Biomedical subjects

Jacques Corbeil

Publications and source records attributed to Jacques Corbeil.

At least 19 recordsLinked to original sources

PubMed2006

Enhanced antiproliferative effects of alkoxyalkyl esters of cidofovir in human cervical cancer cells in vitro.

Nearly all cervical cancers are associated with the high-risk subtypes of human papillomavirus (HPV) expressing the E6 and E7 oncoproteins. The E6 and E7 oncoproteins reduce cellular levels of the p53 and the retinoblastoma (pRb) tumor suppressors, respectively, and represent an important component of the malignant phenotype. Several groups have shown that treatment with cidofovir suppresses levels of E6 and E7, restoring cellular p53 and pRb levels, in turn slowing cell replication and increasing the susceptibility of the cancer cells to radiation and apoptosis. Recently, our group synthesized alkoxyalkyl esters of cidofovir, which were found to be >100 times more active than unmodified cidofovir in vitro against various double-stranded DNA viruses, including cytomegalovirus, herpes simplex virus, adenoviruses, cowpox, vaccinia, and variola viruses. We compared the activity of octadecyloxyethyl-cidofovir (ODE-CDV) and oleyloxyethyl-cidofovir (OLE-CDV) with that of unmodified cidofovir against both HPV-negative and HPV-positive cervical cancer cells. We compared the antiproliferation activity in CaSki, HeLa, and Me-180 cells, prototypical HPV-positive cell lines bearing the HPV-16, HPV-18, and HPV-68 high-risk subtypes, with the activity in C33A cells, a cervical cancer cell line lacking HPV, and in nonmalignant primary human foreskin fibroblast cells. OLE-CDV and ODE-CDV were several logs more potent than cidofovir in CaSki, Me-180, HeLa, and C33A cervical cancer cells as determined by 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt proliferation assay. Cell cycle analysis indicates that the cidofovir analogues interfere with passage of dividing cells through the S phase. ODE-CDV and OLE-CDV were 500 to 17,000 times more active than cidofovir in inhibiting the growth of cervical cancer cells. ODE-CDV and OLE-CDV showed selectivity for cervical cancer cells versus nonmalignant human foreskin fibroblast cells and warrant further investigation as potential therapies for cervical cancer.

Antineoplastic Agents↗

PubMed2005

Methamphetamine stimulates interferon inducible genes in HIV infected brain.

OBJECTIVE: To study the synergism of HIV and methamphetamine. DESIGN AND METHODS: We undertook a microarray study using RNA from the frontal cortex of 15 individuals with HIV infection to initially identify genes that are differentially regulated by HIV encephalitis (HIVE). From the analysis of the microarray data, we identified candidate genes to be validated by quantitative real time PCR (qRT-PCR) and to assess if these genes were differentially modulated in individuals with HIVE and documented methamphetamine use. RESULTS: Analysis of microarray data revealed that genes involved in several categories were dysregulated in HIVE. We then chose 15 candidate genes for validation by qRT-PCR and analyzed the tissue concentration of these genes across three groups: those with HIV infection and no brain pathology, those with HIVE, and those with both HIVE and a history of methamphetamine use. We noted that there was upregulation of interferon inducible genes in the HIVE with methamphetamine using group, which together as a gene group was highly statistically significant (p=0.0064). CONCLUSION: These findings indicate that dysregulation of interferon inducible genes may underlie the pathogenic mechanism resulting in greater neurodegenerative and neurocognitive burden that occurs in methamphetamine using HIV infected individuals.

Adult↗

PubMed2005

Comparative gene expression analysis of blood and brain provides concurrent validation of SELENBP1 up-regulation in schizophrenia.

