Distinct Aggregation Research Articles

Distinguish the toxic differentiations between acute exposure of micro- and nano-plastics on bivalves: An integrated study based on transcriptomic sequencing

Plastic pollution represents one of the most severe marine environmental issues today. In the present study, mussel Mytilus coruscus, was selected as the model organism to probe the toxic effects of acute exposure to different sizes of plastic particles using integrated transcriptomic techniques and histological and biochemical analysis. Nanoplastics (NPs) were efficiently ingested by mussels, thereby inducing a severe inflammatory response. Although no distinct aggregation of microplastics (MPs) was observed, a slight inflammatory response has still occurred. Biochemical analysis revealed a significant up-regulation of biomarkers after exposure to plastic particles. Further, NPs caused more ROS production and higher T-AOC level than MPs. Transcriptomic sequencing was performed, and these differentially expressed genes after MNPs exposure were mostly enriched in pathways involved in stress and immune response. Notably, a contrast expression, substantial upregulation in MPs treatment and downregulation in NPs treatment of specific genes include in these pathways were revealed. Collectively, these results indicated that acute exposure to NPs is more toxic than MPs. Additionally, MPs exposure perhaps caused the impairment of olfactory function and neurotoxicity to mussels. These data provided some new clues for the elucidating of ecotoxicological mechanisms underlying plastic particles exposure.

Influence of matric suction on resilient modulus and CBR of compacted Ballina clay

Road infrastructure is often built above the groundwater table. The materials used are usually compacted and thus generally remain under unsaturated conditions throughout their service life. This paper presents experimental results that highlight the influence of matric suction on the resilient modulus (MR) and California bearing ratio (CBR) of a compacted subgrade Ballina clay (typically found in NSW, Australia). The soil specimens were prepared in a range of water contents and dry unit weights, tested using a series of repeated load triaxial tests and CBR tests, and the associated matric suction was measured using the filter paper method. The tests were complemented by the study of the macrostructure of the compacted specimens using X-ray computed tomography (CT). Test results show that there are intimate relationships between the soil suctions and resilient modulus as well as CBR on the compacted clay at different moisture contents and that both parameters can be defined empirically through matric suction. A linear trend was established between matric suction and MR with a high coefficient of correlation of 0.99. CT scan results reveal that increasing soil moisture increased the inter-pores volume and the aggregations became more compressible and present probable matrix-dominated macrostructure during compaction. While soils compacted at the dry side of optimum moisture content yield distinct aggregations owing to the flocculation and aggregation of soil structure.

Dual improvement in curcumin encapsulation efficiency and lyophilized complex dispersibility through ultrasound regulation of curcumin–protein assembly

Ultrasound has a recognized ability to modulate the structure and function of proteins. Discovering the influential mechanism of ultrasound on the intramolecular interactions of egg-white protein isolate–curcumin (EPI–Cur) nanoparticles and their intermolecular interaction during freeze drying and redispersion is meaningful. In this study, under the extension of pre-sonication time, the protein solubility, surface hydrophobicity, and curcumin encapsulation rate showed an increasing trend, reaching the highest value at 12 min of treatment. However, the values decreased under the followed extension of ultrasound time. After freeze drying and redispersion were applied, the EPI–Cur sample under 12 min of ultrasound treatment exhibited minimal aggregation degree and loss of curcumin. The retention and loading rates of curcumin in the lyophilized powder reached 96 % and 33.60 mg/g EPI, respectively. However, under excessive ultrasound of >12 min, scanning electron microscopy showed distinct blocky aggregates. Overexposure of the hydrophobic region of the protein triggered protein-mediated hydrophobic aggregation after freeze drying. X-ray diffraction patterns showed the highest crystallinity, indicating that the free curcumin-mediated hydrophobic aggregation during freeze drying was enhanced by the concentration effect and intensified the formation of larger aggregates. This work has practical significance for developing the delivery of hydrophobic active substances. It provides theoretical value for the dynamic dispersity change in protein-hydrophobic active substances during freeze drying and redissolving.

