Combination immunotherapy with anti-PD-L1 antibody and depletion of regulatory T cells during acute viral infections results in improved virus control but lethal immunopathology

Combination immunotherapy (CIT) is currently applied as a treatment for different cancers and is proposed as a cure strategy for chronic viral infections. Whether such therapies are efficient during an acute infection remains elusive. To address this, inhibitory receptors were blocked and regulatory T cells depleted in acutely Friend retrovirus-infected mice. CIT resulted in a dramatic expansion of cytotoxic CD4+ and CD8+ T cells and a subsequent reduction in viral loads. Despite limited viral replication, mice developed fatal immunopathology after CIT. The pathology was most severe in the gastrointestinal tract and was mediated by granzyme B producing CD4+ and CD8+ T cells. A similar post-CIT pathology during acute Influenza virus infection of mice was observed, which could be prevented by vaccination. Melanoma patients who developed immune-related adverse events under immune checkpoint CIT also presented with expanded granzyme-expressing CD4+ and CD8+ T cell populations. Our data suggest that acute infections may induce immunopathology in patients treated with CIT, and that effective measures for infection prevention should be applied.

TRIM58 Restrains Intestinal Mucosal Inflammation by Negatively Regulating TLR2 in Myeloid Cells

Balanced control of innate immune signaling in the intestine represents an important host defense mechanism to avoid inappropriate responses that may exacerbate mucosal injury in acute inflammation. In this study, we report that TRIM58, a RING E3-ubiquitin ligase, associates with TLR2. The interaction was found in a yeast two-hybrid screen (human leukocyte and mononuclear library) and confirmed by coimmunoprecipitation of tagged and endogenous proteins. TRIM58 was predominantly expressed by murine and human myeloid-derived cells. Stimulation with a TLR2 ligand modulated TRIM58 synthesis in myeloid cells. Overexpression of TRIM58, but only in presence of the RING domain, promoted proteasome-dependent degradation of TLR2, inhibiting its signaling activity. Genetic deletion of Trim58 in mice (Trim58 ^-/-) led to impaired resolution of acute dextran sodium sulfate-induced colitis, which was characterized by delayed recovery from colonic injury and associated with enhanced expression of TLR2 protein and proinflammatory cyto/chemokine production in inflamed colons. Using myeloid cell-specific deletion of Trim58 in mice, we demonstrated that the myeloid cell compartment was responsible for early colitis acceleration in Trim58 deficiency. In vitro studies revealed that Trim58 ^-/- myeloid cells, which showed constitutive upregulation of TLR2 protein, overreacted to a proinflammatory milieu (TNF-α and IFN-γ) with increased IL-1β protein production, which mechanistically depended on Tlr2 Finally, we found that TRIM58 mRNA and protein expression levels were reduced in colonic specimens from patients with ulcerative colitis. In conclusion, we identify TRIM58 as a novel negative mediator of innate immune control and mucosal homeostasis via TLR2 signaling. Dysfunction of TRIM58 in myeloid cells may contribute to ulcerative colitis pathogenesis.

Characterization of pancreatic glucagon-producing tumors and pituitary gland tumors in transgenic mice overexpressing MYCN in hGFAP-positive cells

Amplification or overexpression of MYCN is involved in development and maintenance of multiple malignancies. A subset of these tumors originates from neural precursors, including the most aggressive forms of the childhood tumors, neuroblastoma and medulloblastoma. In order to model the spectrum of MYCN-driven neoplasms in mice, we transgenically overexpressed MYCN under the control of the human GFAP-promoter that, among other targets, drives expression in neural progenitor cells. However, LSL-MYCN;hGFAP-Cre double transgenic mice did neither develop neural crest tumors nor tumors of the central nervous system, but presented with neuroendocrine tumors of the pancreas and, less frequently, the pituitary gland. Pituitary tumors expressed chromogranin A and closely resembled human pituitary adenomas. Pancreatic tumors strongly produced and secreted glucagon, suggesting that they derived from glucagon- and GFAP-positive islet cells. Interestingly, 3 out of 9 human pancreatic neuroendocrine tumors expressed MYCN, supporting the similarity of the mouse tumors to the human system. Serial transplantations of mouse tumor cells into immunocompromised mice confirmed their fully transformed phenotype. MYCN-directed treatment by AuroraA- or Brd4-inhibitors resulted in significantly decreased cell proliferation in vitro and reduced tumor growth in vivo. In summary, we provide a novel mouse model for neuroendocrine tumors of the pancreas and pituitary gland that is dependent on MYCN expression and that may help to evaluate MYCN-directed therapies.

Proteomics/phosphoproteomics of left ventricular biopsies from patients with surgical coronary revascularization and pigs with coronary occlusion/reperfusion: remote ischemic preconditioning

Remote ischemic preconditioning (RIPC) by repeated brief cycles of limb ischemia/reperfusion reduces myocardial ischemia/reperfusion injury. In left ventricular (LV) biopsies from patients undergoing coronary artery bypass grafting (CABG), only the activation of signal transducer and activator of transcription 5 was associated with RIPC’s cardioprotection. We have now used an unbiased, non-hypothesis-driven proteomics and phosphoproteomics approach to analyze LV biopsies from patients undergoing CABG and from pigs undergoing coronary occlusion/reperfusion without (sham) and with RIPC. False discovery rate-based statistics identified a higher prostaglandin reductase 2 expression at early reperfusion with RIPC than with sham in patients. In pigs, the phosphorylation of 116 proteins was different between baseline and early reperfusion with RIPC and/or with sham. The identified proteins were not identical for patients and pigs, but in-silico pathway analysis of proteins with ≥2-fold higher expression/phosphorylation at early reperfusion with RIPC in comparison to sham revealed a relation to mitochondria and cytoskeleton in both species. Apart from limitations of the proteomics analysis per se, the small cohorts, the sampling/sample processing and the number of uncharacterized/unverifiable porcine proteins may have contributed to this largely unsatisfactory result.

