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Biomedical subjects

J Landry

Publications and source records attributed to J Landry.

At least 19 recordsLinked to original sources
PubMed2004

A comparison of the fixed combination of latanoprost and timolol with the unfixed combination of brimonidine and timolol in patients with elevated intraocular pressure. A six month, evaluator masked, multicentre study in Europe.

PURPOSE: To compare the intraocular pressure (IOP) reducing effect and safety of fixed combination (FC) latanoprost/timolol with unfixed combination (UFC) brimonidine/timolol in patients with increased IOP. METHODS: In this 6 month, randomised, evaluator masked, parallel group European study, patients with glaucoma or ocular hypertension and IOP > or =21 mm Hg on monotherapy or >16 mm Hg on dual therapy received either FC latanoprost/timolol at 8:00AM or UFC brimonidine/timolol at 8:00AM and 8:00PM. The primary outcome was the difference from baseline to month 6 in mean diurnal IOP reduction. RESULTS: 325 of 334 randomised patients were included in intent to treat analyses (FC latanoprost/timolol, 163; UFC brimonidine/timolol, 162). Baseline diurnal IOP levels were similar: FC latanoprost/timolol, 26.4 (SD 2.7) mm Hg; UFC brimonidine/timolol, 26.5 (SD 2.8) mm Hg (p = 0.851). At month 6, levels were 16.9 (SD 2.8) mm Hg in FC latanoprost/timolol patients and 18.2 (SD 3.1) mm Hg in UFC brimonidine/timolol patients (p<0.001). No adverse events were reported by 76.4% and 75.5% of patients receiving FC latanoprost/timolol versus UFC brimonidine/timolol, respectively. Larger proportions of brimonidine/timolol treated patients reported study medication related adverse events (18.6% v 7.3%) and discontinued study participation because of this (10.8% v 1.8%). CONCLUSION: Fixed combination latanoprost/timolol administered once daily is both more effective and better tolerated than twice daily dosing with UFC brimonidine/timolol.

Adult↗
PubMed2001

A kinase-independent function of Ask1 in caspase-independent cell death.

Ask1 (apoptosis signal-regulating kinase 1) is activated as a consequence of cell exposure to a variety of stresses and can then initiate apoptosis. A known pathway of apoptosis downstream of Ask1 involves the activation of the stress-activated protein kinases, the release of cytochrome c from mitochondria, the activation of caspases, and the fragmentation of nuclei. Here, we characterized a novel mechanism of Ask1-mediated cell killing that is triggered by the interaction with Daxx. Co-transfection of Ask1 and Daxx induced a caspase-independent cell-death process characterized at the morphological level by distinctive crumpled nuclei easily distinguishable from the condensed and fragmented nuclei seen during classical caspase-dependent apoptosis. The kinase activity of Ask1 was not involved in this process, because mutants lacking kinase activity were as efficient as wild type Ask1 in mediating Daxx-induced cell death. Ask1N, a deletant that lacks the C-terminal half including the kinase domain of Ask1, was constitutively active in producing crumpled nuclei. In contrast, Ask1DeltaN, the reciprocal deletant that possesses constitutive kinase activity, produced fragmented nuclei typical of caspase-dependent death processes. We conclude that in addition to a caspase-dependent pro-apoptotic function that depends on its kinase activity, Ask1 possesses a caspase-independent killing function that is independent on its kinase activity and is activable by interaction with Daxx. In the physiological situation, such an activity is induced as a consequence of the translocation of Daxx from the nucleus to the cytoplasm, a condition that occurs following activation of the death receptor Fas.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Crystal structure of a SIR2 homolog-NAD complex.

