Biphasic dose responses in biology, toxicology and medicine: accounting for their generalizability and quantitative features

Ultraviolet Resistance of Microorganisms Isolated from Uranium-Rich Minerals from Perus, Brazil

The district of Perus, located in the city of São Paulo, Brazil, is renowned for its weathered granitic-pegmatitic masses, which harbor a significant number of uraniferous minerals that contribute to ionizing radiation levels up to 20 times higher than the background levels. In this study, aseptically collected mineral samples from the area were utilized to isolate 15 microorganisms, which were subjected to pre-screening tests involving UV-C and UV-B radiation. The microorganisms that exhibited the highest resistance to ultraviolet (UV) radiation were selected for the construction of survival curves for UV-C, broad-band UV-B, and solar simulation resistance testing. Subsequently, the four strains that demonstrated superior survival capabilities under UV radiation exposure were chosen for 16S rRNA gene sequencing. Among these, Nocardioides sp. O4R and Nocardioides sp. MA2R demonstrated the most promising outcomes in the UV radiation resistance assessments, showcasing comparable performance to the well-established radioresistant model organism Deinococcus radiodurans. These findings underscore the potential of naturally occurring high-radiation environments as valuable resources for the investigation of UV-resistant microorganisms.

Reduced Insulin Resistance and Oxidative Stress in a Mouse Model of Metabolic Syndrome following Twelve Weeks of Citrus Bioflavonoid Hesperidin Supplementation: A Dose-Response Study

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities affecting ~25% of adults and is linked to chronic diseases such as cardiovascular disease, cancer, and neurodegenerative diseases. Oxidative stress and inflammation are key drivers of MetS. Hesperidin, a citrus bioflavonoid, has demonstrated antioxidant and anti-inflammatory properties; however, its effects on MetS are not fully established. We aimed to determine the optimal dose of hesperidin required to improve oxidative stress, systemic inflammation, and glycemic control in a novel mouse model of MetS. Male 5-week-old C57BL/6 mice were fed a high-fat, high-salt, high-sugar diet (HFSS; 42% kcal fat content in food and drinking water with 0.9% saline and 10% high fructose corn syrup) for 16 weeks. After 6 weeks of HFSS, mice were randomly allocated to either the placebo group or low- (70 mg/kg/day), mid- (140 mg/kg/day), or high-dose (280 mg/kg/day) hesperidin supplementation for 12 weeks. The HFSS diet induced significant metabolic disturbances. HFSS + placebo mice gained almost twice the weight of control mice (p < 0.0001). Fasting blood glucose (FBG) increased by 40% (p < 0.0001), plasma insulin by 100% (p < 0.05), and HOMA-IR by 150% (p < 0.0004), indicating insulin resistance. Hesperidin supplementation reduced plasma insulin by 40% at 140 mg/kg/day (p < 0.0001) and 50% at 280 mg/kg/day (p < 0.005). HOMA-IR decreased by 45% at both doses (p < 0.0001). Plasma hesperidin levels significantly increased in all hesperidin groups (p < 0.0001). Oxidative stress, measured by 8-OHdG, was increased by 40% in HFSS diet mice (p < 0.001) and reduced by 20% with all hesperidin doses (p < 0.005). In conclusion, hesperidin supplementation reduced insulin resistance and oxidative stress in HFSS-fed mice, demonstrating its dose-dependent therapeutic potential in MetS.

Differential roles of cyclooxygenase enzymes in the regulation of murine juvenile undifferentiated spermatogonia

BACKGROUND

Acetaminophen and ibuprofen are widely administered to babies due to their presumed safety as over-the-counter drugs. However, no reports exist on the effects of cyclooxygenase inhibitors on undifferentiated spermatogonia and spermatogonial stem cells. Infancy represents a critical period for spermatogonial stem cell formation and disrupting spermatogonial stem cells or their precursors may be associated with infertility and testicular cancer formation.

OBJECTIVES

The goal of this study was to examine the molecular and functional impact of cyclooxygenase inhibition and silencing on early steps of undifferentiated spermatogonia (u spg) and spermatogonial stem cell development, to assess the potential reproductive risk of pharmaceutical cyclooxygenase inhibitors.

METHODS

The effects of cyclooxygenase inhibition were assessed using the mouse C18-4 undifferentiated juvenile spermatogonial cell line model, previously shown to include cells with spermatogonial stem cell features, by measuring prostaglandins, cell proliferation, and differentiation, using cyclooxygenase 1- and cyclooxygenase 2-selective inhibitors NS398, celecoxib, and FR122047, acetaminophen, and ibuprofen. Cyclooxygenase 1 gene silencing was achieved using a stable short-hairpin RNA approach and clone selection, then assessing gene and protein expression in RNA sequencing, quantitative real-time polymerase chain reaction, and immunofluorescence studies.

RESULTS

Cyclooxygenase 2 inhibitors NS398 and celecoxib, as well as acetaminophen, but not ibuprofen, dose-dependently decreased retinoic acid-induced expression of the spg differentiation gene Stra8, while NS398 decreased the spg differentiation marker Kit, suggesting that cyclooxygenase 2 is positively associated with spg differentiation. In contrast, short-hairpin RNA-based cyclooxygenase 1 silencing in C18-4 cells altered cellular morphology and upregulated Stra8 and Kit, implying that cyclooxygenase 1 prevented spg differentiation. Furthermore, RNA sequencing analysis of cyclooxygenase 1 knockdown cells indicated the activation of several signaling pathways including the TGFb, Wnt, and Notch pathways, compared to control C18-4 cells. Notch pathway genes were upregulated by selective cyclooxygenase inhibitors, acetaminophen and ibuprofen.

CONCLUSION

We report that cyclooxygenase 1 and 2 differentially regulate undifferentiated spermatogonia/spermatogonial stem cell differentiation. Cyclooxygenases regulate Notch3 expression, with the Notch pathway targeted by PGD2. These data suggest an interaction between the eicosanoid and Notch signaling pathways that may be critical for the development of spermatogonial stem cells and subsequent spermatogenesis, cautioning about using cyclooxygenase inhibitors in infants.

Specific CpG sites methylation is associated with hematotoxicity in low-dose benzene-exposed workers

Benzene is a broadly used industrial chemicals which causes various hematologic abnormalities in human. Altered DNA methylation has been proposed as epigenetic biomarkers in health risk evaluation of benzene exposure, yet the role of methylation at specific CpG sites in predicting hematological effects remains unclear. In this study, we recruited 120 low-level benzene-exposed and 101 control male workers from a petrochemical factory in Maoming City, Guangdong Province, China. Urinary S-phenylmercapturic acid (SPMA) in benzene-exposed workers was 3.40-fold higher than that in control workers (P < 0.001). Benzene-induced hematotoxicity was characterized by reduced white blood cells counts and nuclear division index (NDI), along with an increased DNA damage and urinary 8-hydroxy-2'-deoxyguanosine (all P < 0.05). Methylation levels of TRIM36, MGMT and RASSF1a genes in peripheral blood lymphocytes (PBLCs) were quantified by pyrosequencing. CpG site 6 of TRIM36, CpG site 2, 4, 6 of RASSF1a and CpG site 1, 3 of MGMT methylation were recognized as hot CpG sites due to a strong correlation with both internal exposure and hematological effects. Notably, integrating hot CpG sites methylation of multiple genes reveal a higher efficiency in prediction of integrative damage compared to individual genes at hot CpG sites. The negative dose-response relationship between the combined methylation of hot CpG sites in three genes and integrative damage enabled the classification of benzene-exposed individuals into high-risk or low-risk groups using the median cut-off value of the integrative index. Subsequently, a prediction model for integrative damage in benzene-exposed populations was built based on the methylation status of the identified hot CpG sites in the three genes. Taken together, these findings provide a novel insight into application prospect of specific CpG site methylation as epi-biomarkers for health risk assessment of environmental pollutants.

Selective recognition and discrimination of single isomeric changes in peptide strands with a host : guest sensing array

An indirect competitive binding mechanism can be exploited to allow a combination of cationic fluorophores and water-soluble synthetic receptors to selectively recognize and discriminate peptide strands containing a single isomeric residue in the backbone. Peptide isomerization occurs in long-lived proteins and has been linked with diseases such as Alzheimer's, cataracts and cancer, so isomers are valuable yet underexplored targets for selective recognition. Planar cationic fluorophores can selectively bind hydrophobic, Trp-containing peptide strands in solution, and when paired with receptors that provide a competitive host for the fluorophore, can form a differential sensing array that enables selective discrimination of peptide isomers. Residue variations such as D- and L-Asp, D- and L-isoAsp, D-Ser and D-Glu can all be recognized, simply by their effects on the folded structure of the flexible peptide. Molecular dynamics simulations were applied to determine the most favorable conformation of the peptide : fluorophore conjugate, indicating that favorable π-stacking with internal tryptophan residues in a folded binding pocket enables micromolar binding affinity.

