ADRENOCORTICOTROPIC HORMONE ELEVATES GENE EXPRESSION FOR CATECHOLAMINE BIOSYNTHESIS IN RAT SUPERIOR CERVICAL GANGLIA AND LOCUS COERULEUS BY AN ADRENAL INDEPENDENT MECHANISM L. I. SEROVA, V. GUEORGUIEV, S.-Y. CHENG AND E. L. SABBAN* Department of Biochemistry and Molecular Biology, Basic Science Building, New York Medical College, Valhalla, NY 10595, USA Abstract—Classically, upon hypothalamic stimulation, adre- nocorticotropic hormone (ACTH) is released from the pitu- itary and acts on melanocortin 2 receptors (MC2R) in the adrenal cortex, stimulating glucocorticoid synthesis and re- lease. Our earlier studies suggested that ACTH might have a direct effect on sympathetic ganglia. To analyze further the involvement of ACTH in regulation of gene expression of norepinephrine (NE) biosynthetic enzymes, we examined the effect of bilateral adrenalectomy (ADX) of Sprague–Dawley male rats. Fourteen days post-ADX, as expected, plasma ACTH was elevated, and levels of tyrosine hydroxylase (TH), dopamine -hydroxylase (DBH) and MC2R mRNAs in supe- rior cervical ganglia (SCG), and TH mRNA in locus coeruleus (LC) were increased compared with sham-operated animals. To determine effect of pulsatile elevation of ACTH, cortico- sterone pellets were implanted to ADX rats. Similar to immo- bilization (IMO) stress ACTH injections to these animals caused a rise in ACTH in plasma and triggered elevation of TH and DBH mRNAs in SCG and in LC with single and re- peated daily injections, and MC2R mRNA in SCG with single injections. To study the effect of ACTH in isolated cells, primary cultures of rat SCG were transfected with TH and DBH promoter constructs and treated with ACTH. In agree- ment with the in vivo data, ACTH elevated their promoter activities similar to levels triggered by cyclic AMP analog. ACTH in the human SK-N-SH neuroblastoma cells increased TH and DBH promoter activity and endogenous DBH mRNA levels. The results show that ACTH can have a direct effect on transcription and gene expression of NE biosynthetic en- zymes even without contribution of adrenal hormones. © 2008 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: ACTH, superior cervical ganglia, locus coeruleus, tyrosine hydroxylase, dopamine -hydroxylase. Stress triggers important neuroendocrine modifications that enable the organism to survive and restore homeosta- sis. However, prolonged stress is a major contributor to the development of cardiovascular and neuropsychiatric disor- ders [reviewed in (McEwen, 1998; Chrousos, 2000)]. It also increases the body’s susceptibility to infection, auto- immune diseases, chronic fatigue syndrome, and cancer and the propensity of an individual to self-administer drugs of abuse. Moreover, stress can influence the progression of chronic diseases such as diabetes. Key components mediating the broad physiological range of responses to stress include activation of the hypothalamic–pituitary– adrenocortical axis (HPA) and catecholaminergic systems, both central and peripheral. Classically, the release of pituitary adrenocorticotropic hormone (ACTH) under direction of the corticotropin re- leasing hormone (CRH) from the hypothalamus resulting in synthesis and release of glucocorticoids from the adrenal cortex and the subsequent feedback inhibition is a well- characterized response to stress [reviewed in (Dallman, 1993; Jacobson, 2005)]. However, ACTH appears to have functions in stress that are independent of its effect on the adrenal glucocorticoids. The melanocortin 2 receptor (MC2R), responsive only to ACTH, is expressed not only in the adrenal cortex (Voisey et al., 2003), but also in murine (not human) adipocytes (Boston and Cone, 1996) and in skin, where it is believed to bind to ACTH, mediating DNA synthesis and cell proliferation of keratinocytes (Kapas et al., 1998). ACTH MC2Rs are also expressed in sympa- thetic ganglia (Nankova et al., 2003). In addition, the action of ACTH is not restricted to the MC2R as ACTH is also an agonist for other melanocortin receptor subtypes [reviewed in (Wikberg, 1999; Voisey et al., 2003)]. Stress induced release of noradrenaline (NE) from postganglionic sympathetic neurons and epinephrine pre- dominantly from the adrenal medulla. In the brain, the majority of the NE neurons activated by stress originate from the locus coeruleus (LC). A variety of stressors in- crease NE biosynthesis in sympathetic ganglia and the LC [reviewed in (Sabban and Kvetnansky, 2001)]. Tyrosine hydroxylase (TH) and dopamine -hydroxylase (DBH) en- zymatic activity, mRNA levels, transcription of these genes and protein levels are elevated by stress [reviewed by (Kvetnansky and Sabban, 1993; Sabban and Kvetnansky, 2001; Sabban and Serova, 2007; Wong and Tank, 2007)]. The activation of the HPA axis by stress also appears to be involved in the regulation of the gene expression of cate- cholamine (CA) biosynthetic enzymes in the sympatho- neuronal system. We have demonstrated that injections of ACTH to rats were as effective as immobilization (IMO) *Corresponding author. Tel: +1-914-594-4068; fax: +1-914-594-4059. E-mail address: Sabban@nymc.edu (E. L. Sabban). Abbreviations: ACTH, adrenocorticotropic hormone; ADX, adrenalec- tomized; CA, catecholamine; CPT-cAMP, 8-(4-chlorophenylthio) adenosine 3=,5=-cyclic monophosphate sodium salt; CRH, corticotro- phin releasing hormone; DBH, dopamine -hydroxylase; HPA, hypo- thalamic–pituitary–adrenocortical axis; IMO, immobilization; LC, locus coeruleus; MC2R, melanocortin 2 receptor; NE, norepinephrine; PKA, protein kinase A; SCG, superior cervical ganglia; TH, tyrosine hydrox- ylase. Neuroscience 153 (2008) 1380 –1389 0306-4522/08$32.00+0.00 © 2008 IBRO. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.neuroscience.2008.02.059 1380