1. Interactions between L-arginine/L-arginine derivatives and lysozyme and implications to their inhibition effects on protein aggregation
Xiao-Yan Dong, Ming-Tao Gao, Yan Sun Biotechnol Prog . 2013 Sep-Oct;29(5):1316-24. doi: 10.1002/btpr.1766.
L-arginine (Arg), L-homoarginine (HArg), L-arginine ethylester (ArgEE), and L-arginine methylester (ArgME) were found effective in inhibiting protein aggregation, but the molecular mechanisms are not clear. Herein, stopped-flow fluorescence spectroscopy, isothermal titration calorimetry, and mass spectroscopy were used to investigate the folding kinetics of lysozyme and the interactions of the additives with lysozyme. It was found that the interactions of ArgME and ArgEE with lysozyme were similar to that of guanidine hydrochloride and were much stronger than those of Arg and HArg. The binding forces were all mainly hydrogen bonding and cation-π interaction from the guanidinium group, but their differences in molecular states led to the significantly different binding strengths. The additives formed molecular clusters in an increasing order of ArgEE, ArgME, HArg, and Arg. Arg and HArg mainly formed annular clusters with head-to-tail bonding, while ArgME and ArgEE formed linear clusters with guanidinium groups stacking. The interactions between the additives and lysozyme were positively related to the monomer contents. That is, the monomers were the primary species that participated in the direct interactions due to their intact guanidinium groups and small sizes, while the clusters performed as barriers to crowd out the protein-protein interactions for aggregation. Thus, it is concluded that the effects of Arg and its derivatives on protein aggregation stemmed from the direct interactions by the monomers and the crowding effects by the clusters. Interplay of the two effects led to the differences in their inhibition effects on protein aggregation.
2. Metabolism and distribution of pharmacological homoarginine in plasma and main organs of the anesthetized rat
Duygu Naile Günes, Arslan Arinc Kayacelebi, Joel Lundgren, Erik Hanff, Björn Redfors, Dimitrios Tsikas Amino Acids . 2017 Dec;49(12):2033-2044. doi: 10.1007/s00726-017-2465-7.
L-Homoarginine (hArg) and guanidinoacetate (GAA) are produced from L-arginine (Arg) by the catalytic action of arginine:glycine amidinotransferase. Guanidinoacetate methyltransferase methylates GAA on its non-guanidine N atom to produce creatine. Arg and hArg are converted by nitric oxide synthase (NOS) to nitric oxide (NO). NO is oxidized to nitrite and nitrate which circulate in the blood and are excreted in the urine. Asymmetric dimethylarginine (ADMA), an NOS inhibitor, is widely accepted to be exclusively produced after asymmetric NG-methylation of Arg residues in proteins and their regular proteolysis. Low circulating and urinary hArg concentrations and high circulating concentrations of ADMA emerged as risk markers in the human renal and cardiovascular systems. While ADMA's distribution and metabolism are thoroughly investigated, such studies on hArg are sparse. The aim of the present pilot study was to investigate the distribution of exogenous hArg in plasma, liver, kidney, lung, and heart in a rat model of takotsubo cardiomyopathy (TTC). hArg hydrochloride solutions in physiological saline were injected intra-peritoneally at potentially pharmacological, non-toxic doses of 20, 220, or 440 mg/kg body weight. Vehicle (saline) served as control. As hArg has been reported to be a pro-oxidant, plasma and tissue malondialdehyde (MDA) was measured as a biomarker of lipid peroxidation. hArg administration resulted in dose-dependent maximum plasma hArg concentrations and distribution in all investigated organs. hArg disappeared from plasma with an elimination half-life ranging between 20 and 40 min. hArg administration resulted in relatively small changes in the plasma and tissue content of Arg, GAA, ADMA, creatinine, and of the NO metabolites nitrite and nitrate. Remarkable changes were observed for tissue GAA, notably in the kidney. Plasma and tissue MDA concentration did not change upon hArg administration, suggesting that even high-dosed hArg is not an oxidant. The lowest hArg dose of 20 mg/kg bodyweight increased 25-fold the mean hArg maximum plasma concentration. This hArg dose seems to be useful as the upper limit in forthcoming studies on the putative cardioprotective effects of hArg in our rat model of TTC.
3. Nitric oxide regulates IL-8 expression in melanoma cells at the transcriptional level
I J Lindley, H Harant, P J Andrew Biochem Biophys Res Commun . 1995 Sep 25;214(3):949-56. doi: 10.1006/bbrc.1995.2378.
We investigated the role of nitric oxide (NO) in the expression of interleukin-8 (IL-8) in the human melanoma cell line, G361. Three NO donors, 3-morpholinosydnonimine hydrochloride (SIN-1), S-nitroso-N-acetylpenicillamine (SNAP), and S-nitroso-L-glutathione (SNOG), all caused an increase in both IL-8 protein secretion and promoter activity. Truncation of the promoter showed that 101 bp of the 5' flanking region proximal to the transcription start site are sufficient for the response to NO. Furthermore, mutation of the NF-kappa B and NF-IL-6 binding sites led to a significant decrease in NO-stimulated promoter activity. The nitric oxide synthase inhibitor, NG-amino-L-homoarginine (NAHA), inhibited TNF-alpha-stimulated IL-8 promoter activity by 60%. Addition of excess L- but not D-arginine partially reversed the NAHA-mediated inhibition. These results demonstrate that NO is an endogenous regulator of IL-8 production in G361 melanoma cells.
