Heme oxygenase expression and activity in immortalized hypothalamic neurons GT1-7

Heme oxygenase (HO), the main enzyme deputed to heme metabolism, has been identified as two main isoforms called HO-1 and HO-2. HO-1 is inducible and plays a main role in the cellular oxidant/antioxidant balance whereas HO-2 is constitutive and involved in the physiological metabolism of heme. However, it is noteworthy to mention that HO contribute to the regulation of the hypothalamic release of neuropeptides such as corticotrophin-releasing hormone and arginine-vasopressin and could modulate the pulsatile release of gonadotropin releasing hormone (GnRH). GT1-7 cells are immortalized hypothalamic neurons and a valuable tool to evaluate hypothalamic neuroendocrine control of reproduction. The aim of this work was to investigate and characterize the presence of HO isoforms in the GT1-7 hypothalamic neurons. Hemin, a well-known inducer of HO-1, significantly increased HO activity, whereas dexamethasone did not modify HO-2 activity. Moreover, hemin and DEX, in combination, did not have any additive effect on HO activity in GT1-7 neurons. Furthermore, basal HO-1 immunoreactivity identified in GT1-7 cells, was significantly up-regulated by hemin. Conversely, no HO-2 immunoreactivity was detected. Taken together, these results suggest the presence of functional HO-1 in GT1-7 immortalized hypothalamic neurons and open new avenues about the use of this cell line for the study of HO modulation of GnRH secretion and reproduction.