Jill D. Jacobson

Cyclical expression of GnRH and GnRH receptor mRNA in lymphoid organs.

Gonadotropin-releasing hormone (GnRH) is known to possess dirct immunomodulatory effects. We have previously demonstrated that the administration of GnRH analogues modulates the expression of murine lupus independently of effects on gonadal steroids. We speculate that GnRH exerts direct actions at the level of the immune cells. GnRH receptors have been identified on lymphocytes. Because GnRH and GnRH receptor (GnRH-R) expression varies with the estrous cycle at the levels of the hypothalamus and pituitary, we speculated that similar cyclicity might be demonstrable in lymphoid tissue. In this report, we used competitive reverse transcription PCR to quantitate the expression of GnRH and GnRH-R mRNA in lymphoid organs throughout the estrous cycle in mice. We demonstrate that the pattern of expression of GnRH-R mRNA in spleen agrees closely with the pattern in the pituitaries of the same mice and the pattern previously reported in the rat pituitary, with significantly increased levels of expression seen on the afternoon of proestrus compared to the morning of metestrus. A similar pattern is seen with GnRH-R mRNA expression in the thymus. Furthermore, we show that the expression of GnRH mRNA in both thymus and spleen agrees closely with the pattern of expression of its receptor, with significantly increased levels of expression seen on the afternoon of proestrus compared to the morning of metestrus. Additional in vitro studies demonstrate that both GnRH and estradiol significantly increase the expression of GnRH-R mRNA in immune cells. These findings support an active role for GnRH in the immune system.

Gender-Specific Exacerbation of Murine Lupus by Gonadotropin-Releasing Hormone: Potential Role of Gαq/111

We have previously demonstrated that GnRH and its analogues modulate the severity of murine systemic lupus erythematosus. In the present study, we demonstrate that GnRH alters disease severity in a sexually dimorphic fashion, even in gonadectomized mice. GnRH administration leads to an exacerbation of lupus in ovariectomized females, whereas it exerts no effect in castrated males. We initially hypothesized that gender differences in lymphocytic expression of GnRH receptor might explain these observations. Using competitive RT-PCR and binding studies to quantitate GnRH receptor expression in lymphoid organs, we found that GnRH administration led to decreased expression of GnRH receptor messenger RNA (mRNA) and GnRH binding, compared with vehicle, in spleens of ovariectomized females after 2 weeks of treatment. These decreases occurred concurrently with increased expression of interleukin-2 receptor mRNA and protein in females. GnRH administration did not alter GnRH receptor or interleukin-2 receptor mRNA o...

Gonadotropin-releasing hormone increases CD4 + T-lymphocyte numbers in an animal model of immunodeficiency

BACKGROUND Gonadotropin-releasing hormone (GnRH) possesses immunostimulatory properties. We have previously demonstrated that GnRH antagonists decrease lymphocyte numbers in an animal model of autoimmune disease. We speculated that the converse might be true, that GnRH administration would increase lymphocyte numbers or alter lymphocyte subsets in an immunodeficiency state. OBJECTIVE Our purpose was to test the hypothesis that GnRH agonist would increase IgG and CD4 counts in a rat model of immunodeficiency independently of gonadal steroids. METHODS We used diabetes-prone (DP) BB rats. This model has been characterized to have an AIDS-like lymphocyte profile, with lymphopenia and depressed CD4 counts. Ovariectomized female DP rats were randomized to receive subcutaneous injections with GnRH or vehicle 6 times weekly. DR rats were ovariectomized and treated with vehicle as controls. We performed flow cytometric analysis and complete blood cell counts at baseline, 3.5 weeks, and 7 weeks of treatment. We also measured total serum IgG and luteinizing hormone levels. RESULTS GnRH administration significantly increased total serum IgG levels in DP rats compared with vehicle. The percentages of CD4(+) cells in blood were also significantly increased in the GnRH-treated group compared with the vehicle-treated group and compared with baseline. Similarly, the absolute numbers of CD4(+) positive T cells were increased over controls at 7 weeks. The effects of GnRH were specific for the CD4 subset because there were no significant differences in numbers of CD8(+) positive cells between the 2 treatment groups. CONCLUSION GnRH shows potential utility as an immunostimulatory agent in immunodeficient states manifesting diminished numbers of immunocompetent CD4(+) T lymphocytes.

Detection of pro-opiomelanocortin mRNA in human and rat caudal medulla by RT-PCR

Pro-opiomelanocortin (POMC) mRNA has been localized in the NTS of the rat, but not in the human or other species. Here, we report that RT-PCR amplification of human caudal medulla RNA generated a distinct band on agarose gels corresponding in size and sequence to the predicted 742-bp POMC PCR product. The 742-bp signal was undetectable following amplification of cortex, amygdala or caudate nucleus RNA. An homologous, 678-bp band was amplified from rat caudal medulla and, unexpectedly, from other brain regions. Competitive RT-PCR demonstrated that POMC cDNA from rat cortex, striatum and cerebellum was 17%, 22% and 45% of caudal medulla levels. These data indicate that the POMC gene is expressed in human caudal medulla and suggest that small amounts of POMC mRNA are present in regions other than the hypothalamus and NTS of rat brain.

