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

Changes in surrogate markers of intestinal epithelial injury and microbial translocation in young and older men during prolonged occupational heat stress in temperate and hot conditions

PURPOSE

Exertional heat stress can cause damage to the intestinal epithelium and disrupt gastrointestinal barrier integrity, leading to microbial translocation (MT) linked to the development of heat stroke. This study aimed to assess age-related differences in markers of intestinal epithelial injury and MT following non-heat stress and high-heat stress exercise in healthy young and older men.

METHODS

Markers of intestinal epithelial injury (intestinal fatty acid-binding protein-'IFABP') and MT (soluble cluster of differentiation 14-'sCD14'; and lipopolysaccharide-binding protein-'LBP') were assessed in healthy young (18-30 y, n = 13) and older (50-70 y) men (n = 12). Blood samples were collected before, after 180 min of moderate-intensity (metabolic rate: 200 W/m2) walking and following 60 min recovery in either a non-heat stress [temperate: 21.9 °C, 35% relative humidity (RH)] or high-heat stress (hot: 41.4 °C, 35% RH) environment.

RESULTS

There were no differences in IFABP and sCD14 between the young and older groups in the temperate condition, while LBP was greater in the older group (+ 0.66 ug/mL; + 0.08 to + 1.24 ug/mL). In the hot condition, the older group experienced greater increases in IFABP compared to the young group (+ 712 pg/mL/hr; + 269 to + 1154 pg/mL/hr). However, there were no clear between-group differences for sCD14 (+ 0.24 ug/mL/hr, - 0.22 to + 0.70 ug/mL/hr) or LBP (+ 0.86 ug/mL/hr, - 0.73 to + 2.46 ug/mL/hr).

CONCLUSION

While older men may experience greater intestinal epithelial injury following exercise in the heat; this did not lead to a greater magnitude of microbial translocation relative to their younger counterparts.

The increase in core body temperature in response to exertional-heat stress can predict exercise-induced gastrointestinal syndrome

Utilizing metadata from existing exertional and exertional-heat stress studies, the study aimed to determine if the exercise-associated increase in core body temperature can predict the change in exercise-induced gastrointestinal syndrome (EIGS) biomarkers and exercise-associated gastrointestinal symptoms (Ex-GIS). Endurance-trained individuals completed 2 h of running exercise in temperate (21.2-30.0°C) to hot (35.0-37.2°C) ambient conditions (n = 132 trials). Blood samples were collected pre- and post-exercise to determine the change in gastrointestinal integrity biomarkers and systemic inflammatory cytokines. Physiological and thermoregulatory strain variables were assessed every 10-15 min during exercise. The strength of the linear relationship between maximal (M-Tre) and change (Δ Tre) in rectal temperature and EIGS variables was determined via Spearman's rank correlation coefficients. While the strength of prediction was determined via simple and multiple linear regression analyses dependent on screened EIGS and Ex-GIS confounding factors. Significant positive correlations between Tre maximum (M-Tre) and change (Δ Tre) with I-FABP (rs = 0.434, p < 0.001; and rs = 0.305, p < 0.001; respectively), sCD14 (rs = 0.358, p < 0.001; and rs = 0.362, p < 0.001), systemic inflammatory response profile (SIR-Profile) (p < 0.001), and total Ex-GIS (p < 0.05) were observed. M-Tre and Δ Tre significantly predicted (adjusted R2) magnitude of change in I-FABP (R2(2,123)=0.164, p < 0.001; and R2(2,119)=0.058, p = 0.011; respectively), sCD14 (R2(2,81)=0.249, p < 0.001; and R2(2,77)=0.214, p < 0.001), SIR-Profile (p < 0.001), and total Ex-GIS (p < 0.05). Strong to weak correlations were observed between M-Tre and Δ Tre with plasma concentrations of I-FABP, sCD14, SIR-Profile, and Ex-GIS in response to exercise. M-Tre and Δ Tre can predict the magnitude of these EIGS variables and Ex-GIS in response to exercise.

Acute Inflammatory, Anthropometric, and Perceptual (Muscle Soreness) Effects of Postresistance Exercise Water Immersion in Junior International and Subelite Male Volleyball Athletes

ABSTRACT

Horgan, BG, West, NP, Tee, N, Drinkwater, EJ, Halson, SL, Vider, J, Fonda, CJ, Haff, GG, and Chapman, DW. Acute inflammatory, anthropometric, and perceptual (muscle soreness) effects of postresistance exercise water immersion in junior international and subelite male volleyball athletes. J Strength Cond Res 36(12): 3473-3484, 2022-Athletes use water immersion strategies to recover from training and competition. This study investigated the acute effects of postexercise water immersion after resistance exercise. Eighteen elite and subelite male volleyball athletes participated in an intervention using a randomized cross-over design. On separate occasions after resistance exercise, subjects completed 1 of 4 15-minute interventions: control (CON), cold water immersion (CWI), contrast water therapy (CWT), or hot water immersion (HWI). Significance was accepted at p ≤ 0.05. Resistance exercise induced significant temporal changes (time effect) for inflammatory, anthropometric, perceptual, and performance measures. Serum creatine kinase was reduced ( g = 0.02-0.30) after CWI ( p = 0.007), CWT ( p = 0.006), or HWI ( p < 0.001) vs. CON, whereas it increased significantly ( g = 0.50) after CWI vs. HWI. Contrast water therapy resulted in significantly higher ( g = 0.56) interleukin-6 concentrations vs. HWI. Thigh girth increased ( g = 0.06-0.16) after CWI vs. CON ( p = 0.013) and HWI ( p < 0.001) and between CWT vs. HWI ( p = 0.050). Similarly, calf girth increased ( g = 0.01-0.12) after CWI vs. CON ( p = 0.039) and CWT ( p = 0.018), and HWI vs. CON ( p = 0.041) and CWT ( p = 0.018). Subject belief in a postexercise intervention strategy was associated with HSP72 ("believer">"nonbeliever," p = 0.026), muscle soreness ("believer">"nonbeliever," p = 0.002), and interleukin-4 ("nonbeliever">"believer," p = 0.002). There were no significant treatment × time (interaction effect) pairwise comparisons. Choice of postexercise water immersion strategy (i.e., cold, contrast, or hot) combined with a belief in the efficacy of that strategy to enhance recovery or performance improves biological and perceptual markers of muscle damage and soreness. On same or subsequent days where resistance exercise bouts are performed, practitioners should consider athlete beliefs when prescribing postexercise water immersion, to reduce muscle soreness.

