Oxidative stress and neurodegeneration: the involvement of iron

Many evidences indicate that oxidative stress plays a significant role in a variety of human disease states, including neurodegenerative diseases. Iron is an essential metal for almost all living organisms due to its involvement in a large number of iron-containing proteins and enzymes, though it could be also toxic. Actually, free iron excess generates oxidative stress, particularly in brain, where anti-oxidative defences are relatively low. Its accumulation in specific regions is associated with pathogenesis in a variety of neurodegenerative diseases (i.e., Parkinson’s disease, Alzheimer’s disease, Huntington’s chorea, Amyotrophic Lateral Sclerosis and Neurodegeneration with Brain Iron Accumulation). Anyway, the extent of toxicity is dictated, in part, by the localization of the iron complex within the cell (cytosolic, lysosomal and mitochondrial), its biochemical form, i.e., ferritin or hemosiderin, as well as the ability of the cell to prevent the generation and propagation of free radical by the wide range of antioxidants and cytoprotective enzymes in the cell. Particularly, ferrous iron can act as a catalyst in the Fenton reaction that potentiates oxygen toxicity by generating a wide range of free radical species, including hydroxyl radicals (·OH). The observation that patients with neurodegenerative diseases show a dramatic increase in their brain iron content, correlated with the production of reactive oxigen species in these areas of the brain, conceivably suggests that disturbances in brain iron homeostasis may contribute to the pathogenesis of these disorders. The aim of this review is to describe the chemical features of iron in human beings and iron induced toxicity in neurodegenerative diseases. Furthermore, the attention is focused on metal chelating drugs therapeutic strategies.     

MPEG-PCL Copolymeric Micelles for Encapsulation of Azithromycin

Macrolide antibiotics are lipophilic drugs with some limitations including low solubility, limited cellular permeation, patients discomfort, etc. With amphiphilic methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-PCL) copolymer and azithromycin (AZT) as drug carrier and model drug, AZT-loaded micelles were prepared via thin-membrane hydration method in order to overcome these limitations. Encapsulation efficiency of AZT-loaded micelles was 94.40% with good storage stability for 28 days, and AZT’s water solubility was enhanced to 944 μg/mL. Fourier transform infrared spectrum and x-ray diffraction analysis indicated that AZT was enveloped into the micelles in amorphous form due to its interaction with the copolymer. AZT’s in vitro release from the AZT-loaded micelles demonstrated a slow and continuous behavior when compared with raw AZT. The release dynamics was accorded with Weibull equation, meaning that release amount of AZT lowered with time and was proportional to remaining amount of drug in the AZT-loaded micelles. Korsmeyer-Peppas fitting result suggested that drug release process was a classical Fickian diffusion-controlled manner. With Staphylococcus aureus as bacterial strain, antibacterial activity of the AZT-loaded micelles displayed was comparable with raw AZT. In conclusion, MPEG-PCL should be a promising carrier for macrolide antibiotic delivery in treatment of bacterial infections.     

Selenite and ebselen supplementation attenuates <Emphasis Type="SmallCaps">d</Emphasis>-galactose-induced oxidative stress and increases expression of SELR and SEP15 in rat lens

Selenite and ebselen supplementation has been shown to possess anti-cataract potential in some experimental animal models of cataract, however, the underlying mechanisms remain unclear. The present study was designed to evaluate the anti-cataract effects and the underlying mechanisms of selenite and ebselen supplementation on galactose induced cataract in rats, a common animal model of sugar cataract. Transmission electron microscopy images of lens fiber cells (LFC) and lens epithelial cells (LEC) were observed in d-galactose-induced experimental cataractous rats treated with or without selenite and ebselen, also redox homeostasis and expression of proteins such as selenoprotein R (SELR), 15kD selenoprotein (SEP15), superoxide dismutase 1 (SOD1), catalase (CAT), β-crystallin protein, aldose reductase (AR) and glucose-regulated protein 78 (GRP78) were estimated in the lenses. The results showed that d-galactose injection injured rat lens and resulted in cataract formation; however, selenite and ebselen supplementation markedly alleviated ultrastructural injury of LFC and LEC. Moreover, selenite and ebselen supplementation could mitigate the oxidative damage in rat lens and increase the protein expressions of SELR, SEP15, SOD1, CAT and β-crystallin, as well as decrease the protein expressions of AR and GRP78. Taken together, these findings for the first time reveal the anti-cataract potential of selenite and ebselen in galactosemic cataract, and provide important new insights into the anti-cataract mechanisms of selenite and ebselen in sugar cataract.     

