Mitochondrial DNA damage and a hypoxic response are induced by CoCl(2) in rat neuronal PC12 cells

Differential effects of coverslip-induced hypoxia and cobalt chloride mimetic hypoxia on cellular stress, metabolism, and nuclear structure

Hypoxia has profound effects on cell physiology, both in normal or pathological settings like cancer. In this study, we asked whether a variant of coverslip-induced hypoxia that recapitulates the conditions found in the tumor microenvironment would elicit similar cellular responses compared to the well established model of cobalt chloride-induced hypoxia. Comparable levels of nuclear HIF-1α were observed after 24 h of coverslip-induced hypoxia or cobalt chloride treatment in CAL-27 oral squamous carcinoma cells. However, cellular stress levels assessed by reactive oxygen species production and lipid droplet accumulation were markedly increased in coverslip-induced hypoxia compared to cobalt chloride treatment. Conversely, mitochondrial ATP production sharply decreased after coverslip-induced hypoxia but was preserved in the presence of cobalt chloride. Coverslip-induced hypoxia also had profound effects in nuclear organization, assessed by changes in nuclear dry mass distribution, whereas these effects were much less marked after cobalt chloride treatment. Taken together, our results show that coverslip-induced hypoxia effects on cell physiology and structure are more pronounced than mimetic hypoxia induced by cobalt chloride treatment. Considering also the simplicity of coverslip-induced hypoxia, our results therefore underscore the usefulness of this method to recapitulate in vitro the effects of hypoxic microenvironments encountered by cells in vivo.

Investigating the association between blood cobalt and gallstones: a cross-sectional study utilizing NHANES data

Background

With the use of cobalt alloys in medical prosthetics, the risk of cobalt exposure has increased. The objective of this study was to investigate the correlation between blood cobalt levels and the occurrence of gallstones utilizing data from the National Health and Nutrition Examination Survey (NHANES).

Methods

Data collected between 2017 and 2020 were analyzed, encompassing a total of 5,610 participants. Cobalt concentrations in whole blood specimens were directly measured using inductively coupled plasma mass spectrometry (ICP-MS). The presence of gallstones was ascertained through a standardized questionnaire. To assess the association between blood cobalt levels and the presence of gallstones, logistic regression analysis, restricted cubic spline analysis, and subgroup analysis were utilized.

Results

The results of logistic regression analysis revealed a heightened risk of developing gallstones in the Quartiles 2 and Quartiles 4 groups based on blood cobalt levels when compared to the Quartiles 1 group (OR = 1.54, 95% CI: 1.15-2.07; OR = 1.35, 95% CI: 1.03-1.77). The restricted cubic spline analysis exhibited a positive linear correlation between blood cobalt levels and the occurrence of gallstones. Subgroup analyses further demonstrated a statistically significant correlation between the Quartiles 4 category of blood cobalt levels and an elevated risk of gallstones, particularly among individuals aged 60 years or older, females, those with a body mass index (BMI) equal to or exceeding 25, serum total cholesterol levels below 200 mg/dL, as well as individuals diagnosed with hypertension or diabetes.

Conclusion

Our study findings indicate a notable association between elevated blood cobalt levels and an increased risk of gallstones. To establish a causal relationship between blood cobalt levels and the elevated risk of developing gallstones, further prospective cohort studies are warranted.

IGF-I protects porcine granulosa cells from hypoxia-induced apoptosis by promoting homologous recombination repair through the PI3K/AKT/E2F8/RAD51 pathway

Severe hypoxia induced by vascular compromise (ovarian torsion, surgery), obliteration of vessels (aging, chemotherapy, particularly platinum drugs) can cause massive follicle atresia. On the other hand, hypoxia increases the occurrence of DNA double-strand breaks (DSBs) and triggers cellular damage repair mechanisms; however, if the damage is not promptly repaired, it can also induce the apoptosis program. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that plays essential roles in stimulating mammalian follicular development. Here, we report a novel role for IGF-I in protecting hypoxic GCs from apoptosis by promoting DNA repair through the homologous recombination (HR) process. Indeed, the hypoxic environment within follicles significantly inhibited the efficiency of HR-directed DNA repair. The presence of IGF-I-induced HR pathway to alleviate hypoxia-induced DNA damage and apoptosis primarily through upregulating the expression of the RAD51 recombinase. Importantly, we identified a new transcriptional regulator of RAD51, namely E2F8, which mediates the protective effects of IGF-I on hypoxic GCs by facilitating the transcriptional activation of RAD51. Furthermore, we demonstrated that the PI3K/AKT pathway is crucial for IGF-I-induced E2F8 expression, resulting in increased RAD51 expression and enhanced HR activity, which mitigates hypoxia-induced DNA damage and thereby protects against GCs apoptosis. Together, these findings define a novel mechanism of IGF-I-mediated GCs protection by activating the HR repair through the PI3K/AKT/E2F8/RAD51 pathway under hypoxia.

Lauric Acid Overcomes Hypoxia-Induced Gemcitabine Chemoresistance in Pancreatic Ductal Adenocarcinoma

Although gemcitabine (GEM) is widely used in chemotherapy for pancreatic ductal adenocarcinoma (PDA), drug resistance restricts its clinical effectiveness. To examine the mechanism of GEM resistance, we established two GEM-resistant cell lines from human PDA cells by continuous treatment with GEM and CoCl₂-induced chemical hypoxia. One resistant cell line possessed reduced energy production and decreased mitochondrial reactive oxygen species levels, while the other resistant cell line possessed increased stemness. In both cell lines, ethidium bromide-stained mitochondrial DNA levels decreased, suggesting mitochondrial DNA damage. Inhibition of hypoxia-inducible factor-1α in both cell lines did not restore the GEM sensitivity. In contrast, treatment of both cell types with lauric acid (LAA), a medium-chain fatty acid, restored GEM sensitivity. These results suggest that decreased energy production, decreased mitochondrial reactive oxygen species levels, and increased stemness associated with mitochondrial damage caused by GEM lead to GEM resistance, and that hypoxia may promote this process. Furthermore, forced activation of oxidative phosphorylation by LAA could be a tool to overcome GEM resistance. Clinical verification of the effectiveness of LAA in GEM resistance is necessary in the future.

Indole-3-carbinol ameliorated the neurodevelopmental deficits in neonatal anoxic injury in rats

Neonatal anoxia is linked to long-lasting neurodevelopmental deficits. Due to the lack of pharmacological intervention to treat neonatal anoxia, there is interest in finding new molecules for its treatment. Indole-3-carbinol (I3C) has shown neuroprotective effects in some disease conditions. However, the neuroprotective role of I3C in neonatal anoxia has not been explored. Consequently, we have investigated the effect of I3C on neonatal anoxia-induced brain injury and neurodevelopmental deficits. Rat pups after 30 h of birth were subjected to two episodes of anoxia (10 min in each) at a time interval of 24 h by flowing 100% nitrogen. I3C was administered within 30 min of the second episode of anoxia on a postnatal day (PND) 3 and continued for PND 9. Neurodevelopmental deficits, cortical mitochondrial membrane potential (MMP), opening of mitochondrial permeability transition pore (MPTP), electron transport chain (ETC) enzyme activities, oxidative stress, hypoxia-inducible factor-1α (HIF-1α) levels, histopathological changes, and apoptosis were measured. I3C treatment dose-dependently ameliorated the neurodevelopmental deficits and somatic growth in anoxic pups. I3C improved mitochondrial function by enhancing the MMP, mitochondrial ETC enzymes, and antioxidants. It blocked the MPTP opening and release of cytochrome C in anoxic pups. Further, I3C reduced the elevated cortical HIF-1α in neonatal anoxic pups. Furthermore, I3C ameliorated histopathological abnormalities and mitochondrial-mediated apoptotic indicators Cyt C, caspase-9, and caspase-3. Our study concludes that I3C improved neuronal development in anoxic pups by enhancing mitochondrial function, reducing HIF-1α, and mitigating apoptosis.

