A Review on the Biochemical and Molecular Mechanisms of Phthalate-Induced Toxicity in Various Organs with a Focus on the Reproductive System

Plastic compounds and liver diseases: Whether bisphenol A is the only culprit

Plastics, while providing modern conveniences, have become an inescapable source of global concern due to their role in environmental pollution. Particularly, the focus on bisphenol A (BPA) reveals its biohazardous nature and association with liver issues, specifically steatosis. However, research indicates that BPA is just one facet of the problem, as other bisphenol analogues, microplastics, nanoplastics and additional plastic derivatives also pose potential risks. Notably, BPA is implicated in every stage of non-alcoholic fatty liver disease (NAFLD) onset and progression, surpassing hepatitis B virus as a primary cause of chronic liver disease worldwide. As plastic contamination tops the environmental contaminants list, urgent action is needed to assess causative factors and mitigate their impact. This review delves into the molecular disruptions linking plastic pollutant exposure to liver diseases, emphasizing the broader connection between plastics and the rising prevalence of NAFLD.

Evidence of genotoxicity, neurotoxicity, and antioxidant imbalance in silver catfish Rhamdia quelen after subchronic exposure to diisopentyl phthalate

Diisopentyl phthalate (DiPeP) is a plasticizer with significant offer and application in Brazilian industries. This is attributed to its origin, which is closely linked to the refining process of sugarcane for ethanol production in the country. In this work, we developed a model for trophic exposure to environmentally relevant doses (5, 25, and 125 ng/g of DiPeP) to identify possible target tissues and toxic effects promoted by subchronic exposure to DiPeP in a Neotropical catfish species (Rhamdia quelen). After thirty days of exposure, blood, liver, kidney, brain, and muscle were collected and studied regarding DNA damage in blood cells and biochemical analyses. The kidney was the most affected organ, as in the head kidney, genotoxicity was evidenced in all groups exposed to DiPeP. Besides, the caudal kidney showed a reduction in the superoxide dismutase and glutathione peroxidase activities as well as a reduced glutathione concentration. In the liver, exposure to 125 ng/g of DiPeP increased glutathione S-transferase activity and reduced glutathione levels. In muscle, acetylcholinesterase (AChE) was reduced. However, in the brain, an increase in AChE activity was observed after the exposure to lowest doses. In contrast, a significant reduction of brain AChE activity after exposure to the highest dose was detected. The pronounced genotoxicity observed in head kidney cells is of concern, as it may compromise different functions performed by this organ (e.g., hematopoiesis, immune and endocrine functions). In our study, DiPeP proved to be a compound of environmental concern since we have evidenced its nephrotoxic and neurotoxic potential even in low doses.

Effects of dibutyl phthalate and di (2-ethylhexyl) phthalate on hepatic structure and function of adult male mice

The objective of the present research was to determine if dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) alone and combined exposure induced pathological alterations in laboratory reared albino mice. Adult male mice were equally divided (n = 10) into Control, corn oil (CO), DBP, DEHP, and DBP+DEHP treated groups. Dibutyl phthalate (250 mg/kg), DEHP (300 mg/kg), and DBP+DEHP (250+300 mg/kg), respectively, were administered by oral gavage mixed in corn oil (0.2 mL) for 28 days. All animals were sacrificed following 28 days of treatment and blood was collected for serum lipid profiles and liver function tests. Liver samples were also collected for observation of histological changes. Microphotographs of hematoxylin and eosin-stained sections were used for computer-based micrometry. CO, DBP, DEHP, and DBP+DEHP treatment resulted in a significant increase in the mean body and liver weights as compared with the Control group. Histological examination of the livers with DBP and/or DEHP treatment showed marked alterations leading to hepatic hypertrophy. In the treated groups, a significant increase in the mean number of mononucleated, binucleated cells, and oval cells per unit area was noticed with disorganized trabecular arrangement as compared with the Control group. Treatment with DBP and/or DEHP resulted in large regeneration zones in the liver and an increased relative nucleo-cytoplasmic index of mononuclear shepatocytes when compared with the Control group. All treatments caused a significant increases in the liver enzymes and proteins as well as altered serum cholesterol, triglycerides, LDL, and VLDL levels. The histopathological and serological findings confirmed the toxic potentials to hepatic tissue of DBP and DEHP either given alone or in combination.

