Cadmium aggravates the blood-brain barrier disruption via inhibition of the Wnt7A/β-catenin signaling axis

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.

High cadmium exposure impairs adult hippocampal neurogenesis via disruption of store-operated calcium entry

Cadmium (Cd) is a neurotoxicant that gradually accumulates in the human body with age. High Cd burden is correlated with adult hippocampal neurogenesis (AHN) and memory deficits in mammals. However, little knowledge is known about the mechanism by which Cd exposure impairs neurogenesis and cognition. Here, we investigated the roles of store-operated calcium entry (SOCE)-mediated calcium dyshomeostasis in Cd-induced AHN and memory deficits as well as therapeutic potential for the prevention of Cd-induced neurotoxicity. To achieve this goal, 8 weeks-old C57BL/6 J mice were subjected to different concentrations of cadmium chloride (0, 5, 10, 20 ppm) in drinking water for 8 weeks, we then examined the AHN, calcium homeostasis, SOCE channel and memory in Cd-exposed mice by using immunohistochemistry, calcium imaging, Y-maze and fear conditioning test. Our results indicated that chronic Cd exposure markedly increased Cd levels in serum and cerebrospinal fluid by almost 10-fold, and inhibited the proliferation and differentiation of hippocampal adult neural stem cells in a dose-dependent manner. Additionally, Cd exposure impaired the maturation of hippocampal neural stem cells without inducing gliosis. Transcriptome analysis revealed that Cd exposure inhibited the proliferation of neuroblastoma via alteration of calcium signaling pathway, and attenuated SOCE channels played a pivotal role in mediating Cd-induced cytoplasmic calcium overload and depletion of endoplasmic reticulum calcium stores. Activation of SOCE by hyperforin, a natural derivative from medicinal plant, restored intracellular calcium homeostasis and improved AHN and memory in Cd-exposed mice. Together, this study provided novel insights into the mechanism that Cd exposure impaired AHN and memory by prompting neuronal SOCE-mediated calcium dyshomeostasis, and offered a new therapeutic approach for prevention of Cd-induced neurotoxicity.

Cadmium Induces Vascular Endothelial Cell Detachment by Downregulating Claudin-5 and ZO-1 Levels

Cadmium is a contributing factor to cardiovascular diseases and highly toxic to vascular endothelial cells. It has a distinct mode of injury, causing the de-endothelialization of regions in the monolayer structure of endothelial cells in a concentration-dependent manner. However, the specific molecules involved in the cadmium toxicity of endothelial cells remain unclear. The purpose of this study was to identify the specific molecular mechanisms through which cadmium affects endothelial detachment. Cadmium inhibited the expression of claudin-5 and zonula occludens (ZO)-1, which are components of tight junctions (strongest contributors to intercellular adhesion), in a concentration- and time-dependent manner. Compared to arsenite, zinc, and manganese, only cadmium suppressed the expression of both claudin-5 and ZO-1 molecules. Moreover, the knockdown of claudin-5 and ZO-1 exacerbated cadmium-induced endothelial cell injury and expansion of the detachment area, whereas their overexpression reversed these effects. CRE-binding protein inhibition reduced cadmium toxicity, suggesting that CRE-binding protein activation is involved in the cadmium-induced inhibition of claudin-5 and ZO-1 expression and endothelial detachment. These findings provide new insights into the toxicological mechanisms of cadmium-induced endothelial injury and risk of cardiovascular disease.

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.

Nano‑selenium alleviates cadmium-induced blood-brain barrier destruction by restoring the Wnt7A/β-catenin pathway

