Transcriptional and translational regulation of heat shock proteins in leukocytes of endurance runners

Biochemical markers of muscular damage

Muscle tissue may be damaged following intense prolonged training as a consequence of both metabolic and mechanical factors. Serum levels of skeletal muscle enzymes or proteins are markers of the functional status of muscle tissue, and vary widely in both pathological and physiological conditions. Creatine kinase, lactate dehydrogenase, aldolase, myoglobin, troponin, aspartate aminotransferase, and carbonic anhydrase CAIII are the most useful serum markers of muscle injury, but apoptosis in muscle tissues subsequent to strenuous exercise may be also triggered by increased oxidative stress. Therefore, total antioxidant status can be used to evaluate the level of stress in muscle by other markers, such as thiobarbituric acid-reactive substances, malondialdehyde, sulfhydril groups, reduced glutathione, oxidized glutathione, superoxide dismutase, catalase and others. As the various markers provide a composite picture of muscle status, we recommend using more than one to provide a better estimation of muscle stress.

Daily hypoxia increases basal monocyte HSP72 expression in healthy human subjects

Heat shock protein 72 (HSP72) performs vital roles within the body at rest and during periods of stress. In vitro, research demonstrates HSP72 induction in response to hypoxia. Recently, in vivo, an acute hypoxic exposure (75 min at 2,980 m) was sufficient to induce significant increases in monocyte expressed HSP72 (mHSP72) and a marker of oxidative stress in healthy human subjects. The purpose of the current study was to identify the impact of 10 consecutive days of hypoxic exposures (75 min at 2,980 m) on mHSP72 and erythropoietin (EPO) expression, markers of oxidative stress, and maximal oxygen consumption in graded incremental aerobic exercise. Eight male subjects were exposed to daily normobaric hypoxic exposures for 75 min at 2,980 m for 10 consecutive days, commencing and ceasing at 0930 and 1045, respectively. This stressor was sufficient to induce significant increases in mHSP72, which was significantly elevated from day 2 of the hypoxic exposures until 48 h post-final exposure. Notably, this increase had an initial rapid (30% day on day compared to baseline) and final slow phase (16% day on day compared to baseline) of expression. The authors postulate that 7-day hypoxic exposure in this manner would be sufficient to induce near maximum hypoxia-mediated basal mHSP72 expression. Elevated levels of mHSP72 are associated with acquired thermotolerance and provide cross tolerance to non-related stressors in vivo, the protocol used here may provide a useful tool for elevating mHSP72 in vivo. Aside from these major findings, significant transient daily elevations were seen in a marker of oxidative stress, alongside sustained increases in EPO expression. However, no physiologically significant changes were seen in maximal oxygen consumption or time to exhaustion.

Combination of two oxidant stressors suppresses the oxidative stress and enhances the heat shock protein 27 response in healthy humans

We tested the hypothesis that the combination of 2 oxidant stressors (hyperoxia and fatiguing exercise) might reduce or suppress the oxidative stress. We concomitantly measured the plasma concentration of heat shock proteins (Hsp) that protect the cells against the deleterious effects of reactive oxygen species. Healthy humans breathed pure oxygen under normobaric condition for 50-minute periods during which they stayed at rest or executed maximal static handgrip sustained until exhaustion. They also repeated handgrip bouts in normoxic condition. We performed venous blood measurements of 2 markers of the oxidative stress (thiobarbituric acid reactive substances and reduced ascorbic acid) and Hsp27. Under normoxic condition, the handgrip elicited an oxidative stress and a modest increase in plasma Hsp27 level (+7.1 +/- 5.4 ng/mL). Under hyperoxic condition, (1) at rest, compared with the same time schedule in normoxic condition, we measured an oxidative stress (increased thiobarbituric acid reactive substances and decreased reduced ascorbic acid levels) and the plasma Hsp27 level increased (maximal variation, +12.5 +/- 6.0 ng/mL); and (2) after the handgrip, the oxidative stress rapidly disappeared. The combination of both hyperoxia and handgrip bout doubled the Hsp27 response (maximal variation, +24.8 +/- 9.2 ng/mL). Thus, the combination of 2 hits eliciting an oxidative stress seems to induce an adaptive Hsp27 response that might counterbalance an excessive production of reactive oxygen species.

Acute circuit-resistance exercise increases expression of lymphocyte agouti-related protein in young women

Exercise-induced leukocytosis and lymphocytosis is accompanied by up-regulation and down-regulation of hundreds of genes in white blood cells (WBCs). Agouti-related protein (AgRP) is an orexigenic peptide secreted predominantly from the arcuate nucleus in the hypothalamus. AgRP affects feeding behavior and plays a role in energy and glucose homeostasis and adiposity. The purpose of the study was to determine effects of circuit resistance exercise (CRE) (9 exercises, 25 s per exercise) at different intensities on peripheral blood lymphocyte (PBL) AgRP mRNA expression and its concentrations in lymphocytes and plasma. Twenty-five young female college students were randomly divided into five groups: control, 40% 1-repetition maximum (1-RM), 60% 1-RM, 80% 1-RM and combined (40 + 60 + 80% 1-RM) loads. Peripheral blood mononuclear cells were isolated by a lymphocyte density gradient centrifugation method for AgRP mRNA expression. Lymphocyte ATP, glycogen, AgRP, growth hormone (GH), and plasma AgRP, GH and glucose concentrations were measured. CRE increased AgRP mRNA lymphocyte expression significantly ( P < 0.0001) at all intensities. A higher and significant ( P < 0.01) increase was found in the 60% 1-RM group when compared with the other groups. The CRE-induced lymphocyte AgRP expression was accompanied by elevations in plasma AgRP, glucose and GH levels as well as higher WBCs, lymphocytes and neutrophil counts. Lymphocyte AgRP and GH concentrations were significantly reduced ( P < 0.05). Lymphocyte ATP content was unchanged and glycogen was reduced in the combined group but not in the other groups. Data indicate that AgRP mRNA is expressed in PBLs and that CRE increases its expression. Data also reveal that the expression of AgRP was accompanied with higher plasma AgRP and GH concentrations. Findings suggest that AgRP may provide an important signal in the immune environment and that the lymphocyte may be considered as an extra-hypothalamic source of plasma AgRP following exercise stress.

