The thioredoxin system of Helicobacter pylori

This paper describes the purification of thioredoxin reductase (TR) and the characterization, purification, and cloning of thioredoxin (Trx) from Helicobacter pylori. Purification, amino acid sequence analysis, and molecular cloning of the gene encoding thioredoxin revealed that it is a 12-kDa protein which possesses the conserved redox active motif CGPC. The gene encoding Trx was amplified by polymerase chain reaction and inserted into a pET expression vector and used to transform Escherichia coli. Trx was overexpressed by induction with isopropyl-1-thio-beta-D-galactopyranoside as a decahistidine fusion protein and was recovered from the cytoplasm as a soluble and active protein. The redox activity of this protein was characterized using several mammalian proteins of different architecture but all containing disulfide bonds. H. pylori thioredoxin efficiently reduced insulin, human immunoglobulins (IgG/IgA/sIgA), and soluble mucin. Subcellular fractionation analysis of H. pylori revealed that thioredoxin was associated largely with the cytoplasm and inner membrane fractions of the cell in addition to being recovered in the phosphate-buffered saline-soluble fraction of freshly harvested cells. H. pylori TR was purified to homogeneity by chromatography on DEAE-52, Cibacron blue 3GA, and 2',5'-ADP-agarose. Gel filtration revealed that the native TR had a molecular mass of 70 kDa which represented a homodimer composed of two 35-kDa subunits, as determined by SDS-polyacrylamide gel electrophoresis. H. pylori TR (NADPH-dependent) efficiently catalyzed the reduction of 5,5'-dithiobis(nitrobenzoic acid) in the presence of either native or recombinant H. pylori Trx. H. pylori Trx behaved also as a stress response element as broth grown bacteria secreted Trx in response to chemical, biological, and environmental stresses. These observations suggest that Trx may conceivably assist H. pylori in the process of colonization by inducing focal disruption of the oligomeric structure of mucin while rendering host antibody inactive through catalytic reduction.

High multidrug resistance (P-glycoprotein 170) expression in inflammatory bowel disease patients who fail medical therapy

BACKGROUND & AIMS

The multidrug resistance (MDR) gene codes for a drug efflux pump P-glycoprotein 170 (Pgp-170) expressed on the surface of lymphocytes and intestinal epithelial cells. Inflammatory bowel disease (IBD) poorly responsive to medical therapy may relate to MDR expression because glucocorticoids are known Pgp-170 substrates.

METHODS

Using flow cytometry, we measured peripheral blood lymphocyte (PBL) MDR in 153 IBD patients and 50 healthy volunteers, and assessed the relationship between PBL, mucosal intraepithelial lymphocyte (IEL), and mucosal epithelial cell (EC) MDR expression in a further 20 IBD patients and 19 controls.

RESULTS

Compared with controls, PBL MDR was significantly elevated in patients with Crohn's disease who required bowel resection for failed medical therapy (mean +/- SEM, 26.7 +/- 2.8 vs. 11.9 +/- 1.0; P <0.0001) and patients with ulcerative colitis who required proctocolectomy for failed medical therapy (20.3 +/- 2.5 vs. 11.9 +/- 1.0; P = 0.001). PBL MDR remained stable over time and was not influenced by disease activity or glucocorticoid therapy. Both PBL and mucosal MDR expression appeared independent of disease activity, and there was a significant correlation between PBL MDR expression and both IEL expression (r = 0.92; P < 0.0001) and EC expression (r = 0.54; P < 0.001).

CONCLUSIONS

PBL and mucosal MDR expression may play an important role in determining the response of IBD patients to glucocorticoid therapy.

Health outcomes as an organisation-wide quality initiative

Since the burgeoning of the 'health outcomes' movement there has been an ever-increasing body of literature on health outcomes policy debates, directions, frameworks and tools for implementing health outcome-directed initiatives. There is a significant gap in the literature, however, in regard to translating a comprehensive health outcomes policy into practice at a local level. This paper addresses that gap. It describes the local implementation of a comprehensive health outcomes approach which works across the continuum of care. It identifies those organisation-wide structures and processes that support successful progress, thereby providing a useful guide to other organisations wishing to institutionalise the health outcomes approach.

