Sodium sulfite is a potential hypoxia inducer that mimics hypoxic stress in Caenorhabditis elegans

SUB1A-1 anchors a regulatory cascade for epigenetic and transcriptional controls of submergence tolerance in rice

Most rice (Oryza sativa) cultivars cannot survive under prolonged submergence. However, some O. sativa ssp. indica cultivars, such as FR13A, are highly tolerant owing to the SUBMERGENCE 1A-1 (SUB1A-1) allele, which encodes a Group VII ethylene-responsive factor (ERFVII) protein; other submergence-intolerant cultivars contain a SUB1A-2 allele. The two alleles differ only by a single substitution at the 186^th amino acid position from serine in SUB1A-1 to proline in SUB1A-2 resulting in only SUB1A-1 being able to be phosphorylated. Two other ERFVIIs, ERF66 and ERF67, function downstream of SUB1A-1 to form a regulatory cascade in response to submergence stress. Here, we show that SUB1A-1, but not SUB1A-2, interacts with ADA2b of the ADA2b-GCN5 acetyltransferase complex, in which GCN5 functions as a histone acetyltransferase. Phosphorylation of SUB1A-1 at serine 186 enhances the interaction of SUB1A-1 with ADA2b. ADA2b and GCN5 expression was induced under submergence, suggesting that these two genes might play roles in response to submergence stress. In transient assays, binding of SUB1A-1 to the ERF67 promoter and ERF67 transcription were highly induced when SUB1A-1 was expressed together with the ADA2b-GCN5 acetyltransferase complex. Taken together, these results suggest that phospho-SUB1A-1 recruits the ADA2-GCN5 acetyltransferase complex to modify the chromatin structure of the ERF66/ERF67 promoter regions and activate gene expression, which in turn enhances rice submergence tolerance.

Perfluorocarbon Nanoemulsions with Fluorous Chlorin-Type Photosensitizers for Antitumor Photodynamic Therapy in Hypoxia

The efficacy of photodynamic therapy (PDT) strictly depends on the availability of molecular oxygen to trigger the light-induced generation of reactive species. Fluorocarbons have an increased ability to dissolve oxygen and are attractive tools for gas delivery. We synthesized three fluorous derivatives of chlorin with peripheral polyfluoroalkyl substituents. These compounds were used as precursors for preparing nanoemulsions with perfluorodecalin as an oxygen depot. Therefore, our formulations contained hydrophobic photosensitizers capable of absorbing monochromatic light in the long wavelength region and the oxygen carrier. These modifications did not alter the photosensitizing characteristics of chlorin such as the generation of singlet oxygen, the major cytocidal species in PDT. Emulsions readily entered HCT116 colon carcinoma cells and accumulated largely in mitochondria. Illumination of cells loaded with emulsions rapidly caused peroxidation of lipids and the loss of the plasma membrane integrity (photonecrosis). Most importantly, in PDT settings, emulsions potently sensitized cells cultured under prolonged (8 weeks) hypoxia as well as cells after oxygen depletion with sodium sulfite (acute hypoxia). The photodamaging potency of emulsions in hypoxia was significantly more pronounced compared to emulsion-free counterparts. Considering a negligible dark cytotoxicity, our materials emerge as efficient and biocompatible instruments for PDT-assisted eradication of hypoxic cells.

Engineering Tools for Regulating Hypoxia in Tumour Models

Major advances in the field of genomic technologies have led to an improvement in cancer diagnosis, classification and prognostication. However, many cancers remain incurable due to the development of drug resistance, minimal residual disease (MRD) and disease relapse, highlighting an incomplete understanding of the mechanisms underlying these processes. In recent years, the impact of non-genetic factors on neoplastic transformations has increasingly been acknowledged, and growing evidence suggests that low oxygen (O2 ) levels (ie hypoxia) in the tumour microenvironment play a critical role in the development and treatment of cancer. As a result, there is a growing need to develop research tools capable of reproducing physiologically relevant O2 conditions encountered by cancer cells in their natural environments in order to gain in-depth insight into tumour cell metabolism and function. In this review, the authors highlight the importance of hypoxia in the pathogenesis of malignant diseases and provide an overview of novel engineering tools that have the potential to further drive this evolving, yet technically challenging, field of cancer research.

Sleep Analysis in Adult C. elegans Reveals State-Dependent Alteration of Neural and Behavioral Responses

Sleep, a state of quiescence associated with growth and restorative processes, is conserved across species. Invertebrates including the nematode Caenorhabditis elegans exhibit sleep-like states during development, satiety, and stress. Here, we describe behavior and neural activity during sleep and awake states in adult C. elegans hermaphrodites using new microfluidic methods. We observed effects of fluid flow, oxygen, feeding, odors, and genetic perturbations on long-term sleep behavior over 12 h. We developed a closed-loop sleep detection system to automatically deliver chemical stimuli to assess sleep-dependent changes to evoked neural responses in individual animals. Sleep increased the arousal threshold to aversive stimulation, yet the associated sensory neuron and first-layer interneuron responses were unchanged. This localizes adult sleep-dependent neuromodulation within interneurons presynaptic to the premotor interneurons, rather than afferent sensory circuits. However, sleep prolonged responses in appetitive chemosensory neurons, suggesting that sleep modulates responsiveness specifically across sensory systems rather than broadly damping global circuit activity.

