Search

Background: Brain injury often results in high mortality rates and significant sequelae following severe heatstroke (HS). Neuroinflammation aggravates HS-induced brain injury, yet the involvement of microglia in heat-induced neuroinflammation deserves further investigation., Methods: Our study investigated activation status, phenotype markers, production of pro-inflammatory cytokine and reactive oxygen species (ROS) of microglia both in vitro and in vivo under HS. Utilizing high-throughput sequencing, we identified SIRT1 as a potential modulator of microglia phenotype, and observed that SIRT1 alleviated severe heatstroke-induced brain injury following intraperitoneal administration of the SIRT1 agonist SRT-1720 and the inhibitor selisistat. Additionally, the effects of SRT-1720 and selisistat on mitochondrial dynamics and microglial phenotype transition were examined in BV2 cells in vitro., Results: Heatstroke promotes microglia activation, as evidenced by the increased production of pro-inflammatory cytokine and reactive oxygen species. High-throughput sequencing revealed elevated expression of SIRT1 in BV2 cells under HS. Upon inhibition of SIRT1 expression, there was a corresponding increase in pro-inflammatory cytokine, iNOS, and ROS expression in BV2 cells. In vivo experiments with the SIRT1 agonist SRT-1720 showed a mitigation of neuron injury under HS, as assessed by Nissl and HE staining. Activation of SIRT1 was associated with a reduction in mitochondrial injury and a decrease in the phosphorylation of mitochondrial fission protein Drp1 ser616 . Furthermore, the heat-induced activation of microglia was reversed by the Drp1 inhibitor, Mdivi., Conclusions: Our findings provided evidence that SIRT1 played a crucial role in inhibiting heat stress-induced microglial activation. By suppressing the phosphorylation of mitochondrial fission protein Drp1, SIRT1 contributed to the reduction of neuroinflammation and severity of heatstroke-induced brain injury., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests, (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

With the increasing frequency of global heatwaves, the incidence of heatstroke (HS) is significantly rising. The liver plays a crucial role in metabolism and is an organ highly sensitive to temperature. Acute liver injury (ALI) frequently occurs in patients with HS, yet the exact mechanisms driving ALI in HS are still unknown. In this basic study, we investigated the specific molecular mechanisms by which cytosolic phospholipase A2 (cPLA2) mediates ferroptosis, contributing to the development of ALI following HS. We utilized a mouse model of HS and divided the mice into healthy control and HS groups for a series of experiments. Firstly, we assessed oxidative damage markers in tissues and cells, as well as ferroptosis biomarkers. Additionally, we conducted a non-targeted metabolomics analysis to validate the role of key enzymes in metabolism and the ferroptosis pathway. Our results indicated that ferroptosis contributed to the progression of ALI after HS. Administering the ferroptosis inhibitor liproxstatin-1 (10 mg/kg) post-HS onset significantly inhibits HS-induced ALI progression. Mechanistically, heatstroke triggered cPLA2 activation and increased the levels of its metabolic product, arachidonic acid, thereby further promoted the occurrence of ferroptosis. Furthermore, heatstroke mediated cPLA2 activation might involve enhancing transient receptor potential vanilloid subtype 1 (TRPV1) receptor function. Overall, these results highlighted the critical role that cPLA2-mediated ferroptosis plays in the development of ALI following HS, indicating that inhibiting cPLA2 may present a novel therapeutic approach to prevent ALI after HS by limiting liver cell death., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Objective: To investigate the role of Parkin overexpression-induecd mitophagy in alleviating acute lung injury of exertional heat stroke(EHS) rats., Methods: Eighty SD rats were divided into four groups: Control group (CON group), Control Parkin overexpression group (CON + Parkin group), exertional heat stroke group (EHS group), and exertional heat stroke Parkin overexpression group (EHS + Parkin group). Adeno-associated virus carrying the Parkin gene was intravenously injected into the rats to overexpress Parkin in the lung tissue. An exertional heat stroke rat model was established, and survival curves were plotted. Lung Micro-CT was performed, and lung coefficient and pulmonary microvascular permeability were measured. Enzyme-linked immunosorbent assays(ELISA) were used to determine the levels of interleukin-6(IL-6), interleukin-1β(IL-1β), Tumor necrosis factor-α(TNF-α), and reactive oxygen species(ROS). The morphology of mitochondria in type II epithelial cells of lung tissue was observed using transmission electron microscopy. The apoptosis of lung tissue, the level of mitophagy, and the co-localization of Pink1 and Parkin were determined using immunofluorescence. The expression of Pink1, Parkin, MFN2, PTEN-L, PTEN, p62, and microtubule associated protein 1 light chain 3 (LC3) in rat lung tissue was measured by western blot., Results: Compared with the CON group, there were more severe lung injury and more higher levels of IL-6, IL-1β, TNF-α in EHS rats. Both of the LC3-II/LC3-I ratio and the co-localization of LC3 and Tom20 in the lung tissue of EHS rats decreased. Compared with the EHS group, the survival rate of rats in the EHS + Parkin overexpression group was significantly increased, lung coefficient and pulmonary microvascular permeability were reduced, and pathological changes such as exudation and consolidation were significantly alleviated. The levels of IL-6, IL-1β, TNF-α, and ROS were significantly decreased; the degree of mitochondrial swelling in type II alveolar epithelial cells was reduced, and no vacuolization was observed. Lung tissue apoptosis was reduced, and the colocalization fluorescence of Pink1 and Parkin, as well as LC3 and Tom20, were increased. The expression of Parkin and LC3-II/LC3-I ratio in lung tissue were both increased, while the expression of P62, Pink1, MFN2, and PTEN-L was decreased., Conclusion: Pink1/Parkin-mediated mitophagy dysfunction is one of the mechanisms underlying acute lung injury in rats with EHS, and activation of Parkin overexpression induced-mitophagy can alleviate acute lung injury caused by EHS., (© 2024. The Author(s).)

HSO 3 - is an important reactive sulfur species that maintains the normal physiological activities of living organisms and participates in a variety of redox homeostatic processes. It has been found that changes in HSO 3 - levels is closely related to the heat stroke phenomenon of the organism. Heat stroke causes damage to normal cells, which in turn causes damage to the body and even death. It is crucial to accurately monitor and track the physiological behavior of HSO 3 - during heat stroke. Herein, a ratiometric multifunctional fluorescent probe DRM-SO 2 with dual-targeting ability to rapidly and precisely recognize HSO 3 - being constructed based on the FRET mechanism. DRM-SO 2 has extra Large Stokes shift (216 nm), very high sensitivity (DL = 12.2 nM), fast response time and good specificity. When DRM-SO 2 undergoes Michael addition with HSO 3 - , the fluorescence emission peak was blue-shifted from 616 nm to 472 nm, and a clear ratiometric signal appeared. The interaction between lysosomes and mitochondria in maintaining cellular homeostasis was investigated by the dual-targeting ability of the probe using HSO 3 - as a mediator. DRM-SO 2 achieved successful targeting and real-time monitoring of exogenous and endogenous HSO 3 - in the cells. More importantly, imaging experiments in heat stroke mice revealed high HSO 3 - expression in intestinal tissues. This provides new ideas and research tools for early prevention of heat stroke-induced diseases such as intestinal injuries. In addition, the semi-quantitative monitoring experiments for paper-based visualization of HSO 3 - make the probe promising for the design of portable detectors., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2024 Elsevier B.V. All rights reserved.)

