Preservation of native properties of mitochondria in rat liver homogenate

A protocol is developed for preparation of concentrated rat liver homogenate preserving assemblies of mitochondria in isotonic KCl under 0 and 15 degrees C. Assemblies preserve ability for self-organization during storage in homogenate. All key energy functions of mitochondria can be investigated in such a homogenate. Oxidative phosphorylation and membrane potential are stable for 5-7 h and can be still observed on the next day. Substrate-level phosphorylation is better pronounced for mitochondria in KCl than in sucrose medium while Ca2+ capacity is greater and lipid peroxidation is much lower. Sucrose addition impairs these functions. The rate of phosphorylating respiration is lower in large assemblies and higher in small. Transition from large to small assemblies corresponds to the transition from quiescent state of animal to adrenaline induced active state. The proposed method is particularly convenient for clinical investigations with small bioptates.     

Carnosine prevents the development of oxidative stress under the conditions of toxic action of cadmium

Protective effect of the natural dipeptide carnosine on the antioxidant system of rats under conditions of oxidative stress caused by chronic cadmium administration was investigated. Oxidative status of experimental animals were evaluated based on a number of informative parameters of iron-induced chemiluminescence. It was shown that the introduction of cadmium for 7 days reduces the duration of the latent period of chemiluminescence in the brain, liver, and blood plasma suggesting the depletion of endogenous antioxidant defense. Coexposure to carnosine and cadmium led to significant increase in the level of antioxidant protection in plasma, liver, and brain of animals. Carnosine also prevented the increase of lipid hydroperoxides in the brain and prevented the development of lipid peroxidation content in liver and plasma of animals. Mechanism of the protective effect of carnosine under conditions of oxidative stress induced by cadmium administration was shown on human neuroblastoma SH-SY5Y cell culture. Addition of the cadmium to the incubation medium to a final concentration of 5 μM reduced cell viability of a culture, as was determined by MTT assay; simultaneous addition of carnosine (0.25 mM final concentration) with cadmium resulted in increased cell viability during 24 hours of incubation. Thus, carnosine in a final concentration of 1 mM effectively prevented the development of necrotic lesions of neuroblastoma cells, inhibiting the formation of reactive oxygen species as measured by flow cytometry. The results indicate the ability of carnosine to prevent the development of oxidative stress under the toxic action of cadmium.     

Carnosine Protects the Brain of Rats and Mongolian Gerbils against Ischemic Injury: After-Stroke-Effect

Carnosine, a specific constituent of excitable tissues of vertebrates, exhibits a significant antioxidant protecting effect on the brain damaged by ischemic-reperfusion injury when it was administered to the animals before ischemic episode. In this study, the therapeutic effect of carnosine was estimated on animals when this drug was administered intraperitoneally (100 mg/kg body weight) after ischemic episode induced by experimental global brain ischemia. Treatment of the animals with carnosine after ischemic episode under long-term (7–14 days) reperfusion demonstrated its pronounced protective effect on neurological symptoms and animal mortality. Carnosine also prevented higher lipid peroxidation of brain membrane structures and increased a resistance of neuronal membranes to the in vitro induced oxidation. Measurements of malonyl dialdehyde (MDA) in brain homogenates showed its increase in the after brain stroke animals and decreased MDA level in the after brain stroke animals treated with carnosine. We concluded that carnosine compensates deficit in antioxidant defense system of brain damaged by ischemic injury. The data presented demonstrate that carnosine is effective in protecting the brain in the post-ischemic period. Special issue dedicated to Dr. Bernd Hamprecht     

The effect of carnosine on indicators of free radical lipid oxidation during acute stress in rats

The effect of carnosine intraperitoneal injection in rats (in doses 0.2, 2.0 or 20 mg/kg) on the vegetative parameters (arterial blood pressure, Hildebrandt index), the content of free radical oxidation (FRO) products and superoxide dismutase activity in serum and brain homogenates and brain lipid composition under normal condition and after different stress forms have been investigated. The carnosine injection in dose 20 mg/kg preserves and increase in arterial pressure and Hildebrandt index at all steps of stress development. The phase non-unidirectional changes in studied biochemical parameters have been revealed depending on the level of stress development in animals under control. The unidirectional and dose-dependent changes of phospholipid content and the level of brain lipids, decrease of FRO products in tissue and brain cholesterol, the increase of the superoxide dismutase activity of serum and brain homogenates have been found in intact and stressed animals after carnosine injection. A comparison of carnosine pharmacokinetics with concentration dependences of the antioxidative effect under in vitro and in vivo experiments comes to conclusion concerning the carnosine indirect adaptogenic action.     

