Distribution and accumulation of 10 nm silver nanoparticles in maternal tissues and visceral yolk sac of pregnant mice, and a potential effect on embryo growth.

We examined the distribution of silver in pregnant mice and embryos/fetuses following intravenous injections of 10 nm silver nanoparticles (AgNPs) or soluble silver nitrate (AgNO3) at dose levels of 0 (citrate buffer control) or 66 µg Ag/mouse to pregnant mice on gestation days (GDs) 7, 8 and 9. Selected maternal tissues and all embryos/fetuses from control, AgNP- and AgNO3-treated groups on GD10 and control and AgNP-treated groups on GD16 were processed for the measurement of silver concentrations, intracellular AgNP localization, histopathology and gross examination of tissue morphology. Inductively-coupled plasma mass spectrometry revealed silver in all examined tissues following either AgNP or AgNO3 treatment, with highest concentrations of silver in maternal liver, spleen and visceral yolk sac (VYS), and lowest concentrations in embryos/fetuses. For VYS, mean silver concentration following AgNO3 treatment (4.87 ng Ag/mg tissue) was approximately two-fold that following AgNP treatment (2.31 ng Ag/mg tissue); for all other tissues examined, mean silver concentrations following either AgNP or AgNO3 treatment were not significantly different from each other (e.g. 2.57 or 2.84 ng Ag/mg tissue in maternal liver and 1.61 or 2.50 ng Ag/mg tissue in maternal spleen following AgNP or AgNO3 treatment, respectively). Hyperspectral imaging revealed AgNP aggregates in maternal liver, kidney, spleen and VYS from AgNP-treated mice, but not AgNO3-treated mice. Additionally, one or more embryos collected on GD10 from eight of ten AgNP-treated mice appeared small for their age (i.e. Theiler stage 13 [GD8.5] or younger). In the control group (N = 11), this effect was seen in embryos from only one mouse. In conclusion, intravenous injection of 10 nm AgNPs to pregnant mice resulted in notable silver accumulation in maternal liver, spleen and VYS, and may have affected embryonic growth. Silver accumulation in embryos/fetuses was negligible.

Distribution of silver nanoparticles in pregnant mice and developing embryos.

The objective of this study was to evaluate the distribution of silver nanoparticles (NPs) in pregnant mice and their developing embryos. Silver NPs (average diameter 50 nm) were intravenously injected into pregnant CD-1 mice on gestation days (GDs) 7, 8, and 9 at dose levels of 0, 35, or 66 µg Ag/mouse. Mice were euthanised on GD10, and tissue samples were collected and analysed for silver content. Compared with control animals injected with citrate buffer vehicle, silver content was significantly increased (p < 0.05) in nearly all tissues from silver NP-treated mice. Silver accumulation was significantly higher in liver, spleen, lung, tail (injection site), visceral yolk sac, and endometrium compared with other organs from silver NP-treated mice. Furthermore, silver NPs were identified in vesicles in endodermal cells of the visceral yolk sac. In summary, the results demonstrated that silver NPs distributed to most maternal organs, extra-embryonic tissues, and embryos, but did not accumulate significantly in embryos.

What we know and don't know about the bioeffects of nanoparticles: developing experimental approaches for safety assessment.

The Center for Devices and Radiological Health (CDRH) of the US Food and Drug Administration (FDA) regulates nano-based medical products and therefore is required to address the safety and biological effects of nano-scale materials used in these products. Both in vitro and in vivo toxicological research studies are being conducted at the FDA to help determine the risks versus benefits of these new products. This article will briefly summarize some of the initial research findings from FDA-CDRH studies using TiO(2), polystyrene, and silicon nanoparticles.

Effects of prosthetic materials on the host immune response: evaluation of polymethyl-methacrylate (PMMA), polyethylene (PE), and polystyrene (PS) particles.

The main causes for the long-term prosthetic implants' failure are the body's reaction to the implanted material or mechanical stress on the device resulting in the formation of wear particles. Particulate wear debris attracts macrophages, and depending on the chemical composition of the material and particle size, various levels of inflammatory response may occur. While transient inflammation is common, development of chronic inflammation may have serious consequences, leading to implant failure. Such a process may also cause systemic changes to immune functions and long-term effects on the host immune responses. In this study, we evaluated the effects of polystyrene (PS), polyethylene (PE), and polymethylmethacrylate (PMMA) particles on macrophage function and the generation of T-cell responses. Particles of various diameters were injected intraperitoneally into Balb/c mice, and immune functions were examined at 3, 10, and 21 days after the injection. The intensity of phagocytosis by peritoneal exudate cells (PECs) and the proliferative response of spleen cells from treated mice were evaluated. Enumeration of PECs revealed an increase in the total number of cells. Mice injected with PS or PE particles had a higher percentage of cells containing particles than PMMA-injected mice. Macrophages with PS or PE particles tended to adhere to and/or infiltrate peritoneal fibro-fatty tissues surrounding the spleen and pancreas, while the PMMA-carrying macrophages infiltrated the spleen, resulting in an increase of spleen size and "weight. The spleen cell proliferation assay revealed only mild and transient effects on the mitogen response in both PE and PS particle-injected mice. However, in the PMMA-injected mice we observed a lasting increase of the Con A response and a decrease of the LPS response. In vitro exposure of PECs from untreated mice showed a dose-response pattern in nitric oxide (NO) and TNFalpha production. While exposure to either PMMA or PE induced comparable levels of NO, exposure to PMMA induced a markedly higher production of TNFalpha than exposure to PE. The results indicate that particulate biomaterials may, in addition to the initial activation of phagocytes, significantly affect immune functions and compromise the host response to other antigenic stimuli.

