Long-term cadmium exposure impairs cognitive function by activating lnc-Gm10532/m6A/FIS1 axis-mediated mitochondrial fission and dysfunction

The roles of MicroRNAs in cadmium toxicity and in the protection offered by plant food-derived dietary phenolic bioactive substances against cadmium-induced toxicity

Cadmium, a harmful food contaminant, poses severe health risks. There are ongoing efforts to reduce cadmium pollution and alleviate its toxicity, including plant-based dietary intervention. This review hypothesizes that microRNAs (miRNAs), as regulatory eukaryotic transcripts, play crucial roles in modulating cadmium-induced organ damage, and plant food-derived bioactive compounds provide protective effects via miRNA-mediated mechanisms. The review reveals that there are interplays between certain miRNAs and plant food-derived dietary bioactive substances when these bioactives, especially phenolics, counteract cadmium toxicity through regulating physiologic and pathologic events (including oxidative stress, apoptosis, autophagy and inflammation). The review discusses common miRNA-associated physiologic/pathologic events and signal pathways shared by the cadmium toxicity and dietary intervention processes. This paper identifies the existing knowledge gaps and potential future work (e.g. joint actions between miRNAs and other noncoding RNAs in the fights against cadmium). The insights provided by this review can improve food safety strategies and public health outcomes.

Cadmium causes cerebral mitochondrial dysfunction through regulating mitochondrial HSF1

Mitochondria, as the powerhouse of the cell, play a vital role in maintaining cellular energy homeostasis and are known to be a primary target of cadmium (Cd) toxicity. The improper targeting of proteins to mitochondria can compromise the normal functions of the mitochondria. However, the precise mechanism by which protein localization contributes to the development of mitochondrial dysfunction induced by Cd is still not fully understood. For this research, Hy-Line white variety chicks (1-day-old) were used and equally distributed into 4 groups: the Control group (fed with a basic diet), the Cd35 group (basic diet with 35 mg/kg CdCl2), the Cd70 group (basic diet with 70 mg/kg CdCl2) and the Cd140 group (basic diet with 140 mg/kg CdCl2), respectively for 90 days. It was found that Cd caused the accumulation of heat shock factor 1 (HSF1) in the mitochondria, and the overexpression of HSF1 in the mitochondria led to mitochondrial dysfunction and neuronal damage. This process is due to the mitochondrial HSF1 (mtHSF1), causing mitochondrial fission through the upregulation of dynamin-related protein 1 (Drp1) content, while inhibiting oligomer formation of single-stranded DNA-binding protein 1 (SSBP1), resulting in the mitochondrial DNA (mtDNA) deletion. The findings unveil an unforeseen role of HSF1 in triggering mitochondrial dysfunction.

Fluoride exposure-induced gut microbiota alteration mediates colonic ferroptosis through N6-methyladenosine (m6A) mediated silencing of SLC7A11

Fluoride exposure is widespread worldwide and poses a significant threat to organisms, particularly to their gastrointestinal tracts. However, due to limited knowledge of the mechanism of fluoride induced intestinal injury, it has been challenging to develop an effective treatment. To address this issue, we used a series of molecular biology in vitro and in vivo experiments. NaF triggered m6A mediated ferroptosis to cause intestinal damage. Mechanistically, NaF exposure increased the m6A level of SLC7A11 mRNA, promoted YTHDF2 binding to m6A-modified SLC7A11 mRNA, drove the degradation of SLC7A11 mRNA, and led to a decrease in its protein expression, which eventually triggers ferroptosis. Moreover, NaF aggravated ferroptosis of the colon after antibiotics destroyed the composition of gut microbiota. 16 S rRNA sequencing and SPEC-OCCU plots, Zi-Pi relationships, and Spearman correlation coefficients verified that Lactobacillus murinus (ASV54, ASV58, and ASV82) plays a key role in the response to NaF-induced ferroptosis. Collectively, NaF-induced gut microbiota alteration mediates severe intestinal cell injury by inducing m6A modification-mediated ferroptosis. Our results highlight a key mechanism of the gut in response to NaF exposure and suggest a valuable theoretical basis for its prevention and treatment.

