IGF-1 signaling reduces neuro-inflammatory response and sensitivity of neurons to MPTP

Reduced expression of IGF-1R increases lifespan and resistance to oxidative stress in the mouse, raising the possibility that this also confers relative protection against the pro-parkinsonian neurotoxin MPTP, known to involve an oxidative stress component. We used heterozygous IGF-1R^+/− mice and challenged them with MPTP. Interestingly, MPTP induced more severe lesions of dopaminergic neurons of the substantia nigra, in IGF-1R^+/− mice than in wild-type animals. Using electron spin resonance, we found that free radicals were decreased in IGF-1R^+/− mice in comparison with controls, both before and after MPTP exposure, suggesting that the increased vulnerability of dopamine neurons is not caused by oxidative stress. Importantly, we showed that IGF-1R^+/− mice display a dramatically increased neuro-inflammatory response to MPTP that may ground the observed increase in neuronal death. Microarray analysis revealed that oxidative stress-associated genes, but also several anti-inflammatory signaling pathways were downregulated under control conditions in IGF-1R^+/− mice compared to WT. Collectively, these data indicate that IGF signaling can reduce neuro-inflammation dependent sensitivity of neurons to MPTP.     

Mitochondrial dysfunction in Caenorhabditis elegans causes metabolic restructuring, but this is not linked to longevity

Lifespan in Caenorhabditis elegans, Drosophila, and mice can be extended by a decrease in mitochondrial electron transport chain (ETC) function, but the mechanism behind this extension is unknown. In the present study, we combine detailed metabolic analysis with lifespan determination following suppression of individual genes encoding respiratory complexes I-IV. We report that reduced complexes I, III, and IV activity extend lifespan but that complex II disruption does not. However, disruption to all four complexes affected metabolism in a similar manner suggesting that metabolic effects induced by ETC disruption are separable from lifespan extension. We found that suppression of ETC components induces a starvation-like metabolic response via the nuclear hormone receptor NHR-49. This includes induction of genes for mitochondrial fatty-acid β-oxidation (acs-2), the glyoxylate cycle (gei-7), gluconeogensis (PEPCK), and glycolysis (gpd-3). Interestingly, a null mutation of nhr-49 attenuated induction of these metabolic pathways, but did not affect the lifespan extension associated with decreases in complexes I, III, and IV function. Together, our results suggest that restructuring of metabolism via NHR-49 in C. elegans with mitochondrial dysfunction does not cause lifespan extension.     

Levamisole-resitant mutants of the nematode Caenorhabditis elegans appear to lack pharmacological acetylcholine receptors

The body muscles of the nematode Caenorhabditis elegans contract when the animal is cut in solutions of cholinergic agonists. The pharmacological specificity of the apparent nematode cholinergic receptor is most like a vertebrate nicotink ganglionic receptor. The anthelmintic levamisole resembles nicotine in its effects and acts directly or indirectly as both a cholinergic agonist and antagonist. Mutants at 7 loci conferring extreme resistance to levamisole respond very poorly to cholinergic agonists effective on the wild type. These mutants all share the same uncoordinated motor behavior and contract like the wild type in response to the noncholinergic muscle agonist ouabain. The uncoordinated motor behavior of the mutants and the resistance to levamisole and cholinergic agonists can be copied by exposing the wild type to the cholinergic blocking agent mecamylamine. Another class of mutants (8 loci, 5 corresponding to loci also producing extremely resistant alleles) possesses intermediate resistance to levamisole and cholinergic agonists and behaves pharmacologically and genetically like mutants moderately impaired in the levamisole-sensitive function. A third class of mutants (2 loci) with spasmodic muscle twitching is partially resistant to cholinergic agonists and to ouabain and probably represents defects in the muscle-contraction cycle physiologically downstream from the levamisole-sensitive function. Meta-phenyl-substituted derivatives of levamisole retain considerable biological activity and may be useful in the molecular analysis of our mutants. α-bungarotoxin, benzyltrimethyl-ammonium, and 3-quinuclidinyl benzilate, potential probes of cholinergic receptor function, do not show significant activity in our cut worm assay.The nature of the observed cholinergic response and the neuronanatomy of C. elegans suggest that the primary response occurs at muscle synapses. We believe that the physiological defect the extremely resistant mutants share is a severe lack of functional muscle acetylcholine receptors and that most of the wild type function of this molecule is not essential to the life of C. elegans. The ability to obtain such mutants may result from there being more than one pharmacological type of nematode cholinergic muscle receptor and/or from the coexistence of a noncholinergic motor mechanism. More generally, the ease with which levamisole-resistant mutants can be isolated (up to 74 mutants in one gene) makes these mutants a favorable system for understanding how a small group of related genes function in a simple animal.     

