Effect of Unloading Condition on the Healing Process and Effectiveness of Platelet Rich Plasma as a Countermeasure: Study on In Vivo and In Vitro Wound Healing Models

Wound healing is a very complex process that allows organisms to survive injuries. It is strictly regulated by a number of biochemical and physical factors, mechanical forces included. Studying wound healing in space is interesting for two main reasons: (i) defining tools, procedures, and protocols to manage serious wounds and burns eventually occurring in future long-lasting space exploration missions, without the possibility of timely medical evacuation to Earth; (ii) understanding the role of gravity and mechanical factors in the healing process and scarring, thus contributing to unravelling the mechanisms underlying the switching between perfect regeneration and imperfect repair with scarring. In the study presented here, a new in vivo sutured wound healing model in the leech (Hirudo medicinalis) has been used to evaluate the effect of unloading conditions on the healing process and the effectiveness of platelet rich plasma (PRP) as a countermeasure. The results reveal that microgravity caused a healing delay and structural alterations in the repair tissue, which were prevented by PRP treatment. Moreover, investigating the effects of microgravity and PRP on an in vitro wound healing model, it was found that PRP is able to counteract the microgravity-induced impairment in fibroblast migration to the wound site. This could be one of the mechanisms underlying the effectiveness of PRP in preventing healing impairment in unloading conditions.

Body composition and metabolic changes during a 520-day mission simulation to Mars

PURPOSE

The "Mars-500 project" allowed to evaluate the changes in psychological/physiological adaptation over a prolonged confinement, in order to gather information for future missions. Here, we evaluated the impact of confinement and isolation on body composition, glucose metabolism/insulin resistance and adipokine levels.

METHODS

The "Mars-500 project" consisted of 520 consecutive days of confinement from June 3, 2010 to Nov 4, 2011. The crew was composed of six male subjects (three Russians, two Europeans, and one Chinese) with a median age of 31 years (range 27-38 years).

RESULTS

During the 520-day confinement, total body mass and BMI progressively decreased, reaching a significant difference at the end (417 days) of the observation period (- 9.2 and - 5.5%, respectively). Fat mass remained unchanged. A progressive and significant increase of fasting plasma glucose was observed between 249 and 417 days (+ 10/+ 17% vs baseline), with a further increase at the end of confinement (up to + 30%). Median plasma insulin showed a non-significant early increment (60 days; + 86%). Total adiponectin halved (- 47%) 60 days after hatch closure, remaining at this nadir (- 51%) level for a further 60 days. High molecular weight adiponectin remained significantly lower from 60 to 168 days.

CONCLUSIONS

Based on these data, countermeasures may be envisioned to balance the potentially harmful effects of prolonged confinement, including a better exercise program, with accurate monitoring of (1) the individual activity and (2) the relationship between body composition and metabolic derangement.

Effects of caloric restriction and low glycemic index diets associated with metformin on glucose metabolism and cortisol response in overweight/obese subjects: a case series study

BACKGROUND

To determine whether cortisol secretion and glucocorticoid receptors in lymphocytes and monocytes are altered in patients with impaired glucose tolerance, and whether treatment with a hypocaloric diet and metformin could interfere with these aspects.

METHODS

This is an analytical, interventional, case series study. Patients with impaired glucose tolerance were included. They received 500 mg of metformin twice daily and followed a low glycemic index diet for 16 weeks. Cortisol levels were assessed at 8:00 A.M. before and after use of 0.25 mg of dexamethasone at 11:00 P.M. the day before.

RESULTS

Sixteen subjects (9 men) were included. Normal basal levels of cortisol and adequate responses to the low dose of dexamethasone were observed before and after treatment. There was no significant correlation between the parameters evaluated and cortisol levels. Nevertheless, there was a strong correlation between the number of glucocorticoid receptors, BMI (r = 0.88; p = 0.02), and insulin AUC (r = 0.94; p = 0.005) before treatment; after treatment, all these associations ceased to exist.

CONCLUSION

The cortisol secretion remained normal in the group of patients with impaired glucose tolerance. Treatment with metformin and diet did not change this condition. However, glucocorticoid receptor number had a strong correlation with insulin, due to insulin resistance, but this characteristic was lost after treatment.

Platelet derived growth factor (PDGF) contained in Platelet Rich Plasma (PRP) stimulates migration of osteoblasts by reorganizing actin cytoskeleton

Platelet-rich plasma (PRP) is a platelet concentrate in a small volume of plasma. It is highly enriched in growth factors able to stimulate the migration and growth of bone-forming cells. PRP is often used in clinical applications, as dental surgery and fracture healing. Platelet derived growth factor (PDGF), is highly concentrated in PRP and it was shown in our previous studies to provide the chemotactic stimulus to SaOS-2 osteoblasts to move in a microchemotaxis assay. Aim of the present studies is to analyze the effects of a PRP pretreatment (short time course: 30-150 min) of SaOS-2 cells with PRP on the organization of actin cytoskeleton, the main effector of cell mobility. The results indicate that a pretreatment with PRP increases chemokinesis and chemotaxis and concomitantly induces the organization of actin microfilaments, visualized by immunocytochemistry, in a directionally elongated phenotype, which is characteristic of the cells able to move. PRP also produces a transient increase in the expression of PGDF α receptor. This reorganization is blocked by the immunoneutralization of PDGF demonstrating the responsibility of this growth factor in triggering the mechanisms responsible for cellular movements.

Endocrine disrupters: the new players able to affect the epigenome

Epigenetics represents the way by which the environment is able to program the genome; there are three main levels of epigenetic control on genome: DNA methylation, post-translational histone modification and microRNA expression. The term Epigenetics has been widened by NIH to include “both heritable changes in gene activity and expression but also stable, long-term alterations in the transcriptional potential of a cell that are not necessarily heritable.” These changes might be produced mostly by the early life environment and might affect health influencing the susceptibility to develop diseases, from cancer to mental disorder, during the entire life span. The most studied environmental influences acting on epigenome are diet, infections, wasting, child care, smoking and environmental pollutants, in particular endocrine disrupters (EDs). These are environmental xenobiotics able to interfere with the normal development of the male and female reproductive systems of wildlife, of experimental animals and possibly of humans, disrupting the normal reproductive functions. Data from literature indicate that EDs can act at different levels of epigenetic control, in some cases transgenerationally, in particular when the exposure to these compounds occurs during the prenatal and earliest period of life. Some of the best characterized EDs will be considered in this review. Among the EDs, vinclozolin (VZ), and methoxychlor (MXC) promote epigenetic transgenerational effects. Polychlorinated biphenils (PCBs), the most widespread environmental EDs, affect histone post-translational modifications in a dimorphic way, possibly as the result of an alteration of gene expression of the enzymes involved in histone modification, as the demethylase Jarid1b, an enzyme also involved in regulating the interaction of androgens with their receptor.

Learning and memory: Steroids and epigenetics

Memory formation and utilization is a complex process involving several brain structures in conjunction as the hippocampus, the amygdala and the adjacent cortical areas, usually defined as medial temporal lobe structures (MTL). The memory processes depend on the formation and modulation of synaptic connectivity affecting synaptic strength, synaptic plasticity and synaptic consolidation. The basic neurocognitive mechanisms of learning and memory are shortly recalled in the initial section of this paper. The effect of sex hormones (estrogens, androgens and progesterone) and of adrenocortical steroids on several aspects of memory processes are then analyzed on the basis of animal and human studies. A specific attention has been devoted to the different types of steroid receptors (membrane or nuclear) involved and on local metabolic transformations when required. The review is concluded by a short excursus on the steroid activated epigenetic mechanisms involved in memory formation.

