Comprehensive investigation of saliva replacement liquids for the treatment of xerostomia.

The sensation of dry mouth also referred to as xerostomia is becoming increasingly common worldwide. Current treatment strategies include topical agents, sialagogues and saliva substitutes. The latter have been reported to be ineffective as special physicochemical features of natural saliva have so far been ignored (e.g., buffer capacity, osmolality, etc.). The aim of this study was to comprehensively investigate the most relevant physicochemical properties of three products frequently used in the clinics and compare them to unstimulated whole saliva (UWS). Sialin-Sigma®, Glandomed® and Xylitol CVS HealthTM Dry Mouth Spray were characterized regarding their pH, osmolality, electrical conductivity, buffer capacity, rheological behaviour, microstructure, surface tension and wettability and compared to UWS. The influence of residual saliva was examined under consideration of the conditions of xerostomia to assess whether the quantity given in the instruction for use is appropriate. All three products showed significant differences to UWS regarding the values received. Only Xylitol CVS HealthTM Dry Mouth Spray showed a comparable wettability. It could be further determined that the recommended doses were too low. These data can not only be used for an improved understanding of saliva, but also for the development of a replacement fluid to successfully alleviate xerostomia.

Detailed comparison of retroviral vectors and promoter configurations for stable and high transgene expression in human induced pluripotent stem cells.

Correction of patient-specific induced pluripotent stem cells (iPSC) upon gene delivery through retroviral vectors offers new treatment perspectives for monogenetic diseases. Gene-modified iPSC clones can be screened for safe integration sites and differentiated into transplantable cells of interest. However, the current bottleneck is epigenetic vector silencing. In order to identify the most suitable retroviral expression system in iPSC, we systematically compared vectors from different retroviral genera, different promoters and their combination with ubiquitous chromatin opening elements (UCOE), and several envelope pseudotypes. Lentiviral vectors (LV) pseudotyped with vesicular stomatitis virus glycoprotein were superior to gammaretroviral and alpharetroviral vectors and other envelopes tested. The elongation factor 1α short (EFS) promoter mediated the most robust expression, whereas expression levels were lower from the potent but more silencing-prone spleen focus forming virus (SFFV) promoter. Both full-length (A2UCOE) and minimal (CBX3) UCOE juxtaposed to two physiological and one viral promoter reduced transgene silencing with equal efficiency. However, a promoter-specific decline in expression levels was not entirely prevented. Upon differentiation of transgene-positive iPSC into endothelial cells, A2UCOE.EFS and CBX3.EFS vectors maintained highest transgene expression in a larger fraction of cells as compared with all other constructs tested here. The function of UCOE diminished, but did not fully counteract, vector silencing and possibilities for improvements remain. Nevertheless, the CBX3.EFS in a LV background exhibited the most promising promoter and vector configuration for both high titer production and long-term genetic modification of human iPSC and their progeny.

Testosterone induces apoptosis in cardiomyocytes by increasing proapoptotic signaling involving tumor necrosis factor-α and renin angiotensin system.

Anabolic androgenic steroids lead to cardiac complications and have been shown to exhibit proapoptotic effects in cardiac cells; however, the mechanism involved in those effects is unclear. The aim of this study was to assess whether apoptosis and the activation of caspase-3 (Casp-3) induced by testosterone in high concentrations involves increments in tumor necrosis factor-α (TNF-α) concentrations and angiotensin-converting enzyme (ACE) activity in cardiomyocytes (H9c2) cell cultures. Cardiomyocytes were treated with testosterone (5 × 10(-6) mol/L), doxorubicin (9.2 × 10(-6) mol/L), testosterone + etanercept (Eta; 6.67 × 10(-5) mol/L), testosterone + losartan (Los; 10(-7) mol/L), and testosterone + AC-DEVD-CHO (10(-5) mol/L; Casp-3 inhibitor). Apoptosis was determined by flow cytometry and by the proteolytic activity of Casp-3. We demonstrated that incubation of H9c2 cells for 48 h with testosterone causes the apoptotic death of 60-70% of the cells and co-treatments with Eta, Los, or AC-DEVD-CHO reduced this effect. Testosterone also induces apoptosis (concentration dependent) and increases the proteolytic activity of Casp-3, which were reduced by co-treatments. TNF-α and ACE activities were elevated by testosterone treatment, while co-treatment with Los and Eta reduced these effects. We concluded that an interaction between testosterone, angiotensin II, and TNF-α induced apoptosis and Casp-3 activity in cultured cardiomyocytes, which contributed to the reduced viability of these cells induced by testosterone in toxic concentrations.

