Peroxide Treatment Induces Upregulated Apoptosis in the Ames Dwarf Mouse





M.A. Kennedy, S.G. Rakoczy, H.M. Brown-Borg

University of North Dakota School of Medicine and Health Sciences, Department of Pharmacology, Physiology, and Therapeutics, 501 North Columbia Road, Grand Forks, North Dakota 58203



The Ames dwarf mouse is a mammalian model of extended life span, living 50-64% longer than its wild-type siblings. These mice exhibit upregulated antioxidant defenses and lower oxidative DNA and protein damage when compared to age-matched wild-type littermates. The objectives of this study were to compare basal levels of apoptosis-related proteins in several tissues from dwarf and wild-type mice, and to compare the in vitro responses of primary hepatocytes from dwarf and wild-type mice to oxidative stress within culture. Western blotting was performed to compare basal protein levels in various tissues from dwarf and wild-type mice at 3, 6, 12, and 24 months of age. In addition, hepatocytes from 6-month old dwarf and wild-type mice were isolated using collagenase perfusion and cultured in serum-free media. These cells were treated with hydrogen peroxide for 30 minutes, and were evaluated for MTT conversion to formazan, DNA laddering, caspase-3 activity, procaspase-3 protein levels, and morphological structural changes. When protein levels were compared in dwarf and wild-type tissues using Western blotting, higher procaspase-3 protein levels (p< .05) were observed in dwarf kidney and liver tissues at multiple ages, while young wild-type kidney tissues showed higher levels (p< .05) of Bcl-2 protein. In suspension culture, peroxide-treated dwarf hepatocytes showed lower viability (p< .03) and higher caspase-3 activity induction when compared to peroxide-treated wild-type cells. This suggests that when faced with an oxidative challenge, Ames dwarf mice may more readily undergo apoptosis than wild-type mice. This may give an advantage to these dwarf mice by allowing them to more efficiently eliminate damaged cells, which may contribute to their longer lives.




Key words: Apoptosis, Hepatocytes, Ames Dwarf Mouse







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