Distribution of Phthalate Metabolites between Paired Maternal–Fetal

May 14, 2018 - Engineering, Nankai University, Tianjin 300071, China. •S Supporting Information. ABSTRACT: Phthalic acid esters (PAEs) are readily m...
0 downloads 0 Views 1MB Size
Subscriber access provided by - Access paid by the | UCSB Libraries

Ecotoxicology and Human Environmental Health

Distribution of Phthalate Metabolites between Paired Maternal-Fetal Samples Xiaoying Li, Hongwen Sun, Yiming Yao, Zhen Zhao, Xiaolei Qin, Yishuang Duan, and Lei Wang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b00838 • Publication Date (Web): 14 May 2018 Downloaded from http://pubs.acs.org on May 14, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 32

Environmental Science & Technology

1

Distribution of Phthalate Metabolites between Paired Maternal-Fetal

2

Samples

3

Xiaoying Li,† Hongwen Sun,*,† Yiming Yao,† Zhen Zhao,† Xiaolei Qin,† Yishuang

4

Duan,† and Lei Wang†

5 6



7

Criteria, College of Environmental Science and Engineering, Nankai University,

8

Tianjin, China

Ministry of Education Key Laboratory of Pollution Processes and Environmental

9 10

Corresponding author: Hongwen Sun

11

College of Environmental Science and Engineering, Nankai University

12

38 Tongyan Road, Tianjin, 300350, China

13

Tel: 86-22-23509241

14

Fax: 86-22-23501117

15

Email: [email protected]

16 17

Submitted to: Environmental Science &Technology

18

ACS Paragon Plus Environment

Environmental Science & Technology

19

ABSTRACT: Phthalic acid esters (PAEs) are readily metabolized to phthalate

20

metabolites (mPAEs) in the human body. The occurrence of mPAEs in adult human

21

samples is well documented; however, the maternal-fetal transmission of mPAEs has

22

seldom been studied. In this study, 78 paired maternal-fetal samples, including

23

maternal urine (MU), maternal serum (MS), cord serum (CS), and amniotic fluid (AF),

24

were collected from pregnant women in Tianjin, China. Seven mPAEs were detected

25

in MS, CS and AF, whereas all 11 investigated mPAEs were found in MU. The

26

median concentration of mPAEs was the highest in MU (128 ng/mL, with a range of

27

20.2–973 ng/mL), and proceeded in the order of CS (44.9, 13.9–315 ng/mL), MS

28

(24.6, 3.75–156 ng/mL), and AF (10.4, 7.69–79.8 ng/mL). The values of mPAEs and

29

several individual mPAEs were significantly correlated between MU and MS, with

30

generally higher concentrations in MU, which indicated that urinary mPAEs is a good

31

indicator of PAEs’ exposure in adults. Notably, the median CS:MS ratios of mPAEs

32

(1.58) were higher than 1, indicating that fetuses were exposed to mPAEs before birth.

33

Significant correlations were also observed between MS and CS, which suggested that

34

mPAEs in MS provide an indication of the fetal exposure. This study presents the first

35

systematic analysis of the distribution and transmission of various mPAEs between

36

mothers and fetuses.

37

■INTRODUCTION

38

Phthalic acid esters (PAEs) are widely used as plasticizers in industrial and consumer

39

products, including nail polish, plastic packaging, toys, personal care products, and

40

pharmaceutical coatings.1,2 PAEs are readily released into packaged foods and

ACS Paragon Plus Environment

Page 2 of 32

Page 3 of 32

Environmental Science & Technology

41

environmental matrices as they are not chemically bound to plastic polymers.1,2 Hence,

42

PAEs have been detected in various matrices such as air,3 surface water,4 soil,5 and

43

foodstuffs;1,2 thus, there is a high risk of human exposure.2

44

Once entering the human body, PAEs within a few hours or days are rapidly

45

metabolized to their metabolites (mPAEs),6-8 which are more toxic than their parent

46

compounds.9-11 These mPAEs were reported to be associated with many human health

47

outcomes such as biochemical pregnancy loss,12 testosterone-related diseases,13

48

hypertension,14 and diabetes.14 As they are more water soluble than PAEs, mPAEs are

49

more easily excreted in urine. mPAEs have been extensively detected at a wide range

50

of concentrations in human urine (from several to several hundred ng/mL), indicating

51

the prevalence of human exposure to PAEs.1,2 Accordingly, the use of human urinary

52

mPAEs as biomarkers for PAEs exposure has been suggested.1,2 However, the

53

relationship between the mPAEs concentrations in urine and serum samples has not

54

been extensively studied, nor have consistent results concerning correlations been

55

reported.15,16

56

A fetus can be exposed to chemical contaminants via maternal-fetal transmission.