Systemic levels of free 5-aminosalicylic acid depend on the nature of the 5-aminosalicyclic acid derivative and not on disease activity or extent in patients with inflammatory bowel disease

INTRODUCTION

Several new derivatives of sulphasalazine that make use of its active moiety, 5-aminosalicylic acid (5-ASA), have been introduced for the treatment of inflammatory bowel disease (IBD). In rats short term intravenous administration of 5-ASA has been associated with nephrotoxicity. A number of cases of nephrotoxicity have been reported recently in IBD patients taking oral maintenance treatment with 5-ASA compounds.

OBJECTIVE

To study the urinary and serum levels of acetylated 5-ASA (Ac-5-ASA) and the unacetylated 5-ASA (5-ASA) in patients with IBD maintained on sulphasalazine, olsalazine and mesalazine (pH dependent release form). We also sought correlation between levels of 5-ASA, clinical disease activity and extent of disease.

METHODS

We studied 79 patients (male, n = 30; female, n = 49) with established IBD [ulcerative colitis (UC), n = 48; Crohn's disease (CD), n = 31], 72 maintained on 5-ASA compounds (sulphasalazine = 27; olsalazine = 28; mesalazine = 17) and 7 patients were receiving no medication. Urinary and serum analysis of 5-ASA was performed by high performance liquid chromatography (HPLC). Clinical disease activity was quantified using simple index of Harvey and Bradshaw.

RESULTS

Patients receiving mesalazine had significantly higher levels of serum free 5-ASA compared to those who were receiving olsalazine and sulphasalazine (mesalazine mean +/- SEM; range; 2.84 +/- 1.21 (0.00-16.00) vs olsalazine 0.45 +/- 0.18 (0.00-16.20); mumol/L; p < 0.04; sulphasalazine 0.37 +/- 0.25 (0.00-3.74); p < 0.03). Similarly levels of urinary free 5-ASA were significantly higher in patients maintained on mesalazine compared to those on olsalazine or sulphasalazine (mesalazine 219 +/- 80.43 (0.00-1050) vs olsalazine 33.3 +/- 17.23 (0.00-317) mumol/L; p < 0.01; and sulphasalazine 15 +/- 8.86 (0.00-192); p < 0.05). However, no significant difference was observed in the levels of urinary free 5-ASA between olsalazine and sulphasalazine. No significant difference was observed in the levels of free-5-ASA in UC patients with left sided disease and those with extensive disease. Furthermore, no significant difference was observed in the levels of serum and urinary 5-ASA in CD patients with ileo-colic disease and colonic disease. Urinary and serum free-5-ASA did not correlate with the clinical disease activity.

CONCLUSION

Systemic absorption of 5-ASA from sulphasalazine and olsalazine is relatively low. However, pH-dependent mesalazine formulations may release their contents rapidly in the small intestine and proximal colon resulting in higher plasma and urinary concentrations of free 5-ASA. The effects of free 5-ASA on renal function in the human require further evaluation.

Increased HLA-DR and CD44 antigen expression in the gut: evidence of extraarticular immunological activity in rheumatoid arthritis

OBJECTIVE

To examine the gastrointestinal (GI) immune system in rheumatoid arthritis (RA) for evidence of activation.

METHODS

Duodenal biopsies from 25 patients with RA were obtained by endoscopy. Single cell suspensions from the epithelial layer and lamina propria were prepared. Flow cytometry was used to examine the expression of CD4, CD8, T cell receptor-gammadelta (TCR-gammadelta), TCR-alphabeta, HLA-DR, CD44, and interleukin 2 receptor on gut T lymphocytes. Fifteen disease control (DC) individuals and 6 patients with osteoarthritis (OA) taking longterm nonsteroidal antiinflammatory drug (NSAID) therapy were also investigated. Peripheral blood T lymphocytes from all individuals were examined for the expression of these surface molecules.