Self-organization of mitochondrial associates and effects of negative air ions

A convenient model for studying the mechanisms of biological self-organization is described by morphometric investigation of formation of mitochondrion associations in medium containing physiological concentration of potassium ions without nonpolar substances. Association formation was considerably better at 15-18 degrees C during isolation and storage than at 0 degree C. The existence of filamented mitochondria in homogenate was also shown by staining of succinate dehydrogenase. Formation of associations increased in medium pretreated with negative air ions carrying superoxide and is probably due to hydrogen peroxide. The effect of substances influencing the surface charge on association formation was studied.     

Capacity for autoxidation of myoglobin in man and various semi-aquatic animals

Resistance to spontaneous oxidation of oxymyoglobin of man and semi-aquatic animals (beaver, otter, musk-rat) was studied as well as the effect of 2.3-diphosphoglycerate (2.3-DPG) and carnosine on this process. The revealed differences in the autooxidation rate of the studied myoglobins are explained by differences in the conformational state of a protein globule, which more actively protects a heme (in semi-aquatic animals) from spontaneous oxidation under conditions of muscular saturation of cells with oxygen, which is confirmed by the results obtained from the analysis of the universal links of pair amino acid residues which stabilize the protein molecule, 2,3-DPG and carnosine decrease the resistance of myoglobin to autooxidation.     

Incorporation of [14C]histidine into homocarnosine and carnosine of frog brain in vivo and in vitro

1. Homocarnosine, carnosine and histidine were determined in brain from several species and the results compared with values in the literature. 2. [(14)C]Homocarnosine and [(14)C]carnosine were isolated from frog brain after intracerebral injection of [(14)C]histidine in vivo. 3. Whole frog brain, incubated in vitro with l-[(14)C]histidine, formed labelled homocarnosine and carnosine. 4. A frog brain homogenate or supernatant fraction catalysed the incorporation of l-[(14)C]histidine into homocarnosine and carnosine. 5. The results indicate that brain tissue can synthesize homocarnosine and carnosine.     

Carnosine as a regulator of soluble guanylate cyclase

The molecular mechanism of the participation of carnosine in the functioning of soluble guanylate cyclase is discussed. It is shown that carnosine inhibits the activation of soluble guanylate cyclase by sodium nitroprusside and a derivative of furoxan--1,2,5-oxadiazolo-trioxide (an NO donor). However, carnosine has no effect on stimulation of the enzyme by a structural analog of the latter compound, a furazan derivative (1,2,5-oxadiazolo-dioxide) that is not an NO donor; nor was carnosine involved in the enzyme activation by protoporphyrin IX, whose stimulatory effect is not associated with the guanylate cyclase heme. The inhibition by carnosine of guanylate cyclase activation by an NO donor is due to the interaction of carnosine with heme iron with subsequent formation of a chelate complex. It was first demonstrated that carnosine is a selective inhibitor of NO-dependent activation of guanylate cyclase and may be used for suppression of activity of the intracellular signaling system NO-soluble guanylate cyclase-cGMP, whose sharp increase is observed in malignant tumors, sepsis, septic shock, asthma, and migraine.     

Changes in carnosine levels in muscles working in different regimens of stimulation

Carnosine content in muscles functioning under single or tetanic (both direct and indirect) contractions, in the period of active contractility (within the first 10 min of experiment) and in fatigued muscles was determined. In exercising muscle, carnosine content was shown to decrease. The loss of the dipeptide during active contractions was, on the average, 10.5%; that at fatigue--13.8%. At exercise (single contractions), the decrease of carnosine was higher than in the muscles functioning in a short tetanus regime. It was shown that the previously described phenomenon of fatigue elimination by carnosine addition to the Ringer solution washing the muscle is concomitant with the elevation (by 12%) of the intramuscular concentration of exogenous carnosine.     

