Stretching DNA with optical tweezers

Force-extension (F-x) relationships were measured for single molecules of DNA under a variety of buffer conditions, using an optical trapping interferometer modified to incorporate feedback control. One end of a single DNA molecule was fixed to a coverglass surface by means of a stalled RNA polymerase complex. The other end was linked to a microscopic bead, which was captured and held in an optical trap. The DNA was subsequently stretched by moving the coverglass with respect to the trap using a piezo-driven stage, while the position of the bead was recorded at nanometer-scale resolution. An electronic feedback circuit was activated to prevent bead movement beyond a preset clamping point by modulating the light intensity, altering the trap stiffness dynamically. This arrangement permits rapid determination of the F-x relationship for individual DNA molecules as short as -1 micron with unprecedented accuracy, subjected to both low (approximately 0.1 pN) and high (approximately 50 pN) loads: complete data sets are acquired in under a minute. Experimental F-x relationships were fit over much of their range by entropic elasticity theories based on worm-like chain models. Fits yielded a persistence length, Lp, of approximately 47 nm in a buffer containing 10 mM Na1. Multivalent cations, such as Mg2+ or spermidine 3+, reduced Lp to approximately 40 nm. Although multivalent ions shield most of the negative charges on the DNA backbone, they did not further reduce Lp significantly, suggesting that the intrinsic persistence length remains close to 40 nm. An elasticity theory incorporating both enthalpic and entropic contributions to stiffness fit the experimental results extremely well throughout the full range of extensions and returned an elastic modulus of approximately 1100 pN.

Force and velocity measured for single molecules of RNA polymerase

RNA polymerase (RNAP) moves along DNA while carrying out transcription, acting as a molecular motor. Transcriptional velocities for single molecules of Escherichia coli RNAP were measured as progressively larger forces were applied by a feedback-controlled optical trap. The shapes of RNAP force-velocity curves are distinct from those of the motor enzymes myosin or kinesin, and indicate that biochemical steps limiting transcription rates at low loads do not generate movement. Modeling the data suggests that high loads may halt RNAP by promoting a structural change which moves all or part of the enzyme backwards through a comparatively large distance, corresponding to 5 to 10 base pairs. This contrasts with previous models that assumed force acts directly upon a single-base translocation step.

Transcription against an applied force

The force produced by a single molecule of Escherichia coli RNA polymerase during transcription was measured optically. Polymerase immobilized on a surface was used to transcribe a DNA template attached to a polystyrene bead 0.5 micrometer in diameter. The bead position was measured by interferometry while a force opposing translocation of the polymerase along the DNA was applied with an optical trap. At saturating nucleoside triphosphate concentrations, polymerase molecules stalled reversibly at a mean applied force estimated to be 14 piconewtons. This force is substantially larger than those measured for the cytoskeletal motors kinesin and myosin and exceeds mechanical loads that are estimated to oppose transcriptional elongation in vivo. The data are consistent with efficient conversion of the free energy liberated by RNA synthesis into mechanical work.

TLR2 and TLR4 in autoimmune diseases: a comprehensive review

Autoimmune diseases are immune disorders characterized by T cell hyperactivity and B cell overstimulation leading to overproduction of autoantibodies. Although the pathogenesis of various autoimmune diseases remains to be elucidated, environmental factors have been thought to contribute to the initiation and maintenance of auto-respond inflammation. Toll-like receptors (TLRs) are pattern recognition receptors belonging to innate immunity that recognize and defend invading microorganisms. Besides these exogenous pathogen-associated molecular patterns, TLRs can also bind with damage-associated molecular patterns produced under strike or by tissue damage or cells apoptosis. It is believed that TLRs build a bridge between innate immunity and autoimmunity. There are five adaptors to TLRs including MyD88, TRIF, TIRAP/MAL, TRAM, and SARM. Upon activation, TLRs recruit specific adaptors to initiate the downstream signaling pathways leading to the production of inflammatory cytokines and chemokines. Under certain circumstances, ligation of TLRs drives to aberrant activation and unrestricted inflammatory responses, thereby contributing to the perpetuation of inflammation in autoimmune diseases. In the past, most studies focused on the intracellular TLRs, such as TLR3, TLR7, and TLR9, but recent studies reveal that cell surface TLRs, especially TLR2 and TLR4, also play an essential role in the development of autoimmune diseases and afford multiple therapeutic targets. In this review, we summarized the biological characteristics, signaling mechanisms of TLR2/4, the negative regulators of TLR2/4 pathway, and the pivotal function of TLR2/4 in the pathogenesis of autoimmune diseases including rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, Sjogren's syndrome, psoriasis, multiple sclerosis, and autoimmune diabetes.

