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Biomedical subjects

M Lotz

Publications and source records attributed to M Lotz.

At least 55 records · Page 3Linked to original sources
PubMed1998

Chondrocyte apoptosis and nitric oxide production during experimentally induced osteoarthritis.

OBJECTIVE: Chondrocytes produce nitric oxide (NO) and undergo apoptosis in response to exogenous NO. This study sought to examine the relationship between NO synthesis, chondrocyte apoptosis, and the development of cartilage degradation during experimental osteoarthritis (OA). METHODS: OA was induced in rabbits by anterior cruciate ligament transection (ACLT). Knees were harvested after 4 weeks and assessed for OA severity and chondrocyte apoptosis. Conditioned media from cultured cartilage explants were analyzed for nitrite content. Cartilage sections were analyzed by immunohistochemistry for the presence of nitrotyrosine. RESULTS: All ACLT knees demonstrated osteoarthritic changes. Conditioned media from ACLT cartilage organ cultures contained higher levels of nitrite as compared with cartilage samples from the nonoperated side or from rabbits that had not received ACLT. Cultures of specific areas of cartilage from ACLT knees showed high levels of NO production in the medial femoral and medial tibial cartilage. Approximately 28.7% of chondrocytes isolated from ACLT cartilage and 6.7% of chondrocytes from cartilage of the nonoperated side underwent apoptosis. In situ staining demonstrated apoptotic cells in the superficial and middle zones of ACLT cartilage. A high number of apoptotic cells was present at the pannus-cartilage junction. In control cartilage, the superficial zone contained a small number of cells in apoptosis. The prevalence of apoptotic cells was significantly correlated with the levels of nitrite production and OA grade. CONCLUSION: These observations suggest that, during the early phases of OA, NO production may lead to chondrocyte apoptosis, and that both events contribute to the pathogenesis of cartilage degradation. Inhibitors of NO synthesis and chondrocyte apoptosis may therefore be of therapeutic value after cartilage injury and in patients with OA.

Animals↗
PubMed1998

Linkage of chondrocyte apoptosis and cartilage degradation in human osteoarthritis.

OBJECTIVE: To examine the occurrence of apoptosis in human osteoarthritis (OA) cartilage, and to determine its relationship to cartilage degradation. METHODS: Knee cartilage was obtained from subjects at autopsy, from a tissue bank, and from OA patients undergoing total joint replacement surgery. Chondrocytes were isolated and the number of apoptotic cells was analyzed by flow cytometry. Apoptotic cells in cartilage sections were identified by the detection of DNA strand breaks. Electron microscopy was applied to demonstrate morphologic changes, and Safranin O staining was performed to analyze the relationship between apoptosis and proteoglycan depletion. RESULTS: Flow cytometry on cell suspensions prepared from collagenase digests of cartilage showed that approximately 22.3% of OA chondrocytes and 4.8% of normal chondrocytes were undergoing apoptosis. Staining of cartilage sections demonstrated the presence of apoptotic cells in the superficial and middle zones. Cartilage areas that contained apoptotic cells showed proteoglycan depletion, and the number of apoptotic cells was significantly correlated with the OA grade. CONCLUSION: These observations demonstrate increased chondrocyte apoptosis in OA cartilage. Chondrocyte apoptosis and proteoglycan depletion are anatomically linked and may be mechanistically related.

Adult↗
PubMed1998

Parathyroid hormone-related proteins is abundant in osteoarthritic cartilage, and the parathyroid hormone-related protein 1-173 isoform is selectively induced by transforming growth factor beta in articular chondrocytes and suppresses generation of extracellular inorganic pyrophosphate.

