Ageing and inflammation in the male reproductive tract.

Ageing is usually characterised by a mild chronic proinflammatory state. Despite the tight association between both processes, the phenomenon has recently been termed inflammageing. Inflammation in the male reproductive tract is frequently linked with bacterial or virus infections but also with a broad range of noninfectious processes. Prostatitis, epididymitis and orchitis, among others, can lead to infertility. However, in spite of the inflammation theory of disease, chronic inflammation in male urogenital system does not always cause symptoms. With advancing age, inflammatory processes are commonly observed in the male reproductive tract. Nevertheless, the incidence of inflammation in reproductive organs and ducts varies greatly among elderly men. Inflammageing is considered a predictor of pathogenesis and the development of age-related diseases. This article briefly summarises the current state of knowledge on inflammageing in the male reproductive tract. Yet, the precise aetiology of inflammageing in the male urogenital system, and its potential contribution not only to infertility but most importantly to adverse health outcomes remains almost unknown. Thus, further investigations are required to elucidate the precise cross-links between inflammation and male reproductive senescence, and to establish the impact of anti-inflammatory drug treatments on elder men's general health status.

Influence of the lethal yellow (Ay) gene on estrous synchrony in mice.

Introduction of an adult male induces partially synchronous estrus in female laboratory mice that have been caged in groups. In the inbred YS/ChWf strain, this effect was observed only when the male was nonyellow (aa), while males heterozygous for the lethal yellow allele (A(y)a) failed to induce synchrony.

Perinatal exposure to cannabinoids alters male reproductive function in mice.

Oral administration of delta 9-tetrahydrocannabinol or cannabinol to female mice late in pregnancy and during early lactation alters body weight regulation and pituitary-gonadal function and suppresses adult copulatory activity in their male offspring. These findings suggest that both psychoactive and nonpsychoactive constituents of marihuana can affect the development of male reproductive functions in mice.

Cannabinoids inhibit testosterone secretion by mouse testes in vitro.

Addition of delta-9-tetrahydrocannabinol or cannabinol to an incubation medium containing decapsulated mouse testes caused a significant reduction in the accumulation of testosterone in the medium. This result suggests that the reported effects of cannabis on male sexual and reproductive function may result from direct inhibition of testicular steroidogenesis by both psychoactive and nonpsychoactive constituents of marihuana.

Delta9-tetrahydrocannabinol increase plasma testosterone concentrations in mice.

Oral administration of delta 9-tetrahydrocannabinol had a biphasic effect on plasma testosterone concentrations in male mice, causing rapid sustained increases at low doses and subsequent decreases at higher doses. In hypophysectomized and intact mice receiving gonadotropins (human chorionic gonadotropin), treatment with delta 9-tetrahydrocannabinol maintained higher plasma testosterone concentrations. Thus, this cannabinoid may interact with gonadotropin and directly influence testicular steroidogenesis in vivo.

Strange females increase plasma testosterone levels in male mice.

Male house mice paired with a normal female for 1 week do not have higher plasma testosterone levels than do males that remain in all-male groups, but paired males have markedly elevated testosterone levels 30 to 60 minutes after the resident female is replaced by another female. Elevation of testosterone levels in these males is similar to that in isolated males paired with a female, does not depend on copulation with the strange female, occurs under housing conditions that permit continuous exposure to the odors of other females and males, and does not occur when the resident female is replaced by another male for 30 to 60 minutes. The elevation thus appears to be a specific endocrine response to an encounter with a strange female. These results, along with previous findings suggesting that strange males affect endocrine function in females, indicate that bisexual encounters are likely to produce endocrine changes in members of both sexes.

Aging in the Syrian hamster testis: Inflammatory-oxidative status and the impact of photoperiod.

