New considerations on hormetic response against oxidative stress

Potential Defence Mechanisms Triggered by Monosodium Glutamate Sub-Chronic Consumption in Two-Year-Old Wistar Rats

Monosodium glutamate (MSG) is the sodium salt of glutamic acid (GLA), used as a flavour enhancer. MSG is considered a controversial substance. It is incriminated in disturbing the antioxidant system, but also has beneficial effects, as GLA metabolism plays a crucial role in homeostasis. This study highlights which positive or negative aspects of MSG sub-chronic consumption are better reflected in subjects potentially affected by advanced age. Daily doses of MSG were administered to four groups of two-year-old Wistar rats for 90 days: (I) 185 mg/kg bw, (II) 1500 mg/kg bw, (III) 3000 mg/kg bw and (IV) 6000 mg/kg bw, compared to a MSG non-consumer group. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, direct and total bilirubin, total cholesterol, triglycerides, creatinine and urea levels were analysed; stomach, liver and kidney samples were subjected to histopathological analysis. Although, in most cases, there were no statistical differences, interesting aspects of the dose-effect relationship were observed. After MSG sub-chronic consumption, the positive aspects of GLA seem to be reflected better than the negative ones. The hormesis effect, with low-level reactive oxygen species' protective effects and GLA metabolism, may represent the hypothesis of a potential defence mechanism triggered by MSG sub-chronic consumption in ageing rats.

Hormesis-tempting stressors driven by evolutionary factors for mitigating negative impacts instigated over extended exposure to chemical elements

The adaptive responses to moderate environmental challenges by the biological systems have usually been credited to hormesis. Since the hormetic biphasic dose-response illustrates a prominent pattern towards biological responsiveness, the studies concerning such aspects will get much more significance in risk assessment practices and toxicological evaluation research. From this point of view, the past few epochs have witnessed the extending recognition of the notion concerning hormesis. The extraction of its basic foundations of evolutionary perspectives-along with the probable underlying molecular and cellular mechanisms followed by the practical implications to enhance the quality of life. To get better and more effective output in this regard, the present article has evaluated the various observations of previous investigations. The intent of integrating the novel inferences concerning the hormesis-tempting stressors driven by predominant evolutionary factors for mitigating the adverse impacts that were prompted over frequent and continuous exposure to the various chemical elements. Such inferences can offer extensive insight into the implications concerning the risk assessment of hormesis.

The Hormetic Response of Soil P Extraction Induced by Low-Molecular-Weight Organic Acids

The hormetic effect is a toxicological phenomenon in the soil ecosystem. The influence of low-molecular-weight organic acids (LMWOAs) on the release and activation of soil phosphorus (P) has become the focus of toxicological research. To what extent LMWOAs can regulate the hormetic effect of P release and then influence soil P nutrients is worth attention. This study aimed to investigate the effects of different types and concentrations of exogenous LMWOAs on P extraction, establish the relationship between the concentration of LMWOAs and P extraction efficiency, and calculate the hormetic parameters to understand the mechanism of types and concentrations of LMWOAs in P extraction efficiency. Four organic acids, i.e., citric, oxalic, tartaric, and malic acids, induced hormetic effects on P extraction that were concentration dependent. The relationship between LMWOAs and P extraction efficiency was explained by a quadratic polynomial equation. The critical threshold of citric acid concentration was similar to that of oxalic acid, whereas that of tartaric acid was similar to that of malic acid. The critical thresholds of the P concentration extracted by malic acid and citric acid were higher than those extracted by oxalic acid and tartaric acid due to the differences in the structure and properties of LMWOAs. The critical thresholds of P extraction efficiency of oxalic acid were lower than those of the other three organic acid types. These results provide evidence for the use of citric acid and malic acid to increase soil P.

Methotrexate Induces an Antioxidant Hormetic Response in Primary Rat Astrocytes

Neurodegenerative diseases have increased worldwide in recent years. Their relationship with oxidative stress has motivated the research to find therapies and medications capable of suppressing oxidative damage and therefore slowing the progression of these diseases. Glutathione (GSH) is the most important cellular antioxidant in living beings and is responsible for regulating the cellular redox state. However, GSH cannot be administered by any route of administration, so molecules that increase its levels by activating Nrf2-ARE signaling pathway are explored; since Nrf2 regulates the main genes involved in GSH de novo synthesis and recycling. Astrocytes are the most important cell-type in the antioxidant cell response and are responsible for providing GSH and other substrates for neurons to have an efficient antioxidant response. Methotrexate (MTX) is an anti-inflammatory agent that has different cellular effects when administered at low or high concentrations. So in this study, we used MTX different concentrations and exposure times to induce a hormetic antioxidant response in rat primary astrocytes. Our results showed that 20 nM MTX pre-conditioning for 12 h augmented the GSH/GSSG ratio and protected cellular viability against a toxic MTX and H₂O₂ insult, which was abrogated when Nrf2 was inhibited by brusatol. Hence, MTX subsequent studies as a drug to counteract the progression of some stress-associated neurodegenerative diseases are suggested.