The SIR2 protein family comprises a novel class of nicotinamide-adenine dinucleotide (NAD)-dependent protein deacetylases that function in transcriptional silencing, DNA repair, and life-span extension in Saccharomyces cerevisiae. Two crystal structures of a SIR2 homolog from Archaeoglobus fulgidus complexed with NAD have been determined at 2.1 A and 2.4 A resolutions. The structures reveal that the protein consists of a large domain having a Rossmann fold and a small domain containing a three-stranded zinc ribbon motif. NAD is bound in a pocket between the two domains. A distinct mode of NAD binding and an unusual configuration of the zinc ribbon motif are observed. The structures also provide important insights into the catalytic mechanism of NAD-dependent protein deacetylation by this family of enzymes.

Amino Acid Sequence↗
PubMed2001

Markers of neck failure in oral cavity and oropharyngeal carcinomas treated with radiotherapy.

BACKGROUND: Neck management after radiotherapy remains controversial. It is not clear which patients may benefit from postradiotherapy neck dissection. Biologic markers may be useful in this setting. METHOD: This study includes 81 patients with oral cavity and oropharyngeal carcinomas. The primary tumor had been treated with radical radiotherapy. Immunohistochemical staining to p53, ki-67, NEU, HSP-27, and GST has been performed. RESULTS: There were 50 T1-2 and 31 T3-4 patients, as well as 36 NO and 45 N1-3. A total of 25 nodal failures was observed. With expressed HSP2, 23% of patients had neck failure compared with 51% when HSP-27 was absent (p = .02). With NEU overexpression, nodal control decreased from 72% to 34% (p = .008). In a Cox model, NEU (p = .01) and HSP-27 (p = .05) were associated with neck failure. CONCLUSIONS: HSP-27 and NEU expression may play a role in predicting nodal failure. This should be confirmed in a larger, prospective study.

Biomarkers, Tumor↗
PubMed2001

Isolation and quantitation of zeins in waxy and amylose-extender and wild flint and dent maize endosperm using a new solvent sequence for protein extraction.

Protein distribution in endosperm of maize grains differing by their texture, flint or dent, and by their genotype, wild or waxy or amylose-extender, was examined by the successive use of 0.5 M NaCl, 0.5 M NaCl plus 0.6% 2-mercaptoethanol (2ME) at neutral and then alkaline pH, and 55% 2-propanol plus 0.6% 2ME as extractants. Proteins extracted in the presence of 2ME were characterized by their size polymorphism and amino acid composition. Proteins isolated with NaCl plus 2ME at neutral pH corresponded with a mixture of gamma-zein (27 kDa) and glutelin-like proteins. Proteins isolated with NaCl plus 2ME at pH 10 were a mixture of gamma-zeins (27 and 16 kDa) and beta-zeins (14 kDa). Alcohol-soluble proteins consisted of alpha-, beta-, and delta-zeins, alpha subunits being predominant. Zein quantitation was improved by weighing the nitrogen percentage of extracts by their zein content, as estimated from the data on amino acid composition. The data reported by Wolf et al. (Cereal Chem. 1975, 52, 765) were integrated to the results of this work to suggest the occurrence of an inverse correlation between amylose in starch and zeins in proteins.

Amino Acids↗
PubMed2001

Involvement of p38 in apoptosis-associated membrane blebbing and nuclear condensation.

The stress-activated protein kinase p38 is often induced by cytotoxic agents, but its contribution to cell death is ill defined. In Rat-1 cells, we found a strong correlation between activation of p38 and induction of c-Myc-dependent apoptosis. In cells with deregulated c-Myc expression but not in control cells, cis-diamminedichloroplatinum induced p38 activity and typical features of apoptosis, including internucleosomal DNA degradation, induction of caspase activities, and both nuclear (nuclear condensation and fragmentation) and extranuclear (cell blebbing) morphological alterations. The pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone did not block p38 activation and the p38 inhibitor SB203580 had no detectable effect on the activation of caspases or the in vivo cleavage of several caspase substrates, suggesting that p38 and caspase activation can contribute distinct features of apoptosis. Accordingly, we found that cell blebbing was independent of caspase activity and, rather, depended on p38-sensitive changes in microfilament dynamics likely mediated by heat shock protein 27 phosphorylation. Furthermore, p38 activity contributed to both caspase-dependent and caspase-independent nuclear condensation and fragmentation, suggesting a role in an early event triggering both mechanisms of apoptosis or sensitizing the cells to the action of both types of apoptosis executioners. Inhibiting p38 also resulted in a significant enhancement in cell survival estimated by colony formation. This capacity to modulate the sensitivity to apoptosis in cells with deregulated c-Myc expression suggests an important role for p38 in tumor cell killing by chemotherapeutic agents.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Older adults' acceptance of psychological and pharmacological treatments for depression.

