Programmed cell death in rat intestine: effect of feeding and fasting

Remodelling of the intestinal ecosystem during caloric restriction and fasting

Benefits of fasting and caloric restriction on host metabolic health are well established, but less is known about the effects on the gut microbiome and how this impacts renewal of the intestinal mucosa. What has been repeatedly shown during fasting, however, is that bacteria utilising host-derived substrates proliferate at the expense of those relying on dietary substrates. Considering the increased recognition of the gut microbiome's role in maintaining host (metabolic) health, disentangling host-microbe interactions and establishing their physiological relevance in the context of fasting and caloric restriction is crucial. Such insights could aid in moving away from associations of gut bacterial signatures with metabolic diseases consistently reported in observational studies to potentially establishing causality. Therefore, this review aims to summarise what is currently known or still controversial about the interplay between fasting and caloric restriction, the gut microbiome and intestinal tissue physiology.

Dynamic Changes in Colonic Structure and Protein Expression Suggest Regulatory Mechanisms of Colonic Barrier Function in Torpor-Arousal Cycles of the Daurian Ground Squirrel

Background: Both pathological conditions and hibernation can affect the barrier function of small intestine mucosa. However, the effect of hibernation on the barrier function of colonic mucosa remains unclear. Methods: We investigated morphological changes in colonic mucosa, the concentrations of specific proteins and molecules, and the enzymatic activity of diamine oxidase (DAO), in serum and colonic tissue; the expression of tight junction proteins and mucin, and the changes in inflammatory, farnesoid X receptor (FXR)–small heterodimer partner (SHP), and apoptosis-related molecules that could play a role in gut permeability changes in Daurian ground squirrels in summer active (SA), late torpor (LT), and interbout arousal (IBA) periods. Results: The results show that hibernation reduced the thickness of the colonic mucosa and the depth of the crypt, decreased the number of goblet cells (GCs), and damaged the structure of some microvilli. The concentrations of proteins and molecules, and the enzymatic activity of DAO, were all increased in the serum and colon, and the localization of tight junction proteins and mucin in the colonic mucosa were altered (compensatory response). Although the ground squirrels ate during the interbout arousal period, the changes remained similar to the response to torpor. Inflammation, apoptosis–anti-apoptosis, and FXR–SHP signaling may be involved in the possible changes in intestinal gut permeability during the torpor–arousal cycle in Daurian ground squirrels. In addition, periodic interbout arousal may play an inflammation-correcting role during the long hibernation season of Daurian ground squirrels.

Biological Clock and Inflammatory Bowel Disease Review: From the Standpoint of the Intestinal Barrier

Inflammatory bowel disease is a group of chronic, recurrent, nonspecific inflammatory diseases of the intestine that severely affect the quality of life of patients. The pathogenesis of this disease is caused by complex and interactive neural networks composed of factors such as genetic susceptibility, external environment, immune disorders, and intestinal barrier dysfunction. It is well known that there is a strong link between environmental stressors (also known as circadian clocks) that can influence circadian changes and inflammatory bowel disease. Among them, the biological clock is involved in the pathogenesis of inflammatory bowel disease by affecting the function of the intestinal barrier. Therefore, this review is aimed at systematically summarizing the latest research progress on the role of the circadian clock in the pathogenesis of inflammatory bowel disease by affecting intestinal barrier functions (intestinal mechanical barrier, intestinal immune barrier, intestinal microecological barrier, and intestinal chemical barrier) and the potential clinical value of clock genes in the management of inflammatory bowel disease, for the application of circadian clock therapy in the management of inflammatory bowel disease and then the benefit to the majority of patients.

Regulation of gene expression in chickens by heat stress

Abstract

High ambient temperatures are a critical challenge in the poultry industry which is a key producer of the animal-based food. To evaluate heat stress levels, various parameters have been used, including growth rates, blood metabolites, and hormones. The most recent advances have explored expression profiling of genes that may play vital roles under stress. A high ambient temperature adversely affects nutrient uptake and is known to modulate the expression of genes encoding for sodium-dependent glucose transporters, glucose transporters, excitatory amino acid transporters, and fatty acid-binding proteins which are responsible for the absorption of macronutrients in the intestine. Various defensive activities are stimulated to protect the cell of different tissues from the heat-generated stress, including expression of early stress response genes coding for heat shock protein (HSP), c-FOS like protein, brain-derived neurotrophic factor (BDNF), and neuronal nitric oxide synthase (nNOS); antioxidant enzyme genes such as superoxide dismutase (SOD), catalase (CAT), and nicotinamide adenine dinucleotide phosphate oxidase (NOX4); and immune-related genes such as cytokines and toll-like receptors (TLRs). The potential role of HSPs in protecting the cell from stress and their presence in several tissues make them suitable markers to be evaluated under heat stress. BDNF and c-FOS genes expressed in the hypothalamus help cells to adapt to an adverse environment. Heat causes damage to the cell by generating reactive oxygen species (ROS). The NOX4 gene is the inducer of ROS under heat stress, which is in turns controlled by antioxidant enzymes such as SOD and CAT. TLRs are responsible for protecting against pathogenic attacks arising from enhanced membrane permeability, and cytokines help in controlling the pathogen and maintaining homeostasis. Thus, the evaluation of nutrient transporters and defense mechanisms using the latest molecular biology tools has made it possible to shed light on the complex cellular mechanism of heat-stressed chickens. As the impacts of heat stress on the above-mentioned aspects are beyond the extent to which the reduced growth performance could be explained, heat stress has more specific effects on the regulation of these genes than previously thought.

Graphical abstract

Effect of heat exposure on the nutrient transporters, antioxidants, and immune inflammation in chickens. Most of the nutrient transporters were suppressed under heat stress. Increase in the production of reactive oxygen species resulted in enhanced production of antioxidant enzymes. Expression of various proinflammatory cytokines and toll-like receptors were enhanced due to heat stress in chicken.

Human torpor: translating insights from nature into manned deep space expedition

During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (T_b ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.

Cell death in the gut epithelium and implications for chronic inflammation

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

The connection of circadian rhythm to inflammatory bowel disease

Inflammatory bowel disease (IBD) comprises a group of chronic, immune system-mediated inflammatory diseases that primarily affect the gastrointestinal tract. The pathogenesis of the intestinal lesions in IBD remains elusive, but the inflammation process could be the result of dysfunction of the innate and adaptive immune systems induced by genetic and environmental factors. In recent years, research has demonstrated a connection between environmental stressors that can influence day-night variations, also called circadian rhythms, and digestive health. In this review, we focus on alterations in the complex interactions between intestinal mucosa, microbial factors, and the immune response in the intestinal milieu. We introduce the mechanisms that establish circadian rhythms and their regulation by the circadian rhythm genes. Evidence of circadian variation in the defense mechanisms of the intestine and its implication in the maintenance of a healthy microbiota are presented. Disruption of the circadian system can increase the activity of the gut immune system and the release of inflammatory factors. The link between chronodisruption or circadian rhythm impairment and IBD demonstrated by experimental and clinical studies illustrates the potential impact of circadian rhythms on treatment of these diseases. Future studies that investigate aspects of this subject are warranted.