Sulfur oxidation kinetics of Acidithiobacillus caldus and its inhibition on exposure to thiocyanate present in cyanidation tailings wastewater

The sulfur oxidation kinetics of an industrial strain of Acidithiobacillus caldus (At. caldus) cultured on elemental sulfur was explored in batch experiments in the absence and presence of thiocyanate (SCN-), a toxin inherent within cyanidation tailings wastewater. The Contois rate expression accurately described At. caldus sulfate generation (R2 > 0.93) and microbial growth (R2 > 0.87). For a culture maintained at 45 °C a maximum specific growth rate (μmax) of 0.105 h-1, sulfate yield from biomass (Ypx) of 4.8 × 10-9 mg SO42-.cell-1, and Contois affinity coefficient (Kx) of 1.56 × 10-8 mg S.cell-1 were established. The presence of SCN- (0 mg/L - 20 mg/L) in the bulk solution inhibited the microbial system competitively. Moreover, SCN- impeded microbial growth differentially; the rate expression was therefore partitioned with respect to SCN- concentration and inhibition constants (Ki) were determined for each region. Adaptation to discrete concentrations of SCN- (1 mg/L and 20 mg/L) improved SCN- tolerance in At. caldus; however, adapted strains exhibited reduced sulfur oxidation potential when cultured under thiocyanate-free conditions relative to the non-adapted control strain. To describe the adapted systems accurately, the Contois affinity coefficient (Kx) was revised to reflect the suspected metabolic decline. The derived Kx values increased in magnitude and affirmed an innate reduction in microbial substrate affinity or substrate adsorption capacity. Inclusion of these updated Kx constants within the rate equation suitably represented the experimental data for both adapted At. caldus strains with R2 > 0.94. Furthermore, the impact of adaptation on the inhibition kinetics and inhibition mechanism associated with SCN- exposure were reviewed. Thiocyanate inhibited sulfur oxidation non-competitively in the adapted strains, and the shift in inhibition mechanism may be attributed to the compromised metabolic state following adaptation.

Time-dependent hormetic dose responses of skin care product mixtures to Vibrio qinghaiensis sp.-Q67: Appearance and quantification

Hormesis is a widely recognized and extensively studied phenomenon. However, few studies have described the quantitative characteristics of hormesis required for appropriate risk assessment. Although skin care product (SCP) mixtures and their active ingredients can induce the hormesis of Vibrio qinghaiensis sp.-Q67 (Q67), the quantitative characteristics of time-dependent hormetic dose responses in SCPs have not yet been investigated. In this study, 28 SCP mixtures were tested for luminescence toxicity against Q67 after five exposure durations (0.25, 3, 6, 9, and 12 h). With increasing exposure duration, the concentration response curves (CRCs) were classified as constant monotonic nonlinear (S-shaped) for four SCPs, S- to hormetic (J-shaped) for 13 SCPs, and constant J-shaped for 11 SCPs. Of 140 CRCs, 98 were J-shaped. An increased frequency of SCPs inducing hormesis was observed. The toxicity (pEC50) of the SCPs was independent of the exposure duration and product type. The maximum stimulatory effect (Emin) of the 12 SCPs increased with exposure duration. We proposed a modified parameter, the width of inhibition dose zone (WIDZ; EC50/EC10), to depict the width of inhibition dose zone. The WIDZ of S-shaped CRCs were significantly larger than that of J-shaped CRCs. In addition, the characteristic parameters reported in the general literature were analyzed. The good linear relationship between EC50 and the maximum stimulatory effective concentration (ECmin) indicated that toxicity may be transformed into stimulatory effects over exposure durations. The width of stimulation dose zone (WSDZ) and Emin of the seven SCPs had the same increasing trends with increasing exposure duration. The combination of WIDZ with other characteristic parameters (e.g., zero effective concentration point, ECmin, etc.) could better depict hormesis with low-dose stimulation and high-dose inhibition. The quantitative characteristics of the dose-responses of hormesis-inducing SCPs could provide reference basis for the risk assessment of SCP mixtures.

Mechanistic insights into hormesis induced by erythromycin in the marine alga Thalassiosira weissflogii

Erythromycin (ERY) is a typical macrolide antibiotic with large production and extensive use on a global scale. Detection of ERY in both freshwaters and coaster seawaters, as well as relatively high ecotoxicity of ERY have been documented. Notably, hormesis has been reported on several freshwater algae under ERY stress, where growth was promoted at relatively lower exposures but inhibited at higher treatment levels. On the contrary, there is limited information of ERY toxicity in marine algae, hampering the risk assessment on ERY in the coaster waters. The presence of hormesis may challenge the current concept of dose-response adopted in chemical risk assessment. Whether and how exposure to ERY can induce dose-dependent toxicity in marine algae remain virtually unknown, especially at environmentally relevant concentrations. The present study used a model marine diatom Thalassiosira weissflogii (T. weissflogii) to reveal its toxicological responses to ERY at different biological levels and decipher the underlying mechanisms. Assessment of multiple apical endpoints shows an evident growth promotion following ERY exposure at an environmentally relevant concentration (1 µg/L), associated with increased contents reactive oxygen species (ROS) and chlorophyll-a (Chl-a), activated signaling pathways related to ribosome biosynthesis and translation, and production of total soluble protein. By contrast, growth inhibition in the 750 and 2500 µg/L treatments was attributed to reduced viability, increased ROS formation, reduced content of total soluble protein, inhibited photosynthesis, and perturbed signaling pathways involved in xenobiotic metabolism, ribosome, metabolism of amino acid, and nitrogen metabolism. Measurements of multiple apical endpoints coupled with de novo transcriptomics analysis applied in the present study, a systems biology approach, can generate detailed mechanistic information of chemical toxicity including dose-response and species sensitivity difference used in environmental risk assessment.

Evaluation of DNA damage induced by acesulfame potassium: spectroscopic, molecular modeling simulations and toxicity studies

Acesulfame potassium (Ace-K) is a widely used artificial sweetener that has been reported to interact with DNA and cause important genetic damage. However, the type of interaction mechanism is unknown. This study provides an approach to understanding the in vitro mechanism of Ace-K interaction with Ct-DNA using spectroscopic methods combined with molecular simulations. The hypochromic effect as obtained from UV-Vis spectra indicated the formation of the DNA-Ace-K complex in the minor groove. Further evidence for groove binding mode comes from the decrease in Hoechst-DNA fluorescence caused by increasing Ace-K concentrations, alongside no detectable change in MB-DNA emission band intensity. A negative value of ΔH and ΔS represents the hydrogen bonds and van der Waals forces between Ace-K and DNA. Based on the molecular docking, Ace-K was located between the guanine10 and 16 in DNA minor groove and stabilized by two hydrogen bonds and one π-Sulfur interaction. In vitro cell culture results showed that about 5 mg/mL of Ace-K caused the death of 85% of HUVEC cells after 48 h. Communicated by Ramaswamy H. Sarma.

Betalains isolated from underexploited wild plant Atriplex hortensis var. rubra L. exert antioxidant and cardioprotective activity against H9c2 cells

Atriplex hortensis var. rubra L. extracts prepared from leaves, seeds with sheaths, and stems were characterized for betalainic profiles by spectrophotometry, LC-DAD-ESI-MS/MS and LC-Orbitrap-MS techniques. The presence of 12 betacyanins in the extracts was strongly correlated with high antioxidant activity measured by ABTS, FRAP, and ORAC assays. Comparative assessment between samples indicated the highest potential for celosianin and amaranthin (IC₅₀ 21.5 and 32.2 μg/ml, respectively). The chemical structure of celosianin was elucidated for the first time by complete 1D and 2D NMR analysis. Our findings also demonstrate that betalain-rich A. hortensis extracts and purified pigments (amaranthin and celosianin) do not induce cytotoxicity in a wide concentration range in rat cardiomyocytes model (up to 100 μg/ml for extracts and 1 mg/ml for pigments). Furthermore, tested samples effectively protect H9c2 cells from H₂O₂-induced cell death and prevent from apoptosis induced by Paclitaxel. The effects were observed at sample concentrations between 0.1 and 10 μg/ml.