Trials and adventures of the synthesis and evaluation of amphiphilic graft copolymers with dynamic topology

AbstractAmphiphilic graft copolymers were prepared via a grafting through approach to yield materials with a hydrophilic backbone and hydrophobic arms. The thermally responsive macromonomers were designed to contain a Diels–Alder adduct such that cyclo‐reversion would cleave the arms from the backbone thus altering polymer topology, composition and solubility. The macromonomers were prepared via light‐inducted atom transfer radical polymerization followed by post‐polymerization modification to install a polymerizable functionality. Next, free radical polymerization was employed to yield thermally responsive amphiphilic graft copolymers, whose solution state characteristics were extensively characterized by UV/Vis spectroscopy and fluorimetry. Due to the amphiphilic nature of the graft copolymer, some unexpected results occurred because of aggregation and solubility limitations. Furthermore, it was discovered that poly(N‐isopropyl acrylamide) exhibited distinct and unique aggregation properties by itself.

Evaluation of Agricultural Traits, Phytochemical Contents, and Antioxidant Activities in the Leaves of Amaranth Accessions of Nine Species.

Amaranthus species are widely cultivated as dietary crops and are promising sources of phytochemical compounds with antioxidant properties. To explore Amaranthus as a potential medical resource, 289 accessions (nine species) were cultivated, and their agricultural characteristics, total phenolic content (TPC), rutin contents, and antioxidant activities [2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)] were studied. Wide variations in agricultural traits, phytochemical contents, and antioxidant activities were observed between the accessions and across species. The effects of agricultural traits were evaluated, and the results indicated that yellow-flowered amaranth genotypes could be important because of their high values of TPC, rutin contents, DPPH, and ABTS. In addition, leaf length, days until 50% flowering, days until 50% heading and days until maturity, showed positive correlations with TPC, rutin contents, DPPH, and ABTS. The whole dataset was subjected to principal component analysis, and distinctive aggregation was observed across the Amaranthus species. In total, 289 accessions were clustered into three groups, and seven genotypes were determined as being good medical resources due to their high phytochemical content and antioxidant activities. Our findings provide important information for the development of new varieties with high phytochemical contents and high levels of antioxidant activity.

Oxidation Promotes Distinct Huntingtin Aggregates in the Presence and Absence of Membranes.

Expansion of a polyglutamine (polyQ) domain within the first exon of the huntingtin (htt) protein is the underlying cause of Huntington's disease, a genetic neurodegenerative disorder. PolyQ expansion triggers htt aggregation into oligomers, fibrils, and inclusions. The 17 N-terminal amino acids (Nt17) of htt-exon1, which directly precede the polyQ domain enhances polyQ fibrillization and functions as a lipid-binding domain. A variety of post-translational modifications occur within Nt17, including oxidation of two methionine residues. Here, the impact of oxidation within Nt17 on htt aggregation both in the presence and absence of lipid membranes was investigated. Treatment with hydrogen peroxide (H2O2) reduced fibril formation in a dose-dependent manner, resulting in shorter fibrils and an increased oligomer population. With excessive H2O2 treatments, fibrils developed a unique morphological feature around their periphery. In the presence of total brain lipid vesicles, H2O2 impacted fibrillization in a similar manner. That is, oligomerization was promoted at the expense of fibril elongation. The interaction of unoxidized and oxidized htt with supported lipid bilayers was directly observed using in situ atomic force microscopy. Without oxidation, granular htt aggregates developed on the bilayer surface. However, in the presence of H2O2, distinct plateau-like regions initially developed on the bilayer surface that gave way to rougher patches containing granular aggregates. Collectively, these observations suggest that oxidation of methionine residues within Nt17 plays a crucial role in both the aggregation of htt and its ability to interact with lipid surfaces.

Endocannabinoid dysfunction in neurological disease: neuro-ocular DAGLA-related syndrome.