SIGNIFICANCE STATEMENT Much is known about molecular mechanisms that facilitate sleep control. However, it is unclear how these pathways modulate neural circuit-level sensory processing or how misregulation of neural activity contributes to sleep disorders. The nematode Caenorhabditis elegans provides the ability to study neural circuitry with single-neuron resolution, and recent studies examined sleep states between developmental stages and when stressed. Here, we examine an additional form of spontaneous sleep in adult C. elegans at the behavioral and neural activity levels. Using a closed-loop system, we show that delayed behavioral responses to aversive chemical stimulation during sleep arise from sleep-dependent sensorimotor modulation localized presynaptic to the premotor circuit, rather than early sensory circuits.

A comparison between chemical and gas hypoxia as models of global ischemia in zebrafish (Danio rerio)

BACKGROUND

Zebrafish models for neurovascular diseases offer new methods for elucidation of molecular pathways to tissue damage. External fertilization and high fecundity provide opportunities for transgenics and other forms of genetic manipulation that are more accessible than offered by mammalian models of disease. Furthermore, behavioral analyses of zebrafish allow for connection of molecular pathways to organismal outputs such as locomotion, learning, and memory. Unfortunately, a zebrafish model of hypoxia-ischemia has been slow to catch on, possibly due to hypoxia exposure protocols that are challenging to reproduce and result in high mortality.

METHODS

In this study, we have introduced a predictable and simple method of hypoxia induction, the addition of sodium sulfite to aquarium water. The effects of this treatment on zebrafish locomotion were compared to those of zebrafish exposed to hypoxia induced by nitrogen gas bubbling, a method used in previous reports.

RESULTS

We found that hypoxia induced by sodium sulfite significantly impaired locomotion in the hours following treatment, and its effects did not differ from those caused by nitrogen gas hypoxia.

CONCLUSION

These results indicate that hypoxia by sodium sulfite represents an effective and easily reproducible method for the study of hypoxia-ischemia in zebrafish.

GABAergic system's Injuries Induced by Sodium Sulfite in Caenorhabditis elegans Were Prevented by the Anti-Oxidative Properties of Dehydroepiandrosterone Sulfate

Several pathophysiological processes involve Hypoxia conditions, where the nervous system is affected as well. We postulate that the GABAergic system is especially sensitive. Furthermore, drugs improving the resistance to hypoxia have been investigated, such as the neurosteroid dehydroepiandrosterone sulfate (DHEAS) which has shown beneficial effects in hypoxic processes in mammals; however, at the cellular level, its exact mechanism of action has yet to be fully elucidated. Here, we used a chemical hypoxia model through sodium sulfite (SS) exposure in Caenorhabditis elegans (C. elegans), a nematode whose response to hypoxia involves pathways and cellular processes conserved in mammals, and that allows study the direct effect of DHEAS without its conversion to sex hormones. This work aimed to determine the effect of DHEAS on damage to the GABAergic system associated with SS exposure in C. elegans. Worms were subjected to nose touch response (Not Assay) and observed in epifluorescence microscopy. DHEAS decreased the shrinkage response of Not Assay and the level of damage in GABAergic neurons on SS-exposed worms. Also, the enhanced nuclear localization of DAF-16 and consequently the overexpression of chaperone HSP-16.2 by hypoxia were significantly reduced in SS + DHEAS exposed worms. As well, DHEAS increased the survival rate of worms exposed to hydrogen peroxide. These results suggest that hypoxia-caused damage over the GABAergic system was prevented at least partially by DHEAS, probably through non-genomic mechanisms that involve its antioxidant properties related to its chemical structure.

DAF-16 and SMK-1 Contribute to Innate Immunity During Adulthood in Caenorhabditis elegans

Aging is accompanied by a progressive decline in immune function termed "immunosenescence". Deficient surveillance coupled with the impaired function of immune cells compromises host defense in older animals. The dynamic activity of regulatory modules that control immunity appears to underlie age-dependent modifications to the immune system. In the roundworm Caenorhabditis elegans levels of PMK-1 p38 MAP kinase diminish over time, reducing the expression of immune effectors that clear bacterial pathogens. Along with the PMK-1 pathway, innate immunity in C. elegans is regulated by the insulin signaling pathway. Here we asked whether DAF-16, a Forkhead box (FOXO) transcription factor whose activity is inhibited by insulin signaling, plays a role in host defense later in life. While in younger C. elegans DAF-16 is inactive unless stimulated by environmental insults, we found that even in the absence of acute stress the transcriptional activity of DAF-16 increases in an age-dependent manner. Beginning in the reproductive phase of adulthood, DAF-16 upregulates a subset of its transcriptional targets, including genes required to kill ingested microbes. Accordingly, DAF-16 has little to no role in larval immunity, but functions specifically during adulthood to confer resistance to bacterial pathogens. We found that DAF-16-mediated immunity in adults requires SMK-1, a regulatory subunit of the PP4 protein phosphatase complex. Our data suggest that as the function of one branch of the innate immune system of C. elegans (PMK-1) declines over time, DAF-16-mediated immunity ramps up to become the predominant means of protecting adults from infection, thus reconfiguring immunity later in life.

