The influence of apoptosis on intestinal barrier integrity in rats

Gemcitabine enhances pharmacokinetic exposure of the major components of Danggui Buxue Decoction in rat via the promotion of intestinal permeability and down-regulation of CYP3A for combination treatment of non-small cell lung cancer

CONTEXT

Danggui Buxue Decoction (DBD), a traditional Chinese medicine formula, has the potential to enhance the antitumor effect of gemcitabine in non-small cell lung cancer (NSCLC) treatment by increasing gemcitabine's active metabolites. However, whether gemcitabine affects the pharmacokinetics of DBD's major components remains unclear.

OBJECTIVE

This study evaluates the herb-drug interaction between DBD's major components and gemcitabine and validates the underlying pharmacokinetic mechanism.

MATERIALS AND METHODS

The pharmacokinetics of 3.6 g/kg DBD with and without a single-dose administration of 50 mg/kg gemcitabine was investigated in Sprague-Dawley rats. The effects of gemcitabine on intestinal permeability, hepatic microsomal enzymes in rat tissues, and CYP3A overexpressing HepG2 cells were determined using western blot analysis.

RESULTS

The combination of gemcitabine significantly altered the pharmacokinetic profiles of DBD's major components in rats. The Cmax and AUC of calycosin-7-O-β-d-glucoside notably increased through sodium-glucose transporter 1 (SGLT-1) expression promotion. The AUC of ligustilide and ferulic acid was also significantly elevated with the elimination half-life (t1/2) prolonged by 2.4-fold and 7.8-fold, respectively, by down-regulating hepatic CYP3A, tight junction proteins zonula occludens-1 (ZO-1) and occludin expression.

DISCUSSION AND CONCLUSIONS

Gemcitabine could modulate the pharmacokinetics of DBD's major components by increasing intestinal permeability, enhancing transporter expression, and down-regulating CYP3A. These findings provide critical information for clinical research on DBD as an adjuvant for NSCLC with gemcitabine and help make potential dosage adjustments more scientifically and rationally.

Review on the effect of chemotherapy on the intestinal barrier: Epithelial permeability, mucus and bacterial translocation

Chemotherapy kills fast-growing cells including gut stem cells. This affects all components of the physical and functional intestinal barrier, i.e., the mucus layer, epithelium, and immune system. This results in an altered intestinal permeability of toxic compounds (e.g., endotoxins) as well as luminal bacterial translocation into the mucosa and central circulation. However, there is uncertainty regarding the relative contributions of the different barrier components for the development of chemotherapy-induced gut toxicity. This review present an overview of the intestinal mucosal barrier determined with various types of molecular probes and methods, and how they are affected by chemotherapy based on reported rodent and human data. We conclude that there is overwhelming evidence that chemotherapy increases bacterial translocation, and that it affects the mucosal barrier by rendering the mucosa more permeable to large permeability probes. Chemotherapy also seems to impede the intestinal mucus barrier, even though this has been less clearly evaluated from a functional standpoint but certainly plays a role in bacteria translocation. Combined, it is however difficult to outline a clear temporal or succession between the different gastrointestinal events and barrier functions, especially as chemotherapy-induced neutropenia is also involved in intestinal immunological homeostasis and bacterial translocation. A thorough characterization of this would need to include a time dependent development of neutropenia, intestinal permeability, and bacterial translocation, ideally after a range of chemotherapeutics and dosing regimens.

Toll-like Receptor 4 Inflammatory Perspective on Doxorubicin-Induced Cardiotoxicity

Doxorubicin (Dox) is one of the most frequently used chemotherapeutic drugs in a variety of cancers, but Dox-induced cardiotoxicity diminishes its therapeutic efficacy. The underlying mechanisms of Dox-induced cardiotoxicity are still not fully understood. More significantly, there are no established therapeutic guidelines for Dox-induced cardiotoxicity. To date, Dox-induced cardiac inflammation is widely considered as one of the underlying mechanisms involved in Dox-induced cardiotoxicity. The Toll-like receptor 4 (TLR4) signaling pathway plays a key role in Dox-induced cardiac inflammation, and growing evidence reports that TLR4-induced cardiac inflammation is strongly linked to Dox-induced cardiotoxicity. In this review, we outline and address all the available evidence demonstrating the involvement of the TLR4 signaling pathway in different models of Dox-induced cardiotoxicity. This review also discusses the effect of the TLR4 signaling pathway on Dox-induced cardiotoxicity. Understanding the role of the TLR4 signaling pathway in Dox-induced cardiac inflammation might be beneficial for developing a potential therapeutic strategy for Dox-induced cardiotoxicity.

Elevation of HO-1 expression protects the intestinal mucosal barrier in severe acute pancreatitis via inhibition of the MLCK/p-MLC signaling pathway

In severe acute pancreatitis (SAP), intestinal mucosal barrier damage can cause intestinal bacterial translocation and induce or aggravate systemic infections. Heme oxygenase-1 (HO-1) is a validated antioxidant and cytoprotective agent. This research aimed to investigate the effect and mechanism of HO-1 on SAP-induced intestinal barrier damage in SAP rats. Healthy adult male Sprague-Dawley rats were randomly separated into the sham-operated group, SAP group, SAP + Hemin group, and SAP + Znpp group. The rat model of SAP was established by retrograde injection of sodium taurocholate (5%) into the biliopancreatic duct. Hemin (a potent HO-1 activator) and Znpp (a competitive inhibitor of HO-1) were injected intraperitoneally in the selected groups 24 h before SAP. Serum and intestinal tissue samples were collected for analysis after 24 h in each group. Hemin pretreatment significantly reduced systemic inflammation, intestinal oxidative stress, and intestinal epithelial apoptosis in SAP by increasing HO-1 expression. Meanwhile, pretreatment with Hemin abolished the inhibitory effect on the expression of the tight junction proteins and significantly inhibited the activation of the MLCK/P-MLC signaling pathway. Conversely, ZnPP completely reversed these effects. Our study indicates that upregulation of HO-1 expression attenuates the intestinal mucosal barrier damage in SAP. The protective effect of HO-1 on the intestine is attributed to MLCK/p-MLC signaling pathway inhibition.

The progression of doxorubicin-induced intestinal mucositis in rats

Chemotherapy-induced intestinal mucositis is a severe side effect contributing to reduced quality of life and premature death in cancer patients. Despite a high incidence, a thorough mechanistic understanding of its pathophysiology and effective supportive therapies are lacking. The main objective of this rat study was to determine how 10 mg/kg doxorubicin, a common chemotherapeutic, affected jejunal function and morphology over time (6, 24, 72, or 168 h). The secondary objective was to determine if the type of dosing administration (intraperitoneal or intravenous) affected the severity of mucositis or plasma exposure of the doxorubicin. Morphology, proliferation and apoptosis, and jejunal permeability of mannitol were examined using histology, immunohistochemistry, and single-pass intestinal perfusion, respectively. Villus height was reduced by 40% after 72 h, preceded at 24 h by a 75% decrease in proliferation and a sixfold increase in apoptosis. Villus height recovered completely after 168 h. Mucosal permeability of mannitol decreased after 6, 24, and 168 h. There were no differences in intestinal injury or plasma exposure after intraperitoneal or intravenous doxorubicin dosing. This study provides an insight into the progression of chemotherapy-induced intestinal mucositis and associated cellular mucosal processes. Knowledge from this in vivo rat model can facilitate development of preventive and supportive therapies for cancer patients.

Ferric citrate-induced colonic mucosal damage associated with oxidative stress, inflammation responses, apoptosis, and the changes of gut microbial composition

Ferric citrate (FC) has been used as an iron fortifier and nutritional supplement, which is reported to induce colitis in rats, however the underlying mechanism remains to be elucidated. We performed a 16-week study of FC in male healthy C57BL/6 mice (nine-month-old) with oral administration of Ctr (0.9 % NaCl), 1.25 % FC (71 mg/kg/bw), 2.5 % FC (143 mg/kg/bw) and 5 % FC (286 mg/kg/bw). FC-exposure resulted in colon iron accumulation, histological alteration and reduce antioxidant enzyme activities, such as glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC), together with enhanced lipid peroxidation level, including malondialdehyde (MDA) level and 4-Hydroxynonenal (4-HNE) protein expression. Exposure to FC was associated with upregulated levels of the interleukin (IL)- 6, IL-1β, IL-18, IL-8 and tumor necrosis factor α (TNF-α), while down-regulated levels of IL-4 and IL-10. Exposure to FC was positively associated with the mRNA and protein expressions of cysteine-aspartic proteases (Caspase)- 9, Caspase-3, Bcl-2-associated X protein (Bax), while negatively associated with B-cell lymphoma 2 (Bcl2) in mitochondrial apoptosis signaling pathway. FC-exposure changed the diversity and composition of gut microbes. Additionally, the serum lipopolysaccharide (LPS) contents increased in FC-exposed groups when compared with the control group, while the expression of colonic tight junction proteins (TJPs), such as Claudin-1 and Occludin were decreased. These findings indicate that the colonic mucosal injury induced by FC-exposure are associated with oxidative stress generation, inflammation response and cell apoptosis, as well as the changes in gut microbes diversity and composition.

