Hydrogen sulfide alleviates particulate matter-induced emphysema and airway inflammation by suppressing ferroptosis.

BACKGROUND

Redox imbalance is an vital mechanism for COPD. At present, insufficient researches have been conducted on the protective effect of hydrogen sulfide (HS) on PM-induced COPD. However, whether HS exerts the anti-injury role by blocking ferroptosis and restoring redox equilibrium remain to be investigated.

METHODS

Human lung tissue samples were collected for IHC staining, and the expressions of Nrf2, ferritinophagy- and ferroptosis-related proteins were observed. The WT C57BL/6 and Nrf2 knockout mice models were established with PM(200 μg per mouse). NaHS(Exogenous HS) was injected intraperitoneally 30 min in advance. Twenty-nine days later, mice lung tissues were evaluated by HE's and PERLS-DAB's staining. Meanwhile, inflammation and oxidative stress indicators and iron levels were assessed by corresponding ELISA kit. Related protein expressions were detected through Western blot. BEAS-2B cells with or without HS were exposed to PM2.5 for 36 h. Cell viability, mitochondrial morphology, inflammatory cytokines, antioxidant factors, iron levels, autophagic flux and the levels of ROS, LIP ROS, MitoROS, MMP, as well as related protein expressions were detected by specific methods, respectively. In addition, V5-Nrf2, Nrf2 siRNA, Nrf2 inhibitor ML385, PPAR-γ inhibitor GW9662, autophagy inhibitor CQ, iron chelator DFO and ferroptosis inhibitor Fer-1 were used to verify the target signaling pathways.

RESULTS

We found that the expressions of LIP ROS, ROS, COX2, MDA and other oxidative factors increased, while the antioxidant markers GPX4, GSH and GSH-Px significantly decreased, as well as active iron accumulation in COPD patients, PM-exposured WT and Nrf2-KO mice models and PM2.5-mediated cell models. NaHS pretreatment markedly inhibited PM-induced emphysema and airway inflammation by alleviating ferroptotic changes in vivo and vitro. With the use of V5-Nrf2 overexpression plasmid, Nrf2 siRNA and pathway inhibitors, we found NaHS activates the expressions of Nrf2 and PPAR-γ, and inhibites ferritinophagy makers LC3B, NCOA4 and FTH1 in BEAS-2B cells. Moreover, the anti-ferroptotic effect of NaHS was further verified to be related to the activation of Nrf2 signal in MEF cells.

CONCLUSION

This research suggested that HS alleviated PM-induced emphysema and airway inflammation via restoring redox balance and inhibiting ferroptosis through regulating Nrf2-PPAR-ferritinophagy signaling pathway.