RESULTS

HLA-DR expression was significantly increased on intraepithelial lymphocytes (IEL) and enterocytes from patients with RA (n = 13) compared with the 2 control groups (p<0.01). Immunohistochemistry also revealed increased expression of HLA-DR on enterocytes from patients with RA. RA IEL (n = 6) expressed significantly higher levels of CD44 (p<0.02). In the lamina propria, a small but significant gammadelta T lymphocyte population (mean 5.5%, range 2-12%) was detected in rheumatoid factor positive RA patients (n = 8) compared with RF negative RA patients (n = 8, mean 2%, range 0.4-6%; p<0.01) and the disease control group (n = 15, mean 2%, range 0.5-5%; p<0.01). None of these changes were detectable in peripheral blood lymphocytes from patients with RA.

CONCLUSION

This study demonstrates evidence of activation of specific components of the GI immune system in RA. Peripheral blood T lymphocytes from patients with RA did not show increased expression of activation markers, suggesting that changes in the RA GI tract are not systemic but localized. Moreover, these changes appear to be independent of NSAID therapy.

Primary cutaneous B-cell lymphoma: an association of chronic hepatitis C infection

Primary cutaneous B-cell lymphoma is a low-grade malignancy, distinct from other lymphomas in terms of biological activity and response to treatment. We describe a 77-year-old woman with a five-year history of chronic hepatitis C infection who developed a lower-limb lesion over a period of 3 months which was diagnosed as a high-grade cutaneous B-cell lymphoma. Despite a lack of definitive evidence implicating hepatitis C virus (HCV) in the aetiology of lymphomas, there is considerable research which establishes a strong association between these two diseases. On the basis of published research and the demonstration of HCV RNA in the lymphomatous tissue, we consider this to be a rare case of primary cutaneous lymphoma in association with hepatitis C.

Guided versus blind liver biopsy for chronic hepatitis C: clinical benefits and costs

BACKGROUND/AIMS

Our objectives were: (1) to assess the clinical benefits and costs of performing ultrasound-guided liver biopsy with an automated needle compared to blind biopsy with a conventional Trucut needle in patients with chronic hepatitis C; (2) to compare the histological yield of automated needles with Trucut needles.

METHODS

We prospectively studied 166 patients with hepatitis C virus who underwent either ultrasound-guided biopsy using automated ASAP needles or blind biopsy using conventional Trucut needles. Both groups were matched for age, sex, cirrhosis, needle gauge and operator experience. Patient tolerance, complications and histological adequacy were assessed. In a separate in vitro study, we assessed the histological adequacy of liver biopsy specimens obtained using automated and Trucut needles from 10 fresh autopsy cases.

RESULTS

Ultrasound-guided biopsy caused significantly less biopsy pain (36.4% vs. 47.3%; p < 0.0001) and significantly less pain-related morbidity (1.8% vs. 7.7%, p < 0.05). Although, there was no significant difference in diagnostic yield between guided and blind biopsy (98% vs. 94%, p = 0.15), 3 blind biopsies (3.3%), including 2 which yielded extra-hepatic tissue, had to be repeated. The additional expense of performing guided liver biopsy with automated needles was 42 Irish Pounds per patient. In vitro, automated ASAP 15G needles provided liver specimens comparable to Trucut 15G needles and had the highest histopathologic score among the automated needles assessed.

CONCLUSIONS

Even in the absence of major complications, ultrasound-guided liver biopsy with an automated needle in HCV patients is safer, more comfortable and only marginally more expensive than blind Trucut biopsy.

Inside the crawling T cell: leukocyte function-associated antigen-1 cross-linking is associated with microtubule-directed translocation of protein kinase C isoenzymes beta(I) and delta

T cells activated via integrin receptors can polarize and start crawling locomotion with repeated cycles of cytoskeletal reassembly processes, many of which depend on phosphorylation. We demonstrate that protein kinase C (PKC) activation represents an essential event in induction of active T cell motility. We find that in crawling T cells triggered via cross-linking of integrin LFA-1 two PKC isoenzymes, beta(I) and delta, are targeted to the cytoskeleton with specific localization corresponding to the microtubule-organizing center (MTOC) and microtubules, as detected by immunocytochemistry and immunoblotting. Clustering of LFA-1 associated with its signaling function also occurs at the membrane sites adjacent to the MTOC. We further show that cells of a PKC-beta-deficient clone derived from parental PKC-beta-expressing T cell line can neither crawl nor develop a polarized microtubule array upon integrin cross-linking. However, their adhesion and formation of actin-based pseudopodia remain unaffected. Our data demonstrate the critical importance of the microtubule cytoskeleton in T cell locomotion and suggest a novel microtubule-directed intracellular signaling pathway mediated by integrins and involving two distinctive PKC isoforms.

