Splenectomy following MCAO inhibits the TLR4-NF-κB signaling pathway and protects the brain from neurodegeneration in rats

Splenectomy ameliorates liver cirrhosis by restoring the gut microbiota balance

BACKGROUND

Dysbiosis of gut microbiota is frequent in liver cirrhosis (LC) patients, and splenectomy (SP) has been reported to improve LC. Herein, we report the effects of SP on gut microbiota, especially on Veillonella parvula, a Gram-negative coccus of the gastrointestinal tract, in LC mice, and the underlying mechanism.

METHODS

LC mice models were induced by tail vein injection of concanavalin A (ConA), followed by SP. 16 s rRNA sequencing was conducted to analyze the effects of ConA induction and SP on mouse gut microbiota and the gene expression affected by gut microbiota. LC mice receiving SP were gavaged with Veillonella parvula. Likewise, hepatic stellate cells (HSC) and hepatocytes (HC) were induced with conditioned medium (CM) of Veillonella parvula.

RESULTS

SP alleviated LC in mice by restoring gut barrier function and maintaining gut microbiota balance, with Veillonella as the key genus. The Veillonella parvula gavage on LC mice reversed the ameliorative effect of SP. The CM of Veillonella parvula promoted the activation of HSC and the release of IL-6, IL-1β, and TNF-α. Also, the CM of Veillonella parvula induced HC pyroptosis and the release of ALT and AST. Veillonella parvula represented an imbalance in the gut microbiota, thus enhancing gut-derived endotoxins in the liver with the main target being Tlr4/Nlrp3. Inhibition of Tlr4 blocked Veillonella parvula-induced HC damage, HSC activation, and subsequent LC progression.

CONCLUSION

SP-mediated gut microbiota regulation ameliorates ConA-related LC progression by inhibiting Tlr4/Nlrp3 in the liver.

The effects of splenectomy in murine models of ischemic stroke: a systematic review and meta-analysis

Background

The spleen, a substantial reservoir of non-differentiated monocytes, may play a crucial role in the pathophysiology of post-ischemic inflammation and influence outcomes after ischemic stroke.

Aim of the study

To analyze splenectomy as a preclinical intervention in murine models of ischemic stroke.

Methods

Following systematic searches of PubMed, Scopus and Web of Science, a qualitative synthesis of study characteristics was performed, and the effect of splenectomy estimated by a three-level random-effects meta-analysis of infarct volumes and a conventional two-level random-effects meta-analysis of neurological deficit scores.

Results

Database searches identified a total of 14 studies, 13 of which were used for meta-analysis. The ischemic lesion volumes were reduced in splenectomized animals compared to the control groups (difference in standardized mean differences: − 1.42; 95% CI [− 1.98, − 0.85]; 95% PI [− 2.03, − 0.80]; I²₍₂₎ = 19.04%; 95% CI [0.00%, 65.49%]; I²₍₃₎ = 47.24%; 95% CI [0.00%, 85.23%]) and neurological deficit scores were improved (− 1.20; 95% CI [− 2.20, − 0.20]; 95% PI [− 4.58, 2.18]; I² = 77.5%; 95% CI [50.0%, 89.9%]). A subgroup analysis for infarct volumes showed that splenectomy performed prior to ischemia achieved a higher reduction of the ischemic lesion than when splenectomy was performed immediately prior or after stroke. Although the overall effect size of splenectomy could be classified as large, there was a significant presence of risks of bias, study heterogeneity, and a potential presence of publication bias.

Conclusion

Despite limitations related to heterogeneity, risks of bias, and potential publication bias, this meta-analysis points to the spleen and its functional cell populations as promising targets for the therapeutic modulation of post-stroke inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02593-w.

