Resistin is a new player in murine hippocampal neuronal cells: expression and action on cell metabolic activity, proliferation, cell cycle, and expression of selected proliferative and apoptosis genes in HT-22 cells

BACKGROUND: Resistin, initially identified as an adipocyte-derived hormone, is associated with obesity, insulin resistance, and diabetes. However, its role in hippocampal neuronal cells remains unclear. This study aimed to investigate the effects of resistin on neuronal hippocampal cell function. METHODS: Expression of Retn and its receptors (Ror1, Cap1, and Tlr4) was analysed in mouse hippocampal HT-22 cells using RT-qPCR. The effects of resistin (0.1, 1, and 10 ng/ml) on metabolic activity (alamarBlue), proliferation (BrdU), cell cycle distribution and apoptosis (Annexin V/PI flow cytometry) were evaluated. Expression of apoptosis- (Bax, Bcl2, caspases-3, -8, -9, and p53) and proliferation-related markers (cyclins A2, B1, D1, and E1) was assessed using RT-qPCR and Western blotting. Activation of ERK1/2 pathway and the involvement of ERK1/2 and TLR4 signalling in resistin action were examined using pharmacological inhibitors. RESULTS: HT-22 cells expressed resistin and all three investigated receptors. Resistin decreased cellular metabolic activity at 7 h but increased it at 24 h. It stimulated cell proliferation at both time points and altered the cell cycle distribution after 24 h. At a 1 ng/ml, resistin reduced Ccne1 transcript levels and modulated the levels of cyclins and apoptosis-related markers examined. Moreover, resistin decreased the Bax/Bcl2 ratio at both the mRNA and protein levels after 24 h as well as increased ERK1/2 phosphorylation at 5 h. Pharmacological inhibition of ERK1/2 pathway indicated the involvement of ERK1/2 signalling in the resistin-mediated regulation of metabolic activity and proliferation, while TLR4 signalling was involved in the regulation of Casp3 expression and cell proliferation in HT-22 cells. CONCLUSION: Resistin may act as a novel regulator of hippocampal neuronal cell function.