Intestinal alkaline phosphatase improves intestinal permeability and alleviates multiple organ dysfunction caused by heatstroke.

Objective: Heatstroke (HS) is a severe acute disease related to gastrointestinal barrier dysfunction, systemic inflammation and multiple organ injury. Many of the functions of Intestinal alkaline phosphatase (IAP) have been linked to gut homeostasis, gut barrier function and inflammation. However, the protective effect of IAP on heatstroke is not fully elucidated. This study aims to explore the protective effect of IAP on heatstroke by maintaining intestinal barrier and improving permeability. Methods: Male C57BL/6 mice were placed in a controlled climate chamber (ambient temperature: 40.0 ± 0.5 °C; humidity: 60 ± 5 %) until the maximum core temperature (Tc, max) reached 42.7 °C (the received criterion of HS). Then heat exposed mice (n = 195) were divided into three groups: 0.2 mL of 0.9 % physiological saline (HS) or vehicle (HS + Vehicle) or 300 IU IAP (HS + IAP) by gavage at 0, 24, and 48 h after onset. Control group mice (Con) (n = 65) were not exposed to heat and were gavaged with 0.9 % physiological saline of the same volume at the same time. Results: IAP treatment significantly reduced the levels of endotoxin, FD4, and D-lactate in the blood of heatstroke mice, reduced intestinal permeability and maintained the integrity of the intestinal barrier by increasing the expression of tight junction proteins. Meanwhile, IAP treatment alleviated liver and kidney damage caused by heatstroke, reduced serum levels of inflammatory cytokines, and thus improved survival rate of mice after heatstroke. Conclusion: This study indicates that IAP can improve the intestinal barrier function and intestinal permeability by increasing intestinal tight junctions, reduce systemic inflammation and multiple organ injury and improving the survival rate of heatstroke. Therefore, we consider IAP may be added to enteral nutrition formulas as a potential means for diseases characterized by intestinal permeability disorders, including heatstroke.

Holistic view of heat acclimation alleviated intestinal lesion in mice with heat stroke based on microbiome-metabolomics analysis.

The severity of heat stroke (HS) is associated with intestinal injury, which is generally considered an essential issue for HS. Heat acclimation (HA) is considered the best strategy to protect against HS. In addition, HA has a protective effect on intestinal injuries caused by HS. Considering the essential role of gut microbes in intestinal structure and function, we decided to investigate the potential protective mechanism of HA in reducing intestinal injury caused by HS. HA model was established by male C57BL/6J mice (5-6 weeks old, 17-19 g) were exposed at (34 ± 0.7)°C for 4 weeks to establish an animal HA model. The protective effect of HA on intestinal barrier injury in HS was investigated by 16S rRNA gene sequencing and nontargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics. According to the experimental results, HA can change the composition of the gut microbiota, which increases the proportion of lactobacilli, faecal bacteria, and urinobacteria but decreases the proportion of deoxycholic acid. Moreover, HA can reduce liver and kidney injury and systemic inflammation caused by HS and reduce intestinal injury by enhancing the integrity of the intestinal barrier. In addition, HA regulates inflammation by inhibiting NF-κB signalling and increasing tight junction protein expression in HS mice. HA induces changes in the gut microbiota, which may enhance tight junction protein expression, thereby reducing intestinal inflammation, promoting bile acid metabolism, and ultimately maintaining the integrity of the intestinal barrier. In conclusion, HA induced changes in the gut microbiota. Among the gut microbiota, lactobacilli may play a key role in the potential protective mechanism of HA.

A Multiple Mechanism Enhanced Arithmetic Optimization Algorithm for Numerical Problems.

