Astragaloside <scp>IV</scp> Pretreatment Alleviates Pulmonary Ischemia–Reperfusion Injury via the <scp>TLR4</scp>/<scp>MyD88</scp>/<scp>NF</scp>‐<scp>κB</scp> p65 Pathway in Rats

Background and aim Our previous study confirmed that ASIV can protect the lung from ischemia-reperfusion injury. The aim of this study was to determine whether ASIV attenuates PIRI by inhibiting the activation of the TLR4/MyD88/NF-κBp65 pathway. Experimental procedure In vitro, the protection of ASIV, TAK-242, NAC, and DEX to OGD/R-induced cell injury was compared. In vivo, the PIRI model was induced in SD rats. The lung tissue W/D ratio and pathological morphology, as well as the markers of oxidative stress, were monitored. The mRNA and protein expression levels correlated to the TLR4/MyD88/NF-κB p65 pathway were evaluated. Furthermore, we performed molecular docking and binding affinity calculations of the interaction between ASIV and TLR4-MD-2, which was verified with SPR. Key results and conclusions and implications ASIV showed more effective protection than DEX or NAC, and exhibited a synergistic effect with TAK-242. After treatment with ASIV, lung tissue and cellular damage were obviously alleviated, and the levels of T-SOD and GSH-PX were significantly increased, while lung MDA and MPO decreased. Moreover, the ASIV groups showed a significant down-regulation of the TLR4, MyD88, NF-κBp65 and p-NF-κBp65 proteins when compared with the PIRI model group. The prediction showed that ASIV can enter the cavity of TLR4-MD-2 and exhibit strong binding, with a free binding energy of -8.0 kcal·mol^-1. SPR further confirmed that ASIV rapidly bound to the rhTLR4-MD-2 complex with a K_D of 2.17 × 10^-6 M. In conclusion, ASIV can specifically bind to rhTLR4-MD-2, thus alleviating PIRI by suppressing the activation of the TLR4/MyD88/NF-κB65-mediated inflammatory pathway.