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.     

Long-duration freewheel running and submandibular lymphocyte response to forced exercise in older mice

Submandibular lymph nodes (SLN) are crucial for immune surveillance of the anterior ocular chamber and upper respiratory tract; little is known about how training and exercise affect SLN lymphocytes. The intent of this study was to describe the impact of long term freewheel running followed by acute strenuous exercise on SLN lymphocytes in mice. Female C57BL/6 mice were assigned to running wheels or remained sedentary for 8 months, and further randomized to treadmill exercise and sacrifice immediately, treadmill exercise and sacrifice 24 h after exercise cessation, or no treadmill exposure. SLN lymphocytes were isolated and analyzed for CD3, CD4, CD8, and CD19 cell surface markers, phosphatidylserine externalization as a marker of apoptosis, and intracellular glutathione as a marker of oxidative stress. Compared with running wheel mice, older sedentary mice had a lower percent of T cells and higher percent of B cells (p < 0.05). Although intracellular glutathione did not differ between groups, running mice had a lower percent of Annexin V(+) SLN lymphocytes 24 h after treadmill exercise. Further research will be needed to determine if voluntary exercise translates into improved anterior ocular and upper respiratory tract health.     

High Intensity Exercise: A Cause of Lymphocyte Apoptosis?

Post exercise lymphocytopenia is well documented and attributed to egress of lymphocytes from the vascular compartment. Recent studies have reported exercise induced DNA damage in leukocytes and have questioned a possible link to apoptosis. Eleven subjects underwent a ramped treadmill test to exhaustion. Venous blood samples were taken before, immediately post exercise, and 24 and 48 hours after exercise. Single cell gel electrophoresis revealed evidence of single strand DNA damage in 10% of lymphocytes immediately after exercise, but not at other times. Fluorescent microscopy showed three patterns of DNA distribution, similar to those seen in apoptosis, at all times after exercise. Three subjects underwent the same exercise protocol, and lymphocytes were prepared for flow cytometry to determine apoptosis using the TUNEL method. Flow cytometry revealed lymphocyte apoptosis in 63% of lymphocytes immediately after exercise and 86.2%, 24 hours after exercise. Lymphocyte apoptosis is documented for the first time after exercise and may in part account for exercise induced lymphocytopenia and reduced immunity.     

Lymphocyte distribution in mouse submandibular lymph nodes in response to acute treadmill exercise

The submandibular lymph nodes (LN), part of the nasal-associated lymphoid tissue (NALT), are involved in local immune responses in the eye, upper respiratory tract (URT), and oral mucosa. Although athletes have been reported to be at increased risk for URT and ocular infections, little is known about the impact of exercise on LN included in the NALT. The purpose of this study was to examine the impact of intense acute exercise on submandibular lymphocyte distribution. Female C57BL/6 mice were randomly assigned to a nonexercised control condition or a single session of treadmill exercise (32 m.min-1, 8 degrees grade for 90 min) and sacrificed immediately, 2, and 24 h after exercise. Running resulted in a significant increase in plasma corticosterone immediately following exercise compared with other times (p < 0.001). Percentages and total numbers of CD3+ and CD4+CD8- T lymphocytes in submandibular LN were significantly lower 24 h after exercise compared with controls. The percentage of pan-NK and CD19+ B cells increased immediately and 24 h after exercise, respectively, but the total numbers were not affected. The results suggest that decreased percentages and absolute numbers of T cells in submandibular LN following a single session of intense exercise may be partially mediated by increased corticosterone concentrations and may have consequences for ocular health among athletes.     

Antioxidant enzyme levels in intestinal and renal tissues after a 60-minute exercise in untrained mice.