MicroRNA-126 regulates DNA methylation in CD4+ T cells and contributes to systemic lupus erythematosus by targeting DNA methyltransferase 1

OBJECTIVE

To identify microRNA genes with abnormal expression in the CD4+ T cells of patients with systemic lupus erythematosus (SLE) and to determine the role of microRNA-126 (miR-126) in the etiology of SLE.

METHODS

MicroRNA expression patterns in CD4+ T cells from patients with SLE and healthy control subjects were analyzed by microRNA microarray and stem loop quantitative polymerase chain reaction (qPCR). Luciferase reporter gene assays were performed to identify miR-126 targets. Dnmt1, CD11a, and CD70 messenger RNA and protein levels were determined by real-time qPCR, Western blotting, and flow cytometry. CD11a, CD70, and EGFL7 promoter methylation levels were detected by bisulfite sequencing. IgG levels in T cell-B cell cocultures were determined by enzyme-linked immunosorbent assay.

RESULTS

The expression of 11 microRNA was significantly increased or decreased in CD4+ T cells from patients with SLE relative to that in CD4+ T cells from control subjects. Among these, miR-126 was up-regulated, and its degree of overexpression was inversely correlated with Dnmt1 protein levels. We demonstrated that miR-126 directly inhibits Dnmt1 translation via interaction with its 3'-untranslated region, and that overexpression of miR-126 in CD4+ T cells can significantly reduce Dnmt1 protein levels. The overexpression of miR-126 in CD4+ T cells from healthy donors caused the demethylation and up-regulation of genes encoding CD11a and CD70, thereby causing T cell and B cell hyperactivity. The inhibition of miR-126 in CD4+ T cells from patients with SLE had the opposite effects. Expression of the miR-126 host gene EGFL7 was also up-regulated in CD4+ T cells from patients with SLE, possibly in a hypomethylation-dependent manner.

CONCLUSION

Our data suggest that miR-126 regulates DNA methylation in CD4+ T cells and contributes to T cell autoreactivity in SLE by directly targeting Dnmt1.

Myosin V orientates the mitotic spindle in yeast

Coordination of spindle orientation with the axis of cell division is an essential process in all eukaryotes. In addition to ensuring accurate chromosomal segregation, proper spindle orientation also establishes differential cell fates and proper morphogenesis. In both animal and yeast cells, this process is dependent on cytoplasmic microtubules interacting with the cortical actin-based cytoskeleton, although the motive force was unknown. Here we show that yeast Myo2, a myosin V that translocates along polarized actin cables into the bud, orientates the spindle early in the cell cycle by binding and polarizing the microtubule-associated protein Kar9 (refs 7-9). The tail domain of Myo2 that binds Kar9 also interacts with secretory vesicles and vacuolar elements, making it a pivotal component of yeast cell polarization.

The electrophysiological mechanism of ventricular arrhythmias in the long QT syndrome. Tridimensional mapping of activation and recovery patterns

