The role of Drosophila mushroom body signaling in olfactory memory

The mushroom bodies of the Drosophila brain are important for olfactory learning and memory. To investigate the requirement for mushroom body signaling during the different phases of memory processing, we transiently inactivated neurotransmission through this region of the brain by expressing a temperature-sensitive allele of the shibire dynamin guanosine triphosphatase, which is required for synaptic transmission. Inactivation of mushroom body signaling through alpha/beta neurons during different phases of memory processing revealed a requirement for mushroom body signaling during memory retrieval, but not during acquisition or consolidation.

Apoptosis: one of the mechanisms that maintains unresponsiveness of the intestinal mucosal immune system

Intestinal mucosa is constantly exposed to environmental AGS: Activation of lamina propria (LP) T cells by luminal Ags may lead to the production of inflammatory cytokines and subsequent mucosal inflammation and tissue damage. However, in normal circumstances, LP T cells do not respond to antigenic stimulation. The mechanisms of this unresponsiveness in healthy subjects are not fully understood. In this study, we found by in vivo analysis that, except for T cells in lymph nodules of the mucosa, 15% of LP T cells underwent apoptosis in normal individuals. In contrast, there was a marked reduction in apoptosis of LP T cells in patients with inflammatory bowel disease (Crohn's disease and ulcerative colitis) and those with specific colitis. Our findings suggest that apoptosis might be a mechanism that turns off mucosal T cell responses to environmental Ags in healthy subjects, and resistance to apoptosis could be an important cause of mucosal immune dysregulation and tissue inflammation in colitis.

Alterations in peripheral B cells and B cell progenitors following androgen ablation in mice

The production of B lymphocytes is regulated in part by physiologic levels of androgens and estrogens. While these sex hormones down-regulate B lymphopoiesis, augmentation of B lymphopoiesis occurs under conditions where androgen or estrogen levels are decreased. In this study we examine the effect of androgen ablation of male mice on B lymphopoiesis and on the phenotypic composition of peripheral B lymphocyte populations. Spleen and thymic weights are significantly increased following castration, as is the total number of peripheral blood lymphocytes. However, the absolute numbers of B cells in the periphery are selectively increased following castration; the numbers of T cells, NK cells and granulocytes remain unchanged. The increase in circulating B cells is due largely to increases in the numbers of recent bone marrow emigrants expressing a B220(lo+)CD24(hi+) phenotype and these cells remain significantly elevated in castrated mice for up to 54 days post-castration. Similar increases in the percentages of newly emigrated B cells are observed in mice that lack a functional androgen receptor (TFM:). Finally, assessments of B cell progenitors in the bone marrow revealed significant increases in the relative numbers of IL-7-responsive B cell progenitors, including cells in Hardy fractions B (early pro-B cells), C (late pro-B cells), D (pre-B cells) and E (immature B cells). These findings demonstrate that androgen ablation following castration significantly and selectively alters the composition of peripheral B cells in mice. Further, these alterations result from the potentiating effects of androgen ablation on IL-7-responsive pro-B cell progenitors.

Alterations in CD30(+) T cells in monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of unknown significance (MGUS) is a monoclonal B cell expansion characterized by high levels of circulating monoclonal antibody that affects 3% of individuals over the age of 70. Although this is considered benign, a high percentage of MGUS patients develop a debilitating peripheral autoimmune neuropathy and have a significantly increased risk for progression to multiple myeloma. Here we show that the relative numbers of the CD30(+) T cell subset and levels of CD30 expression are elevated in activated lymphocytes from normal aged individuals (> or =60 years) and in MGUS patients, when compared to younger controls. PBL from MGUS patients and age-matched controls produced comparable levels of IL-6 when activated with anti-CD3 plus IL-2, and costimulation with a soluble form of CD30 ligand (sCD30L/CD8alpha) augmented anti-CD3 inducible IL-6 production similarly in both groups. However, MGUS PBL also produced measurable IL-6 when activated with sCD30L/CD8alpha alone. This capability was associated with the unique presence of CD30(+) T cells in the peripheral blood of MGUS patients. Furthermore, a higher percentage of activated MGUS T cells express CD30 when activated by incubation with idiotype-expressing autologous serum (68 +/- 13) than those activated by anti-CD3 plus IL-2 (43 +/- 7). These results indicate that quantitative alterations in CD30(+) T cells accompany aging and MGUS and that these cells may contribute to the chronic activation of B cells though the production of IL-6.

