Publications by authors named "Rebecca Chapman"

28 Publications

  • Page 1 of 1

Integrative molecular characterization of pediatric spinal ependymoma: the UK Children's Cancer and Leukaemia Group study.

Neurooncol Adv 2021 Jan-Dec;3(1):vdab043. Epub 2021 Mar 8.

Children's Brain Tumour Research Centre, School of Medicine, University of Nottingham, Nottingham, UK.

Background: Pediatric spinal ependymomas (SP-EPNs) are rare primary central nervous system tumors with heterogeneous clinical course. Considering that ependymomas in children are biologically distinct from their adult counterparts, this study aimed to define the molecular landscape of SP-EPNs in children.

Methods: In this retrospective study, we have collected tumor samples from 27 SP-EPN patients younger than 18 years and carried out the histological review, DNA methylation, and gene expression profiling.

Results: Unsupervised analyses with methylation profiles revealed 2 subgroups where all grade I tumors ( = 11) were in Group 1, but the grade II/III tumors split into 2 groups ( = 7 in Group 1 and = 9 in Group 2). The Heidelberg classifier assigned Group 1 tumors as spinal myxopapillary ependymomas (SP-MPEs), 5 Group 2 tumors as SP-EPNs, and failed to classify 4 Group 2 tumors. Copy numbers derived from DNA methylation arrays revealed subgroup-specific genetic alterations and showed that SP-EPN tumors lack amplification. Gene expression profiling revealed distinct transcriptomic signatures, including overexpression of genes involved in oxidative phosphorylation in SP-MPEs that were validated by Western blot analysis. We discovered widespread decreases in DNA methylation at enhancer regions that are associated with the expression of oncogenic signaling pathways in SP-MPEs. Furthermore, transcription factor motifs for master regulators, including , , and , were significantly overrepresented in probes specific to distal regulatory regions in SP-MPEs.

Conclusion: Our findings show substantial heterogeneity in pediatric SP-EPN and uncover novel enhancers and transcriptional pathways specific to the SP-MPE subgroup, providing a foundation for future therapeutic strategies.
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http://dx.doi.org/10.1093/noajnl/vdab043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8134525PMC
March 2021

Cross-Species Genomics Reveals Oncogenic Dependencies in ZFTA/C11orf95 Fusion-Positive Supratentorial Ependymomas.

Cancer Discov 2021 Sep 20;11(9):2230-2247. Epub 2021 Apr 20.

Department of Neuropathology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.

Molecular groups of supratentorial ependymomas comprise tumors with or -involving fusions and fusion-negative subependymoma. However, occasionally supratentorial ependymomas cannot be readily assigned to any of these groups due to lack of detection of a typical fusion and/or ambiguous DNA methylation-based classification. An unbiased approach with a cohort of unprecedented size revealed distinct methylation clusters composed of tumors with ependymal but also various other histologic features containing alternative translocations that shared as a partner gene. Somatic overexpression of -associated fusion genes in the developing cerebral cortex is capable of inducing tumor formation , and cross-species comparative analyses identified as a key downstream regulator of tumorigenesis in all tumors. Targeting GLI2 with arsenic trioxide caused extended survival of tumor-bearing animals, indicating a potential therapeutic vulnerability in ZFTA fusion-positive tumors. SIGNIFICANCE: fusions are a hallmark feature of supratentorial ependymoma. We find that ZFTA acts as a partner for alternative transcriptional activators in oncogenic fusions of supratentorial tumors with various histologic characteristics. Establishing representative mouse models, we identify potential therapeutic targets shared by fusion-positive tumors, such as GLI2..
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http://dx.doi.org/10.1158/2159-8290.CD-20-0963DOI Listing
September 2021

A retrospective analysis of recurrent pediatric ependymoma reveals extremely poor survival and ineffectiveness of current treatments across central nervous system locations and molecular subgroups.

Pediatr Blood Cancer 2020 09 2;67(9):e28426. Epub 2020 Jul 2.

Children's Brain Tumor Research Centre, School of Medicine, University of Nottingham, Nottingham, UK.

Background: Relapse occurs in 50% of pediatric ependymoma cases and has poor prognosis. Few studies have investigated the clinical progress of relapsed disease, and treatment lacks a standardized approach.

Methods And Materials: We analyzed 302 pediatric ependymoma cases. Tumor, demographic, and treatment variables were investigated for association with relapse risk, time to recurrence, and survival after relapse. DNA methylation profiling was performed for 135/302 cases, and predominant subgroups were EPN_PFA (n = 95) and EPN_RELA (n = 24). Chromosome 1q status was ascertained for 185/302 cases by fluorescent in-situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA), and DNA methylation profiles.

Results: Sixty-two percent of cases relapsed, with a median of two recurrences with no difference between posterior fossa and supratentorial locations (66% vs 55% relapse rate). One hundred seventeen (38%) cases relapsed within two years and five (2%) beyond 10 years. The late relapses were clinically heterogeneous. Tumor grade and treatment affected risk and time to relapse variably across subgroups. After relapse, surgery and irradiation delayed disease progression with a minimal impact on survival across the entire cohort. In the EPN_PFA and EPN_RELA groups, 1q gain was independently associated with relapse risk (subhazard ratio [SHR] 4.307, P = 0.027 and SHR 1.982, P = 0.010, respectively) while EPN_PFA had increased relapse risk compared with EPN_RELA (SHR = 0.394, P = 0.018).

Conclusions: Recurrent pediatric ependymoma is an aggressive disease with poor outcomes, for which current treatments are inadequate. We report that chromosome 1q gain increases relapse risk in common molecular subgroups in children but a deeper understanding of the underlying biology at relapse and novel therapeutic approaches are urgently needed.
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http://dx.doi.org/10.1002/pbc.28426DOI Listing
September 2020

Limit of detection of troponin discharge strategy versus usual care: randomised controlled trial.

Heart 2020 10 5;106(20):1586-1594. Epub 2020 May 5.

Academic Department of Emergency care, The University Hospitals NHS Foundation trust, Bristol, UK.

Introduction: The clinical effectiveness of a 'rule-out' acute coronary syndrome (ACS) strategy for emergency department patients with chest pain, incorporating a single undetectable high-sensitivity cardiac troponin (hs-cTn) taken at presentation, together with a non-ischaemic ECG, remains unknown.

