Analysis of kinetics of dihydroethidium fluorescence with superoxide using xanthine oxidase and hypoxanthine assay

What can reactive oxygen species (ROS) tell us about the action mechanism of herbicides and other phytotoxins?

Reactive oxygen species (ROS) are formed in plant cells continuously. When ROS production exceeds the antioxidant capacity of the cells, oxidative stress develops which causes damage of cell components and may even lead to the induction of programmed cell death (PCD). The levels of ROS production increase upon abiotic stress, but also during pathogen attack in response to elicitors, and upon application of toxic compounds such as synthetic herbicides or natural phytotoxins. The commercial value of many synthetic herbicides is based on weed death as result of oxidative stress, and for a number of them, the site and the mechanism of ROS production have been characterized. This review summarizes the current knowledge on ROS production in plants subjected to different groups of synthetic herbicides and natural phytotoxins. We suggest that the use of ROS-specific fluorescent probes and of ROS-specific marker genes can provide important information on the mechanism of action of these toxins. Furthermore, we propose that, apart from oxidative damage, elicitation of ROS-induced PCD is emerging as one of the important processes underlying the action of herbicides and phytotoxins.

A Co-Doping Materials Design Strategy for Selective Ozone Electrocatalysts

Catalysts for electrochemical ozone production (EOP) face inherent selectivity challenges stemming from thermodynamic constraints. This work establishes a design strategy for minimizing these limitations and inducing EOP activity in tin oxide, which is an intrinsically EOP-inactive material. We propose that selective ozone production using tin oxide catalysts can be broadly achieved by co-doping with two elements: first, n-type dopants to enhance electrical conductivity, and second, transition metal dopants that leach and homogeneously generate essential hydroperoxyl radical intermediates. Synthesizing tantalum, antimony, and tungsten n-type dopants with nickel, cobalt, and iron as transition metal dopants confirms that properly co-doping tin oxide yields EOP-active catalysts. This study offers a robust framework for advancing EOP catalyst design and serves as a case study for the application of fundamental co-catalysis and solid-state physics principles to induce catalytic activity in inert materials.

Cannabidiol and Aza-BODIPY Coencapsulation for Photodynamic Therapy Enhancement in Liver Cancer Cells

Photodynamic therapy (PDT) and cannabidiol (CBD) have been explored for their potential in synergistic cancer treatment. In this study, we employed CBD oil as a lipid phase, encapsulated within AZB-I@Lec-T to create lipid-based nanoparticles. Here, CBD oil does two tasks: it acts as a pyroptosis agent to destroy liver cancer cells and as a lipid phase to dissolve the photosensitizer. It was expected that this system would offer synergistic therapy between CBD and PDT better than a single use of each treatment. With a series of in vitro experiments, the nanoparticles exhibited induced apoptosis in 68% of HepG2 cells treated with AZB-I@Lec-T@CBD and near-infrared (NIR)-light irradiation, reducing expression levels of antioxidant defense system genes. Furthermore, both components worked well in a submicromolar range when combined in our formulation. These results highlight the potential for amplifying primary cellular damage with the combination of PDT and CBD encapsulation, providing a promising therapeutic approach for liver cancer treatment guidelines.

Interplay between Catalyst Corrosion and Homogeneous Reactive Oxygen Species in Electrochemical Ozone Production

Electrochemical ozone production (EOP), a six-electron water oxidation reaction, offers promising avenues for creating value-added oxidants and disinfectants. However, progress in this field is slowed by a dearth of understanding of fundamental reaction mechanisms. In this work, we combine experimental electrochemistry, spectroscopic detection of reactive oxygen species (ROS), oxygen-anion chemical ionization mass spectrometry, and computational quantum chemistry calculations to determine a plausible reaction mechanism on nickel- and antimony-doped tin oxide (Ni/Sb-SnO2, NATO), one of the most selective EOP catalysts. Antimony doping is shown to increase the conductivity of the catalyst, leading to improved electrochemical performance. Spectroscopic analysis and electrochemical experiments combined with quantum chemistry predictions reveal that hydrogen peroxide (H2O2) is a critical reaction intermediate. We propose that leached Ni4+ cations catalyze hydrogen peroxide into solution phase hydroperoxyl radicals (•OOH); these radicals are subsequently oxidized to ozone. Isotopic product analysis shows that ozone is generated catalytically from water and corrosively from the catalyst oxide lattice without regeneration of lattice oxygens. Further quantum chemistry calculations and thermodynamic analysis suggest that the electrochemical corrosion of tin oxide itself might generate hydrogen peroxide, which is then catalyzed to ozone. The proposed pathways explain both the roles of dopants in NATO and its lack of stability. Our study interrogates the possibility that instability and electrochemical activity are intrinsically linked through the formation of ROS. In doing so, we provide the first mechanism for EOP that is consistent with computational and experimental results and highlight the central challenge of instability as a target for future research efforts.

Alleviation of Photoreceptor Degeneration Based on Fullerenols in rd1 Mice by Reversing Mitochondrial Dysfunction via Modulation of Mitochondrial DNA Transcription and Leakage

Poor therapeutic outcomes of antioxidants in ophthalmologic clinical applications, including glutathione during photoreceptor degeneration in retinitis pigmentosa (RP), are caused by limited anti-oxidative capacity. In this study, fullerenols are synthesized and proven to be highly efficient in vitro radical scavengers. Fullerenol-based intravitreal injections significantly improve the flash electroretinogram and light/dark transition tests performed for 28 days on rd1 mice, reduce the thinning of retinal outer nuclear layers, and preserve the Rhodopsin, Gnat-1, and Arrestin expressions of photoreceptors. RNA-sequencing, RT-qPCR, and Western blotting validate that mitochondrial DNA (mt-DNA)-encoded genes of the electron transport chain (ETC), such as mt-Nd4l, mt-Co1, mt-Cytb, and mt-Atp6, are drastically downregulated in the retinas of rd1 mice, whereas nuclear DNA (n-DNA)-encoded genes, such as Ndufa1 and Atp5g3, are abnormally upregulated. Fullerenols thoroughly reverse the abnormal mt-DNA and n-DNA expression patterns of the ETC and restore mitochondrial function in degenerating photoreceptors. Additionally, fullerenols simultaneously repress Flap endonuclease 1 (FEN1)-mediated mt-DNA cleavage and mt-DNA leakage via voltage-dependent anion channel (VDAC) pores by downregulating the transcription of Fen1 and Vdac1, thereby inactivating the downstream pro-inflammatory cGAS-STING pathway. These findings demonstrate that fullerenols can effectively alleviate photoreceptor degeneration in rd1 mice and serve as a viable treatment for RP.