Human thymic epithelial cells inhibit IL-15- and IL-2-driven differentiation of NK cells from the early human thymic progenitors

T/NK progenitors are present in the thymus; however, the thymus predominantly promotes T cell development. In this study, we demonstrated that human thymic epithelial cells (TEC) inhibit NK cell development. Most ex vivo human thymocytes express CD1a, indicating that thymic progenitors are predominantly committed to the T cell lineage. In contrast, the CD1a(-)CD3(-)CD56(+) NK population comprises only 0.2% (n = 7) of thymocytes. However, we observed increases in the percentage (20- to 25-fold) and absolute number (13- to 71-fold) of NK cells when thymocytes were cultured with mixtures of either IL-2, IL-7, and stem cell factor or IL-15, IL-7, and stem cell factor. TEC, when present in the cultures, inhibited the increases in the percentage (3- to 10-fold) and absolute number (3- to 25-fold) of NK cells. Furthermore, we show that TEC-derived soluble factors inhibit generation of NK-CFU and inhibit IL15- or IL2-driven NK cell differentiation from thymic CD34(+) triple-negative thymocytes. The inhibitory activity was found to be associated with a 8,000- to 30,000 Da fraction. Thus, our data demonstrate that TEC inhibit NK cell development from T/NK CD34(+) triple negative progenitors via soluble factor(s), suggesting that the human thymic microenvironment not only actively promotes T cell maturation but also controls the development of non-T lineage cells such as the NK lineage.

Human small cell lung cancer cells produce brain natriuretic peptide

The tumoral production of brain natriuretic peptide (BNP) was studied using 9 small cell lung cancer (SCLC) cell lines which were established from patients with small cell lung cancer. BNP cDNA fragment was generated from 20 microg total RNA which was prepared from the human right cardiac atrium by reverse transcription-based polymerase chain reaction. Expression of BNP mRNA was detected in 30 microg total cellular RNA from these cell lines by RNase protection assays in 5 of 9 SCLC cell lines. Radioimmunoassays using 125I-radiolabeled human BNP(1-32) and antihuman BNP(1-32) antibody detected immunoreactivity in cell pellets from SCLC cell lines which had detectable BNP mRNA. BNP immunoreactivity in the cell pellets corresponds with the data from BNP mRNA analyses. We conclude that SCLC cells have detectable BNP mRNA by RNase protection assay and BNP immunoreactivity in the cells.

Altered electrophoretic migration of polycyclic aromatic hydrocarbon and styrene oxide adducts at adenine N(6) correlates with adduct-induced structural disorder

Site-specific bay region benzo[a]pyrene (7R,8S,9R,10S)-N(6)-[10-(7,8, 9,10-tetrahydro-7,8,9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadeno syl, (7S,8R,9S,10R)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl, (7S,8R,9R, 10S)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl, and (7R,8S,9S, 10R)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl adducts, bay region benz[a]anthracene (1R,2S,3R,4S)-N(6)-[1-(1,2,3,4-tetrahydro-2,3, 4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl and (1S,2R,3S, 4R)-N(6)-[1-(1,2,3,4-tetrahydro-2,3, 4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl adducts, non-bay region benz[a]anthracenyl (8S,9R,10S,11R)-N(6)-[11-(8,9,10, 11-tetrahydro-8,9,10-trihydroxybenz[a]anthracenyl)]-2'-de oxyadenosyl and (8R,9S,10R,11S)-N(6)-[11-(8,9,10,11-tetrahydro-8,9, 10-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl adducts, and the R- and S-adducts of styrene oxide were located in the ras61 oligodeoxynucleotide and examined with respect to electrophoretic mobility. The results were compared to NMR structural data, and to site-specific mutagenesis data and in vitro DNA replication assays for the same adducts. There was a correlation between adducts having lower electrophoretic mobility and greater disorder at the adduct site as monitored by NMR. The disorder combined with the lower electrophoretic mobilities suggested that these adducts induced flexible hinge joints in the DNA rather than static bending. Usually, these were adenine N(6) adducts having S-stereochemistry at the benzylic carbon. The results also revealed a possible role for the bay region ring in stabilizing adenyl N(6) benz[a]anthracene adducts with respect to hinging at the adduct site. On the other hand, there was not a simple relationship between altered electrophoretic mobility and mutagenesis or DNA replication.

