Growing evidence has indicated that iron deposition in the substantia nigra (SN) plays an important role in Parkinson’s disease (PD). However, the underlying mechanism is still elusive. Using primary dopaminergic neurons and SH-SY5Y cells cultured in vitro, we observed that iron loading increased α-synuclein and reactive oxygen species (ROS) levels in these cells but did not affect the intracellular α-synuclein mRNA levels. Furthermore, iron loading significantly downregulated Beclin-1 levels and decreased the ratio of microtubule-associated protein 1 light chain 3 isoforms (LC3 II/LC3 I). However, a significant change in the levels of autophagy-related gene 5 (Atg5) was not observed in either neurons or SH-SY5Y cells after iron treatment. After treatment with rapamycin, the iron loading-induced increase in the α-synuclein level was significantly reversed and ROS generation was alleviated in both cultured neurons and SH-SY5Y cells. These results indicate that the inhibition of autophagy is critical for the pathological alterations in α-synuclein induced by iron loading. Moreover, treatment with vitamin E did not affect the increase in the α-synuclein levels but significantly eliminated the iron-induced ROS production. Together, our study shows that autophagy dysfunction contributes to iron-induced α-synuclein pathology.

/pdf/iron-deposition-leads-to-neuronal-a-synuclein-pathology-by-1yi7lpjw33.pdf

Iron Deposition Leads to Neuronal α-Synuclein Pathology by Inducing Autophagy Dysfunction.

Accumulation of pathological α-synuclein aggregates plays a major role in Parkinson's disease. Macroautophagy is a mechanism to degrade intracellular protein aggregates by wrapping them into autophagosomes, followed by fusion with lysosomes. We had previously shown that pharmacological activation of macroautophagy protects against α-synuclein-induced toxicity in human neurons. Here, we hypothesized that inhibition of macroautophagy would aggravate α-synuclein-induced cell death.Unexpectedly, inhibition of autophagosome formation by silencing of ATG5 protected from α-synuclein-induced toxicity. Therefore, we studied alternative cellular mechanisms to compensate for the loss of macroautophagy. ATG5 silencing did not affect the ubiquitin-proteasome system, chaperone systems, chaperone-mediated autophagy, or the unfolded protein response. However, ATG5 silencing increased the secretion of α-synuclein via exosomes. Blocking exosomal secretion exacerbated α-synuclein-induced cell death.We conclude that exosomal secretion of α-synuclein is increased after impaired formation of autophagosomes to reduce the intracellular α-synuclein burden. This compensatory mechanism prevents α-synuclein-induced neuronal cell death.

/pdf/exosomal-secretion-of-a-synuclein-as-protective-mechanism-1y9wnuccf4.pdf

Exosomal secretion of α-synuclein as protective mechanism after upstream blockage of macroautophagy

Sequestration of protein aggregates in inclusion bodies and their subsequent degradation prevents proteostasis imbalance, cytotoxicity, and proteinopathies. The underlying molecular mechanisms controlling the turnover of protein aggregates are mostly uncharacterized. Herein, we show that a TRIM family protein, TRIM16, governs the process of stress‐induced biogenesis and degradation of protein aggregates. TRIM16 facilitates protein aggregate formation by positively regulating the p62‐NRF2 axis. We show that TRIM16 is an integral part of the p62‐KEAP1‐NRF2 complex and utilizes multiple mechanisms for stabilizing NRF2. Under oxidative and proteotoxic stress conditions, TRIM16 activates ubiquitin pathway genes and p62 via NRF2, leading to ubiquitination of misfolded proteins and formation of protein aggregates. We further show that TRIM16 acts as a scaffold protein and, by interacting with p62, ULK1, ATG16L1, and LC3B, facilitates autophagic degradation of protein aggregates. Thus, TRIM16 streamlines the process of stress‐induced aggregate clearance and protects cells against oxidative/proteotoxic stress‐induced toxicity in vitro and in vivo . Taken together, this work identifies a new mechanism of protein aggregate turnover, which could be relevant in protein aggregation‐associated diseases such as neurodegeneration.

https://www.embopress.org/doi/epdf/10.15252/embj.201798358

TRIM16 controls assembly and degradation of protein aggregates by modulating the p62‐NRF2 axis and autophagy

The pathological hallmarks of Parkinson’s disease are the progressive loss of nigral dopaminergic neurons and the formation of intracellular inclusion bodies, termed Lewy bodies, in surviving neurons. Accumulation of proteins in large insoluble cytoplasmic aggregates has been proposed to result, partly, from a failure in the function of intracellular protein degradation pathways. Evidence in support for such a hypothesis emerged in the beginning of the years 2000 with studies demonstrating structural and functional deficits in the ubiquitin-proteasome pathway in post-mortem nigral tissue of patients with Parkinson’s disease. These fundamental findings have inspired the development of a new generation of animal models based on the use of proteasome inhibitors to disturb protein homeostasis and trigger nigral dopaminergic neurodegeneration. In this review, we provide an updated overview of the current approaches in employing proteasome inhibitors to model Parkinson’s disease, with particular emphasis on rodent studies. In addition, the mechanisms underlying proteasome inhibition-induced cell death and the validity criteria (construct, face and predictive validity) of the model will be critically discussed. Due to its distinct, but highly relevant mechanism of inducing neuronal death, the proteasome inhibition model represents a useful addition to the repertoire of toxin-based models of Parkinson’s disease that might provide novel clues to unravel the complex pathogenesis of this disorder.