We have previously developed a canine in vivo model of the long QT syndrome (LQTS) using the neurotoxin anthopleurin A (AP-A), which acts by slowing sodium channel inactivation. The recent discovery of a genetic mutation in the cardiac sodium channel in some patients with the congenital LQTS, resulting in abnormal gating behavior similar to sodium channels exposed to AP-A, provides a strong endorsement of this animal model as a valid surrogate to the clinical syndrome of LQTS. In the present study, we conducted high-resolution tridimensional isochronal mapping of both activation and repolarization patterns in puppies exposed to AP-A that developed LQTS and polymorphic ventricular tachyarrhythmias (VTs). To map repolarization, we measured activation-recovery intervals (ARIs) using multiple unipolar extracellular electrograms. We demonstrated, for the first time in vivo, the existence of spatial dispersion of repolarization in the ventricular wall and differences in regional recovery in response to cycle-length changes that were markedly exaggerated after AP-A administration. Analysis of tridimensional activation patterns showed that the initial beat of polymorphic VT consistently arose as focal activity from a subendocardial site, whereas subsequent beats were due to successive subendocardial focal activity, reentrant excitation, or a combination of both mechanisms. Reentrant excitation was due to infringement of a focal activity on the spatial dispersion of repolarization, resulting in functional conduction block and circulating wave fronts. The polymorphic QRS configuration of VT in the LQTS was due to either changing the site of origin of focal activity, resulting in varying activation patterns, or varying orientations of circulating wave fronts.

Opioid activation of toll-like receptor 4 contributes to drug reinforcement

Opioid action was thought to exert reinforcing effects solely via the initial agonism of opioid receptors. Here, we present evidence for an additional novel contributor to opioid reward: the innate immune pattern-recognition receptor, toll-like receptor 4 (TLR4), and its MyD88-dependent signaling. Blockade of TLR4/MD2 by administration of the nonopioid, unnatural isomer of naloxone, (+)-naloxone (rats), or two independent genetic knock-outs of MyD88-TLR4-dependent signaling (mice), suppressed opioid-induced conditioned place preference. (+)-Naloxone also reduced opioid (remifentanil) self-administration (rats), another commonly used behavioral measure of drug reward. Moreover, pharmacological blockade of morphine-TLR4/MD2 activity potently reduced morphine-induced elevations of extracellular dopamine in rat nucleus accumbens, a region critical for opioid reinforcement. Importantly, opioid-TLR4 actions are not a unidirectional influence on opioid pharmacodynamics, since TLR4(-/-) mice had reduced oxycodone-induced p38 and JNK phosphorylation, while displaying potentiated analgesia. Similar to our recent reports of morphine-TLR4/MD2 binding, here we provide a combination of in silico and biophysical data to support (+)-naloxone and remifentanil binding to TLR4/MD2. Collectively, these data indicate that the actions of opioids at classical opioid receptors, together with their newly identified TLR4/MD2 actions, affect the mesolimbic dopamine system that amplifies opioid-induced elevations in extracellular dopamine levels, therefore possibly explaining altered opioid reward behaviors. Thus, the discovery of TLR4/MD2 recognition of opioids as foreign xenobiotic substances adds to the existing hypothesized neuronal reinforcement mechanisms, identifies a new drug target in TLR4/MD2 for the treatment of addictions, and provides further evidence supporting a role for central proinflammatory immune signaling in drug reward.

Quenching of CdSe quantum dot emission, a new approach for biosensing

The emission of CdSe quantum dots linked to the 5'-end of a DNA sequence is efficiently quenched by hybridisation with a complementary DNA strand with a gold nanoparticle attached at the 3'-end; contact of the quantum dot and gold nanoparticle occurs.

Spindles, mitochondria and redox potential in ageing oocytes

Studies of human oocytes obtained from women of advanced reproductive age revealed that spindles are frequently aberrant, with chromosomes sometimes failing to align properly at the equator during meiosis I and II. Chromosomal analyses of donated and spare human oocytes and cytogenetic and molecular studies on the origin of trisomies collectively suggest that errors in chromosome segregation during oogenesis increase with advancing maternal age and as the menopause approaches. Disturbances in the fidelity of chromosome segregation, especially at anaphase I, leading to aneuploidy are prime causes of reduced developmental competence of embryos in assisted reproduction, as well as being responsible for the genesis of genetic disease. This review provides an overview of spindle formation and chromosome behaviour in mammalian oocytes. Evidence of a link between abnormal mitochondrial function in oocytes and somatic follicular cells, and finally disturbances in chromosome cohesion and segregation, and cell cycle control in aged mammalian oocytes, are also discussed.