A prospective study of patients with lung cancer and hyponatremia of malignancy

This study was undertaken to define the impact of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) on sodium homeostasis in patients with lung cancer. Patients had their serum and urine electrolytes and osmolality determined before and after a saline infusion of 500 ml. The plasma hormones, AVP, ANP, plasma renin activity (PRA), angiotensin II, and aldosterone were determined by radioimmunoassay every 15 min before, during and after the saline infusion. Fifty patients, 31 with small cell lung cancer and 19 with non-small cell lung cancer participated in this trial. All 11 patients (10 patients with small cell lung cancer and one patient with non-small cell lung cancer) who presented with hyponatremia had inappropriately elevated levels of AVP. Elevated plasma AVP levels were highly correlated with the presence of hyponatremia (p < 0.00001). Initial plasma ANP levels were not associated with hyponatremia (p = 0.73). Urinary sodium concentration increased during the saline infusion proportional to the initial plasma level of ANP (p = 0.0045). AVP appears to be elevated in nearly all patients with hyponatremia of malignancy. ANP plasma levels in patients with lung cancer are associated with the ability to excrete a sodium load but do not appear to downregulate renin, angiotensin II, and aldosterone production.

TGF-beta differentially modulates epidermal growth factor-mediated increases in leukemia-inhibitory factor, IL-6, IL-1 alpha, and IL-1 beta in human thymic epithelial cells

The regulation of cytokine production by thymic epithelial cells (TEC) in the thymus is under coordinated and temporal control and is important for the development of T cells. Human TEC express TGF-beta R and epidermal growth factor (EGF) receptor, and produce TGF-beta 3 in vitro and in vivo. Furthermore, EGF has been shown to increase IL-1 alpha, IL-1 beta, IL-6 mRNA and protein levels in human TEC. Since EGF has been shown to modulate TGF-beta effector functions, we determined whether TGF-beta can modulate EGF-mediated increases in cytokine gene expression in human TEC. We established that a single TEC expresses both EGF receptor and TGF-beta R. TGF-beta plus EGF synergistically increased leukemia-inhibitory factor (LIF), additively increased IL-6, but had little effect on IL-1 alpha and IL-1 beta mRNA levels. In contrast, TGF-beta alone increased LIF and IL-6, had little effect on IL-1 alpha, and slightly decreased IL-1 beta mRNA levels. The increases in LIF and IL-6 mRNA levels by TGF-beta plus EGF correlate with the increases in LIF and IL-6 concentrations in TEC culture supernatants as detected by ELISA. We also determined the mechanism responsible for the increases in cytokine mRNA levels. TGF-beta plus EGF did not affect transcription of LIF and IL-6 genes; this suggests that the increases in the steady state levels of cytokine mRNA were mediated post-transcriptionally, most likely at the level of mRNA stability. Our data demonstrate that TGF-beta modulates TEC cytokine production. We speculate that TGF-beta produced in situ plays a role in thymocyte development by directly affecting thymocyte differentiation and by indirectly modulating TEC cytokine production.

TGF-beta differentially modulates epidermal growth factor-mediated increases in leukemia-inhibitory factor, IL-6, IL-1 alpha, and IL-1 beta in human thymic epithelial cells

The regulation of cytokine production by thymic epithelial cells (TEC) in the thymus is under coordinated and temporal control and is important for the development of T cells. Human TEC express TGF-beta R and epidermal growth factor (EGF) receptor, and produce TGF-beta 3 in vitro and in vivo. Furthermore, EGF has been shown to increase IL-1 alpha, IL-1 beta, IL-6 mRNA and protein levels in human TEC. Since EGF has been shown to modulate TGF-beta effector functions, we determined whether TGF-beta can modulate EGF-mediated increases in cytokine gene expression in human TEC. We established that a single TEC expresses both EGF receptor and TGF-beta R. TGF-beta plus EGF synergistically increased leukemia-inhibitory factor (LIF), additively increased IL-6, but had little effect on IL-1 alpha and IL-1 beta mRNA levels. In contrast, TGF-beta alone increased LIF and IL-6, had little effect on IL-1 alpha, and slightly decreased IL-1 beta mRNA levels. The increases in LIF and IL-6 mRNA levels by TGF-beta plus EGF correlate with the increases in LIF and IL-6 concentrations in TEC culture supernatants as detected by ELISA. We also determined the mechanism responsible for the increases in cytokine mRNA levels. TGF-beta plus EGF did not affect transcription of LIF and IL-6 genes; this suggests that the increases in the steady state levels of cytokine mRNA were mediated post-transcriptionally, most likely at the level of mRNA stability. Our data demonstrate that TGF-beta modulates TEC cytokine production. We speculate that TGF-beta produced in situ plays a role in thymocyte development by directly affecting thymocyte differentiation and by indirectly modulating TEC cytokine production.