Neuroprotective Effects of an Edible Pigment Brilliant Blue FCF against Behavioral Abnormity in MCAO Rats

Ischemic stroke leads to hypoxia-induced neuronal death and behavioral abnormity, and is a major cause of death in the modern society. However, the treatments of this disease are limited. Brilliant Blue FCF (BBF) is an edible pigment used in the food industry that with multiple aromatic rings and sulfonic acid groups in its structure. BBF and its derivatives were proved to cross the blood-brain barrier and have advantages on the therapy of neuropsychiatric diseases. In this study, BBF, but not its derivatives, significantly ameliorated chemical hypoxia-induced cell death in HT22 hippocampal neuronal cell line. Moreover, protective effects of BBF were attributed to the inhibition of the extracellular regulated protein kinase (ERK) and glycogen synthase kinase-3β (GSK3β) pathways as evidenced by Western blotting analysis and specific inhibitors. Furthermore, BBF significantly reduced neurological and behavioral abnormity, and decreased brain infarct volume and cerebral edema induced by middle cerebral artery occlusion/reperfusion (MCAO) in rats. MCAO-induced increase of p-ERK in ischemic penumbra was reduced by BBF in rats. These results suggested that BBF prevented chemical hypoxia-induced otoxicity and MCAO-induced behavioral abnormity via the inhibition of the ERK and GSK3β pathways, indicating the potential use of BBF for treating ischemic stroke

Neuroinflammation, Stem Cells, and Stroke

Stroke remains a significant unmet clinical need with few treatment options that have a very narrow therapeutic window, thereby causing massive mortality and morbidity in the United States and around the world. Accordingly, finding safe and effective novel treatments with a wider therapeutic window stands as an urgent need in stroke. The progressive inflammation that occurs centrally and peripherally after stroke serves as a unique therapeutic target to retard and even halt the secondary cell death. Stem cell therapy represents a potent approach that can diminish inflammation in both the stroke brain and periphery (eg, spleen), advancing a paradigm shift from a traditionally brain-focused therapy to treating stroke as a neurological disorder with a significant peripheral pathology. The purpose of this review article is to highlight the inflammation-mediated secondary cell death that plagues both brain and spleen in stroke and to evaluate the therapeutic potential of stem cell therapy in dampening these inflammatory responses.

Perspectives on effect of spleen in ischemic stroke

Despite decades of research, stroke therapies are limited to recanalization therapies that can only be used on <10% of stroke patients; the vast majority of stroke patients cannot be treated by these methods. Even if recanalization is successful, the outcome is often poor due to subsequent reperfusion injury. A major damage mechanism operating in stroke is inflammatory injury due to excessive pro-inflammatory cascades. Many studies have shown that, after stroke, splenic inflammatory cells, including neutrophils, monocytes/macrophages, and lymphocytes, are released and infiltrate the brain, heightening brain inflammation, and exacerbating ischemia/reperfusion injury. Clinical studies have observed spleen contraction in acute stroke patients where functional outcome improved with the gradual recovery of spleen volume. These observations are supported by stroke animal studies that have used splenectomy- or radiation-induced inhibition of spleen function to show spleen volume decrease during the acute phase of middle cerebral artery occlusion, and transfer of splenocytes to stroke-injured brain areas. Thus, activation and release of splenic cells are upstream of excessive brain inflammation in stroke. The development of reversible means of regulating splenic activity offers a therapeutic target and potential clinical treatment for decreasing brain inflammation and improving stroke outcomes.

Particulate Matter Exposure Exacerbates Amyloid-β Plaque Deposition and Gliosis in APP/PS1 Mice

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) plaques, neuroinflammation, and neuronal death. There are several well-established genetic and environmental factors hypothesized to contribute to AD progression including air pollution. However, the molecular mechanisms by which air pollution exacerbates AD are unclear.

OBJECTIVE

This study explored the effects of particulate matter exposure on AD-related brain changes using the APP/PS1 transgenic model of disease.

METHODS

Male C57BL/6;C3H wild type and APP/PS1 mice were exposed to either filtered air (FA) or particulate matter sized under 2.5μm (PM2.5) for 6 h/day, 5 days/week for 3 months and brains were collected. Immunohistochemistry for Aβ, GFAP, Iba1, and CD68 and western blot analysis for PS1, BACE, APP, GFAP, and Iba1 were performed. Aβ ELISAs and cytokine arrays were performed on frozen hippocampal and cortical lysates, respectively.

RESULTS

The Aβ plaque load was significantly increased in the hippocampus of PM2.5-exposed APP/PS1 mice compared to their respective FA controls. Additionally, in the PM2.5-exposed APP/PS1 group, increased astrocytosis and microgliosis were observed as indicated by elevated GFAP, Iba1, and CD68 immunoreactivities. PM2.5 exposure also led to an elevation in the levels of PS1 and BACE in APP/PS1 mice. The cytokines TNF-α, IL-6, IL-1β, IFN-γ, and MIP-3α were also elevated in the cortices of PM2.5-exposed APP/PS1 mice compared to FA controls.

