Pluripotent Stem Cells Models for Huntington＇s Disease： Prospects and Challenges

Pluripotent cellular models have shown great promise in the study of a number of neurological disorders.Several advantages of using a stem cell model include the potential for cells to derive disease relevant neuronal cell types,providing a system for researchers to monitor disease progression during neurogenesis,along with serving as a platform for drug discovery.A number of stem cell derived models have been employed to establish in vitro research models of Huntington’s disease that can be used to investigate cellular pathology and screen for drug and cell-based therapies.Although some progress has been made,there are a number of challenges and limitations that must be overcome before the true potential of this research strategy is achieved.In this article we review current stem cell models that have been reported,as well as discuss the issues that impair these studies.We also highlight the prospective application of Huntington’s disease stem cell models in the development of novel therapeutic strategies and advancement of personalized medicine.     

Plants and Animals as Concept Generators for the Development of Biomimetic Cable Entry Systems

Many animals and plants have high potential to serve as concept generators for developing biomimetic materials and structures. We present some ideas based on structural and functional properties of plants and animals that led to the development of two types ofbiomimetic cable entry systems. Those systems have been realized on the level of functional demonstrators.     

Circular Dichroism and Fluorescence Spectroscopic Study of RNA-protein Folding Patterns in Human hnRNP A3 and Their Implications in Human Autoimmune Diseases

In human cells, the heterogeneous nuclear ribonucleoproteins (hnRNP) are represented by a group of polypeptides, with various molecular properties, comprizing the most abundant constituents of the cell nucleus. Autoantibodies to hnRNPs have been reported in patients suffering from different rheumatic dieseases since 1980s. Experimental evidence indicates that hnRNP complexes undergo substantial structural changes during mRNA formation and export. However, how this contributes to disease development still has to be elucidated. Here some preliminary physicochemical features of RNA-protein folding and stability patterns of newly characterized hnRNP A3 with further functional implications in development of systemic human autoimmune states are reported.     

nhe regulation and deregulation of Wnt signaling by PARK genes in health and disease

Wingless/Int （Wnt） signaling pathways are signal transduction mechanisms that have been widely studied In the field of embryogen- esis. Recent work has established a critical role for these pathways in brain development, especially of midbrain dopaminergic neu- rones, However, the fundamental importance of Wnt signaling for the normal function of mature neurones in the adult central nervous system has also lately been demonstrated by an increasing number of studies. Parkinson＇s disease （PD） is the second most prevalent neurodegenerative disease worldwide and is currently incurable. This debilitating disease is characterized by the progres- sive loss of a subset of midbrain dopaminergic neurones in the substontla nigm leadingto typical extrapyramidal motor symptoms. The aetiology of PD is poorly understood but work performed over the Last two decades has identified a growing number of genetic defects that underlie this condition. Herewe review a growing body of data connecting genes implicated in PD--most notablythe PARKgenes-- with Wnt signaling. These observations provide clues to the normal function of these proteins in healthy neurones and suggest that deregulated Wnt signaling might be a frequent pathomechanlsm leading to PD. These observations have implications for the patho- genesis and treatment of neurodegenerative diseases in general.     

Using induced pluripotent stem cells as a tool for modelling carcinogenesis

Cancer is a highly heterogeneous group of diseases that despite improved treatments remain prevalent accounting for over 14 million new cases and 8.2 million deaths per year. Studies into the process of carcinogenesis are limited by lack of appropriate models for the development and pathogenesis of the disease based on human tissues. Primary culture of patient samples can help but is difficult to grow for a number of tissues. A potential opportunity to overcome these barriers is based on the landmark study by Yamanaka which demonstrated the ability of four factors;Oct4, Sox2, Klf4, and c-Myc to reprogram human somatic cells in to pluripotency. These cells were termed induced pluripotent stem cells(i PSCs) and display characteristic properties of embryonic stem cells. This technique has a wide range of potential uses including disease modelling, drug testing and transplantation studies. Interestingly i PSCs also share a number of characteristics with cancer cells including self-renewal and proliferation, expression of stem cell markers and altered metabolism. Recently, i PSCs have been generated from a number of human cancer cell lines and primary tumour samples from a range of cancers in an attempt to recapitulate the development of cancer and interrogate the underlying mechanisms involved. This review will outline the similarities between the reprogramming process and carcinogenesis, and how these similarities have been exploited to generate i PSC models for a number of cancers.     