Methods: A randomised controlled trial, across eight hospitals in the UK, aimed to establish the clinical effectiveness of an undetectable hs-cTn and ECG (limit of detection and ECG discharge (LoDED)) discharge strategy. Eligible adult patients presented with chest pain; the treating clinician intended to perform investigations to rule out an ACS; the initial ECG was non-ischaemic; and peak symptoms occurred <6 hours previously. Participants were randomised 1:1 to either the LoDED strategy or the usual rule-out strategy. The primary outcome was discharge from the hospital within 4 hours of arrival, without a major adverse cardiac event (MACE) within 30 days.

Results: Between June 2018 and March 2019, 632 patients were randomised; 3 were later withdrawn. Of 629 patients (age 53.8 (SD 16.1) years, 41% women), 7% had a MACE within 30 days. For the LoDED strategy, 141 of 309 (46%) patients were discharged within 4 hours, without MACE within 30 days, and for usual care, 114 of 311 (37%); pooled adjusted OR 1.58 (95% CI 0.84 to 2.98). No patient with an initial undetectable hs-cTn had a MACE within 30 days.

Conclusion: The LoDED strategy facilitates safe early discharge in >40% of patients with chest pain. Clinical effectiveness is variable when compared with existing rule-out strategies and influenced by wider system factors.

Trial Registration Number: ISRCTN86184521.
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http://dx.doi.org/10.1136/heartjnl-2020-316692DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7525793PMC
October 2020

Limitations of current models for testing the clinical potential of epigenetic inhibitors for treatment of pediatric ependymoma.

Oncotarget 2018 Nov 23;9(92):36530-36541. Epub 2018 Nov 23.

Children's Brain Tumour Research Centre, School of Medicine, University of Nottingham, Nottingham, UK.

Background: Epigenetic modifications have been shown to play an important role in the classification and pathogenesis of the pediatric brain tumor ependymoma, suggesting they are a potential therapeutic target.

Results: Agents targeting epigenetic modifications inhibited the growth and induced the death of ependymoma cells with variable efficiency. However, this was often not at clinically achievable doses. Additionally, DNA methylation profiling revealed a lack of similarity to primary ependymomas suggesting alterations were induced during culture. Toxicity to fetal neural stem cells was also seen at similar drug concentrations.

Conclusions: Agents targeting epigenetic modifications were able to inhibit the growth and induced the death of ependymoma cells grown . However, many agents were only active at high doses, outside clinical ranges, and also resulted in toxicity to normal brain cells. The lack of similarity in DNA methylation profiles between cultured cells and primary ependymomas questions the validity of using cultured cells for pre-clinical analysis of agents targeting epigenetic mechanisms and suggests further investigation using models that are more appropriate should be undertaken before agents are taken forward for clinical testing.

Materials And Methods: The effects of agents targeting epigenetic modifications on the growth and death of a panel of ependymoma cell lines was investigated, as well as toxicity to normal fetal neural stem cells. The ependymoma cell lines were characterized using DNA methylation profiling.
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http://dx.doi.org/10.18632/oncotarget.26370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6284855PMC
November 2018

Molecular heterogeneity and CXorf67 alterations in posterior fossa group A (PFA) ependymomas.

Acta Neuropathol 2018 08 16;136(2):211-226. Epub 2018 Jun 16.

Department of Oncology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.

Of nine ependymoma molecular groups detected by DNA methylation profiling, the posterior fossa type A (PFA) is most prevalent. We used DNA methylation profiling to look for further molecular heterogeneity among 675 PFA ependymomas. Two major subgroups, PFA-1 and PFA-2, and nine minor subtypes were discovered. Transcriptome profiling suggested a distinct histogenesis for PFA-1 and PFA-2, but their clinical parameters were similar. In contrast, PFA subtypes differed with respect to age at diagnosis, gender ratio, outcome, and frequencies of genetic alterations. One subtype, PFA-1c, was enriched for 1q gain and had a relatively poor outcome, while patients with PFA-2c ependymomas showed an overall survival at 5 years of > 90%. Unlike other ependymomas, PFA-2c tumors express high levels of OTX2, a potential biomarker for this ependymoma subtype with a good prognosis. We also discovered recurrent mutations among PFA ependymomas. H3 K27M mutations were present in 4.2%, occurring only in PFA-1 tumors, and missense mutations in an uncharacterized gene, CXorf67, were found in 9.4% of PFA ependymomas, but not in other groups. We detected high levels of wildtype or mutant CXorf67 expression in all PFA subtypes except PFA-1f, which is enriched for H3 K27M mutations. PFA ependymomas are characterized by lack of H3 K27 trimethylation (H3 K27-me3), and we tested the hypothesis that CXorf67 binds to PRC2 and can modulate levels of H3 K27-me3. Immunoprecipitation/mass spectrometry detected EZH2, SUZ12, and EED, core components of the PRC2 complex, bound to CXorf67 in the Daoy cell line, which shows high levels of CXorf67 and no expression of H3 K27-me3. Enforced reduction of CXorf67 in Daoy cells restored H3 K27-me3 levels, while enforced expression of CXorf67 in HEK293T and neural stem cells reduced H3 K27-me3 levels. Our data suggest that heterogeneity among PFA ependymomas could have clinicopathologic utility and that CXorf67 may have a functional role in these tumors.
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http://dx.doi.org/10.1007/s00401-018-1877-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105278PMC
August 2018

Effect of the Prevent Alcohol and Risk-Related Trauma in Youth (P.A.R.T.Y.) Program among senior school students.

Emerg Med Australas 2018 Apr 21;30(2):209-213. Epub 2018 Jan 21.

National Trauma Research Institute, The Alfred, Melbourne, Victoria, Australia.

Objective: The Prevent Alcohol and Risk-Related Trauma in Youth (P.A.R.T.Y.) Program at The Alfred uses vivid clinical reality to build resilience and prevent injury by following a trauma patient's journey through hospital. The present study aims to analyse the effect of P.A.R.T.Y. on safety perceptions of driving after alcohol, seat belt use and risk-taking activities.

Methods: Pre-programme, immediately post-programme and 3-5 months post-programme surveys with questions focused on the programme aims were distributed to all consented participants.