Androgen receptor activation by polychlorinated biphenyls: epigenetic effects mediated by the histone demethylase Jarid1b

The exposure to environmental endocrine disrupting compounds (EDC), as polychlorinated biphenyls (PCBs), widely diffused in the environment may produce epigenetic changes that affect the endocrine system. We found that PCBs activate AR transcriptional activity and that this effect is potentiated by the demethylase Jarid1b, a histone demethylase that catalyzes the removal of trimethylation of lysine 4 on histone H3 (H3K4me3), induced by PCB. The aim of the present study was to investigate the effect of the treatment of cultured cells (HEK293) with a mixture of the most diffused environmental PCBs and, also with dihydrotestosterone (DHT), on the functional interaction between AR and Jarid1b. Although the effect induced by DHT on the AR transactivation was considerably higher, the PCB mixture produced an AR-mediated transactivation in a dose-dependent manner. Cotransfection with plasmids expressing Jarid1b and various AR isoforms containing polyglutamine tracts (polyQ tracts) of different lengths showed that Jarid1b potentiates the AR transcriptional activity induced by PCBs but only with the shortest AR isoform. The potentiating effect of Jarid1b on the AR is mediated by a direct interaction of the enzyme with the AR promoter. In fact, utilizing constructs containing AR promoters with a different length and a luciferase reporter gene, we showed that the effect of PCBs, but not of DHT, needs the presence of Jarid1b and of at least two DNA binding sites for Jarid1b.

Low-intermediate dose testosterone replacement therapy by different pharmaceutical preparations improves frailty score in elderly hypogonadal hyperglycaemic patients

An open-label follow-up study of low-to-intermediate dose testosterone replacement therapy (TRT) was conducted in 64 overweight patients (aged 65-75 years) with late onset hypogonadism (LOH) and increased fasting plasma glucose (FPG). Patients were subdivided into four treatment groups: oral testosterone (T) (T undecanoate, 80 mg/d), transmucosal T (60 mg/d), transdermal T (30 mg/d) or no treatment (control), and evaluated at 0 and 6 months. FPG, hemoglobin (Hb), prostate-specific antigen (PSA) and total T were measured and the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) index was calculated. Body mass index (BMI), waist circumference, fitness level (6-min walking test), Aging Males' Symptoms (AMS) scale, handgrip strength and energy expenditure with physical activity (Minnesota questionnaire for Leisure Time Physical Activity (LTPA)) were evaluated and a "frailty score" (based on: grip strength, gait speed and LTPA) was calculated. T levels increased in all treatment groups; the oral T group had values still in the hypogonadal range (5.9 ± 1.1 nmol/L). PSA and Hb concentrations did not change in any group. BMI, waist circumference, FPG and HOMA-IR improved in all T-treated groups after 6 months, with a greater effect seen with transmucosal and transdermal T compared with oral T. This study indicates that low-to-intermediate dose TRT may be safely utilized in LOH patients to ameliorate somatic and psychological frailty symptoms in association with improved anthropometric and glycometabolic parameters in aging, overweight men with LOH and impaired fasting glucose.

Polychlorinated biphenyls affect histone modification pattern in early development of rats: a role for androgen receptor-dependent modulation?

Background: The epigenome represents an important target of environmental pollution. Early-life exposure to polychlorinated biphenyls (PCBs) modifies sex steroid enzymes and receptor transcription patterns. Steroid receptors, such as androgen receptor (AR), function as coregulators of histone modification enzymes. Aim: To clarify if a PCB early-life exposure might affect the epigenome in rat liver, we analyzed some histone post-translational modifications (H3K4me3 and H4K16Ac) and the corresponding histone remodeling enzymes, and the AR as a histone enzyme coregulator. Results: We observed a decrease of H4K16Ac and H3K4me3 levels, possibly linked to the induction of chromatin-modifying enzymes SirtT1 and Jarid1b, and a decrease of AR. PCBs also seem to induce AR transcriptional activity. Some of the observed effects are sex dimorphic. Conclusion: Our data suggest that an early-life exposure to PCB sometimes modifies the epigenome in the offspring liver in a dimorphic way. AR might be involved in modulating PCB effects on the epigenome.

Effect of postnatal starvation on the 5 alpha-reductase activity of the brain and of the isolated myelin membranes

The 5 alpha-reductase, the enzyme which converts testosterone into its major "active" metabolite (dihydrotestosterone, DHT), has been found to be present in high concentration in brain structures particularly rich of myelin (white matter structures), as well as in myelin membranes. Previous ontogenetic observations seem to indicate that, during the process of myelinogenesis, the enzyme might be synthesized in the oligodendrocytes, and subsequently incorporated into the myelin membranes. It is well established that postnatal malnutrition produces a decreased formation of myelin, when starvation is performed from birth until to the 2nd or 3rd week of life; on the contrary food deprivation does not produce any significant effect on myelin accumulation when performed after the 14th day of life. The present experiments have been performed in the rat in order to study the effects of postnatal undernutrition (from birth to the 19th day of life: long malnutrition; and from the 14th to the 19th day of life: short malnutrition) on the 5 alpha-reductase activity present in the following brain structures: cerebral cortex, hypothalamus, corpus callosum, pyramidal tract, as well as in isolated myelin membranes. Undernourished animals have been killed at 20 days of age. Normally nourished animals served as controls. Long undernutrition induced a statistically significant decrease of the formation of DHT in the corpus callosum and in the pyramidal tract vs controls. On the contrary, the nutritional deficiency did not decrease the 5 alpha-reductase activity in the cerebral cortex and in the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Feeding behavior in mammals including humans

The complex control of food intake and energy metabolism in mammals relies on the ability of the brain to integrate multiple signals indicating the nutritional state and the energy level of the organism and to produce appropriate responses in terms of food intake, energy expenditure, and metabolic activity. Central regulation of feeding is organized as a long-loop mechanism involving humoral signals and afferent neuronal pathways to the brain, processing in hypothalamic neuronal circuits, and descending commands using vagal and spinal neurons. Sensor mechanisms or receptors sensitive to glucose and fatty acid metabolism, neuropeptide and cannabinoid receptors, as well as neurotransmitters and neuromodulators synthesized and secreted within the brain itself are all signals integrated in the hypothalamus, which therefore functions as an integrator of signals from central and peripheral structures. Homeostatic feedback mechanisms involving afferent neuroendocrine inputs from peripheral organs, like adipose tissue, gut, stomach, endocrine pancreas, adrenal, muscle, and liver, to hypothalamic sites thus contribute to the maintenance of normal feeding behavior and energy balance. In addition to transcriptional events, peripheral hormones may also alter firing and/or connection (synaptology) of hypothalamic neuronal networks in order to modulate food intake. Moreover, intracellular energy sensing and subsequent biochemical adaptations, including an increase in AMP-activated protein kinase activity, occur in hypothalamic neurons. Understanding the regulation of appetite is clearly a major research effort but also seems promising for the development of novel therapeutic strategies for obesity.

Chronic treatment with polychlorinated biphenyls (PCB) during pregnancy and lactation in the rat: Part 1: Effects on somatic growth, growth hormone-axis activity and bone mass in the offspring

Polychlorinated biphenyls (PCBs) are pollutants detected in animal tissues and breast milk. The experiments described in the present paper were aimed at evaluating whether the four PCB congeners most abundant in animal tissues (PCB-138, -153, -180 and -126), administered since fetal life till weaning, can induce long-term alterations of GH-axis activity and bone mass in the adult rat. We measured PCB accumulation in rat brain and liver, somatic growth, pituitary GH expression and plasma hormone concentrations at different ages. Finally, we studied hypothalamic somatostatin expression and bone structure in adulthood, following long-term PCB exposure. Dams were treated during pregnancy from GD15 to GD19 and during breast-feeding. A constant reduction of the growth rate in both male and female offspring from weaning to adulthood was observed in exposed animals. Long-lasting alterations on hypothalamic-pituitary GH axis were indeed observed in PCB-exposed rats in adulthood: increased somatostatin expression in hypothalamic periventricular nucleus (both males and females) and lateral arcuate nucleus (males, only) and decreased GH mRNA levels in the pituitary of male rats. Plasma IGF-1 levels were higher in PCB-exposed male and female animals as compared with controls at weaning and tended to be higher at PN60. Plasma testosterone and thyroid hormone concentrations were not significantly affected by exposure to PCBs. In adulthood, PCBs caused a significant reduction of bone mineral content and cortical bone thickness of tibiae in male rat joint to increased width of the epiphyseal cartilage disk. In conclusion, the developmental exposure to the four selected PCB compounds used in the present study induced far-reaching effects in the adult offspring, the male rats appearing more sensitive than females.

