Radix Rehmanniae Praeparata aqueous extract improves hepatic ischemia/reperfusion injury by restoring intracellular iron homeostasis

Hepatic ischemia-reperfusion injury (HIRI) is a common pathophysiological event that happened during or after liver resection and transplantation and can impair hepatic viability and cause functional impairment. Recently, ferroptosis is a newfound pattern of programmed cell death that has been linked to ischemia-reperfusion injury. Radix Rehmanniae Praeparata (RRP) is widely used as primal medicine in Chinese herbal formulas due to its hepatoprotective, anti-inflammatory and antioxidant properties. However, how RRP improves HIRI and whether this mechanism involves the regulation of ferroptosis remains uncertain. In the current study, we established a HIRI mouse model, monocrotaline (MCT)- and erastin-induced in vitro hepatocyte injury models, and perform a whole-genome transcriptome analysis to reveal protective effects and mechanisms of RRP on HIRI. RRP aqueous extract was identified by acteoside, rehmannioside D and 5-hydroxymethylfurfural. RRP aqueous extract repaired oxidative stress imbalance, improved the intracellular iron ion accumulation and attenuated the HIRI-induced liver injury. We further demonstrated that RRP significantly prevented hepatocyte death by restoring intracellular iron homeostasis both in vivo and in vitro. Mechanistically, RRP aqueous extract inhibited intrahepatocellular iron ion accumulation by inhibiting ZIP14-mediated iron uptake, promoting hepcidin- and ferroportin-mediated iron efflux and repairing mitochondrial iron ion aggregation and iron metabolism by promoting Cisd1 expression. The inhibition of hamp by siRNA also synergistically enhanced the inhibitory effect of RRP aqueous extract on ferroptosis. In conclusion, our study not only elucidates the underlying mechanism of RRP aqueous extracts to alleviate HIRI from the perspective of repairing the iron metabolic network but also provides a viable clinical candidate for HIRI treatment.