Defining the link between oxidative stress, behavioural reproductive suppression and heterothermy in the Natal mole-rat (Cryptomys hottentotus natalensis)

Sub-lethal effects, such as oxidative stress, can be linked to various breeding and thermophysiological strategies, which themselves can be linked to seasonal variability in abiotic factors. In this study, we investigated the subterranean, social living Natal mole-rat (Cryptomys hottentotus natalensis), which, unlike other social mole-rat species, implements heterothermy seasonally in an attempt to avoid exercise-induced hyperthermia and relies solely on behavioural reproductive suppression to maintain reproductive skew in colonies. Subsequently, we investigated how oxidative stress varied between season, sex and breeding status in Natal mole-rats. Oxidative markers included total oxidant status (TOS measure of total peroxides present), total antioxidant capacity (TAC), OSI (oxidative stress index) and malondialdehyde (MDA) to measure oxidative stress. Breeding and non-breeding mole-rats of both sexes were captured during the summer (wet season) and winter (dry season). Seasonal environmental variables (air temperature, soil temperature and soil moisture) had a significant effect on TOS, OSI and MDA, where season affected each sex differently. Unlike other social mole-rat species that use both physiological and behavioural means of reproductive suppression, no oxidative costs to reproduction were present in the Natal mole-rats. Males had significantly higher MDA than females, which was most apparent in summer (wet season). We conclude that the significant oxidative damage in males is a consequence of exercise-induced oxidative stress, exacerbated by increased burrow humidities and poorer heat dissipation abilities as a function of body mass. This study highlights the importance of both breeding and thermophysiological strategies in affecting oxidative stress.

Uptake, translocation, phytotoxicity, and hormetic effects of titanium dioxide nanoparticles (TiO2NPs) in Nigella arvensis L

The extensive application of titanium dioxide nanoparticles (TiO₂NPs) in agro-industrial practices leads to their high accumulation in the environment or agricultural soils. However, their threshold and ecotoxicological impacts on plants are still poorly understood. In this study, the hormetic effects of TiO₂NPs at a concentration range of 0-2500 mg/L on the growth, and biochemical and physiological behaviors of Nigella arvensis in a hydroponic system were examined for three weeks. The translocation of TiO₂NPs in plant tissues was characterized through scanning and transmission electron microscopy (SEM and TEM). The bioaccumulation of total titanium (Ti) was quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Briefly, the elongation of roots and shoots and the total biomass growth were significantly promoted at 100 mg/L TiO₂NPs. As the results indicated, TiO₂NPs had a hormesis effect on the proline content, i.e., a stimulating effect at the low concentrations of 50 and 100 mg/L and an inhibiting effect in the highest concentration of 2500 mg/L. A biphasic dose-response was observed against TiO₂NPs in shoot soluble sugar and protein contents. The inhibitory effects were detected at ≥1000 mg/L TiO₂NPs, where the synthesis of chlorophylls and carotenoid was reduced. At 1000 mg/ L, TiO₂NPs significantly promoted the cellular H₂O₂ generation, and increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Furthermore, it enhanced the total antioxidant content (TAC), total iridoid content (TIC), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. Overall, the study revealed the physiological and biochemical alterations in a medicinal plant affected by TiO₂NPs, which can help to use these NPs beneficially by eliminating their harmful effects.

Reconceptualization of Hormetic Responses in the Frame of Redox Toxicology

Cellular adaptive mechanisms emerging after exposure to low levels of toxic agents or stressful stimuli comprise an important biological feature that has gained considerable scientific interest. Investigations of low-dose exposures to diverse chemical compounds signify the non-linear mode of action in the exposed cell or organism at such dose levels in contrast to the classic detrimental effects induced at higher ones, a phenomenon usually referred to as hormesis. The resulting phenotype is a beneficial effect that tests our physiology within the limits of our homeostatic adaptations. Therefore, doses below the region of adverse responses are of particular interest and are specified as the hormetic gain zone. The manifestation of redox adaptations aiming to prevent from disturbances of redox homeostasis represent an area of particular interest in hormetic responses, observed after exposure not only to stressors but also to compounds of natural origin, such as phytochemicals. Findings from previous studies on several agents demonstrate the heterogeneity of the specific zone in terms of the molecular events occurring. Major factors deeply involved in these biphasic phenomena are the bioactive compound per se, the dose level, the duration of exposure, the cell, tissue or even organ exposed to and, of course, the biomarker examined. In the end, the molecular fate is a complex toxicological event, based on beneficial and detrimental effects, which, however, are poorly understood to date.

The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression

Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.

Fucoidan ameliorates acute and sub-chronic in vivo toxicity of the fungicide cholorothalonil in Oreochromis niloticus (Nile tilapia)

Fucoidans are sulfated glycans from marine algae that have both anti-cancer and anti-microbial properties. Chlorothalonil is a fungicide and insecticide commonly used in agriculture. Chlorothalonil is relatively toxic to fish and can potentially affect the aquaculture practices. In this study, we determined whether fucoidan administration would offer any protection from acute and subchronic toxicity of chlorothalonil on Nile tilapia. First, we tested the effect of chlorothalonil (20 to 140 μg/L, water-applied) on Nile tilapia in an acute exposure (six days). Survival analysis was performed, together with assessment of histopathology, oxidative stress (i.e., antioxidant status, hydrogen peroxide levels, malondialdehyde and nitric oxide levels) and immunohistochemistry to measure indicators of hepatic damage (i.e., caspase 3, p53, mini-chromosome maintenance proteins (MCM), and glutathione peroxidase). Chlorothalonil induced mild to severe histopathological alterations that were dose-dependent in various tissues of Nile tilapia. Chlorothalonil also induced oxidative stress as indicated by elevated biochemical markers. The highest recorded mortalities were associated with p53 expression. Additional feeding experiments were conducted with fucoidan (8 g/kg diet), following acute (40 μg/L for seven days) and sub-chronic (20 μg/L for six weeks) chlorothalonil application in Nile tilapia. Many of these same biochemical biomarkers of stress, oxidative damage response, and tissue pathology (evidence for hepatic neoplasm) were ameliorated by fucoidan, suggesting a protective effect of the compound. Agrochemicals are ubiquitous on a global scale, and the use of fucoidan as a feed additive may be beneficial for protecting aquatic animal health and aquaculture species from the impacts of chemical run-off.

