Associations between prenatal and early-life air pollution exposure and lung function in young children: Exploring influential windows of exposure on lung development.

BACKGROUND: Evidence in the literature suggests that air pollution exposures experienced prenatally and early in life can be detrimental to normal lung development, however the specific timing of critical windows during development is not fully understood. OBJECTIVES: We evaluated air pollution exposures during the prenatal and early-life period in association with lung function at ages 6-9, in an effort to identify potentially influential windows of exposure for lung development. METHODS: Our study population consisted of 222 children aged 6-9 from the Fresno-Clovis metro area in California with spirometry data collected between May 2015 and May 2017. We used distributed-lag non-linear models to flexibly model the exposure-lag-response for monthly average exposure to fine particulate matter (PM2.5) and ozone (O3) during the prenatal months and first three years of life in association with forced vital capacity (FVC), and forced expiratory volume in the first second (FEV1), adjusted for covariates. RESULTS: PM2.5 exposure during the prenatal period and the first 3-years of life was associated with lower FVC and FEV1 assessed at ages 6-9. Specifically, an increase from the 5th percentile of the observed monthly average exposure (7.55 µg/m3) to the median observed exposure (12.69 µg/m3) for the duration of the window was associated with 0.42 L lower FVC (95% confidence interval (CI): -0.82, -0.03) and 0.38 L lower FEV1 (95% CI: -0.75, -0.02). The shape of the lag-response indicated that the second half of pregnancy may be a particularly influential window of exposure. Associations for ozone were not as strong and typically CIs included the null. CONCLUSIONS: Our findings indicate that prenatal and early-life exposures to PM2.5 are associated with decreased lung function later in childhood. Exposures during the latter months of pregnancy may be especially influential.

Increases in ambient air pollutants during pregnancy are linked to increases in methylation of IL4, IL10, and IFNγ.

BACKGROUND: Ambient air pollutant (AAP) exposure is associated with adverse pregnancy outcomes, such as preeclampsia, preterm labor, and low birth weight. Previous studies have shown methylation of immune genes associate with exposure to air pollutants in pregnant women, but the cell-mediated response in the context of typical pregnancy cell alterations has not been investigated. Pregnancy causes attenuation in cell-mediated immunity with alterations in the Th1/Th2/Th17/Treg environment, contributing to maternal susceptibility. We recruited women (n = 186) who were 20 weeks pregnant from Fresno, CA, an area with chronically elevated AAP levels. Associations of average pollution concentration estimates for 1 week, 1 month, 3 months, and 6 months prior to blood draw were associated with Th cell subset (Th1, Th2, Th17, and Treg) percentages and methylation of CpG sites (IL4, IL10, IFNγ, and FoxP3). Linear regression models were adjusted for weight, age, season, race, and asthma, using a Q value as the false-discovery-rate-adjusted p-value across all genes. RESULTS: Short-term and mid-term AAP exposures to fine particulate matter (PM2.5), nitrogen dioxide (NO2) carbon monoxide (CO), and polycyclic aromatic hydrocarbons (PAH456) were associated with percentages of immune cells. A decrease in Th1 cell percentage was negatively associated with PM2.5 (1 mo/3 mo: Q < 0.05), NO2 (1 mo/3 mo/6 mo: Q < 0.05), and PAH456 (1 week/1 mo/3 mo: Q < 0.05). Th2 cell percentages were negatively associated with PM2.5 (1 week/1 mo/3 mo/6 mo: Q < 0.06), and NO2 (1 week/1 mo/3 mo/6 mo: Q < 0.06). Th17 cell percentage was negatively associated with NO2 (3 mo/6 mo: Q < 0.01), CO (1 week/1 mo: Q < 0.1), PM2.5 (3 mo/6 mo: Q < 0.05), and PAH456 (1 mo/3 mo/6 mo: Q < 0.08). Methylation of the IL10 gene was positively associated with CO (1 week/1 mo/3 mo: Q < 0.01), NO2 (1 mo/3 mo/6 mo: Q < 0.08), PAH456 (1 week/1 mo/3 mo: Q < 0.01), and PM2.5 (3 mo: Q = 0.06) while IL4 gene methylation was positively associated with concentrations of CO (1 week/1 mo/3 mo/6 mo: Q < 0.09). Also, IFNγ gene methylation was positively associated with CO (1 week/1 mo/3 mo: Q < 0.05) and PAH456 (1 week/1 mo/3 mo: Q < 0.06). CONCLUSION: Exposure to several AAPs was negatively associated with T-helper subsets involved in pro-inflammatory and anti-inflammatory responses during pregnancy. Methylation of IL4, IL10, and IFNγ genes with pollution exposure confirms previous research. These results offer insights into the detrimental effects of air pollution during pregnancy, the demand for more epigenetic studies, and mitigation strategies to decrease pollution exposure during pregnancy.