Low-dose chemical stimulation and pest resistance threaten global crop production

Pesticide resistance increases and threatens crop production sustainability. Chemical contamination contributes to the development of pest resistance to pesticides, in part by causing stimulatory effects on pests at low sub-toxic doses and facilitating the spread of resistance genes. This article discusses hormesis and low-dose biological stimulation and their relevance to crop pest resistance. It highlights that a holistic approach is needed to tackle pest resistance to pesticides and reduce imbalance in accessing food and improving food security in accordance with the UN's Sustainable Development Goals. Among others, the effects of sub-toxic doses of pesticides should be considered when assessing the impact of synthetic and natural pesticides, while the promotion of alternative agronomical practices is needed to decrease the use of agrochemicals. Potential alternative solutions include camo-cropping, exogenous application of phytochemicals that are pest-suppressing or -repelling and/or attractive to carnivorous arthropods and other pest natural enemies, and nano-technological innovations. Moreover, to facilitate tackling of pesticide resistance in poorer countries, less technology-demanding and low-cost practices are needed. These include mixed cropping systems, diversification of cultures, use of 'push-pull cropping', incorporation of flower strips into cultivations, modification of microenvironment, and application of beneficial microorganisms and insects. However, there are still numerous open questions, and more research is needed to address the ecological and environmental effects of many of these potential solutions, with special reference to trophic webs.

20-Hydroxyecdysone Confers Antioxidant and Antineoplastic Properties in Human Non-Small Cell Lung Cancer Cells

20-Hydroxyecdysone (20E) is an arthropod hormone which is synthesized by some plants as part of their defense mechanism. In humans, 20E has no hormonal activity but possesses a number of beneficial pharmacological properties including anabolic, adaptogenic, hypoglycemic, and antioxidant properties, as well as cardio-, hepato-, and neuroprotective features. Recent studies have shown that 20E may also possess antineoplastic activity. In the present study, we reveal the anticancer properties of 20E in Non-Small Cell Lung Cancer (NSCLC) cell lines. 20E displayed significant antioxidant capacities and induced the expression of antioxidative stress response genes. The RNA-seq analysis of 20E-treated lung cancer cells revealed the attenuation of genes involved in different metabolic processes. Indeed, 20E suppressed several enzymes of glycolysis and one-carbon metabolism, as well as their key transcriptional regulators-c-Myc and ATF4, respectively. Accordingly, using the SeaHorse energy profiling approach, we observed the inhibition of glycolysis and respiration mediated by 20E treatment. Furthermore, 20E sensibilized lung cancer cells to metabolic inhibitors and markedly suppressed the expression of Cancer Stem Cells (CSCs) markers. Thus, in addition to the known beneficial pharmacological activities of 20E, our data uncovered novel antineoplastic properties of 20E in NSCLC cells.

Hormetic effects of neonicotinoid insecticides on Rhizoglyphus robini (Acari: Acaridae)

The stimulation of biological processes by sublethal doses of insecticides or other stressors is known as hormesis. Here, we have evaluated whether exposure to field-relevant or low concentrations of neonicotinoids induce changes in the reproductive capacity of the bulb mite Rhizoglyphus robini (Acari: Acaridae). Among the tested neonicotinoids imidacloprid, thiamethoxam, and dinotefuran, the highest hormetic effect on the reproduction of R. robini occurred 24 h after the 48 h exposure period to imidacloprid at concentrations of 70 and 140 mg a.i./L. Despite the stimulating effects of imidacloprid on mite reproduction, no significant differences were observed in the offspring (F₁) for biological aspects including egg hatch rate, embryonic period and sex ratio, while an increase was found in the duration of development time from egg to adult. Evaluation of the detoxification enzyme activities of treated adults showed that the highest activity of carboxyl/cholinesterases, cytochrome P450s, and glutathione S-transferases was obtained when exposed to 70, 140 and 70 mg a.i./L imidacloprid, immediately after the exposure period, respectively. Also, an increase in the activity of the antioxidant enzyme catalase was observed compared to that of the control. After imidacloprid pretreatment (140 mg a.i./L), the tolerance of adult mites to diazinon was increased about two-fold. This study shows that exposure to imidacloprid can induce hormetic effects on R. robini and could severely complicate its control due to a higher reproduction, enhanced detoxification enzyme activities, and increased tolerance against other pesticides.

Acute arterial stiffness responses to on-ball balance exercises in young and middle-aged adults: Role of posture and cumulative effects

Objective: To examine the acute arterial stiffness changes after maintaining one bout of balance on Swiss ball using different postures in young and middle-aged adults, and to evaluate the cumulative exposure effects on arterial stiffness after multiple exercise bouts in middle-aged adults. Methods: Using crossover design, we first enrolled 22 young adults (24.0 ± 1.1 years) and randomized them to non-exercise control (CON), on-ball balance exercise trial lasting 1 × 5 min in kneeling posture (K1) and sitting posture (S1). In a following crossover experiment, 19 middle-aged adults (53.0 ± 4.7 years) were randomized to non-exercise control (CON), on-ball balance exercise trial lasting 1 × 5 min in kneeling posture (K1) and in sitting posture (S1), and on-ball balance exercise trial lasting 2 × 5 min in kneeling posture (K2) and in sitting posture (S2). Cardio-ankle vascular index (CAVI), an indicator of systemic arterial stiffness, was measured at baseline (BL), immediately after (0 min), and every 10 min after exercise. CAVI changes from BL in the same trial (⊿CAVI) were used for analysis. Results: In K1 trial, ⊿CAVI decreased significantly at 0 min (p < 0.05) in both young and middle-aged adults; however in S1 trial, ⊿CAVI at 0 min increased significantly in young adults (p < 0.05), with ⊿CAVI tending to increase in middle-aged adults. Bonferroni post-test revealed that at 0 min, ⊿CAVI of K1 in both young and middle-aged adults, and ⊿CAVI of S1 in young adults differed significantly from that of CON (p < 0.05). In middle-aged adults, ⊿CAVI decreased significantly at 10 min compared to BL in K2 trial (p < 0.05), and increased at 0 min compared to BL in S2 trial (p < 0.05); however, difference compared to CON was not significant. Conclusion: Single on-ball balance bout in kneeling posture improved arterial stiffness transiently in both young and middle-aged adults; however, sitting posture elicited opposite changes, and this happened only in young adults. Multiple balance bouts resulted in no significant change in arterial stiffness in middle-aged adults.

On the meta-analysis of hormetic effects

The evidence for hormetic responses with chemical effects at doses lower than the no-observed-adverse-effect-level (sub-NOAEL) is increasing, creating a need for meta-analyses of sub-NOAEL effects across studies. However, the distinct features of hormetic responses complicate the procedures of meta-analyses aiming to study sub-NOAEL, hormetic effects, and there is no standardized methodology to serve as a guideline. In this piece, a protocol is proposed, which covers the selection of more holistic keywords to be integrated into the literature search queries, the designation of control, and the identification of NOAEL (and thus sub-NOAEL dose responses). It also considers the selection of the response indicators and the incorporation of time and dose as sources of variation. This protocol can serve as a reference point for a harmonized and more robust methodology to meta-analyze sub-NOAEL effects of chemicals on living organisms.

Acute effects of one-leg standing on arterial stiffness in older women: Role of the vision condition and standing dose

Objective: One-leg standing has been used exclusively for static balance testing and training purposes. We investigated the acute effects of one-leg standing with open or closed eyes on arterial stiffness in older women and explored the role of standing dose in arterial stiffness regulation.

Methods: Eighteen older women (60 ± 2 years) underwent non-intervention control (CON), one-leg standing with open eyes for 2 × 3 min (SO2), and one-leg standing with closed eyes for 1 × 3 min (SC1), 2 × 3 min (SC2), and 3 × 3 min trials (SC3) in a randomized self-controlled crossover fashion. Arterial stiffness in the cardio-ankle vascular index (CAVI) was measured at baseline (BL), immediately (0 min), and 10 and 20 min after standing. CAVI changes from BL in the same trial (⊿CAVI) were used for analysis.

Results: ⊿CAVI of the non-standing and standing side did not change with time in CON and SO2 trials. In SC1, SC2, and SC3 trials, ⊿CAVI of the standing side decreased significantly at 0 min compared to their corresponding BL (p < 0.01) and reverted gradually to the BL level afterward, with ⊿CAVI of the non-standing side undergoing no changes. At the time point of 0 min, only in the SC2 trial, ⊿CAVI of the standing side was significantly lower than that of CON (p < 0.01).