Mechanisms for the impacts of graphene oxide on the developmental toxicity and endocrine disruption induced by bisphenol A on zebrafish larvae

The huge production and application of bisphenol A (BPA) and graphene oxide (GO) inevitably lead to their co-presence in aquatic ecosystems, which might cause joint toxic effects to aquatic organisms. Herein, zebrafish larvae at 3 d post fertilization (dpf) were exposed to BPA, GO, and their mixtures until 7 dpf. GO was ingested and localized in the gut. 5000 μg/L BPA alone induced distinct ultrastructure damage, which was alleviated by GO, indicating that GO reduced the developmental toxicity of BPA. The levels of endocrine-related genes and steroid hormones were all modulated to the greatest extent by 500 μg/L BPA, suggesting that BPA exhibited a remarkable endocrine disruption effect. However, the responses of some of these genes were recovered by GO, indicating that GO also alleviated the BPA-induced endocrine disruption. The mRNA levels of five genes in the extracellular matrix-receptor interaction pathway, two in the oxidative phosphorylation pathway, 18 in the metabolic pathways, and five in the peroxisome proliferator-activated receptor signaling pathway were distinctly altered by 5000 μg/L BPA, but most of them were recovered in the presence of GO. GO might relieve the BPA-induced developmental toxicity and endocrine disruption by recovering the genes related to the corresponding pathways.

Targeting Autophagy to Counteract Obesity-Associated Oxidative Stress

Reactive oxygen species (ROS) operate as key regulators of cellular homeostasis within a physiological range of concentrations, yet they turn into cytotoxic entities when their levels exceed a threshold limit. Accordingly, ROS are an important etiological cue for obesity, which in turn represents a major risk factor for multiple diseases, including diabetes, cardiovascular disorders, non-alcoholic fatty liver disease, and cancer. Therefore, the implementation of novel therapeutic strategies to improve the obese phenotype by targeting oxidative stress is of great interest for the scientific community. To this end, it is of high importance to shed light on the mechanisms through which cells curtail ROS production or limit their toxic effects, in order to harness them in anti-obesity therapy. In this review, we specifically discuss the role of autophagy in redox biology, focusing on its implication in the pathogenesis of obesity. Because autophagy is specifically triggered in response to redox imbalance as a quintessential cytoprotective mechanism, maneuvers based on the activation of autophagy hold promises of efficacy for the prevention and treatment of obesity and obesity-related morbidities.

Inflammaging, hormesis and the rationale for anti-aging strategies

We propose in this review that hormesis, a concept profoundly and systematically addressed by Mark Mattson, has to be considered a sort of comprehensive "contact point" capable of unifying several conceptualizations of the aging process, including those focused on the stress response, oxidative stress and chronic inflammation/inflammaging. A major strength of hormesis and inflammaging is that they have a strong evolutionary basis. Moreover, both hormesis and inflammaging frame the aging process within a lifelong perspective of adaptation to different types of stresses. Such adaptation perspective also suggests that the aging process is malleable, and predicts that effective anti-aging strategies should mimic what evolution did in the course of million years and that we have to learn how to exploit the great potential inherent in the hormetic/inflammatory responses. To this regard, new topics such as the production of mitokines to cope with mitochondrial dysfunction are emerging as possible anti-aging target. This approach opens theoretically the door to the possibility of modulating the individual aging rate and trajectory by adopting the most effective scientifically-based lifestyle regarding fundamentally nutrition and physical activity. In this scenario Mark Mattson's lesson and personal example will permanently enlighten the aging field and the quest for a healthy aging and longevity.

Effect of long-term moderate-exercise combined with metformin-treatment on antioxidant enzymes activity and expression in the gastrocnemius of old female Wistar rats

Oxidative stress is known to be involved in the etiology of sarcopenia, a progressive loss of muscle mass and force related to elderly incapacity. A successful intervention to prevent this condition has been exercise-based therapy. Metformin (MTF), an anti-diabetic drug with pleiotropic effects, is known to retain redox homeostasis. However, the combined use of MTF with exercise has shown controversial experimental results. Our research group has shown that MTF-treatment does not limit the benefits provided by exercise, probably by inducing a hormetic response. Hence, our aim was to evaluate the effect of exercise in combination with MTF-treatment on the redox state of old female Wistar rats. Animals were divided into six groups; three groups preformed exercise on a treadmill for 5 days/week for 20 months and the other three were sedentary. Also, two groups of each, exercised and sedentary animals were treated with MTF for 6 or 12 months correspondingly, beside the untreated groups. Rats were euthanized at 24 months. Muscular functionality was analyzed as the relation between the lean mass free of bone with respect to the grip strength. Superoxide dismutase, catalase, and glutathione peroxidase content, enzymatic activity and redox state were determined in the gastrocnemius muscle. Our results showed that the exercised group treated with MTF for 12 months presented higher GSH/GSSG rate and high antioxidant scavenging power in contrast to the MTF-treatment for 6 months, where the beneficial effect was less noticeable.