Myricetin attenuates hypoxic-ischemic brain damage in neonatal rats via NRF2 signaling pathway

Introduction: Hypoxic-ischemic encephalopathy (HIE) is a crucial cause of neonatal death and neurological sequelae, but currently there is no effective therapy drug for HIE. Both oxidative stress and apoptosis play critical roles in the pathological development of HIE. Myricetin, a naturally extracted flavonol compound, exerts remarkable effects against oxidative stress, apoptosis, and inflammation. However, the role and underlying molecular mechanism of myricetin on HIE remain unclear. Methods: In this study, we established the neonatal rats hypoxic-ischemic (HI) brain damage model in vivo and CoCl₂ induced PC1₂ cell model in vitro to explore the neuroprotective effects of myricetin on HI injury, and illuminate the potential mechanism. Results: Our results showed that myricetin intervention could significantly reduce brain infarction volume, glia activation, apoptosis, and oxidative stress marker levels through activating NRF2 (Nuclear factor-E2-related factor 2) and increase the expressions of NRF2 downstream proteins NQO-1 and HO-1. In addition, the NRF2 inhibitor ML385 could significantly reverse the effects of myricetin. Conclusion: This study found that myricetin might alleviate oxidative stress and apoptosis through NRF2 signaling pathway to exert the protective role for HI injury, which suggested that myricetin might be a promising therapeutic agent for HIE.

Cobalt-mediated oxidative DNA damage and its prevention by polyphenol antioxidants

Although cobalt is a required nutrient, it is toxic due to its ability to generate reactive oxygen species (ROS) and damage DNA. ROS generation by Co²⁺ often has been compared to that of Fe²⁺ or Cu⁺, disregarding the reduction potential differences among these metal ions. In plasmid DNA damage studies, a maximum of 15% DNA damage is observed with Co²⁺/H₂O₂ treatment (up to 50 μM and 400 μM, respectively) significantly lower than the 90% damage observed for Fe²⁺/H₂O₂ or Cu⁺/H₂O₂ treatment. However, when ascorbate is added to the Co²⁺/H₂O₂ system, a synergistic effect results in 90% DNA damage. DNA damage by Fe²⁺/H₂O₂ can be prevented by polyphenol antioxidants, but polyphenols both prevent and promote DNA damage by Cu⁺/H₂O₂. When tested for cobalt-mediated DNA damage affects, eight of ten polyphenols (epicatechin gallate, epigallocatechin gallate, propyl gallate, gallic acid, methyl-3,4,5-trihydroxybenzoate, methyl-4,5-dihydroxybenzoate, protocatechuic acid, and epicatechin) prevent cobalt-mediated DNA damage with IC₅₀ values of 1.3 to 27 μM and two (epigallocatechin and vanillic acid) prevent little to no DNA damage. EPR studies demonstrate cobalt-mediated formation of ^•OH, O₂^•-, and ^•OOH, but not ¹O₂ in the presence of H₂O₂ and ascorbate. Epigallocatechin gallate and methyl-4,5-dihydroxybenzoate significantly reduce ROS generated by Co²⁺/H₂O₂/ascorbate, consistent with their prevention of cobalt-mediated DNA damage. Thus, while cobalt, iron, and copper are all d-block metal ions, cobalt ROS generation and its prevention is significantly different from that of iron and copper.

Pd(II) Binding Strength of a Novel Ambidentate Dipeptide-Hydroxypyridinonate Ligand: A Solution Equilibrium Study

A novel ambidentate dipeptide conjugate (H(L1)) containing N-donor atoms of the peptide part and an (O,O) chelate at the hydroxypyridinone (HP) ring is synthesized and characterized. It is hoped that this chelating ligand can be useful to obtain multitargeted Co(III)/Pt(II) dinuclear complexes with anticancer potential. The Pd(II) (as a Pt(II) model but with faster ligand exchange reactions) binding strength of the ligand was studied in an aqueous solution with the combined use of pH-potentiometry and NMR. In an equimolar solution, (L1)⁻ was found to bind Pd(II) via the terminal amino and increasing number of peptide nitrogens of the peptide backbone over a wide pH range. At a 2:1 Pd(II) to ligand ratio, the presence of [Pd₂H_–x(L1)] (x = 1–4) species, with high stability and with the coordination of the (O,O) chelating set of the ligand, was detected. The reaction of H(L1) with [Co(tren)]³⁺ (tren = tris(2-aminoethyl)amine) indicated the exclusive binding of (L1)⁻ via its (O,O) donor atoms to the metal unit, while treatment of the resulting Co-complex with Pd(II) afforded the formation of a Co/Pd heterobimetallic complex in solution with an (NH₂, N_amide) coordination of Pd(II). Shortening the peptide backbone in H(L1) by one peptide unit compared to the structurally similar ambidentate chelator consisting of three peptide bonds resulted in the slightly more favorable formation of the N-coordinated Pd(II) species, allowing the tailoring of the coordination properties.

Berberine Influences the Survival of Fat Grafting by Inhibiting Autophagy and Apoptosis of Human Adipose Derived Mesenchymal Stem Cells

Objective

Human adipose-derived mesenchymal stem cells (ADSCs) have the potential to be applied to solid organ treatments. However, tissue regeneration is limited by the death of transplanted cells. Ischemia is the main cause of the poor outcome. This study aimed to investigate the effect of berberine (BBR) on ADSCs after fat grafting.

Methods

The antioxidant BBR on apoptosis and autophagy of ADSCs in vitro ischemia model was induced by hypoxia and serum deprivation (HY/SD). The autophagy promoter rapamycin and autophagy inhibitor 3-MA were incubated separately to investigate the crosstalk between autophagy and apoptosis. Pathway inhibitors further verified whether the autophagy and apoptosis were regulated by AMPK/mTor signaling pathway. Fat survival, fibrosis, level of inflammatory cell infiltration, and the effect of angiogenesis after BBR treatment were observed in vivo.

Results

BBR could reduce ROS production and reverse the decreasing cell survival rate. HY/SD would induce apoptosis and autophagy in ADSCs, and BBR could alleviate these processes. After interfering with the level of autophagy, we also proved that apoptosis was regulated by autophagy and changed accordingly. The results also indicated that BBR could protect against autophagy and apoptosis of ADSCs through AMPK/mTor pathway. The treated human-derived adipose tissue was transplanted into BALB/c nude mice, and with the intervention of BBR, the fat grafting had a higher survival rate, lower inflammatory cell infiltration and fibrosis level.

Conclusion

Our present study revealed that BBR was a promising anti-autophagy and apoptosis agent for improving the survival rate of ADSCs during cell transplantation.

Drp-1-Dependent Mitochondrial Fragmentation Contributes to Cobalt Chloride-Induced Toxicity in Caenorhabditis elegans

Excess cobalt may lead to metallosis, characterized by sensorineural hearing loss, visual, and cognitive impairment, and peripheral neuropathy. In the present study, we sought to address the molecular mechanisms of cobalt-induced neurotoxicity, using Caenorhabditis elegans as an experimental model. Exposure to cobalt chloride for 2 h significantly decreased the survival rate and lifespan in nematodes. Cobalt chloride exposure led to increased oxidative stress and upregulation of glutathione S-transferase 4. Consistently, its upstream regulator skn-1, a mammalian homolog of the nuclear factor erythroid 2-related factor 2, was activated. Among the mRNAs examined by quantitative real-time polymerase chain reactions, apoptotic activator egl-1, proapoptotic gene ced-9, autophagic (bec-1 and lgg-1), and mitochondrial fission regulator drp-1 were significantly upregulated upon cobalt exposure, concomitant with mitochondrial fragmentation, as determined by confocal microscopy. Moreover, drp-1 inhibition suppressed the cobalt chloride-induced reactive oxygen species generation, growth defects, and reduced mitochondrial fragmentation. Our novel findings suggest that the acute toxicity of cobalt is mediated by mitochondrial fragmentation and drp-1 upregulation.

