The Administration of Cadmium for 2, 3 and 4 Months Causes a Loss of Recognition Memory, Promotes Neuronal Hypotrophy and Apoptosis in the Hippocampus of Rats

Cadmium Neurotoxicity: Insights into Behavioral Effect and Neurodegenerative Diseases

Cadmium (Cd) induced neurotoxicity has become a growing concern due to its potential adverse effects on the Central Nervous System. Cd is a Heavy Metal (HM) that is released into the environment, through several industrial processes. It poses a risk to the health of the community by polluting air, water, and soil. Cd builds up in the brain and other neural tissues, raising concerns about its effect on the nervous system due to its prolonged biological half-life. Cd can enter into the neurons, hence increasing the production of Reactive Oxygen Species (ROS) in them and impairing their antioxidant defenses. Cd disrupts the Calcium (Ca2+) balance in neurons, affects the function of the mitochondria, and triggers cell death pathways. As a result of these pathways, the path to the development of many neurological diseases affected by environmental factors, especially Cd, such as Alzheimer's Disease (AD) and Amyotrophic Lateral Sclerosis (ALS) is facilitated. There are cognitive deficits associated with long exposure to Cd. Memory disorders are present in both animals and humans. Cd alters the brain's function and performance in critical periods. There are lifelong consequences of Cd exposure during critical brain development stages. The susceptibility to neurotoxic effects is increased by interactions with a variety of risk factors. Cd poses risks to neuronal function and behavior, potentially contributing to neurodegenerative diseases like Parkinson's disease (PD) and AD as well as cognitive issues. This article offers a comprehensive overview of Cd-induced neurotoxicity, encompassing risk assessment, adverse effect levels, and illuminating intricate pathways.

Cadmium exposure induced neuronal ferroptosis and cognitive deficits via the mtROS-ferritinophagy pathway

Exposure to environmental cadmium (Cd) is known to cause neuronal death and cognitive decline in humans. Ferroptosis, a novel iron-dependent type of regulated cell death, is involved in various neurological disorders. In the present study, Cd exposure triggered ferroptosis in the mouse hippocampus and in the HT22 murine hippocampal neuronal cell line, as indicated by significant increases in ferroptotic marker expression, intracellular iron levels, and lipid peroxidation. Interestingly, ferroptosis of hippocampal neurons in response to Cd exposure relied on the induction of autophagy since the suppression of autophagy by 3-methyladenine (3-MA) and chloroquine (CQ) substantially ameliorated Cd-induced ferroptosis. Furthermore, nuclear receptor coactivator 4 (NCOA4)-mediated degradation of ferritin was required for the Cd-induced ferroptosis of hippocampal neurons, demonstrating that NCOA4 knockdown decreased intracellular iron levels and lipid peroxidation and increased cell survival, following Cd exposure. Moreover, Cd-induced mitochondrial reactive oxygen species (mtROS) generation was essential for the ferritinophagy-mediated ferroptosis of hippocampal neurons. Importantly, pretreatment with the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively attenuated Cd-induced hippocampal neuronal death and cognitive impairment in mice. Taken together, these findings indicate that ferroptosis is a novel mechanism underlying Cd-induced neurotoxicity and cognitive impairment and that the mtROS-ferritinophagy axis modulates Cd-induced neuronal ferroptosis.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

Cadmium neurotoxicity and therapeutic strategies

Cadmium (Cd) is a multitarget, carcinogenic, nonessential environmental pollutant. Due to its toxic effects at very low concentrations, lengthy biological half-life, and low excretion rate, exposure to Cd carries a concern. Prolonged exposure to Cd causes severe injury to the nervous system of both humans and animals. Nevertheless, the precise mechanisms responsible for the neurotoxic effects of Cd have yet to be fully elucidated. The accurate chemical mechanism potentially entails the destruction of metal-ion homeostasis, inducing oxidative stress, apoptosis, and autophagy. Here we review the evidence of the neurotoxic effects of Cd and corresponding strategies to protect against Cd-induced central nervous system injury.

Oral administration of resveratrol reduces oxidative stress generated in the hippocampus of Wistar rats in response to consumption of ethanol

Introduction

Chronic ethanol intake has been found to favor hippocampal deterioration and alter neuronal morphological maturation; resveratrol has been suggested as an antioxidant that may counteract these effects. The objective of this study was to analyze the effect of resveratrol on oxidative stress markers, endogenous antioxidant system in the hippocampus, and the behavior of male Wistar rats administered different concentrations of ethanol.

Methods

The animals, at 3 months old, were randomly distributed into 11 study groups (n = 6/group), orally administered (5 days on, 2 days off) with water (control), ethanol (10, 20, 30, 40 or 50%), or ethanol (10, 20, 30, 40 or 50%) plus resveratrol (10 mg/Kg/day) for 2 months. Subsequently, the production of nitrites, malondialdehyde, and 4-hydroxy-alkenal (HNE) and the enzymatic activity of catalase and superoxide dismutase (SOD) were quantified.