The intestinal environment as an evolutionary adaptation to mouthbrooding in the Astatotilapia burtoni cichlid

Many of the various parental care strategies displayed by animals are accompanied by a significant reduction in food intake that imposes a substantial energy trade-off. Mouthbrooding, as seen in several species of fish in which the parent holds the developing eggs and fry in the buccal cavity, represents an extreme example of reduced food intake during parental investment and is accompanied by a range of physiological adaptations. In this study we use 16S sequencing to characterize the gut microbiota of female Astatotilapia burtoni cichlid fish throughout the obligatory phase of self-induced starvation during the brooding cycle in comparison to stage-matched females that have been denied food for the same duration. In addition to a reduction of gut epithelial turnover, we find a dramatic reduction in species diversity in brooding stages that recovers upon release of fry and refeeding that is not seen in females that are simply starved. Based on overall species diversity as well as differential abundance of specific bacterial taxa, we suggest that rather than reflecting a simple deprivation of caloric intake, the gut microbiota is more strongly influenced by physiological changes specific to mouthbrooding including the reduced epithelial turnover and possible production of antimicrobial agents.

Gene expression and morphological changes in the intestinal mucosa associated with increased permeability induced by short-term fasting in chickens

Short-term fasting for 4.5 and 9 hr has been demonstrated to increase intestinal permeability (IP) in chickens. This study aimed to investigate the effects of 0, 4.5, 9 and 19.5 hr fasting on intestinal gene expression and villus-crypt architecture of enterocytes in jejunal and ileal samples. On day 38, Ross-308 male birds were fasted according to their group and then euthanised. Two separate intestinal sections (each 2 cm long, jejunum and ileum) were collected. One section was utilised for villus height and crypt depth measurements. The second section was snap-frozen in liquid nitrogen for quantitative polymerase chain reaction (qPCR) analysis of tight junction proteins (TJP) including claudin-1, claudin-3, occludin, zonula occludens (ZO-1, ZO-2), junctional adhesion molecules (JAM) and E-cadherin. Additionally genes involved in enterocyte protection including glucagon-like peptide (GLP-2), heat-shock protein (HSP-70), intestinal alkaline phosphatase (IAP), mammalian target of rapamycin (mTOR), toll-like receptors (TLR-4), mucin (MUC-2), cluster differentiation (CD-36) and fatty acid-binding protein (FABP-6) were also analysed. Normally distributed data were analysed using one-way analysis of variance ANOVA. Other data were analysed by non-parametric one-way ANOVA. Villus height and crypt depth were increased (p < .05) only in the ileum after fasting for 4.5 and 9 hr compared with non-fasting group. mRNA expression of claudin-3 was significantly reduced in the ileum of birds fasted for 9 and 19.5 hr, suggesting a role in IP modulation. However, all other TJP genes examined were not statistically different from control. Nevertheless, ileal FABP-6 of all fasted groups was significantly reduced, which could possibly be due to reduced bile acid production during fasting.

Integrative Physiology of Fasting

Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

Intestinal redox biology and oxidative stress

The intestinal epithelium sits at the interface between an organism and its luminal environment, and as such is prone to oxidative damage induced by luminal oxidants. Mucosal integrity is maintained by the luminal redox status of the glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS) couples which also support luminal nutrient absorption, mucus fluidity, and a diverse microbiota. The epithelial layer is uniquely organized for rapid self-renewal that is achieved by the well-regulated processes of crypt stem cell proliferation and crypt-to-villus cell differentiation. The GSH/GSSG and Cys/CySS redox couples, known to modulate intestinal cell transition through proliferation, differentiation or apoptosis, could govern the regenerative potential of the mucosa. These two couples, together with that of the thioredoxin/thioredoxin disulfide (Trx/TrxSS) couple are the major intracellular redox systems, and it is proposed that they each function as distinctive redox control nodes or circuitry in the control of metabolic processes and networks of enzymatic reactions. Specificity of redox signaling is accomplished in part by subcellular compartmentation of the individual redox systems within the mitochondria, nucleus, endoplasmic reticulum, and cytosol wherein each defined redox environment is suited to the specific metabolic function within that compartment. Mucosal oxidative stress would result from the disruption of these unique redox control nodes, and the subsequent alteration in redox signaling can contribute to the development of degenerative pathologies of the intestine, such as inflammation and cancer.

Effect of vitamin supplementation on cisplatin-induced intestinal epithelial cell apoptosis in Wistar/NIN rats

OBJECTIVE

Chemotherapeutic agents induce small intestinal mucositis that is characterized structurally by crypt loss and villus atrophy and functionally by absorptive and barrier impairments. We studied the effect of selected individual vitamins and multiple-vitamin mixture supplementation in modulating cisplatin-induced intestinal damage and apoptosis.

METHODS

Thirty-six male Wistar/NIN rats 20 wk old and fed the control diet (AIN-93G) were randomly divided into six groups. Five groups were administered cisplatin (2.61 mg/kg of body weight) once a week for 3 wk and were concomitantly provided the control diet or riboflavin, folate, α- tocopherol, or a multiple-vitamin mixture supplemented diet. The sixth group served as a control for cisplatin and received saline as the vehicle. Intestinal epithelial cell apoptosis was monitored by morphometry, M30 staining, DNA fragmentation, and caspase-3 activity. Functional and structural integrities were determined by measuring activities of alkaline phosphatase and lysine ala-dipeptidyl aminopeptidase and the villus height/crypt depth ratio. Oxidative burden was assessed as the formation of thiobarbituric acid-reactive substances and protein carbonyls. Plasma levels of selected vitamins were also measured.

RESULTS

Cisplatin administration significantly increased intestinal apoptosis in the villus and crypt regions that correlated with increased oxidative damage, decreased Bcl-2/Bax, and compromised functional integrity. Riboflavin, folate, and the multiple-vitamin mixture supplementation attenuated the cisplatin-induced increase in apoptotic indices, with a decrease in oxidative burden, increased Bcl-2/Bax, and improved functional and structural integrities. The α-tocopherol supplementation, although effective in attenuating oxidative stress and improving functional integrity, failed to lower the apoptotic indices.

CONCLUSIONS

Riboflavin, folate, and the multiple-vitamin supplementation proved to be more efficacious in attenuating the cisplatin-induced intestinal damage and associated changes in apoptosis.

