Prenatal exposure to ethanol alters the neuroimmune response to a central nervous system wound in the adult rat.

We examined the long-term effects of in utero ethanol exposure on the expression of tumor necrosis factor-alpha (TNF-alpha), glial fibrillary acidic protein (GFAP), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and ED1 in the tissue at the site of a central nervous system (CNS) wound. Adult rats obtained from dams fed control diets or an ethanol diet were fed either control diets or an ethanol diet 5 days before and after infliction of a CNS wound. In pair-fed controls, the expression of TNF-alpha, GFAP, ICAM-1, VCAM-1, and ED1 immunoreactive proteins was increased in the tissue at the wound site when compared with that in nonlesioned tissues. In adult rats previously exposed to ethanol in utero and then fed a liquid diet before and after infliction of a CNS wound, however, expression of TNF-alpha, GFAP, and ICAM-1 was markedly decreased when compared with findings in pair-fed controls. In contrast, VCAM-1 levels and ED1 immunoreactive proteins were markedly increased when compared with findings for pair-fed controls. Furthermore, in adult rats exposed to ethanol in utero, re-exposure to ethanol before and after sustaining a CNS wound resulted in further decreases in TNF-alpha, GFAP, and ICAM-1 levels and marked increases in VCAM-1 levels and ED1 immunoreactive proteins. Results of these studies suggest to us that prenatal exposure to ethanol has a long-term immunoteratogenic effect in the CNS, resulting in altered responses of key components of the neuroimmune response, which could leave the animal immunocompromised as an adult.

Ethanol inhibits prolactin- and tumor necrosis factor-alpha-, but not gamma interferon-induced expression of intercellular adhesion molecule-1 in human astrocytoma cells.

In humans, alcohol consumption has multiple effects on the immune system. Despite an increase in our understanding of the effects of alcohol on the immune system, little is known about the effect of alcohol on the neuroimmune response. In the central nervous system (CNS), astrocytes and microglial function as immune effector cells. In response to infection of injury, astrocytes increase in number and size, express several proinflammatory cytokines, MHC class I and II antigens, and several adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1). Interactions between ICAM-1 and its counter-receptors play an important role in the regulation of neuroimmune response. In this study, cultured human astrocytoma cells were used to examine the effect of ethanol on ICAM-1 expression. Western blot analyses show that quiescent astrocytes express, at least, four immunoreactive ICAM-1 proteins with apparent molecular weights 55, 67, 82, and 90 kDa. Incubation of human astrocytoma cells with tumor necrosis factor-alpha (TNF-alpha) or prolactin (PRL) resulted in marked increases in all four immunoreactive ICAM-1 proteins. In the presence of ethanol, however, PRL- and TNF-alpha-induced increases in all four immunoreactive ICAM-1 proteins were markedly inhibited. ICAM-1 is a cell surface transmembrane glycoprotein. Using a cell surface specific ICAM-1 adhesion assay we found that in human astrocytoma cells TNF-alpha, interferongamma (IFN-gamma) and PRL increased cell surface ICAM-1 expression. Consistent with our Western blot analyses, ethanol significantly inhibited TNF-alpha- and PRL-induced cell surface ICAM-1 expression. By contrast, IFN-gamma-induced ICAM-1 expression was not inhibited by exposure of the cells to ethanol. Expression of ICAM-1 is regulated predominantly at the transcriptional level. In the present report, we show that TNF-alpha increased ICAM-1 mRNA levels in human astrocytoma cells and that ethanol markedly blocked TNF-alpha-induced increases in ICAM-1 mRNA levels. Further, we found that PRL-induced ICAM-1 expression was, at least in part, due to a PRL-induced increase in TNF-alpha syntheses and secretion. Our results clearly indicate that ethanol has a pronounced effect on ICAM-1 expression in human astrocytoma cells, thus suggesting that ETOH exposure may impair the immune response in the CNS by blocking leukocytes adhesion and migration into the CNS in response to injury or infection.

Ethanol increases the neurotoxic effect of tumor necrosis factor-alpha in cultured rat astrocytes.

BACKGROUND: The central nervous system is particularly sensitive to the cytotoxic effect of ethanol. In vivo and in vitro studies indicate that ethanol decreases cell proliferation in a number of cells types, including neurons and glial cells in the central nervous system. The cellular mechanisms involved in ethanol-induced cell toxicity, however, are unclear. In this study, we examined the effect of ethanol on tumor necrosis factor-alpha (TNFalpha)-induced cell death in a homogeneous population of cultured rat astrocytes. METHODS: Flow cytometric and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenytetrazolium bromide (MTT) dye reduction analyses were performed on cultured rat astrocytes to determine the effect of alcohol on TNFalpha-induced cell death. RESULTS: Flow cytometric analysis revealed that, in quiescent astrocytes, high concentrations of ethanol were required to increase DNA fragmentation and decrease cell viability. Preexposure of astrocytes to low concentrations of ethanol (10 to 50 mM), however, increased the sensitivity of astrocytes to TNFalpha with low TNFalpha concentrations (25 to 50 ng/ml) resulting in increased DNA fragmentation. Furthermore, MTT dye reduction analysis revealed that exposure of astrocytes to 5 mM ethanol was sufficient to increase the susceptibility of astrocytes to the cytotoxic effect of ethanol. In a number of cell types, TNFalpha receptor binding results in the activation of specific signal transduction cascades, including the hydrolysis of sphingomyelin to ceramide. We show that preexposure of astrocytes to a low concentration of ethanol increased the sensitivity of astrocytes to sphingomyelinase, and C2-ceramide resulting in increased DNA fragmentation and decreased cell viability. More importantly, astrocytes prepared from rats exposed to ethanol prenatally showed increased susceptibility to TNFalpha-induced cell death. CONCLUSIONS: These studies suggest that ethanol increases the susceptibility of astrocytes to TNFalpha-induced cell death by shifting the balance of sphingolipid metabolism in favor of a pathway that increases the susceptibility of astrocytes to the cytotoxic effect of TNFalpha.

