In the field of “metals in biology,” metals play unique and crucial roles in biological systems. Copper is an essential trace metal found in nearly every living organism, with a normal human body containing approximately about 100 mg (Wang D. et al., 2023). It is primarily found in muscles, bones, and the liver, with small quantities present in the blood (Festa and Thiele, 2011). Copper exists in two distinct ionic forms, namely, cuprous ions (Cu [I], reduced type) and cupric ions (Cu [II], oxidized type), both of which are involved in the enzymatic modulation of cellular physiological activities. However, redox cycling between Cu(I) and Cu(II) can contribute to the catalytic generation of highly toxic hydroxyl radicals, subsequently damaging macromolecules (Halliwell and Gutteridge, 1984). Therefore, it is necessary to maintain systemic copper levels within a stable range to ensure proper biochemical processes and prevent cellular damage (Figure 1).

Copper is essential for cellular activity, and its intracellular concentration is meticulously regulated to prevent the detrimental effects of both copper deficiency and overload (Dupont et al., 2011; Kim et al., 2013). Copper homeostasis and compartmentalization are mediated by a finely tuned network of copper transport proteins, soluble chaperones, copper enzymes, and copper-dependent transcriptional regulators (Burkhead et al., 2009; Robinson and Winge, 2010; Festa and Thiele, 2011). The levels of copper are maintained within a narrow range through the synergistic actions of these copper-dependent proteins (Figure 2).

Oxidative stress plays a significant role in the occurrence and development of HF, typically resulting from an imbalance between ROS production and antioxidant defense mechanisms (Karabacak et al., 2014). Copper, a transition metal involved in redox reactions, facilitates ROS production, with prolonged exposure leading to oxidative stress (Vo et al., 2020) (Figure 3).

Higher levels of free copper ions may further interact with hydrogen peroxide through Fenton reactions, resulting in the generation of highly reactive hydroxyl radicals (Valko et al., 2005). These radicals induce cellular dysfunction, DNA damage, and lipid and protein peroxidation, ultimately promoting the initiation and progression (Tsutsui et al., 2011) of HF. Specifically, copper can activate various hypertrophic signaling kinases and transcription factors, including protein kinase C, GTP-binding protein Rat sarcoma, Jun N-terminal kinase, and mitogen-activated protein kinases (MAPK) (Grubman and White, 2014). This activation stimulates myocardial development, contributes to cellular dysfunction, and facilitates matrix remodeling. Lipid peroxidation is a chain reaction triggered by the accumulation of ROS in polyunsaturated fatty acids within cell membrane lipids, thereby resulting in lipid molecule oxidative damage. As an intracellular copper scavenger, MT has been demonstrated to be an endogenously expressed and highly inducible antioxidant protein in the heart. Yin et al. reported that mice with silenced MT1/2 genes developed severe HF, cardiac fibrosis, and oxidative stress, with these symptoms exacerbated by intermittent hypoxia. In contrast, mice exhibiting cardiac-specific overexpression of MT-IIa were protected from cardiomyopathy induced by intermittent hypoxia. This protective effect is associated with reduced cardiac lipid peroxidation in the context of copper deficiency (Yin et al., 2014). Furthermore, increased copper levels may increase lipid peroxidation, leading to increased generation of malondialdehyde (MDA) (Dhalla et al., 2000), whose high levels are associated with HF(Díaz-Vélez et al., 1996; Ghatak et al., 1996; Sairam et al., 2017). Additionally, increased copper levels can decrease the activities of antioxidant enzymes, including SOD, total antioxidant capacity, GSH peroxidase (GSH-Px), and catalase, in both serum and heart tissue while also lowering the levels of the nonenzymatic antioxidant GSH (Skrajnowska et al., 2013; Li et al., 2018). Blood GSH levels serve as an independent marker of lipid peroxidation in HF (Campolo et al., 2023). Copper can induce DNA strand breaks and base oxidation through free radicals generated from oxygen (Brezová et al., 2007). Existing evidence suggests that copper-induced oxidative stress significantly impacts HF.