Ectopic production and processing of atrial natriuretic peptide in a small cell lung carcinoma cell line and tumor from a patient with hyponatremia

BACKGROUND

Tumors and tumor cell lines from two patients with small cell lung carcinoma (SCLC) (one with and one without hyponatremia) were studied. Ectopic production and prohormone processing of atrial natriuretic peptide (ANP) were investigated to determine if a biologically active peptide was produced in a tumor cell line from a patient with hyponatremia and no evidence of arginine vasopressin (AVP) production.

METHODS

Ribonuclease (RNase) protection assays were performed on mRNA isolated from tumors and tumor cell lines established from two SCLC patients, one with and one without hyponatremia. Cellular extracts and conditioned media were studied using reversed-phase high performance liquid chromatography (HPLC) to determine the immunoreactive form of ANP. Tumor cell line sonicates were studied for subcellular localization of enzymatic activity that cleaved pro-ANP peptide substrates.

RESULTS

RNase protection assays showed a 200-base pair protected fragment in the mRNA isolated from the tumor and tumor cell line from the patient with hyponatremia (Patient 4). HPLC characterization of the cellular extract and conditioned medium from the tumor and tumor cell line from Patient 4 demonstrated ANP immunoreactivity in the same fraction as ANP- (S99-Y126). The tumor cell line extract that localizes to a subcellular fraction enriched for lysosomes and secretory organelles contains a 60-kilodalton molecular weight protein with enzyme activity that hydrolyzes synthetic pro-ANP substrates and catalyzes the formation of ANP-(S99-Y126).

CONCLUSIONS

A tumor cell line from a patient with hyponatremia was able ectopically to produce, process, and secrete ANP in the same immunoreactive form as the biologically active molecule. Preliminary studies show that tumor cell line NCI-H1284 contains an enzyme that can cleave precursors at the same amino acid sequences needed to produce ANP-(S99-Y126) from pro-ANP.

Comparison of apoptosis signaling through T cell receptor, fas, and calcium ionophore

The SUP-T13 cell line, a human T leukemia, is susceptible to apoptosis by various inducers, including anti-TCR mAb, calcium ionophores, and anti-fas mAb. Induction of apoptosis by these three agents was investigated, and several differences were found. All three agents induced DNA fragmentation with a similar time course, but the kinetics of cell death were different for the three agents. Anti-TCR mAb-induced apoptosis, but not A23187- or anti-fas-induced apoptosis, was rescued by anti-CD3 mAb treatment. In contrast, only anti-fas mAb-mediated apoptosis was rescued by PKC activators such as PMA. These differences suggest that each of these three agents mediate apoptosis by unique signaling pathways. Nevertheless, two variant subclones of SUP-T13 were found to be resistant to all three apoptosis-inducing agents, suggesting a point(s) of common regulation between the different pathways. To determine whether this regulation occurred through bcl-2, p53, or c-myc, their expression in the parental and variant cells was determined. The three clones expressed approximately equal amounts of these proteins, and their levels did not change significantly upon treatment with anti-TCR or anti-TCR plus anti-CD3 mAb. Thus, although the proximal signaling by various apoptosis inducers were quite different, a common mediator(s) (as yet unknown) may still regulate apoptosis induced by these multiple agents.

