Plasma Hsp72 (HSPA1A) and Hsp27 (HSPB1) expression under heat stress: influence of exercise intensity

New Zealand blackcurrant extract modulates the heat shock response in men during exercise in hot ambient conditions

PURPOSE

To determine if 7d of New Zealand blackcurrant (NZBC) extract alters the heat shock, inflammatory and apoptotic response during prolonged exertional-heat stress.

METHODS

Ten men (Age: 29 ± 2 years, Stature: 1.82 ± 0.02 m, Mass: 80.3 ± 2.7 kg, V̇O2max: 56 ± 2 mL·kg-1·min-1) ingested two capsules of CurraNZ™ (NZBC extract: 210 mg anthocyanins·day-1) or PLACEBO for 7d prior to 1 h treadmill run (65% V̇O2max) in hot ambient conditions (34 °C/40% RH). Blood samples were collected before (Pre), immediately after (Post), 1 h after (1-Post), and 4 h after (4-Post) exercise. Heat shock proteins (HSP90, HSP70, HSP32) were measured in plasma. HSP and protein markers of inflammatory capacity (TLR4, NF-κB) and apoptosis (BAX/BCL-2, Caspase 9) were measured in peripheral blood mononuclear cells (PBMC).

RESULTS

eHSP32 was elevated at baseline in NZBC(+ 31%; p < 0.001). In PLACEBO HSP32 content in PBMC was elevated at 4-Post(+ 98%; p = 0.002), whereas in NZBC it fell at Post(- 45%; p = 0.030) and 1-Post(- 48%; p = 0.026). eHSP70 was increased at Post in PLACEBO(+ 55.6%, p = 0.001) and NZBC (+ 50.7%, p = 0.010). eHSP90 was increased at Post(+ 77.9%, p < 0.001) and 1-Post(+ 73.2%, p < 0.001) in PLACEBO, with similar increases being shown in NZBC (+ 49.0%, p = 0.006 and + 66.2%, p = 0.001; respectively). TLR4 and NF-κB were both elevated in NZBC at PRE(+ 54%, p = 0.003 and + 57%, p = 0.004; respectively). Main effects of study condition were also shown for BAX/BCL-2(p = 0.025) and Caspase 9 (p = 0.043); both were higher in NZBC.

CONCLUSION

7d of NZBC extract supplementation increased eHSP32 and PBMC HSP32 content. It also increased inflammatory and apoptotic markers in PBMC, suggesting that NZBC supports the putative inflammatory response that accompanies exertional-heat stress.

Carbohydrate, but not fat, oxidation is reduced during moderate-intensity exercise performed in 33 vs. 18 °C at matched heart rates

PURPOSE

Exposure to environmental heat stress increases carbohydrate oxidation and extracellular heat shock protein 70 (HSP70) concentrations during endurance exercise at matched absolute, external work rates. However, a reduction in absolute work rate typically occurs when unacclimated endurance athletes train and/or compete in hot environments. We sought to determine the effect of environmental heat stress on carbohydrate oxidation rates and plasma HSP70 expression during exercise at matched heart rates (HR).

METHODS

Ten endurance-trained, male cyclists performed two experimental trials in an acute, randomised, counterbalanced cross-over design. Each trial involved a 90-min bout of cycling exercise at 95% of the HR associated with the first ventilatory threshold in either 18 (TEMP) or 33 °C (HEAT), with ~ 60% relative humidity.

RESULTS

Mean power output (17 ± 11%, P < 0.001) and whole-body energy expenditure (14 ± 8%, P < 0.001) were significantly lower in HEAT. Whole-body carbohydrate oxidation rates were significantly lower in HEAT (19 ± 11%, P = 0.002), while fat oxidation rates were not different between-trials. The heat stress-induced reduction in carbohydrate oxidation was associated with the observed reduction in power output (r = 0.64, 95% CI, 0.01, 0.91, P = 0.05) and augmented sweat rates (r = 0.85, 95% CI, 0.49, 0.96, P = 0.002). Plasma HSP70 and adrenaline concentrations were not increased with exercise in either environment.

CONCLUSION

These data contribute to our understanding of how moderate environmental heat stress is likely to influence substrate oxidation and plasma HSP70 expression in an ecologically-valid model of endurance exercise.

Skeletal muscle angiogenic, regulatory, and heat shock protein responses to prolonged passive hyperthermia of the human lower limb

Passive hyperthermia induces a range of physiological responses including augmenting skeletal muscle mRNA expression. This experiment aimed to examine gene and protein responses to prolonged passive leg hyperthermia. Seven young participants underwent 3 h of resting unilateral leg heating (HEAT) followed by a further 3 h of rest, with the contralateral leg serving as an unheated control (CONT). Muscle biopsies were taken at baseline (0 h), and at 1.5, 3, 4, and 6 h in HEAT and 0 and 6 h in CONT to assess changes in selected mRNA expression via qRT-PCR, and HSP72 and VEGFα concentration via ELISA. Muscle temperature (T_m) increased in HEAT plateauing from 1.5 to 3 h (+3.5 ± 1.5°C from 34.2 ± 1.2°C baseline value; P < 0.001), returning to baseline at 6 h. No change occurred in CONT. Endothelial nitric oxide synthase (eNOS), Forkhead box O1 (FOXO-1), Hsp72, and VEGFα mRNA increased in HEAT (P < 0.05); however, post hoc analysis identified that only Hsp72 mRNA statistically increased (at 4 h vs. baseline). When peak change during HEAT was calculated angiopoietin 2 (ANGPT-2) decreased (-0.4 ± 0.2-fold), and C-C motif chemokine ligand 2 (CCL2) (+2.9 ± 1.6-fold), FOXO-1 (+6.2 ± 4.4-fold), Hsp27 (+2.9 ± 1.7-fold), Hsp72 (+8.5 ± 3.5-fold), Hsp90α (+4.6 ± 3.7-fold), and VEGFα (+5.9 ± 3.1-fold) increased from baseline (all P < 0.05). At 6 h T_m were not different between limbs (P = 0.582; CONT = 32.5 ± 1.6°C, HEAT = 34.3 ± 1.2°C), and only ANGPT-2 (P = 0.031; -1.3 ± 1.4-fold) and VEGFα (P = 0.030; 1.1 ± 1.2-fold) differed between HEAT and CONT. No change in VEGFα or HSP72 protein concentration were observed over time; however, peak change in VEGFα did increase (P < 0.05) in HEAT (+140 ± 184 pg·mL^-1) versus CONT (+7 ± 86 pg·mL^-1). Passive hyperthermia transiently augmented ANGPT-2, CCL2, eNOS, FOXO-1, Hsp27, Hsp72, Hsp90α and VEGFα mRNA, and VEGFα protein.

