Simultaneous determination of arginine, citrulline, and asymmetric dimethylarginine in plasma by reverse-phase high-performance liquid chromatography

Nitric Oxide Synthesis Metabolites-As Potential Markers in Chronic Kidney Disease in Children

Nitric oxide (NO) is an important signaling molecule for many physiological and pathological processes. Diseases associated with abnormal NO synthesis include cardiovascular diseases, insulin-dependent diabetes, or chronic kidney disease (CKD). The aim of the paper was to evaluate NO synthesis metabolites, i.e., asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), dimethylamine (DMA), arginine, citrulline in plasma of patients with different severity of CKD and to seek possible links between these parameters and the development of this disease. Forty-eight CKD children and thirty-three age-matched controls were examined. Patients were divided into groups depending on the CKD stages (Group II-stage II, Group III-stage III, Group IV-stage IV, and Group RRT children on dialysis). To determine the concentrations of the above-mentioned metabolites in plasma liquid chromatography-mass spectrometry was used. There were significant differences observed in levels of ADMA, SDMA, DMA, and citrulline between control vis CKD groups (p values ranging from <0.001 to 0.029). Plasma arginine concentration was also higher in CKD patients compared to the control group but statistically insignificant. ADMA levels in CKD children were statistically significantly higher in relation to particular stages of CKD (RRT vis II stage of CKD: p = 0.01; RRT vis III-IV stages of CKD: p < 0.046). Citrulline levels in CKD children were statistically significantly higher in RRT group vis control (p < 0.001). Children with CKD develop disturbances in most metabolites of NO synthesis. Dialysis children treated show the greatest disturbances of plasma ADMA and citrulline levels. ADMA seems to be a good indicator of the gradual progression of the CKD, which is proved by the negative correlation with eGFR.

Multiplexed small molecule impurity monitoring in antibody-based therapeutics by mixed-mode chromatography paired with charged aerosol detection

With advanced genetic engineering technologies and better understanding of disease biology, antibody-based therapeutics are emerging as promising new generation biopharmaceuticals. These novel antibody formats are carefully designed to possess desired features such as enhanced selectivity. However, their high level of structural complexity with multiple components often leads to long development and complex multi-step manufacturing processes, through which a variety of potential small molecule impurities can be introduced. In this work, an in-process assay was developed in which mixed-mode chromatography coupled with charged aerosol detection was utilized for multiplexed detection of nine reagents commonly used in development and manufacturing of antibody-based therapeutics: isopropyl β-d-1-thiogalactopyranoside, methionine sulfoximine, ampicillin, guanidine, dehydroascorbic acid, glutathione, tris(2-carboxyethyl)phosphine, N-acetyl cysteine, and arginine. This method utilized a mixed-mode column with ion-exchange properties operated in the hydrophilic interaction chromatography mode. Various parameters were systematically optimized and under optimal conditions, the method demonstrated excellent specificity, sensitivity, linearity, precision, accuracy, and was successfully applied to determine residual impurities in multiple samples from antibody-derived molecules.

Amino acid arginine and adducts: autoimmune activity

Arginine is derived from dietary intake, body protein breakdown, or endogenous de novo arginine production. Arginine methylation of non-histone proteins is used in transcriptional regulation. Protein-arginine methylation is used for regulation of transcriptional and various physiological pathological processes. Protein methylation may affect protein-protein, protein-DNA, or protein-RNA interaction. Arginine has an effect on the DNA-binding activity of NF-κB, a dominant transcriptional factor in inflammation. Adduct formation results in increased secretion of messenger molecules such as cytokines and chemokines that mediate communication among cells and promote inflammation. Arginine and lysine amino acid-rich histones in nucleosomes on modification by environmental agents form histone-DNA adducts, making it immunogenic. Alteration of DNA resulting from photomodification could lead to the development of antibodies or mutations to modified DNA. Lysine and arginine-rich histones in nucleosomes on modification by environmental agents form histone-DNA adducts, making it immunogenic. Alteration of DNA resulting from photomodification could lead to the development of antibodies or mutations to modified DNA. Therefore, the DNA-arginine photoadduct and modified photoadduct could have important implications in various pathophysiological conditions such as toxicology, carcinogenesis, and autoimmune phenomena. Abbreviations: Arg: Arginine; SLE: systemic lupus erythematosus; UV: ultraviolet; Tm: thermal melting temperature; NO: nitric oxide; O₂.^-: superoxide anion.