Effects of corticosterone on reproduction in male Sprague-Dawley rats

Acute restraint stress rapidly impacts reproductive neuroendocrinology and downstream gonad function in big brown bats (Eptesicus fuscus)

Animals face unpredictable challenges that require rapid, facultative physiological reactions to support survival but may compromise reproduction. Bats have a long-standing reputation for being highly sensitive to stressors, with sensitivity and resilience varying both within and among species, yet little is known about how stress affects the signaling that regulates reproductive physiology. Here, we provide the first description of the molecular response of the hypothalamic-pituitary-gonadal (HPG) axis of male big brown bats (Eptesicus fuscus) in response to short-term stress using a standardized restraint manipulation. This acute stressor was sufficient to upregulate plasma corticosterone and resulted in a rapid decrease in circulating testosterone. While we did not find differences in the mRNA expression of key steroidogenic enzymes (StAR, aromatase, 5-alpha reductase), seminiferous tubule diameter was reduced in stressed bats coupled with a 5-fold increase in glucocorticoid receptor (GR) mRNA expression in the testes. These changes, in part, may be mediated by RFamide-related peptide (RFRP) because fewer immunoreactive cell bodies were detected in the brains of stressed bats compared with controls - suggesting a possible increase in secretion - and increased RFRP expression locally in the gonads. The rapid sensitivity of the bat testes to stress may be connected to deleterious impacts on tissue health and function as supported by significant transcriptional upregulation of key pro-apoptotic signaling molecules (Bax, cytochrome c). Experiments like this broadly contribute to our understanding of the stronger ecological predictions regarding physiological responses of bats within the context of stress, which may impact decisions surrounding animal handling and conservation approaches.

Chronic Inflammation Impairs Male Fertility-A Case-Control Study in Ulcerative Colitis Patients

Recent evidence indicates that a systemic state of inflammation may exert a negative effect on male fertility. The aim of this study is to evaluate sperm quality parameters in male patients with ulcerative colitis (UC). Between December 2019 and December 2020 semen analyses are performed in 50 patients with UC in clinical remission. The control group consists of 50 healthy volunteers. Total sperm count, sperm count, percentage of morphologically normal spermatozoa, viability, and progressive motility, are significantly lower in the study group than in healthy males (p < 0.001). The DNA fragmentation index (DFI) and oxidation-reduction potential (ORP) are significantly higher in the study group (28.9% and 1.55% on average, respectively) than in healthy males (14.6% and 0.79% on average, respectively). Bacteriospermia is more clearly observed in the study group (p = 0.037), and the most frequent pathogen is Enterococcus faecalis. The DFI and ORP are significantly higher in bacteria carriers, compared to males without microbial pathogens from both the study and control groups (p < 0.001). To conclude, UC patients have worse basic sperm parameters compared to their healthy counterparts. Deterioration of semen parameters, as well as an intensified DNA fragmentation could be a result of oxidative stress intensification.

The impact of autoimmune systemic inflammation and associated medications on male reproductive health in patients with chronic rheumatological, dermatological, and gastroenterological diseases: A systematic review

Autoimmune disorders currently affect 5%-8% of the global population, characterized by an aberrant chronic inflammatory response to self-antigens. The aim of this study was to systematically review the current available evidence investigating the impact of systemic autoimmune diseases and associated immunosuppressive treatment on fertility parameters of adult men. Clinical trials, observational studies, and case reports written in English and reporting semen analysis, evaluation of seminal oxidative stress, and/or sperm DNA fragmentation in patients affected by psoriasis and psoriatic arthritis, celiac disease, inflammatory bowel diseases, systemic lupus erythematosus, ankylosing spondylitis, hidradenitis suppurativa, uveitis, dermatomyositis, and rheumatoid arthritis were collected by searching on PubMed, EMBASE, OVID, Scopus, and Cochrane Library databases, with no limit of time. The study quality and the extent of bias in design, methods, and outcome assessment were evaluated by applying the Joanna Briggs Institute Critical Appraisal tools. Evidence suggested that various autoimmune diseases or relevant medications can adversely affect male fertility parameters and that patients may benefit of counseling and sperm cryopreservation. Clinical trials further investigating any adverse effect of autoimmunity and related thereby on male infertility are warranted, to develop appropriate guidelines for males diagnosed and treated for autoimmune disorders.

