Toll-like receptors in inflammation of the central nervous system

Mechanistic insights on TLR-4 mediated inflammatory pathway in neurodegenerative diseases

Neurodegenerative diseases (NDDs) pose a significant issue in healthcare, needing a thorough knowledge of their complex molecular mechanisms. A diverse set of cell signaling mediators and their interactions play critical roles in neuroinflammation. The release of pro-inflammatory mediators in response to neural dysfunction is detrimental to normal cell survival. Moreover, the important role of nuclear factor-κB (NF-κB) in the central nervous system through Toll-like receptor (TLR) activation has been well established. Therefore, through a comprehensive review of current research and experimentation, this investigation elucidates the interactions between novel pharmacological agents (TLR-4/NF-κB inhibitors) and neurodegeneration encompassing Alzheimer's, Parkinson's, Huntington's disease, amyotrophic lateral sclerosis and stroke. Insights garnered from this exploration underscore the potential of TLR-4 as a therapeutic target. Through the revelation of these insights, our aim is to establish a foundation for the development of enhanced and focused therapeutic approaches in the continuous endeavor to combat neurodegeneration. This review thus serves as a roadmap, guiding future research endeavors toward innovative strategies for combatting the complex interplay between TLR-4 signaling and NDDs.

Exosomes derived from human umbilical cord mesenchymal stem cells decrease neuroinflammation and facilitate the restoration of nerve function in rats suffering from intracerebral hemorrhage

Exosomes derived from human umbilical cord mesenchymal stem cells (hUCMSC-ex) have become a hopeful substitute for whole-cell therapy due to their minimal immunogenicity and tumorigenicity. The present study aimed to investigate the hypothesis that hUCMSC-ex can alleviate excessive inflammation resulting from intracerebral hemorrhage (ICH) and facilitate the rehabilitation of the nervous system in rats. In vivo, hemorrhagic stroke was induced by injecting collagenase IV into the striatum of rats using stereotactic techniques. hUCMSC-ex were injected via the tail vein at 6 h after ICH model establishment at a dosage of 200 µg. In vitro, astrocytes were pretreated with hUCMSC-ex and then stimulated with hemin (20 μmol/mL) to establish an ICH cell model. The expression of TLR4/NF-κB signaling pathway proteins and inflammatory factors, including TNF-α, IL-1β, and IL-10, was assessed both in vivo and in vitro to investigate the impact of hUCMSC-ex on inflammation. The neurological function of the ICH rats was evaluated using the corner turn test, forelimb placement test, Longa score, and Bederson score on the 1st, 3rd, and 5th day. Additionally, RT-PCR was employed to examine the mRNA expression of TLR4 following hUCMSC-ex treatment. The findings demonstrated that hUCMSC-ex downregulated the protein expression of TLR4, NF-κB/P65, and p-P65, reduced the levels of pro-inflammatory cytokines TNF-α and IL-1β, and increased the expression of the anti-inflammatory cytokine IL-10. Ultimately, the administration of hUCMSC-ex improved the behavioral performance of the ICH rats. However, the results of PT-PCR indicated that hUCMSC-ex did not affect the expression of TLR4 mRNA induced by ICH, suggesting that hUCMSCs-ex may inhibit TLR4 translation rather than transcription, thereby suppressing the TLR4/NF-κB signaling pathway. We can conclude that hUCMSC-ex mitigates hyperinflammation following ICH by inhibiting the TLR4/NF-κB signaling pathway. This study provides preclinical evidence for the potential future application of hUCMSC-ex in the treatment of cerebral injury.

Hypothermia and temperature modulation for intracerebral hemorrhage (ICH): pathophysiology and translational applications

Background

Intracerebral hemorrhage (ICH) still poses a substantial challenge in clinical medicine because of the high morbidity and mortality rate that characterizes it. This review article expands into the complex pathophysiological processes underlying primary and secondary neuronal death following ICH. It explores the potential of therapeutic hypothermia as an intervention to mitigate these devastating effects.

Methods

A comprehensive literature review to gather relevant studies published between 2000 and 2023.

Discussion

Primary brain injury results from mechanical damage caused by the hematoma, leading to increased intracranial pressure and subsequent structural disruption. Secondary brain injury encompasses a cascade of events, including inflammation, oxidative stress, blood-brain barrier breakdown, cytotoxicity, and neuronal death. Initial surgical trials failed to demonstrate significant benefits, prompting a shift toward molecular mechanisms driving secondary brain injury as potential therapeutic targets. With promising preclinical outcomes, hypothermia has garnered attention, but clinical trials have yet to establish its definitive effectiveness. Localized hypothermia strategies are gaining interest due to their potential to minimize systemic complications and improve outcomes. Ongoing and forthcoming clinical trials seek to clarify the role of hypothermia in ICH management.

Conclusion

Therapeutic hypothermia offers a potential avenue for intervention by targeting the secondary injury mechanisms. The ongoing pursuit of optimized cooling protocols, localized cooling strategies, and rigorous clinical trials is crucial to unlocking the potential of hypothermia as a therapeutic tool for managing ICH and improving patient outcomes.

Toll-like receptors in pathogenesis of neurodegenerative diseases and their therapeutic potential

Toll-like receptors (TLRs) are a family of pattern-recognition receptors triggered by pathogen-derived and tissue-damage-related ligands. TLRs were previously believed to only be expressed in immune cells. However, it is now confirmed that they are ubiquitously expressed in cells within the body including neurons, astrocytes, and microglia of the central nervous system (CNS). Activation of TLRs is capable of inducing immunologic and inflammatory responses to injury or infection of CNS. This response is self-limiting that usually resolves once the infection has been eradicated or the tissue damage has been repaired. However, the persistence of inflammation-inducing insults or a failure in normal resolution mechanisms may result in overwhelming inflammation which may induce neurodegeneration. This implies that TLRs may play a role in mediating the link between inflammation and neurodegenerative diseases namely Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke, and amyotrophic lateral sclerosis. So, new therapeutic approaches that specifically target TLRs may be developed by better understanding TLR expression mechanisms in the CNS and their connections to particular neurodegenerative disorders. Therefore, this review paper discussed the role of TLRs in neurodegenerative diseases.

Regulatory effect of isovitexin on MAPK/NF-κB signal in mice with acute ulcerative colitis

The aim of this study was to investigate the anti-inflammatory effects and mechanism of isovitexin on ulcerative colitis mice and RAW264.7 cells. The results showed that isovitexin had strong antioxidant and anti-inflammatory effects, and could restore intestinal barrier integrity (p < 0.01). In addition, isovitexin inhibited the expression of MyD88, TLR4 and NF-κB p65 proteins. At the same time, isovitexin can inhibit the activation of MAPK/NF-κB signaling pathway in RAW264.7 cells. In conclusion, isovitexin has a protective effect on UC mice, and its improvement mechanism of UC might be related to MAPK/NF-κB signaling pathway.

Protective effect of Moringa oleifera Lam. leaf extract against oxidative stress, inflammation, depression, and apoptosis in a mouse model of hepatic encephalopathy

The present study aimed to assess the antioxidative, anti-inflammatory, antiapoptotic, and anti-depression impacts of Moringa oleifera Lam. leaf ethanolic extract (MOLE) in the hippocampus and cerebral cortex of CCl₄-induced hepatic encephalopathy mouse model. High-performance liquid chromatography was used to detect marker compounds: rutin and β-sitosterol. Animals were divided into four groups: vehicle group, CCl₄-treated group, MOLE-treated group, and (CCl₄ + MOLE) group treated with MOLE for 14 days before CCl₄-induced neurotoxicity. MOLE decreased alanine aminotransferase, aspartate aminotransferase, corticosterone, and ammonia levels in serum and improved the antioxidant status of CCl₄-treated mice in the hippocampus and cerebral cortex. It reduced the expression of toll-like receptor 4 (TLR4), TLR2, myeloid differentiation primary response 88 (MYD88), and nuclear factor-kappa B (NF-κB) genes and the protein levels of the pro-inflammatory cytokines. MOLE also attenuated apoptosis, as revealed by the reduced expression of caspase3, and prevented histological deterioration. Furthermore, MOLE attenuated CCl₄-induced anxiety and depression-like behavioral changes. Collectively, MOLE modulates neuroinflammation, oxidative stress, TLR4/2-MyD88/NF-κB signaling, and apoptosis in the hippocampus and cerebral cortex of the hepatic encephalopathy experimental model.

