Targeting microglial autophagic degradation of the NLRP3 inflammasome for identification of thonningianin A in Alzheimer’s disease

Abstract

Background NLRP3 inflammasome-mediated neuroinflammation plays a critical role in the pathogenesis and development of Alzheimer’s disease (AD). Microglial autophagic degradation not only decreases the deposits of extracellular Aβ fibrils but also inhibits the activation of NRLP3 inflammasome. Here, we aimed to identify the potent autophagy enhancers from Penthorum chinense Pursh (PCP) that alleviate the pathology of AD via inhibiting the NLRP3 inflammasome. Methods At first, autophagic activity-guided isolation was performed to identify the autophagy enhancers in PCP. Secondly, the autophagy effect was monitored by detecting LC3 protein expression using Western blotting and the average number of GFP-LC3 puncta per microglial cell using confocal microscopy. Then, the activation of NLRP3 inflammasome was measured by detecting the protein expression and transfected fluorescence intensity of NLRP3, ASC, and caspase-1, as well as the secretion of proinflammatory cytokines. Finally, the behavioral performance was evaluated by measuring the paralysis in C. elegans, and the cognitive function was tested by Morris water maze (MWM) in APP/PS1 mice. Results Four ellagitannin flavonoids, including pinocembrin-7-O-[4″,6″-hexahydroxydiphenoyl]-glucoside (PHG), pinocembrin-7-O-[3″-O-galloyl-4″,6″-hexahydroxydiphenoyl]-glucoside (PGHG), thonningianin A (TA), and thonningianin B (TB), were identified to be autophagy enhancers in PCP. Among these, TA exhibited the strongest autophagy induction effect, and the mechanistic study demonstrated that TA activated autophagy via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways. In addition, TA effectively promoted the autophagic degradation of NLRP3 inflammasome in Aβ(1–42)-induced microglial cells and ameliorated neuronal damage via autophagy induction. In vivo, TA activated autophagy and improved behavioral symptoms in C. elegans. Furthermore, TA might penetrate the blood-brain barrier and could improve cognitive function and ameliorate the Aβ pathology and the NLRP3 inflammasome-mediated neuroinflammation via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways in APP/PS1 mice. Conclusion We identified TA as a potent microglial autophagy enhancer in PCP that promotes the autophagic degradation of the NLRP3 inflammasome to alleviate the pathology of AD via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways, which provides novel insights for TA in the treatment of AD.

Carpesii fructus extract exhibits neuroprotective effects in cellular and Caenorhabditis elegans models of Parkinson's disease

“…To investigate the functional role of specific genes in C. elegans , worms were subjected to RNAi by feeding them with bacteria expressing double‐stranded RNA (dsRNA) targeting the respective genes. 21 The synchronized NL5901 and BZ555 worms were transferred to NGM plates seeded with mpk‐1 RNAi bacteria and allowed to grow until the desired stage or age for subsequent experiments. Control worms were cultured on NGM plates seeded with HT115 bacteria.…”

“…Natural products derived from plants have gained considerable attention in recent years due to their potential therapeutic properties against various diseases, including neurodegenerative disorders 13,19‐21 . To date, numerous natural products have been reported to have neuroprotective effects in cellular and animal models of PD 22 .…”

“…Natural products derived from plants have gained considerable attention in recent years due to their potential therapeutic properties against various diseases, including neurodegenerative disorders. 13 , 19 , 20 , 21 To date, numerous natural products have been reported to have neuroprotective effects in cellular and animal models of PD. 22 Carpesii fructus , a medicinal herb traditionally used in East Asian medicine, has been reported to possess various pharmacological activities, including antioxidant, 23 antiparasitic, 24 anti‐inflammatory, 25 and anti‐tumor properties.…”

A novel strategy for bioactive natural products targeting NLRP3 inflammasome in Alzheimer’s disease

“…Thonningianin A, an ellagitannin flavonoid isolated from Penthorum chinense Pursh, was reported to induce autophagy in microglia mainly via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways to degrade NLRP3 inflammasome. It also improved cognitive function, ameliorated the Aβ pathology, and inhibited NLRP3 inflammasome in APP/PS1 AD model mice ( Zhou et al, 2022 ).…”

Two 18‐norspirostane steroidal saponins as novel mitophagy enhancers improve Alzheimer's disease

“… 2 Mitophagy enhancers are investigated as potential therapeutic interventions for AD. 3 , 4 Deoxytrillenoside CA (DTCA) and epitrillenoside CA (ETCA), two newly discovered compounds derived from Trillium tschonoskii Maxim. (TTM) (Figure 1A ), have shown antioxidative properties by inducing autophagy.…”