Colocalization of a carnosine-splitting enzyme, tissue carnosinase (CN2)/cytosolic non-specific dipeptidase 2 (CNDP2), with histidine decarboxylase in the tuberomammillary nucleus of the hypothalamus

Dual Effect of Carnosine on ROS Formation in Rat Cultured Cortical Astrocytes

Carnosine is composed of β-alanine and L-histidine and is considered to be an important neuroprotective agent with antioxidant, metal chelating, and antisenescence properties. However, children with serum carnosinase deficiency present increased circulating carnosine and severe neurological symptoms. We here investigated the in vitro effects of carnosine on redox and mitochondrial parameters in cultured cortical astrocytes from neonatal rats. Carnosine did not alter mitochondrial content or mitochondrial membrane potential. On the other hand, carnosine increased mitochondrial superoxide anion formation, levels of thiobarbituric acid reactive substances and oxidation of 2',7'-dichlorofluorescin diacetate (DCF-DA), indicating that carnosine per se acts as a pro-oxidant agent. Nonetheless, carnosine prevented DCF-DA oxidation induced by H2O2 in cultured cortical astrocytes. Since alterations on mitochondrial membrane potential are not likely to be involved in these effects of carnosine, the involvement of N-Methyl-D-aspartate (NMDA) receptors in the pro-oxidant actions of carnosine was investigated. MK-801, an antagonist of NMDA receptors, prevented DCF-DA oxidation induced by carnosine in cultured cortical astrocytes. Astrocyte reactivity induced by carnosine was also prevented by the coincubation with MK-801. The present study shows for the very first time the pro-oxidant effects of carnosine per se in astrocytes. The data raise awareness on the importance of a better understanding of the biological actions of carnosine, a nutraceutical otherwise widely reported as devoid of side effects.

Exploring the structural and dynamic differences between human carnosinase I (CN1) and II (CN2)

Human carnosinases (CNs) are dimeric dipeptidases in the metallopeptidase M20 family. Two isoforms of carnosinases (Zn²⁺ -containing carnosinase 1 (CN1) found in serum and Mn²⁺ -carnosinase 2 (CN2) in tissue) were identified. Both CNs cleave histidine-containing (Xaa-His) dipeptides such as carnosine where CN2 was found to accept a broader spectrum of substrates. A loss of CN function, resulting in a high carnosine concentration, reduces risk for diabetes and neurological disorders. Although several studies on CN activities and its Michaelis complex were conducted, all shed the light on CN1 activity where the CN2 data is limited. Also, the molecular details on CN1 and CN2 similarity and dissimilarity in structure and function remain unclear. Thus, in this work, molecular dynamics (MD) simulations were employed to study structure and dynamics of human CN1 and CN2 in comparison. The results show that the different catalytic ability of both CNs is due to their pocket size and environment. CN2 can accept a wider range of substrate due to the wider mouth of a binding pocket. The L1 loop seems to play a role in gating activity. Comparing to CN2, CN1 provides more electronegative entrance, more wettability, and higher stability of catalytic metal ion-pair in the active site which allow more efficient water-mediated catalysis. The microscopic understanding obtained here can serve as a basis for CN inhibition strategies resulting in higher carnosine levels and consequently mitigating complications associated with diseases such as diabetes and neurological disorder.

Investigation of cattle plasma proteome in response to pain and inflammation using next generation proteomics technique, SWATH-MS

Pain assessment in farm animals has primarily relied on a combination of behavioral and physiological responses, although these are relatively subjective and difficult to quantify. It is essential to develop more effective biomarkers of pain in production animals since they are frequently exposed to routine surgical husbandry procedures. More effective biomarkers of pain would improve welfare, limit the loss of productivity associated with pain and permit better assessment of analgesics. This study aimed to investigate the use of a modern mass spectrometry data independent acquisition strategy, termed Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS), to detect candidate protein biomarkers that are known to associate with nociceptive and inflammatory processes in cattle, which could then be used to assess the efficacy of potential analgesics. Calves were randomly divided into two groups that were either surgically dehorned or subjected to restraint stress, without provision of anaesthesia or analgesia in accordance with current industry standards. Samples were analysed before and after dehorning at multiple timepoints. Significant changes in protein concentrations were detected predominantly at 24 and 96 h following dehorning, including kininogens, proteins associated with the coagulation and complement cascades and serine protease inhibitors. Gene ontology analysis revealed that the identified candidate biomarkers were associated with stress, wound healing, immune response, blood coagulation and the inflammatory and acute phase responses, which could be expected following surgical damage to tissues, but can now be more objectively assessed. These results offer more definitive and quantitative monitoring of response to tissue injury induced pain and inflammation.