Two hundred participants aged 65 and older recruited from 4 different family medicine clinics rated the acceptability of 3 different treatments for geriatric depression: (a) cognitive therapy (CT), (b) cognitive bibliotherapy (CB), and (c) antidepressant medication (AM). Results showed that the acceptability of the treatments is a function of the severity of the symptoms of the depressed patient to whom they would be applied. CT and CB were rated as more acceptable than AM when patient symptoms were mild to moderate. However, CT was more acceptable than both CB and AM when patient symptoms were described as severe. Acceptability ratings were not related to the raters' own depressive symptoms. The practical implications of these results are discussed.

Aged↗
PubMed2001

A novel form of transcriptional silencing by Sum1-1 requires Hst1 and the origin recognition complex.

In the yeast Saccharomyces cerevisiae, a and alpha mating-type information is stored in transcriptionally silenced cassettes called HML and HMR. Silencing of these loci, maintained by the formation of a specialized type of heterochromatin, requires trans-acting proteins and cis-acting elements. Proteins required for silencing include the Sir2 NAD(+)-dependent deacetylase, Sir3, and Sir4. Factors that bind to the cis elements at HMR and HML and that are important for silencing include the origin recognition complex (ORC). Mutations of any of these Sir proteins or combinations of cis elements result in loss of silencing. SUM1-1 was previously identified as a dominant mutation that restores silencing to HMR in the absence of either the Sir proteins or some of the cis elements. We have investigated the novel mechanism whereby Sum1-1 causes Sir-independent silencing at HMR and present the following findings: Sum1-1 requires the Sir2 homolog, Hst1, for silencing and most probably requires the NAD(+)-dependent deacetylase activity of this protein. Sum1-1 interacts strongly with ORC, and this strong interaction is dependent on HMR DNA. Furthermore, ORC is required for Sum1-1-mediated silencing at HMR. These observations lead to a model for Sum1-1 silencing of HMR in which Sum1-1 is recruited to HMR by binding to ORC. Sum1-1, in turn, recruits Hst1. Hst1 then deacetylates histones or other chromatin-associated proteins to cause chromatin condensation and transcriptional silencing.

Fungal Proteins↗
PubMed2001

Higher than normal plasma interleukin-6 concentrations in cancer patients with depression: preliminary findings.

OBJECTIVE: This study investigated whether cancer patients with and without major depression exhibit immune system abnormalities similar to those reported in medically healthy, depressed subjects without cancer. METHOD: The study subjects consisted of patients diagnosed with pancreatic, esophageal, or breast cancer. Other groups consisted of subjects with major depression (without cancer) and healthy comparison subjects. Subjects' diagnoses were made with the Structured Clinical Interview for DSM-III-R. Severity of depression was measured with the Hamilton Depression Rating Scale. Plasma concentrations of interleukin-6 (IL-6) and postdexamethasone cortisol were measured. RESULTS: Cancer patients with depression had markedly higher plasma concentrations of IL-6 than healthy comparison subjects and cancer patients without depression. Although significant correlations were found between Hamilton depression scale scores and plasma concentrations of postdexamethasone cortisol, no significant correlations were found between plasma IL-6 and postdexamethasone cortisol concentrations. CONCLUSIONS: Higher than normal plasma IL-6 concentrations were associated with a diagnosis of major depression in cancer patients. IL-6 may contribute to sickness behavior that has overlapping symptoms with major depression.

