The effect of divalent metal chelators and cadmium on serum phosphotriesterase, lactonase and arylesterase activities of paraoxonase 1

Cadmium-associated protein changes in residents of contaminated areas: Abandoned mine and smelter

Cadmium (Cd), a serious environmental contaminant, is associated with adverse health effects. However, the specific changes that the human body experiences in response to exposure to varying concentrations of cadmium remain unknown. The high levels of heavy metal contamination, especially Cd, in abandoned mines and smelter sites make them ideal locations to investigate the physiological manifestations of Cd exposure. This study found that individuals inhabiting abandoned mine and smelter areas had higher concentrations of Cd in their urine and blood compared to those living outside these areas (i.e., the controls). Furthermore, proteomic profiling of blood samples from all study groups was performed to identify proteomic biomarkers associated with chronic and severe Cd exposure. This analysis showed statistically significant correlations between urine Cd levels and sixteen proteins. Among these proteins, seven exhibited significantly altered expressions in samples from contaminated areas compared with those from control areas. Therefore, these proteins were selected as potential markers representing Cd-related protein alterations. Multiple reaction monitoring analysis was performed to validate the expression patterns of the proteins and four proteins were found to exhibit consistent trends. The findings show that Cd exposure significantly affects the expression of certain proteins in the human body. Understanding the underlying mechanisms and diseases associated with Cd-induced protein alterations can aid in the development of effective preventive and therapeutic strategies for individuals exposed to Cd-linked pollution.

Inter-individual variation in chlorpyrifos toxicokinetics characterized by physiologically based kinetic (PBK) and Monte Carlo simulation comparing human liver microsome and Supersome™ cytochromes P450 (CYP)-specific kinetic data as model input

The present study compares two approaches to evaluate the effects of inter-individual differences in the biotransformation of chlorpyrifos (CPF) on the sensitivity towards in vivo red blood cell (RBC) acetylcholinesterase (AChE) inhibition and to calculate a chemical-specific adjustment factor (CSAF) to account for inter-individual differences in kinetics (HK_AF). These approaches included use of a Supersome^™ cytochromes P450 (CYP)-based and a human liver microsome (HLM)-based physiologically based kinetic (PBK) model, both combined with Monte Carlo simulations. The results revealed that bioactivation of CPF exhibits biphasic kinetics caused by distinct differences in the Km of CYPs involved, which was elucidated by Supersome^™ CYP rather than by HLM. Use of Supersome^™ CYP-derived kinetic data was influenced by the accuracy of the intersystem extrapolation factors (ISEFs) required to scale CYP isoform activity of Supersome^™ to HLMs. The predicted dose–response curves for average, 99th percentile and 1st percentile sensitive individuals were found to be similar in the two approaches when biphasic kinetics was included in the HLM-based approach, resulting in similar benchmark dose lower confidence limits for 10% inhibition (BMDL₁₀) and HK_AF values. The variation in metabolism-related kinetic parameters resulted in HK_AF values at the 99th percentile that were slightly higher than the default uncertainty factor of 3.16. While HK_AF values up to 6.9 were obtained when including also the variability in other influential PBK model parameters. It is concluded that the Supersome^™ CYP-based approach appeared most adequate for identifying inter-individual variation in biotransformation of CPF and its resulting RBC AChE inhibition.

The role of proprotein convertase subtilisin/kexin type-9 concentration and paraoxonase 1 activities in the blood of women with polycystic ovary syndrome

This study aimed to evaluate the concentration of proprotein convertase subtilisin/kexin type-9 (PCSK9) and the activities of paraoxonase 1 in women with and without polycystic ovary syndrome (PCOS). We found significant higher PCSK9, whereas lower high-density lipoprotein concentration in the serum of women with PCOS when compared to the group without PCOS. Also paraoxonase 1 activities were significantly different between women with PCOS than without PCOS. In addition, the women with PCOS and insulin resistance had higher concentrations of PCSK9 than women with PCOS and insulin sensitivity. Higher PCSK9 concentration in the group with PCOS could be also associated with hormones concentrations. Changes in paraoxonase 1 activities and lipid profile parameters as well as higher concentration of PCSK9 in the group of women with PCOS could be associated with metabolism disorders, but due to the small clinical sample size, the study should be continued.