Targeting m6A mRNA demethylase FTO alleviates manganese-induced cognitive memory deficits in mice

Manganese (Mn) induced learning and memory deficits through mechanisms that are not fully understood. In this study, we discovered that the demethylase FTO was significantly downregulated in hippocampal neurons in an experimental a mouse model of Mn exposure. This decreased expression of FTO was associated with Mn-induced learning and memory impairments, as well as the dysfunction in synaptic plasticity and damage to regional neurons. The overexpression of FTO, or its positive modulation with agonists, provides protection against neurological damage and cognitive impairments. Mechanistically, FTO interacts synergistically with the reader YTHDF3 to facilitate the degradation of GRIN1 and GRIN3B through the m6A modification pathway. Additionally, Mn decreases the phosphorylation of SOX2, which specifically impairs the transcriptional regulation of FTO activity. Additionally, we found that the natural compounds artemisinin and apigenin that can bind molecularly with SOX2 and reduce Mn-induced cognitive dysfunction in mice. Our findings suggest that the SOX2-FTO-Grins axis represents a viable target for addressing Mn-induced neurotoxicity and cognitive impairments.

Adolescent co-exposure to environmental cadmium and high-fat diet induces cognitive decline via Larp7 m6A-mediated SIRT6 inhibition

The effects and underlying mechanisms of adolescent exposure to combined environmental hazards on cognitive function remain unclear. Here, using a combined exposure model, we found significant cognitive decline, hippocampal neuronal damage, and neuronal senescence in mice exposed to cadmium (Cd) and high-fat diet (HFD) during adolescence. Furthermore, we observed a significant downregulation of Sirtuin 6 (SIRT6) expression in the hippocampi of co-exposed mice. UBCS039, a specific SIRT6 activator, markedly reversed the above adverse effects. Further investigation revealed that co-exposure obviously reduced the levels of La ribonucleoprotein 7 (LARP7), disrupted the interaction between LARP7 and SIRT6, ultimately decreasing SIRT6 expression in mouse hippocampal neuronal cells. Overexpression of Larp7 reversed the combined exposure-induced SIRT6 decrease and senescence in mouse hippocampal neuronal cells. Additionally, the results showed notably elevated levels of Larp7 m6A and YTH domain family protein 2 (YTHDF2) in mouse hippocampal neuronal cells treated with the combined hazards. Ythdf2 short interfering RNA, RNA immunoprecipitation, and RNA stability assays further demonstrated that YTHDF2 mediated the degradation of Larp7 mRNA under combined exposure. Collectively, adolescent co-exposure to Cd and HFD causes hippocampal senescence and cognitive decline in mice by inhibiting LARP7-mediated SIRT6 expression in an m6A-dependent manner.

SIRT5-Mediated Desuccinylation of RAB7A Protects Against Cadmium-Induced Alzheimer's Disease-Like Pathology by Restoring Autophagic Flux

Cadmium (Cd) is a neurotoxic contaminant that induces cognitive decline similar to that observed in Alzheimer's disease (AD). Autophagic flux dysfunction is attributed to the pathogenesis of AD, and this study aimed to investigate the effect of autophagy on environmental Cd-induced AD progression and the underlying mechanism. Here, Cd exposure inhibited autophagosome-lysosome fusion and impaired lysosomal function, leading to defects in autophagic clearance and then to APP accumulation and nerve cell death. Proteomic analysis coupled with Ingenuity Pathway Analysis (IPA) identified SIRT5 as an essential molecular target in Cd-impaired autophagic flux. Mechanistically, Cd exposure hampered the expression of SIRT5, thus increasing the succinylation of RAB7A at lysine 31 and inhibiting RAB7A activity, which contributed to autophagic flux blockade. Importantly, SIRT5 overexpression led to the restoration of autophagic flux blockade, the alleviation of Aβ deposition and memory deficits, and the desuccinylation of RAB7A in Cd-exposed FAD4T mice. Additionally, SIRT5 levels decrease mainly in neurons but not in other cell clusters in the brains of AD patients according to single-nucleus RNA sequencing data from the public dataset GSE188545. This study reveals that SIRT5-catalysed RAB7A desuccinylation is an essential adaptive mechanism for the amelioration of Cd-induced autophagic flux blockade and AD-like pathogenesis.

