44 results on '"Kristof, Arnold S."'
Search Results
2. A preclinical systematic review and meta-analysis assessing the effect of biological sex in lipopolysaccharide-induced acute lung injury.
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Kuhar, Eva, Chander, Nikesh, Stewart, Duncan J., Jahandideh, Forough, Haibo Zhang, Kristof, Arnold S., Bastarache, Julie A., Schmidt, Eric P., Taljaard, Monica, Thebaud, Bernard, Engelberts, Doreen, Fergusson, Dean A., and Lalu, Manoj M.
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SEX (Biology) ,LUNG injuries ,LIPOPOLYSACCHARIDES - Abstract
It is unclear what effect biological sex has on outcomes of acute lung injury (ALI). Clinical studies are confounded by their observational design. We addressed this knowledge gap with a preclinical systematic review of ALI animal studies. We searched MEDLINE and Embase for studies of intratracheal/intranasal/aerosolized lipopolysaccharide administration (the most common ALI model) that reported sex-stratified data. Screening and data extraction were conducted in duplicate. Our primary outcome was histological tissue injury and secondary outcomes included alveolar-capillary barrier alterations and inflammatory markers. We used a random-effects inverse variance meta-analysis, expressing data as standardized mean difference (SMD) with 95% confidence intervals (CIs). Risk of bias was assessed using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool. We identified six studies involving 132 animals across 11 independent experiments. A total of 41 outcomes were extracted, with the direction of effect suggesting greater severity in males than females in 26/41 outcomes (63%). One study reported on lung histology and found that male mice exhibited greater injury than females (SMD: 1.61, 95% CI: 0.53–2.69). Meta-analysis demonstrated significantly elevated albumin levels (SMD: 2.17, 95% CI: 0.63–3.70) and total cell counts (SMD: 0.80, 95% CI: 0.27–1.33) in bronchoalveolar lavage fluid from male mice compared with female mice. Most studies had an “unclear risk of bias.” Our findings suggest sex-related differences in ALI severity. However, these conclusions are drawn from a small number of animals and studies. Further research is required to address the fundamental issue of biological sex differences in LPS-induced ALI. [ABSTRACT FROM AUTHOR]
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- 2024
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3. Albumin and fibrinogen kinetics in sepsis: a prospective observational study
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Omiya, Keisuke, Sato, Hiroaki, Sato, Tamaki, Wykes, Linda, Hong, Mengyin, Hatzakorzian, Roupen, Kristof, Arnold S., and Schricker, Thomas
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- 2021
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4. Surrogate Humane Endpoints in Small Animal Models of Acute Lung Injury: A Modified Delphi Consensus Study of Researchers and Laboratory Animal Veterinarians*
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McGinn, Ryan, Fergusson, Dean A., Stewart, Duncan J., Kristof, Arnold S., Barron, Carly C., Thebaud, Bernard, McIntyre, Lauralyn, Stacey, Dawn, Liepmann, Mark, Dodelet-Devillers, Aurore, Zhang, Haibo, Renlund, Richard, Lilley, Elliot, Downey, Gregory P., Brown, Earl G., Côté, Lucie, dos Santos, Claudia C., Fox-Robichaud, Alison E., Hussain, Sabah N.A., Laffey, John G., Liu, Mingyao, MacNeil, Jenna, Orlando, Holly, Qureshi, Salman T., Turner, Patricia V., Winston, Brent W., and Lalu, Manoj M.
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- 2021
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5. Biomarkers in critical care nutrition
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Stoppe, Christian, Wendt, Sebastian, Mehta, Nilesh M., Compher, Charlene, Preiser, Jean-Charles, Heyland, Daren K., and Kristof, Arnold S.
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- 2020
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6. Publisher Correction: Regulation of protein kinase Cδ Nuclear Import and Apoptosis by Mechanistic Target of Rapamycin Complex-1
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Layoun, Antonio, Goldberg, Alexander A., Baig, Ayesha, Eng, Mikaela, Attias, Ortal, Nelson, Kristoff, Carella, Alexandra, Amberber, Nahomi, Fielhaber, Jill A., Joung, Kwang-Bo, Schmeing, T. Martin, Han, Yingshan, Downey, Jeffrey, Divangahi, Maziar, Roux, Philippe P., and Kristof, Arnold S.
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- 2020
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7. Regulation of protein kinase Cδ Nuclear Import and Apoptosis by Mechanistic Target of Rapamycin Complex-1
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Layoun, Antonio, Goldberg, Alexander A., Baig, Ayesha, Eng, Mikaela, Attias, Ortal, Nelson, Kristoff, Carella, Alexandra, Amberber, Nahomi, Fielhaber, Jill A., Joung, Kwang-Bo, Schmeing, T. Martin, Han, Yingshan, Downey, Jeffrey, Divangahi, Maziar, Roux, Philippe P., and Kristof, Arnold S.
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- 2019
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8. Tissue‐Engineered Disease Modeling of Lymphangioleiomyomatosis Exposes a Therapeutic Vulnerability to HDAC Inhibition.
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Pietrobon, Adam, Yockell‐Lelièvre, Julien, Melong, Nicole, Smith, Laura J., Delaney, Sean P., Azzam, Nadine, Xue, Chang, Merwin, Nishanth, Lian, Eric, Camacho‐Magallanes, Alberto, Doré, Carole, Musso, Gabriel, Julian, Lisa M., Kristof, Arnold S., Tam, Roger Y., Berman, Jason N., Shoichet, Molly S., and Stanford, William L.
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HISTONE deacetylase inhibitors ,HISTONE deacetylase ,TISSUE engineering ,CELL culture ,CELL death ,RARE diseases - Abstract
Lymphangioleiomyomatosis (LAM) is a rare disease involving cystic lung destruction by invasive LAM cells. These cells harbor loss‐of‐function mutations in TSC2, conferring hyperactive mTORC1 signaling. Here, tissue engineering tools are employed to model LAM and identify new therapeutic candidates. Biomimetic hydrogel culture of LAM cells is found to recapitulate the molecular and phenotypic characteristics of human disease more faithfully than culture on plastic. A 3D drug screen is conducted, identifying histone deacetylase (HDAC) inhibitors as anti‐invasive agents that are also selectively cytotoxic toward TSC2−/− cells. The anti‐invasive effects of HDAC inhibitors are independent of genotype, while selective cell death is mTORC1‐dependent and mediated by apoptosis. Genotype‐selective cytotoxicity is seen exclusively in hydrogel culture due to potentiated differential mTORC1 signaling, a feature that is abrogated in cell culture on plastic. Importantly, HDAC inhibitors block invasion and selectively eradicate LAM cells in vivo in zebrafish xenografts. These findings demonstrate that tissue‐engineered disease modeling exposes a physiologically relevant therapeutic vulnerability that would be otherwise missed by conventional culture on plastic. This work substantiates HDAC inhibitors as possible therapeutic candidates for the treatment of patients with LAM and requires further study. [ABSTRACT FROM AUTHOR]
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- 2023
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9. Pharmacokinetics of Posaconazole Within Epithelial Cells and Fungi: Insights Into Potential Mechanisms of Action During Treatment and Prophylaxis
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Campoli, Paolo, Perlin, David S., Kristof, Arnold S., White, Theodore C., Filler, Scott G., and Sheppard, Donald C.
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- 2013
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10. Downregulation of PERK activity and eIF2α serine 51 phosphorylation by mTOR complex 1 elicits pro-oxidant and pro-death effects in tuberous sclerosis-deficient cells
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Krishnamoorthy, Jothilatha, Tenkerian, Clara, Gupta, Jyotsana, Ghaddar, Nour, Wang, Shuo, Darini, Cedric, Staschke, Kirk A., Ghosh, Abhishek, Gandin, Valentina, Topisirovic, Ivan, Kristof, Arnold S., Hatzoglou, Maria, Simos, George, and Koromilas, Antonis E.