HSP70 as a biomarker of the thin threshold between benefit and injury due to physical exercise when exposed to air pollution

Physical exercise has acute and chronic effects on inflammatory balance, metabolic regulation, and redox status. Exercise-induced adaptations are mediated by enhanced 70-kDa heat shock protein (HSP70) levels and an improved heat shock response (HSR). Therefore, exercise could be useful against disease conditions [obesity, diabetes mellitus (DM), and exposure to atmospheric pollutants] marked by an impaired HSR. However, exercise performed by obese or diabetic subjects under pollution conditions might also be dangerous at certain intensities. Intensity correlates with an increase in HSP70 levels during physical exercise until a critical point at which the effort becomes harmful and impairs the HSR. Establishing a unique biomarker able to indicate the exercise intensity on metabolism and cellular fatigue is essential to ensure adequate and safe exercise recommendations for individuals with obesity or DM who require exercise to improve their metabolic status and live in polluted regions. In this review, we examined the available evidence supporting our hypothesis that HSP70 could serve as a biomarker for determining the optimal exercise intensity for subjects with obesity or diabetes when exposed to air pollution and establishing the fine threshold between anti-inflammatory and pro-inflammatory exercise effects.

Could Heat Therapy Be an Effective Treatment for Alzheimer's and Parkinson's Diseases? A Narrative Review

Neurodegenerative diseases involve the progressive deterioration of structures within the central nervous system responsible for motor control, cognition, and autonomic function. Alzheimer's disease and Parkinson's disease are among the most common neurodegenerative disease and have an increasing prevalence over the age of 50. Central in the pathophysiology of these neurodegenerative diseases is the loss of protein homeostasis, resulting in misfolding and aggregation of damaged proteins. An element of the protein homeostasis network that prevents the dysregulation associated with neurodegeneration is the role of molecular chaperones. Heat shock proteins (HSPs) are chaperones that regulate the aggregation and disaggregation of proteins in intracellular and extracellular spaces, and evidence supports their protective effect against protein aggregation common to neurodegenerative diseases. Consequently, upregulation of HSPs, such as HSP70, may be a target for therapeutic intervention for protection against neurodegeneration. A novel therapeutic intervention to increase the expression of HSP may be found in heat therapy and/or heat acclimation. In healthy populations, these interventions have been shown to increase HSP expression. Elevated HSP may have central therapeutic effects, preventing or reducing the toxicity of protein aggregation, and/or peripherally by enhancing neuromuscular function. Broader physiological responses to heat therapy have also been identified and include improvements in muscle function, cerebral blood flow, and markers of metabolic health. These outcomes may also have a significant benefit for people with neurodegenerative disease. While there is limited research into body warming in patient populations, regular passive heating (sauna bathing) has been associated with a reduced risk of developing neurodegenerative disease. Therefore, the emerging evidence is compelling and warrants further investigation of the potential benefits of heat acclimation and passive heat therapy for sufferers of neurodegenerative diseases.

MC4R Variant rs17782313 Associates With Increased Levels of DNAJC27, Ghrelin, and Visfatin and Correlates With Obesity and Hypertension in a Kuwaiti Cohort

Melanocortin 4 receptor (MC4R), a notable component of the melanocortin system, regulates appetite, body weight, and energy homeostasis. Genome-wide association studies have identified several MC4R variants associated with adiposity; of these, rs17782313, which is associated with increased body mass index (BMI) and overeating behavior, is of particular interest. Another gene associated with increased adiposity in global genome-wide association studies is DNAJC27, a heat shock protein known to be elevated in obesity. The detailed mechanisms underlying the role of MC4R variants in the biological pathways underlying metabolic disorders are not well-understood. To address this, we assessed variations of rs17782313 in a cohort of 282 Arab individuals from Kuwait, who are deeply phenotyped for anthropometric and metabolic traits and various biomarkers, including DNAJC27. Association tests showed that the rs17782313_C allele was associated with BMI and DNAJC27 levels. Increased levels of DNAJC27 reduced the MC4R-mediated formation of cAMP in MC4R ACTOne stable cells. In conclusion, this study demonstrated an association between the rs17782313 variant near MC4R and increased BMI and DNAJC27 levels and established a link between increased DNAJC27 levels and lower cAMP levels. We propose that regulation of MC4R activity by DNAJC27 enhances appetite through its effect on cAMP, thereby regulating obesity.