The involvement of SigmaR1K142 degradation mediated by ERAD in neural senescence linked with CdCl2 exposure

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Due to its uncertain pathogenesis, there is currently no treatment available for AD. Increasing evidences have linked cellular senescence to AD, although the mechanism triggering cellular senescence in AD requires further exploration. To investigate the involvement of cellular senescence in AD, we explored the effects of cadmium chloride (CdCl2) exposure, one of the potential environmental risk factors for AD, on neuron senescence in vivo and in vitro. β-amyloid (Aβ) and tubulin-associated protein (tau) pathologies were found to be enhanced by CdCl2 exposure in the in vitro models, while p53/p21/Rb cascade-related neuronal senescence pathways were activated. Conversely, the use of melatonin, a cellular senescence inhibitor, or a cadmium ion chelator suppressed CdCl2-induced neuron senescence, along with the Aβ and tau pathologies. Mechanistically, CdCl2 exposure activated the suppressor enhancer Lin-12/Notch 1-like (SEL1L)/HMG-CoA reductase degradation 1 (HRD1)-regulated endoplasmic reticulum-associated degradation (ERAD), which enhanced the ubiquitin degradation of sigma-1 receptor (SigmaR1) by specifically recognizing its K142 site, resulting in the activation of the p53/p21/Rb pathway via the induction of Ca2+ dyshomeostasis and mitochondrial dysfunction. In the in vivo models, the administration of the SigmaR1 agonist ANAVEX2-73 rescues neurobehavioral inhibition and alleviates cellular senescence and AD-like pathology in the brain tissue of CdCl2-exposed mice. Consequently, the present study revealed a novel senescence-associated regulatory route for the SEL1L/HRD1/SigmaR1 axis that affects the pathological progression of CdCl2 exposure-associated AD. CdCl2 exposure activated SEL1L/HRD1-mediated ERAD and promoted the ubiquitinated degradation of SigmaR1, activating p53/p21/Rb pathway-regulated neuronal senescence. The results of the present study suggest that SigmaR1 may function as a neuroprotective biomarker of neuronal senescence, and pharmacological activation of SigmaR1 could be a promising intervention strategy for AD therapy.

Tris (2-chloroisopropyl) phosphate and Tris (nonylphenyl) phosphite Promote Human Renal Cell Apoptosis through the ERK/CEPBA/Long Non-Coding RNA Cytoskeleton Regulator Axis

Organophosphorus compounds (OPs) are widely used and have the potential to be harmful environmental toxicants to humans. Long non-coding RNA (lncRNA) plays a crucial regulatory role in cytotoxicity. This study aimed to investigate the effects of OPs on the expression of lncRNAs in cells. The effects of the industrial OPs TNPP and TCPP on both CYTOR and cellular viability were examined in the following human renal cell lines: HEK293T and HK-2. Both TCPP and TNPP downregulated CYTOR expression, increased reactive oxygen species levels, and induced apoptosis; the upregulated expression of CYTOR resulted in a reduction in apoptosis. The results of the luciferase reporter assay and the knock-down assay indicate that CEBPA binds to the upstream promoter region of CYTOR and regulates its transcription. Furthermore, TCPP and TNPP were found to downregulate the phosphorylation of ERK in the signaling pathway that is upstream of CEBPA. These results indicate that TCPP and TNPP can decrease the level of CEBPA by reducing ERK phosphorylation; this leads to a decrease in CYTOR expression, which further promotes cellular reactive oxygen species and apoptosis. Therefore, the ERK/CEBPA/CYTOR axis is one of the pathways by which organophosphates produce cytotoxicity, leading to renal cell injury. This study presents evidence for both the abnormal expression of lncRNA that is caused by organophosphates and the regulatory function of lncRNA regarding downstream cellular viability.