Redox biology of the intestine

The intestinal tract, known for its capability for self-renew, represents the first barrier of defence between the organism and its luminal environment. The thiol/disulfide redox systems comprising the glutathione/glutathione disulfide (GSH/GSSG), cysteine/cystine (Cys/CySS) and reduced and oxidized thioredoxin (Trx/TrxSS) redox couples play important roles in preserving tissue redox homeostasis, metabolic functions, and cellular integrity. Control of the thiol-disulfide status at the luminal surface is essential for maintaining mucus fluidity and absorption of nutrients, and protection against chemical-induced oxidant injury. Within intestinal cells, these redox couples preserve an environment that supports physiological processes and orchestrates networks of enzymatic reactions against oxidative stress. In this review, we focus on the intestinal redox and antioxidant systems, their subcellular compartmentation, redox signalling and epithelial turnover, and contribution of luminal microbiota, key aspects that are relevant to understanding redox-dependent processes in gut biology with implications for degenerative digestive disorders, such as inflammation and cancer.

Survival of exfoliated epithelial cells: a delicate balance between anoikis and apoptosis

The recovery of exfoliated cells from biological fluids is a noninvasive technology which is in high demand in the field of translational research. Exfoliated epithelial cells can be isolated from several body fluids (i.e., breast milk, urines, and digestives fluids) as a cellular mixture (senescent, apoptotic, proliferative, or quiescent cells). The most intriguing are quiescent cells which can be used to derive primary cultures indicating that some phenotypes retain clonogenic potentials. Such exfoliated cells are believed to enter rapidly in anoikis after exfoliation. Anoikis can be considered as an autophagic state promoting epithelial cell survival after a timely loss of contact with extracellular matrix and cell neighbors. This paper presents current understanding of exfoliation along with the influence of methodology on the type of gastrointestinal epithelial cells isolated and, finally, speculates on the balance between anoikis and apoptosis to explain the survival of gastrointestinal epithelial cells in the environment.

Fasting-induced intestinal apoptosis is mediated by inducible nitric oxide synthase and interferon-{gamma} in rat

Nitric oxide (NO) is associated with intestinal apoptosis in health and disease. This study aimed to investigate the role of intestinal NO in the regulation of apoptosis during fasting in rats. Male Wistar rats were divided into two groups and subcutaneously injected with saline (SA) or aminoguanidine (AG), followed by fasting for 24, 48, 60, and 72 h. At each time point, the jejunum was subjected to histological evaluation for enterocyte apoptosis by histomorphometric assessment and TUNEL analysis. We performed immunohistochemistry for inducible NO synthase (iNOS) expression in the jejunum and measured tissue nitrite levels using HPLC and 8-hydroxydeoxyguanosine adduct using ELISA, indicative of endogenous NO production and reactive oxygen species (ROS) production, respectively. Jejunal transcriptional levels of iNOS, neuronal NO synthase (nNOS), and interferon-gamma (IFN-gamma) were also determined by RT-PCR. Fasting caused significant jejunal mucosal atrophy due to attenuated cell proliferation and enhanced apoptosis with increase in iNOS transcription, its protein expression in intestinal epithelial cells (IEC), and jejunal nitrite levels. However, AG treatment histologically reduced apoptosis with inhibition of fasting-induced iNOS transcription, protein expression, and nitrite production. We also observed fasting-induced ROS production and subsequent IFN-gamma transcription, which were all inhibited by AG treatment. Furthermore, we observed reduced transcriptional levels of nNOS, known to suppress iNOS activation physiologically. These results suggest that fasting-induced iNOS activation in IEC may induce apoptosis mediators such as IFN-gamma via a ROS-mediated mechanism and also a possible role of nNOS in the regulation of iNOS activity in fasting-induced apoptosis.

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.

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.

Exfoliated epithelial cells: potentials to explore gastrointestinal maturation of preterm infants

Exfoliated epithelial cells represent valuable source of information on the physiopathological state of the mucosa. However, the interpretation of data obtained from exfoliated cells is complicated by the conditions of isolation as well as the health of the subject. Exfoliation is either: a) a natural loss of body cells implying a molecular signal related to the turnover of terminally differentiated cells and to the progressive mobilization of proliferative as well as stem cells or b) the result of manual exfoliation by applying mechanical constraints like scraping. Depending on the methodology of isolation, exfoliated epithelial cells are believed to be either in apoptosis or in anoïkis. Most studies are using microscopic examination to demonstrate the presence of typical cells along with measurements on a limited number of biomarkers. Only few studies using proteomics or transcriptomics are available and they open discussion about tissue references and normalization. The main advantage of measures realized on exfoliated epithelial cells is that they are strictly non-invasive and open the possibility to evaluate maturation of gastric and intestinal tissues in long-term experiments performed on the same animal or in translational research on samples recovered from preterm infants.

Effects of Lactobacillus acidophilus on gut microflora metabolic biomarkers in fed and fasted rats

BACKGROUND & AIMS

Little is known about fasting effects on gut bacterial metabolism. As probiotics are purported to be beneficial for health, this study aimed to investigate the response of gut microbial metabolism on fasting with or without probiotic administration.

METHODS

Sixty male adult Wistar rats were allocated to six experimental treatments, for 6 days, arranged under three nutritional schemes namely: (a) ad libitum feeding (control), (b) fasting for 3 days and re-feeding for the remainder (re-fed) and (c) fasting for 6 days combined with parenteral liquid treatment during the last 3 days (starved). Each nutritional scheme had one non-probiotic and one probiotic treatment receiving orally Lactobacillus acidophilus. Rat caecal digesta were analyzed for bacterial enzyme activities and volatile fatty acids (VFA).

RESULTS

Fasted rats had significantly lower activities of alpha-galactosidase, alpha-glucosidase and beta-glucosidase and higher activities of beta-galactosidase and azoreductase compared to control and re-fed rats, irrespective of probiotic administration. Results were variable regarding cholylglycine hydrolase (CGH), while there were no differences between treatments regarding beta-glucuronidase and arylsulfatase activity. Fasted rats had significantly lower caecal VFA concentration and different fermentation patterns. L. acidophilus resulted in significantly reduced azoreductase activity and increased caecal acetate levels in fasted rats. Re-feeding appeared to restore most enzyme activities, fermentation intensity and to some extent fermentation patterns at control treatment levels. L. acidophilus resulted in significantly reduced CGH activity and increased butyrate levels in re-fed rats.

CONCLUSION

The results indicate a health beneficial potential of L. acidophilus in fasted and re-fed nutritional states via reduction of harmful azoreductase and CGH activities and promotion of useful VFA components for colonic function and health.

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.

