The protective effect of dexmedetomidine on LPS-induced acute lung injury through the HMGB1-mediated TLR4/NF-κB and PI3K/Akt/mTOR pathways.

The aim of present study was to evaluate the protective effects of dexmedetomidine (DEX) on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and investigate its possible mechanisms mediated by HMGB1. In vivo, pulmonary pathology observation and myeloperoxidase (MPO) activity were also examined to evaluate the protective effect of DEX in the lungs. Tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid (BALF), serum and lung tissues LPS-induced rats were detected. The oxidative indices including superoxide dismutase (SOD), Malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) in serum were also determined. Additionally, nitric oxide (NO), TNF-α, IL-6 and IL-1β, MDA, SOD and GSH-Px in the supernatants of LPS-induced BEAS-2B cells were measured. Furthermore, we detected the protein expression of high mobility group box-1 protein (HMGB1), Toll-like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), inhibitor of NF-κB (IκBα), p-IκBα, nuclear factor kappa-B (NF-κB), p-NF-κB, phosphatidylinositol 3'-kinase (PI3K), p-PI3K, protein kinase B (Akt), p-Akt, mammalian target of rapamycin (mTOR) and p-mTOR in LPS-induced ALI rats and LPS-induced BEAS-2B cells. Immunohistochemical and immunofluorescence analyses of HMGB1 in lung tissues or BEAS-2B cells were also conducted to evaluate the mechanisms of DEX. DEX effectively attenuated pulmonary pathology, and ameliorated the levels of MPO, SOD, MDA, GSH-Px, TNF-α, IL-6, IL-1β and NO in LPS-stimulated rats and BEAS-2B cells. Additionally, treatment with DEX inhibited the expression of HMGB1, TLR4, MyD88, p-IκB, p-NF-κB, p-PI3K, p-Akt and p-mTOR in vivo and in vitro. Immunohistochemical and immunofluorescence analyses also showed that DEX suppressed HMGB1 levels in lung sections and BEAS-2B cells. Treatment with glycyrrhizin, an inhibitor of HMGB1, confirmed that HMGB1 was involved in the mechanism of DEX on LPS-induced ALI. The transfection of HGMB1 siRNA also confirmed these findings in vitro. In conclusion, the present study showed that DEX exerted a protective effect on LPS-induced ALI rats likely through the HMGB1-mediated TLR4/NF-κB and PI3K/Akt/mTOR pathways.

Meng L ，Li L ，Lu S ，Li K ，Su Z ，Wang Y ，Fan X ，Li X ，Zhao G ... -  《-》

Protective effects of polydatin on lipopolysaccharide-induced acute lung injury through TLR4-MyD88-NF-κB pathway.

The purpose of this study was to investigate the protective effect of PD against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and explore its potential mechanism. In vivo, PD and dexamethasone were intraperitoneally administered 1h before LPS stimulation. Then, mice were sacrificed at 6h post-LPS stimulation. Neutrophil number, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid (BALF) were determined, as well as lung wet to dry ratio (W/D) and polymorphonuclear (MPO) activity. The protein expressions of Toll like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), IL-1R-associated kinases 1 (IRAK1), IRAK4, inhibitor of nuclear factor kappa-B kinase (IKK)α, p-IKKα, IKKβ, p-IKKβ, inhibitor of NF-κB (IκBα), p-IκBα and NF-κB in lung tissues were assessed. Besides, we detected the IL-6, IL-1β, IL-8, TNF-α levels and TLR4, MyD88, NF-κB protein expressions in LPS-induced BEAS-2B cells. Consequently, PD significantly inhibited the levels of W/D, MPO, neutrophils number, TNF-α, IL-6, IL-1β and reversed TLR4-MyD88-NF-κB signaling pathway in lung tissues. In vitro assays, PD effectively negatively mediated the inflammatory cytokines and ameliorated the high expressions of TLR4, MyD88, NF-κB caused by LPS simulation in Human bronchial epithelial BEAS-2B cells. This study indicated that PD played a protective role in LPS-induced ALI and BEAS-2B cells. The results supported further study of PD as potential candidate for acute lung injury.

Jiang Q ，Yi M ，Guo Q ，Wang C ，Wang H ，Meng S ，Liu C ，Fu Y ，Ji H ，Chen T ... -  《-》

Dexmedetomidine attenuates lipopolysaccharide induced acute lung injury in rats by inhibition of caveolin-1 downstream signaling.

