Apoptosis of intestinal intraepithelial lymphocytes induced by exogenous and endogenous glucocorticoids

The reduced bactericidal activity of neutrophils as an incisive indicator of water-immersion restraint stress and impaired exercise performance in mice

The incisive evaluation of psychological stress may be required to determine the exercise performance of stressed hosts. We investigated objective markers of psychological stress that reflect exercise performance, focusing on the neutrophil function. We used murine water-immersion restraint (WIR) stress for our assessments. After receiving WIR for 1 or 2 h, mice were exercised on an airtight treadmill that monitors their respiratory exchange ratio. The neutrophil function was analyzed after WIR stress. Although the control mice (without WIR) showed good combustion of both carbohydrates and lipids as energy sources during treadmill exercise, mice that underwent 2-h WIR did not combust carbohydrates or lipids effectively, drastically reducing their performance. In contrast, the 1-h WIR mice showed carbohydrate combustion (albeit a slow response) but did not use lipids for energy, thereby running longer than the 2-h WIR mice but shorter than the control mice. The bactericidal activity of neutrophils, but not their superoxide production or microsphere-phagocytic activity, was significantly reduced by 1-h WIR and further reduced by 2-h WIR, indicating a significant association between WIR stress and exercise performance. The neutrophil bactericidal activity may be a good indicator of psychological stress and a useful tool for precisely assessing exercise performance.

Probiotic sonicates selectively induce mucosal immune cells apoptosis through ceramide generation via neutral sphingomyelinase

Background

Probiotics appear to be beneficial in inflammatory bowel disease, but their mechanism of action is incompletely understood. We investigated whether probiotic-derived sphingomyelinase mediates this beneficial effect.

Methodology/Principal Findings

Neutral sphingomyelinase (NSMase) activity was measured in sonicates of the probiotic L. brevis (LB) and S. thermophilus (ST) and the non-probiotic E. coli (EC) and E. faecalis (EF). Lamina propria mononuclear cells (LPMC) were obtained from patients with Crohn's disease (CD) and Ulcerative Colitis (UC), and peripheral blood mononuclear cells (PBMC) from healthy volunteers, analysing LPMC and PBMC apoptosis susceptibility, reactive oxygen species (ROS) generation and JNK activation. In some experiments, sonicates were preincubated with GSH or GW4869, a specific NSMase inhibitor. NSMase activity of LB and ST was 10-fold that of EC and EF sonicates. LB and ST sonicates induced significantly more apoptosis of CD and UC than control LPMC, whereas EC and EF sonicates failed to induce apoptosis. Pre-stimulation with anti-CD3/CD28 induced a significant and time-dependent increase in LB-induced apoptosis of LPMC and PBMC. Exposure to LB sonicates resulted in JNK activation and ROS production by LPMC. NSMase activity of LB sonicates was completely abrogated by GW4869, causing a dose-dependent reduction of LB-induced apoptosis. LB and ST selectively induced immune cell apoptosis, an effect dependent on the degree of cell activation and mediated by bacterial NSMase.

Conclusions

These results suggest that induction of immune cell apoptosis is a mechanism of action of some probiotics, and that NSMase-mediated ceramide generation contributes to the therapeutic effects of probiotics.

Intrauterine growth restriction modifies the developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization in neonatal pigs

Neonates with intrauterine growth restriction (IUGR) are prone to suffer from digestive diseases. Using neonatal pigs with IUGR, we tested the hypothesis that IUGR may induce alterations in the developmental pattern of intestinal barrier and thereby may be responsible for IUGR-associated increased morbidity. Piglets with a birth weight near the mean birth weight (+/-0.5 SD) were identified as normal birth weight (control) and piglets with a mean -2 SD lower birth weight (-30%) were defined as piglets with IUGR. The developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization was investigated from birth to d 5 postnatal. At birth, intestinal weight and length, ileal and colonic weight per unit of length, and villous sizes were lower (P < 0.05) in piglets with IUGR than in same-age control piglets. These IUGR-induced intestinal alterations further persisted, although they were less marked at d 5. Counts of adherent bacteria to ileal and colonic mucosa were greater (P < 0.05) in 2-d-old piglets with IUGR than in same-age control piglets. Dynamic analyses of the transcriptomic profile of the intestine revealed molecular evidence of IUGR-induced intestinal growth impairment that may result from a change in the cell proliferation-apoptosis balance during the first days of life, while a protective process would occur later on. In addition, changes in the expression of several genes suggest a pivotal role of both glucocorticoids and microbiota in driving IUGR intestinal development during the neonatal period.

