Effects of GnRH immunization on the reproductive axis and thymulin

Effect of GnRH immunocastration on immune function in male rats

The present study aimed to reveal the effects of immunocastration on the development of the immune system in rats. Seventy rats were randomly assigned into two groups: Control (n = 35) and immunized (n = 35). Twenty-day-old rats were immunized with gonadotropin-releasing hormone (GnRH) and booster immunization was administered every two weeks (three immunizations in total). From 20-day-old rats, we collected samples every two weeks, including five immunized rats and five control rats (seven collections in total). We collected blood samples, testicles, thymuses, and spleens. The results showed that GnRH immunization increased the GnRH antibody titers and reduced the testosterone concentration (both P < 0.05). Compared with the control group, the number of CD4+CD8- cells, CD4-CD8+ cells, and CD4+CD8+ cells increased (P < 0.05) whereas the number of CD4-CD8- cells and CD4+CD25+ cells reduced in the immunized group (P < 0.05) over time. GnRH immunization also increased the relative weights of thymus and spleen (P < 0.05), serum concentrations of interleukin (IL)-2, IL-4, IL-6, IL-10, IL-17 and Interferon-γ (IFN-γ) over time (P < 0.05), and changed the mRNA levels of IL-2, IL-4, IL-6. IL-10, IL-17, IFN-γ, CD4, D8, CD19 GnRH, and GnRH receptor (GnRH-R) in thymus and spleen. Thus, GnRH immunization enhanced the immune markers in thymus, spleen, and blood immune cytokines in rats.

Comprehensive analysis of lncRNAs, miRNAs and mRNAs related to thymic development and involution in goose

Thymic involution is a sign of immunosenescence, but little is known about it in goose. miRNAs and lncRNAs are critical factors regulating organ growth and development. In this study, we comprehensively analyzed the profiles of lncRNAs, miRNAs and mRNAs during the development and involution of the thymus in Magang goose. The results showed that 2436 genes, 16 miRNAs and 417 lncRNAs were differentially co-expressed between the developmental (20-embryo age, 3-day post-hatch and 3-month age) and degenerative (6-month age) stages. The functional analysis showed that these differentially expressed genes were significantly enriched in cell proliferation, cell adhesion, apoptotic signaling pathway, and Notch signaling pathway. In addition, we established a gene-gene network through the STRING database and identified 50 key genes. Finally, we constructed a miRNA-mRNA network followed by a lncRNA-miRNA-mRNA network. These results suggest that lncRNAs and miRNAs may be involved in the regulation of thymic development and involution in goose.

Expression of the kisspeptin/gonadotropin-releasing hormone (GnRH) system in the brain of female Chinese sucker (Myxocyprinus asiaticus) at the onset of puberty

The kisspeptin-kisspeptin receptor (kissr)-gonadotropin-releasing hormone (GnRH) system plays a key role in regulating the onset of puberty in mammals. However, the role of this system in fish is still unclear. We examined the relative gene expression patterns for kiss1, kiss2, kissr2, sGnRH, and pjGnRH in all parts of the brains of Chinese sucker (Myxocyprinus asiaticus) females at the prepubertal and pubertal stages by using real-time PCR. We also analyzed the expression of kiss1 and GnRH1 via immunofluorescence. Two variants of kisspeptin; a variant of kissr (kissr2); and two variants of GnRH, pjGnRH (GnRH1), and sGnRH (GnRH3), were expressed in all parts of the brain. The mRNA expression of kiss1 was higher in the telencephalon, mesencephalon, and diencephalon at the pubertal stage than at the prepubertal stage, and the expression of kiss2 was higher in only the telencephalon. The expression of kissr2 was higher in all parts of the brain, except the medulla, at the pubertal stage than at the prepubertal stage. pjGnRH was highly expressed in all parts of the brain at the pubertal stage, whereas sGnRH expression showed no distinct changes, except in the epencephalon. Strong kiss1 and weak GnRH-1 immunoreactivity was observed in the pineal gland, lateral tuberal nucleus (NLT), and ventral part of the NLT in the diencephalon of the Chinese sucker females at the pubertal stage. Our results suggest that the kiss1-kissr2-pjGnRH system was expressed highly at the onset of pubertal female Chinese sucker.

