Luteolin activates Tregs to promote IL-10 expression and alleviating caspase-11-dependent pyroptosis in sepsis-induced lung injury

Abstract

Objectives: Acute respiratory distress syndrome (ARDS) is characterized by an excessive pulmonary inflammatory response. Pyroptosis is a newly form of programmed inflammatory cell death that is triggered by inflammatory caspases. Studies have shown that Luteolin has powerful anti-inflammation effects through activating the function of regulatory T cells (Tregs). The study aimed at investigating the effects of Luteolin on CLP-induced ALI.

Methods: In our study, we employed the mouse cecal ligation and puncture (CLP) model to explore whether Luteolin contributed to alleviated lung injury in vivo. H&E staining and wet/dry (W/D) weight ratios were used to evaluate the severity of lung injury. The serum and BALF of cytokines were assessed by ELISA. The number of neutrophils in the BALF was counted. Immunohistochemistry of IL-10 and MPO in lung tissue was detected. The ROS level in lung was tested by ROS Assay Kit and expression of Gpx4 in lung tissue was detected by qRT-PCR and Western blotting. The regulatory T cells (Treg) population was analyzed in spleen and Peripheral blood mononuclear cells (PBMCs). The levels of caspase-11 protein, caspase-1 protein, GSDMD protein, IL-1α and IL-1β protein in the lung tissue was evaluated by Western blotting.

Results: We found Luteolin significantly inhibits inflammation and attenuated CLP-induced lung injury in vivo, and the levels of, caspase-11, caspase-1, GSDMD, IL-1α and IL-1β protein in the lungs of CLP mice decreased significantly after pretreatment with Luteolin. Furthermore, the results showed that Luteolin could increase Treg frequencies and IL-10 levels in serum and BALF of CLP mice. It is noteworthy that depleting Tregs reverse Luteolin ameliorated lung injury, and IL-10 neutralizing antibodies treatment aggravated lung pyroptosis.

Conclusions: Our study illustrated that Luteolin contributed to alleviated lung injury, and attenuated caspase-11-dependent pyroptosis in the lung tissue of the CLP-induced ALI mouse model. The mechanisms could be related to regulating the frequency of Tregs and the levels of Treg derived IL-10. Treg cells were show to produce IL-10 and could alleviating caspase-11-dependent lung pyroptosis.

Keywords: Lung injury; Luteolin; Pyroptosis; Sepsis; Tregs.