Animal tests like the guinea pig maximization test (GPMT) and murine local lymph node assay (LLNA) were historically used to assess skin sensitization in cosmetics. The EU banned animal testing for cosmetics in 2013, prompting the development of alternative in vitro methods and new approach methodologies (NAMs) based on adverse outcome pathways (AOPs). These NAMs are integrated into Defined Approaches (DAs) to evaluate skin sensitization hazards and potency, which challenge is incorporating them into next-generation risk assessment (NGRA) frameworks. To address this challenge, we aim to achieve quantitative risk assessment in humans. The NGRA framework proposed by Cosmetics Europe emphasizes read-across methods, which predict toxicity using data from similar substances. This approach, which utilizes data from analogues, is described as an effective way to reduce uncertainty in risk assessment. This paper proposes a transparent read-across method using the OECD QSAR Toolbox, ranked by reliability based on structural similarity, protein binding, sensitization alerts, and percutaneous absorption. The sensitization data of the extracted analogues prioritize the LLNA EC3 values, followed by predicted EC3 values from Derek nexus or GPMT data. A case study using p-isobutyl-α-methyl hydrocinnamaldehyde confirmed the target's classification as a moderate sensitizer. The proposed method ensures transparency by relying on publicly available tools, reducing uncertainty in NGRA.
Acute kidney injuries and renal dysfunction caused by ethylene glycol poisoning are often associated with nephrolithiasis. Calcium oxalate (CaOx) crystal formation is considered one of the most common events at the early stage of nephrolithiasis. The aim of this study is to investigate molecular mechanisms underlying CaOx crystal formation on renal tubular epithelial cells in vitro. We applied oxalate or potassium oxalate (final concentrations, 200-1200 µM) in the medium culturing NRK-52E rat proximal tubular epithelial cells. Cell death was observed with levels of oxalate or potassium oxalate above 800 µM 48 hr after addition. Crystals, mainly consisting of CaOx as confirmed by polarized light microscopy, were detected on cells treated with 800 µM oxalate or potassium oxalate. Transcriptome analysis showed that a gene (S100A11-like) belonging to the S100 family, which consists of homologous Ca-binding proteins, many of which can form complexes with annexin family proteins, was the gene most upregulated by 800 µM oxalate. Immunoblot as well as immunocytochemical analysis indicated not only upregulation but also alteration of intracellular localization of S100A11. The same altered pattern of localization was also observed for annexin A2, which has been shown to be involved in the formation of CaOx crystals. This study presents the possibility that, in addition to annexin family proteins, S100 family proteins might be involved in the regulation of CaOx crystal formation and/or other events associated with crystal formation.
Perinatal exposure to chemicals such as valproic acid (VPA) increases the risk of neurodevelopmental disorders, including autism spectrum disorder (ASD). Because maternal drug metabolism complicates the assessment of fetal impacts in mammalian models, Xenopus laevis tadpoles have emerged as an effective alternative for neurotoxicology. Tadpoles exhibit "schooling," a polarized social aggregation behavior. Previous studies, which exposed tadpoles to VPA continuously from stage NF42 to NF49, suggested that VPA-induced social behavior abnormalities are triggered during this period. In this study, we re-evaluated the ontogeny of schooling behavior and its vulnerability to VPA by administering short-term exposures at specific developmental stages. Using computational modeling and statistical analyses, we compared the spatial distribution of live tadpoles with computer-simulated random models. Untreated tadpoles exhibited significant, non-random social aggregation as early as stage NF42, indicating that the sensorimotor circuitry for schooling is established earlier than previously assumed. Furthermore, tadpoles exposed to VPA for 4 days starting at stages NF42 and NF48 maintained schooling behavior, whereas VPA exposure starting at stage NF52 significantly disrupted spatial cohesion. These findings indicate that while social behavior is acquired prior to NF42, NF52 represents a critical window of heightened pharmacological vulnerability to teratogens, providing new insights into the etiology of environmentally induced neurodevelopmental disorders.