METTL14 promotes neuroblastoma formation by inhibiting YWHAH via an m6A-YTHDF1-dependent mechanism

Neuroblastoma (NB) is a common childhood tumor with a high incidence worldwide. The regulatory role of RNA N6-methyladenosine (m6A) in gene expression has attracted significant attention, and the impact of methyltransferase-like 14 (METTL14) on tumor progression has been extensively studied in various types of cancer. However, the specific influence of METTL14 on NB remains unexplored. Using data from the Target database, our study revealed significant upregulation of METTL14 expression in high-risk NB patients, with strong correlation with poor prognosis. Furthermore, we identified ETS1 and YY1 as upstream regulators that control the expression of METTL14. In vitro experiments involving the knockdown of METTL14 in NB cells demonstrated significant inhibition of cell proliferation, migration, and invasion. In addition, suppressing METTL14 inhibited NB tumorigenesis in nude mouse models. Through MeRIP-seq and RNA-seq analyses, we further discovered that YWHAH is a downstream target gene of METTL14. Mechanistically, we observed that methylated YWHAH transcripts, particularly those in the 5' UTR, were specifically recognized by the m6A "reader" protein YTHDF1, leading to the degradation of YWHAH mRNA. Moreover, the downregulation of YWHAH expression activated the PI3K/AKT signaling pathway, promoting NB cell activity. Overall, our study provides valuable insights into the oncogenic effects of METTL14 in NB cells, highlighting its role in inhibiting YWHAH expression through an m6A-YTHDF1-dependent mechanism. These findings also suggest the potential utility of a biomarker panel for prognostic prediction in NB patients.

Association between the circulating very long-chain saturated fatty acid and cognitive function in older adults: findings from the NHANES

BACKGROUND

Age-related cognitive decline has a significant impact on the health and longevity of older adults. Circulating very long-chain saturated fatty acids (VLSFAs) may actively contribute to the improvement of cognitive function. The objective of this study was to investigate the associations between arachidic acid (20:0), docosanoic acid (22:0), tricosanoic acid (23:0), and lignoceric acid (24:0) with cognitive function in older adults.

METHODS

This study used a dataset derived from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). A total of 806 adults (≥ 60 years) were included who underwent comprehensive cognitive testing and plasma fatty acid measurements. Multivariable linear regression, restricted cubic spline (RCS), and interaction analyses were used to assess associations between VLSFAs and cognitive function. Partial Spearman' s correlation analysis was used to examine the correlations between VLSFAs and palmitic acid (16:0), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, triglycerides, systemic inflammatory markers, and dietary nutrients.

RESULTS

Multivariable linear regression analysis, adjusting for sociodemographic, clinical conditions, and lifestyle factors, showed that 22:0 and 24:0 levels were positively associated with better global cognitive function (β = 0.37, 95% confidence interval [CI] = 0.01, 0.73; β = 0.73, 95% CI = 0.29, 1.2, respectively) as well as better CEARD-DR Z-score (β = 0.82, 95% CI = 0.36, 1.3 and β = 1.2, 95% CI = 0.63, 1.8, respectively). RCS analysis showed linear associations between higher 22:0 and 24:0 levels and better cognitive performance in both global cognitive function and CERAD-DR tests.

CONCLUSIONS

The study suggests that higher levels of 22:0 and 24:0 are associated with better global cognitive function in older adults. 22:0 and 24:0 may be important biomarkers for recognizing cognitive impairment, and supplementation with specific VLSFAs (22:0 and 24:0) may be an important intervention to improve cognitive function. Further studies are needed to elucidate the underlying biological mechanisms between VLSFAs and cognitive function.

