1alpha,25(OH)2-Vitamin D3 stimulation of secretion via chloride channel activation in Sertoli cells

Effects of glucagon-like peptide-1 receptor agonists on spermatogenesis-related gene expression in mouse testis and testis-derived cell lines

Glucagon-like peptide-1 (GLP-1) is an incretin released into the gastrointestinal tract after food ingestion, and stimulates insulin secretion from the beta cells of the pancreatic islets. Incretins have recently been reported to have extrapancreatic actions, and they are anticipated to have potential efficacy for conditions such as male infertility as well as diabetes. However, the effects of incretins on male reproductive function remain unclear. In this study, GLP-1 receptor expression and the effects of GLP-1 on spermatogenesis-associated genes were investigated using mouse testes and testis-derived cultured cell lines. Glp1r mRNA and GLP-1 protein were expressed in mouse testes at levels comparable to or greater than those in positive control adipose tissue, and the liver and intestine, and also in a Sertoli cell line (TM4) and a Leydig cell line (MA-10) as well as the GC-1 spg and GC-2 spd (ts) germ cell lines. TM4 cells treated with the GLP-1 receptor agonist exenatide showed transiently and significantly upregulated Kitl, Pdgfa, and Glp1r mRNA expression. Furthermore, at 1 hr post-exenatide administration to male mice, Kitl and Glp1r mRNA expression levels were significantly increased, and Pdgfa mRNA expression level also showed a tendency toward increase. TM4 cells were treated with various cell-activating agents, and bucladesine elicited significantly increased Glp1r mRNA expression. We suggest that GLP-1 provides acute stimulation of Sertoli cells in the mouse testis and has a stimulatory effect on the expression of spermatogenesis-related genes.

Calcium and vitamin D homoeostasis in male fertility

Calcium and vitamin D have well-established roles in maintaining calcium balance and bone health. Decades of research in human subjects and animals have revealed that calcium and vitamin D also have effects on many other organs including male reproductive organs. The presence of calcium-sensing receptor, vitamin D receptor, vitamin D activating and inactivating enzymes and calcium channels in the testes, male reproductive tract and human spermatozoa suggests that vitamin D and calcium may modify male reproductive function. Functional animal models have shown that vitamin D deficiency in male rodents leads to a decrease in successful mating and fewer pregnancies, often caused by impaired sperm motility and poor sperm morphology. Human studies have to a lesser extent validated these findings; however, newer studies suggest a positive effect of vitamin D supplementation on semen quality in cases with vitamin D deficiency, which highlights the need for initiatives to prevent vitamin D deficiency. Calcium channels in male reproductive organs and spermatozoa contribute to the regulation of sperm motility and capacitation, both essential for successful fertilisation, which supports a need to avoid calcium deficiency. Studies have demonstrated that vitamin D, as a regulator of calcium homoeostasis, influences calcium influx in the testis and spermatozoa. Emerging evidence suggests a potential link between vitamin D deficiency and male infertility, although further investigation is needed to establish a definitive causal relationship. Understanding the interplay between vitamin D, calcium and male reproductive health may open new avenues for improving fertility outcomes in men.

Molecular Regulation of the CNS by Vitamin D

Vitamin D is a lipid-soluble vitamin that can be found in some foods. It is also produced endogenously (in the presence of ultraviolet light), transported through the blood to the targets organs and this is the reason to consider vitamin D as a hormone. It is known that vitamin D has genomic and non-genomic effects. This review is focused mainly on the vitamin D receptors, the importance of vitamin D as a neuromodulator, the role of vitamin D in the pathophysiology of devastating neurological disorders such as Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease and the benefit of vitamin D and its derivates in alleviating these disorders.

Predictions from a mathematical approach to model ionic signaling for rapid responses of Sertoli cells exhibit similarities to pharmacological approaches

Sertoli cells are essential for the male reproduction system as they provide morphological support and nutrients for germ cells to guarantee ongoing spermatogenesis. The aim of this work was to predict the electrical properties at the plasma membrane that trigger Sertoli cell rapid responses by involving ionic channels. The rapid responses of Sertoli cells in culture were monitored using patch clamp electrical measurement and compared to data obtained using pharmacological tools (from intact seminiferous tubules). A mathematical model was used to define the roles of potassium channels and the ATP-dependent Na+/K+pump in these responses. Mathematical data verification was also performed to determine the resting and hormonal stimulated membrane potentials of Sertoli cells in the intact seminiferous tubules and of Sertoli cells in culture (patch clamp measurements). The prediction of these data based on mathematical modeling demonstrated, for the first time, the involvement of potassium channels and the activation of Na+/K+pump in the hyperpolarization of Sertoli cells and their consequent rapid responses. Moreover, the mathematical analysis showing the involvement of ionic balance in the rapid responses of these cells to hormones, such as follicle-stimulating hormone, is consistent with previous reports obtained using pharmacological techniques in Sertoli cells. Thus, the validation of such data is reliable and represents a first step in the proposition for a mathematical model to predict rapid responses of Sertoli cells to hormonal stimuli.

Evidence for Involvement of Nonclassical Pathways in the Protection From UV-Induced DNA Damage by Vitamin D-Related Compounds

The vitamin D hormone, 1,25dihydroxyvitamin D₃ (1,25(OH)₂D₃), and related compounds derived from vitamin D₃ or lumisterol as a result of metabolism via the enzyme CYP11A1, have been shown, when applied 24 hours before or immediately after UV irradiation, to protect human skin cells and skin from DNA damage due to UV exposure, by reducing both cyclobutane pyrimidine dimers (CPD) and oxidative damage in the form of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐OHdG). We now report that knockdown of either the vitamin D receptor or the endoplasmic reticulum protein ERp57 by small, interfering RNA (siRNA) abolished the reductions in UV‐induced DNA damage with 20‐hydroxyvitamin D₃ or 24‐hydroxylumisterol_3, as previously shown for 1,25(OH)₂D₃. Treatment with 1,25(OH)₂D₃ reduced oxygen consumption rates in UV‐exposed and sham‐exposed human keratinocytes and reduced phosphorylation of cyclic AMP response binding element protein (CREB). Both these actions have been shown to inhibit skin carcinogenesis after chronic UV exposure, consistent with the anticarcinogenic activity of 1,25(OH)₂D₃. The requirement for a vitamin D receptor for the photoprotective actions of 1,25(OH)₂D₃ and of naturally occurring CYP11A1‐derived vitamin D–related compounds may explain why mice lacking the vitamin D receptor in skin are more susceptible to UV‐induced skin cancers, whereas mice lacking the 1α‐hydroxylase and thus unable to make 1,25(OH)₂D₃ are not more susceptible. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Estradiol and 1α,25(OH)2 vitamin D3 share plasma membrane downstream signal transduction through calcium influx and genomic activation in immature rat testis

