Therapeutic treatment with ascorbate rescues mice from heat stroke-induced death by attenuating systemic inflammatory response and hypothalamic neuronal damage

Astragaloside IV alleviates heatstroke brain injury and neuroinflammation in male mice by regulating microglial polarization via the PI3K/Akt signaling pathway

Heatstroke is a condition caused by overheating of the body that leads to severe central nervous system dysfunction. Although there have been numerous studies on the pathological process of heatstroke, effective treatment methods are lacking. Astragaloside IV can protect the brain from inflammation and brain damage in various inflammation-related diseases, but it has not yet been used clinically for the treatment of heatstroke. Therefore, the aim of this study was to explore the neuroprotective effect of Astragaloside IV on heatstroke-induced central nervous system damage and its mechanism. Brain injury model under heatstroke was established using artificial climate simulation cabin. By scoring neurological deficits, performing histological and immunofluorescence staining of microglia, and detecting cytokine levels, we determined that Astragaloside IV alleviated brain injury and neuroinflammation. To further explore the potential molecular mechanism, RNA sequencing was performed to investigate the differences in the brain. The results revealed that the PI3K/AKT pathway is involved. In vitro experiments further confirmed that Astragaloside IV can abrogate the phenotypic changes in microglia induced by heatstroke. Moreover, Astragaloside IV promotes the polarization of M2 microglia by activating the PI3K/AKT pathway. In summary, these results indicate that Astragaloside IV alleviates neuroinflammation and brain injury induced by heatstroke through the PI3K/AKT pathway. Astragaloside IV is a commonly used therapeutic agent in the clinic, but its use in the treatment of heatstroke-induced brain injury has not been explored. This study reveals that Astragaloside IV may be a new therapeutic agent for the treatment of heatstroke-induced brain injury.

The mechanisms behind heatstroke-induced intestinal damage

With the frequent occurrence of heatwaves, heatstroke (HS) is expected to become one of the main causes of global death. Being a multi-organized disease, HS can result in circulatory disturbance and systemic inflammatory response, with the gastrointestinal tract being one of the primary organs affected. Intestinal damage plays an initiating and promoting role in HS. Multiple pathways result in damage to the integrity of the intestinal epithelial barrier due to heat stress and hypoxia brought on by blood distribution. This usually leads to intestinal leakage as well as the infiltration and metastasis of toxins and pathogenic bacteria in the intestinal cavity, which will eventually cause inflammation in the whole body. A large number of studies have shown that intestinal damage after HS involves the body's stress response, disruption of oxidative balance, disorder of tight junction proteins, massive cell death, and microbial imbalance. Based on these damage mechanisms, protecting the intestinal barrier and regulating the body's inflammatory and immune responses are effective treatment strategies. To better understand the pathophysiology of this complex process, this review aims to outline the potential processes and possible therapeutic strategies for intestinal damage after HS in recent years.

Xuebijing Injection Attenuates Heat Stroke-Induced Brain Injury through Oxidative Stress Blockage and Parthanatos Modulation via PARP-1/AIF Signaling

Heat stroke (HS) is a potentially fatal acute condition caused by an interplay of complex events including inflammation, endothelial injury, and coagulation abnormalities that make its pharmacological treatment a challenging problem. The traditional Chinese medicine Xuebijing injection (XBJ) has been shown to reduce inflammatory responses and prevent organ injuries in HS-induced mice. However, the underlying mechanism of XBJ in HS-induced brain injury remains unclear. In this study, HS-induced rat models and cell models were established to elucidate the effects and underlying mechanisms of XBJ injection on HS-induced brain injury in vivo and in vitro. The results revealed that XBJ injection improved the survival outcome of HS rats and attenuated HS-induced brain injury in a concentration-dependent manner. Subsequently, the reduction in viability and proliferation of neurons induced by HS were reversed by XBJ treatment, while the HS-induced increased ROS levels and neuron death were also inhibited by XBJ injection. Mechanistically, HS activated PARP-1/AIF signaling in vitro and in vivo, inducing the translocation of AIF from the cytoplasm to the nucleus, leading to PARP-1-dependent cell death of neurons. Additionally, we compared XBJ injection effects in young and old age rats. Results showed that XBJ also provided protective effects in HS-induced brain injury in aging rats; however, the treatment efficacy of XBJ injection at the same concentration was more significant in the young age rats. In conclusion, XBJ injection attenuates HS-induced brain injury by inhibiting oxidative stress and Parthanatos via the PARP-1/AIF signaling, which might provide a novel therapeutic strategy for HS treatment.