OBJECTIVE: Parathyroid hormone-related protein (PTHrP) is a major, locally expressed regulator of growth cartilage chondrocyte proliferation, differentiation, synthetic function, and mineralization. Because mechanisms that limit cartilage chondrocytes from maturing and mineralizing are diminished in osteoarthritis (OA), we studied PTHrP expression by articular chondrocytes. METHODS: PTHrP was studied in normal knee cartilage samples and cultured articular chondrocytes, and in cartilage specimens from knees with advanced OA, obtained at the time of joint replacement. RESULTS: PTHrP was more abundant in OA than in normal human knee articular cartilage. Both demonstrated PTH/PTHrP receptor expression. PTHrP 1-173, one of three alternatively spliced PTHrP isoforms, was exclusively expressed and induced by transforming growth factor beta in cultured chondrocytes. Chondrocytes mainly used the GC-rich P2 alternative promoter to express PTHrP messenger RNA. Inhibition by PTHrP 1-173, but not by PTHrP 1-146 or PTHrP 1-87, of inorganic pyrophosphate (PPi) elaboration suggested selective functional properties of the 1-173 isoform. Exposure to a neutralizing antibody to PTHrP increased PPi elaboration by articular chondrocytes. CONCLUSION: Increased expression of PTHrP, including the 1-173 isoform, has the potential to contribute to the pathologic differentiated functions of chondrocytes, including mineralization, in OA.

Adult↗
PubMed1998

Overexpression of pp60c-src elicits invasive behavior in rat colon epithelial cells.

BACKGROUND & AIMS: Src activation is reported as an early event found in preneoplastic colonic adenomas and in 70% of colon carcinomas. The aim of this study was to identify the biological consequences of c-src overexpression in rat colon epithelial cells. METHODS: Introduction and overexpression of c-src in an immortalized rat colon epithelial cell line was achieved using lipofection. Transfectants were tested for changes in growth and cell behavior using different in vitro assay systems. RESULTS: Colon epithelial cells overexpressing c-src showed the ability to form microcolonies in soft agar without acquiring tumorigenic potential. In in vitro assays, c-src transfectants displayed a gain of invasive potential through Matrigel without an accompanying change in migrational ability. No discernible qualitative changes were observed in the phosphotyrosyl protein profile between c-src and v-src transfectants. Assessment of the cadherin/catenin status in these cells revealed an intact, functional complex with no detectable tyrosine phosphorylation of different components of the complex. CONCLUSIONS: Overexpression of c-src in an immortalized rat colon epithelial cell line does not elicit full neoplastic transformation but enhances anchorage-independent growth and confers invasion capability. Increased invasion through Matrigel was not linked to inactivation of the cadherin complex in c-src transfectants.

Animals↗
PubMed1997

The role of IFN regulatory factor-1 in synovitis and nitric oxide production.

The IFN regulatory factor-1 (IRF-1) DNA binding protein regulates expression of genes that are involved with the induction of immune and inflammatory responses. The present study used mice with a targeted disruption of the IFN regulatory factor-1 gene (IRF-1-/-) to examine the role of this transcription factor in synovial inflammation and nitric oxide production. Intraarticular injection of IL-1 or LPS was associated with a significantly reduced intensity of synovial lining hyperplasia and leukocyte infiltration in the IRF-1-/- mice as compared with wild-type mice of the same parental lineage C57BL/6. Nitric oxide (NO) is involved with the pathogenesis of arthritis, and IRF-1 regulates expression of inducible NO synthase (iNOS) in mononuclear phagocytes. Articular chondrocytes from IRF-1-/- mice produced similar levels of NO in response to IL-1 or LPS. Furthermore, the synergistic induction of NO by IFN-gamma and IL-1 or LPS was almost identical in chondrocytes from wild-type and IRF-1-/- mice. This was in contrast to the expected decrease in NO production by peritoneal macrophages from IRF-1-/- mice, suggesting that IRF-1 is not required for iNOS expression in chondrocytes. These results indicate that IRF-1 has a tissue-specific role in the induction of iNOS. Inhibition of this transcription factor may represent a novel approach in controlling inflammatory diseases such as arthritis.

Animals↗
PubMed1997

CD137, a member of the tumor necrosis factor receptor family, is located on chromosome 1p36, in a cluster of related genes, and colocalizes with several malignancies.