Heat-shock protein 70: expression in monocytes of patients with sleep apnoea and association with oxidative stress and tumour necrosis factor-alpha

Obstructive sleep apnoea (OSA) is associated with a variety of nightly stresses, including intermittent hypoxaemia, oxidative stress and sleep fragmentation. Heat-shock proteins (HSPs) are upregulated in response to an array of environmental and metabolic stresses. We hypothesized that the OSA-related stresses would affect the expression of HSP70 in monocytes. Basal (30 min, at 37 degrees C), heat stress-induced HSP70 (30 min, at 43 degrees C) and basal tumour necrosis factor-alpha (TNF-alpha) were determined by flow cytometry in monocytes of 10 patients with OSA and 10 controls matched by age, gender and body mass index. Oxidative stress was determined by thiobarbituric acid-reactive substances (TBARS) and antioxidant paraoxonase-1 activity. Basal HSP70 expression was 1.8-fold higher in patients with OSA as compared with controls (P < 0.0005) and was significantly positively correlated with TBARS (r = 0.56, P < 0.009). However, induction of HSP70 in response to heat stress treatment was lower by 40% in OSA monocytes as compared with controls (P < 0.0003). Furthermore, heat stress-induced HSP70 expression was significantly negatively correlated with basal HSP70 expression independently of apnoea severity (r = -0.69, P < 0.0006). Also, basal intracellular TNF-alpha expression was inversely correlated with heat-shock-induced HSP70 (r = -0.78, P < 0.015) in OSA monocytes but not in controls. In conclusion, basal HSP70 overexpression that is a protective mechanism indicative of disease-associated stress was significantly higher in patients with OSA and was correlated with oxidative stress. On the other hand, in response to a defined heat-stress treatment, the induction of HSP70 was lower in patients with OSA, indicative of a possible maladaptive response to an acute stress. Correlations with oxidative stress and TNF-alpha further support this conclusion.

Peripheral leukocyte response to oncological radiotherapy: Expression of heat shock proteins

PURPOSE

To study Heat Shock Proteins (HSP) expression in patients subjected to radiotherapy and their potential use as biomarkers for radiation tolerance. An evaluation is also made of whether irradiated volume is critical to the outcome of normal tissue injury using polymorphonuclear neutrophils as biosensors, and whether HSP antibodies (Ab) may be involved in post-radiotherapy disease.

MATERIAL AND METHODS

Twelve patients receiving the same total dose of radiotherapy, but in three different volumes, and four healthy volunteers used as controls were analysed. hsp27 and 70i mRNA were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Southern-blot, HSP by flow cytometry, and HSP-Ab by Enzyme-linked Immnoadsorbent Assay (ELISA). The clinical protocol included radiation related toxicity based on clinical and analytical scales.

RESULTS

Radiotherapy caused hsp downregulation, maximum in patients with the largest irradiated volumes, and a decrease in intracellular HSP content. Patients with greatest intraleukocyte HSP levels before treatment suffered more severe radiation morbidity. Patients with endocrine neoplasms presented the highest HSP-Ab titers.

CONCLUSIONS

Radiotherapy downregulates hsp27 and 70i, which would enhance radiosensitivity. HSP content prior to treatment is suggested as a prognostic biomarker for radiation tolerance, with circulating leukocytes as biosensors. HSP-Ab may be biomarkers of tumor disease, but do not seem to be involved in the morbidity of acute post-radiotherapy disease, which is closely related to the volumes irradiated.

The effect of prior exercise onex vivoinduction of heme oxygenase-1 in human lymphocytes

It was postulated that prior demanding exercise would suppress the induction of the oxidant-responsive protein Heme Oxygenase-1 (HO-1) in mononuclear cells following subsequent ex vivo H(2)O(2) treatment. Eight male subjects completed two trials in a randomized order (one rest and one exercise) and ex vivo HO-1 protein induction was determined following H(2)O(2) treatment in lymphocytes and monocytes before and after each trial using a newly developed and reproducible assay. Lymphocytes obtained 2 h post-exercise showed a modest reduction in HO-1 protein expression in response to ex vivo treatment with H(2)O(2) (p<0.05). The plasma concentration of the HO-1 suppressor alpha1-antitrypsin increased immediately post-exercise (p<0.05) and it is tentatively suggested that this may explain the modest transient reduction in ex vivo HO-1 protein induction in lymphocytes in response to an independent oxidant challenge following a prior bout of demanding exercise.

Expression of intracellular cytokines, HSP72, and apoptosis in monocyte subsets during exertional heat stress in trained and untrained individuals

This study examined intracellular cytokine, heat shock protein (HSP) 72, and cellular apoptosis in classic and inflammatory CD14+monocyte subsets during exertional heat stress (EHS). Subjects were divided into endurance-trained [TR; n = 12, peak aerobic power (V̇o2peak) = 70 ± 2 ml·kg lean body mass (LBM)−1·min−1] and sedentary-untrained (UT; n = 11, V̇o2peak= 50 ± 1 ml·kg LBM−1·min−1) groups before walking at 4.5 km/h with 2% elevation in a climatic chamber (40°C, 30% relative humidity) wearing protective clothing until exhaustion (Exh). Venous blood samples at baseline and 0.5°C rectal temperature increments (38.0, 38.5, 39.0, 39.5, and 40.0°C/Exh) were analyzed for cytokines (TNF-α, IL-1β, IL-6, IL-1ra, and IL-10) in CD14++CD16−/CD14+CD16+and HSP72/apoptosis in CD14Bri/CD14Dimsubsets. In addition, serum levels of extracellular (e)HSP72 were also examined. Baseline and Exh samples were separately stimulated with LPS (1 μg/ml) or heat shocked (42°C) and cultured in vitro for 2 h. A greater temperature-dependent increase in CD14+CD16+cells was observed in TR compared with UT subjects as well as a greater LPS tolerance following in vitro LPS stimulation. TNF-α and IL-1β cytokine expression was elevated in CD14+CD16+but not in CD14++CD16−cells. A greater induction of intracellular HSP72 and eHSP72 was observed in TR compared with UT subjects, which coincided with reduced apoptosis at Exh and following in vitro heat shock. Induced HSP in vitro was not uniform across CD14+subsets. Findings suggest that circulating CD14+CD16+, but not CD14++CD16−monocytes, contribute to the proinflammatory cytokine profiles observed during EHS. In addition, the enhanced HSP72 response in endurance-trained individuals may confer improved heat tolerance through both anti-inflammatory and anti-apoptotic mechanisms.

