Increased ambient temperature and housing conditions alter the behavioral and cardiovascular response of C57/BL6 mice following a single eucalyptus wildfire smoke exposure
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Extrinsic factors of urban living are increasingly being recognized as variables that affect the toxicological response. These factors, such as accessibility to green space and increased ambient temperature, have been correlated with various adverse health outcomes due to psychosocial/ physiological stress, specifically anxiety and cardiovascular morbidities. Moreover, those living in an urban environment are consistently exposed to air pollution, underscoring the need to elucidate the synergistic effects of climate change and psychosocial stress on the effects of air pollution. This study was conducted to evaluate the impact of increased living temperature and psychosocial stress on the cardiovascular response to a single eucalyptus wildfire smoke (WS) exposure. C57/BL6 mice were separated into either enriched or depleted housing environment at either 22 (NT) or 31°C (HT) for 22 weeks. During this time, whole body plethysmography, high-frequency echocardiography, and behavioral testing was conducted. A cohort of mice with implanted radiotelemeters were separated into the same temperature and housing paradigm for 6 weeks, providing continuous electrocardiogram, core body temperature and activity data. Animals were exposed to either filtered air or 3mg/m3 WS for one hour. HT caused increased levels of anxiety shown by significant changes in open field testing, significant increases in left ventricle mass, and significant changes in expiratory time (Te), relaxation time (RT), and end expiratory pause (EEP) after WS exposure, including significantly higher RR-I values before and after WS. Further, enriched housing ameliorated the increased heart rate and RR-I values, as well as the anxiety-prone behaviors. These results indicate that higher ambient temperatures may also affect human health through changes in autonomic function and cardiovascular physiology, suggesting environmental enrichment (i.e., greenspace) should be evaluated as future mitigation strategies to create more resilient populations towards climate change and WS exposure. (This abstract does not reflect EPA policy)