The present study was designed to determine the effects of exercise on the antioxidant enzymatic system and lipid peroxidation in small intestine and kidney, during the post-exercise period in untrained mice. Two days after the last adaptation running exercise, animals were ran on the treadmill for 60 min at 18 m/min. 5 degrees slope. After the acute exercise the animals were killed by cervical dislocation, immediately (0 h), 3 hours (3 h) and 24 hours (24 h) after the exercise. Control animals were killed without running exercise. Their proximal small intestinal and renal tissues were quickly removed. Changes in the concentration of thiobarbituric acid reactive substance (TBARS), as an index of lipid peroxidation, in intestine and kidney were studied in mice after the running exercise and in unexercised control group. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined in these tissues. Tissue SOD, GPx activities and TBARS level were not increase by the exercise in kidney. Intestinal SOD activity decreased after exercise (0 h and 3 h respectively, p<0.05, p<0.01) and retumed to control levels. Intestinal GPx activity increased after exercise (0 h, p<0.05) and returned to control levels. There was no significant difference among groups in intestinal tissue TBARS levels. These findings could suggest that submaximal exercise may not cause oxidative stress in proximal small intestinal tissue and kidney.     

Impact of treadmill exercise on early apoptotic cells in mouse thymus and spleen

Lymphocyte apoptosis occurs in response to stressors such as thermal injury, trauma, sepsis, and surgery. This study evaluated the effect of a single bout of physical exercise stress on the induction of apoptosis in murine thymocytes and splenic lymphocytes. Female C57BL/6 mice, treadmill exercised at a submaximal intensity (35 m/min, 6% grade) for 90 min or serving as controls (walking on treadmill at 12 m/min, 6% grade, 5 min), were sacrificed 5 min or 120 min after completion of exercise. The percent of apoptotic, necrotic, and viable thymocytes and splenocytes were determined by flow cytometry using annexin V FITC and propidium iodide. There was a significantly higher percent of viable splenocytes in the mice sampled 120 min after cessation of exercise than treadmill control animals (p<0.05). In the thymus, there was a significantly lower percent of apoptotic (p<0.5) and a significantly higher percent of viable (p<0.05) cells in exercised mice sampled at 120 min after exercise relative to controls. Absolute numbers of thymocytes and splenocytes did not differ by exercise treatment condition. Plasma corticosterone levels were elevated immediately after exercise and were negatively correlated with the percent of viable lymphocytes in the spleen. During the time frame sampled, submaximal exercise is associated with a lower % of thymocytes expressing early markers of apoptosis, despite elevated plasma corticosterone levels. Retention of self-reactive, viable thymocytes which would normally be deleted or selective trafficking of apoptotic thymocytes out of the thymus may be involved in the exercise effect. Additional studies are necessary to identify the mechanisms for this shift in proportions of apoptotic and viable cells in lymphoid compartments with exercise.     

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.     

The effect of carbohydrate ingestion on plasma interleukin-6, hepcidin and iron concentrations following prolonged exercise

The aim of our study was twofold, firstly to examine the relationship between plasma concentrations of IL-6, hepcidin and iron following prolonged exercise and secondly, to assess the effect of carbohydrate ingestion on circulating hepcidin concentration post-exercise. The study was a randomised double-blind cross-over design, with participants consuming either a carbohydrate (CHO) or an isovolumetric placebo drink throughout the trial. Nine healthy, trained males completed a treadmill run at 60% vVO(2max) for 120 min followed by a 5 km time trial. Plasma concentrations of both IL-6 and hepcidin significantly increased post-exercise following both trials (p<.05) and returned to baseline by 24 h post (p>.05). A positive correlation between hepcidin and IL-6 was demonstrated immediately following exercise during PLA while there was a trend for a moderate correlation during CHO (PLA trial rho=0.81, p<0.001; CHO trial rho=0.36, p=0.07). Plasma iron was unaffected immediately post-exercise but significantly reduced by 24 h post-exercise compared to baseline. CHO ingestion significantly reduced post-exercise IL-6 (p<.05) but this had no effect on plasma hepcidin or iron concentration. Our data demonstrate CHO supplementation does not alter the rapid hepcidin response associated with exercise and does not prevent a subsequent fall in plasma iron concentration. This finding adds further support to the theory that an exercise-induced, up-regulation of hepcidin activity is a mechanism causing iron deficiency in endurance athletes.     

