The Effects of Copper on Brain Microvascular Endothelial Cells and Claudin Via Apoptosis and Oxidative Stress

Increased level of serum asymmetric dimethylarginine in individuals with more severe cognitive impairment, as evaluated using Montreal Cognitive Assessment instead of Mini-Mental State Examination

BACKGROUND

This study aimed to explore the link between cognitive impairment and levels of asymmetric dimethylarginine (ADMA).

METHODS

The study included 172 patients from the Department of Geriatrics and Neurology at the Second Affiliated Hospital of Harbin Medical University. The enrollment period spanned from October 2013 to July 2014. To assess their cognitive function, we used the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). Additionally, automatic biochemical analyzers were employed to measure various biochemical blood indexes, while enzyme-linked immunosorbent assay was used to determine the serum ADMA concentrations.

RESULTS

The participants were categorized into four groups based on the MMSE scale, which reflects cognition (higher scores indicating better cognitive function), and five groups based on the MoCA scale, which also measures cognition (higher scores indicating better cognitive function). Various factors were analyzed for their statistical significance in relation to different cognitive impairment groups determined by each scale. Regarding the MoCA scale, the following factors were found to be statistically significant: Age (P = 0.0001), systolic blood pressure (P = 0.0261), ALT (P = 0.0104), AST (P = 0.0106), endogenous creatinine clearance (P = 0.0006), and serum ADMA concentration (P = 0.0383). For the MMSE scale, the following factors showed statistical significance: Age (P = 0.0008), ALT (P = 0.0002), AST (P = 0.0088), CRP (P = 0.0407), and endogenous creatinine clearance (P = 0.0027). Interestingly, as the scores on the MoCA scale decreased, the serum ADMA concentration increased (P=0.0383), but this trend was not observed in the groups classified based on the MMSE scale (P > 0.05).

CONCLUSION

The level of sensitivity measured by the MoCA scale indicated the presence of initial cognitive dysfunction. The extent of cognitive impairment showed a direct correlation with ADMA levels, indirectly implying a connection between impaired endothelial function and cognitive dysfunction.

Copper (II) increases anti-Proliferative activity of thymoquinone in colon cancer cells by increasing genotoxic, apoptotic, and reactive oxygen species generating effects

Thymoquinone is the main active compound derived from the essential oil of the Nigella sativa plant seed. While thymoquinone is an antioxidant, it has been reported in several studies that thymoquinone has dose-dependent pro-oxidant activity with the Fenton reaction in the presence of transition elements such as iron and copper. This study aimed to investigate cytotoxic, apoptotic, genotoxic, and reactive oxygen species (ROS) generating effects of thymoquinone treated with copper in colon cancer cells. HT-29 cells were treated with pro-oxidant-acting doses of thymoquinone alone and together with the non-toxic dose of Copper (II) Sulfate for 24 h. Cytotoxic, apoptotic, genotoxic, and ROS production activities were analyzed by MTT viability test, Acridine Orange/Ethidium Bromide (AO/EB) staining, alkaline single cell gel electrophoresis and H2DCF-DA assay, respectively. Viability results showed that thymoquinone and copper synergistically affect cancer cells, and DNA damage was increased with the synergic effect. The intracellular ROS was increased when thymoquinone and copper were applied together. Applying redox-active copper (II) with thymoquinone increases DNA damage, apoptosis, and cell death by increasing the amount of intracellular ROS through pro-oxidant activity. Treatments targeting copper-related pathways may open new therapeutic avenues for cancer treatment.

Claudin-12: guardian of the tissue barrier or friend of tumor cells

Tight junctions (TJs) are an important component of cellular connectivity. Claudin family proteins, as a constituent of TJs, determine their barrier properties, cell polarity and paracellular permeability. Claudin-12 is an atypical member of the claudin family, as it belongs to the group of non-classical claudins that lack a PDZ-binding domain. It has been shown that claudin-12 is involved in paracellular Ca2+ transients and it is present in normal and hyperplastic tissues in addition to neoplastic tissues. Dysregulation of claudin-12 expression has been reported in various cancers, suggesting that this protein may play an important role in cancer cell migration, invasion, and metastasis. Some studies have shown that claudin-12 gene functions as a tumor suppressor, but others have reported that overexpression of claudin-12 significantly increases the metastatic properties of various tumor cells. Investigating this dual role of claudin-12 is of utmost importance and should therefore be studied in detail. The aim of this review is to provide an overview of the information available to date on claudin-12, including its structure, expression in various tissues and substances that may affect it, with a final focus on its role in cancer.