Ethanol-inducible cytochrome P4502E1: genetic polymorphism, regulation, and possible role in the etiology of alcohol-induced liver disease

In the Tsukamoto-French model, ethanol causes an important 10-20-fold induction of ethanol-inducible cytochrome P4502E1 (CYP2E1), mediated through enzyme stabilization and increased rate of gene transcription. The CYP2E1 induction results in a pronounced increase in the rate of NADPH-dependent microsomal lipid peroxidation, an elevation which is not seen after simultaneous administration of the CYP2E1 inhibitor diallylsulfide. Increased amounts of lipid peroxides are seen in plasma and red blood cells of both rats and humans during high ethanol intake. A mechanism for ethanol-dependent liver damage is proposed which involves the CYP2E1-dependent lipid peroxide formation, either directly by its capability to induce NADPH-dependent peroxidation in the microsomal membranes or indirectly by a hypoxia-mediated transformation of xanthine dehydrogenase to xanthine oxidase, in activation of Ito cells and Kupffer cells to yield cytokine and collagen production. The CYP2E1 gene is polymorphic among Caucasians. Four different unrelated or partially linked polymorphisms have been observed. One polymorphism in the 5'-flanking region has been described to be associated with altered enzyme expression in vitro, and the rare allele was found to be less frequent among Swedish patients having lung cancer when compared to two different control groups. Another polymorphism, detectable with Dra I restriction endonuclease fragment length polymorphism (RFLP), was localized to intron 6, and the rare allele was less common among Italian alcoholics with clinical signs of liver cirrhosis, as compared to controls. Several other mutations in the CYP2E1 gene were found to be associated with this allele. However, further research is needed to relate the CYP2E1 gene polymorphism with incidence of liver cirrhosis.

Alginate lyase: Review of major sources and classification, properties, structure-function analysis and applications

Alginate lyases catalyze the degradation of alginate, a complex copolymer of α-L-guluronate and its C5 epimer β-D-mannuronate. The enzymes have been isolated from various kinds of organisms with different substrate specificities, including algae, marine mollusks, marine and terrestrial bacteria, and some viruses and fungi. With the progress of structural biology, many kinds of alginate lyases of different polysaccharide lyases families have been characterized by obtaining crystal structures, and the catalytic mechanism has also been elucidated. Combined with various studies, we summarized the source, classification and properties of the alginate lyases from different polysaccharide lyases families. The relationship between substrate specificity and protein sequence was also investigated.

A novel G protein-coupled receptor for gonadotropin-inhibitory hormone in the Japanese quail (Coturnix japonica): identification, expression and binding activity

We recently identified a novel hypothalamic dodecapeptide inhibiting gonadotropin release in the Japanese quail (Coturnix japonica). This novel peptide was therefore named gonadotropin-inhibitory hormone (GnIH). The GnIH precursor encoded one GnIH and two GnIH-related peptides (GnIH-RP-1 and GnIH-RP-2) that shared the same C-terminal motif, Leu-Pro-Xaa-Arg-Phe-NH(2) (Xaa=Leu or Gln; LPXRF-amide peptides). Identification of the receptor for GnIH is crucial to elucidate the mode of action of GnIH. We therefore identified the receptor for GnIH in the quail diencephalon and characterized its expression and binding activity. We first cloned a cDNA encoding a putative GnIH receptor by a combination of 3' and 5' rapid amplification of cDNA ends (RACE) using PCR primers designed from the sequence for the receptor for rat RF-amide-related peptide (RFRP), an orthologous peptide of GnIH. Hydrophobic analysis revealed that the putative GnIH receptor possessed seven transmembrane domains, indicating a new member of the G protein-coupled receptor superfamily. The crude membrane fraction of COS-7 cells transfected with the putative GnIH receptor cDNA specifically bound to GnIH and GnIH-RPs in a concentration-dependent manner. Scatchard plot analysis of the binding showed that the identified GnIH receptor possessed a single class of high-affinity binding sites (K(d)=0.752 nM, B(max)=24.8 fmol/mg protein). Southern blotting analysis of reverse transcriptase-mediated PCR products revealed the expression of GnIH receptor mRNA in the pituitary gland and several brain regions including diencephalon in the quail. These results suggest that GnIH acts directly on the pituitary via GnIH receptor to inhibit gonadotropin release. GnIH may also act on the hypothalamus to inhibit gonadotropin-releasing hormone release.

