Biomedical subjects

William A Holtz

Publications and source records attributed to William A Holtz.

2 recordsLinked to original sources

PubMed2006

Oxidative stress-triggered unfolded protein response is upstream of intrinsic cell death evoked by parkinsonian mimetics.

Oxidative stress is a key player in a variety of neurodegenerative disorders including Parkinson's disease. Widely used as a parkinsonian mimetic, 6-hydroxydopamine (6-OHDA) generates reactive oxygen species (ROS) as well as coordinated changes in gene transcription associated with the unfolded protein response (UPR) and apoptosis. Whether 6-OHDA-induced UPR activation is dependent on ROS has not yet been determined. The present study used molecular indicators of oxidative stress to place 6-OHDA-generated ROS upstream of the appearance of UPR markers such as activating transcription factor 3 (ATF3) and phosphorylated stress-activated protein kinase (SAPK/JNK) signaling molecules. Antioxidants completely blocked 6-OHDA-mediated UPR activation and rescued cells from toxicity. Moreover, cytochrome c release from mitochondria was observed after the appearance of early UPR markers, suggesting that cellular stress pathways are responsible for its release. Mechanistically, the 6-OHDA-induced UPR was independent of intracellular calcium changes. Rather, evidence of protein oxidation was observed before the expression of UPR markers, suggesting that the rapid accumulation of damaged proteins triggered cell stress/UPR. Taken together, 6-OHDA-mediated cell death in dopaminergic cells proceeds via ROS-dependent UPR up-regulation which leads to an interaction with the intrinsic mitochondrial pathway and downstream caspase activation.

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PubMedDate not supplied

Microarray expression profiling identifies early signaling transcripts associated with 6-OHDA-induced dopaminergic cell death.

The parkinsonian mimetic 6-hydroxydopamine (6-OHDA) has been shown to cause transcriptional changes associated with cellular stress and the unfolded protein response. As these cellular sequelae depend on upstream signaling events, the present study used functional genomics and proteomic approaches to aid in deciphering toxin-mediated regulatory pathways. Microarray analysis of RNA collected from multiple time points following 6-OHDA treatment was combined with data mining and clustering techniques to identify distinct functional subgroups of genes. Notably, stress-induced transcription factors such as ATF3, ATF4, CHOP, and C/EBP beta were robustly up-regulated, yet exhibited unique kinetic patterns. Genes involved in the synthesis and modification of proteins (various tRNA synthetases), protein degradation (e.g., ubiquitin, Herpud1, Sqstm1), and oxidative stress (Hmox1, Por) could be subgrouped into distinct kinetic profiles as well. Realtime PCR and/or two-dimensional electrophoresis combined with western blotting validated data derived from microarray analyses. Taken together, these data support the notion that oxidative stress and protein dysfunction play a role in Parkinson's disease, as well as provide a time course for many of the molecular events associated with 6-OHDA neurotoxicity.

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