Lipid homeostasis, lipotoxicity and the metabolic syndrome

In the 20th century industrialized nations have become afflicted with an unprecedented pandemic of increased adiposity. In the United States, the epicenter of the epidemic, over 2/3 of the population, is overweight and 1 of every 6 Americans carries the diagnosis of metabolic syndrome. Although genes determine susceptibility to environmental factors, the epidemic is clearly due to increased consumption of calorie-dense, highly lipogenic foods, coupled with a marked decrease in physical exertion resulting from modern technologies. If this lifestyle continues, morbid consequences are virtually inevitable. They include type II diabetes and a cluster of disorders known as "the metabolic syndrome" usually appearing in middle age. The morbid consequences of the chronic caloric surplus are buffered before middle age by the partitioning of these calories as fat in the adipocyte compartment which is specifically designed to store triglycerides. Leptin has been proposed as the major hormonal regulator of the partitioning of surplus calories. However, multiple factors can determine the storage capacity of the fat tissue and when it is exceeded ectopic lipid deposition begins. The organs affected in metabolic syndrome include skeletal muscle, liver, heart and pancreas, which are now known to contain abnormal levels of triglycerides. While neutral fat is probably harmless, it is an index of ectopic lipid overload. Fatty acid derivatives can interfere with the function of the cell and ultimately lead to its demise through lipoapoptosis, the consequences of which are gradual organ failure.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

Effect of restraint stress on the population of intestinal intraepithelial lymphocytes in mice

The impact of restraint stress on the intestinal immune system, particularly on intestinal intraepithelial lymphocytes (i-IEL), has not been described in detail. Thus, the purpose of this study was to assess the effects of restraint stress, including those produced by increases in glucocorticoids and catecholamines, on the population of i-IEL. Mice were exposed to 1 or 4h restraint stress for 4 day, and the number of IEL in the mucosa of the proximal small intestine was determined by immunohistochemistry. The effects of restraint were also analyzed in mice submitted to different procedures: adrenalectomy, chemical sympathectomy, and treatment with a glucocorticoid antagonist (RU486), dexamethasone, and epinephrine. The main findings were that: (1) chronic restraint-stress reduced the i-IEl population in the small intestine; (2) adrenalectomy, treatment with RU-486 and chemical sympathectomy decreased the number of gammadelta, CD4+ and CD8+ T cells in non-stressed groups; (3) dexamethasone reduced the number of gammadelta and CD8+ T cells, and (4) epinephrine reduced the number of gammadelta, CD4+ and CD8+ T cells. These results demonstrated that restraint stress decreased the number of i-IEL in the proximal small intestine of mice, mainly by the combined action of higher concentrations of catecholamines and glucocorticoids, and that lower concentrations of glucocorticoids and catecholamines in unstressed mice preserved the population of i-IEL.

Effect of short-term dietary intake of bovine lactoferrin on intestinal lymphocyte apoptosis in healthy mice

OBJECTIVE

The objective of this study was to describe the effects of short-term dietary exposure of bovine lactoferrin (Lf) on intestinal lymphocyte apoptosis and expression of tumor necrosis factor-alpha (TNF-alpha) in healthy mice.

METHODS

Female C57BL/6 mice were randomly assigned to three treatment groups: 0% Lf (n = 16), 0.2% Lf (n = 16), and 2.0% Lf (n = 15). Bovine Lf was administered orally, as part of the diet, for 4 consecutive days. Intestinal lymphocytes (ILs) were isolated and analyzed for percentages of CD4, CD8, apoptotic CD4, and apoptotic CD8 cells using flow cytometry. Pro- (caspase-3) and anti- (Bcl-2) apoptotic protein expressions and TNF-alpha expression in ILs were determined by Western blotting.

