TLR9信号通路介导缺血性脑损伤的研究进展

炎症反应是缺血性脑损伤的重要机制之一,过度的炎症免疫反应会加剧脑损伤的程度。作为先天免疫系统的重要组成部分,Toll样受体9(Toll like receptor 9,TLR9)通过识别其特异性的配体Cp G-DNA,从而激活先天免疫系统,释放大量前炎症细胞因子,参与缺血性脑损伤的炎症反应过程。近年来,有学者提出将TLR9作为一个新的缺血预处理靶点,即通过启动TLR9信号转导通路增加体内炎症细胞因子的水平来对抗缺血损伤。本文通过对近年TLR9信号通路介导的炎症反应与缺血性脑损伤相关研究进展作一综述,为寻求临床安全高效的缺血性脑损伤防治措施提供理论依据。     

Lrp4 Modulates Extracellular Integration of Cell Signaling Pathways in Development

The extent to which cell signaling is integrated outside the cell is not currently appreciated. We show that a member of the low-density receptor-related protein family, Lrp4 modulates and integrates Bmp and canonical Wnt signalling during tooth morphogenesis by binding the secreted Bmp antagonist protein Wise. Mouse mutants of Lrp4 and Wise exhibit identical tooth phenotypes that include supernumerary incisors and molars, and fused molars. We propose that the Lrp4/Wise interaction acts as an extracellular integrator of epithelial-mesenchymal cell signaling. Wise, secreted from mesenchyme cells binds to BMP''s and also to Lrp4 that is expressed on epithelial cells. This binding then results in the modulation of Wnt activity in the epithelial cells. Thus in this context Wise acts as an extracellular signaling molecule linking two signaling pathways. We further show that a downstream mediator of this integration is the Shh signaling pathway.     

Nitric Oxide Participates in the Induction of Brain Ischemic Tolerance via Activating ERK1/2 Signaling Pathways

The present study was undertaken to observe in vivo changes of expression and phosphorylation of ERK1/2 proteins during brain ischemic preconditioning and effects of inhibiting generation of nitric oxide (NO) on the changes to determine the role of ERKs in the involvement of NO participating in the acquired tolerance. Fifty-five Wistar rats were used. Brain ischemic preconditioning was performed with four-vessel occlusion for 3 min. Total ERK1/2 proteins and phospho-ERK1/2 in the CA1 hippocampus were assayed with Western immunoblot. Total ERK1/2 proteins did not change in period from 5 min to 5 days of reperfusion after preconditioning stimulus. While the level of phospho-ERK1/2 increased obviously to 223, 237, 300, 385 and 254% of sham level at times of 5 min, 2 h, 1, 3 and 5 days after preconditioning stimulus, respectively (P < 0.01). Administration of L-NAME, an inhibitor of NO synthase, 30 min prior to preconditioning stimulus failed to induce change in total ERK1/2 proteins (P > 0.05). However, phospho-ERK1/2 increased only to 138 and 176% of sham level at 2 h and 3 days after preconditioning stimulus, respectively, when animals were pretreated with L-NAME. The magnitudes of the increase were obviously low compared with those (237 and 385%) in animals untreated with L-NAME at corresponding time points (P < 0.01), which indicated that phosphorylation of ERK1/2 normally induced by preconditioning stimulus was blocked apparently by administration of L-NAME. The results suggested that phosphorylation of ERK1/2, rather than synthesis of ERK1/2 proteins, was promoted in brain ischemic preconditioning, and that the promotion was partly mediated by NO signal pathway.     

