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.

Hepatitis C virus replication is directly inhibited by IFN-alpha in a full-length binary expression system

Hepatitis C virus (HCV) is a leading cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The absence of culture systems permissive for HCV replication has presented a major bottleneck to antiviral development. We sought to recapitulate the early steps in the life cycle of HCV by means of DNA-based expression of viral genomic sequences. Here we report expression of replicating HCV RNA by using a, to our knowledge, novel binary expression system in which cells were transfected with a T7 polymerase-driven full-length HCV cDNA plasmid containing a cis-acting hepatitis Delta ribozyme to control 3' cleavage, and infected with vaccinia-T7 polymerase. HCV genomic and replicative strand synthesis, in addition to protein synthesis, was detectable and depended on full-length HCV sequences. Moreover, the system was capable of generating HCV RNA quasispecies, consistent with the action of the low-fidelity HCV NS5B RNA polymerase. IFN-alpha, but not ribavirin, directly inhibited the viral replicative cycle in these cells, identifying the virus itself and not solely the immune system as a direct target of IFN action. The availability of a cell-based test for viral replication will facilitate screening of inhibitory compounds, analysis of IFN-resistance mechanisms, and analysis of virus-host cell interactions.

TBX1 is responsible for cardiovascular defects in velo-cardio-facial/DiGeorge syndrome

Velo-cardio-facial syndrome (VCFS)/DiGeorge syndrome (DGS) is a human disorder characterized by a number of phenotypic features including cardiovascular defects. Most VCFS/DGS patients are hemizygous for a 1.5-3.0 Mb region of 22q11. To investigate the etiology of this disorder, we used a cre-loxP strategy to generate mice that are hemizygous for a 1.5 Mb deletion corresponding to that on 22q11. These mice exhibit significant perinatal lethality and have conotruncal and parathyroid defects. The conotruncal defects can be partially rescued by a human BAC containing the TBX1 gene. Mice heterozygous for a null mutation in Tbx1 develop conotruncal defects. These results together with the expression patterns of Tbx1 suggest a major role for this gene in the molecular etiology of VCFS/DGS.

Microbiology. How to get along--friendly microbes in a hostile world

Microbiologists have long been puzzled by the finding that the gut mucosa does not respond to the myriad varieties of bacteria that normally reside in the gut. As Xavier and Podolsky explain in their Perspective, this may be because bacteria that are indigenous to the gut have learned ways to switch off pathways in gut epithelial cells that lead to switching on of genes involved in inflammation (Neish et al.).

SEK1/MKK4 is required for maintenance of a normal peripheral lymphoid compartment but not for lymphocyte development

SAPK is a member of the group of evolutionary conserved stress-activated kinases that mediate control of cellular death and proliferation. In lymphocytes, the SAPK pathway has been implicated in signaling from antigen, costimulatory, and death receptors; SEK1, which directly activates SAPK, is required for early embryonic development and has also been reported to be essential for normal lymphocyte development. In contrast to the latter findings, we have used RAG-2-deficient blastocyst complementation to show that SEK1-deficient embryonic stem cells support unimpaired T and B lymphocyte development. Moreover, mature SEK1-deficient lymphocytes are capable of SAPK activation. Surprisingly, however, aging SEK1-deficient chimeric mice frequently develop lymphadenopathy and polyclonal B and T cell expansions. Thus, SEK1 is not required for lymphocyte development, but is required for maintaining peripheral lymphoid homeostasis.

Atheroembolic renal failure after invasive procedures. Natural history based on 52 histologically proven cases

Atheromatous plaque material containing cholesterol crystals may dislodge and cause distal ischemia. To characterize atheroembolic renal failure, we retrospectively evaluated all patients at the Massachusetts General Hospital from 1981 to 1990 with both renal failure and histologically proven atheroembolism after angiography or cardiovascular surgery. Over the 10-year period, 52 patients were identified. They tended to be elderly men with a history of hypertension (81%), coronary artery disease (73%), peripheral vascular disease (69%), and current smoking (50%). Within 30 days of their procedure, only 50% of patients had cutaneous signs of atheroembolism, and 14% had documented blood eosinophilia. Urinalysis was often abnormal. Hemodynamically unstable patients died shortly after their procedure, yet renal function in the remainder continued to decline over 3 to 8 weeks. Patients who received dialysis had a higher baseline serum creatinine than those who did not (168 +/- 44 mumol/L versus 133 +/- 18 mumol/L, p = 0.02), with dialysis starting a median of 29 days after the procedure. Patients with renal failure due to atheroembolism alone, as opposed to multiple renal insults, were more likely to recover renal function (24% versus 3%, p = 0.03) and had a lower risk of death during the 6 months after their procedure (log-rank p = 0.002). Renal failure due to procedure-induced AE is characterized by a decline in renal function over 3 to 8 weeks. This time course is not consistent with most other iatrogenic causes of renal failure, such as radiocontrast or nephrotoxic medications, which present earlier and often resolve within 2 to 3 weeks after appropriate intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme replacement therapy for Gaucher disease: skeletal responses to macrophage-targeted glucocerebrosidase