RESULTS

There were significant increases in the percentages of CD4 (P = 0.02) and apoptotic CD4 (P = 0.02) ILs in bovine Lf-fed compared with control mice. Percentages of CD8 and apoptotic CD8 cells and expression of caspase-3 and Bcl-2 in ILs did not differ significantly by diet group. In contrast, the expression of TNF-alpha was significantly lower in Lf-fed versus control mice (P = 0.01).

CONCLUSION

Short-term dietary Lf decreased TNF-alpha expression in ILs and increased apoptosis of CD4 ILs in healthy mice.

Effect of repeated exercise stress on caspase 3, Bcl-2, HSP 70 and CuZn-SOD protein expression in mouse intestinal lymphocytes

The purpose of this study was to characterize the expression of apoptosis (caspase 3, Bcl-2) and survival (HSP 70, antioxidant CuZn-SOD) proteins in intestinal lymphocytes (IL) of mice after repeated exercise stress. Plasma corticosterone concentration was greater than twofold higher immediately after exercise compared with the non-exercised condition. IL numbers decreased 24 h after cessation of exercise (p<0.05); this was associated with increased caspase 3 (p<0.05), HSP 70 (p<0.001) and CuZn-SOD (p<0.05) expression in IL immediately after exercise relative to IL from non-exercised mice. Expression of these proteins returned to control levels 24 h after the cessation of exercise stress.

Effects of dexamethasone on peripheral blood mononuclear cell phenotype in weanling piglets

The aim of this study was to evaluate the effect of dexamethasone treatment on the immune system of weanling piglets. Piglets were administered dexamethasone (DEX; 1mg/kg, IM) every 12h for 2 consecutive days (short-term experiment) or DEX (1mg/kg, IM) daily for 2 weeks (long-term experiment). The relative percentage of CD8(+) T cells in peripheral blood mononuclear cells (PBMCs) was significantly decreased (P<0.05) in both short- and long-term DEX-treated groups compared to their control groups. The percentage of IgM(+) cells in PBMCs of the long-term DEX-treated group was greatly increased (P<0.05) in comparison to the control group. The results of this study indicate that short-term DEX-treatment increases leucocyte function; however, long-term DEX-treatment depresses leucocyte function, especially that of CD8(+) T cells.

In vivo corticosterone administration at levels occurring with intense exercise does not induce intestinal lymphocyte apoptosis in mice

Intestinal lymphocyte apoptosis can occur following physiological and pathophysiological stress as well as exhaustive exercise. In this study we investigated whether corticosterone (CORT) administration at physiological concentrations observed following strenuous exercise induces intestinal lymphocyte apoptosis and cell loss in mice. CORT injection (14 mg/kg; i.p.) caused a four-fold increase in plasma CORT concentrations, but did not affect intestinal lymphocyte cell loss or alter baseline intestinal lymphocyte apoptosis, as measured by phosphatidylserine externalization, cell viability, mitochondrial membrane depolarization, caspase 3, Bcl-2 and cytosolic cytochrome c protein levels. These findings indicate that CORT at levels observed following strenuous exercise is not involved in intestinal lymphocyte apoptosis and cell loss.

N-acetyl-l-cysteine protects intestinal lymphocytes from apoptotic death after acute exercise in adrenalectomized mice

