ALKBH5 modulation of ferroptosis in recurrent miscarriage: implications in cytotrophoblast dysfunction

As one of the most common and abundant internal modifications of eukaryotic mRNA, N⁶-methyladenosine (m⁶A) modifications are closely related to placental development. Ferroptosis is a newly discovered form of programmed cell death. During placental development, placental trophoblasts are susceptible to ferroptosis. However, the interactions of m⁶A and ferroptosis in trophoblast physiology and injury are unclear.

Recurrent miscarriage (RM) was selected as the main gestational disease in this study. Published data (GSE76862) were used to analyze the gene expression profiles in patients with RM. The extent of m⁶A modification in total RNA of villous tissues between patients with RM and healthy controls (HC) was compared. ALKBH5 (encoding AlkB homolog 5, RNA demethylase) was selected as the candidate gene for further research. Quantitative real-time reverse transcription PCR, western blotting, and immunohistochemistry (IHC) confirmed the elevated expression of ALKBH5 in the cytotrophoblasts of patients with RM. Then, cell counting kit-8 assays, glutathione disulfide/glutathione quantification, 2',7'-dichlorfluorescein-diacetate staining, and malonaldehyde assays were used to explore the alterations of ferroptosis-related characteristics following RAS-selective lethal (RSL3) stimulation after overexpression of ALKBH5. Thereafter, we re-analyzed the published RNA sequencing data upon knockdown of ALKBH5, combined with published tissue RNA-seq data, and FTL (encoding ferritin light chain) was identified as the ferroptosis-related gene in cytotrophoblasts of patients with RM that is regulated by ALKBH5. Finally, western blotting and IHC confirmed the increased expression of FTL in the cytotrophoblasts from patients with RM.

Total m⁶A levels were decreased in patients with RM. The most significant differentially m⁶A-related gene was ALKBH5, which was increased in patients with RM. In vitro cell experiments showed that treatment with RSL3 resulted in increased cell death and upregulated ALKBH5 expression. Overexpression of ALKBH5 alleviated RSL3-induced HTR8 cell death and caused decreased levels of intracellular oxidation products. Published transcriptome sequencing revealed that FTL was the major ferroptosis-related gene regulated by ALKBH5 in the villous tissues of patients with RM. Consistent with the expression of ALKBH5, FTL was increased by RSL3-induction and increased in patients with RM.

Elevated ALKBH5 alleviated RSL3-induced cytotrophoblast cell death by promoting the expression of FTL in patients with RM. Our results supported the view that ALKBH5 is an important regulator of the ferroptosis-related etiology of RM and suggested that ALKBH5 could be responsible for epigenetic aberrations in RM pathogenesis.