Conclusion: One-leg standing with closed eyes, but not with open eyes, resulted in transient arterial stiffness improvement in older women. The improvement was restricted to standing leg, and the moderate standing dose had maximal benefit on arterial stiffness.

Perfluorobutanoic Acid (PFBA) Induces a Non-Enzymatic Oxidative Stress Response in Soybean (Glycine max L. Merr.)

Short-chain perfluoroalkyl substances (PFAS) are generally considered to be of less environmental concern than long-chain analogues due to their comparatively shorter half-lives in biological systems. Perfluorobutanoic acid (PFBA) is a short-chain PFAS with the most root–shoot transfer factor of all PFAS. We investigated the impact of extended exposure of soybean plants to irrigation water containing environmentally relevant (100 pg–100 ng/L) to high (100 µg–1 mg/L) concentrations of PFBA using phenotypical observation, biochemical characterization, and transcriptomic analysis. The results showed a non-monotonous developmental response from the plants, with maximum stimulation and inhibition at 100 ng/L and 1 mg/L, respectively. Higher reactive oxygen species and low levels of superoxide dismutase (SOD) and catalase (CAT) activity were observed in all treatment groups. However transcriptomic analysis did not demonstrate differential expression of SOD and CAT coding genes, whereas non-enzymatic response genes and pathways were enriched in both groups (100 ng/L and 1 mg/L) with glycine betaine dehydrogenase showing the highest expression. About 18% of similarly downregulated genes in both groups are involved in the ethylene signaling pathway. The circadian rhythm pathway was the only differentially regulated pathway between both groups. We conclude that, similar to long chain PFAS, PFBA induced stress in soybean plants and that the observed hormetic stimulation at 100 ng/L represents an overcompensation response, via the circadian rhythm pathway, to the induced stress.

Hair methylmercury levels are inversely correlated with arterial stiffness

BACKGROUND AND AIMS

Cardiovascular diseases (CVD), including coronary heart disease, are the leading cause of death worldwide. Several studies investigating the relationship between fish intake, methylmercury exposure, and CVDs in adults have reported inconsistent results. This study aimed to determine the association between hair methylmercury levels and arterial stiffness using brachial-ankle pulse wave velocity (baPWV).

METHODS

This cross-sectional study included 891 seemingly healthy Korean adults (418 men and 473 women). The anthropometric and biochemical profiles, including methylmercury levels in the hair, were measured. Arterial stiffness was measured using baPWV, wherein high baPWV was defined as >1375 cm/s (>75th percentile). The odds ratios for high baPWVs were examined using multivariable logistic regression analysis after adjusting for potential confounders across the quintiles of hair methylmercury levels (Q1 = ≤0.6, Q2 = 0.6-0.8, Q3 = 0.8-1.1, Q4 = 1.1-1.5, and Q5=>1.5 μg/g).

RESULTS

After adjusting for multiple confounders-age, sex, height, body weight, smoking status, weekly alcohol consumption, total metabolic equivalent of task, mean arterial blood pressure, resting heart rate, triglycerides, low density lipoprotein cholesterol, fasting plasma glucose, uric acid and white blood cell count-the odds ratios (95% confidence intervals) for high baPWVs in each quintile of hair methylmercury levels were 1.00, 0.36 (0.17-0.76), 0.38 (0.20-0.76), 0.28 (0.13-0.61), and 0.49 (0.24-0.99), respectively.

CONCLUSIONS

Within non-toxic low levels, higher hair methylmercury levels are independently associated with lower arterial stiffness in seemingly healthy Korean adults regardless of classical cardiovascular risk factors.

LPS and oxLDL-induced S100A12 and RAGE expression in carotid arteries of atherosclerotic Yucatan microswine

BACKGROUND

S100A12, also known as Calgranulin C, is a ligand for the receptor for advanced glycation end products (RAGE) and plays key roles in cardiovascular and other inflammatory diseases. Interactions between S100A12 and RAGE initiate downstream signaling activating extracellular signal-regulated kinases (ERK1/2), mitogen activated protein kinases (MAPK), and transcription factor NF-κB. This increases the expression of pro-inflammatory cytokines to induce the inflammatory response. S100A12, and RAGE play a critical role in the development and progression of atherosclerosis. There is a well-known relationship between the bacterial endotoxin lipopolysaccharide (LPS) and the lipid antigens oxidized low-density lipoprotein (oxLDL) in driving the immune response in atherosclerosis.

METHODS AND RESULTS

Our study aimed to compare the potential of LPS and oxLDL in regulating the expression of S100A12 and RAGE in atherosclerosis. The expression of these proteins was assessed in the harvested carotid arteries from LPS- and oxLDL-treated atherosclerotic Yucatan microswine. Tissues were collected from five different treatment groups: (i) angioplasty alone, (ii) LPS alone, (iii) oxLDL alone, (iv) angioplasty with LPS, and (v) angioplasty with oxLDL. Immunohistochemical findings revealed that angioplasty with LPS induced higher expression of S100A12 and RAGE compared to other treatment groups. The results were further corroborated by testing their gene expression through qPCR in cultured vascular smooth muscle cells (VSMCs) isolated from control carotid arteries and LPS- and oxLDL-treated arteries.

CONCLUSIONS

The results of this study suggest that LPS induces the expression of S100A12 and RAGE more than oxLDL in atherosclerotic artery and both S100A12 and RAGE could be therapeutic targets.

Review of molecular and biochemical responses during stress induced stimulation and hormesis in insects

The biphasic hormetic response to stress, defined by low-dose stimulation and high-dose inhibition is frequently observed in insects. Various molecular and biochemical responses associated with hormesis in insects have been reported in many studies, but no synthesis of all these findings has been undertaken. We conducted a systematic literature review, analyzing papers demonstrating phenotypic stimulatory effect(s) following exposure to stress where molecular or biochemical response(s) were also examined. Responses observed included stimulation of reproduction, survival and longevity, growth and development, and tolerance to temperature, chemical, or starvation and desiccation, in response to stressors including pesticides, oxidative stress, temperature, crowding and starvation, and radiation. Phenotypic stimulation ranged from <25% increased above controls to >100%. Reproductive stimulation was frequently <25% increased above controls, while stimulated temperature tolerance was frequently >100% increased. Molecular and biochemical responses had obvious direct connections to phenotypic responses in many cases, although not in all instances. Increased expression of heat shock proteins occurred in association with stimulated temperature tolerance, and increased expression of detoxification genes with stimulated pesticide or chemical tolerance, but also stimulated reproduction. Changes in the expression or activity of antioxidants were frequently associated with stimulation of longevity and reproduction. Stress induced changes in vitellogenin and juvenile hormone and genes in the IIS/TOR signalling pathway - which are directly responsible for regulating growth, development, and reproduction - were also reported. Our analysis showed that coordination of expression of genes or proteins associated with protection from oxidative stress and DNA and protein damage is important in the hormetic responses of insects.

CpG site-specific methylation as epi-biomarkers for the prediction of health risk in PAHs-exposed populations

Environmental insults can lead to alteration in DNA methylation of specific genes. To address the role of altered DNA methylation in prediction of polycyclic aromatic hydrocarbons (PAHs) exposure-induced genetic damage, we recruited two populations, including diesel engine exhausts (low-level) and coke oven emissions (high-level) exposed subjects. The positive correlation was observed between the internal exposure marker (1-hydroxypyrene) and the extents of DNA damage (P < 0.05). The methylation of representative genes, including TRIM36, RASSF1a, and MGMT in peripheral blood lymphocytes was quantitatively examined by bisulfite-pyrosequencing assay. The DNA methylation of these three genes in response to PAHs exposure were changed in a CpG-site-specific manner. The identified hot CpG site-specific methylation of three genes exhibited higher predictive power for DNA damage than the respective single genes in both populations. Furthermore, the dose-response relationship analysis revealed a nonlinear U-shape curve of TRIM36 or RASSF1a methylation in combined population, which led to determination of the threshold of health risk. Furthermore, we established a prediction model for genetic damage based on the unidirectional-alteration MGMT methylation levels. In conclusion, this study provides new insight into the application of multiple epi-biomarkers for health risk assessment upon PAHs exposure.