Methylisothiazolinone (MIT) is a widely used biocidal preservative in industrial and cosmetic products. However, evidence of its neurotoxic effects is limited, and the mechanistic pathways are poorly defined. This study investigated the neurotoxic potential of MIT and the molecular mechanisms underlying its cellular toxicity in SH-SY5Y cells. After exposing SH-SY5Y cells to MIT various concentrations (30 to 120 μM) for 24 hr, apoptosis and inflammatory responses were quantified alongside the determination of apoptotic-, oxidative stress-, cell survival-, and angiogenic-related biomarkers. To reinforce the experimental findings, a set of in silico chemoinformatics studies, including network toxicology and molecular docking were conducted to pinpoint and evaluate the potential molecular targets of MIT. The IC50 value of MIT was found 115 µM. Total apoptotic cells increasing to 56.5% at 120 µM. ELISA results indicated activation of the intrinsic apoptotic pathway, evidenced by significant upregulation of p53 (9.54-fold), BAX (4.52-fold), and APAF-1 (8.85-fold), along with a disruption in the BAX/BCL-2 (4.52/4.37-fold) balance. Furthermore, an elevation in the COX/COX-2 (8.04/6.93-fold), SRC (7.08-fold), and VEGFR2 (20.96-fold) levels which indicated the concurrent oxidative stress and stress-induced pro-survival signaling at 120 µM. MIT selectively amplified some inflammatory mediators, suggesting inflammasome-driven neuroinflammation. In silico analysis further support MIT as a polypharmacological toxicant with the potential to modulate key molecular targets, including PARP-1, GSK-3β, and iNOS. MIT induced multifaceted neurotoxicity in SH-SY5Y cells through the simultaneous activation of intrinsic apoptotic signaling, oxidative stress, and selective neuroinflammatory pathways. The findings emphasize the potential neurotoxic risks associated with MIT exposure and underscore the necessity for strengthened regulatory evaluation and in vivo validation.
Reliable early prognostic tools for acute poisoning remain limited. This study examined whether four first-measured routine biomarkers - glucose, lactate, bicarbonate, and white blood cell count (WBC) - carry prognostic signal for 30-day mortality in emergency department (ED) patients with acute poisoning, using a pre-processed, de-identified electronic health records dataset derived from MIMIC-IV (Medical Information Mart for Intensive Care, version 3.1; a publicly available critical care database from Beth Israel Deaconess Medical Center, Boston, USA, hosted on PhysioNet; n=12,039 ED visits; 59 deaths; 30-day mortality 0.49%). Due to extreme non-random missingness across all four biomarkers (lactate 95.2%; bicarbonate/glucose/WBC 88-89%), multivariable modelling was restricted to a complete-case subgroup (n=503; deaths=19). This subgroup was markedly non-representative: intensive care unit (ICU) admission rate 66.4% versus 2.1% in excluded visits (standardised mean difference [SMD]=1.844), reflecting selective laboratory ordering in clinically severe patients. In univariable analyses across available cases, all four biomarkers were significantly associated with 30-day mortality. Within the complete-case subgroup, glucose alone demonstrated good discrimination (area under the receiver operating characteristic curve [AUROC]=0.812; 95% confidence interval [CI] 0.721-0.885), and glucose and WBC were independently associated with mortality in multivariable analysis (adjusted odds ratios [aOR] 1.05 and 1.13, respectively). The calibration slope of 0.646 for the primary four-biomarker model indicated systematic overestimation of absolute risk. These findings are strictly exploratory. Critical limitations - extreme non-random missingness, ICU-enriched complete-case subgroup, absent age and vital signs, low event count (n=19), and absence of external validation - preclude clinical application. This work defines data and design requirements for a future adequately powered prospective prognostic study in acute poisoning.
