Cellular Redox Status of Dermal fibroblasts as a Model to Explore Hypoxia Responses Across Diverse Mammals

Abstract

Specializations in energy production pathways can define phenotype in mammals, enabling resilience to environmental stressors and survival in extreme habitats. Most mammals rely on oxygen-based mitochondrial respiration to sustain high rates of ATP production necessary for homeothermy; oxidative phosphorylation is fueled by donation of reducing equivalents (NADH, FADH2) to the electron transport chain. As such, relative redox levels within the cell (NAD+/NADH ratio) indicate cell health and metabolic status. In hypoxic conditions, cells can experience reductive stress, evidenced by a buildup of NADH and altered NAD+/NADH ratio. We are using primary dermal fibroblasts isolated from skin biopsies in n=9 species to compare metabolic changes via the ratio between NAD+ and NADH when exposed to 0.5% O2 for 6-h and 24-h. Species were selected to encompass diverse phylogeny as well as to include species that are adapted to low oxygen environments (high altitude gelada baboons, diving humpback whales and Weddell seals). Control species without adaptation to hypoxic environments included human, dromedary camel, little brown bat, honey badger, and rhinoceros. We expect fibroblasts from species adapted to living with variable oxygen availability to have more stability in NAD+/ NADH ratios when exposed to hypoxia in cell culture compared to those from species that are not adapted to low oxygen environments. We quantified NAD+ and NADH following exposure to hypoxia as well as control normoxic samples. Preliminary data with n=3 biological replicates per species show that fibroblasts from the control animals display significant differences in NAD+/NADH ratio between normoxic and hypoxic treatments (Kruskal-Wallis test, p=0.01), however, there are no significant differences in the ratios presented for tolerant animals (Kruskal-Wallis test, p=0.518). This finding supports our hypothesis that animals adapted to low oxygen reduce variability in the NAD+/NADH ratios. Understanding the metabolic patterns when cells are exposed to reduced oxygen levels can provide a framework for estimating a species resilience to environmental variation. Funded by NSF #2022046, CSUN-OUR Summer Undergraduate Fellowship. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.