Effects of neurosteroids on the human corticotropin-releasing hormone gene

Abstract

Increased activity of hypothalamic-pituitary-adrenal (HPA) axis and hypersecretion of corticotropin-releasing hormone (CRH) are known to be important factors in pathogenesis of some stress-related diseases. Some neurosteroids exert anxiolytic and antidepressant effects probably by inhibition of HPA axis activity. The aim of our study was to find out if neurosteroids can directly affect human CRH gene transcription. The effect of allopregnanolone (ALLO), allotetrahydrodeoxycorticosterone (THDOC), pregnenolone (PGL), PGL sulfate (PGL-S), dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) on CRH expression was determined in differentiated Neuro-2A cells stably transfected with plasmid containing a fragment of human CRH promoter (-663 to + 124 bp) linked to the chloramphenicol acetyltransferase (CAT) reporter gene. It was found that PGL (0.3-30 μM), ALLO (1-30 μM) and THDOC (1-30 μM) present in the culture medium for 5 days in the concentration-dependent manner inhibited CRH-CAT activity. These neurosteroids also inhibited forskolin-stimulated CRH gene transcription with similar potency. In contrast, PGL-S, DHEA and DHEA-S in a concentration from 0.01 to 10 μM had no effect on basal and forskolin-stimulated CRH activity. Further experiments revealed that wortmannin (an inhibitor of phosphatidylinositol 3-kinase; PI3-K) at concentrations of 0.01 and 0.02 μM did not change the inhibitory effect of ALLO (3 μM) and PGL (1 μM) on CRH gene transcription. Moreover, ALLO (3 μM) and PGL (1 μM) present in the culture medium for 5 days did not change the amount of active, phosphorylated form of protein kinase B (PKB, Akt) and extracellular signal-regulated kinase (ERK). The obtained results indicate that PGL, ALLO and THDOC inhibited basal and forskolin-induced CRH gene promoter activity in the differentiated Neuro-2A cells and that these effects did not depend on the activation of PI3-K/Akt and ERK-MAPK pathways.

Allopregnanolone reduces neuroendocrine response to acute stressful stimuli in sheep

“…Furthermore, a decrease in CRH mRNA expression following administration of AL alone may suggest a preventive silencing effect on HPA axis activity at the molecular level. Budziszewska et al (2010) found that AL inhibited CRH gene promoter activity in the differentiated Neuro-2A cells and suggested that the inhibition of CRH gene transcription may be a molecular mechanism responsible, at least partly, for its stress-protective effects. Similarly, such a situation may be related to the reduced expression of CRH and AVP receptors mRNA, as well as POMC mRNA in the AP, since some data point also to the involvement of other possible AL targets, such as intracellular nuclear receptors, protein kinases and microtubule-associated protein (Plassart-Schiess & Baulieu 2001).…”

Regulation of the corticosteroid signalling system in rainbow trout HPI axis during confinement stress

“…In brain and peripheral tissue DOC is converted to THDOC by enzymatic A-ring reduction by the 5α-Reductase and 3α-Hydroxysteroid oxidoreductase activity. THDOC lacks classical steroid hormone properties, but activates the post-synaptic inhibitory GABA A -(γ-aminobutyric acid) receptor function on CRH expression (Reddy 2006) and suppress stress-induced HPA axis activity in rats (Budziszewska et al, 2010). Acute stress triggers a rapid and robust increase in circulating and brain levels of THDOC (Purdy et al, 1991).…”

Neurosteroid Influences on Sensitivity to Ethanol

“…For example, allopregnanolone decreased anxiety in response to heat stress and administration of CRH (Patchev et al, 1994, 1996). A recent report indicated that physiological concentrations of allopregnanolone, THDOC, and pregnenolone in cell culture inhibited CRH reporter gene activity and forskolin-stimulated transcription (Budziszewska et al, 2010). Overall, these data are consistent with the idea that endogenous GABAergic neuroactive steroids exert negative feedback on stress responses.…”