Effect of heat acclimatization training on inflammatory reaction and multiple organ dysfunction syndrome in patients with exertional heat stroke / 中华危重病急救医学

Objective To investigate the effects of heat acclimatization training on the inflammatory reaction and multiple organ dysfunction syndrome (MODS) in patients with exertional heat stroke (EHS). Methods 600 officers and soldiers from a special team who participated in 5 km armed wild training from June to July 2017 were selected as the research object, while 30 healthy officers and men who did not participate in armed wild training during the same period were selected as normal controls. The officers and soldiers who participated in 5 km armed wild training (ambient temperature > 35 ℃, humidity > 65%, 2-3 times a week for 3 weeks) were divided into heat acclimatization group and non-acclimatization group, with 300 in each group. The heat acclimatization group first took part in the heat acclimatization training of wild or long distance running (the initial temperature was 30 ℃, gradually transferred to the hot time of 37 ℃), 2 hours each time, twice a day, and 5 days a week, for a total of 2 weeks. Venous blood was taken before and after heat acclimatization training, before armed wild training, and after the last training or EHS onset, and the contents of serum interleukin (IL-1β, IL-10), tumor necrosis factor-α (TNF-α) and γ-interferon (IFN-γ) were detected by enzyme linked immunosorbent assay (ELISA). The occurrence of EHS and MODS in EHS patients were recorded. Results There was no significant difference in serum inflammatory factors between the officers and soldiers who participated in the training and the healthy control group before heat training or cross-country training. Compared with those before heat training, IL-1β, TNF-α, IFN-γ were significantly increased in all participants of heat acclimatization training while IL-10 was significantly decreased. For those who experienced premonitory (6 cases) and mild (2 cases) heatstroke during training, they could return to normal without severe heatstroke or EHS within 10-30 minutes after being immediately put in a cool and ventilated place and given anti- heatstroke drugs and other interventions. Compared with those before wild training, the levels of inflammatory factors in the two groups of officers and soldiers also changed after wild training, but the increase or decrease of inflammatory indexes in the heat acclimatization group were significantly smaller than those in the non-acclimatization group [IL-1β (ng/L): 10.65±5.18 vs. 12.13±7.91, TNF-α (ng/L): 14.60±5.79 vs. 16.27±8.52, IFN-γ (ng/L): 13.66±5.43 vs. 15.33±8.71, IL-10 (ng/L):8.22±2.68 vs. 7.13±2.63, all P < 0.05]. During armed wild training, a total of 27 cases of EHS occurred. The incidence of EHS in the heat acclimatization group was significantly lower than that in the non-acclimatization group [2.67% (8/300) vs. 6.33% (19/300), χ2= 4.693, P = 0.030]. In patients with EHS, IL-1β, TNF-α, IFN-γ after wild training in the heat acclimatization group were also significantly lower than those in the non-acclimatization group, and IL-10 was significantly higher [IL-1β (ng/L): 34.50±3.74 vs. 39.53±4.51, TNF-α (ng/L): 43.75±2.87 vs. 46.79±2.66, IFN-γ (ng/L): 40.25±1.75 vs. 46.58±1.92, IL-10 (ng/L): 7.50±2.45 vs. 5.42±1.80, all P < 0.01], and the incidence of MODS and organ involvement of EHS patients in the heat acclimation group were significantly lower than that in the non-acclimatization group [50.00% (4/8) vs. 89.47% (17/19), χ2= 5.075, P = 0.024; 28.13% (9/32) vs. 47.79% (65/136), χ2=4.066, P=0.044]. Conclusion Heat acclimatization training before high strength training in high temperature and humidity environment can effectively reduce the degree of inflammation reaction of EHS, protect the physiological functions of EHS organs, and reduce the incidence of MODS.

Change of MicroRNA let-7b in Serum of Rats with Heat Acclimatization/Heat Stroke and Its Significance / 现代检验医学杂志