CD38-Induced Apoptosis and Mitochondrial Damage is Restored by Nicotinamide in Prostate Cancer

Nicotinamide adenine dinucleotide (NAD⁺) is an essential molecule for living organisms. CD38 is a key NAD⁺-dependent enzyme which breaks down NAD⁺ to cyclic ADP-ribose (ADPR) and nicotinamide (NAM, vitamin B3), and NAM can be recycled to synthesize NAD⁺. CD38 expression is consistently silenced by methylation in prostate cancer and progressively downregulated in advanced castration-resistant prostate cancer, suggesting a connection between NAD⁺ and prostate carcinogenesis as well as prostate cancer progression. However, the functional interplay between NAD⁺, CD38, and NAM remains largely uncharacterized in prostate cancer cells. In this study, we generated stable LNCaP95 cell clones expressing varying levels of CD38 upon induction by doxycycline. We demonstrate that CD38 overexpression resulted in growth suppression and apoptosis accompanied by cleavage of poly (ADP-ribose) polymerase 1 (PARP1). CD38 overexpression also dramatically reduced intracellular NAD⁺ levels and decreased mitochondrial respiration as measured by oxygen consumption rate. We further show that some but not all of these CD38-induced phenotypes could be rescued by exogenous NAM. Treatment of cells with NAM rescued CD38-induced apoptosis and mitochondrial stress but did not restore intracellular NAD⁺ levels. We also found that NAM demonstrated biphasic effect on mitochondria function, a finding that can be explained by the dual role of NAM as both a precursor of NAD⁺ and also as a suppressor of a number of NAD⁺-dependent enzymes. Collectively, these findings provide additional insight supporting the functional relevance of CD38 loss in prostate cancer by linking cell-autonomous regulation of mitochondrial function and prostate cancer.

Tributyltin Exposure Is Associated With Recognition Memory Impairments, Alterations in Estrogen Receptor α Protein Levels, and Oxidative Stress in the Brain of Female Mice

Tributyltin (TBT) is a persistent organometallic pollutant widely used in several agricultural and industrial processes. TBT exposure is associated with various metabolic, reproductive, immune, and cardiovascular abnormalities. However, few studies have evaluated the effects of TBT on behavior. In the present study, we aimed to investigate whether TBT exposure results in oxidative, neuroendocrine, and behavioral alterations. TBT was administered to adult female mice (250, 500, or 750 ng/kg/day or veh for 14 days), and their recognition memory was assessed. We have also evaluated estrogen receptor (ER)α protein expression and oxidative stress (OS) in brain areas related to memory, as well as the correlation between them. A reduction in short- and long-term recognition memory (STM and LTM) performance, as well as in total exploration time was observed in TBT mice. Reduced ERα protein expression was observed in the prefrontal cortex (PFC) and hippocampus of TBT mice, while an increase in TBARS concentration was observed in the PFC of treated animals. Collectively, these data suggest that TBT exposure impairs recognition memory in female mice as a result of, at least in part, its toxicological effects on ERα expression and OS in specific brain areas related to memory.

Effects of chronic crude oil exposure on the fitness of polar cod (Boreogadus saida) through changes in growth, energy reserves and survival

Climate models predict extended periods with sea-ice free Arctic waters during the next decade, which will allow more shipping activity and easier access to petroleum resources. Increased industrial activities raise concerns about the biological effects of accidental petroleum release on key species of the Arctic marine ecosystem, such as the polar cod (Boreogadus saida). This study examines effects on physiological traits related to the fitness of adult polar cod, such as growth, survival, and lipid parameters. Fish were exposed to environmentally-relevant crude oil doses through their diet over an 8-month period, concurrent with reproductive development. In liver tissue, lipid class composition differed between treatments while in gonad tissue, lipid class composition varied between sexes, but not treatments. Crude oil did not affect growth and survival, which indicated that polar cod were relatively robust to dietary crude oil exposure at doses tested (0.11-1.14 μg crude oil/g fish/day) in this study.

Transcriptomic profiling reveals gene expression in human peripheral blood after exposure to low-dose ionizing radiation

Although the health effects of exposure to low-dose ionizing radiation have been the focus of many studies, the affected biological functions and underlying regulatory mechanisms are not well-understood. In particular, the influence of radiation exposure at doses of less than 200 mGy on the regulation of genes and pathways remains unclear. To investigate the molecular alterations induced by varying doses of low-dose radiation (LDR), transcriptomic analysis was conducted based on ribonucleic acid (RNA) sequencing following exposure to 50 and 150 mGy doses. Human peripheral blood was collected, and the samples were divided into three groups, including two treatments and one control (no radiation). A total of 876 (318 upregulated and 558 downregulated) and 486 (202 upregulated and 284 downregulated) differentially expressed genes (DEGs) were identified after exposure to 50 mGy and 150 mGy, respectively. Most upregulated genes in both the 50 mGy and 150 mGy groups were associated with 'antigen processing and presentation,' which appeared to be the major targets affected by LDR exposure. Several interacting genes, including HLA-DQA1, HLA-DQA2, HLA-DQB2, HLA-DRB1, and HLA-DRB5 were mapped to 'antigen processing and presentation,' 'immune system-related diseases' and the 'cytokine-mediated signaling pathway,' suggesting that these genes might drive the downstream transmission of these signal transduction pathways. Our results suggest that exposure to LDR may elicit changes in key genes and associated pathways, probably helping further explore the biological processes and molecular mechanism responsible for low-dose occupational or environmental exposures in humans.

HDAC Inhibitor Titration of Transcription and Axolotl Tail Regeneration

New patterns of gene expression are enacted and regulated during tissue regeneration. Histone deacetylases (HDACs) regulate gene expression by removing acetylated lysine residues from histones and proteins that function directly or indirectly in transcriptional regulation. Previously we showed that romidepsin, an FDA-approved HDAC inhibitor, potently blocks axolotl embryo tail regeneration by altering initial transcriptional responses to injury. Here, we report on the concentration-dependent effect of romidepsin on transcription and regeneration outcome, introducing an experimental and conceptual framework for investigating small molecule mechanisms of action. A range of romidepsin concentrations (0-10 μM) were administered from 0 to 6 or 0 to 12 h post amputation (HPA) and distal tail tip tissue was collected for gene expression analysis. Above a threshold concentration, romidepsin potently inhibited regeneration. Sigmoidal and biphasic transcription response curve modeling identified genes with inflection points aligning to the threshold concentration defining regenerative failure verses success. Regeneration inhibitory concentrations of romidepsin increased and decreased the expression of key genes. Genes that associate with oxidative stress, negative regulation of cell signaling, negative regulation of cell cycle progression, and cellular differentiation were increased, while genes that are typically up-regulated during appendage regeneration were decreased, including genes expressed by fibroblast-like progenitor cells. Using single-nuclei RNA-Seq at 6 HPA, we found that key genes were altered by romidepin in the same direction across multiple cell types. Our results implicate HDAC activity as a transcriptional mechanism that operates across cell types to regulate the alternative expression of genes that associate with regenerative success versus failure outcomes.

Some Effects of endo-Brevicomin Background on Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae) Aggregation Behavior

Semiochemical background in the environment can influence insect orientation to release points of the same or different semiochemicals. endo-Brevicomin is a pheromone component of the tree-killing bark beetle Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) that has a biphasic dose-response curve, enhancing attraction at low release rates but reducing attraction at high rates. We investigated the effect of artificial manipulation of background levels of endo-brevicomin on D. frontalis responses to sources of aggregation attractant in the field. Traps baited with the aggregation pheromone component frontalin and the host odor alpha-pinene were deployed either with or without a background of endo-brevicomin produced by three surrounding dispensers of this semiochemical each located 20 m away. Two tested levels of endo-brevicomin background caused catches to increase by an order of magnitude above those in the absence of background. Presence of background also altered the beetles' biphasic dose-response when endo-brevicomin dispensers were added to traps. Background reduced or concealed attraction-enhancement otherwise observed for low-release dispensers added to traps, and it decreased the release rate necessary to produce reductions in catches. We propose that spatial variability in abundance of natural, background sources of endo-brevicomin in the environment (i.e., infested trees) is a cause of the observed variability in effects of endo-brevicomin dispensers on southern pine beetle behavior in the field. Furthermore, our results illustrate the potential complexity of the density-dependent effects of biphasic pheromone components on bark beetle mass attack and colonization behavior.

