Neuroprotective effect of geraniol and curcumin in an acrylamide model of neurotoxicity in Drosophila melanogaster: Relevance to neuropathy

Chronic exposure of acrylamide (ACR) leads to neuronal damage in both experimental animals and
humans. The primary focus of this study was to assess the ameliorative effect of geraniol, (a natural
monoterpene) against ACR-induced oxidative stress, mitochondrial dysfunction and neurotoxicity in a
Drosophila model and compare its efficacy to that of curcumin, a spice active principle with pleiotropic
biological activity. Adult male flies (8–10 days) were exposed (7 days) to ACR (5 mM) with or without
geraniol and curcumin (5–10 lM) in the medium. Both phytoconstituents significantly reduced the incidence
of ACR-induced mortality, rescued the locomotor phenotype and alleviated the enhanced levels of
oxidative stress markers in head/body regions. The levels of reduced glutathione (GSH) and total thiols
(TSH) resulting from ACR exposure was also restored with concomitant elevation in the activities of
detoxifying enzymes. Interestingly, ACR induced mitochondrial dysfunctions (MTT reduction, activities
of SDH and citrate synthase enzymes) were alleviated by both phytoconstituents. While ACR elevated
the activity of acetylcholinesterase in head/body regions, marked diminution in enzyme activity ensued
with co-exposure to phytoconstituents suggesting their potency to mitigate cholinergic function. Furthermore,
phytoconstituents also restored the dopamine levels in head/body regions. The neuroprotective
effect of geraniol was comparable to curcumin in terms of phenotypic and biochemical markers.
Based on our evidences in fly model we hypothesise that geraniol possess significant neuromodulatory
propensity and may be exploited for therapeutic application in human pathophysiology associated with
neuropathy. However, the precise mechanism/s by which geraniol offers neuroprotection needs to be
investigated in appropriate neuronal cell models.