Depleted living conditions and high ambient temperatures worsen cardiac arrhythmias and autonomic dysregulation in C57BL/6 mice
Citation:
Fiamingo, M., W. Oshiro, A. Farraj, AND M. Hazari. Depleted living conditions and high ambient temperatures worsen cardiac arrhythmias and autonomic dysregulation in C57BL/6 mice. Society of Toxicology, Salt Lake City, UT, March 24 - 28, 2024.
Impact/Purpose:
These data demonstrate that depleted living conditions and high temperature alter cardiovascular physiology and worsen arrhythmogenesis. The results suggest that remediation and mitigation strategies can be focused on these factors to improve resiliency.
Description:
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. Climate change is also causing an increased incidence and intensity of extreme heat events, or heat waves, which are associated with increased cardiovascular morbidity and mortality. As such, it is imperative to characterize the cardiovascular and autonomic response to such events to address this growing public health concern. 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, as well as provide novel data on the response to a series of acute extreme heat exposures (EHE) that mimic the heat waves that are commonly being experienced today. Using surgically-implanted biopotential radiotelemeters that provide continuous measurement of heart rate (HR), heart rate variability (HRV), the incidence of arrhythmias, and echocardiography, mice were examined for six weeks and during EHE. Animals living in depleted housing had an increased incidence of arrhythmias, specifically non-conducted p-waves, which are an atrioventricular block of cardiac electrical conduction, compared to mice living in enriched housing. Further, depleted housing combined with increased ambient temperature caused an increase in the incidence of ventricular premature beats during a subsequent flaming eucalyptus wildfire smoke exposure. These mice had a significant decrease in HRV, indicating an increased sympathetic response to the exposure, which was followed by parasympathetic rebound. Lastly, an increased number of arrhythmias was observed in depleted housing mice exposed to EHE and challenged with dobutamine, a sympathomimetic drug to simulate exercise-like stress, compared to enriched housing mice. Importantly, autonomic dysregulation appears to underlie changes in high-frequency echocardiography endpoints, whole-body plethysmography, and behavior. Hence, our findings show that these daily stressors can cause long-lasting autonomic dysregulation and ultimately alter body resiliency against chemical and non-chemical stressors, suggesting that these daily stressors pose an increased risk to health and toxicological insults.