High concentration of blood cobalt is associated with the impairment of blood-brain barrier permeability

Excess heavy metals can lead to many kinds of adverse effects in human. The present study is designed to investigate whether the internal excess burden of heavy metals relate to the disturbance of the Blood-brain-barrier (BBB) and oxidative stress (OS) in subjects, and identify specific metallic constituents responsible for the disturbance. We collected the blood from recruited 122 subjects for our comparison study, 69 were living at an area near e-waste dismantling factories (exposed group), who have higher levels of heavy metals in the body; and others were in a chosen reference area (reference group), who were the general residents in city, in December 2017 in Taizhou, Zhejiang province. The analyses showed that the concentrations of altogether 4 metals, including nickel (Ni), cobalt (Co), mercury (Hg) and stannum (Sn), and the triggers of BBB disruption (Apolipoprotein E4 and matrix-metalloproteinase-9), indicators of BBB (Myelin basic protein, serotonin and dopamine) and biomarkers of OS (Malondialdehyde and 8-isoprostane) were statistically significant higher in exposed group than in reference group. Moreover, they are also significantly positively correlated with each other. Among all the metals, both Pearson correlation and multiple linear regression showed Co was positive correlated with almost all biomarkers. Considering the explicit correlation between Co and BBB permeability, we speculated that high burden of Co in blood may have a connection with neurodegenerative diseases, which propose a requirement for constructing the environmental criteria for Co and might provide a potential new hint for the intervention of dementia.

Pd(ii)-Complexes of a novel pyridinone based tripeptide conjugate: solution and solid state studies

A novel peptide conjugate (H(L2)) incorporating N-donors of the peptide backbone and an (O,O) donor set of a hydroxypyridinone moiety is synthesized and characterized. This ambidentate chelating ligand is intended to develop Co(iii)/Pt(ii) heterobimetallic multitargeted complexes with anticancer potential. To explore its metal ion binding ability the interaction with Pd(ii) (as a Pt(ii) model but with faster ligand exchange reactions) was studied in aqueous solution by the combined use of pH-potentiometry, NMR and HR MS. In an equimolar solution H(L2) was found to bind Pd(ii) via the terminal amino group and increasing number of peptide nitrogens of the peptide backbone over a wide pH range. Around physiological pH an (N,N) and (O,O) chelated 2 : 2 minor species was also identified. At a 2 : 1 Pd(ii) to ligand ratio the formation of dinuclear species, [Pd2H-x(L2)] (x = 1-4), with high stability and with the involvement of the (O,O) chelating set of the ligand too, was demonstrated. Reaction of H3(L2)2+ with Pd(ii) in the presence of chloride ions at pH ∼ 2.0 afforded [PdH(L2)Cl2]·2H2O (3) in a solid state whose molecular structure was assessed by single crystal X-ray diffraction. The structure of 3 revealed that Pd(ii) is coordinated by a (NH2, Namide) chelate of the ligand in a square planar fashion. It also indicates that under suitable conditions a 2N coordinated Pd(ii) complex can also be obtained even in the presence of four available nitrogen donors in the chelatable position in the ligand most likely due to its neutral charge and the decreased conditional stability of the amide-involved chelate(s) under acidic conditions. Reaction of H(L2) with [Co(tren)]3+ (tren = tris(2-aminoethyl)amine) revealed the exclusive coordination of (L2)-via its (O,O) chelate to the metal core while treatment of the Co-complex with Pd(ii) resulted in the formation of a Co/Pd heterobimetallic complex in solution with (NH2, Namide) chelated Pd(ii). Reaction of 3 with 9-methylguanine indicated the N7 coordination of this simple DNA model to Pd(ii) in a 1 : 1 ratio.

Effect of the replacement of tripodal 4N donors by two 2N chelators on the redox and cytotoxic activity of maltolato and deferipronato containing Co(III) complexes

Fourteen novel Co^III ternary complexes with the general formula [Co(4N)(2O)]X₂ or [Co(2N)₂(2O)]X₂ where 4N = tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa); 2N = 1,10-phenantroline (phen), 2,2'-bipyridine (bipy), 1,2-diaminoethane (en) or 2-(aminomethyl)pyridine (ampy) and 2O = 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone (dhpH), 3-hydroxy-2-methyl-4-pyrone (maltH) or 2-ethyl-3-hydroxy-4H-pyran-4-one (etmaltH) were synthesized, characterized and their redox features explored. Molecular structure of some selected [Co(2N)₂(2O)](ClO₄)₂ (2N = phen, bipy, en; 2O = dhp, malt) or [Co(4N)(2O)](ClO₄)₂ (4N = tpa; 2O = etmalt) type complexes were assessed by X-ray diffraction and showed the expected octahedral geometry. Replacement of the 4N donor ligands by two 2N donor ligands resulted in the decrease of the cathodic peak potential of the complexes indicating easier reduction and allowing therefore the tailoring of the redox properties of the complexes. Screening of selected compounds against a human derived cancer cell line, HeLa, showed that, unlike the [Co(4N)(2O)]X₂ derivatives, the complexes containing 2N = bipy or phen ligands have better anticancer activity than cisplatin or carboplatin.

Visualization of O2/ATP cross-talk in living cells with a smart fluorescent nanoprobe

Herein, we propose a dual-responsive fluorescent nanoprobe to visualize the cross-talk between O2 and adenosine triphosphate (ATP) in living cells. We hope it will be a helpful tool for the further understanding of cellular metabolism and further facilitating risk warning in the process of adaptation to consistent environmental pressures in premalignant lesions.

Role of environmental pollutants in Alzheimer's disease: a review

Neurodegenerative disorders are commonly erratic influenced by various factors including lifestyle, environmental, and genetic factors. In recent observations, it has been hypothesized that exposure to various environmental factors enhances the risk of Alzheimer's disease (AD). The exact etiology of Alzheimer's disease is still unclear; however, the contribution of environmental factors in the pathology of AD is widely acknowledged. Based on the available literature, the review aims to culminate in the prospective correlation between the various environmental factors and AD. The prolonged exposure to the various well-known environmental factors including heavy metals, air pollutants (particulate matter), pesticides, nanoparticles containing metals, industrial chemicals results in accelerating the progression of AD. Common mechanisms have been documented in the field of environmental contaminants for enhancing amyloid-β (Aβ) peptide along with tau phosphorylation, resulting in the initiation of senile plaques and neurofibrillary tangles, which results in the death of neurons. This review offers a compilation of available data to support the long-suspected correlation between environmental risk factors and AD pathology. Graphical abstract .