Human thymic epithelial cells produce TGF-beta 3 and express TGF-beta receptors

TGF-beta affects proliferation, differentiation and maturation of T cells; however, the effect of TGF-beta on thymic stromal cells has not been characterized. To better understand the role of TGF-beta in T cell development, we determined whether TGF-beta is present in the human thymus, and identified stromal cells that express TGF-beta receptors and respond to TGF-beta. We demonstrate that primary cultured human thymic epithelial cells (TEC) express TGF-beta 1, TGF-beta 2 and TGF-beta 3, as well as TGF-beta type I receptor (T beta RI) (ALK-5) and TGF-beta type II receptor (T beta RII) transcripts. In vitro, epidermal growth factor (EGF) increases transcript levels of TGF-beta 1, TGF-beta 3 and T beta RII, suggesting that EGF may modulate TGF-beta responses in TEC; however, TGF-beta 2 and T beta RI transcript levels were not affected. We also detect TGF-beta 3 and T beta RII protein in association with keratin-positive TEC in vitro and in vivo. TEC culture supernatants contain TGF-beta 3 as detected by Western blots and, upon heat and acid activation, display growth inhibitory activity on the CCL-64 cells that is neutralized by anti-TGF-beta mAb treatment. We further demonstrate that TGF-beta 1 increases leukemia inhibitory factor transcript levels in TEC, indicating that TEC express functional TGF-beta receptors. Thus, we have shown in the human thymus that TEC produce TGF-beta 3 and express T beta RI and T beta RII. The data suggest that TGF-beta is present in the human thymus and may indirectly affect T cell development by regulating TEC cytokine production.

In situ detection and characterization of apoptotic thymocytes in human thymus. Expression of bcl-2 in vivo does not prevent apoptosis

Apoptosis plays a crucial role in shaping the T cell repertoire during T cell development in the thymus. The observed disappearance in the thymus of CD4+ CD8+ thymocytes with a specific TCR, and the lack of CD4+ or CD8+ single positive mature cells expressing the same TCR specificity in the periphery have led to the conclusion that deletion occurs at the CD4+ CD8+ double positive stage; however, there is no direct evidence demonstrating apoptotic CD4+ CD8+ cells in situ. Apoptosis of thymocytes in situ at other stages of T cell development has also not been reported. Using three-color immunofluorescence and flow cytometric assays on frozen human thymic tissue and freshly isolated human thymocytes respectively, we directly identify CD4+ CD8+ and CD4- CD8- thymocytes in newborn human thymus that contain intracellular fragmented DNA and are therefore apoptotic. We determine that 75% of the apoptotic thymocytes are CD4+ CD8+ double positive apoptotic thymocytes, and interestingly, that 13% are CD4- CD8- double negative thymocytes. The majority of apoptotic thymocytes in situ are detected at the cortical-medullary junction; however, apoptotic thymocytes are also found scattered throughout the cortex. Furthermore, we determine that within the apoptotic thymocyte population, 54% express the apoptotic regulatory protein bcl-2 in vivo, whereas 32% are bcl-2 negative. Thus, our in vivo data directly demonstrate that both CD4+ CD8+ and CD4- CD8- human thymocytes die in situ via an apoptotic process, and that expression of the bcl-2 protein in situ does not prevent immature thymocytes from apoptosis.

In situ detection and characterization of apoptotic thymocytes in human thymus. Expression of bcl-2 in vivo does not prevent apoptosis

Apoptosis plays a crucial role in shaping the T cell repertoire during T cell development in the thymus. The observed disappearance in the thymus of CD4+ CD8+ thymocytes with a specific TCR, and the lack of CD4+ or CD8+ single positive mature cells expressing the same TCR specificity in the periphery have led to the conclusion that deletion occurs at the CD4+ CD8+ double positive stage; however, there is no direct evidence demonstrating apoptotic CD4+ CD8+ cells in situ. Apoptosis of thymocytes in situ at other stages of T cell development has also not been reported. Using three-color immunofluorescence and flow cytometric assays on frozen human thymic tissue and freshly isolated human thymocytes respectively, we directly identify CD4+ CD8+ and CD4- CD8- thymocytes in newborn human thymus that contain intracellular fragmented DNA and are therefore apoptotic. We determine that 75% of the apoptotic thymocytes are CD4+ CD8+ double positive apoptotic thymocytes, and interestingly, that 13% are CD4- CD8- double negative thymocytes. The majority of apoptotic thymocytes in situ are detected at the cortical-medullary junction; however, apoptotic thymocytes are also found scattered throughout the cortex. Furthermore, we determine that within the apoptotic thymocyte population, 54% express the apoptotic regulatory protein bcl-2 in vivo, whereas 32% are bcl-2 negative. Thus, our in vivo data directly demonstrate that both CD4+ CD8+ and CD4- CD8- human thymocytes die in situ via an apoptotic process, and that expression of the bcl-2 protein in situ does not prevent immature thymocytes from apoptosis.