The Arithmetic Optimization Algorithm (AOA) is a meta-heuristic algorithm inspired by mathematical operators, which may stagnate in the face of complex optimization issues. Therefore, the convergence and accuracy are reduced. In this paper, an AOA variant called ASFAOA is proposed by integrating a double-opposite learning mechanism, an adaptive spiral search strategy, an offset distribution estimation strategy, and a modified cosine acceleration function formula into the original AOA, aiming to improve the local exploitation and global exploration capability of the original AOA. In the proposed ASFAOA, a dual-opposite learning strategy is utilized to enhance population diversity by searching the problem space a lot better. The spiral search strategy of the tuna swarm optimization is introduced into the addition and subtraction strategy of AOA to enhance the AOA's ability to jump out of the local optimum. An offset distribution estimation strategy is employed to effectively utilize the dominant population information for guiding the correct individual evolution. In addition, an adaptive cosine acceleration function is proposed to perform a better balance between the exploitation and exploration capabilities of the AOA. To demonstrate the superiority of the proposed ASFAOA, two experiments are conducted using existing state-of-the-art algorithms. First, The CEC 2017 benchmark function was applied with the aim of evaluating the performance of ASFAOA on the test function through mean analysis, convergence analysis, stability analysis, Wilcoxon signed rank test, and Friedman's test. The proposed ASFAOA is then utilized to solve the wireless sensor coverage problem and its performance is illustrated by two sets of coverage problems with different dimensions. The results and discussion show that ASFAOA outperforms the original AOA and other comparison algorithms. Therefore, ASFAOA is considered as a useful technique for practical optimization problems.

Transcriptome sequencing reveals neurotoxicity in embryonic neural stem/progenitor cells under heat stress.

Neural tube malformation is a common kind of human birth defect. High temperature is one of the most common physical teratogenic factors. Several studies have suggested that heat stress may cause neurotoxicity during brain development, but more studies are warranted to reveal the mechanism and draw consistent conclusions. The current study used a cell model of primary mouse embryonic neural stem/progenitor cells (NSPCs) subjected to heat stress of 43 °C for 20 min. Our study investigated the changes in the NSPCs transcriptome under heat stress using high-throughput mRNA-seq. The NSPCs showed remarkably altered genes associated with cell growth, proliferation, cell cycle, and survival when exposed to heat stress. Heat stress reduced cell viability, proliferation, and neurosphere formation and caused cell cycle arrest and apoptosis in cultured NSPCs. PCR arrays confirmed that the TNF receptor family plays an important role in the apoptosis of NSPCs during heat stress. The results of real-time PCR confirmed that heat stress affects the expression of critical genes. We provide transcriptomic insight into heat stress-induced developmental neurotoxic effects and the underlying mechanisms.

Capsaicin decreases fecundity in the Asian malaria vector Anopheles stephensi by inhibiting the target of rapamycin signaling pathway.

BACKGROUND: Mosquito-borne diseases threaten human health, but mosquito control faces various challenges, such as resistance to chemical insecticides. Thus, there is an urgent need for more effective and environment-friendly control agents. Capsaicin can downregulate the mTOR signaling pathway of tumor cells. The TOR signaling pathway can mediate the expression of vitellogenin (Vg) to regulate the fecundity of insects. Whether capsaicin has the potential to inhibit fecundity of mosquitoes by regulating TOR pathway and Vg expression is currently unclear. METHODS: Anopheles stephensi were fed with blood of mice administered capsaicin by gavage or sugar containing capsaicin followed by a blood feeding with normal mice. Then, the engorged female mosquitoes were tubed individually and underwent oviposition. The eggs and individuals in the subsequent development stages, including larvae, pupae, and emerging adults, were counted and compared between the capsaicin treatment and control groups. Additionally, total RNA and protein were extracted from the engorged mosquitoes at 24 h post blood feeding. Real-time PCR and western blot were performed to detect the transcriptional level and protein expression of the key fecundity-related molecules of mosquitoes. Finally, TOR signaling pathway was inhibited via rapamycin treatment, and changes in fecundity and the key molecule transcription and protein expression levels were examined to verify the role of TOR signaling pathway in the effect of capsaicin on mosquito fecundity. RESULTS: The laid and total eggs (laid eggs plus retained eggs) of An. stephensi were significantly reduced by feeding on the blood of capsaicin-treated mice (P < 0.01) or capsaicin-containing sugar (P < 0.01) compared with those in the control group. Moreover, the transcription and protein expression or phosphorylation levels of fecundity-related molecules, such as Akt, TOR, S6K, and Vg, were significantly decreased by capsaicin treatment. However, the effects disappeared between control group and CAP group after the TOR signaling pathway was inhibited by rapamycin. CONCLUSIONS: Capsaicin can decrease the fecundity of An. stephensi by inhibiting the TOR signaling pathway. These data can help us to not only understand the effect of capsaicin on the reproductive ability of An. stephensi and its underlying mechanism, but also develop new efficient, safe, and pollution-free mosquito vector control agents.

