Research published online recently suggests that the presence of artificial light at night disrupts the circadian cycle of cell division and affects transcription levels of genes that are associated with the formation of cancerous tumors and their spread.
You can read about the study, by Dr Rachel Ben-Shlomo of the University of Haifa in Israel and Professor Charalambos P Kyriacou of the University of Leicester in the UK, in the February online issue of the journal Cancer Genetics and Cytogenetics.
The authors wrote in their background information that we have known that cell division follows a circadian pattern for over a hundred years, but exactly how is not clear.
They also knew from an earlier study by Ben-Shlomo that the molecules that make up the biological clock of cells, the so-called circadian “oscillators”, synchronize with the outside world via light, and other time-related cues.
Ben-Shlomo and others at the University of Haifa have performed a number of studies on the effect of artificial light at night.
However, the question of how it might affect gene transcription, the first step of gene expression, was still largely unanswered.
The question is important, because as Ben-Shlomo explained in a media statement:
“Damage to cell division is characteristic of cancer, and it is therefore important to understand the causes of this damage.”
For the study, Ben-Shlomo and Kyriacou exposed two groups of lab mice to a daily dose of light for 12 hours and dark for 12 hours.
During the dark hours, one group of mice was also exposed to artificial light for an hour. The other group did not have this treatment.
The researchers then examined the brains of the two groups of mice to look for and compare changes in gene expression. They used a method called microarray analysis (also termed “lab on a chip”) to do this.
They found that exposure to light pulses interrupted cell division and affected the transcription of a large number of genes, resulting in changes to their expression.
The authors noted that:
“Light pulses consistently affect transcription levels of genes that are essential and directly control the cell cycle mechanism, as well as levels of genes that are associated with the various cell cycle checkpoints.”
Some of the genes affected were involved in the formation and spread of cancer tumors (“enhanced proliferation and metastasis” wrote the authors) and others were involved in fighting cancer.
“What is certain is that the natural division is affected,” said Ben-Shlomo.
In fact, she and Kyriacou went so far as to suggest that:
“The changes in the levels and the direction of these changes could possibly lead to cell cycle arrest.”
“Light pulses administered during the circadian dark phase alter expression of cell cycle associated transcripts in mouse brain .”
R. Ben-Shlomo, C.P. Kyriacou
Cancer Genetics and Cytogenetics, Volume 197, Issue 1, February 2010, Pages 65-70
DOI:10.1016/j.cancergencyto.2009.11.003
Source: University of Haifa.
Written by: Catharine Paddock, PhD