Freewheel running selectively prevents mouse CD4+ intestinal lymphocyte death produced after a bout of acute strenuous exercise

Aerobic endurance training status affects lymphocyte apoptosis sensitivity by induction of molecular genetic adaptations

Apoptosis is a genetically regulated form of programmed cell death which promotes the elimination of potentially detrimental immune cells. However, exercise-associated apoptosis is thought to induce a temporarily decline of the adaptive immune competence in the early post-exercise period. The purpose of the present study was to investigate if the aerobic endurance training status affects the sensitivity of human peripheral blood lymphocytes towards different types of apoptosis inducers and secondly, if this is mediated by the modulation of apoptosis-associated proteins and microRNAs. Collected at resting conditions, isolated lymphocytes of endurance trained athletes (ET) and healthy untrained subjects were either exposed to phytohemagglutinin-L (PHA-L), hydrogen peroxide (H₂O₂), or dexamethasone (DEX) as apoptosis inducer. Results revealed no significant differences between ET and UT in terms of lymphocyte apoptosis immediately following isolation as determined by flow cytometry using annexin V staining. After 24 h of ex vivo cultivation, lymphocytes of ET showed a reduced sensitivity to PHA-L-induced lymphocyte apoptosis which was accompanied by a noticeably up-regulation of the prominent apoptosis inhibitor genes X-linked inhibitor of apoptosis (XIAP) and Cyclin dependent kinase inhibitor 1B (CDKN1B) as analyzed by quantitative real-time PCR. Moreover, a trend was observed for the suppression of the corresponding pro-apoptotic miR-221. Lymphocyte apoptosis in control, H₂O₂ and DEX treated cells was not affected by aerobic endurance training status. However, distinct molecular signatures could be identified in un-treated control samples characterized by a counterbalanced modulation of pro- and anti-apoptotic mediators in ET. The results of the current study suggest that lymphocytes adapt to repetitive endurance exercise training by promoting lymphocyte homeostasis and increasing their resistance to apoptosis. This could be based on an up-regulation of anti-apoptotic proteins and a reduction in pro-apoptotic microRNAs which together tightly regulate the genetically defined apoptotic pathways governed by the type of apoptosis stimuli. Thus, the lymphocytes of endurance-trained athletes may be primed to counteract the transient immune suppression post-exercise.

Apoptotic lymphocytes induce progenitor cell mobilization after exercise

There is evidence that apoptotic cells and their components have immunmodulatory properties and signaling function. The present study investigated first whether exercise-induced apoptosis and exercise-induced mobilization of progenitor cells are similarly affected by subjects' training status and, second, whether the appearance of dying cells in the circulation might mobilize progenitor cells. CD1 SWISS mice were subjected to a 10-wk endurance training using free wheel running or served as untrained controls. Mice of both groups performed an intensive exercise test after the training period at a velocity corresponding to 80% maximal oxygen uptake for 30 min. Cells from blood and bone marrow were analyzed, and apoptosis and number of progenitor cells determined via flow cytometry. In a second experiment, apoptotic cells were transferred into recipient mice, and mobilization of progenitor cells was analyzed while vital cells served as controls. In untrained animals, the exhaustive exercise was followed by an enhanced rate of annexin V positive CD3(+) cells in blood and bone marrow (P < 0.05), whereas no increase was found in trained mice. Similarly, exercise mobilized Sca-1(+)/c-kit(+) and Sca-1(+)/Flk(+) cells in untrained (P < 0.05) but not trained mice. Furthermore, application of apoptotic cells and their supernatant mobilized Sca-1(+)/c-kit(+) cells into the blood (P < 0.05), whereas Sca-1(+)/Flk(+) cells were not affected. The present study demonstrated that both lymphocyte apoptosis, as well as mobilization of progenitor cells are similarly related to training status. Furthermore, apoptotic cells seem to induce signals that effectively mobilize hematopoietic progenitor cells. The relevance of this effect for the adaptation to exercise stimuli remains to be shown.

Voluntary wheel running mitigates the stress-induced bone loss in ovariectomized rats

In estrogen-deficient rodents with osteopenia, repetitive exposure to mild-to-moderate stress, which mimics the chronic aversive stimuli (CAS) of the modern urban lifestyle in postmenopausal women, has been hypothesized to cause the bone microstructure to further deteriorate. Recently, we have provided evidence in rats that voluntary impact exercise, e.g., wheel running, is as effective as pharmacological treatments for stress-induced anxiety and depression. The present study, therefore, aims to investigate whether a 4-week CAS exposure aggravates trabecular bone loss in ovariectomized (Ovx) rats, and whether CAS-induced bone loss can be rescued by voluntary wheel running. CAS was found to elevate the serum levels of corticosterone, a stress hormone from the adrenal gland. Dual energy X-ray absorptiometry revealed a decrease in bone mineral content (BMC) in the tibiae of CAS-exposed Ovx rats as compared to the CAS-free Ovx rats (control), while having no detectable effect on bone mineral density (BMD). Bone histomorphometric analysis of the proximal tibial metaphysis showed that CAS decreased trabecular bone volume and increased trabecular separation, which were completely restored to the baseline values of Ovx rats by voluntary wheel running. This CAS-induced trabecular bone loss in Ovx rats was probably due to an enhancement of osteoclast-mediated bone resorption, as indicated by increases in osteoclast surface and active erosion surface. Moreover, wheel running as well as non-impact exercise (endurance swimming) effectively increased the tibial BMD and BMC of CAS-exposed Ovx rats. It can be concluded that exercise is an effective intervention in mitigating CAS-induced bone loss in estrogen-deficient rats.