The Chinese Herbal Formula Huoxiang Zhengqi Dropping Pills Prevents Acute Intestinal Injury Induced by Heatstroke by Increasing the Expression of Claudin-3 in Rats.

Intestinal injury has been regarded as an important causative factor for systemic inflammation during heatstroke, and maintaining intestinal integrity has been a potential target for the prevention of HS. Huoxiang Zhengqi Dropping Pills (HZPD) is a modern preparation of Huoxiang Zhengqi and widely used to prevent HS. The present study aims to explore the protective effect of HZDP on intestinal injury during heatstroke and analyze its potential pharmacodynamic basis. Male rats in the control and HS groups were given normal saline, and those in the HZDP groups were given HZDP (0.23, 0.46, and 0.92 g/kg) before induction of HS. Serum contents of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), intestinal fatty acid-binding protein (iFABP), and diamine oxidase (DAO) were determined using ELISA. Histopathology of intestinal injury was observed following H&E staining. The expression of claudin-3 was determined using western blot, immunohistochemistry, and immunofluorescence techniques. Moreover, network pharmacological tools were used to analyze the potential pharmacodynamic basis and the mechanism of HZDP. Treatment with HZDP significantly prolonged the time to reach Tc. Compared with the control group, the contents of TNF-α, IL-6, iFABP, and DAO in HS rats increased markedly. HZDP treatments reduced these levels significantly, and the effects in the middle dose group (0.46 g/kg) were most obvious. HZDP also attenuated intestinal injury and significantly reversed the decrease in claudin-3 expression. Bioinformatics analysis suggested that 35 active ingredients and 128 target genes of HZDP were screened from TCMSP and 93 target genes intersected with heatstroke target genes, which were considered potential therapeutic targets. TNF-α and IL-6 were the main inflammatory target genes of HZDP correlated with HS. These results indicated that HZDP effectively protected intestinal barrier function and prevented acute intestinal injury by increasing the expression of claudin-3 in rats, eventually improving heat resistance.

Autophagy involvement in T lymphocyte signalling induced by nickel with quantitative phosphoproteomic analysis.

Nickel-induced allergic contact dermatitis (ACD) is a common skin disease. The mechanism by which nickel causes ACD is not clear. There is no treatment for it, only symptomatic therapy. However, due to the lifetime sensitization characteristics, the recurrence rate in patients is high. T lymphocytes play a key role in nickel-induced ACD. Elucidating the potential mechanism underlying nickel-induced T lymphocyte signalling might make it possible to achieve targeted treatment of nickel-induced ACD. In our study, a phosphoproteomic approach based on tandem mass tag (TMT) labelling and LCMS/MS analyses was employed. An animal model of nickel allergy was established. Splenic T lymphocytes were purified for quantitative phosphoproteomic analysis. The numbers of phosphoproteins, phosphopeptides and phosphosites identified in this study were 3072, 7977 and 10,200, respectively. Comprehensive gene ontology (GO) analysis combined with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that nickel can significantly affect the phosphorylation of the mTOR signalling pathway in T lymphocytes. Western blotting analysis was used to detect changes in the expression of autophagy-related proteins (Beclin 1, LC3II, and p62). Nickel allergy changed autophagy-related protein expression (p < 0.05). It has been demonstrated that nickel causes autophagy of T lymphocytes in the spleen. Using autophagy inhibitors to intervene, it was found that Th1 differentiation was inhibited, and the expression of Th1-related inflammatory factors was downregulated. Overall, the identification of relevant signalling pathways yielded new insights into the molecular mechanisms underlying nickel allergy and might help in the discovery and development of mechanism-based drugs.