Atividade gastroprotetora do extrato etanólico de Pavonia alnifolia A. St. -Hil / Gastro protective activity of the Pavonia alnifolia A.St. -Hil. extract

RESUMO No Brasil, a família Malvaceae está representada por aproximadamente 200 espécies e algumas foram descritas como gastroproteroras. Pavonia alnifolia A.St.-Hil. (Malvaceae) foi selecionada após uma abordagem quimiossistemática, considerando-se sua potencial capacidade em prevenir lesões gástricas. Assim, a atividade gastroprotetora do extrato etanólico de caules de P. alnifolia foi avaliada utilizando o modelo de indução aguda da lesão gástrica por etanol acidificado em camundongos. Além disso, foram quantificados o teor de flavonóides, pelo método de cloreto de alumínio, e de polifenóis, pelo método Folin-Ciocalteu, uma vez que a relação desses componentes com a proteção gástrica foi evidenciada. Os ensaios apontaram redução acentuada das lesões gástricas em camundongos tratados com o extrato da planta em todas as doses ensaiadas (10, 100 e 300 mg/kg). Esse efeito pode estar relacionado com a presença de polifenóis, cujo teor encontrado foi 74,3 ± 7,5 µg equivalente de pirogalol/mg do material vegetal examinado e 82,7 ± 7,1 µg equivalente de pirogalol /mg da amostra no extrato preparado por percolação e teor de flavonoides totais, que por sua vez apresentou um resultado de 17,1 ± 1,4 µg/mg de extrato. O extrato apresentou proteção da mucosa gástrica e este efeito pode estar relacionado à presença dos polifenóis e flavonóides encontrados

ABSTRACT Gastro protective activity of the Pavonia alnifolia A.St.-Hil. extract. In Brazil, the Malvaceae family is represented by at about 200 species. Some of those species are known as gastro protective ones. The Pavonia alnifolia A.St.-Hil (Malvaceae) was selected after a chemosystematic approach. The gastro preventive activity of the ethanol extract of stems Pavonia alnifolia was evaluated through the use of the Ethanol:chlroridric acid model on mice. The quantification of the total flavonoids (aluminum chloride method) and total polyphenols (Folin-Ciocalteu method) was also performed since the relation of those components with gastric protection has been previously highlighted. The tests showed a significant reduction of the ulcer formation in the mice treated with the plant extract (10, 100 and 300 mg/kg). This effect may be related to the presence of polyphenols whose content was found to be 74.3 ± 7.5 µg/mg of vegetal material and 82.7 ± 7.1 µg/mg of crude extract and flavonoids, which in turn showed a content of 17.1 ± 1.4 µg/mg dry extract

[Closing-wedge valgus high tibial osteotomy]. / Vysoká laterální valgizacní osteotomie bérce - technika "closed-wedge"

