The TLR9 ligand, CpG-ODN, induces protection against cerebral ischemia/reperfusion injury via activation of PI3K/Akt signaling

The role of PI3K/AKT signaling pathway in myocardial ischemia-reperfusion injury

Myocardial ischemia has a high incidence and mortality rate, and reperfusion is currently the standard intervention. However, reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MIRI). There are currently no effective clinical treatments for MIRI. The PI3K/Akt signaling pathway is involved in cardiovascular health and disease and plays an important role in reducing myocardial infarct size and restoring cardiac function after MIRI. Activation of the PI3K/Akt pathway provides myocardial protection through synergistic upregulation of antioxidant, anti-inflammatory, and autophagy activities and inhibition of mitochondrial dysfunction and cardiomyocyte apoptosis. Many studies have shown that PI3K/Akt has a significant protective effect against MIRI. Here, we reviewed the molecular regulation of PI3K/Akt in MIRI and summarized the molecular mechanism by which PI3K/Akt affects MIRI, the effects of ischemic preconditioning and ischemic postconditioning, and the role of related drugs or activators targeting PI3K/Akt in MIRI, providing novel insights for the formulation of myocardial protection strategies. This review provides evidence of the role of PI3K/Akt activation in MIRI and supports its use as a therapeutic target.

CircRIMS promotes cerebral ischemia-reperfusion injury through increasing apoptosis and targeting the miR-96-5p/JAK/STAT1 axis

OBJECTIVE

This study aims to explore the function of circRIMS in cerebral ischemia/reperfusion (CIR) and its regulatory mechanism.

METHOD

The expression of the circRIMS was examined in GEO chip data and validated by qRT-PCR analysis. A middle cerebral artery occlusion/repression (MCAO/R) model was developed using C57BL/6J mice. Starbase and circinteractome were employed to identify the target miRNA and mRNA. The result was confirmed by dual-luciferase reporter assay, and biotinylated RNA-pulldown assay. The cell viability and apoptosis were confirmed through CCK-8 and flow cytometry assay.

RESULTS

This study revealed that circRIMS expression was upregulated in MCAO mice model and OGD/RX-simulated cell model. Knockdown circRIMS demonstrated the functional of circRIMS in increasing cell viability, reducing apoptosis, LDH activity and inflammatory factors secretion in OGD/RX-simulated CIR injury in vitro. Additionally, miR-96-5p was identified as a target of circRIMS, while the STAT1 gene is a downstream gene of miR-96-5p, and JAK was also considered to be a downstream gene of the JAK-STAT pathway. Furthermore, inhibition of miR-96-5p or overexpression of STAT1 promoted the progression of CIR injury by elevating apoptosis, reducing cell viability, and increasing the secretion of inflammatory cytokines.

CONCLUSION

CircRIMS contributes to the progression of CIR injury via regulating miR-96-5p/JAK/STAT1 axis.

Inhibition of cGAS-STING pathway alleviates neuroinflammation-induced retinal ganglion cell death after ischemia/reperfusion injury

Acute glaucoma is a vision-threatening disease characterized by a sudden elevation in intraocular pressure (IOP), followed by retinal ganglion cell (RGC) death. Cytosolic double-stranded DNA (dsDNA)-a damage-associated molecular pattern (DAMP) that triggers inflammation and immune responses-has been implicated in the pathogenesis of IOP-induced RGC death, but the underlying mechanism is not entirely clear. In this study, we investigated the effect of the inflammatory cascade on dsDNA recognition and examined the neuroprotective effect of the cyclic GMP-AMP (cGAMP) synthase (cGAS) antagonist A151 on a retinal ischemia/reperfusion (RIR) mouse model. Our findings reveal a novel mechanism of microglia-induced neuroinflammation-mediated RGC death associated with glaucomatous vision loss. We found that RIR injury facilitated the release of dsDNA, which initiated inflammatory responses by activating cGAS-stimulator of interferon genes (STING) pathway. Correspondingly, elevated expressions of cGAS and STING were found in retinal samples from human glaucoma donors. Furthermore, we found that deletion or inhibition of cGAS or STING in microglia transfected with poly(dA:dT) specifically decreased microglia activation and inflammation response. We also observed that A151 treatment promoted poly(dA:dT)--stimulated changes in polarization from the M1 to the M2 phenotype in microglia. Subsequently, A151 administered to mice effectively inhibited the cGAS-STING pathway, absent in melanoma 2 (AIM2) inflammasome and pyroptosis-related molecules. Furthermore, A151 administration significantly reduced neuroinflammation, ameliorated RGC death and RGC-related reductions in visual function. These findings provide a unique perspective on glaucomatous neuropathogenesis and suggest cGAS as an underlying target of retinal inflammation to provide a potential therapeutic for acute glaucoma.

Neutrophil extracellular traps aggravate neuronal endoplasmic reticulum stress and apoptosis via TLR9 after traumatic brain injury

Endoplasmic reticulum (ER) stress and ER stress-mediated apoptosis play an important role during secondary brain damage after traumatic brain injury (TBI). Increased neutrophil extracellular traps (NETs) formation has been demonstrated to be associated with neurological damage after TBI. However, the correlation between ER stress and NETs remains unclear, and the specific function of NETs in neurons has not been defined. In this study, we found that the levels of NETs circulating biomarkers were remarkably elevated in the plasma of TBI patients. We then inhibited NETs formation by peptidylarginine deiminase 4 (PAD4, a critical enzyme for NETs formation) deficiency and discovered that ER stress activation and ER stress-mediated neuronal apoptosis were reduced. The degradation of NETs via DNase I showed similar outcomes. Furthermore, overexpression of PAD4 aggravated neuronal ER stress and ER stress-associated apoptosis, while TLR9 antagonist administration abrogated the damage caused by NETs. In addition to in vivo experiments, in vitro experiments revealed that treatment with a TLR9 antagonist alleviated NETs-induced ER stress and apoptosis in HT22 cells. Collectively, our results indicated that ER stress as well as the accompanying neuronal apoptosis can be ameliorated by disruption of NETs and that suppression of the TLR9-ER stress signaling pathway may contribute to positive outcomes after TBI.

The role of circulating cell-free DNA as an inflammatory mediator after stroke

Stroke is the second leading cause of death worldwide and a leading cause of disability. Clinical and experimental studies highlighted the complex role of the immune system in the pathophysiology of stroke. Ischemic brain injury leads to the release of cell-free DNA, a damage-associated molecular pattern, which binds to pattern recognition receptors on immune cells such as toll-like receptors and cytosolic inflammasome sensors. The downstream signaling cascade then induces a rapid inflammatory response. In this review, we are highlighting the characteristics of cell-free DNA and how these can affect a local as well as a systemic response after stroke. For this purpose, we screened literature on clinical studies investigating cell-free DNA concentration and properties after brain ischemia. We report the current understanding for mechanisms of DNA uptake and sensing in the context of post-stroke inflammation. Moreover, we compare possible treatment options targeting cell-free DNA, DNA-sensing pathways, and the downstream mediators. Finally, we describe clinical implications of this inflammatory pathway for stroke patients, open questions, and potential future research directions.

Short-term toll-like receptor 9 inhibition leads to left ventricular wall thinning after myocardial infarction

AIMS

Ischaemia-reperfusion injury (IRI) following myocardial infarction remains a challenging topic in acute cardiac care and consecutively arising heart failure represents a severe long-term consequence. The extent of neutrophil infiltration and neutrophil-mediated cellular damage are thought to be aggravating factors enhancing primary tissue injury. Toll-like receptor 9 was found to be involved in neutrophil activation as well as chemotaxis and may represent a target in modulating IRI, aspects we aimed to illuminate by pharmacological inhibition of the receptor.

METHODS AND RESULTS

Forty-nine male adult Sprague-Dawley rats were used. IRI was induced by occlusion of the left coronary artery and subsequent snare removal after 30 min. Oligonucleotide (ODN) 2088, a toll-like receptor 9 (TLR9) antagonist, control-ODN, or DNase, were administered at the time of reperfusion and over 24 h via a mini-osmotic pump. The hearts were harvested 24 h or 4 weeks after left coronary artery occlusion and immunohistochemical staining was performed. Echocardiography was done after 1 and 4 weeks to determine ventricular function. Inhibition of TLR9 by ODN 2088 led to left ventricular wall thinning (P = 0.003) in association with drastically enhanced neutrophil infiltration (P = 0.005) and increased markers of tissue damage. Additionally, an up-regulation of the chemotactic receptor CXCR2 (P = 0.046) was found after TLR9 inhibition. No such effects were observed in control-ODN or DNase-treated animals. We did not observe changes in monocyte content or subset distribution, hinting towards neutrophils as the primary mediators of the exerted tissue injury.

