肌肽、丙氨酸和组氨酸抗氧化性的比较研究

肌肽是一种发现于脊椎动物骨骼肌和大脑中的二肽(β-丙氨酰-L-组氨酸).为了探讨肌肤的抗氧化性与其结构之间的关系,试验研究了肌肽、丙氨酸和组氨酸对DPPH自由基的清除作用和对牛血清白蛋白(BSA)氧化修饰的抑制作用.结果表明肌肽对DPPH自由基有显著的清除效果(P＜0.01),组氨酸清除率低于肌肤,而丙氨酸基本无清除自...     

Carnosine and protein carbonyl groups: a possible relationship

Carnosine has been shown to react with low-molecular-weight aldehydes and ketones and has been proposed as a naturally occurring anti-glycating agent. It is suggested here that carnosine can also react with ("carnosinylate") proteins bearing carbonyl groups, and evidence supporting this idea is presented. Accumulation of protein carbonyl groups is associated with cellular ageing resulting from the effects of reactive oxygen species, reducing sugars, and other reactive aldehydes and ketones. Carnosine has been shown to delay senescence and promote formation of a more juvenile phenotype in cultured human fibroblasts. It is speculated that carnosine may intracellularly suppress the deleterious effects of protein carbonyls by reacting with them to form protein-carbonyl-carnosine adducts, i.e., "carnosinylated" proteins. Various fates of the carnosinylated proteins are discussed including formation of inert lipofuscin and proteolysis via proteosome and RAGE activities. It is proposed that the anti-ageing and rejuvenating effects of carnosine are more readily explainable by its ability to react with protein carbonyls than its well-documented antioxidant activity.     

The protective effect of carnosine in hypoxia and reoxygenation of the isolated rat heart]

The effect of carnosine (15 mM) on the contractile activity of isolated rat hearts contracting in an isotonic regime (37 degrees C at a 5 Hz stimulation frequency) has been studied. Carnosine added to the perfusing solution had no effect on the contractile activity either in hypoxia or during reoxygenation but decreased it with a simultaneous increase in the coronary flow during reoxygenation. Carnosine inhibited by 60% the lactate dehydrogenase release from cardiac cells. A conclusion is drawn that the protective effect of carnosine is due to its membrane-stabilizing action which is implemented during inhibition of peroxidation of membrane lipids.     

Carnosine enhances diabetic wound healing in the db/db mouse model of type 2 diabetes

Diabetes mellitus (DM) is a progressive disorder with severe late complications. Normal wound healing involves a series of complex and well-orchestrated molecular events dictated by multiple factors. In diabetes, wound healing is grossly impaired due to defective, and dysregulated cellular and molecular events at all phases of wound healing resulting in chronic wounds that fail to heal. Carnosine, a dipeptide of alanine and histidine and an endogenous antioxidant is documented to accelerate healing of wounds and ulcers. However, not much is known about its role in wound healing in diabetes. Therefore, we studied the effect of carnosine in wound healing in db/db mice, a mice model of Type 2 DM. Six millimeter circular wounds were made in db/db mice and analyzed for wound healing every other day. Carnosine (100?mg/kg) was injected (I.P.) every day and also applied locally. Treatment with carnosine enhanced wound healing significantly, and wound tissue analysis showed increased expression of growth factors and cytokines genes involved in wound healing. In vitro studies with human dermal fibroblasts and microvascular-endothelial cells showed that carnosine increases cell viability in presence of high glucose. These effects, in addition to its known role as an antioxidant and a precursor for histamine synthesis, provide evidence for a possible therapeutic use of carnosine in diabetic wound healing.     

The radiation modifying properties of carnosine

The influence of carnosine (beta-alanyl-l-histidine) on the survival rate of albino mice subjected to whole-body X-irradiation has been investigated. Carnosine (50-200 mg/kg/day) administered per os during a period of 20 days before irradiation (5.0 Gy) increased the survival rate by 45-65%, whereas the administration of carnosine within 30 days after irradiation (5.5 Gy) produced an insignificant protective effect and caused inhibition of the postirradiation histamine accumulation in the spleen.     

Retardation of the Senescence of Cultured Human Diploid Fibroblasts by Carnosine

We have examined the effects of the naturally occurring dipeptide carnosine (β-alanyl-L-histidine) on the growth, morphology, and lifespan of cultured human diploid fibroblasts. With human foreskin cells, HFF-1, and fetal lung cells, MRC-5, we have shown that carnosine at high concentrations (20-50 mM) in standard medium retards senescence and rejuvenates senescent cultures. These late-passage cultures preserve a nonsenescent morphology in the presence of carnosine, in comparison to the senescent morphology first described by Hayflick and Moorhead. Transfer of these late-passage cells in medium containing carnosine to unsupplemented normal medium results in the appearance of the senescent phenotype. The serial subculture of cells in the presence of carnosine does not prevent the Hayflick limit to growth, although the lifespan in population doublings as well as chronological age is often increased. This effect is obscured by the normal variability of human fibroblast lifespans, which we have confirmed. Transfer of cells approaching senescence in normal medium to medium supplemented with carnosine rejuvenates the cells but the extension in lifespan is variable. Neither D -carnosine, (β-alanyl-D-histidine), homocarnosine, anserine, nor β-alanine had the same effects as carnosine on human fibroblasts. Carnosine is an antioxidant, but it is more likely that it preserves cellular integrity by its effects on protein metabolism.     

