Deep hypothermia therapy attenuates LPS-induced microglia neuroinflammation via the STAT3 pathway

Subcutaneous administration of Stattic alleviates neuropathic pain by relieving inflammation in a mouse model of postherpetic neuralgia

Stattic, a commercial inhibitor of STAT3, can drive the development of neuropathic pain. Exploring the connection between Stattic and JAK1/STAT3 signaling may facilitate the understanding of neuropathic pain caused by postherpetic neuralgia (PHN). In the current study, as crucial regulators of inflammation, STAT3 and its associated JAK1/STAT3 pathway were found to be upregulated and activated in the L4-L6 dorsal root ganglion (DRG) of mice in response to resiniferatoxin (RTX)-induced PHN, while subcutaneous administration of Stattic was found to downregulate STAT3 expression and phosphorylation in a PHN model. Stattic administration further attenuated hypersensitivity to mechanical and thermal stimuli in PHN mice, and alleviated inflammation and cell death in the L4-L6 DRG of mice. Overexpression of STAT3 via microinjection of a lentiviral-STAT3 overexpression vector reversed the abnormal decrease of STAT3 at both the mRNA and protein levels in the L4-6 DRGs of PHN mice and significantly promoted hypersensitivity to mechanical stimuli in the mice. Collectively, we found that subcutaneous static administration alleviated RTX-induced neuropathic pain by deactivating JAK1/STAT3 in mice.

Hypothermia Attenuates Neurotoxic Microglial Activation via TRPV4

Therapeutic hypothermia (TH) provides neuroprotection. However, the cellular mechanisms underlying the neuroprotective effects of TH are not fully elucidated. Regulation of microglial activation has the potential to treat a variety of nervous system diseases. Transient receptor potential vanilloid 4 (TRPV4), a nonselective cation channel, is activated by temperature stimulus at 27-35 °C. Although it is speculated that TRPV4 is associated with the neuroprotective mechanisms of TH, the role of TRPV4 in the neuroprotective effects of TH is not well understood. In the present study, we investigated whether hypothermia attenuates microglial activation via TRPV4 channels. Cultured microglia were incubated under normothermic (37 °C) or hypothermic (33.5 °C) conditions following lipopolysaccharide (LPS) stimulation. Hypothermic conditions suppressed the expression of pro-inflammatory cytokines, inducible nitric oxide synthase, and the number of phagocytic microglia. AMP-activated protein kinase (AMPK)-NF-κB signaling was inhibited under hypothermic conditions. Furthermore, hypothermia reduced neuronal damage induced by LPS-treated microglial cells. Treatment with TRPV4 antagonist in normothermic culture replicated the suppressive effects of hypothermia on microglial activation and microglia-induced neuronal damage. In contrast, treatment with a TRPV4 agonist in hypothermic culture reversed the suppressive effect of hypothermia. These findings suggest that TH suppresses microglial activation and microglia-induced neuronal damage via the TRPV4-AMPK-NF-κB pathway. Although more validation is needed to consider differences according to age, sex, and specific central nervous system regions, our findings may offer a novel therapeutic approach to complement TH.

Association between the severity of hypothermia and in-hospital mortality in patients with infectious diseases: The J-Point registry

Aim

Hypothermia is associated with poor prognosis in patients with sepsis. However, no studies have explored the correlation between the severity of hypothermia and prognosis.

Methods

Using data from the Japanese accidental hypothermia network registry (J-Point registry), we examined adult patients aged ≥18 years with infectious diseases whose initial body temperature was ≤35°C from April 1, 2011 to March 31, 2016, in 12 centers. Patients were divided into three groups according to their body temperature: Tertile 1 (T1) (32.0-35.0°C), Tertile 2 (T2) (28.0-31.9°C), and Tertile 3 (T3) (<28.0°C). In-hospital mortality was employed as a metric to assess outcomes. We conducted a multivariate logistic regression analysis to investigate the relationship between the three categories and the occurrence of in-hospital mortality.

Results

A total of 572 patients were registered, and 170 eligible patients were identified. Of these patients, 55 were in T1 (32.0-35.0°C), 76 in T2 (28.0-31.9°C), and 39 in T3 (<28.0°C) groups. The overall in-hospital mortality rate in accidental hypothermia (AH) patients with infectious diseases was 34.1%. The in-hospital mortality rates in the T1, T2, and T3 groups were 34.5%, 36.8%, and 28.2%, respectively. The multivariable analysis demonstrated no significant differences regarding in-hospital mortality among the three groups (T2 vs. T1, adjusted odds ratio [OR]: 1.29; 95% confidence interval [CI]: 0.58-2.89 and T3 vs. T1, adjusted OR: 0.83; 95% CI: 0.30-2.31).

