The dynamic assessment of toxicity and pathological process of DEHP in germ cells of male Sprague Dawley rats

DEHP-mediated oxidative stress leads to impaired testosterone synthesis in Leydig cells through the cAMP/PKA/SF-1/StAR pathway

Leydig cells (LCs) injury is often irreversible upon discovery; hence, early identification of risk factors for injury is crucial. The ubiquitous plasticizer di-2-ethylhexyl phthalate (DEHP) in the environment has been shown to potentially cause damage to LCs. However, the underlying mechanisms remain unclear. The present study utilized scRNA-seq analysis, the advantage of which is the ability to explore the characteristics of various testicular cells, combined with studies in vitro and in vivo, to assay the changes in and damage processes of LCs during DEHP exposure. We found that DEHP disrupted the structure and function of LCs. GO analysis suggested that a series of pathways changed, among which the most significant were the "steroid synthesis" and "oxidative stress" pathways. Moreover, DEHP dramatically changed the manner of interaction between LCs and other cells, and the most significant type was the cell-cell contact, which included NECTIN, APP, CADM, and CD39. In addition, the activity of multiple transcription factors (TFs) decreased after DEHP exposure, and the activity of steroidogenic factor 1 (SF-1, Nr5a1) was the most obviously altered. Next, we found that the LCs region indeed experienced oxidative stress, including increased ROS signals, the decreased SOD activity and T-AOC, and increased concentration of 8-OHdG and MDA content. The testosterone level, as well as the expression of StAR, P450scc, and 3β-HSD, was also reduced. To study the association between testosterone synthesis and oxidative stress, the antioxidants N-acetyl-L-cysteine (NAC) and H2O2 were used, and we found that mono-2-ethylhexyl ester (MEHP, a major biometabolite of DEHP) disrupted testosterone synthesis through the inhibition of the cAMP/PKA/SF-1/StAR pathway by inducing oxidative stress. Our study provides new insights into the role and mechanisms of DEHP in LCs injury.

Ca2+ homeostasis imbalance induced by Pparg: A key factor in di (2-ethylhexyl) phthalate (DEHP)-induced cardiac dysfunction in zebrafish larvae

Widespread application of the typical phthalate plasticizers, di (2-ethylhexyl) phthalate (DEHP), poses a serious potential threat to the health of animals and even humans. Previous studies have confirmed the mechanism of DEHP-induced cardiac developmental defects in zebrafish larvae. However, the mechanism of cardiac dysfunction is still unclear. Thus, this work aimed to comprehensively investigate the mechanisms involved in DEHP-induced cardiac dysfunction through computational simulations, in vivo assays in zebrafish, and in vitro assays in cardiomyocytes. Firstly, molecular docking and western blot initially investigated the activating effect of DEHP on Pparg in zebrafish. Although GW9662 (PPARG antagonist) effectively alleviated DEHP-induced cardiac dysfunction and lipid metabolism disorders, it did not restore significant decreases in mitochondrial membrane potential and ATP levels. In vitro assays in cardiomyocytes, DEHP caused overexpression of PPARG and proteins involved in the regulation of Ca2+ homeostasis, and the above abnormalities were effectively alleviated by GW9662, suggesting that the Ca2+ homeostatic imbalance caused by activation of PPARG by DEHP seems to be the main cause of DEHP-induced cardiac dysfunction. To sum up, this work not only refines the mechanism of toxic effects of cardiotoxicity induced by DEHP, but provides an important theoretical basis for enriching the toxicological effects of DEHP.

Long-term exposure to the mixture of phthalates induced male reproductive toxicity in rats and the alleviative effects of quercetin

Phthalates (PEs), such as di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP) could cause reproductive and developmental toxicities, while human beings are increasingly exposed to them at low-doses. Phytochemical quercetin (Que) is a flavonoid that has estrogenic effect, anti-inflammatory and anti-oxidant effects. This study was conducted to assess the alleviative effect of Que. on male reproductive toxicity induced by the mixture of three commonly used PEs (MPEs) at low-dose in rats, and explore the underlying mechanism. Male rats were treated with MPEs (16 mg/kg/day) and/or Que. (50 mg/kg/d) for 91 days. The results showed that MPEs exposure caused male reproductive injuries, such as decreased serum sex hormones levels, abnormal testicular pathological structure, increased abnormal sperm rate and changed expressions of PIWIL1 and PIWIL2. Furthermore, MPEs also changed the expression of steroidogenic proteins in steroid hormone metabolism, including StAR, CYP11A1, CYP17A1, 17β-HSD, CYP19A1. However, the alterations of these parameters were reversed by Que. MPEs caused male reproductive injuries in rats; Que. inhibited MPEs' male reproductive toxicity, which might relate to the improvement of testosterone biosynthesis.

