc348 had higher germination rate and germination index under severe osmotic stress of -1.5 MPa, above those of Rc10. Rc348 showed up-regulated GA biosynthesis, down-regulated ABA catabolism, and up-regulated α-amylase gene expression in imbibed seeds under PEG treatment compared to that of Rc10. During germination, reactive oxygen species (ROS) play important roles in antagonism between gibberellic acid (GA) and abscisic acid (ABA). Embryo of Rc348 treated with PEG had significantly greater expression of NADPH oxidase genes and higher endogenous ROS levels, together with significantly increased endogenous GA1, GA4 and ABA contents compared to that of Rc10. In aleurone layers treated with exogenous GA, expression of α-amylase genes was higher in Rc348 than in Rc10, and expression of NADPH oxidase genes was enhanced with significantly higher ROS content in Rc348, suggesting higher sensitivity of GA to ROS production and starch degradation in aleurone cells of Rc348. These results suggest that the osmotic stress tolerance of Rc348 is due to enhancement of ROS production, GA biosynthesis, and GA sensitivity, resulting in a higher germination rate under osmotic stress.

Nitrogen limitation and hydrogen peroxide act synergistically to enhance lipids accumulation via ROS/Ca2+ dependent mechanism in Chlorella sorokiniana

The main aim of the present study is to assess the effects of combined nitrogen limitation and hydrogen peroxide (H2O2) treatment on lipid accumulation in Chlorella sorokiniana. Furthermore, to study the regulative networks involved in the lipid accumulation of microalgae, the relationships between reactive oxygen species (ROS), Ca2+ and four lipogenic genes (mitogen-activated protein kinase: MAPK; heteromeric acetyl-CoA carboxylase beta subunit: accD; b-ketoacyl-ACP synthase III: KASIII; diacylglycerol acyltransferase: DGAT) were also analyzed. The results indicated that the contents of chlorophyll a, carbohydrate and protein were decreased, while the lipid content and levels of endogenous ROS, Ca2+ were increased under nitrogen limitation groups with H2O2 added. Further research indicated that the increased ROS level could affect lipid accumulation through lipogenic genes expression. In addition, the interplays of ROS and Ca2+ may be found. This study provides an effective strategy to improve the lipid accumulation in C. sorokiniana, and offers evidence of ROS, Ca2+ and lipogenic genes in the accommodation of lipid biosynthesis in microalgae under combined treatment of nitrogen limitation and H2O2.

Identification and functional characterization of ORF19.5274, a novel gene involved in both azoles susceptibility and hypha development in Candida albicans.

Azole resistance is becoming increasingly serious due to the frequent recurrence of fungal infections and the need for long-term clinical prevention. In our previous study, we discovered ORF19.5274 with an unknown function by TMT™ quantitative proteomics technology after fluconazole (FLC) treatment of Candida albicans. In this study, we created the target gene deletion strain using CRISPR-Cas9 editing technology to see if ORF19.5274 regulates azole sensitivity. The data showed that ORF19.5274 was involved in hyphal development and susceptibility to antifungal azoles. Deleting this gene resulted in defective hyphal growth in solid medium, while only a weak lag in the initiation of hyphal development and restoring hyphal growth during the hyphal maintenance phase under liquid conditions. Moreover, intracellular reactive oxygen species (ROS) assay and propidium iodide staining assays showed increased endogenous ROS levels and membrane permeability, but decreased metabolic activity of biofilm in orf19.5274Δ/Δ after treatment with FLC in comparison with either SC5314 or orf19.5274Δ/Δ::ORF19.5274 strains. More importantly, orf19.5274Δ/Δ significantly enhanced the FLC efficacy against C. albicans in infected Galleria mellonella larvae. The above characteristics were fully or partially restored in the complemented strain indicating that the changes caused by ORF19.5274 deletion were specific. In summary, the ORF19.5274 gene is required for hyphal development of C. albicans, and is correlated with the response to antifungal azoles in vitro and in vivo. The identification of ORF19.5275 is promising to expand the potential candidate targets for azoles.

