Probucol inhibits LPS-induced microglia activation and ameliorates brain ischemic injury in normal and hyperlipidemic mice

Influence of the brain‑gut axis on neuroinflammation in cerebral ischemia‑reperfusion injury (Review)

Stroke, a debilitating cerebrovascular ailment, poses significant threats to human life and health. The intricate interplay between the gut‑brain‑microbiota axis (GBMA) and cerebral ischemia‑reperfusion has increasingly become a focal point of scientific exploration, emerging as a pivotal research avenue in stroke pathophysiology. In the present review, the authors delved into the nexus between the GBMA and neuroinflammation observed post‑stroke. The analysis underscored the pivotal roles of histone deacetylase 3 and neutrophil extracellular traps subsequent to stroke incidents. The influence of gut microbial compositions and their metabolites, notably short‑chain fatty acids and trimethylamine N‑oxide, on neuroinflammatory processes, was further elucidated. The involvement of immune cells, especially regulatory T‑cells, and the intricate signaling cascades including cyclic GMP‑AMP synthase/stimulator of interferon genes/Toll‑like receptor, further emphasized the complex regulatory mechanisms of GBMA in cerebral ischemia/reperfusion injury (CI/RI). Collectively, the present review offered a comprehensive perspective on the metabolic, immune and inflammatory modulations orchestrated by GBMA, augmenting the understanding of its role in neuroinflammation following CI/RI.

Probucol protects against brain damage caused by intra-neural pyroptosis in rats with vascular dementia through inhibition of the Syk/Ros pathway

BACKGROUND

Neuronal injury in chronic cerebral hypoperfusion (CCH) is the main pathogenic factor of vascular dementia (VD). Clinically, there isn't a drug specifically for VD; instead, the majority of medications used to treat Alzheimer's disease (AD) are also used to treat VD. Based on the proven anti-inflammatory and antioxidant effects of Probucol, we hypothesized that it may have therapeutic effects on VD, but more research is required to determine its exact mechanism of action.

METHODS

In vivo experiment: We used SD rats and most commonly used bilateral carotid artery occlusion (2-VO) in VD for modeling. After successful modeling, SD rats were given Probucol 3.5 mg/kg/day for 8 weeks to evaluate the therapeutic effect. In vitro experiment: BV-2 microglia of rats were cultured and divided into Control group and Probucol group. Each group was treated with hypoxia-hypoglycemia, hypoxia-hypoglycemia hydrogen peroxide and hypoxia-hypoglycemia hydrogen peroxide Syk inhibitor respectively.

RESULTS

The results of immunofluorescence and Western blot showed that Probucol could significantly improve the cognitive impairment induced by CCH, and the neuronal damage was also attenuated. On the one hand, the underlying mechanism of Probucol was to reduce oxidative stress and cell apoptosis of hippocampal neurons by inhibiting the expression of phosphorylated spleen tyrosine kinase (P-Syk); On the other hand, it exerted a protective effect by reducing NLRP3-dependent cell pyroptosis and inhibiting neuroinflammation induced by microglia activation.

CONCLUSION

Probucol could reduce oxidative stress and cell apoptosis by inhibiting the Syk/ROS signaling pathway, thereby improving CCH-induced cognitive impairment in vitro and in vivo.

The therapeutic potential of probucol and probucol analogues in neurodegenerative diseases

Neurodegenerative disorders present complex pathologies characterized by various interconnected factors, including the aggregation of misfolded proteins, oxidative stress, neuroinflammation and compromised blood-brain barrier (BBB) integrity. Addressing such multifaceted pathways necessitates the development of multi-target therapeutic strategies. Emerging research indicates that probucol, a historic lipid-lowering medication, offers substantial potential in the realm of neurodegenerative disease prevention and treatment. Preclinical investigations have unveiled multifaceted cellular effects of probucol, showcasing its remarkable antioxidative and anti-inflammatory properties, its ability to fortify the BBB and its direct influence on neural preservation and adaptability. These diverse effects collectively translate into enhancements in both motor and cognitive functions. This review provides a comprehensive overview of recent findings highlighting the efficacy of probucol and probucol-related compounds in the context of various neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and cognitive impairment associated with diabetes.

Meclizine moderates lipopolysaccharide-induced neuroinflammation in mice through the regulation of AKT/ NF-κβ/ERK/JNK signaling pathway

Neuroinflammation is identified as significant inflammatory reactions occurring in the central nervous system. Lipopolysaccharide (LPS) stimulates innate immune reactions and is used as an in vivo animal model for the investigation of inflammation. Meclizine (MCLZ) is a histamine antagonist with potential neuroprotective qualities. Forty adult male Swiss albino mice were divided into four groups (n = 10). Group 1 served as a control negative group. Groups 2-4 were injected with LPS (5 mg/kg; i.p). Group 2 served as LPS-control. Groups 3 & 4 were given MCLZ (12.5 & 25 mg/kg; p.o) respectively for 14 days. LPS administration resulted in significant neuroinflammation in mice as was revealed by significant inflammatory histopathological changes and positive immunohistochemical staining of glial fibrillary acidic proteins (GFAP) accompanied by significant elevations of brain tissue contents of interleukin-1-beta (IL-1β), tumor necrosis factor-alpha (TNF-α), nuclear factor kappa-beta (NF-κβ), protein kinase B (AKT), extracellular signal-regulated kinase (ERK) and C-Jun N-Terminal Kinases (JNK). MCLZ treatment significantly down-regulated all the aforementioned parameters in mice brains. Moreover, MCLZ treatment ameliorated the inflammatory histopathological changes and GFAP immunostaining in brain tissues. The current study identifies for the first time the protective anti-neuroinflammatory effects of MCLZ against LPS-induced neuroinflammation in mice. MCLZ protected against neuroinflammation via the amelioration of inflammatory histopathological changes as well as neuronal GFAP immunostaining and down-regulated the AKT/NF-κβ/ERK/JNK signaling pathway. MCLZ is anticipated as a potential protective candidate for the addition to the treatment protocol of neuroinflammation.

Probucol treatment after traumatic brain injury activates BDNF/TrkB pathway, promotes neuroregeneration and ameliorates functional deficits in mice

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide, yet pharmacotherapies for TBI are currently lacking. Neuroregeneration is important in brain repair and functional recovery. In this study, probucol, a cholesterol-lowering drug with established safety profiles, was examined for its therapeutic effects and neuroregenerative actions in TBI.

EXPERIMENTAL APPROACH

Male mice were subjected to the controlled cortical impact model of TBI, followed by daily administration of probucol. Neurological and cognitive functions were evaluated. Histological analyses of the neocortex and hippocampus were performed to detect the lesion, dendritic degeneration (microtubule-associated protein 2), synaptic density (synaptophysin), neurogenesis (doublecortin), brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) activation. Involvement of BDNF/TrkB pathway in probucol-mediated effects was examined in primary cultures of cortical neurons.

