Release of active peptidyl arginine deiminases by neutrophils can explain production of extracellular citrullinated autoantigens in rheumatoid arthritis synovial fluid

Objective In the majority of patients with rheumatoid arthritis (RA), antibodies specifically recognize citrullinated autoantigens that are generated by peptidylarginine deiminases (PADs). Neutrophils express high levels of PAD and accumulate in the synovial fluid (SF) of RA patients during disease flares. This study was undertaken to test the hypothesis that neutrophil cell death, induced by either NETosis (extrusion of genomic DNA-protein complexes known as neutrophil extracellular traps [NETs]) or necrosis, can contribute to production of autoantigens in the inflamed joint. Methods Extracellular DNA was quantified in the SF of patients with RA, patients with osteoarthritis (OA), and patients with psoriatic arthritis (PsA). Release of PAD from neutrophils was investigated by Western blotting, mass spectrometry, immunofluorescence staining, and PAD activity assays. PAD2 and PAD4 protein expression, as well as PAD enzymatic activity, were assessed in the SF of patients with RA and those with OA. Results Extracellular DNA was detected at significantly higher levels in RA SF than in OA SF (P < 0.001) or PsA SF (P < 0.05), and its expression levels correlated with neutrophil concentrations and PAD activity in RA SF. Necrotic neutrophils released less soluble extracellular DNA compared to NETotic cells in vitro (P < 0.05). Higher PAD activity was detected in RA SF than in OA SF (P < 0.05). The citrullinated proteins PAD2 and PAD4 were found attached to NETs and also freely diffused in the supernatant. PAD enzymatic activity was detected in supernatants of neutrophils undergoing either NETosis or necrosis. Conclusion Release of active PAD isoforms into the SF by neutrophil cell death is a plausible explanation for the generation of extracellular autoantigens in RA

A Web Service Framework for Interactive Analysis of Metabolomics Data

Analyzing mass spectrometry-based metabolomics data presents a major challenge to metabolism researchers, as it requires downloading and processing large data volumes through complex "pipelines", even in cases where only a single metabolite or peak is of interest. This presents a significant hurdle for data sharing, reanalysis, or meta-analysis of existing data sets, whether locally stored or available from public repositories. Here we introduce mzAccess, a software system that provides interactive, online access to primary mass spectrometry data in real-time via a Web service protocol, circumventing the need for bulk data processing. mzAccess allows querying instrument data for spectra, chromatograms, or two-dimensional MZ-RT areas in either profile or centroid modes through a simple, uniform interface that is independent of vendor or instrument type. Using a cache mechanism, mzAccess achieves response times in the millisecond range for typical liquid chromatography-mass spectrometry (LC-MS) peaks, enabling real-time browsing of large data sets with hundreds or even thousands of samples. By simplifying access to metabolite data, we hope that this system will help enable data sharing and reanalysis in the metabolomics field

A web service framework for interactive analysis of metabolomics data

Analyzing mass spectrometry-based metabolomics data presents a major challenge to metabolism researchers, as it requires downloading and processing large data volumes through complex “pipelines”, even in cases where only a single metabolite or peak is of interest. This presents a significant hurdle for data sharing, reanalysis or meta-analysis of existing data sets, whether locally stored or available from public repositories. Here we introduce mzAccess, a software system that provides interactive, online access to primary mass spectrometry data in real time via a web service protocol, circumventing the need for bulk data processing. mzAccess allows querying instrument data for spectra, chromatograms, or two-dimensional MZ-RT areas in either profile or centroid modes through a simple, uniform interface that is independent of vendor or instrument type. Using a cache mechanism, mzAccess achieves response times in the millisecond range for typical LC-MS peaks, enabling real-time browsing of large data sets with hundreds or even thousands of samples. By simplifying access to metabolite data, we hope that this system will help enable data sharing and reanalysis in the metabolomics field

