Andrographolide mitigates neurotoxicity induced by lipopolysaccharide or amyloid-β through modulation of miR-222-mediated p62 and NF-κBp65 expression

MicroRNA-222 (miR-222) plays a crucial role in neurodegeneration and is up-regulated in Alzheimer's disease (AD) patients. Andrographolide (Andro) has been reported to have anti-inflammatory and neuroprotective effects, showing potential for treating AD. The relationship between Andro's anti-AD mechanism and the regulation of miR-222 was discussed in this study. Andro protected against cytotoxicity induced by lipopolysaccharide (LPS) or amyloid-β, accompanied by upregulating p62 and Nrf2 mRNA and protein, downregulating TLR4 and NF-κBp65 mRNA and protein, and increasing LC3Ⅱ protein in vitro. miRNA and mRNA sequencing results showed that Andro downregulated miR-222 and upregulated sqstm1/p62. Andro was observed to inhibit the expression of miR-222 and the phosphorylation of NF-κBp65, while simultaneously enhancing the levels of p62 and LC3Ⅱ proteins, decreasing Aβ levels, and attenuating the release of inflammatory factors in the 3xTg-AD mice. MiR-222 mimic increased NF-κBp65 mRNA and protein levels in LPS-induced cells, while miR-222 inhibitors increased p62 mRNA and protein levels as well as Nrf2 and LC3Ⅱ protein, and decreased p-NF-κBp65 protein level in LPS-induced cells. Furthermore, miR-222 mimic reversed the increase in p62 and LC3Ⅱ protein and the decrease in NF-κBp65 mRNA and protein, as well as the decrease in Tau protein levels induced by Andro in LPS-induced cells. These findings suggest that Andro plays a neuroprotective role through downregulation of miR-222 to promote p62 expression while inhibiting NF-kB p65 expression, providing new insights into the mechanism of action of Andro for treating AD.