Progressive hypoxia-on-a-chip: An in vitro oxygen gradient model for capturing the effects of hypoxia on primary hepatocytes in health and disease

Oxygen is vital to the function of all tissues including the liver and lack of oxygen, that is, hypoxia can result in both acute and chronic injuries to the liver in vivo and ex vivo. Furthermore, a permanent oxygen gradient is naturally present along the liver sinusoid, which plays a role in the metabolic zonation and the pathophysiology of liver diseases. Accordingly, here, we introduce an in vitro microfluidic platform capable of actively creating a series of oxygen concentrations on a single continuous microtissue, ranging from normoxia to severe hypoxia. This range approximately captures both the physiologically relevant oxygen gradient generated from the portal vein to the central vein in the liver, and the severe hypoxia occurring in ischemia and liver diseases. Primary rat hepatocytes cultured in this microfluidic platform were exposed to an oxygen gradient of 0.3-6.9%. The establishment of an ascending hypoxia gradient in hepatocytes was confirmed in response to the decreasing oxygen supply. The hepatocyte viability in this platform decreased to approximately 80% along the hypoxia gradient. Simultaneously, a progressive increase in accumulation of reactive oxygen species and expression of hypoxia-inducible factor 1α was observed with increasing hypoxia. These results demonstrate the induction of distinct metabolic and genetic responses in hepatocytes upon exposure to an oxygen (/hypoxia) gradient. This progressive hypoxia-on-a-chip platform can be used to study the role of oxygen and hypoxia-associated molecules in modeling healthy and injured liver tissues. Its use can be further expanded to the study of other hypoxic tissues such as tumors as well as the investigation of drug toxicity and efficacy under oxygen-limited conditions.

Hypoxic pulmonary vasoconstriction is lacking in rats with type 1 diabetes

Hypoxic pulmonary vasoconstriction (HPV) is the most important feature of intact lung circulation that matches local blood perfusion to ventilation. The main goal of this work was to study the effects of diabetes on the development of HPV in rats. The experimental design comprised diabetes mellitus induction by streptozotocin, video-morphometric measurements of the lumen area of intrapulmonary arteries (iPAs) using perfused lung tissue slices and patch-clamp techniques. It was shown that iPA lumen size was significantly reduced under physical and chemical hypoxia (7-10 mm Hg) in normal iPA, but, on the contrary, it clearly increased in diabetic lung slices. The amplitude of the outward K⁺ current in diabetic iPAs smooth muscle cells (SMCs) was two-fold greater than that seen in healthy cells. Chemical hypoxia led to significant decrease in the amplitude of the K⁺ outward current in healthy iPA SMCs while it was without effect in diabetic cells. The data obtained clearly indicate a significant dysregulation of vascular tone in pulmonary circulation under diabetes, ie diabetes damages the adaptive mechanism for regulating blood flow from poorly ventilated to better ventilated regions of the lung under hypoxia. This effect could be clinically important for patients with diabetes who have acute or chronic lung diseases associated with the lack of blood oxygenation.

How does chronic temperature exposure affect hypoxia tolerance in sheepshead minnows' (Cyprinodon variegatus variegatus) ability to tolerate oxidative stress?

Estuarine environments are characterized by cyclical fluctuations in tides, with tidal shifts drastically, frequently, and acutely altering temperature, dissolved oxygen, and salinity. Despite these ecological challenges, the sheepshead minnow, Cyprinodon variegatus, seems to dominate estuarine landscapes. Here, we held sheepshead minnows to four temperature treatment groups for 1 month. We then tested whether temperature exposure had an effect on acute hypoxia tolerance via oxidative stress. We measured superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, as well as total antioxidant capacity and lipid peroxidation (LPO) damage in white muscle. We found that exposure to increasing temperatures (15, 20, 25, and 30 °C) for 1 month led to significantly higher CTmax in sheepshead minnows. We also found that CAT activity significantly increased in the 20 and 25 °C temperature treatment groups, whereas it did not change between control and hypoxia trials. SOD activity was significantly higher in control groups of the 15 and 30 °C temperature treatment groups compared with hypoxia groups of these same temperature treatments. GPx activity was significantly lower in the 30 °C temperature treatment group regardless of control or hypoxia trials. Hydroxyl scavenging capacity varied across temperature treatment and control/hypoxia groups. Peroxyl scavenging capacity and LPO damage showed no significant differences across temperature treatment groups or between control and hypoxia trials.

hif-1 plays a role in hypoxia-induced gustatory plasticity of Caenorhabditis elegans

Background: Hypoxia-inducible factor 1 (HIF-1) is a key transcription factor in the detection of low oxygen levels, inducing expression of genes involved in mediating the response to hypoxia to maintain cellular oxygen homeostasis. Caenorhabditis elegans is a soil nematode that has evolved specialized chemosensory neurons that detect changes in oxygen levels and guide its behaviour and responses to food. The role of the hif-1 gene in modifying chemosensory behaviour in response to chemical hypoxia however remains unclear. Furthermore, the role of epigenetic modifiers in mediating this behavioural response to hypoxia is unclear. Aims: Our study addresses two questions (a) Do hypoxia-mimetics modify worm behaviour and (b) Are these behaviours modulated by HIF-dependent expression of epigenetic regulators? Material and methods: This study used established behavioural paradigms in hif-1 mutant strains of C. elegans, to study responses to chemical hypoxia. Results: We show that exposure to the hypoxia-mimetic, sodium sulphite, changes the gustatory responses, chemotaxis, gustatory plasticity and associative conditioning behaviour. Longer-term exposure to hypoxia changes the behavioural response of wild type C. elegans, mediated by the HIF pathway. Epigenetic modifiers, lithium chloride and valproic acid, further modulate these behavioural responses.