Results

The levels of nitric oxide and lipid peroxidation products were significantly increased in each ethanol concentration and were statistically different compared to the control group; however, resveratrol significantly reduced oxidative stress caused by high ethanol concentration. The SOD and CAT did not present significant changes with respect to the controls in any of the study groups. In the different concentrations of ethanol used, GR increases significantly in the groups administered with resveratrol but not GPx. Resveratrol was shown to maintain the results similar to the control at most ethanol concentrations.

Discussion

Our results suggest that resveratrol prevents oxidative stress induced by ethanol in the hippocampus by decreasing cellular lipid peroxidation, but does not prevent the activation of catalase or SOD enzymes; however, allows glutathione to be kept active and in adequate concentrations in its reduced form and avoids alterations in the locomotor system.

Cadmium-induced pyroptosis is mediated by PERK/TXNIP/NLRP3 signaling in SH-SY5Y cells

Cadmium (Cd) is a hypertoxic heavy metal that may be exposed to environmental pollutants by humans and animals. It can lead to cognitive disfunction, and is linked to neurodegenerative diseases. Cadmium reportedly can induce endoplasmic reticulum (ER) stress, but few studies have concentrated on it in nerve cells, and the connection between ER stress and neuroinflammation. In this study, in vitro experiments on SH-SY5Y neuroblastoma cells were carried out. We aimed at exploring whether Cd attributed to the cell pyroptosis and the role of PERK in promoting this form of cell damage which can induce strong inflammatory responses. Our results demonstrated that CdCl2 treatment induced excess reactive oxygen species (ROS) production, caused significant modifications in the expression of PERK and increased TXNIP, NLRP3, IL-1β, IL-18, and caspase1 in SH-SY5Y cells. In addition, scavenging ROS with N-acetylcysteine or inhibiting the expression of PERK by using GSK2606414, rescued the SH-SY5Y cells from cadmium-induced pyroptosis. In conclusion, the results suggest that Cd induces pyroptotic death of SH-SY5Y cells through ER stress, and this may be the potential mechanism of Cd incurring neurological diseases.

Association between heavy metals exposure (cadmium, lead, arsenic, mercury) and child autistic disorder: a systematic review and meta-analysis

Background

Studies have found that toxic heavy metals exposure could induce the generation of reactive oxygen species (ROS), and is of epigenetic effect, which might be associated with the occurrence of Autistic Disorder (ASD). This systematic review and meta-analysis aims to elucidate the association between exposure to 4 heavy metals, cadmium (Cd), lead (Pb), arsenic(As), and mercury (Hg), and the occurrence of ASD in children.

Methods

We searched PubMed, Web of Science, Embase, and Cochrane Library, from their inception to October 2022, for epidemiological investigations that explore the association between exposure to Cd, Pb, As, or Hg and the occurrence of child ASD.

Results

A total of 53 studies were included, involving 5,054 individuals aged less than 18 (2,533 ASD patients and 2,521 healthy controls). Compared with the healthy controls, in hair and blood tests, concentrations of the 4 heavy metals were significantly higher in the ASD group than in the healthy control group, and the differences in Pb, arsenic and Hg were statistically significant (P < 0.05). In the urine test, concentrations of arsenic and Hg were significantly higher in the ASD group than in the healthy control group (P < 0.05), while the results of Cd and Pb were opposite to those of arsenic and Hg (P > 0.05). Subgroup analysis for geographic regions showed that ASD patients in Asia and Europe had higher concentrations of the 4 heavy metals, compared with the healthy controls, in which the differences in Pb, arsenic, and Hg were statistically significant (P < 0.05), while in North America, the healthy controls had higher Cd, arsenic, and Hg concentrations (P > 0.05).

Conclusion

Compared with the healthy control group, the ASD group had higher concentrations of Cd, Pb, arsenic, and Hg. These 4 heavy metals play different roles in the occurrence and progression of ASD. Moreover, there is significant heterogeneity among the included studies due to controversies about the study results among different countries and regions and different sources of detection materials. The results of this study firmly support the policies to limit heavy metals exposure, especially among pregnant women and young children, so as to help reduce the incidence of ASD.

Regulation of COX-2 expression by selected trace elements and heavy metals: Health implications, and changes in neuronal plasticity. A review

Trace elements or trace metals are essential components of enzymes, proteins, hormones and play a key role in biochemical processes, cell growth and differentiation, as well as in neurotransmission, affecting human physiology. In nature there are also heavy metals that exhibit toxic effects on the human body, including the brain. The importance of trace elements has been established in neurodegenerative disorders, schizophrenia, depression among others. In parallel, an important regulatory element in the above diseases is cyclooxygenase-2 (COX-2), a modulator of the arachidonic acid (AA) pathway, and a cause of neuroinflammation, and glutamate (Glu) dysregulation, affecting calcium (Ca) metabolism in cells. This review presents the effects of major trace elements and heavy metals on COX-2 expression. Calcium (Ca), zinc (Zn), cadmium (Cd), vanadium (V), nickel (Ni), copper (Cu), and iron (Fe) can potentially increase COX-2 expression, inducing neuroinflammation and Glu excitotoxicity; while magnesium (Mg), lithium (Li), and selenium (Se) can potentially decrease COX-2 expression. The associated mechanisms are described in the article.