Induction of transcription factor interferon regulatory factor-1 by interferon-gamma (IFN gamma) and tumor necrosis factor-alpha (TNF alpha) in FRTL-5 cells.

While it is well known that interferon-gamma (IFN gamma) and tumor necrosis factor-alpha (TNF alpha) play a role in the regulation of thyroid growth and differentiated functions, the cellular and molecular mechanisms involved in mediating the effects of IFN gamma and TNF alpha on thyroid function are unknown. In the present study, we used FRTL-5 rat thyroid cells to examine the effects of IFN gamma and TNF alpha on gene expression of transcription factor interferon regulatory factor-1 (IRF-1), which is involved in mediating the effects of these cytokines in a number of cell types. Northern blot analysis of FRTL-5 mRNA showed a single IRF-1 mRNA at 2.2 Kb. In quiescent FRTL-5 cells, IRF-1 mRNA levels were low but detectable by Northern analysis. Incubation of FRTL-5 cells with IFN gamma or TNF alpha resulted in a dose- and time-dependent increase in IRF-1 mRNA levels. We have shown that TNF-alpha and IFN-gamma act synergistically to block the TSH-induced increase in type I 5'-deiodinase(5'D-I) activity and 5'D-I gene expression in FRTL-5 rat thyroid cells. Incubation of FRTL-5 cells with IFN gamma and TNF alpha in combination, however, did not synergistically increase IRF-1 mRNA levels. Electrophoretic mobility shift assay (EMSA) revealed that IFN gamma induced the formation of a single complex to a IFN gamma activation site (GAS) probe in a dose dependent manner. Several lines of evidence suggest that TNF alpha activates transcription factor nuclear factor-kappa B (NF kappa B) through activation of protein kinase C (PKC) or the hydrolysis of sphingomyelin to ceramide in a number of cell types. Here we demonstrate that hydrolysis of sphingomyelin to ceramide by sphingomyelinase (SMase), but not activation of PKC by 12-O-tetradecanoylphorbol 13-acetate (TPA), was involved in the activation of NF kappa B in FRTL-5 cells. Similarly, hydrolysis of sphingomyelin to ceramide, but not activation of PKC, resulted in an increased in IRF-1 mRNA levels in FRTL-5 cells. The present data demonstrate that IFN gamma and TNF alpha increase IRF-1 mRNA levels in FRTL-5 cells through activation of GAS and NF kappa B binding proteins, respectively. Thus, our results suggest that upregulation of IRF-1 may play a role in mediating the effects of IFN gamma and TNF alpha on thyroid function. Our results also suggest that the induction of IRF-1 mRNA by IFN gamma and TNF alpha is not the cellular mechanism involved in the synergistic effect of these cytokines on thyroid function.

Ethanol inhibits prolactin-induced activation of the JAK/STAT pathway in cultured astrocytes.

Alcohol consumption has multiple effects in the central nervous system (CNS). Whereas, alcohol is an immunosuppressive drug the effect of alcohol on the neuroimmune system, remains unclear. In cultured astrocytes, prolactin (PRL) induces mitogenesis and the expression of inflammatory cytokines, including tumor necrosis factor-alpha (TNF alpha). We have recently shown that whereas ethanol does not inhibit PRL receptor binding, it markedly inhibits PRL-induced mitogenesis and TNF alpha secretion in cultured astrocytes. It is clear that PRL activates the tyrosine phosphorylation of several proteins, including members of a novel family of protein tyrosine kinases, the Janus Kinases (JAKs). The aims of this study were to characterize PRL-induced activation of the JAK/STAT (signal transducers and activators of transcription) pathway, and to determine if ethanol affects JAK/STAT activation in cultured astrocytes. We found that PRL specifically increases the tyrosine phosphorylation of JAK2, but not JAK1, JAK3, or Tyk2, and the subsequent phosphorylation of STAT1 alpha, STAT5a, and STAT5b. Preincubation of astrocytes with ethanol markedly inhibited phosphorylation of JAK2, STAT1 alpha, STAT5a, and STAT5b. In PRL-stimulated astrocytes, ethanol inhibited binding of nuclear proteins to oligonucleotides corresponding to the gamma-interferon activated sequence (GAS). Further, ethanol blocked PRL-induced increases in interferon regulatory factor-1 (IRF-1) mRNA, a PRL/cytokine inducible transcription factor involved in the regulation of a number of cytokine inducible genes. The inhibition of tyrosine phosphorylation by ethanol was not a general effect, however, as we found that ethanol increased basal and NGF-induced tyrosine phosphorylation of extracellular signal-activated protein kinase-1 (ERK-1). These data indicate that ethanol inhibits PRL-induced tyrosine phosphorylation of the JAK/STAT pathway resulting in decreased nuclear GAS DNA binding and inhibition of the PRL inducible gene, IRF-1. Thus, suggesting that ethanol-induced inhibition of JAK2 phosphorylation may be one mechanism though which ethanol could after the brain's response to injury or infection.

