Toxicity of extracellular alpha-synuclein is independent of intracellular alpha-synuclein.

Parkinson´s disease (PD) pathology progresses throughout the nervous system. Whereas motor symptoms are always present, there is a high variability in the prevalence of non-motor symptoms. It has been postulated that the progression of the pathology is based on a prion-like disease mechanism partly due to the seeding effect of endocytosed-alpha-synuclein (ASYN) on the endogenous ASYN. Here, we analyzed the role of endogenous ASYN in the progression of PD-like pathology in vivo and in vitro and compared the effect of endocytosed-ASYN as well as paraquat and rotenone on primary enteric, dopaminergic and cortical neurons from wild-type and ASYN-KO mice. Our results show that, in vivo, pathology progression did not occur in the absence of endogenous ASYN. Remarkably, the damage caused by endocytosed-ASYN, rotenone or paraquat was independent from endogenous ASYN and related to the alteration of the host´s mitochondrial membrane potential. Dopaminergic neurons were very sensitive to these noxae compared to other neuronal subtypes. These results suggest that ASYN-mitochondrial interactions play a major role in initiating the pathological process in the host neuron and endogenous ASYN is essential for the transsynaptical transmission of the pathology. Our results also suggest that protecting mitochondrial function is a valid primary therapeutic target.

A Primeval Mechanism of Tolerance to Desiccation Based on Glycolic Acid Saves Neurons in Mammals from Ischemia by Reducing Intracellular Calcium-Mediated Excitotoxicity.

Stroke is the second leading cause of death and disability worldwide. Current treatments, such as pharmacological thrombolysis or mechanical thrombectomy, reopen occluded arteries but do not protect against ischemia-induced damage that occurs before reperfusion or neuronal damage induced by ischemia/reperfusion. It has been shown that disrupting the conversion of glyoxal to glycolic acid (GA) results in a decreased tolerance to anhydrobiosis in Caenorhabditis elegans dauer larva and that GA itself can rescue this phenotype. During the process of desiccation/rehydration, a metabolic stop/start similar to the one observed during ischemia/reperfusion occurs. In this study, the protective effect of GA is tested in different ischemia models, i.e., in commonly used stroke models in mice and swine. The results show that GA, given during reperfusion, strongly protects against ischemic damage and improves functional outcome. Evidence that GA exerts its effect by counteracting the glutamate-dependent increase in intracellular calcium during excitotoxicity is provided. These results suggest that GA treatment has the potential to reduce mortality and disability in stroke patients.

Pathophysiological Changes in the Enteric Nervous System of Rotenone-Exposed Mice as Early Radiological Markers for Parkinson's Disease.

Parkinson's disease (PD) is known to involve the peripheral nervous system (PNS) and the enteric nervous system (ENS). Functional changes in PNS and ENS appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients like constipation, that can precede the appearance of motor symptoms by years. Here we analyzed the effect of the pesticide rotenone, a mitochondrial Complex I inhibitor, on the function and neuronal composition of the ENS by measuring intestinal contractility in a tissue bath and by analyzing related protein expression. Our results show that rotenone changes the normal physiological response of the intestine to carbachol, dopamine and electric field stimulation (EFS). Changes in the reaction to EFS seem to be related to the reduction in the cholinergic input but also related to the noradrenergic input, as suggested by the non-adrenergic non-cholinergic (NANC) reaction to the EFS in rotenone-exposed mice. The magnitude and direction of these alterations varies between intestinal regions and exposure times and is associated with an early up-regulation of dopaminergic, cholinergic and adrenergic receptors and an irregular reduction in the amount of enteric neurons in rotenone-exposed mice. The early appearance of these alterations, that start occurring before the substantia nigra is affected in this mouse model, suggests that these alterations could be also observed in patients before the onset of motor symptoms and makes them ideal potential candidates to be used as radiological markers for the detection of Parkinson's disease in its early stages.

Changes in the sympathetic innervation of the gut in rotenone treated mice as possible early biomarker for Parkinson's disease.

INTRODUCTION: Involvement of the peripheral nervous system (PNS) is relatively common in Parkinson's disease (PD) patients. PNS alterations appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients. In previous studies, we have shown that environmental toxins can trigger the disease by acting on the enteric nervous system. MATERIAL AND METHODS: Here, we analyzed the effect of mitochondrial Complex I inhibition on sympathetic neuritis in vivo and sympathetic neurons in vitro. Combining in vivo imaging and protein expression profiling. RESULTS: we found that rotenone, a widely used mitochondrial Complex I inhibitor decreases the density of sympathetic neurites innervating the gut in vivo, while in vitro, it induces the redistribution of intracellular alpha-synuclein and neurite degeneration. Interestingly, sympathetic neurons are much more resistant to rotenone exposure than mesencephalic dopaminergic neurons. CONCLUSION: Altogether, these results suggest that enteric sympathetic denervation could be an initial pre-motor alteration in PD progression that could be used as an early biomarker of the disease.

Providing the right cues in nerve guidance conduits: Biofunctionalization versus fiber profile to facilitate oriented neuronal outgrowth.

Following peripheral nerve injury, rapid and spatially oriented axonal outgrowth from the proximal nerve stump is required for successful tissue regeneration. Regenerative strategies such as introducing fiber bundles into the nerve guidance conduits improve the directional growth of neurons and Schwann cells. Recently, it has been proposed that fiber profiling increases cell alignment and could accelerate neuronal growth. Here, we evaluate the impact of fiber profiling on the extent of neurite outgrowth in vitro as compared to non-profiled round fibers. We developed novel profiled trilobal poly(lactic acid) (PLA) fibers and systematically tested their potency to support nerve regeneration in vitro. The profiled fibers did not improve neurite outgrowth as compared to the round fibers. Instead, we show that growing neurites are merely guided by the type and quantity of proteins adsorbed on the polymer surface. Together this data has significant implications for in vivo experiments focusing on directional regrowth of severed axons across lesion sites during peripheral nerve regeneration.

Progression of Parkinson's disease pathology is reproduced by intragastric administration of rotenone in mice.

In patients with Parkinson's disease (PD), the associated pathology follows a characteristic pattern involving inter alia the enteric nervous system (ENS), the dorsal motor nucleus of the vagus (DMV), the intermediolateral nucleus of the spinal cord and the substantia nigra, providing the basis for the neuropathological staging of the disease. Here we report that intragastrically administered rotenone, a commonly used pesticide that inhibits Complex I of the mitochondrial respiratory chain, is able to reproduce PD pathological staging as found in patients. Our results show that low doses of chronically and intragastrically administered rotenone induce alpha-synuclein accumulation in all the above-mentioned nervous system structures of wild-type mice. Moreover, we also observed inflammation and alpha-synuclein phosphorylation in the ENS and DMV. HPLC analysis showed no rotenone levels in the systemic blood or the central nervous system (detection limit [rotenone]<20 nM) and mitochondrial Complex I measurements showed no systemic Complex I inhibition after 1.5 months of treatment. These alterations are sequential, appearing only in synaptically connected nervous structures, treatment time-dependent and accompanied by inflammatory signs and motor dysfunctions. These results strongly suggest that the local effect of pesticides on the ENS might be sufficient to induce PD-like progression and to reproduce the neuroanatomical and neurochemical features of PD staging. It provides new insight into how environmental factors could trigger PD and suggests a transsynaptic mechanism by which PD might spread throughout the central nervous system.