Dysfunction of Wnt signaling and synaptic ：lisassembly in neurodegenerative diseases

The molecular mechanisms that regulate synapse formation have been well documented. However, little is known about the factors that modulate synaptic stability. Synapse loss is an early and invariant feature of neurodegenerative diseases including Alzheimer＇s lAD） and Parkinson＇s disease. Notably, in AD the extent of synapse loss correlates with the severity of the disease. Hence, understanding the molecular mechanisms that underlie synaptic maintenance is crucial to reveal potential targets that will allow the development of ther- apies to protect synapses. Writs play a central role in the formation and function of neuronal circuits. Moreover, Wnt signaling compo- nents are expressed in the adult brain suggesting their role in synaptic maintenance in the adult. Indeed, blockade of Wnts with the Wnt antagonist Dickkopf-1 （Dkkl） causes synapse disassembly in mature hippocampal cells. Dkkl is elevated in brain biopsies from AD patients and animal models. Consistent with these findings, Amyloid-β （Aβ） oUgomers induce the rapid expression of Dkkl. Importantly, Dkkl neutralizing antibodies protect synapses against Aβ toxicity, indicating that Dkkl is required for Aβ-mediated synapse loss. In this review, we discuss the role of Wnt signaling in synapse maintenance in the adult brain, particularly in relation to synaptic loss in neurodegenerative diseases.     

Incorporating functional annotation information in prioritizing disease associated SNPs from genome wide association studies

With recent advances in genotyping and sequencing technologies,many disease susceptibility loci have been identified.However,much of the genetic heritability remains unexplained and the replication rate between independent studies is still low.Meanwhile,there have been increasing efforts on functional annotations of the entire human genome,such as the Encyclopedia of DNA Elements(ENCODE)project and other similar projects.It has been shown that incorporating these functional annotations to prioritize genome wide association signals may help identify true association signals.However,to our knowledge,the extent of the improvement when functional annotation data are considered has not been studied in the literature.In this article,we propose a statistical framework to estimate the improvement in replication rate with annotation data,and apply it to Crohn’s disease and DNase I hypersensitive sites.The results show that with cell line specific functional annotations,the expected replication rate is improved,but only at modest level.     

Neurotrophin treatment to promote regeneration after traumatic CNS injury

Neurotrophins are a family of growth factors that have been found to be central for the development and functional maintenance of the nervous system, participating in neurogenesis, neuronal survival, axonal growth, synaptogenesis and activity-dependent forms of synaptic plasticity. Trauma in the adult nervous system can disrupt the functional circuitry of neurons and result in severe functional deficits. The limitation of intrinsic growth capacity of adult nervous system and the presence of an inhospitable environment are the major hurdles for axonal regeneration of lesioned adult neurons. Neurotrophic factors have been shown to be excellent candidates in mediating neuronal repair and establishing functional circuitry via activating several growth signaling mechanisms including neuron-intrinsic regenerative programs. Here, we will review the effects of various neurotrophins in mediating recovery after injury to the adult spinal cord.     

Construction and Analysis of Functional Networks in the Gut Microbiome of Type 2 Diabetes Patients

Although networks of microbial species have been widely used in the analysis of 16S rRNA sequencing data of a microbiome, the construction and analysis of a complete microbial gene network are in general problematic because of the large number of microbial genes in metagenomics studies. To overcome this limitation, we propose to map microbial genes to functional units, includ-ing KEGG orthologous groups and the evolutionary genealogy of genes:Non-supervised Ortholo-gous Groups (eggNOG) orthologous groups, to enable the construction and analysis of a microbial functional network. We devised two statistical methods to infer pairwise relationships between microbial functional units based on a deep sequencing dataset of gut microbiome from type 2 dia-betes (T2D) patients as well as healthy controls. Networks containing such functional units and their significant interactions were constructed subsequently. We conducted a variety of analyses of global properties, local properties, and functional modules in the resulting functional networks. Our data indicate that besides the observations consistent with the current knowledge, this study provides novel biological insights into the gut microbiome associated with T2D.     