Increased expression of tumor necrosis factor-alpha and decreased expression of thyroglobulin and thyroid peroxidase mRNA levels in the thyroids of iodide-treated BB/Wor rats.

Several lines of evidence suggest that tumor necrosis factor-alpha (TNFalpha) may contribute to the pathogenesis of autoimmune thyroid disease. It is not known, however, whether increased thyroidal TNFalpha levels are associated with changes in thyroid function. The purpose of the present study was to utilize in situ hybridization histochemistry and immunohistochemistry to determine if the expression of TNF-alpha in the thyroid is associated with a decrease in thyroglobulin (Tg) and thyroid peroxidase (TPO) mRNA levels. Lymphocytic thyroiditis was induced in BB/Wor rats by iodide administration, and thyroidal Tg and TPO mRNA levels were assessed by Northern blot analysis and in situ hybridization, and TNFalpha expression by Northern blot analysis and immunohistochemistry. Thyroids were obtained before and 1 and 2 months after iodide administration. Hematoxylin and eosin staining revealed that there was a progressive increase in mononuclear cells in the thyroids of BB/Wor rats ingesting iodide for 1 and 2 months. Northern blot analysis revealed that during the same time course there was a progressive increase in TNFalpha mRNA levels and a progressive decrease in Tg and TPO mRNA levels in the thyroids. In situ hybridization histochemistry was performed to determine if the decrease in Tg and TPO mRNA levels was associated with thyroid follicular cells in contact with infiltrating mononuclear cells. In rats treated with iodide for 1 month, there was a modest decrease in Tg and TPO mRNA levels in follicular cells in contact with infiltrating mononuclear cells. After 2 months of iodide treatment there was clearly a localized decrease in Tg and TPO mRNA levels in follicular cells in contact with infiltrating mononuclear cells. Immunohistochemical analysis did not detect TNFalpha in the thyroids from control rats or from rats treated with iodide for 1 month. In contrast, after 2 months of treatment, TNFalpha was easily detected in infiltrating mononuclear cells and in some thyroid follicular cells. Together, these results suggest that the suppression of Tg and TPO mRNA levels was associated with the expression of TNFalpha and thus are in agreement with in vitro studies demonstrating that TNFalpha inhibits thyroid cell function.

Effects of human lymphocyte-conditioned medium on MG-63 human osteosarcoma cell function.

Lymphocytes are implicated in the pathogenesis of bone disease in chronic inflammation, osteoporosis, transplantation and osteopetrosis. The effects of lymphocytes and lymphocyte-conditioned medium on bone-resorbing activity and osteoclast function have been well studied, but there are few studies of the effects of LCM on bone formation and osteoblast function. The effects of LCM on the function of the MG-63 human osteosarcoma cell line were studied, which, when stimulated with 1,25-(OH)2D3, demonstrates many of the properties of the mature human osteoblast. Lymphocytes contain oestrogen receptors and the model was also used to test the hypothesis that the effects of oestrogen on bone cells may be mediated indirectly via lymphokines. Lymphokines were measured by ELISA in human lymphocyte conditioned medium (LCM) collected following incubation of mixed lymphocytes with or without stimulation for 72 h. Unstimulated LCM increased proliferation of MG-63 cells and this increase was not affected by neutralization of interleukin 1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), tumour necrosis factor (TNF), lymphotoxin alpha, or interferon gamma (IFN-gamma). Phytohaemagglutinin-stimulated LCM decreased proliferation of MG-63 cells, as well as induced expression of IL-6 mRNA, increased alkaline phosphatase production, and inhibited osteocalcin production. The decrease in proliferation was abolished by neutralization of IFN-gamma but was unaffected by neutralization of IL-1, IL-2, IL-3, IL-4, IL-6, GM-CSF, TNF, or lymphotoxin alpha. Neutralization of IFN-gamma in stimulated LCM also partially inhibited the increase in alkaline phosphatase production but had no effects on the decrease in osteocalcin production. Although oestrogen inhibited lymphocyte proliferation, the effects of LCM collected from lymphocytes in the presence of oestrogen on MG-63 cell proliferation and function was no different than the effects of LCM collected in the absence of oestrogen. LCM has multiple effects on MG-63 cell function and gene expression. Lymphocyte stimulation during the preparation of LCM further modulates these effects. Although partially mediated by IFN-gamma, the effects of LCM on these cells cannot be completely explained by individual component lymphokines. This may have implications for understanding the pathophysiology of bone loss in inflammatory disorders as well as possible feedback loops of locally generated cytokines in bone.

