Interferences of gestational exposure to di-n-butyl phthalate and of the excessive intake of saturated lipids on the gerbil prostate: histopathological alterations and mechanisms involved

Abstract

High intake of saturated lipids and exposure to endocrine disrupting chemicals (EDC) are two environmental factors that the current population is exposed and which have negative effects on the development and maintenance of male reproductive system. Di-n-butyl phthalate (DBP) is an EDC widely used in several products, such as food packaging and building products. The DBP deregulates the organogenesis of the male reproductive system when administrated during fetal development, impairing the formation of androgen-dependent organs. However, its impact on the development and consequences for the morphophysiology of the prostate are still few known. The intake of high lipid content also affects the homeostasis of steroid hormones, causing serious damages to fertility and increasing the risk of prostate cancer. Exposure to phthalates and other EDC has been implicated in the etiology of obesity, because these substances act as metabolic disruptors altering the adipocyte differentiation and lipid metabolism. Thus, it becomes relevant to investigate in experimental studies if the gestational exposure to DPB affects the adiposity and the prostate homeostasis at adulthood, as well as the possible interferences of the excessive intake of saturated lipids, in these parameters and in the effects caused by exposure to DBP. Thus, this study aims to investigate the consequences of gestational exposure to high doses of DBP on the prostate histology of male gerbils at adulthood and incidence of pathological lesions, combined or not to excessive intake of saturated lipids throughout the life. For this, adult gerbils (20 weeks) were born from mothers fed standard chow and treated or not with DBP will be used. Half of the offspring from each group will receive, from weaning, chow containing high content of saturated lipids. The DBP will be administrated to mothers, by gavage, from gestational day 8 until 23 at the concentration of 100mg/kg/day. The ventral lobe will be processed for light microscopy and the prostatic response forward exposure to DBP and saturated lipids will be evaluated based on histological, stereological, and morphometric alterations, and in analyses of the incidence and multiplicity of lesions. Additionally, alterations in the levels of cell proliferation and apoptosis will be examined, by immunocytochemistry to PCNA and TUNEL assay, followed by quantitative analyses. To clarify the mechanisms involved in prostatic response to DBP and saturated lipids intake, some analyses will be performed, namely: 1) determination of serum levels of testosterone and estradiol; 2) analyses, by Western blotting (WB), of the expression of AR and ER² receptors, and frequency of cells expressing these receptors in the prostate; 3) determination of the adiposity index, serum levels of leptin and lipid profile; 4) evaluation of the expression of liver X a (LXRa) and peroxisome proliferator-activated ³ (PPAR³) receptors, and cells expressing the same in the prostate; 5) evaluation of signaling pathways involved in the response to insulin and in cellular survival and metabolism, as the PI3K/Akt/mTOR and MEK/ERK pathways, by the estimative of the percentage of phosphorylated and non-phosphorylated proteins by WB; 6) analysis of the content in the serum and prostate of inflammatory response mediators such as IL-1² e IL-6, and of the growth factors TNF-± and IGF-1, by multiplex assays. This study will bring new informations about the toxicology effects of DBP on the prostate of this rodent and also the excessive intake of saturated lipids, besides respond if this habit interferes in data caused by gestational exposure to this phthalate. The elucidation of the cellular mechanisms involved in prostatic response to these environmental factors will probably be useful for the interpretation of modulator factors in the installation and progression of human prostate cancer. (AU)