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122
result(s) for
"Sheppard, Robert J."
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Inhibition of PAD4 activity is sufficient to disrupt mouse and human NET formation
2015
Inhibitors of the PAD4 enzyme that bind the inactive enzyme link this protein deiminase and the resultant arginine-to-citrulline modification to formation of neutrophil extracellular traps, highly decondensed chromatin structures with both host-defense and pathological roles.
PAD4 has been strongly implicated in the pathogenesis of autoimmune, cardiovascular and oncological diseases through clinical genetics and gene disruption in mice. New selective PAD4 inhibitors binding a calcium-deficient form of the PAD4 enzyme have validated the critical enzymatic role of human and mouse PAD4 in both histone citrullination and neutrophil extracellular trap formation for, to our knowledge, the first time. The therapeutic potential of PAD4 inhibitors can now be explored.
Journal Article
A selective jumonji H3K27 demethylase inhibitor modulates the proinflammatory macrophage response
by
Ramirez-Molina, Cesar
,
Wilson, David M.
,
Cheng, Zhongjun
in
631/535
,
631/92/173
,
Amino Acid Sequence
2012
A structure-guided small-molecule and chemoproteomics approach uncovers a catalytic site inhibitor selective for the jumonji subfamily of H3K27me3 demethylases; the inhibitor decreases lipopolysaccharide-induced proinflammatory cytokine production by human primary macrophages.
JMJ demethylase inhibitors and inflammation
Jumonji (JMJ) family histone demethylases have become recognized as key regulators of transcription, although the importance of their enzymatic activity - as opposed to their structural role - has been unclear. JMJD3 demethylases are specific for histone H3 trimethylated at Lys27 (H3K27me3) and are involved in the inflammatory response, as well as other physiological functions. Here, a structure-guided small-molecule and chemoproteomics approach is used to discover a catalytic-site inhibitor selective for the H3K27me3-specific JMJ subfamily. The inhibitor reduces lipopolysaccharide-induced pro-inflammatory cytokine production in human primary macrophages. This study demonstrates the importance of JMJ demethylase activity and suggests that small-molecule inhibitors of JMJ enzymes could have therapeutic applications.
The jumonji (JMJ) family of histone demethylases are Fe
2+
- and α-ketoglutarate-dependent oxygenases that are essential components of regulatory transcriptional chromatin complexes
1
,
2
,
3
,
4
. These enzymes demethylate lysine residues in histones in a methylation-state and sequence-specific context
5
. Considerable effort has been devoted to gaining a mechanistic understanding of the roles of histone lysine demethylases in eukaryotic transcription, genome integrity and epigenetic inheritance
2
,
4
,
6
, as well as in development, physiology and disease
3
,
7
. However, because of the absence of any selective inhibitors, the relevance of the demethylase activity of JMJ enzymes in regulating cellular responses remains poorly understood. Here we present a structure-guided small-molecule and chemoproteomics approach to elucidating the functional role of the H3K27me3-specific demethylase subfamily (KDM6 subfamily members JMJD3 and UTX)
8
. The liganded structures of human and mouse JMJD3 provide novel insight into the specificity determinants for cofactor, substrate and inhibitor recognition by the KDM6 subfamily of demethylases. We exploited these structural features to generate the first small-molecule catalytic site inhibitor that is selective for the H3K27me3-specific JMJ subfamily. We demonstrate that this inhibitor binds in a novel manner and reduces lipopolysaccharide-induced proinflammatory cytokine production by human primary macrophages, a process that depends on both JMJD3 and UTX. Our results resolve the ambiguity associated with the catalytic function of H3K27-specific JMJs in regulating disease-relevant inflammatory responses and provide encouragement for designing small-molecule inhibitors to allow selective pharmacological intervention across the JMJ family.
Journal Article
Probe dependency in the determination of ligand binding kinetics at a prototypical G protein-coupled receptor
2019
Drug-target binding kinetics are suggested to be important parameters for the prediction of
in vivo
drug-efficacy. For G protein-coupled receptors (GPCRs), the binding kinetics of ligands are typically determined using association binding experiments in competition with radiolabelled probes, followed by analysis with the widely used competitive binding kinetics theory developed by Motulsky and Mahan. Despite this, the influence of the radioligand binding kinetics on the kinetic parameters derived for the ligands tested is often overlooked. To address this, binding rate constants for a series of histamine H
1
receptor (H
1
R) antagonists were determined using radioligands with either slow (low k
off
) or fast (high k
off
) dissociation characteristics. A correlation was observed between the probe-specific datasets for the kinetic binding affinities, association rate constants and dissociation rate constants. However, the magnitude and accuracy of the binding rate constant-values was highly dependent on the used radioligand probe. Further analysis using recently developed fluorescent binding methods corroborates the finding that the Motulsky-Mahan methodology is limited by the employed assay conditions. The presented data suggest that kinetic parameters of GPCR ligands depend largely on the characteristics of the probe used and results should therefore be viewed within the experimental context and limitations of the applied methodology.
Journal Article
Kruidenier et al. reply
by
Ramirez-Molina, Cesar
,
Wilson, David M.
,
Cheng, Zhongjun
in
631/154/556
,
Animals
,
brief-communications-arising
2014
Replying to
B. Heinemann
et al. Nature514, 10.1038/nature13688 (2014)
We welcome the accompanying Comment
1
by
Heinemann et al.
