Blood mononuclear cells mobilization and cytokines secretion during prolonged exercises

Immunology of Physical Exercise: Is Equus caballus an Appropriate Animal Model for Human Athletes?

Domestic horses routinely participate in vigorous and various athletic activities. This enables the horse to serve as a model for studying athletic physiology and immunology in other species, including humans. For instance, as a model of physical efforts, such as endurance rides (long-distance running/aerobic exercise) and races (anaerobic exercise), the horse can be useful in evaluating post-exercise response. Currently, there has been significant interest in finding biomarkers, which characterize the advancement of training and adaptation to physical exercise in the horse. The parallels in cellular responses to physical exercises, such as changes in receptor expression and blood cell activity, improve our understanding of the mechanisms involved in the body's response to intense physical activity. This study focuses on the changes in levels of the pro- and anti-inflammatory cytokines and cellular response in the context of post-exercise immune response. Both the direction of changes in cytokine levels and cellular responses of the body, such as proliferation and expression of surface markers on lymphocytes, monocytes and neutrophils, show cross-functional similarities. This review reveals that horses are robust research models for studying the immune response to physical exercise in human athletes.

Acute physical exercise and long-term individual shear rate therapy increase telomerase activity in human peripheral blood mononuclear cells

AIM

Physical activity is a potent way to impede vascular ageing. However, patients who suffer from peripheral artery disease (PAD) are often unable to exercise adequately. For those patients, we have developed individual shear rate therapy (ISRT), which is an adaptation of external counterpulsation and enhances endovascular fluid shear stress to increase collateral growth (arteriogenesis). To evaluate the effects of physical exercise and ISRT on the telomere biology of peripheral blood mononuclear cells (PBMCs), we conducted two clinical trials.

METHODS

In the ISRT-1 study, we assessed PBMC telomerase activity in 26 young healthy volunteers upon a single (short-term) ISRT session and a single treadmill running session. In the ISRT-2 study, we investigated PBMC telomere biology of 14 elderly patients with PAD, who underwent 30 h of (long-term) ISRT within a 5-week period.

RESULTS

We demonstrate that telomerase activity significantly increased from 39.84 Total Product Generated (TPG) Units ± 6.15 to 58.10 TPG ± 10.46 upon a single treadmill running session in healthy volunteers. In the ISRT-2 trial, PBMC telomerase activity and the mRNA expression of the telomere-protective factor TRF2 increased from 40.87 TPG ± 4.45 to 60.98 TPG ± 6.83 and 2.10-fold ± 0.40, respectively, upon long-term ISRT in elderly patients with PAD.

CONCLUSION

In summary, we show that acute exercise and long-term ISRT positively affect PBMC telomerase activity, which is indicative for an improved regenerative potential of immune cells and vascular tissues. Long-term ISRT also enhances the gene expression of the telomere-protective factor TRF2.

A randomized controlled trial examining the effects of 16 weeks of moderate-to-intensive cycling and honey supplementation on lymphocyte oxidative DNA damage and cytokine changes in male road cyclists

The aim of this study was to investigate whether honey supplementation (70g, ninety minutes before each training session) attenuates changes in lymphocyte counts, DNA damage, cytokines, antioxidative and peroxidative biomarkers following moderate-to-intensive exercise training in male road cyclists. Healthy nonprofessional cyclists (n=24, aged 17-26years) were randomly assigned to exercise+supplement (EX+S, n=12) and exercise (EX, n=12) groups for an experimental period of 16weeks. Moderate-to-intensive exercise training increased lymphocytes DNA damage, cytokines and peroxidative biomarkers as well as decreased antioxidative biomarkers in the EX group. These changes were significantly attenuated in the EX+S group. Furthermore, for both groups the observed changes in peroxidative and antioxidative biomarkers could be correlated positively and negatively, respectively, with lymphocyte DNA damage and cytokines. Findings suggest that honey attenuates oxidative stress and lymphocyte DNA damage after exercise, activities that are most likely attributable to its high antioxidant capacity.

Pro- and anti-inflammatory cytokine responses to a 164-km road cycle ride in a hot environment

PURPOSE

The purpose of this study was to examine the circulating cytokine response to a recreational 164-km road cycling event in a high ambient temperature and to determine if this response was affected by self-paced exercise time to completion.

METHODS

Thirty-five men and five women were divided into tertiles based on time to complete the cycling event: slowest (SLOW), moderate (MOD), and fastest (FAST) finishers. Plasma samples were obtained 1-2 h before (PRE) and immediately after (IP) the event. A high-sensitivity multiplex assay kit was used to determine the concentration of plasma anti-inflammatory cytokines (IL-4, IL-5, IL-10, IL-13) and pro-inflammatory cytokines (IL-1β, IL-2, IL-6, IL-7, IL-8, IL-12, GM-CSF, IFN-γ, and TNF-α).