Antiretroviral effect and safety of abacavir alone and in combination with zidovudine in HIV-infected adults. Abacavir Phase 2 Clinical Team

OBJECTIVES

To evaluate, over 12 weeks, the antiretroviral activity and safety of abacavir, used alone and in combination with zidovudine (ZDV), as treatment for HIV-1-infected subjects who had limited or no antiretroviral treatment.

DESIGN

Seventy-nine HIV-1-infected subjects, with CD4 cell counts 200-500 x 10(6)/l and <12 weeks of previous treatment with ZDV were enrolled in a multicenter study. Subjects were randomly assigned to one of four cohorts receiving abacavir monotherapy for the first 4 weeks (200, 400, or 600 mg every 8 h daily, or 300 mg every 12 h daily) and, thereafter, combination therapy of abacavir with 600 mg ZDV or ZDV placebo, administered in a double-blind manner for an additional 8 weeks.

METHODS

Antiretroviral activity was assessed by measuring changes in plasma HIV-1 RNA levels and CD4+ cell counts. Safety was assessed by monitoring clinical adverse events and laboratory abnormalities during the 12-week period and for 4 weeks post-treatment.

RESULTS

Treatment with abacavir, alone or in combination with ZDV, produced marked decreases in plasma HIV-1 RNA loads and increases in CD4+ cell counts in all groups. At week 4, median plasma HIV-1 RNA loads decreased by 1.11-1.77 log10 copies/ml and median CD4+ cell counts increased by 63-111 x 10(6)/l in all groups. At week 12, median HIV-1 RNA loads decreased by 1.02-2.24 log10 copies/ml (abacavir monotherapy) and by 1.81-2.01 log10 copies/ml (abacavir-ZDV); median CD4+ cell counts increased by 79-195 x 10(6)/l (abacavir monotherapy) and by 93-142 x 10(6)/l (abacavir-ZDV). At week 12, the percentage of subjects who had plasma HIV-1 RNA levels below 400 and 40 copies/ml were 28 and 11%, respectively (abacavir monotherapy) and 69 and 22%, respectively (abacavir-ZDV). Eight subjects (10%) discontinued the study prematurely because of adverse events; nausea (n = 4) and hypersensitivity (n = 3) were the most common reasons for withdrawal. There were no deaths among the study subjects.

CONCLUSIONS

In HIV-infected subjects who have received little or no prior antiretroviral therapy, treatment with abacavir alone or in combination with ZDV is well tolerated and resulted in sustained improvements in key immunologic and virologic efficacy parameters through 12 weeks.

Helicobacter pylori disrupts epithelial barrier function in a process inhibited by protein kinase C activators

Helicobacter pylori colonizes the gastric mucosa, and the infection is related to the development of diverse gastric pathologies, possibly by directly or indirectly affecting epithelial-cell function. We analyzed the influence of the bacteria on transepithelial electrical resistance (TER) on a model tight epithelium, T84, grown to confluence in permeable filters. H. pylori sonicates produced a dramatic decrease in TER after 1 to 2 h of exposure, while sonicates from other bacteria did not induce a significant reduction of TER. The effect induced by sonicates was mimicked by a water-soluble fraction from the bacterial surface, was not reproducible with isolated lipopolysaccharide, and was concomitant with a significant increase in the paracellular permeability of the marker molecule [14C]mannitol. Furthermore, H. pylori sonicates also provoked a significant increase in permeability to [14C]mannitol across rat gastric mucosa in vitro. The sonicate-induced decrease in TER in T84 monolayers was inhibited by the protein kinase C (PKC) activator phorbol myristate acetate. As PKC is directly involved in tight junction regulation, we suggest that H. pylori may induce intracellular signalling events counteracting PKC effects. Following long-term H. pylori stimulation, epithelial monolayers regained baseline resistance values slowly after 24 h. The resistance recovery process was inhibited by cycloheximide, indicating its dependency upon protein synthesis. No association between resistance variation and E-cadherin protein levels was observed. These results indicate that H. pylori alters in vitro the barrier properties of the epithelium, probably by generating cell signalling events counteracting the normal function of PKC. This increased permeability may provide a potential mechanism by which H. pylori antigens can reach the gastric lamina propria, thereby activating the mucosal immune system.

