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Parkinson's disease (PD) is an age‐related neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, associated with the accumulation of misfolded α‐synuclein and lysosomal impairment, two events deemed interconnected. Protein aggregation is linked to defects in degradation systems such as the autophagy‐lysosomal pathway, while lysosomal dysfunction is partly related to compromised acidification. We have recently proven that acidic nanoparticles (aNPs) can re‐acidify lysosomes and ameliorate neurotoxin‐mediated dopaminergic neurodegeneration in mice. However, no lysosome‐targeted approach has yet been tested in synucleinopathy models in vivo. Here, we show that aNPs increase α‐synuclein degradation through enhancing lysosomal activity in vitro. We further demonstrate in vivo that aNPs protect nigral dopaminergic neurons from cell death, ameliorate α‐synuclein pathology, and restore lysosomal function in mice injected with PD patient‐derived Lewy body extracts carrying toxic α‐synuclein aggregates. Our results support lysosomal re‐acidification as a disease‐modifying strategy for the treatment of PD and other age‐related proteinopathies. [ABSTRACT FROM AUTHOR]

• Carbon nanotube tracking provides information on nanoscale ECS structure & diffusion. • First super-resolution data on the ECS of adult live brain tissue. • First ECS diffusion data in organotypic brain slices at the nanoscale. • Adult mice acute and rat organotypic slices exhibit diverse ECS diffusion properties. The brain extracellular space (ECS) is a system of narrow compartments whose intricate nanometric structure has remained elusive until very recently. Understanding such a complex organisation represents a technological challenge that requires a technique able to resolve these nanoscopic spaces and simultaneously characterize their rheological properties. We recently used single-walled carbon nanotubes (SWCNTs) as near-infrared fluorescent probes to map with nanoscale precision the local organization and rheology of the ECS. Here we expand our method by tracking single nanotubes through super-resolution imaging in rat organotypic hippocampal slices and acute brain slices from adult mice, pioneering the exploration of the adult brain ECS at the nanoscale. We found a highly heterogeneous ECS, where local rheological properties can change drastically within few nanometres. Our results suggest differences in local ECS diffusion environments in organotypic slices when compared to adult mouse slices. Data obtained from super-resolved maps of the SWCNT trajectories indicate that ECS widths may vary between brain tissue models, with a looser, less crowded nano-environment in organotypic cultured slices. [ABSTRACT FROM AUTHOR]

During brain ischemia, an excessive release of glutamate triggers neuronal death through the overactivation of NMDA receptors (NMDARs); however, the underlying pathways that alter glutamate homeostasis and whether synaptic or extrasynaptic sites are responsible for excess glutamate remain controversial. Here, we monitored ischemia-gated currents in pyramidal cortical neurons in brain slices from rodents in response to oxygen and glucose deprivation (OGD) as a real-time glutamate sensor to identify the source of glutamate release and determined the extent of neuronal damage. Blockade of excitatory amino acid transporters or vesicular glutamate release did not inhibit ischemia-gated currents or neuronal damage after OGD. In contrast, pharmacological inhibition of the cystine/glutamate antiporter dramatically attenuated ischemia-gated currents and cell death after OGD. Compared with control animals, mice lacking a functional cystine/glutamate antiporter exhibited reduced anoxic depolarization and neuronal death in response to OGD. Furthermore, glutamate released by the cystine/glutamate antiporter activated extrasynaptic, but not synaptic, NMDARs, and blockade of extrasynaptic NMDARs reduced ischemia-gated currents and cell damage after OGD. Finally, PET imaging showed increased cystine/glutamate antiporter function in ischemic rats. Altogether, these data suggest that cystine/glutamate antiporter function is increased in ischemia, contributing to elevated extracellular glutamate concentration, overactivation of extrasynaptic NMDARs, and ischemic neuronal death. [ABSTRACT FROM AUTHOR]

The aim of this research was to study how high water temperatures impair the reproductive activity of pejerrey Odontesthes bonariensis, an inland-water atherinopsid fish species from the pampasic region of Argentina. Adult pejerrey of both sexes were kept under a control-temperature regime (19°C) and two experimental temperatures (23° and 27°C) for 8 d. The effect of elevated temperature on the pituitary-gonad axis was analyzed in terms of the expression of gonadotropin (GtH) subunits: follicle-stimulating hormone β, luteinizing hormone β (LH-β), glycoprotein hormone a, and GtH receptors FSH-R and LH-R by semiquantitative reverse transcriptase polymerase chain reaction, plasma levels of sexual steroids by radioimmunoassay, and reproductive status by gonadal histology. The results of this work clearly indicate that short periods of exposure to high water temperatures disrupt pejerrey reproduction. This effect was observed in spawning activity, at the histological level, and in the reduction of plasma estradiol in females and testosterone in males. The mRNA levels of GtH subunits and GtH receptors generally decreased in proportion to the increase in temperature for both sexes. However, the differences between groups were statistically significant only for LH-β and for FSH-R expression in pejerrey females. Thus, the gonads of pejerrey appear to be the primary target of high water temperature. Analysis of the air temperature in this region over the past 40 yr indicated an increase of 1.74°C in mean annual temperature. This increase, coupled with the mechanism of high-temperature sensitivity shown in this study, may be one of the reasons for the decline in pejerrey populations observed in this region over recent decades. [ABSTRACT FROM AUTHOR]

