Acidic nanoparticles protect against α‐synuclein‐induced neurodegeneration through the restoration of lysosomal function

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.     

VPS35 D620N knockin mice recapitulate cardinal features of Parkinson’s disease

D620N mutation in the vacuolar protein sorting 35 ortholog (VPS35) gene causes late‐onset, autosomal dominant familial Parkinson''s disease (PD) and contributes to idiopathic PD. However, how D620N mutation leads to PD‐related deficits in vivo remains unclear. In the present study, we thoroughly characterized the biochemical, pathological, and behavioral changes of a VPS35 D620N knockin (KI) mouse model with chronic aging. We reported that this VPS35 D620N KI model recapitulated a spectrum of cardinal features of PD at 14 months of age which included age‐dependent progressive motor deficits, significant changes in the levels of dopamine (DA) and DA metabolites in the striatum, and robust neurodegeneration of the DA neurons in the SNpc and DA terminals in the striatum, accompanied by increased neuroinflammation, and accumulation and aggregation of α‐synuclein in DA neurons. Mechanistically, D620N mutation induced mitochondrial fragmentation and dysfunction in aged mice likely through enhanced VPS35‐DLP1 interaction and increased turnover of mitochondrial DLP1 complexes in vivo. Finally, the VPS35 D620N KI mice displayed greater susceptibility to MPTP‐mediated degeneration of nigrostriatal pathway, indicating that VPS35 D620N mutation increased vulnerability of DA neurons to environmental toxins. Overall, this VPS35 D620N KI mouse model provides a powerful tool for future disease modeling and pharmacological studies of PD. Our data support the involvement of VPS35 in the development of α‐synuclein pathology in vivo and revealed the important role of mitochondrial fragmentation/dysfunction in the pathogenesis of VPS35 D620N mutation‐associated PD in vivo.     

Vesicular glutamate transporter modulates sex differences in dopamine neuron vulnerability to age‐related neurodegeneration

Age is the greatest risk factor for Parkinson''s disease (PD) which causes progressive loss of dopamine (DA) neurons, with males at greater risk than females. Intriguingly, some DA neurons are more resilient to degeneration than others. Increasing evidence suggests that vesicular glutamate transporter (VGLUT) expression in DA neurons plays a role in this selective vulnerability. We investigated the role of DA neuron VGLUT in sex‐ and age‐related differences in DA neuron vulnerability using the genetically tractable Drosophila model. We found sex differences in age‐related DA neurodegeneration and its associated locomotor behavior, where males exhibit significantly greater decreases in both DA neuron number and locomotion during aging compared with females. We discovered that dynamic changes in DA neuron VGLUT expression mediate these age‐ and sex‐related differences, as a potential compensatory mechanism for diminished DA neurotransmission during aging. Importantly, female Drosophila possess higher levels of VGLUT expression in DA neurons compared with males, and this finding is conserved across flies, rodents, and humans. Moreover, we showed that diminishing VGLUT expression in DA neurons eliminates females'' greater resilience to DA neuron loss across aging. This offers a new mechanism for sex differences in selective DA neuron vulnerability to age‐related DA neurodegeneration. Finally, in mice, we showed that the ability of DA neurons to achieve optimal control over VGLUT expression is essential for DA neuron survival. These findings lay the groundwork for the manipulation of DA neuron VGLUT expression as a novel therapeutic strategy to boost DA neuron resilience to age‐ and PD‐related neurodegeneration.     

