Inhibition of macrophage function prevents intestinal inflammation and postoperative ileus in rodents
Sven Wehner1, Florian F Behrendt, Boris N Lyutenski
1Department of Surgery, University of Bonn, Bonn 53105, Germany.
Background:
Abdominal surgery results in a molecular and cellular inflammatory response in the intestine, leading to postoperative ileus. It was hypothesised that resident macrophages within the intestinal muscularis have an important role in this local inflammation.
Aims:
To investigate whether chemical or genetic depletion of resident muscularis macrophages would lead to a reduction in the local inflammation and smooth-muscle dysfunction.
Methods:
Two rodent models were used to deplete and inactivate macrophages: (1) a rat model in which resident macrophages were depleted by chlodronate liposomes; (2) a model of mice with osteopetrosis mice, completely lacking the resident muscularis macrophages, used as an additional genetic approach. Animals with normal or altered intestinal macrophages underwent surgical intestinal manipulation. The inflammatory response was investigated by quantitative reverse transcriptase-polymerase chain reaction for mRNA of MIP-1alpha, interleukin (IL)1beta, IL6, intracellular adhesion molecule 1 (ICAM-1) and monocyte chemotractant protein 1 (MCP)-1 in the isolated small bowel muscularis. In addition, muscularis whole mounts were used for histochemical and immunohistochemical analysis to quantify leucocyte infiltration and detect cytokine expression. Subsequently, in vitro muscle contractility and in vivo gastrointestinal transit were measured.
Results:
Both models resulted in markedly decreased expression of MIP-1alpha, IL1beta, IL6, ICAM-1 and MCP-1 after manipulation compared with controls. In addition to this decrease in inflammatory mediators, recruitment of leucocytes into the muscularis was also diminished. Macrophage-altered animals had near normal in vitro jejunal circular muscle function and gastrointestinal transit despite surgical manipulation.
Conclusions:
Resident intestinal muscularis macrophages are initially involved in inflammatory responses resulting in postoperative ileus. Depletion and inactivation of the muscularis macrophage network prevents postoperative ileus.
Insights
Depleting intestinal macrophages significantly reduces inflammation and prevents postoperative ileus after abdominal surgery. This research highlights macrophages
Area of Science:
- Gastroenterology
- Immunology
- Surgical Research
Background:
- Abdominal surgery triggers an inflammatory response in the intestine, contributing to postoperative ileus.
- Resident macrophages in the intestinal muscularis are suspected to play a key role in this localized inflammation.
Purpose of the Study:
- To investigate if depleting resident muscularis macrophages reduces intestinal inflammation and smooth muscle dysfunction post-surgery.
- To explore the role of these macrophages in the development of postoperative ileus.
Main Methods:
- Two rodent models were used: rats treated with clodronate liposomes and osteopetrotic mice lacking muscularis macrophages.
- Surgical intestinal manipulation was performed on animals with normal or altered macrophage populations.
- Inflammatory markers (MIP-1alpha, IL1beta, IL6, ICAM-1, MCP-1), leukocyte infiltration, cytokine expression, muscle contractility, and gastrointestinal transit were analyzed.
Main Results:
- Macrophage depletion markedly decreased inflammatory mediator expression (MIP-1alpha, IL1beta, IL6, ICAM-1, MCP-1) post-manipulation.
- Leukocyte recruitment into the muscularis was significantly diminished in treated animals.
- Animals with altered macrophages exhibited near-normal muscle function and gastrointestinal transit despite surgery.
Conclusions:
- Resident intestinal muscularis macrophages are critically involved in the inflammatory cascade leading to postoperative ileus.
- Targeting and depleting the muscularis macrophage network effectively prevents postoperative ileus.