Physiologically based kinetic modelling based prediction of in vivo rat and human acetylcholinesterase (AChE) inhibition upon exposure to diazinon

The present study predicts in vivo human and rat red blood cell (RBC) acetylcholinesterase (AChE) inhibition upon diazinon (DZN) exposure using physiological based kinetic (PBK) modelling-facilitated reverse dosimetry. Due to the fact that both DZN and its oxon metabolite diazoxon (DZO) can inhibit AChE, a toxic equivalency factor (TEF) was included in the PBK model to combine the effect of DZN and DZO when predicting in vivo AChE inhibition. The PBK models were defined based on kinetic constants derived from in vitro incubations with liver fractions or plasma of rat and human, and were used to translate in vitro concentration-response curves for AChE inhibition obtained in the current study to predicted in vivo dose-response curves. The predicted dose-response curves for rat matched available in vivo data on AChE inhibition, and the benchmark dose lower confidence limits for 10% inhibition (BMDL10 values) were in line with the reported BMDL10 values. Humans were predicted to be 6-fold more sensitive than rats in terms of AChE inhibition, mainly because of inter-species differences in toxicokinetics. It is concluded that the TEF-coded DZN PBK model combined with quantitative in vitro to in vivo extrapolation (QIVIVE) provides an adequate approach to predict RBC AChE inhibition upon acute oral DZN exposure, and can provide an alternative testing strategy for derivation of a point of departure (POD) in risk assessment.

A potential risk factor for paraoxonase 1: in silico and in-vitro analysis of the biological activity of proton-pump inhibitors†

Objectives

Proton-pump inhibitors (PPIs) are drugs commonly utilized by about 7% of adults in the world. Recent researches have shown that there are countless and severe side effects of these drugs. This situation has raised concern among clinicians and patients alike. The purpose of this study is to contribute the novel drug discovery and development technology and toxicology field by researching interactions of PPIs on paraoxonase 1.

Methods

In this study, the paraoxonase 1 enzyme was purified from human serum by using rapid and straightforward chromatographic techniques. Subsequently, the inhibition effects of pantoprazole, omeprazole, and esomeprazole, PPIs, were investigated on paraoxonase 1. Besides, molecular docking studies were performed to unravel the binding mechanism between the enzyme and drugs.

Key findings

All drugs showed potent inhibitory activities. IC50 of the drugs values were 54.780 ± 0.524, 86.470 ± 0.818 and 93.390 ± 0.885 mm and Ki constants were found as 39.895 ± 0.005 mm, 70.112 ± 0.010 mm and 78.868 ± 0.008 mm, respectively. The binding scores observed in silico studies were found to agree with the obtained from in-vitro experimental results.

Conclusions

We observed that the drugs decreased PON1 activity at low concentrations. The results show that adjusting the dosages of these medications is a crucial case for each patient. The physicians should more carefully interpret whether there is an essential indication before prescribing PPIs and, if there is, to approve the proper dosing for the situation.

Changes in lipid profile parameters and PON1 status associated with L55M PON1 polymorphism, overweight and exposure to tobacco smoke

OBJECTIVE

The aim of our study was to investigate the effects of paraoxonase 1 (PON1) L55M polymorphism on the enzyme's activity and concentration in the serum as well as its association with lipid profile parameters in a group of healthy persons. We also evaluated the presence of PON1 L55M polymorphism in a group of subjects exposed to tobacco smoke and with overweight or obesity on those parameters.

METHODS

Analysis of L55M polymorphism was done using polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (PCR - RFLP). Serum PON1 concentration and lipid profile parameters were assayed using commercial tests. PON1 activities were measured earlier elaborated procedures.

RESULTS

We observed a statistically significant difference in HDL and PON1 concentration: the highest in the LL genotype and the lowest in the MM genotype with the LM genotype having an intermediate concentration. L55M polymorphism influence on PON1 arylesterase and phosphotriesterase activity, whereas PON1 lactonase activity did not differ in all polymorphic variant groups. Exposure to tobacco smoke and overweight or obesity additionally disorder above mentioned parameters. Overweight and obesity in LM and MM genotype could be associated with higher PON1 phosphotriesterase activity. It is also possible that MM genotype could be a determinant of smoking addiction.

CONCLUSIONS

L55M polymorphism, like exposure to tobacco smoke and overweight, disorders PON1 status and lipid profile parameters; therefore, it could be a crucial risk factor for the development of many metabolic disorders.