Conclusion

In this multicenter retrospective observational study, hypothermia severity was not associated with in-hospital mortality in AH patients with infectious diseases.

Stattic ameliorates the cecal ligation and puncture-induced cardiac injury in septic mice via IL-6-gp130-STAT3 signaling pathway

AIM

Sepsis-induced cardiac dysfunction is the leading cause of higher morbidity and mortality with poor prognosis in septic patients. Our recent previous investigation provides evidence of the hallmarks of signal transducer and activator of transcription3 (STAT3) activation in sepsis and targeting of STAT3 with Stattic, a small-molecule inhibitor of STAT3, has beneficial effects in various septic tissues. We investigated the possible cardioprotective effects of Stattic on cardiac inflammation and dysfunction in mice with cecal ligation and puncture (CLP)-induced sepsis.

MAIN METHODS

A polymicrobial sepsis model was induced by CLP in mice and Stattic (25 mg/kg) was intraperitoneally given at one and twelve hours after CLP operation. The cecum was exposed in sham-control mice without CLP. After 18 h of surgery, electrocardiogram (ECG) for anaesthized mice was registered followed by collecting of samples of blood and tissues for bimolecular and histopathological assessments. Myeloperoxidase, a marker of neutrophil infiltration, was assessed immunohistochemically.

KEY FINDINGS

CLP profoundly impaired cardiac functions as evidenced by ECG changes in septic mice as well as elevation of cardiac enzymes, and inflammatory markers with myocardial histopathological and immunohistochemical alterations. While, Stattic markedly reversed the CLP-induced cardiac abnormalities and restored the cardiac function by its anti-inflammatory activities.

SIGNIFICANCE

Stattic treatment had potential beneficial effects against sepsis-induced cardiac inflammation, dysfunction and damage. Its cardioprotective effects were possibly attributed to its anti-inflammatory activities by targeting STAT3 and downregulation of IL-6 and gp130. Our investigations suggest that Stattic could be a promising target for management of cardiac sepsis and inflammation-related cardiac damage.

Refraining from Packed Red Blood Cells in Cardiopulmonary Bypass Priming as a Method of Neuroprotection in Pediatric Cardiac Surgery

Congenital heart defect (CHD) surgeries are performed with cardiopulmonary bypass (CPB) and are complicated by several factors that affect the child's brain. However, to date, the number of studies on brain protection in cardiac surgery remains small. The aim of this study was to assess the impact of refraining from using packed red blood cells (PRBCs) in priming solutions in children with congenital defects (CHDs) who require surgical interventions using CPB to prevent brain injury in the postoperative period.

MATERIAL AND METHODS

This study included 40 children, and the mean age was 14 (12-22.5) months and the mean weight was 8.8 (7.25-11) kg. All patients underwent CHD closure using CPB. The patients were divided into two groups depending on the use of PRBCs in the priming solution. Brain injury was assessed using three specific blood serum markers, namely S100 calcium-binding protein β (S100β), neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP) before surgery, after the completion of CPB and 16 h after surgery (first, second and third control points). Markers of systemic inflammatory response were also analyzed, including interleukin-1, -6, -10 and tumor necrosis factor alpha (TNF-α). A clinical assessment of brain injury was carried out using a valid, rapid, observational tool for screening delirium in children of this age group, i.e., "Cornell Assessment of Pediatric Delirium".

RESULTS

Factors of the intra- and postoperative period were analyzed, such as hemoglobin levels, oxygen delivery (cerebral tissue oxygenation, blood lactate level and venous oxygen saturation) and indicators of organ dysfunction (creatinine, urea, bilirubin levels, duration of CPB and length of stay in the ICU). Following the procedure, there were no significant differences between the groups and all indicators were within the reference values, thus demonstrating the safety of CHD closure without transfusion. Moreover, the highest level of specific markers of brain injury were noted immediately after the completion of CPB in both groups. The concentration of all three markers was significantly higher in the group with transfusion after the completion of CPB. Moreover, GFAP levels were higher in the transfusion group and 16 h after surgery.

CONCLUSIONS

The results of the study show the safety and effectiveness of brain injury prevention strategies that consist of not conducting PRBC transfusion.