RNA modifications in cellular metabolism: implications for metabolism-targeted therapy and immunotherapy

Cellular metabolism is an intricate network satisfying bioenergetic and biosynthesis requirements of cells. Relevant studies have been constantly making inroads in our understanding of pathophysiology, and inspiring development of therapeutics. As a crucial component of epigenetics at post-transcription level, RNA modification significantly determines RNA fates, further affecting various biological processes and cellular phenotypes. To be noted, immunometabolism defines the metabolic alterations occur on immune cells in different stages and immunological contexts. In this review, we characterize the distribution features, modifying mechanisms and biological functions of 8 RNA modifications, including N6-methyladenosine (m6A), N6,2'-O-dimethyladenosine (m6Am), N1-methyladenosine (m1A), 5-methylcytosine (m5C), N4-acetylcytosine (ac4C), N7-methylguanosine (m7G), Pseudouridine (Ψ), adenosine-to-inosine (A-to-I) editing, which are relatively the most studied types. Then regulatory roles of these RNA modification on metabolism in diverse health and disease contexts are comprehensively described, categorized as glucose, lipid, amino acid, and mitochondrial metabolism. And we highlight the regulation of RNA modifications on immunometabolism, further influencing immune responses. Above all, we provide a thorough discussion about clinical implications of RNA modification in metabolism-targeted therapy and immunotherapy, progression of RNA modification-targeted agents, and its potential in RNA-targeted therapeutics. Eventually, we give legitimate perspectives for future researches in this field from methodological requirements, mechanistic insights, to therapeutic applications.

Long-term cadmium exposure induces epithelial-mesenchymal transition in breast cancer cells by activating CYP1B1-mediated glutamine metabolic reprogramming in BT474 cells and MMTV-Erbb2 mice

Cadmium (Cd) exposure is known to enhance breast cancer (BC) progression. Cd promotes epithelial-mesenchymal transition (EMT) in BC cells, facilitating BC cell aggressiveness and invasion, but the underlying molecular mechanisms are unclear. Hence, transgenic MMTV-Erbb2 mice (6 weeks) were orally administered Cd (3.6 mg/L, approximately equal to 19.64 μΜ) for 23 weeks, and BC cells (BT474 cells) were exposed to Cd (0, 0.1, 1 or 10 μΜ) for 72 h to investigate the effect of Cd exposure on EMT in BC cells. Chronic Cd exposure dramatically expedited tumor metastasis to multiple organs; decreased E-cadherin density; and increased Vimentin, N-cadherin, ZEB1, and Twist density in the tumor tissues of MMTV-Erbb2 mice. Notably, transcriptomic analysis of BC tumors revealed cytochrome P450 1B1 (CYP1B1) as a key factor that regulates EMT progression in Cd-treated MMTV-Erbb2 mice. Moreover, Cd increased CYP1B1 expression in MMTV-Erbb2 mouse BC tumors and in BT474 cells, and CYP1B1 inhibition decreased Cd-induced BC cell malignancy and EMT in BT474 cells. Importantly, the promotion of EMT by CYP1B1 in Cd-treated BC cells was presumably controlled by glutamine metabolism. This study offers novel perspectives into the effect of environmental Cd exposure on driving BC progression and metastasis, and this study provides important guidance for comprehensively assessing the ecological and health risks of Cd.

Neurotoxic effects of heavy metal pollutants in the environment: Focusing on epigenetic mechanisms

The pollution of heavy metals (HMs) in the environment is a significant global environmental issue, characterized by its extensive distribution, severe contamination, and profound ecological impacts. Excessive exposure to heavy metal pollutants can damage the nervous system. However, the mechanisms underlying the neurotoxicity of most heavy metals are not completely understood. Epigenetics is defined as a heritable change in gene function that can influence gene and subsequent protein expression levels without altering the DNA sequence. Growing evidence indicates that heavy metals can induce neurotoxic effects by triggering epigenetic changes and disrupting the epigenome. Compared with genetic changes, epigenetic alterations are more easily reversible. Epigenetic reprogramming techniques, drugs, and certain nutrients targeting specific epigenetic mechanisms involved in gene expression regulation are emerging as potential preventive or therapeutic tools for diseases. Therefore, this review provides a comprehensive overview of epigenetic modifications encompassing DNA/RNA methylation, histone modifications, and non-coding RNAs in the nervous system, elucidating their association with various heavy metal exposures. These primarily include manganese (Mn), mercury (Hg), lead (Pb), cobalt (Co), cadmium (Cd), nickel (Ni), sliver (Ag), toxic metalloids arsenic (As), and etc. The potential epigenetic mechanisms in the etiology, precision prevention, and target therapy of various neurodevelopmental disorders or different neurodegenerative diseases are emphasized. In addition, the current gaps in research and future areas of study are discussed. From a perspective on epigenetics, this review offers novel insights for prevention and treatment of neurotoxicity induced by heavy metal pollutants.

