Nano-Mediated Molecular Targeting in Diagnosis and Mitigation of Wilson Disease

Wilson disease, a rare genetic disorder resulting from mutations in the ATP7B gene disrupts copper metabolism, leading to its harmful accumulation in hepatocytes, the brain, and other organs. It affects roughly 1 in 30,000 individuals, with 1 in 90 being gene carriers. Beyond gene mutations, the disease involves complex factors contributing to copper imbalance. Ongoing research seeks to unravel intricate molecular pathways, offering fresh insights into the disease's mechanisms. Simultaneously, there is a dedicated effort to develop effective therapeutic strategies. Nanotechnology-driven formulations are showing promise for both treatment and early diagnosis of Wilson disease. This comprehensive review covers the entire spectrum of the condition, encompassing pathophysiology, potential biomarkers, established and emerging therapies, ongoing clinical trials, and innovative nanotechnology applications. This multifaceted approach holds the potential to improve our understanding, diagnosis, and management of Wilson's disease, which remains a challenging and potentially life-threatening disorder.

Phenothiazine appended thiophene derivative: a trilateral approach to copper ion detection in living cells and aqueous samples

This research paper unveils a fluorescent probe (PTZ-SCN) engineered for the specific detection of Cu2+, featuring a 10-ethyl-10H-phenothiazine-3-carbaldehyde and 2-(thiophen-2-yl) acetonitrile moiety. The fluorescence sensing behavior of PTZ-SCN towards various metal cations was scrutinized in CH3CN : HEPES (9 : 1) buffer aqueous solution. The UV absorbance of PTZ-SCN displayed a distinct red shift in the presence of Cu2+ cations, whereas other metal cations did not cause any interference. Similarly, the fluorescence emission of the probe was also only quenched by Cu2+ cations. The limit of detection (LOD) was calculated as 1.0461 × 10-8 M. PTZ-SCN showed the ability to identify Cu2+ using the colorimetric method, the fluorometric method and even through visual observation in a trilateral detection. We studied the recognition mechanism of PTZ-SCN for Cu2+ using 1H-NMR, HRMS analysis, and time-dependent density functional theory (TDDFT) calculations. Furthermore, our study encompassed the investigation of PTZ-SCN's practical applicability, bridging the gap from research to real-world implementation. This was achieved by employing test strips and water samples for the detection of Cu2+. Additionally, the PTZ-SCN probe's low cytotoxicity and effective imaging properties for Cu2+ in living cells were confirmed, indicating that PTZ-SCN shows the potential to serve as a promising probe for detecting Cu2+in vivo.

Hepatic depletion of nucleolar protein mDEF causes excessive mitochondrial copper accumulation associated with p53 and NRF1 activation

Copper is an essential component in the mitochondrial respiratory chain complex IV (cytochrome c oxidases). However, whether any nucleolar factor(s) is(are) involved in regulating the mitochondrial copper homeostasis remains unclear. The nucleolar localized Def-Capn3 protein degradation pathway cleaves target proteins, including p53, in both zebrafish and human nucleoli. Here, we report that hepatic depletion of mDEF in mice causes an excessive copper accumulation in the mitochondria. We find that mDEF-depleted hepatocytes show an exclusion of CAPN3 from the nucleoli and accumulate p53 and NRF1 proteins in the nucleoli. Furthermore, we find that NRF1 is a CAPN3 substrate. Elevated p53 and NRF1 enhances the expression of Sco2 and Cox genes, respectively, to allow more copper acquirement in the mDef^loxp/loxp, Alb:Cre mitochondria. Our findings reveal that the mDEF-CAPN3 pathway serves as a novel mechanism for regulating the mitochondrial copper homeostasis through targeting its substrates p53 and NRF1.

The genetic basis of adaptation to copper pollution in Drosophila melanogaster

Introduction: Heavy metal pollutants can have long lasting negative impacts on ecosystem health and can shape the evolution of species. The persistent and ubiquitous nature of heavy metal pollution provides an opportunity to characterize the genetic mechanisms that contribute to metal resistance in natural populations. Methods: We examined variation in resistance to copper, a common heavy metal contaminant, using wild collections of the model organism Drosophila melanogaster. Flies were collected from multiple sites that varied in copper contamination risk. We characterized phenotypic variation in copper resistance within and among populations using bulked segregant analysis to identify regions of the genome that contribute to copper resistance. Results and Discussion: Copper resistance varied among wild populations with a clear correspondence between resistance level and historical exposure to copper. We identified 288 SNPs distributed across the genome associated with copper resistance. Many SNPs had population-specific effects, but some had consistent effects on copper resistance in all populations. Significant SNPs map to several novel candidate genes involved in refolding disrupted proteins, energy production, and mitochondrial function. We also identified one SNP with consistent effects on copper resistance in all populations near CG11825, a gene involved in copper homeostasis and copper resistance. We compared the genetic signatures of copper resistance in the wild-derived populations to genetic control of copper resistance in the Drosophila Synthetic Population Resource (DSPR) and the Drosophila Genetic Reference Panel (DGRP), two copper-naïve laboratory populations. In addition to CG11825, which was identified as a candidate gene in the wild-derived populations and previously in the DSPR, there was modest overlap of copper-associated SNPs between the wild-derived populations and laboratory populations. Thirty-one SNPs associated with copper resistance in wild-derived populations fell within regions of the genome that were associated with copper resistance in the DSPR in a prior study. Collectively, our results demonstrate that the genetic control of copper resistance is highly polygenic, and that several loci can be clearly linked to genes involved in heavy metal toxicity response. The mixture of parallel and population-specific SNPs points to a complex interplay between genetic background and the selection regime that modifies the effects of genetic variation on copper resistance.

