Microbiome-Brain interactions in Parkinson’s neurodegeneration: The effect of microbiota modulation in a PINK1 mutant Drosophila melanogaster model of Parkinson’s disease
Parkinson’s disease (PD) is the second most common neurodegenerative disease. In the last decade, it has been proposed that the gut microbiota is involved in the PD etiopathology. Although several studies have determined microbial imbalance and the bacterial species affected, the mechanisms by which this imbalance can lead to neurodegenerative disorders have yet to be unravelled. Therefore, we are investigating the effect of modulating the D. melanogaster microbiota by supplementing the food with bacteria strains reported as dysregulated in PD patients. We used two fly strains, a wildtype control (W1118) and a PINK1B9 mutant as a model of PD and tested the effect of four strains of bacteria: Lactobacillus acidophilus, Enterococcus faecalis, Escherichia coli and Enterobacter cloacae. We started by investigating the difference between the two models without a microbiota intervention, and lifespan, locomotor ability, mitochondrial function, dopaminergic neuron markers and microbiota composition changes were observed. After microbiota modulation, lifespan records showed significant alterations between the groups with enhanced viability induced by E. cloacae and E. coli in both W1118 and PINK1B9 mutant. Locomotor ability was assessed using a behavioural climbing test with L. acidophilus and E. faecalis slowing the motor function which correlated with a reduction in viability. Mitochondrial respiration was measured using high-resolution respirometry and mitochondrial stress markers were evaluated at mRNA and protein levels, showing changes in the control W1118, versus PINK1B9 mutants, following the bacteria feed. Respiration increased in the control W1118 treated samples and decreased in the PINK1treated mutants’ conditions. Dopaminergic neurons content evaluation showed there was a reduction in neurons in the PINK1 flies. RNA sequencing analysis showed flies genotype and microbiota modulation can influence gene expression. qRT-PCR validated RNA sequencing results for several differently expressed genes, for example the fly defence proteins TotA and TotM, and the mitochondrial marker TOM20 Ultimately, we have found that modulation of Drosophilamicrobiota, leads to different outcomes depending on the bacteria strain and may change physiological pathways in a distinct manner.
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