Phosphoproteomic Analysis of Neurotrophin Receptor TrkB Signaling Pathways in Mouse Brain

SUMMARY 1. The signaling pathways activated by trkB neurotrophin receptor have been studied in detail in cultured neurons, but little is known about the pathways activated by trkB in intact brain. TrkB is a tyrosine kinase and protein phosphorylation is a key regulatory process in the neuronal signal transduction pathways.2. We have investigated trkB signaling in the transgenic mice overexpressing trkB in postnatal neurons (trkB.TK) using phosphoproteomics.3. We found that several proteins are overphosphorylated on tyrosine residues in the brain of trkB.TK mice and identified some of these proteins.4. We demonstrate that the well characterized signaling molecules mitogen-activated protein kinase (MAPK) and cyclic AMP responsive element binding protein (CREB) were phosphorylated at a higher level in the brain of trkB.TK mice when compared to the wild type littermates. Furthermore, we found that β-actin was tyrosine phosphorylated in the brain of the transgenic mice.5. Our results demonstrate that phosphoproteomics is a sensitive approach to investigate signaling pathways activated in mouse brain.     

Enterococcus faecalis from Healthy Infants Modulates Inflammation through MAPK Signaling Pathways

Colonizing commensal bacteria after birth are required for the proper development of the gastrointestinal tract. It is believed that bacterial colonization pattern in neonatal gut affects gut barrier function and immune system maturation. Studies on the development of faecal microbiota in infants showed that the neonatal gut was first colonized with enterococci followed by other microbiota such as Bifidobacterium. Other studies showed that babies who developed allergy were less often colonized with Enterococcus during the first month of life as compared to healthy infants. Many studies have been conducted to elucidate how bifidobacteria or lactobacilli, some of which are considered probiotic, regulate infant gut immunity. However, fewer studies have been focused on enterococi. In our study, we demonstrate that E. faecalis, isolated from healthy newborns, suppress inflammatory responses activated in vivo and in vitro. We found E. faecalis attenuates proinflammatory cytokine secretions, especially IL-8, through JNK and p38 signaling pathways. This finding shed light on how the first colonizer, E.faecalis, regulates inflammatory responses in the host.     

白藜芦醇对大鼠局灶性脑缺血再灌注的治疗作用

目的:观察白藜芦醇对大鼠局灶性脑缺血再灌注损伤的治疗作用及可能的机制。方法:将SD大鼠随机分为2组:对照组(n=16),白藜芦醇组(n=16)。对照组再灌注即刻腹腔给予0.5 ml生理盐水,白藜芦醇组再灌注即刻腹腔给予20 mg/kg白藜芦醇。再灌注22小时后,进行神经功能学评分、脑梗死容积测定,用分光光度仪测定脑组织溶浆中SOD、MDA和MPO的含量。结果:再灌注22小时后,白藜芦醇治疗组可以改善大鼠神经功能学评分和降低脑梗死面积(P<0.05),同时可以增加脑组织溶浆中SOD的活性,降低MDA和MPO的含量。结论:白藜芦醇通过减轻白细胞的浸润、提高自由基的清除率对大鼠局灶性脑缺血再灌注损伤发挥治疗作用。     

Targeting Apoptosis and Multiple Signaling Pathways with Icariside II in Cancer Cells

Cancer is the second leading cause of deaths worldwide. Despite concerted efforts to improve the current therapies, the prognosis of cancer remains dismal. Highly selective or specific blocking of only one of the signaling pathways has been associated with limited or sporadic responses. Using targeted agents to inhibit multiple signaling pathways has emerged as a new paradigm for anticancer treatment. Icariside II, a flavonol glycoside, is one of the major components of Traditional Chinese Medicine Herba epimedii and possesses multiple biological and pharmacological properties including anti-inflammatory, anti-osteoporosis, anti-oxidant, anti-aging, and anticancer activities. Recently, the anticancer activity of Icariside II has been extensively investigated. Here, in this review, our aim is to give our perspective on the current status of Icariside II, and discuss its natural sources, anticancer activity, molecular targets and the mechanisms of action with specific emphasis on apoptosis pathways which may help the further design and conduct of preclinical and clinical trials.Icariside II has been found to induce apoptosis in various human cancer cell lines of different origin by targeting multiple signaling pathways including STAT3, PI3K/AKT, MAPK/ERK, COX-2/PGE2 and β-Catenin which are frequently deregulated in cancers, suggesting that this collective activity rather than just a single effect may play an important role in developing Icariside II into a potential lead compound for anticancer therapy. This review suggests that Icariside II provides a novel opportunity for treatment of cancers, but additional investigations and clinical trials are still required to fully understand the mechanism of therapeutic effects to further validate it in anti-tumor therapy.     

