Early-Life Persistent Vitamin D Deficiency Alters Cardiopulmonary Responses to Particulate Matter-Enhanced Atmospheric Smog in Adult Mice

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.

Effects of vitamin D on associations between air pollution and mental health outcomes in Korean adults: Results from the Korea National Health and Nutrition Examination Survey (KNHANES)

BACKGROUND

Evidence suggests that low individual vitamin D levels enhance adverse effects associated with air pollution on mental health conditions. The aim of this study was to identify associations between ambient air pollution exposure, mental health, and serum vitamin D status in the general population of South Korea.

METHODS

We included national representative data for 29,373 adults in the final analysis. We measured serum 25-hydroxyvitamin D concentrations to assess vitamin D status for each participant. We assessed mental health factors (i.e., perceived stress, depressive symptoms, and suicidal ideation), and analyzed associations between these factors and individuals' annual average exposures to air pollutants, including particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide, and carbon monoxide (CO).

RESULTS

Using an adjusted model, we found PM₁₀ affected mental health outcomes, such as perceived stress (odds ratio [OR] = 1.04; 95 % confidence interval [CI] = 1.00-1.09), depression symptoms (OR = 1.12; 95 % CI = 1.06-1.18), and suicidal ideation (OR = 1.11; 95 % CI = 1.05-1.17). Effects of the pollutants NO₂ and CO were significant only in the group with perceived stress and depressive symptoms. PM₁₀ and NO₂ exposures were significantly associated with increased odds of adverse mental health in participants with vitamin D deficiency.

LIMITATIONS

Since the cross-sectional design of KNHANES data, it is not possible to evaluate the causal relationship between air pollution exposure, vitamin D status and mental health.

CONCLUSIONS

This study results suggest that associations between ambient air pollution and mental health outcomes were stronger in participants with vitamin D deficiency.

Fine particulate matter, vitamin D, physical activity, and major depressive disorder in elderly adults: Results from UK Biobank

OBJECTIVE

The present study aims to investigate the association between PM2.5 exposure and major depressive disorder, and to examine whether vitamin D and physical activity could attenuate the impact of PM2.5 on major depressive disorder.

METHODS

39168 elderly adults (age≥60 years) who had valid estimates on exposure of PM2.5 in 2010 and data on major depressive disorder were extracted from the UK Biobank. Major depressive disorder was assessed by lifetime experience of mild, moderate, and severe major depression with validated instruments. Logistic regression models were used to estimate the association between PM2.5 exposure and major depressive disorder.

RESULTS

A total of 9079 participants had major depressive disorder, with a prevalence of 23.2%. The odds ratio (OR) of major depressive disorder was 1.096 (1.023, 1.175) for participants in the highest quartile compared with the lowest quartile of PM2.5. The correlation of PM2.5 with major depressive disorder generally increased with the decreasing levels of vitamin D. For instance, in participants with the highest quartile of PM2.5, the corresponding ORs were 1.141 (0.951, 1.369), 1.232 (1.027, 1.478), 1.286 (1.072, 1.543), and 1.390 (1.159, 1.667) for those who had adequate, desirable, insufficient, and deficient levels of vitamin D, respectively. Additionally, significant modification effects of physical activity on the relationship between PM2.5 and major depressive disorder were also observed.

CONCLUSIONS

Our study suggests that high levels of vitamin D and physical activity may attenuate the relationship between PM2.5 and major depressive disorder among elderly adults.

PM2.5 exposure and maternal glucose metabolism in early pregnancy: Associations and potential mediation of 25-hydroxyvitamin D