Inhibition of gustatory plasticity due to acute nicotine exposure in the nematode Caenorhabditis elegans

The present study investigated the effect of nicotine exposure on gustatory plasticity in the nematode Caenorhabditis elegans. The chemotactic response of wild-type N2 nematodes pre-exposed to 100 mM NaCl with 3.0 mM nicotine was almost the same as that of mock-conditioned nematodes unexposed to NaCl; however, the response of N2 nematodes pre-exposed to NaCl without nicotine was significantly lower than that of mock-conditioned nematodes. These results indicate that gustatory plasticity is inhibited by acute nicotine exposure. Inhibition of gustatory plasticity was observed when cat-2 mutants with a defect in dopamine biosynthesis were pre-exposed to NaCl with 3.0 mM nicotine. Acute nicotine exposure did not cause inhibition of gustatory plasticity in bas-1 mutants, which had defects in both serotonin and dopamine secretion, and tph-1 mutants, which had a defect in serotonin secretion only. However, inhibition of gustatory plasticity was observed when bas-1 and tph-1 mutants were maintained on a growth plate that included serotonin. These results suggest that serotonin signaling plays an essential role in the modulation of the acute effects of nicotine.     

Human superoxide dismutase 1 overexpression in motor neurons of Caenorhabditis elegans causes axon guidance defect and neurodegeneration

Strong evidence indicates that mutant Cu, Zn-superoxide dismutase 1 (SOD1) exerts toxic effect on motor neurons in amyotrophic lateral sclerosis (ALS). However, the nature of mutant SOD1-mediated motor neuron degeneration is poorly understood. To provide new insight into the mechanism by which mutant SOD1 induces motor neuron injury, we developed novel Caenorhabditis elegans models of ALS. Expression of human wild type or G93A SOD1 specifically in motor neurons of C. elegans caused progressive locomotion defect and paralytic phenotype, which recapitulate some characteristic features of ALS including age-dependent motor dysfunction and degeneration of motor neurons associated with SOD1 aggregation. In addition, the motor neuron loss is independent of cell death protein 3 (CED-3)/cell death protein 4 (CED-4) caspase pathway. We also found that before motor neurons began to die in adulthood, axon guidance defect of motor neuron appeared during the development stages. When green fluorescent protein (GFP)-tagged proteins related to axon guidance were examined in motor neurons, a significantly decreased density and number of GFP-tagged puncta were observed in the transgenic worms. Our models mimic axon developmental defect and the adult-onset degeneration of motor neurons in ALS. Using this model, we uncovered the cell-autonomous damage caused by human SOD1 to motor neurons in vivo, and provided a new insight into the developmental defect mechanism that may contribute to motor neuron degeneration in ALS.     

A method for oral administration of hydrophilic substances to Caenorhabditis elegans: Effects of oral supplementation with antioxidants on the nematode lifespan

Numerous studies using Caenorhabditis elegans have used a protocol in which chemicals are orally delivered by incorporating them into the nematode growth media or mixing them with the food bacteria. However, actual exposure levels are difficult to estimate as they are influenced by both the rates of ingestion into the intestine as well as absorption from the intestinal lumen. We used liposomes loaded with the hydrophilic fluorescent reagent uranin to test oral administration of water-soluble substances to C. elegans. Ingestion of liposomes loaded with fluorescent dye resulted in successful oral delivery of chemicals into the intestines of C. elegans. Using liposomes, oral administration of hydrophilic antioxidants (ascorbic acid, N-acetyl-cysteine, reduced glutathione, and thioproline) prolonged the lifespan of the nematodes, whereas the conventional method of delivery showed neither fluorescence nor longevity effects. Our method efficiently and quantitatively delivers solutes to nematodes.     