Exercise induces superoxide and NOX4 contribution in endothelium-dependent dilation in coronary arterioles from a swine model of chronic myocardial ischemia

Exercise training is an effective, nonpharmacologic therapy and preventative measure for ischemic heart disease. While recent studies have examined reactive oxygen species (ROS) as mediators of exercise training-enhanced coronary blood flow, specific oxidants and their sources have yet to be fully elucidated. We investigated the hypothesis that NADPH oxidase (NOX)-derived superoxide anion would contribute to vasodilation effects in the coronary microcirculation of swine and that these effects would be impaired by chronic ischemia and rescued with exercise training. Adult Yucatan miniature swine were instrumented with an ameroid occluder around the proximal left circumflex coronary artery, resulting in a collateral-dependent myocardial region. Eight weeks post-operatively, swine were randomly assigned to either a sedentary or exercise training (treadmill run; 5 days/week for 14 weeks) protocol. Coronary arterioles were isolated from nonoccluded and collateral-dependent myocardial regions and pressure myography was performed. Exercise training resulted in enhanced endothelium-dependent dilation after occlusion. Scavenging of superoxide via the superoxide dismutase (SOD)-mimetic, tempol, attenuated dilation in both nonoccluded and collateral-dependent arterioles of exercise-trained, but not sedentary swine. NOX1/4 inhibition with GKT136901 attenuated dilation after exercise training but only in collateral-dependent arterioles. High performance liquid chromatography revealed that neither ischemia nor exercise training significantly altered basal or bradykinin-stimulated superoxide levels. Furthermore, superoxide production was not attributable to NOX isoforms nor mitochondria. Immunoblot analyses revealed significantly decreased NOX2 protein after exercise with no differences in NOX1, NOX4, p22phox, SOD proteins. Taken together, these data provide evidence that superoxide and NOX4 independently contribute to enhanced endothelium-dependent dilation following exercise training.

Effects of Phytotoxic Nonenolides, Stagonolide A and Herbarumin I, on Physiological and Biochemical Processes in Leaves and Roots of Sensitive Plants

Phytotoxic macrolides attract attention as prototypes of new herbicides. However, their mechanisms of action (MOA) on plants have not yet been elucidated. This study addresses the effects of two ten-membered lactones, stagonolide A (STA) and herbarumin I (HBI) produced by the fungus Stagonospora cirsii, on Cirsium arvense, Arabidopsis thaliana and Allium cepa. Bioassay of STA and HBI on punctured leaf discs of C. arvense and A. thaliana was conducted at a concentration of 2 mg/mL to evaluate phenotypic responses, the content of pigments, electrolyte leakage from leaf discs, the level of reactive oxygen species, Hill reaction rate, and the relative rise in chlorophyll a fluorescence. The toxin treatments resulted in necrotic and bleached leaf lesions in the dark and in the light, respectively. In the light, HBI treatment caused the drop of carotenoids content in leaves on both plants. The electrolyte leakage caused by HBI was light-dependent, in contrast with that caused by STA. Both compounds induced light-independent peroxide generation in leaf cells but did not affect photosynthesis 6 h after treatment. STA (10 µg/mL) caused strong disorders in root cells of A. thaliana leading to the complete dissipation of the mitochondrial membrane potential one hour post treatment, as well as DNA fragmentation and disappearance of acidic vesicles in the division zone after 8 h; the effects of HBI (50 µg/mL) were much milder. Furthermore, STA was found to inhibit mitosis but did not affect the cytoskeleton in cells of root tips of A. cepa and C. arvense, respectively. Finally, STA was supposed to inhibit the intracellular vesicular traffic from the endoplasmic reticulum to the Golgi apparatus, thus interfering with mitosis. HBI is likely to have another main MOA, probably inhibiting the biosynthesis of carotenoids.

Schizophrenia, Curcumin and Minimizing Side Effects of Antipsychotic Drugs: Possible Mechanisms

Schizophrenia is a mental disorder characterized by episodes of psychosis; major symptoms include hallucinations, delusions, and disorganized thinking. More recent theories focus on particular disorders of interneurons, dysfunctions in the immune system, abnormalities in the formation of myelin, and augmented oxidative stress that lead to alterations in brain structure. Decreased dopaminergic activity and increased phospholipid metabolism in the prefrontal cortex might be involved in schizophrenia. Antipsychotic drugs used to treat schizophrenia have many side effects. Alternative therapy such as curcumin (CUR) can reduce the severity of symptoms without significant side effects. CUR has important therapeutic properties such as antioxidant, anti-mutagenic, anti-inflammatory, and antimicrobial functions and protection of the nervous system. Also, the ability of CUR to pass the blood-brain barrier raises new hopes for neuroprotection. CUR can improve and prevent further probable neurological and behavioral disorders in patients with schizophrenia. It decreases the side effects of neuroleptics and retains lipid homeostasis. CUR increases the level of brain-derived neurotrophic factor and improves hyperkinetic movement disorders. CUR may act as an added counteraction mechanism to retain cell integrity and defense against free radical injury. Thus it appears to have therapeutic potential for improvement of schizophrenia. In this study, we review several properties of CUR and its ability to improve schizophrenia and minimize the side effects of antipsychotic drugs, and we explore the underlying mechanisms by which CUR affects schizophrenia and its symptoms.

Insulin Diminishes Superoxide Increase in Cytosol and Mitochondria of Cultured Cortical Neurons Treated with Toxic Glutamate

Glutamate excitotoxicity is involved in the pathogenesis of many disorders, including stroke, traumatic brain injury, and Alzheimer’s disease, for which central insulin resistance is a comorbid condition. Neurotoxicity of glutamate (Glu) is primarily associated with hyperactivation of the ionotropic N-methyl-D-aspartate receptors (NMDARs), causing a sustained increase in intracellular free calcium concentration ([Ca²⁺]_i) and synchronous mitochondrial depolarization and an increase in intracellular superoxide anion radical (O₂^–•) production. Recently, we found that insulin protects neurons against excitotoxicity by decreasing the delayed calcium deregulation (DCD). However, the role of insulin in O₂^–• production in excitotoxicity still needs to be clarified. The present study aims to investigate insulin’s effects on glutamate-evoked O₂^–• generation and DCD using the fluorescent indicators dihydroethidium, MitoSOX Red, and Fura-FF in cortical neurons. We found a linear correlation between [Ca²⁺]_i and [O₂^–•] in primary cultures of the rat neuron exposed to Glu, with insulin significantly reducing the production of intracellular and mitochondrial O₂^–• in the primary cultures of the rat neuron. MK 801, an inhibitor of NMDAR-gated Ca²⁺ influx, completely abrogated the glutamate effects in both the presence and absence of insulin. In experiments in sister cultures, insulin diminished neuronal death and O₂ consumption rate (OCR).

Fluorescein-Based Type I Supramolecular Photosensitizer via Induction of Charge Separation by Self-Assembly

Photosensitizers (PSs) are critical substances with considerable potential for use in non-invasive photomedicine. Type I PSs, which generate reactive radical species by electron transfer from the excited state induced via photoirradiation, attracted much attention because of their suitability for photodynamic therapy (PDT) irrespective of the oxygen concentration. However, most organic PSs are type II, which activates only oxygen, generating singlet oxygen (¹O₂) via energy transfer from the triplet state. Here, we proposed a strategy to form type I supramolecular PSs (SPSs) utilizing the charge-separated state induced by self-assembly. This was demonstrated using a supramolecular assembly of fluorescein, which is a type II PS in the monomeric state; however, it changes to a type I SPS via self-assembly. The switching mechanism from type II to I via self-assembly was clarified using photophysical and electrochemical analyses, with the type I SPS exhibiting significant PDT effects on cancer cells. This study provides a promising approach for the development of type I PSs based on supramolecular assemblies.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

Free spermidine evokes superoxide radicals that manifest toxicity

Spermidine and other polyamines alleviate oxidative stress, yet excess spermidine seems toxic to Escherichia coli unless it is neutralized by SpeG, an enzyme for the spermidine N-acetyl transferase function. Thus, wild-type E. coli can tolerate applied exogenous spermidine stress, but ΔspeG strain of E. coli fails to do that. Here, using different reactive oxygen species (ROS) probes and performing electron paramagnetic resonance spectroscopy, we provide evidence that although spermidine mitigates oxidative stress by lowering overall ROS levels, excess of it simultaneously triggers the production of superoxide radicals, thereby causing toxicity in the ΔspeG strain. Furthermore, performing microarray experiment and other biochemical assays, we show that the spermidine-induced superoxide anions affected redox balance and iron homeostasis. Finally, we demonstrate that while RNA-bound spermidine inhibits iron oxidation, free spermidine interacts and oxidizes the iron to evoke superoxide radicals directly. Therefore, we propose that the spermidine-induced superoxide generation is one of the major causes of spermidine toxicity in E. coli.