Gestational diabetes mellitus (GDM) has become a new global epidemic with a rapidly increasing prevalence. Previous studies have suggested that air pollution is associated with GDM risk, but the results are inconsistent, and mechanistic studies are limited. Based on a hospital-based cohort, a total of 6374 participants were included in this study. Individual daily PM2.5 exposure at a 1-km resolution was predicted using a full-spatiotemporal-coverage model. The results of multiple linear regression showed that glycated hemoglobin (HbA1c) was significantly associated with PM2.5 both in the 1-month preconception and in the first trimester of pregnancy. Additionally, HbA1c decreased 0.437% (95% CI: -0.629, -0.244) as the serum 25-hydroxyvitamin D (25(OH)D) increased by one interquartile range (IQR) (9.2 ng/ml). An IQR increase in PM2.5 exposure was also negatively associated with serum 25(OH)D (estimated change% and 95% CI: -7.249 (-9.054, -5.408) in the 1-month preconception and - 13.069 (-15.111, -10.979) in the first trimester of pregnancy). Mediation analysis showed that serum 25(OH)D status mediated the association between HbA1c and PM2.5 exposure both in the preconception and in the first trimester (mediated percent: 2.00% and 4.05% (Sobel p＜0.001), respectively). The result suggested a vicious cycle among PM2.5 exposure, lower serum VD status and a higher HbA1c. More studies are warranted since the protective effect of 25(OH)D against glucose disorders associated with air pollution in this study was limited.

Pyridostigmine Protects Against Diabetic Cardiomyopathy by Regulating Vagal Activity, Gut Microbiota, and Branched-Chain Amino Acid Catabolism in Diabetic Mice

The disruption of gut microbes is associated with diabetic cardiomyopathy, but the mechanism by which gut microbes affect cardiac damage remains unclear. We explored gut microbes and branched-chain amino acid (BCAA) metabolite catabolism in diabetic cardiomyopathy mice and investigated the cardioprotective effect of pyridostigmine. The experiments were conducted using a model of diabetic cardiomyopathy induced by a high-fat diet + streptozotocin in C57BL/6 mice. The results of high-throughput sequencing showed that diabetic cardiomyopathy mice exhibited decreased gut microbial diversity, altered abundance of the diabetes-related microbes, and increased abundance of the BCAA-producing microbes Clostridiales and Lachnospiraceae. In addition, diabetes downregulated tight junction proteins (ZO-1, occludin, and claudin-1) and increased intestinal permeability to impair the intestinal barrier. These impairments were accompanied by reduction in vagal activity that manifested as increased acetylcholinesterase levels, decreased acetylcholine levels, and heart rate variability, which eventually led to cardiac damage. Pyridostigmine enhanced vagal activity, restored gut microbiota homeostasis, decreased BCAA-producing microbe abundance, and improved the intestinal barrier to reduce circulating BCAA levels. Pyridostigmine also upregulated BCAT2 and PP2Cm and downregulated p-BCKDHA/BCKDHA and BCKDK to improve cardiac BCAA catabolism. Moreover, pyridostigmine alleviated abnormal mitochondrial structure; increased ATP production; decreased reactive oxygen species and mitochondria-related apoptosis; and attenuated cardiac dysfunction, hypertrophy, and fibrosis in diabetic cardiomyopathy mice. In conclusion, the gut microbiota, BCAA catabolism, and vagal activity were impaired in diabetic cardiomyopathy mice but were improved by pyridostigmine. These results provide novel insights for the development of a therapeutic strategy for diabetes-induced cardiac damage that targets gut microbes and BCAA catabolism.

Early-life persistent vitamin D deficiency-induced cardiovascular dysfunction in mice is mediated by transient receptor potential C channels

BACKGROUND

Studies indicate that chronic vitamin D deficiency (VDD) may predispose to hypertension, yet, there is very little data characterizing its direct cardiac effects. Vitamin D modulates the function of transient receptor potential C cation channels (TRPC), which is a mechanosensitive cation channel that plays a role in cardiac slow-force responses to hemodynamic changes. The purpose of this study was to determine the cardiac effects of VDD and the potential role of TRPC.

METHODS

Three-week old mice were placed on a VDD or normal diet (ND) for 19 weeks. Mice were then implanted with radiotelemeters for the measurement of heart rate (HR) and heart rate variability (HRV), while a separate group was anesthetized to measure blood pressure (BP) and left ventricular function using an intraventricular probe. Animals were treated with a TRPC antagonist or vehicle after which they were challenged with dobutamine to measure cardiac responses.

