Reducing Effect of IL-32α in the Development of Stroke Through Blocking of NF-κB, but Enhancement of STAT3 Pathways

Wnt/β-catenin signaling in corneal epithelium development, homeostasis, and pathobiology

The corneal epithelium is located on the most anterior surface of the eyeball and protects against external stimuli. The development of the corneal epithelium and the maintenance of corneal homeostasis are essential for the maintenance of visual acuity. It has been discovered recently via the in-depth investigation of ocular surface illnesses that the Wnt/β-catenin signaling pathway is necessary for the growth and stratification of corneal epithelial cells as well as the control of endothelial cell stability. In addition, the Wnt/β-catenin signaling pathway is directly linked to the development of common corneal illnesses such as keratoconus, fungal keratitis, and corneal neovascularization. This review mainly summarizes the role of the Wnt/β-catenin signaling pathway in the development, homeostasis, and pathobiology of cornea, hoping to provide new insights into the study of corneal epithelium and the treatment of related diseases.

Voacangine mitigates oxidative stress and neuroinflammation in middle cerebral artery occlusion-induced cerebral ischemia/reperfusion injury by averting the NF-κBp65/MAPK signaling pathways in rats

Ischemic stroke is a leading cause of human mortality. Cerebral ischemia-reperfusion injury (CI/RI) is a primary cause of stroke. Ischemia-reperfusion (I/R) resulting in oxidative stress and inflammatory events may lead to severe neuronal impairments. Thus, anti-oxidative and anti-inflammatory mediators that can alleviate post-I/R neuronal injuries are required for the treatment of CI/RI. An alkaloid, voacangine (VCG) is a recognized antioxidant, anti-inflammatory, and anticancer agent. Hence, the current study intended to explore the neuroprotective potential and the principal mechanisms of VCG in CI/RI. The experimental rats were divided into four sets: control, I/R-induced, I/R + VCG (2.5 mg/kg), I/R + VCG (5 mg/kg). CI/RI was induced by implanting a thread into the middle cerebral artery occlusion (MCAO) model. Brain damages were assessed on the basis of brain edema, brain infarct volume, neurological deficit score, histopathology, oxidative stress, and neuroinflammation. Results revealed that VCG inhibited the triggering of NLRP3 inflammasome, pro-inflammatory cytokines, lipid peroxidation, but enhanced the antioxidant status in MCAO rats. Furthermore, VCG treatment averted brain damage by I/R, neuroinflammation, and oxidative stress by suppressing NF-κBp65/MAPK pathways. The results of the study provide pertinent insights pertaining to the role of VCG as a potential neuroprotective agent against ischemic stroke.

Progesterone improved the behavior of PC12 cells under OGD/R by reducing FABP5 expression and inhibiting TLR4/NF-κB signaling pathway

Herein, PC12 cells were applied to detect the impact of progesterone under oxygen glucose deprivation/reperfusion (OGD/R) stimulation. The cell proliferation of PC12 cells was evaluated by cell counting kit-8 assay, and the concentrations of MDA, ROS and SOD were examined by their corresponding Enzyme Linked Immunosorbent Assay kits. The invasion and migration properties of PC12 cells were evaluated by transwell and wound healing assays, respectively. The expression patterns of related genes were evaluated by western blot and qPCR. Under OGD/R stimulation, progesterone treatment could elevate the viability of PC12 cells, reduce the levels of MDA and ROS, and elevate the concentration of SOD. Moreover, progesterone treatment could strengthen the invasion and migration abilities of PC12 cells under OGD/R condition, as well as decrease the apoptosis and inflammation. FABP5 expression was significantly increased in PC12 cells under OGD/R stimulation, which was reversed after progesterone stimulation. Under OGD/R stimulation, the protective effects of progesterone on PC12 cells were strengthened after si-FABP5 treatment. The protein levels of TLR4, p-P65 NF-κB, and P65 NF-κB in OGD/R-induced PC12 cells were increased, which were inhibited after progesterone treatment. Progesterone exerted protective effects on PC12 cells by targeting FABP5 under OGD/R stimulation.

