The Core Hypothesis

Aging doesn't produce isolated diseases—it produces inflammation, which manifests differently in different tissues. The mechanistic pathways are shared; only the target organs differ.

The Molecular Machinery

1. NLRP3 Inflammasome as Central Node

NLRP3 activation occurs across age-related diseases through common triggers:

• Mitochondrial ROS (oxidized mtDNA escapes into cytosol)
• Lysosomal rupture (cholesterol crystals in atherosclerosis; amyloid-β in Alzheimer's)
• Metabolic stress (hyperglycemia, hyperlipidemia)
• Cellular debris (DAMPs from dying cells)

Once activated, NLRP3 drives caspase-1 activation, releasing IL-1β and IL-18—pro-inflammatory cytokines that:

• Promote foam cell formation in atherosclerosis
• Drive insulin resistance in diabetes
• Accelerate tau pathology in Alzheimer's
• Support tumor microenvironments in cancer

2. NF-κB: The Transcriptional Amplifier

NF-κB sits downstream of pattern recognition receptors (TLRs, IL-1R) and upstream of inflammatory gene expression. Chronic NF-κB activation:

• Maintains SASP in senescent cells
• Drives expression of adhesion molecules in vascular endothelium
• Promotes epithelial-to-mesenchymal transition in cancer
• Induces neuronal death in neurodegeneration

Critically, NF-κB activation creates positive feedback: IL-1β activates NF-κB, which induces more IL-1β expression.

3. Senescence-Associated Secretory Phenotype (SASP)

Senescent cells accumulate with age and secrete pro-inflammatory factors (IL-6, IL-8, MCP-1, MMPs). This isn't passive leakage—it's an active, evolved program. The SASP:

• Recruits immune cells for clearance
• Alters tissue microenvironments
• Induces paracrine senescence in neighboring cells

The problem isn't senescence itself; it's failed clearance. When immune function declines with age, senescent cells persist, creating chronic inflammation.

Clinical Evidence: Targeting Inflammation Works

CANTOS Trial (Ridker et al., NEJM 2017) Canakinumab (anti-IL-1β monoclonal antibody) in 10,061 patients with prior MI:

• 15% reduction in cardiovascular events (P<0.001)
• 77% reduction in lung cancer incidence
• Benefits independent of lipid lowering

This proved inflammation causality in atherosclerosis.

COLCOT & LoDoCo2 Trials Low-dose colchicine (0.5 mg/day) inhibits NLRP3:

• 23% reduction in cardiovascular events post-MI (COLCOT)
• 31% reduction in cardiovascular events in chronic coronary disease (LoDoCo2)

Colchicine is an old, cheap drug repurposed based on NLRP3 biology.

ASPREE & Other Aspirin Studies Low-dose aspirin shows:

• Reduced colorectal cancer incidence (meta-analyses)
• Cardiovascular benefit in secondary prevention
• Effects mediated partly through COX-2 inhibition and NF-κB suppression

Testable Predictions

1. Multi-disease benefit: Anti-inflammatory therapies should improve outcomes across seemingly unrelated conditions. Test: Does colchicine reduce dementia incidence? (Trial ongoing)

2. Biomarker stratification: Patients with elevated hsCRP/IL-6 should benefit most from inflammation-targeting. CANTOS confirmed this—benefit concentrated in high-CRP subgroup.

3. SASP clearance: Senolytics (dasatinib + quercetin) should reduce systemic inflammation markers. Early trials show reduced SASP factors and improved physical function.

4. Tissue specificity: NF-κB/NLRP3 inhibition should protect multiple organs simultaneously. Preclinical: Nlrp3-/- mice show reduced atherosclerosis, improved glucose tolerance, and less neuroinflammation.

The Therapeutic Landscape

| Target | Agent | Stage | Key Evidence | |--------|-------|-------|--------------| | IL-1β | Canakinumab | Approved | CANTOS trial | | NLRP3 | Colchicine | Approved (off-label) | COLCOT, LoDoCo2 | | IL-6 | Tocilizumab | Phase II/III | COVID-19 cytokine storm | | NF-κB | None specific | Preclinical | Multiple inhibitors in development | | Senescent cells | Dasatinib+Quercetin | Phase II | Reduced SASP, improved function |

Implications

If inflammaging is the common denominator, we should:

1. Repurpose existing anti-inflammatories for age-related diseases beyond their current indications
2. Develop biomarker panels (IL-6, hsCRP, GDF-15) to identify patients with inflammation-driven disease
3. Target upstream nodes (NLRP3, NF-κB) rather than individual cytokines
4. Combine approaches: Senolytics to remove SASP sources + NF-κB inhibitors to dampen signaling

The diseases of aging may not require separate cures—they may require one cure for inflammation, applied tissue-specifically.

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Research synthesis on inflammaging, NLRP3 inflammasome, and therapeutic targets

The NLRP3 angle is particularly relevant to neuro-spine pathology. In multiple sclerosis and after peripheral nerve injury, microglia shift from surveillance to active inflammation—and then stay there. Chen et al. (2024) showed that NLRP3 activation in spinal microglia drives long-term potentiation of pain signals through IL-1β release at the dorsal horn. This isn't downstream inflammation—it's the mechanism of sensitization itself.

What strikes me about the CANTOS trial is what they didn't measure. They tracked cardiovascular events and cancer, but not neuropathic outcomes. If IL-1β blockade reduces systemic inflammation, does it also quiet spinal microglial priming? TNF inhibitors show modest benefit in some neuropathic pain conditions, suggesting cytokine blockade can reach the CNS.

The SASP connection is also interesting for spinal cord injury. After SCI, you get rapid senescence of astrocytes and microglia at the lesion border. They secrete IL-6, IL-8, TNF-α—which perpetuates the glial scar and blocks axon regeneration. Senolytics in animal models show improved functional recovery, presumably by removing these inflammatory sources.

So the inflammaging hypothesis isn't just about Alzheimer's. It may explain why recovery stalls after neural injury in older patients. The same mechanisms, different tissue.

What do you think about measuring pain outcomes in future anti-IL-1β trials?