Photochemically altered air pollution mixtures and contractile parameters in isolated murine hearts before and after ischemia

Fish oil and olive oil-enriched diets alleviate acute ozone-induced cardiovascular effects in rats

Fish oil (FO) and olive oil (OO) supplementations attenuate the cardiovascular responses to inhaled concentrated ambient particles in human volunteers. This study was designed to examine the cardiovascular effects of ozone (O₃) exposure and the efficacy of FO and OO-enriched diets in attenuating the cardiovascular effects from O₃ exposure in rats. Rats were fed either a normal diet (ND), a diet enriched with 6% FO or OO starting at 4 weeks of age. Eight weeks following the start of these diet, animals were exposed to filtered air (FA) or 0.8 ppm O₃, 4 h/day for 2 consecutive days. Immediately after exposure, cardiac function was measured as the indices of left-ventricular developed pressure (LVDP) and contractility (dP/dt_max and dP/dt_min) before ischemia. In addition, selective microRNAs (miRNAs) of inflammation, endothelial function, and cardiac function were assessed in cardiac tissues to examine the molecular alterations of diets and O₃ exposure. Pre-ischemic LVDP and dP/dt_max were lower after O₃ exposure in rats fed ND but not FO and OO. Cardiac miRNAs expressions were altered by both diet and O₃ exposure. Specifically, O₃-induced up-regulation of miR-150-5p and miR-208a-5p were attenuated by FO and/or OO. miR-21 was up-regulated by both FO and OO after O₃ exposure. This study demonstrated that O₃-induced cardiovascular responses appear to be blunted by FO and OO diets. O₃-induced alterations in miRNAs linked to inflammation, cardiac function, and endothelial dysfunction support these pathways are involved, and dietary supplementation with FO or OO may alleviate these adverse cardiovascular effects in rats.

Cardiovascular effects of diesel exhaust inhalation: photochemically altered versus freshly emitted in mice

This study was designed to compare the cardiovascular effects of inhaled photochemically altered diesel exhaust (aged DE) to freshly emitted DE (fresh DE) in female C57Bl/6 mice. Mice were exposed to either fresh DE, aged DE, or filtered air (FA) for 4 hr using an environmental irradiation chamber. Cardiac responses were assessed 8 hr after exposure utilizing Langendorff preparation with a protocol consisting of 20 min of perfusion and 20 min of ischemia followed by 2 hr of reperfusion. Cardiac function was measured by indices of left-ventricular-developed pressure (LVDP) and contractility (dP/dt) prior to ischemia. Recovery of post-ischemic LVDP was examined on reperfusion following ischemia. Fresh DE contained 460 µg/m³ of particulate matter (PM), 0.29 ppm of nitrogen dioxide (NO₂) and no ozone (O₃), while aged DE consisted of 330 µg/m³ of PM, 0.23 ppm O₃ and no NO₂. Fresh DE significantly decreased LVDP, dP/dt_max, and dP/dt_min compared to FA. Aged DE also significantly reduced LVDP and dP/dt_max. Data demonstrated that acute inhalation to either fresh or aged DE lowered LVDP and dP/dt, with a greater fall noted with fresh DE, suggesting that the composition of DE may play a key role in DE-induced adverse cardiovascular effects in female C57Bl/6 mice.

Inhalation of Simulated Smog Atmospheres Affects Cardiac Function in Mice

The health effects of individual criteria air pollutants have been well investigated. However, little is known about the health effects of air pollutant mixtures that more realistically represent environmental exposures. The present study was designed to evaluate the cardiac effects of inhaled simulated smog atmospheres (SA) generated from the photochemistry of either gasoline and isoprene (SA-G) or isoprene (SA-Is) in mice. Four-month-old female mice were exposed for 4 h to filtered air (FA), SA-G, or SA-Is. Immediately and 20 h after exposure, cardiac responses were assessed with a Langendorff preparation using a protocol consisting of 20 min of global ischemia followed by 2 h of reperfusion. Cardiac function was measured by index of left-ventricular developed pressure (LVDP) and cardiac contractility (dP/dt) before ischemia. Pre-ischemic LVDP was lower in mice immediately after SA-Is exposure (52.2 ± 5.7 cm H₂O compared to 83.9 ± 7.4 cm H₂O after FA exposure; p = 0.008) and 20 h after SA-G exposure (54.0 ± 12.7 cm H₂O compared to 79.3 ± 7.4 cm H₂O after FA exposure; p = 0.047). Pre-ischemic left ventricular contraction dP/dt_max was lower in mice immediately after SA-Is exposure (2025 ± 169 cm H₂O/sec compared to 3044 ± 219 cm H₂O/sec after FA exposure; p < 0.05) and 20 h after SA-G exposure (1864 ± 328 cm H₂O/sec compared to 2650 ± 258 cm H₂O/sec after FA exposure; p = 0.05). In addition, SA-G reduced the coronary artery flow rate 20 h after exposure compared to the FA control. This study demonstrates that acute SA-G and SA-Is exposures decrease LVDP and cardiac contractility in mice, indicating that photochemically-altered atmospheres affect the cardiovascular system.