The role of GSH efflux in staurosporine-induced apoptosis in colonic epithelial cells

Staurosporine (STP) was shown to induce cell apoptosis through formation of reactive oxygen species, but a role for cellular redox has not been defined. In this study, we report that STP (2 microM) caused apoptosis (24+/-3% at 24 h) of human colon adenocarcinoma epithelial cell line HT29 that was preceded by significant glutathione (GSH) and glutathione disulfide (GSSG) efflux (6 h), but independent of changes in cellular glutathione/glutathione disulfide (GSH/GSSG) redox status. The blockade of GSH efflux by gamma-glutamyl glutamate (gamma-GG) or ophthalmic acid was associated with apoptosis attenuation; however, gamma-GG administration after peak GSH efflux (8 h) did not confer cytoprotection. Moreover, lowering cellular GSH through inhibition of its synthesis prevented extracellular GSH accumulation and cell apoptosis, thus validating a link between cellular GSH export and the trigger of cell apoptosis. Inhibition of gamma-glutamyl transferase (GGT1, EC 2.3.2.2)-catalyzed extracellular GSH degradation with acivicin significantly blocked GSH efflux, suggesting that GSH breakdown is a driving force for GSH export. Interestingly, acivicin treatment enhanced extracellular GSSG accumulation, consistent with GSH oxidation. STP-induced HT29 cell apoptosis was associated with caspase-3 activation independent of caspase-8 or caspase-9 activity; accordingly, inhibitors of the latter caspases were without effect on STP-induced apoptosis. STP similarly induced GSH efflux and apoptosis in a non-malignant human NCM460 colonic cell line in association with caspase-3 activation. Collectively, our results demonstrate that STP induction of apoptosis in malignant and non-malignant colonic cells is temporally linked to the export of cellular GSH and the activation of caspase-3 without caspase-8 or -9 involvement.

Insight into long-term histological, proliferative and apoptotic modifications in ileal orthotopic neobladder and conduit mucosa

Aims and background

To assess the long-term histological, apoptotic and proliferating alterations of the intestinal mucosa of ileal conduits and orthotopic neobladders.

Methods

Fifty patients (46 males, 4 females), aged 52–78 years, who underwent urinary diversion with either ileal orthotopic neobladder (group ON, 20 patients) or conduit (group IC, 30 patients) from 2001 to 2005, were included in this prospective study Ileal samples were collected during surgery (controls) and by random mucosal biopsies 6, 12, 24, 36 and 48 months later. Histological (villi height, crypt depth, eosinophil cell count), proliferation (Ki67 immunochemistry), and apoptotic (Bcl-2 immunochemistry TUNEL) parameters were assessed.

Results

During the 4-year follow-up, we recorded progressive villi area, height and crypt depth reduction, mucosa flattening, and inflammatory and eosinophilic infiltration. Villi height: crypt depth ratio showed a statistically significant difference ( P <0.05) between the two groups from the 6th month. Dysplasia, metaplasia, and neoplasia were not observed. Bcl-2 values showed a progressive increase until 24 months in group ON and 12 months in group IC, followed by a decline thereafter. Ki-67 values showed a progressive increase after 6 months in group ON and an increase until 24 months followed by a decline thereafter in group IC. TUNEL showed two peaks, at 24 and 48 months.

Conclusions

Histological adaptation was revealed in both groups, with statistically significant differences in favor of orthotopic substitution. Proliferative and apoptotic pathways are implicated as demonstrated by relevant modifications of Bcl-2, Ki-67 and TUNEL, in accord with the histological adaptation.

Recently identified a novel neuropeptide manserin colocalize with the TUNEL-positive cells in the top villi of the rat duodenum

We recently isolated a novel 40 amino acid neuropeptide designated manserin from the rat brain. Manserin is derived from secretogranin II, a member of granin acidic secretory protein family by proteolytic processing, as previously reported secretoneurin and EM66. Manserin peptide are localized in the endocrine cells of the pituitary. In this study, we further investigated the manserin localization in the digestive system by immunohistochemical analysis using antimanserin antibody. In the duodenum, manserin immunostaining was exclusively observed in the nuclei of top villi instead of cytosol as observed in neurons in our previous study. Interestingly, manserin-positive cells in the duodenum are colocalized with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) positive cells, the cells whose DNA was damaged. Since the top villi of duodenum epithelial cells are known to undergo spontaneous apoptosis during epithelial cell turn over, and since other peptides such as secretoneurin and EM66 derived from SgII have been reported to be cancer-related, these results indicated that manserin peptide may have a role in apoptosis and/or cancer pathogenesis in the digestive organ.

Fasting induces a biphasic adaptive metabolic response in murine small intestine

BACKGROUND

The gut is a major energy consumer, but a comprehensive overview of the adaptive response to fasting is lacking. Gene-expression profiling, pathway analysis, and immunohistochemistry were therefore carried out on mouse small intestine after 0, 12, 24, and 72 hours of fasting.

RESULTS

Intestinal weight declined to 50% of control, but this loss of tissue mass was distributed proportionally among the gut's structural components, so that the microarrays' tissue base remained unaffected. Unsupervised hierarchical clustering of the microarrays revealed that the successive time points separated into distinct branches. Pathway analysis depicted a pronounced, but transient early response that peaked at 12 hours, and a late response that became progressively more pronounced with continued fasting. Early changes in gene expression were compatible with a cellular deficiency in glutamine, and metabolic adaptations directed at glutamine conservation, inhibition of pyruvate oxidation, stimulation of glutamate catabolism via aspartate and phosphoenolpyruvate to lactate, and enhanced fatty-acid oxidation and ketone-body synthesis. In addition, the expression of key genes involved in cell cycling and apoptosis was suppressed. At 24 hours of fasting, many of the early adaptive changes abated. Major changes upon continued fasting implied the production of glucose rather than lactate from carbohydrate backbones, a downregulation of fatty-acid oxidation and a very strong downregulation of the electron-transport chain. Cell cycling and apoptosis remained suppressed.

CONCLUSION

The changes in gene expression indicate that the small intestine rapidly looses mass during fasting to generate lactate or glucose and ketone bodies. Meanwhile, intestinal architecture is maintained by downregulation of cell turnover.

Morphological changes of the rat intestinal lining in relation to body stores depletion during fasting and after refeeding

Intestinal villus atrophy through prolonged fasting was studied according to two different metabolic phases reached by fasting animals and characterized by (a) the mobilization of fat stores as body fuel and (b) an increase in protein catabolism for energy expenditure. The mechanisms involved in the rapid jejunal restoration after refeeding were also determined. Mucosal structural atrophy during fasting proved to worsen over the two phases due mainly to the retraction of the lacteals in the lamina propria, as observed through the immunolocalization of aquaporin 1 in the endothelial cells of the lymphatic vessels and the detachment of the basal membrane of the epithelial lining at the tip of the villi. Microvilli surface area is preserved through fasting, and apical PepT1 expression increases during both metabolic fasting phases. Refeeding after both fasting phases induces an increase in FATP4 accompanied by a rapid lipid uptake by the enterocytes at the tip of the villi and a rapid extension of the lamina propria due to inflated lymphatic vessels. These mechanisms were more prevalent in animals refed after the phase III fast and could be considered as the major processes allowing complete morphological restoration of the jejunum within only 3 days after refeeding.

