Tabac et fertilité chez la femme et l'homme

Nicotine attenuates global genomic DNA methylation by influencing DNMTs gene expression in human endometrial stromal cells

BACKGROUND

There is increasing evidence indicating an incidence of infertility and also the risk of endometrial cancers among smokers. However, the mechanism underlying nicotine adverse effect on female reproduction remains unclear. Growing evidence has suggested that environmental exposures such as nicotine could modulate the epigenome. No study has yet been published to evaluate the direct effect of nicotine on the epigenome profiling of human endometrial stromal cells (HESC). Herein, we decided to examine the direct effects of nicotine on global genomic DNA methylation status and DNA methyl- transferases (DNMTs) gene expression in HESC. HESC were treated with different doses of nicotine (0 or control, 10- 11, 10- 8 and 10- 6) M for 24 h and their genomic global DNA methylation and gene expression of DNMTs (DNMT1, DNMT3A, and DNMT3B) were investigated using ELISA and real-time PCR, respectively.

RESULTS

Nicotine treatments reduced the average level of DNMTs gene expression by 90, 79, and 73.4% in 10- 11, 10- 8 and 10- 6 M of nicotine treated cells as compared to control cells, respectively (p < 0.05). Also, 10- 8 and 10- 6 M of nicotine concentrations effectively reduced the amounts of 5-methylated cytosine (5-mC) by 1.09 and 1.87% compared to control cells, respectively (p < 0.05). The 5-mC percentages were positively correlated with the relative cellular DNMTs expression in HESC as verified by the Pearson correlation test.

CONCLUSION

An interesting possibility raised by the current study is that the reduced genomic global DNA methylation level in HESC may be partly due to the suppression of DNMTs gene expression caused by nicotine in these cells.

GRAPHICAL ABSTRACT

[First French national survey on lifestyle and toxic factors in infertile couples]

OBJECTIVES

The purpose of our study is to assess, prior to any treatment for infertility, the environment and quality of life of candidate couples for medically assisted procreation (MAP) and the toxic factors which may be related to their difficulty in conceiving.

PATIENTS AND METHODS

A screening questionnaire aimed at 796 patients (348 couples) has been collected by 43 assisted reproductive techniques (ART) centers in France. Stress factors, anxiety, toxic and environmental factors have been recorded and analysed.

RESULTS

Women were on average younger than men (34.9 y ± 5.3 vs. 37.5 y ± 7.5), with a normal BMI, and 78% of them had no children. Sexual relations are regular: 2.14 per week. However, 1 in 8 women reports having sexual problems as opposed to 2 in 100 men (P < 0.0001), the most common problems being painful intercourse, insensitivity and bleeding. Fifty percent of the surveyed women say they have painful periods. Smoking and cannabis use were significantly higher in the men (32% vs. 20% and 6,4% vs. 1,2%). Alcohol consumption is more common in men (32 vs. 23%, P < 0.01). Stress related to infertility was significantly higher in the women (54% vs. 23%; P < 0.001).

DISCUSSION AND CONCLUSION

This first prospective French survey has revealed an increased incidence of smoking and an escalation of sexual problems (decrease in sexual relations, dyspareunia) and dysmenorrhea in women. It has also revealed stress at work in couples, and increased stress levels due to infertility in the female partners participating in this study. Our study suggests that there are numerous toxic and environmental factors which are potentially harmful for a couple's fertility and which should be corrected before any MAP treatment is attempted in order to optimise the results in ART and to increase natural fertility.

Effect of current tobacco consumption on the male reproductive hormone profile

The knowledge about the effect of cigarette smoking on the male reproductive function is still limited. The objective of this study was to evaluate the association between active exposure to tobacco smoke and the male reproductive hormone profile in a group of 136 Mexican flower growers. Serum levels of FSH, LH, prolactin, total testosterone, Inhibin B and estradiol were measured using enzyme-linked immunoabsorbent assay. Weight and height were also measured and a structured questionnaire was applied to get information on sociodemographic characteristics, clinical and work history and alcohol and tobacco consumption (current smoking habit and number of cigarettes smoked per day). Based on this information tobacco consumption was divided into four categories: never-smokers, ex-smokers, current smokers under five cigarettes/day and current smokers over or equal to five cigarettes/day. Using the group of never-smokers as reference and after adjusting for potential confounders, current smokers of five or more cigarettes/day showed significantly higher levels of LH (β=0.33, p=0.01), prolactin (β=0.18, p=0.03) and testosterone (β=0.21, p=0.02). Current smokers of less than five cigarettes/day also showed higher levels of prolactin (β=0.12, p=0.03) and testosterone (β=0.18, p<0.01). Hormone levels of ex-smokers were similar to those of never-smokers. Our results are compatible with the hypothesis that tobacco consumption may act as an endocrine disruptor on the male hormone profile.