Interleukin-1 receptor antagonist reduces the magnitude of the pressor response to acute stress

The purpose of the present study was to establish the effect of chronic central interleukin-1 receptors blockade and central chronic infusion of interleukin-1 beta (IL-1β) on cardiovascular response to an acute stressor. The experiments were performed on 12–14-week-old, male WKY rats, divided into three experimental groups. Each group was subjected to chronic intracerebroventricular (ICV) infusion of one of the following compounds: saline (control, group C), recombinant rat IL-1 receptor antagonist (IL-ANT group) or interleukin-1 beta (IL-1B group). After 5 days of the ICV infusions mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously under baseline conditions and after the application of an air jet stressor. The stressor was applied three times with 10-min intervals. There were no significant differences in MABP and HR between groups under baseline conditions and immediately before the application of the three consecutive air jets. After the first stressor the IL-ANT group responded with a significantly lower increase in blood pressure than the control and IL-1B group. After the application of the two following air jets only the trend for an intergroup difference was present. The results of the present study provide further evidence that cytokines play an important role in the regulation of the circulatory system. The most important new finding is that the magnitude of the pressor response to the alarming stress is strongly influenced by IL-1 receptors in the brain.     

转录因子T-bet/GATA-3比率评价哮喘患者Th1/Th2失衡及CpG ODN干预机制的研究

目的: 探讨哮喘患者PBMCs中转录因子T-bet/GATA-3比率与Th1/Th2细胞失衡的关系及体外CpG干预后T-bet/GATA3比率的变化及其对Th1/Th2细胞平衡的调节作用。方法: 用RT-PCR法测定30例发作期哮喘患者（哮喘组）及20例慢性阻塞性肺病患者（COPD组）及20例正常人（对照组） PBMCs中T-bet mRNA、GATA-3 mRNA及TLR9 mRNA的表达强度，用ELISA法测定血浆IL-4、IL-5、IL-13和IFNγ的表达水平，以观察哮喘患者PBMCs中转录因子T-bet/GATA-3比率与Th1/Th2细胞失衡的关系。将20例发作期哮喘患者的PBMCs分为2部分，一份加入CpG ODN和PHA（CpG组），一份仅加入PHA（对照组），培养48 h后分别收集培养液和细胞，采用RT-PCR法测定细胞中T-bet mRNA、GATA-3 mRNA及TLR9 mRNA的表达强度，ELISA法测定培养液中IL-4、IL-5、IL-13和IFN-γ的表达水平。结果： 哮喘患者PBMCs中T-bet/GATA-3的比率显著低于COPD患者和正常人，IL-4、IL-5、IL-13的水平显著高于COPD患者和正常人，与T-bet/GATA-3的比率呈负相关，而IFN-γ的水平显著降低，与T-bet/GATA-3的比率呈正相关。哮喘组TLR9的表达强度显著弱于COPD患者和正常人。CpG干预组细胞培养液中IL-4、IL-5和IL-13的水平分别显著低于对照组，IFN-γ的水平显著高于对照组。CpG干预组细胞中T-bet mRNA和TLR9 mRNA的表达强度显著强于对照组，GATA-3 mRNA的表达强度显著低于对照组；T-bet/GATA-3的比率显著高于对照组。结论: 哮喘患者T-bet/GATA-3的比率降低，可以作为评价Th1/Th2细胞失衡的精确指标。CpG ODN可以上调T-bet的表达，下调GATA-3的表达，从而上调T-bet/GATA-3的比率，逆转Th1/Th2细胞失衡，是一种很有前景的哮喘治疗手段。     

