Pituitary dependence of bone marrow function

Cyclical haematological changes in a case of hypopituitarism

A 40-year-old woman presented to our emergency department in an altered state following a generalised tonic-clonic seizure. On regaining consciousness, she gave a history of bleeding tendencies and menorrhagia, fatigue, nausea, vomiting and appetite loss for a long time. She had received multiple blood transfusions in the last 10 years. Investigations revealed severe hyponatraemia, transaminitis and pancytopenia, which showed cyclical fluctuations in the hospital. Hyponatraemia was attributed to a central cause owing to secondary hypothyroidism and hypocortisolism on evaluation. A diagnosis of cyclical thrombocytopenia was made by logging the trends of blood cell lines and applying the Lomb-Scargle test. Liver biopsy showed features of transfusion hemosiderosis explaining transaminitis. All of the haematological abnormalities and clinical symptoms resolved on thyroxine and corticosteroid replacement, suggesting causal association hypopituitarism with cyclical thrombocytopenia.

Growth hormone and hematopoiesis: A retrospective analysis on a large cohort of children with growth hormone deficiency

OBJECTIVE

Few large-scale studies regarding the impact of GH deficiency (GHD) on hematopoiesis in children have been reported. Our aim was to investigate hematopoiesis indices in a large cohort of GHD children at diagnosis and during GH treatment (GHT) and any correlation with hormonal parameters.

DESIGN

Clinical and biochemical data of children with idiopathic GHD at diagnosis and annually up to 36 months of GHT were retrospectively evaluated. Overall, 255 children reached 12 months, 140 children 24 months and 86 children 36 months of follow-up during GHT.

RESULTS

At baseline, 18.4% of GHD children and 10.1% of controls showed normocytic anemia. GHD children showed lower hemoglobin (Hb) (p = 0.007), red blood cells (RBC) (p < 0.001) and hematocrit (Ht) (p = 0.001) than controls. During GHT, the percentage of anemic patients decreased from 18.4 to 5.4-3.5 and 4.6% after 12 (p = 0.001), 24 (p < 0.001) and 36 months (p < 0.001) of GHT, respectively. In both anemic and non-anemic patients, a significant increase in Hb (p < 0.001, <0.001 and 0.002), RBC (all p < 0.001) and Ht (all p < 0.001) was found after 12, 24 and 36 months of GHT. The Hb levels were significantly correlated with the GH peak after stimulation test (p < 0.001) at baseline and with IGF-I levels at 36 months of GHT (p = 0.002).

CONCLUSIONS

A significant improvement in erythropoiesis indices occurs during GHT, regardless of any previous presence of anemia.

Arginine vasopressin (AVP): a review of its historical perspectives, current research and multifunctional role in the hypothalamo-hypophysial system

INTRODUCTION

This publication reviews the function of arginine vasopressin and focuses on the morphologic and functional correlation between the hormone and its effect on stress, the hypophysial-adrenocortical axis, neuroimmune responses, renal function and corticotroph pituitary tumors.

MATERIALS AND METHODS

A literature review was performed using various search engines for information regarding the morphology and the multifunctional role of arginine vasopressin.

RESULTS

Although a large number of studies were published discussing these interactions, there are several important areas that are still obscure.

CONCLUSION

The questions of how does arginine vasopressin affect the morphology and function of these various areas, and how does the secretion of ACTH and adrenocortical hormones influence the morphology of arginine vasopressin-producing cells and their hormone secretion requires further investigation.

Hormones and the bone marrow: panhypopituitarism and pancytopenia in a man with a pituitary adenoma

In rare cases, pancytopenia results from hormonal deficiencies that arise in the setting of panhypopituitarism. Here we describe the unusual case of a 60-year-old man who presented with progressive fatigue and polyuria, and whose laboratory workup revealed a deficiency of the five hormones associated with the action of the anterior pituitary (thyroid hormone, testosterone, cortisol, prolactin, and insulin-like growth factor-1). Imaging of the pituitary demonstrated a cystic mass consistent with a pituitary adenoma replacing much of the normal pituitary tissue. His symptoms and hematologic abnormalities rapidly resolved with prednisone and levothyroxine supplementation. While the majority of reported cases of panhypopituitarism with bone marrow suppression are the result of peripartum sepsis or hemorrhage leading to pituitary gland necrosis (Sheehan's syndrome), it is also important to consider the diagnosis of hypopituitarism in patients with hypothyroidism, low cortisol levels, and pancytopenia. The causal relationship between pancytopenia and panhypopituitarism is not well understood, though it does reinforce the important influence of these endocrine hormones on the health of the bone marrow.

Regulation of intestinal morphology and GALT by pituitary hormones in the rat

Here, the effects of neurointermediate (NIL), anterior (AL), and total hypophysectomy (HYPOX) on ileal mucosa cells and gut-associated lymphoid tissue (GALT) are reported. Compared with the sham-operated (SHAM) rats, the villi height and goblet cells numbers were significantly decreased in all groups. Lamina propria area decreased in AL and HYPOX, but not in NIL animals. CD8(+) but not CD4(+) lymphocytes decreased in the HYPOX and NIL groups. Paneth cells did not change, while IgA cells, IgM cells, and secretory IgA were significantly decreased in all groups. NIL but not AL animals lost significant numbers of IgA cells and secretory IgA. In summary, pituitary hormones exert lobe-specific regulatory effects on the gut and on GALT.

Prevalence of hematological abnormalities in patients with Sheehan's syndrome: response to replacement of glucocorticoids and thyroxine

Anemia and other hematological abnormalities are common in patients with Sheehan's syndrome. The response of these abnormalities to replacement of thyroxine and glucocorticoids is not clear. The aim of the present study was to document the profile of hematological abnormalities and response to treatment in patients with Sheehan's syndrome. Forty patients of Sheehan's syndrome and an equal number of age and parity matched healthy controls were studied for prevalence of hematological abnormalities. Hemoglobin concentration, hematocrit, red cell, white cell and platelet count were significantly decreased in patients with Sheehan's syndrome compared to controls. Frequency of anemia, leucopenia, thrombocytopenia and pancytopenia was significantly higher in these patients compared to controls. After achieving euthyroid and eucortisol state, there was a complete recovery of these hematological abnormalities. We conclude that anemia and other cytopenias are common in patients with Sheehan's syndrome and replacement with thyroxine and glucocorticoids results in complete recovery of these abnormalities.