Cadmium-induced hormesis effect in medicinal herbs improves the efficiency of safe utilization for low cadmium-contaminated farmland soil

Compared to other soil remediation technologies, Cd-contaminated farmland soil with low cadmium accumulation (LCA) plant-based safe utilization is more catered to developing countries with food in high demand. Hormesis, which describes the fortification of plant growth performance by a low level of environmental stress, can be innovatively used to achieve increases in crop yield and plant functional components, thus amplifying the safe utilization efficiency of low Cd-contaminated soil by LCA plants. In the present study, the growth and physiological responses of Polygonatum sibiricum, a traditional Chinese medicinal herb, were investigated under laboratory conditions of gradient Cd dosage concentrations and times. As a result, the growth performance of P. sibiricum reached the peak of an inverse U-shaped curve of hormesis under e⁰ mg kg^-1 and 9 months of Cd stress, with elevations in tuber biomass (medicinal part), plant height and polysaccharide content (medicinal components) of 143%, 25% and 90%, respectively. Meanwhile, trace Cd accumulation (0.41 mg kg^-1) in the tuber guaranteed medicinal edible safety. In addition, Cd-induced hormesis in P. sibiricum was verified to be overcompensated by antioxidation systems. In conclusion, such 'win-win' results, including low Cd accumulation and enhancement of plant pharmaceutical value, provided medicinal herbs with a possibility for safe soil utilization.

Anti-Candidal Activity of the Parasitic Plant Orobanche crenata Forssk

Candida albicans (C. albicans) and Candida glabrata (C. glabrata) are part of the human microbiome. However, they possess numerous virulence factors, which confer them the ability to cause both local and systemic infections. Candidiasis can involve multiple organs, including the eye. In the present study, we investigated the anti-candidal activity and the re-epithelizing effect of Orobanche crenata leaf extract (OCLE). By the microdilution method, we demonstrated an inhibitory effect of OCLE on both C. albicans and C. glabrata growth. By crystal violet and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, we showed the ability of OCLE to inhibit the biofilm formation and the viability of yeast cells, respectively. By germ tube and adhesion assays, we proved the capacity of OCLE to affect the morphological transition of C. albicans and the adhesion of both pathogens to human retinal pigment epithelial cells (ARPE-19), respectively. Besides, by MTT and wound healing assay, we evaluated the cytotoxic and re-epithelizing effects of OCLE on ARPE-19. Finally, the Folin-Ciocalteu and the ultra-performance liquid chromatography-tandem mass spectrometry revealed a high content of phenols and the presence of several bioactive molecules in the extract. Our results highlighted new properties of O. crenata, useful in the control of Candida infections.

The highs and lows of ionizing radiation and its effects on protein synthesis

Ionizing radiation (IR) is a constant feature of our environment and one that can dramatically affect organismal health and development. Although the impacts of high-doses of IR on mammalian cells and systems have been broadly explored, there are still challenges in accurately quantifying biological responses to IR, especially in the low-dose range to which most individuals are exposed in their lifetime. The resulting uncertainty has led to the entrenchment of conservative radioprotection policies around the world. Thus, uncovering long-sought molecular mechanisms and tissue responses that are targeted by IR could lead to more informed policymaking and propose new therapeutic avenues for a variety of pathologies. One often overlooked target of IR is mRNA translation, a highly regulated cellular process that consumes more than 40% of the cell's energy. In response to environmental stimuli, regulation of mRNA translation allows for precise and rapid changes to the cellular proteome, and unsurprisingly high-dose of IR was shown to trigger a severe reprogramming of global protein synthesis allowing the cell to conserve energy by preventing the synthesis of unneeded proteins. Nonetheless, under these conditions, certain mRNAs encoding specific proteins are translationally favoured to produce the factors essential to repair the cell or send it down the path of no return through programmed cell death. Understanding the mechanisms controlling protein synthesis in response to varying doses of IR could provide novel insights into how this stress-mediated cellular adaptation is regulated and potentially uncover novel targets for radiosensitization or radioprotection. Here, we review the current literature on the effects of IR at both high- and low-dose on the mRNA translation machinery.

Detrimental or beneficial? Untangling the literature on developmental stress studies in birds

Developing animals display a tremendous ability to change the course of their developmental path in response to the environment they experience, a concept referred to as developmental plasticity. This change in behavior, physiology or cellular processes is primarily thought to allow animals to better accommodate themselves to the surrounding environment. However, existing data on developmental stress and whether it brings about beneficial or detrimental outcomes show conflicting results. There are several well-referred hypotheses related to developmental stress in the current literature, such as the environmental matching, silver spoon and thrifty phenotype hypotheses. These hypotheses speculate that the early-life environment defines the capacity of the physiological functions and behavioral tendencies and that this change is permanent and impacts the fitness of the individual. These hypotheses also postulate there is a trade-off among organ systems and physiological functions when resources are insufficient. Published data on avian taxa show that some effects of developmental nutritional and thermal stressors are long lasting, such as the effects on body mass and birdsong. Although hypotheses on developmental stress are based on fitness components, data on reproduction and survival are scarce, making it difficult to determine which hypothesis these data support. Furthermore, most physiological and performance measures are collected only once; thus, the physiological mechanisms remain undertested. Here, we offer potential avenues of research to identify reasons behind the contrasting results in developmental stress research and possible ways to determine whether developmental programming due to stressors is beneficial or detrimental, including quantifying reproduction and survival in multiple environments, measuring temporal changes in physiological variables and testing for stress resistance later in life.

PI3Kγ Mediates Microglial Proliferation and Cell Viability via ROS

(1) Background: Rapid microglial proliferation contributes to the complex responses of the innate immune system in the brain to various neuroinflammatory stimuli. Here, we investigated the regulatory function of phosphoinositide 3-kinase γ (PI3Kγ) and reactive oxygen species (ROS) for rapid proliferation of murine microglia induced by LPS and ATP. (2) Methods: PI3Kγ knockout mice (PI3Kγ KO), mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) and wild-type mice were assessed for microglial proliferation using an in vivo wound healing assay. Additionally, primary microglia derived from newborn wild-type, PI3Kγ KO and PI3Kγ KD mice were used to analyze PI3Kγ effects on proliferation and cell viability, senescence and cellular and mitochondrial ROS production; the consequences of ROS production for proliferation and cell viability after LPS or ATP stimulation were studied using genetic and pharmacologic approaches. (3) Results: Mice with a loss of lipid kinase activity showed impaired proliferation of microglia. The prerequisite of induced microglial proliferation and cell viability appeared to be PI3Kγ-mediated induction of ROS production. (4) Conclusions: The lipid kinase activity of PI3Kγ plays a crucial role for microglial proliferation and cell viability after acute inflammatory activation.

Effect of microplastics on aquatic biota: A hormetic perspective

As emerging pollutants, microplastics (MPs) have been found globally in various freshwater and marine matrices. This study recompiled 270 endpoints of 3765 individuals from 43 publications, reporting the onset of enhanced biological performance and reduced oxidative stress biomarkers induced by MPs in aquatic organisms at environmentally relevant concentrations (≤1 mg/L, median = 0.1 mg/L). The stimulatory responses of consumption, growth, reproduction and survival ranged from 131% to 144% of the control, with a combined response of 136%. The overall inhibitory response of 9 oxidative stress biomarkers was 71% of the control, and commonly below 75%. The random-effects meta-regression indicated that the extents of MPs-induced responses were independent of habitat, MP composition, morphology, particle size and exposure duration. The results implied that the exposure to MPs at low and high concentrations might induce opposite/non-monotonic responses in aquatic biota. Correspondingly, the hormetic dose response relationships were found at various endpoints, such as reproduction, genotoxicity, immunotoxicity, neurotoxicity and behavioral alteration. Hormesis offers a novel perspective for understanding the dose response mode of aquatic organisms exposed to low and high concentrations of MPs, highlighting the necessity to incorporate the hormetic dose response model into the ecological/environmental risk assessment of MPs.

Identification of glutathione-S-transferase m19 and m34 among responsive GST genes against 1-chloro-2,4-dinitrobenzene treatment of Tetrahymena thermophila

Industrial xenobiotic pollutants have toxic effects on diverse organisms in their natural environments. This study aims to identify the Glutathione-S-transferases (GST) from Tetrahymena thermophila that are highly responsive to the treatment of synthetic substrate 1-chloro-2,4-dinitrobenzene (CDNB). The LD50 value of CDNB was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test as 0.079 mM at 9 h exposure. The glutathione affinity-purified 22 kDa and 23 kDa GSTs from CDNB-treated cells were identified as GSTm19 and GSTm34 with 2D-gel electrophoresis coupled MALDI-Tof MS/MS analysis. The specific activitiy of the affinity-purified GSTs was upregulated upon the treatment of 0.072 mM CDNB with the decreased cell survival. GSTm19 and GSTm34 had also upregulated the mRNA expression under the highest dose treatment. The high cell survival and elevated total GST enzyme activity at 9 h under CDNB doses could be the result of both transcriptional upregulations as well as post-translational modifications. As a result, the cell survival of Tetrahymena thermophila was significantly affected by CDNB exposure in a concentration-dependent manner with the effect of low-dose stimulation and high-dose inhibition.