MDR1A deficiency restrains tumor growth in murine colitis-associated carcinogenesis

Patients with Ulcerative Colitis (UC) have an increased risk to develop colitis-associated colorectal cancer (CAC). Here, we found that protein expression of ABCB1 (ATP Binding Cassette Subfamily B Member 1) / MDR1 (multidrug resistance 1) was diminished in the intestinal mucosa of patients with active UC with or without CAC, but not in non-UC patients with sporadic colon cancer. We investigated the consequences of ABCB1/MDR1 loss-of-function in a common murine model for CAC (AOM/DSS). Mice deficient in MDR1A (MDR1A KO) showed enhanced intratumoral inflammation and cellular damage, which were associated with reduced colonic tumor size and decreased degree of dysplasia, when compared to wild-type (WT). Increased cell injury correlated with reduced capacity for growth of MDR1A KO tumor spheroids cultured ex-vivo. Gene expression analysis by microarray demonstrated that MDR1A deficiency shaped the inflammatory response towards an anti-tumorigenic microenvironment by downregulating genes known to be important mediators of cancer progression (PTGS2 (COX2), EREG, IL-11). MDR1A KO tumors showed increased gene expression of TNFSF10 (TRAIL), a known inducer of cancer cell death, and CCL12, a strong trigger of B cell chemotaxis. Abundant B220+ B lymphocyte infiltrates with interspersed CD138+ plasma cells were recruited to the MDR1A KO tumor microenvironment, concomitant with high levels of immunoglobulin light chain genes. In contrast, MDR1A deficiency in RAG2 KO mice that lack both B and T cells aggravated colonic tumor progression. MDR1A KO CD19+ B cells, but not WT CD19+ B cells, suppressed growth of colonic tumor-derived spheroids from AOM/DSS-WT mice in an ex-vivo co-culture system, implying that B-cell regulated immune responses contributed to delayed tumor development in MDR1A deficiency. In conclusion, we provide first evidence that loss of ABCB1/MDR1 function may represent an essential tumor-suppressive host defense mechanism in CAC.

P-glycoprotein multidrug transporter in inflammatory bowel diseases: More questions than answers

The gastrointestinal barrier is constantly exposed to numerous environmental substrates that are foreign and potentially harmful. These xenobiotics can cause shifts in the intestinal microbiota composition, affect mucosal immune responses, disturb tissue integrity and impair regeneration. The multidrug transporter ABCB1/MDR1 p-glycoprotein (p-gp) plays a key role at the front line of host defence by efficiently protecting the gastrointestinal barrier from xenobiotic accumulation. This Editorial discusses how altered expression and function of ABCB1/MDR1 p-gp may contribute to the development and persistence of chronic intestinal inflammation in inflammatory bowel diseases (IBD). Recent evidence implies multiple interactions between intestinal microbiota, innate immunity and xenobiotic metabolism via p-gp. While decreased efflux activity may promote disease susceptibility and drug toxicity, increased efflux activity may confer resistance to therapeutic drugs in IBD. Mice deficient in MDR1A develop spontaneously chronic colitis, providing a highly valuable murine IBD model for the study of intestinal epithelial barrier function, immunoregulation, infectious co-triggers and novel therapeutic approaches. Possible associations of human ABCB1 gene polymorphisms with IBD susceptibility have been evaluated, but results are inconsistent. Future studies must focus on further elucidation of the pathophysiological relevance and immunological functions of p-gp and how its ambiguous effects could be therapeutically targeted in IBD.

MiR-205 and MiR-373 Are Associated with Aggressive Human Mucinous Colorectal Cancer

Mucinous adenocarcinoma (MAC) represents a distinct histopathological entity of colorectal cancer (CRC), which is associated with disease progression and poor prognosis. Here, we found that expression levels of miR-205 and miR-373 were specifically upregulated only in patients with mucinous colon cancers, but not in CRC that lack mucinous components. To investigate the effects of miR-205 and miR-373 on intestinal epithelial cell (IEC) biology by gain- and loss-of-function experiments in a proof-of-concept approach, we chose previously established in-vitro human Caco-2-based models of differentiated, non-invasive (expressing TLR4 wild-type; termed Caco-2[WT]) versus undifferentiated, invasive (expressing TLR4 mutant D299G; termed Caco-2[D299G]) IEC. Enterocyte-like Caco-2[WT] showed low levels of miR-205 and miR-373 expression, while both miRNAs were significantly upregulated in colorectal carcinoma-like Caco-2[D299G], thus resembling the miRNA expression pattern of paired normal versus tumor samples from MAC patients. Using stable transfection, we generated miR-205- or miR-373-expressing and miR-205- or miR-373-inhibiting subclones of these IEC lines. We found that introduction of miR-205 into Caco-2[WT] led to expansion of mucus-secreting goblet cell-like cells, which was associated with induction of KLF4, MUC2 and TGFβ1 expression. Activation of miR-205 in Caco-2[WT] induced chemoresistance, while inhibition of miR-205 in Caco-2[D299G] promoted chemosensitivity. Caco-2[WT] overexpressing miR-373 showed mitotic abnormalities and underwent morphologic changes (loss of epithelial polarity, cytoskeletal reorganization, and junctional disruption) associated with epithelial-mesenchymal transition and progression to inflammation-associated colonic carcinoma, which correlated with induction of phosphorylated STAT3 and N-CADHERIN expression. Functionally, introduction of miR-373 into Caco-2[WT] mediated loss of cell-cell adhesion and increased proliferation and invasion. Reversely, inhibition of miR-373 allowed mesenchymal IEC to regain epithelial properties, which correlated with absence of neoplastic progression. Using xenografts in mice demonstrated miR-373-mediated acceleration of malignant intestinal tumor growth. In conclusion, our results provide first evidence that miR-205 and miR-373 may differentially contribute to the aggressive phenotype of MAC in CRC.

TLR signaling modulates side effects of anticancer therapy in the small intestine

Intestinal mucositis represents the most common complication of intensive chemotherapy, which has a severe adverse impact on quality of life of cancer patients. However, the precise pathophysiology remains to be clarified, and there is so far no successful therapeutic intervention. In this study, we investigated the role of innate immunity through TLR signaling in modulating genotoxic chemotherapy-induced small intestinal injury in vitro and in vivo. Genetic deletion of TLR2, but not MD-2, in mice resulted in severe chemotherapy-induced intestinal mucositis in the proximal jejunum with villous atrophy, accumulation of damaged DNA, CD11b(+)-myeloid cell infiltration, and significant gene alterations in xenobiotic metabolism, including a decrease in ABCB1/multidrug resistance (MDR)1 p-glycoprotein (p-gp) expression. Functionally, stimulation of TLR2 induced synthesis and drug efflux activity of ABCB1/MDR1 p-gp in murine and human CD11b(+)-myeloid cells, thus inhibiting chemotherapy-mediated cytotoxicity. Conversely, TLR2 activation failed to protect small intestinal tissues genetically deficient in MDR1A against DNA-damaging drug-induced apoptosis. Gut microbiota depletion by antibiotics led to increased susceptibility to chemotherapy-induced mucosal injury in wild-type mice, which was suppressed by administration of a TLR2 ligand, preserving ABCB1/MDR1 p-gp expression. Findings were confirmed in a preclinical model of human chemotherapy-induced intestinal mucositis using duodenal biopsies by demonstrating that TLR2 activation limited the toxic-inflammatory reaction and maintained assembly of the drug transporter p-gp. In conclusion, this study identifies a novel molecular link between innate immunity and xenobiotic metabolism. TLR2 acts as a central regulator of xenobiotic defense via the multidrug transporter ABCB1/MDR1 p-gp. Targeting TLR2 may represent a novel therapeutic approach in chemotherapy-induced intestinal mucositis.

