Reconstitution of proapoptotic BAK function in liposomes reveals a dual role for mitochondrial lipids in the BAK-driven membrane permeabilization process

BAK is a key effector of mitochondrial outer membrane permeabilization (MOMP) whose molecular mechanism of action remains to be fully dissected in intact cells, mainly due to the inherent complexity of the intracellular apoptotic machinery. Here we show that the core features of the BAK-driven MOMP pathway can be reproduced in a highly simplified in vitro system consisting of recombinant human BAK lacking the carboxyl-terminal 21 residues (BAKΔC) and tBID in combination with liposomes bearing an appropriate lipid environment. Using this minimalist reconstituted system we established that tBID suffices to trigger BAKΔC membrane insertion, oligomerization, and pore formation. Furthermore, we demonstrate that tBID-activated BAKΔC permeabilizes the membrane by forming structurally dynamic pores rather than a large proteinaceous channel of fixed size. We also identified two distinct roles played by mitochondrial lipids along the molecular pathway of BAKΔC-induced membrane permeabilization. First, using several independent approaches, we showed that cardiolipin directly interacts with BAKΔC, leading to a localized structural rearrangement in the protein that "primes" BAKΔC for interaction with tBID. Second, we provide evidence that selected curvature-inducing lipids present in mitochondrial membranes specifically modulate the energetic expenditure required to create the BAKΔC pore. Collectively, our results support the notion that BAK functions as a direct effector of MOMP akin to BAX and also adds significantly to the growing evidence indicating that mitochondrial membrane lipids are actively implicated in BCL-2 protein family function.

[Myocardial structural changes in acute left ventricular overload in an experiment]

Acute left ventricular (LV) overload was simulated in rabbits, by applying a metal spiral to narrow the ascending aorta by one third of its baseline diameter. A control group comprised intact animals. Studies were conducted 1, 3, and 5 days after surgery for simulation of LV overload in parallel series. In the first series of the experiment, semifine LV sections were examined by light microscopy and morphometry. The rate of cardiomyocyte (CMC) apoptosis was estimated calculating the free lying nuclei--the morphologically unchanged nuclei that were present in the extracellular space. In the second series, CMC apoptosis underwent immunohistochemical assessment, by running the TUNEL test. During its acute hemodynamic overload, the LV myocardium showed significant tissue destruction and a substantially lower number of viable myofibrils, and an increase in the count of apoptotically altered CMCs.

Contractile function of the heart and the state of some stages of lipid metabolism during acute diphtheritic intoxication

Acute diphtheritic intoxication was modeled in rabbits by intravenous administration of native diphtherin (0.3 minimal lethal dose per 1 kg body weight). The contractile function of the left and right ventricles (peak systolic pressure under conditions of basal hemodynamics and during 5-sec occlusion of the aorta and pulmonary artery, respectively) was estimated 1, 3 and 5 days after the start of the pathological process, the intensity of lipid peroxidation was evaluated by measuring the content of TBA- reactive products in the myocardium. Impairment of the contractile function of both ventricles was observed in the course of intoxication. The level of TBA-reactive products in the left ventricle significantly decreased on day 1, but then returned to normal. Thus, impairment of the contractile function of the left ventricle at the early stages of diphtheritic intoxication is not mediated by activation of lipid peroxidation in cardiomyocytes.

System analysis of changes in cardiovascular circulatory dynamics in experimental diphtheria in rabbit

Trivariate correlation analysis of hemodynamic indices of the cardiovascular system in rabbits with diphtheria showed that adaptation of this system to direct action of diphtherin can be visualized by analysis of trivariate correlation tightness for indices of intraventricular pressure in the left and right ventricles and indices of systemic blood pressure. Using empirical production functions for systemic blood pressure indices we found that the contribution of intraventricular pressure in the left and right ventricles on blood pressure values is changed in diphtheria compared to the control. Basing on entropy analysis we established that the regimen of control over values of working intraventricular pressure in both left and right ventricles in diphtheria is changed from quasidetermined to stochastic.