The relationship between cadmium and cognition in the elderly: a systematic review

Context: The relationship between cadmium (Cd) and the cognition of the elderly is indistinct.Objective: To summarise the studies on the relationship between the cognition of the elderly and Cd.Methods: Literatures were searched in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Wan fang database on April 25, 2022. The entries in the STROBE statement were used to evaluate the literature quality; all the quantitative studies that met the requirements were systematically summarised.Results: Blood Cd was negatively correlated with the cognitive ability of the elderly, corresponding to different cognitive ability assessment methods, the regression coefficients were: -0.11 (-0.20, -0.03), -0.46 (-0.71, -0.21), -0.54 (-0.90, -0.17), -0.19 (-0.37, -0.01), and -2.29 (-3.41, -1.16). The regression coefficients between urinary Cd level and cognition score were -1.42 (-2.38, -0.46), and 0.76 (-1.28, -0.23). When dietary Cd increased by 1 μg/kg, the composite z-score decreased by 3.64 (p = 0.001). There was no significant correlation between drinking water Cd, fingernail Cd and cognition (p > 0.05).Conclusion: We concluded that blood Cd (including whole blood and plasma), urine Cd and dietary Cd were negatively correlated with the cognition of the elderly, but the relationship between Cd in drinking water and fingernails and cognition was not statistically significant.

Environmental exposure of the general population to cadmium as a risk factor of the damage to the nervous system: A critical review of current data

Nowadays, more and more attention has been focused on the risk of the neurotoxic action of cadmium (Cd) under environmental exposure. Due to the growing incidence of nervous system diseases, including neurodegenerative changes, and suggested involvement of Cd in their aetiopathogenesis, this review aimed to discuss critically this element neurotoxicity. Attempts have been made to recognize at which concentrations in the blood and urine Cd may increase the risk of damage to the nervous system and compare it to the risk of injury of other organs and systems. The performed overview of the available literature shows that Cd may have an unfavourable impact on the human's nervous system at the concentration >0.8 μg Cd/L in the urine and >0.6 μg Cd/L in the blood. Because such concentrations are currently noted in the general population of industrialized countries, it can be concluded that environmental exposure to this xenobiotic may create a risk of damage to the nervous system and be involved in the aetiopathogenesis of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, as well as worsening cognitive and behavioural functions. The potential mechanism of Cd neurotoxicity consists in inducing oxidative stress, disrupting the activity of enzymes essential to the proper functioning of the nervous system and destroying the homoeostasis of bioelements in the brain. Thus, further studies are necessary to recognize accurately both the risk of nervous system damage in the general population due to environmental exposure to Cd and the mechanism of this action.

Developmental exposure to corn grown on Lake Erie dredged material: a preliminary analysis

While corn is considered to be a healthy food option, common agricultural practices, such as the application of soil amendments, might be introducing contaminants of concern (COC) into corn plants. The use of dredged material, which contain contaminants such as heavy metals, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), as a soil amendment is increasing. Contaminants from these amendments can accumulate in corn kernels harvested from plants grown on these sediments and potentially biomagnify in organisms that consume them. The extent to which secondary exposure to such contaminants in corn affect the mammalian central nervous system has been virtually unexplored. In this preliminary study, we examine the effects of exposure to corn grown in dredge amended soil or a commercially available feed corn on behavior and hippocampal volume in male and female rats. Perinatal exposure to dredge-amended corn altered behavior in the open-field and object recognition tasks in adulthood. Additionally, dredge-amended corn led to a reduction in hippocampal volume in male but not female adult rats. These results suggest the need for future studies examining how dredge-amended crops and/or commercially available feed corn may be exposing animals to COC that can alter neurodevelopment in a sex-specific manner. This future work will provide insight into the potential long-term consequences of soil amendment practices on the brain and behavior.

Second-generation antipsychotic olanzapine attenuates behavioral and prefrontal cortex synaptic plasticity deficits in a neurodevelopmental schizophrenia-related rat model

Second-generation antipsychotics are the drugs of choice for the treatment of neurodevelopmental-related mental diseases such as schizophrenia. Despite the effectiveness of these drugs to ameliorate some of the symptoms of schizophrenia, specifically the positive ones, the mechanisms beyond their antipsychotic effect are still poorly understood. Specifically, second-generation antipsychotics are reported to have anti-inflammatory, antioxidant and neuroplastic properties. Using the neonatal ventral hippocampus lesion (nVHL) in the rat, an accepted schizophrenia-related model, we evaluated the effect of the second-generation antipsychotic olanzapine (OLZ) in the behavioral, neuroplastic, and neuroinflammatory alterations exhibited in the nVHL animals. OLZ corrected the hyperlocomotion and impaired working memory of the nVHL animals but failed to enhance social disturbances of these animals. In the prefrontal cortex (PFC), OLZ restored the pyramidal cell structural plasticity in the nVHL rats, enhancing the dendritic arbor length, the spinogenesis and the proportion of mature spines. Moreover, OLZ attenuated astrogliosis as well as some pro-inflammatory, oxidative stress, and apoptosis-related molecules in the PFC. These findings reinforce the evidence of anti-inflammatory, antioxidant, and neurotrophic mechanisms of second-generation antipsychotics in the nVHL schizophrenia-related model, which allows for the possibility of developing more specific drugs for this disorder and thus avoiding the side effects of current schizophrenia treatments.