Ginger and 6-gingerol prevent lipopolysaccharide-induced intestinal barrier damage and liver injury in mice

BACKGROUND

Inflammation-related diseases present a significant public health problem. Ginger is a flavoring spice and medicinal herb with anti-inflammatory activity. This study investigated the preventive effects of ginger extract (GE) and its main bioactive component, 6-gingerol (6G), on lipopolysaccharide (LPS)-induced intestinal barrier dysfunction and liver injury in mice.

RESULTS

GE and 6G were orally administered to mice for seven consecutive days before LPS administration. After 24 h, the mice were sacrificed. GE and 6G were found to significantly reverse LPS-induced inflammation in the mouse ileum by modifying the NF-κB pathway. They also alleviated apoptosis in the ileum by downregulating Bax and cytochrome c gene expression and by inhibiting the caspase-3 pathway. Through the aforementioned mechanisms, GE and 6G restored the intestinal barrier by increasing ZO-1 and claudin-1 protein expressions. Gut-derived LPS induced inflammation and apoptosis in the liver; these effects were markedly reversed through GE and 6G treatment. 6G was the most abundant component in GE, as evidenced through liquid chromatography-mass spectrometry, and accounted for >50% of total gingerols and shogaols in GE.

CONCLUSION

The current results support the use of GE and 6G as dietary supplements to protect against gut-derived endotoxemia-associated inflammatory response and disorders. © 2021 Society of Chemical Industry.

Modulation of the PI3K/Akt/mTOR signaling pathway by probiotics as a fruitful target for orchestrating the immune response

The mammalian target of rapamycin (mTOR) and the phosphatidylinositol-3-kinase (PI3K)/protein kinase B or Akt (PKB/Akt) signaling pathways are considered as two but somewhat interconnected significant immune pathways which play complex roles in a variety of physiological processes as well as pathological conditions. Aberrant activation of PI3K/Akt/mTOR signaling pathways has been reported to be associated in a wide variety of human diseases. Over the past few years, growing evidence in in vitro and in vivo models suggest that this sophisticated and subtle cascade mediates the orchestration of the immune response in health and disease through exposure to probiotics. An expanding body of literature has highlighted the contribution of probiotics and PI3K/Akt/mTOR signaling pathways in gastrointestinal disorders, metabolic syndrome, skin diseases, allergy, salmonella infection, and aging. However, longitudinal human studies are possibly required to verify more conclusively whether the investigational tools used to understand the regulation of these pathways might provide effective approaches in the prevention and treatment of various disorders. In this Review, we summarize the experimental evidence from recent peer-reviewed studies and provide a brief overview of the causal relationship between the effects of probiotics and their metabolites on the components of PI3K/Akt/mTOR signaling pathways and human disease.

Attenuation of Doxorubicin-Induced Small Intestinal Mucositis by Pectins is Dependent on Pectin's Methyl-Ester Number and Distribution

SCOPE

Intestinal mucositis is a common side effect of the chemotherapeutic agent doxorubicin, which is characterized by severe Toll-like receptor (TLR) 2-mediated inflammation. The dietary fiber pectin is shown to prevent this intestinal inflammation through direct inhibition of TLR2 in a microbiota-independent manner. Recent in vitro studies show that inhibition of TLR2 is determined by the number and distribution of methyl-esters of pectins. Therefore, it is hypothesized that the degree of methyl-esterification (DM) and the degree of blockiness (DB) of pectins determine attenuating efficacy on doxorubicin-induced intestinal mucositis.

METHODS AND RESULTS

Four structurally different pectins that differed in DM and DB are tested on inhibitory effects on murine TLR2 in vitro, and on doxorubicin-induced intestinal mucositis in mice. These data demonstrate that low DM pectins or intermediate DM pectins with high DB have the strongest inhibitory impact on murine TLR2-1 and the strongest attenuating effect on TLR2-induced apoptosis and peritonitis. Intermediate DM pectin with a low DB is, however, also effective in preventing the induction of doxorubicin-induced intestinal damage.

CONCLUSION

These pectin structures with stronger TLR2-inhibiting properties may prevent the development of doxorubicin-induced intestinal damage in patients undergoing chemotherapeutic treatment with doxorubicin.

Lactobacillus salivarius, a Potential Probiotic to Improve the Health of LPS-Challenged Piglet Intestine by Alleviating Inflammation as Well as Oxidative Stress in a Dose-Dependent Manner During Weaning Transition

Intestinal health is a critical issue for piglets during their weaning transition period. Previous reports have emphasized the promise of distinct probiotics in improving the enteric health. Here in this research, a newly isolated Lactobacillus salivarius strain was pretreated to Lipopolysaccharide (LPS)-challenged piglets and its association with integrity of the intestinal barrier coupled with effective dosage were expected to be signified. In the present study, 72 piglets (Landrace × Yorkshiere × Duroc) were randomly allotted to four groups, each group with six replicates. The subjects in the control group were provided with basal diet while those in other tested groups with extra 0.05, 0.1, and 0.2% L. salivarius, respectively. Fourteen days later, LPS was intraperitoneally injected and sodium pentobarbital was then delivered to euthanize those LPS-challenged piglets. An increase of average daily gain and body weight along with an apparent decline of diarrhea rate were observed in L. salivarius-treated groups. Both 0.1 and 0.2% L. salivarius supplement in total diet had the capability to markedly elevate levels of CAT, GSH-Px, SOD, anti-inflammatory cytokine from the serum as well as tight junction proteins (Claudin-1, Occludin, and ZO-1) extracted from intestine in LPS-challenged piglets. These changes were accompanied by the obvious downregulation of D-lactic acid, DAO, MDA and pro-inflammatory mediators in the serum, including IL-1β, IL-6, IFN-γ, and TNF-α. Meanwhile, the expression levels of TLR2 and TLR4 in spleen and mesenteric lymph nodes were significantly lower whereas the oxidation-related gene, ho-1 was up-regulated with L. salivarius administration. Our findings suggested that relatively high dose L. salivarius (0.1–0.2%) could regulate the progression of inflammatory response and oxidative stress when individuals were exposed to LPS, thus probably offering valuable assistance in restoring barrier function and improving overall performance.

Doxorubicin increases permeability of murine small intestinal epithelium and cultured T84 monolayers

Enteric bacteria and/or their products are necessary for doxorubicin (DXR)-induced small intestine mucosal damage. While DXR does not induce gross loss of epithelium, others have shown elevated serum endotoxin after DXR administration. However, the mechanism of movement is unknown. We hypothesized that DXR treatment resulted in increased paracellular translocation of bacteria or bacterial products through the small intestinal epithelium. We measured permeability after DXR administration using transepithelial resistance and macromolecular flux and assessed tight junctional gene expression and protein localization both in vitro using T84 cells and ex vivo using murine jejunum. DXR treatment increased flux of 4 kDa dextrans in mouse jejenum, but increased flux of 4, 10 and 20 kDa dextrans in T84 cells. Following DXR, we observed increased permeability, both in vitro and ex vivo, independent of bacteria. DXR induced increased expression of Cldn2 and Cldn4 in murine small intestine but increased only CLDN2 expression in T84 cells. DXR treatment induced disorganization of tight junctional proteins. We conclude that DXR increases paracellular transit of small macromolecules, including bacterial products, through the epithelium, by altering expression of tight junctional components and dynamic loosening of cellular tight junctions.