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- 2018
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11. Lymphangioleiomyomatosis and Tuberous Sclerosis Complex in Quebec: Prevalence and Health-care Utilization
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Kristof, Arnold S., Li, Pei Zhi, Major, Philippe, and Landry, Jennifer S.
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- 2015
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12. Protein expression of urotensin II, urotensin-related peptide and their receptor in the lungs of patients with lymphangioleiomyomatosis
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Kristof, Arnold S., You, Zhipeng, Han, Yin-Shan, and Giaid, Adel
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- 2010
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13. Mutations in Mycobacterium tuberculosis Rv0444c, the gene encoding anti-SigK, explain high level expression of MPB70 and MPB83 in Mycobacterium bovis
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Saïd-Salim, Battouli, Mostowy, Serge, Kristof, Arnold S., and Behr, Marcel A.
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- 2006
14. Maximal Oxygen Uptake and Severity of Disease in Lymphangioleiomyomatosis
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Taveira-DaSilva, Angelo M., Stylianou, Mario P., Hedin, Carolyn J., Kristof, Arnold S., Avila, Nilo A., Rabel, Antoinette, Travis, William D., and Moss, Joel
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- 2003
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15. Genetics and Gene Expression in Lymphangioleiomyomatosis*: Giles F. Filley Lecture
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Pacheco-Rodriguez, Gustavo, Kristof, Arnold S., Stevens, Linda A., Zhang, Yi, Crooks, Denise, and Moss, Joel
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- 2002
16. Prevalence and Clinical Characteristics of Lymphangioleiomyomatosis (LAM) in Patients with Tuberous Sclerosis Complex
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MOSS, JOEL, AVILA, NILO A., BARNES, PAULINE M., LITZENBERGER, RUTH A., BECHTLE, JEANMARIE, BROOKS, PAMELA G., HEDIN, CAROLYN J., HUNSBERGER, SALLY, and KRISTOF, ARNOLD S.
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- 2001
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17. Role of Inducible Nitric Oxide Synthase in Endotoxin-induced Acute Lung Injury
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KRISTOF, ARNOLD S., GOLDBERG, PETER, LAUBACH, VICTOR, and HUSSAIN, SABAH N. A.
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- 1998
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18. An Official American Thoracic Society Workshop Report: Translational Research in Rare Respiratory Diseases.
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Kristof, Arnold S., Petrof, Basil J., Hamid, Qutayba, Kolb, Martin, Landry, Jennifer S., MacKenzie, Alex, McCormack, Francis X., Murawski, Inga J., Moss, Joel, Rauch, Frank, Rosas, Ivan O., Shapiro, Adam J., Smith, Benjamin M., Thomas, David Y., Trapnell, Bruce C., Young, Lisa R., Zariwala, Maimoona A., and ATS Assembly on Respiratory Cell and Molecular Biology
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LUNG disease diagnosis ,LUNG disease treatment ,ANIMAL experimentation ,CLINICAL trials ,CONFERENCES & conventions ,GENETIC techniques ,LUNG diseases ,MEDICAL research ,MEDICAL societies ,MICE ,RESEARCH funding ,DIAGNOSIS ,SYMPTOMS ,THERAPEUTICS - Abstract
Rare respiratory diseases (RRDs) are a heterogeneous group of disorders that collectively represent a significant health care burden. In recent years, strong advocacy and policy initiatives have led to advances in the implementation of research and clinical care for rare diseases. The development of specialized centers and research networks has facilitated support for affected individuals as well as emerging programs in basic, translational, and clinical research. In selected RRDs, subsequent gains in knowledge have informed the development of targeted therapies and effective diagnostic tests, but many gaps persist. There was therefore a desire to identify the elements contributing to an effective translational research program in RRDs. To this end, a workshop was convened in October 2015 with a focus on the implementation of effective transnational research networks and collaborations aimed at developing novel diagnostic and therapeutic tools. Key elements included an emphasis on molecular pathogenesis, the continuing engagement of patient advocacy groups and policy makers, the effective use of preclinical models in the translational research pipeline, and the detailed phenotyping of patient cohorts. During the course of the workshop, current logistical and knowledge gaps were identified, and new solutions or opportunities were highlighted. [ABSTRACT FROM AUTHOR]
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- 2017
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19. Protein Delivery in the Intensive Care Unit: Optimal or Suboptimal?
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Heyland, Daren K., Weijs, Peter J. M., Coss-Bu, Jorge A., Taylor, Beth, Kristof, Arnold S., O'Keefe, Grant E., and Martindale, Robert G.
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- 2017
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20. Hyperinsulinemic-normoglycemic clamp administered together with amino acids induces anabolism after cardiac surgery.
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Codère-Maruyama, Takumi, Schricker, Thomas, Shum-Tim, Dominique, Wykes, Linda, Nitschmann, Evan, Guichon, Céline, Kristof, Arnold S., and Hatzakorzian, Roupen
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GLUCOSE clamp technique ,PROTEINS in the body ,CORONARY artery bypass ,PATIENTS - Abstract
Cardiac surgery triggers an inflammatory stress response, leading to protein catabolism, a process that even high-dose insulin therapy alone cannot reverse. To determine whether hyperinsulinemic-normoglycemic clamp and perioperative amino acid (AA) supplementation improves whole body protein balance, 20 patients scheduled for elective coronary artery bypass grafting surgery were randomly assigned to have intra- and postoperative hyperinsulinemic-normoglycemic clamp, with or without intravenous AA supplementation. Primed continuous infusions of [6,6-²H2]glucose and L-[1-
13 C]leucine were used to quantify whole body protein and glucose metabolism before and after surgery. Adipose tissue and serum cytokines were also analyzed to measure their responsiveness to the anabolic effect of AA administration. During hyperinsulinemic-normoglycemic clamp, AA supplementation successfully stimulated whole body protein synthesis, resulting in a positive whole body protein balance after surgery (insulin: -13.6 ± 4.5 vs. insulin + AA: 2.1 ± 5.4 µmol·kg-1 ·h-1 , P < 0.001). Endogenous glucose production was equally suppressed in both groups (insulin: 0.0 ± 3.8 vs. insulin + AA 1.6 ± 1.6 µmol·kg-1 ·min-1 , P = 0.230). AA supplementation led to significant changes in serum and tissue IL-6 (insulin: 246.6 ± 111.2 vs. insulin + AA: 124.5 ± 79.3 pg/ml, P = 0.011). In conclusion, hyperinsulinemic- normoglycemic clamp technique, together with AA supplementation, can induce an anabolic state after open-heart surgery, as quantified by a positive whole body protein balance. [ABSTRACT FROM AUTHOR]- Published
- 2016
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21. Reactive Oxygen Species Regulation of Autophagy in Skeletal Muscles.
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Rahman, Mashrur, Mofarrahi, Mahroo, Kristof, Arnold S., Nkengfac, Bernard, Harel, Sharon, and Hussain, Sabah N.A.
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- 2014
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22. Suspected ventilator-associated respiratory infection in severely ill patients: a prospective observational study.
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Shahin, Jason, Bielinski, Michael, Guichon, Celine, Flemming, Catherine, and Kristof, Arnold S.