Results: There were 2502 participants during the study period and 1315 (53%) responses were received. The mean age was 16.2 (SD 0.8) years, 724 (56%) were women and 892 (68%) possessed a learner's permit for driving. Pre-programme, 1130 (86%) participants reported 'definitely not' likely to drive after drinking alcohol, that improved to 1231 (94%) immediately post-programme and 1215 (93%) at 3-5 months post-programme (P < 0.01). Designating a safe driver after drinking was reported by 1275 (97%) pre-programme, 1295 (98%) immediately post-programme and 1286 (98.2%) 3-5 months post-programme (P = 0.02). The perception of sustaining 'definite' injury after a motor vehicle crash without a seat belt increased from 780 (60%) pre-programme to 1051 (80%) immediately post-programme and 886 (69%) 3-5 months post-programme (P < 0.01). The possibility of sustaining 'definite' injury after risk-taking activities was reported by 158 (12%) pre-programme, 467 (36%) post-programme and 306 (23%) 3-5 months post-programme (P < 0.01).

Conclusions: The P.A.R.T.Y. Program at The Alfred engaged substantial numbers of youths and achieved significant improvements among key outcome measures. Objectives were sustained at 3-5 months post-programme, but demonstrated decay, highlighting the importance of continual reinforcement.
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http://dx.doi.org/10.1111/1742-6723.12878DOI Listing
April 2018

PI3K pathway activation provides a novel therapeutic target for pediatric ependymoma and is an independent marker of progression-free survival.

Clin Cancer Res 2013 Dec 27;19(23):6450-60. Epub 2013 Sep 27.

Authors' Affiliation: Children's Brain Tumour Research Centre, D Floor Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom.

Purpose: Currently, there are few effective adjuvant therapies for pediatric ependymoma outside confocal radiation, and prognosis remains poor. The phosphoinositide 3-kinase (PI3K) pathway is one of the most commonly activated pathways in cancer. PI3Ks transduce signals from growth factors and cytokines, resulting in the phosphorylation and activation of AKT, which in turn induces changes in cell growth, proliferation, and apoptosis.

Experimental Design: PI3K pathway status was analyzed in ependymoma using gene expression data and immunohistochemical analysis of phosphorylated AKT (P-AKT). The effect of the PI3K pathway on cell proliferation was investigated by immunohistochemical analysis of cyclin D1 and Ki67, plus in vitro functional analysis. To identify a potential mechanism of PI3K pathway activation, PTEN protein expression and the mutation status of PI3K catalytic subunit α-isoform gene (PIK3CA) was investigated.

Results: Genes in the pathway displayed significantly higher expression in supratentorial than in posterior fossa and spinal ependymomas. P-AKT protein expression, indicating pathway activation, was seen in 72% of tumors (n = 169) and P-AKT expression was found to be an independent marker of a poorer progression-free survival. A significant association between PI3K pathway activation and cell proliferation was identified, suggesting that pathway activation was influencing this process. PTEN protein loss was not associated with P-AKT staining and no mutations were identified in PIK3CA.

Conclusions: Our results suggest that the PI3K pathway could act as a biomarker, not only identifying patients with a worse prognosis but also those that could be treated with therapies targeted against the pathway, a strategy potentially effective in a high percentage of ependymoma patients.
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http://dx.doi.org/10.1158/1078-0432.CCR-13-0222DOI Listing
December 2013

Lung toxicity and biodistribution of Cd/Se-ZnS quantum dots with different surface functional groups after pulmonary exposure in rats.

Part Fibre Toxicol 2013 Mar 4;10. Epub 2013 Mar 4.

Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.

Background: The potential use of quantum dots (QD) in biomedical applications, as well as in other systems that take advantage of their unique physiochemical properties, has led to concern regarding their toxicity, potential systemic distribution, and biopersistence. In addition, little is known about workplace exposure to QD in research, manufacturing, or medical settings. The goal of the present study was to assess pulmonary toxicity, clearance, and biodistribution of QD with different functional groups in rats after pulmonary exposure.

Methods: QD were composed of a cadmium-selenide (CdSe) core (~5nm) with a zinc sulfide (ZnS) shell functionalized with carboxyl (QD-COOH) or amine (QD-NH2) terminal groups. Male Sprague-Dawley rats were intratracheally-instilled (IT) with saline, QD-COOH, or QD-NH2 (12.5, 5.0, or 1.25 μg/rat). On days 0, 1, 3, 5, 7, 14, and 28 post-IT, the left lung, lung-associated lymph nodes (LALN), heart, kidneys, spleen, liver, brain, and blood were collected for metal analysis of Cd content by neutron activation to evaluate clearance and biodistribution. One right lobe was ligated and fixed for microscopy and histopathological analysis. The remaining right lobes from rats in each group were subjected to bronchoalveolar lavage (BAL) to retrieve BAL fluid and cells for analysis of injury and inflammation.

Results: Lung injury and inflammation was found to be dose-dependent and peaked at days 7 and 14 post-exposure for both forms of QD, with slight variations in degree of toxicity at early and later time points. Both QD appeared to lose their fluorescent properties and destabilize after 1 week in the lung. Cd persisted up to 28 days for both forms of QD; however, clearance rate was slightly greater for QD-COOH over time. No Cd was detected in the liver, spleen, heart, brain, or blood at any time point. Cd appeared in the LALN and kidneys beginning at 1-2 weeks post-exposure.

Conclusions: QD-COOH and QD-NH2 differed in clearance rate and differed slightly in degree of toxicity at different time points; however, the overall pattern of toxicity and biodistribution was similar between the two particles. Toxicity may be dependent on the dissolution rate and bioavailability of free Cd.
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http://dx.doi.org/10.1186/1743-8977-10-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3599433PMC
March 2013

Transcriptomics analysis of lungs and peripheral blood of crystalline silica-exposed rats.

Inhal Toxicol 2012 Aug;24(9):570-9

Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health (NIOSH), Morgantown, WV 26505, USA.

