A continuous flow bioreactor system for high-throughput hyperpolarized metabolic flux analysis

Hyperpolarized carbon-13 labeled compounds are increasingly being used in medical MR imaging (MRI) and MR imaging (MRI) and spectroscopy (MRS) research, due to its ability to monitor tissue and cell metabolism in real-time. Although radiological biomarkers are increasingly being considered as clinical indicators, biopsies are still considered the gold standard for a large variety of indications. Bioreactor systems can play an important role in biopsy examinations because of their ability to provide a physiochemical environment that is conducive for therapeutic response monitoring ex vivo. We demonstrate here a proof-of-concept bioreactor and microcoil receive array setup that allows for ex vivo preservation and metabolic NMR spectroscopy on up to three biopsy samples simultaneously, creating an easy-to-use and robust way to simultaneously run multisample carbon-13 hyperpolarization experiments. Experiments using hyperpolarized [1-13C]pyruvate on ML-1 leukemic cells in the bioreactor setup were performed and the kinetic pyruvate-to-lactate rate constants ( k PL ) extracted. The coefficient of variation of the experimentally found k PL s for five repeated experiments was C V = 35 % . With this statistical power, treatment effects of 30%-40% change in lactate production could be easily differentiable with only a few hyperpolarization dissolutions on this setup. Furthermore, longitudinal experiments showed preservation of ML-1 cells in the bioreactor setup for at least 6 h. Rat brain tissue slices were also seen to be preserved within the bioreactor for at least 1 h. This validation serves as the basis for further optimization and upscaling of the setup, which undoubtedly has huge potential in high-throughput studies with various biomarkers and tissue types.

Na+,K+-ATPase with Disrupted Na+ Binding Sites I and III Binds Na+ with Increased Affinity at Site II and Undergoes Na+-Activated Phosphorylation with ATP

Na+,K+-ATPase actively extrudes three cytoplasmic Na+ ions in exchange for two extracellular K+ ions for each ATP hydrolyzed. The atomic structure with bound Na+ identifies three Na+ sites, named I, II, and III. It has been proposed that site III is the first to be occupied and site II last, when Na+ binds from the cytoplasmic side. It is usually assumed that the occupation of all three Na+ sites is obligatory for the activation of phosphoryl transfer from ATP. To obtain more insight into the individual roles of the ion-binding sites, we have analyzed a series of seven mutants with substitution of the critical ion-binding residue Ser777, which is a shared ligand between Na+ sites I and III. Surprisingly, mutants with large and bulky substituents expected to prevent or profoundly disturb Na+ access to sites I and III retain the ability to form a phosphoenzyme from ATP, even with increased apparent Na+ affinity. This indicates that Na+ binding solely at site II is sufficient to promote phosphorylation. These mutations appear to lock the membrane sector into an E1-like configuration, allowing Na+ but not K+ to bind at site II, while the cytoplasmic sector undergoes conformational changes uncoupled from the membrane sector.

On the track of the lipid transport pathway of the phospholipid flippase ATP8A2 - Mutation analysis of residues of the transmembrane segments M1, M2, M3 and M4

P4-ATPases, also known as flippases, translocate specific lipids from the exoplasmic leaflet to the cytoplasmic leaflet of biological membranes, thereby generating an asymmetric lipid distribution essential for numerous cellular functions. A debated issue is which pathway within the protein the lipid substrate follows during the translocation. Here we present a comprehensive mutational screening of all amino acid residues in the transmembrane segments M1, M2, M3, and M4 of the flippase ATP8A2, thus allowing the functionally important residues in these transmembrane segments to be highlighted on a background of less important residues. Kinetic analysis of ATPase activity of 130 new ATP8A2 mutants, providing Vmax values as well as apparent affinities of the mutants for the lipid substrate, support a translocation pathway between M2 and M4 ("M2-M4 path"), extending from the entry site, where the lipid substrate binds from the exoplasmic leaflet, to a putative exit site at the cytoplasmic surface, formed by the divergence of M2 and M4. The effects of mutations in the M2-M4 path on the function of the entry site, including loss of lipid specificity in some mutants, suggest that the M2-M4 path and the entry site are conformationally coupled. Many of the residues of the M2-M4 path possess side chains with a potential for interacting with each other in a zipper-like mode, as well as with the head group of the lipid substrate, by ionic/hydrogen bonds. Thus, the translocation of the lipid substrate toward the cytoplasmic bilayer leaflet is comparable to unzipping a zipper of salt bridges/hydrogen bonds.

Electrogenic reaction step and phospholipid translocation pathway of the mammalian P4-ATPase ATP8A2

ATP8A2 is a mammalian P4-ATPase (flippase) that translocates the negatively charged lipid substrate phosphatidylserine from the exoplasmic leaflet to the cytoplasmic leaflet of cellular membranes. Using an electrophysiological method based on solid supported membranes, we investigated the electrogenicity of specific reaction steps of ATP8A2 and explored a potential phospholipid translocation pathway involving residues with positively charged side chains. Changes to the current signals caused by mutations show that the main electrogenic event occurs in connection with the release of the bound phosphatidylserine to the cytoplasmic leaflet and support the hypothesis that the phospholipid interacts with specific lysine and arginine residues near the cytoplasmic border of the lipid bilayer during the translocation and reorientation required for insertion into the cytoplasmic leaflet.

