Role of resident macrophages in the immunologic response and smooth muscle dysfunction during acute allograft rejection after intestinal transplantation

Taurodeoxycholic acid and valine reverse obesity-associated augmented alloimmune responses and prolong allograft survival

Obesity initiates a chronic inflammatory network linked to perioperative complications and increased acute rejection rates in organ transplantation. Bariatric surgery is the most effective treatment of obesity recommended for morbidly obese transplant recipients. Here, we delineated the effects of obesity and bariatric surgery on alloimmunity and transplant outcomes in diet-induced obese (DIO) mice. Allograft survival was significantly shorter in DIO-mice. When performing sleeve gastrectomies (SGx) prior to transplantation, we found attenuated T cell-derived alloimmune responses resulting in prolonged allograft survival. Administering taurodeoxycholic acid (TDCA) and valine, metabolites depleted in DIO-mice and restored through SGx, prolonged graft survival in DIO-mice comparable with SGx an dampened Th1 and Th17 alloimmune responses while Treg frequencies and CD4+ T cell-derived IL-10 production were augmented. Moreover, in recipient animals treated with TDCA/valine, levels of donor-specific antibodies had been reduced. Mechanistically, TDCA/valine restrained inflammatory M1-macrophage polarization through TGR5 that compromised cAMP signaling and inhibited macrophage-derived T cell activation. Consistently, administering a TGR5 agonist to DIO-mice prolonged allograft survival. Overall, we provide novel insights into obesity-induced inflammation and its impact on alloimmunity. Furthermore, we introduce TDCA/valine as a noninvasive alternative treatment for obese transplant patients.

Ameliorative effect of fluvoxamine against colon carcinogenesis via COX-2 blockade with oxidative and metabolic stress reduction at the cellular, molecular and metabolic levels

Fluvoxamine's (FLX's) anticancer potential was investigated in pre-clinical research utilizing a DMH-induced colorectal cancer (CRC) rat model. qRT-PCR and immunoblotting validated the mechanistic investigation. The CRC condition was induced in response to COX-2 and IL-6, however, following FLX therapy, the condition returned to normal. FLX's anti-CRC potential may be attributable to COX-2 inhibition since this molecular activity was more apparent for COX-2 than IL-6. FLX repaired the altered metabolites linked to CRC rats, according to ¹H-NMR analysis. FLX was shown to be similar to 5-FU in terms of tumor protection, which may be useful in future medication development.

A study of the mechanisms responsible for the action of new immunosuppressants and their effects on rat small intestinal transplantation

In a series of studies, using an identical rat intestinal transplantation model, we evaluated the effects of several drugs. FK-506 caused a significant attenuation in the proliferation of allogeneic CD4+ T cells and IFN-γ secreting effector functions. FYT720 resulted in a marked reduction in the numbers of lymphocytes, associated with a reduction of T cell recruitment, in grafts. An anti-MAdCAM antibody was next reported to significantly down-regulate CD4+ T cell infiltration in intestinal grafts by blocking the adhesion molecule, and could be useful as an induction therapy. Concerning TAK-779, this CCR5 and CXCR3 antagonist diminished the number of graft-infiltrating cells by suppressing the expression of their receptors in the graft. As a result, it reduced the total number of recipient T cells involved in graft rejection. As the next step, we focused on the participation of monocytes/ macrophages in this field. PQA-18 has been the focus of a novel immunosuppressant that attenuates not only the production of various cytokines, such as IL-2 & TNF-α, on T cells, but the differentiation of macrophages by inhibiting PAK2 as well. In this report, we summarize our previous studies not only regarding the above drugs, but on an anti-complement drug and a JAK inhibitor as well.

Apamin inhibits renal fibrosis via suppressing TGF-β1 and STAT3 signaling in vivo and in vitro

