Down-regulation of specific antigen-driven cytokine production in a population with endemic Schistosoma japonicum infection

Schistosome antigen-driven cytokine responses and antischistosome antibody levels of residents of a Schistosoma japonicum endemic island in Poyang Lake, Jiangxi Province were studied before and 45 days after treatment with praziquantel. IL-4, IL-5, IL-10 and INF-gamma were all detected in the supernatants of whole-blood cultures after stimulation with schistosome soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP). The percentages of subjects producing detectable amounts of each cytokine assayed were higher in the group who were negative by stool examination at the start of the study than in those who were initially stool positive. After praziquantel treatment the percentages of subjects producing both type I and type II cytokines increased. This suggests that the production of both types of cytokine was down-regulated in the presence of live, egg-laying S. japonicum adult worms but that this was reversible by treatment. In contrast, the antibody studies showed higher levels of SWAP and SEA-specific antibodies (IgE, total IgG, IgG4, IgM) in subjects who were originally stool-positive than in those who were stool-negative. After treatment specific IgE responses were elevated, but total IgG and IgG4 anti-SEA and IgM anti-SWAP antibody levels all fell significantly.

Expression of ectolipid phosphate phosphohydrolases in 3T3F442A preadipocytes and adipocytes. Involvement in the control of lysophosphatidic acid production

Because of its production by adipocytes and its ability to increase preadipocyte proliferation, lysophosphatidic acid (LPA) could participate in the paracrine control of adipose tissue development. The aim of the present study was to determine which enzyme activities are involved in exogenous LPA hydrolysis by preadipocytes and adipocytes. Using a quantitative method, we observed that extracellular LPA rapidly disappeared from the culture medium of 3T3F442A preadipocytes. This disappearance was strongly slowed down in the presence of the phosphatase inhibitors, sodium vanadate and sodium pervanadate. By using [(33)P]LPA on intact 3T3F442A preadipocytes, we found that 90% of LPA hydrolysis resulted from LPA phosphatase activity biochemically related to previously described ectolipid phosphate phosphohydrolases (LPPs). Quantitative real time reverse transcriptase-PCR revealed that 3T3F442A preadipocytes expressed mRNAs of three known Lpp gene subtypes (1, 2, and 3), with a predominant expression of Lpp1 and Lpp3. Differentiation of 3T3F442A preadipocytes into adipocytes led to an 80% reduction in ecto-LPA phosphatase activity, with a concomitant down-regulation in Lpp1, Lpp2, and Lpp3 mRNA expression. Despite this regulation, treatment of 3T3F442A adipocytes with sodium vanadate increased LPA production in the culture medium, suggesting the involvement of ecto-LPA phosphatase activity in the control of extracellular production of LPA by adipocytes. In conclusion, these data demonstrate that hydrolysis of extracellular LPA by preadipocytes and adipocytes mainly results from a dephosphorylation activity. This activity (i) occurs at the extracellular face of cell membrane, (ii) exhibits biochemical characteristics similar to those of the LPP, (iii) is negatively regulated during adipocyte differentiation, and (iv) plays an important role in the control of extracellular LPA production by adipocytes. Ecto-LPA phosphatase activity represents a potential target to control adipose tissue development.

hH-Rev107, a class II tumor suppressor gene, is expressed by post-meiotic testicular germ cells and CIS cells but not by human testicular germ cell tumors

By systematic analysis of a human testis library, we have isolated the hH-Rev107-3 cDNA, identical to hH-Rev107-1 cDNA, which was previously described as a class II tumor suppressor gene. In this study, two transcripts (1 and 0.8 kb) were detected by Northern blot in all human tissues, excepted in thymus. The strongest expression was found in testis, skeletal muscle and heart. These two mRNA are probably transcribed from only one gene that we mapped to the q12-q13 region of the chromosome 11. In human testis, hH-Rev107 gene expression was localized, by in situ hybridization, within the round spermatids. To investigate a possible role for hH-Rev107 protein in testicular malignant growth, we examined the expression of this gene in germ cell tumors. A strong hH-Rev107 gene expression was observed in normal testis as well as in samples with preinvasive carcinoma in situ but was completely absent in overt tumors, both seminomas and non-seminomas. By in situ hybridization, CIS was found hH-Rev107 positive and tumor negative. A semi-quantitative assessment of hH-Rev107 mRNA level in testicular germ cell tumors, by RT-PCR, exhibited a ninefold decrease in the gene expression. No gross structural aberrations of hH-Rev107 gene were detected in these human primary tumors. The results suggest that down-regulation of hH-Rev107 may be associated with invasive progression of testicular germ cell tumors.