Heat shock protein 72 response to exercise in humans

Heat shock protein (Hsp) 72 is a unique, ubiquitous molecule. In vitro and in vivo animal models have shown that increased Hsp 72 is associated with improved cellular survivability and tolerance to stressors. The primary focus of this article is to review the Hsp 72 protein response to exercise in humans. Various mechanisms regulate post-transcriptional activity and therefore measurement of messenger RNA (mRNA) does not necessarily represent the level of functional Hsp 72. For this reason, this article incorporates only a few studies that assessed Hsp 72 mRNA response to exercise. Although this article focuses on human studies, it also includes some key animal studies to provide insight into the mechanisms of the response of Hsp 72 to stress.Intra- (IC) and extracellular (EC) Hsp 72 have different functions. IC Hsp 72 confers cellular protection from subsequent stressors, while EC Hsp 72 has a whole-body systemic role in antigen presentation and immunity. An acute exercise bout stimulates an increase in both IC and EC Hsp 72. Long-term training and improved fitness increases the rate of availability of IC Hsp 72 in response to stress. Other factors that affect Hsp 72 production include environmental factors, exercise mode, duration and intensity, age, estrogen, and anti-oxidant and glycogen availability. The functions and roles of Hsp 72 also depend on the tissue of origin. This article describes the Hsp 72 response to exercise in relation to the tissue assayed (i.e. skeletal muscle vs lymphocyte) and the origin of the sample (i.e. venous vs arterial serum). Collectively, the reviewed studies reveal exciting and novel research that encourages future investigation in this area.

Effects of ultra-marathon on circulating DNA and mRNA expression of pro- and anti-apoptotic genes in mononuclear cells

We investigated the effects of an ultra-marathon on cell-free plasma DNA as well as on mRNA expression of pro-apoptotic (Bax, Bad), anti-apoptotic (Bcl-2) and cell-protective (Hsp70, Hsp27 and Hsp32) genes in mononuclear blood cells (MNCs). Blood samples were drawn from 14 athletes before and immediately after 6-h run. In addition, blood samples were also collected and analyzed 2 and 24 h after the end of the run. Levels of plasma DNA were significantly increased immediately after the marathon (P < 0.001) and were still higher 2 h later (P < 0.005), but significantly lower than those immediately after the race (P < 0.05). Cell-free plasma DNA returned to pre-race levels 24 h after the run. mRNA expressions of Hsp70, Hsp32 and Bax significantly increased in MNCs after the race, whereas Hsp27 and Bad mRNA expression levels showed no significant changes. Bcl-2 expressions decreased immediately after the race (P < 0.001), but increased in the 24 h later (P < 0.05). We conclude that apoptotic ladders of cell-free DNA following exhaustive exercise originate from apoptotic cells and that not only skeletal muscle cells but also leukocytes contribute to this phenomenon.

Effect of heat acclimation on heat shock protein 72 and interleukin-10 in humans

Heat acclimation (HA) results in whole body adaptations that increase heat tolerance, and in addition, HA may also result in protective cellular adaptations. We hypothesized that, after HA, basal intracellular heat shock protein (HSP) 72 and extracellular IL-10 levels would increase, while extracellular HSP72 levels decrease. Ten male and two female subjects completed a 10-day exercise/HA protocol (100-min exercise bout at 56% of maximum O2uptake in a 42.5°C DB, 27.9% RH environment); subjects exhibited classic adaptations that accompany HA. Peripheral blood mononuclear cells (PBMCs) were isolated before and after each acclimation session on days 1, 6, and 10; plasma and serum were collected before and after exercise on the 1st and 10th day of HA. SDS-PAGE was used to determine PBMC HSP72 levels during HA, and ELISA was used to measure plasma IL-10 and serum HSP72 concentrations. The increase in PBMC HSP72 from pre- to postexercise on the 1st day of HA was not significant (mean ± SD, 1.0 ± 0 vs. 1.6 ± 0.6 density units). Preexercise HSP72 levels on day 1 were significantly lower compared with the pre- and postexercise samples on days 6 and 10 (mean ± SD, day 6: 2.1 ± 1.0 and 2.2 ± 1.0, day 10: 2.0 ± 1.3 and 2.2 ± 1.0 density units, respectively, P < 0.05). There were no differences in plasma IL-10 and serum HSP72 postexercise or after 10 days of HA. The sustained elevation of HSP72 from days 6 to 10 may be evidence of a cellular adaptation to HA that contributes to improved heat tolerance and reduced heat illness risk.

Elevated core and muscle temperature to levels comparable to exercise do not increase heat shock protein content of skeletal muscle of physically active men

AIM

Exercise-associated hyperthermia is routinely cited as the signal responsible for inducing an increased production of heat shock proteins (HSPs) following exercise. This hypothesis, however, has not been tested in human skeletal muscle. The aim of the present study was to therefore investigate the role of increased muscle and core temperature in contributing to the exercise-induced production of the major HSP families in human skeletal muscle.

METHODS

Seven physically active males underwent a passive heating protocol of 1 h duration during which the temperature of the core and vastus lateralis muscle were increased to similar levels to those typically occurring during moderately demanding aerobic exercise protocols. One limb was immersed in a tank containing water maintained at approximately 45 degrees C whilst the contra-lateral limb remained outside the tank and was not exposed to heat stress. Muscle biopsies were obtained from the vastus lateralis of both legs immediately prior to and at 48 h and 7 days post-heating.

RESULTS

The heating protocol induced significant increases (P < 0.05) in rectal (1.5 +/- 0.2 degrees C) and muscle temperature of the heated leg (3.6 +/- 0.5 degrees C). Muscle temperature of the non-heated limb showed no significant change (P > 0.05) following heating (pre: 36.1 +/- 0.5, post: 35.7 +/- 0.2 degrees C). Heating failed to induce a significant increase (P > 0.05) in muscle content of HSP70, HSC70, HSP60, HSP27, alphaB-crystallin, MnSOD protein content or in the activity of superoxide dismutase and catalase.

CONCLUSIONS

These data demonstrate that increases in both systemic and local muscle temperature per se do not appear to mediate the exercise-induced production of HSPs in human skeletal muscle and suggest that non-heat stress factors associated with contractile activity are of more importance in mediating this response.

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.