Genetic and Pharmacological Modulation of P75 Neurotrophin Receptor Attenuate Brain Damage After Ischemic Stroke in Mice

The precursor nerve growth factor (ProNGF) and its receptor p75 neurotrophin receptor (p75NTR) are upregulated in several brain diseases, including ischemic stroke. The activation of p75NTR is associated with neuronal apoptosis and inflammation. Thus, we hypothesized that p75NTR modulation attenuates brain damage and improves functional outcomes after ischemic stroke. Two sets of experiments were performed. (1) Adult wild-type (WT) C57BL/6 J mice were subjected to intraluminal suture-middle cerebral artery occlusion (MCAO) to induce cerebral ischemia. Pharmacological inhibitor of p75NTR, LM11A-31 (50 mg/kg), or normal saline was administered intraperitoneally (IP) 1 h post-MCAO, and animals survived for 24 h. (2) Adult p75NTR heterozygous knockout (p75NTR+/-) and WT were subjected to photothrombotic (pMCAO) to induce ischemic stroke, and the animals survived for 72 h. The sensory-motor function of animals was measured using Catwalk XT. The brain samples were collected to assess infarction volume, edema, hemorrhagic transformation, neuroinflammation, and signaling pathway at 24 and 72 h after the stroke. The findings described that pharmacological inhibition and genetic knocking down of p75NTR reduce infarction size, edema, and hemorrhagic transformation following ischemic stroke. Additionally, p75NTR modulation significantly decreased several anti-apoptosis markers and improved sensory motor function compared to the WT mice following ischemic stroke. Our observations exhibit that the involvement of p75NTR in ischemic stroke and modulation of p75NTR could improve the outcome of ischemic stroke by increasing cell survival and enhancing motor performance. LM11A-31 has the potential to be a promising therapeutic agent for ischemic stroke. However, more evidence is needed to illuminate the efficacy of LM11A-31 in ischemic stroke.

Protective effects of Eleutheroside E against high-altitude pulmonary edema by inhibiting NLRP3 inflammasome-mediated pyroptosis

Eleutheroside E (EE) is a primary active component of Acanthopanax senticosus, which has been reported to inhibit the expression of inflammatory genes, but the underlying mechanisms remain elusive. High-altitude pulmonary edema (HAPE) is a severe complication of high-altitude exposure occurring after ascent above 2500 m. However, effective and safe preventative measures for HAPE still need to be improved. This study aimed to elucidate the preventative potential and underlying mechanism of EE in HAPE. Rat models of HAPE were established through hypobaric hypoxia. Mechanistically, hypobaric hypoxia aggravates oxidative stress and upregulates (pro)-inflammatory cytokines, activating NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis, eventually leading to HAPE. EE suppressed NLRP3 inflammasome-mediated pyroptosis by inhibiting the nuclear translocation of nuclear factor kappa-Β (NF-κB), thereby protecting the lung from HAPE. However, nigericin (Nig), an NLRP3 activator, partially abolished the protective effects of EE. These findings suggest EE is a promising agent for preventing HAPE induced by NLRP3 inflammasome-mediated pyroptosis.

Role of Crosstalk between Glial Cells and Immune Cells in Blood-Brain Barrier Damage and Protection after Acute Ischemic Stroke

Blood-brain barrier (BBB) damage is the main pathological basis for acute ischemic stroke (AIS)-induced cerebral vasogenic edema and hemorrhagic transformation (HT). Glial cells, including microglia, astrocytes, and oligodendrocyte precursor cells (OPCs)/oligodendrocytes (OLs) play critical roles in BBB damage and protection. Recent evidence indicates that immune cells also have an important role in BBB damage, vasogenic edema and HT. Therefore, regulating the crosstalk between glial cells and immune cells would hold the promise to alleviate AIS-induced BBB damage. In this review, we first introduce the roles of glia cells, pericytes, and crosstalk between glial cells in the damage and protection of BBB after AIS, emphasizing the polarization, inflammatory response and crosstalk between microglia, astrocytes, and other glia cells. We then describe the role of glial cell-derived exosomes in the damage and protection of BBB after AIS. Next, we specifically discuss the crosstalk between glial cells and immune cells after AIS. Finally, we propose that glial cells could be a potential target for alleviating BBB damage after AIS and we discuss some molecular targets and potential strategies to alleviate BBB damage by regulating glial cells after AIS.

Maresin1 ameliorates postoperative cognitive dysfunction in aged rats by potentially regulating the NF-κB pathway to inhibit astrocyte activation