Expression of the normal epithelial cell-specific 1 (NES1; KLK10) candidate tumour suppressor gene in normal and malignant testicular tissue

The normal epithelial cell-specific 1 (NES1) gene (official name kallikrein gene 10; KLK10) is a new member of the expanding human kallikrein gene family and encodes for a secreted serine protease. Experimental evidence suggests that NES1 controls normal cell growth and may function as a tumour suppressor. NES1 is down-regulated during breast cancer progression. The NES1 gene is highly expressed in testicular as well as in other tissues. In this study, we investigated the expression level of the NES1 gene in cancerous and normal testicular tissues with reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. In all 14 primary testicular germ-cell tumours examined, the NES1 gene expression was markedly reduced compared to adjacent (paired) normal tissues. We further examined 6 randomly selected primary germ-cell tumours and 8 normal tissues (obtained from different individuals). We confirmed the differential expression of the NES1 gene in germ-cell tumours (GCT) and pre-malignant carcinoma in situ (CIS). Our findings suggest that NES1 may act as a tumour suppressor and may play a role in the pathogenesis and progression of this malignancy.

Heterogeneous increases of cytoplasmic calcium: distinct effects on down-regulation of cell surface sodium channels and sodium channel subunit mRNA levels

1. Long-term (> or = 12 h) treatment of cultured bovine adrenal chromaffin cells with A23187 (a Ca(2+) ionophore) or thapsigargin (TG) [an inhibitor of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)] caused a time- and concentration-dependent reduction of cell surface [(3)H]-saxitoxin (STX) binding capacity, but did not change the K:(D:) value. In A23187- or TG-treated cells, veratridine-induced (22)Na(+) influx was reduced (with no change in veratridine EC(50) value) while it was enhanced by alpha-scorpion venom, beta-scorpion venom, or Ptychodiscus brevis toxin-3, like in nontreated cells. 2. The A23187- or TG-induced decrease of [(3)H]-STX binding was diminished by BAPTA-AM. EGTA also inhibited the decreasing effect of A23187. A23187 caused a rapid, monophasic and persistent increase in intracellular concentration of Ca(2+) ([Ca(2+)](i)) to a greater extent than that observed with TG. 2,5-Di-(t-butyl)-1,4-benzohydroquinone (DBHQ) (an inhibitor of SERCA) produced only a rapid monophasic increase in [Ca(2+)](i), without any effect on [(3)H]-STX binding. 3. Reduction in [(3)H]-STX binding capacity induced by A23187 or TG was attenuated by Gö6976 (an inhibitor of conventional protein kinase C) or calpastatin peptide (an inhibitor of calpain). When the internalization rate of cell surface Na(+) channels was measured in the presence of brefeldin A (an inhibitor of vesicular exit from the trans-Golgi network), A23187 or TG accelerated the reduction of [(3)H]-STX binding capacity. 4. Six hours treatment with A23187 lowered Na(+) channel alpha- and beta(1)-subunit mRNA levels, whereas TG had no effect. 5. These results suggest that elevation of [Ca(2+)](i) caused by A23187, TG or DBHQ exerted differential effects on down-regulation of cell surface functional Na(+) channels and Na(+) channel subunit mRNA levels.

Endomorphin-1 induced desensitization and down-regulation of the recombinant mu-opioid receptor

1. Endomorphin-1 (E1) is a peptide with high affinity and selectivity for the mu-opioid receptor. The aim of this study was to determine if endomorphin-1 caused desensitization and down-regulation of the mu-opioid receptor expressed in Chinese hamster ovary cells. 2. Following 10 microM E1 pre-treatment, desensitization was assessed by measuring cyclic AMP inhibition, down-regulation was assessed by [(3)H]-diprenorphine ([(3)H]-DPN) binding and immuno-blotting. 3. Pre-treatment of CHO mu cells with 10 microM E1 for 11 and 18 h caused significant reduction in cyclic AMP inhibition. (11 h=39.0+/-16.7%, 18 h 47.0+/-11.1% reduction). 4. At 18 h E1 pre-treatment there was an enhancement (4.5 fold) of cyclic AMP production under forskolin stimulated conditions accompanied by a small rightward shift in the concentration-response curve (pEC(50) control=7.8+/-0.3, pEC(50) E1=7.3+/-0.2) when cells were re-challenged with E1. 5. In membranes prepared from untreated and 0.5 h E1 pre-treated cells, addition of GTP gamma S produced a significant rightward shift in the concentration response curves for E1 displacement of [(3)H]-DPN (0 h K(i) control=7.86+/-0.11, GTP gamma S=7.37+/-0.15; 0.5 h K(i) control=7.92+/-0.12, GTP gamma S=7.36+/-0.08) This was not observed in membranes prepared from cells that had been treated with E1 for 18 h (18 h K(i) control=7.69+/-0. 11, GTP gamma S=7.75+/-0.08). 6. In whole cells E1 treatment caused a rapid loss of cell surface receptors such that at 0.5 h there was a 30.5+/-1.5 reduction (this was unchanged for 18 h). In crude membranes a loss of receptors was also observed using radioligand binding or immuno-blotting protocols. 7. These data show that E1 causes desensitization and down-regulation of the rat mu-opioid receptor expressed in CHO cells. However, these two responses appear temporally distinct.

