Wlodarczyk B J, Bennett G D, Calvin J A, Finnell R H
Department of Veterinary Anatomy and Public Health, Texas A & M University, College Station 77843-4458, USA.
Reprod Toxicol. 1996 Nov-Dec;10(6):447-54. doi: 10.1016/s0890-6238(96)00131-1.
The potential of arsenic to cause neural tube defects (NTD) in the human population remains a topic of controversy. While clearly toxic, the lack of well-defined human epidemiologic studies on this subject has made it difficult to fully understand the effects arsenic may have on the developing human neural tube. In the absence of good clinical data, we have tried to develop a murine model where hypotheses about the reproductive toxicity of arsenate can be tested. For these studies a murine strain (LM/Bc) that has proven to be susceptible to arsenic-induced NTD was use. Because cellular proliferation is vital for normal neural tube closure (NTC) to occur, in the present study we investigated whether an acute arsenate treatment could alter the expression of several cell cycle genes during murine neurulation. Pregnant LM/Bc dams were injected intraperitoneally on gestation day (GD) 7:12 (day:hour) and 8:12 with 40 mg/kg of arsenate, a treatment that causes exencephaly in 90 to 100% of the exposed fetuses. Neural tubes were then isolated from both control and arsenic treated embryos at GD 9:00, 9:12, 10:00, and 10:12, which encompasses all the stages of neurulation for this murine strain. Using the molecular techniques of in situ transcription and antisense RNA amplification (RT/aRNA) the expression pattern for bc1-2, p53, wee-1, and wnt-1 was analyzed at each of these time points. In the neural tubes isolated from control embryos, the expression of all four genes was significantly altered as neurulation progressed, demonstrating their developmental regulation. Following arsenate treatment, however, there was a significant upregulation in the expression of bc1-2 and p53 at gestational day 9:0, compared to their control values. The heightened expression of both of these genes suggests that arsenic inhibits cell proliferation, rather than inducing apoptosis, which delayed NTC and ultimately led to the neural tube defects observed in exposed embryos.
砷在人群中导致神经管缺陷（NTD）的可能性仍是一个存在争议的话题。虽然砷具有明确的毒性，但缺乏关于该主题的明确的人类流行病学研究，这使得难以充分了解砷对发育中的人类神经管可能产生的影响。在缺乏良好临床数据的情况下，我们试图建立一种小鼠模型，在该模型中可以测试关于砷酸盐生殖毒性的假设。对于这些研究，使用了已被证明对砷诱导的神经管缺陷敏感的小鼠品系（LM/Bc）。由于细胞增殖对于正常的神经管闭合（NTC）至关重要，在本研究中，我们调查了急性砷酸盐处理是否会改变小鼠神经胚形成过程中几个细胞周期基因的表达。怀孕的LM/Bc母鼠在妊娠第7天12时（天：小时）和第8天12时腹腔注射40mg/kg砷酸盐，这种处理会导致90%至100%的暴露胎儿出现无脑畸形。然后在妊娠第9天0时、9时12分、10时0分和10时12分从对照和砷处理的胚胎中分离神经管，这涵盖了该小鼠品系神经胚形成的所有阶段。使用原位转录和反义RNA扩增（RT/aRNA）的分子技术，在每个时间点分析bc1-2、p53、wee-1和wnt-1的表达模式。在从对照胚胎分离的神经管中，随着神经胚形成的进展，所有四个基因的表达均发生了显著变化，表明它们受到发育调控。然而，砷酸盐处理后，与对照值相比，在妊娠第9天0时bc1-2和p53的表达显著上调。这两个基因的表达升高表明砷抑制细胞增殖，而不是诱导细胞凋亡，这延迟了神经管闭合并最终导致暴露胚胎中观察到的神经管缺陷。
