Activation of caspases in intestinal villus epithelial cells of normal and nematode infected rats

Ferroptosis, Inflammation, and Microbiome Alterations in the Intestine in the Göttingen Minipig Model of Hematopoietic-Acute Radiation Syndrome

Hematopoietic acute radiation syndrome (H-ARS) involves injury to multiple organ systems following total body irradiation (TBI). Our laboratory demonstrated that captopril, an angiotensin-converting enzyme inhibitor, mitigates H-ARS in Göttingen minipigs, with improved survival and hematopoietic recovery, as well as the suppression of acute inflammation. However, the effects of captopril on the gastrointestinal (GI) system after TBI are not well known. We used a Göttingen minipig H-ARS model to investigate captopril's effects on the GI following TBI (60Co 1.79 or 1.80 Gy, 0.42-0.48 Gy/min), with endpoints at 6 or 35 days. The vehicle or captopril (0.96 mg/kg) was administered orally twice daily for 12 days, starting 4 h post-irradiation. Ilea were harvested for histological, protein, and RNA analyses. TBI increased congestion and mucosa erosion and hemorrhage, which were modulated by captopril. GPX-4 and SLC7A11 were downregulated post-irradiation, consistent with ferroptosis at 6 and 35 days post-irradiation in all groups. Interestingly, p21/waf1 increased at 6 days in vehicle-treated but not captopril-treated animals. An RT-qPCR analysis showed that radiation increased the gene expression of inflammatory cytokines IL1B, TNFA, CCL2, IL18, and CXCL8, and the inflammasome component NLRP3. Captopril suppressed radiation-induced IL1B and TNFA. Rectal microbiome analysis showed that 1 day of captopril treatment with radiation decreased overall diversity, with increased Proteobacteria phyla and Escherichia genera. By 6 days, captopril increased the relative abundance of Enterococcus, previously associated with improved H-ARS survival in mice. Our data suggest that captopril mitigates senescence, some inflammation, and microbiome alterations, but not ferroptosis markers in the intestine following TBI.

Exosomes Facilitate Transmission of Enterovirus A71 From Human Intestinal Epithelial Cells

BACKGROUND

Enterovirus A71 (EV-A71) has been noted for its tendency to lead to neurological manifestations in young children and infants. Although the alimentary tract has been identified as the primary replication site of this virus, how EV-A71 replicates in the gut and is transmitted to other organs remains unclear.

METHODS

By using differentiated C2BBe1 cells as a model, we observed that intestinal epithelial cells (IECs) were permissive to EV-A71 infection, and viral particles were released in a nonlytic manner.

RESULTS

The coexistence of active caspase 3 and EV-A71 protein was observed in the infected undifferentiated C2BBe1 and RD cells but not in the infected differentiated C2BBe1 cells. Furthermore, EV-A71 infection caused differentiated C2BBe1 and intestinal organoids to secrete exosomes containing viral components and have the ability to establish active infection. Inhibition of the exosome pathway decreased EV-A71 replication and release in IECs and increased the survival rates of infected animals.

CONCLUSIONS

Our findings showed that EV-A71 is able to be actively replicated in enterocytes, and that the exosome pathway is involved in the nonlytic release of viral particles, which may be useful for developing antiviral strategies.

Cell death in the gut epithelium and implications for chronic inflammation

The intestinal epithelium has one of the highest rates of cellular turnover in a process that is tightly regulated. As the transit-amplifying progenitors of the intestinal epithelium generate ~300 cells per crypt every day, regulated cell death and sloughing at the apical surface keeps the overall cell number in check. An aberrant increase in the rate of intestinal epithelial cell (IEC) death underlies instances of extensive epithelial erosion, which is characteristic of several intestinal diseases such as inflammatory bowel disease and infectious colitis. Emerging evidence points to a crucial role of necroptosis, autophagy and pyroptosis as important modes of programmed cell death in the intestine in addition to apoptosis. The mode of cell death affects tissue restitution responses and ultimately the long-term risks of intestinal fibrosis and colorectal cancer. A vicious cycle of intestinal barrier breach, misregulated cell death and subsequent inflammation is at the heart of chronic inflammatory and infectious gastrointestinal diseases. This Review discusses the underlying molecular and cellular underpinnings that control programmed cell death in IECs, which emerge during intestinal diseases. Translational aspects of cell death modulation for the development of novel therapeutic alternatives for inflammatory bowel diseases and colorectal cancer are also discussed.