The aim of this study was to investigate the rapid response pathway and gene and protein expression profiles of the rat testis in response to estradiol (E₂) and 1α,25(OH)₂ vitamin D₃ (1,25-D₃), to understand how they mediate their effects on the first spermatogenic wave. To do this, we compared the effects of 1,25-D₃ and E₂ on ⁴⁵calcium(Ca²⁺) uptake and the involvement of estrogen receptors (ESR) in their rapid responses. Additionally, we studied the downstream signal transduction effects of 1,25-D₃ and E₂ on cyclin A1/B1 and cellular cycle protein expression. As previously observed for 1,25-D₃, E₂ also increased ⁴⁵Ca²⁺ uptake in immature rat testes via voltage-dependent Ca²⁺ channels, Ca²⁺-dependent chloride channels and via the activation of protein kinase C, protein kinase A and mitogen-activated protein kinase kinase (MEK). Elevated aromatase expression by testes was observed in the presence of 1,25-D₃ and both hormones decreased ESR mRNA expression. Furthermore, 1,25-D₃ and E₂ diminished cyclin A1 mRNA expression, but E₂ did not affect cyclin B1 mRNA levels. Consistent with these findings, the immunocontent of cyclin A1 and B1 in the testes was also increased by 1,25-D₃ and E₂. 1,25-D₃ increased expressions of the p16 and p53 proteins, supporting the anti-proliferative and pro-apoptotic properties of 1,25-D_3, while E₂ also augmented p16. Data indicate that both hormones trigger rapid responses at the plasma membrane that may control the expression of gene and proteins related to cell cycle regulation, and thereby modulate spermatogenesis.

Cytotoxicity of glucoevatromonoside alone and in combination with chemotherapy drugs and their effects on Na+,K+-ATPase and ion channels on lung cancer cells

Cardiac glycosides (CGs) are useful drugs to treat cardiac illnesses and have potent cytotoxic and anticancer effects in cultured cells and animal models. Their receptor is the Na⁺,K⁺ ATPase, but other plasma membrane proteins might bind CGs as well. Herein, we evaluated the short- and long-lasting cytotoxic effects of the natural cardenolide glucoevatromonoside (GEV) on non-small-cell lung cancer H460 cells. We also tested GEV effects on Na⁺,K⁺ -ATPase activity and membrane currents, alone or in combination with selected chemotherapy drugs. GEV reduced viability, migration, and invasion of H460 cells spheroids. It also induced cell cycle arrest and death and reduced the clonogenic survival and cumulative population doubling. GEV inhibited Na⁺,K⁺-ATPase activity on A549 and H460 cells and purified pig kidney cells membrane. However, it showed no activity on the human red blood cell plasma membrane. Additionally, GEV triggered a Cl-mediated conductance on H460 cells without affecting the transient voltage-gated sodium current. The administration of GEV in combination with the chemotherapeutic drugs paclitaxel (PAC), cisplatin (CIS), irinotecan (IRI), and etoposide (ETO) showed synergistic antiproliferative effects, especially when combined with GEV + CIS and GEV + PAC. Taken together, our results demonstrate that GEV is a potential drug for cancer therapy because it reduces lung cancer H460 cell viability, migration, and invasion. Our results also reveal a link between the Na⁺,K⁺-ATPase and Cl^- ion channels.

Functional effects of vitamin D: From nutrient to immunomodulator

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

Role of bisphenol A on calcium influx and its potential toxicity on the testis of Danio rerio

This study investigated the acute in vitro effect of low-concentration bisphenol A (BPA) on calcium (⁴⁵Ca²⁺) influx in zebrafish (Danio rerio) testis and examined whether intracellular Ca²⁺ was involved in the effects of BPA on testicular toxicity. In vitro studies on ⁴⁵Ca²⁺ influx were performed in the testes after incubation with BPA for 30 min. Inhibitors were added 15 min before the addition of ⁴⁵Ca²⁺ and BPA to testes to study the mechanism of action of BPA. The involvement of intracellular calcium from stores on lactate dehydrogenase (LDH) release and on triacylglycerol (TAG) content were carried out after in vitro incubation of testes with BPA for 1 h. Furthermore, gamma-glutamyl transpeptidase (GGT) and aspartate aminotransferase (AST) activities were analyzed in the liver at 1 h after in vitro BPA incubation of D. rerio. Our data show that the acute in vitro treatment of D. rerio testes with BPA at very low concentration activates plasma membrane ionic channels, such as voltage-dependent calcium channels and calcium-dependent chloride channels, and protein kinase C (PKC), which stimulates Ca²⁺ influx. In addition, BPA increased cytosolic Ca²⁺ by activating inositol triphosphate receptor (IP₃R) and inhibiting sarco/endoplasmic reticulum calcium ATPase (SERCA) at the endoplasmic reticulum, contributing to intracellular Ca²⁺ overload. The protein kinases, PKC, MEK 1/2 and PI3K, are involved in the mechanism of action of BPA, which may indicate a crosstalk between the non-genomic initiation effects mediated by PLC/PKC/IP₃R signaling and genomic responses of BPA mediated by the estrogen receptor (ESR). In vitro exposure to a higher concentration of BPA caused cell damage and plasma membrane injury with increased LDH release and TAG content; both effects were dependent on intracellular Ca²⁺ and mediated by IP₃R. Furthermore, BPA potentially induced liver damage, as demonstrated by increased GGT activity. In conclusion, in vitro effect of BPA in a low concentration triggers cytosolic Ca²⁺ overload and activates downstream protein kinases pointing to a crosstalk between its non-genomic and genomic effects of BPA mediated by ESR. Moreover, in vitro exposure to a higher concentration of BPA caused intracellular Ca²⁺-dependent testicular cell damage and plasma membrane injury. This acute toxicity was reinforced by increased testicular LDH release and GGT activity in the liver.

