Sex-specific respiratory and systemic endocrine effects of acute acrolein and trichloroethylene inhalation

Connecting volatile organic compounds exposure to osteoporosis risk via oxidative stress based on adverse outcome pathway methodology

Existing evidence has demonstrated the association between exposure to volatile organic compounds (VOCs) and osteoporosis (OP) risk, but the underlying mechanistic framework remains unclear. This study aimed to explore potential pathways using adverse outcome pathway (AOP) analysis, and evidence this association in middle-to-old-aged American adults using the updated National Health and Nutrition Examination Survey data. Multivariable-adjusted general linear and weighted quantile sum models were employed to analyze associations of VOC metabolites (VOCMs), representing internal VOCs exposure levels, with OP-related phenotypes. An AOP framework based on network analysis was developed by extracting target genes and phenotypes. Among 3555 American adults aged ≥ 40 years (539 OP participants), we found that increasing urinary 3- and 4-methylhippuric acid, N-acetyl-S-(n-propyl)-l-cysteine (BPMA), and N-acetyl-S-(3-hydroxypropyl)-l-cysteine were associated with elevated OP odds with odds ratios (ORs) (95 % confidence intervals, 95 % CIs) being 1.254 (1.016 to 1.548), 1.182 (1.014 to 1.377), and 1.244 (1.029 to 1.505), respectively, per standard deviation. Urinary BPMA and N-acetyl-S-(2-cyanoethyl)-l-cysteine were inversely associated with lumbar spine bone mineral density (BMD), while urinary N-acetyl-S-(2-hydroxypropyl)-l-cysteine was positively associated with hip BMD. Additionally, OP odds increased by 46.0 % (95 % CI: 3.9 % to 105.1 %) per quartile increment in the VOC mixture. AOP analysis identified 53 target genes and 9 target phenotypes, and 5 of 9 target phenotypes were oxidative stress (OS)-related. Literature and the "AOP 482″ framework implied the core role of OS in the VOC exposure and prevalent OP association, with the interleukin-6 as the molecular initiating event. Our findings provided a theoretical basis for further investigation.

Adrenergic receptor subtypes differentially influence acrolein-induced ventilatory, vascular leakage, and inflammatory responses

Adrenergic receptors (AR) are manipulated therapeutically for the treatment of pulmonary and cardiovascular diseases; however, their role in air pollutant-induced respiratory effects is poorly understood. We examined the contribution of AR-subtypes in acrolein-induced respiratory effects through selective receptor inhibition. We pre-treated 12-week-old male Wistar-Kyoto rats intraperitoneally daily for 9-days with subtype-specific AR antagonists prazosin (PRZ, α1-AR antagonist; 2-mg/kg-day), yohimbine (YOH, α2-AR antagonist; 5-mg/kg-day), or propranolol (PROP, β-AR antagonist; 10-mg/kg-day). On day-8 and day-9 of treatment, rats were exposed nose-only to air or acrolein (1.6 or 3.2 ppm), ∼4 h/day. Head-out plethysmography during exposure on Day-9 revealed overall concentration-dependent acrolein-related reduced ventilatory capacity, which was exacerbated in PRZ- and YOH-treated animals. Nasal (NALF) and bronchoalveolar lavage fluid (BALF), and blood samples were collected on day-9. Plasma epinephrine levels did not change; however, corticosterone decreased in YOH- and PROP-treated air-exposed animals. Adrenal and spleen weights were higher in PRZ-treated animals. Acrolein, 3.2-ppm depleted circulating lymphocytes in saline-treated and increased neutrophils in PRZ- and YOH-treated animals. NALF and BALF analysis indicated 3.2-ppm acrolein-induced neutrophilic and lymphocytic inflammation (NALF>BALF), which was exacerbated in lung of PRZ- and YOH-treated rats and slightly dampened in PROP-treated rats. However, acrolein-induced vascular protein leakage and increases in inflammatory cytokines in NALF were reduced by PROP-treatment. In conclusion, this study highlights sympathetically-mediated adrenoreceptor influence on acrolein-indued respiratory health effects, and AR subtype-specific modulation of breathing, hemodynamic, and inflammatory responses. These results have broader translational implications, as those receiving adrenergic agonistic/antagonistic therapies might experience variable air pollution-related respiratory health effects.

Neuroendocrine contribution to sex-related variations in adverse air pollution health effects

Air pollution exposure is ranked as a leading environmental risk factor for not only cardiopulmonary diseases but also for systemic health ailments including diabetes, reproductive abnormalities, and neuropsychiatric disorders, likely mediated by central neural stress mechanisms. Current experimental evidence links many air pollution health outcomes with activation of neuroendocrine sympathetic-adrenal-medullary and hypothalamic-pituitary-adrenal (HPA) stress axes associated with resultant increases in adrenal-derived hormone levels acting as circulating mediators of multi-organ stress reactions. Epidemiological and experimental investigations also demonstrated sex-specific responses to air pollutant inhalation, which may be attributed to hormonal interactions within the stress and reproductive axes. Sex hormones (androgens and estrogens) interact with neuroendocrine functions to influence hypothalamic responses, subsequently augmenting stress-mediated metabolic and immune changes. These neurohormonal interactions may contribute to innate sex-specific responses to inhaled irritants, inducing differing individual susceptibility. The aim of this review was to: (1) examine neuroendocrine co-regulation of the HPA axis by gonadal hormones, (2) provide experimental evidence demonstrating sex-specific respiratory and systemic effects attributed to air pollutant inhalation exposure, and (3) postulate proposed mechanisms of stress and sex hormone interactions during air pollution-related stress.