Selenium (Se), a highly beneficial animal feed additive, exhibits remarkable antioxidant and anti-inflammatory properties. Nano‑selenium (Nano-Se) is an advanced formulation of Se featuring a specialized drug delivery vehicle, with good bioavailability, higher efficacy, and lower toxicity compared to the traditional form of Se. With the advancement of industry, cadmium (Cd) contamination occurs in different countries and regions and thereby contaminating different food crops, and the degree of pollution is degree increasing year by year. The present investigation entailed the oral administration of CdCl2 and/or Nano-Se to male chickens of the Hy-Line Variety White breed, which are one day old, subsequent to a 7-day adaptive feeding period, for a duration of 90 days. The study aimed to elucidate the potential protective impact of Nano-Se on Cd exposure. The study found that Nano-Se demonstrates potential in mitigating the blood-brain barrier (BBB) dysfunction characterized by impairment of adherens junctions (AJS) and tight junctions (TJS) by inhibiting reactive oxygen species (ROS) overproduction. In addition, the data uncovered that Nano-Se demonstrates a proficient ability in alleviating BBB impairment and inflammatory reactions caused by Cd through the modulation of the Wnt7A/β-catenin pathway, highlights its potential to maintain brain homeostasis. Hence, this research anticipates that the utilization of Nano-Se effectively mitigate the detrimental impacts associated with Cd exposure on the BBB.

Adsorption dynamics of Cd2+(aq) on microwave-synthetized pristine biochar from cocoa pod husk: Green, experimental, and DFT approaches

Biochar obtained via microwave-assisted pyrolysis (MAP) at 720 W and 15 min from cocoa pod husk (CPH) is an efficient adsorbent of Cd2+(aq). Biochar of residual biomass of CPH (BCCPH) possesses favorable physicochemical and morphological properties, featuring a modest surface area yet a suitable porous structure. Adsorption, predominantly governed by physisorption, is influenced by the oxygen-containing active sites (-COOR, -C(R)O, and -CH2OR; R = H, alkyl). CdCO3 formation occurs during adsorption. Experimental data were well-fitted into various kinetic models for a broad understanding of the sorption process. Langmuir model indicates a maximum adsorption capacity of 14.694 mg/g. The thermodynamic study confirms the spontaneous and endothermic sorption. Studies at the molecular level have revealed that the Cd2+ ion tends to bind to surface aromatic carbon atoms. This sustainable approach produces BCCPH via MAP as a solution for waste transformation into water-cleaning materials.

Sulforaphane Ameliorate Cadmium-Induced Blood-Thymus Barrier Disruption by Targeting the PI3K/AKT/FOXO1 Axis

Cadmium (Cd) is a transition metal ion that is extremely harmful to human and animal biological systems. Cd is a toxic substance that can accumulate in the food chain and cause various health issues. Sulforaphane (SFN) is a natural bioactive compound with potent antioxidant properties. In our study, 80 1 day-old chicks were fed with Cd (140 mg/kg BW/day) and/or SFN (50 mg/kg BW/day) for 90 days. The blood-thymus barrier (BTB) is a selective barrier separating T-lymphocytes from blood and cortical capillaries in the thymus cortex. Our research revealed that Cd could destroy the BTB by downregulating Wnt/β-catenin signaling and induce immunodeficiency, leading to irreversible injury to the immune system. The study emphasizes the health benefits of SFN in the thymus. SFN could ameliorate Cd-triggered BTB dysfunction and pyroptosis in the thymus tissues. SFN modulated the PI3K/AKT/FOXO1 axis, improving the level of claudin-5 (CLDN5) in the thymus to alleviate BTB breakdown. Our findings indicated the toxic impact of Cd on thymus, and BTB could be the specific target of Cd toxicity. The finding also provides evidence for the role of SFN in maintaining thymic homeostasis for Cd-related health issues.

Neurotoxic effects of metals on blood brain barrier impairment and possible therapeutic approaches

Exposure to neurotoxic and heavy metals (Pb2+, As3+, Mn2+, Cd2+, etc) has increased over time and has shown to negatively affect brain health. Heavy metals can cross the blood brain barrier (BBB) in various ways including receptor or carrier-mediated transport, passive diffusion, or transport via gaps in the endothelial cells of the brain. In high concentrations, these metals have been shown to cause structural and functional impairment to the BBB, by inducing oxidative stress, ion dyshomeostasis, tight junction (TJ) loss, astrocyte/pericyte damage and interference of gap junctions. The structural and functional impairment of the BBB results in increased BBB permeability, which ultimately leads to accumulation of these heavy metals in the brain and their subsequent toxicity. As a result of these effects, heavy metals are correlated with various neurological disorders. The pathological effects of these heavy metals can be effectively mitigated via chelation. In addition, it is possible to treat the associated disorders by counteracting the molecular mechanisms associated with the brain and BBB impairment.