Selenocysteine mimics the effect of dietary restriction on lifespan via SKN‑1 and retards age‑associated pathophysiological changes in Caenorhabditis elegans

Selenocysteine, a sulfur-containing amino acid, can modulate cellular oxidative stress defense systems by incorporating into anti-oxidant enzymes such as glutathione peroxidase and thioredoxin reductase. Selenocysteine can also prevent cancer, neurodegenerative diseases and cardiovascular diseases. A recent study revealed that dietary supplementation with selenocysteine can increase the resistance of Caenorhabditis elegans to environmental stressors and its lifespan. The objective of the present study was to identify the underlying mechanism involved in the lifespan-extending effect of selenocysteine and the effect of selenocysteine on age-associated pathophysiological changes. Lifespan assays with known long-lived mutants of age-1 (the ortholog of the phosphoinositide 3-kinase), clk-1 (the ortholog of demethoxyubiquinone hydroxylase) and eat-2 (a ligand-gated ion channel subunit) revealed that the effect of selenocysteine on lifespan specifically overlapped with that of the eat-2 mutation, a genetic model of dietary restriction (DR). Selenocysteine mimicked the effect of DR on the bacterial dilution method. It required SKN-1 (the ortholog of mammalian nuclear factor-erythroid-related factor) for lifespan extension. In addition, selenocysteine significantly delayed the paralysis induced by human amyloid-β gene, positively correlated with the incidence of Alzheimer's disease. The effect of selenocysteine on amyloid-β-induced toxicity was dependent on the nuclear localization of DAF-16. Reduced survival caused by high-glucose-diet was recovered by selenocysteine. Selenocysteine also reduced the cellular level of reactive oxygen species known to be increased by high-glucose-diet. The results of the present study suggested that selenocysteine can mimic the effect of DR on lifespan and age-associated pathophysiological alterations, providing scientific evidence for the development of DR mimetics using selenocysteine.

Comparative transcriptome analysis of the swimbladder reveals expression signatures in response to low oxygen stress in channel catfish, Ictalurus punctatus

Channel catfish is the leading aquaculture species in the US, and one of the reasons for its application in aquaculture is its relatively high tolerance against hypoxia. However, hypoxia can still cause huge economic losses to the catfish industry. Studies on hypoxia tolerance, therefore, are important for aquaculture. Fish swimbladder has been considered as an accessory respiration organ surrounded by a dense capillary countercurrent exchange system. In this regard, we conducted RNA-Seq analysis with swimbladder samples of catfish under hypoxic and normal conditions to determine if swimbladder was responsive to low oxygen treatment and to reveal genes, their expression patterns, and pathways involved in hypoxia responses in catfish. A total of 155 differentially expressed genes (DEGs) were identified from swimbladder of adult catfish, whereas a total of 2,127 DEGs were identified from swimbladder of fingerling catfish under hypoxic condition as compared with untreated controls. Subsequent pathway analysis revealed that many DEGs under hypoxia were involved in HIF signaling pathway ( nos2, eno2, camk2d2, prkcb, cdkn1a, eno1, and tfrc), MAPK signaling pathway (voltage-dependent calcium channel subunit genes), PI3K/Akt/mTOR signaling pathway ( itga6, g6pc, and cdkn1a), Ras signaling pathway ( efna3 and ksr2), and signaling by VEGF ( fn1, wasf3, and hspb1) in catfish swimbladder. This study provided insights into regulation of gene expression and their involved gene pathways in catfish swimbladder in response to low oxygen stresses.

Protective Effect of miR-374a on Chemical Hypoxia-Induced Damage of PC12 Cells In Vitro via the GADD45α/JNK Signaling Pathway

To explore the effect of microRNA-374a (miR-374a) on chemical hypoxia-induced pheochromocytoma (PC12) cell damage by mediating growth arrest and the DNA damage-45 alpha (GADD45α)/c-Jun N-terminal kinase (JNK) signaling pathway. PC12 cells were divided into a Control group (no treatment), Model group (treated with CoCl₂ for 24 h), negative control (NC) group (transfected with miR-374a negative control sequence and treated with CoCl₂ for 24 h), and miR-374a mimic group (transfected with miR-374a mimics and treated with CoCl₂ for 24 h). The viability and apoptosis of PC12 cells were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry, while the mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) content were assessed by Rh123 and dichloro-dihydro-fluorescein diacetate (DCFH-DA) methods. The expression of miR-374a and GADD45α/JNK proteins was detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. A significant decrease was found in the survival rate, MMP and miR-374a expression, while an increase was shown in the ROS content and GADD45α and p-JNK expression in hypoxic PC12 cells (all P < 0.05). A luciferase reporter gene assay demonstrated that GADD45α is the target gene of miR-374a. When transfected with miR-374a mimics, hypoxic PC12 cells showed an obvious elevation in survival rate and MMP but a great reduction in cell apoptosis and ROS content, as well as in the expression of GADD45α and p-JNK proteins (all P < 0.05). MiR-374a can protect PC12 cells against hypoxia-induced injury by inhibiting the GADD45α/JNK pathway, enhancing cell viability, suppressing oxidative stress, and inhibiting cell apoptosis, thereby becoming a potential therapeutic target for hypoxic damage.