Effects of postweaning cadmium exposure on socioemotional behaviors in adolescent male mice

Exposure to cadmium (Cd), a toxic heavy metal classified as an environmental endocrine disruptor, can exert significant toxicity in both animals and humans. However, the potential effects of Cd exposure on socioemotional behaviors are still poorly understood, as are the underlying mechanisms. In the present study, employing a series of behavioral tests as well as 16 S rRNA sequencing analysis, we investigated the long-term effects of Cd exposure on socioemotional behaviors and their associated mechanisms in mice based on the brain-gut interaction theory. The results showed that postweaning exposure to Cd reduced the ability to resist depression, decreased social interaction, subtly altered sexual preference, and changed the composition of the gut microbiota in male mice during adolescence. These findings provided direct evidence for the deleterious effects of exposure to Cd in the postweaning period on socioemotional behaviors later in adolescence, and suggested that these effects of Cd exposure may be linked to changes in the gut microbiota.

Novel insights into DEHP-induced zebrafish spleen damage: Cellular apoptosis, mitochondrial dysfunction, and innate immunity

DEHP (Di(2-ethylhexyl) phthalate) is the most abundant phthalate component detected in environmental samples as it is widely used in the manufacturing of children's toys, medical devices and furniture. Due to its wide prevalence and propensity to accumulate in the food chain, significant concerns have risen about the safety profile of DEHP. Here, we used a zebrafish model to investigate the toxicity mechanisms of DEHP. Our results indicated that exposure to DEHP altered the ROS content in zebrafish spleen and inhibited the activities of antioxidant enzymes SOD and CAT, detoxification enzyme GSH-Px and induced histopathological damage. In addition, elucidated the mechanism of DEHP significantly promoted apoptosis and caused damage in spleen cells through the bax/bcl-2 pathway. Further genetic testing demonstrated significant alterations in mitochondrial biogenesis, fission, and fusion-related genes and suggested potential mechanistic pathways, including GM10532/m6A/FIS1 axis, the STAT3/POA1 axis, and the NFR1/TFAM axis. Serological and genomic analysis indicated that DEHP exposure activated the C3 complement cascade immune pathway and interfered with innate immune function. IBRv2 analysis proposes that innate immunity may serve as a signal indicator of early toxic responses to DEHP pollutants. This study provided comprehensive cellular and genetic data for DEHP toxicity studies and emphasized the need for future management and remediation of DEHP contamination. It also provides data to specifically support the health risk assessments of DEHP, as well as contributing to broader health and environmental research.

Organoids and organoids-on-a-chip as the new testing strategies for environmental toxicology-applications & advantages

An increasing number of harmful environmental factors are causing serious impacts on human health, and there is an urgent need to accurately identify the toxic effects and mechanisms of these harmful environmental factors. However, traditional toxicity test methods (e.g., animal models and cell lines) often fail to provide accurate results. Fortunately, organoids differentiated from stem cells can more accurately, sensitively and specifically reflect the effects of harmful environmental factors on the human body. They are also suitable for specific studies and are frequently used in environmental toxicology nowadays. As a combination of organoids and organ-on-a-chip technology, organoids-on-a-chip has great potential in environmental toxicology. It is more controllable to the physicochemical microenvironment and is not easy to be contaminated. It has higher homogeneity in the size and shape of organoids. In addition, it can achieve vascularization and exchange the nutrients and metabolic wastes in time. Multi-organoids-chip can also simulate the interactions of different organs. These advantages can facilitate better function and maturity of organoids, which can also make up for the shortcomings of common organoids to a certain extent. This review firstly discussed the limitations of traditional toxicology testing platforms, leading to the introduction of new platforms: organoids and organoids-on-a-chip. Next, the applications of different organoids and organoids-on-a-chip in environmental toxicology were summarized and prospected. Since the advantages of the new platforms have not been sufficiently considered in previous literature, we particularly emphasized them. Finally, this review also summarized the opportunities and challenges faced by organoids and organoids-on-a-chip, with the expectation that readers will gain a deeper understanding of their value in the field of environmental toxicology.

