Vimentin-Mediated Steroidogenesis Induced by Phthalate Esters: Involvement of DNA Demethylation and Nuclear Factor κB

Abstract

Di-n-butyl phthalate (DBP) and its active metabolite, monobutyl phthalate (MBP) are the most common endocrine disrupting chemicals. Many studies indicate that high-doses of DBP and/or MBP exhibit toxicity on testicular function, however, little attention have been paid to the effects of low levels of DBP/MBP on steroidogenesis. As we all know, the steroidogenic acute regulatory protein (StAR) is a key regulator involved in the steroidogenesis. Here we found that, in addition to StAR, MBP/DBP increased the steroidogenesis by a cytoskeletal protein, vimentin. Briefly, in murine adrenocortical tumor (Y1) and the mouse Leydig tumor (MLTC-1) cells, vimentin regulated the secretion of progesterone. When these two cells were exposure to MBP, the DNA demethylation in the vimentin promoter was observed. In addition, MBP also induced the activation of nuclear factor kappa B (NF-κB, a transcriptional regulator of vimentin). These two processes improved the transcriptional elevation of vimentin. Knockdown of NF-κB/vimentin signaling blocked the DBP/MBP-induced steroidogenesis. These in vitro results were also confirmed via an in vivo model. By identifying a mechanism whereby DBP/MBP regulates vimentin, our results expand the understanding of the endocrine disrupting potential of phthalate esters.

Adult Exposure to Di-N-Butyl Phthalate (DBP) Induces Persistent Effects on Testicular Cell Markers and Testosterone Biosynthesis in Mice

“…In Sertoli cells, vimentin has a critical role in spermatogenesis and maintaining the structural integrity of the seminiferous epithelium [ 23 , 32 ]. Consistent with our results, it has been shown in vitro that exposure to the DBP metabolite monobutyl phthalate (MBP) upregulated vimentin expression in the murine Y1 and MLTC-1 tumour cell lines [ 33 ]. The increased vimentin expression resulted from activation of the NF-kB pathway and demethylation of the vimentin promoter [ 33 ].…”

“…Consistent with our results, it has been shown in vitro that exposure to the DBP metabolite monobutyl phthalate (MBP) upregulated vimentin expression in the murine Y1 and MLTC-1 tumour cell lines [ 33 ]. The increased vimentin expression resulted from activation of the NF-kB pathway and demethylation of the vimentin promoter [ 33 ]. In rats, it has been shown that in utero (GD 12–20) exposure to 500 mg/kg/day DBP-induced transient effects on vimentin cytoskeleton organization indicating abnormal contact between Sertoli and germ cells in fetal life [ 34 ].…”

Nonmonotonic Effects of Chronic Low-Dose Di(2-ethylhexyl) Phthalate on Gonadal Weight and Reproductive

“…The suggested mechanisms which affects reproductive function are various including follows: an anti-androgenicity ( Latini et al, 2003 ; Akingbemi et al, 2004 ), suppressor of the expression of steroidogenesis related factors and activation of PPARs ( Borch et al, 2006 ; Howdeshell et al, 2007 ; Wilson et al, 2008 ), activator of caspanse-3 in specific cells through deacetylation of SP3 ( Guida et al, 2014 ), and inducing agent of inflammation ( Ferguson et al, 2012 ). Recently a suggested mechanisms of phthalate is the role of low dose of phthalate as androgen effects on steroidogenesis but high doses as antiandrogen action ( Fan et al, 2010 ; Li et al, 2016 ; Liu et al, 2017 ).…”

NF-κB-vimentin is involved in steroidogenesis stimulated by di-n-butyl phthalate in prepubertal female rats

“…In the recent past, the role of NF-κB in the interference with male steroidogenesis of DBP/MBP was verified in vivo and in vitro in our lab. 53,54 Accordingly, exposure to DBP/MBP could induce p-p65 upregulation and then improve the elevation of vimentin expression and progesterone production in steroidogenic tissues.…”