RESULTS

The concentration of plasma IL-10 increased significantly (p < 0.05) in FAST and MOD groups and had no change in the SLOW group in response to a 164-km cycling event in the hot environment. Other cytokine responses were not influenced by the Time to completion. Pro-inflammatory cytokines IL-1β, IL-2, GM-CSF, and TNF-α decreased; whereas, IL-6 and IL-8 increased from PRE to IP. Additionally, anti-inflammatory cytokines IL-4 and IL-13 decreased.

CONCLUSIONS

Completion of a 164-km cycling event induced substantial changes in circulating pro- and anti-inflammatory cytokine concentrations. Time to completion appears to have a greater influence on the systemic IL-10 response than the environmental condition; however, it is possible that a threshold for absolute intensity must be reached for environmental conditions to affect the IL-10 response to exercise. Thus, cyclists from the FAST/MOD groups appear more likely to experience an acute transient immune suppression than cyclists from the SLOW group.

Inflammation and adipose tissue: effects of progressive load training in rats

Introduction

Cytokines (IL-6, IL-10 and TNF-α) are increased after exhaustive exercise in the rat retroperitoneal (RPAT) and mesenteric adipose tissue (MEAT) pads. On the other hand, these cytokines show decreased expression in these depots in response to a chronic exercise protocol. However, the effect of exercise with overload combined with a short recovery period on pro- and anti-inflammatory cytokine expression is unknown. In the present study, we investigated the regulation of cytokine production in the adipose tissue of rats after an overtraining-inducing exercise protocol.

Methods

Male Wistar rats were divided into four groups: Control (C), Trained (Tr), Overtrained (OT) and recovered overtrained (R). Cytokines (IL-6, TNF-α and IL-10) levels and Toll Like Receptor 4 (TLR4), Nuclear Factor kBp65 (NF-kBp65), Hormone Sensitive Lipase (HSL) and, Perilipin protein expression were assessed in the adipose tissue. Furthermore, we analysed plasma lipid profile, insulin, testosterone, corticosterone and endotoxin levels, and liver triacylglycerol, cytokine content, as well as apolipoprotein B (apoB) and TLR4 expression in the liver.

Results

OT and R groups exhibited reduced performance accompanied by lower testosterone and increased corticosterone and endotoxin levels when compared with the control and trained groups. IL-6 and IL-10 protein levels were increased in the adipose tissue of the group allowed to recover, in comparison with all the other studied groups. TLR-4 and NF-kBp65 were increased in this same group when compared with both control and trained groups. The protein expression of HSL was increased and that of Perilipin, decreased in the adipose in R in relation to the control. In addition, we found increased liver and serum TAG, along with reduced apoB protein expression and IL-6 and IL-10 levels in the of R in relation to the control and trained groups.

Conclusion

In conclusion, we have shown that increases in pro-inflammatory cytokines in the adipose tissue after an overtraining protocol may be mediated via TLR-4 and NF-kBp65 signalling, leading to an inflammatory state in this tissue.

Systemic inflammation after inspiratory loading in chronic obstructive pulmonary disease

Objective

Patients with chronic obstructive pulmonary disease (COPD) present systemic inflammation. Strenuous resistive breathing induces systemic inflammation in healthy subjects. We hypothesized that the increased respiratory load that characterizes COPD can contribute to systemic inflammation in these patients.

Patients and methods

To test this hypothesis, we compared leukocyte numbers and levels of circulating cytokines (tumor necrosis factor alpha [TNFα], interleukin-1β [IL-1β], IL-6, IL-8, and IL-10), before and 1 hour after maximal incremental inspiratory loading in 13 patients with stable COPD (forced expiratory volume in one second [FEV₁] 29 ± 2.5% ref) and in 8 healthy sedentary subjects (FEV₁ 98 ± 5% ref).

Results

We found that: (1) at baseline, patients with COPD showed higher leukocyte counts and IL-8 levels than controls (p < 0.01); and, (2) one hour after maximal inspiratory loading these values were unchanged, except for IL-10, which increased in controls (p < 0.05) but not in patients with COPD.

Conclusions

This study confirms the presence of systemic inflammation in COPD, shows that maximal inspiratory loading does not increase the levels of pro-inflammatory cytokines (IL-1β, IL-8) in COPD patients or controls, but suggests that the former may be unable to mount an appropriate systemic anti-inflammatory response to exercise.