Microarray techniques hold great promise for identifying risk factors for schizophrenia (SZ) but have not yet generated widely reproducible results due to methodological differences between studies and the high risk of type I inferential errors. Here we established a protocol for conservative analysis and interpretation of gene expression data from the dorsolateral prefrontal cortex of SZ patients using statistical and bioinformatic methods that limit false positives. We also compared brain gene expression profiles with those from peripheral blood cells of a separate sample of SZ patients to identify disease-associated genes that generalize across tissues and populations and further substantiate the use of gene expression profiling of blood for detecting valid SZ biomarkers. Implementing this systematic approach, we: (i) discovered 177 putative SZ risk genes in brain, 28 of which map to linked chromosomal loci; (ii) delineated six biological processes and 12 molecular functions that may be particularly disrupted in the illness; (iii) identified 123 putative SZ biomarkers in blood, 6 of which (BTG1, GSK3A, HLA-DRB1, HNRPA3, SELENBP1, and SFRS1) had corresponding differential expression in brain; (iv) verified the differential expression of the strongest candidate SZ biomarker (SELENBP1) in blood; and (v) demonstrated neuronal and glial expression of SELENBP1 protein in brain. The continued application of this approach in other brain regions and populations should facilitate the discovery of highly reliable and reproducible candidate risk genes and biomarkers for SZ. The identification of valid peripheral biomarkers for SZ may ultimately facilitate early identification, intervention, and prevention efforts as well.

Biomarkers↗

PubMed2005

Intra-uterine growth restriction and the programming of left ventricular remodelling in female rats.

Epidemiological studies link intra-uterine growth restriction (IUGR) with increased incidence of hypertension and cardiac disease in adulthood. Our rat model of IUGR supports this contention and provides evidence for the programming of susceptibility for hypertension in all offspring. Moreover, in the female offspring only, gross anatomical changes (cardiac ventricle to body ratios) and increased left cardiac ventricular atrial natriuretic peptide (ANP) mRNA levels provide evidence for programming of cardiac disease in this gender. The aim of the current study was to measure changes in cardiac tissue that support remodelling that could be implicated in the initiation of hypertrophy. Adult female rats from our IUGR model and age- and sex-matched controls were killed at 12 weeks of age. Left cardiac ventricles were removed and used for monitoring changes in several key genes, Na+,K+-ATPase beta1 protein expression, cardiomyocyte morphology and contractility as well as citrate synthase and aconitase activities. When compared to controls, female offspring of our IUGR rat model exhibit higher expression (mRNA) of ANP and the atrial isoform of the myosin light chain, lower levels of Na+,K+-ATPase beta1 protein, increased cardiomyocyte depth and volume, increased sarcomere length, diminished cardiomyocyte contractility and lower aconitase activity. Female offspring of our IUGR rat model exhibit changes as adults that are consistent with the onset of cardiac remodelling. The decrease in aconitase activity suggests that oxidative stress may be implicated in this response.

Animals↗

PubMed2004

Mitogen-activated protein kinase pathways defend against bacterial pore-forming toxins.

Cytolytic pore-forming toxins are important for the virulence of many disease-causing bacteria. How target cells molecularly respond to these toxins and whether or not they can mount a defense are poorly understood. By using microarrays, we demonstrate that the nematode Caenorhabditis elegans responds robustly to Cry5B, a member of the pore-forming Crystal toxin family made by Bacillus thuringiensis. This genomic response is distinct from that seen with a different stressor, the heavy metal cadmium. A p38 mitogen-activated protein kinase (MAPK) kinase and a c-Jun N-terminal-like MAPK are both transcriptionally up-regulated by Cry5B. Moreover, both MAPK pathways are functionally important because elimination of either leads to animals that are (i) hypersensitive to a low, chronic dose of toxin and (ii) hypersensitive to a high, brief dose of toxin such that the animal might naturally encounter in the wild. These results extend to mammalian cells because inhibition of p38 results in the hypersensitivity of baby hamster kidney cells to aerolysin, a pore-forming toxin that targets humans. Furthermore, we identify two downstream transcriptional targets of the p38 MAPK pathway, ttm-1 and ttm-2, that are required for defense against Cry5B. Our data demonstrate that cells defend against pore-forming toxins by means of conserved MAPK pathways.