The FAK/occludin/ZO-1 complex is critical for cadmium-induced testicular damage by disruption of the integrity of the blood-testis barrier in chickens

Cadmium (Cd) is a well-known testis toxicant. The blood-testis barrier (BTB) is a crucial component of the testis. Cd can disrupt the integrity of the BTB and reproductive function. However, the mechanism of Cd-induced disruption of BTB and testicular damage has not been fully elucidated. Here, our study investigates the effects of Cd on BTB integrity and testicular dysfunction. 80 (aged 1 day) Hy-Line white variety chickens were randomly designed into 4 groups and treated for 90 days, as follows: control group (essential diet), 35 Cd, 70 Cd and 140 Cd groups (35, 70 and 140 mg/kg Cd). The results found that Cd exposure diminished volume of the testes and induced histopathological lesions in the testes. Exposure to Cd induced an inflammatory response, disrupted the structure and function of the FAK/occludin/ZO-1 protein complex and disrupted the tight junction and adherens junction in the BTB. In addition, Cd exposure reduced the expression of steroid-related proteins and inhibited testosterone synthesis. Taken together, these data elucidate that Cd disrupts the integrity of the BTB and further inhibits spermatogenesis by dissociating the FAK/occludin/ZO-1 complex, which provides a basis for further investigation into the mechanisms of Cd-induced impairment of male reproductive function and pharmacological protection.

Mechanisms of Heavy Metal Cadmium (Cd)-Induced Malignancy

The environmental pollution of cadmium is worsening, and its significant carcinogenic effects on humans have been confirmed. Cadmium can induce cancer through various signaling pathways, including the ERK/JNK/p38MAPK, PI3K/AKT/mTOR, NF-κB, and Wnt. It can also cause cancer by directly damaging DNA and inhibiting DNA repair systems, or through epigenetic mechanisms such as abnormal DNA methylation, LncRNA, and microRNA. However, the detailed mechanisms of Cd-induced cancer are still not fully understood and require further investigation.

Flunitrazepam and its metabolites induced brain toxicity: Insights from molecular dynamics simulation and transcriptomic analysis

Psychoactive drugs frequently contaminate aquatic environments after human consumption, raising concerns about their residues and ecological harm. This study investigates the effects of flunitrazepam (FLZ) and its metabolite 7-aminoflunitrazepam (7-FLZ), benzodiazepine-class psychoactive drugs, on brain accumulation, blood-brain barrier (BBB), and neuroinflammation of the model organism zebrafish. Molecular dynamics simulation and transcriptome sequencing were used to uncover their toxic mechanisms. Results demonstrate that both FLZ and 7-FLZ can accumulate in the brain, increasing Evans blue levels by 3.4 and 0.8 times, respectively. This increase results from abnormal expression of tight junction proteins, particularly ZO-1 and Occludin, leading to elevated BBB permeability. Furthermore, FLZ and 7-FLZ can also induce neuroinflammation, upregulating TNFα by 91% and 39%, respectively, leading to pathological changes and disrupted intracellular ion balance. Molecular dynamics simulation reveals conformational changes in ZO-1 and Occludin proteins, with FLZ exhibiting stronger binding forces and greater toxicity. Weighted gene co-expression network analysis identifies four modules correlated with BBB permeability and neuroinflammation. KEGG enrichment analysis of genes within these modules reveals pathways like protein processing in the endoplasmic reticulum, NOD-like receptor signaling pathway, and arginine and proline metabolism. This study enhances understanding of FLZ and 7-FLZ neurotoxicity and assesses environmental risks of psychoactive substances. ENVIRONMENTAL IMPLICATION: With the increasing prevalence of mental disorders and the discharge of psychoactive drugs into water, even low drug concentrations (ng/L-μg/L) can pose neurological risks. This study, utilizing molecular dynamic (MD) simulations and transcriptome sequencing, investigate the neurotoxicity and mechanisms of flunitrazepam and 7-aminoflunitrazepam. It reveals that they disrupt the blood-brain barrier in zebrafish and induce neuroinflammation primarily by inducing conformational changes in tight junction proteins. MD simulations are valuable for understanding pollutant-protein interactions. This research offers invaluable insights for the environmental risk assessment of psychoactive drugs and informs the development of strategies aimed at prevention and mitigation.