Morphological changes of the rat intestinal lining in relation to body stores depletion during fasting and after refeeding

Intestinal villus atrophy through prolonged fasting was studied according to two different metabolic phases reached by fasting animals and characterized by (a) the mobilization of fat stores as body fuel and (b) an increase in protein catabolism for energy expenditure. The mechanisms involved in the rapid jejunal restoration after refeeding were also determined. Mucosal structural atrophy during fasting proved to worsen over the two phases due mainly to the retraction of the lacteals in the lamina propria, as observed through the immunolocalization of aquaporin 1 in the endothelial cells of the lymphatic vessels and the detachment of the basal membrane of the epithelial lining at the tip of the villi. Microvilli surface area is preserved through fasting, and apical PepT1 expression increases during both metabolic fasting phases. Refeeding after both fasting phases induces an increase in FATP4 accompanied by a rapid lipid uptake by the enterocytes at the tip of the villi and a rapid extension of the lamina propria due to inflated lymphatic vessels. These mechanisms were more prevalent in animals refed after the phase III fast and could be considered as the major processes allowing complete morphological restoration of the jejunum within only 3 days after refeeding.

Local glutathione redox status does not regulate ileal mucosal growth after massive small bowel resection in rats

Glutathione (GSH) concentration affects cell proliferation and apoptosis in intestinal and other cell lines in vitro. However, in vivo data on gut mucosal GSH redox status and cell turnover are limited. We investigated the effect of altered GSH redox status on the ileal mucosa in a rat model of short bowel syndrome following massive small bowel resection (SBR). Rats underwent 80% mid-jejunoileal resection (RX) or small bowel transection (TX; as operative controls), with administration of either saline or D, L-buthionine-sulfoximine (BSO), a specific inhibitor of cellular GSH synthesis. Ileal mucosal redox, morphology, and indices of cell proliferation and apoptosis were determined at different days after surgery. Ileal GSH redox status was assessed by GSH and GSH disulfide (GSSG) concentrations and the redox potential of GSH/GSSG (Eh). Ileal lipid peroxidation [free malondialdehyde (MDA)] was measured as an index of lipid peroxidation. BSO markedly decreased ileal mucosal GSH, oxidized GSH/GSSG Eh, and increased MDA content without inducing morphological damage as assessed by light or electron microscopy. As expected, SBR stimulated adaptive growth of ileal villus height and total mucosal height at 7 d after surgery, but this response was unaffected by BSO treatment despite a modest increase in crypt cell apoptosis. Ileal cell proliferation (crypt cell bromodeoxyuridine incorporation) increased at 2 d after SBR but was unaffected by BSO. Collectively, our in vivo data show that marked depletion of ileal GSH and oxidation of the GSH redox pool does not alter indices of ileal epithelial proliferation or SBR-induced ileal mucosal adaptive growth.

Efeitos da isquemia e da reperfusão na ocorrência de apoptose no jejuno em eqüinos

Investigou-se o resultado da isquemia, da congestão e da reperfusão na ocorrência de apoptose. Modelos de obstrução vascular total - artériovenosa e venosa - foram induzidos no jejuno por 2h, seguidos de reperfusão durante 12h. As amostras de tecidos foram processadas, e os dados analisados pelo teste de Friedman. As colorações de Schorr e hematoxilina-eosina evidenciaram anoiquia, condensação da cromatina, fragmentação nuclear e celular características de apoptose. Índices apoptóticos significativamente mais baixos ocorreram em 2h e 12h de reperfusão na região das vilosidades, e tenderam à estabilidade na região das criptas. A apoptose constitui uma importante parcela na perda de células intestinais durante a isquemia, congestão e reperfusão, além da necrose.

Circadian tempo: A paradigm for genome stability?

Circadian clocks are molecular time-keeping systems that underlie daily biological rhythms in anticipation of the changing light and dark cycles. These clocks mediate daily rhythms in physiology and behavior that are thought to confer an adaptive advantage for organisms. It is hypothesized that cell cycle checkpoints are gated to an intrinsic circadian clock to protect DNA from diurnal exposure to mutagens (e.g.; UV radiation peaks with daylight and dissolved genotoxins that fluctuate with feeding periods). It is proposed that DNA replication arrest in response to genotoxic stress is a likely basis for the evolution of circadian-gated DNA replication. This protective mechanism is highly conserved and can be traced along the evolutionary time-line to the early prokaryotes, unicellular eukaryotes and viruses. Peak DNA repair capacity is normally synchronous to the crest of mutagenic stress as they oscillate with respect to time. Mutator phenotypes with increased vulnerability to genotoxic stress may therefore develop when the circadian pattern of cell cycle control, DNA repair or apoptotic response are phase-shifted relative to the rhythm of mutagenic stress. The accumulating mutations would lead to accelerated aging, genome instability and neoplasia. The proposed model delineates areas of research with potentially profound implications for carcinogenesis.

Starvation induces phase-specific changes in the proteome of mouse small intestine

Food deprivation results in metabolic, structural, and functional changes in the small intestine that influences gut mucosal integrity, epithelial cell proliferation, mucin synthesis, and other processes. The underlying mechanisms are still unclear, which lead to the study of molecular effects of short-term and long-term starvation in the intestine of mice. A comparative proteomics approach, combining two-dimensional gel electrophoresis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, was used to identify intestinal proteins whose expression is changed under different starvation conditions (0, 12, 24, and 72 h). In total, the expression levels of 80 protein spots changed significantly between the different groups. The results demonstrate that after 12 h of starvation, mainly proteins involved in glycolysis and energy metabolism show decreased expression levels. Starvation for 24 h results in a down-regulation of proteins involved in protein synthesis and amino acid metabolism. Simultaneously, proteins with a protective role, e.g., reg I and II, glutathione peroxidase 3, and carbonic anhydrase 3, are clearly up-regulated. The last starvation phase (72 h) is characterized by increased ezrin expression, which may enhance villus morphogenesis critical for survival. Together, these results provide novel insights in the intestinal starvation response and may contribute to improved nutritional support during conditions characterized by malnutrition.

Morphology of the pancreas of some species belonging to the genera Phelsuma and Gecko (family Gekkonidae): evidence of apoptotic process during the seasonal cycle

In this study we investigated comparative morphology of the endocrine pancreas of several species belonging to the family Gekkonidae and apoptotic processes of the pancreas which may be correlated to the seasonal cycle. The following species of the family Gekkonidae were studied: Phelsuma lineata, P. madagascariensis, P. dubia, P. abotti, Gekko gecko, G. vittatus, and Geckonia chazaliae. In all these species the pancreas consisted of large and medium islets as well as endocrine cells which were scattered throughout the acinar cells. Exocrine parenchyma consisted of tubuli-acini. Four mayor cell types were identified in the endocrine pancreas, using immunocytochemistry: glucagon-immunoreactive (A) cells, insulin-immunoreactive (B) cells, somatostatin-immunoreactive (D) cells, and pancreatic polypeptide immunoreactive (PP) cells. In the endocrine pancreas the amount of A cells and B cells was either equal or a prevalence of A cells was observed. In the wet season the pancreatic morphology presented normal features with very rare apoptotic cells. The animals belonging to the genus Phelsuma taken in the dry season (July) showed numerous vacuolated, Caspase 3, 9 and 11-immunoreactive acinar and some endocrine cells containing picnotic nuclei which were positive to tunel reaction. The animals belonging to the genus Gekko taken at the end of the dry season (October) exhibited strongly vacuolated, Caspase 3, 9 and 11-immunoreactive endocrine and some acinar cells containing nuclei which were positive to tunel reaction. These apoptosis events could be a reaction in response to stress mechanisms, such as a starvation period during the dry season.