Traffic-related air pollution, biomarkers of metabolic dysfunction, oxidative stress, and CC16 in children.

BACKGROUND: Previous research has revealed links between air pollution exposure and metabolic syndrome in adults; however, these associations are less explored in children. OBJECTIVE: This study aims to investigate the association between traffic-related air pollutants (TRAP) and biomarkers of metabolic dysregulation, oxidative stress, and lung epithelial damage in children. METHODS: We conducted cross-sectional analyses in a sample of predominantly Latinx, low-income children (n = 218) to examine associations between air pollutants (nitrogen dioxide (NO2), nitrogen oxides (NOx), elemental carbon, polycyclic aromatic hydrocarbons, carbon monoxide (CO), fine particulates (PM2.5)) and biomarkers of metabolic function (high-density lipoprotein (HDL), hemoglobin A1c (HbA1c), oxidative stress (8-isoprostane), and lung epithelial damage (club cell protein 16 (CC16)). RESULTS: HDL cholesterol showed an inverse association with NO2 and NOx, with the strongest relationship between HDL and 3-month exposure to NO2 (-15.4 mg/dL per IQR increase in 3-month NO2, 95% CI = -27.4, -3.4). 8-isoprostane showed a consistent pattern of increasing values with 1-day and 1-week exposure across all pollutants. Non-significant increases in % HbA1c were found during 1-month time frames and decreasing CC16 in 3-month exposure time frames. CONCLUSION: Our results suggest that TRAP is significantly associated with decreased HDL cholesterol in longer-term time frames and elevated 8-isoprostane in shorter-term time frames. TRAP could have the potential to influence lifelong metabolic patterns, through metabolic effects in childhood.

Traffic-related air pollution is associated with glucose dysregulation, blood pressure, and oxidative stress in children.

BACKGROUND: Metabolic syndrome increases the risk of cardiovascular disease in adults. Antecedents likely begin in childhood and whether childhood exposure to air pollution plays a contributory role is not well understood. OBJECTIVES: To assess whether children's exposure to air pollution is associated with markers of risk for metabolic syndrome and oxidative stress, a hypothesized mediator of air pollution-related health effects. METHODS: We studied 299 children (ages 6-8) living in the Fresno, CA area. At a study center visit, questionnaire and biomarker data were collected. Outcomes included hemoglobin A1c (HbA1c), urinary 8-isoprostane, systolic blood pressure (SBP), and BMI. Individual-level exposure estimates for a set of four pollutants that are constituents of traffic-related air pollution (TRAP) - the sum of 4-, 5-, and 6-ring polycyclic aromatic hydrocarbon compounds (PAH456), NO2, elemental carbon, and fine particulate matter (PM2.5) - were modeled at the primary residential location for 1-day lag, and 1-week, 1-month, 3-month, 6-month, and 1-year averages prior to each participant's visit date. Generalized additive models were used to estimate associations between each air pollutant exposure and outcome. RESULTS: The study population was 53% male, 80% Latinx, 11% Black and largely low-income (6% were White and 3% were Asian/Pacific Islander). HbA1c percentage was associated with longer-term increases in TRAP; for example a 4.42 ng/m3 increase in 6-month average PAH456 was associated with a 0.07% increase (95% CI: 0.01, 0.14) and a 3.62 µg/m3 increase in 6-month average PM2.5 was associated with a 0.06% increase (95% CI: 0.01, 0.10). The influence of air pollutants on blood pressure was strongest at 3 months; for example, a 6.2 ppb increase in 3-month average NO2 was associated with a 9.4 mmHg increase in SBP (95% CI: 2.8, 15.9). TRAP concentrations were not significantly associated with anthropometric or adipokine measures. Short-term TRAP exposure averages were significantly associated with creatinine-adjusted urinary 8-isoprostane. DISCUSSION: Our results suggest that both short- and longer-term estimated individual-level outdoor residential exposures to several traffic-related air pollutants, including ambient PAHs, are associated with biomarkers of risk for metabolic syndrome and oxidative stress in children.