Assessment of biological responses of EpiAirway 3-D cell constructs versus A549 cells for determining toxicity of ambient air pollution

CONTEXT

EpiAirway™ 3-D constructs are human-derived cell cultures of differentiated airway epithelial cells that may represent a more biologically relevant model of the human lung. However, limited information is available on their utility for exposures to air pollutants at the air-liquid interface (ALI).

OBJECTIVE

To assess the biological responses of EpiAirway™ cells in comparison to the responses of A549 human alveolar epithelial cells after exposure to air pollutants at ALI.

METHODS

Cells were exposed to filtered air, 400 ppb of ozone (O3) or a photochemically aged Synthetic Urban Mixture (SynUrb54) consisting of hydrocarbons, nitrogen oxides, O3 and other secondary oxidation products for 4 h. Basolateral supernatants and apical washes were collected at 9 and 24 h post-exposure. We assessed cytotoxicity by measuring lactate dehydrogenase (LDH) release into the culture medium and apical surface. Interleukin 6 (IL-6) and interleukin 8 (IL-8) proteins were measured in the culture medium and in the apical washes to determine the inflammatory response after exposure.

RESULTS

Both O3 and SynUrb54 significantly increased basolateral levels of LDH and IL-8 in A549 cells. No significant changes in LDH and IL-8 levels were observed in the EpiAirway™ cells, however, IL-6 in the apical surface was significantly elevated at 24 h after O3 exposure.

CONCLUSION

LDH and IL-8 are robust endpoints for assessing toxicity in A549 cells. The EpiAirway™ cells show minimal adverse effects after exposure suggesting that they are more toxicologically resistant compared to A549 cells. Higher concentrations or longer exposure times are needed to induce effects on EpiAirway™ cells.

Ozone co-exposure modifies cardiac responses to fine and ultrafine ambient particulate matter in mice: concordance of electrocardiogram and mechanical responses

Background

Studies have shown a relationship between air pollution and increased risk of cardiovascular morbidity and mortality. Due to the complexity of ambient air pollution composition, recent studies have examined the effects of co-exposure, particularly particulate matter (PM) and gas, to determine whether pollutant interactions alter (e.g. synergistically, antagonistically) the health response. This study examines the independent effects of fine (FCAPs) and ultrafine (UFCAPs) concentrated ambient particles on cardiac function, and determine the impact of ozone (O₃) co-exposure on the response. We hypothesized that UFCAPs would cause greater decrement in mechanical function and electrical dysfunction than FCAPs, and that O₃ co-exposure would enhance the effects of both particle-types.

Methods

Conscious/unrestrained radiotelemetered mice were exposed once whole-body to either 190 μg/m³ FCAPs or 140 μg/m³ UFCAPs with/without 0.3 ppm O₃; separate groups were exposed to either filtered air (FA) or O₃ alone. Heart rate (HR) and electrocardiogram (ECG) were recorded continuously before, during and after exposure, and cardiac mechanical function was assessed using a Langendorff perfusion preparation 24 hrs post-exposure.

Results

FCAPs alone caused a significant decrease in baseline left ventricular developed pressure (LVDP) and contractility, whereas UFCAPs did not; neither FCAPs nor UFCAPs alone caused any ECG changes. O₃ co-exposure with FCAPs caused a significant decrease in heart rate variability when compared to FA but also blocked the decrement in cardiac function. On the other hand, O₃ co-exposure with UFCAPs significantly increased QRS-interval, QTc and non-conducted P-wave arrhythmias, and decreased LVDP, rate of contractility and relaxation when compared to controls.

Conclusions

These data suggest that particle size and gaseous interactions may play a role in cardiac function decrements one day after exposure. Although FCAPs + O₃ only altered autonomic balance, UFCAPs + O₃ appeared to be more serious by increasing cardiac arrhythmias and causing mechanical decrements. As such, O₃ appears to interact differently with FCAPs and UFCAPs, resulting in varied cardiac changes, which suggests that the cardiovascular effects of particle-gas co-exposures are not simply additive or even generalizable. Additionally, the mode of toxicity underlying this effect may be subtle given none of the exposures described here impaired post-ischemia recovery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0054-4) contains supplementary material, which is available to authorized users.