Synthesis and biological assessment of 3,7-dihydroxytropolones.

3,7-Dihydroxytropolones (3,7-dHTs) are highly oxygenated troponoids that have been identified as lead compounds for several human diseases. To date, structure-function studies on these molecules have been limited due to a scarcity of synthetic methods for their preparation. New synthetic strategies towards structurally novel 3,7-dHTs would be valuable in further studying their therapeutic potential. Here we describe the successful adaptation of a [5 + 2] oxidopyrilium cycloaddition/ring-opening for 3,7-dHT synthesis, which we apply in the synthesis of a plausible biosynthetic intermediate to the natural products puberulic and puberulonic acid. We have also tested these new compounds in several biological assays related to human immunodeficiency virus (HIV), hepatitis B virus (HBV) and herpes simplex virus (HSV) in order to gain insight into structure-functional analysis related to antiviral troponoid development.

BH3-only proteins in apoptosis and beyond: an overview.

BH3-only BCL-2 family proteins are effectors of canonical mitochondrial apoptosis. They discharge their pro-apoptotic functions through BH1-3 pro-apoptotic proteins such as BAX and BAK, while their activity is suppressed by BH1-4 anti-apoptotic BCL-2 family members. The precise mechanism by which BH3-only proteins mediate apoptosis remains unresolved. The existing data are consistent with three mutually non-exclusive models (1) displacement of BH1-3 proteins from complexes with BH1-4 proteins; (2) direct interaction with and conformational activation of BH1-3 proteins; and (3) membrane insertion and membrane remodeling. The BH3-only proteins appear to play critical roles in restraining cancer and inflammatory diseases such as rheumatoid arthritis. Molecules that mimic the effect of BH3-only proteins are being used in treatments against these diseases. The cell death activity of a subclass of BH3-only members (BNIP3 and BNIP3L) is linked to cardiomyocyte loss during heart failure. In addition to their established role in apoptosis, several BH3-only members also regulate diverse cellular functions in cell-cycle regulation, DNA repair and metabolism. Several members are implicated in the induction of autophagy and autophagic cell death, possibly through unleashing of the BH3-only autophagic effector Beclin 1 from complexes with BCL-2/BCL-xL. The Chapters included in the current Oncogene Review issues provide in-depth discussions on various aspects of major BH3-only proteins.

[Clinical heterogeneity of X-linked adrenoleukodystrophy ]. / Klinicheskoe raznoobrazie X-stseplennoi adrenoleikodistrofii.

X-linked adrenoleukodystrophy (X-ALD) is a relatively common world spread disease characterized by significant clinical heterogeneity. Clinico-biochemical examination in the Medico-genetic research center identified, 20 X-ALD cases in 17 families over 5 years. Prevalence of children (60%) and adolescence (25%) cerebral forms is explained, in part, by patients referring for medical-genetic counseling. Adrenomyeloneuropathy was diagnosed in one patient. In two healthy siblings presymptomatic stage was found. A main X-ALD biochemical marker is an increase of very long chain fatty acids (VLCFA) level, which does not depend on clinical form of the disease. Most interesting appeared to be a family including 5 patients in 3 generations with intrafamilial combination of childhood and adolescence cerebral forms, and atypically mild disease course in proband. Regarding symptoms of childhood and adolescence cerebral forms, attention has been drawn to 3 patients with tics, which mask organic nature of the disease on its initial stage. X-ALD is so far incurable, but its timely diagnosis provides an adequate medico-genetic help on the base of modern prenatal diagnosis.

Calcium vs. iron-mediated processes in hydrogen peroxide toxicity to L929 cells: effects of glucose.

H2O2 toxicity was studied in L929 cells in the presence and absence of glucose. The data obtained in the absence of glucose suggest a Ca2+-dependent mechanism of cell injury. No evidence was found for any involvement of iron in the process. In particular, cell injury was unaffected by the intracellular iron chelators 2,2'-dipyridyl and deferoxamine or by the hydroxyl radical scavengers DMSO and DMPO. On the other hand, the intracellular Ca2+ chelator BAPTA/AM provided significant protection. The cytosolic Ca2+ level rapidly and consistently increased after H2O2 addition, prior to visible bleb formation and loss of cell viability. Additionally, GSH not only prevented cell death but also significantly decreased cytosolic calcium accumulation. In the presence of glucose, however, Ca2+ does not seem to play any role in H2O2 toxicity. Cell death is now mainly mediated by iron: the iron chelators and hydroxyl radical scavengers prevented cell injury, the increase in cytosolic Ca2+ was significantly less pronounced, and BAPTA/AM did not exert any protection under these conditions. Hence, the metabolic state of the L929 cells, as given by the availability of glucose, decisively determines the biochemical mechanism of H2O2 cell injury.

Hydrogen peroxide formation by reaction of peroxynitrite with HEPES and related tertiary amines. Implications for a general mechanism.