Mesenchymal stem cell‐conditioned medium attenuates the retinal pathology in amyloid‐β‐induced rat model of Alzheimer's disease: Underlying mechanisms

Amyloid‐beta (Aβ) oligomer is known to contribute to the pathophysiology of age‐related macular degeneration. Herein, we aimed to elucidate the in vivo and in vitro effects of Aβ_1‐42 application on retinal morphology in rats. Our in vivo studies revealed that intracerebroventricular administration of Aβ_1‐42 oligomer caused dysmorphological changes in both retinal ganglion cells and retinal pigment epithelium. In addition, in vitro studies revealed that ARPE‐19 cells following Aβ_1‐42 oligomer application had decreased viability along with apoptosis and decreased expression of the tight junction proteins, increased expression of both phosphor‐AKT and phosphor‐GSK3β and decreased expression of both SIRT1 and β‐catenin. Application of conditioned medium (CM) obtained from mesenchymal stem cells (MSC) protected against Aβ_1‐42 oligomer‐induced retinal pathology in both rats and ARPE‐19 cells. In order to explore the potential role of peptides secreted from the MSCs, we applied mass spectrometry to compare the peptidomics profiles of the MSC‐CM. Gene ontology enrichment analysis and String analysis were performed to explore the differentially expressed peptides by predicting the functions of their precursor proteins. Bioinformatics analysis showed that 3‐8 out of 155–163 proteins in the MSC‐CM maybe associated with SIRT1/pAKT/pGSK3β/β‐catenin, tight junction proteins, and apoptosis pathway. In particular, the secretomes information on the MSC‐CM may be helpful for the prevention and treatment of retinal pathology in age‐related macular degeneration.     

α‐synuclein suppresses microglial autophagy and promotes neurodegeneration in a mouse model of Parkinson’s disease

The cell‐to‐cell transfer of α‐synuclein (α‐Syn) greatly contributes to Parkinson''s disease (PD) pathogenesis and underlies the spread of α‐Syn pathology. During this process, extracellular α‐Syn can activate microglia and neuroinflammation, which plays an important role in PD. However, the effect of extracellular α‐Syn on microglia autophagy is poorly understood. In the present study, we reported that extracellular α‐Syn inhibited the autophagy initiation, as indicated by LC3‐II reduction and p62 protein elevation in BV2 and cultured primary microglia. The in vitro findings were verified in microglia‐enriched population isolated from α‐Syn‐overexpressing mice induced by adeno‐associated virus (AAV2/9)‐encoded wildtype human α‐Syn injection into the substantia nigra (SN). Mechanistically, α‐Syn led to microglial autophagic impairment through activating toll‐like receptor 4 (Tlr4) and its downstream p38 and Akt‐mTOR signaling because Tlr4 knockout and inhibition of p38, Akt as well as mTOR prevented α‐Syn‐induced autophagy inhibition. Moreover, inhibition of Akt reversed the mTOR activation but failed to affect p38 phosphorylation triggered by α‐Syn. Functionally, the in vivo evidence showed that lysozyme 2 Cre (Lyz2 ^cre)‐mediated depletion of autophagy‐related gene 5 (Atg5) in microglia aggravated the neuroinflammation and dopaminergic neuron losses in the SN and exacerbated the locomotor deficit in α‐Syn‐overexpressing mice. Taken together, the results suggest that extracellular α‐Syn, via Tlr4‐dependent p38 and Akt‐mTOR signaling cascades, disrupts microglial autophagy activity which synergistically contributes to neuroinflammation and PD development.     

DAF‐2/insulin IGF‐1 receptor regulates motility during aging by integrating opposite signaling from muscle and neuronal tissues