Testicular aging is linked to histological, morphological and functional alterations. In the present study, we investigated whether aging affects the inflammatory and oxidative status in the testis by comparing young adult, middle-aged adult and aged hamsters. The Syrian hamster, a thoroughly studied seasonal breeder, was chosen as the experimental model since it allows further investigations on the role of photoperiod and melatonin in testicular aging with a minimal impact of the experimental intervention on the animal well-being and the subsequent results achieved. In testes of aged hamsters, we found a decrease in melatonin concentration, a thickening of the wall of the seminiferous tubules as well as a significant increase in IL-1ß, NLRP3 and cyclooxygenase 2 expression, PGD2 production, macrophages numbers, lipid peroxidation and anti-oxidant enzyme catalase levels. Interestingly, when aged hamsters were transferred from a long day (LD) to a short day (SD) photoperiod for 16 weeks, testicular melatonin concentration increased while local inflammatory processes and oxidative stress were clearly reduced. Overall, these results indicate that melatonin might display anti-inflammatory and anti-oxidant capacities in the aged testes.

Vitamin D3 cannot revert desensitization of growth hormone (GH)-induced STAT5-signaling in GH-overexpressing mice non-calcemic tissues.

Growth hormone (GH) binding to a membrane receptor dimer triggers multiple intracellular signaling pathways. Signal transducers and activators of transcription are the most relevant of these pathways for GH action. GH also activates several inhibitory mechanisms, particularly suppressors of cytokine signaling (SOCS/CIS) proteins. GH-overexpressing mice exhibit hepatic desensitization of the JAK2/STAT5 GH-signaling pathway, associated with an increased abundance of CIS. Vitamin D3 has been shown to inhibit GH-induced expression of CIS and SOCS-3 and therefore prolong GH signaling in osteoblast-like cells. The purpose of the present study is to determine if vitamin D3 could attenuate CIS expression in GH-overexpressing mice, and consequently allow GH JAK2/STAT5 signaling in GH-responsive tissues in these animals. The abundance of CIS, SOCS-2, SOCS-3, STAT5b and GHR, as well as STAT5b tyrosine phosphorylation after a GH stimulus, were measured in liver and muscle of GHRH-transgenic mice treated with 1alpha,25-dihydroxyvitamin D3 for 7 days. This treatment did not diminish CIS expression in GH-overexpressing mice tissues, nor did the content of SOCS-2 and SOCS-3 significantly vary. GH-induced STAT5b phosphorylation levels were similar to basal values in transgenic mice liver treated with or without vitamin D; the refractoriness to GH was also present in muscle. Therefore, treatment with vitamin D was not sufficient to revert STAT5 GH signaling desensitization in non-calcemic tissues in GH-overexpressing mice.

Differential regulation of membrane associated-growth hormone binding protein (MA-GHBP) and growth hormone receptor (GHR) expression by growth hormone (GH) in mouse liver.

Growth hormone (GH) binding to GH receptor (GHR) is the initial step that leads to the physiological functions of the hormone. Proteolytical cleavage of the GHR in humans and rabbits and alternative processing of the GHR transcript in rodents generates circulating growth hormone binding protein (GHBP). Moreover, other GHR truncated forms that result from alternative processing of the GHR mRNA transcript have been described. These GHR short forms are inserted in the plasma membrane but they are unable to transduce the signal. In rodents, membrane associated-GHBP (MA-GHBP), which accounts for a significant proportion of liver GH binding capacity, represents the main GHR short form found in membranes, and may therefore function as a negative form of the receptor. In the present study, GHR and MA-GHBP content in liver were analyzed using mutant and transgenic mice expressing different concentrations of growth hormone to evaluate the correlation between GH levels, body weight (BW), GHR and MA-GHBP expression. It was found that GH deficiency was associated with diminished BW, GHR and MA-GHBP expression, while increased GH concentration led to increased BW, GHR and MA-GHBP expression, but MA-GHBP upregulation was more pronounced than the observed increase in GHR expression. Since GHR and MA-GHBP both contribute to liver GH binding capacity, GH-induced enrichment of the dominant negative form would represent a compensatory mechanism triggered by high levels of the hormone. This attempt to attenuate the effects of supraphysiological concentrations of GH may be critical to reduce or prevent their plausible damaging effects on the organism.