Decreased microRNA-142-3p/5p expression causes CD4+ T cell activation and B cell hyperstimulation in systemic lupus erythematosus

OBJECTIVE

To examine the role of microRNA-142-3p/5p (miR-142-3p/5p) in the development of autoimmunity in patients with systemic lupus erythematosus (SLE).

METHODS

MicroRNA-142-3p/5p expression levels were determined by real-time quantitative polymerase chain reaction, and potential target genes were verified using luciferase reporter gene assays. The effects of miR-142-3p/5p on T cell function were assessed by transfection with miR-142-3p/5p inhibitors or mimics. Histone modifications and methylation levels within a putative regulatory region of the miR-142 locus were detected by chromatin immunoprecipitation assay and bisulfite sequencing, respectively.

RESULTS

We confirmed that miR-142-3p and miR-142-5p were significantly down-regulated in SLE CD4+ T cells compared with healthy controls and observed that miR-142-3p/5p levels were inversely correlated with the putative SLE-related targets signaling lymphocytic activation molecule-associated protein (SAP), CD84, and interleukin-10 (IL-10). We demonstrated that miR-142-3p and miR-142-5p directly inhibit SAP, CD84, and IL-10 translation, and that reduced miR-142-3p/5p expression in CD4+ T cells can significantly increase protein levels of these target genes. Furthermore, inhibiting miR-142-3p/5p in healthy donor CD4+ T cells caused T cell overactivation and B cell hyperstimulation, whereas overexpression of miR-142-3p/5p in SLE CD4+ T cells had the opposite effect. We also observed that the decrease in miR-142 expression in SLE CD4+ T cells correlated with changes to histone modifications and DNA methylation levels upstream of the miR-142 precursor sequence.

CONCLUSION

The results of this study indicate that reduced expression of miR-142-3p/5p in the CD4+ T cells of patients with SLE causes T cell activity and B cell hyperstimulation.

The critical role of epigenetics in systemic lupus erythematosus and autoimmunity

One of the major disappointments in human autoimmunity has been the relative failure on genome-wide association studies to provide "smoking genetic guns" that would explain the critical role of genetic susceptibility to loss of tolerance. It is well known that autoimmunity refers to the abnormal state that the dysregulated immune system attacks the healthy cells and tissues due to the loss of immunological tolerance to self-antigens. Its clinical outcomes are generally characterized by the presence of autoreactive immune cells and (or) the development of autoantibodies, leading to various types of autoimmune disorders. The etiology and pathogenesis of autoimmune diseases are highly complex. Both genetic predisposition and environmental factors such as nutrition, infection, and chemicals are implicated in the pathogenic process of autoimmunity, however, how much and by what mechanisms each of these factors contribute to the development of autoimmunity remain unclear. Epigenetics, which refers to potentially heritable changes in gene expression and function that do not involve alterations of the DNA sequence, has provided us with a brand new key to answer these questions. In the recent decades, increasing evidence have demonstrated the roles of epigenetic dysregulation, including DNA methylation, histone modification, and noncoding RNA, in the pathogenesis of autoimmune diseases, especially systemic lupus erythematosus (SLE), which have shed light on a new era for autoimmunity research. Notably, DNA hypomethylation and reactivation of the inactive X chromosome are two epigenetic hallmarks of SLE. We will herein discuss briefly how genetic studies fail to completely elucidate the pathogenesis of autoimmune diseases and present a comprehensive review on landmark epigenetic findings in autoimmune diseases, taking SLE as an extensively studied example. The epigenetics of other autoimmune diseases such as rheumatic arthritis, systemic sclerosis and primary biliary cirrhosis will also be summarized. Importantly we emphasize that the stochastic processes that lead to DNA modification may be the lynch pins that drive the initial break in tolerance.