Men With Inflammatory Bowel Disease: Sexual Function, Fertility, Medication Safety, and Prostate Cancer

Half of patients with inflammatory bowel disease (IBD) are men, yet less attention has been focused on their sexual issues despite higher rates of sexual dysfunction and infertility than the general population. Depression and IBD disease activity are the most consistently reported risk factor for sexual dysfunction among men with IBD. Methotrexate and sulfasalazine have been rarely associated with impotence. Sulfasalazine reversibly reduces male fertility. No other medications used in IBD significantly affect fertility in humans. There is no increase in adverse fetal outcomes among offspring of fathers with IBD. Patients with IBD seem to be at a higher risk for prostate cancer; therefore, screening as recommended for high-risk patients should be considered.

Insights into the treatment of inflammatory bowel disease in pregnancy

Patients diagnosed with inflammatory bowel disease (IBD) are most commonly diagnosed in late adolescence or early adulthood, with half of patients being diagnosed before age 32, thus impacting peak years of reproduction and family planning. While controlled IBD has no negative effects on the ability to conceive, there is overall a trend towards voluntary childlessness due to patients' concerns for adverse fetal outcomes from underlying IBD and from adverse medication effects. Active disease at the time of conception is associated with worsening disease activity during pregnancy and carries a higher risk of poor fetal outcomes. It is therefore important to maintain remission during pregnancy, which is often achieved with pharmacologic therapy. The goal of this paper is to provide a comprehensive review of the current literature and safety data for pharmacologic treatment of IBD in pregnancy, in breastfeeding women, and in men planning to have children.

Sexual Dysfunction and Fertility Problems in Men with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that is usually diagnosed in young individuals. Crohn's disease and ulcerative colitis are the 2 principal forms of IBD. Patients with IBD demonstrate varying degrees of disease activity and sometimes need to undergo bowel surgery such as proctocolectomy with ileal pouch-anal anastomosis that involves removal of the entire colon and rectum with consequent sexual dysfunction. Several studies have shown that sulfasalazine, affects male fertility. Additionally, many men with IBD are unable to control their smoking, drinking, and eating habits, which can cause worsening of disease activity and fertility. Therefore, infertility and sexual dysfunction are important issues in young patients diagnosed with IBD because they are related to optimal management of the disease and patients' quality of life. Only a few studies have reported sexual dysfunction and infertility in men with IBD. Therefore, this study reviewed the current literature describing male sexual dysfunction scales and evaluated the causes of sexual dysfunction and infertility in men with IBD.

Tocotrienol-rich fraction supplementation prevents foetal loss in females mated with corticosterone-treated male Sprague-Dawley rats

This study examined whether tocotrienol supplementation to corticosterone-treated male rats could prevent foetal loss in females upon their mating. Epididymides of adult male Sprague-Dawley (SD) rats with proven fertility were surgically separated at the testis-caput junction. Twenty-four hours post-surgery, these animals received for 7 days either: tocopherol-stripped corn oil (Control), corticosterone 25 mg/kg s.c. (CORT), CORT 25 mg/kg s.c. and tocotrienol-rich fraction (TRF) 100 mg/kg orally (CORT + TRF) or TRF 100 mg/kg orally (TRF). On day 8, males were cohabited with proestrus females. A spermatozoa-positive vaginal smear indicated pregnancy. Males were euthanised for analysis of testosterone and antioxidant activities. Reproductive organs were weighed. On day 8 of pregnancy, females were laparotomised to count the number of implantation sites. Pregnancy was continued until term. Number of pups delivered and their weights were determined. Data were analysed using ANOVA. Malondialdehyde levels were significantly lower in CORT + TRF group compared with CORT group. Enzymatic antioxidant activities, testosterone level and reproductive organ weights were significantly higher in CORT + TRF group compared with CORT group. Number of implantation sites and live pups delivered, and their birth weights from females mated with CORT + TRF males were significantly higher compared to CORT group. Therefore, TRF prevents foetal loss in females mated with CORT + TRF-treated males.

