Gut microbiota-derived gamma-aminobutyric acid from metformin treatment reduces hepatic ischemia/reperfusion injury through inhibiting ferroptosis.

Hepatic ischemia/reperfusion injury (HIRI) is a common and inevitable factor leading to poor prognosis in various liver diseases, making the outcomes of current treatments in clinic unsatisfactory. Metformin has been demonstrated to be beneficial to alleviate HIRI in recent studies, however, the underpinning mechanism remains unclear. In this study, we found metformin mitigates HIRI-induced ferroptosis through reshaped gut microbiota in mice, which was confirmed by the results of fecal microbiota transplantation treatment but showed the elimination of the beneficial effects when gut bacteria were depleted using antibiotics. Detailedly, through 16S rRNA and metagenomic sequencing, we identified that the metformin-reshaped microbiota was characterized by the increase of gamma-aminobutyric acid (GABA) producing bacteria. This increase was further confirmed by the elevation of GABA synthesis key enzymes, glutamic acid decarboxylase and putrescine aminotransferase, in gut microbes of metformin-treated mice and healthy volunteers. Furthermore, the benefit of GABA against HIRI-induced ferroptosis was demonstrated in GABA-treated mice. Collectively, our data indicate that metformin can mitigate HIRI-induced ferroptosis by reshaped gut microbiota, with GABA identified as a key metabolite.

Ischemia/reperfusion-activated ferroptosis in the early stage triggers excessive inflammation to aggregate lung injury in rats.

Objective: Lung ischemia/reperfusion injury (LIRI) is a clinical syndrome of acute lung injury that occurs after lung transplantation or remote organ ischemia. Ferroptosis and inflammation are involved in the pathogenesis of LIRI according to the results of several studies on animal models. However, the interactive mechanisms between ferroptosis and inflammation contributing to LIRI remain unclear. Methods: HE staining and indicators of oxidative stress were used to evaluated the lung injury. The reactive oxygen species (ROS) level was examined by DHE staining. The quantitative Real-time PCR (qRT-PCR) and western blot analysis were employed to detect the level of inflammation and ferroptosis, and deferoxamine (DFO) was used to assess the importance of ferroptosis in LIRI and its effect on inflammation. Results: In the present study, the link of ferroptosis with inflammation was evaluated at reperfusion 30-, 60- and 180-minute time points, respectively. As the results at reperfusion 30-minute point shown, the pro-ferroptotic indicators, especially cyclooxygenase (COX)-2 and acyl-CoA synthetase long-chain family member 4 (ACSL4), were upregulated while the anti-ferroptotic factors glutathione peroxidase 4 (GPX4), cystine-glumate antiporter (XCT) and ferritin heavy chain (FTH1) were downregulated. Meanwhile, the increased level of interleukin (IL)-6, tumor necrosis factor alpha (TNF-α) and IL-1ß were observed beginning at reperfusion 60-minute point but mostly activated at reperfusion 180-minute point. Furthermore, deferoxamine (DFO) was employed to block ferroptosis, which can alleviate lung injury. Expectedly, the survival rate of rats was increased and the lung injury was mitigated containing the improvement of type II alveolar cells ultrastructure and ROS production. In addition, at the reperfusion 180-minute point, the inflammation was observed to be dramatically inhibited after DFO administration as verified by IL-6, TNF-α and IL-1ß detection. Conclusion: These findings suggest that ischemia/reperfusion-activated ferroptosis plays an important role as the trigger for inflammation to further deteriorate lung damages. Inhibiting ferroptosis may have therapeutic potential for LIRI in clinical practice.