Targeted Extracellular Vesicle Gene Therapy for Modulating Alpha-Synuclein Expression in Gut and Spinal Cord.

The development of effective disease-modifying therapies to halt Parkinson's disease (PD) progression is required. In a subtype of PD patients, alpha-synuclein pathology may start in the enteric nervous system (ENS) or autonomic peripheral nervous system. Consequently, strategies to decrease the expression of alpha-synuclein in the ENS will be an approach to prevent PD progression at pre-clinical stages in these patients. In the present study, we aimed to assess if anti-alpha-synuclein shRNA-minicircles (MC) delivered by RVG-extracellular vesicles (RVG-EV) could downregulate alpha-synuclein expression in the intestine and spinal cord. RVG-EV containing shRNA-MC were injected intravenously in a PD mouse model, and alpha-synuclein downregulation was evaluated by qPCR and Western blot in the cord and distal intestine. Our results confirmed the downregulation of alpha-synuclein in the intestine and spinal cord of mice treated with the therapy. We demonstrated that the treatment with anti-alpha-synuclein shRNA-MC RVG-EV after the development of pathology is effective to downregulate alpha-synuclein expression in the brain as well as in the intestine and spinal cord. Moreover, we confirmed that a multidose treatment is necessary to maintain downregulation for long-term treatments. Our results support the potential use of anti-alpha-synuclein shRNA-MC RVG-EV as a therapy to delay or halt PD pathology progression.

Impact of endolysosomal dysfunction upon exosomes in neurodegenerative diseases.

Although the factors contributing to the pathogenesis of neurodegenerative diseases remain elusive, endolysosomal pathway is emerging as a key player in the pathogenesis of neurodegenerative diseases. The link between endolysosomal dysfunction and neurodegeneration is supported by genetic studies identifying disease mutations in genes controlling endolysosomal function. Growing evidence suggests that endolysosomal dysfunction affect the production, secretion and content of exosomes. Current data suggests that exosomes play a key role in Parkinson's disease (PD) and Alzheimer's disease (AD) progression, interfering with the transmission of pathological proteins or neuroinflammatory factors related to neurodegenerative diseases. This review summarizes recent advances in the role of endolysosomal dysfunction in the spreading of pathological proteins mediated by exosomes in the two most common neurodegenerative diseases, AD and PD.

The Two Faces of Exosomes in Parkinson's Disease: From Pathology to Therapy.

Accumulating evidence suggests that exosomes play a key role in Parkinson's disease (PD). Exosomes may contribute to the PD progression facilitating the spread of pathological alpha-synuclein or activating immune cells. Glial cells also release exosomes, and transmission of exosomes derived from activated glial cells containing inflammatory mediators may contribute to the propagation of the neuroinflammatory response. Glia-to-neuron transmission of exosomes containing alpha-synuclein may contribute to alpha-synuclein propagation and neurodegeneration. Additionally, miRNAs can be transmitted among cells via exosomes inducing changes in the genetic program of the target cell contributing to PD progression. Exosomes also represent a promising drug delivery system. The brain is a difficult target for drugs of all classes because the blood-brain barrier excludes most macromolecular drugs. One of the major challenges is the development of vehicles for robust delivery to the brain. Targeted exosomes may have the potential for delivering therapeutic agents, including proteins and gene therapy molecules, into the brain. This review summarizes recent advances in the role of exosomes in PD pathology progression and their potential use as drug delivery system for PD treatment, the two faces of the exosomes in PD.

Biomonitoring of Mycotoxins in Plasma of Patients with Alzheimer's and Parkinson's Disease.