Reduced muscle carnosine content in type 2, but not in type 1 diabetic patients

Carnosine is present in high concentrations in skeletal muscle where it contributes to acid buffering and functions also as a natural protector against oxidative and carbonyl stress. Animal studies have shown an anti-diabetic effect of carnosine supplementation. High carnosinase activity, the carnosine degrading enzyme in serum, is a risk factor for diabetic complications in humans. The aim of the present study was to compare the muscle carnosine concentration in diabetic subjects to the level in non-diabetics. Type 1 and 2 diabetic patients and matched healthy controls (total n=58) were included in the study. Muscle carnosine content was evaluated by proton magnetic resonance spectroscopy (3 Tesla) in soleus and gastrocnemius. Significantly lower carnosine content (-45%) in gastrocnemius muscle, but not in soleus, was shown in type 2 diabetic patients compared with controls. No differences were observed in type 1 diabetic patients. Type II diabetic patients display a reduced muscular carnosine content. A reduction in muscle carnosine concentration may be partially associated with defective mechanisms against oxidative, glycative and carbonyl stress in muscle.     

Stimulating effects of carnosine on hemopoietic stem cells]

It was shown that intake of carnosine in a dose of 50-100 mg/kg of body weight before X-ray irradiation resulted in an increase of the survival of experimental mice. The protective effect of carnosine was manifested, when it was injected either before or after irradiation, but the effect was more pronounced in the case of shortening time between irradiation and injection. An enhancement of colony forming index of bound cells in spleen was also observed simultaneously with protective action of carnosine. These effects are supposed to be the result of immunomodulating activity of carnosine.     

Carnosine Synthesis in Olfactory Tissue During Ontogeny: Effect of Exogenous β-Alanine

Carnosine has now been demonstrated by chemical analysis to be present in rat olfactory mucosa on day 16 of gestation. The tissue content of this dipeptide then increases progressively during fetal and postnatal life. Radioactive carnosine can be isolated from cultured embryonic rat olfactory mucosa incubated with [14C]beta-alanine as early as 13-14 days of gestation. The amount of incorporation also increases progressively with the initial age of the explant and with time in culture indicating in vitro maturation of the carnosine synthesis capability of olfactory tissue. To test whether the level of beta-alanine was limiting the synthesis of carnosine, we evaluated the effect of elevated beta-alanine levels on tissue carnosine content. Exogenous beta-alanine caused an increase in the tissue content of carnosine at several ages in vivo and in vitro. In adult animals this increase was observed in olfactory bulb, olfactory mucosa, and skeletal muscle. However, there was no associated alteration in carnosine synthetase activity. In addition, the different half-lives of carnosine in olfactory tissue and muscle seemed unaltered, arguing against any effect on degradative enzymes. Thus, tissue carnosine levels are regulated, at least in part, by substrate availability. The early appearance of carnosine synthetic capacity during prenatal development indicates that this enzyme activity should be a valuable aid in studying early events in olfactory neuron maturation.     

The effect of dopamine on in vitro methemoglobin formation in erythrocytes of patients with Parkinson’s disease under oxidative stress

Using electron paramagnetic resonance, the dose-dependence effect of dopamine on methemoglobin formation in erythrocytes of patients with Parkinson’s disease under the activation of oxidative stress induced by acrolein and the possibilities for the correction of this pathological process using carnosine in vitro experiments have been examined. It was shown that incubation of erythrocytes with 1.5 mM dopamine did not change the methemoglobin content, while incubation with 15 mM dopamine caused a two fold increase in the methemoglobin content compared to its initial level; 10 μM acrolein increased methemoglobin formation threefold. Administration of 15 mM dopamine and, after 1 h, 10 μM acrolein to the incubation system increased methemoglobin formation tenfold compared to its initial level. Preincubation of erythrocytes with 5 mM carnosine followed by acrolein addition prevented the increase in the methemoglobin content, while carnosine had no effect on methemoglobin formation induced by dopamine.     