KEY RESULTS

Probucol reduced brain lesion volume, enhanced the recovery of body symmetry, improved motor function and attenuated memory dysfunction after TBI. Meanwhile, probucol promoted post-injury dendritic growth and synaptogenesis and increased hippocampal proliferating neuronal progenitor cells, along with the formation as well as the survival of newborn neurons. Moreover, probucol enhances BDNF expression and TrkB activation. In vitro, probucol promoted neurite outgrowth, which was inhibited by a selective TrkB antagonist ANA-12.

CONCLUSIONS AND IMPLICATIONS

Probucol enhanced functional restoration and ameliorated cognitive impairment after TBI by promoting post-injury neuronal remodelling and neurogenesis. Increased activation of BDNF/TrkB pathway by probucol, at least in part, contributed to the neuroregenerative effects of probucol. Together, it may be promising to repurpose probucol for TBI.

Probucol suppresses osteoclastogenesis via activating Nrf2 signaling and ameliorates ovariectomy-induced bone loss

Osteoporosis is a systemic and endocrine bone disorder distinguished by declined bone mineral density, compromised bone strength, and destruction of trabecular structure. The abnormally excessive osteoclastogenesis and bone erosion play imperative roles in the progression of osteoporosis. However, treatment of osteoporosis is far from satisfactory due to poor adherence to existing medications and adverse reactions, there is an urgent to develop novel therapies for osteoporosis. Probucol, a synthetic compound with two characteristic phenolic rings, owns anti-inflammatory and antioxidant properties. Accumulating evidence have indicated that intracellular reactive oxygen species (ROS) is closely related to osteoclastogenesis. Hence, we investigated the potential effects of probucol on osteoclastogenesis in vivo and in vitro. In this study, TRAP staining and bone slice resorption assay showed that probucol suppressed RANKL-induced osteoclast formation and function. The mRNA and protein levels of osteoclastogenesis marker genes were reduced by probucol in a concentration-dependent manner. Besides, probucol suppressed osteoclast differentiation by inhibiting ROS production, MAPKs and NF-κB signaling pathways, while Nrf2 silencing reversed the inhibitory effect of probucol on osteoclast formation and function. Consistent with the above findings, in vivo experiments demonstrated that probucol visibly alleviated bone loss caused by estrogen deficiency. In brief, these results showed the potential of anti-oxidant compound probucol in the treatment of osteoporosis, highlighting Nrf2 as a promising target in osteoclast-related disease.

Prevention of LPS-Induced Acute Kidney Injury in Mice by Bavachin and Its Potential Mechanisms

Acute kidney injury (AKI) is a serious complication of sepsis with a rapid onset and high mortality rate. Bavachin, an active component of Psoralea corylifolia L., reportedly has antioxidant, anti-apoptotic, and anti-inflammatory effects; however, its beneficial effects on AKI remain undetermined. We investigated the protective effect of bavachin on lipopolysaccharide (LPS)-induced AKI in mice and elucidated the underlying mechanism in human renal tubular epithelial HK-2 cells. Increased serum creatinine and blood urea nitrogen levels were observed in LPS-injected mice; however, bavachin pretreatment significantly inhibited this increase. Bavachin improved the kidney injury score and decreased the expression level of tubular injury markers, such as neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), in both LPS-injected mice and LPS-treated HK-2 cells. LPS-induced oxidative stress via phosphorylated protein kinase C (PKC) β and upregulation of the NADPH oxidase (NOX) 4 pathway was also significantly decreased by treatment with bavachin. Moreover, bavachin treatment inhibited the phosphorylation of MAPKs (P38, ERK, and JNK) and nuclear factor (NF)-κB, as well as the increase in inflammatory cytokine levels in LPS-injected mice. Krüppel-like factor 5 (KLF5) expression was upregulated in the LPS-treated HK-2 cells and kidneys of LPS-injected mice. However, RNAi-mediated silencing of KLF5 inhibited the phosphorylation of NF-kB, consequently reversing LPS-induced KIM-1 and NGAL expression in HK-2 cells. Therefore, bavachin may ameliorate LPS-induced AKI by inhibiting oxidative stress and inflammation via the downregulation of the PKCβ/MAPK/KLF5 axis.

Evaluating the effect of LPS from periodontal pathogenic bacteria on the expression of senescence-related genes in human dental pulp stem cells

The human dental pulp stem cells (hDPSCs) are one of the readily available sources of multipotent mesenchymal stem cells (MSCs) and can be considered as a type of tool cells for cell‐based therapies. However, the main limitation in the clinical use of these cells is DPSC senescence, which can be induced by lipopolysaccharide (LPS) of oral pathogenic bacteria. Up to now, far little attention has been paid to exploring the molecular mechanisms of senescence in DPSCs. So, the current study aimed to investigate the underlying molecular mechanism of senescence in hDPSCs stimulated with Porphyromonas gingivalis (P. gingivalis) and Escherichia coli (E. coli)‐derived LPSs, by evaluating both mRNA and protein expression of four important senescence‐related genes, including TP53, CDKN1A, CDKN2A and SIRT1. To this purpose, hDPSCs were stimulated with different LPSs for 6, 24 and 48 h and then the gene expression was evaluated using quantitative real‐time polymerase chain reaction (qPCR) and western blotting. Following stimulation with P. gingivalis and E. coli‐derived LPSs, the relative mRNA and protein expression of all genes were significantly up‐regulated in a time‐dependent manner, as compared with unstimulated hDPSCs. Moreover, the hDPSCs stimulated with P. gingivalis LPS for 6 and 24 h had the highest mRNA expression of CDKN1A and SIRT1, respectively (p < 0.0001), whereas the highest mRNA expression of CDKN2A and TP53 was seen in hDPSCs stimulated with E. coli LPS for 48 h (p < 0.0001). In summary, because DPSCs have been reported to have therapeutic potential for several cell‐based therapies, targeting molecular mechanisms aiming at preventing DPSC senescence could be considered a valuable strategy.