The human TLR4 variant D299G mediates inflammation-associated cancer progression in the intestinal epithelium

Homeostatic TLR4 signaling protects the intestinal epithelium in health. Evidence suggests that perturbed TLR4 signaling is linked to carcinogenesis. We have recently demonstrated that the common human TLR4 variant D299G exerts pro-inflammatory effects and drives malignant tumor progression in human colon cancer.

Loss of TLR2 worsens spontaneous colitis in MDR1A deficiency through commensally induced pyroptosis

Variants of the multidrug resistance gene (MDR1/ABCB1) have been associated with increased susceptibility to severe ulcerative colitis (UC). In this study, we investigated the role of TLR/IL-1R signaling pathways including the common adaptor MyD88 in the pathogenesis of chronic colonic inflammation in MDR1A deficiency. Double- or triple-null mice lacking TLR2, MD-2, MyD88, and MDR1A were generated in the FVB/N background. Deletion of TLR2 in MDR1A deficiency resulted in fulminant pancolitis with early expansion of CD11b(+) myeloid cells and rapid shift toward TH1-dominant immune responses in the lamina propria. Colitis exacerbation in TLR2/MDR1A double-knockout mice required the unaltered commensal microbiota and the LPS coreceptor MD-2. Blockade of IL-1β activity by treatment with IL-1R antagonist (IL-1Ra; Anakinra) inhibited colitis acceleration in TLR2/MDR1A double deficiency; intestinal CD11b(+)Ly6C(+)-derived IL-1β production and inflammation entirely depended on MyD88. TLR2/MDR1A double-knockout CD11b(+) myeloid cells expressed MD-2/TLR4 and hyperresponded to nonpathogenic Escherichia coli or LPS with reactive oxygen species production and caspase-1 activation, leading to excessive cell death and release of proinflammatory IL-1β, consistent with pyroptosis. Inhibition of reactive oxygen species-mediated lysosome degradation suppressed LPS hyperresponsiveness. Finally, active UC in patients carrying the TLR2-R753Q and MDR1-C3435T polymorphisms was associated with increased nuclear expression of caspase-1 protein and cell death in areas of acute inflammation, compared with active UC patients without these variants. In conclusion, we show that the combined defect of two UC susceptibility genes, MDR1A and TLR2, sets the stage for spontaneous and uncontrolled colitis progression through MD-2 and IL-1R signaling via MyD88, and we identify commensally induced pyroptosis as a potential innate immune effector in severe UC pathogenesis.

Commensal-innate immune miscommunication in IBD pathogenesis

Commensal microbiota plays a key role in the health and disease of the host. The innate immune system comprises an essential functional component of the intestinal mucosal barrier, maintaining hyporesponsiveness to omnipresent harmless commensals in the lumen, but rapidly recognizing and combating invading bacteria through diverse antimicrobial mechanisms. Interactions between commensals and innate immune cells are constant, multidimensional and entirely context-dependent. Environment, genetics and host defense differentially modulate commensal-innate immune effects and functions in the intestinal mucosa. In IBD, dysbiosis, mucus layer disruption, impairment in bacterial clearance, intestinal epithelial cell barrier dysfunction and/or immune cell deregulation may lead to commensal-innate immune miscommunication, which critically drives mucosal inflammation and associated cancer.

Toll-like receptor 4 variant D299G induces features of neoplastic progression in Caco-2 intestinal cells and is associated with advanced human colon cancer

BACKGROUND & AIMS

The Toll-like receptor (TLR) 4 mediates homeostasis of the intestinal epithelial cell (IEC) barrier. We investigated the effects of TLR4-D299G on IEC functions.

METHODS

We engineered IECs (Caco-2) to stably overexpress hemagglutinin-tagged wild-type TLR4, TLR4-D299G, or TLR4-T399I. We performed gene expression profiling using DNA microarray analysis. Findings were confirmed by real-time, quantitative, reverse-transcriptase polymerase chain reaction, immunoblot, enzyme-linked immunosorbent assay, confocal immunofluorescence, and functional analyses. Tumorigenicity was tested using the CD1 nu/nu mice xenograft model. Human colon cancer specimens (N = 214) were genotyped and assessed for disease stage.

RESULTS

Caco-2 cells that expressed TLR4-D299G underwent the epithelial-mesenchymal transition and morphologic changes associated with tumor progression, whereas cells that expressed wild-type TLR4 or TLR4-T399I did not. Caco-2 cells that expressed TLR4-D299G had significant increases in expression levels of genes and proteins associated with inflammation and/or tumorigenesis compared with cells that expressed other forms of TLR4. The invasive activity of TLR4-D299G Caco-2 cells required Wnt-dependent activation of STAT3. In mice, intestinal xenograft tumors grew from Caco-2 cells that expressed TLR4-D299G, but not cells that expressed other forms of TLR4; tumor growth was blocked by a specific inhibitor of STAT3. Human colon adenocarcinomas from patients with TLR4-D299G were more frequently of an advanced stage (International Union Against Cancer [UICC] ≥III, 70% vs 46%; P = .0142) with metastasis (UICC IV, 42% vs 19%; P = .0065) than those with wild-type TLR4. Expression of STAT3 messenger RNA was higher among colonic adenocarcinomas with TLR4-D299G than those with wild-type TLR4.

CONCLUSIONS

TLR4-D299G induces features of neoplastic progression in intestinal epithelial Caco-2 cells and associates with aggressive colon cancer in humans, implying a novel link between aberrant innate immunity and colonic cancerogenesis.

Spontaneous bacterial keratitis in CD36 knockout mice

PURPOSE

CD36 is a Class B scavenger receptor that is constitutively expressed in the corneal epithelium and has been implicated in many homeostatic functions, including the homeostasis of the epidermal barrier. The aim of this study is to determine (1) whether CD36 is required for the maintenance of the corneal epithelial barrier to infection, and (2) whether CD36-deficient mice present with an increased susceptibility to bacterial keratitis.

METHODS

The corneas of CD36(-/-), TSP1(-/-), TLR2(-/-), and C57BL/6 WT mice were screened via slit lamp microscopy or ex vivo analysis. The epithelial tight junctions and mucin layer were assessed via LC-biotin and Rose Bengal staining, respectively. Bacterial quantification was performed on corneal buttons and GFP-expressing Staphylococcus aureus was used to study bacterial binding.