Sexual differentiation of the rodent hypothalamus: hormonal and environmental influences

Brain sexual differentiation is a complex developmental phenomenon influenced by the genetic background, sex hormone secretions and environmental inputs, including pollution. The main hormonal drive to masculinize and defeminize the rodent brain is testosterone secreted by the testis. The hormone does not influence sex brain differentiation only in its native configuration, but it mostly needs local conversion into active metabolites (estradiol and DHT) through the action of specific enzymatic systems: the aromatase and 5alpha-reductase (5alpha-R), respectively. This allows the hormone to control target cell gene expression either through the estrogen (ER) or the androgen (AR) receptors. The developmental profile of testosterone metabolizing enzymes, different in the two sexes, is therefore of the utmost importance in affecting the bioavailability of the steroids active in brain differentiation. Widely diffused pollutants, like polychlorinated biphenyls (PCBs) are able to affect the production and/or action of testosterone metabolites, exerting detrimental influences on reproduction and sex behavior. The main studies performed in our and other laboratories concerning the pattern of expression and the control of the enzymatic systems involved in brain androgen action and metabolism are shortly reviewed. Some recent data on the influence exerted by PCBs on these metabolic systems are also reported.

Estrogen receptor beta (ERbeta) and inhibition of prostate cancer cell proliferation: studies on the possible mechanism of action in DU145 cells

Estrogen receptor beta (ERbeta) plays a protective role against uncontrolled cell proliferation. ERbeta is lost during prostate cancer (CaP) progression suggesting its direct involvement in contrasting tumor proliferation in this disease; however, the molecular mechanism at the basis of this effect has not been clearly defined yet. Possible molecular targets of ERbeta were assessed in DU145 cells, a CaP cell line expressing only ERbeta. Cells treated from 1 to 9 days with different doses of estradiol or diarylpropionitrile (DPN, an ERbeta-selective agonist) show a time-dependent decrease in cell proliferation. The reduced proliferation rate is accompanied by the stimulation of ERbeta expression and the increase of cyclin-dependent kinase inhibitor p21. We demonstrate that the endogenous ERbeta is one of the mediator of the antiproliferative action of estrogens enhancing the synthesis of molecules such as p21 that control cell cycle, an effect amplified by the autoregulation of ERbeta expression. Our observations suggest that CaP, when expressing a functional ERbeta, might be sensitive to the antiproliferative action of estrogens; therefore, ERbeta specific agonists might be valid candidates for new pharmacological approaches to this disease.

Prenatal Aroclor 1254 exposure and brain sexual differentiation: Effect on the expression of testosterone metabolizing enzymes and androgen receptors in the hypothalamus of male and female rats

Polychlorinated biphenyls (PCBs) are industrial pollutants detected in human milk, serum and tissues. They readily cross the placenta to accumulate in fetal tissues, particularly the brain. These compounds affect normal brain sexual differentiation by mechanisms that are incompletely understood. The aim of this study was to verify whether a technical mixture of PCBs (Aroclor 1254) would interfere with the normal pattern of expression of hypothalamic aromatase and 5-alpha reductase(s), the two main enzymatic pathways involved in testosterone activation and of androgen receptor (AR). Aroclor 1254 was administered to pregnant rats at a daily dose of 25 mg/kg by gavage from days 15 to 19 of gestation (GD15-19). At GD20 the expression of aromatase, 5-alpha reductase types 1 and 2 and androgen receptor (AR) and aromatase activity were evaluated in the hypothalamus of male and female embryos. The direct effect of Aroclor was also evaluated on aromatase activity adding the PCB mixture to hypothalamic homogenates or to primary hypothalamic neuronal cultures. The data indicate that aromatase expression and activity is not altered by prenatal PCB treatment; 5-alpha reductase type 1 is similarly unaffected while 5-alpha reductase type 2 is markedly stimulated by the PCB exposure in females. Aroclor also decreases the expression of the AR in females. The observed in vivo effects are indicative of a possible adverse effect of PCBs on the important metabolic pathways by which testosterone produces its brain effects. In particular the changes of 5-alpha reductase type 2 and AR in females might be one of the mechanisms by which Aroclor exposure during fetal development affects adult sexual behavior in female rats.

Effect of platelet-rich plasma on migration and proliferation of SaOS-2 osteoblasts: role of platelet-derived growth factor and transforming growth factor-beta

Platelet-enriched plasma (PRP) is used in therapy as a source of growth factors in bone fracture and wound healing; however, few data exist on its role in the different aspects of the healing process. The effect of PRP and of the two main growth factors present in this preparation (platelet-derived growth factor [PDGF] and transforming growth factor-beta [TGF-beta]) was evaluated in vitro using the human osteoblastic cell line SaOS-2, which was shown by reverse transcription-polymerase chain reaction to express both PDGF-alpha and -beta receptors. Batroxobine-activated PRP was added in different concentrations to SaOS-2 cells to assess cell migration (by a microchemotaxis assay) and cell proliferation (by [3H]-thymidine incorporation into the DNA). Immunoneutralization with anti-PDGF-beta or anti-TGF-beta antibodies allowed the assessment of the specific role of these growth factors. The overall results obtained indicate that PRP dose-dependently stimulates both chemotaxis and cell proliferation. PDGF and TGF-beta appear to exert distinct effects on the two parameters, the former involved in stimulating cell migration and the latter in inhibiting cell proliferation. It is concluded that the different growth factors present in activated PRP can specifically contribute to the main processes of tissue regeneration.

Ontogenetic development, sexual differentiation, and effects of Aroclor 1254 exposure on expression of the arylhydrocarbon receptor and of the arylhydrocarbon receptor nuclear translocator in the rat hypothalamus

Interaction of polychlorinated biphenyls (PCBs) with the aryl hydrocarbon receptor (AhR)/nuclear translocator (ARNT) system might interfere with the mechanisms controlling the sexual differentiation of the developing hypothalamus. The aim of this study was to evaluate the presence of AhR/ARNT in brain cells and the developmental profile of their expression in the hypothalamus of male and female rats during the perinatal period. Brain accumulation of the main PCB congeners after prenatal exposure to Aroclor 1254 and its influence on hypothalamic expression of AhR/ARNT was also assessed. The results show that: (a) AhR and ARNT are expressed both in neurons and in glia; (b) AhR expression progressively increases in the developing hypothalamus particularly in males, while ARNT is relatively constant in both sexes; (c) the prenatal administration of Aroclor to dams produces a differential accumulation of PCBs, depending on the chlorine atom number, and stimulates AhR expression only in the male hypothalamus. In conclusion, the developing male hypothalamus might be more sensitive to disrupting potential of PCBs.

Dimorphic expression of testosterone metabolizing enzymes in the hypothalamic area of developing rats

Androgen transformation into estrogens through the aromatase enzyme, occurring in the rat hypothalamus during fetal life, leads to male-specific sexual differentiation of brain. Aromatase shows a peak of expression and activity in a limited period during late gestation; however, the possible dimorphism in its expression during embryogenesis is unclear. One of the mechanisms controlling tissue-specific aromatase expression might be the formation of transcript variants, that differ in the 5'-untranslated regions (5'-UTR). Exon If is the major 5'-UTR used in rodent hypothalamic-preoptic area, with low amounts of other variants encoded by different exons I also present. Another enzymatic conversion, possibly involved in brain differentiation, is the 5 alpha-reduction of Testosterone to DHT, catalyzed by two 5 alpha-reductases (5 alpha-R type1 and 2). Aim of the present study is to evaluate, in parallel, by semiquantitative RT-PCR, the dimorphic profile of the three enzymes and the pattern of the brain-specific aromatase expression in male and female rats from gestation-day 16 to postnatal-day 5 (or 15 only for 5 alpha-R1). It has been observed that, in both sexes, 5 alpha-R1 is significantly higher around birth than prenatally, and that 5 alpha-R2 expression appears to be higher in males than in females, particularly just after birth. Moreover, aromatase has two expression peaks, that are male-specific, before and after birth; only exon If is used in males, while different transcripts might be present in females postnatally. It is concluded that rodent brain sexual differentiation probably involves the activation of both 5 alpha-R2 and aromatase enzymes in a sex- and time-specific pattern.

