The Embryolethality of Lipopolysaccharide in CD-1 and Metallothionein I-II Null Mice: Lack of a Role for Induced Zinc Deficiency or Metallothionein Induction

Abstract

Lipopolysaccharide (LPS) is embryolethal in CD-1 mice. LPS induces metallothionein (MT) via cytokines, including TNF-alpha, IL-1, and IL-6, which initiate and maintain the acute phase response. Maternal hepatic MT induction in pregnant rats, by diverse toxicants, can result in maternal hypozincemia and subsequent embryonal zinc (Zn) deficiency. We examined the hypothesis that LPS causes embryo toxicity in CD-1 mice via MT induction and subsequent embryo Zn deficiency by (1) determining whether LPS induces maternal hepatic MT and causes Zn redistribution, (2) assessing the effects of maternal Zn supplementation on LPS developmental toxicity, and (3) assessing the role of MT with MT I-II null mice (MTKO). Timed pregnant CD-1 mice were dosed i.p. with LPS (S. typhimurium) (0.05 mg/kg) on gestation day (gd) 9. Zn supplementation was administered on gd 8 (10 mg/kg, pretreatment) or on gd 9 as a cotreatment (5 or 10 mg/kg). MTKO and wild type (WT) mice were dosed with LPS (0.05 or 0.1 mg/kg) on gd 9, and maternal liver MT and Zn and plasma Zn were measured. In CD-1 mice, maternal hepatic MT was elevated 24 h after LPS treatment, and cotreatment with Zn caused further elevation of MT. Maternal hepatic Zn concentrations paralleled hepatic MT concentrations. Maternal plasma Zn on gd 10 showed no consistent effect of LPS treatment or Zn cotreatment on gd 9. Zn pretreatment (10 mg/kg) on gd 8 did not ameliorate LPS embryolethality, while Zn cotreatment (5 or 10 mg/kg) on gd 9 exacerbated the toxicity of LPS. LPS produced a similar incidence of embryolethality in MTKO and WT strains on gd10. Plasma Zn concentrations were similar in both strains, while hepatic Zn concentrations were significantly higher in WT than in the MTKO strain. In conclusion, while LPS can induce maternal hepatic MT and Zn redistribution in CD-1 mice, this does not appear to be a key mechanism leading to LPS embryotoxicity.

Peculiarities of the Molecular Structure and Functions of Metallothioneins in the Central Nervous System

“…Insufficiency of MTs results in restriction of antioxidant defense and, according to the principle of chain reactions, leads to activation of lipid peroxidation, protein nitrooxidation, and oxidation of DNA. Altogether, these effects result in mass death of neurons [55,56].…”

Critical evaluation of current developmental toxicity testing strategies: a case of babies and their bathwater

“…Relative to in vitro systems which typically represent one or a few discrete aspects of this complex biology, another major advantage of whole animal models is the ability to assess toxicity driven by interactions between distant organs and/or tissues. For example, lipopolysaccharide was not directly toxic to cultured mouse embryos, yet it caused placental infarction and embryo death when administered to pregnant mice, perhaps due to consequences from the induction of the acute phase response resulting in increased maternal serum levels of Tumor Necrosis Factor‐α, among other cytokines (Leazer et al, 2003). A related maternally mediated mode of toxic action that is relevant to a diverse range of chemicals involves a cascade initiated by maternal tissue damage and associated induction of a maternal acute phase response.…”

Maternal Obesity Does Not Exacerbate the Effects of LPS Injection on Pregnancy Outcomes in Mice

“…We hypothesized that the immunological changes caused by this HFD could exacerbate the inflammatory effects of infection. Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, is frequently used to induce inflammation in mice, and injection around gestational day (GD) 7-9 of pregnancy (where the day after mating is day 0) increases the rate of fetal resorption [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] and reduces fetal weight [ 14 , 19 ]. Few studies have combined HFD and LPS during pregnancy [ 21 , 22 ], but these examined adult offspring phenotypes rather than pregnancy outcomes and did not begin the HFD prior to pregnancy to induce maternal obesity.…”