Sodium nitroprusside-induced osteoblast apoptosis is mediated by long chain ceramide and is decreased by raloxifene.

in Biochemical Pharmacology (2005), 69(6), 891-901

Release of high levels of nitric oxide (NO) is associated with osteoblastic cell death. The mechanisms of NO-induced cytotoxicity are not well documented and it is presently not known if estrogenic ... [more ▼]

Release of high levels of nitric oxide (NO) is associated with osteoblastic cell death. The mechanisms of NO-induced cytotoxicity are not well documented and it is presently not known if estrogenic compounds prevent this effect. We studied the role of ceramides in cell death induced by the NO donor sodium nitroprusside (SNP) and we tested the possibility that 17beta-estradiol, the anti-estrogen ICI 182.780 and two selective estrogen receptor modulators raloxifene and tamoxifen modify osteoblastic cell apoptosis. SNP dose-dependently decreased MC3T3-E1 osteoblast viability, increased NO production in the culture media and enhanced the release of intracellular ceramides C22 and C24. Cell death induced by SNP was partially inhibited when MC3T3-E1 cells were pretreated with raloxifene and tamoxifen but was not modified when the cells were pretreated with 17beta-estradiol or ICI 182.780. Cell death induced by SNP resulted from apoptosis as demonstrated by Annexin-V and propidium iodide labeling and a reduction of SNP-induced MC3T3-E1 apoptosis was confirmed in the presence of raloxifene and tamoxifen. SNP induction of C22 and C24 production was inhibited by a pretreatment with raloxifene but not with 17beta-estradiol. Moreover, the synthetic ceramide C24 (0.75 and 1microM) decreased MC3T3-E1 cell viability and osteoblast cell death induced by C24 was partially decreased by raloxifene and to a lesser extent by 17beta-estradiol. These data demonstrate that SNP-induced cell death is mediated by the long chain ceramides C22 and C24 and that raloxifene protected osteoblast from apoptosis induced by SNP, an effect that might be relevant to its pharmacological properties on bone remodeling. [less ▲]

Protein phosphorylation as a key mechanism for the regulation of BCL-3 activity

in Cell Cycle (Georgetown, Tex.) (2004), 3(12), 1498-1501

Constitutive NF-kappaB activation, a hallmark of many human cancers, upregulates anti-apoptotic gene expression and therefore disrupts the balance between apoptosis and proliferation. In some lymphomas ... [more ▼]

Constitutive NF-kappaB activation, a hallmark of many human cancers, upregulates anti-apoptotic gene expression and therefore disrupts the balance between apoptosis and proliferation. In some lymphomas, this constitutive NF-kappaB activity is the result of point mutations or translocations of the genes coding for NF-kappaB inhibitors, namely IkappaBalpha or p100. The BCL-3 protein is another member of the IkappaB family and is overexpressed in a subset of human B-cell chronic lymphocytic leukemias because of a chromosomal translocation. This oncoprotein is phosphorylated by multiple kinases including GSK3 and this phosphorylation regulates BCL-3 function by modulating its oncogenic potential and by regulating the expression of a subset of its target genes. Therefore, deciphering the NF-kappaB/IkappaB protein phosphorylations is critical in order to better understand the molecular mechanisms of NF-kappaB-mediated oncogenesis. [less ▲]

Discovery of new rheumatoid arthritis biomarkers using SELDI-TOF-MS ProteinChip approach

in Arthritis and Rheumatism (2004, September), 50(9, Suppl. S), 124

Regulation of HER-2 oncogene expression by cyclooxygenase-2 and prostaglandin E2

in Oncogene (2004), 23(8), 1631-1635

The oncoprotein HER-2/neu is a prosurvival factor and its overexpression has been correlated with adverse prognosis in breast cancers. High levels of the cyclooxygenase-2 (COX-2), a proinflammatory and ... [more ▼]