Caspase-3 probes for PET imaging of apoptotic tumor response to anticancer therapy

Apoptosis is a highly regulated process involved in the normal organism development and homeostasis. In the context of anticancer therapy, apoptosis is also studied intensively in an attempt to induce cell death in cancer cells. Caspase activation is a known key event in the apoptotic process. In particular, active caspase-3 and -7 are the common effectors in several apoptotic pathways, therefore effector caspase activation may be a promising biomarker for response evaluation to anticancer therapy. Quantitative imaging of apoptosis in vivo could provide early assessment of therapeutic effectiveness and could also be used in drug development to evaluate the efficacy as well as potential toxicity of novel treatments. Positron Emission Tomography (PET) is a highly sensitive molecular imaging modality that allows non-invasive in vivo imaging of biological processes such as apoptosis by using radiolabeled probes. Here we describe the development and evaluation of fluorine-18-labeled caspase-3 activity-based probes (ABPs) for PET imaging of apoptosis. ABPs were selected by screening of a small library of fluorine-19-labeled DEVD peptides containing different electrophilic warhead groups. An acyloxymethyl ketone was identified with low nanomolar affinity for caspase-3 and was radiolabeled with fluorine-18. The resulting radiotracer, [18F]MICA-302, showed good labeling of active caspase-3 in vitro and favorable pharmacokinetic properties. A μPET imaging experiment in colorectal tumor xenografts demonstrated an increased tumor accumulation of [18F]MICA-302 in drug-treated versus control animals. Therefore, our data suggest this radiotracer may be useful for clinical PET imaging of response to anticancer therapy.

The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases

Glutamine, the most abundant free amino acid in the human body, is a major substrate utilized by intestinal cells. The roles of glutamine in intestinal physiology and management of multiple intestinal diseases have been reported. In gut physiology, glutamine promotes enterocyte proliferation, regulates tight junction proteins, suppresses pro-inflammatory signaling pathways, and protects cells against apoptosis and cellular stresses during normal and pathologic conditions. As glutamine stores are depleted during severe metabolic stress including trauma, sepsis, and inflammatory bowel diseases, glutamine supplementation has been examined in patients to improve their clinical outcomes. In this review, we discuss the physiological roles of glutamine for intestinal health and its underlying mechanisms. In addition, we discuss the current evidence for the efficacy of glutamine supplementation in intestinal diseases.

Synergistic effect of aluminum and ionizing radiation upon ultrastructure, oxidative stress and apoptotic alterations in Paneth cells of rat intestine

Environmental and occupational exposure to aluminum along with ionizing radiation results in serious health problems. This study was planned to investigate the impact of oxidative stress provoked by exposure to ionizing radiation with aluminum administration upon cellular ultra structure and apoptotic changes in Paneth cells of rat small intestine . Animals received daily aluminum chloride by gastric gavage at a dose 0.5 mg/Kg BW for 4 weeks. Whole body gamma irradiation was applied at a dose 2 Gy/week up to 8 Gy. Ileum malondialdehyde, advanced oxidative protein products, protein carbonyl and tumor necrosis factor-alpha were assessed as biomarkers of lipid peroxidation, protein oxidation and inflammation respectively along with superoxide dismutase, catalase, and glutathione peroxidase activities as enzymatic antioxidants. Moreover, analyses of cell cycle division and apoptotic changes were evaluated by flow cytometry. Intestinal cellular ultra structure was investigated using transmission electron microscope.Oxidative and inflammatory stresses assessment in the ileum of rats revealed that aluminum and ionizing radiation exposures exhibited a significant effect upon the increase in oxidative stress biomarkers along with the inflammatory marker tumor necrosis factor-α accompanied by a significant decreases in the antioxidant enzyme activities. Flow cytometric analyses showed significant alterations in the percentage of cells during cell cycle division phases along with significant increase in apoptotic cells. Ultra structurally, intestinal cellular alterations with marked injury in Paneth cells at the sites of bacterial translocation in the crypt of lumens were recorded. The results of this study have clearly showed that aluminum and ionizing radiation exposures induced apoptosis with oxidative and inflammatory disturbance in the Paneth cells of rat intestine, which appeared to play a major role in the pathogenesis of cellular damage. Furthermore, the interaction of these two intestinal toxic routes was found to be synergistic.