Primary Cortical Cell Tri-Culture-Based Screening of Neuroinflammatory Response in Toll-like Receptor Activation

The activation of toll-like receptors (TLRs) in the central nervous system (CNS) can lead to neuroinflammation and contribute to many neurological disorders, including autoimmune diseases. Cell culture models are powerful tools for studying specific molecular and cellular mechanisms that contribute to these disease states and identifying potential therapeutics. However, most cell culture models have limitations in capturing biologically relevant phenomena, due in part to the non-inclusion of necessary cell types. Neurons, astrocytes, and microglia (critical cell types that play a role in neuroinflammation) all express at least a subset of TLRs. However, the response of each of these cell types to various TLR activation, along with their relative contribution to neuroinflammatory processes, is far from clear. In this study, we demonstrate the screening capabilities of a primary cortical cell tri-culture of neuron, astrocyte, and microglia from neonatal rats. Specifically, we compare the neuroinflammatory response of tri-cultures to that of primary neuron-astrocyte co-cultures to a suite of known TLR agonists. We demonstrate that microglia are required for observation of neurotoxic neuroinflammatory responses, such as increased cell death and apoptosis, in response to TLR2, 3, 4, and 7/8 activation. Additionally, we show that following TLR3 agonist treatment, microglia and astrocytes play opposing roles in the neuroinflammatory response, and that the observed response is dictated by the degree of TLR3 activation. Overall, we demonstrate that microglia play a significant role in the neuroinflammatory response to TLR activation in vitro and, hence, the tri-culture has the potential to serve as a screening platform that better replicates the in vivo responses.

Zhongfeng Capsules protects against cerebral ischemia-reperfusion injury via mediating the phosphoinositide 3-kinase/Akt and toll-like receptor 4/nuclear factor kappa B signaling pathways by regulating neuronal apoptosis and inflammation

Inflammatory reaction and neuronal apoptosis are the major pathophysiological mechanisms involved in cerebral ischemia-reperfusion injury (CI/RI). It has been reported that Zhongfeng Capsules (ZFCs), which contain Panax notoginseng, Hirudo, Red ginseng, Eupolyphaga sinensis, Pangolin scales, Rhubarb, and Radix Salvia miltiorrhizae, have a definite therapeutic effect on CI/RI. However, the specific molecular mechanisms of ZFCs are unclear. In this study, the effects of ZFCs on middle cerebral artery occlusion were investigated in rats. Our results showed that neurological impairment and neuronal apoptosis were alleviated in ZFC-treated rats. Additionally, infarct volume and cerebral edema decreased and there was an improvement in histopathological features. Furthermore, the expression levels of IL-1β, IL-6, and TNF-α were downregulated in ZFC-treated rats. TLR 4, NF-κB, Bax, and Caspase-3 expression also tended to decrease, whereas the expression of Bcl-2, p-PI3K, p-Akt, and I-κBα increased. The results indicate that the ZFCs effectively protected the rats against CI/RI possibly via the TLR4/NF-κB signaling pathway. Additionally, the formulation regulated the transcriptional activity of NF-κB, secretion of downstream inflammatory factors, and the expression of Bcl-2-Bax proteins in the PI3K/Akt pathway. Our findings suggest that ZFCs suppress neuronal apoptosis and inflammatory reaction via the PI3K/Akt and TLR4/NF-κB signaling pathways, respectively. Moreover, activation of the PI3K/Akt pathway may result in the inhibition of proinflammatory cytokine secretion, which may be another mechanism by which ZFCs alleviate CI/RI.

Effects of astrocytes and microglia on neuroinflammation after spinal cord injury and related immunomodulatory strategies

Spinal cord injury (SCI) is a catastrophic event which is still without adequate therapies. Neuroinflammation is the main pathogenesis of secondary damage post-SCI, leading to tissue loss and neurological dysfunction. Previous studies have shown that microglia and astrocytes are the major immune cells in the central nervous system (CNS) and play a crucial role in modulating neuroinflammatory responses. In this study, we mainly review the effects of neuroinflammation in SCI, focusing on the contributions of microglia and astrocytes and their cross-talk. Furthermore, we will also discuss therapeutic strategies on how to regulate their immunophenotype to suppress robust inflammation and facilitate injury prognosis.

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

Bone mesenchymal stem cell-derived extracellular vesicles deliver microRNA-23b to alleviate spinal cord injury by targeting toll-like receptor TLR4 and inhibiting NF-κB pathway activation

Bone mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) are known for recovery of injured tissues. We investigated the possible mechanism of BMSC-EVs in spinal cord injury (SCI). EVs were isolated from BMSCs and injected into SCI rats to evaluate the recovery of hindlimb motor function. The spinal cord tissue was stained after modeling to analyze spinal cord structure and inflammatory cell infiltration and detect microRNA (miR)-23b expression. The activity of lipopolysaccharide (LPS)-induced BV2 inflammatory cells was detected. The protein contents of interleukin (IL)-6, IL-1β, IL-10 and tumor necrosis factor-α (TNF-α) in spinal cord and BV2 cells were measured. Western blot analysis was used to detect the level of toll-like receptor (TLR)4, p65, p-p65, iNOS, and Arg1 in spinal cord tissue and cells. TLR4 was overexpressed in rats and cells to evaluate the content of inflammatory cytokines. After EV treatment, the motor function of SCI rats was improved, SCI was relieved, and miR-23b expression was increased. After treatment with EV-miR-23b, iNOS, IL-6, IL-1β, and TNF-α contents were decreased, while Arg1 and IL-10 were increased. The levels of TLR4 and p-p65 in spinal cord and BV2 cells were decreased. The rescue experiments verified that after overexpression of TLR4, the activity of BV2 cells was decreased, the contents of IL-6, IL-1β, TNF-α, and p-p65 were increased, IL-10 was decreased, and SCI was aggravated. To conclude, The miR-23b delivered by BMSC-EVs targets TLR4 and inhibits the activation of NF-κB pathway, relieves the inflammatory response, so as to improve SCI in rats.

Nutritional Supplementation of Naturally Occurring Vitamin D to Improve Hemorrhagic Stroke Outcomes

Vitamin D deficiency, if left untreated, is associated with bone disorders, cardiovascular damage, and an increased risk of ischemic stroke. While there are various nutritional options for the natural intake of vitamin D, we hope to elucidate the potential mechanisms dietary vitamin D may play in hemorrhagic stroke pathology. This scoping review outlines findings from studies relevant to the biochemical activity of vitamin D, the impact of vitamin D deficiency on hemorrhagic stroke outcomes, and the potential benefit of nutritional vitamin D on hemorrhagic stroke outcomes. Here, we analyze the relevant factors that can lead to vitamin D deficiency, and subsequently, a higher risk of hemorrhagic stroke incidence with worsened subsequent outcomes. The neuroprotective mechanisms through which vitamin D works to attenuate hemorrhagic stroke onset and post-stroke outcomes have not yet been thoroughly examined. However, researchers have proposed several potential protective mechanisms, including reduction of blood brain barrier disturbance by inhibiting the production of reactive oxygen species, mitigation of inflammation through a reduction of levels of proinflammatory cytokines, and prevention of cerebral vasospasm and delayed cerebral ischemia following subarachnoid hemorrhage and intracerebral hemorrhage. While more research is needed and there are limitations to vitamin D supplementation, vitamin D as a whole may play a significant role in the dynamics of hemorrhagic stroke. Further research should focus on expanding our understanding of the neuroprotective capacity and mechanisms of vitamin D, as well as how vitamin D supplementation could serve as an effective course of treatment of hemorrhagic strokes.

Hypoxia-inducible factor-1: Regulatory mechanisms and drug development in stroke

Stroke is an acute cerebrovascular disease caused by sudden rupture of blood vessels in the brain or blockage of blood vessels, which has now become one of the main causes of adult death. During stroke, hypoxia-inducible factor-1 (HIF-1), as an important regulator under hypoxia conditions, is involved in the pathological process of stroke by regulating multi-pathways, such as glucose metabolism, angiogenesis, erythropoiesis, cell survival. However, the roles of HIF-1 in stroke are still controversial, which are related with ischemic time and degree of ischemia. The regulatory mechanisms of HIF-1 in stroke include inflammation, autophagy, oxidative stress, apoptosis and energy metabolism. The potential drugs targeting HIF-1 have attracted more attention, such as HIF-1 inhibitors, HIF-1 stabilizers and natural products. Based on the role of HIF-1 in stroke, HIF-1 is expected to be a potential target for stroke treatment. Resolving when and what interventions for HIF-1 to take during stroke will provide novel strategies for stroke treatment.