Design considerations for open-well microfluidic platforms for hypoxic cell studies

Regions of hypoxia are common in solid tumors and are associated with enhanced malignancy, metastasis, and chemo/radio resistance. Real-time hypoxic cellular experimentation is challenging due to the constant need for oxygen control. Most microfluidic platforms developed thus far for hypoxic cell studies are burdened by complex design parameters and are difficult to use for uninitiated investigators. However, open-well microfluidic platforms enable short and long term hypoxic cell studies with an ease of use workflow. Specifically, open-well platforms enable manipulation and addition of cells, media, and reagents using a micropipette for hypoxic cell studies in tunable dissolved oxygen concentrations as low 0.3 mg/l. We analyzed design considerations for open-well microfluidic platforms such as media height, membrane thickness, and impermeable barriers to determine their effects on the amount of dissolved oxygen within the platform. The oxygen concentration was determined by experimental measurements and computational simulations. To examine cell behavior under controlled oxygen conditions, hypoxia-induced changes to hypoxia inducible factor activity and the mitochondrial redox environment were studied. A fluorescent reporter construct was used to monitor the stabilization of hypoxia inducible factors 1α and 2α throughout chronic hypoxia. Reporter construct fluorescence intensity inversely correlated with dissolved oxygen in the medium, as expected. Additionally, the glutathione redox poise of the mitochondrial matrix in living cancer cells was monitored throughout acute hypoxia with a genetically encoded redox probe and was observed to undergo a reductive response to hypoxia. Overall, these studies validate an easy to use open-well platform suitable for studying complex cell behaviors in hypoxia.

Survival assays using Caenorhabditis elegans

Caenorhabditis elegans is an important model organism with many useful features, including rapid development and aging, easy cultivation, and genetic tractability. Survival assays using C. elegans are powerful methods for studying physiological processes. In this review, we describe diverse types of C. elegans survival assays and discuss the aims, uses, and advantages of specific assays. C. elegans survival assays have played key roles in identifying novel genetic factors that regulate many aspects of animal physiology, such as aging and lifespan, stress response, and immunity against pathogens. Because many genetic factors discovered using C. elegans are evolutionarily conserved, survival assays can provide insights into mechanisms underlying physiological processes in mammals, including humans.

Inactivation of GABAA receptor is related to heat shock stress response in organism model Caenorhabditis elegans

The mechanisms underlying oxidative stress (OS) resistance are not completely clear. Caenorhabditis elegans (C. elegans) is a good organism model to study OS because it displays stress responses similar to those in mammals. Among these mechanisms, the insulin/IGF-1 signaling (IIS) pathway is thought to affect GABAergic neurotransmission. The aim of this study was to determine the influence of heat shock stress (HS) on GABAergic activity in C. elegans. For this purpose, we tested the effect of exposure to picrotoxin (PTX), gamma-aminobutyric acid (GABA), hydrogen peroxide, and HS on the occurrence of a shrinking response (SR) after nose touch stimulus in N2 (WT) worms. Moreover, the effect of HS on the expression of UNC-49 (GABAA receptor ortholog) in the EG1653 strain and the effect of GABA and PTX exposure on HSP-16.2 expression in the TJ375 strain were analyzed. PTX 1 mM- or H2O2 0.7 mM-exposed worms displayed a SR in about 80 % of trials. GABA exposure did not cause a SR. HS prompted the occurrence of a SR as did PTX 1 mM or H2O2 0.7 mM exposure. In addition, HS increased UNC-49 expression, and PTX augmented HSP-16.2 expression. Thus, the results of the present study suggest that oxidative stress, through either H2O2 exposure or application of heat shock, inactivates the GABAergic system, which subsequently would affect the oxidative stress response, perhaps by enhancing the activity of transcription factors DAF-16 and HSF-1, both regulated by the IIS pathway and related to hsp-16.2 expression.

miR-30e Blocks Autophagy and Acts Synergistically with Proanthocyanidin for Inhibition of AVEN and BIRC6 to Increase Apoptosis in Glioblastoma Stem Cells and Glioblastoma SNB19 Cells

Glioblastoma is the most common and malignant brain tumor in humans. It is a heterogeneous tumor harboring glioblastoma stem cells (GSC) and other glioblastoma cells that survive and sustain tumor growth in a hypoxic environment via induction of autophagy and resistance to apoptosis. So, a therapeutic strategy to inhibit autophagy and promote apoptosis could greatly help control growth of glioblastoma. We created hypoxia using sodium sulfite (SS) for induction of substantiated autophagy in human GSC and glioblastoma SNB19 cells. Induction of autophagy was confirmed by acridine orange (AO) staining and significant increase in Beclin-1 in autophagic cells. microRNA database (miRDB) search suggested that miR-30e could suppress the autophagy marker Beclin-1 and also inhibit the caspase activation inhibitors (AVEN and BIRC6). Pro-apoptotic effect of proanthocyanidin (PAC) has not yet been explored in glioblastoma cells. Combination of 50 nM miR-30e and 150 μM PAC acted synergistically for inhibition of viability in both cells. This combination therapy most effectively altered expression of molecules for inhibition of autophagy and induced extrinsic and intrinsic pathways of apoptosis through suppression of AVEN and BIRC6. Collectively, combination of miR-30e and PAC is a promising therapeutic strategy to inhibit autophagy and increase apoptosis in GSC and SNB19 cells.