Blue Laser Irradiation Decreases the ATP Level in Mouse Skin and Increases the Production of Superoxide Anion and Hypochlorous Acid in Mouse Fibroblasts

Simple Summary

Photobiomodulation studies have reported that blue light irradiation induces the production of reactive oxygen species. We examined the effect of blue laser (405 nm) irradiation on ATP level in the skin and measured the types of reactive oxygen species and reactive nitrogen species. The decrease in the skin ATP level due to blue light irradiation may be caused by oxidative stress due to the generation of reactive oxygen species. These findings highlight the need to consider the effects on the skin when performing photobiomodulation treatment using blue light.

Abstract

Photobiomodulation studies have reported that blue light irradiation induces the production of reactive oxygen species. We investigated the effect of blue laser (405 nm) irradiation on the ATP levels in mouse skin and determined the types of reactive oxygen species and reactive nitrogen species using cultured mouse fibroblasts. Blue laser irradiation caused a decrease in the ATP level in the mouse skin and triggered the generation of superoxide anion and hypochlorous acid, whereas nitric oxide and peroxynitrite were not detected. Moreover, blue laser irradiation resulted in reduced cell viability. It is believed that the decrease in the skin ATP level due to blue light irradiation results from the increased levels of oxidative stress due to the generation of reactive oxygen species. This method of systematically measuring the levels of reactive oxygen species and reactive nitrogen species may be useful for understanding the effects of irradiation conditions.

Lipid Droplets Protect Aging Mitochondria and Thus Promote Lifespan in Yeast Cells

Besides their role as a storage for neutral lipids and sterols, there is increasing evidence that lipid droplets (LDs) are involved in cellular detoxification. LDs are in close contact to a broad variety of organelles where protein- and lipid exchange is mediated. Mitochondria as a main driver of the aging process produce reactive oxygen species (ROS), which damage several cellular components. LDs as highly dynamic organelles mediate a potent detoxification mechanism by taking up toxic lipids and proteins. A stimulation of LDs induced by the simultaneously overexpression of Lro1p and Dga1p (both encoding acyltransferases) prolongs the chronological as well as the replicative lifespan of yeast cells. The increased number of LDs reduces mitochondrial fragmentation as well as mitochondrial ROS production, both phenotypes that are signs of aging. Strains with an altered LD content or morphology as in the sei1∆ or lro1∆ mutant lead to a reduced replicative lifespan. In a yeast strain defective for the LON protease Pim1p, which showed an enhanced ROS production, increased doubling time and an altered mitochondrial morphology, a LRO1 overexpression resulted in a partially reversion of this "premature aging" phenotype.

MTS1338 in Mycobacterium tuberculosis promotes detoxification of reactive oxygen species under oxidative stress

Diverse mechanisms exist in Mycobacterium tuberculosis for adaptation to stresses leading to its persistence in the hostile environment of macrophages. Small RNA (sRNA)-mediated regulatory mechanisms have been scarcely explored in M. tuberculosis. MTS1338, a sRNA present only in pathogenic mycobacteria, was discovered to be highly abundant during infection and significantly contributes to host-pathogen interaction. A variety of stresses have been implicated for its accumulation. Herein, we showed that MTS1338 is an oxidative stress induced sRNA, which promotes the detoxification of reactive oxygen species (ROS) under oxidative stress. Current study identified a new role of MTS1338 in M. tuberculosis under oxidative stress.

Highly Efficient Ir(III)-Coumarin Photo-Redox Catalyst for Synergetic Multi-Mode Cancer Photo-Therapy

Four photo-catalysts of the general formula [Ir(CO6/ppy)₂ (L)]Cl where CO6=coumarin 6 (Ir1-Ir3), ppy=2-phenylpyridine (Ir4), L=4'-(3,5-di-tert-butylphenyl)-2,2' : 6',2''-terpyridine (Ir1), 4'-(3,5-bis(trifluoromethyl)phenyl)-2,2' : 6',2''-terpyridine (Ir2 and Ir4), and 4-([2,2' : 6',2''-terpyridin]-4'-yl)-N,N-dimethylaniline (Ir3) were synthesized and characterized. These photostable photo-catalysts (Ir1-Ir3) showed strong visible light absorption between 400-550 nm. Upon light irradiation (465 and 525 nm), Ir1-Ir3 generated singlet oxygen and induced rapidly photo-catalytic oxidation of cellular coenzymes NAD(P)H. Ir1-Ir3 showed time-dependent cellular uptake with excellent intracellular retention efficiency. Upon green light irradiation (525 nm), Ir2 provided a much higher photo-index (PI=793) than the clinically used photosensitizer, 5-aminolevulinicacid (5-ALA, PI>30) against HeLa cancer cells. The observed necro-apoptotic anticancer activity of Ir2 was due to the Ir2 triggered photo-induced intracellular redox imbalance (by NAD(P)H oxidation and ROS generation) and change in the mitochondrial membrane potential. Remarkably, Ir2 showed in vivo photo-induced catalytic anticancer activity in mouse models.

Superparamagnetic Iron Oxide Nanoparticles: Cytotoxicity, Metabolism, and Cellular Behavior in Biomedicine Applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely investigated and applied in the field of biomedicine due to their excellent superparamagnetic properties and reliable traceability. However, with the optimization of core composition, shell types and transfection agents, the cytotoxicity and metabolism of different SPIONs have great differences, and the labeled cells also show different cellular behaviors. Therefore, a holistic review of the construction and application of SPIONs is desired. This review focuses the advances of SPIONs in the field of biomedicine in recent years. After summarizing the toxicity of different SPIONs, the uptake, distribution and metabolism of SPIONs in vitro were discussed. Then, the regulation of labeled-cells behavior is outlined. Furthermore, the major challenges in the optimization process of SPIONs and insights on its future developments are proposed.

