Assessment of the role of paraoxonase gene polymorphism (Q192R) and paraoxonase activity in the susceptibility to atherosclerosis among lead-exposed workers

Modulatory Effect of Lifestyle-Related, Environmental and Genetic Factors on Paraoxonase-1 Activity: A Review

Paraoxonase-1 (PON1) is a calcium-dependent, HDL-bound serum hydrolase active toward a wide variety of substrates. PON1 displays three types of activities, among which lactonase, paraoxonase, arylesterase and phosphotriesterase can be distinguished. Not only is this enzyme a major organophosphate compound detoxifier, but it is also an important constituent of the cellular antioxidant system and has anti-inflammatory and antiatherogenic functions. The concentration and activity of PON1 is highly variable among individuals, and these differences can be both of genetic origin and be a subject of epigenetic regulation. Owing to the fact that, in recent decades, the exposure of humans to an increasing number of different xenobiotics has been continuously rising, the issues concerning the role and activity of PON1 shall be reconsidered with particular attention to growing pharmaceuticals intake, dietary habits and environmental awareness. In the following manuscript, the current state of knowledge concerning the influence of certain modifiable and unmodifiable factors, including smoking, alcohol intake, gender, age and genotype variation on PON1 activity, along with pathways through which these could interfere with the enzyme's protective functions, is presented and discussed. Since exposure to certain xenobiotics plays a key role in PON1 activity, the influence of organophosphates, heavy metals and several pharmaceutical agents is also specified.

Single Nucleotide Polymorphism of TWIST2 May Be a Modifier for the Association between High-Density Lipoprotein Cholesterol and Blood Lead (Pb) Level

The association between lead (Pb) exposure and lower high-density lipoprotein cholesterol (HDL-C) was reported; however, the mechanism was unclear. Our purpose was to investigate the association of Pb, lipid profile, and to study the associated SNPs using a genome-wide association study (GWAS). A total of 511 participants were recruited to check blood Pb levels, lipid profile, and genotypes with Taiwan Biobank version 2.0 (TWB2). Our main result shows that HDL-C was significantly negatively associated with blood Pb levels, adjusted for gender, body mass index (BMI), and potential confounders. In addition, via the TWB2 GWAS, only two SNPs were found, including rs150813626 (single-nucleotide variation in the TWIST2 gene on chromosome 2), and rs1983079 (unclear SNP on chromosome 3). Compared to the rs150813626 GG carriers, the AA and AG carriers were significantly and negatively associated with HDL-C. We analyzed the interaction of rs150813626 SNP and blood Pb, and the HDL-C was consistently and negatively associated with blood Pb, male, BMI, and the rs150813626 AA and AG carriers. Moreover, the rs150813626 AA and blood Pb interaction was significantly and positively associated with HDL-C. In conclusion, the SNPs rs150813626 and rs1983079 were significantly associated with HDL-C in Pb-exposed workers. Furthermore, the interaction of rs150813626 AA and blood Pb had a positive influence on HDL-C. TWIST may inhibit osteoblast maturation, which might relate to bone Pb deposition and calcium metabolism. The mechanism needs more investigation in the future.

Association Between Blood Heavy Metal Concentrations and Dyslipidemia in the Elderly

Our objective was to evaluate the relationship of blood metal levels including strontium, cadmium, lead, vanadium, aluminum, cobalt, and manganese with dyslipidemia in the elderly Chinese population. In this study, stratified cluster sampling was adopted in the elderly in two communities of Lu'an City from June to September 2016, and 1013 participants were finally included. The inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the metals' concentrations in whole blood. After multivariable adjustment, the odds ratios (95% confidence interval [CI]) of dyslipidemia associated with the highest quartile of metal concentrations were 1.32 (0.89 ~ 1.96), 1.28 (0.83 ~ 1.97), 1.86 (1.23 ~ 2.80), 0.80 (0.55 ~ 1.16), 0.76 (0.51 ~ 1.13), 0.76 (0.53 ~ 1.11), and 1.14 (0.78 ~ 1.67) for strontium, cadmium, lead, vanadium, aluminum, cobalt, and manganese, respectively, compared with the lowest quartile. After reducing the dimensionality of metal elements by principal component analysis, we found that the combined exposure of aluminum, cobalt, and vanadium was the protective factor of non-dyslipidemia, while the combined exposure of cadmium, strontium, and lead was the risk factor of dyslipidemia.