Transient hypoxia reprograms differentiating adipocytes for enhanced insulin sensitivity and triglyceride accumulation

Objective

To investigate the impact of transient (2-4 h) hypoxia on metabolic reprogramming of adipocytes.

Methods

The impact of transient hypoxia on metabolic reprogramming was investigated in 3T3-L1 cells before and after differentiation. Glucose uptake, fatty acid oxidation, lipolysis, and mitochondria were examined to determine the hypoxia effects. Preadipocytes were exposed to transient hypoxia (4h/day) in the course of differentiation. Insulin sensitivity and TG accumulation was examined in the cells at the end of differentiation to determine the reprogramming effects. AMPK activity and gene expression were determined by quantitative RT-PCR and Western blotting in search for mechanism of the reprogramming.

Results

In acute response to hypoxia, adipocytes exhibited an increase in insulin-dependent and -independent glucose uptake. Fatty acid β-oxidation and pyruvate dehydrogenase (PDH) activity were decreased. Multiple exposures of differentiating adipocytes to transient hypoxia enhanced insulin signaling, TG accumulation, expression of antioxidant genes in differentiated adipocytes in the absence of hypoxia. The metabolic memory was associated with elevated AMPK activity and gene expression (GLUT1, PGC-1α, PPARγ, SREBP, NRF-1, ESRRα, LPL). The enhanced insulin sensitivity was blocked by an AMPK inhibitor.

Conclusions

Repeated exposure of differentiating adipocytes to transient hypoxia is able to reprogram the cells for increased TG accumulation and enhanced insulin sensitivity. The metabolic alterations were observed in post-differentiated cells under normoxia. The reprogramming involves AMPK activation and gene expression in the metabolic pathways in cytosol and mitochondria.

microRNA regulation of the embryonic hypoxic response in Caenorhabditis elegans

Layered strategies to combat hypoxia provide flexibility in dynamic oxygen environments. Here we show that multiple miRNAs are required for hypoxic survival responses during C. elegans embryogenesis. Certain miRNAs promote while others antagonize the hypoxic survival response. We found that expression of the mir-35 family is regulated by hypoxia in a HIF-1-independent manner and loss of mir-35-41 weakens hypoxic survival mechanisms in embryos. In addition, correct regulation of the RNA binding protein, SUP-26, a mir-35 family target, is needed for survival in chronic hypoxia. The identification of the full mRNA target repertoire of these miRNAs will reveal the miRNA-regulated network of hypoxic survival mechanisms in C. elegans.

Methods to study the tumor microenvironment under controlled oxygen conditions

The tumor microenvironment (TME) is a complex heterogeneous assembly composed of a variety of cell types and physical features. One such feature, hypoxia, is associated with metabolic reprogramming, the epithelial-mesenchymal transition, and therapeutic resistance. Many questions remain regarding the effects of hypoxia on these outcomes; however, only a few experimental methods enable both precise control over oxygen concentration and real-time imaging of cell behavior. Recent efforts with microfluidic platforms offer a promising solution to these limitations. In this review, we discuss conventional methods and tools used to control oxygen concentration for cell studies, and then highlight recent advances in microfluidic-based approaches for controlling oxygen in engineered platforms.

CoCl2-induced biochemical hypoxia down regulates activities and expression of super oxide dismutase and catalase in cerebral cortex of mice

Hypoxia-induced oxidative stress is one of the major hallmark reasons underlying brain dysfunction. In the present manuscript, we have used CoCl2-induced hypoxic mice to investigate alterations in the activities of chief antioxidative stress enzymes- superoxide dismutase (SOD) and catalase (CAT) and expression of their genes Sod1 and Cat in the cerebral cortex as this model has not been routinely used for carrying out such study. Hypoxia mimetic mice model was accordingly developed by oral CoCl2 administration to mice and validated by analyzing alterations in the expression of the hypoxia inducible factor gene Hif-1α and its immediate responsive genes. Our Western blot data demonstrated that a dose of 40 mg/kg BW of CoCl2 was able to generate hypoxia like condition in mice in which Hif-1α and its immediate responsive genes-glutamate transporter-1 (Slc2a1) and erythropoietin (Epo) expression were up regulated. Our in-gel assay data indicated that SOD and CAT activities significantly declined and it was associated with significant down regulation of Sod1 and Epo expression as evident from our semi quantitative RT-PCR and Western blot data, which might be correlated with up regulation of Hif-1α expression in the cerebral cortex of the CoCl2-treated hypoxic mice. Our findings suggest that CoCl2-induced hypoxic mouse model is useful for studying alterations in the anti oxidative enzymes and biochemical/molecular/neurobiological analysis of hypoxia-induced alterations in brain function.