Effects of L-1-methyl-histidine and the muscle dipeptides carnosine and anserine on the activities of muscle calpains

1. Carnosine, anserine and L-1-methyl-histidine activated muscle calpain II assayed at 2.5 mM Ca2+. 2. At 5 microM Ca2+, none of these compounds activated calpain II sufficiently to bring its activity up to the level measured at 2.5 mM Ca2+. 3. Carnosine increased, whereas both anserine and L-1-methyl-histidine decreased the inhibitory effect of calpastatin on calpain II. 4. These results suggest that although the compounds are not potent activators of calpain II, the ratio of the dipeptides in muscle may have an effect on calpain II-calpastatin interaction.     

Protective effect of orally administered carnosine on bleomycin-induced lung injury

Carnosine is an endogenously synthesized dipeptide composed of beta-alanine and L-histidine. It acts as a free radical scavenger and possesses antioxidant properties. Carnosine reduces proinflammatory and profibrotic cytokines such as transforming growth factor-beta (TGF-beta), IL-1, and TNF-alpha in different experimental settings. In the present study, we investigated the efficacy of carnosine on the animal model of bleomycin-induced lung injury. Mice were subjected to intratracheal administration of bleomycin and were assigned to receive carnosine daily by an oral bolus of 150 mg/kg. One week after fibrosis induction, bronchoalveolar lavage (BAL) cell counts and TGF-beta levels, lung histology, and immunohistochemical analyses for myeloperoxidase, TGF-beta, inducible nitric oxide synthase, nitrotyrosine, and poly(ADP-ribose) polymerase were performed. Finally, apoptosis was quantified by terminal deoxynucleotidyltransferase-mediated UTP end-labeling assay. After bleomycin administration, carnosine-treated mice exhibited a reduced degree of lung damage and inflammation compared with wild-type mice, as shown by the reduction of 1) body weight, 2) mortality rate, 3) lung infiltration by neutrophils (myeloperoxidase activity and BAL total and differential cell counts), 4) lung edema, 5) histological evidence of lung injury and collagen deposition, 6) lung myeloperoxidase, TGF-beta, inducible nitric oxide synthase, nitrotyrosine, and poly(ADP-ribose) polymerase immunostaining, 7) BAL TGF-beta levels, and 8) apoptosis. Our results indicate that orally administered carnosine is able to prevent bleomycin-induced lung injury likely through its direct antioxidant properties. Carnosine is already available for human use. It might prove useful as an add-on therapy for the treatment of fibrotic disorders of the lung where oxidative stress plays a role, such as for idiopathic pulmonary fibrosis, a disease that still represents a major challenge to medical treatment.     

A senescent cell bystander effect: senescence-induced senescence

Senescent cells produce and secrete various bioactive molecules including interleukins, growth factors, matrix-degrading enzymes and reactive oxygen species (ROS). Thus, it has been proposed that senescent cells can damage their local environment, and a stimulatory effect on tumour cell growth and invasiveness has been documented. However, it was unknown what effect, if any, senescent cells have on their normal, proliferation-competent counterparts. We show here that senescent cells induce a DNA damage response, characteristic for senescence, in neighbouring cells via gap junction-mediated cell-cell contact and processes involving ROS. Continuous exposure to senescent cells induced cell senescence in intact bystander fibroblasts. Hepatocytes bearing senescence markers clustered together in mice livers. Thus, senescent cells can induce a bystander effect, spreading senescence towards their neighbours in vitro and, possibly, in vivo.     

Carnosine Inhibits the Proliferation of Human Gastric Cancer SGC-7901 Cells through Both of the Mitochondrial Respiration and Glycolysis Pathways

Carnosine, a naturally occurring dipeptide, has been recently demonstrated to possess anti-tumor activity. However, its underlying mechanism is unclear. In this study, we investigated the effect and mechanism of carnosine on the cell viability and proliferation of the cultured human gastric cancer SGC-7901 cells. Carnosine treatment did not induce cell apoptosis or necrosis, but reduced the proliferative capacity of SGC-7901 cells. Seahorse analysis showed SGC-7901 cells cultured with pyruvate have active mitochondria, and depend on mitochondrial oxidative phosphorylation more than glycolysis pathway for generation of ATP. Carnosine markedly decreased the absolute value of mitochondrial ATP-linked respiration, and reduced the maximal oxygen consumption and spare respiratory capacity, which may reduce mitochondrial function correlated with proliferative potential. Simultaneously, carnosine also reduced the extracellular acidification rate and glycolysis of SGC-7901 cells. Our results suggested that carnosine is a potential regulator of energy metabolism of SGC-7901 cells both in the anaerobic and aerobic pathways, and provided a clue for preclinical and clinical evaluation of carnosine for gastric cancer therapy.     