Properties of recombinant extracellular N-terminal domain of human high-affinity copper transporter 1 (hNdCTR1) and its interactions with Cu(II) and Ag(I) ions

High-affinity copper transporter 1 (CTR1) is a key link in the transfer of copper (Cu) from the extracellular environment to the cell. Violation in the control system of its expression, or mutations in this gene, cause a global copper imbalance. However, the mechanism of copper transfer via CTR1 remains unclear. It has been shown that transformed bacteria synthesizing the fused GB1-NdCTR become resistant to toxic silver ions. According to UV-Vis spectrophotometry and isothermal titration calorimetry, electrophoretically pure GB1-NdCTR specifically and reversibly binds copper and silver ions, and binding is associated with aggregation. Purified NdCTR1 forms SDS-resistant oligomers. The link between nontrivial properties of NdCTR1 and copper import mechanism from extracellular space, as well as potential chelating properties of NdCTR1, are discussed.

Re-evaluation of the existing health-based guidance values for copper and exposure assessment from all sources

Copper is an essential micronutrient and also a regulated product used in organic and in conventional farming pest management. Both deficiency and excessive exposure to copper can have adverse health effects. In this Scientific Opinion, the EFSA 2021 harmonised approach for establishing health-based guidance values (HBGVs) for substances that are regulated products and also nutrients was used to resolve the divergent existing HBGVs for copper. The tightly regulated homeostasis prevents toxicity manifestation in the short term, but the development of chronic copper toxicity is dependent on copper homeostasis and its tissue retention. Evidence from Wilson disease suggests that hepatic retention is indicative of potential future and possibly sudden onset of copper toxicity under conditions of continuous intake. Hence, emphasis was placed on copper retention as an early marker of potential adverse effects. The relationships between (a) chronic copper exposure and its retention in the body, particularly the liver, and (b) hepatic copper concentrations and evidence of toxicity were examined. The Scientific Committee (SC) concludes that no retention of copper is expected to occur with intake of 5 mg/day and established an Acceptable Daily Intake (ADI) of 0.07 mg/kg bw. A refined dietary exposure assessment was performed, assessing contribution from dietary and non-dietary sources. Background copper levels are a significant source of copper. The contribution of copper from its use as plant protection product (PPP), food and feed additives or fertilisers is negligible. The use of copper in fertilisers or PPPs contributes to copper accumulation in soil. Infant formula and follow-on formula are important contributors to dietary exposure of copper in infants and toddlers. Contribution from non-oral sources is negligible. Dietary exposure to total copper does not exceed the HBGV in adolescents, adults, elderly and the very elderly. Neither hepatic copper retention nor adverse effects are expected to occur from the estimated copper exposure in children due to higher nutrient requirements related to growth.

Atp7b-dependent choroid plexus dysfunction causes transient copper deficit and metabolic changes in the developing mouse brain

Copper (Cu) has a multifaceted role in brain development, function, and metabolism. Two homologous Cu transporters, Atp7a (Menkes disease protein) and Atp7b (Wilson disease protein), maintain Cu homeostasis in the tissue. Atp7a mediates Cu entry into the brain and activates Cu-dependent enzymes, whereas the role of Atp7b is less clear. We show that during postnatal development Atp7b is necessary for normal morphology and function of choroid plexus (ChPl). Inactivation of Atp7b causes reorganization of ChPl' cytoskeleton and cell-cell contacts, loss of Slc31a1 from the apical membrane, and a decrease in the length and number of microvilli and cilia. In ChPl lacking Atp7b, Atp7a is upregulated but remains intracellular, which limits Cu transport into the brain and results in significant Cu deficit, which is reversed only in older animals. Cu deficiency is associated with down-regulation of Atp7a in locus coeruleus and catecholamine imbalance, despite normal expression of dopamine-β-hydroxylase. In addition, there are notable changes in the brain lipidome, which can be attributed to inhibition of diacylglyceride-to-phosphatidylethanolamine conversion. These results identify the new role for Atp7b in developing brain and identify metabolic changes that could be exacerbated by Cu chelation therapy.

Hepatic ultrastructural features distinguish paediatric Wilson disease from NAFLD and autoimmune hepatitis

BACKGROUND AND AIMS

Wilson disease (WD) has diverse presentations that frequently mimic other liver diseases. Distinguishing WD from non-alcoholic fatty liver disease (NAFLD) and autoimmune hepatitis (AIH), can be difficult and has critical implications for medical management. This study aimed to examine the utility of histological features of WD in children compared to those with NAFLD and AIH.

METHODS

A review of liver biopsy slides was performed in children with a clinical and/or genetic diagnosis of WD, seen at the Hospital for Sick Children between 1981 and 2019 and compared to controls with NAFLD and AIH. 37 children with WD and 37 disease controls (20 NAFLD; 17 AIH) were included. Three pathologists, blind to clinical details and diagnosis, reviewed all liver biopsies to reach consensus. Clinical and histopathologic features were compared between groups.

RESULTS

Most WD cases displayed steatosis or steatohepatitis on histology (34/37), active AIH-pattern in 1 and inactive cirrhosis in 2 cases. Electron microscopy (EM) findings of mitochondrial abnormalities including dilated tips of cristae, pleomorphism, membrane duplication and dense matrix were more frequent in the WD group as compared to disease controls (p < 0.0001). In WD, dilated tips of mitochondrial cristae had a sensitivity of 91% and specificity of 86%, best among EM features.

CONCLUSIONS

Light microscopic findings display considerable overlap among children with WD, NAFLD and AIH. Ultrastructural findings of mitochondrial abnormalities are important to distinguish WD from NAFLD and AIH. EM examination should be considered essential in the diagnostic work-up of paediatric liver biopsies.

Nutritional Status and Body Composition in Wilson Disease: A Cross-Sectional Study From China

Background: Abnormal nutritional status is frequently seen in patients with chronic diseases. To date, no study has investigated the detailed characteristics of abnormal nutritional status among Wilson's disease (WD) patients in the Chinese cohort. This study aimed to describe the nutritional status of WD patients, with a particular focus on the differences between patients with different phenotypes.