The endocannabinoid system is a highly conserved and ubiquitous signalling pathway with broad-ranging effects. Despite critical pathway functions, gene variants have not previously been conclusively linked to human disease.We identified nine children from eight families with heterozygous, de novo truncating variants in the last exon of DAGLA with a neuro-ocular phenotype characterized by developmental delay, ataxia and complex oculomotor abnormality. All children displayed paroxysms of nystagmus or eye deviation accompanied by compensatory head posture and worsened incoordination most frequently after waking. RNA sequencing showed clear expression of the truncated transcript and no differences were found between mutant and wild-type DAGLA activity. Immunofluorescence staining of patient-derived fibroblasts and HEK cells expressing the mutant protein showed distinct perinuclear aggregation not detected in control samples.This report establishes truncating variants in the last DAGLA exon as the cause of a unique paediatric syndrome. Because enzymatic activity was preserved, the observed mislocalization of the truncated protein may account for the observed phenotype. Potential mechanisms include DAGLA haploinsufficiency at the plasma membrane or dominant negative effect. To our knowledge, this is the first report directly linking an endocannabinoid system component with human genetic disease and sets the stage for potential future therapeutic avenues.

The molybdenum storage protein forms and deposits distinct polynuclear tungsten oxygen aggregates

Some N2-fixing bacteria store Mo to maintain the formation of the vital FeMo-cofactor dependent nitrogenase under Mo depleting conditions. The Mo storage protein (MoSto), developed for this purpose, has the unique capability to compactly deposit molybdate as polyoxometalate (POM) clusters in a (αβ)3 hexameric cage; the same occurs with the physicochemically related tungstate. To explore the structural diversity of W-based POM clusters, MoSto loaded under different conditions with tungstate and two site-specifically modified MoSto variants were structurally characterized by X-ray crystallography or single-particle cryo-EM. The MoSto cage contains five major locations for POM clusters occupied among others by heptanuclear, Keggin ion and even Dawson-like species also found in bulk solvent under defined conditions. We found both lacunary derivatives of these archetypical POM clusters with missing WOx units at positions exposed to bulk solvent and expanded derivatives with additional WOx units next to protecting polypeptide segments or other POM clusters. The cryo-EM map, unexpectedly, reveals a POM cluster in the cage center anchored to the wall by a WOx linker. Interestingly, distinct POM cluster structures can originate from identical, highly occupied core fragments of three to seven WOx units that partly correspond to those found in MoSto loaded with molybdate. These core fragments are firmly bound to the complementary protein template in contrast to the more variable, less occupied residual parts of the visible POM clusters. Due to their higher stability, W-based POM clusters are, on average, larger and more diverse than their Mo-based counterparts.

Lattice-model analysis of the effect of protein surface charge distribution on amorphous aggregation and condensation

We describe a lattice model to analyze the effect of protein surface charge distributions on protein solubility, aggregation, and condensation. Surface charges were modeled by considering a protein as a cubic particle with each face covered by two negative and positive patches (net zero charge). Particles were moved to adjacent lattice points according to a Monte Carlo algorithm. We observed that proteins having the same isoelectric point can have distinct aggregation propensities, depending on surface charge arrangements. Furthermore, with regard to the effect of heterogeneous intracellular environment, mixing two particle types affected the aggregation properties of the individual type.

Alterations in Self-Aggregating Neuropeptides in Cerebrospinal Fluid of Patients with Parkinsonian Disorders.

