Sultan Ahmed

Arsenic-Associated Oxidative Stress, Inflammation, and Immune Disruption in Human Placenta and Cord Blood

Background Arsenic (As) exposure during pregnancy induces oxidative stress and increases the risk of fetal loss and low birth weight. Objectives In this study we aimed to elucidate the effects of As exposure on immune markers in the placenta and cord blood, and the involvement of oxidative stress. Methods Pregnant women were enrolled around gestational week (GW) 8 in our longitudinal, population-based, mother–child cohort in Matlab, an area in rural Bangladesh with large variations in As concentrations in well water. Women (n = 130) delivering at local clinics were included in the present study. We collected maternal urine twice during pregnancy (GW8 and GW30) for measurements of As, and placenta and cord blood at delivery for assessment of immune and inflammatory markers. Placental markers were measured by immunohistochemistry, and cord blood cytokines by multiplex cytokine assay. Results In multivariable adjusted models, maternal urinary As (U-As) exposure both at GW8 and at GW30 was significantly positively associated with placental markers of 8-oxoguanine (8-oxoG) and interleukin-1β (IL-1β); U-As at GW8, with tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ); and U-As at GW30, with leptin; U-As at GW8 was inversely associated with CD3+ T cells in the placenta. Cord blood cytokines (IL-1β, IL-8, IFNγ, TNFα) showed a U-shaped association with U-As at GW30. Placental 8-oxoG was significantly positively associated with placental proinflammatory cytokines. Multivariable adjusted analyses suggested that enhanced placental cytokine expression (TNFα and IFNγ) was primarily influenced by oxidative stress, whereas leptin expression appeared to be mostly mediated by As, and IL-1β appeared to be influenced by both oxidative stress and As. Conclusion As exposure during pregnancy appeared to enhance placental inflammatory responses (in part by increasing oxidative stress), reduce placental T cells, and alter cord blood cytokines. These findings suggest that effects of As on immune function may contribute to impaired fetal and infant health.

Effects of in utero arsenic exposure on child immunity and morbidity in rural Bangladesh.

Chronic exposure to arsenic, a potent carcinogen and toxicant, via drinking water is a worldwide public health problem. Because little is known about early-life effects of arsenic on immunity, we evaluated the impact of in utero exposure on infant immune parameters and morbidity in a pilot study. Pregnant women were enrolled at 6-10 weeks of gestation in Matlab, a rural area of Bangladesh, extensively affected by arsenic contamination of tubewell water. Women (n=140) delivering at local clinics were included in the study. Anthropometry and morbidity data of the pregnant women and their children, as well as infant thymic size by sonography were collected. Maternal urine and breast milk were collected for immune marker and arsenic assessment. Maternal urinary arsenic during pregnancy showed significant negative correlation with interleukin-7 (IL-7) and lactoferrin (Ltf) in breast milk and child thymic index (TI). Urinary arsenic was also positively associated with fever and diarrhea during pregnancy and acute respiratory infections (ARI) in the infants. The effect of arsenic exposure on ARI was only evident in male children. The findings suggest that in utero arsenic exposure impaired child thymic development and enhanced morbidity, probably via immunosuppression. The effect seemed to be partially gender dependent. Arsenic exposure also affected breast milk content of trophic factors and maternal morbidity.

Sex-specific effects of early life cadmium exposure on DNA methylation and implications for birth weight

Dietary cadmium exposure was recently found to alter DNA methylation in adults, but data on effects early in life are lacking. Our objective was to evaluate associations between prenatal cadmium exposure, DNA methylation and birth weight. In total 127 mother-child pairs from rural Bangladesh were studied. For comparison, we included 56 children at 4.5 y. Cadmium concentrations in mothers’ blood (gestational week 14) and children’s urine were measured by ICPMS. Global DNA methylation was analyzed by Infinium HumanMethylation450K BeadChip in cord blood and children’s blood. Maternal cadmium exposure was associated with cord blood DNA methylation (p-value < 10–16). The association was markedly sex-specific. In boys, 96% of the top 500 CpG sites showed positive correlations (rS-values > 0.50), whereas most associations in girls were inverse; only 29% were positive (rS > 0.45). In girls we found overrepresentation of methylation changes in genes associated with organ development, morphology and mineralization of bone, whereas changes in boys were found in cell death-related genes. Several individual CpG sites that were positively associated with cadmium were inversely correlated with birth weight, although none statistically significant after correction for multiple comparisons. The associations were, however, fairly robust in multivariable-adjusted linear regression models. We identified CpG sites that were significantly associated with cadmium exposure in both newborns and 4.5-y-old children. In conclusion, cadmium exposure in early life appears to alter DNA methylation differently in girls and boys. This is consistent with previous findings of sex-specific cadmium toxicity. Cadmium-related changes in methylation were also related to lower birth weight.