Effects of hypothyroidism and endocrine disruptor-dependent non-thyroidal illness syndrome on the GnRH-gonadotroph axis of the adult male rat

Effects of primary hypothyroidism (HYPO) on the male gonadal axis are controversial, with only scanty data on the gonadotroph cell response and no information on GnRH tuberoinfundibular neurons, even in animal models. HYPO has been reported to variably induce hypogonadotropic hypogonadism, a hypergonadotropic state, or to have no effects on basal levels of pituitary gonadotropins, both in adult male rats and humans. Similarly, the exogenous administration of GnRH to HYPO rats and humans may increase or decrease gonadotropin secretion. Since inhibitory effects of HYPO on the GnRH-gonadotropin axis are reversed by replacement with L-T4, it has been suggested that thyroid hormone (TH) may regulate tuberoinfundibular GnRH and pituitary gonadotropin biosynthesis and/or secretion. To shed light on this hypothesis, we conducted immunocytochemical studies on the distribution and immunostaining characteristics of hypophysiotropic GnRH neurons, LH, PRL and vasoactive intestinal polypeptide (VIP) immunoreactive (IR) cells in the pituitary of adult, male rats. We show that HYPO reduces IR-GnRH in a restricted population of tuberoinfundibular perikarya and their proximal axons compared to euthyroid controls, but increases IR-VIP both in pituitary cells in direct association with LH-gonadotrophs and within IR-LH cells, itself. We propose that VIP may serve as a juxtacrine/paracrine/autocrine regulator of LH secretion and that, when GnRH biosynthesis is reduced by HYPO, gonadotropin secretion may be rescued by local activating effects of VIP. Polychlorinated biphenyls (PCB), industry toxicants found in food and water, also have inhibitory effects on the gonadal axis, decreasing fertility and suppressing basal and GnRHinduced LH release in male rats. Since PCB may also exert endocrine disruptor-dependent (EDD) effects on the thyroid axis producing a non-thyroidal illness syndrome (NTIS) (coined EDD-NTIS), we developed a rat model of EDD-NTIS to determine whether central hypothyroidism may contribute to the pathophysiology of PCB-induced hypogonadism. On the basis of preliminary animal data, we speculate that one of the mechanisms for Partial Androgen Deficiency of the Aging Male may involve central hypothyroidism and EDD-NTIS, resulting in inhibition of the GnRH-gonadotroph axis.

Sexual differentiation of the brain: role of testosterone and its active metabolites

The sex-related morphological differences of many brain nuclei are mainly determined by the hormonal environment present during embryonic development. These morphological differences are at the basis of the gender-specific secretion of many hypothalamic and pituitary hormones, of sexual and aggressive behavior, etc. It is known that, at least in rodents, testosterone (T) secreted by the fetal testes plays a key role in the permanent organization of the developing central nervous system (CNS) toward masculine patterns. The main aspect concerning the mechanism of action of T is that the brain, and especially the hypothalamus, possesses the enzymes that transforms this hormone into compounds which amplify (dihydrotestosterone) or differentiate (estrogens) its action; these enzymatic systems are the 5alpha-reductase and the aromatase respectively. In this short review are summarized the main results obtained in our and other laboratories concerning some characteristics of the two enzymatic pathways in the developing CNS and the possible dimorphism in their expression during ontogenesis. On the basis of diseases in which alterations of the normal levels and/or of the mechanism of action of gonadal hormones during embryogenesis are present, in the last part of the paper some hypotheses on the possible influence of T metabolites in the sexual differentiation of the human brain are also drawn.

The metabolic effects of inhibitors of 5-lipoxygenase and of cyclooxygenase 1 and 2 are an advancement in the efficacy and safety of anti-inflammatory therapy

Chronic treatment of inflammatory diseases with non-steroidal anti-inflammatory drugs is effective but not always devoid of serious side effects. In particular, the use of traditional non-steroidal aspirin-like drugs has been associated with a high incidence of gastrointestinal bleedings. The development of a new class of drugs, the selective cyclooxygenase type 2 (COX-2) inhibitors, has generated much expectation on the possibility to have safer compounds. After the initial enthusiasm of the scientific community, a re-evaluation of some large, randomized double-blind clinical studies performed with two of these compounds, has disclosed that the late serious gastrointestinal complications are not significantly reduced in comparison with non-selective inhibitors and that cardiovascular concerns might arise particularly if theses drugs are utilized in patients with underlying heart diseases. A new promising class of drugs to control inflammatory diseases is in advanced clinical development. The balanced inhibitors of 5-lipoxygenase (5-LOX) and of cyclooxygenase (both types 1 and 2) block the formation of all the enzymatically arachidonic acid-derived metabolites, both prostaglandins (like COX inhibitors) and leukotrienes (LT); these drugs have been shown to possess a very good anti-inflammatory efficacy without serious side effects. Licofelone, previously known as ML3000, is the molecule in the most advanced phase of clinical development (phase III) among this class of compounds; it is a potent, competitive, and well balanced inhibitor of 5-LOX and COX pathways. The drug has been shown to possess analgesic, anti-inflammatory, antipyretic antibronchocostrictory and antiplatelet properties at doses which are safe for the gastrointestinal tract. Moreover, the newly performed preclinical studies, here briefly reviewed, appear to indicate that the compound seems particularly suitable to protect the articular cartilage and the synovial space in degenerative joint disease and to exert a relevant antithrombotic activity. Preliminary results of clinical studies of licofelone in osteoarthritis indicate that the drug has a comparable or slightly better efficacy than that of naproxen but possesses a much better gastrointestinal safety. This latter important aspect has been also evaluated by an endoscopic study in normal volunteers randomly assigned to a 4-week treatment with licofelone, placebo or naproxen. The results indicate that no ulcers occurred in either licofelone group or the placebo group, while ulcers with unequivocal depth were present in 20% of the naproxen-treated subjects.

Characterization and pharmacological actions of tecostanine, an alkaloid of Tecoma stans

Tecostanine (1) was isolated from Tecoma stans leaves. Its sterochemistry was elucidated as well as its antihyperglycemic activity and its affinity to opioid and nicotinic receptors. The oxalate salt of 1 did not significantly affect blood glucose levels in normoglycaemic and hyperglycaemic rats. It did not appear to interact with opioid receptors (mu type) and showed only moderate affinity to the nicotinic receptor.

Pathogenesis of diabetic neuropathy--do hyperglycemia and aldose reductase inhibitors affect neuroactive steroid formation in the rat sciatic nerves?

The activation of the polyol pathway through aldose reductase (AR) might be involved in diabetic neuropathy. A considerable structural similarity exists between AR and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) (both belonging to aldo-keto reductase superfamily); 3alpha-HSD forms 5alpha-reduced-3alpha-hydroxylated steroids, possibly possessing neurotrophic functions. Aim of these experiments was to test "in vitro" in rat sciatic nerves, whether glucose concentrations in the diabetic range might affect the capacity of 3alpha-HSD to transform dihydroprogesterone (DHP) into tetrahydroprogesterone (THP), a steroid proved to possess neurotrophic effects. The capability of AR inhibitors, drugs used to avoid diabetic complications, to decrease THP formation was also assessed. 3alpha-HSD activity was evaluated by the conversion of labelled DHP into THP (in a single case dihydrotestosterone was used as substrate, and the corresponding 3alpha-hydroxylated metabolite was evaluated). Freshly prepared rat sciatic nerve homogenates were used as source of the enzyme. Whole brain, liver and prostate served as "control" tissues. The results show that glucose added up to a concentration of 400 mg/dL (well above the euglycemic upper level) does not affect the 3alpha-HSD activity in the sciatic nerve and in the other tissues considered. Similarly, when the enzyme was challenged by two AR inhibitors, tolrestat and sorbinil, added in a concentration about 10 times higher than their IC50 for AR, no significant changes were observed. Analogous results were achieved when DHT was used in presence of glucose (400 mg/dL) and sorbinil. We conclude that hyperglycemia or the administration of the AR inhibitors do not affect 3alpha-HSD activity in peripheral nerves and therefore do not reduce the formation of steroid metabolites possibly endowed with neurotrophic action.