During aging, preservation of locomotion is generally considered an indicator of sustained good health, in elderlies and in animal models. In Caenorhabditis elegans, mutants of the insulin‐IGF‐1 receptor DAF2/IIRc represent a paradigm of healthy aging, as their increased lifespan is accompanied by a delay in age‐related loss of motility. Here, we investigated the DAF‐2/IIRc‐dependent relationship between longevity and motility using an auxin‐inducible degron to trigger tissue‐specific degradation of endogenous DAF‐2/IIRc. As previously reported, inactivation of DAF‐2/IIRc in neurons or intestine was sufficient to extend the lifespan of worms, whereas depletion in epidermis, germline, or muscle was not. However, neither intestinal nor neuronal depletion of DAF‐2/IIRc prevented the age‐related loss of motility. In 1‐day‐old adults, DAF‐2/IIRc depletion in neurons reduced motility in a DAF‐16/FOXO dependent manner, while muscle depletion had no effect. By contrast, DAF‐2 depletion in the muscle of middle‐age animals improved their motility independently of DAF‐16/FOXO but required UNC‐120/SRF. Yet, neuronal or muscle DAF‐2/IIRc depletion both preserved the mitochondria network in aging muscle. Overall, these results show that the motility pattern of daf‐2 mutants is determined by the sequential and opposing impact of neurons and muscle tissues and can be dissociated from the regulation of the lifespan. This work also provides the characterization of a versatile tool to analyze the tissue‐specific contribution of insulin‐like signaling in integrated phenotypes at the whole organism level.     

“Reframing” dopamine signaling at the intersection of glial networks in the aged Parkinsonian brain as innate Nrf2/Wnt driver: Therapeutical implications

Dopamine (DA) signaling via G protein‐coupled receptors is a multifunctional neurotransmitter and neuroendocrine–immune modulator. The DA nigrostriatal pathway, which controls the motor coordination, progressively degenerates in Parkinson''s disease (PD), a most common neurodegenerative disorder (ND) characterized by a selective, age‐dependent loss of substantia nigra pars compacta (SNpc) neurons, where DA itself is a primary source of oxidative stress and mitochondrial impairment, intersecting astrocyte and microglial inflammatory networks. Importantly, glia acts as a preferential neuroendocrine–immune DA target, in turn, counter‐modulating inflammatory processes. With a major focus on DA intersection within the astrocyte–microglial inflammatory network in PD vulnerability, we herein first summarize the characteristics of DA signaling systems, the propensity of DA neurons to oxidative stress, and glial inflammatory triggers dictating the vulnerability to PD. Reciprocally, DA modulation of astrocytes and microglial reactivity, coupled to the synergic impact of gene–environment interactions, then constitute a further level of control regulating midbrain DA neuron (mDAn) survival/death. Not surprisingly, within this circuitry, DA converges to modulate nuclear factor erythroid 2‐like 2 (Nrf2), the master regulator of cellular defense against oxidative stress and inflammation, and Wingless (Wnt)/β‐catenin signaling, a key pathway for mDAn neurogenesis, neuroprotection, and immunomodulation, adding to the already complex “signaling puzzle,” a novel actor in mDAn–glial regulatory machinery. Here, we propose an autoregulatory feedback system allowing DA to act as an endogenous Nrf2/Wnt innate modulator and trace the importance of DA receptor agonists applied to the clinic as immune modifiers.     

IFN‐β rescues neurodegeneration by regulating mitochondrial fission via STAT5, PGAM5, and Drp1

Mitochondrial homeostasis is essential for providing cellular energy, particularly in resource‐demanding neurons, defects in which cause neurodegeneration, but the function of interferons (IFNs) in regulating neuronal mitochondrial homeostasis is unknown. We found that neuronal IFN‐β is indispensable for mitochondrial homeostasis and metabolism, sustaining ATP levels and preventing excessive ROS by controlling mitochondrial fission. IFN‐β induces events that are required for mitochondrial fission, phosphorylating STAT5 and upregulating PGAM5, which phosphorylates serine 622 of Drp1. IFN‐β signaling then recruits Drp1 to mitochondria, oligomerizes it, and engages INF2 to stabilize mitochondria–endoplasmic reticulum (ER) platforms. This process tethers damaged mitochondria to the ER to separate them via fission. Lack of neuronal IFN‐β in the Ifnb ^–/– model of Parkinson disease (PD) disrupts STAT5‐PGAM5‐Drp1 signaling, impairing fission and causing large multibranched, damaged mitochondria with insufficient ATP production and excessive oxidative stress to accumulate. In other PD models, IFN‐β rescues dopaminergic neuronal cell death and pathology, associated with preserved mitochondrial homeostasis. Thus, IFN‐β activates mitochondrial fission in neurons through the pSTAT5/PGAM5/^S622Drp1 pathway to stabilize mitochondria/ER platforms, constituting an essential neuroprotective mechanism.     