Full toxicity assessment of Genkwa Flos and the underlying mechanism in nematode Caenorhabditis elegans

Genkwa Flos (GF), the dried flower bud from Daphne genkwa Sieb. et Zucc. (Thymelaeaceae), is a well-known and widely used traditional Chinese medicine. However, we know little about the in vivo mechanism of GF toxicity. Nematode Caenorhabditis elegans has been considered as a useful toxicity assay system by offering a system best suited for asking the in vivo questions. In the present study, we employed the prolonged exposure assay system of C. elegans to perform the full in vivo toxicity assessment of raw-processed GF. Our data show that GF exposure could induce the toxicity on lifespan, development, reproduction, and locomotion behavior. GF exposure not only decreased body length but also induced the formation of abnormal vulva. The decrease in brood size in GF exposed nematodes appeared mainly at day-1 during the development of adult nematodes. The decrease of locomotion behavior in GF exposed nematodes might be due to the damage on development of D-type GABAergic motor neurons. Moreover, we observed the induction of intestinal reactive oxygen species (ROS) production and alteration of expression patterns of genes required for development of apical domain, microvilli, and apical junction of intestine in GF exposed nematodes, implying the possible dysfunction of the primary targeted organ. In addition, GF exposure induced increase in defecation cycle length and deficits in development of AVL and DVB neurons controlling the defecation behavior. Therefore, our study implies the usefulness of C. elegans assay system for toxicity assessment from a certain Chinese medicine or plant extract. The observed toxicity of GF might be the combinational effects of oxidative stress, dysfunction of intestine, and altered defecation behavior in nematodes.

Adverse effects from clenbuterol and ractopamine on nematode Caenorhabditis elegans and the underlying mechanism

In the present study, we used Caenorhabditis elegans assay system to investigate in vivo toxicity from clentuberol and ractopamine and the possible underlying mechanism. Both acute and prolonged exposures to clentuberol or ractopamine decreased brood size and locomotion behavior, and induced intestinal autofluorescence and reactive oxygen species (ROS) production. Although acute exposure to the examined concentrations of clentuberol or ractopamine did not induce lethality, prolonged exposure to 10 µg/L of clentuberol and ractopamine reduced lifespan. At relatively high concentrations, ractopamine exhibited more severe toxicity than clentuberol on nematodes. Overexpression of sod-2 gene encoding a Mn-SOD to prevent induction of oxidative stress effectively inhibited toxicity from clentuberol or ractopamine. Besides oxidative stress, we found that clentuberol might reduce lifespan through influencing insulin/IGF signaling pathway; however, ractopamine might reduce lifespan through affecting both insulin/IGF signaling pathway and TOR signaling pathway. Ractopamine more severely decreased expression levels of daf-16, sgk-1, skn-1, and aak-2 genes than clentuberol, and increased expression levels of daf-2 and age-1 genes at the examined concentration. Therefore, the C. elegans assay system may be useful for assessing the possible toxicity from weight loss agents, and clentuberol and ractopamine may induce toxicity through different molecular mechanisms.

Beneficial effects of wheat gluten hydrolysate to extend lifespan and induce stress resistance in nematode Caenorhabditis elegans

Previous studies have showed that wheat gluten hydrolysate (WGH) has the anti-oxidative property. In the present study, we examined the possible safety property of WGH and the beneficial effects of WGH to extend lifespan and induce stress resistance using nematode Caenorhabditis elegans as the in vivo assay system. We found that WGH at concentrations of 0.1–1 mg/mL did not cause lethality, influence development, alter locomotion behavior and brood size, and induce significant intestinal autofluorescence and reactive oxygen species (ROS) production in young adults. Treatment with 0.1–1 mg/mL of WGH significantly extended lifespans of nematodes under the normal conditions. Moreover, WGH treatment significantly inhibited the induction of intestinal autofluorescence and suppressed the decrease in locomotion behavior during the aging process of nematodes. Furthermore, pre-treatment with 1 mg/mL of WGH significantly suppressed the adverse effects caused by heat-stress or oxidative stress on nematodes as indicated by the alterations of both lifespan and intestinal ROS production. Therefore, WGH treatment is relatively safe and has beneficial effects on nematodes under both the normal conditions and the stress conditions.

High concentration of vitamin E decreases thermosensation and thermotaxis learning and the underlying mechanisms in the nematode Caenorhabditis elegans

α-tocopherol is a powerful liposoluble antioxidant and the most abundant isoform of vitamin E in the body. Under normal physiological conditions, adverse effects of relatively high concentration of vitamin E on organisms and the underlying mechanisms are still largely unclear. In the present study, we used the nematode Caenorhabditis elegans as an in vivo assay system to investigate the possible adverse effects of high concentration of vitamin E on thermosensation and thermotaxis learning and the underlying mechanisms. Our data show that treatment with 100-200 µg/mL of vitamin E did not noticeably influence both thermosensation and thermotaxis learning; however, treatment with 400 µg/mL of vitamin E altered both thermosensation and thermotaxis learning. The observed decrease in thermotaxis learning in 400 µg/mL of vitamin E treated nematodes might be partially due to the moderate but significant deficits in thermosensation, but not due to deficits in locomotion behavior or perception to food and starvation. Treatment with 400 µg/mL of vitamin E did not noticeably influence the morphology of GABAergic neurons, but significantly decreased fluorescent intensities of the cell bodies in AFD sensory neurons and AIY interneurons, required for thermosensation and thermotaxis learning control. Treatment with 400 µg/mL of vitamin E affected presynaptic function of neurons, but had no remarkable effects on postsynaptic function. Moreover, promotion of synaptic transmission by activating PKC-1 effectively retrieved deficits in both thermosensation and thermotaxis learning induced by 400 µg/mL of vitamin E. Therefore, relatively high concentrations of vitamin E administration may cause adverse effects on thermosensation and thermotaxis learning by inducing damage on the development of specific neurons and presynaptic function under normal physiological conditions in C. elegans.