Solute leakage, lipid peroxidation, and protein degradation during the senecence of Iris tepals

A colour change and inrolling of the tepal edges are the first symptoms of senescence of Iris flowers ( Iris x hollandica Tub., cv. Blue Magic). Tepals showed an increase in leakage of both ions and anthocyanins, prior to the visible senescence symptoms. Increased leakage occurred irrespective of the time at which the tepals were severed and placed in water, indicating that the senescence process is inherent in the tepal cells. Net loss of proteins in the tepal edges started after flower opening, and after two more days, when the first symptoms of senescence were observed, the protein level was only 20% of that at harvest. Cycloheximide delayed senescence and resulted in a lower rate of protein loss. Phenylmethylsulfony fluoride (PMSF), a protease inhibitor, had a similar effect on protein levels but did not affect the time to visible senescence, and also several other protease inhibitors did not affect the time to senescence.
During senescence the rate of respiration of the tepals remained unchanged and their rate of ethylene production decreaased. The rate of ethane production, an indicator of lipid peroxidation, was very low and remained unaltered. Antioxidants ( l ascorbic acid, benzoic acid, butylated hydroxytoluene, diphenylamine, propyl gallate, propyl- p -hydroxybenzoate and sodium benzoate) had no effect on the time to tepal senescence. It is concluded that tepal wilting is due to transfer of solutes from the symplast to the apoplast. Although net protein degradation occurs early during the senescence process, its inhibition is not correlated with a delay in the time to senescence. Furthermore, the results do not support the hypothesis that the increase in solute leakage is due to (free radical-mediated) peroxidation of membrane lipids. The present results are in contrast with the ethylene-regulated petal senescence of carnation, which is accompanied by lipid peroxidation.     

N-t-butyl hydroxylamine, a hydrolysis product of alpha-phenyl-N-t-butyl nitrone, is more potent in delaying senescence in human lung fibroblasts

Alpha-phenyl-N-t-butyl nitrone (PBN), a spin trap, scavenges hydroxyl radicals, protects tissues from oxidative injury, and delays senescence of both normal human lung fibroblasts (IMR90) and senescence-accelerated mice. N-t-butyl hydroxylamine and benzaldehyde are the breakdown products of PBN. N-t-Butyl hydroxylamine delays senescence of IMR90 cells at concentrations as low as 10 microM compared with 200 microM PBN to produce a similar effect, suggesting that N-t-butyl hydroxylamine is the active form of PBN. N-Benzyl hydroxylamine and N-methyl hydroxylamine compounds unrelated to PBN were also effective in delaying senescence, suggesting the active functional group is the N-hydroxylamine. All the N-hydroxylamines tested significantly decreased the endogenous production of oxidants, as measured by the oxidation of 2', 7'-dichlorodihydrofluorescin and the increase in the GSH/GSSG ratio. The acceleration of senescence induced by hydrogen peroxide is reversed by the N-hydroxylamines. DNA damage, as determined by the level of apurinic/apyrimidinic sites, also decreased significantly following treatment with N-hydroxylamines. The N-hydroxylamines appear to be effective through mitochondria; they delay age-dependent changes in mitochondria as measured by accumulation of rhodamine-123, they prevent reduction of cytochrome C(FeIII) by superoxide radical, and they reverse an age-dependent decay of mitochondrial aconitase, suggesting they react with the superoxide radical.     

Carnosine as a stimulator of cytotoxic and phagocytic function of peritoneal macrophages]

Biochemical changes in peritoneal macrophages and their relatedness to the cytostatic and phagocytotic function in C3HA mice injected with a single intraperitoneal dose of 0.45 mM carnosine and 4-methyluracil or stimulated with peptone have been studied. During the first 24 hours after injection both carnosine and 4-methyluracil increase the activity of adenosine deaminase and purine nucleoside phosphorylase, the key enzymes of purine catabolism which is the main source of O2-. radicals in macrophages. In carnosine-stimulated macrophages the activity of membrane 5'-AMP nucleotidase decreases on days 1-3 after injection which points to alleviation of adenosine-induced inhibition as well as to macrophage activation. Carnosine increases the cytostatic and phagocytotic activities of macrophage coupled to O2-. production. The mechanism of the stimulating effect of carnosine on macrophages seems to consist in the dipeptide interaction with specific receptors localized on the plasma membrane of macrophagal cells.     