Lymphocyte apoptosis has been observed after strenuous exercise. Both glucocorticoids (GC) and reactive oxygen species (ROS) have been suggested to contribute to exercise-induced lymphocyte apoptosis. The aims of this study were to 1) examine the direct contribution of GC during exercise-induced intestinal lymphocyte (IL) apoptosis and 2) determine the contribution of oxidative stress, in the absence of GC, to exercise-induced IL apoptosis. Mice were bilaterally adrenalectomized (ADX) and randomly assigned to receive saline (SAL) or N-acetyl-l-cysteine (NAC) 30 min before treadmill exercise (EX). EX consisted of 90 min of continuous running at a 2 degrees slope (30 min at 22 m/min, 30 min at 25 m/min; and 30 min at 28 m/min), and then killed immediately (Imm) or 24 h (24 h) postexercise. Control mice were exposed to a nonexercised (NonEX) condition consisting of treadmill noise and vibration without running. ILs were isolated and measured for apoptotic (phosphatidylserine externalization, mitochondrial membrane depolarization, Bcl-2, caspase 3, and cytosolic cytochrome c) and oxidative stress (H(2)O(2) and glutathione) markers. Plasma was analyzed for corticosterone (CORT) by radioimmunoassay. ADX eliminated the exercise-induced elevation in CORT but did not prevent IL apoptosis and cell loss relative to NonEX mice. In contrast, administration of NAC to ADX mice protected ILs from apoptotic cell death and inhibited post-exercise cell loss. These findings suggest that GC are not responsible for exercise-induced apoptosis and cell loss of ILs. The protective effect provided by the antioxidant NAC strongly suggest that oxidative stress is the primary pathway for IL apoptosis and cell loss after strenuous exercise.

Intraepithelial but not lamina propria lymphocytes in the porcine gut are affected by dexamethasone treatment

It is well established that glucocorticoids are key regulators of the immune system and act as immunosuppressive agents in high concentrations. In the pig, effects on the gut immune system and trafficking of lymphocytes between tissues and blood plasma were not investigated so far. Twelve pigs of 70 kg were fed 0.4 mg portions of dexamethasone (Dexa) twice daily for 9 days or remained untreated (controls) and were sacrificed for tissue collection at the end of Dexa treatment. Another six pigs with jugular vein catheters were left untreated for 7 days (control period) and then received Dexa for 9 days. Blood was drawn twice during the control period and at days 3, 6 and 9 of the Dexa period for characterization of peripheral blood leukocytes. Cells were obtained from thymus, mesenteric lymph nodes, jejunal mucosa and Peyer's patches. Lymphoid cells from gut tissue were isolated from two fractions: the EDTA-fraction, containing the intraepithelial lymphocytes (IEL), and the Collagenase-fraction, containing the lamina propria lymphocytes (LPL). In all samples, cell counts and phenotypic characterization of cells by flow cytometry (FCM) were performed. In thymus, Dexa led to a more than 90% reduction of the absolute cell number, which was mainly found in the CD4+CD8+ subpopulation. Dexa effects on lymphocytes from mesenteric lymph nodes were less severe (50%) and led mainly to a decrease (71%) of B-lymphocytes. The number of lymphocytes in the EDTA-fraction (IEL) of the jejunal mucosa decreased significantly by 56% in the Dexa-treated animals compared to the controls, whereas the number of lymphocytes in the Collagenase-fraction (LPL) decreased only moderately. In the Peyer's patches, a decreasing tendency in the number of lymphocytes in the EDTA-fraction was observed which, however, was not significant. In blood, monocytes and granulocytes were significantly increased in an order of 60%. The data show that supraphysiological amounts of Dexa remarkably reduce cell numbers in thymus and also in the intraepithelial compartment of the jejunal mucosa and ileal Peyer's patches. In blood, a notable homeostasis was observed for several leukocyte populations whereas both monocytes and granulocytes increased.

Polyethylene glycol but not mifepristone prevents intestinal lymphocyte loss following treadmill exercise in mice

Circulating lymphocyte numbers decrease following intense physical activity, possibly due to exercise-induced apoptosis. Increased reactive oxygen species (ROS) and glucocorticoids (GC) following exercise contribute to lymphocyte apoptosis. Intestinal lymphocyte (IL) numbers also decrease following exercise.

AIM

The purpose of this study was to determine the contribution of GC to exercise-induced IL loss.

