Xiuli Chang

Paraquat inhibits cell viability via enhanced oxidative stress and apoptosis in human neural progenitor cells

Paraquat (PQ) is one of the most widely used herbicides in the world. Although available evidence indicates that people exposed to PQ have a higher risk of developing Parkinsons disease, adverse effects of PQ on neural progenitor cells have not been investigated yet. In this study, we investigated the in vitro effect of PQ on immortalized human embryonic neural progenitor cells (hNPCs) by treating them with various concentrations of PQ (0, 0.1, 1, 10 and 100 μM) for 24h. We show that PQ treatment reduces the cell viability and proliferation and induces reactive oxygen species (ROS) production in a dose-dependent manner. In addition, apoptosis induced by PQ was significantly increased at a concentration of as low as 1 μM. To illustrate the underlying molecular mechanisms, we examined the caspase-3 activity, intracellular calcium level, the NF-κB activity, as well as expression of p21, p53 and metallothionein-III mRNA. PQ significantly increased caspase-3 activity at the concentration of 100 μM. Similarly, PQ triggered intracellular Ca(2+) releases and activation of NF-κB was observed after exposure of hNPCs at low concentrations of PQ (1 μM). Meanwhile, p53 and p21 mRNA transcripts were significantly up-regulated at 10 μM and 1 μM of PQ, respectively. MT-III mRNA and protein expression was significantly up-regulated at 1 μM of PQ and reached peak at 10 μM. These results suggest that PQ could reduce viability of hNPCs by inducing oxidative stress and apoptosis.

Metallothionein I isoform mRNA expression in peripheral lymphocytes as a biomarker for occupational cadmium exposure.

It is reported that metallothionein (MT) mRNA expression in human peripheral blood lymphocytes (HPBLs) could be used as exposure biomarkers in occupationally cadmium-exposed workers. Several MT isoforms have been identified in humans. The relationship between MT isoforms and cadmium toxicity has not been fully elucidated in occupational settings. In this study, the MT-IA, IE, IF, IX mRNA expressions in HPBLs were tested by RT-PCR technique, and the relationship between MT isoforms mRNA expression and cadmium-induced renal dysfunction was evaluated in cadmium-exposed workers. The MT-IE, IF, IX mRNA levels were found to increase with increasing blood cadmium (BCd) levels and MT-IA mRNA levels increased with increased urinary cadmium (UCd) levels. The MT-IE, IF, IX mRNA levels were significantly correlated with the BCd levels (P < 0.05), and MT-IA mRNA levels were significantly correlated with the UCd levels. This confirmed that MT-I isoforms mRNA expression in HPBLs is a biomarker of cadmium exposure and internal dose. The MT-IA mRNA levels were significantly correlated with renal dysfunction biomarkers, such as urinary β2-microglobulin (Uβ2-MG) (r = 0.294, P < 0.01) and urinary albumin (UALB) (r = 0.305, P < 0.01). The latter finding indicates that MT-IA mRNA expression in HPBLs may be used as a biomarker for renal dysfunction in occupational cadmium exposure.

Pyrrolidine dithiocarbamate attenuates paraquat-induced lung injury in rats.

Paraquat (PQ) has been demonstrated that the main target organ for the toxicity is the lung. This study aimed to investigate the potential protective effect of PDTC on the PQ-induced pulmonary damage. Fifty-four rats were divided into control, PQ-treated and PQ+PDTC-treated groups. Rats in the PQ group were administrated 40 mg/kg PQ by gastric gavage, and PDTC group with 40 mg/kg PQ followed by injection of 120 mg/kg PDTC (IP). On the days 3, 7, 14 and 21 after treatments, the activities of GSH-Px, SOD, MDA level and the content of HYP were measured. TGF-β1 mRNA and protein were assayed by RT-PCR and ELISA. MDA level in plasma and BALF was increased and the activities of GSH-Px and SOD were decreased significantly in the PQ-treated groups (P < .05) compared with control group. While the activities of GSH-Px and SOD in the PQ+PDTC-treated groups was markedly higher than that of PQ-treated groups (P < .05), and in contrast, MDA level was lower. TGF-β1 mRNA and protein were significantly lower in the PQ+PDTC-treated groups than that of PQ-treated groups (P < .05). The histopathological changes in the PQ+PDTC-treated groups were milder than those of PQ groups. Our results suggested that PDTC treatment significantly attenuated paraquat-induced pulmonary damage.

