Increased small bowel epithelial turnover in interleukin-1 receptor knockout mice

Schlafen 12 Interaction with SerpinB12 and Deubiquitylases Drives Human Enterocyte Differentiation

BACKGROUND/AIMS

Human enterocytic differentiation is altered during development, fasting, adaptation, and bariatric surgery, but its intracellular control remains unclear. We hypothesized that Schlafen 12 (SLFN12) regulates enterocyte differentiation.

METHODS

We used laser capture dissection of epithelium, qRT-PCR, and immunohistochemistry to evaluate SLFN12 expression in biopsies of control and fasting human duodenal mucosa, and viral overexpression and siRNA to trace the SLFN12 pathway in human Caco-2 and HIEC6 intestinal epithelial cells.

RESULTS

Fasting human duodenal mucosa expressed less SLFN12 mRNA and protein, accompanied by decreases in enterocytic markers like sucrase-isomaltase. SLFN12 overexpression increased Caco-2 sucrase-isomaltase promoter activity, mRNA, and protein independently of proliferation, and activated the SLFN12 putative promoter. SLFN12 coprecipitated Serpin B12 (SERPB12). An inactivating SLFN12 point mutation prevented both SERPB12 binding and sucrase-isomaltase induction. SERPB12 overexpression also induced sucrase-isomaltase, while reducing SERPB12 prevented the SLFN12 effect on sucrase-isomaltase. Sucrase-isomaltase induction by both SLFN12 and SERPB12 was attenuated by reducing UCHL5 or USP14, and blocked by reducing both. SERPB12 stimulated USP14 but not UCHL5 activity. SERPB12 coprecipitated USP14 but not UCHL5. Moreover, SLFN12 increased protein levels of the sucrase-isomaltase-promoter-binding transcription factor cdx2 without altering Cdx2 mRNA. This was prevented by reducing UCHL5 and USP14. We further validated this pathway in vitro and in vivo. SLFN12 or SERPB12 overexpression induced sucrase-isomaltase in human non-malignant HIEC-6 enterocytes.

CONCLUSIONS

SLFN12 regulates human enterocytic differentiation by a pathway involving SERPB12, the deubiquitylases, and Cdx2. This pathway may be targeted to manipulate human enterocytic differentiation in mucosal atrophy, short gut or obesity.

Significance of IL-1RA Polymorphism in Iranian Patients with Inflammatory Bowel Disease

BACKGROUND AND AIM

Interleukin (IL)-1 family members play an important role in the pathogenesis of inflammatory bowel disease (IBD). There are conflicting results regarding the association of IL-1 gene cluster single nucleotide polymorphisms (SNPs) with IBD and its clinical features. The aim of this study was to examine IL-1α -889 C/T, IL-1β -511 C/T, IL-1β +3962 C/T, IL-1R Pst-I1970 C/T, and IL-1RA Mspa-I11100 C/T SNPs in Iranian patients.

METHODS

In this study, SNPs of IL-1 family members were investigated in 75 patients with IBD (40 CD and 35 UC), using polymerase chain reaction with sequence-specific primers method.

RESULTS

IL-1β -511 CC genotype was significantly less present in UC compared to controls, while IL-1RA Mspa-I11100 CC was significantly associated with both Crohn's disease (CD) and ulcerative colitis (UC). IL-1α -889 TT genotype was more frequently associated with extraintestinal manifestations. A significant association was observed between IL-1β +3962 TT genotype and the disease activity in IBD. IL-1RA Mspa-I11100 CC was significantly less frequent in CD patients who need immunosuppressive therapy. IL-1RA Mspa-I11100 CT was associated with earlier age of onset in IBD, while TT genotype was associated with higher age of onset in IBD.

CONCLUSIONS

IL-1 SNPs seem to be associated with IBD and could affect the disease severity as well.

Parenteral glutamine supplementation in combination with enteral nutrition improves intestinal immunity in septic rats

OBJECTIVES

The gut-associated lymphoid tissue is continuously exposed to antigens in the gut lumen and becomes the first line of defense against enteric bacteria and associated toxin. The aim of this study was to investigate the effects of parenteral glutamine (GLN) supplementation in combination with enteral nutrition (EN) on intestinal mucosal immunity in septic rats by cecal ligation and puncture (CLP).

