Interaction of pituitary hormones and expression of clock genes modulated by bone morphogenetic protein-4 and...

Area of Science:

• Endocrinology
• Chronobiology
• Molecular Biology

Background:

• The anterior pituitary regulates crucial endocrine functions.
• Clock genes play a role in circadian rhythms and hormone secretion.
• Bone morphogenetic protein-4 (BMP-4) and melatonin are known modulators of pituitary hormone expression.

Purpose of the Study:

• To investigate the functional interactions between clock genes and pituitary hormones.
• To elucidate the roles of BMP-4 and melatonin in regulating clock gene expression and hormone synthesis in anterior pituitary cells.

Main Methods:

• Utilized AtT20 (corticotrope) and GH3 (lactosomatotrope) cell lines.
• Employed siRNA-mediated knockdown of clock genes (Per2, Clock, Bmal1).
• Measured mRNA and protein levels of POMC, PRL, and clock genes using RT-PCR and Western blotting.
• Applied treatments with BMP-4, melatonin, and forskolin.

Main Results:

• A significant correlation was found between pro-opiomelanocortin (POMC) and Per2 mRNA in corticotrope cells.
• Per2 knockdown reduced POMC mRNA levels, and BMP-4/melatonin suppressed both POMC and Per2 expression.
• A correlation between prolactin (PRL) and Clock mRNA was observed in lactosomatotrope cells.
• Clock knockdown reduced PRL mRNA levels, while Clock expression remained stable despite BMP-4, melatonin, or forskolin treatments.

Conclusions:

• Per2 and Clock genes exhibit distinct regulatory relationships with POMC and PRL, respectively, in specific anterior pituitary cell types.
• Melatonin and BMP-4 modulate Per2 expression, suggesting their influence on circadian regulation of ACTH secretion.
• Clock gene expression shows differential stability, potentially impacting the circadian rhythm of PRL secretion.