Raw Bowl Tea (Tuocha) Polyphenol Prevention of Nonalcoholic Fatty Liver Disease by Regulating Intestinal Function in Mice

A high-fat diet-induced C57BL/6N mouse model of non-alcoholic fatty liver disease (NAFLD) was established. The effect and mechanism of Raw Bowl Tea polyphenols (RBTP) on preventing NAFLD via regulating intestinal function were observed. The serum, liver, epididymis, small intestine tissues, and feces of mice were examined by biochemical and molecular biological methods, and the composition of RBTP was analyzed by HPLC assay. The results showed that RBTP could effectively reduce the body weight, liver weight, and liver index of NAFLD mice. The serum effects of RBTP were: (1) decreases in alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), D-lactate (D-LA), diamine oxidase (DAO), lipopolysaccharide (LPS), and an increase of high density lipoprotein cholesterol (HDL-C) levels; (2) a decrease of inflammatory cytokines such as interleukin 1 beta (IL-1β), interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α), and interferon gamma (INF-γ); (3) a decrease the reactive oxygen species (ROS) level in liver tissue; and (4) alleviation of pathological injuries of liver, epididymis, and small intestinal tissues caused by NAFLD and protection of body tissues. qPCR and Western blot results showed that RBTP could up-regulate the mRNA and protein expressions of LPL, PPAR-α, CYP7A1, and CPT1, and down-regulate PPAR-γ and C/EBP-α in the liver of NAFLD mice. In addition, RBTP up-regulated the expression of occludin and ZO-1, and down-regulated the expression of CD36 and TNF-α in the small intestines of NAFLD mice. Studies on mice feces showed that RBTP reduced the level of Firmicutes and increased the minimum levels of Bacteroides and Akkermansia, as well as reduced the proportion of Firmicutes/Bacteroides in the feces of NAFLD mice, which play a role in regulating intestinal microecology. Component analysis showed that RBTP contained seven polyphenolic compounds: Gallic acid, (-)-epigallocatechin, catechin, L-epicatechin, (-)-epigallocatechin gallate, (-)-gallocatechin gallate, and (-)-epicatechin gallate (ECG), and high levels of caffeine, (-)-epigallocatechin (EGC), and ECG. RBTP improved the intestinal environment of NAFLD mice with the contained active ingredients, thus playing a role in preventing NAFLD. The effect was positively correlated with the dose of 100 mg/kg, which was even better than that of the clinical drug bezafibrate.

Brain-Derived Neurotrophic Factor Modulates Intestinal Barrier by Inhibiting Intestinal Epithelial Cells Apoptosis in Mice

We aimed to investigate the effects of brain-derived neurotrophic factor (BDNF) on apoptosis of intestinal epithelial cells (IECs) and alterations of intestinal barrier integrity using BDNF knock-out mice model. Colonic tissues from BDNF+/+ mice and BDNF+/- mice were prepared for this study. The integrity of colonic mucosa was evaluated by measuring trans-mucosa electrical resistance and tissue conductance in Ussing chamber. The colonic epithelial structure was analyzed by transmission electron microscopy. Apoptosis involvement was determined with TUNEL staining, active caspase-3 immunostaining and Western blotting for the protein expression of active caspase-3, Bax and Bcl-2. The expression levels and distribution of tight junction proteins were evaluated by immunohistochemistry or Western blots. Compared with BDNF+/+ mice, BDNF+/- mice displayed impaired integrity and ultrastructure alterations in their colonic mucosa, which was characterized by diminished microvilli, mitochondrial swelling and epithelial cells apoptosis. Altered intestinal barrier function was linked to excessive apoptosis of IECs demonstrated by the higher proportion of TUNEL-positive apoptotic cells and enhanced caspase activities in BDNF+/- mice. Increased expression of Bax and claudin-2 proteins and reduced Bcl-2 and tight junction proteins (occludin, ZO-1 and claudin-1) expression were also detected in the colonic mucosa of BDNF+/- mice. BDNF may play a role in the maintenance of intestinal barrier integrity via its anti-apoptotic properties.

Fortunellin-Induced Modulation of Phosphatase and Tensin Homolog by MicroRNA-374a Decreases Inflammation and Maintains Intestinal Barrier Function in Colitis

Activation of phosphatase and tensin homolog (PTEN) is known to induce cell apoptosis. MicroRNA-374a (miR-374a), which can suppress PTEN expression, has been found abnormally expressed in inflammatory bowel disease (IBD). Fortunellin is a citrus flavonoid that is a potential anti-inflammation agent in inflammatory diseases. The present study investigated the effects and mechanisms underlying fortunellin-induced inhibition of PTEN in IBD. Colitis was established in rats by the intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid to mimic human ulcerative colitis, which is the main type of IBD. miR-374a expression was measured by quantitative real-time polymerase chain reaction, and the regulation of PTEN by miR-374a was evaluated by dual luciferase reporter assay. Western blotting was used to measure the corresponding protein expression. Fortunellin ameliorated colitis symptoms, including excessive inflammation and oxidative stress. Fortunellin decreased epithelial cell apoptosis through inhibiting PTEN expression in colitis. Fortunellin-induced downregulation of PTEN could be counteracted by miR-374a depletion. Moreover, knockdown of miR-374a in vivo partly inhibited the effects of fortunellin on rat colitis. In conclusion, PTEN inhibition contributes to the amelioration effects of fortunellin on colitis. It was confirmed that fortunellin targets miR-374a, which is a negative regulator of PTEN. This study provides novel insights into the pathological mechanisms and treatment alternatives of colitis.

Effect of feeding soybean meal and differently processed peas on intestinal morphology and functional glucose transport in the small intestine of broilers

Peas are locally grown legumes being rich in protein and starch. However, the broad usage of peas as a feed component in poultry nutrition is limited to anti-nutritional factors, which might impair gut morphology and function. This study investigated the effect of feeding raw or differently processed peas compared with feeding a soybean meal-based control diet (C) on intestinal morphology and nutrient transport in broilers. A total of 360 day-old broiler chicks were fed with one of the following diets: The C diet, and 3 diets containing raw peas (RP), fermented peas (FP) and enzymatically pre-digested peas (EP), each supplying 30% of dietary crude protein. After 35 d, jejunal samples of broilers were taken for analyzing histomorphological parameters, active glucose transport in Ussing chambers and the expression of genes related to glucose absorption, intestinal permeability and cell maturation. Villus length (P = 0.017) and crypt depth (P = 0.009) of EP-fed broilers were shorter compared to birds received C. The villus surface area was larger in broilers fed C compared to those fed with the pea-containing feed (P = 0.005). Glucose transport was higher for broilers fed C in comparison to birds fed with the EP diet (P = 0.044). The sodium-dependent glucose co-transporter 1 (SGLT-1) expression was down-regulated in RP (P = 0.028) and FP (P = 0.015) fed broilers. Correlation analyses show that jejunal villus length negatively correlates with the previously published number of jejunal intraepithelial T cells (P = 0.014) and that jejunal glucose transport was negatively correlated with the occurrence of jejunal intraepithelial leukocytes (P = 0.041). To conclude, the feeding of raw and processed pea containing diets compared to a soybean based diet reduced the jejunal mucosal surface area of broilers, which on average was accompanied by lower glucose transport capacities. These morphological and functional alterations were associated with observed mucosal immune reactions. Further studies are required elucidating the specific components in peas provoking such effects and whether these effects have a beneficial or detrimental impact on gut function and animal health.

Lactobacillus reuteri ZJ617 maintains intestinal integrity via regulating tight junction, autophagy and apoptosis in mice challenged with lipopolysaccharide

Live probiotics are effective in reducing gut permeability and inflammation. We have previously reported that Lactobacillus reuteri ZJ617 (ZJ617) with high adhesive and Lactobacillus rhamnosus GG (LGG) can ameliorate intestine inflammation induced by lipopolysaccharide (LPS). The present study was aimed at elucidating the roles of ZJ617 and LGG in alleviating the LPS-induced barrier dysfunction of ileum in mice. Six C57BL/6 mice per group were orally inoculated with ZJ617 or LGG for one week (1× 10⁸ CFU/mouse) and intraperitoneally injected with LPS (10 mg/kg body weight) for 24 h. The results demonstrated that pretreatment with ZJ617 and LGG attenuated LPS-induced increase in intestinal permeability. The probiotics supplementation suppressed LPS-induced oxidative stress. Both ZJ617 and LGG strongly reversed the decline of occludin and claudin-3 expression induced by LPS challenge. ZJ617 relieved LPS-induced apoptosis by decreasing caspase-3 activity. Noticeably, ratio of microtubule-associated light chain 3 (LC3)-II/LC3-I and LC3 activity were elevated by LPS stimulation, whereas such increases were obviously attenuated by both of the probiotics treatment. Moreover, phosphorylated mammalian target of rapamycin (p-mTOR) was significantly inhibited by LPS, whereas complementation of ZJ617 and LGG markedly increased the expression of p-mTOR. Collectively, our results indicated that ZJ617 could protect LPS-induced intestinal barrier dysfunction via enhancing antioxidant activities and tight junction and attenuating apoptosis and autophagy via mTOR signaling pathway. These findings could serve as systematic mechanisms through which probiotics promote and maintain gut homeostasis.