The iTRAQ-based quantitative proteomics reveals metabolic changes in Scylla paramamosain under different light intensities during indoor overwintering

Light intensity is one of the ecological factors that appreciably affects the metabolism of Scylla paramamosain during overwintering. This study adopted the isobaric tag for relative and absolute quantitation (iTRAQ) method to investigate metabolic changes of S. paramamosain under three illumination levels (0, 1.43 and 40.31 μmol m^-2·s^-1) for four months during indoor overwintering. The iTRAQ identified 3282 proteins, among which 267 exhibited significant differential expression (122 upregulated and 145 downregulated) in the low light group, and 299 with significant differential expression (252 upregulated and 47 downregulated) in the high light group. Analysis of these results showed that there were different metabolic regulatory patterns under different light intensities. Low light is more conducive to the survival of S. paramamosain, which needs to produce and consume relatively less energy to sustain physiological activities. Thus, the essential proteins associated with physiological activities were significantly upregulated, while those related to energy production were significantly downregulated. In contrast, high light exerts a certain stress on the survival of S. paramamosain and required more energy to cope with this stress, which forced a significant upregulation of proteins related to stress response and energy production. The findings of this study highlighted the metabolic regulatory mechanisms of S. paramamosain under different light intensities.

Carnosinase, diabetes mellitus and the potential relevance of carnosinase deficiency

Carnosinase (CN1) is a dipeptidase, encoded by the CNDP1 gene, that degrades histidine-containing dipeptides, such as carnosine, anserine and homocarnosine. Loss of CN1 function (also called carnosinase deficiency or aminoacyl-histidine dipeptidase deficiency) has been reported in a small number of patients with highly elevated blood carnosine concentrations, denoted carnosinaemia; it is unclear whether the variety of clinical symptoms in these individuals is causally related to carnosinase deficiency. Reduced CN1 function should increase serum carnosine concentrations but the genetic basis of carnosinaemia has not been formally confirmed to be due to CNDP1 mutations. A CNDP1 polymorphism associated with low CN1 activity correlates with significantly reduced risk for diabetic nephropathy, especially in women with type 2 diabetes, and may slow progression of chronic kidney disease in children with glomerulonephritis. Studies in rodents demonstrate antiproteinuric and vasculoprotective effects of carnosine, the precise molecular mechanisms, however, are still incompletely understood. Thus, carnosinemia due to CN1 deficiency may be a non-disease; in contrast, carnosine may potentially protect against long-term sequelae of reactive metabolites accumulating, e.g. in diabetes and chronic renal failure.

The clinical pharmacology of non-sedating antihistamines

We previously reported on brain H₁ receptor occupancy measurements of antihistamines in human brain using [¹¹C]doxepin and positron emission tomography (PET). We proposed the use of brain H₁ receptor occupancy to classify antihistamines objectively into three categories of sedating, less-sedating, and non-sedating antihistamines according to their sedative effects. Non-sedating antihistamines are recommended for the treatment of allergies such as pollinosis and atopic dermatitis because of their low penetration into the central nervous system. Physicians and pharmacists are responsible for fully educating patients about the risks of sedating antihistamines from pharmacological points of view. If a sedating antihistamine must be prescribed, its sedative effects should be thoroughly considered before choosing the drug. Non-sedating antihistamines should be preferentially used whenever possible as most antihistamines are equally efficacious, while adverse effects of sedating antihistamines can be serious. This review summarizes the pharmacological properties of clinically useful non-sedating antihistamines from the perspective of histamine function in the CNS.

Carnosine Attenuates the Development of both Type 2 Diabetes and Diabetic Nephropathy in BTBR ob/ob Mice

We previously demonstrated that polymorphisms in the carnosinase-1 gene (CNDP1) determine the risk of nephropathy in type 2 diabetic patients. Carnosine, the substrate of the enzyme encoded by this gene, is considered renoprotective and could possibly be used to treat diabetic nephropathy (DN). In this study, we examined the effect of carnosine treatment in vivo in BTBR (Black and Tan, BRachyuric) ob/ob mice, a type 2 diabetes model which develops a phenotype that closely resembles advanced human DN. Treatment of BTBR ob/ob mice with 4 mM carnosine for 18 weeks reduced plasma glucose and HbA1c, concomitant with elevated insulin and C-peptide levels. Also, albuminuria and kidney weights were reduced in carnosine-treated mice, which showed less glomerular hypertrophy due to a decrease in the surface area of Bowman's capsule and space. Carnosine treatment restored the glomerular ultrastructure without affecting podocyte number, resulted in a modified molecular composition of the expanded mesangial matrix and led to the formation of carnosine-acrolein adducts. Our results demonstrate that treatment with carnosine improves glucose metabolism, albuminuria and pathology in BTBR ob/ob mice. Hence, carnosine could be a novel therapeutic strategy to treat patients with DN and/or be used to prevent DN in patients with diabetes.

