Dexamethasone improves heat stroke-induced multiorgan dysfunction and damage in rats

Jiawei Bai-Hu-decoction ameliorated heat stroke-induced brain injury by inhibiting TLR4/NF-κB signal and mitophagy of glial cell

ETHNOPHARMACOLOGICAL RELEVANCE

Jiawei Bai-Hu-Decoction (JWBHD), a prescription formulated with seven traditional Chinese medicinal material has demonstrated clinical efficacy in mitigating brain injury among heat stroke (HS) patients.

AIM OF THE STUDY

This study aimed to evaluate the therapeutic efficacy of JWBHD on rat model of HS and to explore its therapeutic mechanisms by integrating network pharmacology and pharmacodynamic methodologies, which major components were analyzed by using UPLC-MS/MS.

MATERIALS AND METHODS

The network pharmacology analysis was firstly conducted to predict the potential active ingredients and therapeutic targets of JWBHD. The anti-HS effectiveness of JWBHD was then evaluated on rats experienced HS. Rat brain tissues were harvested for a comprehensive array of experiments, including Western blot, PCR, H&E staining, Nissl staining, ELISA, transmission electron microscope, flow cytometry and immunofluorescence to validate the protective effects of JWBHD against HS-induced brain damage. Furthermore, the inhibitory effects of JWBHD on TLR4/NF-κB signal and mitophagy of glial were further verified on HS-challenged F98 cell line. Finally, the chemical compositions of the water extract of JWBHD were analyzed by using UPLC-MS/MS.

RESULTS

Network pharmacology has identified fifty core targets and numerous HS-related signaling pathways as potential therapeutic targets of JWBHD. Analysis of protein-protein interaction (PPI) and GO suggests that JWBHD may suppress HS-induced inflammatory signals. In experiments conducted on HS-rats, JWBHD significantly reduced the core temperature, restored blood pressure and alleviated neurological defect. Furthermore, JWBHD downregulated the counts of white blood cells and monocytes, decreased the levels of inflammatory cytokines such as IL-1β, IL-6 and TNF-α in peripheral blood, and suppressed the expression of TLR4 and NF-κB in the cerebral cortex of HS-rats. Besides, JWBHD inhibited the apoptosis of cortical cells and mitigated the damage to the cerebral cortex in HS group. Conversely, overactive mitophagy was observed in the cerebral cortex of HS-rats. However, JWBHD restored the mitochondrial membrane potential and downregulated expressions of mitophagic proteins including Pink1, Parkin, LC3B and Tom20. JWBHD reduced the co-localization of Pink1 and GFAP, a specific marker of astrocytes in the cerebral cortex of HS-rats. In addition, the inhibitory effect of JWBHD on TLR4/NF-κB signaling and overactive mitophagy were further confirmed in F98 cells. Finally, UPLC-MS/MS analysis showed that the main components of JWBHD include isoliquiritigenin, liquiritin, dipotassium glycyrrhizinate, ginsenoside Rb1, ginsenoside Re, etc. CONCLUSIONS: JWBHD protected rats from HS and prevented HS-induced damage in the cerebral cortex by suppressing TLR4/NF-κB signaling and mitophagy of glial.

Catalpol alleviates heat stroke-induced liver injury in mice by downregulating the JAK/STAT signaling pathway

BACKGROUND

Heat stroke (HS) generated liver injury is a lethal emergency that occurs when the body is exposed to temperatures up to 40 °C for a few hours.

PURPOSE

This study aimed to evaluate the therapeutic prospects of Catalpol (CA) from the blood-cooling herb Rehamanniae Radix on liver injury by HS.

STUDY DESIGN AND METHODS

A murine HS model (41 ± 0.5 °C, 60 ± 5 % relative humidity) and two cell lines (lipopolysaccharide + 42 °C) were used to assess the protective effects of CA on physiological, pathological, and biochemical features in silico, in vivo, and in vitro.