With global warming, extreme environmental heat is becoming a social issue of concern, which can cause adverse health results including heatstroke (HS). Severe heat stress is characterized by cell death of direct heat damage, excessive inflammatory responses, and coagulation disorders that can lead to multiple organ dysfunction (MODS) and even death. However, the significant pathophysiological mechanism and treatment of HS are still not fully clear. Various modes of cell death, including apoptosis, pyroptosis, ferroptosis, necroptosis and PANoptosis are involved in MODS induced by heatstroke. In this review, we summarized molecular mechanism, key transcriptional regulation as for HSF1, NRF2, NF-κB and PARP-1, and potential therapies of cell death resulting in CNS, liver, intestine, reproductive system and kidney injury induced by heat stress. Understanding the mechanism of cell death provides new targets to protect multi-organ function in HS., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Hypoxia-induced inflammation and apoptosis are important pathophysiological features of heat stroke-induced acute kidney injury (HS-AKI). Hypoxia-inducible factor (HIF) is a key protein that regulates cell adaptation to hypoxia. HIF-prolyl hydroxylase inhibitor (HIF-PHI) stabilizes HIF to increase cell adaptation to hypoxia. Herein, we reported that HIF-PHI pretreatment significantly improved renal function, enhanced thermotolerance, and increased the survival rate of mice in the context of HS. Moreover, HIF-PHI could alleviate HS-induced mitochondrial damage, inflammation, and apoptosis in renal tubular epithelial cells (RTECs) by enhancing mitophagy in vitro and in vivo. By contrast, mitophagy inhibitors Mdivi-1, 3-MA, and Baf-A1 reversed the renoprotective effects of HIF-PHI. Mechanistically, HIF-PHI protects RTECs from inflammation and apoptosis by enhancing Bcl-2 adenovirus E18 19-kDa-interacting protein 3 (BNIP3)-mediated mitophagy, while genetic ablation of BNIP3 attenuated HIF-PHI-induced mitophagy and abolished HIF-PHI-mediated renal protection. Thus, our results indicated that HIF-PHI protects renal function by upregulating BNIP3-mediated mitophagy to improve HS-induced inflammation and apoptosis of RTECs, suggesting HIF-PHI as a promising therapeutic agent to treat HS-AKI., (© 2024 The Author(s). The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Background: The effects of heat acclimation (HA) on the hypothalamus after exertional heatstroke (EHS) and the specific mechanism have not been fully elucidated, and this study aimed to address these questions., Methods: In the present study, rats were randomly assigned to the control, EHS, HA, or HA + EHS groups (n = 9). Hematoxylin and eosin (H&E) staining was used to examine pathology. Tandem mass tag (TMT)-based proteomic analysis was utilized to explore the impact of HA on the protein expression profile of the hypothalamus after EHS. Bioinformatics analysis was used to predict the functions of the differentially expressed proteins. The differential proteins were validated by western blotting. An enzyme-linked immunosorbent assay was used to measure the expression levels of inflammatory cytokines in the serum., Results: The H&E staining (n = 5) results revealed that there were less structural changes in hypothalamus in the HA + EHS group compared with the EHS group. Proteomic analysis (n = 4) revealed that proinflammatory proteins such as argininosuccinate synthetase (ASS1), high mobility group protein B2 (HMGB2) and vimentin were evidently downregulated in the HA + EHS group. The levels of interleukin (IL)-1β, IL-1, and IL-8 were decreased in the serum samples (n = 3) from HA + EHS rats., Conclusions: HA may alleviate hypothalamic damage caused by heat attack by inhibiting inflammatory activities, and ASS1, HMGB2 and vimentin could be candidate factors involved in the exact mechanism., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). Published by IMR Press.)

