Mono-(2-ethylhexyl) phthalate (MEHP) induces testicular alterations in male guinea pigs at prepubertal stage

From oxidative imbalance to compromised standard sperm parameters: Toxicological aspect of phthalate esters on spermatozoa

The exponential rise in global male infertility and subfertility-related issues raises severe concern. One of the major contributors is phthalate esters, typical endocrine disruptors affecting millions of lives. The inevitable exposure to phthalates due to their universal application as plasticizers leaves the human population vulnerable to this silent threat. This review explicitly deals with the spermiotoxic effects of different phthalate esters on in vivo and in vitro models and on surveyed human populations to find the most plausible link between global usage of phthalates and poor sperm health. As the free radicals in spermatozoa are prerequisites for their standard structure and functioning, the precise regulation and phthalate-mediated impairment of pro-oxidant:anti-oxidant balance with subsequent loss of structural and functional integrity have also been critically discussed. Furthermore, we also provided future directives, which, if addressed, will fill the still-existing lacunae in phthalate-mediated male reproductive toxicity research.

Toxicokinetics of mono-(2-ethylhexyl) phthalate with low-dose exposure applying fluorescence tracing technique

Di(2-ethylhexyl) phthalate (DEHP) belongs to environmental endocrine disrupting chemicals (EEDCs) and can be rapidly hydrolyzed into the ultimate toxicant mono-2-ethylhexyl phthalate (MEHP). In this study, we used 5-aminofluorescein modified MEHP (MEHP-AF) as a fluorescence tracer to explore the toxicokinetics, including toxicokinetic parameters, absorption and transport across the intestinal mucosal barrier, distribution and pathological changes of organs. While the dose was as lower than 10 mg/kg by intragastric administration, the toxicokinetic parameters obtained by fluorescence microplate method were similar to those with the literatures by chromatography. MEHP-AF can be rapidly absorbed through the intestinal mucosal barrier in rats. In situ organ distribution in mice showed that MEHP-AF was mainly concentrated in the liver, kidney and testis. Our results suggested that the fluorescence tracing technique had the advantages with easy processing, less time-consuming, higher sensitivity for the quantitative determination, In addition, this technology also avoids the interference of exogenous or endogenous DEHP and MEHP in the experimental system. It also can be utilized to the visualization detection of MEHP in situ localization in the absorption organ and the toxic target organ. The results show that this may be a more feasible MEHP toxicological research method.

Phthalate exposure in association with serum hormone levels, sperm DNA damage and spermatozoa apoptosis: A cross-sectional study in China

Exposure to phthalates has been demonstrated to cause reproductive toxicity in animals, but evidence of the association between phthalates and markers of male reproductive function have been inconsistent in human studies. Here we examined whether environmental exposure to phthalates contributes to altered reproductive hormone levels, sperm DNA damage and spermatozoa apoptosis in a Chinese population. From March to June 2013, repeated urine samples collected from male partners of couples attending an infertility clinic in Wuhan, China were analyzed for 8 phthalate metabolites. Associations of the urinary phthalate metabolites with serum hormone levels (n=483), sperm DNA damage parameters (n=509) and spermatozoa apoptosis measures (n=467) were assessed using multivariable linear regression models. After adjusting for potential confounders, mono-(2-ethylhexyl) phthalate (MEHP), a metabolite of di-(2-ethylhexyl)-phthalate (DEHP), was inversely associated with serum levels of estradiol, total testosterone (T) and free T (all P for trend<0.05). Additionally, we found positive dose-response relationships between the percentage of DEHP metabolites excreted as MEHP (%MEHP) and percentages of tail DNA (P for trend<0.05) and between three metabolites of DEHP [MEHP, mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP)] and percentages of Annexin V+/PI- spermatozoa (all P for trend<0.05). Our findings strengthen the emerging evidence that exposure to DEHP may alter hormone levels, disrupt sperm DNA integrity and induce spermatozoa apoptosis.

Mono(2-ethylhexyl) phthalate induces apoptosis in p53-silenced L02 cells via activation of both mitochondrial and death receptor pathways

Mono(2-ethylhexyl) phthalate (MEHP) is one of the main metabolites of di(2-ethylhexyl) phthalate. The evidence shows that DEHP may exert its toxic effects primarily via MEHP, which is 10-fold more potent than its parent compound in toxicity in vitro. MEHP-induced apoptosis is mediated by either p53-dependent or -independent pathway. However, the detailed mechanism of its toxicity remains unclear. In this study, immortalized normal human liver cell line L02 was chosen, as an in vitro model of nonmalignant liver, to elucidate the role of p53 in MEHP-induced apoptosis. The cells were treated with MEHP (6.25, 12.50, 25.00, 50.00, and 100.00 μM) for 24 and 36 h, then small interfering RNA (siRNA) was used to specifically silence p53 gene of L02 cells. The results indicated that MEHP caused oxidative DNA damage and apoptosis in L02 cells were associated with the p53 signaling pathway. Further study found that MEHP (50.00 and 100.00 μM) induced apoptosis in p53-silenced L02 cells, along with the up-regulations of Fas and FasL proteins as well as increased the Bax/Bcl-2 ratio and Caspase 3, 8, and 9 activities. Additionally, both FasL inhibitor (AF-016) and Caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp- fluoromethylketone (Z-VAD-FMK) could prevent the cell apoptosis induced by MEHP. The findings suggested that MEHP-induced apoptosis in L02 cells involving a Caspases-mediated mitochondrial signaling pathway and/or death receptor pathway. p53 was not absolutely necessary for MEHP-induced L02 cell apoptosis.