Age-associated changes in SAPK/JNK and p38 MAPK signaling in response to the generation of ROS by 3-nitropropionic acid

Mitochondrial dysfunction has been identified as a major source of oxidative stress in aged tissues. In this study we asked whether activities of components of the SAPK/JNK and p38 MAPK stress response signaling pathways are indicative of oxidative stress in aged mouse livers and whether these pathways are responsive to oxidative stress generated by 3-nitropropionic acid (3-NPA), an inhibitor of complex II (succinic dehydrogenase). We asked whether (a) aging affects the basal activity of the SAPK/JNK stress signaling pathway; (b) specific isoforms of JNK, i.e. 46 or 54 kDa JNKs are activated by 3-NPA; (c) aging affects the response of this signaling pathway to 3-NPA; (d) there is a cross pathway activation of JNK or p38 MAPK by upstream activators. Our studies have shown that although their protein pool levels are not altered, the basal JNK activities using c-Jun as substrate is elevated. Furthermore, in aged livers, JNK activity is induced to a greater extent and takes longer to recover from 3-NPA treatment. The activities of the upstream activators of JNKs, MAP kinase kinase (MKK) 4 and 7, are also elevated in livers of aged C57BL/6 male mice. These activator kinases, which are induced (phosphorylated) by 3-NPA in young livers, are not inducible by this inhibitor in aged livers. In fact, these proteins are highly phosphorylated in the control aged livers and are dephosphorylated in response to 3-NPA. Finally, we demonstrate for the first time that MKK7 serves as an upstream activator of p38 MAPK and that MKK3 and MKK6 activates 54 kDa JNK2 in aged liver. Our studies suggest that failure to respond to 3-NPA may be indicative of the susceptibility of aged tissue to oxidative stress, supporting our hypothesis that aged tissues (especially liver) develop a state of chronic stress even in the absence of a challenge.     

The role of the hok/sok locus in bacterial response to stressful growth conditions

The hok/sok locus is renowned for its plasmid stabilization effect via post-segregational killing of plasmid-free daughter cells. However, the function(s) of the chromosome-encoded loci, which are more abundant in pathogenic strains of a broad range of enteric bacteria, are yet to be understood. Also, the frequent occurrence of this toxin/antitoxin addiction system in multi-drug resistance plasmids suggests additional roles. In this study, the effects of the hok/sok locus on the growth of bacteria in stressful growth-limiting conditions such as high temperature and antibiotic burden were investigated using hok/sok plasmids. The results showed that the hok/sok locus prolonged the lag phase of host cell cultures, thereby enabling the cells to adapt, respond to the stress and eventually thrive in these growth-limiting conditions by increasing the growth rate at exponential phase. The hok/sok locus also enhanced the survival and growth of cells in low cell density cultures irrespective of unfavourable growth conditions, and may complement existing or defective SOS mechanism. In addition to the plasmid stabilization function, these effects would enhance the ability of pathogenic bacteria to establish infections and propagate the antibiotic resistance elements carried on these plasmids, thereby contributing to the virulence of such bacteria.     

Supplementation with l-glutathione improves oxidative status and reduces protein nitration in myenteric neurons in the jejunum in diabetic Rattus norvegicus

