Short Photoperiod Reduces Oxidative Stress by Up-Regulating the Nrf2–Keap1 Signaling Pathway in Hamster Kidneys

Abstract Photoperiod can impact seasonal reproduction as well as the expression of antioxidant enzymes and the level of oxidative stress in animals. The kidney is an important metabolic organ, however studies on the effects of the photoperiod on oxidative stress and antioxidant pathways in the kidney remain limited. In the present study, we investigated the effects of different photoperiods (e.g., SD, short daylight; MD, moderate daylight; LD, long daylight) on oxidative stress levels, antioxidant enzyme expression levels, and the Nrf2–Keap1 signaling pathway in the kidneys of striped dwarf hamsters (Cricetulus barabensis). Compared with the MD group, oxidative stress was decreased in the SD group but increased in the LD group. In contrast, antioxidant enzyme activity and expression were increased in the SD group but decreased in the LD group. The Nrf2–Keap1 signaling pathway was also up-regulated in the SD group, but not in the LD group. We further explored the regulatory mechanism underlying oxidative stress and antioxidant defense in hamsters under different photoperiods. The differences in reactive oxygen species (ROS) under different photoperiods were closely associated with regulation of the Nrf2–Keap1 signaling pathway and expression of the antioxidant enzymes. Under short light exposure, expression of downstream antioxidant enzymes was increased via up-regulation of the Nrf2–Keap1 signaling pathway, which reduced oxidative stress. In contrast, under long light exposure, antioxidant enzyme activity decreased, which may be due to protein damage caused by increased oxidative stress.