Renal fibrosis is a progressive and chronic process that influences kidneys with chronic kidney disease (CKD), irrespective of cause, leading to irreversible failure of renal function and end-stage kidney disease. Among the signaling related to renal fibrosis, transforming growth factor-β1 (TGF-β1) signaling is a major pathway that induces the activation of myofibroblasts and the production of extracellular matrix (ECM) molecules. Apamin, a component of bee venom (BV), has been studied in relation to various diseases. However, the effect of apamin on renal interstitial fibrosis has not been investigated. The aim of this study was to estimate the beneficial effect of apamin in unilateral ureteral obstruction (UUO)-induced renal fibrosis and TGF-β1-induced renal fibroblast activation. This study revealed that obstructive kidney injury induced an inflammatory response, tubular atrophy, and ECM accumulation. However, apamin treatment suppressed the increased expression of fibrotic-related genes, including α-SMA, vimentin, and fibronectin. Administration of apamin also attenuated the renal tubular cells injury and tubular atrophy. In addition, apamin attenuated fibroblast activation, ECM synthesis, and inflammatory cytokines such as TNF-α, IL-1β, and IL-6 by suppressing the TGF-β1-canonical and non-canonical signaling pathways. This study showed that apamin inhibits UUO-induced renal fibrosis in vivo and TGF-β1-induced renal fibroblasts activation in vitro. Apamin inhibited the inflammatory response, tubular atrophy, ECM accumulation, fibroblast activation, and renal interstitial fibrosis through suppression of TGF-β1/Smad2/3 and STAT3 signaling pathways. These results suggest that apamin might be a potential therapeutic agent for renal fibrosis. KEY MESSAGES: UUO injury can induce renal dysfunction; however, apamin administration prevents renal failure in UUO mice. Apamin inhibited renal inflammatory response and ECM deposition in UUO-injured mice. Apamin suppressed the activation of myofibroblasts in vivo and in vitro. Apamin has the anti-fibrotic effect on renal fibrosis via regulation of TGF-β1 canonical and non-canonical signaling.

Ectopic expression of recipient CD47 inhibits mouse macrophage-mediated immune rejection against human stem cell transplants

Like conventional transplants, immunosuppression is required to facilitate survival and function of human embryonic stem cell (hESC) derivatives after implantation into xenogeneic recipients. We have previously reported that T cells alone are sufficient to reject allogeneic murine ESC derivatives; and strategies that inhibit T-cell activation, including coreceptor and costimulation blockade, prevent hESC derivatives from being rejected. This study aimed to investigate, in addition to T cells, whether macrophages contribute to transplant rejection of hESC xenografts with nonobese diabetic (NOD)/SCID mice that lack functional T and B cells but have macrophages. We show that acute rejection against hESC-derived endothelial cells (hESC-ECs) was mediated, to some degree, by infiltrating macrophages that phagocytosed them. Transgenic expression of murine CD47 on cell surface of hESC-ECs mitigates macrophage-mediated phagocytosis and improves their survival after transplantation. Our results highlight that innate immune cells, such as macrophages, can reject hESC derivatives, raising concern against the use of NOD/SCID as transplant recipients for testing in vivo function of hESC-derived tissues. Augmenting CD47 signaling promotes survival and function of hESC derivatives after xenogeneic transplantation.-Leung, C. S., Li, J., Xu, F., Wong, A. S. L., Lui, K. O. Ectopic expression of recipient CD47 inhibits mouse macrophage-mediated immune rejection against human stem cell transplants.

Novel 1,3,4-thiadiazoles inhibit colorectal cancer via blockade of IL-6/COX-2 mediated JAK2/STAT3 signals as evidenced through data-based mathematical modeling

We attempted a preclinical study using DMH-induced CRC rat model to evaluate the antitumor potential of our recently synthesized 1,3,4-thiadiazoles. The molecular insights were confirmed through ELISA, qRT-PCR and western blot analyses. The CRC condition was produced in response to COX-2 and IL-6 induced activation of JAK2/STAT3 which, in turn, was due to the enhanced phosphorylation of JAK2 and STAT3. The treatment with 1,3,4-thiadiazole derivatives (VR24 and VR27) caused the significant blockade of this signaling pathway. The behavior of STAT3 populations in response to IL-6 and COX-2 stimulations was further confirmed through data-based mathematical modeling using the quantitative western blot data. Finally, VR24 and VR27 restored the perturbed metabolites associated to DMH-induced CRC as evidenced through ¹H NMR based serum metabolomics. The tumor protecting ability of VR24 and VR27 was found comparable or to some degree better than the marketed chemotherapeutics, 5-flurouracil.

Muscularis macrophages: Key players in intestinal homeostasis and disease

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Muscularis macrophages densily colonize the outermost layer of the gastrointestinal tract.

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Muscularis macrophages communicate with enteric neurons in a bidirectional matter.

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Muscularis macrophages are tissue-protective but can contribute to disease.

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Current challenges are to decipher therapeutic potentials of muscularis macrophages.