Exposure to environmental contaminants might play an important role in neurodegenerative disease pathogenesis, such as Parkinson´s disease (PD) and Alzheimer´s disease (AD). For the first time in Spain, the plasmatic levels of 19 mycotoxins from patients diagnosed with a neurodegenerative disease (44 PD and 24 AD) and from their healthy companions (25) from La Rioja region were analyzed. The studied mycotoxins were aflatoxins B1, B2, G1, G2 and M1, T-2 and HT-2, ochratoxins A (OTA) and B (OTB), zearalenone, sterigmatocystin (STER), nivalenol, deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, deepoxy-deoxynivalenol, neosolaniol, diacetoxyscirpenol and fusarenon-X. Samples were analyzed by LC-MS/MS before and after treatment with ß-glucuronidase/arylsulfatase in order to detect potential metabolites. Only OTA, OTB and STER were detected in the samples. OTA was present before (77% of the samples) and after (89%) the enzymatic treatment, while OTB was only detectable before (13%). Statistically significant differences in OTA between healthy companions and patients were observed but the observed differences might seem more related to gender (OTA levels higher in men, p-value = 0.0014) than the disease itself. STER appeared only after enzymatic treatment (88%). Statistical analysis on STER, showed distributions always different between healthy controls and patients (patients' group > controls, p-value < 0.0001). Surprisingly, STER levels weakly correlated positively with age in women (rho = 0.3384), while OTA correlation showed a decrease of levels with age especially in the men with PD (rho = -0.4643).

siRNA Loaded-Exosomes.

Exosomes are membrane-bound vesicles (40-100 nm) of endocytic origin released by numerous cell types that act as natural carriers of mRNA, microRNA, and proteins between cells. We developed a new system that uses intravenous injection of modified exosomes for siRNA delivery into the brain. Here we describe the generation of unmodified and modified exosomes, which specifically target the brain, and the method to load siRNA into the exosomes.

Oral subchronic exposure to the mycotoxin ochratoxin A induces key pathological features of Parkinson's disease in mice six months after the end of the treatment.

Some epidemiological studies with different levels of evidence have pointed to a higher risk of Parkinson's disease (PD) after exposure to environmental toxicants. A practically unexplored potential etiological factor is a group of naturally-occurring fungal secondary metabolites called mycotoxins. The mycotoxin ochratoxin A (OTA) has been reported to be neurotoxic in mice. To further identify if OTA exposure could have a role in PD pathology, Balb/c mice were orally treated with OTA (0.21, 0.5 mg/kg bw) four weeks and left for six months under normal diet. Effects of OTA on the onset, progression of alpha-synuclein pathology and development of motor deficits were evaluated. Immunohistochemical and biochemical analyses showed that oral subchronic OTA treatment induced loss of striatal dopaminergic innervation and dopaminergic cell dysfunction responsible for motor impairments. Phosphorylated alpha-synuclein levels were increased in gut and brain. LAMP-2A protein was decreased in tissues showing alpha-synuclein pathology. Cell cultures exposed to OTA exhibited decreased LAMP-2A protein, impairment of chaperone-mediated autophagy and decreased alpha-synuclein turnover which was linked to miRNAs deregulation, all reminiscent of PD. These results support the hypothesis that oral exposure to low OTA doses in mice can lead to biochemical and pathological changes reported in PD.

Oral Sub-chronic Ochratoxin A Exposure Induces Gut Microbiota Alterations in Mice.

Gut microbiota plays crucial roles in maintaining host health. External factors, such as diet, medicines, and environmental toxins, influence the composition of gut microbiota. Ochratoxin A (OTA) is one of the most prevalent and relevant mycotoxins and is a highly abundant food and animal feed contaminant. In the present study, we aimed to investigate OTA gut microbiome toxicity in mice sub-chronically exposed to low doses of OTA (0.21, 0.5, and 1.5 mg/kg body weight) by daily oral gavage for 28 days. Fecal microbiota from control and OTA-treated mice was analyzed using 16S ribosomal RNA (rRNA) gene sequencing followed by metagenomics. OTA exposure caused marked changes in gut microbial community structure, including the decrease in the diversity of fecal microbiota and the relative abundance of Firmicutes, as well as the increase in the relative abundance of Bacteroidetes at the phylum level. At the family level, six bacterial families (unclassified Bacteroidales, Porphyromonadaceae, unclassified Cyanobacteria, Streptococcaceae, Enterobacteriaceae, Ruminococcaceae) were significantly altered by OTA exposure. Interestingly, OTA-induced changes were observed in the lower-dose OTA groups, while high-dose OTA group microbiota was similar to control group. Our results demonstrated that sub-chronic exposure at low doses of OTA alters the structure and diversity of the gut microbial community.

