Apoptosis of human intestinal epithelial cells after bacterial invasion.

Epithelial cells that line the human intestinal mucosa are the initial site of host invasion by bacterial pathogens. The studies herein define apoptosis as a new category of intestinal epithelial cell response to bacterial infection. Human colon epithelial cells are shown to undergo apoptosis following infection with invasive enteric pathogens, such as Salmonella or enteroinvasive Escherichia coli. In contrast to the rapid onset of apoptosis seen after bacterial infection of mouse monocyte-macrophage cell lines, the commitment of human intestinal epithelial cell lines to undergo apoptosis is delayed for at least 6 h after bacterial infection, requires bacterial entry and replication, and the ensuing phenotypic expression of apoptosis is delayed for 12-18 h after bacterial entry. TNF-alpha and nitric oxide, which are produced as components of the intestinal epithelial cell proinflammatory program in the early period after bacterial invasion, play an important role in the later induction and regulation of the epithelial cell apoptotic program. Apoptosis in response to bacterial infection may function to delete infected and damaged epithelial cells and restore epithelial cell growth regulation and epithelial integrity that are altered during the course of enteric infection. The delay in onset of epithelial cell apoptosis after bacterial infection may be important both to the host and the invading pathogen since it provides sufficient time for epithelial cells to generate signals important for the activation of mucosal inflammation and concurrently allows invading bacteria time to adapt to the intracellular environment before invading deeper mucosal layers.

[Sweet syndrome and erythema nodosum in ulcerative colitis, refractory to steroids: successful treatment with tacrolimus]. / Sweet-Syndrom und Erythema nodosum bei steroidrefraktärer Colitis ulcerosa. Erfolgreiche Behandlung mit Tacrolimus.

BACKGROUND: Inflammatory bowel disease is accompanied by cutaneous manifestations in about 10% of cases. Erythema nodosum and pyoderma gangraenosum are most frequently observed, which often subside on treatment of the underlying disease. CASE REPORT: A 30-year-old male with a history of long-standing ulcerative colitis experienced an acute attack despite treatment with azathioprine. Further he noticed dull red, elevated and tender maculae on the forelegs. A disseminated and papulosquamous exanthema arose on the back of the trunk and the upper extremities without pruritus. Well-being was compromised and blood sampling revealed an inflammatory response. High-dose steroids with antibiotics were without benefit until they were combined with tacrolimus, an immunosuppressive agent acting similar to ciclosporin. Remission occurred rapidly and the skin lesions resolved. Six months later the patient is currently still in remission and developed no signs of recurrent exanthema. CONCLUSION: The cutaneous lesions are thought to be related to ulcerative colitis and were classified as erythema nodosum and Sweet syndrome. This is the first report on the successful use of tacrolimus in steroid-refractory ulcerative colitis with extraintestinal cutaneous involvement.

Enhanced human beta-defensin-2 (hBD-2) expression by corticosteroids is independent of NF-kappaB in colonic epithelial cells (CaCo2).

Beta-defensins are small cationic peptides with antimicrobial properties that contribute to innate host defense. Unlike human beta-defensin-1 (hBD-1), which is produced constitutively, human beta-defensin-2 (hBD-2) is expressed after adequate stimulation by cytokines and/or bacterial endotoxins in epithelial tissue and mononuclear phagocytes but may be deficient in patients with Crohn's disease. To further elucidate the role of the intestinal epithelium in antimicrobial host defense, gene regulation of hBD-2 and the interaction with NF-kappaB were analyzed in a cell culture model. Human colonic epithelial cells (CaCo2) were stimulated by pro-inflammatory cytokines (IL-1beta, TNF-alpha, IF-gamma) to induce hBD-2 mRNA transcription. Interactions with NF-kappaB were analyzed using specific inhibitors (sulfasalazine, gliotoxine, dexamethasone) at different concentrations. Defensin mRNA expression was quantified by competitive RT-PCR and antibacterial capacity of supernatants was determined by an antimicrobial assay. HBD-2 mRNA transcription and antimicrobial activity of CaCo2 cells were induced by stimulation with pro-inflammatory cytokines. Induction was not inhibited by sulfasalazine or gliotoxine, whereas dexamethasone further enhanced both gene transcription and antimicrobial capacity. The lack of inhibition of induced hBD-2 expression by specific NF-kappaB antagonists suggests an additional pathway of activation, independent of NF-kappaB. The induction of hBD-2 expression in cytokine-stimulated CaCo2 cells by corticosteroids indicates further immunomodulatory ability of steroid hormones not yet understood.