3,6'‐disinapoyl sucrose attenuates Aβ1‐42‐ induced neurotoxicity in Caenorhabditis elegans by enhancing antioxidation and regulating autophagy

The aggregation of β‐amyloid (Aβ) has the neurotoxicity, which is thought to play critical role in the pathogenesis of Alzheimer''s disease (AD). Inhibiting Aβ deposition and neurotoxicity has been considered as an important strategy for AD treatment. 3,6''‐Disinapoyl sucrose (DISS), one of the oligosaccharide esters derived from traditional Chinese medicine Polygalae Radix, possesses antioxidative activity, neuroprotective effect and anti‐depressive activity. This study was to explore whether DISS could attenuate the pathological changes of Aβ_1‐42 transgenic Caenorhabditis elegans (C. elegans). The results showed that DISS (5 and 50 μM) treatment significantly prolonged the life span, increased the number of egg‐laying, reduced paralysis rate, decreased the levels of lipofuscin and ROS and attenuated Aβ deposition in Aβ_1‐42 transgenic C. elegans. Gene analysis showed that DISS could up‐regulate the mRNA expression of sod‐3, gst‐4, daf‐16, bec‐1 and lgg‐1, while down‐regulate the mRNA expression of daf‐2 and daf‐15 in Aβ_1‐42 transgenic C. elegans. These results suggested that DISS has the protective effect against Aβ_1‐42‐induced pathological damages and prolongs the life span of C. elegans, which may be related to the reduction of Aβ deposition and neurotoxicity by regulating expression of genes related to antioxidation and autophagy.     

Age‐related changes in hippocampal‐dependent synaptic plasticity and memory mediated by p75 neurotrophin receptor

The plasticity mechanisms in the nervous system that are important for learning and memory are greatly impacted during aging. Notably, hippocampal‐dependent long‐term plasticity and its associative plasticity, such as synaptic tagging and capture (STC), show considerable age‐related decline. The p75 neurotrophin receptor (p75^NTR) is a negative regulator of structural and functional plasticity in the brain and thus represents a potential candidate to mediate age‐related alterations. However, the mechanisms by which p75^NTR affects synaptic plasticity of aged neuronal networks and ultimately contribute to deficits in cognitive function have not been well characterized. Here, we report that mutant mice lacking the p75^NTR were resistant to age‐associated changes in long‐term plasticity, associative plasticity, and associative memory. Our study shows that p75^NTR is responsible for age‐dependent disruption of hippocampal homeostatic plasticity by modulating several signaling pathways, including BDNF, MAPK, Arc, and RhoA‐ROCK2‐LIMK1‐cofilin. p75^NTR may thus represent an important therapeutic target for limiting the age‐related memory and cognitive function deficits.     

Parkin drives pS65‐Ub turnover independently of canonical autophagy in Drosophila

Parkinson''s disease‐related proteins, PINK1 and Parkin, act in a common pathway to maintain mitochondrial quality control. While the PINK1‐Parkin pathway can promote autophagic mitochondrial turnover (mitophagy) following mitochondrial toxification in cell culture, alternative quality control pathways are suggested. To analyse the mechanisms by which the PINK1–Parkin pathway operates in vivo, we developed methods to detect Ser65‐phosphorylated ubiquitin (pS65‐Ub) in Drosophila. Exposure to the oxidant paraquat led to robust, Pink1‐dependent pS65‐Ub production, while pS65‐Ub accumulates in unstimulated parkin‐null flies, consistent with blocked degradation. Additionally, we show that pS65‐Ub specifically accumulates on disrupted mitochondria in vivo. Depletion of the core autophagy proteins Atg1, Atg5 and Atg8a did not cause pS65‐Ub accumulation to the same extent as loss of parkin, and overexpression of parkin promoted turnover of both basal and paraquat‐induced pS65‐Ub in an Atg5‐null background. Thus, we have established that pS65‐Ub immunodetection can be used to analyse Pink1‐Parkin function in vivo as an alternative to reporter constructs. Moreover, our findings suggest that the Pink1‐Parkin pathway can promote mitochondrial turnover independently of canonical autophagy in vivo.     

