Limits...
Cycles of circadian illuminance are sufficient to entrain and maintain circadian locomotor rhythms in Drosophila

View Article: PubMed Central - PubMed

ABSTRACT

Light at night disrupts the circadian clock and causes serious health problems in the modern world. Here, we show that newly developed four-package light-emitting diodes (LEDs) can provide harmless lighting at night. To quantify the effects of light on the circadian clock, we employed the concept of circadian illuminance (CIL). CIL represents the amount of light weighted toward the wavelengths to which the circadian clock is most sensitive, whereas visual illuminance (VIL) represents the total amount of visible light. Exposure to 12 h:12 h cycles of white LED light with high and low CIL values but a constant VIL value (conditions hereafter referred to as CH/CL) can entrain behavioral and molecular circadian rhythms in flies. Moreover, flies re-entrain to phase shift in the CH/CL cycle. Core-clock proteins are required for the rhythmic behaviors seen with this LED lighting scheme. Taken together, this study provides a guide for designing healthful white LED lights for use at night, and proposes the use of the CIL value for estimating the harmful effects of any light source on organismal health.

No MeSH data available.


Related in: MedlinePlus

12 h:12 h cycles of white LED light with high and low circadian illuminance (CIL) produce robust behavioral and molecular rhythms.Flies were exposed to conventional constant light (LL) conditions for 2 days and then were maintained on 12 h:12 h cycles of 10,000 K white LED light with high CIL (CH) and 2,000 K white LED light with low CIL (CL) for 11 days. (A and B) Averaged actograms of flies of the indicated genotypes are shown. Each row of the actogram was double-plotted. The numbers of flies used for the analyses were 61 (CS), 60 (w1118). Light blue and pink horizontal bars indicate CH and CL, respectively. (C to H) Head extracts from CS flies on day 5 of the CH/CL cycle were obtained and processed for immunoblotting with anti-PER (C), anti-TIM (D), and anti-CRY (E) antibodies. Actin served as a loading control. Relative levels of PER (F), TIM (G), and CRY (H) were determined by measuring band densities using Image J software. Three replicates were used for the calculation. Values represent mean ± SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5121609&req=5

f2: 12 h:12 h cycles of white LED light with high and low circadian illuminance (CIL) produce robust behavioral and molecular rhythms.Flies were exposed to conventional constant light (LL) conditions for 2 days and then were maintained on 12 h:12 h cycles of 10,000 K white LED light with high CIL (CH) and 2,000 K white LED light with low CIL (CL) for 11 days. (A and B) Averaged actograms of flies of the indicated genotypes are shown. Each row of the actogram was double-plotted. The numbers of flies used for the analyses were 61 (CS), 60 (w1118). Light blue and pink horizontal bars indicate CH and CL, respectively. (C to H) Head extracts from CS flies on day 5 of the CH/CL cycle were obtained and processed for immunoblotting with anti-PER (C), anti-TIM (D), and anti-CRY (E) antibodies. Actin served as a loading control. Relative levels of PER (F), TIM (G), and CRY (H) were determined by measuring band densities using Image J software. Three replicates were used for the calculation. Values represent mean ± SEM.

Mentions: Flies were first exposed to typical LL conditions under >2000-lx white fluorescent light to eliminate any existing circadian rhythm, and subsequently to CH/CL cycle conditions. We have tested two different control strains of flies, Canton S (CS) and w1118. Whereas both strains showed arrhythmic locomotor activity under typical LL conditions, locomotor activity peaks appeared on day 2 of CH/CL cycle, and the rhythms of locomotor activity persisted until the end of CH/CL cycles (Fig. 2A and B). Nonetheless, the daily locomotor activity distribution of CS and w1118 flies in CH/CL cycles differed from those in typical LD cycles. In CH/CL cycles, CS flies manifested a unimodal peak of activity that occurred around ZT10 (ZT0 means when CH light is on) preceded by a gradual increase in anticipatory activity. Because the locomotor activity peak appeared in the afternoon during the CH/CL cycle we refer to this as the afternoon peak. In contrast, w1118 flies exhibited a unimodal peak of activity that occurred primarily at the transition from CH to CL light, with a gradual increase in anticipatory activity before the transition (Fig. 2A and B, Fig. 3C). These data indicate that some characteristics of the light might affect behavioral outcomes in these flies, and that strain-specific variation may exist.


