Scientists suggest ways to increase the radioresistance of people for space colonization

The main sources of radiation in space An
international group of scientists from 20 organizations from around the world, with the participation of specialists from the Moscow Institute of Physics and Technology (MIPT), has compiled a list of activities to increase the radioresistance of the human body . Resistance to ionizing radiation is a necessary condition for successful space colonization, scientists say.

Radioresistance is the immunity of cells, tissues, organs or organisms to the effects of ionizing radiation. It is known that many living organisms on Earth have amazing radioresistance. For example, bacteria Deinococcus radiodurans and tardigrades capable of withstanding the highest dose of ionizing radiation of about 5,000 gray (5 million rad), that is, 5 kilojoules per kilogram of mass, while doses of more than 1000 gray make tardigrades infertile. At the same time, for a person, only 4-10 gray is considered a lethal dose . The record among living organisms belongs to the archaea-extremophile Thermococcus gammatolerans , which can be guaranteed to be killed only by radiation of more than 30,000 gray .

Cosmic radiation and microgravity are two main factors affecting human health when in space outside the protective magnetic field of the Earth. These factors significantly limit the prospects of long-term space flights. It should be recognized that the need to protect the human body from the harmful effects of cosmic radiation is largely ignored. For example, Elon Musk planned the start of Martian colonization in 2024, but did not present a comprehensive radiation protection scheme.

But for flights into deep space, including flight to Mars, radiation exposure is one of several categories of unacceptable risk since the cumulative doses received by astronauts are likely to significantly exceed the dose limits established under the current NASA radiation protection system . In accordance with the NASA paradigm, for travel to Mars , the maximum limit on the risk of death due to radiation exposure is within 3% . That is, out of six astronauts with a probability of 83%, five (0.97 ^ 6) should survive, and out of twelve with a probability of 69%, eleven (0.97 ^ 12) will survive. This is a perfectly acceptable result. Among all the fatal cases, mainly death will come from malignant tumors (cancer), analysts say.

To achieve mortality within the normal range (3%) or lower, it is necessary to introduce additional protection systems, including new biotechnological concepts that will solve this problem and provide an opportunity to begin the era of manned flights into outer space.

The main components of cosmic radiation are solar proton events (SPS) and galactic cosmic radiation (SCI). Obviously, the contribution of ATP to the total radiation dose of astronauts will be insignificant during long missions far from the Earth and the Sun. Consequently, the main type of radiation in the effect on the body is GKI, consisting mainly of high-energy particles.

In principle, ionizing radiation interacts along tracks of charged particles with biological molecules such as DNA. The process is largely stochastic and can damage DNA through direct interactions (e.g., ionization and excitation) or through indirect interactions, such as the production of reactive oxygen species as a result of radiolysis of water molecules.

According to current estimates , traveling to Mars and back will expose astronauts to radiation doses of 660 mSv. Although there are great uncertainties regarding health risk assessments (cancer) from exposure to cosmic radiation, this dose alone makes up more than half of the total exposure limit for the entire NASA astronaut’s career, which is set in 800-1200 mSv . Obviously, in accordance with the current principles of radioprotection, longer missions will be unacceptable to people in terms of the risk of cancer.

The European Space Agency (ESA) is currently conducting intensive research on the possibility of long-range space flights. Given that the flight will take place mainly under the control of automatic systems, where the participation of astronauts is practically not required, the space crew will literally be in custody for many months without any work. Such situations can be dangerous, especially for the astronauts themselves. Therefore, the ESA believes that it is wiser to immerse people in suspended animation (hibernation, that is, hibernation). ESA is currently implementing Aurora project, which is considering the option of hibernating the crew . Scientists intend to use biological mechanisms that will allow the crew to sleep and thereby reduce the body’s metabolism to an absolute minimum.