Low concentrations of ethanol inhibits prolactin-induced mitogenesis and cytokine expression in cultured astrocytes.

Whereas the immunosuppressive effects of chronic alcohol use have been well documented, little is known about the effect of ethanol on the neuroimmune response. We previously demonstrated that PRL is a potent mitogen and induces the expression of several inflammatory cytokines, including tumor necrosis factor-alpha (TNF alpha) in cultured rat astrocytes. The aim of this study was to examine the effects of ethanol on PRL-induced mitogenesis and TNF alpha expression in cultured rat astrocytes. We found that low concentrations of ethanol blocked PRL-induced increases in [3H]thymidine incorporation and TNF alpha levels. In contrast, ethanol had no effect on platelet-derived growth factor- or fibroblast growth factor-induced increases in [3H]thymidine incorporation. Radioligand binding analysis revealed that ethanol did not effect PRL receptor binding. We also examined the effect of prenatal alcohol exposure (PAE) on PRL-induced mitogenesis and cytokine expression. PAE during the last 5 days of gestation blunted the PRL-induced increase in [3H]thymidine incorporation and TNF alpha levels in cells grown in the absence of ethanol in the culture medium. Addition of ethanol to primary PAE astrocyte cultures resulted in a modest increase in basal [3H]thymidine incorporation, but completely blocked the PRL-induced increase in [3H]thymidine incorporation and TNF alpha levels. In contrast, platelet-derived growth factor- and serum (10%)-induced increases in [3H]thymidine incorporation remained intact. Together, these data indicate that ethanol blocks PRL-induced mitogenesis and the expression of TNF alpha in cultured rat astrocytes and are consistent with the possible inhibition of the astrocytic response by ethanol in vivo.

Effects of ceramide and protein kinase C on the regulation of type I 5'-deiodinase in FRTL-5 rat thyroid cells.

Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic cytokine that is involved in the regulation of thyroid growth and differentiated functions. The cellular and molecular mechanisms involved in mediating the effects of TNF alpha on thyroid function, however, are unknown. In a number of cell types, TNF alpha receptor binding results in the activation of specific signal transduction cascades, including protein kinase C (PKC) and the hydrolysis of sphingomyelin to ceramide. In the present study, we examined the possible role of PKC and the hydrolysis of sphingomyelin to ceramide in the regulation of TSH-induced increases in 5'-deiodinase (5'D-I) activity and 5'D-I messenger RNA (mRNA) levels in FRTL-5 cells. Further, we have recently shown that TNF alpha and interferon-gamma (IFN gamma) act synergistically to block TSH-induced increases in type I 5'D-I activity and 5'D-I gene expression in FRTL-5 rat thyroid cells. Thus, we tested the hypothesis that the activation of one or both pathways is involved in synergistic effect of TNF alpha and IFN gamma on thyroid function. In TSH-stimulated FRTL-5 cells, the addition of 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of PKC, inhibited TSH-induced increases in 5'D-I activity and 5'D-I mRNA levels in a dose-dependent manner. Incubation of FRTL-5 cells with TPA and a minimal effective concentration of IFN gamma (12.5 U/ml) in combination, however, failed to result in a synergistic inhibition of the TSH-induced increase in 5'D-I activity or 5'D-I mRNA levels. Similarly, incubation of FRTL-5 cells with sphingomyelinase (SMase), which converts sphingomyelin to ceramide, inhibited TSH-induced increases in 5'D-I activity and 5'D-I mRNA levels in a dose-dependent manner. Coincubation of FRTL-5 cells with SMase and IFN gamma failed to show a synergistic inhibition of the TSH-induced increase in 5'D-I activity or 5'D-I mRNA levels. Further, incubation of FRTL-5 cells with TPA plus SMase in the presence of IFN gamma failed to result in the synergistic inhibition of TSH-induced increases in 5'D-I activity or 5'D-I mRNA levels. The effect of TPA and SMase on TSH-induced cAMP production was examined. Low concentrations of TPA, which inhibit TSH-induced 5'D-I activity, failed to inhibit TSH-induced cAMP production or the cAMP-induced increase in 5'D-I activity. In contrast, SMase inhibited TSH-induced cAMP production in a dose-dependent manner. In the presence of IFN gamma, however, activation of either or both pathways is not sufficient to result in a synergistic inhibition of 5'D-I activity or 5'D-I gene expression. Together, our results suggest that TNF alpha-induced activation of PKC and hydrolysis of sphingomyelin can inhibit thyroid cell function. The activation of additional signal transduction pathways, however, by TNF alpha is required for the synergistic inhibition of thyroid function by TNF alpha and IFN gamma.

Involvement of tyrosine phosphorylation in the regulation of 5'-deiodinases in FRTL-5 rat thyroid cells and rat astrocytes.