Synthesis and identification of a novel derivative of salidroside as a selective, competitive inhibitor of monoamine oxidase B with enhanced neuroprotective properties

Salidroside [(2R,3S,4S,5R,6R)-2-(hydroxymethyl)-6-(4-hydroxyphenethoxy)tetrahy-dro-2H-pyran-3,4,5-triol] is an antioxidant, anti-inflammatory and neuroprotective agent, but its drug-like properties are unoptimized and its mechanism of actions is uncertain. We synthesized twenty-six novel derivatives of salidroside and examined them in CoCl₂-treated PC12 cells using MTT assay. pOBz, synthesized by esterifying the phenolic hydroxyl group of salidroside with benzoyl chloride, was one of five derivatives that were more cytoprotective than salidroside, with an EC₅₀ of 0.038 μM versus 0.30 μM for salidroside. pOBz was also more lipophilic, with log P of 1.44 versus -0.89 for salidroside. Reverse virtual docking predicted that pOBz would bind strongly with monoamine oxidase (MAO) B by occupying its entrance and substrate cavities, and by interacting with the inter-cavity gating residue Ile199 and Tyr435 of the substrate cavity. Enzymatic studies confirmed that pOBz competitively inhibited the activity of purified human MAO-B (K_i = 0.041 μM versus K_i = 0.92 μM for salidroside), and pOBz was highly selective for MAO-B over MAO-A. In vivo, pOBz inhibited cerebral MAO activity after middle cerebral artery occlusion with reperfusion in rats, and it reduced cerebral infarct volume, improved neurological function and NeuN expression, and inhibited complement C3 expression and apoptosis. Our results suggest that pOBz is a structurally novel type of competitive and selective MAO-B inhibitor, with potent neuroprotective properties after cerebral ischemia-reperfusion injury in rats.

Cancer cell migration and cancer drug screening in oxygen tension gradient chip

Cancer metastasis, which is prevalent in malignant tumors, is present in a variety of cases depending on the primary tumor and metastatic site. The cancer metastasis is affected by various factors that surround and constitute a tumor microenvironment. One of the several factors, oxygen tension, can affect cancer cells and induce changes in many ways, including motility, directionality, and viability. In particular, the oxygen tension gradient is formed within a tumor cluster and oxygen is lower toward the center of the cluster from the perivascular area. The simple and efficient designing of the tumor microenvironment using microfluidic devices enables the simplified and robust platform of the complex in vivo microenvironment while observing a clear cause-and-effect between the properties of cancer cells under oxygen tension. Here, a microfluidic device with five channels including a gel channel, media channels, and gas channels is designed. MDA-MB-231cells are seeded in the microfluidic device with hydrogel to simulate their three-dimensional movement in the body. The motility and directionality of the cancer cells under the normoxic and oxygen tension gradient conditions are compared. Also, the viability of the cancer cells is analyzed for each condition when anticancer drugs are applied. Unlike the normoxic condition, under the oxygen tension gradient, cancer cells showed directionality toward higher oxygen tension and decreased viability against the certain anticancer drug. The simplified design of the tumor microenvironment through microfluidic devices enables comprehension of the response of cancer cells to varying oxygen tensions and cancer drugs in the hypoxic tumor microenvironment.

Polycyclic aromatic hydrocarbon and hypoxia exposures result in mitochondrial dysfunction in zebrafish

Organisms are routinely subjected to a variety of environmental and chemical perturbations simultaneously. Often, multi-stressor exposures result in unpredictable toxicity that occurs through unidentified mechanisms. Here, we focus on polycyclic aromatic hydrocarbons (PAHs) and hypoxia, two environmental and physiological stressors that are known to co-occur in the environment. The aim of this study was to assess whether interactive mitochondrial dysfunction resulted from co-exposures of PAHs and hypoxia. Zebrafish embryos were co-exposed to non-teratogenic concentrations of an environmental PAH mixture and hypoxia beginning at 6 hpf for an acute period of 24 h and afterwards were given either no recovery period, 45 min, 5 -hs, or 18 -hs of recovery time in clean conditions. Mitochondrial function and integrity were assessed through the use of both in ovo and in vitro assays. Hypoxia exposures resulted in drastic reductions in parameters relating to mitochondrial respiration, ATP turnover, and mitochondrial DNA integrity. PAH exposures affected ATP production and content, as well as mitochondrial membrane dynamics and lactate content. While PAH and hypoxia exposures caused a broad range of effects, there appeared to be very little interaction between the two stressors in the co-exposure group. However, because hypoxia significantly altered mitochondrial function, the possibility remains that these effects may limit an individual's ability to respond to PAH toxicity and therefore could cause downstream interactive effects.

NO/cGMP/PKG activation protects Drosophila cells subjected to hypoxic stress

The anoxia-tolerant fruit fly, Drosophila melanogaster, has routinely been used to examine cellular mechanisms responsible for anoxic and oxidative stress resistance. Nitric oxide (NO), an important cellular signaling molecule, and its downstream activation of cGMP-dependent protein kinase G (PKG) has been implicated as a protective mechanism against ischemic injury in diverse animal models from insects to mammals. In Drosophila, increased PKG signaling results in increased survival of animals exposed to anoxic stress. To determine if activation of the NO/cGMP/PKG pathway is protective at the cellular level, the present study employed a pharmacological protocol to mimic hypoxic injury in Drosophila S2 cells. The commonly used S2 cell line was derived from a primary culture of late stage (20-24 h old) Drosophila melanogaster embryos. Hypoxic stress was induced by exposure to either sodium azide (NaN₃) or cobalt chloride (CoCl₂). During chemical hypoxic stress, NO/cGMP/PKG activation protected against cell death and this mechanism involved modulation of downstream mitochondrial ATP-sensitive potassium ion channels (mitoK_ATP). The cellular protection afforded by NO/cGMP/PKG activation during ischemia-like stress may be an adaptive cytoprotective mechanism and modulation of this signaling cascade could serve as a potential therapeutic target for protection against hypoxia or ischemia-induced cellular injury.

Effects of Low-Level Laser Irradiation in a Mouse Model of Allergic Rhinitis

BACKGROUND AND OBJECTIVES

To evaluate the antiallergic effect of low-level laser irradiation (LLLI) at 650 nm in a mouse model of allergic rhinitis (AR), and to examine the underlying mechanisms.

STUDY DESIGN/MATERIALS AND METHODS

BALB/c mice were sensitized with ovalbumin (OVA) and alum and challenged intranasally with OVA. Straight- and diffusion-type LLLI were applied directly into the intranasal cavity of the mice once daily for 10 days (650 nm, 5 mW, 15 min/day) and multiple allergic parameters were evaluated.

RESULTS

LLLI reduced allergic symptoms, such as rubbing and sneezing, and suppressed the serum total immunoglobulin E (IgE), OVA-specific IgE, and OVA-specific IgG1 levels. Diffusion-type LLLI significantly reduced eosinophil infiltration of nasal mucosa and lymph nodes (LNs). LLLI reduced the expression of interleukin-4 (IL-4) and IL-17 in cervical LN and splenocyte culture supernatant, as well as their messenger RNA levels in nasal mucosa. However, the expression of interferonγ (IFN-γ) and IL-6 was unaffected by LLLI. The levels of reactive oxygen species (ROS) and nitric oxide (NO) in LN cells and the nasal mucosa, which were increased in the AR group, were reduced by LLLI, suggesting involvement of ROS and NO within their mechanism.

CONCLUSIONS

LLLI exerted an antiallergic effect by decreasing local and systemic IL-4, IL-17, and IgE levels, as well as eosinophilic infiltration into the nasal mucosa, in a mouse model of AR by modulating ROS and NO levels. Diffusion-type LLLI exhibited greater efficacy against AR than straight-type LLLI. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Glycine Protects against Hypoxic-Ischemic Brain Injury by Regulating Mitochondria-Mediated Autophagy via the AMPK Pathway

Hypoxic-ischemic encephalopathy (HIE) is detrimental to newborns and is associated with high mortality and poor prognosis. Thus, the primary aim of the present study was to determine whether glycine could (1) attenuate HIE injury in rats and hypoxic stress in PC12 cells and (2) downregulate mitochondria-mediated autophagy dependent on the adenosine monophosphate- (AMP-) activated protein kinase (AMPK) pathway. Experiments conducted using an in vivo HIE animal model and in vitro hypoxic stress to PC12 cells revealed that intense autophagy associated with mitochondrial function occurred during in vivo HIE injury and in vitro hypoxic stress. However, glycine treatment effectively attenuated mitochondria-mediated autophagy. Additionally, after identifying alterations in proteins within the AMPK pathway in rats and PC12 cells following glycine treatment, cyclosporin A (CsA) and 5-aminoimidazole-4-carboxamide-1-b-4-ribofuranoside (AICAR) were administered in these models and indicated that glycine protected against HIE and CoCl₂ injury by downregulating mitochondria-mediated autophagy that was dependent on the AMPK pathway. Overall, glycine attenuated hypoxic-ischemic injury in neurons via reductions in mitochondria-mediated autophagy through the AMPK pathway both in vitro and in vivo.