Silver Nanoparticles Modulate the Epithelial-to-Mesenchymal Transition in Estrogen-Dependent Breast Cancer Cells In Vitro

Silver nanoparticles (AgNPs) are frequently detected in many convenience goods, such as cosmetics, that are applied directly to the skin. AgNPs accumulated in cells can modulate a wide range of molecular pathways, causing direct changes in cells. The aim of this study is to assess the capability of AgNPs to modulate the metastasis of breast cancer cells through the induction of epithelial-to-mesenchymal transition (EMT). The effect of the AgNPs on MCF-7 cells was investigated via the sulforhodamine B method, the wound healing test, generation of reactive oxygen species (ROS), the standard cytofluorimetric method of measuring the cell cycle, and the expression of EMT marker proteins and the MTA3 protein via Western blot. To fulfill the results, calcium flux and HDAC activity were measured. Additionally, mitochondrial membrane potential was measured to assess the direct impact of AgNPs on mitochondria. The results indicated that the MCF-7 cells are resistant to the cytotoxic effect of AgNPs and have higher mobility than the control cells. Treatment with AgNPs induced a generation of ROS; however, it did not affect the cell cycle but modulated the expression of EMT marker proteins and the MTA3 protein. Mitochondrial membrane potential and calcium flux were not altered; however, the AgNPs did modulate the total HDAC activity. The presented data support our hypothesis that AgNPs modulate the metastasis of MCF-7 cells through the EMT pathway. These results suggest that AgNPs, by inducing reactive oxygen species generation, alter the metabolism of breast cancer cells and trigger several pathways related to metastasis.

Response of platelets to silver nanoparticles designed with different surface functionalization

Despite increasing use of silver nanoparticles (AgNPs) in different medicinal products, knowledge about their effects on hemostasis and platelets functionality is still scarce. Published scientific reports provide neither data on oxidative stress response of platelets to AgNPs nor information about the effects of AgNPs physicochemical properties on functionality and activation of platelets. This study aimed to explore the role of AgNPs surface functionalization on cell viability, particle uptake, oxidative stress response, and activation of platelets. Small sized, spherical AgNPs were surface functionalized by negatively charged sodium bis(2-ethylhexyl) sulphosuccinate (AOT), neutral polymer polyvinylpyrrolidone (PVP), positively charged polymer poly-l-lysine (PLL) and bovine serum albumin (BSA). Platelet viability, activation and particle uptake were evaluated by flow cytometry. Oxidative stress response was evaluated by measuring the levels of intracellular glutathione (GSH), peroxy and superoxide radicals using assays based on fluorescence dies. Cytotoxicity and uptake of AgNPs to platelets were found to be dose-dependent in a following order PLL-AgNP >> > BSA-AgNP > AOT-AgNP > PVP-AgNP. Particle internalization was further confirmed by transmission electron microscopy. Treatment of platelets with AgNPs induced superoxide radical formation, depletion of GSH and hyperpolarization of the mitochondrial membrane. Small, but statistically significant increase of P-selectin expression in cells treated with all AgNPs compared to non-treated controls evidenced AgNPs-induced activation of platelets. Increased PAC-1 expression was found only in platelets treated with PLL-AgNPs. Obtained results demonstrate that different surface decoration of AgNPs determines their biological effects on platelets highlighting the importance of careful design of AgNPs-based medicinal products regarding their biocompatibility and functionality.

Dexamethasone may inhibit placental growth by blocking glucocorticoid receptors via phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin and reactive oxygen species/AMP-activated protein kinase signalling pathways in human placental JEG-3 cells

This study explored the molecular mechanism underlying the effects of dexamethasone (DEX, 1µM) on glucose transporters (GLUT) in JEG-3 human placental choriocarcinoma cells. JEG-3 cells were treated with DEX, an expression plasmid encoding human glucocorticoid receptor α (GRα), pcDNA3.1-GRα, GRα short interference (si) RNA, LY294002, xanthine oxidase (XO)/hypoxanthine (HX), rapamycin, insulin-like growth factor (IGF) 1, N-acetylcysteine (NAC) or phosphatidic acid (PA), and cell proliferation, apoptosis, mitochondrial membrane potential (MMP), human chorionic gonadotrophin (hCG) content, human placental lactogen (hPL) content, glucose uptake, reactive oxygen species levels and signalling pathway modulation were evaluated. Treatment of JEG-3 cells with DEX (1µM), GRα siRNA, LY294002 (50µM), XO/HX (7.2µM/36nM) or rapamycin (80nM) inhibited cell proliferation, induced apoptosis, significantly decreased MMP and hCG and hPL content and increased ROS levels. In addition, glucose uptake was decreased through downregulation of the mRNA and protein expression of GRα, GLUT1 and GLUT3. Treatment of JEG-3 cells with GRα siRNA, LY294002, XO/HX or rapamycin inhibited phosphorylation of phosphatidylinositol 3-kinase (PI3K), Akt, glycogen synthase kinase 3 and mammalian target of rapamycin (mTOR) and induced the phosphorylation of AMP-activated protein kinase (AMPK) and tuberous sclerosis complex 2. The effects of GRα overexpression and IGF1 (100nM), NAC (5nM) or PA (100µM) treatment on JEG-3 cells contrasted with those of DEX treatment. DEX blocked glucose uptake by downregulating GRα expression, which reduced GLUT1 and GLUT3 mRNA and protein expression, which, in turn, may have inhibited the PI3K/AKT/mTOR pathway and activated the ROS/AMPK pathway.

Potential Use of Amla (Phyllanthus emblica L.) Fruit Extract to Protect Skin Keratinocytes from Inflammation and Apoptosis after UVB Irradiation

Ultraviolet B (UVB) exposure is the primary risk factor for the deadliest type of skin cancer—melanoma. Incorporating natural antioxidants in skin protection products is currently a favored research theme. For this study, we selected Phyllanthus emblica L. fruit extract (PE) to assess its potential use in dermal protection against UVB-induced keratinocyte inflammation and apoptosis. High-performance liquid chromatography (HPLC) was used to investigate PE’s phytochemical constituents (ascorbic acid, ellagic acid, gallic acid, chlorogenic acid, and quercetin), while ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), total ROS, OH^•, O₂^•−, and H₂O₂-scavenging activities were used to determine the antioxidant properties. PE significantly increased the cell viability (MTT assay) and reduced apoptosis (Hoechst staining) in HaCaT cells exposed to UVB (40 mJ/cm²). PE abolished oxidative stress by reducing the production of intracellular ROS, O₂^•− and H₂O₂ production. Catalase activity (but not superoxide dismutase or glutathione peroxidase activity) was enhanced in keratinocytes incubated with PE prior to UVB exposure. Western blot analysis suggested that PE inhibited cytochrome c release and inhibited the dysregulation of PI3K/Akt without any impact on p38 activation. PE attenuated the inflammatory response to UVB irradiation by inhibiting AP-1, NF-κB, and the mediator PGE₂. Thus, PE is a candidate with great potential for use as an active ingredient in skin care products.

Kinetic spectroscopic quantification using two-step chromogenic and fluorogenic reactions: From theoretical modeling to experimental quantification of biomarkers in practical samples

Kinetic chromogenic (CG) and fluorogenic (FG) quantification deduces analyte concentration based on the reaction rate between the CG/FG probe and its targeted molecule. Little progress has been made in the past half century in either the theory or the applications of the kinetic spectroscopic quantification methods. Current kinetic CG/FG quantification is limited only to a subset of CG/FG reactions that can be approximated as the single-step process, and more problematically, to research samples with no matrix interferences. Reported herein is a kinetic quantification model established for multistep CG/FG reactions and a proof-of-concept demonstration of direct kinetic FG quantification of biomarkers in practical samples. The kinetic spectral intensity of the CG/FG reactions with two rate-limiting steps comprises three temporal regions: an accelerating period where rate of signal change is increasingly rapid, a linear region where the rate of signal change is approximately constant, and a deceleration region where the rate of signal increase becomes progressively small. Kinetic quantification is performed through simple linear-curve-fitting of the kinetic signal in its linear time-course region. The theoretical model is validated with the dual CG/FG 2-thiobarbituric acid (TBA) and malondialdehyde (MDA) reaction. Proof-of-concept kinetic spectroscopic quantification of analytes in practical samples is demonstrated with the FG quantification of MDA in canned chicken. The only sample preparation is bench-top centrifugation followed by two sequential syringe filtrations. The total kinetic FG assay time is less than 10 min, more than 10 times more efficient than the current equilibrium-based MDA assay. The theoretical model and the measurement design strategies offered by this work should help transform the current kinetic spectroscopic quantification from a niche research tool to an indispensable technique for time-sensitive applications.

