Andrographolide ameliorates sepsis-induced acute lung injury by promoting autophagy in alveolar macrophages via the RAGE/PI3K/AKT/mTOR pathway

Autophagy in alveolar macrophages (AMs) is an important mechanism for maintaining immune homeostasis and normal lung tissue function, and insufficient autophagy in AMs may mediate the development of sepsis-induced acute lung injury (SALI). Insufficient autophagy in AMs and the activation of the NLRP3 inflammasome were observed in a mouse model with SALI induced by cecal ligation and puncture (CLP), resulting in the release of a substantial quantity of proinflammatory factors and the formation of SALI. However, after andrographolide (AG) intervention, autophagy in AMs was significantly promoted, the activation of the NLRP3 inflammasome was inhibited, the release of proinflammatory factors and pyroptosis were suppressed, and SALI was then ameliorated. In the MH-S cell model stimulated with LPS, insufficient autophagy was discovered to promote the overactivation of the NLRP3 inflammasome. AG was found to significantly promote autophagy, inhibit the activation of the NLRP3 inflammasome, and attenuate the release of proinflammatory factors. The primary mechanism of AG promoting autophagy was to inhibit the activation of the PI3K/AKT/mTOR pathway by binding RAGE to the membrane. In addition, it inhibited the activation of the NLRP3 inflammasome to ameliorate SALI. Our findings suggest that AG promotes autophagy in AMs through the RAGE/PI3K/AKT/mTOR pathway to inhibit the activation of the NLRP3 inflammasome, remodel the functional homeostasis of AMs in SALI, and exert anti-inflammatory and lung-protective effects. It has also been the first to suggest that RAGE is likely a direct target through which AG regulates autophagy, providing theoretical support for a novel therapeutic strategy in sepsis.