Heat stroke induced cerebral damage via neuroinflammation. This study aimed to approach whether heat stress would promote NOD-like receptor protein 3 (NLRP3) inflammasome via reactive oxygen species (ROS). The mice were randomly divided into the sham group, the heat stress group, and the heat stress + TEMPOL (ROS scavenger) group. And the NLRP3 -/- mice were applied and divided into the NLRP3 -/-  + sham group and the NLRP3 -/-  + heat stress group. Furthermore, the BV2 cells were divided into four groups following the intervention measures: the heat stress + TEMPOL group, the heat stress + Z-VAD-FMK (caspase-1 inhibitor) group, the heat stress group, and the control group. ROS levels were examined. The expression levels of NLRP3, caspase-1, IL-1β, and IL-18 were detected by western blotting and double immunofluorescence. We found that heat stress attack induced excessive ROS in microglia and subsequently activated NLRP3 inflammasome in both mice and BV2 cells. When ROS scavenged, the expression level of NLRP3 was downregulated. Furthermore, with NLRP3 inflammasome activation, the expression levels of caspase-1, IL-1β, and IL-18 were increased. In NLRP3 -/- mice, however, the caspase-1, IL-1β, and IL-18 were significantly declined. Further experiments showed that pretreatment of caspase-1 inhibitor decreased the expression levels of IL-1β and IL-18. These results suggest that heat stress attack caused neuroinflammation via excessive ROS activating the NLRP3 inflammasome in microglia cells., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Endothelial barrier disruption plays a key role in the pathophysiology of heat stroke (HS). Knockout of DNAJA1 (DNAJA1‑KO) is thought to be protective against HS based on a genome‑wide CRISPR‑Cas9 screen experiment. The present study aimed to illustrate the function of DNAJA1‑KO against HS in human umbilical vein endothelial cells. DNAJA1‑KO cells were infected using a lentivirus to investigate the role of DNAJA1‑KO in HS‑induced endothelial barrier disruption. It was shown that DNAJA1‑KO could ameliorate decreased cell viability and increased cell injury, according to the results of Cell Counting Kit‑8 and lactate dehydrogenase assays. Moreover, HS‑induced endothelial cell apoptosis was inhibited by DNAJA1‑KO, as indicated by Annexin V‑FITC/PI staining and cleaved‑caspase‑3 expression using flow cytometry and western blotting, respectively. Furthermore, the endothelial barrier function, as measured by transepithelial electrical resistance and FITC‑Dextran, was sustained during HS. DNAJA1‑KO was not found to have a significant effect on the expression and distribution of cell junction proteins under normal conditions without HS. However, DNAJA1‑KO could effectively protect the HS‑induced decrease in the expression and distribution of cell junction proteins, including zonula occludens‑1, claudin‑5, junctional adhesion molecule A and occludin. A total of 4,394 proteins were identified using proteomic analysis, of which 102 differentially expressed proteins (DEPs) were activated in HS‑induced wild‑type cells and inhibited by DNAJA1‑KO. DEPs were investigated by enrichment analysis, which demonstrated significant enrichment in the 'calcium signaling pathway' and associations with vascular‑barrier regulation. Furthermore, the 'myosin light‑chain kinase (MLCK)‑MLC signaling pathway' was proven to be activated by HS and inhibited by DNAJA1‑KO, as expected. Moreover, DNAJA1‑KO mice and a HS mouse model were established to demonstrate the protective effects on endothelial barrier in vivo . In conclusion, the results of the present study suggested that DNAJA1‑KO alleviates HS‑induced endothelial barrier disruption by improving thermal tolerance and suppressing the MLCK‑MLC signaling pathway.

Background: The incidence of exertional heat stroke (EHS) escalates during periods of elevated temperatures, potentially leading to persistent cognitive impairment postrecovery. Currently, effective prophylactic or therapeutic measures against EHS are nonexistent., Methods: The selection of days 14 and 23 postinduction for detailed examination was guided by TEM of neuronal cells and HE staining of intestinal villi and the hippocampal regions. Fecal specimens from the ileum and cecum at these designated times were analyzed for changes in gut microbiota and metabolic products. Bioinformatic analyses facilitated the identification of pivotal microbial species and metabolites. The influence of supplementing these identified microorganisms on behavioral outcomes and the expression of functional proteins within the hippocampus was subsequently assessed., Results: TEM analyses of neurons, coupled with HE staining of intestinal villi and the hippocampal region, indicated substantial recovery in intestinal morphology and neuronal injury on Day 14, indicating this time point for subsequent microbial and metabolomic analyses. Notably, a reduction in the Lactobacillaceae family, particularly Lactobacillus murinus, was observed. Functional annotation of 16S rDNA sequences suggested diminished lipid metabolism and glycan biosynthesis and metabolism in EHS models. Mice receiving this intervention (EHS + probiotics group) exhibited markedly reduced cognitive impairment and increased expression of BDNF/TrKB pathway molecules in the hippocampus during behavioral assessment on Day 28., Conclusion: Probiotic supplementation, specifically with Lactobacillus spp., appears to mitigate EHS-induced cognitive impairment, potentially through the modulation of the BDNF/TrKB signaling pathway within the hippocampus, illustrating the therapeutic potential of targeting the gut-brain axis., (© 2024. The Author(s).)

