Abstract
Autophagy degrades impaired organelles and toxic proteins to maintain cellular homeostasis. Dysregulated autophagy is a pathogenic participant in Alzheimer's disease (AD) progression. In early-stage AD, autophagy is beneficially initiated by mild endoplasmic reticulum (ER) stress to alleviate cellular damage and inflammation. However, chronic overproduction of toxic Aβ oligomers eventually causes Ca2+ dysregulation in the ER, subsequently elevating ER-stress and impairing autophagy. Our previous work showed that a novel anthranilate analogue (SI-W052) inhibited lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α and interleukin (IL)-6 on microglia. To investigate its mechanism of action, herein, we postulate that SI-W052 exhibits anti-inflammatory activity through ER-stress-mediated autophagy. We initially demonstrate that autophagy inhibits inflammation, but it becomes impaired during acute inflammation. SI-W052 significantly induces the conversion ratio of LC3 II/I and inhibits LPS-upregulated p-mTOR, thereby restoring impaired autophagy to modulate inflammation. Our signaling study further indicates that SI-W052 inhibits the upregulation of ER-stress marker genes, including Atf4 and sXbp1/tXbp1, explaining compound activity against IL-6. This evidence encouraged us to evaluate ER-stress-triggered ER-phagy using TEX264. ER-phagy mediates ER-turnover by the degradation of ER fragments to maintain homeostasis. TEX264 is an important ER-phagy receptor involved in ATF4-mediated ER-phagy under ER-stress. In our study, elevated TEX264 degradation is identified during inflammation; SI-W052 enhances TEX264 expression, producing a positive effect in ER-turnover. Our knockdown experiment further verifies the important role of TEX264 in SI-W052 activity against IL-6 and ER-stress. In conclusion, this study demonstrates that an anthranilate analogue is a novel neuroinflammation agent functioning through ER-stress-mediated autophagy and ER-phagy mechanisms.