METHODS

Female C57BL/6 mice (n = 178) were randomized to five drug conditions: (1) single injection of the glucocorticoid receptor antagonist mifepristone (MIF) solubilized in polyethylene glycol (PEG); (2) three injections of MIF (repeated MIF) PEG; (3) single injection of PEG (PEG); (4) three injections of PEG (repeated PEG); or (5) repeated injections of saline (SAL). Within each drug group mice were further randomized to exercise conditions: (1) control condition (non-exercised); (2) treadmill running with sacrifice immediately following the exercise; or (3) treadmill running with sacrifice 24 h after completion of the exercise.

RESULTS

There was a significant exercise effect, across all T lymphocyte subsets, in SAL (P < 0.01), PEG (P < 0.01) and MIF (P < 0.01) treated mice but not in mice given repeated PEG or repeated MIF exposure. The exercise effect was due to reduced IL numbers 24 h post-exercise compared with non-exercised controls.

CONCLUSION

These results suggest that GC are not directly responsible for IL cell loss following exercise. Repeated exposure to PEG may confer protection in the gastrointestinal tract from exercise-induced lymphocyte depletion. Because PEG inhibits ROS generation in experimental cell injury, the mechanisms for IL loss after exercise may involve oxidative stress.

Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2 degrees slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45(+) cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45(+), CD3alphabeta(+), CD3gammadelta(+), CD8beta(+), CD8alpha(+), CD4(+), and NK(+) phenotypic markers. ADX mice had significantly more intestinal CD45(+) leukocytes (P < 0.05) and CD3alphabeta(+) (P < 0.05), CD3gammadelta(+) (P < 0.01), CD8alpha(+) (P < 0.001), and NK(+) (P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45(+) leukocytes (P < 0.01) and CD3alphabeta(+) (P < 0.05), CD8alpha(+) (P < 0.001), and CD4(+) (P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical x exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise (P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.

Repeated Stress Suppresses Interferon-.GAMMA. Production by Murine Intestinal Intraepithelial Lymphocytes

Intestinal intraepithelial lymphocytes (IEL), one of the major effector components in the mucosal immune system, are phenotypically and functionally distinct from thymic and peripheral T cells. To investigate the effect of repeated stress on the number and function of IEL, we exposed male C3H/HeN mice to mild electric foot shock for 30 min/day for 5 consecutive days. Immediately after the final foot shock stress, the blood, spleen, thymus and small intestine of each of the mice were obtained. As a functional measure, we evaluated interferon (IFN)- gamma production by IEL, since IFN-gamma is a key immunomodulating cytokine in mucosal immune responses. Serum corticosterone level was elevated immediately after foot shock stress. There were no significant changes in the number of whole IEL and CD3+ IEL subsets after the stress. In contrast, the stress led to a significant decrease in the total number of thymocytes, particularly the reduction in the number of CD4+CD8+ thymocytes. Thymocytes expressed the highest level of intracellular glucocorticoid receptor (GR), followed by splenocytes and IEL. The foot shock stress induced a marked suppression of IFN-gamma production by IEL, when stimulated with immobilized anti-CD3 monoclonal antibody. Furthermore, corticosterone suppressed the IFN-gamma production by cultured IEL, which was prevented by Mifepristone (RU486), a GR antagonist. In summary, repeated foot shock stress did not alter the numbers of IEL and CD3+ IEL subsets, but suppressed IFN-gamma production by IEL, which was probably mediated by the elevated corticosterone. We therefore propose that stress influences host defense by suppressing the production of IFN-gamma in IEL.

Treadmill exercise in mice increases intestinal lymphocyte loss via apoptosis

Strenuous exercise is associated with a transient decline in circulating lymphocytes, possibly through increased apoptosis. Intestinal lymphocytes are important effector cells of intestinal immune function but have not been studied in relation to exercise.

AIM

The purpose of the present study was to examine the effect of exercise on intestinal lymphocyte phenotypes and apoptosis.

METHODS

Female C57BL/6 mice (n = 112) were randomized to: (1) treadmill running (90 min, 32 m min-1, 8 degrees grade) and killed immediately after exercise, (2) treadmill running and killed 2 h after exercise, (3) treadmill running and killed 24 h after exercise or (4) a non-exercised control condition with exposure to treadmill noise and vibration without running.