Leonurine Reduces Oxidative Stress and Provides Neuroprotection against Ischemic Injury via Modulating Oxidative and NO/NOS Pathway

Leonurine (Leo) has been found to have neuroprotective effects against cerebral ischemic injury. However, the exact molecular mechanism underlying its neuroprotective ability remains unclear. The aim of the present study was to investigate whether Leo could provide protection through the nitric oxide (NO)/nitric oxide synthase (NOS) pathway. We firstly explored the effects of NO/NOS signaling on oxidative stress and apoptosis in in vivo and in vitro models of cerebral ischemia. Further, we evaluated the protective effects of Leo against oxygen and glucose deprivation (OGD)-induced oxidative stress and apoptosis in PC12 cells. We found that the rats showed anxiety-like behavior, and the morphology and number of neurons were changed in a model of photochemically induced cerebral ischemia. Both in vivo and in vitro results show that the activity of superoxide dismutase (SOD) and glutathione (GSH) contents were decreased after ischemia, and reactive oxygen species (ROS) and malondialdehyde (MDA) levels were increased, indicating that cerebral ischemia induced oxidative stress and neuronal damage. Moreover, the contents of NO, total NOS, constitutive NOS (cNOS) and inducible NOS (iNOS) were increased after ischemia in rat and PC12 cells. Treatment with L-nitroarginine methyl ester (L-NAME), a nonselective NOS inhibitor, could reverse the change in NO/NOS expression and abolish these detrimental effects of ischemia. Leo treatment decreased ROS and MDA levels and increased the activity of SOD and GSH contents in PC12 cells exposed to OGD. Furthermore, Leo reduced NO/NOS production and cell apoptosis, decreased Bax expression and increased Bcl-2 levels in OGD-treated PC12 cells. All the data suggest that Leo protected against oxidative stress and neuronal apoptosis in cerebral ischemia by inhibiting the NO/NOS system. Our findings indicate that Leo could be a potential agent for the intervention of ischemic stroke and highlighted the NO/NOS-mediated oxidative stress signaling.

Exploring biomarkers for ischemic stroke through integrated microarray data analysis

Stroke is the third leading cause of disability-adjusted life years worldwide, and drugs available for its treatment are limited. This study aimed to explore high-confidence candidate genes associated with ischemic stroke (IS) through bioinformatics analysis and identify potential diagnostic biomarkers and gene-drug interactions. Weighted gene coexpression network analysis (WGCNA) and differentially expressed genes (DEGs) were integrated to identify overlapping genes. Then, high-confidence candidate genes were screened by least absolute shrinkage and selection operator (LASSO) regression. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic value of high-confidence candidate genes as biomarkers for IS. The NetworkAnalyst database was used to construct the TF-gene network and miRNA-TF regulatory network of the high-confidence candidate genes. The DGIdb database was used to identified gene-drug interactions. Through the comprehensive analysis of GSE58294 and GSE16561, 10 high-confidence candidate genes were identified by LASSO regression: ARG1, LY96, ABCA1, SLC22A4, CD163, TPM2, SLC25A42, ID3, FAM102A and CD79B. FAM102A had the highest diagnostic value, and the area under curve (AUC), sensitivity and specificity values were 0.974, 0.919 and 0.936, respectively. The HPA database demonstrated that 10 high-confidence candidate genes were expressed in the brain and blood in normal humans. Finally, DGIdb database analysis identified 8 gene-drug interactions. We identified IS-related diagnostic biomarkers and gene-drug interactions that potentially provide new insights into the diagnosis and treatment of IS.

Enhanced Antioxidant Effects of the Anti-Inflammatory Compound Probucol when Released from Mesoporous Silica Particles

Brain endothelial cells mediate the function and integrity of the blood brain barrier (BBB) by restricting its permeability and exposure to potential toxins. However, these cells are highly susceptible to cellular damage caused by oxidative stress and inflammation. Consequent disruption to the integrity of the BBB can lead to the pathogenesis of neurodegenerative diseases. Drug compounds with antioxidant and/or anti-inflammatory properties therefore have the potential to preserve the structure and function of the BBB. In this work, we demonstrate the enhanced antioxidative effects of the compound probucol when loaded within mesoporous silica particles (MSP) in vitro and in vivo zebrafish models. The dissolution kinetics were significantly enhanced when released from MSPs. An increased reduction in lipopolysaccharide (LPS)-induced reactive oxygen species (ROS), cyclooxygenase (COX) enzyme activity and prostaglandin E₂ production was measured in human brain endothelial cells treated with probucol-loaded MSPs. Furthermore, the LPS-induced permeability across an endothelial cell monolayer by paracellular and transcytotic mechanisms was also reduced at lower concentrations compared to the antioxidant ascorbic acid. Zebrafish pre-treated with probucol-loaded MSPs reduced hydrogen peroxide-induced ROS to control levels after 24-h incubation, at significantly lower concentrations than ascorbic acid. We provide compelling evidence that the encapsulation of antioxidant and anti-inflammatory compounds within MSPs can enhance their release, enhance their antioxidant effects properties, and open new avenues for the accelerated suppression of neuroinflammation.

Protective Effects of Probucol on Different Brain Cells Exposed to Manganese

Manganese (Mn) is an essential metal for many functions in the body. However, in excess, it can be neurotoxic and cause a Parkinson-like syndrome, known as manganism. Here, we aimed to identify a protective effect of probucol, a lipid-lowering agent with anti-inflammatory and antioxidant properties, against Mn-induced toxicity in human neuroblastoma (SH-SY5Y) and glioblastoma (C6) cell lines. The cells were incubated with increasing concentrations of Mn followed by probucol addition 1, 3, 6, and/or 24 h to assess the metal toxic doses and measure the protective effect of probucol against Mn-induced oxidative damage. Longer exposition to Mn showed decreased SH-SY5Y cellular viability in concentrations higher than 100 µM, and probucol was able to prevent this effect. The C6 cells were more sensitive to the Mn deleterious actions, decreasing the cell viability after 6 h of 500 µM Mn exposure. In addition, probucol prevents the complex I and II of the mitochondrial respiratory chain (MRC) inhibition caused by Mn and decreased the intracellular ROS production. Taken together, our results showed that Mn toxicity affects differently both cell lines and probucol has a protective effect against the oxidative imbalance in the central nervous system.

The mechanism of microglia-mediated immune inflammation in ischemic stroke and the role of natural botanical components in regulating microglia: A review

Ischemic stroke (IS) is one of the most fatal diseases. Neuroimmunity, inflammation, and oxidative stress play important roles in various complex mechanisms of IS. In particular, the early proinflammatory response resulting from the overactivation of resident microglia and the infiltration of circulating monocytes and macrophages in the brain after cerebral ischemia leads to secondary brain injury. Microglia are innate immune cells in the brain that constantly monitor the brain microenvironment under normal conditions. Once ischemia occurs, microglia are activated to produce dual effects of neurotoxicity and neuroprotection, and the balance of the two effects determines the fate of damaged neurons. The activation of microglia is defined as the classical activation (M1 type) or alternative activation (M2 type). M1 type microglia secrete pro-inflammatory cytokines and neurotoxic mediators to exacerbate neuronal damage, while M2 type microglia promote a repairing anti-inflammatory response. Fine regulation of M1/M2 microglial activation to minimize damage and maximize protection has important therapeutic value. This review focuses on the interaction between M1/M2 microglia and other immune cells involved in the regulation of IS phenotypic characteristics, and the mechanism of natural plant components regulating microglia after IS, providing novel candidate drugs for regulating microglial balance and IS drug development.

Effects and mechanisms of probucol on aging-related hippocampus-dependent cognitive impairment

BACKGROUND

In the present study, we aimed to investigate the effects of probucol on aging-related hippocampus-dependent cognitive impairment and explore the potential mechanisms.