Therapeutic hypothermia for stroke: Unique challenges at the bedside

Therapeutic hypothermia has shown promise as a means to improving neurological outcomes at several neurological conditions. At the clinical level, it has been shown to improve outcomes in comatose survivors of cardiac arrest and in neonatal hypoxic ischemic encephalopathy, but has yet to be convincingly demonstrated in stroke. While numerous preclinical studies have shown benefit in stroke models, translating this to the clinical level has proven challenging. Major obstacles include cooling patients with typical stroke who are awake and breathing spontaneously but often have significant comorbidities. Solutions around these problems include selective brain cooling and cooling to lesser depths or avoiding hyperthermia. This review will cover the mechanisms of protection by therapeutic hypothermia, as well as recent progress made in selective brain cooling and the neuroprotective effects of only slightly lowering brain temperature. Therapeutic hypothermia for stroke has been shown to be feasible, but has yet to be definitively proven effective. There is clearly much work to be undertaken in this area.

Stattic alleviates acute hepatic damage induced by LPS/d-galactosamine in mice

Increasing evidence indicates that signal transducer and activator of transcription 3 (STAT3), a vital transcription factor, plays crucial roles in the regulation of inflammation. STAT3 has become a novel therapeutic target for intervention in inflammation-related disorders. However, it remains unclear whether STAT3 plays a part in acute hepatic damage. To investigate the effects of STAT3 here, LPS/d-GalN-induced hepatic damage was induced in mice, the STAT3 inhibitor Stattic was administered, and the degree of liver injury, inflammation, and hepatocyte apoptosis were investigated. The results showed that Stattic mitigated the hepatic morphologic abnormalities and decreased the level of aminotransferase in LPS/D-GalN-insulted mice. The results also indicated that Stattic decreased the levels of TNF-α and IL-6, prevented the activation of the caspase cascade, suppressed cleavage of PARP, and decreased the quantity of TUNEL-positive cells. These results suggest that Stattic provided protective benefits in LPS/d-GalN-induced hepatic damage, and the protective effects might be associated with its anti-inflammatory and anti-apoptotic effects. Therefore, STAT3 might become a novel target for intervening in inflammation-based and apoptosis-based hepatic disorders.

The novel DYRK1A inhibitor KVN93 regulates cognitive function, amyloid-beta pathology, and neuroinflammation

Regulating amyloid beta (Aβ) pathology and neuroinflammatory responses holds promise for the treatment of Alzheimer's disease (AD) and other neurodegenerative and/or neuroinflammation-related diseases. In this study, the effects of KVN93, an inhibitor of dual-specificity tyrosine phosphorylation-regulated kinase-1A (DYRK1A), on cognitive function and Aβ plaque levels and the underlying mechanism of action were evaluated in 5x FAD mice (a mouse model of AD). KVN93 treatment significantly improved long-term memory by enhancing dendritic synaptic function. In addition, KVN93 significantly reduced Aβ plaque levels in 5x FAD mice by regulating levels of the Aβ degradation enzymes neprilysin (NEP) and insulin-degrading enzyme (IDE). Moreover, Aβ-induced microglial and astrocyte activation were significantly suppressed in the KVN-treated 5xFAD mice. KVN93 altered neuroinflammation induced by LPS in microglial cells but not primary astrocytes by regulating TLR4/AKT/STAT3 signaling, and in wild-type mice injected with LPS, KVN93 treatment reduced microglial and astrocyte activation. Overall, these results suggest that the novel DYRK1A inhibitor KVN93 is a potential therapeutic drug for regulating cognitive/synaptic function, Aβ plaque load, and neuroinflammatory responses in the brain.

Therapeutic interventions for fetal inflammatory response syndrome (FIRS)

Fetal inflammatory response syndrome (FIRS) is a condition defined by systemic inflammation in the fetus, a rapid increase of pro-inflammatory cytokines into the fetal circulation (including interleukin-1 and interleukin-6), as well as a cellular response (such as increased neutrophils, monocyte/macrophages, and T cells) and the presence of funisitis. FIRS can lead to death and multisystem organ damage in the fetus and newborn. Brain injuries and subsequent risk of cerebral palsy and cognitive impairments are the most threatening long-term complications. This paper reviews the definition of FIRS, summarizes its associated complications, briefly describes the available methods to study FIRS, and discusses in more detail the potential therapeutic candidates that have been so far studied to protect the fetus/newborn from FIRS and to alleviate its associated complications and sequelae.