Phthalate exposure with sperm quality among healthy Chinese male adults: The role of sperm cellular function

Adverse male reproduction caused by phthalate ester (PAE) exposure has been well documented in vivo. However, existing evidence from population studies remains inadequate to demonstrate the impact of PAE exposure on spermatogenesis and underlying mechanisms. Our present study aimed to explore the potential link between PAE exposure and sperm quality and the possible mediation by sperm mitochondrial and telomere in healthy male adults recruited from the Hubei Province Human Sperm Bank, China. Nine PAEs were determined in one pooled urine sample prepared from multiple collections during the spermatogenesis period from the same participant. Sperm telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were determined in sperm samples. The sperm concentration and count per quartile increment in mixture concentrations were -4.10 million/mL (-7.12, -1.08) and -13.52% (-21.62%, -4.59%), respectively. We found one quartile increase in PAE mixture concentrations to be marginally associated with sperm mtDNAcn (β = 0.09, 95% CI: -0.01, 0.19). Mediation analysis showed that sperm mtDNAcn significantly explained 24.6% and 32.5% of the relationships of mono-2-ethylhexyl phthalate (MEHP) with sperm concentration and sperm count (β = -0.44 million/mL, 95% CI: -0.82, -0.08; β = -1.35, 95% CI: -2.54, -0.26, respectively). Our study provided a novel insight into the mixed effect of PAEs on adverse semen quality and the potential mediation role of sperm mtDNAcn.

Impacts of di-(2-ethylhexyl) phthalate on Folsomia candida (Collembola) assessed with a multi-biomarker approach

Di-(2-ethylhexyl) phthalate (DEHP) is extensively used as an additive to produce plastics, but it may damage non-target organisms in soil. In this study, the effects of DEHP on Folsomia candida in terms of survival, reproduction, enzyme activities, and DNA damage were investigated in spiked artificial soil using a multi-biomarker strategy. The 7-day LC₅₀ (median lethal concentration) and 28-day EC₅₀ (median effect concentration) values of DEHP were 1256.25 and 19.72 mg a.i. (active ingredient) kg^-1 dry soil, respectively. Biomarkers involved in antioxidant defense including catalase (CAT-catalase), glutathione S-transferases (GST), detoxifying enzymes including acetylcholinesterase (AChE), Cytochrome P450 (CYP450), and peroxidative damage (LPO-lipid peroxide) were also measured (EC₁₀, EC₂₀, and EC₅₀) after exposure for 2, 4, 7, and 14 days. The Comet assay was also applied to assess the level of genetic damage. The activity of CAT and LPO was drastically enhanced by the highest dose (EC₅₀) of DEHP on day two. The activities of GST and AChE in DEHP treatment groups were found to be blocked. In contrast, the activity of CYP450 was significantly enhanced compared to the respective control groups during the first four days of incubation. The Comet assay in F.candida demonstrated that DEHP (EC₅₀) could induce DNA damage. The obtained multi-biomarker data were analyzed using an integrated biomarker response (IBR) index, indicating that limited-time exposure triggered higher stress than long-term exposure at low concentrations of DEHP. These results demonstrate that DEHP may cause biochemical and genetic toxicity to F. candida, which illustrated the potential risks of DEHP in the soil environment and might affect soil ecosystem processes. Further studies are necessary to elucidate the toxic mechanisms of DEHP on other non-target organisms in soil.

mRNA expression and protein-protein interaction (PPI) network analysis of adrenal steroidogenesis in response to exposure to phthalates in rats

Phthalate esters such as di-butyl phthalate (DBP) and di-ethyl hexyl phthalate (DEHP) used in personal care and consumer products and medical devices have potential to affect human health. We studied the effect of DBP and DEHP on critical enzymes of glucocorticoid biosynthesis pathway in the adrenal gland and pro-inflammatory cytokines in the serum in male Wistar rats. DEHP and DBP treatment altered the mRNA expression of enzymes of glucocorticoid biosynthesis pathway accompanied by a reduction in glucocorticoid production and elevation in the level of glucocorticoid regulated pro-inflammatory cytokines indicating a cascading effect of phthalates. The analysis of PPI (protein - protein interaction) network involving Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) of enzymes through STRING database revealed that all the proteins have the maximum level of interaction with the selected number of proteins. The STRING database analysis together with in vivo data indicates the potential effects of phthalates on various targets of steroidogenesis pathway with a global biological impact.

