Novel copper amine oxidase activity from rat liver mitochondria matrix

Construction and validation of cuproptosis-related lncRNA prediction signature for bladder cancer and immune infiltration analysis

Bladder cancer (BC) is a common urologic tumor with a high recurrence rate. Cuproptosis and long noncoding RNAs (lncRNAs) have demonstrated essential roles in the tumorigenesis of many malignancies. Nevertheless, the prognostic value of cuproptosis-related lncRNA (CRLs) in BC is still unclear. The public data used for this study were acquired from the Cancer Genome Atlas database. A comprehensive exploration of the expression profile, mutation, co-expression, and enrichment analyses of cuproptosis-related genes was performed. A total of 466 CRLs were identified using Pearson's correlation analysis. 16 prognostic CRLs were then retained by univariate Cox regression. Unsupervised clustering divided the patients into two clusters with diverse survival outcomes. The signature consists of 7 CRLs was constructed using the least absolute shrinkage and selection operator (LASSO) Cox regression analyses. Survival curves and receiver operating characteristics showed the prognostic signature possessed good predictive value, which was validated in the testing and entire sets. The reliability and stability of our signature were further confirmed by stratified analysis. Additionally, the signature-based risk score was confirmed as an independent prognostic factor. Gene set enrichment analysis showed molecular alteration in the high-risk group was closely associated with cancer. We then developed the clinical nomogram using independent prognostic indicators. Notably, the infiltration of immune cells and expression of immune checkpoints were higher in the high-risk group, suggesting that they may benefit more from immunotherapy. In summary, the prognostic signature might effectively predict the prognosis and provide new insight into the clinical treatment of BC patients.

Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?

Agmatine, the decarboxylation product of arginine, was largely neglected as an important player in mammalian metabolism until the mid-1990s, when it was re-discovered as an endogenous ligand of imidazoline and α2-adrenergic receptors. Since then, a wide variety of agmatine-mediated effects have been observed, and consequently agmatine has moved from a wallflower existence into the limelight of clinical neuroscience research. Despite this quantum jump in scientific interest, the understanding of the anabolism and catabolism of this amine is still vague. The purification and biochemical characterization of natural mammalian arginine decarboxylase and agmatinase still are open issues. Nevertheless, the agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review. Particularly with respect to major depression, agmatine, its derivatives, and metabolizing enzymes show great promise for the development of an improved treatment of this common disease.

Milestones and recent discoveries on cell death mediated by mitochondria and their interactions with biologically active amines

Mitochondria represent cell "powerhouses," being involved in energy transduction from the electrochemical gradient to ATP synthesis. The morphology of their cell types may change, according to various metabolic processes or osmotic pressure. A new morphology of the inner membrane and mitochondrial cristae, significantly different from the previous one, has been proposed for the inner membrane and mitochondrial cristae, based on the technique of electron tomography. Mitochondrial Ca(2+) transport (the transporter has been isolated) generates reactive oxygen species and induces the mitochondrial permeability transition of both inner and outer mitochondrial membranes, leading to induction of necrosis and apoptosis. In the mitochondria of several cell types (liver, kidney, and heart), mitochondrial oxidative stress is an essential step in the induction of cell death, although not in brain, in which the phenomenon is caused by a different mechanism. Mitochondrial permeability transition drives both apoptosis and necrosis, whereas mitochondrial outer membrane permeability is characteristic of apoptosis. Adenine nucleotide translocase remains the most important component involved in membrane permeability, with the opening of the transition pore, although other proteins, such as ATP synthase or phosphate carriers, have been proposed. Intrinsic cell death is triggered by the release from mitochondria of proteic factors, such as cytochrome c, apoptosis inducing factor, and Smac/DIABLO, with the activation of caspases upon mitochondrial permeability transition or mitochondrial outer membrane permeability induction. Mitochondrial permeability transition induces the permeability of the inner membrane in sites in contact with the outer membrane; mitochondrial outer membrane permeability forms channels on the outer membrane by means of various stimuli involving Bcl-2 family proteins. The biologically active amines, spermine, and agmatine, have specific functions on mitochondria which distinguish them from other amines. Enzymatic oxidative deamination of spermine by amine oxidases in tumor cells may produce reactive oxygen species, leading to transition pore opening and apoptosis. This process could be exploited as a new therapeutic strategy to combat cancer.

Protective Effects of Agmatine against Chlorpromazine- Induced Toxicity in the Liver of Wistar Rats

The metabolic pathways of chlorpromazine (CPZ) toxicity were tracked by assessing oxidative/nitrosative stress markers. The main objective of the study was to test the hypothesis that agmatine (AGM) prevents oxidative/nitrosative stress in the liver of Wistar rats 15 days after administration of CPZ. All tested substances were administered intraperitoneally (i.p.) for 15 consecutive days. The rats were divided into four groups: the control group (C, 0.9 % saline solution), the CPZ group (CPZ, 38.7 mg/kg b.w.), the CPZ+AGM group (AGM, 75 mg/kg b.w. immediately after CPZ, 38.7 mg/kg b.w. i.p.) and the AGM group (AGM, 75 mg/kg b.w.).