Sexual and reproductive issues and inflammatory bowel disease: a neglected topic in men

There has been considerable literature on sexual issues in women with inflammatory bowel disease (IBD), but relatively little attention has been paid to these aspects in men. To review the available literature and to provide the best management of sexual and reproductive issues in male patients with IBD. The scientific literature on sexual and reproductive issues in men with IBD was reviewed. Several factors, including surgical and medication treatments, disease activity, lifestyle, and psychological factors, may play a role in the development of infertility and sexual dysfunction and may negatively impact pregnancy outcomes. Proctocolectomy with ileal pouch-anal anastomosis increases the risk of erectile and ejaculatory dysfunction by up to 26%. A treatment with sildenafil can be effective. Sperm banking should be advised to young men with IBD before surgery. Both sulfasalazine and methotrexate may be responsible for reversible sexual dysfunction and infertility. Furthermore, sulfasalazine should be switched to mesalazine at least 4 months before conception because of a higher risk of congenital malformations in pregnancies fathered by men treated with this drug. Psychotropic drugs, frequently used in IBD, may cause sexual dysfunction up to 80%. Last but not the least, voluntary childlessness occurs frequently, mainly because of concerns about medication safety in pregnancy and fear of transmitting disease. Accurate counseling, and where necessary, psychological support can decrease any misperceptions and fears. Close collaboration between the gastroenterologist and the patient is recommended for the best management of these relevant, neglected aspects in men with IBD.

Gonadotropin inhibitory hormone and RF9 stimulate hypothalamic-pituitary-adrenal axis in adult male rhesus monkeys

Stress activates gonadotropin inhibitory hormone (GnIH), hypothalamic-pituitary-adrenal axis (HPA-axis) and represses hypothalamic-pituitary-gonadal axis (HPG-axis) but RF9 administration relieves stress-induced repression of the HPG-axis. Importantly, it was not known whether GnIH signaling and RF9 synthetic peptide modulate the HPA axis. To assess this, mammalian orthologs of GnIH (RFRP-1 and RFRP-3) and RF9 were administered to intact adult male rhesus monkeys. RFRP-1 (125μg/animal), RFRP-3 (250μg/animal) and RF9 (0.1mg/kg BW) were intravenously (iv) injected into normal fed (n=4) monkeys. Additionally, a single bolus iv injection of RF9 (0.1mg/kg BW) was also administered to 48h fasted monkeys (n=4) to check the effects of RF9 signaling on an activated HPA-axis. Serial blood samples were collected, centrifuged and the obtained plasma was used for the analysis of cortisol by specific enzyme immunoassay. RFRP-1 treatment significantly increased cortisol levels while RFRP-3 increased the plasma cortisol, but the effect was non-significant. RF9 treatment significantly increased cortisol levels in normal fed animals. In contrast, RF9 injection did not significantly alter circulating cortisol in fasted monkeys. In conclusion, our results suggest stimulatory action of RFRPs and RF9 on the HPA axis in the adult male monkeys. However, the mechanism and site of action of RFRP-1 and RF9 along the HPA-axis is still unknown. Therefore, further studies are needed to decipher the mechanism and site of action of RFRPs and RF9 on the HPA axis in primates.

RFamide-related peptide-3 (RFRP-3) suppresses sexual maturation in a eusocial mammal

Neuroendocrine mechanisms underlying social inhibition of puberty are not well understood. Here, we use a model exhibiting the most profound case of pubertal suppression among mammals to explore a role for RFamide-related peptide-3 [RFRP-3; mammalian ortholog to gonadotropin-inhibitory hormone (GnIH)] in neuroendocrine control of reproductive development. Naked mole rats (NMRs) live in sizable colonies where breeding is monopolized by two to four dominant animals, and no other members exhibit signs of puberty throughout their lives unless they are removed from the colony. Because of its inhibitory action on the reproductive axis in other vertebrates, we investigated the role of RFRP-3 in social reproductive suppression in NMRs. We report that RFRP-3 immunofluorescence expression patterns and RFRP-3/GnRH cross-talk are largely conserved in the NMR brain, with the exception of the unique presence of RFRP-3 cell bodies in the arcuate nucleus (Arc). Immunofluorescence comparisons revealed that central expression of RFRP-3 is altered by reproductive status, with RFRP-3 immunoreactivity enhanced in the paraventricular nucleus, dorsomedial nucleus, and Arc of reproductively quiescent NMRs. We further observed that exogenous RFRP-3 suppresses gonadal steroidogenesis and mating behavior in NMRs given the opportunity to undergo puberty. Together, our findings establish a role for RFRP-3 in preserving reproductive immaturity, and challenge the view that stimulatory peptides are the ultimate gatekeepers of puberty.