Minimally invasive approaches to detect/predict target organ toxicity have significant practical applications in occupational toxicology. The potential application of peripheral blood transcriptomics as a practical approach to study the mechanisms of silica-induced pulmonary toxicity was investigated. Rats were exposed by inhalation to crystalline silica (15 mg/m(3), 6 h/day, 5 days) and pulmonary toxicity and global gene expression profiles of lungs and peripheral blood were determined at 32 weeks following termination of exposure. A significant elevation in bronchoalveolar lavage fluid lactate dehydrogenase activity and moderate histological changes in the lungs, including type II pneumocyte hyperplasia and fibrosis, indicated pulmonary toxicity in the rats. Similarly, significant infiltration of neutrophils and elevated monocyte chemotactic protein-1 levels in the lungs showed pulmonary inflammation in the rats. Microarray analysis of global gene expression profiles identified significant differential expression [>1.5-fold change and false discovery rate (FDR) p < 0.01] of 520 and 537 genes, respectively, in the lungs and blood of the exposed rats. Bioinformatics analysis of the differentially expressed genes demonstrated significant similarity in the biological processes, molecular networks, and canonical pathways enriched by silica exposure in the lungs and blood of the rats. Several genes involved in functions relevant to silica-induced pulmonary toxicity such as inflammation, respiratory diseases, cancer, cellular movement, fibrosis, etc, were found significantly differentially expressed in the lungs and blood of the silica-exposed rats. The results of this study suggested the potential application of peripheral blood gene expression profiling as a toxicologically relevant and minimally invasive surrogate approach to study the mechanisms underlying silica-induced pulmonary toxicity.
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http://dx.doi.org/10.3109/08958378.2012.697926DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672741PMC
August 2012

Pulmonary Toxicity, Distribution, and Clearance of Intratracheally Instilled Silicon Nanowires in Rats.

J Nanomater 2012;2012:398302

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA.

Silicon nanowires (Si NWs) are being manufactured for use as sensors and transistors for circuit applications. The goal was to assess pulmonary toxicity and fate of Si NW using an experimental model. Male Sprague-Dawley rats were intratracheally instilled with 10, 25, 50, 100, or 250 g of Si NW (~20-30 nm diameter; ~2-15 m length). Lung damage and the pulmonary distribution and clearance of Si NW were assessed at 1, 3, 7, 28, and 91 days after-treatment. Si NW treatment resulted in dose-dependent increases in lung injury and inflammation that resolved over time. At day 91 after treatment with the highest doses, lung collagen was increased. Approximately 70% of deposited Si NW was cleared by 28 days with most of the Si NW localized exclusively in macrophages. In conclusion, Si NW induced transient lung toxicity which may be associated with an early rapid particle clearance; however, persistence of Si NW over time related to dose or wire length may lead to increased collagen deposition in the lung.
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http://dx.doi.org/10.1155/2012/398302DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4668952PMC
January 2012

Blood gene expression profiling detects silica exposure and toxicity.

Toxicol Sci 2011 Aug 19;122(2):253-64. Epub 2011 May 19.

Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA.

Blood gene expression profiling was investigated as a minimally invasive surrogate approach to detect silica exposure and resulting pulmonary toxicity. Rats were exposed by inhalation to crystalline silica (15 mg/m³, 6 h/day, 5 days), and pulmonary damage and blood gene expression profiles were determined after latency periods (0-16 weeks). Silica exposure resulted in pulmonary toxicity as evidenced by histological and biochemical changes in the lungs. The number of significantly differentially expressed genes in the blood, identified by microarray analysis, correlated with the severity of silica-induced pulmonary toxicity. Functional analysis of the differentially expressed genes identified activation of inflammatory response as the major biological signal. Induction of pulmonary inflammation, as suggested by the blood gene expression data, was supported by significant increases in the number of macrophages and infiltrating neutrophils as well as the activity of pro-inflammatory chemokines observed in the lungs of the silica-exposed rats. A gene expression signature developed using the blood gene expression data predicted the exposure of rats to lower, minimally toxic and nontoxic concentrations of silica. Taken together, our findings suggest the potential application of peripheral blood gene expression profiling as a minimally invasive surrogate approach to detect pulmonary toxicity induced by silica in the rat. However, further research is required to determine the potential application of our findings specifically to monitor human exposure to silica and the resulting pulmonary effects.
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http://dx.doi.org/10.1093/toxsci/kfr125DOI Listing
August 2011

Toxicological evaluation of lung responses after intratracheal exposure to non-dispersed titanium dioxide nanorods.

J Toxicol Environ Health A 2011 ;74(12):790-810

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA.

Fine- and coarse-sized titanium dioxide (TiO₂) particles are considered to be relatively inert when inhaled. The goal of this study was to assess potential lung toxicity associated with well-characterized, non-dispersed rutile TiO₂ nanorods (10 × 40 nm). In vitro bioreactivity of TiO₂ nanorods was determined by electron spin resonance (ESR) to measure free radical production. To assess pulmonary effects in vivo, Sprague-Dawley rats were intratracheally instilled with saline, silica, or TiO₂ nanorods (10 μg, 100 μg, or 1 mg/rat). On d 1, 3, and 6 posttreatment, left lungs were preserved for microscopy and histopathology, and lung lavage was performed on right lungs. Additional rats were treated with saline or TiO₂ nanorods (100 μg or 1 mg/rat) on d 0, intratracheally inoculated with 5 × 10(5) Listeria monocytogenes on d 3, and bacterial clearance was assessed. ESR showed a significant concentration-dependent generation of hydroxyl radicals by TiO₂ nanorods in the presence and absence of macrophages; however, the hydroxyl radical signals from TiO₂ samples were low compared to silica. Rats exposed to 1 mg of TiO₂ nanorods had significantly elevated levels of lung injury, inflammation, and lavage fluid monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-2 on d 1 and 3 that subsided by d 6, unlike the silica response that persisted. Immune cytokine secretion in the lung and bacterial clearance were not affected by preexposure to TiO₂ nanorods. To summarize, non-dispersed TiO₂ nanorods were found to induce radical formation and cellular oxidant production, and to generate transient and reversible pneumotoxic effects, and to not markedly alter pulmonary immune function.
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http://dx.doi.org/10.1080/15287394.2011.567954DOI Listing
July 2011

Arginase activities and global arginine bioavailability in wild-type and ApoE-deficient mice: responses to high fat and high cholesterol diets.

PLoS One 2010 Dec 6;5(12):e15253. Epub 2010 Dec 6.

Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health, Morgantown, West Virginia, United States of America.