H2O2-preconditioned human adipose-derived stem cells (HC016) increase their resistance to oxidative stress by overexpressing Nrf2 and bioenergetic adaptation

BACKGROUND

Mesenchymal stem cells, including those derived from human adipose tissue (hASCs), are currently being widely investigated for cell therapy. However, when transplanted at the site of injury, the survival and engraftment rates of hASCs are low, mainly due to the harsh microenvironment they encounter, characterized by inflammation and oxidative stress. To overcome these therapeutic limitations, cell preconditioning with low-concentration of hydrogen peroxide (H2O2) has been proposed as a plausible strategy to increase their survival and adaptation to oxidative stress. Nonetheless, the underlying mechanisms of this approach are not yet fully understood. In this study, we analyzed molecular and bioenergetic changes that take place in H2O2 preconditioned hASCs.

METHODS

Long-term exposure to a low concentration of H2O2 was applied to obtain preconditioned hASCs (named HC016), and then, their response to oxidative stress was analyzed. The effect of preconditioning on the expression of Nrf2 and its downstream antioxidant enzymes (HO-1, SOD-1, GPx-1, and CAT), and of NF-κB and its related inflammatory proteins (COX-2 and IL-1β), were examined by Western blot. Finally, the Seahorse XF96 Flux analysis system was used to evaluate the mitochondrial respiration and glycolytic function, along with the total ATP production.

RESULTS

We found that under oxidative conditions, HC016 cells increased the survival by (i) decreasing intracellular ROS levels through the overexpression of the transcription factor Nrf2 and its related antioxidant enzymes HO-1, SOD-1, GPx-1, and CAT; (ii) reducing the secretion of pro-inflammatory molecules COX-2 and IL-1β through the attenuation of the expression of NF-κB; and (iii) increasing the total ATP production rate through the adaption of their metabolism to meet the energetic demand required to survive.

CONCLUSIONS

H2O2 preconditioning enhances hASC survival under oxidative stress conditions by stimulating their antioxidant response and bioenergetic adaptation. Therefore, this preconditioning strategy might be considered an excellent tool for strengthening the resistance of hASCs to harmful oxidative stress.

The S100B Protein and Partners in Adipocyte Response to Cold Stress and Adaptive Thermogenesis: Facts, Hypotheses, and Perspectives

In mammals, adipose tissue is an active secretory tissue that responds to mild hypothermia and as such is a genuine model to study molecular and cellular adaptive responses to cold-stress. A recent study identified a mammal-specific protein of the endoplasmic reticulum that is strongly induced in the inguinal subcutaneous white adipocyte upon exposure to cold, calsyntenin 3β (CLSTN3β). CLSTN3β regulates sympathetic innervation of thermogenic adipocytes and contributes to adaptive non-shivering thermogenesis. The calcium- and zinc-binding S100B is a downstream effector in the CLSTN3β pathways. We review, here, the literature on the transcriptional regulation of the S100b gene in adipocyte cells. We also rationalize the interactions of the S100B protein with its recognized or hypothesized intracellular (p53, ATAD3A, CYP2E1, AHNAK) and extracellular (Receptor for Advanced Glycation End products (RAGE), RPTPσ) target proteins in the context of adipocyte differentiation and adaptive thermogenesis. We highlight a chaperon-associated function for the intracellular S100B and point to functional synergies between the different intracellular S100B target proteins. A model of non-classical S100B secretion involving AHNAK/S100A10/annexin2-dependent exocytosis by the mean of exosomes is also proposed. Implications for related areas of research are noted and suggestions for future research are offered.

A trigger mechanism of herbicides to phytoplankton blooms: From the standpoint of hormesis involving cytochrome b559, reactive oxygen species and nitric oxide

The cause of phytoplankton blooms has been extensively discussed and largely attributed to favorable external conditions such as nitrogen/phosphorus resources, pH and temperature. Here from the standpoint of hormesis response, we propose that phytoplankton blooms are initiated by stimulatory effects of low concentrations of herbicides as environmental contaminants spread over estuaries and lakes. The experimental results revealed general stimulations by herbicides on Microcystis aeruginosa and Selenastrum capricornutum, with the maximum stimulation in the 30-60% range, depending on the agent and experiment. In parallel with enhancing stimulation, the ratio of HP (high-potential) form to LP (low-potential) form of cytochrome b₅₅₉ (RHL) was observed decreasing, while intracellular reactive oxygen species (ROS) were observed increasing. We propose that the ROS originated from the thermodynamic transformation of cytochrome b₅₅₉, enhancing the stimulatory response. Furthermore, the results also proved that thermodynamic states of cytochrome b₅₅₉ could be modulated by nitric oxide, thus affecting cellular equilibrium of oxidative stress (OS) and correspondingly causing the inhibitory effect of higher concentrations of herbicides on phytoplankton. This suggests that hormesis substantially derives from equilibrium shifting of OS. Moreover, it is reasonable to infer that phytoplankton blooms would be motivated by herbicides or other environmental pollutants. This study provides a new thought into global phytoplankton blooms from a contaminant perspective.

Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

Hormesis, which describes the stimulatory effect of low doses of toxic substances on growth, is a well-known phenomenon in the plant and animal kingdoms. However, the mechanisms that are involved in this phenomenon are still poorly understood. We performed preliminary studies on corn coleoptile sections, which showed a positive correlation between the stimulation of growth by Cd or Pb and an increase in the auxin and H₂O₂ content in the coleoptile sections. Subsequently, we grew corn seedlings in hydroponic culture and tested a wide range of Cd or Pb concentrations in order to determine hormetic growth stimulation. In these seedlings the gas exchange and the chlorophyll a fluorescence, as well as the content of chlorophyll, flavonol, auxin and hydrogen peroxide, were measured. We found that during the hormetic stimulation of growth, the response of the photosynthetic apparatus to Cd and Pb differed significantly. While the application of Cd mostly caused a decrease in various photosynthetic parameters, the application of Pb stimulated some of them. Nevertheless, we discovered that the common features of the hormetic stimulation of shoot growth by heavy metals are an increase in the auxin and flavonol content and the maintenance of hydrogen peroxide at the same level as the control plants.