Effects on secretory IgA levels in small intestine of mice that underwent moderate exercise training followed by a bout of strenuous swimming exercise

Intestinal homeostasis effectors, secretory IgA (SIgA) and polymeric immunoglobulin receptor (pIgR), have been evaluated in proximal and distal small intestine with moderate-exercise training but not with strenuous exercise or a combination of these two protocols. Therefore, two groups of mice (n=6-8) were submitted to strenuous exercise, one with and one without previous training. The control group had no exercise protocol. Assessment was made of intestinal SIgA and plasma adrenal hormones (by immunoenzymatic assay), alpha-chain and pIgR proteins in intestinal mucosa (by Western blot), lamina propria IgA plasma-cells (by cytofluorometry), mRNA expression (by real-time PCR) for pIgR, alpha- and J-chains in liver and intestinal mucosa, and pro- and anti-inflammatory cytokines in mucosa samples. Compared to other exercise protocols, training plus strenuous exercise elicited: (1) higher levels of SIgA and pIgR in the proximal intestine (probably by hepatobiliary contribution); (2) higher levels of SIgA in the distal segment; (3) lower mRNA expression of some SIgA- and most pro-inflammatory pIgR-producing cytokines. SIgA and pIgR in both segments were derived from an existing pool of their corresponding producing cells. The apparent decreased translation of mRNA transcripts underlies lower levels of SIgA and pIgR in distal than proximal small intestine. There was no significant difference in the relatively high adrenal hormone levels found in both exercised groups. Further study is required about the effects of training plus strenuous exercise on pool-derived SIgA levels and mRNA expression of pro-inflammatory pIgR-producing cytokines. These results could have important implications for intestinal disorders involving inflammation and infection.

A comparison of low- and high-impact forced exercise: effects of training paradigm on learning and memory

In this study we compared two types of forced exercise-a low impact paradigm to minimize stress, which included speeds up to 10 m/min and a stressful high impact paradigm, with speeds up to 21 m/min. 150 male C57BL/6J mice were randomly assigned to the low impact, high impact, or sedentary control conditions and were tested on the rotorod and Morris water maze (MWM) as indices of motor learning and spatial memory. We found that 5 weeks of stressful high speed forced exercise led to significant improvement in rotorod performance, as high impact runners outperformed both low impact runners and controls at 15 and 25 rpm speeds. These differences were the result of improved physical fitness due to exercise and likely do not reflect enhanced learning in these mice. In the MWM, 5 weeks of stressful high impact exercise led to significant impairment in spatial memory acquisition compared to low impact runners and controls. Low impact exercise for 10 weeks significantly improved retention of spatial memory compared to high impact exercise. Results suggested that these two paradigms produced different effects of forced exercise on learning and memory. The low impact paradigm led to some improvements, whereas the stressful high impact program caused significant impairment. Comparison of these two paradigms begins to address the window between the beneficial and detrimental effects of forced exercise, and have suggested a boundary of exercise intensity that leads to impairment in learning.

Effect of moderate exercise on IgA levels and lymphocyte count in mouse intestine

The aim of the present study was to determine the effect of moderate exercise on the production and secretion of IgA in mouse duodenum, on lymphocyte levels in the lamina propria, and on gene expression encoding for cytokines that regulate the synthesis of α-chain of IgA and the expression of pIgR in the lamina propria. Two groups of young Balb/c mice were fed ad libitum, one sedentary and the other with an exercise program (swimming) for 16 weeks. IgA levels in the duodenum were quantified by ELISA; the number of IgA containing cells as well as B cells, CD4(+) and CD8(+) T cells in the duodenal mucosa was determined by immunohistochemistry; gene expression was analyzed by real-time PCR, and the expression of proteins by Western blotting. Because of physical training, in the duodenum there was a decrease in the number of IgA producing cells, but an increase in the levels of IgA. Additionally, exercise increased the expression of the genes encoding for IL-4, IL-6, IL-10, TNF-α and TGF β, cytokines that regulate the synthesis of IgA and pIgR, the inflammatory response, and the immune response in the intestine. Thus, the increased IgA found in the duodenal lumen is probably due to the increased production of IgA in the LP and the increased transport of the pIgA-pIgR complex across epithelial cells. Possibly the increased S-IgA levels in the bile also contribute to the change in IgA levels.

