Oxidative stress increases in liver of lactating rats after BPF-low-dose exposure: perinatal effects in the offspring

Abstract

Bisphenol F (BPF) is replacing Bisphenol A (BPA) in the manufacture of products due to endocrine-disrupting effects. BPF monomers can also be released into the environment and enter the food chain, resulting in human exposure to low doses. Since bisphenols are primarily metabolized by the liver, this organ is more vulnerable to lower doses of bisphenols than others. Exposure during prenatal development may increase the risk of diseases in adulthood. The aim was to evaluate whether BPF administration could generate oxidative stress in liver of lactating rats, and whether these effects may be also observed in female and male postnatal day 6 (PND6) offspring. Long Evans rats received oral treatment: Control, BPF-low-dose (LBPF) 0.0365 mg/kg b.w./day, and BPF-high-dose (HBPF) 3.65 mg/kg b.w./day. The levels of antioxidant enzymes (CAT, SOD, GR, GPx and GST), glutathione system (GSH, GSSG) and lipid damage markers (MDA, LPO) were measured using colorimetric methods in liver of both lactating dams and in PND6 offspring. Mean values were analyzed using Prism-7. LBPF affected liver defense mechanisms (antioxidant enzymes and glutathione system), increasing ROS levels and producing lipid peroxidation in lactating dams. Similar effects were found in female and male PND6 offspring as a consequence of perinatal exposure.

Figure 1

Effects of BPF administration on antioxidant enzymes, glutathione concentrations and oxidative stress biomarkers in liver from lactating dams. (a) Enzymatic activity of catalase (CAT) in nmol/min/mg protein; (b) Superoxide dismutase (SOD) in U/mg protein; (c) Glutathione peroxidase (GPx) in nmol/min/mg protein; (d) Glutathione reductase (GR) in nmol/min/mg protein; and (e) Glutathione S-transferase (GST) in nmol/min/mg protein. (f) Concentration of reduced glutathione (GSH) in nmol/mg protein; (g) Concentration of oxidized glutathione (GSSG) in nmol/mg protein. (h) GSSG/GSH ratio. (i) Malondialdehyde (MDA) content in nmol/mg protein. j) Lipid hydroperoxide (LPO) content in nmol/mg tissue. Data represent mean ± SD. n = 6 lactating control dams; n = 6 lactating LBPF dams; n = 10 lactating HBPF dams (two replicates for each sample). Statistical significance was determined by one-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 compared to Control group. ∇∇P < 0.01, LBPF vs. HBPF.

Figure 2

Effects of BPF administration on antioxidant enzymes in liver from female and male PND6 offspring. (a) Enzymatic activity of catalase (CAT) in nmol/min/mg protein; (b) Superoxide dismutase (SOD) in U/mg protein; (c) Glutathione peroxidase (GPx) in nmol/min/mg protein; d) Glutathione reductase (GR) in nmol/min/mg protein; and (e) Glutathione S-transferase (GST) in nmol/min/mg protein. Data represent mean ± SD. n = 12 female PND6 pups; n = 12 male PND6 pups for each experimental group with two replicates for each sample (control, LBPF and HBPF). Statistical significance was determined by one-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001 compared to Control group. ∇P < 0.05; ∇∇P < 0.01, LBPF vs. HBPF.

Figure 3

Effects of BPF administration on glutathione concentrations and oxidative stress biomarkers in liver from female and male PND6 offspring. (a) Concentration of reduced glutathione (GSH) in nmol/mg protein. b) Concentration of oxidized glutathione (GSSG) in nmol/mg protein. (c) GSSG/GSH ratio. (d) Malondialdehyde (MDA) content in nmol/mg protein. e) Lipid hydroperoxide (LPO) content in nmol/mg tissue. Data represent mean ± SD. n = 12 female PND6 pups; n = 12 male PND6 pups for each experimental group with two replicates for each sample (control, LBPF and HBPF). Statistical significance was determined by one-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 compared to Control group. ∇∇P < 0.01; ∇∇∇P < 0.001, ∇∇∇∇P < 0.0001, LBPF vs. HBPF. ♦ LBPF Female vs. LBPF Male.

Figure 4

Experimental design. Female and male Long Evans rats (F0) were exposed to a low or high dose of BPF (LBPF or HBPF) or control diet from premating until the end of the experiment. Six days after birth and lactation of the pups, lactating dams (F0) and PND6 pups (females and males) were sacrificed to study the oxidant/antioxidant balance in the liver. Endogenous antioxidant agents include enzymes such as superoxide dismutase (SOD), which eliminates the first oxygen free radical (O₂) produced during oxygen utilization, the superoxide anion (O₂⁻.); catalase (CAT), which is responsible for converting hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂); and the main enzymes involved in the glutathione system, glutathione peroxidase (GPx), which catalyzes the elimination of peroxides, such as hydrogen peroxide (H₂O₂), using reduced glutathione (GSH) and converting it to oxidized glutathione (GSSG), glutathione reductase (GR), which recomposes GSH so that it can be used by GPx, and also glutathione-S-transferase (GST), which catalyzes the conjugation of glutathione with xenobiotics, playing a role in the inactivation of free radicals. Figure created with Prism v7 (GraphPad Software, Inc, CA, USA).