METHODS

Male Sprague-Dawley rats were randomly assigned into four groups: A sham CLP + EN + saline group (n = 10), a sham CLP + EN + GLN group (n = 10), a CLP + EN + saline group (n = 10), and a CLP + EN + GLN group (n = 10). At 2 h after CLP or sham CLP, all rats in each of the four groups received an identical enteral nutrition solution as their base formula. Then, the rats in the sham CLP + EN + GLN group and CLP + EN + GLN group were given 0.35 g GLN/kg body weight daily for 7 d, all at the same time, via a tail vein injection; whereas those in the sham CLP + EN + saline group and CLP + EN + saline group were daily administered isovolumic sterile 0.9% saline for comparison. All rats in each of the four groups were given 290 kcal/kg body wt/d for 7 d. At the end of the seventh day after the nutritional program was finished, all rats were euthanized and the entire intestine was collected. Total Peyer's patches (PP) cell yield was counted by a hemocytometer. The percentage of PP lymphocyte subsets was analyzed by flow cytometry. The number of intestinal lamina propria IgA plasma cells was determined by the immunohistochemistry technique. The intestinal immunoglobulin A (IgA) levels were assessed by ELISA. PP apoptosis was evaluated by terminal deoxyuridine nick-end labeling.

RESULTS

The results revealed total PP cell yield, the numbers of PP lymphocyte subsets, intestinal lamina propria IgA plasma cells, and intestinal IgA levels in the CLP + EN + GLN group were significantly increased when compared with the CLP + EN + saline group (P < 0.05). On the other hand, the number of TUNEL-stained cells within PPs in the CLP + EN + GLN group was markedly decreased as compared with the CLP + EN + saline group (P < 0.05).

CONCLUSION

The results of this study show that parenteral glutamine supplementation in combination with enteral nutrition may attenuate PP apoptosis, increase PP cell yield and intestinal lamina propria IgA plasma cells, and subsequently improve intestinal mucosal immunity. Clinically, these results suggest therapeutic efforts at improving intestinal immunity may contribute to the prevention and treatment of sepsis.

Proximal gut mucosal epithelial homeostasis in aged IL-1 type I receptor knockout mice after starvation

BACKGROUND

Previous studies have shown that starvation induces small bowel atrophy, and that atrophy diminishes with aging. In this experiment, we assessed whether starvation-induced atrophy of proximal gut mucosa is associated with the Interleukin-1 receptor (IL-1R) signaling pathway in aged mice.

MATERIALS AND METHODS

Thirty 26-month-old IL-1R knockout mice and age-matched wild-type C57BL/6 mice were randomly divided into two groups: ad libitum fed and fasted. Mice were euthanized 12 or 48 hours after starvation. The proximal small bowel was harvested for morphologic analysis. Gut epithelial cell proliferation was detected using immunohistochemical staining for proliferating cell nuclear antigen (PCNA), and apoptosis was identified using terminal deoxyuridine nick-end labeling (TUNEL) staining.

RESULTS

Aged IL-1R knockout mice were larger than aged-matched wild-type mice (P < 0.05). Proximal gut mucosal height and mucosal cell number were not different between aged IL-1R knockout and wild-type groups. The apoptosis index in gut epithelial cells was higher in fed IL-1R knockout versus wild-type mice (P < 0.05), while there was no significant difference in cell proliferation between both groups. Mucosal atrophy was induced in both aged IL-1R knockout and wild-type groups by starvation (P < 0.05), however, aged IL-1R knockout mice experienced greater loss in proximal gut weight, mucosal length, and corresponding cell number than did wild-type mice at the 12-h time point (P < 0.05). The apoptosis index in gut epithelial cells significantly increased in both groups after starvation (P < 0.05). Starvation decreased cell proliferation in IL-1R knockout mice (P < 0.05), but not in wild-type mice.

CONCLUSIONS

The response in aged IL-1R knockout mice differs from wild-type mice in that starvation increases atrophy and is associated with decreased cell proliferation rather than increased apoptosis.

Medium-chain triglycerides enhance mucous secretion and cell proliferation in the rat

BACKGROUND

The specific purpose of this study was to investigate the effects of medium-chain triglycerides (MCTs) on intestinal cell proliferation and mucous secretion of the small intestine in the rat.

METHODS

Rats were fed chow diet and given MCTs or the same weight of corn oil (5 g/kg per day) by gavage daily for 2 weeks, and then tissue samples of the small intestines were harvested. Leptin concentration in the small intestine was measured. Cell proliferation and apoptosis in the small intestine was determined by immunohistochemistry. Diamine oxidase (DAO) activity was measured by colorimetric assay.

RESULTS

In rats fed only chow diet (normal rats), the number of goblet cells per villi was 14.2 +/- 0.75 in the jejunum and 15.2 +/- 1.12 in the ileum. The number of goblet cells increased significantly in rats given MCTs compared with rats given corn oil or normal rats. Ki-67-positive cells were detected on the entire villi and the crypts in the small intestine. Furthermore, the proliferative index and the apoptotic index were also significantly greater in rats given MCTs than rats given corn oil or normal rats. Moreover, DAO activity and leptin concentration in the small intestine were significantly greater in rats given MCTs than rats given corn oil or normal rats.

