Are intraepithelial lymphocytes in celiac mucosa responsible for inducing programmed cell death (apoptosis) in enterocytes? Histochemical demonstration of perforins in cytoplasmic granules of intraepithelial lymphocytes

Effect of addition of short course of prednisolone to gluten-free diet on mucosal epithelial cell regeneration and apoptosis in celiac disease: a pilot randomized controlled trial

BACKGROUND

Identification of adjuvant treatment is necessary for rapid and effective treatment in patients with celiac disease. In a pilot randomized controlled trial, the effect of prednisolone on enterocyte apoptosis and regeneration in celiac disease was investigated.

PATIENTS AND METHODS

Thirty-three treatment-naïve patients with celiac disease were randomized to either gluten-free diet (GFD, n = 17) or GFD + prednisolone (1 mg/kg for 4 weeks, n = 16). Duodenal biopsies were taken at baseline and at 4 and 8 weeks posttreatment. Six patients with functional dyspepsia were recruited as controls. All these biopsies were stained for markers of intrinsic apoptotic pathway (AIF, H2AX, p53), common apoptotic pathway (CC3, M30), apoptotic inhibitors (XIAP, Bcl2), and epithelial proliferation (Ki-67). Apoptotic (AI) and proliferation indices (PI) were compared.

RESULTS

At baseline duodenal biopsies, the end apoptotic products H2AX and M30 were significantly increased. In comparison with those treated with GFD alone, after 4 weeks of GFD + prednisolone treatment, some markers of both intrinsic and common apoptotic pathways showed rapid decline. After prednisolone withdrawal, there was overexpression of H2AX, CC3, and p53 in the latter group. In comparison with those treated with only GFD, patients treated with prednisolone showed suppression of mucosal PI, which started rising again after withdrawal of prednisolone.

CONCLUSIONS

Apoptosis takes place in mucosal epithelium in celiac disease. Addition of short course of prednisolone suppresses apoptosis rapidly. However, it also suppresses epithelial regeneration; hence, if used, it should be withdrawn after an initial short course.

New insights in celiac disease

Celiac disease (CD) is an autoimmune disorder occurring in genetically susceptible subjects. The incidence of CD is around 1%, and it is much more common in first-degree relatives of CD patients, 10%-18%. However, the pattern of the genetic inheritance is still obscure. Environmental factors are undoubtedly affecting the disease's clinical presentation, time at presentation, and may have an effect on the characteristics of the disease. The clinical presentation of CD has shifted during the previous decades from the classical presentation in which the toddler suffers from diarrhea, constipation, vomiting, failure to thrive, abdominal distension, etc., to the child with a monosymptomatic presentation, such as anemia, as well as an enlarged list of extra-intestinal disorders. The diagnosis of CD is being established by symptoms consistent with CD and positive serology. The ultimate diagnosis should be made upon histological evaluation of the small bowel mucosa. The treatment of CD is a lifelong, strict gluten-free diet (GFD). Compliance with a GFD is quite difficult. Therefore, new strategies for prevention and treatment modalities other than GFD are greatly needed. Recently several promising therapeutic modalities have been developed; these include resuming traditional baking techniques. Another methodology is using probiotic-driven prolylendopeptidase. Another pathway to tackle the therapeutic option in CD is by down-regulation of the activity of zonulin-the active pump enabling gluten to enter the enterocytes. We are facing an era where other modalities beyond a GFD might allow CD patients to be able to tolerate occasionally a small amount of gluten in their diet.

Increased expression of serum- and glucocorticoid-regulated kinase-1 in the duodenal mucosa of children with coeliac disease

OBJECTIVES

Enterocyte apoptosis induced by activated intraepithelial lymphocytes is increased in coeliac disease (CD). Serum- and glucocorticoid-regulated kinase-1 (SGK1) is a serine/threonine protein kinase that may inhibit apoptosis and compensate for the excessive death of surface epithelial cells. The significance of SGK1 in CD is elusive so far. The aim of this study was to characterise the expression and localisation of SGK1 in duodenal biopsy samples taken from children with untreated CD, children with treated CD, and controls.

PATIENTS AND METHODS

Duodenal biopsy specimens were collected from 16 children with untreated CD, 9 children with treated CD, and 10 controls. The mRNA expression of SGK1 was determined by real-time reverse transcription-polymerase chain reaction. SGK1 and phosphorylated (P)-SGK1 protein levels and their localisation were determined by Western blot and immunofluorescent staining, respectively.

