Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Protein kinase C-dependent phosphorylation and mitochondrial translocation of aldose reductase

Although aldose reductase (AR) is a critical participant in osmoregulation, and the metabolism of glucose and aldehydes derived from lipid peroxidation, post-translational mechanisms regulating its activity have not been identified. In this paper, we report that stimulation of protein kinase C (PKC) in several cell types induces phosphorylation of AR and translocation of the phosphorylated protein to the mitochondria. In vitro, recombinant AR was directly phosphorylated by activated PKC, suggesting that AR may be an in vivo PKC substrate. Together, these observations reveal a novel link between PKC activation and the regulation of glucose and aldehyde metabolism.     

Nitric oxide synthase inhibition in human sperm affects sperm-oocyte fusion but not zona pellucida binding

There is recent evidence that mouse and human spermatozoa contain constitutive nitric oxide synthase (cNOS) and can synthesize nitric oxide. The aim of this study was to investigate whether the inhibition of human sperm cNOS could affect sperm-oocyte fusion and sperm binding to the zona pellucida (ZP). N(G)-nitro-L-arginine methyl ester (L-NAME) was used as cNOS inhibitor. Sperm-oocyte fusion was evaluated using the hamster egg penetration test (HEPT). The ZP binding was evaluated using the hemizona assay. L-NAME added from the onset of capacitation strongly inhibited sperm-oocyte fusion. This inhibitory effect was dose dependent, stereospecific, and suppressed by L-arginine in a dose-dependent manner. L-NAME also inhibited sperm-oocyte fusion in the HEPT enhanced with progesterone (P), where P (5 microM) was added for 15 min to capacitated sperm. A lesser but significant inhibition was also observed when sperm suspensions were exposed to L-NAME following capacitation in both versions of HEPT. On the contrary, L-NAME did not affect ZP binding. In conclusion, the present study provides the evidence that cNOS plays a role in the human sperm's capacity to fuse with oocyte but not in the ZP binding.     

Mitochondrial Profiling of Acute Myeloid Leukemia in the Assessment of Response to Apoptosis Modulating Drugs

BH3 profiling measures the propensity of transformed cells to undergo intrinsic apoptosis and is determined by exposing cells to BH3-mimicking peptides. We hypothesized that basal levels of prosurvival BCL-2 family proteins may modulate the predictive power of BH3 profiling and termed it mitochondrial profiling. We investigated the correlation between cell sensitivity to apoptogenic agents and mitochondrial profiling, using a panel of acute myeloid leukemias induced to undergo apoptosis by exposure to cytarabine, the BH3 mimetic ABT-199, the MDM2 inhibitor Nutlin-3a, or the CRM1 inhibitor KPT-330. We found that the apoptogenic efficacies of ABT-199 and cytarabine correlated well with BH3 profiling reflecting BCL2, but not BCL-XL or MCL-1 dependence. Baseline BCL-2 protein expression analysis increased the ability of BH3 profiling to predict resistance mediated by MCL-1. By utilizing engineered cells with overexpression or knockdown of BCL-2 family proteins, Ara-C was found to be independent, while ABT-199 was dependent on BCL-XL. BCL-2 and BCL-XL overexpression mediated resistance to KPT-330 which was not reflected in the BH3 profiling assay, or in baseline BCL-2 protein levels. In conclusion, mitochondrial profiling, the combination of BH3 profiling and prosurvival BCL-2 family protein analysis, represents an improved approach to predict efficacy of diverse agents in AML and may have utility in the design of more effective drug combinations.     

Radiation of the Tnt1 retrotransposon superfamily in three Solanaceae genera

Background  

Tnt1 was the first active plant retrotransposon identified in tobacco after nitrate reductase gene disruption. The Tnt1 superfamily comprises elements from Nicotiana (Tnt1 and Tto1) and Lycopersicon (Retrolyc1 and Tlc1) species. The study presented here was conducted to characterise Tnt1-related sequences in 20 wild species of Solanum and five cultivars of Solanum tuberosum.     

Unresolved molecular phylogenies of gibbons and siamangs (Family: Hylobatidae) based on mitochondrial, Y-linked, and X-linked loci indicate a rapid Miocene radiation or sudden vicariance event

According to recent taxonomic reclassification, the primate family Hylobatidae contains four genera (Hoolock, Nomascus, Symphalangus, and Hylobates) and between 14 and 18 species, making it by far the most species-rich group of extant hominoids. Known as the "small apes", these small arboreal primates are distributed throughout Southeast, South and East Asia. Considerable uncertainty surrounds the phylogeny of extant hylobatids, particularly the relationships among the genera and the species within the Hylobates genus. In this paper we use parsimony, likelihood, and Bayesian methods to analyze a dataset containing nearly 14 kilobase pairs, which includes newly collected sequences from X-linked, Y-linked, and mitochondrial loci together with data from previous mitochondrial studies. Parsimony, likelihood, and Bayesian analyses largely failed to find a significant difference among phylogenies with any of the four genera as the most basal taxon. All analyses, however, support a tree with Hylobates and Symphalangus as most closely related genera. One strongly supported phylogenetic result within the Hylobates genus is that Hylobates pileatus is the most basal taxon. Multiple analyses failed to find significant support for any singular genus-level phylogeny. While it is natural to suspect that there might not be sufficient data for phylogenetic resolution (whenever that situation occurs), an alternative hypothesis relating to the nature of gibbon speciation exists. This lack of resolution may be the result of a rapid radiation or a sudden vicariance event of the hylobatid genera, and it is likely that a similarly rapid radiation occurred within the Hylobates genus. Additional molecular and paleontological evidence are necessary to better test among these, and other, hypotheses of hylobatid evolution.     

PKR regulates B56(alpha)-mediated BCL2 phosphatase activity in acute lymphoblastic leukemia-derived REH cells

Protein phosphatase 2A (PP2A) is a heterotrimer comprising catalytic, scaffold, and regulatory (B) subunits. There are at least 21 B subunit family members. Thus PP2A is actually a family of enzymes defined by which B subunit is used. The B56 family member B56alpha is a phosphoprotein that regulates dephosphorylation of BCL2. The stress kinase PKR has been shown to phosphorylate B56alpha at serine 28 in vitro, but it has been unclear how PKR might regulate the BCL2 phosphatase. In the present study, PKR regulation of B56alpha in REH cells was examined, because these cells exhibit robust BCL2 phosphatase activity. PKR was found to be basally active in REH cells as would be predicted if the kinase supports B56alpha-mediated dephosphorylation of BCL2. Suppression of PKR promoted BCL2 phosphorylation with concomitant loss of B56alpha phosphorylation at serine 28 and inhibition of mitochondrial PP2A activity. PKR supports stress signaling in REH cells, as suppression of PKR promoted chemoresistance to etoposide. Suppression of PKR promoted B56alpha proteolysis, which could be blocked by a proteasome inhibitor. However, the mechanism by which PKR supports B56alpha protein does not involve PKR-mediated phosphorylation of the B subunit at serine 28 but may involve eIF2alpha activation of AKT. Phosphorylation of serine 28 by PKR promotes mitochondrial localization of B56alpha, because wild-type but not mutant S28A B56alpha promoted mitochondrial PP2A activity. Cells expressing wild-type B56alpha but not S28A B56alpha were sensitized to etoposide. These results suggest that PKR regulates B56alpha-mediated PP2A signaling in REH cells.