Exposure to Benzo(a)pyrene promotes proliferation and inhibits differentiation of stromal cells in mice during decidualization.

The environmental pollutant Benzo(a)pyrene (BaP) has an adverse effect on the reproductive performance of mammals. We previously showed that BaP treatment during early pregnancy damages endometrial morphology and impairs embryo implantation. Endometrial decidualization at the implantation site (IS) after embryo implantation is crucial for pregnancy maintenance and placental development. The balance between proliferation and differentiation in endometrial stromal cells (ESCs) is a crucial event of decidualization, which is regulated by the cell cycle. Here, we report that abnormal decidualization caused by BaP is associated with cell cycle disturbance of stromal cells. The mice in the treatment group were gavaged with 0.2 mg/kg/day BaP from day 1-8 of pregnancy, while those in control were gavaged with corn oil in parallel. BaP damaged the decidualization of ESCs and reduced the number of polyploid cells. Meanwhile, BaP up-regulated the expression of Ki67 and PCNA, affecting the differentiation of stromal cells. The cell cycle progression analysis during decidualization in vivo and in vitro showed that BaP induced polyploid cells deficiency with enhanced expressions of CyclinA(E)/CDK2, CyclinD/CDK4 and CyclinB/CDK1, which promote the transformation of cells from G1 to S phase and simultaneously activate the G2/M phase. The above results indicated that BaP exposure accelerates cell cycle progression, promotes ESC proliferation, inhibits differentiation, and impedes proper decidualization and polyploidy development. Thus, the imbalance of ESC proliferation and differentiation would be an important mechanism for BaP-induced defective decidualization.

Exposure to Benzo(a)pyrene damages mitochondrial function via suppressing mitochondrial melatonin receptors in ovarian corpus luteum during early pregnancy.

Benzo(a)pyrene (BaP) is a well-known environmental endocrine pollutant, which has ovarian toxicity in mammals. Ovarian corpus luteum (CL), as the main source of progesterone synthesis in early pregnant female, requires a large number of mitochondria for energy supply. We previously demonstrated that BaP and its metabolite benzo(a)pyren-7, 8-dihydrodiol-9, 10-epoxide (BPDE) inhibited the ovarian melatonin receptors (MTRs) expression and decreased the levels of estrogen and progesterone during early pregnancy in mice. Emerging researches show that MTRs also exist on mitochondrial membrane and participate in the regulation of mitochondrial function. However, the relationship between BaP, MTRs on mitochondrial membrane and mitochondrial function remains unknown. Consequently, this study focuses on the effect and potential mechanism of BaP on ovarian luteal mitochondrial function during early pregnancy. We found that BaP and its metabolite BPDE decreased MTRs in early pregnant CL and luteinized KGN cells, especially in mitochondria. Furthermore, BaP or BPDE up-regulated the expression of SIRT3, Mfn2 and Drp-1, damaged mitochondrial morphology and decreased the MMP and the ATP levels, thereby causing mitochondrial dysfunction. Notably, activation of the MTRs on mitochondrial membrane by MTRs agonist ramelteon partially alleviated BPDE-induced up-regulation of SIRT3, Mfn2 and Drp-1, reduced mitochondrial fragmentation and enhanced the MMP and the ATP levels, thus restoring the expression of steroid rate-limiting enzymes. Together, these findings firstly proved that BaP and BPDE down-regulate MTRs on mitochondrial membrane, and further injure mitochondrial function in early pregnant rats' CL, which provides a new insight for understanding the exact mechanism of the BaP-induced ovarian toxicity.

Melatonin alleviates benzo(a)pyrene-induced ovarian corpus luteum dysfunction by suppressing excessive oxidative stress and apoptosis.

Benzo(a)pyrene (B(a)P) is a widespread persistent organic pollutant (POP) and a well-known endocrine disruptor. Exposure to BaP is known to disrupt the steroid balance and impair embryo implantation, but the mechanism under it remains unclear. The corpus luteum (CL), the primary source of progesterone during early pregnancy, plays a pivotal role in embryo implantation and pregnancy maintenance. The inappropriate luteal function may result in implantation failure and spontaneous abortions. Therefore, this study was conducted to assess the effects and potential mechanisms of B(a)P on the CL function. Our results showed that pregnant mice received B(a)P displayed impaired embryo implantation and dysfunction of ovarian CL. The estrogen and progesterone levels decreased by B(a)P. In vitro, exposure to BPDE, which is the metabolite of B(a)P, affected the luteinization of granular cell KK-1. Additionally, melatonin and its receptors, which are important for ovarian function and anti-oxidative damage, were affected by B(a)P or BPDE. B(a)P or BPDE-treated alone impaired antioxidant capacity of ovarian granulosa cells, caused an increasing of ROS and cell apoptosis, and disrupted the PI3K/AKT/GSK3ß signaling pathway in vivo and in vitro. Co-treatment with melatonin alleviated B(a)P or BPDE-induced CL dysfunction by ameliorating oxidative stress, counteracting phosphorylation of PI3K/AKT/GSK3ß signaling pathway, decreasing the apoptosis of the ovarian cells. Moreover, activation of the melatonin receptor by ramelteon in KK-1 cells exhibits an analogous protective effect as melatonin. In conclusion, our findings not only firstly clarify the potential mechanisms of BaP-induced CL dysfunction, but also extend the understanding about the ovarian protection of melatonin and its receptors against B(a)P exposure.