57

Several contaminants, such as polychlorinated biphenyls (PCBs),17 polybrominated

58

diphenyl ethers (PBDEs),18,19 polycyclic aromatic hydrocarbons (PAHs),20,21 and poly-

59

and perfluoroalkyl substances (PFASs),22,23 are known to be able to cross the placenta

60

and enter the umbilical cord. To date, only a few studies have investigated the mPAEs

61

in the umbilical cord and the total number of mPAEs studied is also rather limited.24,25

62

On the other hand, both animal toxicity studies and epidemiological investigation

ACS Paragon Plus Environment

Environmental Science & Technology

63

showed the adverse effects of mPAEs on the development of fetuses.26-28 Thus, the

64

data on prenatal exposure to mPAEs are highly needed so as to accurately assess the

65

risk of maternal PAEs exposure on newborn infants.

66

The CS:MS (maternal serum) concentrations ratio of a contaminant is often used

67

as an important indicator to assess the transmission efficiency from the mother to the

68

fetus. In previous studies, both the CS:MS ratios larger than 1 and less than 1 were

69

reported,18-22,29 and the former indicates accumulation against the concentration

70

gradient, for which active transport may be involved. Some studies reported the

71

association between the transmission ratios and chemical properties. Usually, nonionic

72

or highly lipid-soluble compounds (with molecular weight (MW) < 600 Da and 0.9 

73

logKow5.0) can cross the placenta easily through passive diffusion.30-33 A plot of the

74

transmission efficiencies of perfluoroalkyl carboxylic acids (PFCAs) between

75

maternal-fetal samples against fluorine-carbon chain length presented as a U-shape;

76

and the lowest value was found in perfluorodecanoic acid and both shorter-chain and

77

longer-chain analogs had higher transfer efficiencies.23 As for ionic organic

78

contaminants like mPAEs, they have great water solubility and low logKow and the

79

speciation changes with circumstance parameters such as pH, and accordingly, their

80

distribution within organisms may depend not only on the partition in the lipid phase

81

but also on binding affinity to proteins and other macrobiomolecules and are likely to

82

be influenced by circumstance parameters such as pH.34-36 In addition to chemical

83

properties, the physiological status of the mother and fetus may also exert an impact,

84

which may explain why the same chemicals have different transfer ratios in different

ACS Paragon Plus Environment

Page 4 of 32

Page 5 of 32

Environmental Science & Technology

85

studies.18,19 Besides, as the metabolites of PAEs, mPAEs in the fetus may come both

86

from the transmission from the mother and from the metabolism of PAEs in the fetus.

87

In summary, knowledge of the maternal-fetal transmission pathway of mPAEs is still

88

incomplete.

89

In addition to CS, amniotic fluid (AF) is also an important medium that reflects

90

the chemical prenatal exposure in the fetus. AF is derived from urine, the excretion of

91

gastrointestinal tract, and the mass exchange with umbilical cord of the fetus in the

92

third trimester.37 Mass exchange occurs mainly between the fetus and AF and, to a

93

lesser extent between AF and the mother through the fetal membrane.37,38 Hence, the

94

distribution of mPAEs between AF and CS or MS (AF:CS and AF:MS) are also

95

important indices for the evaluation of fetal exposure to chemicals. The occurrence

96

of mPAEs in AF has been previously reported and significant positive correlations

97

between creatinine-adjusted mono-n-butyl phthalate (MBP) in maternal urine (MU)

98

and MBP in AF39 and between mono-(2-isobutyl) phthalate (MiBP) in MU and that in

99

AF40 were found. However, the association of various mPAEs in AF with maternal

100

and umbilical cord samples has not been previously determined.

101

In this study, we collected 78 paired maternal-fetal samples from pregnant

102

women in Tianjin, China. The aims of this study were 1) to investigate the

103

concentrations and composition profiles of 11 mPAEs in these samples and explore

104

their possible associations with maternal and fetal socio-demographic characteristics;

105

2) to evaluate the distribution and associations of various mPAEs among the different

106

matrices of MU, MS, CS, and AF; and 3) to elucidate the associations between the

ACS Paragon Plus Environment

Environmental Science & Technology

Page 6 of 32

107

transmission efficiencies of the detected mPAEs and their chemical properties.