Functional compensation by Egr4 in Egr1-dependent luteinizing hormone regulation and Leydig cell steroidogenesis.

The Egr family of zinc finger transcription factors, whose members are encoded by Egr1 (NGFI-A), Egr2 (Krox20), Egr3, and Egr4 (NGFI-C) regulate critical genetic programs involved in cellular growth, differentiation, and function. Egr1 regulates luteinizing hormone beta subunit (LHbeta) gene expression in the pituitary gland. Due to decreased levels of LHbeta, female Egr1-deficient mice are anovulatory, have low levels of progesterone, and are infertile. By contrast, male mutant mice show no identifiable defects in spermatogenesis, testosterone synthesis, or fertility. Here, we have shown that serum LH levels in male Egr1-deficient mice are adequate for maintenance of Leydig cell steroidogenesis and fertility because of partial functional redundancy with the closely related transcription factor Egr4. Egr4-Egr1 double mutant male mice had low steady-state levels of serum LH, physiologically low serum levels of testosterone, and atrophy of androgen-dependent organs that were not present in either Egr1- or Egr4-deficient males. In double mutant male mice, atrophic androgen-dependent organs and Leydig cell steroidogenesis were fully restored by administration of exogenous testosterone or human chorionic gonadotropin (an LH receptor agonist), respectively. Moreover, a normal distribution of gonadotropin-releasing hormone-containing neurons and normal innervation of the median eminence in the hypothalamus, as well as decreased levels of LH gene expression in Egr4-Egr1-relative to Egr1-deficient male mice, indicates a defect of LH regulation in pituitary gonadotropes. These results elucidate a novel level of redundancy between Egr4 and Egr1 in regulating LH production in male mice.

Ovarian aging and the activation of the primordial follicle reserve in the long-lived Ames dwarf and the short-lived bGH transgenic mice.

The aim of this study was to evaluate the effect of growth hormone (GH) in the maintenance of the ovarian primordial follicle reserve. Ovaries from 16 mo old GH-deficient Ames Dwarf (df/df) and Normal (N/df) mice were used. A subgroup of df/df and N mice received GH or saline injections for six weeks starting at 14 mo of age. In addition, ovaries from 12 mo old mice overexpressing bovine GH (bGH) and controls were used. df/df mice had higher number of primordial and total follicles than N/df mice (p < 0.05), while GH treatment decreased follicle counts in both genotypes (p < 0.05). In addition, bGH mice had lower number of primordial and total follicles than the controls (p < 0.05). pFoxO3a levels were higher in mice treated with GH and in bGH mice (p < 0.05) when comparing with age match controls. These results indicate that increased circulating GH is associated with a reduced ovarian primordial follicle reserve and increased pFoxO3a content in oocytes.

Growth hormone actions during development influence adult phenotype and longevity.

There is considerable evidence that exposure to undernutrition, overnutrition, stress or endocrine disruptors during fetal development can increase the probability of obesity, hypertension, cardiovascular disease and other problems in adult life. In contrast to these findings, reducing early postnatal growth by altering maternal diet or number of pups in a litter can increase longevity. In hypopituitary Ames dwarf mice, which are remarkably long lived, a brief period of growth hormone therapy starting at 1 or 2weeks of age reduces longevity and normalizes ("rescues") multiple aging-related traits. Collectively, these findings indicate that nutritional and hormonal signals during development can have profound impact on the trajectory of aging. We suspect that altered "programming" of aging during development may represent one of the mechanisms of the Developmental Origins of Health and Disease (DOHaD) and the detrimental effects of "catch-up" growth.

Increased SH2-Bbeta content and membrane association in transgenic mice overexpressing GH.