Phthalide derivative CD21 attenuates tissue plasminogen activator-induced hemorrhagic transformation in ischemic stroke by enhancing macrophage scavenger receptor 1-mediated DAMP (peroxiredoxin 1) clearance

BACKGROUND

Hemorrhagic transformation (HT) is a critical issue in thrombolytic therapy in acute ischemic stroke. Damage-associated molecular pattern (DAMP)-stimulated sterile neuroinflammation plays a crucial role in the development of thrombolysis-associated HT. Our previous study showed that the phthalide derivative CD21 attenuated neuroinflammation and brain injury in rodent models of ischemic stroke. The present study explored the effects and underlying mechanism of action of CD21 on tissue plasminogen activator (tPA)-induced HT in a mouse model of transient middle cerebral artery occlusion (tMCAO) and cultured primary microglial cells.

METHODS

The tMCAO model was induced by 2 h occlusion of the left middle cerebral artery with polylysine-coated sutures in wildtype (WT) mice and macrophage scavenger receptor 1 knockout (MSR1^-/-) mice. At the onset of reperfusion, tPA (10 mg/kg) was intravenously administered within 30 min, followed by an intravenous injection of CD21 (13.79 mg/kg/day). Neuropathological changes were detected in mice 3 days after surgery. The effect of CD21 on phagocytosis of the DAMP peroxiredoxin 1 (Prx1) in lysosomes was observed in cultured primary microglial cells from brain tissues of WT and MSR1^-/- mice.

RESULTS

Seventy-two hours after brain ischemia, CD21 significantly attenuated neurobehavioral dysfunction and infarct volume. The tPA-infused group exhibited more severe brain dysfunction and hemorrhage. Compared with tPA alone, combined treatment with tPA and CD21 significantly attenuated ischemic brain injury and hemorrhage. Combined treatment significantly decreased Evans blue extravasation, matrix metalloproteinase 9 expression and activity, extracellular Prx1 content, proinflammatory cytokine mRNA levels, glial cells, and Toll-like receptor 4 (TLR4)/nuclear factor κB (NF-κB) pathway activation and increased the expression of tight junction proteins (zonula occludens-1 and claudin-5), V-maf musculoaponeurotic fibrosarcoma oncogene homolog B, and MSR1. MSR1 knockout significantly abolished the protective effect of CD21 against tPA-induced HT in tMCAO mice. Moreover, the CD21-induced phagocytosis of Prx1 was MSR1-dependent in cultured primary microglial cells from WT and MSR1^-/- mice, respectively.

CONCLUSION

The phthalide derivative CD21 attenuated tPA-induced HT in acute ischemic stroke by promoting MSR1-induced DAMP (Prx1) clearance and inhibition of the TLR4/NF-κB pathway and neuroinflammation.

White Matter Injury After Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 15% of all stroke cases. ICH is a devastating form of stroke associated with high morbidity, mortality, and disability. Preclinical studies have explored the mechanisms of neuronal death and gray matter damage after ICH. However, few studies have examined the development of white matter injury (WMI) following ICH. Research on WMI indicates that its pathophysiological presentation involves axonal damage, demyelination, and mature oligodendrocyte loss. However, the detailed relationship and mechanism between WMI and ICH remain unclear. Studies of other acute brain insults have indicated that WMI is strongly correlated with cognitive deficits, neurological deficits, and depression. The degree of WMI determines the short- and long-term prognosis of patients with ICH. This review demonstrates the structure and functions of the white matter in the healthy brain and discusses the pathophysiological mechanism of WMI following ICH. Our review reveals that the development of WMI after ICH is complex; therefore, comprehensive treatment is essential. Understanding the relationship between WMI and other brain cells may reveal therapeutic targets for the treatment of ICH.

Mechanism of White Matter Injury and Promising Therapeutic Strategies of MSCs After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke with high disability and high mortality rates, and there is no effective treatment. The predilection site of ICH is in the area of the basal ganglia and internal capsule (IC), where exist abundant white matter (WM) fiber tracts, such as the corticospinal tract (CST) in the IC. Proximal or distal white matter injury (WMI) caused by intracerebral parenchymal hemorrhage is closely associated with poor prognosis after ICH, especially motor and sensory dysfunction. The pathophysiological mechanisms involved in WMI are quite complex and still far from clear. In recent years, the neuroprotection and repairment capacity of mesenchymal stem cells (MSCs) has been widely investigated after ICH. MSCs exert many unique biological effects, including self-recovery by producing growth factors and cytokines, regenerative repair, immunomodulation, and neuroprotection against oxidative stress, providing a promising cellular therapeutic approach for the treatment of WMI. Taken together, our goal is to discuss the characteristics of WMI following ICH, including the mechanism and potential promising therapeutic targets of MSCs, aiming at providing new clues for future therapeutic strategies.

Inflammatory Foreign Body Response Induced by Neuro-Implants in Rat Cortices Depleted of Resident Microglia by a CSF1R Inhibitor and Its Implications

Inflammatory encapsulation of implanted cortical-neuro-probes [the foreign body response (FBR)] severely limits their use in basic brain research and in clinical applications. A better understanding of the inflammatory FBR is needed to effectively mitigate these critical limitations. Combining the use of the brain permeant colony stimulating factor 1 receptor inhibitor PLX5622 and a perforated polyimide-based multielectrode array platform (PPMP) that can be sectioned along with the surrounding tissue, we examined the contribution of microglia to the formation of inflammatory FBR. To that end, we imaged the inflammatory processes induced by PPMP implantations after eliminating 89-94% of the cortical microglia by PLX5622 treatment. The observations showed that: (I) inflammatory encapsulation of implanted PPMPs proceeds by astrocytes in microglia-free cortices. The activated astrocytes adhered to the PPMP's surfaces. This suggests that the roles of microglia in the FBR might be redundant. (II) PPMP implantation into control or continuously PLX5622-treated rats triggered a localized surge of microglia mitosis. The daughter cells that formed a "cloud" of short-lived (T 1 / 2 ≤ 14 days) microglia around and in contact with the implant surfaces were PLX5622 insensitive. (III) Neuron degeneration by PPMP implantation and the ensuing recovery in time, space, and density progressed in a similar manner in the cortices following 89-94% depletion of microglia. This implies that microglia do not serve a protective role with respect to the neurons. (IV) Although the overall cell composition and dimensions of the encapsulating scar in PLX5622-treated rats differed from the controls, the recorded field potential (FP) qualities and yield were undistinguishable. This is accounted for by assuming that the FP amplitudes in the control and PLX5622-treated rats were related to the seal resistance formed at the interface between the adhering microglia and/or astrocytes and the PPMP platform rather than across the scar tissue. These observations suggest that the prevention of both astrocytes and microglia adhesion to the electrodes is required to improve FP recording quality and yield.

Babao Dan improves neurocognitive function by inhibiting inflammation in clinical minimal hepatic encephalopathy

BACKGROUND AND PURPOSE

Inflammation has been considered a precipitating event that contributes to neurocognitive dysfunction in minimal hepatic encephalopathy (MHE). Inhibition TLR-4 related inflammation can effectively improve neurocognitive dysfunction of MHE. Our previous study showed that Babao Dan (BBD) effectively inhibited inflammation and ameliorated neurocognitive function in rats with acute hepatic encephalopathy (HE) and chronic HE. The mechanism may lie in the regulation of TLR4 signaling pathway. Therefore, this study aimed to evaluate the role of BBD in the treatment of MHE patients with cirrhosis and to elucidate the underlying mechanism by which BBD regulated TLR4 pathway to alleviate inflammation.

METHODS

A randomized controlled trial (n = 62) was conducted to evaluate the clinical efficacy between BBD plus lactulose (n = 31) and lactulose alone (n = 31) in MHE patients by testing neurocognitive function (NCT-A and DST), blood ammonia, liver function (ALT, AST and TBIL) and blood inflammation (IL-1β, IL-6 and TNF-α). Afterward, we detected NO, inflammatory cytokines (IL-1β, IL-6 and TNF-α) and the phosphorylation of P65, JNK, ERK as well as P38 in LPS-activated rat primary bone marrow-derived macrophages (BMDMs), peritoneal macrophages (PMs), and mouse primary BMDMs/PMs/microglia/astrocytes, to investigate the underlying mechanism of BBD inhibiting inflammation through TLR4 pathway. Also, the survival rate of mice, liver function (ALT, AST), blood inflammation (IL-1β, IL-6 and TNF-α), inflammatory cytokines (IL-1β, IL-6 and TNF-α) and histopathological changes in the liver, brain and lung were measured to assess the anti-inflammatory effect of BBD on neurocognitive function in endotoxin shock/endotoxemia mice.