CD137 (ILA/4-1BB) is a member of the tumor-necrosis-factor receptor family. Members of this receptor family and their structurally related ligands are important regulators of a wide variety of physiological processes and play an especially important role in the regulation of immune responses. CD137 regulates cell proliferation and survival of T-lymphocytes. Using Southern blot analysis and polymerase chain reaction, we localized the CD137 gene to chromosome 1p36. This chromosomal region harbors the genes of several other members of this receptor family and is associated with deletions and rearrangements in several malignancies.

Chromosome Deletion↗
PubMed1997

Glucocorticoids induce Kaposi's sarcoma cell proliferation through the regulation of transforming growth factor-beta.

Glucocorticoid (GC) use is known to induce or enhance the growth of Kaposi's sarcoma (KS) in many clinical settings including human immunodeficiency virus infection, collagen vascular disease, lymphoproliferative disorders, and renal transplantation. Because GCs may induce immune suppression and thus tumor growth, we determined whether GCs had a direct effect on KS growth. We found that GCs directly induce the growth of KS cell lines. In examining the mechanism of action of GCs, we did not observe induction of known autocrine growth factors for KS including interleukin-1 (IL-1), IL-6, oncostatin-M, basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF). We thus examined factor(s) that inhibit KS growth. Transforming growth factor-beta (TGF-beta) is produced by KS cells and has pleiotropic effects, including inhibiting the growth of hematopoietic and endothelial cells. We show that TGF-beta is produced by KS cells in both the latent and active forms, and that TGF-beta is an autocrine growth inhibitory factor. We then studied the effects of GCs on the regulation of TGF-beta and found that GCs do not inhibit TGF-beta transcription, but significantly inhibit TGF-beta activation. This effect is mediated through regulation of the TGF-beta activation pathway. TGF-beta is activated by plasmin which is positively regulated by plasminogen activator (PA) and PA receptor (PAR), and negatively regulated by plasminogen activator inhibitor (PAI). GCs downregulated PAR and upregulated PAI. Thus, glucocorticoids enhance KS cell growth through the regulation of TGF-beta activation.

Cell Division↗
PubMed1997

Differential effects of aging on human chondrocyte responses to transforming growth factor beta: increased pyrophosphate production and decreased cell proliferation.

OBJECTIVE: To address the influence of age on inorganic pyrophosphate (PPi) accumulation in human articular chondrocytes. METHODS: Articular cartilage was obtained from men and women in 2 different age groups: ages 15-55 and 56-91. The effects of transforming growth factor beta1 (TGFbeta1) on PPi levels in the media and cell lysates of chondrocytes were investigated. In addition, the effects of TGFbeta on PPi accumulation were compared with chondrocyte proliferation. RESULTS: TGFbeta1 increased PPi levels to a greater extent in chondrocytes from subjects in the older age group compared with those obtained from younger subjects. Treatment of chondrocytes with TGFbeta1 led to a similar increase in total intracellular protein in both age groups. Although TGFbeta increased nucleoside triphosphate pyrophosphohydrolase activity and decreased alkaline phosphatase activity, these effects did not differ between the 2 age groups. Analysis of the same cell preparations showed an age-related decrease in TGFbeta-induced chondrocyte proliferation, whereas these same cells showed an increased response with respect to PPi elaboration. CONCLUSION: These results show that aging differentially affected TGFbeta-induced PPi accumulation versus proliferation in human articular chondrocytes. These differences in TGFbeta response are likely to contribute to the development of age-associated cartilage diseases such as osteoarthritis.

Adolescent↗
PubMed1997

Fas/Fas ligand expression and induction of apoptosis in chondrocytes.