Role of heavy metals (copper (Cu), arsenic (As), cadmium (Cd), iron (Fe) and lithium (Li)) induced neurotoxicity

Parkinson's disease (PD) is a neurodegenerative condition characterized by the dopamine (DA) neuronal loss in the substantia nigra. PD impairs motor controls symptoms such as tremor, rigidity, bradykinesia and postural imbalance gradually along with non-motor problems such as olfactory dysfunction, constipation, sleeping disorder. Though surplus of factors and mechanisms have been recognized, the precise PD etiopathogenesis is not yet implied. Reports suggest that various environmental factors play a crucial role in the causality of the PD cases. Epidemiological studies have reported that heavy metals has a role in causing defects in substantia nigra region of brain in PD. Though the reason is unknown, exposure to heavy metals is reported to be an underlying factor in PD development. Metals are classified as either essential or non-essential, and they have a role in physiological processes such protein modification, electron transport, oxygen transport, redox reactions, and cell adhesion. Excessive metal levels cause oxidative stress, protein misfolding, mitochondrial malfunction, autophagy dysregulation, and apoptosis, among other things. In this review, we check out the link between heavy metals like copper (Cu), arsenic (As), cadmium (Cd), iron (Fe), and lithium (Li) in neurodegeneration, and how it impacts the pathological conditions of PD. In conclusion, increase or decrease in heavy metals involve in regulation of neuronal functions that have an impact on neurodegeneration process. Through this review, we suggest that more research is needed in this stream to bring more novel approaches for either disease modelling or therapeutics.

Effect of cadmium administration on the antioxidant system and neuronal death in the hippocampus of rats

Cadmium (Cd) is a heavy metal classified as a carcinogen whose exposure could affect the function of the central nervous system. Studies suggest that Cd modifies neuronal morphology in the hippocampus and affects cognitive tasks. The oxidative stress pathway is proposed as a mechanism of toxicity. However, this mechanism is not precise yet. This study aimed to evaluate the effect of Cd administration on oxidative stress markers in the male rat's hippocampus. Male Wistar rats were divided into (1) control (drinking water) and (2) treatment with Cd (32.5 ppm of cadmium chloride (CdCl₂ ) in water). The Cd was administered for 2, 3, and 4 months. The results show that the oral administration of CdCl₂ increased the concentration of Cd in plasma and hippocampus, and this response is time-dependent on its administration. Likewise, it caused an increase in lipid peroxidation and nitrosative stress markers. Moreover, it increased reactive astrogliosis and antioxidant enzyme activity. Consequently, the progression of the oxidative response exacerbated neurodegeneration in hippocampal cells. Our results suggest that Cd exposure induces a severe oxidative response that contributes critically to hippocampal neurodegeneration. It is suggested that exposure to Cd increases the risk of developing neurological diseases, which contributes to a decrease in the quality of life of the human and the environment in which it lives.

The protective effects of chitosan oligosaccharide (COS) on cadmium-induced neurotoxicity in Wistar rats

The aim of the study was to investigate the influence of chitosan oligosaccharide (COS) on some antioxidant and cytokine levels in the rat hippocampus as well as synaptophysin (SYP) immunoreactivity in the cerebral cortex of the cadmium (Cd) exposed rats. Thirty-two male albino Wistar rats were divided randomly into four equal groups as control (C; n = 8), Cd (n = 8), COS (n = 8), and Cd + COS (CdCOS; n = 8). The rats in the Cd and CdCOS groups received Cd chloride (CdCl₂) (2 mg/kg/d) orally by gastric gavage three times a week for 4 weeks. Besides, COS (200 mg/kg/d) was administered to COS and CdCOS groups five times a week for 4 weeks. Then, they were decapitated and hippocampal/cerebral cortex tissue samples were taken for measurement of GSH levels, CAT and SOD activities, MDA values, TNF-α, IL-6, and IL-10 levels as well as SYP immunoreactivity. Although tissue GSH levels were determined the lowest in the Cd group, these values were attenuated with COS treatment in the CdCOS group (p < .01). In addition, TNF-α levels were alleviated by COS treatment in the CdCOS group when compared to Cd (p < .01). SYP-positive cells were investigated in the cerebral cortex and found mild in the CdCOS group. COS exhibits potential protective effects on Cd-induced neurotoxicity in rats.

