Saliva and common proteins from blood and muscle appear to protect human cells from powerful DNA-destroying toxins in tea, coffee, and liquid smoke flavoring, new research shows.
The findings suggest that our bodies naturally launch multiple defenses against these toxins—plant chemicals called pyrogallol-like polyphenols (PLPs)—and could explain why they don’t cripple cells and cause the illness that would be expected from their presence in human diets.
Last year, researchers demonstrated that PLPs could do significant damage by breaking strands of DNA, the carrier of genetic information.
The effect of the toxins was so strong—in some cases producing 20 times the damage of chemotherapy drugs delivered to cancer patients—that the researchers immediately thought to find out why there wasn’t more damage, and to look for ways that cells might be fighting back.
“If these chemicals are so widespread—they’re in flavorings, tea, coffee—and they damage DNA to such a high degree,” says Scott Kern, professor of oncology and pathology at Johns Hopkins University School of Medicine, “we thought there must be defense mechanisms that protect us on a daily basis from plants we choose to eat.”
In the new study, published in Food and Chemical Toxicology, Kern and colleagues found that an enzyme in saliva called alpha-amylase, the blood protein albumin, and the muscle protein myoglobin all protect cells from DNA breakage by tea, coffee, and isolated PLPs.
EVOLVING DEFENSES
Kern emphasizes that the saliva enzyme and the proteins don’t protect against chemotherapy drugs, which also damage DNA. That suggests that defenses against PLPs may have evolved, in response to natural plant compounds that have been part of human diets for a long time.
Surprisingly, cells do not seem to need the protein protectors after a period of exposure to the toxins.
“After about two weeks, we found it difficult to get the cells to be damaged by the same chemicals, even if they were damaged by the chemicals weeks earlier,” Kern says. “They seem to have some innate ability to respond to the damage or sense it and somehow protect themselves against it, even in the absence of albumin, muscle proteins, or saliva components.”
“It made us wonder, do people who eat the same PLP-containing diet day after day develop a natural cellular protection to the toxins,” Kern says, “so that, as has been said before, what doesn’t kill us makes us stronger?”
The researchers plan to explore further how albumin, myoglobin, and salivary alpha-amylase protect against PLPs and learn more about other possible innate defenses against the chemicals. Kern also plans to study how these natural defenses might be circumvented in some people, causing cancers or other illnesses.
The National Institutes of Health and the Everett and Marjorie Kovler Professorship in Pancreas Cancer Research supported the study.
Source: Johns Hopkins University