RESULTS

We found increased SGK1-mRNA expression as well as higher SGK1 and P-SGK1 protein levels in the duodenal mucosa of children with untreated CD compared with controls. In the duodenal mucosa of children with treated CD, SGK1-mRNA expression was decreased and SGK1 and P-SGK1 protein levels were lower than in untreated CD. SGK1 and P-SGK1 staining intensity was stronger in duodenal villous enterocytes of children with untreated CD compared with treated CD.

CONCLUSIONS

Our results of increased expression of SGK1 in untreated CD may suggest its contribution to the enterocyte survival in this disease.

Duodenal cytotoxic lymphocytes in cow's milk protein sensitive enteropathy and coeliac disease

OBJECTIVE

Pathogenetic mechanisms of cow's milk protein-sensitive enteropathy (CMSE) are poorly defined, but elevated serum granzyme levels and an increase in duodenal intraepithelial lymphocytes (IELs) expressing TIA-1 suggest the involvement of abnormal lymphocyte cytotoxicity. To evaluate cytotoxicity in CMSE we analysed the expression of cytotoxic granule components in duodenal IELs. For comparison, we studied subjects with coeliac disease (CD), in which lymphocyte cytotoxicity is pathogenically important.

MATERIAL AND METHODS

Fifty-four children were examined by endoscopy for gastrointestinal complaints. Twenty-one subjects had a final diagnosis of CMSE, 15 children had untreated CD and 18 controls showed no definite gastrointestinal disease. Mucosal samples furnished from the bulb and descending duodenum were stained for CD3, perforin, granzymes A and B and TIA-1.

RESULTS

In both CMSE and CD, increase of mid-duodenal TIA-1, perforin and granzyme A expressing IELs was seen, the counts in CD being much higher, and increased expression was also seen in the bulb. Granzyme B expression was increased only in CD. In CMSE, no evidence of villous atrophy was seen.

CONCLUSIONS

Increase in duodenal IELs expressing cytotoxic granules is a characteristic feature in CMSE, although to a lesser degree than in CD. Cytotoxicity is suggested to be involved in the pathogenesis of intestinal dysfunction in CMSE, but based on the absence of villous abnormalities may not be mainly targeted to enterocytes. The mechanisms leading to the accumulation of these cells in CMSE need further investigation.

Cytotoxic T cells are preferentially activated in the duodenal epithelium from patients with florid coeliac disease

Villous atrophy and increased numbers of intraepithelial T cells in duodenal biopsies represent a hallmark of coeliac disease. In the present study, an attempt has been made to define whether cytotoxic cell subsets are activated in situ in the affected mucosa of susceptible individuals early after ingestion of a gluten-containing diet. Duodenal biopsies from 11 patients with coeliac disease who repeatedly underwent endoscopic biopsy after ingestion of individually dosed amounts of gluten were used for immunohistochemistry and in situ hybridization. To identify the cell subsets expressing perforin mRNA and protein, in situ hybridization and FACS analyses were performed on cells isolated from fresh biopsies. Compared with normal mucosa, the number of intraepithelial lymphocytes containing perforin mRNA and protein increased significantly in tissue samples showing moderate or florid coeliac disease and closely paralleled the severity of morphological alteration, whereas the frequency of perforin-expressing lamina propria lymphocytes increased only moderately. Cells isolated from florid biopsies that expressed perforin mRNA and protein were preferentially T-cell receptor (TCR) alphabeta T cells. The increase in both the absolute number and the percentage of lymphocytes expressing perforin mRNA indicates in situ activation of lymphocytes within the epithelial compartment in florid coeliac disease upon ingestion of a gluten-containing diet in patients predisposed to coeliac disease.

Abundant expression of granzyme A, but not perforin, in granules of CD8+ T cells in GALT: implications for immune control of HIV-1 infection

Because GALT is a major portal of entry for HIV-1 and reservoir for viral replication, we hypothesized that an ineffective cellular immune response in intestinal mucosa might partially explain the failure of immune control in AIDS. In this study, we demonstrate that the vast majority of CD8+ T cells in rectal tissue, including HIV-1-specific cells, fail to express the cytolytic protein, perforin. However, rectal CD8+ T cells do express granzyme A, and are also capable of releasing IFN-gamma upon stimulation with cognate peptide. Confocal microscopy showed that granzyme A was located in intracellular granules in the absence of perforin. The majority of rectal CD8+ T cells exhibit an effector memory phenotype, expressing CD45RO but not CCR7. Quantitative real-time PCR analysis demonstrated that perforin RNA is expressed in rectal CD8+ T cells from healthy and HIV-1-positive individuals. In HIV-1-positive individuals, similar amounts of perforin RNA were detected in CD8+ T cells from rectal tissue and PBMC, despite a relative absence of perforin protein in rectal tissue. These findings demonstrate an important difference in perforin expression between CD8+ T cells in blood and mucosa. Furthermore, the relative absence of armed effector cells may serve to protect the integrity of rectal mucosa under normal conditions, but might also provide an early advantage to HIV-1 and other sexually transmitted viruses.