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RESPIRATORY infections ,ANTI-infective agents ,BLOOD cell count ,ARTIFICIAL respiration ,IMMUNOSUPPRESSION ,CLINICAL trials - Abstract
Introduction Ventilator-associated respiratory infection (VARI) is an important cause of morbidity in critically-ill patients. Clinical trials performed in heterogeneous populations have suggested there are limited benefits from invasive diagnostic testing to identify patients at risk or to target antimicrobial therapy. However, multiple patient subgroups (for example, immunocompromised, antibiotic-treated) have traditionally been excluded from randomization. We hypothesized that a prospective surveillance study would better identify patients with suspected VARI (sVARI) at high risk for adverse clinical outcomes, and who might be specifically targeted in future trials. Methods We performed a prospective observational study in all patients ventilated for greater than 48 hours. sVARI was identified by surveillance for changes in white blood cell count, temperature, sputum, and/or new chest X-ray infiltrates. Indices of disease co-morbidity, as well as mortality, duration of mechanical ventilation, and length of hospital or ICU stay were correlated with sVARI. Results Of 1806 patients admitted to the ICU over 14 months, 267 were ventilated for greater than 48 hours, and 77 developed sVARI. Incidence of sVARI was associated with iatrogenic immunosuppression or admission for respiratory illness. Any sVARI, whether suspected ventilator-associated pneumonia (sVAP) or ventilator-associated tracheobronchitis (sVAT), was associated with increased length of stay and duration of mechanical ventilation. Conclusions Clinical surveillance for sVARI identifies patients at risk for increased morbidity. Iatrogenically immunosuppressed patients, a subgroup previously excluded from randomized clinical trials, represent a growing proportion of the critically-ill at risk for sVARI who might be targeted for future investigations on diagnostic or therapeutic modalities. [ABSTRACT FROM AUTHOR]
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- 2013
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23. Paradoxical Effects of Rapamycin on Experimental House Dust Mite-Induced Asthma.
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Fredriksson, Karin, Fielhaber, Jill A., Lam, Jonathan K., Yao, Xianglan, Meyer, Katharine S., Keeran, Karen J., Zywicke, Gayle J., Qu, Xuan, Yu, Zu-Xi, Moss, Joel, Kristof, Arnold S., and Levine, Stewart J.
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HOUSE dust mites ,ASTHMA ,BRONCHIAL diseases ,RAPAMYCIN ,IMMUNOSUPPRESSIVE agents ,IMMUNE response ,CELL proliferation - Abstract
The mammalian target of rapamycin (mTOR) modulates immune responses and cellular proliferation. The objective of this study was to assess whether inhibition of mTOR with rapamycin modifies disease severity in two experimental murine models of house dust mite (HDM)-induced asthma. In an induction model, rapamycin was administered to BALB/c mice coincident with nasal HDM challenges for 3 weeks. In a treatment model, nasal HDM challenges were performed for 6 weeks and rapamycin treatment was administered during weeks 4 through 6. In the induction model, rapamycin significantly attenuated airway inflammation, airway hyperreactivity (AHR) and goblet cell hyperplasia. In contrast, treatment of established HDM-induced asthma with rapamycin exacerbated AHR and airway inflammation, whereas goblet cell hyperplasia was not modified. Phosphorylation of the S6 ribosomal protein, which is downstream of mTORC1, was increased after 3 weeks, but not 6 weeks of HDM-challenge. Rapamycin reduced S6 phosphorylation in HDM-challenged mice in both the induction and treatment models. Thus, the paradoxical effects of rapamycin on asthma severity paralleled the activation of mTOR signaling. Lastly, mediastinal lymph node re-stimulation experiments showed that treatment of rapamycin-naive T cells with ex vivo rapamycin decreased antigen-specific Th2 cytokine production, whereas prior exposure to in vivo rapamycin rendered T cells refractory to the suppressive effects of ex vivo rapamycin. We conclude that rapamycin had paradoxical effects on the pathogenesis of experimental HDM-induced asthma. Thus, consistent with the contextdependent effects of rapamycin on inflammation, the timing of mTOR inhibition may be an important determinant of efficacy and toxicity in HDM-induced asthma. [ABSTRACT FROM AUTHOR]
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- 2012
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24. Activity of the Ste20-kinase, SLK, is enhanced by homodimerization.
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Delarosa, Sierra, Guillemette, Julie, Papillon, Joan, Ying-Shan Han, Kristof, Arnold S., and Cybulsky, Andrey V.
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GENE expression ,GENETIC transcription ,GENETIC regulation ,GENETIC translation ,APOPTOSIS ,PROTEIN kinases ,GEL permeation chromatography - Abstract
The expression and activation of the Ste20-like kinase, SLK, is increased during renal development and recovery from ischemic acute renal failure. SLK promotes apoptosis, and during renal injury and repair, transcriptional induction or posttranscriptional control of SLK may, therefore, regulate cell survival. SLK contains protein interaction (coiled-coil) domains, suggesting that posttranslational homodimerization may also modulate SLK activity. We therefore expressed coiled-coil regions in the C-terminal domain of SLK as fusion proteins and demonstrated their homodimerization. By gel-filtration chromatography, endogenous and heterologously expressed SLK were detected in a macromolecular protein complex. To test the role of homodimerization in kinase activation, we constructed a fusion protein consisting of the SLK catalytic domain (amino acids 1-373) and a modified FK506 binding protein, Fv (Fv-SLK 1-373). Addition of AP20187 (an analog of FK506) enhanced the homodimerization of Fv-SLK 1-373. In an in vitro kinase assay, the dimeric Fv-SLK 1-373 displayed greater kinase activity than the monomeric form. In cells expressing Fv-SLK 1-373, homodimerization increased activation-specific phosphorylation of the proapoptotic kinases, c-Jun N-terminal kinase and p38 kinase. Compared with the monomer, dimeric Fv-SLK 1-373 enhanced the activation of a Bax promoter-luciferase reporter. Finally, expression of Fv-SLK 1-373 induced apoptosis, and the effect was increased by homodimerization. Thus the activity, downstream signaling, and functional effects of SLK are enhanced by dimerization of the kinase domain. [ABSTRACT FROM AUTHOR]
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- 2011
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25. Phosphatidylinositol 3-Kinase-dependent Suppression of the Human Inducible Nitric-oxide Synthase Promoter Is Mediated by FKHRL1.
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Kristof, Arnold S., Fielhaber, Jill, Triantafillopoulos, Alexandra, Nemoto, Shino, and Moss, Joel
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NITRIC-oxide synthases , *PHOSPHOINOSITIDES , *CYTOKINES , *TRANSCRIPTION factors , *PROTEIN kinases , *OXIDOREDUCTASES - Abstract
The synthesis of nitric oxide by inducible nitric-oxide synthase (iNOS) plays an important role in the innate immune response by promoting microbial killing and cell damage. In response to inflammatory cytokines and bacterial products, the human iNOS (hiNOS) gene undergoes rapid transcriptional activation via binding of stimulatory transcription factors (e.g. AP-1 and NF-κB) to its 5′-flanking region. However, maximal hiNOS promoter induction was suppressed via an unknown phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. We hypothesized that inhibition of the transcription factor FKHRL1 by the PI3K/protein kinase B pathway attenuates hiNOS promoter induction by bacterial lipopolysaccharide and interferon-gamma (LPS/IFN-γ). Human lung epithelial adenocarcinoma (A549) cells were transiently transfected with an 8.3-kb hiNOS promoter luciferase reporter construct. Co-expression of dominant-negative protein kinase B potentiated LPS/IFN-γ-stimulated hiNOS promoter activity. In response to LPS/IFN-γ, FKHRL1 was phosphorylated in a PI3K- and time-dependent fashion. Co-expression of constitutively active FKHRL1 increased hiNOS promoter activity and mRNA levels, Dominant-negative siRNA expression showed that FKHRL1 was necessary for the inhibitory effects of PI3K on hiNOS induction. The same effect was observed upon mutation of a consensus FKHRL1-binding site in the hiNOS promoter. By gel-shift analysis, the corresponding oligonucleotide probe bound endogenous FKHRL1 in an LPS/IFN-γ- and PI3K-sensitive fashion. Regulation of the hiNOS promoter by FKHRL1 represents a potentially important molecular mechanism by which the PI3K pathway might suppress pro-inflammatory and pro-apoptotic responses to cytokines and bacterial products. [ABSTRACT FROM AUTHOR]
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- 2006
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26. Stimulation of Signal Transducer and Activator of Transcription-1 (STAT1)-dependent Gene Transcription by Lipopolysaccharide and Interferon-γ Is Regulated by Mammalian Target of Rapamycin.