ZBP1 and heatstroke

Heatstroke, which is associated with circulatory failure and multiple organ dysfunction, is a heat stress-induced life-threatening condition characterized by a raised core body temperature and central nervous system dysfunction. As global warming continues to worsen, heatstroke is expected to become the leading cause of death globally. Despite the severity of this condition, the detailed mechanisms that underlie the pathogenesis of heatstroke still remain largely unknown. Z-DNA-binding protein 1 (ZBP1), also referred to as DNA-dependent activator of IFN-regulatory factors (DAI) and DLM-1, was initially identified as a tumor-associated and interferon (IFN)-inducible protein, but has recently been reported to be a Z-nucleic acid sensor that regulates cell death and inflammation; however, its biological function is not yet fully understood. In the present study, a brief review of the main regulators is presented, in which the Z-nucleic acid sensor ZBP1 was identified to be a significant factor in regulating the pathological characteristics of heatstroke through ZBP1-dependent signaling. Thus, the lethal mechanism of heatstroke is revealed, in addition to a second function of ZBP1 other than as a nucleic acid sensor.

Exertional heat stroke: nutritional considerations

NEW FINDINGS

What is the topic of this review? The potential role of nutrition in exertional heat stroke. What advances does it highlight? Certain nutritional and dietary strategies used by athletes and workers may exert a protective effect the pathophysiological processes of exertional heat stroke, whereas others may be detrimental. While current evidence suggests that some of these practices may be leveraged as a potential countermeasure to exertional heat stroke, further research on injury-related outcomes in humans is required.

ABSTRACT

Exertional heat stroke (EHS) is a life-threatening illness and an enduring problem among athletes, military servicemen and -women, and occupational labourers who regularly perform strenuous activity, often under hot and humid conditions or when wearing personal protective equipment. Risk factors for EHS and mitigation strategies have generally focused on the environment, health status, clothing, heat acclimatization and aerobic conditioning, but the potential role of nutrition is largely underexplored. Various nutritional and dietary strategies have shown beneficial effects on exercise performance and health and are widely used by athletes and other physically active populations. There is also evidence that some of these practices may dampen the pathophysiological features of EHS, suggesting possible protection or abatement of injury severity. Promising candidates include carbohydrate ingestion, appropriate fluid intake and glutamine supplementation. Conversely, some nutritional factors and low energy availability may facilitate the development of EHS, and individuals should be cognizant of these. Therefore, the aims of this review are to present an overview of EHS along with its mechanisms and pathophysiology, discuss how selected nutritional considerations may influence EHS risk focusing on their impact on the key pathophysiological processes of EHS, and provide recommendations for future research. With climate change expected to increase EHS risk and incidence in the coming years, further investigation on how diet and nutrition may be optimized to protect against EHS would be highly beneficial.

Lessons From Heat Stroke for Understanding Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

We here provide an overview of the pathophysiological mechanisms during heat stroke and describe similar mechanisms found in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Both conditions are characterized by disturbed homeostasis in which inflammatory pathways play a central role. Splanchnic vasoconstriction, increased gut permeability, gut-related endotoxemia, systemic inflammatory response, central nervous system dysfunction, blood coagulation disorder, endothelial-cell injury, and mitochondrial dysfunction underlie heat stroke. These mechanisms have also been documented in ME/CFS. Moreover, initial transcriptomic studies suggest that similar gene expressions are altered in both heat stroke and ME/CFS. Finally, some predisposing factors for heat stroke, such as pre-existing inflammation or infection, overlap with those for ME/CFS. Notwithstanding important differences - and despite heat stroke being an acute condition - the overlaps between heat stroke and ME/CFS suggest common pathways in the physiological responses to very different forms of stressors, which are manifested in different clinical outcomes. The human studies and animal models of heat stroke provide an explanation for the self-perpetuation of homeostatic imbalance centered around intestinal wall injury, which could also inform the understanding of ME/CFS. Moreover, the studies of novel therapeutics for heat stroke might provide new avenues for the treatment of ME/CFS. Future research should be conducted to investigate the similarities between heat stroke and ME/CFS to help identify the potential treatments for ME/CFS.

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.