RESULTS

CA treatment significantly improved survival rates in vivo and cell viability in vitro over those of the untreated group. Additionally, CA treatment reduced core body temperature, enhanced survival time, and mitigated liver tissue damage. Furthermore, CA treatment also reduced the activities of AST and ALT enzymes in the serum samples of HS mice. Molecular docking analysis of the 28 overlapping targets between HS and CA revealed that CA has strong binding affinities for the top 15 targets. These targets are primarily involved in nine major signaling pathways, with the JAK-STAT pathway being highly associated with the other eight pathways. Our findings also indicate that CA treatment significantly downregulated the expression of proinflammatory cytokines both in vivo and in vitro while upregulating the expression of anti-inflammatory cytokines. Moreover, CA treatment reduced the levels of JAK2, phospho-STAT5, and phospho-STAT3 both in vivo and in vitro, which is consistent with its inhibition of the apoptotic markers p53, Bcl2, and Bax.

CONCLUSIONS

Heat stroke-induced liver injury was inhibited by CA through the downregulation of JAK/STAT signaling.

Heat stroke: Pathogenesis, diagnosis, and current treatment

Recently, the incidence of heat-related illnesses has exhibited a steadily upward trend, which is closely associated with several environmental factors such as climate change and air pollution. The progression of heat-related illnesses is a continuous process and can progress to the terminal period when it transforms into heat stroke, the most severe form. Heat stroke is markedly by a core body temperature above 40°C and central nervous system dysfunction. Current knowledge suggests that the pathogenesis of heat stroke is complex and varied, including inflammatory response, oxidative stress, cell death, and coagulation dysfunction. This review consolidated recent research progress on the pathophysiology and pathogenesis of heat stroke, with a focus on the related molecular mechanisms. In addition, we reviewed common strategies and sorted out the drugs in various preclinical stages for heat stroke, aiming to offer a comprehensive research roadmap for more in-depth researches into the mechanisms of heat stroke and the reduction in the mortality of heat stroke in the future.

NLRP3 ablation enhances tolerance in heat stroke pathology by inhibiting IL-1β-mediated neuroinflammation

Background

Patients with prior illness are more vulnerable to heat stroke-induced injury, but the underlying mechanism is unknown. Recent studies suggested that NLRP3 inflammasome played an important role in the pathophysiology of heat stroke.

Methods

In this study, we used a classic animal heat stroke model. Prior infection was mimicked by using lipopolysaccharide (LPS) or lipoteichoic acid (LTA) injection before heat stroke (LPS/LTA 1 mg/kg). Mice survival analysis curve and core temperature (T_C) elevation curve were produced. NLRP3 inflammasome activation was measured by using real-time PCR and Western blot. Mice hypothalamus was dissected and neuroinflammation level was measured. To further demonstrate the role of NLRP3 inflammasome, Nlrp3 knockout mice were used. In addition, IL-1β neutralizing antibody was injected to test potential therapeutic effect on heat stroke.

Results

Prior infection simulated by LPS/LTA injection resulted in latent inflammation status presented by high levels of cytokines in peripheral serum. However, LPS/LTA failed to cause any change in animal survival rate or body temperature. In the absence of LPS/LTA, heat treatment induced heat stroke and animal death without significant systemic or neuroinflammation. Despite a decreased level of IL-1β in hypothalamus, Nlrp3 knockout mice demonstrated no survival advantage under mere heat exposure. In animals with prior infection, their heat tolerance was severely impaired and NLRP3 inflammasome induced neuroinflammation was detected. The use of Nlrp3 knockout mice enhanced heat tolerance and alleviated heat stroke-induced death by reducing mice hypothalamus IL-1β production with prior infection condition. Furthermore, IL-1β neutralizing antibody injection significantly extended endotoxemic mice survival under heat stroke.

Conclusions

Based on the above results, NLRP3/IL-1β induced neuroinflammation might be an important mechanistic factor in heat stroke pathology, especially with prior infection. IL-1β may serve as a biomarker for heat stroke severity and potential therapeutic method.