CONCLUSION

Our data suggest that chronic particulate matter exposure exacerbates AD by increasing Aβ plaque load, gliosis, and the brain inflammatory status.

Curcumin targets vascular endothelial growth factor via activating the PI3K/Akt signaling pathway and improves brain hypoxic-ischemic injury in neonatal rats

This study aimed to evaluate the effect of curcumin on brain hypoxic-ischemic (HI) damage in neonatal rats and whether the phosphoinositide 3-kinase (PI3K)/Akt/vascular endothelial growth factor (VEGF) signaling pathway is involved. Brain HI damage models were established in neonatal rats, which received the following treatments: curcumin by intraperitoneal injection before injury, insulin-like growth factor 1 (IGF-1) by subcutaneous injection after injury, and VEGF by intracerebroventricular injection after injury. This was followed by neurological evaluation, hemodynamic measurements, histopathological assessment, TUNEL assay, flow cytometry, and western blotting to assess the expression of p-PI3K, PI3K, p-Akt, Akt, and VEGF. Compared with rats that underwent sham operation, rats with brain HI damage showed remarkably increased neurological deficits, reduced right blood flow volume, elevated blood viscosity and haematocrit, and aggravated cell damage and apoptosis; these injuries were significantly improved by curcumin pretreatment. Meanwhile, brain HI damage induced the overexpression of p-PI3K, p-Akt, and VEGF, while curcumin pretreatment inhibited the expression of these proteins. In addition, IGF-1 treatment rescued the curcumin-induced down-regulated expression of p-PI3K, p-Akt, and VEGF, and VEGF overexpression counteracted the inhibitory effect of curcumin on brain HI damage. Overall, pretreatment with curcumin protected against brain HI damage by targeting VEGF via the PI3K/Akt signaling pathway in neonatal rats.

Beyond the Brain: The Systemic Pathophysiological Response to Acute Ischemic Stroke

Stroke research has traditionally focused on the cerebral processes following ischemic brain injury, where oxygen and glucose deprivation incite prolonged activation of excitatory neurotransmitter receptors, intracellular calcium accumulation, inflammation, reactive oxygen species proliferation, and ultimately neuronal death. A recent growing body of evidence, however, points to far-reaching pathophysiological consequences of acute ischemic stroke. Shortly after stroke onset, peripheral immunodepression in conjunction with hyperstimulation of autonomic and neuroendocrine pathways and motor pathway impairment result in dysfunction of the respiratory, urinary, cardiovascular, gastrointestinal, musculoskeletal, and endocrine systems. These end organ abnormalities play a major role in the morbidity and mortality of acute ischemic stroke. Using a pathophysiology-based approach, this current review discusses the pathophysiological mechanisms following ischemic brain insult that result in end organ dysfunction. By characterizing stroke as a systemic disease, future research must consider bidirectional interactions between the brain and peripheral organs to inform treatment paradigms and develop effective, comprehensive therapeutics for acute ischemic stroke.

Suppressors of cytokine signalling (SOCS)-1 inhibits neuroinflammation by regulating ROS and TLR4 in BV2 cells

OBJECTIVE

The suppressors of cytokine signaling (SOCS) proteins are physiological suppressors of cytokine signaling which have been identified as a negative feedback loop to weaken cytokine signaling. However, the underlying molecular mechanisms is unknown. This study was to investigate the role of SOCS1 in the oxygen-glucose deprivation and reoxygenation (OGDR) or LPS-induced inflammation in microglia cell line BV-2 cells.

MATERIALS AND METHODS

BV-2 microglial cells were used to construct inflammation model. A SOCS1 over-expression plasmid was constructed, and the SOCS1-deficient cells were generated by utilizing the CRISPR/CAS9 system. BV-2 microglial cells were pretreated with over-expression plasmid or SOCS1 CRISPR plasmid before OGDR and LPS stimulation. The effect of SOCS1 on proinflammatory cytokines, toll-like receptor 4 (TLR4), and reactive oxygen species (ROS) were evaluated.