Resolvin D1 prevents cadmium chloride-induced memory loss and hippocampal damage in rats by activation/upregulation of PTEN-induced suppression of PI3K/Akt/mTOR signaling pathway

This study evaluated the protective effect of resolvin D1 (RVD1) against cadmium chloride (CdCl₂ )-induced hippocampal damage and memory loss in rats and investigated if such protection is mediated by modulating the PTEN/PI3K/Akt/mTOR pathway. Adult male Wistar rats (n = 18/group) were divided as control, control + RVD1, CdCl₂ , CdCl₂  + RVD1 and CdCl₂  + RVD1 + bpV(pic), a PTEN inhibitor. All treatments were conducted for 4 weeks. Resolvin D1 improved the memory function as measured by Morris water maze (MWM), preserved the structure of CA1 area of the hippocampus, and increased hippocampal levels of RVD1 in the CdCl₂ -treated rats. Resolvin D1 also suppressed the generation of reactive oxygen species (ROS), tumour necrosis factor-α and interleukine-6 (IL-6), inhibited nuclear factor κB (NF-κB) p65, stimulated levels of glutathione (GSH), manganese superoxide dismutase (MnSOD), and Bcl2 but reduced the expression of Bax and cleaved caspase 3 in hippocampi of CdCl₂ -treated rats. Concomitantly, it stimulated levels and activity of PTEN and reduced the phosphorylation (activation) of PI3K, Akt and mTOR in hippocampi of CdCl₂ -treated rats. In conclusion, RVD1 attenuates CdCl₂ -induced memory loss and hippocampal damage in rats mainly by activating PTEN-induced suppression of PI3K/Akt/mTOR, an effect that seems secondary to its' anti-oxidant and anti-inflammatory potential.

Resolvin D1 protects against cadmium chloride-induced memory loss and hippocampal damage in rats: A comparison with docosahexaenoic acid

BACKGROUND

Intoxication with cadmium (Cd) ions leads to hippocampal damage and cognitive impairment. However, omega-3 polyunsaturated fatty acids (n-3 PUFAs) exert neuroprotective effects in different animal models of neurodegeneration.

PURPOSE

This study compared the neuroprotective effect of the n-3 PUFA, docosahexaenoic acid (DHA), and its downstream metabolite, resolvin D1 (RVD1), on hippocampal damage and memory deficits in cadmium chloride (CdCl₂)-treated rats.

RESEARCH DESIGN

Control or CdCl₂ (0.5 mg/kg)-treated rats were subdivided into three groups (n = 18/each) and treated for 6 weeks as follows: (1) fed control diet, (2) fed DHA-rich diets (0.7 g/100 g), or (3) treated with RVD1 (0.2 μg/kg, i.p).

RESULTS

Treatment with a DHA-rich diet or RVD1 significantly increased the levels of docosahexaenoic acid and RVD1, respectively, in the hippocampal of CdCl₂-treated rats without affecting the reduction in the expression of the 15-lipooxygenase-1 (ALOX15). These effects were associated with improvements in rats' memory function and hippocampal structure, as well as a redction in the hippocampal levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), nuclear localization of the nuclear factor-kappa beta p65 (NF-κB p65), and expression of cleaved caspase-3. Concomitantly, hippocampi of both groups of rats showed significantly higher levels of Bcl-2, superoxide dismutase (SOD), and glutathione (GSH), as well as enhanced nuclear levels of the nuclear factor erythroid 2-related factor 2 (Nrf-2). The effects of RVD1 on all these markers in the CdCl₂-induced rats were more profound than those of DHA. Also, the increase in the nuclear protein levels of Nrf-2 and the decrease in the levels of Bax and nuclear protein levels of NF-κB p65 were only seen in the hippocampal of CdCl₂ + RVD1-treated rats.

CONCLUSION

RVD1 is more powerful than DHA in preventing CdCl₂-induced memory loss and hippocampal damage in rats.

Cadmium exposure promotes activation of cerebrum and cerebellum ferroptosis and necrosis in swine

Cadmium(Cd) is a toxic and carcinogenic heavy metal pollutant leading to serious damage in various organs. Ferroptosis and necrosis as inflammation-related cell death are involved in several diseases of nervous system. In the present study, 10 weaning piglets with similar weight for 6 weeks were randomly divided into two groups. The daily grain containing 0 mg and 20 mg/kg of Cd chloride was fed in 20-26 ℃ environment, animals were sacrificed to collect cerebrum and cerebellum tissues after 40 days. Morphology and ultrastructure results were observed using HE and TEM. Moreover, molecular biological technologies western blot and qRT-PCR were used to detect the expression abundance of genes. Cerebrum and cerebellum injury was observed in Cd-exposed group, antioxidant capacity decreased significantly and oxidative stress increased; immunofluorescence, real-time quantification, and western blot results showed decreased necrosis genes and increased ferroptosis pathway genes abundance in cerebrum, whereas the results were reversed in cerebellum. These results indicated that Cd exposure can activated necrosis and ferroptosis pathways by increased oxidative stress, further resulting in cerebrum and cerebellum damage in pigs. These findings may provide a theoretical basis for early monitoring of Cd exposure in environment.