Efeitos dos exercícios físicos sobre o edema inflamatório agudo em ratos Wistar

Os exercícios físicos têm sido associados a importantes e variados benefícios à saúde, como aqueles relacionados a função imune específica e não-específica, destacando-se, nesta última, o processo inflamatório. Contudo, dependendo do tipo, intensidade, freqüência e duração, os exercícios também podem causar certos prejuízos ao organismo. De fato, estudo prévio mostrou que a hipernocicepção de origem inflamatória, em ratos, foi influenciada pelo protocolo de exercícios físicos realizados em esteira ergométrica. Assim, este trabalho teve como objetivo estudar os efeitos dos exercícios físicos de baixa e alta intensidade sobre a resposta inflamatória aguda. Para isso, foram utilizados ratos machos, adultos, da linhagem Wistar, os quais foram submetidos (grupo treinado) ou não (grupo não treinado) a exercícios em esteira ergométrica. A inflamação aguda foi induzida pela injeção de carragenina-0,5% no coxim da pata posterior esquerda dos ratos, sendo o volume de edema inflamatório agudo mensurado por meio de pletismografia, antes e após 1, 2, 3, 4, 6, 8 e 24 horas da indução do processo inflamatório. A análise estatística dos resultados mostrou aumento significante no volume de edema inflamatório nos momentos H1, H2 e H3 (P<0,01) e nos momentos H4 e H6 (P<0,05) nos animais treinados em baixa intensidade. Entretanto, não ocorreram alterações estatisticamente significantes no volume de edema inflamatório agudo em nenhum dos momentos avaliados (P>0,05) nos animais do grupo treinado em alta intensidade em relação aos não treinados. Concluiu-se, então, que os exercícios físicos de baixa intensidade, em esteira ergométrica, aumentaram o volume de edema inflamatório agudo em ratos, provavelmente ocasionado pelo aumento na síntese e secreção de prostaglandinas e/ou aumento nos níveis plasmáticos das citocinas IL-1, IL-6 e TNF-alfa entre outros fatores. Tal fato não foi observado com os exercícios de alta intensidade, mostrando assim, a influência da intensidade, freqüência e duração dos exercícios sobre este parâmetro inflamatório.

Lack of effect of repeated suberythemal ultraviolet-B exposures on human blood dendritic subtypes

BACKGROUND/PURPOSE

Dendritic cells (DC) play a major role in the afferent immune response. They are found as a minor cell population in the blood as three main subtypes that can be distinguished phenotypically: plasmacytoid DC (PDC), and myeloid DC1 and 2 (MDC1 and 2). The aim of the study was to examine the effect of repeated whole-body suberythemal ultraviolet (UV) B irradiation on the percentages of DC subsets in the blood and skin, and to test for photoadaptation by the subsequent administration of a local erythemal UV dose.

METHODS

Thirty subjects in each group were irradiated with either 0.7 personal minimal erythema dose (MED) UVB daily for 10 days (whole body), or for the 10 days followed by a single three MED UVB exposure of a local body site, or with the single three MED UVB exposure of a local body site only. Blood was collected before and after the exposures and the percentage of DC and DC subtypes assessed by flow cytometry. Skin biopsies were collected at the same times, and the number and position of the DC subsets examined by immunofluorescent microscopy.

RESULTS

The whole-body repeated UVB irradiations did not result in a change in the blood DC (BDC) or the subsets percentages in the blood, except that there was a small but significant rise in the percentage of the MDC2 subset. No alteration occurred following the local erythemal UVB exposure. The total number of BDC in the skin was small, with the PDC being located mainly in the dermis and the myeloid subtypes mainly in the epidermis. No change in cutaneous numbers or distribution was revealed following the irradiation protocols.

CONCLUSIONS

Repeated whole-body suberythemal UVB irradiation does not cause a change in BDC or BDC subsets in the blood or skin, except for a small increase in the percentage of MDC2 in the blood. Local erythemal UVB irradiation does not alter the BDC subsets in blood or skin.

Influence of carbohydrate delivery on the immune response during exercise and recovery from exercise

Acute, sustained, moderate- to high-intensity exercise has been shown to induce significant alterations in the distribution and function of leukocytes during recovery. In many instances, these changes have been found to reflect a transient impairment of immune function in vitro during recovery from such exercise. Carbohydrate supplementation during exercise has been associated with an attenuation of cortisol production. Because cortisol has been linked to immunosuppression, a growing body of research has examined the influence of carbohydrate supplementation on immune function in response to exercise. New areas along this line of inquiry involve examination of the cytokine response to exercise and the role that carbohydrate may play in regulating the production of proinflammatory cytokines. Inter-relations among the immune response, production of specific cytokines, and cortisol are also examined. The clinical significance of an attenuated immune response when exercising as a result of the administration of supplemental carbohydrate is yet to be determined.

Effect of dietary fat intake and exercise on inflammatory mediators of the immune system in sedentary men and women

OBJECTIVE

Dietary fat intake and exercise affect the immune system. This study determined the changes in inflammatory components of the immune system in response to maximal exercise with three levels of dietary fat intake: 19%, 30%, and 50% of total calories.

