Tissue-specific glucocorticoid regulation of tryptophan hydroxylase mRNA levels
Tissue-specific glucocorticoid regulation of tryptophan hydroxylase mRNA levels
复制标题
DOI：
10.1016/s0169-328x(97)00106-x
复制
发表时间：
1997-09-01
期刊：
影响因子：
--
通讯作者：
Russo, AF
中科院分区：
文献类型：
--
作者：
Clark, MS;Russo, AF
糖皮质激素调节5-羟色胺（5-HT）产生的一个潜在的长期目标是色氨酸羟化酶（TPH）基因表达。然而，TPH基因表达的研究受到了大脑中TPH mRNA水平极低的阻碍，并且关于糖皮质激素对5-HT水平的影响的报道相互矛盾。为了克服这些障碍，我们已经开发了一种灵敏的竞争性RT-PCR检测直接测量TPH mRNA水平从大鼠脑。我们观察到TPH mRNA水平的组织特异性调制的褪黑激素生产松果体和5-羟色胺生产中缝核的大脑。用合成糖皮质激素地塞米松长期治疗肾上腺切除大鼠1周后，松果体中TPH mRNA增加了16倍，而脑中TPH mRNA降低至对照水平的16%。为了解决地塞米松抑制TPH mRNA水平的机制，我们随后测试了来自大鼠甲状腺C细胞的多巴胺能神经元样细胞系。地塞米松引起TPH mRNA水平迅速下降，在CA 77 C细胞中接近对照值的20%。这是通过竞争性RT-PCR和标准杂交测定来测量的，这证实了RT-PCR测定的有效性。此外，TPH mRNA水平的降低与CA 77 C细胞中5-HT水平的降低相关。因此，糖皮质激素可能会改变血清素和褪黑激素的生物合成能力的细胞特异性调制的TPH基因。
A potential long-term target of glucocorticoid modulation of serotonin (5-HT) production is tryptophan hydroxylase (TPH) gene expression. However, studies on TPH gene expression have been hampered by the extremely low levels of TPH mRNA in the brain, and there have been contradictory reports on the effects of glucocorticoids on 5-HT levels. To overcome these obstacles, we have developed a sensitive competitive RT-PCR assay to directly measure TPH mRNA levels from the rat brain. We observed a tissue-specific modulation of TPH mRNA levels in the melatonin producing pineal gland and the serotonin producing raphe nuclei of the brain. Following chronic treatment of adrenalectomized rats with the synthetic glucocortcoid dexamethasone for 1 week, there was a 16-fold increase in TPH mRNA in the pineal gland that was contrasted by a decrease in TPH mRNA to 16% of the control levels in the brain. To address the mechanism of dexamethasone repression of TPH mRNA levels, we then tested a serotonergic neuronal-like cell line derived from rat thyroid C cells. Dexamethasone caused a rapid decrease in TPH mRNA levels to approximate to 20% of control values in CA77 C cells. This was measured by both competitive RT-PCR and a standard hybridization assay, which confirmed the validity of the RT-PCR assay. Furthermore, the reduction of TPH mRNA levels was associated with a decrease in 5-HT levels in the CA77 C cells. Hence, glucocorticoids may alter serotonin and melatonin biosynthetic capacity by cell-specific modulation of the TPH gene.