Arachidonic Acid Metabolism: A Multifaceted Role in The Aging Process And Intervention Strategies

I. Core Mechanisms of Arachidonic Acid (AA) Metabolism and Its Link to Aging

Arachidonic acid (AA), one of the most abundant polyunsaturated fatty acids in the human body, plays a pivotal role in the aging process through its complex metabolic network. AA is metabolized via three major pathways - cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) - generating bioactive metabolites such as prostaglandins (PGs), leukotrienes (LTs), hydroxyeicosatetraenoic acids (HETEs), and epoxyeicosatrienoic acids (EETs). These metabolites are not only involved in inflammatory regulation but also closely associated with core mechanisms of aging, including cellular senescence, mitochondrial dysfunction, and oxidative stress.

For instance, PGE2 produced via the COX pathway exacerbates chronic inflammation by activating the NF-κB signaling pathway. LOX-derived LTB4 recruits immune cell infiltration and accelerates tissue degeneration. Moreover, 20-HETE from the CYP pathway is directly linked to vascular aging and cognitive decline, while EETs maintain vascular elasticity by regulating calcium signaling, demonstrating dual roles in aging.

II. Dual Roles of AA Metabolism in Age-Related Diseases

(1) Skeletal and Muscular Aging

In osteoporosis, AA metabolism regulates osteoclast differentiation through the OPG/RANKL signaling pathway. Low concentrations of PGE2 promote osteoblast proliferation via the IGF-1 pathway, whereas high concentrations inhibit bone formation by inducing mesenchymal stem cells to differentiate into adipocytes through the PPAR-γ pathway. Clinical studies suggest that AA intake is negatively correlated with hip fracture risk, though the underlying mechanism likely involves local microenvironmental balance of AA metabolites. Notably, combining AA with DHA can reduce osteoclastogenesis by inhibiting the RANKL pathway, underscoring the importance of n-6/n-3 fatty acid ratio regulation.

(2) Neurological Aging

AA exhibits concentration-dependent dual effects in Alzheimer's disease (AD): physiological levels support synaptic plasticity, while excessive levels activate 5-LOX, promoting Aβ deposition and neuroinflammation. AD patients show elevated 5-LOX expression, with its metabolite 5-HETE aggravating tau phosphorylation; inhibition of 5-LOX improves cognition in animal models. The endocannabinoid system (e.g., 2-AG) modulates Aβ metabolism via CB2 receptors, although its impact on cognitive function requires further investigation. In Parkinson's disease (PD), the association between AA metabolism and α-synuclein misfolding remains controversial. However, monoacylglycerol lipase (MAGL) inhibitors, which reduce AA and PGs, demonstrate neuroprotective potential.

(3) Cardiovascular Aging

AA metabolism plays a central role in atherosclerosis. TXA2 from the COX pathway promotes platelet aggregation, whereas PGI2 exerts protective effects by vasodilation; imbalance between these two directly affects thrombosis risk. EETs from the CYP pathway exhibit anti-inflammatory and anti-smooth muscle proliferation properties, but their production declines during aging, leading to reduced vascular elasticity. Clinical data indicate a positive correlation between arterial stiffness and AA/LA ratios, suggesting that modulating AA metabolism could serve as an intervention target for cardiovascular aging. Notably, transient activation of COX-2 during myocardial ischemia exerts protective effects via ischemic preconditioning, highlighting the spatiotemporal specificity of AA metabolism.

(4) Metabolic Disorders and Skin Aging

In obesity, AA promotes white adipocyte generation and suppresses brown fat "browning" through PG/calcium signaling pathways. Regarding skin aging, exogenous AA induces fibroblast senescence via COX-2 and inhibits collagen synthesis, while endogenous AA depletion correlates with impaired skin barrier function. Interestingly, dietary AA may delay skin aging by suppressing hypothalamic-pituitary-adrenal (HPA) axis activity, revealing interactions between local and systemic metabolism.