Voluntary exercise training in mice increases the expression of antioxidant enzymes and decreases the expression of TNF-alpha in intestinal lymphocytes

Acute exercise in mice induces intestinal lymphocyte (IL) apoptosis. Freewheel running reduces apoptosis and forced exercise training increases splenocyte antioxidant levels. The purpose of this study was to examine the effect of freewheel running and acute exercise on mouse IL numbers and concentrations of apoptosis and antioxidant proteins and pro-inflammatory cytokines in IL. Female C57BL/6 mice had access to in-cage running wheels (RW) or cages without wheels (NRW) for 16 weeks and were randomized at the end of training to no exercise control (TC) or to treadmill exercise with sacrifice after 90 min of running (TREAD; 30 min, 22 m min(-1); 30 min, 25 m min(-1); 30 min, 28 m min(-1); 2 degrees slope). IL were analyzed for pro-(caspase 3 and 7) and anti-(Bcl-2) apoptotic proteins, endogenous antioxidants (glutathione peroxidase: GPx; catalase: CAT) and the pro-inflammatory cytokine, TNF-alpha. RW mice had higher cytochrome oxidase (p<0.001) and citrate synthase (p<0.01) activities in plantaris and soleus muscles and higher GPx and CAT expression in IL (p<0.05) (indicative of training) compared with NRW mice. TNF-alpha expression was lower (p<0.05) and IL numbers higher (p<0.05) in RW vs. NRW mice. No training effect was observed for apoptotic protein expression, although TREAD resulted in higher caspase and lower Bcl-2. These results suggest that freewheel running in mice for 16 weeks enhances antioxidant and reduces TNF-alpha expression in IL but does not reduce pro-apoptotic protein expression after acute exercise. Results are discussed in terms of implications for inflammatory bowel diseases where apoptotic proteins and TNF-alpha levels are elevated.

Physical activity and breast cancer survival

Physical activity improves quality of life after a breast cancer diagnosis, and a beneficial effect on survival would be particularly welcome. Four observational studies have now reported decreased total mortality among physically active women with breast cancer; the two largest have also reported decreased breast cancer specific mortality. The estrogen pathway and the insulin pathway are two potential mechanisms by which physical activity could affect breast cancer survival. Randomized trials are ongoing but trials of lifestyle factors are notoriously challenging to perform. Women with breast cancer have little to lose and may possibly gain from moderate exercise.

Exercise enhances vaccine-induced antigen-specific T cell responses

Regular moderate exercise has been proposed to enhance immune function, but its effects on immunity and their consequences have not been well studied. Mice without (AL) or with access (AL+EX) to voluntary running wheels were vaccinated with a model antigen (ovalbumin (OVA)) via intranasal or subcutaneous routes to target the mucosal and systemic immune compartments, respectively. EX enhanced OVA-specific CD4(+) T cell cytokine production and proliferation in all lymphoid organs examined without changes in cell distribution in any organ. These results suggest that coupling moderate exercise with vaccination may enhance vaccine efficacy for the prevention and/or therapy of numerous diseases.

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.

Physical training attenuates the stress-induced changes in rat T-lymphocyte function

BACKGROUND/AIMS

Modulations in the immune function by stress are a well-known phenomenon. Acute restraint stress may induce impaired T-lymphocyte responses. Moderate physical training is associated with beneficial effects on immunological functions. We investigated the effects of a moderate physical training on T-lymphocyte function in rats submitted to acute restraint stress.

METHODS

Thirty male Wistar rats weighing 210-226 g were randomly divided into four groups: non-trained rats (NT, n = 7), and non-trained rats submitted to stress (NT + S, n = 8); trained rats (T, n = 7), and trained rats submitted to stress (T + S, n = 8). Trained rats were submitted to a program of moderate running over a period of 8 weeks. Rats subjected to restraint stress were kept immobilized in glass cylinders (8 cm in diameter and 24 cm long) during 60 min. Plasma corticosterone concentration, peripheral blood leukocyte number, indicators of apoptosis of T lymphocytes in blood and lymphoid organs, and mitogen-induced proliferation of T lymphocytes in lymphoid organs were evaluated.

RESULTS

Acute stress exposure raised plasma corticosterone concentration (p < 0.001), but not in previously trained animals. Restraint stress induced an increase in the percentage of lymphocytes in apoptosis, and a decrease in the concanavalin-A-induced proliferation of lymphocytes from the thymus and lymph nodes, and an increase in lymphocytes of the spleen. Neither of these alterations was observed in trained animals submitted to acute restraint stress.

CONCLUSIONS

Our data confirm that acute restraint stress is associated with changes in T-lymphocyte function. Moreover, moderate physical training attenuates the effects of acute stress by a mechanism that involves the hypothalamic-pituitary-adrenal axis and an increase in tolerance of leukocytes.