Evidence for an essential role of intradimer interaction in catalytic function of carnosine dipeptidase II using electrospray-ionization mass spectrometry

Carnosine dipeptidase II (CN2/CNDP2) is an M20 family metallopeptidase that hydrolyses various dipeptides including β-alanyl-L-histidine (carnosine). Crystallographic analysis showed that CN2 monomer is composed of one catalytic and one dimerization domains, and likely to form homodimer. In this crystal, H228 residue of the dimerization domain interacts with the substrate analogue bestatin on the active site of the dimer counterpart, indicating that H228 is involved in enzymatic reaction. In the present study, the role of intradimer interaction of CN2 in its catalytic activity was investigated using electrospray-ionization time-of-flight mass spectrometry (ESI-TOF MS). First, a dimer interface mutant I319K was prepared and shown to be present as a folded monomer in solution as examined by using ESI-TOF MS. Since the mutant was inactive, it was suggested that dimer formation is essential to its enzymatic activity. Next, we prepared H228A and D132A mutant proteins with different N-terminal extended sequences, which enabled us to monitor dimer exchange reaction by ESI-TOF MS. The D132A mutant is a metal ligand mutant and also inactive. But the activity was partially recovered time-dependently when H228A and D132A mutant proteins were incubated together. In parallel, H228A/D132A heterodimer was formed as detected by ESI-TOF MS, indicating that interaction of a catalytic center with H228 residue of the other subunit is essential to the enzymatic reaction. These results provide evidence showing that intradimer interaction of H228 with the reaction center of the dimer counterpart is essential to the enzymatic activity of CN2.

Carnosine and Related Peptides: Therapeutic Potential in Age-Related Disorders

Imidazole dipeptides (ID), such as carnosine (β-alanyl-L-histidine), are compounds widely distributed in excitable tissues of vertebrates. ID are also endowed of several biochemical properties in biological tissues, including antioxidant, bivalent metal ion chelating, proton buffering, and carbonyl scavenger activities. Furthermore, remarkable biological effects have been assigned to such compounds in age-related human disorders and in patients whose activity of serum carnosinase is deficient or undetectable. Nevertheless, the precise biological role of ID is still to be unraveled. In the present review we shall discuss some evidences from clinical and basic studies for the utilization of ID as a drug therapy for age-related human disorders.

Patenting strategies, the authentication US fiscal methodology, discovery and development of imidazole-containing peptide compounds with free-radical scavenging and transglycating properties acting as targeted drug regulators and homeostatic agents with diverse therapeutic activities for pharmacy of diabetes and metabolic diseases

INTRODUCTION

Diabetes mellitus is the seventh-leading cause of death in the US and diabetic complications are interlaced with specific diverse microvascular and macrovascular pathologies resulting from hyperglycemia. The society should expand prowess and patenting of biotechnology to cure disease and complications.

AREAS COVERED

The work summarizes biological activities of patented carnosine mimetics resistant in formulations to enzymatic hydrolysis with human carnosinases that are acting as a universal form of antioxidant, deglycating and transglycating agents that inhibit sugar-mediated protein crosslinking, chelate or inactivate a number of transition metal ions (including ferrous and copper ions), possess lipid peroxidase type of activity and protection of antioxidant enzymes from inactivation. L-Carnosine released systemically from N-acetylcarnosine lubricant eye drops or from skeletal muscle during exercise is transported into hypothalamic tuberomammillary nucleus-histamine neurons and hydrolyzed. The resulting L-histidine is subsequently converted into histamine acting as metabolic fuel feeding for the hypothalamic histaminergic system. This mechanism is responsible for the effects of L-carnosine on autonomic neurotransmission and physiological function of pancreas, stimulating in vivo regeneration of insulin-producing β cells.

EXPERT OPINION

Therapeutic benefits for imidazole-containing antioxidants (nutraceutical non-hydrolyzed carnosine, carcinine, D-carnosine, ophthalmic prodrug N-acetylcarnosine, leucyl-histidylhydrazide and patented formulations thereof) are an essential part of diabetes treatment.