108

■MATERIAL AND METHODS

109

Chemicals

and

Reagents.

The

target

mPAEs

compounds

included

110

mono-2-ethylhexyl phthalate (MEHP), MiBP, MBP, mono-(3-carboxypropyl)

111

phthalate (MCPP), mono-ethyl phthalate (MEP), mono-methyl phthalate (MMP),

112

mono-benzyl phthalate (MBzP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP),

113

mono-[(2-carboxymethyl) hexyl] phthalate (MCMHP), mono-(2-ethyl-5-oxohexyl)

114

phthalate (MEOHP), and 5-mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP).

115

Select properties and commercial sources for the 11 mPAEs and the corresponding

116

PAEs are listed in Table S1 in the Supporting Information (SI). Detailed information

117

for all chemicals and reagents is given in the SI.

118

Sampling Campaign. All samples were collected from Tianjin Central Hospital

119

of Gynecology Obstetrics, and 83 pregnant women were recruited during

120

October-December, 2015. There were a total of 83 MU, 82 MS, 80 CS, and81 AF

121

samples, among which 78 were composed of totally paired samples of

122

MU-MS-AF-CS. This research was approved by the Ethics Committee of Tianjin

123

Central Hospital of Gynecology Obstetrics, and the informed consent together with

124

questionnaires was dispatched to participants and collected. MU and MS samples

125

were collected two hours before delivery, while the CS and AF samples were sampled

126

during delivery. All samples were stored at -80C before analysis. All participants

127

were healthy and without any infectious diseases. A summary of detailed information

128

of the study population is shown in Table 1.

ACS Paragon Plus Environment

Page 7 of 32

Environmental Science & Technology

129

Sample Preparation and Instrumental Analysis. Samples were analyzed using

130

a previously described method with some modifications (see Sample Preparation,

131

SI).41,42 Briefly, mPAEs in 0.5 mL of the fluid samples(i.e., MU, MS, CS, and AF)

132

were extracted using CNW Poly-Sery MAX cartridges (150 mg/6 mL, CNW ANPEL,

133

Shanghai, China) to include free mPAEs and their conjugates after enzymolysis.

134

The mPAEs in the treated samples were analyzed with high-performance liquid

135

chromatography (Agilent 1200) interfaced to triple quadrupole tandem mass

136

spectrometry (Agilent G6410B) (HPLC-MS/MS) and equipped with an electrospray

137

ionization (ESI) interface in negative mode. The mPAEs were separated with a

138

BETASIL C18 column (100 mm×2.1 mm×5 μm; Thermo Scientific, PA, U.S.) and

139

monitored with multiple reaction monitoring (MRM). The detailed instrument

140

parameters and mobile phase programs are given in the SI (Instrumental Analysis and

141

Table S2).

142

Quality Assurance and Quality Control. To ensure data quality, a procedural

143

blank, an instrumental blank, and matrix-spiked samples were co-analyzed in every

144

batch of 20 samples. The procedural blank was prepared by substitution of the real

145

samples with 0.5 mL Milli-Q water and treated with the same procedure. The target

146

mPAEs were not detected in the procedural or instrumental blanks. Twenty-five

147

nanograms of three mixed isotopically labeled standards of mPAEs (i.e.,

148

13

149

extraction and analysis procedure. Standard samples (10 ng/mL) and pure solvent

150

(acetonitrile) were injected every 20 samples to check the instrument conditions and

C4-MEP, and

13

13

C4-MBP,

C4-MECPP) was spiked into sample matrices for correction of

ACS Paragon Plus Environment

Environmental Science & Technology

151

the carryover of instrument contamination. A 10-point calibration curve (0.1–100

152

ng/mL) was prepared at the beginning of every day, and the regression coefficient of

153

calibration was above 0.99.