Obesity and low-fat diets in pediatrics

The field of pediatric nutrition continues to advance, with increasing evidence that diets early in life have long-lasting effects on health and disease well into adulthood. Pediatricians and nutritionists have long appreciated the importance of adequate nutrition in infancy for optimal growth and development, but only in recent years has the link between pediatric nutrition and diseases of so-called "adult onset" been realized. Two important topics in the field, obesity and the use of low-fat diets early in life, have been the subject of recent literature, and developments in these areas are summarized. Although the genetic basis for some causes of obesity are becoming clear, reliable assessment and treatment of obese children are still wanting in many cases. The ease with which healthy pediatric diets meet the recommended dietary guidelines for fat intake is also reviewed. Finally, the possibility that changes in federal funding of food assistance programs might have adverse effects on pediatric nutrition is also noted.

H pylori infection is associated with downregulation of E-cadherin, a molecule involved in epithelial cell adhesion and proliferation control

Extracellular matrix proteins and proteins involved in epithelial adhesion are essential for maintenance of tissue structure. Helicobacter pylori is the major aetiological agent in peptic ulcer disease and has been shown to increase gastric cancer risk up to ninefold. In this study, changes induced by H pylori on the expression of extracellular matrix proteins (collagen IV, fibronectin, and laminin) as well as two essential proteins for cell-basement and cell-cell adhesion (alpha 6-integrin and E-cadherin) were assessed. Immunohistochemistry was performed in antral biopsy sections obtained from infected and non-infected patients, and light microscopy was used to determine the distribution and intensity of specific staining. The results showed that the infection was significantly associated with downregulation of E-cadherin, an essential protein for maintenance of solid tissues and differentiation, but did not induce changes in the expression of alpha 6-integrin or the extracellular matrix proteins.

The development of hepatic granulomas following interferon-alpha2b therapy for chronic hepatitis C infection

Hepatic granulomas have been detected in cases of chronic hepatitis C virus (CHCV) infection. Here we report upon three selected cases of CHCV infection who were treated with IFN alpha, in whom hepatic granulomas were absent on initial liver biopsies, but in whom granulomas developed following IFN alpha therapy. In one case, complete regression of these granulomas was noted 17 months following discontinuation of treatment, more strongly implicating IFN alpha in the aetiopathogenesis of such granulomas in this case. These findings suggest that IFN alpha may have a biological role in the pathogenesis of granulomatous liver disease in these patients. All three cases were poor/non-responders to IFN alpha, suggesting that the development of hepatic granulomas during IFN alpha therapy may be associated with a poor response to treatment.

Protein kinase C and the cytoskeleton

The protein kinase C family of serine-threonine kinases are important signal transducers participating in many different agonist-induced signalling cascades. PKC is activated by increases in diacylglycerol produced in response to agonist-induced hydrolysis of inositol phospholipids. PKC is thought to reside in the cytosol in an inactive conformation and translocate to the plasma membrane upon cell activation where it modifies various cellular functions through phosphorylation of target substrates. Increasing evidence has illustrated that this family of enzymes is capable of translocating to other subcellular sites than the plasma membrane. A key to understanding the functions of the members of this family is identifying their physiological substrates and their relationship with those target substrates. The idea that PKC may be an important regulator of cytoskeletal function has been suggested by numerous studies. Activation of PKC in a variety of different cell types leads to changes in the cell cytoskeleton including lymphocyte surface receptor capping, smooth muscle contraction and actin rearrangement in T cells and neutrophils. Given the ubiquitous expression of PKC and the diversity of cytoskeletons in different cell types it is not surprising that PKC has been shown to be associated with and/or phosphorylate a wide range of cytoskeletal components. This review examines the interaction of PKC with the cytoskeleton and discusses some of the cytoskeletal functions ascribed to PKC to date.