Panhypopituitarism secondary to a macroprolactinoma manifesting with pancytopenia: case report and literature review

OBJECTIVE

To present a case of pancytopenia associated with hypopituitarism secondary to a macroprolactinoma.

METHODS

We report the clinical features on presentation and results of laboratory investigation. Findings on magnetic resonance imaging are illustrated. The response to hormone replacement therapy is summarized.

RESULTS

A 46-year-old man was referred with pancytopenia and secondary hypothyroidism. Laboratory investigation revealed hypopituitarism and a substantially increased prolactin level. Magnetic resonance imaging of the head demonstrated a macroprolactinoma. Hematologic investigation disclosed no other cause for the pancytopenia. Hormone replacement therapy was initiated with hydrocortisone, levothyroxine, and testosterone. Cabergoline was used to induce regression of the prolactinoma. A rapid improvement was seen in the cytopenias, with normalization of the blood cell counts after 8 months of treatment. This result has been sustained during 29 months of follow-up.

CONCLUSION

Pancytopenia associated with hypopituitarism has been reported in the literature as a rare occurrence limited to isolated case reports, predominantly associated with Sheehan syndrome. To our knowledge, this is the first reported case of pancytopenia associated with a macroprolactinoma. This finding is noteworthy because prolactin alone has been reported to support hematopoiesis in animal studies.

A review of the effects of growth hormone changes on symptoms of frailty in the elderly with chronic kidney disease

The incidence and prevalence of chronic kidney disease (CKD) is increasing worldwide, especially in the elderly. Recently, functional impairment and frailty have been recognized as factors affecting the quality of life, and outcomes in elderly patients with CKD and therapeutic interventions to improve function and reduce frailty are therefore being considered. Growth hormone (GH) levels decrease with age and GH actions are impaired in CKD patients. GH stimulates protein synthesis, bone, and glucose metabolism, and affects body composition by reducing body fat and increasing lean body mass. An increase in lean body mass may reduce frailty and thus avoid functional impairment. Thus, providing GH to elderly CKD patients could potentially improve outcomes and quality of life by lowering the risk of frailty and associated functional impairment. There are few studies assessing the long-term effects of GH administration on symptoms of frailty in elderly patients with CKD. In this review we will try to shed some light on the trials assessing the administration of GH to elderly subjects and to patients with CKD and focus on the possible role GH administration may play to improve frailty and quality of life in those patients.

Effect of human recombinant growth hormone therapy on circulating levels of erythropoietin and granulocyte-colony stimulating factor in short children

Several reports suggest a role of growth hormone (GH) in the regulation of the haematopoietic system, as regards the normal differentiation and function of blood cells. The aim of this study was to evaluate the influence of rhGH therapy on erythropoietin (Epo) and granulocyte-colony stimulating factor (G-CSF) levels in 18 prepubertal short children with idiopathic GH deficiency (GHD) (n = 8) or without GHD (n = 10), during the first year of treatment. In non-GHD children Epo levels significantly decreased and G-CSF levels increased from basal to 12 months of therapy, whereas in GHD children they did not change significantly. Circulating levels of G-CSF are significantly lower in GHD than in non-GHD children. In non-GHD children the number of red blood cells, haemoglobin and haematocrit values significantly increased after 1 year of rhGH treatment. rhGH therapy influences Epo and G-CSF levels in short non-GHD children, while it shows no effects in GHD children.

Neuroimmune regulation in immunocompetence, acute illness, and healing

Adaptive immunocompetence is maintained by growth hormone (GH), prolactin (PRL), and vasopressin (VP). Innate or natural immunocompetence depends on cytokines, hormones (especially of the hypothalamus-pituitary-adrenal axis), and catecholamines. The acute phase response (APR, or acute febrile illness) is an emergency defense reaction whereby the adaptive, T cell-dependent, immune reactions are suppressed and the innate immune function is dramatically amplified. Infection and various forms of injury induce APR. Cytokines [interleukin (IL)-1beta, tumor necrosis factor-alpha, and IL-6] stimulate corticotropin-releasing hormone (CRH) and VP secretion and cause a "sympathetic outflow." Colony-stimulating factors activate leukocytes. CRH is a powerful activator of the pituitary adrenocortical axis and elevates glucocorticoid (GC) levels. Cytokines, GCs, and catecholamines play fundamental roles in the amplification of natural immune defense mechanisms. VP supports the APR at this stage. However, VP remains active and is elevated for a longer period than is CRH. VP, but not CRH, is elevated during chronic inflammatory diseases. VP controls adaptive immune function and stimulates adrenocorticotropic hormone (ACTH) and PRL secretion. PRL maintains the function of the thymus and of the T cell-dependent adaptive immune system. The ACTH-adrenal axis stimulates natural immunity and of suppressor/regulatory T cells, which suppress the adaptive immune system. VP also has a direct effect on lymphoid cells, the significance of which remains to be elucidated. It is suggested that VP regulates the process of recovery from acute illness.

Reproductive experience modifies dopaminergic function, serum levels of prolactin, and macrophage activity in female rats

Reproductive experience (RE), i.e. pregnancy and lactation, induces physiological changes in mammals. Recent data show that neuroimmune interactions are modulated by a diversity of events involving neurotransmitters and neuropeptides. These molecules, particularly dopamine (DA), were reported to mediate the relevant cross talk between immune and neuroendocrine systems. Moreover, DA-mediated regulation of leukocyte function is a reasonable approach to investigate the DA-operated regulatory switch for immune-competent cells, such as macrophages. Therefore, the goals of the present study were to determine the effects of RE on: (1) dopaminergic function through hypothalamic levels of DA, dihydroxyphenylacetic acid (DOPAC), homovanilic acid (HVA), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA); (2) basal levels of circulating prolactin (PRL); and (3) activity of peritoneal macrophage (phagocytosis and oxidative burst). A total of 16 adult (200-250 g) female Wistar rats were used, divided in two groups: nulliparous and primiparous. Approximately 2-3 weeks after weaning pups from the primiparous group, both groups of rats were tested. The findings indicate that: (1) DOPAC concentrations, DOPAC/DA and HVA+DOPAC/DA ratios decreased in primiparous rats as compared to virgin rats, (2) primiparous rats showed significantly lower serum PRL levels, and (3) phorbol miristate acetate (PMA)-induced oxidative burst was decreased in peritoneal macrophage from primiparous rats as compared to virgin rats. To test the possible positive correlation between serum levels of PRL and the intensity of oxidative burst by peritoneal macrophage, an extra experiment was done with adult virgin female rats treated with domperidone, an antagonist of DA receptors. Domperidone-treated animals showed increased serum levels of PRL and simultaneous increase in peritoneal macrophage oxidative burst. Thus, suggesting an indirect participation of hyperprolactinemia, induced by this treatment in peritoneal macrophage activity of female rats. These results suggest that a previous RE can modulate the activity of dopaminergic hypothalamic systems, while decreasing PRL serum levels and the oxidative burst of peritoneal macrophage. The neurochemical and hormonal RE-induced changes correlate with the immune alterations.

