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Biomedical subjects

David S Pisetsky

Publications and source records attributed to David S Pisetsky.

14 recordsLinked to original sources
PubMed2003

Informed consent in a clinical trial of a novel treatment for rheumatoid arthritis.

OBJECTIVE: To evaluate the informed consent process for a clinical trial of intravenous doxycycline for rheumatoid arthritis. METHODS: Participants completed a self-administered questionnaire about the consent process at baseline and 16 weeks following enrollment in a clinical trial. RESULTS: Respondents (n = 30) affirmed voluntary participation in the parent trial. Participants acknowledged hope and altruism as reasons for entering the trial more than expectation of personal benefit or outside influences. Many respondents did not understand randomization (14/30), placebos (15/30), or risks of study medications; 11/30 respondents believed that the study drug was completely safe. CONCLUSION: Respondents generally understood the experimental nature of the trial and confirmed their participation was voluntary. However, gaps existed in participants understanding of trial design, raising the question of whether they were adequately informed about the research study prior to enrollment. Further education of potential participants in clinical trials may be required to achieve valid informed consent.

Adult↗
PubMed2003

Role of macrophages in the generation of circulating blood nucleosomes from dead and dying cells.

After apoptosis or necrosis, macrophages clear dead cells by phagocytosis. Although this process is efficient, circulating nucleosomes can occur in certain diseases, presumably reflecting either increased production or impaired clearance. To investigate the generation of blood nucleosomes, graded numbers of apoptotic and necrotic cells were administered to healthy mice, and levels of blood nucleosomes and DNA were determined. Using Jurkat cells as a model, nucleosomes and DNA were detected in the blood after the administration of 108 apoptotic or necrotic cells per mouse by the intraperitoneal route. The kinetics of the response were similar for both types of cells. The role of macrophages was assessed by eliminating these cells with clodronate liposomes or silica. Although clodronate treatment alone produced a peak level of blood DNA, the subsequent administration of dead cells caused no change in DNA levels. In contrast, silica treatment alone did not elicit a blood DNA response, though this treatment limited the rise in DNA from administered cells. Molecular studies showed that the blood DNA following the administration of apoptotic or necrotic cells arose from the mouse and the Jurkat cells, and its size distribution was consistent with apoptosis. Together, these findings suggest that the generation of blood nucleosomes depends on macrophages, with apoptosis a concomitant of a high burden of dead and dying cells.

Animals↗
PubMed2003

Regulation of matrix turnover in meniscal explants: role of mechanical stress, interleukin-1, and nitric oxide.

The meniscus is an intra-articular fibrocartilaginous structure that serves essential biomechanical roles in the knee. With injury or arthritis, the meniscus may be exposed to significant changes in its biochemical and biomechanical environments that likely contribute to the progression of joint disease. The goal of this study was to examine the influence of mechanical stress on matrix turnover in the meniscus in the presence of interleukin-1 (IL-1) and to determine the role of nitric oxide (NO) in these processes. Explants of porcine menisci were subjected to dynamic compressive stresses at 0.1 MPa for 24 h at 0.5 Hz with 1 ng/ml IL-1, and the synthesis of total protein, proteoglycan, and NO was measured. The effects of a nitric oxide synthase 2 (NOS2) inhibitor were determined. Dynamic compression significantly increased protein and proteoglycan synthesis by 68 and 58%, respectively, compared with uncompressed explants. This stimulatory effect of mechanical stress was prevented by the presence of IL-1 but was restored by specifically inhibiting NOS2. Release of proteoglycans into the medium was increased by IL-1 or mechanical compression and further enhanced by IL-1 and compression together. Stimulation of proteoglycan release in response to compression was dependent on NOS2 regardless of the presence of IL-1. These finding suggest that IL-1 may modulate the effects of mechanical stress on extracellular matrix turnover through a pathway that is dependent on NO.

Animals↗
PubMed2003

Screening the genome for rheumatoid arthritis susceptibility genes: a replication study and combined analysis of 512 multicase families.