Human thymic epithelial cells: adhesion molecules and cytokine production

The ability to culture human thymic epithelial cells has greatly facilitated studies of direct cell-cell interaction between thymic epithelial cells and T lymphocytes in vitro, as well as cytokine production and regulation of cytokine production. In vitro, human thymic epithelial cells bind to T lymphocytes via two adhesion pathways: CD2-lymphocyte function-associated antigen-3 and lymphocyte function-associated antigen-1-intercellular adhesion molecule-1. Cultured human thymic epithelial cells produce interleukins-1 alpha, -1 beta, -3, -6 and -8, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, leukemia inhibitory factor and transforming growth factor-alpha. Production of thymic epithelial cell-derived cytokines is regulated by both adhesion molecules (lymphocyte function-associated antigen-3) and soluble factors via both autocrine (interleukin-1 alpha, transforming growth factor-alpha) and paracrine (interleukin-4, interferon-gamma) pathways. Transforming growth factor-alpha and epidermal growth factor regulate various cytokine mRNA at a post-transcriptional level by increasing cytokine mRNA stability.

Human small cell lung cancer cell lines express functional atrial natriuretic peptide receptors

Small cell lung cancer cell (SCLC) lines, NCI-H82, NCI-H660, and NCI-H1284, and HeLa cells were analyzed for the presence of atrial natriuretic peptide (ANP) receptors. In these SCLC cell lines and HeLa cells, ANP A receptor mRNA was identified by Southern blot analyses of polymerase chain reaction products and RNase protection assays using poly(A)(+)-selected RNA. Saturable binding assays revealed that HeLa cells had 2000 to 5000 high affinity atrial natriuretic peptide receptors per cell with a dissociation constant of 140 pM. In the SCLC cell lines, the binding was saturable but too low to accurately estimate the number of binding sites. After addition of human ANP, radioimmunoassays revealed accumulation of cyclic GMP in SCLC cells as well as HeLa cells in a dose-dependent fashion. The half-maximal stimulation concentration of cyclic GMP accumulation in HeLa and these SCLC cell lines was approximately 2 nM. Tetrazolyl blue assays and tritiated thymidine incorporation did not show any remarkable growth inhibition or growth stimulation of SCLC cell lines after addition of human ANP up to 3.3 microM, more than 1000-fold greater than the half-maximal stimulation concentration of cyclic GMP accumulation. Our results indicate that human SCLC cells express functional ANP receptors but ANP addition produced no detectable change in their growth pattern.

Atrial natriuretic factor and arginine vasopressin production in tumor cell lines from patients with lung cancer and their relationship to serum sodium

Patients with lung cancer (n = 263) were studied to determine the relationship among ectopic production of atrial natriuretic factors (ANF) and arginine vasopressin (AVP), serum sodium, and patient outcome. Of 133, 21 (16%) patients with small cell lung cancer (SCLC) had hyponatremia (serum sodium, < 130 mmol/liter), compared to none of 130 (0%) patients with non-small cell lung cancer (P < 0.0001). Patients with extensive-stage SCLC and hyponatremia had shorter survival than patients with extensive stage SCLC and normal serum sodium values (P = 0.012). Of the 11 hyponatremic patients with SCLC and tumor cell lines available for study, 9 produced ANF mRNA, 7 of 11 produced AVP mRNA, and 5 of 11 produced both ANF mRNA and AVP mRNA. All 11 cell lines produced either ANF mRNA and ANF peptide or AVP mRNA and AVP peptide, or both. The quantity of AVP peptide in the tumor cell lines was more closely associated with hyponatremia in the patients (P = 0.0026, r2 = 0.28) than was the production of ANF peptide (P = 0.066, r2 = 0.12), although neither association was strong. All tumor cell lines studied from SCLC patients with hyponatremia produce ANF and/or AVP mRNA and peptides.

