Induction of autophagy via the TLR4/NF-?B signaling pathway by astragaloside IV contributes to the amelioration of inflammation in RAW264.7 cells

Cigarette smoking-related lung injury is one of the most common and fatal etiologies of many respiratory diseases, for which no effective interventions are available. Astragaloside IV (ASIV) is an active component extracted from Astragalus membranaceus. It is prescribed as a treatment for upper respiratory tract infections. Here, we report the potential anti-inflammatory effects and mechanisms of ASIV on cigarette smoking extract(CSE)-exposed RAW264.7 cells. Murine macrophages were exposed to CSE, followed by administration of ASIV at 25?100 ?g/mL for 24 h. ASIV significantly rescued CSE-induced cell death by inhibition of release pro inflammatory cytokines. We measured autophagy as an intracellular scavenger by analyzing autophagic flux using tandem mRFP-GFP-LC3 fluorescence microscopy. Following administration with ASIV in CSE-exposed RAW264.7 cells, there was a notable increase in autophagosomes and a range of autophagic vacuoles were generated, as seen with transmission electron microscopy. Loss of autophagy following transfection siRNA aggravated inflammatory injury and release of inflammatory cytokines. Mechanistically, ASIV-triggered autophagy is mediated by the TLR4/NF-?B signaling pathway to reduce inflammation. Taken together, our findings suggest that ASIV acts stimulates autophagy, and that ASIV induces autophagy by inhibiting the TLR4/NF-?B signaling pathway, contributing to alleviation of inflammation.

Automated summary

ASIV, extracted from Astragalus membranaceus, shows significant anti-inflammatory effects on CSE-exposed cells by promoting autophagy and inhibiting the TLR4/NF-κB signaling pathway, thus alleviating inflammation.