神经血管单元和Notch信号通路在缺血性卒中后的作用

缺血性卒中是临床常见疾病,且致死致残率高,幸存的患者预后多不同程度的患有偏瘫等后遗症,但目前还没有好的治疗方法。很长一段时间以来,卒中后的治疗关注点在于神经元的保护,割裂了神经元和周围细胞的联系。2001年,"神经血管单元"概念的提出为缺血性卒中的临床治疗提供了新的角度。此外,有研究表明Notch信号通路参与了神经、血管再生过程,对于卒中后神经血管单元的修复有调节作用。因此,本文从神经血管单元和Notch信号通路两个切入点综述了二者在缺血性卒中发生后的作用。     

Multiple Signaling Pathways of the Insulin-Like Growth Factor 1 Receptor in Protection from Apoptosis

The type 1 insulin-like growth factor receptor (IGF-1R), activated by its ligands, protects several cell types from a variety of apoptotic injuries. The main signaling pathway for IGF-1R-mediated protection from apoptosis has been previously elucidated and rests on the activation of phosphatidylinositol 3-kinase, Akt/protein kinase B, and the phosphorylation and inactivation of BAD, a member of the Bcl-2 family of proteins. In 32D cells (a murine hemopoietic cell line devoid of insulin receptor substrate 1 [IRS-1]), the IGF-1R activates alternative pathways for protection from apoptosis induced by withdrawal of interleukin-3. One of these pathways leads to the activation of mitogen-activated protein kinase, while a third pathway results in the mitochondrial translocation of Raf and depends on the integrity of a group of serines in the C terminus of the receptor that are known to interact with 14.3.3 proteins. All three pathways, however, result in BAD phosphorylation. The presence of multiple antiapoptotic pathways may explain the remarkable efficacy of the IGF-1R in protecting cells from apoptosis.     

Motor Imagery Learning Modulates Functional Connectivity of Multiple Brain Systems in Resting State

Background

Learning motor skills involves subsequent modulation of resting-state functional connectivity in the sensory-motor system. This idea was mostly derived from the investigations on motor execution learning which mainly recruits the processing of sensory-motor information. Behavioral evidences demonstrated that motor skills in our daily lives could be learned through imagery procedures. However, it remains unclear whether the modulation of resting-state functional connectivity also exists in the sensory-motor system after motor imagery learning.

Methodology/Principal Findings

We performed a fMRI investigation on motor imagery learning from resting state. Based on previous studies, we identified eight sensory and cognitive resting-state networks (RSNs) corresponding to the brain systems and further explored the functional connectivity of these RSNs through the assessments, connectivity and network strengths before and after the two-week consecutive learning. Two intriguing results were revealed: (1) The sensory RSNs, specifically sensory-motor and lateral visual networks exhibited greater connectivity strengths in precuneus and fusiform gyrus after learning; (2) Decreased network strength induced by learning was proved in the default mode network, a cognitive RSN.

Conclusions/Significance

These results indicated that resting-state functional connectivity could be modulated by motor imagery learning in multiple brain systems, and such modulation displayed in the sensory-motor, visual and default brain systems may be associated with the establishment of motor schema and the regulation of introspective thought. These findings further revealed the neural substrates underlying motor skill learning and potentially provided new insights into the therapeutic benefits of motor imagery learning.     