Increased catabolism of arginine by arginase is increasingly viewed as an important pathophysiological factor in cardiovascular disease, including atherosclerosis induced by high cholesterol diets. Whereas previous studies have focused primarily on effects of high cholesterol diets on arginase expression and arginine metabolism in specific blood vessels, there is no information regarding the impact of lipid diets on arginase activity or arginine bioavailability at a systemic level. We, therefore, evaluated the effects of high fat (HF) and high fat-high cholesterol (HC) diets on arginase activity in plasma and tissues and on global arginine bioavailability (defined as the ratio of plasma arginine to ornithine + citrulline) in apoE(-/-) and wild-type C57BL/6J mice. HC and HF diets led to reduced global arginine bioavailability in both strains. The HC diet resulted in significantly elevated plasma arginase in both strains, but the HF diet increased plasma arginase only in apoE(-/-) mice. Elevated plasma arginase activity correlated closely with increased alanine aminotransferase levels, indicating that liver damage was primarily responsible for elevated plasma arginase. The HC diet, which promotes atherogenesis, also resulted in increased arginase activity and expression of the type II isozyme of arginase in multiple tissues of apoE(-/-) mice only. These results raise the possibility that systemic changes in arginase activity and global arginine bioavailability may be contributing factors in the initiation and/or progression of cardiovascular disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0015253PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2997799PMC
December 2010

Persistence of deposited metals in the lungs after stainless steel and mild steel welding fume inhalation in rats.

Arch Toxicol 2011 May 6;85(5):487-98. Epub 2010 Oct 6.

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.

Welding generates complex metal fumes that vary in composition. The objectives of this study were to compare the persistence of deposited metals and the inflammatory potential of stainless and mild steel welding fumes, the two most common fumes used in US industry. Sprague-Dawley rats were exposed to 40 mg/m(3) of stainless or mild steel welding fumes for 3 h/day for 3 days. Controls were exposed to filtered air. Generated fume was collected, and particle size and elemental composition were determined. Bronchoalveolar lavage was done on days 0, 8, 21, and 42 after the last exposure to assess lung injury/inflammation and to recover lung phagocytes. Non-lavaged lung samples were analyzed for total and specific metal content as a measure of metal persistence. Both welding fumes were similar in particle morphology and size. Following was the chemical composition of the fumes-stainless steel: 57% Fe, 20% Cr, 14% Mn, and 9% Ni; mild steel: 83% Fe and 15% Mn. There was no effect of the mild steel fume on lung injury/inflammation at any time point compared to air control. Lung injury and inflammation were significantly elevated at 8 and 21 days after exposure to the stainless steel fume compared to control. Stainless steel fume exposure was associated with greater recovery of welding fume-laden macrophages from the lungs at all time points compared with the mild steel fume. A higher concentration of total metal was observed in the lungs of the stainless steel welding fume at all time points compared with the mild steel fume. The specific metals present in the two fumes were cleared from the lungs at different rates. The potentially more toxic metals (e.g., Mn, Cr) present in the stainless steel fume were cleared from the lungs more quickly than Fe, likely increasing their translocation from the respiratory system to other organs.
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http://dx.doi.org/10.1007/s00204-010-0601-1DOI Listing
May 2011

Pulmonary toxicity and extrapulmonary tissue distribution of metals after repeated exposure to different welding fumes.

Inhal Toxicol 2010 Aug;22(10):805-16

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virgina 26505, USA.

Welders are exposed to fumes with different metal profiles. The goals of this study were to compare lung responses in rats after treatment with chemically different welding fumes and to examine the extrapulmonary fate of metals after deposition in the lungs. Rats were treated by intratracheal instillation (0.5 mg/rat, once a week for 7 weeks) with gas metal arc-mild steel (GMAW-MS) or manual metal arc-hardsurfacing (MMAW-HS) welding fumes. Controls were treated with saline. At 1, 4, 35, and 105 days after the last treatment, lung injury and inflammation were measured, and elemental analysis of different organs was determined to assess metal clearance. The MMAW-HS fume was highly water-soluble and chemically more complex with higher levels of soluble Mn and Cr compared to the GMAW-MS fume. Treatments with the GMAW-MS fume had no effect on toxicity when compared with controls. The MMAW-HS fume induced significant lung damage early after treatment that remained elevated until 35 days. Metals associated with each fume sample was cleared at different rates from the lungs. Mn was cleared from the lungs at a faster rate and to a greater extent compared to the other metals over the 105-day recovery period. Mn and Cr in the MMAW-HS fume translocated from the respiratory tract and deposited in other organs. Importantly, increased deposition of Mn, but not other metals, was observed in discrete brain regions, including dopamine-rich areas (e.g., striatum and midbrain).
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http://dx.doi.org/10.3109/08958371003621641DOI Listing
August 2010

Dopaminergic neurotoxicity following pulmonary exposure to manganese-containing welding fumes.

Arch Toxicol 2010 Jul 12;84(7):521-40. Epub 2010 Mar 12.

Health Effects Laboratory Division, National Institute For Occupational Safety and Health, Morgantown, WV 26505, USA.

The potential for development of Parkinson's disease (PD)-like neurological dysfunction following occupational exposure to aerosolized welding fumes (WF) is an area of emerging concern. Welding consumables contain a complex mixture of metals, including iron (Fe) and manganese (Mn), which are known to be neurotoxic. To determine whether WF exposure poses a neurological risk particularly to the dopaminergic system, we treated Sprague-Dawley rats with WF particulates generated from two different welding processes, gas metal arc-mild steel (GMA-MS; low Mn, less water-soluble) and manual metal arc-hard surfacing (MMA-HS; high Mn, more water-soluble) welding. Following repeated intratracheal instillations (0.5 mg/rat, 1/week x 7 weeks) of GMA-MS or MMA-HS, elemental analysis and various molecular indices of neurotoxicity were measured at 1, 4, 35 or 105 days after last exposure. MMA-HS exposure, in particular, led to increased deposition of Mn in striatum and midbrain. Both fumes also caused loss of tyrosine hydroxylase (TH) protein in the striatum (~20%) and midbrain (~30%) by 1 day post-exposure. While the loss of TH following GMA-MS was transient, a sustained loss (34%) was observed in the midbrain 105 days after cessation of MMA-HS exposure. In addition, both fumes caused persistent down-regulation of dopamine D2 receptor (Drd2; 30-40%) and vesicular monoamine transporter 2 (Vmat2; 30-55%) mRNAs in the midbrain. WF exposure also modulated factors associated with synaptic transmission, oxidative stress, neuroinflammation and gliosis. Collectively, our findings demonstrate that repeated exposure to Mn-containing WF can cause persistent molecular alterations in dopaminergic targets. Whether such perturbations will lead to PD-like neuropathological manifestations remains to be elucidated.
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http://dx.doi.org/10.1007/s00204-010-0525-9DOI Listing
July 2010

Application of multinuclear magnetic resonance and gauge-including projector-augmented-wave calculations to the study of solid group 13 chlorides.