Flavonols modulate lateral root emergence by scavenging reactive oxygen species in Arabidopsis thaliana

Flavonoids are a class of specialized metabolites with subclasses including flavonols and anthocyanins, which have unique properties as antioxidants. Flavonoids modulate plant development, but whether and how they impact lateral root development is unclear. We examined potential roles for flavonols in this process using Arabidopsis thaliana mutants with defects in genes encoding key enzymes in flavonoid biosynthesis. We observed the tt4 and fls1 mutants, which produce no flavonols, have increased lateral root emergence. The tt4 root phenotype was reversed by genetic and chemical complementation. To more specifically define the flavonoids involved, we tested an array of flavonoid biosynthetic mutants, eliminating roles for anthocyanins and the flavonols quercetin and isorhamnetin in modulating lateral root development. Instead, two tt7 mutant alleles, with defects in a branchpoint enzyme blocking quercetin biosynthesis, formed reduced numbers of lateral roots and tt7-2 had elevated levels of kaempferol. Using a flavonol-specific dye, we observed that in the tt7-2 mutant, kaempferol accumulated within lateral root primordia at higher levels than wild-type. These data are consistent with kaempferol, or downstream derivatives, acting as a negative regulator of lateral root emergence. We examined ROS accumulation using ROS-responsive probes and found reduced fluorescence of a superoxide-selective probe within the primordia of tt7-2 compared with wild-type, but not in the tt4 mutant, consistent with opposite effects of these mutants on lateral root emergence. These results support a model in which increased level of kaempferol in the lateral root primordia of tt7-2 reduces superoxide concentration and ROS-stimulated lateral root emergence.

Sonochemiluminescence of lucigenin using amines as coreactant: Reactivity and mechanism studies

Sonochemiluminescence (SCL) from aqueous solution of lucigenin (Luc²⁺) has been studied using aliphatic amines as coreactant. The SCL intensity are strongly dependent on the dissolved gases such as air, oxygen, nitrogen and argon. The most strong SCL signals are observed from oxygen saturated alkaline solution containing Luc²⁺ when small amount of trialkylamine, such as tripropylamine (TPrA) was added into the solution. In an ultrasonic field, TPrA can adsorb onto the cavitation bubble/solution interface where TPrA is oxidized by OH to form a radical cation TPrA⁺ and subsequently produce a highly reducing TPrA species through a deprotonation reaction of the TPrA⁺. TPrA is suggested to initiate the reduction reactions of Luc²⁺ and molecule oxygen to produce Luc⁺ and superoxide radical anion (O₂^-), respectively. The radical-radical coupling reaction between Luc⁺ and O₂^- is expected to initiate the light emission. The production of O₂^- is examined by spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as a fluorescent probe. The results show that the production of O₂^- by ultrasound was more efficient in oxygen saturated solution in the presence of coreactants, consistent with the results with SCL measurements.

Therapeutic hypothermia reduces inflammation and oxidative stress in the liver after asphyxial cardiac arrest in rats

BACKGROUND

Few studies have evaluated the effects of hypothermia on cardiac arrest (CA)-induced liver damage. This study aimed to investigate the effects of hypothermic therapy on the liver in a rat model of asphyxial cardiac arrest (ACA).

METHODS

Rats were subjected to 5-minute ACA followed by return of spontaneous circulation (RoSC). Body temperature was controlled at 33°C±0.5°C or 37°C±0.5°C for 4 hours after RoSC in the hypothermia group and normothermia group, respectively. Liver tissues in each group were collected at 6 hours, 12 hours, 1 day, and 2 days after RoSC. To examine hepatic inflammation, mast cells were stained with toluidine blue. Superoxide anion radical production was evaluated using dihydroethidium fluorescence straining and expression of endogenous antioxidants (superoxide dismutase 1 [SOD1] and SOD2) was examined using immunohistochemistry.

RESULTS

There were significantly more mast cells in the livers of the normothermia group with ACA than in the hypothermia group with ACA. Gradual increase in superoxide anion radical production was found with time in the normothermia group with ACA, but production was significantly suppressed in the hypothermia group with ACA relative to the normothermia group with ACA. SOD1 and SOD2 levels were higher in the hypothermia group with ACA than in the normothermia group with ACA.

CONCLUSIONS

Experimental hypothermic treatment after ACA significantly inhibited inflammation and superoxide anion radical production in the rat liver, indicating that this treatment enhanced or maintained expression of antioxidants. Our findings suggest that hypothermic therapy after CA can reduce mast cell-mediated inflammation through regulation of oxidative stress and the expression of antioxidants in the liver.

Oxidation of ethidium-based probes by biological radicals: mechanism, kinetics and implications for the detection of superoxide

Hydroethidine (HE) and hydropropidine (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {HPr}^{+}$$\end{document}HPr+) are fluorogenic probes used for the detection of the intra- and extracellular superoxide radical anion (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {O}_{ {2}}^{\bullet -}$$\end{document}O2∙-). In this study, we provide evidence that HE and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {HPr}^{+}$$\end{document}HPr+ react rapidly with the biologically relevant radicals, including the hydroxyl radical, peroxyl radicals, the trioxidocarbonate radical anion, nitrogen dioxide, and the glutathionyl radical, via one-electron oxidation, forming the corresponding radical cations. At physiological pH, the radical cations of the probes react rapidly with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {O}_{ {2}}^{\bullet -}$$\end{document}O2∙-, leading to the specific 2-hydroxylated cationic products. We determined the rate constants of the reaction between \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {O}_{ {2}}^{\bullet -}$$\end{document}O2∙- and the radical cations of the probes. We also synthesized N-methylated analogs of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {HPr}^{+}$$\end{document}HPr+ and HE which were used in mechanistic studies. Methylation of the amine groups was not found to prevent the reaction between the radical cation of the probe and the superoxide, but it significantly increased the lifetime of the radical cation and had a substantial effect on the profiles of the oxidation products by inhibiting the formation of dimeric products. We conclude that the N-methylated analogs of HE and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {HPr}^{+}$$\end{document}HPr+ may be used as a scaffold for the design of a new generation of probes for intra- and extracellular superoxide.

Understanding gold toxicity in aerobically-grown Escherichia coli

Background

There is an emerging field to put into practice new strategies for developing molecules with antimicrobial properties. In this line, several metals and metalloids are currently being used for these purposes, although their cellular effect(s) or target(s) in a particular organism are still unknown. Here we aimed to investigate and analyze Au³⁺ toxicity through a combination of biochemical and molecular approaches.