Immunosuppressants and Male Reproduction

Prolonged use of immunosuppressant medications is occasionally seen in infertile men with chronic inflammatory conditions; autoimmune disorders; or an organ or hematopoietic stem cell transplant. Chronic inflammation impacts negatively on male reproductive endpoints, so immunosuppressant therapy can produce improvements. Corticosteroids have been used to treat antisperm antibodies and even as an empirical treatment for male infertility in general. Trials of these methods have provided mixed results on semen quality and fertility, with improvement, no change and negative effects reported by different investigators. In a substantial number of observational studies, patients on long-term therapy with prednisone for chronic inflammatory disease, testosterone levels were lower compared to untreated controls, though randomized controlled trials have not been conducted. Similarly decreases in testosterone have been reported in men receiving corticosteroids to minimize transplant rejection; however, most were treated with multiple immunosuppressive medications that may have contributed to this effect. A large number of trials of healthy men treated with corticosteroids have shown some disruption in reproductive hormone levels, but other studies reported no effect. Studies in monkeys, rats (at human equivalent dose), cattle, sheep, and horses have shown endocrine disruption, including low testosterone with dexamethasone treatment. Of the cytostatic immunosuppressives, which have high potential for cellular damage, cyclophosphamide has received the most attention, sometimes lowering sperm counts significantly. Methotrexate may decrease sperm numbers in humans and has significant negative impacts in rodents. Other chemotherapeutic drugs used as immunosuppressants are likely to impact negatively on male fertility endpoints, but few data have been collected. The TNF-α Inhibitors have also received little experimental attention. There is some evidence that the immunophilin modulators: cyclosporine, sirolimus, and everolimus cause endocrine disruption and semen quality impairment. As we review in this chapter, results in experimental species are concerning, and well-designed studies are lacking for the effects of these medications on reproductive endpoints in men.

Expression and actions of GnIH and its orthologs in vertebrates: Current status and advanced knowledge

The physiology of reproduction is very complex and is regulated by multiple factors, including a number of hypothalamic neuropeptides. In last few decades, various neuropeptides have been discovered to be involved in stimulation or inhibition of reproduction. In 2000, Tsutsui and colleagues uncovered gonadotropin-inhibitory hormone (GnIH), a neuropeptide generating inhibitory drive to the reproductive axis, in the brain of Coturnix quail. Afterward, GnIH orthologs were discovered in other vertebrates from fish to mammals including human. In these vertebrates, all the discovered GnIH and its ortholgs have LPXRFamide (X=L or Q) sequence at C-terminus. GnIH orthologs of mammals and primates are also termed as RFamide-related peptide (RFRP)-1 and -3 that too have an LPXRFamide (X=L or Q) motif at their C-terminus. GnIH and its orthologs form a member of the RFamide peptide family. GnIH signals via its canonical G protein coupled receptor 147 (GPR147). Both GnIH and GPR147 are expressed in hypothalamus and other brain regions. Besides actions through the hypothalamic GnRH and kisspeptinergic neurons, GnIH-GPR147 signaling exerts inhibitory effect on the reproductive axis via pituitary gonadotropes and directly at gonadal level. Various factors including availability and quality of food, photoperiod, temperature, social interaction, various stresses and some diseases modulate GnIH-GPR147 signaling. In this review, we have discussed expression and actions of GnIH and its orthologs in vertebrates. Special emphasis is given on the role of GnIH-GPR147 signaling pathway in the regulation of reproduction. We have also reviewed and discussed currently available literature on the participation of GnIH-GPR147 signaling pathway in the stress modulation of reproduction.