Methods: The study subjects comprised 119 healthy controls, 129 inpatients (hepatic subtype, n = 34; neurological subtype, n = 95) who were being treated at the affiliated hospital of the Institute of Neurology, Anhui University of Chinese Medicine. All of the subjects were assessed for body composition by using bioelectrical impedance analysis. All WD patients received anthropometry, nutritional risk screening 2002 (NRS2002), and laboratory test (hemocyte and serum biomarkers) additionally.

Results: Compared with healthy controls, the fat mass and rate of total body and trunk were significantly higher in WD patients (P < 0.001), the muscle and skeletal muscle mass of total body and trunk were significantly lower in WD patients (P < 0.001). Compared with hepatic subtype patients, the fat mass and rate of total body, trunk, and limbs were significantly lower in neurological subtype patients (P<0.01); while there were no significant differences in muscle and skeletal muscle between these two subtypes. The overall prevalence of abnormal nutritional status in WD patients was 43.41% (56/129). The prevalence of high-nutritional risk and overweight in WD patients was 17.83% (23 of 129) and 25.58% (33 of 129), respectively. Compare with patients with high nutritional risk, macro platelet ratio, alkaline phosphatase, the basal metabolic rate (p < 0.05), creatinine, trunk fat rate (p < 0.01) and appendicular skeletal muscle mass (p < 0.001) were significantly higher in patients without nutritional risk (p < 0.001). Patients with a high nutritional risk tend to have a lower cholinesterase concentration (x² = 4.227, p < 0.05).

Conclusion: Both patients with H-subtype and N-subtype are prone to have an abnormal nutritional status. Longitudinal studies are required to investigate if nutritional status and body composition could reflect prognosis in WD patients, and which of these body composition indexes contribute to malnutrition and worse prognosis.

Tracking Labile Copper Fluctuation In Vivo/Ex Vivo: Design and Application of a Ratiometric Near-Infrared Fluorophore Derived from 4-Aminostyrene-Conjugated Boron Dipyrromethene

Specimen differences, tissue-dependent background fluorescence and scattering, and deviated specimen position and sensor concentration make optical imaging for labile copper fluctuation in animals questionable, and a signal comparison between specimens is infeasible. We proposed ratiometric optical imaging as an alternative to overcome these disadvantages, and a near-infrared (NIR) ratiometric sensor, BDPS1, was devised therefore by conjugating boron dipyrromethene (BODIPY) with 4-aminostyrene and modifying the 4-amino group as a Cu+ chelator. BDPS1 possessed an excitation ratiometric copper-sensing ability to show the ratio of NIR emission (710 nm) upon excitation at 600 nm to that at 660 nm, Fex600/Fex660, increasing from 2.8 to 10.7. This sensor displayed still the opposite copper response of its internal charge transfer (ICT; 670 nm) and local (581 nm) emission bands. Ratiometric imaging with this sensor disclosed a higher labile copper region near the nucleus apparatus, and HEK-293T cells were more sensitive to copper incubation than MCF-7 cells. Dual excitation ratiometric imaging with this sensor realized tracking of labile copper fluctuation in mice, and the whole-body imaging found that tail intravenous injection of CUTX-101, a therapeutical agent for Menkes disease, led to a distinct labile copper increase in the upper belly. The ex vivo imaging of the resected viscera of mice revealed that CUTX-101 injection enhanced the labile copper level in the liver, intestine, lung, and gall bladder in sequence, yet the kidney, heart, and spleen showed almost no response. This study indicated that modifying BODIPY as an extended ICT fluorophore, with its electron-donating group being derived as a metal chelator, is an effective design rationale of NIR ratiometric sensors for copper tracking in vivo/ex vivo.

Characterization of a fluorescent 1,8-naphthalimide-functionalized PAMAM dendrimer and its Cu(ii) complexes as cytotoxic drugs: EPR and biological studies in myeloid tumor cells

The activity and interacting ability of a polyamidoamine (PAMAM) dendrimer modified with 4-N-methylpiperazine-1,8-naphthalimide units (termed D) and complexed by Cu(ii) ions, towards healthy and cancer cells were studied. Comparative electron paramagnetic resonance (EPR) studies of the Cu(ii)-D complex are presented: coordination mode, chemical structure, flexibility and stability of these complexes, in the absence and presence of myeloid cancer cells and peripheral blood mononuclear cells (PBMC). The interactions of Cu(ii) ions in the biological media at different equilibrium times were studied, highlighting different stability and interacting conditions with the cells. Furthermore, flow cytometry and confocal analysis, trace the peculiar properties of the dendrimers in PBMC and U937 cells. Indeed, a new probe (Fly) was used as a potential fluorescent tool for biological imaging of Cu(ii). The study highlights that dendrimer and, mainly, the Cu(ii) metallodendrimer are cytotoxic agents for the cells, specifically for U937 tumor cells, inducing mitochondrial dysfunction, ROS increase and lysosome involvement. The metallodendrimer shows antitumor selectivity, fewer affecting healthy PBMC, inducing a massive apoptotic cell death on U937 cells, in line with the high stability of this complex, as verified by EPR studies. The results underline the potentiality of this metallodendrimer to be used as anticancer drug.