Benznidazole, a drug employed in the treatment of Chagas' disease, down-regulates the synthesis of nitrite and cytokines by murine stimulated macrophages

Benznidazole (BZL) is a nitroheterocyclic drug employed in the chemotherapy of Chagas' disease, a protozoan disease caused by Trypanosoma cruzi. Because this parasite mostly replicates in macrophages, we investigated whether BZL was likely to modify the synthesis of macrophage mediators such as nitrite, tumour necrosis factor-alpha (TNF-alpha), IL-1beta, IL-6 and IL-10. Control and stimulated murine macrophages (lipopolysaccharide (LPS) and/or interferon-gamma (IFN-gamma)) were treated with BZL and measurements were carried out in culture supernatants collected 24 h later. Synthesis of nitrite, IL-6 and IL-10 was maximal upon combined stimulation with LPS + IFN-gamma, whereas lower amounts of the three mediators were detected when both stimuli were given alone. BZL treatment significantly reduced nitrite, IL-6 and IL-10 production, to undetectable levels in some cases, particularly IL-6 and IL-10. LPS was the most potent stimulus of IL-1beta and TNF-alpha production, followed by LPS + IFN-gamma and IFN-gamma in decreasing order. BZL partly inhibited TNF-alpha synthesis, but this effect was smaller than that observed for nitrite, IL-6 and IL-10. LPS-induced production of IL-1beta was also affected by BZL. Semiquantification of gene expression for inducible nitric oxide synthase (iNOS) showed that BZL completely inhibited iNOS gene induction by IFN-gamma, and resulted in respective inhibitions of 30% and 50% with LPS- and LPS + IFN-gamma-stimulated cells. BZL was not cytotoxic on macrophage cultures, as shown by the lactate dehydrogenase activity. Besides its trypanocidal activity, BZL may also alter the balance between pro- and anti-inflammatory mediators with important consequences for the course of T. cruzi infection.

On down-regulation of the immune response to metastatic malignant melanoma

Treatment of metastatic malignant melanoma with interferon alpha (IFNalpha) results in objective remission in approximately 15% of patients. In a previous investigation, we found that about 50% of the patients achieved at least minor or short-lived remissions. In some tumours extensive areas of regressive tumour change occurred. However, even in these areas remnants of tumour cells were generally found. The short duration of the immune response in some patients and the incomplete eradication of the tumour can be due either to selection of non-immunogenic tumour cells or to down-regulation of the immune reactivity to the tumour. In the present paper, the expression of the zeta chain of the T cell receptor in CD3+ lymphocytes and the expression of CD28 in CD3+, CD4+ and CD8+ lymphocytes was studied in resectable melanoma metastases from 20 treated (IFNalpha or IFNalpha in combination with cisplatinum and dacarbazine) and 16 untreated patients. A double-staining technique was used, and the occurrence and distribution of lymphocytes showing down-regulation of the zeta chain or CD28 were separately registered in different areas of the metastases: close to the tumour cells in areas of unaffected tumour growth, in areas with regressive tumour changes, in areas with marked fibrosis and in stromal areas with densely packed lymphocytes. CD3+ zeta lymphocytes were found in all metastases, but their number and distribution varied considerably. Down-regulation of the zeta chain was most often found in areas of regressive changes. In contrast, T lymphocytes infiltrating close to the tumour cells had a stronger expression of the zeta chain (P = 0.016). Down-regulation was also found in stromal areas of densely packed lymphocytes and in areas of fibrosis. The pattern of down-regulation of CD28 in various subsets of lymphocytes was similar to that of zeta chain. The same pattern of down-regulation of CD28 and the zeta chain was found in both untreated and treated patients, indicating that the down-regulation is not due to treatment but to the release of immunosuppressor factors from areas with high tumour cell density or extensive destruction of tumour cells. These results concur well with the view that IFNalpha treatment can result in immune-mediated tumour cell destruction early in the treatment period and that this immune response to the tumour can be followed by immunosuppression within a few weeks.