Insights into regulatory molecules of intestinal epithelial cell turnover during experimental infection by Heterophyes heterophyes

Heterophyiasis is an intestinal disease that remains endemic in many parts of the world, particularly the Nile Delta of Egypt and Southeast Asia, yet the populations at risk of infection expand throughout the world. The main histopathological feature of infection is villous atrophy, but the underlying factors are not well understood. Apoptosis of the villous epithelial cells was previously reported to be enhanced during intestinal parasitic infections; however, the role of Heterophyes heterophyes on enterocyte apoptosis was to be explored. Therefore, intestinal sections from mice experimentally infected with H. heterophyes were studied histopathologically and immunohistochemically for caspase-3 and NF-κB and compared to non-infected control mice. Atrophic villi covered by poorly differentiated epithelial cells were observed in the 2nd week post-infection. Also, we noted marked hyperplasia of the intestinal crypts with abundant inflammatory cellular infiltrate in the lamina propria, as well as apoptosis of cells lining the intestinal villi. Both caspase-3 and NF-κB showed positive staining in the intestinal epithelial cells with varying grades of intensity over the length of infection. Caspase-3 expression rose at the 2nd week p.i. then decreased over time, whereas NF-κB expression showed progressive increase throughout the weeks of infection. In conclusion, caspase-3 activation may be an important factor in the apoptotic pathway in early heterophyiasis, and, on the other hand, NF-κB seems to play a role in protecting the intestinal cells from excessive apoptosis. These observations may help open new avenues for tissue protective therapies that avoid or control the deleterious processes of apoptosis in various inflammatory conditions.

Beneficial effects of ulinastatin on gut barrier function in sepsis

BACKGROUND & OBJECTIVES

The gut contains some endogenous and exogenous microorganisms that can become potential pathogens of sepsis under certain circumstances. Therefore, the integrity and normal function of gut barrier is important for preventing the development of sepsis. The present study was designed to assess the effects of ulinastatin, a urinary trypsin inhibitor on gut barrier function and mortality in experimental sepsis.

METHODS

Male Sprague-Dawley rats were subjected to ceacal ligation and puncture (CLP) or sham procedure. Rats were then treated with ulinastatin 50,000 U/kg/day or saline. The mortality rate was determined. Histology, apoptosis assays, and PCR were performed using ileum specimens at 3, 6, and 12 h following CLP. Serum levels of tumour necrosis factor α (TNF-α) and interleukin-6 (IL-6) were also measured at 0, 3, 6, and 12 h following CLP.

RESULTS

Compared with the saline-treated CLP rats, the ulinastatin CLP rats had significantly increased survival time (P<0.05), lower histopathological scores of intestinal injury (P<0.05), reduced apoptosis detected by terminal deoxynucleotidyl transferase dUTP nick end labelling assay and caspase 3 activity (P<0.01). Moreover, RD-5 mRNA expression was significantly higher in ulinastatin-treated CLP animals than saline controls (P<0.05). These results suggested a preserved integrity and function of the gut barrier. Significantly lower plasma TNFα and IL-6 levels were detected in CLP rats with ulinastatin treatment, which contributed to increased survival time.

INTERPRETATION & CONCLUSIONS

Our results suggest that ulinastatin has a therapeutic potential to prevent gut barrier dysfunction in the early stage of sepsis, thereby improving the outcome of sepsis. Further studies need to be done to understand the mechanism of action of ulinastatin.