RESULTS

CD36(-/-) mice develop spontaneous corneal defects that increased in frequency and severity with age. The mild corneal defects were characterized by a disruption in epithelial tight junctions and the mucin layer, an infiltrate of macrophages, and increased bacterial binding. Bacterial quantification revealed high levels of Staphylococcus xylosus in the corneas of CD36(-/-) mice with severe defects, but not in wild-type controls.

CONCLUSIONS

CD36(-/-) mice develop spontaneous bacterial keratitis independent of TLR2 and TSP1. The authors conclude that CD36 is a critical component of the corneal epithelial barrier, and in the absence of CD36 the barrier breaks down, allowing bacteria to bind to the corneal epithelium and resulting in spontaneous keratitis. This is the first report of spontaneous bacterial keratitis in mice.

Toll-like receptors in inflammatory bowel diseases: a decade later

Differential alteration of Toll-like receptor (TLR) expression in inflammatory bowel disease (IBD) was first described 10 years ago. Since then, studies from many groups have led to the current concept that TLRs represent key mediators of innate host defense in the intestine, involved in maintaining mucosal as well as commensal homeostasis. Recent findings in diverse murine models of colitis have helped to reveal the mechanistic importance of TLR dysfunction in IBD pathogenesis. It has become evident that environment, genetics, and host immunity form a multidimensional and highly interactive regulatory triad that controls TLR function in the intestinal mucosa. Imbalanced relationships within this triad may promote aberrant TLR signaling, critically contributing to acute and chronic intestinal inflammatory processes in IBD colitis and associated cancer.

Colitis-associated variant of TLR2 causes impaired mucosal repair because of TFF3 deficiency

BACKGROUND & AIMS

Goblet cells (GC) facilitate mucosal protection and epithelial barrier repair, yet the innate immune mechanisms that selectively drive GC functions have not been defined. The aim of this study was to determine whether Toll-like receptor (TLR) 2 and modulation of GC-derived trefoil factor (TFF) 3 are functionally linked in the intestine.

METHODS

GC modulation was assessed using quantitative real-time polymerase chain reaction analysis (qRT-PCR), Western blotting, and confocal microscopy. Dextran sulfate sodium (DSS) colitis was induced in wild-type, TFF3(-/-), and TLR2(-/-) mice. Recombinant TLR2 ligand or TFF3 peptide were orally administered after DSS termination. Caco-2 cells overexpressing full-length TLR2 or mutant TLR2-R753Q were tested for TFF3 synthesis and functional-related effects in a wounding assay.

RESULTS

Data from in vitro (Ls174T) and ex vivo models of murine and human GC reveal that TLR2 activation selectively induces synthesis of TFF3. In vivo studies using TFF3(-/-) or TLR2(-/-) mice demonstrate the ability for oral treatment with a TLR2 agonist to confer antiapoptotic protection of the intestinal mucosa against inflammatory stress-induced damage through TFF3. Recombinant TFF3 rescues TLR2-deficient mice from increased morbidity and mortality during acute colonic injury. Severe ulcerative colitis (UC) has recently been found to be associated with the R753Q polymorphism of the TLR2 gene. The relevance of the observed functional effect of TLR2 in regulating GC is confirmed by the finding that the UC-associated TLR2-R753Q variant is functionally deficient in the ability to induce TFF3 synthesis, thus leading to impaired wound healing.

CONCLUSIONS

These data demonstrate a novel function of TLR2 in intestinal GC that links products of commensal bacteria to innate immune protection of the host via TFF3.

TLR2 mediates gap junctional intercellular communication through connexin-43 in intestinal epithelial barrier injury

Gap junctional intercellular communication (GJIC) coordinates cellular functions essential for sustaining tissue homeostasis; yet its regulation in the intestine is not well understood. Here, we identify a novel physiological link between Toll-like receptor (TLR) 2 and GJIC through modulation of Connexin-43 (Cx43) during acute and chronic inflammatory injury of the intestinal epithelial cell (IEC) barrier. Data from in vitro studies reveal that TLR2 activation modulates Cx43 synthesis and increases GJIC via Cx43 during IEC injury. The ulcerative colitis-associated TLR2-R753Q mutant targets Cx43 for increased proteasomal degradation, impairing TLR2-mediated GJIC during intestinal epithelial wounding. In vivo studies using mucosal RNA interference show that TLR2-mediated mucosal healing depends functionally on intestinal epithelial Cx43 during acute inflammatory stress-induced damage. Mice deficient in TLR2 exhibit IEC-specific alterations in Cx43, whereas administration of a TLR2 agonist protects GJIC by blocking accumulation of Cx43 and its hyperphosphorylation at Ser368 to prevent spontaneous chronic colitis in MDR1alpha-deficient mice. Finally, adding the TLR2 agonist to three-dimensional intestinal mucosa-like cultures of human biopsies preserves intestinal epithelial Cx43 integrity and polarization ex vivo. In conclusion, Cx43 plays an important role in innate immune control of commensal-mediated intestinal epithelial wound repair.

Therapeutic impact of toll-like receptors on inflammatory bowel diseases: a multiple-edged sword

Recent studies have begun to define the mechanisms through which Toll-like receptors (TLRs) regulate intestinal homeostasis in health and disease. Current therapies for inflammatory bowel diseases (IBDs) mostly aim at interrupting the inflammatory cascade through agents that regulate TH1 or TH2 cytokine responses. As recognition grows for TLR dysfunction to play a role in IBD pathogenesis, TLRs could provide another valid interventional target for novel therapy development. However, seemingly contradictory results from studying different murine models of colitis have so far confounded whether therapeutically useful modulation of TLRs is best accomplished by activating, inhibiting, or rather a combination of both at different stages of mucosal disease. This review evaluates potential strategies as well as their rationale and future prospects.

Toll-like receptor 2 controls mucosal inflammation by regulating epithelial barrier function

BACKGROUND & AIMS

Toll-like receptors (TLRs) represent a class of transmembrane pattern recognition receptors essential for microbial recognition and control of innate immune responses. Commensal bacteria play an important role in maintaining tolerance and active stability of the intestinal epithelial barrier by suppressing intestinal inflammation, yet the mechanisms of action are unknown. The aim of this study was to determine the functional relevance of TLR2 to control tight junction (TJ)-associated intestinal epithelial barrier integrity to balance mucosal homeostasis against inflammatory stress-induced damage.