Association of Musculoskeletal Disorders and Inflammation Markers in Workers Exposed to Lead (Pb) from Pb-battery Manufacturing plant

Background:

Lead (Pb) deposits in the skeletal system on chronic exposure and releases to circulation over a period. The musculoskeletal disorders (MSDs) are associated with enhanced expression of inflammation. The combination of Pb-exposure and MSDs induced inflammation was not attempted.

Objective:

This study was conducted to examine the association between MSDs and inflammatory markers in workers exposed to Pb from Pb-battery plant.

Material and Methods:

In a case-control study design, the study enrolled 176 male Pb-exposed workers as study subjects and 80 healthy workers with no occupational exposure to Pb as control subjects. The Nordic musculoskeletal questionnaire was used to assess the MSDs. From the blood sample, blood lead level (BLL) and High Sensitivity C-reactive protein (Hs-CRP) were estimated as markers of Pb-exposure and Inflammatory marker respectively. The BLL was estimated by flame atomic absorption spectrometric method and the Hs-CRP by using a diagnostic kit method.

Results:

Significantly high proportions of MSDs were noted in study subjects as compared to controls. The MSDs identified in the study subjects were at low back (33%) followed by knee (26%), shoulders (16%), neck (14%), ankle/foot (11%), wrist/hand (10%), elbows (8%), upper back (7%), and hips/thighs (5%). The significant association between Pb-exposure and MSDs among study subjects was mainly noted in low back and ankle/foot. Also, significantly high serum Hs-CRP levels were noted among study subjects with ankle/foot MSDs.

Conclusion:

Pb-exposure and inflammatory markers were significantly associated with lower limbs of MSDs.

Low-level lead exposure and cardiovascular disease: the roles of telomere shortening and lipid disturbance

Lead exposure contributing to cardiovascular diseases is known and recognized widely. As the deleterious effects of low lead exposure attained increasing attention over the last decades, there have been numerous studies exploring the association of low levels of lead exposure and cardiovascular diseases. Moreover, it has been observed that lead exposure could cause telomere shortening and lipid disturbance, and that telomere shortening and lipid disturbance are closely related with cardiovascular diseases. Hence, telomere shortening and lipid disturbance might play an important role in the pathophysiological process of chronic low levels of lead exposure contributing to cardiovascular diseases. This review is intended to explore views of the rarely mentioned mechanism, telomere shortening and lipid disturbance, and the cardiovascular effects of low levels of lead exposure.

Elevated inflammatory Lp-PLA2 and IL-6 link e-waste Pb toxicity to cardiovascular risk factors in preschool children

Cardiovascular toxicity of lead (Pb) manifests primarily as an effect on blood pressure and eventual increased risk of atherosclerosis and cardiovascular events. Therefore, we investigated vascular inflammatory biomarkers and cardiovascular effects of Pb-exposed children. A total of 590 children (3-7 years old) were recruited from Guiyu (n = 337), an electronic waste (e-waste)-exposed group, and Haojiang (n = 253), a reference group, from November to December 2016. We measured child blood Pb levels (BPbs), and systolic and diastolic blood pressure. Pulse pressure was calculated for the latter two. Serum biomarkers including lipid profiles and inflammatory cytokines, and plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) were detected. Unadjusted regression analysis illustrated that higher ln-transformed BPb associated with lower systolic blood pressure and pulse pressure. After adjustment for various confounders, the relational degree of lnBPb and blood pressure measures became slightly attenuated or not significant. Elevated BPb was associated with higher Lp-PLA2, interleukin (IL)-6, triglycerides (TG) and lower high-density lipoprotein (HDL). Lp-PLA2 remained inversely associated with pulse pressure and HDL, but positively with ratios of total cholesterol to HDL (Tc/HDL) and low-density lipoprotein to HDL (LDL/HDL). IL-6 was associated negatively with systolic blood pressure, pulse pressure and HDL, and positively associated with TG, Tc/HDL and LDL/HDL. The mediation effect of biomarkers on the association of BPb with pulse pressure was insignificant except for Lp-PLA2. Available data supports the conclusion that e-waste-exposed children with higher BPbs and concomitant abnormal measures of cardiovascular physiology have an augmented prevalence of vascular inflammation, as well as lipid disorder.

Declining exposures to lead and cadmium contribute to explaining the reduction of cardiovascular mortality in the US population, 1988-2004

Background

Lead and cadmium exposures have markedly declined in the USA following the implementation of large-scale public health policies and could have contributed to the unexplained decline in cardiovascular mortality in US adults. We evaluated the potential contribution of lead and cadmium exposure reductions to explain decreasing cardiovascular mortality trends occurring in the USA from 1988-94 to 1999-2004.

