Biomedical subjects

Eric Solary

Publications and source records attributed to Eric Solary.

44 records · Page 3Linked to original sources

PubMed2003

Longterm protection of mice against collagen-induced arthritis after short-term LF 15-0195 treatment: modulation of B and T lymphocyte activation.

OBJECTIVES: LF 15-0195 is an immunosuppressive agent obtained by organic synthesis, currently under clinical development for the treatment of vasculitis. We define the effects of LF 15-0195 in the murine collagen-induced arthritis (CIA) model, an experimental model of human rheumatoid arthritis. METHODS: In our model, CIA was elicited in DBA/1 mice by immunization with bovine type II collagen (CII) in Freund's complete adjuvant, followed by a repeat injection 21 days later. Disease onset was observed 6 days after booster injection. In these experiments, mice were treated with 5 daily LF 15-0195 injections starting after the booster injection (days 21-25). The mice were observed for 40 days after the start of treatment, during which time arthritis was scored using clinical score and paw swelling assessment. Modulation of humoral immunity was documented by measuring the serum level of anti-CII IgG1 and IgG2a and cellular immunity by cytokines production by lymph node cells (LNC) and their proliferation in vitro. RESULTS: Short-term treatment of LF 15-0195 after booster injection prevented longterm development of CIA. LF 15-0195 inhibited B cell differentiation with a marked suppression of anti-CII IgG1 and IgG2a synthesis. Functional analyses of T lymphocytes showed that LF 15-0195 treatment reduces cytokine production by LNC after CII, anti-CD3, lipopolysaccharide stimulation. CONCLUSION: LF 15-0195 treatment during a short time period prevented development of arthritis, inhibited humoral-specific response longterm, induced a decrease in the number of LNC, and decreased cytokine production of T LNC after ex vivo stimulation.

Animals↗

PubMed2002

Differential influence of etoposide on two caspase-2 mRNA isoforms in leukemic cells.

Etoposide (VP-16) is an anticancer agent that induces apoptosis in human leukemic cell lines such as U937 and HL60. We performed RNase protection assays, with two distinct cRNA panels covering most of caspase and BCL-2-related genes, using total RNA from cell lines exposed to various concentrations of the drug. Our results show that VP-16 down-regulates expression of most surveyed genes with the noticeable exception of casp-2S mRNA that is up regulated whereas casp-2L mRNA is decreased. Since these mRNAs are produced by the alternative splicing of exon 9, we devised a reverse transcriptase-polymerase chain reaction method using primers from exons 8 and 10 to demonstrate that VP-16 stimulates the production of exon 9-containing sequences, irrespective of active transcription. However, this effect is specific of the 3'-end of the CASP-2 gene since no difference in the relative amounts of the 5'-end of the mRNA species is detected. Nevertheless, the level of full-length casp-2L mRNA together with that of procaspase-2L protein, which is pro-apoptotic, are decreased under VP-16 treatment, suggesting that an early cell response to treatment by cytotoxic agents is to down-regulate expression of selected pro-apoptotic proteins.

Alternative Splicing↗

PubMed2002

An atypical caspase-independent death pathway for an immunogenic cancer cell line.

REGb cell line, a highly immunogenic tumor cell variant isolated from a rat colon cancer, yields regressive tumors when injected into syngeneic hosts. We previously demonstrated that REGb tumor immunogenicity was related to the capacity of releasing dead cells in vivo. Also, in vitro, REGb cell monolayers release dead cells, especially when cultured in serum-free medium. In the current study, we show that the release of dead cells results from an atypical death process associating features of necrosis and apoptosis. In spite of features considered as hallmarks of caspase-dependent apoptosis, including chromatin fragmentation and DNA oligonucleosomal cleavage, caspases are not activated and caspase inhibitors are ineffective to prevent REGb cell death. In contrast with a number of other types of cell death, the spontaneous death of REGb cells in culture depends on de novo protein synthesis as this death is blocked by low doses of the mRNA translation inhibitor cycloheximide. This unusual mode of cell death that associates necrotic and apoptotic features could provide optimal conditions for triggering a specific immune response.

