Morpho-functional indicators changes of rats’ myocardium in experimental doxorubicin-induced chronic heart failure and its pharmacological modulation with new 4-amino-1,2,4-triazole derivative

Bromide 1 - (β-phenylethyl)-4-amino-1,2,4-triazolium (Hypertril) has the properties of a beta-blocker and of NO-mimetic, is assigned to the IV class of toxicity. All these effects make Hypertril a promising drug for the treatment of cardiovascular diseases. The aim of this paper was to study the cardioprotective action of Hypertril in terms of the effect on the morpho-functional parameters of the myocardium in rats with experimental chronic heart failure (CHF). CHF was modeled on 80 white outbred rats weighing 190–220g by administering doxorubicin at a cumulative dose of 15 mg/kg. Hypertril and the reference drug metoprolol succinate were administered within 30 days after CHF modeling, intragastrically at doses of 3.5 mg/kg and 15 mg/kg. Morphometric analysis of the cellular structure of the myocardium was carried out on an Axioskop microscope (Zeiss, Germany), in an automatic mode using a macro program developed in a specialized programming environment VIDAS-2.5 (Kontron Elektronik, Germany). The administration of Hypertril to animals with CHF led to an increase in the density of nuclei of cardiomyocytes, the area of myocardiocyte nuclei, an increase in the nuclear cytoplasmic ratio and an increase in the concentration of RNA in the nuclei and cytoplasm of cardiomyocytes compared with the group of untreated animals, which indicated the presence of a pronounced cardioprotective effect in the drug candidate. In terms of such indicators as the density of surviving cardiomyocytes and the content of RNA in them, the nuclear-cytoplasmic ratio of Hypertril is significantly (p < 0.05) superior to metoprolol.

Antihypertensive and cardioprotective effects of new compound 1-(β-phenylethyl)-4-amino-1,2,4-triazolium bromide (Hypertril)

Despite the success which was achieved in the treatment of arterial hypertension, the problem remains actual. At the departments of pharmaceutical chemistry and pharmacology of the Zaporozhye State Medical Institute (Ukraine), our research team isolated the compound 1-(β-phenylethyl)-4-amino-1,2,4-triazolium bromide (Hypertril) as derivative of 4-amino-1,2,4-triazole. The objectives of this investigation were the study of cardioprotective and antihypertensive activities of this new compound Hypertril and we used the Spontaneously hypertensive rats (SHR) as an experimental model. We discovered that Hypertril has a reliable dose-dependent antihypertensive effect in the dose range 5-20 mg/kg after 30-day administration and this antihypertensive effect of Hypetril competes or significantly exceeds Metoprolol (20 mg/kg). Our studies obtained evidence of a dose-dependent improvement of myocardial energy metabolism. Hypertril reduces the manifestations of secondary mitochondrial dysfunction due to arterial hypertension. Hypertril can prevent oxidative modification of the protein; also Hypertril reduces the insufficiency of mitochondrial pores. As a result, Hypertril increases the content of ATP in the myocardium of SHR, normalizes the activity of mitochondrial enzymes, decreases lactate production and increases pyruvate. Hypertril enhances the cardioprotective effects of NO and increases the resistance of the cardiomyocytes to ischemia. The use of Hypertril leads to a dose-dependent increase of the density of cardiomyocyte nuclei, significant increase RNA content in nuclei and the cytoplasm of cardiomyocytes, and an increase of the nuclear-cytoplasmic index. These changes indicate a decrease of myocardial hypertrophy.

The N-B Interaction through a Water Bridge: Understanding the Chemoselectivity of a Fluorescent Protein Based Probe for Peroxynitrite

Boronic acid and esters have been extensively utilized for molecular recognition and chemical sensing. We recently reported a genetically encoded peroxynitrite (ONOO(-))-specific fluorescent sensor, pnGFP, based on the incorporation of a boronic acid moiety into a circularly permuted green fluorescent protein (cpGFP) followed by directed protein evolution. Different from typical arylboronic acids and esters, the chromophore of pnGFP is unreactive to millimolar concentrations of hydrogen peroxide (H2O2). The focus of this study is to explore the mechanism for the observed unusual chemoselectivity of pnGFP toward peroxynitrite over hydrogen peroxide by using site-directed mutagenesis, X-ray crystallography, (11)B NMR, and computational analysis. Our data collectively support that a His residue on the protein scaffold polarizes a water molecule to induce the formation of an sp(3)-hybridized boron in the chromophore, thereby tuning the reactivity of pnGFP with various reactive oxygen and nitrogen species (ROS/RNS). Our study demonstrates the first example of tunable boron chemistry in a folded nonnative protein, which offers wide implications in designing selective chemical probes.