Hormetic responses of soil microbiota to exogenous Cd: A step toward linking community-level hormesis to ecological risk assessment

We investigated hormetic responses of soil microbial communities to exogenous Cd by assessing microbial count, bacterial and fungal abundance, and microbial community diversity. We found that the bacterial count (BC) decreased (3-40%) by 0.2-40 mg Cdkg^-1. Addition of 0.6-2.0 mgkg^-1 significantly increased fungal count (FC) by 7-42%, while addition of 4.0-40 mgkg^-1 Cd decreased FC by 29-51%, indicating a hormetic dose response. We also found that the FC/BC ratio increased by 0.6-2.0 mg Cdkg^-1, with a maximum stimulation of 51%, and decreased (18-27%) by 4.0-40 mg Cdkg^-1. Cd had no adverse effect on the α-diversity of bacterial or fungal communities. For relative abundances (RAs) of bacteria and fungi at phylum level, Bacteroidetes RA exhibited a biphasic dose-response curve, with an 18-24% increase at 0.6-4.0 mgkg^-1 and a 10% decrease at 40 mgkg^-1 compared with control. The results of FC, FC/BC, and Bacteroidetes RAs suggest that hormesis occurred at microbial community level, with positive effects occurring at 0.6-2.0 mgkg^-1. This study can contribute to incorporating microbial community hormesis into the ecological risk assessments in the future.

Hormesis: Transforming disciplines that rely on the dose response

This article tells the story of hormesis from its conceptual and experimental origins, its dismissal by the scientific and medical communities in the first half of the 20th century, and its rediscovery over the past several decades to be a fundamental evolutionary adaptive strategy. The upregulation of hormetic adaptive mechanisms has the capacity to decelerate the onset and reduce the severity of a broad spectrum of common age-related health, behavioral, and performance decrements and debilitating diseases, thereby significantly enhancing the human health span. Incorporation of hormetic-based lifestyle options within the human population would have profoundly positive impacts on the public health, significantly reducing health care costs.

Effects of Topical Gabapentin on Ocular Pain and Tear Secretion

Neuropathic ocular pain is a frequent occurrence in medium to severe dry eye disease (DED). Only palliative treatments, such as lubricants and anti-inflammatory drugs, are available to alleviate patients’ discomfort. Anesthetic drugs are not indicated, because they may interfere with the neural feedback between the cornea and the lacrimal gland, impairing tear production and lacrimation. Gabapentin (GBT) is a structural analog of gamma-amino butyric acid that has been used by systemic administration to provide pain relief in glaucomatous patients. We have already shown in a rabbit model system that its topic administration as eye drops has anti-inflammatory properties. We now present data on rabbits’ eyes showing that indeed GBT given topically as eye drops has analgesic but not anesthetic effects. Therefore, opposite to an anesthetic drug such as oxybuprocaine, GBT does not decrease lacrimation, but–unexpectedly–even stimulates it, apparently through the upregulation of acetylcholine and norepinephrine, and by induction of aquaporin 5 (AQP5) expression in the lacrimal gland. Moreover, data obtained in vitro on a primary human corneal epithelial cell line also show direct induction of AQP5 by GBT. This suggests that corneal cells might also contribute to the lacrimal stimulation promoted by GBT and participate with lacrimal glands in the restoration of the tear film, thus reducing friction on the ocular surface, which is a known trigger of ocular pain. In conclusion, GBT is endowed with analgesic, anti-inflammatory and secretagogue properties, all useful to treat neuropathic pain of the ocular surface, especially in case of DED.

Hydrogen sulfide in longevity and pathologies: Inconsistency is malodorous

Hydrogen sulfide (H₂S) is one of the biologically active gases (gasotransmitters), which plays an important role in various physiological processes and aging. Its production in the course of methionine and cysteine catabolism and its degradation are finely balanced, and impairment of H₂S homeostasis is associated with various pathologies. Despite the strong geroprotective action of exogenous H₂S in C. elegans, there are controversial effects of hydrogen sulfide and its donors on longevity in other models, as well as on stress resistance, age-related pathologies and aging processes, including regulation of senescence-associated secretory phenotype (SASP) and senescent cell anti-apoptotic pathways (SCAPs). Here we discuss that the translation potential of H₂S as a geroprotective compound is influenced by a multiplicity of its molecular targets, pleiotropic biological effects, and the overlapping ranges of toxic and beneficial doses. We also consider the challenges of the targeted delivery of H₂S at the required dose. Along with this, the complexity of determining the natural levels of H₂S in animal and human organs and their ambiguous correlations with longevity are reviewed.

Smoke-water commonly induces hormetic dose responses in plants

A detailed evaluation was made of the literature concerning the dose response features of smoke-water extracts and other types of biological pyrolysis products on seed germination and plant growth. The evaluation was undertaken to extend our research on the occurrence and importance of hormesis in plant biology, as no similar assessment on smoke water biology had been published and that a preliminary survey suggested widespread occurrence of hormesis. It was determined that hormetic-like biphasic dose responses were commonly reported within the smoke-water plant literature for seed germination and plant growth. These findings were independent of the type of plant evaluated, the type of plant material used for the smoke-water extract, and the process of pyrolysis and extraction. The magnitude of the maximal stimulation of the biphasic dose responses was consistent with the hormetic concept, with maximal responses typically being approximately 30-60% greater than control values and with a stimulatory dose/concentration width less than 10 fold. These findings, which represent dose response features of a spectrum of novel and chemically diverse complex mixtures, support the generality of the hormetic dose response and its potential utility in enhancing the quality of study designs, including selection of dose/concentration number and spacing as well as biological model and endpoint.

Characterization and toxicity evaluation of air-borne particles released by grinding from two dental resin composites in vitro

OBJECTIVE

The project aims to evaluate whether inhalation of particles released upon grinding of dental composites may pose a health hazard to dentists. The main objective of the study was to characterize the dust from polymer-based dental composites ground with different grain sized burs and investigate particle uptake and the potential cytotoxic effects in human bronchial cells.

METHODS

Polymerized blocks of two dental composites, Filtek™ Z250 and Filtek™ Z500 from 3M™ ESPE, were ground with super coarse (black) and fine (red) burs inside a glass chamber. Ultrafine airborne dust concentration and particle size distribution was measured real-time during grinding with a scanning mobility particle sizer (SMPS). Filter-collected airborne particles were characterized with dynamic light scattering (DLS) and scanning electron microscopy (SEM). Human bronchial epithelial cells (HBEC-3KT) were exposed to the dusts in dose-effect experiments. Toxicity was measured with lactate dehydrogenase (LDH) assay and cell counting kit-8 (CCK8). Cellular uptake was observed with transmission electron microscopy (TEM).

RESULTS

Airborne ultrafine particles showed that most particles were in the size range 15-35 nm (SMPS). SEM analysis proved that more than 80% of the particles have a minimum Feret diameter less than 1 μm. In solution (DLS), the particles have larger diameters and tend to agglomerate. Cell toxicity (LDH, CCK8) is shown after 48 h and 72 h exposure times and at the highest doses. TEM showed presence of the particles within the cell cytoplasm.

SIGNIFICANCE

Prolonged and frequent exposure through inhalation may have negative health implications for dentists.

Hormesis Mediates Acquired Resilience: Using Plant-Derived Chemicals to Enhance Health

This review provides an assessment of hormesis, a highly conserved evolutionary dose-response adaptive strategy that leads to the development of acquired resilience within well-defined temporal windows. The hormetic-based acquired resilience has a central role in affecting healthy aging, slowing the onset and progression of numerous neurodegenerative and other age-related diseases, and reducing risks and damage due to heart attacks, stroke, and other serious conditions of public health and medical importance. The review provides the historical foundations of hormesis, its dose-response features, its capacity for generalization across biological models and endpoints measured, and its mechanistic foundations. The review also provides a focus on the adaptive features of hormesis, i.e., its capacity to upregulate acquired resilience and how this can be mediated by numerous plant-derived extracts, such as curcumin, ginseng, Ginkgo biloba, resveratrol, and green tea, that induce a broad spectrum of chemopreventive effects via hormesis.