The Basic Requirement of Tight Junction Proteins in Blood-Brain Barrier Function and Their Role in Pathologies

This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways.

Effects of CuSO4 on hepatic mitochondrial function, biogenesis and dynamics in mice

Copper is an essential trace element for animal. Excessive intake of copper will cause a large accumulation of copper in the body, especially in the liver, and induce hepatotoxicity, however, there are few studies on the effects of copper on hepatic mitochondrial biogenesis and mitochondrial dynamics. In this study, mice were treated with different doses of CuSO4 (0, 10, 20, and 40 mg/kg) for 21 and 42 days by gavage. The results verified that CuSO4 decreased the content of mitochondrial respiratory chain complexes I-IV in mouse liver. CuSO4 treatment resulted the decrease in the protein and mRNA expression levels of PGC-1α, TFAM, and NRF1, which were the mitochondrial biogenesis regulator proteins. Meanwhile, the proteins involved in mitochondrial fusion were reduced by CuSO4 , such as Mfn1 and Mfn2, however, mitochondrial fission proteins Drip1 and Fis1 were significantly increased. Abovementioned results show that CuSO4 could induce mitochondria damage in the liver of mice, and mitochondrial biogenesis and mitochondrial dynamics are involved in the molecular mechanism of CuSO4 -induced hepatotoxicity.

Protein Carbonyl, Lipid Peroxidation, Glutathione and Enzymatic Antioxidant Status in Male Wistar Brain Sub-regions After Dietary Copper Deficiency

Copper a quintessential transitional metal is required for development and function of normal brain and its deficiency has been associated with impairments in brain function. The present study investigates the effects of dietary copper deficiency on brain sub-regions of male Wistar rats for 2-, 4- and 6-week. Pre-pubertal rats were divided into four groups: negative control (NC), copper control (CC), pairfed (PF) and copper deficient (CD). In brain sub regions total protein concentration, glutathione concentration and Cu-Zn SOD activity were down regulated after 2-, 4- and 6 weeks compared to controls and PF groups. Significant increase in brain sub regions was observed in protein carbonyl and lipid peroxidation concentration as well as total SOD, Mn SOD and catalase activities after 2-, 4- and 6 weeks of dietary copper deficiency. Experimental evidences indicate that impaired copper homeostasis has the potential to generate reactive oxygen species enhancing the susceptibility to oxidative stress by inducing up- and down-regulation of non-enzymatic and enzymatic profile studied in brain sub regions causing loss of their normal function which can consequently lead to deterioration of cell structure and death if copper deficiency is prolonged.

Copper neurotoxicity: Induction of cognitive dysfunction: A review

Cognitive dysfunction occurs mainly in certain diseases and in the pathological process of aging. In addition to this, it is also widespread in patients undergoing anesthesia, surgery, and cancer chemotherapy. Neuroinflammation, oxidative stress, mitochondrial dysfunction, impaired synaptic plasticity, and lack of neurotrophic support are involved in copper-induced cognitive dysfunction. In addition, recent studies have found that copper mediates cuproptosis and adversely affects cognitive function. Cuproptosis is a copper-dependent, lipoylated mitochondrial protein-driven, non-apoptotic mode of regulated cell death, which provides us with new avenues for identifying and treating related diseases. However, the exact mechanism by which cuproptosis induces cognitive decline is still unclear, and this has attracted the interest of many researchers. In this paper, we analyzed the pathological mechanisms and therapeutic targets of copper-associated cognitive decline, mainly in the context of neurodegenerative diseases, psychiatric and psychological disorders, and diabetes mellitus.