GhHSP24.7 mediates mitochondrial protein acetylation to regulate stomatal conductance in response to abiotic stress in cotton

During seed germination, the cotton chaperone protein HSP24.7 regulates the release, from the mitochondrial electron transport chain, of reactive oxygen species (ROS), a stimulative signal regulating germination. The function of HSP24.7 during vegetative stages remains largely unknown. Here we propose that suppression of GhHSP24.7 in cotton seedlings increases tolerance to heat and drought stress. Elevation of GhHSP24.7 was found to be positively associated with endogenous levels of ROS. We identified a new client protein of GhHSP24.7, cotton lysine deacetylase (GhHDA14), which is involved in mitochondrial protein modification. Elevated levels of GhHSP24.7 suppressed deacetylase activity in mitochondria, leading to increased acetylation of mitochondrial proteins enriched in the subunit of F-type ATPase, V-type ATPase, and cytochrome C reductase, ultimately reducing leaf ATP content. Consequently, in combination with altered ROS content, GhHSP24.7 transgenic lines were unable to coordinate stomatal closure under stress. The regulation circuit composed of GhHSP24.7 and GhHDA14 represents a post-translation level mechanism in plant abiotic stress responses that integrates the regulation of ROS and ATP.

Ignored role of polyphenol in boosting reactive oxygen species generation for polyphenol/chemodynamic combination therapy.

Chemodynamic therapy (CDT) is a promising tumor-specific treatment, but still suffering insufficient reactive oxygen species (ROS) levels due to its limited efficacy of Fenton/Fenton-like reaction. Polyphenol, as a natural reductant, has been applied to promote the efficacy of Fenton/Fenton-like reactions; however, its intrinsic pro-apoptosis effects was ignored. Herein, a novel CDT/polyphenol-combined strategy was designed, based on Avenanthramide C-loaded dendritic mesoporous silica (DMSN)-Au/Fe3O4 nanoplatforms with folic acid modification for tumor-site targeting. For the first time, we showed that the nanocomplex (DMSNAF-AVC-FA) induced ROS production in the cytoplasm via Au/Fe3O4-mediated Fenton reactions and externally damaged the mitochondrial membrane; simultaneously, the resultant increased mitochondrial membrane permeability can facilitate the migration of AVC into mitochondrial, targeting the DDX3 pathway and impairing the electron transport chain (ETC) complexes, which significantly boosted the endogenous ROS levels inside the mitochondrial. Under the elevated oxidative stress level via both intra- and extra-mitochondrial ROS production, the maximum mitochondrial membrane permeability was achieved by up-regulation of Bax/Bcl-2, and thereby led to massive release of Cytochrome C and maximum tumor cell apoptosis via Caspase-3 pathway. As a result, the as-designed strategy achieved synergistic cytotoxicity to 4T1 tumor cells with the cell apoptosis rate of 99.12% in vitro and the tumor growth inhibition rate of 63.3% in vivo, while very minor cytotoxicity to normal cells with cell viability of 95.4%. This work evidenced that natural bioactive compounds are powerful for synergistically boosting ROS level, providing new insight for accelerating the clinical conversion progress of CDT with minimal side effects.

Effect of enzymatic pro-oxidant and antioxidant systems on bovine oocyte in vitro maturation

Abstract The role of reactive oxygen species (ROS) during oocyte in vitro maturation (IVM) is still controversial. Although an increase in ROS production may cause deleterious effects in cells, these reactive species may also act as signaling molecules influencing different cell functions. The aim of this study was to examine the effect of varying endogenous ROS levels during IVM on the process of bovine oocyte maturation. To do so, different enzymatic antioxidant (catalase, or superoxide dismutase + catalase, or diphenyl iodonium) or pro-oxidant systems (xanthine + xanthine oxidase, or xanthine + xanthine oxidase + catalase) were added to the culture medium. ROS levels were determined by 2′,7′-dichlorodihydrofluorescein diacetate stain, nuclear maturation was evaluated by the presence of the metaphase II chromosome configuration at 22h of IVM and cleavage rate was recorded 48h post- in vitro fertilization. ROS levels were only significantly increased (P<0.05) by the O2 .- generating system (xanthine + xanthine oxidase + catalase), but meiotic maturation rates were significantly lower (P<0.05) in all the evaluated systems compared with the control, except for the diphenyl iodonium group. However, this last group presented a significantly lower (P<0.05) cleavage rate in comparison to the control group. These results indicate that ROS would play an essential role during oocyte maturation, since its increase or decrease beyond a physiological level significantly reduced nuclear or cytoplasmic maturation rates in bovine oocytes.

