Minocycline chelates Ca<Superscript>2+</Superscript>, binds to membranes,and depolarizes mitochondria by formation of Ca<Superscript>2+</Superscript>-dependent ion channels

Minocycline (an anti-inflammatory drug approved by the FDA) has been reported to be effective in mouse models of amyotrophic lateral sclerosis and Huntington disease. It has been suggested that the beneficial effects of minocycline are related to its ability to influence mitochondrial functioning. We tested the hypothesis that minocycline directly inhibits the Ca²⁺-induced permeability transition in rat liver mitochondria. Our data show that minocycline does not directly inhibit the mitochondrial permeability transition. However, minocycline has multiple effects on mitochondrial functioning. First, this drug chelates Ca²⁺ ions. Secondly, minocycline, in a Ca²⁺-dependent manner, binds to mitochondrial membranes. Thirdly, minocycline decreases the proton-motive force by forming ion channels in the inner mitochondrial membrane. Channel formation was confirmed with two bilayer lipid membrane models. We show that minocycline, in the presence of Ca²⁺, induces selective permeability for small ions. We suggest that the beneficial action of minocycline is related to the Ca²⁺-dependent partial uncoupling of mitochondria, which indirectly prevents induction of the mitochondrial permeability transition.     

Peptide-induced membrane leakage by lysine derivatives of gramicidin A in liposomes,planar bilayers,and erythrocytes

Introducing a charged group near the N-terminus of gramicidin A (gA) is supposed to suppress its ability to form ion channels by restricting its head-to-head dimerization. The present study dealt with the activity of [Lys1]gA, [Lys3]gA, [Glu1]gA, [Glu3]gA, [Lys2]gA, and [Lys5]gA in model membrane systems (planar lipid bilayers and liposomes) and erythrocytes. In contrast to the Glu-substituted peptides, the lysine derivatives of gA caused non-specific liposomal leakage monitored by fluorescence dequenching of lipid vesicles loaded with carboxyfluorescein or other fluorescent dyes. Measurements of electrical current through a planar lipid membrane revealed formation of giant pores by Lys-substituted analogs, which depended on the presence of solvent in the bilayer lipid membrane. The efficacy of unselective pore formation in liposomes depended on the position of the lysine residue in the amino acid sequence, increasing in the row: [Lys2]gA < [Lys5]gA < [Lys1]gA < [Lys3]gA. The similar series of potency was exhibited by the Lys-substituted gA analogs in facilitating erythrocyte hemolysis, whereas the Glu-substituted analogs showed negligible hemolytic activity. Oligomerization of the Lys-substituted peptides is suggested to be involved in the process of nonselective pore formation.     

Electrogenic proton transport across lipid bilayer membranes mediated by cationic derivatives of rhodamine 19: comparison with anionic protonophores

Protonophores can be considered as candidates for anti-obesity drugs and tools to prevent excessive reactive oxygen species production in mitochondria by means of a limited decrease in the mitochondrial potential. Experimentally used protonophores are weak acids that can carry protons across a membrane in a neutral (protonated) form, and they come back in an anionic (deprotonated) form. A cationic derivative of rhodamine 19 and plastoquinone (SkQR1) was recently shown to possess uncoupling activity in mitochondria and in intact cells. In this article, we studied the mechanism of action of SkQR1 and its plastoquinone-lacking analog (C₁₂R1) on a planar bilayer lipid membrane by applying voltage jumps. The steady-state current was proportional to the C₁₂R1 concentration in a manner as if the monomeric form of the carrier were operative. As predicted by the carrier model, at high pH, when rhodamines were mainly deprotonated, the current changed immediately following a jump in the applied potential and then remained constant. By contrast, at low pH, the current relaxed from an initially high value to a lower value since the protonated carrier cations were redistributed in the membrane. An inverse pH dependence was revealed with the anionic protonophore CCCP. The dependence of the SkQR1 protonophorous activity on voltage exhibited an increase at high voltages, an effect that might facilitate mild (self-limited) uncoupling of mitochondria.     

On occurrence and biology of Berg wrymouth <Emphasis Type="Italic">Cryptacanthodes bergi</Emphasis> (Cryptacanthodidae) in the north-western part of the Sea of Japan

With consideration of the data obtained in the period from 1981 to 2009, the occurrence of Berg wrymouth Cryptacanthodes bergi is estimated in the north-western part of the Sea of Japan. Almost all captures of wrymouth were made in Peter the Great Bay (only once was it caught in the Northern Primor’e) in a bathymetric range 18–60 m. Captures of Berg wrymouth are confined to aleurite bottom sediments. The size of captured specimens varied from 11 to 29 cm. The ratio of males and females in collections was close to 8: 1. In July–September, the gonads of females were at maturity stages III and IV and gonadosomatic index varied from 3 to 14%; in males, gonads were at stages II–III and III and gonadosomatic index varied from 0.5–2.7%, respectively.     