Heat precondition is a potential strategy to combat hepatic injury triggered by severe heat stress

AIM

Environmental heat stress alters physiological and biochemical functions which leads to multiorgan dysfunction including severe hepatic injury in animals. We hypothesize that heat preconditioning can be potential intervention in combating heat illnesses.

MAIN METHODS

Sprague Dawley rats were exposed to moderate heat stress, severe heat stress and heat preconditioning in heat simulation chamber. Mean arterial pressure, heart rate, skin and core temperature were monitored in pre and post heat exposed animals. After stress exposure, blood for hemodynamic and liver tissue for liver function tests, oxidative stress, inflammatory variables and structural studies were collected from rats. Hepatic mitochondria were isolated to study the key structural alterations and functional changes by transmission electron microscopy.

KEY FINDINGS

The effect of heat precondition shows improvement in time to attain the core temperature, weight loss, blood pressure and heart rate in rats. Results exhibited decreased levels of liver function tests, elevated levels of free radicals and inflammatory cytokines in heat exposed liver as compared with heat preconditioned animals. Expression levels of mitochondrial heat shock protein 60, superoxide dismutase 1 and uncoupling protein 1 along with activity of electron transport chain complexes I-V were examined and found to be increased in heat preconditioned as compared to heat stressed animals. Morphological studies of liver parenchyma demonstrated reduction in structural deterioration of hepatic lobules and restoration of mitochondrial structural integrity in heat preconditioned rats.

SIGNIFICANCE

Present study suggests that heat preconditioning intervention plays a crucial role in protection against heat induced hepatic injury in animals.

The efficacy of steroids in reducing morbidity and mortality from extreme hyperthermia and heatstroke-A systematic review

Severe hyperthermia from classical or exertional heatstroke, or from drug ingestion or other noninfective pyrogens, is associated with a high mortality and morbidity. A systemic pro-inflammatory response occurs during heatstroke, characterized by elevated cytokines with endotoxemia from elevated lipopolysaccharide (LPS) levels. Corticosteroids reduce LPS and cytokine levels, suggesting that they may improve outcome. A systematic review searching Embase, MEDLINE, and PubMed from the earliest date available until September 2019 was conducted, according to the PRISMA guidelines, with five papers identified. In four studies, systemic steroids administered before or at the onset of heat stress improved mortality or reduced organ dysfunction. Survival time was greatest when steroid administration preceded heat stress. In one study, a nonsignificant increase in mortality was seen. A dose response was observed, with higher doses extending survival time. Animal studies suggest that steroids improve mortality and/or organ dysfunction after an episode of heat stress or extreme hyperthermia.

The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures

Exertional heat stroke (EHS) is a life-threatening medical condition involving thermoregulatory failure and is the most severe condition along a continuum of heat-related illnesses. Current EHS policy guidance principally advocates a thermoregulatory management approach, despite growing recognition that gastrointestinal (GI) microbial translocation contributes to disease pathophysiology. Contemporary research has focused to understand the relevance of GI barrier integrity and strategies to maintain it during periods of exertional-heat stress. GI barrier integrity can be assessed non-invasively using a variety of in vivo techniques, including active inert mixed-weight molecular probe recovery tests and passive biomarkers indicative of GI structural integrity loss or microbial translocation. Strenuous exercise is strongly characterised to disrupt GI barrier integrity, and aspects of this response correlate with the corresponding magnitude of thermal strain. The aetiology of GI barrier integrity loss following exertional-heat stress is poorly understood, though may directly relate to localised hyperthermia, splanchnic hypoperfusion-mediated ischemic injury, and neuroendocrine-immune alterations. Nutritional countermeasures to maintain GI barrier integrity following exertional-heat stress provide a promising approach to mitigate EHS. The focus of this review is to evaluate: (1) the GI paradigm of exertional heat stroke; (2) techniques to assess GI barrier integrity; (3) typical GI barrier integrity responses to exertional-heat stress; (4) the aetiology of GI barrier integrity loss following exertional-heat stress; and (5) nutritional countermeasures to maintain GI barrier integrity in response to exertional-heat stress.

