Mitochondrial Ca(2+) and apoptosis

Mitochondria are key decoding stations of the apoptotic process. In support of this view, a large body of experimental evidence has unambiguously revealed that, in addition to the well-established function of producing most of the cellular ATP, mitochondria play a fundamental role in triggering apoptotic cell death. Various apoptotic stimuli cause the release of specific mitochondrial pro-apoptotic factors into the cytosol. The molecular mechanism of this release is still controversial, but there is no doubt that mitochondrial calcium (Ca(2+)) overload is one of the pro-apoptotic ways to induce the swelling of mitochondria, with perturbation or rupture of the outer membrane, and in turn the release of mitochondrial apoptotic factors into the cytosol. Here, we review as different proteins that participate in mitochondrial Ca(2+) homeostasis and in turn modulate the effectiveness of Ca(2+)-dependent apoptotic stimuli. Strikingly, the final outcome at the cellular level is similar, albeit through completely different molecular mechanisms: a reduced mitochondrial Ca(2+) overload upon pro-apoptotic stimuli that dramatically blunts the apoptotic response.     

TRPV6 and Calbindin-D9k-expression and localization in the bovine uterus and placenta during pregnancy

ABSTRACT: BACKGROUND: Transient receptor potential channel type 6 (TRPV6) and Calbindin-D9k (CaBP-9 k) are involved in the active calcium (Ca2+) transport mechanism in many tissues including placenta and uterus, suggesting a role in the establishment and maintenance of pregnancy. Moreover, TRPV6 and CaBP-9 k seem to support the materno-fetal Ca2+ transport that is crucial for fetal Ca2+ homeostasis, bone growth and development. However, it is unknown if these proteins are also involved in the aetiology of pathologies associated with parturition in cows, such as retained fetal membranes (RFM). The aim of the current study was to create an expression profile of uterine and placentomal TRPV6 and CaBP-9 k mRNAs and proteins during pregnancy and postpartum in cows with and without fetal membrane release. METHODS: Uteri and placentomes of 27 cows in different stages of pregnancy and placentomes of cows with and without RFM were collected. Protein and mRNA expression of TRPV6 and CaBP-9 k was investigated by real-time PCR, immunohistochemistry and Western blot. RESULTS: In the uterine endometrium, highest TRPV6 and CaBP-9 k expression was found in the last trimester of pregnancy, with a particular increase of protein in the glandular epithelium. In the placentomes, a gradual increase in TRPV6 mRNA was detectable towards parturition, while protein expression did not change significantly. Placentomal CaBP-9 k expression did not change significantly throughout pregnancy but immunohistochemistry revealed an increase in staining intensity in the maternal crypt epithelium. Immunohistochemical, stronger placental CaBP-9 k signals were seen in animals with RFM compared to animals with an undisturbed fetal membrane release, while protein levels, measured by Western blot analyses did not change significantly. CONCLUSIONS: The results of the present study demonstrate a dynamic expression of TRPV6 and CaBP-9 k during pregnancy in the bovine uterine endometrium and placentomes, suggesting a functional role for these proteins in Ca2+ metabolism during pregnancy. The temporal and spatial expression patterns indicate that TRPV6 and CaBP-9 k may be involved in materno-fetal Ca2+ transport, mainly through an interplacentomal transport, and that both proteins may participate in physiological processes that are crucial for fetal and placental development. However, neither TRPV6 nor CaBP-9 k seem to be causative in the retention of fetal membranes.     

Clinical efficacy of antazoline in rapid cardioversion of paroxysmal atrial fibrillation -- a protocol of a single center, randomized, double-blind, placebo-controlled study (the AnPAF Study)

ABSTRACT: BACKGROUND: Rapid conversion of atrial fibrillation (AF) to sinus rhythm may be achieved by the administration of class IA, IC and III antiarrhythmic drugs or vernakalant hydrochloride. However, that treatment may be related to potential pro-arrhythmia, lack of efficacy or the exceptionally high cost of a compound used. Antazoline is a first generation antihistaminic agent with chinidin-like properties. When administered intravenously, antazoline exerts a strong antiarrhythmic effect on supraventricular arrhythmia, especially on AF, facilitating rapid conversion to sinus rhythm. Despite a relative lack of published data antazoline has been marketed in Poland and widely used in cardiology wards and emergency rooms for many years due to its efficacy, safety and rapid onset of action within minutes of administration. METHODS: A randomized, double blind, placebo-controlled, superiority clinical trial was designed to assess clinical efficacy of antazoline in rapid conversion of AF to sinus rhythm. Eligible patients will present AF lasting less than 43 hours, will be in stable cardio-pulmonary condition and will have no prior history of advanced heart failure or significant valvular disease. Long-term antiarrhythmic therapy is not considered an exclusion criterion. Subjects who fulfill selection criteria will be randomly assigned to receive intravenously either antazoline or placebo in divided doses and observed for 1.5 hours after conversion to sinus rhythm or after the last i.v. bolus. Primary end point will be the conversion of AF to sinus rhythm confirmed in an electrocardiogram (ECG) during the observation period. Secondary end points will be comprised of time to conversion and return of AF during the observation period. Special consideration will be given to the observation of any adverse events. A sample size of 80 patients was calculated based on the following assumptions: two-tailed test, a type I error of 0.01, a power of 90%, efficacy of placebo 5%, efficacy of antazoline 50% and 20% drop-out rate to fulfill the criteria of intention-to-treat analysis. Due to the presumed lack of statistical power, the secondary end points and safety endpoints will be considered exploratory.Clinical trials registryClinicalTrials.gov, NCT01527279.     