METHODS

D-galactose (100 mg/kg, once daily for 6 weeks) was subcutaneously injected to induce aging in mice. Then the mice were administered with probucol or vehicle once a day for 2 weeks. The hippocampus-related cognition was evaluated with Morris water maze test, novel object recognition test, and contextual fear conditioning test. Moreover, synaptic plasticity was assessed, and RNA-sequencing was applied to further explore the molecular mechanisms.

RESULTS

Aging mice induced by D-galactose showed conspicuous learning and memory impairment, which was significantly ameliorated by probucol. Meanwhile, probucol enhanced the spine density and dendritic branches, improved long-term potentiation, and increased the expression of PSD95 of aging mice. Probucol regulated 70 differentially expressed genes compared to D-galactose group, of which 38 genes were upregulated and 32 genes were downregulated. At last, RNA-sequencing results were verified by quantitative reverse transcription-polymerase chain reaction.

CONCLUSIONS

Probucol improved learning and memory in aging mice through enhancing synaptic plasticity and regulating gene expression, indicating the potential application of probucol to prevent and treat aging-related disorders.

CQMUH-011 Inhibits LPS-Induced Microglia Activation and Ameliorates Brain Ischemic Injury in Mice

Excessive microglial activation-mediated neuroinflammation is closely involved in the pathogenesis of several neurological diseases. CQMUH-011, as a novel adamantane sulfonamide compound, has been shown anti-inflammatory properties in activated macrophages (RAW264.7). However, the role of CQMUH-011 in microglial activation-induced neuroinflammation and neuroprotective properties has yet to be elucidated. In the present study, we investigated the potential effects and mechanisms of CQMUH-011 on lipopolysaccharide (LPS)-stimulated primary microglia in vitro and transient middle cerebral artery occlusion (t-MCAO)-induced acute cerebral ischemia/reperfusion (I/R) injury in vivo. The results demonstrated that CQMUH-011 significantly suppressed the production of tumor necrosis factor (TNF)-α and interleukin (IL)-1β by LPS-stimulated primary microglia. In addition, CQMUH-011 inhibited the proliferation of activated microglia by arresting the cell cycle at the G1/S phase accompanied by downregulating the expression of cell cycle regulatory proteins such as proliferating cell nuclear antigen (PCNA) and cyclin D1. CQMUH-011 was seen to induce apoptosis in activated microglia by regulating the expression of Bax and Bcl-2. Furthermore, CQMUH-011 markedly attenuated the protein expression of Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) as well as the phosphorylation levels of nuclear factor-kappa (NF-κB) subunit p65, inhibitory kappa B-alpha (IκBα), and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK) and p38 kinases. In vivo, CQMUH-011 administration significantly improved neurological function and infarct volume, and ameliorated the inflammatory cytokines and microglia amount around the injury site of mice. In conclusion, these results suggested that CQMUH-011 has a notable anti-inflammatory effect and protects mice from I/R injure. Thus, CQMUH-011 may be a candidate drug for the treatment of cerebral ischemia patients.

RIP3-mediated necroptosis increases neuropathic pain via microglia activation: necrostatin-1 has therapeutic potential

Neuropathic pain (NP) is a clinical symptom that accompanies many diseases. We investigated the effect of receptor‐interacting protein kinase 3 (RIP3)‐regulated necroptosis on NP and explored its relationship with microglia, in order to provide a theoretical basis for further research and provide new insights into the treatment of NP. In this study, the spared nerve injury (SNI) model was used along with intervention with necrostatin and the inhibitor of necroptosis necrostatin‐1 (Nec‐1). Pain behavior tests were performed 1 and 3 days before the nerve injury (or sham) operation, and on days 1, 3, 5, 7, 10, and 14 after the operation. The spinal cord tissues were collected for detection of RIP3 expression and distribution, changes in the number of microglia cells, activation of necroptosis, and the level of proinflammatory factors. Collected spinal cord tissues were analyzed using western blot, immunohistochemistry, immunofluorescence, immunoprecipitation assays, and ELISA, respectively. We found that, compared with the sham group, the expression of RIP3 protein in the spinal cord of rats in the SNI group increased from 3 to 14 days after surgery. Immunofluorescence staining showed that RIP3 was coexpressed with the microglia and the number of microglia increased significantly in the SNI model group. The results of immunoprecipitation assays suggested that a RIP3‐mediated necroptosis pathway promotes NP. After treatment with Nec‐1, the expression of RIP3 protein and the number of microglia were significantly reduced, and the expression levels of TNF‐α, IL‐1β, and IL‐6 in spinal dorsal horns were significantly decreased. These results indicate that RIP3 promotes necroptosis to increase the occurrence of NP via microglia.

Autophagy is Involved in Neuroprotective Effect of Alpha7 Nicotinic Acetylcholine Receptor on Ischemic Stroke

The α7 nicotinic acetylcholine receptor (α7nAChR) belongs to the superfamily of cys loop cationic ligand-gated channels, which consists of homogeneous α7 subunits. Although our lab found that activation of α7nAChR could alleviate ischemic stroke, the mechanism is still unknown. Herein, we explored whether autophagy is involved in the neuroprotective effect mediated by α7nAChR in ischemic stroke. Transient middle cerebral artery occlusion (tMCAO) and oxygen and glucose deprivation (OGD/R) exposure were applied to in vivo and in vitro models of ischemic stroke, respectively. Neurological deficit score and infarct volume were used to evaluate outcomes of tMCAO in the in vivo study. Autophagy-related proteins were detected by Western blot, and autophagy flux was detected by using tandem fluorescent mRFP-GFP-LC3 lentivirus. At 24 h after tMCAO, α7nAChR knockout mice showed worse neurological function and larger infarct volume than wild-type mice. PNU282987, an α7nAChR agonist, protected against OGD/R-induced neuronal injury, enhanced autophagy, and promoted autophagy flux. However, the beneficial effects of PNU282987 were eliminated by 3-methyladenine (3-MA), an autophagy inhibitor. Moreover, we found that PNU282987 treatment could activate the AMPK-mTOR-p70S6K signaling pathway in the in vitro study, while the effect was attenuated by compound C, an AMPK inhibitor. Our results demonstrated that the beneficial effect on neuronal survival via activation of α7nAChR was associated with enhanced autophagy, and the AMPK-mTOR-p70S6K signaling pathway was involved in α7nAChR activation-mediated neuroprotection.