Metallosis mimicking a metabolic disorder: a case report

Metalic prosthesis or occupational exposure are potential sources of systemic cobalt and chromium ion toxicity. The resultant multisystemic clinical presentation can lead to unnecessary investigations before a final etiologic diagnosis is made; with an average delay of a year or more commonly noted.

A 58-year old man presented with cardiomyopathy, pericardial effusion, polycytaemia, polyneuropathy, visual impairment, sudden hearing loss and hypothyroidism over a 2-year period post a metal-on-polyethylene hip replacement surgery.

Biochemistry test results showed serum lactate of 3.8 mmol/L (0.5–2.2 mmol/L). Urine organic acid screen showed mild increases in excretion of tricarboxylic acid cycle intermediates and 2-ethylhydracryllate; suggestive of primary or secondary mitochondrial dysfunction. There were also slight increases in excretion of 4-hydroxyphenyllactate and 4-hydroxyphenylpyruvate suggestive of liver dysfunction. Acylcarnitine profile showed slight increase in hydroxybutyrylcarnitine and tetradeceneoylcarnitine that may reflect ketosis.

In view of his clinical presentation and abnormal metabolic investigations, the initial working diagnosis was mitochondrial disease.

Subsequently, patient presented with hip pain, and radiologic and imaging studies revealed high density collections lateral to the right proximal part of the femur, and medial to the right ilium with signal changes suggestive of metallic content. This prompted toxicology screen which revealed elevated plasma cobalt concentration (903.32 μg/L; reference range: 0.1–0.4) and chromium (71.32 μg/L; <0.5). Six months post right hip prosthesis removal the concentrations have declined and was 61.72 μg/L and chromium 23.97 μg/L. Patient felt some improvement symptomatically, without evident deterioration in his vision or hearing.

This case emphasises careful consideration of past medical history, in patients presenting with multisystemic disease suggestive of mitochondrial dysfunction, and potential causality related to exposure to toxic agents. In retrospect, the absence of a family history could be viewed as a pertinent negative finding. Not uncommonly, specialist focus on their favored system and may not search for a unifying diagnosis. It is likely further delays in diagnosis would have occurred had the patient not developed hip pains, and ultimately referred to the orthopedic surgeons more familiar with similar cases.

Inhibition of autophagy enhanced cobalt chloride‑induced apoptosis in rat alveolar type II epithelial cells

Hypoxia is a type of cellular stress that may result in apoptosis and autophagy. The molecular mechanisms underlying the association between autophagy and apoptosis remain unclear, particularly in hypoxic conditions. Transmission electron microscope, AO-PI staining, flow cytometry and western blot were used to examine the crosstalk between autophagy and apoptosis in hypoxic conditions. Rat alveolar type II epithelial RLE-6TN cells were cultured in a long-term hypoxic environment established by cobalt (II) chloride. It was demonstrated that autophagy and apoptosis occurred in RLE-6TN cells under hypoxic conditions. Treatment of RLE-6TN cells with the autophagy inhibitor 3-methyladenine increased the generation of reactive oxygen species, mitochondrial damage and hypoxia-induced apoptosis. The expression of caspases, particularly caspase-9, increased and may have participated in these processes. The data indicated that the inhibition of autophagy enhanced apoptosis through the mitochondria-mediated intrinsic pathway. These findings provide important insight into the molecular mechanism of autophagy and apoptosis crosstalk. This may provide new insights into pulmonary disease surveillance, diagnosis and treatment.

Promoter Methylation Status of Survival-Related Genes in MOLT- 4 Cells Co-Cultured with Bone Marrow Mesenchymal Stem Cells under Hypoxic Conditions

OBJECTIVES

DNA methylation is a well-studied epigenetic mechanism that is a potent arm of the gene expression controlling machinery. Since the hypoxic situation and the various cells of bone marrow microenvironment, e.g. mesenchymal stem cells, play a role in the in vivo and in vitro biology of leukemic cells, we decided to study the effects of hypoxia and mesenchymal stem cells (MSCs) on the promoter methylation pattern of BAX and BCL2 genes.

MATERIALS AND METHODS

In this experimental study, the co-culture of MOLT-4 cells with MSCs and treatment with CoCl₂ was done during 6, 12, and 24 hour periods. Total DNA was extracted using commercial DNA extraction kits, and sodium bisulfite (SBS) treatment was performed on the extracted DNA. Methylation specific polymerase chain reaction (MSP) was used to evaluate the methylation status of the selected genes' promoter regions.

RESULTS

The BAX and BCL2 promoters of untreated MOLT-4 cells were in partial methylated and fully unmethylated states, respectively. After incubating the cancer cells with CoCl₂ and MSCs, the MSP results after 6, 12, and 24 hours were the same as untreated MOLT-4 cells. In other words, the exposure of MOLT-4 cells to the hypoxia-mimicry agent and MSCs in various modes and different time frames showed that these factors have exerted no change on the methylation signature of the studied fragments from the promoter region of the mentioned genes.

CONCLUSIONS

Hypoxia and MSCs actually have no notable effect on the methylation status of the promoters of BAX and BCL2 in the specifically studied regions. DNA methylation is probably not the main process by which MSCs and CoCl₂ induced hypoxia regulate the expression of these genes. Finally, we are still far from discovering the exact functional mechanisms of gene expression directors, but these investigations can provide new insights into this field for upcoming studies.

Benzoquinone induces ROS-dependent mitochondria-mediated apoptosis in HL-60 cells

Benzene exposure affects the hematopoietic system and leads to the occurrence of various types of leukemia and hematotoxicity. It has been confirmed that active metabolites of benzene, including 1,4-benzoquinone (1,4-BQ), can induce reactive oxygen species (ROS) and apoptosis in the bone marrow, and recent studies have also suggested that benzene exposure can affect mitochondrial function in both experimental animals and cell lines. However, the potential relationship among ROS production, mitochondrial damages, and subsequent apoptosis following benzene exposure has not been well studied in detail. In the present study, we utilized HL-60 cells, a well-characterized human myeloid cell line, as an in vitro model and examined the effects of 1,4-BQ on intracellular ROS formation, mitochondria damage, and the occurrence of apoptotic events with or without using the ROS scavenger N-acetyl-l-cysteine (NAC). The results demonstrated that 1,4-BQ could dose-dependently induce production of ROS and mitochondrial damage as characterized by mitochondrial membrane potential disruption, mitochondrial ultrastructure alteration, and induced apoptosis and activated caspase-3 and caspase-9. Preincubation of HL-60 cells with NAC prior to 1,4-BQ treatment could block 1,4-BQ-induced production of ROS and the occurrence of apoptosis. These results demonstrated that 1,4-BQ induced apoptosis in HL-60 cells through a ROS-dependent mitochondrial-mediated pathway.

