Expression of retinoic acid receptor subtypes and cellular retinoic acid binding protein-II mRNAs during differentiation of human trophoblast cells

An in vitro model of trophoblast cell differentiation has been used to examine the developmental expression of retinoid receptor mRNAs during the differentiation of human placental cytotrophoblast cells to syncytiotrophoblast cells. The levels of RAR alpha, RAR beta, RXR alpha mRNA increased by 12, 7, and 3 fold, respectively, during trophoblast differentiation, while the levels of RAR gamma mRNA remained relatively constant; and the increase in retinoid receptor mRNA expression preceded the increase in the expression of placental lactogen (hPL), a specific marker of syncytiotrophoblast cells. CRABP-II mRNA levels were lower in cytotrophoblast cells than in syncytiotrophoblast cells. Mobility shift assays demonstrated the appearance of a specific band that bound to a labeled DNA probe containing a retinoic acid responsive element (RARE) that was most intense from nuclear extracts from syncytiotrophoblast cells. These results suggest possible roles for these receptors in the regulation of trophoblast differentiation and hPL gene expression.

Effects of glucocorticoids and chronic inflammatory stress upon anterior pituitary interleukin-6 mRNA expression in the rat

During development of adjuvant arthritis (AA) in the rat, anterior pituitary interleukin-6 (IL-6) mRNA expression was increased. Following adrenalectomy and AA there was a further increase in the accumulation of pituitary IL-6 transcript. Corticosterone (B) replacement in adrenalectomized (ADX) animals resulted in a dose-dependent reduction in pituitary IL-6 mRNA accumulation, while in ADX plus AA animals these effects of B were less marked. Cyclosporine A (CsA) markedly reduced the AA-induced increase in IL-6 mRNA. These data are consistent with an immunologically-mediated activation of pituitary IL-6 mRNA in AA, which may contribute to the increased activity of the pituitary-adrenal axis seen in this condition.

Direct stimulation of the pituitary by transfer of activated leucocytes

Some strains of rat develop arthritis, and have profoundly elevated adrenocorticotropin (ACTH) and corticosterone, following intradermal injection of an adjuvant containing heat-killed mycobacteria. Transfer to syngeneic recipients of immune spleen (IS) cells taken from arthritic rats 14 days after injection of the adjuvant, but not of non-immune cells, causes increased circulating ACTH and increased pituitary proopiomelanocortin (POMC) mRNA. Transfer of immune cells does not transfer the disease, but does protect recipients from subsequent challenge with the adjuvant. In these immune-protected rats, the secondary immune response raises ACTH and POMC to levels similar to those seen in arthritic rats. These data show that endogenous inflammatory mediators have direct actions on the neuroendocrine system.

Modulation of IGF-2 expression during growth and differentiation of human neuroblastoma cells: retinoic acid may induce IGF-2

Insulin-like growth factor 2 (IGF-2) is the major autocrine growth factor for neuroblastoma. IGF-2 mRNA can just be detected in SK-N-BE(2) cell line; higher levels are present in two clones derived from it [BE(2)-C; BE(2)-M17]. IGF-2 mRNA is increased by retinoic acid (RA) only in the clones. IGF-2 expression/induction is more marked in BE(2)-M17, which shows more RA-resistance (evaluated as growth inhibition, neurite outgrowth and induction of programmed cell death). Under RA exposure, the parental line shows a more pronounced growth inhibition, neurite outgrowth and programmed cell death, as compared to its clones. BE(2)-C cells also express type 1 IGF receptor mRNA, though with a different time course than for expression of IGF-2. The data suggest that IGF-2 expression is correlated with growth, and may counteract the growth retardation, neurite outgrowth and programmed cell death effects of retinoic acid. Therefore the autocrine pattern of IGF-2 production by neuroblastoma cells may promote RA-resistance.