Postoperative cognitive dysfunction (POCD) is one of the most serious postoperative complications in the elderly population. Perioperative central neuroinflammation is considered to be an important pathological mechanism of POCD, with the activation of astrocytes playing a key role in central neuroinflammation. Maresin1 (MaR1) is a specific pro-resolving mediator synthesized by macrophages in the resolution stage of inflammation, and provides unique anti-inflammatory and pro-resolution effects by limiting excessive neuroinflammation and promoting postoperative recovery. However, the question remains whether MaR1 can have a positive effect on POCD. The objective of this study was to investigate the protective effect of MaR1 on POCD cognitive function in aged rats after splenectomy. Morris water maze test and IntelliCage test showed that splenectomy could cause transient cognitive dysfunction in aged rats; however, the cognitive impairment of rats was significantly mitigated when MaR1 pretreatment was administered. MaR1 significantly alleviated the fluorescence intensity and protein expression of glial fibrillary acidic protein and central nervous system specific protein in the cornu ammonis 1 region of the hippocampus. Simultaneously, the morphology of astrocytes was also severely altered. Further experiments showed that MaR1 inhibited the mRNA and protein expression of several key proinflammatory cytokines-interleukin-1β, interleukin-6, and tumor necrosis factor-α in the hippocampus of aged rats following splenectomy. The molecular mechanism underlying this process was explored by evaluating expression of components of the nuclear factor κB (NF-κB) signaling pathway. MaR1 substantially inhibited the mRNA and protein expression of NF-κB p65 and κB inhibitor kinase β. Collectively, these results suggest that MaR1 ameliorated splenectomy-induced transient cognitive impairment in elderly rats, and this neuroprotective mechanism may occur through regulating the NF-κB pathway to inhibit astrocyte activation.

Immune regulation based on sex differences in ischemic stroke pathology

Ischemic stroke is one of the world's leading causes of death and disability. It has been established that gender differences in stroke outcomes prevail, and the immune response after stroke is an important factor affecting patient outcomes. However, gender disparities lead to different immune metabolic tendencies closely related to immune regulation after stroke. The present review provides a comprehensive overview of the role and mechanism of immune regulation based on sex differences in ischemic stroke pathology.

Pro-survival Phenotype of HIF-1α: Neuroprotection Through Inflammatory Mechanisms

Hypoxia-inducible factor 1 (HIF-1) is a major player in the oxygen sensor system as well as a transcription factor. HIF-1 is also associated in the pathogenesis of many brain diseases including Alzheimer's disease (AD), epilepsy and stroke. HIF-1 regulates the expression of many genes such as those involved in glycolysis, erythropoiesis, angiogenesis and proliferation in hypoxic condition. Despite several studies, the mechanism through which HIF-1 confers neuroprotection remains unclear, one of them is modulating metabolic profiles and inflammatory pathways. Characterization of the neuroprotective role of HIF-1 may be through its stabilization and the regulation of target genes that aid in the early adaptation to the oxidative stressors. It is interesting to note that mounting data from recent years point to an additional crucial regulatory role for hypoxia-inducible factors (HIFs) in inflammation. HIFs in immune cells regulate the production of glycolytic energy as well as innate immunity, pro-inflammatory gene expression, and mediates activation of pro-survival pathways. The present review highlights the contribution of HIF-1 to neuroprotection where inflammation is the crucial factor in the pathogenesis contributing to neural death. The potential mechanisms that contribute to neuroprotection as a result of the downstream targets of HIF-1α are discussed. Such mechanisms include those mediated through IL-10, an anti-inflammatory molecule involved in activating pro-survival signaling mechanisms via AKT/ERK and JAK/STAT pathways.

Identification of potential regulating effect of baicalin on NFκB/CCL2/CCR2 signaling pathway in rats with cerebral ischemia by antibody-based array and bioinformatics analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Baicalin is one of the major bioactive compounds extracted from the root of Scutellaria baicalensis Georgi, which was used to treat cerebral ischemia for thounds of years. However, its biological mechanisms remains to be further explored.

AIM OF THE REVIEW

This study aims to identify potential biological mechanisms of baicalin against cerebral ischemia combining antibody-based array and bioinformatics analysis.

METHODS

A rat model of middle cerebral artery occlusion (MCAO) was constructed. Sprague-Dawley rats were randomly divided into three groups: control group, ischemic model group, and baicalin 100 mg/kg treatment group respectively. Bederson score and 2, 3, 5-triphenyl tetrazolium chloride (TTC) staining were examined to evaluate the pharmacodynamics of baicalin treatment. Antibody-based array technology, enzyme linked immunosorbent assay (ELISA), western-blot, molecular docking, transcription factor perdiction, hematoxylin and eosin (H&E), and immunofluorescence staining were used to study the regulation of baicalin on inflammatory response after cerebral ischemia in vivo. LPS-induced RAW 264.7 macrophage inflammation model was prepared to observe the anti-inflammatory effect of baicalin in vitro.

RESULTS

Baicalin (100 mg/kg) reduced neurological injury score, cerebral infarction volume, and necrotic cells in MCAO rats. Baicalin inhibited the expression of CCL2, and reduced the phosphorylation levels of p65, IκBα protein and down-regulated level of CCR2. Besides, baicalin could bond to CCR2 directly, which prevented CCL2 from binding to CCR2. Furthermore, baicalin down-regulated the number of monocytes in the peripheral blood and improved the spleen index post-cerebral ischemia. In vitro, baicalin significantly inhibited the secretion of NO, IL6, TNFα, and CCL2 in macrophages and promoted the secretion of IL13, IFNG, and IL1a.

