Evaluating a Time Course of Recovery of DNA Damage in HBEC-3KT Cells Following X Ray and Neutron Irradiation Open Access

Abstract

Humans are increasingly becoming space-faring creatures. But with that travel comes exposure to galactic cosmic radiation (GCR) and its associated dangers. Especially concerning is GCR’s ability to cause double stranded breaks (DSB) in DNA. Therefore, it is critical to study the effects of GCR on DNA damage in order to develop therapeutics. To do this, a local radiation source where high-throughput screening can be conducted is needed. This study evaluates the ability of a deuterium-deuterium (DD) neutron generator at the Georgia Institute of Technology to serve as such a resource. It is hypothesized the neutron irradiation will not only cause a biological effect, but the nature of which will be markedly different than that of a reference X ray irradiation. Human bronchial epithelial cells (HBEC-3KT) were irradiated by the DD generator at 1, 2, and 3 Gy and allowed to recover for 0.5 and 6 h. The DNA damage was compared to a reference X ray source, which irradiated cells at 1 Gy with 0.5, 2, 6, and 24 h recovery times. Compared to X ray radiation, neutron radiation generated a lower number of DSBs, but damage was more clustered and complex. This was evidenced by the slower recovery time and visual differences of neutron-caused damage compared to that of X ray. Overall, the DD neutron generator was indeed able to cause a biological effect, and its pattern of irradiation was distinct from a reference X ray radiation.

Table of Contents

Table of Contents

Introduction. 1

A. Galactic Cosmic Radiation. 1

B. Deposition of Radiant Energy. 2

C. X Ray and Neutron Radiation. 2

D. DNA Repair Foci 3

E. Experimental Objectives. 4

Figure 1. LET spectra of the lunar surface and DT neutrons. 5

Materials and Methods. 6

A. Cell Culture. 6

B. X Ray Irradiation. 7

Table 1. Experimental set-up for X ray irradiation. 8

C. Neutron Irradiation. 8

Table 2. Experimental set-up for neutron irradiation. 9

D. Staining for Imaging. 9

E. Visualizing DNA Repair Foci 10

F. Quantifying DNA Repair Foci 11

G. Statistical Tests. 11

Results. 12

A. X Ray Irradiation. 12

Figure 2. Representative images of HBEC-3KT cells at different times of recovery following X ray irradiation  12

Figure 3. DNA repair foci counts following X ray irradiation. 13

B. Neutron Irradiation. 14

Figure 4. Representative images of HBEC-3KT cells at different times of recovery following neutron irradiation  15

Figure 5. X ray and neutron foci close-up. 16

Figure 6. Non-irradiation related foci present in neutron experiment cells. 16

Figure 7. DNA repair foci counts following neutron irradiation. 17

Table 3. Median and mean values for X ray groups. 18

Table 4. Median and mean values for neutron groups. 18

Discussion. 19

References. 22

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Biochemistry
Keyword	galactic cosmic radiation
Committee Chair / Thesis Advisor	William Dynan, Emory University
Committee Members	David Lynn, Emory University Brian Dyer, Emory University

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