Perioperative urinary heat shock protein 72 as an early marker of acute kidney injury in dogs

OBJECTIVE

Acute kidney injury (AKI) may be a complication in dogs undergoing surgery. Urinary heat shock protein 72 (uHSP72) is a sensitive biomarker of canine AKI. To assess the occurrence of perioperative AKI, based on uHSP72 compared with serum creatinine (sCr), and whether its occurrence is associated with the American Society of Anesthesiology physical status (ASA status).

STUDY DESIGN

Clinical prospective study.

ANIMALS

A total of 80 client-owned and shelter dogs.

METHODS

Dogs scheduled for elective or emergency surgery were assigned ASA status (ASA I-IV). Preoperative and 24 hour postoperative serum and urine samples were collected. sCr, uHSP72 and urinary creatinine (uCr) were measured.

RESULTS

Postoperative uHSP72/uCr concentration [median (range)] of all dogs undergoing surgery [2.40 (0.14-252) ng mg^-1] was significantly increased compared with preoperative uHSP72/uCr [1.30 (0.11-142) ng mg^-1] concentration (p < 0.001). Conversely, postoperative sCr concentration of all dogs [0.88 (0.3-1.6) mg dL^-1] significantly decreased compared with preoperative sCr concentration [0.8 (0.2-5.0) mg dL^-1; p = 0.001]. Median uHSP72/uCr concentration differed both preoperatively (p = 0.007) and postoperatively (p = 0.019) among the ASA status groups. Increased uHSP/uCr was measured in 20 dogs preoperatively and 33 dogs postoperatively, whereas only five dogs fulfilled the criteria of AKI based on sCr.

CONCLUSIONS

The occurrence of increased uHSP72/uCr perioperatively suggests that the proportion of dogs with AKI is considerably higher than perceived.

CLINICAL RELEVANCE

Dogs undergoing surgery should be closely monitored for AKI before and after anesthesia, using currently available markers (e.g., sCr) and more sensitive markers.

The beneficial effects of 15 units of high-intensity circuit training in women is modified by age, baseline insulin resistance and physical capacity

AIM

To investigate the effect of a single and 15 units of high-intensity circuit training (HICT) programme on glucose metabolism, myokines' response and selected genes' expression in women.

METHODS

Thirty-three, non-active women (mean age: 38 ± 12) were split into a HICT (n = 20) or a control group (CON, n = 13). The training protocol included three circuits of nine exercises with own body weight as a workload performed 3 times a week for five weeks. The CON group performed HICT twice. Blood samples were taken before, 1 h and 24 h after the first and last unit to determine IGF-1, myostatin, irisin, decorin, HSP27, interleukin-15 concentrations using the ELISA immunoenzymatic method. To evaluate HSPB1, TNF-α and DCN mRNA, real-time PCR was used. Pre- and post-intervention, the oral glucose test and body composition assessment were completed.

RESULTS

The following parameters tended to decrease after the 5-week HICT program: insulin and HOMA-IR Training diminished insulin/IGF-1 ratio (51% CI: -63% to -34%) and induced the drop of myostatin concentration but significantly only among middle-aged women and at baseline insulin resistance.

CONCLUSION

Obtained data revealed that HICT improved an insulin sensitivity and diminished myostatin concentration among older, insulin-resistant women with lower baseline physical capacity.

Impaired Heat Adaptation From Combined Heat Training and "Live High, Train Low" Hypoxia

Purpose: To determine whether combining training in heat with "Live High, Train Low" hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0] mL·min^-1·kg^-1) completed 3-wk training in 1 of 3 conditions: (1) heat training combined with "LHTL" hypoxia (H+H; F_iO₂ = 14.4% [3000 m], 13 h·d^-1; train at <600 m, 33°C, 55% relative humidity [RH]), (2) heat training (HOT; live and train <600 m, 33°C, 55% RH), and (3) temperate training (CONT; live and train <600 m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1 wkP, and 3 wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = -0.60 [-0.89; -0.32]) and core temperature (ES = -0.55 [-0.99; -0.10]) were reduced in HOT until 1 wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = -0.82 [-1.48; -0.16]) were, respectively, increased and decreased until 3 wkP in HOT. Submaximal heart rate (ES = -0.38 [-0.85; 0.08]) was likely reduced in H+H at 3 wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and "LHTL" hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments.

Chronic probiotic supplementation with or without glutamine does not influence the eHsp72 response to a multi-day ultra-endurance exercise event

Probiotic and glutamine supplementation increases tissue Hsp72, but their influence on extracellular Hsp72 (eHsp72) has not been investigated. The aim of this study was to investigate the effect of chronic probiotic supplementation, with or without glutamine, on eHsp72 concentration before and after an ultramarathon. Thirty-two participants were split into 3 independent groups, where they ingested probiotic capsules (PRO; n = 11), probiotic + glutamine powder (PGLn; n = 10), or no supplementation (CON; n = 11), over a 12-week period prior to commencement of the Marathon des Sables (MDS). eHsp72 concentration in the plasma was measured at baseline, 7 days pre-race, 6-8 h post-race, and 7 days post-race. The MDS increased eHsp72 concentrations by 124% (F_[1,3] = 22.716, p < 0.001), but there was no difference in the response between groups. Additionally, PRO or PGLn supplementation did not modify pre- or post-MDS eHsp72 concentrations compared with CON (p > 0.05). In conclusion, the MDS caused a substantial increase in eHsp72 concentration, indicating high levels of systemic stress. However, chronic PRO or PGLn supplementation did not affect eHsp72 compared with control pre- or post-MDS. Given the role of eHsp72 in immune activation, the commercially available supplements used in this study are unlikely to influence this cascade.