OBJECTIVE: To examine the expression of Fas/Fas ligand and the role of this ligand/receptor interaction in the regulation of apoptosis in normal human articular chondrocytes and in osteoarthritis (OA) cartilage. METHODS: Normal and OA human knee cartilage and cells isolated from these tissues were tested for Fas expression by flow cytometry. Induction of apoptosis by antibody to Fas was analyzed by DAPI staining and electron microscopy. RESULTS: Treatment of freshly isolated normal human articular chondrocytes with an agonistic Fas antibody induced apoptosis in a subpopulation (approximately 20%) of the cells. Apoptosis induced by anti-Fas was not dependent on nitric oxide (NO), and anti-Fas also did not induce NO production. Analysis of isolated cells demonstrated similar levels of Fas expression on normal and OA chondrocytes (28% and 32%, respectively). In normal articular cartilage, Fas-positive cells were located mainly in the superficial and midzones. In contrast, in fibrillated OA cartilage, surface layers were partially absent and Fas-expressing cells were also detected in the deeper layers. Fas ligand messenger RNA was not detectable in resting or activated normal or OA chondrocytes. Analysis by electron microscopy showed the nuclear and cytoplasmic changes typical of apoptosis in cultures treated with antibody to Fas. CONCLUSION: A subpopulation of chondrocytes expresses Fas and is susceptible to Fas-induced apoptosis. Fas-mediated chondrocyte apoptosis may contribute to cartilage degradation in arthritis.

Antibodies↗
PubMed1997

Differentiation-dependent and stimulus-specific expression of ILA, the human 4-1BB-homologue, in cells of mesenchymal origin.

OBJECTIVE: Examine the expression of ILA, a member of the human NGF/TNF receptor family and the homologue of the murine 4-1BB, in mesenchymal cells. METHODS: ILA mRNA was analyzed by quantitative polymerase chain reaction and Northern blotting in human articular chondrocytes and fibroblasts. ILA protein expression was examined by flow cytometry. RESULTS: The proinflammatory stimuli interleukin-1 beta (IL-1 beta), tumour necrosis factor (TNF) alpha, leukemia inhibitory factor (LIF), interferon (IFN) gamma and lipopolysaccharide (LPS) induced ILA mRNA in primary human articular chondrocytes. TGF beta and dexamethasone inhibited IL-1 induced ILA expression. Chondrocytes expressed the 4.8, 4.0 and 1.9 kb isoforms of ILA mRNA which had previously been observed in lymphocytes and additional isoforms at 3.2, 1.5 and 1.2 kb. Cycloheximide alone induced ILA mRNA in primary chondrocytes while the combination of IL-1 and cycloheximide resulted in ILA superinduction. In contrast to primary chondrocytes, activated human synovial or skin fibroblasts did not express ILA mRNA. Furthermore, ILA was no longer inducible by IL-1 in subcultured, dedifferentiated chondrocytes. However, repression of ILA in fibroblasts and dedifferentiated chondrocytes was overcome by cycloheximide and IL-1 further increased ILA mRNA levels in the presence of cycloheximide. Flow cytometric analysis of ILA protein expression with monoclonal antibodies revealed increased cell-surface expression on IL-1 or TNF alpha, but not on TGF beta stimulated chondrocytes. CONCLUSION: ILA is not only expressed in the immune system but also in mesenchymal cells. ILA expression is induced by specific stimuli and modulated by the differentiation status of the cells. ILA can serve as a model and marker to analyze differentiation-dependent gene expression in mesenchymal cells.

Cartilage, Articular↗
PubMed1997

Pannocytes: distinctive cells found in rheumatoid arthritis articular cartilage erosions.

A distinctive cell was identified from sites of rheumatoid arthritis cartilage injury. Similar cells are not found in lesions of osteoarthritis cartilage. We have designated them as pannocytes (PCs). Their rhomboid morphology differs from the bipolar shape of fibroblast-like synoviocytes or the spherical configuration of primary human articular chondrocytes. Chondrocytes are short-lived, whereas the original PC line grew for 25 passages before becoming senescent. Features in common with cultured primary chondrocytes include maximal proliferation in response to transforming growth factor-beta a catabolic response to interleukin-1 beta, collagenase production, and mRNA for the induced lymphocyte antigen and inducible nitric oxide synthase. Despite the presence of the inducible nitric oxide synthase message, PCs do not produce NO either constitutively or when cytokine stimulated. Each of the mesenchymal cells, fibroblast-like synoviocytes, primary chondrocytes, and PCs have the gene for type I collagen, but the type II collagen gene is detected only in primary chondrocytes. PCs can be distinguished from fibroblast-like synoviocytes and primary chondrocytes by their morphology, bright VCAM-1 staining, and growth response to cytokines and growth factors. Their prolonged life span in vitro suggests that PCs might represent an earlier stage of mesenchymal cell differentiation, and they could have a heretofore unrecognized role in rheumatoid arthritis joint destruction.

