Growth Hormone, Thyroid Hormones and Estradiol Interplay In Vivo to Regulate Gene Expression of Suppressor of Cytokine Signalling (SOCS)

Abstract

The SOCS proteins negatively regulate cytokine receptor signalling. The concentration of SOCS proteins is constitutively low but increases rapidly by stimulation with different stimuli. Physiological regulation of SOCS has not been well characterized. To evaluate the role of hormones on regulation of SOCS genes as well as E2 interaction with T3 and/or GH in vivo we used castrated-hypothyroid (TX) male rats. TX reduced BWG and it was recovered by hormonal replacement; in the presence of E2, however, recovery of BWG was fully abolished. TX decreased SOCS2 and CIS mRNA expression levels and they were induced by GH. In contrast, TX induced SOCS3 mRNA levels and T3 treatment restored them. E2 treatment induced SOCS2 and CIS mRNA levels. In the presence of E2, however, GH stimulation of SOCS2 and CIS was inhibited whereas T3 superinduced SOCS3. Taken together, these data suggest a complex interplay among these hormones to regulate physiological levels of SOCS.