Conversion of androstenedione to testosterone and other androgens in guinea-pig alveolar macrophages

Mouse testicular macrophages can independently produce testosterone and are regulated by Cebpb

BACKGROUND

Testicular macrophages (TM) have long been recognized for their role in immune response within the testicular environment. However, their involvement in steroid hormone synthesis, particularly testosterone, has not been fully elucidated. This study aims to explore the capability of TM to synthesize and secrete testosterone de novo and to investigate the regulatory mechanisms involved.

RESULTS

Transcriptomic analysis revealed significant expression of Cyp11a1, Cyp17a1, Hsd3b1, and Hsd17b3 in TM, which are key enzymes in the testosterone synthesis pathway. qPCR analysis and immunofluorescence validation confirmed the autonomous capability of TM to synthesize testosterone. Ablation of TM in mice resulted in decreased physiological testosterone levels, underscoring the significance of TM in maintaining testicular testosterone levels. Additionally, the study also demonstrated that Cebpb regulates the expression of these crucial genes, thereby modulating testosterone synthesis.

CONCLUSIONS

This research establishes that TM possess the autonomous capacity to synthesize and secrete testosterone, contributing significantly to testicular testosterone levels. The transcription factor Cebpb plays a crucial role in this process by regulating the expression of key genes involved in testosterone synthesis.

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.

An intracrine view of sex steroids, immunity, and metabolic regulation

Background

Over the past two decades, parallel recognition has grown of the importance of both sex steroids and immune activity in metabolic regulation. More recently, these discrete areas have been integrated in studies examining the metabolic effects of sex steroid immunomodulation. Implicit in these studies has been a traditional, endocrine model of sex steroid delivery from the gonads to target cells, including immune cells. Thus, research to date has focused on the metabolic effects of sex steroid receptor signaling in immune cells. This endocrine model, however, overlooks the extensive capacity of immune cells to generate and metabolize sex steroids, enabling the production of sex steroids for intracrine signaling – that is, sex steroid production for signaling within the cell of origin. Intracrine function allows highly cell-autonomous regulation of sex steroid exposure, and sex steroid secretion by immune cells could confer paracrine signaling effects in neighboring cells within metabolic tissues. In this review, immune cell intracrinology will denote sex steroid production within immune cells for either intracrine or paracrine signaling. This intracrine capacity of immune cells has been well established, and prior work has supported its importance in autoimmune disorders, trauma, and cancer. The potential relevance of immune cell intracrine function to the regulation of energy balance, body weight, body composition, and insulin sensitivity has yet to be explored.

Scope of review

The following review will detail findings to date regarding the steroidogenic and steroid metabolizing capacity of immune cells, the regulation of immune cell intracrine function, and the biological effects of immune-derived sex steroids, including the clinical relevance of immune cell intracrinology in fields other than metabolism. These findings will serve as the basis for a proposed model of immune cell intracrinology constituting a new frontier in metabolism research.

Major conclusions

The development of highly sensitive mass spectrometric methods for sex steroid measurement and quantitation of metabolic flux now allows unprecedented ability to interrogate sex steroid production, metabolism and secretion by immune cells. Immune cell intracrinology could reveal key mechanisms underlying immune cell-mediated metabolic regulation.

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Sex steroids exert immunomodulatory effects that may influence metabolic health.

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Immune cells can synthesize, modify, and metabolize sex steroids.

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Immune cell-derived sex steroids may play intracrine, autocrine, paracrine, and possibly even endocrine roles.

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Immune cell steroidogenesis is a largely unexplored area of metabolism research.

Androgens are bronchoactive drugs that act by relaxing airway smooth muscle and preventing bronchospasm