Melatonin: A Versatile Protector against Oxidative DNA Damage

Oxidative damage to DNA has important implications for human health and has been identified as a key factor in the onset and development of numerous diseases. Thus, it is evident that preventing DNA from oxidative damage is crucial for humans and for any living organism. Melatonin is an astonishingly versatile molecule in this context. It can offer both direct and indirect protection against a wide variety of damaging agents and through multiple pathways, which may (or may not) take place simultaneously. They include direct antioxidative protection, which is mediated by melatonin's free radical scavenging activity, and also indirect ways of action. The latter include, at least: (i) inhibition of metal-induced DNA damage; (ii) protection against non-radical triggers of oxidative DNA damage; (iii) continuous protection after being metabolized; (iv) activation of antioxidative enzymes; (v) inhibition of pro-oxidative enzymes; and (vi) boosting of the DNA repair machinery. The rather unique capability of melatonin to exhibit multiple neutralizing actions against diverse threatening factors, together with its low toxicity and its ability to cross biological barriers, are all significant to its efficiency for preventing oxidative damage to DNA.

Culturing with modified EGM2 medium enhances porcine neonatal islet-like cell clusters resistance to apoptosis in islet xenotransplantation

BACKGROUND

Neonatal pig islet-like cell clusters (NICC) are an attractive source of insulin-producing tissue for potential transplantation treatment of type 1 diabetic patients. However, a considerable loss of NICC after their transplantation due to apoptosis resulted from islet isolation and instant blood-mediated inflammatory reaction remains to be overcome.

METHODS

EGM2 medium depleted with hydrocortisone and supplemented with 50 mmol/L isobutylmethylxanthine, 10 mmol/L nicotinamide, and 10 mmol/L glucose was used to culture NICC at day 1, the day after isolation and changed every other day. NICC cultured with EGM2 or control Ham's F-10 medium were collected at day 7 of culture for the following assays. The viability of NICC was evaluated by AO/EB staining and FACS. Static assay and oxygen consumption rate analysis were performed to assess the function of NICC. Insulin and glucagon gene expression were measured by real-time PCR. Tubing loops model and TUNEL assay were performed to confirm the apoptosis-resistant ability of NICC cultured with modified EGM2 medium. Serum starvation and hypoxia treatment were used to test the tolerant capability of NICC in the microenvironment of hypoxia/nutrient deficiency in vitro. The molecules involved in apoptosis pathways in NICC were analyzed by Western blotting.

RESULTS

Compared with Ham's F-10 medium, culturing NICC with EGM2 medium led to increased number and viability of NICC with higher stimulation index, upregulated gene expression of both insulin and glucagon, and enhanced mitochondria function. Furthermore, fewer modified EGM2 medium cultured NICC were found under apoptosis when evaluated in an in vitro tubing loop model of IBMIR. Moreover, EGM2 medium cultured NICC demonstrated much less apoptotic cells under either serum starvation or hypoxia condition than their Ham's F-10 medium cultured counterparts. The enhanced capability of EGM2 cultured NICC to resist apoptosis was associated with their elevated protein levels of anti-apoptotic Bcl-2 family member Mcl-1.

CONCLUSION

Culturing NICC with EGM2 provides a simple and effective approach not only to increase NICC yield, viability, and maturation but also to enhance their resistance to apoptosis to preserve the initial graft mass for successful islet xenotransplantation.

Lack of mitochondrial DNA impairs chemical hypoxia-induced autophagy in liver tumor cells through ROS-AMPK-ULK1 signaling dysregulation independently of HIF-1α

Alterations in mitochondrial DNA (mtDNA) and autophagy activation are common events in tumors. Here we have investigated the effect of mitochondrial genome depletion on chemical hypoxia-induced autophagy in liver tumor cells. Human SK-Hep-1 wild-type and mtDNA-depleted (Rho) cells were exposed to the hypoxia mimetic agents CoCl₂ and deferoxamine (DFO). Up-regulation of HIF-1α, but not HIF-2α was observed. The expression of several HIF-1α target genes was also found. In human SK-Hep-1 and mouse Hepa 1-6 liver tumor cells, but not in the counterpart Rho derived lines, chemical hypoxia increased the abundance of autophagosomes and autolysosomes. In wild-type and Rho cells, chemical hypoxia induced down-regulation of HIF-1α-dependent autophagy inhibitors Bcl-2 and mTOR, whereas activation of AMPK/ULK1-mediated pro-autophagy pathway occurred only in wild-type cells. Chemical (compound C) and genetic (shRNA) inhibition of AMPK activation resulted in reduced autophagy. ATP levels were similar in both cell types, whereas constitutive and chemical hypoxia-induced reactive oxygen species (ROS) generation was lower in Rho cells. In wild-type cells, the antioxidant N-acetylcysteine blocked CoCl₂- and DFO-induced AMPK and autophagy activation, but not endoplasmic reticulum stress induced by CoCl₂. Enhanced Bax-α/Bcl-2 ratio and cell death was induced by hypoxia mimetic agents more markedly in wild-type than in Rho cells. Upon blocking autophagy activation with 3-methyladenine, DFO-induced cell death was partially prevented whereas that induced by CoCl₂ was increased, but only in wild-type cells. These results suggest that mitochondrial dysfunction associated with the lack of mtDNA impairs the signaling pathways mediated by ROS, controlling autophagy activation in liver tumor cells, which may contributes to cancer development.

Inhibition of histone/lysine acetyltransferase activity kills CoCl2-treated and hypoxia-exposed gastric cancer cells and reduces their invasiveness

Hypoxia enhances immortality and metastatic properties of solid tumors. Deregulation of histone acetylation has been associated with several metastatic cancers but its effect on hypoxic responses of cancer cells is not known. This study aimed at understanding the effectiveness of the hydrazinocurcumin, CTK7A, an inhibitor of p300 lysine/histone acetyltransferase (KAT/HAT) activity, in inducing apoptosis of gastric cancer cells (GCCs) exposed to cobalt chloride (CoCl₂), a hypoxia-mimetic chemical, or 1% O₂. Here, we show that CTK7A-induced hydrogen peroxide (H₂O₂) generation in CoCl₂-exposed and invasive gastric cancer cells (GCCs) leads to p38 MAPK-mediated Noxa expression and thereafter, mitochondrial apoptotic events. Noxa induction in normal immortalized gastric epithelial cells after CTK7A and hypoxia-exposure is remarkably less in comparison to similarly-treated GCCs. Moreover, hypoxia-exposed GCCs, which have acquired invasive properties, become apoptotic after CTK7A treatment to a significantly higher extent than normoxic cells. Thus, we show the potential of CTK7A in sensitizing hypoxic and metastatic GCCs to apoptosis induction.

Krüppel-like Factor 13 Is a Major Mediator of Glucocorticoid Receptor Signaling in Cardiomyocytes and Protects These Cells from DNA Damage and Death

Glucocorticoid receptor (GR) signaling has recently been shown to play a direct role in the regulation of cardiomyocyte function. In this study, we investigated the potential role of KLF13 as a downstream effector of GR action utilizing both in vivo and in vitro approaches. Our data show that KLF13 mRNA and protein levels are significantly diminished in the hearts of mice lacking GR in cardiomyocytes. Glucocorticoid administration up-regulated Klf13 mRNA in the mouse heart, in isolated primary cardiomyocytes, and in immortal cardiomyocyte cell lines. Glucocorticoid Klf13 gene expression was abolished by treatment with a GR antagonist (RU486) or by knockdown of GR in cardiomyocytes. Moreover, glucocorticoid induction of Klf13 mRNA was resistant to de novo protein synthesis inhibition, demonstrating that Klf13 is a direct glucocorticoid receptor gene target. A glucocorticoid responsive element (GRE) was identified in the Klf13 gene and its function was verified by chromatin immunoprecipitation in HL-1 cells and mouse hearts. Functional studies showed that GR regulation of Klf13 is critical to protect cardiomyocytes from DNA damage and cell death induced by cobalt(II) chloride hexahydrate (CoCl2·6H2O) and the antineoplastic drug doxorubicin. These results established a novel role for GR and KLF13 signaling in adult cardiomyocytes with potential clinical implications for the prevention of cardiotoxicity induced heart failure.