Exercise-induced modulation of monocytes in breast cancer survivors

Background

Exercise training reduces inflammation in breast cancer survivors; however, the mechanism is not fully understood.

Objectives

The effects of acute and chronic exercise on monocyte toll-like receptor (TLR2 and 4) expression and intracellular cytokine production were examined in sedentary breast cancer survivors.

Methods

Eleven women with stage I, II, or III breast cancer within one year of treatment completion performed an acute, intermittent aerobic exercise trial. Blood samples were obtained before, immediately, and 1 h after a 45-min acute exercise trial that was performed before and after 16 weeks of combined aerobic and resistance. LPS-stimulated intracellular IL-1ß, TNF, and IL-6 production, and TLR2 and TLR4 expression were evaluated in CD14⁺CD16^- and CD14⁺CD16⁺ monocytes using flow cytometry.

Results

Exercise training decreased IL-1ß⁺CD14⁺CD16^- proportion (24.6%, p=0.016), IL-1ß⁺CD14⁺CD16^- mean fluorescence intensity (MFI) (-9989, p=0.014), IL-1ß⁺CD14⁺CD16⁺ MFI (-11101, p=0.02), and IL-6⁺CD14⁺CD16^- proportion (16.9%, P=0.04). TLR2 and TLR4 expression did not change following exercise training but decreased 1 h after acute exercise in CD14⁺CD16^- (-63, p=0.002) and CD14⁺CD16⁺ (-18, p=0.006) monocytes, respectively. Immediately after the acute exercise, both monocyte subgroup cell concentration increased, with CD14⁺CD16⁺ concentrations being decreased at 1 h post without changes in intracellular cytokine production.

Conclusions

Exercise training reduced monocyte intracellular pro-inflammatory cytokine production, especially IL-1ß, although these markers did not change acutely. While acute exercise downregulated the expression of TLR2 and TLR4 on monocytes, this was not sustained over the course of training. These results suggest that the anti-inflammatory effect of combined aerobic and resistance exercise training in breast cancer survivors may be, in part, due to reducing resting monocyte pro-inflammatory cytokine production.

Physical exercise-induced thermoregulatory responses in trained rats: Effects of manipulating the duration and intensity of aerobic training sessions

This study investigated the effects of increasing the intensity and/or duration of aerobic training sessions on thermoregulatory responses in rats subjected to exercises in temperate and warm environments. Thirty-two adult male Wistar rats were divided into four groups: a control (CON) group and three groups that were subjected to an 8-week aerobic training, during which the physical overload was achieved by predominantly increasing the exercise intensity (INT), duration (DUR) or by increasing both in an alternate manner (ID). During the last week of training, the rats received an abdominal sensor implant to measure their core body temperature (TCORE) by telemetry. After the training protocol, the 32 rats were subjected to incremental speed-exercises in temperate (23 °C) and warm (32 °C) environments. The rats had their TCORE recorded while running on a treadmill, and the ratio between the increase in TCORE and distance traveled was calculated to estimate thermoregulatory efficiency. All training protocols increased the rats' thermoregulatory efficiency during the incremental-speed exercise at 23 °C; i.e., trained rats attained faster running speeds but unchanged TCORE at fatigue compared to CON rats. However, none of the load components of training sessions - intensity or duration - was more effective than the other in improving this efficiency. At 32 °C, the aerobic training protocols did not influence the exercise-induced thermoregulatory responses. Our data indicate that different progressions in aerobic training performed at temperate conditions improved thermoregulatory efficiency during incremental exercise in the same environment; this training-induced adaptation was not clearly observed when running in warmer conditions.

Differential effects of whole blood heat treatment on the ex vivo inflammatory profile of untrained and trained men

This study evaluated the effects of heat stress on the ex vivo inflammatory profile in untrained and trained men. Whole blood samples from untrained (UT) and trained (TR) individuals were incubated for 2 h at 37 °C or 40 °C. The whole blood of a subsample of the participants (n = 5 in both TR and UT groups) were stimulated with lipopolysaccharide (LPS, 10 ng/mL) concomitant to heat treatment (37 °C versus 40 °C). Flow cytometry was used to assess the intracellular NF-κB activation in CD4+ T cells and CD14+ monocytes, the expression of Toll-Like Receptor-4 (TLR-4), the frequencies of CD4+CD25-CD39+ and CD4+CD25+CD39+ T cells and monocyte subsets (CD14+CD16-; CD14+CD16+; CD14-CD16+), the mitochondrial membrane potential (MMP) and the reactive oxygen species (ROS) production by lymphocytes and monocytes. The production of interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α) by LPS-stimulated whole blood were also evaluated. Heat treatment (40 °C) increased the proportions of CD14+CD16- and CD14+CD16+ monocytes and the lymphocyte MMP in the UT group. The frequencies of CD14-CD16+ monocytes and the activation of NF-κB in CD14+ monocytes decreased in UT and TR groups after heat treatment, while a reduction in CD4+CD25-CD39+ T-cells was observed only in the UT group. Higher TLR-4 and NF-κB activation were found in LPS-stimulated monocytes of UT men concomitant with higher TNF-α production and diminished IL-10 production after heat treatment. TR individuals presented lower NF- κB activation in LPS-stimulated monocytes after heat treatment. Our data suggest that the training status of individuals may impact on the anti-inflammatory response of heat treatment.

Influence of aerobic fitness on gastrointestinal barrier integrity and microbial translocation following a fixed-intensity military exertional heat stress test

PURPOSE

Exertional-heat stress adversely disrupts gastrointestinal (GI) barrier integrity, whereby subsequent microbial translocation (MT) can result in potentially serious health consequences. To date, the influence of aerobic fitness on GI barrier integrity and MT following exertional-heat stress is poorly characterised.