Macrophages residing in the muscularis externa of the gastrointestinal tract are highly specialized cells that are essential for tissue homeostasis during steady-state conditions as well as during disease. They are characterized by their unique protective functional phenotype that is undoubtedly a consequence of the reciprocal interaction with their environment, including the enteric nervous system. This muscularis macrophage-neuron interaction dictates intestinal motility and promotes tissue-protection during injury and infection, but can also contribute to tissue damage in gastrointestinal disorders such as post-operative ileus and gastroparesis. Although the importance of muscularis macrophages is clearly recognized, different aspects of these cells remain largely unexplored such their origin, longevity and instructive signals that determine their function and phenotype. In this review, we will discuss the phenotype, functions and origin of muscularis macrophages during steady-state and disease conditions. We will highlight the bidirectional crosstalk with neurons and potential therapeutic strategies that target and manipulate muscularis macrophages to restore their protective signature as a treatment for disease.

5H-benzo[h]thiazolo[2,3-b]quinazolines ameliorate NDEA-induced hepatocellular carcinogenesis in rats through IL-6 downregulation along with oxidative and metabolic stress reduction

5H-benzo[h]thiazolo[2,3-b]quinazoline scaffold is known to have an antitumor effect on certain types of malignancies; however, its effect on hepatocellular carcinoma (HCC) remains unclear. Previously, we reported p-toluenesulfonic acid-promoted syntheses, molecular modeling and in vitro antitumor activity of 5H-benzo[h]thiazolo[2,3-b]quinazoline against human hepatoma (Hep-G2) cells where compounds 4A and 6A were found to be potent inhibitors among the series. In continuation to our previous effort to develop novel therapeutic strategies for HCC treatment, here we investigated the in vivo antitumor activity and the mechanism underlying the effects of 4A and 6A in N-nitrosodiethylamine (NDEA)-induced HCC using male Wistar rats. NDEA was administered weekly intraperitoneally at a dose of 100 mg/kg for 6 weeks. Various physiological and morphological changes, oxidative parameters, liver marker enzymes and cytokines were assessed to evaluate the antitumor effect of 4A and 6A. In addition, proton nuclear magnetic resonance-based serum metabolomics were performed to analyze the effects of 4A and 6A against HCC-induced metabolic alterations. Significant tumor incidences with an imbalance in carcinogen metabolizing enzymes and cellular redox status were observed in carcinogenic rats. Tumor inhibitory effects of 4A and 6A were noted by histopathology and biochemical profiles in NDEA-induced hepatic cancer. Compounds 4A and 6A had a potential role in normalizing the elevated levels of inflammatory mediators such as interleukin-1β (IL-1β), IL-2, IL-6 and IL-10. At molecular level, the real-time quantitative reverse-transcribed polymerase chain reaction analysis revealed that 4A and 6A attenuated the IL-6 gene overexpression in hepatic cancer. Further, orthogonal partial least squares discriminant analysis scores plot demonstrated a significant separation of 4A and 6A-treated groups from carcinogen control group. Both the compounds have potential to restore the imbalanced metabolites due to HCC, signifying promising hepatoprotective activities. All these findings suggested that 4A and 6A could be potential drug candidates to treat HCC.

Gut Permeability and Glucose Absorption Are Affected at Early Stages of Graft Rejection in a Small Bowel Transplant Rat Model

Supplemental digital content is available in the text.

Background

Intestinal transplantation (ITx) faces many challenges due to the complexity of surgery and to the multiple immunological reactions that lead to the necessity of rigorous follow-up for early detection of acute cellular rejection (ACR). Our aim was to determine the kinetics of ACR using an experimental ITx model, with emphasis in the characterization of the process using different approaches, including the use of functional assays of absorptive and barrier function.

Methods

ITx in rats conducting serial sampling was performed. Clinical monitoring, graft histology, proinflammatory gene expression, and nitrosative stress determination were performed. Also, glucose absorption, barrier function using ovalbumin translocation, and contractile function were analyzed.

Results

The model used reproduced the different stages of ACR. Allogeneic ITx recipients showed signs of rejection from postoperative day (POD) 5, with increasing severity until 12 POD. Histological evaluation showed mild rejection in early sampling and severe rejection at late stages, with alterations in all graft layers. IL-6, CXCL 10, IFNg, and nitrite plasmas levels showed behavior coincident with histopathology. Remarkably, allogeneic grafts showed a marked alteration of glucose absorptive capacity from POD 5 that was sustained until endpoint. Coincidently, barrier function alteration was evidenced by luminal ovalbumin translocation to serum. Contractile function was progressively impaired along ACR.

