Cigarette smoke is a complex mixture of toxic chemicals, including nicotine, carbon monoxide, and several recognized carcinogens and mutagens. Nicotine has a direct disturbing influence on steroid hormones (estrogen and progesterone), which are essential components of the female reproductive system, but the effect of nicotine on the hormone receptors is not yet clear. The aim of this study was to elucidate the effect of nicotine on the expression of estrogen receptor (ER), progesterone receptor (PR), and vascular endothelial growth factor (VEGF) in endometrial stromal cells. Expression levels of PR, ER, and VEGF in human endometrial stromal primary cells treated with nicotine (0, 10⁻¹¹, 10⁻⁸, and 10⁻⁶μM) for 24 h were measured by quantitative real-time PCR. MTT assay demonstrated that nicotine decreased cell viability in a dose-dependent manner. Real-time PCR data showed that despite decrease in ER expression in the nicotine-treated groups compared with the control, nicotine exerted an increased inhibitory effect on PR expression compared to that on ER expression. VEGF mRNA expression in nicotine-treated endometrial stromal cells was increased. The results from this study provide novel evidence for inhibitory effects of nicotine on steroid hormones receptor expression in human primary endometrial cells. Also, our data suggest that nicotine might have angiogenesis effects on these cells.

Background: Vitamin D (Vit.D) has an important role in protecting COVID‐19 patients. This study investigated the changes in vitamin D receptor (VDR) expression and interleukin 6 levels in patients with COVID‐19.Materials and methods: 120 hospitalized patients and 120 healthy people participated in this study, both group adjusted by sex and age. Vit.D was measured with HPLC, the expression of VDR gene was done with Real‐time PCR, and IL‐6 was measured with ELISA assay.Results: Our findings showed no significant difference in the case of Vit.D (25‐OH‐D3) between the two studied groups, interestingly the expression of VDR was statistically lower in the patients with COVID‐19, p‐value = 0.003. VDR expression was lower in the patient with diabetes, hypertension and cardiovascular disease, significantly, p‐value = 0.002. The level of IL‐6 was statistically higher in the COVID‐19 group, p‐value = 0.003.Conclusion: Alongside the important role of 25‐OH‐D3 in COVID‐19 patients, the quality and quantity of the VDR expression and its role in the level of IL‐6 are the promising risk factors in the future. Further studies are needed to determine the factors increasing the expression level of VDR, especially in the patients with diabetes, hypertension and cardiovascular disease.