CONCLUSIONS

Baicalin inhibited cerebral ischemia-induced activation of the NFκB/CCL2/CCR2 pathway with multiple target effect. These data promote the therapeutic utilization of baicalin in preventing cerebral ischemia clinically.

Interleukins and Ischemic Stroke

Ischemic stroke after cerebral artery occlusion is one of the major causes of chronic disability worldwide. Interleukins (ILs) play a bidirectional role in ischemic stroke through information transmission, activation and regulation of immune cells, mediating the activation, multiplication and differentiation of T and B cells and in the inflammatory reaction. Crosstalk between different ILs in different immune cells also impact the outcome of ischemic stroke. This overview is aimed to roughly discuss the multiple roles of ILs after ischemic stroke. The roles of IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-12, IL-13, IL-15, IL-16, IL-17, IL-18, IL-19, IL-21, IL-22, IL-23, IL-32, IL-33, IL-34, IL-37, and IL-38 in ischemic stroke were discussed in this review.

Interleukin-10 level is associated with post-stroke depression in acute ischaemic stroke patients

BACKGROUND

Interleukin-10 (IL-10) is a pathophysiological factor in acute ischaemic stroke (AIS) and is relevant to mood disorders after stroke. We evaluated the predictive value of IL-10 in patients with post-stroke depression (PSD).

METHODS

A total of 350 stroke patients were recruited at baseline, and 151 AIS patients were screened and completed a 1-month follow-up. Serum IL-10 levels were measured within 24 h of admission. We used the 17-item Hamilton Depression Scale (HAMD-17) to evaluate depression symptoms; PSD was defined as an HAMD score ≥ 7.

RESULTS

Fifty-one (33.8%) patients showed a more serious stroke degree, larger infarction volume, and poorer daily life activities and prognosis (P < 0.05) and were diagnosed with PSD at the 1-month follow-up. Their IL-10 level decreased significantly compared to the non-PSD group (P < 0.001). After adjusting for confounders, IL-10 could be used as an independent predictor for PSD with an adjusted odds ratio (OR) of 0.615 (95% CI 0.410-0.923, P = 0.019). In addition, the optimal cut-off value of IL-10 was 0.615 pg/mL based on an area under the receiver operating characteristic curve of 0.692 (95% CI 0.604-0.781, P < 0.001), demonstrating that IL-10 could predict the occurrence of PSD. Moreover, IL-10 was an indicator of stroke severity, living ability, and functional outcomes (P < 0.05).

LIMITATIONS

IL-10 was only measured upon admission; dynamic changes need to be further monitored. This was also a single-centre study with a relatively small sample.

CONCLUSIONS

Lower IL-10 levels may be used to predict PSD.

Immune Cells in the BBB Disruption After Acute Ischemic Stroke: Targets for Immune Therapy?

Blood-Brain Barrier (BBB) disruption is an important pathophysiological process of acute ischemic stroke (AIS), resulting in devastating malignant brain edema and hemorrhagic transformation. The rapid activation of immune cells plays a critical role in BBB disruption after ischemic stroke. Infiltrating blood-borne immune cells (neutrophils, monocytes, and T lymphocytes) increase BBB permeability, as they cause microvascular disorder and secrete inflammation-associated molecules. In contrast, they promote BBB repair and angiogenesis in the latter phase of ischemic stroke. The profound immunological effects of cerebral immune cells (microglia, astrocytes, and pericytes) on BBB disruption have been underestimated in ischemic stroke. Post-stroke microglia and astrocytes can adopt both an M1/A1 or M2/A2 phenotype, which influence BBB integrity differently. However, whether pericytes acquire microglia phenotype and exert immunological effects on the BBB remains controversial. Thus, better understanding the inflammatory mechanism underlying BBB disruption can lead to the identification of more promising biological targets to develop treatments that minimize the onset of life-threatening complications and to improve existing treatments in patients. However, early attempts to inhibit the infiltration of circulating immune cells into the brain by blocking adhesion molecules, that were successful in experimental stroke failed in clinical trials. Therefore, new immunoregulatory therapeutic strategies for acute ischemic stroke are desperately warranted. Herein, we highlight the role of circulating and cerebral immune cells in BBB disruption and the crosstalk between them following acute ischemic stroke. Using a robust theoretical background, we discuss potential and effective immunotherapeutic targets to regulate BBB permeability after acute ischemic stroke.

Physcion Protects Rats Against Cerebral Ischemia-Reperfusion Injury via Inhibition of TLR4/NF-kB Signaling Pathway

Background

Ischemic stroke (IS) is characterized by the rapid loss of brain function due to ischemia. Physcion has been found to have a neuroprotective effect against cerebral ischemia-reperfusion (I/R) injury. However, the mechanism by which physcion regulates cerebral I/R injury remains largely unknown.