The comparative physiology of food deprivation: from feast to famine

The ability of animals to survive food deprivation is clearly of considerable survival value. Unsurprisingly, therefore, all animals exhibit adaptive biochemical and physiological responses to the lack of food. Many animals inhabit environments in which food availability fluctuates or encounters with appropriate food items are rare and unpredictable; these species offer interesting opportunities to study physiological adaptations to fasting and starvation. When deprived of food, animals employ various behavioral, physiological, and structural responses to reduce metabolism, which prolongs the period in which energy reserves can cover metabolism. Such behavioral responses can include a reduction in spontaneous activity and a lowering in body temperature, although in later stages of food deprivation in which starvation commences, activity may increase as food-searching is activated. In most animals, the gastrointestinal tract undergoes marked atrophy when digestive processes are curtailed; this structural response and others seem particularly pronounced in species that normally feed at intermittent intervals. Such animals, however, must be able to restore digestive functions soon after feeding, and these transitions appear to occur at low metabolic costs.

Intestinal apoptotic changes linked to metabolic status in fasted and refed rats

Intestinal apoptosis and expression of apoptosis inducers--the cytokines TNFalpha, TGFbeta1--and the intestinal transcription factor Cdx2, were studied according to two different metabolic and hormonal phases which characterize long-term fasting: the long period of protein sparing during which energy expenditure is derived from lipid oxidation (phase II), and the later phase characterized by a rise in body protein utilization and plasma corticosterone (phase III). Apoptosis was further studied in 2, 6, and 24 h refed rats. Morphological apoptotic events were observed by environmental and conventional scanning electron microscopy and a TUNEL test was used to characterize the final stages of apoptotic death. The gene and protein expressions of TNFalpha, TGFbeta1, and Cdx2 were measured. Apoptotic events and TNFalpha, TGFbeta1, and Cdx2 gene and protein expressions did not vary significantly during phase II as compared to the normally fed animals. However, a phase III fasting induced a delay in intestinal epithelial apoptosis, along with a 92, 58, and 25% decrease in TNFalpha, TGFbeta1, and Cdx2 mRNAs, respectively. The amounts of TNFalpha, TGFbeta1, and Cdx2 proteins decreased by 70, 36, and 25%, respectively. Apoptosis was restored rapidly after a 2 h refeeding following the phase III, accompanied by a significant increase in TNFalpha, TGFbeta1, and Cdx2 mRNA and the protein levels, compared to the phase III fasting values. The concomitant decreases in cytokines and Cdx2 and in apoptotic cells during phase III suggest the preservation of enterocytes during this critical fasting period in order to optimize nutrient absorption as soon as food is available and thus, to rapidly restore body mass.

Decreased susceptibility of differentiated PC12 cells to oxidative challenge: relationship to cellular redox and expression of apoptotic protease activator factor-1

We previously showed that tert-butyl hydroperoxide (TBH) induced apoptosis in naïve rat pheochromocytoma (nPC12) cells that correlated with cellular redox imbalance and mitochondrial apoptotic signaling. In this study, we tested the hypothesis that differentiation of nPC12 cells results in altered susceptibility to TBH utilizing a model of differentiated PC12 (dPC12) cells induced by nerve growth factor. TBH (100 microM) induced dPC12 apoptosis (12% at 24 h) at levels lower than naïve cells (35%). This resistance was associated with elevated GSH, NADPH (reduced nicotinamide adenine dinucleotide phosphate), TBH metabolism, redox enzyme activities, reduced cellular GSH/GSSG (glutathione disulfide) status and preservation of mitochondrial membrane potential. Altering cellular GSH with ethacrynic acid or N-acetylcysteine, respectively, exacerbated or protected against dPC12 apoptosis. dPC12 apoptosis was mediated by caspase-9 and -3 activation and apoptosis protease activator protein-1 (Apaf-1) expression. These results show that nPC12 transition to dPC12 cells afforded protection against oxidative challenge due to maintenance of reduced GSH/GSSG and decreased Apaf-1 expression.

Apoptosis in rat jejunal mucosa is regulated partly through the central nervous system, which controls feeding behavior

AIM

The aim of this study was to investigate whether central nervous system-related feeding behavior regulates mucosal apoptosis in rat small intestines.

METHODS

The test solutions used in this study were an H(1) receptor antagonist (chlorpheniramine maleate), 2-deoxy-D-glucose, leptin, and 1-deoxy-D-glucosamine (2-amino-1,5-anhydro-2-deoxy-D-glucitol). Test solutions were injected into the third cerebroventricles of rats. Feeding behavior and jejunal apoptosis were evaluated both with and without truncal vagotomy. Intestinal apoptosis was evaluated by percentage fragmented DNA, electrophoresis, and TUNEL staining.

RESULTS

Chlorpheniramine and 2-deoxy-D-glucose elicited feeding, whereas leptin and 1-deoxy-D-glucosamine suppressed feeding. The test solutions, which elicited feeding (0.24 and 24 micromol/rat of chlorpheniramine and 2-deoxy-D-glucose, respectively), suppressed mucosal apoptosis in the rat jejunum 1 h after cerebroventricular infusion. In contrast, the test solutions, which suppressed feeding (8 and 24 micromol/rat of leptin and 1-deoxy-D-glucosamine, respectively), induced jejunal mucosal apoptosis 3 h after infusion. The effects of the test solutions on feeding behavior and changes in apoptosis were not affected by truncal vagotomy.

CONCLUSION

The central nervous system, which regulates feeding behavior, might control intestinal function through the regulation of intestinal apoptosis.

Intestinal glutathione: determinant of mucosal peroxide transport, metabolism, and oxidative susceptibility

The intestine is a primary site of nutrient absorption and a critical defense barrier against dietary-derived mutagens, carcinogens, and oxidants. Accumulation of oxidants like peroxidized lipids in the gut lumen can contribute to impairment of mucosal metabolic pathways, enterocyte dysfunction independent of cell injury, and development of gut pathologies, such as inflammation and cancer. Despite this recognition, we know little of the pathways of intestinal transport, metabolism, and luminal disposition of dietary peroxides in vivo or of the underlying mechanisms of lipid peroxide-induced genesis of intestinal disease processes. This chapter summarizes our current understanding of the determinants of intestinal absorption and metabolism of peroxidized lipids. I will review experimental evidence from our laboratory and others (Table 1) supporting the pivotal role that glutathione (GSH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) play in mucosal transport and metabolism of lipid hydroperoxides and how reductant availability can be compromised under chronic stress such as hypoxia, and the influence of GSH on oxidative susceptibility, and redox contribution to genesis of gut disorders. The discussion is pertinent to understanding dietary lipid peroxides and GSH redox balance in intestinal physiology and pathophysiology and the significance of luminal GSH in preserving the integrity of the intestinal epithelium.