RESULTS

BBD combined with lactulose significantly ameliorated neurocognitive function by decreasing NCT-A (p＜0.001) and increasing DST (p＜0.001); inhibited systemic inflammation by decreasing IL-1β (p＜0.001), IL-6(p＜0.001) and TNF-α (p＜0.001); reduced ammonia level (p = 0.005), and improved liver function by decreasing ALT(p = 0.043), AST(p = 0.003) and TBIL (p = 0.026) in MHE patients. Furthermore, BBD inhibited gene and protein expression of IL-1β, IL-6 and TNF-α as well as NO in rat primary BMDMs/PMs, and mouse primary BMDMs/PMs/microglia/astrocytes in a dose-dependent manner. BBD inhibited the activation of mouse primary BMDMs/PMs/microglia/astrocytes by regulating TLR4 pathway involving the phosphorylation of P65, JNK, ERK and P38. Also, BBD reduced the mortality of mice with endotoxin shock/endotoxemia; serum levels of ALT, AST, IL-1β, IL-6 and TNF-α; gene expression of IL-1β, IL-6 and TNF-α in the liver, brain and lung, and tissue damage in the liver and lung.

CONCLUSION

Our study provided for the first time clinical and experimental evidence supporting the use of BBD in MHE, and revealed that BBD could play a crucial role in targeting and regulating TLR4 inflammatory pathway to improve neurocognitive function in MHE patients.

S-equol, a metabolite of dietary soy isoflavones, alleviates lipopolysaccharide-induced depressive-like behavior in mice by inhibiting neuroinflammation and enhancing synaptic plasticity

Systemic injection with lipopolysaccharide can lead to depressive-like behavior in experimental animals by inducing neuroinflammation and is considered to be a classic model of depression. S-equol is a major metabolite of dietary soy isoflavones with antioxidant and anti-inflammatory effects, and it has many beneficial effects on human health, including alleviation of menopausal symptoms, osteoporosis, cancer, obesity, chronic kidney disease, and cognitive dysfunction. A recent study reported that S-equol inhibited lipopolysaccharide-stimulated neuroinflammation in astrocytes. However, there is no research on the antidepressant-like effects of S-equol. Therefore, the present study was conducted to evaluate the antidepressant-like effects of S-equol in a lipopolysaccharide-induced depression model in mice and explore its underlying mechanisms. Our results demonstrated that treatment with S-equol (10, 20 and 40 mg kg-1) for 19 days markedly reversed the behavior of acute LPS (1.0 mg kg-1) treated mice in sucrose preference, tail suspension and forced swimming tests, exerting antidepressant-like effects. In addition, S-equol administration significantly decreased the levels of pro-inflammatory cytokines (tumor necrosis factor, interleukin-6, interleukin-10, interleukin-1β), increased the levels of 5-hydroxytryptamine and norepinephrine, and normalized the release of tryptophan and kynurenine in the hippocampi of lipopolysaccharide-treated mice. Moreover, treatment with S-equol significantly up-regulated the expression of synaptic plasticity-related proteins (phospho synapsin, synapsin, postsynaptic density-95) and down-regulated the toll-like receptor 4/nuclear factor kappa B signaling pathway in the hippocampi of lipopolysaccharide-treated mice. These findings demonstrated that S-equol significantly alleviated the depressive-like behavior induced by acute systemic injection of LPS, and its antidepressant action was related to mediation of neuroinflammation via the TLR4/NF-κB signaling pathway, normalization of the monoamine neurotransmitter levels, reversal of tryptophan metabolism dysfunction, and enhancement of synaptic plasticity. The current study provides insight into the potential of S-equol in the prevention of depression.

Natural Cinnamaldehyde and Its Derivatives Ameliorate Neuroinflammatory Pathways in Neurodegenerative Diseases

Neurodegenerative diseases are devastating and incurable disorders characterized by neuronal dysfunction. The major focus of experimental and clinical studies are conducted on the effects of natural products and their active components on neurodegenerative diseases. This review will discuss an herbal constituent known as cinnamaldehyde (CA) with the neuroprotective potential to treat neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). Accumulating evidence supports the notion that CA displays neuroprotective effects in AD and PD animal models by modulating neuroinflammation, suppressing oxidative stress, and improving the synaptic connection. CA exerts these effects through its action on multiple signaling pathways, including TLR4/NF-κB, NLRP3, ERK1/2-MEK, NO, and Nrf2 pathways. To summarize, CA and its derivatives have been shown to improve pathological changes in AD and PD animal models, which may provide a new therapeutic option for neurodegenerative interventions. To this end, further experimental and clinical studies are required to prove the neuroprotective effects of CA and its derivatives.

TAK‑242 exerts a neuroprotective effect via suppression of the TLR4/MyD88/TRIF/NF‑κB signaling pathway in a neonatal hypoxic‑ischemic encephalopathy rat model

Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the main causes of death and nervous system damage in neonates. The aim of the present study was to investigate the effect of the Toll-like receptor 4 (TLR4) antagonist TAK-242 on HIE. The Rice-Vannucci method was used for ligation of the left common carotid artery, followed by hypoxic treatment for 2.5 h to establish a neonatal HIE rat model. Rats were intraperitoneally injected with 7.5 ml/kg TAK-242 after hypoxia-ischemia. It was demonstrated that TAK-242 significantly reduced the infarct volume and cerebral edema content of neonatal rats after HIE, alleviating neuronal damage and neurobehavioral function deficits. Furthermore, TAK-242 decreased the protein expression levels of TLR4, MyD88, TIR-domain-containing adapter-inducing interferon-β (TRIF), NF-κB, tumor necrosis factor α (TNF-α) and interleukin-1β in the hippocampus. The present results suggested that TAK-242 may exert a neuroprotective effect after HIE by inhibiting the TLR4/MyD88/TRIF/NF-κB signaling pathway, and reducing the release of downstream inflammatory cytokines.

Resatorvid protects against hypoxic-ischemic brain damage in neonatal rats

Secondary brain damage caused by hyperactivation of autophagy and inflammatory responses in neurons plays an important role in hypoxic-ischemic brain damage (HIBD). Although previous studies have implicated Toll-like receptor 4 (TLR4) and nuclear factor kappa-B (NF-κB) in the neuroinflammatory response elicited by brain injury, the role and mechanisms of the TLR4-mediated autophagy signaling pathway in neonatal HIBD are still unclear. We hypothesized that this pathway can regulate brain damage by modulating neuron autophagy and neuroinflammation in neonatal rats with HIBD. Hence, we established a neonatal HIBD rat model using the Rice-Vannucci method, and injected 0.75, 1.5, or 3 mg/kg of the TLR4 inhibitor resatorvid (TAK-242) 30 minutes after hypoxic ischemia. Our results indicate that administering TAK-242 to neonatal rats after HIBD could significantly reduce the infarct volume and the extent of cerebral edema, alleviate neuronal damage and neurobehavioral impairment, and decrease the expression levels of TLR4, phospho-NF-κB p65, Beclin-1, microtubule-associated protein l light chain 3, tumor necrosis factor-α, and interleukin-1β in the hippocampus. Thus, TAK-242 appears to exert a neuroprotective effect after HIBD by inhibiting activation of autophagy and the release of inflammatory cytokines via inhibition of the TLR4/NF-κB signaling pathway. This study was approved by the Laboratory Animal Ethics Committee of Affiliated Hospital of Yangzhou University, China (approval No. 20180114-15) on January 14, 2018.

