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Updated: Jul 14, 2026
Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation
Published on: April 29, 2015
Toll-like receptor 4 plays a role in macrophage phagocytosis during peritoneal sepsis
Rahul J Anand1, Jeffrey W Kohler, Jaime A Cavallo
1Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213, USA.
Background:
Peritoneal sepsis is a significant cause of mortality in infants with necrotizing enterocolitis, caused in part by impaired bacterial clearance. Recent studies have identified toll-like receptor-4 (TLR4) as a receptor for endotoxin (lipopolysaccharide [LPS]). We hypothesized that TLR4 regulates bacterial clearance from the peritoneal cavity and sought to investigate whether macrophage phagocytosis was involved.
Methods:
Peritoneal sepsis was induced in mice expressing either functional TLR4 (TLR4-wild-type [WT]) or mutant TLR4 by intraperitoneal injection of either live Escherichia coli or LPS. Phagocytosis was assessed by measuring the uptake of opsonized red cells. To assess bacterial clearance, we irrigated peritoneal cavities of injected animals with saline and plated it on gram-negative selective media.
Results:
LPS significantly increased the rate of phagocytosis by peritoneal macrophages from TLR4-WT mice, but not in those from TLR4-mutant mice, suggesting a role for TLR4 in phagocytosis. LPS also increased the rates of phagocytosis in cultured macrophages expressing TLR4, confirming these findings. The yield of gram-negative bacteria obtained from the peritoneal cavities of septic TLR4-WT mice was greater than that from TLR4 mutants, consistent with TLR4-dependent alterations in their septic course.
Conclusions:
We conclude that TLR4 plays a critical role in the response to intraperitoneal E. coli through effects on phagocytosis by macrophages, suggesting the possibility of using TLR4 as a therapeutic target in diseases of peritoneal sepsis.
Insights
Toll-like receptor-4 (TLR4) enhances macrophage phagocytosis of bacteria in peritoneal sepsis. This TLR4-dependent bacterial clearance suggests potential therapeutic applications for sepsis treatment.
Area of Science:
- Immunology
- Microbiology
- Neonatal Research
Background:
- Peritoneal sepsis in necrotizing enterocolitis leads to infant mortality due to poor bacterial clearance.
- Toll-like receptor-4 (TLR4) is identified as an endotoxin (lipopolysaccharide [LPS]) receptor.
- Impaired bacterial clearance suggests a potential role for TLR4 in regulating peritoneal immune responses.
Purpose of the Study:
- To investigate the role of TLR4 in bacterial clearance from the peritoneal cavity.
- To determine if macrophage phagocytosis is a mechanism regulated by TLR4 in peritoneal sepsis.
Main Methods:
- Induction of peritoneal sepsis in mice with functional (wild-type) or mutant TLR4 using Escherichia coli or LPS.
- Assessment of macrophage phagocytosis via opsonized red blood cell uptake.
- Quantification of bacterial clearance by plating peritoneal lavage fluid.
Main Results:
- LPS significantly enhanced macrophage phagocytosis in TLR4-wild-type mice but not in TLR4-mutant mice.
- In vitro studies confirmed TLR4's role in enhancing phagocytosis by cultured macrophages.
- TLR4-wild-type mice exhibited greater bacterial clearance compared to TLR4-mutant mice during sepsis.
Conclusions:
- TLR4 plays a crucial role in the host response to intraperitoneal E. coli infection.
- TLR4 mediates bacterial clearance through enhanced macrophage phagocytosis.
- Targeting TLR4 may offer a therapeutic strategy for peritoneal sepsis.
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