Impact of quercetin on tight junctional proteins and BDNF signaling molecules in hippocampus of PCBs-exposed rats

Abstract

Polychlorinated biphenyls (PCBs) consist of a range of toxic substances which are directly proportional to carcinogenesis and tumor-promoting factors as well as having neurotoxic properties. Reactive oxygen species, which are produced from PCBs, alter blood-brain barrier (BBB) integrity, which is paralleled by cytoskeletal rearrangements and redistribution and disappearance of tight junction proteins (TJPs) like claudin-5 and occludin. Brain-derived neurotrophic factor (BDNF), plays an important role in the maintenance, survival of neurons and synaptic plasticity. It is predominant in the hippocampal areas vital to learning, memory and higher thinking. Quercetin, a flavonoid, had drawn attention to its neurodefensive property. The study is to assess the role of quercetin on serum PCB, estradiol and testosterone levels and mRNA expressions of estrogen receptor α and β, TJPs and BDNF signaling molecules on the hippocampus of PCBs-exposed rats. Rats were divided into 4 groups of 6 each. Group I rats were intraperitoneally (i.p.) administered corn oil (vehicle). Group II received quercetin 50 mg/kg/bwt (gavage). Group III received PCBs (Aroclor 1254) at 2 mg/kg bwt (i.p). Group IV received quercetin 50 mg/kg bwt (gavage) simultaneously with PCBs 2 mg/kg bwt (i.p.). The treatment was given daily for 30 days. The rats were euthanized 24 h after the experimental period. Blood was collected for quantification of serum PCBs estradiol and testosterone. The hippocampus was dissected and processed for PCR and Western blot; serum PCB was observed in PCB treated animals, simultaneously quercetin treated animals showed PCB metabolites. Serum testosterone and estradiol were decreased after PCB exposure. Quercetin supplementation brought back normal levels. mRNA expressions of estrogen α and β were decreased in the hippocampus of PCB treated rats. TJPS and BDNF signalling molecules were decreased in hippocampus of PCB treated rats. Quercetin supplementation retrieved all the parameters. Quercetin alone treated animals showed no alteration. Thus in PCB caused neurotoxicity, quercetin protects and prevents neuronal damage in the hippocampus.

Keywords: BDNF; GC-MS; PCBs; Quercetin; TJPs.

Figure 1

Effect of quercetin on serum PCBs leves in PCBs-exposed adult rats.

Figure 2

Effect of quercetin on serum testosterone and estradiol of PCBs-exposed adult rats. Each bar represents mean ± SEM of 6 animals. Statistical significance at p<0.05. a- control vs. others; b- quercetin vs. others; c- PCB vs. PCB + quercetin.

Figure 3

Effect of quercetin on mRNA expression of estrogen receptor α and β in hippocampus of PCBs-exposed adult rats. Each bar represents mean ± SEM of 3 independent observations. Statistical significance at p<0.05. a- control vs. others; b- quercetin vs. PCB, PCB + Quercetin; c- PCB vs. PCB + quercetin.

Figure 4

Effect of quercetin on mRNA expression of (tight junctional proteins) Integral membrane and cytoplasmatic accessory proteins in hippocampus of PCBs-exposed adult rats. Each bar represents mean ± SEM of 3 independent observations. Statistical significance at p<0.05. a- control vs. others; b- Quercetin vs. PCB, PCB + quercetin; c- PCB vs. PCB + quercetin.

Figure 5

Effect of quercetin on mRNA expression of BDNF signaling molecules in hippocampus of PCBs-exposed adult rats. Each bar represents mean ± SEM of 3 independent observations. Statistical significance at p<0.05. a- control vs. others; b- Quercetin vs. PCB, PCB + quercetin; c- PCB vs. PCB + quercetin.

Figure 6

Effect of quercetin on on protein expressions of BDNF signaling molecules in hippocampus of PCBs-exposed adult rats. Each bar represents mean ± SEM of 3 independent observations. Statistical significance at p<0.05. a- control vs. others; b- quercetin vs. PCB, PCB + Quercetin; c- PCB vs. PCB + quercetin.