Methods

Prospective study in 15 421 adults ≥40 years old who had participated in the National Health and Nutrition Examination Survey 1988-94 or 1999-2004. We estimated the amount of change in cardiovascular mortality over time that can be independently attributed to the intermediate pathway of changes in blood lead and urine cadmium concentrations.

Results

There was a 42.0% decrease in blood lead and a 31.0% decrease in urine cadmium concentrations. The cardiovascular mortality rate ratio [95% confidence intervals (CIs)] associated with a doubling of metal levels was 1.19 (1.07, 1.31) for blood lead and 1.20 (1.09, 1.32) for urine cadmium. The absolute reduction in cardiovascular deaths comparing 1999-2004 to 1988-94 was 230.7 deaths/100 000 person-years, in models adjusted for traditional cardiovascular risk factors. Among these avoided deaths, 52.0 (95% CI 8.4, 96.7) and 19.4 (4.3, 36.4) deaths/100 000 person-years were attributable to changes in lead and cadmium, respectively.

Conclusions

Environmental declines in lead and cadmium exposures were associated with reductions in cardiovascular mortality in US adults. Given the fact that lead and cadmium remain associated with cardiovascular disease at relatively low levels of exposure, prevention strategies that further minimize exposure to lead and cadmium may be needed.

Metals and Paraoxonases

The paraoxonases (PONs) are a three-gene family which includes PON1, PON2, and PON3. PON1 and PON3 are synthesized primarily in the liver and a portion is secreted in the plasma, where they are associated with high-density lipoproteins (HDLs), while PON2 is an intracellular enzyme, expressed in most tissues and organs, including the brain. PON1 received its name from its ability to hydrolyze paraoxon, the active metabolite of the organophosphorus (OP) insecticide parathion, and also more efficiently hydrolyzes the active metabolites of several other OPs. PON2 and PON3 do not have OP-esterase activity, but all PONs are lactonases and are capable of hydrolyzing a variety of lactones, including certain drugs, endogenous compounds, and quorum-sensing signals of pathogenic bacteria. In addition, all PONs exert potent antioxidant effects. PONs play important roles in cardiovascular diseases and other oxidative stress-related diseases, modulate susceptibility to infection, and may provide neuroprotection (PON2). Hence, significant attention has been devoted to their modulation by a variety of dietary, pharmacological, lifestyle, or environmental factors. A number of metals have been shown in in vitro, animal, and human studies to mostly negatively modulate expression of PONs, particularly PON1, the most studied in this regard. In addition, different levels of expression of PONs may affect susceptibility to toxicity and neurotoxicity of metals due to their aforementioned antioxidant properties.

Methylmercury-induced inhibition of paraoxonase-1 (PON1)-implications for cardiovascular risk

Methylmercury (MeHg) has been associated with increased risk for cardiovascular disease in some but not all epidemiology studies. These inconsistent results may stem from the fact that exposure typically occurs in the context of fish consumption, which is also associated with cardioprotective factors such as omega-3 fatty acids. Mechanistic information may help to understand whether MeHg represents a risk to cardiovascular health. MeHg is a pro-oxidant that inactivates protein sulfhydryls. These biochemical effects may diminish critical antioxidant defense mechanism(s) involved in protecting against atherosclerosis. One such defense mechanism is paraoxonase-1 (PON1), an enzyme present on high-density lipoproteins and that prevents the oxidation of blood lipids and their deposition in vascular endothelium. PON1 is potentially useful as a clinical biomarker of cardiovascular risk, as well as a critical enzyme in the detoxification of certain organophosphate oxons. MeHg and other metals are known to inhibit PON1 activity in vitro. MeHg is associated with lowered serum PON1 activity in a fish-eating population. The implications of lowering PON1 are evaluated by predicting the shift in PON1 population distribution induced by various doses of MeHg. An MeHg dose of 0.3 μg/kg/d is estimated to decrease the population average PON1 level by 6.1% and to increase population risk of acute cardiovascular events by 9.7%. This evaluation provides a plausible mechanism for MeHg-induced cardiovascular risk and suggests means to quantify the risk. This case study exemplifies the use of upstream disease biomarkers to evaluate the additive effect of chemical toxicity with background disease processes in assessing human risk.