SIAH proteins regulate the degradation and intra‐mitochondrial aggregation of PINK1: Implications for mitochondrial pathology in Parkinson's disease

Parkinson''s disease (PD) is characterized by degeneration of neurons, particularly dopaminergic neurons in the substantia nigra. PD brains show accumulation of α‐synuclein in Lewy bodies and accumulation of dysfunctional mitochondria. However, the mechanisms leading to mitochondrial pathology in sporadic PD are poorly understood. PINK1 is a key for mitophagy activation and recycling of unfit mitochondria. The activation of mitophagy depends on the accumulation of uncleaved PINK1 at the outer mitochondrial membrane and activation of a cascade of protein ubiquitination at the surface of the organelle. We have now found that SIAH3, a member of the SIAH proteins but lacking ubiquitin‐ligase activity, is increased in PD brains and cerebrospinal fluid and in neurons treated with α‐synuclein preformed fibrils (α‐SynPFF). We also observed that SIAH3 is aggregated together with PINK1 in the mitochondria of PD brains. SIAH3 directly interacts with PINK1, leading to their intra‐mitochondrial aggregation in cells and neurons and triggering a cascade of toxicity with PINK1 inactivation along with mitochondrial depolarization and neuronal death. We also found that SIAH1 interacts with PINK1 and promotes ubiquitination and proteasomal degradation of PINK1. Similar to the dimerization of SIAH1/SIAH2, SIAH3 interacts with SIAH1, promoting its translocation to mitochondria and preventing its ubiquitin‐ligase activity toward PINK1. Our results support the notion that the increase in SIAH3 and intra‐mitochondrial aggregation of SIAH3‐PINK1 may mediate α‐synuclein pathology by promoting proteotoxicity and preventing the elimination of dysfunctional mitochondria. We consider it possible that PINK1 activity is decreased in sporadic PD, which impedes proper mitochondrial renewal in the disease.     

1‐Undecene from Pseudomonas aeruginosa is an olfactory signal for flight‐or‐fight response in Caenorhabditis elegans

Animals possess conserved mechanisms to detect pathogens and to improve survival in their presence by altering their own behavior and physiology. Here, we utilize Caenorhabditis elegans as a model host to ask whether bacterial volatiles constitute microbe‐associated molecular patterns. Using gas chromatography–mass spectrometry, we identify six prominent volatiles released by the bacterium Pseudomonas aeruginosa. We show that a specific volatile, 1‐undecene, activates nematode odor sensory neurons inducing both flight and fight responses in worms. Using behavioral assays, we show that worms are repelled by 1‐undecene and that this aversion response is driven by the detection of this volatile through AWB odor sensory neurons. Furthermore, we find that 1‐undecene odor can induce immune effectors specific to P. aeruginosa via AWB neurons and that brief pre‐exposure of worms to the odor enhances their survival upon subsequent bacterial infection. These results show that 1‐undecene derived from P. aeruginosa serves as a pathogen‐associated molecular pattern for the induction of protective responses in C. elegans.     