CONCLUSIONS

Our data indicate a TLR9-dependent, negative regulation of neutrophil infiltration. Blockage of TLR9 appears to prevent the down-regulation of CXCR2, followed by an uncontrolled migration of neutrophils towards the area of infarction and the exertion of disproportional tissue injury resulting in potential aneurysm formation. In comparison with previous studies conducted in TLR^-/- mice, we deliberately chose a transient pharmacological inhibition of TLR9 to highlight effects occurring in the first 24 h following IRI.

Melatonin protects against methotrexate hepatotoxicity in young rats: Impact of PI3K/Akt/mTOR signaling

With the improvement in children's acute lymphoblastic leukemia (ALL) care, the survival rate in children ALL has improved much. Methotrexate (MTX) plays an essential role in the success of children's ALL treatment. Since hepatotoxicity is commonly reported in individuals treated with intravenous or oral MTX, our study further examined the hepatic effect following intrathecal MTX treatment, which is an essential treatment for leukemia patients. Specifically, we examined the pathogenesis of MTX hepatotoxicity in young rats and explored the impact of melatonin treatment in protection against MTX hepatotoxicity. Successfully, we found that melatonin was able to protect against MTX hepatotoxicity.

Cytosine-phosphate-guanine oligodeoxynucleotides regulate the cell cycle, apoptosis, and steroidogenesis of mouse ovarian granulosa cells by targeting inhibin alpha (1 ~ 32) fragments

Cytosine-phosphate-guanine oligodeoxynucleotides (CpG-ODNs), which exist in vertebrate, bacterial, and viral genomes, are regarded as strong immune adjuvants. To date, the biological activities of CpG-ODNs in reproduction remain unknown. Here, we investigated the effects of CpG-ODNs on the cell cycle, apoptosis, and steroidogenesis in mouse granulosa cells (mGCs), in combination with inhibin alpha (1 ~ 32) fragments. mGCs were transfected with pEGFP (containing green fluorescent protein, as a control), pEGISI (containing inhibin alpha (1 ~ 32) fragments), or pEGISI-CpG-ODNs (containing inhibin alpha (1 ~ 32) fragments and CpG-ODNs motifs) plasmid for 48 h in vitro. Our results showed that the mRNA and protein expression levels of inhibin alpha were downregulated in mGCs transfected with pEGISI-CpG-ODNs, compared to those transfected with pEGISI. Flow cytometry demonstrated that pEGISI-CpG-ODNs transfection promoted cell proliferation (for example, increasing the number of cells in S and G2 phases) and decreased apoptosis, compared to pEGISI transfection. The present study also indicated that the expression of cell cycle-related genes (cyclin D2, cyclin D3, cyclin E1, Cdk2, and Cdk6) was increased, while the expression of apoptosis-related factors (Fas, FasL, caspase-8, and caspase-3) decreased after pEGISI-CpG-ODNs treatment. Additionally, pEGISI-CpG-ODNs reversed the effect of pEGISI on the secretion of estradiol in mGCs, which was further validated by upregulating the levels of its synthesis-related factors (StAR, Cyp11a1, and 17β-HSD II). Nevertheless, pEGISI-CpG-ODNs or pEGISI did not affect the concentration of progesterone nor changed the expression levels of its synthesis-related factors (3β-HSD I and Cyp19a1). In conclusion, this study demonstrated that CpG-ODNs may affect the cell cycle, apoptosis, and steroidogenesis by targeting the effects of inhibin alpha (1 ~ 32) fragments, supporting the potential role of CpG-ODNs in the development of granulosa cells.

Pathogenetic Mechanisms of Hypertension-Brain-Induced Complications: Focus on Molecular Mediators

There is growing evidence that hypertension is the most important vascular risk factor for the development and progression of cardiovascular and cerebrovascular diseases. The brain is an early target of hypertension-induced organ damage and may manifest as stroke, subclinical cerebrovascular abnormalities and cognitive decline. The pathophysiological mechanisms of these harmful effects remain to be completely clarified. Hypertension is well known to alter the structure and function of cerebral blood vessels not only through its haemodynamics effects but also for its relationships with endothelial dysfunction, oxidative stress and inflammation. In the last several years, new possible mechanisms have been suggested to recognize the molecular basis of these pathological events. Accordingly, this review summarizes the factors involved in hypertension-induced brain complications, such as haemodynamic factors, endothelial dysfunction and oxidative stress, inflammation and intervention of innate immune system, with particular regard to the role of Toll-like receptors that have to be considered dominant components of the innate immune system. The complete definition of their prognostic role in the development and progression of hypertensive brain damage will be of great help in the identification of new markers of vascular damage and the implementation of innovative targeted therapeutic strategies.

YBX has functional roles in CpG-ODN against cold stress and bacterial infection of Misgurnus anguillicaudatus

Misgurnus anguillicaudatus (M. anguillicaudatus) is a widely cultivated fish. However, in M. anguillicaudatus breeding, the frequent cold stress during daily breeding could induce immune suppression and increase the risk of infection, causing serious economic loss. Based on existing findings, CpG Oligonucleotides (CpG-ODNs) may be an ideal protective agent for low temperature fish breeding, performing anti-infective when faced with cold stress with cold shock proteins Y box binding proteins (YBX). Although YBX has pleiotropic functions, its roles in CpG-ODNs-mediated immunity (especially under cold situations) remain largely unexplored. To clarify the relationship among them, we identified the YBX1/YBX2 in M. anguillicaudatus and analyzed using a series of bioinformatics methods. After that, we immunized the fish with 3 types of CpG-ODNs and challenged with Aeromonas hydrophila (A. hydrophila). Here we showed that the best anti-bacterial effect of CpG-B was accompanied by the significant upregulation of YBX1. And the detection of the YBX1 downstream effectors confirmed that CpG-B induced the YBX1-mediated Th1 oriented responses to A. hydrophila by regulation of the NLRP3 (Caspase-A/-B), IL-1β, IL-12 and IFN-γ. Afterwards, we found that under cold stress, CpG-B can activate the NLRP3 and NF-κB pathways through YBX1, a key mediator of anti-A. hydrophila in CpG-B immunization. In this study, we demonstrated CpG-B protection against infection in low temperature, and its interaction with YBX1, expanded the research of CpG-ODN under cold stress, and provided a new CpG-ODN application for low temperature fish farming.

Systemic toll-like receptor 9 agonist CpG oligodeoxynucleotides exacerbates aminoglycoside ototoxicity

The Toll-like receptor (TLR) signaling pathway is the key regulator of the innate immune system in response to systemic infection. Several studies have reported that the systemic TLR4 agonist lipopolysaccharide exacerbates aminoglycoside ototoxicity, but the influence of virus-associated TLR7 and TLR9 signaling cascades on the cochlea is unclear. The present study aimed to investigate the auditory effects of systemic TLR7 and TLR9 agonists during chronic kanamycin treatment. CBA/CaJ mice received the TLR7 agonist gardiquimod or TLR9 agonist CpG oligodeoxynucleotides (ODN) one day before kanamycin injection and on the 5th and 10th days during a 14-day course of kanamycin treatment. We observed that systemic gardiquimod or CpG ODN alone did not affect the baseline auditory brainstem response (ABR) threshold. Three weeks after kanamycin treatment, gardiquimod did not significantly change ABR threshold shifts, whereas CpG ODN significantly increased kanamycin-induced ABR threshold shifts. Furthermore, outer hair cell (OHC) evaluation revealed that CpG ODN reduced distortion product otoacoustic emission amplitudes and increased kanamycin-induced OHC loss. CpG ODN significantly elevated cochlear Irf-7, Tnf-α, Il-1, and Il-6 transcript levels. In addition, an increased number of Iba-1⁺ cells, which represented activated macrophages, was observed in the cochlea treated with CpG ODN. Our results indicated that systemic CpG ODN exacerbated kanamycin-induced ototoxicity and increased cochlear inflammation. This study implies that patients with underlying virus infection may experience more severe aminoglycoside-induced hearing loss if it occurs.

Toll-Like Receptor Signaling Pathways: Novel Therapeutic Targets for Cerebrovascular Disorders

Toll-like receptors (TLRs), a class of pattern recognition proteins, play an integral role in the modulation of systemic inflammatory responses. Cerebrovascular diseases (CVDs) are a group of pathological conditions that temporarily or permanently affect the brain tissue mostly via the decrease of oxygen and glucose supply. TLRs have a critical role in the activation of inflammatory cascades following hypoxic-ischemic events and subsequently contribute to neuroprotective or detrimental effects of CVD-induced neuroinflammation. The TLR signaling pathway and downstream cascades trigger immune responses via the production and release of various inflammatory mediators. The present review describes the modulatory role of the TLR signaling pathway in the inflammatory responses developed following various CVDs and discusses the potential benefits of the modulation of different TLRs in the improvement of functional outcomes after brain ischemia.