The effect of passive heating on heat shock protein 70 and interleukin-6: A possible treatment tool for metabolic diseases?

Increasing physical activity remains the most widely publicized way of improving health and wellbeing. However, in populations that benefit most from exercise (EX), adherence is often poor and alternatives to EX are important to bring about health improvements. Recent work suggests a role for passive heating (PH) and heat shock proteins (HSP) in improving cardio-metabolic health. The aim of this study was to investigate the expression of HSP70 and interleukin-6 in response to either EX or PH and the subsequent effect on glucose control. Fourteen males volunteered and were categorized lean (BMI 23.5 ± 2.2 kg·m^-2) or overweight (29.2 ± 2.7 kg·m^-2) and completed 60 minutes of either moderate cycling at a fixed rate of metabolic heat production (EX) or warm water immersion in 40°C water (PH). Extracellular HSP70 increased from baseline in both conditions with no differences between PH (0.98 ± 1.1 ng·mL^-1) or EX (0.84 ± 1.0 ng·mL^-1, p = 0.814). IL-6 increased following both conditions with a two-fold increase after PH and four-fold after EX. Energy expenditure increased by 61.0 ± 14.4 kcal·h^-1 (79%) after PH. Peak glucose concentration after a meal immediately following PH was reduced when compared with EX (6.3 ± 1.4 mmol·L^-1 versus 6.8 ± 1.2 mmol·L^-1; p < 0.05). There was no difference in 24-hour glucose area under the curve (AUC) between conditions. These data indicate the potential for thermal therapy as an alternative treatment and management strategy for those at risk of developing metabolic disease where adherence, or ability to EX, may be compromised.

Expression times for hsp27 and hsp70 as an indicator of thermal stress during death due to fire

The expression of heat shock proteins (hsps) increases in cases of hyperthermal cellular stress in order to protect cellular structures. Hsps can be visualized with immunohistochemical staining. We examined 48 cases of death from fire and excessive heat and a control group of 100 deaths without any perimortem thermal stress, measuring both the hsp27 and hsp70 expressions in myocardial, pulmonary, and renal tissues. The results revealed a correlation between hsp expression and survival time. Hsps are expressed rapidly within seconds or minutes after exposure to heat stress. In particular, hsp27 is expressed fast in high levels, whereas hsp70 expression is higher in the pulmonary and renal tissue of long-term survivors. In the myocardial tissue, hsp27 expression dominated in both short- and long-term survival. The expression pattern is strongly dependent on the organ structure and the survival time, which should be considered in future postmortem studies on hsps.

In vitro Stability of Heat Shock Protein 27 in Serum and Plasma Under Different Pre-analytical Conditions: Implications for Large-Scale Clinical Studies

The effects of storage temperatures, repeated freeze-thaw cycles, or delays in separating plasma or serum from blood samples are largely unknown for heat shock protein 27 (HSP27). We evaluated (1) the imprecision of the HSP27 assay used in this study; (2) the in vitro stability of HSP27 in blood samples stored at 4℃ for up to 6 hr with immediate and delayed serum/plasma separation from cells; and (3) the in vitro stability of HSP27 in blood samples stored at -80℃ after repeated freeze-thaw cycles. The ELISA to detect HSP27 in this study showed a within-run CV of <9% and a total CV of <15%. After 4-6 hr of storage at 4℃, HSP27 concentrations remained stable when using serum tubes irrespective of sample handling, but HSP27 concentrations decreased by 25-45% when using EDTA plasma tubes. Compared with baseline HSP27, one freeze-thaw cycle had no effect on serum concentrations. However, plasma concentrations increased by 3.1-fold after one freeze-thaw cycle and by 7.3-fold after five freeze-thaw cycles. In conclusion, serum is an appropriate biological sample type for use in epidemiological and large-scale clinical studies.

Cellular Stress Response Gene Expression During Upper and Lower Body High Intensity Exercises

Objectives

The aim was to compare the effect of upper and lower body high-intensity exercise on chosen genes expression in athletes and non-athletes.

Method

Fourteen elite male artistic gymnasts (EAG) aged 20.6 ± 3.3 years and 14 physically active men (PAM) aged 19.9 ± 1.0 years performed lower and upper body 30 s Wingate Tests. Blood samples were collected before, 5 and 30 minutes after each effort to assess gene expression via PCR.

Results

Significantly higher mechanical parameters after lower body exercise was observed in both groups, for relative power (8.7 ± 1.2 W/kg in gymnasts, 7.2 ± 1.2 W/kg in controls, p = 0.01) and mean power (6.7 ± 0.7 W/kg in gymnasts, 5.4 ± 0.8 W/kg in controls, p = 0.01). No differences in lower versus upper body gene expression were detected for all tested genes as well as between gymnasts and physical active man. For IL-6 m-RNA time-dependent effect was observed.

Conclusions

Because of no significant differences in expression of genes associated with cellular stress response the similar adaptive effect to exercise may be obtained so by lower and upper body exercise.

