A Drosophila model of sleep restriction therapy for insomnia

Abstract

Insomnia is the most common sleep disorder among adults, especially affecting individuals of advanced age or with neurodegenerative disease. Insomnia is also a common comorbidity across psychiatric disorders. Cognitive behavioral therapy for insomnia (CBT-I) is the first-line treatment for insomnia; a key component of this intervention is restriction of sleep opportunity, which optimizes matching of sleep ability and opportunity, leading to enhanced sleep drive. Despite the well-documented efficacy of CBT-I, little is known regarding how CBT-I works at a cellular and molecular level to improve sleep, due in large part to an absence of experimentally-tractable animals models of this intervention. Here, guided by human behavioral sleep therapies, we developed a Drosophila model for sleep restriction therapy (SRT) of insomnia. We demonstrate that restriction of sleep opportunity through manipulation of environmental cues improves sleep efficiency in multiple short-sleeping Drosophila mutants. The response to sleep opportunity restriction requires ongoing environmental inputs, but is independent of the molecular circadian clock. We apply this sleep opportunity restriction paradigm to aging and Alzheimer's disease fly models, and find that sleep impairments in these models are reversible with sleep restriction, with associated improvement in reproductive fitness and extended lifespan. This work establishes a model to investigate the neurobiological basis of CBT-I, and provides a platform that can be exploited toward novel treatment targets for insomnia.

Figure 1.. Sleep opportunity extension impairs sleep in Drosophila.

(A) Schematic of sleep degradation with mismatch of sleep opportunity and sleep ability. (B) Diagram of experimental extension of dark time from 12 hours (12:12 LD) to 14 hours (10:14 LD) or 16 hours (8:16 LD). (C) Representative sleep traces of wild type iso flies under 12:12 LD (top panel), 10:14 LD (middle panel) or 8:16 LD conditions (bottom panel). Gray shading indicates dark phase. Quantification of sleep efficiency (D), sleep bout duration (E), sleep bout number (F), total sleep time (G), sleep latency (H), and wake after sleep onset (I) following 3 nights of sleep opportunity extension in wild type iso flies (n = 48 flies per condition). (J) Analysis of sleep efficiency based on time within the dark period. For all figures, error bars represent SEM; *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 2.. Sleep opportunity restriction enhances sleep in fumin mutants.

(A) Schematic of hypothesis that sleep opportunity restriction aligns sleep opportunity and sleep ability, leading to efficient sleep. (B) Diagram of experimental protocol for restriction of sleep opportunity by manipulating the dark period. (C-E) Representative sleep traces of fumin mutants under 12:12 LD conditions (C, gray shading indicates dark phase), sleep restriction protocol (D, blue shading indicates dark phase), and both plots overlaid (E). (F-K) Quantification of sleep measures with restriction of sleep opportunity in fumin mutants (n = 551 flies for 12:12 LD; n = 192 for 20:4 LD; n = 204 for 18:6 LD; n = 199 for 16:8 LD; and n = 55 for 14:10 LD). (L) Sleep efficiency in fumin mutants with 18:6 LD dark period restriction occurring at different times of night (n = 53 for 9p-3a, n = 172 for 12a-6a, n = 105 for 3a-9a).

Figure 3.. Sleep opportunity restriction improves sleep in multiple short-sleeping mutants.

Representative sleep traces under 12:12 LD conditions (top panel, gray shading indicates dark phase), compressed sleep opportunity (middle panel, blue shading indicates dark phase) and overlaid plots (bottom panel) for sleepless (A), redeye (F), and wide awake (K) mutants. Quantification of sleep efficiency (B,G,L), sleep bout duration (C,H,M), sleep latency (D,I,N), and wake after sleep onset (E,J,O) for each genotype (sleepless: n = 210 for 12:12 LD, n = 64 for 20:4 LD, n = 69 for 18:6 LD, n = 68 for 16:8 LD, and n = 33 for 14:10 LD; redeye: n = 63 for 12:12 LD, n = 60 for 16:8 LD, n = 58 for 14:10 LD; wide awake: n = 62 for 12:12 LD, n = 62 for 14:10 LD). (P) Arousal threshold of wide awake mutants following mechanical stimulation (n = 246 sleep episodes in 96 flies for 12:12 LD and n = 250 sleep episodes in 96 flies for 14:10 LD).