Immunological characteristics of patients infected with common intestinal helminths: results of a study based on reverse-transcriptase PCR

To determine whether common helminth infections could modify the intestinal immunopathological status of the host, the expression in the human duodenal mucosa of cytokines, eosinophil- and mast-cell-specific molecules and monosaccharide transporters of the glucose-transporter (GLUT) family was explored. The 31 subjects were all patients at the gastro-intestinal disease unit of Nongkhai Hospital, Thailand. Four of the 10 patients who presented with eosinophilia (> or = 6.0% of their leucocytes were eosinophils), and five of the other 21 patients, had intestinal infections with helminths when they presented or within the previous 3 months. Studies based on semi-quantitative, reverse-transcriptase PCR revealed that the interleukin-5/interferon-gamma ratio was significantly higher in the noneosinophilic, helminth-infected patients than in the non-eosinophilic, uninfected patients, whereas the IgE receptor type I (Fc epsilon RI)/mast-cell tryptase ratio was significantly higher in the eosinophilic, helminth-infected patients than in the eosinophilic, uninfected patients. Expression of Charcot-Leyden-crystal protein, GLUT-1 and GLUT-5, however, showed no significant inter-group differences. Principal-components analysis of the data on eosinophils, interleukin-5, interferon-gamma, Fc epsilon RI and mast-cell tryptase revealed that one principal component could discriminate the patients who had helminth infection from the non-eosinophilic, uninfected patients, but not from the eosinophilic, uninfected patients. These results indicate that, whatever the intestinal pathology, patients infected with common intestinal helminths tend to develop a mucosal immunological response of the Th2 type.

Dietary l-arginine supplementation improves the intestinal development through increasing mucosal Akt and mammalian target of rapamycin signals in intra-uterine growth retarded piglets

Intra-uterine growth retardation (IUGR) impairs postnatal growth and development of the small intestine (SI) in neonatal pigs and infants. l-Arginine (Arg), a critical amino acid involved in promoting growth and metabolism in young mammals, is more deficient in IUGR fetuses. However, little is known whether dietary Arg supplementation would accelerate the impaired development of the SI induced by IUGR in piglets. In the present study, a total of six litters of newborn piglets were used. In each litter, one normal and two IUGR littermates were obtained. Piglets were fed milk-based diets supplemented with 0 (Normal), 0 (IUGR) and 0·60% Arg (IUGR+Arg) from 7 to 14 d of age, respectively. Compared with Normal piglets at 14 d of age, IUGR decreased (P < 0·05) the growth performance, entire SI weight, and villus height in the jejunum and ileum. IUGR piglets had lower (P < 0·05) mucosal concentrations of Arg, insulin, insulin growth factor 1, as well as phosphorylated Akt, mammalian target of rapamycin (mTOR) and p70 S6 kinase but higher (P < 0·05) enterocyte apoptosis index (AI). After Arg treatment in IUGR piglets, the growth performance, weight of entire SI and mucosa, and villus height in the jejunum and ileum were increased (P < 0·05). Diet supplemented with Arg also increased (P < 0·05) the levels of Arg, insulin, phosphorylated Akt and mTOR in SI mucosa of IUGR piglets, and decreased (P < 0·05) the AI and caspase-3 activity. In conclusion, Arg has a beneficiary effect in improving the impaired SI development in IUGR piglets via regulating cell apoptosis and activating Akt and mTOR signals in SI mucosa.

[Ca(2+)]i homeostasis and caspase-3 gene expression in verapamil-induced retinal pigment epithelium cells apoptosis in vitro

AIM

To study caspase-3 gene expression and [Ca(2+)]i homeostasis in verapamil (Ver)-induced human retinal pigment epithelium (RPE) cells apoptosis.

METHODS

Ver 80mg/L was applied in cultured human RPE cells for 12, 24 and 48 hours to induce RPE cells apoptosis. The expression of apoptotic effector gene caspase-3 was assessed by reverse transcription polymerase chain reaction (RT-PCR). Single cell was measured using fluorescence indicator Fura-3/AM with MetaFluo4.5/coolsnapfx/IX70 intracellular Ca(2+) fluorescence imaging system.

RESULTS

High levels of expression of caspase-3 mRNA were observed in normal RPE cells and it significantly increased after co-cultured with Ver. The fluorescence in resting RPE cells was strong and distributed throughout the cells. The nucleus appeared more fluorescent than the cytoplasm. Calcium fluorescence of RPE cells attenuated after co-cultured with Ver.

CONCLUSION

Up-regulation of caspase-3 gene expression and disturbance of [Ca(2+)]i homeostasis might play pivotal roles in Ver-induced RPE cells apoptosis.

