Prepubertal Di-n-Butyl Phthalate Exposure Alters Sertoli and Leydig Cell Function and Lowers Bone Density in Adult Male Mice

Abstract

Phthalate exposure impairs testis development and function; however, whether phthalates affect nonreproductive functions is not well understood. To investigate this, C57BL/6J mice were fed 1-500 mg di-n-butyl phthalate (DBP) in corn oil, or vehicle only, daily from 4 to 14 days, after which tissues were collected (prepubertal study). Another group was fed 1-500 mg/kg·d DBP from 4 to 21 days and then maintained untreated until 8 weeks for determination of adult consequences of prepubertal exposure. Bones were assessed by microcomputed tomography and dual-energy X-ray absorptiometry and T by RIA. DBP exposure decreased prepubertal femur length, marrow volume, and mean moment of inertia. Adult animals exposed prepubertally to low DBP doses had lower bone mineral content and bone mineral density and less lean tissue mass than vehicle-treated animals. Altered dynamics of the emerging Leydig population were found in 14-day-old animals fed 100-500 mg/kg·d DBP. Adult mice had variable testicular T and serum T and LH concentrations after prepubertal exposure and a dose-dependent reduction in cytochrome p450, family 11, subfamily A, polypeptide 1. Insulin-like 3 was detected in Sertoli cells of adult mice administered the highest dose of 500 mg/kg·d DBP prepubertally, a finding supported by the induction of insulin-like 3 expression in TM4 cells exposed to 50 μM, but not 5 μM, DBP. We propose that low-dose DBP exposure is detrimental to bone but that normal bone mineral density/bone mineral content after high-dose DBP exposure reflects changes in testicular somatic cells that confer protection to bones. These findings will fuel concerns that low-dose DBP exposure impacts health beyond the reproductive axis.

Cytoprotective potency of naringin against di-n-butylphthalate (DBP)-induced oxidative testicular damage in male rats

“…Testosterone, the main steroid male sex-hormone, is secreted by Leydig cells of the testes under the control of complex neuroendocrine interactions and is responsible for male sexual activity (El-Kashoury et al 2010 ). The present findings revealed a pronounced decrease in serum testosterone level following exposure of male rats to DBP perhaps due to the activation of estrogen receptors (Alam et al 2010 ), direct adverse effect of the DBP on testicular Leydig cells (Bielanowicz et al 2016 ), inhibition of 3β-HSD and 17β-HSD enzyme, which are essential for steroidogenesis and testosterone biosynthesis (Nelli and Pamanji 2017 ), or due to the induction of oxidative stress (Aly et al 2016 ). Evaluation of the sperm quality indices, including sperm motility, sperm count and sperm viability is valuable indicators of the testicular function and the male reproductive performance (Jenardhanan et al 2016 ).…”

“…Recently, many studies suspected the involvement of DBP and other phthalates in male reproductive health problems, mainly due to their endocrine-disrupting effects (Zhou et al 2010 ; 2011 ). Several mechanisms have been implicated in the DBP- induced reproductive disorders, including deterioration of sperm quality (Aly et al 2016 ), male reproductive tract deformities (Liu et al 2016 ), Sertoli and Leydig cell dysfunctions (Bielanowicz et al 2016 ), impairment of male fertility, spermatogenesis and steroidogenesis (Nelli and Pamanji 2017 ), and apoptosis of spermatogenic cells (Alam and Hoque 2018 ). Oxidative stress and lipid peroxidation are the main possible mechanisms by which DBP could induce male reproductive disorders as a result of high polyunsaturated fat content in the membrane of sperm ( Zhou et al 2010 , 2011 ; Nelli and Pamanji 2017 ).…”

Dibutyl phthalate causesMC3T3‐E1cell damage by increasingROSto promote thePINK1/Parkin‐mediated mitophagy

“…Some animal experiments have also confirmed that DBP is toxic to brain, lungs, liver, testes, and kidneys 11–14 . In addition, Bielanowicz et al reported that DBP exposure can reduce femoral length, bone mineral content, and bone mineral density in mice 15 . Pu et al reported that DBP exposure can lead to down‐regulation of bone growth‐related gene expression, achondroplasia disorder, and spinal curvature in zebrafish 16 .…”

“…[11][12][13][14] In addition, Bielanowicz et al reported that DBP exposure can reduce femoral length, bone mineral content, and bone mineral density in mice. 15 Pu et al reported that DBP exposure can lead to down-regulation of bone growth-related gene expression, achondroplasia disorder, and spinal curvature in zebrafish. 16 However, the specific mechanism of skeletal dysplasia caused by DBP has not been studied.…”

Phthalates and bone mineral density: a systematic review

“…Recent animal studies provide experimental evidence of a link between phthalate exposure and inhibitory effects on healthy bone processes and homeostasis in rodents. Two experimental studies found that adult male mice exposed to low dibutyl phthalate (DBP) doses prepubertally [ 10 ] and to di(2-ethylhexyl) phthalate (DEHP) in adulthood [ 11 ] had lower BMD and altered bone microstructure. Additional studies determined that BMD was significantly reduced in ovariectomized mice treated with high doses of DEHP [ 12 ] and in intact mice injected with diisononyl phthalate (DINP) [ 13 ].…”