Adult↗
PubMed2000

Silent information regulator 2 family of NAD- dependent histone/protein deacetylases generates a unique product, 1-O-acetyl-ADP-ribose.

Conflicting reports have suggested that the silent information regulator 2 (SIR2) protein family employs NAD(+) to ADP-ribosylate histones [Tanny, J. C., Dowd, G. J., Huang, J., Hilz, H. & Moazed, D. (1999) Cell 99, 735-745; Frye, R. A. (1999) Biochem. Biophys. Res. Commun. 260, 273-279], deacetylate histones [Landry, J., Sutton, A., Tafrov, S. T., Heller, R. C., Stebbins, J., Pillus, L. & Sternglanz, R. (2000) Proc. Natl. Acad. Sci. USA 97, 5807-5811; Smith, J. S., Brachmann, C. B., Celic, I., Kenna, M. A., Muhammad, S., Starai, V. J., Avalos, J. L., Escalante-Semerena, J. C., Grubmeyer, C., Wolberger, C. & Boeke, J. D. (2000) Proc. Natl. Acad. Sci. USA 97, 6658-6663], or both [Imai, S., Armstrong, C. M., Kaeberlein, M. & Guarente, L. (2000) Nature (London) 403, 795-800]. Uncovering the true enzymatic function of SIR2 is critical to the basic understanding of its cellular function. Therefore, we set out to authenticate the reaction products and to determine the intrinsic catalytic mechanism. We provide direct evidence that the efficient histone/protein deacetylase reaction is tightly coupled to the formation of a previously unidentified acetyl-ADP-ribose product (1-O-acetyl-ADP ribose). One molecule of NAD(+) and one molecule of acetyl-lysine are readily catalyzed to one molecule of deacetylated lysine, nicotinamide, and 1-O-acetyl-ADP-ribose. A unique reaction mechanism involving the attack of enzyme-bound acetate or the direct attack of acetyl-lysine on an oxocarbenium ADP-ribose intermediate is proposed. We suggest that the reported histone/protein ADP-ribosyltransferase activity is a low-efficiency side reaction that can be explained through the partial uncoupling of the intrinsic deacetylation and acetate transfer to ADP-ribose.

Adenosine Diphosphate Ribose↗
PubMed2000

Role of NAD(+) in the deacetylase activity of the SIR2-like proteins.

In this report we describe the role of NAD(+) in the deacetylation reaction catalyzed by the SIR2 family of enzymes. We first show that the products of the reaction detected by HPLC analysis are ADP-ribose, nicotinamide, and a deacetylated peptide substrate. These products are in a 1:1:1 molar ratio, indicating that deacetylation involves the hydrolysis of one NAD(+) to ADP-ribose and nicotinamide for each acetyl group removed. Three results suggest that deacetylation requires an enzyme-ADP-ribose intermediate. First, the enzyme can promote an NAD(+) if nicotinamide exchange reaction that depends on an acetylated substrate. Second, a non-hydrolyzable NAD(+) analog is a competitive inhibitor of the enzyme, and, third, nicotinamide shows product inhibition of deacetylase activity.

Adenosine Diphosphate Ribose↗
PubMed2000

p38-dependent enhancement of cytokine-induced nitric-oxide synthase gene expression by heat shock protein 70.