154

Details of the recoveries and the method detection limits (MDL) of the 11

155

mPAEs are provided in Table S3 for the four matrices. Values below MDL were

156

recognized as 0. Because the concentrations of chemicals vary with urine volume at

157

each sampling event, the creatinine level was employed for normalization of mPAEs

158

concentrations in urine samples.41

159

Statistical Analyses. Spearman rank correlation analyses were conducted with

160

SPSS, Version 22.0 (IL, U.S.). A value of p95%), whereas MEHHP, MEOHP,

250

MCPP, and MBzP were not detected; similarly, MEP was only detected in 15.0% of

251

CS samples (Table 2). MMP (17.5 ng/mL), MBP (9.56ng/mL), and MiBP (5.36

252

ng/mL), were the most abundant mPAEs in CS, contributing for 43.6%, 23.8%, and

253

13.3% of mPAEs, respectively (Figure 1). These results indicated that low MW

254

(LMW) mPAEs (i.e., MBP, MiBP, MMP, and MEP) presented the main risk to the

255

fetuses compared with high MW (HMW) mPAEs (i.e., MCPP, MBzP, MEHP, MECPP,

256

MEHHP, MEOHP, and MCMHP). Previous studies have found that LMW

257

contaminants could easily cross the placental barrier.30-33 This study provided the first

258

evidence for MEP exposure to fetuses even though it occurred at a low concentration

259

and DR. Spearman correlations among 6 individual mPAEs and ∑mPAEs in CS were

260

similar to those in MS (Table S6).

ACS Paragon Plus Environment

Page 12 of 32

Page 13 of 32

Environmental Science & Technology

261

Only limited studies have reported the occurrence of mPAEs in cord samples. In

262

Italy, MEHP was investigated in CS of 84 newborns, and MEHP concentrations in CS

263

(mean value: 520±610 ng/mL) were positively correlated with gestational age.25 In a

264

nested case-control study in Shanghai, the MEHP concentrations in cord blood

265

samples from 88 newborns with low birth weight and 113 healthy controls were 2500

266

and 1100 ng/mL, respectively, whereas MBP was not detected.24 In France, the

267

median value of MBP in 41 cord blood samples was found to be 2.90 ng/mL.53 Five

268

mPAEs (MMP, MEP, MBP, MBzP, and MEHP) were investigated in 30 CS samples in

269

Tianjin, with median concentrations of 26.9, 12.0, 17.0, 3.23, and 5.48 ng/mL,

270

respectively.54 The results in this study were similar to those of the previous study in

271

Tianjin,54 but were much lower than those found in a study conducted in Shanghai.24

272

High levels of other emerging chemicals like PFCAs have been reported in human

273

samples in Shanghai,55 which should be paid attention as a hot spot in future studies.

274

Concentrations and Profiles of mPAEs in AF. MECPP, MCMHP, MEHP, MBP,

275

MiBP, and MMP were the most frequently detected mPAEs and presented in more

276

than 95.0% of the AF samples. The DR of MEP in AF samples (67.0%) was higher

277

than those in MS and CS samples; furthermore, MEHHP, MEOHP, MCPP, and MBzP

278

were not detected. This was the same as for MS and CS, which was indicative of

279

associations between AF and MS or CS. The detection of mPAEs in AF provided

280

further confirmation for the fetal exposure to mPAEs. The median mPAEs

281

concentration (10.4 ng/mL) in AF was substantially lower than those in MU (128

282

ng/mL), MS (24.6 ng/mL), and CS (44.9 ng/mL). This could be explained by the

ACS Paragon Plus Environment

Environmental Science & Technology

Page 14 of 32

283

limited elimination capacity of the fetus, which indicated that high exposure of the

284

fetus to mPAEs occurred mainly owing to the enclosed environment. Moreover, the

285

mPAEs concentrations might be diluted by the peak AF volume at 38 weeks of

286

gestation in the sampling time.37 In the four matrices, the median concentrations of

287

LMW mPAEs were all higher than those of HMW mPAEs (Figure S2). Moreover,

288

the proportion of the LMW mPAEs was higher in CS and AF as compared to MS

289

and MU. This seems to indicate that LMW mPAEs accumulate in organs with long

290

residence time. The correlations of mPAEs in AF were quite different from those in

291

MS and CS (Table S6). The source of mPAEs in AF is complex since it can originate

292

from both MS and CS.37 The median concentration of mPAEs in AF in this study was

293

close to those observed mPAEs in AF samples in other regions/cities (Table S8).

294

Factors Influencing the mPAEs Concentrations in MU, MS, CS, and AF. To

295

establish the reliable factors that influence mPAEs concentrations in the four matrices,

296

correlations

297

socio-demographicindices were studied, including age, body mass index, gestational

298

week, pregnancy, parity, sex, and fetal weight (Table S9). Pregnancy showed

299

significant negative correlations with MECPP and MEOHP in MU, MECPP in MS,

300

MEHP, MiBP, and MMP in CS, and MEHP in AF(all p