Amino Acid Chloromethyl Ketones↗

PubMed2002

LF 15-0195 immunosuppressive agent enhances activation-induced T-cell death by facilitating caspase-8 and caspase-10 activation at the DISC level.

The deoxyspergualin derivative LF 15-0195 has demonstrated some efficacy in animal models of autoimmune and graft-versus-host diseases and is currently tested in clinics. The molecular mechanisms of LF 15-0195 immunosuppressive activity remained unknown. We show that exposure to LF 15-0195 sensitizes Jurkat T cells to apoptosis induced by an agonistic anti-CD95 antibody (CH11 clone) and by the cytokine TNF-related apoptosis-inducing ligand. LF 15-0195 does not demonstrate any significant effect on the postmitochondrial activation of caspases, nor does it modify overall expression of CD95, Fas-associated death domain, and procaspase-8. The compound facilitates the recruitment of these molecules to the death-inducing signaling complex (DISC) and enhances caspase-8 and -10 activation, thus increasing cytochrome c and direct IAP binding with low pI (DIABLO)/Smac mitochondrial release. LF 15-0195 also sensitizes Jurkat T cells to CD3-mediated apoptosis, an in vitro model for activation-induced T-cell death (AICD). LF 15-0195-mediated sensitization to AICD was further confirmed in human peripheral T cells exposed to anti-CD3 antibodies, then cultured in the presence of interleukin-2. In these cells, LF 15-0195 increased apoptosis triggered by either anti-CD95 antibodies or CD3 restimulation, whereas no effect was observed on "passive apoptosis." Finally, in bone marrow recipient mice, LF 15-0195 enhanced allogeneic donor T-cell death, which required a functional CD95 pathway. These results suggest that LF 15-0195 sensitizes T cells to AICD by increasing caspase activation at the DISC level in response to CD95 engagement. This original mechanism, together with LF 15-0195 efficacy in various disease models, makes this compound a promising immunosuppressive drug.

Animals↗

PubMed2002

Specific involvement of caspases in the differentiation of monocytes into macrophages.

Caspases are cysteine proteases involved in apoptosis and cytokine maturation. In erythroblasts, keratinocytes, and lens epithelial cells undergoing differentiation, enucleation has been regarded as a caspase-mediated incomplete apoptotic process. Here, we show that several caspases are activated in human peripheral blood monocytes whose differentiation into macrophages is induced by macrophage colony-stimulating factor (M-CSF). This activation is not associated with cell death and cannot be detected in monocytes undergoing dendritic cell differentiation in the presence of interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF). The mechanisms and consequences of caspase activation were further studied in U937 human monocytic cells undergoing phorbol ester-induced differentiation into macrophages. Differentiation-associated caspase activation involves the release of cytochrome c from the mitochondria and leads to the cleavage of the protein acinus while the poly(ADP-ribose)polymerase remains uncleaved. Inhibition of caspases by either exposure to the broad-spectrum inhibitor benzyloxycarbonyl-Val-Ala-(DL)-Asp-fluoromethylketone (z-VAD-fmk) or expression of the p35 baculovirus inhibitory protein or overexpression of Bcl-2 inhibits the differentiation process. In addition, z-VAD-fmk amplifies the differentiation-associated production of radical oxygen species in both phorbol ester-differentiated U937 cells and M-CSF-treated monocytes, shifting the differentiation process to nonapoptotic cell death. Altogether, these results indicate that caspase activation specifically contributes to the differentiation of monocytes into macrophages, in the absence of cell death.

Adult↗

PubMed2002

Atypical protein kinase C zeta as a target for chemosensitization of tumor cells.