Glucocorticoid-mediated responses of plasma ACTH and anterior pituitary pro-opiomelanocortin, growth hormone and prolactin mRNAs during adjuvant-induced arthritis in the rat

Adjuvant arthritis (AA) in the rat leads to chronic stimulation of the hypothalamic-pituitary-adrenal (HPA) axis and the loss of its diurnal rhythmicity. We have investigated the effects of adrenalectomy (ADX) and different levels of corticosterone replacement upon plasma ACTH levels and anterior pituitary pro-opiomelanocortin (POMC), GH and prolactin mRNAs during the development of AA. In control ADX animals, we observed the negative feedback effects of exogenous corticosterone on plasma ACTH and anterior pituitary POMC mRNA. In the ADX animal with AA, however, the increased POMC mRNA which was observed was not reduced by exogenous corticosterone on day 7 of AA, although the negative feedback effect of corticosterone on plasma ACTH was intact. On day 14, however, even high dose corticosterone replacement failed to have a significant feedback effect on the raised levels of plasma ACTH. In control ADX animals, corticosterone replacement resulted in increased anterior pituitary GH mRNA and reduced prolactin mRNA. In contrast, in ADX animals with AA, GH mRNA was reduced and there was a further decrease in prolactin mRNA. In these animals, corticosterone replacement did not affect GH or prolactin mRNA expression. These data demonstrate a disruption of the normal mechanisms underlying feedback inhibition of the HPA axis by glucocorticoids during AA. Similarly, the glucocorticoid-dependent regulation of GH and prolactin mRNA expression is altered in AA.

Effects of cyclosporine A on the hypothalamic-pituitary-adrenal axis and anterior pituitary interleukin-6 mRNA expression during chronic inflammatory stress in the rat

In the rat, adjuvant arthritis (AA) is an inflammatory joint disease associated with chronic stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. We have investigated the effects of the immunosuppressive agent cyclosporine A (CsA) on plasma levels of adrenocorticotropin (ACTH) and corticosterone (B), as well as on anterior pituitary proopiomelanocortin (POMC) and interleukin (IL)-6 mRNA accumulation in control and adjuvant-injected animals. In control animals, CsA reduced basal anterior pituitary POMC and IL-6 mRNA and decreased plasma levels of ACTH and B. Adjuvant-injected animals that were treated with CsA showed no clinical signs of AA. Moreover, CsA inhibited the arthritis-induced increases in pituitary POMC and IL-6 mRNA levels and in circulating ACTH and B. In vitro, CsA reduced the POMC mRNA content of cultured anterior pituitary cells and diminished the stimulatory effects of corticotropin-releasing hormone (CRH) on POMC mRNA expression and ACTH secretion from these cells. These data indicate that CsA has a direct action on the HPA axis and also reduces the activation of the HPA axis seen in chronic inflammatory arthritis.

IGF-II mRNA expression in LI human glioblastoma cell line parallels cell growth

A human glioblastoma cell line was found to express in vitro mRNA transcripts specific for insulin-like growth factor-II (IGF-II) and growth-hormone releasing-hormone (GHRH). In the absence of gross morphological changes, retinoic acid reduced the growth rate without major change of IGF-II mRNA expression, while alpha-difluoromethylornithine produced a complete growth arrest and a sharp decrease of IGF-II mRNA expression. Both reagents increased the expression of GHRH mRNA. Also in this glioblastoma cell line, like other neuroectodermal tumours, IGF-II mRNA is expressed independently from GHRH and seems to be parallel to growth rate.

Interleukin-6 and corticotrophin-releasing hormone mRNA are modulated during differentiation of human neuroblastoma cells

Two cell clones [BE(2)-C and BE(2)-M17] derived from the human neuroblastoma cell line SK-N-BE(2) express corticotrophin-releasing hormone as well as interleukin-6 mRNA. Both genes are overexpressed, although with a different time course, following exposure to 5 microM retinoic acid, in parallel to the induction of neuroblastic differentiation. On the contrary, we are unable to detect interleukin-1 beta mRNA in these cell lines. Both cytokines are known to increase hypothalamic CRH mRNA. The production of cytokines and neuropeptides by neuroblastoma cells indicate a complex dialogue between tumour cells and anti-tumour immunity.

Action of interleukin-2 and interleukin-4 on CRF mRNA in the hypothalamus and POMC mRNA in the anterior pituitary

We have used the technique of in situ hybridization histochemistry to determine corticotropin-releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus (PVN) and proopiomelanocortin (POMC) mRNA in the anterior pituitary of rats given a single ip injection of either interleukin (IL)-2 or IL-4. IL-2 increased POMC mRNA in the anterior pituitary in a dose-dependent manner. The effect was apparent both at 4 and 24 h after injection. No effect of IL-2 on CRF mRNA in the PVN was detected in these animals, suggesting that the increase in POMC mRNA was not driven by an increase in CRF. IL-4 was without effect at the hypothalamic level although this cytokine did result in a decrease in POMC mRNA in the anterior pituitary.