Neuroendocrine immune-regulatory of a neuropeptide ChGnRH from the Hongkong oyster, Crassostrea Hongkongensis

It is increasingly appreciated that neuroendocrine-immune interactions hold the key to understand the complex immune system. In this study, we explored the role of a reproductive regulation-related hormone, GnRH, in the regulation of immunity in Hong Kong oysters. We found that vibrio bacterial strains injection increased the expression of ChGnRH. Moreover, ChGnRH neuropeptide promotes the phagocytic ability and bacterial clearance effect of hemocytes which regarded to be the central immune organ. The content of cAMP after incubation with ChGnRH peptide was increased, which could be blocked by adenylyl cyclase inhibitor SQ 22,536. Furthermore, the stimulated effect of ChGnRH peptide on the phagocytosis and bacterial clearance was also blocked by SQ 22,536, H89 and enzastaurin, strongly demonstrating that cAMP dependent PKA and PKC signaling pathway was involved in ChGnRH mediated immune regulation. In conclusion, this study confirms the presence of neuroendocrine-immune regulatory system in marine invertebrates, which contributes to understand the complexity of oyster immune defense system.

Effect of active immunization using a novel GnRH vaccine on reproductive function in rats

To investigate the effect of gonadotropin-releasing hormone 2-multiple antigen peptide (GnRH2-MAP) on reproductive function. In our study, 20-day-old male rats (n = 90) were randomly allocated to one of three treatment groups: GnRH2-MAP immunization, GnRH2 immunization, and non-immunized control groups. The immunized animals were administered three doses of GnRH2-MAP or GnRH2 vaccines from 0 to 6 weeks at 2-week intervals. The control group only received oil adjuvant. Blood and right testis samples were collected, and the left testis was weighed and its volume was measured at 0, 2, 4, 6, 8, 10 and 12 weeks after the first immunization. The serum antibody titer and testosterone concentration were determined by ELISA, and the right testis samples were collected for histological analysis. The results revealed that the serum of vaccinated rats elicited a significantly higher antibody titer and a lower T concentration compared with the control group two weeks after the first immunization (P < 0.05), but the highest antibody titer and lowest T concentration were found in animals treated with GnRH2-MAP (P < 0.05). The second immunization resulted in a significant decrease in testicular weight and volume (P < 0.05) in both immunized groups compared to the control, but these values were significantly lower in the GnRH2-MAP group than in the GnRH2 group. Furthermore, seminiferous tubules revealed more significant atrophy in the GnRH2-MAP group than in the GnRH2 group, and no sperm were observed in rats of the GnRH2-MAP group. Thus, GnRH2-MAP may be an effective antigen and a potential immunocastration vaccine with higher effectiveness.

Effects of active immunization against GnRH versus surgical castration on hypothalamic-pituitary function in boars