STED microscopy is one of several fluorescence microscopy techniques that permit imaging at higher spatial resolution than what the diffraction-limit of light dictates. STED imaging is unique among these super-resolution modalities in being a beam-scanning microscopy technique based on confocal or 2-photon imaging, which provides the advantage of superior optical sectioning in thick samples. Compared to the other super-resolution techniques that are based on widefield microscopy, this makes STED particularly suited for imaging inside live brain tissue, such as in slices or in vivo. Notably, the 50 nm resolution provided by STED microscopy enables analysis of neural morphologies that conventional confocal and 2-photon microscopy approaches cannot resolve, including all-important synaptic structures. Over the course of the last 20 years, STED microscopy has undergone extensive developments towards ever more versatile use, and has facilitated remarkable neurophysiological discoveries. The technique is still not widely adopted for live tissue imaging, even though one of its particular strengths is exactly in resolving the nanoscale dynamics of synaptic structures in brain tissue, as well as in addressing the complex morphologies of glial cells, and revealing the intricate structure of the brain extracellular space. Not least, live tissue STED microscopy has so far hardly been applied in settings of pathophysiology, though also here it shows great promise for providing new insights. This review outlines the technical advantages of STED microscopy for imaging in live brain tissue, and highlights key neurobiological findings brought about by the technique. [ABSTRACT FROM AUTHOR]

The brain extracellular space (ECS) is a vast interstitial reticulum of extreme morphological complexity, composed of narrow gaps separated by local expansions, enabling interconnected highways between neural cells. Constituting on average 20% of brain volume, the ECS is key for intercellular communication, and understanding its diffusional properties is of paramount importance for understanding the brain. Within the ECS, neuroactive substances travel predominantly by diffusion, spreading through the interstitial fluid and the extracellular matrix scaffold after being focally released. The nanoscale dimensions of the ECS render it unresolvable by conventional live tissue compatible imaging methods, and historically diffusion of tracers has been used to indirectly infer its structure. Novel nanoscopic imaging techniques now show that the ECS is a highly dynamic compartment, and that diffusivity in the ECS is more heterogeneous than anticipated, with great variability across brain regions and physiological states. Diffusion is defined primarily by the local ECS geometry, and secondarily by the viscosity of the interstitial fluid, including the obstructive and binding properties of the extracellular matrix. ECS volume fraction and tortuosity both strongly determine diffusivity, and each can be independently regulated e.g. through alterations in glial morphology and the extracellular matrix composition. Here we aim to provide an overview of our current understanding of the ECS and its diffusional properties. We highlight emerging technological advances to respectively interrogate and model diffusion through the ECS, and point out how these may contribute in resolving the remaining enigmas of the ECS. [ABSTRACT FROM AUTHOR]

Background: Glutamate excitotoxicity contributes to oligodendrocyte and tissue damage in multiple sclerosis (MS). Intriguingly, glutamate level in plasma and cerebrospinal fluid of MS patients is elevated, a feature which may be related to the pathophysiology of this disease. In addition to glutamate transporters, levels of extracellular glutamate are controlled by cystine/glutamate antiporter xc-, an exchanger that provides intracellular cystine for production of glutathione, the major cellular antioxidant. The objective of this study was to analyze the role of the system xc- in glutamate homeostasis alterations in MS pathology. Methods: Primary cultures of human monocytes and the cell line U-937 were used to investigate the mechanism of glutamate release. Expression of cystine glutamate exchanger (xCT) was quantified by quantitative PCR, Western blot, flow cytometry and immunohistochemistry in monocytes in vitro, in animals with experimental autoimmune encephalomyelitis (EAE), the animal model of MS, and in samples of MS patients. Results and discussion: We show here that human activated monocytes release glutamate through cystine/glutamate antiporter xc- and that the expression of the catalytic subunit xCT is upregulated as a consequence of monocyte activation. In addition, xCT expression is also increased in EAE and in the disease proper. In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells. In particular, cells from monocyte-macrophage-microglia lineage have higher xCT expression in MS and in EAE, indicating that immune activation upregulates xCT levels, which may result in higher glutamate release and contribution to excitotoxic damage to oligodendrocytes. Conclusions: Together, these results reveal that increased expression of the cystine/glutamate antiporter system xc- in MS provides a link between inflammation and excitotoxicity in demyelinating diseases. [ABSTRACT FROM AUTHOR]

Synaptic protein α-synuclein (α-SYN) modulates neurotransmission in a complex and poorly understood manner and aggregates in the cytoplasm of degenerating neurons in Parkinson's disease. Here, we report that α-SYN present in dopaminergic nigral afferents is essential for the normal cycling and maintenance of neural stem cells (NSCs) in the brain subependymal zone of adult male and female mice. We also show that premature senescence of adult NSCs into non-neurogenic astrocytes in mice lacking α-SYN resembles the effects of dopaminergic fiber degeneration resulting from chronic exposure to l-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine or intranigral inoculation of aggregated toxic α-SYN. Interestingly, NSC loss in α-SYN-deficient mice can be prevented by viral delivery of human α-SYN into their sustantia nigra or by treatment with l-DOPA, suggesting that α-SYN regulates dopamine availability to NSCs. Our data indicate that α-SYN, present in dopaminergic nerve terminals supplying the subependymal zone, acts as a niche component to sustain the neurogenic potential of adult NSCs and identify α-SYN and DA as potential targets to ameliorate neurogenic defects in the aging and diseased brain. [ABSTRACT FROM AUTHOR]