Osteoporosis in a Chinese Population Due to Occupational Exposure to Lead

BACKGROUND Recent studies indicate that lead may exert actions both directly on osteoblast and osteoclast function, and indirectly via kidney dysfunction on bone turnover. The main focus of this study was to investigate whether occupational lead exposure is associated with low bone mass in a population working in a storage battery plant. METHODS Monophoton absorptiometry was used to measure bone mineral density (BMD) in the population and the Z score was introduced to define osteoporosis (Z score <-2). Lead concentration of urine and blood was determined by graphite-furnace atomic absorption spectrophotometry as an exposure biomarker. A total of 249 persons (191 males and 58 females) participated and completed a questionnaire in order to obtain information on height, weight, age, medical and drug history, cigarette smoking, alcohol consumption, job position, work year, physical exercise, etc. RESULTS The BMD was significantly decreased in the groups of the high urinary lead (UPb) level compared with the low UPb level with a significant difference (P < 0.05) in both genders, but no such significant difference was observed in the relationship between blood lead (BPb) and BMD. The prevalence of osteoporosis would increase significantly with the increase of the UPb (P < 0.01) in the linear correlation manner (P < 0.01). There was also such a significant relationship between BPb and osteoporosis (P < 0.01). There was a dose-response relationship between lead exposure and prevalence of osteoporosis. CONCLUSIONS In contrast to BPb, UPb had a more close relationship with osteoporosis caused by lead. It was concluded that occupational exposure to lead is associated with osteoporosis.

Urinary metabolite levels of pyrethroid insecticides in infants living in an agricultural area of the Province of Jiangsu in China

Pyrethroid insecticides are extensively and increasingly applied in agricultural and residential environments in China. Childrens exposure to pesticides attracted global concerns because of their particular vulnerability. Several studies have reported residual pyrethroid levels in urine both in adults and in children. However, few published data focused on very young infants. The study aimed to assess exposure to pyrethroid insecticides in young infants and investigate the potential influence factors on pyrethroid exposure levels. Data on pyrethroids exposure was based on questionnaire items and measurement of urinary metabolite levels among 481 infants. We detected pyrethroid metabolites of 3-phenoxybenzoic acid (3-PBA), cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-DCCA and trans-DCCA) in urine using a gas chromatography-mass spectrometry method. Median values for urinary pyrethroid metabolites in these infants were 0.39 μgL(-1) for 3-PBA, 0.18 μgL(-1) for cis-DCCA, 0.92 μgL(-1) for trans-DCCA, respectively. About 60.9% of the infants had urinary concentrations of three pyrethroid metabolites that were above the level of 0.10 μgL(-1) (limit of detection, LOD). These findings of the urinary metabolites were comparable or slightly higher than those children from the other countries. From questionnaire, we learned that more than 70% of households reported that they or family members had applied mosquito repellents in infants. Above data indicated the need to assess the potential adverse effects of pyrethroids exposure on infants in order to take adequate measures to protect them from pesticide exposures during early childhood.

A polymorphism in metallothionein 1A (MT1A) is associated with cadmium-related excretion of urinary beta 2-microglobulin