Methods

An oxygen-glucose deprivation/reperfusion (OGD/R) model in SH-SY5Y cells and a rat cerebral ischemia-reperfusion (I/R) model were established, respectively. CCK-8 and flow cytometry assays were used to detect the viability and apoptosis of SH-SY5Y cells. Moreover, enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of SOD, MDA, GSH-Px, TNF-α, IL-1β, IL-6 and IL-10 in the supernatant of SH-SY5Y cells. Meanwhile, Western blot assay was used to detect the expressions of TLR4, p-p65 and p-IκB in SH-SY5Y cells and I/R rats.

Results

In this study, physcion treatment significantly rescued OGD/R-induced neuronal injury. In addition, physcion decreased inflammatory response in SH-SY5Y cells after OGD/R insult, as shown by the decreased levels of the pro-inflammatory factors TNF-α, IL-1β, IL-6 and IL-10. Moreover, physcion attenuated the oxidative stress in OGD/R-treated SY-SY5Y cells, as evidenced by the increased SOD and GSH levels and the decreased ROS and MDA levels. Meanwhile, physcion significantly reduced cerebral infarction, attenuated neuronal injury and apoptosis in I/R rats. Furthermore, physcion markedly decreased the expressions of TLR4, p-NF-κB p65 and p-IκB in the brain tissues of rats subjected to I/R and in SH-SY5Y cells exposed to OGD/R.

Conclusion

In conclusion, our study indicated that physcion protected neuron cells against I/R injury in vitro and in vivo by inhibition of the TLR4/NF-kB pathway; thus, physcion might serve as a promising therapeutic candidate for IS.

Uric Acid Neuroprotection Associated to IL-6/STAT3 Signaling Pathway Activation in Rat Ischemic Stroke

Despite the promising neuroprotective effects of uric acid (UA) in acute ischemic stroke, the seemingly pleiotropic underlying mechanisms are not completely understood. Recent evidence points to transcription factors as UA targets. To gain insight into the UA mechanism of action, we investigated its effects on pertinent biomarkers for the most relevant features of ischemic stroke pathophysiology: (1) oxidative stress (antioxidant enzyme mRNAs and MDA), (2) neuroinflammation (cytokine and Socs3 mRNAs, STAT3, NF-κB p65, and reactive microglia), (3) brain swelling (Vegfa, Mmp9, and Timp1 mRNAs), and (4) apoptotic cell death (Bcl-2, Bax, caspase-3, and TUNEL-positive cells). Adult male Wistar rats underwent intraluminal filament transient middle cerebral artery occlusion (tMCAO) and received UA (16 mg/kg) or vehicle (Locke's buffer) i.v. at 20 min reperfusion. The outcome measures were neurofunctional deficit, infarct, and edema. UA treatment reduced cortical infarct and brain edema, as well as neurofunctional impairment. In brain cortex, increased UA: (1) reduced tMCAO-induced increases in Vegfa and Mmp9/Timp1 ratio expressions; (2) induced Sod2 and Cat expressions and reduced MDA levels; (3) induced Il6 expression, upregulated STAT3 and NF-κB p65 phosphorylation, induced Socs3 expression, and inhibited microglia activation; and (4) ameliorated the Bax/Bcl-2 ratio and induced a reduction in caspase-3 cleavage as well as in TUNEL-positive cell counts. In conclusion, the mechanism for morphological and functional neuroprotection by UA in ischemic stroke is multifaceted, since it is associated to activation of the IL-6/STAT3 pathway, attenuation of edematogenic VEGF-A/MMP-9 signaling, and modulation of relevant mediators of oxidative stress, neuroinflammation, and apoptotic cell death.

Interleukin 32: A novel player in perioperative neurocognitive disorders

Perioperative neurocognitive disorders (PND) are highly prevalent after surgery, especially in aged patients. PND results in long-term morbidity and mortality with unclear pathophysiologic mechanisms. As a key hallmark of PND, surgery-induced neuroinflammation resulted from the invading of exogenous tracers into the cerebral parenchyma, causing hippocampal neuroinflammation and cognitive impairment. IL-32, with different isoforms, played a significant regulatory role in various inflammatory diseases. Its prevalence in peripheral circulating blood was closely associated with the central nervous system (CNS) diseases. Beyond that, specific subtype of IL-32 was reported to involve in the neuroinflammation regulation in cerebral ischemia impairment, multiple sclerosis, Alzheimer's Disease, and so on. Thus, we speculate that IL-32 may participate in the regulation of the surgery-induced neuroinflammation during the parthenogenesis of PND. The isoforms, spatio-temporal regulation of IL-32 may determine its pro- or anti-inflammation properties in parthenogenesis of PND. Therefore, IL-32 could be a putative therapeutic target for the prevention and reversal of PND in the future.