The objective of this study was to examine the mechanisms underlying endocytic uptake, cytotoxicity, oxidative stress, and lysosomal damage caused by silica micro/nanoparticles (SiPs) in murine RAW-Blue macrophages. In parallel studies, we also assessed the effects of NF-κB on lysosomal membrane permeabilization (LMP). Three types of SiPs, 3 μm-plain (3 μm diameter particles without surface modification), 50 nm-plain (50 nm diameter particles without surface modification), and 50 nm-NH2 (50 nm diameter particles with an amine functional group as surface modification) were tested. A significant decrease in cell proliferation and a significant increase in cell death were evident, when cells were treated with 50 nm-plain. All types of SiPs plus a lysosomal inhibitor caused a significant increase and a significant decrease in cell proliferation and cell death, respectively. When cells were treated with 50 nm-plain, puncta formation was seen. Treatment with 50 nm-plain significantly increased the expression level of inflammatory cytokine/chemokine genes, whereas inhibitors of clathrin-mediated endocytosis, lysosomal function, and cathepsin activity significantly attenuated these responses. Taken together, the present findings suggest that lysosomal dysfunction is closely associated with 50 nm-plain-induced cytotoxic and inflammatory responses. Our findings also provide relevant findings for safe and effective design of SiPs and a framework to maximize their biomedical potential while mitigating lysosomal damage.
Aconite contains four highly toxic diester-diterpene alkaloids (DDAs): aconitine, mesaconitine, hypaconitine, and jesaconitine. The efficacy of charcoal hemoperfusion (CHP) in treating aconite poisoning has recently been reported in several East Asian cases. This study evaluated the potential efficacy of CHP using two simulation experiments and one clinical case. One simulation examined the saturated adsorption capacity of activated charcoal for aconitine, whereas the other assessed the time course of perfusate aconitine concentrations at the inlet and outlet of an activated-charcoal column. The clinical case involved a 61-year-old female with stage V chronic kidney disease who underwent CHP for an electrical storm due to aconite poisoning. Her initial plasma DDA concentration was markedly higher than those reported in previous cases. This elevated concentration raises the possibility of substantial ingestion, although the exact amount cannot be determined. CHP was initiated 2 hr after ingestion and continued for 7 hr. In the simulations, activated charcoal showed a saturated adsorption capacity of 110 mg of aconitine per gram, and the column removed most aconitine in a single pass. In the clinical case, plasma DDA concentrations rapidly decreased after 7 hr of CHP, with a clearance rate of approximately 70 mL/min at a blood-flow rate of 100 mL/min. The terminal elimination half-life of plasma DDAs was 109.5 hr, likely reflecting the patient's underlying kidney disease. Taken together, these findings suggest that CHP may contribute to DDA elimination under severe renal impairment, although its broader clinical relevance remains uncertain.
The increasing demand for non-animal approaches in food safety assessment underscores the need for methods capable of predicting human internal exposure. We systematically evaluated the applicability of a physiologically based pharmacokinetic (PBPK) model-originally developed for pharmaceuticals and general chemicals, to predict physicochemical and pharmacokinetic parameters from chemical structure information and simulate human plasma profiles-to human internal exposure prediction. Food-related compounds were selected from published papers, and human single-dose pharmacokinetic studies were curated when all of the following criteria were met: 1) single administration in humans, 2) dose clearly specified as the target compound amount, 3) unchanged parent compound measured, 4) area under the curve (AUC) analyzed, and 5) no formulation/processing intended to control absorption. Using predicted parameters as PBPK inputs, peak plasma concentration (Cmax) and AUC were simulated and compared with observed values. In the absence of applicability restrictions, prediction ratios (predicted value/observed value) ranged from 0.00970 to 825 for Cmax and from 0.0000299 to 1628 for AUC; 20/36 Cmax and 19/40 AUC data points were within the three-fold error range (0.33-3). Restricting the applicability domain to compounds with predicted intestinal absorption/bioavailability > 0.5 and excluding a specific chemical-space region improved predictivity, with 11/12 (91.6%) Cmax and 9/12 (75.0%) AUC data points within the three-fold error range. Taken together, these results indicate that the in silico PBPK-based approach provides a practical and reasonably accurate estimate of human internal exposure for a subset of food-related compounds when an appropriate applicability domain is defined.