Temperature instability of a mutation at a multidomain junction in Na,K-ATPase isoform ATP1A3 (p.Arg756His) produces a fever-induced neurological syndrome

ATP1A3 encodes the α3 isoform of Na,K-ATPase. In the brain, it is expressed only in neurons. Human ATP1A3 mutations produce a wide spectrum of phenotypes, but particular syndromes are associated with unique substitutions. For arginine 756, at the junction of membrane and cytoplasmic domains, mutations produce encephalopathy during febrile infections. Here we tested the pathogenicity of p.Arg756His (R756H) in isogenic mammalian cells. R756H protein had sufficient transport activity to support cells when endogenous ATP1A1 was inhibited. It had half the turnover rate of wildtype, reduced affinity for Na⁺, and increased affinity for K⁺. There was modest endoplasmic reticulum retention during biosynthesis at 37 °C but little benefit from the folding drug phenylbutyrate (4-PBA), suggesting a tolerated level of misfolding. When cells were incubated at just 39 °C, however, α3 protein level dropped without loss of β subunit, paralleled by an increase of endogenous α1. Elevated temperature resulted in internalization of α3 from the surface along with some β subunit, accompanied by cytoplasmic redistribution of a marker of lysosomes and endosomes, lysosomal-associated membrane protein 1. After return to 37 °C, α3 protein levels recovered with cycloheximide-sensitive new protein synthesis. Heating in vitro showed activity loss at a rate 20- to 30-fold faster than wildtype, indicating a temperature-dependent destabilization of protein structure. Arg756 appears to confer thermal resistance as an anchor, forming hydrogen bonds among four linearly distant parts of the Na,K-ATPase structure. Taken together, our observations are consistent with fever-induced symptoms in patients.

Role of a conserved ion-binding site tyrosine in ion selectivity of the Na+/K+ pump

The essential transmembrane Na+ and K+ gradients in animal cells are established by the Na+/K+ pump, a P-type ATPase that exports three Na+ and imports two K+ per ATP hydrolyzed. The mechanism by which the Na+/K+ pump distinguishes between Na+ and K+ at the two membrane sides is poorly understood. Crystal structures identify two sites (sites I and II) that bind Na+ or K+ and a third (site III) specific for Na+. The side chain of a conserved tyrosine at site III of the catalytic α-subunit (Xenopus-α1 Y780) has been proposed to contribute to Na+ binding by cation-π interaction. We substituted Y780 with natural and unnatural amino acids, expressed the mutants in Xenopus oocytes and COS-1 cells, and used electrophysiology and biochemistry to evaluate their function. Substitutions disrupting H-bonds impaired Na+ interaction, while Y780Q strengthened it, likely by H-bond formation. Utilizing the non-sense suppression method previously used to incorporate unnatural derivatives in ion channels, we were able to analyze Na+/K+ pumps with fluorinated tyrosine or phenylalanine derivatives inserted at position 780 to diminish cation-π interaction strength. In line with the results of the analysis of mutants with natural amino acid substitutions, the results with the fluorinated derivatives indicate that Na+-π interaction with the phenol ring at position 780 contributes minimally, if at all, to the binding of Na+. All Y780 substitutions decreased K+ apparent affinity, highlighting that a state-dependent H-bond network is essential for the selectivity switch at sites I and II when the pump changes conformational state.

ATP1A2- and ATP1A3-associated early profound epileptic encephalopathy and polymicrogyria

Constitutional heterozygous mutations of ATP1A2 and ATP1A3, encoding for two distinct isoforms of the Na+/K+-ATPase (NKA) alpha-subunit, have been associated with familial hemiplegic migraine (ATP1A2), alternating hemiplegia of childhood (ATP1A2/A3), rapid-onset dystonia-parkinsonism, cerebellar ataxia-areflexia-progressive optic atrophy, and relapsing encephalopathy with cerebellar ataxia (all ATP1A3). A few reports have described single individuals with heterozygous mutations of ATP1A2/A3 associated with severe childhood epilepsies. Early lethal hydrops fetalis, arthrogryposis, microcephaly, and polymicrogyria have been associated with homozygous truncating mutations in ATP1A2. We investigated the genetic causes of developmental and epileptic encephalopathies variably associated with malformations of cortical development in a large cohort and identified 22 patients with de novo or inherited heterozygous ATP1A2/A3 mutations. We characterized clinical, neuroimaging and neuropathological findings, performed in silico and in vitro assays of the mutations' effects on the NKA-pump function, and studied genotype-phenotype correlations. Twenty-two patients harboured 19 distinct heterozygous mutations of ATP1A2 (six patients, five mutations) and ATP1A3 (16 patients, 14 mutations, including a mosaic individual). Polymicrogyria occurred in 10 (45%) patients, showing a mainly bilateral perisylvian pattern. Most patients manifested early, often neonatal, onset seizures with a multifocal or migrating pattern. A distinctive, 'profound' phenotype, featuring polymicrogyria or progressive brain atrophy and epilepsy, resulted in early lethality in seven patients (32%). In silico evaluation predicted all mutations to be detrimental. We tested 14 mutations in transfected COS-1 cells and demonstrated impaired NKA-pump activity, consistent with severe loss of function. Genotype-phenotype analysis suggested a link between the most severe phenotypes and lack of COS-1 cell survival, and also revealed a wide continuum of severity distributed across mutations that variably impair NKA-pump activity. We performed neuropathological analysis of the whole brain in two individuals with polymicrogyria respectively related to a heterozygous ATP1A3 mutation and a homozygous ATP1A2 mutation and found close similarities with findings suggesting a mainly neural pathogenesis, compounded by vascular and leptomeningeal abnormalities. Combining our report with other studies, we estimate that ∼5% of mutations in ATP1A2 and 12% in ATP1A3 can be associated with the severe and novel phenotypes that we describe here. Notably, a few of these mutations were associated with more than one phenotype. These findings assign novel, 'profound' and early lethal phenotypes of developmental and epileptic encephalopathies and polymicrogyria to the phenotypic spectrum associated with heterozygous ATP1A2/A3 mutations and indicate that severely impaired NKA pump function can disrupt brain morphogenesis.