Human small intestinal epithelial cells secrete interleukin-7 and differentially express two different interleukin-7 mRNA Transcripts: implications for extrathymic T-cell differentiation

The small intestinal epithelium, composed of epithelial cells (EC) and intraepithelial T lymphocytes, is exposed to numerous ingested antigens. Small intestinal EC may act as accessory and/or antigen presenting cells for intestinal T cells, some of which may mature extrathymically and regulate local immunity and tolerance. Since interleukin-7 (IL-7) plays an essential role in T cell maturation and activation, we examined its expression by human small intestinal EC. IL-7 was detected by ELISA in supernatants from 4 of 4 epithelial layer (EpL) cultures. Using RT-PCR, IL-7 mRNA was detected in 4 EpL studied, and two distinct IL-7 transcripts were identified in 3 of the 4. The ratios of the intensities of the larger to the smaller bands varied amongst individuals. Furthermore, the intensity ratios were higher in whole-thickness intestine and lamina propria preparations than in their corresponding EpL. This is the first report of the expression of two IL-7 transcripts in human intestine and of IL-7 secretion by human small intestinal EpL cells. This supports the hypothesis that small intestinal EC may influence differentiation and/or activation of neighboring T cells. The differential expression of the two transcripts may have important implications for immune regulation in the intestinal epithelium.

Effect of a bicycle safety program and free bicycle helmet distribution on the use of bicycle helmets by elementary school children

OBJECTIVE

Each year in the United States, 300,000 children are treated in emergency departments for bicycle injuries; one third have head injuries. The purpose of this study was to determine the effectiveness of educational interventions and free helmet distribution in increasing the use of helmets by elementary school children.

METHODS

Self-report questionnaires on the use of bicycle helmets were used for students at two elementary schools (n = 1610). Testing was done both before and after the administration of a bicycle safety program and the distribution of free helmets. Pretest and posttest answers were then compared for changes in helmet use.

RESULTS

Helmet usage increased significantly after the bicycle safety program, from 38% to 46% overall (p < 0.005). Children who were given free helmets were significantly more likely to wear their helmets (61.4%) than children who already owned helmets (43.4%) (p > 0.016). Children who attended the school in which free helmets were distributed showed a significant increase in helmet use (p < 0.01), whereas those at the school that had a safety program alone did not show a significant increase (p > 0.17).

DISCUSSION

The results of this study suggest that bicycle safety programs and free helmet distribution may increase the consistent use of helmets in elementary school children.

Subcellular localization and translocation of protein kinase C isoforms zeta and epsilon in human peripheral blood lymphocytes

The calcium-independent members of the protein kinase C (PKC) family may play a significant role in T cell function. We have characterized the subcellular localization and redistribution of calcium-independent kinase C activity and of two specific members of this family (zeta and epsilon) in response to activation of human peripheral blood lymphocytes with phorbol myristate acetate (PMA) or through the TCR-CD3 complex. Both PMA and OKT3, an antibody against the TCR-associated CD3 complex, induce an increase in membrane and cytoskeletal activity with a concomitant decrease in cytosolic activity. By Western blot analysis, PKC epsilon is present in resting cytosol and membrane fractions, and is detected in the membrane following activation with PMA and in both the membrane and cytoskeleton following OKT3 activation. By contrast, PKC zeta is progressively lost from the cytoskeleton following activation with anti-CD3. Immunocytochemistry reveals distinct redistribution patterns for these enzymes in response to activation through anti-CD3 and by PMA. These findings demonstrate that signaling through the CD3 complex induces significant changes in calcium-independent PKC activity and in the intracellular distribution of specific isoenzymes, and support a role for specific functions for individual isoenzymes in T cell activation. Lastly, changes in the cytoskeletal distribution of these isoenzymes suggest a potential role in the modulation of cell structure in response to activation.