Effects of aging on hypothalamic-pituitary-adrenal (HPA) axis activity and reactivity in virgin male and female California mice (Peromyscus californicus)

Life history theory posits that organisms face a trade-off between current and future reproductive attempts. The physiological mechanisms mediating such trade-offs are still largely unknown, but glucocorticoid hormones are likely candidates as elevated, post-stress glucocorticoid levels have been shown to suppress both reproductive physiology and reproductive behavior. Aged individuals have a decreasing window in which to reproduce, and are thus predicted to invest more heavily in current as opposed to future reproduction. Therefore, if glucocorticoids are important in mediating the trade-off between current and future reproduction, aged animals are expected to show decreased hypothalamic-pituitary-adrenal (HPA) axis responses to stressors and to stimulation by corticotropin-releasing hormone (CRH), and enhanced responses to glucocorticoid negative feedback, as compared to younger animals. We tested this hypothesis in the monogamous, biparental California mouse by comparing baseline and post-stress corticosterone levels, as well as corticosterone responses to dexamethasone (DEX) and CRH injections, between old (∼18-20months) and young (∼4months) virgin adults of both sexes. We also measured gonadal and uterine masses as a proxy for investment in potential current reproductive effort. Adrenal glands were weighed to determine if older animal had decreased adrenal mass. Old male mice had lower plasma corticosterone levels 8h after DEX injection than did young male mice, suggesting that the anterior pituitary of older males is more sensitive to DEX-induced negative feedback. Old female mice had higher body-mass-corrected uterine mass than did young females. No other differences in corticosterone levels or organ masses were found between age groups within either sex. In conclusion, we did not find strong evidence for age-related change in HPA activity or reactivity in virgin adult male or female California mice; however, future studies investigating HPA activity and reproductive outcomes in young and old breeding adults would be illuminating.

The mouse as a model to investigate sex steroid metabolism in the normal and pathological prostate

Metabolism of sex steroids within the prostate is an important factor affecting its growth and pathology. Mouse models with genetic gain- and especially loss-of-function have characterised different steroid metabolic pathways and their contribution to prostate pathology. With reference to the human prostate, this review aims to summarize the steroidogenic pathways in the mouse prostate as the basis for using the mouse as a model for intraprostatic steroid signalling. In this review we summarize the current information for three main components of the steroid signalling pathway in the mouse prostate: circulating steroids, steroid receptors and steroidogenic enzymes with regard to signalling via androgen, estrogen, progesterone and glucocorticoid pathways. This review reveals many opportunities for characterisation steroid metabolism in various mouse models. The knowledge of steroid metabolism within prostate tissue and in a lobe (rodent)/region (human) specific manner, will give valuable information for future, novel hypotheses of intraprostatic control of steroid actions. This review summarizes knowledge of steroid metabolism in the mouse prostate and its relevance to the human.

Long-term corticosterone treatment induced lobe-specific pathology in mouse prostate

BACKGROUND

Glucocorticoids influence prostate development and pathology, yet the underlying mechanisms including possible direct glucocorticoid effect on the prostate are not well characterized.

METHODS

We evaluated the expression of the glucocorticoid receptor (GR) together with the effects of supraphysiological glucocorticoid (corticosterone) on mouse prostate morphology and epithelial proliferation. Mature male mice were treated by weekly subdermal implantation of depot pellets containing either 1.5 mg corticosterone or placebo providing steady-state release for 4 weeks.

RESULTS

Corticosterone treatment significantly increased dorsolateral and anterior prostate weights as well as prostate epithelial cell proliferation while epithelial apoptosis remained low upon corticosterone treatment. Histological analysis of the anterior lobe demonstrated abnormal, highly disorganized luminal epithelium with frequent formation of bridge-like structures lined by continuous layer of basal cells not observed following placebo treatment. Molecular analysis revealed corticosterone-induced increase in expression of stromal growth factor Fgf10 which, together with prominent stromal GR expression, suggest that glucocorticoid modify stromal-to-epithelial signaling in the mouse prostate. The mitogenic effects were prostate specific and not mediated by systemic effects on testosterone production suggesting that corticosterone effects were primarily mediated via prostate GR expression.

CONCLUSION

These data demonstrate that murine prostate is significantly and directly influenced by corticosterone treatment via aberrant stromal-to-epithelial growth factor signaling.