Nano-selenium alleviates cadmium-induced neurotoxicity in cerebrum via inhibiting gap junction protein connexin 43 phosphorylation

Cadmium (Cd) as a ubiquitous toxic heavy metal is reported to affect the nervous system. Selenium (Se) has been shown to have antagonistic effects against heavy metal toxicity. In addition, it shows potential antioxidant and anti-inflammatory properties. Thus, the purpose of this study was to determine the possible mechanism of brain injury after high Cd exposure and the mitigation of Nano-selenium (Nano-Se) against Cd-induced brain injury. In this study, the Cd-treated group showed a decrease in the number of neurons in brain tissue, swelling of the endoplasmic reticulum and mitochondria, and the formation of autophagosomes. Nano-Se intervention restored Cd-caused alterations in neuronal morphology, endoplasmic reticulum, and mitochondrial structure, thereby reducing neuronal damage. Furthermore, we found that some differentially expressed genes were involved in cell junction and molecular functions. Subsequently, we selected eleven (11) related differentially expressed genes for verification. The qRT-PCR results revealed the same trend of results as determined by RNA-Seq. Our findings also showed that Nano-Se supplementation alleviated Cx43 phosphorylation induced by Cd exposure. Based on immunofluorescence colocalization it was demonstrated that higher expression of GFAP and lower expressions of Cx43 were restored by Nano-Se supplementation. In conclusion, the data presented in this study establish a direct association between the phosphorylation of Cx43 and the occurrence of autophagy and neuroinflammation. However, it is noteworthy that the introduction of Nano-Se supplementation has been observed to mitigate these alterations. These results elucidate the relieving effect of Nano-Se on Cd exposure-induced brain injury.

Arrestin domain-containing protein 1-mediated microvesicles (ARMMs) protect against cadmium-induced neurotoxicity

Exposure to environmental heavy metals such as cadmium (Cd) is often linked to neurotoxicity but the underlying mechanisms remain poorly understood. Here we show that Arrestin domain-containing protein 1 (ARRDC1)-mediated microvesicles (ARMMs)--an important class of extracellular vesicles (EVs) whose biogenesis occurs at the plasma membrane--protect against Cd-induced neurotoxicity. Cd increased the production of EVs, including ARMMs, in a human neural progenitor cell line, ReNcell CX (ReN) cells. ReN cells that lack ARMMs production as a result of CRISPR-mediated ARRDC1 knockout were more susceptible to Cd toxicity as evidenced by increased LDH production as well as elevated level of oxidative stress markers. Importantly, adding ARMMs back to the ARRDC1-knockout ReN cells significantly reduced Cd-induced toxicity. Consistent with this finding, proteomics data showed that anti-oxidative stress proteins are enriched in ARMMs secreted from ReN cells. Together our study reveals a novel protective role of ARMMs in Cd neurotoxicity and suggests that ARMMs may be used therapeutically to reduce neurotoxicity caused by exposure to Cd and potentially other metal toxicants.

Cadmium Transforms Astrocytes into the A1 Subtype via Inducing Gap Junction Protein Connexin 43 into the Nucleus

Cadmium is highly toxic and present in the environment and can be accumulated among various levels of the food chain. Both humans and animals are at risk from toxicity associated with cadmium. However, the neurological endpoint caused by cadmium has not been revealed. The aim of our research is to explore the potential target of cadmium attack when causing neurotoxicity. 80 male chickens (one day old, weighing 36.49 ± 2.88 g) were randomly divided into four groups and independently treated with 0, 35, 70, or 140 mg/kg CdCl2 in diet for 90 days. The result showed that the striatum was damaged due to a high dose of cadmium in the brain, which was characterized by degeneration of neurons and astrocyte dysfunction. Transcriptome analysis demonstrated that striatal astrocytes were transformed into the A1 state under cadmium exposure. Deeper investigation revealed that the internalization of gap junction protein connexin 43 was responsible for this transformation. Eventually, we can conclude that the internalized gap junction protein connexin 43 of astrocytes is the target of cadmium anchoring, and this process was accompanied by the transformation of astrocytes into the A1 subtype. This study provides a new direction for exploring the effects of cadmium on the nervous system and the treatment of subsequent nervous system diseases.