Hsp72 and Hsp90α mRNA transcription is characterised by large, sustained changes in core temperature during heat acclimation

Increased intracellular heat shock protein-72 (Hsp72) and heat shock protein-90α (Hsp90α) have been implicated as important components of acquired thermotolerance, providing cytoprotection during stress. This experiment determined the physiological responses characterising increases in Hsp72 and Hsp90α mRNA on the first and tenth day of 90-min heat acclimation (in 40.2 °C, 41.0 % relative humidity (RH)) or equivalent normothermic training (in 20 °C, 29 % RH). Pearson's product-moment correlation and stepwise multiple regression were performed to determine relationships between physiological [e.g. (Trec, sweat rate (SR) and heart rate (HR)] and training variables (exercise duration, exercise intensity, work done), and the leukocyte Hsp72 and Hsp90α mRNA responses via reverse transcription quantitative polymerase chain reaction (RT-QPCR) (n = 15). Significant (p < 0.05) correlations existed between increased Hsp72 and Hsp90α mRNA (r = 0.879). Increased core temperature was the most important criteria for gene transcription with ΔTrec (r = 0.714), SR (r = 0.709), Trecfinal45 (r = 0.682), area under the curve where Trec ≥ 38.5 °C (AUC38.5 °C; r = 0.678), peak Trec (r = 0.661), duration Trec ≥ 38.5 °C (r = 0.650) and ΔHR (r = 0.511) each demonstrating a significant (p < 0.05) correlation with the increase in Hsp72 mRNA. The Trec AUC38.5 °C (r = 0.729), ΔTrec (r = 0.691), peak Trec (r = 0.680), Trecfinal45 (r = 0.678), SR (r = 0.660), duration Trec ≥ 38.5 °C (r = 0.629), the rate of change in Trec (r = 0.600) and ΔHR (r = 0.531) were the strongest correlate with the increase in Hsp90α mRNA. Multiple regression improved the model for Hsp90α mRNA only, when Trec AUC38.5 °C and SR were combined. Training variables showed insignificant (p > 0.05) weak (r < 0.300) relationships with Hsp72 and Hsp90α mRNA. Hsp72 and Hsp90α mRNA correlates were comparable on the first and tenth day. When transcription of the related Hsp72 and Hsp90α mRNA is important, protocols should rapidly induce large, prolonged changes in core temperature.

Heat stress and dehydration in adapting for performance: Good, bad, both, or neither?

Physiological systems respond acutely to stress to minimize homeostatic disturbance, and typically adapt to chronic stress to enhance tolerance to that or a related stressor. It is legitimate to ask whether dehydration is a valuable stressor in stimulating adaptation per se. While hypoxia has had long-standing interest by athletes and researchers as an ergogenic aid, heat and nutritional stressors have had little interest until the past decade. Heat and dehydration are highly interlinked in their causation and the physiological strain they induce, so their individual roles in adaptation are difficult to delineate. The effectiveness of heat acclimation as an ergogenic aid remains unclear for team sport and endurance athletes despite several recent studies on this topic. Very few studies have examined the potential ergogenic (or ergolytic) adaptations to ecologically-valid dehydration as a stressor in its own right, despite longstanding evidence of relevant fluid-regulatory adaptations from short-term hypohydration. Transient and self-limiting dehydration (e.g., as constrained by thirst), as with most forms of stress, might have a time and a place in physiological or behavioral adaptations independently or by exacerbating other stressors (esp. heat); it cannot be dismissed without the appropriate evidence. The present review did not identify such evidence. Future research should identify how the magnitude and timing of dehydration might augment or interfere with the adaptive processes in behaviorally constrained versus unconstrained humans.

Comparison of GFAP and HSP27 concentrations in acute moderate-intensity aerobic exercise of different duration

Background: Glial fibrillary acidic protein (GFAP) and heat shock protein -27 (HSP27) plasma can be used as the parameters of exercise-induced astrocyte reactivity. The American College of Sports Medicine (ACSM) recommends an exercise of 30 minutes or 10 minutes duration (each performing bout accumulated toward 30 minutes). The aim of this study was to compare GFAP and HSP27 plasma concentrations in young adults undergoing acute moderate-intensity aerobic exercise of different durations (10 minutes vs 30 minutes).Methods: An experimental study with pre-post design was conducted on 22 participants assigned to either 10 minutes or 30 minutes duration of single bout exercise. Blood sampling was performed before and after the exercise. GFAP and HSP27 plasma levels were measured with ELISA methods. Plasma GFAP and HSP27 levels before and after exercise were analyzed using paired t -test, while GFAP and HSP27 levels after exercise between the two groups were processed using unpaired t-test.Results: Plasma GFAP concentration decreased significantly (0,45 ng/mL) after 30 minutes of aerobic exercise (p<0.05). Plasma HSP27 concentration decreased significantly (1,71 ng/mL) after 10 minutes of aerobic exercise (p<0.05). No significant difference in plasma GFAP and HSP27 concentrations between 10 minutes (GFAP=0.49 ng/mL; HSP27=2.09 ng/mL) and 30 minutes duration of exercise (GFAP=0.45 ng/mL; HSP27=1,71 ng/mL).Conclusion: Acute moderate-intensity aerobic exercise with 10- and 30-minutes duration reduces the reactivity of astrocytes indication the increase of the synapse plasticity. The decrease in GFAP concentration occurred after 30 minutes of exercise and the decrease in HSP27 occurred after 10 minutes of exercise. These results showed that the body responds differently to different treatment duration in order to obtain the same effect on the body.