Particularities of blood lymphocyte response to irradiation in vitro in breast cancer patients

DNA breaks and their repair efficiency were analyzed in irradiated in vitro lymphocytes (at doses 1 Gy, gamma-radiation of 60Co, dose rate 1 Gy/min) isolated from peripheral blood of 41 untreated patients with breast cancer and 25 healthy donors using the DNA comet assay under non-denaturing conditions (mainly double-strand DNA breaks (DSB), as well as apoptotic cell death using the DNA halo assay. To estimate the expression of bystander effect, the cells were incubated in a culture medium obtained from lymphocytes irradiated in vitro at doses 1 Gy. The average DSB level in blood lymphocytes of breast cancer patients was shown to be significantly higher (p < 0.05) compared with that in control donors. In general, the following effects were observed in irradiated in vitro lymphocytes of cancer patients: (1) increased sensitivity to y-radiation-induced DNA DSBs compared with lymphocytes from healthy donors, (2) reduced repair efficiency of these damages. Incubation of irradiated blood lymphocytes in a medium from irradiated cells led to an increased relative number of DNA DSBs and an elevated fraction of cells dying through apoptotic pathway both in blood lymphocytes from cancer patients and control donors. However, these non-targeted effects were more expressed for the blood lymphocytes of breast cancer patients.     

Effect of liposomes on energy-dependent uptake of the antioxidant SkQR1 by isolated mitochondria

The mitochondria-targeted antioxidant SkQR1 composed of a plastoquinone part covalently bound to a cationic rhodamine 19 moiety via a decane linker was previously shown to effectively protect brain and kidney from ischemia injury accompanying generation of reactive oxygen species. In the present paper the energy-dependent SkQR1 uptake by isolated rat liver mitochondria was studied by fluorescence correlation spectroscopy peak intensity analysis (FCS PIA). This approach can be used to measure the number of fluorescent molecules per single mitochondrion. A large portion of SkQR1 appeared to be taken up by mitochondria in an energy-independent fashion because of its high affinity to membranes. Liposomes were found to compete effectively with mitochondria for the energy-independent SkQR1 binding, thereby facilitating, as an "SkQR1-buffer", observation of energy-dependent SkQR1 accumulation in mitochondria. The rate of energy-dependent SkQR1 uptake by mitochondria observed in the presence of liposomes was rather low (minutes) which was apparently due to slow redistribution of SkQR1 between liposomal and mitochondrial membranes. This can explain the low rate of staining of mitochondria by SkQR1 in living cells containing, besides mitochondria, other membrane components (endoplasmic reticulum, Golgi membranes, endosomes, lysosomes, etc.) which can compete with mitochondria for the energy-independent SkQR1 binding.     

Occurrence of skate <Emphasis Type="Italic">Raja pulchra</Emphasis> (Rajidae,Rajiformes) in Russian waters of the Sea of Japan

According to data of long-term observations in Russian waters of the Sea of Japan, it was shown that skate Raja pulchra occurs only off the coasts of western Sakhalin. In all probability, it is a constant inhabitant of these waters during the course of the year; like the overwhelming majority of bottom and near-bottom fish, it performs seasonal bathymetric migrations in autumn, for wintering to the insular slope to a depth of 695 m, and in spring to shallow waters. Maximum length of R. pulchra recorded in catches is 106 cm. The main food items of R. pulchra are decapods and fish. The stock of R. pulchra off the coasts of western Sakhalin is assessed as 520 t.     

Cellular and humoral indicators of antibody formation in rats with liver lesions caused by the antihepatocytotoxic serum]

As revealed, antihepatocitotoxic serum caused a sharp suppression of antibody genesis in rats at the early period (the 3rd day) after its 5 administrations; this was indicated by a marked reduction of the antibody-forming cell count in the spleen and reduction of the circulating antibody titres (hemolysins and hemagglutinins). Along with this, antibody formation was stimulated in the liver in the course of the whole month of study. By the end of the month suppression of antibody formation was replaced by its stimulation.     

Measurements of non-electrogenic fluxes through lipid bilayers induced by Men+/nH+-exchangers

In the presence of concentration gradient of metal ions on bilayer lipid membrane (BLM) the addition of non-electrogenic carriers results in a formation of concentration gradient of hydrogen ions in the unstirred layers near membrane. Addition of protonophore under these conditions brings about the formation of diffusion potential of hydrogen ions. This effect underlies the method of measuring non-electrogenic fluxes on BLM initiated in the presence of Men+/nH+ - exchangers. The proposed method was tested on the following Men+/nH+ - exchangers: nigericin, monensin and A23187. The order of cationic selectivity of the given carriers obtained by measuring the potentials on BLM in the presence of protonophores agrees with literature data, which were obtained by direct measurements of ionic fluxes.     

Electrostatically Induced Recruitment of Membrane Peptides into Clusters Requires Ligand Binding at Both Interfaces

Protein recruitment to specific membrane locations may be governed or facilitated by electrostatic attraction, which originates from a multivalent ligand. Here we explored the energetics of a model system in which this simple electrostatic recruitment mechanism failed. That is, basic poly-L-lysine binding to one leaflet of a planar lipid bilayer did not recruit the triply-charged peptide (O-Pyromellitylgramicidin). Clustering was only observed in cases where PLL was bound to both channel ends. Clustering was indicated (i) by the decreased diffusional PLL mobility D_PLL and (ii) by an increased lifetime τ_PLL of the clustered channels. In contrast, if PLL was bound to only one leaflet, neither D_PLL nor τ_P changed. Simple calculations suggest that electrostatic repulsion of the unbound ends prevented neighboring OPg dimers from approaching each other. We believe that a similar mechanism may also operate in cell signaling and that it may e.g. contribute to the controversial results obtained for the ligand driven dimerization of G protein-coupled receptors.