Increased Fetal Thymocytes Apoptosis Contributes to Prenatal Nicotine Exposure-induced Th1/Th2 Imbalance in Male Offspring Mice

Abstract

Nicotine, a definite risk factor during pregnancy, is an immunomodulator. This study was designed to investigate the effects of prenatal nicotine exposure (PNE) on the balance of Th1/Th2 in offspring, and further explore the developmental origin mechanisms from the perspective of fetal thymocytes apoptosis. Pregnant Balb/c mice were administered 1.5 mg/kg nicotine subcutaneously twice per day from gestational day (GD) 9 to GD18. Results showed that PNE could cause a Th2 shift in male offspring, manifested as increased ratio of IgG1/IgG2a, IL-4 production in serum, and IL-4/IFN-γ expression ratio in spleen. Increased apoptosis of total thymocytes and CD4SP and reduced cell proportion of CD4SP were found in PNE male offspring on postnatal day (PND) 14 and PND 49. In the fetuses, decreased body weight and organ index of fetal thymus, histological changes in fetal thymus, reduced CD4SP proportion and increased fetal thymocyte apoptosis were observed in nicotine group. The increased mRNA expression of genes involved in Fas-mediated apoptotic pathway and protein expression of Fas were also detected. In conclusion, PNE could cause a Th2 shift in male offspring mediated by reduced CD4+ T cells output, which may result from the increasing apoptosis of total thymocytes and CD4SP.

α7 nAChR mediated Fas demethylation contributes to prenatal nicotine exposure-induced programmed thymocyte apoptosis in mice

“…The dose of 3 mg/kg/d of nicotine and the Balb/C strain were widely used to establish the PNE model for representing prenatal cigarette smoke exposure [ 30 – 32 ]. The 3 mg/kg/d dose of nicotine used in this study could equate to a moderate smoker during pregnancy (exposure to 6–8 cigarettes per day) [ 33 , 34 ]. A mouse embryo starts implantation on GD 4.5 till GD 6.5, and the fetal thymus organogenesis is initiated on GD 11.5 and continues until birth [ 29 , 35 ].…”

“…The S . pneumoniae used in the present study is a T cell-dependent antigen, which can induce the immune system to produce cytokines (such as IL-4) and IgG antibodies [ 34 ]. It was evident that females are more susceptible to immune disorders.…”

“…Additionally, Abbas and Vadesilho reported that the increased IL-4 production could cause an abnormal increase of the ratio of IgG1/IgG2, which in turn polarized the offspring immune system toward immune diseases [ 44 , 45 ]. Additionally, our previous study showed that the PNE male offspring showed an increased IgG1/IgG2a ratio and higher IL-4 content after antigen stimulation [ 34 ]. In this study, the changes in the IgG1, IgG2a, and IL-4 contents in PNE female offspring were different from those of the males.…”

“…Single cells were obtained by centrifugation at 335 × g for 5 min at 4°C and resuspended at 1 × 10 7 cells/ml in flow cytometry staining (FCS) buffer (PBS, 1% FBS, 0.02% sodium azide). A cell apoptosis assay was performed using flow cytometry according to the method previously described [ 34 ]. Briefly, thymocytes were stained with 100 μl of antibody cocktail (FITC-CD3, APC-CD4 and PE-cy7-CD8) in FCS buffer for 30 min on ice in the dark.…”

Maternal Glucocorticoid Elevation and Associated Fetal Thymocyte Apoptosis are Involved in Immune Disorders of Prenatal Caffeine Exposed Offspring Mice

“…Additionally, the different thymocyte subpopulations, at various stages of maturation and at different surface molecule expression levels, might be more or less susceptible to different immuno-toxicants. Prenatal nicotine exposure can not only increase thymocyte apoptosis through the Fas apoptotic pathway but can also promote CD4SP thymocyte apoptosis during negative selection 56 . DES showed stronger pro-apoptotic effects in fetal DN thymocytes (the most immature thymocyte) than in mature thymocytes 57 .…”