Glial activation precedes alpha-synuclein pathology in a mouse model of Parkinson's disease.

Neuroinflammation is increasingly recognized as an important feature in the pathogenesis of Parkinson's disease (PD). However, it remains unclear whether neuroinflammation contributes to nigral degeneration in PD or is merely a secondary marker of neurodegeneration. We aimed to investigate the temporal relationship between synucleopathy, neuroinflammation and nigrostriatal degeneration in a mouse model of PD. Mice received unilateral intrastriatal injection of alpha-synuclein pre-formed fibrils, alpha-synuclein monomer or vehicle and were sacrificed at 15, 30 and 90 days post-injection. Intrastriatal inoculation of alpha-synuclein fibrils led to significant alpha-synuclein aggregation in the substantia nigra peaking at 30 days after injection while the significant increase in Iba-1 cells, GFAP cells and IL-1ß expression peaked earlier at 15 days. At 90 days, the striatal dopaminergic denervation was associated with astroglial activation. Alpha-synuclein monomer did not result in long-term glia activation or increase in inflammatory markers. The spread of alpha-synuclein aggregates into the cortex was not associated with any changes to neuroinflammatory markers. Our results demonstrate that in the substantia nigra glial activation is an early event that precedes alpha-synuclein inclusion formation, suggesting neuroinflammation could play an important early role in the pathogenesis of PD.

Systemic Exosomal Delivery of shRNA Minicircles Prevents Parkinsonian Pathology.

The development of new therapies to slow down or halt the progression of Parkinson's disease is a health care priority. A key pathological feature is the presence of alpha-synuclein aggregates, and there is increasing evidence that alpha-synuclein propagation plays a central role in disease progression. Consequently, the downregulation of alpha-synuclein is a potential therapeutic target. As a chronic disease, the ideal treatment will be minimally invasive and effective in the long-term. Knockdown of gene expression has clear potential, and siRNAs specific to alpha-synuclein have been designed; however, the efficacy of siRNA treatment is limited by its short-term efficacy. To combat this, we designed shRNA minicircles (shRNA-MCs), with the potential for prolonged effectiveness, and used RVG-exosomes as the vehicle for specific delivery into the brain. We optimized this system using transgenic mice expressing GFP and demonstrated its ability to downregulate GFP protein expression in the brain for up to 6 weeks. RVG-exosomes were used to deliver anti-alpha-synuclein shRNA-MC therapy to the alpha-synuclein preformed-fibril-induced model of parkinsonism. This therapy decreased alpha-synuclein aggregation, reduced the loss of dopaminergic neurons, and improved the clinical symptoms. Our results confirm the therapeutic potential of shRNA-MCs delivered by RVG-exosomes for long-term treatment of neurodegenerative diseases.

Outstanding Phenotypic Differences in the Profile of Amyloid-ß between Tg2576 and APPswe/PS1dE9 Transgenic Mouse Models of Alzheimer's Disease.

APPswe/PS1dE9 and Tg2576 are very common transgenic mouse models of Alzheimer's disease (AD), used in many laboratories as tools to research the mechanistic process leading to the disease. In order to augment our knowledge about the amyloid-ß (Aß) isoforms present in both transgenic mouse models, we have developed two chromatographic methods, one acidic and the other basic, for the characterization of the Aß species produced in the brains of the two transgenic mouse models. After immunoprecipitation and micro-liquid chromatography-electrospray ionization mass spectrometry/mass spectrometry, 10 species of Aß, surprisingly all of human origin, were detected in the brain of Tg2576 mouse, whereas 39 species, of both murine and human origin, were detected in the brain of the APP/PS1 mouse. To the best of our knowledge, this is the first study showing the identification of such a high number of Aß species in the brain of the APP/PS1 transgenic mouse, whereas, in contrast, a much lower number of Aß species were identified in the Tg2576 mouse. Therefore, this study brings to light a relevant phenotypic difference between these two popular mice models of AD.