Phthalate Exposure and Biomarkers of Oxidation of Nucleic Acids: Results on Couples Attending a Fertility Center

Phthalates are substances used as plasticizing agents and solvents that can increase the risk of infertility and that appear to induce oxidative stress. The aim of the study was to show the possible relationship between urinary concentrations of phthalates metabolites, namely MEP, MBzP, MnBP, MEHP, MEHHP, and MnOP and biomarkers of nucleic acids oxidation, methylation, or protein nitroxidation. The oxidative stress biomarkers measured in human urine were 8-oxo-7,8-dihydroguanine, 8-oxo-7,8-dihydroguanosine, 8-oxo-7,8-dihydro-2′-deoxyguanosine, 3-nitrotyrosine, and 5-methylcytidine. Two hundred and seventy-four couples were enrolled, undergoing an assisted reproduction technology (ART) treatment, urine samples were analyzed in HPLC/MS-MS, and then two sub-groups with urinary concentration > 90th or <10th percentile were identified, reducing the sample size to 112 subjects. The levels of oxidative stress biomarkers were measured in both groups, reduced to 52 men and 60 women. A statistically significantly difference for 8-oxoGuo and 3-NO2Tyr between men and women, with higher levels in men, was found. The levels of oxidative stress biomarkers were directly correlated with some phthalate concentrations in both sexes.

Role of endocrine disruptors in male infertility and impact of COVID-19 on male reproduction

Several epidemiological studies suggest strong association of endocrine disruptors (EDs) with impaired male reproduction. High levels of polychlorinated biphenyls in serum are associated with low sperm count and poor fertility. A high dichloro diphenyl trichloroethane (DDT) concentration results in low serum testosterone (T) and poor semen quality. DDT stimulates estrogen production by acting as estrogen receptor agonist and potent androgen receptor antagonist. Phthalates, another group of EDs, induce seminiferous tubule degeneration with impaired spermatogenesis via disruption of gene expression that regulates cholesterol and lipid homeostasis resulting in low T. Bisphenol A, a strong exogenous estrogen with antiandrogen effect, lowers serum follicle-stimulating hormone, luteinizing hormone, and T, resulting in impaired development of seminiferous tubules and spermatogenesis. Di(2-ethylhexyl) phthalates can exert their antiandrogenic action by directly inhibiting testosterone biosynthesis via cytochrome P-450 dysfunction. Since these EDs are commonly found in plastic bottles, cosmetics, pesticides, some metal food cans, etc., and accumulate in the environment, it is very important to observe caution and avoid their exposure. This updated chapter also reviews the impact of COVID-19-related infection on male reproduction.

The Role of Environmental Toxicant-Induced Oxidative Stress in Male Infertility

Infertility is a serious public health issue affecting around 15% of couples globally. Of the 60-80 million people of reproductive age affected by infertility, 40-50% are due to male factor while 30-40% of cases are still idiopathic. The recent global deterioration in sperm quality raises apprehensions regarding the toxic effects of environmental pollutants on reproductive health of males. Environmental toxicants have shown strong evidences for inducing oxidative stress affecting spermatogenesis severely, thereby leading to reduced sperm motility, count, and DNA damage. Reactive oxygen species (ROS) influences the spermatozoa development and transit process both internally and externally. Low level of ROS is indispensable for critical physiological sperm processes like sperm capacitation, motility, acrosome reaction, hyper-activation, sperm-oocyte interaction, etc., while excessive ROS disrupt antioxidant molecules which is detrimental to normal functioning of the sperm. Hence, identification of potential environmental toxicant may have clinical relevance for early screening and diagnosis of male infertility.