Induction of autophagy via the ROS-dependent AMPK-mTOR pathway protects copper-induced spermatogenesis disorder

Copper (Cu) is a necessary micronutrient at lower concentration, while excessive Cu exposure or Cu homeostasis disorders can lead to toxicity. The mechanism of male reproductive toxicity induced by Cu is still unknown. This study aims to investigate whether autophagy plays an important role in copper-induced spermatogenesis disorder in vivo and vitro. The present study showed that copper sulfate (CuSO₄) might significantly promote autophagy level in the testis and mouse-derived spermatogonia cell line GC-1 spg cells. Concurrently, CuSO₄ could induce autophagy via AMPK-mTOR pathway that downregulated p-mTOR/mTOR and subsequently upregulated p-AMPKα/AMPKα as well as p-ULK1/ULK1. In the meanwhile, CuSO₄ treatment could also increase expression levels of the autophagy-related proteins. Then, the role of oxidative stress in CuSO₄-induced autophagy was investigated. The findings demonstrated that oxidative stress inhibitor (NAC) attenuated CuSO₄-induced autophagy in vivo and vitro, reversing the activation for AMPK-mTOR pathway. Additionally, the study also investigated how autophagy worked under the spermatogenesis disorder induced by CuSO₄. Inhibition of autophagy could decrease cell viability, and enhance the ROS accumulation and apoptosis in the GC-1 cells, meanwhile, the spermatogenesis disorder, oxidative stress and histopathological changes were increased in the testis. Furthermore, co-treatment with the apoptosis inhibitor (Z-VAD-FMK) could decrease the spermatogenesis disorder but not influence autophagy. Besides, the crosslink between autophagy and ferroptosis were also measured, the data showed that inhibition of autophagy could suppress CuSO₄-induced ferroptosis in in vivo and vitro. Altogether, abovementioned results indicated that CuSO₄ induced autophagy via oxidative stress-dependent AMPK-mTOR pathway in the GC-1 cells and testis, and autophagy activation possibly led to the generation of protection mechanism through oxidative damage and apoptosis inhibition, however, autophagy also aggravate CuSO₄ toxicology through promoting ferroptosis. Overall, autophagy plays a positive role for attenuating CuSO₄-induced testicular damage and spermatogenesis disorder. Our study provides a possible targeted therapy for Cu overload-induced reproduction toxicology.

The effects of particle size and surface coating on the cytotoxicity of nickel ferrite

The safety and toxicity of nanoparticles are of growing concern despite their significant scientific interests and promising potentials in many applications. The properties of nanoparticles depend not only on the size but also the structure, microstructure and surface coating. These in turn are controlled by the synthesis and processing conditions. The dependence of cytotoxicity on particle size and on the presence of oleic acid as surfactant on nickel ferrite particles were investigated in vitro using the Neuro-2A cell line as a model. For nickel ferrite particles without oleic acid prepared by ball milling, cytotoxicity was independent of particle size within the given mass concentrations and surface areas accessible to the cells. For nickel ferrite particles coated with oleic acid prepared by the polyol method, the cytotoxicity significantly increased when one or two layers of oleic acid were deposited. Large particles (150+/-50 nm diameter) showed a higher cytotoxicity than smaller particles (10+/-3 nm diameter).

Pharmacological characterization of the opioid inactive isomers (+)-naltrexone and (+)-naloxone as antagonists of toll-like receptor 4

BACKGROUND AND PURPOSE

The toll-like receptor TLR4 is involved in neuropathic pain and in drug reward and reinforcement. The opioid inactive isomers (+)-naltrexone and (+)-naloxone act as TLR4 antagonists, reversing neuropathic pain and reducing opioid and cocaine reward and reinforcement. However, how these agents modulate TLR4 signalling is not clear. Here, we have elucidated the molecular mechanism of (+)-naltrexone and (+)-naloxone on TLR4 signalling.

EXPERIMENTAL APPROACH

BV-2 mouse microglial cell line, primary rat microglia and primary rat peritoneal macrophages were treated with LPS and TLR4 signalling inhibitors. Effects were measured using Western blotting, luciferase reporter assays, fluorescence microscopy and ELISA KEY RESULTS: (+)-Naltrexone and (+)-naloxone were equi-potent inhibitors of the LPS-induced TLR4 downstream signalling and induction of the pro-inflammatory factors NO and TNF-α. Similarly, (+)-naltrexone or (+)-naloxone inhibited production of reactive oxygen species and increased microglial phagocytosis, induced by LPS. However, (+)-naltrexone and (+)-naloxone did not directly inhibit the increased production of IL-1β, induced by LPS. The drug interaction of (+)-naloxone and (+)-naltrexone was additive. (+)-Naltrexone or (+)-naloxone inhibited LPS-induced activation of IFN regulatory factor 3 and production of IFN-β. However, they did not inhibit TLR4 signalling via the activation of either NF-κB, p38 or JNK in these cellular models.