Increased miR-155 in Microglial Exosomes Following Heat Stress Accelerates Neuronal Autophagy via Their Transfer Into Neurons.

Background: Heat stroke is the outcome of excessive heat stress, which results in core temperatures exceeding 40°C accompanied by a series of complications. The brain is particularly vulnerable to damage from heat stress. In our previous studies, both activated microglia and increased neuronal autophagy were found in the cortices of mice with heat stroke. However, whether activated microglia can accelerate neuronal autophagy under heat stress conditions is still unknown. In this study, we aimed to investigate the underlying mechanism that caused neuronal autophagy upregulation in heat stroke from the perspective of exosome-mediated intercellular communication. Methods: In this study, BV2 and N2a cells were used instead of microglia and neurons, respectively. Exosomes were extracted from BV2 culture supernatants by ultracentrifugation and then characterized via transmission electron microscopy, nanoparticle tracking analysis and Western blotting. N2a cells pretreated with/without miR-155 inhibitor were cocultured with microglial exosomes that were treated with/without heat stress or miR-155 overexpression and subsequently subjected to heat stress treatment. Autophagy in N2a cells was assessed by detecting autophagosomes and autophagy-related proteins through transmission electron microscopy, immunofluorescence, and Western blotting. The expression of miR-155 in BV2 and BV2 exosomes and N2a cells was measured using real-time reverse transcription polymerase chain reaction. Target binding analysis was verified via a dual-luciferase reporter assay. Results: N2a autophagy moderately increased in response to heat stress and accelerated by BV2 cells through transferring exosomes to neurons. Furthermore, we found that neuronal autophagy was positively correlated with the content of miR-155 in microglial exosomes. Inhibition of miR-155 partly abolished autophagy in N2a cells, which was increased by coculture with miR-155-upregulated exosomes. Mechanistic analysis confirmed that Rheb is a functional target of miR-155 and that microglial exosomal miR-155 accelerated heat stress-induced neuronal autophagy mainly by regulating the Rheb-mTOR signaling pathway. Conclusion: Increased miR-155 in microglial exosomes after heat stroke can induce neuronal autophagy via their transfer into neurons. miR-155 exerted these effects by targeting Rheb, thus inhibiting the activity of mTOR signaling. Therefore, miR-155 could be a promising target for interventions of neuronal autophagy after heat stroke.

Transmission-Blocking Strategies Against Malaria Parasites During Their Mosquito Stages.

Malaria is still the most widespread parasitic disease and causes the most infections globally. Owing to improvements in sanitary conditions and various intervention measures, including the use of antimalarial drugs, the malaria epidemic in many regions of the world has improved significantly in the past 10 years. However, people living in certain underdeveloped areas are still under threat. Even in some well-controlled areas, the decline in malaria infection rates has stagnated or the rates have rebounded because of the emergence and spread of drug-resistant malaria parasites. Thus, new malaria control methods must be developed. As the spread of the Plasmodium parasite is dependent on the part of its life cycle that occurs in mosquitoes, to eliminate the possibility of malaria infections, transmission-blocking strategies against the mosquito stage should be the first choice. In fact, after the gametocyte enters the mosquito body, it undergoes a series of transformation processes over a short period, thus providing numerous potential blocking targets. Many research groups have carried out studies based on targeting the blocking of transmission during the mosquito phase and have achieved excellent results. Meanwhile, the direct killing of mosquitoes could also significantly reduce the probability of malaria infections. Microorganisms that display complex interactions with Plasmodium, such as Wolbachia and gut flora, have shown observable transmission-blocking potential. These could be used as a biological control strategy and play an important part in blocking the transmission of malaria.