Microglia activated by microbial neuraminidase contributes to ependymal cell death

The administration of microbial neuraminidase into the brain ventricular cavities of rodents represents a model of acute aseptic neuroinflammation. Ependymal cell death and hydrocephalus are unique features of this model. Here we demonstrate that activated microglia participates in ependymal cell death. Co-cultures of pure microglia with ependymal cells (both obtained from rats) were performed, and neuraminidase or lipopolysaccharide were used to activate microglia. Ependymal cell viability was unaltered in the absence of microglia or inflammatory stimulus (neuraminidase or lipopolysaccharide). The constitutive expression by ependymal cells of receptors for cytokines released by activated microglia, such as IL-1β, was demonstrated by qPCR. Besides, neuraminidase induced the overexpression of both receptors in ventricular wall explants. Finally, ependymal viability was evaluated in the presence of functional blocking antibodies against IL-1β and TNFα. In the co-culture setting, an IL-1β blocking antibody prevented ependymal cell death, while TNFα antibody did not. These results suggest that activated microglia are involved in the ependymal damage that occurs after the administration of neuraminidase in the ventricular cavities, and points to IL-1β as possible mediator of such effect. The relevance of these results lies in the fact that brain infections caused by neuraminidase-bearing pathogens are frequently associated to ependymal death and hydrocephalus.

CQMUH-011 Inhibits LPS-Induced Microglia Activation and Ameliorates Brain Ischemic Injury in Mice

Excessive microglial activation-mediated neuroinflammation is closely involved in the pathogenesis of several neurological diseases. CQMUH-011, as a novel adamantane sulfonamide compound, has been shown anti-inflammatory properties in activated macrophages (RAW264.7). However, the role of CQMUH-011 in microglial activation-induced neuroinflammation and neuroprotective properties has yet to be elucidated. In the present study, we investigated the potential effects and mechanisms of CQMUH-011 on lipopolysaccharide (LPS)-stimulated primary microglia in vitro and transient middle cerebral artery occlusion (t-MCAO)-induced acute cerebral ischemia/reperfusion (I/R) injury in vivo. The results demonstrated that CQMUH-011 significantly suppressed the production of tumor necrosis factor (TNF)-α and interleukin (IL)-1β by LPS-stimulated primary microglia. In addition, CQMUH-011 inhibited the proliferation of activated microglia by arresting the cell cycle at the G₁/S phase accompanied by downregulating the expression of cell cycle regulatory proteins such as proliferating cell nuclear antigen (PCNA) and cyclin D1. CQMUH-011 was seen to induce apoptosis in activated microglia by regulating the expression of Bax and Bcl-2. Furthermore, CQMUH-011 markedly attenuated the protein expression of Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) as well as the phosphorylation levels of nuclear factor-kappa (NF-κB) subunit p65, inhibitory kappa B-alpha (IκBα), and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK) and p38 kinases. In vivo, CQMUH-011 administration significantly improved neurological function and infarct volume, and ameliorated the inflammatory cytokines and microglia amount around the injury site of mice. In conclusion, these results suggested that CQMUH-011 has a notable anti-inflammatory effect and protects mice from I/R injure. Thus, CQMUH-011 may be a candidate drug for the treatment of cerebral ischemia patients.

LMTK2 regulates inflammation in lipopolysaccharide-stimulated BV2 cells

Microglia activation plays vital roles in neuroinflammatory pathologys. Lemurs tyrosine kinase 2 (LMTK2) was reported to regulate NF-κB signals. In the present study, the roles of LMTK2 were investigated in lipopolysaccharide (LPS)-treated BV-2 cells. Reverse transcription-quantitative (RT-q)PCR and western blotting (WB) were utilized to analyze LMTK2 levels in LPS-treated BV2 cells. MTT assay determined cell viabilities. Nitric oxide (NO) and prostaglandin E2 (PGE2) levels were assessed through Griess and enzyme-linked immunosorbent assay (ELISA), respectively. The expression level of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) were detected through RT-qPCR and WB. The release of inflammatory mediators under LPS stimulation, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6 and IL-10, were analyzed through ELISA. WB was used to analyze the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1)/NAD(P)H dehydrogenase quinone 1 (NQO1) signal pathway. The results showed that the levels of the inflammatory mediators, iNOS, NO, COX-2 and PGE2, along with pro-inflammatory factors, TNF-α, IL-1β and IL-6, were significantly decreased following the induction of exogenous LMTK2 expression by LMTK2 overexpression plasmids in LPS-induced BV2 microglia. In contrast, anti-inflammatory factor IL-10 showed obvious decrease. Additionally, LMTK2 overexpression induced the elevation of Nrf2 in the cytoplasm and nucleus, along with the upregulation of HO-1 and NQO1 expression. In conclusion, LMTK2 is postulated to regulate neuroinflammation possibly through Nrf2 pathway. The present study is essential to reveal the underlying function of LMTK2 and to identify novel therapeutic targets for drug development in treating neuroinflammation.

Atorvastatin alleviates microglia-mediated neuroinflammation via modulating the microbial composition and the intestinal barrier function in ischemic stroke mice

Our previous work has shown that atorvastatin exerts anti-inflammatory properties in ischemic stroke, and recent studies have revealed that intestinal microbiota plays a vital role in the pathogenesis of stroke. However, it is not clear whether the anti-inflammatory effects of atorvastatin against ischemic stroke is related to gut function and microbiota. We report herein that atorvastatin significantly ameliorated the defects in sensorimotor behaviors and reduced microglia-mediated neuroinflammation by inhibiting proinflammatory polarization of microglia in the peri-infarct cortex of the mice with permanent middle cerebral artery occlusion (pMCAO). Moreover, atorvastatin reversed microbial composition (characterized by increased abundance of Firmicutes and Lactobacillus and decreased Bacteroidetes abundance), increased fecal butyrate level, promoted intestinal barrier function (elevated protein levels of claudin-1, occludin and mucoprotein 2), as well as regulated intestinal immune function (decreased MCP-1, TNF-α and increased IL-10). Atorvastatin also significantly reduced the level of circulating endotoxin (lipopolysaccharide-binding protein), which is a biomarker of leaky gut. Transplantation of fecal microbiota collected from atorvastatin treated mice potently attenuated neuroinflammation in pMCAO mice, and the anti-inflammatory effects of fecal microbiota transplantation were similar to those of oral atorvastatin administration. These results suggested that the atorvastatin-mediated restoration of gut microbiota, improvement of intestinal barrier function and regulation of intestinal immunity were involved in the anti-inflammatory function in stroke mice.

Ischemic stroke, obesity, and the anti-inflammatory role of melatonin

Obesity is a predominant risk factor in ischemic stroke and is commonly comorbid with it. Pathologies following these conditions are associated with systemic and local inflammation. Moreover, there is increasing evidence that the susceptibility for ischemic brain damage increases substantially in experimental models of ischemic stroke with concomitant obesity. Herein, we explore the proinflammatory events that occur during ischemic stroke and obesity, and we discuss the influence of obesity on the inflammatory response and cerebral damage outcomes in experimental models of brain ischemia. In addition, because melatonin is a neurohormone widely reported to exhibit protective effects in various diseases, this study also demonstrates the anti-inflammatory role and possible mechanistic actions of melatonin in both epidemic diseases. A summary of research findings suggests that melatonin administration has great potential to exert an anti-inflammatory role and provide protection against obesity and ischemic stroke conditions. However, the efficacy of this hormonal treatment on ischemic stroke with concomitant obesity, when more serious inflammation is generated, is still lacking.

