Few effective
therapies exist for the treatment of
neurodegenerative diseases that have been characterized as
protein misfolding disorders. Upregulation of
heat shock proteins (Hsps) mitigates against the accumulation of misfolded, aggregation-prone
proteins and synaptic dysfunction, which is recognized as an early event in
neurodegenerative diseases. Enhanced induction of a set of Hsps in differentiated human SH-SY5Y neuronal cells was observed following co-application of
celastrol and
arimoclomol, compared to their individual application. The dosages employed did not affect cell viability or neuronal process morphology. The induced Hsps included the little studied HSPA6 (Hsp70B'), a potentially neuroprotective
protein that is present in the human genome but not in rat and mouse and hence is missing in current animal models of
neurodegenerative disease. Enhanced induction of HSPA1A (Hsp70-1), DNAJB1 (Hsp40), HO-1 (Hsp32), and HSPB1 (Hsp27) was also observed.
Celastrol activates
heat shock transcription factor 1 (HSF1), the master regulator of Hsp gene transcription, and also exhibits potent anti-inflammatory and
anti-oxidant activities.
Arimoclomol is a co-activator that prolongs the binding of activated HSF1 to heat shock elements (HSEs) in the promoter regions of inducible Hsp genes. Elevated Hsp levels peaked
at 10 to 12 h for HSPA6, HSPA1A, DNAJB1, and HO-1 and at 24 h for HSPB1. Co-application of
celastrol and
arimoclomol induced higher Hsp levels compared to heat shock paired with
arimoclomol. The co-application strategy of
celastrol and
arimoclomol targets multiple
neurodegenerative disease-associated pathologies including
protein misfolding and
protein aggregation, inflammatory and oxidative stress, and synaptic dysfunction.