Electromagnetic field exposure-induced depression features could be alleviated by heat acclimation based on remodeling the gut microbiota.

BACKGROUND: Electromagnetic pollution cannot be ignored. Long-term low-dose electromagnetic field (EMF) exposure can cause central nervous system dysfunction without effective prevention. MATERIALS/METHODS: Male C57BL/6J mice (6-8 weeks, 17-20 g) were used in this study. Depression-like and anxiety-like behaviors detected by behavioral experiments were compared among different treatments. 16S rRNA gene sequencing and non-targeted liquid chromatography-mass spectrometry (LC-MS) metabolomics were used to explore the relationship between EMF exposure and heat acclimation (HA) effects on gut microbes and serum metabolites. RESULTS: Both EMF and HA regulated the proportions of p_Firmicutes and p_Bacteroidota. EMF exposure caused the proportions of 6 kinds of bacteria, such as g_Butyricicoccus and g_Anaerotruncus, to change significantly (p < 0.05). HA restored the balance of gut microbes that was affected by EMF exposure and the proportion of probiotics (g_Lactobacillus) increased significantly (p < 0.01). Serum metabolite analysis suggested that HA alleviated the disturbance of serum metabolites (such as cholesterol and D-mannose) induced by EMF exposure. Both the metabolic KEGG pathways and PICRUSt functional analysis demonstrated that tryptophan metabolism, pyrimidine metabolism and amino acid biosynthesis were involved. CONCLUSIONS: EMF exposure not only led to depression-like neurobehavioral disorders, but also to gut microbiota imbalance. HA alleviated the depression features caused by EMF exposure. Based on the analysis of gut microbiota associated with serum metabolites, we speculated that gut microbiota might play a vital role in the cross-tolerance provided by HA.

Lack of lymphocytes exacerbate heat stroke severity in male mice through enhanced inflammatory response.

Though it has long been thought that the immune system is implicated in the pathophysiology of heat stroke, the underlying mechanisms are still poorly understood. As it has been reported in the literature that lymphocyte disturbance occurs in heat stroke patients or animals, we attempted to seek experimental evidence to define the role of lymphocytes in the pathophysiology of heat stroke. In our study, we used male Balb/c mice to establish a passive heat stroke model. We found that lymphocyte-deficient Severe combined immunodeficient (SCID) mice exposed to heat stress exhibited exacerbated heat stroke severity, which could be indicated by increased rates of mortality and serum levels of inflammatory cytokines compared to wildtype control mice. We further showed, through the depletion of T lymphocytes in wildtype mice and the transfer of wildtype lymphocytes into SCID mice, respectively, that T lymphocytes were both necessary and sufficient to alleviate the severity of heat stroke by inhibiting the early inflammatory response. Moreover, we found that the severity of heat injuries in heat-stressed wildtype mice showed great inter-individual variability, and the early number of T lymphocytes could be negatively associated with the severity of heat stroke. Our results suggest that lack of T lymphocytes could exacerbate the severity of heat stroke by augmenting inflammatory response, and the early circulating T lymphocytes may serve as a potential biomarker for the diagnosis of heat stroke.

The involvement of microglial CX3CR1 in heat acclimation-induced amelioration of adult hippocampal neurogenesis impairment in EMF-exposed mice.