A human gut ecosystem protects against C. difficile disease by targeting TcdA

BACKGROUND

A defined Microbial Ecosystem Therapeutic (MET-1, or "RePOOPulate") derived from the feces of a healthy volunteer can cure recurrent C. difficile infection (rCDI) in humans. The mechanisms of action whereby healthy microbiota protect against rCDI remain unclear. Since C. difficile toxins are largely responsible for the disease pathology of CDI, we hypothesized that MET-1 exerts its protective effects by inhibiting the effects of these toxins on the host.

METHODS

A combination of in vivo (antibiotic-associated mouse model of C. difficile colitis, mouse ileal loop model) and in vitro models (FITC-phalloidin staining, F actin Western blots and apoptosis assay in Caco2 cells, transepithelial electrical resistance measurements in T84 cells) were employed.

RESULTS

MET-1 decreased both local and systemic inflammation in infection and decreased both the cytotoxicity and the amount of TcdA detected in stool, without an effect on C. difficile viability. MET-1 protected against TcdA-mediated damage in a murine ileal loop model. MET-1 protected the integrity of the cytoskeleton in cells treated with purified TcdA, as indicated by FITC-phalloidin staining, F:G actin assays and preservation of transepithelial electrical resistance. Finally, co-incubation of MET-1 with purified TcdA resulted in decreased detectable TcdA by Western blot analysis.

CONCLUSIONS

MET-1 intestinal microbiota confers protection against C. difficile and decreases C. difficile-mediated inflammation through its protective effects against C. difficile toxins, including enhancement of host barrier function and degradation of TcdA. The effect of MET-1 on C. difficile viability seems to offer little, if any, contribution to its protective effects on the host.

Depletion of enteric bacteria diminishes leukocyte infiltration following doxorubicin-induced small intestinal damage in mice

Background & aims

While enteric bacteria have been shown to play a critical role in other forms of intestinal damage, their role in mediating the response to the chemotherapeutic drug Doxorubicin (Doxo) is unclear. In this study, we used a mouse model of intestinal bacterial depletion to evaluate the role enteric bacteria play in mediating Doxo-induced small intestinal damage and, more specifically, in mediating chemokine expression and leukocyte infiltration following Doxo treatment. An understanding of this pathway may allow for development of intervention strategies to reduce chemotherapy-induced small intestinal damage.

Methods

Mice were treated with (Abx) or without (NoAbx) oral antibiotics in drinking water for four weeks and then with Doxo. Jejunal tissues were collected at various time points following Doxo treatment and stained and analyzed for apoptosis, crypt damage and restitution, and macrophage and neutrophil number. In addition, RNA expression of inflammatory markers (TNFα, IL1-β, IL-10) and cytokines (CCL2, CC7, KC) was assessed by qRT-PCR.

Results

In NoAbx mice Doxo-induced damage was associated with rapid induction of apoptosis in jejunal crypt epithelium and an increase weight loss and crypt loss. In addition, we observed an increase in immune-modulating chemokines CCL2, CCL7 and KC and infiltration of macrophages and neutrophils. In contrast, while still positive for induction of apoptosis following Doxo treatment, Abx mice showed neither the overall weight loss nor crypt loss seen in NoAbx mice nor the increased chemokine expression and leukocyte infiltration.

Conclusion

Enteric bacteria play a critical role in Doxo-induced small intestinal damage and are associated with an increase in immune-modulating chemokines and cells. Manipulation of enteric bacteria or the damage pathway may allow for prevention or treatment of chemotherapy-induced small intestinal damage.

Intestinal bacteria are necessary for doxorubicin-induced intestinal damage but not for doxorubicin-induced apoptosis

Doxorubicin (DOXO) induces significant, but transient, increases in apoptosis in the stem cell zone of the jejunum, followed by mucosal damage involving a decrease in crypt proliferation, crypt number, and villus height. The gastrointestinal tract is home to a vast population of commensal bacteria and numerous studies have demonstrated a symbiotic relationship between intestinal bacteria and intestinal epithelial cells (IEC) in maintaining homeostatic functions of the intestine. However, whether enteric bacteria play a role in DOXO-induced damage is not well understood. We hypothesized that enteric bacteria are necessary for induction of apoptosis and damage associated with DOXO treatment. Conventionally raised (CONV) and germ free (GF) mice were given a single injection of DOXO, and intestinal tissue was collected at 6, 72, and 120 h after treatment and from no treatment (0 h) controls. Histology and morphometric analyses quantified apoptosis, mitosis, crypt depth, villus height, and crypt density. Immunostaining for muc2 and lysozyme evaluated Paneth cells, goblet cells or dual stained intermediate cells. DOXO administration induced significant increases in apoptosis in jejunal epithelium regardless of the presence of enteric bacteria; however, the resulting injury, as demonstrated by statistically significant changes in crypt depth, crypt number, and proliferative cell number, was dependent upon the presence of enteric bacteria. Furthermore, we observed expansion of Paneth and goblet cells and presence of intermediate cells only in CONV and not GF mice. These findings provide evidence that manipulation and/or depletion of the enteric microbiota may have clinical significance in limiting chemotherapy-induced mucositis.

Effects of hyperbaric oxygen on intestinal mucosa apoptosis caused by ischemia-reperfusion injury in rats

BACKGROUND

Hyperbaric oxygen (HBO) is an effective adjuvant therapy for ischemia- reperfusion (I/R) injury of the brain, small intestine and testis in addition to crushing injury. Studies have shown that HBO increases the activity of villi of the ileum 30 minutes after I/R injury. The present study aimed to observe the effect of HBO on apoptosis of epithelial cells in the small intestine during different periods of I/R and to elucidate the potential mechanisms.

METHODS

Rats were subjected to 60-minute ischemia by clamping the superior mesenteric artery and 60-minute reperfusion by removal of clamping. The rats were randomly divided into four groups: I/R group, HBO precondition or HBO treatment before ischemia (HBO-P), HBO treatment during ischemia period (HBO-I), and HBO treatment during reperfusion (HBO-R). After 60-minute reperfusion, samples of the small intestine were prepared to measure the level of ATP by using the colorimetric method and immunochemical expression of caspase-3. The levels of TNF-α in intestinal tissue were measured using the enzyme-linked immunosorbent assay method (Elisa).

RESULTS

TNF-α levels were significantly lower in the HBO-I group than in the HBO-P (P<0.05), HBO-R and I/R groups; there was no significant difference between the HBO-R and I/R groups (P>0.05). The expression of caspas-3 was significantly lower in the HBO-I group than in the HBO-P group (P<0.05); it was also significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05). ATP level was significantly lower in the HBO-I group than in the HBO-P group (P<0.05), and also it was significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05).

CONCLUSIONS

There is an association between HBO, small intestinal I/R injury, and mucosa apoptosis. HBO maintains ATP and aerobic metabolism, inhibites TNF-α production, and thus prevents intestinal mucosa from apoptosis. Best results can be obtained when HBO is administered to patients in the period of ischemia, and no side effects are produced when HBO is given during the period of reperfusion.

Effect of N-acetyl cysteine on enterocyte apoptosis and intracellular signalling pathways' response to oxidative stress in weaned piglets

N-acetyl cysteine (NAC) has been widely used for preventing reactive oxygen species-induced damage. However, little is known as to whether dietary NAC supplementation would alleviate intestinal injury in weaned piglets. The present study evaluated the effect of NAC on enterocyte apoptosis and intracellular signalling pathways' response to weaning stress. The control piglets were normally suckling, and piglets in the weaning and NAC groups were fed the basal diet and basal+NAC diet from 14 to 25 d of age, respectively. Compared with the control piglets, weaning increased cortisol concentrations (P< 0·05), decreased superoxide dismutase and glutathione peroxidase activities (P< 0·05), increased malondialdehyde content (P< 0·05) in serum and enhanced enterocyte apoptosis index (AI) and concentrations of caspase-3, caspase-8 and caspase-9 (P< 0·05). Gene expression analyses indicated that weaning induced apoptosis via Fas signalling and mitochondrial pathways in weaned piglets. Dietary NAC supplementation decreased (P< 0·05) cortisol concentrations and the AI, increased (P< 0·05) antioxidant status in serum and alleviated histopathological changes in the intestine. It also inhibited Fas, caspase-3, caspase-8 and integrin αvβ6 (αvβ6) gene expressions in the NAC-treated piglets. However, no significant decrease (P>0·10) in caspase-3, caspase-8 and caspase-9 concentrations was observed in the NAC group compared with the weaning group. In conclusion, weaning may induce enterocyte apoptosis via the activation of Fas-dependent and mitochondria-dependent apoptosis. Although NAC had no effect on caspase concentrations, it was clearly beneficial for preserving morphological integrity in weaned piglets via the regulation of cell apoptosis and the inhibition of Fas-dependent apoptosis and αvβ6 expression.