Cycles of circadian illuminance are sufficient to entrain and maintain circadian locomotor rhythms in Drosophila
12 h:12 h cycles of white LED light with high and low circadian illuminance (CIL) produce robust behavioral and molecular rhythms.Flies were exposed to conventional constant light (LL) conditions for 2 days and then were maintained on 12 h:12 h cycles of 10,000 K white LED light with high CIL (CH) and 2,000 K white LED light with low CIL (CL) for 11 days. (A and B) Averaged actograms of flies of the indicated genotypes are shown. Each row of the actogram was double-plotted. The numbers of flies used for the analyses were 61 (CS), 60 (w1118). Light blue and pink horizontal bars indicate CH and CL, respectively. (C to H) Head extracts from CS flies on day 5 of the CH/CL cycle were obtained and processed for immunoblotting with anti-PER (C), anti-TIM (D), and anti-CRY (E) antibodies. Actin served as a loading control. Relative levels of PER (F), TIM (G), and CRY (H) were determined by measuring band densities using Image J software. Three replicates were used for the calculation. Values represent mean ± SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121609&req=5

f2: 12 h:12 h cycles of white LED light with high and low circadian illuminance (CIL) produce robust behavioral and molecular rhythms.Flies were exposed to conventional constant light (LL) conditions for 2 days and then were maintained on 12 h:12 h cycles of 10,000 K white LED light with high CIL (CH) and 2,000 K white LED light with low CIL (CL) for 11 days. (A and B) Averaged actograms of flies of the indicated genotypes are shown. Each row of the actogram was double-plotted. The numbers of flies used for the analyses were 61 (CS), 60 (w1118). Light blue and pink horizontal bars indicate CH and CL, respectively. (C to H) Head extracts from CS flies on day 5 of the CH/CL cycle were obtained and processed for immunoblotting with anti-PER (C), anti-TIM (D), and anti-CRY (E) antibodies. Actin served as a loading control. Relative levels of PER (F), TIM (G), and CRY (H) were determined by measuring band densities using Image J software. Three replicates were used for the calculation. Values represent mean ± SEM.
Mentions: Flies were first exposed to typical LL conditions under >2000-lx white fluorescent light to eliminate any existing circadian rhythm, and subsequently to CH/CL cycle conditions. We have tested two different control strains of flies, Canton S (CS) and w1118. Whereas both strains showed arrhythmic locomotor activity under typical LL conditions, locomotor activity peaks appeared on day 2 of CH/CL cycle, and the rhythms of locomotor activity persisted until the end of CH/CL cycles (Fig. 2A and B). Nonetheless, the daily locomotor activity distribution of CS and w1118 flies in CH/CL cycles differed from those in typical LD cycles. In CH/CL cycles, CS flies manifested a unimodal peak of activity that occurred around ZT10 (ZT0 means when CH light is on) preceded by a gradual increase in anticipatory activity. Because the locomotor activity peak appeared in the afternoon during the CH/CL cycle we refer to this as the afternoon peak. In contrast, w1118 flies exhibited a unimodal peak of activity that occurred primarily at the transition from CH to CL light, with a gradual increase in anticipatory activity before the transition (Fig. 2A and B, Fig. 3C). These data indicate that some characteristics of the light might affect behavioral outcomes in these flies, and that strain-specific variation may exist.

View Article: PubMed Central - PubMed

ABSTRACT

Light at night disrupts the circadian clock and causes serious health problems in the modern world. Here, we show that newly developed four-package light-emitting diodes (LEDs) can provide harmless lighting at night. To quantify the effects of light on the circadian clock, we employed the concept of circadian illuminance (CIL). CIL represents the amount of light weighted toward the wavelengths to which the circadian clock is most sensitive, whereas visual illuminance (VIL) represents the total amount of visible light. Exposure to 12 h:12 h cycles of white LED light with high and low CIL values but a constant VIL value (conditions hereafter referred to as CH/CL) can entrain behavioral and molecular circadian rhythms in flies. Moreover, flies re-entrain to phase shift in the CH/CL cycle. Core-clock proteins are required for the rhythmic behaviors seen with this LED lighting scheme. Taken together, this study provides a guide for designing healthful white LED lights for use at night, and proposes the use of the CIL value for estimating the harmful effects of any light source on organismal health.

No MeSH data available.


Related in: MedlinePlus