Long-Term Moderate Exercise Combined with Metformin Treatment Induces an Hormetic Response That Prevents Strength and Muscle Mass Loss in Old Female Wistar Rats

Sarcopenia is a syndrome characterized by a progressive and generalized skeletal muscle mass and strength loss, as well as a poor physical performance, which as strongly been associated with aging. Sedentary lifestyle in the elderly contributes to this condition; however, physical activity improves health, reducing morbidity and mortality. Recent studies have shown that metformin (MTF) can also prevent muscle damage promoting muscular performance. To date, there is great controversy if MTF treatment combined with exercise training improves or nullifies the benefits provided by physical activity. This study is aimed at evaluating the effect of long-term moderate exercise combined with MTF treatment on body composition, strength, redox state, and survival rate during the life of female Wistar rats. In this study, rats performed moderate exercise during 20 of their 24 months of life and were treated with MTF for one year or for 6 months, i.e., from 12 to 24 months old and 18 to 24 months old. The body composition (percentage of fat, bone, and lean mass) was determined using a dual-energy X-ray absorption scanner (DXA), and grip strength was determined using a dynamometer. Likewise, medial and tibial nerve somatosensory evoked potentials were evaluated and the redox state was measured by HPLC, calculating the GSH/GSSG ratio in the gastrocnemius muscle. Our results suggest- that the MTF administration, both in the sedentary and the exercise groups, might activate a mechanism that is directly related to the induction of the hormetic response through the redox state modulation. MTF treatment does not eliminate the beneficial effects of exercise throughout life, and although MTF does not increase muscle mass, it increases longevity.

Inhibitory effect of purple rice husk extract on AFB1-induced micronucleus formation in rat liver through modulation of xenobiotic metabolizing enzymes

Background

Rice husk, a waste material produced during milling, contains numerous phytochemicals that may be sources of cancer chemopreventive agents. Various biological activities of white and colored rice husk have been reported. However, there are few comparative studies of the cancer chemopreventive effects of white and colored rice husk.

Methods

This study investigated the cancer chemopreventive activities of two different colors of rice husk using in vitro and in vivo models. A bacterial mutation assay using Salmonella typhimurium strains TA98 and TA100 was performed; enzyme induction activity in murine hepatoma cells was measured, and a liver micronucleus test was performed in male Wistar rats.

Results

The white rice husk (WRHE) and purple rice husk (PRHE) extracts were not mutagenic in Salmonella typhimurium TA98 or TA100 in the presence or absence of metabolic activation. However, the extracts exhibited antimutagenicity against aflatoxin B₁ (AFB₁) and 2-amino-3,4 dimethylimidazo[4,5-f]quinolone (MeIQ) in a Salmonella mutation assay. The extracts also induced anticarcinogenic enzyme activity in a murine Hepa1c1c7 hepatoma cell line. Interestingly, PRHE but not WRHE exhibited antigenotoxicity in the rat liver micronucleus test. PRHE significantly decreased the number of micronucleated hepatocytes in AFB₁-initiated rats. PRHE contained higher amounts of phenolic compounds and vitamin E than WRHE in both tocopherols and tocotrienols as well as polyphenol such as cyanidin-3-glucoside, protocatechuic acid and vanillic acid. Furthermore, PRHE increased CYP1A1 and 1A2 activities while decreasing CYP3A2 activity in the livers of AFB₁-treated rats. PRHE also enhanced various detoxifying enzyme activities, including glutathione S-transferase, NAD(P)H quinone oxidoreductase and heme oxygenase.

Conclusions

PRHE showed potent cancer chemopreventive activity in a rat liver micronucleus assay through modulation of phase I and II xenobiotic metabolizing enzymes involved in AFB₁ metabolism. Vitamin E and phenolic compounds may be candidate antimutagens in purple rice husk.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2647-9) contains supplementary material, which is available to authorized users.

In vivo anti-arthritic effect and repeated dose toxicity of standardized methanolic extracts of Buddleja cordata Kunth (Scrophulariaceae) wild plant leaves and cell culture

ETHNOPHARMACOLOGICAL RELEVANCE

Buddleja cordata Humb. Bonpl. & Kunth, known by the population as Tepozán blanco, is a shrub plant used in traditional herbal medicine in Mexico for the treatment of tumors, cancer, sores, skin burns, rheumatic pains and diseases related to inflammatory processes such as arthritis; authors adjudicate this etno-medicinal effect to the presence of secondary metabolites in the plant such as verbascoside, however due to its low concentration in recent years biotechnological tools are applied as cell culture to biosynthesize these pharmacological active metabolites in greater quantities.

AIM OF THE STUDY

Evaluate the possible toxic effect after a daily administration of MeOH extracts from wild plant leaves (Bc-Wp), and cell culture (Bc-Cc) of B. cordata for 28 days, and after their anti-edematous and antioxidant activities in vivo, as well their effect on the cytokines profile during experimental arthritis induced by complete Freund's adjuvant.

MATERIALS AND METHODS

Both extracts were evaluated in CD1 male mice first in a toxicity test of repeated dose administrations (1 g/kg) for 28 days, after which pharmacological activity of both extracts was measure during experimental induced arthritis where three doses were tested, at the end of the study edema formation, body weight gain and antioxidant activity were measure in edema and ganglionic tissues. Finally, dose that exerted the best protective effect (250 mg/kg) was evaluated to quantify its effect over ganglionic tissue concentration of lymphocytes T CD4⁺, and cytokines (IL-1β, TNF-α and IL-10), as well histological analysis in arthritic mice.