Changes in the androgen levels in asthmatic men may be associated with the severity of asthma. Androgens induce a nongenomic relaxation in airway smooth muscle, but the underlying mechanisms remain unclear. The aim of this study was to investigate the potential bronchorelaxing action of testosterone (TES) and its metabolites (5α- and 5β-dihydrotestosterone (DHT). A preventive effect on ovalbumin (OVA)-induced bronchospasm was observed in sensitized guinea pigs for each androgen. Androgens were studied in response to bronchoconstrictors: carbachol (CCh) and KCl in isolated trachea rings with and without epithelium from non-sensitized and sensitized animals as well as on OVA-induced contraction. Androgens concentration-dependently abolished the contraction in response to CCh, KCl, and OVA. There were significant differences in the sensitivity to the relaxation induced by each androgen. 5β-DHT was more potent for relaxing KCl-induced contraction, while TES and 5α-DHT were more potent for CCh- and OVA-induced contraction. No differences were found in preparations with and without epithelium or in the presence of a nitric oxide (NO) synthase inhibitor or an inhibitor of K(+) channels. These data indicate the absence of involvement of the epithelium-, NO- and K(+) channels-dependent pathway in androgen-induced relaxation. However, in dissociated tracheal myocytes loaded with the calcium-binding fluorescent dye Fura -2, physiological concentrations of androgens decreased the KCl-induced [Ca(2+)]i increment. 5β-DHT was the most potent at decreasing KCl-induced [Ca(2+)]i increment and preventing bronchospasm. We suggest that androgen-induced brochorelaxation was mediated via decreased Ca(2+) influx through L-type Ca(2+)channels but additional Ca(2+) entry blockade may be involved. Molecular changes in androgen structure may determine its preferential site of action.

Patterns of peripheral steroid metabolism vary with sex, season, and tissue type in blotched blue-tongued lizards (Tiliqua nigrolutea)

We examined sexual and seasonal variation in the ability of reproductively relevant tissues (liver, skin, adrenal gland, cloaca, kidney, renal sexual segment, epididymis, oviduct, muscle, testis, and ovary) to metabolise a primary steroid [testosterone (T) or estradiol (E2)] in the scincid lizard, Tiliqua nigrolutea. We observed considerable variation between sexes and across seasons in the patterns of conjugation and derivatisation of the primary steroids by these tissues. All tissues demonstrated the ability to conjugate the relevant primary steroid. Other general trends included increased conjugation by all tissues of gestating females, reduced metabolism of E2 by female tissues during late vitellogenesis, and reduced metabolism of T by males during early spermatogenesis. 5alpha-Dihydrotestosterone was the most commonly detected derivative in males, and production varied with season and tissue type. We suggest that seasonal variation in the ability of reproductively relevant tissues may be important in the physiological regulation of reproduction in this species.

Influence of cytokines and growth factors on distinct steroidogenic enzymes in vitro: a short tabular data collection

Cytokines (IL-1, IL-6, IL-8, IL-11, TNF, IFN-gamma, and TGF-beta) and growth factors (EGF, bFGF, aFGF, and KGF) play an important role in modulation of hormone secretion by directly influencing specific enzyme steps of steroidogenesis in various endocrine cell types. For this tabular data collection, the following enzyme steps were considered: steroidogenic acute regulatory protein (StAR), side chain cleavage enzyme (P450scc), 3 beta-hydroxysteroid dehydrogenase, 17-alpha-hydroxylase/17,20-lyase (P450c17), 17-beta-hydroxysteroid-dehydrogenase, aromatase complex, 5-alpha-reductase, P450c21, DHEAS sulfatase, and DHEA sulfotransferase. This collection summarizes the current information on how the mentioned cytokines and growth factors influence particular enzyme steps.

Evidence of 3 beta-hydroxysteroid dehydrogenase activity in several murine embryonal carcinoma cell lines

This report describes, for the first time to our knowledge, a possible steroidogenic activity in established murine embryonal carcinoma cell lines (PCC3, PCC4, F9), revealed by a 3 beta-hydroxysteroid dehydrogenase activity (revelation of NADH2 by staining, and RIA assessment of delta 4-androstenedione). The remarkable analogy between such totipotent cells and embryonal cells may suggest that this activity could be present before histologic organization of the embryonal testis. Nonmalignant embryonal cells such as fibroblasts (3/A/1/D-3) or myoblasts (T984) were also found to possess a 3 beta-hydroxysteroid dehydrogenase activity, thus suggesting that this enzyme is not specific to hormone-secreting cells, but the sign of a more general phenomenon.

Effect of cryptorchidism on the morphology of testicular macrophages: evidence for a Leydig cell-macrophage interaction in the rat testis

Macrophages and Leydig cells in the testes of adult rats which had been made bilaterally or unilaterally cryptorchid at birth were examined by morphometry for total mass, total number, volume density, and individual cell profile area. The total Leydig cell mass and the average size of Leydig cells, as well as the total mass and the average size of macrophages, were reduced in unilateral abdominal testes, but were unchanged in bilateral abdominal testes when compared to scrotal testes. Leydig cell and macrophage morphology were correlated suggesting a functional coupling between these cell types. The physiological significance of this cell interaction remains to be discovered.