METHODS

TLR2 ligand (synthetic Pam(3)Cys-SK4 [PCSK])-induced activation of signaling cascades and TJ-associated distribution was assessed by using Western blotting and confocal microscopy combined with functional transfection and inhibitor studies in model intestinal epithelial cell (IEC) lines (IEC-6, Caco-2) or primary IEC cultured short-term ex vivo. DSS colitis was induced by standard protocol in wild-type, TLR2-/-, and MyD88-/- mice. Spontaneous apoptosis was assessed by terminal deoxinucleotidyl-transferase-mediated dUTP-biotin nick end-labeling.

RESULTS

Data from in vitro and ex vivo models of intestinal epithelial cells revealed that TLR2 stimulation effectively preserves TJ-associated barrier assembly against stress-induced damage through promotion of PI3K/Akt-mediated cell survival via MyD88. Furthermore, in vivo studies underscored that TLR2-mediated TJ regulation critically determines susceptibility to intestinal injury and inflammation. Inflammatory stress in mice deficient of TLR2 or MyD88 induced early TJ-associated disruption interrelated with anti-apoptotic failure of the intestinal epithelial barrier. Oral treatment of colitis with the TLR2 ligand PCSK significantly suppressed mucosal inflammation and apoptosis by efficiently restoring TJ-associated integrity of the intestinal epithelium in vivo.

CONCLUSION

TLR2 may provide a target to pharmacologically modulate mucosal injury and intestinal inflammation.

Toll-Like Receptor Signaling and its Relevance to Intestinal Inflammation

This review discusses the current progress in the understanding of how commensal-mediated activation of toll-like receptors (TLRs) may be involved in the regulation of physiological and pathophysiological processes of the intestinal mucosa including tissue regeneration and inflammation. While regulation of TLRs and their downstream signaling mediators might be used to prevent and treat inflammatory bowel diseases, paradoxically, at this time, it remains uncertain whether this would be more effectively accomplished by enhancing or inhibiting these pathways.

Trypsin-sensitive modulation of intestinal epithelial MD-2 as mechanism of lipopolysaccharide tolerance

Intestinal epithelial cells (IEC) are constantly exposed to both high concentrations of the bacterial ligand LPS and the serine protease trypsin. MD-2, which contains multiple trypsin cleavage sites, is an essential accessory glycoprotein required for LPS recognition and signaling through TLR4. The aim of this study was to characterize the expression and subcellular distribution of intestinal epithelial MD-2 and to delineate potential functional interactions with trypsin and then alteration in inflammatory bowel disease (IBD). Although MD-2 protein expression was minimal in primary IEC of normal colonic or ileal mucosa, expression was significantly increased in IEC from patients with active IBD colitis, but not in ileal areas from patients with severe Crohn's disease. Endogenous MD-2 was predominantly retained in the calnexin-calreticulin cycle of the endoplasmic reticulum; only a small fraction was exported to the Golgi. MD-2 expression correlated inversely with trypsin activity. Biochemical evidence and in vitro experiments demonstrated that trypsin exposure resulted in extensive proteolysis of endogenous and soluble MD-2 protein, but not of TLR4 in IEC, and was associated with desensitization of IEC to LPS. In conclusion, the present study suggests that endoplasmic reticulum-associated MD-2 expression in IBD may be altered by ileal protease in inflammation, leading to impaired LPS recognition and hyporesponsiveness through MD-2 proteolysis in IEC, thus implying a physiologic mechanism that helps maintain LPS tolerance in the intestine.

Functional and biochemical characterization of epithelial bactericidal/permeability-increasing protein

Epithelial cells of many mucosal organs have adapted to coexist with microbes and microbial products. In general, most studies suggest that epithelial cells benefit from interactions with commensal microorganisms present at the lumenal surface. However, potentially injurious molecules found in this microenvironment also have the capacity to elicit local inflammatory responses and even systemic disease. We have recently demonstrated that epithelia cells express the anti-infective molecule bactericidal/permeability-increasing protein (BPI). Here, we extend these findings to examine molecular mechanisms of intestinal epithelial cell (IEC) BPI expression and function. Initial experiments revealed a variance of BPI mRNA and protein expression among various IEC lines. Studies of BPI promoter expression in IECs identified regulatory regions of the BPI promoter and revealed a prominent role for CCAAT/enhancer binding protein and especially Sp1/Sp3 in the basal regulation of BPI. To assess the functional significance of this protein, we generated an IEC line stably transfected with full-length BPI. We demonstrated that, whereas epithelia express markedly less BPI protein than neutrophils, epithelial BPI contributes significantly to bacterial killing and attenuating bacterial-elicted proinflammatory signals. Additional studies in murine tissue ex vivo revealed that BPI is diffusely expressed along the crypt-villous axis and that epithelial BPI levels decrease along the length of the intestine. Taken together, these data confirm the transcriptional regulation of BPI in intestinal epithelia and provide insight into the relevance of BPI as an anti-infective molecule at intestinal surfaces.

Bacterial interactions with cells of the intestinal mucosa: Toll-like receptors and NOD2

Toll-like receptors (TLR) and NOD2 are emerging as key mediators of innate host defence in the intestinal mucosa, crucially involved in maintaining mucosal as well as commensal homeostasis. Recent observations suggest new (patho-) physiological mechanisms of how functional versus dysfunctional TLRx/NOD2 pathways may oppose or favour inflammatory bowel disease (IBD). In health, TLRx signalling protects the intestinal epithelial barrier and confers commensal tolerance whereas NOD2 signalling exerts antimicrobial activity and prevents pathogenic invasion. In disease, aberrant TLRx and/or NOD2 signalling may stimulate diverse inflammatory responses leading to acute and chronic intestinal inflammation with many different clinical phenotypes.

Intestinal epithelial Tollerance versus inTollerance of commensals

This brief review summarizes the current understanding of Toll-like receptor (TLRs) mediated intestinal epithelial mechanisms of commensal tolerance versus intolerance and provides an update on the downstream negative control of signaling responses through decreased surface expression, interregulation with NOD2, overexpression of Tollip, various inhibitors of NF-kappaB as well as soluble tolerizing mediators present in lumen and serum which all may maintain or--when dysregulated--impair mucosal homeostasis in health or disease, respectively.

Toll-like receptor 2 enhances ZO-1-associated intestinal epithelial barrier integrity via protein kinase C

BACKGROUND & AIMS

Protein kinase C (PKC) has been implicated in regulation of intestinal epithelial integrity in response to lumenal bacteria. Intestinal epithelial cells (IECs) constitutively express Toll-like receptor (TLR)2, which contains multiple potential PKC binding sites. The aim of this study was to determine whether TLR2 may activate PKC in response to specific ligands, thus potentially modulating barrier function in IECs.