the influence oflentinus edodes(shiitake mushroom) preparations on bacteriological and morphological aspects of the small intestine in piglets

Among substances intended to replace growth promoting antibiotics in pig nutrition, non-digestible oligosaccharides or polysaccharides could be potential alternative compounds. Therefore, the influence of beta-1,3-1,6 glucans on bacteriological, biochemical and morphological aspects of the small intestine in weaned piglets was investigated. As sources of beta-glucans, Lentinan (extract of Lentinus edodes mycelium) or dried L. edodes mycelium were added to the diet. Four homogenous groups of 5 newly weaned piglets (4 weeks of age) received one of four diets: control diet (C), C supplemented with Avilamycin (50 mg/kg, positive control), C supplemented with 0.1% of Lentinan and C supplemented with 5% of dried L. edodes mycelium powder. A first group of 10 piglets was euthanized after 11 days and the remaining 10 on day 12 of the experiment. The gastrointestinal tract was divided in segments and samples taken from digesta (stomach, proximal and distal jejunum, caecum), mucosal scrapings (jejunum) and ring shaped tissue samples (1 cm) of proximal and distal jejunum. Bacterial counts were made with digesta and mucosal samples, and short-chain fatty acids (SCFA), lactic acid and ammonia concentrations were determined. Tissue samples of both jejunal sites were embedded in paraffin wax for morphometrical (villus length, crypt depth) and histological observations (numbers of intraepithelial lymphocytes (IEL), goblet cells, apoptotic enterocytes on villi, mitotic cells in crypts). Only the diet containing 5% of dried L. edodes consistently resulted in lower viable counts (ca. 1-2 log10 CFU) of total bacteria, E. coli, streptococci and lactic acid bacteria, and luminal and mucosal effects agreed very well. With this diet, acetate and butyrate concentrations in the distal jejunum were doubled, which is favourable in view of the trophic effect on enterocytes and colonocytes. Villus length (V) was increased with both diets containing beta-glucans while crypt depth (C) was not altered, but V/C was higher. IEL counts were decreased by both diets although bacterial numbers, which is only one parameter of bacterial load, were only diminished with the L. edodes feed. The three supplemented feeds lowered the number of apoptotic enterocytes on the villi, but these numbers were very low (control diet : 44 cells per 100 villi), making clear interpretation difficult. The mitotic index was slightly lower with the L. edodes feed, although not statistically significant. Decreased viable counts observed with the latter diet is a favourable effect as it is accepted that a lower bacterial load causes lower turnover rates of the intestinal epithelial cells, while there is also less competition for specific substrates. A higher V/C ratio, a smaller number of IEL in the epithelium and a lower apoptotic index also indicate slower turnover rate of the mucosa when Lentinan and L. edodes diets were fed. The inconsistent effects observed with Lentinan were probably due to the low amount added to the diet. It should be taken into account that the influence of L. edodes mycelium powder was more likely due to the presence of antibacterial compounds (eg. lenthionine, lentinamycin, terpenoids, polyphenols), rather than to an immunostimulating action of beta-glucans with increased release of IgA onto the mucosa surface.

Immunohistochemical study of the apoptotic mechanisms in the intestinal mucosa during children's coeliac disease

Mechanisms leading to morphological changes of the small intestine during coeliac disease (CD) are not yet completely recognized; however, two main processes have been suggested recently: remodeling of mucosa by matrix metalloproteinases, and mucosal atrophy by apoptosis. The aim of this study was analysis of the expression of proteins regulating apoptosis in the small intestine of children with active CD (ACD) and potential CD (PCD). Jejunal biopsies of 43 children with PCD and untreated ACD and 21 control samples were analyzed by means of standard indirect immunohistochemical technique for Fas, Fas ligand (Fas-L), tissue transglutaminase (tTG), Bcl-2, and glutathione S-transferase (GST) expression. We found significantly lower numbers of Fas-expressing enterocytes in the ACD patients than in PCD patients and controls. Similarly, the number of Fas-positive mucosal lymphocytes was decreased in ACD when compared with PCD. The number of Fas-L- and tTG-expressing enterocytes and mucosal lymphocytes was higher in both PCD and ACD. On the other hand, the number of Bcl-2-positive mucosal lymphocytes in PCD as well as ACD was significantly lower. The expression of tTG in extracellular matrix was significantly higher in PCD and ACD when compared with controls. Our results showed that Fas and/or Fas-L, Bcl-2, and tTG may be involved in apoptotic pathways leading to mucosal atrophy in children with CD. tTG changes are in agreement with the presumed role of this protein in the pathogenesis of CD.

