Activating Sig-1R inhibits microvascular permeability by reducing LRRK2 expression in lipopolysaccharide-induced acute lung injury

Background: Endothelial cells are the first and most damaged target cells during acute lung injury (ALI). Endothelial dysfunction increases pulmonary microvascular permeability, subsequently leading to pulmonary oedema and organ dysfunction; however, clinical treatments against microvascular permeability show poor efficacy. Herein, we aimed to explore the role of the Sigma-1 receptor (Sig-1R) in pulmonary microvascular permeability by constructing ALI animal and cell models, and further investigated the specific mechanisms.

Methods: The effects of Sig-1R on lung injury and endothelial barrier disruption were examined in lipopolysaccharide (LPS)-induced mice and human umbilical vein endothelial cells (HUVECs), respectively. Transcriptome sequencing was carried out to identify possible targets of Sig-1R, and the specific mechanisms of Sig-1R action were investigated using RNA interference and plasmid transfection.

Results: Analysis of a Gene expression omnibus dataset suggested that Sig-1R plays a protective role against vascular hyperpermeability in ALI. Downregulation of Sig-1R expression and endothelial barrier disruption were both observed in mice and HUVECs upon LPS stimulation. Sig-1R agonists attenuated vascular hyperpermeability in vivo and in vitro, further improving ALI. Sig-1R activation downregulated Leucine-rich repeat kinase 2 (LRRK2) expression in mice and HUVECs. LRRK2 knockdown ameliorated endothelial barrier disruption in mice and HUVECs. Overexpression of LRRK2 reversed the protective effect of Sig-1R activation on LPS-induced endothelial hyperpermeability. Furthermore, Sig1r knockdown exacerbated LPS-induced microvascular hyperpermeability, which was rescued by inhibition of LRRK2.

Conclusions: Sig-1R activation exerts a protective effect against LPS-induced microvascular hyperpermeability by downregulating LRRK2 expression, which could lead to the development of novel therapeutic strategies for treating ALI.