An inducible cell line (Natasha), from a neuroblastoma patient with circulating HSR-positive blasts, expressing neurohormones

A cell line, established from a neuroblastoma patient, expresses NCAM and L1 cell adhesion molecules. Two chromosomal abnormalities were present in bone marrow (10%) and cell line (82%) metaphases: (i) a homogeneously staining region (HSR) at the distal part of chromosome 14, and (ii) an insertion of unidentified dark G-banding material in 1 p36. The identification in the patient of chr 14-HSR-positive tumour cells, before the in vitro adaptation, suggests a direct HSR formation without preceding double minutes (dms; or a very early in vivo dms----HSR transformation). N-myc was amplified in the HSR. Cells expressed proopiomelanocortin and corticotropin releasing factor mRNAs. Untreated cells were relatively differentiated; nevertheless they dramatically responded to retinoic acid, forming extensive neurites, growth-cones, cell-cell and cell-neurite junctions. Neurofilaments and synaptic figures containing many dense core granules were identified. This differentiation was irreversible. This cell line is therefore useful for the study of differentiation and in particular for the involvement of neurohormones in the differentiation process.

The effects of recombinant human interleukin (IL)-1 alpha, IL-1 beta or IL-6 on hypothalamo-pituitary-adrenal axis activation

We have investigated the effects of recombinant human interleukin (IL)-1 alpha, IL-1 beta and IL-6 on the activation of the hypothalamo-pituitary-adrenal axis. We have determined the effects of a single i.p. injection of cytokine on circulating ACTH and corticosterone levels, corticotrophin-releasing factor (CRF) mRNA in the parvocellular cells of the paraventricular nucleus and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary at both 4 h and 24 h after injection. IL-1 alpha had no effect on any of the parameters measured at either time-point. In contrast, IL-1 beta increased CRF mRNA in the parvocellular paraventricular nucleus and POMC mRNA in the anterior pituitary 4 h after injection. Plasma ACTH and corticosterone were increased at 4 h and circulating ACTH was still increased at 24 h after treatment with IL-1 beta. IL-6 had no effect on message levels but did increase circulating ACTH and corticosterone levels both 4 h and 24 h after injection. The mechanism responsible for the increase in circulating ACTH after IL-6 injection is unclear but would appear to be different from that which is activated by IL-1 beta which also results in increased CRF and POMC gene expression.

Characterisation of a human glioblastoma cell line (LI) expressing hypothalamic and pituitary hormones

The human glioblastoma cell line LI showed morphological features typical of its neuroectodermal origin. Cells were positive by immunofluorescence to GFAP, MHC class II, and L1 determinants. Cytogenetic analysis showed the presence of a modal chromosome number of 63, ranging from 58 to 69 chromosomes (DNA index was 1.6). Northern blot analysis demonstrated the presence of mRNA transcripts specific for transglutaminase C (type II or "tissue"), growth-hormone releasing-hormone (GHRH), insulin-like growth factor II (IGF-II), and proopiomelanocortin (POMC). The GHRH mRNA was present in two different sizes, one similar to the normal hypothalamic species of 0.75 kb, whilst the second species was a large transcript of approximately 10 kb size. Treatment with 5 microM retinoic acid or 5 mM alpha-difluoromethylornithine for 5 days sharply reduced the growth rate and also induced modulation of the ultrastructure and antigenic profile. This cell line may be useful to study glial differentiation and the relationship of GHRH, IGF-II and POMC expression with differentiation in neuroectodermal tumours.

Chronic activation of the hypothalamo-pituitary-adrenal axis and loss of circadian rhythm during adjuvant-induced arthritis in the rat

Adjuvant-induced arthritis (AA) in Sprague-Dawley rats resulted in a chronic increase in plasma levels of ACTH and corticosterone (B). Joint inflammation became clinically apparent between days 12-15 after injection of adjuvant and reached a peak on day 21, after which time it subsided. In AA animals, plasma ACTH and B levels in the morning (0800-0900 h) on days 7, 8, 9, and 21 were significantly higher than those in control animals (day 0). The corresponding evening ACTH and B levels in AA animals were not significantly different from evening levels in the control animals. Adrenal weight in AA animals was increased on day 21, while thymic weight diminished gradually from days 7-21 postinjection. Development of AA was associated with activation of the hypothalamo-pituitary-adrenal axis, with increased morning ACTH and B levels and abolition of normal diurnal ACTH and B rhythms. This model of chronic inflammatory stress clearly activates the ACTH drive despite increased corticosteroid feedback in the morning, resulting overall in chronically increased B secretion.