Toll-like receptor 4(TLR-4)/nuclear factor-kappa B(NF-κB) pathway plays an important role in inducing acute lung injury (ALI). Studies have proved Dexmedetomidine (Dex) inhibits inflammatory response to mitigate lipopolysaccharide (LPS)-induced ALI and protect against multiorgan injury in various scenarios via restraining TLR-4/NF-κB signaling pathway. Many of the known downstream molecules have been orientated with a protein caveolin-1(Cav-1), which is supposed to take part in regulating TLR4-mediated inflammatory responses. However, its mechanisms have not been confirmed. The aim of this study is to evaluate the protective effects and potential mechanisms of Dex against LPS-induced ALI in male rats. Male rats received tail-vein injection of LPS to form ALI model. Rats were administrated with intraperitoneal injection Dex0.5 h before ALI. At 6 h after LPS injection, bronchoalveolar lavage fluid (BALF) and lung tissue were harvested. We stained the lung tissue sections with hematoxylin eosin (HE) staining to observe the histopathological damage and measure the ALI pathology score. We also measured the wet-to-dry(W/D) weight ratio of lung tissue. Lung myeloperoxidase (MPO) and inflammatory cytokines in the BALF were detected by Enzyme-linked immunosorbent assay(ELISA). Protein levels of Cav-1, TLR-4 and NF-κB in lung tissue were tested by immunohistochemistry method. The mRNA expression of Cav-1, TLR4 and the NF-κB in lung tissue were measured to determine the related mechanisms by quantitative real-time polymerase chain reaction(RT-PCR). It was indicated that Dex pretreatment markedly mitigated pathomorphologic changes and pathological lung injury scores. Besides, Dex pretreatment obviously decreased the W/D weight ratio of lung tissue, attenuated MPO activity significantly, along with LPS-stimulated augment of lung inflammatory cells infiltration in BALF. Moreover, compared with LPS model group, Dex pretreatment apparently increased the protein levels of Cav-1 downregulated by sepsis and decreased the protein levels of TLR-4 and NF-κB in lung tissue. Furthermore, Dex pretreatment apparently upregulated the expression of Cav-1 mRNA, restrained TLR4 and NF-κB mRNA. Dex pretreatment protects against LPS-induced ALI via inhibiting the activation of the TLR-4/NF-kB signaling pathway by upregulating the expression of Cav-1 downregulated by sepsis.

Liu J ，Huang X ，Hu S ，He H ，Meng Z ... -  《-》

Bakuchiol regulates TLR4/MyD88/NF-κB and Keap1/Nrf2/HO-1 pathways to protect against LPS-induced acute lung injury in vitro and in vivo.

Bakuchiol (Bak) possesses a protective effect in acute lung injury (ALI). Nonetheless, the molecular processes that regulate the protective activity of Bak in ALI remain elusive. Lipopolysaccharide (LPS)-treated rats and RLE-6TN cells were used as the ALI models in vivo and in vitro to investigate the function and mechanism of Bak. Rats were divided into four groups: control, LPS, LPS + Bak (30 mg/kg), and LPS + Bak (60 mg/kg). RLE-6TN cells were assigned into four groups: control, LPS, LPS + Bak (10 µM), and LPS + Bak (20 µM). Myeloperoxidase (MPO) and 4-hydroxy-2-nonenal (4-HNE) levels were detected by immunohistochemistry (IHC). The levels of TNF-α, IL-6, and IL-1β were quantified by ELISA. Apoptosis was analyzed by TdT-mediated dUTP nick-end labeling (TUNEL) staining and flow cytometry. Malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and reactive oxygen species (ROS) were assayed to evaluate oxidative stress. In LPS-induced rats, Bak attenuated pathological injury, lung wet/dry weight ratio, MPO expression, and protein concentration and cell number in bronchial alveolar lavage fluid (BALF). Bak decreased the secretion of TNF-α, IL-6, and IL-1β in BALF. Bak reduced MDA content and 4-HNE expression, and increased SOD and GSH-Px activities in lung tissues. Bak also repressed pulmonary apoptosis by decreasing Bax expression and enhancing Bcl-2 expression. In LPS-treated RLE-6TN cells, Bak downregulated the mRNA levels of TNF-α, IL-6, and IL-1β and inhibited the protein expression of iNOS and COX2. Bak decreased MDA level and ROS production and increased SOD and GSH-Px activities. Bak also suppressed cell apoptosis, reduced Bax expression, and increased Bcl-2 expression. Moreover, Bak decreased the expression of TLR4, MyD88, p-IκBα, and p-p65. Additionally, Bak inhibited Keap1 expression and increased Nrf2 and HO-1 levels. Bak protects against LPS-induced inflammation, oxidative stress, and apoptosis in ALI by regulating TLR4/MyD88/NF-κB and Keap1/Nrf2/HO-1 pathways.

Zhao L ，Zhang Z ，Li P ，Gao Y ，Shi Y ... -  《-》

Dexmedetomidine Post-Conditioning Alleviates Cerebral Ischemia-Reperfusion Injury in Rats by Inhibiting High Mobility Group Protein B1 Group (HMGB1)/Toll-Like Receptor 4 (TLR4)/Nuclear Factor kappa B (NF-κB) Signaling Pathway.

Zhai Y ，Zhu Y ，Liu J ，Xie K ，Yu J ，Yu L ，Deng H ... -  《MEDICAL SCIENCE MONITOR》