19 research outputs found
Значение специфических инфекций у беременных в развитии хронической плацентарной недостаточности
ПЛАЦЕНТАРНАЯ НЕДОСТАТОЧНОСТЬБЕРЕМЕННОСТИ ОСЛОЖНЕНИЯПОЛОВЫМ ПУТЕМ ПЕРЕДАВАЕМЫЕ БОЛЕЗНИИНФЕКЦИ
Biochemical Properties of Highly Neuroinvasive Prion Strains
Infectious prions propagate from peripheral entry sites into the central nervous system (CNS), where they cause progressive neurodegeneration that ultimately leads to death. Yet the pathogenesis of prion disease can vary dramatically depending on the strain, or conformational variant of the aberrantly folded and aggregated protein, PrPSc. Although most prion strains invade the CNS, some prion strains cannot gain entry and do not cause clinical signs of disease. The conformational basis for this remarkable variation in the pathogenesis among strains is unclear. Using mouse-adapted prion strains, here we show that highly neuroinvasive prion strains primarily form diffuse aggregates in brain and are noncongophilic, conformationally unstable in denaturing conditions, and lead to rapidly lethal disease. These neuroinvasive strains efficiently generate PrPSc over short incubation periods. In contrast, the weakly neuroinvasive prion strains form large fibrillary plaques and are stable, congophilic, and inefficiently generate PrPSc over long incubation periods. Overall, these results indicate that the most neuroinvasive prion strains are also the least stable, and support the concept that the efficient replication and unstable nature of the most rapidly converting prions may be a feature linked to their efficient spread into the CNS
Prion Strain Interactions Are Highly Selective
Various misfolded and aggregated neuronal proteins commonly coexist in neurodegenerative disease, but whether the proteins coaggregate and alter the disease pathogenesis is unclear. Here we used mixtures of distinct prion strains, which are believed to differ in conformation, to test the hypothesis that two different aggregates interact and change the disease in vivo. We tracked two prion strains in mice histopathologically and biochemically, as well as by spectral analysis of plaque-bound PTAA (polythiophene acetic acid), a conformation-sensitive fluorescent amyloid ligand. We found that prion strains interacted in a highly selective and strain-specific manner, with (1) no interaction, (2) hybrid plaque formation, or (3) blockage of one strain by a second (interference). The hybrid plaques were maintained on additional passage in vivo and each strain seemed to maintain its original conformational properties, suggesting that one strain served only as a scaffold for aggregation of the second strain. These findings not only further our understanding of prion strain interactions but also directly demonstrate interactions that may occur in other protein aggregate mixtures.Original Publication: Peter Nilsson, Shivanjali Joshi-Barr, Olivia Winson and Christina J Sigurdson, Prion Strain Interactions Are Highly Selective, 2010, JOURNAL OF NEUROSCIENCE, (30), 36, 12094-12102. http://dx.doi.org/10.1523/JNEUROSCI.2417-10.2010 Copyright: Society for Neuroscience http://www.sfn.org/</p
Prion transmission prevented by modifying the β2-α2 loop structure of host PrPC
Zoonotic prion transmission was reported after the bovine spongiform encephalopathy (BSE) epidemic, when >200 cases of prion disease in humans were diagnosed as variant Creutzfeldt-Jakob disease. Assessing the risk of cross-species prion transmission remains challenging. We and others have studied how specific amino acid residue differences between species impact prion conversion and have found that the β2-α2 loop region of the mouse prion protein (residues 165-175) markedly influences infection by sheep scrapie, BSE, mouse-adapted scrapie, deer chronic wasting disease, and hamster-adapted scrapie prions. The tyrosine residue at position 169 is strictly conserved among mammals and an aromatic side chain in this position is essential to maintain a 310-helical turn in the β2-α2 loop. Here we examined the impact of the Y169G substitution together with the previously described S170N, N174T "rigid loop" substitutions on cross-species prion transmission in vivo and in vitro. We found that transgenic mice expressing mouse PrP containing the triple-amino acid substitution completely resisted infection with two strains of mouse prions and with deer chronic wasting disease prions. These studies indicate that Y169 is important for prion formation, and they provide a strong indication that variation of the β2-α2 loop structure can modulate interspecies prion transmission