RESULTS

We found that SOCS1 increased in OGDR or LPS-treated BV-2 microglial cells in vitro. SOCS1 over-expression significantly reduced the production of proinflammatory cytokines including tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6, and CRISPR/CAS9-mediated SOCS1 knockout reversed this effect. Also we determined that SOCS1 over-expression reduced the level of reactive oxygen species (ROS) while the absence of SOCS1 increased the production of ROS after OGDR or LPS-stimulated inflammation. Furthermore, we found that OGDR and LPS induced the expression of toll-like receptor 4 (TLR4) in BV2 cells. Nevertheless, SOCS1 over-expression attenuated the expression of TLR4, while knockdown of SOCS1 upregulated TLR4.

CONCLUSIONS

Our study indicated that SOCS1 played a protective role under inflammatory conditions in OGDR or LPS treated BV-2 cells through regulating ROS and TLR4. These data demonstrated that SOCS1 served as a potential therapeutic target to alleviate inflammation after ischemic stroke.

Immune response mediates the cardiac damage after subarachnoid hemorrhage

Cardiac dysfunction is a common adverse effect of subarachnoid hemorrhage (SAH). Autopsy of SAH patients shows immunocyte infiltration into the heart. In this study, a SAH model of endovascular perforation was performed in adult male mice in order to test whether SAH causes cardiac dysfunction in non-primary cardiac disease young adult male mice and whether immune response mediates SAH induced cardiac and neurological deficit. Splenectomy was performed on a subpopulation of mice one week prior to induction of the SAH. Neurological functional tests, transthoracic Doppler echocardiography, immunofluorescent staining, and flow cytometry were performed to investigate neurological and cardiac function and immune/inflammatory effects of SAH in mice with or without splenectomy. We found that SAH significantly induces ventricular fibrillation and cardiac dysfunction identified by significantly reduced left ventricular ejection fraction, left ventricular fractional shortening, decreased heart rate, as well as increased macrophage and neutrophil infiltration into heart and inflammatory factor expression in the heart compared to sham control mice. SAH also induces neurological deficit, increases astrocyte and microglial activity, and inflammatory cell infiltration into brain as well as up-regulates inflammatory factor expression in the brain tissue. Splenectomy not only significantly improves neurological function, but also reduces cardiac dysfunction compared to SAH alone mice. Splenectomy in SAH mice significantly reduces inflammatory cell infiltration, and decreases NADPH oxidase-2 and macrophage chemokine protein-1 expression in heart and brain when compared to non-splenectomy SAH mice. Our data suggest that, SAH induces acute cardiac dysfunction in non-primary cardiac disease mice. Secondary immune response may play an important role in mediating brain-heart damage after SAH.

Rab7b Overexpression-Ameliorated Ischemic Brain Damage Following tMCAO Involves Suppression of TLR4 and NF-κB p65

Cerebral stroke is one of the leading causes of death and permanent disability worldwide. Toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) p65 play a critical role in brain damage following ischemia-induced stroke. Rab7b, a lysosome-associated small Rab GTPase, has been implicated in TLR4 regulation; however, its role in cerebral stroke is poorly understood. In this study, by investigating a rat model with cerebral stroke, we found that Rab7b was upregulated in the rat brain following the transient middle cerebral artery occlusion (tMCAO). Functionally, overexpression of Rab7b in the brain by DNA transfection reduced cerebral infarction and improved neurological outcome following tMCAO, suggesting that Rab7b alleviates ischemic brain damage. Mechanistically, Rab7b overexpression suppressed the expression of TLR4 and NF-κB p65 and also inhibited the activation of NF-κB p65. Furthermore, Rab7b overexpression suppressed the production of proinflammatory mediators including TNF-α, IFN-γ, IL-1β, and IL-6 in the brain following tMCAO. In summary, these results suggest that Rab7b protects against ischemic brain damage following tMCAO and that this protection may relate to the suppressed inflammatory response mediated by TLR4 and NF-κB p65. Our study might offer Rab7b as a novel therapeutic target in the treatment of cerebral stroke.