Chemoprotective effects of carnosine against genotoxicity induced by cyclophosphamide in mice bone marrow cells

The protective effects of carnosine as a natural dipeptide were investigated in mouse bone marrow cells against genotoxicity induced by cyclophosphamide. Mice were injected with solutions of carnosine at three different doses (10, 50 and 100?mg kg(-1) bw) for five consecutive days. On the fifth day of treatment, mice were injected cyclophosphamide and killed after 24?h. The frequency of micronuclei in polychromatic erythrocytes and the ratio of polychromatic erythrocyte/polychromatic erythrocyte?+?normochromatic erythrocyte [PCE/(PCE?+?NCE)] were evaluated by May-Grunwald/Giemsa staining. Histopathology of bone marrow was examined in mice treated with cyclophosphamide and carnosine. Carnosine significantly reduced micronucleated polychromatic erythrocytes (MnPCEs) induced by cyclophosphamide at all three doses. Carnosine at dose of 100?mg kg(-1) bw reduced MnPCEs 3.76-fold and completely normalized the PCE/(PCE?+?NCE) ratio. Administration of carnosine inhibited bone marrow toxicity induced by cyclophosphamide. It appeared that carnosine with protective activity reduced the oxidative stress and genotoxicity induced by cyclophosphamide in bone marrow cells of mice. Copyright ? 2012 John Wiley & Sons, Ltd.     

Senescence-Accelerated Mouse (SAM) with Special References to Neurodegeneration Models,SAMP8 and SAMP10 Mice

The SAM strains, a group of related inbred strains consisting of senescence-prone inbred strains (SAMP) and senescence-resistant inbred strains (SAMR), have been successfully developed by selective inbreeding of the AKR/J strain of mice donated by the Jackson laboratory in 1968. The characteristic feature of aging common to the SAMP and SAMR is accelerated senescence and normal aging, respectively. Furthermore, SAMP and SAMR strains of mice manifest various pathobiological phenotypes spontaneously. Among SAMP strains, SAMP8 and SAMP10 mice show age-related behavioral deterioration such as deficits in learning and memory, emotional disorders (reduced anxiety-like behavior and depressive behavior) and altered circadian rhythm associated with certain pathological, biochemical and pharmacological changes. Here, the previous and recent literature on SAM mice are reviewed with an emphasis on SAMP8 and SAMP10 mice. A spontaneous model like SAM with distinct advantages over the gene-modified model is hoped by investigators to be used more widely as a biogerontological resource to explore the etiopathogenesis of accelerated senescence and neurodegenerative disorders.     

Water stress, ammonium, and leaf senescence in detached rice leaves

Ammonium accumulation in relation to water stress-promoted senescence of detached rice leaves was investigated. The effect of water stress on the senescence of detached rice leaves is associated with the accumulation of ammonium. The accumulation of ammonium in detached rice leaves by water stress is attributed to a decrease in glutamine synthetase activity. Ammonium accumulation in detached rice leaves, induced by water stress, was accompanied by an increase in tissue sensitivity to ethylene which, in turn, accelerated leaf senescence.     

Carnosine treatment largely prevents alterations of renal carnosine metabolism in diabetic mice

Recently, we identified an allelic variant of human carnosinase 1 (CN1) that results in increased enzyme activity and is associated with susceptibility for diabetic nephropathy in humans. Investigations in diabetic (db/db) mice showed that carnosine ameliorates glucose metabolism effectively. We now investigated the renal carnosinase metabolism in db/db mice. Kidney CN1 activity increased with age and was significantly higher in diabetic mice compared to controls. Increased CN1 activity did not affect renal carnosine levels, but anserine concentrations were tenfold lower in db/db mice compared to controls (0.24±0.2 vs. 2.28±0.3 nmol/mg protein in controls; p<0.001). Homocarnosine concentrations in kidney tissue were low in both control and db/db mice (below 0.1 nmol/mg protein, p=n.s.). Carnosine treatment for 4 weeks substantially decreased renal CN1 activity in diabetic mice (0.32±0.3 in non-treated db/db vs. 0.05±0.05 μmol/mg/h in treated db/db mice; p<0.01) close to normal activities. Renal anserine concentrations increased significantly (0.24±0.2 in non-treated db/db vs. 5.7±1.2 μmol/mg/h in treated db/db mice; p<0.01), while carnosine concentrations remained unaltered (53±6.4 in non-treated vs. 61±15 nmol/mg protein in treated db/db mice; p=n.s.). Further, carnosine treatment halved proteinuria and reduced vascular permeability to one-fifth in db/db mice. In renal tissue of diabetic mice carnosinase activity is significantly increased and anserine concentrations are significantly reduced compared to controls. Carnosine treatment largely prevents the alterations of renal carnosine metabolism.