METHOD

Ten untrained (UT; VO_2max = 45 ± 3 ml·kg^-1·min^-1) and ten highly trained (HT; VO_2max = 64 ± 4 ml·kg^-1·min^-1) males completed an ecologically valid (military) 80-min fixed-intensity exertional-heat stress test (EHST). Venous blood was drawn immediately pre- and post-EHST. GI barrier integrity was assessed using the serum dual-sugar absorption test (DSAT) and plasma Intestinal Fatty-Acid Binding Protein (I-FABP). MT was assessed using plasma Bacteroides/total 16S DNA.

RESULTS

UT experienced greater thermoregulatory, cardiovascular and perceptual strain (p < 0.05) than HT during the EHST. Serum DSAT responses were similar between the two groups (p = 0.59), although Δ I-FABP was greater (p = 0.04) in the UT (1.14 ± 1.36 ng·ml^-1) versus HT (0.20 ± 0.29 ng·ml^-1) group. Bacteroides/Total 16S DNA ratio was unchanged (Δ; -0.04 ± 0.18) following the EHST in the HT group, but increased (Δ; 0.19 ± 0.25) in the UT group (p = 0.05). Weekly aerobic training hours had a weak, negative correlation with Δ I-FABP and Bacteroides/total 16S DNA responses.

CONCLUSION

When exercising at the same absolute workload, UT individuals are more susceptible to small intestinal epithelial injury and MT than HT individuals. These responses appear partially attributable to greater thermoregulatory, cardiovascular, and perceptual strain.

Association between occupational heat stress and DNA damage in lymphocytes of workers exposed to hot working environments in a steel industry in Southern India

Occupational heat stress apart from adverse heat-related health consequences also induces DNA damage in workers exposed to high working temperatures. We investigated the association between chronic heat exposures and Micronuclei (MN) frequency in lymphocytes of 120 workers employed in the steel industry. There was a significant increase in the MN-frequency in exposed workers compared to the unexposed workers (X² = 47.1; p < 0.0001). While exposed workers had higher risk of DNA damage (Adj. OR = 23.3, 95% CI 8.0-70.8) compared to the unexposed workers, among the exposed workers, the odds of DNA damage was much higher for the workers exposed to high-heat levels (Adj. OR = 81.4; 95% CI 21.3-310.1) even after adjusting for confounders. For exposed workers, years of exposure to heat also had a significant association with higher induction of MN (Adj. OR = 29.7; 95% CI 2.8-315.5). Exposures to chronic heat stress is a significant occupational health risk including damages in sub-cellular level, for workers. Developing protective interventions to reduce heat exposures is imperative in the rising temperature scenario to protect millions of workers across the globe.

Identifying Hub Genes for Heat Tolerance in Water Buffalo (Bubalus bubalis) Using Transcriptome Data

Heat stress has a detrimental effect on the physiological and production performance of buffaloes. Elucidating the underlying mechanisms of heat stress is challenging, therefore identifying candidate genes is urgent and necessary. We evaluated the response of buffaloes (n = 30) to heat stress using the physiological parameters, ELISA indexes, and hematological parameters. We then performed mRNA and microRNA (miRNA) expression profiles analysis between heat tolerant (HT, n = 4) and non-heat tolerant (NHT, n = 4) buffaloes, as well as the specific modules, significant genes, and miRNAs related to the heat tolerance identified using the weighted gene co-expression network analysis (WGCNA). The results indicated that the buffaloes in HT had a significantly lower rectal temperature (RT) and respiratory rate (RR) and displayed a higher plasma heat shock protein (HSP70 and HSP90) and cortisol (COR) levels than those of NHT buffaloes. Differentially expressed analysis revealed a total of 753 differentially expressed genes (DEGs) and 16 differentially expressed miRNAs (DEmiRNAs) were identified between HT and NHT. Using the WGCNA analysis, these DEGs assigned into 5 modules, 4 of which were significantly correlation with the heat stress indexes. Interestingly, 158 DEGs associated with heat tolerance in the turquoise module were identified, 35 of which were found within the protein-protein interaction network. Several hub genes (IL18RAP, IL6R, CCR1, PPBP, IL1B, and IL1R1) were identified that significantly enriched in the Cytokine-cytokine receptor interaction. The findings may help further elucidate the underlying mechanisms of heat tolerance in buffaloes.

The effect of temperature and heat shock protein 72 on the ex vivo acute inflammatory response in monocytes

The acute inflammatory response to active or passive activities that increase body temperature may aid to reduce chronic low-grade inflammation. This study investigates the impact of temperature and extracellular heat shock protein 72 (eHsp72) on the acute intracellular Hsp72 (iHsp72) and interleukin-6 (iIL-6) response in monocytes. Whole blood was incubated for 2 h at 37.0 °C, 38.5 °C and 40.0 °C, in the absence or presence of 0.5 μg/ml eHsp72. Flow cytometry was used to assess iHsp72 and iIL-6 expression in total monocytes and the three monocyte subsets. Incubation at 40.0 °C (p < 0.001) but not 38.5 °C (p = 0.085) increased iHsp72 expression when compared with 37.0 °C, while there was no effect of temperature on iIL-6 expression (p = 0.635). Following incubation with eHsp72, the expression of iHsp72 in classical monocytes was reduced at all temperatures (p < 0.001), while there was no effect of eHsp72 on iIL-6 expression (p = 0.071). Large temperature elevations are needed to induce an acute iHsp72 response in monocytes. In addition, contrary to its suggested role as a danger signal for the innate immune system, eHsp72 reduced iHsp72 and iIL-6 expression in monocytes.

Heat and Hypoxic Acclimation Increase Monocyte Heat Shock Protein 72 but Do Not Attenuate Inflammation following Hypoxic Exercise