Regulation of cytokine production in the human thymus: epidermal growth factor and transforming growth factor alpha regulate mRNA levels of interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6 in human thymic epithelial cells at a post-transcriptional level

Human thymic epithelial (TE) cells produce interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6, cytokines that are important for thymocyte proliferation. The mRNAs for these cytokines are short-lived and are inducible by multiple stimuli. Thus, the steady-state levels for IL-1 and IL-6 mRNAs are critical in establishing the final cytokine protein levels. In this study we have evaluated the effect of epidermal growth factor (EGF), a growth factor for TE cells, and its homologue transforming growth factor alpha (TGF-alpha), on primary cultures of normal human TE cells for the levels of IL-1 alpha, IL-1 beta, IL-6, and TGF-alpha mRNA. We showed that TE cells expressed EGF receptors (EGF-R) in vitro and in vivo, and that treatment of TE cells with EGF or TGF-alpha increased IL-1 and IL-6 biological activity and mRNA levels for IL-1 alpha, IL-1 beta, and IL-6. Neither EGF nor TGF-alpha increased transcription rates of IL-1 alpha, IL-1 beta, and IL-6 genes, but rather both EGF and TGF-alpha increased cytokine mRNA stability. By indirect immunofluorescence assay, TGF-alpha was localized in medullary TE cells and thymic Hassall's bodies while EGF-R was localized to TE cells throughout the thymus. Thus, TGF-alpha and EGF are critical regulatory molecules for production of TE cell-derived cytokines within the thymus and may function as key modulators of human T cell development in vivo.

Thymic microenvironment induces HIV expression. Physiologic secretion of IL-6 by thymic epithelial cells up-regulates virus expression in chronically infected cells

The hallmark of infection with HIV-1 is progressive depletion and qualitative dysfunction of the CD4+ Th cell population in infected individuals. Clinical trials of antiretroviral agents have shown that, despite suppression of virus replication, regeneration of the T cell pool does not occur. One proposed explanation for the defective regenerative capacity of the CD4+ T cell pool is infection of early T lymphocyte progenitors or stem cells. An additional explanation could be failure of cells of the intrathymic microenvironment (thymic epithelial (TE) cells) to carry out critical nurturing functions for developing thymocytes, i.e., secretion of thymocyte-trophic cytokines and expression of adhesion molecules. This study examines the effect of HIV on cultured TE cells and determines the role of TE cells in the regulation of viral expression in chronically HIV-infected cells. We found no evidence of infection of TE cells after exposure to HIV-1. However, normal human serum induced secretion of IL-6 by TE cells; induction of TE IL-6 was partially blocked by anti-IFN-gamma antibodies. Moreover, supernatants from TE cells maintained in normal human serum up-regulated HIV replication in chronically HIV-1-infected cells. Because intrathymic T cell precursors can be infected with HIV and T cell precursors come into close contact with TE cells in the thymus, IL-6 secreted by TE cells during normal intrathymic development may induce HIV expression in infected thymocytes in vivo and promote the intrathymic spread of HIV.

Thymic microenvironment induces HIV expression. Physiologic secretion of IL-6 by thymic epithelial cells up-regulates virus expression in chronically infected cells

The hallmark of infection with HIV-1 is progressive depletion and qualitative dysfunction of the CD4+ Th cell population in infected individuals. Clinical trials of antiretroviral agents have shown that, despite suppression of virus replication, regeneration of the T cell pool does not occur. One proposed explanation for the defective regenerative capacity of the CD4+ T cell pool is infection of early T lymphocyte progenitors or stem cells. An additional explanation could be failure of cells of the intrathymic microenvironment (thymic epithelial (TE) cells) to carry out critical nurturing functions for developing thymocytes, i.e., secretion of thymocyte-trophic cytokines and expression of adhesion molecules. This study examines the effect of HIV on cultured TE cells and determines the role of TE cells in the regulation of viral expression in chronically HIV-infected cells. We found no evidence of infection of TE cells after exposure to HIV-1. However, normal human serum induced secretion of IL-6 by TE cells; induction of TE IL-6 was partially blocked by anti-IFN-gamma antibodies. Moreover, supernatants from TE cells maintained in normal human serum up-regulated HIV replication in chronically HIV-1-infected cells. Because intrathymic T cell precursors can be infected with HIV and T cell precursors come into close contact with TE cells in the thymus, IL-6 secreted by TE cells during normal intrathymic development may induce HIV expression in infected thymocytes in vivo and promote the intrathymic spread of HIV.