PURPOSE OF THE STUDY: The aim of the study was to evaluate the group of patients treated for varus arthritic knee by the method of high tibial osteotomy from the lateral approach and to assess its role in the present-day orthopaedic surgery which also offers other options such as distraction osteotomy from the medial approach, autologous chondrocyte transplantation or alloplasty. MATERIAL AND METHODS: The study included 101 patients, 41 women and 60 men, undergoing lateral valgus high tibial osteotomy at our department between 2003 and 2007. The age of patients at the time of surgery ranged from 34 to 61 years, with an average of 54 years. The follow-up period was in the range of 2 to 7 years, with an average of 5.2 years. Moderate varus gonarthrosis was the most frequent indication for osteotomy. Each procedure was preceded by arthroscopy with treatment of the pathologies found; these most frequently included a torn medial meniscus, synovitis or medial compartment chondropathy. The outcomes were evaluated using a system of clinical and radiographic assessment (A) and the Lysholm score (B) before and after surgery. RESULTS: The A system evaluation showed excellent, good and poor results in 42, 47 and 12 patients, respectively. The average Lysholm score was 51 points before surgery and 73 points at the final follow-up examination; the average improvement was by 22 points. The average mechanical axis was 2 degrees of varus before and 6 degrees of valgus after surgery. The minimal correction of the axis was 4 degrees and the maximal correction was 18 degrees. The average change of the axis was 8 degrees. Complications were recorded in 21% of the patients. None of the patients had delayed healing, pseudoarthrosis, fracture of the tibial plateau or peroneal nerve palsy. DISCUSSION: Long-term excellent and good outcomes were found more often in the patients with a greater resulting valgus angle. After surgery the average anatomical axis was 7.4 degrees of valgus for good and excellent results, and 4.3 degrees of valgus for poor results. This is in agreement with the common recommendation that osteotomy should produce mild overcorrection. The 95% osteotomy survival rate in this study is in accordance with the results reported by Coventry et al. and Sprenger et al. With strict adherence to the indication criteria, we did not find any clear relationship between the severity of knee injury before surgery and the subjective evaluation of post-operative clinical outcome. The patient's body mass index (BMI) had no effect on the outcome, but the majority of our patients had a BMI below 30 (average, 28.2). The range of motion after surgery was not significantly limited. Both the occurrence of complications and alignment maintenance are comparable with the results of distraction osteotomy. CONCLUSIONS: The mid-term results of valgus osteotomy performed by the technique described by Coventry et al. testify to the lasting success of this method. Satisfaction with its outcome can be expected in about 90% of the patients in a 5-year post-operative period. To achieve this, it is necessary to strictly observe the indication criteria, operative technique and thorough arthroscopic treatment of the joint. Also, the necessity of slight over-correction to 8 degrees of valgus is emphasised.

[Stump forming after traumatic foot amputation of a child--description of a new surgical procedure and literature review of lawnmower accidents]. / Stumpfbildung nach traumatischer Fussamputation beim Kind--Beschreibung eines neuen Operationsverfahrens und Literaturrecherche von Rasenmäherunfällen.

AIM: Amputation injuries in children occur in motor vehicle, farming and, importantly, lawn mower accidents. Treatment of lawn mower related injuries is complicated by gross wound contamination, avascular tissue, soft tissue defects and exposed bone. Many treatment options exist and often an adequate prosthetic supply is needed for rehabilitation. We report on an 8-year old boy who got under a ride-on lawn mower and sustained a subtotal amputation of his right foot. After initial surgery an amputation was subsequently necessary. For this, it had to be taken into account that the traumatic loss of the talus, calcaneus and parts of the cuboid bone would result in a length shortening of the right leg and so far not injured metatarsal and tarsal bones had to be sacrificed. Thus, we aimed to develop a new operation technique to optimize stump length as well as preserve tarsal bones and the possibility of limb growth. METHOD: In order to achieve this, we performed a new stump forming operation in which we integrated uninjured tarsal and metatarsal bones. First a Lisfranc's amputation was performed and a metatarsal bone was kept aside. The talus, calcaneus as well as the cuboid bone were either completely or almost completely destroyed and were removed. The remaining cuneiform bones were transfixed by a notched metatarsal bone, thus achieving a tarsal arthrodesis, and the cartilages of the proximal joint surfaces were removed. The cartilage of the cranial and caudal navicular as well as the distal tibial joint surface was also removed and an arthrodesis between the distal tibia and the navicular bone was achieved by crossed Kirschner wires. Finally the cuneiform bones were placed inferior to the navicular bone. Further stump coverage was managed by skin and muscle flaps as well as split skin graft. RESULT: Our patient was discharged on day 34. A fluent gait without crutches as well as sports activities were possible again as early as 6 1/2 months after the injury. CONCLUSION: Using our stump forming technique we hope to prevent some complications of amputation injuries. Because of the intact epiphysis a bone overgrowth is hopefully prevented and growth potential is preserved and by inclusion of tarsal and metatarsal bones in the stump formation a length discrepancy is minimized.