Cannabinoids and Reproduction: A Lasting and Intriguing History

Starting from an historical overview of lasting Cannabis use over the centuries, we will focus on a description of the cannabinergic system, with a comprehensive analysis of chemical and pharmacological properties of endogenous and synthetic cannabimimetic analogues. The metabolic pathways and the signal transduction mechanisms, activated by cannabinoid receptors stimulation, will also be discussed. In particular, we will point out the action of cannabinoids and endocannabinoids on the different neuronal networks involved in reproductive axis, and locally, on male and female reproductive tracts, by emphasizing the pivotal role played by this system in the control of fertility.

Stress increases putative gonadotropin inhibitory hormone and decreases luteinizing hormone in male rats

The subjective experience of stress leads to reproductive dysfunction in many species, including rodents and humans. Stress effects on reproduction result from multilevel interactions between the hormonal stress response system, i.e., the hypothalamic-pituitary-adrenal (HPA) axis, and the hormonal reproductive system, i.e., the hypothalamic-pituitary-gonadal (HPG) axis. A novel negative regulator of the HPG axis known as gonadotropin-inhibitory hormone (GnIH) was recently discovered in quail, and orthologous neuropeptides known as RFamide-related peptides (RFRPs) have also been identified in rodents and primates. It is currently unknown, however, whether GnIH/RFRPs influence HPG axis activity in response to stress. We show here that both acute and chronic immobilization stress lead to an up-regulation of RFRP expression in the dorsomedial hypothalamus (DMH) of adult male rats and that this increase in RFRP is associated with inhibition of downstream HPG activity. We also show that adrenalectomy blocks the stress-induced increase in RFRP expression. Immunohistochemistry revealed that 53% of RFRP cells express receptors for glucocorticoids (GCs), indicating that adrenal GCs can mediate the stress effect through direct action on RFRP cells. It is thought that stress effects on central control of reproduction are largely mediated by direct or indirect effects on GnRH-secreting neurons. Our data show that stress-induced increases in adrenal GCs cause an increase in RFRP that contributes to hypothalamic suppression of reproductive function. This novel insight into HPA-HPG interaction provides a paradigm shift for work on stress-related reproductive dysfunction and infertility, and indicates that future work on stress and reproductive system interactions must include investigation of the role of GnIH/RFRP.

Effects of administration of sodium glutamate during the neonatal period on behavior and blood corticosterone levels in male mice

Treatment of male DBA/2 mice with sodium glutamate (4 mg/g) on postnatal days 1, 3, 5, 7, and 9 induced reductions in the numbers of square crossings, vertical rearings, excursions to the center, and the time spent in the center in adulthood, as compared with a group of males given physiological saline at the same times. These measures showed no change as compared with intact animals. In the light-dark test, the time spent by mice in the light sector was greater after administration of sodium glutamate than after administration of physiological saline but did not differ from that in intact animals. In the acoustic startle reflex test, sodium glutamate decreased startle amplitude but had no effect on the magnitude of prestimulus inhibition. Sexual motivation in males decreased after sodium glutamate, physiological saline producing a tendency to decreased sexual motivation. Neonatal administration of sodium glutamate increased basal blood corticosterone in adult males by a factor of 4, while physiological saline had no effect on this measure. These results lead to the conclusion that neonatal administration of sodium glutamate decreases motor and investigative activity, anxiety, and sexual motivation in adult male mice and increases basal corticosterone. Physiological saline increased all these parameters apart from sexual motivation, though this was not associated with changes in basal corticosterone.

Review article: Reproduction in the patient with inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) affects mainly the young population. The effect of IBD and its treatment on fertility and pregnancy is therefore an important clinical consideration.

AIM

To review the best management of IBD in the reproductive and pregnant population.

METHODS

A MEDLINE and an EMBASE search were performed using mainly the search phrases 'pregnancy AND IBD,''sulphasalazine AND male fertility,''abdominal surgery AND female fertility,''AZA AND placenta' and 'infliximab AND pregnancy.' No language or date restrictions were placed. References of review articles were examined.

RESULTS

Overall male and female fertility are not affected by IBD. Sulphasalzine reduces male fertility. No other drugs used in IBD affect significantly fertility in humans. The risk of pregnancy-related complications and the disease behaviour during pregnancy depends mainly on disease activity at time of conception. Proactive treatment for maintenance of disease remission during gestation is recommended. Except for methotrexate, drugs used in IBD appear safe in pregnancy. Breast feeding should be encouraged.