Depleted intestinal goblet cells and severe pathological changes in SCID mice infected with Heligmosomoides polygyrus

To determine the role of T cells and mast cells in intestinal pathology and immune expulsion of intestinal nematodes, worm burdens, goblet cell responses and villus structures were analysed in T- and B-cell-deficient severe combined immunodeficiency (SCID) mice, athymic nu/nu mice and mast cell deficient W/W(v) mice after infection with the nematode Heligmosomoides polygyrus. SCID and nu/nu mice showed significantly higher worm burdens at week 9 post-infection compared with the wild-type controls. SCID and nu/nu mice showed compromised goblet cell hyperplasia and/or Muc 2 expression, indicating that both events are T-cell dependant. On the other hand, the SCID mice showed increased pathology (villus atrophy and crypt hyperplasia) and increased numbers of proliferating cell nuclear antigen positive cells compared to the wild-type controls. W/W(v) mice, conversely, were able to expel the worms normally, had normal goblet cell hyperplasia, and did not demonstrate the changes in mucosal architecture seen in SCID mice, confirming that a normal mast cell response is not necessarily required for these changes. These results suggest that a functional T-cell response, but not a mast cell response, is necessary for anti-parasite responses, goblet cell function, and maintaining normal mucosal architecture.

Indigestible Material Attenuated Changes in Apoptosis in the Fasted Rat Jejunal Mucosa

We have previously demonstrated that fasting induced apoptosis and decreased cell proliferation in the rat intestinal mucosa. The aim was to investigate the effect of expanded polystyrene as indigestible material on apoptosis and cell proliferation in rat small intestinal mucosa during fasting. Male SD rats were divided into 3 groups. The first group was fed with chow and water ad libitum. The second group fasted for 72 hrs. The third group was fasted for 24 hrs and was fed expanded polystyrene. Intestinal apoptosis was evaluated by percent fragmented DNA assay, terminal deoxynucleotidyl transferase–mediated dUDP-biotin nick end-labeling (TUNEL) staining, and caspase-3 assay. Cell proliferation was analyzed by 5-bromo-2′-deoxyuridine (5-BrdU) uptake. Truncal vagotomy was performed to evaluate a role of the central nervous system. In the 72-hr fasted rat, mucosal height of the rat jejunum was decreased to 73% of that in rats fed ad libitum, and this decrease was partly restored to 90% in rats fed expanded polystyrene. The fragmented DNA was increased in fasted rats (28.0%) when compared with that in rats fed ad libitum (2.6%). The increase in fragmented DNA in fasted rats was recovered by feeding them expanded polystyrene (8.3%). TUNEL staining confirmed this result. The effect of polystyrene on apoptosis was decreased by truncal vagotomy. Expression of cleaved caspase-3 was increased in fasted rats, which was then decreased by feeding of expanded polystyrene. In contrast to apoptosis, feeding of expanded polystyrene had no reconstructive effect on 5-BrdU uptake in the intestinal epithelium, which was decreased by fasting to 60% of that in rats fed ad libitum. In conclusion, feeding of indigestible material partly restored the decrease in intestinal mucosal length in the fasted rats through the apoptotic pathway without any influence on BrdU uptake. Further exploration focused on the mechanism of this effect of indigestible material is required.

T cell-dependent and -independent expression of intestinal epithelial cell-related molecules in rats infected with the nematode Nippostrongylus brasiliensis

To determine how T cells of thymic origin regulate the intestinal mucous response induced by nematode infection, mucin production and goblet cell-specific secretory peptide expression were examined in euthymic rnu/+ and athymic rnu/rnu rats infected with the nematode Nippostrongylus brasiliensis. Euthymic rats showed transient goblet cell hyperplasia and upregulation of mucin production, which returned to preinfection levels by 21 days postinfection, when nematodes had been rejected from the intestine. In athymic rats, which failed to reject nematodes, goblet cell hyperplasia and accelerated mucin production continued at least until 21 days postinfection. Gene transcription of mucin-core peptide (MUC)-2 and -3 and trefoil factor (TFF)-2 and -3 in the jejunal epithelium was upregulated parallel to the levels of goblet cell hyperplasia in both euthymic and athymic rats. On the other hand, resistin-like molecule (Relm)beta, sialyltransferase Siat4c and sulfotransferase 3ST1 showed significantly higher transcription levels in euthymic than in athymic rats at 7 and/or 10 days postinfection. These results suggest that the induction of intestinal mucin production occurs without the activation of thymus-derived T cells, while the expression of Relmbeta, Siat4c and 3ST1 in the intestinal epithelial cells seems to be regulated at least partly by thymus-dependent mechanisms.