Conclusions

Glucose absorption and barrier function are altered at early stages of ACR when histological alterations or gene expression changes were much subtle. This observation may provide simple evaluation tools that could be eventually translated to the clinics to contribute to early ACR diagnosis.

Ameliorative effects of pyrazinoic acid against oxidative and metabolic stress manifested in rats with dimethylhydrazine induced colonic carcinoma

Pyrazinoic acid (PA) is structurally similar to nicotinic acid which acts on G-protein-coupled receptor (GPR109A). GPR109A expresses in colonic and intestinal epithelial sites, and involves in DNA methylation and cellular apoptosis. Therefore, it may be assumed that PA has similar action like nicotinic acid and may be effective against colorectal carcinoma (CRC). CRC was produced via subcutaneous injection of dimethylhydrazine (DMH) at 40 mg/kg body weight once in a week for 4 weeks. After that, PA was administered orally at 2 doses of 10 and 25 mg/kg daily for 15 d to observe the antiproliferative effect. Various physiologic, oxidative stress, molecular parameters, histopathology, RT-PCR and NMR based metabolomics were performed to evaluate the antiproliferative potential of PA. Our results collectively suggested that PA reduced body weight, tumor volume and incidence no. to normal. It restored various oxidative stress parameters and normalized IL-2, IL-6, and COX-2 as compared with carcinogen control. In molecular level, overexpressed IL-6 and COX-2 genes became normal after PA administration. Again, normal tissue architecture was prominent after PA administration. Score plots of PLS-DA models exhibited that PA treated groups were significantly different from CRC group. We found that CRC rat sera have increased levels of acetate, glutamine, o-acetyl-glycoprotein, succinate, citrulline, choline, o-acetyl choline, tryptophan, glycerol, creatinine, lactate, citrate and decreased levels of 3-hydroxy butyrate, dimethyl amine, glucose, maltose, myoinositol. Further the PA therapy has ameliorated the CRC-induced metabolic alterations, signifying its antiproliferative properties. In conclusion, our study provided the evidence that PA demonstrated good antiproliferative effect on DMH induced CRC and thus demonstrated the potential of PA as a useful drug for future anticancer therapy.

Macrophages as Effectors of Acute and Chronic Allograft Injury

Organ transplants give a second chance of life to patients with end-stage organ failure. However, the immuno-logical barriers prove to be very challenging to overcome and graft rejection remains a major hurdle to long-term transplant survival. For decades, adaptive immunity has been the focus of studies, primarily based on the belief that T cells are necessary and sufficient for rejection. With better-developed immunosuppressive drugs and protocols that effectively control adaptive cells, innate immune cells have emerged as key effector cells in triggering graft injury and have therefore attracted much recent attention. In this review, we discuss current understanding of macrophages and their role in transplant rejection, their dynamics, distinct phenotypes, locations, and functions. We also discuss novel therapeutic approaches under development to target macrophages in transplant recipients.

Difficulties, guidelines and review of developing an acute rejection model after rat intestinal transplantation

Experimental small bowel transplantation (SBT) in rats has been proven to be a useful tool for the study of ischemia-reperfusion and immunological aspects related to solid organ transplantation. However, the model is not completely refined, specialized literature is scarce and complex technical details are typically omitted or confusing. Most studies related to acute rejection (AR) use the orthotopic standard, with small sample sizes due to its high mortality, whereas those studying chronic rejection (CR) use the heterotopic standard, which allows longer term survival but does not exactly reflect the human clinical scenario. Various animal strains have been used, and the type of rejection and the timing of its analysis differ among authors. The double purpose of this study was to develop an improved unusual AR model of SBT using the heterotopic technique, and to elaborate a guide useful to implement experimental models for studying AR. We analyzed the model's technical details and expected difficulties in overcoming the learning curve for such a complex microsurgical model, identifying the potential problem areas and providing a step-by-step protocol and reference guide for future surgeons interested in the topic. We also discuss the historic and more recent options in the literature.

The divergent roles of macrophages in solid organ transplantation

PURPOSE OF REVIEW

This review summarizes the phenotype and function of macrophages in the context of solid organ transplantation and will focus on fundamental insights into their paradoxical pro-inflammatory versus suppressive function. We will also discuss the therapeutic potential of regulatory macrophages in tolerance induction.