Membrane disruption boosts iron overload and endogenous oxidative stress to inactivate Escherichia coli by nanoscale zero-valent iron

The inactivation of microorganisms by nanoscale zero-valent iron (nZVI) was extensively reported, but what happens inside the cells is rarely explored. Herein, we revealed that nZVI caused the drastic increase of intracellular iron concentrations, which subsequently catalyzed the Haber-Weiss reaction to produce high levels of endogenous reactive oxygen species (ROSs) and inactivated E. coli cells by oxidative damage of DNA, evidenced by the significantly higher inactivation efficiencies of E. coli mutant strains deficient in iron uptake regulation and DNA repair than the parental strain. The intracellular iron levels, endogenous ROSs levels and the inactivation efficiencies of E. coli were positively correlated. The permeabilized cytomembrane due to the close contact between nZVI and E. coli was responsible for the iron overload. This work demonstrates experimentally for the first time that nZVI causes iron overload and endogenous oxidative stress to inactivate E. coli, thus deepening our knowledge of the nZVI antimicrobial mechanism.

Endogenous ROS production in early differentiation state suppresses endoderm differentiation via transient FOXC1 expression

Oxidative stress plays a pivotal role in the differentiation and proliferation of cells and programmed cell death. However, studies on the role of oxidative stress in differentiation have mainly employed the detection of reactive oxygen species (ROS) during differentiation or generated by ROS inducers. Therefore, it is difficult to clarify the significance of endogenous ROS production in the differentiation of human cells. We developed a system to control the intracellular level of ROS in the initial stage of differentiation in human iPS cells. By introducing a specific substitution (I69E) into the SDHC protein, a component of the mitochondrial respiratory chain complex, the endogenous ROS level increased. This caused impaired endoderm differentiation of iPS cells, and this impairment was reversed by overproduction of mitochondrial-targeted catalase, an anti-oxidant enzyme. Expression of tumor-related FOXC1 transcription factor increased transiently as early as 4 h after ROS-overproduction in the initial stage of differentiation. Knockdown of FOXC1 markedly improved impaired endoderm differentiation, suggesting that endogenous ROS production in the early differentiation state suppresses endoderm differentiation via transient FOXC1 expression.

Hypomagnetic Field Induces the Production of Reactive Oxygen Species and Cognitive Deficits in Mice Hippocampus.

Previous studies have found that hypomagnetic field (HMF) exposure impairs cognition behaviors in animals; however, the underlying neural mechanisms of cognitive dysfunction are unclear. The hippocampus plays important roles in magnetoreception, memory, and spatial navigation in mammals. Therefore, the hippocampus may be the key region in the brain to reveal its neural mechanisms. We recently reported that long-term HMF exposure impairs adult hippocampal neurogenesis and cognition through reducing endogenous reactive oxygen species (ROS) levels in adult neural stem cells that are confined in the subgranular zone (SGZ) of the hippocampus. In addition to adult neural stem cells, the redox state of other cells in the hippocampus is also an important factor affecting the functions of the hippocampus. However, it is unclear whether and how long-term HMF exposure affects ROS levels in the entire hippocampus (i.e., the dentate gyrus (DG) and ammonia horn (CA) regions). Here, we demonstrate that male C57BL/6J mice exposed to 8-week HMF exhibit cognitive impairments. We then found that the ROS levels of the hippocampus were significantly higher in these HMF-exposed mice than in the geomagnetic field (GMF) group. PCR array analysis revealed that the elevated ROS levels were due to HMF-regulating genes that maintain the redox balance in vivo, such as Nox4, Gpx3. Since high levels of ROS may cause hippocampal oxidative stress, we suggest that this is another reason why HMF exposure induces cognitive impairment, besides the hippocampal neurogenesis impairments. Our study further demonstrates that GMF plays an important role in maintaining hippocampal function by regulating the appropriate endogenous ROS levels.

