Trehalose does not improve neuronal survival on exposure to alpha-synuclein pre-formed fibrils

Abstract

Parkinson's disease is a debilitating neurodegenerative disorder that is pathologically characterized by intracellular inclusions comprised primarily of alpha-synuclein (αSyn) that can also be transmitted from neuron to neuron. Several lines of evidence suggest that these inclusions cause neurodegeneration. Thus exploring strategies to improve neuronal survival in neurons with αSyn aggregates is critical. Previously, exposure to αSyn pre-formed fibrils (PFFs) has been shown to induce aggregation of endogenous αSyn resulting in cell death that is exacerbated by either starvation or inhibition of mTOR by rapamycin, both of which are able to induce autophagy, an intracellular protein degradation pathway. Since mTOR inhibition may also inhibit protein synthesis and starvation itself can be detrimental to neuronal survival, we investigated the effects of autophagy induction on neurons with αSyn inclusions by a starvation and mTOR-independent autophagy induction mechanism. We exposed mouse primary cortical neurons to PFFs to induce inclusion formation in the presence and absence of the disaccharide trehalose, which has been proposed to induce autophagy and stimulate lysosomal biogenesis. As expected, we observed that on exposure to PFFs, there was increased abundance of pS129-αSyn aggregates and cell death. Trehalose alone increased LC3-II levels, consistent with increased autophagosome levels that remained elevated with PFF exposure. Interestingly, trehalose alone increased cell viability over a 14-d time course. Trehalose was also able to restore cell viability to control levels, but PFFs still exhibited toxic effects on the cells. These data provide essential information regarding effects of trehalose on αSyn accumulation and neuronal survival on exposure to PFF.

Trehalose as a promising therapeutic candidate for the treatment of Parkinson's disease

“…Various studies have shown that exogenous application of α-synuclein preformed fibrils (PFFs) promotes the formation of protein aggregation in cells (Luk et al, 2012;Volpicelli-Daley et al, 2011). Interestingly, it has been shown that when primary cortical neurons are treated with trehalose alone, the LC3-II levels increase and remained elevated on treatment with both trehalose and α-synuclein PFFs, whereas no significant changes were observed in the levels of aggregated α-synuclein, indicating that PFFs were resistant to degradation even with augmentation of macroautophagy (Table 1; Redmann et al, 2017).…”

Emerging Treatment Approaches for Parkinson’s Disease

“…Whilst it has been suggested that its ability to reduce protein aggregation occurs due to a chaperone activity, or through binding and stabilization of abnormal proteins ( Tanaka et al, 2004 ; Davies et al, 2006 ), it has also been shown to act via an mTOR-independent pathway to increase autophagy ( Sarkar et al, 2007 ; Rodríguez-Navarro et al, 2010 ). These studies have clearly prompted interest in this compound, though a recent study of mouse primary cortical neurons found that trehalose did not prevent toxicity from exposure to α-synuclein pre-formed fibrils ( Redmann et al, 2017 ).…”

Developmental exposure to the organochlorine pesticide dieldrin causes male-specific exacerbation of α-synuclein-preformed fibril-induced toxicity and motor deficits

“…[38][39][40][41][42][43][44] PFF-induced α-syn inclusions resemble LBs in that they are compact intracytoplasmic structures of hyperphosphorylated (ser129) α-syn (psyn), co-localize with ubiquitin and p62, and are thioflavin-S-positive and proteinase-k Western blotting: Western blots for α-syn, DAT and VMAT2 were carried out as previously described. 33,39,42,[59][60][61] Striatal tissue punches were homogenized in tissue lysis buffer (Tris buffered saline with 1% SDS) and centrifuged at 1150 x g for 5 minutes at 4˚C. Protein levels were quantified by BCA protein assay.…”