Oxidation of an antitumor drug ellipticine by peroxidases

Ellipticine is a potent antineoplastic agent, whose mode of action is considered to be based mainly on DNA intercalation and/or inhibition of topoisomerase II. Since we found that ellipticine also forms the cytochrome P450 (CYP)-mediated covalent DNA adducts, this anticancer drug is considered to function as a pro-drug, whose pharmacological efficiency and/or genotoxic side effects are dependent on its enzymatic activation in target tissues. Here, we demonstrate that ellipticine is also oxidized by peroxidases, which are abundantly expressed in several target tumor tissues. Lactoperoxidase, myeloperoxidase and horseradish peroxidase were used as models. Peroxidases in the presence of hydrogen peroxide oxidize ellipticine to an ellipticine dimer and N(2)-oxide of ellipticine as the major and minor metabolite, respectively. Inhibition of the peroxidase-mediated ellipticine oxidation by radical scavengers ascorbate, glutathione and NADH suggests a one-electron mechanism of the oxidation. The implication of the oxidation of ellipticine by peroxidases in its mechanism of action is discussed.     

Using of electrochemical methods for studying of metallothionein content in the human blood serum of a patient poisoned by lead and treated by platinum

Metallothioneins belong to the group of intracellular, high molecular and cysteine-rich proteins whose content increase with increasing concentration of a heavy metal. Here we applied the adsorptive transfer stripping differential pulse voltammetry Brdicka reaction for the determination of metallothionein in human blood serum of patient poisoned by lead and/or treated by platinum. The increased metallothionein concentrations in both cases were observed.     

A liquid chromatographic-mass spectrometric evidence of dihydrosanguinarine as a first metabolite of sanguinarine transformation in rat

Adult rats were orally administered with a single dose of sanguinarine (10 mg SA per 1 kg body weight) in 1.0 ml water. In the plasma and the liver, dihydrosanguinarine (DHSA) was identified as a SA metabolite by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC/ESI-MS). Significantly higher levels of DHSA were found in both the plasma and the liver in comparison with those of SA. SA and DHSA were not detected in the urine. The formation of DHSA might be the first step of SA detoxification in the organism and its subsequent elimination in phase II reactions. Benz[c]acridine (BCA), in the literature cited SA metabolite, was found neither in urine nor in plasma and liver.     

Occurrence of adventitious sprouting in short-lived monocarpic herbs: a field study of 22 weedy species

Background and Aims

Adventitious sprouting from the hypocotyle and roots in monocarpic herbs has been confirmed in previous experimental studies as a means to avoid bud limitation after severe injury in annual and biennial plants. Data regarding the role of adventitious sprouting in natural populations, however, were lacking. The aim of the present study was to assess whether adventitious sprouting occurs in natural populations and how it is affected by plant size, plant injury, plant cover and environmental characteristics.

Methods

Data were sampled from 14 037 individual plants from 389 populations belonging to 22 annual and biennial species. Growth parameters were measured in individual plants, species composition and plant cover in communities were evaluated, and environmental characteristics were estimated using Ellenberg indicator values.

Key Results

It was confirmed that adventitious sprouting occurs in natural populations of all but five species examined. Adventitious sprouting was positively affected by plant size and plant injury. Environmental factors including availability of soil nitrogen were not shown to affect adventitious sprouting. Annual and biennial plants did not differ in sprouting, but upright annuals had a lower number of and longer adventitious shoots than prostrate annuals.

Conclusions

Adventitious bud formation is used to overcome meristem limitation when stem parts are lost due to injury, and thus resprouting in short-lived monocarps should not be overlooked.     

Membrane Curvature Induction and Tubulation Are Common Features of Synucleins and Apolipoproteins

Synucleins and apolipoproteins have been implicated in a number of membrane and lipid trafficking events. Lipid interaction for both types of proteins is mediated by 11 amino acid repeats that form amphipathic helices. This similarity suggests that synucleins and apolipoproteins might have comparable effects on lipid membranes, but this has not been shown directly. Here, we find that α-synuclein, β-synuclein, and apolipoprotein A-1 have the conserved functional ability to induce membrane curvature and to convert large vesicles into highly curved membrane tubules and vesicles. The resulting structures are morphologically similar to those generated by amphiphysin, a curvature-inducing protein involved in endocytosis. Unlike amphiphysin, however, synucleins and apolipoproteins do not require any scaffolding domains and curvature induction is mediated by the membrane insertion and wedging of amphipathic helices alone. Moreover, we frequently observed that α-synuclein caused membrane structures that had the appearance of nascent budding vesicles. The ability to function as a minimal machinery for vesicle budding agrees well with recent findings that α-synuclein plays a role in vesicle trafficking and enhances endocytosis. Induction of membrane curvature must be under strict regulation in vivo; however, as we find it can also cause disruption of membrane integrity. Because the degree of membrane curvature induction depends on the concerted action of multiple proteins, controlling the local protein density of tubulating proteins may be important. How cellular safeguarding mechanisms prevent such potentially toxic events and whether they go awry in disease remains to be determined.     

Adiponectin added into the plasma of healthy probands does not affect platelet aggregability

Six healthy non-obese probands without medical therapy and history of disease were tested. In all of them platelet aggregability with addition of human recombinant adiponectin in different concentrations (100; 75; 50 and 25 ng/l) were measured. It is concluded that increased level of adiponectin has no significant antiaggregation effect on platelets from individuals without hypoadiponectinemia.     

Damage detection by the UvrABC pathway: crystal structure of UvrB bound to fluorescein-adducted DNA

UvrB is the damage recognition element of the highly conserved UvrABC pathway that functions in the removal of bulky DNA adducts. Pivotal to this is the formation of a damage detection complex that relies on the ability of UvrB to locate and sequester diverse lesions. Whilst structures of UvrB bound to DNA have recently been reported, none address the issue of lesion recognition. Here, we describe the crystal structure of UvrB bound to a pentanucleotide containing a single fluorescein-adducted thymine that reveals a unique mechanism for damage detection entirely dependent on the exclusion of lesions larger than an undamaged nucleotide.