/pdf/the-proteasome-inhibition-model-of-parkinson-s-disease-3ikayuh750.pdf

The Proteasome Inhibition Model of Parkinson's Disease.

Cisplatin [cis-diamminedichloroplatinum II (CDDP)] is one of the most classical and effective chemotherapeutic drugs for the treatment of cancers including lung cancer. However, the presence of cisplatin resistance in cancer lowers its curative effect and limits its usage in the clinic. The aim of the present study was to investigate the underlying mechanisms of cisplatin resistance in lung cancer involving endoplasmic reticulum (ER) stress and autophagy. In the present study, we detected the effect of cisplatin on cell viability, ER stress and autophagy in lung cancer cell lines A549 and H460. We also tested the effects of ER stress and autophagy on apoptosis induced by cisplatin. The results showed that cisplatin induced apoptosis, ER stress and autophagy in lung cancer cell lines. In addition, the inhibition of ER stress by 4-phenylbutyric acid (4-PBA) or tauroursodeoxycholic acid sodium (TUDC) enhanced cisplatin-induced apoptosis in the human lung cancer cells. Meanwhile, combination treatment with the autophagic inhibitor 3-methyladenine (3-MA) or chloroquine (CQ) further increased the apoptosis induced by cisplatin in the human lung cancer cells. The present study provides a novel treatment strategy - cisplatin in combination with an autophagic inhibitor or an ER stress inhibitor leads to increased apoptosis in human lung cancer cells.

/pdf/er-stress-and-autophagy-are-involved-in-the-apoptosis-16i3z8blda.pdf

ER stress and autophagy are involved in the apoptosis induced by cisplatin in human lung cancer cells

The aim of the present study was to examine the effects of proteasome inhibitor (PI)‑induced autophagy on PC12 cells overexpressing A53T mutant α‑synuclein (α‑syn) by detecting alterations in the levels of microtubule‑associated protein 1A/1B light chain (LC3)+ autophagosomes and the lysotracker‑positive autolysosomes using immunofluorescence, the expression of LC3‑II using western blot analysis and the morphology of PC12 cells using transmission electron microscopy It was found that the addition of MG132 (500 nmol/l) significantly increased the number of autophagosomes and autolysosomes and upregulated the expression of LC3‑II The autophagy inhibitor 3‑methyladenine (3‑MA) completely inhibited the autophagy induced by MG132 (500 nmol/l) The autophagy enhancer trehalose significantly increased the number of autophagosomes and autolysosomes and improved the protein level of LC3‑II induced by MG132 To examine the effect of PI‑induced autophagy on the degradation of A53T mutant α‑syn, the expression of α‑syn was detected by western blot analysis It was revealed that MG132 increased the expression of A53T α‑syn and trehalose counteracted the increase of A53T α‑syn induced by MG132 Combined inhibition of 3‑MA and PI significantly increased the accumulation of A53T α‑syn as compared with treatment using either single agent In addition, combination of MG132 (500 nmol/l) with trehalose (50 mmol/l) or 3‑MA (2 mmol/l) markedly decreased the cell viability as compared with treatment using either single agent individually as demonstrated using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay These results suggest that the PI, MG132, could induce autophagy in PC12 cells overexpressing A53T mutant α‑syn and this autophagy could be completely inhibited by 3‑MA, indicating that PI‑induced autophagy is mediated by the upregulation of the macroautophagy class III PI3K pathway PI‑induced autophagy may act as a compensatory degradation system for degradation of A53T α‑syn when the ubiquitin‑proteasome system is impaired Autophagy activation may directly contribute to the survival of PC12 cells treated with proteasome inhibitors The present study may assist in illuminating the association between PI and autophagy in the pathogenesis of Parkinson's disease

https://www.spandidos-publications.com/10.3892/mmr.2014.3011/download

Proteasome inhibitor-induced autophagy in PC12 cells overexpressing A53T mutant α-synuclein

Hydrometallurgical process for extracting bismuth from by-product of lead smelting based on methanesulfonic acid system

OBJECTIVE To evaluate the effectiveness of Semont maneuver for posterior semicircular canal benign paroxysmal positional vertigo (PC-BPPV). METHOD Forty patients with PC-BPPV were treated with Semont maneuver from January to August in 2004. RESULT After a single treatment session of Semont maneuver,the symptoms disappeared completely in 32 patients, the first success rate was 80%. Among 19 patients who had only 1 week duration of PC-BPPU, the symptoms disappeared in 16 patients after a single treatment. The symptoms disappeared in 3 patients after twice, 2 patients after 3 times and 1 patient after 4 times of Semont maneuver sessions, the total success rate was 95%. No effectiveness was found 2 patients; PC-BPPU recurred in 5 patients during follow-up and the recurrent rate was 12.5%. it was still effective for another Semont maneuver therapy session. CONCLUSION The Semont maneuver therapy is safe and effective for PC-BPPV. Repeated Semont maneuver therapy is still effective for them.

Wen-zhao Wang

Papers

Proteasome inhibitor-induced autophagy in PC12 cells overexpressing A53T mutant α-synuclein

Hydrometallurgical process for extracting bismuth from by-product of lead smelting based on methanesulfonic acid system

The treatment of Semont maneuver for 40 patients with posterior semicircular canal benign paroxysmal positional vertigo