Neuroprotective Effects of Fucoxanthin Against Alzheimer's Disease Pathology: Targeting Amyloid-β Accumulation, Carbonyl Stress-Mediated Neuroinflammation, and Autophagy- Ferroptosis Crosstalk = 알츠하이머성 치매에서 푸코잔틴의 신경보호 효과: 아밀로이드 베타 축적, 카르보닐 스트레스 매개 신경염증 및 자가포식-페롭토시스 조절을 중심으로

다국어 초록 (Multilingual Abstract)

Alzheimer's disease （AD） is a progressive neurodegenerative disorder in which aberrant proteolytic processing of amyloid precursor protein （APP） initiates a self-reinforcing pathological cascade. BACE1- and γ-secretase-dependent cleavage generates amyloid-β （Aβ） peptides that accumulate as senile plaques, while QC-mediated N-terminal cyclization produces pyroglutamate-3-Aβ （pE3-Aβ）, a post-translationally modified variant with enhanced aggregation propensity and resistance to proteolytic clearance. As Aβ accumulates, it disrupts neuronal energy metabolism and drives the formation of reactive carbonyl species, particularly methylglyoxal （MGO）, which activates the RAGE/NF-κB signaling axis and sustains chronic neuroinflammation. This is further compounded by failure of autophagic-lysosomal clearance, which allows pathological proteins to persist intracellularly and creates conditions that favor iron-dependent lipid peroxidation and ferroptosis. The present study investigated the neuroprotective effects of fucoxanthin, a marine carotenoid abundant in brown algae, focusing on Aβ generation and pE3-Aβ-associated aggregation, carbonyl stress-linked neuroinflammation, and autophagy-lysosome-associated clearance.
In Part I, fucoxanthin （0.1-5 µM） modulated APP processing through PI3K/Akt/GSK-3β signaling, suppressing amyloidogenic cleavage and QC-mediated pE3-Aβ formation while enhancing non-amyloidogenic processing, resulting in reduced Aβ1-42 production, pE3-Aβ levels, and pE3-Aβ-seeded Aβ aggregation. In a model of acute amyloid-associated pathology, oral fucoxanthin （100 or 200 mg/kg） improved memory performance and reduced hippocampal Aβ and pE3-Aβ levels. In Part II, fucoxanthin attenuated the metabolic and neuroinflammatory consequences of early Aβ accumulation by reducing systemic MGO levels and suppressing hippocampal RAGE/NF-κB activation, with reduced microglial activation and restored synaptic protein expression in the hippocampus. In Part III, in a model reflecting progressive amyloid accumulation and chronic proteostatic stress, fucoxanthin restored autophagy-lysosome-associated clearance through AMPK/mTOR-dependent regulation and enhanced lysosomal degradative capacity, reducing amyloid plaque burden and attenuating ferroptosis-associated lipid peroxidation.
Collectively, these findings suggest that fucoxanthin attenuates AD-related pathology by acting on the linked processes that sustain Aβ burden, including amyloid generation, pE3-Aβ-associated aggregation, carbonyl stress-linked neuroinflammation, and impaired autophagy-lysosome-associated clearance. These results provide experimental evidence supporting the potential value of fucoxanthin as a marine-derived functional food ingredient for modulating Aβ-centered pathological progression and its downstream neurodegenerative responses.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• 1.1. Alzheimer’s disease 1
• 1.2. Amyloid precursor protein （APP） processing and Aβ generation 1
• 1.2.1. Amyloidogenic pathway 2
• 1.2.2. Non-amyloidogenic pathway 3
• 1.3. Pyroglutamate-3-Aβ （pE3-Aβ） as a post-translationally modified Aβ species 4
• 1.4. PI3K/Akt/GSK-3β signaling in the regulation of Aβ generation and accumulation 5
• 1.5. Methylglyoxal and carbonyl stress in neuronal metabolism 6
• 1.6. RAGE/NF-κB signaling and microglial activation in carbonyl stress 7
• 1.7. Autophagy-lysosome pathway as an Aβ clearance mechanism 8
• 1.8. Regulation of autophagy by the AMPK/mTOR signaling pathway 9
• 1.9. Ferroptosis-mediated lipid peroxidation 10
