Current Research in Toxicology最新文献

The global surge in Alzheimer's disease poses a significant public health concern. In response, we study the efficacy of carnosic acid and related abietane-type diterpenes extracted from rosemary as acetylcholinesterase (AChE) inhibitors. Our analyses, using in silico techniques, encompassed all the compounds within this extract. Through molecular docking, we explored how these compounds interact with the active site of the AChE protein. The docking scores, ranging from −5.560 Kcal/mol to −7.270 Kcal/mol, indicate robust binding affinities. Assessment of the ADME/T (Adsorption, Distribution, Metabolism, Excretion, and Toxicity) properties and pharmacokinetics of these compounds reveal favorable profiles for all the tested substances. These encouraging results suggest the potential of these compounds as candidates for further development to prevent and/or treat Alzheimer's disease. Among these compounds, we find rosmanol as the most likely candidate for further research and clinical trials to validate their efficacy.

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Full treatment of the second most common neurodegenerative disorder, Parkinson’s disease (PD), is still considered an unmet need. As the psychostimulants, amphetamine (AMPH) and methylphenidate (MPH), were shown to be neuroprotective against stroke and other neuronal injury diseases, this study aimed to evaluate their neuroprotective potential against two dopaminergic neurotoxicants, 6-hydroxydopamine (6-OHDA) and paraquat (PQ), in differentiated human dopaminergic SH-SY5Y cells.

Neither cytotoxicity nor mitochondrial membrane potential changes were seen following a 24-hour exposure to either therapeutic concentration of AMPH or MPH (0.001–10 μM). On the other hand, a 24-hour exposure to 6-OHDA (31.25–500 μM) or PQ (100–5000 μM) induced concentration-dependent mitochondrial dysfunction, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and lysosomal damage, evaluated by the neutral red uptake assay. The lethal concentrations 25 and 50 retrieved from the concentration-toxicity curves in the MTT assay were 99.9 µM and 133.6 µM for 6-OHDA, or 422 µM and 585.8 µM for PQ. Both toxicants caused mitochondrial membrane potential depolarization, but only 6-OHDA increased reactive oxygen species (ROS). Most importantly, PQ-induced toxicity was partially prevented by 1 μM of AMPH or MPH. Nonetheless, neither AMPH nor MPH could prevent 6-OHDA toxicity in this experimental model.

According to these findings, AMPH and MPH may provide some neuroprotection against PQ-induced neurotoxicity, but further investigation is required to determine the exact mechanism underlying this protection.

For decades, regulatory guidelines for safety assessment in rodents for drugs, chemicals, pesticides, and food additives with developmental neurotoxic potential have recommended a single test of learning and memory (L&M). In recent years some agencies have requested two such tests. Given the importance of higher cognitive function to health, and the fact that different types of L&M are mediated by different brain regions assessing higher functions represents a step forward in providing better evidence-based protection against adverse brain effects. Given the myriad of tests available for assessing L&M in rodents this leads to the question of which tests best fit regulatory guidelines. To address this question, we begin by describing the central role of two types of L&M essential to all mammalian species and the regions/networks that mediate them. We suggest that the tests recommended possess characteristics that make them well suited to the needs in regulatory safety studies. By brain region, these are (1) the hippocampus and entorhinal cortex for spatial navigation, which assesses explicit L&M for reference and episodic memory and (2) the striatum and related structures for egocentric navigation, which assesses implicit or procedural memory and path integration. Of the tests available, we suggest that in this context, the evidence supports the use of water mazes, specifically, the Morris water maze (MWM) for spatial L&M and the Cincinnati water maze (CWM) for egocentric/procedural L&M. We review the evidentiary basis for these tests, describe their use, and explain procedures that optimize their sensitivity.