Alternative binding sites at the vitamin D receptor and their ligands

In recent decades, the majority of ligands developed for the vitamin D receptor (VDR) bind at its deeply buried genomic ligand binding pocket. Theses ligands can be categorized into agonists and partial agonists/antagonists. A limited number of ligands, most of them peptides, bind the VDR‒coactivator binding site that is formed in the presence of an agonist and inhibit coactivator recruitment, and therefore transcription. Another solvent exposed VDR‒ligand binding pocket was identified for lithocholic acid, improving the overall stability of the VDR complex. Additional proposed interactions with VDR are discussed herein that include the alternative VDR‒ligand binding pocket that may mediate both non-genomic cellular responses and binding function 3 that was identified for the androgen receptor. Many VDR ligands increase blood calcium levels at therapeutic concentrations in vivo, thus the identification of alternative VDR‒ligand binding pockets might be crucial to develop non-calcemic and potent ligands for VDR to treat cancer and inflammatory disease.

Different roles of cAMP/PKA and PKC signaling in regulating progesterone and PGE2 levels in immortalized rat granulosa cell cultures

Follicular cells from various species secrete steroids and prostaglandins, which are crucial for reproduction, in response to gonadotropins. Here, we examined prostaglandin E₂ (PGE₂) secretion from immortalized rat granulosa cells derived from preovulaotry follicles expressing the rat follicle stimulating hormone receptor (denoted as FSHR cells) that produce progesterone in response to gonadotropins. The cells were stimulated with a) pregnant mare's serum gonadotropin (PMSG; a rat FSH receptor agonist), b) activators of the protein kinase A (PKA) pathway (forskolin and a cell permeable cAMP analog Dibutyryl-cAMP (DB-cAMP)) and c) protein kinase C (PKC) (12-O-tetradecanoylphorbol 13-acetate; TPA), alone and in combination for 24 h. Thereafter, PGE₂ and progesterone levels in the culture media were determined. In accordance with previous studies, while PMSG and the PKA pathway activators induced progesterone accumulation in the media, TPA did not. In contrast, our data indicate that TPA, but neither PMSG, forskolin and DB-cAMP evoked PGE₂ accumulation in the media. Western Blot analysis of cell lysate showed a drastic TPA induced increase of COX-2 levels, which was not seen with neither PMSG nor forskolin treatment. This association between the COX-2 and PGE₂ levels suggests that the enzyme activity is the likely factor that determines the synthesis and levels of the prostaglandin in the culture media of the granulosa-derived cells. The addition of the PKA inhibitor H-89 to the FSHR cultures suppressed the gonadotropin and forskolin induction of progesterone secretion. Incubation in the presence of GF109203X (a PKC inhibitor) attenuated the TPA induced PGE₂ accumulation in the culture media of the cells (a dose dependent reduction of 40-70%). In addition, while TPA inhibited the PMSG and forskolin induced-accumulation of progesterone in the media, the gonadotropin and forskolin inhibited the elevation of PGE₂ levels evoked by TPA (a dose dependent decrease of 35-55%). These data suggest that cAMP/PKA and PKC signaling have opposite effects on PGE₂ and progesterone synthesis in FSHR cells. We propose that this PKA and PKC interplay on progesterone and PGE₂ may be advantageous for the coordination of these key mediators for successful ovulation and luteinization.

Pathogenic roles of alterations in vitamin D and vitamin D receptor in gastric tumorigenesis

Gastric cancer is currently the second leading cause of cancer-related death worldwide, especially in Japan, Korea and China, and the 5-year survival rate of gastric cancer is less than 30%. Thus, it is important to shed more lights on novel agents to prevent gastric cancer or to improve survival rate of the patients. Vitamin D not only maintains calcium and bone homeostasis, but also mostly inhibits tumor genesis, invasion, and metastasis through activation of vitamin D receptor. Although epidemiological results are not consistent, accumulating evidence from gastric cancer cells, animal models, and clinical trials suggest that vitamin D deficiency may increase the risk and mortality of gastric cancer, but vitamin D supplement might be a safe and economical way to prevent or treat gastric cancer. Here, we reviewed the current studies on vitamin D and its receptor and focused on the pathogenic roles of their alterations in gastric tumorigenesis.

Vitamin D and melanoma: state of the art and possible therapeutic uses

Despite the presence of several studies in literature, the real connection between vitamin D serological levels, vitamin D receptor and melanoma remains unclear, probably because of the complex correlation between vitamin D and melanoma. Indeed, UV radiations are not reported as the main risk factor for melanoma in non-sun-exposed, while systemic immunosuppression, anatomical and physiological features may contribute to malignancy. Therefore, the correlation between melanoma cells in sun-exposed areas and vitamin D, as well as vitamin D receptor could be different from the one in melanoma of sun-shielded sites. These differences may also explain the controversial results reported in the literature regarding the correlation between melanoma and vitamin D, as well as the different outcomes in melanoma patients treated with vitamin D as adjuvant therapy. The aim of this review is to highlight the most recent findings about vitamin D and melanoma, focusing on the anatomic site of the primary tumor as well as on the possible therapeutic uses of vitamin D in melanoma patients.

Vitamin D and the brain: Genomic and non-genomic actions

1,25(OH)₂D₃ (vitamin D) is well-recognized as a neurosteroid that modulates multiple brain functions. A growing body of evidence indicates that vitamin D plays a pivotal role in brain development, neurotransmission, neuroprotection and immunomodulation. However, the precise molecular mechanisms by which vitamin D exerts these functions in the brain are still unclear. Vitamin D signalling occurs via the vitamin D receptor (VDR), a zinc-finger protein in the nuclear receptor superfamily. Like other nuclear steroids, vitamin D has both genomic and non-genomic actions. The transcriptional activity of vitamin D occurs via the nuclear VDR. Its faster, non-genomic actions can occur when the VDR is distributed outside the nucleus. The VDR is present in the developing and adult brain where it mediates the effects of vitamin D on brain development and function. The purpose of this review is to summarise the in vitro and in vivo work that has been conducted to characterise the genomic and non-genomic actions of vitamin D in the brain. Additionally we link these processes to functional neurochemical and behavioural outcomes. Elucidation of the precise molecular mechanisms underpinning vitamin D signalling in the brain may prove useful in understanding the role this steroid plays in brain ontogeny and function.