Treatment with Isorhamnetin Protects the Brain Against Ischemic Injury in Mice

Ischemic stroke is a major cause of morbidity and mortality, yet lacks effective neuroprotective treatments. The aim of this work was to investigate whether treatment with isorhamnetin protected the brain against ischemic injury in mice. Experimental stroke mice underwent the filament model of middle cerebral artery occlusion with reperfusion. Treatment with isorhamnetin or vehicle was initiated immediately at the onset of reperfusion. It was found that treatment of experimental stroke mice with isorhamnetin reduced infarct volume and caspase-3 activity (a biomarker of apoptosis), and improved neurological function recovery. Treatment of experimental stroke mice with isorhamnetin attenuated cerebral edema, improved blood–brain barrier function, and upregulated gene expression of tight junction proteins including occludin, ZO-1, and claudin-5. Treatment of experimental stroke mice with isorhamnetin activated Nrf2/HO-1, suppressed iNOS/NO, and led to reduced formation of MDA and 3-NT in ipsilateral cortex. In addition, treatment of experimental stroke mice with isorhamnetin suppressed activity of MPO (a biomarker of neutrophil infiltration) and reduced protein levels of IL-1β, IL-6, and TNF-α in ipsilateral cortex. Furthermore, it was found that treatment of experimental stroke mice with isorhamnetin reduced mRNA and protein expression of NMDA receptor subunit NR1 in ipsilateral cortex. In conclusion, treatment with isorhamnetin protected the brain against ischemic injury in mice. Isorhamnetin could thus be envisaged as a countermeasure for ischemic stroke but remains to be tested in humans.     

Resveratrol Pretreatment Decreases Ischemic Injury and Improves Neurological Function Via Sonic Hedgehog Signaling After Stroke in Rats

Resveratrol has neuroprotective effects for ischemic cerebral stroke. However, its neuroprotective mechanism for stroke is less well understood. Beneficial actions of the activated Sonic hedgehog (Shh) signaling pathway in stroke, such as improving neurological function, promoting neurogenesis, anti-oxidative, anti-apoptotic, and pro-angiogenic effects, have been noted, but relatively little is known about the role of Shh signaling in resveratrol-reduced cerebral ischemic injury after stroke. The present study tests whether the Shh pathway mediates resveratrol to decrease cerebral ischemic injury and improve neurological function after stroke. We observed that resveratrol pretreatment significantly improved neurological function, decreased infarct volume, enhanced vitality, and reduced apoptosis of neurons in vivo and vitro after stroke. Meanwhile, expression levels of Shh, Ptc-1, Smo, and Gli-1 mRNAs were significantly upregulated and Gli-1 was relocated to the nucleus. Intriguingly, in vivo and in vitro inhibition of the Shh signaling pathway with cyclopamine, a Smo inhibitor, completely reversed the above effects of resveratrol. These results suggest that decreased cerebral ischemic injury and improved neurological function by resveratrol may be mediated by the Shh signaling pathway.     

Signaling Pathways in Bacterial Chemotaxis

The sensory transduction pathways between the transducing proteins and the switch on the flagellar motors have been investigated in Escherichia coli and Salmonella typhimurium. ATP, not GTP, is required for normal chemotaxis. A site of ATP action appears to be the conversion of an inactive form of the CheY protein to an active form, designated CheY*, that binds to the motor switch and initiates clockwise rotation. The methylation-dependent and methylation-independent pathways for chemotaxis have a common requirement for the CheA, CheW, and CheY proteins in addition to the switch and flagellar motor. It is concluded that the receptor/transducing proteins and the adaptation mechanism differ in the two types of pathway, but that other components of the transduction pathway are common to the methylation-dependent and methylation-independent pathways.     

Signaling Pathways in Cell Polarity

A key function of signal transduction during cell polarization is the creation of spatially segregated regions of the cell cortex that possess different lipid and protein compositions and have distinct functions. Polarity can be initiated spontaneously or in response to signaling inputs from adjacent cells or soluble factors and is stabilized by positive-feedback loops. A conserved group of proteins, the Par proteins, plays a central role in polarity establishment and maintenance in many contexts. These proteins generate and maintain their distinct locations in cells by actively excluding one another from specific regions of the plasma membrane. The Par signaling pathway intersects with multiple other pathways that control cell growth, death, and organization.     