CONCLUSIONS

MCTs enhance cell proliferation of the intestinal epithelium and mucous secretion from goblet cells in the small intestine. These effects may protect the gut in patients suffering from inflammatory bowel disease or enterogenous infection.

Second hit post burn increased proximal gut mucosa epithelial cells damage

Secondary infections after burn are common and are a major contributor to morbidity and mortality. We previously showed that burn disrupted proximal gut mucosal homeostasis through increased epithelial cell apoptosis. In the present study, we sought to determine whether proximal gut mucosal disruption is additively affected by secondary endotoxemia after a severe burn. C57BL/6 mice received 30% total body surface area full-thickness scald burns and were randomized to receive saline or LPS 1 mg/kg body weight given intraperitoneally 72 h after burn. Proximal small bowel was harvested 12 h after LPS injection. Mucosal height and epithelial cell number were assessed on hematoxylin-eosin sections, intestinal epithelial cell apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen. Results showed that proximal gut mucosa impairment occurred 12 h after injury, including significantly decreased proximal gut wet weight, gut mucosal height, and epithelial cell number associated with increased proximal gut epithelial apoptosis (P < 0.05). This impairment diminished 72 h after burn. Second-hit endotoxemia caused additional proximal gut mucosa damage with decreased proximal gut weight, cell number, and mucosal height (P < 0.05) and significantly increased small intestinal epithelial apoptosis and mucosal atrophy, even after the first event, indicating a second detrimental effect of endotoxemia after the initial injury.

Weaning is associated with an upregulation of expression of inflammatory cytokines in the intestine of piglets

Cytokines play a central role in immune cell response, but they also participate in the maintenance of tissue integrity. Changes in the cytokine network of the pig gut may be expected at weaning, because abrupt changes in dietary and environmental factors lead to important morphological and functional adaptations in the gut. This study measured the gene expression of 6 inflammatory cytokines along the small intestine (SI) and the proximal colon in 28-d-old piglets (n = 45) at different time points (0, 1, 2, 5 and 8 d) postweaning, using RT-PCR. Villus-crypt architecture and enzymatic activities of lactase and sucrase in the SI were also examined. The results confirmed that weaning is associated with morphological and enzymatic changes in the SI. In addition, the data indicated that cytokine response in the gut could be divided into two periods: an early acute response (0 to 2 d postweaning) and a late long-lasting response (2 to 8 d postweaning). Between d 0 and d 2, the levels of IL-1beta, IL-6, and TNF-alpha messenger RNA (mRNA) increased. Marked upregulation of IL-1beta mRNA occurred in most parts of the intestine, whereas IL-6 and TNF-alpha mRNA markedly increased only at specific sites in the intestine. Between d 2 and d 8, the levels of IL-1beta, IL-6, and TNF-alpha mRNA rapidly returned to preweaning values, except that the level of TNF-alpha mRNA remained high in the distal SI. Levels of IL-12 subunit p40 (IL-12p40) and IL-18 mRNA also decreased, compared to those on d 0. Taken together, these results demonstrate that weaning in piglets is associated with an early and transient response in gene expression of inflammatory cytokines in the gut.

Burn-Induced Gut Mucosal Homeostasis in TCR ?? Receptor-Deficient Mice

Gammadelta T lymphocytes make up approximately 50% of lymphocytes in the intestine. These cells have been shown to prime macrophages for TNF-alpha production after burn. We previously showed that neutralizing anti-TNF-alpha antibodies reduce mucosal atrophy by decreasing gut epithelial apoptosis after severe burn. We hypothesized that burn-induced mucosal turnover is diminished in T cell receptor delta gene knockout (TCR delta-/-) mice through diminished TNF-alpha activity. Forty-two wild-type and 42 TCR delta-/- mice (C57-BL6) were randomly assigned to burn and sham burn groups. The burn group underwent a 25% total body surface area (TBSA) scald burn. The proximal small intestine was harvested at 2, 12, and 48 h. To assess mucosal atrophy, mucosal height and cell numbers in the villi and crypts were determined on hematoxylin and eosin-stained tissue sections. Apoptotic gut epithelium was identified by terminal deoxyuridine nick-end labeling (TUNEL) staining, and cell proliferation was detected by immunostaining for proliferative cell nuclear antigen (PCNA). TNF-alpha mRNA expression was measured by RT-PCR. Caspase-8 activity was measured by colorimetric assay. Statistical analysis was performed with two-way analysis of variance and t testing. Significance was accepted at P < 0.05. Data are expressed as means +/- SEM. TNF-alpha mRNA expression was significantly decreased in TCR delta-/- mice at 2 h after burn. Gut epithelial apoptosis and proliferation in both wild-type and TCR delta-/- mice were significantly increased after burn, but TCR delta-/- mice had a significantly lower levels of apoptosis (P < 0.01) and proliferation (P < 0.05) when compared with wild-type mice. Burn-induced mucosal atrophy was identified in groups by decreasing villus height, crypt depth, and villus and crypt cell number (P < 0.001) compared with sham, but no difference was found between wild-type and TCR delta-/- mice. Caspase-8 activity was significantly diminished in TCR delta-/- mice compared with wild-type mice. Gammadelta T cells are associated with increased TNF-alpha expression and gut epithelial turnover in the small bowel after severe burn. However, absence of delta T cell receptor did not inhibit mucosal atrophy after severe burn. This study suggests that gut mucosal atrophy after severe burn is a multifactorial process associated with increased TNF-alpha activity.