METHODS

TLR2 agonist (synthetic bacterial lipopeptide Pam(3)CysSK4, peptidoglycan)-induced activation of PKC-related signaling cascades were assessed by immunoprecipitation, Western blotting, immunofluorescence, and kinase assays-combined with functional transfection studies in the human model IEC lines HT-29 and Caco-2. Transepithelial electrical resistance characterized intestinal epithelial barrier function.

RESULTS

Stimulation with TLR2 ligands led to activation (phosphorylation, enzymatic activity, translocation) of specific PKC isoforms (PKCalpha and PKCdelta). Phosphorylation of PKC by TLR2 ligands was blocked specifically by transfection with a TLR2 deletion mutant. Ligand-induced activation of TLR2 greatly enhanced transepithelial resistance in IECs, which was prevented by pretreatment with PKC-selective antagonists. This effect correlated with apical tightening and sealing of tight junction (TJ)-associated ZO-1, which was mediated via PKC in response to TLR2 ligands, whereas morphologic changes of occludin, claudin-1, or actin cytoskeleton were not evident. Downstream the endogenous PKC substrate myristoylated alanine-rich C kinase substrate (MARCKS), but not transcriptional factor activator protein-1 (AP-1), was activated significantly on stimulation.

CONCLUSIONS

The present study provides evidence that PKC is an essential component of the TLR2 signaling pathway with the physiologic consequence of directly enhancing intestinal epithelial integrity through translocation of ZO-1 on activation.

Mechanisms of cross hyporesponsiveness to Toll-like receptor bacterial ligands in intestinal epithelial cells

BACKGROUND & AIMS

Despite the ability to participate in immune responses and the continuous presence of bacteria and bacterial products, functional responses of intestinal epithelial cells (IEC) seem to be muted. Previously, tolerance to Toll-like receptors (TLRs) ligands has been described in monocytic cells. However, mechanisms in the intestine are unknown.

METHODS

The effect of purified lipopolysaccharide (LPS) and lipoteichoic acid (LTA) on expression and function of TLRs in intestinal epithelial cells (Colo205, SW480, T84) was assessed by Northern and Western blot and FACS analysis, kinase activity assays, immunohistochemistry, and ELISA.

RESULTS

Expression of TLRs except 10 was detected in primary IEC and TLR1-10 in the cultured cells. Short-term stimulation with LPS or LTA activated proinflammatory signaling cascades in IEC, including phosphorylation of IRAK and MAP kinases and increased IL-8 secretion, whereas prolonged incubation resulted in a state of hyporesponsiveness with no reactivation of the cells by a second challenge with either substance detected. The cells remained responsive to tumor necrosis factor (TNF). Hyporesponsive cells showed no alteration in expression of TLR or signaling molecules but revealed a decrease in TLR surface expression and IRAK activity. Toll-interacting protein (Tollip) mRNA and protein expression were increased in hyporesponsive cells, and overexpression of Tollip in IEC resulted in a significantly decreased proinflammatory response.

CONCLUSIONS

Continuous presence of specific bacterial components results in a status of hyporesponsiveness in otherwise reactive IEC. Down-regulation of TLR surface expression and up-regulation of inhibitory Tollip with decreased phosphorylation of IRAK might all contribute to this hyporesponsiveness.

Toll-like receptors and intestinal defence: molecular basis and therapeutic implications

Toll-like receptors (TLRs) play a principle role in distinct pathogen recognition and in the initiation of innate immune responses of the intestinal mucosa. Activated innate immunity interconnects downstream with adaptive immunity in complex feedback regulatory loops. Intestinal disease might result from inappropriate activation of the mucosal immune system driven by TLRs in response to normal luminal flora.

"For whom the bell tolls!" -- innate defense mechanisms and survival strategies of the intestinal epithelium against lumenal pathogens

The intestinal epithelium serves as an essential defensive barrier of the mucosal immune system that forms a bipolar interface between the diverse populations of microbes of the lumen and subjacent immune cells present in the lamina propria. Intestinal epithelial cells express various pattern recognition receptors -- poised to recognize microbial "pathogen-associated molecular patterns" as "non-self" and to rapidly initiate innate immune responses of survival and active defense strategies against lumenal pathogens. Current understanding of the variety of innate immune features present in intestinal epithelium to maintain homeostasis is summarized and the mechanisms through which dysregulation may play a central role in initiation and perpetuation of inflammatory bowel disease are discussed.

Toll-like receptors and gastrointestinal diseases: from bench to bedside?

The family of Toll-like receptors (TLRs) plays a key role in mediating innate immune responses to numerous luminal commensal- and pathogen-derived pattern molecules by the intestinal mucosa. Recent findings have identified several ligands recognized by TLRs as well as the complex downstream signaling effects resulting from activation of these receptors. Understanding is emerging of the importance of TLRs in mucosal host defense-potentially triggering gastrointestinal diseases.

Commensal-associated molecular patterns induce selective toll-like receptor-trafficking from apical membrane to cytoplasmic compartments in polarized intestinal epithelium

Commensal-associated molecular patterns, the major products of nonpathogenic bacteria, are present at high concentrations at the apical surface of the intestinal epithelium. However, the nature of the interaction of commensal-associated molecular patterns with the lumenal surface of the epithelium has not been defined. We have recently demonstrated that intestinal epithelial cells constitutively express several Toll-like receptors (TLRs) in vitro and in vivo that seem to be the key receptors responsible for immune cell activation in response to various bacterial products. In this study we characterize the subcellular distribution of two major TLRs, TLR2 and TLR4, and their ligand-specific dynamic regulation in the model human intestinal epithelial cell line T84. Immunocytochemical studies indicate that TLR2 and TLR4 are constitutively expressed at the apical pole of differentiated T84 cells. After stimulation with lipopolysaccharide or peptidoglycan, TLRs selectively traffic to cytoplasmic compartments near the basolateral membrane. Thus, we demonstrate that TLRs are positioned at the apical pole where they are poised to monitor the sensitive balance of the lumenal microbial array. The results of this dynamic epithelial surveillance can then be conveyed to the underlying cell populations of the lamina propria via these innate immune pattern recognition receptors.

Role of tumor necrosis factor receptor 2 (TNFR2) in colonic epithelial hyperplasia and chronic intestinal inflammation in mice

BACKGROUND & AIMS

Tumor necrosis factor (TNF) induces multiple effects including cell proliferation and death by ligation with TNF receptor type II (TNFR2). We studied the role of TNFR2 in chronic inflammation-induced colonic epithelial alteration.