Background:Parkinson’s disease (PD), progressive supranuclear palsy (PSP), and multiple system atrophy (MSA) present with similar movement disorder symptoms but distinct protein aggregates upon pathological examination.Objective:Discovery and validation of candidate biomarkers in parkinsonian disorders for differential diagnosis of subgroup molecular etiologies.Methods:Untargeted liquid chromatography (LC)-mass spectrometry (MS) proteomics was used for discovery profiling in cerebral spinal fluid (CSF) followed by LC-MS/MS based multiple reaction monitoring for validation of candidates. We compared clinical variation within the parkinsonian cohort including PD subgroups exhibiting tremor dominance (TD) or postural instability gait disturbance and those with detectable leukocytes in CSF.Results:We have identified candidate peptide biomarkers and validated related proteins with targeted quantitative multiplexed assays. Dopamine-drug naïve patients at first diagnosis exhibit reduced levels of signaling neuropeptides, chaperones, and processing proteases for packaging of self-aggregating peptides into dense core vesicles. Distinct patterns of biomarkers were detected in the parkinsonian disorders but were not robust enough to offer a differential diagnosis. Different biomarker changes were detected in male and female patients with PD. Subgroup specific candidate biomarkers were identified for TD PD and PD patients with leukocytes detected in CSF.Conclusion:PD, MSA, and PSP exhibit overlapping as well as distinct protein biomarkers that suggest specific molecular etiologies. This indicates common sensitivity of certain populations of selectively vulnerable neurons in the brain, and distinct therapeutic targets for PD subgroups. Our report validates a decrease in CSF levels of self-aggregating neuropeptides in parkinsonian disorders and supports the role of native amyloidogenic proteins in etiologies of neurodegenerative diseases.

The spatial prediction and optimization of production-living-ecological space based on Markov–PLUS model: A case study of Yunnan Province

Abstract Production-living-ecological space (PLES) reflects the main function of land use types. It is one of the main directions that many scholars researched to evaluate, predict, and optimize the land space from the perspective of PLES. Yunnan Province is affected by such factors as economy, topography, and natural environment. The conflict of PLES is serious, and the problems of spatial planning development are prominent. This study aims at the current status of PLES, based on the establishment of restrictive constraints such as ecological red line, arable land minimum, and natural reserves. Meanwhile, these constraints were combined with the development planning of the Yunnan Province to forecast the quantitative structure change in the PLES in Yunnan Province in 2035 and 2050, coupling Markov and PLUS models to optimize the future space layout. This study can provide a scientific basis for the optimization of land space in Yunnan Province and other areas. The prediction accuracy of the Markov–PLUS model is 98.55%, which can be effectively used to simulate and predict the distribution of PLES in Yunnan in 2035 and 2050. From 2010 to 2015, the disordered layout of PLES in the Yunnan Province was obvious, and the ecological space (ES) seriously occupied the production space (PS) and living space (LS). In 2035 and 2050, the industrial production space (IPS) of Yunnan Province expands and presents distinct regional aggregation. LS and the water ecological space (WES) areas have increased. The layout of PLES in 2035 and 2050 of Yunnan Province mainly centers on PS. The orderly development of IPS promotes the regional economic growth, ensures that the agricultural production space (APS) will not be damaged and allocates the ES reasonably. It will also promote the overall optimization and coordinated development of PLES in Yunnan Province.

Lysozyme Amyloid Fibril Structural Variability Dependence on Initial Protein Folding State.

Amyloid fibril formation is associated with several amyloidoses, including neurodegenerative Alzheimer’s or Parkinson’s diseases. The process of such fibrillar structure formation is still not fully understood, with new mechanistic insights appearing on a regular basis. This, in turn, has limited the development of potential anti-amyloid compounds, with only a handful of effective cures or treatment modalities available. One of the multiple amyloid aggregation factors that requires further examination is the ability of proteins to form multiple, structurally distinct aggregates, based on the environmental conditions. In this work, we examine how the initial folding state affects the fibrilization of lysozyme—an amyloidogenic protein, often used in protein aggregation studies. We show that there is a correlation between the initial state of the protein and the aggregate formation lag time, rate of elongation, resulting aggregate structural variability and dye-binding properties, as well as formation lag time and rate of elongation.