Microglial CX3C chemokine receptor 1 (CX3CR1) has been implicated in numerous cellular mechanisms, including signalling pathways that regulate brain homoeostasis and adult hippocampal neurogenesis. Specific environmental conditions can impair hippocampal neurogenesis-related cognition, learning and memory. However, the role of CX3CR1 in the neurogenic alterations resulting from the cross-tolerance protection conferred by heat acclimation (HA) against the effects of electromagnetic field (EMF) exposure is less well understood. Here, we investigated the role of microglial CX3CR1 signalling in adult hippocampal neurogenesis induced by HA in EMF-exposed mice. We found that EMF exposure significantly decreased the number of proliferating and differentiating cells in the dentate gyrus (DG) of the hippocampus, resulting in a reduced neurogenesis rate. Moreover, alterations in the phenotypes of activated microglia and decreased expression levels of CX3CR1, but not sirtuin 1 (SIRT1), were observed in the brains of EMF-exposed mice. Remarkably, HA treatment improved microglial phenotypes, restored the expression of CX3CR1, and ameliorated the decrease in the adult hippocampal neurogenesis rate following EMF exposure. Moreover, pharmacological inhibition of CX3CR1 and SIRT1 failed to restore CX3CR1 expression and ameliorate hippocampal neurogenesis impairment following HA plus EMF stimulation. These results indicate that microglial CX3CR1 is involved in the cross-tolerance protective effect of HA on adult hippocampal neurogenesis upon EMF exposure.

Modulation of microglial phenotypes by dexmedetomidine through TREM2 reduces neuroinflammation in heatstroke.

No FDA approved pharmacological therapy is available to reduce neuroinflammation following heatstroke. Previous studies have indicated that dexmedetomidine (DEX) could protect against inflammation and brain injury in various inflammation-associated diseases. However, no one has tested whether DEX has neuro-protective effects in heatstroke. In this study, we focused on microglial phenotypic modulation to investigate the mechanisms underlying the anti-inflammatory effects of DEX in vivo and in vitro. We found that DEX treatment reduced the expression of CD68, iNOS, TNF-α, and IL-1ß, and increased the expression of CD206, Arg1, IL-10 and TGF-ß in microglia, ameliorating heatstroke induced neuroinflammation and brain injury in mice. TREM2, whose neuro-protective function has been validated by genetic studies in Alzheimer's disease and Nasu-Hakola disease, was significantly promoted by DEX in the microglia. TREM2 esiRNA reversed the DEX-induced activation of PI3K/Akt signalling. Overall these findings indicated that DEX may serve, as a potential therapeutic approach to ameliorate heatstroke induced neuroinflammation and brain injury via TREM2 by activating PI3K/Akt signalling.

Bacillus sphaericus exposure reduced vector competence of Anopheles dirus to Plasmodium yoelii by upregulating the Imd signaling pathway.

BACKGROUND: Vector control with Bacillus sphaericus (Bs) is an effective way to block the transmission of malaria. However, in practical application of Bs agents, a sublethal dose effect was often caused by insufficient dosing, and it is little known whether the Bs exposure would affect the surviving mosquitoes' vector capacity to malaria. METHODS: A sublethal dose of the Bs 2362 strain was administrated to the early fourth-instar larvae of Anopheles dirus to simulate shortage use of Bs in field circumstance. To determine vector competence, mosquitoes were dissected and the oocysts in the midguts were examined on day 9-11 post-infection with Plasmodium yoelii. Meanwhile, a SYBR quantitative PCR assay was conducted to examine the transcriptional level of the key immune molecules of mosquitoes, and RNA interference was utilized to validate the role of key immune effector molecule TEP1. RESULTS: The sublethal dose of Bs treatment significantly reduced susceptibility of An. dirus to P. yoelii, with the decrease of P. yoelii infection intensity and rate. Although there existed a melanization response of adult An. dirus following challenge with P. yoelii, it was not involved in the decrease of vector competence as no significant difference of melanization rates and densities between the control and Bs groups was found. Further studies showed that Bs treatment significantly increased TEP1 expression in the fourth-instar larvae (L4), pupae (Pu), 48 h post-infection (hpi) and 72 hpi (P < 0.001). Further, gene-silencing of TEP1 resulted in disappearance of the Bs impact on vector competence of An. dirus to P. yoelii. Moreover, the transcriptional level of PGRP-LC and Rel2 were significantly elevated by Bs treatment with decreased expression of the negative regulator Caspar at 48 hpi, which implied that the Imd signaling pathway was upregulated by Bs exposure. CONCLUSIONS: Bs exposure can reduce the vector competence of An. dirus to malaria parasites through upregulating Imd signaling pathway and enhancing the expression of TEP1. The data could not only help us to understand the impact and mechanism of Bs exposure on Anopheles' vector competence to malaria but also provide us with novel clues for wiping out malaria using vector control.

