Stress Triggered Changes in Gene Expression in Adrenal Medulla: Transcriptional Responses to Acute and Chronic Stress

Abstract

1. Stress elicits activation of several transcription factors involved in the regulation of catecholamine biosynthetic enzyme gene expression depending on its duration or repetition. However, the dynamic of the conversion of transient transcriptional activation with acute stress to sustained changes in transcription in response to repeated exposure to stress in adrenomedullary catecholaminergic systems is not clear. 2. Here, we analyzed changes in levels of phospho-CREB (P-CREB), phospho-ERK1/2 (P-ERK1/2) and Fra-2 by Western Blot analysis in adrenal medulla of Sprague Dawley male rats exposed to single or repeated immobilization stress (IMO). For single stress, rats were immobilized for 5 min, 30 min, or 2 h and sacrificed immediately afterwards. In the repeated stress conditions, animals were immobilized for 2 h daily on each consecutive day prior to the final day (day 2 for 2x IMO, day 6 for 6x IMO) in which the rats were immobilized for a session lasting 5 min, 30 min or 2 h. There were two control groups, an absolute control (AC) not exposed to stress, and a handled control (HC) gently handled daily for 6 days. 3. Phosphorylation of CREB was rapid and elevated at the earliest time examined, even with single stress. However, with a second daily episode of stress the increase in P-CREB was observed for at least the entire duration of the stress. In contrast, phosphorylation of ERK1/2 was only significant after brief exposure to a single IMO. The elevation of Fra-2 protein level was slower, but was significant after 2 h of a single IMO. With repeated IMO, there were marked elevations of Fra-2 throughout the 2 h IMO, which were especially pronounced at the end of the immobilization. 4. The transient nature of the phosphorylation of CREB may be responsible for the short-lived induction of transcription of catecholamine biosynthetic enzymes after brief exposure to a single immobilization stress. The sustained phosphorylation of CREB throughout the repeated stress coupled with induction of Fra-2 may mediate the longer lasting responses to repeated stress.

Stress Triggered Changes in Expression of Genes for Neurosecretory Granules in Adrenal Medulla

“…We have previously shown that both acute and repeated IMO leads to a very marked induction of Egr1 expression (Papanikolaou and Sabban 1999;Liu et al 2008). However, in contrast, phosphorylation of CREB in the adrenal medulla is only robustly increased with repeated exposure to IMO (Sabban et al 2006) and may be involved in the induction of CgA and CgB gene expression observed here. Enhanced phosphorylation of CREB is also involved in transactivation of the CgA gene (Cramer et al 2008).…”

Functional Remodeling of Gap Junction-Mediated Electrical Communication between Adrenal Chromaffin Cells in Stressed Rats

“…Alternatively, interaction between ZO-1 and Cx36/Cx43 may modify their trafficking and/or facilite their interactions with other proteins. As shown by qPCR experiments and reported for genes encoding catecholamine-synthesizing enzymes and related transcription factors (Baruchin et al, 1990;Sabban and Kvetnansky, 2001;Sabban et al, 2006), mechanisms taking place at the transcriptional level can also be involved. We show that in cold stressed rats, the Cx36 protein expression level faithfully parallels the Cx36 mRNA expression level, as opposed to Cx43, for which the mRNA expression level remains unchanged.…”

Learning about stress: neural, endocrine and behavioral adaptations

“…Sabban et al (2004) extended these findings by reporting elevations in catecholamine biosynthetic enzymes in sympathetic ganglia. Finally, when chronically immobilized rats are exposed to novel stressors, levels of TH and PNMT in the adrenal medulla increase even further (Kvetnansky, 2004;Sabban & Serova, 2007;Sabban et al, 2006).…”