RECENT FINDINGS

Macrophages are emerging as an essential element of solid organ transplantation. Macrophages are involved in the pathogenesis of ischemia reperfusion injury, as well as both acute and chronic rejection, exacerbating injury through secretion of inflammatory effectors and by amplifying adaptive immune responses. Notably, not all responses associated with macrophages are deleterious to the graft, and graft protection can in fact be conferred by macrophages. This has been attributed to the presence of macrophages with tissue-repair capabilities, as well as the effects of regulatory macrophages.

SUMMARY

The explosion of new information on the role of macrophages in solid organ transplantation has opened up new avenues of research and the possibility of therapeutic intervention. However, the role of myeloid cells in graft rejection, resolution of rejection and tissue repair remains poorly understood. A better understanding of plasticity and regulation of monocyte polarization is vital for the development of new therapies for the treatment of acute and chronic transplant rejection.

The novel guanylhydrazone CPSI-2364 ameliorates ischemia reperfusion injury after experimental small bowel transplantation

BACKGROUND

Resident macrophages within the tunica muscularis are known to play a crucial role in initiating severe inflammation in response to ischemia reperfusion injury after intestinal transplantation contributing to graft dysmotility, bacterial translocation, and possibly, acute rejection. The p38 mitogen-activated protein kinase is a key player in the signaling of proinflammatory cytokine synthesis in macrophages. Therefore, we investigated the effects of CPSI-2364, an apparent macrophage-specific inhibitor of the p38 mitogen-activated protein kinase pathway in an isogenic intestinal rat transplantation model.

METHODS

Recipient and donor animals were treated perioperatively with CPSI-2364 (1 mg/kg, intravenously) or vehicle solution. Nontransplanted animals served as control. Animals were killed 30 min, 3 hr, and 18 hr after reperfusion.

RESULTS

CPSI-2364 treatment resulted in significantly less leukocyte infiltration and significantly improved graft motor function (18 hr). Messenger RNA expression of proinflammatory cytokines (interleukin 6) and kinetic active mediators (NO) was reduced by CPSI-2364 in the early phase after transplantation. Histologic evaluation revealed the protective effects of CPSI-2364 treatment by a significantly less destruction of mucosal integrity at all time points. Perioperative treatment with CPSI-2364 improves graft motor function through impaired inflammatory responses to ischemia reperfusion injury by inhibition of proinflammatory cytokines and suppression of nitric oxide production in macrophages.

CONCLUSIONS

CPSI-2364 presents as a promising complementary pharmacological approach preventing postoperative dysmotility for clinical intestinal transplantation.

The role of lymphoid tissue in the attenuation of the postoperative ileus

Standardized intestinal manipulation (IM) leads to local bowel wall inflammation subsequently spreading over the entire gastrointestinal tract. Previously, we demonstrated that this so-called gastrointestinal field effect (FE) is immune-mediated. The aim of this study was to investigate the role of secondary lymphoid organs [mesenteric lymph nodes (MLN), gut-associated lymphoid tissue (GALT)] in IM-mediated FE by employing mice with deficient secondary lymphoid organs (aly/aly, MLN ex) or by administration of 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol (FTY720), an immunomodulating agent that inhibits emigration of lymphocytes out of lymphoid organs. Small bowel muscularis, and colonic muscularis from wild-type mice as control, from aly/aly mice, FTY720-treated mice (daily dose of 1.0 mg/kg mouse ip starting 3 days before surgical procedure), and wild-type mice that had undergone removal of mesenteric lymph nodes before IM (MLN ex mice) were obtained after selective IM of the jejunum or sham operation. FE was analyzed by measuring transit time of orally administered fluorescent dextran in the gastrointestinal tract [geometric center (GC) of fluorescent dextran], colonic transit time, infiltration of myeloperoxidase-positive cells, and circular smooth muscle contractility. Furthermore, mRNA levels of inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor (TNF)-α, macrophage inflammatory protein (MIP)-1α] were determined by Taqman-PCR. We observed a significantly reduced upregulation of proinflammatory cytokines (IL-6, TNF-α, MIP-1α) in colonic muscularis of MLN ex mice, aly/aly mice, and FTY720-treated mice compared with wild-type mice. Contractility of circular muscularis strips of the colon but not the jejunum was significantly improved in aly/aly mice and FTY720-treated wild-type mice. Additionally, inflammation of the colon determined by the number of myeloperoxidase-positive cells and colonic transit time were significantly improved in aly/aly mice, FTY720-treated wild-type mice, and in MLN ex mice. In summary, lack of secondary lymphoid organs (MLN + GALT) in aly/aly mice or administration of FTY720 abrogated FE after IM as opposed to wild-type mice. These data demonstrate that secondary lymphoid organs are involved in the propagation of FE and postoperative ileus. FTY720 indirectly affects FE by inhibiting migration of activated T cells from the jejunum and adjacent secondary lymphoid organs to the colon. These findings support the crucial role of the adaptive immune system in FE, most likely by a sphyngosine 1-phosphate-dependent mechanism.