Analysis of peripheral blood mononuclear cells gene expression in endurance horses by cDNA-AFLP technique

The knowledge of molecular mechanisms of stress response in athlete horses can allow us to plan an appropriate and high-grade training to obtain better performance and to preserve horse welfare. It is well known that excessive muscular exercise can lead to a number of responses which may be associated with modification of the mRNA levels for a number of metabolic genes such as those involved in the immune response. In the present study cDNA-AFLP technique was applied to Arab endurance horses under stressing conditions to visualise variations of transcriptional profiles; 49 transcript derived fragments (TDFs), differentially expressed, were cloned and sequenced. Four of these showed high sequence similarity with genes probably involved in exercise-induced stress response and resulted to be not sequenced in the horse. Their modulation was confirmed by RT-PCR and the full-length transcripts were isolated by RACE-PCR. The mRNAs sequences obtained were included in the GenBank database as Equus caballus interleukin 8 (IL8), E. caballus retinoblastoma binding protein 6 mRNA (RBBP6), E. caballus eukaryotic translation initiation factor 4 gamma 3 (eIF4G3) and E. caballus heat shock protein 90 (Hsp90). The expression pattern of these genes was verified in other endurance horses under stressing conditions, strengthening the hypothesis of their real involvement in exercise stress-induced response.

Exercise affects the gene expression profiles of human white blood cells

White blood cells (WBCs) express tens of thousands of genes, whose expression levels are modified by genetic and external factors. The purpose of the present study was to investigate the effects of acute exercise on gene expression profiles (GEPs) of WBCs and to identify suitable genes that may serve as surrogate markers for monitoring exercise and training load. Five male participants performed an exhaustive treadmill test (ET) at 80% of their maximal O2uptake (V̇o2 max) and a moderate treadmill test (MT) at 60% V̇o2 maxfor exactly the same time ∼2 wk later. WBCs were isolated by the erythrocyte lysis method. GEPs were measured using the Affymetrix GeneChip technology. After scaling, normalization, and filtering, groupwise comparisons of gene expression intensities were performed, and several measurements were validated by real-time PCR. We found 450 genes upregulated and 150 downregulated (>1.5-fold change; ANOVA with Benjamini-Hochberg correction, P < 0.05) after ET that were closely associated with the gene ontology lists “response to stress” and “inflammatory response”. Analysis of mean expression levels after MT showed that the extent of up- and downregulation was workload dependent. The genes for the stress (heat shock) proteins HSPA1A and HSPH1 and for the matrix metalloproteinase MMP-9 showed the most prominent increases, whereas the YES1 oncogene (YES1) and CD160 (BY55) were most strongly reduced. Despite different methodological approaches used, the consistency of our results with the expression data of another study (Connolly PH, Caiozzo VJ, Zaldivar F, Nemet D, Larson J, Hung SP, Heck JD, Hatfield GW, Cooper DM. J Appl Physiol 97: 1461–1469, 2004) suggests that expression fingerprints are useful tools for monitoring exercise and training loads and thereby help to avoid training-associated health risks.

Exertional heat illness and human gene expression

Microarray analysis of gene expression at the level of RNA has generated new insights into the relationship between cellular responses to acute heat shock in vitro, exercise, and exertional heat illness. Here we discuss the systemic physiology of exertional hyperthermia and exertional heat illness, and compare the results of several recent microarray studies performed in vitro on human cells subjected to heat shock and in vivo on samples obtained from subjects performing exercise or suffering from exertional heat injury. From these comparisons, a concept of overlapping component responses emerges. Namely, some of the gene expression changes observed in peripheral blood mononuclear cells during exertional heat injury can be accounted for by normal cellular responses to heat, exercise, or both; others appear to be specific to the disease state itself. If confirmed in future studies, these component responses might provide a better understanding of adaptive and pathological responses to exercise and exercise-induced hyperthermia, help find new ways of identifying individuals at risk for exertional heat illness, and perhaps even help find rational molecular targets for therapeutic intervention.

The time-profile of the PBMC HSP70 response to in vitro heat shock appears temperature-dependent

Heat shock proteins (HSPs) are synthesised by cells subsequent to a stress exposure and are known to confer protection to the cell in response to a second challenge. HSP induction and decay are correlated to thermotolerance and may therefore be used as a biomarker of thermal history. The current study tested the temperature-dependent nature of the heat shock response and characterised its time profile of induction. Whole blood from 6 healthy males (Age: 26 +/- (SD) 2 yrs; Body mass 74.2 +/- 3.8 kgs; VO(2max): 49.1 +/- 4.0 ml.kg(-1).min(-1)) were isolated and exposed to in vitro heat shock (HS) at 37, 38, 39, 40, and 41 degrees C for a period of 90 min. After HS the temperature was returned to 37 degrees C and intracellular HSP70 was quantified from the leukocytes at 0, 2, 4, and 6 h after heat treatment. The concentration of HSP70 was not different between temperatures (P > 0.05), but the time-profile of HSP70 synthesis appeared temperature-dependent. At control (37 degrees C) and lower temperatures (38-39 degrees C) the mean HSP70 concentration increased up to 4 h post HS (P < 0.05) and then returned towards baseline values by 6 h post HS. With in vitro hyperthermic conditions (40-41 degrees C), the time-profile was characterised by a sharp rise in HSP70 levels immediately after treatment (P < 0.05 for 40 degrees C at 0 h), followed by a progressive decline over time. The results suggest a temperature-dependent time-profile of HSP70 synthesis. In addition, the temperature at which HSP70 is inducted might be lower than 37 degrees C.

Effect of training and detraining on the expression of heat shock proteins in m. triceps brachii of untrained males and females

Forty untrained persons were randomized to four different training protocols that exercised the m. triceps brachii. Group 1 and 2 performed high intensity (HI) elbow extensions and group 3 and 4 performed low intensity (LI) elbow extensions. Group 1 and 3 trained until they had accumulated a matching high volume (HV) of training, while group 2 and 4 trained until they had accumulated a matching low volume (LV) of training. Training for 5-8 weeks increased the HSP72, HSP27 and GRP75 levels in the subjects' m. triceps brachii by 111, 71 and 192%, respectively (Fig. 1a-c). There were, however, no significant differences in the heat shock protein (HSP) responses to training between the four training groups (Fig. 2a-c). The frequency of extreme responses to exercise was, however, higher after HI exercise than after LI exercise, indicating that HI exercise induces extreme HSP reactions in some subjects. When we assigned the subjects to three clusters, according to the total number of repetitions they had lifted, the subjects who had lifted the highest number of repetitions had lower PostExc HSP levels compared with subjects that lifted the lowest number of repetitions (Fig. 3a-c). Additionally, there was a negative non-linear regression (Fig. 4a-c) between the subjects PreExc levels of HSP72, HSP27 and GRP75 and the percentage change in their respective protein concentration after training (r = -0.75, -0.89 and -0.88, all P < 0.0001). Thus, the PreExc level of HSPs seems to be an important "regulator" of HSP expression following the training.