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway in the duodenal mucosa of rats subjected to water immersion and restraint stress

The insulin growth factor 1/phosphatase and tensin homologue deleted on chromosome 10/Akt/forkhead box (IGF-1/PTEN/Akt/FoxO) signaling pathway reportedly exhibits gastroprotective effects by reducing water immersion and restraint stress (WRS)-induced gastric mucosal cell apoptosis. We examined the expression and localization of IGF-1, PTEN, Akt, and FoxO proteins, caspase-3 activity, and the number of apoptotic cells in the duodenal mucosa of rats subjected to WRS to confirm whether the IGF-1/PTEN/Akt/FoxO signaling pathway has a role in the duodenal mucosa. The results indicated that WRS enhanced cell apoptosis in the duodenal mucosa. In addition, in normal rats, PTEN was found mainly in the cellular cytoplasm of the duodenal glands and lamina propria of villi. IGF-1 and total Akt were observed in the cellular cytoplasm of the duodenal glands. In addition, total Akt was found in the cellular cytoplasm of the myenteric plexus. FoxO3a and FoxO4 were primarily concentrated in the cellular cytoplasm of the lamina propria. Specifically, PTEN, FoxO3a and FoxO4 were also localized in the cellular cytoplasm of lamina propria of restituted villi in the duodenal mucosa of rat subjected to WRS. In addition, messenger RNA transcript levels of IGF-1, PTEN, Akt1, Akt2, FoxO3, and FoxO4 were upregulated in the duodenal mucosa, with a peak between the 4th and 8th day after 7 h of WRS. Furthermore, the results also suggested that Akt3 messenger RNA transcript levels in the duodenal mucosa of rats after WRS showed no significant differences compared with those in the non-WRS group. Collectively, our results implied that the IGF-1/ PTEN/Akt/FoxO signaling pathway was effective in regulating cellular apoptosis in the duodenal mucosa of rats after WRS.

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway on the development and healing of water immersion and restraint stress-induced gastric ulcers in rats

Insulin-like growth factor 1 (IGF-1) and Akt [also known as protein kinase B (PKB)] proteins have been reported to exhibit gastroprotective effects by reducing water immersion and restraint stress (WRS)-induced gastric mucosal cellular apoptosis. To confirm whether the IGF-1/PTEN/Akt/FoxO signaling pathway is effective in protecting against gastric ulcers, our current study was conducted to examine the expression and localization of IGF-1, phosphatase and tensin homologue deleted on chromosome 10 (PTEN), Akt and O subfamily of forkhead box (FoxO) proteins, caspase-3 activity and the number of apoptotic cells in gastric mucosa of rats subjected to WRS. Our results demonstrated that WRS induced gastric ulcers by enhancing cell apoptosis in rat gastric mucosa. In addition, in normal rat gastric mucosa, PTEN, total Akt and FoxO1 were found mainly in the cell cytoplasm of fundic glands in the lamina propria close to the muscularis mucosa. In addition, strong staining of IGF-1, FoxO3a and FoxO4 in the gastric mucosa was primarily concentrated in the cell cytoplasm of the fundic glands in whole lamina propria. However, in rat gastric ulcers, IGF-1, total Akt, FoxO3a and FoxO4 were localized in proximity to the base of the ulcer margin and were also present in the granulation tissues of the gastric ulcers. Moreover, in the rat gastric ulcers, the mRNA transcript levels of IGF-1, PTEN, Akt-1, Akt-2, FoxO3 and FoxO4 were upregulated in the gastric ulcer margin, with a peak between Days 4 and 8 following 7 h of WRS. In conclusion, our results imply that the IGF-1/PTEN/Akt/FoxO signaling pathway plays a certain role(s) in the protection against ulceration through the regulation of cellular apoptosis as observed in the development and healing of rat gastric ulcers.

Transport of Aflatoxin M(1) in Human Intestinal Caco-2/TC7 Cells

Aflatoxin M(1) (AFM(1)) is a hydroxylated metabolite of aflatoxin B(1) (AFB(1)). After it is formed, it is secreted in the milk of mammals. Despite the potential risk of human exposure to AFM(1), data reported in literature on the metabolism, toxicity, and bioavailability of this molecule are limited and out of date. The aim of the present research was to study the absorption profile of AFM(1) and possible damage to tight junctions (TJ) of the intestinal Caco-2/TC7 clone grown on microporous filter supports. These inserts allowed for the separation of the apical and basolateral compartments which correspond to the in vivo lumen and the interstitial space/vascular systems of intestinal mucosa respectively. In this study, the Caco-2/TC7 cells were treated with different AFM(1) concentrations (10-10,000 ng/kg) for short (40 min) and long periods of time (48 h). The AFM(1) influx/efflux transport and effects on TJ were evaluated by measuring trans-epithelial electrical resistance and observing TJ protein (Zonula occludens-1 and occludin) localization. The results showed that: (i) when introduced to the apical and basolateral compartments, AFM(1) was poorly absorbed by the Caco-2/TC7 cells but its transport across the cell monolayer occurred very quickly (P(app) value of 105.10 ± 7.98 cm/s × 10(-6)). (ii) The integrity of TJ was not permanently compromised after exposure to the mycotoxin. Viability impairment or barrier damage did not occur either. The present results contribute to the evaluation of human risk exposure to AFM(1), although the AFM(1) transport mechanism need to be clarified.

The Fontan pathway: What's down the road?

The Fontan circulation results from routing of the systemic venous blood to the pulmonary circulation without a hydraulic source of a ventricle. Although a hypertrophied right atrium was thought to be essential for this circulation, the current form of the operation has neither the right atrium nor any valves in the venous circulation that is connected to the pulmonary arteries directly. Modifications in the operative model was one of the early steps in improving outcome. Use of fenestration, staging of Fontan completion and better perioperative management have led to a significant drop in mortality rates in the current era. Despite this, there is late attrition of patients with complications such as arrhythmias, ventricular dysfunction, and unusual clinical syndromes of protein-losing enteropathy (PLE) and plastic bronchitis. Management of failing Fontan includes a detailed hemodynamic and imaging assessment to treat any correctable lesions such as obstruction within the Fontan circuit, early control of arrhythmia and maintenance of sinus rhythm, symptomatic treatment for PLE and plastic bronchitis, manipulation of systemic and pulmonary vascular resistance, and Fontan conversion of less favorable atriopulmonary connection to extra-cardiac total cavopulmonary connection with arrythmia surgery. Cardiac transplantation remains the only successful definitive palliation in the failing Fontan patients.

Norovirus non-structural protein p20 leads to impaired restitution of epithelial defects by inhibition of actin cytoskeleton remodelling

OBJECTIVE

Norovirus is the most common cause of acute gastroenteritis in humans worldwide. Typical symptoms are vomiting, nausea and severe watery diarrhea. Because of the lack of cell lines susceptible to human norovirus infection, pathomechanisms and replication cycle are largely unknown. Here, we address the issue of how norovirus infection could lead to epithelial barrier dysfunction.

MATERIAL AND METHODS

Expression of the non-structural norovirus protein p20 in the epithelial cell line HT-29/B6 was activated through a tetracycline sensitive promoter. Tight junction proteins were studied by Western blot and confocal laser scanning microscopy. Apoptoses were detected in TUNEL stainings. Epithelial restitution was monitored by conductance scanning after induction of single cell lesions.

RESULTS

Changes in the expression or localization of the tight junction proteins occludin and/or claudin-1, -2,- 3, -4, -5, -7 and -8 could be ruled out to mediate epithelial barrier modulation. Cell motility was also unaltered by p20. Investigation of epithelial apoptosis revealed an accumulation of apoptic cells in epithelial monolayers after induction of p20 expression. In epithelial cell restitution assays, an arrest was identified in p20 expressing cells. Fluorescence microscopy revealed an inability for condensation and redistribution of cellular actin, which led to a reduced transepithelial electrical resistance.

CONCLUSIONS

Functional data for norovirus protein p20 suggest a role in modulation of the actin cytoskeleton leading to barrier dysfunction through impairment of restitution of epithelial defects.