Z-Guggulsterone attenuates astrocytes-mediated neuroinflammation after ischemia by inhibiting toll-like receptor 4 pathway

Inflammatory damage plays a pivotal role in ischemic stroke pathogenesis and may represent one of the therapeutic targets. Z-Guggulsterone (Z-GS), an active component derived from myrrh, has been used to treat various diseases. The traditional uses suggest that myrrh is a good candidate for anti-inflammatory damage. This study was to investigate the anti-inflammatory and neuroprotective effects of Z-GS following cerebral ischemic injury, as well as the exact mechanisms behind them. Rat middle cerebral artery occlusion (MCAO) model and in vitro astrocytes oxygen-glucose deprivation (OGD) model were adopted to simulate ischemic stroke. Z-GS (30 or 60 mg/kg) was administered intraperitoneally immediately after reperfusion, while astrocytes were maintained in 30 or 60 μM Z-GS before OGD treatment. The results indicated that Z-GS significantly alleviated neurological deficits, infarct volume and histopathological damage in vivo, and increased the astrocytes viability in vitro. Moreover, the treatment of Z-GS inhibited the astrocytes activation and down-regulated the mRNA levels of pro-inflammatory cytokines. Furthermore, the activated TLR4-NF-κB signaling pathways induced by MCAO or OGD were significantly suppressed by Z-GS treatment, which was achieved via inhibiting the phosphorylation of JNK. Our results demonstrated that Z-GS exerted neuroprotective and anti-inflammatory properties through preventing activation of TLR4-mediated pathway in the activated astrocytes after ischemia injury. Therefore, Z-GS could be considered as a promising candidate for the treatment of ischemic stroke.

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

Background:

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

Methods:

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

Results:

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

Conclusion:

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

The splenic response to stroke: from rodents to stroke subjects

Background

Stroke is the fifth leading cause of death and the leading cause of long-term disability in the USA, costing $40.2 billion in direct and indirect costs. Globally, stroke is the second leading cause of death and has a higher prevalence in lower- and middle-income countries compared to high-income countries.

The role of the spleen in stroke has been studied in rodent models of stroke and is seen as a major contributor to increased secondary neural injury after stroke. Splenectomy 2 weeks prior to ischemic and hemorrhagic stroke in mice and rats shows decreased infarct volumes. Additionally, the spleen decreases in size following stroke in rodents. Pro-inflammatory mediators are also increased in the spleen and subsequently the brain after stroke. These data in preclinical models of stroke have led stroke neurologists to look at the splenic response in stroke subjects. The outcomes of these studies suggest the spleen is responding in a similar manner in stroke subjects as it is in animal models of stroke.

Conclusion

Animal models demonstrating the detrimental role of the spleen in stroke are providing strong evidence of how the spleen is responding during stroke in human subjects. This indicates treatments targeting the splenic immune response in animals could provide useful targets and treatments for stroke subjects.

MicroRNA‑497 attenuates cerebral infarction in patients via the TLR4 and CREB signaling pathways

The aim of the present study was to investigate the function and mechanism of microRNA‑497 (miRNA/miR‑149) in the regulation of cerebral infarction. In patients with cerebral infarction, the serum of microRNA‑497 expression was upregulated compared with that in healthy controls. In N2A cells, overexpression of miR‑497 induced cell proliferation, decreased apoptosis and caspase‑3 and caspase‑9 activities, and suppressed Bax protein expression compared with that in the negative control group. Overexpression of miR‑497 reduced inflammation factors, and suppressed the Toll‑like receptor 4 (TLR4), myeloid differentiation primary response protein MyD88 (MyD88) and nuclear factor‑κB (NF‑κB) protein expression of the N2A cells. Next, miR‑497 overexpression suppressed the protein expression of interleukin‑1 receptor associated kinase (IRAK1) and phosphorylated cyclic AMP response element binding protein (p-CREB) in the N2A cells. Following miR‑497 overexpression, TLR4 inhibitor was found to suppress the inflammation factors, suppress the TLR4, MyD88 and NF‑κB protein expression, and reduce the IRAK1 and p‑CREB protein expression of the N2A cells. Lastly, CREB inhibitor also suppressed p‑CREB protein expression, induced cell proliferation, decreased apoptosis and caspase‑3 and caspase‑9 activities, and suppressed Bax protein expression in the N2A cells following miR‑497 overexpression. Taken together, these data demonstrated that miR‑497 attenuated cerebral infarction in patients by regulating the TLR4 and CREB signaling pathways.

