Oxygen, reactive oxygen species and developmental redox networks: Evo-Devo Evil-Devils?

Molecular oxygen (O2), reactive oxygen species (ROS), and associated redox networks are cornerstones of aerobic life. These molecules and networks have gained recognition as fundamental players in mechanisms that regulate the development of multicellular organisms. First, we present a brief review in which we provide a historical description of some relevant discoveries that led to this recognition. We also discuss the fact that, despite its abundance in nature, oxygen is a limiting factor, and its high availability variation impacted the evolution of adaptive mechanisms to guarantee the proper development of diverse species under such extreme environments. Finally, some examples of when oxygen and ROS were identified as relevant for the control of developmental processes are discussed. We take into account not only the current knowledge on animal redox developmental biology, but also briefly discuss potential scenarios on the origin and evolution of redox developmental mechanisms and the importance of the ever-changing environment.

Role of the Suprachiasmatic and Arcuate Nuclei in Diurnal Temperature Regulation in the Rat.

In mammals, daily changes in body temperature (Tb) depend on the integrity of the suprachiasmatic nucleus (SCN). Fasting influences the Tb in the resting period and the presence of the SCN is essential for this process. However, the origin of this circadian/metabolic influence is unknown. We hypothesized that, not only the SCN but also the arcuate nucleus (ARC), are involved in the Tb setting through afferents to the thermoregulatory median preoptic nucleus (MnPO). Therefore, we investigated by neuronal tracing and microdialysis experiments the possible targeting of the MnPO by the SCN and the ARC in male Wistar rats. We observed that vasopressin release from the SCN decreases the temperature just before light onset, whereas α-melanocyte stimulating hormone release, especially at the end of the dark period, maintains high temperature. Both peptides have opposite effects on the brown adipose tissue activity through thermoregulatory nuclei such as the dorsomedial nucleus of the hypothalamus and the dorsal raphe nucleus. The present study indicates that the coordination between circadian and metabolic signaling within the hypothalamus is essential for an adequate temperature control. SIGNIFICANCE STATEMENT: When circadian and metabolic systems are not well synchronized, individuals may develop metabolic diseases. The underlying mechanisms are unknown. Here, we demonstrate that the balance between the releases of neuropeptides derived from the biological clock and from a metabolic sensory organ as the arcuate nucleus, are essential for an adequate temperature control. These observations show that brain areas involved in circadian and metabolic functions of the body need to interact to produce a coherent arrangement of physiological processes associated with temperature control.