RESUMO
Testicular Leydig cells (LC) are modulated by several pathways, one of them being the histaminergic system. Heme oxygenase-1 (HO-1), whose upregulation comprises the primary response to oxidative noxae, has a central homeostatic role and might dysregulate LC functions when induced. In this report, we aimed to determine how hemin, an HO-1 inducer, affects LC proliferative capacity and whether HO-1 effects on LC functions are reversible. It was also evaluated if HO-1 interacts in any way with histamine, affecting its regulatory action over LC. MA-10 and R2C cell lines and immature rat LC were used as models. Firstly, we show that after a 24-h incubation with 25 µmol/L hemin, LC proliferation is reversibly impaired by cell cycle arrest in G2/M phase, with no evidence of apoptosis induction. Even though steroid production is abrogated after a 48-h exposure to 25 µmol/L hemin, steroidogenesis can be restored to control levels in a time-dependent manner if the inducer is removed from the medium. Regarding HO-1 and histamine interaction, it is shown that hemin abrogates histamine biphasic effect on steroidogenesis and proliferation. Working with histamine receptors agonists, we elucidated that HO-1 induction affects the regulation mediated by receptor types 1, 2 and 4. In summary, HO-1 induction arrests LC functions, inhibiting steroid production and cell cycle progression. Despite their reversibility, HO-1 actions might negatively influence critical phases of LC development and differentiation affecting their function as well as other androgen-dependent organs. What's more, we have described a hitherto unknown interaction between HO-1 induction and histamine effects.
Assuntos
Heme Oxigenase-1/metabolismo , Histamina/farmacologia , Células Intersticiais do Testículo/metabolismo , Animais , Apoptose/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Fase G2/efeitos dos fármacos , Hemina/farmacologia , Células Intersticiais do Testículo/citologia , Células Intersticiais do Testículo/efeitos dos fármacos , Masculino , Camundongos , Mitose/efeitos dos fármacos , Ratos Sprague-Dawley , Esteroides/biossínteseRESUMO
Histamine (HA) is a neurotransmitter synthesized in most mammalian tissues exclusively by histidine decarboxylase enzyme. Among the plethora of actions mediated by HA, the modulatory effects on steroidogenesis and proliferation in Leydig cells (LCs) have been described recently. To determine whether the effects on LCs reported could be extrapolated to all steroidogenic systems, in this study, we assessed the effect of this amine on adrenal proliferation and steroidogenesis, using two adrenocortical cell lines as experimental models, murine Y1 cells and human NCI-H295R cells. Even when steroidogenesis was not modified by HA in adrenocortical cells, the biogenic amine inhibited the proliferation of H295R cells. This action was mediated by the activation of HRH1 subtype and an increase in the production of inositol phosphates as second messengers, causing cell-cycle arrest in the G2/M phase. These results indicate a new role for HA in the proliferation of human adrenocortical cells that could contribute to a better understanding of tumor pathology as well as to the development of new therapeutic agents.
Assuntos
Córtex Suprarrenal/citologia , Córtex Suprarrenal/metabolismo , Proliferação de Células , Histamina/metabolismo , Esteroides/metabolismo , Animais , Linhagem Celular , Pontos de Checagem da Fase G2 do Ciclo Celular , Humanos , Pontos de Checagem da Fase M do Ciclo Celular , CamundongosRESUMO
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.
Assuntos
AMP Cíclico/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Histamina/metabolismo , Tumor de Células de Leydig/metabolismo , Células Intersticiais do Testículo/metabolismo , Receptores Histamínicos H2/metabolismo , Sistemas do Segundo Mensageiro , Animais , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , AMP Cíclico/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , MAP Quinases Reguladas por Sinal Extracelular/antagonistas & inibidores , Agonistas dos Receptores Histamínicos/metabolismo , Agonistas dos Receptores Histamínicos/farmacologia , Histidina Descarboxilase/antagonistas & inibidores , Histidina Descarboxilase/biossíntese , Histidina Descarboxilase/metabolismo , Tumor de Células de Leydig/tratamento farmacológico , Tumor de Células de Leydig/enzimologia , Células Intersticiais do Testículo/citologia , Células Intersticiais do Testículo/efeitos dos fármacos , Células Intersticiais do Testículo/enzimologia , Masculino , Camundongos , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/metabolismo , Fosforilação/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores Histamínicos H2/química , Sistemas do Segundo Mensageiro/efeitos dos fármacos , Células-Tronco/citologia , Células-Tronco/efeitos dos fármacos , Células-Tronco/metabolismoRESUMO
In the present study, we demonstrate the expression of heme oxygenase (HO) isozymes, HO-1 and HO-2 (listed as HMOX1 and HMOX2 in the MGI Database), in MA-10 Leydig tumor cells and its effect on steroidogenesis. The well-known HO inducer, hemin, increased both HO-1 and HO-2 protein levels and HO-specific activity. Induction of HO by hemin inhibited basal, hCG-, and dibutyryl cAMP (db-cAMP)-induced steroidogenesis in a reversible way. When we studied the effect of HO isozymes along the steroid synthesis, we found that steroidogenic acute regulatory protein levels were decreased, and the conversion of cholesterol to pregnenolone was inhibited by hemin treatment, with no changes in the content of cholesterol side-chain cleavage enzyme (P450scc). hCG and db-cAMP also stimulated the expression of HO-1 and HO-2, and HO enzymatic activity in MA-10 cells. Basal and hCG-stimulated testosterone synthesis was also inhibited by hemin in rat normal Leydig cells. Taken together, these results suggest that: i) at least one of HO products (presumably carbon monoxide) inhibits cholesterol transport to the inner mitochondrial membrane and Leydig cell steroidogenesis by binding to the heme group of the cytochrome P450 enzymes, in a similar way as we described for nitric oxide, and ii) hCG stimulation results in the induction of an antioxidant enzymatic system (HO) acting as a cytoprotective mechanism in Leydig cells, as already demonstrated in the adrenal gland.