Splenectomy protects aged mice from injury after experimental stroke

Elderly stroke patients and aged animals subjected to experimental stroke have significantly worse functional recovery and higher mortality compared to younger subjects. Activation of the peripheral immune system is known to influence stroke outcome. Prior studies have shown that splenectomy reduces ischemic brain injury in young mice. As immune function changes with aging, it is unclear whether splenectomy will confer similar benefits in aged animals. We investigated the contribution of spleen to brain injury after cerebral ischemia in aged male mice. Splenic architecture and immune cell composition were altered in aged mice. Splenectomy 2 weeks before stroke resulted in improved neurobehavioral and infarct outcomes in aged male mice. In addition, there was a reduction in peripheral immune cell infiltration into the brain and decreased levels of peripheral inflammatory cytokines after stroke in aged splenectomized mice. Splenectomy immediately after reperfusion also improved behavioral and infarct outcomes. This study suggests that inhibition of the splenic immune response is a translationally relevant target to pursue for stroke treatment in aged individuals.

Neuroprotective Effect of Modified Xijiao Dihuang Decoction against Oxygen-Glucose Deprivation and Reoxygenation-Induced Injury in PC12 Cells: Involvement of TLR4-MyD88/NF-κB Signaling Pathway

Modified Xijiao Dihuang (XJDH) decoction has been shown to exert powerful neuroprotective properties in clinical ischemic stroke treatment. It consists of 4 Chinese herbs: Buffalo Horn, Paeonia suffruticosa Andrews, Rehmannia glutinosa (Gaertn.) DC, and Paeonia lactiflora Pall. In the present study, the neuroprotective effect and specific mechanisms of XJDH in protecting PC12 cells from oxygen-glucose deprivation-induced injury were investigated. It was found that OGD/R significantly decreased the cell viability and lactate dehydrogenase (LDH) activity and increased the release of IL-1β, IL-6, and TNF-α in PC12 cells, and these effects were suppressed by XJDH and one of its major active constituents, paeoniflorin. Additionally, XJDH inhibited caspase-3 activity and reduced cleaved caspase-3 level. Mechanistic studies showed that the expressions of TLR4, MyD88, TRAF6, and NF-κB p65 and phosphorylation of IκBα and p65 were significantly lower in the XJDH-treated group than in the OGD/R control group. Additionally, XJDH reversed the OGD/R-induced increases in p-JNK and p-ERK1/2 expression. These results suggest that XJDH protects PC12 cells from oxygen-glucose deprivation-induced injury, which may be associated with the inhibition of the TLR4-MyD88/NF-κB signaling pathway. As an anti-inflammation factor, XJDH might be used as a neuronal protection strategy for the ischemia injury and related diseases.

Dioscin inhibits ischemic stroke‑induced inflammation through inhibition of the TLR4/MyD88/NF‑κB signaling pathway in a rat model

Diosgenin, as an essential natural steroidal saponin, can be extracted from numerous sources, primarily from fenugreek. It is an important raw material for the synthesis of steroid hormone drugs. It exhibits antitumor, anti‑inflammatory, antioxidation and several other significant pharmacologic actions, and is of high pharmaceutical value. In the present study, the activities and underlying mechanisms of dioscin in the inhibition of ischemic stroke in rats were investigated. Inflammatory responses wer analyzed using ELISA kits and caspase‑3 and caspase‑9 activity was analyzed using Caspase‑3 and caspase‑9 activity kits. Western blot analysis was used to measure Toll‑like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), nuclear factor‑κB (NF‑κB), transforming growth factor‑β1 (TGF‑β1), high‑mobility group protein 1 (HMGB‑1), interleukin‑1 receptor‑associated kinase 1 (IRAK1), and tumor necrosis factor receptor‑associated factor 6 (TRAF6) protein expression. Dioscin inhibited infarct volume and neurological scores in the ischemic stroke rat model. The results demonstrated that dioscin reduced inflammatory responses, and suppressed the expression of TLR4, MyD88, NF‑κB, TGF‑β1, HMGB‑1, IRAK1, and TRAF6 in the rat ischemic stroke model. Taken together, these findings suggested that dioscin inhibited ischemic stroke‑induced inflammation through inhibition of the TLR4/MyD88/NF‑kB‑induced inflammation the rat model, which provided novel insights into the mechanisms underlying the effect of dioscin as an anti‑inflammatory candidate for the treatment of ischemic stroke in in the future.