RESULTS

Flow cytometry indicated that the total intestinal CD3+T (P < 0.01), CD4+T (P < 0.005), CD8+T (P < 0.05), pan-NK (P < 0.005) and CD19+B (P < 0.05) lymphocytes were significantly lower 24 h after exercise compared with non-exercised controls. Significantly more CD3+T (P < 0.05) and CD8+T (P < 0.05) intestinal lymphocytes stained positive for annexin V, a marker of apoptosis, at 24 h after exercise compared with intestinal lymphocytes from non-exercised controls. Plasma corticosterone and 8-isoprostane concentrations were also significantly higher immediately after exercise compared with other exercise conditions.

CONCLUSION

Acute strenuous exercise increases intestinal T (CD3+ and CD8+) lymphocyte loss and apoptosis. The extent to which the exercise-induced apoptosis in intestinal lymphocytes is mediated by increased glucocorticoid concentrations in the gastrointestinal tract will require further studies.

Effects of dexamethasone on lymphoid tissue in the gut and thymus of neonatal calves fed with colostrum or milk replacer

An increased susceptibility to disease in neonatal calves may be attributable to high glucocorticoid levels that influence immune reactions. We tested whether dexamethasone (DEXA) administration influences the proliferation, apoptosis, and number of B- and T-lymphocytes in Peyer's patches (PP) and thymus in calves fed colostrum (C) or a milk-derived formula. All calves were subcutaneously administered bovine colostrum-derived immunoglobulin G and fed chicken-egg derived immunoglobulins that protected against rotavirus and pathogenic Escherichia coli. The DEXA (30 microg/kg of BW daily) was injected for 4 d into groups fed colostrum on the first 3 d (CD+) and those fed the formula that contained nutrients in amounts as in colostrum but no immunoglubulin G (FD+). Groups CD- and FD were fed the same as the other two groups, but did not receive DEXA. Immunohistochemical methods were used to evaluate cell proliferation rates (by labeling of 5-bromo-2'-deoxyuridine), apoptosis rates (by terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling). Numbers of T- and B-lymphocytes were determined with antibodies specific for CD3 and CD79 surface proteins. There were significant effects (P < 0.05) of DEXA treatment (decrease of cell proliferation rates in follicles of PP and thymus, increase of apoptotic rate in follicles of PP and thymus, decrease of B-lymphocyte numbers in follicles of PP, increase of B-lymphocyte numbers in domes of PP, increase of T-lymphocyte numbers in follicles of PP, and a decrease of intraepithelial T-lymphocyte numbers). There were significant effects (P < 0.05) of C feeding (decrease of cell proliferation rates in follicles of PP and of B-lymphocyte numbers in interfollicular areas, domes, and follicular-associated epithelium of PP, and an increase of cell proliferation rate in the thymus). A DEXA x feeding interaction (P < 0.001) was found for cell proliferation rate in the thymus. In conclusion, DEXA treatment decreased cell proliferation rates in follicles of PP and thymus and enhanced apoptotic rates in follicles of PP. Colostrum feeding decreased cell proliferation rates, likely of B-lymphocytes, in follicles of PP and numbers of B-lymphocytes in domes, follicular-associated epithelium, and interfollicular areas of PP and enhanced cell proliferation rates and selectively modified DEXA effects in the thymus.

Prevention of dexamethasone-induced lymphocytic apoptosis in the intestine and in Peyer patches by enteral nutrition

BACKGROUND

Apoptosis is a programmed cell death, genetically controlled, that can be activated by physiological and pathophysiological events and by the administration of several drugs, including the exogenous administration of corticosteroids. The aim of this study was to develop a rat model of intestinal lymphocytic apoptosis induced by dexamethasone to determine if apoptosis could be prevented by enteral or parenteral nutrition.

