Marcus Allan, M.Sc. Biology, 2010

Nuclear factor (NF)-kappaB regulation in the hibernating thirteen-lined ground squirrel, Spermophilus tridecemlineatus.



When environmental conditions become unfavorable, such as during winter, many small mammals are able to enter into a state of dormancy known as hibernation in order to conserve energy. Energy conservation is accomplished via a drastic decline in metabolic and physiological activity in association with a decrease in body temperature, which is periodically interspersed with brief bouts of arousal back to their euthermic values. These drastic changes in oxygen consumption and concentration, perfusion of tissues and energy consumption results in an elevated susceptibility to oxidative stress which can cause severe tissue damage. Hibernators are able to mitigate this damage using antioxidants and their associated pathways in a coordinated response. In the present study, the role of the redox sensitive transcription factor NF-κB was investigated to gain insight into its regulation during hibernation. NF-κB is an essential transcription factor which is known to regulate many targets including antioxidant, antiapoptotic/pro-survival and pro-inflammatory genes. The extent and duration of the NF-κBs response depends on its interactions with its multiple upstream effectors. During hibernation it was found that NF-κB and its signaling components have different expression patterns which are tissue dependant and change along the torpor–arousal cycle. Overall, NF-κB was found to be maximally activated during entrance into torpor, with its cytoprotective downstream genes being upregulated in time for next subsequent arousal in both liver and skeletal muscle tissue. Therefore, these results suggest that antioxidant defenses are upregulated throughout torpor-arousal and that NF-κB may help mediate such protective responses.