Excessive copper is been related to the pathogenic mechanisms of HF because it can cause inflammation. Since its first discovery by Levine et al. (1990), higher circulating levels of proinflammatory factors have been associated with poor HF outcomes (Aukrust et al., 2002; Heymans et al., 2009; Hansson and Hermansson, 2011). Reportedly, increased copper levels can stimulate increases in the serum levels of tumor necrosis factor α (TNF-α) and C-reactive protein in rats, contributing to inflammatory damage in multiple organs, including the heart, and inducing myocardial fibrosis (Wang et al., 2022). In vitro experiments revealed that copper enhances interleukin (IL)-6 release while activating MAPK extracellular signal-regulated kinase 1/2 and p38 in primary cardiac cells (Ansteinsson et al., 2009), which are associated with mechanisms of cardiac hypertrophy, an important risk factor for the development of HF(Bueno and Molkentin, 2002; Wenzel et al., 2005). Copper-mediated oxidative stress further exacerbates inflammation, as excess copper leads to excessive ROS accumulation, which then increases myeloperoxidase activity, activates the nuclear factor-κB (NF-κB) pathway, inhibits anti-inflammatory cytokines, and leads to a proinflammatory environment (Pereira et al., 2016; Jian et al., 2020).

Additionally, the molecular interplay between copper homeostasis and immune signaling pathways has revealed novel mechanisms by which copper drives excessive and deleterious inflammation during disease progression. Copper uptake, which is mediated by CD44, regulates immune cell activation; however, dysregulated activation triggers uncontrolled inflammation, leading to tissue damage and organ failure, with copper directly acting as a catalytic metal (Solier et al., 2023). Furthermore, copper has been shown to activate the innate immune pathway through ALPK1 in a kinase-dependent manner, amplifying downstream signaling and increasing proinflammatory cytokine production (Lu et al., 2024). Although autoimmunity is not a predominant driver of cardiac dysfunction, it remains a potential target for HF prevention (Martini et al., 2024).

Patients with HF typically exhibit features of inadequate cardiac energy metabolism, primarily because of reduced mitochondrial oxidative capacity (Lopaschuk et al., 2021). Copper serves as a cofactor for several enzymes involved in the antioxidant system and the mitochondrial respiratory chain (Nair and Mason, 1967). However, copper accumulation negatively affects mitochondrial activity and may contribute to HF progression by reducing mitochondrial metabolism (Fan et al., 2005; Rines and Ardehali, 2013). For example, increased copper levels can lead to excessive ROS generation, which facilitates lipid peroxidation, depletes antioxidants, damages mitochondrial DNA, and reduces mitochondrial ATP production (Sugamura and Keaney, 2011; Tsutsui et al., 2011). Furthermore, the failing heart also exhibits a marked decrease in key enzymatic activities, such as mitochondrial creatine kinase (CKmito), which operates at the intersection of energy metabolism and oxidative stress (Keceli et al., 2022). CKmito dysfunction disrupts efficient energy transfer between mitochondria and myofibrils, exacerbating energy deprivation in cardiomyocytes (Keceli et al., 2022). Mitochondrial ATP is primarily generated through fatty acid oxidation, which serves as the heart’s main fuel source (Yamamoto and Sano, 2022). Copper can also directly impair enzymes associated with the mitochondrial oxidative phosphorylation (OXPHOS) chain and fatty acid β-oxidation, resulting in mitochondrial insufficiency and energy starvation (Mazi et al., 2020). This cascade of events ultimately contributes to HF progression.

High copper levels are associated with cell death, such as pyroptosis, apoptosis, ferroptosis, and autophagy (Jiang et al., 2022).

