Site of Macrophage Inhibition of Luteinizing Hormone-Stimulated Testosterone Production by Purified Leydig Cells1

Abstract

It has been observed that testicular macrophages and testicular macrophage-conditioned medium reduce LH-stimulated, but not basal, testosterone production by purified Leydig cells in vitro. In order to determine how this inhibition occurs, we have examined the effects of testicular macrophages and testicular macrophage-conditioned medium at discrete stages of the steroidogenic pathway. The lesion in steroidogenesis is located at a step beyond cAMP formation, because the addition of dibutyryl cAMP or cholera toxin did not overcome the testicular macrophage-conditioned medium inhibition of LH-stimulated steroidogenesis by Leydig cells. This effect of testicular macrophage-conditioned medium on Leydig cell testosterone production is first observed at 18 h after initiation of culture. However, subsequent additions of 22R-hydroxycholesterol, pregnenolone, dehydroepiandrosterone, or androstenedione to the Leydig cell cultures can overcome the inhibition so that, after a further 6 h of incubation, testosterone production is not significantly different from that of control Leydig cells cultured in the absence of testicular macrophage-conditioned medium. These results suggest that the block in steroidogenesis is beyond cAMP production but prior to the formation of pregnenolone, dehydroepiandrosterone, and androstenedione. Since the medium for these cultures contained lipoprotein, it is possible that the testicular macrophage-conditioned medium metabolizes the lipoprotein, making it unavailable to the Leydig cells. However, our results show that preincubation of lipoprotein with testicular macrophage-conditioned medium does not significantly alter testosterone production by the Leydig cells in the culture. It is concluded that testicular macrophage-conditioned medium affects the transport or availability of cholesterol to mitochondria prior to further steps in the steroidogenic pathway.

The effect of testicular macrophages, macrophage-conditioned medium and interleukin-1α on bank vole Leydig cell steroidogenesis

“…We found that neither peritoneal macrophages nor peritoneal macrophage-conditioned medium had an influence on the level of testosterone release. Contrary to our results, Sun and Risbridger (1994) described inhibitory effect of both testicular and peritoneal macrophages and respective conditioned media on LH-stimulated testosterone secretion. Although there is much evidence in literature on the effect of macrophage-conditioned media, but it is difficult to draw firm conclusions from these studies.…”

The role of cyclic AMP production, calcium channel activation and enzyme activities in the inhibition of testosterone secretion by amphetamine

“…The testicular cell preparation we employed included a population of macrophages. Since macrophage‐conditioned medium is inhibitory to both basal (Lombard‐Vignon et al , 1991) and LH/hCG‐stimulated testosterone production (Sun et al , 1993; Sum & Risbridger, 1994) and cytokines, such as in‐terleukin‐1 and tumour necrosis factor‐ α , either added exo‐genously or generated in vivo , inhibit steroidogenesis in Leydig cells (Sun & Risbridger, 1994; Hales, 1996), it is also possible that the effects of amphetamine on testosterone production described here are mediated in part by cytokines.…”

Morphofunctional changes in Leydig cells throughout the continuous spermatogenesis of the freshwater teleost fish, Serrasalmus spilopleura (Characiformes, Characidae): an ultrastructural and enzyme study

“…In mammals, macrophage-derived factors seem to modulate steroidogenic activity in Leydig cells (for a review, see Gaytan et al 1994). Studies of mammals have demonstrated that proinflammatory cytokines produced by macrophages inhibit androgen synthesis in Leydig cells by diminishing the activity of the enzymes of the steroidogenic pathway (Sun and Risbridger 1994;Watson et al 1994;Hales 1996). In teleosts, Lister and Van der Kraak (2002) have demonstrated that tumour necrosis factor α, which is produced by macrophages, inhibits testosterone synthesis at several enzyme sites and have suggested that the regulation of steroidogenesis in fish, as in mammals, involves multiple paracrine and autocrine factors.…”