Circulating endothelial progenitor cells are inversely correlated with the median oxygen tension in the tumor tissue of patients with cervical cancer.

Tumor hypoxia leads to adaptive responses in cancer cells, including an induction of vasculogenesis initiated by circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs). The aim of the present study was to correlate the number of EPCs and CECs with the oxygenation of cervical cancer. Blood concentrations of EPCs were detected by FACS analysis with antibodies for CD34 and vascular endothelial growth factor receptor 2 (VEGFR2). CECs were evaluated by double staining for 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-labeled acetylated low density lipoprotein (Di-LDL) and lectin in a cell culture assay. Ten patients with cervical cancer were compared with ten healthy volunteers. Intratumoral oxygen tension was assessed polarographically with the computerized Eppendorf histography system. Analysis of CEC numbers revealed no difference between patients and controls. However, patients had lower concentrations of CD34-positive hematopoietic stem cells (HSCs) but a significantly higher fraction of EPCs related to the number of HSCs (1.09% versus 0.53%). This fraction was significantly inversely correlated to the median oxygen tension (r = -0.74, p = 0.015). Our study shows for the first time a significant inverse correlation between the fraction of EPCs and intratumoral oxygen tension. We conclude that the fraction of EPCs should be further evaluated as a useful and convenient marker in the prediction of tumor tissue oxygenation.

Transforming growth factor beta1 inhibits aldosterone and cortisol production in the human adrenocortical cell line NCI-H295R through inhibition of CYP11B1 and CYP11B2 expression.

Transforming growth factor beta1 (TGFbeta1) has been shown to exert strong inhibitory effects on adrenocortical cell steroidogenesis. However, the molecular targets of TGFbeta1 in adrenocortical cells appear to differ between species. Here, we report the first characterization of the regulatory effects of TGFbeta1 on the steroidogenic functions of the human adrenocortical tumor cell line NCI-H295R. After treatment with 2 ng/ml TGFbeta1 for 24 h, basal production of corticosterone, cortisol and androstenedione was dramatically decreased. When TGFbeta1 was added simultaneously with forskolin, the production of cortisol and 11-hydroxyandrostenedione was decreased by 85% whereas that of deoxycortisol was increased. When TGFbeta1 was added simultaneously with angiotensin II, aldosterone production was reduced by 80%. We observed that TGFbeta1 strongly inhibits forskolin-induced steroid 11beta-hydroxylase activity and CYP11B1 mRNA levels, as well as angiotensin II-induced aldosterone synthase activity and CYP11B2 mRNA levels. CYP11B1 and CYP11B2 gene products thus appear as the major steroidogenic enzymes down-regulated by TGFbeta1 in the human adrenocortical tumor cell line NCI-H295R.

A Chlamydia pneumoniae-specific peptide induces experimental autoimmune encephalomyelitis in rats.

It has been reported recently that the bacterial respiratory pathogen Chlamydia pneumoniae is present in the cerebrospinal fluid of a subset of multiple sclerosis (MS) patients. However, it is not known whether this organism is a causative agent of MS, or merely an opportunistic pathogen that takes advantage of a disease process initiated by some other means. We report identification of a 20-mer peptide from a protein specific to C. pneumoniae which shares a 7-aa motif with a critical epitope of myelin basic protein, a major CNS Ag targeted by the autoimmune response in MS. This bacterial peptide induces a Th1 response accompanied by severe clinical and histological experimental autoimmune encephalomyelitis in Lewis rats, a condition closely reflective of many aspects of MS. Studies with peptide analogues suggest that different populations of encephalitogenic T cells are activated by the C. pneumoniae and myelin basic protein Ags. Mild experimental autoimmune encephalomyelitis was also observed when rats were immunized with sonicated C. pneumoniae in CFA.