Donor-derived bone marrow transfusion produces mixed chimerism and promotes a Th2 shift in Th1/Th2 balance in rat heterotopic small bowel transplantation

BACKGROUND AND AIM

In this study, we investigated immunomodulatory effects of donor-derived bone marrow transfusion in rat heterotopic small bowel transplantation.

METHODS

Rat heterotopic segmental small bowel transplantation models (male Brown Norway to female Lewis) were established. The recipients were randomly divided into control group (pute small bowel transplantation), tacrolimus group (small bowel transplantation plus oral tacrolimus) and small bowel transplantation plus oral tacrolimus and intraportal infusion of donor-derived bone marrow cells group. We investigated the survival time, graft pathologic injuries and rejection grade by haematoxylin-eosin staining, serum IL-2 and IL-10 detection by enzyme labelled immunosorbent assay after small bowel transplantation. The recipients mixed chimerism were observed by detecting sex-determining region of Y chromosome gene in blood, liver, spleen and intestine by using real-time polymerase chain reaction and fluorescence in situ hybridization.

RESULTS

Bone marrow cells group showed a superior survival than the other groups, accompanied by milder pathologic injuries and lower rejection grade, decreasing serum IL-2 and increasing serum IL-10. The recipient chimerism rate in blood, liver, spleen and intestine in bone marrow cells group was significantly higher than the other groups.

CONCLUSION

Transfusion of donor-derived bone marrow cells via portal vein induces mixed chimerism in rats after small bowel transplantation, which may promote a Th2 shift in Th1/Th2 balance and facilitate the induction of immune tolerance.

Intestinal regeneration, residual function and immunological priming following rescue therapy after rat small bowel transplantation

Clinical evidence suggests that recurrent acute cellular rejection (ACR) may trigger chronic rejection and impair outcome after intestinal transplantation. To test this hypothesis and clarify underlying molecular mechanisms, orthotopic/allogenic intestinal transplantation was performed in rats. ACR was allowed to occur in a MHC-disparate combination (BN-LEW) and two rescue strategies (FK506monotherapy vs. FK506+infliximab) were tested against continuous immunosuppression without ACR, with observation for 7/14 and 21 days after transplantation. Both, FK506 and FK506+infliximab rescue therapy reversed ACR and resulted in improved histology and less cellular infiltration. Proinflammatory cytokines and chemotactic mediators in the muscle layer were significantly reduced in FK506 treated groups. Increased levels of CD4, FOXP3 and IL-17 (mRNA) were observed with infliximab. Contractile function improved significantly after FK506 rescue therapy, with a slight benefit from additional infliximab, but did not reach nontransplanted controls. Fibrosis onset was detected in both rescue groups by Sirius-Red staining with concomitant increase of the fibrogenic mediator VEGF. Recovery from ACR could be attained by both rescue therapy regimens, progressing steadily after initiation of immunosuppression. Reversal of ACR, however, resulted in early stage graft fibrosis. Additional infliximab treatment may enhance physiological recovery of the muscle layer and enteric nervous system independent of inflammatory reactions.

Combination therapy of tacrolimus and infliximab reduces inflammatory response and dysmotility in experimental small bowel transplantation in rats

BACKGROUND

Intestinal transplantation initiates a functionally relevant inflammatory response by activation of resident macrophages within the muscularis associated with dysmotility. Infliximab is used successfully as a potent anti-inflammatory agent for the treatment of chronic inflammatory bowel diseases and as rescue therapy in acute steroid-resistant rejection in selected settings in clinical small bowel transplantation. We hypothesize that additional perioperative treatment with infliximab diminishes initiation of the inflammatory cascade and improves motility in small bowel grafts using a standard tacrolimus immunosuppressive protocol.