Recent studies suggest that protein tyrosine phosphorylation may play a role in the regulation of thyroid growth and function. In the present study, we used genistein, a specific inhibitor of tyrosine phosphorylation, to determine if tyrosine phosphorylation is involved in the regulation of type I 5'-deiodinase (5'D-I) expression in FRTL-5 cells and type II 5'-deiodinase (5'D-II) in rat astrocytes. Incubation of FRTL-5 cells with genistein (100 microM) for 3 days had no effect on cell viability as assessed by trypan blue exclusion. In TSH-deprived cells, incubation of FRTL-5 cells with genistein (100 microM) resulted in a modest, but not significant, decrease in 5'D-I activity. Incubation of FRTL-5 cells with TSH (100 microU/ml), Bu2cAMP (0.5 mM) or forskolin (1 microM) resulted in marked increases in 5'D-I activity. In the presence of genistein (100 microns), however, the TSH, Bu2cAMP and forskolin-induced increases in 5'D-I activity were completely inhibited. In Bu2cAMP-stimulated FRTL-5 cells, incubation with genistein (1, 10, and 100 microM) resulted in a dose-dependent decrease in 5'D-I activity, with 100 microns genistein completely blocking the Bu2cAMP-induced increase in 5'D-I activity. Similarly, we found that in FRTL-5 cells, genistein (100 microns) completely blocked the Bu2cAMP-induced increase in 5'D-I messenger RNA (mRNA) levels, DNA synthesis as assessed by [3H]thymidine incorporation, and the T3-induced increase in 5'D-I activity. To determine if addition of genistein to FRTL-5 cells resulted in a general inhibition of Bu2cAMP-induced responses, we examined its effect on the Bu2cAMP-induced increase in c-fos mRNA levels. Bu2cAMP-induced c-fos mRNA levels were not affected by the treatment of cells with genistein (100 microM). We then examined the effect of genistein on the Bu2cAMP and hydrocortisone-induced 5'D-II activity in cultured rat astrocytes. Genistein (100 microM) had no effect on cell viability as assessed by trypan blue exclusion. In serum deprived astrocytes, addition of Bu2cAMP (1 mM) and hydrocortisone (100 nM) resulted in a 110-fold increase in 5'D-II activity. Addition of genistein (100 microM) to stimulated astrocytes completely blocked the Bu2cAMP and hydrocortisone-induced increase in 5'D-II activity. The present data suggest that tyrosine phosphorylation-dephosphorylation may play an important role in the regulation of thyroid hormone deiodination and action in the thyroid and brain.

Acidic fibroblast growth factor inhibits osteoblast differentiation in vitro: altered expression of collagenase, cell growth-related, and mineralization-associated genes.

Fibroblast growth factors (FGF) are osteoblast mitogens, but their effects on bone formation are not clearly understood. Most in vitro studies examining the effects of FGFs on osteoblasts have been performed only during the initial proliferative stage of osteoblast culture. In these studies, we examined the consequential effect of acidic FGF in cultures of rat fetal diploid osteoblasts that undergo a developmental differentiation program producing a mineralized bone-like matrix. During the initial growth period (days 1-10), addition of acidic FGF (100 micrograms/ml) to actively proliferating cells increased (P < 0.05) 3H-thymidine uptake (2,515 +/- 137, mean +/- SEM vs. 5,884 +/- 818 cpm/10(4) cells). During the second stage of maturation (days 10-15), osteoblasts form multilayered nodules of cells and accumulate matrix, followed by mineralization (stage 3, days 16-29). Addition of acidic FGF to the osteoblast cultures from days 7 to 15 completely blocked nodule formation. Furthermore, addition of acidic FGF after nodule formation (days 14-29) inhibited matrix mineralization, which was associated with a marked increase in collagenase gene expression, and resulted in a progressive change in the morphology of the nodules, with only a few remnants of nonmineralized nodules present by day 29. Histochemical and biochemical analyses revealed a decrease in alkaline phosphatase and mineral content, confirming the acidic FGF-induced inhibition of nodule and matrix formation. To identify mechanisms contributing to these changes, we examined expression of cell growth and bone phenotypic markers. Addition of acidic FGF during the proliferative phase (days 7-8) enhanced histone H4, osteopontin, type I collagen, and TGF-beta mRNA levels, which are coupled to proliferating osteoblasts, and blocked the normal developmental increase in alkaline phosphatase and osteocalcin gene expression and calcium accumulation. Addition of acidic FGF to the cultures during matrix maturation (days 14-15) reactivated H4, osteopontin, type I collagen, and TGF-beta gene expression, and decreased alkaline phosphatase and osteocalcin gene expression. In an in vivo experiment, rats were treated with up to 60 micrograms/kg/day acidic FGF intravenously for 30 days. Proliferation of osteoblasts and deposition of bone occurred in the marrow space of the diaphysis of the femur in a dose-related fashion. The metaphyseal areas were unaffected by treatment. In conclusion, our data suggest that acidic FGF is a potent mitogen for early stage osteoblasts which leads to modifications in the formation of the extracellular matrix; increases in TGF-beta and collagenase are functionally implicated in abrogating competency for nodule formation. Persistence of proliferation prevented expression of alkaline phosphatase and osteocalcin, also contributing to the block in the progression of the osteoblast developmental sequence.

Regulation of prolactin receptor expression by estradiol in the female rat brain.