Natural Genetic Variation of Integrin Alpha L (Itgal) Modulates Ischemic Brain Injury in Stroke

During ischemic stroke, occlusion of the cerebrovasculature causes neuronal cell death (infarction), but naturally occurring genetic factors modulating infarction have been difficult to identify in human populations. In a surgically induced mouse model of ischemic stroke, we have previously mapped Civq1 to distal chromosome 7 as a quantitative trait locus determining infarct volume. In this study, genome-wide association mapping using 32 inbred mouse strains and an additional linkage scan for infarct volume confirmed that the size of the infarct is determined by ancestral alleles of the causative gene(s). The genetically isolated Civq1 locus in reciprocal recombinant congenic mice refined the critical interval and demonstrated that infarct size is determined by both vascular (collateral vessel anatomy) and non-vascular (neuroprotection) effects. Through the use of interval-specific SNP haplotype analysis, we further refined the Civq1 locus and identified integrin alpha L (Itgal) as one of the causative genes for Civq1. Itgal is the only gene that exhibits both strain-specific amino acid substitutions and expression differences. Coding SNPs, a 5-bp insertion in exon 30b, and increased mRNA and protein expression of a splice variant of the gene (Itgal-003, ENSMUST00000120857), all segregate with infarct volume. Mice lacking Itgal show increased neuronal cell death in both ex vivo brain slice and in vivo focal cerebral ischemia. Our data demonstrate that sequence variation in Itgal modulates ischemic brain injury, and that infarct volume is determined by both vascular and non-vascular mechanisms.     

Serum Metabolomic Profiling in Acute Alcoholic Hepatitis Identifies Multiple Dysregulated Pathways

Background and Objectives

While animal studies have implicated derangements of global energy homeostasis in the pathogenesis of acute alcoholic hepatitis (AAH), the relevance of these findings to the development of human AAH remains unclear. Using global, unbiased serum metabolomics analysis, we sought to characterize alterations in metabolic pathways associated with severe AAH and identify potential biomarkers for disease prognosis.

Methods

This prospective, case-control study design included 25 patients with severe AAH and 25 ambulatory patients with alcoholic cirrhosis. Serum samples were collected within 24 hours of the index clinical encounter. Global, unbiased metabolomics profiling was performed. Patients were followed for 180 days after enrollment to determine survival.

Results

Levels of 234 biochemicals were altered in subjects with severe AAH. Random-forest analysis, principal component analysis, and integrated hierarchical clustering methods demonstrated that metabolomics profiles separated the two cohorts with 100% accuracy. Severe AAH was associated with enhanced triglyceride lipolysis, impaired mitochondrial fatty acid beta oxidation, and upregulated omega oxidation. Low levels of multiple lysolipids and related metabolites suggested decreased plasma membrane remodeling in severe AAH. While most measured bile acids were increased in severe AAH, low deoxycholate and glycodeoxycholate levels indicated intestinal dysbiosis. Several changes in substrate utilization for energy homeostasis were identified in severe AAH, including increased glucose consumption by the pentose phosphate pathway, altered tricarboxylic acid (TCA) cycle activity, and enhanced peptide catabolism. Finally, altered levels of small molecules related to glutathione metabolism and antioxidant vitamin depletion were observed in patients with severe AAH. Univariable logistic regression revealed 15 metabolites associated with 180-day survival in severe AAH.

Conclusion

Severe AAH is characterized by a distinct metabolic phenotype spanning multiple pathways. Metabolomics profiling revealed a panel of biomarkers for disease prognosis, and future studies are planned to validate these findings in larger cohorts of patients with severe AAH.