METHODS

TNFR2 expression in colonic epithelial cells (CECs) was assessed by ribonuclease protection assay (RPA) and immunohistochemistry (IHC) in patients with inflammatory bowel disease (IBD) and murine colitis models. TNFR2 expression was also analyzed using COLO205 cells. The role of TNFR2 in colonic epithelial homeostasis was examined by generating interleukin 6-deficient TCR alpha KO (alpha IL-6DKO) or TNFR2-deficient TCR alpha (alpha TNFR2DKO) mice.

RESULTS

TNFR2 expression was up-regulated in CEC in both human ulcerative colitis and Crohn's disease. In vitro studies showed that TNFR2 expression was up-regulated by a cooperative effect of key proinflammatory cytokines. By RPA, the increased expression of TNFR2 was detectable in TCR alpha KO mice with colitis compared with TCR alpha KO mice without colitis or wild-type mice. In alpha IL-6DKO mice, TNFR2 expression, proliferation, and nuclear factor kappa B activation of CECs were markedly reduced compared with TCR alpha KO mice. alpha TNFR2 mice also showed significantly less colonic epithelial proliferation compared with TCR alpha KO mice.

CONCLUSIONS

Expression of TNFR2 is consistently increased on CECs in both murine colitis models as well as patients with IBD. TNFR2 may play an important role in colonic inflammation-associated alteration in the intestinal epithelium.

Differential alteration in intestinal epithelial cell expression of toll-like receptor 3 (TLR3) and TLR4 in inflammatory bowel disease

Initiation and perpetuation of the inflammatory intestinal responses in inflammatory bowel disease (IBD) may result from an exaggerated host defense reaction of the intestinal epithelium to endogenous lumenal bacterial flora. Intestinal epithelial cell lines constitutively express several functional Toll-like receptors (TLRs) which appear to be key regulators of the innate response system. The aim of this study was to characterize the expression pattern of TLR2, TLR3, TLR4, and TLR5 in primary intestinal epithelial cells from patients with IBD. Small intestinal and colonic biopsy specimens were collected from patients with IBD (Crohn's disease [CD], ulcerative colitis [UC]) and controls. Non-IBD specimens were assessed by immunofluorescence histochemistry using polyclonal antibodies specific for TLR2, TLR3, TLR4, and TLR5. Primary intestinal epithelial cells (IEC) of normal mucosa constitutively expressed TLR3 and TLR5, while TLR2 and TLR4 were only barely detectable. In active IBD, the expression of TLR3 and TLR4 was differentially modulated in the intestinal epithelium. TLR3 was significantly downregulated in IEC in active CD but not in UC. In contrast, TLR4 was strongly upregulated in both UC and CD. TLR2 and TLR5 expression remained unchanged in IBD. These data suggest that IBD may be associated with distinctive changes in selective TLR expression in the intestinal epithelium, implying that alterations in the innate response system may contribute to the pathogenesis of these disorders.

Effects of exogenous zinc supplementation on intestinal epithelial repair in vitro

BACKGROUND

Substitution of zinc modulates antioxidant capabilities within the intestinal mucosa and improves intestinal wound healing in zinc-deficient patients with inflammatory bowel diseases. The aim of this study was to characterize the modulating effects of zinc on intestinal epithelial cell function in vitro.

MATERIALS AND METHODS

The effects of zinc on intestinal epithelial cell morphology were assessed by phase contrast and transmission electron microscopy using the non-transformed small intestinal epithelial cell line IEC-6. Zinc-induced apoptosis was assessed by DNA fragmentation analysis, lactate dehydrogluase (LDH) release and flow cytometry with propidium iodine staining. Furthermore, the effects of zinc on IEC-6 cell proliferation were assessed using a colorimetric thiazolyl blue (MTT) assay and on IEC-6 cell restitution using an in vitro wounding model.

RESULTS

Physiological concentrations of zinc (25 microM) did not significantly alter the morphological appearance of IEC-6 cells. However, a 10-fold higher dose of zinc (250 microM) induced epithelial cell rounding, loss of adherence and apoptotic characteristics. While physiological zinc concentrations (< 100 microM) did not induce apoptosis, supraphysiological zinc concentrations (> 100 microM) caused apoptosis. Physiological concentrations of zinc (6.25-50 microM) had no significant effect on intestinal epithelial cell proliferation. In contrast, physiological concentrations of zinc (12.5-50 microM) significantly enhanced epithelial cell restitution through a transforming growth factor-beta (TGFbeta)-independent mechanism. Simultaneous addition of TGFbeta and zinc resulted in an additive stimulation of IEC-6 cell restitution.

CONCLUSION

Zinc may promote intestinal epithelial wound healing by enhancement of epithelial cell restitution, the initial step of epithelial wound healing. Zinc supplementation may improve epithelial repair; however, excessive amounts of zinc may cause tissue injury and impair epithelial wound healing.

Transforming growth factor-beta and hepatocyte growth factor plasma levels in patients with inflammatory bowel disease

OBJECTIVE

An increased mucosal expression of transforming growth factor-beta (TGF-beta) and hepatocyte growth factor (HGF) has been reported in patients with active inflammatory bowel diseases (IBD) and in proximity to injured gastric and intestinal mucosal surfaces. The aim of this study was to measure systemic concentrations of TGF-beta and HGF and to assess their potential value to predict disease activity or severity of inflammation in patients with inflammatory bowel diseases.

DESIGN AND METHODS

Plasma HGF and TGF-beta1 peptide levels were determined in 29 patients with ulcerative colitis, 45 patients with Crohn's disease and 28 healthy controls using commercial ELISA assays. Peptide levels were correlated with disease activity indices and various laboratory parameters.

RESULTS

HGF and TGF-beta1 plasma levels were detected in all control and IBD subjects. Although a tendency towards increased HGF and TGF-beta1 peptide levels in IBD patients was observed, differences between groups were not significant In ulcerative colitis patients HGF plasma levels positively correlated with white blood cell counts and negatively correlated with serum albumin concentrations and haematocrit. In Crohn's disease patients, a positive correlation between TGF-beta and platelet count was observed.

CONCLUSIONS

HGF and TGF-beta1 plasma concentrations are not significantly different in IBD and healthy control subjects. Stratification of IBD patients according to disease activity did not reveal any substantial differences, suggesting that HGF and TGF-beta plasma levels have no value in the assessment of disease activity or severity of inflammation in patients with IBD.