RESULTS

Both extracts (Bc-Wp and Bc-Cc) did not exert lethality, however body weight gain and food in-take were lower than in healthy mice administered with vehicles, also extract-treated animals showed a decrease in serum lipid concentration and only Bc-Wp extract treated animals decrease serum alkaline phosphatase after 28 daily administration compared to healthy un-treated mice. During experimental arthritis best inhibition effect over edema development was observed in those animals administered with both extracts at dose of 250 mg/kg (Bc-Wp and Bc-Cc) on day 28, compared to CFA un-treated mice. Also both extracts reduce oxidative damage over lipids and proteins at the same dose, in both ganglionic and edema tissue, as well antioxidant enzymatic response was reduced in both tissues compared to arthritic un-treated group. In ganglionic tissue of arthritic mice, CD4⁺ lymphocytes concentration was reduced by Bc-Wp and Bc-Cc treatment (250 mg/kg) respectively, as well IL-1β, and TNF-α levels. Only arthritic animals treated with Bc-Cc extract at 250 mg/kg generated a significant increase of IL-10 doubling the levels compared to CFA un-treated group. Histological analysis of popliteal ganglion showed that both extracts decrease the incidence of lytic lesions, lipid inclusions and leukocyte infiltration.

CONCLUSION

Methanolic extracts of wild Buddleja cordata and its cell cultures did not generated lethality after a daily administration for 28 days at 1 g/kg, but it was observed that both showed a lipid-lowering effect. Also at dose of 250 mg/kg both extracts exerted anti-edematous, protection against the oxidation of lipid and proteins, regulation on antioxidant enzymatic response, down-regulation on lymphocytes CD4⁺ producers of IL-1β and TNF-α, an increase in IL-10 levels, which caused a decrease in leukocyte infiltration in ganglionic tissue during experimental arthritis.

Behavioral and biochemical effects of the antifouler and antidandruff zinc pyrithione on the freshwater fish Gambusia holbrooki

The presence of pharmaceutical residues in the aquatic environment is receiving great attention since the levels of these substances have significantly increased in this compartment, potentially leading to adverse ecological effects. Zinc pyrithione (ZnPt) is a widely used organometallic biocide, which is incorporated into antifouling formulas, such as paints, to prevent the establishment of biofilms on surfaces exposed to the aquatic environment. It is also used in cosmetics, such as antidandruff shampoos and soaps. Considering this wide use, and the absence of a significant amount of data on the toxicity of ZnPt especially towards non-target organisms, the objective of this study was to characterize the toxicity of ZnPt, on several ecological relevant endpoints assessed in the fish Gambusia holbrooki. For this purpose, we measured traits related to feeding and aggressive behavior, as well as indicators of oxidative stress (CAT and GSTs), neurotoxicity (AChE), and anaerobic metabolism (LDH), after acute and chronic exposures to ZnPt. In terms of behavioral features, the feeding test showed the occurrence of significant differences between the control animals and those exposed to a concentration of ZnPt of 45 μg/L. In addition, ZnPt caused changes in terms of oxidative stress biomarkers (CAT and GSTs), for both exposure periods. ZnPt was also capable of causing changes in the cholinergic neurotransmission functioning and anaerobic metabolism, but only following the chronic exposure.

Effect of 3-nitropropionic acid inducing oxidative stress and apoptosis of granulosa cells in geese

The mechanism of action by which oxidative stress induces granulosa cell apoptosis, which plays a vital role in initiating follicular atresia, is not well understood. In the present study, the effect of 3-nitropropionic acid (3-NPA) on oxidative stress and apoptosis in granulosa cells in geese was investigated. Our results showed that treatment with 3-NPA at 5.0 mmol/l for 24 h increased intracellular reactive oxygen species (ROS) production by 25.4% and decreased granulosa cell viability by 45.5% (P<0.05). Catalase and glutathione peroxidase gene expression levels in granulosa cells treated with 3-NPA were 1.32- and 0.49-fold compared with those of the control cells, respectively (P <0.05). A significant decrease in the expression level of B-cell lymphoma 2 (Bcl-2) protein and remarkable increases in the levels of Bax, p53 and cleaved-Caspase 3 proteins and the ratio of Bax/Bcl-2 expression in granulosa cells treated with 3-NPA were observed (P<0.05). Furthermore, a 38.43% increase in the percentage of early apoptotic cells was also observed in granulosa cells treated with 3-NPA (P<0.05). Moreover, the expression levels of NF-κB, Nrf2, Fhc, Hspa2 and Ho-1 in granulosa cells treated with 3-NPA were elevated 4.36-, 1.63-, 3.62-, 27.54- and 10.48-fold compared with those of the control cells (P<0.05), respectively. In conclusion, the present study demonstrates that treatment with 3-NPA induces ROS production and apoptosis and inhibits the viability of granulosa cells in geese. Furthermore, 3-NPA triggers increases in the expression of cleaved-Caspase 3 protein and the ratio of Bax/Bcl-2 expression, and induces the early apoptosis of granulosa cells.