Effective microorganism - X attenuates circulating superoxide dismutase following an acute bout of intermittent running in hot, humid conditions

This study determined the effectiveness of antioxidant supplementation on high-intensity exercise-heat stress. Six males completed a high-intensity running protocol twice in temperate conditions (TEMP; 20.4°C), and twice in hot conditions (HOT; 34.7°C). Trials were completed following7 days supplementation with 70 ml·day(-1) effective microorganism-X (EM-X; TEMPEMX or HOTEMX) or placebo (TEMPPLA or HOTPLA). Plasma extracellular Hsp72 (eHsp72) and superoxide dismutase (SOD) were measured by ELISA. eHsp72 and SOD increased pre-post exercise (p < 0.001), with greater eHsp72 (p < 0.001) increases observed in HOT (+1.5 ng·ml(-1)) compared to TEMP (+0.8 ng·ml(-1)). EM-X did not influence eHsp72 (p > 0.05). Greater (p < 0.001) SOD increases were observed in HOT (+0.22 U·ml(-1)) versus TEMP (+0.10 U·ml(-1)) with SOD reduced in HOTEMX versus HOTPLA (p = 0.001). Physiological and perceptual responses were all greater (p < 0.001) in HOT versus TEMP conditions, with no difference followed EM-X (p > 0.05). EM-X supplementation attenuated the SOD increases following HOT, potentiating its application as an ergogenic aid to ameliorate oxidative stress.

Swimming in warm water is ineffective in heat acclimation and is non-ergogenic for swimmers

Heat acclimation (HA) in air confers adaptations that improve exercise capabilities in hot and possibly temperate air. Swimmers may benefit from HA, yet immersion may constrain adaptation. Therefore, we examined whether warm-water swimming constitutes effective HA. In a randomized-crossover study, eight male swimmers swam 60 min/day on 7 days in 33 °C (HA) or 28 °C (CON) water. They performed 20-min distance trials before and after each regime: in 33 °C water (Warm); 28 °C water (Temperate); and cycling in 29 °C air (Terrestrial) following standardized exercise. Rectal temperature (Tre ) rose ∼ 1 °C in HA sessions, and sweat loss averaged 1.4 L/h. After accounting for CON, HA did not confer any clear expansion of plasma volume [1.9% (95% CI: 7.7)], reduction in heart rate during standardized cycling exercise [1 b/min (9)], reduction in Tre during rest [+0.1 °C (0.1)] or exercise, or change in sudomotor function. Only perceived temperature and discomfort tended to improve. Performance was clearly not improved for Warm [+0.3% (1.8)] or Temperate [+0.3% (1.9)], was unclear for Terrestrial [+0.4% (17.7)], and was unrelated to changes in resting plasma volume (r < 0.3). In conclusion, short-term HA using swimming in 33 °C water confers little adaptation and is not ergogenic for warm or temperate conditions.

Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports

Exercise heat acclimation induces physiological adaptations that improve thermoregulation, attenuate physiological strain, reduce the risk of serious heat illness, and improve aerobic performance in warm-hot environments and potentially in temperate environments. The adaptations include improved sweating, improved skin blood flow, lowered body temperatures, reduced cardiovascular strain, improved fluid balance, altered metabolism, and enhanced cellular protection. The magnitudes of adaptations are determined by the intensity, duration, frequency, and number of heat exposures, as well as the environmental conditions (i.e., dry or humid heat). Evidence is emerging that controlled hyperthermia regimens where a target core temperature is maintained, enable more rapid and complete adaptations relative to the traditional constant work rate exercise heat acclimation regimens. Furthermore, inducing heat acclimation outdoors in a natural field setting may provide more specific adaptations based on direct exposure to the exact environmental and exercise conditions to be encountered during competition. This review initially examines the physiological adaptations associated with heat acclimation induction regimens, and subsequently emphasizes their application to competitive athletes and sports.

Hospitalized dogs recovery from naturally occurring heatstroke; does serum heat shock protein 72 can provide prognostic biomarker?

Heatstroke is a serious illness in dogs characterized by core temperatures above 41°C with central nervous system dysfunction. Experimental heatstroke models have tried to correlate biomarker levels with the severity of the syndrome. Serum heat shock protein (eHSP70) levels were recently evaluated as a biomarker of heat tolerance and acclimation, their role as a marker of heatstroke is inconclusive. Here, we monitored eHSP70 levels in correlation with systemic biomarkers in 30 naturally occurring canine heatstroke cases. Thirty dogs diagnosed with environmental (33%) or exertional (66%) heatstroke admitted to hospital (0-14 h post-injury) were tested for biomarkers of organ damage and coagulation parameters. eHSP70 levels were measured upon admission and 4, 12, and 24 h later (T1, T2, and T3, respectively). No differences were found between exertional and environmental heatstroke cases. The eHSP profile demonstrated an inverted bell shape, with the lowest levels at the 12 h time point. A positive correlation between eHSP70, lactate, and aPPT was also noted at T2 in all the dogs in the study. Twenty-four h after presentation, eHSP70 levels returned to those measured upon admission, this change was only significant in the survivors. The obtained results suggest that eHSP72 level profile may be predictive of survival.

Moderate- and high-intensity exhaustive exercise in the heat induce a similar increase in monocyte Hsp72

This study examined the relationship between exhaustive exercise in the heat at moderate and high intensities on the intracellular heat shock protein 72 (iHsp72) response. Twelve male subjects cycled to exhaustion at 60 and 75% of maximal oxygen uptake in hot conditions (40 °C, 50% RH). iHsp72 concentration was measured in monocytes before, at exhaustion and 24 h after exercise. Rectal temperature, heart rate and oxygen uptake were recorded during exercise. Volitional exhaustion occurred at 58.9 ± 12.1 and 27.3 ± 9.5 min (P < 0.001) and a rectal temperature of 39.8 ± 0.4 and 39.2 ± 0.6 °C (P = 0.002), respectively, for 60 and 75 %. The area under the curve above a rectal temperature of 38.5 °C was greater at 60 % (17.5 ± 6.6 °C min) than 75 % (3.4 ± 4.8 °C min; P < 0.001), whereas the rate of increase in rectal temperature was greater at 75 % (5.1 ± 1.7 vs. 2.2 ± 1.4 °C h(-1); P < 0.001). iHsp72 concentration increased similarly at exhaustion relative to pre-exercise (P = 0.044) and then increased further at 24 h (P < 0.001). Multiple regression analysis revealed no predictor variables associated with iHsp72 expression; however, a correlation was observed between exercise intensities for the increase in iHsp expression at exhaustion and 24 h (P < 0.05). These results suggest that iHsp72 expression increased in relation to the level of hyperthermia attained and sustained at 60 % and the higher metabolic rate and greater rate of increase in core temperature at 75 %, with the further increase in iHsp72 concentration 24 h after exercise reinforcing its role as a chaperone and cytoprotective agent.

