Interleukin 1-beta injected into the testis acutely stimulates and later attenuates testicular steroidogenesis of the immature rat

Immune Cells as Critical Regulators of Steroidogenesis in the Testis and Beyond

Steroidogenesis is an essential biological process for embryonic development, reproduction, and adult health. While specific glandular cells, such as Leydig cells in the testis, are traditionally known to be the principal players in steroid hormone production, there are other cell types that contribute to the process of steroidogenesis. In particular, immune cells are often an important component of the cellular niche that is required for the production of steroid hormones. For several decades, studies have reported that testicular macrophages and Leydig cells are intimately associated and exhibit a dependency on the other cell type for their proper development; however, the mechanisms that underlie the functional relationship between macrophages and Leydig cells are unclear. Beyond the testis, in certain instances immune cells themselves, such as certain types of lymphocytes, are capable of steroid hormone production, thus highlighting the complexity and diversity that underlie steroidogenesis. In this review we will describe how immune cells are critical regulators of steroidogenesis in the testis and in extra-glandular locations, as well as discuss how this area of research offers opportunities to uncover new insights into steroid hormone production.

Impaired macrophages and failure of steroidogenesis and spermatogenesis in rat testes with cytokines deficiency induced by diacerein

The role of cytokines in testicular function under normal conditions has not been completely understood. Here, we evaluated testicular macrophages (TM), steroidogenesis by Leydig cells (LC) and seminiferous tubules integrity in cytokines-deficient rat testes induced by diacerein, an anti-inflammatory drug that inhibits interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-α). Male rats received daily 100 mg/kg of diacerein (DIAG; n = 8) or saline (CG; n = 8) for 30 days. Serum testosterone (T) levels were measured and the seminiferous tubule (ST) area, epithelial area (EA), frequency of damaged ST and number of Sertoli cells (SC) were evaluated. TUNEL method and immunoreactions for detection of pro-IL-1β, TNF-α, steroidogenic acute regulatory protein (StAR), 17β-hydroxysteroid dehydrogenase (17β-HSD), androgen receptor (AR) and scavenger receptor for hemoglobin-haptoglobin complexes (CD163), a TM marker, were performed. Testicular AR, 17β-HSD and IL-1β levels were detected by Western blot. Data were submitted to Student t test (p ≤ 0.05). In DIAG, T and testicular AR, 17β-HSD and IL-1β levels decreased significantly (p < 0.05). The number of TUNEL-positive interstitial cells increased and LC showed weak StAR, 17β-HSD and AR immunoexpression in association with reduced IL-1β immunoexpression and number of CD163-positive TM in the interstitial tissue from diacerein-treated rats. Numerous damaged ST were found in DIAG, and reduction in the EA were associated with germ cells death. Moreover, the number of SC reduced and weak AR and TNF-α immunoexpression was observed in SC and germ cells, respectively. The cytokines deficiency induced by diacerein impairs TM, LC and spermatogenesis, and points to a role of IL-1β in steroidogenesis under normal conditions. In the ST, the weak AR and TNF-α immunoexpression in SC and germ cells, respectively, reinforces the idea that TNF-α plays a role in the SC androgenic control.

Impacts of Immunometabolism on Male Reproduction

The physiological process of male reproduction relies on the orchestration of neuroendocrine, immune, and energy metabolism. Spermatogenesis is controlled by the hypothalamic-pituitary-testicular (HPT) axis, which modulates the production of gonadal steroid hormones in the testes. The immune cells and cytokines in testes provide a protective microenvironment for the development and maturation of germ cells. The metabolic cellular responses and processes in testes provide energy production and biosynthetic precursors to regulate germ cell development and control testicular immunity and inflammation. The metabolism of immune cells is crucial for both inflammatory and anti-inflammatory responses, which supposes to affect the spermatogenesis in testes. In this review, the role of immunometabolism in male reproduction will be highlighted. Obesity, metabolic dysfunction, such as type 2 diabetes mellitus, are well documented to impact male fertility; thus, their impacts on the immune cells distributed in testes will also be discussed. Finally, the potential significance of the medicine targeting the specific metabolic intermediates or immune metabolism checkpoints to improve male reproduction will also be reassessed.