Exposure of tumor cells to cytotoxic agents simultaneously activates a variety of intracellular signaling pathways. Some of these pathways involve enzymes from the protein kinase C (PKC) family of serine/threonine kinases. This family includes isoenzymes that negatively influence cell death, whereas other demonstrate an opposite effect. The present study analyzes the role of the zeta atypical PKC isoform in tumor cell response to cytotoxic agents. Using a histone H1 phosphorylation assay, we showed that both tumor necrosis factor alpha and etoposide activate PKCzeta in U937 human leukemic cells. Stable transfection of a kinase-dead, dominant-negative PKCzeta mutant in U937 cells decreases Bcl-2 expression while increasing the expression of Bax and several procaspases. This transfection also prevents etoposide-induced nuclear factor-kappaB nuclear translocation and accumulation of X-linked inhibitor of apoptosis protein. PKCzeta inhibition accelerates the occurrence of apoptosis in leukemic cells exposed to etoposide and tumor necrosis factor alpha. This sensitization was confirmed in vitro by use of a clonogenic assay. In addition, PKCzeta inhibition sensitized tumor cells grown in nude mice to etoposide. These results indicate that PKCzeta isoform is a protective signals that is activated in tumor cells exposed to a cytotoxic agent. This inducible resistance factor thus appears an attractive target for chemosensitization of tumor cells.

Antineoplastic Agents↗

PubMed2002

Influence of the nitric oxide donor glyceryl trinitrate on apoptotic pathways in human colon cancer cells.

BACKGROUND & AIMS: We have previously reported the role of nitric oxide in colon tumor regression in vivo. The present study was designed to explore the influence of an endogenous nitric oxide donor, glyceryl trinitrate (GTN), on cell death pathways in colon cancer cells. METHODS: Human colon cancer cell lines were treated with the NO donor GTN. Apoptosis was identified by morphological criteria and the terminal deoxynucleotidyl transferase-mediated deoxyuridine (TUNEL) method. The mitochondrial transmembrane potential was studied by flow cytometry, cytochrome c release by Western blot, and caspase activation by combining fluorogenic peptide substrates, peptide inhibitors, and immunoblotting. Expression of death receptors was studied by flow cytometry and confocal microscopy. RESULTS: GTN induces a dose- and time-dependent cell death by apoptosis in colon cancer cells. This cell death pathway involves the mitochondria and caspases, mainly caspase-1 and caspase-10. In contrast, caspase-3 activation is a late and limited event. Death receptors are not involved in GTN-mediated cell death, while GTN sensitizes tumor cells to Fas-ligand-induced apoptosis. This permissive effect correlates with an increased expression of Fas receptor and a decreased expression of several endogenous inhibitors of apoptosis (IAPs). CONCLUSIONS: Our results indicate that GTN (1) activates an unusual caspase cascade to induce apoptosis in colon cancer cells and (2) sensitizes these cells to Fas-mediated cell death by increasing the expression of Fas and decreasing the expression of several IAPs.

Apoptosis↗

PubMedDate not supplied

Small heat shock proteins HSP27 and alphaB-crystallin: cytoprotective and oncogenic functions.

Heat shock protein-27 (HSP27) and alphaB-crystallin are ubiquitous small heat shock proteins whose expression is induced in response to a wide variety of physiological and environmental insults. They allow the cells to survive in otherwise lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of these small heat shock proteins. First, these proteins are powerful molecular chaperones whose main function is to prevent the aggregation of nascent and stress-accumulated misfolded proteins. Second, they interact directly with various components of the tightly regulated programmed cell death machinery, upstream and downstream of the mitochondrial events. Third, they appear to play a role in the proteasome-mediated degradation of selected proteins. Both HSP27 and alphaB-crystallin were also proposed to participate in the development of neurodegenerative diseases and malignant tumors in which their overexpression could induce drug resistance. Altogether, these properties suggest that these small heat shock proteins are appropriate targets for modulating cell death pathways.

Apoptosis↗