TSH promotes chemerin/CMKLR1–cAMP/ERK–DIO2 signaling in primary rat ependymal cells in vitro

Abstract In mammals, chemerin and its receptor CMKLR1 might be downstream effectors in response to a 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 levels 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. Main points Chemerin/CMKLR1 interaction in primary rat ependymal cells is discussed. Chemerin/CMKLR1 signals through cAMP and ERK phosphorylation to induce deiodinase 2 expression in primary ependymal cells. TSH promotes the effect of chemerin/CMKLR1 signaling on deiodinase 2 expression.