[Myocardial architectonic changes and cardiomyocytic apoptosis in the course of experimental diphtheria intoxication]

Diphtheria intoxication was simulated in rabbits, by intravenously injecting native diphtheria toxin in a dose of 0.3 MLD (minimal lethal dose) per kg body weight. Intact rabbits were used as a control. Following 1, 3, and 5 days of the onset on intoxication, the chests were opened under 2% rometar anesthesia and the hearts were extirpated, semithin left and right ventricular myocardial sections were prepared and light microscopic morphometry (at a magnification of x 1000) was carried out with video-assisted imaging. The rate of cardiomyocytic (CMC) apoptosis was determined, by calculating the free lying nuclei - the morphologically changed nuclei that were present in the extracellular space. Both ventricular CMC destruction characteristic of necrotic death was ascertained to significantly increase just on day 1 of the experiment and to further enhance during its course. By day 5, the rate of CMC apoptosis increased in both the left and right ventricles. Furthermore, there was an increasing reduction in myocardial collagen levels.

Domain-driven morphogenesis of cellular membranes

Cellular membrane systems delimit and organize the intracellular space. Most of the morphological rearrangements in cells involve the coordinated remodeling of the lipid bilayer, the core of the membranes. This process is generally thought to be initiated and coordinated by specialized protein machineries. Nevertheless, it has become increasingly evident that the most essential part of the geometric information and energy required for membrane remodeling is supplied via the cooperative and synergistic action of proteins and lipids, as cellular shapes are constructed using the intrinsic dynamics, plasticity and self-organizing capabilities provided by the lipid bilayer. Here, we analyze the essential role of proteo-lipid membrane domains in conducting and coordinating morphological remodeling in cells.

Cooperative elastic stresses, the hydrophobic effect, and lipid tilt in membrane remodeling

One of the fundamental properties of biological membranes is the high lateral integrity provided by the lipid bilayer, the structural core and the foundation of their barrier function. This tensile strength is due to the intrinsic properties of amphiphilic lipid molecules, which spontaneously self-assemble into a stable bilayer structure due to the hydrophobic effect. In the highly dynamic life of cellular membranes systems, however, this integrity has to be regularly compromised. One of the emerging puzzles is the mechanism of localized rupture of lipid monolayer, the formation of tiny hydrophobic patches and flipping of lipid tails between closely apposed monolayers. The energy cost of such processes is prohibitively high, unless cooperative deformations in a small membrane patch are carefully organized. Here we review the latest experimental and theoretical data on how such deformations can be conducted, specifically describing how elastic stresses yield tilting of lipids leading to cooperative restructuring of lipid monolayers. Proteins specializing in membrane remodeling assemble into closely packed circular complexes to arrange these deformations in time and space.

[The influence of GPIIIA gene polymorphism on the variability of standard electrocardiogram in patients with acute coronary syndrome]

The authors analyse effect of GPIIIA gene (PI a allele) polymorphism on the frequency of complicated coronary heart disease in patients with dyslipidemia and hypertensive disease. Specific features of ventricular repolarization (T-wave variability) in patients with acute coronary syndrome are described.

Analysis of central blood pressure during diphtheria intoxication in rabbits

Diphtheria intoxication was induced in rabbits by a single intravenous injection of native diphtheria toxin in dose of 0.3 MLD/kg, preliminary titrated on guinea pigs. Significant decrease in diastolic and systolic blood pressure and in intraventricular pressure in the left ventricle was established to take place during intoxication. Pulse wave propagation time was prolonged, likely due to prolongation of pressure wave, while the reflection wave appeared at the same time. Reduction of central blood pressure was concluded to result from changes in biomechanical characteristics of the left ventricle, and not to be associated with changes in elastic properties of the arterial wall.

Seasonal adaptation of the cardiovascular system in rabbits

Analysis of the effects of seasonal changes in the myocardium on variability of arterial and intraventricular pressure in both ventricles showed that the objects of homeostatic regulation were the values of these parameters and their probability distribution. The adaptation mechanisms are mainly visualized by the analysis of the characteristics of probability distribution of the parameters (asymmetry and excess coefficients).

On some pathogenetic and adaptation mechanisms of acute coronary disease

Acute coronary failure was modeled in rabbits by ligation of the descending left coronary artery at the interface of its middle and lower thirds. The function and morphology of left-ventricular and right-ventricular myocardium were studied on days 1, 3, and 5 of the pathological process. It was found that left-ventricular contractility decreased, while right-ventricular contractility increased. Deep morphological changes were observed in both ventricles: pronounced extracellular edema, increased content of collagen, decreased percentage of myofibrils. Hence, acute coronary failure involves both compartments of the heart, but the adaptive mechanisms more actively develop in the right ventricle.

