Path 10: Chronic Inflammation (Inflammaging)

Rationale: The slow burn: quieting the inflammatory fires of aging. Aging organisms exhibit a chronic, low-grade inflammatory state (inflammaging). The aged immune system becomes deregulated: innate immune cells overproduce inflammatory cytokines while adaptive immunity weakens. This smoldering inflammation damages tissues and is a risk factor for nearly all diseases of aging. Break this inflammation cycle and we might slow age-related pathology.

Prerequisites: Immunology, cell signaling (NF-κB pathway, cytokines), pathology.

Dependencies: Strong overlap with Path 8 (senescent cells SASP as major inflammation source). Linked to Path 11 (microbiome) for gut-derived inflammation, and Path 7 (metabolism) since metabolic dysfunction provokes inflammation.

Signs of Progress: Successful trials of anti-inflammatories extending healthy aging. Targeting a specific inflammatory pathway (NLRP3, TNF) in mid-life extending animal lifespan. Therapies rejuvenating the immune system (thymus regeneration). Vaccines clearing chronic infections to lighten immune load.

BC10.1: The Aging Immune System (Immunosenescence)

Scope: Thymus shrinkage, memory T cell expansion, reduced B cell output, innate immune cells becoming pro-inflammatory but less effective.

• Weinberger, B. & Grubeck-Loebenstein, B. “The aging of the immune system.” Wiener Klin. Wochenschr., 2012. – Solid overview of immunosenescence.
• Nikolich-Zugich, J. “The twilight of immunity.” Nat. Immunol., 2018. – Molecular reasons: shortened telomeres, senescence of immune cells, inhibitory receptors.
• Franceschi, C. et al. “The immunology of exceptional individuals: the lesson of centenarians.” Immunity & Ageing, 2017. – Centenarians often have high inflammatory markers yet cope.

BC10.2: Sources of Chronic Inflammation in Aging

Scope: Senescent cells/SASP, visceral fat, gut leakiness, chronic infections, NLRP3 inflammasome activation.

• Ferrucci, L. & Fabbri, E. “Inflammageing: chronic inflammation in ageing, cardiovascular disease, and frailty.” Nat. Rev. Cardiol., 2018. – Thorough review linking inflammaging to frailty and disease.
• Salminen, A. et al. “Activation of innate immunity system during aging: NF-κB signaling is the mastermind.” Aging Res. Rev., 2008. – NF-κB often elevated in aging tissues.
• Thevaranjan, N. et al. “Age-associated microbial dysbiosis promotes intestinal permeability.” Cell Host Microbe, 2017. – Age leads to gut microbiome changes -> leaky gut -> inflammation.

BC10.3: Consequences of Inflammaging

Scope: Inflammation -> atherosclerosis, neurodegeneration, insulin resistance, muscle wasting. Accelerates other hallmarks.

• Franceschi, C. & Campisi, J. “Chronic inflammation (inflammaging) and its potential contribution to age-associated diseases.” J. Gerontol. A, 2014. – Persistent inflammation as common soil for many diseases.
• Furman, D. et al. “Chronic inflammation in the etiology of disease across the life span.” Nat. Med., 2019. – Broad review connecting inflammation to diabetes, Alzheimer’s, cancer.
• Ridker, P.M. et al. “Antiinflammatory therapy with canakinumab for atherosclerotic disease.” N Engl J Med, 2017. – Clinical trial: IL-1β blocker reduced heart attack risk.

BC10.4: Anti-Inflammatory Interventions

Scope: Lifestyle (exercise, diet), drugs (statins, biologics, JAK inhibitors, NLRP3 inhibitors), senolytics.

• Olshansky, S.J. et al. “Position statement on human aging: the case for geroscience.” J. Gerontol. A, 2016. – Targeting fundamental aging (like inflammation) could extend healthspan.
• Flynn, M.G. & McFarlin, B.K. “Physical activity and its role in inflammation and innate immunity.” Brain Behav. Immun., 2006. – How regular exercise lowers chronic inflammation.
• Xiao, L. et al. “The immunosenescence of diet-induced obesity.” Gerontology, 2020. – Obesity as a driver of inflammaging.

Bibliography (Path 10)

• Franceschi, Claudio et al. “Inflammaging and Anti-Inflammaging.” Mech. Ageing Dev. 128(1): 92–105, 2007. (Introduced concept of inflammaging)
• Ferrucci, Luigi & Emanuele Fabbri. “Inflammageing: Chronic Inflammation in Ageing.” Nat. Rev. Cardiol. 15(9): 505–522, 2018. (Comprehensive review linking inflammatory markers to outcomes)
• Xia, Shumin et al. “NLRP3 Inflammasome: A Therapeutic Target for Age-Related Diseases.” Transl. Res. 223: 121–141, 2020. (Targeting NLRP3 could ameliorate multiple age-related pathologies)
• Bektas, Ayse et al. “Aging, Inflammation and the Immune System.” J. Gerontol. A 72(2): 209–217, 2017. (Immune aging: thymic involution, shift to memory T cells)
• Furman, D. et al. “Chronic Inflammation in the Etiology of Disease Across the Life Span.” Nat. Med. 25(12): 1822–1832, 2019. (Multi-omics data connecting inflammation with most chronic aging diseases)