Human resting extracellular heat shock protein 72 concentration decreases during the initial adaptation to exercise in a hot, humid environment

Heat shock protein (Hsp) 72 is a cytosolic protein that also is present in the circulation. Extracellular Hsp72 (eHsp72) is inducible by exercise and is suggested to act as a danger signal to the immune system. The adaptive response of eHsp72 to repeated exercise-heat exposures in humans remains to be determined. An intracellular animal study found a reduced Hsp72 response, with no change in resting levels, during heat stress after a single day of passive heat acclimation. The current study therefore tested whether adaptations in human eHsp72 levels would similarly occur 24 hours after a single exercise-heat exposure. Seven males completed cycle exercise (42.5% V(O2peak) for 2 hours) in a hot, humid environment (38 degrees C, 60% relative humidity) on each of 2 consecutive days. Blood samples were obtained from an antecubital vein before exercise and 0 hours and 22 hours postexercise for the analysis of eHsp72. Exercise-heat stress resulted in enhanced eHsp72, with a similar absolute increase found on both days (day 1: 1.26 ng/mL [0.80 ng/mL]; day 2: 1.29 ng/mL [1.60 ng/mL]). Resting eHsp72 decreased from rest on day 1 to day 2's 22-hour postexercise sample (P < 0.05). It is suggested that the reduction in resting eHsp72 after 2 consecutive exercise-heat exposures is possibly due to an enhanced removal from the circulation, for either immunoregulatory functions, or for improved cellular stress tolerance in this initial, most stressful period of acclimation.

cDNA microarray analysis reveals novel candidate genes expressed in human peripheral blood following exhaustive exercise

It is generally accepted that exhausting endurance exercise exhibits strong effects on the immune system. Such effects have been attributed to changes in the cellular composition of peripheral blood as well as to changes in the expression of plausible candidate genes. The list of candidate genes is far from being complete, since this issue has not yet been investigated in a systematic way. In this study, we used a custom-made cDNA microarray focused on inflammation as a screening approach to study gene expression in eight one-half marathon runners before, immediately after, and 24 h after exercise. Significant differential gene expression was verified by quantitative real-time PCR. Linear regression analysis showed that microarray expression analysis of cell type-specific surface molecules reflects the observed individual cellular shifts in peripheral blood cells with high statistical significance. In line with the results of former studies, we observed an upregulation of mitogen-activated protein kinase-activated protein kinase-2 (MAPKAP-K2), l-selectin, and IL-1 receptor antagonist (IL-1ra) after exhaustive exercise. The main results of this study report, for the first time, the downregulation of CD81; the upregulation of thioredoxin, which may play an important part in anti-oxidative defense; and, surprisingly, the downregulation of the anti-carcinogenic gene glutathione- S-transferase-3 (GSTM3) in peripheral blood. The study shows cDNA microarray expression analysis as a reliable systematic instrument to complete the list of candidate genes that may play a role in exhaustive exercise-induced modulation of the immune response.

Effect of concentric or eccentric weight training on the expression of heat shock proteins in m. biceps brachii of very well trained males

Increased HSP expression in response to acute exercise is well documented in animal studies, and there is growing evidence that similar responses occur in man. In general, many human exercise studies have investigated the HSP response to low force continuous activity, while the knowledge about the HSP response to high force intermittent type of activity, like weight training, is so far sparse. In addition, most studies have used untrained subjects, and a common observation is that acute low force continuous activity in untrained individuals increases the HSP expression in these individuals. The main scope of this study was to investigate the HSP response in very well trained males subjected to longitudinal high intensity exercise, and if this response was dependent on exercise modality [i.e. eccentric (ECC) or concentric (CON) contractions]. Very well trained males performed progressive strength training consisting of either high force ECC or high force CON elbow flexions 2-3 times a week for 12 weeks. Compared with pre-exercise levels, HSP72 expression decreased by 46.1% (P<0.05) after CON contractions. GRP75 expression was unchanged after ECC or CON contractions, while ubiquitin expression decreased by 19.9% (P<0.02) after ECC contractions. These findings imply that chronic, intensive exercise may attenuate the HSP response in well-trained males.

Heat shock protein 27 expression in patients with chronic liver damage

The aim of this study was to evaluate a possible relationship between lymphomonocyte expression of heat shock proteins (HSP) 60/27 and plasma levels of pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-6) and markers of antioxidant/oxidative status [glutathione (GSH), alpha glutathione-S-transferase activity (alpha GST), malonyldialdeyde (MDA), 4-hydroxinonenal (4-HNE), and S-nitrosothiols (S-NO)] in patients with chronic liver diseases. Entered into the study were 47 subjects: 10 healthy controls, 16 patients with HCV-related chronic hepatitis (CH), and 16 patients with HCV-related and 5 with alcohol-related liver cirrhosis (10 Child A and 11 Child B+C). HSP60 was clearly expressed only in 5% of patients and lowly in the control group. HSP27 was clearly expressed in 46.7% of CH and 71.4% of cirrhotic patients but was lowly present in healthy subjects. A significant difference was found between patients with a low expression of HSP27 (negative patients) and those with a high HSP27 expression (positive patients) of plasma levels both of antioxidants (GSH, p < 0.05), and of markers of enhanced production of free radicals and cytokines (alpha GST, TNF-alpha and IL-6, p < 0.05; MDA, 4-HNE and S-NO, p < 0.01) as well as for alcohol use and degree of liver impairment. The present data are the first showing that, particularly in conditions of enhanced oxidative stress, lymphomonocytes from liver disease patients present an increased expression of HSP27.

Heat stress, cytokines, and the immune response to exercise

To examine the effect of exercise and heat stress on cytokine production, seven males (77 +/- 2 kg; VO(2peak) = 4.7 +/- 0.4 L min(-1)) completed two (15 degrees C; CON or 35 degrees C; HEAT) 90 min cycling trials at 70% VO(2peak). Blood samples were collected throughout and analysed for spontaneous, and LPS-stimulated intracellular monocyte cytokine production, plasma cytokine levels, and circulating stress hormone concentration. Plasma epinephrine, norepinephrine, and cortisol concentration were elevated (P < .05) as a result of exercise in CON. HEAT increased (P < .05) epinephrine and norepinephrine levels, however, cortisol concentration was not different between the two trials. Exercise had no effect on the concentration of circulating monocytes spontaneously producing IL-6, TNF-alpha or IL-1alpha, however, there was a decrease in the amount of TNF-alpha per cell post-compared with pre-exercise. HEAT had no effect on spontaneous intracellular cytokine production. Circulating levels of both IL-6 and TNF-alpha were elevated in HEAT, but not in CON. Upon stimulation with LPS, the concentration of monocytes positive for IL-6, TNF-alpha, and IL-1alpha production was elevated (P < .01) post- and 2 h post-compared with pre-exercise. Stimulated cells, however, produced less (P < .05) TNF-alpha post-exercise and less (P < .05) TNF-alpha and IL-6 2 h post-exercise. HEAT resulted in an increase (P < .05) in the concentration of stimulated cells positive for TNF-alpha and IL-1alpha, however, did not affect the amount of cytokine produced by stimulated monocytes. These results demonstrate that exercise decreases the amount of cytokine produced by LPS-stimulated monocytes, possibly due to elevated levels of circulating stress hormones. Heat stress did not, however, augment the suppression in the amount of cytokine produced by circulating monocytes upon stimulation, despite elevated catecholamines.