Exposure to Benzo[a]pyrene impairs the corpus luteum vascular network in rats during early pregnancy.

Benzo [a]pyrene (BaP) is a well-known endocrine disruptor. Exposure to BaP is known to impair embryo implantation. The corpus luteum (CL), the primary source of progesterone during early pregnancy, plays a pivotal role in embryo implantation and pregnancy maintenance. The inappropriate luteal function may result in implantation failure and spontaneous abortions. However, the effect of BaP on CL remains unknown. This study investigated the deleterious effects of BaP on the structure and function of CL during early pregnancy. Pregnant rats were dosed with BaP at 0.2 mg.kg-1. d from day 1 (D1) to day 9 (D9) of gestation. We found that BaP reduced the number of CLs, disturbed the secretion of steroid and impacted the luteal vascular networks. BaP significantly decreased the angiogenesis factor (VEGFR, Ang-1 and Tie2) and increased the anti-angiogenic factor THBS1. Inhibited THBS1 function by LSKL partially rescued the angiogenesis defect caused by BaP. In vitro, BaP metabolite BPDE also interfered the expression levels of angiogenesis-related factors in HUVECs and impaired the angiogenesis, whereas supplemented with rAng-1 can alleviate the anti-angiogenic effect of BPDE. Furthermore, Notch signaling molecules, including Notch1, Dll4, Jag1 and Hey2, which are essential for the establishment and maturation of vascular networks, were affected by BaP exposure. Collectively, BaP broke the molecular regulatory balance between luteal angiogenesis and vascular maturation, impaired the construction of luteal vascular networks, and further affected luteal formation and endocrine function during early pregnancy. Our findings might provide new insight into the relationship between BaP and luteal insufficiency in early pregnancy. These data also give a new line of evidence for curtailing BaP emissions and protecting the women of childbearing age from occupational exposure.

Benzo(a)pyrene inhibits endometrial cell apoptosis in early pregnant mice via the WNT5A pathway.

Benzo(a)pyrene (BaP) is an endocrine-disrupting pollutant present in various aspects of daily life, and studies have demonstrated that BaP exerts reproductive toxicity. We previously showed that BaP damages endometrial morphology and decreases the number of implantation sites in early pregnant mice, but the mechanisms underlying these effects remain unclear. The endometrial function is crucial for implantation, which is associated with endometrial cell apoptosis. In this study, we focused on the effect of BaP on endometrial cell apoptosis and the role of WNT signaling during this process. Pregnant mice were gavaged with corn oil (control group) or 0.2 mg·kg-1 ·day -1 BaP (treatment group) from Days 1 to 6 of pregnancy. BaP impaired endometrial function by decreasing the expression of HOXA10 and BMP2, two markers of receptivity and decidualization. WNT5A and ß-catenin were activated in the BaP group. BaP affected the expression of apoptosis-related proteins and inhibited the apoptosis of endometrial stromal cells. In vitro, human endometrial stromal cells (HESCs) were treated with different concentrations of BaP (dimethyl sulfoxide (DMSO); 5, 10 µM). WNT5A and ß-catenin were also upregulated in the BaP treatment group. HESC apoptosis was restrained by BaP. Inhibiting WNT5A by SFRP5 partially restored the effect of BaP on apoptosis. In summary, these results suggested that BaP exposure during early pregnancy activates WNT5A/ß-catenin signaling pathway, which inhibits the endometrial cell apoptosis and potentially destroys endometrial function.

Low local blood perfusion, high white blood cell and high platelet count are associated with primary tumor growth and lung metastasis in a 4T1 mouse breast cancer metastasis model.

It was originally thought that no single routine blood test result would be able to indicate whether or not a patient had cancer; however, several novel studies have indicated that the median survival and prognosis of cancer patients were markedly associated with the systemic circulation features of cancer patients. In addition, certain parameters, such as white blood cell (WBC) count, were largely altered in malignant tumors. In the present study, routine blood tests were performed in order to observe the change of blood cells in tumor-bearing mice following the implantation of 4T1 breast cancer cells into the mammary fat pad; in addition, blood flow in breast tumor sites was measured indirectly using laser Doppler perfusion imaging (LDPI), in an attempt to explain the relevance between the blood circulation features and the growth or metastasis of breast cancer in mice model. The LDPI and blood test results indicated that the implantation of 4T1 breast cancer cells into BALB/c mice led to thrombosis as well as high WBC count, high platelet count, high plateletcrit and low blood perfusion. Following implantation of the 4T1 cells for four weeks, the lung metastatic number was determined and the Pearson correlation coefficient revealed that the number of visceral lung metastatic sites had a marked negative association with the ratio of basophils (BASO%; r=-0.512; P<0.01) and the mean corpuscular hemoglobin was significantly correlated with primary tumor weight (r=0.425; P<0.05). In conclusion, the results of the present study demonstrated that tumor growth led to thrombosis and acute anemia in mice; in addition, when blood BASO% was low, an increased number of lung metastases were observed in tumor-bearing mice.