XQ-1H promotes cerebral angiogenesis via activating PI3K/Akt/GSK3β/β-catenin/VEGF signal in mice exposed to cerebral ischemic injury

Stroke still ranks as a most lethal disease worldwide. Angiogenesis during the chronic phase of ischemic stroke can alleviate ischemic injury and attenuate neurological deficit. XQ-1H is a new compound derived from the structure modification of ginkgolide B, which exerts anti-inflammation and neuroprotection against cerebral ischemic injury during the acute or subacute phase. However, whether XQ-1H facilitates angiogenesis and neural functional recovery during the chronic phase remains unclear. This research was designed to explore whether XQ-1H promotes angiogenesis after ischemic stroke and to preliminarily elucidate the mechanism. In vitro, XQ-1H was found to facilitate proliferation, migration and tube formation in bEnd.3 cells. In vivo, XQ-1H raised the CD31 positive microvessel number and increased focal cerebral blood flow in mice exposed to cerebral ischemic injury, and improved the neurological function. Mechanism studies revealed that XQ-1H exerted angiogenesis promoting effect via the PI3K/Akt/GSK3β/β-catenin/VEGF signal pathway, which was reversed by LY294002 (the specific inhibitor of PI3K/Akt). In conclusion, XQ-1H exerts angiogenetic effect both in vivo and in vitro, which is a potential agent against ischemic stroke during chronic phase.

The Trinity of cGAS, TLR9, and ALRs Guardians of the Cellular Galaxy Against Host-Derived Self-DNA

The immune system has evolved to protect the host from the pathogens and allergens surrounding their environment. The immune system develops in such a way to recognize self and non-self and develops self-tolerance against self-proteins, nucleic acids, and other larger molecules. However, the broken immunological self-tolerance leads to the development of autoimmune or autoinflammatory diseases. Pattern-recognition receptors (PRRs) are expressed by immunological cells on their cell membrane and in the cytosol. Different Toll-like receptors (TLRs), Nod-like receptors (NLRs) and absent in melanoma-2 (AIM-2)-like receptors (ALRs) forming inflammasomes in the cytosol, RIG (retinoic acid-inducible gene)-1-like receptors (RLRs), and C-type lectin receptors (CLRs) are some of the PRRs. The DNA-sensing receptor cyclic GMP–AMP synthase (cGAS) is another PRR present in the cytosol and the nucleus. The present review describes the role of ALRs (AIM2), TLR9, and cGAS in recognizing the host cell DNA as a potent damage/danger-associated molecular pattern (DAMP), which moves out to the cytosol from its housing organelles (nucleus and mitochondria). The introduction opens with the concept that the immune system has evolved to recognize pathogens, the idea of horror autotoxicus, and its failure due to the emergence of autoimmune diseases (ADs), and the discovery of PRRs revolutionizing immunology. The second section describes the cGAS-STING signaling pathway mediated cytosolic self-DNA recognition, its evolution, characteristics of self-DNAs activating it, and its role in different inflammatory conditions. The third section describes the role of TLR9 in recognizing self-DNA in the endolysosomes during infections depending on the self-DNA characteristics and various inflammatory diseases. The fourth section discusses about AIM2 (an ALR), which also binds cytosolic self-DNA (with 80–300 base pairs or bp) that inhibits cGAS-STING-dependent type 1 IFN generation but induces inflammation and pyroptosis during different inflammatory conditions. Hence, this trinity of PRRs has evolved to recognize self-DNA as a potential DAMP and comes into action to guard the cellular galaxy. However, their dysregulation proves dangerous to the host and leads to several inflammatory conditions, including sterile-inflammatory conditions autoinflammatory and ADs.

Neurotrophin-3 upregulation associated with intravenous transplantation of bone marrow mononuclear cells induces axonal sprouting and motor functional recovery in the long term after neocortical ischaemia

Bone marrow mononuclear cells (BMMCs) have been identified as a relevant therapeutic strategy for the treatment of several chronic diseases of the central nervous system. The aim of this work was to evaluate whether intravenous treatment with BMMCs facilitates the reconnection of lesioned cortico-cortical and cortico-striatal pathways, together with motor recovery, in injured adult Wistar rats using an experimental model of unilateral focal neocortical ischaemia. Animals with cerebral cortex ischaemia underwent neural tract tracing for axonal fibre analysis, differential expression analysis of genes involved in apoptosis and neuroplasticity by RT-qPCR, and motor performance assessment by the cylinder test. Quantitative and qualitative analyses of axonal fibres labelled by an anterograde neural tract tracer were performed. Ischaemic animals treated with BMMCs showed a significant increase in axonal sprouting in the ipsilateral neocortex and in the striatum contralateral to the injured cortical areas compared to untreated rodents. In BMMC-treated animals, there was a trend towards upregulation of the Neurotrophin-3 gene compared to the other genes, as well as modulation of apoptosis by BMMCs. On the 56th day after ischaemia, BMMC-treated animals showed significant improvement in motor performance compared to untreated rats. These results suggest that in the acute phase of ischaemia, Neurotrophin-3 is upregulated in response to the lesion itself. In the long run, therapy with BMMCs causes axonal sprouting, reconnection of damaged neuronal circuitry and a significant increase in motor performance.

RiPerC Attenuates Cerebral Ischemia Injury through Regulation of miR-98/PIK3IP1/PI3K/AKT Signaling Pathway

Background

Cerebral ischemic stroke is a refractory disease which seriously endangers human health. Remote ischemic perconditioning (RiPerC) by which the sublethal ischemic stimulus is administered during the ischemic event is beneficial after an acute stroke. However, the regulatory mechanism of RiPerC that relieves cerebral ischemic injury is still not completely clear.

Methods

In the present study, we investigated the regulatory mechanism of RiPerC in a rat model of ischemia induced by the middle cerebral artery occlusion (MCAO). Forty-eight adult male Sprague-Dawley (SD) rats were injected intracerebroventricularly with miR-98 agomir, miR-98 antagomir, or their negative controls (agomir-NC, antagomir-NC) 2 h before MCAO or MCAO+RiPerC followed by animal behavior tests and infraction volume measurement at 24 h after MCAO. The expression of miR-98, PIK3IP1, and tight junction proteins in rat hippocampus and cerebral cortex tissues was detected by quantitative polymerase chain reaction (qPCR) and Western blot (WB). Enzyme-linked immunosorbent assay (ELISA) was used to assess the IL-1β, IL-6, and TNF-α levels in the rat serum.

Results

The results showed that in MCAO group, the expression of PIK3IP1 was upregulated, but decreased after RiPerC treatment. Then, we found that PIK3IP1 was a potential target of miR-98. Treatment with miR-98 agomir decreased the infraction volume, reduced brain edema, and improved neurological functions compared to control rats. But treating with miR-98 antagomir in RiPerC group, the protective effect on cerebral ischemia injury was canceled.

Conclusion

Our finding indicated that RiPerC inhibited the MCAO-induced expression of PIK3IP1 through upregulated miR-98, thereby reducing the apoptosis induced by PIK3IP1 through the PI3K/AKT signaling pathway, thus reducing the cerebral ischemia-reperfusion injury.

Intestinal TLR9 deficiency exacerbates hepatic IR injury via altered intestinal inflammation and short-chain fatty acid synthesis

Mice deficient in intestinal epithelial TLR9 develop small intestinal Paneth cell hyperplasia and higher Paneth cell IL-17A levels. Since small intestinal Paneth cells and IL-17A play critical roles in hepatic ischemia reperfusion (IR) injury, we tested whether mice lacking intestinal TLR9 have increased hepatic IR injury. Mice lacking intestinal TLR9 had profoundly increased liver injury after hepatic IR compared to WT mice with exacerbated hepatocyte necrosis, apoptosis, neutrophil infiltration, and inflammatory cytokine generation. Moreover, we observed increased small intestinal inflammation and apoptosis after hepatic IR in intestinal TLR9 deficient mice. As a potential explanation for increased hepatic IR injury, fecal short-chain fatty acids butyrate and propionate levels were lower in intestinal TLR9 deficient mice. Suggesting a potential therapy for hepatic IR, exogenous administration of butyrate or propionate protected against hepatic IR injury in intestinal TLR9 deficient mice. Mechanistically, butyrate induced small intestinal IL-10 expression and downregulated the claudin-2 expression. Finally, IL-10 neutralization abolished the protective effects of butyrate against hepatic IR injury. Our studies show intestinal TLR9 deficiency results in exacerbated hepatic IR injury with increased small intestinal apoptosis and inflammation. Furthermore, short-chain fatty acids butyrate and propionate protect against hepatic IR injury and intestinal apoptosis/inflammation in intestinal TLR9 deficient mice.

