Citrulline protects against LPS‑induced acute lung injury by inhibiting ROS/NLRP3‑dependent pyroptosis and apoptosis via the Nrf2 signaling pathway

Abstract

Acute lung injury (ALI) is a common complication in patients with sepsis and is accompanied by high mortality. The present study aimed to investigate if the organic compound citrulline has a protective against lipopolysaccharide (LPS)-stimulated ALI and its potential mechanisms. ALI was induced in mice by intraperitoneal (i.p.) injection of LPS (10 mg/kg). Citrulline (1 g/kg/day) was administrated i.p. 7 days prior to LPS injection. Mouse lung vascular endothelial cells (MLVECs) were divided into five groups: Control, LPS, LPS + Cit, LPS + N-acetyl-L-cysteine (NAC) and LPS + Cit + ML385. Lung injury was determined by morphology changes. Apoptosis and pyroptosis were detected using western blot analysis and immunofluorescence. The present results indicated that citrulline can significantly attenuate ALI. Citrulline pretreatment decreased the expression of NOD-, LRR-and pyrin domain-containing protein 3 (NLRP3) inflammasome and decreased pyroptosis and apoptosis. Intervention with the total reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine attenuated NLRP3 inflammasome-associated pyroptosis and apoptosis in LPS-treated MLVECs. Citrulline pretreatment inhibited pyroptotic cell death and apoptosis induced by LPS. Citrulline decreased accumulation of intracellular ROS and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. Furthermore, the Nrf2 inhibitor ML385 reversed ROS generation, NLRP3 inflammasome-mediated pyroptosis and apoptosis suppressed by citrulline. In summary, the present data demonstrated that citrulline may confer protection against ALI via inhibition of ROS/NLRP3 inflammasome-dependent pyroptosis and apoptosis via the Nrf2 signaling pathway.

Citrulline inhibits LPS‐induced pyroptosis of RAW264.7 macrophages through NF‐κB signaling pathway

“…It is reported to possess anti‐inflammatory effects by suppressing pyroptosis. A previous study has revealed that citrulline inhibits pyroptosis, apoptosis, and inflammatory changes induced by LPS in lung 19 . Consistently, the results in this study indicated that citrulline promoted LPS‐induced cell viability and suppressed pyroptosis of RAW264.7 cells.…”

The Co-Localization of NLRP3 and ASC Specks Does Not Automatically Entail NLRP3 Inflammasome Functionality in PDAC Cell Lines

“…We also observed a difference in the ASC amount between cell lines, but a higher ASC amount was not associated with more ASC speck formation. A high expression of ASC protein is often used as a marker for inflammasome formation in multiple types of cancer [21,31,[43][44][45][46][47][48][49]. The ASC protein levels [13] and PYCARD gene expression [50] (Figure 5e) were increased in the PDAC tissue, but our results imply that the ASC amount alone may be a poor marker for inflammasome formation.…”

Global research progress of endothelial cells and ALI/ARDS: a bibliometric analysis

“…Moreover, recent studies have revealed that high-mobility group box 1 (HMGB1) can also activate Caspase-1 in hemorrhagic shock-induced ALI, thus amplifying LPS-triggered endothelial cell pyroptosis ( Yang et al, 2016 ). Secondly, in terms of pharmacological interventions, beyond metformin, small molecule compounds like Isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate—one of the primary bioactive metabolites of the Chinese medicinal herb Danshen—and Citrulline have shown promise in reducing endothelial cell pyroptosis by inhibiting NLRP3 activity ( Xue et al, 2022 ; Zhang ML. et al, 2023 ).…”