METHODS

Five men and six women were randomly assigned to consume diets with 19% and 50% calories from fat for three weeks each, with a one-week washout. The habitual and washout diets were 30% calories from fat. At the beginning and the end of each diet, body composition and maximal exercise tests were performed. Blood samples were collected before and after exercise to determine the immunological parameters.

RESULTS

The subject's energy intake was balanced to expenditure on the 30% and 50% diets, but was in negative balance on the 19% diet. Exercise led to significant increases in the concentrations of leukocytes, neutrophils, lymphocytes, monocytes, plasma tumour necrosis factor (TNF)-alpha, plasma interleukin (IL)-2, plasma soluble vascular cell adhesion molecule (sVCAM)-1, and the production of IL-1beta and IL-6 by peripheral blood mononuclear (PBMN) cells stimulated with lipopolysaccharide (LPS), irrespective of diets (p < 0.05). The 19% fat diet resulted in increased plasma soluble intercellular adhesion molecule (sICAM)-1 after exercise. Leukotriene (LT) B4 concentration released by neutrophils stimulated with LPS was higher in the 50% fat diet, compared to the lower fat diets, and the sICAM-1 production of neutrophils stimulated with LPS was significantly increased after exercise only with 30% fat diet.

CONCLUSION

While a short, intense bout of exercise increased pro-inflammatory mediators of the immune system, decreasing fat intake to 19% on a caloric deficient diet caused a greater increase in plasma TNF-alpha, sVCAM-1 and sICAM-1 concentration than the 30% and 50% fat diets in male and female subjects. Increasing fat calories to 50% with caloric balance did not exacerbate pro-inflammatory mediators compared to a 30% fat diet.

Exposure to low doses of solar-simulated radiation induces an increase in the myeloid subtype of blood dendritic cells

Exposure to ultraviolet radiation causes alterations of cutaneous and systemic immunity. The aim of our study was to assess the influence of low doses of solar-simulated radiation (SSR) on the phenotypes of blood dendritic cells (BDC). Healthy volunteers (94) were irradiated with a dose of 1.2 SED (standard erythema dose) of SSR for 2, 10 or 30 consecutive days. Blood samples were taken before the first exposure and 24 h after final exposure. The three main subsets of BDC were distinguished by flow cytometry: BDCA-2(+)/CD123(+)/HLA-DR(+) (plasmacytoid, PDC) and two myeloid subtypes BDCA-1(+)/CD11c(+)/HLA-DR(+) (MDC1) and BDCA-3(+)/CD32(-)/HLA-DR(+) (MDC2). The percentage of total DC was elevated in all groups by the UV exposure and was significantly increased after 2 and 30 days of irradiation (P = 0.006 and P = 0.018, respectively). A particularly distinct increase was observed in the percentage of the MDC1 after 2 and 30 days (P = 0.022 and P < 0.0001, respectively). The MDC2 showed an increase after 10 days and a subsequent significant decrease after 30 days of irradiation (P = 0.031). A significant increase in PDC was found after 2 days of irradiation (P = 0.0006). Exposure to SSR induced an increase in the percentage of BDC in healthy human individuals, especially apparent in the MDC1 subtype.

Effects of exercise on gene expression in human peripheral blood mononuclear cells

Exercise leads to increases in circulating levels of peripheral blood mononuclear cells (PBMCs) and to a simultaneous, seemingly paradoxical increase in both pro- and anti-inflammatory mediators. Whether this is paralleled by changes in gene expression within the circulating population of PBMCs is not fully understood. Fifteen healthy men (18–30 yr old) performed 30 min of constant work rate cycle ergometry (∼80% peak O2 uptake). Blood samples were obtained preexercise (Pre), end-exercise (End-Ex), and 60 min into recovery (Recovery), and gene expression was measured using microarray analysis (Affymetrix GeneChips). Significant differential gene expression was defined with a posterior probability of differential expression of 0.99 and a Bayesian P value of 0.005. Significant changes were observed from Pre to End-Ex in 311 genes, from End-Ex to Recovery in 552 genes, and from Pre to Recovery in 293 genes. Pre to End-Ex upregulation of PBMC genes related to stress and inflammation [e.g., heat shock protein 70 (3.70-fold) and dual-specificity phosphatase-1 (4.45-fold)] was followed by a return of these genes to baseline by Recovery. The gene for interleukin-1 receptor antagonist (an anti-inflammatory mediator) increased between End-Ex and Recovery (1.52-fold). Chemokine genes associated with inflammatory diseases [macrophage inflammatory protein-1α (1.84-fold) and -1β (2.88-fold), and regulation-on-activation, normal T cell expressed and secreted (1.34-fold)] were upregulated but returned to baseline by Recovery. Exercise also upregulated growth and repair genes such as epiregulin (3.50-fold), platelet-derived growth factor (1.55-fold), and hypoxia-inducible factor-I (2.40-fold). A single bout of heavy exercise substantially alters PBMC gene expression characterized in many cases by a brisk activation and deactivation of genes associated with stress, inflammation, and tissue repair.