Glial-derived neurotrophic factor regulates intestinal epithelial barrier function and inflammation and is therapeutic for murine colitis

Although enteric glial cells (EGCs) have been demonstrated to play a key role in maintaining intestinal epithelial barrier integrity, it is not known how EGCs regulate this integrity. We therefore hypothesized that glial-derived neurotrophic factor (GDNF) produced by EGCs might be involved in this regulation. Here we investigated the role of GDNF in regulating epithelial barrier function in vivo. Recombinant adenoviral vectors encoding GDNF (Ad-GDNF) were administered intracolonically in experimental colitis induced by dextran sulphate sodium (DSS). The disease activity index (DAI) and histological score were measured. Epithelial permeability was assayed using Evans blue dye. The anti-apoptotic potency of GDNF in vivo was evaluated. The expression of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and myeloperoxidase (MPO) activity were measured by ELISA assay and/or RT-PCR. The expression of ZO-1, Akt, caspase-3, and NF-kappaB p65 was analysed by western blot assay. Our results showed that GDNF resulted in a significant reduction in enhanced permeability, inhibited MPO activity, IL-1beta and TNF-alpha expression, and increased ZO-1 and Akt expression. Moreover, GDNF strongly prevented apoptosis in vivo and significantly ameliorated experimental colitis. Our findings indicate that GDNF participates directly in restoring epithelial barrier function in vivo via reduction of increased epithelial permeability and inhibition of mucosal inflammatory response, and is efficacious in DSS-induced colitis. These findings support the notion that EGCs are able to regulate intestinal epithelial barrier integrity indirectly via their release of GDNF in vivo. GDNF is namely an important mediator of the cross-talk between EGCs and mucosal epithelial cells. GDNF may be a useful therapeutic approach to the treatment of inflammatory bowel disease.

Commensal Escherichia coli reduces epithelial apoptosis through IFN-alphaA-mediated induction of guanylate binding protein-1 in human and murine models of developing intestine

Appropriate microbial colonization protects the developing intestine by promoting epithelial barrier function and fostering mucosal tolerance to luminal bacteria. Commensal flora mediate their protective effects through TLR9-dependent activation of cytokines, such as type I IFNs (alpha, beta) and IL-10. Although IFN-beta promotes apoptosis, IFN-alpha activates specific antiapoptotic target genes whose actions preserve epithelial barrier integrity. We have recently identified guanylate binding protein-1 (GBP-1) as an antiapoptotic protein, regulated by both type I and type II IFNs, that promotes intestinal epithelial barrier integrity in mature intestine. However, the mechanisms by which commensal bacteria regulate epithelial apoptosis during colonization of immature intestine and the contributions of GBP-1 are unknown. The healthy newborn intestine is initially colonized with bacterial species present in the maternal gastrointestinal tract, including nonpathogenic Escherichia coli. Therefore, we examined the influence of commensal E. coli on cytokine expression and candidate mediators of apoptosis in preweaned mice. Specifically, enteral exposure of 2 wk-old mice to commensal E. coli for 24 h selectively increased both IFN-alphaA and GBP-1 mRNA expression and prevented staurosporine-induced epithelial apoptosis. Exogenous IFN-alphaA treatment also induced GBP-1 expression and protected against staurosporine-induced apoptosis in a GBP-1 dependent manner, both in vitro and ex vivo. These findings identify a role for IFN-alphaA-mediated GBP-1 expression in the prevention of intestinal epithelial apoptosis by commensal bacteria. Thus IFN-alphaA mediates the beneficial effects of commensal bacteria and may be a promising therapeutic target to promote barrier integrity and prevent the inappropriate inflammatory responses seen in developing intestine as in necrotizing enterocolitis.

Protective effect and mechanisms of radix astragali injection on the intestinal mucosa of rats with obstructive jaundice

Objective. To research the protective effects and mechanisms of Radix Astragali injection on the intestinal mucosa of rats with obstructive jaundice (OJ). Methods. The rats were randomly divided into sham-operated, model control and Radix Astragali treated group. We observed the pathological changes of intestinal mucosa, expression levels of Bax and NF-κB proteins, and apoptosis indexes in intestinal mucosa as well as serum NO, MDA and SOD contents, respectively, on 7d, 14d, 21d and 28d after operation. Results. The pathological severity score (on 7d and 14d), apoptotic indexes (on 14d) of the intestinal mucosa and serum MDA content (on 14d) of treated group were significantly lower than those in the model control group (P < .05). The serum SOD contents (on all time points) of treated group were significantly higher than those in the model control group (P < .05). The sham-operated group (on 21d) of the product of staining intensity and positive rate of Bax protein was significantly lower than model control group (P < .05). Conclusion. Radix Astragali injection could protect the intestinal mucosa of OJ rats by increasing the content of SOD, reducing the content of MDA, inhibiting the apoptosis and relieving the pathological changes of intestinal mucosa.

A role for Campylobacter jejuni-induced enteritis in inflammatory bowel disease?

The inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis, are T cell-mediated diseases that are characterized by chronic, relapsing inflammation of the intestinal tract. The pathogenesis of IBD involves the complex interaction between the intestinal microflora, host genetic and immune factors, and environmental stimuli. Epidemiological analyses have implicated acute bacterial enteritis as one of the factors that may incite or exacerbate IBD in susceptible individuals. In this review, we examine how interactions between the common enteric pathogen Campylobacter jejuni (C. jejuni), the host intestinal epithelium, and resident intestinal microflora may contribute to the pathogenesis of IBD. Recent experimental evidence indicates that C. jejuni may permit the translocation of normal, noninvasive microflora via novel processes that implicate epithelial lipid rafts. This breach in intestinal barrier function may, in turn, prime the intestine for chronic inflammatory responses in susceptible individuals. Insights into the interactions between enteric pathogens, the host epithelia, and intestinal microflora will improve our understanding of disease processes that may initiate and/or exacerbate intestinal inflammation in patients with IBD and provide impetus for the development of new therapeutic approaches for the treatment of IBD.

Regeneration of intestinal stem/progenitor cells following doxorubicin treatment of mice

The intestinal epithelium is in a constant state of renewal. The rapid turnover of cells is fed by a hierarchy of transit amplifying and stem/progenitor cells destined to give rise to the four differentiated epithelial lineages of the small intestine. Doxorubicin (Dox) is a commonly used chemotherapeutic agent that preferentially induces apoptosis in the intestinal stem cell zone (SCZ). We hypothesized that Dox treatment would initially decrease "+4" intestinal stem cell numbers with a subsequent expansion during mucosal repair. Temporal assessment following Dox treatment demonstrated rapid induction of apoptosis in the SCZ leading to a decrease in the number of intestinal stem/progenitor cells as determined by flow cytometry for CD45(-) SP cells, and immunohistochemistry of cells positive for putative +4 stem cell markers beta-cat(Ser552) and DCAMKL1. Between 96 and 168 h postinjection, overall proliferation in the crypts increased concomitant with increases in both absolute and relative numbers of goblet, Paneth, and enteroendocrine cells. This regeneration phase was also associated with increases of CD45(-) SP cells, beta-cat(Ser552)-positive cells, crypt fission, and crypt number. We used Lgr5-lacZ mice to assess behavior of Lgr5-positive stem cells following Dox and found no change in this cell population. Lgr5 mRNA level was also measured and showed no change immediately after Dox but decreased during the regeneration phase. Together these data suggest that, following Dox-induced injury, expansion of intestinal stem cells occurs during mucosal repair. On the basis of available markers this expansion appears to be predominantly the +4 stem cell population rather than those of the crypt base.

Insulin-like growth factor-I reduces stress-induced gastric mucosal injury by inhibiting neutrophil activation in mice

OBJECTIVE

We previously reported that activated neutrophils are critically involved in the development of stress-induced gastric mucosal injury in mice. Caspase activation plays an important role in the pathogenesis of tissue injury by activating neutrophils through an increase in the expression of endothelial monocyte-activating polypeptide-II (EMAP-II), a chemoattractant for neutrophils. Since insulin-like growth factor-I (IGF-I) inhibits caspase activation, it is possible that IGF-I reduces gastric mucosal injury by inhibiting neutrophil activation. In the present study, we examined this possibility in mice subjected to water-immersion restraint stress (WIR).

DESIGN

Mice were intraperitoneally administered with IGF-I or vehicle before being subjected to WIR. Gastric mucosal injury, gastric myeloperoxidase (MPO) activity, the immunofluorescence intensity of MPO, caspase-3 activity, number of apoptotic cells, EMAP-II expression and activation of Akt and glycogen synthase kinase-3beta (GSK-3beta) in gastric mucosa were determined in mice subjected to WIR. Neutropenia was induced by administration of methotrexate (MTX).