Soluble curcumin ameliorates motility, adhesiveness and abrogate parthanatos in cadmium-exposed retinal pigment epithelial cells

Cadmium (Cd) is a nonessential transition metal and one of the most toxic environmental pollutants. Industrial, agricultural and urban activities are the main sources of Cd environmental contamination. Multiple deleterious effects of Cd exposure were reported for different cell types and living organisms in a great number of research papers. Cd bioaccumulation hazard is mediated by the relatively long half-life of this metal in an organism. For example, in mammals its half-life lasts for about 10–30 years. Cd exposure affects many tissues. However, some of them, including the central nervous system and sensory organs, are most susceptible to its toxicity. The harmful effects of Cd could be linked to oxidative stress generation and consequently intracellular signalling disruption. Since Cd induces redox imbalance the antioxidants could be a prospective tool to ameliorate Cd cytotoxicity. In present work, we have studied the protective efficacy of soluble curcumin on Cd-caused retinal pigment epithelium (RPE) cells viability, reactive oxygen species production, adhesive and extracellular matrix proteins expression, cell migration and parthanatos level. Low dose (5 µM) of soluble curcumin ameliorated all aforementioned indices of Cd-induced cytotoxicity. Curcumin has restored the RPE cells motility as well as fibronectin and E-cadherin expression. Therefore, the modulation of RPE adhesiveness could be regarded as a cytoprotective effect of curcumin. Furthermore, Cd-caused poly(ADP-ribose) polymerase-1 (PARP-1) suppression and cleaved PARP-1 upregulation were ameliorated by curcumin exposure. Therefore, the protective effect of soluble curcumin could be related, at least partially, to the modulation of PARP activity and inhibition of parthanatos flux. The observed results have demonstrated that low doses of soluble curcumin are a promising tool to protect RPE cells against Cd-caused retinal injury.

Cadmium, an Environmental Contaminant, Exacerbates Alzheimer's Pathology in the Aged Mice's Brain

Cadmium (Cd) is an environmental contaminant, which is a potential risk factor in the progression of aging-associated neurodegenerative diseases. Herein, we have assessed the effects of chronic administration of Cd on cellular oxidative stress and its associated Alzheimer's disease (AD) pathologies in animal models. Two groups of mice were used, one group administered with saline and the other with Cd (1 mg/kg/day; intraperitoneally) for 3 months. After behavioral studies, molecular/biochemical (Immunoblotting, ELISAs, ROS, LPO, and GSH assays) and morphological analyses were performed. We observed an exacerbation of memory and synaptic deficits in chronic Cd-injected mice. Subacute and chronic Cd escalated reactive oxygen species (ROS), suppressed the master antioxidant enzymes, e.g., nuclear factor-erythroid 2-related factor 2 and heme oxygenase-1, and evoked the stress kinase phospho-c-Jun N-terminal kinase 1 signaling pathways, which may escalate AD pathologies possibly associated with amyloidogenic processes. These findings suggest the regulation of oxidative stress/ROS and its associated amyloid beta pathologies for targeting the Cd-exacerbated AD pathogenesis. In addition, these preclinical animal studies represent a paradigm for epidemiological studies of the human population exposed to chronic and subacute administration of Cd, suggesting avoiding environmental contaminants.

The protective effect of nnano-selenium against cadmium-induced cerebellar injury via the heat shock protein pathway in chicken

Cadmium (Cd) is one of the toxic environmental heavy metals that poses health hazard to animals due to its toxicity. Nano-Selenium (Nano-Se) is a Nano-composite form of Se, which has emerged as a promising therapeutic agent for its protective roles against heavy metals-induced toxicity. Heat shock proteins (HSPs) play a critical role in cellular homeostasis. However, the potential protective effects of Nano-Se against Cd-induced cerebellar toxicity remain to be illustrated. To investigate the toxic effects of Cd on chicken's cerebellum, and the protective effects of Nano-Se against Cd-induced cerebellar toxicity, a total of 80 male chicks were divided into four groups and treated as follows: (A) 0 mg/kg Cd, (B) 1 mg/kg Nano-Se (C) 140 mg/kg Cd + 1 mg/kg Nano-Se (D) 140 mg/kg Cd for 90 days. We tested heat shock protein pathway-related factors including heat shock factors (HSFs) HSF1, HSF2, HSF3 and heat shock proteins (HSPs) HSP10, HSP25, HSP27, HSP40, HSP60, HSP70 and HSP90 expressions. Histopathological results showed that Cd treatment caused degradation of Purkinje cells. In addition, HSFs and HSPs expression decreased significantly in the Cd group. Nano-Se co-treatment with Cd enhanced the expression of HSFs and HSPs. In summary, our findings explicated a potential protective effect of Nano-Se against Cd-induced cerebellar injury in chicken, suggesting that Nano-Se is a promising therapeutic agent for the treatment of Cd toxicity.

Melatonin Ameliorates Cadmium-Induced Affective and Cognitive Impairments and Hippocampal Oxidative Stress in Rat

