Selective degeneration of dopaminergic neurons by MPP⁺ and its rescue by D2 autoreceptors in Drosophila primary culture

Abstract

Drosophila melanogaster is widely used to study genetic factors causing Parkinson’s disease (PD) due largely to the use of sophisticated genetic approaches and the presence of a high conservation of gene sequence/function between Drosophila and mammals. However, in Drosophila little has been done to study the environmental factors which cause over 90% of PD cases. We used Drosophila primary neuronal culture to study degenerative effects of a well-known PD toxin MPP+. DA neurons were selectively degenerated by MPP+ whereas cholinergic and GABAergic neurons were not affected. This DA neuronal loss was due to post-mitotic degeneration, not by inhibition of DA neuronal differentiation. We also found that MPP+-mediated neurodegeneration was rescued by D2 agonists quinpirole and bromocriptine. This rescue was through activation of Drosophila D2 receptor DD2R, as D2 agonists failed to rescue MPP+-toxicity in neuronal cultures prepared from both a DD2R deficiency line and a transgenic line pan-neuronally expressing DD2R RNAi. Furthermore, DD2R autoreceptors in DA neurons played a critical role in the rescue. When DD2R RNAi was expressed only in DA neurons, MPP+ toxicity was not rescued by D2 agonists. Our study also showed that rescue of DA neurodegeneration by Drosophila DD2R activation was mediated through suppression of action potentials in DA neurons.

Pharmacological and signalling properties of a D2-like dopamine receptor (Dop3) in Tribolium castaneum

“…Functional data in T. castaneum were obtained using RNA interference (RNAi), which induced high mortality during the larval stage and impaired moult to the pupal stage (Bai et al, 2011). TricaDop3 is therefore suggested to play an important role during larval growth and development, perhaps by modulating neural development and locomotor activity as reported in D. melanogaster (Draper et al, 2007;Wiemerslage et al, 2013). Expression in the brain is also in line with Dop3 expression in the honey bee.…”

“…This is in accordance with the general perception of a neurotransmitter role for DA and is consistent with previous studies in insects. In the fruit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 fly, DromeDop3 is highly expressed in the head and brain, and an important role in early neural development and central nervous system function has been suggested (Wiemerslage et al, 2013); FlyAtlas, URL: http://www.flyatlas.org). Functional data in T. castaneum were obtained using RNA interference (RNAi), which induced high mortality during the larval stage and impaired moult to the pupal stage (Bai et al, 2011).…”

Role of Drosophila calcium channel cacophony in dopaminergic neurodegeneration and neuroprotection

“…We present the following results using primary neuronal cultures from Drosophila, which we have previously shown to be useful in studying neuroprotection in PD [28]. These current experiments highlight the importance of Ca 2+ in the vulnerability of DA neurons.…”

“…The embryonic contents were harvested and plated on coverslips (Bellco Glass Inc., Vineland, NJ) as previously described [21,28]. Cultures were then incubated in 5% CO 2 at 24-25 • C and maintained for 9 days in vitro (DIV).…”

“…Furthermore, L-type Ca 2+ channel blockers prevent degeneration in a toxin-based, mouse model of PD [16]. And activation of dopamine type 2 receptors (D2R) decreases the activity of L, N, and P/Q Ca 2+ channels [19], and functional D2R is required for the neuroprotection of DA neurons by D2 agonists [28]. Thus, Ca 2+ is an important signaling molecule in PD pathology and its modulation likely has therapeutic potential.…”