Results

We found that Au³⁺ triggers a major oxidative unbalance in Escherichia coli, characterized by decreased intracellular thiol levels, increased superoxide concentration, as well as by an augmented production of the antioxidant enzymes superoxide dismutase and catalase. Because ROS production is, in some cases, associated with metal reduction and the concomitant generation of gold-containing nanostructures (AuNS), this possibility was evaluated in vivo and in vitro.

Conclusions

Au³⁺ is toxic for E. coli because it triggers an unbalance of the bacterium’s oxidative status. This was demonstrated by using oxidative stress dyes and antioxidant chemicals as well as gene reporters, RSH concentrations and AuNS generation.

Anti-Oxidizing Radical Polymer-Incorporated Perovskite Layers and their Photovoltaic Characteristics in Solar Cells

A small amount of a radical-bearing redox-active polymer, poly(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl methacrylate) (PTMA), incorporated into the photovoltaic organo-lead halide perovskite layer significantly enhanced durability of both the perovskite layer and its solar cell and even exposure to ambient air or oxygen. PTMA acted as an eliminating agent of the superoxide anion radical formed upon light irradiation on the layer, which can react with the perovskite compound and decompose it to lead halide. A cell fabricated with a PTMA-incorporated perovskite layer and a hole-transporting polytriarylamine layer gave a photovoltaic conversion efficiency of 18.8 % (18.2 % for the control without PTMA). The photovoltaic current was not reduced in the presence of PTMA in the perovskite layer probably owing to a carrier conductivity of PTMA. The incorporated PTMA also worked as a water-repelling coating for providing humidity-resistance to the organo-lead halide perovskite layer.

Pretreatment of Populus tomentiglandulosa protects hippocampal CA1 pyramidal neurons from ischemia-reperfusion injury in gerbils via increasing SODs expressions and maintaining BDNF and IGF-I expressions

To examine the effects of Populus tomentiglandulosa (PT) extract on the expressions of antioxidant enzymes and neurotrophic factors in the cornu ammonis 1 (CA1) region of the hippocampus at 5 min after inducing transient global cerebral ischemia (TGCI) in gerbils, TGCI was induced by occlusion of common carotid arteries for 5 min. Before ischemic surgery, 200 mg·kg^-1 PT extract was orally administrated once daily for 7 d. We performed neuronal nuclear antigen immunohistochemistry and Fluoro-Jade B staining. Furthermore, we determined in situ production of superoxide anion radical, expression levels of SOD1 and SOD2 as antioxidant enzymes and brain-derived neurotrophic factor (BDNF) and insulin-like growth factor I (IGF-I) as neurotrophic factors. Pretreatment with 200 mg·kg^-1 PT extract prevented neuronal death (loss). Furthermore, pretreatment with 200 mg·kg^-1 PT extract significantly inhibited the production of superoxide anion radical, increased expressions of SODs and maintained expressions of BDNF and IGF-I. Such increased expressions of SODs were maintained in the neurons after IRI. In summary, pretreated PT extract can significantly increase levels of SODs and protect the neurons against TGCI, suggesting that PT can be a useful natural agent to protect against TGCI.

Screening of X-ray responsive substances for the next generation of radiosensitizers

X-ray responsivity resulting in the generation of reactive oxygen species (ROS) was investigated in 9600 organic compounds that were selected by considering their structural diversity. We focused on superoxides that were primarily detected using dihydroethidium (DHE) and hydroxyl radicals, that were identified fluorometrically using 3'-(p-aminophenyl) Fluorescein (APF). Many organic compounds were discovered that responded to the DHE and/or APF assay using X-ray irradiation. These results suggest that some of these organic compounds emit either superoxides or hydroxyl radicals whereas others emit both under the influence of X-ray irradiation. The response of the derivatives of a hit compound with a partial change in the structure was also investigated. The products produced from DHE by X-ray irradiation were identified by HPLC to confirm the integrity of the process. Although, the reactions were suppressed by the superoxide dismutase (SOD), not only 2-hydroxyethidium (2-OH-E⁺), but also ethidium (E⁺) were detected. The results suggest that apart from a direct reaction, an indirect reaction may occur between DHE and the superoxides. Although X-ray responsiveness could not be inferred due to the molecular complexity of the investigated compounds, delineation of these reactions will facilitate the development of the next generation of radiosensitizers.

Co-loading antioxidant N-acetylcysteine attenuates cytotoxicity of iron oxide nanoparticles in hypoxia/reoxygenation cardiomyocytes

Purpose

Myocardial delivery of magnetic iron oxide nanoparticles (MNPs) might produce iron overload-induced myocardial injury, and the oxidative stress was regarded as the main mechanism. Therefore, we speculated antioxidant modification might be a reasonable strategy to mitigate the toxicity of MNPs.

Methods and results

Antioxidant N-acetylcysteine (NAC) was loaded into magnetic mesoporous silica coated Fe₃O₄ nanoparticles. Neonatal rat hypoxia/reoxygenation (H/R) cardiomyocytes were incubated with nanoparticles for 24 hrs. NAC can effectively mitigate iron-induced oxidative injury of cardiomyocytes, evidenced by reduced production of MDA, 8-iso-PGF2α, and 8-OHDG and maintained concentrations of SOD, CAT, GSH-Px, and GSH in ELISA and biochemical tests; downregulated expression of CHOP, GRP78, p62, and LC3-II proteins in Western Blot, and less cardiomyocytes apoptosis in flow cytometric analysis.

Conclusions

NAC modifying could suppress the toxic effects of Fe₃O₄ nanoparticles in H/R cardiomyocytes model in vitro, indicating a promising strategy to improve the safety of iron oxide nanoparticles.

Osmotic Stress Activates Two Reactive Oxygen Species Pathways with Distinct Effects on Protein Nanodomains and Diffusion

Physiological acclimation of plants to an everchanging environment is governed by complex combinatorial signaling networks that perceive and transduce various abiotic and biotic stimuli. Reactive oxygen species (ROS) serve as one of the second messengers in plant responses to hyperosmotic stress. The molecular bases of ROS production and the primary cellular processes that they target were investigated in the Arabidopsis (Arabidopsis thaliana) root. Combined pharmacological and genetic approaches showed that the RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) pathway and an additional pathway involving apoplastic ascorbate and iron can account for ROS production upon hyperosmotic stimulation. The two pathways determine synergistically the rate of membrane internalization, within minutes after activation. Live superresolution microscopy revealed at single-molecule scale how ROS control specific diffusion and nano-organization of membrane cargo proteins. In particular, ROS generated by RBOHs initiated clustering of the PLASMA MEMBRANE INTRINSIC PROTEIN2;1 aquaporin and its removal from the plasma membrane. This process is contributed to by clathrin-mediated endocytosis, with a positive role of RBOH-dependent ROS, specifically under hyperosmotic stress.

Evaluation of the elastic Young's modulus and cytotoxicity variations in fibroblasts exposed to carbon-based nanomaterials

Background

The conventional approaches to assess the potential cytotoxic effects of nanomaterials (NMs) mainly rely on in vitro biochemical assays. These assays are strongly dependent on the properties of the nanomaterials, for example; specific surface area (SSA), size, surface defects, and surface charge, and the host response. The NMs properties can also interfere with the reagents of the biochemical and optical assays leading to skewed interpretations and ambiguous results related to the NMs toxicity. Here, we proposed a structured approach for cytotoxicity assessment complemented with cells’ mechanical responses represented as the variations of elastic Young’s modulus in conjunction with conventional biochemical tests. Monitoring the mechanical properties responses at various times allowed understanding the effects of NMs to the filamentous actin cytoskeleton. The elastic Young’s modulus was estimated from the force volume maps using an atomic force microscope (AFM).