Biochemical Changes in Response to Intensive Resistance Exercise Training in the Elderly

BACKGROUND

It is assumed that low-grade inflammation, characterized by increased circulating IL-6 and TNF-alpha, is related to the development of sarcopenia. Physical exercise, especially high intensity resistance training, has been shown to be effective in restoring the strength deficit in the elderly. Intensive exercise is accompanied by significant release of IL-6 and TNF-alpha into the blood circulation, but does not result in muscle wasting. Exercise-induced changes in heat-shock protein (Hsp), responsible for cellular protection during stressful situations, might interfere with the acute phase reaction and muscle adaptation.

OBJECTIVE

To investigate if intensive strength training in elderly persons induces changes in Hsp70 expression, and if these changes are related to changes in the acute phase reaction or muscle adaptation.

METHODS

31 elderly persons (aged 68.4+/-5.4 years) performed 6 weeks' intensive strength training. At baseline and after 6 weeks, muscle strength, functional performance (physical activity profile, 6-min walk, 30- second chair stand, grip strength, chair sit & reach and back scratch), linear isokinetic leg extension, circulating IL-6, TNF-alpha, IL-10 and TGF-beta, and Hsp70 in monocytes (M) and lymphocytes (L) immediately after sampling (IAS), after incubation at 37 and 42 degrees C were determined. In 12 participants, cytokines were determined in untrained and trained conditions before and after a single training session.

RESULTS

After 6 weeks' training, muscle strength and functional performance improved significantly, together with decreased Hsp70 IAS and Hsp70 37 degrees C and increased Hsp70 42 degrees C (all p<0.05). Strength gains correlated positively with baseline Hsp70 37 degrees C and training-induced changes of Hsp70 42 degrees C in M and L. In an untrained condition, training induced an increase of IL-6 (p<0.05) and a tendency of IL-10 to decrease (p=0.06). In a trained condition the decrease of IL-10 disappeared. Baseline physical activity and 6-min walk distance correlated negatively with circulating IL-6 (p<0.05); except for a negative correlation between TGF-beta and Hsp70 37 degrees C L (p<0.05), no significant relationships were found between cytokines and Hsp70. After the training program, Hsp70 37 degrees C was negatively related to circulating TNF-alpha, IL-10 and TGF-beta.

CONCLUSION

Strength training in the elderly induces changes in Hsp70 expression, associated to strength gains and circulating cytokines.

Myocardial ischaemia and the inflammatory response: release of heat shock protein 70 after myocardial infarction

OBJECTIVES

To test the hypothesis that heat shock protein (Hsp) 70 may be released into the circulation after acute myocardial infarction (AMI) by exploring the kinetics of Hsp70 release and the relations between Hsp70 and markers of inflammation and myocardial damage in AMI.

DESIGN

Blood samples from 24 patients were prospectively collected through to the first day after AMI. Hsp70, interleukin (IL) 6, IL-8, and IL-10 in serum were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Median Hsp70 concentrations in AMI patients measured at arrival, six hours thereafter, and the following morning were 686, 868, and 607 pg/ml, respectively. These concentrations were all significantly different from those of the control patients with angina with a median serum Hsp70 concentration of 306 pg/ml. Peak Hsp70 correlated with creatine kinase (CK) MB (r = 0.62, p < 0.01) and cardiac troponin T (r = 0.58, p < 0.01). Furthermore, serum Hsp70 correlated with IL-6 and IL-8 at six hours (r = 0.60, p < 0.01 and r = 0.59, p < 0.01, respectively).

CONCLUSIONS

In this study, Hsp70 was rapidly released into the circulation after AMI. Circulating Hsp70 is suggested as a marker of myocardial damage. In addition, Hsp70 may have a role in the inflammatory response after AMI.

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.

Correlation of lymphocyte heat shock protein 70 levels with neurologic deficits in elderly patients with cerebral infarction

PURPOSE

To assess the association between heat shock protein 70 (HSP70) levels and the severity of ischemic stroke in elderly patients.

METHODS

We conducted a case-control study to investigate the changes in lymphocyte HSP70 levels by immunoblot in 65 elderly patients with mild (n = 22), intermediate (n = 21), or severe (n = 22) stroke, and in 34 healthy controls. We analyzed correlations between HSP70 levels and neurologic deficit scores on days 1, 15, and 30 after the onset of stroke.

RESULTS

Mean (+/- SD) HSP70 levels were higher in all stroke patients compared with controls (mild stroke: 709 +/- 194 units; intermediate: 585 +/- 165 units; severe: 421 +/- 124 units; controls: 86 +/- 34 units on day 1). Patients with mild stroke had higher levels at day 1 and 15 than did patients with severe stroke. HSP70 levels decreased rapidly from days 1 to 30 in all patients, except in patients with severe stroke, in whom levels decreased slowly between days 15 and 30. There were significant negative correlations between HSP70 levels and neurologic deficit scores in patients on days 1 (r = -0.53, P < 0.001) and 15 (r = -0.54, P < 0.001), but a positive correlation on day 30 (r = 0.49, P < 0.001).

CONCLUSION

These data suggest that HSP70 may be a marker for neuroprotection in the early stage of ischemic stroke and a marker for a crisis in the later stages of severe cerebral infarction. Further studies on the use of lymphocyte HSP70 levels in predicting clinical outcomes and underlying mechanisms in cerebral infarction are warranted.

Fatal exertional heat stroke: a case series

BACKGROUND

Exertional heat stroke (EHS) is one of the most serious conditions that occur when excess heat, generated by muscular exercise, exceeds the body's heat-dissipation rate. The consequent elevated body core temperature causes damage to the body's tissues, resulting in a characteristic multiorgan syndrome, which is occasionally fatal.