Anchoring zinc-doped carbon dots on a paper-based chip for highly sensitive fluorescence detection of copper ions

In this work, zinc-doped carbon dots (Zn-CDs) were anchored on a three-dimensional wheel type paper-based microfluidic chip, and were decorated with 6-mercaptonicotinic acid (MNA) and L-cysteine (L-Cys) for highly sensitive and rapid fluorescence detection of Cu²⁺. Zn-CDs were first anchored on paper through the amide bonds between the carboxyl groups of the Zn-CDs and the amino groups of the paper. Afterwards, Zn-CDs were decorated with MNA and L-Cys, effectively preventing the Zn-CDs from aggregation. The nitrogen atom on the pyridine ring and the carboxylic acid groups in MNA and L-Cys coordinated with Cu²⁺ to form a nonfluorescent ground-state complex, causing the fluorescence quenching of the Zn-CDs. The three-dimensional rotary design could simplify the operation process and achieve simultaneous analysis of multiple samples with different concentrations. Under optimal conditions, the fluorescent sensor exhibits linear response for the determination of Cu²⁺ in the range from 0.1 to 60 μg L^-1 with the detection limit (LOD) of 0.018 μg L^-1. The proposed strategy provides a novel way for the highly sensitive detection of Cu²⁺ in a complex water environment.

Inhibition of ASIC1a-Mediated ERS Improves the Activation of HSCs and Copper Transport Under Copper Load

Hepatolenticular degeneration (HLD) is an autosomal recessive genetic disease caused by the toxic accumulation of copper in the liver. Excessive copper will disrupt the redox balance in cells and tissues, causing ischemia, hypoxia, and inflammation. Acid-sensitive ion channel 1a is a cationic channel activated by extracellular acid and allowing Ca²⁺ and Na⁺ to flow into cells. Its expression appears in inflammation, arthritis, fibrotic tissue, and damaged environment, but its role in hepatolenticular degeneration has not been studied. This study established a Wistar rat model of high copper accumulation and used CuSO₄ to induce the activation of HSC-T6 in an in vitro experiment. In vivo, Wistar rats were examined to determine the serum copper concentration, serum ALT and AST activities, and liver copper accumulation, and liver tissue HE staining and immunohistochemical analyses were conducted. The expression of ASIC1a, α-SMA, Collagen-Ι, GRP78, XBP1, ATP7B, and CCS were detected. Besides, immunofluorescence technology can detect the expression of the phosphorylated protein in vitro. It is suggested that ASIC1a is involved in the quality control of the endoplasmic reticulum, which degrades mutant ATP7B and increases the accumulation of copper. After blocking or silencing the expression of ASIC1a, ELISA can detect the level of inflammatory factors, the expression of endoplasmic reticulum stress-related factors, and ATP7B was improved in a higher copper environment reduction of copper deposition was observed in liver Timm’s staining. Collectively, we conclude that ASIC1a is involved in the HSC activation induced by copper accumulation and promotes the occurrence of hepatolenticular fibrosis.

Retromer retrieves the Wilson disease protein ATP7B from endolysosomes in a copper-dependent manner

The Wilson disease protein, ATP7B maintains copper (herein referring to the Cu+ ion) homeostasis in the liver. ATP7B traffics from trans-Golgi network to endolysosomes to export excess copper. Regulation of ATP7B trafficking to and from endolysosomes is not well understood. We investigated the fate of ATP7B after copper export. At high copper levels, ATP7B traffics primarily to acidic, active hydrolase (cathepsin-B)-positive endolysosomes and, upon subsequent copper chelation, returns to the trans-Golgi network (TGN). At high copper, ATP7B colocalizes with endolysosomal markers and with a core member of retromer complex, VPS35. Knocking down VPS35 did not abrogate the copper export function of ATP7B or its copper-responsive anterograde trafficking to vesicles; rather upon subsequent copper chelation, ATP7B failed to relocalize to the TGN, which was rescued by overexpressing wild-type VPS35. Overexpressing mutants of the retromer complex-associated proteins Rab7A and COMMD1 yielded a similar non-recycling phenotype of ATP7B. At high copper, VPS35 and ATP7B are juxtaposed on the same endolysosome and form a large complex that is stabilized by in vivo photoamino acid labeling and UV-crosslinking. We demonstrate that retromer regulates endolysosome to TGN trafficking of copper transporter ATP7B in a manner that is dependent upon intracellular copper.

Switching of C-C and C-N Coupling/Cleavage for Hypersensitive Detection of Cu2+ by a Catalytically Mediated 2-Aminoimidazolyl-Tailored Six-Membered Rhodamine Probe

A robust six-membered rhodamine spirocyclic probe 1 containing a versatile 2-aminoimidazolyl moiety was elaborately designed and synthesized via an attractive C-C and C-N coupling strategy to improve the performance in the detection of ultralow transition metal ions. Probe 1 allowed the highly hypersensitive detection of Cu²⁺ with a superior picomolar limit of detection (35 pM) and nanomolar naked-eye performance (80 nM) via the switching of C-C and C-N cleavage by a catalytic hydrolysis mode.

Copper Ionophores as Novel Antiobesity Therapeutics

The therapeutic utility of the copper ionophore disulfiram was investigated in a diet-induced obesity mouse model (C57BL/6J background), both through administration in feed (0.05 to 1% (w/w)) and via oral gavage (150 mg/kg) for up to eight weeks. Mice were monitored for body weight, fat deposition (perigonadal fat pads), metabolic changes (e.g., glucose dyshomeostasis) and pathologies (e.g., hepatic steatosis, hyperglycaemia and hypertriglyceridemia) associated with a high-fat diet. Metal-related pharmacological effects across major organs and serums were investigated using inductively coupled plasma mass spectrometry (ICP-MS). Disulfiram treatments (all modes) augmented hepatic copper in mice, markedly moderated body weight and abolished the deleterious systemic changes associated with a high-fat diet. Likewise, another chemically distinct copper ionophore H2(gtsm), administered daily (oral gavage), also augmented hepatic copper and moderated mouse body weight. Postmortem histological examinations of the liver and other major organs, together with serum aminotransferases, supported the reported therapeutic safety of disulfiram. Disulfiram specifically altered systemic copper in mice and altered hepatic copper metabolism, perturbing the incorporation of copper into ceruloplasmin (holo-ceruloplasmin biosynthesis) and subsequently reducing serum copper concentrations. Serum ceruloplasmin represents a biomarker for disulfiram activity. Our results establish copper ionophores as a potential class of antiobesity agents.