Results

Our results show a significant decrease on Young’s modulus, ~ 20%, in cells exposed to low concentrations of graphene flakes (GF), ~ 10% decrease for cells exposed to low concentrations of multiwalled carbon nanotubes (MWCNTs) than the control cells. These considerable changes were directly correlated to the disruption of the cytoskeleton actin fibers. The length of the actin fibers in cells exposed to GF was 50% shorter than the fibers of the cells exposed to MWCNT. Applying both conventional biochemical approach and cells mechanics, we were able to detect differences in the actin networks induced by MWCNT inside the cells and GF outside the cell’s membrane. These results contrast with the conventional live/dead assay where we obtained viabilities greater than 80% after 24 h; while the elasticity dramatically decreased suggesting a fast-metabolic stress generation.

Conclusions

We confirmed the production of radical oxygen species (ROS) on cells exposed to CBNs, which is related to the disruption of the cytoskeleton. Altogether, the changes in mechanical properties and the length of F-actin fibers confirmed that disruption of the F-actin cytoskeleton is a major consequence of cellular toxicity. We evidenced the importance of not just nanomaterials properties but also the effect of the location to assess the cytotoxic effects of nanomaterials.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0460-8) contains supplementary material, which is available to authorized users.

Curcumin loading potentiates the neuroprotective efficacy of Fe3O4 magnetic nanoparticles in cerebellum cells of schizophrenic rats

BACKGROUND

The aim of this study was to investigate the neurotoxic effects of Fe₃O₄ magnetic- CurNPs on isolated schizophrenia mitochondria of rats as an in vivo model.

METHODS

We designed CMN loaded superparamagnetic iron oxide nanoparticles (SPIONs) (Fe₃O₄ magnetic- CurNPs) to achieve an enhanced therapeutic effect. The physicochemical properties of Fe₃O₄ magnetic- CurNPs were characterized using X-ray diffraction (XRD), and dynamic laser light scattering (DLS) and zeta potential. Further, to prove Fe₃O₄ magnetic- CurNPs results in superior therapeutic effects, and also, the mitochondrial membrane potential collapse, mitochondrial complex II activity, reactive oxygen species generation, ATP level, cytochrome c release and histopathology of cerebellums were determined in brains of schizophrenic rats.

RESULTS

We showed that effective treatment with CMN reduced or prevented Fe₃O₄ magnetic-induced oxidative stress and mitochondrial dysfunction in the rat brain probably, as well as mitochondrial complex II activity, MMP, and ATP level were remarkably reduced in the cerebellum mitochondria of treated group toward control (p < 0.05). Therewith, ROS generation, and cytochrome c release were notably (p < 0.05) increased in the cerebellum mitochondria of treated group compared with control group.

CONCLUSION

Taken together, Fe₃O₄ magnetic- CurNPs exhibits potent antineurotoxicity activity in cerebellums of schizophrenic rats. This approach can be extended to preclinical and clinical use and may have importance in schizophernia treatment in the future. To our knowledge this is the first report that provides the Fe₃O₄ magnetic- CurNPs could enhance the neuroprotective effects of CMN in the Schizophrenia.

Hydroxychavicol, a key ingredient of Piper betle induces bacterial cell death by DNA damage and inhibition of cell division

Antibiotic resistance is a global problem and there is an urgent need to augment the arsenal against pathogenic bacteria. The emergence of different drug resistant bacteria is threatening human lives to be pushed towards the pre-antibiotic era. Botanical sources remain a vital source of diverse organic molecules that possess antibacterial property as well as augment existing antibacterial molecules. Piper betle, a climber, is widely used in south and south-east Asia whose leaves and nuts are consumed regularly. Hydroxychavicol (HC) isolated from Piper betle has been reported to possess antibacterial activity. It is currently not clear how the antibacterial activity of HC is manifested. In this investigation we show HC generates superoxide in E. coli cells. Antioxidants protected E. coli against HC induced cell death while gshA mutant was more sensitive to HC than wild type. DNA damage repair deficient mutants are hypersensitive to HC and HC induces the expression of DNA damage repair genes that repair oxidative DNA damage. HC treated E. coli cells are inhibited from growth and undergo DNA condensation. In vitro HC binds to DNA and cleaves it in presence of copper. Our data strongly indicates HC mediates bacterial cell death by ROS generation and DNA damage. Damage to iron sulfur proteins in the cells contribute to amplification of oxidative stress initiated by HC. Further HC is active against a number of Gram negative bacteria isolated from patients with a wide range of clinical symptoms and varied antibiotic resistance profiles.

Cytochrome b5 reductase is the component from neuronal synaptic plasma membrane vesicles that generates superoxide anion upon stimulation by cytochrome c

In this work, we measured the effect of cytochrome c on the NADH-dependent superoxide anion production by synaptic plasma membrane vesicles from rat brain. In these membranes, the cytochrome c stimulated NADH-dependent superoxide anion production was inhibited by antibodies against cytochrome b5 reductase linking the production to this enzyme. Measurement of the superoxide anion radical generated by purified recombinant soluble and membrane cytochrome b5 reductase corroborates the production of the radical by different enzyme isoforms. In the presence of cytochrome c, a burst of superoxide anion as well as the reduction of cytochrome c by cytochrome b5 reductase was measured. Complex formation between both proteins suggests that cytochrome b5 reductase is one of the major partners of cytochrome c upon its release from mitochondria to the cytosol during apoptosis. Superoxide anion production and cytochrome c reduction are the consequences of the stimulated NADH consumption by cytochrome b5 reductase upon complex formation with cytochrome c and suggest a major role of this enzyme as an anti-apoptotic protein during cell death.

Antimicrobial properties of a new type of photosensitizer derived from phthalocyanine against planktonic and biofilm forms of Staphylococcus aureus

BACKGROUND

Bacterial infection is a common clinical problem. Community-associated Staphylococcus aureus (S. aureus) infections can cause extensive tissue damage and necrosis. Photodynamic antimicrobial chemotherapy (PACT) has recently attracted attention as a feasible bacterial therapy. Octa-cationic zinc phthalocyanines are newly identified photosensitizers derived from phthalocyanines bearing 1, 2-ethanediamine groups and quaternized derivatives with different numbers of positive charges (ZnPcⁿ⁺, n = 4 or 8). Here we report the antimicrobial effects of ZnPcⁿ⁺-mediated PACT on planktonic and biofilm cultures of S. aureus.

METHODS

ZnPcⁿ⁺ uptake was detected by photometry after alkaline lysis. Dark-toxicity and light-mediated antimicrobial effects of the drug was determined by the plate count method. The production of intracellular reactive oxygen species (ROS) was detected by flow cytometry. SYTO 9 and propidium iodide (PI) were used to detect the bacterial cell membrane permeability. DNA damage after ZnPcⁿ⁺-PACT was analyzed by flow cytometry and PI staining. The destruction of biofilm was evaluated by scanning electron microscope (SEM).