Figure 4.. Response to sleep restriction requires ongoing environmental cues.

(A) Representative sleep traces under 12:12 LD conditions (top panel, gray shading indicates dark phase), 18:6 LD dark time restriction (middle panel, blue shading indicates dark phase) and overlaid plots (bottom panel) for per⁰¹; fumin mutants. Quantification of sleep efficiency (B), bout duration (C), and sleep latency (D) in per⁰¹; fumin mutants (n = 61 for 12:12 LD, n = 62 for 18:6 LD). (E) Representative sleep traces in fumin mutants under constant dark (DD) conditions (top panel, gray indicates 26°C) or with compressed sleep opportunity using temperature change (TC; middle panel, blue indicates 18°C). Quantification of sleep efficiency (F), bout duration (G), and sleep latency (H) in fumin mutants under DD conditions with sleep opportunity restriction using temperature changes (n = 144 for DD, n = 62 for 20:4 TC, n = 56 for 18:6 TC, n = 28 for 16:8 TC). (I) Sleep efficiency in fumin mutants with sleep restriction via tapered protocol versus sleep restriction initiated with the indicated dark period (n = 54,33 for 18:6 LD, n = 25,24 for 16:8 LD, n = 54,54 for 14:10 LD). (J) Sleep efficiency in fumin mutants under 18:6 LD conditions and after shift back to 12:12 LD (n = 32). (L-O) Sleep opportunity restriction in light processing mutants. Overlaid sleep traces of fumin;glass (L) and fumin;cry⁰² (M). Black traces indicate 12:12 LD (gray shading indicates dark period); blue traces indicate sleep restriction (blue shading indicates dark period). Quantification of sleep efficiency (N) and sleep latency (O; n = 48 for fumin;glass, n = 54 for fumin;cry⁰²).

Figure 5.. Sleep opportunity restriction improves sleep degradation associated with aging and Aβ accumulation

(A) Histogram of sleep bout durations of aged flies (53 days old) under 12:12 LD (black bars, n = 75), 12:12 LD+TC (26°C:18°C, gray bars, n = 78), or 14:10 LD+TC conditions (blue bars, n = 77). (B) Number of eggs laid by aged female flies under 12:12 LD, 12:12 LD plus 10 hours of low temperature during the light phase, or 14:10 LD+TC conditions (n = 100 flies per condition). (C) Representative sleep traces in flies with pan-neuronal overexpression of AβArctic under 12:12 LD conditions (top panel; gray shading indicates dark phase), sleep opportunity restriction (middle panel; blue shading indicates dark phase) and overlaid plots (bottom panel). (D-I) Quantification of sleep measures for elav-Gal4/+ (n = 60), UAS-AβArctic/+ (n = 53), and elav-Gal4/UAS-AβArctic flies under 12:12 LD (n = 59) or 14:10 LD conditions (n = 60). (J) Arousal threshold of elav-Gal4/UAS-AβArctic flies following mechanical stimulation (n = 149 sleep episodes in 32 flies for 12:12 LD and n = 147 sleep episodes in 32 flies for 14:10 LD). (K) Survival curves with pan-neuronal overexpression of AβArctic or genetic controls under 12:12 LD or 14:10 LD conditions (n=100 males for each condition; elav-Gal4/+: 12:12 LD (light green) and 14:10 LD (dark green); UAS-AβArctic/+: 12:12 LD (light red) and 14:10 LD (dark red); elav-Gal4>UAS-AβArctic: 12:12 LD (gray) and 14:10 LD restriction (blue). Inset shows enlarged survival curves of elav-Gal4>UAS-AβArctic flies under each condition.