Emerging roles of Toll-like receptor 9 in cardiometabolic disorders

Growing evidence suggests that damage-associated molecule patterns (DAMPs) and their receptors, pattern recognition receptors (PRRs), are associated with the progression of cardiometabolic disorders, including obesity-related insulin resistance and atherosclerosis. Cardiometabolic disorders share sterile chronic inflammation as a major cause; however, the exact mechanisms are still obscure. Toll-like receptor 9 (TLR9), one of the nucleic acid-sensing TLRs, recognizes DNA fragments derived from pathogens and contributes to self-defense by activation of the innate immune system. In addition, previous studies demonstrated that TLR9 recognizes DNA fragments released from host cells, accelerating sterile inflammation, which is associated with inflammatory diseases such as autoimmune diseases. In obese adipose tissue and atherosclerotic vascular tissue, various stresses release DNA fragments and/or nuclear proteins as DAMPs from degenerated adipocytes and vascular cells. Recent studies indicated that the activation of TLR9 in immune cells including macrophages and dendritic cells by recognition of these DAMPs promotes inflammation in these tissues, which causes cardiometabolic disorders. This review discusses recent advances in understanding the role of sterile inflammation associated with TLR9 and its endogenous ligands in cardiometabolic disorders. New insights into innate immunity may provide better understanding of cardiometabolic disorders and new therapeutic options for these major health threats in recent decades.

Astrocyte-derived exosome-transported microRNA-34c is neuroprotective against cerebral ischemia/reperfusion injury via TLR7 and the NF-κB/MAPK pathways

Exosomes and microRNAs (miRs) are critical in reducing ischemia/reperfusion (I/R) injury, but the mechanism of astrocyte-derived exosome (ATC-Exo)-transported miR-34c in cerebral I/R injury is unclear. A rat model of cerebral I/R injury was established in this study, and the rats were injected with ATC-Exos. An oxygen glucose deprivation/reperfusion (OGD/R) model in N2a cells was utilized to mimic cerebral I/R injury in vitro, and the effects of ATC-Exo-transported miR-34c on the biological episodes of OGD/R-stimulated N2a cells were evaluated. The downstream gene and pathway of miR-34c were verified, and a rescue experiment of the pathway was performed. Consequently, we found that I/R damaged neurons, and ATC-Exo-transported miR-34c alleviated the neuronal injury caused by I/R. In addition, ATC-Exo-transported miR-34c promoted proliferation and inhibited apoptosis in OGD/R-stimulated N2a cells. miR-34c targeted Toll-like receptor 7 (TLR7) and downregulated the NF-κB/MAPK axis. Treatment with NF-κB- or MAPK-specific inhibitors partially restored the impaired protection against I/R that was caused by ATC-Exos with low expression of miR-34c. Overall, ATC-Exo-transported miR-34c targets TLR7 to downregulate the NF-κB/MAPK axis and relieve neurological damage induced by I/R. This study may offer novel insight for the treatment of cerebral I/R injury.

Cepharanthine attenuates cerebral ischemia/reperfusion injury by reducing NLRP3 inflammasome-induced inflammation and oxidative stress via inhibiting 12/15-LOX signaling

Cepharanthine (CEP) is a potential candidate for treatment of cerebral ischemia/reperfusion (I/R) injury, due to its anti-inflammatory and anti-oxidative properties. To investigate the effect of CEP on cerebral I/R injury, we established a mouse model of transient middle cerebral artery occlusion (tMCAO) and a microglia cell model of oxygen and glucose deprivation/reoxygenation (OGD/R). Administration of CEP attenuated neurological deficits, reduced infarct volume and edema, and decreased microglia activation in MCAO mice. Immunofluorescence staining showed an up-regulation in NLR Family Pyrin Domain Containing 3 (NLRP3) immunoreactivity in Iba1-labled microglia together with total Iba1 and NLRP3 expression in the brain following tMCAO, while down-regulated by CEP treatment. In both tMCAO-induced mice and OGD/R-treated BV-2 cells, CEP exhibited dose-dependent inhibition on the expression of NLRP3, ASC and cleaved caspase-1. Importantly, CEP attenuated tMCAO or OGD/R-induced overproduction of M1 microglia-regulated pro-inflammation cytokines IL-1β and IL-18, suggesting that CEP might involve in suppressing microglia polarization to M1 phenotype in vivo and in vitro. Moreover, CEP dose-dependently inhibited tMCAO-induced arachidonate 15 lipoxygenase (ALOX15) together with Iba1-labled microglia. The subsequent ALOX15-mediated oxidative stress was decreased by CEP treatment in vivo and in vitro, as evidenced by reduced ROS generation and MDA level, and increased SOD activity. Taken together, we demonstrate that CEP attenuates cerebral I/R injury probably by inhibiting microglia activation and NLRP3 inflammasome-induced inflammation and reducing oxidative stress via suppressing 12/15-LOX signaling.

CpG-Oligodeoxynucleotides Alleviate Tert-Butyl Hydroperoxide-Induced Macrophage Apoptosis by Regulating Mitochondrial Function and Suppressing ROS Production

Oxidative stress and mitochondrial dysfunction are related to disease pathogenesis. Oligodeoxynucleotide containing CpG motifs (CpG ODN) demonstrate possibilities for immunotherapy applications. The aim of the present work is to explore the underlying mechanism of the cytoprotective function of CpG ODN by employing the oxidative stress modulation in immune cells. We used the imaging flow cytometry to demonstrate that tert-butyl hydroperoxide (t-BHP) induces mitochondrial-mediated apoptosis and ROS production in RAW264.7 cells. After pretreatment with CpG ODN, the percentage of apoptotic cells and ROS production was both markedly reduced. The decrease in mitochondrial membrane potential (MMP) induced by t-BHP was partially reversed by CpG ODN. The t-BHP induced upregulation of the expression of apoptosis-related proteins (cleaved-caspase 3, cleaved-caspase 9, cleaved-PARP, and bax) was notably decreased in the presence of CpG ODN. Furthermore, we found that CpG ODN enhanced phosphorylation of ERK1/2 and Akt to inhibit ROS production. In conclusion, the protective effect of CpG ODN in mitigation of t-BHP-induced apoptosis is dependent on the reduction of ROS.

The role of Toll-like receptor signaling pathways in cerebrovascular disorders: the impact of spreading depolarization

Cerebral vascular diseases (CVDs) are a group of disorders that affect the blood supply to the brain and lead to the reduction of oxygen and glucose supply to the neurons and the supporting cells. Spreading depolarization (SD), a propagating wave of neuroglial depolarization, occurs in different CVDs. A growing amount of evidence suggests that the inflammatory responses following hypoxic-ischemic insults and after SD plays a double-edged role in brain tissue injury and clinical outcome; a beneficial effect in the acute phase and a destructive role in the late phase. Toll-like receptors (TLRs) play a crucial role in the activation of inflammatory cascades and subsequent neuroprotective or harmful effects after CVDs and SD. Here, we review current data regarding the pathophysiological role of TLR signaling pathways in different CVDs and discuss the role of SD in the potentiation of the inflammatory cascade in CVDs through the modulation of TLRs.

Inhibition of double-strand DNA-sensing cGAS ameliorates brain injury after ischemic stroke

Cytosolic double‐stranded DNA (dsDNA) is a danger signal that is tightly monitored and sensed by nucleic acid‐sensing pattern recognition receptors. We study the inflammatory cascade on dsDNA recognition and investigate the neuroprotective effect of cyclic GMP‐AMP (cGAMP) synthase (cGAS) antagonist A151 and its mechanisms of neuroprotection in a mouse model of experimental stroke. Here, we found that cerebral ischemia promoted the release of dsDNA into the cytosol, where it initiated inflammatory responses by activating the cGAS. A151 effectively reduced the expression of cGAS, absent in melanoma 2 (AIM2) inflammasome, and pyroptosis‐related molecules, including caspase‐1, gasdermin D, IL‐1β, and IL‐18. Furthermore, mice treated with A151 showed a dampened immune response to stroke, with reduced counts of neutrophils, microglia, and microglial production of IL‐6 and TNF‐α after MCAO. Moreover, A151 administration significantly reduced infarct volume, attenuated neurodeficits, and diminished cell death. Notably, the protective effect of A151 was blocked in a microglia‐specific cGAS knockout mouse. These findings offer unique perspectives on stroke pathogenesis and indicate that inhibition of cGAS could attenuate brain inflammatory burden, representing a potential therapeutic opportunity for stroke.