Ascorbic acid regulates mouse spermatogonial stem cell proliferation in a Wnt/β-catenin/ROS signaling dependent manner

Spermatogonial stem cells (SSCs) provide a foundation for spermatogenesis, but the mechanism of SSC proliferation is still poorly understood. To investigate whether and how ascorbic acid (AA) regulates the growth of mouse SSCs in vitro, the SSCs were cultured in different concentration AA medium for 14 days. The proliferation, apoptosis and the reactive oxygen species (ROS) levels of SSCs in different AA groups were respectively detected. Moreover, the SSC activity in 40 μg/mL AA group and the control was tested by a transplantation assay. To explore the mechanism of AA regulating mouse SSCs proliferation, the dishevelled homolog 2 (DVL2) and nucleoredoxin (NRX) protein levels, the expression of axis inhibition protein 2 (Axin2), leucine-rich G-protein coupled receptor 5 (Lgr5), B-cell lymphoma-2 (Bcl-2), BCL2-Associated X (Bax), c-myc and cyclin D1 genes in Wnt/β-catenin pathway were respectively confirmed. The results showed that the adding concentration of AA did not affect the main shape of SSCs. A 40 μg/mL AA in culture medium promoted the proliferation, and decreased the ROS production and apoptosis rate of SSCs. Moreover, colonization efficiency in the seminiferous tubules of the recipient testis in 40 μg/mL AA group was higher compared with the control group by a transplantation assay. Finally, the appropriate ROS in the 40 μg/mL AA group further adjust the levels of DVL2 and NRX protein in the Wnt/β-catenin pathway to maintain the nuclear intensity of β-catenin, in turn, the expression of apoptosis gene Bax decreased, while the expression of Bcl2, Axin2, Lgr5, c-myc and cyclin D1 genes increased. The study confirmed that AA adjusts the endogenous ROS level to impact on SSC proliferation in a dose-dependent manner by Wnt/β-catenin signaling pathway.

Sodium nitroprusside pretreatment alters responses of Chinese cabbage seedlings to subsequent challenging stresses

ABSTRACT Nitric oxide (NO) is a self-regulating gaseous molecule as well as an interacting partner with different reactive oxygen species (ROS). Endogenous NO increased, but hydrogen peroxide (H2O2) and superoxide radical anion () decreased in Chinese cabbage leaves treated with sodium nitroprusside (SNP) (0.5 mM). Antioxidant enzyme genes BrCat1, BrCat2, BrAPX, BrGR1, and BrGST1 expressions were transiently induced by the SNP (0.5 mM). Pretreated SNP (0.5 mM) enhanced tolerance to subsequent challenges by phytotoxic SNP (5 mM) and methyl viologen (MV) (50 μM), but accelerated cellular damage by H2O2 (4 M) shown by electrolyte leakage and lipid peroxidation. The SNP (0.5 mM) differentially modulated endogenous NO and ROS levels as well as antioxidant enzyme gene expressions by excess SNP, MV, and H2O2 stresses. These results suggest that NO as a signal molecule differentially interacts with challenging stresses in Chinese cabbage leaves, followed by differential cellular damage and antioxidant responses.

The Elevated Endogenous Reactive Oxygen Species Contribute to the Sensitivity of the Amphotericin B-Resistant Isolate of Aspergillus flavus to Triazoles and Echinocandins.