METHODS

Orthotopic intestinal transplantation was performed in rats. In two treatment groups (24/168 hr), infliximab was administered intravenously directly after reperfusion and tacrolimus was injected intramuscularly after transplantation and once a day. Two other treatment groups (24/168 hr) received standard immunosuppressive therapy with tacrolimus. Isogenic and allogenic transplanted vehicle-treated animals (24/168 hr) and native gut served as control.

RESULTS

Infliximab-treated grafts exhibited significantly less leukocyte infiltration at 24/168 hr after transplantation and at 168 hr significantly less apoptosis in the tunica muscularis compared with tacrolimus monotherapy. Additional infliximab treatment resulted in increased smooth muscle contractility (30%) after 24 hr compared with tacrolimus control.

CONCLUSIONS

Dysmotility of transplanted small bowel results from reperfusion injury and acute rejection. Additional perioperative treatment with infliximab reduces early unspecific inflammatory responses and complements immunosuppressive therapy with tacrolimus.

T-helper cell type 1 memory cells and postoperative ileus in the entire gut

PURPOSE OF REVIEW

The pathophysiological riddle of the clinically important postoperative ileus (POI) has been solved more and more over the last decade. The POI is caused by inflammation and paralysis at the manipulated site propagating to the entire, unmanipulated gastrointestinal tract. Intestinal macrophages produce mediators that paralyze myocytes, but it is unclear how macrophages are activated, particularly those in unmanipulated areas. In addition to direct or neurally mediated activation of intestinal macrophages, a new immunologically mediated activation has been proposed.

RECENT FINDINGS

Recently, it has been shown that the surgical trauma induces interleukin-12 (IL-12) production by intestinal dendritic cells, which activates TH1-memory cells at the manipulated site. Those TH1-memory cells produce interferon-γ (IFN-γ). Those TH1 CCR9 cells also migrate to unmanipulated parts of the gastrointestinal tract. Their IFN-γ stimulates intestinal macrophages to produce nitirc oxide paralyzing myocytes leading to gastrointestinal hypomotility.

SUMMARY

The involvement of the adaptive (T-helper type 1 cell-mediated immune response) and of the innate (mast cells, intestinal macrophages) immune system in the pathophysiology of POI displays possible targets for objective monitoring and treatment of POI.

Perioperative infliximab application has marginal effects on ischemia-reperfusion injury in experimental small bowel transplantation in rats

PURPOSE

Ischemia-reperfusion injury leads to impaired smooth muscle function and inflammatory reactions after intestinal transplantation. In previous studies, infliximab has been shown to effectively protect allogenic intestinal grafts in the early phase after transplantation with resulting improved contractility. This study was designed to reveal protective effects of infliximab on ischemia-reperfusion injury in isogenic transplantation.

METHODS

Isogenic, orthotopic small bowel transplantation was performed in Lewis rats (3 h cold ischemia). Five groups were defined: non-transplanted animals with no treatment (group 1), isogenic transplanted animals with vehicle treatment (groups 2/3) or with infliximab treatment (5 mg/kg body weight intravenously, directly after reperfusion; groups 4/5). The treated animals were sacrificed after 3 (group 2/4) or 24 h (group 3/5). Histological and immunohistochemical analysis, TUNEL staining, real-time RT-PCR, and contractility measurements in a standard organ bath were used for determination of ischemia-reperfusion injury.

RESULTS

All transplanted animals showed reduced smooth muscle function, while no significant advantage of infliximab treatment was observed. Reduced infiltration of neutrophils was noted in the early phase in animals treated with infliximab. The structural integrity of the bowel and infiltration of ED1-positive monocytes and macrophages did not improve with infliximab treatment. At 3 h after reperfusion, mRNA expression of interleukin (IL)-6, TNF-α, IL-10, and iNOS and MCP-1 displayed increased activation in the infliximab group.

CONCLUSION

The protective effects of infliximab in the early phase after experimental small bowel transplantation seem to be unrelated to ischemia-reperfusion injury. The promising effects in allogenic transplantation indicate the need for further experiments with infliximab as complementary treatment under standard immunosuppressive therapy. Further experiments should focus on additional infliximab treatment in the setting of acute rejection.