Mechanisms for the stimulatory effects of a five-component mixture of antibiotics in Microcystis aeruginosa at transcriptomic and proteomic levels

Antibiotic contaminants could promote the formation of harmful cyanobacterial blooms through hormetic stimulation, but the mechanisms underlying these stimulatory effects remain unclear. This study investigated the biochemical, transcriptomic, and proteomic responses of a dominant bloom-forming cyanobacterium, Microcystis aeruginosa, to a five-component mixture of frequently detected antibiotics at current contamination levels. The growth rate of M. aeruginosa presented a U-shaped dose-response to 50-500 ng L^-1 of mixed antibiotics. Alterations in the transcriptome of M. aeruginosa suggested the excitation of both photosynthesis and carbon metabolism, increasing energy generation in response to oxidative stress induced by low-dose antibiotics, and thus contributing to the significant (p < 0.05) increase in growth rate, F_v/F_m, and cell density. Comparison between transcriptomic and proteomic responses further confirmed the action mode of the mixed antibiotics. Proteins and their corresponding genes related to ROS scavenging, photosynthesis, carbon fixation, electron transport, oxidative phosphorylation, and biosynthesis, showed consistent expression tendencies in response to 200 ng L^-1 of mixed antibiotics, which were credible action targets of mixed antibiotics in M. aeruginosa. Mixed antibiotics stimulated microcystin synthesis by upregulating a microcystin synthetase and its encoding gene (mcyC), which could increase the hazard of M. aeruginosa in aquatic environments.

Influence of Perfluorobutanoic Acid (PFBA) on the Developmental Cycle and Damage Potential of the Beet Armyworm Spodoptera exigua (Hübner) (Insecta: Lepidoptera: Noctuidae)

Perfluorobutanoic acid (PFBA), one of the short-chain replacement perfluoroalkyl substances, has been shown to accumulate in plants. The potential of PFBA to modulate the developmental cycle of the beet armyworm, Spodoptera exigua, a polyphagous pest, was investigated. Second-instar larvae were fed with PFBA-spiked artificial diets and leaves from soybean plants grown with PFBA-spiked irrigation water. Spiked PFBA concentrations were 200 μg/kg for the artificial diet, whereas 405 to 15,190 ng/kg accumulated in the soybean leaves. The larvae fed with the PFBA-spiked diet showed a significant increase in weight gain compared with the controls over a 7-day exposure period. A similar weight gain trend was observed with larvae fed with the PFBA-containing soybean leaves, with the dose-response data fitting into a Brain-Cousens hormesis model with a 57% stimulation over controls. The artificial diet treatments showed 66.7% metamorphosed larva to pupa at 9 days after exposure (dpe) compared with 33.3% of the controls. The adult emergence at 16-dpe followed a similar trend with 57.7% and 33.3%, respectively, for the exposed and control groups. The duration of transition from larvae to adults was more symmetrical and 0.5 day faster for the exposed groups over controls. The beet armyworm caused more damage on leaves from the PFBA exposed plants in a nonmonotonic dose-response manner. The results suggest PFBA may have a stimulatory impact on some hormonal signaling pathways at low doses.

Low Doses of a Neonicotinoid Stimulate Reproduction in a Beneficial Predatory Insect

Biological stimulation induced by low doses of toxicants or other stressors is known as hormesis. Hormetic stimulation of life history traits in insect pests can negatively impact agriculture, but stimulation of beneficial insects could be leveraged to enhance biological control agents. We examined whether low doses of imidacloprid could enhance oviposition, fecundity, fertility, and survival in the beneficial stink bug predator, Podisus maculiventris (Say) (Hemiptera: Pentatomidae), exposed at different life stages and across two generations. When treated as young adults, P. maculiventris fecundity was stimulated at 0.5 and 1.0 mg/liter imidacloprid (<2% of the field rate) without changes in time to oviposition, fertility, and survival. Nymphs exposed to 0.015 mg/liter imidacloprid (<1% of the field rate) also had stimulated reproduction without effects on oviposition, fertility, and survival, but treatment of nymphs at 0.15 and 1.5 mg/liter imidacloprid stimulated fecundity at the expense of fertility and survival. In another experiment we found reproductive stimulation can occur trans-generationally without major reduction in fertility or survival. Our results suggest biocontrol producers may be able to strategically apply low doses of stress to natural enemies during culturing without compromising fitness in subsequent generations.

Extremely-low frequency magnetic field exposure for simulating geomagnetic pulsations in Alexandrium pacificum and Gymnodinium catenatum cultures

Growth and chain formation in cultures of the chain-forming dinoflagellates Alexandrium pacificum and Gymnodinium catenatum were previously found to be susceptible to space weather variables. A clock drive was used to deliver a frequency of 0.5 Hz and central amplitude of 7 µT in order to perform in vitro simulation of geomagnetic pulsations (composed of extremely low-frequency magnetic fields, ELFMF) which occur during high geomagnetic activity (GMA) periods. Short-term exposure (hours) to this ELFMF increased relative cell growth around 10 nT of naturally occurring GMA. Relative growth outside these intervals gradually approached 0% or was negative for G. catenatum. Differential survival to a subsequent shock was inversely related to growth, and minimal survival coincided with the same 10 nT interval. Relative growth and survival displayed opposite hormetic curves towards GMA: inverted U-shaped for growth, and J-shaped for survival. After exposure to this ELFMF, positive phototaxis response was not lost, but the percentage of cells swimming was slightly reduced. Long-term exposure (days) increased relative growth in A. pacificum but reduced in G. catenatum when low GMA was taking place. These alterations in growth were both associated with a reduction in the cellular pool of mycosporine-like amino acids (MAAs). MAAs that are more susceptible to oxidation were more reduced than those resistant, highlighting that an ELFMF can act by increasing cellular oxidative stress status. The higher susceptibility of G. catenatum found is in compliance with the previous association of its natural populations at the western Iberia coast with periods of solar activity minima and GMA minima.

In Vitro Hormetic Effect Investigation of Thymol on Human Fibroblast and Gastric Adenocarcinoma Cells

The concept of hormesis includes a biphasic cellular dose-response to a xenobiotic stimulus defined by low dose beneficial and high dose inhibitory or toxic effects. In the present study, an attempt has been made to help elucidate the beneficial and detrimental effects of thymol on different cell types by evaluating and comparing the impact of various thymol doses on cancerous (AGS) and healthy (WS-1) cells. Cytotoxic, genotoxic, and apoptotic effects, as well as levels of reactive oxygen species and glutathione were studied in both cell lines exposed to thymol (0–600 µM) for 24 h. The results showed significant differences in cell viability of AGS compared to WS-1 cells exposed to thymol. The differences observed were statistically significant at all doses applied (P ≤ 0.001) and revealed hormetic thymol effects on WS-1 cells, whereas toxic effects on AGS cells were detectable at all thymol concentrations. Thymol at low concentrations provides antioxidative protection to WS-1 cells in vitro while already inducing toxic effects in AGS cells. In that sense, the findings of the present study suggest that thymol exerts a dose-dependent hormetic impact on different cell types, thereby providing crucial information for future in vivo studies investigating the therapeutic potential of thymol.

Hormesis and Ginseng: Ginseng Mixtures and Individual Constituents Commonly Display Hormesis Dose Responses, Especially for Neuroprotective Effects

This paper demonstrates that ginseng mixtures and individual ginseng chemical constituents commonly induce hormetic dose responses in numerous biological models for endpoints of biomedical and clinical relevance, typically providing a mechanistic framework. The principal focus of ginseng hormesis-related research has been directed toward enhancing neuroprotection against conditions such as Alzheimer's and Parkinson's Diseases, stroke damage, as well as enhancing spinal cord and peripheral neuronal damage repair and reducing pain. Ginseng was also shown to reduce symptoms of diabetes, prevent cardiovascular system damage, protect the kidney from toxicities due to immune suppressant drugs, and prevent corneal damage, amongst other examples. These findings complement similar hormetic-based chemoprotective reports for other widely used dietary-type supplements such as curcumin, ginkgo biloba, and green tea. These findings, which provide further support for the generality of the hormetic dose response in the biomedical literature, have potentially important public health and clinical implications.