Transgenic mice overexpressing GH present a marked GH signaling desensitization, reflected by low basal phosphorylation levels of the tyrosine kinase JAK2, and signal transducer and activator of transcription-5 (STAT5) and a lack of response of these proteins to a high GH dose. To evaluate the mechanisms involved in the regulation of JAK2 activity by high GH levels in vivo, the content and subcellular distribution of SH2-Bbeta were studied in GH-overexpressing transgenic mice. SH2-B is a member of a conserved family of adapter proteins characterized by the presence of a C-terminal SH2 domain, a central pleckstrin homology (PH) domain, and an N-terminal proline rich region. The isoform SH2-Bbeta modulates JAK2 activity by binding to the phosphorylated enzyme, further increasing its activity. However, it may also interact with non-phosphorylated inactive JAK2 via lower affinity binding sites, preventing abnormal activation of the kinase. SH2-Bbeta may also function as an adapter protein, acting as a GH signaling mediator. We now report that, in an animal model of GH excess in which JAK2 is not phosphorylated, although it is increased in the membrane-fraction, both the level of SH2-Bbeta, and especially its association to membranes, are augmented (67% and 13-fold vs normal mice values respectively), suggesting SH2-Bbeta could modulate JAK2 activity in vivo.

Increased sensitivity to GH in liver of Ames dwarf (Prop1df/Prop1df) mice related to diminished CIS abundance.

To investigate the influence of chronic GH deficiency on GH signaling in vivo, we have analyzed Janus kinase (JAK) 2/signal transducers and activators of transcription (STAT) 5 GH signaling pathway, and its regulation by the suppressors of the cytokine signaling SOCS and by the JAK2-interacting protein SH2-Bbeta, in liver of Ames dwarf (Prop1df/Prop1df) mice, which are severely deficient in GH, prolactin and TSH, and of their normal littermates. Prop1df/Prop1df mice displayed unaltered GH receptor, JAK2 and STAT5a/b protein levels. No significant differences in the basal tyrosine-phosphorylation levels of JAK2 and STAT5a/b were found between both groups of animals. After in vivo administration of a high GH dose (5 microg/g body weight (BW)), the tyrosine-phosphorylation levels of JAK2 and STAT5a/b increased significantly, reaching similar values in normal and dwarf mice. However, after stimulation with lower GH doses (50 and 15 ng/g BW) the tyrosine-phosphorylation level of STAT5a/b was higher in dwarf mice. The protein content of CIS, a SOCS protein that inhibits STAT5 signaling, was approximately 80% lower in dwarf mice liver, while SOCS-2 and SOCS-3 levels were unaltered. The content of SH2-Bbeta, a modulator of JAK2 activity, was reduced by approximately 30% in dwarf mice, although this was associated with normal JAK2 response to a high GH dose. In summary, Prop1df/Prop1df mice display increased hepatic sensitivity to GH, an effect that could be related to the lower abundance of CIS in this tissue. Furthermore, the lower CIS content found in this model of GH deficiency suggests that CIS protein levels are regulated by GH in vivo.

The impact of altered insulin-like growth factor-I secretion on the neuroendocrine and testicular functions.

There is unequivocal evidence that the biosynthesis and secretion of gonadotropins by the pituitary gland is controlled by the hypothalamic GnRH and the function of the testis is mainly regulated by FSH and LH. However, a number of investigations have suggested the role of other hormones/factors, including insulin-like growth factor-I (IGF-I) in the control of pituitary and gonadal functions. The role of growth hormone (GH) and IGF-I is poorly investigated in humans. In animals with altered IGF-I secretion, the gonadotropin and androgen secretions are affected. Similarly, there is evidence that fertility, the onset of puberty and sexual maturation are affected in some patients with Laron syndrome and in acromegaly. In this minireview, we have presented some data obtained in humans and also included results from several experimental models with altered GH/IGF-I secretion, in the hope that the results from animals will possibly help in understanding the important role of IGF-I in the control of neuroendocrine-testicular function in humans.

Differential effects of short photoperiod on the release of progesterone and testosterone by hamster testes in vitro.