[Massive pulmonary embolism after endoscopic therapy for gastric variceal bleeding]. / Massive Lungenembolie nach endoskopischer Therapie einer Fundusvarizenblutung.

A 60-year-old woman with alcoholic cirrhosis of the liver was admitted to the ICU because of haemodynamic instability, hematemesis and presumed acute variceal bleeding. An upper endoscopy was performed and varices of the distal esophagus and an actively bleeding varix of the gastric fundus were detected. The bleeding was successfully treated with 2 consecutive injections of 0.5 ml n-butyl-2-cyanoacrylate and 0.5 ml lipiodol. The patient was intubated prior to the endoscopy to avoid blood aspiration. However, severe hypoxaemia with a need for prolonged mechanical ventilation and signs of right heart strain developed after endoscopy. A chest X-ray and CT scan of the thorax documented an extensive embolisation of the pulmonary arteries. The patient's varices were retreated with band ligation but rebleeding occurred. Finally, a TIPS application was needed to stop recurrent haemorrhage. This case demonstrates that embolisation of the pulmonary arterial bed is a rare complication of endoscopic sclerotherapy for gastric variceal bleeding. The severity of this complication may depend on the volume of liquid acrylate being injected and pre-existing lung tissue alterations. Since histoacryl is not lysable, severe pulmonary emboli with lung tissue damage and pulmonary hypertension may occur. Factors contributing to this complication are analysed and therapeutic alternatives are discussed.

The TCR-delta repertoire in human intestine undergoes characteristic changes during fetal to adult development.

The TCR-delta repertoire in adult human intestine is oligoclonal and unique in each individual. In the present study, changes in the junctional regions of TCR-delta transcripts in human intestine that occur during development from fetal to adult life were used to characterize fundamental changes in the TCR-delta repertoire in the human intestinal tract during ontogeny. At mid-gestation, the fetal repertoire was polyclonal, but limited, in its junctional diversity by the relative lack of N region nucleotide additions and by the frequent formation of coding region joins at regions of short sequence homology. In addition, identical TCRDV2 transcripts that resemble canonical TCR-delta sequences in mice were present in the intestine of different fetuses. In the early period after birth, the intestinal TCR-delta repertoire was polyclonal, and more diverse than the fetal repertoire, with junctional regions that contained extensive N nucleotide additions and frequently were as complex as those of adults. The intestinal TCR-delta repertoire showed increasing restriction with age and, by 14 to 17 yr, the repertoire was oligoclonal and resembled the repertoire of individuals in the sixth to seventh decade. Moreover, the adult TCR-delta repertoire was almost identical at multiple sites throughout the intestine, suggesting a model in which gammadelta T cell clones, selected by ligands in the intestinal tract, undergo expansion and recirculation before lodging throughout the small intestine or colon.

Enteroinvasive bacteria directly activate expression of iNOS and NO production in human colon epithelial cells.

In these studies, we investigated whether bacterial infection of human colon epithelial cells is a sufficient stimulus to upregulate epithelial cell expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production. Human colon epithelial cells (Caco-2 and HT-29) rapidly upregulated iNOS mRNA and protein expression and NO production after infection with enteroinvasive Escherichia coli, Salmonella dublin, or Shigella flexneri but not after infection with noninvasive E. coli or an invasion-deficient mutant of S. dublin. Bacterial infection in the absence of added cytokines was as potent or more potent a stimulus of iNOS expression and NO production as stimulation of cells with combinations of cytokines known to strongly upregulate this epithelial cell response. Enteroinvasive E. coli increased epithelial NO production to a greater extent than S. dublin, although S. dublin was a stronger stimulus of epithelial cell interleukin-8 (IL-8) production. After enteroinvasive E. coli infection of polarized epithelial cell monolayers, nitrite, a stable NO end product, was released predominately into the apical compartment early after infection, whereas IL-8 was released in parallel into the basolateral compartment. These studies suggest NO and/or its redox products are an important component of the intestinal epithelial cell response to microbial infection.