Selective nanoparticle-mediated targeting of renal tubular Toll-like receptor 9 attenuates ischemic acute kidney injury

We developed an innovative therapy for ischemic acute kidney injury with discerning kidney-targeted delivery of a selective Toll-like receptor 9 (TLR9) antagonist in mice subjected to renal ischemia reperfusion injury. Our previous studies showed that mice deficient in renal proximal tubular TLR9 were protected against renal ischemia reperfusion injury demonstrating a critical role for renal proximal tubular TLR9 in generating ischemic acute kidney injury. Herein, we used 300-400 nm polymer-based mesoscale nanoparticles that localize to the renal tubules after intravenous injection. Mice were subjected to sham surgery or 30 minutes renal ischemia and reperfusion injury after receiving mesoscale nanoparticles encapsulated with a selective TLR9 antagonist (unmethylated CpG oligonucleotide ODN2088) or mesoscale nanoparticles encapsulating a negative control oligonucleotide. Mice treated with the encapsulated TLR9 antagonist either six hours before renal ischemia, at the time of reperfusion or 1.5 hours after reperfusion were protected against ischemic acute kidney injury. The ODN2088-encapsulated nanoparticles attenuated renal tubular necrosis, inflammation, decreased proinflammatory cytokine synthesis. neutrophil and macrophage infiltration and apoptosis, decreased DNA fragmentation and caspase 3/8 activation when compared to the negative control nanoparticle treated mice. Taken together, our studies further suggest that renal proximal tubular TLR9 activation exacerbates ischemic acute kidney injury by promoting renal tubular inflammation, apoptosis and necrosis after ischemia reperfusion. Thus, our studies suggest a potential promising therapy for ischemic acute kidney injury with selective kidney tubular targeting of TLR9 using mesoscale nanoparticle-based drug delivery.

CpG Oligonucleotides Protect Mice From Alphavirus Encephalitis: Role of NK Cells, Interferons, and TNF

Arboviruses including alphavirus are responsible for most emerging infectious diseases worldwide. Recent outbreaks of chikungunya virus serve as a stark reminder to their pathogenic potential. There are no vaccines or therapeutics currently available to contain alphavirus outbreaks. In this study we evaluated the effect of immunomodulatory CpG ODN on the clinical progression of neurotropic Sindbis virus infection. Neonatal C57Bl-6 mice challenged with Sindbis virus AR339 (25 PFU Subcutaneous) infect neurons in the CNS leading to the development of ataxia, seizures, paralysis, and death. We show that systemic administration of CpG ODN modulates the cytokine and chemokine gene expression levels in the CNS and ultimately protects neonatal mice from lethal neurotropic infection. The protection conferred by CpG ODN is controlled by innate immune response and T and B cells were dispensable. Further, protection required Type I, Type II interferons, and TNF as well as functional NK cells, but did not involve iNOS. This study confirms that administration of innate immune modulators can be used as a strategy to boost host innate immune responses and protect against neurotropic viruses reducing their pathogenic footprint.

Pellino1 Contributes to Morphine Tolerance by Microglia Activation via MAPK Signaling in the Spinal Cord of Mice

Chronic morphine-induced antinociceptive tolerance is a major unresolved issue in clinical practices, which is associated with microglia activation in the spinal cord. E3 ubiquitin ligase Pellino1 (Peli1) is known to be an important microglia-specific regulator. However, it is unclear whether Peli1 is involved in morphine tolerance. Here, we found that Peli1 levels in the spinal cord were significantly elevated in morphine tolerance mouse model. Notably, Peli1 was expressed in a great majority of microglia in the spinal dorsal horn, while downregulation of spinal Peli1 attenuated the development of morphine tolerance and associated hyperalgesia. Our biochemical data revealed that morphine tolerance-induced increase in Peli1 was accompanied by spinal microglia activation, activation of mitogen-activated protein kinase (MAPK) signaling, and production of proinflammatory cytokines. Peli1 additionally was found to promote K63-linked ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6) in the spinal cord after repeated morphine treatment. Furthermore, knocking down Peli1 in cultured BV2 microglial cells significantly attenuated inflammatory reactions in response to morphine challenge. Therefore, we conclude that the upregulation of Peli1 in the spinal cord plays a curial role in the development of morphine tolerance via Peli1-dependent mobilization of spinal microglia, activation of MAPK signaling, and production of proinflammatory cytokines. Modulation of Peli1 may be a potential strategy for the prevention of morphine tolerance.

The Role of Circular RNAs in Brain Injury

Circular RNAs are an increasingly important topic in non-coding RNA biology, drawing considerable attention in recent years. Accumulating evidence suggests a critical role for circular RNAs in both early and latent stages of disease pathogenesis. Circular RNAs are abundantly expressed in brain tissue, with significant implications for neural development and disease progression. Disruption of these processes, including those seen in response to brain injury, can have serious consequences such as hemiplegia, aphasia, coma, and death. In this review, we describe the role of circular RNAs in the context of brain injury and explore the potential connection between circular RNAs, brain hypoxic ischemic injury, ischemia-reperfusion injury, and traumatic injury.

Enteral virus depletion modulates experimental acute pancreatitis via toll-like receptor 9 signaling

Enteric viruses that inhabit the intestine have profound effects on innate and adaptive immunity of the gut and thus distant organs. Acute pancreatitis (AP) is a common abdominal inflammatory disease, in which gut bacteria play an indispensable part, particularly in the severe form with local and systemic complications. So far, little is known about the role of enteric viruses in the pathophysiology of AP. In this study, we evaluated the effect of enteric virus depletion by oral anti-viral cocktail (AVC) on caerulein (Cae)-hyperstimulation induced experimental AP and underlying mechanisms. We found that AVC treatment alleviated experimental AP, accompanied by suppressed innate immune cell infiltration and TLR9 expression and signaling in pancreas and intestine. Furthermore, AVC administration reduced AP-induced interleukin-6 (IL-6) production, IL-6-activated signal transducers and activators of transcription 3 (STAT3) signaling. Concordantly, expression of AP-induced STAT3-responsive chemokines, especially monocyte chemotactic protein-1 (MCP-1) and chemokine (C-X-C motif) ligand 1 (CXCL1) was reduced, thereby contributing to modulated pancreatic immune milieu. Treatment of mice with a toll-like receptor 9 (TLR9) agonist abolished the protective effect of AVC by activation of IL6/STAT3 signaling and downstream chemokine production. Conversely, treatment of mice with TLR9 antagonists, mimicking AVC, exerted protective effects against AP. Collectively, these results suggest that depletion of enteric viruses protects mice from experimental AP through inhibiting TLR9 signaling. Our study therefore implies a previously unrecognized role of enteric viruses in AP.

Nobiletin ameliorates myocardial ischemia and reperfusion injury by attenuating endoplasmic reticulum stress-associated apoptosis through regulation of the PI3K/AKT signal pathway

BACKGROUND

Nobiletin is a natural polymethoxylated flavone that confers antioxidative, anti-inflammatory and anti-apoptotic efficacies. However, the potential benefits of nobiletin preconditioning on myocardial ischemia and reperfusion injury (MIRI) remains largely unknown.

METHODS

MIRI was induced by ligation of the left anterior descending coronary artery and reperfusion. Pre-treatment with nobiletin, with or without PI3K/AKT inhibitor LY294002, was performed at the onset of reperfusion. Histological analyses, apoptotic evaluation, plasma biomarkers of myocardial injury, echocardiographic evaluation of cardiac function and myocardial levels of endoplasmic reticulum stress (ERS)-related molecules were observed.

RESULTS

Nobiletin pre-treatment significantly deceased the infract size and number of apoptotic cells in the myocardium of MIRI rats, as determined by Terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Moreover, the plasma levels of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) also markedly decreased. In addition, pre-treatment with nobiletin restored the impaired cardiac systolic function, as evidenced by echocardiographic evaluation results. Importantly, pre-treatment with nobiletin significantly downregulated the myocardial mRNA and protein levels of ERS-related signal molecules, including GRP78, CHOP and caspase-12, but upregulated the levels of p-PI3K and p-AKT. Interestingly, co-treatment with LY294002 significantly abolished the benefits of nobiletin pre-treatment on cardiac function, myocardial apoptosis, cardiomyocyte injuries, and changes in myocardial levels of ERS-related signaling molecules.

CONCLUSION

Nobiletin pre-treatment may alleviate MIRI probably via the attenuation of PI3K/AKT-mediated ERS-related myocardial apoptosis.

Inhibition of HDAC3 Ameliorates Cerebral Ischemia Reperfusion Injury in Diabetic Mice In Vivo and In Vitro

BACKGROUND

A substantial increase in histone deacetylase 3 (HDAC3) expression is implicated in the pathological process of diabetes and stroke. However, it is unclear whether HDAC3 plays an important role in diabetes complicated with stroke. We aimed to explore the role and the potential mechanisms of HDAC3 in cerebral ischemia/reperfusion (I/R) injury in diabetic state.