Combination interleukin-2 and interleukin-12 induces severe gastrointestinal toxicity and epithelial cell apoptosis in mice

Interleukin 2 (IL-2) and interleukin 12 (IL-12) have potent anti-tumour activity as single agent therapy against several different murine and human tumours. Combining these cytokines may result in improved therapeutic effectiveness, however, the toxicity associated with simultaneous administration is prohibitive. This study was designed to determine the specific histopathologic changes associated with combination therapy. Mice were treated with 5 days of interleukin-2, interleukin-12, or both using standard doses and schedules. Histologic specimens were prepared from all internal organs on a daily basis to identify specific pathologic abnormalities. Treatment with interleukin-2, interleukin-12, or both resulted in pathologic insult to the liver and gastrointestinal tract. Mild lymphoplasmacytic infiltrates were seen in the liver. The most significant pathology was seen in the large bowel and consisted of apoptosis of colonic epithelial cells. While recovery of injured gastrointestinal mucosa occurred in mice treated with interleukin-2 or interleukin-12 alone, combination therapy resulted in death before recovery was possible. Combination interleukin-2 and interleukin-12 therapy results in irreversible injury of the colon as manifested by increased epithelial cell apoptosis and death in mice. Understanding the pathologic changes associated with combination cytokine therapy may lead to strategies that prevent toxicity while maintaining therapeutic effects.

Adenoviral vector which delivers FasL-GFP fusion protein regulated by the tet-inducible expression system

Fas ligand (FasL) is a member of the tumor necrosis family and when bound to its receptor, Fas, induces apoptosis. It plays important roles in immune response, degenerative and lymphoproliferative diseases, development and tumorigenesis. It is also involved in generation of immune privilege sites in the eye and testis. Harnessing the power of this molecule is expected to lead to a powerful chemotherapeutic. We describe the construction and characterization of replication-deficient adenoviral vectors that express a fusion of murine FasL and green fluorescent protein (GFP). FasL-GFP retains full activity of wild-type FasL, at the same time allowing for easy visualization and quantification in both living and fixed cells. The fusion protein is under the control of a tetracycline-regulated gene expression system. Tight control of expression is achieved by creating a novel 'double recombinant' Ad vector, in which the tet-responsive element and the transactivator element are built into the opposite ends of the same vector to avoid enhancer interference. Expression can be conveniently regulated by tetracycline or its derivatives in a dose-dependent manner. The vector was able to deliver FasL-GFP gene to cells in vitro efficiently, and the expression level and function of the fusion protein was modulated by the concentration of doxycycline. This regulation allows us to produce high titers of the vector by inhibiting FasL expression in an apoptosis-resistant cell line. Induction of apoptosis was demonstrated in all cell lines tested. These results indicate that our vector is a potentially valuable tool for FasL-based gene therapy of cancer and for the study of FasL/Fas-mediated apoptosis and immune privilege.

Cytolytic mechanisms of intraepithelial lymphocytes in coeliac disease (CoD)

The effector arm of the mucosal immune system comprises lymphocytes scattered at intraepithelial and lamina propria levels. Intraepithelial lymphocytes (IEL) are a large population of oligoclonal resting cells which exhibit phenotypic and functional characteristics of cytolytic T cells when activated. Several mechanisms have been demonstrated to account for their cytotoxicity. Among them, one is mediated by perforin and granzyme molecules, another is mediated by Fas ligand (FasL) which delivers apoptotic signals through Fas receptor on target cells. There is good evidence that a flat intestinal mucosa may be produced by activated T cells. The aim of our study was to evaluate FasL and perforin expression by IEL, and its possible correlation with the increased enterocyte apoptosis in coeliac mucosa. Endoscopic duodenal biopsy specimens from 10 untreated coeliac patients, 10 treated coeliac patients, and 10 biopsied controls were evaluated for enterocyte apoptosis by terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine triphosphate nick end label method, for perforin expression by immunohistochemistry, and for FasL expression by immunocytochemistry. In untreated CoD there was a significant increase of percentage of both FasL+ and perforin+ IEL which positively correlated with enterocyte apoptosis in comparison with controls. All these parameters were significantly lower in treated CoD, even though they did not normalize. Our study demonstrates that in untreated CoD FasL and perforin expression by IEL is increased, and significantly correlates with the level of enterocyte apoptosis.