Optimized protocol for amyloid-ß extraction from the brain.

Brain levels of amyloid-ß (Aß) are frequently assessed in transgenic mice models of Alzheimer's disease. The procedure involves tissue sample homogenization using different buffers in a sequential process. No attempt has been made to assess if these procedures are able to extract the total amount of Aß present in the samples. Here we present data suggesting that standard protocols can lead to a dramatic underestimation of the Aß content. Results show that higher extraction buffer volumes and at least two repetitions of the soluble and membrane-bound extraction steps are necessary for a more accurate estimation of the Aß content in brain tissues.

Administration of neurotoxic doses of MDMA reduces sensitivity to ethanol and increases GAT-1 immunoreactivity in mice striatum.

RATIONALE: Mice with reduced dopamine activity following neurotoxic doses of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') consume more ethanol (EtOH) and show greater preference for EtOH. In keeping with human studies and other animal models where alcohol consumption and preference are also high, MDMA treatment will reduce sensitivity to certain physiological effects of EtOH. OBJECTIVE: We have examined the sensitivity to the acute effects of EtOH in MDMA-lesioned mice and the effects of EtOH on striatal gamma-aminobutyric acid (GABA) accumulation and expression of GABA subtype-1 transporter (GAT-1). METHODS: C57BL/6J mice were injected with neurotoxic MDMA (30 mg/kg, three times, every 3 h, i.p.). Seven days later, mice were given EtOH (3 g/kg, i.p.) to determine the loss of righting response and the development of rapid tolerance to the hypothermic effect of EtOH. The effect of EtOH on the striatal accumulation of GABA after inhibiting GABA transaminase and on GAT-1 immunoreactivity was also determined. RESULTS: Mice pre-treated with a neurotoxic dose of MDMA were less sensitive to the sedative-hypnotic effect of acute EtOH and exhibited alterations in the development of rapid tolerance to the hypothermic effect of EtOH. These animals showed an increase in striatal GAT-1 immunoreactivity. EtOH reduced GABA concentration in the striatum of non-lesioned mice, an effect not observed in MDMA-lesioned mice. CONCLUSION: These findings indicate that mice with a MDMA-induced dopaminergic lesion show increased expression of striatal GAT-1 that may contribute to the lower sensitivity to EtOH-induced sedative effects and the resistance to the development of rapid tolerance to hypothermia produced by EtOH.

A study on the mechanisms by which minocycline protects against MDMA ('ecstasy')-induced neurotoxicity of 5-HT cortical neurons.

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is a selective 5-HT neurotoxin in rat brain which has been shown to produce acute neuroinflammation characterized by activation of microglia and release of interleukin-1beta (IL-1beta). We aimed to determine whether or not minocycline, a semi-synthetic tetracycline antibiotic capable of inhibiting microglial activation, could prevent the inflammatory response and reduce the toxicity induced by MDMA. Adult male Dark Agouti rats were given minocycline twice a day for 2 days (45 mg/kg on the first day and 90 mg/kg on the second day; 12-h apart, i.p.). MDMA (12.5 mg/kg; i.p.) was given after the third minocycline injection and animals were killed either 1 h later for the determination of NFkappaB binding activity, 3 h later for the determination of IL-1beta, 24 h later for the determination of microglial activation or 7 days later for the determination of [(3)H]-paroxetine binding as a measure of 5-HT neurotoxicity. MDMA increased NFkappaB activation, IL-1beta release and microglial activation both in the frontal cortex and in the hypothalamus and 7 days later produced a reduction in the density of 5-HT uptake sites in both these brain areas. Minocycline prevented the MDMA-induced increase in NFkappaB activation, IL-1beta release and microglial activation in the frontal cortex and prevented the 5-HT neurotoxicity 7 days later. However, in the hypothalamus, in spite of preventing MDMA-induced microglial activation, minocycline failed to prevent MDMA-induced NFkappaB activation, IL-1beta release and neurotoxicity. This suggests that the protective mechanism of minocycline against MDMA-induced neurotoxicity in frontal cortex involves inhibition of MDMA-induced NFkappaB activation possibly through a reduction in IL-1beta signalling.