Prolactin (PRL) receptors have been identified in many tissues, including the brain, but little is known about their distribution and regulation. In the female rat brain, ovariectomy significantly (p < 0.05) decreased PRL binding capacity, but not the affinity, in the hypothalamus and pons-medulla. Using reverse transcription and polymerase chain reaction (RT-PCR) amplification and Western blot analyses we found both the long and short forms of the PRL receptor mRNAs and proteins in the hypothalamus, pons-medulla and cortex in the female rat. Ovariectomy decreased the expression of short, but not the long form of the PRL receptor in the hypothalamus and pons-medulla, but not the cortex. Administration of estradiol (1.0 mg per 100 g b.w.) restored the PRL binding capacity, protein and mRNA levels of the short form of the receptor back to control levels. These results suggest that the expression and distribution of PRL receptors in the brain are differentially regulated in specific brain regions.

Tumor necrosis factor-alpha and interferon-gamma modulate gene expression of type I 5'-deiodinase, thyroid peroxidase, and thyroglobulin in FRTL-5 rat thyroid cells.

Interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) have many effects on a number of cell types, including thyrotrophs. In the present study, we used FRTL5 cells, a cultured rat thyroid follicular cell line, to examine the effects of IFN-gamma and TNF-alpha on type I 5'-deiodinase (5'D-I) activity and 5'D-I, thyroid peroxidase (TPO) and thyroglobulin (Tg) gene expression. Incubation of FRTL5 cells with the highest concentrations of TNF-alpha and IFN-gamma tested (1000 ng/ml or 1000 U/ml, respectively) for 72 h in the presence and absence of TSH had no effect on cell viability as assessed by trypan blue exclusion. In TSH-deprived FRTL-5 cells, TNF-alpha and IFN-gamma resulted in a small but dose-dependent decrease in 5'D-I activity. TNF-alpha or IFN-gamma blocked the TSH- or cAMP-induced rise in 5'D-I activity. 100 ng/ml TNF-alpha and 100 U/ml IFN-gamma completely blocked the TSH- or cAMP-induced rise in 5' D-I activity. However, when cells were incubated with TNF-alpha and IFN-gamma, in combination, there was a marked decrease in 5'D-I activity, with TNF-alpha (25 ng/ml) plus IFN-gamma (25 U/ml) completely blocking the TSH-induced rise in 5'D-I activity. Northern blot analyses were performed to examine the effect of TNF-alpha and IFN-gamma on 5'D-I gene expression. TNF-alpha had little effect on 5'D-I messenger RNA (mRNA) levels, while IFN-gamma resulted in a modest decrease in 5'D-I mRNA levels in TSH-deprived cells, and in TSH-stimulated FRTL-5 cells. However, when TNF-alpha and IFN-gamma were added in combination there was a marked decrease in 5'D-I gene expression with TNF-alpha (50 ng/ml) plus IFN-gamma (50 U/ml) decreasing 5'D-I mRNA levels by 89 percent in TSH-deprived cells. In TSH-stimulated cells incubated with 500 ng/ml TNF-alpha plus 500 U/ml IFN-gamma, 5'D-I mRNA levels were almost undetectable. We also examined the effect of IFN-gamma and TNF-alpha on TPO and Tg gene expression. As observed with 5'D-I mRNA levels, there was a synergistic effect of IFN-gamma and TNF-alpha on the inhibition of basal and TSH-stimulated TPO and Tg gene expression. These findings indicate that TNF-alpha and IFN-gamma in combination have a marked inhibitory effect on thyroid function, which is consistent with a decrease in thyroid hormone synthesis and metabolism.

Prolactin induced expression of interleukin-1 alpha, tumor necrosis factor-alpha, and transforming growth factor-alpha in cultured astrocytes.

Prolactin (PRL) is a potent mitogen in cultured astrocytes. Because one of the major effects of astrocyte proliferation is the expression of inflammatory cytokines, we examined the effect of PRL-induced mitogenesis on the expression of interleukin-1 (IL-1 alpha), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-alpha (TGF-alpha) in cultured astrocytes. Astrocytes were stimulated with PRL or growth hormone (GH), and the expression of cytokines was determined by immunohistochemistry and Western blot analysis. Following incubation of astrocytes with 1 nM PRL for 6 h, strong positive staining of IL-1 alpha and TNF-alpha, but not TGF-alpha, was found. No detectable staining for the above cytokines was found in vehicle, or GH treated astrocytes. When astrocytes were incubated in the presence of 1 nM PRL for 18 h, strong positive staining for IL-1 alpha and TGF-alpha was found. Immunocytochemical analysis of the expression of TNF-alpha and IL-1 alpha in PRL stimulated astrocytes suggested that the expression of IL-1 alpha preceded the expression of TNF-alpha. To confirm this observation, Western blot analyses were performed on extracts from astrocytes incubated with 1 nM PRL in unstimulated astrocytes, IL-1 alpha levels were not detectable. In astrocytes stimulated with 1 nM PRL, expression of IL-1 alpha was clearly detected after 1 h of incubation, and IL-1 alpha levels continued to increase during the course of the experiment (6 h). In contrast, in astrocytes stimulated with 1 nM PRL, an increase in the expression of TNF-alpha was first apparent after 2 h of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin induced expression of glial fibrillary acidic protein and tumor necrosis factor-alpha at a wound site in the rat brain.