Homologous regulation of the alpha2C-adrenoceptor subtype in human hepatocarcinoma, HepG2

1. Previous studies of the regulation of the alpha2C-adrenoceptor in OK and in transfected cells have led to discrepant conclusions. In the present work, we examined the homologous regulation of the human alpha2C-adrenoceptor in the hepatocarcinoma cell-line, HepG2; a model which expresses this subtype spontaneously. 2. Short-period treatment of the cells with UK14304 provoked neither a diminution of the potency of the alpha2-agonist to inhibit forskolin-induced cyclic AMP-accumulation nor a change in the degree of receptor coupling to G-proteins. 3. Long-period exposure to UK14304 resulted in a large reduction of [3H]MK912 binding sites (55% decrease). The action of UK14304 was dose-dependent (EC50 = 190 +/- 45 nM), rapid (t1/2 = 4.2 h) and reversible. Receptor down-regulation was also observed with clonidine or (-)adrenaline (38 and 36% decrease, respectively) and was blocked by the addition of alpha2-antagonists. 4. Conversely to that observed with alpha2-agonists, treatment of the cells with RX821002 or yohimbine alone, but not with phentolamine, promoted a significant increase of the receptor expression. 5. The observed alterations of receptor density are not the reflection of changes at the alpha2C4 mRNA level. Estimation of the receptor protein turnover and measurement of its half-life demonstrated that down-regulation by alpha2-agonists and up-regulation by alpha2-antagonists, with inverse-agonist efficacy, are respectively the consequence of increased and decreased rate of receptor degradation. 6. In conclusion, our data show that alpha2C-adrenoceptor does not undergo desensitization but is down-regulated in HepG2. The lack of desensitization agrees with previous results obtained in cells transfected with the alpha2C4 gene, but not with observations made in OK cells. Inversely, down-regulation fits with results obtained in OK but not in transfected cells. The reasons for these discrepancies are discussed. Our results also demonstrated that certain alpha2-antagonists behave as inverse agonist on the HepG2 model and thus provide for the first time evidence of inverse efficacy of antagonists on a cellular model expressing physiological level of a wild-type alpha2-adrenoceptor.

Central benzodiazepine receptor autoradiography in hippocampal sclerosis

1. The gamma-aminobutyric acid (GABA)A/central benzodiazepine receptor (cBZR) complex is a major inhibitory receptor in the vertebrate CNS. Binding of [11C]-flumazenil to this complex in vivo is reduced in hippocampal sclerosis (HS). It has been uncertain whether reduced cBZR binding is entirely due to neuronal loss in HS. 2. The objective of this study was to characterize abnormalities of the cBZR in HS with a correlative autoradiographic and quantitative neuropathological study. 3. Saturation autoradiographic studies were performed with [3H]-flumazenil to investigate relationships between neuronal density and receptor availability (Bmax) and affinity (Kd) in HS. Hippocampal tissue was obtained at surgery from 8 patients with intractable temporal lobe epilepsy (TLE) due to HS and autopsies of 6 neurologically normal controls. Neuronal densities were obtained by means of a 3-D counting method. 4. Bmax values for [3H]-flumazenil binding in the subiculum, CA1, CA2, CA3, hilus and dentate gyrus were all found to be significantly reduced in HS compared with controls and significant increases in affinity were observed in the subiculum, hilus and dentate gyrus. In HS, cBZR density in the CA1 region was significantly reduced (P < 0.05) to a greater extent than could be attributable to neurone loss. In other regions, Bmax was reduced in parallel with neuronal density. 5. In HS, there is a loss of cBZR in CA1 over and above loss of neurones. This finding and increases in affinity for flumazenil in subiculum, hilus and dentate gyrus imply a functional abnormality of the GABAA/cBZR complex that may have a role in the pathophysiology of epileptogenicity in HS.