Regulation of uterine hsp90alpha, hsp72 and HSF-1 transcription in B6C3F1 mice by beta-estradiol and bisphenol A: involvement of the estrogen receptor and protein kinase C.

We have previously demonstrated that bisphenol A (BPA)- and beta-estradiol (E2)-induced increases in uterine weight and heat shock protein (hsp) 90alpha and hsp72 levels are mediated through the estrogen receptor (ER). It is not, however, clear if BPA and E2 regulation of hsps is at the transcriptional or post-transcriptional level. Therefore, in this study we examined the ability of BPA and E2 to increase uterine weight and regulate transcription of these hsps and of heat shock factor (HSF)-1 in ovariectomized B6C3F1 mice at 6 or 24 h after a single subcutaneous injection of E2 (1 microg/kg) or BPA (100 mg/kg). The role of the ER and protein kinase C (PKC) in these E2 and BPA effects was evaluated by co-administration of the antiestrogen ICI 182,780 (5 mg/kg) or the PKC inhibitor GF 109203X (0.5 mg/kg), respectively. The results demonstrated ER involvement in uterine weight increases. Uterine hsp mRNA levels are increased by E2 and BPA through a direct effect on their transcription and/or, in the case of E2, through an increase in HSF-1 mRNA. PKC is involved in the BPA-induced increases in hsp90alpha mRNA levels. We conclude that E2 and BPA regulate hsp90alpha and hsp72alpha transcription via similar and distinct pathways.

Increases in mouse uterine heat shock protein levels are a sensitive and specific response to uterotrophic agents.

There is increasing consensus that the uterotrophic estrogenicity assay should be coupled with other morphometric or molecular end points that might enhance its sensitivity. We have previously shown that bisphenol A (BPA), similarly to 17ss-estradiol (E2), increases levels of uterine heat shock proteins (hsps), mainly hsp90alpha and glucose-regulated protein (grp) 94. In this study we investigated whether increases in uterine hsp levels are a specific response of estrogens or estrogen mimics. We therefore examined the ability of a) E2, diethylstilbestrol (DES), and tamoxifen (TAM); b) the xenoestrogens coumestrol (CM), methoxychlor (MXC), BPA, and dibutyl phthalate (DBP); c) the progestin medroxyprogesterone (MED); d) the glucocorticoid dexamethasone (DEX); and e) phytol (PHY), a precursor to a retinoid X and peroxisome proliferator-activating receptor agonist, to increase uterine weights and alter uterine morphology and hsp levels. We showed that DES, TAM, CM, MXC, and BPA significantly increased uterine weights and uterine hsp90alpha and grp94 levels. Even though the doses of CM, MXC, and BPA used were much higher than the E2 dose, those treatments resulted in lower increases in uterine weight. On the other hand, increases in grp94 levels were equal to those induced by E2 treatment. Treatments with MED, DEX, DBP, or PHY did not significantly alter uterine weight or morphology and had no significant effects on uterine hsp levels. The results of this study suggest that only the estrogens increase uterine hsp90alpha and grp94 levels, and that this hsp effect is a more sensitive uterotrophic response than uterine weight increase.

Effects of 17 alpha-methyltestosterone on uterine morphology and heat shock protein expression are mediated through estrogen and androgen receptors.

Testosterone and the synthetic androgen, 17 alpha-methyltestosterone (MT), have been shown to increase uterine weights and alter uterine morphology. However, whereas the mechanism of action of testosterone in the uterus has been studied, it is not known if the actions of MT are mediated through androgen (AR) or estrogen (ER) receptors. In the present study, we have shown that MT, at 0.5 or 10 mg/kg per day, increases uterine weight and alters uterine morphology in a dose-dependent manner. Co-administration of the anti-androgen, flutamide, or the anti-estrogen, ICI 182,780, with MT revealed that the effects of the low dose of MT are mediated through the ER, whereas those of the high dose are mediated through both the ER and AR. In addition, we have studied the effects of MT on uterine heat shock proteins (hsps), a group of estrogen-regulated proteins whose levels increase in response to growth signals and protein damage. MT increased levels of hsp90 alpha, hsp72, and grp94. All effects on uterine hsp levels were antagonized by the anti-estrogen and not the anti-androgen. Collectively, the results of the present study indicate that the effects of MT in the uterus are mediated through the AR and ER.