Impact of CCR7 on the gastrointestinal field effect

Standardized intestinal manipulation (IM) leads to local bowel wall inflammation subsequently spreading over the entire gastrointestinal tract. Previously, we demonstrated that this so-called gastrointestinal field effect (FE) is immune mediated. This study aimed to investigate the role of CCR7 in IM-induced FE. Since CCR7 is expressed on activated dendritic cells and T cells and is well known to control their migration, we hypothesized that lack of CCR7 reduces or abolishes FE. Small bowel muscularis and colonic muscularis from CCR7(-/-) and wild-type (WT) mice were obtained after IM of the jejunum or sham operation. FE was analyzed by measuring gastrointestinal transit time of orally given fluorescent dextran (geometric center), colonic transit time, infiltration of MPO-positive cells, and circular smooth muscle contractility. Furthermore, mRNA levels of the inflammatory cytokine IL-6 were determined by RT-PCR. The number of dendritic cells and CD3+CD25+ T cells separately isolated from jejunum and colon was determined in mice after IM and sham operation. There was no significant difference in IL-6 mRNA upregulation in colonic muscularis between sham-operated WT and CCR7(-/-) mice after IM. Contractility of circular muscularis strips of the colon was significantly improved in CCR7(-/-) animals following IM and did not vary significantly from sham-operated animals. Additionally, inflammation of the colon determined by the number of MPO-positive cells and colonic transit time was significantly reduced in CCR7(-/-) mice. In contrast, jejunal contractility and jejunal inflammation of transgenic mice did not differ significantly from WT mice after IM. These data are supported by a significant increase of CD3+CD25+ T cells in the colonic muscularis of WT mice after IM, which could not be observed in CCR7(-/-) mice. These data demonstrate that CCR7 is required for FE and postoperative ileus. CCR7 indirectly affects FE by inhibiting migration of activated dendritic cells and of T cells from the jejunum to the colon. These findings support the critical role of the adaptive immune system in FE.

T helper type 1 memory cells disseminate postoperative ileus over the entire intestinal tract

Localized abdominal surgery can lead to disruption of motility in the entire gastrointestinal tract (postoperative ileus). Intestinal macrophages produce mediators that paralyze myocytes, but it is unclear how the macrophages are activated, especially those in unmanipulated intestinal areas. Here we show that intestinal surgery activates intestinal CD103(+)CD11b(+) dendritic cells (DCs) to produce interleukin-12 (IL-12). This promotes interferon-γ (IFN-γ) secretion by CCR9(+) memory T helper type 1 (T(H)1) cells which activates the macrophages. IL-12 also caused some T(H)1 cells to migrate from surgically manipulated sites through the bloodstream to unmanipulated intestinal areas where they induced ileus. Preventing T cell migration with the drug FTY720 or inhibition of IL-12, T-bet (T(H)1-specific T box transcription factor) or IFN-γ prevented postoperative ileus. CCR9(+) T(H)1 memory cells were detected in the venous blood of subjects 1 h after abdominal surgery. These findings indicate that postoperative ileus is a T(H)1 immune-mediated disease and identify potential targets for disease monitoring and therapy.

Perioperative infliximab application ameliorates acute rejection associated inflammation after intestinal transplantation

As we have shown in the past, acute rejection-related TNF-α upregulation in resident macrophages in the tunica muscularis after small bowel transplantation (SBTx) results in local amplification of inflammation, decisively contributing to graft dysmotility. Therefore, the aim of this study is to investigate the effectiveness of the chimeric-monoclonal-anti-TNF-α antibody infliximab as perioperative single shot treatment addressing inflammatory processes during acute rejection early after transplantation. Orthotopic, isogenic and allogenic SBTx was performed in rats (BN-Lewis/BN-BN) with infliximab treatment. Vehicle and IV-immunoglobulin-treated animals served as controls. Animals were sacrificed after 24 and 168 h. Leukocyte infiltration was investigated in muscularis whole mounts by immunohistochemistry, mediator mRNA expression by Real-Time-RT-PCR, apoptosis by TUNEL and smooth muscle contractility in a standard organ bath. Both, infliximab and Sandoglobulin® revealed antiinflammatory effects. Infliximab resulted in significantly less leukocyte infiltration compared to allogenic controls and IV-immunoglobulin, which was accompanied by lower gene expression of MCP-1 (24 h), IFN-γ (168 h) and infiltration of CD8-positive cells. Smooth muscle contractility improved significantly after 24 h compared to all controls in infliximab treated animals accompanied by lower iNOS expression. Perioperative treatment with infliximab is a possible pharmaceutical approach to overcome graft dysmotility early after SBTx.