Compensation effects of coated cysteamine on meat quality,amino acid composition,fatty acid composition,mineral content in dorsal muscle and serum biochemical indices in finishing pigs offered reduced trace minerals diet

<正>Dear Editor.Trace mineral elements (ME) and amino acids have been demonstrated to be essential bioelements in animal nutrition.If there is a deficiency in ME,a number of biological functions in animals may be affected,including physical growth,psychomotor development,and immunity.Supplementation of pig diets with ME is known to improve the animals'growth,reproduction,and their immunity against oxidative stress and cell damage.Pigs that are fed diets with high-dose supplemental Zn or Cu have been shown to have an increased ADG and a decreased F:G ratio (Zhu et al.,     

Association of cholesteryl ester transfer protein with HDL particles reduces its proteolytic inactivation by mast cell chymase

Human atherosclerotic intima contains mast cells that secrete the neutral protease chymase into the intimal fluid, which also contains HDL-modifying proteins, such as cholesteryl ester transfer protein (CETP), in addition to abundant amounts of nascent discoidal HDL particles. Here, we studied chymase-dependent degradation of a) CETP isolated from human plasma and b) CETP-HDL complexes as well as the functional consequences of such degradations. Incubation with chymase caused a rapid cleavage of CETP, yielding a specific proteolytic pattern with a concomitant reduction in its cholesteryl ester transfer activity. These chymase-dependent effects were attenuated after CETP was complexed with HDL. This attenuation was more effective when CETP was complexed with HDL(3) and HDL(2) than with discoidal reconstituted high density lipoprotein (rHDL). Conversely, rHDL, but not spherical HDLs, was protected in such CETP complexes against functional inactivation by chymase. Thus, in contrast to the complexes of CETP with spherical HDLs, the ability of the CETP-rHDL complexes to promote cholesterol efflux from macrophage foam cells remained unchanged, despite treatment with chymase. In summary, complexation of CETP and HDL modifies their resistance to proteolytic inactivation: spherical HDLs protect CETP, and CETP protects discoidal HDL. These results suggest that in inflamed atherosclerotic intima, CETP, via its complexation with HDL, has a novel protective role in early steps of reverse cholesterol transport.     

Thematic Review Series: High Density Lipoprotein Structure,Function, and Metabolism: Cardioprotective functions of HDLs

Multiple human population studies have established the concentration of high density lipoprotein (HDL) cholesterol as an independent, inverse predictor of the risk of having a cardiovascular event. Furthermore, HDLs have several well-documented functions with the potential to protect against cardiovascular disease. These include an ability to promote the efflux of cholesterol from macrophages in the artery wall, inhibit the oxidative modification of low density lipoproteins (LDLs), inhibit vascular inflammation, inhibit thrombosis, promote endothelial repair, promote angiogenesis, enhance endothelial function, improve diabetic control, and inhibit hematopoietic stem cell proliferation. There are undoubtedly other beneficial functions of HDLs yet to be identified. The HDL fraction in human plasma is heterogeneous, consisting of several subpopulations of particles of varying size, density, and composition. The functions of the different HDL subpopulations remain largely unknown. Given that therapies that increase the concentration of HDL cholesterol have varying effects on the levels of specific HDL subpopulations, it is of great importance to understand how distribution of different HDL subpopulations contribute to the potentially cardioprotective functions of this lipoprotein fraction. This review summarizes current understanding of the relationship of HDL subpopulations to their cardioprotective properties and highlights the gaps in current knowledge regarding this important aspect of HDL biology.     

High-density lipoproteins protect endothelial cells from apoptosis induced by oxidized low-density lipoproteins

Summary Endothelial lesion by oxidized low-density liproproteins (LDL) is one of the first stages in the development of atherosclerosis. The effect of these lipoproteins can range from a functional lesion of the endothelium to death of the endothelial cells by apoptosis. High-density lipoproteins (HDL) are one of the factors which can have a protective effect against the development of atheromatous plaques. The aim of this study is to establish whether the death of endothelial cells by apoptosis induced by oxidized LDLs is prevented by HDLs. ECV304 endothelial cells and bovine aorta endothelial cells were incubated with native LDLs, oxidized LDLs, and a combination of both oxidized LDLs and HDLs. Oxidized LDLs caused a significant increase of mortality mainly by apoptosis. However, when HDLs were added together with oxidized LDLs the percentage of total mortality, the degree of lipoprotein oxidation in the medium, and the percentage of cells in apoptosis were all significantly decreased. HDLs protect against the cytotoxicity of oxidized LDLs possibly by preventing the propagation of the oxidative chain in these lipoproteins.Abbreviations LDL low-density lipoproteins - HDL high-density lipoproteins - BAEC bovine aortic endothelial cell - TBARS thiobarbituric acid-reactive substances     

HDL‐paraoxonase and Membrane Lipid Peroxidation: A Comparison Between Healthy and Obese Subjects