Construction of oxygen and chemical concentration gradients in a single microfluidic device for studying tumor cell-drug interactions in a dynamic hypoxia microenvironment

Recent microfluidic advancements in oxygen gradients have greatly promoted controllable oxygen-sensitive cellular investigations at microscale resolution. However, multi-gradient integration in a single microfluidic device for tissue-mimicking cell investigation is not yet well established. In this study, we describe a method that can generate oxygen and chemical concentration gradients in a single microfluidic device via the formation of an oxygen gradient in a chamber and a chemical concentration gradient between adjacent chambers. The oxygen gradient dynamics were systematically investigated, and were quantitatively controlled using simple exchange between the aerial oxygen and the oxygen-free conditions in the gas-permeable polydimethylsiloxane channel. Meanwhile, the chemical gradient dynamics was generated using a special channel-branched device. For potential medical applications of the established oxygen and chemical concentration gradients, a tumor cell therapy assessment was performed using two antitumor drugs (tirapazamine and bleomycin) and two tumor cell lines (human lung adenocarcinoma A549 cells and human cervical carcinoma HeLa cells). The results of the proof-of-concept experiment indicate the dose-dependent antitumor effect of the drugs and hypoxia-induced cytotoxicity of tirapazamine. We demonstrate that the integration of oxygen and chemical concentration gradients in a single device can be applied to investigating oxygen- and chemical-sensitive cell events, which can also be valuable in the development of multi-gradient generating procedures and specific drug screening.

Oxidative stress-related PMK-1 P38 MAPK activation as a mechanism for toxicity of silver nanoparticles to reproduction in the nematode Caenorhabditis elegans

In the present study, a toxic mechanism of silver nanoparticles (AgNPs) was investigated in the nematode, Caenorhabditis elegans, focusing on the involvement of oxidative stress in reproduction toxicity. Initially, AgNPs were tested as potential oxidative stress inducers, and increased formation of reactive oxygen species (ROS) was observed in AgNP-exposed C. elegans. Subsequently, the potential upstream signaling pathway activated in response to AgNP exposure was investigated, paying special attention to the C. elegans PMK-1 p38 mitogen-activated protein kinase (MAPK). Increased PMK-1 p38 MAPK gene and protein expressions were observed in C. elegans exposed to AgNPs. Expression of the p38-dependent transcription factor genes and glutathione S-transferase (GST) enzyme activity was also investigated in wildtype (N2) and pmk-1 mutant (km25) C. elegans exposed to AgNPs. The results indicated that AgNP exposure led to increased ROS formation, increased expression of PMK-1 p38 MAPK and hypoxia-inducible factor (HIF-1), GST enzyme activity, and decreased reproductive potential in wildtype (N2) C. elegans; whereas in the AgNP-exposed pmk-1 (km25) mutant, ROS formation and HIF-1 and GST activation were not observed, and decreased reproductive potential was rescued. These results suggest that oxidative stress is an important mechanism of AgNP-induced reproduction toxicity in C. elegans, and that PMK-1 p38 MAPK plays an important role in it. The results also suggest that GST and HIF-1 activation by AgNP exposure are PMK-1 p38 MAPK-dependent, and that both play an important role in the PMK-1 p38 MAPK-mediated defense pathway to AgNP exposure in C. elegans.

Glyceraldehyde-3-phosphate dehydrogenase: a universal internal control for Western blots in prokaryotic and eukaryotic cells

In the current study, we examined the expression level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein in a number of organisms and the stability of GAPDH under various conditions. Our results revealed that GAPDH is present in multiple Escherichia coli strains, the yeast strain GS115, Caenorhabditis elegans, rat PC12 cells, and both mouse and rat brain. Furthermore, GAPDH was stably expressed under different concentrations of inducer and at different times of induction in E. coli (BL21) cells and yeast GS115 cells. Stable expression of GAPDH protein was also observed in C.elegans and PC12 cells that were treated with different concentrations of paraquat or sodium sulfite, respectively. In addition, we were able to detect and identify the endogenous gapA protein in E.coli via immunoprecipitation and MALDI-TOF-MS analysis. Endogenous gapA protein and exogenously expressed (subcloned) GAPDH proteins were detected in E. coli BL21 but not for gapC. With the exception of gapC in E. coli, the various isoforms of GAPDH possessed enzymatic activity. Finally, sequence analysis revealed that the GAPDH proteins were 76% identical, with the exception of E. coli gapC. Taken together, our results indicate that GAPDH could be universally used as an internal control for the Western blot analysis of prokaryotic and eukaryotic samples.