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Kristof, Arnold S., Marks-Konczalik, Joanna, Billings, Eric, and Moss, Joel
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RAPAMYCIN , *ENDOTOXINS , *INTERFERONS - Abstract
Mammalian target of rapamycin (mTOR) and phosphatidylinositol 3-kinase (PI3K) regulate cell growth, protein synthesis, and apoptosis in response to nutrients and mitogens. As an important source of nitric oxide during inflammation, human inducible nitric oxide synthase also plays a role in the regulation of cytokine-driven cell proliferation and apoptosis. The role of mTOR and PI3K in the activation of human inducible nitric oxide synthase transcription by cytokines and lipopolysaccharide (LPS) was investigated in lung epithelial adenocarcinoma (A549) cells. LY294002, a dual mTOR and PI3K inhibitor, blocked human inducible nitric oxide synthase (hiNOS) promoter activation and mRNA induction by cytokines and LPS in a PI3Kindependent fashion. On gene expression analysis, LY294002 selectively blocked the induction of a subset of 14 LPS/interferon-γ (IFN-γ)-induced genes, previously characterized as signal transducer and activator of transcription-1 (STAT1)-dependent. LY294002, but not wortmannin, inhibited LPS/IFN-γ-dependent STAT1 phosphorylation at Ser-727 and STAT1 activity. Consistent with dual inhibition of mTOR and PI3K by LY294002, dominant-negative mTOR, anti-mTOR small interfering RNA, or rapamycin each inhibited phosphorylation of STAT1 only in the presence of wortmannin. LPS/IFN-γ led to the formation of a macromolecular complex containing mTOR, STAT1, as well as protein kinase Cδ, a known STAT1α kinase. Thus, LPS and IFN-γ activate the PI3K and mTOR pathways, which converge to regulate STAT1-dependent transcription of pro-apoptotic and pro-inflammatory genes in a rapamycin-insensitive manner. [ABSTRACT FROM AUTHOR]
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- 2003
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27. Giles F. Filley Lecture. Genetics and gene expression in lymphangioleiomyomatosis.
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Pacheco-Rodriguez, Gustavo, Kristof, Arnold S, Stevens, Linda A, Zhang, Yi, Crooks, Denise, and Moss, Joel
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Lymphangioleiomyomatosis (LAM) is a disease of unknown etiology that is characterized by the proliferation of abnormal smooth muscle cells (LAM cells) in the lung, which leads to cystic parenchymal destruction and progressive respiratory failure. Recent evidence suggests that the proliferative and invasive nature of LAM cells may be due, in part, to somatic mutations in the TSC2 gene, which has been implicated in the pathogenesis of tuberous sclerosis complex. Here, we describe the clinical and molecular characteristics of LAM, as well as the efforts now under way to understand the genetic and biochemical factors that lead to progressive pulmonary destruction and, ultimately, to lung transplantation or death. [ABSTRACT FROM AUTHOR]
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- 2002
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28. Avoidable statistical pitfalls in analyzing length of stay in intensive care units or hospitals.
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Wolkewitz, Martin, Shahin, Jason, and Kristof, Arnold S.
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- 2014
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29. The initial validation of a novel outcome measure in severe burns- the Persistent Organ Dysfunction +Death: Results from a multicenter evaluation.
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Stoppe, Christian, Hill, Aileen, Day, Andrew G, Kristof, Arnold S, Hundeshagen, Gabriel, Kneser, Ulrich, Beier, Justus, Lumenta, David, Kim, Bong-Sung, Plock, Jan, Collins, Declan P, Gille, Jochen, Jiang, Xuran, and Heyland, Daren K
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BODY surface area , *QUALITY of life , *BURN patients , *LONGITUDINAL method , *CLINICAL trials , *CHEMICAL burns , *INHALATION injuries , *MENTAL health , *BURNS & scalds complications , *INTENSIVE care units , *LENGTH of stay in hospitals , *RESEARCH , *BURNS & scalds , *RESEARCH methodology , *MULTIPLE organ failure , *HEALTH status indicators , *MEDICAL cooperation , *EVALUATION research , *ANXIETY testing , *COMPARATIVE studies , *CHI-squared test , *RESEARCH funding , *FEAR of death - Abstract
Introduction: A need exists to improve the efficiency of clinical trials in burn care. The objective of this study was to validate "Persistent Organ Dysfunction" plus death as endpoint in burn patients and to demonstrate its statistical efficiency.Methods: This secondary outcome analysis of a dataset from a prospective international multicenter RCT (RE-ENERGIZE) included patients with burned total body surface area >20% and a 6-month follow-up. Persistent organ dysfunction was defined as persistence of organ dysfunction with life-supportiing technologies and ICU care.Results: In the 539 included patients, the prevalence of 0p p+ pdeath was 40% at day 14 and of 27% at day 28. At both timepoints, survivors with POD (vs. survivors without POD) had a higher mortality rate, longer ICU- and hospital-stays, and a reduced quality of life. POD + death as an endpoint could result in reduced sample size requirements for clinical trials. Detecting a 25% relative risk reduction in 28-day mortality would require a sample size of 4492 patients, whereas 1236 patients would be required were 28-day POD + death used.Conclusions: POD + death represents a promising composite outcome measure that may reduce the sample size requirements of clinical trials in severe burns patients. Further validation in larger clinical trials is warranted.Study Type: Prospective cohort study, level of evidence: II. [ABSTRACT FROM AUTHOR]- Published
- 2021
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30. Regulation of ULK1 Expression and Autophagy by STAT1.
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Goldberg, Alexander A., Nkengfac, Bernard, Sanchez, Anthony M. J., Moroz, Nikolay, Qureshi, Salman T., Koromilas, Antonis E., Shuo Wang, Burelle, Yan, Hussain, Sabah N., and Kristof, Arnold S.
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RAPAMYCIN , *STAT proteins , *DEPHOSPHORYLATION , *CHEMICAL reactions , *AUTOPHAGY , *IMMUNOSUPPRESSIVE agents - Abstract
Autophagy involves the lysosomal degradation of cytoplasmic contents for regeneration of anabolic substrates during nutritional or inflammatory stress. Its initiation occurs rapidly after inactivation of the protein kinase mammalian target of rapamycin (mTOR) (or mechanistic target of rapamycin), leading to dephosphorylation of Unc-51-like kinase 1 (ULK1) and autophagosome formation. Recent studies indicate that mTOR can, in parallel, regulate the activity of stress transcription factors, including signal transducer and activator of transcription-1 (STAT1). The current study addresses the role of STAT1 as a transcriptional suppressor of autophagy genes and autophagic activity. We show that STAT1-deficient human fibrosarcoma cells exhibited enhanced autophagic flux as well as its induction by pharmacological inhibition of mTOR. Consistent with enhanced autophagy initiation, ULK1 mRNA and protein levels were increased in STAT1-deficient cells. By chromatin immunoprecipitation, STAT1 bound a putative regulatory sequence in the ULK1 5'-flanking region, the mutation of which increased ULK1 promoter activity, and rendered it unresponsive to mTOR inhibition. Consistent with an anti-apoptotic effect of autophagy, rapamycin- induced apoptosis and cytotoxicity were blocked in STAT1-deficient cells but restored in cells simultaneously exposed to the autophagy inhibitor ammonium chloride. In vivo, skeletal muscle ULK1 mRNA and protein levels as well as autophagic flux were significantly enhanced in STAT1-deficient mice. These results demonstrate a novel mechanism by which STAT1 negatively regulates ULK1 expression and autophagy. [ABSTRACT FROM AUTHOR]
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- 2017
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31. Identification of Tpr and α-actinin-4 as two novel SLK-interacting proteins.