Blood-Related Toxicity after Traumatic Brain Injury: Potential Targets for Neuroprotection

Emergency visits, hospitalizations, and deaths due to traumatic brain injury (TBI) have increased significantly over the past few decades. While the primary early brain trauma is highly deleterious to the brain, the secondary injury post-TBI is postulated to significantly impact mortality. The presence of blood, particularly hemoglobin, and its breakdown products and key binding proteins and receptors modulating their clearance may contribute significantly to toxicity. Heme, hemin, and iron, for example, cause membrane lipid peroxidation, generate reactive oxygen species, and sensitize cells to noxious stimuli resulting in edema, cell death, and increased morbidity and mortality. A wide range of other mechanisms such as the immune system play pivotal roles in mediating secondary injury. Effective scavenging of all of these pro-oxidant and pro-inflammatory metabolites as well as controlling maladaptive immune responses is essential for limiting toxicity and secondary injury. Hemoglobin metabolism is mediated by key molecules such as haptoglobin, heme oxygenase, hemopexin, and ferritin. Genetic variability and dysfunction affecting these pathways (e.g., haptoglobin and heme oxygenase expression) have been implicated in the difference in susceptibility of individual patients to toxicity and may be target pathways for potential therapeutic interventions in TBI. Ongoing collaborative efforts are required to decipher the complexities of blood-related toxicity in TBI with an overarching goal of providing effective treatment options to all patients with TBI.

Inhibition of the cluster of differentiation 14 innate immunity pathway with IAXO-101 improves chronic microelectrode performance

OBJECTIVE

Neuroinflammatory mechanisms are hypothesized to contribute to intracortical microelectrode failures. The cluster of differentiation 14 (CD14) molecule is an innate immunity receptor involved in the recognition of pathogens and tissue damage to promote inflammation. The goal of the study was to investigate the effect of CD14 inhibition on intracortical microelectrode recording performance and tissue integration.

APPROACH

Mice implanted with intracortical microelectrodes in the motor cortex underwent electrophysiological characterization for 16 weeks, followed by endpoint histology. Three conditions were examined: (1) wildtype control mice, (2) knockout mice lacking CD14, and (3) wildtype control mice administered a small molecule inhibitor to CD14 called IAXO-101.

MAIN RESULTS

The CD14 knockout mice exhibited acute but not chronic improvements in intracortical microelectrode performance without significant differences in endpoint histology. Mice receiving IAXO-101 exhibited significant improvements in recording performance over the entire 16 week duration without significant differences in endpoint histology.

SIGNIFICANCE

Full removal of CD14 is beneficial at acute time ranges, but limited CD14 signaling is beneficial at chronic time ranges. Innate immunity receptor inhibition strategies have the potential to improve long-term intracortical microelectrode performance.

Pathophysiological Mechanisms and Potential Therapeutic Targets in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a subtype of hemorrhagic stroke with high mortality and morbidity. The resulting hematoma within brain parenchyma induces a series of adverse events causing primary and secondary brain injury. The mechanism of injury after ICH is very complicated and has not yet been illuminated. This review discusses some key pathophysiology mechanisms in ICH such as oxidative stress (OS), inflammation, iron toxicity, and thrombin formation. The corresponding therapeutic targets and therapeutic strategies are also reviewed.

CD200-CD200R Interaction: An Important Regulator After Stroke

The high mortality and morbidity rate of stroke is a chronic problem that plagues human society. The activation of microglia is one of the principal reasons why neuroinflammation induces cerebral dysfunction. Because of their vital functions in the regulation of neuroinflammation, microglia constitute an important target for stroke. Given that there is an innate self-preservation mechanism between neurons and microglia, the transmembrane glycoproteins on the surface of their membranes, namely CD200 and CD200R, have become a popular topic of research. Numerous studies have demonstrated that CD200-CD200R interaction, microglial activation, and poststroke neuroinflammatory damage are inextricably linked. In this review, we describe the above relationship from a new perspective. We specifically focus on neuroinflammation after stroke. The role of crosstalk of CD200-CD200R inhibitory immune ligand receptors in immune regulation will also be illustrated. Thus, we will see how poststroke injury can be influenced by the CD200-CD200R crosstalk. Finally, we will discuss the possibility of clinical application of the result of CD200-CD200R interaction to manage neuroinflammatory injury after stroke.

Understanding the Role of Innate Immunity in the Response to Intracortical Microelectrodes

Intracortical microelectrodes exhibit enormous potential for researching the nervous system, steering assistive devices and functional electrode stimulation systems for severely paralyzed individuals, and augmenting the brain with computing power. Unfortunately, intracortical microelectrodes often fail to consistently record signals over clinically useful periods. Biological mechanisms, such as the foreign body response to intracortical microelectrodes and self-perpetuating neuroinflammatory cascades, contribute to the inconsistencies and decline in recording performance. Unfortunately, few studies have directly correlated microelectrode performance with the neuroinflammatory response to the implanted devices. However, of those select studies that have, the role of the innate immune system remains among the most likely links capable of corroborating the results of different studies, across laboratories. Therefore, the overall goal of this review is to highlight the role of innate immunity signaling in the foreign body response to intracortical microelectrodes and hypothesize as to appropriate strategies that may become the most relevant in enabling brain-dwelling electrodes of any geometry, or location, for a range of clinical applications.

Clinical significance of neutrophil to lymphocyte ratio and platelet to lymphocyte ratio in acute cerebral hemorrhage with gastrointestinal hemorrhage, and logistic regression analysis of risk factors

The aim of the present study was to determine the predictive value of the neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) in patients with acute cerebral hemorrhage with or without gastrointestinal hemorrhage. Risk factors of gastrointestinal hemorrhage in patients with acute cerebral hemorrhage were also assessed. A total of 335 patients with acute cerebral hemorrhage admitted to our hospital between January 2012 and January 2017 were enrolled. The 86 patients who experienced gastrointestinal hemorrhage during hospitalization were selected as the observation group, while the 249 remaining cases were assigned to the negative control group. The neutrophil, white blood cell and platelet count, as well as the NLR and PLR of each subject were recorded. Furthermore, sex, age, blood pressure, the site of cerebral hemorrhage, the amount of bleeding, the Glasgow Coma Scale (GCS) score and presence of hematosepsis were also recorded and assessed as potential risk factors for gastrointestinal hemorrhage in patients with acute cerebral hemorrhage. The NLR and PLR were markedly higher in the observation group compared with those in the negative control group. Furthermore, the NLR and PLR in the observation group were negatively associated with the 90-day overall survival of patients with acute cerebral hemorrhage and gastrointestinal hemorrhage. In the negative control group, only the PLR was negatively associated with overall survival. Logistic regression analysis indicated that a cerebral hemorrhage volume of >30 ml, lower GCS score and hematosepsis were independently associated with gastrointestinal hemorrhage in patients with acute cerebral hemorrhage (P<0.05). A high NLR and PLR indicated an elevated risk of gastrointestinal hemorrhage in patients with acute cerebral hemorrhage. A higher NLR and PLR were also negatively associated with overall survival and prognosis of patients with cerebral hemorrhage. In addition, a cerebral hemorrhage volume of >30 ml, lower GCS score and hematosepsis were independent risk factors of gastrointestinal hemorrhage in patients with acute cerebral hemorrhage.

Regulation of Toll-Like Receptor (TLR) Signaling Pathway by Polyphenols in the Treatment of Age-Linked Neurodegenerative Diseases: Focus on TLR4 Signaling

Neuronal dysfunction initiates several intracellular signaling cascades to release different proinflammatory cytokines and chemokines, as well as various reactive oxygen species. In addition to neurons, microglia, and astrocytes are also affected by this signaling cascade. This release can either be helpful, neutral or detrimental for cell survival. Toll-like receptors (TLRs) activate and signal their downstream pathway to activate NF-κB and pro-IL-1β, both of which are responsible for neuroinflammation and linked to the pathogenesis of different age-related neurological conditions. However, herein, recent aspects of polyphenols in the treatment of neurodegenerative diseases are assessed, with a focus on TLR regulation by polyphenols. Different polyphenol classes, including flavonoids, phenolic acids, phenolic alcohols, stilbenes, and lignans can potentially target TLR signaling in a distinct pathway. Further, some polyphenols can suppress overexpression of inflammatory mediators through TLR4/NF-κB/STAT signaling intervention, while others can reduce neuronal apoptosis via modulating the TLR4/MyD88/NF-κB-pathway in microglia/macrophages. Indeed, neurodegeneration etiology is complex and yet to be completely understood, it may be that targeting TLRs could reveal a number of molecular and pharmacological aspects related to neurodegenerative diseases. Thus, activating TLR signaling modulation via natural resources could provide new therapeutic potentiality in the treatment of neurodegeneration.