The oncoprotein HER-2/neu is a prosurvival factor and its overexpression has been correlated with adverse prognosis in breast cancers. High levels of the cyclooxygenase-2 (COX-2), a proinflammatory and antiapoptotic enzyme, were detected in HER-2-positive tumors and this observation was linked to an HER-2-mediated induction of COX-2 gene transcription. Here, we report that COX-2 expression, and synthesis of its major enzymatic product, PGE2, leads in turn to an enhanced HER-2 expression. Moreover, COX-2 enzymatic inhibition dramatically reduced HER-2 protein levels, efficiently increased the cancer cells sensitility to chemotherapeutic treatment and acted in synergy with HER-2 inhibitor, trastuzumab. Therefore, we propose an original model where HER-2 and COX-2 transcriptionally regulate each other in a positive loop. [less ▲]

15-deoxy-delta12,14-prostaglandin J2 inhibits Bay 11-7085-induced sustained extracellular signal-regulated kinase phosphorylation and apoptosis in human articular chondrocytes and synovial fibroblasts

in Journal of Biological Chemistry (2004), 279(21), 399-403

We have previously shown that nuclear factor-kappaB inhibition by adenovirus expressing mutated IkappaB-alpha or by proteasome inhibitor increases human articular chondrocytes sensibility to apoptosis ... [more ▼]

We have previously shown that nuclear factor-kappaB inhibition by adenovirus expressing mutated IkappaB-alpha or by proteasome inhibitor increases human articular chondrocytes sensibility to apoptosis. Moreover, the nuclear factor-kappaB inhibitor BAY11-7085, a potent anti-inflammatory drug in rat adjuvant arthritis, is itself a proapoptotic agent for chondrocytes. In this work, we show that BAY 11-7085 but not the proteasome inhibitor MG-132 induced a rapid and sustained phosphorylation of extracellular signal-regulated kinases (ERK1/2) in human articular chondrocytes. The level of ERK1/2 phosphorylation correlated with BAY 11-7085 concentration and chondrocyte apoptosis. 15-Deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) and its precursor prostaglandin (PG) D2 but not PGE2 and PGF2alpha rescued chondrocytes from BAY 11-7085-induced apoptosis. 15d-PGJ2 markedly inhibited BAY 11-7085-induced phosphorylation of ERK1/2. BAY 11-7085 also induced ERK1/2 phosphorylation and apoptosis in human synovial fibroblasts, and these reactions were down-regulated by 15d-PGJ2. Further analysis in synovial fibroblasts showed that only molecules that suppressed BAY 11-7085-induced phosphorylation of ERK1/2 (i.e. 15d-PGJ2, PGD2, and to a lesser extent, MEK1/2 inhibitor UO126, but not prostaglandins E2 and F2alpha or peroxisome proliferator-activated receptor-gamma agonist ciglitazone) were able protect cells from apoptosis. These results suggested that the antiapoptotic effect of 15d-PGJ2 on chondrocytes and synovial fibroblasts might involve inhibition of ERK1/2 phosphorylation. [less ▲]

Modulation of the HSV-TK/ganciclovir bystander effect by n-butyrate in glioblastoma: correlation with gap-junction intercellular communication.

in International Journal of Oncology (2004), 25(1), 187-92

The efficacy of HSV-TK/ganciclovir gene therapy largely relies on the bystander effect, i.e. the ability of transfected cells to kill the adjacent, untrasfected cells. This mechanism itself depends ... [more ▼]

The efficacy of HSV-TK/ganciclovir gene therapy largely relies on the bystander effect, i.e. the ability of transfected cells to kill the adjacent, untrasfected cells. This mechanism itself depends chiefly on the transfer via gap junctions of phosphorylated ganciclovir between cells, and is often deficient in glioblastomas. In this report, we demonstrate that n-butyrate markedly enhances the gap junction intercellular communication of GJIC-deficient glioma cells, and significantly increases the bystander effect in such cells. This effect of n-butyrate appears to be independent from its HDAC inhibitory effect, since trichostatin A does not reproduce it. [less ▲]

