Intense Terahertz Pulses Cause DNA Damage But Also Induce DNA Repair

My Note: This piece is a little dated, but I just came across it, and thought it was worth including on the DNA damage question. Happy New Year to everyone!

Source : The Optical Society

http://www.biocompare.com/Life-Science-News/132917-Intense-Terahertz-Pulses-Cause-DNA-Damage-But-Also-Induce-DNA-Repair/

Biomedical Optics Express research details how terahertz pulses that destroy skin tissue at the same time increase tumor-suppressing proteins

Terahertz (THz) radiation, a slice of the electromagnetic spectrum that occupies the middle ground between microwaves and infrared light, is rapidly finding important uses in medical diagnostics, security, and scientific research. As scientists and engineers find evermore practical uses for this form of radiation, questions persist about its potential human health risks.

New research performed on lab-grown human skin suggests that short but powerful bursts of THz radiation may both cause DNA damage and increase the production of proteins that help the body fight cancer. The findings, which are the result of a collaboration between physicists at the University of Alberta and molecular biologists at the University of Lethbridge in Canada, are published today in the Optical Society's (OSA) open-access journal Biomedical Optics Express.

"While these investigations of the biological effects of intense THz pulses are only just beginning," said Lyubov Titova, with the University of Alberta and a member of the research team, "the fact that intense THz pulses can induce DNA damage but also DNA repair mechanisms in human skin tissue suggests that intense THz pulses need to be evaluated for possible therapeutic applications."

THz photons, like their longer wavelength cousins in the microwave range, are not energetic enough to break the chemical bonds that bind DNA together in the nucleus of cells. These waves, however, have just the right frequency to energize water molecules, causing them to vibrate and produce heat, which is why microwave ovens are so efficient at cooking food. For this reason, it was believed that heat-related injuries were the principal risks posed by THz radiation exposure.

Recent theoretical studies, however, suggest that intense THz pulses of picosecond (one trillionth of a second) duration may directly affect DNA by amplifying natural vibrations (the so-called "breathing" mode) of the hydrogen bonds that bind together the two strands of DNA. As a result, "bubbles" or openings in DNA strands can form. According to the researchers, this raised the question: "Can intense THz pulses destabilize DNA structure enough to cause DNA strand breaks?"

As shown in earlier animal cell culture studies, THz exposure may indeed affect biological function under specific conditions such as high power and extended exposure. There is, however, a vast gulf between animal research and conclusions that can be drawn about human health.

In a first of its kind study, the Canadian researchers exposed laboratory-grown human skin tissue to intense pulses of THz electromagnetic radiation and have detected the telltale signs of DNA damage through a chemical marker known as phosphorylated H2AX. At the same time, they observed THz-pulse induced increases in the levels of multiple tumor suppressor and cell-cycle regulatory proteins that facilitate DNA repair. This may suggest that DNA damage in human skin arising from intense picosecond THz pulse exposure could be quickly and efficiently repaired, therefore minimizing the risk of carcinogenesis.

The researchers used a skin tissue model made of normal, human-derived epidermal and dermal cells. This tissue is able to undergo mitosis (cell division) and is metabolically active, thus providing an appropriate platform for assessing the effects of exposure to high intensity THz pulses on human skin. For their study, Titova and her colleagues exposed the skin tissue to picosecond bursts of THz radiation at levels far above what would typically be used in current real-world applications. They then studied the sample for the presence of phosphorylated H2AX, which "flags" the DNA double strand break site and attracts cellular DNA repair machinery to it.

"The increase in the amount of phosphorylated H2AX in tissues exposed to intense THz pulses compared to unexposed controls indicated that DNA double strand breaks were indeed induced by intense THz pulses," observed Titova. Once DNA breaks occur, they can eventually lead to tumors if unrepaired. "This process," she continued, "is very slow and cells have evolved many effective mechanisms to recognize damage, pause cell cycle to allow time for damage to be repaired, and – in case repair is unsuccessful – to prevent damage accumulation by inducing apoptosis, or programmed cell death of the affected cell."