Impaired immune responses in broiler hatchling hindgut following delayed access to feed

One of the key stimulators of intestinal development in the chick is physical exposure to feed, while feed withholding delays the onset of gut development. A delay of 24-72 h in onset of feeding is quite common in the poultry industry due to variation in hatching time and hatchery treatments. As intestinal development occurs in concert with the development of the gut associated lymphoid tissue (GALT), we investigated the effects of short term feed withholding on development of GALT in broiler hatchlings. GALT activity was determined by antibody production (systemic and locally in the gut), distribution of B and T lymphocytes in the gut, expression of lymphocyte specific genes, and distribution of B and T lymphocytes in the cloacal bursa. Our findings show that while development of GALT in the foregut (duodenum, jejunum, ileum) was only slightly and temporarily impeded by feed withholding, GALT activity in the hindgut and the gut-related cloacal bursa was significantly delayed during the first 2 weeks of life: Systemic and intestinal antibody responses following rectal immunization to antigen were lower, colonization of the hindgut (cecum and colon) by T and B lymphocytes was delayed, as well as the expression of chIL-2 mRNA in hindgut T lymphocytes. We also found that the increase of B and T population size in the cloacal bursa was delayed with time. Full recovery occurred from 2 weeks of age. The 2-week vulnerable period should be seriously considered in circumstances where hatchlings are in transit for extended periods from hatcheries to farms.

Short-term fasting induces intra-hepatic lipid accumulation and decreases intestinal mass without reduced brush-border enzyme activity in mink (Mustela vison) small intestine

For many mammalian species short-term fasting is associated with intestinal atrophy and decreased digestive capacity. Under natural conditions, strictly carnivorous animals often experience prey scarcity during winter, and they may therefore be particularly well adapted to short-term food deprivation. To examine how the carnivorous gastrointestinal tract is affected by fasting, small-intestinal structure, brush-border enzyme activities and hepatic structure and function were examined in fed mink (controls) and mink that had been fasted for 1-10 days. During the first 1-2 days of fasting, intestinal mass decreased more rapidly than total body mass and villus heights were reduced 25-40%. In contrast, tissue-specific activity of the brush-border enzymes sucrase, maltase, lactase, aminopeptidase A and dipeptidylpeptidase IV increased 0.5- to 1.5-fold at this time, but returned to prefasting levels after 6 days of fasting. After 6-10 days of fasting there was a marked increase in the activity of hepatic enzymes and accumulation of intra-hepatic lipid vacuoles. Thus, mink may be a useful model for studying fasting-induced intestinal atrophy and adaptation as well as mechanisms involved in accumulation of intra-hepatic lipids following food deprivation in strictly carnivorous domestic mammals, such as cats and ferrets.

Effects of fasting and refeeding on jejunal morphology and cellular activity in rats in relation to depletion of body stores

BACKGROUND

Intestinal mucosa atrophy following a period of starvation characterized by the mobilization of fat stores for energy expenditure (phase II) worsen after a long fast marked by an increase in protein catabolism (phase III). However, the morphology of the jejunum is completely restored after 3 days of refeeding. The aim of this study was to determine the mechanisms involved in the rapid jejunal restoration following the critical phase III.

METHODS

Jejunal structure was observed through conventional and environmental scanning electron microscopy, whilst cellular dynamics were studied using classical optic microscopy tools and immunohistochemistry.

RESULTS

Mucosal structural atrophy during fasting proved to worsen over the two phases. During phase II, apoptosis is still present at the tip of the villi, the number of mitosis in crypts showed a 30% decrease and a transient drop in cell migration is observed. During phase III, however, an 85% rise in mitosis was noticed along with an increase in cell migration and the disappearance of apoptotic cells at the villus tips. This increased cell renewal continues after food ingestion.

CONCLUSIONS

Starved rats appeared to be in a phase of energy sparing in phase II, with depressed cellular events in the intestinal mucosa. In phase III, however, the preservation of functional cells and the early increase in crypt cell proliferation should prepare the mucosa to refeeding and could explain why jejunal repairs are complete after 3 days of refeeding following either phase II or phase III.

Intracerebroventricular administration of leptin-induced apoptosis in the rat small intestinal mucosa

The localization of leptin and leptin receptors in the stomach and small intestine has been reported. Their function is still unknown, although leptin is a hormone that regulates appetite and fat-related metabolism. The small intestine is one of the important organs for regulating metabolism. The purpose of the present study was to investigate whether leptin regulates apoptosis in the small intestinal mucosa. Intestinal apoptosis was evaluated by percent fragmented DNA, electrophoresis, TUNEL staining, and western blotting analysis of caspase-3. Mucosal apoptosis in the rat jejunum and ileum was evaluated at 0, 3, 6, 12, and 24 hrs after injection. Rats were tested after ad libitum feeding and 24-hr fasting to exclude the anorectic effect of leptin. Leptin was injected intraperitoneally (ip) at a dose of 200 microg/rat and infused into the rat third cerebroventricle (icv) at a dose of 8 microg/rat. Leptin at a dose of 8 microg/rat significantly induced intestinal apoptosis in the small intestine at 3 and 6 hrs after icv administration in both ad libitum feeding and 24-hr fasted rats. This increase in apoptosis was not attenuated by vagotomy. Intestinal apoptosis increased 12 and 24 hrs after ip injection of leptin at a dose of 200 microg/rat. The peak of the increase in apoptosis in icv rats appeared earlier than that in ip rats. Leptin induced jejunal and ileal mucosal apoptosis in the rat, indicating that leptin might control intestinal function through the regulation of intestinal apoptosis.

Enterocyte apoptosis and barrier function are modulated by SIgA after exposure to bacteria and hypoxia/reoxygenation

BACKGROUND

Secretory immunoglobulin A (SIgA) is the principal immune defense against luminal pathogens at gut mucosal surfaces. It also has anti-inflammatory activities that may be important for the maintenance of mucosal surface integrity. Enterocyte apoptosis (Apo) is increased after challenge with invasive bacteria and ischemia-reperfusion insults. Increased Apo also has been associated with impaired intestinal barrier function. However, the impact of SIgA on enterocyte apoptosis and mucosal barrier integrity after challenge with commensal bacteria and ischemia-reperfusion is unknown.

