Abstract
Purpose:
Light-emitting diodes (LEDs) deliver high levels of blue light to the retina and supposed to affect circadian rhythm. We investigated the role of blue light on circadian rhythm using a mouse model.
Methods:
C57/B6 mice were housed in a standard animal maintenance facility under a 12 hours light: 12 hours dark (LD) cycle. These mice were exposed to 30-minute light pulse at Zeitgeber time (ZT) 14 on the last day of LD using a white LED (Toshiba Materials) or a blue light cut LED (Toshiba Materials). Their circadian behavior was monitored by wheel-running activity and phase shift was analyzed. Expression of per2 in the suprachiasmatic nucleus (SCN) and the retina were analyzed by quantitative PCR at 1, 3, 6 hours after light pulse.
Results:
Phase delay response to light pulse with blue light-cut LED (44.7 + 31.3 min) was significantly shorter than response to light pulse with white LED (107.7 + 27.8 min) (P=0.001). Per2 expression in SCN of mice exposed to blue light-cut LED was significantly lower than mice exposed to white LED 3 hours after light pulse.
Conclusions:
The current behavioral studies suggest blue light induced phase shift and affect circadian clock in SCN. Suppression of blue light has protective role on circadian rhythm.