Phys Chem Chem Phys 2009 Aug 18;11(32):6987-98. Epub 2009 Jun 18.

Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada.

A series of four anhydrous group 13 chloride salts has been studied by (35/37)Cl solid-state NMR spectroscopy and complementary quantum chemical calculations. Due to the large (35/37)Cl quadrupolar interactions in these salts, a high magnetic field (21.1 T) and the variable-offset QCPMG technique was used to obtain full chlorine central transition (m = -1/2 <--> 1/2) NMR spectra. Analyses of the NMR spectra of the synthetically important Lewis acid trichlorides of aluminium, gallium, and indium, as well as gallium dichloride, allowed for characterisation of the chlorine electric field gradient (EFG) tensors and, in three cases, the chlorine chemical shift (CS) tensors. The quadrupolar interaction was found to dominate the central transition chlorine NMR spectrum in all cases, with chlorine-35 quadrupolar coupling constants (C(Q)) ranging in magnitude from 22.45 +/- 2.00 to 40.44 +/- 2.00 MHz, and the spectral breadths ranging from approximately 1.0 to 2.5 MHz. For the trichloride salt of gallium, it was confirmed that the terminal chlorine sites exhibit larger chlorine C(Q) values than do the bridging chlorines. The isotropic chemical shifts range from 150 +/- 100 to 375 +/- 100 ppm while the largest CS tensor span is 500 +/- 200 ppm, for InCl(3). The chlorine chemical shift was found to increase with increasing M-Cl distance in all cases. Quantum chemical calculations of the EFG and magnetic shielding tensors, performed using the gauge-including projector-augmented-wave (GIPAW) method as implemented in the CASTEP program, were found to be in excellent agreement with the experimentally determined values, reproducing C(Q)((35)Cl) to within 7% in all cases. The agreement between experiment and theory substantiates the accuracy of the NMR parameters. Solid-state NMR spectra of the cation species (aluminium-27, gallium-69/71 and indium-113/115) were also collected, and the EFG and CS parameters were determined in some cases. The study demonstrates the utility of multinuclear solid-state magnetic resonance studies of half-integer spin quadrupolar nuclei in ionic systems when the central transition is broadened greatly by the quadrupolar interaction, and in particular contributes to our understanding of the relationship between solid-state structure and chlorine NMR interaction tensors.
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http://dx.doi.org/10.1039/b906627fDOI Listing
August 2009

Network-based activity induced by 4-aminopyridine in rat dorsal horn in vitro is mediated by both chemical and electrical synapses.

J Physiol 2009 Jun 9;587(Pt 11):2499-510. Epub 2009 Apr 9.

Institute for Membrane and Systems Biology, University of Leeds, Leeds, UK.

This study investigated the role of electrical and chemical synapses in sustaining 4-aminopyridine (4-AP)-evoked network activity recorded extracellularly from substantia gelatinosa (SG) of young rat spinal cord in vitro. Superfusion of 4-AP (50 microM) induced two types of activity, the first was observed as large amplitude field population spiking activity and the second manifested within the inter-spike interval as low amplitude rhythmic oscillations in the 4-12 Hz frequency range (mean peak of 8.0 +/- 0.1 Hz). The AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM) abolished field population spiking and disrupted 4-12 Hz rhythmic oscillatory activity whereas the NMDA receptor antagonist D-AP5 (50 microM) had no significant effect on either activity component. The glycine receptor antagonist strychnine (4 microM) and the GABA(A) receptor antagonist bicuculline (10 microM) diminished and abolished, respectively, field population spiking and both antagonists reduced the power of 4-12 Hz oscillations. The non-specific gap junction blockers carbenoxolone (100 microM) and octanol (1 mM) attenuated both types of 4-AP-induced activity. By comparison, the neuronal-specific gap junction uncouplers quinine (250 microM) and mefloquine (500 nM) both disrupted 4-12 Hz oscillations but only quinine reduced the frequency of field population spiking. These data demonstrate the existence of 4-AP-sensitive neuronal networks within SG that can generate rhythmic activity, are differentially modulated by excitatory and inhibitory ionotropic neurotransmission and are at least partly reliant on neuronal and/or glial-mediated electrical connectivity. The physiological significance of these putative intrinsic SG networks and the implications in the context of processing of nociceptive inputs are discussed.
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http://dx.doi.org/10.1113/jphysiol.2009.171777DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714016PMC
June 2009

Diabetic cardiomyopathy-associated dysfunction in spatially distinct mitochondrial subpopulations.

Am J Physiol Heart Circ Physiol 2009 Feb 5;296(2):H359-69. Epub 2008 Dec 5.

Division of Exercise Physiology, Center for Interdisciplinary Research in Cardiovascular Sciences, West Virginia University School of Medicine, Morgantown, WV, USA.

Diabetic cardiomyopathy is the leading cause of heart failure among diabetic patients, and mitochondrial dysfunction has been implicated as an underlying cause in the pathogenesis. Cardiac mitochondria consist of two spatially, functionally, and morphologically distinct subpopulations, termed subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM). SSM are situated beneath the plasma membrane, whereas IFM are embedded between myofibrils. The goal of this study was to determine whether spatially distinct cardiac mitochondrial subpopulations respond differently to a diabetic phenotype. Swiss-Webster mice were subjected to intraperitoneal injections of streptozotocin or citrate saline vehicle. Five weeks after injections, diabetic hearts displayed decreased rates of contraction, relaxation, and left ventricular developed pressures (P < 0.05 for all three). Both mitochondrial size (forward scatter, P < 0.01) and complexity (side scatter, P < 0.01) were decreased in diabetic IFM but not diabetic SSM. Electron transport chain complex II respiration was decreased in diabetic SSM (P < 0.05) and diabetic IFM (P < 0.01), with the decrease being greater in IFM. Furthermore, IFM complex I respiration and complex III activity were decreased with diabetes (P < 0.01) but were unchanged in SSM. Superoxide production was increased only in diabetic IFM (P < 0.01). Oxidative damage to proteins and lipids, indexed through nitrotyrosine residues and lipid peroxidation, were higher in diabetic IFM (P < 0.05 and P < 0.01, respectively). The mitochondria-specific phospholipid cardiolipin was decreased in diabetic IFM (P < 0.01) but not SSM. These results indicate that diabetes mellitus imposes a greater stress on the IFM subpopulation, which is associated, in part, with increased superoxide generation and oxidative damage, resulting in morphological and functional abnormalities that may contribute to the pathogenesis of diabetic cardiomyopathy.
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http://dx.doi.org/10.1152/ajpheart.00467.2008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2643887PMC
February 2009

Group I mGluRs increase locomotor network excitability in Xenopus tadpoles via presynaptic inhibition of glycinergic neurotransmission.