Copper deficiency contributes to the occurrence and progression of HF through multiple mechanisms, particularly its impact on oxidative stress. Copper is an essential cofactor for several antioxidant enzymes, including Cu/Zn superoxide dismutase (Cu/Zn SOD), CP, and LOX (Al-Aubaidy et al., 2015). Consequently, copper deficiency can impair the activity of these enzymes, leading to a compromised antioxidant defense system and increased susceptibility to oxidative stress (Chen et al., 1994; Lynch and Colón, 2006; DiNicolantonio et al., 2018). In addition to its effects on antioxidant enzymes, copper deficiency can decrease COX activity, leading to the oxidative inactivation of complex I (NADH:ubiquinone oxidoreductase). This process can subsequently increase ROS production in copper-deficient cells, thereby exacerbating oxidative stress (Johnson and Thomas, 1999). Copper supplementation has been shown to restore COX activity, resulting in the reversal of myocardial hypertrophy (Jiang Y. et al., 2007). Copper deficiency also disrupts NO homeostasis, particularly by affecting Cu/Zn SOD activity in endothelial cells (Lynch et al., 1997). NO is a crucial vasodilator that plays an essential role in maintaining cardiovascular health. Reduced copper levels lower NO production, leading to endothelial dysfunction, impaired vasodilation, increased oxidative stress, and vascular complications associated with HF(Al-Aubaidy et al., 2015). Interestingly, copper deficiency has a different effect on NO generation in the heart than in endothelial cells. For example, Sarri et al. reported that copper deficiency promoted NO production in the rat heart by increasing the expression of inducible NO synthase and endothelial NO synthase proteins (Saari and Dahlen, 1998; Saari, 2000; Saari et al., 2007). While NO can facilitate HF through its interaction with superoxide to form peroxynitrite, a reactive and long-lived radical that amplifies oxidative stress (Kim et al., 1999; Wollert and Drexler, 2002), excess ROS can also directly quench bioavailable NO. As noted by Paolocci et al., this reduction in NO bioavailability impairs its vasorelaxant capacity and contributes to endothelial dysfunction (Paolocci et al., 2001). The balance between these two effects—NO consumption through peroxynitrite formation and reduced NO availability due to ROS quenching—underpins the endothelial dysfunction and vascular complications observed in HF in the context of copper deficiency. Furthermore, copper deficiency increases cyclic guanosine monophosphate levels, which can impair cardiac contractility and exacerbate HF progression in animal models (Saari and Dahlen, 1998; Saari, 2000; Saari et al., 2007). Collectively, these findings underscore the complex role of NO in the pathophysiology of heart disease associated with copper deficiency. However, further studies are needed to elucidate the molecular mechanisms by which NO regulates cardiac pathologies in the context of copper deficiency.

Decreased responsiveness to β-adrenergic stimulation is a hallmark of copper deficiency-induced HF, as evidenced by the reduced sensitivity of copper-deficient mouse hearts to the β-adrenergic agonist isoproterenol (Elsherif et al., 2003). β-Adrenergic receptors, members of the G-protein-coupled receptor family, are regulated through changes in expression and function in response to external stimuli, resulting in alterations in heart rate, contractility, relaxation, and automaticity (Pfleger et al., 2019). Dysregulation of β-adrenergic receptor signaling has been associated with congestive heart failure caused by cardiomyopathy. Proposed mechanisms include reduced receptor expression, downregulation of G-proteins, or impaired adenylate cyclase activity due to phosphorylation (Elsherif et al., 2003). The impaired adrenergic responsiveness observed in copper-deficient hearts raises questions about its potential relationship with altered catecholamine metabolism under copper-deficient conditions (Gross and Prohaska, 1990; Prohaska et al., 1990; Seidel et al., 1991). Notably, functional changes have been shown to precede structural damage in copper deficiency. In rats subjected to a copper-restricted diet for 9 or 15 months, both diastolic and systolic dysfunctions were observed. This was indicated by a blunted response in the maximal left ventricular pressure elevation rate (+dP/dt), the maximal left ventricular pressure decrease rate (-dP/dt), and the left ventricular end-diastolic pressure in response to isoproterenol (Li et al., 2005). In a previous study, feeding copper-deficient mice a diet adequate in copper for 4 weeks completely restored cardiac systolic and diastolic functions, as well as responsiveness to β-adrenergic stimulation (Elsherif et al., 2004b). These findings indicate that the response of the heart to β-adrenergic stimulation is dependent on copper levels.