RESULTS

Administration of IGF-I at dosages higher than 200 microg/kg significantly reduced gastric mucosal injury and inhibited increases in gastric MPO activities after 8h of WIR. Administration of MTX also reduced the gastric mucosal injury as well as inhibiting increases in both gastric mucosal MPO activities and circulating neutrophil number. IGF-I (500 microg/kg) inhibited the increases in both gastric MPO activity and the immunofluorescence intensity of MPO observed in the gastric mucosa, but had no effect on the increase in circulating neutrophil number after 8h of WIR. It also markedly blunted WIR-induced increases in caspase-3 activities and the number of apoptotic cells in the gastric mucosa after 8h of WIR. Gastric expression of EMAP-II was markedly increased at 8h after starting WIR and this increase was inhibited by IGF-I administration. Administration of IGF-I enhanced WIR-induced phosphorylation of Akt and GSK-3beta in the gastric mucosa.

CONCLUSION

These observations indicate that IGF-I reduces stress-induced gastric mucosal injury by inhibiting gastric accumulation of neutrophils through inhibition of caspase-3-mediated EMAP-II activation. Furthermore, IGF-I might inhibit caspase-3 activation through Akt/GSK-3beta signaling.

Starvation-induced proximal gut mucosal atrophy diminished with aging

BACKGROUND

Starvation induces small bowel atrophy with increased intestinal epithelial apoptosis and decreased proliferation. The authors examined these parameters after starvation in aged animals.

METHODS

Sixty-four 6-week-old and 26-month-old C57BL/6 mice were randomly assigned to either an ad libitum fed or fasted group. The small bowel was harvested at 12, 48, and 72 hours following starvation. Proximal gut mucosal height was measured and epithelial cells counted. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. Proliferation was determined by immunohistochemical staining for proliferating cell nuclear antigen. Comparison of fed vs fasted and adult vs old groups was done by one-way ANOVA with Tukey's test and unpaired Student's t test. Significance was accepted at P < .05.

RESULTS

Aged mice had higher proximal gut weights, mucosal heights, and cell numbers at baseline compared with the adult group (P < .05). The rate of apoptosis was lower in the aged (P < .05), but proliferation was not different between groups before starvation. After starvation, proximal gut wet weight decreased only in adult mice (P < .05). Gut mucosal height and mucosal cell number decreased more in adult than in aged mice (P < .05). This was related to decreased proliferation only in the adult group (P < .05). The fold of epithelial apoptosis that increased was higher in the aged group than in the adult group after starvation (P < .05).

CONCLUSIONS

Gut mucosal kinetics change with age and have lower rates of apoptosis and greater mucosal mass; the character of starvation-induced atrophy is diminished with aging.

Enterobacter sakazakii enhances epithelial cell injury by inducing apoptosis in a rat model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder that affects 2%-5% of all premature infants. Enterobacter sakazakii, a common contaminant of milk-based powdered infant formula, has been implicated as a causative agent of sepsis, meningitis, and NEC in newborn infants, with high mortality rates. However, the role played by E. sakazakii in the pathogenesis of NEC is, to date, not known. Here, we demonstrate for the first time that E. sakazakii can induce clinical and histological NEC in newborn rats. E. sakazakii was found to bind to enterocytes in rat pups at the tips of villi and to intestinal epithelial cells (IEC-6) in culture, with no significant invasion. Exposure to E. sakazakii induced apoptosis and increased the production of interleukin-6 in IEC-6 cells and in the animal model. These data suggest that E. sakazakii could be a potential pathogen that induces NEC and triggers intestinal disease by modulating enterocyte intracellular signaling pathways.

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.

The role of pro-inflammatory cytokines in cancer treatment-induced alimentary tract mucositis: pathobiology, animal models and cytotoxic drugs

Alimentary tract (AT) mucositis can be a major problem for patients undergoing cancer treatment. It has significant clinical and economic consequences and is a major factor that can compromise the provision of optimal treatment for patients. The pathobiology of AT mucositis is complex and the exact mechanisms that underlie its development still need to be fully elucidated. Current opinion considers that there is a prominent interplay between all of the compartments of the mucosa involving, at a molecular level, the activation of transcription factors, particularly nuclear factor-kappaB, and the subsequent upregulation of pro-inflammatory cytokines and inflammatory mediators. The purpose of this review is to examine the literature relating to what is currently known about the pathobiology of AT mucositis, particularly with respect to the involvement of pro-inflammatory cytokines, as well as currently used animal models and the role of specific cytotoxic chemotherapy agents in the development of AT mucositis.

Chronic psychological stress alters epithelial cell turn-over in rat ileum

Dysregulated epithelial cell kinetics associated with mucosal barrier dysfunction may be involved in certain intestinal disorders. We previously showed that chronic psychological stress, in the form of repetitive sessions of water avoidance stress (WAS), has a major detrimental impact on ileal barrier function. We hypothesized that these changes were related to a disturbance in enterocyte kinetics. Rats were submitted to WAS (1 h/day) for 5 or 10 days. As previously shown, permeability to macromolecules was enhanced in rats stressed for 5 and 10 days compared with controls. WAS induced a decrease in crypt depth at day 5 associated with an increased number of apoptotic cells. Cell proliferation was significantly increased at days 5 and 10. Villus height and the specific activity of sucrase were significantly reduced at day 10. We concluded that WAS induces a disturbance of epithelial cell kinetics, with the pattern depending on the duration of the stress period. These findings help to explain the mechanism underlying altered epithelial barrier function resulting from exposure to chronic psychological stress.

The role of caspase-3 in lipopolysaccharide-mediated disruption of intestinal epithelial tight junctions

The mechanisms responsible for microbially induced epithelial apoptosis and increased intestinal permeability remain unclear. This study assessed whether purified bacterial lipopolysaccharide (LPS) increases epithelial apoptosis and permeability and whether these changes are dependent on caspase-3 activation. In nontumorigenic epithelial monolayers, Escherichia coli O26:B6 LPS increased apoptosis, as shown by nuclear breakdown, caspase-3 activation, and PARP cleavage, and induced disruption of tight junctional ZO-1. Apical, but not basolateral, exposure to LPS increased epithelial permeability. Addition of a caspase-3 inhibitor abolished the effects of LPS. The findings describe a novel mechanism whereby apical LPS may disrupt epithelial tight junctional ZO-1 and barrier function in a caspase-3-dependent fashion.

Protein-losing enteropathy after fontan operation: investigations into possible pathophysiologic mechanisms

BACKGROUND

Protein-losing enteropathy (PLE) is an enigmatic disease with significant morbidity and mortality seen after the Fontan operation. The pathophysiology is poorly understood. The purpose of this study is to investigate the association between PLE after the Fontan operation and candidate pathophysiologic mechanisms of the disease by searching for abnormalities of the following: (1) mesenteric blood flow; (2) systemic inflammation; (3) neurohormonal activation; (4) protein glycosylation.

METHODS

A cross-sectional analysis of 62 patients after the Fontan operation was performed. Twenty-four hour stool sample was collected for alpha-1-antitrypsin (A1AT) clearance, to determine the presence of abnormal enteric protein loss (AEPL) defined as either an abnormal fecal A1AT clearance of greater than 27 mL/24 hours, or an abnormal fecal A1AT concentration of greater than 54 mg/dL. Subjects underwent ultrasonography of the mesenteric and celiac artery blood flow and blood draw for tumor necrosis factor-alpha (TNF-a), high sensitivity C reactive protein (CRP), brain natriuretic peptide (BNP), angiotensin II, coagulation factors protein S, protein C, and antithrombin III (AT III), and serum transferrin for determination of glycosylation defect.

RESULTS

Age at study was 10.9 +/- 3.4 years; 8.6 +/- 3.9 years after the Fontan operation. Seven subjects had AEPL. Mesenteric-to-celiac artery flow ratio was lower for the AEPL group, than for the non-AEPL group (p < 0.05). The TNF-a, CRP, BNP, and angiotensin II levels were elevated; however, there was no correlation with AEPL. Abnormalities in coagulation factors were present but did not correlate with AEPL. No glycosylation defects were identified.

CONCLUSIONS

Potential candidate mechanisms for elucidation of the pathophysiology of PLE include abnormal mesenteric vascular resistance and inflammation, conditions uniquely present after the Fontan operation. Targeted investigations of these parameters may provide clues as to the mechanism of onset of PLE after Fontan operation.