III. Anti-Aging Strategies Targeting Arachidonic Acid Metabolism

(1) Pharmacological Interventions: From Enzyme Inhibitors to Natural Products

- COX Inhibitors: Nonsteroidal anti-inflammatory drugs (NSAIDs) like celecoxib selectively inhibit COX-2 to reduce inflammation, though long-term use raises gastrointestinal concerns. Novel COX-2 inhibitor licofelone simultaneously inhibits 5-LOX and demonstrates dual anti-inflammatory effects in glomerulonephritis models.

- LOX Inhibitors: Zileuton, a 5-LOX inhibitor approved for asthma, is being explored for neurodegenerative diseases. Natural compounds such as curcumin and resveratrol inhibit both LOX and COX pathways, showing anti-fibrotic and anti-tumor effects in animal models.

- CYP Modulators: PVPA, an EET analog, improves vascular function in hypertensive rats by activating CYP450 pathways, indicating CYP metabolites as promising targets for vascular aging. HET0016, an inhibitor of 20-HETE, alleviates diabetic vascular injury, offering new therapeutic avenues for metabolic vascular diseases.

(2) Nutritional Regulation: Fatty Acid Balance and Dietary Intervention

n-3 Polyunsaturated fatty acids (e.g., EPA/DHA) competitively inhibit AA-metabolizing enzymes, reducing pro-inflammatory mediator production. The WHO recommends an n-6/n-3 intake ratio below 10:1; fish oil supplementation lowers risks of arthritis and cardiovascular diseases. Notably, the AA:DHA ratio in breast milk (~1:1) is crucial for infant immune development, emphasizing early-life nutritional interventions. Probiotics regulate gut microbiota to promote short-chain fatty acid production, indirectly suppressing pro-inflammatory AA metabolite formation, offering insights into "gut-joint axis" modulation.

(3) Traditional Medicine and Natural Products

Traditional Chinese medicine (TCM) formulas like Fufang Zhenzhu Tiaozhi Tablets (FTZ) delay liver aging by downregulating LTs and TNF-α, acting through AA metabolic pathways. Single herbs such as Huanglian Jiedu Tang exert multi-component synergistic effects by inhibiting COX-2/5-LOX, alleviating cerebral ischemia injury. Natural extracts like capsaicin and gingerols inhibit TRPV1 receptors and LOX pathways, showing analgesic and anti-inflammatory effects in inflammatory diseases with better safety profiles than synthetic drugs.

(4) Future Challenges and Precision Medicine Directions

Despite promising results in animal models, clinical translation of AA metabolic inhibitors faces challenges. For example, cardiovascular risks of COX-2 inhibitors require structural optimization, and pharmacokinetic characteristics of natural products need clarification. Precision medicine strategies can tailor interventions based on individual genetic polymorphisms in AA metabolic enzymes (e.g., CYP2C9, PLA2G4A). Additionally, nanocarrier delivery systems can target AA inhibitors to aging tissues, minimizing systemic side effects - for instance, liposomal curcumin achieves localized joint accumulation in arthritis models.

IV. Conclusion and Outlook

As a central regulatory network in aging, arachidonic acid metabolism exhibits complexity due to the spatiotemporal specificity and concentration dependence of its metabolites. At the mechanistic level, AA metabolism drives multi-organ degenerative changes through the "inflammation-metabolism-aging" axis. Effective intervention strategies must balance the suppression of pro-inflammatory pathways with the preservation of physiological functions (e.g., EET-mediated vascular protection).

Future research should integrate single-cell sequencing and metabolomics to map tissue-specific metabolic profiles and develop non-invasive biomarkers (e.g., serum 12-HETE levels) for aging risk prediction. With interdisciplinary technological advances, precise targeting of AA metabolism holds promise as a key approach to delaying aging and preventing age-related diseases.

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Reference:

Arachidonic acid in aging: New roles for old players https://doi.org/10.1016/j.jare.2024.05.003