Structural features of interfacially adsorbed acyl-l-carnitines

HypothesisAcyl-l-carnitines (CnLCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and adsorption at the air/water interface, this work examines how they adsorb at the hydrophilic solid/liquid interface. ExperimentsAs the SiO2/water interface has served as the model substrate for many interfacial adsorption studies, so it has been used in this work as the solid substrate to facilitate dynamic adsorption by spectroscopic ellipsometry (SE) and structural determination of the adsorbed layers by neutron reflection (NR) under different conditions at the SiO2/water interface from a group of CnLC (n = 12, 14, and 16). FindingsCnLC surfactants are zwitterionic at neutral pH. They reached saturated adsorption above their critical micellar concentrations (CMCs) and formed a sandwich bilayer with a head–tail-head structure at the hydrophilic SiO2/water interface. The total thicknesses of the adsorbed layers at CMC were found to be 33 ± 2, 35 ± 2, and 37 ± 2 Å for C12LC, C14LC, and C16LC, respectively, with their inner and outer head layers remaining similar but the thickness of the interdigitated middle layer increasing with acyl chain length. As the solution becomes acidic, the carboxyl groups become protonated and the l-carnitine heads are net positively charged, resulting in increased repulsion between the head groups. In this situation, the CnLC surfactants are adsorbed as distinct aggregates to reduce repulsive interaction, resulting in reduced surfactant volume fraction and layer thickness. However, a high ionic strength can screen the repulsive interaction and enhance the adsorbed amount, effectively diminishing the impact of pH. This information provides a useful basis for exploring the technological applications of CnLCs involving a solid substrate.

Elongation of Fibrils Formed by a Tau Fragment is Inhibited by a Transient Dimeric Intermediate.

The formation and propagation of aggregates of the tau protein in the brain are associated with the tauopathy group of neurodegenerative diseases. Different tauopathies have been shown to be associated with structurally distinct aggregates of tau. However, the mechanism by which different structural folds arise remains poorly understood. In this study of fibril formation by the fragment tau-K18 of tau, it is shown that the Lys 280 → Glu mutation in the variant tau-K18 K280E forms fibrils that are morphologically distinct from those formed by wild-type (wt) tau-K18. The mutant fibrils appear to have two protofilaments twisted around each other, whereas the wt fibrils are straight and appear to have a single protofilament. Modeling the kinetics of seeded aggregation, using a simple Michaelis-Menten-like mechanism, reveals that the two morphologically distinct fibrils are elongated with different catalytic efficiencies. Surprisingly, when the elongation of monomeric tau-K18 is seeded with tau-K18 K280E fibrils, it is seen to be inhibited at high monomer concentrations. Such inhibition is not seen when elongation is seeded with tau-K18 fibrils. The mechanism of inhibition is shown to be describable as uncompetitive inhibition, in which a transient dimeric form of tau-K18 acts as an uncompetitive inhibitor. Importantly, a dimeric form of tau-K18 is seen to be populated to a detectable extent early during aggregation. A covalently linked tau dimer, with an inter-molecular disulphide linkage, is shown to be capable of acting as an inhibitor. In summary, a quantitative kinetic approach has provided an understanding of how the formation of distinct structural folds of tau fibrils can be modulated by mutation and how the elongation of one fibril type, but not the other, is inhibited by a transiently formed dimer.

Influence of protein configuration on aggregation kinetics of nanoplastics in aquatic environment