A comparison of two commercially available ELISA methods for the quantification of human plasma heat shock protein 70 during rest and exercise stress

This study compared resting and exercise heat/hypoxic stress-induced levels of plasma extracellular heat shock protein 70 (eHSP70) in humans using two commercially available enzyme-linked immunosorbent assay (ELIS)A kits. EDTA plasma samples were collected from 21 males during two separate investigations. Participants in part A completed a 60-min treadmill run in the heat (HOT70; 33.0 ± 0.1 °C, 28.7 ± 0.8 %, n = 6) at 70 % V̇O2max. Participants in part B completed 60 min of cycling exercise at 50 % V̇O2max in either hot (HOT50; 40.5 °C, 25.4 relative humidity (RH)%, n = 7) or hypoxic (HYP50; fraction of inspired oxygen (FIO2) = 0.14, 21 °C, 35 % RH, n = 8) conditions. Samples were collected prior to and immediately upon termination of exercise and analysed for eHSP70 using EKS-715 high-sensitivity HSP70 ELISA and new ENZ-KIT-101 Amp'd(™) HSP70 high-sensitivity ELISA. ENZ-KIT was superior in detecting resting eHSP70 (1.54 ± 3.27 ng · mL(-1); range 0.08 to 14.01 ng · mL(-1)), with concentrations obtained from 100 % of samples compared to 19 % with EKS-715 assay. The ENZ-KIT requires optimisation prior to running samples in order to ensure participants fall within the standard curve, a step not required with EKS-715. Using ENZ-KIT, a 1:4 dilution allowed for quantification of resting HSP70 in 26/32 samples, with a 1:8 (n = 3) and 1:16 (n = 3) dilution required to determine the remaining samples. After exercise, eHSP70 was detected in 6/21 and 21/21 samples using EKS-715 and ENZ-KIT, respectively. eHSP70 was increased from rest after HOT70 (p < 0.05), but not HOT50 (p > 0.05) or HYP50 (p > 0.05) when analysed using ENZ-KIT. It is recommended that future studies requiring the precise determination of resting plasma eHSP70 use the ENZ-KIT (i.e. HSP70 Amp'd(®) ELISA) instead of the EKS-715 assay, despite additional assay development time and cost required.

Human monocyte heat shock protein 72 responses to acute hypoxic exercise after 3 days of exercise heat acclimation

The aim of this study was to determine whether short-term heat acclimation (STHA) could confer increased cellular tolerance to acute hypoxic exercise in humans as determined via monocyte HSP72 (mHSP72) expression. Sixteen males were separated into two matched groups. The STHA group completed 3 days of exercise heat acclimation; 60 minutes cycling at 50% V̇O2peak in 40°C 20% relative humidity (RH). The control group (CON) completed 3 days of exercise training in 20°C, 40% RH. Each group completed a hypoxic stress test (HST) one week before and 48 hours following the final day of CON or STHA. Percentage changes in HSP72 concentrations were similar between STHA and CON following HST1 (P = 0.97). STHA induced an increase in basal HSP72 (P = 0.03) with no change observed in CON (P = 0.218). Basal mHSP72 remained elevated before HST2 for the STHA group (P < 0.05) and was unchanged from HST1 in CON (P > 0.05). Percent change in mHSP72 was lower after HST2 in STHA compared to CON (P = 0.02). The mHSP72 response to hypoxic exercise was attenuated following 3 days of heat acclimation. This is indicative of improved tolerance and ability to cope with the hypoxic insult, potentially mediated in part by increased basal reserves of HSP72.

Evaluation of Rhodiola rosea supplementation on skeletal muscle damage and inflammation in runners following a competitive marathon

Adaptogens modulate intracellular signaling and increase expression of heat shock protein 72 (HSP72). Rhodiola rosea (RR) is a medicinal plant with demonstrated adaptogenic properties. The purpose of this study was to measure the influence of RR supplementation on exercise-induced muscle damage, delayed onset of muscle soreness (DOMS), plasma cytokines, and extracellular HSP72 (eHSP72) in experienced runners completing a marathon. Experienced marathon runners were randomized to RR (n=24, 6 female, 18 male) or placebo (n=24, 7 female, 17 male) groups and under double-blinded conditions ingested 600mg/day RR extract or placebo for 30days prior to, the day of, and seven days post-marathon. Blood samples were collected, and vertical jump and DOMS assessed the day before, 15min post- and 1.5h post-marathon. DOMS was also assessed for seven days post-marathon. Marathon race performance did not differ between RR and placebo groups (3.87±0.12h and 3.93±0.12h, respectively, p=0.722). Vertical jump decreased post-marathon (time effect, p<0.001) with no difference between groups (interaction effect, p=0.673). Post-marathon DOMS increased significantly (p<0.001) but the pattern of change did not differ between groups (p=0.700). Myoglobin (Mb), creatine phosphokinase (CPK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), interleukin (IL)-6, IL-8, IL-10, monocyte chemotactic protein-1 (MCP-1), granulocyte-colony-stimulating factor (G-CSF), C-reactive protein (CRP), and eHSP72 all increased post-marathon (all p<0.001), with no group differences over time (all p>0.300). In conclusion, RR supplementation (600mg/day) for 30days before running a marathon did not attenuate the post-marathon decrease in muscle function, or increases in muscle damage, DOMS, eHSP72, or plasma cytokines in experienced runners.