Acclimation to heat or hypoxic stress activates the heat shock response and accumulation of cytoprotective heat shock proteins (HSPs). By inhibiting the NF-κB pathway HSP72 can preserve epithelial function and reduce systemic inflammation. The aim of this study was to determine the time course of mHSP72 accumulation during acclimation, and to assess intestinal barrier damage and systemic inflammation following hypoxic exercise. Three groups completed 10 × 60-min acclimation sessions (50% normoxic VO₂peak) in control (n = 7; 18°C, 35% RH), hypoxic (n = 7; F_iO₂ = 0.14, 18°C, 35% RH), or hot (n = 7; 40°C, 25% RH) conditions. Tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin 10 (IL-10), and intestinal fatty acid binding protein (I-FABP) were determined at rest and following a cycling normoxic stress test (NST; ~2 weeks before acclimation), pre-acclimation hypoxic stress test (HST1; F_iO₂ = 0.14, both at 50% normoxic VO₂peak; ~1 week before acclimation) and post-acclimation HST (48 h; HST2). Monocyte HSP72 (mHSP72) was determined before and after exercise on day 1, 3, 5, 6, and 10 of acclimation. Accumulation of basal mHSP72 was evident from day 5 (p < 0.05) of heat acclimation and increased further on day 6 (p < 0.01), and day 10 (p < 0.01). In contrast, basal mHSP72 was elevated on the final day of hypoxic acclimation (p < 0.05). Following the NST, plasma TNF-α (–0.11 ± 0.27 ng^.mL⁻¹), IL-6 (+0.62 ± 0.67 ng^.mL⁻¹) IL-10 (+1.09 ± 9.06 ng^.mL⁻¹) and I-FABP (+37.6 ± 112.8 pg^.mL⁻¹) exhibited minimal change. After HST1, IL-6 (+3.87 ± 2.56 ng^.mL⁻¹), IL-10 (+26.15 ± 26.06 ng^.mL⁻¹) and I-FABP (+183.7 ± 182.1 pg^.mL⁻¹) were elevated (p < 0.01), whereas TNF-α was unaltered (+0.08 ± 1.27; p > 0.05). A similar trend was observed after HST2, with IL-6 (+3.09 ± 1.30 ng^.mL⁻¹), IL-10 (+23.22 ± 21.67 ng^.mL⁻¹) and I-FABP (+145.9 ±123.2 pg^.mL⁻¹) increased from rest. Heat acclimation induces mHSP72 accumulation earlier and at a greater magnitude compared to matched work hypoxic acclimation, however neither acclimation regime attenuated the systemic cytokine response or intestinal damage following acute exercise in hypoxia.

Acute Strenuous Exercise Induces an Imbalance on Histone H4 Acetylation/Histone Deacetylase 2 and Increases the Proinflammatory Profile of PBMC of Obese Individuals

This study evaluated the response of global histone H4 acetylation (H4ac), histone deacetylase 2 (HDAC2) activity, as well as the production of proinflammatory cytokines and monocyte phenotypes of lean and obese males after exercise. Ten lean and ten obese sedentary men were submitted to one session of strenuous exercise, and peripheral blood mononuclear cells (PBMC) were stimulated in vitro with lipopolysaccharide (LPS). Global H4ac levels, HDAC2 activity in PBMC, and IL-6, IL-8, and TNF-α production were analyzed. Monocyte phenotype was determined in accordance with the expression of CD14 and CD16. At rest, obese individuals presented higher frequency of proinflammatory CD14⁺CD16⁺ monocytes. LPS induced a significant augment in global H4ac and in the production of IL-6, IL-8, and TNF-α mainly in obese individuals. After exercise, the increased production of IL-8 and TNF-α and peripheral frequency of CD14⁺CD16⁺ were observed in both groups. In addition, exercise also induced a significant hyperacetylation of histone H4 and decreased HDAC2 activity in both nonstimulated and LPS-stimulated PBMC of obese individuals. Our data indicate that the obesity impacts on H4ac levels and that strenuous exercise leads to an enhanced chronic low-grade inflammation profile in obesity via an imbalance on H4ac/HDAC2.

The Hsp72 and Hsp90α mRNA Responses to Hot Downhill Running Are Reduced Following a Prior Bout of Hot Downhill Running, and Occur Concurrently within Leukocytes and the Vastus Lateralis

The leukocyte heat shock response (HSR) is used to determine individual's thermotolerance. The HSR and thermotolerance are enhanced following interventions such as preconditioning and/or acclimation/acclimatization. However, it is unclear whether the leukocyte HSR is an appropriate surrogate for the HSR in other tissues implicated within the pathophysiology of exertional heat illnesses (e.g., skeletal muscle), and whether an acute preconditioning strategy (e.g., downhill running) can improve subsequent thermotolerance. Physically active, non-heat acclimated participants were split into two groups to investigate the benefits of hot downhill running as preconditioning strategy. A hot preconditioning group (HPC; n = 6) completed two trials (HPC1_HOTDOWN and HPC2_HOTDOWN) of 30 min running at lactate threshold (LT) on -10% gradient in 30°C and 50% relative humidity (RH) separated by 7 d. A temperate preconditioning group (TPC; n = 5) completed 30 min running at LT on a -1% gradient in 20°C and 50% (TPC1_TEMPFLAT) and 7 d later completed 30 min running at LT on -10% gradient in 30°C and 50% RH (TPC2_HOTDOWN). Venous blood samples and muscle biopsies (vastus lateralis; VL) were obtained before, immediately after, 3, 24, and 48 h after each trial. Leukocyte and VL Hsp72, Hsp90α, and Grp78 mRNA relative expression was determined via RT-QPCR. Attenuated leukocyte and VL Hsp72 (2.8 to 1.8 fold and 5.9 to 2.4 fold; p < 0.05) and Hsp90α mRNA (2.9 to 2.4 fold and 5.2 to 2.4 fold; p < 0.05) responses accompanied reductions (p < 0.05) in physiological strain [exercising rectal temperature (-0.3°C) and perceived muscle soreness (~ -14%)] during HPC2_HOTDOWN compared to HPC1_HOTDOWN (i.e., a preconditioning effect). Both VL and leukocyte Hsp72 and Hsp90α mRNA increased (p < 0.05) simultaneously following downhill runs and demonstrated a strong relationship (p < 0.01) of similar magnitudes with one another. Hot downhill running is an effective preconditioning strategy which ameliorates physiological strain, soreness and Hsp72 and Hsp90α mRNA responses to a subsequent bout. Leukocyte and VL analyses are appropriate tissues to infer the extent to which the HSR has been augmented.

