MyD88 and TRIF mediate the cyclic adenosine monophosphate (cAMP) induced corticotropin releasing hormone (CRH) expression in JEG3 choriocarcinoma cell line

Classically protein kinase A (PKA) and transcription factor activator protein 1 (AP-1) mediate the cyclic AMP (cAMP) induced-corticotrophin releasing hormone (CRH) expression in the placenta. However enteric Gram (-) bacterial cell wall component lipopolysaccharide (LPS) may also induce-CRH expression via Toll like receptor (TLR)4 and its adaptor molecule Myd88.

Here we investigated the role of MyD88, TRIF and IRAK2 on cAMP-induced CRH promoter activation in JEG3 cells in the absence of LPS/TLR4 stimulation.

Methods: JEG3 cells were cotransfected with CRH-luciferase and Beta-galactosidase expression vectors and either empty or dominant-negative (DN)-MyD88, DN-TRIF or DN-IRAK2 vectors using Fugene6 (Roche). cAMP-induced CRH promoter activation was examined by using a luminometer and luciferase assay.

Calorimetric Beta-galactosidase assays were performed to correct for transfection efficiency. Luciferase expression vectors of cAMP-downstream molecules, CRE and AP-1, were used to further examine the signaling cascades.

Results: cAMP stimulation induced AP-1 and CRE promoter expression and led to a dose-dependent CRH promoter activation in JEG3 cells.

Inhibition of MyD88 signaling blocked cAMP-induced CRE and CRH promoter activation. Inhibition of TRIF signaling blocked cAMP-induced CRH but not CRE expression, while inhibition of IRAK2 did not have an effect on cAMP-induced CRH expression.

Conclusion: MyD88 and TRIF exert direct regulatory effect on cAMP-induced CRH promoter activation in JEG3 cells in the absence of infection.

MyD88 most likely interacts with molecules upstream of IRAK2 to regulate cAMP-induced CRH expression.

Author: Andy UhCharles SimmonsCatherine BreseeNasif KhouryAdrian GombartRichard NicholsonHande KocakOzlem Equils
Credits/Source: Reproductive Biology and Endocrinology 2009, 7:74

Published on: 2009-07-17

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