, in which the authors use an extensive panel of sensitive KDM assays to independently confirm our results
2
that GSK-J1 is a potent KDM6 inhibitor. Additionally, Heinemann
et al.
1
demonstrate that GSK-J1 has some, albeit weaker, activity towards KDM5B and KDM5C, for which we only had preliminary data available at the time of our original publication. As our jumonji assay portfolio expands, we have continued to update the GSK-J1 activity profile on the SGC website (
http://www.thesgc.org/chemical-probes/GSKJ1
); this includes KDM5 inhibition activity by GSK-J1 similar to that reported by Heinemann. In conclusion, GSK-J1 remains the most selective KDM inhibitor yet disclosed and thus a valuable chemical tool.
Journal Article
Inhibition of demethylases by GSK-J1/J4/Kruidenier et al. reply
by
Lees, Michael J
,
Nielsen, Jesper Morten
,
Mander, Palwinder K
in
Amino acids
,
Biomedical research
,
Epigenetics
2014
Here we show that the inhibitor is not specific for the H3K27me3/me2-demethylase subfamily in vitro and in tissue culture assays. Thus, the inhibitor cannot be used alone for drawing conclusions regarding the specific role of H3K27me3/me2-demethylase activity in biological processes or disease.
Journal Article
The impact of a stress management training program on symptoms of fibromyalgia
Fibromyalgia is a noninflammatory rheumatic disorder characterized by musculoskeletal pain, nonrestorative sleep, and mood disturbance. Emotional stress is frequently reported as a factor that exacerbates symptoms. This study was designed to assess the impact of stress management training on perceived stress and fibromyalgia symptoms. Four female subjects with fibromyalgia participated on an individual basis in a 10 week stress management training program, which was administered in the fixed sequence of training in self-monitoring, relaxation, cognitive behavioral skills, and assertion. The effects of the training on self-report measures of perceived stress, pain, functional disability, sleep disruption, daytime fatigue, and depression were assessed using a multiple baseline across subjects design. It was hypothesized that stress management training would produce clinically significant improvements across these variables. Two subjects displayed notable decreases on measures of stress, pain, and depression. The other two subjects displayed no sustained decreases on these measures. None of the four subjects displayed sustained reductions on measures of physical disability, sleep disruption, or fatigue. These findings offer qualified support for the efficacy of this stress management training program in decreasing stress, pain, and depression for some fibromyalgia patients. The question remains as to whether specifically targeting stress was the key to the positive changes observed in the two subjects who responded to treatment, because one of these subjects displayed decreases in depression before her stress level decreased. The wide range of techniques used in the training program may have directly impacted pain and depression, rather than pain and depression decreasing as a secondary response to diminished stress. Subject characteristics were examined in an attempt to explain the differences in response patterns between the responders and nonresponders. Implications for treatment strategies were discussed in light of the qualified support of the hypothesis.
Dissertation
It's time to change to 42 CFR Part 84...and it's easier than you think
1997
July 10, 1998, is the deadline set by NIOSH when safety equipment manufacturers will no longer be able to make and sell non-powered, air-purifying particulate-filter respirators approved under the old standard, 30 CFR Part 11. Instead, manufacturers must comply with a new standard, 42 CFR Part 84, adopted by NIOSH to accommodate advances in respirator testing and filter manufacturing technology. Those responsible for their companies' safety programs are feeling the pressure. An explanation of the new standard is presented and ways companies can comply are discussed.
Magazine Article
An Extensive Salmonella Typhimurium Outbreak of Probable Waterborne Origin
1979
A massive outbreak of salmonella gastroenteritis triggered an exploration of probable sources and modes of transmission and the institution of preventive measures to avert future outbreaks.
Journal Article
The Fungal Exopolysaccharide Galactosaminogalactan Mediates Virulence by Enhancing Resistance to Neutrophil Extracellular Traps
by
Lee, Mark J.
,
Kaminskyj, Susan G. W.
,
Sheppard, Donald C.
in
Animals
,
Aspergillosis
,
Aspergillus
2015
Of the over 250 Aspergillus species, Aspergillus fumigatus accounts for up to 80% of invasive human infections. A. fumigatus produces galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetyl-galactosamine (GalNAc) that mediates adherence and is required for full virulence. Less pathogenic Aspergillus species were found to produce GAG with a lower GalNAc content than A. fumigatus and expressed minimal amounts of cell wall-bound GAG. Increasing the GalNAc content of GAG of the minimally pathogenic A. nidulans, either through overexpression of the A. nidulans epimerase UgeB or by heterologous expression of the A. fumigatus epimerase Uge3 increased the amount of cell wall bound GAG, augmented adherence in vitro and enhanced virulence in corticosteroid-treated mice to levels similar to A. fumigatus. The enhanced virulence of the overexpression strain of A. nidulans was associated with increased resistance to NADPH oxidase-dependent neutrophil extracellular traps (NETs) in vitro, and was not observed in neutropenic mice or mice deficient in NADPH-oxidase that are unable to form NETs. Collectively, these data suggest that cell wall-bound GAG enhances virulence through mediating resistance to NETs.
Journal Article
Spinal Anesthesia or General Anesthesia for Hip Surgery in Older Adults
2021
A randomized trial evaluating spinal as compared with general anesthesia for hip-fracture surgery in adults 50 years of age or older did not show superiority of spinal anesthesia with respect to a composite of death or an inability to walk unassisted at 60 days. Postoperative delirium occurred in similar percentages of patients in the two groups.
Journal Article