The molecular mechanisms underlying HF induced by copper deficiency involve disrupted cellular calcium homeostasis. Altered myocardial contractility during end-stage HF is associated with changes in Ca²⁺ cycling (Hasenfuss et al., 1996; Hasenfuss and Pieske, 2002). This homeostasis is regulated primarily by sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA), ryanodine receptors (RyRs), and the sodium/calcium exchanger (NCX) (Bers, 2002). Kang et al. reported that a copper-deficient diet markedly altered the expression of calcium cycling genes in the mouse heart, including a reduction in L-type calcium channels, which affected calcium release from the sarcoplasmic reticulum via potassium-dependent NCX and RyRs. Although there is a lack of cardiac functional data, the expression of these calcium-regulating genes was notably normalized in mice with copper deficiency following supplementation with a copper-replete diet (Elsherif et al., 2004a). Additionally, copper deficiency may impair calcium homeostasis and cardiac contractile activity by increasing phospholamban levels, which inhibits SERCA2a-mediated calcium uptake (Elsherif et al., 2007).

Additionally, copper deficiency has been reported to lead to alterations in myocardial gene expression in mice, particularly in genes involved in cardiac contractility, fibrosis, and inflammation. These changes are potential factors contributing to the alterations in cardiac activity observed in mice with copper deficiency (Elsherif et al., 2007). Further studies are essential to explore the underlying mechanisms of these findings.

Copper-mediated cell death was first discovered in the late 1970s when Chan et al. identified mechanisms regulating copper levels within healthy fibroblasts, noting that increased copper levels resulted in cell death (Chan et al., 1978). However, the precise mechanisms remain unknown. Since then, the copper-mediated cell death mechanism has garnered significant attention from researchers, and copper has been found to have dual effects. Over the last decade, the toxicity of essential trace metals to mammalian cells has become increasingly understood. In a recent study, such metals were found to induce cell death through mechanisms independent of established pathways, such as apoptosis or necrosis, as observed with zinc and iron (Dineley et al., 2003; Kagan et al., 2017; Du et al., 2021). This observation may also signal the gradual emergence of a mechanism for a noncanonical copper-induced cell death pathway.

In March 2022, Tsvetkov et al. published a groundbreaking paper in Science unveiling cuproptosis, a unique form of regulated cell death resulting from mitochondrial copper accumulation (Tsvetkov et al., 2022); they reported that copper accumulation in cells was a major factor triggering cuproptosis. Notably, after copper ionophores induce cell death, traditional markers of cell death, such as caspase-3, are not detected. Furthermore, only copper chelators can rescue cells from elesclomol-induced death. Inhibiting established cell death pathways—such as apoptosis, necroptosis, oxidative stress, and ferroptosis—fails to prevent cell death, highlighting the distinct nature of cuproptosis.

Tsvetkov et al. reported that copper ionophore-induced cell death is dependent on mitochondrial respiration, as evidenced by the heightened sensitivity of mitochondria-dependent cells to copper ionophores, which are 1,000 times more sensitive than glycolytic cells (Tsvetkov et al., 2022). Further investigations revealed a time-dependent increase of tricarboxylic acid (TCA) cycle metabolite levels in cells exposed to copper ionophores, underscoring the close relationship between cuproptosis and the TCA cycle (Li Y. et al., 2022). In cuproptosis, copper in cells can bind to lipoylated components of the TCA cycle, resulting in the aggregation of copper-bound lipoylated mitochondrial proteins. This aggregation disrupts the TCA cycle, thereby impairing cellular energy generation. Ferredoxin and lipoyl synthase, two upstream regulatory factors, play significant roles in this process and have been identified as key contributors to copper toxicity through whole-genome clustered regularly interspaced short palindromic repeat selection (Dreishpoon et al., 2023). The aggregation of proteins and the subsequent decrease in iron‒sulfur clusters—important cofactors for various cellular processes, such as enzymatic reactions and electron transport (Lill and Freibert, 2020)—promote toxic protein stress, ultimately leading to cell death (Figure 4).