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Jaberi, Aala, Hooker, Erika, Guillemette, Julie, Papillon, Joan, Kristof, Arnold S., and Cybulsky, Andrey V.
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ACTININ , *MICROFILAMENT proteins , *NONMUSCLE actinin , *KINASES , *BIOSYNTHESIS - Abstract
Expression and activity of the Ste20-like kinase, SLK, are increased during kidney development and recovery from ischemia–reperfusion injury. SLK mediates apoptosis in various cells, and can regulate cell cycle progression and cytoskeletal remodeling. In cells, SLK is detected in a high molecular mass complex, suggesting that SLK is a dimer/oligomer, or is in tight association with other proteins. To better understand the regulation, localization and function of SLK, we sought to identify proteins in this high molecular mass complex. Analysis by mass spectroscopy identified the nucleoporin, translocated promoter region (Tpr), and the cytoskeletal protein, α-actinin-4, as potential SLK-interacting proteins. Using a protein complementation assay, we showed that the 350 amino acid C-terminal, coiled-coil domain of SLK was responsible for homodimerization, as well as interaction with Tpr and α-actinin-4. The association of SLK with Tpr and α-actinin-4, respectively, was confirmed by co-immunoprecipitation. Subsets of total cellular SLK colocalized with Tpr at the nuclear envelope, and α-actinin-4 in the cytoplasm. Expression of Tpr attenuated activation-specific autophosphorylation of SLK, and blocked SLK-induced apoptosis and AP-1 activity. In contrast to the effect of Tpr, autophosphorylation of SLK was not affected by α-actinin-4. Thus, SLK interacts with Tpr and α-actinin-4 in cells, and these protein–protein interactions may control the subcellular localization and the biological activity of SLK. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
32. Inhibition of Mammalian Target of Rapamycin Augments Lipopolysaccharide-Induced Lung Injury and Apoptosis.
- Author
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Fielhaber, Jill A., Carroll, Scott F., Dydensborg, Anders B., Shourian, Mitra, Triantafillopoulos, Alexandra, Harel, Sharon, Hussain, Sabah N., Bouchard, Maxime, Qureshi, Salman T., and Kristof, Arnold S.
- Subjects
- *
RAPAMYCIN , *LIPOPOLYSACCHARIDES , *APOPTOSIS , *LUNG injuries , *BACTERIAL diseases , *EPITHELIAL cells - Abstract
Acute lung injury during bacterial infection is associated with neutrophilic inflammation, epithelial cell apoptosis, and disruption of the alveolar-capillary barrier. TLR4 is required for lung injury in animals exposed to bacterial LPS and initiates proinflammatory responses in part via the transcription factor NF-&kgr;B . Ligation of TLR4 also initiates a proapoptotic response by activating IFN-β and STATl-dependent genes. We recently demonstrated that mammalian target of rapamycin (mTOR), a key controller of cell growth and survival, can physically interact with STAT1 and suppress the induction of STATl-dependent apoptosis genes. We therefore hypothesized that the mTOR inhibitor rapamycin would increase LPS-induced apoptosis and lung injury in vivo. Rapamycin increased lung injury and cellular apoptosis in C57BL/6J mice exposed to intratracheal LPS for 24 h. Rapamycin also augmented STAT1 activation, and the induction of STATl-dependent genes that mediate cellular apoptosis (i.e., Fas, caspase- 3). LPS-induced lung injury was attenuated in STAT1 knockout mice. In addition, LPS and IFN-β-induced apoptosis was absent in cultured cells lacking STAT1, and, unlike in wild-type cells, a permissive effect of rapamycin was not observed. In contrast to its effect on STAT1, rapamycin inhibited NF-&kgr;B activation in vivo and reduced selected markers of inflammation (i.e., neutrophils in the bronchoalveolar lavage fluid, TNF-α). Therefore, although it inhibits NF-&kgr;B and neutrophilic inflammation, rapamycin augments LPS-induced lung injury and apoptosis in a mechanism that involves STAT1 and the induction of STATl-dependent apoptosis genes. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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- View/download PDF
33. Regulation of Karyopherin α1 and Nuclear Import by Mammalian Target of Rapamycin.
- Author
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Fielhaber, Jill A., Tan, Jason, Joung, Kwang-Bo, Attias, Ortal, Huegel, Stefanie, Bader, Michael, Roux, Philippe P., and Kristof, Arnold S.
- Subjects
- *
KARYOPHERINS , *RAPAMYCIN , *KINASES , *APOPTOSIS , *TRANSCRIPTION factors , *IMMUNOREGULATION , *IMMUNOLOGY - Abstract
Under conditions of reduced mitogen or nutritional substrate levels, the serine/threonine kinase target of rapamycin can augment the nuclear content of distinct transcription factors and promote the induction of stress response genes. In its latent (i.e., unphosphorylated) form, the transcription factor STAT1 regulates a subset of genes involved in immune modulation and apoptosis. Based on previous work indicating a functional relationship between mammalian target of rapamycin (mTOR) and the nuclear content of latent STAT1, we investigated the mechanism by which mTOR controls STAT1 nuclear import. By fluorescence confocal microscopy, inactivation ofmTORwith rapamycin promoted the nuclear translocation of unphosphorylated STAT1, but not that of a STAT1 mutant incapable of binding its nuclear import adaptor karyopherin-α1 (KPNA1). By immunoprecipitation, KPNA1was physically associated withmTORand STAT1in a complex that translocated to the nucleus in response to rapamycin. Although mTOR is not a kinase for KPNA1, the mTOR-associated phosphatase protein phosphatase 2A catalytic interacted directly with KPNA1 and regulated nuclear import of the mTOR-KPNA1 complex. KPNA1, or its interaction with STAT1, was required for the nuclear import of latent STAT1, transcriptional induction of the STAT1 gene, and caspase-3 activation under conditions of reduced mTOR activity (i.e. rapamycin, glucose starvation, serum withdrawal). Therefore, at low mitogen or nutrient levels,mTORand protein phosphatase 2A catalytically control the constitutive nuclear import of latent STAT1 by KPNA1, which are key modulators of STAT1 expression and apoptosis. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
34. Inactivation of Mammalian Target of Rapamycin Increases STAT1 Nuclear Content and Transcriptional Activity in α4- and Protein Phosphatase 2A-dependent Fashion.
- Author
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Fielhaber, Jill A., Han, Ying-Shan, Tan, Jason, Xing, Shuo, Biggs, Catherine M., Joung, Kwang-Bo, and Kristof, Arnold S.