Interleukin-1 beta and interleukin-6 mRNA are expressed in human glioblastoma and neuroblastoma cells respectively

We report the expression of different interleukins (IL) in four human glioblastoma and neuroblastoma cell lines. The glioblastoma cell line LI, expresses IL-1 beta and IL-6 mRNA, though not IL-2 and IL-4. The expression of the former gene is modulated by retinoic acid. Two cell clones [BE(2)-C and BE(2)-M17] as well as the neuroblastoma cell line SK-N-BE(2), from which both clones were derived, express IL-6 mRNA, but not IL-1 beta, IL-2 or IL-4. Both IL-1 beta and IL-6 cytokines are known to increase hypothalamic CRH mRNA, a gene reported to be expressed in all these cell lines. The production of both cytokines and neuropeptides indicates a complex dialogue between tumour cells and anti-tumour immunity.

Response of pituitary and spleen pro-opiomelanocortin mRNA, and spleen and thymus interleukin-1 beta mRNA to adjuvant arthritis in the rat

During development of adjuvant-induced arthritis (AA) in the rat, pituitary pro-opiomelanocortin (POMC) mRNA expression was increased. Pituitary POMC mRNA was much higher following adrenalectomy and AA. Spleen POMC mRNA also increased with a similar time kinetics, although the levels in the spleen were much lower than those in the pituitary. In control animals, spleen interleukin-1 beta (IL-1 beta mRNA) was undetectable, whereas AA led to the accumulation of IL-1 beta mRNA and the highest levels were seen in the adrenalectomised AA group. Thymic IL-1 beta expression was also increased in AA animals. These results suggest that AA leads to the activation of both the neuroendocrine and the immune systems and the interaction between these systems may play a role in this disease state.

Characteristics and kinetics of proopiomelanocortin mRNA expression by human leucocytes

Northern blot analysis of total and poly(A)+ RNA demonstrated that human leucocytes contain several proopiomelanocortin (POMC) mRNA species, including 0.8-, 1.2-, 1.5-, and 9.5-kb transcripts. Peripheral blood lymphocytes (PBL) were found to express all four species. The other cell types had either the 0.8-kb species alone or both 0.8- and 9.5-kb species. Neutrophils were the only cells to express the 9.5-kb transcript alone. In T cell clones, both interleukin (IL)-2 alone or the antigen for which the clone was specific induced POMC accumulation within 18-24 h. Cytoplasmic dot blot analysis of PBL RNA demonstrated that POMC expression could be induced by corticotrophin releasing factor, rIL-1, and phorbol ester, but not by calcium ionophore (A23187). In PBL activated in a mixed lymphocyte culture there was increased expression, particularly of the smaller species (0.8, 1.2, and 1.5 kb), within 1-3 days of activation. The intensity of the bands began to decline thereafter. The 9.5-kb POMC transcript essentially disappeared by Day 3.

Production of a growth hormone-releasing hormone-like peptide and its mRNA by human lymphocytes

Human peripheral blood lymphocytes (PBL) contain immunoreactive growth hormone-releasing hormone (irGRH). Both the intracellular content and the release of irGRH from PBL are increased following lymphocyte activation. Although binding of lymphocyte-derived irGRH to a GRH1-44 antibody dilutes in parallel with standard GRH1-44, irGRH elutes earlier on gel chromatography with an apparent molecular weight of approximately 50 kD. On reverse-phase high performance liquid chromatography, irGRH elutes later than GRH1-44. Northern blot analysis also detected the presence of two GRH mRNA transcripts in PBL, one similar in size to the hypothalamic species of 0.75 kb and another larger transcript of approximately 10 kb. Despite these differences in physicochemical behaviour, both the lymphocyte-derived irGRH GRH1-44 were biologically active as demonstrated by enhancing the transcription of growth hormone mRNA both in dispersed rat pituitary cells and in PBL.