Single UV or Near IR Triggering Event Leads to Polymer Degradation into Small Molecules
We report two polymers with UV- and NIR-removable end-caps
that
respond to a single light activated event by complete cleavage of
the polymer backbone via a self-immolative mechanism. Two photocleavable
protecting groups were used to cap the polymers; <i>o</i>-nitrobenzyl alcohol (ONB) and bromo-coumarin (Bhc). GPC and <sup>1</sup>H NMR confirmed complete degradation of the ONB-containing
polymer in response to UV. The polymers were formulated into nanoparticles;
fluorescence measurements of encapsulated Nile red confirmed release
upon photolysis of the end-caps. Contrary to previous work using a
similar backbone structure that degrades upon hydrolysis, here, the
disassembly process and burst release of the payload are only activated
on demand, illustrating the powerful capacity of light to trigger
release from polymeric nanoparticles. Our design allows the signal
to be amplified in a domino effect to fully degrade the polymer into
small molecules. Thus, polymers and nanoparticles can reach maximal
degradation without having to use intense or long periods of irradiation
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Distinct ON/OFF fluorescence signals from dual-responsive activatable nanoprobes allows detection of inflammation with improved contrast
Visualization of biochemical changes associated with disease is of great clinical significance, as it should allow earlier, more accurate diagnosis than structural imaging, facilitating timely clinical intervention. Herein, we report combining stimuli-responsive polymers and near-infrared fluorescent dyes (emission max: 790 nm) to create robust activatable fluorescent nanoprobes capable of simultaneously detecting acidosis and oxidative stress associated with inflammatory microenvironments. The spectrally-resolved mechanism of fluorescence activation allows removal of unwanted background signal (up to 20-fold reduction) and isolation of a pure activated signal, which enables sensitive and unambiguous localization of inflamed areas; target-to-background ratios reach 22 as early as 3 h post-injection. This new detection platform could have significant clinical impact in early detection of pathologies, individual tailoring of drug therapy, and image-guided tumor resection
Biocompatible Polymeric Nanoparticles Degrade and Release Cargo in Response to Biologically Relevant Levels of Hydrogen Peroxide
Oxidative stress is caused predominantly by accumulation
of hydrogen
peroxide and distinguishes inflamed tissue from healthy tissue. Hydrogen
peroxide could potentially be useful as a stimulus for targeted drug
delivery to diseased tissue. However, current polymeric systems are
not sensitive to biologically relevant concentrations of H<sub>2</sub>O<sub>2</sub> (50–100 μM). Here we report a new biocompatible
polymeric capsule capable of undergoing backbone degradation and thus
release upon exposure to such concentrations of hydrogen peroxide.
Two polymeric structures were developed differing with respect to
the linkage between the boronic ester group and the polymeric backbone:
either direct (<b>1</b>) or via an ether linkage (<b>2</b>). Both polymers are stable in aqueous solution at normal pH, and
exposure to peroxide induces the removal of the boronic ester protecting
groups at physiological pH and temperature, revealing phenols along
the backbone, which undergo quinone methide rearrangement to lead
to polymer degradation. Considerably faster backbone degradation was
observed for polymer <b>2</b> over polymer <b>1</b> by
NMR and GPC. Nanoparticles were formulated from these novel materials
to analyze their oxidation triggered release properties. While nanoparticles
formulated from polymer <b>1</b> only released 50% of the reporter
dye after exposure to 1 mM H<sub>2</sub>O<sub>2</sub> for 26 h, nanoparticles
formulated from polymer <b>2</b> did so within 10 h and were
able to release their cargo selectively in biologically relevant concentrations
of H<sub>2</sub>O<sub>2</sub>. Nanoparticles formulated from polymer <b>2</b> showed a 2-fold enhancement of release upon incubation with
activated neutrophils, while controls showed a nonspecific response
to ROS producing cells. These polymers represent a novel, biologically
relevant, and biocompatible approach to biodegradable H<sub>2</sub>O<sub>2</sub>-triggered release systems that can degrade into small
molecules, release their cargo, and should be easily cleared by the
body
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De novo prion aggregates trigger autophagy in skeletal muscle.