METHODS

Male Sprague-Dawley rats were used. On day 0, the right internal jugular vein was catheterized for parenteral nutrition, and a silicone tube was inserted into the duodenum for enteral feeding. Animals (n = 6/group) were randomly assigned to one of the following 3 feeding regimens: an immune-enhancing enteral diet; its placebo (the same formula without immunonutrients); and isocaloric isonitrogenous parenteral nutrition. On the seventh day, 200 microg of dexamethasone or vehicle were administered by i.v. bolus, and the diets were continued for 1 more day. Intestinal Peyer patches and thymic lymphocytic apoptosis were determined both by flow-cytometry and immunohistochemistry.

RESULTS

A single dexamethasone dose (200 microg/rat) administered to surgically treated rats fasted for 18 hours, 24 hours later, caused massive intestinal and Peyer patches lymphocytic apoptosis (96 +/- 2% and 85 +/- 5%, respectively; p < .0001 versus vehicle in both kinds of tissue). Lymphocytic apoptosis was reduced to almost indetectable levels in intestinal and lamina propia lymphocytes (from 96 +/- 2% to <0.6%; p < .0001). Peyer patches lymphocytic apoptosis was reduced as well (from 85 +/- 5% to 15 +/- 7.1%; p < .001) in animals prefed the 2 enteral nutrition formulas. Those prefed parenteral nutrition only showed a partial decrease of lymphocytic apoptosis in the intestine (from 96 +/- 2% to 53 +/- 23%; p < .001). Nutrition had no effect on the dexamethasone-induced thymus involution.

CONCLUSIONS

Enteral nutrition prevents intestinal intraepithelial and lamina propia lymphocytic apoptosis due to dexamethasone. These findings support the use of early enteral nutrition in critically ill patients treated with corticosteroids.

Fas mediates apoptosis in steroid-induced myopathy of rats

Recently, apoptotic cell death has been reported in differentiated skeletal muscle, where apoptosis was generally assumed not to occur. To investigate whether apoptosis may contribute to the steroid-induced myopathy, rats treated with triamcinolone acetonide (TA) for 9 days were sacrificed for detecting apoptosis by in situ end-labelling (ISEL) and DNA electrophoresis in soleus muscles. Immunohistochemical stainings of Fas antigen and p53 protein were performed to examine whether apoptosis-related proteins were present in the myopathy. Muscle fibre necrosis and apoptotic myonuclei appeared in soleus muscles following administration of TA, while control muscles showed no evidences for apoptosis. Fas antigen was not detected in control muscles, but expressed in soleus muscles of steroid-induced myopathy. Some of the Fas antigen-expressing muscle fibres were positive for ISEL. p53 Protein was not detected in any muscle fibres. These findings indicate that TA can induce apoptosis in differentiated skeletal muscles, and Fas antigen might be partly related to apoptotic muscle death in steroid-induced myopathy.

Regulation of cell death and survival in intestinal intraepithelial lymphocytes

Intraepithelial lymphocytes (IEL) of the small murine bowel represent a unique population of mostly CD8(+) T lymphocytes that reside within the epithelial cell layer of the intestinal mucosa. The close interaction with epithelial cells appears to be crucial for IEL survival since isolation and ex vivo culture induces massive apoptosis in this lymphocyte population. Here, we provide evidence that this form of IEL cell death may be mediated at least in part by endogenously produced glucocorticoids since adrenalectomy or treatment of mice with a glucocorticoid receptor antagonist significantly enhanced ex vivo survival of IEL. We further demonstrate that ex vivo activation of IEL induces upregulation of anti-apoptotic gene products, compensates for the lack of survival cytokines and rescues from apoptotic cell death. Thus, similar to thymocytes and T cell hybridomas, IEL survival may be regulated by the antagonistic action of TCR activation and glucocorticoids.

