Given that ER[alpha] was required for the Gen-mediated antagonism of GR-induced GILZ expression, ChIP assays were performed on human genomic DNA from Ishikawa cells treated for 1 hr with vehicle, Dex, Gen, or Dex + Gen to examine the recruitment of ER[alpha] to the GILZ promoter in vitro (Figure 4B).
Altered GR and ER[alpha] recruitment to the promoter of the glucocorticoidinduced gene GILZ mediates the antagonistic regulation by Dex and [E.
Transcriptional regulation of LEFTYI and GILZ by Dex and the environmental estrogen Gen has not been previously reported (Whirledge and Cidlowski 2013; Whirledge et al.
A) Expression of GILZ mRNA measured by QRT-PCR following 6 hr treatment with vehicle (Veh), 100 nM Dex, 10 nM E2, 100 nM Gen, 100 nM BPA, or Dex + E2, Dex + Gen, or Dex + BPA (concentrations used in combination were the same as independent treatment).
B) mRNA expression of CA12 (carbonic anhydrase 12; top), LEFTY1 (left-right determination factor 1; center), and GILZ (glucocorticoid-induced leucine zipper; bottom) in cells pretreated 1 hr with ICI (left) or RU486 (RU; right) and then treated with vehicle (Veh), Dex, Gen, or Dex + Gen for 6 hr.
While GILZ is induced by glucocorticoids, directly overexpressing the protein appears to better target sources of bone loss and inflammation and avoid these serious side effects.
To look specifically at the impact on bone loss, the researchers crossed mice bred to overexpress tumor necrosis factor alpha throughout the body with mice that overexpressed GILZ in just their mesenchymal stem cells.
While the mice that overexpressed only tumor necrosis factor alpha quickly developed arthritis along with significant bone and weight loss, those that also overexpressed GILZ had significantly less bone loss, Shi said.
Our previous studies have shown that the GILZ transgenic mouse can make more bone," said Dr.
Next steps include developing an oral medication, a peptide specifically, that increases GILZ expression rather than the genetic alterations the researchers have used in animal models, said Yang.