The neurotoxicity of iron, copper and cobalt in Parkinson's disease through ROS-mediated mechanisms

Parkinson's disease (PD) is the second most common neurodegenerative disease with gradual loss of dopaminergic neurons. Despite extensive research in the past decades, the etiology of PD remains elusive. Nevertheless, multiple lines of evidence suggest that oxidative stress is one of the common causes in the pathogenesis of PD. It has also been suggested that heavy metal-associated oxidative stress may be implicated in the etiology and pathogenesis of PD. Here we review the roles of redox metals, including iron, copper and cobalt, in PD. Iron is a highly reactive element and deregulation of iron homeostasis is accompanied by concomitant oxidation processes in PD. Copper is a key metal in cell division process, and it has been shown to have an important role in neurodegenerative diseases such as PD. Cobalt induces the generation of reactive oxygen species (ROS) and DNA damage in brain tissues.

Time-dependent activity of Na+/H+ exchanger isoform 1 and homeostasis of intracellular pH in astrocytes exposed to CoCl2 treatment

Hypoxia causes injury to the central nervous system during stroke and has significant effects on pH homeostasis. Na+/H+ exchanger isoform 1 (NHE1) is important in the mechanisms of hypoxia and intracellular pH (pHi) homeostasis. As a well-established hypoxia-mimetic agent, CoCl2 stabilizes and increases the expression of hypoxia inducible factor‑1α (HIF-1α), which regulates several genes involved in pH balance, including NHE1. However, it is not fully understood whether NHE1 is activated in astrocytes under CoCl2 treatment. In the current study, pHi and NHE activity were analyzed using the pHi‑sensitive dye BCECF‑AM. Using cariporide (an NHE1‑specific inhibitor) and EIPA (an NHE nonspecific inhibitor), the current study demonstrated that it was NHE1, not the other NHE isoforms, that was important in regulating pHi homeostasis in astrocytes during CoCl2 treatment. Additionally, the present study observed that, during the early period of CoCl2 treatment (the first 2 h), NHE1 activity and pHi dropped immediately, and NHE1 mRNA expression was reduced compared with control levels, whereas expression levels of the NHE1 protein had not yet changed. In the later period of CoCl2 treatment, NHE1 activity and pHi significantly increased compared with the control levels, as did the mRNA and protein expression levels of NHE1. Furthermore, the cell viability and injury of astrocytes was not changed during the initial 8 h of CoCl2 treatment; their deterioration was associated with the higher levels of pHi and NHE1 activity. The current study concluded that NHE1 activity and pHi homeostasis are regulated by CoCl2 treatment in a time-dependent manner in astrocytes, and may be responsible for the changes in cell viability and injury observed under hypoxia-mimetic conditions induced by CoCl2 treatment.

Aged garlic extract and S-allylcysteine prevent apoptotic cell death in a chemical hypoxia model

Background

Aged garlic extract (AGE) and its main constituent S-allylcysteine (SAC) are natural antioxidants with protective effects against cerebral ischemia or cancer, events that involve hypoxia stress. Cobalt chloride (CoCl₂) has been used to mimic hypoxic conditions through the stabilization of the α subunit of hypoxia inducible factor (HIF-1α) and up-regulation of HIF-1α-dependent genes as well as activation of hypoxic conditions such as reactive oxygen species (ROS) generation, loss of mitochondrial membrane potential and apoptosis. The present study was designed to assess the effect of AGE and SAC on the CoCl₂-chemical hypoxia model in PC12 cells.

Results

We found that CoCl₂ induced the stabilization of HIF-1α and its nuclear localization. CoCl₂ produced ROS and apoptotic cell death that depended on hypoxia extent. The treatment with AGE and SAC decreased ROS and protected against CoCl₂-induced apoptotic cell death which depended on the CoCl₂ concentration and incubation time. SAC or AGE decreased the number of cells in the early and late stages of apoptosis. Interestingly, this protective effect was associated with attenuation in HIF-1α stabilization, activity not previously reported for AGE and SAC.

Conclusions

Obtained results show that AGE and SAC decreased apoptotic CoCl₂-induced cell death. This protection occurs by affecting the activity of HIF-1α and supports the use of these natural compounds as a therapeutic alternative for hypoxic conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s40659-016-0067-6) contains supplementary material, which is available to authorized users.

SP1 and USF differentially regulate ADAMTS1 gene expression under normoxic and hypoxic conditions in hepatoma cells

ADAM metallopeptidase with thrombospondin type I motif, 1 (ADAMTS1) that has both antiangiogenic and aggrecanase activity was dysregulated in many pathophysiologic circumstances. However, there is limited information available on the transcriptional regulation of ADAMTS1 gene. Therefore, this study mainly aimed to identify regulatory regions important for the regulation of ADAMTS1 gene under normoxic and hypoxic conditions in human hepatoma cells (HEP3B). Cultured HEP3B cells were exposed to normal oxygen condition, and Cobalt chloride (CoCl2) induced the hypoxic condition, which is an HIF-1 inducer. The cocl2-induced hypoxic condition led to the induced ADAMTS1 mRNA and protein expression in Hepatoma cells. Differential regulation of SP1 and USF transcription factors on ADAMTS1 gene expression was determined by transcriptional activity, mRNA and protein level of ADAMTS1 gene. Ectopic expression of SP1 and USF transcription factors resulted in the decrease in ADAMTS1 transcriptional activity of all promoter constructs consistent with mRNA and protein level in normoxic condition. However, overexpression of SP1 and USF led to the increase of ADAMTS1 gene expressions at mRNA and protein level in hypoxic condition. On the other hand, C/EBPα transcription factor didn't show any statistically significant effect on ADAMTS1 gene expression at mRNA, protein and transcriptional level under normoxic and hypoxic condition.

Systemic cobalt toxicity from total hip arthroplasties

Recently, the use of metal-on-metal articulations in total hip arthroplasty (THA) has led to an increase in adverse events owing to local soft-tissue reactions from metal ions and wear debris. While the majority of these implants perform well, it has been increasingly recognised that a small proportion of patients may develop complications secondary to systemic cobalt toxicity when these implants fail. However, distinguishing true toxicity from benign elevations in cobalt ion levels can be challenging.

The purpose of this two part series is to review the use of cobalt alloys in THA and to highlight the following related topics of interest: mechanisms of cobalt ion release and their measurement, definitions of pathological cobalt ion levels, and the pathophysiology, risk factors and treatment of cobalt toxicity. Historically, these metal-on-metal arthroplasties are composed of a chromium-cobalt articulation.

The release of cobalt is due to the mechanical and oxidative stresses placed on the prosthetic joint. It exerts its pathological effects through direct cellular toxicity.

This manuscript will highlight the pathophysiology of cobalt toxicity in patients with metal-on-metal hip arthroplasties.

Take home message: Patients with new or evolving hip symptoms with a prior history of THA warrant orthopaedic surgical evaluation. Increased awareness of the range of systemic symptoms associated with cobalt toxicity, coupled with prompt orthopaedic intervention, may forestall the development of further complications.

Cite this article: Bone Joint J 2016;98-B:6–13.

HIF-1α Upregulation due to Depletion of the Free Ubiquitin Pool

Hypoxia-inducible factor 1alpha (HIF-1α), which transactivates a variety of hypoxia-induced genes, is rapidly degraded under nomoxia through the hydroxylation-ubiquitination-proteasome pathway. In this study, we addressed how HIF-1α is stabilized by proteasome inhibitors. The ubiquitin pool was rapidly reduced after proteasome inhibition, followed by the accumulation of non-ubiquitinated HIF-1α. The poly-ubiquitination of HIF-1α was resumed by restoration of free ubiquitin, which suggests that the HIF-1α stabilization under proteasome inhibition is attributed to depletion of the free ubiquitin pool. Ni(2+) and Zn(2+) also stabilized HIF-1α with depletion of the free ubiquitin pool and these effects of metal ions were attenuated by restoration of free ubiquitin. Ni(2+) and Zn(2+) may disturb the recycling of free ubiquitin, as MG132 does. Based on these results, the state of the ubiquitin pool seems to be another critical factor determining the cellular level of HIF-1α.

