The extracts of Ardisia elliptica fruit attenuate inflammation in LPS-activated BV2 microglia via JNK, ERK1/2, p38, and NF-κB signaling inhibition.

Background: Neuroinflammation is a pivotal defense mechanism against brain infections and injury; the dysregulation contributes to neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease, and multiple sclerosis. Ardisia elliptica Thunb. (Primulaceae), known as Ram Yai or Pilangkasa in Thai traditional medicine, has been used to treat diarrhea with fever. However, the potential of A. elliptica fruit to modulate neuroinflammation remains unexplored.

Purpose: This study aimed to investigate the anti-neuroinflammatory properties of A. elliptica fruit extracts in activated microglia as well as their anti-amyloidogenic effects in vitro.

Methods: Lipopolysaccharide (LPS), a potent inflammatory stimulus, was used to activate both BV2 microglia, a well-established model of neuroinflammation, and RAW264.7 macrophages. In the inflammatory studies, assays including qRT-PCR, Western blotting, and phagocytic activity were performed. In the amyloidogenic study, thioflavin T and atomic force microscopy assays were conducted.

Results: A. elliptica fruit was extracted using ethanol and water. The extracts significantly reduced the mRNA and protein expression of IL-1β, TNF-α, and iNOS in LPS-activated BV2 cells and RAW264.7 cells. The 90 % ethanol extract of A. elliptica fruit exhibited greater efficacy compared to 50 % ethanol or water extracts. In addition, A. elliptica fruit extract significantly decreased the phosphorylation of JNK, ERK1/2, p38, and NF-κB, while markedly attenuating excessive phagocytic activity by reducing uptake of fluorescent beads and Aβ fibrils in LPS-activated BV2 cells. Notably, the extracts inhibited Aβ fibril formation and disassembled preformed fibril aggregates. Embelin was identified as a major bioactive constituent of the extracts, accounting for part of the identified activities.

Conclusion: Our study elucidates the mechanisms by which A. elliptica fruit extract suppresses inflammation through inhibition of JNK, ERK1/2, p38, and NF-kB pathways in LPS-activated microglia. A. elliptica fruit extracts exhibit both anti-inflammatory and anti-amyloidogenic activities, suggesting the potential as a promising multi-target candidate natural product for neuroinflammatory disorders such as AD.