Functional iron deficiency in toxic milk mutant mice (tx-J) despite high hepatic ferroportin: a critical role of decreased GPI-ceruloplasmin expression in liver macrophages

Jackson toxic milk mutant mice (tx-J) carrying a missense mutation in the Atp7b gene are animal models of the Wilson disease. In both the Wilson patients and the tx-J mice, mutations in the ATP7B/Atp7b gene lead to disturbances in copper metabolism. The dysfunction of ATP7B/Atp7b leads to a reduction in the incorporation of copper into apoceruloplasmin; this decreases the ferroxidase activity of ceruloplasmin necessary for the efflux of iron from cells and reduces the release of copper from hepatocytes to the bile; this results in a massive hepatic copper accumulation. A decrease in the ferroxidase activity of ceruloplasmin in the tx-J mice emphasises the practicality of this animal model for the exploration of disturbances in iron balance triggered by dysregulation of copper metabolism. We found that 6-month-old tx-J mutants developed mild anaemia caused by functional iron deficiency. The tx-J mutants showed decreased plasma iron levels with concomitant iron accumulation in hepatocytes and liver macrophages. Hepatic iron retention was accompanied by decreased expression of the membrane form of ceruloplasmin in both liver cell types. Interestingly, in the liver of mutants, we found high levels of ferroportin (an iron exporter) on the surface of liver macrophages despite increased hepatic expression of hepcidin, a peptide inducing internalization and degradation of ferroportin. We conclude that even when the ferroportin expression is high, ceruloplasmin remains a limiting factor in the release of iron to the extracellular environment.

Lipid and energy metabolism in Wilson disease

Copper accumulation and deficiency are reciprocally connected to lipid metabolism. In Wilson disease (WD), which is caused by a genetic loss of function of the copper-transporting P-type ATPase beta, copper accumulates mainly in the liver and lipid metabolism is dysregulated. The underlying mechanisms linking copper and lipid metabolism in WD are not clear. Copper may impair metabolic machinery by direct binding to protein and lipid structures or by generating reactive oxygen species with consequent damage to cellular organelles vital to energy metabolism. In the liver, copper overload results in mitochondrial impairment, down-regulation of lipid metabolism, and the development of steatosis with an etiology not fully elucidated. Little is known regarding the effect of copper overload on extrahepatic energy homeostasis. This review aims to discuss alterations in hepatic energy metabolism associated with WD, highlights potential mechanisms involved in the development of hepatic and systemic dysregulation of lipid metabolism, and reviews current knowledge on the effects of copper overload on extrahepatic energy metabolism.

Copper Does Not Induce Tenogenic Differentiation but Promotes Migration and Increases Lysyl Oxidase Activity in Adipose-Derived Mesenchymal Stromal Cells

Background

Copper belongs to the essential trace metals that play a key role in the course of cellular processes maintaining the whole body's homeostasis. As there is a growing interest in transplanting mesenchymal stromal cells (MSCs) into the site of injury to improve the regeneration of damaged tendons, the purpose of the study was to verify whether copper supplementation may have a positive effect on the properties of human adipose tissue-derived MSCs (hASCs) which potentially can contribute to improvement of tendon healing.

Results

Cellular respiration of hASCs decreased with increasing cupric sulfate concentrations after 5 days of incubation. The treatment with CuSO₄ did not positively affect the expression of genes associated with tenogenesis (COL1α1, COL3α1, MKX, and SCX). However, the level of COL1α1 protein, whose transcript was decreased in comparison to a control, was elevated after a 5-day exposition to 25 μM CuSO₄. The content of the MKX and SCX protein in hASCs exposed to cupric sulfate was reduced compared to that of untreated control cells, and the level of the COL3α1 protein, whose transcript was decreased in comparison to a control, was elevated after a 5-day exposition to 25 μM CuSO₄. The content of the MKX and SCX protein in hASCs exposed to cupric sulfate was reduced compared to that of untreated control cells, and the level of the COL3.

Conclusion

Copper sulfate supplementation can have a beneficial effect on tendon regeneration not by inducing tenogenic differentiation, but by improving the recruitment of MSCs to the site of injury, where they can secrete growth factors, cytokines and chemokines, and prevent the effects of oxidative stress at the site of inflammation, as well as improve the stabilization of collagen fibers, thereby accelerating the process of tendon healing.

A novel colorimetric and "turn-off" fluorescent probe based on catalyzed hydrolysis reaction for detection of Cu2+ in real water and in living cells

A novel and highly selective fluorescent 1,8-naphthalimide-based probe, 3, was designed and synthesized for rapid Cu²⁺ detection in a CH₃CN-H₂O (3:1, v/v, pH = 7.4) solution by means of a distinct hydrolysis mechanism via its Cu²⁺-promoting feature. Upon treatment with Cu²⁺, the fluorescence response of probe 3 at 550 nm abruptly decreased, which was visible to the naked eye, and this response was accompanied by a clear change of the color of the solution; the color changed from the original yellow color to colorless. This color change occurred due to the Cu²⁺-promoted hydrolysis of 3, which yielded a fluorescence-quenched product. It is inspiring that probe 3 exhibited excellent sensitivity, a short response time and strong anti-interference recognition. Compared with the allowable amount of Cu²⁺ (∼20 μM) in drinking water, the detection limit of 3 for Cu²⁺ is calculated to be 9.15 nM, which is much lower than the amount defined by standards. The probe can be successfully applied for the determination of Cu²⁺ in real aqueous samples. Furthermore, probe 3 can be used as a fluorescent sensor to detect Cu²⁺ in biological environments, demonstrating its low toxicity to organisms and good cell permeability in live cell imaging.

