The Impacts of Housing Conditions on the Cardiopulmonary and Neurobehavioral Responses of Mice to High Temperature and Wildfire Smoke.

Climate change is a serious global public health concern that is associated with increased cardiovascular morbidity and mortality and adverse neurobehavioral outcomes. Moreover, it is contributing to increased wildfires, which pose a distinct threat to cardiovascular and respiratory health, especially in the presence of other stressors. Living conditions can be a significant nonchemical stressor that alters physiology and impacts wildfire smoke responsiveness, especially when combined with ambient heat. To determine the combined impact of housing and temperature on behavioral health and the cardiopulmonary response to wildfire smoke (WS), female mice were split into enriched (EH) and depleted housing (DH) at normal (NT) and high temperatures (HT) for 20 weeks and assessed at baseline and after a single filtered air (FA) or WS exposure. Separate radiotelemetered mice were similarly housed for 4 weeks and then exposed to FA sham and then WS. EH mice had higher activity and body temperature and lower heart rate at NT, and these effects were blocked at HT. HT-DH mice had an increased heart rate variability following WS and increased arrhythmias. Interestingly, HT-EH caused increased anxiety-like behavior. Thus, although EH likely protects cardiopulmonary health, it might also negatively impact the behavior at HT in mice. As such, the living temperature and housing conditions should be carefully considered when assessing susceptibility to disease and environmental exposures.