Apamin Suppresses LPS-Induced Neuroinflammatory Responses by Regulating SK Channels and TLR4-Mediated Signaling Pathways

Neuroinflammation plays a vital role in neurodegenerative conditions. Microglia are a key component of the neuroinflammatory response. There is a growing interest in developing drugs to target microglia and thereby control neuroinflammatory processes. Apamin (APM) is a specifically selective antagonist of small conductance calcium-activated potassium (SK) channels. However, its effect on neuroinflammation is largely unknown. We examine the effects of APM on lipopolysaccharide (LPS)-stimulated BV2 and rat primary microglial cells. Regarding the molecular mechanism by which APM significantly inhibits proinflammatory cytokine production and microglial cell activation, we found that APM does so by reducing the expression of phosphorylated CaMKII and toll-like receptor (TLR4). In particular, APM potently suppressed the translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/signal transducer and activator of transcription (STAT)3 and phosphorylated mitogen-activated protein kinases (MAPK)-extracellular signal-regulated kinase (ERK). In addition, the correlation of NF-κB/STAT3 and MAPK-ERK in the neuroinflammatory response was verified through inhibitors. The literature and our findings suggest that APM is a promising candidate for an anti-neuroinflammatory agent and can potentially be used for the prevention and treatment of various neurological disorders.

Therapeutic Hypothermia and Neuroprotection in Acute Neurological Disease

Therapeutic hypothermia has consistently been shown to be a robust neuroprotectant in many labs studying different models of neurological disease. Although this therapy has shown great promise, there are still challenges at the clinical level that limit the ability to apply this routinely to each pathological condition. In order to overcome issues involved in hypothermia therapy, understanding of this attractive therapy is needed. We review methodological concerns surrounding therapeutic hypothermia, introduce the current status of therapeutic cooling in various acute brain insults, and review the literature surrounding the many underlying molecular mechanisms of hypothermic neuroprotection. Because recent work has shown that body temperature can be safely lowered using pharmacological approaches, this method may be an especially attractive option for many clinical applications. Since hypothermia can affect multiple aspects of brain pathophysiology, therapeutic hypothermia could also be considered a neuroprotection model in basic research, which would be used to identify potential therapeutic targets. We discuss how research in this area carries the potential to improve outcome from various acute neurological disorders.

Sleeve Gastrectomy Reversed Obesity-Induced Hypogonadism in a Rat Model by Regulating Inflammatory Responses in the Hypothalamus and Testis

BACKGROUND

Obesity is a metabolic disease with a serious health burden in children and adults, and it induces a variety of conditions including subfecundity. Sleeve gastrectomy showed encouraging results in terms of weight loss and improve quality of life, and this study aimed to determine whether sleeve gastrectomy could reverse obesity-induced impaired fertility in male Sprague-Dawley rats.

METHODS

After 16 weeks of a chow diet (CD) or a high-fat diet (HFD) challenge, rats on the HFD were given a sleeve gastrectomy or sham operation and then fed an HFD for another 8 weeks. Serum glucose, insulin, lipids, sex hormone, sperm quality, inflammatory profile of the testis, and hypothalamic Kiss1 expression in the three study groups were compared.

RESULTS

Sleeve gastrectomy significantly decreased HFD-induced obesity and serum glucose and insulin levels. It also reversed the HFD-induced increase in teratozoospermia and decreases in sperm motility and progressive motility. Testicular morphological abnormalities were also improved after sleeve gastrectomy. Enzyme-linked immunosorbent assay showed that the expression of sex hormones increased after sleeve gastrectomy and that expression of inflammatory factors decreased. The HFD induced a hypothalamic inflammatory response that inhibited Kiss1 expression, which in turn mediated sex hormone expression. Sleeve gastrectomy treatment improved the hypothalamic response.

CONCLUSIONS

The results consistently showed that sleeve gastrectomy reversed obesity-induced male fertility impairment by decreasing the inflammatory responses of the testis and hypothalamus.