Molecular interactions and functions of IL-32

IL-32 is a multifaceted cytokine associated with several diseases and inflammatory conditions. Its expression is induced in response to cellular stress such as hypoxia, infections, and pro-inflammatory cytokines. IL-32 can be secreted from cells and can induce the production of pro-inflammatory cytokines from several cell types but are also described to have anti-inflammatory functions. The intracellular form of IL-32 is shown to play an important role in various cellular processes, including the defense against intracellular bacteria and viruses and in modulation of cell metabolism. In this review, we discuss current literature on molecular interactions of IL-32 with other proteins. We also review data on the role of intracellular IL-32 as a metabolic regulator and its role in antimicrobial host defense.

NF-κB as a Key Mediator of Brain Inflammation in Alzheimer's Disease

Alzheimer's disease is the most common form of dementia. It is characterized by betaamyloid peptide fibrils which are extracellular deposition of a specific protein, accompanied by extensive neuroinflammation. Various studies show the presence of a number of inflammation markers in the AD brain: elevated inflammatory cytokines and chemokines, and an accumulation of activated microglia in the damaged regions. NF-κB is a family of redox sensitive transcriptional factors, and it is known that NF-κB has binding sites in the promoter region of the genes involved in amyloidogenesis and inflammation. Long-term use of non-steroidal anti-inflammatory drugs prevents progression of AD and delays its onset, suggesting that there is a close correlation between NF-κB and AD pathogenesis. This study aims to (1) assess the association between NF-κB activity and AD through discussion of a variety of experimental and clinical studies on AD and (2) review treatment strategies designed to treat or prevent AD with NF-κB inhibitors.

A dual inhibitor of the proteasome catalytic subunits LMP2 and Y attenuates disease progression in mouse models of Alzheimer's disease

The immunoproteasome (iP) is a variant of the constitutive proteasome (cP) that is abundantly expressed in immune cells which can also be induced in somatic cells by cytokines such as TNF-α or IFN-γ. Accumulating evidence support that the iP is closely linked to multiple facets of inflammatory response, eventually leading to the development of several iP inhibitors as potential therapeutic agents for autoimmune diseases. Recent studies also found that the iP is upregulated in reactive glial cells surrounding amyloid β (Aβ) deposits in brains of Alzheimer’s disease (AD) patients, but the role it plays in the pathogenesis of AD remains unclear. In this study, we investigated the effects of several proteasome inhibitors on cognitive function in AD mouse models and found that YU102, a dual inhibitor of the iP catalytic subunit LMP2 and the cP catalytic subunit Y, ameliorates cognitive impairments in AD mouse models without affecting Aβ deposition. The data obtained from our investigation revealed that YU102 suppresses the secretion of inflammatory cytokines from microglial cells. Overall, this study indicates that there may exist a potential link between LMP2/Y and microglia-mediated neuroinflammation and that inhibition of these subunits may offer a new therapeutic strategy for AD.

Pterostilbene Attenuates Astrocytic Inflammation and Neuronal Oxidative Injury After Ischemia-Reperfusion by Inhibiting NF-κB Phosphorylation

Astrocyte-mediated inflammation and oxidative stress elicit cerebral ischemia-reperfusion (IR) injury after stroke. Nuclear factor (NF)-κB activates astrocytes and generates pro-inflammatory factors. The purpose of the present study is to elucidate the effect of pterostilbene (PTE, a natural stilbene) on astrocytic inflammation and neuronal oxidative injury following cerebral ischemia-reperfusion injury. A middle cerebral artery occlusion-reperfusion (MCAO/R) mouse model and HT22/U251 co-culture model subjected to oxygen-glucose deprivation and re-introduction (OGD/R) were employed, with or without PTE treatment. The data showed that PTE delivery immediately after reperfusion, at 1 h after occlusion, decreased infarct volume, brain edema, and neuronal apoptosis and improved long-term neurological function. PTE decreased oxidation (i.e., production of reactive oxygen species, malondialdehyde) and inflammatory mediators (tumor necrosis factor-α, interleukin-1β, and interleukin-6) and increased anti-oxidative enzyme activities (i.e., of superoxide dismutase, glutathione peroxidase), by inhibiting phosphorylation and nuclear translocation of NF-κB. In conclusion, PTE attenuated astrocyte-mediated inflammation and oxidative injury following IR via NF-κB inhibition. Overall, PTE is a promising neuroprotective agent.