Carnosine is a quencher of 4-hydroxy-nonenal: through what mechanism of reaction?

The aim of this study was to understand the mechanism of action through which carnosine (beta-alanyl-L-histidine) acts as a quencher of cytotoxic alpha,beta-unsaturated aldehydes, using 4-hydroxy-trans-2,3-nonenal (HNE) as a model aldehyde. In phosphate buffer solution (pH 7.4), carnosine was 10 times more active as an HNE quencher than L-histidine and N-acetyl-carnosine while beta-alanine was totally inactive; this indicates that the two constitutive amino acids act synergistically when incorporated as a dipeptide and that the beta-alanyl residue catalyzes the addition reaction of the histidine moiety to HNE. Two reaction products of carnosine were identified, in a pH-dependent equilibrium: (a) the Michael adduct, stabilized as a 5-member cyclic hemi-acetal and (b) an imine macrocyclic derivative. The adduction chemistry of carnosine to HNE thus appears to start with the formation of a reversible alpha,beta-unsaturated imine, followed by ring closure through an intra-molecular Michael addition. The biological role of carnosine as a quencher of alpha,beta-unsaturated aldehydes was verified by detecting carnosine-HNE reaction adducts in oxidized rat skeletal muscle homogenate.     

Carnosine as a potential anti-senescence drug

The naturally occurring dipeptide carnosine (beta-alanyl-L-histidine) has been found to exert an anti-senescence effect when used as a dietary supplement. Carnosine clearly improved the external appearance of experimental animals and provided beneficial physiological effects, thus maintaining the animals in better condition than control animals receiving no carnosine or a mixture of beta-alanine and L-histidine.     

Role of carnosine in preventing thioacetamide-induced liver injury in the rat

Carnosine (beta-alanyl-L-histidine) is a dipeptide with antioxidant properties. Free radicals are involved in the pathogenesis of acute liver injury induced by thioacetamide (TAA). In this study, we investigated the effect of carnosine treatment on TAA-induced oxidative stress and hepatotoxicity. Rats were injected intraperitoneally with TAA (500 mg/kg) and carnosine (250 mg/kg, intraperitoneal) was co-administered with TAA. All animals were killed 24 h after injections. TAA administration resulted in hepatic necrosis, significant increases in plasma transaminase activities as well as hepatic lipid peroxide levels. In addition, hepatic antioxidant system was found to be depressed following TAA administration. When carnosine was co-administered with TAA in rats, plasma transaminase activities were found to approach to normal values in rats. Histological findings also suggested that carnosine has preventive effect on TAA-induced hepatic necrosis. Carnosine treatment caused significant decreases in lipid peroxide levels in TAA-treated rats without any changes in enzymatic and non-enzymatic antioxidants except vitamin E in the liver of rats. Our findings indicate that carnosine, in vivo may have a preventive effect on TAA-induced oxidative stress and hepatotoxicity by acting as an non-enzymatic antioxidant itself.     

Carnosine and related compounds protect the double-chain DNA from oxidative damages

Carnosine and its derivatives in the concentrations corresponding to their level in excitable tissues have been shown to protect DNA from oxidative damages. Their efficiency (5 mM) was of the following order: ophidine > carnosine ≈ anserine > homocarnosine > N-acetylcarnosine. β-Alanine and gamma-aminobutyric acid (GABA) did not have any capability for protection. The revealed effect can be one of the causes of oxidative stability of the brain and muscle tissue in vertebrate animals.     

Transport of carnosine by mouse intestinal brush-border membrane vesicles

The characteristics of carnosine (beta-alanyl-L-histidine) transport have been studied using purified brush-border membrane vesicles from mouse small intestine. Uptake curves did not exhibit any overshoot phenomena, and were similar under Na+, K+ or choline+ gradient conditions (extravesicular greater than intravesicular). However, uptake of histidine showed an overshoot phenomenon in the presence of a Na+-gradient. There was no detectable hydrolysis of carnosine during 15 min of incubation with membrane vesicles under conditions used for transport experiments. Analysis of intravesicular contents further showed the complete absence of the constituent free amino acids of carnosine, and indicates that intact carnosine is transported. Studies on the effect of concentration on peptide uptake revealed that transport occurred by a saturable process conforming to Michaelis-Menten kinetics with a Km of 9.6 +/- 1.4 mM and a Vmax of 2.9 +/- 0.2 nmol/mg protein per 0.4 min. Uptake of carnosine was inhibited by both di- and tripeptides with a maximum inhibition of 68% by glycyl-L-leucyltyrosine. These results clearly demonstrate that carnosine is transported intact by a carrier-mediated, Na+-independent process.     

