Species-Specific Dibutyl Phthalate Fetal Testis Endocrine Disruption Correlates with Inhibition of SREBP2-Dependent Gene Expression Pathways

Abstract

Fetal rat phthalate exposure produces a spectrum of male reproductive tract malformations downstream of reduced Leydig cell testosterone production, but the molecular mechanism of phthalate perturbation of Leydig cell function is not well understood. By bioinformatically examining fetal testis expression microarray data sets from susceptible (rat) and resistant (mouse) species after dibutyl phthalate (DBP) exposure, we identified decreased expression of several metabolic pathways in both species. However, lipid metabolism pathways transcriptionally regulated by sterol regulatory element-binding protein (SREBP) were inhibited in the rat but induced in the mouse, and this differential species response corresponded with repression of the steroidogenic pathway. In rats exposed to 100 or 500 mg/kg DBP from gestational days (GD) 16 to 20, a correlation was observed between GD20 testis steroidogenic inhibition and reductions of testis cholesterol synthesis endpoints including testis total cholesterol levels, Srebf2 gene expression, and cholesterol synthesis pathway gene expression. SREBP2 expression was detected in all fetal rat testis cells but was highest in Leydig cells. Quantification of SREBP2 immunostaining showed that 500 mg/kg DBP exposure significantly reduced SREBP2 expression in rat fetal Leydig cells but not in seminiferous cords. By Western analysis, total rat testis SREBP2 levels were not altered by DBP exposure. Together, these data suggest that phthalate-induced inhibition of fetal testis steroidogenesis is closely associated with reduced activity of several lipid metabolism pathways and SREBP2-dependent cholesterologenesis in Leydig cells.

Retraction: <i>In utero</i>-exposed di(<i>n</i>-butyl) phthalate induce dose dependent, age-related changes of morphology and testosterone-biosynthesis enzymes/associated proteins of Leydig cell mitochondria in rats

“…Testosterone gets produced by steroidogenesis enzymes/associated proteins located in the LC mitochondrion (Mt) and smooth endoplasmic reticulum (sER). LC viability and testosterone production are critical during fetal development for male sexual differentiation, and postnatally for initiation and maintenance of spermatogenesis, and expression of male secondary sex characteristics (Johnson et al, 2011(Johnson et al, , 2012. Recently we reported, following prenatal DBP oral exposure to rats, a significant LC-sER decrease in postpuberty rats , but the detailed morphological alterations of LC-Mt remained ambiguous.…”

“…As a function of the alcohol chain length, they may be separated into two distinct groups: i) low molecular-weight phthalates containing three to six carbons in the ester functionality, and ii) high molecular-weight phthalates that contain greater than six carbons in the ester functionality (Blount et al, 2000;Barlow and Foster, 2003;Barlow et al, 2004). Phthalates are used to impact product flexibility, durability, transparency, and longevity; and are present in many common products; children's toys, cosmetics, detergents, electronics, food packaging, paints, personal care products, pharmaceuticals, and waxes (Wolf et al, 1999;OSHA, 2009;Hannas et al, 2011;Johnson et al, 2011Johnson et al, , 2012Guo et al, 2013). The fact that phthalates are present in many products means that their inherent human exposures and health-risk assessments are a concern.…”

Di (2-ethylhexyl) phthalate exposure during pregnancy disturbs temporal sex determination regulation in mice offspring

“…However, the mode of action of DEHP in mice seems to be different from that in rats. Several studies found that mouse testosterone production was unaffected by phthalate exposure (Johnson et al, 2011;van den Driesche et al, 2012). However, some researchers found that the reproductive disorder of fetal mouse were induced by in utero phthalate exposure, including induced multinucleated germ cells (MNGs), increased seminiferous cord diameters, and altered expression of thousands of fetal testis genes (Gaido et al, 2007;Johnson et al, 2011;Lehraiki et al, 2009).…”

“…Several studies found that mouse testosterone production was unaffected by phthalate exposure (Johnson et al, 2011;van den Driesche et al, 2012). However, some researchers found that the reproductive disorder of fetal mouse were induced by in utero phthalate exposure, including induced multinucleated germ cells (MNGs), increased seminiferous cord diameters, and altered expression of thousands of fetal testis genes (Gaido et al, 2007;Johnson et al, 2011;Lehraiki et al, 2009). A recent study found that dipentyl phthalate (DPeP) significantly reduced testosterone production by 25-30% at a dose level that did not induce any maternal or fetal toxicity in mice, but the 50% effective dose for this effect was about fourfold higher than in the rat (Furr et al, 2014).…”

Dose-dependent short-term study of di-n-butyl phthalate on the testicular antioxidant system of Wistar rats

“…c and d Same at higher magnification showing degeneration and loss of germ cells and Sertoli cells with evident granulation and vacuolization of the cytoplasm as well as degeneration of Leydig cells. H&E ×1,in Leydig cells(Johnson et al 2011) with PPARα probably acting as an indirect transrepressor of steroidogenic factor 1 (SF1) on steroidogenic genes(Plummer et al 2013). However,Hu et al (2013) reported that the lowdose MBP-a metabolite of DBP enhanced SF1 regulation on steroidogenic acute regulatory protein (StAR) which although is modulated by numerous transcription factors induced steroidogenesis whileNair et al (2008) observed decline in serum testosterone production.…”