Fasted and fed state human duodenal fluids: Characterization, drug solubility, and comparison to simulated fluids and with human bioavailability

Accurate in vivo predictions of intestinal absorption of low solubility drugs require knowing their solubility in physiologically relevant dissolution media. Aspirated human intestinal fluids (HIF) are the gold standard, followed by simulated intestinal HIF in the fasted and fed state (FaSSIF/FeSSIF). However, current HIF characterization data vary, and there is also some controversy regarding the accuracy of FaSSIF and FeSSIF for predicting drug solubility in HIF. This study aimed at characterizing fasted and fed state duodenal HIF from 16 human volunteers with respect to pH, buffer capacity, osmolarity, surface tension, as well as protein, phospholipid, and bile salt content. The fasted and fed state HIF samples were further used to investigate the equilibrium solubility of 17 representative low-solubility small-molecule drugs, six of which were confidential industry compounds and 11 were known and characterized regarding chemical diversity. These solubility values were then compared to reported solubility values in fasted and fed state HIF, FaSSIF and FeSSIF, as well as with their human bioavailability for both states. The HIF compositions corresponded well to previously reported values and current FaSSIF and FeSSIF compositions. The drug solubility values in HIF (both fasted and fed states) were also well in line with reported solubility data for HIF, as well as simulated FaSSIF and FeSSIF. This indicates that the in vivo conditions in the proximal small intestine are well represented by simulated intestinal fluids in both composition and drug equilibrium solubility. However, increased drug solubility in the fed vs. fasted states in HIF did not correlate with the human bioavailability changes of the same drugs following oral administration in either state.

Evaluation and Safety Validation of Dehydrating Methods for Goat Meat in Rural Malawi

ObjectivesThis study was conducted to evaluate the dehydration methods of goat meat based in Malawi and the effects on food safety.Materials and MethodsGoat meat was prepared as ground, minced, and whole muscle strips. Samples were treated with 6% lemon juice marinade, 6% vinegar marinade, or salt rub. During phase 1, dehydration of the meat was performed with a solar dehydrator (n = 108), electric oven (n = 108) or drum oven (n = 108). Qualitative data on the three drying methods was collected from a panel of students from Mzuzu University, Malawi, on the practicality of each method in a local rural setting. Additionally, visual observations were conducted 30 d prior to drying for the presence of mold and insects to give an indication of shelf life. Phase 2 was performed at Texas Tech University in Lubbock, Texas where whole muscle strips of lamb were submerged in a five-strain Escherichia coli surrogate cocktail of Escherichia coli for 5 min, allowed 30 min for cell attachment, then dried using an electric and drum oven, replicating the dehydration procedure in Malawi. For each replicate (n = 2), attachment samples (n = 10), samples dried in the electric oven (n = 10) and samples dried in drum oven samples (n = 10) were aseptically plated on MacConkey agar with a TSA overlay and enumerated for E. coli.ResultsIn phase 1, mold growth was observed on 15.7% (34/216) of samples dried in the solar dehydrator and drum oven. Of those positive for mold, 32.4% (n = 11) were minced, and 67.6% (n = 23) were whole muscle strips. No samples dried using the electric oven displayed mold (0/108). No samples displayed insects. Based on qualitative data that was gathered, top reasons to dry goat meat using the drum oven include “not requiring electricity” and “drum ovens are a common piece of equipment in villages”. Top reasons against using a drum oven include “unequal distribution of heat” and “high level of oversight required during drying”. Top reasons to dry goat meat using electric oven include “fast drying time”, “uniform distribution of heat”, and “limited oversight required”. Top reasons against using electric oven to dry goat meat include “requiring electricity” and “low knowledge of electric oven operation in a community setting”. Top reasons to use the solar dehydrator to dry goat meat include “not requiring electricity or firewood” and “limited oversight required”. Top reasons against using the solar dehydrator to dry goat meat include “slow drying time” and “uneven heat distribution due to time of day and shadows”. In phase 2, a 5-log reduction was observed for all electric oven treatment replicates (100%, 2/2) and half drum oven (50%, 1/2) replicates. However, variation in the reduction of E.coli is a direct result of weather and fuel provided to the drum oven.ConclusionElectric drying oven displayed the most consistent results for shelf life and safety. However, in rural Malawi, dehydrating methods should be chosen on a case by case basis.

