Neuropeptides and Adrenocortical Proliferation in Vitro

Abstract

Vasoactive intestinal peptide (VIP) and Neuropeptide Y (NPY) are localised in the capsule and zona glomerulosa region of the adrenal cortex, where they play an important role in regulating steroidogenesis and adrenal blood flow. This study investigates the effect of these neuropeptides on adrenocortical cellular proliferation and steroidogenesis in vitro. Capsular/glomerulosa and innerzone/medulla preparations were either stimulated acutely with NPY or VIP (both 10(-6) M) for up to 2 hours or for 24 hours, four and eight days in vitro in eagles MEM (3.4 mM K+). DNA synthesis was determined using immunocytochemistry through the incorporation of the thymidine analogue 5-bromo-2'-deoxyridine (BrdU, 20 mg/mL). Phosphorylation of mitogen activated protein kinase ERK1/2 was assessed by western blotting. Both VIP (10(-6) M) and NPY (10(-6) M) treatment caused an increase in DNA synthesis after four days in culture. Acute NPY treatment caused an increase in ERK1 and 2 phosphorylation (p < 0.01) in the capsular/zona glomerulosa. Vasoactive intestinal peptide treatment caused a significant increase in ERK 1/2 phosphorylation (p < 0.05) only in innerzones/medulla preparations. Both responses were maximal between 10 and 30 min of incubation and decrease thereafter. These data provide further evidence for the role of the mitogen activated protein kinases ERK1 and 2 in the proliferative events in the adrenal gland and demonstrate stimulation of cell division by the adrenal neuropeptides VIP and NPY in vitro.

Increased extracellular signal regulated kinases phosphorylation in the adrenal gland in response to chronic ACTH treatment

“…Our present findings support the idea that ACTH also acts on glomerulosa cells by activating ERKs, although one can only speculate as to what their other functions may be. This is not in contradiction with the fact that other adrenal stimulating factors such as angiotensin-II and several neuropeptides can also induce ERKs activation in the adrenal ZG (Watanabe et al 1996, Whitworth et al 2002, McNeill et al 2005.…”

Mechanisms of adrenal gland growth: signal integration by extracellular signal regulated kinases1/2

“…By contrast, the control of cell size in zona fasciculata cells has been attributed to the phosphoinositol-3-kinase pathway (Lawlor et al 2002). The effects of ERK1/2 on cell number can be exerted by different mechanisms: A) an induction of cell proliferation , Andreis et al 2000, 2003, Whitworth et al 2002, Mazzocchi et al 2004, Ho et al 2005, Ferreira et al 2007, B) by blockade of apoptosis (Mazzocchi et al 2004, Edwin & Patel 2008 or C) by promoting cell survival (Ziegler et al 2006). Although it is widely accepted that ERK activity is required for cell proliferation and mitosis (Chambard et al 2007), it has been shown recently that too high ERK1/2 activity also can block the entry into mitosis (Rahmouni et al 2006).…”

“…Importantly, also estrogenic pollutants ( Yanagihara et al 2005) and phytoestrogens ( Yanagihara et al 2008) have been shown to stimulate or block catecholamine synthesis via ERKs depending on their respective concentration. A number of additional growth factors, like epidermal growth factor (EGF; , Ho et al 2005, insulin (Sugano et al 2006), vasoactive intestinal peptide (VIP; Whitworth et al 2002) and urocortin-2 ( Nemoto et al 2005) were found to affect ERK activation in different medullary cell systems. In addition to the aforementioned growth factors also pharmaceutical agents such as milnacipran (Shinkai et al 2007), chemical factors such as histamine , and nicotine (Cox et al 1996), or even environmental pollutants such as cadmium (Leal et al 2007) impact on medullary ERK activation and in part also catecholamine secretion.…”

“…In addition to these factors, many other agents (Fig. 2) including neuropeptides and sex steroids have been demonstrated to affect the activity of ERK1/2 (Cote et al 1998, Mazzocchi et al 2000, McNeill & Vinson 2000, Whitworth et al 2002, Chien et al 2005, McNeill et al 2005, Shah et al 2005, Brizuela et al 2007, Kovzun 2007, Keramidas et al 2008, which might suggest cross activation by receptor tyrosine kinase (RTK) and G-protein-coupled receptors (GPCR; see below).…”

“…The permanent perception of diverse factors affecting adrenal growth and function argues in favor of one common intracellular target, which coordinates and integrates the different stimuli and which further represents a potent effector of central cellular responses like proliferation, survival, apoptosis, or differentiation. As a potential candidate for an intracellular target in adrenal cells extracellular signal regulated kinases 1/2 (ERK1/2) have been demonstrated to affect cell proliferation , Andreis et al 2000, Lepique et al 2000, Lotfi et al 2000, Whitworth et al 2002, Ferreira et al 2007, apoptosis (Mazzocchi et al 2004, Edwin & Patel 2008 cell survival (Ziegler et al 2006), cell migration (Ho et al 2001(Ho et al , 2005, or synthesis and secretion of cortical ( Wu et al 2002, Otis et al 2005, Kempná et al 2007, Chang et al 2008 or medullary hormones (Cox & Parsons 1997, Shibuya et al 2002. Thus, in fact, ERK1/2 have the potential and format to represent such common targets with multiple biological effects in the adrenal gland as proposed before (Chabre et al 1995).…”