Corilagin Interferes With Toll-Like Receptor 3-Mediated Immune Response in Herpes Simplex Encephalitis

Herpes simplex encephalitis (HSE) is the most common infectious disease of the central nervous system worldwide. However, the pathogenesis of HSE is not clear. Research has shown that the immune response mediated by the toll-like receptor 3 (TLR3) signaling pathway is essential to protect the central nervous system against herpes simplex virus (HSV) infection. However, an excessive immune response may cause tissue damage accompanied by pathological changes. The aim of this study was to explore the molecular mechanism via which corilagin controls HSE through the TLR3 signaling pathway in vitro and in vivo. Cells and mice were pre-treated with polyriboinosinic polyribocytidylic acid [poly(I:C)] or HSV type 1, and then treated with corilagin. After treatment, the mRNA and protein levels of TLR3, TLR-like receptor-associated interferon factor (TRIF), tumor necrosis factor (TNF) receptor type 1-associated DEATH domain protein (TRADD), TNF receptor-associated factor (TRAF) 3 and 6, nuclear factor-kappa-B (NF-κB) essential modulator (NEMO), P38, and interferon regulatory factor 3 (IRF3) were decreased. Interleukin-6 (IL-6), TNF-α, and type 1 interferon-β were also decreased. When TLR3 expression was silenced or increased, corilagin still inhibited the expression of TLR3 and its downstream mediators. Hematoxylin-eosin (HE) staining and immunohistochemical examinations of mouse brain tissues revealed that corilagin lessened the degree of brain inflammation. Altogether, these results suggest that corilagin may regulate the immune response in HSE and relieve inflammatory injury by interfering with the TLR3 signaling pathway.

Role and mechanisms of cytokines in the secondary brain injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common and severe cerebrovascular disease that has high mortality. Few survivors achieve self-care. Currently, patients receive only symptomatic treatment for ICH and benefit poorly from this regimen. Inflammatory cytokines are important participants in secondary injury after ICH. Increases in proinflammatory cytokines may aggravate the tissue injury, whereas increases in anti-inflammatory cytokines might be protective in the ICH brain. Inflammatory cytokines have been studied as therapeutic targets in a variety of acute and chronic brain diseases; however, studies on ICH are limited. This review summarizes the roles and functions of various pro- and anti-inflammatory cytokines in secondary brain injury after ICH and discusses pathogenic mechanisms and emerging therapeutic strategies and directions for treatment of ICH.

Interferon β-Mediated Protective Functions of Microglia in Central Nervous System Autoimmunity

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) leading to demyelination and axonal damage. It often affects young adults and can lead to neurological disability. Interferon β (IFNβ) preparations represent widely used treatment regimens for patients with relapsing-remitting MS (RRMS) with therapeutic efficacy in reducing disease progression and frequency of acute exacerbations. In mice, IFNβ therapy has been shown to ameliorate experimental autoimmune encephalomyelitis (EAE), an animal model of MS while genetic deletion of IFNβ or its receptor augments clinical severity of disease. However, the complex mechanism of action of IFNβ in CNS autoimmunity has not been fully elucidated. Here, we review our current understanding of the origin, phenotype, and function of microglia and CNS immigrating macrophages in the pathogenesis of MS and EAE. In addition, we highlight the emerging roles of microglia as IFNβ-producing cells and vice versa the impact of IFNβ on microglia in CNS autoimmunity. We finally discuss recent progress in unraveling the underlying molecular mechanisms of IFNβ-mediated effects in EAE.

Effects of transection of cervical sympathetic trunk on cognitive function of traumatic brain injury rats

Objective: To observe the effects of transection of cervical sympathetic trunk (TCST) on the cognitive function of traumatic brain injury (TBI) rats and the potential mechanisms. Methods: A total of 288 adult male SD rats were divided into 3 groups using a random number table: TBI group (n=96), TBI + TCST group (n=96) and Sham group (n=96). The water maze test was performed before TBI (T0) and at day 1 (T₁), day 2 (T₂), day 3 (T₃), 1 week (T₄), 2 weeks (T₅), 6 weeks (T₆) and 12 weeks (T₇) after TBI. The levels of α1-adrenergic receptors (α1-ARs), α2-adrenergic receptors (α2-ARs), toll-like receptor 4 (TLR-4) and P38 in hippocampi were detected by real-time PCR. Hippocampal P38 expression was assayed by Western blot. The expressions of interleukin-6 (IL-6), tumor necrosis factor (TNF-α) and brain-derived neurotrophic factor (BDNF) were examined by immunohistochemistry. Noradrenaline (NE) expression in plasma was evaluated by ELISA. The respiratory control ratio (RCR) of brain mitochondria was detected using a Clark oxygen electrode. Results: TCST effectively improved the cognitive function of TBI rats. TCST significantly inhibited sympathetic activity in the rats and effectively inhibited inflammatory responses. The expression of BDNF at T₁-T₆ in TBI+TCST group was higher than that in TBI group (P<0.05). Furthermore, P38 expression was inhibited more effectively in TBI+TCST group (P<0.05), than in TBI group (P<0.05), and the RCR of the brain was significantly higher in TBI+TCST group than in TBI group (P<0.05). Conclusions: TCST can enhance cognitive function in TBI rats by inhibiting sympathetic activity, reducing inflammatory responses and brain edema, upregulating BDNF and improving brain mitochondrial function.

The Role of Toll-Like Receptor 2 and 4 Innate Immunity Pathways in Intracortical Microelectrode-Induced Neuroinflammation

We have recently demonstrated that partial inhibition of the cluster of differentiation 14 (CD14) innate immunity co-receptor pathway improves the long-term performance of intracortical microelectrodes better than complete inhibition. We hypothesized that partial activation of the CD14 pathway was critical to a neuroprotective response to the injury associated with initial and sustained device implantation. Therefore, here we investigated the role of two innate immunity receptors that closely interact with CD14 in inflammatory activation. We implanted silicon planar non-recording neural probes into knockout mice lacking Toll-like receptor 2 (Tlr2-/-), knockout mice lacking Toll-like receptor 4 (Tlr4-/-), and wildtype (WT) control mice, and evaluated endpoint histology at 2 and 16 weeks after implantation. Tlr4-/- mice exhibited significantly lower BBB permeability at acute and chronic time points, but also demonstrated significantly lower neuronal survival at the chronic time point. Inhibition of the Toll-like receptor 2 (TLR2) pathway had no significant effect compared to control animals. Additionally, when investigating the maturation of the neuroinflammatory response from 2 to 16 weeks, transgenic knockout mice exhibited similar histological trends to WT controls, except that knockout mice did not exhibit changes in microglia and macrophage activation over time. Together, our results indicate that complete genetic removal of Toll-like receptor 4 (TLR4) was detrimental to the integration of intracortical neural probes, while inhibition of TLR2 had no impact within the tests performed in this study. Therefore, approaches focusing on incomplete or acute inhibition of TLR4 may still improve intracortical microelectrode integration and long term recording performance.

Redox Signaling, Neuroinflammation, and Neurodegeneration

Production of pro-inflammatory and anti-inflammatory cytokines is part of the defense system that mostly microglia and macrophages display to induce normal signaling to counteract the deleterious actions of invading pathogens in the brain. Also, redox activity in the central nervous system (CNS) constitutes an integral part of the metabolic processes needed by cells to exert their normal molecular and biochemical functions. Under normal conditions, the formation of reactive oxygen and nitrogen species, and the following oxidative activity encounter a healthy balance with immunological responses to preserve cell functions in the brain. However, under different pathological conditions, inflammatory responses recruit pro-oxidant signals and vice versa. The aim of this article is to review the basic concepts about the triggering of inflammatory and oxidative responses in the CNS. Recent Advances: Diverse concurrent toxic pathways are described to provide a solid mechanistic scope for considering intervention at the experimental and clinical levels that are aimed at diminishing the harmful actions of these two contributing factors to nerve cell damage. Critical Issues and Future Directions: The main conclusion supports the existence of a narrow cross-talk between pro-inflammatory and oxidative signals that can lead to neuronal damage and subsequent neurodegeneration. Further investigation about critical pathways crosslinking oxidative stress and inflammation will strength our knowlegde on this topic. Antioxid. Redox Signal. 28, 1626-1651.

Volatile Anesthetics and Immunity

Historically, volatile anesthetics have demonstrated interesting interactions with both the innate and adaptive immune systems. This review organizes these interactions into four phases: recognition, recruitment, response, and resolution. These phases represent a range of proinflammatory, inflammatory, and innate and adaptive immune regulatory responses. The interaction between volatile anesthetics and the immune system is discussed in the context of pathogenesis of infectious disease.