Chlorella vulgaris culture supernatant (CVS) reduces psychological stress-induced apoptosis in thymocytes of mice

A glycoprotein prepared from Chlorella vulgaris culture supernatant (CVS) is a biological response modifier (BRM) which exhibits protective activities against tumor metastasis and 5-fluorouracil-induced immunosuppression. We here show that oral administration of CVS prevented significantly the apoptosis of thymocytes in mice undergoing psychological stress in a communication box. Mice were exposed to the emotional stress for 14 days by witnessing other mice being exposed to foot-shock. The numbers in thymocytes, especially CD4(+)CD8(+) population, were decreased significantly and apoptotic cells, as assessed by Annexin V expression, were reciprocally increased after the exposure to the psychological stress. C. vulgaris culture supernatant (CVS) administration significantly suppressed the increase in serum corticosterone level in the psychologically stressed mice. These results suggest that CVS prevents psychological stress and maintain homeostasis in the face of external environmental changes.

Glucocorticoid and Fas ligand induced mucosal lymphocyte apoptosis after burn injury

BACKGROUND

The purpose of this study was to examine the effects of a steam burn injury on apoptosis in gut-associated lymphoid tissue and to determine whether endogenous glucocorticoid and Fas ligand signaling were involved in this process.

METHODS

Histologic analysis, in situ deoxynucleotidyl transferase dUTP nick-end labeling staining and annexin V and 7-amino-actinomycin-D flow cytometry of lymphocyte populations were evaluated in intraepithelial lymphocytes and Peyer's patch. Additional mice were pretreated with a glucocorticoid receptor antagonist (mifepristone) before the steam burn. Similarly, C3H/HeJ-FasL(gld) mice lacking functional Fas ligand were also studied.

RESULTS

Apoptosis was significantly increased in intraepithelial lymphocytes and Peyer's patch after the burn injury. Mifepristone pretreatment significantly reduced apoptosis in both T- and B-cell populations in intraepithelial lymphocytes after the burn injury. In contrast, the increased apoptosis seen in B-cells from Peyer's patch was not seen in C3H/HeJFasL(gld) mice, whereas the increased apoptosis in CD8+ T-cells was unaffected.

CONCLUSION

Both corticosteroids and FasL contribute to the apoptosis in gut-associated lymphoid tissues early after burn injury.

Interleukin-15 production at the early stage after oral infection with Listeria monocytogenes in mice

We previously reported that exogenous interleukin-15 (IL-15) induces proliferation and activation of intestinal intraepithelial lymphocytes (i-IEL) in naive mice. To investigate the ability of endogenous IL-15 to stimulate i-IEL in vivo, we monitored i-IEL and intestinal epithelial cells (i-EC) in mice after an oral infection with Listeria monocytogenes. Although the populations of alphabeta and gammadelta i-IEL were not significantly changed after the oral infection, the expression level of interferon-gamma (IFN-gamma) was increased both at transcriptional and protein levels, and a conversely marked decrease in interleukin-4 (IL-4) was detected in the i-IEL on day 1 after infection as compared with before infection. The T helper 1 (Th1)-biased response of i-IEL coincided with a peak response of IL-15 production in the i-EC after oral infection. These results suggested that IL-15 produced from i-EC may be at least partly involved in the stimulation of i-IEL to produce IFN-gamma after oral infection with L. monocytogenes.

Interleukin-15 preferentially promotes the growth of intestinal intraepithelial lymphocytes bearing gamma delta T cell receptor in mice

Several cytokines including stem cell factor (SCF) and interleukin (IL)-7 are known to be required for development of gamma delta T cell receptor (TCR) intestinal intraepithelial lymphocytes (i-IEL) in mice. We show here the effects of IL-15 on the proliferation and maintenance of murine gamma delta i-IEL in vitro. gamma delta i-IEL constitutively expressed a high level of IL-15 receptor alpha mRNA and proliferated in response to IL-15 more vigorously than alpha beta i-IEL. V gamma/delta repertoire analysis revealed that IL-15, like IL-2, induced polyclonal expansion of gamma delta i-IEL, whereas gamma delta i-IEL responding to IL-7 showed a V gamma/delta repertoire skewed towards V gamma 1/V delta 4, V delta 5. IL-15 efficiently prevented gamma delta i-IEL from apoptosis induced by growth factor deprivation. This rescue was accompanied by up-regulation of Bcl-2 expression. These results suggest that IL-15 plays important roles in proliferation and maintenance of gamma delta i-IEL.