Functional consequences of the CAPOS mutation E818K of Na+,K+-ATPase

The cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) syndrome is caused by the single mutation E818K of the α3-isoform of Na⁺,K⁺-ATPase. Here, using biochemical and electrophysiological approaches, we examined the functional characteristics of E818K, as well as of E818Q and E818A mutants. We found that these amino acid substitutions reduce the apparent Na⁺ affinity at the cytoplasmic-facing sites of the pump protein and that this effect is more pronounced for the lysine and glutamine substitutions (3-4-fold) than for the alanine substitution. The electrophysiological measurements indicated a more conspicuous, ∼30-fold reduction of apparent Na⁺ affinity for the extracellular-facing sites in the CAPOS mutant, which was related to an accelerated transition between the phosphoenzyme intermediates E₁P and E₂P. The apparent affinity for K⁺ activation of the ATPase activity was unaffected by these substitutions, suggesting that primarily the Na⁺-specific site III is affected. Furthermore, the apparent affinities for ATP and vanadate were WT-like in E818K, indicating a normal E₁-E₂ equilibrium of the dephosphoenzyme. Proton-leak currents were not increased in E818K. However, the CAPOS mutation caused a weaker voltage dependence of the pumping rate and a stronger inhibition by cytoplasmic K⁺ than the WT enzyme, which together with the reduced Na⁺ affinity of the cytoplasmic-facing sites precluded proper pump activation under physiological conditions. The functional deficiencies could be traced to the participation of Glu-818 in an intricate hydrogen-bonding/salt-bridge network, connecting it to key residues involved in Na⁺ interaction at site III.

The α2β2 isoform combination dominates the astrocytic Na+ /K+ -ATPase activity and is rendered nonfunctional by the α2.G301R familial hemiplegic migraine type 2-associated mutation

Synaptic activity results in transient elevations in extracellular K+ , clearance of which is critical for sustained function of the nervous system. The K+ clearance is, in part, accomplished by the neighboring astrocytes by mechanisms involving the Na+ /K+ -ATPase. The Na+ /K+ -ATPase consists of an α and a β subunit, each with several isoforms present in the central nervous system, of which the α2β2 and α2β1 isoform combinations are kinetically geared for astrocytic K+ clearance. While transcript analysis data designate α2β2 as predominantly astrocytic, the relative quantitative protein distribution and isoform pairing remain unknown. As cultured astrocytes altered their isoform expression in vitro, we isolated a pure astrocytic fraction from rat brain by a novel immunomagnetic separation approach in order to determine the expression levels of α and β isoforms by immunoblotting. In order to compare the abundance of isoforms in astrocytic samples, semi-quantification was carried out with polyhistidine-tagged Na+ /K+ -ATPase subunit isoforms expressed in Xenopus laevis oocytes as standards to obtain an efficiency factor for each antibody. Proximity ligation assay illustrated that α2 paired efficiently with both β1 and β2 and the semi-quantification of the astrocytic fraction indicated that the astrocytic Na+ /K+ -ATPase is dominated by α2, paired with β1 or β2 (in a 1:9 ratio). We demonstrate that while the familial hemiplegic migraine-associated α2.G301R mutant was not functionally expressed at the plasma membrane in a heterologous expression system, α2+/G301R mice displayed normal protein levels of α2 and glutamate transporters and that the one functional allele suffices to manage the general K+ dynamics.

Neurological disease mutations of α3 Na+,K+-ATPase: Structural and functional perspectives and rescue of compromised function

Na⁺,K⁺-ATPase creates transmembrane ion gradients crucial to the function of the central nervous system. The α-subunit of Na⁺,K⁺-ATPase exists as four isoforms (α1-α4). Several neurological phenotypes derive from α3 mutations. The effects of some of these mutations on Na⁺,K⁺-ATPase function have been studied in vitro. Here we discuss the α3 disease mutations as well as information derived from studies of corresponding mutations of α1 in the light of the high-resolution crystal structures of the Na⁺,K⁺-ATPase. A high proportion of the α3 disease mutations occur in the transmembrane sector and nearby regions essential to Na⁺ and K⁺ binding. In several cases the compromised function can be traced to disturbance of the Na⁺ specific binding site III. Recently, a secondary mutation was found to rescue the defective Na⁺ binding caused by a disease mutation. A perspective is that it may be possible to develop an efficient pharmaceutical mimicking the rescuing effect.

Glutamate transporter activity promotes enhanced Na+ /K+ -ATPase-mediated extracellular K+ management during neuronal activity

KEY POINTS

Management of glutamate and K⁺ in brain extracellular space is of critical importance to neuronal function. The astrocytic α2β2 Na⁺ /K⁺ -ATPase isoform combination is activated by the K⁺ transients occurring during neuronal activity. In the present study, we report that glutamate transporter-mediated astrocytic Na⁺ transients stimulate the Na⁺ /K⁺ -ATPase and thus the clearance of extracellular K⁺ . Specifically, the astrocytic α2β1 Na⁺ /K⁺ -ATPase subunit combination displays an apparent Na⁺ affinity primed to react to physiological changes in intracellular Na⁺ . Accordingly, we demonstrate a distinct physiological role in K⁺ management for each of the two astrocytic Na⁺ /K⁺ -ATPase β-subunits.