Effects of cold on murine brain mitochondrial function

Therapeutic hypothermia is a strategy that reduces metabolic rate and brain damage during clinically-relevant hypoxic events. Mitochondrial respiration is compromised by hypoxia, with deleterious consequences for the mammalian brain; however, little is known about the effects of reduced temperature on mitochondrial metabolism. Therefore, we examined how mitochondrial function is impacted by temperature using high resolution respirometry to assess electron transport system (ETS) function in saponin-permeabilized mouse brain at 28 and 37°C. Respirometric analysis revealed that, at the colder temperature, ETS respiratory flux was ~ 40–75% lower relative to the physiological temperature in all respiratory states and for all fuel substrates tested. In whole brain tissue, the enzyme maximum respiratory rates for complexes I-V were similarly reduced by between 37–88%. Complexes II and V were particularly temperature-sensitive; a temperature-mediated decrease in complex II activity may support a switch to complex I mediated ATP-production, which is considerably more oxygen-efficient. Finally, the mitochondrial H⁺-gradient was more tightly coupled, indicating that mitochondrial respiration is more efficient at the colder temperature. Taken together, our results suggest that improvements in mitochondrial function with colder temperatures may contribute to energy conservation and enhance cellular viability in hypoxic brain.

Ibrutinib suppresses LPS-induced neuroinflammatory responses in BV2 microglial cells and wild-type mice

Background

The FDA-approved small-molecule drug ibrutinib is an effective targeted therapy for patients with chronic lymphocytic leukemia (CLL). Ibrutinib inhibits Bruton’s tyrosine kinase (BTK), a kinase involved in B cell receptor signaling. However, the potential regulation of neuroinflammatory responses in the brain by ibrutinib has not been comprehensively examined.

Methods

BV2 microglial cells were treated with ibrutinib (1 μM) or vehicle (1% DMSO), followed by lipopolysaccharide (LPS; 1 μg/ml) or PBS. RT-PCR, immunocytochemistry, and subcellular fractionation were performed to examine the effects of ibrutinib on neuroinflammatory responses. In addition, wild-type mice were sequentially injected with ibrutinib (10 mg/kg, i.p.) or vehicle (10% DMSO, i.p.), followed by LPS (10 mg/kg, i.p.) or PBS, and microglial and astrocyte activations were assessed using immunohistochemistry.

Results

Ibrutinib significantly reduced LPS-induced increases in proinflammatory cytokine levels in BV2 microglial and primary microglial cells but not in primary astrocytes. Ibrutinib regulated TLR4 signaling to alter LPS-induced proinflammatory cytokine levels. In addition, ibrutinib significantly decreased LPS-induced increases in p-AKT and p-STAT3 levels, suggesting that ibrutinib attenuates LPS-induced neuroinflammatory responses by inhibiting AKT/STAT3 signaling pathways. Interestingly, ibrutinib also reduced LPS-induced BV2 microglial cell migration by inhibiting AKT signaling. Moreover, ibrutinib-injected wild-type mice exhibited significantly reduced microglial/astrocyte activation and COX-2 and IL-1β proinflammatory cytokine levels.

Conclusions

Our data provide insights on the mechanisms of a potential therapeutic strategy for neuroinflammation-related diseases.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1308-0) contains supplementary material, which is available to authorized users.

TREM2 inhibits inflammatory responses in mouse microglia by suppressing the PI3K/NF-κB signaling

This study aimed to investigate the effects of triggering receptor expressed on myeloid cell‐2 (TREM2) on the production of pro‐inflammatory mediators and cytokines induced by lipopolysaccharide (LPS) in BV2 microglia. TREM2 expression or TREM2‐specific siRNA were used to induce TREM2 overexpression or silencing. The BV2 cells were pre‐treated with the PI3 K inhibitor of LY294002 for 1 h and stimulated with LPS for 24 h. Then, the cell viability, apoptosis, phagocytosis, nitric oxide (NO), lactate dehydrogenase (LDH), and cytokine production, as well as the activation of AKT and NF‐kB were determined, respectively. We found LPS stimulation significantly reduced BV2 cell viability, enhanced BV2 cell phagocytosis and apoptosis compared to the control groups. In addition, LPS stimulation significantly increased the production of NO, LDH, TNF‐α, IL‐1β, and the activation of AKT and NF‐kB, while decreased the levels of IL‐10 and TGF‐β1. However, these pro‐inflammatory effects were significantly attenuated by TREM2 overexpression or pre‐treatment with LY294002, while enhanced by TREM2 silencing. Thus, we concluded that TREM2 inhibited neuroinflammation by down‐regulating PI3 K/AKT and NF‐kB signaling in BV2 microglia. Above all, therapeutic enhanced TREM2 expression may be a new strategy for intervention of neuroinflammatory diseases.