Exposure to Intermittent Noise Exacerbates the Cardiovascular Response of Wistar-Kyoto Rats to Ozone Inhalation and Arrhythmogenic Challenge

The effect of enriched versus depleted housing on eucalyptus smoke-induced cardiovascular dysfunction in mice

Objectives: Living conditions play a major role in health and well-being, particularly for the cardiovascular and pulmonary systems. Depleted housing contributes to impairment and development of disease, but how it impacts body resiliency during exposure to environmental stressors is unknown. This study examined the effect of depleted (DH) versus enriched housing (EH) on cardiopulmonary function and subsequent responses to wildfire smoke. Materials and Methods: Two cohorts of healthy female mice, one of them surgically implanted with radiotelemeters for the measurement of electrocardiogram, body temperature (Tco) and activity, were housed in either DH or EH for 7 weeks. Telemetered mice were exposed for 1 h to filtered air (FA) and then flaming eucalyptus wildfire smoke (WS) while untelemetered mice, which were used for ventilatory assessment and tissue collection, were exposed to either FA or WS. Animals were continuously monitored for 5-7 days after exposure. Results: EH prevented a decrease in Tco after radiotelemetry surgery. EH mice also had significantly higher activity levels and lower heart rate during and after FA and WS. Moreover, EH caused a decreased number of cardiac arrhythmias during WS. WS caused ventilatory depression in DH mice but not EH mice. Housing enrichment also upregulated the expression of cardioprotective genes in the heart. Conclusions: The results of this study indicate that housing conditions impact overall health and cardiopulmonary function. More importantly, depleted housing appears to worsen the response to air pollution. Thus, non-chemical factors should be considered when assessing the susceptibility of populations, especially when it comes to extreme environmental events.

Heart rate variability in male rats

The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on myocardial activity. Heart rate variability (HRV) is a readily available metric used to assess heart rate control by the autonomic nervous system. HRV can provide information about neural (parasympathetic, sympathetic, reflex) and humoral (hormones, thermoregulation) control of myocardial activity. Because there are no relevant reference values for HRV parameters in rats in the scientific literature, all experimental results are only interpreted on the basis of changes from currently measured control or baseline HRV values, which are, however, significantly different in individual studies. Considering the significant variability of published HRV data, the present study focused primarily on comparing control or baseline HRV values under different conditions in in vivo experiments involving rats. The aim of the study was therefore to assess whether there are differences in the starting values before the experiment itself.

Mixture Math: Deciding What to Add in a Cumulative Risk Assessment

Component-based approaches for cumulative risk assessment provide an important tool for informing public health policy. While current quantitative cumulative risk assessments focus narrowly on pesticides that share a mechanism of action, growing scientific evidence supports expansion of their application to encompass stressors that target a common disease. Case studies have demonstrated dose additive effects of chemicals with different mechanisms of action on liver steatosis, craniofacial malformations, and male reproductive tract developmental disruption. Evidence also suggests that nonchemical stressors such as noise or psychosocial stress can modify effects of chemicals. Focused research attention is required before nonchemical stressors can routinely be included in quantitative cumulative risk assessments.

Noise exposure and its relationship with postinfarction cardiac remodeling: implications for NLRP3 inflammasome activation

In recent years, high-decibel noise has emerged as a causative risk factor for ischemic heart disease. Massive noise overdose is associated with increased endocrine, neural, and immune stress responses. The NLRP3 (nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing 3) inflammasome, the most characterized supramolecular complex and a potent mediator of inflammatory signaling, has been reported to be a marker of increased ischemic heart disease vulnerability. Our study evaluated the association of noise exposure with postinfarction cardiac remodeling and its effect on NLRP3 inflammasome activation. Rats were exposed to a noisy environment (14 days, 24 h/per day, 70 ± 5 dB), and speck formation by the NLRP3 inflammasome scaffold protein ASC (apoptosis-associated speck-like protein) was assessed by confocal immunofluorescence. Echocardiography, pathological analysis, and in vivo electrophysiology were performed. Our results revealed the improved postinfarction cardiac function, mitigated fibrosis, and decreased arrhythmia vulnerability and sympathetic sprouting in low-environment noise groups. Moreover, western blotting of NLRP3, caspase-1, ASC, IL-1β, and IL-18 and confocal microscopy of ASC speck showed that the priming and activation of NLRP3 inflammasome were higher in the NE group than in the NI group. In conclusion, our findings reveal a previously unidentified association between NLRP3 inflammasome activation and noise exposure, underscoring the significance of effective noise prevention in improving postinfarction prognosis.