ABSTRACT

Neuronal activity is associated with transient [K⁺ ]_o increases. The excess K⁺ is cleared by surrounding astrocytes, partly by the Na⁺ /K⁺ -ATPase of which several subunit isoform combinations exist. The astrocytic Na⁺ /K⁺ -ATPase α2β2 isoform constellation responds directly to increased [K⁺ ]_o but, in addition, Na⁺ /K⁺ -ATPase-mediated K⁺ clearance could be governed by astrocytic [Na⁺ ]_i . During most neuronal activity, glutamate is released in the synaptic cleft and is re-absorbed by astrocytic Na⁺ -coupled glutamate transporters, thereby elevating [Na⁺ ]_i . It thus remains unresolved whether the different Na⁺ /K⁺ -ATPase isoforms are controlled by [K⁺ ]_o or [Na⁺ ]_i during neuronal activity. Hippocampal slice recordings of stimulus-induced [K⁺ ]_o transients with ion-sensitive microelectrodes revealed reduced Na⁺ /K⁺ -ATPase-mediated K⁺ management upon parallel inhibition of the glutamate transporter. The apparent intracellular Na⁺ affinity of isoform constellations involving the astrocytic β2 has remained elusive as a result of inherent expression of β1 in most cell systems, as well as technical challenges involved in measuring intracellular affinity in intact cells. We therefore expressed the different astrocytic isoform constellations in Xenopus oocytes and determined their apparent Na⁺ affinity in intact oocytes and isolated membranes. The Na⁺ /K⁺ -ATPase was not fully saturated at basal astrocytic [Na⁺ ]_i , irrespective of isoform constellation, although the β1 subunit conferred lower apparent Na⁺ affinity to the α1 and α2 isoforms than the β2 isoform. In summary, enhanced astrocytic Na⁺ /K⁺ -ATPase-dependent K⁺ clearance was obtained with parallel glutamate transport activity. The astrocytic Na⁺ /K⁺ -ATPase isoform constellation α2β1 appeared to be specifically geared to respond to the [Na⁺ ]_i transients associated with activity-induced glutamate transporter activity.

Importance of a Potential Protein Kinase A Phosphorylation Site of Na+,K+-ATPase and Its Interaction Network for Na+ Binding

The molecular mechanism underlying PKA-mediated regulation of Na(+),K(+)-ATPase was explored in mutagenesis studies of the potential PKA site at Ser-938 and surrounding charged residues. The phosphomimetic mutations S938D/E interfered with Na(+) binding from the intracellular side of the membrane, whereas Na(+) binding from the extracellular side was unaffected. The reduction of Na(+) affinity is within the range expected for physiological regulation of the intracellular Na(+) concentration, thus supporting the hypothesis that PKA-mediated phosphorylation of Ser-938 regulates Na(+),K(+)-ATPase activity in vivo Ser-938 is located in the intracellular loop between transmembrane segments M8 and M9. An extended bonding network connects this loop with M10, the C terminus, and the Na(+) binding region. Charged residues Asp-997, Glu-998, Arg-1000, and Lys-1001 in M10, participating in this bonding network, are crucial to Na(+) interaction. Replacement of Arg-1005, also located in the vicinity of Ser-938, with alanine, lysine, methionine, or serine resulted in wild type-like Na(+) and K(+) affinities and catalytic turnover rate. However, when combined with the phosphomimetic mutation S938E only lysine substitution of Arg-1005 was compatible with Na(+),K(+)-ATPase function, and the Na(+) affinity of this double mutant was reduced even more than in single mutant S938E. This result indicates that the positive side chain of Arg-1005 or the lysine substituent plays a mechanistic role as interaction partner of phosphorylated Ser-938, transducing the phosphorylation signal into a reduced affinity of Na(+) site III. Electrostatic interaction of Glu-998 is of minor importance for the reduction of Na(+) affinity by phosphomimetic S938E as revealed by combining S938E with E998A.

Rescue of Na+ affinity in aspartate 928 mutants of Na+,K+-ATPase by secondary mutation of glutamate 314

The Na(+),K(+)-ATPase binds Na(+) at three transport sites denoted I, II, and III, of which site III is Na(+)-specific and suggested to be the first occupied in the cooperative binding process activating phosphorylation from ATP. Here we demonstrate that the asparagine substitution of the aspartate associated with site III found in patients with rapid-onset dystonia parkinsonism or alternating hemiplegia of childhood causes a dramatic reduction of Na(+) affinity in the α1-, α2-, and α3-isoforms of Na(+),K(+)-ATPase, whereas other substitutions of this aspartate are much less disruptive. This is likely due to interference by the amide function of the asparagine side chain with Na(+)-coordinating residues in site III. Remarkably, the Na(+) affinity of site III aspartate to asparagine and alanine mutants is rescued by second-site mutation of a glutamate in the extracellular part of the fourth transmembrane helix, distant to site III. This gain-of-function mutation works without recovery of the lost cooperativity and selectivity of Na(+) binding and does not affect the E1-E2 conformational equilibrium or the maximum phosphorylation rate. Hence, the rescue of Na(+) affinity is likely intrinsic to the Na(+) binding pocket, and the underlying mechanism could be a tightening of Na(+) binding at Na(+) site II, possibly via movement of transmembrane helix four. The second-site mutation also improves Na(+),K(+) pump function in intact cells. Rescue of Na(+) affinity and Na(+) and K(+) transport by second-site mutation is unique in the history of Na(+),K(+)-ATPase and points to new possibilities for treatment of neurological patients carrying Na(+),K(+)-ATPase mutations.

Sertraline inhibits the transport of PAT1 substrates in vivo and in vitro

BACKGROUND AND PURPOSE

Intestinal nutrient transporters may mediate the uptake of drugs. The aim of this study was to investigate whether sertraline interacts with the intestinal proton-coupled amino acid transporter 1 PAT1 (SLC36A1).

