Parkinson's disease (PD) is the result of complex interactions between genetic and environmental factors. Two chemically distinct environmental stressors relevant to PD are the metal manganese and the pesticide rotenone. Both are thought to exert neurotoxicity at least in part via oxidative stress resulting from impaired mitochondrial activity. Identifying shared mechanism of action may reveal clues towards an understanding of the mechanisms underlying PD pathogenesis. Here we compare the effects of manganese and rotenone in human-induced pluripotent stem cells-derived postmitotic mesencephalic dopamine neurons by assessing several different oxidative stress endpoints. Manganese, but not rotenone caused a concentration and time-dependent increase in intracellular reactive oxygen/nitrogen species measured by quantifying the fluorescence of oxidized chloromethyl 2',7'-dichlorodihydrofluorescein diacetate (DCF) assay. In contrast, rotenone but not manganese caused an increase in cellular isoprostane levels, an indicator of lipid peroxidation. Manganese and rotenone both caused an initial decrease in cellular reduced glutathione; however, glutathione levels remained low in neurons treated with rotenone for 24 h but recovered in manganese-exposed cells. Neurite length, a sensitive indicator of overall neuronal health was adversely affected by rotenone, but not manganese. Thus, our observations suggest that the cellular oxidative stress evoked by these 2 agents is distinct yielding unique oxidative stress signatures across outcome measures. The protective effect of rasagiline, a compound used in the clinic for PD, had negligible impact on any of oxidative stress outcome measures except a subtle significant decrease in manganese-dependent production of reactive oxygen/nitrogen species detected by the DCF assay.

The xbp-1 mRNA encodes the XBP-1 transcription factor, a critical part of the unfolded protein response. Here we report that an RNA fragment produced from xbp-1 mRNA cleavage is a biologically active non-coding RNA (ncRNA) in Caenorhabditis elegans neurons, providing the first example of ncRNA derived from mRNA cleavage. We show that the xbp-1 ncRNA is crucial for axon regeneration in vivo, and that it acts independently of the proteincoding function of the xbp-1 transcript. Structural analysis indicates that the function of the xbp-1 ncRNA depends on a single RNA stem; and this stem forms only in the cleaved xbp-1 ncRNA fragment. Disruption of this stem abolishes the non-coding but not coding function of the endogenous xbp-1 transcript. Thus, cleavage of the xbp-1 mRNA bifurcates it into a coding and a non-coding pathway; modulation of the two pathways may allow neurons to fine-tune their response to injury and other stresses.

The xbp-1 mRNA encodes the XBP-1 transcription factor, a critical part of the unfolded protein response. Here we report that an RNA fragment produced from xbp-1 mRNA 10 cleavage is a biologically active non-coding RNA (ncRNA) in Caenorhabditis elegans neurons, providing the first example of ncRNA derived from mRNA cleavage. We show that the xbp-1 12 ncRNA is crucial for axon regeneration in vivo, and that it acts independently of the proteincoding function of the xbp-1 transcript. Structural analysis indicates that the function of the xbp-141 ncRNA depends on a single RNA stem; and this stem forms only in the cleaved xbp-1 ncRNA fragment. Disruption of this stem abolishes the non-coding but not coding function of the 16 endogenous xbp-1 transcript. Thus, cleavage of the xbp-1 mRNA bifurcates it into a coding and a non-coding pathway; modulation of the two pathways may allow neurons to fine-tune their 18 response to injury and other stresses.Graphic abstract: 20 22