Animals↗

PubMed2004

Interferon gene expression following HIV type 1 infection of monocyte-derived macrophages.

Macrophages represent one of the primary targets of HIV-1 infection. Changes in gene expression in primary human monocyte-derived macrophages following virus exposure were assessed using oligonucleotide arrays. Over a third of the 100 most modulated genes belonged to the interferon system. Upregulated interferon-stimulated genes included those essential for the innate immune response and also those involved in interferon and virus signal transduction from the cell surface. The promoter regions of a cluster of highly upregulated interferon-stimulated genes were analyzed for common regulatory elements. The nuclear factor in activated T cells (NFAT) and members of the interferon family of transcription factors appeared to be responsible for the upregulation of this set of interferon-stimulated genes following HIV-1 exposure.

Cells, Cultured↗

PubMed2004

The density of coreceptors at the surface of CD4+ T cells contributes to the extent of human immunodeficiency virus type 1 viral replication-mediated T cell death.

Chemokine receptors serve as coreceptors for HIV-1 entry into CD4(+) T cells. Several reports have mentioned that density of CCR5 expression modulates in vitro viral replication and in vivo the course of the disease. Our goal was to investigate the impact of coreceptor density at the surface of a CD4(+) cell line on HIV-1 entry, replication, spreading, and programmed cell death. We engineered a CEM cell line that expresses constitutively CD4 and CXCR4 and CCR5 after transfection. This model allows us to compare the effect of the X4 and R5 strains to induce T cell death in the same T cell host. We show here that the extent of T cell death correlates with the rate of virus replication. X4 induces faster T cell death than R5 that depends at least in part on the higher density of CXCR4 compared to CCR5. Furthermore, sorting CEM populations expressing low, intermediate, and high densities of CCR5 molecules but constant amount of CD4, we found that the capacity to induce T cell death depends at least in part on the level of CCR5 when low amount of virus was used to infect the CEM cells. Moreover, viral transcription, assessed by cell-associated HIV-1 RNA/DNA ratio, was increased in CCR5high as compared to CCR5low cells, while inhibition of replication by zidovudine was more effective in CCR5low cells. Our data indicate that the density of chemokine receptors expressed on CD4(+) T cells may be a critical parameters for the cytopathic effect of HIV strains and may have major impact on CD4 T cell depletion during HAART.

Apoptosis↗

PubMed2004

Genetic basis of hypersusceptibility to protease inhibitors and low replicative capacity of human immunodeficiency virus type 1 strains in primary infection.

The initial virus strains from as many as 12% of individuals with primary human immunodeficiency virus (HIV) infection have a 50% inhibitory concentration </=0.4-fold that of HIV type 1(NL4-3) (HIV-1(NL4-3)) to ritonavir (hypersusceptibility [HS]). There is also substantial variation in replicative capacity (RC) or an in vitro assay of the contributions of protease (PR) and reverse transcriptase to viral fitness. In chronically infected antiretrovirally treated patients, amprenavir HS has been associated with the mutation N88S in PR, but this mutation is not seen in untreated patients. In this study, virus strains from 182 cases of primary HIV infection were analyzed, and a highly significant association between HS and low RC (</=10% that of HIV-1(NL4-3)) was observed (P < 10(-6)). Multivariate analysis was used to determine the genotypic basis of ritonavir HS, analyzing all polymorphic amino acid sites and insertions from p7gag through PR. Decision tree models developed on the entire Gag-plus-PR data set and on PR alone gave overall correct classifications of 73 and 72%, respectively, on cross-validation. They were also able to predict low RC, with sensitivities of 69 and 62% and specificities of 84 and 70%, respectively. The analysis shows that ritonavir HS in untreated primary HIV infection is not associated with single mutations but with combinations of amino acids at polymorphic sites and that the same genotypes which confer HS to PR inhibitors confer low RC. This supports the view that variation in PR function is directly responsible for variation in fitness among strains in primary infection.