A Novel Ruthenium(II) Polypyridyl Complex Bearing 1,8-Naphthyridine as a High Selectivity and Sensitivity Fluorescent Chemosensor for Cu2+ and Fe3+ Ions

A novel ruthenium(II) polypyridyl complex bearing 1,8-naphthyridine was successfully designed and synthesized. This complex was fully characterized by EI-HRMS, NMR, and elemental analyses. The recognition properties of the complex for various metal ions were investigated. The results suggested that the complex displayed high selectivity and sensitivity for Cu²⁺ and Fe³⁺ ions with good anti-interference in the CH₃CN/H₂O (1:1, v/v) solution. The fluorescent chemosensor showed obvious fluorescence quenching when the Cu²⁺ and Fe³⁺ ions were added. The detection limits of Cu²⁺ and Fe³⁺ were 39.9 nmol/L and 6.68 nmol/L, respectively. This study suggested that this Ru(II) polypyridyl complex can be used as a high selectivity and sensitivity fluorescent chemosensor for Cu²⁺ and Fe³⁺ ions.

Metal-dependent hormone function: the emerging interdisciplinary field of metalloendocrinology

For over 100 years, there has been an incredible amount of knowledge amassed concerning hormones in the endocrine system and their central role in human health. Hormones represent a diverse group of biomolecules that are released by glands, communicate signals to their target tissue, and are regulated by feedback loops to maintain organism health. Many disease states, such as diabetes and reproductive disorders, stem from misregulation or dysfunction of hormones. Increasing research is illuminating the intricate roles of metal ions in the endocrine system where they may act advantageously in concert with hormones or deleteriously catalyze hormone-associated disease states. As the critical role of metal ions in the endocrine system becomes more apparent, it is increasingly important to untangle the complex mechanisms underlying the connections between inorganic biochemistry and hormone function to understand and control endocrinological phenomena. This tutorial review harmonizes the interdisciplinary fields of endocrinology and inorganic chemistry in the newly-termed field of "metalloendocrinology". We describe examples linking metals to both normal and aberrant hormone function with a focus on highlighting insight to molecular mechanisms. Hormone activities related to both essential metal micronutrients, such as copper, iron, zinc, and calcium, and disruptive nonessential metals, such as lead and cadmium are discussed.

Raposo MM, Martínez-Máñez R, Sancenón F. N,N-Diphenylanilino-heterocyclic aldehyde-based chemosensors for UV-vis/NIR and fluorescence Cu(ii) detection

Cu(ii) coordination with aldehyde-containing probes induced the appearance of NIR bands coupled with remarkable colour changes.

Carnosine modulates the Sp1-Slc31a1/Ctr1 copper-sensing system and influences copper homeostasis in murine CNS-derived cells

Carnosine (CAR) is an endogenous dipeptide physiologically present in excitable tissues, such as central nervous system (CNS) and muscle. CAR is acknowledged as a substrate involved in many homeostatic pathways and mechanisms and, due to its biochemical properties, as a molecule intertwined with the homeostasis of heavy metals such as copper (Cu). In CNS, Cu excess and dysregulation imply oxidative stress, free-radical production, and functional impairment leading to neurodegeneration. Here, we report that CAR intercepts the regulatory routes of Cu homeostasis in nervous cells and tissues. Specifically, in a murine neuron-derived cell model, i.e., the B104 neuroblastoma cells, extracellular CAR exposure up to 24 h influenced intracellular Cu entry and affected (downregulated) the key Cu-sensing system, consisting of the gene coding for the Slc31a1 transmembrane Cu importer (alias Ctr1), and the gene coding for the Cu-responsive transcription factor Sp1 ( Sp1). Also, CAR exposure upregulated CAR biosynthesis ( Carns1), extracellular degradation ( Cndp1), and transport ( Slc15a4, alias Pht1) genes and elicited CAR intracellular accumulation, contributing to the outline of functional association between CAR and Cu within the cell. Interestingly, the same gene modulation scheme acting in vitro operates in vivo in brains of mice undergoing dietary administration of CAR in drinking water for 2 wk. Overall, our findings describe for the first time a regulatory interaction between CAR and Cu pathways in CNS and indicate CAR as a novel active molecule within the network of ligands and chaperones that physiologically regulate Cu homeostasis.

A lipidomic approach to understand copper resilience in oyster Crassostrea hongkongensis

Copper (Cu) can cause oxidative stress and inflammatory responses, and there is arising evidence between Cu toxicity and lipid disturbance. In this study, we examined the relationships between Cu exposure and lipid metabolism in an estuarine oyster (Crassostrea hongkongensis) and aimed to understand the effects and resilience strategies of Cu on oyster metabolism. We exposed the oysters to waterborne Cu (10 and 50 μg/L) and measured the physiological changes (condition index and clearance rate), lipid accumulation and lipid peroxidation in the oysters. We found more altered lipid responses in oysters exposed to a lower Cu concentration (10 μg/L), and speculated that oysters exposed to 50 μg/L may upregulate the defenses. We further evaluated the changes in lipidome profiling of the Cu-exposed oysters in aspects of membrane dynamics, lipid signaling and energy metabolism. We documented the phospholipid remodeling as well as quick modulation in inflammatory responses and extensive vesicle formation for subcellular compartmentalization and autophagosome formation, as well as the possible impacts on mitochondrial bioenergetics in the Cu-exposed oysters. The lipidomics approach provided a comprehensive lipid profile of possible alteration by Cu exposure. In combination with other omics approaches, it may be possible to elucidate the pathways and mechanisms in stress acclimation and resilience associated between Cu contamination and lipid metabolism.