The effect of mono-(2-ethylhexyl) phthalate on apoptosis of rat ovarian granulosa cells in vitro

Mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of di-(2-ethylhexyl) phthalate (DEHP), is considered to be a reproductive toxicant. This study was performed to evaluate the effect of MEHP on apoptosis of rat ovarian granulosa cells and explore potential mechanism. Granulosa cells were treated with MEHP (0, 25, 50, and 100 μmol/l). Inhibited cell viability and increased apoptosis rate were observed in 50 and 100 μmol/l groups. CASPASE3 activity and BAX expression were significantly raised in all MEHP-treated groups; BCL2 expression was elevated in 25 μmol/l group, while inhibited in 50 and 100 μmol/l groups; BAX/BCL2 ratio was increased in a typical dose-effect relationship. In conclusion, this study showed that MEHP exposure induced cell viability decrease and apoptosis, associated with increase of CASPASE3 activity and BAX/BCL2 ratio. Moreover, CASPASE3 activity showed a reversed dose-dependent effect in MEHP-treated groups, indicating there might exist other CASPASE-independent pathway involved in MEHP-induced apoptosis.

Mono-2-ethylhexyl phthalate stimulates androgen production but suppresses mitochondrial function in mouse leydig cells with different steroidogenic potential

Numerous studies have reported on testicular toxicity of phthalates in different experimental paradigms and showed that Leydig cells (LCs) were one of the main targets of phthalate actions. Adverse effects of phthalates on LCs steroidogenesis have been attributed to their metabolites, monophthalates. This study focuses on investigation whether LCs responsiveness to monophthalates action is associated with their potential to produce androgens. We found that of 3 monophthalates investigated [ie, mono-2-ethylhexyl phthalate (MEHP), mono-n-butyl phthalate, and mono-n-benzyl phthalate] only MEHP caused biological effects on the mouse LCs function. This monophthalate stimulated basal steroidogenesis associated with upregulation of StAR protein expression with no effect on hCG-stimulated androgen production by LCs from CBA/Lac and C57BL/6j mouse genotypes were observed. Further, MEHP attenuated ATP production and increased superoxide generation by both phenotypes of mouse LCs that indicated on mitochondrial dysfunction induced by the monophthalate. All together, our data indicate that MEHP-mediated stimulation of steroidogenesis and perturbation in mitochondrial function are not associated with the capacity of the LCs to synthesize androgens. We suggest that this effect of MEHP observed in LCs of rodent origin needs to be taken into consideration in analysis of earlier start of puberty in boys and may highlight a possible influence of phthalates on reproductive health in males.

Mono-(2-ethylhexyl) phthalate-induced disruption of junctional complexes in the seminiferous epithelium of the rodent testis is mediated by MMP2

Tight junctions between Sertoli cells of the testicular seminiferous epithelium establishes the blood-testis barrier (BTB) and creates a specialized adluminal microenvironment above the BTB that is required for the development of the germ cells that reside there. Actin filament-based anchoring junctions between Sertoli cells and germ cells are important for maintaining close physical contact between these cells as well as regulating the release of mature spermatids into the lumen. Previously, we reported that Sertoli cell injury in rodents after mono-(2-ethylhexyl) phthalate (MEHP) exposure results in the activation of matrix metalloproteinase 2 (MMP2) and increases the sensitivity of germ cells to undergo apoptosis. A disruption in the physical association between Sertoli cells and germ cells and premature loss of germ cells from the seminiferous epithelium has been widely described after phthalate treatment. In this study, we investigate the functional participation of MMP2 in the mechanism underlying MEHP-induced disruption of junction complexes and the resultant loss of germ cells. Exposure of C57BL/6J mice to MEHP (1 g/kg, oral gavage) decreased the expression of occludin in the tight junctions between Sertoli cells and caused gaps between adjacent Sertoli cells as observed by transmission electron microscopy. A reduced expression of laminin-gamma3 and beta1-integrin in apical ectoplasmic specializations between Sertoli cells and germ cells in a time-dependent manner was also observed. Treatment with specific MMP2 inhibitors (TIMP2 and SB-3CT) both in vitro and in vivo significantly suppressed MEHP-induced germ cell sloughing and changes in the expression of these junctional proteins, indicating that MMP-2 plays a primary role in this process. Furthermore, the detachment of germ cells from Sertoli cells appears to be independent of the apoptotic signaling process since MEHP-induced germ cell detachment from Sertoli cells could not be prevented by the addition of a pan-caspase inhibitor (z-VAD-FMK).