In vitro and in vivo toxicity of urban and rural particulate matter from California.

Particulate matter (PM) varies in chemical composition and mass concentration based on location, source, and particle size. This study sought to evaluate the in vitro and in vivo toxicity of coarse (PM10-2.5) and fine (PM25) PM samples collected at 5 diverse sites within California. Coarse and fine PM samples were collected simultaneously at 2 rural and 3 urban sites within California during the summer. A human pulmonary microvascular endothelial cell line (HPMEC-ST1.6R) was exposed to PM suspensions (50 µg/mL) and analyzed for reactive oxygen species (ROS) after 5 hours of treatment. In addition, FVB/N mice were exposed by oropharyngeal aspiration to 50 µg PM, and lavage fluid was collected 24 hrs post-exposure and analyzed for total protein and %PMNs. Correlations between trace metal concentrations, endotoxin, and biological endpoints were calculated, and the effect of particle size range, locale (urban vs. rural), and location was determined. Absolute principal factor analysis was used to identify pollution sources of PM from elemental tracers of those sources. Ambient PM elicited an ROS and pro-inflammatory-related response in the cell and mouse models, respectively. These responses were dependent on particle size, locale, and location. Trace elements associated with soil and traffic markers were most strongly linked to the adverse effects in vitro and in vivo. Particle size, location, source, and composition of PM collected at 5 locations in California affected the ROS response in human pulmonary endothelial cells and the inflammatory response in mice.

The synergetic effect of ambient PM2.5 exposure and rhinovirus infection in airway dysfunction in asthma: a pilot observational study from the Central Valley of California.

BACKGROUND: Elevated levels of particulate matter PM2.5 and rhinovirus infection have been known to exacerbate asthma. However, the combined effect of rhinovirus infection and high PM2.5 has not been investigated. PURPOSE: To investigate the effect of PM2.5 and concomitant rhinovirus infection on airway function in asthma in an area with high PM2.5 concentration. METHODS: Asthmatics and their matched controls were monitored for lung function, exhaled nitric oxide (eNO) and respiratory symptoms on days with varying levels of PM2.5. As the study was a repeated measure design, repeated clinical findings, and laboratory data were used in the mixed model analysis. RESULTS: Wheezing and dyspnea in asthmatics were worsened with increasing ambient PM2.5. Increasing PM2.5 decreased FEV1% predicted (-0.51, -0.79 to -0.23) and FEF25-75% predicted (-0.66, -1.07 to -0.24) in subjects with asthma (all P < .01). Rhino viral infection reduced FEF25-75% predicted in subjects with asthma (-11.7, -20 to -2.9). The reductions in FEV25-75 and FEV1 per 10 µg/m(3) increase in ambient PM2.5 were 6% and 5% respectively. A significant interaction was observed between presence of rhinovirus infection and elevated PM2.5 in asthmatics causing a 4-fold decrease in FEF25-75 (P = .01) and a 2-fold decrease in FEV1% predicted values (P = .01) compared with asthmatics with no rhino viral infection. CONCLUSIONS: Increasing ambient PM2.5 and low temperature independently worsened airway function in asthma. The interaction between rhinovirus and PM2.5 significantly impairs airway function in asthma. A larger sample size study is suggested to investigate these observations.

Lung volume abnormalities and its correlation to spirometric and demographic variables in adult asthma.