MEHP induces alteration of mitochondrial function and inhibition of steroid biosynthesis in MA-10 mouse tumor Leydig cells

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is widely used in manufacturing. Previous studies have shown that mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of DEHP, has inhibitory effects on luteinizing hormone (LH)-stimulated steroid biosynthesis by Leydig cells. The molecular mechanisms underlying its effects, however, remain unclear. In the present study, we examined the effects of MEHP on changes in mitochondrial function in relationship to reduced progesterone formation by MA-10 mouse tumor Leydig cells. Treatment of MA-10 cells with MEHP (0-300 μM for 24 h) resulted in dose-dependent inhibition of LH-stimulated progesterone biosynthesis. Biochemical analysis data revealed that the levels of the mature steroidogenic acute regulatory protein (STAR), a protein that works at the outer mitochondrial membrane to facilitate the translocation of cholesterol for steroid formation, was significantly reduced in response to MEHP exposures. MEHP also caused reductions in MA-10 cell mitochondrial membrane potential (ΔΨm) and mitochondrial respiration as evidenced by decreases in the ability of the mitochondria to consume molecular oxygen. Additionally, significant increases in the generation of mitochondrial superoxide were observed. Taken together, these results indicate that MEHP inhibits steroid formation in MA-10 cells at least in part by its effects on mitochondrial function.

Intermittent fasting ameliorates di-(2-ethylhexyl) phthalate-induced precocious puberty in female rats: A study of the hypothalamic-pituitary-gonadal axis

Di-(2-ethylhexyl) phthalate has been reported to interfere with the development and function of animal reproductive systems. However, hardly any studies provide methods to minimize or prevent the adverse effects of DEHP on reproduction. The energy balance state of mammals is closely related to reproductive activities, and the reproductive axis can regulate reproductive activities according to changes in the body's energy balance state. In this study, the effects of every other day fasting (EODF), as a way of intermittent fasting, on preventing the precocious puberty induced by DEHP in female rats was studied. EODF significantly improved the advancement of vaginal opening age (as the markers of puberty onset) and elevated serum levels of luteinizing hormone and estradiol (detected by ELISA) induced by 5 mg kg^-1 DEHP exposure (D5). The mRNA and western blot results showed that the EODF could minimized the increase of gonadotropin-releasing hormone expression induced by DEHP exposure. The administration of DEHP could elevate the levels of kisspeptin protein and the number of kisspeptin-immunoreactive neurons in anteroventral periventricular nucleu, and this increase was diminished considerably by EODF treatment. In contrast, the D5 and D0 groups showed no remarkable difference in the level of Kiss1 expression in arcuate nucleus, whereas the D5 + EODF group had a remarkable decrease in kisspeptin expression as compared with the other two groups. Our results indicated that EODF might inhibit the acceleration of puberty onset induced by DEHP exposure via HPG axis.

Exposure to Di-2-ethylhexyl Phthalate and Benign Prostatic Hyperplasia, NHANES 2001-2008

30% of men suffer from benign prostatic hyperplasia (BPH) worldwide. As one of the most important members of Phthalate esters, previous studies suggested ubiquitous Di-(2-ethylhexyl) phthalate (DEHP) exposure is associated with such male disorders by interfering with endocrine system, however, little is known about the association between DEHP exposure and BPH. The objective of this study was to study the potential association by the 2001-2008 National Health and Nutrition Examination Survey (NHANES) data. The data was collected, and multiple logistic regression was adapted to measure the association. The concentrations of DEHP (∑DEHP) were calculated by each metabolite and split into quartiles for analysis. Results showed that the odds ratio (OR) decreased with increased ∑DEHP concentration. In the crude model, the OR for the second quartile (OR = 1.60, 95%CI [1.24, 2.07]) was obviously higher compared with the lowest quartile. However, the OR for the highest quartile (OR = 0.55, 95%CI [0.44,0.69]) was lower than that for the third quartile (OR = 0.77, 95%CI [0.61, 0.97]), and the OR for the third and the highest quartile were significantly lower than that of the lowest quartile, which suggested biphasic effects of DEHP based on concentration. The results showed the same trend after adjusting confounding factors. The study suggested that the DEHP exposure is associated with DEHP, and the results adds limited evidence to study this topic, however, further researches are needed to determine if the status of BPH can be changed by controlling DEHP exposure.