GTPase cycle of dynamin is coupled to membrane squeeze and release, leading to spontaneous fission

The GTPase dynamin is critically involved in membrane fission during endocytosis. How does dynamin use the energy of GTP hydrolysis for membrane remodeling? By monitoring the ionic permeability through lipid nanotubes (NT), we found that dynamin was capable of squeezing NT to extremely small radii, depending on the NT lipid composition. However, long dynamin scaffolds did not produce fission: instead, fission followed GTPase-dependent cycles of assembly and disassembly of short dynamin scaffolds and involved a stochastic process dependent on the curvature stress imposed by dynamin. Fission happened spontaneously upon NT release from the scaffold, without leakage. Our calculations revealed that local narrowing of NT could induce cooperative lipid tilting, leading to self-merger of the inner monolayer of NT (hemifission), consistent with the absence of leakage. We propose that dynamin transmits GTP's energy to periodic assembling of a limited curvature scaffold that brings lipids to an unstable intermediate.

ER biogenesis: self-assembly of tubular topology by protein hairpins

The structure of the endoplasmic reticulum (ER) depends on members of the reticulon and DP1/Yop1p families. Two of these proteins are sufficient to form tubular membrane networks from pure phospholipid vesicles, thus revealing a new paradigm of ER morphogenesis.

Flexible scaffolding made of rigid BARs

Crescent-shaped BAR domains are generic actors in the creation of membrane curvature. In this issue, Frost et al. (2008) reveal how collective twisting of rigid F-BAR domains on a soft membrane surface may lead to different membrane curvatures.

Possible mechanisms for the regulation of neutrophil apoptosis during allergic inflammation

The neutrophil-mediated inflammatory response is regulated via activation of the apoptosis program, which decreases the degree of tissue alteration. In rabbits with allergic inflammation a significant negative correlation was revealed between the intensity of neutrophil apoptosis and blood interferon-gamma concentration.

Vesicle formation by self-assembly of membrane-bound matrix proteins into a fluidlike budding domain

The shape of enveloped viruses depends critically on an internal protein matrix, yet it remains unclear how the matrix proteins control the geometry of the envelope membrane. We found that matrix proteins purified from Newcastle disease virus adsorb on a phospholipid bilayer and condense into fluidlike domains that cause membrane deformation and budding of spherical vesicles, as seen by fluorescent and electron microscopy. Measurements of the electrical admittance of the membrane resolved the gradual growth and rapid closure of a bud followed by its separation to form a free vesicle. The vesicle size distribution, confined by intrinsic curvature of budding domains, but broadened by their merger, matched the virus size distribution. Thus, matrix proteins implement domain-driven mechanism of budding, which suffices to control the shape of these proteolipid vesicles.

Pathophysiological aspects of functional modulation of human peripheral blood neutrophils with propranolol

We studied the effect of beta-adrenoceptor antagonist propranolol on the regulation of spontaneous apoptosis in neutrophils, priming of lipopolysaccharide-treated neutrophils, and expression of neutrophil adhesion factors. The influence of propranolol on apoptosis, adhesion, and generation of oxygen radicals by neutrophils was shown to be an additional mechanism of the action of beta-adrenoceptor antagonists. This pathophysiological mechanism probably mediates the effect of neuroendocrine transmitters and explains the role of adrenergic antagonists in the pathogenesis and therapy of inflammation, cardiovascular diseases, and bronchial asthma.

[Ecological pathophysiology]

Ecological pathophysiology is characterized. Some mechanisms of development of diseases resultant from impaired natural relations between humans and environment are analysed.

Laser diffraction for standardization of heterogeneous pharmaceutical preparations

A new quantitative method for standardization of heterogeneous pharmaceutical preparations and their quality control during storage based on laser diffraction is proposed. A series of pharmaceutical dosage forms--suspensions, emulsions, tinctures, decoctions, cell preparations and others, are heterogeneous medicines. In some cases disperse phase can be formed during storage as a result of layering (L1/L2) or precipitation (S/L). Laser diffraction method proposed in this study can be used for standardization and quality control of medicines.

Blood Pressure and Contractile Function of Heart Ventricles at the Early Stages of Hypertonic Process

In rabbits, arterial hypertension was characterized by progressive elevation of systolic and diastolic blood pressure. The contractile function of the left ventricle augmented, but its potential working capacity decreased. Opposite changes were observed in the right ventricle. It was hypothesized that the compensatory mechanisms in the right ventricle during arterial hypertension are triggered at the very onset of the pathology, while in the left ventricle they develop later.