The in vitro modulation of steroidogenesis by inflammatory cytokines and insulin in TM3 Leydig cells

BACKGROUND

Cytokines and hormones, including insulin, are known to modulate the hypothalamic-pituitary-testes axis and steroidogenesis, both centrally and peripherally. In the context of chronic inflammation and hyperinsulinaemia mediating male hypogonadism associated with obesity, metabolic syndrome and type 2 diabetes mellitus, these mechanisms are poorly understood and the impact of cytokines and insulin on Leydig cell steroidogenesis has not been fully elicited. This study aimed to further investigate the in vitro impact of TNFα, IL1ß, IL6, IL8 and insulin on Leydig cell function and steroidogenesis.

METHODS

hCG-stimulated TM3 Leydig cells were exposed to various concentrations of TNFα, IL1ß, IL6, IL8 (100 ng/ml, 10 ng/ml, 1 ng/ml and 0.1 ng/ml) and insulin (10 ng/ml, 1 ng/ml, 0.1 ng/ml and 0.01 ng/ml) in optimal cell culture conditions over 48 h. Cell viability (XTT) and testosterone and progesterone concentrations (ELISA) were assessed using standardised laboratory techniques.

RESULTS

TNFα significantly decreased cell viability and progesterone and testosterone concentrations in a dose-dependent relationship. IL1ß and IL6 had a subtle but significant negative effect on cell viability and testosterone concentrations, with a marked significant decrease in progesterone concentration at all concentrations investigated. IL8 showed an increase in cell viability, with no significant effect on testosterone concentrations alongside a significant decrease in progesterone concentrations. Insulin significantly increased cell viability and testosterone concentrations in a dose dependent relationship, but interestingly significantly decreased progesterone concentrations.

CONCLUSIONS

The inflammatory cytokines TNFα, IL1β and IL6 cause a dose dependent decline in steroidogenesis in TM3 Leydig cells. These results suggest that chronic inflammation may downregulate steroidogenesis in males via direct modulation of Leydig cell function. However, IL8 may stimulate TM3 Leydig cell growth. Insulin is associated with a dose-dependent increase in testosterone synthesis, with a significant decline in progesterone synthesis. With the phenomenon of insulin resistance, the literature is unclear on the potential role of hyperinsulinaemia in steroidogenesis. Further studies are warranted in order to fully elicit the molecular mechanisms and interactions of these molecules on male steroidogenesis.

A high-fat diet impairs reproduction by decreasing the IL1β level in mice treated at immature stage

Obesity causes low-grade inflammation that is involved in male infertility. Interleukin 1 beta (IL1β) plays an important role in this process. A high-fat diet (HFD) is the most common cause of obesity. However, the effect of a HFD on IL1β and its consequence in reproduction remain unclear. We established a HFD model in mice treated at immature stage (mice-TIS) and mice treated at mature stage (mice-TMS). Surprisingly, we found that a HFD decreased IL1β levels and was accompanied by an increase in testosterone in mice-TIS, while the reverse results were observed in mice-TMS. In addition, a HFD caused a reduction in testis macrophages and in the expression of inflammasome-related genes and proteins in mice-TIS. Furthermore, we found that IL1β inhibited testosterone secretion through down-regulating the gene expression of P450SCC and P450c17. However, the influence on mice-TIS that were induced by a HFD was recovered by stopping the HFD. In this study, we are the first to report that a HFD impairs the reproductive system by decreasing IL1β and enhancing testosterone levels in mice-TIS, which are different from the effects in mice-TMS. This provides new ideas for the treatment of obesity-induced infertility.

Innervation and serotoninergic receptors of the testis interact with local action of interleukin-1beta on steroidogenesis

Testosterone secretion by Leydig cells is affected by interleukin-1beta (IL-1beta). The aim of the present study was to investigate whether partial denervation of the testis or local administration of a serotonin (5-HT) receptor antagonist could alter the changes in testicular steoidogenesis induced by IL-1beta. Intratesticular administration of IL-1beta was combined with vasectomy or local injection of ketanserin (5-HT type 2 receptor antagonist) in immature hemicastrated rats and the effect of the interventions on testicular steroidogenesis was studied. One day after treatment with local injection of IL-1beta induced a significant rise in testosterone secretion that could be prevented by vasectomy (that also means transection of the inferior spermatic nerve). In a model in which neither IL-1beta nor ketanserin interfered with steroidogenesis, administration of the receptor antagonist just prior to IL-1beta treatment significantly reduced testosterone secretion. Data indicate interaction between testicular nerves and IL-1beta action and interaction between testicular 5-HT2 receptors and local effect of IL-1beta on testosterone secretion.