97 - Contribution of Thioredoxin1 in Modulation of Lysosomal Autophagy

Abstract

The involvement of oxidative stress in pathogenesis of neurodegenerative diseases is well established. Mild oxidative conditions induce protective lysosomal autophagy, however failure of autophagy and ubiquitin systems leads to accumulation of over-oxidized proteins, followed by activation of apoptosis process. Cellular glutathione and thioredoxin systems play pivotal role in maintaining the redox balance and render protective effect by donating reducing protons to oxidized proteins. Thioredoxin 1 (Trx1) and thioredoxin reductase 1 (TrxR1), the enzyme responsible for reducing the oxidized Trx1, have protective roles against oxidative stress-mediated cytotoxicity. Moreover, in neurodegenerative conditions such as Alzheimer’s disease (AD), lower Trx1 levels have been reported in the autopsy of patients’ brains, while TrxR1 levels is increased (Lovel MA, et al. FRBM 2000). We hypothesized that dysregulated levels of Trx system may affect neuronal autophagy and apoptosis. We therefore used a model neuronal oxidative stress induction by serum deprivation in SH-SY5Y cells. Trx1 was pharmacologically inhibited using 1-methylpropyl 2-imidazolyl disulfide (PX-12), and we examined its effect of progression of autophagy and apoptosis. We found that PX-12 treated cells showed evidence of protein ubiquitination disruption and autophagy interruption, causing more apoptotic cell death. Similar to AD brain, inhibition of Trx1 was associated with increased TrxR1 protein level. Although lysosomal biosynthesis was increased after SD and in PX-12 cells, lysosomal activity was significantly decreased as assessed using lysotracker. Our data indicate that Trx1 is important for maintaining lysosomal activity and perhaps acidification. We did not observe any significant changes in mitochondrial Trx system. These data are in agreement with our previous reports that link a healthy balance of Trx-TrxR to proper protein degradation system. This project was supported by Paralyzed Veterans of America and University of Manitoba. AAS received an undergraduate summer studentship from University of Manitoba. NP received Research Manitoba/Will-to-Win studentship. JB, was supported by a MITACS Global Research Internship award.