Substrate interaction with 5alpha-reductase enzyme: influence of the 17beta-chain chirality in the mechanism of action of 4-azasteroid inhibitors

A series of steroidal compounds were synthesized in order to evaluate the possible influence of the configuration of a stereocenter in the 17beta-side chain on the inhibitory activity on the enzyme 5alpha-reductase (5AR). For this purpose diastereomerically pure 4-azasteroids epimers at C-22 were prepared (compounds 1-11) and tested as inhibitors of 5AR in "in vitro" tests. The obtained data showed that in most cases the couples of epimers possess a significant difference in their biological activity. We also considered, for the tested molecules, a series of chemico-physical parameters in order to find a possible correlation with their biological activity. The findings allowed us to propose a model of the binding site of 5AR which comprises also, for 4-azasteroid inhibitors, the configurational aspect of the 17beta-side chain.

Aromatase expression and activity in male and female cultured rat hypothalamic neurons: effect of androgens

Aromatase is possibly involved in male brain sexual differentiation. Aim of these experiments was to evaluate the role of testosterone (T) and of DHT, in the regulation of aromatase expression and activity. The experiments were done utilizing rat primary cultures of hypothalamic neurons from 16-day old embryos sex-screened by SRY gene. Aromatase expression was assessed semiquantitatively by RT-PCR using a neuronal marker (MAP2c) as coamplification product; enzymatic activity was estimated by the 3H(2)O method. The results indicate that (1) cultured neurons possess a functional aromatase, which increases significantly during a 5-days culture period; (2) neurons from males possess a higher expression and activity of the enzyme than females; (3) androgens negatively control expression/activity of aromatase in males, DHT is more active than T; (4) on the contrary, in females T produces a small stimulation of aromatase expression, but not of activity (DHT has produced inconsistent results). The results obtained in this model indicate that T does not stimulate aromatase; therefore, it is not responsible for triggering the perinatal enzymatic peak, nor for the sexual dimorphic aromatase expression. A model is proposed in which DHT might induce, at least in males, the descending phase of the aromatase peak.

Anti-inflammatory drugs: new multitarget compounds to face an old problem. The dual inhibition concept

In this short review we have tried to focus on some new relevant aspects of the pharmacological control of inflammation. The clinical availability of new drugs able to produce a selective inhibition of type 2 cyclooxygenase (COX-2), the enzyme thought to be mainly responsible for generating arachidonic-acid-derived inflammatory mediators, has been the origin of much hope. However, expectations of having an effective and completely safe non-steroidal anti-inflammatory drug (NSAID) have been only partially fulfilled. Emerging information has challenged some aspects of the original hypothesis indicating COX-2 as devoid of 'housekeeping' physiological functions. Moreover, the recently available clinical studies have indicated only a relatively small improvement in the tolerability of the newer 'selective' COX-2 inhibitors over the classical COX-1/COX-2 mixed type NSAIDs. The new appreciation of the role of other arachidonic acid derivatives, the leukotrienes (LTS), in producing and maintaining inflammation has generated considerable interest in drugs able to block LTS receptors or to produce a selective inhibition of 5-lipoxygenase (5-LO), the initial key enzyme of the leukotriene pathway. These drugs are now included among the effective therapies of asthma but appear, in the few clinical studies performed, to be an insufficient single therapeutic approach in other inflammatory diseases. Drugs able to block equally well both COX and 5-LO metabolic pathways (dual inhibitors) have been developed and experimentally evaluated in the last few years, but none are available on the market yet. The pharmacological rationale at the basis of their development is strong, and animal studies are indicative of a wide range of anti-inflammatory activity. What appears most impressive from the available studies on dual inhibitors is their almost complete lack of gastric toxicity, the most troublesome side effect of NSAIDs. The mechanism of the gastric-sparing properties of these drugs is not yet completely understood; however, it appears that leukotrienes significantly contribute to gastric epithelial injury particularly when these compounds represent the major arachidonic acid derivatives present in the gastric mucosa after inhibiton of prostanoid production.

Dietary calcium and mineral/vitamin supplementation: a controversial problem

There is a consensus that adequate calcium intake during bone development, and possibly in adulthood and senescence, helps to prevent bone resorption and osteoporosis. The uptake of dietary calcium should be sufficient to maintain both normal serum calcium concentrations and parathyroid hormone levels in the low normal range throughout the day, otherwise, increased bone resorption occurs. Calcium intake varies with race and with environmental and dietary conditions. Estimating the appropriate amount of calcium to be added to dietary sources for an optimal supplementation regimen is therefore difficult. Few intervention studies have evaluated the dose-effect relationship for calcium supplementation conclusively. The mechanisms regulating fractional calcium absorption as a function of intake suggest that very high daily doses are probably useless. They may be unsafe in the long term because of the risks of hypercalciuria and kidney stones, and of an imbalance in the ratio of calcium to magnesium. Concomitant supplementation with limited amounts of magnesium may reduce this risk and improve mineralization. Dietary intake is 500-600 mg/day in most studies, making 400 mg/day an appropriate supplementary dose for most premenopausal women (RDA 1000 mg/day). After the menopause and during lactation (RDA 1200-1500 mg/day), 800 mg/day is probably appropriate, particularly if low doses of vitamin D are taken concomitantly.

5 alpha-reductase isozymes in the central nervous system

The enzyme 5 alpha-reductase (5 alpha-R) activates several delta 4-3keto steroids to more potent derivatives which may also acquire new biological actions. Testosterone gives rise to the most potent natural androgen dihydrotestosterone (DHT), and progesterone to dihydroprogesterone (DHP), a precursor of the endogenous anxiolytic/anesthetic steroid tetrahydroprogesterone (THP). Two isoforms of 5 alpha-R, with a limited degree of homology, different biochemical properties and distinct tissue distribution have been cloned: 5 alpha-R type 1 and type 2. In androgen-dependent structures DHT is almost exclusively formed by 5 alpha-R type 2; 5 alpha-R type 1 is widely distributed in the body, with the highest levels in the liver, and may be involved in steroid catabolism. In the brain, the roles of the two isozymes are still largely unknown. This brief review will summarize recent experimental data from our laboratory which try to assign possible functional roles to the process of 5 alpha-reduction, and to the two 5 alpha-R isoforms in the CNS.

Transient expression of the 5alpha-reductase type 2 isozyme in the rat brain in late fetal and early postnatal life

The enzyme 5alpha-reductase plays a key role on several brain functions controlling the formation of anxiolytic/anesthetic steroids derived from progesterone and deoxycorticosterone, the conversion of testosterone to dihydrotestosterone, and the removal of excess of potentially neurotoxic steroids. Two 5alpha-reductase isoforms have been cloned: 5alpha-reductase type 1 is widely distributed in the body, and 5alpha-reductase type 2 is confined to androgen-dependent structures. In this study, the gene expression of the two 5alpha-reductase isozymes has been analyzed in fetal, postnatal, and adult rat brains by RT-PCR followed by Southern analysis. 5Alpha-reductase type 1 messenger RNA is always detectable in the rat brain [from gestational day 14 (GD14) to adulthood]. 5Alpha-reductase type 2 messenger RNA expression is undetectable on GD14, increases after GD18, peaks on postnatal day 2, then decreases gradually, becoming low in adulthood. This pattern of expression appears to be correlated with the rate of production of testosterone by the testis. The possible control by androgens of gene expression of the two isozymes has been studied in brain tissues of animals exposed in utero to the androgen antagonist flutamide; the sex of the animals was determined by genetic sex screening of the SRY gene located on the Y-chromosome. In the brain of male embryos, flutamide treatment inhibited the expression of 5alpha-reductase type 2; this effect was much less pronounced in females. Moreover, 5alpha-reductase type 2 gene expression in cultured hypothalamic neurons is highly induced by testosterone and by the phorbol ester 12-O-tetradecanoyl-phorbol-13 acetate. The transient, androgen-regulated, expression of 5alpha-reductase type 2 overlaps the critical period of development, which may be important for sexual differentiation of the brain and for the formation of anxiolytic/anesthetic steroids involved in the stress responses associated with parturition.