RESULTS

The study of uptake showed that the relative fluorescence intensity of ZnPcⁿ⁺ in S. aureus peaked at 15 min. Generation of reactive oxygen species (ROS) by ZnPcⁿ⁺ was enhanced in PACT treatment groups. SYTO 9 and PI staining indicated that cell membrane was damaged. Flow cytometry and PI staining revealed DNA damage. Biofilms were damaged in PACT treatment groups.

CONCLUSIONS

Our results suggest that light-activated ZnPcⁿ⁺ can efficiently inhibit planktonic and biofilm cultures of S. aureus.

Anionic Cerium Oxide Nanoparticles Protect Plant Photosynthesis from Abiotic Stress by Scavenging Reactive Oxygen Species

Plant abiotic stress leads to accumulation of reactive oxygen species (ROS) and a consequent decrease in photosynthetic performance. We demonstrate that a plant nanobionics approach of localizing negatively charged, sub-11 nm, spherical cerium oxide nanoparticles (nanoceria) inside chloroplasts in vivo augments ROS scavenging and photosynthesis of Arabidopsis thaliana plants under excess light (2000 μmol m^-2 s^-1, 1.5 h), heat (35 °C, 2.5 h), and dark chilling (4 °C, 5 days). Poly(acrylic acid) nanoceria (PNC) with a hydrodynamic diameter (10.3 nm)-lower than the maximum plant cell wall porosity-and negative ζ-potential (-16.9 mV) exhibit significantly higher colocalization (46%) with chloroplasts in leaf mesophyll cells than aminated nanoceria (ANC) (27%) of similar size (12.6 nm) but positive charge (9.7 mV). Nanoceria are transported into chloroplasts via nonendocytic pathways, influenced by the electrochemical gradient of the plasma membrane potential. PNC with a low Ce³⁺/Ce⁴⁺ ratio (35.0%) reduce leaf ROS levels by 52%, including hydrogen peroxide, superoxide anion, and hydroxyl radicals. For the latter ROS, there is no known plant enzyme scavenger. Plants embedded with these PNC that were exposed to abiotic stress exhibit an increase up to 19% in quantum yield of photosystem II, 67% in carbon assimilation rates, and 61% in Rubisco carboxylation rates relative to plants without nanoparticles. In contrast, PNC with high Ce³⁺/Ce⁴⁺ ratio (60.8%) increase overall leaf ROS levels and do not protect photosynthesis from oxidative damage during abiotic stress. This study demonstrates that anionic, spherical, sub-11 nm PNC with low Ce³⁺/Ce⁴⁺ ratio can act as a tool to study the impact of oxidative stress on plant photosynthesis and to protect plants from abiotic stress.

The cathepsin B inhibitor z-FA-CMK induces cell death in leukemic T cells via oxidative stress

The cathepsin B inhibitor benzyloxycarbonyl-phenylalanine-alanine-chloromethyl ketone (z-FA-CMK) was recently found to induce apoptosis at low concentrations in Jurkat T cells, while at higher concentrations, the cells die of necrosis. In the present study, we showed that z-FA-CMK readily depletes intracellular glutathione (GSH) with a concomitant increase in reactive oxygen species (ROS) generation. The toxicity of z-FA-CMK in Jurkat T cells was completely abrogated by N-acetylcysteine (NAC), suggesting that the toxicity mediated by z-FA-CMK is due to oxidative stress. We found that L-buthionine sulfoximine (BSO) which depletes intracellular GSH through the inhibition of GSH biosynthesis in Jurkat T cells did not promote ROS increase or induce cell death. However, NAC was still able to block z-FA-CMK toxicity in Jurkat T cells in the presence of BSO, indicating that the protective effect of NAC does not involve GSH biosynthesis. This is further corroborated by the protective effect of the non-metabolically active D-cysteine on z-FA-CMK toxicity. Furthermore, in BSO-treated cells, z-FA-CMK-induced ROS increased which remains unchanged, suggesting that the depletion of GSH and increase in ROS generation mediated by z-FA-CMK may be two separate events. Collectively, our results demonstrated that z-FA-CMK toxicity is mediated by oxidative stress through the increase in ROS generation.

New cofactors and inhibitors for a DNA-cleaving DNAzyme: superoxide anion and hydrogen peroxide mediated an oxidative cleavage process

Herein, we investigated the effects of new cofactors and inhibitors on an oxidative cleavage of DNA catalysis, known as a pistol-like DNAzyme (PLDz), to discuss its catalytic mechanism. PLDz performed its catalytic activity in the presence of ascorbic acid (AA), in which Cu²⁺ promoted, whereas Fe²⁺ significantly inhibited the catalytic function. Since Fe²⁺/AA-generated hydroxyl radicals are efficient on DNA damage, implying that oxidative cleavage of PLDz had no relation with hydroxyl radical. Subsequently, we used Fe²⁺/H₂O₂ and Cu²⁺/H₂O₂ to identify the role of hydroxyl radicals in PLDz catalysis. Data showed that PLDz lost its activity with Fe²⁺/H₂O₂, but exhibited significant cleavage with Cu²⁺/H₂O₂. Because Fe²⁺/H₂O₂ and Cu²⁺/H₂O₂ are popular reagents to generate hydroxyl radicals and the latter also produces superoxide anions, we excluded the possibility that hydroxyl radical participated in oxidative cleavage and confirmed that superoxide anion was involved in PLDz catalysis. Moreover, pyrogallol, riboflavin and hypoxanthine/xanthine oxidase with superoxide anion and hydrogen peroxide generation also induced self-cleavage of PLDz, where catalase inhibited but superoxide dismutase promoted the catalysis, suggesting that hydrogen peroxide played an essential role in PLDz catalysis. Therefore, we proposed a catalytic mechanism of PLDz in which superoxide anion and hydrogen peroxide mediated an oxidative cleavage process.

Protective role of biliverdin against bile acid-induced oxidative stress in liver cells

The accumulation of bile acids affects mitochondria causing oxidative stress. Antioxidant defense is accepted to include biotransformation of biliverdin (BV) into bilirubin (BR) through BV reductase α (BVRα). The mutation (c.214C>A) in BLVRA results in a non-functional enzyme (mutBVRα). Consequently, homozygous carriers suffering from cholestasis develop green jaundice. Whether BVRα deficiency reduces BV-dependent protection against bile acids is a relevant question because a screening of the mut-BLVRA allele (a) in 311 individuals in Greenland revealed that this SNP was relatively frequent in the Inuit population studied (1% a/a and 4.5% A/a). In three human liver cell lines an inverse correlation between BVRα expression (HepG2>Alexander>HuH-7) and basal reactive oxygen species (ROS) levels was found, however the ability of BV to reduce oxidative stress and cell death induced by deoxycholic acid (DCA) or potassium dichromate (PDC) was similar in these cells. The transduction of BVRα or mutBVRα in human placenta JAr cells with negligible BVRα expression or the silencing of endogenous BVRα expression in liver cells had no effect on DCA-induced oxidative stress and cell death or BV-mediated cytoprotection. DCA stimulated both superoxide anion and hydrogen peroxide production, whereas BV only inhibited the latter. DCA and other dihydroxy-bile acids, but not PDC, induced up-regulation of both BVRα and heme oxygenase-1 (HO-1) in liver cells through a FXR independent and BV insensitive mechanism. In conclusion, BV exerts direct and BVRα-independent antioxidant and cytoprotective effects, whereas bile acid accumulation in cholestasis stimulates the expression of enzymes favoring the heme biotransformation into BV and BR.