Microglia polarization in heat-induced early neural injury

Introduction

In the occurrence and development of heat stroke (HS), factors such as hyperthermia, ischemia and hypoxia are essential to the central nervous system (CNS) inflammatory response, but the main mechanism underlying CNS inflammation remains unclear. The aim of the study was to observe the polarization of microglia in response to heat-induced early nerve injury and to explore its possible mechanism of action.

Material and methods

To establish a heatstroke animal model in Beagle dogs, 18 Beagle dogs were divided into control (group A) and experimental groups (group B, group C and group D) according to a random numbers table. The animals in the experimental groups were placed on an electric blanket of an animal body temperature maintaining apparatus. The temperature was set at 40 ±0.5°C, and the rectal temperature was monitored every 5 min until the target body temperature was reached. Once the target temperature was reached, the dogs were transferred to an environment of 26 ±0.5°C and 60 ±0.5% humidity. Western blot analysis was used to detect the expression of microglia-specific markers CD45, iNOS, arginase, and CD206 in normal and heat-damaged brain tissues at different time points (1 h, 6 h, 24 h). The expression of CD45 and arginase was further determined by co-localization with immunofluorescence.

Results

CD45 and iNOS protein expression was detected in group A. The two protein markers in group B were significantly higher than those in group A (p < 0.05), and the protein markers in group C were still higher than those in group A (p < 0.05). There was no statistically significant difference among the animals in group A (p > 0.05). Arginase and CD206 protein expression was also detected in group A. Levels of the two protein markers in group B were higher than those in group A (p < 0.05), and the protein marker levels in group C were even higher than those in group A (p < 0.05). Further analysis of the two groups of protein markers in group D showed significantly higher levels than those in group A (p < 0.001). Immunofluorescence co-localization of CD45 and arginase showed significantly increased fluorescence density at 6 h and 24 h after thermal injury (p < 0.001).

Conclusions

After heat-induced disease, microglia were found to be active in the brain tissues of dogs. The microglia activated in the early 1-6 h of CNS injury were mainly the M1 type, which were then converted to the M2 type after 6 h. The 24 h M2 type was dominant. The relationship between M1/M2 polarization trends and early brain injury in heat-induced disease may be a key to understanding CNS injury in heat-induced disease.

Therapeutic treatment with vitamin C reduces focal cerebral ischemia-induced brain infarction in rats by attenuating disruptions of blood brain barrier and cerebral neuronal apoptosis

Stroke is a major public health problem and ranks third most common cause of death in adults worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury, mainly caused by oxidative/nitrosative stress injury, after revascularization therapy can result in worsening outcomes. For better clinical prognosis, more and more studies have focused on the pharmaceutical neuroprotective therapies against free radical damage. The impact of vitamin C (ascorbic acid) on oxidative stress-related diseases is moderate because of its limited oral bioavailability and rapid clearance. However, recent evidence of the clinical benefit of parenteral vitamin C administration has emerged, especially in critical care. In this study we demonstrated that parenteral administration of vitamin C significantly improved neurological deficits and reduced brain infarction and brain edema by attenuating the transient middle cerebral artery occlusion (tMCAO)-induced nitrosative stress, inflammatory responses, and the resultant disruptions of blood brain barrier and cerebral neuronal apoptosis. These results suggest that parenteral administration of vitamin C has potential as an adjuvant agent with intravenous thrombolysis or endovascular thrombectomy in acute treatment of ischemic stroke.

Evaluation of different commercial antibodies for their ability to detect human and mouse tissue factor by western blotting

BACKGROUND

Western blotting is used to measure protein expression in cells and tissues. Appropriate interpretation of resulting data is contingent upon antibody validation.

OBJECTIVES

We assessed several commercial anti-human and anti-mouse tissue factor (TF) antibodies for their ability to detect TF by western blotting.

MATERIAL AND METHODS

We used human pancreatic cancer cell lines expressing different levels of TF and a mouse pancreatic cancer cell line expressing TF with a matched knockout derivative.

RESULTS

Human and mouse TF protein detected by western blotting correlated with levels of TF mRNA in these cell lines. The apparent molecular weight of TF is increased by N-linked glycosylation and, as expected, deglycosylation decreased the size of TF based on western blotting. We found that four commercial anti-human TF antibodies detected TF in a TF-positive cell line HPAF-II whereas no signal was observed in a TF-negative cell line MIA PaCa-2. More variability was observed in detecting mouse TF. Two anti-mouse TF antibodies detected mouse TF in a TF-positive cell line and no signal was observed in a TF knockout cell line. However, a third anti-mouse TF antibody detected a nonspecific protein in both the mouse TF-positive and TF-negative cell lines. Two anti-human TF antibodies that are claimed to cross react with mouse TF either recognized a nonspecific band or did not detect mouse TF.