Organic amine-based buffer compounds such as HEPES (Good's buffers) are commonly applied in experimental systems, including those where the biological effects of peroxynitrite are studied. In such studies 3-morpholinosydnonimine N-ethylcarbamide (SIN-1), a compound that simultaneously releases nitric oxide (.NO) and superoxide (O-2), is often used as a source for peroxynitrite. Whereas in mere phosphate buffer H2O2 formation from 1.5 mM SIN-1 was low ( approximately 15 microM), incubation of SIN-1 with Good's buffer compounds resulted in continuous H2O2 formation. After 2 h of incubation of 1.5 mM SIN-1 with 20 mM HEPES about 190 microM H2O2 were formed. The same amount of H2O2 could be achieved from 1.5 mM SIN-1 by action of superoxide dismutase in the absence of HEPES. The increased H2O2 level, however, could not be related to a superoxide dismutase or to a NO scavenger activity of HEPES. On the other hand, SIN-1-mediated oxidation of both dihydrorhodamine 123 and deoxyribose as well as peroxynitrite-dependent nitration of p-hydroxyphenylacetic acid were strongly inhibited by 20 mM HEPES. Furthermore, the peroxynitrite scavenger tryptophan significantly reduced H2O2 formation from SIN-1-HEPES interactions. These observations suggest that peroxynitrite is the initiator for the enhanced formation of H2O2. Likewise, authentic peroxynitrite (1 mM) also induced the formation of both O-2 and H2O2 upon addition to HEPES (400 mM)-containing solutions in a pH (4.5-7.5)-dependent manner. In accordance with previous reports it was found that at pH >/=5 oxygen is released in the decay of peroxynitrite. As a consequence, peroxynitrite(1 mM)-induced H2O2 formation ( approximately 80 microM at pH 7.5) also occurred under hypoxic conditions. In the presence of bicarbonate/carbon dioxide (20 mM/5%) the production of H2O2 from the reaction of HEPES with peroxynitrite was even further stimulated. Addition of SIN-1 or authentic peroxynitrite to solutions of Good's buffers resulted in the formation of piperazine-derived radical cations as detected by ESR spectroscopy. These findings suggest a mechanism for H2O2 formation in which peroxynitrite (or any strong oxidant derived from it) initially oxidizes the tertiary amine buffer compounds in a one-electron step. Subsequent deprotonation and reaction of the intermediate alpha-amino alkyl radicals with molecular oxygen leads to the formation of O-2, from which H2O2 is produced by dismutation. Hence, HEPES and similar organic buffers should be avoided in studies of oxidative compounds. Furthermore, this mechanism of H2O2 formation must be regarded to be a rather general one for biological systems where sufficiently strong oxidants may interact with various biologically relevant amino-type molecules, such as ATP, creatine, or nucleic acids.

The critical role of Hepes in SIN-1 cytotoxicity, peroxynitrite versus hydrogen peroxide.

The cytotoxicity of the superoxide anion radical- and nitric oxide-releasing compound SIN-1 to L929 cells was studied in Krebs-Henseleit buffer. pH 7.4, in the presence and absence of Hepes. SIN-1 cytotoxicity was significantly higher in the presence of Hepes than in the absence of Hepes. The available amount of peroxynitrite formed from SIN-1, however, was significantly decreased by Hepes as indicated by decreased oxidation of dihydrorhodamine 123. On the other hand, Hepes largely increased the formation of H2O2 from SIN-1. Catalase protected the L929 cells from SIN-1 cytotoxicity in the buffer with Hepes. In the buffer without Hepes catalase did not have any protective effect. In contrast, tyrosine and tryptophan provided significant protection against SIN-1 cytotoxicity independent of the presence of Hepes. These results demonstrate that the immediate toxic agent formed from SIN-1 decisively depends on the presence of Hepes. In its absence cytotoxicity is most likely mediated by peroxynitrite while in the presence of Hepes, cytotoxicity is conveyed by co-operative action of hydrogen peroxide and reactive nitrogen species.

[Contents of plutonium and microelements in the hair of Belarus inhabitants living in the areas contaminated during the Chernobyl AES accident]. / Soderzhanie plutoniia i nekotorykh mikroélementov v volosakh zhitelei Belarusi, prozhivaiushchikh na territorii, postradavshei pri avarii na Chernobyl'skoi AES.

The levels of plutonium were studied in the body of inhabitants of the Minsk and Gomel Regions. Their hair was used as the indicator of its levels. The hair concentrations of plutonium correlated with its content in the ribs. The hair levels of lead in the inhabitants of some populated localities of the Gomel Region were found to be higher than those in the residents of unpolluted areas and industrial centers of the Republic of Belarus.

[Activity of the antioxidant system of rat liver in benzidine poisoning and administration of enomelanin]. / Aktivnost' antioksidantnoi sistemy pecheni krys pri benzidinovoi intoksikatsii i vvedenii énomelanina.

It has been shown that benzidine administered in vivo attenuates the protective effect of the antioxidant system manifested as a reduction of the total antioxidant activity of rat liver cytosol and decreasing activities of superoxide dismutase and catalase. Enomelanin promotes the reconstitution of the superoxide dismutase activity. The data obtained suggest that the toxic effect of benzidine may be due to disturbances in the antioxidant protective mechanisms of liver cells responsible for the control over the free radical processes occurring in those cells.

[Rat liver antioxidant defense mechanism to the action of aromatic amines]. / Mekhanizm antioksidantnoi zashchity pecheni krys pri deistvii aromaticheskikh aminov.

The effects of diaminobiphenyl, biphenylamine and tetraaminobiphenyl on lipid peroxidation and antioxidant protective mechanisms in the subcellular fractions of rat liver have been studied. It was found that activation of lipid peroxidation plays a crucial role in the manifestation of hepatotoxic activities of diaminobiphenyl and biphenylamine, this effect being due to the decrease of the protective activity of the antioxidant system during intoxication by these compounds. Tetraaminobiphenyl does not influence the rate of lipid peroxidation. It is concluded that structural differences determine the differences in the mechanisms of adaptation of the antioxidant system to the effect of aromatic amines.