Effects of inhibiting mTOR with rapamycin on behavior, development, neuromuscular physiology, and cardiac function in larval Drosophila

Abstract

Rapamycin and other mTOR inhibitors are being heralded as possible treatments for many human ailments. It is currently being utilized clinically as an immunomodulator after transplantation procedures and as a treatment for certain forms of cancer, but it has numerous potential clinical indications. Some studies have shown profound effects on life cycle and muscle physiology, but these issues have not been addressed in an organism undergoing developmental processes. This paper fills this void by examining the effect of mTOR inhibition by rapamycin on several different qualities of larval Drosophila. Various dosages of the compound were fed to second instar larvae. These larvae were monitored for pupae formation to elucidate possible life cycle effects, and a delay to pupation was quantified. Behavioral deficits were documented in rapamycin-treated larvae. Electrophysiological measurements were taken to discern changes in muscle physiology and synaptic signaling (i.e. resting membrane potential, amplitude of excitatory post-synaptic potentials, synaptic facilitation). Pupation delay and effects on behavior that are likely due to synaptic alterations within the central nervous system were discovered in rapamycin-fed larvae. These results allow for several conclusions as to how mTOR inhibition by rapamycin affects a developing organism. This could eventually allow for a more informed decision when using rapamycin and other mTOR inhibitors to treat human diseases, especially in children and adolescents, to account for known side effects.

Genotype and Trait Specific Responses to Rapamycin Intake in Drosophila melanogaster

“…In this time-period the rapamycin treated flies had lower fecundity in four of the six lines. Since manipulation of TOR can affect developmental speed [40], some lines may have reduced fecundity early in life but increased fecundity at later ages. Longevity-fertility trade-offs is a common observation in studying life-history traits [11,41], thus lifelong fecundity should preferably be investigated in future studies on the effect of rapamycin on fecundity and longevity.…”

Defects of full-length dystrophin trigger retinal neuron damage and synapse alterations by disrupting functional autophagy

“…Standard diet with rapamycin vehicle was used as control (mock treatment). Behavioral deficits (reduced body-wall contractions, mouth-hook movements and responses to mechanical stimuli) have been recently reported in rapamycin fed D. melanogaster larvae (Canton S strain) [ 61 ]. Additionally, a dose–response relationship between rapamycin feeding and time to pupation was observed, with 10–100 μM dosages taking longer to pupate.…”

“…Using published protocols [60], flies were raised on a standard corn meal agar food (pH 5.5) at 25 °C. We prepared fly food as follows: for 1.2 l of water 100 g of live yeast, 110 g [61]. Additionally, a dose-response relationship between rapamycin feeding and time to pupation was observed, with 10-100 μM dosages taking longer to pupate.…”

Thermal and Oxygen Flight Sensitivity in Ageing Drosophila melanogaster Flies: Links to Rapamycin-Induced Cell Size Changes

“…In addition to the effects on cell size, the inhibition of TOR by rapamycin prolonged larval development and resulted in smaller bodies of adult flies, which were also characterized by relatively larger wings and, thus, a lower wing load during flight. Longer development and late eclosion of flies growing on media containing rapamycin was previously reported by Oldham et al [ 58 ], Zhang et al [ 59 ], Potter et al [ 85 ] and Scott et al [ 86 ], but to our knowledge, the effects of rapamycin supplementation on adult body size with reference to wing load have not previously been studied, especially in light of the cellular mechanisms of organ size changes. In ectotherms, including insects, the adaptive value of life history responses to environmental parameters, such as thermal conditions, is a subject of ongoing research and scientific debate [ 87 ].…”