Heat Shock Protein-70 (Hsp-70) Suppresses Paraquat-Induced Neurodegeneration by Inhibiting JNK and Caspase-3 Activation in <i>Drosophila</i> Model of Parkinson's Disease

<div><p>Parkinson's disease (PD) is one of the most common neurodegenerative disorders with limited clinical interventions. A number of epidemiological as well as case-control studies have revealed an association between pesticide exposure, especially of paraquat (PQ) and occurrence of PD. Hsp70, a molecular chaperone by function, has been shown as one of the modulators of neurological disorders. However, paucity of information regarding the protective role of Hsp70 on PQ-induced PD like symptoms led us to hypothesize that modulation of <i>hsp70</i> expression in the dopaminergic neurons would improve the health of these cells. We took advantage of <i>Drosophila</i>, which is a well-established model for neurological research and also possesses genetic tools for easy manipulation of gene expression with limited ethical concern. Over-expression of <i>hsp70</i> was found to reduce PQ-induced oxidative stress along with JNK and caspase-3 mediated dopaminergic neuronal cell death in exposed organism. Further, anti-apoptotic effect of <i>hsp70</i> was shown to confer better homeostasis in the dopaminergic neurons of PQ-exposed organism as evidenced by their improved locomotor performance and survival. The study has merit in the context of human concern since we observed protection of dopaminergic neurons in PQ-exposed organism by over-expressing a human homologue of <i>hsp70, HSPA1L,</i> in these cells. The effect was parallel to that observed with <i>Drosophila hsp70.</i> These findings reflect the potential therapeutic applicability of <i>hsp70</i> against PQ-induced PD like symptoms in an organism.</p></div

Calycosin Alleviates Paraquat-Induced Neurodegeneration by Improving Mitochondrial Functions and Regulating Autophagy in a Drosophila Model of Parkinson&rsquo;s Disease

Parkinson&rsquo;s disease (PD) is the second most common age-related neurodegenerative disorder with limited clinical treatments. The occurrence of PD includes both genetic and environmental toxins, such as the pesticides paraquat (PQ), as major contributors to PD pathology in both invertebrate and mammalian models. Calycosin, an isoflavone phytoestrogen, has multiple pharmacological properties, including neuroprotective activity. However, the paucity of information regarding the neuroprotective potential of calycosin on PQ-induced neurodegeneration led us to explore whether calycosin can mitigate PD-like phenotypes and the underlying molecular mechanisms. We used a PQ-induced PD model in Drosophila as a cost-effective in vivo screening platform to investigate the neuroprotective efficacy of natural compounds on PD. We reported that calycosin shows a protective role in preventing dopaminergic (DA) neuronal cell death in PQ-exposed Canton S flies. Calycosin-fed PQ-exposed flies exhibit significant resistance against PQ-induced mortality and locomotor deficits in terms of reduced oxidative stress, loss of DA neurons, the depletion of dopamine content, and phosphorylated JNK-caspase-3 levels. Additionally, mechanistic studies show that calycosin administration improves PQ-induced mitochondrial dysfunction and stimulates mitophagy and general autophagy with reduced pS6K and p4EBP1 levels, suggestive of a maintained energy balance between anabolic and catabolic processes, resulting in the inhibition of neuronal cell death. Collectively, this study substantiates the protective effect of calycosin against PQ-induced neurodegeneration by improving DA neurons&rsquo; survival and reducing apoptosis, likely via autophagy induction, and it is implicated as a novel therapeutic application against toxin-induced PD pathogenesis

Correlation among ROS generation and % survival in PQ-exposed <i>Drosophila.</i>

<p>Negative correlation was observed between generation of ROS (O₂⁻/ONOO⁻) and percent survival in different strains of <i>Drosophila</i> exposed to 20 mM PQ for 24 h. n = 4 degree of freedom; <b>**</b><i>p</i><0.01.</p

Composition of reaction mixture for assaying SOD activity.

<p>Composition of reaction mixture for assaying SOD activity.</p

PQ estimation in the head of different fly strains after 24

<p>Data represent mean ± SD of three identical experiments made in triplicates; values were represented in µM. ND: not detected.</p