OBJECTIVES Cadmium (Cd) toxicity of the kidney varies between individuals despite similar exposure levels. In humans Cd is mainly bound to metallothioneins (MT), which scavenge its toxic effects. Here we analyzed whether polymorphisms in MT genes MT1A and MT2A influence Cd-related kidney damage. METHODS In a cross-sectional study N=512 volunteers were selected from three areas in South-Eastern China, which to varying degree were Cd-polluted from a smelter (control area [median Cd in urine U-Cd=2.67 μg/L], moderately [U-Cd=4.23 μg/L] and highly [U-Cd=9.13 μg/L] polluted areas). U-Cd and blood Cd (B-Cd) concentrations were measured by graphite-furnace atomic absorption spectrometry. MT1A rs11076161 (G/A), MT2A rs10636 (G/C) and MT2A rs28366003 (A/G) were determined by Taqman assays; urinary N-Acetyl-beta-(D)-Glucosaminidase (UNAG) by spectrometry, and urinary β2-microglobulin (UB2M) by ELISA. RESULTS Higher B-Cd (natural log-transformed) with increasing number of MT1A rs11076161 A-alleles was found in the highly polluted group (p-value trend=0.033; all p-values adjusted for age, sex, and smoking). In a linear model a significant interaction between rs11076161 genotype and B-Cd was found for UNAG (p=0.001) and UB2M concentrations (p=0.001). Carriers of the rs11076161 AA genotype showed steeper slopes for the associations between Cd in blood and natural log-transformed UB2M (β=1.2, 95% CI 0.72-1.6) compared to GG carriers (β=0.30, 95% CI 0.15-0.45). Also for UNAG (natural log-transformed) carriers of the AA genotype had steeper slopes (β=0.55, 95% CI 0.27-0.84) compared to GG carriers (β=0.018, 95% CI -0.79-0.11). CONCLUSIONS MT1A rs11076161 was associated with B-Cd concentrations and Cd-induced kidney toxicity at high exposure levels.

Nrf2/ARE Pathway Involved in Oxidative Stress Induced by Paraquat in Human Neural Progenitor Cells

Compelling evidences have shown that diverse environmental insults arising during early life can either directly lead to a reduction in the number of dopaminergic neurons or cause an increased susceptibility to neurons degeneration with subsequent environmental insults or with aging alone. Oxidative stress is considered the main effect of neurotoxins exposure. In this study, we investigated the oxidative stress effect of Paraquat (PQ) on immortalized human embryonic neural progenitor cells by treating them with various concentrations of PQ. We show that PQ can decrease the activity of SOD and CAT but increase MDA and LDH level. Furthermore, the activities of Cyc and caspase-9 were found increased significantly at 10 μM of PQ treatment. The cytoplasmic Nrf2 protein expressions were upregulated at 10 μM but fell back at 100 μM. The nuclear Nrf2 protein expressions were upregulated as well as the downstream mRNA expressions of HO-1 and NQO1 in a dose-dependent manner. In addition, the proteins expression of PKC and CKII was also increased significantly even at 1 μM. The results suggested that Nrf2/ARE pathway is involved in mild to moderate PQ-induced oxidative stress which is evident from dampened Nrf2 activity and low expression of antioxidant genes in PQ induced oxidative damage.

Estimation of benchmark dose for bone damage and renal dysfunction in a Chinese male population occupationally exposed to lead.

OBJECTIVES The aim of this study was to examine a possible relationship between lead nephropathy and its effects on the skeleton in male population occupationally exposed to lead in China. METHODS One hundred and fifty-five lead-exposed male workers in a storage battery plant in Shanghai were selected as the exposed subjects while the 36 healthy male officers in the plant who were not occupationally exposed to lead were treated as the control. Blood lead (BPb) and urine lead were used as biomarkers for exposure. Z score, urine hydroxyproline (HYP), serum alkaline phosphatase (bone isoenzyme) (BALP) and serum osteocalcin (BGP) were used as biomarkers for bone effects. Urine N-acetyl-beta-D-glucosaminidase (UNAG) and urine albumin (UALB) were applied as biomarkers of renal tubular and glomerular dysfunction. Bone mineral density was measured by the monophoton absorptiometry (SPA-4). RESULTS It was found that there were linear correlate relationships between lead exposure and NAG, ALB, BALP, BGP, HYP, Z score (P < 0.01), after controlling confounders such as age and work year. NAG, ALB, BALP, BGP and HYP would increase with the increase of lead exposure. Z score would decrease with the increase of lead exposure. Of 21 subjects with osteoporosis, nine subjects were suffering from renal dysfunction. The prevalence of renal dysfunction (42.86%) was significantly higher in the subjects with osteoporosis than in those without osteoporosis (17.65%) (chi(2) = 7.310, P = 0.007). The prevalence of osteoporosis had relationship with renal tubular damage, but not with renal glomerular damage. This showed that glomerular dysfunction plays a smaller role than tubular dysfunction in the causation of bone damage. Benchmark dose in terms of BPb was calculated using Benchmark Dose Software Version 1.3.2 software. The benchmark dose lower limit of a one-sided 95% confidence interval (BMDL) for 10% excess risk was also determined. It was found that BMDL(-05) for BALP, UNAG, BGP, HYP, Z score and UALB of BPb increased sequentially. The BMDL values for UNAG (10.13 microg dL(-1)) were lower than those of Z score (14.17 microg dL(-1)). CONCLUSIONS The present study has thus demonstrated the combined adverse effects (osteoporosis and renal dysfunction) caused by occupational exposure to lead. There was a dose-response relationship between lead exposure and prevalence of osteoporosis, renal dysfunction and bone metabolism. The renal dysfunction might develop earlier than osteoporosis. Osteoporosis caused by lead was related to the change of bone metabolism and renal dysfunction, which was especially to tubular damage but not to glomerular damage.