Copper-dependent amino oxidase 3 governs selection of metabolic fuels in adipocytes

Copper (Cu) has emerged as an important modifier of body lipid metabolism. However, how Cu contributes to the physiology of fat cells remains largely unknown. We found that adipocytes require Cu to establish a balance between main metabolic fuels. Differentiating adipocytes increase their Cu uptake along with the ATP7A-dependent transport of Cu into the secretory pathway to activate a highly up-regulated amino-oxidase copper-containing 3 (AOC3)/semicarbazide-sensitive amine oxidase (SSAO); in vivo, the activity of SSAO depends on the organism's Cu status. Activated SSAO oppositely regulates uptake of glucose and long-chain fatty acids and remodels the cellular proteome to coordinate changes in fuel availability and related downstream processes, such as glycolysis, de novo lipogenesis, and sphingomyelin/ceramide synthesis. The loss of SSAO-dependent regulation due to Cu deficiency, limited Cu transport to the secretory pathway, or SSAO inactivation shifts metabolism towards lipid-dependent pathways and results in adipocyte hypertrophy and fat accumulation. The results establish a role for Cu homeostasis in adipocyte metabolism and identify SSAO as a regulator of energy utilization processes in adipocytes.

Tuning the Color Palette of Fluorescent Copper Sensors through Systematic Heteroatom Substitution at Rhodol Cores

Copper is an essential nutrient for sustaining life, and emerging data have expanded the roles of this metal in biology from its canonical functions as a static enzyme cofactor to dynamic functions as a transition metal signal. At the same time, loosely bound, labile copper pools can trigger oxidative stress and damaging events that are detrimental if misregulated. The signal/stress dichotomy of copper motivates the development of new chemical tools to study its spatial and temporal distributions in native biological contexts such as living cells. Here, we report a family of fluorescent copper sensors built upon carbon-, silicon-, and phosphorus-substituted rhodol dyes that enable systematic tuning of excitation/emission colors from orange to near-infrared. These probes can detect changes in labile copper levels in living cells upon copper supplementation and/or depletion. We demonstrate the ability of the carbon-rhodol based congener, Copper Carbo Fluor 1 (CCF1), to identify elevations in labile copper pools in the Atp7a-/- fibroblast cell model of the genetic copper disorder Menkes disease. Moreover, we showcase the utility of the red-emitting phosphorus-rhodol based dye Copper Phosphorus Fluor 1 (CPF1) in dual-color, dual-analyte imaging experiments with the green-emitting calcium indicator Calcium Green-1 to enable simultaneous detection of fluctuations in copper and calcium pools in living cells. The results provide a starting point for advancing tools to study the contributions of copper to health and disease and for exploiting the rapidly growing palette of heteroatom-substituted xanthene dyes to rationally tune the optical properties of fluorescent indicators for other biologically important analytes.

Association of Copper Status with Lipid Profile and Functional Status in Patients with Amyotrophic Lateral Sclerosis

Oxidative stress is one of the main mechanisms associated with the pathogenesis of amyotrophic lateral sclerosis (ALS). Copper can affect cellular oxidation and lipid metabolism. The aim of this study was to evaluate the association of copper status with lipid profile and functional status in patients with ALS. A cross-sectional study was carried out including 27 patients with ALS (case group) and 26 healthy individuals (control group). Copper status was evaluated by habitual dietary copper intake, plasma copper, and serum ceruloplasmin concentrations. The lipid profile included analysis of serum total cholesterol (TC), LDL-cholesterol (LDL-c), HDL-cholesterol (HDL-c), and triglycerides (TGL). The functional status of patients with ALS was assessed by the ALS Functional Rating Scale-Revised (ALSFRS-R). In the case group, plasma copper was lower compared with the control group (133.9 versus 164.1 μg/dL, p=0.0001) and was positively correlated with HDL-c (r_s=0.398, p=0.044). In the control group, plasma copper was positively correlated with serum ceruloplasmin (r_s=0.646, p < 0.001), TC (r_s=0.446, p=0.025), LDL-c (r_s=0.445, p=0.029), and HDL-c (r_s=0.479, p=0.015), and serum ceruloplasmin was positively correlated only with LDL-c (r_s=0.407, p=0.043). In the case group, dietary copper intake (B=−0.373, p < 0.001), plasma copper (B=−0.005, p=0.033), and TC (B=−0.312, p=0.001) were inversely associated with the functional status of patients with ALS. In contrast, serum ceruloplasmin (B=0.016, p=0.044), LDL-c (B=0.314, p=0.001), HDL-c (B=0.308, p=0.001), and TGL (B=0.062; p=0.001) were positively associated with their functional status. In conclusion, this study suggests a disturbance of copper status and its connection with the lipid profile in patients with ALS. Furthermore, copper status and lipid profile may influence the functional status of patients with ALS, standing out as potential biomarkers of disease severity.

Comparison of the effect of dietary copper nanoparticles and one copper (II) salt on the copper biodistribution and gastrointestinal and hepatic morphology and function in a rat model

The aim of the study was to investigate the effect of two forms (CuCO₃ (CuS); and Cu nanoparticles (CuNP)) and dosages (standard 6.5 mg/kg (H), half of the standard (L)) of additional dietary Cu administered to growing rats on gastrointestinal and hepatic function and morphology. Copper in the form of CuNP vs CuS caused lower Cu faecal/urinal excretion and increased Cu accumulation in the brain tissue. Hepatic high-grade hydropic degeneration and necrotic lesions were observed only in the CuNP-H animals. In the lower gut, the dietary application of CuNP stifled bacterial enzymatic activity of caecal gut microbiota and resulted in lower SCFA production. That diminishing effect of CuNP on caecal microbiota activity was accompanied by a relative increase in the secretion of glycoside hydrolases by bacterial cells. The results showed that in comparison to Cu from CuCO₃, Cu nanoparticles to a greater extent were absorbed from the intestine, accumulated in brain tissue, exerted antimicrobial effect in the caecum, and at higher dietary dose caused damages in the liver of rats.