Long-term treadmill exercise induces neuroprotective molecular changes in rat brain

Exercise enhances general health. However, its effects on neurodegeneration are controversial, and the molecular pathways in the brain involved in this enhancement are poorly understood. Here, we examined the effect of long-term moderate treadmill training on adult male rat cortex and hippocampus to identify the cellular mechanisms behind the effects of exercise. We compared three animal groups: exercised (30 min/day, 12 m/min, 5 days/wk, 36 wk), handled but nonexercised (treadmill handling procedure, 0 m/min), and sedentary (nonhandled and nonexercised). Moderate long-term exercise induced an increase in IGF-1 levels and also in energy parameters, such as PGC-1α and the OXPHOS system. Moreover, the sirtuin 1 pathway was activated in both the exercised and nonexercised groups but not in sedentary rats. This induction could be a consequence of exercise as well as the handling procedure. To determine whether the long-term moderate treadmill training had neuroprotective effects, we studied tau hyperphosphorylation and GSK3β activation. Our results showed reduced levels of phospho-tau and GSK3β activation mainly in the hippocampus of the exercised animals. In conclusion, in our rodent model, exercise improved several major brain parameters, especially in the hippocampus. These improvements induced the upregulation of sirtuin 1, a protein that extends life, the stimulation of mitochondrial biogenesis, the activation of AMPK, and the prevention of signs of neurodegeneration. These findings are consistent with other reports showing that physical exercise has positive effects on hormesis.     

Skeletal muscle plasma membrane glucose transport and glucose transporters after exercise

Recent reports have shown that immediately after an acute bout of exercise the glucose transport system of rat skeletal muscle plasma membranes is characterized by an increase in both glucose transporter number and intrinsic activity. To determine the duration of the exercise response we examined the time course of these changes after completion of a single bout of exercise. Male rats were exercised on a treadmill for 1 h (20 m/min, 10% grade) or allowed to remain sedentary. Rats were killed either immediately or 0.5 or 2 h after exercise, and red gastrocnemius muscle was used for the preparation of plasma membranes. Plasma membrane glucose transporter number was elevated 1.8- and 1.6-fold immediately and 30 min after exercise, although facilitated D-glucose transport in plasma membrane vesicles was elevated 4- and 1.8-fold immediately and 30 min after exercise, respectively. By 2 h after exercise both glucose transporter number and transport activity had returned to nonexercised control values. Additional experiments measuring glucose uptake in perfused hindquarter muscle produced similar results. We conclude that the reversal of the increase in glucose uptake by hindquarter skeletal muscle after exercise is correlated with a reversal of the increase in the glucose transporter number and activity in the plasma membrane. The time course of the transport-to-transporter ratio suggests that the intrinsic activity response reverses more rapidly than that involving transporter number.     

Treadmill Exercise Induces Neutrophil Recruitment into Muscle Tissue in a Reactive Oxygen Species-Dependent Manner. An Intravital Microscopy Study

Intense exercise is a physiological stress capable of inducing the interaction of neutrophils with muscle endothelial cells and their transmigration into tissue. Mechanisms driving this physiological inflammatory response are not known. Here, we investigate whether production of reactive oxygen species is relevant for neutrophil interaction with endothelial cells and recruitment into the quadriceps muscle in mice subjected to the treadmill fatiguing exercise protocol. Mice exercised until fatigue by running for 56.3±6.8 min on an electric treadmill. Skeletal muscle was evaluated by intravital microscopy at different time points after exercise, and then removed to assess local oxidative stress and histopathological analysis. We observed an increase in plasma lactate and creatine kinase (CK) concentrations after exercise. The numbers of monocytes, neutrophils, and lymphocytes in blood increased 12 and 24 hours after the exercise. Numbers of rolling and adherent leukocytes increased 3, 6, 12, and 24 hours post-exercise, as assessed by intravital microscopy. Using LysM-eGFP mice and confocal intravital microscopy technology, we show that the number of transmigrating neutrophils increased 12 hours post-exercise. Mutant gp91^phox-/- (non-functional NADPH oxidase) mice and mice treated with apocynin showed diminished neutrophil recruitment. SOD treatment promoted further adhesion and transmigration of leukocytes 12 hours after the exercise. These findings confirm our hypothesis that treadmill exercise increases the recruitment of leukocytes to the postcapillary venules, and NADPH oxidase-induced ROS plays an important role in this process.     