MAPK: A Key Player in the Development and Progression of Stroke

Conclusion:

Stroke is a complex disease caused by genetic and environmental factors, and its etiological mechanism has not been fully clarified yet, which brings great challenges to its effective prevention and treatment. MAPK signaling pathway regulates gene expression of eukaryotic cells and basic cellular processes such as cell proliferation, differentiation, migration, metabolism and apoptosis, which are considered as therapeutic targets for many diseases. Up to now, mounting evidence has shown that MAPK signaling pathway is involved in the pathogenesis and development of ischemic stroke. However, the upstream kinase and downstream kinase of MAPK signaling pathway are complex and the influencing factors are numerous, the exact role of MAPK signaling pathway in the pathogenesis of ischemic stroke has not been fully elucidated. MAPK signaling molecules in different cell types in the brain respond variously after stroke injury, therefore, the present review article is committed to summarizing the pathological process of different cell types participating in stroke, discussed the mechanism of MAPK participating in stroke. We further elucidated that MAPK signaling pathway molecules can be used as therapeutic targets for stroke, thus promoting the prevention and treatment of stroke.

The antidepressant effects of asperosaponin VI are mediated by the suppression of microglial activation and reduction of TLR4/NF-κB-induced IDO expression

AIM

Indoleamine 2,3-dioxygenase 1 (IDO) is responsible for the progression of the kynurenine pathway, which has been implicated in the pathophysiology of inflammation-induced depression. It has been reported that asperosaponin VI (ASA VI) could play a neuroprotective role through anti-inflammatory and antioxidant. In this study, we examined the antidepressant effect of ASA VI in lipopolysaccharide (LPS)-treated mice and further explored its molecular mechanism by looking into the microglial kynurenine pathway.

METHODS

To generate the model, LPS (0.83 mg/kg) was administered intraperitoneally to mice. The mice received ASA VI (10 mg/kg, 20 mg/kg, 40 mg/kg, and 80 mg/kg, i.p.) 30 min before LPS injection. Depressive-like behaviors were evaluated based on the duration of immobility in the forced swim test. Microglial activation and inflammatory cytokines were detected by immunohistochemistry, real-time PCR, and ELISA. The TLR4/NF-κB signaling pathway and the expression of IDO, GluA2, and CamKIIβ were also measured by western blotting.

RESULTS

ASA VI exhibited significant antidepressant activity in the presence of LPS on immobility and latency times in the forced swim test. The LPS-induced activation of microglia and inflammatory response were inhibited by ASA VI, which showed a dose-dependent pattern. TLR4/NF-κB signaling pathway also was suppressed by ASA VI in the hippocampus and prefrontal cortex of LPS-treated mice. Furthermore, ASA VI inhibited the increase in IDO protein expression and normalized the aberrant glutamate transmission in the hippocampus and prefrontal cortex caused by LPS administration.

CONCLUSION

Our results propose a promising antidepressant effect for ASA VI possibly through the downregulation of IDO expression and normalization of the aberrant glutamate transmission. This remedying effect of ASA VI could be attributed to suppress microglia-mediated neuroinflammatory response via inhibiting the TLR4/NF-κB signaling pathway.

Probucol Ameliorates Complete Freund's Adjuvant-Induced Hyperalgesia by Targeting Peripheral and Spinal Cord Inflammation

The effect of the lipid-lowering agent probucol in inflammatory hyperalgesia and leukocyte recruitment was evaluated in a model of subacute inflammation by Complete Freund's adjuvant (CFA). As CFA induces long-lasting nociception characterized by peripheral and spinal cord inflammation, the anti-inflammatory activity of probucol was assessed at both foci. Probucol at 0.3-3 mg/kg was administrated per oral daily starting 24 h after CFA intraplantar injection. Mechanical and thermal hyperalgesia induced by CFA were determined using an electronic anesthesiometer and hot plate apparatus, respectively. Post-treatment with probucol at 3 mg/kg inhibited CFA-induced hyperalgesia over the course of 7 days as well as paw edema. Overt pain-like behaviors, which were determined by the number of flinches and time spent licking paw immediately following CFA injection, were also reduced by probucol at 3 mg/kg administered as a pre-treatment. To investigate the mechanisms underlying the analgesic effect of probucol, neutrophil recruitment to paw was assessed by myeloperoxidase activity, cytokine production, Cox-2 expression, and NF-κB activation in both paw and spinal cord by ELISA. Iba-1, GFAP, and substance P protein expression and nuclear localization of phosphorylated NF-κB were evaluated in the spinal cord by immunofluorescence. Probucol at 3 mg/kg attenuated neutrophil recruitment, cytokine levels, and NF-κB activation as well microglia and astrocyte activation, and substance P staining in the spinal cord. Taken together, the results suggest that probucol exerts its analgesic and anti-inflammatory activity in an experimental model of persistent inflammation by targeting the NF-κB pathway in peripheral and spinal cord foci.

Sphingosine 1-Phosphate Signaling Is Involved in Impaired Blood-Brain Barrier Function in Ischemia-Reperfusion Injury

Sphingosine 1-phosphate (S1P) is a major bioactive lipid mediator in the vascular and immune system. Here, we have shown that inhibition of S1P signaling prevents blood-brain barrier (BBB) dysfunction after ischemia both in vitro and in vivo. In the in vitro BBB models, oxygen-glucose deprivation and reoxygenation (OGD/R) enhanced the expression of an S1P synthesizing enzyme (Sphk1) and S1P transporters (Abca1, Spns2), increasing S1P in culture media. Inhibitors of Sphk1 (SKI-II) or Abca1 (probucol) attenuated the decrease in transendothelial electrical resistance and the increase in permeability caused by OGD/R. In the middle cerebral artery occlusion and reperfusion (MCAO/R) model of mice, probucol administration after MCAO operation reduced the infarction area and vascular leakage, preserving the integrity of tight junction proteins. Furthermore, MCAO/R caused activation of STAT3, a downstream mediator of S1P signaling, which was suppressed by postoperative probucol administration. Accordingly, S1P activated STAT3, both in cultured vascular endothelial cells and pericytes, and STAT3 signaling inhibitor (Stattic) protected BBB dysfunction in OGD/R-treated in vitro BBB models. These results suggest that inhibition of S1P signaling is a strategy to treat BBB impairment after cerebral ischemia and highlight the potential alternative use of probucol, a classical anti-hyperlipidemic drug, for emergency treatment of stroke.

Effects of lithium on inflammatory and neurotrophic factors after an immune challenge in a lisdexamfetamine animal model of mania

Objective:

To evaluate whether an animal model of mania induced by lisdexamfetamine dimesylate (LDX) has an inflammatory profile and whether immune activation by lipopolysaccharides (LPS) has a cumulative effect on subsequent stimuli in this model. We also evaluated the action of lithium (Li) on inflammatory and neurotrophic factors.