A comparative study based on activity, conformation and computational analysis on the inhibition of human salivary aldehyde dehydrogenase by phthalate plasticizers: Implications in assessing the safety of packaged food items

Phthalate plasticizers are commonly used in various consumer-end products. Human salivary aldehyde dehydrogenase (hsALDH) is a detoxifying enzyme which defends us from the toxic aldehydes. Here, the effect of phthalates [Di-2-ethylhexyl phthalate (DEHP), Diethyl phthalate (DEP) and Dibutyl phthalate (DBP)] on hsALDH has been investigated. These plasticizers inhibited hsALDH, and the IC₅₀ values were 0.48 ± 0.04, 283.20 ± 0.09 and 285.00 ± 0.14 μM for DEHP, DEP and DBP, respectively. DEHP was the most potent inhibitor among the three plasticizers. They exhibited mixed-type linear inhibition with inclination towards competitive-non-competitive inhibition. They induced both tertiary and secondary structural changes in the enzyme. Quenching of intrinsic hsALDH fluorescence in a constant manner was observed with a binding constant (K_b) of 8.91 × 10⁶, 2.80 × 10⁴, and 1.31 × 10⁵ M^-1, for DEHP, DEP and DBP, respectively. Computational analysis showed that these plasticizers bind stably in the proximity of hsALDH catalytic site, reciprocating via non-covalent interactions with some of the amino acids which are evolutionary conserved. Therefore, exposure to these plasticizers inhibits hsALDH which increases the risk of aldehyde induced toxicity, adversely affecting oral health. The study has implications in assessing the safety of packaged food items which utilize phthalates.

Comprehensive Insight from Phthalates Occurrence: From Health Outcomes to Emerging Analytical Approaches

Phthalates are a group of chemicals used in a multitude of important industrial products (e.g., medical devices, children's toys, and food packages), mainly as plasticizers to improve mechanical properties such as flexibility, transparency, durability, and longevity of polyvinyl chloride (PVC). The wide occurrence of phthalates in many consumer products, including foods (e.g., bottled water, soft drinks, wine, milk, and meat) brings that most people are exposed to phthalates every day, which raises some concerns. Adverse health outcomes from phthalates exposure have been associated with endocrine disruption, deformities in the human reproductive system, increased risk of preterm birth, carcinogen exposure, among others. Apprehension related to the health risks and ubiquitous incidence of phthalates in foods inspires the development of reliable analytical approaches that allow their detection and quantification at trace levels. The purpose of the current review is to provide information related to the presence of phthalates in the food chain, highlighting the health risks associated with their exposure. Moreover, an overview of emerging extraction procedures and high-resolution analytical approaches for a comprehensive quantification of phthalates is presented.

Application of cell-based assays for toxicity characterization of complex wastewater matrices: Possible applications in wastewater recycle and reuse

Exposure to pre-concentrated inlet or outlet STP wastewater extracts at different concentrations (0.001% to 1%) induced dose-dependent toxicity in MCF-7 cells, whereas drinking water extracts did not induce cytotoxicity in cells treated. GC-MS analysis revealed the occurrence of xenobiotic compounds (Benzene, Phthalate, etc.) in inlet/outlet wastewater extracts. Cells exposed to inlet/outlet extract showed elevated levels of reactive oxygen species (ROS: inlet: 186.58%, p<0.05, outlet, 147.8%, p<0.01) and loss of mitochondrial membrane potential (Δψm: inlet, 74.91%, p<0.01; outlet, 86.70%, p<0.05) compared to the control. These concentrations induced DNA damage (Tail length: inlet: 34.4%, p<0.05, outlet, 26.7%, p<0.05) in treated cells compared to the control (Tail length: 7.5%). Cell cycle analysis displayed drastic reduction in the G1 phase in treated cells (inlet, G1:45.0%; outlet, G1:58.3%) compared to the control (G1:67.3%). Treated cells showed 45.18% and 28.0% apoptosis compared to the control (1.2%). Drinking water extracts did not show any significant alterations with respect to ROS, Δψm, DNA damage, cell cycle and apoptosis compared to the control. Genes involved in cell cycle and apoptosis were found to be differentially expressed in cells exposed to inlet/outlet extracts. Herein, we propose cell-based toxicity assays to evaluate the efficacies of wastewater treatment and recycling processes.