Production of nitric oxide by murine peritoneal macrophages in vitro on treatment with prolactin and growth hormone: Involvement of protein tyrosine kinases, Ca++, and MAP kinase signal transduction pathways

Prolactin (PRL) and growth hormone (GH) (somatotropin) have been known to possess immunomodulatory properties. In the present studies we have investigated the production of nitric oxide (NO) and TNF-alpha by murine peritoneal macrophages in vitro on treatment with PRL and GH and the signal transduction mechanism involved. It is observed that significantly enhanced production of NO is induced in macrophages on treatment with PRL and GH. It is further observed that protein tyrosine kinases, MAP kinases and Ca(++) channeling are involved in NO production by macrophages on in vitro treatment with PRL and GH. GH and PRL induced nitric oxide did not have any effect on the expression and production of TNF-alpha. PRL or GH induced TNF-alpha production by murine macrophages was insensitive in the presence of competitive inhibitor of NOS, L-NMMA. Similarly, there is no autocrine or paracrine effect of TNF-alpha on GH or PRL induced NO production and iNOS expression.

Growth hormone replacement therapy in growth hormone deficient children and adults: Effects on hemochrome

Several lines of evidence have suggested a role of the GH/IGF-I axis in the regulation of hemochrome. Many studies have been carried out in GH deficient children and adults about this topic, reporting predominantly a positive effect of recombinant human GH (rhGH) on red series, with no action on serum leucocytes and platelets counts. The aim of this study was to assess the impact of GH deficiency (GHD) and of rhGH replacement on blood cells count in 17 pre-pubertal children with idiopathic isolated GHD (11 males and 6 females, aged 9.1+/-0.8 yr) and in 18 patients with adult-onset GHD (12 males and 6 females, aged 47.9+/-3.0 yr). Evaluation of absolute and SD score (SDS) values of red blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelets and white blood cells was performed at baseline and after 12 months of rhGH treatment (0.045+/-0.001 mg/kg bw/day and 4.2+/-0.5 microg/kg bw/day for children and adults, respectively). At baseline, all patients showed low IGF-I levels. Effectiveness of rhGH therapy was documented by significant increase in height SDS, height velocity and serum IGF-I levels in children. In adults, adequacy of rhGH was demonstrated by significant increase in serum IGF-I and significant decrease in body fat. At baseline, about 25% of patients (4 of 17 children and 4 of 18 adults) showed normochromic normocytic anemia, while the other indices were normal. In 7 of the 8 anemic patients, normal levels of hemoglobin were restored on rhGH, while no change in all the other indices was observed. In conclusion, rhGH therapy at physiological doses has no effect on erythropoiesis in GHD children and adults with normal blood cells count, while in patients with normochromic normocytic anemia rhGH is able to restore normal hemoglobin levels.

Hypopituitarism and anemia: effect of replacement therapy with hydrocortisone and/or levothyroxine

Although common, anemia associated with hypopituitarism has received little attention. We conducted a retrospective study to elucidate the effect of replacement therapy with hydrocortisone and/or levothyroxine on the decreased hemoglobin (Hb) level. A total of 68 patients who had been suffering from anterior pituitary deficiencies for more than 12 months were studied. The Hb level was significantly lower in patients with hypopituitarism (p=0.0012). Decreased Hb level (<12.0 g/dl) was observed in 22 patients (32.4%). It was related to hypocortisolism (regression weights=0.39), hypothyroidism (0.37), GHD (0.32) and hypogonadism in men (0.17). Among 68 patients, 30 patients had been receiving replacement therapy for at least 12 months. Hydrocortisone and levothyroxine increased the Hb level in 20 patients whose data were available before the replacement (p=0.0002). However, the Hb level was still lower in 30 patients receiving the replacement (p=0.0001). In 13 patients (8 men) with decreased Hb level (<12.0 g/dl) despite the replacement, GH and testosterone were deficient in 12 (92.3%) and 8 (100%) patients, respectively. In conclusion, replacement therapy with hydrocortisone and/or levothyroxine is effective in most patients but is not sufficient, at least in some patients, to improve the decreased Hb level. These results suggest that additional replacement therapy, i.e. with GH and/or androgen, is necessary to obtain further improvement.

Effect of recombinant human GH on circulating granulocyte colony-stimulating factor and neutrophils in patients with adult GH deficiency

BACKGROUND

We previously reported that short-term continuous subcutaneous infusion (CSI) of recombinant human growth hormone (rhGH) increased plasma erythropoietin levels and hemoglobin concentrations in patients with adult GH deficiency. In the present study, we investigated the effect of rhGH on plasma granulocyte colony-stimulating factor (G-CSF) levels and neutrophil counts in patients with adult GH deficiency.

METHODS

rhGH was administrated for 1 year in six patients with adult GH deficiency (age range, 24-69 years; mean +/- S.E.M., 51.7 +/- 5.8 years; two males and four females) by means of CSI at a rate of 0.25 U/kg per week. Blood samples were obtained in the morning after overnight fasting every month before and after the start of rhGH administration. Plasma GH, insulin-like growth factor I (IGF-I) and G-CSF levels, and neutrophil counts, were measured.

RESULTS

Mean ( +/- S.E.M.) plasma GH levels increased from 0.26 +/- 0.14 to 2.28 +/- 0.20 microg/l 1 month after the start of rhGH administration. An increase of the plasma GH levels was accompanied by an increase in the plasma IGF-I levels from 64.7 +/- 8.5 to 293.3 +/- 80.6 microg/l. Plasma G-CSF levels increased at 2, 3, 8, 9 and 10 months after the start of rhGH administration compared with 28.6 +/- 11.0 ng/l at time 0. The neutrophil counts increased at 2, 3, 7, 8, 9, 11 and 12 months after the start of rhGH administration compared with 2822 +/- 377 neutrophils/microl at time 0.

