Self-Assembly of an Antitumor Dipeptide Induced Near-Infrared Fluorescence and Improved Stability for Theranostic Applications.

It has been found that the self-assembly of nonfluorescent peptides can generate fluorescent peptide nanoparticles (f-PNPs) to perform multiple functions, including drug delivery and imaging and tracking therapeutic agents. Both pharmacologically inactive peptides and tumor-targeting peptides have been explored to construct biocompatible f-PNPs; however, the application of this technology in delivering antitumor peptides has never been reported. Herein, the self-assembly of an antitumor dipeptide, carnosine, into fluorescent carnosine nanoparticles (f-Car NPs) in the presence of zinc ions is demonstrated. The generated f-Car NPs exhibit fluorescence in the visible and near-infrared (NIR) ranges for fluorescence tracing in vitro and in vivo. On the other hand, the f-Car NPs minimize the contact between the dipeptide and the serum, which overcomes the dipeptide instability resulted from inefficient antitumor activity. In addition, the preparation of f-Car NPs does not introduce extra carrier materials, so the f-Car NPs exhibit biocompatibility to normal fibroblast cells in vitro and negligible toxicity against major organs in vivo. This study provides a new peptide drug delivery strategy with NIR fluorescence tracing ability.

Glycotoxins: Dietary and Metabolic Origins; Possible Amelioration of Neurotoxicity by Carnosine, with Special Reference to Parkinson's Disease.

There is a strong association between neurodegeneration and protein glycation; possible origins of neurotoxic glycated protein, also called glycotoxins, include (i) diet (i.e., proteins cooked at high temperatures), (ii) protein glycation in the gut, and (iii) intracellular reaction of proteins with deleterious aldehydes, especially methylglyoxal (MG). It is likely that excessive glycolysis provokes increased generation of dihydroxyacetone phosphate which decomposes into MG due to activity-induced deamidation of certain asparagine residues in the glycolytic enzyme triose-phosphate isomerase (TPI). It is suggested that, following hyperglycemia, erythrocytes (i) possibly participate in MG distribution throughout the body and (ii) could provide a source of glycated alpha-synuclein which also accumulates in PD brains as Lewy bodies. The dipeptide carnosine, recently shown to be present in erythrocytes, could help to protect against MG reactivity by scavenging the reactive bicarbonyl, especially if glyoxalase activity is insufficient, as often occurs during aging. By reacting with MG, carnosine may also prevent generation of the neurotoxin 1-acetyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (ADTIQ), which accumulates in PD and diabetic brains. It is suggested that carnosine's therapeutic potential could be explored via nasal administration in order to avoid the effects of serum carnosinase. The possibility that some glycated proteins (e.g., alpha-synuclein) could possess prion-like properties is also considered.

Impairment of electron transfer chain induced by acute carnosine administration in skeletal muscle of young rats.

Serum carnosinase deficiency is an inherited disorder that leads to an accumulation of carnosine in the brain tissue, cerebrospinal fluid, skeletal muscle, and other tissues of affected patients. Considering that high levels of carnosine are associated with neurological dysfunction and that the pathophysiological mechanisms involved in serum carnosinase deficiency remain poorly understood, we investigated the in vivo effects of carnosine on bioenergetics parameters, namely, respiratory chain complexes (I-III, II, and II-III), malate dehydrogenase, succinate dehydrogenase, and creatine kinase activities and the expression of mitochondrial-specific transcription factors (NRF-1, PGC-1α , and TFAM) in skeletal muscle of young Wistar rats. We observed a significant decrease of complexes I-III and II activities in animals receiving carnosine acutely, as compared to control group. However, no significant alterations in respiratory chain complexes, citric acid cycle enzymes, and creatine kinase activities were found between rats receiving carnosine chronically and control group animals. As compared to control group, mRNA levels of NRF-1, PGC-1α , and TFAM were unchanged. The present findings indicate that electron transfer through the respiratory chain is impaired in skeletal muscle of rats receiving carnosine acutely. In case these findings are confirmed by further studies and ATP depletion is also observed, impairment of bioenergetics could be considered a putative mechanism responsible for the muscle damage observed in serum carnosinase-deficient patients.

Safety evaluation of chicken breast extract containing carnosine and anserine.