Whole body precooling attenuates the extracellular HSP72, IL-6 and IL-10 responses after an acute bout of running in the heat

The impact of whole-body precooling on the extracellular heat shock protein 72 (eHSP72) and cytokine responses to running in the heat is undefined. The aim of this study was to determine whether precooling would attenuate post-exercise eHSP72 and cytokine responses. Eight male recreational runners completed two 90-minute bouts of running at 65% [Formula: see text]O₂max in 32 ± 0.9°C and 47 ± 6 % relative humidity (RH) preceded by either 60-minutes of precooling in 20.3 ± 0.3°C water (COOL) or 60 min rest in an air-conditioned laboratory (20.2 ± 1.7°C, 60 ± 3% RH; CON). eHSP72, TNF-α, IL-6, IL-10 IL-1ra were determined before and immediately after exercise. The elevation in post-exercise eHSP72 was attenuated after COOL (+0.04 ± 0.10 ng.mL^-1) compared to CON (+ 0.29 ± 0.26 ng.mL^-1;P < 0.001). No changes in TNF-α were observed at any stage. COOL reduced the absolute post-exercise change in IL-6 (P = 0.011) and IL-10 (P = 0.03) compared to CON. IL-1ra followed this trend (P = 0.063). A precooling-induced attenuation of eHSP72 and proinflammatory cytokines may aid recovery during multi-day sporting events, but could be counterproductive if a training response or adaptation to environmental stress is a desired outcome.

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.

Physical activity and exercise attenuate neuroinflammation in neurological diseases

Major depressive disorder (MDD), schizophrenia (SCH), Alzheimer's disease (AD), and Parkinson's disease (PD) are devastating neurological disorders, which increasingly contribute to global morbidity and mortality. Although the pathogenic mechanisms of these conditions are quite diverse, chronic neuroinflammation is one underlying feature shared by all these diseases. Even though the specific root causes of these diseases remain to be identified, evidence indicates that the observed neuroinflammation is initiated by unique pathological features associated with each specific disease. If the initial acute inflammation is not resolved, a chronic neuroinflammatory state develops and ultimately contributes to disease progression. Chronic neuroinflammation is characterized by adverse and non-specific activation of glial cells, which can lead to collateral damage of nearby neurons and other glia. This misdirected neuroinflammatory response is hypothesized to contribute to neuropathology in MDD, SCH, AD, and PD. Physical activity (PA), which is critical for maintenance of whole body and brain health, may also beneficially modify neuroimmune responses. Since PA has neuroimmune-modifying properties, and the common underlying feature of MDD, SCH, AD, and PD is chronic neuroinflammation, we hypothesize that PA could minimize brain diseases by modifying glia-mediated neuroinflammation. This review highlights current evidence supporting the disease-altering potential of PA and exercise through modifications of neuroimmune responses, specifically in MDD, SCH, AD and PD.

Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia

BACKGROUND

The potential for cross acclimation between environmental stressors is not well understood. Thus, the aim of this investigation was to determine the effect of fixed-workload heat or hypoxic acclimation on cellular, physiological, and performance responses during post acclimation hypoxic exercise in humans.

METHOD

Twenty-one males (age 22 ± 5 years; stature 1.76 ± 0.07 m; mass 71.8 ± 7.9 kg; [Formula: see text]O2 peak 51 ± 7 mL(.)kg(-1.)min(-1)) completed a cycling hypoxic stress test (HST) and self-paced 16.1 km time trial (TT) before (HST1, TT1), and after (HST2, TT2) a series of 10 daily 60 min training sessions (50% N [Formula: see text]O2 peak) in control (CON, n = 7; 18°C, 35% RH), hypoxic (HYP, n = 7; fraction of inspired oxygen = 0.14, 18°C, 35% RH), or hot (HOT, n = 7; 40°C, 25% RH) conditions.

RESULTS

TT performance in hypoxia was improved following both acclimation treatments, HYP (-3:16 ± 3:10 min:s; p = 0.0006) and HOT (-2:02 ± 1:02 min:s; p = 0.005), but unchanged after CON (+0:31 ± 1:42 min:s). Resting monocyte heat shock protein 72 (mHSP72) increased prior to HST2 in HOT (62 ± 46%) and HYP (58 ± 52%), but was unchanged after CON (9 ± 46%), leading to an attenuated mHSP72 response to hypoxic exercise in HOT and HYP HST2 compared to HST1 (p < 0.01). Changes in extracellular hypoxia-inducible factor 1-α followed a similar pattern to those of mHSP72. Physiological strain index (PSI) was attenuated in HOT (HST1 = 4.12 ± 0.58, HST2 = 3.60 ± 0.42; p = 0.007) as a result of a reduced HR (HST1 = 140 ± 14 b.min(-1); HST2 131 ± 9 b.min(-1) p = 0.0006) and Trectal (HST1 = 37.55 ± 0.18°C; HST2 37.45 ± 0.14°C; p = 0.018) during exercise. Whereas PSI did not change in HYP (HST1 = 4.82 ± 0.64, HST2 4.83 ± 0.63).

CONCLUSION

Heat acclimation improved cellular and systemic physiological tolerance to steady state exercise in moderate hypoxia. Additionally we show, for the first time, that heat acclimation improved cycling time trial performance to a magnitude similar to that achieved by hypoxic acclimation.

Salivary extracellular heat shock protein 70 (eHSP70) levels increase after 59 min of intense exercise and correlate with resting salivary secretory immunoglobulin A (SIgA) levels at rest

This study aimed to identify the response of a salivary stress protein, extracellular heat shock protein (eHSP70), to intense exercise and to investigate the relationship between salivary eHSP70 and salivary immunoglobulin A (SIgA) levels in response to exercise. Sixteen healthy sedentary young males (means ± SD 23.8 ± 1.5 years, 172.2 ± 6.4 cm, 68.3 ± 7.4 kg) performed 59 min of cycling exercise at 75% VO2max. Saliva and whole blood samples were collected before (Pre), immediately after (Post), and at 1, 2, 3, and 4 h after completion of the exercise (1, 2, 3, and 4 h). The salivary eHSP70 and SIgA levels were measured by enzyme-linked imunosorbent assay (ELISA), and the secretion rates were computed by multiplying the concentration by the saliva flow rate. White blood cells were analyzed using an automated cell counter with a direct-current detection system. The salivary eHSP70 secretion rates were 1.11 ± 0.86, 1.51 ± 1.47, 1.57 ± 1.32, 2.21 ± 2.04, 3.36 ± 2.72, and 6.89 ± 4.02 ng · min(-1) at Pre, Post, and 1, 2, 3, and 4 h, respectively. The salivary eHSP70 secretion rate was significantly higher at 4 h than that at Pre, Post, 1, and 3 h (p < 0.05). The SIgA secretion rates were 26.9 ± 12.6, 20.3 ± 10.4, 19.6 ± 11.0, 21.8 ± 12.8, 21.5 ± 11.9, and 21.9 ± 11.7 μg · min(-1) at Pre, Post, 1, 2, 3, and 4 h, respectively. The salivary SIgA secretion rate was significantly lower between 1 and 4 h than that at Pre (p < 0.05). There was a positive correlation between salivary eHSP70 and SIgA in both concentration and secretion rates before exercise (p < 0.05). The absolute number of white blood cells significantly increased after exercise, with a maximum at 2 h (p < 0.05). The neutrophil/lymphocyte ratio was significantly increased from 1 to 4 h when compared with that in the Pre samples (p < 0.05). The present study revealed that salivary eHSP70 significantly increased at 4 h after the 59 min of intense exercise in sedentary male subjects. Exercise stress can induce elevated salivary eHSP70 level and upregulate oral immune function partially.

