TSH promotes Chemerin/CMKLR1-cAMP/ ERK-DIO2 signaling in primary rat ependymal cells in vitro

In mammals, chemerin and its receptor CMKLR1 might be downstream effectors in response to long photoperiod in the ependymal cells lining the third ventricle in rats. Iodothyronine deiodinase 2 (DIO2) is a main product of the involvement of TSH in photoperiodic signaling. Thus, the potential interplay of TSH and Chemerin/CMKLR1 signaling might exist during photoperiodic changes. Our study aimed to investigate whether Chemerin/CMKLR1 signaling could stimulate DIO2 production and how TSH could affect Chemerin/CMKLR1 signaling in primary rat ependymal cells. Colocalization of Chemerin with its receptor, CMKLR1, was observed using immunohistochemistry assay. The expression of chemerin and CMKLR1 was identified using real-time PCR and western blot analysis respectively. DIO2 expression, which involves a dual signaling pathway (an increase in cAMP levels and phosphorylation of ERK1/2, was detected by western blot assay and enzyme-linked immunosorbent assay (ELISA). Our study showed the potential interaction between Chemerin and CMKLR1 in primary rat ependymal cells. TSH could upregulate the expression of chemerin and CMKLR1 in Chemerin-pretreated primary ependymal cells. In vitro treatment of primary ependymal cells with Chemerin (10 ng/mL) or TSH (60 mIU/mL) could induce an increase in cAMP levels, ERK1/2 phosphorylation and DIO2 expression. Furthermore, we found that TSH could promote the effect of Chemerin/CMKLR1 signaling on DIO2 production through an increase in cAMP level and the phosphorylation of ERK1/2. We concluded that Chemerin/CMKLR1 signaling could enhance DIO2 activity in primary rat ependymal cells in vitro, and this effect could be promoted by TSH through cAMP and phosphorylation of ERK1/2.