Melanosome–iron interactions within retinal pigment epithelium‐derived cells

Melanosomes were recently shown to protect ARPE‐19 cells, a human retinal pigment epithelium (RPE) cell line, against oxidative stress induced by hydrogen peroxide. One postulated mechanism of antioxidant action of melanin is its ability to bind metal ions. The aim here was to determine whether melanosomes are competent to bind iron within living cells, exhibiting a property previously shown only in model systems. The outcomes indicate retention of prebound iron and accumulation of iron by granules after iron delivery to cells via the culture medium, as determined by both colorimetric and electron spin resonance analyses for bound‐to‐melanosome iron. Manipulation of iron content did not affect the pigment's ability to protect cells against H₂O₂, but the function of pigment granules within RPE cells should be extended beyond a role in light irradiation to include participation in iron homeostasis.     

Secondary structure and orientation of the pore-forming toxin lysenin in a sphingomyelin-containing membrane

Lysenin is a sphingomyelin-recognizing toxin which forms stable oligomers upon membrane binding and causes cell lysis. To get insight into the mechanism of the transition of lysenin from a soluble to a membrane-bound form, surface activity of the protein and its binding to lipid membranes were studied using tensiometric measurements, Fourier-transform infrared spectroscopy (FTIR) and FTIR-linear dichroism. The results showed cooperative adsorption of recombinant lysenin-His at the argon-water interface from the water subphase which suggested self-association of lysenin-His in solution. An assembly of premature oligomers by lysenin-His in solution was confirmed by blue native gel electrophoresis. When a monolayer composed of sphingomyelin and cholesterol was present at the interface, the rate of insertion of lysenin-His into the monolayer was considerably enhanced. Analysis of FTIR spectra of soluble lysenin-His demonstrated that the protein contained 27% beta-sheet, 28% aggregated beta-strands, 10% alpha-helix, 23% turns and loops and 12% different kinds of aggregated forms. In membrane-bound lysenin-His the total content of alpha-helices, turns and loops, and beta-structures did not change, however, the 1636cm(-1) beta-sheet band increased from 18% to 31% at the expense of the 1680cm(-1) beta-sheet structure. Spectral analysis of the amide I band showed that the alpha-helical component was oriented with at 41 degrees to the normal to the membrane, indicating that this protein segment could be anchored in the hydrophobic core of the membrane.     

Canine olfactory receptor gene polymorphism and its relation to odor detection performance by sniffer dogs

The outstanding sensitivity of the canine olfactory system has been acknowledged by using sniffer dogs in military and civilian service for detection of a variety of odors. It is hypothesized that the canine olfactory ability is determined by polymorphisms in olfactory receptor (OR) genes. We investigated 5 OR genes for polymorphic sites which might affect the olfactory ability of service dogs in different fields of specific substance detection. All investigated OR DNA sequences proved to have allelic variants, the majority of which lead to protein sequence alteration. Homozygous individuals at 2 gene loci significantly differed in their detection skills from other genotypes. This suggests a role of specific alleles in odor detection and a linkage between single-nucleotide polymorphism and odor recognition efficiency.     

The role of mitochondrial permeability transition pore in physiology and pathology of the cell

Mitochondrial megachannel, a multiprotein complex, is localized in close contacts of the outer and the inner mitochondrial membranes. It plays important role in many aspects of cell physiology and its opening can have different consequences. This review summarizes the present knowledge about structure and function of the megachannel in the cell.     

Modeling studies of potato nucleoside triphosphate diphosphohydrolase NTPDase1: an insight into the catalytic mechanism

Nucleoside triphosphate diphosphohydrolase--NTPDase1 (apyrase, EC 3.6.1.5) was modeled based on sequence homology. The single polypeptide chain of apyrase is folded into two domains. The putative catalytic site with the apyrase conserved regions (ACR 1-5) is located between these two domains. Modeling confirmed that apyrase belongs to the actin superfamily of proteins. The amino acids interacting with the nucleoside triphosphate substrate and probably involved in the catalyzed hydrolysis were identified. The proposed two-step catalytic mechanism of hydrolysis involves Thr127 and Thr55 as potential nucleophilic factors responsible for the cleavage of the Pgamma and Pbeta anhydride bonds, respectively. Their action seems to be assisted by Glu170 and Glu78 residues, respectively. The presence of two nucleophiles in the active site of apyrase explains the differences in the hydrolytic activity between apyrases and other enzymes belonging to the NTPDase family.