Daily Light–Dark Cycles Influence Hypoxia‐Inducible Factor 1 and Heat Shock Protein Levels in the Pacemakers of Crayfish

Abstract

It has been proposed that at moderate concentrations, reactive oxygen species (ROS) play an important role as regulatory mediators in signaling processes. Many of the ROS-mediated responses, such as those mediated by the glutathione (GSH) system, protect cells against oxidative stress and reestablish "redox homeostasis." The response to stress is controlled by specific transcription factors, such as hypoxia-inducible factor 1 (HIF-1), which interacts with chaperones such as heat shock proteins (HSP) that stabilize intracellular components. We have reported that the oxidation produced by extreme light cycles was coupled to cellular fluctuations in the production of free radicals and ROS in crayfish. Herein, we investigated whether ROS resulting from light-dark cycles (20:4 LD) with a long photoperiod activated HIF-1α in the putative pacemakers of crayfish. Our results indicate that both the light resulting from equatorial and extreme daily light cycles and the constant darkness-induced HIF-1α and heat shock protein 70 (HSP70) appeared to regulate each other. The interaction between these proteins and the ability of crayfish to shift from the oxidative to glycolytic pathways, thereby synchronizing to extreme illumination conditions and maintaining a rhythmic predictive relationship with the environment, suggest HIF-1 as a key factor in these rhythmic metabolic interactions.