Insufficient intake of L-histidine reduces brain histamine and causes anxiety-like behaviors in male mice

L-histidine is one of the essential amino acids for humans, and it plays a critical role as a component of proteins. L-histidine is also important as a precursor of histamine. Brain histamine is synthesized from L-histidine in the presence of histidine decarboxylase, which is expressed in histamine neurons. In the present study, we aimed to elucidate the importance of dietary L-histidine as a precursor of brain histamine and the histaminergic nervous system. C57BL/6J male mice at 8 wk of age were assigned to 2 different diets for at least 2 wk: the control (Con) diet (5.08 g L-histidine/kg diet) or the low L-histidine diet (LHD) (1.28 g L-histidine/kg diet). We measured the histamine concentration in the brain areas of Con diet-fed mice (Con group) and LHD-fed mice (LHD group). The histamine concentration was significantly lower in the LHD group [Con group vs. LHD group: histamine in cortex (means ± SEs): 13.9 ± 1.25 vs. 9.36 ± 0.549 ng/g tissue; P = 0.002]. Our in vivo microdialysis assays revealed that histamine release stimulated by high K(+) from the hypothalamus in the LHD group was 60% of that in the Con group (P = 0.012). However, the concentrations of other monoamines and their metabolites were not changed by the LHD. The open-field tests showed that the LHD group spent a shorter amount of time in the central zone (87.6 ± 14.1 vs. 50.0 ± 6.03 s/10 min; P = 0.019), and the light/dark box tests demonstrated that the LHD group spent a shorter amount of time in the light box (198 ± 8.19 vs. 162 ± 14.1 s/10 min; P = 0.048), suggesting that the LHD induced anxiety-like behaviors. However, locomotor activity, memory functions, and social interaction did not differ between the 2 groups. The results of the present study demonstrated that insufficient intake of histidine reduced the brain histamine content, leading to anxiety-like behaviors in the mice.

Interactive cellular proteins related to classical swine fever virus non-structure protein 2 by yeast two-hybrid analysis

Classical swine fever is caused by the classical swine fever virus (CSFV), which has a special affinity to endothelial cells. This fever is characterized by hemorrhage and necrosis of vascular injury. Very little information is available on the interaction between vascular endothelial cells and CSFV. In the current report, the cDNA library of swine umbilical vein endothelial cell (SUVEC) was constructed by the switching mechanism at 5' end of the RNA transcript approach. The yeast two-hybrid (Y2H) system was adopted to screen non-structure 2 protein (NS2) interactive proteins in the SUVEC line. Alignment with the NCBI database revealed 11 interactive proteins: GOPC, HNRNPH1, DNAJA1, ATP6, CSDE1, CNDP2, FANCL, TMED4, DNAJA4, MOAP1, and PNMA1. These proteins were mostly related to apoptosis, stress response and oxidation reduction, or metabolism. In the protein interaction network constructed based on proteins with NS2, the more important proteins were MOAP1, DNAJA1, GOPC, FANCL, TMED4, and CSDE1. The interactions detected by the Y2H should be regarded only as preliminary indications. However, the CSFV NS2 interactive proteins in the SUVEC cDNA library obtained in the current study provides valuable information for gaining a better understanding of the host protein-virus interactions of the CSFV NS2 protein.

Anti-stress effects of carnosine on restraint-evoked immunocompromise in mice through spleen lymphocyte number maintenance

Carnosine (β-alanyl-L-histidine), a naturally occurring dipeptide, has been characterized as a putative neurotransmitter and serves as a reservoir for brain histamine, which could act on histaminergic neurons system to relieve stress-induced damages. However, understanding of the role of carnosine in stress-evoked immunocompromise is limited. In this study, results showed that when mice were subjected to restraint stress, spleen index and the number of spleen lymphocytes including Natural Killer (NK) cells were obviously decreased. Results also demonstrated that restraint stress decreased the cytotoxic activity of NK cells per spleen (LU₁₀/spleen) while the activity of a single NK cell (LU₁₀/10⁶ cells) was not changed. However, oral administration of carnosine (150 and 300 mg/kg) increased spleen index and number of spleen lymphocytes (including NK cells), and elevated the cytotoxic activity of NK cells per spleen in restraint-stressed mice. These results indicated that carnosine ameliorated stress-evoked immunocompromise through spleen lymphocyte number maintenance. Carnosine was further found to reduce stress-induced elevation of plasma corticosterone level. On the other hand, results showed that carnosine and RU486 (a glucocorticoids receptor antagonist) treatment prevented the reduction in mitochondrion membrane potential and the release of mitochondrial cytochrome c into cytoplasm, increased Bcl-2/Bax mRNA ratio, as well as decreased terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells in spleen lymphocytes of stressed mice. The results above suggested that the maintenance of spleen lymphocyte number by carnosine was related with the inhibition of lymphocytes apoptosis caused by glucocorticoids overflow. The stimulation of lymphocyte proliferation by carnosine also contributed to the maintenance of spleen lymphocyte number in stressed mice. In view of the elevated histamine level, the anti-stress effects of carnosine on restraint-evoked immunocompromise might be via carnosine-histamine metabolic pathway. Taken together, carnosine maintained spleen lymphocyte number by inhibiting lymphocyte apoptosis and stimulating lymphocyte proliferation, thus prevented immunocompromise in restraint-stressed mice.

