Neuregulin 4 (Nrg4) cooperates with melatonin to regulate the PRL expression via ErbB4/Erk signaling pathway as a potential prolactin (PRL) regulator

Abstract Neuregulin‐4 (Nrg4) and melatonin play vital roles in endocrine diseases. However, there is little discussion about the function and potential mechanism of Nrg4 and melatonin in prolactin (PRL) regulation. The human normal pituitary data from Gene Expression Profiling Interactive Analysis (GEPIA) database was used to explore the correlation between NRG4 and PRL. The expression and correlation of NRG4 and PRL were determined by Immunofluorescence staining (IF) and human normal pituitary tissue microarray. Western Blot (WB) was used to detect the expression of PRL, p‐ErbB2/3/4, ErbB2/3/4, p‐Erk1/2, Erk1/2, p‐Akt and Akt in PRL‐secreting pituitary GH3 and RC‐4B/C cells treated by Nrg4, Nrg4‐small interfering RNA, Erk1/2 inhibitor FR180204 and melatonin. The expression of NRG4 was significantly positively correlated with that of PRL in the GEPIA database and normal human pituitary tissues. Nrg4 significantly increased the expression and secretion of PRL and p‐Erk1/2 expression in GH3 cells and RC‐4B/C cells. Inhibition of Nrg4 significantly inhibited PRL expression. The increased levels of p‐Erk1/2 and PRL induced by Nrg4 were abolished significantly in response to FR180204 in GH3 and RC‐4B/C cells. Additionally, Melatonin promotes the expression of Nrg4, p‐ErbB4, p‐Erk1/2, and PRL and can further promote the expression of p‐Erk1/2 and PRL in combination with Nrg4. Further investigation into the function of Nrg4 and melatonin on PRL expression and secretion may provide new clues to advance the clinical control of prolactinomas and hyperprolactinemia.