Eur J Neurosci 2008 Sep 8;28(5):903-13. Epub 2008 Aug 8.

School of Biology, Bute Medical Buildings, University of St Andrews, St Andrews, Fife, UK.

The group I metabotropic glutamate receptor agonist (S)-3,5-dihyroxyphenylglycine (DHPG) increases the frequency of rhythmic swimming activity in Xenopus tadpoles. This study explores the possibility that group I receptor modulation occurs in part via depression of inhibitory synaptic transmission. Applications of the glycine receptor antagonist strychnine occluded the effects of DHPG, providing preliminary evidence that group I receptors affect motor network output by reducing glycinergic transmission. This evidence was supported further by intracellular and whole-cell patch-clamp recordings from presumed motorneurons. DHPG applications produced two prominent effects: (i) during swimming activity, glycinergic mid-cycle IPSPs were reduced in amplitude; and (ii) during quiescent periods, the frequency of spontaneous miniature IPSPs was also reduced. No change in membrane potential or input resistance following group I receptor activation was detected. The reduction in fast synaptic inhibition provides a plausible explanation for the increased excitability of the locomotor network, although other contributory mechanisms activated in parallel by group I receptors cannot be discounted. Aspects of this work have been published previously in abstract form [R. J. Chapman & K. T. Sillar (2003) SFN Abstracts 277.8].
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http://dx.doi.org/10.1111/j.1460-9568.2008.06391.xDOI Listing
September 2008

A high-field solid-state 35/37Cl NMR and quantum chemical investigation of the chlorine quadrupolar and chemical shift tensors in amino acid hydrochlorides.

Phys Chem Chem Phys 2007 Dec 8;9(47):6219-30. Epub 2007 Nov 8.

Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, CanadaK1N6N5.

A series of six L-amino acid hydrochloride salts has been studied by 35/37Cl solid-state NMR spectroscopy (at 11.75 and 21.1 T) and complementary quantum chemical calculations. Analyses of NMR spectra acquired under static and magic-angle-spinning conditions for the six hydrochloride salts, those of aspartic acid, alanine, cysteine, histidine, methionine and threonine, allowed the extraction of information regarding the chlorine electric field gradient (EFG) and chemical shift tensors, including their relative orientation. Both tensors are found to be highly dependent on the local environment, with chlorine-35 quadrupolar coupling constants (CQ) ranging from -7.1 to 4.41 MHz and chemical shift tensor spans ranging from 60 to 100 ppm; the value of CQ for aspartic acid hydrochloride is the largest in magnitude observed to date for an organic hydrochloride salt. Quantum chemical calculations performed on cluster models of the chloride ion environment demonstrated agreement between experiment and theory, reproducing CQ to within 18%. In addition, the accuracy of the calculated values of the NMR parameters as a function of the quality of the input structure was explored. Selected X-ray structures were determined (L-Asp HCl; L-Thr HCl) or re-determined (L-Cys HCl.H2O) to demonstrate the benefits of having accurate crystal structures for calculations. The self-consistent charge field perturbation model was also employed and was found to improve the accuracy of calculated quadrupolar coupling constants, demonstrating the impact of the neighbouring ions on the EFG tensor of the central chloride ion. Taken together, the present work contributes to an improved understanding of the factors influencing 35/37Cl NMR interaction tensors in organic hydrochlorides.
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http://dx.doi.org/10.1039/b712688cDOI Listing
December 2007

K-39 quadrupolar and chemical shift tensors for organic potassium complexes and diatomic molecules.

J Phys Chem A 2007 Dec 17;111(50):12859-63. Epub 2007 Nov 17.

Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada.

Solid-state potassium-39 NMR spectra of two potassium complexes of crown-ether-based organic ligands (1.KI and 2) have been acquired at 11.75 and 21.1 T and interpreted to provide information on the 39K quadrupolar and chemical shift tensors. The analyses reveal a large potassium chemical shift tensor span of 75+/-20 ppm for 1.KI. This appears to be the first such measurement for potassium in an organic complex, thereby suggesting the utility of potassium chemical shift tensors for characterizing organic and biomolecular K+ binding environments. Compound 2 exhibits a cation-pi interaction between K+ and a phenyl group, and therefore, the 39K NMR tensors obtained for this compound must be partly representative of this interaction. Analyses of potassium-39 spin-rotation data for gaseous 39K19F and 39K35Cl available from molecular beam experiments performed by Cederberg and co-workers reveal the largest potassium CS tensor spans known to date, 84.39 and 141 ppm, respectively. Collectively, the results obtained highlight the potential of ultrahigh-field potassium-39 solid-state NMR spectroscopy and, in particular, the wide range of the anisotropy of the potassium CS tensor when organic and diatomic systems are considered.
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http://dx.doi.org/10.1021/jp0774239DOI Listing
December 2007

Modulation of a spinal locomotor network by metabotropic glutamate receptors.

Eur J Neurosci 2007 Oct 25;26(8):2257-68. Epub 2007 Sep 25.

School of Biology, Bute Medical Buildings, University of St. Andrews, St. Andrews, Fife KY16 9TS, UK.