CONCLUSION

rhGH administration increased plasma G-CSF levels and neutrophil counts. GH and/or IGF-I might stimulate neutrophil production and/or release via G-CSF.

Complete remission of hyperprolactinemia and erythrocytosis after hysterectomy for a uterine fibroid in a woman with a previous diagnosis of prolactin-secreting pituitary microadenoma

A 44-year-old woman who had been suffering for 10 years from amenorrhea and hyperprolactinemia resistant to high doses of bromocriptine was hospitalized with erythrocytosis, normal serum erythropoietin (sEpo) levels, and hypertension. Erythrocytosis secondary to uterine myoma and a prolactin-secreting pituitary microadenoma were initially diagnosed. The hyperprolactinemia was bromocriptine resistant, despite gradual increase of the dosage to 30 mg/day. Both hyperprolactinemia and erythrocytosis unexpectedly regressed completely after the patient underwent hysterectomy for a uterine fibroid 9 months after the erythrocytosis was first disclosed. Given the well-known effects of prolactin on hematopoietic cells, we hypothesize that--in this very unusual case--the two main, apparently unrelated abnormalities (erythrocytosis with normal sEpo levels and hyperprolactinemia) may have been the clinical consequence of the functional redundancy and pleiotropy of the "pituitary" hormone prolactin, inappropriately secreted by a uterine fibroid for more than 10 years.

Prolactin and prolactin receptor gene polymorphisms in multiple sclerosis and systemic lupus erythematosus

Genes encoding for prolactin (PRL) and its receptor (PRLR) are possible candidates for multiple sclerosis (MS) and systemic lupus erythematosus (SLE) susceptibility. In fact: (1) a prolactin secretion dysfunction has been described in several autoimmune diseases including SLE and MS and their animal models; (2) both PRL and PRLR are structurally related to members of the cytokine/hematopoietin family and have a role in the regulation of the immune response; and (3) both PRL and PRLR genes map in genomic regions that showed linkage with autoimmunity. Prolactin maps on chromosome 6p, about 11-kb telomeric to HLA-DRB1 and PRLR in 5p12-13, which revealed evidence of linkage with MS in different populations. To evaluate a possible role of these two genes in SLE and MS we performed an association study of 19 PRL and PRLR single nucleotide polymorphisms (SNPs). These were directly searched by DHPLC in a panel of SLE and MS patients and selected from databases and the literature. The SNP allele frequencies were determined on patient and control DNA pools by primer-extension genotyping and HPLC analysis. Moreover a panel of HLA typed SLE and control individuals were individually genotyped for the PRL G-1149T polymorphism previously described to be associated with SLE. No statistically significant difference in the allele distribution was observed for any of the tested variations.

Effects of prolactin on hematopoiesis

The presence of extra-pituitary prolactin and its cognitive receptors in the hematopoietic micro-environment raises the question of whether prolactin plays a role in lympho-hematopoiesis and under what conditions. Current studies suggest that endogenous prolactin does not play a significant role under normal steady-state conditions. Rather, prolactin has been implicated as a 'stress hormone', functioning to restore hematopoietic homeostasis under conditions of dysregulation. The stress response of prolactin as well as its complex relationship with other hormones and factors has resulted in conflicting reports in the literature regarding prolactin's role in lympho-hematopoiesis. A review of this literature is provided as well as discussion of conditions under which lymphohematopoietic activity of prolactin may be evident.

Age-associated loss of bone marrow hematopoietic cells is reversed by GH and accompanies thymic reconstitution

Deterioration of the thymus gland during aging is accompanied by a reduction in plasma GH. Here we report gross and microscopic results from 24-month-old Wistar-Furth rats treated with rat GH derived from syngeneic GH3 cells or with recombinant human GH. Histological evaluation of aged rats treated with either rat or human GH displayed clear morphologic evidence of thymic regeneration, reconstitution of hematopoietic cells in the bone marrow, and multiorgan extramedullary hematopoiesis. Quantitative evaluation of formalin-fixed, hematoxylin and eosin-stained sections of bone marrow from aged rats revealed at least a 50% reduction in the number hematopoietic bone marrow cells, compared with that of young 3-month-old rats. This age-associated decline in bone marrow leukocytes, as well as the increase in bone marrow adipocytes, was significantly reversed by in vivo treatment with GH. Restoration of bone marrow cellularity was caused primarily by erythrocytic and granulocytic cells, but all cell lineages were represented and their proportions were similar to those in aged control rats. On a per-cell basis, GH treatment in vivo significantly increased the number of in vitro myeloid colony forming units in both bone marrow and spleen. Morphological evidence of enhanced extramedullary hematopoiesis was observed in the spleen, liver, and adrenal glands from animals treated with GH. These results confirm that GH prevents thymic aging. Furthermore, these data significantly extend earlier findings by establishing that GH dramatically promotes reconstitution of another primary hematopoietic tissue by reversing the accumulation of bone marrow adipocytes and by restoring the number of bone marrow myeloid cells of both the erythrocytic and granulocytic lineages.

Effect of long-term administration of recombinant human growth hormone (rhGH) on plasma erythropoietin (EPO) and haemoglobin levels in anaemic patients with adult GH deficiency

OBJECTIVE

We investigated the effect of recombinant human GH (rhGH) on erythropoietin (EPO) and haemoglobin (Hb) concentrations in anaemic patients with adult GH deficiency.

PATIENTS AND DESIGN

rhGH was administrated in 8 patients with adult GH deficiency, three males and five females, aged from 24 to 69 years, mean (+/- SD) of 48.8 +/- 16.4 years, for 1 year by means of continuous subcutaneous infusion (CSI) at a flow rate of 0.036 U/kg/day using a portable syringe pump. Blood samples were obtained in the morning after an overnight fast every week for 1 month, followed by each month before and after the start of rhGH administration.