It is worth emphasizing that the idea of ​​possible hibernation during long space flights was also investigated in the USSR in 1969, but, unfortunately, after the death of the head of the Soviet space program Sergey Korolev, the project of the manned Soviet mission to Mars was closed, and all work related to it implementation terminated. The results of these studies included data on hyperresistance to various damaging factors, including lethal doses of ionizing radiation, long-term fatal overloads, and hypobaric hypoxia in mice (see book “Hypobiosis and cryobiosis: past, present and future” by Nikolai Nikolayevich Timofeev, MD, specialist in aviation and space medicine, head of the laboratory of nanocytophysiology of the Institute of Nanotechnology of the International Fund for Conversion).

There is a theory that radioresistance can be trained by pre-irradiating the body with small doses of ionizing radiation. It has been well established that radioresistance can be set genetically and be inherited in at least some organisms. There are also medications with radioprotective properties:

  • preparation en: Ex-Rad (ON 01210.Na), which is a sodium salt of 4-carboxystyryl-4-chlorobenzylsulfone;
  • en: CBLB502;
  • amifostine (en: amifostine) 'WR2721';
  • filgrastim (en: Filgrastim) ('Neupogen');
  • pegfilgrastim (en: Pegfilgrastim) ('Neulasta');
  • kojic acid.

The published work lists possible ways to reduce the health risk of astronauts from ionizing radiation. Scientists suggest several approaches: medical selection of radioresistant radiation-resistant candidates (and their descendants to whom genes are transmitted), tissue regeneration technologies and cell therapy, genetic engineering, gene therapy, experimental evolution, hibernation, biobanking, etc.

Ways to reduce health risks from space radiation during space travel

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Owing to the very high energies of the charged particles of HKI, they easily penetrate passive protective materials. Despite the fact that active shielding technologies are also being studied, significant progress has not yet been achieved in significantly reducing GKI fluxes to levels suitable for prolonged human space flights (see analysis for evaluating the effectiveness of all possible active protection options ).

In this regard, it is important to study the various prospects of increasing the radioresistance of a person using the latest achievements in the field of biotechnology. So, what are some of the ways scientists can improve radioresistance?

Ways to increase radioresistance in humans

  1. Conducting genetic changes using breakthrough technologies in gene editing in combination with modern knowledge of the molecular pathways to counteract radiation-induced DNA damage.
  2. Regenerative medicine.
  3. Low-dose radio adaptation.
  4. The use of deuterated organic compounds.
  5. Biostasis (a significant slowdown of all vital processes in the body).

A combination of all these methods is possible.

In addition, much attention is paid to radio protection in this scientific work. Some of the ideas could potentially be used to alleviate other detrimental effects of long space travel, such as muscle and bone deterioration, the authors say. The described biotechnologies such as genetic engineering, regenerative medicine, biostasis and cryogenic sleep in the future may find application not only in astronautics, but also in terrestrial medicine, including for prolonging human life.

“In this paper, we are exploring observable options that can be used to increase human biomedical stability for space exploration and colonization. It also seeks to identify the link between aging, longevity, and radioresistance, and explores ways in which studies to increase human radioresistance could synergistically improve people's health. Ultimately, we study how work in the well-funded field of aerospace research can drive progress in biomedical gerontology, which suffers from severe underfunding despite serious economic difficulties caused by demographic aging, ” says Franco Cortese, lead author of the paper, deputy director of the Biogerontology Research Foundation.

“This roadmap lays the foundation for enhancing human biology beyond our natural limits to ensure not only long life expectancy and disease resistance, but also safety during future space research,” said João Pedro de Magalhães ), co-author of the article, trustee of the Biogeronology Research Foundation.

Sooner or later, we will have to do this - to leave the Earth and go into deep space, says Dmitry Klokov, head of the radiobiology and healthcare section of the Canadian nuclear laboratories, one of the authors of the scientific work. Such a journey outside the terrestrial magnetosphere will cause great harm to the health of astronauts due to the effects of cosmic radiation. Therefore, it is better to start thinking in advance about how we will cope with this task.

The scientific article was published on March 6, 2018 in the journal Oncotarget (doi: 10.18632 / oncotarget.24461).