The role of vitamin D in male fertility: A focus on the testis

In the last decade, vitamin D has emerged as a pleiotropic molecule with a multitude of autocrine, paracrine and endocrine functions, mediated by classical genomic as well as non-classical non-genomic actions, on multiple target organs and systems. The expression of vitamin D receptor and vitamin D metabolizing enzymes in male reproductive system, particularly in the testis, suggests the occurrence of vitamin D synthesis and regulation as well as function in the testis. The role of vitamin D in the modulation of testis functions, including hormone production and spermatogenesis, has been investigated in animals and humans. Experimental studies support a beneficial effect of vitamin D on male fertility, by modulating hormone production through genomic and non-genomic actions, and, particularly, by improving semen quality essentially through non-genomic actions. However, clinical studies in humans are controversial. Indeed, vitamin D seems to contribute to the modulation of the bioavailable rather than total testosterone. Moreover, although an increased prevalence or risk for testosterone deficiency was reported in men with vitamin D deficiency in observational studies, the majority of interventional studies demonstrated the lack of effect of vitamin D supplementation on circulating levels of testosterone. The most consistent effect of vitamin D was reported on semen quality. Indeed, vitamin D was shown to be positively associated to sperm motility, and to exert direct actions on spermatozoa, including non-genomic driven modulation of intracellular calcium homeostasis and activation of molecular pathways involved in sperm motility, capacitation and acrosome reaction. The current review provides a summary of current knowledge on the role of vitamin D in male fertility, by reporting clinical and experimental studies in humans and animals addressing the relationship between vitamin D and testis function.

Interactions between oestrogen and 1α,25(OH)2-vitamin D3 signalling and their roles in spermatogenesis and spermatozoa functions

Oestrogens and 1α,25(OH)₂-vitamin D₃ (1,25-D₃) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D₃ are regulators of spermatogenesis. Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D₃ in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones.

1,25(OH)2 vitamin D3 signalling on immature rat Sertoli cells: gamma-glutamyl transpeptidase and glucose metabolism

1α,25-Dihydroxyvitamin D₃ (1,25-D₃) is critical for the maintenance of normal male reproduction since reduced fertility is observed in vitamin D-deficient rats. Gamma-glutamyl transpeptidase (GGT) is a membrane-bound enzyme that is localized on Sertoli cells and catalyses the transfer of the gamma-glutamyl residues to an amino acid or peptide acceptor. Sertoli cells are also responsible for providing nutrients, as lactate, to the development of germ cells. The aim of this study was to investigate the effect and the mechanism of action of 1,25-D₃ on GGT on Sertoli cell functions from 30-day-old immature rat testis. Results demonstrated that 1,25-D₃ stimulates GGT activity at Sertoli cells plasma membrane through a PKA-dependent mechanism of action, which was not dependent of active de novo protein synthesis. The hormone increases glucose uptake, as well as lactate production and release by Sertoli cells without altering the reactive oxygen species (ROS) generation. In addition, 1,25-D₃ did not change reduced glutathione (GSH) amount or oxygen consumption, and diminished Sertoli cell death. These findings demonstrate that 1,25-D₃ stimulatory effect on GGT activity, glucose uptake, LDH activity and lactate production seem to be an important contribution of Sertoli cells for germ cells nutrition and for a full and active ongoing spermatogenesis.

Molecular actions of vitamin D in reproductive cell biology

Vitamin D (VitD) is an important secosteroid and has attracted attention in several areas of research due to common VitD deficiency in the population, and its potential to regulate molecular pathways related to chronic and inflammatory diseases. VitD metabolites and the VitD receptor (VDR) influence many tissues including those of the reproductive system. VDR expression has been demonstrated in various cell types of the male reproductive tract, including spermatozoa and germ cells, and in female reproductive tissues including the ovaries, placenta and endometrium. However, the molecular role of VitD signalling and metabolism in reproductive function have not been fully established. Consequently, the aim of this work is to review current metabolic and molecular aspects of the VitD–VDR axis in reproductive medicine and to propose the direction of future research. Specifically, the influence of VitD on sperm motility, calcium handling, capacitation, acrosin reaction and lipid metabolism is examined. In addition, we will also discuss the effect of VitD on sex hormone secretion and receptor expression in primary granulosa cells, along with the impact on cytokine production in trophoblast cells. The review concludes with a discussion of the recent developments in VitD–VDR signalling specifically related to altered cellular bioenergetics, which is an emerging concept in the field of reproductive medicine.

NORMALIZATION OF SERUM VITAMIN D IMPROVES SEMEN MOTILITY PARAMETERS IN PATIENTS WITH IDIOPATHIC MALE INFERTILITY

Context

Idiopathic male infertility is evident in half of infertile males. Vitamin D receptors are expressed throughout male reproductive tract, including spermatozoa, promoting motility. Epidemiological studies revealed the positive association between serum vitamin D and semen quality. However, there are no clinical studies examining the differential role of vitamin D in idiopathic male infertility.

Objectives

1) To investigate the association between vitamin D deficiency and idiopathic male infertility, and 2) To determine whether vitamin D deficient males would show restoration of semen quality parameters upon supplementation with vitamin D.

Design

This was a year-long case-control study from November 2015 to November 2016. A therapeutic intervention cohort for 2 months was also performed.

Subjects and Methods

117 Jordanian males were enrolled. Following a clinical evaluation by a urologist, baseline serum vitamin D and semen fluid analyses were collected. Participants were stratified into 3 groups: controls (n=30), idiopathic infertility (n=67), and secondary infertility (n=20). Idiopathic infertility patients with low vitamin D (n= 45) were supplemented with oral vitamin D, 5000 IU, once daily for two months. Thereafter, serum vitamin D and semen fluid analyses were reassessed (n= 34; 11 patients were lost to follow up).

