Differential Translocation of Nuclear Factor-KappaB in a Cardiac Muscle Cell Line Under Gravitational Changes

Microgravity (micro-g) environments have been shown to elicit dysregulation of specific genes in a wide assay of cell types. It is known that the activation of transcription factors and molecular signaling pathways influence various physiological outcomes associated with stress and adaptive responses. Nuclear factor-kappa B $(NF-κB)$ is one of the most prevailing oxidation-sensitive transcription factors. It is hypothesized that simulated microgravity would activate $NF-κB$ and its downstream transcriptional networks, thus suggesting a role for $NF-κB$ in microgravity induced muscle atrophy. To investigate the activation of $NF-κB$ in a rat cardiac cell line (H9c2) under micro-g, rotating wall vessel bioreactors were used to simulate micro-g conditions. Western blotting revealed that mean nuclear translocation of $NF-κB$ p65 subunit was 69% for micro-g and 46% for unit-g dynamic control as compared with a 30 min $TNF-α$ positive control $(p<0.05,n=3)$⁠. The results from western blots were confirmed by enzyme-linked immunosorbent assay, which showed 66% for micro-g and 45% for dynamic control as compared with positive control $(p<0.05,n=3)$⁠. These results show significant differential translocation of $NF-κB$ p65 under simulated micro-g. These results may be expanded upon to explain physiological changes such as muscle atrophy and further identify the regulatory pathways and effector molecules activated under exposure to micro-g.