- Subjects
- *
RAPAMYCIN , *PHOSPHATASES , *PROTEIN synthesis , *SACCHAROMYCES cerevisiae , *TRANSCRIPTION factors , *APOPTOSIS - Abstract
Target of rapamycin (TOR) is a highly conserved serine/threonine kinase that controls cell growth, primarily via regulation of protein synthesis. In Saccharomyces cerevisiae, TOR can also suppress the transcription of stress response genes by a mechanism involving Tap42, a serine/threonine phosphatase subunit, and the transcription factor Msn2. A physical association between mammalian TOR (mTOR) and the transcription factor signal transducer and activator of transcription-i (STAT!) was recently identified in human cells, suggesting a similar role for mTOR in the transcription of interferon-γ-stimulated genes. In the current study, we identified a macromolecular protein complex composed of mTOR, STAT1, the Tap42 homologue α4, and the protein phosphatase 2A catalytic subunit (PP2Ac). Inactivation of mTOR enhanced its association with STAT1 and increased STAT1 nuclear content in PP2Ac-dependent fashion. Depletion of α4, PP2A, or mTOR enhanced the induction of early (i.e. IRF-1) and late (i.e. caspase-1, hiNOS, and Fas) STAT1-dependent genes. The regulation of IRF-1 or caspase-1 by mTOR was independent of other known mTOR effectors p70 S6 kinase and Akt. These results describe a new role for mTOR and α4/PP2A in the control of STAT 1 nuclear content, and the expression of interferon-γ-sensitive genes involved in immunity and apoptosis. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
35. Stress Ulcer Prophylaxis during Invasive Mechanical Ventilation.
- Author
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Cook D, Deane A, Lauzier F, Zytaruk N, Guyatt G, Saunders L, Hardie M, Heels-Ansdell D, Alhazzani W, Marshall J, Muscedere J, Myburgh J, English S, Arabi YM, Ostermann M, Knowles S, Hammond N, Byrne KM, Chapman M, Venkatesh B, Young P, Rajbhandari D, Poole A, Al-Fares A, Reis G, Johnson D, Iqbal M, Hall R, Meade M, Hand L, Duan E, Clarke F, Dionne JC, Tsang JLY, Rochwerg B, Karachi T, Lamontagne F, D'Aragon F, St Arnaud C, Reeve B, Geagea A, Niven D, Vazquez-Grande G, Zarychanski R, Ovakim D, Wood G, Burns KEA, Goffi A, Wilcox ME, Henderson W, Forrest D, Fowler R, Adhikari NKJ, Ball I, Mele T, Binnie A, Trop S, Mehta S, Morgan I, Loubani O, Vanstone M, Fiest K, Charbonney E, Cavayas YA, Archambault P, Rewa OG, Lau V, Kristof AS, Khwaja K, Williamson D, Kanji S, Sy E, Dennis B, Reynolds S, Marquis F, Lellouche F, Rahman A, Hosek P, Barletta JF, Cirrone R, Tutschka M, Xie F, Billot L, Thabane L, and Finfer S
- Subjects
- Humans, Male, Middle Aged, Female, Aged, Gastrointestinal Hemorrhage prevention & control, 2-Pyridinylmethylsulfinylbenzimidazoles therapeutic use, 2-Pyridinylmethylsulfinylbenzimidazoles adverse effects, 2-Pyridinylmethylsulfinylbenzimidazoles administration & dosage, Peptic Ulcer prevention & control, Intensive Care Units, Pneumonia, Ventilator-Associated prevention & control, Double-Blind Method, Stress, Physiological, Adult, Pantoprazole therapeutic use, Pantoprazole adverse effects, Pantoprazole administration & dosage, Respiration, Artificial adverse effects, Proton Pump Inhibitors therapeutic use, Proton Pump Inhibitors adverse effects, Proton Pump Inhibitors administration & dosage, Critical Illness
- Abstract
Background: Whether proton-pump inhibitors are beneficial or harmful for stress ulcer prophylaxis in critically ill patients undergoing invasive ventilation is unclear., Methods: In this international, randomized trial, we assigned critically ill adults who were undergoing invasive ventilation to receive intravenous pantoprazole (at a dose of 40 mg daily) or matching placebo. The primary efficacy outcome was clinically important upper gastrointestinal bleeding in the intensive care unit (ICU) at 90 days, and the primary safety outcome was death from any cause at 90 days. Multiplicity-adjusted secondary outcomes included ventilator-associated pneumonia, Clostridioides difficile infection, and patient-important bleeding., Results: A total of 4821 patients underwent randomization in 68 ICUs. Clinically important upper gastrointestinal bleeding occurred in 25 of 2385 patients (1.0%) receiving pantoprazole and in 84 of 2377 patients (3.5%) receiving placebo (hazard ratio, 0.30; 95% confidence interval [CI], 0.19 to 0.47; P<0.001). At 90 days, death was reported in 696 of 2390 patients (29.1%) in the pantoprazole group and in 734 of 2379 patients (30.9%) in the placebo group (hazard ratio, 0.94; 95% CI, 0.85 to 1.04; P = 0.25). Patient-important bleeding was reduced with pantoprazole; all other secondary outcomes were similar in the two groups., Conclusions: Among patients undergoing invasive ventilation, pantoprazole resulted in a significantly lower risk of clinically important upper gastrointestinal bleeding than placebo, with no significant effect on mortality. (Funded by the Canadian Institutes of Health Research and others; REVISE ClinicalTrials.gov number, NCT03374800.)., (Copyright © 2024 Massachusetts Medical Society.)
- Published
- 2024
- Full Text
- View/download PDF
36. Novel rare genetic variants in idiopathic pulmonary fibrosis.
- Author
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Kristof AS
- Subjects
- Humans, Mutation, Pulmonary Surfactant-Associated Protein A, Idiopathic Pulmonary Fibrosis genetics, Lung Diseases, Interstitial, Lung Neoplasms
- Abstract
Competing Interests: Conflict of interest: A.S. Kristof has nothing to disclose.
- Published
- 2020
- Full Text
- View/download PDF
37. The discovery of novel mechanisms for lymphangioleiomyomatosis pathogenesis through GWAS: a rarity in rare respiratory disorders.
- Author
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Kristof AS and Ortega VE
- Subjects
- COUP Transcription Factor II, Genome-Wide Association Study, Humans, Rare Diseases, Lung Neoplasms, Lymphangioleiomyomatosis, Tuberous Sclerosis
- Abstract
Competing Interests: Conflict of interest: A.S. Kristof has nothing to disclose. Conflict of interest: V.E. Ortega has nothing to disclose.
- Published
- 2019
- Full Text
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38. Human Pluripotent Stem Cell-Derived TSC2 -Haploinsufficient Smooth Muscle Cells Recapitulate Features of Lymphangioleiomyomatosis.
- Author
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Julian LM, Delaney SP, Wang Y, Goldberg AA, Doré C, Yockell-Lelièvre J, Tam RY, Giannikou K, McMurray F, Shoichet MS, Harper ME, Henske EP, Kwiatkowski DJ, Darling TN, Moss J, Kristof AS, and Stanford WL
- Subjects
- Animals, Cell Proliferation physiology, Female, Haploinsufficiency, Humans, Mice, Mice, Inbred NOD, Mice, SCID, Myocytes, Smooth Muscle metabolism, Myocytes, Smooth Muscle pathology, Pluripotent Stem Cells metabolism, Pluripotent Stem Cells pathology, Lymphangioleiomyomatosis genetics, Lymphangioleiomyomatosis pathology, Myocytes, Smooth Muscle physiology, Pluripotent Stem Cells physiology
- Abstract
Lymphangioleiomyomatosis (LAM) is a progressive destructive neoplasm of the lung associated with inactivating mutations in the TSC1 or TSC2 tumor suppressor genes. Cell or animal models that accurately reflect the pathology of LAM have been challenging to develop. Here, we generated a robust human cell model of LAM by reprogramming TSC2 mutation-bearing fibroblasts from a patient with both tuberous sclerosis complex (TSC) and LAM (TSC-LAM) into induced pluripotent stem cells (iPSC), followed by selection of cells that resemble those found in LAM tumors by unbiased in vivo differentiation. We established expandable cell lines under smooth muscle cell (SMC) growth conditions that retained a patient-specific genomic TSC2
+/- mutation and recapitulated the molecular and functional characteristics of pulmonary LAM cells. These include multiple indicators of hyperactive mTORC1 signaling, presence of specific neural crest and SMC markers, expression of VEGF-D and female sex hormone receptors, reduced autophagy, and metabolic reprogramming. Intriguingly, the LAM-like features of these cells suggest that haploinsufficiency at the TSC2 locus contributes to LAM pathology, and demonstrated that iPSC reprogramming and SMC lineage differentiation of somatic patient cells with germline mutations was a viable approach to generate LAM-like cells. The patient-derived SMC lines we have developed thus represent a novel cellular model of LAM that can advance our understanding of disease pathogenesis and develop therapeutic strategies against LAM. Cancer Res; 77(20); 5491-502. ©2017 AACR ., (©2017 American Association for Cancer Research.)- Published