Age‐specific habitat preference,carrying capacity,and landscape structure determine the response of population spatial variability to fishing‐driven age truncation

1. Understanding the mechanisms underlying spatial variability of exploited fish is critical for the sustainable management of fish stocks. Empirical studies suggest that size‐selective fishing can elevate fish population spatial variability (i.e., more heterogeneous distribution) through age truncation, making the population less resilient to changing environment. However, species differ in how their spatial variability responds to age truncation and the underlying mechanisms remain unclear.
2. We hypothesize that age‐specific habitat preference, together with environmental carrying capacity and landscape structure, determines the response of population spatial variability to fishing‐induced age truncation. To test these hypotheses, we design an individual‐based model of an age‐structured fish population on a two‐dimensional landscape under size‐selective fishing. Individual fish reproduces and survives, and moves between habitats according to age‐specific habitat preference and density‐dependent habitat selection.
3. Population spatial variability elevates with increasing age truncation, and the response is stronger for populations with stronger age‐specific habitat preference. On a gradient landscape, reducing carrying capacity elevates the relative importance of density dependence in habitat selection, which weakens the response of spatial variability to age truncation for populations with strong age‐specific habitat preference. On a fragmented landscape, both populations with strong and weak age‐specific habitat preferences are restricted at local optimal habitats, and reducing carrying capacity weakens the responses of spatial variability to age truncation for both populations.
4. Synthesis and applications. We demonstrate that to track and predict the changes in population spatial variability under exploitation, it is essential to consider the interactive effects of age‐specific habitat preference, carrying capacity, and landscape structure. To improve spatial management in fisheries, it is crucial to enhance empirical and theoretical developments in the methodology to quantify age‐specific habitat preference of marine fish, and to understand how climatic change influences carrying capacity and landscape continuity.

     

Müller Glia maintain their regenerative potential despite degeneration in the aged zebrafish retina

Ageing is a significant risk factor for degeneration of the retina. Müller glia cells (MG) are key for neuronal regeneration, so harnessing the regenerative capacity of MG in the retina offers great promise for the treatment of age‐associated blinding conditions. Yet, the impact of ageing on MG regenerative capacity is unclear. Here, we show that the zebrafish retina undergoes telomerase‐independent, age‐related neurodegeneration but that this is insufficient to stimulate MG proliferation and regeneration. Instead, age‐related neurodegeneration is accompanied by MG morphological aberrations and loss of vision. Mechanistically, yes‐associated protein (Yap), part of the Hippo signalling, has been shown to be critical for the regenerative response in the damaged retina, and we show that Yap expression levels decline with ageing. Despite this, morphologically and molecularly altered aged MG retain the capacity to regenerate neurons after acute light damage, therefore, highlighting key differences in the MG response to high‐intensity acute damage versus chronic neuronal loss in the zebrafish retina.     

Epac‐2 ameliorates spontaneous colitis in Il‐10 −/− mice by protecting the intestinal barrier and suppressing NF‐κB/MAPK signalling

Intestinal barrier dysfunction and intestinal inflammation interact in the progression of Crohn''s disease (CD). A recent study indicated that Epac‐2 protected the intestinal barrier and had anti‐inflammatory effects. The present study examined the function of Epac‐2 in CD‐like colitis. Interleukin‐10 gene knockout (Il‐10 ^−/−) mice exhibit significant spontaneous enteritis and were used as the CD model. These mice were treated with Epac‐2 agonists (Me‐cAMP) or Epac‐2 antagonists (HJC‐0350) or were fed normally (control), and colitis and intestinal barrier structure and function were compared. A Caco‐2 and RAW 264.7 cell co‐culture system were used to analyse the effects of Epac‐2 on the cross‐talk between intestinal epithelial cells and inflammatory cells. Epac‐2 activation significantly ameliorated colitis in mice, which was indicated by reductions in the colitis inflammation score, the expression of inflammatory factors and intestinal permeability. Epac‐2 activation also decreased Caco‐2 cell permeability in an LPS‐induced cell co‐culture system. Epac‐2 activation significantly suppressed nuclear factor (NF)‐κB/mitogen‐activated protein kinase (MAPK) signalling in vivo and in vitro. Epac‐2 may be a therapeutic target for CD based on its anti‐inflammatory functions and protective effects on the intestinal barrier.