HSP70 and constitutively active HSF1 mediate protection against CDCrel-1-mediated toxicity

Defects in cellular quality control mechanisms are thought to contribute to the neuropathology of Parkinson's disease (PD). Overexpressing heat shock proteins (HSPs) may constitute a powerful therapeutic strategy for PD, because they boost the ability of the cell to eliminate unwanted proteins. We investigated the neuroprotective potential of HSP70, HSP40, and H-BH, a constitutively active form of heat shock factor 1, in a rat model of PD based on adeno-associated virus (AAV) vector-mediated overexpression of CDCrel-1, a parkin substrate known to be toxic to dopaminergic neurons. AAV vector-mediated overexpression of H-BH and of HSP70 afforded similar levels of protection against CDCrel-1 toxicity, with approximately 20% improvement in survival of dopaminergic neurons as compared to the controls. The assessment of protection conferred was made using tyrosine hydroxylase (TH) and HuC/D immunohistochemistry and Fluoro-Gold retrograde tracing, and by observing the extent of preservation of spontaneous function and also the extent of drug-induced motor function. In contrast to H-BH and HSP70, HSP40 overexpression exacerbated CDCrel-1-mediated cell death. Real-time reverse transcriptase (RT)-PCR analysis showed that H-BH had the effect of upregulating endogenous HSP70 and HSP40 mRNA levels 10-fold and 4-fold over basal levels, respectively, whereas AAV vector-mediated HSP70 and HSP40 mRNA levels were over 100-fold higher. Our results suggest that a comparatively modest upregulation of multiple HSPs may be an effective approach for achieving significant neuroprotection in PD.