The present work aims to evaluate the effect of melatonin (Mel) on affective and cognitive disorders induced by chronic exposure to Cadmium (Cd). Male and female Wistar rats received either an intraperitoneal injection of saline solution NaCl (0.9%), Mel (4 mg/kg), Cd (1 mg/kg), or Cd (1 mg/kg) + Mel (4 mg/kg) for 8 weeks. Behavioral disorders were evaluated by different tests mainly the open field and elevated plus maze tests for anxiety-like behavior, forced swimming test (FST) for depression-like behavior, and the Y-maze and Morris water maze (MWM) tests for cognitive disorders. Thereafter, oxidative stress indices and histology of the hippocampus were evaluated. The results confirm that Cd administration has anxiogenic-like effects in both anxiety tests and depressive-like effects in the FST and leads to memory and learning disabilities in the Y-maze and MWM. We also report that Mel counteracts these neurobehavioral disorders. Biochemical assays showed that rats intoxicated with Cd significantly increased levels of nitric oxide (NO) and lipid peroxidation (LPO), while the activities of catalase (CAT) and superoxide dismutase (SOD) were significantly decreased in the hippocampus. In contrast, Mel administration attenuates the Cd-induced changes. The histopathological studies in the hippocampus of rats also supported that Mel markedly reduced the Cd-induced neuronal loss in CA3 sub-region. Overall, our results suggest that Mel could be used to protect against Cd-induced neurobehavioral changes via its antioxidant properties in the hippocampus. The effects of Cd and Mel are sex-dependent, knowing that Cd is more harmful in males, while Mel is more protective in females.

Single-cell RNA sequencing of mouse neural stem cell differentiation reveals adverse effects of cadmium on neurogenesis

Cadmium (Cd) is a toxic heavy metal and widely exists in the environment. Extensive studies have revealed that Cd exposure can elicit neurotoxicity and potentially interfere with neurogenesis. However, underlying mechanisms by which Cd exposure affects neurogenesis remain unclear. In this study, we performed single-cell RNA sequencing (scRNA-seq) of the differentiated mixture from neonatal mouse Neural Stem Cells (mNSCs) that were exposed to Cd for 24 h and differentiated for 7 days. Our results showed that Cd exposure led to an increase in the differentiation of NSCs into astrocytes while a decrease into neurons. Besides, Cd induced subtype-specific response and dysregulated cell-to-cell communication. Collectively, our scRNA-seq data suggested that Cd had toxic effects on NSCs differentiation at the single-cell level, which offered insight into the potential molecular mechanism of Cd on neurogenesis. Furthermore, our findings provided a new method for assessing the neurodevelopmental toxicity of environmental pollutants.

Memory and dendritic spines loss, and dynamic dendritic spines changes are age-dependent in the rat

Brain aging is a widely studied process, but due to its complexity, much of its progress is unknown. There are many studies linking memory loss and reduced interneuronal communication with brain aging. However, only a few studies compare young and old animals. In the present study, in male rats aged 3, 6, and 18 months, we analyzed the locomotor activity and also short and long-term memory using the novel object recognition test (NORT), in addition to evaluating the dendritic length and the number of dendritic spines in the prefrontal cortex (PFC) and in the CA1, CA3 and DG regions of the dorsal hippocampus using Golgi-Cox staining. We also analyzed the types of dendritic spines in the aforementioned regions. 6- and 18-month old animals showed a reduction in locomotor activity, while long-term memory deficit was observed in 18-month old rats. At 18 months old, the dendritic length was reduced in all the studied regions. The dendritic spine number was also reduced in layer 5 of the PFC, and the CA1 and CA3 of the hippocampus. The dynamics of dendritic spines changed with age, with a reduction of the mushroom spines in all the studied regions, with an increase of the stubby spines in all the studied regions except from the CA3 region, that showed a reduction. Our data suggest that age causes changes in behavior, which may be the result of morphological changes at the dendrite level, both in their length and in the dynamics of their spines.

Kaempferol protects against cadmium chloride-induced hippocampal damage and memory deficits by activation of silent information regulator 1 and inhibition of poly (ADP-Ribose) polymerase-1

The neuroprotective effect of Kaempferol against cadmium chloride (CdCl₂) -induced neurotoxicity is well reported. The silent information regulator 1 (SIRT1) and poly (ADP-Ribose) polymerase-1 (PARP1) are two related cellular molecules that can negatively affect the activity of each other to promote or inhibit cell survival, respectively. It is still largely unknown if the neurotoxicity of CdCl₂ or the neuroprotection of Kaempferol are mediated by modulating SIRT1 and/or PAPR1 activities. In this study, we tested the hypothesis that CdCl₂-induced memory deficit and hippocampal damage are associated with downregulation/inhibition of SIRT1 and activation of PAPR1, an effect that can be reversed by co-treatment with Kaempferol. Rats (n = 12/group) were divided into 4 groups as control, control + Kaempferol (50 mg//kg), CdCl₂ (0.5 mg/kg), and CdCl₂ + Kaempferol. All treatments were administered orally for 30 days daily. As compared to control rats, CdCl2 reduced rat's final body weights (21.8%) and their food intake (30%), induced oxidative stress and apoptosis in their hippocampi, and impaired their short and long-term recognition memory functions. Besides, the hippocampi of CdCl₂-treated rats had higher levels of TNF-α (197%), and IL-6 (190%) with a concomitant increase in nuclear activity and levels of NF-κB p65 (721% & 554%). Besides, they showed reduced nuclear activity (53%) and levels (74%) of SIRT1, higher nuclear activity and levels of PARP1 (292% & 138%), increased nuclear levels of p53 (870%), and higher acetylated levels of NF-κB p65 (513%), p53 (644%), PARP1 (696%), and FOXO-2 (149%). All these events were significantly reversed in the CdCl₂ + Kaempferol-treated rats. Of note, Kaempferol also increased levels of MnSOD (73.5%), and GSH (40%), protein levels of Bcl-2 (350%), and nuclear activity (67%) and levels (46%) of SIRT1 in the hippocampi of the control rats. In conclusion, Kaempferol ameliorates CdCl₂-induced memory deficits and hippocampal oxidative stress, inflammation, and apoptosis by increasing SIRT1 activity and inhibiting PARP1 activity.