Time-course of changes in inflammatory response after whole-body cryotherapy multi exposures following severe exercise

The objectives of the present investigation was to analyze the effect of two different recovery modalities on classical markers of exercise-induced muscle damage (EIMD) and inflammation obtained after a simulated trail running race. Endurance trained males (n = 11) completed two experimental trials separated by 1 month in a randomized crossover design; one trial involved passive recovery (PAS), the other a specific whole body cryotherapy (WBC) for 96 h post-exercise (repeated each day). For each trial, subjects performed a 48 min running treadmill exercise followed by PAS or WBC. The Interleukin (IL) -1 (IL-1), IL-6, IL-10, tumor necrosis factor alpha (TNF-α), protein C-reactive (CRP) and white blood cells count were measured at rest, immediately post-exercise, and at 24, 48, 72, 96 h in post-exercise recovery. A significant time effect was observed to characterize an inflammatory state (Pre vs. Post) following the exercise bout in all conditions (p<0.05). Indeed, IL-1β (Post 1 h) and CRP (Post 24 h) levels decreased and IL-1ra (Post 1 h) increased following WBC when compared to PAS. In WBC condition (p<0.05), TNF-α, IL-10 and IL-6 remain unchanged compared to PAS condition. Overall, the results indicated that the WBC was effective in reducing the inflammatory process. These results may be explained by vasoconstriction at muscular level, and both the decrease in cytokines activity pro-inflammatory, and increase in cytokines anti-inflammatory.     

Beta-adrenergic receptor blockade during exercise decreases intestinal lymphocyte apoptosis but not cell loss in mice

Catecholamines induce apoptosis in various lymphoid populations. This process can occur with both alpha- and beta-adrenoreceptors. Heavy exercise increases plasma catecholamine concentrations, and is also a cause of lymphocyte apoptosis, a possible explanation for postexercise lymphocytopenia. The purpose of this study was to examine the effects of adrenoreceptor antagonism on exercise-induced decreases and apoptosis of intestinal lymphocytes. Mice received an intraperitoneal injection of phentolamine (a nonselective alpha-blocker), nadolol (a nonselective beta-blocker), or saline (vehicle) prior to an exhaustive bout of exercise. Total intestinal lymphocyte numbers, percent and number of CD3+ lymphocytes, and cell viability were assessed. Neither alpha- nor beta-antagonism prevented exercise-induced cell loss in the intestine; however, pretreatment with nadolol significantly reduced the number of apoptotic and necrotic cells. Phentolamine administration appeared to increase the incidence of cell death among intestinal lymphocytes. Both drugs decreased the percentage of CD3+ intestinal lymphocytes. Our study suggests that catecholamines are not responsible for postexercise lymphocytopenia, but beta-adrenoceptor blockade may confer protection against exercise-induced apoptosis of intestinal lymphocytes.     

Splenic immune responses following treadmill exercise in mice

The in vitro proliferation response to lipopolysaccharide and pokeweek mitogen by splenic lymphocytes and the effect on the total splenic lymphocyte number were examined in C57BL/6J mice following an 8-week treadmill training program (30 m/min, 8 degrees slope, 30 min/day, 5 times/week) and after a single bout of exhaustive exercise (50% stepwise increases in final running speed for 10-min intervals). Plasma corticosterone levels were also measured to evaluate whether changes in adrenocortical activation were associated with exercise-induced immunomodulation. In comparison to sedentary controls, trained mice had an increase of 35% in succinate dehydrogenase activity per unit of protein in the quadriceps femoris muscle. Trained mice showed an increase in splenic lymphocyte proliferation to both mitogens which was evident 72 h after completion of the final training session, relative to sedentary controls. Immediately following exercise, however, lymphocyte proliferative responses were depressed compared with the training and the control values. The exercise regimen resulted in a reduction in total number of mononuclear cells per spleen. Changes in plasma corticosterone levels after exercise were not clearly associated with immunodepression or immunoenhancement of splenic lymphocyte mitogenesis. Taken together, the data suggest that moderate endurance training augments splenic B lymphocyte mitogenesis and further, that the immediate effects of exercise on splenic immune function vary with the duration and intensity of the work.     