Mice with decreased cerebral dopamine function following a neurotoxic dose of MDMA (3,4-methylenedioxymethamphetamine, "Ecstasy") exhibit increased ethanol consumption and preference.

MDMA (3,4-methylenedioxymethamphetamine, "ecstasy") administration to mice produces relatively selective long-term neurotoxic damage to dopaminergic pathways. There is strong evidence indicating that the dopamine system plays a key role in the rewarding effects of ethanol and modulates ethanol intake. Using a two-bottle free-choice paradigm, we examined the voluntary consumption and preference for ethanol in mice deficient in cerebral dopamine concentration and dopamine transporter density by previous repeated MDMA administration. The current study shows that mice pre-exposed to a neurotoxic dose of MDMA exhibited a higher consumption of and preference for ethanol compared with saline-treated animals. The D(1) receptor full agonist SKF81297 [(6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide)] attenuated the enhanced ethanol intake, an effect that was reversed by SCH23390 [((R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride], a D(1) receptor antagonist. MDMA-exposed mice also showed a reduced release of basal dopamine in the nucleus accumbens compared with saline-injected animals and a modest increase in D(1) receptor density in caudate-putamen and nucleus accumbens. Intraperitoneal administration of ethanol elevated extracellular dopamine release in the nucleus accumbens of saline-treated mice, but this effect was almost abolished in MDMA-treated mice. Differences between saline- and MDMA-treated animals did not appear to be secondary to changes in acute ethanol clearance. These results indicate that mice with reduced dopamine activity following a neurotoxic dose of MDMA exhibit increased ethanol consumption and preference and suggest that animals might need to consume more alcohol to reach the threshold for the rewarding effects of ethanol.

Binge ethanol administration enhances the MDMA-induced long-term 5-HT neurotoxicity in rat brain.

RATIONALE: Ecstasy abuse commonly occurs in hot, overcrowded environments in combination with alcohol. Around 90% of ecstasy users take ethanol; over 70% of these users also often drink alcohol at hazardous levels. OBJECTIVES: We wished to examine whether binge ethanol administration enhanced the long-lasting 5-HT neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in rats maintained at high ambient temperature and the role of acetaldehyde. MATERIALS AND METHODS: Rats were treated with a 4-day ethanol regimen leading to plasma ethanol levels of around 450 mg/dl. On day 5, rats were placed at 30 degrees C and administered MDMA (5 mg/kg). Rectal temperature and hydroxyl radical formation were measured immediately before and up to 6 h after MDMA. 5-HT concentration and 5-HT transporter density were determined 7 days later. A group of rats received cyanamide (50 mg/kg) on days 1 and 3 of the 4-day-ethanol inhalation. RESULTS: In ethanol treated rats, MDMA produced a hyperthermic response similar to that observed in controls but enhanced the loss of 5-HT concentration and 5-HT transporter density in the hippocampus. Cyanamide elevated the plasma acetaldehyde concentration fivefold to sevenfold, reduced the MDMA-induced hyperthermia and increased the neuronal damage with neurotoxicity also appearing in the cortex. MDMA increased hydroxyl radical production in the hippocampus, the effect being more marked in rats pre-exposed to ethanol. CONCLUSIONS: Binge ethanol administration enhances the MDMA-induced long-term 5-HT neurotoxicity by a mechanism not related to changes in acute hyperthermia but probably involving hydroxyl radical formation. The magnitude of this effect is more pronounced after increasing plasma acetaldehyde levels by aldehyde dehydrogenase inhibition.