Anterior gradient 2 is a binding stabilizer of hypoxia inducible factor-1α that enhances CoCl2 -induced doxorubicin resistance in breast cancer cells

Hypoxia inducible factor-1α (HIF-1α) is associated with human breast cancer chemoresistance. Various reports have suggested that multiple pathways are involved in HIF-1α induction and that the molecular mechanisms regulating HIF-1α-induced chemoresistance are still not fully understood. Here, we report that anterior gradient 2 (AGR2), a proposed breast cancer biomarker, is an essential regulator in hypoxia-induced doxorubicin resistance through the binding and stabilization of HIF-1α. Our results show that knockdown of AGR2 in MCF-7 cells leads to the suppression of HIF-1α-induced doxorubicin resistance, whereas elevated levels of AGR2 in MDA-MB-231 cells enhance HIF-1α-induced doxorubicin resistance. AGR2 expression, in turn, is upregulated by the hypoxic induction of HIF-1α at both translational and transcriptional levels via a hypoxia-responsive region from −937 to −912 bp on the AGR2 promoter sequence. By specific binding to HIF-1α, the increased level of intracellular AGR2 stabilizes HIF-1α and delays its proteasomal degradation. Finally, we found that AGR2-stabilized HIF-1α escalates multiple drug resistance protein 1 (MDR1) mRNA levels and limits doxorubicin intake of MCF-7 cells, whereas MCF-7/ADR, a doxorubicin resistant cell line with deficient AGR2 and HIF-1α, acquires wild-type MDR1 overexpression. Our findings, for the first time, describe AGR2 as an important regulator in chemical hypoxia-induced doxorubicin resistance in breast cancer cells, providing a possible explanation for the variable levels of chemoresistance in breast cancers and further validating AGR2 as a potential anti-breast cancer therapeutic target.

Fucoidan protects mesenchymal stem cells against oxidative stress and enhances vascular regeneration in a murine hindlimb ischemia model

BACKGROUND

Mesenchymal stem cells (MSCs) have the potential to differentiate into multiple cell lineages. Given this potential for tissue regeneration, MSC-based therapeutic applications have been considered in recent years. However, ischemia-induced apoptosis has been reported to be one of the main causes of MSC death following transplantation. The primary objective of this study was to determine whether a natural antioxidant, fucoidan, could protect MSCs from ischemia-induced apoptosis in vitro and in vivo. Furthermore, we investigated the mechanism of action of fucoidan's anti-ischemic effect in MSCs.

METHODS AND RESULT

Pre-treatment with fucoidan (10 μg/mL) suppressed the increase in H2O2-induced reactive oxygen species (ROS) levels and drastically reduced apoptotic cell death in MSCs. Fucoidan inhibited the activation of the pro-apoptotic proteins p38-mitogen-activated protein kinase (MAPK), Jun N-terminal kinase (JNK), and caspase-3, and augmented the expression of the anti-apoptosis protein cellular inhibitor of apoptosis (cIAP). Moreover, fucoidan significantly increased manganese superoxide dismutase (MnSOD) expression and decreased cellular ROS levels via the Akt pathway, resulting in enhanced cell survival. In a murine hindlimb ischemia model, transplanted fucoidan-treated MSCs showed significantly enhanced cell survival and proliferation in ischemic tissues. Functional recovery and limb salvage also remarkably improved in mice injected with fucoidan-stimulated MSCs compared with mice injected with non-stimulated MSCs.

CONCLUSION

Taken together, these results show that fucoidan protects MSCs from ischemia-induced cell death by modulation of apoptosis-associated proteins and cellular ROS levels through regulation of the MnSOD and Akt pathways, suggesting that fucoidan could be powerful therapeutic adjuvant for MSC-based therapy in ischemic diseases.

Salidroside-Mediated Neuroprotection is Associated with Induction of Early Growth Response Genes (Egrs) Across a Wide Therapeutic Window

Salidroside exhibits anti-inflammatory, anti-oxidative, and anti-apoptotic properties. To identify whether salidroside might be a candidate for treating ischemic stroke, we investigated the effects of salidroside or vehicle, given daily for 6 days, after middle cerebral artery occlusion (MCAO) for 2 h and reperfusion for either 1 or 48 h in rats. Salidroside reduced cerebral infarct volume and significantly improved neurological scores whether started after 1 or 48 h of reperfusion. Microarray analysis showed that 20 % (133/678) of the genes down-regulated by ischemia and 1 h of reperfusion were up-regulated by salidroside, whereas 13 % (105/829) of the genes induced by ischemia-reperfusion were inhibited by salidroside, suggesting that salidroside can reverse effects of ischemia-reperfusion on gene expression. The main enriched functional categories induced by salidroside were genes related to synaptic plasticity, whereas salidroside inhibited genes related to inflammation. Induction of Egr1, Egr2, Egr4, and Arc by salidroside was confirmed by qRT-PCR and western blotting in ischemic brains treated after either 1 or 48 h of reperfusion. The potential protective role of Egr4 in salidroside-mediated neuroprotection was subsequently investigated in CoCl2-treated PC12 cells. Egr4 was dose-dependently induced by salidroside in PC12 cells, and depleting Egr4 with target-specific siRNA increased caspase-3 activity and Bax, but decreased Bcl-xl, which were reversed by salidroside. Finally, we confirmed that salidroside inhibited the Bax/Bcl-xl-related apoptosis after MCAO with reperfusion. In conclusion, salidroside is highly neuroprotective with a wide therapeutic time window after ischemia-reperfusion injury in the rat, and this partially involves induction of Egrs, leading to inhibition of Bax/Bcl-xl-related apoptosis.

Hypoxia and free radicals: role in tumor progression and the use of engineering-based platforms to address these relationships

Hypoxia is a feature of all solid tumors, contributing to tumor progression and therapy resistance. Through stabilization of the hypoxia-inducible factor 1 alpha (HIF-1α), hypoxia activates the transcription of a number of genes that sustain tumor progression. Since the seminal discovery of HIF-1α as a hypoxia-responsive master regulator of numerous genes and transcription factors, several groups have reported a novel mechanism whereby hypoxia mediates stabilization of HIF-1α. This process occurs as a result of hypoxia-generated reactive oxygen species (ROS), which, in turn, stabilize the expression of HIF-1α. As a result, a number of genes regulating tumor growth are expressed, fueling ongoing tumor progression. In this review, we outline a role for hypoxia in generating ROS and additionally define the mechanisms contributing to ROS-induced stabilization of HIF-1α.We further explore how ROS-induced HIF-1α stabilization contributes to tumor growth, angiogenesis, metastasis, and therapy response. We discuss a future outlook, describing novel therapeutic approaches for attenuating ROS production while considering how these strategies should be carefully selected when combining with chemotherapeutic agents. As engineering-based approaches have been more frequently utilized to address biological questions, we discuss opportunities whereby engineering techniques may be employed to better understand the physical and biochemical factors controlling ROS expression. It is anticipated that an improved understanding of the mechanisms responsible for the hypoxia/ROS/HIF-1α axis in tumor progression will yield the development of better targeted therapies.

Cytoprotective effects of fisetin against hypoxia-induced cell death in PC12 cells

Fisetin protects cells under hypoxia through ROS scavenging and the HIF1α-, MAPK/ERK-, p38 MAPK- and PI3 K/Akt-dependent pathways in PC12 cells.