Biomedical subjects

Jean de Vellis

Publications and source records attributed to Jean de Vellis.

23 records · Page 2Linked to original sources

PubMed2002

Induction of radioprotective peroxiredoxin-I by ionizing irradiation.

Results of this study indicate a radioprotective effect of peroxiredoxin-I. Peroxiredoxin-I is an antioxidant that scavenges hydroperoxides, whereas reactive oxygen species are the main mediators of ionizing radiation toxicity. We hypothesized that peroxiredoxin-I might be induced by cellular exposure to radiation and act to protect them against its cytotoxic effects. Western blot and Northern blot analyses were used to assess peroxiredoxin-I protein and mRNA expression. Rat C6 glioma cells were engineered to overexpress sense or antisense human peroxiredoxin-I using retroviral vectors. Clonogenic cell survival was used to assess radiosensitivities of the engineered cells. Ionizing radiation induced peroxiredoxin-I protein and mRNA expression in human HT29 colon cancer and rat C6 glioma cells in a dose- and time-dependent manner over a 24 hr period. To determine the effect of peroxiredoxin-I on radiation responses, C6 glioma cells were engineered to overexpress sense or antisense human peroxiredoxin-I. In clonogenic assays, cells overexpressing peroxiredoxin-I were more radioresistant. Cells transduced with antisense peroxiredoxin-I were marginally more sensitive to radiation toxicity. Irradiation can induce peroxiredoxin-I expression, and the increased peroxiredoxin-I may protect cells from further radiation damage. These results suggest that protection by peroxiredoxin-I may play an important role in the survival of glioma and colon cancer cells in patients undergoing radiation therapy.

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PubMed2002

Selective specification of CNS stem cells into oligodendroglial or neuronal cell lineage: cell culture and transplant studies.

Neural stem cells (NSCs) were isolated from embryonic day 16 Sprague-Dawley rats and cultured in a novel serum-free stem cell medium that selected for the growth of NSCs and against the growth of GFAP(+) cells (astrocytes). NSCs maintained in culture for extended periods of time retained immunoreactivity for both nestin and PSA-NCAM, two markers characteristic of the stem cell phenotype. Moreover, using an oligodendrocyte (OL) specification medium, NSCs differentiated into OL as evidenced by their morphology and expression of multiple oligodendrocyte/myelin-specific markers. In addition, NSCs are capable of acquiring a neuronal phenotype as evidenced by expressing neuronal markers, such as neurofilament (NF) and NeuN when cultured in a defined medium for neurons indicating that these cells are also a good source of neuroblasts, which could be used to replace neuronal populations in the brain. We also showed successful propagation and differentiation of NSCs into OL after cryostorage, allowing for the later use of stored NSCs. The long-term goal of culturing NSCs and committed oligodendrocyte progenitors (OLP) is to obtain homogeneous populations for transplantation with the goal of remyelinating the myelin-deficient CNS. Our preliminary experiments carried out on normal and myelin deficient rats demonstrate that these cells survive and migrate extensively in both types of hosts. NSCs grafted as such, as well as cells derived from NSCs exposed to selective specification before grafting, are able to differentiate within the host brain. As expected, NSCs are capable of giving rise to astrocytes in a medium favoring this phenotype.

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PubMed2002

Expression of the p75 TNF receptor is linked to TNF-induced NFkappaB translocation and oxyradical neutralization in glial cells.

Tumor necrosis factor (TNF)-family cytokines induce reactive oxygen species (ROS) that injure vulnerable populations of brain cells. Among glia, oligodendrocytes are particularly susceptible to TNF-induced ROS whereas microglia are protected. We previously found that oligodendrocytes in vitro predominantly express the p55 type-1 TNF receptor, while microglial cells express both type-1 and p75 type-2 receptors. We hypothesized that differential TNF receptor expression and attendant signaling underlies the relative vulnerability of oligodendrocytes, versus microglia, to TNF-induced injury. To test this hypothesis, purified cultures of glial cells were incubated 0-48 hr with TNFalpha or lymphotoxin-alpha, following which levels of ROS, glutathione (GSH), nuclear factor kappa-B (NFkappaB) translocation, and anti-oxidant proteins and activity were measured. 48 hr exposure to TNF increased ROS levels 28% and decreased GSH levels 17% in oligodendrocytes, but decreased levels ROS levels 24% and increased GSH levels 112% increase in microglia. Thirty to 180 min exposure to TNF increased NFkappaB nuclear translocation to a greater extent and for a longer time in microglia versus oligodendrocytes, and this was followed 24-48 hr later with 3- to 13-fold increases in microglia manganese superoxide dismutase protein levels and 6-fold increases in enzyme activity. Collectively, these data suggest that signals transduced through the p75 receptor activate anti-oxidant mechanisms that protect microglia from TNF-induced injury. Lacking such signals, oligodendrocytes are considerably more vulnerable to the injurious effects of TNF.

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PubMedDate not supplied

Expression of heat shock protein (HSP)-25 and HSP-32 in the rat spinal cord reconstructed with Neurogel.

We recently showed a successful reconstruction of the cat spinal cord using NeuroGel a polymer hydrogel bridge between the two spinal stumps. The polymer graft supports axonal elongation, myelination and angiogenesis up to 21 months, Wallerian degeneration was diminished and gliotic scarring was prevented. In the present study, we report the expression patterns of two stress proteins, (HSPs) HSP-25 and HSP-32 after spinal cord hemisection with and without reparative surgery with NeuroGel. Double immunofluorescence using cell specific markers for neurons, astrocytes and oligodendrocytes (OL), in combination with antibodies for HSP-25 and 32 showed that mainly neurons express both proteins. Both HSPs displayed different temporal expression patterns in the reconstructed spinal cords with a concomitant reduction of secondary damage. In conclusion, Neurogel reconstruction of the spine during the acute phase considerably reduces secondary damage resulting in a rapid and stable regenerative response.

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PubMedDate not supplied

Tumor necrosis factor modulates transcription of myelin basic protein gene through nuclear factor kappa B in a human oligodendroglioma cell line.

Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of inflammation and it is involved in many neurological disorders such as multiple sclerosis. Levels of TNF-alpha and lymphotoxin-alpha have been found elevated in plaques, bloods, and cerebral spinal fluids from multiple sclerosis patients. The expression of myelin basic protein (MBP), a major protein of the myelin sheath, is affected by cytokines secreted by activated immune cells. To determine the signal transduction pathway involving tumor necrosis factor's action in myelination and demyelination, we have cloned and analyzed cis-elements on promoters of the human and mouse MBP genes. There are two putative nuclear factors kappa-B (NF-kappaB) cis-elements on the human and one on the mouse gene promoter. In an electrophoretic mobility shift assay, all three NF-kappaB cis-elements showed binding to a protein, which was recognized by an antibody against NF-kappaB P65 component. The specificity of the binding was demonstrated in a competitive assay using NF-kappaB consensus oligonucleotides. A two base pair site-directed mutation on the mouse NF-kappaB cis-element abolished its binding activity. We created a DNA construct by linking the mouse MBP gene promoter containing the NF-kappaB cis-element to luciferase gene. Transfection of this construct into a human oligodendroglioma cell line showed TNF-alpha increased the transgene expression. Furthermore the mutation of NF-kappaB site abolished TNF-alpha -induction of the transgene. The data demonstrate that NF-kappaB is the mediator between tumor necrosis factor's action and MBP gene expression. Elucidating the molecular mechanisms underlying TNF-alpha regulation of MBP gene expression provides new scientific bases for the development of therapy against oligodendrocyte-specific and myelin-related disorders such as multiple sclerosis.

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