Accelerating The Clearance Of Mutant Huntingtin Protein Aggregates Through Autophagy Induction By Europium Hydroxide Nanorods

Neurodegenerative Deseases(NDs) are very harmful to the old people’health and difficult to cure. Tremendous accumulation of misfolded aggregates in the neurons of patients suffering from NDs, subsequently results in severe functional impairment of brain cells or cell death, and progessively impairs the Exercise and cognitive function of patients. the two principal mechanistic pathways used for eukaryotic protein modifications and intracellular proteolysis are the autophagy-lysosomal pathway and ubiquitin-proteasome system (UPS). The UPS selectively degrades short-lived nuclear or cytosolic proteins, while autophagy-lysosomal pathway mainly removes bulk intracellular organelles or long half-lived cytosolic proteins. Pathogenic misfolded proteins and protein aggregates, usually escaping UPS-mediated protein quality control due to their sizes, subsequently causing the toxic disruption for normal cellular processes, could be cleared by autophagy-lysosomal pathway to maintain cell homeostasis. Autophagy, also called as cellular self-digestion and related with development, differentiation, survival, and homeostasis, is a evolutionarily conserved, lysosome-dependent and dynamic degradative process in eukaryotic organisms for clearance of misfolded proteins and damaged organelles. Autophagy is also related to NDs. The deficiency of autophagy is reported to increase the amount of intracellular protein aggregates and aggravate the state of NDs. Conversely, the increasment of the level of autophagy using genetic method or small molecular autophagy inducer will accelerate the clearance of protein aggregates, subsequently target the therapy of Neurodegenerative Desease at the level of cell, Drosophila, mouse model etc. Some small molecular agents such as rapamycin, lithium, trehalose etc are potential for the therapy of NDs by increasing the autophagy flux, while sharing the different molecular mechanism of autophagy induction. Previous reports show that all of these agents could be used for the therapy of NDs. But due to their own limitations or various unwanted side effects, these chemical autophagy inducers have not be translated for the clinical therapy of NDs.Many magic functions arouse from unique property of nanomaterials. For example, nanoparticles are able to selectively accumulate in tumor sites because of their small sizes plus large specific surface area, which has been widely used for the targeted therapy and diagnosis of tumors. Recently, plenty of reports illustrate that nanomaterials could induce autophay, which is another property of them. Nanoparticles (nano-VO2, Ag nanoparticles, etc) could induce protective autophagy to inhibit cell death. Nanoparticles, including Rare earth elements contained nanoparticle could accelerate the degradation of p62/SQSTM1through autophagy induction.In this context, we illustrated the non-toxic and especially pro-angiogenic Eu(OH)3nanorods sythesized by microwave-assisted hydrothernal method could upregulate the level of autophagy to acceletate the degradation of mutant huntingtin protein aggregates. And we also further tapped the detailed molecular mechanism of these nanorods-induced autophagy.In part Ⅰ, Eu(OH)3nanorods were prepared using microwave-assisted hydrothernal method and characterizated in detail. Eu(OH)3nanorods have a good biocompatibility without any the sub-cellular toxicity while increasing lysosome degradation capacity. Then, we found Eu(OH)3nanorods could result in the formation of autophagosome. In depth study showed that Eu(OH)3nanorods induce autophagy flux without interfering the autophagosome-lysosome fusion indicated by further increasment of LC3-Ⅱ elicited by Eu(OH)3nanorods in the presence of Chloroquine(CQ) and the degradation of autophagic substrate p62/SQSTM1. Additionally, Autophagy related protein ATG5participated Eu(OH)3nanorods induced autophagosome assembly. Lastly, we found Eu(OH)3nanorods could accelerate autophagy-mediated clearance of mutant huntingtin aggregates in Neuro2a and PC12cells.In part Ⅱ, we illustrated the molecular mechanism of autophagy induction by Eu(OH)3nanorods. Autophagy induction by Eu(OH)3nanorods was not negatively regulated mTOR activity. However, Phorsphorylation of ERK1/2participated in upregulating the level of autophagy induced by Eu(OH)3nanorods. MEK specific inhibitor U0126, inhibiting the Phorsphorylation of ERK1/2improved by Eu(OH)3nanorods, simultaneously abrogated the formation of autophagosome and the clearance of autophagic cargo. Additionally, we verified that trehalose, an mTOR-independent autophagy inducer, induced autophagy flux independent of the activity of ERK1/2. Interestingly, the combinatory use of inorganic nanorods and trehalose cause more degradation of mutant huntingtin protein aggregation than that obtained with single treatments of either nanorods or trehalose.