Benzene exposure is a major risk factor for hematologic malignancies, including acute myeloid leukemia (AML), through mechanisms involving genotoxicity, oxidative stress, and dysregulation of hematopoietic signaling pathways. This study investigated the protective effects of melatonin, vitamin C, and their combination against benzene-induced pre-leukemic alterations in rats, with emphasis on bone marrow genotoxicity, oxidative stress, and activin A/follistatin expression. Forty male Wistar rats were allocated into five groups (n=8): control, benzene, benzene + melatonin, benzene + vitamin C, and benzene + combined treatment. Genotoxicity was assessed using bone marrow micronucleus assays, while oxidative stress biomarkers, serum activin A/follistatin levels, and bone marrow gene expression were evaluated using biochemical assays, ELISA, and qPCR, respectively. Benzene exposure significantly increased micronucleus frequency, reduced %PCE and PCE/NCE ratio, elevated %NCE, and suppressed activin A and follistatin expression. Melatonin or vitamin C alone partially attenuated these abnormalities, whereas combined treatment demonstrated the strongest protective effects, including marked improvement of genotoxicity indices, restoration of catalase activity, and significant upregulation of activin A and follistatin gene expression. Combined melatonin and vitamin C supplementation attenuated benzene-associated pre-leukemic alterations, particularly genotoxic and oxidative stress-related abnormalities. Combined melatonin and vitamin C supplementation attenuated benzene-associated pre-leukemic alterations in rats, particularly genotoxic and oxidative stress-related abnormalities. These protective effects were accompanied by modulation of activin A/follistatin expression patterns, suggesting a potential association between restoration of this signaling axis and improved bone marrow homeostasis. However, further mechanistic studies are required to determine whether activin A/follistatin signaling directly contributes to the observed protective effects.
The prevalence of pediatric neurological disorders has increased in recent years and has emerged as a major social concern. While genetic factors play a role, environmental factors may also contribute to these disorders, particularly exposure to harmful chemicals in the fetal environment during pregnancy. However, the concentrations of these chemicals in the fetal environment are extremely low compared with those in experimental conditions, and their influence on the development of neurological disorders after birth remains unclear. Epigenetic regulation plays a crucial role in gene expression and/or chromatin formation, ensuring normal cellular development and differentiation. The relationship between impaired epigenetic regulation and neurological disorders has been previously reported. Therefore, this study aimed to identify chemicals that disrupt epigenetic systems at detectable concentrations in pregnant mothers' serum using a human neural differentiation model. Among the 11 chemicals, including pesticides and heavy metals, exposure to octachlorodipropyl ether (S-421) altered heterochromatin formation in neural stem cells at concentrations found in maternal and umbilical cord blood serum. Additionally, exposure to several chemicals, including S-421, affected neural differentiation, leading to excessive neural fiber growth. Furthermore, S-421 exposure induced DNA hypermethylation of the neural-related genes Cadherin 2 (CDH2) and Sry-related HMG-Box gene 10 (SOX10) in neural stem cells. These findings suggest that S-421, which is present in the fetal environment, functions as an epimutagen that disrupts the epigenetic system within biologically relevant exposure levels. The established epimutagenic screening is expected to provide new insights into the relationship between prenatal chemical exposure and postnatal childhood neurological disorders.
Chronic hyperlipidemia and/ or hyperglycemia can impair various organs, such as the liver, kidney, and pancreas, through metabolic abnormalities. Metabolic dysfunction-associated steatohepatitis (MASH), related from nonalcoholic steatohepatitis (NASH), exhibits complex pathophysiological features, and animal models of MASH are essential for elucidating its underlying mechanisms. This study aimed to induce MASH-like lesions in obese type 2 diabetic mice by feeding them a high-fat/high-sucrose/high-cholesterol (HFSC) diet. C57BL/6J, db/db, and KK-Ay mice at 6 weeks of age were fed an HFSC diet for 8 weeks. Collected samples were subjected to hematobiochemical, gene expression, and histopathological analyses. At 14 weeks of age, both diabetic mouse models showed hyperglycemia and hyperlipidemia, with hypercholesterolemia observed in HFSC-fed groups. HFSC-fed db/db and KK-Ay mice showed increased hepatic steatosis, and KK-Ay mice also showed partial hepatic fibrosis in pericentral venous and perivascular areas. mRNA analysis revealed upregulation of hepatic genes involved in lipid synthesis, inflammation, and fibrosis in diabetic mice fed the HFSC diet. Obese type 2 diabetic mice fed a high-fat/high-sucrose/high-cholesterol diet showed early indications of MASH-like lesions, supporting their utility as MASH animal models.
