The immune system lies at the core of nearly all facets of life. As immunocompetence declines with age and immunosenescence accumulates, a progressive dysregulation of several other physiological systems occurs in conjunction. Immunosenescence is potentiated by accretion of DNA damage and associated mutations, oxidative stress, metabolic disturbance, chronic inflammation, and shortened telomeres. Hematopoeisis becomes impaired, the thymus shrinks, immune cell populations fall, T and B cell function and diversity falter, and resolution of inflammation stalls. These effects collectively amplify vulnerability to infection, cancer, and autoimmune disease, all the while blunting therapeutic response.
At the cellular level, senescence can be viewed as an adaptive response to the stress induced by immediate damage. Aging increases the occurrence of misplaced or flawed DNA, RNA, lipids, proteins, ATP, and uric acid. Mislocalized components are seen as damage-associated molecular patterns that elicit an inflammatory cascade. The cell enters a state of permanent growth arrest in order to contain the dysfunction. However, this is a maladaptive process that evades autophagy and clearance, culminating in a sick cell that perpetually secretes noxious compounds that spread to the tissue around it.
To add insult to injury, alterations to DNA compromise the ability of immune cells to counter and control threats such as pathogens. Pathogen-associated molecular patterns subsequently accumulate due to hindered removal. Furthermore, aging correlates with energetic failure resulting from slowed rates of mitophagy that allow for defective mitochondria to persist. These mitochondria exhibit diminished respiratory capacity and produce excess reactive oxygen species. A reciprocal relationship can thus be noted between immunocompetence and metabolism whereby metabolic aberrations accrue in parallel with declines in immune performance.
Like all aspects of physiology, the immune system exhibits a dynamic push and pull between catabolic and anabolic processes. Bioenergetic pathways provide the requisite substrates for the biosynthesis of immune cells. During an immune response, there is a coordinated shift in immunometabolism that enables naive immune cells to become active and capable of defending imposing health threats. While T cells rely heavily on glycolysis, the mitochondria must engage in efficient oxidative phosphorylation to provide the requisite ATP for the high-energy process of immune activation.
Aging is correlated with metabolic disturbances that compromise organ system function, including that of the immune system. Immune cell metabolism becomes less adaptive, inefficiently switching between metabolic states. This leads to energy crises, oxidative stress, diminished immune cell function and activation, poor antigen recognition and response, slowed debris or pathogen clearance, and impaired inflammation resolution. Immune cells themselves become pro-inflammatory, spewing out cytokines that further potentiate progressive immune dysregulation and mitochondrial dysfunction.
Research is ongoing to elucidate compounds that may attenuate immune deficiency and senescence. Spermidine has been shown to enhance mitochondrial metabolism, thereby helping to restore T cell function. Another important component of proper metabolic function is NAD+, the levels of which fall with age. NAD+ is acutely involved in redox homeostasis and mitochondrial energy production. Provision of NAD+-metabolites to boost NAD+ levels, or preventing NAD+ degradation via supplementation of CD38, may ameliorate cell metabolism and prevent senescence.
Additionally, both metformin and rapamycin act to interrupt NF-kB and c-myc/HIF1a signaling pathways that otherwise provoke glycolysis, inflammation, and senescence. Senolytics including dasatinib, fisetin, and quercetin upregulate apoptosis and promote clearance of damaged mitochondria, thereby preventing impending senescence. In the same vein, compounds that improve antioxidant status, scavenge reactive oxygen species, and trigger autophagy assist in mitophagy amplification. Taurine is also implicated in immune cell metabolism, acting to protect against DNA damage, mitochondrial impairment, reactive oxygen species generation, and inflammation.
A new frontier in combatting immunosenescence involves nano-particle based approaches designed to restore immunometabolic health. Implementation of nanoparticles may enhance drug delivery, allowing for more precise targeting and intensifying potency. Compounds loaded into nano-based carriers are distributed more selectively and discretely, and nano-particles can be designed to specifically locate senescent cells and provide sustained delivery. This level of efficiency attenuates toxicity and permits lower dosing. Collectively, nano-based immunometabolic agents may accelerate metabolic reprogramming of defective immune cells and prevent age-associated senescence. While more research is necessary to refine nanointerventions, nanodelivery systems are a promising technology in the realm of personalized immune rejuvenation.
Nair PG, Sheela UB, Vijayan VV, Howlett SE, Cullis P, Gujar S. Targeting Age-Associated Immune Senescence via Nanoparticle-Based Metabolic Reprogramming. ACS Nano. 2026;20(20):14313-14326. doi:10.1021/acsnano.5c18638
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