Antigens, Surface↗
PubMed1996

Selective activation of the mitogen-activated protein kinase subgroups c-Jun NH2 terminal kinase and p38 by IL-1 and TNF in human articular chondrocytes.

Previous studies suggested that tyrosine kinase activation is an important signal transduction event in the IL-1 response of chondrocytes. The present study identifies the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase (ERK)-1 and ERK-2 as major tyrosine phosphorylated proteins in IL-1 stimulated chondrocytes. Kinase assays on immunoprecipitates with myelin basic protein as substrate showed that ERK-1 and ERK-2 activation was detectable within 5 min after IL-1 stimulation and decreased to baseline within 60 min. Analysis of other members of the MAP kinase family showed that chondrocytes also express c-Jun NH2 terminal kinase (JNK)-1, JNK-2, and p38 proteins. These kinases were time-dependently activated by IL-1. Among other chondrocyte activators tested, only TNF activated all three of the MAP kinase subgroups. JNK and p38 were not activated by any of the other cytokines and growth factors tested. However, ERK was also activated by PDGF, IGF-1, and IL-6. Phorbol 12-myristate 13-acetate, calcium ionophore, and cAMP analogues only increased ERK activity but had no significant effects on JNK or p38. These results suggest differential activation of MAP kinase subgroups by extracellular stimuli. ERK is activated in response to qualitatively diverse extracellular stimuli and various second messenger agonists. In contrast, JNK and p38 are only activated by IL-1 or TNF, suggesting that these kinases participate in the induction of the catabolic program in cartilage.

Calcium↗
PubMed1996

Immunostimulatory DNA sequences necessary for effective intradermal gene immunization.

Vaccination with naked DNA elicits cellular and humoral immune responses that have a T helper cell type 1 bias. However, plasmid vectors expressing large amounts of gene product do not necessarily induce immune responses to the encoded antigens. Instead, the immunogenicity of plasmid DNA (pDNA) requires short immunostimulatory DNA sequences (ISS) that contain a CpG dinucleotide in a particular base context. Human monocytes transfected with pDNA or double-stranded oligonucleotides containing the ISS, but not those transfected with ISS-deficient pDNA or oligonucleotides, transcribed large amounts of interferon-alpha, interferon-beta, and interleukin-12. Although ISS are necessary for gene vaccination, they down-regulate gene expression and thus may interfere with gene replacement therapy by inducing proinflammatory cytokines.

Amino Acid Sequence↗
PubMed1996

ILA, a member of the human nerve growth factor/tumor necrosis factor receptor family, regulates T-lymphocyte proliferation and survival.

ILA, a gene induced by lymphocyte activation, is a member of the human nerve growth factor tumor necrosis factor receptor family and the human homologue of murine 4-1BB. The present study analyzed the role of ILA in the regulation of human peripheral blood T-lymphocyte function. Antibodies raised against different fusion proteins recognized ILA on activated lymphocytes. These antibodies significantly increased anti-CD3--induced T-lymphocyte proliferation. When anti-CD3--stimulated cells were incubated on ILA-expressing CHO cells, proliferation was inhibited. CHO cells transfected with a control construct and not expressing ILA did not reduce T-cell proliferation. A purified fusion protein containing the extracellular domain of ILA and the constant domain of human IgG (ILA-IgG) also inhibited lymphocyte proliferation. Results obtained by 3H-thymidine incorporation were confirmed by cell cycle analysis that showed a decrease in the number of lymphocytes in S phase. Lymphocyte morphology in cultures with ILA-expressing CHO cells was suggestive of apoptosis. Flow cytometry on propidium iodide-stained cells showed a time-dependent increase in the number of hypodiploid apoptotic cells when lymphocytes were cultured on ILA-expressing CHO cells. Internucleosomal DNA cleavage was seen in these cultures, but not in the presence of ILA-negative CHO cells. Studies on the mechanism by which ILA regulates T-cell function showed that ILA-IgG inhibited anti-CD3-induced T-cell proliferation when presented in immobilized but not in soluble form. These results suggest that ILA may act by cross-linking its ligand and thereby inhibit T-cell proliferation.