The matrix metalloproteinase system: changes, regulation, and impact throughout the ovarian and uterine reproductive cycle

The ovary and uterus undergo extensive tissue remodeling throughout each reproductive cycle. This remodeling of the extracellular environment is dependent upon the cyclic hormonal changes associated with each estrous or menstrual cycle. In the ovary, tissue remodeling is requisite for growth and expansion of the follicle, breakdown of the follicular wall during the ovulatory process, transformation of the postovulatory follicle into the corpus luteum, as well as the structural dissolution of the corpus luteum during luteal regression. In the uterus, there is extraordinary turnover of the endometrial connective tissue matrix during each menstrual cycle. This turnover encompasses the complete breakdown and loss of this layer, followed by its subsequent regrowth. With implantation, extensive remodeling of the uterus occurs to support placentation. These dynamic changes in the ovarian and uterine extracellular architecture are regulated, in part, by the matrix metalloproteinase (MMP) system. The MMP system acts to control connective tissue remodeling processes throughout the body and is comprised of both a proteolytic component, the MMPs, and a regulatory component, the associated tissue inhibitors of metalloproteinases. The current review will highlight the key features of the MMPs and tissue inhibitors of metalloproteinases, focus on the changes and regulation of the MMP system that take place throughout the estrous and menstrual cycles, and address the impact of the dynamic tissue remodeling processes on ovarian and uterine physiology.

Interleukin-1beta expression in human gastric carcinoma with Epstein-Barr virus infection

The KT tumor is a transplantable strain of a human Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC), established in severe combined immunodeficiency (SCID) mice, with which the cytokine expression of EBVaGC can be investigated without interference from the infiltrating lymphocytes. As a part of a high-density oligonucleotide array (GeneChip) analysis of EBVaGC, the interleukin-1beta (IL-1beta) gene was the only cytokine gene that showed markedly higher expression in the KT tumor cells than in two tumor strains of EBV-negative GC. The results were confirmed by Northern blotting, Western blotting, and enzyme-linked immunosorbent assay. Furthermore, we demonstrated a positive signal for IL-1beta mRNA in the carcinoma cells of a surgically resected EBVaGC, but not in EBV-negative GC, by in situ hybridization. In vitro, IL-1beta increased the cell growth of a GC cell line, TMK1. Thus, IL-1beta may act as an autocrine growth factor in EBVaGC.

Endogenous IL-1 and type II IL-1 receptor expression modulate anoikis in intestinal epithelial cells

We previously reported that IL-1beta and the decoy receptor for IL-1 (IL-1RII) are expressed by intestinal epithelial cells (IEC) during detachment-induced cell death, or "anoikis." We now investigated whether IL-1 regulates anoikis. Skewing the balance in favor of IL-1, by blocking IL-1RII or by adding IL-1beta to detached rat IEC-18 cells, reduced cell death. The protective effect of anti-IL-1RII was reversed by blocking IL-1beta, confirming the anti-apoptotic effect was due to endogenous IL-1beta. Added IL-1beta also rescued cells from anoikis and was associated with considerable aggregation of the detached cells. Aggregate formation and the anti-apoptotic effect of added IL-1beta were prevented by blocking E-cadherin, indicating that IL-1 promoted aggregation and indirectly, survival. On the other hand, treating detached cells with IL-1beta and an anti-beta(1) integrin antibody abolished the protective effect of IL-1beta but not the aggregates. We conclude that the anti-apoptotic effect of IL-1 is mediated through a beta(1) integrin-dependent event secondary to cell-cell adhesion. This illustrates a previously uncharacterized role for IL-1 in the intestine wherein this cytokine may facilitate the preservation of the epithelial monolayer integrity.