Among Gerontogens, Heavy Metals Are a Class of Their Own: A Review of the Evidence for Cellular Senescence

Advancements in modern medicine have improved the quality of life across the globe and increased the average lifespan of our population by multiple decades. Current estimates predict by 2030, 12% of the global population will reach a geriatric age and live another 3-4 decades. This swelling geriatric population will place critical stress on healthcare infrastructures due to accompanying increases in age-related diseases and comorbidities. While much research focused on long-lived individuals seeks to answer questions regarding how to age healthier, there is a deficit in research investigating what aspects of our lives accelerate or exacerbate aging. In particular, heavy metals are recognized as a significant threat to human health with links to a plethora of age-related diseases, and have widespread human exposures from occupational, medical, or environmental settings. We believe heavy metals ought to be classified as a class of gerontogens (i.e., chemicals that accelerate biological aging in cells and tissues). Gerontogens may be best studied through their effects on the "Hallmarks of Aging", nine physiological hallmarks demonstrated to occur in aged cells, tissues, and bodies. Evidence suggests that cellular senescence-a permanent growth arrest in cells-is one of the most pertinent hallmarks of aging and is a useful indicator of aging in tissues. Here, we discuss the roles of heavy metals in brain aging. We briefly discuss brain aging in general, then expand upon observations for heavy metals contributing to age-related neurodegenerative disorders. We particularly emphasize the roles and observations of cellular senescence in neurodegenerative diseases. Finally, we discuss the observations for heavy metals inducing cellular senescence. The glaring lack of knowledge about gerontogens and gerontogenic mechanisms necessitates greater research in the field, especially in the context of the global aging crisis.

Sex-specific associations of early postnatal blood copper levels with neurodevelopment at 2 years of age

Copper (Cu) is an essential trace element; however, it can be harmful in excess. Previous studies have shown that prenatal Cu levels may affect childhood neurodevelopment; however, studies focused on early postnatal Cu levels are limited. We studied 843 children born in Wuhan City and investigated the associations between early life Cu levels and neurodevelopment in 2-year-old children. Blood samples collected from children at 12 and 24 months of age were used to analyze Cu levels. Neurodevelopment was scored using the Bayley Scale of Children at 24 months of age. We found that a higher Cu level at 12 months of age was positively associated with mental development index (MDI) in boys (β = 6.75, 95 %CI: 1.12, 12.38). Further non-linear analysis showed an inverted U-shape association between Cu level at 20 months and PDI in boys, indicating that Cu levels may have an optimal concentration for neurodevelopment (p for overall association = 0.01, p for non-linear association < 0.01). In addition, all meaningful results mentioned above were observed only in boys, and a statistically significant sex-related modifying effect was observed (p < 0.05). In conclusion, this study repeated measures early life Cu levels and suggested sex-specific associations between early life Cu levels and neurodevelopment in 2-year-old children.

Role of Copper on Mitochondrial Function and Metabolism

Copper is essential for life processes like energy metabolism, reactive oxygen species detoxification, iron uptake, and signaling in eukaryotic organisms. Mitochondria gather copper for the assembly of cuproenzymes such as the respiratory complex IV, cytochrome c oxidase, and the antioxidant enzyme superoxide dismutase 1. In this regard, copper plays a role in mitochondrial function and signaling involving bioenergetics, dynamics, and mitophagy, which affect cell fate by means of metabolic reprogramming. In mammals, copper homeostasis is tightly regulated by the liver. However, cellular copper levels are tissue specific. Copper imbalances, either overload or deficiency, have been associated with many diseases, including anemia, neutropenia, and thrombocytopenia, as well as tumor development and cancer aggressivity. Consistently, new pharmacological developments have been addressed to reduce or exacerbate copper levels as potential cancer therapies. This review goes over the copper source, distribution, cellular uptake, and its role in mitochondrial function, metabolic reprograming, and cancer biology, linking copper metabolism with the field of regenerative medicine and cancer.

The Immunomodulatory Potential of Copper and Silver Based Self-Assembled Metal Organic Biohybrids Nanomaterials in Cancer Theranostics