High‐density lipoproteins (HDLs) play a key role in the protection against oxidative damage. The enzyme paraoxonase‐1 (PON1) associated at the surface of HDL modulates the antioxidant and anti‐inflammatory role of HDL. Previous studies have demonstrated a decrease of serum PON in obese patients. The aim of this study was to investigate whether modifications of PON1 activity reflect in a different ability to protect and/or repair biological membranes against oxidative damage. Thirty obese patients at different grades of obesity (BMI ranging from 30.4 to 64.0 kg/m²) and 62 age‐matched control subjects (BMI <25 kg/m²) were included in the study. The ability of HDL to protect membranes against oxidative damage was studied using erythrocyte membranes oxidized with 2,2‐azobis(2 amidinopropane)dihydrochloride (AAPH) (ox‐membrane). The membrane lipid hydroperoxide levels were evaluated after the incubation of ox‐membranes in the absence or in the presence of HDL of controls or obese patients. The results confirm that HDL exerts a protective effect against lipid peroxidation. The ability of HDL to repair erythrocyte membranes was positively correlated with HDL‐PON activity and negatively correlated with lipid hydroperoxide levels in HDL. These results suggest that PON modulates the HDL repairing ability. HDL from obese patients repaired less efficiently erythrocyte membranes against oxidative damage with respect to HDL from healthy subjects. A negative relationship has been established between BMI of obese patients and the protective effect of HDL. In conclusion, the decrease of HDL‐PON activity and the lower HDL protective action against membrane peroxidation in obese patients could contribute to accelerate the cellular oxidative damage and arteriosclerosis in obesity.     

In vivo interactions of apoA-II, apoA-I, and hepatic lipase contributing to HDL structure and antiatherogenic functions

Studies with mice have revealed that increased expression of apolipoprotein A-II (apoA-II) results in elevations in high density lipoprotein (HDL), the formation of larger HDL, and the development of early atherosclerosis. We now show that the increased size of HDL results in part from an inhibition of the ability of hepatic lipase (HL) to hydrolyze phospholipids and triglycerides in the HDL and that the ratio of apoA-I to apoA-II determines HDL functional and antiatherogenic properties. HDL from apoA-II transgenic mice was relatively resistant to the action of HL in vitro. To test whether HL and apoA-II influence HDL size independently, combined apoA-II transgenic/HL knockout (HLko) mice were examined. These mice had HDL similar in size to apoA-II transgenic mice and HLko mice, suggesting that they do not increase HDL side by independent mechanisms. Overexpression of apoA-I from a transgene reversed many of the effects of apoA-II overexpression, including the ability of HDL to serve as a substrate for HL. Combined apoA-I/apoA-II transgenic mice exhibited significantly less atherosclerotic lesion formation than did apoA-II transgenic mice. These results were paralleled by the effects of the transgenes on the ability of HDL to protect against the proinflammatory effects of oxidized low density lipoprotein (LDL). Whereas nontransgenic HDL protected against oxidized LDL induction of adhesion molecules in endothelial cells, HDL from apoA-II transgenic mice was proinflammatory. HDL from combined apoA-I/apoA-II transgenic mice was equally as protective as HDL from nontransgenic mice. Our data suggest that as the ratio of apoA-II to apoA-I is increased, the HDL become larger because of inhibition of HL, and lose their antiatherogenic properties.     

Crystal Structure of Δ(185–243)ApoA-I Suggests a Mechanistic Framework for the Protein Adaptation to the Changing Lipid Load in Good Cholesterol: From Flatland to Sphereland via Double Belt,Belt Buckle,Double Hairpin and Trefoil/Tetrafoil

Apolipoprotein A-I (apoA-I) is the major protein of plasma high-density lipoproteins (HDLs), macromolecular assemblies of proteins and lipids that remove cell cholesterol and protect against atherosclerosis. HDL heterogeneity, large size (7.7–12 nm), and ability to exchange proteins have prevented high-resolution structural analysis. Low-resolution studies showed that two apoA-I molecules form an antiparallel α-helical “double belt” around an HDL particle. The atomic-resolution structure of the C-terminal truncated lipid-free Δ(185–243)apoA-I, determined recently by Mei and Atkinson, provides unprecedented new insights into HDL structure–function. It allows us to propose a molecular mechanism for the adaptation of the full-length protein to increasing lipid load during cholesterol transport. ApoA-I conformations on small, midsize, and large HDLs are proposed based on the tandem α-helical repeats and the crystal structure of Δ(185–243)apoA-I and are validated by comparison with extensive biophysical data reported by many groups. In our models, the central half of the double belt (“constant” segment 66–184) is structurally conserved while the N- and C-terminal half (“variable” segments 1–65 and 185–243) rearranges upon HDL growth. This includes incremental unhinging of the N-terminal bundle around two flexible regions containing G39 and G65 to elongate the belt, along with concerted swing motion of the double belt around G65–P66 and G185–G186 hinges that are aligned on various-size particles, to confer two-dimensional surface curvature to spherical HDLs. The proposed conformational ensemble integrates and improves several existing HDL models. It helps provide a structural framework necessary to understand functional interactions with over 60 other HDL-associated proteins and, ultimately, improve the cardioprotective function of HDL.     