Apoptotic pathway in the rat small intestinal mucosa is different between fasting and ischemia-reperfusion

We have previously demonstrated that fasting and ischemia-reperfusion (I/R) induced apoptosis in rat intestinal mucosa. It is widely accepted that apoptosis is induced through two main pathways. This study aimed to compare apoptotic pathways following fasting and I/R. Rats were divided into two groups: the I/R group involved occlusion of the superior mesenteric artery for 60 min, followed by 60-min reperfusion, whereas the fasting group involved fasting for 24 or 48 h. Intestinal apoptosis was assessed as percentage of fragmented DNA, by electrophoresis and by a terminal deoxynucleotidyl transferase mediated dUDP-biotin nick- end labeling (TUNEL) assay. Apoptotic proteins including death ligands/receptors and caspases were evaluated by Western blot analysis. Small intestinal mucosal height and mitochondrial dehydrogenase function were assessed. Fasting and I/R significantly induced intestinal apoptosis. Mucosal height was significantly decreased in fasting rats, and mitochondrial dysfunction was induced only by I/R. Expressions of Fas, Fas ligand, and TNF-alpha type 1 receptor were enhanced in fasting and I/R rats. After I/R, expressions of cytochrome c and cleaved caspase-9 were significantly increased. In contrast, expressions of cleaved caspase-8 and cleaved caspase-3 increased in fasting rats. Fasting promoted mucosal apoptosis via a receptor-mediated type I apoptotic pathway in the rat small intestine, and I/R induced apoptosis via a mitochondria-mediated type II pathway.

Altered expression of goblet cell- and mucin glycosylation-related genes in the intestinal epithelium during infection with the nematode Nippostrongylus brasiliensis in rat

Intestinal nematode infection induces marked goblet cell hyperplasia and mucus secretion, but the mechanisms of regulation of the changes still remain to be elucidated. In the present study, epithelial cells were isolated from the rat small intestine at various times after Nippostrongylus brasiliensis infection, and the levels of expression of goblet cell- and mucin glycosylation-related genes were estimated by semi-quantitative reverse transcription (RT)-PCR. Among the genes investigated, mucin core peptide (MUC) 2, sialyltransferase (Siat) 4c and trefoil factor family (TFF) 3 were upregulated as early as 2-4 days post-infection, suggesting that they are associated with an early innate protective response. Seven days post-infection and thereafter, when the nematodes reached maturity, significant upregulation of MUC3, MUC4, resistin-like molecule beta (Relmbeta) and 3O-sulfotransferase (3ST)1 was observed, while 3ST2 expression levels increased after the majority of the worms were expelled from the intestine. Similar alterations of glycosylation-related gene expression were also observed in mast-cell-deficient Ws/Ws rats, suggesting that mast cells in the epithelium are not relevant to the upregulation of these genes. The present finding that the expression level of each goblet cell- or glycosylation-related gene was altered differently during the time course of infection indicates the progression of sequential qualitative changes in the mucus layer after infection.

Intestinal damage in strongyloidiasis: the imbalance between cell death and proliferation

Strongyloidiasis is an endemic tropical parasitosis caused by Strongyloides stercoralis that also affects immigrants in nontropical countries. The nematode colonizes the duodenum and upper jejunum, inducing mucosal alterations. Because integrity is essential for a functional barrier, we aimed to study apoptosis and proliferation in the small bowel epithelium infected with S. stercoralis. We evaluated 23 patients and 17 controls. Apoptotic cells were detected by TUNEL and M30 immunolabelling, whereas proliferation was scored by Ki67 immunostaining and mitotic counting. Infection increased apoptotic indices in duodenum and jejunum (P < 0.001). Conversely, it decreased cell proliferation in both segments (P < 0.001). Our results showed that intestinal strongyloidiasis promotes an imbalance between cell death and proliferation. This is the first evidence of disruption of the epithelial kinetics with S. stercoralis infection, though the mechanisms remain unclear. Furthermore, our results support the idea that strongyloidiasis disturbs the mucosal integrity and can compromise the intestinal barrier.