Neuroprotective effect of carnosine on primary culture of rat cerebellar cells under oxidative stress

Dipeptide carnosine (β-alanyl-L-histidine) is a natural antioxidant, but its protective effect under oxidative stress induced by neurotoxins is studied insufficiently. In this work, we show the neuroprotective effect of carnosine in primary cultures of rat cerebellar cells under oxidative stress induced by 1 mM 2,2′-azobis(2-amidinopropane)dihydrochloride (AAPH), which directly generates free radicals both in the medium and in the cells, and 20 nM rotenone, which increases the amount of intracellular reactive oxygen species (ROS). In both models, adding 2 mM carnosine to the incubation medium decreased cell death calculated using fluorescence microscopy and enhanced cell viability estimated by the MTT assay. The antioxidant effect of carnosine inside cultured cells was demonstrated using the fluorescence probe dichlorofluorescein. Carnosine reduced by half the increase in the number of ROS in neurons induced by 20 nM rotenone. Using iron-induced chemiluminescence, we showed that preincubation of primary neuronal cultures with 2 mM carnosine prevents the decrease in endogenous antioxidant potential of cells induced by 1 mM AAPH and 20 nM rotenone. Using liquid chromatographymass spectrometry, we showed that a 10-min incubation of neuronal cultures with 2 mM carnosine leads to a 14.5-fold increase in carnosine content in cell lysates. Thus, carnosine is able to penetrate neurons and exerts an antioxidant effect. Western blot analysis revealed the presence of the peptide transporter PEPT2 in rat cerebellar cells, which suggests the possibility of carnosine transport into the cells. At the same time, Western blot analysis showed no carnosine-induced changes in the level of apoptosis regulating proteins of the Bcl-2 family and in the phosphorylation of MAP kinases, which suggests that carnosine could have minimal or no side effects on proliferation and apoptosis control systems in normal cells.     

Some properties of a homocarnosine-carnosine synthetase isolated from rat brain

—An enzyme from rat brain catalysing the synthesis of the histidine-containing dipeptides carnosine and homocarnosine (l .-histidine: β-alanine ligase (AMP) [EC 6.3.2.11]) was purified about 30-40-fold from a 100,000 g supernatant. Assays were conducted by measuring the incorporation of L-[14C]histidine into carnosine and homocarnosine isolated by paper electrophoresis from the incubation mixture. The ratios of specific activities for the formation of carnosine and homocarnosine were not significantly different for the various purification steps. This was taken as evidence of one enzyme synthesizing both dipeptides. In studying the properties of this enzyme, a pH optimum of 7.4 was shown for carnosine synthesis. The concentrations of amino acid substrates giving maximal synthesis of both dipeptides were in the physiological range found for rat brain. An apparent requirement for ATP, Mg²⁺, and DPN was seen for dipeptide synthesis. A substrate dependent, enzymecatalysed ³²PPi-ATP exchange reaction was observed, suggesting the formation of an aminoacyl-AMP intermediate. Certain other nucleoside triphosphates could substitute for the ATP; this effect showed a specificity toward the dipeptide being synthesized. The apparent requirement for DPN was quite specific, with a number of related compounds having no effect. The stoichiometry of enzyme-catalysed carnosine synthesis was studied. A one to one relationship between carnosine formed and ATP hydrolysed was demonstrated. However, the ratio between carnosine synthesized and DPN hydrolysed was about 6 to 1, indicating a catalytic role for the DPN. The breakdown of DPN did not occur with enzyme alone but was dependent on the presence of substrate.