由 Brendon Nafziger
, DOTmed News Associate Editor | October 28, 2009
In a breakthrough that could change the lives of cancer victims, pilots and nuclear power plant workers, researchers might have found a way to protect cells from radiation damage.
In a study published in the new AAAS journal Science Translational Medicine (see video below), researchers at the University of Pittsburgh School of Medicine and the National Cancer Institute found that they could protect healthy cells from radiation injury by turning off an inhibitory pathway that regulates nitric oxide.
"[Nitric oxide] is a bio gas, produced by enzymes in cells, and flies around almost at light speed compared to other processes," Jeff Isenberg, M.D., a professor at Pitt's school of medicine, tells DOTmed News.
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While nitric oxide mostly works to prevent clotting of arteries, it also appears to help animals survive stress conditions.
But Dr. Isenberg and his team made the discovery that by switching off a related inhibitory pathway that controls nitric oxide, they could give animals "near immunity to record levels of radiation," he says.
In mice, when Dr. Isenberg and his team introduced a drug that prevented a protein, thrombospondin-1, from binding to a surface cell receptor called CD47, the animals could endure almost unheard-of doses of radiation with virtually no ill effects.
In cellular studies, cells could withstand up to the tested amount: 60 Gy. And in whole animal studies, mice could endure the limit they were given: 40 Gy.
"Primarily, [on mice] people are using 5-10 Gy. This is off the scale from what they've published," he says.
Shockingly, the irradiated rodents were almost completely unharmed. Other than some mild hair loss at the site of dosage, there was almost no cell death or damage when histological samples were checked.
"There was no skin laceration or muscle loss," Dr. Isenberg says. "When we stained for cell death, we didn't even see significant loss of bone marrow, which is exquisitely sensitive...to radiation damage."
In comparison, control mice -- who didn't get the pathway-blocking treatment -- were eaten away with tissue loss and "frank necrosis of the limbs."
In fact, one reason Dr. Isenberg doesn't know the upper-limits of protection the drug confers to a whole animal is that ethics boards refuse to give permission to expose mice to much more than 40 Gy. (Whatever he gives to the treated mice -- who will be fine -- he has to give to the untreated mice, who will not.)
However, he says at some point radiation would damage tissue through thermal energy, which this process might not be able to stop.