Protective effect of curcumin on hepatolenticular degeneration through copper excretion and inhibition of ferroptosis

Abstract

Background: Hepatolenticular degeneration (HLD) is an autosomal recessive disorder concerning copper metabolism. Copper overload is also accompanied by iron overload in HLD patients, which can lead to ferroptosis. Curcumin, the active component in turmeric, has the potential to inhibit ferroptosis.

Purpose: The current study proposed a systematic investigation of the protective effects of curcumin against HLD and the underlying mechanisms.

Methods: The protective effect of curcumin on toxic milk (TX) mice was studied. Liver tissue was observed via hematoxylin-eosin (H&E) staining and the ultrastructure of the liver tissue was observed through transmission electron microscopy. Copper levels in the tissues, serum, and metabolites were measured by atomic absorption spectrometry (AAS). In addition, serum and liver indicators were evaluated. In cellular experiments, the effect of curcumin on the viability of rat normal liver cells (BRL-3A) was determined via the 3-[4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide (MTT) assay. Cell and mitochondrial morphology were observed in curcumin-mediated HLD model cells. The intracellular copper ion fluorescence intensity was observed via fluorescence microscopy, and intracellular copper iron content was detected using AAS. Further, oxidative stress indicators were evaluated. Cellular reactive oxygen species (ROS) and cellular mitochondrial membrane potential were examined via flow cytometry. Furthermore, the expression levels of nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and glutathione peroxidase 4 (GPX4) were determined via western blotting (WB).

Results: The histopathology of the liver confirmed the hepatoprotective effects of curcumin. Curcumin improved copper metabolism in TX mice. Both serum liver enzyme markers and antioxidant enzyme levels indicated the protective effect of curcumin against HLD-related liver injury. The MTT assay results showed that curcumin was protective against excess copper-induced injury. Curcumin improved the morphology of HLD model cells and their mitochondrial morphology. The Cu²⁺ fluorescent probe and the AAS results indicated that curcumin reduced Cu²⁺ content in HLD hepatocytes. In addition, curcumin improved oxidative stress levels and prevented the decline of mitochondrial membrane potential in HLD model cells. The ferroptosis inducer Erastin reversed these effects of curcumin. WB revealed that curcumin promoted Nrf2, HO-1, and GPX4 protein expression in HLD model cells, and the Nrf2 inhibitor ML385 reversed the effects of curcumin.

Conclusion: Curcumin demonstrates a protective role by expelling copper and inhibiting ferroptosis, activating the Nrf2/HO-1/GPX4 signaling pathway in HLD.

Keywords: Copper excretion; Curcumin; Ferroptosis; HLD model cells; Hepatolenticular degeneration; TX mice.