Multiple chemical sensitivity (MCS) is characterized by neuropsychological symptoms including anxiety, depression, and fatigue following exposure to environmental chemicals, yet its underlying mechanisms remain poorly understood. Linalool, a monoterpene alcohol widely used in consumer products, has been suggested as a potential contributor to MCS. To elucidate its neural effects, we examined the behavioral effects of linalool inhalation in mice. Linalool exposure induced both anxiety- and depression-like behaviors. While the depression-like behavior required olfactory input, the anxiety-like behavior occurred independently of olfactory perception. Our previous studies demonstrated that inhaled linalool accumulates in the brain and undergoes cytochrome P450 (P450)-dependent metabolism. We therefore tested whether P450-mediated metabolism contributes to the behavioral effects of linalool. Significantly, inhibition of P450 activity abolished the anxiety-like behavior. These findings reveal an olfactory-independent mechanism by which inhaled linalool induces anxiety-like behavior in mice and suggest that P450 activity is required for this effect, providing a basis for investigating fragrance-induced MCS-like neurobehavioral responses.
Cisplatin is a widely used platinum-based chemotherapeutic agent whose dose-limiting toxicities, including nephrotoxicity, neurotoxicity, and myelosuppression, have been extensively characterized. In contrast, skeletal muscle has not traditionally been regarded as a primary target of cisplatin toxicity. However, accumulating experimental evidence indicates that cisplatin administration leads to a significant reduction in skeletal muscle mass and fiber size, even in the absence of tumor burden or overt cachexia. These findings suggest that cisplatin itself can directly induce skeletal muscle atrophy as a form of drug-induced toxicity. Animal and cell-based studies have demonstrated that cisplatin activates catabolic signaling in skeletal muscle, most notably through enhanced protein degradation via the ubiquitin-proteasome system. This response is accompanied by increased expression of muscle-specific E3 ubiquitin ligases, including muscle RING finger 1 (MuRF1) and muscle atrophy F-box protein (MAFbx/atrogin-1), which are established mediators of skeletal muscle atrophy. In parallel, suppression of anabolic signaling, particularly impairment of the insulin-like growth factor-1/Akt/mechanistic target of rapamycin complex 1 (mTORC1) pathway, has been reported, indicating a shift in muscle protein turnover toward a catabolic state. Recent studies suggest that cellular stress responses, such as endoplasmic reticulum stress, may be involved in regulating these processes. This review summarizes experimental evidence supporting cisplatin-induced skeletal muscle atrophy and discusses the underlying toxicological processes from a muscle-centered perspective. By distinguishing drug-induced muscle toxicity from cancer cachexia and other wasting conditions, we propose that skeletal muscle should be recognized as a clinically relevant but underestimated target organ of cisplatin toxicity. Improved understanding of these processes may support the development of strategies to preserve muscle mass and function during cancer chemotherapy.
Arsenite (As(III)) is a widespread environmental contaminant that increases susceptibility to oxidative stress. We recently reported that As(III) suppresses the induction of glutathione peroxidases (GPx) by various selenium sources in cultured cells; however, its underlying mechanism remains unclear. GPx contains a selenocysteine (Sec) residue essential for catalytic activity, and Sec biosynthesis requires multiple steps of selenium metabolism. Selenite is directly incorporated into the Sec biosynthetic pathway via selenophosphate synthetase 2 (SEPHS2) and utilized for Sec-tRNASec formation. Because Sec-tRNASec decodes UGA codons, impaired synthesis of Sec-tRNASec leads to nonsense-mediated decay or truncated translation of selenoprotein mRNAs. Here, we developed an inductively coupled plasma (ICP)-MS based method to evaluate Sec-tRNASec and found that As(III) inhibits Sec charging of tRNA. As(III) markedly suppressed GPx protein induction with minimal effects on mRNA abundance. As(III) did not affect total tRNASec levels; however, As(III) significantly decreased RNA-bound selenium released by deacylation, indicating reduced Sec-tRNASec formation. These results suggest that As(III) impairs selenoprotein translation by inhibiting Sec charging of tRNA.