Sertoli cell morphological alterations in albino rats treated with etoposide during prepubertal phase

Sertoli cells are very important to spermatogenesis homeostasis because they control germ cell proliferation, differentiation, and death. Damages to Sertoli cells cause germ cell death and affect fertility. Etoposide is a potent chemotherapeutic drug largely used against a variety of cancers. However, this drug also kills normal cells, especially those undergoing rapid proliferation. In the testis, etoposide acts predominantly on intermediate and type B spermatogonia. Etoposide was shown to permanently alter Sertoli cell function when administered to prepubertal rats. Based on this, we decided to investigate whether etoposide can affect Sertoli cell morphology. For this, 25-day-old rats were treated with etoposide during 8 consecutive days and killed at 32, 45, 64, 127, and 180 days old. Testes were fixed in Bouin's liquid or in a mixture of 2.5% glutaraldehyde and 2% formaldehyde for analysis under light and electron microscopes, respectively. Sertoli cells showed morphological alterations such as the presence of chromatin clumps close to the nuclear membrane, nucleus displacement, and cytoplasmic vacuolization. Some Sertoli cells also showed nuclear and cytoplasmic degenerative characteristics, suggesting that etoposide causes severe damages to Sertoli cell.

Disappearance of vimentin in Sertoli cells: a mono(2-ethylhexyl) phthalate effect

The effects of mono(2-ethylhexyl) phthalate (MEHP) on 21-day-old C57Bl/6N mice and their Sertoli cell cultures were studied. Mice were given a single dose of 800 mg/kg MEHP by oral gavage and sacrificed 24 h later. At the same time, testes were harvested from another batch of mice for Sertoli cell cultures. Cultures were subsequently exposed to 0, 1, and 100 nmol/ml MEHP for 0, 3, 6, 12, and 24 h. An antivimentin antibody was used to detect intermediate filament changes in Sertoli cells. Meanwhile, detection of preapoptotic signals and presence of apoptotic cells were done using annexin V-FITC (fluorescein isothiocyanate) and TUNEL (deoxynucleotidyltransferase-mediated dUTP nick end labeling) analyses, respectively. In vivo results showed a correlation between the increase in TUNEL-positive cells and the vimentin disruption in treated mice. Toluidine blue staining of the Sertoli cell cultures showed the increased number and size of vacuoles in Sertoli cell cytoplasm. Vimentin immunohistochemistry showed gradual disappearance of vimentin in Sertoli cell cultures as time and dose increased. Some Sertoli cells were found to be annexin V-FITC positive, but no TUNEL-positive cells were found. Taken together, these results show that the appearance of vacuoles and the vimentin disappearance caused by MEHP in the Sertoli cells are related with each other and can be observed in relation to time. This can be used as an indicator of the loss of mechanical support for spermatogenic cells, which in the end causes apoptosis of spermatogenic cells.

Di-(2-ethylhexyl)phthalate and deep venous thrombosis in children: a clinical and experimental analysis

BACKGROUND

Five children with catheter-related deep venous thrombosis were encountered in our PICU. Three types of polyvinyl chloride tubing for the administration of intravenous solutions were in use (Terumo, Codan, and Perfusend). All were di-(2-ethylhexyl)phthalate plasticized. We suspected problems with the Codan tubing.

METHODS

Different types of tubing at different time intervals in vitro were investigated. Tubing segments were assessed on structural alterations by surface electron microscopy. High-performance liquid chromatography-diode array detection and liquid chromatography-mass spectrometry-diode array detection were performed to identify and to quantify di-(2-ethylhexyl)phthalate. The hospital's minimal clinical data set (coded with the International Classification of Diseases, Ninth Revision, Clinical Modification) was investigated on catheter-related deep venous thrombosis between 2000 and 2004.

RESULTS

Surface electron microscopy demonstrated that the Codan tubing's inner surface was severely altered, showing large particles (34.5 +/- 6.1 microm). High-performance liquid chromatography documented that all Codan samples showed a peak at the di-(2-ethylhexyl)phthalate retention time. The analysis of the minimal clinical data set for total catheter-related deep venous thrombosis showed an unusual high incidence in 2001 (52) compared with the expected 36 per year.

CONCLUSIONS

Such occurrence of catheter-related deep venous thrombosis led to the assumption that disintegration of intravenous tubing resulted in intravenous administration of debris. Our data suggested that the particles derived from the tubing are of such size that they might induce catheter-related deep venous thrombosis. The absence of catheter-related deep venous thrombosis caused by the introduction of submicron inline filters outlines the important pathophysiological role of di-(2-ethylhexyl)phthalate-plasticized particles in the onset of catheter-related deep venous thrombosis. Our data indicate that a considerable number of patients might have been exposed to di-(2-ethylhexyl)phthalate, and a major concern is whether this jeopardized the health of the patients at that time.