METHODS

Diabetic mice were subjected to 1 h ischemia, followed by 24 h reperfusion. PC12 cells were exposed to high glucose for 24 h, followed by 3 h of hypoxia and 6 h of reoxygenation (H/R). Diabetic mice received RGFP966 (the specific HDAC3 inhibitor) or vehicle 30 minutes before the middle cerebral artery occlusion (MCAO), and high glucose-incubated PC12 cells were pretreated with RGFP966 or vehicle 6 h before H/R.

RESULTS

HDAC3 inhibition reduced the cerebral infarct volume, ameliorated pathological changes, improved the cell viability and cytotoxicity, alleviated apoptosis, attenuated oxidative stress, and enhanced autophagy in cerebral I/R injury model in diabetic state in vivo and in vitro. Furthermore, we found that the expression of HDAC3 was remarkably amplified, and the Bmal1 expression was notably decreased in diabetic mice with cerebral I/R, whereas this phenomenon was obviously reversed by RGFP966 pretreatment.

CONCLUSIONS

These results suggested that the HDAC3 was involved in the pathological process of the complex disease of diabetic stroke. Suppression of HDAC3 exerted protective effects against cerebral I/R injury in diabetic state in vivo and in vitro via the modulation of oxidative stress, apoptosis, and autophagy, which might be mediated by the upregulation of Bmal1.

NK cells in cerebral ischemia

As a vital cell type in immune system and infiltrating cells in ischemic brain, NK cells can bridge the crosstalk between immune system and nervous system in stroke setting. The mechanism of action of NK cells is complicated, involving direct and indirect actions. NK cells are closely associated with poststroke inflammation, immunodepression and infections. The excessive inflammatory response in ischemic brain is one of the important causes for aggravating cerebral ischemic injury. Besides the inflammation induced by ischemia itself, thrombolytic drug tissue plasminogen activator (tPA) administration could also induce deteriorative inflammation, which is unfavorable for stroke control and recovery. Regulating NK cells may has the potential to modulate the immune response, limiting the development of ischemic damage and getting better outcome. In addition, post-stroke immunosuppression may lead to infections which contribute to higher severity and mortality of ischemic stroke (IS). Targeting NK cells may help to find novel pathways for IS therapy, which can both ameliorate the infarction itself, but also reduce the infectious complications. NK cells may also link IS and related diseases, suggesting NK cells can be used as a diagnostic or prognostic biomarker for IS prevention and treatment.

Potential Medications or Compounds Acting on Toll-like Receptors in Cerebral Ischemia

Background:

Toll-like receptors play an integral role in the process of inflammatory response after ischemic in-jury. The therapeutic potential acting on TLRs is worth of evaluations. The aim of this review was to introduce readers some potential medications or compounds which could alleviate the ischemic damage via TLRs.

Methods:

Research articles online on TLRs were reviewed. Categorizations were listed according to the follows, methods acting on TLRs directly, modulations of MyD88 or TRIF signaling pathway, and the ischemic tolerance induced by the pre-conditioning or postconditioning with TLR ligands or minor cerebral ischemia via acting on TLRs.

Results:

There are only a few studies concerning on direct effects. Anti-TLR4 or anti-TLR2 therapies may serve as promis-ing strategies in acute events. Approaches targeting on inhibiting NF-κB signaling pathway and enhancing interferon regu-latory factor dependent signaling have attracted great interests. Not only drugs but compounds extracted from traditional Chinese medicine have been used to identify their neuroprotective effects against cerebral ischemia. In addition, many re-searchers have reported the positive therapeutic effects of preconditioning with agonists of TLR2, 3, 4, 7 and 9. Several trails have also explored the potential of postconditioning, which provide a new idea in ischemic treatments. Considering all the evidence above, many drugs and new compounds may have great potential to reduce ischemic insults.

Conclusion:

This review will focus on promising therapies which exerting neuroprotective effects against ischemic injury by acting on TLRs.

Membrane vesicles from Pseudomonas aeruginosa activate the noncanonical inflammasome through caspase-5 in human monocytes

Outer membrane vesicles (OMVs) are constitutively produced by Gram-negative bacteria both in vivo and in vitro. These lipid-bound structures carry a range of immunogenic components derived from the parent cell, which are transported into host target cells and activate the innate immune system. Recent advances in the field have shed light on some of the multifaceted roles of OMVs in host-pathogen interactions. In this study, we investigated the ability of OMVs from two clinically important pathogens, Pseudomonas aeruginosa and Helicobacter pylori, to activate canonical and noncanonical inflammasomes. P. aeruginosa OMVs induced inflammasome activation in mouse macrophages, as evidenced by "speck" formation, as well as the cleavage and secretion of interleukin-1β and caspase-1. These responses were independent of AIM2 and NLRC4 canonical inflammasomes, but dependent on the noncanonical caspase-11 pathway. Moreover, P. aeruginosa OMVs alone were able to activate the inflammasome in a TLR-dependent manner, without requiring an exogenous priming signal. In contrast, H. pylori OMVs were not able to induce inflammasome activation in macrophages. Using CRISPR/Cas9 knockout THP-1 cells lacking the human caspase-11 homologs, caspase-4 and -5,we demonstrated that caspase-5 but not caspase-4 is required for inflammasome activation by P. aeruginosa OMVs in human monocytes. In contrast, free P. aeruginosa lipopolysaccharide (LPS) transfected into cells induced inflammasome responses via caspase-4. This suggests that caspase-4 and caspase-5 differentially recognize LPS depending on its physical form or route of delivery into the cell. These findings have relevance to Gram-negative infections in humans and the use of OMVs as novel vaccines.

Xingnaojing Injection Protects against Cerebral Ischemia Reperfusion Injury via PI3K/Akt-Mediated eNOS Phosphorylation

Xingnaojing (XNJ) injection, derived from traditional Chinese medicine formulation, has a protective effect against stroke, but the underlying mechanism is unclear, which severely limited its clinical application. This research aims to elucidate the role and mechanism of XNJ in reducing cerebral ischemic reperfusion (I/R) injury. Rats received 2 h cerebral ischemia followed by reperfusion of 24 h and were intraperitoneally given 5, 10, or 15 ml/kg XNJ 24 h before ischemia and at the onset of reperfusion, respectively. TTC staining, HE staining, and neurological score were implied to evaluate the effectiveness of XNJ. The protein expressions of PI3K/Akt and eNOS signaling were measured. Experiments were further performed in human brain microvascular endothelial cells (HBMECs) to investigate the protective mechanisms of XNJ. HBMECs were subjected to 3 h oxygen and glucose deprivation following 24 h of reoxygenation (OGD) to mimic cerebral I/R in vitro. PI3K inhibitor LY294002 was added with or without the preconditioning of XNJ. Multiple methods including western blot, immunofluorescence, DAPI staining, JC-1, and flow cytometry were carried out to evaluate the effect of XNJ on HBMECs. XNJ could improve rat cerebral ischemic injury and OGD induced HBMECs apoptosis. In vivo and in vitro researches indicated that the mechanism might be relevant to the activation of PI3K/Akt/eNOS signaling.

SC79, the AKT Activator Protects Cerebral Ischemia in a Rat Model of Ischemia/Reperfusion Injury

Background

Activation of AKT pathway attenuates brain damage and neuronal apoptosis during cerebral ischemia/reperfusion (I/R) injury. SC79 is a novel, selective and highly-efficient Akt activator. This study aimed to investigate the neuroprotective effect of SC79 against cerebral I/R injury in a rat model, and to explore the possible underlying mechanisms.

Material/Methods

Male Sprague-Dawley rats received cerebral ischemia for 1 hour, followed by brain reperfusion for 0.5–24 hours. The cerebral I/R injury animal model were treated with SC79 alone or SC79 in combination with LY294002. Western blots were used to detect the levels of expression of phosphatidylinositol AKT (p-Akt), Bax, and bcl-2. Twenty-four hours after cerebral I/R, the degree of brain injury was evaluated by detecting the neurological deficit score (NDS). The infarct rate of brain tissue was observed by TTC (2, 3, 5-triphenyltetrazolium chloride) staining. TUNEL (terminal deoxynucleotidyl transferase-mediated UTP nick end labeling) staining was used to detect cell apoptosis.

Results

p-Akt was activated during early cerebral I/R at 0.5 hours, and reached the highest levels at 4 hours, then gradually decreased from 6 hours, and reached and maintained the lowest levels at 12–24 hours. Bax expression was gradually increased from 6 hours and reached the highest level at 24 hours. However, bcl-2 expression was gradually increased and reached the highest levels at 4 hours, then gradually decreased from 6 hours, and reached the lowest levels at 24 hours. Administration of SC79 decreased infarct volumes and improved neurological function significantly. LY294002 in combination with SC79 lost the capability of SC79 to resist the cerebral I/R injury. SC79 treatment alone activated p-Akt and promoted anti-apoptotic bcl-2 and inhibited anti-apoptotic Bax expression in middle cerebral artery occlusion (MCAO) mice. However, combined SC79 and LY294002 treatment abolished SC79-induced p-Akt activity, inhibited anti-apoptotic bcl-2 and promoted anti-apoptotic Bax expression in MCAO mice. Furthermore, SC79 treatment alone attenuated apoptotic neuronal cell death, but abolished this effect in SC79 in combination with LY294002 treated groups.

