Drosophila mutant model of Parkinson's disease revealed an unexpected olfactory performance: Morphofunctional evidences

Parkinson's disease (PD) is one of the most common neurodegenerative diseases characterized by the clinical triad: tremor, akinesia, and rigidity. Several studies have suggested that PD patients show disturbances in olfaction as one of the earliest, nonspecific nonmotor symptoms of disease onset. We sought to use the fruit fly Drosophila melanogaster as a model organism to explore olfactory function in LRRK loss-of-function mutants, which was previously demonstrated to be a useful model for PD. Surprisingly, our results showed that the LRRK mutant, compared to the wild flies, presents a dramatic increase in the amplitude of the electroantennogram responses and this is coupled with a higher number of olfactory sensilla. In spite of the above reported results, the behavioural response to olfactory stimuli in mutant flies is impaired compared to that obtained in wild type flies. Thus, behaviour modifications and morphofunctional changes in the olfaction of LRRK loss-of-function mutants might be used as an index to explore the progression of parkinsonism in this specific model, also with the aim of studying and developing new treatment

Functional and morphological correlates in the drosophila LRRK2 loss-of-function model of Parkinson's disease: drug effects of Withania somnifera (Dunal) administration

The common fruit fly Drosophila melanogaster (Dm) is a simple animal species that contributed significantly to the development of neurobiology whose leucine-rich repeat kinase 2 mutants (LRRK2) loss-of-function in the WD40 domain represent a very interesting tool to look into physiopathology of Parkinson's disease (PD). Accordingly, LRRK2 Dm have also the potential to contribute to reveal innovative therapeutic approaches to its treatment. Withania somnifera Dunal, a plant that grows spontaneously also in Mediterranean regions, is known in folk medicine for its anti-inflammatory and protective properties against neurodegeneration. The aim of this study was to evaluate the neuroprotective effects of its standardized root methanolic extract (Wse) on the LRRK2 loss-of-function Dm model of PD. To this end mutant and wild type (WT) flies were administered Wse, through diet, at different concentrations as larvae and adults (L+/A+) or as adults (L-/A+) only. LRRK2 mutants have a significantly reduced lifespan and compromised motor function and mitochondrial morphology compared toWT flies 1% Wse-enriched diet, administered to Dm LRRK2 as L-/A+and improved a) locomotor activity b) muscle electrophysiological response to stimuli and also c) protected against mitochondria degeneration. In contrast, the administration of Wse to Dm LRRK2 as L+/A+, no matter at which concentration, worsened lifespan and determined the appearance of increased endosomal activity in the thoracic ganglia. These results, while confirming that the LRRK2 loss-of-function in the WD40 domain represents a valid model of PD, reveal that under appropriate concentrations Wse can be usefully employed to counteract some deficits associated with the disease. However, a careful assessment of the risks, likely related to the impaired endosomal activity, is require

Palpal receptors of the olive fly bactrocera oleae play a key role in foraging behaviorand host finding.

The olive fly Bactrocera oleae (Rossi) is a serious pest of olives in several countries in the Mediterranean basin causing important losses in the oil industry. The olive fly is known to respond behaviorally to volatile compounds present in its habitat and, more specifically, to those released from its host plant that play an important role in guiding the oviposition behavior of gravid females. A recent research by Liscia et al. (2013) on a laboratory strain of B. oleae demonstrated that that volatiles released from a bacterial filtrate (obtained culturing Pseudomonas putida) are mainly detected by palpal olfactory receptors rather than the antennal sensilla. On the contrary, α- pinene, a key compound in triggering the oviposition (Scarpati et al., 1993) that is emitted by leaves and half–ripe olives is mainly detected by male insects with the antennal receptors. On these bases, this study has been aimed to further investigate the role of maxillary palps in detecting food and oviposition sites in wild B. oleae adults obtained from pupae collected in different areas of olive orchards in Sardinia. Electrophysiological (EAG and EpG) and behavioral bioassays (Y-tube olfactometer and wind tunnel) were performed to test bacterial filtrate volatiles and some host plant (α-pinene) and food sources (acetic acid) related compounds. Dose-response relationships and differences in sensitivity related to insect sex and physiological condition were identified. Responses were compared to those obtained in lab insects. The results obtained in wild insects confirmed that palpi have a higher sensitivity to bacterial filtrate than the antennae. Otherwise, the EpG recorded in mated females in response to α-pinene and acetic acid, showed a lower threshold and a greater signal amplitude than those recorded in lab insects both in the palpi and the antennae. Electrophysiological results are complementary with the behavioral ones. In conclusion, the maxillary palp olfactory receptors play a primary role in the short-range detection of chemicals cues from host plant and epiphytic bacteria. These findings open new perspectives for improving olive fly control strategies

Opposite effects of 5-HT/AKH and octopamine on the crop contractions in adult Drosophila melanogaster: Evidence of a double brain-gut serotonergic circuitry.

