Rapamycin treatment augments motor neuron degeneration in SOD1(G93A) mouse model of amyotrophic lateral sclerosis

The Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Autophagy (Impact Factor: 11.75). 04/2011; 7(4):412-25. DOI: 10.4161/auto.7.4.14541
Source: PubMed


Aberrant protein misfolding may contribute to the pathogenesis of amyotrophic lateral sclerosis (ALS) but the detailed mechanisms are largely unknown. Our previous study has shown that autophagy is altered in the mouse model of ALS. In the present study, we systematically investigated the correlation of the autophagic alteration with the motor neurons (MNs) degeneration in the ALS mice. We have demonstrated that the autophagic protein marker LC3-II is markedly and specifically increased in the spinal cord MNs of the ALS mice. Electron microscopy and immunochemistry studies have shown that autophagic vacuoles are significantly accumulated in the dystrophic axons of spinal cord MNs of the ALS mice. All these changes in the ALS mice appear at the age of 90 d when the ALS mice display modest clinical symptoms; and they become prominent at the age of 120 d. The clinical symptoms are correlated with the progression of MNs degeneration. Moreover, we have found that p62/SQSTM1 is accumulated progressively in the spinal cord, indicating that the possibility of impaired autophagic flux in the SOD1(G93A) mice. Furthermore, to our surprise, we have found that treatment with autophagy enhancer rapamycin accelerates the MNs degeneration, shortens the life span of the ALS mice, and has no obvious effects on the accumulation of SOD1 aggregates. In addition, we have demonstrated that rapamycin treatment in the ALS mice causes more severe mitochondrial impairment, higher Bax levels and greater caspase-3 activation. These findings suggest that selective degeneration of MNs is associated with the impairment of the autophagy pathway and that rapamycin treatment may exacerbate the pathological processing through apoptosis and other mechanisms in the ALS mice.

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    • "However, complete inhibition of mTOR by high concentrations of rapamycin has detrimental effects on long-term memory facilitation and consolidation , and causes amnesia (Bove et al., 2011; Tischmeyer et al., 2003). In addition, rapamycin treatment in mutant superoxide dismutase 1 (SOD1) mice exacerbates ALS pathology (Zhang et al., 2011). Therefore, rapamycin may act as a neuroprotective agent for fighting neurodegenerative diseases, but some attentions should be paid not only to the dosage of rapamycin but also to the mutations of some genes (e.g. "
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    ABSTRACT: Cadmium (Cd), a toxic environmental contaminant, contributes to neurodegeneration. Rapamycin, a macrocyclic lactone, has shown preventive effect on Cd-induced neuronal cell death. However, the underlying mechanism is not fully understood. Here, we show that rapamycin prevented Cd-induced apoptotic cell death in neuronal cells. Coincidently, rapamycin markedly blocked Cd-induced phosphorylation of Akt, S6K1 and 4E-BP1 in the cells. Expression of a rapamycin-resistant and kinase-active mTOR (S2035T, mTOR-T), but not a rapamycin-resistant and kinase-dead mTOR (S2035T/D2357E, mTOR-TE), conferred resistance to rapamycin inhibition of Cd-induced cell death, implying that the preventive effect of rapamycin on Cd-induced neurotoxicity is mTOR kinase activity-dependent. It appeared that both mTORC1 and mTORC2 were involved in the inhibitory activity of rapamycin, as silencing raptor, rictor or raptor/rictor enhanced rapamycin's blockage of Cd-induced cell death. Furthermore, downregulation of S6K1, ectopic expression of constitutively hypophosphorylated 4E-BP1 or dominant negative Akt, or co-treatment with Akt inhibitor also potentiated the rapamycin's inhibitory effect. The findings indicate that rapamycin prevents Cd-induced neuronal cell death via suppressing both mTORC1 and mTORC2 pathways. Our results highlight that rapamycin may be exploited for the prevention of Cd-induced neurodegenerative disorders. Copyright © 2015. Published by Elsevier Ltd.
    Neuropharmacology 05/2015; 97. DOI:10.1016/j.neuropharm.2015.05.008 · 5.11 Impact Factor
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    • "In a nutrient-depleted environment, phosphorylation of mTOR is inhibited, leading to autophagy activation (Diaz-Troya et al. 2008). Thus, a reduced ratio of p-mTOR/mTOR is an indication of autophagy activation (Zhang et al. 2011). We evaluated the protein level of both p-mTOR and mTOR in G93A muscle and found no significant changes in the ratio but a dramatic reduction in the overall mTOR expression level (including pmTOR and mTOR) compared to the wild-type muscle. "
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    ABSTRACT: Accumulation of abnormal protein inclusions is implicated in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Autophagy, an intracellular process targeting misfolded proteins and damaged organelles for lysosomal degradation, plays crucial roles in survival and diseased conditions. Efforts were made to understand the role of autophagy in motor neuron degeneration and to target autophagy in motor neuron for ALS treatment. However, results were quite contradictory. Possible autophagy defects in other cell types may also complicate the results. Here, we examined autophagy activity in skeletal muscle of an ALS mouse model G93A. Through overexpression of a fluorescent protein LC3-RFP, we found a basal increase in autophagosome formation in G93A muscle during disease progression when the mice were on a regular diet. As expected, an autophagy induction procedure (starvation plus colchicine) enhanced autophagy flux in skeletal muscle of normal mice. However, in response to the same autophagy induction procedure, G93A muscle showed significant reduction in the autophagy flux. Immunoblot analysis revealed that increased cleaved caspase-3 associated with apoptosis was linked to the cleavage of several key proteins involved in autophagy, including Beclin-1, which is an essential molecule connecting autophagy and apoptosis pathways. Taking together, we provide the evidence that the cytoprotective autophagy pathway is suppressed in G93A skeletal muscle and this suppression may link to the enhanced apoptosis during ALS progression. The abnormal autophagy activity in skeletal muscle likely contributes muscle degeneration and disease progression in ALS.
    01/2015; 3(1). DOI:10.14814/phy2.12271
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    • "Different pharmacological approaches to stimulate autophagy have been tested. Two independent studies showed a negative effect on disease progression by treating mouse models of ALS with rapamycin, which is an FDA-approved drug that induces autophagy (Bhattacharya et al., 2012; Zhang et al., 2011). This negative effect was probably due to the immunosuppressive function of rapamycin, as the disease could be slowed down in immunodeficient ALS mice (Staats et al., 2013). "
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is characterized by the selective death of motor neurons in the motor cortex, brainstem and spinal cord. It is a neurodegenerative disorder with high genetic and phenotypic variability. In most patients, the cause of the disease is unknown. Until now, no treatment strategy has been discovered with the exception of riluzole which has a moderate effect on the disease process. While developing a new causal therapy targeting a specific disease-causing gene can have a huge effect on the disease process, only a limited number of ALS patients will benefit from such a therapy. Alternatively, pathogenic processes that are common in ALS patients with different etiology can also be targeted. The effect of such a modifying treatment will be smaller, but the target population will be larger as more ALS patients could benefit. In this review, we summarize the evidence for the involvement of different biological processes in the pathogenesis of ALS and will discuss how strategies influencing these processes can be translated into new therapeutic approaches. In order to further improve this translational step, there is an urgent need for a better understanding of the underlying mechanism(s), for new ALS animal models and for rigorous protocols to perform preclinical studies.
    Experimental Neurology 12/2014; 262. DOI:10.1016/j.expneurol.2014.07.001 · 4.70 Impact Factor
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