Diabetes mellitus is a syndrome with multiple etiologies, characterized by chronic hyperglycemia that increases the production of reactive oxygen species and decreases antioxidant defenses. The present study evaluated oxidative stress parameters and protein nitration in myenteric neurons in the jejunum in diabetic rats supplemented with l-glutathione. Rats (90?days of age) were distributed into four groups (n?=?6/group): normoglycemic (N), normoglycemic supplemented with l-glutathione (NGT), diabetic (D), and diabetic supplemented with l-glutathione (DGT). At 210?days of age, the animals were sacrificed, and the jejunum was collected, washed, and subjected to various procedures: tert-butyl hydroperoxide chemiluminescence (CL), determination of total antioxidant capacity (TAC), determination of catalase activity, quantification of nitric oxide (NO), and double-labeling of HuC/D-immunoreactive myenteric neurons and nitrotyrosine (3-NT). Diabetes increased oxidative stress in the jejunum in the D group, reflected by increases in lipid peroxidation, TAC, catalase activity, and NO. The D group exhibited an increase in the percentage of myenteric neurons that were double-labeled with 3-NT. Supplementation with l-glutathione did not cause differences in the average CL curves between the D and DGT groups, but reductions of TAC and catalase activity were observed. Supplementation with l-glutathione promoted a reduction of neurons that contained 3-NT in the DGT group. Diabetes mellitus promoted oxidative stress in the jejunum, and supplementation with l-glutathione improved oxidative status by preventing protein nitration in myenteric neurons in diabetic animals that received supplementation.     

f57f4.4p::gfp as a fluorescent reporter for analysis of the C. elegans response to bacterial infection

Host defense mechanisms are multi-layered and involve constitutive as well as inducible components. The dissection of these complex processes can be greatly facilitated using a reporter gene strategy with a transparent animal. In this study, we use Caenorhabditis elegans as a model host and introduce a new pathogen-inducible fluorescent reporter involving the promoter of f57f4.4, a gene encoding a putative component of the glycocalyx. We show that this reporter construct does not respond to heavy metal or hypertonic environments, but is specifically and locally induced in the intestine upon Photorhabus luminescens and Pseudomonas aeruginosa infections. We further demonstrate that its upregulation requires live pathogens as well as elements of the nematode p38 MAP kinase and TGF-beta pathways. In addition to introducing a new tool for the study of the interactions between C. elegans and a pathogen, our results suggest a role for the glycocalyx in gut immunity.     

巨细胞病毒感染对小鼠心肌组织TH1/TH2类细胞因子及其特异性转录因子T-bet/GATA-3表达的影响

目的动态观测MCMV感染对小鼠心肌组织TH1/TH2类细胞因子及其特异性转录因子T-bet／GATA-3表达的影响。方法建立小鼠巨细胞病毒感染心肌炎模型。观察小鼠血清删浓度变化，心肌组织病理损害和心肌组织细胞因子IFN-γ、IL-4表达水平以及脾组织中转录因子T-bet、GATA-3表达强度。结果心肌组织病理积分和血清cTnI浓度在MCMV感染后第3天增高，第7天达高峰，第14天仍维持较高水平；IFN-γ在MCMV感染第3天时表达迅速增高达到峰值，随后下降，第14天基本下落至正常水平；IL-4在MCMV感染第5天表达迅速增高达到峰值，随后下降，在第14天又升高；MCMV感染第3天转录因子T-bet蛋白表达达峰值，随后逐渐降低，到第14天时降低更为显著。转录因子GATA-3在MCMV感染第7天时表达明显增强，第14天时增强更为显著。结论MCMV感染通过上调GATA-3转录因子和叫表达，下调T-bet转录因子和IFN-γ表达，导致TH1/TH2平衡失调，表现为TH2细胞优势应答状态，使心肌损害加重。这可能是CMV感染致宿主特异性细胞免疫功能降低并造成组织损伤的机制之一。     

Melatonin reduces membrane rigidity and oxidative damage in the brain of SAMP8 mice

We evaluated the autophagy-lysosomal pathway and membrane fluidity in brain cells and mitochondrial membranes obtained from senescence-accelerated (SAMP₈) and senescence-resistant (SAMR₁) mice at 5 and 10 months of age. Moreover, we studied whether chronic treatment from age 1 to 10 months with melatonin stabilizes membrane fluidity. Fluidity was measured by polarization changes of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene-p-toluene sulfonate. Results showed that in untreated animals at 5 months of age, synaptosomal and mitochondrial fluidity was decreased in SAMP₈ compared to SAMR₁, as was the cathepsin D/B ratio, indicating dysfunction of the autophagy-lysosomal pathway. Moreover, we detected synaptosomal rigidity and programmed cell death capability in both groups at 10 months of age. Mitochondrial fluidity, however, did not show a significant age-dependent change but was lower in SAMP₈ than in SAMR₁ at the 5- and 10-month time points. Melatonin administration prevented rigidity in the mitochondrial membrane and seemed to decrease age-related autophagy-lysosomal alterations. These data suggest that melatonin may act to slow down the aging process because of its ability to enhance membrane fluidity and maintain structural pathways.     

