The Effects Of Cigarette Smoke Extract On Oocyte And Ovarian Antioxidant Enzymes Expression In Mice

Objective：Cigarette smoking has become prevalant among young female worldwide.Smoking is associated with decerased pregnancy rate, increased spontaneous abortionand decreased live birth rate. This study observed the effects of cigarette smokeextract (CSE) on oocytes and ovarian antioxidant enzymes expression in mice, whichcould reveal whether the NRF2-ARE (nuclear factor erythroid2-related factor2-antioxidant response element) pathway was activated or not，trying to explore theunderlying mechanisms of the effects of smoking on the ability of oocyte. This studymay apply basic evidence for the infertility therapy for the cigarette smoke exposingwomen.Materials and Methods:The present study tested CSE on ovulation, the maturity, morphology andfunction of oocytes and ovarian antioxidant enzymes expression using C57BL/6mice.Mice in the CSE experimental group were administered a CSE solution (2mg/ml)orally daily, while the control group was given dimethylsulfoxide (DMSO). Apositive control group was used that received an intraperitoneal injection of15mg/kgmenadione in oil solution daily. After4-week adminstration, the mice was givensuperovulation intervention. And then oocytes collection was for the observation ofthe number of retrieved oocytes, immaturity rate, morphology of oocytes and themorphology of first polar body (PB). Ovaries isolation was for the qRT-PCR of themRNA level of NRF2and the antioxidant enzymes in NRF2-ARE pathway.Results:(1) Compared with control group, the diameter of zona pellucida-free oocyte(ZP-free OD) of CSE group was significantly dicreased (control76.56±0.12, CSE76.10±0.13, P <0.05), the rate of the PB with appropriate size, round shape and smooth surface (ARS-PB) was significantly lower (control15.2%, CSE6.6%, P<0.05), and the rate of the PB with small size, strip-like shape and rough surface(SSR-PB) was significantly higher (control7.6%, CSE24.3%, P<0.01).(2)Compared with the positive control group, in CSE group, the immaturity rate ofoocytes was significantly lower (positive control9.8%, CSE3.3%, P <0.05), the sizeof the perivitelline space (PVS) was significantly smaller (positive control10.05μm,CSE9.28μm, P <0.05), the rate of SSR-PB was significantly higher (positive control13.3%, CSE24.3%, P <0.05).(3) There was no significant change in the expressionof NRF2and the other8antioxidant enzymes between CSE group and control group(p>0.05).(4) Compared with CSE group, the expression of GSTM1(glutathione-s-transferase mu1) in positive control was significantly lower (CSE0.34±0.06, positive control0.12±0.02, P <0.05).Conclusion:In conclusion:(1)CSE exposure can harm oocytes,(2)the ovotoxicity phenotypeof menadione is different from that of CSE,(3)NRF2-ARE pathway was not activatedin the exposure of CSE or menadione,(4)the expression of GSTM1maybe inhibitedby other certain pathway in menadione exposure model. This study applied somebasic evidences for the infertility therapy for the cigarette smoke exposing women.