Acute impact of submaximal resistance exercise on immunological and hormonal parameters in young men

In this study, we examined the acute effects of submaximal resistance exercise on immunological and hormonal parameters in 7 resistance-trained and 10 non-resistance-trained males. The participants, who were aged 29.5 +/- 7.1 years (mean +/- s), performed submaximal resistance exercise at 75% of their one-repetition maximum. Blood samples were taken before, during, immediately after, and 30, 60 and 120 min after exercise and analysed for leukocyte subpopulations and stress hormones. Total leukocytes, neutrophils and monocytes increased during exercise, reaching their maximum 2 h after exercise. Lymphocytes increased during exercise, T-helper cells returned to resting values after exercise, and natural killer cells and T-suppressor cells decreased below resting values. The CD4/CD8 ratio decreased during exercise but increased during recovery. The resistance-trained participants tended to have lower T-helper cell counts before, during and immediately after exercise and a lower CD4/CD8 ratio during recovery than the non-resistance-trained participants. Plasma cortisol correlated positively with leukocytes during exercise (r = 0.572, P < 0.05), but negatively with T-helper cells 30 and 60 min after exercise (r = -0.573, P < 0.05; r = -0.642, P < 0.01, respectively). Our results indicate that resistance exercise leads to acute changes in leukocyte counts, despite moderate hormonal changes, independent of training status. Regular resistance exercise might lead to decreased T-helper cell counts and a lower CD4/CD8 ratio, which could increase susceptibility to infections.

Immunomodulatory action of chronic exercise on macrophage and lymphocyte cytokine production in mice

This study was designed to evaluate the effects of 8-week voluntary running exercise on cytokine production of macrophages and lymphocytes. Seven-week-old-male BALB/c inbred mice were divided into two groups: a group given voluntary exercise (exercise group, n=32), and the other, a non-exercise group (control group, n=32). Exercise consisted of spontaneous running in wheels for 3 days per week over 8 weeks. The levels of nitric oxide (NO2-) and interleukin (IL)-1 beta production by lipopolysaccharide (LPS)-stimulated peritoneal macrophages from the exercise group was significantly higher than that in the control group (P < 0.05-P < 0.01). In the exercise group, stimulation indices by concanavalin A (Con A) was significantly higher than they were in the control group (P < 0.05-P < 0.001). When compared with the control group, the exercise group showed a significant (P < 0.05) increase in the splenic lymphocyte production of IL-2 stimulated by Con A (449.5 +/- 28.2 and 853.7 +/- 116.0 pg 4 x 10(5) cells(-1) 48 h(-1) for the control group and the exercise group, respectively). IL-4 production of splenocytes stimulated by Con A in the exercise group (37.6 +/- 5.1 pg 4 x 10(5) cells(-1) 48 h(-1)) was higher than that in the control group (30.9 +/- 3.9 pg 4 x 10(5) cells(-1) 48 h(-1)); however, the difference was not statistically significant. These results suggest that 8-week voluntary running exercise effectively enhanced macrophage and lymphocyte functions in mice.

Surgical and physical stress increases circulating blood dendritic cell counts independently of monocyte counts

Dendritic cells (DCs) are specialized antigen-presenting cells that have the unique ability to initiate a primary immune response. The effect of physiologic stress on circulating blood DCs has thus far not been studied. In this study, we applied a recently developed method of counting blood DCs to test the hypothesis that significant stress to the body such as surgery and exercise might induce measurable changes in the DC numbers, subsets, phenotype, and function. Twenty-six patients scheduled for elective laparoscopic cholecystectomy, 4 for elective hysterectomy, 56 controls, and 5 volunteers who underwent a stress exercise test were enrolled in the study. Absolute DC counts increased acutely (71.7% +/- 11% [SEM], P =.0001) in response to the stress of surgery and dropped below preoperative levels (-25% +/- 14% [SEM], P =.05) on days 2-3. The perioperative DC subset balance remained constant. Interestingly, DC counts changed independently of monocyte counts. Exercise also induced a rise in DC counts but coincidentally with monocyte counts. Surprisingly, no phenotypic or functional activation of DCs was seen in either stress situations in vivo. DCs are rapidly mobilized into the circulation in response to surgical and exercise stress, which may serve to prepare the host's immune defenses against trauma. The independent regulation of the DC and monocyte counts reinforces the distinction between these 2 cell populations.