Although the importance of polymorphic cytochrome P450 2C19 (CYP2C19) in the metabolism of proton pump inhibitors is well recognized, genotyping patients for CYP2C19 before prescribing proton pump inhibitors is not currently recommended in some Asian countries. Adverse events in patients prescribed 30-mg lansoprazole alone have been reported in the Japanese Adverse Drug Event Report database. This study aimed to evaluate virtual internal exposure to lansoprazole in CYP2C19 poor metabolizers using a simplified physiologically based pharmacokinetic (PBPK) model. The input parameters for the simplified PBPK model were based on reported plasma concentrations for 30-mg lansoprazole. For poor metabolizers, the in vivo hepatic intrinsic clearance value was reduced from 13.4 L/hr to 3.4 L/hr. For comparison, a population-based (full) model was used based on the incorporated parameters for lansoprazole (latest Simcyp Simulator version 25). High virtual plasma and hepatic maximum concentrations and the areas under the concentration-time curves of lansoprazole in the poor metabolizers were generated by the simplified and full PBPK models. These results suggest that virtual internal exposure to lansoprazole in CYP2C19 poor metabolizers can be evaluated using PBPK modeling systems. Despite the limited references to CYP2C19 polymorphisms in current Asian drug labeling, such in silico information could be informative.
Cigarette smoking is a risk factor for various diseases, including chronic obstructive pulmonary disease (COPD). Cell death induced by cigarette smoke is one of the underlying causes of COPD. Unsaturated carbonyl compounds, such as acrolein and methyl vinyl ketone, are major cytotoxic factors in the gas phase of cigarette smoke. To elucidate the molecular mechanisms for induction of cell death by the unsaturated carbonyl compounds in respiratory cells, two lung cancer cell lines, A549 cells and SBC-3 cells, were exposed to the unsaturated carbonyl compounds. A549 cells were resistant to the unsaturated carbonyl compounds, while SBC-3 cells were sensitive to these compounds. Pharmacological analyses revealed that these compounds induce protein kinase C-dependent ferroptosis in SBC-3 cells. Inhibition of glutathione (GSH) synthesis increased the sensitivity of A549 cells to unsaturated carbonyl compounds. GSH level in A549 cells was approximately four times higher than that in SBC-3 cells. Inhibition of SLC7A11, a cystine transporter, in A549 cells increased their sensitivity to unsaturated carbonyl compounds, while overexpression of SLC7A11 in SBC-3 cells decreased their sensitivity to these compounds. These results indicate that the GSH synthetic capacity determines cell sensitivity to unsaturated carbonyl compounds. Accordingly, GSH may be a key factor for the pathogenesis of cigarette smoke-induced COPD.
In general toxicity studies in rodents, groups are initially assigned based on body weight, highlighting the importance of matching the body weights of test article groups when creating Virtual Control Groups (VCGs). In this study, we aimed to generate VCGs by linking toxicity parameters to initial body weights and to verify the significance of body-weight matching. The Concurrent Control Groups (CCGs) from nine 4-week rat studies at a single facility served as Historical Control Data (HCD). VCGs were generated by random sampling of initial body weights in HCD, and a ± 5 g range from the mean initial body weight of the test article group was used as the body-weight-matching criteria. VCGs were used to assess statistical differences in aspartate aminotransferase (AST), alanine aminotransferase (ALT), and liver weight at the end of one specific study. Of the 10 VCGs generated, two had deviations of more than 5 g from the mean initial body weight value. Statistically significant differences in AST and ALT levels observed in CCGs tended to become non-significant in VCGs, regardless of the mean initial body weight of VCGs. Meanwhile, VCGs outside the ± 5 g range revealed new statistically significant differences in liver weight. Liver weight was weakly correlated with initial body weight, suggesting that deviations in initial body weight influenced the statistical significance of liver-weight differences at the end of the study. The importance of matching body weight in VCGs was confirmed, particularly for toxicity parameters that correlate with initial body weight values.