Parental genes do not codominantly confer susceptibility to experimental autoimmune encephalomyelitis in F1 rats.

Lewis (LEW) and DA rats are highly susceptible to experimental autoimmune encephalomyelitis (EAE) induced with guinea pig myelin basic protein (MBP), but respond to different epitopes. The dominant epitope for LEW rats is MBP73-86, and disease is mediated primarily by Vbeta8.2 Th1 cells. DA rats lack conventional Vbeta8.2 T cells and do not respond to MBP73-86. Rather, DA rats respond to the cryptic epitope MBP63-81, which is not encephalitogenic for LEW rats. Responses to these neuroantigens were investigated in (DAxLEW) F1 hybrids to determine if experimental findings in inbred rats remain valid in more genetically complex models. Surprisingly, MBP63-81, a cryptic epitope for DA rats, induced moderate-to-severe EAE in F1 hosts, whereas MBP73-86, the dominant LEW epitope, was only weakly encephalitogenic in F1 hosts. The poor clinical response to MBP73-86 appears to be a consequence of an inability to expand Vbeta8.2 T cells. These results suggest that parental responses to neuroantigens are poor predictors for determining encephalitogenicity in F1 progeny.

A comparison of folding techniques in the chemical synthesis of the epidermal growth factor-like domain in neu differentiation factor alpha/beta.

The 52-residue alpha/beta chimera of the epidermal growth factor-like domain in neu differentiation factor (NDFealpha/beta) has been synthesized and folded to form a three disulfide bridge (Cys182-Cys196, Cys190-Cys210, Cys212-Cys221) containing peptide. We investigated two general strategies for the formation of the intramolecular disulfide bridges including, the single-step approach, which used fully deprotected and reduced peptide, and a sequential approach that relied on orthogonal cysteine protection in which specific pairs are excluded from the first oxidation step. Because there are 15 possible disulfide bridge arrangements in a peptide with six cysteines, the one-step approach may not always provide the desired disulfide pairing. Here, we compare the single-step approach with a systematic evaluation of the sequential approach. We employed the acetamidomethyl group to protect each pair of cysteines involved in disulfide bridges, i.e. Cys182 to Cys196, Cys190 to Cys210 and Cys212 to Cys221. This reduced the number of possible disulfide patterns from 15 to three in the first folding step. We compared the efficiencies of folding for each protected pair using RP-HPLC, mapped the disulfide connectivity of the predominant product and then formed the final disulfide from the partially folded intermediate via 12 oxidation. Only the peptide having the Cys182-Cys196 pair blocked with acetamidomethyl forms the desired disulfide isomer (Cys190-Cys210/Cys212-Cys221) as a single homogeneous product. By optimizing both approaches, as well as other steps in the synthesis, we can now rapidly provide large-scale syntheses of NDFealpha/beta and other novel EGF-like peptides.

A Neu differentiation factor (NDF) domain essential for proliferation and alterations in morphology of colonic epithelial cells in vitro.

The Neu Differentiation Factors (NDFs, also termed "heregulins") are a family of proteins that were first isolated as ligands for the HER2 (ergB2, or p185neu) receptor protein tyrosine kinase. Here we show that NDF acts to stimulate the proliferation and alter the cellular morphology of colonic epithelial cells in culture. Dramatic NDF-induced changes in cellular morphology were noted in the colonic epithelial cell line, LIM 1215. In addition, the expression of specific cell proteins, such as carcinoembryonic antigen and integrin beta 4, was induced in LIM 1215 cells by NDF. These effects were more pronounced with the beta isoform than with the alpha isoform of NDF. The EGF-homology domain of NDF beta was sufficient to stimulate the proliferation and alteration in cell morphology. The use of chemically synthesized chimeric NDF alpha and NDF beta proteins enabled use to identify a region of seven amino acids in the EGF-homology domain of NDF beta that is required for both activities. These in vitro experiments suggest that NDF may act as a regulator of growth and differentiation of colonic epithelial cells in vivo.

