Effects of thymulin and GnRH on the release of gonadotropins by in vitro pituitary cells obtained from rats in each day of estrous cycle

Hinojosa, Lorena; García, Lorena; Domı́nguez, Roberto; Romano, Marta; Damián-Matsumura, Pablo; Castillo, Lourdes; Rosas, Patricia

doi:10.1016/j.lfs.2004.07.017

Cited by 12 publications

(19 citation statements)

References 26 publications

(31 reference statements)

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“…These results suggested that thymulin could exert positive feedback regulation on the secretion of GnRH in the hypothalamus of rats actively immunized with GnRH. This is consistent with the hypothesis that thymulin may be part of a feedback loop acting on neuroendocrine organs, such as the hypothalamus, and modulates the stimulatory activity of GnRH on LH and FSH release from pituitary cells (Hinojosa et al 2004, Siemion et al 2005. In addition, thymulin plays a neuroprotective role in different areas of the brain that interact with a set of cytokines (Safieh-Garabedian et al 2011).…”

Section: Figuresupporting

confidence: 89%

“…In thymulin deficient nude mice, morphometric analysis revealed that athymic nudes have reduced numbers of brain gonadotropin-releasing hormone (GnRH) neurons and pituitary gonadotropic cells, compared with heterozygotes, and neonatal thymulin gene therapy could prevent these changes (Reggiani et al 2009b, Martines et al 2011. Other studies suggested that thymulin stimulates luteinizing hormone (LH) and follicle stimulating hormone (FSH) release from perfused rat pituitaries (Brown et al 2000, Hinojosa et al 2004. Moreover, thymulin could augment LH-mediated stimulation of androgen increases in vitro and in vivo in boar testis (Wise & Ford 1999).…”

Section: Introductionmentioning

confidence: 99%

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Effects of GnRH immunization on the reproductive axis and thymulin

Su¹,

Sun²,

Zhou³

et al. 2015

Journal of Endocrinology

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The bidirectional regulation of thymulin in the reproductive-endocrine function of the hypothalamic-pituitary-gonadal (HPG) axis of rats immunized against GnRH remains largely unclear. We explored the alterations in hormones in the HPG axis in immunized rats to dissect the repressive effect of immunization on thymulin, and to clarify the interrelation of reproductive hormones and thymulin in vivo. The results showed that, in the first 2 weeks of booster immunization, thymulin was repressed when reproductive hormones were severely reduced. The self-feedback regulation of thymulin was then stimulated in later immune stages: the rising circulating thymulin upregulated LH and FSH, including GnRH in the hypothalamus, although the levels of those hormones were still significantly lower than in the control groups. In astrocytes, thymulin produced a feedback effect in regulated GnRH neurons. However, in the arcuate nucleus (Arc) and the median eminence (ME), the mediator of astrocytes and other glial cells were also directly affected by reproductive hormones. Thus, in immunized rats, the expression of glial fibrillary acidic protein was distinctly stimulated in the Arc and ME. This study demonstrated that thymulin was downregulated by immunization against GnRH in early stage. Subsequently, the self-feedback regulation was provoked by low circulating thymulin. Thereafter, rising thymulin levels promoted pituitary gonadotropins levels, while acting directly on GnRH neurons, which was mediated by astrocytes in a region-dependent manner in the hypothalamus.

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Section: Figuresupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Effects of GnRH immunization on the reproductive axis and thymulin

Su¹,

Sun²,

Zhou³

et al. 2015

Journal of Endocrinology

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show abstract

“…Thymulin has a gonadotropin releasing (GnRH) activity. Also studied in suspension of rat pituitary anterior lobes, thymulin had a dual role in the release of gonadotropins, which was dependent on the hormonal status of the donor's pituitary [38]. In combination with gonadotropin stimulation, thymulin increases testicular steroidogenesis [39,40].…”

Section: Effect Of Thymic Self-hormones On Non-immune Cells and Functmentioning

confidence: 99%

The Immunoendocrine Thymus as a Pacemaker of Lifespan

Csaba¹

2016

Acta Microbiologica et Immunologica Hungarica

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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.

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“…As we have previously shown that Zn is present in the pituitary [29] , we also measured Zn concentration in the hypothalamus and serum following the methodology previously used [29] . The values obtained were 27.2 8 0.2 ng/mg tissue for the hypothalamus and 1,018 8 33.4 ng/ml for the serum, while the values previously found for the pituitary were 34.9 8 1.0 ng/mg [29] .…”

Section: Microinjection Procedures For Injecting Thymulin or Saline Smentioning

confidence: 99%

Effects of Injecting Thymulin into the Anterior or Medial Hypothalamus or the Pituitary on Induced Ovulation in Prepubertal Mice

García¹,

Hinojosa²,

Domı́nguez³

et al. 2005

Neuroimmunomodulation

Self Cite

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In prepubertal mice, subcutaneous thymulin injection before equine chorionic gonadotrophin (eCG) treatment simulates ovulation; seemingly, the thymulin could be acting at the hypothalamus-pituitary axis level. Objective: This study was designed to analyze the effects of injecting thymulin into the hypothalamus or pituitary on induced ovulation of prepubertal mice. Method: Female mice, 19 days old, were anesthetized with ether and injected with saline solution or thymulin into the anterior or medial hypothalamus or the pituitary and treated with eCG when 20 days old. The ova shed were counted and serum concentrations of 17β-estradiol were measured. In the ovaries, the morphometrical analysis was performed and the atresia evaluated. Results: Ether anesthesia treatment blocked eCG-induced ovulation in almost all animals. Mice anesthetized and treated with eCG and gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin (hCG) ovulated a full quota of ova. Injecting saline solution into the anterior or medial hypothalamus or the pituitary did not reduce the blocking effects of ether anesthesia on induced ovulation, but the incidence of atretic follicles was higher. Injecting thymulin directly into the anterior hypothalamus did not restore ovulation, nor diminish the number of atretic follicles. In contrast, injecting thymulin into the medial hypothalamus restored the ovulation ratio and decreased the percentage of atretic follicles. Similar results were obtained by injecting thymulin into the pituitary, though thymulin treatment in the pituitary resulted in a higher number of ova shed and lower follicular atresia. Conclusion: The present results suggest that thymulin acts at the medial hypothalamus level, facilitating the release of GnRH and at the pituitary level regulating gonadotrophin release.

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Effects of thymulin and GnRH on the release of gonadotropins by in vitro pituitary cells obtained from rats in each day of estrous cycle

Cited by 12 publications

References 26 publications

Effects of GnRH immunization on the reproductive axis and thymulin

Effects of GnRH immunization on the reproductive axis and thymulin

The Immunoendocrine Thymus as a Pacemaker of Lifespan

Effects of Injecting Thymulin into the Anterior or Medial Hypothalamus or the Pituitary on Induced Ovulation in Prepubertal Mice

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