Mitochondria serve as significant reservoirs of intracellular copper, which is a critical component that regulates mitochondrial function. Hence, pathologies and diseases resulting from copper metabolism disorders are closely linked to mitochondrial metabolism (Tian et al., 2023). Mitochondria are highly vulnerable to copper-mediated injury, leading to oxidative damage to their membranes (Arciello et al., 2005; Cobine et al., 2021).

Copper serves as a cofactor for various mitochondrial enzymes involved in ATP production, a process that relies on the TCA cycle and OXPHOS within mitochondria (Arnold and Finley, 2023). However, increased copper content in cells can impair mitochondrial activity by altering critical enzymes associated with these processes (Sheline and Choi, 2004; Wang Z. et al., 2023). This disruption also generates ROS, which subsequently damage the inner mitochondrial membrane, impair the electron transport chain, and compromise mitochondrial DNA. This damage leads to mitochondrial dysfunction and reduced ATP production, ultimately accelerating cell death (Tsutsui et al., 2011).

Furthermore, metabolic enzymes may undergo lipoylation, a conserved posttranslational modification (Rowland et al., 2018). Lipoylation has been identified in glycine cleavage system protein H, dihydrolipoamide branched-chain transacylase E2, dihydrolipoamide S-acetyltransferase, and dihydrolipoamide S-succinyltransferase, all of which are associated with metabolic complexes that regulate the entry points of carbon into the TCA cycle (Rowland et al., 2018; Solmonson and DeBerardinis, 2018). Lipoylation involves the attachment of lipoic acid, a small sulfur-containing metabolite, to substrate proteins. Notably, lipoic acid can bind copper, leading to the toxic accumulation of lipoylated mitochondrial enzymes within the mitochondria (Kahlson and Dixon, 2022).

Moreover, excessive copper concentrations within the mitochondria can compromise mitochondrial membrane integrity by disrupting the membrane potential and increasing membrane permeability (Gyulkhandanyan et al., 2003; Reddy et al., 2008a). The opening of transmembrane pores, a critical factor in mitochondrial permeability transition, is not fully understood in terms of its precise chemical nature, but it is likely associated with the release of necrotic or apoptotic factors (Zazueta et al., 1998; Su et al., 2011). Additionally, the strong oxidizing nature of Cu(I) further contributes to potentially irreversible damage to the mitochondrial membrane (Reddy et al., 2008b).

The heart is the central organ for energy production in the human body, with about 95% of its ATP generated through oxidative metabolism in the mitochondria (Zhou and Tian, 2018). Consequently, mitochondrial dysfunction is linked to the onset and progression of various cardiovascular diseases. Mitochondrial dysfunction has been reported to affect cardiac energy supply, inflammatory mechanisms, calcium modulation, oxidative stress, and cell death, all of which are critical therapeutic targets for HF(Hammadah et al., 2014; Zhang et al., 2020; Yuan et al., 2022). In studies involving rats with HF, copper chelation and restoration within cardiomyocytes have been shown to repair mitochondria while improving cardiac function (Zhang et al., 2020). Hence, cuproptosis represents a novel mechanism for treating HF.

As a chelator, triethylenetetramine (TETA) specifically and selectively binds to Cu(II) and is used as a second-line therapy for Wilson’s disease (Walshe, 1982; Cooper, 2011). TETA treatment can enhance the regeneration of cardiac structure and function in HF model mice with diabetes (Cooper et al., 2004; Zhang et al., 2007; 2014; Nurchi et al., 2016) and reduce pathological left ventricular hypertrophy in patients with diabetes (Cooper et al., 2004; 2009). Moreover, TETA can restore cardiac pump activity by enhancing the activities of mitochondrial proteins such as COX, mitochondrial CCS, and SOD1, as well as by reinstating the expression of peroxisome proliferator-activated receptor gamma coactivator-1α, an important regulatory factor for mitochondrial biogenesis (Zhang et al., 2020). TETA has reportedly advanced to drug development for treating HF (Cooper G, 2012).