Copper high aspect ratio structures (CuHARS) and silver cystine nanoparticles (AgCysNPs) are two unique micro/nano particles under study here that show extensive anti-cancer effects on a glioma tumor cell line. These micro/nano particles have shown potent toxicity in the presence of inflammatory stimulus (combination of tumor necrosis factor, [TNF] and lipo-polysaccharide, LPS). CuHARS with a concentration of 20 μg/ml uniquely increased the catalytic generation of nitric oxide (NO), an important contributor in the immune system. This NO was generated in a cell culture tumor microenvironment (TME) in the presence of 25 µM S-nitrosothiol (cysteine-NO) and the inflammatory stimulus. CuHARS increased the NO production by 68.75% when compared to untreated glioma cells with CysNO and inflammatory stimulus. The production of NO was significantly higher under similar circumstances in the case of normal primary structural cells like brain microvascular endothelial cells (BMVECs). The production of NO by BMVECs went up by 181.25% compared to glioma cells. This significant increase in the NO concentration could have added up to tumorigenesis but the anti-cancer effect of CuHARS was prominent enough to lower down the viability of glioma cells by approximately 20% and increased the metabolism of structural cells, BMVECs by approximately 200%. The immunomodulatory effect of NO in the TME under these circumstances in the presence of the novel micro/nano material, CuHARS has risen up compared to the effect of inflammatory stimulus alone. The potency and specific nature of these materials toward tumor cells may make them suitable candidates for cancer treatment. Successive treatment of CuHARS to glioma cells also proved to be an effective approach considering the decrease in the total count of cells by 11.84 fold in case of three successive treatments compared to a single dose which only decreased the cell count by 2.45 fold showing the dose-dependent increasing toxicity toward glioma cells. AgCysNPs are another potent nanomaterial which also proved its significant toxic nature toward tumor cell lines as demonstrated here, but their immunomodulatory response is still unclear and needs to be explored further.

Curcumin Ameliorates Copper-Induced Neurotoxicity Through Inhibiting Oxidative Stress and Mitochondrial Apoptosis in SH-SY5Y Cells

Impaired homeostasis of copper has been linked to different pathophysiological mechanisms in neurodegenerative diseases and oxidative injury has been proposed as the main mechanism. This study aims to use curcumin, a widely used antioxidative and anti-apoptotic agent, to exert the neuroprotective effect against copper in vitro and illuminate the underlying mechanism. The effect of curcumin was examined by using a cell counting kit-8 assay, flow cytometry, immunofluorescence, spectrophotometer, and western blot. Results revealed that after pretreatment with curcumin for 3 h, copper-induced toxicity and apoptosis show a significant decline. Further experiments showed that curcumin not only decreased the production of ROS and MDA but also increased the activities of the ROS scavenging enzymes SOD and CAT. Moreover, curcumin treatment alleviated the decrease in mitochondrial membrane potential and the nuclear translocation of cytochrome c induced by copper. The protein levels of pro-caspase 3, pro-caspase 9, and PARP1 were up-regulated and the Bax/Bcl-2 ratio was down-regulated in the presence of curcumin. Taken together, our study demonstrates that curcumin has neuroprotective properties against copper in SH-SY5Y cells and the potential mechanisms might be related to oxidative stress and mitochondrial apoptosis.

Oxidative stress, apoptosis and inflammatory responses involved in copper-induced pulmonary toxicity in mice

At present, there are few studies focused on the relationship between copper (Cu) and oxidative stress, apoptosis, or inflammatory responses in animal and human lungs. This study was conducted to explore the effects of Cu on pulmonary oxidative stress, apoptosis and inflammatory responses in mice orally administered with 0 mg/kg (control), 10 mg/kg, 20 mg/kg, and 40 mg/kg of CuSO₄ for 42 days. The results showed that CuSO₄ increased ROS production, and MDA, 8-OHdG and NO contents as well as iNOS activities and mRNA expression levels. Meanwhile, CuSO₄ reduced the activities and mRNA expression levels of antioxidant enzymes (GSH-Px, CAT, and SOD) and GSH contents, and ASA and AHR abilities. Also, CuSO₄ induced apoptosis, which was accompanied by decreasing Bcl-2, Bcl-xL mRNA expression levels and protein expression levels, and increasing Bax, Bak, cleaved-caspase-3, cleaved-caspase-9 mRNA, and protein expression levels, and Bax/Bcl-2 ratio. Concurrently, CuSO₄ caused inflammation by increasing MPO activities and activating the NF-κB signalling pathway, and down-regulating the mRNA and protein expression levels of anti-inflammatory cytokines (IL-2, IL-4, IL-10). In conclusion, the abovementioned findings demonstrated that over 10 mg/kg CuSO₄ can cause oxidative stress, apoptosis, and inflammatory responses, which contribute to pulmonary lesions and dysfunction in mice.

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.

