Edited and reviewed by: Luis de Lecea, Stanford University, United States
This article was submitted to Sleep and Circadian Rhythms, a section of the journal Frontiers in Neuroscience
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Brain barriers (BB) are the gatekeepers of the central nervous system, essential to protect the brain from xenobiotics, microorganisms, and other harmful agents. Conversely, disruption of BB is a key event responsible for several changes during the onset and progression of brain diseases (Han and Jiang,
Along with BB disruption, disturbances in the circadian rhythms are considered a risk factor for Alzheimer's disease and major determinants of many mood, anxiety, and psychotic disorders (Chen et al.,
BB functions are regulated by circadian rhythms (Cuddapah et al.,
If dysfunctions of the BB and disturbed circadian rhythms are clear contributors to brain diseases, it follows that circadian-oriented interventions could prevent or delay the onset of brain diseases.
Therefore, this Research Topic gathers different contributions highlighting the involvement of the circadian rhythms in health and disease, contributing to the early identification and control of brain diseases.
It is well-established that disturbances in the circadian rhythms are observed in patients recovering from traumatic brain injury (TBI), which are critical for the recuperation process. The first article of this Research Topic, shows that circadian rhythms are crucial determinants of TBI outcome. The authors showed that health parameters and scores vary depending on the light-dark cycle at which induced TBI occurred, in male Wistar rats (
The urgent need for new therapies for primary insomnia with minimal side effects, turned out to be the main objective of one of the other articles published. Although the transcutaneous auricular vagus nerve stimulation, has been reported as an effective treatment for insomnia, the inter-individual variations in the efficacy of this treatment are not well-understood. The authors observed that during continuous transcutaneous auricular vagus nerve stimulation, patients with primary insomnia showed variable sensitivity, that might be explained by the distinct control of the sensorimotor network by the autonomic nervous system (
The link between circadian rhythms and mood and anxiety disorders, was another subject addressed in this Research Topic. The authors analyzed the involvement of the master clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus, in regulating psychiatric-related behaviors in mice using optogenetic stimulation paradigms. They concluded that SCN-mediated dampening of rhythms is directly correlated with depressive- and anxiety-like behaviors (
Finally, the last published article also tried to relate alterations in biological rhythms with depressive disorders and consequently possible changes in tumor markers, due to the development of chronic inflammatory diseases. They concluded that the incidence of non-suicidal self-injury, a risk factor for suicide in depressive patients, was relatively high in adolescents. Furthermore, the construction of an index including a combination of depression score, tumor marker levels, and age can identify non-suicidal self-injury behaviors among adolescent patients with diagnosed depressive disorders (
In summary, this Research Topic is a step forward to understanding the influence of circadian rhythms in health and disease and we hope that the reader will find it a useful reference in the emerging field of adequate “rhythmic” therapeutic strategies taking into consideration the influence of the circadian biology.
TQ wrote the first draft. CS, JC-N, MK, and IG provided critical comments and editorial suggestions for revisions. All authors agreed on the submitted version.
This work was developed within the scope of the CICS-UBI projects UIDB/00709/2020 and UIDP/00709/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES.
MK was employed by Immungenetics AG. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.