- 2017
- Full Text
- View/download PDF
39. Oncogenic effects of urotensin-II in cells lacking tuberous sclerosis complex-2.
- Author
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Goldberg AA, Joung KB, Mansuri A, Kang Y, Echavarria R, Nikolajev L, Sun Y, Yu JJ, Laporte SA, Schwertani A, and Kristof AS
- Subjects
- Animals, Cell Adhesion, Cell Line, Tumor, Cell Movement, Cell Proliferation, Cell Survival, Chemotaxis, Female, Germ-Line Mutation, Humans, Lung Diseases metabolism, MAP Kinase Signaling System, Mice, Mice, SCID, Neoplasm Invasiveness, Neoplasm Metastasis, Phenotype, Rats, Receptors, G-Protein-Coupled metabolism, Sulfonamides pharmacology, Tuberous Sclerosis Complex 2 Protein, Uterine Neoplasms genetics, Xenograft Model Antitumor Assays, Tumor Suppressor Proteins genetics, Urotensins pharmacology, Uterine Neoplasms metabolism
- Abstract
Lymphangioleiomyomatosis (LAM) is a destructive lung disease that can arise sporadically or in adults suffering from the tumor syndrome tuberous sclerosis complex (TSC). Microscopic tumors ('LAM nodules') in the lung interstitium arise from lymphatic invasion and metastasis. These consist of smooth muscle-like cells (LAM cells) that exhibit markers of neural crest differentiation and loss of the tumor suppressor protein 'tuberous sclerosis complex-2' (TSC2). Consistent with a neural phenotype, expression of the neuropeptide urotensin-II and its receptor was detected in LAM nodules. We hypothesized that loss of TSC2 sensitizes cells to the oncogenic effects of urotensin-II. TSC2-deficient Eker rat uterine leiomyoma ELT3 cells were stably transfected with empty vector or plasmid for the expression of TSC2. Urotensin-II increased cell viability and proliferation in TSC2-deficient cells, but not in TSC2-reconstituted cells. When exposed to urotensin-II, TSC2-deficient cells exhibited greater migration, anchorage-independent cell growth, and matrix invasion. The effects of urotensin-II on TSC2-deficient cells were blocked by the urotensin receptor antagonist SB657510, and accompanied by activation of Erk mitogen-activated protein kinase and focal adhesion kinase. Urotensin-II-induced proliferation and migration were reproduced in TSC2-deficient human angiomyolipoma cells, but not in those stably expressing TSC2. In a mouse xenograft model, SB657510 blocked the growth of established ELT3 tumors, reduced the number of circulating tumor cells, and attenuated the production of VEGF-D, a clinical biomarker of LAM. Urotensin receptor antagonists may be selective therapeutic agents for the treatment of LAM or other neural crest-derived neoplasms featuring loss of TSC2 or increased expression of the urotensin receptor., Competing Interests: None of the authors declare financial interests or relationships that would represent a conflict of interest with respect to the subject matter of this manuscript.
- Published
- 2016
- Full Text
- View/download PDF
40. mTORC2 Balances AKT Activation and eIF2α Serine 51 Phosphorylation to Promote Survival under Stress.
- Author
-
Tenkerian C, Krishnamoorthy J, Mounir Z, Kazimierczak U, Khoutorsky A, Staschke KA, Kristof AS, Wang S, Hatzoglou M, and Koromilas AE
- Subjects
- Animals, Cell Line, Tumor, Endoplasmic Reticulum Stress drug effects, Endoplasmic Reticulum Stress physiology, Fibrosarcoma drug therapy, Fibrosarcoma metabolism, Fibrosarcoma pathology, Humans, Mechanistic Target of Rapamycin Complex 2, Mice, Multiprotein Complexes antagonists & inhibitors, Phosphorylation, Proto-Oncogene Proteins c-akt metabolism, Serine metabolism, Signal Transduction, Sirolimus pharmacology, TOR Serine-Threonine Kinases antagonists & inhibitors, Transfection, Up-Regulation, eIF-2 Kinase metabolism, Eukaryotic Initiation Factor-2 metabolism, Multiprotein Complexes metabolism, TOR Serine-Threonine Kinases metabolism
- Abstract
Unlabelled: The mTOR nucleates two complexes, namely mTOR complex 1 and 2 (mTORC1 and mTORC2), which are implicated in cell growth, survival, metabolism, and cancer. Phosphorylation of the α-subunit of translation initiation factor eIF2 at serine 51 (eIF2αS51P) is a key event of mRNA translation initiation and a master regulator of cell fate during cellular stress. Recent studies have implicated mTOR signaling in the stress response, but its connection to eIF2αS51P has remained unclear. Herein, we report that genetic as well as catalytic inhibition of mTORC2 induces eIF2αS51P. On the other hand, the allosteric inhibitor rapamycin induces eIF2αS51P through pathways that are independent of mTORC1 inactivation. Increased eIF2αS51P by impaired mTORC2 depends on the inactivation of AKT, which primes the activation of the endoplasmic reticulum (ER)-resident kinase PERK/PEK. The biologic function of eIF2αS51P was characterized in tuberous sclerosis complex (TSC)-mutant cells, which are defective in mTORC2 and AKT activity. TSC-mutant cells exhibit increased PERK activity, which is downregulated by the reconstitution of the cells with an activated form of AKT1. Also, TSC-mutant cells are increasingly susceptible to ER stress, which is reversed by AKT1 reconstitution. The susceptibility of TSC-mutant cells to ER stress is further enhanced by the pharmacologic inhibition of PERK or genetic inactivation of eIF2αS51P. Thus, the PERK/eIF2αS51P arm is an important compensatory prosurvival mechanism, which substitutes for the loss of AKT under ER stress., Implications: A novel mechanistic link between mTOR function and protein synthesis is identified in TSC-null tumor cells under stress and reveals potential for the development of antitumor treatments with stress-inducing chemotherapeutics., (©2015 American Association for Cancer Research.)
- Published
- 2015
- Full Text
- View/download PDF
41. Activity of the Ste20-like kinase, SLK, is enhanced by homodimerization.
- Author
-
Delarosa S, Guillemette J, Papillon J, Han YS, Kristof AS, and Cybulsky AV
- Subjects
- Animals, Apoptosis physiology, COS Cells, Cell Line, Chlorocebus aethiops, Epithelial Cells cytology, Epithelial Cells metabolism, Kidney cytology, Models, Animal, Rats, Signal Transduction physiology, Kidney metabolism, Protein Multimerization physiology, Protein Serine-Threonine Kinases metabolism
- Abstract
The expression and activation of the Ste20-like kinase, SLK, is increased during renal development and recovery from ischemic acute renal failure. SLK promotes apoptosis, and during renal injury and repair, transcriptional induction or posttranscriptional control of SLK may, therefore, regulate cell survival. SLK contains protein interaction (coiled-coil) domains, suggesting that posttranslational homodimerization may also modulate SLK activity. We therefore expressed coiled-coil regions in the C-terminal domain of SLK as fusion proteins and demonstrated their homodimerization. By gel-filtration chromatography, endogenous and heterologously expressed SLK were detected in a macromolecular protein complex. To test the role of homodimerization in kinase activation, we constructed a fusion protein consisting of the SLK catalytic domain (amino acids 1-373) and a modified FK506 binding protein, Fv (Fv-SLK 1-373). Addition of AP20187 (an analog of FK506) enhanced the homodimerization of Fv-SLK 1-373. In an in vitro kinase assay, the dimeric Fv-SLK 1-373 displayed greater kinase activity than the monomeric form. In cells expressing Fv-SLK 1-373, homodimerization increased activation-specific phosphorylation of the proapoptotic kinases, c-Jun N-terminal kinase and p38 kinase. Compared with the monomer, dimeric Fv-SLK 1-373 enhanced the activation of a Bax promoter-luciferase reporter. Finally, expression of Fv-SLK 1-373 induced apoptosis, and the effect was increased by homodimerization. Thus the activity, downstream signaling, and functional effects of SLK are enhanced by dimerization of the kinase domain.