Sex-dependent responses to exertional heat stroke in mice

With increasing participation of females in endurance athletics and active military service, it is important to determine if there are inherent sex-dependent susceptibilities to exertional heat injury or heat stroke. In this study we compared responses of male and female adult mice to exertional heat stroke (EHS). All mice were instrumented for telemetry core temperature measurements and were exercise-trained for 3 wk before EHS. During EHS, environmental temperature was 37.5°C (35% RH) while the mice ran on a forced running wheel, using incremental increases in speed. The symptom-limited endpoint was loss of consciousness, occurring at ~42.2°C core temperature. Females ran greater distances (623 vs. 346 m, P < 0.0001), reached faster running speeds (7.2 vs. 5.1 m/min, P < 0.0001), exercised for longer times (177 vs. 124 min, P < 0.0001), and were exposed to greater internal heat loads (240 vs.160°C·min; P < 0.0001). Minimum Tc during hypothermic recovery was ~32.0°C in both sexes. Females lost 9.2% body weight vs. 7.5% in males ( P < 0.001). Females demonstrated higher circulating corticosterone (286 vs 183 ng/ml, P = 0.001, at 3 h), but most plasma cytokines were not different. A component of performance in females could be attributed to greater body surface area/mass and greater external power performance. However, there were significant and independent effects of sex alone and a crossed effect of "sex × power" on performance. These results demonstrate that female mice have greater resistance to EHS during exercise in hyperthermia and that these effects cannot be attributed solely to body size. NEW & NOTEWORTHY Female mice are surprisingly more resistant to exertional heat stroke than male mice. They run faster and longer and can withstand greater internal heat loads. These changes cannot be fully accounted for by increased body surface/mass ratio in females or on differences in aerobic performance. Although the stress-immune response in males and females was similar, females exhibited markedly higher plasma corticosteroid levels, which were sustained over 14 days of recovery.

Sodium tanshinone IIA sulfonate improves inflammation, aortic endothelial cell apoptosis, disseminated intravascular coagulation and multiple organ damage in a rat heat stroke model

The aim of the present study was to investigate the effects of sodium tanshinone IIA sulfonate (STS) on inflammatory responses, aortic endothelial cell apoptosis, disseminated intravascular coagulation (DIC) and multiple organ damage in an animal model of classic heat stroke (CHS). The rats in the heat stroke (HS) and STS-treated heat stroke (STS-HS) groups were placed into a pre-warmed animal temperature controller (ATC) at 35°C. The moment at which the rectal temperature reached 43.5°C was considered as the time of onset of HS. In the HS groups, the rats were removed from the ATC and allowed to recover at 26°C for 0, 2, 6 or 12 h. In the STS-HS groups, the rats received femoral vein injections of 5–40 mg/kg STS immediately following the onset of HS and were subsequently placed at a temperature of 26°C to recover for 6 h. In the present study, the serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were assessed using ELISA, and the numbers of apoptotic aortic endothelial cells were investigated using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling combined with immunofluorescence. In the HS groups, the serum levels of TNF-α, IL-1β and IL-6, as well as the numbers of apoptotic aortic endothelial cells were increased compared with the normothermic control group. Additionally, the plasma prothrombin time, activated partial thromboplastin time and D-dimer level were significantly increased in the HS group compared with the normothermic control group following recovery for 6 h. By contrast, the platelet count was decreased in the HS group compared with the normothermic control group. The serum levels of creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase were increased and histopathological damage to multiple organs was observed in the HS group following recovery for 6 h. In the STS-HS groups, cytokine levels and apoptotic aortic endothelial cell numbers were reduced compared with the HS group after 6 h recovery. STS (40 mg/kg) treatment additionally improved the serum levels of organ injury indicators and plasma indicators of coagulopathy, and prevented histopathological damage to multiple organs. These findings demonstrated that STS treatment may ameliorate multiple organ damage by attenuating inflammatory responses, aortic endothelial cell apoptosis and DIC in CHS. These results suggested that STS may hold potential as an alternative therapeutic strategy for the treatment of patients with HS.