Type IV collagen induces down-regulation of steroidogenic response to gonadotropins in adult rat Leydig cells involving mitogen-activated protein kinase

Abstract

We have previously shown that type IV collagen (alpha1 (IV) and alpha2 (IV) collagen chains) (Col-IV) inhibits testosterone (T) production by Leydig cells (LC). The aim of this study was to analyze mechanism/s by which Col-IV exerts this effect. No significant differences in the specific binding of hCG to LH/hCG receptors in LC cultured on uncoated or Col-IV coated plates were observed. An inhibition of cAMP production in hCG-stimulated LC cultured on Col-IV was detected. The inhibition exerted by Col-IV on T production in response to hCG was also observed when cells were stimulated with 8Bromo-cAMP. In addition, conversion of steroid precursors to T in LC cultured on uncoated and Col-IV coated plates was similar. On the other hand, we detected an increase of ERK1/2 phosphorylation in hCG-stimulated LC cultured on Col-IV. Genistein added to LC cultures reduced the ability of Col-IV to increase ERK1/2 phosphorylation and reverted the inhibitory effect of Col-IV on T production. An inhibitor of MEK, PD98059 added to LC cultures also reverted the inhibitory effect of Col-IV on T production. A decrease of steroidogenic acute regulatory protein (StAR) expression in hCG-stimulated LC cultured on Col-IV coated plates that could be reverted by addition of PD98059 to the cultures was also demonstrated. All together these results suggest that Col-IV inhibits T production in LC by binding to integrins, activating ERK1/2, decreasing cAMP production and decreasing StAR expression.

Gonadotropin-releasing hormone positively regulates steroidogenesis via extracellular signal-regulated kinase in rat Leydig cells

“…Although it is difficult to exclude the influence of non-specific effects of PD-98059, this inhibitor is well recognized as a specific antagonist of ERK1/2 and has been employed in many previous studies involving many cell types, including Leydig cells. 34,35 While our findings are mostly consistent with the results from a recent study reporting that inhibition of LH-activated ERK1/2 MAPK decreases steroidogenesis in Leydig cells, 18 the mechanisms of steroidogenesis may vary in different experimental systems. Although both PKA and MAPK are activated by LH in mLTC-1 Leydig cells, only cAMP-mediated PKA activation is essential, as the MAPK pathway is only involved in the early stage (30-60 min) 30 of steroidogenesis.…”

Changes in MAPK pathway in neonatal and adult testis following fetal estrogen exposure and effects on rat testicular cells

“…Interestingly, it was recently shown in MA-10 mouse tumoral Leydig cells that the c-AMP-dependent activation of Erk1/2 resulted in the transient mitochondrial localization of phosphorylated Erk1/2, where it phosphorylated StAR in a cholesterol-dependent manner (Poderoso et al, 2008). Moreover, cultures of adult rat Leydig cells were clearly shown to express Erk1/2 by western blot analysis (Diaz et al, 2005). Taken together, these studies indicate that Erk1/2 plays a role in Leydig cell function.…”

Serine proteases and serine protease inhibitors in testicular physiology: the plasminogen activation system

“…For instance, it was shown that fibronectin and collagen IV induce down-regulation of the steroidogenic response to gonadotropins (Diaz et al 2005). Furthermore, TGFb, known to cause augmented fibronectin deposition and to elicit cytoskeletal changes in Leydig cells similar to those evidenced when these cells are cultured on plates precoated with fibronectin, antagonizes gonadotropin steroidogenic action in Leydig cells (Dickson et al 2002).…”