MicroRNA-155 Promotes Heat Stress-Induced Inflammation via Targeting Liver X Receptor α in Microglia.

Background: The neuroinflammatory responses of microglial cells play an important role in the process of brain dysfunction caused by heat stroke. MicroRNAs are reportedly involved in a complex signaling network and have been identified as neuroinflammatory regulators. In this study, we determined the biological roles of microRNA-155 in the inflammatory responses in heat-stressed microglia and explored the underlying mechanisms. Methods: MicroRNA-155 mimic and inhibitor were used to separately upregulate or downregulate microRNA-155 expression. The activation state of BV-2 microglial cells (BV-2 cells) was assessed via immunoreactions using the microglial marker CD11b and CD68. Levels of induced interleukin-1ß (IL-1ß), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured using real-time reverse transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assays (ELISAs). The activation of nuclear factor kappa B (NF-κB) signaling proteins was evaluated by Western blotting for inhibitory kappa B alpha (IκBα) and NF-κB p65 phosphorylation and indirect immunofluorescence analysis using a p65 phosphorylation antibody. A luciferase reporter assay was used to verify liver X receptor α (LXRα) as a target gene of microRNA-155. Results: Heat stress significantly induced IL-1ß, IL-6, and TNF-α release and increased the expression of CD11b and CD68. In addition, IκBα and NF-κB p65 phosphorylation were dramatically increased by heat stress, and microRNA-155 expression was also elevated. High expression of microRNA-155 in heat-stressed microglial cells was inversely correlated with LXRα expression. We then determined the role of microRNA-155 in the heat stress-induced inflammatory responses. The results revealed that by targeting LXRα, microRNA-155 enhanced NF-κB signaling activation and facilitated immune inflammation in heat stress-treated BV-2 cells. Conclusion: MicroRNA-155 promotes heat stress-induced inflammatory responses in microglia. The underlying mechanisms may include facilitating inflammatory factors expression by increasing NF-κB pathway activation via targeting LXRα.

TREM2 Regulates Heat Acclimation-Induced Microglial M2 Polarization Involving the PI3K-Akt Pathway Following EMF Exposure.

The function of triggering receptor expressed on myeloid cells-2 (TREM2) has been described within microglia with a beneficial activated phenotype. However, the role of TREM2 underlying microglial phenotypic alterations in the cross-tolerance protection of heat acclimation (HA) against the inflammatory stimuli electromagnetic field (EMF) exposure is less well known. Here, we investigated the TREM2-related signaling mechanism induced by HA in EMF-stimulated N9 microglial cells (N9 cells). We found that EMF exposure significantly increased the production of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α, IL-1ß, and IL-6), and the expression of M1 markers (CD11b and CD86); meanwhile, decreased the levels of anti-inflammatory cytokines (IL-4 and IL-10) and the expression of M2 markers (CD206 and Arg1) in N9 cells. Clearly, HA treatment decreased the secretion of TNF-α, IL-1ß and IL-6 and the expression of CD11b and CD86, and enhanced the production of IL-4 and IL-10 and the expression of CD206 and Arg1. Moreover, TREM2 esiRNA and selective inhibitor of PI3K clearly decreased anti-inflammatory cytokines production, M2 markers expression, and phosphorylation of PI3K and Akt following HA plus EMF stimulation. These results indicate that TREM2 and PI3K-Akt pathway are involved in the cross-tolerance protective effect of HA in microglial polarization towards the EMF exposure. This finding inspires future studies that aim to explore the non-drug approaches underlying EMF stimulation and other central nervous system (CNS) inflammatory diseases.