CXCL8 gene silencing promotes neuroglial cells activation while inhibiting neuroinflammation through the PI3K/Akt/NF-κB-signaling pathway in mice with ischemic stroke

OBJECTIVE

Ischemic stroke is known as a neurodegenerative disorder, which induces long-period tissue damage. Chemokine (C-X-C motif) ligand 8 (CXCL8) is involved in acute inflammation and tumor progression through the phosphoinositide-3-kinase/protein kinase B/nuclear factor-κB (PI3K/Akt/NF-κB)-signaling pathway. In this study, we aimed to explore the mechanism of CXCL8 in ischemic stroke in relation to the PI3K/Akt/NF-κB-signaling pathway.

METHODS

Microarray-based gene expression profiling of peripheral blood mononuclear cells was used to identify ischemic stroke-related differentially expressed genes and explore role of CXCL8 in ischemic stroke. Next, the ischemic mice model was successfully established, with transfection efficiency detected. After that, deflection index, recovery of nervous system, infarct sizes, ischemia-induced apoptosis, and neuroinflammatory response in ischemic stroke were measured. At last, the content of inflammatory factors as well as the expression of CXCL8, caspase-3, caspase-9, Bad, interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNF-α), Akt, PI3K, and NF-κB were determined.

RESULTS

Comprehensive gene expression profiling analysis identified that CXCL8 might affect the development of ischemic stroke through regulating the PI3K/Akt/NF-κB-signaling pathway. CXCL8 silencing significantly reduced deflection index and infarct size, improved neurological function, and suppressed neuroglial cell loss and apoptosis index. In addition, glial fibrillary acidic portein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA-1) expressions were decreased following CXCL8 suppression, suggesting CXCL8 affected neuroglial activation. Importantly, we also found that CXCL8 silencing activated neuroglial cell and suppressed inflammatory cytokine production in ischemic stroke mice.

CONCLUSION

Taken together, these findings highlight that functional suppression of CXCL8 promotes neuroglial activation and inhibits neuroinflammation by regulating the PI3K/Akt/NF-κB-signaling pathway in mice with ischemic stroke, which might provide new insight for ischemic stroke treatment.

Loss of NLRX1 Exacerbates Neural Tissue Damage and NF-κB Signaling following Brain Injury

Traumatic and nontraumatic brain injury results from severe disruptions in the cellular microenvironment leading to massive loss of neuronal populations and increased neuroinflammation. The progressive cascade of secondary events, including ischemia, inflammation, excitotoxicity, and free-radical release, contribute to neural tissue damage. NLRX1 is a member of the NLR family of pattern recognition receptors and is a potent negative regulator of several pathways that significantly modulate many of these events. Thus, we hypothesized that NLRX1 limits immune system signaling in the brain following trauma. To evaluate this hypothesis, we used Nlrx1^-/- mice in a controlled cortical impact (CCI) injury murine model of traumatic brain injury (TBI). In this article, we show that Nlrx1^-/- mice exhibited significantly larger brain lesions and increased motor deficits following CCI injury. Mechanistically, our data indicate that the NF-κB signaling cascade is significantly upregulated in Nlrx1^-/- animals. This upregulation is associated with increased microglia and macrophage populations in the cortical lesion. Using a mouse neuroblastoma cell line (N2A), we also found that NLRX1 significantly reduced apoptosis under hypoxic conditions. In human patients, we identify 15 NLRs that are significantly dysregulated, including significant downregulation of NLRX1 in brain injury following aneurysm. We further demonstrate a concurrent increase in NF-κB signaling that is correlated with aneurysm severity in these human subjects. Together, our data extend the function of NLRX1 beyond its currently characterized role in host-pathogen defense and identify this highly novel NLR as a significant modulator of brain injury progression.

Role of Interleukin-10 in Acute Brain Injuries

Interleukin-10 (IL-10) is an important anti-inflammatory cytokine expressed in response to brain injury, where it facilitates the resolution of inflammatory cascades, which if prolonged causes secondary brain damage. Here, we comprehensively review the current knowledge regarding the role of IL-10 in modulating outcomes following acute brain injury, including traumatic brain injury (TBI) and the various stroke subtypes. The vascular endothelium is closely tied to the pathophysiology of these neurological disorders and research has demonstrated clear vascular endothelial protective properties for IL-10. In vitro and in vivo models of ischemic stroke have convincingly directly and indirectly shown IL-10-mediated neuroprotection; although clinically, the role of IL-10 in predicting risk and outcomes is less clear. Comparatively, conclusive studies investigating the contribution of IL-10 in subarachnoid hemorrhage are lacking. Weak indirect evidence supporting the protective role of IL-10 in preclinical models of intracerebral hemorrhage exists; however, in the limited number of clinical studies, higher IL-10 levels seen post-ictus have been associated with worse outcomes. Similarly, preclinical TBI models have suggested a neuroprotective role for IL-10; although, controversy exists among the several clinical studies. In summary, while IL-10 is consistently elevated following acute brain injury, the effect of IL-10 appears to be pathology dependent, and preclinical and clinical studies often paradoxically yield opposite results. The pronounced and potent effects of IL-10 in the resolution of inflammation and inconsistency in the literature regarding the contribution of IL-10 in the setting of acute brain injury warrant further rigorously controlled and targeted investigation.