RESULTS

VDD mice had significantly increased BP (72 ± 3 mmHg vs. 62 ± 2 mmHg) and left ventricular pressure (LVP) (84.6 ± 0.8 mmHg vs. 78.2 ± 2.0 mmHg), and decreased cardiac contractility (-3 % vs. + 11 %) and HR response (+8 % vs. + 13 %) to dobutamine when compared to ND. These responses were blocked by the TRPC antagonist. HRV decreased with increasing dobutamine doses in ND but not VDD mice, however, the antagonist had no effect.

CONCLUSION

VDD increases BP and alters cardiac mechanical function in mice, the latter appears to be mediated by TRPC, in particular TRPC6. Although the cardiac effects might be due to increased BP, it is likely that VDD also affects the function of the heart directly. This is the first study to demonstrate the potentially deleterious effects of VDD on cardiac function and the role of TRPC6 in this response.

Effects of vitamin D on inflammatory and oxidative stress responses of human bronchial epithelial cells exposed to particulate matter

BACKGROUND

Particulate matter (PM) pollutant exposure, which induces oxidative stress and inflammation, and vitamin D insufficiency, which compromises immune regulation, are detrimental in asthma.

OBJECTIVES

Mechanistic cell culture experiments were undertaken to ascertain whether vitamin D abrogates PM-induced inflammatory responses of human bronchial epithelial cells (HBECs) through enhancement of antioxidant pathways.

METHODS

Transcriptome analysis, PCR and ELISA were undertaken to delineate markers of inflammation and oxidative stress; with comparison of expression in primary HBECs from healthy and asthmatic donors cultured with reference urban PM in the presence/absence of vitamin D.

RESULTS

Transcriptome analysis identified over 500 genes significantly perturbed by PM-stimulation, including multiple pro-inflammatory cytokines. Vitamin D altered expression of a subset of these PM-induced genes, including suppressing IL6. Addition of vitamin D suppressed PM-stimulated IL-6 production, although to significantly greater extent in healthy versus asthmatic donor cultures. Vitamin D also differentially affected PM-stimulated GM-CSF, with suppression in healthy HBECs and enhancement in asthmatic cultures. Vitamin D increased HBEC expression of the antioxidant pathway gene G6PD, increased the ratio of reduced to oxidised glutathione, and in PM-stimulated cultures decreased the formation of 8-isoprostane. Pre-treatment with vitamin D decreased CXCL8 and further decreased IL-6 production in PM-stimulated cultures, an effect abrogated by inhibition of G6PD with DHEA, supporting a role for this pathway in the anti-inflammatory actions of vitamin D.

CONCLUSIONS

In a study using HBECs from 18 donors, vitamin D enhanced HBEC antioxidant responses and modulated the immune response to PM, suggesting that vitamin D may protect the airways from pathological pollution-induced inflammation.

Evaluation of an Air Quality Health Index for Predicting the Mutagenicity of Simulated Atmospheres

No study has evaluated the mutagenicity of atmospheres with a calculated air quality health index (AQHI). Thus, we generated in a UV-light-containing reaction chamber two simulated atmospheres (SAs) with similar AQHIs but different proportions of criteria pollutants and evaluated them for mutagenicity in three Salmonella strains at the air-agar interface. We continuously injected into the chamber gasoline, nitric oxide, and ammonium sulfate, as well as either α-pinene to produce SA-PM, which had a high concentration of particulate matter (PM): 119 ppb ozone (O3), 321 ppb NO2, and 1007 μg/m3 PM2.5; or isoprene to produce SA-O3, which had a high ozone (O3) concentration: 415 ppb O3, 633 ppb NO2, and 55 μg/m3 PM2.5. Neither PM2.5 extracts, NO2, or O3 alone, nor nonphoto-oxidized mixtures were mutagenic or cytotoxic. Both photo-oxidized atmospheres were largely direct-acting base-substitution mutagens with similar mutagenic potencies in TA100 and TA104. The mutagenic potencies [(revertants/h)/(mgC/m3)] of SA-PM (4.3 ± 0.4) and SA-O3 (9.5 ± 1.3) in TA100 were significantly different ( P < 0.0001), but the mutation spectra were not ( P = 0.16), being ∼54% C → T and ∼46% C → A. Thus, the AQHI may have some predictive value for the mutagenicity of the gas phase of air.