RESULTS

Mean (+/- SE) plasma GH levels increased from 0.24 +/- 0.09 microg/l to 2.32 +/- 0.23 microg/l 1 week after the start of rhGH administration to maintain a steady state. Plasma IGF-I levels increased from 70.1 +/- 13.8 microg/l to 282.8 +/- 70.6 microg/l 1 week after the start of rhGH administration to maintain the steady state. Plasma EPO levels increased from 25.9 +/- 2.6 IU/l to 37.6 +/- 4.2 IU/l and 34.3 +/- 3.6 IU/l at 1 week and 2 weeks after the start of rhGH administration, respectively, and then decreased gradually to 14-9 +/- 2.1 IU/l at 10 months after the start of rhGH administration. Reticulocyte counts increased from 0.88 +/- 0.06% to 1.49 +/- 0.21% at 1 week. Hb concentrations increased from 103 +/- 5 g/l to 106 +/- 5 g/l at 2 weeks after the start of rhGH administration, and then increased gradually to reach the normal range.

CONCLUSIONS

We conclude that EPO secretion was stimulated in the initial 2 weeks after the start of CSI of rhGH in anaemic patients with adult GH deficiency. Increased Hb concentrations after long-term administration of rhGH might be explained by direct stimulatory effects of rhGH and IGF-I on erythroid cells, which was accompanied by suppressed EPO secretion, in combination with a more generalized indirect impact of rhGH on physical activety. These findings suggest a beneficial effect of rhGH replacement in anaemic patients with adult GH deficiency.

Pituitary involvement in T cell renewal during development and metamorphosis of Xenopus laevis

Studies of pituitary-deficient dwarf mice show that in the absence of a normally functioning pituitary, thymus development is impaired. Treatment with growth hormone, prolactin, and thyroid hormones restores thymus development. Smaller thymus size in pituitary-deficient animals could be due to defective development of precursors, impaired precursor immigration, impaired thymocyte expansion, or development of a smaller epithelial/stromal compartment in the thymus of pituitary-deficient animals. Using a well-characterized amphibian model to study stem cell immigration into the thymus, we show here that hypophysectomy (hypx) of young tadpoles interferes with overall growth of the frogs and with the broad lymphocyte expansion that occurs after metamorphosis, but it does not interfere with the immigration of T cell precursors into an implanted thymus. Diploid host cells moving into a triploid thymus implant do so at the same rate and to the same extent in hypx hosts as they do in intact control hosts. Analysis of cell division in the implanted thymus populations shows a significantly greater proportion of cells arrested in the G(0)/G(1) phase and a significantly lower proportion of cells in the S phase and G(2) + M phase of the cell cycle in hypx hosts than in intact hosts. Thus, smaller thymus size in hypx hosts could be due to a slower rate of expansion of precursors that migrate there.

Effects of growth hormone and prolactin on hematopoiesis

The use of the neuroendocrine hormones growth hormone (GH) and prolactin (PRL) in preclinical models, demonstrating promotion of hematopoietic recovery and immune function, offers promise for several clinical situations. These hormones do not appear to produce the same extent of immune/hematopoietic effects when compared to conventional hematopoietic and immune stimulating cytokines (i.e. G-CSF or interleukin-2). However, their pleiotropic effects and limited toxicity after systemic administration makes them attractive to test in myeloablative situations. More work needs to be performed to understand the mechanism(s) of GH and PRL action, particularly with regard to hematopoietic progenitor cell expansion and differentiation both in normal and pathologic situations.

Humoral and cell-mediated immunity in mice with genetic deficiencies of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormone

Prolactin (PRL), growth hormone (GH), insulin-like growth factor-I (IGF-I), and thyroid hormones have been proposed as critical immunoregulatory mediators, and their clinical use is being considered. The precise role played by each of these hormones in the generation of humoral and cell-mediated immune responses was assessed in a panel of mice with mutations that result in a selective reduction of PRL, GH, IGF-I, and/or thyroid hormone production. A surprising result, in view of previous studies indicating an immunoregulatory role for these hormones, was that all mice generated normal humoral and cell-mediated immune responses following challenge with T-independent and T-dependent antigens and with Listeria monocytogenes. A review of these findings in the context of previous data has resulted in the formulation of a working hypothesis proposing that these hormones act as anabolic and/or stress modulating mediators with effects on most cells, including those of the immune system. When considered in this context, it is possible to reconcile the contradictory data.

The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency

An extensive literature suggesting that PRL, GH, IGF-I, and thyroid hormones play an important role in immunity has evolved. Because the use of one or more of these hormones as immunostimulants in humans is being considered, it is of critical importance to resolve their precise role in immunity. This review addresses new experimental evidence from analysis of lymphocyte development and function in mice with genetic defects in expression of these hormones or their receptors that calls into question the presumed role played by some of these hormones and reveals unexpected effects of others. These recent findings from the mutant mouse models are integrated and placed in context of the wider literature on endocrine-immune system interactions. The hypothesis that will be developed is that, with the exception of a role for thyroid hormones in B cell development, PRL, GH, and IGF-I are not obligate immunoregulators. Instead, they apparently act as anabolic and stress-modulating hormones in most cells, including those of the immune system.

Dopamine, a neurotransmitter, influences the immune system

Dopamine (DA) is a monoamine neurotransmitter of both central and peripheral nervous system. Its role in the neural-immune communication has been discussed in the present review. Results reveal that in vivo damage or stimulation of specific central dopaminergic system suppresses or enhances functional activities of the immune effector cells. The possible influences of other immunomodulators of the brain by altering brain DA may be the underlying mechanism. Direct effects of DA on the immune effector cells are also contradictory, it is suppressive in vitro, while in pharmacological doses, it is mostly stimulatory in vivo. The possible mechanisms have been discussed. Lastly, future areas of relevance on DA and immunity have been highlighted to advance our knowledge regarding DA as an immune regulator.

Effect of long-term treatment with recombinant human growth hormone on erythropoietin secretion in an anemic patient with panhypopituitarism

We studied the effect of treatment with recombinant human GH in an anemic patient with panhypopituitarism in which hemoglobin (Hb) concentration remained as low as 11.0 g/dl in spite of appropriate replacement with thyroid and adrenocortical hormones. Recombinant human GH was subcutaneously and constantly infused for 12 months using a portable syringe pump at a rate of 0.25 U/kg/week. After the treatment with human GH plasma erythropoietin (EPO) levels increased from 12.2 to 25.1 mIU/ml, with a concomitant increase of Hb concentration to 13.6 g/dl. When the administration of human GH was interrupted, both plasma EPO levels and Hb concentrations decreased. There was a close correlation between plasma GH and EPO levels before and during the human GH administration (y=2.444x+1 3.423, r=0.641, p<0.05). Plasma GH levels were well correlated with Hb concentrations before and during human GH administration (y=0.529x+11.313, r=0.690, p<0.01). Plasma IGF4 levels were also correlated with Hb concentrations (y=0.007x+10.874, r=0.832, p<0.001), but not with plasma EPO levels. These findings suggest that GH treatment may be useful in anemic patients with panhypopituitarism.