Conclusions

SC79 significantly increased Akt activation and reduced infarct volume and subsequently improved neurological function in ischemic brain after cerebral I/R injury in rats. These findings suggested that SC79 may be as a neuroprotective drug to be potentially used in the clinic.

Role of microglia under cardiac and cerebral ischemia/reperfusion (I/R) injury

Both cerebral and cardiac ischemia causes loss of cerebral blood flow, which may lead to neuronal cell damage, neurocognitive impairment, learning and memory difficulties, neurological deficits, and brain death. Although reperfusion is required immediately to restore the blood supply to the brain, it could lead to several detrimental effects on the brain. Several studies demonstrate that microglia activity increases following cerebral and cardiac ischemic/reperfusion (I/R) injury. However, the effects of microglial activation in the brain following I/R remains unclear. Some reports demonstrated that microglia were involved in neurodegeneration and oxidative stress generation, whilst others showed that microglia did not respond to I/R injury. Moreover, microglia are activated in a time-dependent manner, and in a specific brain region following I/R. Recently, several therapeutic approaches including pharmacological interventions and electroacupuncture showed the beneficial effects, while some interventions such as hyperthermia and hyperoxic resuscitation, demonstrated the deteriorated effects on the microglial activity after I/R. Therefore, the present review summarized and discussed those studies regarding the effects of global and focal cerebral as well as cardiac I/R injury on microglia activation, and the therapeutic interventions.

High Tidal Volume Induces Mitochondria Damage and Releases Mitochondrial DNA to Aggravate the Ventilator-Induced Lung Injury

Objective

This study aimed to determine whether high tidal volume (HTV) induce mitochondria damage and mitophagy, contributing to the release of mitochondrial DNA (mtDNA). Another aim of the present study was to investigate the role and mechanism of mtDNA in ventilator-induced lung injury (VILI) in rats.

Methods

Rats were tracheotomized and allowed to breathe spontaneously or mechanically ventilated for 4 h. After that, lung injury was assessed. Inhibition of toll-like receptor 9 (TLR9), named ODN2088, was used to determine the involvement of TLR9/myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway in VILI. The mitochondrial damage and release of mtDNA were assessed. Pharmacological inhibition of mtDNA (chloroquine) was used to determine whether mtDNA trigger inflammation via TLR9 in VILI. EDU-labeled mtDNA deriving from mitophagy was assessed by immunofluorescence. The role of mitophagy in VILI was shown by administration of antimycin A and cyclosporine A.

Main results

Rats subjected to HTV showed more severe pulmonary edema and inflammation than the other rats. The decreased expression of TLR9, MyD88, and NF-κB were observed following the use of ODN2088. Mechanical ventilation (MV) with HTV damaged mitochondria which resulted in dysfunctional ATP synthesis, accumulation of reactive oxygen species, and loss of mitochondrial membrane potential. Moreover, the results of distribution of fluorescence in rats upon HTV stimulation indicated that mtDNA cleavage was associated with mitophagy. The expression levels of mitophagy related genes (LC3B-II/LC3B-I, PINK1, Parkin, and mitofusin 1) in animals ventilated with HTV were significantly upregulated. Administration of antimycin A aggregated the histological changes and inflammation after MV, but these effects were attenuated when administered in the presence of cyclosporine A.

Conclusion

MV with HTV induces mitochondrial damage and mitophagy, contributing to the release of mtDNA, which may be induced VILI in rat via TLR9/MyD88/NF-κB signaling pathway.

Kidney Proximal Tubular TLR9 Exacerbates Ischemic Acute Kidney Injury

The role for kidney TLR9 in ischemic acute kidney injury (AKI) remains unclear. In this study, we tested the hypothesis that renal proximal tubular TLR9 activation exacerbates ischemic AKI by promoting renal tubular epithelial apoptosis and inflammation. To test this hypothesis, we generated mice lacking TLR9 in renal proximal tubules (TLR9^fl/fl PEPCK Cre mice). Contrasting previous studies in global TLR9 knockout mice, mice lacking renal proximal tubular TLR9 were protected against renal ischemia/reperfusion (IR) injury, with reduced renal tubular necrosis, inflammation (decreased proinflammatory cytokine synthesis and neutrophil infiltration), and apoptosis (decreased DNA fragmentation and caspase activation) when compared with wild-type (TLR9^fl/fl) mice. Consistent with this, a selective TLR9 agonist oligonucleotide 1668 exacerbated renal IR injury in TLR9^fl/fl mice but not in renal proximal tubular TLR9-null mice. Furthermore, in cultured human and mouse proximal tubule cells, TLR9-selective ligands induced NF-κB activation, proinflammatory cytokine mRNA synthesis, as well as caspase activation. We further confirm in the present study that global TLR9 deficiency had no impact on murine ischemic AKI. Taken together, our studies show that renal proximal tubular TLR9 activation exacerbates ischemic AKI by promoting renal tubular inflammation, apoptosis as well as necrosis, after IR via NF-κB and caspase activation. Our studies further suggest the complex nature of TLR9 activation, as renal tubular epithelial TLR9 promotes cell injury and death whereas TLR9 signaling in other cell types may promote cytoprotective effects.

CpG-ODN exerts a neuroprotective effect via the TLR9/pAMPK signaling pathway by activation of autophagy in a neonatal HIE rat model

Hypoxic Ischemic Encephalopathy (HIE) is an injury caused to the brain due to prolonged lack of oxygen and blood supply which results in death or long-term disabilities. The main aim of this study was to investigate the role of Cytosine-phospho-guanine oligodeoxynucleotide (CpG-ODN) in autophagy after HIE. Ten-day old (P10) rat pups underwent right common carotid artery ligation followed by 2.5h of hypoxia as previously described by Rice-Vannucci. At 1h post HIE, rats were intranasally administered with recombinant CpG-ODN. Time-course expression levels of endogenous key proteins, TLR9, pAMPK/AMPK, LC3II/I, and LAMP1 involved in CpG-ODN's protective effects were measured using western blot. Short (48h) and long (4w) term neurobehavior studies were performed using righting reflex, negative geotaxis, water maze, foot fault and Rota rod tests. Brain samples were collected after long term for histological analysis. Furthermore, to elucidate the pathway via which CpG-ODN confers protection, TLR9 and AMPK inhibitors were used. Time course results showed that the expression of TLR9, pAMPK/AMPK, LC3II/I, LAMP1 increased after HIE. Neurobehavioral studies showed that HIE induced a significant delay in development and resulted in cognitive and motor function deficits. However, CpG-ODN ameliorated HIE-induced outcomes and improved long term neurological deficits. In addition, CpG-ODN increased expression of pAMPK/AMPK, p-ULK1/ULK1, P-AMBRA1/AMBRA1, LC3II/I and LAMP1 while inhibition of TLR9 and AMPK reversed those effects. In summary, CpG-ODN increased HIE-induced autophagy and improved short and long term neurobehavioral outcomes which may be mediated by the TLR9/pAMPK signaling pathway after HIE.

CpG oligodeoxynucleotide preconditioning improves cardiac function after myocardial infarction via modulation of energy metabolism and angiogenesis

Unmethylated CpG oligodeoxynucleotide (CpG-ODN), a Toll-like receptor 9 (TLR9) ligand, has been shown to protect against myocardial ischemia/reperfusion injury. However, the potential effects of CpG-ODN on myocardial infarction (MI) induced by persistent ischemia remains unclear. Here, we investigated whether and how CpG-ODN preconditioning protects against MI in mice. C57BL/6 mice were treated with CpG-ODN by i.p. injection 2 hr prior to MI induction, and cardiac function, and histology were analyzed 2 weeks after MI. Both 1826-CpG and KSK-CpG preconditioning significantly improved the left ventricular (LV) ejection fraction (LVEF) and LV fractional shortening (LVFS) when compared with non-CpG controls. Histological analysis further confirmed the cardioprotection of CpG-ODN preconditioning. In vitro studies further demonstrated that CpG-ODN preconditioning increases cardiomyocyte survival under hypoxic/ischemic conditions by enhancing stress tolerance through TLR9-mediated inhibition of the SERCA2/ATP and activation of AMPK pathways. Moreover, CpG-ODN preconditioning significantly increased angiogenesis in the infarcted myocardium compared with non-CpG. However, persistent TLR9 activation mediated by lentiviral infection failed to improve cardiac function after MI. Although CpG-ODN preconditioning increased angiogenesis in vitro, both the persistent stimulation of CpG-ODN and stable overexpression of TLR9 suppressed the tube formation of cardiac microvascular endothelial cells. CpG-ODN preconditioning significantly protects cardiac function against MI by suppressing the energy metabolism of cardiomyocytes and promoting angiogenesis. Our data also indicate that CpG-ODN preconditioning may be useful in MI therapy.