Arsenic exposure in early pregnancy alters genome-wide DNA methylation in cord blood, particularly in boys

Early-life inorganic arsenic exposure influences not only child health and development but also health in later life. The adverse effects of arsenic may be mediated by epigenetic mechanisms, as there are indications that arsenic causes altered DNA methylation of cancer-related genes. The objective was to assess effects of arsenic on genome-wide DNA methylation in newborns. We studied 127 mothers and cord blood of their infants. Arsenic exposure in early and late pregnancy was assessed by concentrations of arsenic metabolites in maternal urine, measured by high performance liquid chromatography-inductively coupled plasma mass spectrometry. Genome-wide 5-methylcytosine methylation in mononuclear cells from cord blood was analyzed by Infinium HumanMethylation450K BeadChip. Urinary arsenic in early gestation was associated with cord blood DNA methylation (Kolmogorov–Smirnov test, P-value<10–15), with more pronounced effects in boys than in girls. In boys, 372 (74%) of the 500 top CpG sites showed lower methylation with increasing arsenic exposure (r S-values>−0.62), but in girls only 207 (41%) showed inverse correlation (r S-values>−0.54). Three CpG sites in boys (cg15255455, cg13659051 and cg17646418), but none in girls, were significantly correlated with arsenic after adjustment for multiple comparisons. The associations between arsenic and DNA methylation were robust in multivariable-adjusted linear regression models. Much weaker associations were observed with arsenic exposure in late compared with early gestation. Pathway analysis showed overrepresentation of affected cancer-related genes in boys, but not in girls. In conclusion, early prenatal arsenic exposure appears to decrease DNA methylation in boys. Associations between early exposure and DNA methylation might reflect interference with de novo DNA methylation.

Phenylbutyrate Counteracts Shigella Mediated Downregulation of Cathelicidin in Rabbit Lung and Intestinal Epithelia: A Potential Therapeutic Strategy

Background Cathelicidins and defensins are endogenous antimicrobial peptides (AMPs) that are downregulated in the mucosal epithelia of the large intestine in shigellosis. Oral treatment of Shigella infected rabbits with sodium butyrate (NaB) reduces clinical severity and counteracts the downregulation of cathelicidin (CAP-18) in the large intestinal epithelia. Aims To develop novel regimen for treating infectious diseases by inducing innate immunity, we selected sodium 4-phenylbutyrate (PB), a registered drug for a metabolic disorder as a potential therapeutic candidate in a rabbit model of shigellosis. Since acute respiratory infections often cause secondary complications during shigellosis, the systemic effect of PB and NaB on CAP-18 expression in respiratory epithelia was also evaluated. Methods The readouts were clinical outcomes, CAP-18 expression in mucosa of colon, rectum, lung and trachea (immunohistochemistry and real-time PCR) and release of the CAP-18 peptide/protein in stool (Western blot). Principal findings Significant downregulation of CAP-18 expression in the epithelia of rectum and colon, the site of Shigella infection was confirmed. Interestingly, reduced expression of CAP-18 was also noticed in the epithelia of lung and trachea, indicating a systemic effect of the infection. This suggests a causative link to acute respiratory infections during shigellosis. Oral treatment with PB resulted in reduced clinical illness and upregulation of CAP-18 in the epithelium of rectum. Both PB and NaB counteracted the downregulation of CAP-18 in lung epithelium. The drug effect is suggested to be systemic as intravenous administration of NaB could also upregulate CAP-18 in the epithelia of lung, rectum and colon. Conclusion Our results suggest that PB has treatment potential in human shigellosis. Enhancement of CAP-18 in the mucosal epithelia of the respiratory tract by PB or NaB is a novel discovery. This could mediate protection from secondary respiratory infections that frequently are the lethal causes in dysentery.

Efficient Arsenic Metabolism - The AS3MT Haplotype Is Associated with DNA Methylation and Expression of Multiple Genes Around AS3MT.