Heat shock protein (hsp) 70 protects cells against stress by means of its ability to chaperone denatured proteins and to modulate stress-activated signaling pathways. Because inflammatory processes are often accompanied by hsp expression and because stress and cytokines share several signaling pathways, we investigated the possibility that hsp70 might modulate the cellular response to cytokines. We found that stable cell clones overexpressing hsp70, or cells shortly after transfection with hsp70, produced 2 times more nitric oxide and inducible nitric-oxide synthase (iNOS) protein and mRNA in response to cytokines than control cells expressing undetectable amounts of hsp70. Since mitogen-activated protein kinases participate in the activation of iNOS by cytokines, we investigated whether hsp70 affected the activation of these signaling pathways. hsp70 overexpression led to a specific enhancement of the activation of the p38 pathway by cytokines, producing little or no effect on the activation of extracellular signal-regulated kinase or Jun N-terminal kinase. Blocking p38 activity with SB203580 totally abolished the enhancing effect of hsp70 on cytokine-induced endogenous iNOS mRNA accumulation or transcription of an iNOS promoter-driven luciferase gene, while having little effect on the cytokine response observed in control cells. We conclude that the p38 pathway acts as an enhancing factor in the activation of iNOS by cytokines and that hsp70 can modulate the cellular response to cytokines by acting on signaling elements upstream of p38.

Animals↗
PubMed2000

The silencing protein SIR2 and its homologs are NAD-dependent protein deacetylases.

Homologs of the chromatin-bound yeast silent information regulator 2 (SIR2) protein are found in organisms from all biological kingdoms. SIR2 itself was originally discovered to influence mating-type control in haploid cells by locus-specific transcriptional silencing. Since then, SIR2 and its homologs have been suggested to play additional roles in suppression of recombination, chromosomal stability, metabolic regulation, meiosis, and aging. Considering the far-ranging nature of these functions, a major experimental goal has been to understand the molecular mechanism(s) by which this family of proteins acts. We report here that members of the SIR2 family catalyze an NAD-nicotinamide exchange reaction that requires the presence of acetylated lysines such as those found in the N termini of histones. Significantly, these enzymes also catalyze histone deacetylation in a reaction that absolutely requires NAD, thereby distinguishing them from previously characterized deacetylases. The enzymes are active on histone substrates that have been acetylated by both chromatin assembly-linked and transcription-related acetyltransferases. Contrary to a recent report, we find no evidence that these proteins ADP-ribosylate histones. Discovery of an intrinsic deacetylation activity for the conserved SIR2 family provides a mechanism for modifying histones and other proteins to regulate transcription and diverse biological processes.

Acetylation↗
PubMed2000

Vascular endothelial growth factor (VEGF)-driven actin-based motility is mediated by VEGFR2 and requires concerted activation of stress-activated protein kinase 2 (SAPK2/p38) and geldanamycin-sensitive phosphorylation of focal adhesion kinase.

In endothelial cells, vascular endothelial growth factor (VEGF) induces an accumulation of stress fibers associated with new actin polymerization and rapid formation of focal adhesions at the ventral surface of the cells. This cytoskeletal reorganization results in an intense motogenic activity. Using porcine endothelial cells expressing one or the other type of the VEGF receptors, VEGFR1 or VEGFR2, or human umbilical vein endothelial cells pretreated with a VEGFR2 neutralizing antibody, we show that VEGFR2 is responsible for VEGF-induced activation of the stress-activated protein kinase-2/p38 (SAPK2/p38), phosphorylation of focal adhesion kinase (FAK), and enhanced migratory activity. Activation of SAPK2/p38 triggered actin polymerization whereas FAK, which was phosphorylated independently of SAPK2/p38, initiated assembly of focal adhesions. Both processes contributed to the formation of stress fibers. Geldanamycin, an inhibitor of HSP90 blocked tyrosine phosphorylation of FAK, assembly of focal adhesions, actin reorganization, and cell migration, all of which were reversed by overexpressing HSP90. We conclude that VEGFR2 mediates the physiological effect of VEGF on cell migration and that two independent pathways downstream of VEGFR2 regulate actin-based motility. One pathway involves SAPK2/p38 and leads to enhanced actin polymerization activity. The other involves HSP90 as a permissive signal transduction factor implicated in FAK phosphorylation and assembly of focal adhesions.

Actins↗
PubMed2000

Overexpression of the 27 KDa heat shock protein is associated with thermoresistance and chemoresistance but not with radioresistance.