The researchers confirmed that these cellular repair mechanisms were taking place by detecting an elevated presence of multiple proteins that play vital roles in DNA repair, including protein p53 (often called "a guardian of the genome"); p21, which works to stop cell division to allow time for repair; protein Ku70, which helps reconnect the broken DNA strands; and several other important cell proteins with known tumor-suppressor roles. These observations indicate that exposure to intense THz pulses activates cellular mechanisms that repair DNA damage. However, the researchers note, it is too soon to make predictions on the long-term implications of exposure.

"In our study we only looked at one moment in time – 30 minutes after exposure," Titova said. "In the future, we plan to study how all the observed effects change with time after exposure, which should allow us to establish how quickly any induced damage is repaired."

The Canadian researchers hope to explore the potential therapeutic effects of intense THz radiation exposure to see if directed treatment with intense THz pulses can become a new tool to fight cancer.

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Paper: "Intense THz pulses cause H2AX phosphorylation and activate DNA damage response in human skin in vivo," Titova, L. V. et al., Biomedical Optics Express, Vol. 4, Issue 4, pp. 559-568 (2013) (link: http://www.opticsinfobase.org/boe/abstract.cfm?URI=boe-4-4-559).

Outer space research could benefit inner space

http://www.lethbridgeherald.com/local-news/outer-space-researchcould-benefit-inner-space-112611.htmlCaroline Zentner
lethbridge herald
czentner@lethbridgeherald.com
The medical tricorder used by Bones in the Star Trek series is getting closer to reality as local scientists work to develop ultra-sensitive diagnostic technology.
That it came from the world of astronomy should be no surprise. David Naylor, a physics professor at the University of Lethbridge, said the terahertz imaging technology on the Herschel space observatory is built to look deep into space at wavelengths far beyond visible light.
That same kind of sensitivity can be useful in medicine. Blue Sky Spectroscopy, a privately owned company in Lethbridge started by Naylor in partnership with the University of Lethbridge and the University of Calgary, is working on a terahertz imaging detector to diagnose breast cancer.
"It's been proven by a group in Taiwan, a research team there that has links with a medical faculty, that you can actually measure breast cancer with 100 per cent accuracy, which is amazing, without using a pathologist," Naylor said.
Current diagnostic methods can result in false test results that can be dangerous for patients and expensive for the health-care system.
"In astronomy we have to have the most sensitive detectors because our galaxies are so far away. Of all disciplines astronomy has the most sensitive detectors of anybody," Naylor said. "If I can see something a billion light years away, of course I can see something under a microscope a few millimetres in front of me."
Such an imager could be used in the operating room to tell surgeons the exact size and location of the cancer. As it stands, no real-time measurement of the cancer is possible, Naylor said. Surgeons estimate how much tissue to excise, but a second surgery is sometimes required if the first surgery didn't get all of the cancer.
That's just one of the items Naylor shared with those at the Canadian Space Society conference in Calgary this past week. He was speaking on astronomy and technology, including SPICA, the space infrared telescope for cosmology and astrophysics. Naylor is the Canadian principal investigator for the project which is being led by the Japanese Space Agency. The project has not yet received formal acceptance.
"If it goes ahead, the U of L will be leading Canada's interest in it," he said. "We're the only university in which a group is leading Canada in two space missions."
SPICA is expected to provide superior sensitivity and high spatial resolution with its unique design and scientists hope it will help answer questions about how galaxies were formed and how they evolved.
On the ground, the sensitive terahertz imaging detectors could also have applications beyond medicine.
"Terahertz imaging can penetrate many materials," Naylor said.
The technology could be used in locating improvised explosive devices (IEDs), to find masterpieces hidden behind walls in Italian palaces, to identify drugs, explosives and contraband cargo, and as security body scanners at airports.
"We joke that you'll be able to go through the airport (and) with a terahertz scanner they'll clear you for carrying weapons and they'll tell you if you've got cancer," Naylor said.
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