Arsenic is a very potent toxicant. One major susceptibility factor for arsenic-related toxicity is the efficiency of arsenic metabolism. The efficiency, in turn, is associated with non-coding single nucleotide polymorphisms (SNPs) in the arsenic methyltransferase AS3MT on chromosome 10q24. However, the mechanism of action for these SNPs is not yet clarified. Here, we assessed the influence of genetic variation in AS3MT on DNA methylation and gene expression within 10q24, in people exposed to arsenic in drinking water. DNA was extracted from peripheral blood from women in the Argentinean Andes (N = 103) and from cord blood from new-borns in Bangladesh (N = 127). AS3MT SNPs were analyzed with Sequenom or Taqman assays. Whole genome epigenetic analysis with Infinium HumanMethylation450 BeadChip was performed on bisulphite-treated DNA. Whole genome gene expression analysis was performed with Illumina DirectHyb HumanHT-12 v4.0 on RNA from peripheral blood. Arsenic exposure was assessed by HPLC-ICPMS. In the Argentinean women, the major AS3MT haplotype, associated with more efficient arsenic metabolism, showed increased methylation of AS3MT (p = 10−6) and also differential methylation of several other genes within about 800 kilobasepairs: CNNM2 (p<10−16), NT5C2 (p<10−16), C10orf26 (p = 10−8), USMG5 (p = 10−5), TRIM8 (p = 10−4), and CALHM2 (p = 0.038) (adjusted for multiple comparisons). Similar, but weaker, associations between AS3MT haplotype and DNA methylation in 10q24 were observed in cord blood (Bangladesh). The haplotype-associated altered CpG methylation was correlated with reduced expression of AS3MT and CNNM2 (rs = −0.22 to −0.54), and with increased expression of NT5C2 and USMG5 (rs = 0.25 to 0.58). Taking other possibly influential variables into account in multivariable linear models did only to a minor extent alter the strength of the associations. In conclusion, the AS3MT haplotype status strongly predicted DNA methylation and gene expression of AS3MT as well as several genes in 10q24. This raises the possibility that several genes in this region are important for arsenic metabolism.

Arsenic exposure and cell-mediated immunity in pre-school children in rural Bangladesh.

Prenatal arsenic exposure has been associated with reduced thymic index and increased morbidity in infants, indicating arsenic-related impaired immune function. We aimed at elucidating potential effects of pre- and postnatal arsenic exposure on cell-mediated immune function in pre-school aged children. Children born in a prospective mother-child cohort in rural Bangladesh were followed up at 4.5 years of age (n = 577). Arsenic exposure was assessed by concentrations of arsenic metabolites (U-As) in child urine and maternal urine during pregnancy, using high-performance liquid chromatography online with inductively coupled plasma mass spectrometry. For assessment of delayed type hypersensitivity response, an intradermal injection of purified protein derivative (PPD) was given to Bacillus Calmette-Guerin vaccinated children. The diameter (mm) of induration was measured after 48-72 h. Plasma concentrations of 27 cytokines were analyzed by a multiplex cytokine assay. Childrens concurrent, but not prenatal, arsenic exposure was associated with a weaker response to the injected PPD. The risk ratio (RR) of not responding to PPD (induration <5 mm) was 1.37 (95% confidence interval (CI): 1.07, 1.74) in children in the highest quartile of U-As (range 126-1228 μg/l), compared with the lowest (range 12-34 μg/l). The p for trend across the quartiles was 0.003. The association was stronger in undernourished children. Childrens U-As in tertiles was inversely associated with two out of 27 cytokines only, i.e., IL-2 and TNF-α, both Th1 cytokines (in the highest tertile, regression coefficients (95% CI): -1.57 (-2.56, -0.57) and -4.53 (-8.62, -0.42), respectively), but not with Th2 cytokines. These associations were particularly strong in children with recent infections. In conclusion, elevated childhood arsenic exposure appeared to reduce cell-mediated immunity, possibly linked to reduced concentrations of Th1 cytokines.

Detection of Antibodies Secreted from Circulating Mycobacterium tuberculosis-Specific Plasma Cells in the Diagnosis of Pediatric Tuberculosis