Development of highly selective SH3 binding peptides for Crk and CRKL which disrupt Crk-complexes with DOCK180, SoS and C3G.

Many Src Homology 3 (SH3) domains function as molecular adhesives in intracellular signal transduction. Based on previous ultrastructural studies, short motifs which bind to the first SH3 domains of the adapters Crk and CRKL were selectively mutagenised to generate Crk/CRKL SH3-binding peptides of very high affinity and selectivity. Affinities were increased up to 20-fold compared to the best wildtype sequences, while the selectivity against a similar SH3 domain [Grb2SH3(N)] was not only retained, but sometimes increased. Blot techniques with GST-fusion peptides and in solution precipitation assays with biotinylated high affinity Crk binding peptides (HACBPs) were subsequently used to analyse the binding of these sequences to a large panel of SH3 domain-containing fusion proteins. Only those proteins which contained the CrkSH3(1) or CRKLSH3(1) domains bound efficiently to the HACBPs. A GST-HACBP fusion protein precipitated Crk and CRKL proteins out of 35S-labelled and unlabelled cell lysates. Very little binding of other cellular proteins to HACBP was detectable, indicative of a great preference for Crk and CRKL when compared to the wide variety of other endogenous cellular proteins. Moreover, HACBP disrupted in vitro preexisting Crk-complexes with DOCK180 and the exchange factors SoS and C3G, which are known targets of Crk adapters, in a concentration dependent manner. HACBP-based molecules should therefore be useful as highly selective inhibitors of intracellular signalling processes involving Crk and CRKL.

Identification of cardiac myosin peptides capable of inducing autoimmune myocarditis in BALB/c mice.

Immunization with cardiac myosin induces T cell-mediated myocarditis in genetically predisposed mice and serves as a model for autoimmune heart disease. This study was undertaken to identify pathogenic epitopes on the myosin molecule. Our approach was based on the comparison of the pathogenicity between cardiac (alpha-)myosin and soleus muscle (beta-)myosin. We show that alpha-myosin is the immunodominant isoform and induces myocarditis at high severity and prevalence whereas beta-myosin induces little disease. Therefore the immunodominant epitopes of alpha-myosin must reside in regions of different amino acid sequence between alpha- and beta-myosin isoforms. Cardiac myosin peptides corresponding to these regions of difference were synthesized and tested for their ability to induce inflammatory heart disease. Three pathogenic peptides were identified. One peptide that is located in the head portion of the molecule induced severe myocarditis, whereas two others that reside in the rod portion possessed only minor pathogenicity. The identification of pathogenic epitopes on the cardiac myosin molecule will allow detailed studies on the recognition of this antigen by the immune system and might be used to downmodulate ongoing heart disease.

Zone-specific localization of cytochrome P45011B1 in human adrenal tissue by PCR-derived riboprobes.

Cytochrome P45011B1 (11 beta-hydroxylase) was detected in the human adrenal cortex and in human adenomas by in situ hybridization methods. Specific riboprobes were generated by in vitro transcription of 11 beta-hydroxylase--specific synthetic oligonucleotides with attached T7 and SP6 polymerase promotors. [35S]- and digoxigenin-labeled riboprobes were hybridized to sections of an aldosterone-producing adenoma (APA), the non-tumour portion of the corresponding adrenal gland, and two adenomas not related to hyperaldosteronism using standard protocols and varying washing conditions. After exposure of the radiolabeled sections to X-ray film, the signals were quantified and compared by statistical tests. Following autoradiography or immunohistochemical detection of the digoxigenin cytochrome P45011B1 mRNA was clearly localized in the zona fasciculata/reticularis of non-tumour portion of an human adrenal with an APA. Zona glomerulosa, medulla and connective tissue were free of label. As revealed by the semi-quantitative analysis, 11 beta-hydroxylase mRNA signals in the APA were significantly lower than those in the attached non-tumour portion and the other two adenomas. The results confirm known observations on the occurrence of cytochrome P45011B1 in the adrenal cortex of other species, but show, contrary to several immunohistochemical studies, that the enzyme is obviously not expressed in the zona glomerulosa.