Aspergillus flavus has been frequently reported as the second cause of invasive aspergillosis (IA), as well as the leading cause in certain tropical countries. Amphotericin B (AMB) is a clinically important therapy option for a range of invasive fungal infections including invasive aspergillosis, and in vitro resistance to AMB was associated with poor outcomes in IA patients treated with AMB. Compared with the AMB-susceptible isolates of A. terreus, the AMB-resistant isolates of A. terreus showed a lower level of AMB-induced endogenous reactive oxygen species (ROS), which was an important cause of AMB resistance. In this study, we obtained one AMB-resistant isolate of A. flavus, with an AMB MIC of 32 μg/mL, which was sensitive to triazoles and echinocandins. This isolate presented elevated endogenous ROS levels, which strongly suggested that no contribution of decreased AMB-induced endogenous ROS for AMB-resistance, opposite to those observed in A. terreus. Further, we confirmed that the elevated endogenous ROS contributed to the sensitivity of the AMB-resistant A. flavus isolate to triazoles and echinocandins. Further investigation is needed to elucidate the causes of elevated endogenous ROS and the resistance mechanism to AMB in A. flavus.

Catalase Protects Biofilm of Staphylococcus aureus against Daptomycin Activity.

Daptomycin is recommended for the treatment of Staphylococcus aureus infections due to its bactericidal activity. However, its mechanism of action is poorly understood. The involvement of reactive oxygen species (ROS) in the bactericidal activity of daptomycin has been proved against planktonic S. aureus, but not against the biofilm of S. aureus. Therefore, we evaluated if ROS contributes to the effect of daptomycin against biofilm of S. aureus. Biofilms of wild type, catalase deficient and daptomycin-resistant S. aureus strains were grown in microtiter-plates. After three days, the biofilms were exposed to daptomycin with or without thiourea in the presence of a ROS indicator. After overnight incubation, the amount of ROS and the percentage of surviving bacteria were determined. The bacterial survival was higher and the amount of ROS was lower in the wild type than in the catalase deficient biofilm, demonstrating a protective effect of catalase against daptomycin. The induction of cytotoxic ROS formation by daptomycin was verified by the addition of thiourea, which reduced the amount of ROS and protected the wild type biofilm against high concentrations of daptomycin. Accordingly, only the highest concentration of daptomycin reduced the bacterial survival and increased the ROS formation in the resistant biofilm. In conclusion, daptomycin induced the production of cytotoxic levels of endogenous ROS in S. aureus biofilm and the presence of catalase protected the biofilm against the lethality of the induced ROS.

Long-term exposure to a hypomagnetic field attenuates adult hippocampal neurogenesis and cognition

Adult hippocampal neurogenesis contributes to learning and memory, and is sensitive to a variety of environmental stimuli. Exposure to a hypomagnetic field (HMF) influences the cognitive processes of various animals, from insects to human beings. However, whether HMF exposure affect adult hippocampal neurogenesis and hippocampus-dependent cognitions is still an enigma. Here, we showed that male C57BL/6 J mice exposed to HMF by means of near elimination of the geomagnetic field (GMF) exhibit significant impairments of adult hippocampal neurogenesis and hippocampus-dependent learning, which is strongly correlated with a reduction in the content of reactive oxygen species (ROS). However, these deficits seen in HMF-exposed mice could be rescued either by elevating ROS levels through pharmacological inhibition of ROS removal or by returning them back to GMF. Therefore, our results suggest that GMF plays an important role in adult hippocampal neurogenesis through maintaining appropriate endogenous ROS levels.

Human INCL fibroblasts display abnormal mitochondrial and lysosomal networks and heightened susceptibility to ROS-induced cell death.