Aggregation kinetics of nanoplastics in aquatic environment are influenced by their interactions with proteins having different structures and properties. This study employed time-resolved dynamic light scattering (TR-DLS) to investigate the effects of 5 proteins (bovine hemoglobin (BHb), bovine (BSA) and human serum albumin (HSA), collagen type I (Col I), and bovine casein (CS)) on aggregation kinetics of polystyrene nanoplastics (PSNPs) under natural water conditions, which were simulated using various ionic strength (1-1000 mM NaCl and 0.01-100 mM CaCl2), pH (3-9), and protein concentration (1-5 mg/L of total organic carbon). The results indicated that the interactions between proteins and PSNPs strongly depended on electrostatic properties, protein structures, and solution chemistries, which induced distinct aggregation behaviors in NaCl and CaCl2 solutions. Electrostatic repulsion and steric hindrance dominated their interactions in NaCl solution by stabilizing PSNPs with the order of spherical BSA and disordered CS > heart-shaped HSA > fibrillar Col I; whereas positively charged BHb destabilized PSNPs with aggregation rate of 1.71 nm/s at 300 mM NaCl. In contrast, at CaCl2 concentration below 20 mM, proteins destabilized PSNPs following the sequence of HSA > BHb > Col I > BSA depending on counterbalance among double layer compression, cation bridging, and steric hindrance; whereas CS stabilized PSNPs by precipitating Ca2+ that inhibited charge screening effect. Both protein concentration and solution pH affected protein corona formation, surface charge, and protein structure that altered stability of PSNPs. Characterizations using fluorescence spectroscopy, circular dichroism, and two-dimensional correlation analysis spectroscopy showed fluorescence quenching and ellipticity reduction of proteins, indicating strong adsorption affinity between PSNPs and proteins. The study provides insight to how protein configuration and water chemistry affect fate and transport of nanoplastics in aquatic environment.

Relevance of Amorphous and Amyloid-Like Aggregates of the p53 Core Domain to Loss of its DNA-Binding Activity.

The anti-oncogenic protein p53 is a transcription factor that prevents tumorigenesis by inducing gene repair proteins or apoptosis under DNA damage. Since the DNA-binding domain of p53 (p53C) is aggregation-prone, the anti-oncogenic function of p53 is often lost in cancer cells. This tendency is rather severe in some tumor-related p53 mutants, such as R175H. In this study, we examined the effect of salts, including KCl and sugars, on the aggregation of p53C by monitoring two distinct aggregates: amorphous-like and amyloid-like. The amorphous aggregates are detectable with 8-(phenylamino)-1-naphthalenesulfonic acid (ANS) fluorescence, whereas the amyloid aggregates are sensitive to thioflavin-T (ThT) fluorescence. We found that KCl inhibited the formation of amorphous aggregates but promoted the formation of amyloid aggregates in a p53C R175H mutant. The salts exhibited different effects against the wild-type and R175H mutants of p53C. However, the ratio of ANS/ThT fluorescence for the wild-type and R175H mutant remained constant. KCl also suppressed the structural transition and loss of the DNA-binding function of p53C. These observations indicate the existence of multiple steps of p53C aggregation, probably coupled with the dissociation of Zn. Notably, amorphous aggregates and amyloid aggregates have distinct properties that could be discriminated by various small additives upon aggregation.

Internationalisation, teacher education and institutional identities: a comparative analysis

ABSTRACT Teachers are under increasing pressure to promote various and many times conflicting and fluid sets of values—both global/local—cosmopolitan and national. Teachers are expected to possess meaningful skills, theoretical grounding and practical tools to effectively undertake this role. One way in which to prepare teachers for this, is through internationalisation of teacher education (IoTE). Teacher education programmes are situated within a distinctive niche between higher education (HE) and schools and are expected to both compete with other local/global HEIs and to engage with and supply graduates for the local (often, national) education system. This distinctive position requires teacher education programmes to foster multiple constituencies and identities. In this study, we aim to explore these multiple identities, and how they shape IoTE. We investigate how internationalisation is expressed in two teacher education colleges in Israel. Drawing on internationalisation and organisational identity literature, we explore the role of organisational identities and how multiple organisational identities are negotiated and shape IoTE. We reveal two distinctive strategies, aggregation and compartmentalisation, employed to manage multiple organisational identities. We argue that these divergent strategies produce different forms of IoTE and are closely tied to the institution’s conception of the nation.