ABSTRACT Diagnosis of tuberculosis (TB) in children is difficult because symptoms are often nonspecific or absent in infected children, diagnostic specimens are difficult to obtain from younger children, and >50% have negative TB cultures. Thus, there is an urgent need for improved diagnosis of pediatric TB. This study aimed to evaluate the diagnostic value of a new serological method, the ALS (antibodies in lymphocyte supernatant) assay, for the diagnosis of active TB in children with clinically identified TB. The ALS test is based on the concept that antigen-specific plasma cells are present in the circulation only at times of acute infection and not in latency. A cross-sectional study of pediatric patients (age range, 11 to 167 months) who were clinically identified as TB (n = 58) or non-TB (n = 16) patients was conducted, and they were monitored for 6 months. Healthy children (n = 58) were enrolled as controls. Spontaneous release of TB antigen-specific antibodies by in vitro-cultured, unstimulated peripheral blood mononuclear cells was assessed by an enzyme-linked immunosorbent assay using Mycobacterium bovis bacillus Calmette-Guérin (BCG) as the detecting antigen. Of the patients clinically diagnosed with TB, 15% had culture-confirmed TB, 64% were positive for TB by clinically established scoring charts (K. Edwards, P. N. G. Med. J. 30: 169-178, 1987; G. Stegen, K. Jones, and P. Kaplan, Pediatrics 43: 260-263, 1969; and stop TB Partnership, Childhood TB subgroup, World Health Organization, Int. J. Tuberc. Lung Dis. 10: 1091-1097, 2006), and 91% were TB positive by the ALS method. All TB patients had significantly higher BCG-specific ALS titers at enrollment (optical density [OD], 1.06 ± 0.32) than healthy-control children (OD, 0.18 ± 0.06) and non-TB children (OD, 0.21 ± 0.10) (P = 0.001). The ALS titers declined in children with active disease from enrollment through 6 months following anti-TB therapy (P = 0.001). The ALS assay is a novel diagnostic method with potential applications in the diagnosis of pediatric TB and in subsequent monitoring of treatment effectiveness.

Impact of Ficoll density gradient centrifugation on major and trace element concentrations in erythrocytes and blood plasma.

PROJECT Ficoll density gradient centrifugation is widely used to separate cellular components of human blood. We evaluated the suitability to use erythrocytes and blood plasma obtained from Ficoll centrifugation for assessment of elemental concentrations. PROCEDURE We determined 22 elements (from Li to U) in erythrocytes and blood plasma separated by direct or Ficoll density gradient centrifugation, using inductively coupled plasma mass spectrometry. RESULTS Compared with erythrocytes and blood plasma separated by direct centrifugation, those separated by Ficoll had highly elevated iodine and Ba concentration, due to the contamination from the Ficoll-Paque medium, and about twice as high concentrations of Sr and Mo in erythrocytes. On the other hand, the concentrations of Ca in erythrocytes and plasma were markedly reduced by the Ficoll separation, to some extent also Li, Co, Cu, and U. The reduced concentrations were probably due to EDTA, a chelator present in the Ficoll medium. Arsenic concentrations seemed to be lowered by Ficoll, probably in a species-specific manner. The concentrations of Mg, P, S, K, Fe, Zn, Se, Rb, and Cs were not affected in the erythrocytes, but decreased in plasma. Concentrations of Mn, Cd, and Pb were not affected in erythrocytes, but in plasma affected by EDTA and/or pre-analytical contamination. CONCLUSIONS Ficoll separation changed the concentrations of Li, Ca, Co, Cu, As, Mo, I, Ba, and U in erythrocytes and blood plasma, Sr in erythrocytes, and Mg, P, S, K, Fe, Zn, Se, Rb and Cs in blood plasma, to an extent that will invalidate evaluation of deficiencies or excess intakes.

Arsenic Metabolism in Children Differs From That in Adults

Arsenic toxicity in adults is associated with methylation efficiency, influenced by factors such as gender, genetics, and nutrition. The aim of this study was to evaluate influencing factors for arsenic metabolism in children. For 488 children (9 years), whose mothers participated in a study on arsenic exposure during pregnancy (nested into the MINIMat trial) in rural Bangladesh, we measured urinary concentrations of inorganic arsenic (iAs) and its metabolites methylarsonic acid (MMA) and dimethylarsinic acid (DMA) by HPLC-HG-ICPMS. Methylation efficiency was assessed by relative amounts (%) of the metabolites. We evaluated the impact of factors such as maternal urinary metabolite pattern, arsenic exposure, gender, socioeconomic status, season of sampling, and nutritional factors, including erythrocyte selenium (Ery-Se), and plasma folate and vitamin B12. Children had higher %DMA and lower %iAs in urine compared to their mothers, unrelated to their lower exposure [median urinary arsenic (U-As) 53 vs 78 µg/l]. Surprisingly, selenium status (Ery-Se) was strongly associated with children’s arsenic methylation; an increase in Ery-Se from the 5–95th percentile was associated with: +1.8 percentage points (pp) for %iAs (P  =  .001), +1.4 pp for %MMA (P  =  .003), and −3.2 pp for %DMA (P  <  .001). Despite this, Ery-Se was positively associated with U-As (5–95th percentile: +41 µg/l, P  =  .026). As expected, plasma folate was inversely associated with %iAs (5–95th percentile: −1.9 pp, P  =  .001) and positively associated with %DMA (5–95th percentile: +2.2 pp, P  =  .008). Children methylated arsenic more efficiently than their mothers. Also influencing factors, mainly selenium and folate, differed. This warrants further research.