Consequences of Artificial Light at Night: The Linkage between Chasing Darkness Away and Epigenetic Modifications

Epigenetics is an important tool for understanding the relation between environmental exposures and cellular functions, including metabolic and proliferative responses. At our research center, we have devolved a mouse model for characterizing the relation between exposure to artificial light at night (ALAN) and both global DNA methylation (GDM) and breast cancer. Generally, the model describes a close association between ALAN and cancer responses. Cancer responses are eminent at all light spectra, with the prevalent manifestation at the shorter end of the visible spectrum. ALAN-induced pineal melatonin suppression is the principal candidate mechanism mediating the environmental exposure at the molecular level by eliciting aberrant GDM modifications. The carcinogenic potential of ALAN can be ameliorated in mice by exogenous melatonin treatment. In contrast to BALB/c mice, humans are diurnal species, and thus, it is of great interest to evaluate the ALAN-melatonin-GDM nexus also in a diurnal mouse model. The fat sand rat (Psammomys obesus) provides an appropriate model as its responses to photoperiod are comparable to humans. Interestingly, melatonin and thyroxin have opposite effects on GDM levels in P. obesus. Melatonin, GDM levels, and even thyroxin may be utilized as novel biomarkers for detection, staging, therapy, and prevention of breast cancer progression