CONCLUSIONS AND IMPLICATIONS

(+)-Naltrexone and (+)-naloxone were TRIF-IFN regulatory factor 3 axis-biased TLR4 antagonists. They blocked TLR4 downstream signalling leading to NO, TNF-α and reactive oxygen species. This pattern may explain, at least in part, the in vivo therapeutic effects of (+)-naltrexone and (+)-naloxone.

Extracellular hmgb1 functions as an innate immune-mediator implicated in murine cardiac allograft acute rejection

Hmgb1, an evolutionarily conserved chromosomal protein, was recently re-discovered to be an innate immune-mediator contributing to both innate and adaptive immune responses. Here, we show a pivotal role for Hmgb1 in acute allograft rejection in a murine cardiac transplantation model. Extracellular Hmgb1 was found to be a potent stimulator for adaptive immune responses. Hmgb1 can be either passively released from damaged cells after organ harvest and ischemia/reperfusion insults, or actively secreted by allograft infiltrated immune cells. After transplantation, allografts show a significant temporal up-regulation of Hmgb1 expression accompanied by inflammatory infiltration, a consequence of graft destruction. These data suggest the involvement of Hmgb1 in acute allograft rejection. In line with these observations, treatment of recipients with rA-box, a specific blockade for endogenous Hmgb1, significantly prolonged cardiac allograft survival as compared to those recipients treated with either rGST or control vehicle. The enhanced graft survival is associated with reduced allograft expression of TNFalpha, IFNgamma and Hmgb1 and impaired Th1 immune response.

Mimicking the Key Functions of Photosystem II in Artificial Photosynthesis for Photoelectrocatalytic Water Splitting

It has been anticipated that learning from nature photosynthesis is a rational and effective way to develop artificial photosynthesis system, but it is still a great challenge. Here, we assembled a photoelectrocatalytic system by mimicking the functions of photosystem II (PSII) with BiVO₄ semiconductor as a light harvester protected by a layered double hydroxide (NiFeLDH) as a hole storage layer, a partially oxidized graphene (pGO) as biomimetic tyrosine for charge transfer, and molecular Co cubane as oxygen evolution complex. The integrated system exhibited an unprecedentedly low onset potential (0.17 V) and a high photocurrent (4.45 mA cm^-2), with a 2.0% solar to hydrogen efficiency. Spectroscopic studies revealed that this photoelectrocatalytic system exhibited superiority in charge separation and transfer by benefiting from mimicking the key functions of PSII. The success of the biomimetic strategy opened up new ways for the rational design and assembly of artificial photosynthesis systems for efficient solar-to-fuel conversion.

Phenothiazine inhibitors of trypanothione reductase as potential antitrypanosomal and antileishmanial drugs

Given the role of trypanothione in the redox defenses of pathogenic trypanosomal and leishmanial parasites, in contrast to glutathione for their mammalian hosts, selective inhibitors of trypanothione reductase are potential drug leads against trypanosomiasis and leishmaniasis. In the present study, the rational drug design approach was used to discover tricyclic neuroleptic molecular frameworks as lead structures for the development of inhibitors, selective for trypanothione reductase over host glutathione reductase. From a homology-modeled structure for trypanothione reductase, replaced in the later stages of the study by the X-ray coordinates for the enzyme from Crithidia fasciculata, a series of inhibitors based on phenothiazine was designed. These were shown to be reversible inhibitors of trypanothione reductase from Trypanosoma cruzi, linearly competitive with trypanothione as substrate and noncompetitive with NADPH, consistent with ping-pong bi bi kinetics. Analogues, synthesized to define structure-activity relationships for the active site, included N-acylpromazines, 2-substituted phenothiazines, and trisubstituted promazines. Analysis of Ki and I50 data, on the basis of calculated log P and molar refractivity values, provided evidence of a specially favored fit of small 2-substituents (especially 2-chloro and 2-trifluoromethyl), with a remote hydrophobic patch on the enzyme accessible for larger, hydrophobic 2-substituents. There was also evidence of an additional hydrophobic enzymic region available to suitable N-substituents of the promazine nucleus. Ki data also indicated that the phenothiazine nucleus can adopt more than one inhibitory orientation in its binding site. Selected compounds were tested for in vitro activity against Trypanosoma brucei, T. cruzi, and Leishmania donovani, with selective activities in the micromolar range being determined for a number of them.