EXPERIMENTAL APPROACH

In vitro investigations of interactions between sertraline and human (h)PAT1, hSGLT1 (sodium-glucose linked transporter 1) and hPepT1 (proton-coupled di-/tri-peptide transporter 1) were conducted in Caco-2 cells using radiolabelled substrates. In vivo pharmacokinetic investigations were conducted in male Sprague-Dawley rats using gaboxadol (10 mg·kg(-1), p.o.) as a PAT1 substrate and sertraline (0-30.6 mg·kg(-1)). Gaboxadol was quantified by hydrophilic interaction chromatography followed by MS/MS detection.

KEY RESULTS

Sertraline inhibited hPAT1-mediated L-[(3)H]-Pro uptake in Caco-2 cells. This interaction between sertraline and PAT1 appeared to be non-competitive. The uptake of the hSGLT1 substrate [(14)C]-α-methyl-D-glycopyranoside and the hPepT1 substrate [(14)C]-Gly-Sar in Caco-2 cells was also decreased in the presence of 0.3 mM sertraline. In rats, the administration of sertraline (0.1-10 mM, corresponding to 0.3-30.6 mg·kg(-1), p.o.) significantly reduced the maximal gaboxadol plasma concentration and AUC after its administration p.o.

CONCLUSIONS AND IMPLICATIONS

Sertraline is an apparent non-competitive inhibitor of hPAT1-mediated transport in vitro. This inhibitory effect of sertraline is not specific to hPAT1 as substrate transport via hPepT1 and hSGLT1 was also reduced in the presence of sertraline. In vivo, sertraline reduced the amount of gaboxadol absorbed, suggesting that the inhibitory effect of sertraline on PAT1 occurs both in vitro and in vivo. Hence, sertraline could alter the bioavailability of drugs absorbed via PAT1.

Relationship between intracellular Na+ concentration and reduced Na+ affinity in Na+,K+-ATPase mutants causing neurological disease

The neurological disorders familial hemiplegic migraine type 2 (FHM2), alternating hemiplegia of childhood (AHC), and rapid-onset dystonia parkinsonism (RDP) are caused by mutations of Na(+),K(+)-ATPase α2 and α3 isoforms, expressed in glial and neuronal cells, respectively. Although these disorders are distinct, they overlap in phenotypical presentation. Two Na(+),K(+)-ATPase mutations, extending the C terminus by either 28 residues ("+28" mutation) or an extra tyrosine ("+Y"), are associated with FHM2 and RDP, respectively. We describe here functional consequences of these and other neurological disease mutations as well as an extension of the C terminus only by a single alanine. The dependence of the mutational effects on the specific α isoform in which the mutation is introduced was furthermore studied. At the cellular level we have characterized the C-terminal extension mutants and other mutants, addressing the question to what extent they cause a change of the intracellular Na(+) and K(+) concentrations ([Na(+)]i and [K(+)]i) in COS cells. C-terminal extension mutants generally showed dramatically reduced Na(+) affinity without disturbance of K(+) binding, as did other RDP mutants. No phosphorylation from ATP was observed for the +28 mutation of α2 despite a high expression level. A significant rise of [Na(+)]i and reduction of [K(+)]i was detected in cells expressing mutants with reduced Na(+) affinity and did not require a concomitant reduction of the maximal catalytic turnover rate or expression level. Moreover, two mutations that increase Na(+) affinity were found to reduce [Na(+)]i. It is concluded that the Na(+) affinity of the Na(+),K(+)-ATPase is an important determinant of [Na(+)]i.

Function and expression of the proton-coupled amino acid transporter PAT1 along the rat gastrointestinal tract: implications for intestinal absorption of gaboxadol

BACKGROUND AND PURPOSE

Intestinal absorption via membrane transporters may determine the pharmacokinetics of drug compounds. The hypothesis is that oral absorption of gaboxadol (4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridine-3-ol) in rats occurs via the proton-coupled amino acid transporter, rPAT1 (encoded by the gene rSlc36a1). Consequently, we aimed to elucidate the in vivo role of rPAT1 in the absorption of gaboxadol from various intestinal segments obtained from Sprague-Dawley rats.

EXPERIMENTAL APPROACH

The absorption of gaboxadol was investigated following its administration into four different intestinal segments. The intestinal expression of rSlc36a1 mRNA was measured by quantitative real-time PCR. Furthermore, the hPAT1-/rPAT1-mediated transport of gaboxadol or L-proline was studied in hPAT1-expressing Xenopus laevis oocytes, Caco-2 cell monolayers and excised segments of the rat intestine.

KEY RESULTS

The absorption fraction of gaboxadol was high (81.3-91.3%) following its administration into the stomach, duodenum and jejunum, but low (4.2%) after administration into the colon. The pharmacokinetics of gaboxadol were modified by the co-administration of L-tryptophan (an hPAT1 inhibitor) and L-proline (an hPAT1 substrate). The in vitro carrier-mediated uptake rate of L-proline in the excised intestinal segments was highest in the mid jejunum and lowest in the colon. The in vitro uptake and the in vivo absorption correlated with the expression of rSlc36a1 mRNA along the rat intestine.

CONCLUSIONS AND IMPLICATIONS

These results suggest that PAT1 mediates the intestinal absorption of gaboxadol and therefore determines its oral bioavailability. This has implications for the in vivo role of PAT1 and may have an influence on the design of pharmaceutical formulations of PAT1 substrates.