To determine if PRL stimulates astrocyte proliferation and cytokine expression in vivo, we examined the effect of PRL on the wound-induced increase in the expression of glial fibrillary acid protein (GFAP) and tumor necrosis factor-alpha (TNF-alpha) in the CNS. Low levels of GFAP detected by Western blot analysis were identified in the non-wounded controls. Five days after the infliction of the wound, the relative abundance of GFAP in the tissue surrounding the wound site was greater than those of intact controls. Injection of PRL into the wound site markedly increased GFAP expression in the hypothalamus. Western blot analysis failed to detect TNF-alpha in the hypothalamus of non-wounded animals. In contrast, TNF-alpha was easily detected in the hypothalamus of wounded rats, and was markedly increased in PRL injected animals. To confirm the PRL-induced increase in TNF-alpha levels, TNF-alpha levels in hypothalamic extracts were measured by bioassay. In non-wounded controls, low but detectable TNF-alpha levels were found in the hypothalamus by bioassay (0.13 +/- 0.02 ng/mg protein). Infliction of a hypothalamic wound markedly increased TNF-alpha levels to 1.4 +/- 0.3 ng/mg protein. Injection of PRL into the wound site resulted in a further increase in TNF-alpha levels to 11.4 +/- 2.6 ng/mg protein. Further, infliction of the hypothalamic wound increased hypothalamic PRL content and PRL mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of fibroblast growth factor on type I 5'-deiodinase in FRTL-5 rat thyroid cells.

In the present study, we used FRTL-5 cells to study the effects of fibroblast growth factors (FGFs) on 5'-deiodinase (5'D) activity and messenger RNA (mRNA) levels. In FRTL-5 cells deprived of TSH for 7 days, type I 5'-deiodinase (5'D-I) activity decreased to low, but detectable levels. Incubation of cells with acidic and basic FGFs significantly decreased 5'D-I activity below the basal levels. After 7 days of TSH deprivation, the addition of TSH (100 microU/ml) to the medium for 3 days resulted in an increase in 5'D-I activity. This TSH-induced increase in 5'D-I activity was blocked by the FGFs in a dose-dependent manner. Kinetic analysis revealed that both acidic and basic FGFs decreased the maximum velocity of 5'D-I activity in the presence or absence of TSH, without any significant effect on the Km of enzyme binding. HPLC analysis of the products of the 5'D-I assay revealed that there was no sequential deiodination of rT3. Incubation of FRTL-5 cells with acidic or basic FGF did not affect basal cAMP concentrations, nor did they block the TSH-induced rise in cAMP. However, acidic and basic FGFs inhibited forskolin- and (Bu)2cAMP-induced increases in 5'D-I activity. Incubation of FRTL-5 cells with TSH, (Bu)2cAMP, and forskolin increased 5'D-I mRNA levels. Incubation of FRTL-5 cells with acidic and basic FGFs decreased steady state 5'D-I mRNA levels and blocked the TSH-, forskolin-, and (Bu)2cAMP-induced increases in 5'D-I mRNA. In conclusion, we have demonstrated that FGFs inhibit 5'D-I activity and mRNA levels in FRTL-5 cells in the presence or absence of TSH. The inhibitory effect of FGFs on 5'D-I in FRTL-5 cells is mediated through either a cAMP-independent pathway or pathways distal to the generation of cAMP. The present data together with the identification of FGF in the thyroid gland suggest that FGF may play a physiological role in the regulation of thyroid hormone secretion.

Gene expression and serum thyroxine-binding globulin are regulated by adrenal status and corticosterone in the rat.

Supraphysiological doses of glucocorticoids reduce serum T4-binding globulin (TBG) concentrations when administered to human subjects. Studies were performed in rats to determine if glucocorticoid administration alters serum TBG in another species, if circulating concentrations of glucocorticoids tonically affect serum TBG concentrations, and if changes in TBG production are likely to be a cause of the glucocorticoid-induced changes in serum TBG concentrations that are observed in humans. The serum TBG-binding capacity was 14.9 +/- 2.3 nmol/liter in adrenalectomized male rats compared to 6.6 +/- 1.0 nmol/liter in intact male rats and 4.8 +/- 0.9 nmol/liter in adrenalectomized male rats that received corticosterone in a dose equal to or less than the replacement dose, as assessed by thymus weight (P < 0.01 for serum TBG in adrenalectomized vs. intact or adrenalectomized corticosterone-treated groups). Hepatic TBG mRNA content, as assessed by polymerase chain reaction amplification and expressed as a ratio of beta-actin mRNA content, was 0.10 +/- 0.03 density units in intact male rats, 0.59 +/- 0.17 density units in adrenalectomized male rats, and 0.05 +/- 0.02 density units in adrenalectomized corticosterone-treated male rats (P < 0.03 for adrenalectomized vs. intact or adrenalectomized corticosterone-treated rats). Adrenalectomy increased the serum TBG-binding capacity in female rats (intact female rats, 13.9 +/- 1.0 nmol/liter; adrenalectomized female rats, 39.0 +/- 6.4 nmol/liter; P < 0.01). These studies indicate that serum TBG is tonically down-regulated by adrenal glucocorticoids, because corticosterone decreases the TBG production rate, probably at the level of transcription. This effect is similar to that described for corticosterone-binding globulin, but differs from that for many proteins of the serine protease inhibitor family that are related to TBG.