- Published
- 2011
- Full Text
- View/download PDF
42. mTOR signaling in lymphangioleiomyomatosis.
- Author
-
Kristof AS
- Subjects
- Animals, Humans, Lymphangioleiomyomatosis drug therapy, Lymphangioleiomyomatosis pathology, TOR Serine-Threonine Kinases, Antineoplastic Agents therapeutic use, Intracellular Signaling Peptides and Proteins metabolism, Lymphangioleiomyomatosis metabolism, Protein Serine-Threonine Kinases metabolism, Signal Transduction
- Abstract
The protein mammalian target of rapamycin (mTOR) plays a central role in cell growth and proliferation. Excessive mTOR activity is a prominent feature of many neoplasms and hamartoma syndromes, including lymphangioleiomyomatosis (LAM), a destructive lung disease that causes progressive respiratory failure in women. Although pharmacological inhibitors of mTOR should directly target the pathogenesis of these disorders, their clinical efficacy has been suboptimal. Recent scientific findings reviewed here have greatly improved our understanding of mTOR signaling mechanisms, provided new insights into the control of cell growth and proliferation, and facilitated the development of new therapeutic approaches in LAM, as well as other neoplastic disorders that exhibit excessive mTOR activity.
- Published
- 2010
- Full Text
- View/download PDF
43. Angiopoietin-1 promotes endothelial cell proliferation and migration through AP-1-dependent autocrine production of interleukin-8.
- Author
-
Abdel-Malak NA, Srikant CB, Kristof AS, Magder SA, Di Battista JA, and Hussain SN
- Subjects
- Animals, Cell Proliferation drug effects, Cells, Cultured, Endothelial Cells enzymology, Enzyme Activation drug effects, Gene Expression Regulation drug effects, Humans, Interleukin-8 genetics, Mice, Mitogen-Activated Protein Kinases metabolism, Models, Biological, NF-kappa B metabolism, Phosphatidylinositol 3-Kinases metabolism, RNA Stability drug effects, RNA, Messenger genetics, RNA, Messenger metabolism, Retroviridae, Transduction, Genetic, Umbilical Veins cytology, Umbilical Veins drug effects, Umbilical Veins enzymology, Angiopoietin-1 pharmacology, Autocrine Communication drug effects, Cell Movement drug effects, Endothelial Cells cytology, Endothelial Cells drug effects, Interleukin-8 biosynthesis, Transcription Factor AP-1 metabolism
- Abstract
Angiopoietin-1 (Ang-1), ligand for the endothelial cell-specific Tie-2 receptors, promotes migration and proliferation of endothelial cells, however, whether these effects are promoted through the release of a secondary mediator remains unclear. In this study, we assessed whether Ang-1 promotes endothelial cell migration and proliferation through the release of interleukin-8 (IL-8). Ang-1 elicited in human umbilical vein endothelial cells (HUVECs) a dose- and time-dependent increase in IL-8 production as a result of induction of mRNA and enhanced mRNA stability of IL-8 transcripts. IL-8 production is also elevated in HUVECs transduced with retroviruses expressing Ang-1. Neutralization of IL-8 in these cells with a specific antibody significantly attenuated proliferation and migration and induced caspase-3 activation. Exposure to Ang-1 triggered a significant increase in DNA binding of activator protein-1 (AP-1) to a relatively short fragment of IL-8 promoter. Upstream from the AP-1 complex, up-regulation of IL-8 transcription by Ang-1 was mediated through the Erk1/2, SAPK/JNK, and PI-3 kinase pathways, which triggered c-Jun phosphorylation on Ser63 and Ser73. These results suggest that promotion of endothelial migration and proliferation by Ang-1 is mediated, in part, through the production of IL-8, which acts in an autocrine fashion to suppress apoptosis and facilitate cell proliferation and migration.
- Published
- 2008
- Full Text
- View/download PDF
44. LY303511 (2-piperazinyl-8-phenyl-4H-1-benzopyran-4-one) acts via phosphatidylinositol 3-kinase-independent pathways to inhibit cell proliferation via mammalian target of rapamycin (mTOR)- and non-mTOR-dependent mechanisms.
- Author
-
Kristof AS, Pacheco-Rodriguez G, Schremmer B, and Moss J
- Subjects
- Animals, Casein Kinase II metabolism, Cell Cycle drug effects, Cell Proliferation drug effects, Cells, Cultured, Humans, Male, Mice, Muscle, Smooth, Vascular cytology, Muscle, Smooth, Vascular drug effects, Muscle, Smooth, Vascular metabolism, Phosphoinositide-3 Kinase Inhibitors, Phosphorylation, Prostatic Neoplasms drug therapy, Protein Serine-Threonine Kinases metabolism, Proto-Oncogene Proteins metabolism, Proto-Oncogene Proteins c-akt, Pulmonary Artery drug effects, Ribosomal Protein S6 Kinases metabolism, TOR Serine-Threonine Kinases, Antineoplastic Agents pharmacology, Chromones pharmacology, Phosphatidylinositol 3-Kinases physiology, Piperazines pharmacology, Protein Kinases physiology
- Abstract
Mammalian target of rapamycin (mTOR), a serine/threonine kinase, regulates cell growth and proliferation in part via the activation of p70 S6 kinase (S6K). Rapamycin is an antineo-plastic agent that, in complex with FKBP12, is a specific inhibitor of mTOR through interaction with its FKBP12-rapamycin binding domain, thereby causing G(1) cell cycle arrest. However, cancer cells often develop resistance to rapamycin, and alternative inhibitors of mTOR are desired. 2-(4-Morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) blocks mTOR kinase activity, but it also inhibits phosphatidylinositol 3-kinase (PI3K), an enzyme that regulates cellular functions other than proliferation. We hypothesized that a close structural analog, 2-piperazinyl-8-phenyl-4H-1-benzopyran-4-one (LY303511) might inhibit mTOR-dependent cell proliferation without unwanted effects on PI3K. In human lung epithelial adenocarcinoma (A549) cells, LY303511, like rapamycin, inhibited mTOR-dependent phosphorylation of S6K, but not PI3K-dependent phosphorylation of Akt. LY303511 blocked proliferation in A549 as well as in primary pulmonary artery smooth muscle cells, without causing apoptosis. In contrast to rapamycin, LY303511 reduced G(2)/M progression as well as G(2)/M-specific cyclins in A549 cells. Consistent with an additional mTOR-independent kinase target, LY303511 inhibited casein kinase 2 activity, a known regulator of G(1) and G(2)/M progression. In addition to its antiproliferative effect in vitro, LY303511 inhibited the growth of human prostate adenocarcinoma tumor implants in athymic mice. Given its inhibition of cell proliferation via mTOR-dependent and independent mechanisms, LY303511 has therapeutic potential with antineoplastic actions that are independent of PI3K inhibition.
- Published
- 2005
- Full Text
- View/download PDF
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