The 5alpha-reductase in the central nervous system: expression and modes of control

The present paper will summarize two important aspects of the interactions between steroids and the brain, which have recently been studied in the authors' laboratory. In particular the paper will consider data on: (1) the significance of the two isoforms of the 5alpha-R during brain ontogenesis and development, and (2) the cross-talk between glial and neuronal elements, particularly in relation to the metabolism of sex hormones. (1) The data obtained have shown that the 5alpha-R type 1 enzyme is constitutively expressed in the rat CNS at all stages of brain development. Moreover, the expression of the 5alpha-R type 1 is similar in males and in females, and does not appear to be controlled by androgens. The gene expression of the 5alpha-R type 2 is totally different. This isoform appears to be expressed in the rat brain almost exclusively in the late fetal/early post-natal life and is controlled by testosterone. (2) The present data show that two cell lines derived respectively from a rat glioma (C6 cell line) and from a human astrocytoma (1321N1 cell line) are able to convert testosterone and progesterone into their corresponding 5alpha-reduced metabolites dihydrotestosterone and dihydroprogesterone. The possibility that secretory products of normal and tumoral brain cells might be able to influence steroid metabolism occurring in the two glial cell lines previously mentioned has been considered.

Steroid metabolism in the mammalian brain: 5alpha-reduction and aromatization

Several steroid molecules, including androgens, estrogens, progestagens, and corticostereroids, are able to modulate the brain development and functions. These compounds are not always active in their own natural molecular configuration but they often need to be transformed at the level of their target cells into 'active metabolites'. The two major metabolic pathways that transform steroids in the brain are: the 5alpha-reductase-3alpha-hydroxy-steroid dehydrogenase and the aromatase pathways. Both are present in the brain and probably exert specific roles in the mechanism of action of hormonal steroids. In this article we briefly review some important findings achieved in our own and in other laboratories concerning the cellular and subcellular brain distribution, development, regulation, cloning, and molecular characterization of the involved enzymes. In particular, the recent identification of two isoforms of the 5alpha-reductase, the type 1 and type 2, possessing different structural, biochemical, and distribution characteristics has attracted a considerable attention. The few data available on their brain distribution have been carefully considered. Finally, we have tried to focus on the role of the steroid metabolites in the brain, both when they interact with genomic and with membrane receptors. In particular, some unpublished observations on the effects of two 5alpha-reductase inhibitors on progesterone-induced anesthesia, a phenomenon mediated through the GABA(A) receptor, are presented.

Identification of type 1 5alpha-reductase in myelin membranes of male and female rat brain

The formation of the 5alpha-reduced metabolites of testosterone (T) and of progesterone (P) is a very active process in the brain, since the enzyme 5alpha-reductase (5alpha-R) is present in almost any central nervous system (CNS) structure. A particularly elevated 5alpha-R activity has been shown in myelin sheaths. Two isoforms of the enzyme have been cloned, with different localisation as well as different biochemical properties. The present study was performed to determine whether both isoforms of the 5alpha-R, or only one of them, are/is responsible for the enzymatic activity observed in myelin. Kinetic analyses have been performed on purified myelin membranes prepared from the male or female rat brain, using both T and P as substrates. The 5alpha-R present appears to possess a pH optimum at basic values. The Vmax values obtained in the Lineweaver-Burk analysis were comparable in male and female preparations independently on whether T or P were used as the substrates, suggesting that a single enzymatic form is present in all samples examined; the Km obtained using [14C]T (Km: male 1.14 microM; female 1.46 microM) or [14C]P (Km: male 0.5 microM; female 0.64 microM) as substrates, were in good agreement with those obtained for the recombinant type 1 isoform. These data suggest that the type 1 isoform is the most relevant 5alpha-R present in myelin. To confirm this, a new polyclonal antibody was raised against the type 1 5alpha-R enzymatic protein, and used in immunohistochemical studies. The experiments were performed on the optic nerve, a myelinated structure very rich in 5alpha-R activity and the results clearly indicated the presence of a specific type 1 enzyme immunoreactivity in the myelin sheaths of axons.

Expression of androgen-activating enzymes in cultured cells of developing rat brain

Dihydrotestosterone and estradiol, two active metabolites formed locally in the brain from testosterone, modulate several functions of the developing rat CNS; these compounds derive from the 5 alpha-reduction or the aromatization of the A-ring of the hormone. Also, progesterone and corticosteroids may be 5 alpha-reduced and subsequently 3 alpha-hydroxylated, becoming modulators of specific neuronal functions. Although the aromatase is a single enzyme, two types of 5 alpha-reductase have been cloned, showing peculiar biochemical properties and probably different functions. Therefore, the isoform(s) of the enzyme 5 alpha-reductase(s) present in early stage of brain development have been characterized in primary neuronal and glial cell cultures obtained from the fetal or neonatal rat brain, respectively. Aromatase expression was also studied. The results have shown that in all the brain cells examined type 1 5 alpha-reductase mRNA is expressed. No specific transcript of type 2 5 alpha-reductase is detectable in any of the cell types examined. Finally, the aromatase gene is expressed only in cultured fetal neurons and especially in those derived from the hypothalamic area of the rat embryos. It is interesting that no aromatase mRNA is detectable in mixed glia or in type 1 astrocytes and oligodendrocytes cultured separately.

Testosterone and progesterone metabolism in the central nervous system: cellular localization and mechanism of control of the enzymes involved

This paper summarizes the most recent data obtained in the authors' laboratory on the metabolism of testosterone and progesterone in neurons and in the glia. 1. The activities of 5 alpha-reductase (the enzyme that converts testosterone into dihydrotestosterone; DHT) and of 3 alpha-hydroxy steroid dehydrogenase (the enzyme that converts DHT into 5 alpha-androstane-3 alpha, 17 beta-diol; 3 alpha-diol) were first evaluated in primary cultures of neurons, oligodendrocytes, and type-1 and type-2 astrocytes, obtained from the fetal or neonatal rat brain. The formation of DHT and 3 alpha-diol was evaluated incubating the different cultures with labeled testosterone or labeled DHT as substrates. The results obtained indicate that the formation of DHT takes place preferentially in neurons; however, also type-2 astrocytes and oligodendrocytes possess considerable 5 alpha-reductase activity. A completely different localization was observed for 3 alpha-hydroxysteroid dehydrogenase; the formation of 3 alpha-diol appears to be prevalently, if not exclusively, present in type-1 astrocytes; 3 alpha-diol is formed in very low yields by neurons, type-2 astrocytes, and oligodendrocytes. Moreover, the results indicate that, in type 1 astrocytes, both 5 alpha-reductase and 3 alpha-HSD are stimulated by coculture with neurons and by the addition of neuron-conditioned medium, suggesting that secretory products released by neurons might intervene in the control of glial cell function. 2. Subsequently it was shown that, similarly to what happens when testosterone is used as the substrate, 5 alpha-reductase, which metabolizes progesterone into 5 alpha-pregnane-3,20-dione, (DHP), shows a significantly higher activity in neurons than in glial cells; however, also type-1 and type-2 astrocytes as well as oligodendrocytes possess some ability to 5 alpha-reduce progesterone. On the contrary, 3 alpha-hydroxysteroid dehydrogenase, the enzyme which converts DHP into 5 alpha-pregnane-3 alpha-ol-20-one (THP), appears to be present mainly in type-1 astrocytes; much lower levels of this enzyme are present in neurons and in type-2 astrocytes. At variance with the previous results obtained using androgens as precursors, oligodendrocytes show considerable 3 alpha-hydroxysteroid dehydrogenase activity, even if this is statistically lowe than that present in type-1 astrocytes. The existence of isoenzymatic forms of the enzymes involved in androgen and progesterone metabolism is discussed.