Colorectal cancer (CRC) is the third leading cause of cancer-related mortalities in the USA and around 52,550 people were expected to die from this disease by December 2023. The objective of this study was to investigate the effect of diet type on benzo(a)pyrene [B(a)P]-induced colon cancer in an adult male rat model, the Polyposis In the Rat Colon (PIRC) kindred type. Groups of PIRC rats (n = 10) were fed with AIN-76A regular diet (RD) or Western diet (WD) and received 25, 50 and 100 µg B(a)P/kg body wt. via oral gavage for 60 days. Rats fed diets alone, but no B(a)P, served as controls. After exposure, rats were euthanized; colon and liver samples were analyzed for activation of drug metabolizing enzymes (DMEs) CYP1A1, CYP1B1, SULT and GST. Plasma and tissue samples were analyzed by reverse phase-HPLC for B(a)P metabolites. In addition to these studies, DNA isolated from colon and liver tissues was analyzed for B(a)P-induced DNA adducts by the ³²P-postlabeling method using a thin-layer chromatography system. Western diet consumption resulted in a marked increase in DME expression and B(a)P metabolite concentrations in rats that were administered 100 µg/kg B(a)P + WD (p < 0.05) compared to other treatment groups. Our findings demonstrate that WD accelerates the development of colon tumors induced by B(a)P through enhanced biotransformation, and the products of this process (metabolites) were found to bind with DNA and form B(a)P-DNA adducts, which may have given rise to colon polyps characterized by gain in tumor number, sizes, and dysplasia.

At present, hundreds of long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been confirmed to be related to the toxicity of cadmium (Cd). However, the role of circular RNAs (circRNAs) in the toxicity of Cd and the underlying regulatory mechanisms remain unclear. In this study, we chose human normal liver cells (L-02) as a model to investigate changes in transcriptome expression levels following exposure to Cd. Total RNA of each sample was extracted by Trizol method, and the expression profiles of circRNAs, miRNAs and mRNAs of each sample were determined by microarray hybridization and scanning. After standardizing the data, differential circRNAs, miRNAs, and mRNAs associated with the toxic effects of Cd were identified. By screening the predicted circRNAs, miRNAs, and mRNAs, we constructed a competing endogenous RNA (ceRNA) network, and predicted the main biological functions and metabolic pathways influenced by Cd toxicity. Our comprehensive screening strategy led to the identification of 266 different circRNAs, 223 different miRNAs and 519 different mRNAs exhibiting differential expression. Following further screening, even circRNAs, 10 miRNAs and 97 mRNAs were incorporated into the ceRNA network. After performing GO enrichment and KEGG pathway analyses on the 97 mRNAs within the ceRNA network, which indicated that the circRNAs in the ceRNA network are poised to modulate key cellular processes, including cell proliferation, apoptosis, oxidative stress and inflammatory responses under the toxic effects of Cd-induced damage in L-02 cells.

The Comparative Thyroid Assay (CTA, USEPA) is a screening test for thyroid hormone (TH) disruption in peripheral blood of dams and offspring. Recently, we began investigating feasible improvements to the CTA by adding examination of offspring brain TH concentrations and brain histopathology. In addition, we hypothesize that the number of animals required could be reduced by 50 % while still maintaining sensitivity to characterize treatment related changes in THs. Previously, we showed that the prenatal test cohort of the modified CTA could detect 1000 ppm sodium phenobarbital (NaPB)-induced suppression of brain T3 (by 9 %) and T4 (by 33 %) with no significant changes in serum T3 and T4 (less than 8 %). In the current study we expanded the dose response in a prenatal test cohort. Pregnant SD rats (N = 10/group) were exposed to 0, 1000 or 1500 ppm NaPB in the diet from gestational days (GD) 6 to GD20. Serum THs concentrations in GD20 dams together with serum/brain THs concentrations and brain histopathology in the GD20 fetuses were examined. NaPB dose-dependently suppressed serum T3 (up to −26 %) and T4 (up to −44 %) in dams, with suppression of T3 in serum (up to −26 %) and brain (up to −18 %) and T4 in serum (up to −26 %) and brain (up to −29 %) of fetuses but without clear dose dependency. There were no remarkable findings that deviated significantly from controls in GD20 fetal brain by qualitative histopathology. Overall, the present study suggests that the prenatal test cohort of this modified CTA is able to detect the expected fetal TH disruptions by prenatal exposure to NaPB, while also reducing the number of animals used by 50 %, consistent with the results of our previous study. These findings add to the suggestion that lowering group sizes and adding endpoints may be a useful alternative to the original CTA design.