1α,25 dihydroxyvitamin D3 enhances cellular defences against UV-induced oxidative and other forms of DNA damage in skin

DNA damage induced by ultraviolet radiation is the key initiator for skin carcinogenesis since mutations may arise from the photoproducts and it also contributes to photoimmune suppression. The active vitamin D hormone, 1α,25 dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) reduces thymine dimers, the major photoproduct found in human skin after UV exposure, and suppresses the accumulation of nitric oxide derivatives that lead to more toxic reactive nitrogen species (RNS). We examined whether other forms of DNA damage are reduced by 1,25(OH)(2)D(3), and hypothesized that photoprotection by 1,25(OH)(2)D(3) is, in part, due to the suppression of various forms of promutagenic DNA damage, including thymine dimers, through a reduction of genotoxic RNS. Different forms of UV-induced DNA damage were investigated in irradiated skin cells treated with or without 1,25(OH)(2)D(3), or inhibitors of metabolism and inducible nitric oxide synthase. Keratinocytes were also treated with nitric oxide donors in the absence of UV light. DNA damage was assessed by comet assay incorporating site specific DNA repair endonucleases, and by immunohistochemistry using antibodies to thymine dimers or 8-oxo-7,8-dihydro-2'-deoxyguanosine, and quantified by image analysis. Strand breaks in T4 endonuclease V, endonuclease IV and human 8-oxoguanine DNA glycosylase digests increased more than 2-fold in UV irradiated human keratinocytes, and were reduced by 1,25(OH)(2)D(3) treatment after UV exposure, and also by low temperature, sodium azide and an inhibitor of inducible nitric oxide synthase. Conversely, nitric oxide donors induced all three types of DNA damage in the absence of UV. We present data to show that 1,25(OH)(2)D(3) protects skin cells from at least three forms of UV-induced DNA damage, and provide further evidence to support the proposal that a reduction in RNS by 1,25(OH)(2)D(3) is a likely mechanism for its photoprotective effect against oxidative and nitrative DNA damage, as well as cyclobutane pyrimidine dimers.

Oxidation of thiamine on reaction with nitrogen dioxide generated by ferric myoglobin and hemoglobin in the presence of nitrite and hydrogen peroxide

It is shown that nitrogen dioxide oxidizes thiamine to thiamine disulfide, thiochrome, and oxodihydrothiochrome (ODTch). The latter is formed during oxidation of thiochrome by nitrogen dioxide. Nitrogen dioxide was produced by incubation of nitrite with horse ferric myoglobin and human hemoglobin in the presence of hydrogen peroxide. After addition of tyrosine or phenol to aqueous solutions containing oxoferryl forms of the hemoproteins, thiamine, and nitrite, the yield of thiochrome greatly increased, whereas the yield of ODTch decreased. In the presence of high concentrations of tyrosine or phenol compounds ODTch was not formed at all. The neutral form of thiamine with the closed thiazole cycle and minor tricyclic form of thiamine do not enter the heme pocket of the protein and do not interact with the oxoferryl heme complex Fe(IV=O) or porphyrin radical. The tricyclic form of thiamine is oxidized to thiochrome by tyrosyl radicals located on the surface of the hemoprotein. The thiol form of thiamine is oxidized to thiamine disulfide by both hemoprotein tyrosyl radicals and oxoferryl heme complexes. Nitrite and also tyrosine, tyramine, and phenol readily penetrate into the heme pocket of the protein and reduce the oxyferryl complex to ferric cation. These reactions yield nitrogen dioxide as well as tyrosyl and phenoxyl radicals of tyrosine molecules and phenol compounds, respectively. Tyrosyl and phenoxyl radicals of low molecular weight compounds oxidize thiamine only to thiochrome and thiamine disulfide. The effect of oxoferryl forms of myoglobin and hemoglobin, nitrogen dioxide, and phenol on thiamine oxidative transformation as well as antioxidant properties of the hydrophobic thiamine metabolites thiochrome and ODTch are discussed.