Isorhamnetin is a natural flavonoid compound, rich in brass, alkaloids, and sterols with a high medicinal value. This study investigated the effects of isorhamnetin on liver injury and oxidative and inflammatory responses in heat-stroke-affected rats in a dry-heat environment. Fifty Sprague Dawley rats were randomly divided into five groups: normal temperature control (NC, saline), dry-heat control (DHC, saline), low-dose isorhamnetin-pretreated (L-AS, 25 mg/Kg), medium-dose isorhamnetin-pretreated (M-AS, 50 mg/Kg), and high-dose isorhamnetin-pretreated (H-AS, 100 mg/Kg) group. Saline was administered to the NC and DHC groups and corresponding concentrations of isorhamnetin were administered to the remaining three groups for 1 week. Blood and liver tissue were analyzed for oxidative stress and inflammation. The liver histopathological injury score, serum liver enzyme (alanine transaminase, aspartate transaminase, and lactate dehydrogenase), liver oxidative stress index (superoxide dismutase [SOD], catalase [CAT], and malondialdehyde), and inflammation index (tumor necrosis factor α [TNF-α], interleukin [IL]-1β, IL-6, and lipopolysaccharides) were significantly higher in the DHC group than in the NC group (P < 0.05). These index values in the L-AS, M-AS, and H-AS groups were significantly lower than those in the DHC group (P < 0.05). The index values decreased significantly with an increase in the concentration of isorhamnetin (P < 0.05), while the index values of CAT and SOD showed the opposite tendency (P < 0.05). The expression of liver tissue nuclear factor kappa B (NF-κB), caspase-3, and heat shock protein (HSP-70) was higher in the DHC group than in the NC group (P < 0.05). Comparison between the isorhamnetin and DHC groups revealed that the expression of NF-кB and caspase-3 was decreased, while that of HSP-70 continued to increase (P < 0.05). The difference was significant for HSP-70 among all the isorhamnetin groups (P < 0.05); however, the NF-кB and caspase-3 values in the L-AS and H-AS groups did not differ. In summary, isorhamnetin has protective effects against liver injury in heat-stroke-affected rats. This protective effect may be related to its activities concerning antioxidative stress, anti-inflammatory response, inhibition of NF-кB and caspase-3 expression, and enhancement of HSP-70 expression., (© 2024. The Author(s).)

Background and Objective: Exertional heatstroke (EHS) mainly occurs in healthy young people with rapid onset and high mortality. EHS immune disorders can cause systemic inflammatory responses and multiple organ failure; however, the underlying mechanisms remain unclear. As high mobility group box 1 (HMGB1) is a prototypical alarmin that activates inflammatory and immune responses, this study aimed to investigate the effect and mechanism of HMGB1 in the pathogenesis of EHS., Methods: Peripheral blood mononuclear cell (PBMC) transcriptome sequencing of healthy volunteers, classical heatstroke patients, and EHS patients was performed. A mouse model of EHS was established and murine tissue damage was evaluated by H&E staining. HMGB1 localization and release were visualized using immunofluorescence staining. Human umbilical vein endothelial cells (HUVECs) and THP-1 cells were co-cultured to study the effects of HMGB1 on macrophages. A neutralizing anti-HMGB1 antibody was used to evaluate the efficacy of EHS treatment in mice., Results: Plasma and serum HMGB1 levels were significantly increased in EHS patients or mice. EHS-induced endothelial cell pyroptosis promoted HMGB1 release in mice. HMGB1 derived from endothelial cell pyroptosis enhanced macrophage pyroptosis, resulting in immune disorders under EHS conditions. Administration of anti-HMGB1 markedly alleviated tissue injury and systemic inflammatory responses after EHS., Conclusions: The release of HMGB1 from pyroptotic endothelial cells after EHS promotes pyroptosis of macrophages and systemic inflammatory response, and HMGB1-neutralizing antibody therapy has good application prospects for EHS.