Rats were decapitated 15 days after the appropriate treatment. In the CPZ group, CPZ concentration was significantly increased compared to C values (p<0.01), while AGM treatment induced the significant decrease in CPZ concentration in the CPZ+AGM group (p<0.05) and the AGM group (p<0.01). CPZ application to healthy rats did not lead to any changes of lipid peroxidation in the liver compared to the C group, but AGM treatment decreased that parameter compared to the CPZ group (p<0.05). In CPZ liver homogenates, nitrite and nitrate concentrations were increased compared to controls (p<0.001), and AGM treatment diminished that parameter in the CPZ group (p<0.05), as well as in the AGM group (p<0.001). In CPZ animals, glutathione level and catalase activity were decreased in comparison with C values (p<0.01 respectively), but AGM treatment increased the activity of catalase in comparison with CPZ animals (p<0.05 respectively). Western blot analysis supported biochemical findings in all groups. Our results showed that treatment with AGM significantly supressed the oxidative/nitrosative stress parameters and restored antioxidant defense in rat liver.

A novel enzyme with spermine oxidase properties in bovine liver mitochondria: identification and kinetic characterization

The uptake of spermine into mammalian mitochondria indicated the need to identify its catabolic pathway in these organelles. Bovine liver mitochondria were therefore purified and their capacity for natural polyamine uptake was verified. A kinetic approach was then used to determine the presence of an MDL 72527-sensitive enzyme with spermine oxidase activity in the matrix of bovine liver mitochondria. Western blot analysis of mitochondrial fractions and immunogold electron microscopy observations of purified mitochondria unequivocally confirmed the presence of a protein recognized by anti-spermine oxidase antibodies in the mitochondrial matrix. Preliminary kinetic characterization showed that spermine is the preferred substrate of this enzyme; lower activity was detected with spermidine and acetylated polyamines. Catalytic efficiency comparable to that of spermine was also found for 1-aminododecane. The considerable effect of ionic strength on the Vmax/KM ratio suggested the presence of more than one negatively charged zone inside the active site cavity of this mitochondrial enzyme, which is probably involved in the docking of positively charged substrates. These findings indicate that the bovine liver mitochondrial matrix contains an enzyme belonging to the spermine oxidase class. Because H2O2 is generated by spermine oxidase activity, the possible involvement of the latter as an important signaling transducer under both physiological and pathological conditions should be considered.

Interactions of melatonin with mammalian mitochondria. Reducer of energy capacity and amplifier of permeability transition

Melatonin, a metabolic product of the amino acid tryptophan, induces a dose-dependent energy drop correlated with a decrease in the oxidative phosphorylation process in isolated rat liver mitochondria. This effect involves a gradual decrease in the respiratory control index and significant alterations in the state 4/state 3 transition of membrane potential (ΔΨ). Melatonin, alone, does not affect the insulating properties of the inner membrane but, in the presence of supraphysiological Ca2+, induces a ΔΨ drop and colloid-osmotic mitochondrial swelling. These events are sensitive to cyclosporin A and the inhibitors of Ca2+ transport, indicative of the induction or amplification of the mitochondrial permeability transition. This phenomenon is triggered by oxidative stress induced by melatonin and Ca2+, with the generation of hydrogen peroxide and the consequent oxidation of sulfydryl groups, glutathione and pyridine nucleotides. In addition, melatonin, again in the presence of Ca2+, can also induce substantial release of cytochrome C and AIF (apoptosis-inducing factor), thus revealing its potential as a pro-apoptotic agent.

Agmatine prevents the Ca(2+)-dependent induction of permeability transition in rat brain mitochondria

The arginine metabolite agmatine is able to protect brain mitochondria against the drop in energy capacity by the Ca(2+)-dependent induction of permeability transition (MPT) in rat brain mitochondria. At normal levels, the amine maintains the respiratory control index and ADP/O ratio and prevents mitochondrial colloid-osmotic swelling and any electrical potential (DeltaPsi) drop. MPT is due to oxidative stress induced by the interaction of Ca(2+) with the mitochondrial membrane, leading to the production of hydrogen peroxide and, subsequently, other reactive oxygen species (ROS) such as hydroxyl radicals. This production of ROS induces oxidation of sulfhydryl groups, in particular those of two critical cysteines, most probably located on adenine nucleotide translocase, and also oxidation of pyridine nucleotides, resulting in transition pore opening. The protective effect of agmatine is attributable to a scavenging effect on the most toxic ROS, i.e., the hydroxyl radical, thus preventing oxidative stress and consequent bioenergetic collapse.