Baicalin exerts protective effects against lipopolysaccharide-induced acute lung injury by regulating the crosstalk between the CX3CL1-CX3CR1 axis and NF-κB pathway in CX3CL1-knockout mice

Acute lung injury (ALI) as a serious diseases with high mortality and is considered a threat to human health and life. A number of studies have focused on the treatment and prevention of lung injury. However, the molecular mechanisms responsible for the development of lung injury are not yet fully understood, and this has impeded the development of effective drugs and treatment strategies. Hence, in the present study, mice with lipopolysaccharide (LPS)-induced ALI were used as a model to investigate the crosstalk between the CX3CL1-CX3CR1 axis and the nuclear factor (NF)-kappa B signaling pathway in the process of lung injury. CX3CL1-knockout (CX3CL1-KO or CX3CL1(-/-)) mice were used to examine the role of the CX3CL1-CX3CR1 axis in LPS-induced lung injury. We used baicalin, a natural product, to investigate its anti-inflammatory effects and its protective effects against lung injury. Western blot analysis, reverse transcription-quantitavie PCR (RT-qPCR), immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and the analysis of biochemical indicators were used to determine the key signaling pathway involved in the development of lung injury. The results indicated that, on the one hand, baicalin exerted potent anti-inflammatory effects by inhibiting the activation of the CX3CL1-CX3CR1 axis and NF-kappa B, thus preventing the the crosstalk between the CX3CL1-CX3CR1 axis and NF-kappa B pathway. In addition, the phosphorylation of AKT, which was significantly induced by LPS-induced ALI through the CX3CL1-CX3CR1 axis, was inhibited by treatment with baicalin. On the other hand, we further investigated the role of the CX3CL1-CX3CR1 axis in lung injury. We determined the diffrences in the expression levels of CX3CR1 between wild-type (WT) and CX3CL1(-/-) mice in order to establish its association with lung injury. Our results indicated that CX3CL1 may be the central and major indicator in the process of lung injury, which mediates the CX3CR1 receptor to activate AKT and further promote NF-kappa B activation. These findings demonstrate that the crosstalk between the CX3CL1-CX3CR1 axis and NF-kappa B signaling pathway plays a direct role in LPS-induced lung injury. The inhibition of the activation of the CX3CL1-CX3CR1 axis may thus suppress the development of ALI. In addition, baicalin inhibited the crosstalk between the CX3CL1-CX3CR1 axis and NF-kappa B pathway in mice with LPS-induced ALI. Thus, treatment with baicalin may be a potential therapeutic strategy for ALI.