Animals↗
PubMed1996

TSG-6 expression in human articular chondrocytes. Possible implications in joint inflammation and cartilage degradation.

OBJECTIVE: The hyaluronan-binding protein TSG-6 (tumor necrosis factor-stimulated gene 6) forms a stable complex with the serine protease inhibitor, inter-alpha-inhibitor, potentiates the inhibition of plasmin activity, and has antiinflammatory effects in vivo. This study examines the expression of TSG-6 in human articular chondrocytes and cartilage. METHODS: Human articular chondrocytes and cartilage explants were stimulated with cytokines, growth factors, and other agents. TSG-6 expression was analyzed by imaging-assisted Northern and Western blotting. RESULT: TSG-6 messenger RNA (mRNA) expression was upregulated by cytokines and growth factors, predominantly interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), platelet-derived growth factor AA (PDGF-AA), and transforming growth factor beta 1 (TGF beta 1). TSG-6 mRNA induction by TGF beta 1 was delayed as compared with IL-1beta. Treatment of the cells with the glucocorticoid dexamethasone neither induced TSG-6 mRNA nor did it affect IL-1 beta-induced transcript levels. TSG-6 mRNA induction may involve several signal transduction pathways. The strong transcriptional stimulation by phorbol myristate acetate suggests protein kinase C (PKC)-mediated signaling. In contrast, PKA- and Ca- dependent signals are only marginally involved as messengers leading to increased TSG-6 levels after IL-1beta and TNF alpha treatment. In chondrocyte and cartilage organ cultures, both free TSG-6 (35 kd) and the complex with inter-alpha-inhibitor (120 kd) were present and upregulated by IL-1 beta, TNF alpha, or TGF beta 1. CONCLUSION: Chondrocytes are a source of TSG-6 which may play a role in cartilage remodeling and joint inflammation.

Cartilage, Articular↗
PubMed1996

The nerve growth factor/tumor necrosis factor receptor family.

Receptors in the nerve growth factor/tumor necrosis factor receptor family are characterized by the presence of cysteine-rich motifs of approximately 40 amino acids in the extracellular domain. The ligands are type II transmembrane proteins with beta-strands that form a jelly-roll beta-sandwich. The receptors recognize soluble or cell-surface-bound ligands and mediate diverse cellular responses. Activation of intracellular signals is mediated at least in part by the association of proteins with a RING finger motif or a death domain to the cytoplasmic domains of the receptors. In addition to cell-membrane-bound receptors soluble forms have been described for most of the receptors. Activation of intracellular signals not only occurs through ligand binding to the receptors but cross-linking of at least some members of the ligand family can regulate cell functions.

Animals↗
PubMed1996

[Quality assurance in clinical social work: specific interventions for specific problem areas in different psychiatric patient groups?].

Based on the standardized data of 2643 treatment episodes documented over 11 years in a psychiatric hospital, this study investigates the issues, activities, and outcome of social work with 2038 psychiatric inpatients from the perspective of quality assurance. A primary objective was to study how the social workers' interventions relate to the patients' problems also with regard to sociodemographic characteristics and type of disorder of the patient. The social workers' estimation of the outcome was also studied in relation to these variables. Interventions were found to correspond significantly with problems, and were mostly depending on age, sex, and diagnosis. Impaired social functioning, predominantly present in chronic disorders, was the major concern of social work interventions.

Activities of Daily Living↗