Proteomic profiling of the substantia nigra demonstrates CNDP2 overexpression in Parkinson's disease

Despite decades of intensive investigations, the precise sequence of molecular events and the specific proteins mediating the degenerative process underlying Parkinson's disease (PD) remain unraveled. Proteomic strategies may provide unbiased tools to identify novel candidates and explore original mechanisms involved in PD. Substantia nigra pars compacta (SN) tissue, whose degeneration is the hallmark of PD, was dissected from neuropathologically confirmed PD patients (n=3) and control subjects (n=3), before being submitted to a comparative 2-DE analysis. The present study revealed a subset of neuronal and/or glial proteins that appears to be deregulated in PD and likely to contribute to neurodegeneration. Observed alterations not only consolidate well accepted concepts surrounding PD pathogenesis such as oxidative stress and mitochondrial dysfunction but also point out to novel pathways. Among the latter, cytosolic non specific dipeptidase 2 (CNDP2), a relatively unknown protein not yet reported to be associated with PD pathogenesis, was shown to be increased in the SN of PD patients, as confirmed by Western blot. Immunohistochemical analyses demonstrated the presence of CNDP2 within the cytoplasm of SN dopaminergic neurons. Altogether, our findings support a key role of CNDP2 in PD neurodegeneration, by mechanisms that could involve oxidative stress, protein aggregation or inflammation. This article is part of a Special Issue entitled: Translational Proteomics.

Carnosine ameliorates stress-induced glucose metabolism disorder in restrained mice

Carnosine is a natural dipeptide that has shown multiple benefits in the treatment of various diseases. This study investigated the ameliorative effects of carnosine on glucose metabolism in restraint-stressed mice. Our results showed that restraint stress could significantly influence glucose metabolism, as reflected by lowered glucose tolerance, hepatic and muscle glycogen content, and increased plasma corticosterone concentration in mice. Oral administration of carnosine (150 and 300 mg/kg) not only reverted stress-induced decline in glucose tolerance and glycogen content in liver and muscle, but also reduced plasma corticosterone level. Carnosine has also significantly suppressed mRNA expression of glucose-6-phosphatase, while elevating glycogen synthase 2, glucokinase and glucose transporter 2 expressions in the liver. The obtained results demonstrated the harmful effects induced by restraint stress, while proving that carnosine could ameliorate stress-induced glucose metabolism disturbance. It is presumable that carnosine exerts its anti-stress effects by indirectly affecting the histaminergic neuron system, modulating the stress-activated hypothalamic-pituitary-adrenal axis and improving glucose metabolism through regulation of the enzymes in the glucose metabolic pathways.

Proteomic analysis of rat brains in a model of neuropathic pain following exposure to electroconvulsive stimulation

Some reports have shown that electroconvulsive shock therapy is effective for treating refractory neuropathic pain. However, its mechanism of action remains unknown. This study analyzes changes in protein expression in the brainstems of neuropathic pain model rats with or without electroconvulsive stimulation (ECS). A neuropathic pain model rat is produced by chronic constrictive injury (CCI) of the sciatic nerve. An ECS was administered to rodents once daily for 6 days after the CCI operation. After ECS, the latency to withdrawal from thermal stimulation was significantly increased. The expression of several proteins was changed after CCI. Ten proteins that increased after CCI then had decreased expression levels (close to control) after ECS, and 8 proteins that decreased after CCI then had increased expression levels (close to control) after ECS. In conclusion, ECS improved thermal hypersensitivity in a rat CCI model. Proteomic analysis showed that altered expression levels of proteins in the brainstem of CCI model rats returned to close to control levels after ECS, including many proteins associated with pain. This trend suggests an association of ECS with improved hypersensitivity, and these results may help elucidate the mechanism of this effect.