Methods:

Adult male Wistar rats were subjected to an animal model of mania. After the open-field test, they were given LPS to induce systemic immune activation. Subsequently, the animals’ blood was collected, and their serum levels of brain-derived neurotrophic factor and inflammatory markers (tumor necrosis factor [TNF]-α, interleukin [IL]-6, IL-1β, IL-10, and inducible nitric oxide synthase [iNOS]) were measured.

Results:

LDX induced hyperactivity in the animals, but no inflammatory marker levels increased except brain-derived neurotrophic factor (BDNF). Li had no effect on serum BDNF levels but prevented iNOS levels from increasing in animals subjected to immune activation.

Conclusion:

Although Li prevented an LPS-induced increase in serum iNOS levels, its potential anti-inflammatory effects in this animal model of mania were conflicting.

Dietary n-3 long chain PUFA supplementation promotes a pro-resolving oxylipin profile in the brain

The brain is highly enriched in long chain polyunsaturated fatty acids (LC-PUFAs) that display immunomodulatory properties in the brain. At the periphery, the modulation of inflammation by LC-PUFAs occurs through lipid mediators called oxylipins which have anti-inflammatory and pro-resolving activities when derived from n-3 LC-PUFAs and pro-inflammatory activities when derived from n-6 LC-PUFAs. However, whether a diet rich in LC-PUFAs modulates oxylipins and neuroinflammation in the brain has been poorly investigated. In this study, the effect of a dietary n-3 LC-PUFA supplementation on oxylipin profile and neuroinflammation in the brain was analyzed. Mice were given diets deficient or supplemented in n-3 LC-PUFAs for a 2-month period starting at post-natal day 21, followed by a peripheral administration of lipopolysaccharide (LPS) at adulthood. We first showed that dietary n-3 LC-PUFA supplementation induced n-3 LC-PUFA enrichment in the hippocampus and subsequently an increase in n-3 PUFA-derived oxylipins and a decrease in n-6 PUFA-derived oxylipins. In response to LPS, n-3 LC-PUFA deficient mice presented a pro-inflammatory oxylipin profile whereas n-3 LC-PUFA supplemented mice displayed an anti-inflammatory oxylipin profile in the hippocampus. Accordingly, the expression of cyclooxygenase-2 and 5-lipoxygenase, the enzymes implicated in pro- and anti-inflammatory oxylipin synthesis, was induced by LPS in both diets. In addition, LPS-induced pro-inflammatory cytokine increase was reduced by dietary n-3 LC-PUFA supplementation. These results indicate that brain n-3 LC-PUFAs increase by dietary means and promote the synthesis of anti-inflammatory derived bioactive oxylipins. As neuroinflammation plays a key role in all brain injuries and many neurodegenerative disorders, the present data suggest that dietary habits may be an important regulator of brain cytokine production in these contexts.

Antidepressant Effects of Probucol on Early-Symptomatic YAC128 Transgenic Mice for Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a trinucleotide expansion in the HD gene, resulting in an extended polyglutamine tract in the protein huntingtin. HD is traditionally viewed as a movement disorder, but cognitive and neuropsychiatric symptoms also contribute to the clinical presentation. Depression is one of the most common psychiatric disturbances in HD, present even before manifestation of motor symptoms. Diagnosis and treatment of depression in HD-affected individuals are essential aspects of clinical management in this population, especially owing to the high risk of suicide. This study investigated whether chronic administration of the antioxidant probucol improved motor and affective symptoms as well as hippocampal neurogenic function in the YAC128 transgenic mouse model of HD during the early- to mild-symptomatic stages of disease progression. The motor performance and affective symptoms were monitored using well-validated behavioral tests in YAC128 mice and age-matched wild-type littermates at 2, 4, and 6 months of age, after 1, 3, or 5 months of treatment with probucol (30 mg/kg/day via water supplementation, starting on postnatal day 30). Endogenous markers were used to assess the effect of probucol on cell proliferation (Ki-67 and proliferation cell nuclear antigen (PCNA)) and neuronal differentiation (doublecortin (DCX)) in the hippocampal dentate gyrus (DG). Chronic treatment with probucol reduced the occurrence of depressive-like behaviors in early- and mild-symptomatic YAC128 mice. Functional improvements were not accompanied by increased progenitor cell proliferation and neuronal differentiation. Our findings provide evidence that administration of probucol may be of clinical benefit in the management of early- to mild-symptomatic HD.

The Anti-neuroinflammatory Activity of Tectorigenin Pretreatment via Downregulated NF-κB and ERK/JNK Pathways in BV-2 Microglial and Microglia Inactivation in Mice With Lipopolysaccharide

The activation of microglia is decisively involved with the neurodegeneration observed in many neuroinflammatory pathologies, such as multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease. Tectorigenin (TEC) is an isoflavone isolated from various medicinal plants, such as Pueraria thunbergiana Benth, Belamcanda chinensis, and Iris unguicularis. In the present study, the neuroinflammatory effects of TEC were evaluated in both lipopolysaccharide (LPS)-treated BV-2 microglial and mouse models. TEC remarkably inhibited reactive oxygen species (ROS) generation. TEC also inhibits the production and expression of nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in LPS-stimulated BV-2 cells. In addition, TEC suppressed the LPS-induced activation of nuclear factor-κB (NF-κB), phosphorylation of extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) to regulate the inflammatory mediators, such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α, and IL-6. These results indicate that TEC may inhibit neuronal inflammation through the downregulation of inflammatory mediators, including iNOS, COX-2, TNF-α, and IL-6 by suppressing NF-κB/ERK/JNK-related signaling pathways. Furthermore, cotreatment with TEC and ERK inhibitor SCH772984 or JNK inhibitor SP600125 suppressed the overproduction of LPS-induced NO production in BV-2 cells. Consistent with the results of in vitro experiments, an LPS-induced brain inflammation mouse model, administration of TEC effectively decrease the levels of malondialdehyde, iNOS in hippocampus, and prevented increases in the levels of TNF-α and IL-6 in the serum. TEC showed marked attenuation of microglial activation. Finally, TEC inhibited protein expression of toll-like receptor 4 and myeloid differentiation factor 88 in LPS-activated BV-2 microglia and mouse models. Taken altogether, the cumulative findings suggested that TEC holds the potential to develop as a neuroprotective drug for the intervention of neuroinflammatory disorders.