Results

Vitamin D was significantly lower in patients with idiopathic infertility than in both controls and men with secondary infertility. Significant improvement of progressive and total sperm motility was observed after vitamin D treatment. Vitamin D correlated significantly with semen quality in the study population. However, no correlation was found between vitamin D and any of the semen quality parameters in the idiopathic infertility group.

Conclusions

Vitamin D supplementation improves sperm motility in idiopathic male infertility patients with low vitamin D. Larger and longer clinical trials are warranted to validate the use of vitamin D in these cases.

In vitro vitamin K(2) and 1α,25-dihydroxyvitamin D(3) combination enhances osteoblasts anabolism of diabetic mice

In this study, we evaluated the anabolic effect and the underlying cellular mechanisms involved of vitamin K2 (10 nM) and 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) (10 nM), alone and in combination, on primary osteoblasts harvested from the iliac crests of C57BL/KsJ lean (+/+) and obese/diabetic (db/db) mice. A lower alkaline phosphatase (ALP) activity plus a reduced expression of bone anabolic markers and bone formation transcription factors (osteocalcin, Runx2, Dlx5, ATF4 and OSX) were consistently detected in osteoblasts of db/db mice compared to lean mice. A significantly higher calcium deposits formation in osteoblasts was observed in lean mice when compared to db/db mice. Co-administration of vitamin K2 (10 nM) and 1,25(OH)2D3 (10 nM) caused an enhancement of calcium deposits in osteoblasts in both strains of mice. Vitamins K2 and 1,25(OH)2D3 co-administration time-dependently (7, 14 and 21 days) increased the levels of bone anabolic markers and bone formation transcription factors, with a greater magnitude of increase observed in osteoblasts of db/db mice. Combined vitamins K2 plus 1,25(OH)2D3 treatment significantly enhanced migration and the re-appearance of surface microvilli and ruffles of osteoblasts of db/db mice. Thus, our results illustrate that vitamins K2 plus D3 combination could be a novel therapeutic strategy in treating diabetes-associated osteoporosis.

Functional Importance of 1α,25(OH)2-Vitamin D3 and the Identification of Its Nongenomic and Genomic Signaling Pathways in the Testis

The 1α,25(OH)2-vitamin D3 (1,25-D3) is known by its classic effects on Ca2+ metabolism and regulation of cellular proliferation and differentiation. The hormone 1,25-D3 acts in the testis through nongenomic and genomic events being implicated in the success of spermatogenesis in rats and in human being. The aim of this review was to highlight the effect and intracellular pathways of 1,25-D3 to modulate the spermatogenesis. The pivotal role of 1,25-D3 in male reproduction is reinforced by the presence of VDR and 1α-hydroxylase in reproductive tract. Also, the marked expression of VDR and the VD metabolizing enzymes in human testis, ejaculatory tract, and mature spermatozoa implicates the 1,25-D3 in spermatogenesis and maturation of human spermatozoa. Among genomic events, 1,25-D3 influences the expression of calcium binding protein and stimulates aromatase gene expression through a nongenomic activation of the membrane-bound VDR receptor involving the PKA pathway in the testis. Also, 1,25-D3 stimulates amino acid transport and exocytosis in testis by nongenomic events coupled to ionic currents triggered at plasma membrane. All together, the demonstration that 1,25-D3 regulates both Sertoli cell and sperm function may be useful for the study and development of new therapeutic strategies for the male reproductive disorders.

Rapid responses to reverse T₃ hormone in immature rat Sertoli cells: calcium uptake and exocytosis mediated by integrin

There is increasing experimental evidence of the nongenomic action of thyroid hormones mediated by receptors located in the plasma membrane or inside cells. The aim of this work was to characterize the reverse T₃ (rT₃) action on calcium uptake and its involvement in immature rat Sertoli cell secretion. The results presented herein show that very low concentrations of rT₃ are able to increase calcium uptake after 1 min of exposure. The implication of T-type voltage-dependent calcium channels and chloride channels in the effect of rT₃ was evidenced using flunarizine and 9-anthracene, respectively. Also, the rT₃-induced calcium uptake was blocked in the presence of the RGD peptide (an inhibitor of integrin-ligand interactions). Therefore, our findings suggest that calcium uptake stimulated by rT₃ may be mediated by integrin αvβ₃. In addition, it was demonstrated that calcium uptake stimulated by rT₃ is PKC and ERK-dependent. Furthermore, the outcomes indicate that rT₃ also stimulates cellular secretion since the cells manifested a loss of fluorescence after 4 min incubation, indicating an exocytic quinacrine release that seems to be mediated by the integrin receptor. These findings indicate that rT₃ modulates the calcium entry and cellular secretion, which might play a role in the regulation of a plethora of intracellular processes involved in male reproductive physiology.

Interactions between vitamin D and IGF-I: from physiology to clinical practice

The interplay between vitamin D and IGF-I is complex and occurs at both endocrine and paracrine/autocrine levels. Vitamin D has been shown to increase circulating IGF-I and IGFBP-3, with the consistent finding of a positive correlation between vitamin D and IGF-I serum values in population-based cohorts of healthy subjects. The modulation of IGF-I and IGFBP-3 concentrations by vitamin D may impact recombinant human (rh) GH dosing for the treatment of GHD. It might also underlie some of the extra-skeletal beneficial effects ascribed to vitamin D. On the other hand, IGF-I stimulates renal production of 1,25-dihydroxyvitamin D, which increases calcium and phosphate availability in the body and suppresses PTH secretion. This effect is responsible for an altered calcium-phosphate balance in uncontrolled acromegaly and might also account for the improvement in bone metabolism associated with rhGH treatment in patients with GHD. Data on the paracrine/autocrine vitamin D-IGF-I interactions are abundant, but mostly not linked to one another. As a result, it is not possible to draw a comprehensive picture of the physiological and/or pathological interrelations between vitamin D, IGF-I and IGF-binding proteins (IGFBP) in different tissues. A potential role of vitamin D action is related to its association with carcinogenesis, a paradigm being breast cancer. Current evidence indicates that, in breast tumours, vitamin D modulates the IGF-I/IGFBP ratio to decrease proliferation and increase apoptosis.

