Dual role of Nrf2/HO-1 pathway in Z-ligustilide-induced ferroptosis against AML cells.

Background: The scarcity of drugs targeting AML cells poses a significant challenge in AML management. Z-Ligustilide (Z-LIG), a phthalide compound, shows promising pharmacological potential as a candidate for AML therapy. However, its precise selective mechanism remains unclear.

Purpose: In order to assess the selective inducement effects of Z-LIG on ferroptosis in AML cells and explore the possible involvement of the Nrf2/HO-1 pathway in the regulation of ferroptosis.

Methods: Through in vitro cell proliferation and in vivo tumor growth tests, the evaluation of Z-LIG's anticancer activity was conducted. Ferroptosis was determined by the measurement of ROS and lipid peroxide levels using flow cytometry, as well as the observation of mitochondrial morphology. To analyze the iron-related factors, western blot analysis was employed. The up-regulation of the Nrf2/HO-1 axis was confirmed through various experimental techniques, including CRISPR/Cas9 gene knockout, fluorescent probe staining, and flow cytometry. The efficacy of Z-LIG in inducing ferroptosis was further validated in a xenograft nude mouse model.

Results: Our study revealed that Z-LIG specifically triggered lipid peroxidation-driven cell death in AML cells. Z-LIG downregulated the total protein and nuclear entrance levels of IRP2, resulting in upregulation of FTH1 and downregulation of TFR1. Z-LIG significantly increased the susceptibility to ferroptosis by upregulating ACSL4 levels and simultaneously suppressing the activity of GPX4. Notably, the Nrf2/HO-1 pathway displayed a twofold impact in the ferroptosis induced by Z-LIG. Mild activation suppressed ferroptosis, while excessive activation promoted it, mainly driven by ROS-induced labile iron pool (LIP) accumulation in AML cells, which was not observed in normal human cells. Additionally, Nrf2 knockout and HO-1 knockdown reversed iron imbalance and mitochondrial damage induced by Z-LIG in HL-60 cells. Z-LIG effectively inhibited the growth of AML xenografts in mice, and Nrf2 knockout partially weakened its antitumor effect by inhibiting ferroptosis.

Conclusion: Our study presents biological proof indicating that the selective initiation of ferroptosis in leukemia cells is credited to the excessive activation of the Nrf2/HO-1 pathway triggered by Z-LIG.