人参皂苷Rg1对小鼠脑缺血再灌注后脑组织损伤及Nrf2/HO-1途径的影响

 目的：观察人参皂苷Rg1对小鼠脑缺血再灌注后脑组织损伤的影响,并从核因子E2相关因子2（Nrf2）/血红素加氧酶1（HO-1）信号通路研究其作用机制。方法：C57BL/6小鼠随机分组,连续给药3 d,末次给药1 h后,结扎双侧颈总动脉造成脑缺血20 min,再灌注24 h。以具有抗氧化应激损伤作用、治疗缺血性脑血管病有效的药物依达拉奉作为阳性对照药。取脑组织行海马CA1区神经细胞病理学测定,RT-PCR法测定Nrf2和HO-1 mRNA表达,Western bloting测定脑组织胞核、胞浆Nrf2和全细胞HO-1蛋白含量。结果：(1)缺血再灌注24 h后,神经细胞出现病理性损伤,细胞存活率显著降低。人参皂苷Rg1和依达拉奉可使神经细胞损伤明显减轻,细胞存活率显著升高。(2)脑缺血再灌注24 h,脑组织Nrf2 mRNA和HO-1 mRNA表达增强,同时脑组织胞核和胞浆中Nrf2蛋白含量增加,核转位率升高,HO-1蛋白表达增强。人参皂苷Rg1和依达拉奉均能降低脑组织胞浆Nrf2蛋白含量,升高胞核Nrf2含量,使Nrf2核转位率升高,并使脑组织HO-1 mRNA和蛋白表达显著增加。依达拉奉的作用强于人参皂苷Rg1,但两药对脑组织Nrf2 mRNA表达无显著影响。结论：人参皂苷Rg1具有抗脑缺血再灌注损伤的作用,其机制可能与激活Nrf2/HO-1信号途径、促进Nrf2合成和核转位、从而促进下游抗氧化蛋白HO-1的表达有关。     

The apoptotic response to strenuous exercise of the gastrocnemius and solues muscle fibers in rats

The purposes of this study were to investigate the effects of strenuous exercise on apoptosis of the gastrocnemius and soleus muscle fibers and clarify the role of oxidative metabolism in the strenuous exercise-induced apoptosis. The experiment was designed with 49 (n = 49) male, 24-week-old, L. Wistar albino rats. Strenuous exercise model was applied to 42 (n = 42) rats and seven (n = 7) rats served as rested controls. All rats were randomly assigned to one of the following groups (n = 7): rested control (C), immediately after exercise (0 h) and 3, 6, 12, 24, and 48 h after exercise. Apoptotic nuclei were shown by single stranded DNA (ssDNA) determination. Oxidative damage in mitochondrial fractions of the muscle tissues was evaluated by malondialdehyde (MDA) levels and reduced/oxidized glutathione (GSH/GSSG) ratios. Caspase-9, -8 and -3 activities and the level of cytochrome c (Cyt c) were measured in the cytosolic fractions of muscle tissues to follow mitochondrial-dependent (intrinsic) or ligand-mediated death receptor (extrinsic) pathways of apoptosis. Plasma interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels were also determined. Based on our results, apoptosis is significantly triggered in muscle fibers by strenuous exercise (P < 0.05). Apoptosis in the soleus muscle tissues mostly depends on the intrinsic pathway and may be triggered by increased oxidative stress. In contrast, extrinsic pathway of apoptosis was predominant in the gastrocnemius muscle and increases of TNF-α and IL-6 may play a significant role.