Characterization of Paraquat-Induced miRNA Profiling Response in hNPCs Undergoing Proliferation

Aberration during the development of the central nervous system (CNS) due to environmental factors underlies a variety of adverse developmental outcomes. Paraquat (PQ) is a widely studied neurotoxicant that perturbs the normal structure/function of adult CNS. Yet, the impacts of PQ exposure on the developing CNS remain unclear. miRNAs represent a class of small non-coding RNA molecules involved in the regulation of neural development. Thus in the present study, we analyzed the impacts of PQ on the miRNome of human neural progenitor cells (hNPCs) during proliferation by using the Exiqon miRCURY™ LNA Array. A total of 66 miRNAs were identified as differentially expressed in proliferating hNPCs upon PQ treatment. miRTarBase prediction identified 1465 mRNAs, including several genes (e.g., nestin, sox1, ngn1) previously proved to be associated with the neural proliferation and differentiation, as target genes of PQ-induced differentially expressed miRNAs. The database for annotation, visualization and integrated discovery (DAVID) bioinformatics analysis showed that target genes were enriched in regulation of cell proliferation and differentiation, cell cycle and apoptosis as well as tumor protein 53 (p53), Wnt, Notch and mitogen-activated protein kinases (MAPK) signaling pathways (p < 0.001). These findings were confirmed by real-time RT-PCR. Based on our results we conclude that PQ-induced impacts on the miRNA profiling of hNPCs undergoing proliferation may underlie the developmental neurotoxicity of PQ.

Adverse Associations of both Prenatal and Postnatal Exposure to Organophosphorous Pesticides with Infant Neurodevelopment in an Agricultural Area of Jiangsu Province, China

Background: Prenatal exposure to organophosphorous (OP) pesticides has been found to be associated with adverse effects on child neurodevelopment, but evidence on potential effects induced by both prenatal and postnatal OP exposure in infants is limited. Objectives: Our aim was to investigate the associations of both prenatal and postnatal OP exposure with birth outcomes and infant neurodevelopment. Methods: Exposure to OP in 310 mother–infant pairs was assessed by measuring dimethylphosphate (DM), diethylphosphate (DE), and total dialkylphosphate (DAP) metabolites in urines from pregnant women and their children at 2 years of age. The Gesell Developmental Schedules was administered to examine neurodevelopment of 2-year-old children. Results: Based on the Gesell Developmental Schedules, the proportions of children with developmental delays were < 6%. Adverse associations between head circumference at birth and prenatal OP exposure were demonstrated. Both prenatal and postnatal OP exposure was significantly associated with increased risk of being developmentally delayed. Specifically, odds ratio (OR) value for prenatal DEs was 9.75 (95% CI: 1.28, 73.98, p = 0.028) in the adaptive area, whereas in the social area, OR values for postnatal DEs and DAPs were 9.56 (95% CI: 1.59, 57.57, p = 0.014) and 12.00 (95% CI: 1.23, 117.37, p = 0.033), respectively. Adverse associations were observed only in boys, not in girls. Conclusions: Both prenatal and postnatal OP exposure may adversely affect the neurodevelopment of infants living in the agricultural area. The present study adds to the accumulating evidence on associations of prenatal and postnatal OP exposure with infant neurodevelopment. Citation: Liu P, Wu C, Chang X, Qi X, Zheng M, Zhou Z. 2016. Adverse associations of both prenatal and postnatal exposure to organophosphorous pesticides with infant neurodevelopment in an agricultural area of Jiangsu Province, China. Environ Health Perspect 124:1637–1643; http://dx.doi.org/10.1289/EHP196