Development of a novel nanoflow liquid chromatography-parallel reaction monitoring mass spectrometry-based method for quantification of angiotensin peptides in HUVEC cultures

Optimized LC-MS/MS methods for quantifying antibody-drug conjugate payloads in cell culture media containing phenol red

Aim: Phenol red is commonly used in cell culture media, but can be detrimental to bioanalysis of in vitro samples as it may impact instrument reliability. Many researchers do their final stage of culture in 'phenol red free' media, but in collaborative work this is not always feasible.Materials & methods: A comparison was made between typical extraction methods to reduce phenol red matrix interferences, including organic solvent precipitation and solid phase extraction.Results: The final method was demonstrated to be precise and accurate for the measurement of a target analyte by LC-MS/MS, and was applied to an in vitro ADC deconjugation study.Conclusion: This method allows for for continued bioanalytical support of in vitro models used in drug development.

Hydrogen Sulfide Exerted a Pro-Angiogenic Role by Promoting the Phosphorylation of VEGFR2 at Tyr797 and Ser799 Sites in Hypoxia-Reoxygenation Injury

The protective effects of hydrogen sulfide (H2S) against ischemic brain injury and its role in promoting angiogenesis have been established. However, the specific mechanism underlying these effects remains unclear. This study is designed to investigate the regulatory impact and mechanism of H2S on VEGFR2 phosphorylation. Following expression and purification, the recombinant His-VEGFR2 protein was subjected to LC-PRM/MS analysis to identify the phosphorylation sites of VEGFR2 upon NaHS treatment. Adenovirus infection was used to transfect primary rat brain artery endothelial cells (BAECs) with the Ad-VEGFR2WT, Ad-VEGFR2Y797F, and Ad-VEGFR2S799A plasmids. The expression of VEGFR2 and recombinant Flag-VEGFR2, along with Akt phosphorylation, cell proliferation, and LDH levels, was assessed. The migratory capacity and tube-forming potential of BAECs were assessed using wound healing, transwell, and tube formation assays. NaHS notably enhanced the phosphorylation of VEGFR2 at Tyr797 and Ser799 sites. These phosphorylation sites were identified as crucial for mediating the protective effects of NaHS against hypoxia-reoxygenation (H/R) injury. NaHS significantly enhanced the Akt phosphorylation, migratory capacity, and tube formation of BAECs and upregulated the expression of VEGFR2 and recombinant proteins. These findings suggest that Tyr797 and Ser799 sites of VEGFR2 serve as crucial mediators of H2S-induced pro-angiogenic effects and protection against H/R injury.

A comprehensive profiling of renin-angiotensin system in mouse and human plasma by a rapid quantitative analysis of 14 angiotensin peptides using ultrahigh-performance liquid chromatography with tandem mass spectrometry

BACKGROUND

The renin-angiotensin system produces a series of biologically active angiotensin (Ang) peptides. These Ang peptides are the major regulators of blood pressure and Na homeostasis, and play a critical role in maintaining cardiovascular and fluid homeostasis. The concentration of Ang peptides in the body is at trace levels, making their detection and quantification a challenge. In this study, a rapid and sensitive analytical method using mass spectrometry coupled with ultrahigh-performance liquid chromatography (UHPLC/MS) was developed to simultaneously quantify 14 Ang peptides.

METHODS

UHPLC/MS was employed to quantify 14 Ang peptides in mouse and human plasma. An HSS T3 column (2.1 × 100 mm, 1.8 μm) with an HSS T3 precolumn and triple-quadrupole mass spectrometer combined with an electrospray ionization source were utilized. Sample pretreatment involved a one-step protein precipitation using methanol. The total analysis time was within 7.5 min and the target peptides were detected in positive ion mode and quantified by selected reaction monitoring mode.

RESULTS

The method was validated for linearity, detection and quantification limits, precision, stability, recovery and matrix effect. The limits of detection of Ang II, Ang III, Ang-(1-7), Ang-(2-7), Ang-(3-7), Ang-(1-9), bradykinin, Asn1 and Val5 -Ang II are all less than 1 pg mL-1 , indicating high sensitivity. The intra-day and inter-day precision was within 15%, and the accuracy was between 85% and 115%. Meanwhile, the sample and reference solution were stable within 48 h, and the recovery and matrix effect met the quantitative requirements.

CONCLUSIONS

The method is currently reported to allow the largest number of Ang peptide species to be detected at one time. In addition, the proposed method offers a fast and reliable approach for comprehensive analysis of Ang metabolism in biological samples, facilitating research on the physiological and pathological states of cardiovascular, kidney and respiratory diseases.

Robust analysis of angiotensin peptides in human plasma: Column switching-parallel LC/ESI-SRM/MS without adsorption or enzymatic decomposition

Angiotensin (Ang) peptides are the main effectors of the renin-angiotensin system (RAS) regulating diverse physiological conditions and are involved in renal and vascular diseases. Currently, quantitative analyses of Ang peptides in human plasma mainly rely on radioimmunoassay-based methods whose reported levels are quite divergent. Analyses are further complicated by the potential of Ang peptides to bind to solid surfaces, to be enzymatically decomposed during sample preparation, and to undergo post-translational modifications. A column switching-parallel LC/ESI-SRM/MS method has been developed for seven Ang peptides (Ang I, Ang II, Ang III, Ang IV, Ang 1-9, Ang 1-7, and Ang A) in human plasma. Aqueous acetonitrile (5%) containing 50 mM arginine (Arg) as a dissolving solution and a combination of protease inhibitors with formic acid were used to prevent adsorption and enzymatic degradation, respectively. Plasma samples were simply deproteinized with acetonitrile followed by clean-up with an on-line trap column via column-switching. Stable isotope dilution with [¹³C₅,¹⁵N₁-Val]-Ang peptides as internal standards was employed for quantitative analysis. The current methodology has been successfully applied to determine the plasma levels of Ang peptides in healthy participants, suggesting future applicability to studies of various diseases related to RAS.

The rise of single‐cell proteomics

Mass spectrometry‐based proteomics comprehensively defines proteome expression patterns in thousands of cells majorly contributing to our current understanding of many biological processes. More recently, single‐cell transcriptome and genome studies, however, have demonstrated overwhelming heterogeneity of tissues and cellular subpopulations. These studies have indicated different cellular functionality and identity, which are mainly driven by proteins and their posttranscriptional modifications. The rapidly emerging field of single‐cell proteomics aims at complementing transcriptome and genome data by generating comparative protein expression profiles from individual cells. Recent developments demonstrated tremendous improvements in sample preparation workflows and MS instrumentation, quantifying over 1000 proteins from a single cell. Efficient and reproducible sample processing in conjunction with sensitive MS acquisition strategies will allow to further increase the proteome coverage of tissues with single‐cell resolution. The required throughput and data reliability of such studies are still subject to further developments. Therefore, we herein discuss recent progress on specialized workflows and instrumentation next to advancements outside the field, which we expect to contribute to the development of comprehensive single‐cell proteomics.