Chitosan oligosaccharides improve the disturbance in glucose metabolism and reverse the dysbiosis of gut microbiota in diabetic mice

The aim of this study is to investigate the effect of chitosan oligosaccharides (COS) on type 2 diabetes mellitus. Wild type C57BL/6J mice or diabetic db/db mice were treated with vehicle or COS for three months. COS treatment significantly decreased the blood glucose (P < 0.01) and reversed the insulin resistance (P < 0.05) in db/db mice, which was accompanied by suppressing the inflammation mediators (P < 0.05), down-regulating the lipogenesis (P < 0.01) and inhibiting the adipocyte differentiation (P < 0.05) in white adipose tissue. Additionally, COS treatment inhibited the reduction of occludin (P < 0.01) and relieved the gut dysbiosis in diabetic mice by promoting Akkermansia (P < 0.01) and suppressing Helicobacter (P < 0.05). Spearman's correlation analysis indicates that the COS-modulated bacteria are positively correlated with inflammation, hyperglycemia and dyslipidemia. The functional profiling based on the microbiota composition implicated that COS treatment may regulate the metabolic pathways of gut microbiota. In summary, COS treatment remarkably improved the glucose metabolism and reshaped the unbalanced gut microbiota of diabetic mice. Our study provided the evidence for application of COS to the treatment of diabetes mellitus.

Tethered particle motion method for studying transcript elongation by a single RNA polymerase molecule

Schafer et al. (Nature 352:444-448 (1991)) devised the tethered particle motion (TPM) method to detect directly the movement of single, isolated molecules of a processive nucleic acid polymerase along a template DNA molecule. In TPM studies, the polymerase molecule is immobilized on a glass surface, and a particle (e.g., a 0.23 microns diameter polystyrene bead) is attached to one end of the enzyme-bound DNA molecule. Time-resolved measurements of the DNA contour length between the particle and the immobilized enzyme (the "tether length") are made by determining the magnitude of the Brownian motion of the DNA-tethered particle using light microscopy and digital image processing. We report here improved sample preparation methods that permit TPM data collection on transcript elongation by the Escherichia coli RNA polymerase at rates (approximately 10(2)-fold higher than those previously obtained) sufficient for practical use of microscopic kinetics techniques to analyze polymerase reaction mechanisms. In earlier TPM experiments, calculation of tether length from the observed Brownian motion was based on an untested numerical simulation of tethered bead Brownian motion. Using the improved methods, we have now empirically validated the TPM technique for tether lengths of 308-1915 base pairs (bp) using calibration specimens containing particles tethered by individual DNA molecules of known lengths. TPM analysis of such specimens yielded a linear calibration curve relating observed Brownian motion to tether length and allowed determination of the accuracy of the technique and measurement of how temporal bandwidth, tether length, and other experimental variables affect measurement precision. Under a standard set of experimental conditions (0.23 microns diameter bead, 0.23 Hz bandwidth, 23 degrees), accuracy is 108 and 258 bp r.m.s. at tether lengths of 308 and 1915 bp, respectively. Precision improves linearly with decreasing tether length to an extrapolated instrumentation limit of 10 bp r.m.s. and improves proportionally to the inverse square root of measurement bandwidth (1.9 x 10(2) bp Hz-1/2 for 1090-bp tethers). Measurements on large numbers of individual polymerase molecules reveal that time-averaged single-molecule elongation rates are more variable than is predicted from the random error in TPM measurements, demonstrating that the surface-immobilized RNA polymerase molecules are kinetically heterogeneous.