Decision Trees↗

PubMed2003

Gene expression profiling detects patterns of human macrophage responses following Mycobacterium tuberculosis infection.

High-density oligonucleotide microarrays allow simultaneous monitoring of the expression of a large number of cellular genes. Microarrays were used to screen the global human monocyte-derived macrophage transcriptional response to infection with the intracellular pathogen Mycobacterium tuberculosis. The microarray detected reproducible patterns of regulated gene expression. Analysis of the expression data showed induction of cytokines and chemokines, ribosomal proteins, and the interferon-response gene Stat1. Several changes were validated by quantitative reverse transcription polymerase chain reaction and immunoblot assays. Augmentation of the respiratory burst and preservation of the response to interferon-gamma were also demonstrated. These data supplement existing knowledge on macrophage responses to tuberculosis infection.

Cells, Cultured↗

PubMed2003

Modulation of gene expression in Leishmania drug resistant mutants as determined by targeted DNA microarrays.

In the protozoan parasite Leishmania, drug resistance can be a complex phenomenon. Several metabolic pathways and membrane transporters are implicated in the resistance phenotype. To monitor the expression of these genes, we generated custom DNA microarrays with PCR fragments corresponding to 44 genes involved with drug resistance. Transcript profiling of arsenite and antimony resistant mutants with these arrays pinpointed a number of genes overexpressed in mutants, including the ABC transporter PGPA, the glutathione biosynthesis genes gamma-glutamylcysteine synthetase (GSH1) and the glutathione synthetase (GSH2). Competitive hybridisations with total RNA derived from sensitive and methotrexate resistant cells revealed the overexpression of genes coding for dihydrofolate reductase (DHFR-TS), pteridine reductase (PTR1) and S-adenosylmethionine synthase (MAT2) and a down regulation of one gene of the folate transporter (FT) family. By labelling the DNA of sensitive and resistant parasites we could also detect several gene amplification events using DNA microarrays including the amplification of the S-adenosyl homocysteine hydrolase gene (SAHH). Alteration in gene expression detected by microarrays was validated by northern blot analysis, while Southern blots indicated that most genes overexpressed were also amplified, although other mechanisms were also present. The microarrays were useful in the study of resistant parasites to pinpoint several genes linked to drug resistance.

Animals↗

PubMed2003

2HAPI: a microarray data analysis system.

SUMMARY: 2HAPI (version 2 of High density Array Pattern Interpreter) is a web-based, publicly-available analytical tool designed to aid researchers in microarray data analysis. 2HAPI includes tools for searching, manipulating, visualizing, and clustering the large sets of data generated by microarray experiments. Other features include association of genes with NCBI information and linkage to external data resources. Unique to 2HAPI is the ability to retrieve upstream sequences of co-regulated genes for promoter analysis using MEME (Multiple Expectation-maximization for Motif Elicitation) AVAILABILITY: 2HAPI is freely available at http://array.sdsc.edu. Users can try 2HAPI anonymously with pre-loaded data or they can register as a 2HAPI user and upload their data.

Algorithms↗

PubMed2003

Polyclonal proliferation and apoptosis of CCR5+ T lymphocytes during primary human immunodeficiency virus type 1 infection: regulation by interleukin (IL)-2, IL-15, and Bcl-2.

We measured apoptosis of subsets of T lymphocytes by single-cell analysis of caspase activation, to confirm high turnover of chemokine receptor CCR5(+) T cells in subjects with acute, primary human immunodeficiency virus type 1 (HIV-1) infection (PHI). High levels of spontaneous apoptosis, consisting mainly of CD8(+) T lymphocytes, were closely associated with increases in the activation markers Ki-67, CD38, and the HIV coreceptor CCR5 and with decreases in Bcl-2 and the interleukin (IL)-7 receptor at the single-cell level. Increased expression of Ki-67 and CCR5 ex vivo, as well as increased apoptosis, was seen in all T cell receptor beta-chain variable region (TCRBV) subfamilies studied. The addition of IL-2 or IL-15, but not IL-7, significantly inhibited caspase activation, increased Bcl-2 expression, and rapidly initiated proliferation in vitro of CD8(+) T cells expressing CCR5 and multiple TCRBV subfamilies. Furthermore, IL-15 receptor alpha-chain messenger RNA levels were increased in peripheral blood mononuclear cells during PHI. These results suggest that CCR5(+)Ki-67(+)Bcl-2(dim) activated T cells generated during PHI traffic via blood to tissue sites, where the cells may survive and/or further proliferate under the local influence of IL-2 or IL-15. Understanding cytokine effects on CCR5(+) T cells will be important in understanding chronic HIV-1 replication and pathogenesis.

