Benzoylpaeoniflorin alleviates ulcerative colitis by inhibiting ferroptosis through targeting phosphogluconic dehydrogenase.

Background: Ulcerative colitis (UC) is a clinically refractory diseases of the digestive system. Benzoylpaeoniflorin (BP) is a compound from Baishao, a Chinese herbal medicine documented with effects of anti-enteritis. However, the potential of BP in treating UC, along with its underlying mechanisms, requires further elucidation.

Purpose: This research was conducted to assess the effects of BP on dextran sulfate sodium (DSS)-induced UC and to elucidate its underlying mechanisms.

Methods: The C57BL/6 mouse model of UC was developed by administering the mice to freely drink DSS solution for 7 days. The mice were also subjected to intragastric administration of BP. Histopathology, nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways, and ferroptosis indicators were determined in vivo. Besides, NCM460 cells were used to further evaluate the anti-ferroptosis effect of BP and its potential mechanisms. Ferroptosis agonists iron-dextrin (ID) and Erastin were employed to investigate whether BP exerts anti-UC effect by inhibiting ferroptosis. Similarly, Nrf2 inhibitor ML385 was conducted to ascertain the role of the Nrf2 signaling pathway in the downregulating ferroptosis effect of BP. Moreover, an ultra-performance liquid chromatography coupled with mass spectrometry was utilized to evaluate the changes in glucose metabolism within colon tissues of UC mice following BP treatment. Cellular thermal shift assay (CETSA), surface-plasmon resonance (SPR) and molecular docking were carried out to reveal the binding ability of BP and phosphogluconate dehydrogenase (PGD) protein. The PGD inhibitor, 6PGD-IN-S3 was used to evaluated whether BP inhibits anti-ferroptosis effect by upregulating the expression of PGD.

Results: BP exhibited significant anti-UC activity, leading to a reduction in both the disease activity index and histological damage in mice afflicted with UC. BP effectively mitigated DSS-induced ferroptosis both in vivo and in vitro. Additionally, ID and Erastin treatment diminished the therapeutic efficacy of BP against UC. A similar trend was observed in mice treated with ML385. Metabolomics analysis indicated that BP had a notable effect in restoring the pentose phosphate pathway (PPP) of colon tissues following DSS administration. The treatment of BP upregulated the activity of PGD. The inhibition of PGD weakened the anti-ferroptosis effect of BP. Subsequent analysis revealed that BP has the potential to effectively bind to PGD, thereby inhibiting PGD entries lysosomes.

Conclusion: The above findings provide robust evidence for the anti-UC mechanism of BP in inhibiting ferroptosis through upregulation of the Nrf2 signal. PGD, a key enzyme in the PPP, is proved as the target protein of BP to inhibit ferroptosis first time. BP has been further proved to inhibit the lysosomal degradation pathway of PGD.