Date of Award

7-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical and Chemical Engineering and Sciences

First Advisor

Kunal Mitra

Second Advisor

Vipuil Kishore

Third Advisor

James Brenner

Fourth Advisor

Ted Conway

Abstract

Human exploration beyond the earth's orbit poses many risks for the crew on these missions. One of the major health risks is exposure to space radiation environment beyond the earth’s magnetic field. The space environment exposes astronauts to high levels of ionizing radiation such as galactic cosmic rays. The radiations can have acute and delayed effects on the human body. The primary response to tissue injury is increased oxidative stress and inflammation. The overall objective of this study was to analyze the effects of ionizing radiation in heart tissue by quantifying its impact on the expression of genes that correlate with chronic inflammatory responses and indicative of the presence of reactive oxygen species (ROS). Irradiated 900 c57b16 breed mice heart samples were obtained, and gene expression studies were performed to assess the alterations in genes after exposure to different types of radiation and doses by employing real-time PCR analysis. This study analyzed the regulation of inflammatory marker interleukin-6 (IL-6) and antioxidative enzyme superoxide dismutase (Sod2). Heart tissue samples were crushed, and RNA was isolated using the TRIzol method. RNA was reverse transcribed to synthesize cDNA, and real-time PCR run was performed by using TaqMan Gene Expression assays. Target gene expression was quantified using the 2- (▲▲Ct) method by normalizing the expression of target gene with housekeeping genes (Actb, GAPDH, and Hprt) and relative to their expression on control non-irradiated samples. A total of thirteen irradiated samples and three control samples were assessed. The quantity and purity of isolated RNA was confirmed by spectrophotometric analysis, which showed that the ratio of absorbance at 260 nm versus 280 nm was between 1.8 and 2.0 for all samples. In tissues exposed to 50 cGy oxygen irradiation, it was observed that the regulation of gene expression was not consistent in all samples as some samples showed up-regulation of IL-6 and Sod2 gene while others showed down-regulation of the genes. These results suggest that 50 cGy Oxygen ionizing radiation had different effects on these tissue samples and modulated the gene expression discretely. By contrast, the tissues that were exposed to 50 cGy Fe showed down-regulation of IL-6 gene and up-regulation of Sod2 gene in all samples. The results for this sample indicated that long-term effects are not induced in the tissues after the exposure. Therefore, these results suggest that 50 cGy Fe ionizing radiation is too low to induce delayed or chronic effects in the tissues. The tissues that were exposed to 200 cGy Gamma radiation showed up-regulation of IL-6 and Sod2 gene, suggesting that the exposure to this radiation might have induced delayed or chronic effects in the tissues and may develop into cardiovascular diseases with time.

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