Elevated levels of circulating soluble adhesion molecules in peripheral blood of patients with unstable angina

We have demonstrated increased levels of the circulating soluble adhesion molecules (sCAMs), ICAM-1, VCAM-1, and E-selectin in patients with unstable angina compared with healthy controls. Our findings support the role of inflammation in clinically unstable coronary disease, and may indicate a potential role for measurement of peripheral sICAM levels as a marker for inflammatory activity in atherosclerotic plaque.

Identification and characterization of a metalloprotease activity from Helicobacter pylori

Helicobacter pylori produces a metalloprotease with a native molecular size of approximately 200 kDa, as determined by size-exclusion chromatography. Subcellular distribution studies demonstrated that the activity was associated with the outer membrane fraction of the bacterium. In addition, the protease was secreted by the bacterium when grown in liquid culture. The enzyme activity was measured by hydrolysis of azocasein and biotinylated casein and exhibited optimal caseinolytic activity at pH 8.0 (37 degrees C). The activity was inhibited by EDTA, 1,10-phenanthroline, phosphoramidon, pyridine-2,6-dicarboxylic acid, and 8-hydroxyquinoline-5-sulfonic acid (HQSA). Inhibition by HQSA was reversed by zinc, whereas inhibition due to EDTA was reversed by excess calcium, thus indicating that the enzyme was a zinc-dependent, calcium-stabilized endoproteinase. Furthermore, titration with Zn2+ of a desalted, active-site zinc-chelated preparation of the protease demonstrated that Zn2+ was essential for activity. Leupeptin, phenylmethylsulfonyl fluoride, E-64, pepstatin A, dithiothreitol, and 2-mercaptoethanol had no effect on enzymatic activity. Addition of Ca2+ or Mg2+ to the incubation medium resulted in approximately a twofold stimulation of the azocaseinolytic activity of the enzyme. The protease was stably expressed since it was active even after repeated subculture of the bacterium. Bovine serum albumin, hide powder azure, and elastin-Congo red remained intact even after prolonged exposure to the enzyme. The surface expression of this metalloprotease activity raises the possibility that this enzyme may be involved in the proteolysis of a variety of host proteins in vivo and thereby contributes to gastric pathology.

Changes in barrier function of a model intestinal epithelium by intraepithelial lymphocytes require new protein synthesis by epithelial cells

BACKGROUND

Elements of the mucosal immune system may play an important part in regulating epithelial barrier function in the intestinal tract. Intraepithelial lymphocytes (IELs) represent a subtype of immunocyte which is strategically placed to regulate epithelial function at most mucosal sites.

AIMS AND METHODS

An IEL derived cell line (SC1) was used to examine its effects on the model epithelium T84--a tumour derived cell line which retains the phenotype of colonic crypt cells. Transepithelial electrical resistance (TER) was used as a marker of epithelial integrity.

RESULTS

Coculture of T84 cells with SC1 produced a significant fall in TER as did exposure of T84 monolayers to IEL derived supernatant. Recombinant interferon-gamma (rIFN gamma) also reduced TER in T84 monolayers. Cycloheximide prevented the effects of IEL supernatant and of rIFN gamma on TER. The fall in TER in response to rIFN gamma was attenuated by blocking antibodies, which did not alter the fall in resistance induced by IEL supernatant. Fractions of IEL supernatant, separated on the basis of size, evoked temporally distinct changes in TER. Ultrastructural studies support the hypothesis that the slow onset but severe fall in TER indicates catastrophic effects on the monolayer. The more rapid onset fall in TER was not associated with gross changes in monolayer morphology. Reduction of TER by IEL supernatant was not influenced by inhibitors of tyrosine phosphatase or of protein kinase C. Although herbimycin did reduce the rapid onset change in TER, the tyrosine kinase inhibitor genistein did not alter responses to IEL supernatant.

CONCLUSIONS

Mucosal T cells may influence barrier function by a process involving new protein synthesis by epithelial cells. This model may have relevance in some inflammatory conditions of the gastrointestinal tract.