Moving in extreme environments: open water swimming in cold and warm water

Open water swimming (OWS), either ‘wild’ such as river swimming or competitive, is a fast growing pastime as well as a part of events such as triathlons. Little evidence is available on which to base high and low water temperature limits. Also, due to factors such as acclimatisation, which disassociates thermal sensation and comfort from thermal state, individuals cannot be left to monitor their own physical condition during swims. Deaths have occurred during OWS; these have been due to not only thermal responses but also cardiac problems. This paper, which is part of a series on ‘Moving in Extreme Environments’, briefly reviews current understanding in pertinent topics associated with OWS. Guidelines are presented for the organisation of open water events to minimise risk, and it is concluded that more information on the responses to immersion in cold and warm water, the causes of the individual variation in these responses and the precursors to the cardiac events that appear to be the primary cause of death in OWS events will help make this enjoyable sport even safer.

Two years of combined high-intensity physical training and heat acclimatization affect lymphocyte and serum HSP70 in purebred military working dogs

Military working dogs in hot countries undergo exercise training at high ambient temperatures for at least 9 mo annually. Physiological adaptations to these harsh conditions have been extensively studied; however, studies focusing on the underlying molecular adaptations are limited. In the current study, military working dogs were chosen as a model to examine the effects of superimposing endurance exercise on seasonal acclimatization to environmental heat stress. The lymphocyte HSP70 profile and extracellular HSP70 were studied in tandem with physiological performance in the dogs from their recruitment for the following 2 yr. Aerobic power and heat shock proteins were measured at the end of each summer, with physical performance tests (PPTs) in an acclimatized room (22°C). The study shows that together with a profound enhancement of aerobic power and physical performance, hsp72 mRNA induction immediately post-PPT and 45 min later, progressively increased throughout the study period (relative change in median lymphocyte hsp72 mRNA first PPT, 4.22 and 12.82; second PPT, 17.19 and 109.05, respectively), whereas induction of HSP72 protein was stable. These responses suggest that cellular/molecular adaptive tools for maintaining HSP72 homeostasis exist. There was also a significant rise in basal and peak median optical density extracellular HSP at the end of each exercise test (first PPT, 0.13 and 0.15; second PPT, 1.04 and 1.52, respectively). The relationship between these enhancements and improved aerobic power capacity is not yet fully understood.

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

Extracellular heat shock protein 72 (eHsp72) concentration increases during exercise-heat stress when conditions elicit physiological strain. Differences in severity of environmental and exercise stimuli have elicited varied response to stress. The present study aimed to quantify the extent of increased eHsp72 with increased exogenous heat stress, and determine related endogenous markers of strain in an exercise-heat model. Ten males cycled for 90 min at 50 % [Formula: see text] in three conditions (TEMP, 20 °C/63 % RH; HOT, 30.2 °C/51%RH; VHOT, 40.0 °C/37%RH). Plasma was analysed for eHsp72 pre, immediately post and 24-h post each trial utilising a commercially available ELISA. Increased eHsp72 concentration was observed post VHOT trial (+172.4 %) (p < 0.05), but not TEMP (-1.9 %) or HOT (+25.7 %) conditions. eHsp72 returned to baseline values within 24 h in all conditions. Changes were observed in rectal temperature (Trec), rate of Trec increase, area under the curve for Trec of 38.5 and 39.0 °C, duration Trec ≥38.5 and ≥39.0 °C, and change in muscle temperature, between VHOT, and TEMP and HOT, but not between TEMP and HOT. Each condition also elicited significantly increasing physiological strain, described by sweat rate, heart rate, physiological strain index, rating of perceived exertion and thermal sensation. Stepwise multiple regression reported rate of Trec increase and change in Trec to be predictors of increased eHsp72 concentration. Data suggests eHsp72 concentration increases once systemic temperature and sympathetic activity exceeds a minimum endogenous criteria elicited during VHOT conditions and is likely to be modulated by large, rapid changes in core temperature.

Extracellular heat shock proteins: a new location, a new function

The expression of heat shock proteins (HSPs) is a basic and well-conserved cellular response to an array of stresses. These proteins are involved in the repair of cellular damage induced by the stress, which is necessary for the salutary resolution from the insult. Moreover, they confer protection from subsequent insults, which has been coined stress tolerance. Because these proteins are expressed in subcellular compartments, it was thought that their function during stress conditions was circumscribed to the intracellular environment. However, it is now well established that HSPs can also be present outside cells where they appear to display a function different than the well-understood chaperone role. Extracellular HSPs act as alert stress signals priming other cells, particularly of the immune system, to avoid the propagation of the insult and favor resolution. Because the majority of HSPs do not possess a secretory peptide signal, they are likely to be exported by a nonclassic secretory pathway. Different mechanisms have been proposed to explain the export of HSPs, including translocation across the plasma membrane and release associated with lipid vesicles, as well as the passive release after cell death by necrosis. Extracellular HSPs appear in various flavors, including membrane-bound and membrane-free forms. All of these variants of extracellular HSPs suggest that their interactions with cells may be quite diverse, both in target cell types and the activation signaling pathways. This review addresses some of our current knowledge about the release and relevance of extracellular HSPs.