Sedimentary Factors are Key Predictors of Carbon Storage in SE Australian Saltmarshes

Although coastal vegetated ecosystems are widely recognised as important sites of long-term carbon (C) storage, substantial spatial variability exists in quantifications of these ‘blue C’ stocks. To better understand the factors behind this variability we investigate the relative importance of geomorphic and vegetation attributes to variability in the belowground C stocks of saltmarshes in New South Wales (NSW), southeast Australia. Based on the analysis of over 140 sediment cores, we report mean C stocks in the surface metre of sediments (mean ± SE = 164.45 ± 8.74 Mg C ha^?1) comparable to global datasets. Depth-integrated stocks (0–100 cm) were more than two times higher in fluvial (226.09 ± 12.37 Mg C ha^?1) relative to marine (104.54 ± 7.11) geomorphic sites, but did not vary overall between rush and non-rush vegetation structures. More specifically, sediment grain size was a key predictor of C density, which we attribute to the enhanced C preservation capacity of fine sediments and/or the input of stable allochthonous C to predominantly fine-grained, fluvial sites. Although C density decreased significantly with sediment depth in both geomorphic settings, the importance of deep C varied substantially between study sites. Despite modest spatial coverage, NSW saltmarshes currently hold approximately 1.2 million tonnes of C in the surface metre of sediment, although more C may have been returned to the atmosphere through habitat loss over the past approximately 200 years. Our findings highlight the suitability of using sedimentary classification to predict blue C hotspots for targeted conservation and management activities to reverse this trend.     

Landscape genetics of a tropical rescue pollinator

Pollination services are increasingly threatened by the loss and modification of natural habitats, posing a risk to the maintenance of both native plant biodiversity and agricultural production. In order to safeguard pollination services, it is essential to examine the impacts of habitat degradation on the population dynamics of key pollinators and identify potential “rescue pollinators” capable of persisting in these human-altered landscapes. Using a landscape genetic approach, we assessed the impact of landscape structure on genetic differentiation in the widely-distributed tropical stingless bee Trigona spinipes (Apidae: Meliponini) across agricultural landscape mosaics composed of coffee plantations and Atlantic forest fragments in southeastern Brazil. We genotyped 115 bees at 16 specific and highly polymorphic microsatellite loci, developed using next-generation sequencing. Our results reveal that T. spinipes is capable of dispersing across remarkably long distances, as we did not find genetic differentiation across a 200 km range, nor fine-scale spatial genetic structure. Furthermore, gene flow was not affected by forest cover, land cover, or elevation, indicating that reproductive individuals are able to disperse well through agricultural landscapes and across altitudinal gradients. We also found evidence of a recent population expansion, suggesting that this opportunistic stingless bee is capable of colonizing degraded habitats. Our results thus suggest that T. spinipes can persist in heavily-altered landscapes and can be regarded as a rescue pollinator, potentially compensating for the decline of other native pollinators in degraded tropical landscapes.     

Possible Role of the Glycogen Synthase Kinase-3 Signaling Pathway in Trimethyltin-Induced Hippocampal Neurodegeneration in Mice

Trimethyltin (TMT) is an organotin compound with potent neurotoxic effects characterized by neuronal destruction in selective regions, including the hippocampus. Glycogen synthase kinase-3 (GSK-3) regulates many cellular processes, and is implicated in several neurodegenerative disorders. In this study, we evaluated the therapeutic effect of lithium, a selective GSK-3 inhibitor, on the hippocampus of adult C57BL/6 mice with TMT treatment (2.6 mg/kg, intraperitoneal [i.p.]) and on cultured hippocampal neurons (12 days in vitro) with TMT treatment (5 µM). Lithium (50 mg/kg, i.p., 0 and 24 h after TMT injection) significantly attenuated TMT-induced hippocampal cell degeneration, seizure, and memory deficits in mice. In cultured hippocampal neurons, lithium treatment (0–10 mM; 1 h before TMT application) significantly reduced TMT-induced cytotoxicity in a dose-dependent manner. Additionally, the dynamic changes in GSK-3/β-catenin signaling were observed in the mouse hippocampus and cultured hippocampal neurons after TMT treatment with or without lithium. Therefore, lithium inhibited the detrimental effects of TMT on the hippocampal neurons in vivo and in vitro, suggesting involvement of the GSK-3/β-catenin signaling pathway in TMT-induced hippocampal cell degeneration and dysfunction.     