OBJECTIVES

Reversal of the hematologic and visceral abnormalities characteristic of Gaucher disease, the most common lipid storage disorder, with biweekly infusions of macrophage-targeted glucocerebrosidase (glucosylceramidase) is well documented. The extent to which the skeleton responds to enzyme replacement therapy has not been systematically investigated.

METHODS

To assess the skeletal response to enzyme replacement therapy, we treated 12 patients with type 1 Gaucher disease, who had intact spleens, with macrophage-targeted glucocerebrosidase. The initial dose of enzyme was 60 U/kg body weight every 2 weeks for 24 months, followed by reduction in dosage to 30 and then 15 U/kg body weight every 2 weeks, each for 9 months.

RESULTS

The lipid composition of bone marrow, determined by direct chemical analysis, began to improve after 6 months of treatment at a time when noninvasive imaging studies showed no significant changes. By 42 months, improvement in marrow composition was demonstrable on all noninvasive, quantitative imaging modalities (magnetic resonance score, quantitative xenon scintigraphy, and quantitative chemical shift imaging) used in this study. Quantitative chemical shift imaging, the most sensitive technique, demonstrated a dramatic normalization of the marrow fat content in all patients. Net increases in either cortical or trabecular bone mass, as assessed by combined cortical thickness measurements and dual-energy quantitative computed tomography, respectively, occurred in 10 patients.

CONCLUSIONS

Prolonged treatment over 3 1/2 years with macrophage-targeted glucocerebrosidase produces objective reversal of disease in both the axial and appendicular skeleton in patients with Gaucher disease. Marked improvement occurs in marrow composition and bone mass in both children and adults.

Peroxynitrite-induced rat colitis--a new model of colonic inflammation

BACKGROUND

Excessive production of nitric oxide, characteristic of inflamed states, may have deleterious effects through its facile conversion (in the presence of O2) to peroxynitrite, which promotes lipid and sulfhydryl oxidation. This study assessed the effect of peroxynitrite on the rat colon.

METHODS

Peroxynitrite was administered intrarectally to rats. One, 3, 7, and 21 days after treatment, a distal colonic segment was isolated and tissue was obtained for histological evaluation and determination of myeloperoxidase activity and NOX, and eicosanoids generation.

RESULTS

Within 24 hours, the exposed segment was edematous and congested with occasional hemorrhagic mucosal ulceration. On day 7, the lumen was narrow; at day 21, there were signs of stenosis. Histological analysis showed transmucosal necrosis, acute inflammation, and exudative edema 24 hours after treatment. Surface re-epithelization and infiltration of granulation tissue were present at 1 week. Resolution of edema, mucin repletion, thickening of muscularis mucosa and propria, and fibrosis were observed at 3 weeks. Significant increase in NOX generation and myeloperoxidase and NO synthase activities were observed at 24 hours, whereas enhanced leukotriene generation was observed only at 21 days.

CONCLUSIONS

Peroxynitrite-induced colonic inflammation provides a novel model of NO-related tissue injury and offers the opportunity to further explore the potential role of NO in the pathogenesis of inflammatory bowel disease.

Value of the history and stool occult blood test in selection of patients for upper endoscopy in Zimbabwe

Patients with abdominal pain and no definite diagnosis referred for endoscopy were studied to define discriminating features in the history, and the value of a stool occult blood test, in predicting the presence of upper gastrointestinal disease. Endoscopy was performed in 116 patients; pathology was seen in 32 (duodenal ulcer 17, gastric carcinoma 4, gastric ulcer 3, miscellaneous 8) and no pathology was seen in 84 patients. Features that predicted upper gastrointestinal pathology were, in descending order of rank: a positive pointing sign, a positive stool Fecult test, a history of vomiting, loss of weight, and alcohol intake. Using these discriminating features together it was possible to correctly predict 95% of patients with abnormal endoscopy and 82% of patients with a normal endoscopy. The history and the stool occult blood test are useful predictors of the presence of upper gastrointestinal pathology and may aid rational selection of patients for endoscopy.