HT-2 Toxin Affects Porcine Oocytes Maturation And Parthenogenetic Embryonic Developmental Competence

Mycotoxins are toxic,secondary metabolites produced by fungi that commonly contaminate staple foods and feeds and is toxic to human as well as animals.In terms of chronic toxicity,mycotoxins are concerned as a major public health threaten.They are the most hazardous of all food and feed contaminants.The major mycotoxins include aflatoxins B1,deoxynivalenol,zearalenone,ochratoxin A and HT-2 toxin.Plenties of studies have shown that exposure to mycotoxins have been linked to reproductive disorders in animals.However,there is little report about toxic effects of mycotoxins on oocyte maturation and developmental competence.In this study,we first explored different sensibilities of mouse and porcine oocytes to different mycotoxins in graded doses.And we take the maturation rate as a symbol.We found that porcine oocyte is more sensitive to most major mycotoxins,including AFB1,DON,ZEA and OTA,except for HT-2 toxin.Then we chose HT-2 toxin to explore its toxic effects on porcine oocyte in vitro maturation and developmental competence.Project 1:HT-2 toxin has adverse effects on porcine oocyte maturationT-2 toxin is a main type A trichothecene mycotoxin which is the most toxic trichothecence.T-2 toxin has posed various toxic effects on human and animals in vigorous cell proliferation tissues like lymphoid,hematopoietic and gastrointestinal tissues,while HT-2 toxin is the major metabolite which is deacetylated by T-2 toxin.In this study,we focused on the toxic effects of HT-2 on porcine oocyte maturation.We treated the porcine oocyte with HT-2 toxin in vitro,and we first found that HT-2 treatment inhibited porcine oocyte polar body extrusion and cumulus cell expansion.We observed the disrupted meiotic spindle morphology after treatment,which might be due to the reduced p-MAPK protein level.Actin distribution was also disturbed,indicating that HT-2 affects cytoskeleton of porcine oocytes.We next explored the causes for the failure of oocyte maturation after HT-2 treatment.We found that HT-2 treated oocytes showed the increased ROS level,which indicated that oxidative stress had occurred.We also detected autophagy as well as early apoptosis in the treatment oocytes.Due to the fact that oxidative stress could induced apoptosis,our results indicated that HT-2 toxin caused oxidative stress induced apoptosis and autophagy,which further affected porcine oocyte maturationProject 2:HT-2 toxin affects developmental competence of porcine parthenogenetic embryoT-2 toxin is a type A mycotoxin produced by various Fusarium species,while HT-2 toxin is the major metabolism of T-2 toxin.Both T-2 toxin and HT-2 toxin are shown to have toxic effects on animals.However,there is few study about HT-2 toxin effects on porcine oocyte developmental competence.Our previous work showed that HT-2 treatment caused the failure of oocyte maturation.In this study,we showed that HT-2 affected porcine oocyte developmental competence and embryo development.We also explored possible mechanisms of HT-2 effects on embryo development from the aspect of epigenetic modification.The analysis of fluorescence intensity showed that 5-methyl cytosine(5mC)level was increased after exposure to HT-2 toxin in metaphase II stage oocytes,indicating that the general DNA methylation level increased in the treated porcine oocytes.In addition,histone modifications were also changed.H3K4me2 and H3K9me2 levels were increased in the treatment group.Our results indicated that HT-2 toxin may decrease porcine oocyte developmental competence by affecting epigenetic modifications.