Excessive long-term manganese intake can inflict irreversible damage to the nervous system, with a predominant effect on the substantia nigra-striatum pathway. Through a mouse model simulating manganese exposure, we delved into its implications on the central nervous motor system, uncovering autophagy-lysosome dysfunction as a pivotal factor in manganese-induced neurotoxicity. Our research illuminated the molecular mechanisms behind TFEB’s role in manganese-triggered neuronal autophagy dysfunction, offering insights into the cellular and molecular mechanisms of manganese-induced abnormal protein accumulation. This study lays a significant theoretical foundation for future endeavors aimed at safeguarding against manganese neurotoxicity. Furthermore, TFEB emerges as a potential early molecular biomarker for manganese exposure, providing a solid basis for preemptive protection and clinical treatment for populations exposed to manganese.

Our previous study showed promising results in replicating early-stage atherosclerosis when vascular endothelial cells (VECs) were exposed to cigarette smoke (CS) extract via M0 macrophages. We used an organ-on-a-chip system as an alternative to animal testing to model atherosclerosis, which is a complex disease involving endothelial and immune cell communications. By incorporating macrophages into the vascular-on-a-chip system, we aimed to mimic the indirect effects of inhalable substances, such as CS, on VECs. In the current study, we further examined the suitability of our in vitro system for mimicking early-stage atherosclerosis by transcriptomic analyses of VECs exposed to CS directly or indirectly via macrophages. We also incorporated M1 macrophages to replicate a preexisting inflammatory state. We found a greater number of differentially expressed genes (DEGs) in direct exposure methods than indirect exposure methods. However, a pathway analysis showed that the direct exposure of CS to VECs primarily caused cell death-related pathway alterations, and the “Atherosclerosis Signaling” pathway was predicted to be negatively regulated. Indirect exposure via M0 macrophages similarly showed that the identified DEGs were related to cell death, while the “Atherosclerosis Signaling” pathway was predicted to be activated. In contrast, cell death-related pathway alterations were not observed by indirect exposure of CS to VECs via M1 macrophages, but the pathway perturbations were similar to a pro-inflammatory positive control. In addition, the “Atherosclerosis Signaling” pathway was predicted to be activated in VECs that were indirectly exposed to CS via M1 macrophages. These results suggest that M0 or M1 macrophages contribute to atherogenic transcriptomic changes in VECs, although they affect cell death-related pathways differently. We also used indirect exposure methods to compare the effects of CS and heated tobacco product (HTP) aerosol. Notably, gene expression changes related to atherosclerosis were less pronounced in HTP aerosol-exposed VECs than CS. Our study highlights the utility of the vascular-on-a-chip system with indirect exposure of CS extract via macrophages for replicating atherogenesis and suggests a reduced risk potential of the HTP. This research contributes to advancing alternatives to animal testing for toxicological and disease modeling studies.

Ethylene dimethanesulfonate (EDS) is a molecule with known selective cytotoxicity on adult Leydig cells. A single intraperitoneal injection in rats but not mice, leads to male androgen deprivation and infertility. In vitro studies using rat and mouse immortalized Leydig cell lines, showed similar effects of cell death promoted by EDS in rat cells as seen in vivo, and suggest that EDS affects gene transcription, which could firstly compromise steroidogenesis before the apoptosis process. Using gene reporter assay, this study aimed to investigate EDS effects on the promoter activity of genes important for endocrine function (Star, Insl3) and response to toxic agents (Gsta3) in immortalized Leydig cell lines (rat R2C and mouse MA-10 cells), as well as identify possible EDS-responsive elements in the Star gene promoter. EDS exposure of R2C and MA-10 Leydig cells increased Gsta3 promoter activity after 4 h of treatment and decreased Insl3 promoter activity only in R2C cells after 24 h of treatment. EDS also decreased Star promoter activity in both Leydig cell lines. Using R2C cells, the EDS-responsive region in the Star promoter was located between −400 and −195 bp. This suggests that this region and the associated transcription factors, which include MEF2, might be targeted by EDS. Additional somatic gonadal cell lines expressing Star were used and EDS did not affect Star promoter activity in DC3 granulosa cells while Star promoter activity was increased in MSC-1 Sertoli cells after 24 h of treatment. This study contributes to the knowledge regarding the mechanism of EDS action in Leydig cells, and in other gonadal cell lineages, and brings new light regarding the rats and mice differential susceptibility to EDS effects, in addition to providing new avenues for experimental approaches to better understand Leydig cell function and dynamics in different rodent species.