METHODS

Caco2 intestinal epithelial cell monolayers were subjected to 21% O(2) (control) or 95% N(2)/15% CO(2) (hypoxic) conditions for 90 minutes, followed by 21% O(2). Escherichia coli and SIgA were added in subsets. Caco2 cell Apo was identified by flow cytometry and barrier function indexed by permeability to dextran-fluorescein isothiocyanate.

RESULTS

There were no differences in the percentage of Apo Caco2 cells after exposure to either bacteria or hypoxic-reoxygenation versus control. There was a significant increase in Apo after the combined bacteria/hypoxia-reoxygenation challenge. SIgA abrogated the Apo response and preserved barrier function after this combined challenge.

CONCLUSION

Modulation of enterocyte Apo by SIgA may serve to maintain intestinal barrier function and thereby decrease the systemic inflammatory response after clinical conditions associated with gut ischemia-reperfusion insults.

Effects of immunonutrition on intestinal mucosal apoptosis, mucosal atrophy, and bacterial translocation in head injured rats

BACKGROUND

Immunonutrition has been demonstrated to modulate gut function, reduce infectious complications, hospital stay, and ventilator days in the critical patients.

AIM OF THE STUDY

We assessed the effect of immunonutrition for the prevention of intestinal mucosal atrophy, apoptosis, and bacterial translocation in head injured rats.

METHODS

Thirty five rats were randomised into 5 groups. Following moderate closed head injury, in Group 1; Standard Enteral Nutrition, Group 2; Immunonutrition, Group 3; TPN, Group 4; pe. saline were applied. Group 5 was control group (chow-fed). The rats were sacrificed and segments of the ileum were removed for histologic examination, and samples of tissues taken for microbiologic evaluation.

RESULTS

Both intestinal apoptosis and mucosal atrophy were significantly lower in Group 2 and Group 5 (p<0.008). Bacterial translocation was significantly lower in Group 2 than Group 1 (p<0.008).

CONCLUSION

The enteral immunonutrition prevents intestinal barrier function in brain injured rats.

Effects of antioxidative agents on apoptosis induced by ischaemia-reperfusion in rat intestinal mucosa

BACKGROUND AND AIM

We have previously demonstrated that ischaemia-reperfusion induces apoptosis in the intestinal mucosa. To evaluate that reactive oxygen species enhanced intestinal apoptosis after ischaemia-reperfusion, we examined whether antioxidants reduced apoptosis.

METHODS

Rats were infused through a duodenal tube with antioxidative agents, glutathione, rebamipide and dymethylsulfoxide during 2 h before an ischaemic insult. The superior mesenteric artery was occluded for 60 min, followed by 60 min reperfusion. Apoptosis was evaluated by percentage fragmented DNA (fragmented DNA/total DNA) and immunochemical staining.

RESULTS

Increase in apoptosis in the intestinal mucosa after ischaemia-reperfusion was attenuated by intraduodenal infusion of antioxidative agents, but was not completely abolished.

CONCLUSION

Scavenging effects of the antioxidative agents attenuated increases in intestinal apoptosis, indicating that oxidative stress after ischaemia-reperfusion plays an important role in induction of apoptosis in the intestinal mucosa.

Homeostasis in the small intestinal mucosa balanced between cell proliferation and apoptosis is regulated partly by the central nervous system

The aim of this study was to investigate whether the central nervous system regulates mucosal cell growth and apoptosis in the rat small intestine. Ornithine decarboxylase is a key enzyme for polyamine synthesis, which plays an important role in intestinal mucosal growth. The increase in ornithine decarboxylase activity in the duodenum just before a dark period was abolished by truncal vagotomy. An infusion of 2-deoxy-D-glucose into the third cerebroventricle activated the enzyme activity in the small intestine. Epithelial homeostasis is balanced by the regulation of cell proliferation and cell death. Intestinal mucosal apoptosis decreased in rats with ventromedial hypothalamus lesions, which induced hyperphagia and obesity. In contrast, sustained anorexia induced by 1-deoxy-D-glucosamine increased intestinal apoptosis. These results indicate that the central nervous system, in addition to local factors, is related to the regulation of mucosal homeostasis in the intestinal mucosa.

iNOS enhances rat intestinal apoptosis after ischemia-reperfusion

The aim of this study was to demonstrate (i) the role of iNOS (inducible nitric oxide synthase) on apoptosis in the rat intestinal mucosa after ischemia-reperfusion, and (ii) the effect of iNOS on the release of cytochrome c from mitochondria. The superior mesenteric artery was occluded for 60 min and was followed by a 60 min reperfusion. Rats were pretreated with an intraperitoneal injection of the following iNOS inhibitors: N-nitro-L-arginine methyl ester, aminoguanidine, and (1S,5S,6R,7R)-7- chloro-3-imino-5-methyl-2-azabicyclo [4. 1. 0] heptane hydrochloride (ONO-1714). Apoptosis was evaluated and NO(X) in the portal vein was assayed. The amount of iNOS, caspase-3, and cytochrome c were determined by a Western blot analysis. Intestinal mucosal epithelial mitochondrial dehydrogenase activity was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoilium bromide. Ischemia-reperfusion increased intestinal mucosal apoptosis, NO(X) production in the portal vein, the amount of iNOS protein, and the release of cytochrome c, but not caspase-3. Inhibitors of iNOS significantly attenuated the induction of apoptosis, increased NO(X) production, and release of cytochrome c. Mitochondrial dysfunction was induced by ischemia-reperfusion, which was ameliorated by iNOS inhibitors. Our results indicate that iNOS is related to increased mucosal apoptosis in the rat small intestine after ischemia-reperfusion, which is partly explained by the release of cytochrome c from mitochondria to cytosols following mitochondrial dysfunction.

Starving affects CDX gene expression during small intestinal development in the chick

The small intestine of the chicken undergoes intensive changes in the immediate posthatch period, increasing in size and developing crypts, villi and mature enterocytes. During this time, chicks are also transferring from nutrition based on the lipid-rich yolk to exogenous carbohydrate-rich feeds. The cdx homeobox genes participate in axial patterning and in definition of cell identity in embryos, and some cdx genes remain active postpartum in organs such as the intestine. In this study, the transcription patterns of two of these genes, cdxA and cdxB, were examined in the small intestine of the embryo and posthatch chick; in addition, the effects on these genes of starving for 48 h at hatch were examined. Both cdx transcription factors were upregulated toward the time of hatch and were observed in proliferating enterocytes; this enhanced expression continued posthatch. Distribution of cdxA changed with age and was found at higher concentrations in mature enterocytes. Starving from 0 to 48 h posthatch retarded growth and decreased enterocyte proliferation and expression of cdxA and cdxB. After access to feed, expression of cdx genes was enhanced. Chicken homeobox genes cdxA and cdxB are expressed in all enterocytes during embryonic and posthatch development; however, cdxA may have a role in enterocyte maturation posthatch. CdxB was expressed later in development then previously reported.