Effects of beta 2-agonist- and dexamethasone-treatment on relaxation and regulation of beta-adrenoceptors in human bronchi and lung tissue

1. Long-term treatment with beta 2-adrenoceptor agonists can lead to a decreased therapeutic efficacy of bronchodilatation in patients with obstructive pulmonary disease. In order to examine whether or not this is due to beta-adrenoceptor desensitization, human bronchial muscle relaxation was studied in isolated bronchial rings after pretreatment with beta 2-adrenoceptor agonists. Additionally, the influence of pretreatment with dexamethasone on desensitization was studied. 2. The effect of beta 2-agonist incubation alone and after coincubation with dexamethasone on density and affinity of beta-adrenoceptors was investigated by radioligand binding experiments. 3. In human isolated bronchi, isoprenaline induces a time- and concentration-dependent beta-adrenoceptor desensitization as judged from maximal reduction in potency by a factor of 7 and reduction of 73 +/- 4% in efficacy of isoprenaline to relax human bronchial smooth muscle. 4. After an incubation period of 60 min with 100 mumol l-1 terbutaline, a significant decline in its relaxing efficacy (81 +/- 8%) and potency (by a factor 5.5) occurred. 5. Incubation with 30 mumol l-1 isoprenaline for 60 min did not impair the maximal effect of a subsequent aminophylline response but led to an increase in potency (factor 4.4). 6. Coincubation of dexamethasone with isoprenaline (120 min; 30 mumol l-1) preserved the effect of isoprenaline on relaxation (129 +/- 15%). 7. In radioligand binding experiments, pretreatment of lung tissue for 60 min with isoprenaline (30 mumol l-1) resulted in a decrease in beta-adrenoceptor binding sites (Bmax) to 64 +/- 1.6% (P < 0.05), while the antagonist affinity (KD) for [3H]-CGP-12177 remained unchanged. 8. In contrast, radioligand binding studies on lung tissue pretreated with either dexamethasone (30 mumol l-1) or isoprenaline (30 mumol l-1) plus dexamethasone (30 mumol l-1) for 120 min did not lead to a significant change of Bmax (160 +/- 22.1% vs 142.3 +/- 28.7%) or KD (5.0 nmol l-1 vs 3.5 nmol l-1) compared to the controls. 9. In conclusion, pretreatment of human bronchi with beta-adrenoceptor agonists leads to functional desensitization and, in lung tissue, to down-regulation of beta-adrenoceptors. This effect can be counteracted by additional administration of dexamethasone. Our model of desensitization has proved useful for the identification of mechanisms of beta-adrenoceptor desensitization and could be relevant for the evaluation of therapeutic strategies to counteract undesirable effects of long-term beta-adrenoceptor stimulation.

Glucuronidase Expression in Transgenic Tobacco Roots with a Parasponia Promoter on Infection with Meloidogyne javanica

The expression of a g-us reporter gene linked to a Parasponia andersonii hemoglobin promoter has been studied in transgenic tobacco plants after infection by Meloidogyne javanica. Transgenic roots were harvested at different times after nematode inoculation, and stained histochemically for expression of the gus gene. During the early stages of infection (0-2 weeks) there was little expression in giant cells, in contrast to other cells of the root. In later stages of infection (3-6 weeks) there was strong gus expression in giant cells, with virtually no expression in other cells of the root. The Parasponia hemoglobin promoter therefore appears to direct down-regulation of linked genes on induction of giant cells, but up-regulation in mature giant cells. This reflects different metabolic activities in the giant cells depending on their stage of development. The Parasponia hemoglobin promoter may respond to oxygen tension in giant cells. This suggests that oxygen tension may be limited in the metabolically active giant cells that are associated with egg-laying females.

Analyses of RBC insulin receptor bindings in chronic liver disease

¹²⁵I-insulin binding to erythrocytes was measured to evaluate the role of insulin receptors in the mechanism of insulin resistance in partients with chronic liver disease (CLD). Patients with CLD were divided into two groups by the fasting plasma glucose level (FBS) and the glucose disappearance rate (k-glucose) during intravenous glucose tolerance tests: one with normal FBS and normal k-glucose (group I), and the other with higher FBS and lower k-glucose (group II). Insulin receptor bindings were reduced in group I patients compared with those of normal controls, but were not reduced in group II patients. Fasting insulin levels were significantly higher in group I patients than those in normal subjects, and down-regulation by hyperinsulinemia might be the cause of reduced insulin receptor bindings in these patients. However down-regulation of insulin receptors was not associated with glucose intolerance. So it is suggested that insulin resistance in CLD is not due to a primary defect of insulin receptors in peripheral tissues, and down-regulation of insulin receptors is an epiphenomenon of hyperinsulinemia.