Summary: Researchers revealed a fundamental failure in the body’s internal clearance system: as we age, long-lived tissue-resident macrophages lose their ability to engulf and remove expiring neutrophils. When these short-lived white blood cells are not cleared, they convert into highly toxic, senescent “zombie” neutrophils that damage healthy tissues and drive chronic inflammation across organs.
By blocking a single pro-inflammatory receptor, EP2, specifically on tissue-resident macrophages, scientists were able to restore the macrophages’ youthful clearance function. This targeted intervention reduced systemic inflammation and preserved the function of multiple organs in aged mice.
Key Facts
- The neutrophil clearance problem: The body generates roughly 100 billion neutrophils each day. These frontline immune cells typically survive only 12–24 hours, after which tissue-resident macrophages remove them. With age, increased levels of the lipid mediator prostaglandin E2 (PGE2) signal through the EP2 receptor on macrophages, impairing their phagocytic (cell-eating) capacity.
- Emergence of toxic, senescent neutrophils: When clearance fails, old neutrophils rapidly enter a senescent, pro-inflammatory state. These cells accumulate in organs such as the liver, spleen and bone marrow, releasing destructive substances that injure neighboring cells and amplify systemic inflammation.
- Multi-organ preservation by targeting EP2: Selectively disabling or pharmacologically blocking EP2 on tissue-resident macrophages in aged mice produced broad rejuvenating effects:
- Brain health: Reduced hippocampal inflammation and preserved memory and spatial navigation abilities.
- Metabolic and liver function: Lower visceral fat, maintained skeletal muscle mass, and normalization of the majority of age-altered blood proteins—many linked to restored liver homeostasis.
- Physical function: Treated older mice appeared leaner and matched young animals in speed, balance and grip strength.
- Relevance to humans: Analysis of human liver data confirmed the mouse findings: older and diseased human livers show neutrophil accumulation, higher neutrophil senescence, and elevated EP2 activity on tissue-resident macrophages.
- Precision medicine approach: Unlike broad-acting NSAIDs that blunt PGE2 production and affect multiple prostaglandin pathways, a selective EP2 inhibitor would aim to block only the harmful receptor on macrophages while preserving beneficial prostaglandin signaling elsewhere.
Source: Stanford
Overview: A Stanford Medicine study in mice and human cells points to tissue-resident macrophages as key drivers of organ aging. Blocking a single receptor on these long-lived immune cells preserved youthful function across the brain, heart, liver, skeletal muscle, spleen, bone marrow, kidney and colon by restoring efficient clearance of senescent neutrophils.
Tissue-resident macrophages are long-lived cells that take up permanent residence in organs during development and perform specialized roles appropriate to each tissue. One of their most important tasks is removing dying and senescent cells, including the huge daily influx of neutrophils. Over time, however, these macrophages themselves become impaired, in part due to rising PGE2 signaling acting through EP2. That signaling reduces macrophage mitochondrial function and their capacity to phagocytose spent neutrophils, leading to neutrophil accumulation, tissue damage and chronic inflammation—commonly called inflammaging.
The Stanford team engineered mice in which the EP2 receptor could be removed specifically from tissue-resident macrophages. Older mice lacking EP2 on these cells maintained youthful neutrophil clearance, had fewer senescent neutrophils in tissues, and showed reduced inflammatory markers across blood, liver, colon, heart, kidney and hippocampus. Functionally, these animals preserved cognitive ability, mobility and muscular strength at levels comparable to young mice.
The researchers also tested an experimental EP2-blocking drug in aged mice. Two months of treatment lowered total and senescent neutrophil counts toward youthful ranges and restored the phagocytic function of isolated macrophages in culture. Finally, mining a large human liver cell atlas revealed the same age-related pattern observed in mice: neutrophil buildup, increased cellular senescence and elevated EP2 activity in older or diseased livers.
Implications and next steps
These results underline the central role of macrophage-mediated clearance in preventing chronic inflammation and multi-organ decline. The findings support development of selective EP2 inhibitors as a therapeutic strategy to restore macrophage function without broadly suppressing prostaglandins. Such a precision approach could slow or reverse multiple age-related dysfunctions at once by addressing a shared upstream cause: failure of cellular garbage clearance.
Key Questions Answered:
A: Neutrophils are aggressive first responders designed to neutralize pathogens quickly and then die. When macrophages promptly clear them, inflammation resolves. With aging, macrophage clearance weakens, allowing neutrophils to persist and enter a senescent, toxic state. These senescent neutrophils release damaging substances that injure surrounding tissue and perpetuate chronic inflammation.
A: Common NSAIDs reduce PGE2 production broadly, but PGE2 does many roles through different receptors—some beneficial. Non-selective inhibition can cause side effects such as gastrointestinal or kidney issues. A drug that selectively blocks EP2 would aim to prevent the harmful macrophage signal while preserving helpful prostaglandin pathways.
A: Rather than treating each organ’s aging separately, this work suggests a shared upstream mechanism—failed clearance by tissue-resident macrophages—drives multi-organ decline. Restoring that clearance could simultaneously slow aging-related dysfunction across brain, heart, liver, muscle and other tissues, enabling more unified therapeutic strategies.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff editors.
About this aging research news
Author: Bruce Goldman
Source: Stanford
Contact: Bruce Goldman – Stanford
Image: The image is credited to Neuroscience News
Original Research: Open access. “Restored clearance of senescent neutrophils by tissue-resident macrophages limits organ aging” by Abel Bermudez et al. DOI: 10.1126/science.aea3075
Abstract
Restored clearance of senescent neutrophils by tissue-resident macrophages limits organ aging
Increased inflammation accompanies aging and contributes to declining tissue function. Tan et al. investigated age-related changes in tissue-resident macrophages and how those changes influence aging phenotypes in mice. They found increased prostaglandin E2 signaling in these cells. Preventing elevated PGE2 signaling maintained mitochondrial function in macrophages and limited several aging-related impairments. A key consequence was restored clearance of senescent neutrophils, which reduced inflammation and helped preserve organ function. These findings highlight macrophages and neutrophil clearance as important contributors to age-related tissue dysfunction.