Morphological and metabolic changes in microglia exposed to cadmium: Cues on neurotoxic mechanisms

Microglial cells play a key role in protecting the central nervous system from pathogens and toxic compounds and are involved in the pathogenesis of different neurodegenerative diseases. Cadmium is a widespread toxic heavy metal, released into the environment at a rate of 30,000 tons/year by anthropogenic activities; it is easily uptaken by the human body through diet and cigarette smoke, as well as by occupational exposure. Once inside the body, cadmium enters the cells and substitutes to zinc and other divalent cations altering many biological functions. Its extremely long half-life makes it a serious health threat. Recent data suggest a role for heavy metals in many neurodegenerative diseases; however, the role of cadmium is still to be elucidated. In this work we report the investigation of cadmium toxicity towards murine BV2 microglial cells, a widely used model for the study of neurodegeneration. Results show that increasing cadmium concentrations increase oxidative stress, a proposed mechanism of neurodegeneration, but also that BV2 cells can keep oxidative stress under control by increasing glutathione reduction. Moreover, cadmium induces alterations of cell morphology and metabolism leading to mitochondrial impairment, without switching the cells to Warburg effect. Finally cadmium induces the release of proinflammatory cytokines, but does not markedly switch BV2 cells to M1 phenotype.

Chronic cadmium exposure triggered ferroptosis by perturbing the STEAP3-mediated glutathione redox balance linked to altered metabolomic signatures in humans

Cadmium (Cd), a predominant environmental pollutant, is a canonical toxicant that acts on the kidneys. However, the nephrotoxic effect and underlying mechanism activated by chronic exposure to Cd remain unclear. In the present study, male mice (C57BL/6J, 8 weeks) were treated with 0.6 mg/L cadmium chloride (CdCl2) administered orally for 6 months, and tubular epithelial cells (TCMK-1 cells) were treated with low-dose (1, 2, and 3 μM) CdCl2 for 72 h (h). Our study results revealed that environmental Cd exposure triggered ferroptosis and renal dysfunction. Spatially resolved metabolomics enabled delineation of metabolic profiles and visualization of the disruption to glutathione homeostasis related to ferroptosis in mouse kidneys. Multiomics analysis revealed that chronic Cd exposure induced glutathione redox imbalance that depended on STEAP3-driven lysosomal iron overload. In particular, glutathione metabolic reprogramming linked to ferroptosis emerged as a metabolic hallmark in the blood of Cd-exposed workers. In conclusion, this study provides the first evidence indicating that chronic Cd exposure triggers ferroptosis and renal dysfunction that depend on STEAP3-mediated glutathione redox imbalance, greatly increasing our understanding of the metabolic reprogramming induced by Cd exposure in the kidneys and providing novel clues linking chronic Cd exposure to nephrotoxicity.

Chronic cadmium exposure induces Parkinson-like syndrome by eliciting sphingolipid disturbance and neuroinflammation in the midbrain of C57BL/6J mice