• 1.10. Crosstalk between autophagy and ferroptosis 11
• 1.11. Marine algae and the bioactive properties of brown algae 12
• 1.12. Fucoxanthin as a brown algae-derived carotenoid 12
• Ⅱ. Part 1: Modulatory effects of fucoxanthin on Aβ and pE3-Aβ accumulation 14
• 2.1. Materials and methods 14
• 2.1.1. Chemicals and reagents 14
• 2.1.2. SweAPP N2a cell culture and treatment 14
• 2.1.3. Cell viability assay 15
• 2.1.4. Extracellular Aβ1-40 and Aβ1-42 measurement 15
• 2.1.5. Aβ aggregation analysis 16
• 2.1.6. Animals and Aβ1-42 intracerebroventricular （i.c.v.） injection 16
• 2.1.7. Sample treatment 17
• 2.1.8. Behavioral experiments 17
• 2.1.8.1. Passive avoidance test 17
• 2.1.8.2. Y-maze test 18
• 2.1.8.3. MWM test 18
• 2.1.9. Western blot analysis 18
• 2.1.10. Statistical analysis 19
• 2.2. Results and discussion 21
• 2.2.1. FX reduces Aβ secretion and intracellular accumulation in SweAPP N2a cells 21
• 2.2.2. FX suppresses spontaneous and pE3-Aβ-seeded Aβ aggregation 25
• 2.2.3. FX modulates dual APP processing pathways in SweAPP N2a cells 28
• 2.2.4. FX inhibits QC-mediated pE3-Aβ production 31
• 2.2.5. FX activates the PI3K/Akt/GSK-3β pathway to suppress Aβ and pE3-Aβ production in SweAPP N2a cells 33
• 2.2.6. FX ameliorates cognitive deficits in Aβ1-42-injected mice 37
• 2.2.7. FX reduces hippocampal Aβ1-42 and pE3-Aβ accumulation by suppressing BACE1 and QC in Aβ1-42-injected mice 44
• Ⅲ. Part 2: Modulatory effects of fucoxanthin on carbonyl stress-driven neuroinflammation 49
• 3.1. Materials and methods 49
• 3.1.1. Chemicals and reagents 49
• 3.1.2. Preparation of Aβ peptides 49
• 3.1.3. PC12 cell culture and treatment 50
• 3.1.4. Cell viability assay 50
• 3.1.5. Animals 51
• 3.1.6. Aβ1-42 i.c.v. injection and FX treatment 51
• 3.1.7. Serum methylglyoxal （MGO） measurement 51
• 3.1.8. Iba-1 immunohistochemical （IHC） analysis 52
• 3.1.9. Western blot analysis 52
• 3.1.10. Statistical analysis 52
• 3.2. Results and discussion 55
• 3.2.1. FX attenuates Aβ25-35-induced cytotoxicity in PC12 cells 55
• 3.2.2. FX attenuates Aβ25-35-induced RAGE expression and NF-κB activation in PC12 cells 57
• 3.2.3. FX suppresses NF-κB-dependent pro-inflammatory mediator expression in Aβ25-35-treated PC12 cells 61
• 3.2.4. FX reduces serum MGO levels in Aβ1-42-injected mice 65
• 3.2.5. FX suppresses RAGE/NF-κB-mediated inflammatory responses in Aβ1-42-injected mice 69
• 3.2.6. FX attenuates microglial activation associated with carbonyl stress-related inflammatory signaling in Aβ1-42-injected mice 74
• 3.2.7. FX attenuates synaptic protein alterations in Aβ1-42-injected mice 77
• Ⅳ. Part 3: Modulatory effects of fucoxanthin on autophagic clearance and ferroptosis 81
• 4.1. Materials and methods 81
• 4.1.1. Chemicals and reagents 81
• 4.1.2. SweAPP N2a cell culture and treatment 81
• 4.1.3. Cell viability assay 82
• 4.1.4. Intracellular reactive oxygen species （ROS） measurement 82
• 4.1.5. LC3 immunofluorescence analysis 82
• 4.1.6. 5XFAD mouse model and FX treatment 83
• 4.1.7. Tissue preparation 83
• 4.1.8. Thioflavin S （ThS） staining 84
• 4.1.9. pE3-Aβ IHC analysis 84
• 4.1.10. Western blot analysis 84
• 4.1.11. Statistical analysis 85
• 4.2. Results and discussion 87
• 4.2.1. FX attenuated ferroptosis-associated oxidative injury in SweAPP N2a cells 87
• 4.2.2. FX modulated autophagy-lysosome pathway in SweAPP N2a cells 90
• 4.2.3. FX modulated AMPK/mTOR signaling and early autophagy-related proteins in SweAPP N2a cells 93
• 4.2.4. FX enhances autophagic flux in SweAPP N2a cells 97
• 4.2.5. FX reduced amyloid plaque burden in 5XFAD mice 100
• 4.2.6. FX modulated autophagy-lysosome proteins in 5XFAD mice 105
• 4.2.7. FX attenuates mTOR hyperactivation in 5XFAD mice 108
• 4.2.8. FX reduced lipid peroxidation and modulated ferroptosis-related proteins in 5XFAD mice 110
• Ⅴ. Conclusion 114
• References 115
• 국문초록 138