The effects of propofol and ketamine on gut mucosal epithelial apoptosis in rats after burn injury

BACKGROUND AND OBJECTIVES

Apoptosis occurs after thermal injury and may result from either ischaemic intestinal insult or inflammatory mediators released after burn injury. The aim of the study was to investigate the effects of propofol and ketamine on gut epithelium apoptosis after burn injury.

METHODS

Sixty male Wistar Albino rats were randomly assigned into four groups. Anaesthesia was induced and maintained with propofol in Groups 1 and 2, and ketamine in Groups 3 and 4 over 12 h. Groups 2 and 4 received 30% total body surface area burn. Groups 1 and 3 had no burn injury. Mean arterial pressure was maintained within 10% of baseline levels in all animals. At 12 h postburn, animals were sacrificed and tissue samples were taken from small intestine for determination of lipid peroxidation, apoptosis and proliferation. Also blood samples were taken for measurement of serum tumor necrosis factor-alpha (TNF-alpha) levels.

RESULTS

Ileal malondialdehyde (MDA) concentration (extent of lipid peroxidation) increased significantly in Group 4 (112.4 +/- 10.2 nmol g-1) compared to Group 3 (48.4 +/- 5.6 nmol g-1) and Group 2 (59.8 +/- 3.2 nmol g-1). The mean TNF-alpha level in Group 4 (118.9 +/- 10.5 pg mL-1) at 12 h postburn was significantly higher than the mean in Group 2 (56.4 +/- 4.3 pg mL-1). Group 4 had the highest mean TUNEL index (terminal deoxyuridine nick-end labelling--an index of extent of apoptosis) of all the groups (265/10). Also the mean TUNEL index value in Group 2 (53/10) was higher than that of Group 1 (3/10) and Group 3 (5/10). The proliferating cell nuclear antigen index (extent of proliferation) remained unchanged among groups.

CONCLUSIONS

Propofol could offer a protection against apoptosis of enterocytes with a stable tissue MDA and serum TNF-alpha level compared to ketamine anaesthesia in an animal model of burn injury.

The effect of hepatocyte growth factor on gut mucosal apoptosis and proliferation, and cellular mediators after severe trauma

BACKGROUND

A severe burn injury is associated with an impairment of gut mucosal integrity and function, which is due to increases in small-bowel epithelial cell apoptosis and decreases in cell proliferation. Hepatocyte growth factor (HGF) was shown to improve regeneration in the liver, mesentery, and skin. The purpose of this study was to determine whether HGF can improve small-bowel homeostasis after injury and the cellular mechanisms by which these changes occur.

METHODS

Rats were pair-fed, underwent thermal trauma, and received saline (0.9% NaCl; n = 28) or HGF (200 microg/kg iv every 12 hours, n = 28). Small intestine and serum were taken at 1, 2, 5, and 7 days after injury. Measures were mucosal apoptosis, proliferation, villous morphology, and apoptotic and proliferative mediators, such as caspase-3 and caspase-7, Fas and Fas-ligand, Bcl-2, and Bax. In addition, serum cytokines were determined.

RESULTS

Gut epithelial cell apoptosis was increased in the saline and HGF groups after the thermal injury. Despite an increase in serum tumor necrosis factor-alpha and interleukin-1beta, HGF did not affect small-bowel cell apoptosis, but it improved proliferation at days 1 and 2 after injury, which was associated with increased villous height and cell per villous, compared with saline controls, P < .05. Increased mucosal cell proliferation was associated with increased Bcl-2 in the HGF group, P < .05. HGF had no effect on apoptotic mediators, such as Fas, Fas-L, or caspase-3 and caspase-7.

CONCLUSIONS

HGF improves small-bowel morphology after a severe burn by increasing mucosal Bcl-2 and, concomitantly, small-bowel epithelial cell proliferation.

The Pivotal Role of Tumor Necrosis Factor-?? in Signaling Apoptosis in Intestinal Epithelial Cells under Shock Conditions

BACKGROUND

Apoptosis is essential for the regulation of cell number and function of intestinal epithelial cells but may contribute to intestinal barrier failure after shock and other low-flow conditions to the gut.

METHODS

Caco2 intestinal cell monolayers were challenged with recombinant tumor necrosis factor (TNF). In a second group of experiments, Caco2 cells were exposed to bacteria and/or hypoxia followed by reoxygenation. Apoptosis was detected using annexin-V propidium-iodide staining. Cell culture supernatants were also obtained in the second group of experiments and TNF levels quantitated. Monolayer integrity was assessed by measurement of paracellular permeability and transepithelial electrical resistance.

RESULTS

Apical but not basal recombinant TNF increased Caco2 apoptosis. Exposure to either bacteria alone or hypoxia/reoxygenation alone did not increase apoptosis; however, the combined insults significantly increased apoptosis. The increased apoptosis occurred in a delayed fashion in both groups. TNF was released in a polar fashion, and the greatest levels were noted after exposure to both bacteria and hypoxia-reoxygenation. There was also an increase in paracellular permeability in this group; however, no change in transepithelial electrical resistance was noted. The effects on apoptosis and permeability were abrogated by anti-TNF antibodies.

CONCLUSION

Intestinal epithelial cell apoptosis contributes to barrier failure after shock conditions and is related to augmented TNF release.

The effect of growth hormone on gut mucosal homeostasis and cellular mediators after severe trauma

BACKGROUND

Gut mucosal integrity and function is impaired after severe trauma with associated increases in small bowel epithelial cell apoptosis and decreases in cell proliferation. Growth hormone improves gastrointestinal function during chemotherapy and has anabolic effects on protein synthesis. The purpose of this study was to determine whether growth hormone can improve small bowel homeostasis after injury and by which cellular mechanisms these changes occur.

MATERIALS AND METHODS

Rats were pair-fed, given a thermal trauma, and received saline (n = 28) or GH (2.5 mg/kg every 24 h, n = 28). Small intestine and serum were taken at 1, 2, 5, and 7 days after injury. Measures were mucosal apoptosis, proliferation, villous morphology, apoptotic, and proliferative mediators, such as Caspases-3, -8, Fas and Fas-Ligand, Bcl-2, and Bcl-x. In addition serum cytokines were determined.

RESULTS

Gut epithelial cell apoptosis and proliferation were increased in both groups after the thermal injury (P < 0.05). GH had neither an effect on small bowel epithelial cell apoptosis or proliferation, nor dependent cellular mediators after thermal injury. However, GH significantly improved villous morphology (height and cell number) when compared with controls (P < 0.05). RhGH was found to significantly increase serum TNF-alpha compared to controls (P < 0.05).

CONCLUSION

Growth hormone improves small bowel homeostasis after severe trauma independent from small bowel epithelial cell apoptosis or proliferation, probably by increasing the life span.

Insulin treatment improves hepatic morphology and function through modulation of hepatic signals after severe trauma

OBJECTIVE

The purpose of the present study was to determine the effect of insulin therapy on hepatic function, structure, and hepatic mRNA and protein cytokine expression during the hypermetabolic cascade post burn.

SUMMARY BACKGROUND DATA

Liver function and morphology are crucial for survival of patients suffering from trauma, operations, or infections. Insulin decreased mortality and prevented the incidence of multiorgan failure in critically ill patients.

METHODS

Rats received a thermal injury and were randomly divided into the insulin or control group. Our outcome measures encompassed the effect of insulin on hepatic proteins, hepatic pro- and anti-inflammatory cytokines mRNA and proteins, hepatocyte proliferation, including Bcl-2 and hepatocyte apoptosis, with caspases-3 and caspases-9.

RESULTS

Insulin significantly improved hepatic protein synthesis by increasing albumin and decreasing c-reactive protein and fat (P < 0.05). Insulin decreased the hepatic inflammatory response signal cascade by decreasing hepatic pro-inflammatory cytokines mRNA and proteins IL-1beta and tumor necrosis factor at pretranslational levels. Insulin increased hepatic cytokine mRNA and protein expression of IL-2 and IL-10 at a pretranslational level when compared with controls (P < 0.05). Insulin increased hepatocyte proliferation along with Bcl-2 concentration, while decreasing hepatocyte apoptosis along with decreased caspases-3 and -9 concentration, thus improving liver morphology (P < 0.05).

CONCLUSIONS

Our data provide insight that insulin attenuates the inflammatory response by decreasing the pro-inflammatory and increasing the anti-inflammatory cascade, thus restoring hepatic homeostasis, which has been shown to be critical for organ function and survival of critically ill patients.