A Web Service Framework for Interactive Analysis of Metabolomics Data

Analyzing mass spectrometry-based metabolomics data presents a major challenge to metabolism researchers, as it requires downloading and processing large data volumes through complex “pipelines”, even in cases where only a single metabolite or peak is of interest. This presents a significant hurdle for data sharing, reanalysis, or meta-analysis of existing data sets, whether locally stored or available from public repositories. Here we introduce mzAccess, a software system that provides interactive, online access to primary mass spectrometry data in real-time via a Web service protocol, circumventing the need for bulk data processing. mzAccess allows querying instrument data for spectra, chromatograms, or two-dimensional MZ-RT areas in either profile or centroid modes through a simple, uniform interface that is independent of vendor or instrument type. Using a cache mechanism, mzAccess achieves response times in the millisecond range for typical liquid chromatography–mass spectrometry (LC–MS) peaks, enabling real-time browsing of large data sets with hundreds or even thousands of samples. By simplifying access to metabolite data, we hope that this system will help enable data sharing and reanalysis in the metabolomics field

The Effects of 5‑Fluorouracil on the Proteome of Colon Cancer Cells

The pyrimidine analogue 5-fluorouracil (5FU) is used as a treatment for solid tumors, but its mechanism of action is not fully understood. We have used mass spectrometry to study the mechanism of action of 5FU, and we have measured the effects of this drug on the composition and on the turnover of the proteome of RKO cancer cells. We have identified novel potential targets of 5FU that are affected after very short exposure times. We have also shown that 5FU has a massive effect on the proteins involved in RNA metabolism. After only 1 h of treatment, 5FU causes a post-transcriptional reduction in the abundance of components of the translation machinery (mostly ribosomal proteins), and this reduction is accompanied by a down-regulation of the translational capacity of the cells. Neither rapamycin nor raltitrexed, two drugs that also block cell proliferation, reduce the abundances of ribosomal proteins as 5FU does, which suggests that the down-regulation of ribosomal proteins is coupled to the mechanism of action of 5FU. Some of our observations conflict with previous reports based on RNA quantification. This shows how important it is to complement RNA profiling studies with analyses of drug toxicity at the protein level

The Effects of 5‑Fluorouracil on the Proteome of Colon Cancer Cells

The pyrimidine analogue 5-fluorouracil (5FU) is used as a treatment for solid tumors, but its mechanism of action is not fully understood. We have used mass spectrometry to study the mechanism of action of 5FU, and we have measured the effects of this drug on the composition and on the turnover of the proteome of RKO cancer cells. We have identified novel potential targets of 5FU that are affected after very short exposure times. We have also shown that 5FU has a massive effect on the proteins involved in RNA metabolism. After only 1 h of treatment, 5FU causes a post-transcriptional reduction in the abundance of components of the translation machinery (mostly ribosomal proteins), and this reduction is accompanied by a down-regulation of the translational capacity of the cells. Neither rapamycin nor raltitrexed, two drugs that also block cell proliferation, reduce the abundances of ribosomal proteins as 5FU does, which suggests that the down-regulation of ribosomal proteins is coupled to the mechanism of action of 5FU. Some of our observations conflict with previous reports based on RNA quantification. This shows how important it is to complement RNA profiling studies with analyses of drug toxicity at the protein level

Adding colour to mass spectra: Charge Determination Analysis (CHARDA) assigns charge state to every ion peak

Traditionally, mass spectrometry (MS) output is the ion abundance plotted versus ionic mass-to-charge ratio m/z. While employing only commercially available equipment, Charge Determination Analysis (CHARDA) adds a third dimension to MS, estimating for individual peaks their charge states z, starting from z=1, and colour-coding z in m/z spectra. CHARDA combines the analysis of ion signal decay rates in the time-domain data (transients) in Fourier transform (FT) MS with the interrogation of mass defects of biopolymers. Being applied to individual isotopic peaks in a complex protein tandem (MS/MS) dataset, CHARDA facilitates charge state deconvolution of large ionic species in crowded regions, estimating z even in the absence of isotopic distribution (e.g., for monoisotopic mass spectra). CHARDA is fast, robust and consistent with conventional FT MS and FT MS/MS data acquisition procedures. An effective charge state resolution Rz≥6 is obtained, with potential for further improvements