Prolactin-stimulated mitogenesis of cultured astrocytes is mediated by a protein kinase C-dependent mechanism.

Prolactin (PRL) has been reported to activate cellular proliferation in nonreproductive tissue, such as liver, spleen, and thymus. Recently, we have extended the possible role of PRL as a mammalian mitogen by demonstrating a mitogenic effect of PRL in cultured astrocytes. Although the cellular mechanisms by which PRL regulates cell growth are not fully understood, protein kinase C (PKC) has been implicated as one of the transmembrane signaling systems involved in the regulation of PRL-induced cell proliferation in Nb2 lymphoma cells and liver. In the present studies, we examined the possible role of PKC in PRL-induced proliferation of cultured astrocytes. Incubation of cultured astrocytes with 1 nM PRL resulted in a rapid translocation of PKC from the cytosol to the membrane, with maximal PKC activity in the membrane occurring 30 min after exposure to PRL. Translocation of PKC activity occurred over a physiological range of PRL, with maximal PKC activation occurring at 1 nM. At concentrations greater than 10 nM PRL, there was a decrease in the amount of PKC activity associated with the membrane fraction compared with that of cells stimulated with 1 nM PRL. Incubation of astrocytes with PRL in the presence of the PKC inhibitors staurosporine, 1-(-5-isoquinolinesulfonyl)-2-methylpiperazine, or polymyxin B blocked the PRL-induced increase in cell number with IC50 values of approximately 2 nM, 10 microM, and 6 microM, respectively. PKC is the only known cellular receptor for 12-O-tetradecanoylphorbol 13-acetate (TPA), which stimulates the translocation of PKC from the cytosol to the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidic fibroblast growth factor modulates gene expression in the rat thyroid in vivo.

We have recently demonstrated that the iv administration of acidic fibroblast growth factor (a-FGF) to rats for 6 days results in a marked increase in thyroid weight with colloid accumulation and flat, quiescent follicular cells. Whereas a-FGF administration consistently increases thyroid weight, there are only minor alterations in serum TSH and thyroid hormones, and no change in intrathyroidal metabolism of 125I metabolism. In the present work, we studied the effects of 1 or 6 daily injections of a-FGF (60 micrograms/kg BW) or vehicle on the mRNA levels for histone, c-fos, actin, type I 5' deiodinase (5'D-I), thyroid peroxidase, and thyroglobulin and cathepsin D in the thyroid, liver and bone. Rats were sacrificed 0.5, 2, 4, 8 and 24 h after the 1st or the 6th a-FGF injection and thyroid, liver, and calvarium were removed. The relative amounts of mRNAs were determined by slot blot analysis. There was a 43% increase in thyroid weight in rats treated with a-FGF for 6 days compared to vehicle-treated rats. We observed an increase in c-fos mRNA content in the thyroid gland 0.5 to 4 h after 1 or 6 injections of a-FGF. In contrast, treatment with a-FGF for 1 or 6 days did not affect histone mRNA content, a marker of proliferative activity or actin mRNA levels. Treatment with a-FGF caused a marked decrease in thyroid 5' D-I mRNA content in the thyroid. The decrease was present 2 h after the first injection and reached a nadir 8 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

Estradiol increases prolactin synthesis and prolactin messenger ribonucleic acid in selected brain regions in the hypophysectomized female rat.

Immunoreactive PRL which is not of pituitary origin, has been identified in many regions of the rat brain. We have previously demonstrated that estradiol increases hypothalamic immunoreactive PRL content in hypophysectomized female rats. To determine if estradiol stimulates PRL synthesis, we examined the effect of estradiol on the in vivo production of PRL, and on the expression of PRL messenger RNA (mRNA) in the hypothalamus, pons, and cerebral cortex. To examine the effect of estradiol on the in vivo production of PRL, [35S] methionine was injected into the lateral ventricle and its incorporation into immunoprecipitable PRL was determined by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In estradiol, but not vehicle-treated hypophysectomized rats, a 24,000 M(r) immunoprecipitable PRL protein was detected in the hypothalamus and pons-medulla, 2 and 4 h after methionine administration. No immunoprecipitable PRL proteins were detected in the amygdala, hippocampus, cortex, or serum at either time point. In addition, in the hypothalamus, but not the pons-medulla, a second PRL band was detected with an apparent mol wt of 16,000K. To determine if estradiol increased the expression of PRL mRNA, copy DNA was obtained by reverse transcription of poly(A+) mRNA prepared from intact and vehicle or estradiol-treated hypophysectomized rats and analyzed by polymerase chain reaction amplification. In tissues from hypophysectomized rats, there was little, or no, detectable levels of PRL mRNA. In contrast, in estradiol-treated hypophysectomized rats PRL mRNA was easily detected in the hypothalamus and pons-medulla by polymerase chain reaction amplification. These data suggest that estradiol increases the PRL content in the hypothalamus and pons-medulla by increasing PRL gene expression, in a manner similar to that reported in the pituitary.