Surgical and physical stress increases circulating blood dendritic cell counts independently of monocyte counts

Dendritic cells (DCs) are specialized antigen-presenting cells that have the unique ability to initiate a primary immune response. The effect of physiologic stress on circulating blood DCs has thus far not been studied. In this study, we applied a recently developed method of counting blood DCs to test the hypothesis that significant stress to the body such as surgery and exercise might induce measurable changes in the DC numbers, subsets, phenotype, and function. Twenty-six patients scheduled for elective laparoscopic cholecystectomy, 4 for elective hysterectomy, 56 controls, and 5 volunteers who underwent a stress exercise test were enrolled in the study. Absolute DC counts increased acutely (71.7% ± 11% [SEM],P = .0001) in response to the stress of surgery and dropped below preoperative levels (−25% ± 14% [SEM],P = .05) on days 2-3. The perioperative DC subset balance remained constant. Interestingly, DC counts changed independently of monocyte counts. Exercise also induced a rise in DC counts but coincidentally with monocyte counts. Surprisingly, no phenotypic or functional activation of DCs was seen in either stress situations in vivo. DCs are rapidly mobilized into the circulation in response to surgical and exercise stress, which may serve to prepare the host's immune defenses against trauma. The independent regulation of the DC and monocyte counts reinforces the distinction between these 2 cell populations.

Cytokine changes after a marathon race

The influence of carbohydrate (1 l/h of a 6% carbohydrate beverage), gender, and age on pro- and anti-inflammatory plasma cytokine and hormone changes was studied in 98 runners for 1.5 h after two competitive marathon races. The marathoner runners were randomly assigned to carbohydrate (C, n = 48) and placebo (P, n = 50) groups, with beverages administered during the races in a double-blind fashion using color codes. Plasma glucose was higher and cortisol was lower in the C than in the P group after the race (P < 0.001). For all subjects combined, plasma levels of interleukin (IL)-10, IL-1 receptor antagonist (IL-1ra), IL-6, and IL-8 rose significantly immediately after the race and remained above prerace levels 1.5 h later. The pattern of change in all cytokines did not differ significantly between the 12 women and 86 men in the study and the 23 subjects > or =50 yr of age and the 75 subjects <50 yr of age. The pattern of change in IL-10, IL-1ra, and IL-8, but not IL-6, differed significantly between the C and the P group, with higher postrace values measured for IL-10 (109% higher) and IL-1ra (212%) in the P group and for IL-8 (42%) in the C group. In conclusion, plasma levels of IL-10, IL-1ra, IL-6, and IL-8 rose strongly in runners after a competitive marathon, and this was not influenced by age or gender. Carbohydrate ingestion, however, had a major effect in attenuating increases in cortisol and two anti-inflammatory cytokines, IL-10 and IL-1ra.

The cytokine response to physical activity and training

Cytokines are soluble glycoproteins that are produced by and mediate communication between and within immune and nonimmune cells, organs and organ systems throughout the body. Pro- and anti-inflammatory mediators constitute the inflammatory cytokines, which are modulated by various stimuli, including physical activity, trauma and infection. Physical activity affects local and systemic cytokine production at different levels, often exhibiting striking similarity to the cytokine response to trauma and infection. The present review examines the cytokine response to short term exercise stress, with an emphasis on the balance between pro- and anti-inflammatory mechanisms and modulation of both innate and specific immune parameters through cytokine regulation. The effects of long term exercise on cytokine responses and the possible impact on various facets of the immune system are also discussed, with reference to both cross-sectional and longitudinal studies of exercise training. Finally, the validity of using exercise as a model for trauma and sepsis is scruti- nised in the light of physiological changes, symptomatology and outcome, and limitations of the model are addressed. Further studies, examining the effect of exercise, trauma and infection on novel cytokines and cytokine systems are needed to elucidate the significance of cytokine regulation by physical activity and, more importantly, to clarify the health implications of short and long term physical activity with respect to overall immune function and resistance to infection.

Exercise elevates plasma levels but not gene expression of IL-1beta, IL-6, and TNF-alpha in blood mononuclear cells

Physical activity induces a subclinical inflammatory response, mediated in part by leukocytes, and manifested by elevated concentrations of circulating proinflammatory cytokines, including interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha). However, the source of the cytokines that appear during exercise remains unknown. In this study, we examined exercise-induced changes in plasma cytokine concentrations and their corresponding mRNA expression in peripheral blood mononuclear cells. Ten healthy [peak oxygen uptake = 48.8 +/- 6.5 (SD) ml. kg(-1). min(-1)] but untrained men [age = 25 +/- 5 (SD) yr] undertook 3 h of exercise (cycling and inclined walking) at 60-65% peak oxygen uptake. Circulating leukocyte subset counts were elevated during and 2 h postexercise but returned to normal within 24 h. Plasma concentrations of IL-1beta, IL-6, and TNF-alpha peaked at the end of exercise and remained elevated at 2 h (IL-6) and up to 24 h (IL-1beta and TNF-alpha) postexercise. Cytokine gene expression in circulating mononuclear cells was measured by using the reverse transcriptase-polymerase chain reaction; mRNA accumulation did not change with exercise. In conclusion, mRNA accumulation of IL-1beta, IL-6, and TNF-alpha in circulating mononuclear cells is not affected by 3 h of moderate endurance exercise and does not seem to account for the observed increases in plasma cytokines.