Characterization of rat 5alpha-reductases type 1 and type 2 expressed in Saccharomyces cerevisiae

Two isoforms of the rat 5alpha-reductase (5alpha-R), the enzyme that converts testosterone into dihydrotestosterone (DHT), and other delta4-3-keto steroids (e.g. progesterone and corticoids) into their 5alpha-reduced metabolites, have been cloned. In this study, a convenient and efficient system was developed to overexpress the two isoenzymes in Saccharomyces cerevisiae by using the ubiquitin-fusion expression system. Two yeast expression vectors have been prepared, YEpR1 and YEpR2, which code for 5alpha-R type 1 and 5alpha-R type 2 respectively; they contain the copper-responsive yeast metallothionein promoter (CUP1) upstream of the ubiquitin coding sequence, and the full-length rat 5alpha-R type 1 or 5alpha-R type 2 cDNAs in frame to the 3' end of the ubiquitin cDNA. The activity of the two isoenzymes produced in yeast was determined in cell lysates at the enzyme pH optima (type 1, pH 7.5; type 2, pH 5.5) and a possible differential intracellular distribution was also evaluated. The kinetic parameters were: type 1, Km 4.6 microM, Vmax.100.6 micrograms/h per mg of protein; type 2, Km 68.6 nM, Vmax. 0.84 micrograms/h per mg of protein. Yeast cell lysates were fractionated by differential centrifugation and the 5alpha-R type 1 activity was maximal in fractions containing nuclei (1000 g and 2500 g), whereas the maximal activity of 5alpha-R type 2 was present in subcellular fractions sedimenting at higher speeds (20000g). The data indicate that yeasts overexpress the two 5alpha-R isoenzymes, maintaining their native biochemical properties, and that the two isoforms are probably differentially localized within the yeast cell.

Metabolism of steroids in pure cultures of neurons and glial cells: role of intracellular signalling

In the brain, the 5 alpha-reductase converting testosterone (T) is present both in neurons and in glial cells, even if it prevails in neurons; the 3 alpha-hydroxysteroid-dehydrogenase (3 alpha-HSD), the enzyme converting dihydrotestosterone (DHT) into 3 alpha-diol, is particularly concentrated in type 1 astrocytes. In glial cells, since the 5 alpha-reductase is activated by a cAMP analogue, PKA seems to be involved in the control of this enzyme, postulating that nervous inputs utilizing cAMP as the second messenger might modify the activity of this enzyme in glial cells. Moreover, the results indicate that, in type 1 astrocytes, both the 5 alpha-reductase and the 3 alpha-HSD are stimulated by the co-culture with neurons and by the addition of neuron-conditioned medium, suggesting that secretory products released by neurons might intervene in the control of glial cell function.

Estrogen receptor is expressed in different types of glial cells in culture

Estrogens derived from the aromatization of androgens are believed to be responsible for the induction of the sexual differentiation of the CNS interacting with specific estrogen receptors (ER) present in developing neurons. However, the brain cellular distribution of ER is not so well documented. The aim of this study was to investigate the qualitative and quantitative expression of ER mRNA in well characterized cultures of rat type 1 and type 2 astrocytes and of oligodendrocytes by polymerase chain reaction. A series of amplifications with a set of primers spanning along the entire ER mRNA was utilized in the different types of glial cells, in a positive control (uterus), and in a negative control (SK-N-BE cell line) previously shown to be devoid of ER. The data obtained show that ER mRNA is expressed in all three types of glial cell analyzed in almost equal amounts, which are 25-50 times lower than those in the uterus. The mRNA expressed in the glia is homologous with that expressed in the uterine tissue.

Progesterone 5-alpha-reduction in neuronal and in different types of glial cell cultures: type 1 and 2 astrocytes and oligodendrocytes

Progesterone, like testosterone, can be converted in the brain into 5-alpha-reduced metabolites (5-alpha-pregnan-3,20-dione, DHP; 5-alpha-pregnan-3-alpha-ol-20-one, THP). Recently we have shown that testosterone is 5-alpha-reduced to DHT mainly in neurons, while glial cells possess this enzymatic activity only in limited amounts. On the other hand, a glial cell type (type 1 astrocytes) is almost exclusively responsible for the further metabolism of DHT into 3-alpha-diol. The aim of the present studies was that of evaluating the formation of the 5-alpha-reduced metabolites of progesterone in cultures of neurons, type 1 and 2 astrocytes and oligodendrocytes. The data here presented indicate that, similarly to what happens when testosterone is used as the substrate, the 5-alpha-reductase which metabolizes progesterone shows a significantly higher activity in neurons than in glial cells; however, also type-1 and type-2 astrocytes as well as oligodendrocytes possess some ability to 5-alpha-reduce progesterone. On the contrary, the 3-alpha-hydroxysteroid dehydrogenase (3-alpha-HSD), the enzyme which converts DHP into THP, appears to be mainly present in type-1 astrocytes; much lower levels of this enzyme are present in neurons and in type-2 astrocytes. At variance with the previous results obtained utilizing androgens as precursors, oligodendrocytes show a considerable 3-alpha-HSD activity, even if this is statistically lower than that present in type-1 astrocytes. The existence of isoforms of the enzymes involved in androgen and progesterone metabolism may explain these data.

Distribution of aromatase activity in cultured neurons and glia cells

Aromatase plays a crucial role in the mechanism of action of testosterone in the central nervous system. Nevertheless, the exact cellular localization of this enzymatic complex within the different cell populations of the brain is still uncertain. In the experiments described here the presence of aromatase (assayed by the tritiated water method) has been evaluated in the two main cellular components of the brain: neurons and glia. Neurons, mixed glial cells, type 1 astrocytes, were obtained in cultures; oligodendrocytes were prepared by gradient ultracentrifugation. The results indicate that, among the different cells tested, only neurons possess a significant degree of aromatase activity, while the enzymatic activity is extremely low in mixed glial cell and in astrocyte preparations. Oligodendrocytes seem to be completely inactive in this respect.

Differential localization of the 5 alpha-reductase and the 3 alpha-hydroxysteroid dehydrogenase in neuronal and glial cultures

The activities of the 5 alpha-reductase [the enzyme that converts testosterone into dihydrotestosterone (DHT)] and 3 alpha-hydroxysteroid dehydrogenase [the enzyme that converts DHT into 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol)] have been evaluated in primary cultures of neurons, oligodendrocytes, and type 1 and 2 astrocytes obtained from fetal or neonatal rat brain. All cultures were used on the fifth day. The formation of DHT and 3 alpha-diol was evaluated by incubating the different cultures with [14C]testosterone or [14C]DHT as substrates. The results obtained indicate that the formation of DHT takes place preferentially in neurons; however, type 2 astrocytes and oligodendrocytes also possess considerable 5 alpha-reductase activity, while type 1 astrocytes show a much lower enzymatic activity. A completely different localization was observed for 3 alpha-hydroxysteroid dehydrogenase. The formation of 3 alpha-diol appears to be mainly, if not exclusively, present in type 1 astrocytes. 3 alpha-Diol is formed in very low yields by neurons, type 2 astrocytes and oligodendrocytes. The compartmentalization of two strictly correlated enzymes (5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase) in separate central nervous system cell populations suggests the simultaneous participation of neurons and glial cells in the 5 alpha-reductive metabolism of testosterone and possibly other hormonal steroids (e.g. progesterone, corticoids, etc.).

Anabolic steroids: a review of their effects on the muscles, of their possible mechanisms of action and of their use in athletics

Anabolic steroids are synthetic molecules developed in the hope of obtaining a complete separation of the androgenic and myotrophic (anabolic) actions of testosterone. Such a goal has never been fully achieved. However, some synthetic steroids present a partial dissociation between these two activities. Since a single hormonal receptor apparently mediates the androgenic as well as the anabolic actions of testosterone, differences in patterns of androgen metabolization in the muscles and the sex accessory organs have been proposed as a possible cause of this phenomenon. Undoubtedly, androgens are able to exert a trophic effect on skeletal and cardiac muscle fibres in subjects with low circulating levels of testosterone such as prepubertal or hypogonadal males and females; however, the widespread use of anabolic steroids in male athletes to increase their physical performances poses the question of whether these compounds are active in the presence of normal circulating levels of testosterone. Most experimental animal studies indicate that anabolic steroids are ineffective in this situation. Since the results of the experiments performed in humans are largely contradictory, it is still not clear whether anabolic steroids are able to improve athletic performances. These and other relevant issues are reviewed.