Ginsenoside Rd Attenuates Myocardial Ischemia/Reperfusion Injury via Akt/GSK-3β Signaling and Inhibition of the Mitochondria-Dependent Apoptotic Pathway

Evidence suggests Ginsenoside Rd (GSRd), a biologically active extract from the medical plant Panax Ginseng, exerts antioxidant effect, decreasing reactive oxygen species (ROS) formation. Current study determined the effect of GSRd on myocardial ischemia/reperfusion (MI/R) injury (a pathological condition where ROS production is significantly increased) and investigated the underlying mechanisms. The current study utilized an in vivo rat model of MI/R injury and an in vitro neonatal rat cardiomyocyte (NRC) model of simulated ischemia/reperfusion (SI/R) injury. Infarct size was measured by Evans blue/TTC double staining. NRC injury was determined by MTT and lactate dehydrogenase (LDH) leakage assay. ROS accumulation and apoptosis were assessed by flow cytometry. Mitochondrial membrane potential (MMP) was determined by 5, 5′, 6, 6′-tetrachloro-1, 1′, 3, 3′-tetrathylbenzimidazol carbocyanine iodide (JC-1). Cytosolic translocation of mitochondrial cytochrome c and expression of caspase-9, caspase-3, Bcl-2 family proteins, and phosphorylated Akt and GSK-3β were determined by western blot. Pretreatment with GSRd (50 mg/kg) significantly augmented rat cardiac function, as evidenced by increased left ventricular ejection fraction (LVEF) and ±dP/dt. GSRd reduced myocardial infarct size, apoptotic cell death, and blood creatine kinase/lactate dehydrogenase levels after MI/R. In NRCs, GSRd (10 µM) inhibited SI/R-induced ROS generation (P<0.01), decreased cellular apoptosis, stabilized the mitochondrial membrane potential (MMP), and attenuated cytosolic translocation of mitochondrial cytochrome c. GSRd inhibited activation of caspase-9 and caspase-3, increased the phosphorylated Akt and GSK-3β, and increased the Bcl-2/Bax ratio. Together, these data demonstrate GSRd mediated cardioprotective effect against MI/R–induced apoptosis via a mitochondrial-dependent apoptotic pathway.     

高通量测序技术及其在表观遗传学上的应用

DNA测序技术是现代生命科学研究的重要工具之一,而高通量测序技术在全基因组的研究中发挥着越来越重要的作用。简要回溯DNA测序技术的产生与发展,着重从PCR扩增测序和单分子测序两个方面全面描述了高通量测序中众多代表性的技术及直接测序技术,并从DNA甲基化、组蛋白修饰、非编码RNA调控等方面阐述了高通量测序技术在表观遗传学上的运用。     

湖南湖北两省H6亚型禽流感病毒表面基因的序列分析

2008年至2009年间,在湖南和湖北两省的活禽市场中分离到了14株H6亚型禽流感病毒,为了解这14株病毒之间的分子特征和差异,我们运用PCR和测序鉴定对这14株病毒的NA基因进行了分型,并对其表面基因HA和NA进行序列测定及序列分析.14株H6亚型病毒中,H6N2亚型12株,H6N6亚型2株.序列测定和进化分析结果显示:DK/HN/284的HA基因与其它13株的HA差异性较大,差异性达到19.4%～20.2%,其余13株毒同源性在94.2%～99.9%;N2亚型NA基因的同源性在91.1%～99.9%,差异性比较大;两株N6亚型NA基因同源性为89.5%,差异明显.这些数据表明:不同毒株呈现一定的地域性差异.与我国周边其它地区的H6亚型禽流感毒株序列进行比较发现,只有DK/HN/284的HA基因与香港早期的毒株可能有着共同的来源,其余都与香港和韩国等的毒株有着较大的差异性,并且各个毒株的HA基因上潜在的糖基化位点和受体结合位点也有所不同,这些数据表明,这些毒株表现出明显的异源性.     

Engineering bacteria toward tumor targeting for cancer treatment: current state and perspectives

One of the primary limitations of cancer therapy is lack of selectivity of therapeutic agents to tumor cells. Current efforts are focused on discovering and developing anticancer agents that selectively target only tumor cells and spare normal cells to improve the therapeutic index. The use of preferentially replicating bacteria as an oncolytic agent is one of the innovative approaches for the treatment of cancer. This is based on the observation that some obligate or facultative anaerobic bacteria are capable of multiplying selectively in tumors and inhibiting their growth. Meanwhile, bacteria have been demonstrated to colonize and destroy tumor, and have emerged as biological gene vectors to tumor microenvironment. To improve the efficacy and safety of the bacterial therapy, a further understanding of bacteria between with immune system is required. Furthermore, we want to evaluate how bacterial infection facilitates the “bystander effect” of chemotherapeutic agent and assess if it can be used for additional antitumor effect when combined with chemotherapy. This study may not only evaluate therapeutic efficacy of bacteria for the treatment of cancer but also elucidate the mechanisms underlying antitumor activities mediated by bacteria, which involve host immune responses and the cellular molecular responses.