Altered sarcoplasmic reticulum function after high-intensity exercise

This study examined the effects of acute high-intensity exercise on the rate and capacity of Ca2+ uptake and Ca2+-stimulated adenosinetriphosphatase (ATPase) activity of the sarcoplasmic reticulum and the reversibility of these effects. Thoroughbred horses were run at maximal O2 uptake on a high-speed treadmill until fatigued. Muscle temperatures and biopsy samples were collected at rest, immediately after exercise, and 30 and 60 min after exercise. Blood samples were collected at rest and 5 min after exercise. Muscle and blood (lactate concentration) were three- and fivefold greater than pre-exercise values. Muscle temperature and pH immediately after post-exercise were 43 degrees C and 6.55, respectively, but approached rest values by 60 min after exercise. The initial rate and maximal capacity of Ca2+ uptake of muscle homogenates and isolated sarcoplasmic reticulum were significantly depressed immediately after exercise. This depression was paralleled by decreased activity of the Ca2+-stimulated ATPase. However, both Ca2+ uptake (rate and capacity) and Ca2+4-ATPase activity had returned to normal by 60 min after exercise. These findings demonstrate that changes in sarcoplasmic reticulum function after high-intensity exercise may be induced but not sustained by local changes in muscle pH and/or temperature.     

Acute effect of physical exercise on glycogen content and lipoprotein lipase activity in untrained diabetic rats

The effect of acute physical exercise on skeletal muscle glycogen content and on lipoprotein lipase activity of muscle, adipose and lung tissues was studied in streptozotocin diabetic and control rats. Rats were accustomed to treadmill running for two weeks after streptozotocin treatment. For an exercise bout of moderate intensity rats were randomly divided into two groups: one was sacrificed immediately after exercise and the other 24 hours afterwards. In addition there was a nonexercised sedentary group. No depletion of glycogen was observed after exercise in the vastus lateralis muscle of control (nondiabetic) rats. No difference in glycogen utilization was found in soleus muscle between diabetic and control rats. In diabetic rats a slight decrease occurred in the lipoprotein lipase activity in adipose tissue immediately after exercise, while in control rats there was a significant decline 24 hours after exercise. In soleus muscle a slight but significant increase of lipoprotein lipase activity occurred 24 hours after exercise in diabetic rats but not in control rats. The results suggest that nonketotic streptozotocin diabetes of short duration does not influence muscle glycogen in the resting state, but glycogen utilization is disturbed in white muscle during moderate treadmill running in untrained diabetic rats. The increase in lipoprotein lipase activity after physical exercise in red muscle of diabetic rats occurs during the recovery phase.     

The effect of estrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women

This study assessed the influence of estrogen (E₂) on muscle damage biomarkers [skeletal muscle - creatine kinase (CK); cardiac muscle - CK-MB] responses to prolonged aerobic exercise. Eumenorrheic women (n=10) who were physically active completed two 60-minute treadmill running sessions at ∼60-65% maximal intensity during low E₂ (midfollicular menstrual phase) and high E₂ (midluteal menstrual phase) hormonal conditions. Blood samples were collected prior to exercise (following supine rest), immediately post-, 30 min post-, and 24 hours post-exercise to determine changes in muscle biomarkers. Resting blood samples confirmed appropriate E₂ hormonal levels Total CK concentrations increased following exercise and at 24 hours post-exercise were higher in the midfollicular low E₂ phase (p<0.001). However, CK-MB concentrations were unaffected by E₂ level or exercise (p=0.442) resulting in the ratio of CK-MB to total CK being consistently low in subject responses (i.e., indicative of skeletal muscle damage). Elevated E₂ levels reduce the CK responses of skeletal muscle, but had no effect on CK-MB responses following prolonged aerobic exercise. These findings support earlier work showing elevated E₂ is protective of skeletal muscle from exercise-induced damage associated with prolonged aerobic exercise.     

