Distinct Effects of Copper Ionophores on Intracellular Copper and Cell Viability in Wild-Type and CTR1-Deficient SH-SY5Y Cells

Abstract

Copper homeostasis is essential for neuronal function, and its dysregulation has been implicated in neurodegenerative disorders. In particular, reduced intracellular copper levels alongside with elevated extracellular copper concentrations have been associated with Alzheimer’s disease (AD). Therefore, strategies aimed at restoring intracellular copper levels represent a potential therapeutic approach. In this study, we investigated the effects of selected copper-binding compounds─α-lipoic acid (LA), elesclomol (ES), disulfiram (DSF), thiourea (TU), and triapine (3-AP)─on copper uptake and cytotoxicity in SH-SY5Y wild-type (WT) and CTR1-deficient (CTR1–/–) cells. Intracellular copper levels were quantified using inductively coupled plasma mass spectrometry (ICP-MS), and cell viability was assessed by using propidium iodide assay under various treatment conditions. Among the tested compounds, LA, ES, and DSF significantly increased intracellular copper levels in both WT and CTR1–/– cells, whereas TU and 3-AP did not enhance copper accumulation beyond copper-only treatment. Notably, CTR1–/– cells exhibited reduced sensitivity to copper-associated toxicity compared to WT cells. Under copper-supplemented conditions, DSF and ES displayed concentration-dependent cytotoxicity, while LA and TU induced only mild effects. In contrast, 3-AP toxicity was abolished in the presence of copper. Furthermore, cotreatment with LA and copper increased cell proliferation and promoted differentiation-associated morphological changes in CTR1–/– cells. Overall, our results demonstrate that copper ionophores can enhance intracellular copper levels dependently and independently of CTR1, with distinct effects on cell viability. Among the tested compounds, LA and DSF showed a favorable profile by increasing copper levels while maintaining low cytotoxicity, highlighting their potential for modulating cellular copper homeostasis.