Distinct aggregate stratification of antibiotic resistome in farmland soil with long-term manure application

Agricultural soils, which are closely linked to human health via food supply, have been recognized as an important reservoir for antibiotic resistance genes (ARGs). However, there is still a lack of knowledge regarding the role of soil aggregates in shaping ARG profile. In this study, we collected soils from long-term experimental farmland plots receiving inorganic and/or organic fertilizers and examined the patterns of antibiotic resistome distribution among differently sized soil aggregates using high-throughput quantitative polymerase chain reaction (HT-qPCR). Our results showed that the distribution of soil ARGs could be affected by manure application and aggregate size individually but not interactively. More diverse and abundant ARGs were found in the manured soils, compared to the non-manured soils. The aggregate size fraction of <53 μm exhibited the highest diversity and abundance of ARGs. Variation partitioning analysis revealed that soil traits, mobile genetic elements, and bacterial community collectively contributed to the variation of soil antibiotic resistance. The knowledge about aggregation stratification of soil ARGs obtained in this study is fundamental and essential to understanding the fate of soil ARGs at the microscale.

X-ray computed tomography, electron microscopy, and energy-dispersive X-ray spectroscopy of severed Zelkova serrata roots (Japanese elm tree)

X-ray computed tomography (XCT), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS) were evaluated for imaging and element identification of woody plant roots. Lateral roots of Japanese zelkova (Zelkova serrata) were severed in spring and maintained in soil for six months. The lateral roots were observed using XCT without maceration and sectioning. The general wood characteristics were discernible to reveal the bark and xylem structures in contrast-inverted tomograms. Virtual sections showed a newly formed ring of woundwood encircling the severed lateral roots. FESEM exhibited secondary xylem structures in which tyloses, fungal hyphae, and aggregates were present. While silicon was dispersed in and around the fungal hyphae, calcium was localized as distinct aggregates using EDS. These results suggest that the combined use of XCT, FESEM, and EDS has merit into the morphological assessment of tree health care, providing virtual sections, high-resolution images, and element composition from an entire woodblock.

Rotenone induces regionally distinct α-synuclein protein aggregation and activation of glia prior to loss of dopaminergic neurons in C57Bl/6 mice

Rotenone is a naturally occurring insecticide that inhibits mitochondrial complex I and leads to neurochemical and neuropathological deficits closely resembling those in Parkinson's disease (PD). Deficits include loss of dopaminergic neurons (DAn) in the substantia nigra pars compacta (SNpc), decreased dopamine levels and aggregation of misfolded alpha-synuclein (p129). In rat models of rotenone-induced parkinsonism, the progression of neuronal injury has been associated with activation of microglia and astrocytes. However, these neuroinflammatory changes have been challenging to study in mice, in part because the systemic rotenone exposure model utilized in rats is more toxic to mice. To establish a reproducible murine model of rotenone-induced PD, we therefore investigated the progression of neuroinflammation, protein aggregation and DAn loss in C57Bl/6 mice by exposing animals to 2.5 mg/kg/day rotenone for 14 days, followed by a two-week period where neuroinflammation is allowed to progress. Our results indicate that initial cellular dysfunction leads to increased formation of proteinase K-resistant p129 aggregates in the caudate-putamen and SNpc. Clearance of these aggregates was region- and cell type-specific, with the early appearance of reactive astrocytes coinciding with accumulation of p129 in the SNpc. Phagocytic microglial cells containing p129 aggregates were observed proximal to p129+ DAn in the SNpc. The majority of neuronal loss in the SNpc occurred during the two-week period after rotenone exposure, subsequent to the peak of microglia and astrocyte activation, as well as the peak of p129 aggregation. A secondary peak of p129 coincided with neurodegeneration at later timepoints. These data indicate that systemic exposure to rotenone in C57Bl/6 mice causes progressive accumulation and regional spread of p129 aggregates that precede maximal loss of DAn. Thus, activation of glial cells and aggregation of p129 appear to drive neuronal loss following neurotoxic stress imposed by exposure to rotenone.