We have explored the potential involvement of the three main classes of metabotropic glutamate receptor in the modulation of a spinal locomotor network using tadpoles of the anuran amphibian Xenopus laevis. Selective activation of group I receptors in Xenopus embryos and young larvae using the general group I agonist DHPG [(S)-3,5-dihyroxyphenylglycine] significantly increased the frequency of swimming and the number of spontaneously occurring swimming episodes, as monitored by extracellular recordings from ventral roots. Group I receptor activation was without significant effect on the duration or amplitude of motor bursts, the duration of swimming episodes, or the head-to-tail delay in the propagation of swimming activity. Activation of either group II or group III receptors, however, following bath applications of the specific agonists APDC [(2R,4R)-aminopyrrolidine-2,4-dicarboxylic acid] and L-AP4 (L-2-amino-4-phosphonobutanoate), respectively, produced a net inhibitory effect on many of the parameters of fictive swimming at both developmental stages, including a reduction in swimming frequency and episode duration, along with a significant reduction in motor burst amplitude and duration in larval animals only. Applications of selective antagonists provide evidence for activation of all three groups during swimming. The group II and III antagonists EGLU (1-ethyl-2-benzimidazolinone) and MAP4 [(S)-2-amino-2-methyl-4-phosphonobutanoate], respectively, increased, while group I antagonists, CPCCOEt and MPEP, decreased swim frequency. Our findings thus provide evidence for the presence and endogenous activation of three classes of metabotropic glutamate receptor which may function as an intrinsic modulatory control system during fictive swimming in Xenopus tadpoles.
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http://dx.doi.org/10.1111/j.1460-9568.2007.05817.xDOI Listing
October 2007

Mechanisms of skeletal muscle injury and repair revealed by gene expression studies in mouse models.

J Physiol 2007 Jul 3;582(Pt 2):825-41. Epub 2007 May 3.

Division of Physical Therapy, Georgia State University, Atlanta, GA 30303, USA.

Common acute injuries to skeletal muscle can lead to significant pain and disability. The current therapeutic approaches for treating muscle injuries are dependent on the clinical severity but not on the type of injury. In the present studies, the pathophysiology and molecular pathways associated with two different types of skeletal muscle injury, one induced by direct destruction of muscle tissue (i.e. FI) and the other induced by a contractile overload (more specifically high-force eccentric contractions, i.e. CI) were compared side by side. Histopathological evaluation and measurements of muscle strength were accompanied by analyses of expression for 12 488 known genes at four time points ranging from 6 h to 7 days after injury. Real-time RT-PCR was used to confirm some of the injury type differences in the temporal profiles of gene expression. Our data revealed several pools of genes, including early induction of transcription, myogenic and stress-responsive factors, common for both types of injury as well as pools of genes expressed specifically with one of the injury types. Only CI activated a set of genes associated with the repair of impaired proteins and structures including genes related to apoptosis, whereas FI uniquely activated gene sets involved in extensive inflammatory responses, tissue remodelling, angiogenesis and myofibre/extracellular matrix synthesis. In conclusion, knowledge of the sets of genes associated specifically with the nature of the injury may have application for development of new strategies for acceleration of the recovery process in injured skeletal muscle.
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http://dx.doi.org/10.1113/jphysiol.2007.132373DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075314PMC
July 2007

Cardiovascular effects of pulmonary exposure to single-wall carbon nanotubes.

Environ Health Perspect 2007 Mar 4;115(3):377-82. Epub 2006 Dec 4.

Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.

Background: Engineered nanosized materials, such as single-wall carbon nanotubes (SWCNT), are emerging as technologically important in different industries.

Objective: The unique physical characteristics and the pulmonary toxicity of SWCNTs raised concerns that respiratory exposure to these materials may be associated with cardiovascular adverse effects.

Methods: In these studies we evaluated aortic mitochondrial alterations by oxidative stress assays, including quantitative polymerase chain reaction of mitochondrial (mt) DNA and plaque formation by morphometric analysis in mice exposed to SWCNTs.

Results: A single intrapharyngeal instillation of SWCNTs induced activation of heme oxygenase-1 (HO-1), a marker of oxidative insults, in lung, aorta, and heart tissue in HO-1 reporter transgenic mice. Furthermore, we found that C57BL/6 mice, exposed to SWCNT (10 and 40 mug/mouse), developed aortic mtDNA damage at 7, 28, and 60 days after exposure. mtDNA damage was accompanied by changes in aortic mitochondrial glutathione and protein carbonyl levels. Because these modifications have been related to cardiovascular diseases, we evaluated whether repeated exposure to SWCNTs (20 mug/mouse once every other week for 8 weeks) stimulates the progression of atherosclerosis in ApoE(-/-) transgenic mice. Although SWCNT exposure did not modify the lipid profiles of these mice, it resulted in accelerated plaque formation in ApoE(-/-) mice fed an atherogenic diet. Plaque areas in the aortas, measured by the en face method, and in the brachiocephalic arteries, measured histopathologically, were significantly increased in the SWCNT-treated mice. This response was accompanied by increased mtDNA damage but not inflammation.

Conclusions: Taken together, the findings are of sufficient significance to warrant further studies to evaluate the systemic effects of SWCNT under workplace or environmental exposure paradigms.
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http://dx.doi.org/10.1289/ehp.9688DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1849906PMC
March 2007

Macrophages and skeletal muscle regeneration: a clodronate-containing liposome depletion study.

Am J Physiol Regul Integr Comp Physiol 2006 Jun 19;290(6):R1488-95. Epub 2006 Jan 19.

Health Effects Laboratory Div., National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.

The study evaluates the influence of monocytes/macrophages in the mechanisms of skeletal muscle injury using a mouse model and selective depletion of peripheral monocyte with systemic injections of liposomal clodronate (dichloromethylene bisphosphonate). This pharmacological treatment has been demonstrated to induce specific apoptotic death in monocytes and phagocytic macrophages. In the current studies, the liposomal clodronate injections resulted in a marked attenuation of the peak inflammatory response in the freeze-injured muscle in the first three days after injury. The effect was accompanied by a transient reduction (at day 1 or 3 postinjury) of the expression of several genes coding for inflammatory, as well as growth-related mediators, including TNF, monocyte chemoattractant protein (MCP)-1, thioredoxin, high-mobility group AT-hook 1, insulin-like growth factor-binding protein (IGFBP), and IGF-1. In contrast, the expression of major myogenic factors (i.e., MyoD and myogenin) directly involved in the activation/proliferation and differentiation of muscle precursor cells was not altered by the clodronate liposome treatment. The repair process in the injured muscle of clodronate liposome-treated mice was characterized by prolonged clearance of necrotic myofibers and a tendency for increased muscle fat accumulation at day 9 and 14 postinjury, respectively. In conclusion, a significant reduction of the initial monocyte/macrophage influx into the injured muscle is associated with not improved, but moderately impaired, repair processes after skeletal muscle injury.
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http://dx.doi.org/10.1152/ajpregu.00465.2005DOI Listing
June 2006
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