Human adrenal CYP11B1: localization by in situ-hybridization and functional expression in cell cultures.

CYP11B1 was detected in the human adrenal cortex and in human adenomas by in situ-hybridization methods. Specific riboprobes were generated and hybridized to sections of an Aldosterone Producing Adenoma (APA), the non-tumour portion of the corresponding adrenal gland and two adenomas not related to hyperaldosteronism. P45011B1 mRNA was clearly localized in the zona fasciculata/reticularis. Semi-quantitative analysis has been performed and seems to be applicable for a further classification of adrenal tumours. Stable expression of CYP11B1 cDNA was performed in V79 cells. The interference of different substances (metyrapone, spironolactone and different imidazole derivatives) with CYP11B1 activity was studied using this cell line. The cell line revealed to be suitable for analysis of the active site of CYP11B1 as well as for analysis of side effects of drugs on steroidogenesis.

Structural and functional studies on the human hepatic interleukin-6 receptor. Molecular cloning and overexpression in HepG2 cells.

cDNAs coding for the human hepatic interleukin-6 receptor (IL-6-R) have been isolated from a library made from poly(A) RNA of dexamethasone-treated human hepatoma cells (HepG2). We found the hepatic IL-6-R to be identical to the one expressed by leucocytes. A polyclonal antiserum was raised in rabbits against the IL-6-R protein expressed in Escherichia coli. Although the entire IL-6-R protein was used for immunization, only antibodies to the cytoplasmic domain of the IL-6-R were obtained. It is demonstrated by affinity cross-linking and subsequent immunoprecipitation with antibodies against the ligand as well as against the receptor that the cloned cDNA codes for the functional IL-6-R on HepG2 cells. When the hepatic IL-6-R cDNA was overexpressed in HepG2 cells, these cells became more sensitive to low concentrations of IL-6 with respect to the induction of gamma-fibrinogen mRNA.

Structural and functional studies on the human interleukin-6 receptor. Binding, cross-linking, internalization, and degradation of interleukin-6 by fibroblasts transfected with human interleukin-6-receptor cDNA.

A cDNA coding for the human interleukin-6 receptor (IL-6-R) has been expressed stably in murine NIH/3T3 fibroblasts. Transfected cells exhibited a single class of binding sites for 125I-labeled recombinant human interleukin-6 (125I-rhIL-6) (Kd = 440 pM, 20,000 receptors per cell). Affinity cross-linking of 125I-rhIL-6 to the IL-6-R-expressing NIH/3T3 cells led to the detection of three 125I-rhIL-6-containing protein complexes with molecular masses of 100, 120, and 200 kDa suggesting a complex organization of the IL-6-R in the plasma membrane. IL-6 added to the transfected NIH/3T3 cells exerted growth inhibition. This anti-growth effect was observed by the measurement of cell numbers and ornithine decarboxylase mRNA expression. IL-6-R overexpressing fibroblasts internalized 125I-rhIL-6. Intracellular limited proteolysis of IL-6 could be demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A possible implication of skin fibroblasts in the catabolism of IL-6 is discussed.

Studies on the structure and regulation of the human hepatic interleukin-6 receptor.

Affinity cross-linking of 125I-labeled recombinant human interleukin-6 (IL-6) to human hepatoma cells (HepG2) allowed the detection of three IL-6-containing complexes with molecular masses of 100 kDa, 120 kDa and 200 kDa. Treatment of HepG2 cells with dexamethasone led to a time- and dose-dependent up-regulation of IL-6-receptor mRNA levels. By the use of cross-linking this effect was also seen at the protein level, where all three IL-6-binding complexes increased upon incubation of HepG2 cells with dexamethasone. Under conditions of IL-6-receptor up-regulation by dexamethasone, gamma-fibrinogen mRNA induction by IL-6 is stronger and occurs earlier than without dexamethasone. We propose therefore that the expression of the IL-6 receptor might be a rate-limiting step in acute-phase-protein induction.