Interleukin 32, inflammation and cancer

Interleukin-32 (IL-32) is a novel cytokine involved in inflammation and cancer development. IL-32 gene consists of eight small exons, and IL-32 mRNA has nine alternative spliced isoforms, and was thought to be secreted because it contains an internal signal sequence and lacks a transmembrane region. IL-32 is initially expressed selectively in activated T cells by mitogen and activated NK cells and their expression is strongly augmented by microbes, mitogens, and other cytokines. The IL-32 is induced mainly by pathogens and pro-inflammatory cytokines, but IL-32 is more prominent in immune cells than in non-immune tissues. The IL-32 transcript is expressed in various human tissues and organs such as the spleen, thymus, leukocyte, lung, small intestine, colon, prostate, heart, placenta, liver, muscle, kidney, pancreas, and brain. Cytokines are critical components of cell signaling pathways that are involved in the regulation of cell growth, metabolism, hormone signaling, immune regulation and a variety of other physiological functions. Earlier studies have demonstrated that IL-32 regulates cell growth, metabolism and immune regulation and is therefore involved in the pathologic regulator or protectant of inflammatory diseases. Previous studies defined that IL-32 is upregulated in the patients with several inflammatory diseases, and is induced by inflammatory responses. However, several reports suggested that IL-32 is downregulated in several inflammatory diseases including asthma, HIV infection disease, neuronal diseases, metabolic disorders, experimental colitis and metabolic disorders. IL-32 is also involved in various cancer malignancies including renal cancer, esophageal cancer and hepatocellular carcinoma, lung cancer, gastric cancer, breast cancer, pancreatic cancer, lymphoma, osteosarcoma, breast cancer, colon cancer and thyroid carcinoma. Other studies suggested that IL-32 decreases tumor development including cervical cancer, colon cancer and prostate cancer, melanoma, pancreatic cancer, liver cancer and chronic myeloid leukemia. Nevertheless, review articles that discuss the roles and its mechanism of IL-32 isoforms focusing on the therapeutic approaches have not yet been reported. In this review article, we will discuss recent findings regarding IL-32 in the development of diseases and further discuss therapeutic approaches targeting IL-32. Moreover, we will suggest that IL-32 could be the target of several diseases and the therapeutic agents for targeting IL-32 may have potential beneficial effects for the treatment of inflammatory diseases and cancers. Future research should open new avenues for the design of novel therapeutic approaches targeting IL-32.

Myelin oligodendrocyte glycoprotein (MOG35-55)-induced experimental autoimmune encephalomyelitis is ameliorated in interleukin-32 alpha transgenic mice

Multiple sclerosis (MS), also known as disseminated sclerosis or encephalomyelitis disseminate, is an inflammatory disease in which myelin in the spinal cord and brain are damaged. IL-32α is known as a critical molecule in the pathophysiology of immune-mediated chronic inflammatory disease such as rheumatoid arthritis, chronic pulmonary disease, and cancers. However, the role of IL-32α on spinal cord injuries and demyelination is poorly understood. Recently, we reported that the release of proinflammatory cytokines were reduced in IL-32α-overexpressing transgenic mice. In this study, we investigated whether IL-32α plays a role on MS using experimental autoimmune encephalomyelitis (EAE), an experimental mouse model of MS, in human IL-32α Tg mice. The Tg mice were immunized with MOG_35-55 suspended in CFA emulsion followed by pertussis toxin, and then EAE paralysis of mice was scored. We observed that the paralytic severity and neuropathology of EAE in IL-32α Tg mice were significantly decreased compared with that of non-Tg mice. The immune cells infiltration, astrocytes/microglials activation, and pro-inflammatory cytokines (IL-1β and IL-6) levels in spinal cord were suppressed in IL-32α Tg mice. Furthermore, NG2 and O4 were decreased in IL-32α Tg mice, indicating that spinal cord damaging was suppressed. In addition, in vitro assay also revealed that IL-32α has a preventive role against Con A stimulation which is evidenced by decrease in T cell proliferation and inflammatory cytokine levels in IL-32α overexpressed Jurkat cell. Taken together, our findings suggested that IL-32α may play a protective role in EAE by suppressing neuroinflammation in spinal cord.