Cadmium (Cd) is known as a widespread environmental neurotoxic pollutant. Cd exposure is recently recognized as an etiological factor of Parkinson's disease (PD) in humans. However, the mechanism underlying Cd neurotoxicity in relation to Parkinsonism pathogenesis is unclear. In our present study, C57BL/6 J mice were exposed to 100 mg/L CdCl2 in drinking water for 8 weeks. It was found Cd exposure caused motor deficits, decreased DA neurons and induced neuropathological changes in the midbrain. Non-targeted lipidomic analysis uncovered that Cd exposure altered lipid profile, increased the content of proinflammatory sphingolipid ceramides (Cer), sphingomyelin (SM) and ganglioside (GM3) in the midbrain. In consistency with increased proinflammatory lipids, the mRNA levels of genes encoding sphingolipids biosynthesis in the midbrain were dysregulated by Cd exposure. Neuroinflammation in the midbrain was evinced by the up-regulation of proinflammatory cytokines at mRNA and protein levels. Blood Cd contents and lipid metabolites in Parkinsonism patients by ICP-MS and LC-MS/MS analyses demonstrated that elevated blood Cd concentration and proinflammatory lipid metabolites were positively associated with the score of Unified Parkinson's Disease Rating Scale (UPDRS). 3 ceramide metabolites in the blood showed good specificity as the candidate biomarkers to predict and monitor Parkinsonism and Cd neurotoxicity (AUC>0.7, p < 0.01). In summary, our present study uncovered that perturbed sphingomyelin lipid metabolism is related to the Parkinsonism pathogenesis and Cd neurotoxicity, partially compensated for the deficiency in particular metabolic biomarkers for Parkinsonism in relation to Cd exposure, and emphasized the necessity of reducing Cd exposure at population level.

Environmental cadmium exposure facilitates mammary tumorigenesis via reprogramming gut microbiota-mediated glutamine metabolism in MMTV-Erbb2 mice

Cadmium (Cd) is a heavy metal that has been widely reported to be linked to the onset and progression of breast cancer (BC). However, the mechanism of Cd-induced mammary tumorigenesis remains elusive. In our study, a transgenic mouse model that spontaneously develops tumors through overexpression of wild-type Erbb2 (MMTV-Erbb2) was constructed to investigate the effects of Cd exposure on BC tumorigenesis. The results showed that oral exposure to 3.6 mg/L Cd for 23 weeks dramatically accelerated tumor appearance and growth, increased Ki67 density and enhanced focal necrosis and neovascularization in the tumor tissue of MMTV-Erbb2 mice. Notably, Cd exposure enhanced glutamine (Gln) metabolism in tumor tissue, and 6-diazo-5-oxo-l-norleucine (DON), a Gln metabolism antagonist, inhibited Cd-induced breast carcinogenesis. Then our metagenomic sequencing and mass spectrometry-based metabolomics confirmed that Cd exposure disturbed gut microbiota homeostasis, especially Helicobacter and Campylobacter abundance remodeling, which altered the gut metabolic homeostasis of Gln. Moreover, intratumoral Gln metabolism profoundly increased under Cd-elevated gut permeability. Importantly, depletion of microbiota with an antibiotic cocktail (AbX) treatment led to a significant delay in the appearance of palpable tumors, inhibition of tumor growth, decrease in tumor weight, reduction in Ki67 expression and low-grade pathology in Cd-exposed MMTV-Erbb2 mice. Also, transplantation of Cd-modulated microbiota decreased tumor latency, accelerated tumor growth, increased tumor weight, upregulated Ki67 expression and exacerbated neovascularization as well as focal necrosis in MMTV-Erbb2 mice. In summary, Cd exposure induced gut microbiota dysbiosis, elevated gut permeability and increased intratumoral Gln metabolism, leading to the promotion of mammary tumorigenesis. This study provides novel insights into environmental Cd exposure-mediated carcinogenesis.

Emerging Roles for DNA 6mA and RNA m6A Methylation in Mammalian Genome

Epigenetic methylation has been shown to play an important role in transcriptional regulation and disease pathogenesis. Recent advancements in detection techniques have identified DNA N6-methyldeoxyadenosine (6mA) and RNA N6-methyladenosine (m6A) as methylation modifications at the sixth position of adenine in DNA and RNA, respectively. While the distributions and functions of 6mA and m6A have been extensively studied in prokaryotes, their roles in the mammalian brain, where they are enriched, are still not fully understood. In this review, we provide a comprehensive summary of the current research progress on 6mA and m6A, as well as their associated writers, erasers, and readers at both DNA and RNA levels. Specifically, we focus on the potential roles of 6mA and m6A in the fundamental biological pathways of the mammalian genome and highlight the significant regulatory functions of 6mA in neurodegenerative diseases.