The objective was to compare effects of anti-GnRH immunization (immunocastration) versus surgical castration on hypothalamic-pituitary function in boars. Thirty-six boars were randomly divided into three groups (n = 12/group): control, surgically castrated, or immunized against GnRH at 10 wk of age (boostered 8 wk later). Compared to intact boars, immunocastration reduced (P < 0.05) serum concentrations of LH, FSH, testosterone and inhibin B and caused severe testicular atrophy, whereas surgical castration increased (P < 0.05) serum concentrations of LH and FSH. Both immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis, with decreased (P < 0.05) mRNA expressions of GnRH, GnRH up-stream gatekeeper genes kiss1 and its receptor (GPR54), and androgen receptor in the hypothalamic arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV), as well as GnRH content in the median eminence. Inconsistently, mRNA expressions of gonadotropin-inhibitory hormone (GnIH) in ARC and AVPV as well as its receptor (GPR147) in pituitary were selectively reduced (P < 0.05), but mRNA expressions of estrogen receptor alpha and aromatase (CPY17A1) in pituitary were selectively increased (P < 0.05) in surgical castrates. In response to selectively attenuated suppressive signaling from GnIH and testosterone, mRNA expressions of GnRH receptor (GnRHR), LH-β and FSH-β in pituitary were increased (P < 0.05) in surgical castrates, whereas these pituitary gene expressions were decreased (P < 0.05) in immunocastrates, due to loss of hypothalamic GnRH signaling. We concluded that immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis due to a testosterone deficiency disrupting testosterone-Kisspeptin-GPR54-GnRH signaling pathways. Furthermore, selectively attenuated GnIH and testosterone signaling in the pituitary increased gonadotropin production in surgical castrates.

Effect of gonadotropin-releasing hormone vaccination on T lymphocyte changes in male rats

The aim of this study was to detect the effect of immunization against gonadotropin-releasing hormone (GnRH) on cell-meditated immunity. Three-week-old male Sprague-Dawley rats (n=32) were randomly and equally assigned to two groups: 1) GnRH-tandem-ovalbumin immunized group; and 2) the control group (injected with an equivalent Al(OH)₃ adjuvant). Blood samples were collected at two-week intervals to assess the level of GnRH-specific antibodies and testosterone. Moreover, blood and thymus samples were also collected to analyze the T lymphocyte subpopulations one and two months after the last booster immunization. T lymphocyte immunity against GnRH was activated during the first month post-immunization as exhibited by increased numbers of CD3+ (P<0.05) and CD4+ (P<0.05)T lymphocytes following testosterone suppression (P<0.01), which was then restored and maintained at appropriate levels in the second month. In contrast, the differentiation of T lymphocytes in the thymus was reduced during the first month after immunization as exhibited by the significant decreased number of CD3+ (P<0.05) cells, followed by the restoration and heightened numbers at later time points for both the number of CD3+ (P<0.05) and CD4+ (P<0.01)T lymphocytes. These results suggest that immunization against GnRH interferes with the number of lymphocytes during the early time points following immunization. The number of T lymphocytes initially decreased in the peripheral blood following immunization, but was replenished by newly exported cells from the thymus which eventually restored the T lymphocytes to normal levels.

The Immunoendocrine Thymus as a Pacemaker of Lifespan

The thymus develops from an endocrine area of the foregut, and retains the ancient potencies of this region. However, later it is populated by bone marrow originated lymphatic elements and forms a combined organ, which is a central part of the immune system as well as an influential element of the endocrine orchestra. Thymus produces self-hormones (thymulin, thymosin, thymopentin, and thymus humoral factor), which are participating in the regulation of immune cell transformation and selection, and also synthesizes hormones similar to that of the other endocrine glands such as melatonin, neuropeptides, and insulin, which are transported by the immune cells to the sites of requests (packed transport). Thymic (epithelial and immune) cells also have receptors for hormones which regulate them. This combined organ, which is continuously changing from birth to senescence seems to be a pacemaker of life. This function is basically regulated by the selection of self-responsive thymocytes as their complete destruction helps the development (up to puberty) and their gradual release in case of weakened control (after puberty) causes the erosion of cells and intercellular material, named aging. This means that during aging, self-destructive and non-protective immune activities are manifested under the guidance of the involuting thymus, causing the continuous irritation of cells and organs. Possibly the pineal body is the main regulator of the pacemaker, the neonatal removal of which results in atrophy of thymus and wasting disease and its later corrosion causes the insufficiency of thymus. The co-involution of pineal and thymus could determine the aging and the time of death without external intervention; however, external factors can negatively influence both of them.