Cytochrome P450s (P450s) are essential for xenobiotic metabolism, and their inhibition is associated with chemical-induced liver toxicity. While qualitative associations between P450 inhibition and hepatotoxicity have been reported, the quantitative relationship between the degree of inhibition and the severity of hepatotoxicity remains unclear. In this study, we explored the quantitative association between P450 inhibition and hepatotoxicity using lowest observed effect levels (LOELs) from rat repeated-dose toxicity (RDT) studies on 326 chemicals. Inhibitory activities against seven rat P450 isoforms were compared between compounds positive and negative for six liver-related group endpoints (gEPs). The results revealed that inhibitory activity against CYP1A1, CYP2B1, CYP2C6, and CYP3A2 was significantly higher in compounds positive for hepatocellular hypertrophy or dyslipidemia than in negative compounds. Although regression analyses did not show clear linear relationships between P450 inhibition and LOELs, nonparametric trend tests revealed modest monotonic associations, with increased P450 inhibition corresponding to lower LOELs. To identify structural factors influencing inhibition among highly toxic compounds, we compared molecular descriptors between those exhibiting strong or weak P450 inhibition. Descriptors related to aqueous solubility, Verhaar baseline toxicity, and structural complexity were consistently higher in the weak-inhibition group across multiple P450-gEP combinations. These findings suggest that inhibition of CYP1A1, CYP2B1, CYP2C6, and CYP3A2 partly contributes to the severity of hepatocellular hypertrophy and dyslipidemia, whereas highly toxic compounds with low P450 inhibition may exert their toxicity through P450-independent mechanisms.
Humans rely heavily on visual function to gather information, and loss of vision has a significant impact on quality of life. However, it is difficult to quantitatively evaluate the effects of chemical compounds on visual function in toxicity studies using animals (such as OECD guideline studies). Consequently, evaluation including ophthalmological and histopathological examinations has played a major role to date. Visually evoked potential (VEP) is a type of brain wave that reflects the activity of the entire visual pathway, including the retina, optic nerve, and visual cortex. We investigated whether VEP could detect the effects of acrylamide, a toxicant known to affect peripheral nerves, on visual function. Acrylamide was administered to rats via drinking water at concentrations of 0 (control) and 200 ppm for 4 weeks, and electroretinograms (ERGs) and VEPs were recorded at weeks 0, 2, and 4. After the 4-week treatment period, the eyes and optic nerves were examined by light microscope. Acrylamide exposure significantly delayed VEP latency, while no effects were observed on the retina and optic nerve by ERG or histopathology. A significant decrease in grip strength in the hindlimbs and degeneration of sciatic nerve fibers were observed in the acrylamide-treated group, indicating that acrylamide damaged peripheral nerves. In conclusion, our study demonstrated that VEP can detect the effects of acrylamide on visual function earlier than histopathological examination, suggesting that VEP could be useful for detecting early-phase effects of chemical compounds on visual function and for evaluating whether morphological changes observed in toxicity studies are toxicologically significant.
Methylmercury (MeHg) is a potent environmental toxicant that frequently coexists with other heavy metals, raising concerns about combined toxic effects. Increasing evidence indicates that co-exposure to multiple metals can lead to synergistic or greater-than-additive effects; however, the molecular mechanisms underlying such interactions remain poorly understood. Among the tested metals, only co-exposure with Cd markedly enhanced MeHg cytotoxicity. Here, our objective was to evaluate the impact of MeHg co-exposure on cytotoxicity of various heavy metals in HeLa cells. We used cell viability assays, western blot analysis, and reverse-transcription-quantitative polymerase chain reactions to determine toxicity. Co-treatment with MeHg significantly reduced cell viability compared with that of Cd alone. Mechanistically, MeHg suppressed nuclear factor erythroid 2-related factor 2 (NRF2) expression more strongly at earlier time points than Cd alone, thereby impairing antioxidant and detoxification responses. This suppression was accompanied by increased intracellular mercury (Hg) retention, leading to enhanced cytotoxicity. Our results provide a mechanistic basis for metal-metal interactions and highlight the importance of considering co-exposure scenarios in environmental risk assessment.