BACKGROUND: Presence of airflow obstruction in asthma has been based on a fixed FEV1(forced expiratory volume at 1 second)/FVC (forced vital capacity) ratio abnormality. The accuracy of FEV1/FVC ratio in diagnosing airflow obstruction remains controversial. Lung volume abnormalities have been observed in severe asthma. We utilized simultaneously measured spirometry and lung volume to determine the utility of residual volume (RV)/total lung capacity (TLC) ratio in diagnosing airflow obstruction and to identify predictors of abnormal RV in asthmatic subjects. METHODS: Data from physician-diagnosed asthmatics referred for lung function tests were collected retrospectively. Patient demographics and lung function data were analyzed using general linear modeling. RESULTS: Of the 321 subjects, 221 were female (69%). The ethnicity was Caucasian in 157 (49%), Hispanic in 131 (41%), and African-American in 33 (10%). The percentage of subjects with FEV(1)/FVC ratio <70%, FEV(1)-predicted <80%, and FEF25-75% <65% were 25%, 25%, and 38%, respectively. Fifty-two and fifty-seven percent of the patients had abnormal residual volume and abnormal RV/TLC ratio, respectively. A significant bronchodilator response was observed in 32% of the patients. A positive correlation was observed between RV to age (r = 0.4) and height (r = 0.3). A negative correlation was observed between RV to FEF25-75% (r = 0.5) and body weight (r = 0.07). There was no significant correlation between FEV1 reversibility and residual volume (r = 0.1). RV correlated significantly better with FEF25-75% (r(2) = 0.25) than FEV(1) (r(2) = 0.16). CONCLUSION: A significant proportion of asthmatic patients have elevated residual volume and abnormal RV/TLC ratio in the presence of normal FEV1/FVC ratio and absence of significant bronchodilator response. The clinical significance of these findings in asthma needs further prospective study.

Accelerated wound closure in a diabetic mouse model after exposure to phenanthrenequinone.

BACKGROUND: Reactive oxygen species (ROS) have been shown to be important in wound healing by promoting angiogenesis (also mentioned by Ushio-Fukai and Nakamura). Likewise ROS have been implicated by toxicological studies as a primary mechanism of air pollution-associated morbidity. We sought to determine how exposure to a reactive diesel exhaust chemical (phenanthrenequinone [PQ]), which promotes formation of ROS and is considered an air pollutant, would affect wound healing. Since wound healing is compromised in diabetic (db) individuals, we examined the effects of PQ on wound healing in a db mouse model. METHODS: db mice consumed PQ-containing chow for a short period (2 weeks) before wounding and through generations. Wound closure rates and wound vascularization were evaluated 10 days after wounding. The effects of PQ on endothelial cell proliferation and ROS generation in vitro were also measured. RESULTS: db mice exposed to short-term PQ and PQ-exposed first-generation db mice demonstrated the highest closure rates, significantly better than control db mice (P < 0.05). Furthermore, a higher concentration of PQ in sera of db mice coincides with the higher rate of closure. PQ was also shown to produce ROS in cell culture and stimulate endothelial cell proliferation at nanomolar concentrations. Second- and third-generation db mice exposed to PQ did not show improved wound healing. CONCLUSIONS: This study suggests that the free radical-generating air pollutant PQ enhances wound closure in the db mouse model possibly by stimulating angiogenesis, as suggested by in vitro results. We speculate that PQ may increase oxidation levels systemically and therefore help modulate inflammation at the wound site. Alternatively, antioxidant mechanisms recruited for wound healing may interfere with PQ metabolism and elimination as it accumulates in sera. Generational resistance to improve wound healing in PQ-exposed db mice could also be due to disturbances in metabolism caused by continuous exposure. In either case, these results introduce a new perspective on the effects of air pollution on wound healing.

Method development for the measurement of quinone levels in urine.

A method was developed for the quantification of 1-4 ring quinones in urine samples using liquid-liquid extraction followed by analysis with gas chromatography-mass spectrometry. Detection limits for the ten quinones analyzed are in the range 1-2 nmol dm(-3). The potential use of this approach to monitor urinary quinone levels was then evaluated in urine samples from both Sprague-Dawley rats and human subjects. Rats were exposed to 9,10-phenanthraquinone (PQ) by both injection and ingestion (mixed with solid food and dissolved in drinking water). Urinary levels of PQ were found to increase by up to a factor of ten compared to control samples, and the levels were found to depend on both the dose and duration of exposure. Samples were also collected and analyzed periodically from human subjects over the course of six months. Eight quinones were detected in the samples, with levels varying from below the detection limit up to 3 µmol dm(-3).

Effects of collagen nerve guide on neuroma formation and neuropathic pain in a rat model.