On-chip multi-electrochemical sensor array platform for simultaneous screening of nitric oxide and peroxynitrite

In this work we report on the design, microfabrication and analytical performances of a new electrochemical sensor array (ESA) which allows for the first time the simultaneous amperometric detection of nitric oxide (NO) and peroxynitrite (ONOO(-)), two biologically relevant molecules. The on-chip device includes individually addressable sets of gold ultramicroelectrodes (UMEs) of 50 µm diameter, Ag/AgCl reference electrode and gold counter electrode. The electrodes are separated into two groups; each has one reference electrode, one counter electrode and 110 UMEs specifically tailored to detect a specific analyte. The ESA is incorporated on a custom interface with a cell culture well and spring contact pins that can be easily interconnected to an external multichannel potentiostat. Each UME of the network dedicated to the detection of NO is electrochemically modified by electrodepositing thin layers of poly(eugenol) and poly(phenol). The detection of NO is performed amperometrically at 0.8 V vs. Ag/AgCl in phosphate buffer solution (PBS, pH = 7.4) and other buffers adapted to biological cell culture, using a NO-donor. The network of UMEs dedicated to the detection of ONOO(-) is used without further chemical modification of the surface and the uncoated gold electrodes operate at -0.1 V vs. Ag/AgCl to detect the reduction of ONOOH in PBS. The selectivity issue of both sensors against major biologically relevant interfering analytes is examined. Simultaneous detection of NO and ONOO(-) in PBS is also achieved.

BODIPY-based fluorescent probe for peroxynitrite detection and imaging in living cells

A fluorescent probe, HKGreen-2, has been developed based on a specific reaction between ketone and peroxynitrite (ONOO(-)). This probe is highly sensitive and selective for the detection of peroxynitrite not only in abiotic but also in biological systems. With this probe, we successfully detected peroxynitrite generated in murine macrophage cells activated by phorbol 12-myristate 13-acetate (PMA), interferon-gamma (IFN-gamma), and lipopolysaccharide (LPS). This new probe will be a useful tool for studying the roles of peroxynitrite in biological processes.

Reactive macrophages increase oxidative stress and alpha-synuclein nitration during death of dopaminergic neuronal cells in co-culture: relevance to Parkinson's disease

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons and a substantial decrease in the neurotransmitter dopamine in the nigro-striatal region of the brain. Increased markers of oxidative stress, activated microglias and elevated levels of pro-inflammatory cytokines have been identified in the brains of patients with PD. Although the precise mechanism of loss of neurons in PD remains unclear, these findings suggest that microglial activation may contribute directly to loss of dopaminergic neurons in PD patients. In the present study, we tested the hypothesis that activated microglia induces nitric oxide-dependent oxidative stress which subsequently causes death of dopaminergic neuronal cells in culture. We employed lipopolysaccharide (LPS) stimulated mouse macrophage cells (RAW 264.7) as a reactive microglial model and SH-SY5Y cells as a model for human dopaminergic neurons. LPS stimulation of macrophages led to increased production of nitric oxide in a time and dose dependent manner as well as subsequent generation of other reactive nitrogen species such as peroxynitrite anions. In co-culture conditions, reactive macrophages stimulated SH-SY5Y cell death characterized by increased peroxynitrite concentrations and nitration of alpha-synuclein within SH-SY5Y cells. Importantly 1,400 W, an inhibitor of the inducible nitric oxide synthase provided protection from cell death via decreasing the levels of nitrated alpha-synuclein. These results suggest that reactive microglias could induce oxidative stress in dopaminergic neurons and such oxidative stress may finally lead to nitration of alpha-synuclein and death of dopaminergic neurons in PD.