Functional analyses of copper transporter genes in the human liver cell line HepG2

Pretreatment with aqueous Moringa oleifera Lam. leaf extract prevents cadmium-induced hepatotoxicity by improving cellular antioxidant machinery and reducing cadmium accumulation

Cadmium (Cd) is a highly harmful pollutant that poses a serious threat to human health. The liver is the primary organ for Cd accumulation, and Cd-induced hepatotoxicity has been shown to be strongly correlated with an oxidative imbalance in hepatocytes. Our previous studies in the eukaryotic model organism Saccharomyces cerevisiae revealed that not only co-treatment but also pretreatment with aqueous Moringa oleifera Lam. leaf extract (AMOLE) effectively mitigated Cd toxicity by reducing intracellular Cd accumulation and Cd-mediated oxidative stress. In this study, we therefore investigated the preventive effect of AMOLE against Cd toxicity in human HepG2 hepatocytes. The results showed that, similar to the case of the yeast model, pretreatment with AMOLE prior to Cd exposure also significantly inhibited Cd-induced oxidative stress in HepG2 cells. Untargeted LC-MS/MS-based metabolomic analysis of AMOLE revealed that its major phytochemical constituents were organic acids, particularly phenolic acids and carboxylic acids. Additionally, DPPH-HPTLC fingerprints suggested that quercetin and other flavonoids possibly contribute to the antioxidant activities of AMOLE. Based on our findings, it appears that pretreatment with AMOLE prevented Cd-induced hepatotoxicity via three possible mechanisms: i) direct elimination of free radicals by AMOLE antioxidant compounds; ii) upregulation of antioxidant defensive machinery (GPx1, and HO-1) via Nrf2 signaling cascade to improve cellular antioxidant capacity; and iii) reduction of intracellular Cd accumulation, probably by suppressing Cd uptake. These data strongly suggest the high potential of AMOLE for clinical utility in the prevention of Cd toxicity.

Copper transporter gene ATP7A: A predictive biomarker for immunotherapy and targeted therapy in hepatocellular carcinoma

BACKGROUND

ATP7A is an important copper transporter that regulates numerous cellular biological processes. However, the role of ATP7A in immunotherapy and targeted therapy, especially for hepatocellular carcinoma (HCC), remains unknown.

METHODS

We analyzed ATP7A expression and its effect on digestive system tumor prognoses, assessed its expression in tissue microarrays from 319 HCC patients, and investigated the relationship between ATP7A expression and tumor immunity. Specifically, we evaluated the possible association between ATP7A and programmed death ligand 1 (PD-L1) expression in human HCC tissues. Finally, we analyzed the effect of ATP7A on sorafenib efficacy in HCC.

RESULTS

ATP7A is generally highly expressed in digestive system tumors but related to poor prognosis only in HCC. ATP7A levels are positively associated with immune cell infiltration and immune checkpoint expression (especially PD-L1). HCC patients coexpressing APT7A and PD-L1 demonstrate poor prognoses. Moreover, HCC patients with high ATP7A levels were more sensitive to sorafenib and demonstrated higher survival rates after sorafenib treatment.

CONCLUSIONS

This study provides insights into the correlation between ATP7A levels and tumor immune infiltration and immune checkpoint function in HCC, sheds light on the significance of ATP7A in cancer progression, and provides guidance for more effective and general therapeutic strategies.

Promotion of cadmium uptake and cadmium-induced toxicity by the copper transporter CTR1 in HepG2 and ZFL cells

Cadmium (Cd²⁺) is considered a human carcinogen as it causes oxidative stress and alters DNA repair responses. However, how Cd²⁺ is taken up by cells remains unclear. We hypothesized that Cd²⁺ could be transported into cells via a membrane copper (Cu) transporter, CTR1. CTR1 expression was not affected by Cd²⁺ exposure at the mRNA or protein level. Stable cell lines overexpressing either hCTR1, in the human liver cell line HepG2, or zCTR1, in the zebrafish liver cell line ZFL, were created to study their responses to Cd²⁺ insult. It was found that both HepG2 and ZFL cells overexpressing CTR1 had higher Cd²⁺ uptake and thus became sensitive to Cd²⁺. In contrast, hCTR1 knockdown in HepG2 cells led to a reduced uptake of Cd²⁺, making the cells relatively resistant to Cd²⁺. Localization studies revealed that hCTR1 had a clustered pattern after Cd²⁺ exposure, possibly in an attempt to reduce both Cd²⁺ uptake and Cd²⁺-induced toxicity. These in vitro results indicate that CTR1 can transport Cd²⁺ into the cell, resulting in Cd²⁺ toxicity.