Objective To explore the change of microRNA let-7b in heat acclimatization/heat stroke rat models and its relation with HSP70,IL-6,TNF-α,TGF-3 and IL-12,and analyze its clinical significance.Methods 60 male rats with almost the same anal temperature,weight,and weeks' age were selected from Laboratory Animal Center in the Second Military Medical University.They were randomly divided into control,heat acclimatization,heat stroke groups averagely.Heat acclimatization/heat stroke rat models were built in hot climate simulated animal tank,blood was collected from cordis apex and serum was separated.Real-time fluorescent quantitative polymerase chain reaction (qRT-PCR) was used to test microRNA let-7b in serum,enzyme-linked immunosorbent reaction (ELISA) was to measure the protein level of HSP70,IL-6,TNF-α,TGF-β and IL-12 in serum.Kruskal-Wallis H test was used to analyze quantitative data in the three groups,Spearman rank correlation coefficient was used to reveal relation between two variables in heat stroke group.Results M values of miRNA let-7b in control,heat acclimatization,heat stroke groups were 0.99,1.04 and 1.93 separately,Q values were 0.30,0.25 and 0.44 (x2 =38.95,P＜0.001),separately,with statistical significance.The results of pairwise comparison showed no statistical difference in control and heat acclimatization (P＞0.05),but there were differences in control and heat stroke,heat acclimatization and heat stroke groups statistically (P＜0.05).Spearman correlation analysis showed that in heat stroke group,let-7b was positively related with HSP70,TNF-α and IL-6 (rs =0.579,0.498 and 0.609,P＜0.05) with statistical significance.Conclusion miR let-7b might involve in the pathology of heat stroke,it provided a potential biomarker for monitoring patients in high temperature and humidity clinically.

Effect of the Heat-exposure on Peripheral Sudomotor Activity Including the Density of Active Sweat Glands and Single Sweat Gland Output

Tropical inhabitants are able to tolerate heat through permanent residence in hot and often humid tropical climates. The goal of this study was to clarify the peripheral mechanisms involved in thermal sweating pre and post exposure (heat-acclimatization over 10 days) by studying the sweating responses to acetylcholine (ACh), a primary neurotransmitter of sudomotor activity, in healthy subjects (n=12). Ten percent ACh was administered on the inner forearm skin for iontophoresis. Quantitative sudomotor axon reflex testing, after iontophoresis (2 mA for 5 min) with ACH, was performed to determine directly activated (DIR) and axon reflex-mediated (AXR) sweating during ACh iontophoresis. The sweat rate, activated sweat gland density, sweat gland output per single gland activated, as well as oral and skin temperature changes were measured. The post exposure activity had a short onset time (p<0.01), higher active sweat rate [(AXR (p<0.001) and DIR (p<0.001)], higher sweat output per gland (p<0.001) and higher transepidermal water loss (p<0.001) compared to the pre-exposure measurements. The activated sweat rate in the sudomotor activity increased the output for post-exposure compared to the pre-exposure measurements. The results suggested that post-exposure activity showed a higher active sweat gland output due to the combination of a higher AXR (DIR) sweat rate and a shorter onset time. Therefore, higher sudomotor responses to ACh receptors indicate accelerated sympathetic nerve responsiveness to ACh sensitivity by exposure to environmental conditions.

Heat Acclimatization in Hot Summer for Ten Weeks Suppress the Sensitivity of Sweating in Response to Iontophoretically-administered Acetylcholine

To determine the peripheral mechanisms involved in thermal sweating during the hot summers in July before acclimatization and after acclimatization in September, we evaluated the sweating response of healthy subjects (n=10) to acetylcholine (ACh), a primary neurotransmitter involved in peripheral sudomotor sensitivity. The quantitative sudomotor axon reflex test (QSART) measures sympathetic C fiber function after iontophoresed ACh evokes a measurable reliable sweat response. The QSART, at 2 mA for 5 min with 10% ACh, was applied to determine the directly activated (DIR) and axon reflex-mediated (AXR) sweating responses during ACh iontophoresis. The AXR sweat onset-time by the axon reflex was 1.50+/-0.32 min and 1.84+/-0.46 min before acclimatization in July and after acclimatization in September, respectively (p<0.01). The sweat volume of the AXR(1) [during 5 min 10% iontophoresis] by the axon reflex was 1.45+/-0.53 mg/cm2 and 0.98+/-0.24 mg/cm2 before acclimatization in July and after acclimatization in September, respectively (p<0.001). The sweat volume of the AXR(2) [during 5 min post-iontophoresis] by the axon reflex was 2.06+/-0.24 mg/cm2 and 1.39+/-0.32 mg/cm2 before and after acclimatization in July and September, respectively (p<0.001). The sweat volume of the DIR was 5.88+/-1.33 mg/cm2 and 4.98+/-0.94 mg/cm2 before and after acclimatization in July and September, respectively (p<0.01). These findings suggest that lower peripheral sudomotor responses of the ACh receptors are indicative of a blunted sympathetic nerve response to ACh during exposure to hot summer weather conditions.