Ursolic Acid Ameliorates Inflammation in Cerebral Ischemia and Reperfusion Injury Possibly via High Mobility Group Box 1/Toll-Like Receptor 4/NFκB Pathway

Toll-like receptors (TLRs) play key roles in cerebral ischemia and reperfusion injury by inducing the production of inflammatory mediators, such as interleukins (ILs) and tumor necrosis factor-alpha (TNF-α). According to recent studies, ursolic acid (UA) regulates TLR signaling and exhibits notable anti-inflammatory properties. In the present study, we explored the mechanism by which UA regulates inflammation in the rat middle cerebral artery occlusion and reperfusion (MCAO/R) model. The MCAO/R model was induced in male Sprague–Dawley rats (MCAO for 2 h, followed by reperfusion for 48 h). UA was administered intragastrically at 0.5, 24, and 47 h after reperfusion. The direct high mobility group box 1 (HMGB1) inhibitor glycyrrhizin (GL) was injected intravenously after 0.5 h of ischemia as a positive control. The degree of brain damage was estimated using the neurological deficit score, infarct volume, histopathological changes, and neuronal apoptosis. We assessed IL-1β, TNF-α, and IL-6 levels to evaluate post-ischemic inflammation. HMGB1 and TLR4 expression and phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) were also examined to explore the underlying mechanism. UA (10 and 20 mg/kg) treatment significantly decreased the neurological deficit scores, infarct volume, apoptotic cells, and IL-1β, TNF-α, and IL-6 concentrations. The infarct area ratio was reduced by (33.07 ± 1.74), (27.05 ± 1.13), (27.49 ± 1.87), and (39.74 ± 2.14)% in the 10 and 20 mg/kg UA, GL, and control groups, respectively. Furthermore, UA (10 and 20 mg/kg) treatment significantly decreased HMGB1 release and the TLR4 level and inactivated NFκB signaling. Thus, the effects of intragastric administration of 20 mg/kg of UA and 10 mg/kg of GL were similar. We provide novel evidence that UA reduces inflammatory cytokine production to protect the brain from cerebral ischemia and reperfusion injury possibly through the HMGB1/TLR4/NFκB signaling pathway.

The application of nanoparticles for neuroprotection in acute ischemic stroke

Stroke still represents one of the most common causes of death and disability worldwide. Acute ischemic stroke (AIS), caused by brain arterial occlusion resulting from a thrombus or embolus, is the most common form of stroke. However, current therapies in AIS are inadequate, and the only US FDA approved treatment is the thrombolytic drug Alteplase. Therefore, establishing effective therapeutic strategies for AIS is urgently needed. Using nanoparticle-based technologies to deliver neuroprotective agents to the ischemic area has attracted increasing attention of late. In this review, the important molecular pathological mechanisms in cerebral ischemia are briefly summarized, the potential of nanoparticulate drug-delivery systems for AIS intervention and recovery are introduced and problems in the medical application of nanoparticles will also be discussed.

Sparstolonin B improves neurological outcomes following intracerebral hemorrhage in mice

Inflammation serves an important role in inducing secondary injury following intracerebral hemorrhage (ICH). It has been demonstrated that sparstolonin B (SsnB) is able to attenuate the lipopolysaccharide-induced inflammatory response in sepsis. Mouse ICH models were used to explore the efficacy of SsnB on the ICH-induced inflammatory response. Mice underwent a working memory version of Morris water maze (MWM) test. They underwent 5 successive days of training consisting of 4 trials each day. The ICH model was established on the last training day. Mice were injected intraperitoneally either with vehicle or SsnB once a day for 3 consecutive days following the establishment of the ICH model. The MWM was used to determine the effect of SsnB on short-term memory following ICH. Neurological deficit scores and brain water content were measured following the MWM. Furthermore, the expression of inflammatory factors and signaling molecules downstream of TLR4 were measured. The results demonstrated that 5 mg/kg SsnB significantly improved the MWM path and time latency (P<0.05). Furthermore, neurological deficit scores were decreased in SsnB-treated mice compared with vehicle-treated mice (P<0.01). Brain water content, levels of inflammatory cytokines and the expression of inflammation-associated proteins were also significantly reduced in the SsnB-treated group (P<0.05). These results indicate that SsnB treatment stimulates short-term neurobehavioral recovery and reduces neurological deficits and this may inhibit the inflammatory response. Therefore, SsnB may attenuate the inflammatory response following ICH.

The Potential Role of Toll-Like Receptor 4 in Mediating Dopaminergic Cell Loss and Alpha-Synuclein Expression in the Acute MPTP Mouse Model of Parkinson's Disease

Toll-like receptors (TLRs) may have a role in Parkinson's disease (PD). In this study, we aimed at investigating the dopaminergic cell loss and alpha-synuclein (α-SYN) expression in TLR4-deficient mice (TLR4^-/-) acutely exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a pharmacological PD model. TLR4 ablation restrained the number of dopaminergic neurons in the substantia nigra (SN), as assessed by tyrosine hydroxylase (TH) protein expression. Intriguingly, TLR4^-/- mice showed massive α-SYN protein accumulation in the midbrain along with high α-SYN mRNA levels in cerebral cortex, striatum, hippocampus, and cerebellum. Contrary to expectations, the high levels of α-SYN do not correlate with greater dopaminergic neuronal loss. The levels of nigral α-SYN protein in TLR4^-/- mice further, but not significantly, increased during MPTP treatment. Contrariwise, MPTP treatment significantly induced the mRNA expression of α-SYN in examined brain regions of WT and TLR4^-/- mice. Protein levels of GATA2, a transcription factor proposed to control α-SYN gene expression, did not change in TLR4^-/- mice at baseline and after MPTP treatment. These findings suggest a role for TLR4 in mediating dopaminergic cell loss and in the constitutive expression of brain α-SYN. However, further exploration is needed in order to establish the actual role of α-SYN in the relative absence of TLR4.

Pretreatment with Erythropoietin Attenuates Lung Ischemia/Reperfusion Injury via Toll-Like Receptor-4/Nuclear Factor-κB (TLR4/NF-κB) Pathway

Background

Lung ischemia/reperfusion injury (LIRI) is a medical problem featuring pulmonary dysfunction and damage. The present study aimed to investigate the protective effects of erythropoietin (EPO), which has been reported to be an anti-inflammatory agent, on LIRI through inhibiting the TLR-4/NF-κB signaling pathway.

Material/Methods

All rats were randomly divided into 3 groups (n=8): a control group, a vehicle+LIRI group, and an EPO+LIRI group. LIRI included 90-min ischemia and 120-min reperfusion, while RhEpo was administered (3 kU/kg) intraperitoneally 2 h before the operation. Levels of pulmonary inflammatory responses were examined by analyzing pulmonary permeability index (PPI), oxygenation index, histology, and expressions of inflammatory cytokines.

Results

Pretreatment with EPO significantly decreased lung W/D ratio, BALF leukocytes count and percentage, and PPI but increased oxygenation index compared with the LIRI group (P<0.05). More importantly, with EPO pretreatment there was less pathological damage compared with the vehicle group. Expressions of inflammatory cytokines (TNF-α, IL-6, and IL-1β) in the serum were significantly lower in the EPO group than in the LIRI group (P<0.05). In addition, gene expression and protein expression of TLR-4 and NF-κB were significantly inhibited with EPO pretreatment compared with the LIRI group (P<0.05).

Conclusions

Our study id the first to report that EPO protects lung injuries after LIRI through inhibiting the TLR4-NF-κB signaling pathway, which provides solid evidence for the use of EPO as a therapeutic agent for treating LIRI in the future.

Increase of reactive oxygen species in different tissues during lipopolysaccharide-induced fever and antipyresis: an electron paramagnetic resonance study

Fever is a regulated increase in body temperature and a component of the acute-phase response, triggered mainly after the invasion of pathogens in the body. Reactive oxygen species (ROS) are generated during the physiological and pathological processes, and can act as both signalling molecules as well as promoters of oxidative stress. Male Wistar rats, pretreated with oral doses of acetaminophen, celecoxib, dipyrone, or ibuprofen 30 min before an intravenous lipopolysaccharide (LPS) or sterile saline injection, showed a reduced febrile response in all animals tested. The formation of ROS in the fresh blood, liver, brown adipose tissue (BAT), and hypothalamus of febrile and antipyretic-treated animals was assessed by electron paramagnetic resonance using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH). While the CM^• concentrations remained unaltered in the blood samples examined 5 h after the induction of fever, we found increased CM^• levels in the liver (in µM, saline: 290 ± 42; LPS: 512 ± 34), BAT (in µM, saline: 509 ± 79, LPS: 855 ± 79), and hypothalamus (in µM, saline: 292 ± 35; LPS: 467 ± 8) at the same time point. Importantly, none of the antipyretics were seen to alter the CM^• accumulation profile. Data from this study suggest that there is an increased formation of ROS in the different tissues during fever, which may cause oxidative stress, and that the antipyretics tested do not interfere with ROS production.