Suppression of testicular activity in hamsters and voles exposed to constant darkness or short photoperiod is associated with reduced ability of the testes to convert C21 steroid precursors to C19 androgens. In the present study, we have examined the time course of changes in testicular secretion of progesterone and testosterone in vitro in adult male golden hamsters exposed to short photoperiod. Gradual decrease in testicular weight after 1, 2, and 3 months of exposure to short photoperiod was accompanied by significant increase in the amount of progesterone released per milligram of testicular tissue in response to gonadotropin stimulation. In contrast, testosterone response to gonadotropic stimulus progressively decreased. These results suggest that photoperiod-related gonadal atrophy may be accompanied by reduced activity of the 17 alpha-hydroxylase: C17,20-lyase enzyme complex in the testes, and that seasonal transitions between the states of reproductive activity and quiescence involve changes in both the amount of steroids produced by the testes and the relative proportions of testosterone and its precursors.

Neuroendocrine regulation of seasonal reproductive activity in the male golden hamster.

Golden (Syrian) hamsters are seasonal breeders. Under natural photoperiodic conditions, their reproductive systems are functional during spring and summer and atrophic during the fall and winter. This reproductive cycle can be duplicated in the laboratory by exposing the animals to artificially-created photoperiods. The endocrine correlates of photoperiod-induced changes in reproductive activity of the male hamster are fairly well characterized, but the neural control of seasonal reproductive activity has not been as extensively studied. Recent studies indicate that short day (less than 12.5 hr light/day) exposure leads to complex changes in central neurotransmitter metabolism, as well as neurotransmitter and hormonal receptor content, which, in turn, are reversed by exposure to long days or during the period of spontaneous testicular recrudescence. Many of these endocrine and neuroendocrine changes are dependent on the presence of the pineal gland, but photoperiod-induced changes in neurotransmitter metabolism have also been described in pinealectomized hamsters. Further studies of the neuroendocrine transduction of photoperiodic signals will not only provide a better understanding of seasonal reproductive and metabolic activities, but will increase our basic understanding of the neural control of the endocrine system.

Effects of age and endogenously secreted human growth hormone on the regulation of gonadotropin secretion in female and male transgenic mice expressing the human growth hormone gene.

In aging rats and humans, GH secretion is reduced. In transgenic mice bearing the human (h) GH gene, hGH is secreted during the entire lifespan. To evaluate the effects of endogenously secreted hGH on age-related changes in hypothalamic-pituitary function, the following two experiments were conducted in young (2.5-4 months of age) and old (11-14 months of age) female and male transgenic mice expressing the hGH gene and their normal siblings. In Exp I, young and old female transgenic mice and their normal siblings were ovariectomized. On days 8 and 9 after ovariectomy, mice were injected (sc) with oil or primed with 0.5 micrograms estradiol benzoate (EB) in oil, 24 h later treated with 10 micrograms EB/100 g BW, and a day later bled for the determination of FSH, LH, PRL, and hGH levels by RIAs. In Exp II, young and old male transgenic mice and their normal littermates were castrated and injected with either peanut oil or testosterone propionate (TP; 1 microgram/g BW) in oil. Blood samples were obtained 18-20 h after oil or TP injection. Plasma FSH, LH, PRL, and hGH levels were measured by RIAs. hGH was present in the circulation of young and old transgenic mice, but not in normal siblings. Circulating FSH and LH levels were significantly lower in ovariectomized young and old transgenic mice than in similarly treated young and old normal siblings. The suppressive effect of EB on LH secretion was reduced in ovary-ablated young and old transgenic mice. The PRL response to EB treatment was increased (P < 0.005) in old ovariectomized transgenic mice. In the male, the castration-induced increase in plasma LH levels was higher (P < 0.05) in young transgenic mice. Administration of TP failed to suppress the absolute plasma LH levels in castrated young and old transgenic mice. However, the percent decrease in circulating LH levels was lower in young and old transgenic mice. The castration-induced increase in FSH secretion was reduced (P < 0.005) in aged transgenic mice. The effects of TP on plasma FSH levels were similar to its effects on LH secretion. Gonad-ablated young and old transgenic mice of both sexes are hypoprolactinemic. These observations demonstrate that endogenously secreted hGH modulates gonadotropin and PRL secretion in young and old mice bearing the hGH gene and indicate that the changes in the hypothalamic-pituitary system of mice expressing the hGH gene are similar to those observed in aging human subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of growth hormone in the control of gonadotropin secretion in adult male rats.