In vitro and in vivo performance of novel supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS)

Novel supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) containing the poorly water-soluble drug halofantrine above equilibrium solubility (150% S(eq)) were compared in vitro and in vivo with conventional SNEDDS containing the drug below equilibrium solubility (75% S(eq)). Pre-concentrates comprising of either medium chain lipids (Captex 300/Capmul MCM) or long chain lipids (soybean oil/Maisine), Cremophor RH40 and ethanol were formulated maintaining the lipid-to-surfactant-to-cosolvent ratio constant (55:35:10, w/w %). The ability of super-SNEDDS to increase the absorption of halofantrine in dogs, as well as the predictivity of the dynamic in vitro lipolysis model was studied. In vitro lipolysis of SNEDDS and super-SNEDDS showed rapid drug precipitation from all formulations while the same drug concentrations in the digestion medium were found during digestion of equal amounts of SNEDDS and super-SNEDDS. Elevated halofantrine solubilisation during in vitro lipolysis was observed only when multiple capsules of conventional SNEDDS were subjected to in vitro digestion. After lipolysis the isolated super-SNEDDS pellets were characterised by XRPD revealing no crystalline halofantrine from any of the investigated formulations. Subsequent dissolution studies of the super-SNEDDS pellet in the lipolysis medium demonstrated enhanced dissolution of halofantrine suggesting that halofantrine in the pellet was amorphous. The enhanced dissolution of the amorphous halofantrine was also reflected in vivo since two capsules of conventional SNEDDS were needed to achieve similar AUC and C(max) as obtained after dosing of a single capsule of super-SNEDDS. The study demonstrated that the absorption of halofantrine was not hampered by drug precipitation. Super-SNEDDS lead to precipitation of halofantrine in an amorphous form, which can be the driving force for enhanced absorption. Since super-SNEDDS were also physically stable for at least 6 months they represent a potential novel oral lipid-based drug delivery system for low aqueous soluble compounds.

Inhibition of phosphorylation of na+,k+-ATPase by mutations causing familial hemiplegic migraine

The neurological disorder familial hemiplegic migraine type II (FHM2) is caused by mutations in the α2-isoform of the Na(+),K(+)-ATPase. We have studied the partial reaction steps of the Na(+),K(+)-pump cycle in nine FHM2 mutants retaining overall activity at a level still compatible with cell growth. Although it is believed that the pathophysiology of FHM2 results from reduced extracellular K(+) clearance and/or changes in Na(+) gradient-dependent transport processes in neuroglia, a reduced affinity for K(+) or Na(+) is not a general finding with the FHM2 mutants. Six of the FHM2 mutations markedly affect the maximal rate of phosphorylation from ATP leading to inhibition by intracellular K(+), thereby likely compromising pump function under physiological conditions. In mutants R593W, V628M, and M731T, the defective phosphorylation is caused by local perturbations within the Rossmann fold, possibly interfering with the bending of the P-domain during phosphoryl transfer. In mutants V138A, T345A, and R834Q, long range effects reaching from as far away as the M2 transmembrane helix perturb the function of the catalytic site. Mutant E700K exhibits a reduced rate of E(2)P dephosphorylation without effect on phosphorylation from ATP. An extremely reduced vanadate affinity of this mutant indicates that the slow dephosphorylation reflects a destabilization of the phosphoryl transition state. This seems to be caused by insertion of the lysine between two other positively charged residues of the Rossmann fold. In mutants R202Q and T263M, effects on the A-domain structure are responsible for a reduced rate of the E(1)P to E(2)P transition.

The proton-coupled amino acid transporter, SLC36A1 (hPAT1), transports Gly-Gly, Gly-Sar and other Gly-Gly mimetics

BACKGROUND AND PURPOSE The intestinal proton-coupled amino acid transporter, SLC36A1, transports zwitterionic α-amino acids and drugs such as vigabatrin, gaboxadol and δ-aminolevulinic acid. We hypothesize that SLC36A1 might also transport some dipeptides. The aim of the present study was to investigate SLC36A1-mediated transport of Gly-Gly and Gly-Gly mimetics, and to investigate Gly-Sar transport via SLC36A1 and the proton-coupled dipeptide/tripeptide transporter, SLC15A1 in Caco-2 cells. EXPERIMENTAL APPROACH Transport of a compound via SLC36A1 was determined by its ability to induce an increase in the inward current of two-electrode voltage clamped SLC36A1 cRNA-injected Xenopus laevis oocytes. SLC36A1-mediated L-[³H]Pro uptake in Caco-2 cells was measured in the absence and presence of Gly-Gly or Gly-Sar. In addition, apical [¹⁴C]Gly-Sar uptake was measured in the absence and presence of the SLC36A1 inhibitor 5-hydroxy-L-tryptophan (5-HTP) or the SLC15A1 inhibitor L-4,4'-biphenylalanyl-L-proline (Bip-Pro). KEY RESULTS In SLC36A1-expressing oocytes, an inward current was induced by Gly-Sar, Gly-Gly, δ-aminolevulinic acid, β-aminoethylglycine, δ-aminopentanoic acid, GABA, Gly and Pro, whereas Val, Leu, mannitol, 5-HTP and the dipeptides Gly-Ala, Gly-Pro and Gly-Phe did not evoke currents. In Caco-2 cell monolayers, the apical uptake of 30 mM Gly-Sar was inhibited by 20 and 22% in the presence of 5-HTP or Bip-Pro, respectively, and by 48% in the presence of both. CONCLUSION AND IMPLICATIONS Our results suggest that whereas Gly-Gly amid bond bioisosteres are widely accepted by the hPAT1 carrier, dipeptides in general are not; and therefore, Gly-Sar might structurally define the size limit of dipeptide transport via SLC36A1.

