“Be sure to eat dark leafy greens” is a common refrain from nutritionists, smug diet gurus, and – for many of us – our mothers. And while it may be well-known that this category of vegetables is excellent for one’s health, the molecular machinations behind these protective effects remained mysterious.
But now, a team of researchers from the Francis Crick Institute in London have shown how indole-3-carbinol (I3C) – a chemical produced in large concentrations in plants of the mustard genus Brassica (such as kale, broccoli, cabbage, and brussels sprouts) – helps prevent the intestinal inflammation that leads to colon cancer.
Past research in mice has revealed that blocking the activity of a type of cellular protein called the aryl hydrocarbon receptor (AhR) causes the animals to develop deadly infections and intestinal tumors. In both mice and humans, AhRs act as environmental sensors, and are thus found on cells that get exposed to elements to the outside world: the skin, lung, and gut. In the layer of the intestinal lining that separates the body’s own cells from the trillions of bacteria that colonize the internal surface, the receptor mediates signaling pathways involved in repairing damaged tissue, preventing infection by pathogenic bacteria, and suppressing an immune response against the many species of beneficial bacteria that constitute our microbiome.
In a series of experiments in genetically engineered live mice and mouse cell cultures, the Francis Crick team not only discovered how AhR oversees these essential intestinal functions – through the regulation of the stem cells that differentiate into intestine-lining cells – but they determined that I3C, which is one of many molecules that can bind to AhR, can activate AhR pathways when the receptor itself is absent or impaired. The results are published in the journal Immunity.