Cytoplasmic I kappa B alpha increases NF-kappa B-independent transcription through binding to histone deacetylase (HDAC) 1 and HDAC3

in Journal of Biological Chemistry (2003), 278(47), 46541-46548

IkappaBalpha is an inhibitory molecule that sequesters NF-kappaB dimers in the cytoplasm of unstimulated cells. Upon stimulation, NF-kappaB moves to the nucleus and induces the expression of a variety of ... [more ▼]

IkappaBalpha is an inhibitory molecule that sequesters NF-kappaB dimers in the cytoplasm of unstimulated cells. Upon stimulation, NF-kappaB moves to the nucleus and induces the expression of a variety of genes including IkappaBalpha. This newly synthesized IkappaBalpha also translocates to the nucleus, removes activated NF-kappaB from its target genes, and brings it back to the cytoplasm to terminate the phase of NF-kappaB activation. We show here that IkappaBalpha enhances the transactivation potential of several homeodomain-containing proteins such as HOXB7 and Pit-1 through a NF-kappaB-independent association with histone deacetylase (HDAC) 1 and HDAC3 but not with HDAC2, -4, -5, and -6. IkappaBalpha bound both HDAC proteins through its ankyrin repeats, and this interaction was disrupted by p65. Immunofluorescence experiments demonstrated further that IkappaBalpha acts by partially redirecting HDAC3 to the cytoplasm. At the same time, an IkappaBalpha mutant, which lacked a functional nuclear localization sequence, interacted very efficiently with HDAC1 and -3 and intensively enhanced the transactivation potential of Pit-1. Our results support the hypothesis that the NF-kappaB inhibitor IkappaBalpha regulates the transcriptional activity of homeodomain-containing proteins positively through cytoplasmic sequestration of HDAC1 and HDAC3, a mechanism that would assign a new and unexpected role to IkappaBalpha. [less ▲]

The antiangiogenic factor 16K human prolactin induces caspase-dependent apoptosis by a mechanism that requires activation of nuclear factor-kappa B

in Molecular Endocrinology (2003), 17(9), 1815-1823

We have previously shown that the 16-kDa N-terminal fragment of human prolactin (16K hPRL) has antiangiogenic properties, including the ability to induce apoptosis in vascular endothelial cells. Here, we ... [more ▼]

We have previously shown that the 16-kDa N-terminal fragment of human prolactin (16K hPRL) has antiangiogenic properties, including the ability to induce apoptosis in vascular endothelial cells. Here, we examined whether the nuclear factor-kappaB (NF-kappaB) signaling pathway was involved in mediating the apoptotic action of 16K hPRL in bovine adrenal cortex capillary endothelial cells. In a dose-dependent manner, treatment with 16K hPRL induced inhibitor kappaB-alpha degradation permitting translocation of NF-kappaB to the nucleus and reporter gene activation. Inhibition of NF-kappaB activation by overexpression of a nondegradable inhibitor kappaB-alpha mutant or treatment with NF-kappaB inhibitors blocked 16K hPRL-induced apoptosis. Treatment with 16K hPRL activated the initiator caspases-8 and -9 and the effector caspase-3, all of which were essential for stimulation of DNA fragmentation. This activation of the caspase cascade by 16K hPRL was also NF-kappaB dependent. These findings support the conclusion that NF-kappaB signaling plays a central role in 16K hPRL-induced apoptosis in vascular endothelial cells. [less ▲]

Raloxifene protects Osteoblasts from apoptosis induced by sodium nitroprusside: Potential involvement of ceramide

in Journal of Bone and Mineral Research (2003, September), 18(Suppl. 2), 136

Interleukin-1beta and tumor necrosis factor-alpha enhance the shedding of Interleukin-6 receptor in osteoblastic cells: Involvement of tumor necrosis factor-alpha converting enzyme

in Arthritis and Rheumatism (2003, September), 48(9, Suppl. S), 482