Repeated stimulation by LPS promotes the senescence of DPSCs via TLR4/MyD88-NF-κB-p53/p21 signaling

Dental pulp stem cells (DPSCs), one type of mesenchymal stem cells, are considered to be a type of tool cells for regenerative medicine and tissue engineering. Our previous studies found that the stimulation with lipopolysaccharide (LPS) might introduce senescence of DPSCs, and this senescence would have a positive correlation with the concentration of LPS. The β-galactosidase (SA-β-gal) staining was used to evaluate the senescence of DPSCs and immunofluorescence to show the morphology of DPSCs. Our findings suggested that the activity of SA-β-gal has increased after repeated stimulation with LPS and the morphology of DPSCs has changed with the stimulation with LPS. We also found that LPS bound to the Toll-like receptor 4 (TLR4)/myeloid differentiation factor (MyD) 88 signaling pathway. Protein and mRNA expression of TLR4, MyD88 were enhanced in DPSCs with LPS stimulation, resulting in the activation of nuclear factor-κB (NF-κB) signaling, which exhibited the expression of p65 improved in the nucleus while the decreasing of IκB-α. Simultaneously, the expression of p53 and p21, the downstream proteins of the NF-κB signaling, has increased. In summary, DPSCs tend to undergo senescence after repeated stimulation in an inflammatory microenvironment. Ultimately, these findings may lead to a new direction for cell-based therapy in oral diseases and other regenerative medicines.

Sulfosuccinimidyl oleate sodium is neuroprotective and alleviates stroke-induced neuroinflammation

BACKGROUND

Ischemic stroke is one of the main causes of death and disability worldwide. It is caused by the cessation of cerebral blood flow resulting in the insufficient delivery of glucose and oxygen to the neural tissue. The inflammatory response initiated by ischemic stroke in order to restore tissue homeostasis in the acute phase of stroke contributes to delayed brain damage.

METHODS

By using in vitro models of neuroinflammation and in vivo model of permanent middle cerebral artery occlusion, we demonstrate the neuroprotective and anti-inflammatory effects of sulfosuccinimidyl oleate sodium (SSO).

RESULTS

SSO significantly reduced the lipopolysaccharide/interferon-γ-induced production of nitric oxide, interleukin-6 and tumor necrosis factor-α, and the protein levels of inflammatory enzymes including nitric oxide synthase 2, cyclooxygenase-2 (COX-2), and p38 mitogen-activated protein kinase (MAPK) in microglia, without causing cell toxicity. Although SSO failed to directly alleviate glutamate-induced excitotoxicity in murine cortical neurons, it prevented inflammation-induced neuronal death in microglia-neuron co-cultures. Importantly, oral administration of SSO in Balb/c mice subjected to permanent occlusion of the middle cerebral artery reduced microglial activation in the peri-ischemic area and attenuated brain damage. This in vivo neuroprotective effect of SSO was associated with a reduction in the COX-2 and heme oxygenase-1 immunoreactivities.

CONCLUSIONS

Our results suggest that SSO is an anti-inflammatory and a possible therapeutic candidate in diseases such as stroke where inflammation is a central hallmark.

Neuroprotective effect of total flavonoids from Ilex pubescens against focal cerebral ischemia/reperfusion injury in rats

Ilex pubescens is commonly used in traditional Chinese medicine to treat cardiovascular and cerebrovascular diseases, such as coronary artery disease and stroke. However, the underlying mechanisms remain to be fully elucidated. The aim of the present study was to investigate the effects of Ilex pubescens total flavonoids (IPTF) on neuroprotection and the potential mechanisms in a rat model of focal cerebral ischemia/reperfusion (I/R) injury. Rats were pretreated with intragastric administration of IPTF at doses of 200 and 100 mg/kg for 5 days; middle cerebral artery occlusion surgery was then performed to induce cerebral I/R injury. Neurological deficits were determined using the 5‑point neurological function score evaluation system, brain infarct sizes were determined by 2,3,5‑triphenyltetrazolium chloride staining and alterations in brain histology were determined by hematoxylin and eosin staining. The neurological deficit score, the infarcted area and the brain tissue pathological injury were significantly reduced when the rats were pretreated with IPTF. In addition, inflammatory mediators and neurotrophic factors in the brain were investigated. IPTF pretreatment decreased the activities of total nitric oxide synthase (TNOS), induced NOS (iNOS) and constitutive NOS (cNOS), and the levels of nitric oxide (NO), interleukin‑1β (IL‑1β) and tumor necrosis factor‑α (TNF‑α), however, it increased the levels of IL‑10 in brain tissues. Furthermore, pretreatment with IPTF also increased the protein expressions of brain‑derived neurotrophic factor, glial cell‑derived neurotrophic factor and vascular endothelial growth factor, when compared with the model group. In conclusion, the results of the present study demonstrated that IPTF has a neuroprotective effect against focal cerebral I/R injury in rats. The mechanism may be associated with the decreased production of certain proinflammatory cytokines including NO, IL‑1β, TNF‑α, TNOS, iNOS and cNOS, the increased production of the anti‑inflammatory cytokine IL‑10 and the increased secretion of neurotrophic factors.

Probucol attenuates hyperoxia-induced lung injury in mice

Hyperoxic lung injury is pathologically characterized by alveolar edema, interlobular septal edema, hyaline membrane disease, lung inflammation, and alveolar hemorrhage. Although the precise mechanism by which hyperoxia causes lung injury is not well defined, oxidative stress, epithelial cell death, and proinflammatory cytokines are thought to be involved. Probucol—a commercially available drug for treating hypercholesterolemia—has been suggested to have antioxidant and antiapoptotic effects. This study aimed to assess whether probucol could attenuate hyperoxic lung injury in mice. Mice were exposed to 95% O₂ for 72 h, with or without pre-treatment with 130 μg/kg probucol intratracheally. Probucol treatment significantly decreased both the number of inflammatory cells in the bronchoalveolar lavage fluid and the degree of lung injury in hyperoxia-exposed mice. Probucol treatment reduced the number of cells positive for 8-hydroxyl-2′-deoxyguanosine or terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and suppressed NF-κB activation, Bax expression, and caspase-9 activation in lung tissues from hyperoxia-exposed mice. These results suggest that probucol can reduce oxidative DNA damage, apoptotic cell death, and inflammation in lung tissues. Intratracheal administration of probucol may be a novel treatment for lung diseases induced by oxidative stress, such as hyperoxic lung injury and acute respiratory distress syndrome.

Regulation of microglial activation in stroke

When ischemic stroke occurs, oxygen and energy depletion triggers a cascade of events, including inflammatory responses, glutamate excitotoxicity, oxidative stress, and apoptosis that result in a profound brain injury. The inflammatory response contributes to secondary neuronal damage, which exerts a substantial impact on both acute ischemic injury and the chronic recovery of the brain function. Microglia are the resident immune cells in the brain that constantly monitor brain microenvironment under normal conditions. Once ischemia occurs, microglia are activated to produce both detrimental and neuroprotective mediators, and the balance of the two counteracting mediators determines the fate of injured neurons. The activation of microglia is defined as either classic (M1) or alternative (M2): M1 microglia secrete pro-inflammatory cytokines (TNFα, IL-23, IL-1β, IL-12, etc) and exacerbate neuronal injury, whereas the M2 phenotype promotes anti-inflammatory responses that are reparative. It has important translational value to regulate M1/M2 microglial activation to minimize the detrimental effects and/or maximize the protective role. Here, we discuss various regulators of microglia/macrophage activation and the interaction between microglia and neurons in the context of ischemic stroke.