Suppressing Endoplasmic Reticulum Stress Alleviates LPS-Induced Acute Lung Injury via Inhibiting Inflammation and Ferroptosis

Acute lung injury (ALI) is a life-threatening clinical disorder with high mortality rate. Ferroptosis is a new type of programmed cell death with lipid peroxidation and iron ion overloading as the main characteristics. Endoplasmic reticulum (ER) stress and ferroptosis play pivotal roles in the pathogenesis of ALI. The study aimed to investigate the underlying relationship between ER stress and ferroptosis in ALI. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated LPS-induced inflammation, and decreased IL-1 beta, IL-6, and TNF-alpha levels in BALF and lungs. The increased MDA and decreased GSH induced by LPS were partially reversed by 4-PBA, which also inhibited the expressions of ferroptosis-related protein ACSL4, COX-2, and FTH1. TEM further confirmed the ferroptosis within airway epithelia cells was ameliorated by 4-PBA. Moreover, 4-PBA reduced the production of ROS and lipid ROS in LPS-exposed BEAS-2B cells in a concentration-dependent way. Meanwhile, 4-PBA mitigated LPS-induced cell apoptosis in vivo and in vitro. Mechanistically, the MAPK signaling pathway activated by LPS was downregulated by 4-PBA. Collectively, these findings suggested that 4-PBA protected against ALI by inhibiting inflammation and ferroptosis through downregulating ER stress, thus providing a potential intervention for ALI and revealing the possible interaction between ER stress and ferroptosis in ALI.