Inhibition of macrophage function prevents intestinal inflammation and postoperative ileus in rodents.
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.


OBJECTIVE
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.
Wehner
Sven
S
Department of Surgery, University of Bonn, Bonn 53105, Germany.
Behrendt
Florian F
FF
Lyutenski
Boris N
BN
Lysson
Mariola
M
Bauer
Anthony J
AJ
Hirner
Andreas
A
Kalff
Jörg C
JC
D000818:Animals; D018932:Chemokine CCL2 / Q000032:analysis; D005769:Gastrointestinal Motility / Q000276:immunology; D045823:Ileus / Q000276:immunology / Q000517:prevention & control*; D007150:Immunohistochemistry / Q000379:methods; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D053583:Interleukin-1beta / Q000032:analysis; D015850:Interleukin-6 / Q000032:analysis; D007421:Intestine, Small / Q000276:immunology; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000276:immunology; D009130:Muscle, Smooth / Q000276:immunology; D009135:Muscular Diseases / Q000276:immunology / Q000517:prevention & control*; D011183:Postoperative Complications / Q000276:immunology / Q000517:prevention & control*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
D018932:Chemokine CCL2; D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D018799:Intercellular Adhesion Molecule-1