Villus epithelial injury induced by infection with the nematode Nippostrongylus brasiliensis is associated with upregulation of granzyme B

Intestinal parasite infections induce thymus-dependent villus atrophy, but the effector mechanisms directly responsible for the development of villus atrophy are not thoroughly understood. In this study, we analyzed the expression of cytotoxic factors or ligands in athymic nude rnu/rnu rats and their littermate euthymic rnu/+ rats infected with the nematode Nippostrongylus brasiliensis. Morphometric analyses showed that partial villus atrophy developed 10 days after infection in euthymic but not in athymic rats, whereas crypt hyperplasia occurred in both types of animal. Reverse transcription-polymerase chain reaction analyses of the isolated jejunal epithelial fraction showed that the development of villus atrophy in euthymic rats was positively correlated with an increase of granzyme B transcript levels but not with Fas ligand or tumor necrosis factor-alpha expression. In addition, the number of granzyme B-immunoreactive cells was increased significantly in euthymic rat villus epithelium and the propria mucosa after infection. The CD8+ cell number did not change significantly. Collectively, these findings showed that significant increases in the number of cells that express the cytotoxic factor granzyme B occur in the nematode-infected small intestine of immunocompetent hosts. The type of cells that express granzyme B and their role in the progression of enteropathy remain to be elucidated.

Intectin, a Novel Small Intestine-specific Glycosylphosphatidylinositol-anchored Protein, Accelerates Apoptosis of Intestinal Epithelial Cells

Intestinal epithelial cells undergo rapid turnover and exfoliation especially at the villus tips. This process is modulated by various nutrients especially fat. Apoptosis is one of the important regulatory mechanisms of this turnover. Therefore, identification of the factors that control epithelial cell apoptosis should help us understand the mechanism of intestinal mucosal turnover. Here, we report the identification of a novel small intestine-specific member of the Ly-6 family, intectin, by signal sequence trap method. Intectin mRNA expression was exclusively identified in the intestine and localized at the villus tips of intestinal mucosa, which is known to undergo apoptosis. Intectin mRNA expression was modulated by nutrition. Intestinal epithelial cells expressing intectin were more sensitive to palmitate-induced apoptosis, compared with control intestinal epithelial cells, and such effect was accompanied by increased activity of caspase-3. Intectin expression also reduced cell-cell adhesion of intestinal epithelial cells.

Uteroplacental insufficiency decreases small intestine growth and alters apoptotic homeostasis in term intrauterine growth retarded rats

Human and animal studies demonstrate that uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) decrease intestinal growth and lead to both an increased incidence of feeding intolerance and necrotizing enterocolitis. Our objective was to determine the effects of uteroplacental insufficiency upon small intestine growth, histology, gene expression of the apoptosis related proteins Bcl-2, Bax and p53, and caspase-3 activity. For this purpose, we induced uteroplacental insufficiency through bilateral uterine artery ligation on day 19 of gestation in fully anesthetized pregnant Sprague-Dawley rats and harvested pups at term 2 days latter. Pups from sham surgeries served as controls. Uteroplacental insufficiency reduced cell count per crypt and decreased small intestinal weight. In association with these changes, IUGR intestinal Bcl-2 mRNA levels were decreased significantly, and Bax and p53 mRNA were significantly increased in distal ileum. Immunohistochemistry for Bcl-2, Bax, and p53 revealed similar findings. In association with the decreased Bcl-2 and the increased Bax gene expression, increased caspase-3 activity characterized the IUGR distal ileum. We conclude that uteroplacental insufficiency affects intestinal growth and morphology in association with altered gene expression of apoptosis related proteins. We speculate that the morphological change and associated altered apoptotic homeostasis contribute to the increased morbidity of infants affected by uteroplacental insufficiency.