METHODS

We analyzed the fatal EHS cases that occurred in the Israeli Defence Forces during the last decade according to Minard's paradigm for evaluation of EHS predisposing factors, aiming to characterize the common features and unique circumstances leading to fatality.

RESULTS

Accumulation of predisposing factors, particularly those concerning training regulations, coupled with inappropriate treatment at site, were found to be strong predictors of a grave prognosis. Analysis of the pathologic findings of the fatal EHS cases on autopsy revealed a possible association between the duration and length of exercise prior to EHS occurrence and the extent of pathologic findings.

CONCLUSIONS

Strict adherence to existing training regulations may prevent further heat stroke fatalities.

Extreme Running Competition Decreases Blood Antioxidant Defense Capacity

OBJECTIVE

We tested whether an extreme running competition ("Marathon of Sands") might alter the blood's enzymatic and non-enzymatic antioxidant status in 6 well-trained athletes.

METHODS

The Marathon of Sands is a competition consisting of six long duration races in the desert in which the athletes carry their own food. Blood samples were collected from an antecubital vein while the athletes were at rest before the competition and then again 72 hours after. Erythrocyte antioxidant enzyme activity (glutathione peroxidase, superoxide dismutase), erythrocyte glutathione level, plasma non-enzymatic status (vitamin C, alpha-tocopherol, retinol, beta-carotene and carotenoids) and plasma lipid peroxidation marker (TBARS) were measured.

RESULTS

The Marathon of Sands induced a significant alteration of the blood antioxidant defense capacity. Indeed, 72 hours after the race, significant decreases were recorded in erythrocyte superoxide dismutase activity and in plasma concentrations of retinol, beta-carotene and other carotenoids. These changes were associated with a concomitant increase in erythrocyte glutathione and in plasma TBARS levels.

CONCLUSION

This study indicated that such extreme competition induced an imbalance between oxidant and antioxidant protection.

Exercise-induced oxidative stress and muscle stress protein responses in trotters

Acute exercise induces oxidative stress and heat shock protein (HSP) expression. Information on the protection of stress proteins against oxidant insult and muscle damage during moderate exercise is scanty. We aimed to show how a single bout of moderate exercise affects the markers of oxidative stress and heat shock factor-1 (HSF1; the transcriptional regulator of HSP synthesis), and HSP70, HSP90 and glucose-regulated protein (GRP75) expression in horses. Eight clinically normal and regularly trained standardbred trotters were treadmill-exercised for 45 min at moderate intensity. Blood samples were collected prior to and immediately after exercise and at 4 and 24 h of recovery. Muscle biopsy samples from the middle gluteal muscle were taken before exercise and after 4 h of recovery. Acute exercise did not activate HSF1 or induce expression of HSP70, HSP90 or GRP75 in skeletal muscle. One bout of acute exercise increased protein oxidation, which was measured by protein carbonyls in plasma and muscle, but it did not effect 4-hydroxynonenal protein adducts, which are markers of lipid peroxidation. Furthermore, mild muscle damage was observed 4 h after exercise. Our results showed that horses are susceptible to oxidative stress. One bout of exercise at moderate intensity and duration did not induce HSP responses despite the increased protein oxidation and tissue inflammation in equine muscle.

Exertional heat injury and gene expression changes: a DNA microarray analysis study

This study examined gene expression changes associated with exertional heat injury (EHI) in vivo and compared these changes to in vitro heat shock responses previously reported by our laboratory. Peripheral blood mononuclear cell (PBMC) RNA was obtained from four male Marine recruits (ages 17-19 yr) who presented with symptoms consistent with EHI, core temperatures ranging from 39.3 to 42.5°C, and elevations in serum enzymes such as creatine kinase. Controls were age- and gender-matched Marines from whom samples were obtained before and several days after an intense field-training exercise in the heat (“The Crucible”). Expression analysis was performed on Affymetrix arrays (containing ∼12,600 sequences) from pooled samples obtained at three times for EHI group (at presentation, 2-3 h after cooling, and 1-2 days later) and compared with control values (average signals from two chips representing pre- and post-Crucible samples). After post hoc filtering, the analysis identified 361 transcripts that had twofold or greater increases in expression at one or more of the time points assayed and 331 transcripts that had twofold or greater decreases in expression. The affected transcripts included sequences previously shown to be heat-shock responsive in PBMCs in vitro (including both heat shock proteins and non-heat shock proteins), a number of sequences whose changes in expression had not previously been noted as a result of in vitro heat shock in PBMCs (including several interferon-induced sequences), and several nonspecific stress response genes (including ubiquitin C and dual-specificity phosphatase-1). We conclude that EHI produces a broad stress response that is detectable in PBMCs and that heat stress per se can only account for some of the observed changes in transcript expression. The molecular evidence from these patients is thus consistent with the hypothesis that EHI can result from cumulative effects of multiple adverse interacting stimuli.

Habitual physical activity facilitates stress-induced HSP72 induction in brain, peripheral, and immune tissues

The mechanism(s) for how physically active organisms are resistant to many damaging effects of acute stressor exposure is unknown. Cellular induction of heat-shock proteins (e.g., HSP72) is one successful strategy used by the cell to survive the damaging effects of stress. It is possible, therefore, that the stress-buffering effect of physical activity may be due to an improved HSP72 response to stress. Thus the purpose of the current study was to determine whether prior voluntary freewheel running facilitates the stress-induced induction of HSP72 in central (brain), peripheral, and immune tissues. Adult male Fischer 344 rats were housed with either a mobile running wheel (Active) or a locked, immobile wheel [sedentary (Sed)] for 8 wk before stressor exposure. Rats were exposed to either inescapable tail-shock stress (IS; 100 1.6-mA tail shocks, 5-s duration, 60-s intertrial interval), exhaustive exercise stress (EXS; treadmill running to exhaustion), or no stress (controls). Blood, brain, and peripheral tissues were collected 2 h after stressor termination. The kinetics of HSP72 induction after IS was determined in cultured mesenteric lymph node cells. Activation of the stress response was verified by measuring serum corticosterone (RIA). Tissue and cellular HSP72 content were measured using HSP72 ELISA in cell lysates. Both Active and Sed rats had elevated levels of serum corticosterone after stress. In contrast, Active but not Sed rats exposed to IS and/or EXS had elevated HSP72 in dorsal vagal complex, frontal cortex, hippocampus, pituitary, adrenal, liver, spleen, mesenteric lymph nodes, and heart. In addition, Active rats exposed to IS demonstrated a faster induction of lymphocyte HSP72 compared with Sed rats. Thus Active rats responded to stress with both greater and faster HSP72 responses compared with Sed rats. These results indicate that previous physical activity potentiates HSP72 expression after a wide range of stressors. Facilitated induction of HSP72 may contribute to the increased stress resistance previously reported in physically active organisms.