Heavy Metal-Induced Cerebral Small Vessel Disease: Insights into Molecular Mechanisms and Possible Reversal Strategies

Heavy metals are considered a continuous threat to humanity, as they cannot be eradicated. Prolonged exposure to heavy metals/metalloids in humans has been associated with several health risks, including neurodegeneration, vascular dysfunction, metabolic disorders, cancer, etc. Small blood vessels are highly vulnerable to heavy metals as they are directly exposed to the blood circulatory system, which has comparatively higher concentration of heavy metals than other organs. Cerebral small vessel disease (CSVD) is an umbrella term used to describe various pathological processes that affect the cerebral small blood vessels and is accepted as a primary contributor in associated disorders, such as dementia, cognitive disabilities, mood disorder, and ischemic, as well as a hemorrhagic stroke. In this review, we discuss the possible implication of heavy metals/metalloid exposure in CSVD and its associated disorders based on in-vitro, preclinical, and clinical evidences. We briefly discuss the CSVD, prevalence, epidemiology, and risk factors for development such as genetic, traditional, and environmental factors. Toxic effects of specific heavy metal/metalloid intoxication (As, Cd, Pb, Hg, and Cu) in the small vessel associated endothelium and vascular dysfunction too have been reviewed. An attempt has been made to highlight the possible molecular mechanism involved in the pathophysiology, such as oxidative stress, inflammatory pathway, matrix metalloproteinases (MMPs) expression, and amyloid angiopathy in the CSVD and related disorders. Finally, we discussed the role of cellular antioxidant defense enzymes to neutralize the toxic effect, and also highlighted the potential reversal strategies to combat heavy metal-induced vascular changes. In conclusion, heavy metals in small vessels are strongly associated with the development as well as the progression of CSVD. Chelation therapy may be an effective strategy to reduce the toxic metal load and the associated complications.

Microglia dependent BDNF and proBDNF can impair spatial memory performance during persistent inflammatory pain

Inflammatory pain is commonly associated with cognitive impairment. However, its molecular mechanisms are poorly understood. Thus, this study was conducted to investigate the molecular mechanisms of behavioral changes associated with inflammatory pain. Briefly, 36 Wistar rats were randomly divided into two main groups: CFA group treated with 100 μL of Complete Freunds' Adjuvant (CFA) and CFA + Minocycline group treated with 100 μL of CFA+40 mg/kg/day of minocycline). After that, each group was divided into three subgroups based on different time points of the study. The pain was induced using CFA and subsequent behavioral changes (i.e., hyperalgesia and learning and spatial memory) were analyzed by the Morris Water Maze (MWM) task and Radiant Heat. Then, the cellular and molecular changes were assessed using Western Blotting, Immunohistochemistry, and Terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL) techniques. Results of the study indicated that CFA-induced pain impaired spatial learning and memory functions. Studying the cellular changes showed that persistent inflammatory pain increased the microglial activity in CA1 and Dentate Gyrus (DG) regions. Furthermore, an increase was observed in the percentage of TUNEL-positive cells. Also, pro-Brain-Derived Neurotrophic Factor (BDNF)/BDNF ratio, Caspase3, and Receptor-Interacting Protein kinase 3 (RIP3) levels increased in the rats' hippocampus following induction of persistent inflammatory pain. These changes were reversed following the cessation of pain as well as the injection of minocycline. Taking together, the results of the current study for the first time revealed that an increase in the microglia dependent proBDNF/BDNF ratio following persistent inflammatory pain leads to cell death of the CA1 and DG neurons that subsequently causes a cognitive deficit in the learning and spatial memory functions.

Effects of metformin on recognition memory and hippocampal neuroplasticity in rats with metabolic syndrome

Metabolic syndrome (MS) is a health problem that is characterized by body fat accumulation, hypertension, dyslipidemia, and hyperglycemia; recently, it has been demonstrated that MS also damages memory processes. The first-line drug in the treatment of MS and type 2 diabetes mellitus is metformin, which is an antihyperglycemic agent. This drug has been shown to produce neuroprotection and to improve memory processes. However, the mechanism involved in this neuroprotection is unknown. A 90-day administration of metformin improved the cognitive processes of rats with MS as evaluated by the novel object recognition test, and this finding could be explained by an increase in the neuronal spine density and spine length. We also found that metformin increased the immunoreactivity of synaptophysin, sirtuin-1, AMP-activated protein kinase, and brain-derived neuronal factor, which are important plasticity markers. We conclude that metformin is an important therapeutic agent that increases neural plasticity and protects cognitive processes. The use of this drug is important in the minimization of the damage caused by MS.