PURPOSE: The heat shock protein (hsp27) correlates with thermotolerance and chemoresistance. Our main objective was to assess the response to radiotherapy both in vitro and in vivo in correlation with various concentrations of hsp27. The second objective was to evaluate the relation between hsp27 and glutathione-s-transferase pi (GST pi). METHODS AND MATERIALS: For the in vitro study, thermoresistant cell lines, expressing various amounts of hsp27, were used to assess the role of this protein in radioresistance. To verify the efficiency of hsp27 in these cells lines to confer resistance to cytotoxic agents, these cells were also treated with heat shock and cisplatin. Furthermore, the role of hsp27 expression was studied in vivo by immunochemistry in 98 patients with head and neck squamous cell carcinoma treated by radiotherapy. hsp27 was correlated with local control of the tumor and with clinical and biologic factors potentially able to affect the local control, including p53, ki-67, ploidy, and GST. RESULTS: In vitro, high constitutive levels of expression of hsp27 did not significantly influence the survival curves of transfected cells exposed to radiation as compared to control cells although hsp27 overexpression was confirmed to increased the cellular resistance to heat and to cisplatinum. In vivo, we showed that overexpression of various amounts of hsp27 did not correlate with local control of the tumor. In vivo, hsp27 was only significantly associated with GST pi. Expression of GST pi was associated with poor local (p = 0.01) control and survival (p = 0.08) in a Cox model. CONCLUSIONS: It is concluded that the mechanisms responsible for hsp27-mediated heat and drug resistance are not involved in radioprotection.

Animals↗
PubMed2000

The interaction of HSP27 with Daxx identifies a potential regulatory role of HSP27 in Fas-induced apoptosis.

The heat shock protein HSP27 protects cells against a wide variety of toxic treatments and blocks apoptosis induced by exposures to anticancer drugs and activation of the death receptor Fas. The molecular mechanisms of protection are unknown but appear to be regulated by phosphorylation of HSP27. Two apoptotic pathways can be activated downstream of Fas. The Fas-adaptor FADD mediates a caspase-dependent pathway. Fas also activates a caspase-independent pathway which correlates with Fas-induced translocation of Daxx from the nucleus to the cytoplasm and involves the interaction of Daxx with Fas and Ask1. We found that phosphorylated dimers of HSP27 interact with Daxx, preventing its interaction with Ask1 and Fas and blocking Daxx-mediated apoptosis. Expression of HSP27 also prevents the translocation of Daxx from the nucleus to the cytoplasm which is induced upon expression of Ask1 or stimulation of Fas. The observations reveal a new level of regulation of the Fas pathway. Whereas the FADD axis can be modulated by expression of FLIP, a natural inhibitor of FADD, our results show that HSP27 can accomplish a similar function for the Daxx axis.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Inhibition of Daxx-mediated apoptosis by heat shock protein 27.

Heat shock protein 27 (HSP27) confers cellular protection against a variety of cytotoxic stresses and also against physiological stresses associated with growth arrest or receptor-mediated apoptosis. Phosphorylation modulates the activity of HSP27 by causing a major change in the supramolecular organization of the protein, which shifts from oligomers to dimers. Here we show that phosphorylated dimers of HSP27 interact with Daxx, a mediator of Fas-induced apoptosis, preventing the interaction of Daxx with both Ask1 and Fas and blocking Daxx-mediated apoptosis. No such inhibition was observed with an HSP27 phosphorylation mutant that is only expressed as oligomers or when apoptosis was induced by transfection of a Daxx mutant lacking its HSP27 binding domain. HSP27 expression had no effect on Fas-induced FADD- and caspase-dependent apoptosis. However, HSP27 blocked Fas-induced translocation of Daxx from the nucleus to the cytoplasm and Fas-induced Daxx- and Ask1-dependent apoptosis. The observations revealed a new level of regulation of the Fas pathway and suggest a mechanism for the phosphorylation-dependent protective function of HSP27 during stress and differentiation.

Adaptor Proteins, Signal Transducing↗