Effect of the FE2+ chelation by 2,2'-dipyridyl in the doxorubicin-induced lethality in breast tumor cell lines

Breast cancer cells may exhibit changes in iron homeostasis, which results in increased labile iron pool (LIP) levels. Several studies highlight the crucial role of high LIP levels in the maintenance of tumor cell physiology. Iron chelators have been tested in anticancer therapy in combination with chemotherapeutic agents, to improve drug efficacy. Thus, the aim of this study was to evaluate the effect of 2,2'-dipyridyl (DIP), a Fe²⁺ chelator, in combination with doxorubicin (DOX) in breast tumor cells. The maximum concentration of DIP that did not significantly reduce the viability of MDA-MB-231 cells was 10μM and for MCF-7 cells was 50μM. We observed that MCF-7 had higher LIP levels than MDA-MB-231 cells. DIP alone increased ROS generation in MCF-7 cells, and DIP pretreatment reduced ROS generation induced by DOX treatment. In conclusion, the increase in MCF-7 cell viability induced by DIP pretreatment in DOX-treated cells seems to be related to an increase in the cellular antioxidant capacity and the iron chelator did not improve drug efficacy in the two breast tumor cell lines analyzed.

3-NP-induced Huntington's-like disease impairs Nrf2 activation without loss of cardiac function in aged rats

Cardiovascular diseases (CVDs) are one of the leading causes of death in patients over 60years with Huntington's disease (HD). Here, we investigated if age-related oxidative stress (OS) is a relevant factor to develop cardiac damage in an in vivo model of striatal neurodegeneration induced by 3-nitropropionic acid (3-NP). We also evaluated the potential effect of tert-butylhydroquinone (tBHQ) to increase the Nrf2-regulated antioxidant response in hearts from adult and aged rats intoxicated with 3-NP. Our results showed that 3-NP-treatment did not induce cardiac dysfunction, neither in adult nor in aged rats. However, at the cellular level, adult animals showed higher susceptibility to 3-NP-induced damage than aged rats, which suggest that chronic oxidative stress ongoing during aging might have induced an hormetic response that probably prevented from further 3-NP damage. We also found that the oxidative unbalance concurs with unresponsiveness of the Nrf2-mediated antioxidant response in old animals.

Tert-buthylhydroquinone pre-conditioning exerts dual effects in old female rats exposed to 3-nitropropionic acid

The brain is a very susceptible organ to structural and functional alterations caused by oxidative stress and its vulnerability increases with age. Understanding the antioxidant response activated by the transcription factor Nrf2 has become very important in the aging field in order to activate cellular protection. However, the role of Nrf2 inducers during old age has not been completely understood. Our aim was to activate the Nrf2 pathway by pre-treating old rats with a widely used Nrf2-inducer, tert-buthylhydroquinone (tBHQ), prior to 3-nitropropionic acid (3-NP) insult, in order to evaluate its effects at a behavioral, morphological and biochemical levels. 3-NP has been used to reproduce the biochemical and pathophysiological characteristics of Huntington's disease due to an oxidative effect. Our results suggest that tBHQ confers an important protective effect against 3-NP toxicity; nevertheless, Nrf2 seems not to be the main protective pathway associated to neuroprotection. Hormetic responses include the activation of more than one transcription factor. Nrf2 and NFκB are known to simultaneously initiate different cellular responses against stress by triggering parallel mechanisms, therefore NFκB nuclear accumulation was also evaluated.

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Old rats are able to activate an hormetic response against 3NP toxicity.

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tBHQ pre-conditioning exerts an antioxidant-prooxidant, dual role in old rats.

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tBHQ activates a crosstalk mechanism between NFκB and Nrf2.

Role of oxidative stress and antioxidants in daily nutrition and human health

Diet may be defined as a complex process that should involve a deeper comprehension of metabolism, energy balance, and the molecular pathways involved in cellular stress response and survival, gut microflora genetics, enzymatic polymorphism within the human population, and the role of plant-derived polyphenols in this context. Metabolic syndrome, encompassing pathologies with a relatively high morbidity, such as type 2 diabetes, obesity, and cardiovascular disease, is a bullet point of the big concern about how daily dietary habits should promote health and prevent metabolic impairments to prevent hospitalization and the need for health care. From a clinical point of view, very few papers deal with this concern, whereas most of the evidence reported focuses on in vitro and animal models, which study the activity of phytochemicals contained in the daily diet. A fundamental issue addressed by dietitians deals with the role exerted by redox-derived reactive species. Most plant polyphenols act as antioxidants, but recent evidence supports the idea that these compounds primarily activate a mild oxidative stress to elicit a positive, beneficial response from cells. How these compounds may act upon the detoxifying system exerting a scavenging role from reactive oxygen or nitrogen species is still a matter of debate; however, it can be argued that their role is even more complex than expected, acting as signaling molecules in the cross-talk mitochondria-endoplasmic reticulum and in enzymatic pathways involved in the energetic balance. In this relationship, a fundamental role is played by the brain-adipose tissue-gut axis. The aim of this review was to elucidate this topic and the state of art about the role of reactive species in cell signaling and the function of metabolism and survival to reappraise the role of plant-derived chemicals.

Investigation of the oxidative stress condition for occupational exposure to methyl methacrylate

The purpose of this study is the evaluation of possible toxicological effects on dental personnel, who are exposed to the production materials of prostheses during their entire working life. In this study, the level of methyl methacrylate (MMA) in ambient air was measured as an indicator of external exposure on the personnel. In order to evaluate the possible toxic effects of oxidative stress, which is thought to play an important role in the formation process of many diseases such as cancer, blood samples of volunteers were examined via the ultraviolet-spectroscopic determination of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase antioxidant enzyme activities, comparing occupationally MMA-exposed ( n = 69) and control ( n = 67) groups. In these groups, malondialdehyde (MDA) and glutathione levels were also determined by the same method. The results showed that SOD activity and MDA and glutathione levels were significantly higher in the exposed group when compared with the control group ( p < 0.001). A significant decrease was determined in the glutathione peroxidase activities of the exposed group ( p < 0.05). No significant difference in CAT activities between the groups has been found. When the results obtained in the study are considered, it is suggested that an adaptive response might be developed by dental technicians against low-level MMA exposure.