Human thymic epithelial cells produce IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor

The development of conditions for culturing normal human thymic epithelial (TE) cells free from contaminating stromal cells has allowed us to characterize a number of cytokines produced by TE cells. Using cDNA probes for human IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor (LIF), we identified mRNA for these cytokines by RNA blot analysis of total RNA preparations derived from TE cells. We demonstrated that TE cells produced IL-6 transcripts and that TE cell culture supernatants contained IL-6 biologic activity, as determined by the ability to support proliferation of the T1165 plasmacytoma line. The 1.0-kilobase (kb) transcript of granulocyte-monocyte-CSF was also detected in TE cell-derived total RNA. TE cell culture supernatants contained LIF activity, as determined by proliferation of the murine cell line DA-1a, and a 4.0-kb LIF transcript was detected in TE cell-derived total RNA preparations. The 4.0-kb LIF transcript from TE cell-derived total RNA corresponded in size to the LIF transcripts in PMA-activated T lymphocytes. Thus, using biologic assays and RNA blot analysis, we demonstrated that cultured normal human TE cells produced both immunoregulatory cytokines and cytokines that drive various differentiation stages of human hematopoiesis. Our findings support the hypothesis that TE cells may play a role in providing cytokines that are important for the proliferation and differentiation of hematopoietic precursor cells that migrate to the thymus during fetal and postnatal human thymic development.

Human thymic epithelial cells produce IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor

The development of conditions for culturing normal human thymic epithelial (TE) cells free from contaminating stromal cells has allowed us to characterize a number of cytokines produced by TE cells. Using cDNA probes for human IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor (LIF), we identified mRNA for these cytokines by RNA blot analysis of total RNA preparations derived from TE cells. We demonstrated that TE cells produced IL-6 transcripts and that TE cell culture supernatants contained IL-6 biologic activity, as determined by the ability to support proliferation of the T1165 plasmacytoma line. The 1.0-kilobase (kb) transcript of granulocyte-monocyte-CSF was also detected in TE cell-derived total RNA. TE cell culture supernatants contained LIF activity, as determined by proliferation of the murine cell line DA-1a, and a 4.0-kb LIF transcript was detected in TE cell-derived total RNA preparations. The 4.0-kb LIF transcript from TE cell-derived total RNA corresponded in size to the LIF transcripts in PMA-activated T lymphocytes. Thus, using biologic assays and RNA blot analysis, we demonstrated that cultured normal human TE cells produced both immunoregulatory cytokines and cytokines that drive various differentiation stages of human hematopoiesis. Our findings support the hypothesis that TE cells may play a role in providing cytokines that are important for the proliferation and differentiation of hematopoietic precursor cells that migrate to the thymus during fetal and postnatal human thymic development.

Ligand binding to the LFA-3 cell adhesion molecule induces IL-1 production by human thymic epithelial cells

We have shown that human thymic epithelial (TE) cells produce IL-1 alpha, IL-1 beta, and TE cells bind to thymocytes by CD2 and LFA-1 molecules on thymocytes and LFA-3, ICAM-1 on TE cells. We investigated whether ligand binding to LFA-3 on human TE cells can modulate TE cell IL-1 production. First, we investigated the ability of human thymocytes to regulate IL-1 release by TE cells. Both autologous and allogenic emetine-treated thymocytes when cultured with TE cells augmented IL-1 release by TE cells. The augmentation of IL-1 release was cell density dependent. Inasmuch as the interaction between thymocytes and TE cells is mediated in part by CD2 molecules on thymocytes and LFA-3 molecules on TE cells we next determined the effect on IL-1 release of ligand binding (anti-LFA-3 mAb TS2/9) to TE cell surface LFA-3. Purified anti-LFA-3 mAb augmented IL-1 release in a concentration-dependent fashion. The anti-LFA-3-mediated augmentation of IL-1 release required both new protein and RNA synthesis as shown by the ability of cycloheximide and actinomycin-D to inhibit augmentation of IL-1 production by TE cells, and by direct quantitation of IL-1 alpha and IL-1 beta mRNA by Northern blot analysis. Both F(ab)'2 and Fab' fragments of anti-LFA-3 mAb augmented IL-1 alpha and IL-1 beta mRNA production, indicating that monovalent binding to cell surface LFA-3 was sufficient to provide the inducing signal. The identification of LFA-3, the cell surface ligand for thymocyte CD2 molecules, as a molecule via which TE cell-derived cytokine production may be regulated suggests a mechanism at the cell surface by which direct TE cell-thymocyte interaction might result in the triggering of local IL-1 release within the human thymic microenvironment.