Prolactin exerts hematopoietic growth-promoting effects in vivo and partially counteracts myelosuppression by azidothymidine

Prolactin (PRL) is a neuroendocrine hormone that influences immune and hematopoietic development. The mechanism of action of this hormone in vivo remains unclear; therefore, we assessed the effects of PRL on hematopoiesis in vivo and in vitro. Normal resting mice were treated with 0, 1, 10, or 100 microg of recombinant human prolactin (rhPRL) for 4 consecutive days and euthanized on the fifth day for analysis of myeloid and erythroid progenitors in the bone marrow and spleen. Both frequencies and absolute numbers of splenic colony-forming unit granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-e) were significantly increased in mice receiving rhPRL compared to the controls that had received saline only. Bone marrow cellularities were not significantly affected by any dose of rhPRL, but the absolute numbers and frequencies of bone marrow CFU-GM and BFU-e were augmented by rhPRL. These results suggest that rhPRL can promote hematopoiesis in vivo. Because rhPRL augments myeloid development in vivo, we examined the potential of the hormone to reverse the anemia and myelosuppression induced by azidothymidine (AZT). Mice were given rhPRL injections concurrent with 2.5 mg/mL AZT in drinking water. rhPRL partially restored hematocrits in the animals after 2 weeks of treatment and increased CFU-GM and BFU-e in both spleens and bone marrow. The experiments with AZT and rhPRL support the conclusion that the hormone increases myeloid and erythroid progenitor numbers in vivo, and they suggest that the hormone is clinically useful in reversing myelosuppression induced by AZT or other myeloablative therapies.

Effect of hypophysectomy on the proliferation and differentiation of rat bone marrow stromal cells

Conditions such as estrogen deficiency, skeletal unloading, and aging have all been demonstrated to have various effects on the proliferation and differentiation of bone marrow stroma-derived osteoprogenitor cells. Here we have sought to examine the effects of pituitary hormone deficiency on the proliferation and the differentiation of these osteoprogenitor cells using the hypophysectomized (HX) rat as a model. In the present study, we use an in vitro culture system to examine the effects of HX on the osteogenic potential of rat bone marrow stroma. With the intact animal as a control, we used [3H]thymidine incorporation and cell number as indexes of proliferation. We also measured alkaline phosphatase enzyme activity, relative levels of osteocalcin expression with RT-PCR, and osteopontin and bone sialoprotein steady-state levels by Northern blot to delineate the effect on differentiation. Our results indicate that osteoprogenitor cells exposed to a pituitary hormone-deficient environment in vivo demonstrate an enhanced proliferative capacity and also exhibit an augmented expression of differentiation markers when exposed to an optimal environment in vitro.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Defective mammopoiesis, but normal hematopoiesis, in mice with a targeted disruption of the prolactin gene

Prolactin (PRL) has been implicated in numerous physiological and developmental processes. The mouse PRL gene was disrupted by homologous recombination. The mutation caused infertility in female mice, but did not prevent female mice from manifesting spontaneous maternal behaviors. PRL-deficient males were fertile and produced offspring with normal Mendelian gender and genotype ratios when they were mated with heterozygous females. Mammary glands of mutant female mice developed a normal ductal tree, but the ducts failed to develop lobular decorations, which is a characteristic of the normal virgin adult mammary gland. The potential effect of PRL gene disruption on antigen-independent primary hematopoiesis was assessed. The results of this analysis indicated that myelopoiesis and primary lymphopoiesis were unaltered in the mutant mice. Consistent with these observations in PRL mutant mice, PRL failed to correct the bone marrow B cell deficiency of Snell dwarf mice. These results argue that PRL does not play any indispensable role in primary lymphocyte development and homeostasis, or in myeloid differentiation. The PRL-/- mouse model provides a new research tool with which to resolve a variety of questions regarding the involvement of both endocrine and paracrine sources of PRL in reproduction, lactogenesis, tumorigenesis and immunoregulation.

Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

Endocrine, paracrine and autocrine actions of prolactin on immune cells

The immune response is regulated by locally released factors, collectively referred to as cytokines. Data on the human immune system have convincingly demonstrated that the hormone prolactin (PRL), in addition to exerting its endocrine control on the immune system, acts as a cytokine in that it is released within the immune system and regulates the lymphocyte response by paracrine and autocrine mechanisms. Both lymphocyte and pituitary PRLs are under the control of immune factors. Synthesis of human PRL by lymphocytes is induced by T-cell stimuli, while increased release of PRL by the pituitary, observed in vivo after immune challenge, may be mediated by cytokines produced by monocyte-macrophages. Since hyperprolactinemia and hypoprolactinemia are both immunosuppressive, physiological levels of circulating PRL must be necessary to maintain basal immunocompetence. The effects of Cyclosporin (CsA) on IL-2 and PRL gene activation and the analysis of the intracellular signaling events downstream IL-2 and PRL receptors suggest coordinate actions of these two cytokines during T cell activation.

The immune effects of neuropeptides

Current evidence indicates that the neuroendocrine system is the highest regulator of immune/inflammatory reactions. Prolactin and growth hormone stimulate the production of leukocytes, including lymphocytes, and maintain immunocompetence. The hypothalamus-pituitary-adrenal axis constitutes the most powerful circuit regulating the immune system. The neuropeptides constituting this axis, namely corticotrophin releasing factor, adrenocorticotrophic hormone, alpha-melanocyte stimulating hormone, and beta-endorphin are powerful immunoregulators, which have a direct regulatory effect on lymphoid cells, regulating immune reactions by the stimulation of immunoregulatory hormones (glucocorticoids) and also by acting on the central nervous system which in turn generates immunoregulatory nerve impulses. Peptidergic nerves are major regulators of the inflammatory response. Substance P and calcitonin gene-related peptide are pro-inflammatory mediators and somatostatin is anti-inflammatory. The neuroendocrine regulation of the inflammatory response is of major significance from the point of view of immune homeostasis. Malfunction of this circuit leads to disease and often is life-threatening. The immune system emits signals towards the neuroendocrine system by cytokine mediators which reach significant blood levels (cytokine-hormones) during systemic immune/inflammatory reactions. Interleukin-1, -6, and TNF-alpha are the major cytokine hormones mediating the acute phase response. These cytokines induce profound neuroendocrine and metabolic changes by interacting with the central nervous system and with many other organs and tissues in the body. Corticotrophin releasing factor functions under these conditions as a major co-ordinator of the response and is responsible for activating the ACTH-adrenal axis for regulating fever and for other CNS effects leading to a sympathetic outflow. Increased ACTH secretion leads to glucocorticoid production. alpha-melanocyte stimulating hormone functions under these conditions as a cytokine antagonist and an anti-pyretic hormone. The sympathetic outflow, in conjunction with increased adrenal activity. leads to the elevation of catecholamines in the bloodstream and in tissues. Current evidence suggests that neuroimmune mechanisms are essential in normal physiology, such as tissue turnover, involution, atrophy, intestinal function, and reproduction. Host defence against infection, trauma and shock relies heavily on the neuroimmunoregulatory network. Moreover, abnormalities of neuroimmunoregulation contribute to the aetiology of autoimmune disease, chronic inflammatory disease, immunodeficiency, allergy, and asthma. Finally, neuroimmune mechanisms play an important role in regeneration and healing.