Associations of air pollution exposure with blood pressure and heart rate variability are modified by oxidative stress genes: A repeated-measures panel among elderly urban residents

BACKGROUND

Oxidative stress has been suggested as a major cause of elevated blood pressure (BP) and reduced heart rate variability (HRV) due to air pollution. We hypothesized that the associations of air pollution exposure with BP and HRV are modified by oxidative stress gene polymorphisms.

METHODS

Between 2008 and 2010, we conducted up to 5 surveys of 547 elderly participants, measured their BP and HRV, and genotyped 47 single nucleotide polymorphisms (SNPs) in 18 oxidative stress genes. Linear mixed models were constructed to evaluate the associations of particulate matter ≤10 μm, nitrogen dioxide, and sulfur dioxide with BP and HRV, as well as the modifications of these associations by the genotyped SNPs.

RESULTS

Single-SNP analyses revealed interactions between air pollution and 15 SNPs (for BP) and 33 SNPs (for HRV) (all, P for interaction < 0.05). When we generated genetic risk scores for BP and HRV, using the SNPs with interactions in the single-SNP models, we found that associations of air pollution exposure with BP and HRV were modified by the genetic risk scores (P for interaction < 0.05).

CONCLUSIONS

These results strongly suggest that the associations of air pollution with BP and HRV are mediated by oxidative stress pathways.

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.

Hormetic effect of rotenone in primary human fibroblasts

BACKGROUND

Rotenone inhibits the electron transfer from complex I to ubiquinone, in this way interfering with the electron transport chain in mitochondria. This chain of events induces increased levels of intracellular reactive oxygen species, which in turn can contribute to acceleration of telomere shortening and induction of DNA damage, ultimately resulting in aging. In this study, we investigated the effect of rotenone treatment in human fibroblast strains.

RESULTS

For the first time we here describe that rotenone treatment induced a hormetic effect in human fibroblast strains. We identified a number of genes which were commonly differentially regulated due to low dose rotenone treatment in fibroblasts independent of their cell origin. However, these genes were not among the most strongly differentially regulated genes in the fibroblast strains on treatment with rotenone. Thus, if there is a common hormesis regulation, it is superimposed by cell strain specific individual responses. We found the rotenone induced differential regulation of pathways common between the two fibroblast strains, being weaker than the pathways individually regulated in the single fibroblast cell strains. Furthermore, within the common pathways different genes were responsible for this different regulation. Thus, rotenone induced hormesis was related to a weak pathway signal, superimposed by a stronger individual cellular response, a situation as found for the differentially expressed genes.

CONCLUSION

We found that the concept of hormesis also applies to in vitro aging of primary human fibroblasts. However, in depth analysis of the genes as well as the pathways differentially regulated due to rotenone treatment revealed cellular hormesis being related to weak signals which are superimposed by stronger individual cell-internal responses. This would explain that in general hormesis is a small effect. Our data indicate that the observed hormetic phenotype does not result from a specific strong well-defined gene or pathway regulation but from weak common cellular processes induced by low levels of reactive oxygen species. This conclusion also holds when comparing our results with those obtained for C. elegans in which the same low dose rotenone level induced a life span extending, thus hormetic effect.

Prooxidant and antioxidant properties of salicylaldehyde isonicotinoyl hydrazone iron chelators in HepG2 cells

BACKGROUND

Salicylaldehyde isonicotinoyl hydrazone (SIH) is an iron chelator of the aroylhydrazone class that displays antioxidant or prooxidant effects in different mammalian cell lines. Because the liver is the major site of iron storage, elucidating the effect of SIH on hepatic oxidative metabolism is critical for designing effective hepatic antioxidant therapies.

METHODS

Hepatocyte-like HepG2 cells were exposed to SIH or to analogs showing greater stability, such as N'-[1-(2-Hydroxyphenyl)ethyliden]isonicotinoyl hydrazide (HAPI), or devoid of iron chelating properties, such as benzaldehyde isonicotinoyl hydrazone (BIH), and toxicity, oxidative stress and antioxidant (glutathione) metabolism were evaluated.

RESULTS

Autoxidation of Fe(2+)in vitro increased in the presence of SIH or HAPI (but not BIH), an effect partially blocked by Fe(2+) chelation. Incubation of HepG2 cells with SIH or HAPI (but not BIH) was non-toxic and increased reactive oxygen species (ROS) levels, activated the transcription factor Nrf2, induced the catalytic subunit of γ-glutamate cysteine ligase (Gclc), and increased glutathione concentration. Fe(2+) chelation decreased ROS and inhibited Nrf2 activation, and Nrf2 knock-down inhibited the induction of Gclc in the presence of HAPI. Inhibition of γ-glutamate cysteine ligase enzymatic activity inhibited the increase in glutathione caused by HAPI, and increased oxidative stress.

CONCLUSIONS

SIH iron chelators display both prooxidant (increasing the autoxidation rate of Fe(2+)) and antioxidant (activating Nrf2 signaling) effects.

GENERAL SIGNIFICANCE

Activation by SIH iron chelators of a hormetic antioxidant response contributes to their antioxidant properties and modulates the anti- and pro-oxidant balance.