Basal and inducible levels of Hsp70 in patients with acute heat illness induced during training

Heat shock proteins (Hsps) or stress proteins, and, in particular, the inducible, cytosolic Hsp70, represent a highly conserved response to heat exposure and to a variety of noxious stimuli. Many investigations have shown correlations between the aberrant expression of Hsps and disease states. Whether the basal and inducible levels of Hsp70 are of any biological significance in patients with heat-induced diseases remains unknown. In the present study, we compared the basal and inducible levels of Hsp70 by flow cytometry in lymphocytes of patients with heat-induced diseases and after recovery from this disease, and in matched controls. Both groups comprised individuals who exercised by running in the same hot environment. The level of inducible Hsp70 was also measured after a heat treatment of lymphocytes in vitro. The results show that there is variation of basal and inducible Hsp70 levels among individuals. However, the group of patients suffering from heat-induced illnesses in May shows a significantly higher basal (P = 0.02) level of Hsp70 than does the control group. Individuals who have an increased level of Hsp70 may be more sensitive to heat or may respond differently. The level of Hsp70 may represent a biomarker to evaluate whether they are more susceptible to stresses than other individuals. Interestingly, the basal level of Hsp70 is higher in both the patient group and the control group in November than in May. In fact, the basal levels of Hsp70 in the patient and control groups are essentially the same in November, perhaps reflecting the successful stress conditioning of both groups.

Exercise increases serum Hsp72 in humans

Recent evidence suggests that heat shock proteins (Hsps) may have an important systemic role as a signal to activate the immune system. Since acute exercise is known to induce Hsp72 (the inducible form of the 70-kDa family of Hsp) in a variety of tissues including contracting skeletal muscle, we hypothesized that such exercise would result in the release of Hsp72 from stressed cells into the blood. Six humans (5 males, 1 female) ran on a treadmill for 60 minutes at a workload corresponding to 70% of their peak oxygen consumption. Blood was sampled from a forearm vein at rest (R), 30 minutes during exercise, immediately postexercise (60 minutes), and 2, 8, and 24 hours after exercise. These samples were analyzed for serum Hsp72 protein. In addition, plasma creatine kinase (CK) was measured at these time points as a crude marker of muscle damage. With the exception of the sample collected at 30 minutes, muscle biopsies (n = 5 males) were also obtained from the vastus lateralis at the time of blood sampling and analyzed for Hsp72 gene and protein expression. Serum Hsp72 protein increased from rest, both during and after exercise (0.13 0.10 vs 0.87+/-0.24 and 1.02+/-0.41 ng/mL at rest, 30 and 60 minutes, respectively, P < 0.05, mean SE). In addition, plasma CK was elevated (P < 0.05) 8 hours postexercise. Skeletal muscle Hsp72 mRNA expression increased 6.5-fold (P < 0.05) from rest 2 hours postexercise, and although there was a tendency for Hsp72 protein expression to be elevated 2 and 8 hours following exercise compared with rest, results were not statistically significant. The increase in serum Hsp72 preceded any increase in Hsp72 gene or protein expression in contracting muscle, suggesting that Hsp72 was released from other tissues or organs. This study is the first to demonstrate that acute exercise can increase Hsp72 in the peripheral circulation, suggesting that during stress these proteins may indeed have a systemic role.

HSP70 and HSP90 expression in leucocytes after exercise in moderately trained humans

In this study, we examined expression of heat shock proteins (HSP) 70 and 90 in human leucocytes after moderate-to-heavy exercise. We also compared baseline levels of HSP70 and HSP90 in trained (TR) and untrained (UT) subjects. Eleven TR subjects ran on a treadmill for 1 h at 70% of maximal oxygen consumption. The HSP levels were measured prior to exercise and 15 and 24 h after exercise. Baseline HSP levels were also measured in eight UT controls. Fifteen hours and 24 h after exercise, TR subjects showed no significant increases in HSP70 (P > 0.05). The HSP90 levels also did not change (P > 0.05). Baseline HSP70 levels in TR subjects were lower than in UT subjects (2.04 +/- 0.51 ng vs. 4.52 +/- 0.95 ng, P < 0.05), while HSP90 levels were similar in TR and UT subjects. We conclude that exercise at an intensity that is within normal limits for a moderately trained individual is not a sufficient stimulus of HSP70 production in leucocytes. We also conclude that blunted levels of baseline HSP70 expression in TR subjects might be a chronic adaptation to training.

Exercise increases serum Hsp72 in humans

Recent evidence suggests that heat shock proteins (Hsps) may have an important systemic role as a signal to activate the immune system. Since acute exercise is known to induce Hsp72 (the inducible form of the 70-kDa family of Hsp) in a variety of tissues including contracting skeletal muscle, we hypothesized that such exercise would result in the release of Hsp72 from stressed cells into the blood. Six humans (5 males, 1 female) ran on a treadmill for 60 minutes at a workload corresponding to 70% of their peak oxygen consumption. Blood was sampled from a forearm vein at rest (R), 30 minutes during exercise, immediately postexercise (60 minutes), and 2, 8, and 24 hours after exercise. These samples were analyzed for serum Hsp72 protein. In addition, plasma creatine kinase (CK) was measured at these time points as a crude marker of muscle damage. With the exception of the sample collected at 30 minutes, muscle biopsies (n = 5 males) were also obtained from the vastus lateralis at the time of blood sampling and analyzed for Hsp72 gene and protein expression. Serum Hsp72 protein increased from rest, both during and after exercise (0.13 0.10 vs 0.87+/-0.24 and 1.02+/-0.41 ng/mL at rest, 30 and 60 minutes, respectively, P < 0.05, mean SE). In addition, plasma CK was elevated (P < 0.05) 8 hours postexercise. Skeletal muscle Hsp72 mRNA expression increased 6.5-fold (P < 0.05) from rest 2 hours postexercise, and although there was a tendency for Hsp72 protein expression to be elevated 2 and 8 hours following exercise compared with rest, results were not statistically significant. The increase in serum Hsp72 preceded any increase in Hsp72 gene or protein expression in contracting muscle, suggesting that Hsp72 was released from other tissues or organs. This study is the first to demonstrate that acute exercise can increase Hsp72 in the peripheral circulation, suggesting that during stress these proteins may indeed have a systemic role.