Prolactin increases the susceptibility of primary leukemia cells to NK and LAK effectors

Our previous studies have shown that prolactin (PRL), a pituitary and lymphocyte hormone and a ligand of the cytokine/hemopoietin receptors (R) superfamily, acts synergistically with interleukin (IL)-2 on the development of lymphokine activated killer (LAK) cells and enhances the effects of GM-CSF and IL-3 on myeloid progenitors' proliferation and differentiation. More recently, we have demonstrated that GM-CSF and IL-3 increase the sensitivity of acute myeloid leukemic (AML) cells to LAK activity. Together, these findings have prompted us to study the role of PRL on the target arm of the LAK response. We show here that CD33+ blasts from AML patients express membrane PRL-R and that the PRL/PRL-R interaction is followed by increased susceptibility to natural killer (NK) (p < 0.02) and LAK (p < 0.001) cells. As predicted from the dimerization model of PRL-R and in agreement with previous reports, the response of AML blasts to PRL was bell-shaped with a trend peak at 25 ng/ml. Although enhanced lysis occurred at the target recognition level, it was not accompanied by changes in the MHC class I, cellular adhesion molecules, or myeloid differentiation antigens. Cell cycle recruitment and lysis increased concurrently in three cases studied, suggesting a modulatory action of PRL on the expression of putative cycle-related NK/LAK-target structures. Together, these data strengthen the role of PRL in the LAK response.

Regulatory action of prolactin on the in vitro growth of CD34+ve human hemopoietic progenitor cells

The pituitary hormone prolactin (Prl) is known to act as a local regulator of immune cell function, and Prl-binding receptors (Prl-R) have been described to share distinctive features with the members of the newly described cytokine/hemopoietin receptor superfamily. Here we show that the hormone can functionally interact with lineage-specific hemopoietic factors. When highly purified progenitor cells (CD34+ve) were seeded in semisolid methylcellulose cultures in the presence of interleukin (IL)-3, granulocyte-macrophage colony stimulating factor (GM-CSF), and erythropoietin (Epo), a selective enhancing effect of Prl on the formation of colony forming unit-granulocyte (CFU-G) and burst forming unit-erythroid (BFU-E) colonies was observed. The effect of the hormone was plotted as a bell shaped curve, with the optimal response at the supraphysiological concentration of 50 ng/ml. Limiting dilution analysis showed that Prl acted directly on hemopoietic progenitors. This was confirmed by the observation on the CD34+ve cells of Prl-binding sites reacting with the specific monoclonal antibodies (mAbs), U5 and PrR-7A. Immunoprecipitation of the metabolically labeled CD34+ve cells with the PrR-7A mAb revealed a structure of 43 kD under reducing conditions. Analysis of the early events associated with the Prl/Prl-R interaction showed an increased number of cells engaged in DNA and hemoglobin synthesis. Enhanced erythroid differentiation of CD34+ve cells in the presence of Prl was secondary to upmodulation of receptors for the lineage-specific factor Epo. Together these data demonstrate the existence of a functional interplay between Prl and hemopoietic factors.

Selection and characterization of an erythroeosinophilic subclone (LAMA-87) and an eosinophilic subclone (LAMA-88) from the multipotential cell line LAMA-84

The human leukemic cell line LAMA-84 was established and characterized as an erythromegakaryocytic cell line. In the present study we show that these cells can differentiate in estrone-treated athymic mice and give rise to an erythroeosinophilic cell line (LAMA-87). This new cell line expressed glycoporin A, alpha beta and gamma globin chain mRNA but also eosinophilic peroxidase. Hemin slightly increased the total hemoglobin production of the cells and phorbol diester (TPA), dimethyl sulfoxide (DMSO) and sodium butyrate (SB) increased the expression of megakaryocytic markers (gpIIb/IIIa complex). When inoculated into non-treated athymic mice, LAMA-87 cells can differentiate to give rise to eosinomonocytic cells (LAMA-88). This new cell line expresses eosinophilic peroxidase, Luxol fast blue stain and synthesizes lysozyme. Depending on the inducer used, LAMA-88 can differentiate along a monocytic lineage (TPA, DMSO, SB and vitamin D3). These three LAMA cell lines should be useful in further studies of the molecular regulation of the pluripotent cell commitment and may provide a model for the understanding of human hematopoiesis.

Effects of growth hormone and prolactin on testicular macrophages in long-term hypophysectomized rats

Long-term hypophysectomized (LTHX) rats were treated for 1 week with growth hormone (rGH, 600 micrograms/kg body wt.), prolactin (rPRL, 600 micrograms/kg body wt.), combined rGH/rPRL or vehicle, to study the effects of these hormones on testicular macrophages. Growth hormone and, to a lesser extent, prolactin significantly increased the number and size of testicular macrophages. The in vivo phagocytic capacity of testicular macrophages was tested by their ability to clear the testicular interstitium of dead Leydig cells after treatment with the specific cytotoxic reagent ethylene dimethane sulphonate (EDS). In vehicle- or rPRL-treated rats, abundant EDS-killed Leydig cells (about 50% of the pre-existent population) remained in the testicular interstitium 72 h after EDS treatment, whereas clearance of the testicular interstitium of dead Leydig cells was largely achieved in rGH- or rGH/rPRL-treated rats. These results indicate that growth hormone and prolactin have stimulatory effects on testicular macrophages in LTHX rats.

