A Study of the Effects of Light on Aryl Hydrocarbon Receptor (AhR) Signaling
Circadian rhythms are controlled by a number of clock genes including Clock, BMAL1, Per1, Per2, and CRY. Clock protein binds to BMAL1 protein to form a heterodimer which activates the transcription of proteins including Per1. The "pacemaker" of circadian rhythm resides in the suprachiasmatic nucleus (SCN) of the brain, which primarily relies on light and dark cycles to synchronize the various circadian rhythms throughout the body. We hypothesize that the aryl hydrocarbon receptor (AhR) plays a role in circadian rhythm and is the mechanism by which light signals are transmitted to peripheral organs. Once AhR is activated by certain environmental pollutants and/or tryptophan photoproducts, it enters into the nucleus of a cell and induces the production of Cytochrome P450 1A1 (CYP1A1) and CYP1B1 proteins. To investigate the possible role of AhR signaling as a transducer of light, the presence of these proteins was examined during a light exposure study in liver, heart and skin tissues using immunohistochemistry. In addition, expression of Per1 which is one of the clock genes known to be induced by light signal in the SCN was examined in these tissues as well. However, due to technical difficulties of Per1 staining, expression of this protein was inconclusive in all tissues. We found an increase of CYP1A1 in the liver and an increase of CYP1B1 in both the skin and heart. Therefore an increase in AhR signaling was observed in mice after exposure to light. This supports our hypothesis that light induces AhR signaling.
School:
University of Illinois at Urbana-Champaign
Department:
Animal Sciences Biotechnology, Pre-Veterinary Medicine
Research Advisor:
Shelley Tischkau
Department of Research Advisor:
Veterinary Biosciences
Year of Publication:
2005