This study showed that in adult Drosophila melanogaster, the type of sugar-either present within the crop lumen or in the bathing solution of the crop-had no effect on crop muscle contraction. What is important, however, is the volume within the crop lumen. Electrophysiological recordings demonstrated that exogenous applications of serotonin on crop muscles increases both the amplitude and the frequency of crop contraction rate, while adipokinetic hormone mainly enhances the crop contraction frequency. Conversely, octopamine virtually silenced the overall crop activity. The present study reports for the first time an analysis of serotonin effects along the gut-brain axis in adult D. melanogaster. Injection of serotonin into the brain between the interocellar area shows that brain applications of serotonin decrease the frequency of crop activity. Based on our results, we propose that there are two different, opposite pathways for crop motility control governed by serotonin: excitatory when added in the abdomen (i.e., directly bathing the crop) and inhibitory when supplied within the brain (i.e., by injection). Finally, our results point to a double brain-gut serotonergic circuitry suggesting that not only the brain can affect gut functions, but the gut can also affect the central nervous system. On the basis of our results, and data in the literature, a possible mechanism for these two discrete serotonergic functions is suggested

Chemicals affecting crop muscle contractions in adult flies.

<p>Species: 1-<i>D</i>. <i>melanogaster</i>; 2-<i>P</i>. <i>regina;</i> 3-<i>M</i>. <i>domestica</i>; Pumps/Valves based on Thomson [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174172#pone.0174172.ref061" target="_blank">61</a>].</p

Crop preparation and recording of muscle activity.

<p>Recording layout of <i>D</i>. <i>melanogaster</i> crop activity (a) and schematic diagram of the typical dipteran foregut (b) showing various sphincters, pumps, crop nerve bundle and small segment of the muscles of the crop lobes. Shown in the circle area is a typical recording from a suction electrode from the crop P4. (c) Sample of a double simultaneous recording of crop muscle activity, showing the mAPs electrophysiologically recorded from P4 (upper trace), as compared to contractions of P5 (lower trace), that were determined by means of the Aviline software analysis [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174172#pone.0174172.ref057" target="_blank">57</a>]. Note that the two pumps can display either phase-locked or totally desynchronized (dashed rectangle) activities.</p

Effect of various sugars ingested and their influence on crop contraction rate in adult <i>D</i>. <i>melanogaster</i>.

<p>Mean values ± SE (vertical bars) from 20 insects (yw-1118 strain) for each sugar tested. No significant differences were detected amongst the sugars ingested (P > 0.05; Tukey-Kramer test subsequent to one-way ANOVA).</p

Effect of various sugars bathing the crop and their influence on crop contraction rate in adult <i>D</i>. <i>melanogaster</i>.

<p>Frequency of mPAs electrophysiologically recorded from P4 (a) and of contractions visually recorded from P5 (b) of <i>Drosophila</i> Canton-S strain, determined over a 1-min interval, following replacement of hemolymph with 0.1 M trehalose, glucose or fructose with respect to <i>Drosophila</i> saline (basal activity). Mean values ± SE (vertical bars) from 8 (trehalose and glucose) or 7 (fructose) replicates in (a) and from 18 (trehalose and 20 (glucose and fructose) replicates in (b). No significant differences were detected among sugars for both P4 and P5 (P > 0.05; Tukey test subsequent to one-way ANOVA).</p

Reports using various techniques (microscopy, antibodies or molecular probes, liquid chromatography (LC) and mass spectrometry (MS)) showing the nerve going to the crop and in some cases its content.

<p>Reports using various techniques (microscopy, antibodies or molecular probes, liquid chromatography (LC) and mass spectrometry (MS)) showing the nerve going to the crop and in some cases its content.</p

Effect of various neuromodulators on crop contraction rate in adult <i>D</i>. <i>melanogaster</i>.

<p>(a) Frequency of contractions visually recorded from P5 in <i>Drosophila</i> Canton-S strain, determined over a 1-min interval, following replacement of hemolymph with 1 mM 5-HT, octopamine (OA) and ketanserin (ket) and 0.1 mM AKH, as compared to the activity in <i>Drosophila</i> saline (basal). Mean values ± SE (vertical bars); number of replicates for each compound is indicated in brackets. Bars followed by different letters are significantly different (P < 0.05; Tukey test subsequent to one-way ANOVA). (b) Frequency of P5 contractions in the same Canton-S strain, classified on the basis of the percentage of maximal contraction amplitude elicited, as assessed by the Aviline software analysis [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174172#pone.0174172.ref057" target="_blank">57</a>]. Mean values ± SE (vertical bars); number of replicates for each compound is indicated in brackets. Filled symbols represent significant differences with respect to the basal level (P < 0.05; Tukey test subsequent to one-way ANOVA).</p