Nonylphenol induces the death of neural stem cells due to activation of the caspase cascade and regulation of the cell cycle

Abstract

Endocrine disruptors (EDs) are a great concern throughout the world, because they have adverse effects on human health and wildlife. In the present study, we investigated the effects of EDs on the proliferation and survival of murine neural stem cells (NSCs). In contrast to bisphenol A, phthalic acid benzyl n-butyl ester, phthalic acid di-n-butyl ester and phthalic acid di(2-ethylhexyl) ester, the treatment of NSCs with 4-nonylphenol for 24 h inhibited cell growth in a concentration-dependent manner. In addition, treatment with 4-nonylphenol resulted in nuclear condensation and DNA fragmentation (morphological changes due to apoptosis) in NSCs after 12 h of exposure, and activated caspase-3 after 6 h and 9 h of exposure. Furthermore, an exposure to 4-nonylphenol led to the accumulation of cells at the G 2 /M phase interface and down-regulated the protein levels of cyclin A and B1, which are the major regulatory proteins at the G 2 to M transition of the cell cycle. Together, these results indicate that, in contrast to other EDs, 4-nonylphenol may exhibit a potent cytotoxicity through apoptosis via the caspase cascade and cell cycle arrest at the G 2 /M phase, and suggest that 4-nonylphenol may affect neurogenesis in the CNS. Keywords: apoptosis, cell cycle, central nervous system, endocrine disruptors, neural stem cells, 4-nonylphenol. There have been many reports concerning the adverse effects of endocrine disruptors (EDs) on wildlife, human health and the environment, including defects in reproductive function and immune function or behavior and causing cancer (Smialowicz et al. 1989;Pinter et al. 1990;Weiss 1998;Ohtani et al. 2000;Cupp et al. 2001). Most of the adverse effects of EDs reported previously have targeted the reproductive system. The principal mechanism for the effect of EDs on the reproductive system may be mediated through binding the estrogen receptor or androgen receptor, and mimicking the effects of estrogen and antagonizing the effects of androgen, which disrupts the normal effects of the sex hormones (Kelce et al. 1998;Sonnenschein and Soto 1998). However, other potential adverse effects, particularly on the development CNS, have not been examined extensively. A high concentration of EDs exists in the environment, including bisphenol A (BPA), which is used in polycarbonate plastics or dental resin-based composites, 4-nonylphenol (4-NP), which is used in surfactants or plastic and petroleum processing, and phthalate esters, which are used as plasticizers in polyvinylchloride applications or nitrocellulose Address correspondence and reprint requests to K. Wada, Department of Pharmacology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. E-mail: kwada@dent.osaka-u.ac.jpAbbreviations used: BBP, phthalic acid benzyl n-butyl ester; BPA, bisphenol A; CNS, central nervous system; DBP, phthalic acid di-n-butyl ester; DEHP, phthalic acid di(2-ethylhexyl) ester; DEVD-AMC, AspGlu-Val-Asp-7-amino-4-metyl-coumarin; EDs, endocrine disruptors; ERs, estrog...

Stage-Related Increase in the Proportion of Apoptotic Germ Cells and Altered Frequencies of Stages in the Spermatogenic Cycle Following Gestational, Lactational, and Direct Exposure of Male Rats to p-Nonylphenol

“…A body of evidence from mainly in vitro studies, however, has demonstrated the estrogenicity (Soto et al, 1991 ;Vivacqua et al, 2003 ;White et al, 1994 ), cell proliferative-inducing (Masuno et al, 2003 ;Miura et al, 2005 ;Soto et al, 1991 ) and caspase-dependent death-inducing (Kudo et al, 2004 ;Yao et al, 2006 ) effects of weak estrogenic chemicals such as alkylphenolic compounds (e.g., nonylphenol and octylphenol). Nonylphenol production, which in the United States was 147 million pounds in 1980 and grew to over 230 million pounds in 2000 (Blankenship and Coady, 2005 ), are for diverse uses, ranging from industrial detergents and wetting agents to pesticides, hair dyes, and intravaginal spermicides (Bolt et al, 2001 ).…”

Actions of endocrine-disrupting chemicals on stem/progenitor cells during development and disease

“…This study suggested that modulation of NSC 'stemness', growth, and differentiation was EDC dependent. Furthermore, NSCs in the early stages of differentiation were more sensitive to endocrine disruption than undifferentiated neurospheres or differentiated neurons (Kudo et al 2004).…”

“…The EDC 4-NP also regulated neural stem cell (NSC) survival and proliferation (Kudo et al 2004). 4-NP exposure inhibited murine NSC proliferation in a dosedependent manner by inducing G2/M phase arrest, downregulating cyclin A and B1 expression and promoting apoptosis.…”

“…4-NP exposure inhibited murine NSC proliferation in a dosedependent manner by inducing G2/M phase arrest, downregulating cyclin A and B1 expression and promoting apoptosis. Furthermore, 4-NP inhibited the growth of NSCs at a lower concentration when compared with BPA, butyl benzyl phthalate (BBP), di-n-butyl phthalate (DBP), and DEHP (Kudo et al 2004). Interestingly, BPA promoted neurosphere formation and immature neuron cell growth, suggesting that its activity could maintain in part the stem cell characteristics of NSCs.…”

Apoptosis Inducing and Enhancing Activities of Environmental Estrogenic Compounds

“…It is also caused by pathological or environmental factors such as certain viruses, bacteria, radiations, natural compounds, and chemicals. Various EDCs have been reported to induce apoptosis in various types of cells, [2][3][4][5][6][7][8][9][10][11][12][13][14] suggesting that those chemicals exert cell toxicity by triggering the apoptotic signals. However, another possibility that EDCs may enhance or suppress the apoptotic signals induced by physiological or other factors has not been investigated.…”