Attenuating Effect Of Lycopene On Chromium-induced Developmental Toxicity Of The Chicken Ovary

Chromium is an important raw material in industrial production and is widely used in leather tanning and metal plating.In recent years,the increased usage of chromium and the inappropriate disposal of chromium waste have contributed to the increased pollution of soil and water,which has caused worldwide concern.Hexavalent chromium is a kind of potential toxic heavy metal element and its damage to kidney,liver,cancer and reproductive system has been reported,but its influence on early ovarian development in the chicken is still unclear.Lycopene,as a natural compound in plants,has been well known for its wild biological effects,particularly for its antioxidant(AOX)properties and its application as a feed additive has a very broad prospect.Eggs are the valuable source of dietary proteins for human beings.Laying performance of hens is closely related to the ovarian function and the normal development of follicles.Interruption of various harmful toxicant during follicle development can lead to the reduced laying performance and lower feeding value.In this study,a CrVI-induced damage model of chick ovaries in both vivo and vitro was established to verify the protective effects of lycopene and their related mechanisms.From these studies,we expected to provide theoretic guidance for protecting ovaries from CrVI-induced developmental toxicity and application of lycopene as a feed additive.1.The attenuating effect of lycopene on potassium dichromate-induced damage of the chick ovary in vivoWe first determined the contents of heavy metal elements in different tissues of hyline hens.The results showed that chromium and nickel are the main heavy metal toxicant,and the content of chromium in the ovary was higher than nickel.Subsequently,chicks were exposed to different concentrations of potassium dichromate through gavage in order to the further understanding of the chromium(VI)toxicity.The results showed that after potassium dichromate treatment,the arrangements of the granulosa cells become loose and irregular.potassium dichromate also caused cell morphological changes,follicular degeneration,and decreased proportion of primary follicles.The concentration of 50 mg/kg BW is appropriate for toxicity model in vivo.The appropriate concentration of lycopene treatment(40 mg/kg BW)could inhibit potassium dichromate-induced ovarian injury.The morphology of the ovaries was observed after treatment of lycopene alone,and no significant difference was found.Ultrastructural observation by electron microscopy showed that potassium dichromate treatment could lead to nuclear pyknosis and swelling structure of mitochondria of ovarian cells.Lycopene had protective effects on it.We also find that the decline of cell proliferation and the increase of cell apoptosis in the potassium dichromate-induced damaged ovarian tissues in vivo could be prevented by lycopene.Treatment with lycopene alone did not have obvious effects on cell proliferation or apoptosis in the chick ovaries in vivo.Furthermore,lycopene could rescue the decreased antioxidant capacity by increasing the activities of antioxidases and regulating the transcription level of antioxidant genes(Sod,Cat,Mgst,Gsta)in vivo.In conclusion,lycopene has protective effects on potassium dichromate-induced developmental toxicity of the chick ovary in vivo.2.Lycopene protects the ovary against CrVI-induced ovarian development disorder via activation of Nrf2/HO-1 pathway in vitroIn order to the further understanding of the protective effects of lycopene on CrVI-induced ovarian development disorder and related molecular mechanisms,we first established a CrVI-induced damage model of the chick ovary in vitro,and then explored the appropriate does of lycopene to protect the ovary against CrVI-induced toxicity.We found that the appropriate concentration of hexavalent chromium is 2.5 mg/L and appropriate concentration of lycopene is 200 ng/L in vitro.After the model in vitro is built,we then explored the protective effects of lycopene on cell proliferation,cell apoptosis,and antioxidant capacity in the CrVI-induced damaged ovarian tissues.Results from the BrdU and TUNEL assays show that both the decline of somatic cell proliferation and the increase of cell apoptosis was prevented by lycopene supplementation.We also found the oxidative stress induced by hexavalent chromium had been markedly inhibited in ovarian tissues by lycopene To evaluate the effects of chromium alone,lycopene alone or hexavalent chromium combined with lycopene on the Nrf2/HO-1 pathway in ovarian tissues,the mRNA abundance of Nrf2/HO-1 related downstream genes(Gclc,Gclm,Gsr,Glrx,Txn,Txnrd)were determined The results showed that the downstream genes had been markedly down-regulated by hexavalent chromium and lycopene had protective effects on that.We then treated ovaries with the Nrf2/HO-1 activator(4-Octyl Itaconate)and the antagonist(ML385)to find whether the effect of lycopene was dependent on the induction of the Nrf2/HO-1 pathway.Results showed that protective effects of lycopene was similar to the effects of activator and could be abolished by ML385.In conclusion,lycopene can protect the ovary against CrVI-induced oxidative stress via activation of Nrf2/HO-1 pathway in vitro.Summary:The results show that lycopene can attenuate the CrVI-induced developmental toxicity of chick ovaries in both vivo and vitro,which is related to its protective effects on cell proliferation,cell apoptosis,antioxidant capacity,nuclear pyknosis,mitochondria injury.And the oxidative stress prevention effects of lycopene on CrVI-induced ovaries were dependent on the induction of the Nrf2/HO-1 pathway.The results provide theoretical basis for application of lycopene as a promising feed additive on the protection of laying performance of chickens.