Aromatase activity in cultured brain cells: difference between neurons and glia

At the level of the central nervous system (CNS) of several mammalian and non-mammalian species, estrogens may be intracellularly formed from circulating androgens through the action of the aromatase complex. Estrogenic steroids play a crucial role in organizing and directing certain behavioral and neuroendocrine responses both during the fetal/neonatal life and in adulthood. Biochemical and immunocytochemical studies have shown that the aromatase is particularly concentrated in CNS areas involved in the control of reproductive functions, such as the hypothalamus, the preoptic area and the limbic system; despite this large body of evidence, the exact cellular localization of this enzymatic complex within the different cell populations of the brain is still uncertain. In the experiments described here, the presence of the aromatase has been evaluated in the two main cellular components of the brain: the neurons and the glia. In these experiments, cultures of neurons obtained from the brains of 14-15-day-old rat embryos, mixed glial cells from 1-day-old rats and type 1 astrocytes derived from cultured glial cells, have been utilized. The aromatase has been also evaluated in oligodendrocytes isolated from adult male rat brain by density gradient ultracentrifugation. The aromatase activity has been assayed by an 'in vitro' radiometric method which quantifies the production of tritiated water from [1 beta-3H]-androstenedione as an index of estrogen formation. The validity of the method has been verified both on the placental microsomes and on rat hypothalamic tissue, in which the actual formation of estrogens has also been measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Is the 5 alpha-reductase-3 alpha-hydroxysteroid dehydrogenase complex associated with the myelin in the peripheral nervous system of young and old male rats?

The formation of the 5 alpha-reduced metabolites of testosterone, 5 alpha-androstan-17 beta-ol-3-one (dihydroxytestosterone, DHT) and 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol) was evaluated in sciatic nerve fragments and homogenates and in the myelin purified from the sciatic nerve of adult (60-90-day-old) male rats. The effects of aging on the metabolism of testosterone in the sciatic nerve was also evaluated using 20-month-old animals. In the sciatic nerve, tissue homogenization and myelin purification are associated with a marked decrease in the 5 alpha-reductase activity; these data do not appear to be consistent with a possible association of the enzyme with myelin membranes, as it occurs in the CNS. However, the results may be subject to other interpretations which are presented in the discussion. The formation of 3 alpha-diol is higher in sciatic nerve fragments than in homogenates or in the purified myelin. This occurs when testosterone is used as the substrate. In aged animals, the same pattern is observed but at a lower level. In the incubations in which the formation of 3 alpha-diol was evaluated using DHT as the substrate in fragments, homogenates and purified myelin of the sciatic nerve of either adult or old animals, it was found that the yields of this metabolite are higher than those obtained following incubation with testosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular signalling systems controlling the 5 alpha-reductase in glial cell cultures

Glial cells are able to metabolize testosterone into DHT through the action of the enzyme 5 alpha-reductase. DHT may be further processed to 3 alpha-diol by the 3 alpha-hydroxysteroid-dehydrogenase. The aim of this study was to analyze if a modulation of two second messenger systems might be able to modify the 5 alpha-reductase and the 3 alpha-hydroxysteroid-dehydrogenase activities present in glial cells. To this purpose, the formation of DHT has been measured in rat glial cell cultures after different time of exposure to TPA, 4 alpha-Ph, an active and an inactive phorbol ester respectively, and 8-Br-cAMP. The results obtained indicate that the formation of DHT is not modified by the addition of phorbol esters. On the contrary, a statistically significant increase of 5 alpha-reductase activity, over control levels, has been observed after 6, 12, and 24 h of incubation with 8-Br-cAMP (10(-3) M). The effect of the cAMP analogue appears to be specific for the 5 alpha-reductase, since the 3 alpha-hydroxysteroid-dehydrogenase did not show any variation after exposure to the drug. In conclusion, the present data suggest that proteinkinase A (PKA) might be involved in the control of the 5 alpha-reductase in glial cells. It is postulated that nervous inputs utilizing cAMP as the second messenger might modify the activity of this enzyme in glial cells.

The 5 alpha-reductase in the brain: molecular aspects and relation to brain function

All the classes of hormonal steroids physiologically produced in the body (androgens, estrogens, progestagens, and corticosteroids) are able to exert important effects on the brain, but the mechanisms of their actions are not always well understood. Steroids may interact with intracellular receptors to activate the genome, but some of their effects are probably extragenomic and involve interactions with cellular membranes. Moreover, not all the steroids act always in their native molecular form; a large group of them must actually be transformed into "active" metabolites. This may occur at the level of their respective target structures. For example, androgens are metabolized in the brain into estrogens and into 5 alpha-reduced androgens, like 5 alpha-androstan-17 beta-ol-3-one (dihydrotestosterone; DHT) and 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol). Progesterone, and possibly corticosteroids, may also be transformed into their corresponding 5 alpha-reduced metabolites. Also the cellular target (neurons and/or glial cells) of the hormonal steroids in the brain is not always clear. This review analyzes in detail one of the two major enzymatic systems that transform steroids in the brain, namely the 5 alpha-reductase-3 alpha-(3 beta)-hydroxysteroid dehydrogenase pathway. An active 5 alpha-reductase-3 alpha-hydroxysteroid dehydrogenase system is widely distributed in practically all CNS structures in all phases of development. In the brain, this enzymatic system is not regulated by castration or sex steroid administration; furthermore, neural inputs seem to be ineffective at the hypothalamic level. A recent interesting finding is the presence of high concentrations of the 5 alpha-reductase in the white matter. This probably is due to the fact that the white matter is particularly rich in myelin membranes, with which the enzymatic activity appears to be associated. An active 5 alpha-reductase activity has also been shown to be present in peripheral myelinated nerves. The localization in myelin membranes may suggest a possible involvement of 5 alpha-reduced metabolites of the different steroids in the process of myelination. The presence of the 5 alpha-reductase was analyzed in neurons, astrocytes, and oligodendrocytes isolated from the brains of male rats, as well as in neurons and glial cells grown in culture. Neurons appear to be more active than glial cells in converting testosterone into DHT. Only neurons possess aromatase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Testosterone metabolism in brain cells and membranes

The central nervous system (CNS) is considered a target structure for the action of all the classes of hormonal steroids produced by the organism. Well-characterized genomic and less well-understood membrane mechanisms of action are probably involved in the steroid modulation of brain activities. Moreover, some classes of steroids need to be converted into "active" metabolites before interacting with their effector systems. In particular, testosterone (T) exerts many of its effects after conversion to 5 alpha-dihydrotestosterone (DHT) and estrogens. The CNS possesses both the 5 alpha-reductase, the enzyme which produces DHT and the aromatase which transforms T into estrogens; however, the relative role and distribution of these enzymes in the various structural components of the CNS has not been clarified so far. The 5 alpha-reductase has been found to be present in high concentrations in brain white matter structures because these are particularly rich in myelin membranes, to which the enzymatic activity appears to be associated. This membrane localization might suggest a possible involvement of steroidal 5 alpha-reduced metabolites in membrane-mediated events in the CNS. Moreover, the distribution of 5 alpha-reductase was studied in neurons, astrocytes and oligodendrocytes isolated from the brain of male rats by density gradient ultracentrifugation, as well as in neurons and glial cells grown in culture. The aromatase activity was also evaluated in neurons and glial cells grown in culture and in isolated oligodendrocytes. Among the three cell types isolated, neurons appear to be more active than oligodendrocytes and astrocytes, respectively, in converting T into DHT. Also, in cell culture experiments, neurons are more active in forming DHT than glial cells. Only neurons possess aromatase activity, while glial cells are apparently unable to aromatize T.