Owing to its copper-chelating properties, tetrathiomolybdate (TTM), which was initially developed for treating Wilson’s disease, has been explored for its potential therapeutic benefits in HF(Pufahl et al., 1997; Alvarez et al., 2010), which effectively prevents copper transport and its subsequent incorporation into cuproproteins. Although the effects of TTM on cardiac conditions remain elusive, some studies have highlighted its ability to reduce systemic copper overload and its associated proinflammatory consequences, which are relevant in the context of HF. For example, Wei et al. reported that TTM suppresses the expression of NF-κB, TNF-α, and monocyte chemoattractant protein-1 in the aorta and heart (Wei et al., 2011), which play crucial roles in inflammation. These findings open avenues for exploring the role of TMM in HF treatment, indicating the need for further research to directly assess its efficacy in treating cardiac diseases.

Copper ion chelation therapies can reduce copper levels; however, they lead to various side effects and disrupt various copper-dependent physiological processes (Chen et al., 2011). On the other hand, while copper supplementation can address copper deficiency, it carries the risk of copper overload. Excessive copper levels can exacerbate oxidative stress through the generation of ROS, impair mitochondrial function, and disrupt cellular homeostasis, particularly in the heart and liver (Kaplan and Maryon, 2016). These challenges highlight the need for more targeted approaches to modulate copper homeostasis in HF therapy. To minimize these adverse effects, small-molecule inhibitors of copper chaperone proteins offer a promising alternative. Unlike chelation or supplementation strategies, these inhibitors focus on the selective redistribution and regulation of intracellular copper levels, thereby reducing the risks associated with copper imbalance.

DCAC50 is a promising small-molecule inhibitor that selectively disrupts the functions of copper chaperones by binding to proteins such as CCS and ATOX1 (Karginova et al., 2019). ATOX1 is involved in transporting copper to the cytosol, whereas CCS facilitates the delivery of copper to SOD1 (Rosenzweig and O'Halloran, 2000). In studies of atherosclerosis, ATOX1 is increased in the intima of atherosclerotic lesions in ApoE^−/− mice and is localized to the nucleus under pathological conditions, including hypertensive and atherosclerotic vessels (Jeney et al., 2005; Itoh et al., 2008). Similarly, CCS plays a vital role in angiogenesis and wound healing, with its ability to impair these processes and contribute to the progression of cardiovascular diseases (Fukai et al., 2018). While both ATOX1 and CCS are critical for normal physiology, their dysregulation under pathological conditions underscores the potential for selectively targeting copper chaperones as a therapeutic strategy. Given the pivotal role of copper homeostasis in maintaining cardiac function, DCAC50 offers a targeted approach to modulate copper chaperone activity while preserving physiological copper-dependent processes. Further studies on small-molecule inhibitors of copper chaperone proteins are needed to develop effective treatments for HF.

Copper ionophores represent another therapeutic strategy for modulating copper levels and influencing related cellular pathways in HF. Unlike copper chelators, which remove copper from cells, copper ionophores facilitate the delivery of copper into cells, thereby increasing the intracellular copper concentration. Some examples of these ionophores include pyrithione, disulfiram, elesclomol, and chloroquine (Xue et al., 2023a). Among them, elesclomol has garnered considerable attention owing to its sensitivity to tumor cells and its application in clinical studies for cancer therapy (O’Day et al., 2013). However, the mechanisms underlying its selectivity remain unelucidated, warranting further investigation to determine whether this selectivity can be adapted for treating HF with additional copper ionophores. Su et al. incorporated metal supplements via a targeted ion carrier approach designed to deliver metals to specific sites within the body (Su et al., 2018). This strategy addresses the limitations of conventional copper ionophores, particularly their multifunctionality and lack of specificity, thereby opening new avenues for applying copper in HF treatment. Additionally, nanomedicine-based drug delivery systems are being widely explored to enable the precise delivery of therapeutic agents (Su et al., 2018). These developments underscore the need for future research focused on developing more selective and targeted copper ionophores for HF therapy.