Preclinical Development of a Prophylactic Neuroprotective Therapy for the Preventive Treatment of Anticipated Ischemia-Reperfusion Injury

Ischemia-reperfusion brain injury can be iatrogenically induced secondary to life-saving procedures. Prophylactic treatment of these patients offers a promising prevention for lifelong complications. We postulate that a cytosine-guanine (CpG) oligodeoxynucleotide (ODN) can provide robust antecedent protection against cerebral ischemic injury with minimal release of pro-inflammatory cytokines, making it an ideal candidate for further clinical development. Mouse and nonhuman primate (NHP) models of cerebral ischemic injury were used to test whether an A-type CpG ODN, which induces minimal systemic inflammatory cytokine responses, can provide prophylactic protection. Extent of injury in the mouse was measured by histological staining of live tissue. In the NHP, injury was assessed 2 and 7 days post-occlusion from T2-weighted magnetic resonance images and neurological and motor deficits were cataloged daily. Plasma cytokine levels were measured using species-specific Luminex assays. Prophylactic administration of an A-type CpG ODN provided robust protection against cerebral ischemic injury in the mouse with minimal systemic inflammation. Rhesus macaques treated with D192935, a mixture of human optimized A-type CpG ODNs, had smaller infarcts and demonstrated significantly less neurological and motor deficits following ischemic injury. Our findings demonstrate the translational potential of D192935 as a prophylactic treatment for patients at risk of cerebral ischemic injury.

Toll-like receptor 9 mediates paraquat-induced acute lung injury: an in vitro and in vivo study

AIMS

This study aimed to investigate the role of Toll-like receptor 9 in paraquat-induced acute lung injury (ALI).

MAIN METHODS

For in vivo study,C57BL mice were randomly assigned into the vehicle control group, paraquat group, paraquat + TLR9 antagonist (ODN2088) group, and TLR9 antagonist (ODN2088) group (n=36 per group). After paraquat 30mg/kg ip for 2, 24 and 48h, serum samples and lung tissues were collected to evaluate ALI and TLR9 signaling by lung injury score, protein levels of TLR9, MyD88, p-IRAK4, p-p65, and serum TNF-α and IL-1β levels. As for in vitro research A549 cells were randomly divided into the control group, paraquat group, paraquat + TLR9 siRNA group, and TLR9 siRNA group. After paraquat treatment for 24h, the cells and supernatant were collected to measureTLR9, TNF-α, IL-1 mRNA expression, and detect activation of NF-κB, caspase-3.

KEY FINDINGS

In vivo, the lung injury score, the TLR9, MyD88, p-IRAK4 and p-p65 protein levels, and cytokines TNF-α and IL-1β levels in paraquat group were significantly higher than that in the control group;TLR9 blocker ODN2088 pretreatment attenuated lung injury, inhibited MyD88 and NF-κB activation, and reduced TNF-α and IL-1β in serum. In vitro result shows that the gene silencing of TLR9 reduced the mRNA expression of TLR9, TNF-α and IL-1, inhibited NF-κB and caspase-3 activation, attenuated cell apoptosis.

SIGNIFICANCE

TLR9 mediates paraquat-induced ALI, antagonizing TLR9 or silencing TLR9gene may attenuate paraquat-induced ALI.

The protective effects of shikonin on hepatic ischemia/reperfusion injury are mediated by the activation of the PI3K/Akt pathway

Hepatic ischemia/reperfusion (I/R) injury, which can result in severe liver injury and dysfunction, occurs in a variety of conditions such as liver transplantation, shock, and trauma. Cell death in hepatic I/R injury has been linked to apoptosis and autophagy. Shikonin plays a significant protective role in ischemia/reperfusion injury. The purpose of the present study was to investigate the protective effect of shikonin on hepatic I/R injury and explore the underlying mechanism. Mice were subjected to segmental (70%) hepatic warm ischemia to induce hepatic I/R injury. Two doses of shikonin (7.5 and 12.5 mg/kg) were administered 2 h before surgery. Balb/c mice were randomly divided into four groups: normal control, I/R, and shikonin preconditioning at two doses (7.5 and 12.5 mg/kg). The serum and liver tissues were collected at three time points (3, 6, and 24 h). Shikonin significantly reduced serum AST and ALT levels and improved pathological features. Shikonin affected the expression of Bcl-2, Bax, caspase 3, caspase 9, Beclin-1, and LC3, and upregulated PI3K and p-Akt compared with the levels in the I/R group. Shikonin attenuated hepatic I/R injury by inhibiting apoptosis and autophagy through a mechanism involving the activation of PI3K/Akt signaling.

Toll-like Receptors in the Vascular System: Sensing the Dangers Within

Toll-like receptors (TLRs) are components of the innate immune system that respond to exogenous infectious ligands (pathogen-associated molecular patterns, PAMPs) and endogenous molecules that are released during host tissue injury/death (damage-associated molecular patterns, DAMPs). Interaction of TLRs with their ligands leads to activation of downstream signaling pathways that induce an immune response by producing inflammatory cytokines, type I interferons (IFN), and other inflammatory mediators. TLR activation affects vascular function and remodeling, and these molecular events prime antigen-specific adaptive immune responses. Despite the presence of TLRs in vascular cells, the exact mechanisms whereby TLR signaling affects the function of vascular tissues are largely unknown. Cardiovascular diseases are considered chronic inflammatory conditions, and accumulating data show that TLRs and the innate immune system play a determinant role in the initiation and development of cardiovascular diseases. This evidence unfolds a possibility that targeting TLRs and the innate immune system may be a novel therapeutic goal for these conditions. TLR inhibitors and agonists are already in clinical trials for inflammatory conditions such as asthma, cancer, and autoimmune diseases, but their study in the context of cardiovascular diseases is in its infancy. In this article, we review the current knowledge of TLR signaling in the cardiovascular system with an emphasis on atherosclerosis, hypertension, and cerebrovascular injury. Furthermore, we address the therapeutic potential of TLR as pharmacological targets in cardiovascular disease and consider intriguing research questions for future study.

Reprint of: Microglial toll-like receptors and Alzheimer's disease

Microglial activation represents an important pathological hallmark of Alzheimer's disease (AD), and emerging data highlight the involvement of microglial toll-like receptors (TLRs) in the course of AD. TLRs have been observed to exert both beneficial and detrimental effects on AD-related pathologies, and transgenic animal models have provided direct and credible evidence for an association between TLRs and AD. Moreover, analyses of genetic polymorphisms have suggested interactions between genetic polymorphisms in TLRs and AD risk, further supporting the hypothesis that TLRs are involved in AD. In this review, we summarize the key evidence in this field. Future studies should focus on exploring the mechanisms underlying the potential roles of TLRs in AD.

Functions and mechanisms of microglia/macrophages in neuroinflammation and neurogenesis after stroke

Microglia/macrophages are the major immune cells involved in the defence against brain damage. Their morphology and functional changes are correlated with the release of danger signals induced by stroke. These cells are normally responsible for clearing away dead neural cells and restoring neuronal functions. However, when excessively activated by the damage-associated molecular patterns following stroke, they can produce a large number of proinflammatory cytokines that can disrupt neural cells and the blood-brain barrier and influence neurogenesis. These effects indicate the important roles of microglia/macrophages in the pathophysiological processes of stroke. However, the modifiable and adaptable nature of microglia/macrophages may also be beneficial for brain repair and not just result in damage. These distinct roles may be attributed to the different microglia/macrophage phenotypes because the M1 population is mainly destructive, while the M2 population is neuroprotective. Additionally, different gene expression signature changes in microglia/macrophages have been found in diverse inflammatory milieus. These biofunctional features enable dual roles for microglia/macrophages in brain damage and repair. Currently, it is thought that the proper inflammatory milieu may provide a suitable microenvironment for neurogenesis; however, detailed mechanisms underlying the inflammatory responses that initiate or inhibit neurogenesis remain unknown. This review summarizes recent progress concerning the mechanisms involved in brain damage, repair and regeneration related to microglia/macrophage activation and phenotype transition after stroke. We also argue that future translational studies should be targeting multiple key regulating molecules to improve brain repair, which should be accompanied by the concept of a "therapeutic time window" for sequential therapies.