Dinter Juliane, Khajavi Noushafarin, Mühlhaus Jessica, Wienchol Carolin Leonie, Cöster Maxi, Hermsdorf Thomas, Stäubert Claudia, Köhrle Josef, Schöneberg Torsten, Kleinau Gunnar, Mergler Stefan, Biebermann Heike
Institut für Experimentelle Pädiatrische Endokrinologie, Berlin, Germany.
Department of Ophthalmology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Eur Thyroid J. 2015 Sep;4(Suppl 1):21-9. doi: 10.1159/000381801. Epub 2015 May 29.
3-Iodothyronamine (3-T1AM), a signaling molecule with structural similarities to thyroid hormones, induces numerous physiological responses including reversible body temperature decline. One target of 3-T1AM is the trace amine-associated receptor 1 (TAAR1), which is a member of the rhodopsin-like family of G protein-coupled receptors (GPCRs). Interestingly, the effects of 3-T1AM remain detectable in TAAR1 knockout mice, suggesting further targets for 3-T1AM such as adrenergic receptors. Therefore, we evaluated whether β-adrenergic receptor 1 (ADRB1) and 2 (ADRB2) signaling is affected by 3-T1AM in HEK293 cells and in human conjunctival epithelial cells (IOBA-NHC), where these receptors are highly expressed endogenously.
A label-free EPIC system for prescreening the 3-T1AM-induced effects on ADRB1 and ADRB2 in transfected HEK293 cells was used. In addition, ADRB1 and ADRB2 activation was analyzed using a cyclic AMP assay and a MAPK reporter gene assay. Finally, fluorescence Ca(2+) imaging was utilized to delineate 3-T1AM-induced Ca(2+) signaling.
3-T1AM (10(-5)-10(-10)M) enhanced isoprenaline-induced ADRB2-mediated Gs signaling but not that of ADRB1-mediated signaling. MAPK signaling remained unaffected for both receptors. In IOBA-NHC cells, norepinephrine-induced Ca(2+) influxes were blocked by the nonselective ADRB blocker timolol (10 µM), indicating that ADRBs are most likely linked with Ca(2+) channels. Notably, timolol was also found to block 3-T1AM (10(-5)M)-induced Ca(2+) influx.
The presented data support that 3-T1AM directly modulates β-adrenergic receptor signaling. The relationship between 3-T1AM and β-adrenergic signaling also reveals a potential therapeutic value for suppressing Ca(2+) channel-mediated inflammation processes, occurring in eye diseases such as conjunctivitis.
3-碘甲腺原氨酸（3-T1AM）是一种与甲状腺激素结构相似的信号分子，可引发多种生理反应，包括可逆性体温下降。3-T1AM的一个靶点是痕量胺相关受体1（TAAR1），它是视紫红质样G蛋白偶联受体（GPCR）家族的成员。有趣的是，在TAAR1基因敲除小鼠中仍可检测到3-T1AM的作用，这表明3-T1AM还有其他靶点，如肾上腺素能受体。因此，我们评估了在人胚肾293（HEK293）细胞和人结膜上皮细胞（IOBA-NHC）中，β-肾上腺素能受体1（ADRB1）和2（ADRB2）信号传导是否受3-T1AM影响，这些受体在这两种细胞中均有内源性高表达。
使用一种无标记的EPIC系统对转染的HEK293细胞中3-T1AM对ADRB1和ADRB2的诱导作用进行预筛选。此外，使用环磷酸腺苷检测法和丝裂原活化蛋白激酶（MAPK）报告基因检测法分析ADRB1和ADRB2的激活情况。最后，利用荧光Ca(2+)成像来描绘3-T1AM诱导的Ca(2+)信号传导。
3-T1AM（10^(-5)-10^(-10)M）增强了异丙肾上腺素诱导的ADRB2介导的Gs信号传导，但未增强ADRB1介导的信号传导。两种受体的MAPK信号传导均未受影响。在IOBA-NHC细胞中，去甲肾上腺素诱导的Ca(2+)内流被非选择性ADRB阻滞剂噻吗洛尔（10 μM）阻断，这表明ADRB很可能与Ca(2+)通道相关。值得注意的是，还发现噻吗洛尔可阻断3-T1AM（10^(-5)M）诱导的Ca(2+)内流。
所呈现的数据支持3-T1AM直接调节β-肾上腺素能受体信号传导。3-T1AM与β-肾上腺素能信号传导之间的关系还揭示了其在抑制Ca(2+)通道介导的炎症过程中的潜在治疗价值，这种炎症过程发生在结膜炎等眼部疾病中。