Mechanistic insights regarding neuropsychiatric and neuropathologic impacts of air pollution

Air pollution is a significant environmental health risk for urban areas and developing countries. Air pollution may contribute to the incidence of cardiopulmonary and metabolic diseases. Evidence also points to the role of air pollution in worsening or developing neurological and neuropsychiatric conditions. Inhaled pollutants include compositionally differing mixtures of respirable gaseous and particulate components of varied sizes, solubilities, and chemistry. Inhalation of combustibles and volatile organic compounds (VOCs) or other irritant particulate matter (PM) may trigger lung sensory afferents which initiate a sympathetic stress response via activation of the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes. Activation of SAM and HPA axes are associated with selective inhibition of hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-thyroid (HPT) axes following exposure. Regarding chronic exposure in susceptible hosts, these changes may become pathological by causing neuroinflammation, neurotransmitter, and neuroendocrine imbalances. Soluble PM, such as metals and nano-size particles may translocate across the olfactory, trigeminal, or vagal nerves through retrograde axonal transport, or through systemic circulation which may disrupt the blood-brain barrier (BBB) and deposit in neural tissue. Neuronal deposition of metallic components can have a negative impact through multiple molecular mechanisms. In addition to systemic translocation, the release of pituitary and stress hormones, altered metabolic hormonal status and resultant circulating metabolic milieu, and sympathetically and HPA-mediated changes in immune markers, may secondarily impact the brain through a variety of regulatory adrenal hormone-dependent mechanisms. Several reviews covering air pollution as a risk factor for neuropsychiatric disorders have been published, but no reviews discuss the in-depth intersection between molecular and stress-related neuroendocrine mechanisms, thereby addressing adaptation and susceptibility variations and link to peripheral tissue effects. The purpose of this review is to discuss evidence regarding neurochemical, neuroendocrine, and molecular mechanisms which may contribute to neuropathology from air pollution exposure. This review also covers bi-directional neural and systemic interactions which may raise the risk for air pollution-related systemic illness.

Association Between Home Renovation and Sleeping Problems Among Children Aged 6-18 Years: A Nationwide Survey in China

BACKGROUND

Although the indoor environment has been proposed to be associated with childhood sleep health, to our knowledge no study has investigated the association between home renovation and childhood sleep problems.

METHODS

The study included 186,470 children aged 6-18 years from the National Chinese Children Health Study (2012-2018). We measured childhood sleeping problems via the Chinese version of the Sleep Disturbance Scale for Children (C-SDSC). Information on home renovation exposure within the recent 2 years was collected via parent report. We estimated associations between home renovation and various sleeping problems, defined using both continuous and categorized (binary) C-SDSC t-scores, using generalized mixed models. We fitted models with city as a random effect variable, and other covariates as fixed effects.

RESULTS

Out of the overall participants, 89,732 (48%) were exposed to recent home renovations. Compared to the unexposed group, children exposed to home renovations had higher odds of total sleep disorder (odd ratios [OR] = 1.3; 95% confidence interval [CI] = 1.2, 1.4). Associations varied when we considered different types of home renovation materials. Children exposed to multiple types of home renovation had higher odds of sleeping problems. We observed similar findings when considering continuous C-SDSC t-scores. Additionally, sex and age of children modified the associations of home renovation exposure with some of the sleeping problem subtypes.

CONCLUSIONS

We found that home renovation was associated with higher odds of having sleeping problems and that they varied when considering the type of renovation, cumulative exposure, sex, and age differences.

Serum metabolome and liver transcriptome reveal acrolein inhalation-induced sex-specific homeostatic dysfunction

Acrolein, a respiratory irritant, induces systemic neuroendocrine stress. However, peripheral metabolic effects have not been examined. Male and female WKY rats were exposed to air (0 ppm) or acrolein (3.16 ppm) for 4 h, followed by immediate serum and liver tissue collection. Serum metabolomics in both sexes and liver transcriptomics in males were evaluated to characterize the systemic metabolic response. Of 887 identified metabolites, > 400 differed between sexes at baseline. An acrolein biomarker, 3-hydroxypropyl mercapturic acid, increased 18-fold in males and 33-fold in females, indicating greater metabolic detoxification in females than males. Acrolein exposure changed 174 metabolites in males but only 50 in females. Metabolic process assessment identified higher circulating free-fatty acids, glycerols, and other lipids in male but not female rats exposed to acrolein. In males, acrolein also increased branched-chain amino acids, which was linked with metabolites of nitrogen imbalance within the gut microbiome. The contribution of neuroendocrine stress was evident by increased corticosterone in males but not females. Male liver transcriptomics revealed acrolein-induced over-representation of lipid and protein metabolic processes, and pathway alterations including Sirtuin, insulin-receptor, acute-phase, and glucocorticoid signaling. In sum, acute acrolein inhalation resulted in sex-specific serum metabolomic and liver transcriptomic derangement, which may have connections to chronic metabolic-related diseases.