Adult↗

PubMed2003

Effect of micromechanical stimulations on osteoblasts: development of a device simulating the mechanical situation at the bone-implant interface.

Many experimental models have been developed to investigate the effects of mechanical stimulation of cells, but none of the existing devices can simulate micromotions at the cellular-mechanical interface with varying amplitudes and loads. Osteoblasts are sensitive to mechanical stimuli, so to study the bone-implant interface it would be important to quantify their reaction in a situation mimicking the mechanical situation arising at that interface. In this study, we present the development of a new device allowing the application of micromotions and load on cells in vitro. The new device allowed the cells to be stimulated with sinusoidal motions of amplitudes comprised between +/- 5 and +/- 50 microm, frequencies between 0.5 and 2 Hz, and loads between 50 and 1000 Pa. The device, with a total length of 20 cm, was designed to work in an incubator at 37 degrees C and 100% humidity. Expression of various bone important genes was monitored by real-time RT-PCR. Micromotions and load were shown to affect the behavior of osteoblasts by down-regulating the expression of genes necessary for the creation of organic extracellular matrix (collagen type I) as well as for genes involved in the mineralization process (osteocalcin, osteonectin). The developed device could then be used to simulate different mechanical situations at the bone-implant interface.

Bone and Bones↗

PubMed2003

Surface CD4 expression modulated by a cellular factor induced by HIV type 1 infection.

Human immunodeficiency virus type 1 (HIV-1) alters gene expression in infected cells, leading to cellular dysfunction. We uncovered a number of host cell genes that are modulated in both CD4(+) T cell lines and primary CD4(+) T lymphocytes infected with HIV-1, using high-density oligonucleotide probe microarray technology. We focused on one gene in particular, nuclear factor I-B2 (NFI-B2), because of its high level of expression. NFI-B2 is a member of the nuclear factor I family of nuclear proteins, which are known to be involved in viral and cellular transcription. To better understand the role of NFI-B2 during HIV-1 infection, we generated a Jurkat T cell line that constitutively expressed NFI-B2. After infection with HIV-1, these cells produced fewer viruses because of a downregulation of surface CD4 expression. The surface expression of the coreceptor, CXCR4, remained unchanged. Furthermore, levels of CD4 mRNA were reduced in NFI-B2-producing cells, suggesting that expression of NFI-B2 impairs CD4 transcription. Modulation of NFI-B2 by HIV-1 may represent yet another mechanism by which HIV infection reduces cell surface expression of CD4.

CCAAT-Enhancer-Binding Proteins↗

PubMed2003

A new perspective on V3 phenotype prediction.

The particular coreceptor used by a strain of HIV-1 to enter a host cell is highly indicative of its pathology. HIV-1 coreceptor usage is primarily determined by the amino add sequences of the V3 loop region of the viral envelope glycoprotein. The canonical approach to sequence-based prediction of coreceptor usage was derived via statistical analysis of a less reliable and significantly smaller data set than is presently available. We aimed to produce a superior phenotypic classifier by applying modern machine learning (ML) techniques to the current database of V3 loop sequences with known phenotype. The trained classifiers along with the sequence data are available for public use at the supplementary website: http://genomiac2.ucsd.edu:8080/wetcat/v3.html and http://www.cs.waikato.ac.nz/ml/weka[corrected].