Vitamin D in human reproduction: a narrative review

BACKGROUND

Special attention has been given to the effect of vitamin D supplementation on fertility outcomes in both sexes.

AIMS

The purpose of this narrative review was to elucidate the role of vitamin D in male and female reproduction, providing current evidence from both animal and human studies.

MATERIALS AND METHODS

Using PubMed and Medline, we searched for publications during the last 30 years regarding the role of vitamin D in human reproduction.

RESULTS

Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the reproductive system in both genders. In women, vitamin D status has been associated with in vitro fertilization (IVF) outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. Although several data converge towards a beneficial effect of vitamin D supplementation in metabolic disturbances in women with PCOS, a significant knowledge gap precludes the establishment of a clear cause-effect relationship. In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology. There is evidence for a favourable effect of vitamin D supplementation on semen quality, testosterone concentrations and fertility outcomes.

DISCUSSION

Studies with superior methodological characteristics are needed in order to establish a role for vitamin D on the treatment of female and male infertility.

CONCLUSIONS

Recent data on vitamin D provide new insights in the complex pathogenesis and treatment of infertility.

Small-molecule hormones: molecular mechanisms of action

Small-molecule hormones play crucial roles in the development and in the maintenance of an adult mammalian organism. On the molecular level, they regulate a plethora of biological pathways. Part of their actions depends on their transcription-regulating properties, exerted by highly specific nuclear receptors which are hormone-dependent transcription factors. Nuclear hormone receptors interact with coactivators, corepressors, basal transcription factors, and other transcription factors in order to modulate the activity of target genes in a manner that is dependent on tissue, age and developmental and pathophysiological states. The biological effect of this mechanism becomes apparent not earlier than 30-60 minutes after hormonal stimulus. In addition, small-molecule hormones modify the function of the cell by a number of nongenomic mechanisms, involving interaction with proteins localized in the plasma membrane, in the cytoplasm, as well as with proteins localized in other cellular membranes and in nonnuclear cellular compartments. The identity of such proteins is still under investigation; however, it seems that extranuclear fractions of nuclear hormone receptors commonly serve this function. A direct interaction of small-molecule hormones with membrane phospholipids and with mRNA is also postulated. In these mechanisms, the reaction to hormonal stimulus appears within seconds or minutes.

Gestational doxorubicin alters fetal thyroid-brain axis

Administration of chemotherapy during pregnancy may represent a big risk factor for the developing brain, therefore we studied whether the transplacental transport of doxorubicin (DOX) may affect the development of neuroendocrine system. DOX (25 mg/kg; 3 times interaperitoneally/week) was given to pregnant rats during whole gestation period. The disturbances in neuroendocrine functions were investigated at gestation day (GD) 15 and 20 by following the maternal and fetal thyroid hormone levels, fetal nucleotides (ATP, ADP, AMP) levels and adenosine triphosphatase (Na(+), K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase) activities in two brain regions, cerebrum and cerebellum. In control group, the levels of maternal and fetal serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and fetal serum growth hormone (GH) increased from days 15 to 20, whereas in the DOX group, a decrease in maternal and fetal T4, T3 and increase in TSH levels (hypothyroid status) were observed. Also, the levels of fetal GH decreased continuously from GD 15 to 20 with respect to control group. In cerebrum and cerebellum, the levels of fetal nucleotides and the activities of fetal ATPases in control group followed a synchronized course of development. The fetal hypothyroidism due to maternal administration of DOX decreased the levels of nucleotides, ATPases activities, and total adenylate, instead, the adenylate energy charge showed a trend to an increase in both brain regions at all ages tested. These alterations were dose- and age-dependent and this, in turn, may impair the nerve transmission. Finally, DOX may act as neuroendocrine disruptor causing hypothyroidism and fetal brain energetic dysfunction.

Acute effect of β-sitosterol on calcium uptake mediates anti-inflammatory effect in murine activated neutrophils

OBJECTIVES

To evaluate the effect of β-sitosterol on ⁴⁵Ca²⁺ uptake in activated murine neutrophils, and upon myeloperoxidase and adenosine deaminase activity, and interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) levels, in carrageenan-induced inflammation in the mouse air pouch model.

METHODS

Dried Esenbeckia leiocarpa bark was macerated and extracted resulting in a crude hydroalcoholic extract (CHE) that was partitioned to obtain an alkaloid fraction. The alkaloid was then partitioned in polar and nonpolar subfractions. β-Sitosterol was isolated from the nonpolar subfraction and identified by comparison with the literature. The effect of β-sitosterol on ⁴⁵Ca²⁺ uptake in activated murine neutrophils, and upon myeloperoxidase and adenosine deaminase activity, IL-1β and TNF-α levels in carrageenan-induced inflammation in mice were evaluated.

KEY FINDINGS

β-Sitosterol promoted a time- and dose-dependent increase of the calcium uptake in activated neutrophils that was promptly reversed by nifedipine, BAPTA-AM, LY294002, and colchicine. β-Sitosterol inhibited myeloperoxidase and adenosine deaminase activity, and IL-1β and TNF-α levels.

CONCLUSIONS

β-Sitosterol inhibited either myeloperoxidase and adenosine deaminase activity or IL-1β and TNF-α levels. This effect seemed to be mediated by the calcium uptake in activated neutrophils in a time- and concentration-dependent manner through L-type voltage dependent calcium channels, intracellular calcium, phosphoinositide kinase-3, and microtubule modulation.

