Author: Zhu Guan, et al.
Anesthesia & Analgesia. 2026;143(1):43–58.
Older patients with sepsis experience greater organ injury and mortality, but the biological mechanisms responsible for this increased vulnerability remain incompletely understood. This study examined whether aging impairs macrophage clearance of neutrophil extracellular traps, or NETs, resulting in greater inflammation and liver injury during sepsis.
Study Design
The investigators used a cecal ligation and puncture model of sepsis in young, 8-week-old mice and aged, 100-week-old mice. They evaluated liver injury, inflammatory responses, NET accumulation, macrophage phagocytosis, and signaling through the calcium/calmodulin-dependent protein kinase kinase 2 and AMP-dependent protein kinase pathway.
The researchers also studied blood samples from 40 patients with sepsis:
- 25 elderly patients between 65 and 89 years old
- 15 younger patients between 31 and 62 years old
Interventions included DNase I to degrade NETs, transplantation of young bone marrow into aged mice, and activation of AMP-dependent protein kinase with 5-aminoimidazole-4-carboxamide ribonucleotide.
Key Findings
Aged septic mice experienced significantly greater liver injury, inflammation, NET accumulation, and 7-day mortality than young septic mice.
The risk of death in aged mice was approximately 2.5 times that observed in younger mice. Aged animals also demonstrated significantly worse liver histopathology and greater accumulation of hepatic NETs.
Treatment with DNase I reduced NET accumulation, liver enzyme elevations, and inflammatory responses, suggesting that excessive NETs contributed directly to septic liver injury.
Transplanting young bone marrow into aged mice significantly reduced hepatic NET accumulation. This finding indicated that age-related abnormalities in bone marrow-derived immune cells, particularly macrophages, played an important role.
Role of AMP-Dependent Protein Kinase
Macrophages normally remove NETs through phagocytosis. In aged septic mice, activation of AMP-dependent protein kinase and its upstream regulator, calcium/calmodulin-dependent protein kinase kinase 2, was markedly reduced.
Activating AMP-dependent protein kinase with 5-aminoimidazole-4-carboxamide ribonucleotide:
- Reduced hepatic NET accumulation
- Improved liver histopathology
- Decreased inflammatory injury
- Reduced 7-day mortality
The mortality hazard was reduced by approximately 63% in treated aged mice compared with untreated aged septic mice.
Human Findings
Blood samples from elderly patients with sepsis demonstrated findings consistent with the animal experiments.
Compared with younger patients, elderly patients had:
- Higher levels of NET-related markers
- Reduced AMP-dependent protein kinase phosphorylation
- Significantly impaired macrophage phagocytosis of NETs
These findings suggest that age-related impairment of NET clearance may also occur in humans with sepsis.
Clinical Implications
NETs are released by activated neutrophils to trap pathogens, but excessive or persistent NET accumulation can injure tissues and intensify inflammation.
This study suggests that aged macrophages are less capable of clearing NETs because of impaired calcium/calmodulin-dependent protein kinase kinase 2 and AMP-dependent protein kinase signaling. The resulting NET accumulation may contribute to the disproportionate severity of liver injury and mortality among elderly patients with sepsis.
Therapies that enhance AMP-dependent protein kinase activity or promote NET clearance could potentially reduce septic organ injury in older patients. However, the compounds evaluated in this study are not established treatments for human sepsis.
Limitations
Much of the mechanistic evidence came from a mouse model, and the human component included only 40 patients. The clinical experiments were primarily laboratory based and did not evaluate whether targeting this pathway improves patient outcomes.
Additional studies are needed to determine whether NET degradation or AMP-dependent protein kinase activation can be translated safely into clinical treatment.
Conclusion
Aging impairs the ability of macrophages to remove neutrophil extracellular traps during sepsis. Reduced calcium/calmodulin-dependent protein kinase kinase 2 and AMP-dependent protein kinase signaling leads to NET accumulation, increased liver inflammation, greater organ injury, and increased mortality.
Restoring AMP-dependent protein kinase activity improved NET clearance, reduced liver injury, and increased survival in aged septic mice. This pathway represents a promising potential therapeutic target for protecting elderly patients from sepsis-induced organ damage.
We thank Anesthesia & Analgesia for allowing us to summarize this important research.