Biochemical Changes in Alzheimer Model of Drosophila melanogaster fed with African Eggplant (Solanum macrocarpon L.) and Black Nightshade (Solanum nigrum L.) Leaves Supplemented-Diets

Abstract

This study sought to determine the effect of two green leafy vegetables; African eggplant (AE) (Solanum. macrocarpon L) and Black nightshade (BN) (Solanum. nigrum L) on behavioural and biochemical indices in fruit fly (Drosophila melanogaster) model of Alzheimer´s disease (AD). In the first and second bioassays, wild flies (Oregon strain) were exposed to AlCl3 (1.60 mg/g) and HgCl2 (0.30 mg/g) respectively, alone or in combination with the leaves (0.1 and 1.0%) of either African eggplant or Black nightshade in their diets for seven days. Each of the bioassays were followed by determining the behavioural parameters (survival rate, locomotor performance and memory index). Furthermore, .the reactive oxygen species (ROS) level, total thiol content, as well as activities of catalase, glutathione-S-transferase (GST) and acetylcholinesterase (AChE) in the fly head homogenate were determined. Also, the expression of antioxidant-mediator (SOD, cnc/Nrf2, Jafrac1 and FOXO), AChE, pro-apoptotic caspase-like (Dronc) and its regulator (reaper), as well as pro-inflammatory-like (NF-ҝB/Relish) genes were determined. In the third bioassay, transgenic flies expressing human Amyloid Precursor Protein (hAPP) and β-secretase (hBACE 1) genes were exposed to the samples (0.1 and 1.0%) in their diets for fourteen days. Thereafter, the flies were assessed for their behavioural parameters. Furthermore, the fly head homogenate were assayed for β-amyloid, ROS, lipid peroxidation and total thiol contents, as well as the activities of AChE, BACE-1, catalase and GST. Results showed that in the first and second bioassays, there was significant (p<0.05) reduction in behavioural parameters, elevated ROS, reduced total thiol, catalase, GST and AChE activities in AlCl3 (Al)-and HgCl2 (Hg)-exposed flies; however, these impairments were significantly ameliorated (p<0.05) in Al/Hg-exposed flies fed the vegetable diets (0.1 and 1.0%).. In addition, the impairments in gene expression levels were mitigated in Al/Hg-exposed flies fed the vegetable diets. Results from the third bioassay showed that the significantly lower (p<0.05) behavioural parameters, higher AChE and BACE-1 activities, higher β-amyloid, ROS and lipid peroxidation levels, as well as reduced total thiol level, GST and catalase activities observed in transgenic flies, were significantly ameliorated when they were fed on the vegetable diets. This study has shown that leaves of AE and BN ameliorated behavioural and biochemical indices in D. melanogaster models of AD via neural enzyme modulatory, anti-inflammatory and antioxidant mechanisms. Therefore, these vegetables can serve as functional foods with neuroprotective properties against AD; however, considering the various parameters examined, BN leaves showed relatively better neuroprotective properties.