Apolipoprotein M is required for prebeta-HDL formation and cholesterol efflux to HDL and protects against atherosclerosis

High-density lipoproteins (HDLs) are considered antiatherogenic because they mediate reverse cholesterol transport from the periphery to the liver for excretion and degradation. Here we show that mice deficient in apolipoprotein M (apoM), a component of the HDL particle, accumulated cholesterol in large HDL particles (HDL(1)) while the conversion of HDL to prebeta-HDL was impaired. Accordingly, apoM-deficient mice lacked prebeta-HDL, a subclass of lipid-poor apolipoproteins that serves as a key acceptor of peripheral cellular cholesterol. This deficiency led to a markedly reduced cholesterol efflux from macrophages to apoM-deficient HDL compared to normal HDL in vitro. Overexpression of apoM in Ldlr(-/-) mice protected against atherosclerosis when the mice were challenged with a cholesterol-enriched diet, showing that apoM is important for the formation of prebeta-HDL and cholesterol efflux to HDL, and thereby inhibits formation of atherosclerotic lesions.     

Effect of high-density lipoproteins on the expression of adhesion molecules in endothelial cells

There are several potential mechanisms by which HDLs protect against atherosclerosis. One relates to the ability of HDLs to promote the efflux of cholesterol from macrophages. Another is the ability of HDLs to inhibit one of the earliest events in the development of atherosclerosis, namely the expression of vascular cell adhesion molecules in activated endothelial cells. This property has been reported in vitro in studies with both native and reconstituted HDLs. The inhibitory activity of reconstituted HDLs is influenced by the phospholipid composition of the particles. An inhibition of endothelial cell adhesion molecule expression has also been observed in some (but not all) studies conducted in vivo in mice and pigs. The mechanism of this potentially anti-atherogenic effect of HDLs remains uncertain, as does its contribution to the cardioprotective effects of HDLs in vivo.     

Does paraoxonase play a role in susceptibility to cardiovascular disease?

Human serum paraoxonase (PON1) is an esterase that is bound to high-density lipoproteins (HDLs). It can hydrolyze organophosphates and its activity is inversely related to atherosclerosis. Some studies also suggest that a relationship exists between polymorphisms of the gene that encodes paraoxonase and coronary heart disease (CHD), whereas other studies, in different populations, have not found such an association. One mechanism by which certain PON1 allozymes might protect against atherosclerosis is by inhibition of the oxidation of HDL and low-density lipoprotein (LDL). Experimental studies suggest that this protection is associated with the ability of PON1 to hydrolyze specific lipid peroxides in oxidized lipoproteins. Interventions that preserve or enhance PON1 activity, as well as manipulations of PON1 polymorphisms, might help delay the onset of CHD.     

New insights into the emerging effects of inflammatory response on HDL particles structure and function

According to the increasing results, it has been well-demonstrated that the chronic inflammatory response, including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel disease are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism whereby inflammatory response up-regulates the risk of cardio-metabolic disorder disease is multifactorial; furthermore, the alterations in high density lipoprotein (HDL) structure and function which occur under the inflammatory response could play an important modulatory function. On the other hand, the serum concentrations of HDL cholesterol (HDL-C) have been shown to be reduced significantly under inflammatory status with remarked alterations in HDL particles. Nevertheless, the potential mechanism whereby the inflammatory response reduces serum HDL-C levels is not simply defined but reduces apolipoprotein A1 production. The alterations in HDL structure mediated by the inflammatory response has been also confirmed to decrease the ability of HDL particle to play an important role in reverse cholesterol transport and protect the LDL particles from oxidation. Recently, it has been shown that under the inflammatory condition, diverse alterations in HDL structure could be observed which lead to changes in HDL function. In the current review, the emerging effects of inflammatory response on HDL particles structure and function are well-summarized to elucidate the potential mechanism whereby different inflammatory status modulates the pathogenic development of dyslipidemia.