Evidence for alterations in stimulatory G proteins and oxytocin levels in children with autism.

The neurotransmitter oxytocin plays an important role in social affiliation. Low oxytocin levels and defects in the oxytocin receptor have been reported in childhood autism. However, little is known about oxytocins post-receptor signaling pathways in autism. Oxytocin signals via stimulatory and inhibitory G proteins. c-fos mRNA expression has been used as a marker of OT signaling as well as of G protein signaling. Herein, we hypothesized that oxytocin and its signaling pathways would be altered in children with autism. We measured plasma oxytocin levels by ELISA, G-protein and c-fos mRNA by PCR, and G proteins by immunoblot in cultured peripheral blood mononuclear cells (PBMCs) in children with autism and in age-matched controls. Males with autism displayed elevated oxytocin levels compared to controls (p<0.05). Children with autism displayed significantly higher mRNA for stimulatory G proteins compared to controls (p<0.05). Oxytocin levels correlated strongly positively with c-fos mRNA levels, but only in control participants (p<0.01). Oxytocin, G-protein, and c-fos mRNA levels correlated inversely with measures of social and emotional behaviors, but only in control participants. These data suggest that children with autism may exhibit a dysregulation in oxytocin and/or its signaling pathways.

Gender Differences and Hormonal Modulation of G Proteins Gαq/11 Expression in Lymphoid Organs

Androgens and estrogens exert potent divergent feedback effects on gonadotropin-releasing hormone (GnRH) production at the level of the hypothalamus and GnRH action at the level of the pituitary. Androgens exert generally suppressive effects on GnRH production and action, whereas rising levels of estradiol increase both GnRH release and action. In addition to its known endocrine actions, GnRH possesses immunomodulatory effects. We have previously demonstrated gender differences in immune responsiveness to GnRH that parallel gender differences in endocrine responsiveness: females appear to be more immunologically responsive to GnRH than males. GnRH exerts its actions via the stimulatory G protein Gαq and Gα11 (referred to collectively as Gαq/11) as well as via Gαs. We have recently demonstrated that the heightened immune responsiveness to GnRH in lupus-prone female mice correlated with increased expression of Gαq/11 in lymphoid cells from females compared to males. We hypothesize that the hormonal milieu of females may contribute to increased expression of stimulatory G proteins and to the heightened immune and endocrine responsiveness to GnRH. In this report, we document gender differences in expression of Gαq/11 protein in lymphoid organs in non-autoimmune DBA/2 mice. In an effort to address the mechanisms for the gender differences in G-protein expression, we used competitive reverse transcription PCR to quantitate mRNA for stimulatory G proteins in immune cells under various hormonal conditions. We quantitated the expression of Gαq/11 mRNA and protein under physiologic hormonal alterations, i.e. throughout the estrous cycle in female mice. We demonstrate that expression of Gαq/11 mRNA and protein in lymphoid organs is significantly increased on the afternoon of proestrus compared to metestrus. Additional studies demonstrate that exposure to GnRH or to estrogens significantly increases the expression of Gαq/11 mRNA in immune cells. These findings support an active role for hormonal modulation of G proteins in the gender differences in endocrinologic and immunologic responsiveness to GnRH.

Allergic manifestations and cutaneous histamine responses in patients with McCune Albright syndrome

BackgroundMcCune Albright syndrome (MAS) is a rare disorder characterized by precocious puberty, café-au-lait spots, and fibrous dysplasia. Its cause is an activating mutation in the GNAS gene, encoding a subunit of the stimulatory G protein, Gsalpha (Gsα). The action of any mediator that signals via Gsα and cyclic AMP can be up regulated in MAS. We had observed gastritis, gastroesophageal reflux, and anaphylaxis in McCune Albright patients.ObjectiveAs histamine is known to signal via histamine 1 (H1) and histamine 2 (H2) receptors, which couple with stimulatory G proteins, we attempted to mechanistically link histamine responsiveness to the activating GNAS mutation. We hypothesized that responsiveness to histamine skin testing would differ between MAS patients and healthy controls.Patients and methodsAfter obtaining informed consent, we performed a systematic review of histamine responsiveness and allergic manifestations in 11 MAS patients and 11 sex-matched, Tanner-stage matched controls. We performed skin prick testing, quantifying the orthogonal diameters of wheals and erythema. We also quantitated G protein mRNA expression.ResultsThe peak wheal and flare responses to histamine were significantly higher in MAS patients compared to controls.ConclusionsThis study suggests that MAS patients may be at risk for exaggerated histamine responsiveness compared to unaffected controls.