The role of prolactin in the pathogenesis of autoimmune disease

Prolactin has emerged in recent years as a major regulator of both the maturation and the function of lymphocytes. Prolactin abnormalities, which include elevated serum levels, decreased bioactivity, abnormal circadian rhythm, and exaggerated secretion after stimulation by TRH, are associated with various autoimmune conditions in humans. Some animal experiments and observations in humans indicate that proiactin has an important role in the pathogenesis of autoimmune disease. There are several mechanisms through which prolactin could promote the development of autoimmunity. It is concluded that prolactin abnormalities alone are not likely to cause autoimmunity, but rather additional regulatory defects are perhaps also required for disease to develop.

Somatolactogens, somatomedins, and immunity

The neuroendocrine and immune systems participate as active partners in host homeostatic and defense mechanisms. This partnership involves a complex intercommunication system employing an array of shared ligands and receptors. Hormones of the somatolactogen family have marked influences on immune events in vivo, including the maintenance of lymphoid tissue cellularity, the promotion of DNA synthesis in these tissues, and the stimulation of a number of immune effector mechanisms. Both growth hormone and prolactin function to promote erythropoiesis and DNA synthesis in bone marrow precursors. Our results have shown that the somatolactogens and a member of the somatomedin family, IGF-I, are particularly effective in modulating the effector functions in phagocytic cells, including the production of reactive oxygen intermediates and tumor necrosis factor-alpha and the oxygen-dependent killing of bacteria. Evidence indicating a role of IGF-I in modulating immune functions is more recent but nonetheless compelling. Accumulated data suggest that somatolactogenic hormones, as well as one member of the somatomedins, are produced by cells of the immune system and can regulate local immune events. Although the molecular mechanisms by which the somatolactogens and somatomedins exert their effects on immune tissues are only now being explored, the pleiotropic nature of these effects suggests that these hormones participate at endocrine, paracrine, and perhaps autocrine sites of action.

Placental lactogen is a haemopoietic hormone

The anaemia and thrombocytopenia of hypophysectomized (Hypox) rats could be corrected readily by daily treatment with human placental lactogen. Spontaneous DNA synthesis in the bone marrow of Hypox rats was grossly impaired, which was also normalized by placental lactogen. Human placental lactogen exerted a direct mitogenic effect on rat bone marrow cells in vitro. These results indicate that placental lactogen is a potent haemopoietic hormone.

Neurohormonal immunoregulation

The immune system may be divided into primary lymphoid organs (bone marrow, bursa of Fabricius, and thymus), which produce mature leukocytes and secondary organs (spleen, lymph nodes, tonsils, Peyer's patches, etc.), which are concerned with specific immune responses. In the primary organs, stem cells proliferate and differentiate into various subsets of polymorphonuclear and mononuclear cells. Evidence is increasing that cell proliferation in the primary lymphoid organs is dependent on pituitary growth hormone (GH) and prolactin (PRL), which control the expression of growth regulatory genes (protooncogenes) such as c-myc and also induce essential growth factors (insulinlike growth factor, thymic and bursal hormones, etc.) and, possibly, their receptors. The adrenocorticotropic hormone-adrenal axis serves as an inhibitory pathway, antagonizing the action of PRL and GH on primary lymphoid tissue. The effect of glucocorticoids is especially forceful on thymocytes through the activation of the genetically programmed suicide pathway. Sex hormones also regulate the primary lymphoid organs, but their mechanism of action remains to be clarified. Thymus-derived feedback signals toward the pituitary gland have already been described. The pituitary gland exerts a similar regulatory influence on mature lymphocytes during their antigen-driven differentiation. PRL or GH is required for primary immune reactions; however, the secondary immune response may be less dependent on these hormones. Once the immune system is primed, antigen itself becomes a primary regulator. Exposure of memory cells to antigen leads to the production of growth factors (interleukins) and to the expression of their receptors. Therefore, antigen appears to fulfill, at this stage, a role that is originally played by GH or PRL in the primary lymphoid organs and, to some extent, also during antigen-driven differentiation. During immune reactions, interleukin-1 and tumor necrosis factor activate the adrenocorticotropic hormoneadrenal axis, which plays an important role in setting upper limits to and terminating responses. Lymphocytes have receptors for and react to numerous hormones, neurotransmitters, and mediators derived from a number of organs and tissues. Therefore, ultimately the reaction of a lymphocyte will be the vector of all positive and negative signals received. A hierarchy and sequential system of signals exists. Primary regulatory signals (competence signals) represent the most powerful regulators (e.g., PRL, GH or antigen) of lymphoid cells. The delivery of a competence signal is the prerequisite for subsequent lymphoproliferation, which is regulated by growth factors that are specific for a certain developmental stage of the lymphoid cell and act sequentially. Hormonal factors that promote growth and differentiation deliver the second regulatory signals. Competence factors and growth and differentiation hormones regulate gene expression in lymphocytes. The third class of signals modulate the function of mature effector cells (e.g., locomotion, secretion, phagocytosis, cytotoxicity). Neuro-transmitters appear to function as secondary signal modulators and tertiary functional regulators.

Hypophysectomy and growth hormone replacement effects on multiple immune responses in rats

Male Fischer 344 rats were hypophysectomized at 8 weeks of age. At 10 weeks of age, one group of these animals was treated with 40 micrograms of bovine somatotropin given daily sc for 13 days. A third group was sham-operated and injected daily with saline. All animals were sacrificed on Day 14 and multiple immune responses were assessed in each rat. Immune responses assayed included specific antibody production and delayed-type hypersensitivity (DTH) reactions to antigen, natural killer (NK) cell cytotoxicity, and production of interleukin 2 (IL2). Body and lymphoid organ weights, hematologic parameters, and spleen cell numbers were also recorded. Hypophysectomized (Hx) rats had reduced antibody synthesis, DTH reactions, NK cytotoxicity, IL2 (or IL4) production, body and organ weights, rbc counts, packed cell volumes, and hematocrits compared to sham-operated controls. White blood cell counts were elevated. Treatment of Hx animals with GH restored antibody and IL2 production and thymic weights and partially restored DTH reactions. These data indicate the pituitary is important in maintaining normal immune functions, and part of this effect may be via production of GH. It is postulated that GH may act through stimulation of IL2 (or IL4).