In certain sporadic, familial, and infectious prion diseases, the prion protein misfolds and aggregates in skeletal muscle in addition to the brain and spinal cord. In myocytes, prion aggregates accumulate intracellularly, yet little is known about clearance pathways. Here we investigated the clearance of prion aggregates in muscle of transgenic mice that develop prion disease de novo. In addition to neurodegeneration, aged mice developed a degenerative myopathy, with scattered myocytes containing ubiquitinated, intracellular prion inclusions that were adjacent to myocytes lacking inclusions. Myocytes also showed elevated levels of the endoplasmic reticulum chaperone Grp78/BiP, suggestive of impaired protein degradation and endoplasmic reticulum stress. Additionally, autophagy was induced, as indicated by increased levels of beclin-1 and LC3-II. In C2C12 myoblasts, inhibition of autophagosome maturation or lysosomal degradation led to enhanced prion aggregation, consistent with a role for autophagy in prion aggregate clearance. Taken together, these findings suggest that the induction of autophagy may be a central strategy for prion aggregate clearance in myocytes. IMPORTANCE In prion diseases, the prion protein misfolds and aggregates in the central nervous system and sometimes in other organs, including muscle, yet the cellular pathways of prion aggregate clearance are unclear. Here we investigated the clearance of prion aggregates in the muscle of a transgenic mouse model that develops profound muscle degeneration. We found that endoplasmic reticulum stress pathways were activated and that autophagy was induced. Blocking of autophagic degradation in cell culture models led to an accumulation of aggregated prion protein. Collectively, these findings suggest that autophagy has an instrumental role in prion protein clearance
De novo prion aggregates trigger autophagy in skeletal muscle.
In certain sporadic, familial, and infectious prion diseases, the prion protein misfolds and aggregates in skeletal muscle in addition to the brain and spinal cord. In myocytes, prion aggregates accumulate intracellularly, yet little is known about clearance pathways. Here we investigated the clearance of prion aggregates in muscle of transgenic mice that develop prion disease de novo. In addition to neurodegeneration, aged mice developed a degenerative myopathy, with scattered myocytes containing ubiquitinated, intracellular prion inclusions that were adjacent to myocytes lacking inclusions. Myocytes also showed elevated levels of the endoplasmic reticulum chaperone Grp78/BiP, suggestive of impaired protein degradation and endoplasmic reticulum stress. Additionally, autophagy was induced, as indicated by increased levels of beclin-1 and LC3-II. In C2C12 myoblasts, inhibition of autophagosome maturation or lysosomal degradation led to enhanced prion aggregation, consistent with a role for autophagy in prion aggregate clearance. Taken together, these findings suggest that the induction of autophagy may be a central strategy for prion aggregate clearance in myocytes. IMPORTANCE In prion diseases, the prion protein misfolds and aggregates in the central nervous system and sometimes in other organs, including muscle, yet the cellular pathways of prion aggregate clearance are unclear. Here we investigated the clearance of prion aggregates in the muscle of a transgenic mouse model that develops profound muscle degeneration. We found that endoplasmic reticulum stress pathways were activated and that autophagy was induced. Blocking of autophagic degradation in cell culture models led to an accumulation of aggregated prion protein. Collectively, these findings suggest that autophagy has an instrumental role in prion protein clearance