Study on the effects of different vitamin A levels on thyroid cell apoptosis and related gene expression of mice taking excessive iodine / 中国地方病学杂志

ABSTRACT

Objective To explore the effects of different vitamin A(VA) levels on thyroid cells apoptosis and its gene expression of mice taking excessive iodine. Methods Kunming mice were randomly divided into 6 groups according to body weight 3 weeks after born normal control(NI) group, high iodine(HI) group, low vitamin (LVA) group, high iodine plus low vitamin A(HI+LVA) group, high iodine plus vitamin A1 (HI+VA1) group, high iodine plus vitamin A2(HI+VA2) group. The VA was given in food(4000,4000,0,0,8000,16 000 U/kg), and the iodine was given as potassium iodate in water (I-50,3000,50,3000,3000,3000 μg/L). The apoptosis was tested using in situ end labehng(TUNEL) method. Reverse transcription polymerase chain reaction (RT-PCR) were used to measure the level of mRNA of apoptosis gene(Fas, FasL, Bcl-2) in tissues. Results Apoptotic index measured by TUNEL method was rising along with the mice age. Compared to NI group[(14.09±5.68)%], apoptotic index was significantly increased in HI[(20.91±9.57)%], HI+LVA[(20.29±9.90)%]and HI+VA2 [(19.51±8.25)%]groups in the three months(P < 0.05). Compared to NI group[(16.80±9.90)%], apoptotic index was significantly increased(P < 0.05) in HI[(23.22±8.58)%],LVA[(22.56±6.17)%],HI+LVA [(25.99±9.62)%],HI+VA1 [(21.65±7.74)%]groups in the six months. Compared with the NI group(Fas 1.29±0.25,1.27±0.26; FasL 1.60±0.13,1.65±0.13), the mRNA levels of Fas and FasL in HI group(Fas 1.57±0.36,1.49±0.35; FasL 1.85±0.46,1.84±0.32) were increased, but the differences were not remarkable(P > 0.05) in the three and six months. Compared with the HI group, the mRNA levels of Fas in HI+ VA1, HI+VA2(1.33±0.35, 1.30±0.26) groups were decreased to the level in NI group in the six months. The mRNA levels of Fas and FasL were not different (P > 0.05) between HI+LVA(I.60±0.27,1.88±0.46) and HI groups in the three months. The mRNA levels of Bcl-2 were not remarkably differences in the three months (1.05±0.19,0.96±0.33,0.95±0.26,1.18±0.27,1.10±0.19,0.98±0.36, all P > 0.05), and in the six months (1.35±0.28,1.60±0.25,1.48±0.18,1.71±0.26,1.66±0.29,1.56±0.35, all P > 0.05). Conclusions Excessive iodine can cause thyroid cells apoptosis in mice. Supplementation of suitable amount of VA can regulate the levels of the apoptosis-related genes expression, and partly antagonize the apoptosis caused by high iodine.