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.

Effects of an interleukin-1 receptor antagonist on human sleep, sleep-associated memory consolidation, and blood monocytes

Pro-inflammatory cytokines like interleukin-1 beta (IL-1) are major players in the interaction between the immune system and the central nervous system. Various animal studies report a sleep-promoting effect of IL-1 leading to enhanced slow wave sleep (SWS). Moreover, this cytokine was shown to affect hippocampus-dependent memory. However, the role of IL-1 in human sleep and memory is not yet understood. We administered the synthetic IL-1 receptor antagonist anakinra (IL-1ra) in healthy humans (100mg, subcutaneously, before sleep; n=16) to investigate the role of IL-1 signaling in sleep regulation and sleep-dependent declarative memory consolidation. Inasmuch monocytes have been considered a model for central nervous microglia, we monitored cytokine production in classical and non-classical blood monocytes to gain clues about how central nervous effects of IL-1ra are conveyed. Contrary to our expectation, IL-1ra increased EEG slow wave activity during SWS and non-rapid eye movement (NonREM) sleep, indicating a deepening of sleep, while sleep-associated memory consolidation remained unchanged. Moreover, IL-1ra slightly increased prolactin and reduced cortisol levels during sleep. Production of IL-1 by classical monocytes was diminished after IL-1ra. The discrepancy to findings in animal studies might reflect species differences and underlines the importance of studying cytokine effects in humans.

Differential acute effects of sleep on spontaneous and stimulated production of tumor necrosis factor in men

Tumor necrosis factor (TNF) is considered a key molecule in the regulation of sleep in health and disease. Conversely, sleep compared to sleep deprivation can modulate TNF release, but overall results are conflicting. In this study we focused on the influence of sleep on spontaneous, i.e., unstimulated TNF production, which might be involved in sleep regulation under normal non-infectious conditions, and on lipopolysaccharide (LPS)-stimulated TNF production, which reflects the capacity of the immune system to respond to a pathogen. To this end, we monitored 10 healthy men during a regular sleep-wake cycle and during 24h of wakefulness while blood was sampled repeatedly to analyze circulating TNF levels in serum as well as intracellular TNF production in monocytes spontaneously and after stimulation with LPS employing whole blood cell cultures. In addition we assessed numbers of monocyte subsets and levels of various hormones in blood. In comparison with nocturnal wakefulness, sleep acutely decreased serum TNF levels, with no parallel decrease in spontaneous monocytic TNF production, but was associated with a striking nighttime increase in the percentage of TNF producing monocytes after stimulation with LPS. The following day circulating TNF showed a reverse pattern with higher levels after regular sleep than after the nocturnal vigil. The mechanisms mediating the differential effects of sleep on circulating TNF (acutely decreased) vs. stimulated monocytic TNF production (acutely increased) remain unclear, although explorative correlational analyses pointed to a regulatory involvement of cortisol, norepinephrine and prolactin. The acute enhancing effect of sleep on LPS stimulated monocytic TNF production adds to the notion that nocturnal sleep favors immune defense to a microbial challenge.

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.

Downhill running and exercise in hot environments increase leukocyte Hsp72 (HSPA1A) and Hsp90α (HSPC1) gene transcripts

Stressors within humans and other species activate Hsp72 and Hsp90α mRNA transcription, although it is unclear which environmental temperature or treadmill gradient induces the largest increase. To determine the optimal stressor for priming the Hsp system, physically active but not heat-acclimated participants (19.8 ± 1.9 and 20.9 ± 3.6 yr) exercised at lactate threshold in either temperate (20°C, 50% relative humidity; RH) or hot (30°C, 50% RH) environmental conditions. Within each condition, participants completed a flat running (temperate flat or hot flat) and a downhill running (temperate downhill or hot downhill) experimental trial in a randomized counterbalanced order separated by at least 7 days. Venous blood samples were taken immediately before (basal), immediately after exercise, and 3 and 24 h postexercise. RNA was extracted from leukocytes and RT-quantitative PCR conducted to determine Hsp72 and Hsp90α mRNA relative expression. Leukocyte Hsp72 mRNA was increased immediately after exercise following downhill running (1.9 ± 0.9-fold) compared with flat running (1.3 ± 0.4-fold; P = 0.001) and in hot (1.9 ± 0.6-fold) compared with temperate conditions (1.1 ± 0.5-fold; P = 0.003). Leukocyte Hsp90α mRNA increased immediately after exercise following downhill running (1.4 ± 0.8-fold) compared with flat running (0.9 ± 0.6-fold; P = 0.002) and in hot (1.6 ± 1.0-fold) compared with temperate conditions (0.9 ± 0.6-fold; P = 0.003). Downhill running and exercise in hot conditions induced the largest stimuli for leukocyte Hsp72 and Hsp90α mRNA increases.

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.

