Neurodegenerative diseases (NDDs) are a class of cognitive and motor disorders including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic Lateral Sclerosis (ALS), and others. They are caused by lesions in cells and tissues of the central nervous system, resulting in corresponding dysfunctions and consequent decline in cognitive and motor functions. Neural tissues are extremely vulnerable to oxidative stress, which plays critical biological roles in NDDs. Aromatic compounds are found extensively in natural plants and have substantial effects of anti-oxidative stress damage, which not only have a wide range of research applications in cosmetics, foods, etc., but are also frequently utilized in the treatment of various central nervous system diseases. This review summarizes the relevant oxidative stress mechanisms in NDDs (AD, PD, HD, and ALS) and reviews aromatic compounds such as polyphenols, terpenoids, and flavonoids that can be used in the management of neurodegenerative diseases, as well as their specific mechanisms of antioxidant action. This review will serve as a reference for future experimental studies on neurodegenerative illnesses while also offering fresh insights into clinical therapy.

Rheumatoid arthritis (RA) is frequently accompanied by depression, a comorbidity arising from the interplay of chronic systemic inflammation, neuroimmune activation, oxidative stress, and dysregulation of the gut–brain axis. Increasing evidence suggests that nanomedicine offers unique opportunities for the integrated management of RA-associated depression by enabling precise modulation of both peripheral inflammation and central nervous system (CNS) pathology. This review outlines the biological mechanisms linking RA and depression—including cytokine cascades, mitochondrial dysfunction, reactive oxygen species (ROS) accumulation, and microbial metabolite imbalance—and highlights recent progress in nanocarrier platforms capable of dual-site intervention. Liposomes, polymeric nanoparticles (NPs), exosomes, inorganic nanozymes, and emerging carbon-based nanomaterials have demonstrated the ability to target inflamed synovium, reprogram macrophage phenotypes, traverse the blood–brain barrier (BBB), suppress microglial overactivation, enhance neuroplasticity, and restore gut microbial homeostasis. Furthermore, stimulus-responsive nanoplatforms activated by ROS, pH, enzymes, or hypoxia provide spatiotemporally controlled drug release, thereby improving therapeutic precision. Finally, we discuss integrative designs such as dual-targeting nanomedicines, co-delivery systems, and microbiota-modulating nano-interventions, which offer promising strategies for the comprehensive treatment of RA-associated depression. This review aims to provide mechanistic insights and design principles to guide the development of next-generation nanomedicine for coordinated systemic-central modulation in RA comorbidity.

Alzheimer’s (AD) and Parkinson’s disease (PD) are prominent neurodegenerative disorders characterized by early synaptic loss, which correlates more closely with clinical symptoms than neuronal death. This synaptic impairment is primarily driven by disruptions in synaptic vesicle (SV) trafficking, a critical process for maintaining synaptic integrity through a tightly regulated cycle involving clustering, docking-priming, Ca²⁺-triggered fusion, and endocytosis. In AD, amyloid-β (Aβ) oligomers interfere with SNARE-mediated fusion and endocytosis, while hyperphosphorylated tau obstructs vesicle mobility and docking, resulting in cumulative toxicity that aggravates SV defects. Conversely, in PD, α-synuclein (α-syn) aggregation alters vesicle clustering, membrane fusion, and recycling, and these effects are further influenced by Leucine-rich repeat kinase 2 (LRRK2)-Rab-related trafficking defects and the selective vulnerability of dopaminergic terminals. Different from previous reviews that address synaptic dysfunction in a broader manner, the present review is specifically organized around the SV trafficking cycle and compares both shared presynaptic endpoints and disease-specific upstream mechanisms in AD and PD. In addition, recent mechanism-oriented therapeutic strategies are summarized. This vesicle-cycle-centered perspective may provide a clearer framework for understanding presynaptic pathology and for guiding the development of earlier and more targeted interventions.

Neurodegenerative diseases (NDDs) are a class of cognitive and motor disorders that include Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and others. They are caused by lesions in cells and tissues of the central nervous system, resulting in corresponding dysfunctions and consequent decline in cognitive and motor functions. Neural tissues are extremely vulnerable to oxidative stress, which plays critical biological roles in NDDs. Aromatic compounds are found extensively in natural plants and have substantial effects of anti-oxidative stress damage, which not only have a wide range of research applications in cosmetics, foods, etc., but are also frequently utilized in the treatment of various central nervous system diseases. This review summarizes the relevant oxidative stress mechanisms in NDDs (AD, PD, HD, and ALS) and reviews aromatic compounds such as polyphenols, terpenoids, and flavonoids that can be used in the management of neurodegenerative diseases, as well as their specific mechanisms of antioxidant action. This review will serve as a reference for future experimental studies on neurodegenerative illnesses while also offering fresh insights into clinical therapy.