Infantile Neuronal Ceroid Lipofuscinosis (INCL) is a pediatric neurodegenerative disorder characterized by progressive retinal and central nervous system deterioration during infancy. This lysosomal storage disorder results from a deficiency in the Palmitoyl Protein Thioesterase 1 (PPT1) enzyme—a lysosomal hydrolase which cleaves fatty acid chains such as palmitate from lipid-modified proteins. In the absence of PPT1 activity, these proteins fail to be degraded, leading to the accumulation of autofluorescence storage material in the lysosome. The underlying molecular mechanisms leading to INCL pathology remain poorly understood. A role for oxidative stress has been postulated, yet little evidence has been reported to support this possibility. Here we present a comprehensive cellular characterization of human PPT1-deficient fibroblast cells harboring Met1Ile and Tyr247His compound heterozygous mutations. We detected autofluorescence storage material and observed distinct organellar abnormalities of the lysosomal and mitochondrial structures, which supported previous postulations about the role of ER, mitochondria and oxidative stress in INCL. An increase in the number of lysosomal structures was found in INCL patient fibroblasts, which suggested an upregulation of lysosomal biogenesis, and an association with endoplasmic reticulum stress response. The mitochondrial network also displayed abnormal spherical punctate morphology instead of normal elongated tubules with extensive branching, supporting the involvement of mitochondrial and oxidative stress in INCL cell death. Autofluorescence accumulation and lysosomal pathologies can be mitigated in the presence of conditioned wild type media suggesting that a partial restoration via passive introduction of the enzyme into the cellular environment may be possible. We also demonstrated, for the first time, that human INCL fibroblasts have a heightened susceptibility to exogenous reactive oxygen species (ROS)-induced cell death, which suggested an elevated basal level of endogenous ROS in the mutant cell. Collectively, these findings support the role of intracellular organellar networks in INCL pathology, possibly due to oxidative stress.

Hydrogen peroxide and salinity stress act synergistically to enhance lipids production in microalga by regulating reactive oxygen species and calcium

The main purpose of the present study is to evaluate the effects of the combined salt stress and hydrogen peroxide (H2O2) treatment on the accumulation of lipids in Monoraphidium sp. QLY-1. Furthermore, to study the regulatory networks involved in the growth and development of microalgae, the relationships between reactive oxygen species (ROS), Ca2+ and mitogen-activated protein kinase (MAPK) under salinity stress were also analyzed. The results showed that the maximal lipid productivity (107.25 mg L−1 d−1) was achieved under combined 1 mM H2O2 and 171.12 mM (10 g L−1) NaCl treatment, which was 14.28% and 43.31% higher than the 171.12 mM NaCl treatment alone and the control, respectively. The protein content and levels of endogenous ROS, Ca2+ were increased and the expression levels of four lipogenic genes and MAPK were enhanced, while the contents of carbohydrate and chlorophyll were decreased under H2O2 and NaCl treatment. Further research indicated that the increased cytosolic Ca2+ level could alleviate the H2O2-induced oxidative stress under salinity stress by activating glutathione (GSH) activity and modulating calmodulin (CaM) and MAPK expression levels, resulting in biomass modulation and lipid accumulation. The present study provides an effective strategy to improve the lipid production in Monoraphidium sp. QLY-1 using combined H2O2 treatment with salinity stress, and offers evidence of crosstalk between ROS, Ca2+ in the regulation of cell growth and lipid synthesis in microalgae under abiotic stress.

A Photodynamic Tool to Promote a Sustained, ROS-Dependent Growth of Human Hair Follicles in Ex Vivo Culture.

Reactive oxygen species (ROS) may severely affect the biochemical viability of most cells. However, ROS may act also as key second messengers regulating important physiological functions in eukaryotic organisms. Of special interest is the potential role of ROS in the regulation of stem cell function and tissue homeostasis and regeneration in adult mammalian tissues. In this context, the hair follicle constitutes an excellent experimental model to study this aspect of ROS biology.Here we present a robust protocol to promote a sustained growth of ex vivo cultured human hair follicles based on the induction of a transient/modulable production of nonlethal endogenous ROS levels in the tissue through a protoporphyrin IX-dependent photodynamic procedure. The light-switchable ROS production activates hair follicle stem cell niches, induces cell proliferation, and maintains the growth/anagen phase for long time. This approach constitutes a complementary experimental tool to study the physiological roles of ROS in human tissues.