Alterations in hexose, amino acid and peptide transporter expression in intestinal epithelial cells during Nippostrongylus brasiliensis infection in the rat

Infection with the nematode Nippostrongylus brasiliensis induces various types of cytological alterations in the intestinal villus epithelium. The aim of this study was to analyse the expression of hexose, peptide and amino acid transporters in the small intestinal epithelium after infection. Brown-Norway rats were infected with 2000 N. brasiliensis L3 larvae and villus epithelial cells were isolated at various time points after infection. Expression of hexose transporters Na(+)/glucose cotransporter SGLT1 and glucose transporter GLUT-1, -2 and -5, a peptide transporter (PepT1) and an amino acid transporter (LAT2) was examined by reverse transcription-PCR, Western blotting or immunohistochemistry. Semi-quantitative reverse transcription-PCR studies of separated jejunal epithelial cells showed that expression levels of GLUT5, PepT1 and LAT2 were significantly decreased 7 and 14 days after infection, while these changes were not observed in the ileal epithelium. Although the apical surface glucose transporter SGLT1 showed no significant alteration in mRNA expression, Western blotting analyses of jejunal epithelial cell lysate showed a marked decrease. Contrary to SGLT1, GLUT5, PepT1 and LAT2, expression of GLUT1, which is essential in maintaining high rates of glucose influx, was significantly up-regulated in the jejunal epithelium 7 and 14 days after infection in reverse transcription-PCR as in Western blotting analyses. Immunohistochemical studies showed that GLUT1 immunoreactivity was localised to the basolateral membrane of intestinal epithelial cells 7 days after infection. These results show that N. brasiliensis infection results in an increase in GLUT1 and a decrease in various hexose, amino acid and peptide transporter expression in jejunal epithelial cells. Up-regulation of GLUT1 might be a compensatory response in injured epithelial cells.

General suitability of techniques for in situ detection of apoptosis in small intestinal epithelium

The present study was designed to evaluate different techniques for the in situ detection of apoptosis in human and rat small intestinal epithelium. The techniques included light microscopy (LM) and transmission electron microscopy (TEM) observation of epoxy resin-embedded tissue, scanning electron microscopy (SEM), TUNEL assay, and antibodies directed against caspase cleavage products of caspase 3, cytokeratin 18 (CK 18), and apoptotic single-strand DNA (ssDNA). All techniques, if the labeling was positive, showed apoptotic cells exclusively at the villus tip. LM and TEM were the most reliable and revealed morphological signs typical of cells that have died via apoptosis. SEM indicated the extension of the process. The antibody recognizing cleaved caspase 3 could be considered an appropriate marker for apoptotic epithelial cells in human and rat small intestine. However, the majority of epithelial cells lining the proximal small intestinal villus contained only low levels of intact CK 18. Therefore, sufficient amounts of cleaved CK 18 for immunohistochemical detection were not generated during apoptosis, rendering the application of the antibody inappropriate. The antibody detecting formamide-denatured ssDNA in apoptotic cells was both suitable and reliable; however, the particular staining procedure used compromised the tissue preservation. In comparison to this, the TUNEL assay was less reliable. Although it was performed with a commercially available ready-to-use kit, its application conditions had to be adjusted for each specimen on the basis of the findings produced by other techniques.

Quantification of G6PD in small and large intestine of rat during aging

Numerous studies have demonstrated a decrease in glucose-6-phosphate dehydrogenase (G6PD) activity during aging in many cell types, including red blood cells, fibroblasts and lens cells. Moreover, the intracellular activity of G6PD has been shown to be regulated by binding to cell organelles. To investigate whether binding of G6PD to cell organelles is related with the decrease in its activity during aging, distribution patterns of G6PD activity and protein were assessed in small (SI) and large (LI) intestine of 3-month-old and 28-month-old rats. Enzyme activity, as measured spectrophotometrically, did not show any significant change with aging in SI or LI. Enzyme histochemistry, performed by subtracting activity staining of 6-phosphogluconate dehydrogenase (6PGD) from that of G6PD, showed a lower net G6PD activity in SI and LI epithelium of old rats in comparison with young rats. G6PD activity did not change significantly with aging in the muscularis externa of SI and LI. Immunoelectron microscopic analysis of G6PD protein allowed us to measure the density of G6PD molecules in cellular compartments, and the fraction of enzyme bound to cell organelles. In SI and LI epithelia, density of G6PD molecules was higher in old rats than in young rats; however, the fraction of enzyme bound to cell organelles also increased with aging. These data suggest that G6PD activity in epithelium of SI and LI decreases with aging due to the accumulation of significant amounts of enzyme bound to cell organelles, a condition which makes it less active than the soluble enzyme.