OBJECTIVE: A number of non-HLA loci that have shown evidence (P < 0.05) for linkage with rheumatoid arthritis (RA) have been previously identified. The present study attempts to confirm these findings. METHODS: We performed a second genome-wide screen of 256 new multicase RA families recruited from across the United States by the North American Rheumatoid Arthritis Consortium. Affected sibling pair analysis on the new data set was performed using SIBPAL. We subsequently combined our first and second data sets in an attempt to enhance the evidence for linkages in a larger sample size. We also evaluated the impact of covariates on the support for linkage, using LODPAL. RESULTS: Evidence of linkage at 1p13 (D1S1631), 6p21.3 (the HLA complex), and 18q21 (D18S858) (P < 0.05) was replicated in this independent data set. In addition, there was new evidence for linkage at 9p22 (D9S1121 [P = 0.001]) and 10q21 (D10S1221 [P = 0.0002] and D10S1225 [P = 0.0038]) in the current data set. The combined analysis of both data sets (512 families) showed evidence for linkage at the level of P < 0.005 at 1p13 (D1S1631), 1q43 (D1S235), 6q21 (D6S2410), 10q21 (D10S1221), 12q12 (D12S398), 17p13 (D17S1298), and 18q21 (D18S858). Linkage at HLA was also confirmed (P < 5 x 10(-12)). Inclusion of DRB1*04 as a covariate significantly increased the probability of linkage on chromosome 6. In addition, some linkages on chromosome 1 showed improved significance when modeling DRB1*04 or rheumatoid factor positivity as covariates. CONCLUSION: These results provide a rational basis for pursuing high-density linkage and association studies of RA in several regions outside of the HLA region, particularly on chromosomes 1p, 1q, and 18q.

Arthritis, Rheumatoid↗
PubMed2003

The expression of plasma nucleosomes in mice undergoing in vivo apoptosis.

Nucleosomes occur in the blood of patients with systemic lupus erythematosus and are thought to result from in vivo cell death. To determine the conditions for the release of nucleosomes into the blood, normal mice were treated with four agents that have the potential to induce apoptosis or immune cell activation in vivo: LPS, CpG DNA, anti-Fas antibody, and dexamethasone. Blood nucleosomes were measured by a capture ELISA immunoassay, with the DNA component assessed by fluorimetry with the dye PicoGreen. Following treatment with LPS and a monoclonal anti-Fas antibody, nucleosomes and DNA appeared in the plasma in a dose-dependent fashion. In contrast, dexamethasone treatment, despite causing significant thymocyte loss, did not elicit plasma nucleosomes. Similarly, CpG DNA, while inducing an IL-12 response comparable to that of LPS, also did not elicit plasma nucleosomes. These results suggest that plasma nucleosome levels reflect specific patterns of cell death and are not an invariable consequence of in vivo apoptosis or immune cell activation.

Adjuvants, Immunologic↗
PubMed2003

Effect of cytofectins on the immune response of murine macrophages to mammalian DNA.

DNA, depending on base sequence, can induce a wide range of immune responses. While bacterial DNA is stimulatory, mammalian DNA is inactive alone and can, moreover, inhibit the response to bacterial DNA. To determine whether the mode of cell entry affects the immune properties of mammalian DNA, we have investigated the effects of the cytofectin agents Fugene 6 (Roche Diagnostics Corp., Indianapolis, IN), Lipofectin and Lipofectamine (Life Technologies, Grand Island, NY) on the responses of murine macrophages to DNA from calf thymus and human placenta. Whereas calf thymus and human placenta DNA alone failed to stimulate J774 or RAW264.7 cell lines or bone marrow-derived macrophages, these DNAs in complexes with cytofectin agents stimulated macrophages to produce nitric oxide but not interleukin 12. Both single-stranded and double-stranded DNAs were active in the presence of cytofectins. Macrophage activation by the DNA-cytofectin complexes was reduced by chloroquine, suggesting a role of endosomal acidification in activation. As shown by flow cytometry and confocal microscopy, the cytofectins caused an increase in the uptake of DNA into cells. Our findings indicate that macrophages vary in their response to DNA depending on uptake pathway, suggesting that activation by DNA reflects not only sequence but also context or intracellular location.

Animals↗
PubMed2003

Enhancing immunogenicity by CpG DNA.

Bacterial DNA and oligonucleotides containing unmethylated CpG dinucleotides (CpG DNA) can stimulate immune responses and have potential for use as novel agents to enhance immunogenicity. CpG DNA can interact with toll-like receptor 9 and cause activation through a myeloid differentiation primary response gene (MyD88)-dependent signaling pathway. Due to its pattern of immune cell activation, CpG DNA can induce a cytokine milieu to promote T-helper cell responses and serve as an adjuvant. Furthermore, CpG DNA can provide protection against pathogens in animal models and has therapeutic applications in clinical settings such as in cancer and allergy.

