Depleted living conditions and high ambient temperatures worsen cardiovascular and autonomic dysregulation in C57BL/6 mice
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Background and Purpose: The American Heart Association released a scientific statement describing the importance of housing on cardiovascular health and emphasized the impact of the broader physical and social environment. Increased ambient temperature due to climate change and lack of environmental enrichment (e.g. inaccessibility to greenspace) represent two of the most pressing issues facing certain populations in the United States. Thus, this presentation will describe the impact of housing conditions (i.e. depleted/increased psychosocial stress vs. enriched) on cardiovascular function in C57BL/6 mice, both in normal and high ambient living temperatures.
Methods: Female C57BL/6J mice were surgically implanted with biopotential radiotelemeters that provide continuous physiological measurements, including heart rate, electrocardiogram, body temperature, and activity levels. The mice were then randomly placed into either a high temperature (31°C, HT) or normal temperature (22°C, NT) room, and then further split into either enriched (EH) or depleted housing (DH) for 5 weeks. They were then exposed to a 1-hour filtered air (FA) sham and a 1-hour flaming eucalyptus wildfire smoke (WS) exposure.
Results: Mice living in DH had an increased number of arrhythmias, and combined with HT portrayed an increase in the incidence of ventricular premature beats during the WS exposure. These mice also exhibited signs of an increased sympathetic response to the exposure, which was followed by parasympathetic rebound 1-wk later. Moreover, in NT living conditions, housing modulates core body temperature and activity, wherein DH decreases both parameters. These effects are minimized in HT living conditions. However, during the WS exposure, HT mice experience a more pronounced hypothermic response to the exposure.
Conclusions: Depleted housing alters baseline cardiovascular and physiological parameters and further alters physiological resiliency to a single WS exposure. Further, a combination of DH and HT alters the cardiovascular, autonomic, and thermoregulatory response to WS, ultimately indicating a heightened vulnerability to the exposure. Hence, our findings show that these daily stressors (housing, heat, etc.) potentially cause long-lasting autonomic dysregulation and ultimately alter body resiliency against chemical and non-chemical stressors. (This abstract does not reflect EPA policy.)