Chicken breast extract (CBEX) is obtained via hot water extraction of chicken breast and contains among its primary constituents carnosine and anserine, which are histidine-containing dipeptides present in the muscle tissues of most vertebrate species. Dietary intake of CBEX has been previously shown to buffer hydrogen ions formed during high-intensity exercise in human skeletal muscle cells, thereby inhibiting a decrease in muscle cell pH and subsequent muscle fatigue. The objective of this paper is to report the results of safety studies completed on CBEX. CBEX was determined to have an oral LD(50) value of more than 6000 mg/kg body weight in rats. Gavage doses of 500 or 2000 mg CBEX/kg body weight/day administered to rats for 90 days produced no toxicologically significant, dose-related, differences between control and treated animals with respect to body weight gain, food consumption, behavioral effects, hematological and clinical chemistry parameters, absolute and relative organ weights, or gross and microscopic findings. In the presence or absence of metabolic activation, CBEX exerted no mutagenic activity in the Ames assay conducted in various strains of Salmonella typhimurium and Escherichia coli. The results of these studies support the safety of CBEX as a potential dietary source of carnosine and anserine.

L-methionine induces stage-dependent changes of differentiation and oxidative activity in sea urchin embryogenesis.

This study was to investigate developmental toxicity of some selected low molecular weight antioxidants, by utilising sea urchin embryos and gametes as model system. Sea urchin embryos or sperm were exposed at different developmental stages to L-methionine or some selected low molecular weight antioxidants: a) N-acetylcysteine; b) L-carnosine; c) L-homocarnosine, and d) L-anserine. L-methionine displayed developmental toxicity at levels > or = 10(-5) M, whereas the other agents tested were mostly active at levels > or = 10(-4) M. When embryos were exposed to 10(-4) M L-methionine or N-acetylcysteine at different developmental stages, the most severe effects were exerted by early exposures (0 to 2 hr after fertilisation), whereas later exposures turned to lesser or no effects. Cytogenetic analysis of L-methionine-exposed embryos showed a significant mitogenic effect and increase of mitotic aberrations. Fertilisation success was decreased by L-methionine (10(-6) M to 10(-3) M) added at the moment of fertilisation, with increasing developmental and cytogenetic abnormalities in the offspring. The formation of reactive oxygen species in embryos and gametes was determined by: a) analysing the DNA oxidative product, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and b) luminol-dependent chemiluminescence. The results showed that: 1) 8-OHdG levels were increased during embryogenesis; 2) fertilisation was associated with a double-wave luminol-dependent chemiluminescence emission; 3) luminol-dependent chemiluminescence was maximal in cleavage, declining down to zero in plutei, and 4) an embryotoxic L-methionine or N-acetylcysteine level (10(-4) M) turned to a decrease in reactive oxygen species formation. The data suggest that L-methionine- or N-acetylcysteine-induced developmental toxicity is confined to early stages. A role for oxidative activity is suggested in modulating cell differentiation and embryogenesis, consistent with antioxidant-induced damage to early life stages.

Changes in tissue contents of zinc, copper and iron in rats and beagle dogs treated with polaprezinc.

Zinc, copper and iron levels of tissues in rats or beagle dogs were measured after a 13- or 52-week toxicity study of polaprezinc, which contains a zinc element. The zinc content in almost all rat tissues remarkably increased with a conspicuous decrease of copper and various changes of iron at doses of 600 mg/kg/day or more. Zinc and copper levels increased and decreased respectively, at 300 mg/kg/day. At a dose of 150 mg/kg/day, there was a slight increase of zinc in some tissues at 52-weeks, but no copper decrease. The results obtained from beagle dogs differed somewhat from that in rats. Dogs treated with polaprezinc at 50 mg/kg/day or more accumulated zinc in some tissues. A copper decrement was seen only in the liver and heart from the group given 300 mg/kg/day, whereas copper levels in the kidney of all treated groups were higher than that in the control, suggesting that canine polaprezinc toxicity is due to direct zinc toxic effects.

Non-enzymatic glycosylation of the dipeptide L-carnosine, a potential anti-protein-cross-linking agent.

The dipeptide carnosine (beta-alanyl-L-histidine) was readily glycosylated non-enzymatically upon incubation with the sugars glucose, galactose, deoxyribose and the triose dihydroxyacetone. Carnosine inhibited glycation of actyl-Lys-His-amide by dihydroxyacetone and it protected alpha-crystallin, superoxide dismutase and catalise against glycation and cross-linking mediated by ribose, deoxyribose, dihydroxyacetone, dihydroxyacetone phosphate and fructose. Unlike certain glycated amino acids, glycated carnosine was non-mutagenic. The potential biological and therapeutic significance of these observations are discussed.