Adjuvants, Immunologic↗
PubMed2002

Influence of hypoxia and reoxygenation on cytokine-induced production of proinflammatory mediators in articular cartilage.

OBJECTIVE: Articular cartilage is an avascular tissue that functions at a lower oxygen tension than do most tissues. With mobilization, arthritic joints may undergo cycles of hypoxia and reoxygenation. The goal of this study was to determine the effects of hypoxia and reoxygenation on cytokine-induced nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production in articular cartilage. METHODS: Porcine cartilage explants were incubated at 37 degrees C for 72 hours in either 1% O(2) (hypoxia) or 20% O(2) (normoxia) in media supplemented with interleukin-1alpha (IL-1alpha) or tumor necrosis factor alpha (TNFalpha), with or without the NO synthase 2 (NOS2) selective inhibitor 1400W. Culture media were then removed and replaced with freshly prepared media and incubated for a further 24 hours in normoxia. RESULTS: NO levels were significantly higher in explants supplemented with IL-1alpha and TNFalpha compared with controls, in both hypoxia and normoxia. Compared with normoxia, hypoxia decreased IL-1alpha- and TNFalpha-induced NO production significantly. Reoxygenation of hypoxic explants resulted in sustained significant NO production in response to either cytokine. However, comparably high levels of NO production were not sustained in explants cultured continuously in normoxia. Although IL-1alpha alone did not significantly increase PGE(2) production, significant PGE(2) superinduction occurred in cartilage stimulated with IL-1alpha and the NOS2 inhibitor 1400W compared with stimulation with IL-1alpha alone in hypoxia, but not in normoxia. CONCLUSION: Oxygen tension significantly affects cytokine-induced proinflammatory mediator production in articular cartilage. Furthermore, hypoxia alters NO mediation of PGE(2) production. Hypoxia and reoxygenation can affect cytokine-induced proinflammatory mediator production, suggesting that oxygen tension may influence inflammation associated with cartilage injury and disease.

Animals↗
PubMed2002

Inhibition of murine macrophage nitric oxide production by synthetic oligonucleotides.

Synthetic 30-mer phosphorothioate (Ps) oligonucleotides (ODN) comprised of single bases (SdA30, SdC30, SdG30, and SdT30) were assessed for their effects on nitric oxide (NO) production by murine bone marrow macrophages (BMMC) and macrophage cell lines J774 and RAW264.7. Pretreatment of these cells with any of the four Ps ODN inhibited NO production induced by CpG ODN, E. coli DNA (EC DNA), or LPS. This inhibition was time- and dose-dependent and was observed even if the Ps ODN were added as long as 12 h after stimulation. As in the case of stimulatory ODN, inhibition was dependent on backbone structure and length. Thus, all four 30-mer, single-base Ps ODN were inhibitory, and only dG30 among phosphodiester ODN was inhibitory. Together, these observations indicate that Ps ODN can inhibit macrophage production of inflammatory mediators, suggesting a role of these compounds as immunomodulatory agents.

Animals↗
PubMed2002

Inhibition of murine dendritic cell activation by synthetic phosphorothioate oligodeoxynucleotides.

Depending on sequence and backbone structure, DNA can inhibit as well as stimulate immune responses. As previously shown, single-base phosphorothioate (Ps) oligodeoxynucleotides (ODN) can inhibit murine macrophage activation. To determine whether these compounds can also affect dendritic cells (DC), the effects of 30-mer Ps ODN (SdA, SdT, SdG, and SdC) on DC activation were assessed in an in vitro system. With DC preparations obtained from murine bone marrow cultured in granulocyte macrophage-colony stimulating factor, the Ps ODN blocked the production of interleukin-12 and nitric oxide induced by bacterial DNA, an immunostimulatory cytosine phosphate guanosine dinucleotide (CpG) ODN and lipopolysaccharide (LPS). Furthermore, these compounds inhibited up-regulation of costimulatory molecules CD40 and CD86 as well as major histocompatibility complex-II molecules, indicating an effect on DC maturation. Although the Ps ODN limited uptake of CpG ODN as assessed by flow cytometry, the Ps ODN did not affect LPS uptake, suggesting that these compounds inhibit DC responses by effects on downstream signaling pathways. Together, these observations extend the range of action of inhibitory ODN to DC and suggest a role of these compounds as immunomodulatory agents.

Animals↗