Modulatory effect of N-acetylcysteine on pro-antioxidant status and haematological response in healthy men

The aim of this study was to follow up whether the modification of pro-antioxidant status by 8-day oral application of N-acetylcysteine (NAC) in healthy men affects the haematological response, whether there is a direct relationship between antioxidant defences and erythropoietin (EPO) secretion and whether NAC intake enhances exercise performance. Fifteen healthy men were randomly assigned to one of two groups: control or NAC (1,200 mg d⁻¹ for 8 days prior to and 600 mg on the day of exercise trial). To measure the ergogenic effectiveness of NAC, subjects performed incremental cycle exercise until exhaustion. NAC administration significantly influenced the resting and post-exercise level of glutathione (+31%) as well as the resting activity of glutathione enzymes (glutathione reductase, −22%; glutathione peroxidase, −18%). The oxidative damage markers, i.e., protein carbonylation and lipid peroxidation products (thiobarbituric acid reactive substance) were reduced by NAC by more than 30%. NAC noticeably affected the plasma level of EPO (+26%), haemoglobin (+9%), haematocrit (+9%) and erythrocytes (−6%) at rest and after exercise. The mean corpuscular volume and the mean corpuscular haemoglobin increased by more than 12%. Plasma total thiols increased by 17% and directly correlated with EPO level (r = 0.528, P < 0.05). NAC treatment, contrary to expectations, did not significantly affect exercise performance. Our study has shown that 8-day NAC intake at a daily dose of 1,200 mg favours a pro-antioxidant status and affects haematological indices but does not enhance exercise performance.     

The influence of severe long-term exercise on the mouse hippocampus

To determine whether severe long-term exercise affects on the brain, we investigated the mice brain after 12-week treadmill exercise. The mice (ddN, male, 25-35 g in body weight) were divided into severe, mild, and non-exercise group. Mice in severe groups ran on a treadmill at a speed of 25 m/min for 12 weeks and mice in mild group ran on a treadmill at a speed of 10 m/min for 12 weeks. The mice were killed by transcardial perfusion with 0.1 M phosphate-buffered saline (PBS) followed by ice-cold 4% paraformaldehyde in 0.1 M PB. The another sets of mice were fixed by 2.5% glutaraldehyde-2% osmium tetroxide for electromicroscope (EM). The brains were serially sectioned in the coronal plane at a thickness of 20-microns with a vibratome and then processed for histology, by means of hematoxylin-eosin (HE) staining and immunohistochemistry. Fifty % of mice in severe exercise showed hyperchromatic and shrunken nerve cells with nuclear pyknosis (dark neuron) in the hippocampus, but not in mild exercise and non-exercise groups. The immunoreactivity of microtuble associated protein-2 (MAP-2) decreased, while the heat-shock protein/cognate 70 (HSP/C 70) increased in the hippocampus of severe exercise group. Many destroyed mitochondria were observed in dark neurons by Electron micrograph. These findings suggested that severe long-term exercise might damage hippocampal neurons.     

Exercise suppresses macrophage antigen presentation.

This study determined the effects of exercise on the ability of macrophages (Mphi) to present antigen to T cells. Pathogen-free male Balb/c mice (8 +/- 2 wk of age) were randomly assigned to either home cage control, moderate exercise (Mod; 18 m/min, 5% grade, 0.5 h/day), exhaustive exercise (Exh, 18-30 m/min, 3 h/day), or treadmill control groups. The mice underwent treatments for 4 days during peritoneal thioglycolate inflammation. Peritoneal Mphi were harvested, purified, and incubated with chicken ovalbumin (C-OVA; 0-10 mg/ml) for 18 h. Mphi were then cocultured with C-OVA-specific T cells for 48 h, and the supernatants were analyzed via ELISA for interleukin-2 as an indication of Mphi antigen presentation (AP). Exh exhibited suppressed ( approximately 25-34%) Mphi AP across a wide range of C-OVA doses when measured immediately, 3, and 24 h postexercise. In contrast, Mod had reduced Mphi AP only at 3 h postexercise. Mphi AP was also lower in the treadmill control (4-27%) compared with the home cage control group, but was significantly higher than Exh. The reduction in Mphi AP was not due to exercise-induced differences in Mphi number, percentage, or expression of intercellular adhesion molecule-1, B7-2, or major histocompatability complex II, molecules important in AP. In conclusion, our data lend evidence that may help explain the increased incidence of infection observed after prolonged exhaustive exercise or overtraining.