Amino Acid Sequence↗

PubMed2002

Gene expression analysis of osteoblastic cells contacted by orthopedic implant particles.

Particles generated from orthopedic implants through years of wear play an essential role in the aseptic loosening of a prosthesis. We have investigated the biocompatibility of these orthopedic particles on different osteoblast-like cells representative of different stages of osteoblast maturation. We found the particles induced a caspase-dependent apoptosis of osteoblasts, with less mature osteoblasts being the most susceptible. An analysis of gene expression was performed on the less mature osteoblasts, which were in contact with the particles. We found that the particles had a profound impact on genes that code for inflammatory cytokines and genes involved in controlling the nuclear architecture. Results from this study suggest that the peri-implant osteolysis after a total joint replacement can be due in part to a decrease of bone formation and not solely to an overstimulation of bone resorption as is generally proposed. Development of new drugs that promote normal bone formation and osteoblast survival would possibly control peri-implant osteolysis, resulting in a better prognosis for patients with orthopedic implants.

Animals↗

PubMed2002

Large-scale gene expression analysis of osteoblasts cultured on three different Ti-6Al-4V surface treatments.

To improve implant biocompatibility, we developed a simple cost-effective thermal surface treatment allowing an increase in the oxide layer thickness of a titanium (Ti) alloy used in orthopaedic implants. The goal of this study was to test in vitro the reaction of osteoblasts to the developed surface treatment and to compare it to the osteoblast reaction to two other surface treatments currently used in the practice of implant surgery. Quantification of osteoblast gene expression on a large scale was used in this study. The kinetics of gene expression over 120 h was followed for 58 genes to quantify the effect of the developed surface treatment. Twenty eight genes were further selected to compare the effects of surface treatments on osteoblasts. Based on the genes studied, we could propose a general pathway for the cell reaction according to the surface treatments used: (1) metal ion release changes the time course of gene expression in the FAK pathway; (2) once the accumulation of metal ions released from the Ti surface exceeds a threshold value, cell growth is diminished and apoptosis may be activated; (3) PTK up-regulation is also induced by metal ion release; (4) the expression of Bcl-2 family and Bax may suggest that metal ions induce apoptosis. The developed treatment seems to increase the Ti-6Al-4V biocompatibility as highlighted by the lower impact of this treatment by the different pathways studied, on the lower inflammatory reaction that could be induced, as well as by the lower induced osteoblast apoptosis compared to the two other surface treatments.

Alloys↗

PubMed2002

Effects of antiretroviral drugs on human immunodeficiency virus type 1-induced CD4(+) T-cell death.

Apoptosis of peripheral blood T cells plays an important role in the pathogenesis of human immunodeficiency virus (HIV) infection. In this study, we found that HIV type 1 (HIV-1) primes CD4(+) T cells from healthy donors for apoptosis, which occurs after CD95 ligation or CD3-T-cell receptor (TCR) stimulation. CD95-mediated death did not depend on CD4 T-cell infection, since it occurred in the presence of the reverse transcriptase inhibitor didanosine (ddI). In contrast, apoptosis induced by productive infection (CD3-TCR stimulation) is prevented by both CD95 decoy receptor and ddI. Our data suggest that HIV-1 triggers at least two distinct death pathways: a CD95-dependent pathway that does not require viral replication and a viral replication-mediated cell death independent of the CD95 pathway. Further experiments indicated that saquinavir, a protease inhibitor, at a 0.2 microM concentration, decreased HIV-mediated CD95 expression and thus cell death, which is independent of its role in inhibiting viral replication. However, treatment of peripheral blood mononuclear cells from healthy donors with a higher concentration (10 microM) of an HIV protease inhibitor, saquinavir or indinavir, induced both a loss in mitochondrial membrane potential (DeltaPsim) and cell death. Thus, protease inhibitors have the potential for both beneficial and detrimental effects on CD4(+) T cells independent of their antiretroviral effects.

Anti-HIV Agents↗