Biophysical evidence for differential gallated green tea catechins binding to membrane type-1 matrix metalloproteinase and its interactors

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a transmembrane MMP which triggers intracellular signaling and regulates extracellular matrix proteolysis, two functions that are critical for tumor-associated angiogenesis and inflammation. While green tea catechins, particularly epigallocatechin gallate (EGCG), are considered very effective in preventing MT1-MMP-mediated functions, lack of structure-function studies and evidence regarding their direct interaction with MT1-MMP-mediated biological activities remain. Here, we assessed the impact in both cellular and biophysical assays of four ungallated catechins along with their gallated counterparts on MT1-MMP-mediated functions and molecular binding partners. Concanavalin-A (ConA) was used to trigger MT1-MMP-mediated proMMP-2 activation, expression of MT1-MMP and of endoplasmic reticulum stress biomarker GRP78 in U87 glioblastoma cells. We found that ConA-mediated MT1-MMP induction was inhibited by EGCG and catechin gallate (CG), that GRP78 induction was inhibited by EGCG, CG, and gallocatechin gallate (GCG), whereas proMMP-2 activation was inhibited by EGCG and GCG. Surface plasmon resonance was used to assess direct interaction between catechins and MT1-MMP interactors. We found that gallated catechins interacted better than their ungallated analogs with MT1-MMP as well as with MT1-MMP binding partners MMP-2, TIMP-2, MTCBP-1 and LRP1-clusterIV. Overall, current structure-function evidence supports a role for the galloyl moiety in both direct and indirect interactions of green tea catechins with MT1-MMP-mediated oncogenic processes.

Toll-Like Receptor 4 Knockdown Attenuates Brain Damage and Neuroinflammation After Traumatic Brain Injury via Inhibiting Neuronal Autophagy and Astrocyte Activation

Toll-like receptor 4 (TLR4) has been linked to various pathophysiological conditions, such as traumatic brain injury (TBI). It is reported that posttraumatic neuroinflammation is an essential event in the progression of brain injury after TBI. Recent evidences indicate that TLR4 mediates glial phagocytic activity and inflammatory cytokines production. Thus, TLR4 may be an important therapeutic target for neuroinflammatory injury post-TBI. This study was designed to explore potential effects and underlying mechanisms of TLR4 in rats suffered from TBI. TBI model was induced using a controlled cortical impact in rats, and application of TLR4 shRNA silenced TLR4 expression in brain prior to TBI induction. Elevated TLR4 was specifically observed in the hippocampal astrocytes and neurons posttrauma. Interestingly, TLR4 shRNA decreased the concentrations of interleukin (IL)-1β, IL-6, and tissue necrosis factor-α; alleviated hippocampal neuronal damage; reduced brain edema formation; and improved neurological deficits after TBI. Meanwhile, to further explore underlying molecular mechanisms of this neuroprotective effects of TLR4 knockdown, our results showed that TLR4 knockdown significantly inhibited the upregulation of autophagy-associated proteins caused by TBI. More importantly, an autophagy inducer, rapamycin pretreated, could partially abolish neuroprotective effects of TLR4 knockdown on TBI rats. Furthermore, TLR4 silencing markedly suppressed GFAP upregulation and improved cell hypertrophy to attenuate TBI-induced astrocyte activation. Taken together, these findings suggested that TLR4 knockdown ameliorated neuroinflammatory response and brain injury after TBI through suppressing autophagy induction and astrocyte activation.

Toll-Like Receptor-3 Mediates HIV-1-Induced Interleukin-6 Expression in the Human Brain Endothelium via TAK1 and JNK Pathways: Implications for Viral Neuropathogenesis

HIV-1-associated neurocognitive disorders (HAND) is associated with blood-brain-barrier (BBB) inflammation, and inflammation involves toll-like receptors (TLRs) signaling. It is not known whether primary human brain microvascular endothelial cells (HBMEC), the major BBB component, express TLRs or whether TLRs are involved in BBB dysfunction and HAND. We demonstrate that HBMEC express TLR3, 4, 5, 7, 9, and 10, and TLR3 was the most abundant. HIV-1 and TLR3 activation increased endothelial TLR3 transcription and expression. HIV-1-positive human subjects showed significantly higher TLR3 expression in brain tissues and blood vessels, with higher TLR3 levels in subjects with HAND. HIV-1 and TLR3 activation increased endothelial IL6 expression by 6-to-127-fold (P < 0.001), activated c-jun(serine-63) and SAPK/JNK(Thr183/Tyr185). HIV-1 upregulated IL6 through interleukin-1 receptor-associated-kinase (IRAK)-1/4/TAK1/JNK pathways, via ATP-dependent JNK activation. TLR3 activation upregulated IL6 through TAK1/JNK pathways, via ATP-dependent or -independent JNK activation. HIV-1 and TLR3 activation also upregulated transcription factors associated with IL6 and TAK1/JNK pathways (Jun, CEBPA, STAT1). Blocking TLR3 activation prevented HIV-1- and TLR3 ligands-induced upregulation of these transcription factors, prevented IL6 transcription and expression, c-jun and JNK activation. HIV-1 and TLR3 ligands significantly increased monocytes adhesion and migration through the BBB, and decreased endothelial claudin-5 expression. Blocking TLR3 and JNK activation prevented HIV-1- and TLR3 ligands-induced claudin-5 downregulation, monocytes adhesion and transendothelial migration. These data suggest that viral immune recognition via endothelial TLR3 is involved in endothelial inflammation and BBB dysfunction in HIV/AIDS and HAND. Our data provides novel insights into the molecular basis of these HIV-1- and TLR3-mediated effects.

Preclinical Studies and Translational Applications of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) which refers to bleeding in the brain is a very deleterious condition with high mortality and disability rate. Surgery or conservative therapy remains the treatment option. Various studies have divided the disease process of ICH into primary and secondary injury, for which knowledge into these processes has yielded many preclinical and clinical treatment options. The aim of this review is to highlight some of the new experimental drugs as well as other treatment options like stem cell therapy, rehabilitation, and nanomedicine and mention some translational clinical applications that have been done with these treatment options.

Pinocembrin protects hemorrhagic brain primarily by inhibiting toll-like receptor 4 and reducing M1 phenotype microglia

Neuroinflammation is a major contributor to intracerebral hemorrhage (ICH) progression, but no drug is currently available to reduce this response and protect against ICH-induced injury. Recently, the natural product pinocembrin has been shown to ameliorate neuroinflammation and is undergoing a phase II clinical trial for ischemic stroke treatment. In this study, we examined the efficacy of pinocembrin in an ICH model, and further examined its effect on microglial activation and polarization. In vivo, pinocembrin dose-dependently reduced lesion volume by ∼47.5% and reduced neurologic deficits of mice at 72h after collagenase-induced ICH. The optimal dose of pinocembrin (5mg/kg) suppressed microglial activation as evidenced by decreases in CD68-positive microglia and reduced proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Pinocembrin also reduced the number of classically activated M1-like microglia without affecting M2-like microglia in the perilesional region. Additionally, pinocembrin decreased the expression of toll-like receptor (TLR)4 and its downstream target proteins TRIF and MyD88. The protection by pinocembrin was lost in microglia-depleted mice and in TLR4^lps-del mice, and pinocembrin failed to decrease the number of M1-like microglia in TLR4^lps-del mice. In lipopolysaccharide-stimulated BV-2 cells or primary microglia, pinocembrin decreased M1-related cytokines and markers (IL-1β, IL-6, TNF-α, and iNOS), NF-κB activation, and TLR4 expression, but it did not interfere with TLR4/MyD88 and TLR4/TRIF interactions or affect microglial phagocytosis of red blood cells. Inhibition of the TLR4 signaling pathway and reduction in M1-like microglial polarization might be the major mechanism by which pinocembrin protects hemorrhagic brain. With anti-inflammatory properties, pinocembrin could be a promising new drug candidate for treating ICH and other acute brain injuries.