Discovery of novel vitamin D receptor interacting proteins that modulate 1,25-dihydroxyvitamin D3 signaling

The nuclear vitamin D receptor (VDR) modulates gene transcription in 1,25-dihydroxyvitamin D(3) (1,25D) target tissues such as kidney, intestine, and bone. VDR is also expressed in heart, and 1,25D deficiency may play a role in the acceleration of cardiovascular disease. Employing a yeast two-hybrid system and a human heart library, using both a 1,25D-independent and 1,25D-dependent screen, we discovered six candidate VDR interacting proteins (VIPs). These novel VIPs include CXXC5, FASTK, NR4A1, TPM2, MYL3 and XIRP1. Mammalian two-hybrid assays as well as GST pull-downs were used to confirm VIP-VDR interaction, and the combination of these two assays reveals that CXXC5, XIRP1, FASTK and NR4A1 interactions with VDR may be modulated by 1,25D. The functional effects of these VIPs on 1,25D-mediated gene expression were explored in transcriptional assays employing three separate and distinct 1,25D-responsive element (VDRE)-driven luciferase reporter genes in transfected Caco-2 and HEK-293 cells, and in a C2C12 myoblast line. FASTK and TPM2 activated expression in all cell line and promoter contexts, while CXXC5 and XIRP1 exhibited differing effects depending on the cell line and promoter employed, suggesting promoter and cell-specific effects of these unique VIPs on VDR signaling. Further evaluation of the interaction between CXXC5 and VDR revealed that CXXC5 acts in a dose-dependent manner to stimulate VDR-mediated transcription on select VDREs. Identification of novel heart VIPs and their influence on VDR activity may increase our understanding of how vitamin D impacts cardiac physiology and may facilitate development of VDR/VIP drug analogs to combat heart disease.

Vitamin D in exercise: physiologic and analytical concerns

Despite a wide number of studies performed on the general population, little is known about the Vitamin D status of athletes. A particular influence of many factors, including skin pigmentation, early- or late-day training, indoor training, geographic location and extensive sunscreen use, has been observed in this specific population. The need of supplementation with Vitamin D in athletes is not defined or, when supplementation is needed, even the optimal amount of Vitamin D to be used is not specified. The periodic measurement of Vitamin D is the only procedure capable to define athletes' status. Although various methods for the measurement of Vitamin D are routinely used, they often give discordant and poorly reproducible results; thus, it is necessary to standardize the various methods, in order to have comparable results. In conclusion, current available data indicate both that little is known about the Vitamin D status of athletes and that is still unclear if supplementation could be desirable. Finally, it must be pointed out that all the papers about Vitamin D status should indicate in detail the method used for really allowing a correct interpretation of data.

Vitamin D metabolism, sex hormones, and male reproductive function

The spectrum of vitamin D (VD)-mediated effects has expanded in recent years, and VD is now recognized as a versatile signaling molecule rather than being solely a regulator of bone health and calcium homeostasis. One of the recently identified target areas of VD is male reproductive function. The VD receptor (VDR) and the VD metabolizing enzyme expression studies documented the presence of this system in the testes, mature spermatozoa, and ejaculatory tract, suggesting that both systemic and local VD metabolism may influence male reproductive function. However, it is still debated which cell is the main VD target in the testis and to what extent VD is important for sex hormone production and function of spermatozoa. This review summarizes descriptive studies on testicular VD metabolism and spatial distribution of VDR and the VD metabolizing enzymes in the mammalian testes and discusses mechanistic and association studies conducted in animals and humans. The reviewed evidence suggests some effects of VD on estrogen and testosterone biosynthesis and implicates involvement of both systemic and local VD metabolism in the regulation of male fertility potential.

1α,25-dihydroxyvitamin D3 modulates the hair-inductive capacity of dermal papilla cells: therapeutic potential for hair regeneration

Dermal papilla cells (DPCs) have the potential to induce differentiation of epithelial stem cells into hair, and Wnt signaling is deeply involved in the initiation process. The functional limitation of expanded adult DPCs has been a difficult challenge for cell-based hair regrowth therapy. We previously reported that 1α,25-dihydroxyvitamin D(3) (VD(3)) upregulates expression of transforming growth factor (TGF)-β2 and alkaline phosphatase (ALP) activity, both features of hair-inducing human DPCs (hDPCs). In this study, we further examined the effects and signaling pathways associated with VD(3) actions on DPCs. VD(3) suppressed hDPC proliferation in a dose-dependent, noncytotoxic manner. Among the Wnt-related genes investigated, Wnt10b expression was significantly upregulated by VD(3) in hDPCs. Wnt10b upregulation, as well as upregulation of ALPL (ALP, liver/bone/kidney) and TGF-β2, by VD(3) was specific in hDPCs and not detected in human dermal fibroblasts. Screening of paracrine or endocrine factors in the skin indicated that all-trans retinoic acid (atRA) upregulated Wnt10b gene expression, although synergistic upregulation (combined atRA and VD(3)) was not seen. RNA interference with vitamin D receptor (VDR) revealed that VD(3) upregulation of Wnt10b, ALPL, and TGF-β2 was mediated through the genomic VDR pathway. In a rat model of de novo hair regeneration by murine DPC transplantation, pretreatment with VD(3) significantly enhanced hair folliculogenesis. Specifically, a greater number of outgrowing hair shafts and higher maturation of regenerated follicles were observed. Together, these data suggest that VD(3) may promote functional differentiation of DPCs and be useful in preserving the hair follicle-inductive capacity of cultured DPCs for hair regeneration therapies.

1α,25(OH)2-Vitamin D3 stimulates rapid plasma membrane calcium influx via MAPK activation in immature rat Sertoli cells

It was characterized that the rapid response to 1α,25(OH)(2)-vitamin D(3) (1,25D(3)) on (45)Ca(2+) influx in rat Sertoli cells was mediated by voltage-dependent Ca(2+) channels (VDCCs), PKC, ERK1/2 and p38 MAPK pathways. In primary culture of 10 day-old rat Sertoli cells as well as in the whole testis, the time-course of (45)Ca(2+) influx did not change significantly in basal conditions. However, 1,25D(3) showed stimulatory effect on (45)Ca(2+) influx from 10(-15) to 10(-8) M after 60 s of incubation. The maximum effect was around 140% at 10(-12) M on purified Sertoli cells showing a steady state on (45)Ca(2+) influx between 10(-11) and 10(-9) M. Under this experimental condition, 1,25D(3) stimulated (45)Ca(2+) influx from 73% to 106% and no effect was observed at 10(-16), 10(-8) and 10(-7) M in whole testis. VDCC activities are mandatory for a full and complete stimulatory effect of 1,25D(3) in these approaches. K(+) and Cl(-) channels also are strongly involved in this rapid response coordinated by 1,25D(3). The participation of some selected kinases, points to PKC and ERK1/2 upstream activity to p38 MAPK activation suggesting an intracellular cross-talk between rapid (45)Ca(2+) influx and nuclear events. In addition, the comparative effect of microtubule disassembles and ClC-3 channel blocker on (45)Ca(2+) influx provides evidence of secretory activity of Sertoli cells triggered by 1,25D(3). Our results suggest that 1,25D(3) activates p38 MAPK and reorganizes microtubules, involving Ca(2+), PKC and ERK1/2 as upstream regulators and that extracellular Ca(2+) have a central role to rapidly start hormone-induced gene transcription and/or the secretory activity of Sertoli cell.