Gene and miRNA expression profiles of hematopoietic progenitor cells vary depending on their origin

Hematopoietic progenitor cells (HPCs) from granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood (G-PB), bone marrow (BM), or umbilical cord blood (CB) have differing biological properties and differing kinetics of engraftment post-transplantation, which might be explained, at least in part, by differing gene and miRNA expression patterns. To assess the differences in gene and miRNA expression, we analyzed whole genome expression profiles as well as the expression of 384 miRNAs in CD34(+) cells isolated from 18 healthy individuals (6 individuals per subtype of HPC source). We identified 43 genes and 36 miRNAs differentially expressed in the various CD34(+) cell sources. We observed that CD34(+) cells from CB and BM showed similar gene and miRNA expression profiles, whereas CD34(+) cells from G-PB had a very different expression pattern. Remarkably, 20 of the differentially expressed genes are targets of the differentially expressed miRNAs. Of note, the majority of genes differentially expressed in CD34(+) cells from G-PB are involved in cell cycle regulation, promoting the process of proliferation, survival, hematopoiesis, and cell signaling, and are targets of overexpressed and underexpressed miRNAs in CD34(+) cells from the same source. These data suggest significant differences in gene and miRNA expression among the various HPC sources used in transplantation. We hypothesize that the differentially expressed genes and miRNAs involved in cell cycle and proliferation might explain the differing kinetics of engraftment observed after transplantation of hematopoietic stem cells obtained from these different sources.

Heat shock protein 72 expressing stress in sepsis: unbridgeable gap between animal and human studies--a hypothetical "comparative" study

Heat shock protein 72 (Hsp72) exhibits a protective role during times of increased risk of pathogenic challenge and/or tissue damage. The aim of the study was to ascertain Hsp72 protective effect differences between animal and human studies in sepsis using a hypothetical “comparative study” model. Forty-one in vivo (56.1%), in vitro (17.1%), or combined (26.8%) animal and 14 in vivo (2) or in vitro (12) human Hsp72 studies (P < 0.0001) were enrolled in the analysis. Of the 14 human studies, 50% showed a protective Hsp72 effect compared to 95.8% protection shown in septic animal studies (P < 0.0001). Only human studies reported Hsp72-associated mortality (21.4%) or infection (7.1%) or reported results (14.3%) to be nonprotective (P < 0.001). In animal models, any Hsp72 induction method tried increased intracellular Hsp72 (100%), compared to 57.1% of human studies (P < 0.02), reduced proinflammatory cytokines (28/29), and enhanced survival (18/18). Animal studies show a clear Hsp72 protective effect in sepsis. Human studies are inconclusive, showing either protection or a possible relation to mortality and infections. This might be due to the fact that using evermore purified target cell populations in animal models, a lot of clinical information regarding the net response that occurs in sepsis is missing.

Encapsulated environment

In many occupational settings, clothing must be worn to protect individuals from hazards in their work environment. However, personal protective clothing (PPC) restricts heat exchange with the environment due to high thermal resistance and low water vapor permeability. As a consequence, individuals who wear PPC often work in uncompensable heat stress conditions where body heat storage continues to rise and the risk of heat injury is greatly enhanced. Tolerance time while wearing PPC is influenced by three factors: (i) initial core temperature (Tc), affected by heat acclimation, precooling, hydration, aerobic fitness, circadian rhythm, and menstrual cycle (ii) Tc tolerated at exhaustion, influenced by state of encapsulation, hydration, and aerobic fitness; and (iii) the rate of increase in Tc from beginning to end of the heat-stress exposure, which is dependent on the clothing characteristics, thermal environment, work rate, and individual factors like body composition and economy of movement. Methods to reduce heat strain in PPC include increasing clothing permeability for air, adjusting pacing strategy, including work/rest schedules, physical training, and cooling interventions, although the additional weight and bulk of some personal cooling systems offset their intended advantage. Individuals with low body fatness who perform regular aerobic exercise have tolerance times in PPC that exceed those of their sedentary counterparts by as much as 100% due to lower resting Tc, the higher Tc tolerated at exhaustion and a slower increase in Tc during exercise. However, questions remain about the importance of activity levels, exercise intensity, cold water ingestion, and plasma volume expansion for thermotolerance.

Sex differences in heat shock protein 72 expression in peripheral blood mononuclear cells to acute exercise in the heat

BACKGROUND

Heat shock protein 72 (Hsp72) is responsible for maintaining critical cellular function during heat stress. Hsp72 confers thermotolerance and may play a role in heat acclimation. Animal research suggests a difference between sexes in Hsp72 expression in response to exercise, however, human data is lacking.

OBJECTIVES

To determine sex differences in intracellular heat shock protein 72 (Hsp72) following exercise in the heat.

PATIENTS AND METHODS

Nine non-heat acclimated women with normal menstrual cycles (VO2pk 58 ± 5 mL.kgFFM(-1).min(-1)) and nine non-heat acclimated men (VO2pk 60 ± 7 ml.kgFFM(-1).min(-1)) completed 2 treadmill bouts at 60% VO2pk for 60 min in a 42°C, 20% RH environment. Women were tested in follicular (fol) and luteal (lut) phases. The duplicate trials were separated by 12 days for men and women. Blood samples were drawn pre, immediately post, 1, and 4 hrs post-exercise.

RESULTS

Men and women differed in their Hsp72 response after exercise (time X sex X trial interaction; P < 0.05). Men increased Hsp72 after exercise more than women. Both men and women produced less Hsp72 during trial 2 compared to trial 1. Estrogen (r = 0.24; P > 0.05) and progesterone (r = 0.27, P > 0.05) concentrations were not correlated with Hsp72.

CONCLUSION

Our findings suggest that men and women differ in their cellular stress response. Men up-regulated Hsp72 after a single bout of exercise in the heat, which persists for 12 days, suggesting an accumulation of Hsp72 which may lead to acquired cellular thermotolerance.

Exertional heat stroke

The increasing popularity of mass participation endurance events necessitates that on-site medical teams be well versed in the management of both common and life-threatening conditions. Exertional heat stroke is one such condition, which if left untreated can be fatal.