Effect of exercise on cytokines and growth mediators in prepubertal children

Many of the anabolic effects of exercise are mediated through insulin-like growth factor-I (IGF-I), but in adolescents, brief exercise training leads to reductions, rather than the expected increase, in circulating IGF-I. Certain cytokines--interleukin-(IL) 1beta (IL-1beta), IL-6 (IL-6), and tumor necrosis factor-alpha--are increased by exercise in adults and are known to inhibit IGF-I. To test the hypothesis that these cytokines might play a role in the adaptation to exercise, we measured the acute effects of exercise on selected cytokines and growth factors in 17 healthy 8- to 11-y-old children (4 females). Designed to mimic patterns and intensity of exercise found in the real lives of American children, the exercise protocol consisted of a 1.5-h soccer practice (of which about 40 min constituted of vigorous exercise). Pre- and postexercise urine and saliva samples were obtained in all subjects and both blood and urine in nine subjects. The exercise led to significant increases in circulating tumor necrosis factor-alpha (18 +/- 7%, p < 0.05) and IL-6 (125 +/- 35%, p < 0.01) as well as a significant increase in the antiinflammatory cytokine IL-1 receptor antagonist (33 +/- 10%, p < 0.01). Urine levels of IL-6 were also substantially increased by exercise (440 +/- 137%, p < 0.0001). Circulating levels of IGF-I were reduced to a small but significant degree (-6.4 +/- 3.2%, p < 0.05), although IGF-binding protein-1 (known to inhibit IGF-I) was substantially increased (156 +/- 40%, p < 0.001). Cytokines are systemically increased after relatively brief exercise in healthy children. This increase may alter critical anabolic agents such as IGF-I and its binding proteins.

Strenuous resistive breathing induces proinflammatory cytokines and stimulates the HPA axis in humans

Interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), powerful stimulants of the hypothalamic-pituitary-adrenal (HPA) axis, increase in response to whole body exercise. Strenuous inspiratory resistive breathing (IRB), a form of clinically relevant "exercise" for the respiratory muscles, produces beta-endorphin through a largely unknown mechanism. We investigated (in 11 healthy humans) whether strenuous IRB produces proinflammatory cytokines and beta-endorphin in parallel with stimulation of the HPA axis, assessed by concurrent measurement of ACTH. Subjects underwent either severe [at 75% of maximal inspiratory pressure (P(m) (max))] or moderate (at 35% of P(m) (max)) IRB. Plasma cytokines, beta-endorphin, and ACTH were measured at rest (point R), at the point at which the resistive load could not be sustained (point F), and at exhaustion [15 min later (point E)]. During severe IRB, IL-1beta increased from 0.83 +/- 0.12 pg/ml at point R to 1.88 +/- 0. 53 and 4.06 +/- 1.27 pg/ml at points F and E, respectively (P < 0. 01). IL-6 increased from 5.30 +/- 1.02 to 10.33 +/- 2.14 and 11.66 +/- 2.29 pg/ml at points F and E, respectively (P = 0.02). ACTH and beta-endorphin fluctuated from 20.87 +/- 5.49 and 25.03 +/- 3.97 pg/ml at point R to 22.97 +/- 4.41 and 26.32 +/- 3.93 pg/ml, respectively, at point F and increased to 46.96 +/- 8.55 and 40.32 +/- 5.94 pg/ml, respectively, at point E (P < 0.01, point E vs. point F). There was a positive correlation between the IL-6 at point F and the ACTH and beta-endorphin at point E (r = 0.88 and 0.94, respectively; P < 0.01) as well as between the increase in IL-6 (between points R and F) and the increases in ACTH and beta-endorphin (between points F and E, r = 0.91 and 0.92, respectively; P < 0.01). Moderate IRB did not produce any change. We conclude that severe IRB produces proinflammatory cytokines and stimulates the HPA axis in humans secondary to the production of cytokines (especially IL-6).