Vitamin D receptor (VDR)-mediated actions of 1α,25(OH)₂vitamin D₃: genomic and non-genomic mechanisms

The conformationally flexible secosteroid, 1α,25(OH)₂vitamin D₃ (1α,25(OH)₂D₃) initiates biological responses via binding to the vitamin D receptor (VDR). The VDR contains two overlapping ligand binding sites, a genomic pocket (VDR-GP) and an alternative pocket (VDR-AP), that respectively bind a bowl-like ligand configuration (gene transcription) or a planar-like ligand shape (rapid responses). When occupied by 1α,25(OH)₂D₃, the VDR-GP interacts with the retinoid X receptor to form a heterodimer that binds to vitamin D responsive elements in the region of genes directly controlled by 1α,25(OH)₂D₃. By recruiting complexes of either coactivators or corepressors, activated VDR modulates the transcription of genes encoding proteins that promulgate the traditional genomic functions of vitamin D, including signaling intestinal calcium and phosphate absorption to effect skeletal and calcium homeostasis. 1α,25(OH)₂D₃/VDR control of gene expression and rapid responses also delays chronic diseases of aging such as osteoporosis, cancer, type-1 and -2 diabetes, arteriosclerosis, vascular disease, and infection.

Vitamin D receptor (VDR) regulation of voltage-gated chloride channels by ligands preferring a VDR-alternative pocket (VDR-AP)

We have postulated that the vitamin D receptor (VDR) contains two overlapping ligand binding sites, a genomic pocket and an alternative pocket (AP), that mediate regulation of gene transcription and rapid responses, respectively. Flexible VDR + ligand docking calculations predict that the major blood metabolite, 25(OH)-vitamin D(3) (25D3), and curcumin (CM) bind more selectively to the VDR-AP when compared with the seco-steroid hormone 1α,25(OH)(2)-vitamin D(3) (1,25D3). In VDR wild-type-transfected COS-1 cells and TM4 Sertoli cells, 1,25D3, 25D3, and CM each trigger voltage-gated, outwardly rectifying chloride channel (ORCC) currents that can be blocked by the VDR antagonist 1β,25(OH)(2)-vitamin D(3) and the chloride channel antagonist (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid). VDR mutational analysis in transfected COS-1 cells demonstrate the DNA-binding domain is not, but the ligand binding and hinge domains of the VDR are, required for 1,25D3 and 25D3 to activate the ORCC. Dose-response studies demonstrate that 25D3 and 1,25D3 are approximately equipotent in stimulating ORCC rapid responses, whereas 1 nm 1,25D3 was 1000-fold more potent than 25D3 and CM in stimulating gene expression. The VDR-AP agonist effects of 1,25D3, 25D3, and low-dose CM are lost after pretreatment of TM4 cells with VDR small interfering RNA. Collectively, these results are consistent with an essential role for the VDR-AP in initiating the signaling required for rapid opening of ORCC. The fact that 25D3 is equipotent to 1,25D3 in opening ORCC suggests that reconsideration of the ability of 25D3 to generate biological responses in vivo may be in order.

Membrane-initiated actions of thyroid hormones on the male reproductive system

The presence of specific nuclear receptors to thyroid hormones, described in prepubertal Sertoli cells, implies the existence of an early and critical influence of these hormones on testis development. Although the mechanism of action thyroid hormones has been classically established as a genomic action regulating testis development, our research group has demonstrated that these hormones exert several effects in Sertoli cells lacking nuclear receptor activation. These findings led to the identification of non-classical thyroid hormone binding elements in the plasma membrane of testicular cells. Through binding to these sites, thyroid hormones could exert nongenomic effects, including those on ion fluxes at the plasma membrane, on signal transduction via kinase pathways, on amino acid accumulation, on modulation of extracellular nucleotide levels and on vimentin cytoskeleton. The evidence of the participation of different K(+), Ca(2+) and Cl(-) channels in the mechanism of action of thyroid hormones, characterizes the plasma membrane as an important microenvironment able to coordinate strategic signal transduction pathways in rat testis. The physiological responses of the Sertoli cells to hormones are dependent on continuous cross-talking of different signal transduction pathways. Apparently, the choice of the signaling pathways to be activated after the interaction of the hormone with cell surface binding sites is directly related to the physiological action to be accomplished. Yet, the enormous complexity of the nongenomic actions of thyroid hormones implies that different specific binding sites located on the plasma membrane or in the cytosol are believed to initiate specific cell responses.

Regulation of aromatase expression by 1α,25(OH)2 vitamin D3 in rat testicular cells

It is well known that the vitamin D endocrine system is involved in physiological and biochemical events in numerous tissues, especially gut, bone and kidney but also testis. Therefore, in this study the effect and mechanisms of action of 1α,25(OH)2 vitamin D3 (1,25D) on aromatase gene expression in immature rat Sertoli cells were evaluated. Vitamin D receptor transcripts were present in immature Sertoli cells as well as in adult testicular germ cells and somatic cells. The treatment of immature Sertoli cells with 100 nM 1,25D increased the amount of aromatase transcript, mainly in 30-day-old rats. The protein kinase A (PKA) blocker, H89, partially inhibited the 1,25D effect. The stimulation of aromatase gene expression in 30-day-old Sertoli cells by the agonist 1α,25(OH)2 lumisterol3, and the suppression of the 1,25D effect by the antagonists 1β,25(OH)2 vitamin D3 and (23S)-25-dehydro-1α (OH)-vitamin D3-26,23-lactone suggested, besides a genomic effect of 1,25D, the existence of non-genomic activation of the membrane-bound vitamin D receptor involving the PKA pathway.