Catalytic Generation of Nitric Oxide from Poly(ε-caprolactone)/Phosphobetainized Keratin Mats for a Vascular Tissue Engineering Scaffold

Tissue-engineered vascular graft (TEVG) is a promising alternative to meet the clinical demand of organ shortages. Herein, human hair keratin was extracted by the reduction method, followed by modification with zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) through thiol-Michael addition to improve blood clotting nature. Then, phosphobetainized keratin (PK) was coelectrospun with poly(ε-caprolactone) (PCL) to afford PCL/PK mats with a ratio of 7:3. The surface morphology, chemical structure, and wettability of these mats were characterized. The biocomposite mats selectively enhanced adhesion, migration, and growth of endothelial cells (ECs) while suppressed proliferation of smooth muscle cells (SMCs) in the presence of glutathione (GSH) and GSNO due to the catalytic generation of NO. In addition, these mats exhibited good blood anticoagulant activity by reducing platelet adhesion, prolonging blood clotting time, and inhibiting hemolysis. Taken together, these NO-generating PCL/PK mats have potential applications as a scaffold for vascular tissue engineering with rapid endothelialization and reduced SMC proliferation.

Different Sources of Copper Effect on Intestinal Epithelial Cell: Toxicity, Oxidative Stress, and Metabolism

Copper (Cu) is widely used in the swine industry to improve the growth performance of pigs. However, high doses of copper will induce cell damage and toxicity. The aim of this study was to evaluate toxicity, bioavailability, and effects on metabolic processes of varying copper sources using porcine intestinal epithelial cells (IPEC-J2) as a model. The IPEC-J2 were treated with two doses (30 and 120 μM) of CuSO₄, Cu Glycine (Cu-Gly), and Cu proteinate (Cu-Pro) for 10 h, respectively. Cell damage and cellular copper metabolism were measured by the changes in cell viability, copper uptake, oxidative stress biomarkers, and gene/protein expression levels. The results showed that cell viability and ratio of reduced and oxidized glutathione (GSH/GSSG) decreased significantly in all treatment groups; intracellular copper content increased significantly in all treatment groups; total superoxide dismutase (SOD) activity increased significantly in the 120 μM exposed groups; SOD1 protein expression levels were significantly upregulated in 30 μM Cu-Pro, 120 μM Cu-Gly, and 120 μM Cu-Pro treatment groups; intracellular reactive oxygen species (ROS) generation and malondialdehyde (MDA) content increased significantly in 30 μM treatment groups and 120 μM CuSO₄ treatment group. CTR1 and ATP7A gene expression were significantly downregulated in the 120 μM exposed groups. While upregulation of ATOX1 expression was observed in the presence of 120 μM Cu-Gly and Cu-Pro. ASCT2 gene expression was significantly upregulated after 120 μM Cu-Glycine and CuSO₄ exposure, and PepT1 gene expression was significantly upregulated after Cu-Pro exposure. In addition, CTR1 protein expression level decreased after 120 μM CuSO₄ and Cu-Gly exposure. PepT1 protein expression level was only upregulated after 120 μM Cu-Pro exposure. These findings indicated that extra copper supplementation can induce intestinal epithelial cell injury, and different forms of copper may have differing effects on cell metabolism.

Advances in the mechanism of high copper diets in restraining pigs growth

High copper feed has been widely used as an inexpensive and highly effective feed additive to promote growth performance of pigs. However, long-term feeding of high copper feed may reduce the growth-promoting effects of copper, time-dependent accumulation of copper in animal tissues and organs, and copper toxicity thereby reducing the growth performance of pigs. Due to the widespread effects of high copper supplementation in animals' diets, the benefits and drawbacks of high copper feeding in pigs have been reported in several studies. Meanwhile, few of these studies have systematically described the mechanism by which high copper diets restrain pig growth. Therefore, to address the concerns and give a better understanding of the mechanism of high copper diet in restraining pig growth in different systems, this paper reviews the research progress of long-term supplementation of high copper on the growth of pigs and provides some suggestions and further research directions.

A positron-emission tomography (PET)/magnetic resonance imaging (MRI) platform to track in vivo small extracellular vesicles

Here we report a two-step surface modification methodology to radiolabel small extracellular vesicles (SEVs) with 64CuCl2 for PET/MRI imaging. The modification did not change or damage the morphology, surface receptor proteins and internal RNA content. Radiolabeled SEVs could be detected in organs with low accumulation such as the brain (0.4-0.5% ID g-1) and their brain location determined by MRI.