Although it is known that GH plays an important role in normal growth and development, its influence on the control of gonadotropin secretion is poorly understood. To address this issue, we have treated adult male rats with bovine GH via osmotic pumps (250 microg/day for 2 weeks; Exp design I) or immunized rats against ovine GH (100 microg/month for 6-7 months; Exp design II) and evaluated their neuroendocrine function. Vehicle-treated animals served as controls. Two experiments were conducted to evaluate the gonadotropin responses to: 1) GnRH (in saline) in gonad-intact rats and 2) testosterone propionate (TP; in oil) in castrated rats. Saline- or oil-injected rats served as controls. Circulating GH antibodies, LH, FSH, PRL, testosterone, and insulin-like growth factor I levels were measured by RIAs. Plasma LH levels were decreased (P < 0.025) in rats treated with GH. The plasma LH and FSH responses to GnRH treatment were similar in rats treated with either saline or GH. The suppressive effect of TP on LH secretion was attenuated (P < 0.025) in GH-treated rats on day 8 after castration. The FSH response to TP administration was similar in both subgroups of rats. Administration of GH decreased (P < 0.01) PRL secretion. Plasma testosterone levels were not altered by GH treatment. As expected, GH antibodies were detected and plasma insulin-like growth factor I levels were decreased (P < 0.001) in rats immunized against GH. The basal LH and FSH levels were higher (LH, P < 0.005; FSH, P < 0.025) in rats previously immunized against GH. The percent increase in plasma LH levels after GnRH treatment was decreased in GH-immunized animals. Furthermore, the percent increase in circulating FSH levels was higher in GH-immunized rats than in adjuvant-injected control rats. Administration of TP to adjuvant-injected castrated rats decreased plasma gonadotropin levels. However, similar treatment to rats immunized against GH failed to suppress plasma LH and FSH levels. The basal testosterone levels were not changed by immunization against GH. These results demonstrate that induction of GH excess decreases PRL and LH secretion, whereas biological neutralization of endogenous GH increased circulating gonadotropin concentrations. Thus, GH modulates the hypothalamic-pituitary function in adult male rats.

Prolactin modulates the gonadotropin response to the negative feedback effect of testosterone in immature male rats.

The effects of hyperprolactinemia (hyperPRL) and hypoprolactinemia (hypoPRL) on pituitary gonadotropin secretion and the feedback sensitivity to testosterone (T) were evaluated in immature male rats. At 34 days of age, rats were divided into three groups: group 1, controls, injected with oil; group 2, treated with bromocriptine mesylate (CB-154; 250 micrograms in oil/rat X day); and group 3, subjected to the transplantation of one pituitary from an adult female rat under the kidney capsule and treated with oil. The treatments were continued for 14 days. On day 8, each of these groups were further divided into three subgroups: intact, castrated, and castrated plus T treated. T treatment consisted of injection of T propionate (TP; 50 micrograms in oil/rat) on alternate days starting immediately after castration. Blood samples were obtained by cardiac puncture throughout the study. Plasma PRL levels were significantly reduced by CB-154 treatment and significantly increased by the pituitary graft (P less than 0.001). In intact immature male rats, hyper- or hypoPRL did not affect plasma LH levels, whereas hyperPRL reduced (P less than 0.01) plasma FSH concentrations. The postcastration increase in circulating LH levels was significantly increased (P less than 0.001) in rats treated with CB-154 24 h after castration. Moreover, the suppressive effects of TP on plasma LH and FSH levels were significantly (P less than 0.05) attenuated in hypoPRL rats. In pituitary-grafted rats, effects of castration and TP replacement on plasma LH levels did not differ from those in control rats. These results demonstrate that subnormal levels of PRL reduce the sensitivity of the hypothalamic-pituitary system to feedback inhibition by T. In contrast to previous findings in the adult rats, acute hyperPRL in immature male rats did not affect the negative feedback action of T on gonadotropin secretion.