BACKGROUND: Posttraumatic neuroma formation is a major cause of neuropathic pain that can occur after elective surgery, amputation, or trauma. This study examined the use of biosynthetic collagen nerve guides to prevent the development of posttraumatic neuromas. METHODS: Collagen nerve guides were applied after neurectomy in a rat sciatic nerve model in an effort to stimulate linear neuronal outgrowth and reduce random axon sprouting. Animals were monitored for evidence of neuropathic pain--autotomy scores were recorded for 8 weeks posttransection--after which proximal stumps were excised and processed for histologic analyses. RESULTS: Moderate to severe autotomy was observed in 88% (7 of 8) of the control (neurectomy) animals. In contrast, 13% (1 of 8) of animals receiving collagen nerve guides developed autotomy, which was significantly less than controls (P < .01). Qualitative analyses of neurofilament and Schwann cell-labeled nerve sections showed a significant enhancement in Schwann cell migration away from the proximal stump and advanced linear axonal regrowth in the collagen nerve guide-treated animals. CONCLUSIONS: Collagen nerve guides alter the regrowth of transected nerves and reduce the severity of symptoms associated with neuropathic pain.

Dichloroacetate reduces tissue necrosis in a rat transverse rectus abdominis musculocutaneous flap model.

OBJECTIVE: Ischemia-related complications may occur during postmastectomy transverse rectus abdominis musculocutaneous (TRAM) flap reconstruction. The aim of our study was to investigate whether necrosis of susceptible flap regions could be reduced by dichloroacetate (DCA)-induced stimulation of oxidative metabolism in hypoxic tissue. METHODS: The study was a randomized control trial using male Sprague-Dawley rats. A pedicled TRAM flap based upon the right inferior epigastric artery was elevated and reapproximated. Animals were randomly assigned to 1 of 5 treatment groups (n = 6). Group I received no DCA; groups II through V were administered 75 mg/kg DCA orally 24 hours preoperative; in addition, groups II through IV received 75 mg/kg/d DCA orally postoperative for 4 days; group III also received 75 mg/kg DCA (IP) intraoperatively; groups IV and V were given 15 mg/kg/d DCA orally for 6 days before the 24-hour preoperative treatment. Four days postsurgery, skin paddles were photographed and assessed for viability. Underlying TRAM muscle was biopsied for histologic analysis. Blood lactate levels were measured at pre- and postoperative time points. The mean percentages of viable skin paddle were as follows: 32.0%+/- 4.0% (group I), 68.1% +/- 6.2% (group II), 84.3% +/- 5.9% (group III), 92.8% +/- 2.0% (group IV), 82.6% +/- 5.8% (group V). RESULTS: Statistically significant differences were found in all experimental (DCA) groups relative to the controls (P < 0.01). Group IV (6-day DCA preconditioning, plus 24-hour preoperative and 4-day postoperative treatment) displayed the greatest improvement in flap viability, significantly better than other DCA groups (P < 0.01). Group IV also had significantly lower serum lactate levels than controls (P < 0.05). Histologic examination of muscle biopsies revealed reductions in inflammation and necrosis correlating with DCA treatment and skin paddle survival. CONCLUSIONS: This study indicates that DCA may provide a useful pharmacologic tool for reducing ischemia-related necrosis in TRAM flaps.

Propofol improves skin flap survival in a rat model: correlating reduction in flap-induced neutrophil activity.

Accumulation of neutrophils in a random pattern skin flap has been demonstrated to contribute to the necrosis of distal flap tissue. This study proposes that administration of propofol anesthesia can effectively reduce neutrophil activity and enhance skin flap survival. The study was a randomized controlled trial using male Sprague-Dawley rats as subjects. For flap survival studies, a 3- by 12-cm, dorsal, cranial-based, random pattern skin flap was elevated and reapproximated. Flaps were examined for viability 10 days postsurgery. To assess neutrophil activity, flap biopsies were taken 12, 24, or 48 hours postsurgery from distal, middle, and proximal flap regions, and myeloperoxidase enzyme content was analyzed. Animals were randomly assigned to 1 of 4 groups: group 1, ketamine anesthesia (controls); group 2, propofol anesthesia; group 3, ketamine anesthesia plus 10% lipid emulsion (propofol vehicle); group 4, ketamine anesthesia without flap elevation (nonoperated controls for myeloperoxidase study). Flap survival was significantly improved in the propofol group compared with both the ketamine and vehicle control groups (P <0.01). Increased flap viability was correlated with a reduction in myeloperoxidase content in the propofol group compared with control operated animals, with minor variations observed in the different flap regions and time points tested. This study indicates that the use of propofol can potentially improve skin flap survival. The beneficial effects may be attributed to a reduction in neutrophil activity within the flap.