Thymol mitigates lipopolysaccharide-induced endometritis by regulating the TLR4- and ROS-mediated NF-κB signaling pathways

The purpose of this study was to investigate the effects of thymol on lipopolysaccharide (LPS)-induced inflammatory responses and to clarify the potential mechanism of these effects. LPS-induced mouse endometritis was used to confirm the anti-inflammatory action of thymol in vivo. RAW264.7 cells were used to examine the molecular mechanism and targets of thymol in vitro. In vivo, thymol markedly alleviated LPS-induced pathological injury, myeloperoxidase (MPO) activity, and the production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in mice. Further studies were performed to examine the expression of the Toll-like receptor 4 (TLR4) -mediated nuclear factor-κB (NF-κB) pathway. These results showed that the expression of the TLR4-mediated NF-κB pathway was inhibited by thymol treatment. In vitro, we observed that thymol dose-dependently inhibited the expression of TNF-α, IL-1β, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in LPS-stimulated RAW264.7 cells. Moreover, the results obtained from immunofluorescence assays also indicated that thymol dose-dependently suppressed LPS-induced reactive oxygen species (ROS) production. Silencing of TLR4 inhibited NF-κB pathway activation. Furthermore, H₂O₂ treatment increased the phosphorylation of p65 and IκBα, which were decreased when treated with N-acetyl cysteine or thymol. In conclusion, the anti-inflammatory effects of thymol are associated with activation of the TLR4 or ROS signaling pathways, contributing to NF-κB activation, thereby alleviating LPS-induced oxidative and inflammatory responses.

Xyloketal B alleviates cerebral infarction and neurologic deficits in a mouse stroke model by suppressing the ROS/TLR4/NF-κB inflammatory signaling pathway

Xyloketal B (Xyl-B) is a novel marine compound isolated from mangrove fungus Xylaria sp. We previously demonstrated that pretreatment with Xyl-B exerted neuroprotective effects and attenuated hypoxic-ischemic brain injury in neonatal mice. In the present study we investigated the neuroprotective effects of pre- and post-treatment with Xyl-B in adult mice using a transient middle cerebral artery occlusion (tMCAO) model, and explored the underlying mechanisms. Adult male C57 mice were subjected to tMCAO surgery. For the pre-treatment, Xyl-B was given via multiple injections (12.5, 25, and 50 mg·kg^-1·d^-1, ip) 48 h, 24 h and 30 min before ischemia. For the post-treatment, a single dose of Xyl-B (50 mg/kg, ip) was injected at 0, 1 or 2 h after the onset of ischemia. The regional cerebral perfusion was monitored using a laser-Doppler flowmeter. TTC staining was performed to determine the brain infarction volume. We found that both pre-treatment with Xyl-B (50 mg/kg) and post-treatment with Xyl-B (50 mg/kg) significantly reduced the infarct volume, but had no significant hemodynamic effects. Treatment with Xyl-B also significantly alleviated the neurological deficits in tMCAO mice. Furthermore, treatment with Xyl-B significantly attenuated ROS overproduction in brain tissues; increased the MnSOD protein levels, suppressed TLR4, NF-κB and iNOS protein levels; and downregulated the mRNA levels of proinflammatory cytokines, including IL-1β, TNF-α, IL-6 and IFN-γ. Moreover, Xyl-B also protected blood-brain barrier integrity in tMCAO mice. In conclusion, Xyl-B administered within 2 h after the onset of stroke effectively protects against focal cerebral ischemia; the underlying mechanism may be related to suppressing the ROS/TLR4/NF-κB inflammatory signaling pathway.

Orientin Attenuates Cerebral Ischemia/Reperfusion Injury in Rat Model through the AQP-4 and TLR4/NF-κB/TNF-α Signaling Pathway

BACKGROUND

Orientin has been reported to have extensive pharmaceutical effects of antioxidant, anti-inflammatory, antithrombosis, antiapoptosis, and so on. In the present study, we tried to investigate the protective effects of orientin on cerebral ischemia-reperfusion (I/R) injury and explored the possible mechanisms.