Purpose: The incidence of heatstroke (HS) is not particularly high; however, once it occurs, the consequences are serious. It is reported that calcitonin gene-related peptide (CGRP) is protective against brain injury in HS rats, but detailed molecular mechanisms need to be further investigated. In this study, we further explored whether CGRP inhibited neuronal apoptosis in HS rats via protein kinase A (PKA)/p-cAMP response element-binding protein (p-CREB) pathway., Methods: We established a HS rat model in a pre-warmed artificial climate chamber with a temperature of (35.5 ± 0.5) °C and a relative humidity of 60% ± 5%. Heatstress was stopped once core body temperature reaches above 41 °C. A total of 25 rats were randomly divided into 5 groups with 5 animals each: control group, HS group, HS+CGRP group, HS+CGRP antagonist (CGRP8-37) group, and HS+CGRP+PKA/p-CREB pathway blocker (H89) group. A bolus injection of CGRP was administered to each rat in HS+CGRP group, CGRP8-37 (antagonist of CGRP) in HS+CGRP8-37 group, and CGRP with H89 in HS+CGRP+H89 group. Electroencephalograms were recorded and the serum concentration of S100B, neuron-specific enolase (NSE), neuron apoptosis, activated caspase-3 and CGRP expression, as well as pathological morphology of brain tissue were detected at 2 h, 6 h, and 24 h after HS in vivo. The expression of PKA, p-CREB, and Bcl-2 in rat neurons were also detected at 2 h after HS in vitro. Exogenous CGRP, CGRP8-37, or H89 were used to determine whether CGRP plays a protective role in brain injury via PKA/p-CREB pathway. The unpaired t-test was used between the 2 samples, and the mean ± SD was used for multiple samples. Double-tailed p < 0.05 was considered statistically significant., Results: Electroencephalogram showed significant alteration of θ (54.50 ± 11.51 vs. 31.30 ± 8.71, F = 6.790, p = 0.005) and α wave (16.60 ± 3.21 vs. 35.40 ± 11.28, F = 4.549, p = 0.020) in HS group compared to the control group 2 h after HS. The results of triphosphate gap terminal labeling (TUNEL) showed that the neuronal apoptosis of HS rats was increased in the cortex (9.67 ± 3.16 vs. 1.80 ± 1.10, F = 11.002, p = 0.001) and hippocampus (15.73 ± 8.92 vs. 2.00 ± 1.00, F = 4.089, p = 0.028), the expression of activated caspase-3 was increased in the cortex (61.76 ± 25.13 vs. 19.57 ± 17.88, F = 5.695, p = 0.009) and hippocampus (58.60 ± 23.30 vs. 17.80 ± 17.62, F = 4.628, p = 0.019); meanwhile the expression of serum NSE (5.77 ± 1.78 vs. 2.35 ± 0.56, F = 5.174, p = 0.013) and S100B (2.86 ± 0.69 vs. 1.35 ± 0.34, F = 10.982, p = 0.001) were increased significantly under HS. Exogenous CGRP decreased the concentrations of NSE and S100B, and activated the expression of caspase-3 (0.41 ± 0.09 vs. 0.23 ± 0.04, F = 32.387, p < 0.001) under HS; while CGRP8-37 increased NSE (3.99 ± 0.47 vs. 2.40 ± 0.50, F = 11.991, p = 0.000) and S100B (2.19 ± 0.43 vs. 1.42 ± 0.30, F = 4.078, p = 0.025), and activated the expression caspase-3 (0.79 ± 0.10 vs. 0.23 ± 0.04, F = 32.387, p < 0.001). For the cell experiment, CGRP increased Bcl-2 (2.01 ± 0.73 vs. 2.15 ± 0.74, F = 8.993, p < 0.001), PKA (0.88 ± 0.08 vs. 0.37 ± 0.14, F = 20.370, p < 0.001), and p-CREB (0.87 ± 0.13 vs. 0.29 ± 0.10, F = 16.759, p < 0.001) levels; while H89, a blocker of the PKA/p-CREB pathway reversed the expression., Conclusions: CGRP can protect against HS-induced neuron apoptosis via PKA/p-CREB pathway and reduce activation of caspase-3 by regulating Bcl-2. Thus CGRP may be a new target for the treatment of brain injury in HS., (Copyright © 2023 Chinese Medical Association. Production and hosting by Elsevier B.V. All rights reserved.)