Resveratrol, the polyphenolic compound found in red wine and the prominent focus of medical researchers, may be able to fight off viruses, according to a new Italian study. While the chemical has shown hints of anti-viral properties in previous studies, the new work shows that it appears to prevent virus replication at the cellular level. More research is needed to see how widespread the effect is.
Viruses, from the common cold to polio and the H1N1 "swine flu," are infectious agents that can only reproduce inside the cells of a host, inserting their genetic material into the cells. The new study, published in the July issue of the Journal of Experimental & Clinical Cancer Research, finds that the polyomavirus is unable to hijack a cell for this purpose if resveratrol is around.
"The continuous presence of resveratrol in the culture medium is necessary to exert its antiviral action," said Gianfranco Risuleo, a genetic and molecular biologist at Sapienza University in Rome and a co-author of the study. "[The chemical] shows effects on the synthesis of viral DNA; the action is not at cell entry level but rather at the nuclear level."
Polyomavirus, a family of viruses that can trigger tumor growth, is often chosen for research because its reproduction is totally dependent on the metabolism of the infected cell and therefore can be measured during several stages of its proliferation.
For the current study, the researchers exposed two different lines of mouse tissue, one with tumors and one without, to polyomavirus and then to either 20 or 40 micromoles of resveratrol. (The average glass of red wine has 10 times less resveratrol.) Control groups were not given any resveratrol.
The researchers found that in the tissue without tumors, after 24 hours, 20 micromoles of resveratrol reduced the number of viable infected cells to 80 percent. By 48 hours, that number dipped to 60 percent. With 40 micromoles, only 60 percent of the infected cells were viable after 24 hours, with only 42 percent still healthy after 48 hours.
While the exact process requires further study, the research indicates that resveratrol somehow blocks the ability of a virus to use the nucleus of a cell to replicate its own DNA. In cases where resveratrol was removed from the experiment after only four hours, the virus was soon reproducing freely.
Risuleo added that the results show a definite clinical, if curious, potential for the red-wine compound. "Resveratrol shows a paradoxical effect on cultured cells: i.e. it is likely innocuous at low concentrations while it becomes significantly toxic at higher concentrations, in the range of 40 to 50 micromoles." Risuleo said similar results can be expected in similar viral lines, such as chicken pox (Varicella zoster), herpes simplex and even influenza A.
The resveratrol also prevented viral reproduction in tumor cells. "Interestingly, tumor cells seem slightly more sensitive to the drug," Risuleo said. Recent studies suggest some viruses may play a role in triggering some types of cancer. For example, according to a new study published online on Sept. 23 in the Journal of the National Cancer Institute, polyomavirus is now believed to be associated with a rare skin cancer, known as Merkel cell carcinoma.
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