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

Extracellular heat-shock protein 72 (eHsp72) expression during exercise-heat stress is suggested to increase with the level of hyperthermia attained, independent of the rate of heat storage. This study examined the influence of exercise at various intensities to elucidate this relationship, and investigated the association between eHsp72 and eHsp27. Sixteen male subjects cycled to exhaustion at 60% and 75% of maximal oxygen uptake in hot conditions (40°C, 50% RH). Core temperature, heart rate, oxidative stress, and blood lactate and glucose levels were measured to determine the predictor variables associated with eHsp expression. At exhaustion, heart rate exceeded 96% of maximum in both conditions. Core temperature reached 39.7°C in the 60% trial (58.9 min) and 39.0°C in the 75% trial (27.2 min) (P < 0.001). The rate of rise in core temperature was 2.1°C h(-1) greater in the 75% trial than in the 60% trial (P < 0.001). A significant increase and correlation was observed between eHsp72 and eHsp27 concentrations at exhaustion (P < 0.005). eHsp72 was highly correlated with the core temperature attained (60% trial) and the rate of increase in core temperature (75% trial; P < 0.05). However, no common predictor variable was associated with the expression of both eHsps. The similarity in expression of eHsp72 and eHsp27 during moderate- and high-intensity exercise may relate to the duration (i.e., core temperature attained) and intensity (i.e., rate of increase in core temperature) of exercise. Thus, the immuno-inflammatory release of eHsp72 and eHsp27 in response to exercise in the heat may be duration and intensity dependent.

Hypoxia-mediated prior induction of monocyte-expressed HSP72 and HSP32 provides protection to the disturbances to redox balance associated with human sub-maximal aerobic exercise

HSP72 is rapidly expressed in response to a variety of stressors in vitro and in vivo (including hypoxia). This project sought a hypoxic stimulus to elicit increases in HSP72 and HSP32 in attempts to confer protection to the sub-maximal aerobic exercise-induced disturbances to redox balance. Eight healthy recreationally active male subjects were exposed to five consecutive days of once-daily hypoxia (2,980 m, 75 min). Seven days prior to the hypoxic acclimation period, subjects performed 60 min of cycling on a cycle ergometer (exercise bout 1-EXB1), and this exercise bout was repeated 1 day post-cessation of the hypoxic period (exercise bout 2-EXB2). Blood samples were taken immediately pre- and post-exercise and 1, 4 and 8 h post-exercise for HSP72 and immediately pre, post and 1 h post-exercise for HSP32, TBARS and glutathione [reduced (GSH), oxidised (GSSG) and total (TGSH)], with additional blood samples obtained immediately pre-day 1 and post-day 5 of the hypoxic acclimation period for the same indices. Monocyte-expressed HSP32 and HSP72 were analysed by flow cytometry, with measures of oxidative stress accessed by commercially available kits. There were significant increases in HSP72 (P < 0.001), HSP32 (P = 0.03), GSSG (t = 9.5, P < 0.001) and TBARS (t = 5.6, P = 0.001) in response to the 5-day hypoxic intervention, whereas no significant changes were observed for GSH (P = 0.22) and TGSH (P = 0.25). Exercise-induced significant increases in HSP72 (P < 0.001) and HSP32 (P = 0.003) post-exercise in EXB1; this response was absent for HSP72 (P ≥ 0.79) and HSP32 (P ≥ 0.99) post-EXB2. The hypoxia-mediated increased bio-available HSP32 and HSP72 and favourable alterations in glutathione redox, prior to exercise commencing in EXB2 compared to EXB1, may acquiesce the disturbances to redox balance encountered during the second physiologically identical exercise bout.

Toward establishment of temperature thresholds for immunological impact of heat exposure in humans

There is interest in understanding the health impact of thermal effects as a result of exposure of humans to radiofrequency/microwave (RF/MW) fields. Immune cells and responses are affected by modest changes in temperature and it is important to quantify these effects and establish safety thresholds similar to what has been done with other tissue targets. Since previous summaries of thresholds for thermal damage to normal tissues have not focused much attention to cells of the immune system, this summary highlights recent studies which demonstrate positive and some negative effects of temperature shifts on human immune cells. We emphasise literature reporting adverse immunological endpoints (such as cell damage, death and altered function) and provide the temperature at which these effects were noted. Whereas there have been many in vitro studies of adverse temperature effects on immune cells, there has been limited validation of these temperature effects in vivo. However, data from heat stress/stroke patients do provide some information regarding core temperatures (40°C) at which thermal damage to immunological processes can begin to occur. We conclude that there is considerable need for more quantitative time temperature assessments using relevant animal models, more complete kinetic analyses to determine how long immunological effects persist, and for analysis of whether frequency of exposure has impact on immune function. To date, no attempt to categorise effects by using cumulative thermal dose measurements (e.g. cumulative equivalent minutes at a given temperature) has been conducted for cells or tissues of the immune system, representing a major gap in this field.

Heat shock proteins as biomarkers for the rapid detection of brain and spinal cord ischemia: a review and comparison to other methods of detection in thoracic aneurysm repair

The heat shock proteins (HSPs) are members of highly conserved families of molecular chaperones that have multiple roles in vivo. We discuss the HSPs in general, and Hsp70 and Hsp27 in particular, and their rapid induction by severe stress in the context of tissue and organ expression in physiology and disease. We describe the current state of knowledge of the relationship and interactions between extra- and intracellular HSPs and describe mechanisms and significance of extracellular expression of HSPs. We focus on the role of the heat shock proteins as biomarkers of central nervous system (CNS) ischemia and other severe stressors and discuss recent and novel technologies for rapid measurement of proteins in vivo and ex vivo. The HSPs are compared to other proposed small molecule biomarkers for detection of CNS injury and to other methods of detecting brain and spinal cord ischemia in real time. While other biomarkers may be of use in prognosis and in design of appropriate therapies, none appears to be as rapid as the HSPs; therefore, no other measurement appears to be of use in the immediate detection of ongoing severe ischemia with the intention to immediately intervene to reduce the severity or risk of permanent damage.

Basics of standardization and calibration in cytometry--a review

Standardization, calibration, and controls (negative and positive controls) are essential for quality assurance. Cytometers are capable of reliable and repeatable cellular analyses. However, a prerequisite is instrument calibration and standardized preanalytics. Calibration is often done by beads. Beads are available for different quality control applications, e.g. calibration of size and measuring scale, compensation, absolute cell counting, and laser alignment. Results can be standardized by converting MFI values into MESF or ABC values. Standardized data allow comparison of experiments over a long period of time and between different instruments and laboratories. Alterations in the sensitivity of the cytometer can be detected by routinely performing quality control. The process of quality assurance quantifies and helps manage the variance from the desired value. Results can thus be compared objectively with those of other laboratories. Standardization is the basis of cytometry and a prerequisite for obtaining reliable data.