METHODS

Middle cerebral artery occlusion rat model was established and then treated with low, middle, and high concentrations of orientin, respectively, with edaravone as a positive control. The treatment effect of orientin was evaluated by measuring the neurological deficit score, cerebral infarction, brain edema, oxidative stress, excitatory amino acids release, the expression levels of aquaporin-4 (AQP-4), and related inflammatory molecules using different methods including immunohistochemistry, enzyme-linked immunosorbent assay, real-time PCR, and western blot. Moreover, morphological and structural changes were also observed by hematoxylin-eosin staining and transmission electron microscope.

RESULTS

Orientin provided a significant reduction on neurological deficits, cerebral infarction, cerebral edema, oxidative damage, and neurotoxicity of excitatory amino acids compared to model group (P < .05) in a dose-dependent manner. In addition, orientin substantially downregulated AQP-4 and inflammatory factors expression (P < .05) and improved cell morphology and structure in rats following I/R injury.

CONCLUSION

Orientin was able to mediate noticeable protection against cerebral I/R injury through the attenuation of oxidative stress and neurotoxicity of amino acids and inhibiting the upregulation of AQP-4 and inflammatory cytokines.

When friend turns foe: central and peripheral neuroinflammation in central nervous system injury

Injury to the central nervous system (CNS) is common, and though it has been well studied, many aspects of traumatic brain injury (TBI) and stroke are poorly understood. TBI and stroke are two pathologic events that can cause severe, immediate impact to the neurostructure and function of the CNS, which has been recognized recently to be exacerbated by the body’s own immune response. Although the brain damage induced by the initial trauma is most likely unsalvageable, the secondary immunologic deterioration of neural tissue gives ample opportunity for therapeutic strategists seeking to mitigate TBI’s secondary detrimental effects. The purpose of this paper is to highlight the cell death mechanisms associated with CNS injury with special emphasis on inflammation. The authors discuss sources of inflammation, and introduce the role of the spleen in the systemic response to inflammation after CNS injury.

Splenectomy Does Not Improve Long-Term Outcome After Stroke

BACKGROUND AND PURPOSE

Immune responses to brain antigens after stroke contribute to poor outcome. We hypothesized that splenectomy would lessen the development of such responses and improve outcome.

METHODS

Male Lewis rats (275-350 g) underwent 2-hour middle cerebral artery occlusion immediately after splenectomy or sham splenectomy. Animals were survived to 4 weeks (672 hrs), and immune responses to myelin basic protein determined at euthanasia. Infarct volume was determined in a subset of animals euthanized at 72 hours. Behavioral outcomes were assessed to 672 hours.

RESULTS

Splenectomy was associated with worse neurological scores early after stroke, but infarct size at 72 hours was similar in both groups. Behavioral outcomes and immune responses to myelin basic protein were also similar among splenectomized and sham-operated animals 672 hours after middle cerebral artery occlusion.

CONCLUSIONS

Splenectomy did not alter the immune responses to brain antigens or improve outcome after stroke. Differences between this study and other studies of splenectomy and stroke are examined.

Neutrophil granulocytes in cerebral ischemia - Evolution from killers to key players

Neutrophil granulocytes (or polymorphonuclear cells, PMNs) have long been considered as crude killing machines, particularly trained to attack bacterial or fungal pathogens in wounds or infected tissues. That perspective has fundamentally changed over the last decades, as PMNs have been shown to exert a livery exchange between other cells of the innate and adaptive immune system. PMNs do provide major immunomodulatory contribution during acute inflammation and subsequent clearance. Following sterile inflammation like cerebral ischemia, PMNs are among the first hematogenous cells attracted to the ischemic tissue. As inflammation is a crucial component within stroke pathophysiology, several studies regarding the role of PMNs following cerebral ischemia have been carried out. And indeed, recent research suggests a direct connection between PMNs' influx and brain damage severity. This review highlights the latest research regarding the close interconnection between PMNs and co-working cells following cerebral ischemia. We describe how PMNs are attracted to the site of injury and their tasks within the inflamed brain tissue and the periphery. We further report of new findings regarding the interaction of PMNs with resident microglia, immigrating macrophages and T cells after stroke. Finally, we discuss recent research results from experimental studies in the context with current clinical trials and point out potential new therapeutic applications that could emerge from this new knowledge on the action and interaction of PMNs following cerebral ischemia.