Our previous results indicate that Akt mediates 17??-estradiol and/or estrogen receptor ?? to inhibit the LPS induced the JNK activity, TNF?? protein expression, and exhibit the cardioprotective effects. TLR4 mRNAs often contain AU-rich elements (AREs) in their 3’untranslated regions (3’UTR) which have a high affinity for RNA-binding proteins. It is not known whether E2 and ER?? affect the TLR4 mRNA stability and TLR4 protein expression through regulating the RNA-binding proteins, human antigen R (HuR), TTP and AUF-1 in myocardial cells. Therefore, we would like to investigate if the LPS induce these RNA-binding proteins to regulate TLR4 mRNAs of cardiomyocytes, and whether the E2/ER?? reduces the TLR4 mRNA stability induced by LPS through the inhibition of RNA-binding protein expression. Using doxycycline(Dox)-induced Tet-On ER?? H9c2 myocardic cell model, we want to identify whetherE2 and/or ER???nmanipulate the LPS-induced TLR4 mRNA stability.
The result of western blotting and RT-PCR assays demonstrated that LPS significantly increased the level of cytoplasmic HuR protein and the stability of TLR4 mRNA, and farther induced the TLR4 protein expression in H9c2 cells. This effect was mediated through the phosphorylation of intracellular JNK. Interesting, E2 and ER?? decreased the cytoplasmic HuR level and TLR4 mRNA stability, and farther decreased the level of HuR protein and IL-6 proteins induced by LPS in H9c2 cardiomyoblast cells.
