Proliferative Effect of Histamine on MA-10 Leydig Tumor Cells Mediated Through HRH2 Activation, Transient Elevation in cAMP Production, and Increased Extracellular Signal-Regulated Kinase Phosphorylation Levels1

Abstract

Mast cells (MC) occur normally in the testis with a species-specific distribution, yet their precise role remains unclear. Testicular MC express histidine decarboxylase (HDC), the unique enzyme responsible for histamine (HA) generation. Evidence to date supports a role for HA as a local regulator of steroidogenesis via functional H₁ and H₂ receptor subtypes (HRH1 and HRH2, respectively) present in Leydig cells. Given that HA is a well-known modulator of physiological and pathological proliferation in many different cell types, we aimed in the present study to evaluate whether HA might contribute to the regulation of Leydig cell number as well as to the control of androgen production. Herein, we demonstrate, to our knowledge for the first time, that MA-10 Leydig tumor cells, but not normal immature Leydig cells (ILC), exhibit a proliferative response upon stimulation with HA that involves HRH2 activation, transient elevation of cAMP levels, and increased extracellular signal-regulated kinase (ERK) phosphorylation. Our results also reveal that MA-10 cells show significantly heightened HDC expression compared to normal ILC or whole-testicular lysate and that inhibition of HDC activity decreases MA-10 cell proliferation, suggesting a possible correlation between autocrine overproduction of HA and abnormally increased proliferation in Leydig cells. The facts that germ cells are also both source and target of HA and that multiple testicular cells are susceptible to HA action underline the importance of the present study, which we hope will serve as a first step for further research into regulation of non-MC-related HDC expression within the testis and its significance for testicular function.

Histamine inhibits adrenocortical cell proliferation but does not affect steroidogenesis

“…The existence of a functional histaminergic system in the testis of different species has been demonstrated previously by us (Mondillo et al 2005, Pagotto et al 2012 and others (Mayerhofer et al 1989, Pap et al 2002, Albrecht et al 2005, Khan & Rai 2007. Particularly, we have reported that low concentrations of HA (10 K9 M) stimulate LC steroidogenesis and higher concentrations (10 K5 M) inhibit it (Mondillo et al 2005).…”

“…In this respect, it has been shown that HA can act as both an anti-mitogenic (Cricco et al 2006, Petit-Bertron et al 2009, Meng et al 2011) and a mitogenic (Molina-Hernandez & Velasco 2008, Francis et al 2009, Medina et al 2011, Stoyanov et al 2012 agent, depending on the cell type and the HA receptor pattern expressed. In particular our recent studies have shown, for the first time to our knowledge, the proliferative effect of HA in MA-10 LCs, mediated via HRH2 activation and increased cAMP production and ERK phosphorylation (Pagotto et al 2012).…”

“…Compounds used were as follows: FMPH as the HRH1 agonist, AMTH as the HRH2 agonist, IMET as the HRH3 agonist, and VUF as the HRH4 agonist, all at a concentration 10 K5 M, which we have used previously (Mondillo et al 2005, Medina et al 2011, Pagotto et al 2012. As can be seen in Fig.…”

“…As an approach to demonstrating more directly the role of HDC and HA content in Y1 and H295R cell proliferation, we evaluated the effect of the catechin EGCG, known to potently inhibit HDC activity, as has been recently shown by us (Pagotto et al 2012) and others (Nitta et al 2007, Ruiz-Perez et al 2012, on the proliferation of Y1 cells. As can be seen in Fig.…”

H4 histamine receptors inhibit steroidogenesis and proliferation in Leydig cells

“…Accordingly, numerous studies from our group and others over the past few years have documented the ability of HA to modulate Leydig cell steroidogenesis through HRH1 and HRH2 (Mayerhofer et al 1989, Mondillo et al 2005, 2007, Khan & Rai 2007, and a very recent publication from our group has suggested a role for HA as an autocrine-paracrine regulator of Leydig cell proliferation under testicular pathological conditions (Pagotto et al 2012). Considering that germ cells express HDC (Safina et al 2002), and that HA has been implicated in spermatogenesis, penile erection and sexual behavior as well as steroidogenesis (Cara et al 1995, Par et al 2003, Sinha et al 2006), it appears that the amine plays an integral role in the regulation of male reproductive function, which certainly deserves further investigation.…”