Inducible nitric oxide synthase expression in the intestinal muscularis mediates severe smooth muscle dysfunction during acute rejection in allogenic rodent small bowel transplantation.
BACKGROUND
Acute rejection in small bowel transplantation is associated with dysmotility. Therefore, host and organ not only face the threat of destructive immunological processes but also the risk of bacterial translocation, endotoxemia, and systemic inflammatory response syndrome. We hypothesized that dysmotility during acute rejection is based on an alloreactive leukocyte infiltrate and coexpression of the kinetically active mediator inducible nitric oxide synthase (iNOS) in the muscularis propria.


METHODS
Allogenic and isogenic rat small bowel transplantation (SBTx; Brown Norway [BN] to Lewis and BN to BN) was performed without immunosuppression. Animals were sacrificed 4 and 7 d after SBTx. Leukocyte infiltration and iNOS protein was investigated by immunohistochemistry and immunohistology. Real-time reverse transcription polymer chain reaction was used to detect iNOS expression. Griess reaction was used to evaluate NO production. Spontaneous, bethanechol-stimulated, and L-N(6)-(1-iminoethyl)-L-Lysin-blocked jejunal circular muscle contractions were measured in a standard organ bath in vitro.


RESULTS
On d 7 after SBTx, allogenic transplanted animals showed significant infiltration with ED-1- and ED-2-positive monocytes and macrophages within the muscularis parallel to the manifestation of acute rejection. Additionally, immunohistochemistry localized iNOS protein in leukocytes within the muscularis. Reverse transcription polymer chain reaction showed a significant increase in iNOS mRNA expression (460-fold) in allogenic transplanted muscularis compared to isogenic transplanted muscularis (2.5-fold). Compared to controls, allogenic grafts showed a 73% decrease in smooth muscle contractility, while isogenic grafts showed only an 8% decrease of contractility on d 7. L-N(6)-(1-iminoethyl)-L-Lysin application in vitro significantly improved muscle contractility and decreased NO production.


CONCLUSIONS
The data show that inflammation associated iNOS expression in the intestinal graft muscularis is involved in motoric graft dysfunction during acute rejection.
Schaefer
Nico
N
Department of Surgery, Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany. nico.schaefer@ukb.uni-bonn.de
Tahara
Kazunori
K
Pech
Thomas
T
Websky
Martin V
MV
Fujishiro
Jun
J
Pantelis
Dimitrios
D
Abu-Elmagd
Kareem
K
Kalff
Jörg C
JC
Hirner
Andreas
A
Türler
Andreas
A
D000818:Animals; D005769:Gastrointestinal Motility; D006084:Graft Rejection / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007249:Inflammation / Q000503:physiopathology; D007421:Intestine, Small / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology / Q000637:transplantation*; D007962:Leukocytes / Q000473:pathology / Q000502:physiology*; D008297:Male; D009130:Muscle, Smooth / Q000473:pathology / Q000503:physiopathology*; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D014185:Transplantation, Isogeneic
D012333:RNA, Messenger; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II