Potential effects of low molecular weight phthalate esters (C16H22O4 and C12H14O4) on the freshwater fish Cyprinus carpio

The aim of the present study is to assess the toxic effect of dibutyl phthalate (DBP) and diethyl phthalate (DEP) on the freshwater fish Cyprinus carpio. The median lethal concentrations of DBP and DEP for 96 h are found to be 35 and 53 mg L-1, respectively. Fish were exposed to 3.5 mg L-1 (Treatment I) and 1.75 mg L-1 (Treatment II) of DBP and 5.3 mg L-1 (Treatment I) and 2.65 mg L-1 (Treatment II) of DEP for a period of 35 days. The DBP and DEP exposed fish show a concentration based toxic effect on the selected parameters of this study. The hematological parameters, such as hemoglobin (Hb), hematocrit (Hct) and erythrocyte (RBC), were found to decrease in the DBP and DEP treated fish, whereas their leucocyte (WBC) count increased compared to that of the control groups. A biphasic response is noted in the erythrocyte indices, such as mean cellular volume (MCV), mean cellular hemoglobin (MCH) and mean cellular hemoglobin concentration (MCHC), throughout the study period. Exposure to DBP and DEP caused a significant (p < 0.05) decrease in sodium (Na+), potassium (K+), and chloride (Cl-) levels in the gill and brain of the fish throughout the study period when compared to that of their respective controls. The plasma protein level decreased in all the treatments, whereas the plasma glucose level significantly increased in the DBP and DEP exposed fish. Maximum inhibition of Na+/K+-ATPase activity was noticed in the gill and brain of the fish exposed to DBP and DEP. The cholinesterase (ChE) activity in the brain of the fish significantly decreased throughout the study period. A significant (p < 0.05) increase in glutamate oxaloacetate transaminase (GOT) and glutamic pyruvate transaminase (GPT) activity was noted in the fish exposed to both toxicants. The antioxidant enzymatic parameters such as superoxide dismutase (SOD) and catalase (CAT) activities were found to decrease in the gill and liver of the DBP and DEP treated fish, whereas a significant (p < 0.05) increase in lipid peroxidation (LPO) was observed. The above mentioned parameters could be used as potential biomarkers in clinical trials for the assessment of plasticizers. This study provides indispensable information towards future research on the effect of plasticizers on non-target organisms including humans.

Environmental exposure to human carcinogens in teenagers and the association with DNA damage

BACKGROUND

We investigated whether human environmental exposure to chemicals that are labeled as (potential) carcinogens leads to increased (oxidative) damage to DNA in adolescents.

MATERIAL AND METHODS

Six hundred 14-15-year-old youngsters were recruited all over Flanders (Belgium) and in two areas with important industrial activities. DNA damage was assessed by alkaline and formamidopyrimidine DNA glycosylase (Fpg) modified comet assays in peripheral blood cells and analysis of urinary 8-hydroxydeoxyguanosine (8-OHdG) levels. Personal exposure to potentially carcinogenic compounds was measured in urine, namely: chromium, cadmium, nickel, 1-hydroxypyrene as a proxy for exposure to other carcinogenic polycyclic aromatic hydrocarbons (PAHs), t,t-muconic acid as a metabolite of benzene, 2,5-dichlorophenol (2,5-DCP), organophosphate pesticide metabolites, and di(2-ethylhexyl) phthalate (DEHP) metabolites. In blood, arsenic, polychlorinated biphenyl (PCB) congeners 118 and 156, hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and perfluorooctanoic acid (PFOA) were analyzed. Levels of methylmercury (MeHg) were measured in hair. Multiple linear regression models were used to establish exposure-response relationships.

RESULTS

Biomarkers of exposure to PAHs and urinary chromium were associated with higher levels of both 8-OHdG in urine and DNA damage detected by the alkaline comet assay. Concentrations of 8-OHdG in urine increased in relation with increasing concentrations of urinary t,t-muconic acid, cadmium, nickel, 2,5-DCP, and DEHP metabolites. Increased concentrations of PFOA in blood were associated with higher levels of DNA damage measured by the alkaline comet assay, whereas DDT was associated in the same direction with the Fpg-modified comet assay. Inverse associations were observed between blood arsenic, hair MeHg, PCB 156 and HCB, and urinary 8-OHdG. The latter exposure biomarkers were also associated with higher fish intake. Urinary nickel and t,t-muconic acid were inversely associated with the alkaline comet assay.

CONCLUSION

This cross-sectional study found associations between current environmental exposure to (potential) human carcinogens in 14-15-year-old Flemish adolescents and short-term (oxidative) damage to DNA. Prospective follow-up will be required to investigate whether long-term effects may occur due to complex environmental exposures.