Autophagy directly regulates the amyloid beta-peptide (Aβ) clearance, and its dysfunction occurs in the early pathogenesis of Alzheimer’s disease (AD). We previously reported that docosahexaenoic acid-acylated astaxanthin monoester (AST-DHA) showed neuroprotection against AD pathology. However, its in-depth mechanism and autophagic responses in AD brains are poorly understood. Herein, SH-SY5Y cells overexpressing the Swedish mutation (K595N/M596L) of APP gene were established to preliminarily evaluate the actions of AST-DHA on reducing Aβ_1-42 levels and regulating autophagy. In microglial BV2 cells, AST-DHA and free astaxanthin (F-AST) recovered p62 and LC3Ⅱ/Ⅰ levels, and restored autophagy flux by rescuing the late phase of microglial autophagy. Notably, autophagic inhibitor bafilomycin A1 blunted the abilities of AST-DHA to reduce Aβ_1-42 and fibral Aβ, suggesting that AST-DHA probably promoted Aβ clearance in a microglial autophagy-dependent manner. Further studies in APP/PS1 mice verified that dietary AST-DHA and F-AST promoted Aβ phagocytosis via microglial autophagy. Significant decreases of Iba1 and p62 were observed around Aβ plaque in the hippocampus and cortex using triple fluorescence staining. Furthermore, AST-DHA exhibited superior performance over F-AST in restoring autophagic dysfunction, ameliorating Aβ burden and cognitive deficit. Our findings suggest a possible mechanism of AST-DHA in improving AD by which it restores microglial autophagy to facilitate cerebral Aβ clearance. It supports the future application of AST-DHA as an autophagic regulator in maintaining brain function.

Ganglioside is a sialic acid-containing sphingolipid with multiple biological functions in neurodevelopment and neurodegeneration. The st8sia1-encoding GD3 synthase (GD3S) is involved in the biosynthesis of gangliosides GD3 and GD2, which are highly expressed in the developmental brain. However, the effect of exogenous ganglioside and endogenous glycosyltransferases GD3S on neurodevelopment still need to be determined due to the lack of in vivo ganglioside-deficient model. This study generated st8sia1 knockout zebrafish using CRISPR/Cas9-mediated gene editing. A st8sia1 guide-RNA was designed to target exon 1 in zebrafish and generate the homozygote with a 13-bp frameshift deletion, which caused the loss of GD3S function and disturbed the patterns of gangliosides. The st8sia1 mutant showed delayed development, impaired locomotor behavior, and neurodevelopmental defects represented by increased apoptosis of brain cells and small brain size. Further RNA-Seq analysis revealed that most regulated genes were enriched in axonal and cellular developmental, neurogenesis, and neuroactive ligand-receptor interaction pathways. Notably, the application of exogenous GM4(1S) and GD3 could improve the phenotypes and behavioral activity of st8sia1 knockout zebrafish, as well as restore the abnormal neurodevelopment with the underlying mechanism via upregulating the nestin, bdnf, map2, islet1, and elavl3 gene expressions. This study established a genetic model to elucidate the function of GD3S and exogenous ganglioside intervention in neurodevelopment. It provides the potential for high-throughput bioactive screening for brain nutrition.

A novel and reactive oxygen species (ROS) responsive astaxanthin phenylboronic acid derivative (AstaD-PBA) was constructed by grafting phenylboronic acid (PBA) onto astaxanthin succinate diester (AstaD), and its chemical structure and physicochemical property were identifi ed. AstaD-PBA could effectively improve the ROS quenching ability in the lipopolysaccharide (LPS)-induced RAW264.7 cell inflammation model. Then, the bioactivity of AstaD-PBA was studied by 4 zebrafi sh ROS-responsive infl ammatory models induced by LPS, copper (Cu²⁺), high-fat diet, and dextran sodium sulfate (DSS). The results suggest that AstaD-PBA might have high biosafety and the best effect on ulcerative colitis (UC) induced by DSS. Furtherly, AstaD-PBA signifi cantly alleviated and treated weight loss and colonic shrinkage, inhibited infl ammatory cytokines, and maintained microbiota homeostasis to improve UC in C57BL/6J mice. Alistipes and Oscillibacter were expected to be considered UC marker fl ora according to the Metastats analysis and Pearson correlation Mantel test (P < 0.01) of 16S rRNA gene sequencing data. In conclusion, AstaD-PBA has been promised to be a functional compound to improve UC and maintain intestinal microbiota homeostasis.