CONCLUSION

The management of IBD in the young and pregnant population remains controversial because the literature comes mostly from retrospective studies. Further studies particularly large prospective trials are needed to guide clinicians in decision making.

Rapid modulation of TRH and TRH-like peptide levels in rat brain and peripheral tissues by corticosterone

Disturbance of glucocorticoid signaling has been implicated in several neuropsychiatric disorders including unipolar and bipolar depression and anxiety induced by maternal deprivation. Antidepressants have been shown to be neuroprotective and able to reverse damage to glia and neurons. Thyrotropin-releasing hormone (TRH) is an endogenous antidepressant that reduces the expression of glycogen synthase kinase-3beta (GSK-3beta), an enzyme that hyperphosphorylates tau and is implicated in bipolar depression, diabetes and Alzheimer's disease. In order to understand the potential role of TRH and TRH-like peptides both as mediators of the depressogenic effects of glucocorticoids and as potential therapeutics for neuropsychiatric disease, 300 g male Sprague-Dawley rats were injected i.p. with 4 mg corticosterone/0.5 ml 50% DMSO+50% ethanol and sacrificed 0, 2, 4 and 8h later. Levels of TRH and TRH-like peptides were measured in various brain regions involved in mood regulation and pancreas and reproductive tissues that mediate the metabolic and reproductive impairments associated with high glucocorticoid levels. Significant increases, ranging from 2- to 12-fold, in TRH or TRH-like peptide levels were observed in almost all brain regions studied at 4h after corticosterone injection. In cerebellum, TRH and TRH-like peptides increased 4-14-fold by 8h. TRH-like peptide levels fell 86-98% at 4h after treatment in testis. TRH, derived only from Leydig cells, was not affected. TRH and TRH-like peptides increased 2-4-fold at 8h in pancreas. TRH and TRH-like peptide concentrations in prostate were not affected by corticosterone up to 8h after injection. The 4h needed to detect a highly significant change in the TRH and TRH-like peptide levels in brain and peripheral tissues is consistent with the mediation of most corticosterone-effects via alterations in gene transcription.

The type I and type II 11beta-hydroxysteroid dehydrogenase enzymes

Local tissue concentrations of glucocorticoids are modulated by the enzyme 11beta-hydroxysteroid dehydrogenase which interconverts cortisol and the inactive glucocorticoid cortisone in man, and corticosterone and 11-dehydrocorticosterone in rodents. The type I isoform (11beta-HSD1) is a bidirectional enzyme but acts predominantly as a oxidoreductase to form the active glucocorticoids cortisol or corticosterone, while the type II enzyme (11beta-HSD2) acts unidirectionally producing inactive 11-keto metabolites. There are no known clinical conditions associated with 11beta-HSD1 deficiency, but gene deletion experiments in the mouse indicate that this enzyme is important both for the maintenance of normal serum glucocorticoid levels, and in the activation of key hepatic gluconeogenic enzymes. Other important sites of action include omental fat, the ovary, brain and vasculature. Congenital defects in the 11beta-HSD2 enzyme have been shown to account for the syndrome of apparent mineralocorticoid excess (AME), a low renin severe form of hypertension resulting from the overstimulation of the non-selective mineralocorticoid receptor by cortisol in the distal tubule of the kidney. Inactivation of the 11beta-HSD2 gene in mice results in a phenotype with similar features to AME. In addition, these mice show high neonatal mortality associated with marked colonic distention, and remarkable hypertrophy and hyperplasia of the distal tubule epithelia. 11Beta-HSD2 also plays an important role in decreasing the exposure of the fetus to the high levels of maternal glucocorticoids. Recent work suggests a role for 11beta-HSD2 in non-mineralocorticoid target tissues where it would modulate glucocorticoid access to the glucocorticoid receptor, in invasive breast cancer and as a mechanism providing ligand for the putative 11-dehydrocorticosterone receptor. While previous homologies between members of the SCAD superfamily have been of the order of 20-30% phylogenetic analysis of a new branch of retinol dehydrogenases indicates identities of > 60% and overlapping substrate specificities. The availability of crystal structures of family members has allowed the mapping of conserved 11beta-HSD domains A-D to a cleft in the protein structure (cofactor binding domain), two parallel beta-sheets, and an alpha-helix (active site), respectively.