Lipopolysaccharide activates distinct signaling pathways in intestinal epithelial cell lines expressing Toll-like receptors

LPS elicits several immediate proinflammatoy responses in peripheral blood leukocytes via a recently described pathway including CD14, Toll-like receptors (TLR), serine-threonine kinases, and NF-kappaB transcription factor. However, the functional responses of intestinal epithelial cells (IEC) to stimulation with LPS are unknown. Expression of mRNA and protein for CD14 and TLRs were assessed by RT-PCR, immunoblotting, and immunohistochemistry in mouse and human IEC lines. LPS-induced activation of signaling pathways (p42/p44 mitogen-activated protein kinase (MAPK), c-Jun NH2-terminal kinase (JNK), p38, p65, NF-kappaB) were assessed by immunoblotting and gel shifts. CD14 mRNA and protein expression were not detectable in IEC. However, human TLR2, TLR3, and TLR4 mRNA were present in IEC. TLR4 protein was expressed in all cell lines; however, TLR2 protein was absent in HT29 cells. Immunofluorescent staining of T84 cells demonstrated the cell-surface presence of the TLRs. LPS-stimulation of IEC resulted in activation (>1.5-fold) of the three members of the MAPK family. In contrast, LPS did not significantly induce activation of JNK and p38 in CMT93 cells, p38 in T84 cells and MAPK and JNK in HT29 cells. Downstream, LPS activated NF-kappaB in IEC in a time-, dose-, and serum-dependent manner. IEC express TLRs that appear to mediate LPS stimulation of specific intracellular signal transduction pathways in IEC. Thus, IEC may play a frontline role in monitoring lumenal bacteria.

Peripheral blood mononuclear cells promote intestinal epithelial restitution in vitro through an interleukin-2/interferon-gamma-dependent pathway

BACKGROUND

Acute intestinal mucosal inflammation is associated with recruitment of peripheral blood mononuclear cells (PBMN) into the mucosa and migration across the epithelium. It has recently been shown that several PBMN-derived cytokines, including transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) may modify intestinal epithelial cell function, resulting in rapid improvement of wound repair. Our aim was to characterize the modulating effects of PBMN on intestinal epithelial restitution, the initial step of wound healing.

METHODS

PBMN were separated from whole blood, obtained from healthy volunteers, by using a density gradient. The effect of PBMN on intestinal epithelial restitution was assessed by using an in vitro coculture wounding model with non-transformed small-intestinal epithelial IEC-6 cells.

RESULTS

Coculture of PBMN caused a significant enhancement of epithelial cell restitution in vitro. The modulatory effects of PBMN could be significantly blocked by adding immunoneutralizing anti-IL-2 or anti-IFN-gamma to the culture media, suggesting that PBMN may modulate intestinal epithelial migration through an IL-2- and IFN-gamma-dependent pathway. In contrast, PBMN-induced stimulation of intestinal epithelial restitution was not influenced by addition of anti-TGF-beta or anti-TNF-alpha, suggesting that these cytokines are not critical for the modulation of restitution by PBMN.

CONCLUSIONS

These findings suggest that PBMN may promote intestinal epithelial wound repair by enhancing restitution through secretion of various cytokines, among them IL-2 and IFN-gamma, which are abundantly expressed in the course of several inflammatory diseases of the gut.

Factor XIII modulates intestinal epithelial wound healing in vitro

BACKGROUND

An acquired deficiency of blood coagulation factor XIII has been proposed to cause an impairment of intestinal wound healing and hemostasis in patients with inflammatory bowel diseases. Substitution of factor XIII seems to result in a rapid improvement of intestinal wound healing. Our aim was therefore to characterize the role of factor XIII in the modulation of intestinal wound healing in vitro.

METHODS

Factor XIII was added to subconfluent cultures of two non-transformed small-intestinal epithelial cell lines (IEC-6, IEC-18) and three human colon cancer-derived epithelial cell lines (T84, CaCo-2, HT-29) with subsequent assessment of cell proliferation with a colorimetric 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenylformazan (MTT) assay. The effects on epithelial cell migration in vitro were assessed with an in vitro wounding model of confluent IEC-6 cell monolayers.

RESULTS

Factor XIII caused a modest inhibition of proliferation of IEC-6 and IEC-18 cells. However, factor XIII significantly stimulated proliferation of T84, CaCo-2. and HT-29 cell lines. In addition, thrombin-activated factor Xill promoted intestinal epithelial cell restitution in vitro on average 2.5-fold. The modulatory effects of factor XIII could not be significantly blocked by anti-transforming growth factor beta (TGFbeta).

CONCLUSIONS

Factor XIII may promote intestinal epithelial wound healing by enhancement of epithelial cell restitution through a TGFbeta-independent pathway. This may explain previously described beneficial effects of factor XIII in the treatment of active ulcerative colitis.

Diagnostic dilemma in pancreatic lymphoma. Case report and review

Non-Hodgkin's lymphoma predominantly involving the pancreas is a rare tumor of the gastrointestinal tract. Diagnosis can be difficult, since lymphoma may mimic carcinoma or pancreatitis. Lymphoproliferative diseases induced by immunosuppressive therapy frequently occur in the gastrointestinal tract of posttransplant patients. However, pancreatic involvement of posttransplant lymphoma is an exceptional condition. We present the case of a cyclosporin-treated renal transplant recipient with pancreatic lymphoma mimicking carcinomatous or inflammatory tumors. The diagnostic difficulties and treatment options of pancreatic lymphoma as well as lymphoproliferative disorders in immunosuppressed renal recipients are discussed in light of the current literature.

[Trimethoprim-sulfamethoxazole-induced cholestatic hepatitis. Clinico-immunological demonstration of its allergic origin]

HISTORY AND CLINICAL FINDINGS

A 22-year-old woman was given trimethoprim plus sulphamethoxazole for a urinary infection (160 and 800 mg, respectively, daily), drugs she had not previously taken. After 2 weeks she noticed a rash of small spots on her trunk. In addition she had nausea and vomiting. The rash faded within 2 days of stopping the drug, but progressive jaundice developed.

INVESTIGATIONS

SGPT and SGOT concentrations rose to maximally 328 and 83 U/l, total bilirubin to maximally 5.9 mg/dl. There was no evidence for viral hepatitis (B or C, cytomegalovirus, Epstein-Barr), autoimmune hepatitis or primary biliary hepatitis. Liver biopsy showed central acinar cholestasis, which suggested drug-induced liver damage.

COURSE

The patient's symptoms regressed over several weeks without any specific treatment and 8 weeks after onset of the rash the laboratory tests also became normal. The allergic cause of the cholestatic hepatitis was confirmed by a lymphocyte transformation test.

CONCLUSION

Clinical suspicion of drug allergy as cause of a cholestatic hepatitis can be confirmed reliably and without any risk to the patient with the lymphocyte transformation test.