DISCUSSION

Our results indicate that there is a range in quality of commercial anti-TF antibodies.

CONCLUSION

We recommend that all commercial antibodies should be validated to ensure that they detect TF.

Intestinal Injury in Heat Stroke

BACKGROUND

Heat stroke is a life-threatening syndrome that is characterized by its severe clinical symptoms, rapid progression, and high rate of mortality. Recently, research has indicated that a dysfunctional intestinal epithelia barrier plays an important role in the pathophysiology of heat stroke. Protecting the intestines from heat stress had been identified as a potentially effective treatment for patients with heat stroke and may reduce the innate immune response caused by endotoxins in circulation.

OBJECTIVES

The aim of this review is to discuss this key event in heat stroke and to describe the mechanism during progression.

DISCUSSION

Direct injuries and secondary impairments of the intestine induced by heat stress are discussed; recent studies that refer to intestine-specific prevention and treatment in heat stroke and heat stress-induced injuries are also summarized.

CONCLUSIONS

A more detailed pathogenesis of heat stroke needs to be elucidated so that potentially effective means of treatment and prevention of heat stroke can be developed and studied.

A review of micronutrients in sepsis: the role of thiamine, l-carnitine, vitamin C, selenium and vitamin D

Sepsis is defined as the dysregulated host response to an infection resulting in life-threatening organ dysfunction. The metabolic demand from inefficiencies in anaerobic metabolism, mitochondrial and cellular dysfunction, increased cellular turnover, and free-radical damage result in the increased focus of micronutrients in sepsis as they play a pivotal role in these processes. In the present review, we will evaluate the potential role of micronutrients in sepsis, specifically, thiamine, l-carnitine, vitamin C, Se and vitamin D. Each micronutrient will be reviewed in a similar fashion, discussing its major role in normal physiology, suspected role in sepsis, use as a biomarker, discussion of the major basic science and human studies, and conclusion statement. Based on the current available data, we conclude that thiamine may be considered in all septic patients at risk for thiamine deficiency and l-carnitine and vitamin C to those in septic shock. Clinical trials are currently underway which may provide greater insight into the role of micronutrients in sepsis and validate standard utilisation.

Transcriptome Sequencing Reveals Astrocytes as a Therapeutic Target in Heat-Stroke

Heat-stroke is a serious form of hyperthermia with high mortality, and can induce severe central nervous system disorders. The neurovascular unit (NVU), which consists of vascular cells, glial cells, and neurons, controls blood-brain barrier (BBB) permeability and cerebral blood flow, and maintains the proper functioning of neuronal circuits. However, the detailed function of each BBB component in heat-stroke remains unknown. In order to interpret alterations caused by heat stress, we performed transcriptome comparison of neuron and astrocyte primary cultures after heat treatment. Differentially-expressed genes were then selected and underwent Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Gene-act networks were also constructed, and the expression of pivotal genes was validated by quantitative PCR, as well as single-cell qPCR in heat-stroke rats. Our work provides valuable information on the transcriptional changes in NVU cells after heat stress, reveals the diverse regulatory mechanisms of two of these cellular components, and shows that a cell-type-specific approach may be a promising therapeutic strategy for heat-stroke treatments.

Vitamin C and Infections

In the early literature, vitamin C deficiency was associated with pneumonia. After its identification, a number of studies investigated the effects of vitamin C on diverse infections. A total of 148 animal studies indicated that vitamin C may alleviate or prevent infections caused by bacteria, viruses, and protozoa. The most extensively studied human infection is the common cold. Vitamin C administration does not decrease the average incidence of colds in the general population, yet it halved the number of colds in physically active people. Regularly administered vitamin C has shortened the duration of colds, indicating a biological effect. However, the role of vitamin C in common cold treatment is unclear. Two controlled trials found a statistically significant dose-response, for the duration of common cold symptoms, with up to 6-8 g/day of vitamin C. Thus, the negative findings of some therapeutic common cold studies might be explained by the low doses of 3-4 g/day of vitamin C. Three controlled trials found that vitamin C prevented pneumonia. Two controlled trials found a treatment benefit of vitamin C for pneumonia patients. One controlled trial reported treatment benefits for tetanus patients. The effects of vitamin C against infections should be investigated further.