A glimpse into the regulation of the Wilson disease protein, ATP7B, sheds light on the complexity of mammalian apical trafficking pathways

Wilson disease (WD), a Mendelian disorder of copper metabolism caused by mutations in the ATP7B gene, manifests a large spectrum of phenotypic variability. This phenomenon of extensive symptom variation is not frequently associated with a monogenic disorder. We hypothesize that the phenotypic variability in WD is primarily driven by the variations in interacting proteins that regulate the ATP7B function and localization in the cell. Based on existing literature, we delineated a potential molecular mechanism for ATP7B mediated copper transport in the milieu of its interactome, its dysfunction in WD and the resulting variability in the phenotypic manifestation. Understanding the copper-induced apical trafficking of ATP7B also significantly contributes to the appreciation of the complexities of the ligand-induced transport pathway. We believe that this holistic view of WD will pave the way for a better opportunity for rational drug design and therapeutics.

Structure and Synaptic Function of Metal Binding to the Amyloid Precursor Protein and its Proteolytic Fragments

Alzheimer’s disease (AD) is ultimately linked to the amyloid precursor protein (APP). However, current research reveals an important synaptic function of APP and APP-like proteins (APLP1 and 2). In this context various neurotrophic and neuroprotective functions have been reported for the APP proteolytic fragments sAPPα, sAPPβ and the monomeric amyloid-beta peptide (Aβ). APP is a metalloprotein and binds copper and zinc ions. Synaptic activity correlates with a release of these ions into the synaptic cleft and dysregulation of their homeostasis is linked to different neurodegenerative diseases. Metal binding to APP or its fragments affects its structure and its proteolytic cleavage and therefore its physiological function at the synapse. Here, we summarize the current data supporting this hypothesis and provide a model of how these different mechanisms might be intertwined with each other.

A highly selective “ON–OFF” probe for colorimetric and fluorometric sensing of Cu2+in water

A new diformyl phenol based probe for selective detection of Cu²⁺in aqueous medium, applicable for cell imaging in Vero cells. Theoretical studies were performed to establish the underlying keto–enol tautomerism and optimization of the Cu²⁺complex.

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

Copper is a required metal nutrient for life, but global or local alterations in its homeostasis are linked to diseases spanning genetic and metabolic disorders to cancer and neurodegeneration. Technologies that enable longitudinal in vivo monitoring of dynamic copper pools can help meet the need to study the complex interplay between copper status, health, and disease in the same living organism over time. Here, we present the synthesis, characterization, and in vivo imaging applications of Copper-Caged Luciferin-1 (CCL-1), a bioluminescent reporter for tissue-specific copper visualization in living animals. CCL-1 uses a selective copper(I)-dependent oxidative cleavage reaction to release d-luciferin for subsequent bioluminescent reaction with firefly luciferase. The probe can detect physiological changes in labile Cu+ levels in live cells and mice under situations of copper deficiency or overload. Application of CCL-1 to mice with liver-specific luciferase expression in a diet-induced model of nonalcoholic fatty liver disease reveals onset of hepatic copper deficiency and altered expression levels of central copper trafficking proteins that accompany symptoms of glucose intolerance and weight gain. The data connect copper dysregulation to metabolic liver disease and provide a starting point for expanding the toolbox of reactivity-based chemical reporters for cell- and tissue-specific in vivo imaging.

Copper regulates cyclic-AMP-dependent lipolysis

Cell signaling relies extensively on dynamic pools of redox-inactive metal ions such as sodium, potassium, calcium and zinc, but their redox-active transition metal counterparts such as copper and iron have been studied primarily as static enzyme cofactors. Here we report that copper is an endogenous regulator of lipolysis, the breakdown of fat, which is an essential process in maintaining body weight and energy stores. Using a mouse model of genetic copper misregulation, in combination with pharmacological alterations in copper status and imaging studies in a 3T3-L1 white adipocyte model, we found that copper regulates lipolysis at the level of the second messenger, cyclic AMP (cAMP), by altering the activity of the cAMP-degrading phosphodiesterase PDE3B. Biochemical studies of the copper-PDE3B interaction establish copper-dependent inhibition of enzyme activity and identify a key conserved cysteine residue in a PDE3-specific loop that is essential for the observed copper-dependent lipolytic phenotype.

Thioether Coordination Chemistry for Molecular Imaging of Copper in Biological Systems

Copper is an essential element in biological systems. Its potent redox activity renders it necessary for life, but at the same time, misregulation of its cellular pools can lead to oxidative stress implicated in aging and various disease states. Copper is commonly thought of as a static cofactor buried in protein active sites; however, evidence of a more loosely bound, labile pool of copper has emerged. To help identify and understand new roles for dynamic copper pools in biology, we have developed selective molecular imaging agents for this metal, drawing inspiration from both biological binding motifs and synthetic model complexes that reveal thioether coordination as a general design strategy for selective and sensitive copper recognition. In this review, we summarize some contributions, primarily from our own laboratory, on fluorescence- and magnetic resonance-based molecular-imaging probes for studying copper in living systems using thioether coordination chemistry.

A novel cyclometalated Ir(iii) complex based luminescence intensity and lifetime sensor for Cu2+

A novel green luminescent complex [Ir(dfppy)₂(bpy-BiDPA)]PF₆ was prepared for the reversible detection of Cu²⁺.

Metabolomics analysis reveals heavy metal copper-induced cytotoxicity in HT-29 human colon cancer cells

LC-MS based metabolomics analysis reveals heavy metal copper-induced cytotoxicity in a human intestinal cell line, HT-29.

Non-ceruloplasmin bound copper and ATP7B gene variants in Alzheimer's disease

ATP7B, a protein mainly expressed in the hepatocytes, is a copper chaperone that loads the metal into the serum copper–protein ceruloplasmin during its synthesis and also escorts superfluous copper into the bile, by a sophisticated trafficking mechanism.