Nutrition, exercise, and immune system function

Many components of the immune system exhibit adverse change after prolonged, intense exertion. During this "open window" of impaired immunity (which may last 3-72 h, depending on the immune measure), viruses and bacteria may gain a foothold, increasing the risk for subclinical and clinical infection. The influence of nutritional supplements, primarily zinc, vitamin C, glutamine, and carbohydrate, on the acute immune response to prolonged exercise has been measured in endurance athletes. Vitamin C and glutamine have received much attention, but the data thus far are inconclusive. The most impressive results have been reported with carbohydrate supplementation. Carbohydrate beverage ingestion has been associated with increased plasma glucose levels, an attenuated cortisol and growth hormone response, fewer perturbations in blood immune cell counts, decreased granulocyte and monocyte phagocytosis and oxidative burst activity, and a diminished pro-inflammatory and anti-inflammatory cytokine response. Overall these data indicate that the physiologic stress to the immune system is reduced when endurance athletes use carbohydrate beverages before, during, and after prolonged and intense exertion. The clinical significance of these carbohydrate-induced effects on the endocrine and immune systems awaits further research.

Influence of mode and carbohydrate on the cytokine response to heavy exertion

OBJECTIVE AND METHODS

This randomized, double-blind, placebo-controlled study was designed to determine the influence of exercise mode and 6% carbohydrate (C) versus placebo (P) beverage ingestion, on blood cell counts, plasma glucose, hormone, and inflammatory cytokine responses (five total samples over 9 h) to 2.5 h of high-intensity running and cycling (approximately 75% VO2max) by 10 triathletes who acted as their own controls. Statistical significance was set at P < or = 0.05.

RESULTS

C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin, lower plasma cortisol and growth hormone, and diminished perturbation in blood immune cell counts. The pattern of change over time for interleukin (IL)-6 was significantly different between C and P conditions (P = 0.021) and between running and cycling modes (P < 0.001), with the lowest postexercise values seen in the C-cycling sessions (10.7 +/- 1.8 pg x mL(-1)) and the highest in the P-running sessions (51.6 +/- 14.2 pg x mL(-1)). The pattern of change over time between C and P conditions (but not modes) was significantly different for IL-1 receptor antagonist (P = 0.003), with values once again lowest for the C-cycling sessions (1.5 h postexercise, 301 +/- 114 pg x mL(-1)) and highest for the P-running sessions (1171 +/- 439 pg x mL(-1)).

CONCLUSION

These data indicate that carbohydrate versus placebo ingestion (4 mL x kg(-1) carbohydrate or placebo every 15 min of the 2.5-h exercise bout) is associated with higher plasma glucose levels, an attenuated cortisol response, and a diminished pro- and anti-inflammatory cytokine response.

Immune response to heavy exertion

Epidemiological data suggest that endurance athletes are at increased risk for upper respiratory tract infection during periods of heavy training and the 1- to 2-wk period following race events. There is growing evidence that, for several hours subsequent to heavy exertion, several components of both the innate (e.g., natural killer cell activity and neutrophil oxidative burst activity) and adaptive (e.g., T and B cell function) immune system exhibit suppressed function. At the same time, plasma pro- and anti-inflammatory cytokines are elevated, in particular interleukin-6- and interleukin-1-receptor antagonist. Various mechanisms explaining the altered immunity have been explored, including hormone-induced trafficking of immune cells and the direct influence of stress hormones, prostaglandin-E2, cytokines, and other factors. The immune response to heavy exertion is transient, and further research on the mechanisms underlying the immune response to prolonged and intensive endurance exercise is necessary before meaningful clinical applications can be drawn. Some attempts have been made through chemical or nutritional means (e.g., indomethacin, glutamine, vitamin C, and carbohydrate supplementation) to attenuate immune changes following intensive exercise.

Carbohydrate and the cytokine response to 2.5 h of running

This randomized, double-blind, placebo-controlled study was designed to determine the influence of 6% carbohydrate (C) vs. placebo (P) beverage ingestion on cytokine responses (5 total samples over 9 h) to 2.5 h of high-intensity running (76.7 +/- 0.4% maximal O2 uptake) by 30 experienced marathon runners. For interleukin-6 (IL-6), a difference in the pattern of change between groups was found, highlighted by a greater increase in P vs. C immediately postrun (753 vs. 421%) and 1.5 h postrun (193 vs. 86%) [F(4,112) = 3.77, P = 0.006]. For interleukin-1-receptor antagonist (IL-1ra), a difference in the pattern of change between groups was found, highlighted by a greater increase in P vs. C 1.5 h postrun (231 vs. 72%) [F(2,50) = 6.38, P = 0.003]. No significant interaction effects were seen for bioactive IL-6 or IL-1 beta. The immediate postrun plasma glucose concentrations correlated negatively with those of plasma cortisol (r = -0.67, P < 0.001); postrun plasma cortisol (r = 0.70, P < 0.001) and IL-6 levels (r = 0.54, P = 0.003) correlated positively with levels of IL-1ra. Taken together, the data indicate that carbohydrate ingestion attenuates cytokine levels in the inflammatory cascade in response to heavy exertion.