An updated and simplified method for bile duct cannulation of rats

The single bile duct cannulated rat model was used for short-term intestinal absorption studies. Rats were randomly assigned to three groups: (A) bile duct cannulated, (B) control laparotomy and (C) no treatment. The body weight and health of the rats were monitored before and until day 5 after surgery, while bile flow was measured in group A on day 2. On the fifth day, tail vein blood was harvested, and alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin were quantified. Analysis of variance showed no significant difference between the groups for these parameters. This study demonstrated the suitability of a surgical rat model feasible for evaluation of the impact of bile in pharmacokinetic studies.

The rapid-onset dystonia parkinsonism mutation D923N of the Na+, K+-ATPase alpha3 isoform disrupts Na+ interaction at the third Na+ site

Rapid-onset dystonia parkinsonism (RDP), a rare neurological disorder, is caused by mutation of the neuron-specific alpha3-isoform of Na(+), K(+)-ATPase. Here, we present the functional consequences of RDP mutation D923N. Relative to the wild type, the mutant exhibits a remarkable approximately 200-fold reduction of Na(+) affinity for activation of phosphorylation from ATP, reflecting a defective interaction of the E(1) form with intracellular Na(+). This is the largest effect on Na(+) affinity reported so far for any Na(+), K(+)-ATPase mutant. D923N also affects the interaction with extracellular Na(+) normally driving the E(1)P to E(2)P conformational transition backward. However, no impairment of K(+) binding was observed for D923N, leading to the conclusion that Asp(923) is specifically associated with the third Na(+) site that is selective toward Na(+). The crystal structure of the Na(+), K(+)-ATPase in E(2) form shows that Asp(923) is located in the cytoplasmic half of transmembrane helix M8 inside a putative transport channel, which is lined by residues from the transmembrane helices M5, M7, M8, and M10 and capped by the C terminus, recently found involved in recognition of the third Na(+) ion. Structural modeling of the E(1) form of Na(+), K(+)-ATPase based on the Ca(2+)-ATPase crystal structure is consistent with the hypothesis that Asp(923) contributes to a site binding the third Na(+) ion. These results in conjunction with our previous findings with other RDP mutants suggest that a selective defect in the handling of Na(+) may be a general feature of the RDP disorder.

A review of molecular pathological markers in vulvar carcinoma: lack of application in clinical practice

Vulvar carcinoma is a rare female genital neoplasia. Radical surgery, which has been the standard treatment approach, is often accompanied by considerable morbidity. To reduce the incidence of complications there has been a movement toward individualised therapy and less radical surgery. Associated with this, new tumour markers that could serve as prognostic indicators would be of considerable value to guide treatment decision. In this review, a brief update of molecular pathological markers of vulvar carcinomas is provided, and their impact as prognostic markers is addressed. p16, p21, p14, p27, cyclin A, cyclin D1, p53, vascular endothelial growth factor (VEGF), transforming growth factor alpha, HER-2 and epidermal growth factor receptor (EGFR) have been found to be important in the pathogenesis and/or progression of vulvar carcinomas. Furthermore, human papillomavirus, p16, p21, p14, p53, VEGF, CD44v3, CD44v6, CD44v4, CD44v9, CD44v10, HER-2, EGFR, matrix metalloproteinase-12, caspase 3, Bcl-2 and nm23-H1 have been correlated to clinical outcome of patients with vulvar carcinomas. However, due to the relative small number of studies reported for each molecular pathological marker, and the relative small number of vulvar carcinomas included and the lack of multivariate analysis in the majority of these studies, no conclusion regarding the prognostic value of these markers can be drawn. Therefore, the investigated markers have not yet earned a place in standard clinical diagnostics or treatment, and further studies are needed to clarify the clinical value of these markers.

Intestinal gaboxadol absorption via PAT1 (SLC36A1): modified absorption in vivo following co-administration of L-tryptophan

BACKGROUND AND PURPOSE

Gaboxadol has been in development for treatment of chronic pain and insomnia. The clinical use of gaboxadol has revealed that adverse effects seem related to peak serum concentrations. The aim of this study was to investigate the mechanism of intestinal absorption of gaboxadol in vitro and in vivo.

EXPERIMENTAL APPROACH

In vitro transport investigations were performed in Caco-2 cell monolayers. In vivo pharmacokinetic investigations were conducted in beagle dogs. Gaboxadol doses of 2.5 mg.kg(-1) were given either as an intravenous injection (1.0 mL.kg(-1)) or as an oral solution (5.0 mL.kg(-1)).

KEY RESULTS

Gaboxadol may be a substrate of the human proton-coupled amino acid transporter, hPAT1 and it inhibited the hPAT1-mediated L-[(3)H]proline uptake in Caco-2 cell monolayers with an inhibition constant K(i) of 6.6 mmol.L(-1). The transepithelial transport of gaboxadol was polarized in the apical to basolateral direction, and was dependent on gaboxadol concentration and pH of the apical buffer solution. In beagle dogs, the absorption of gaboxadol was almost complete (absolute bioavailability, F(a), of 85.3%) and T(max) was 0.46 h. Oral co-administration with 2.5-150 mg.kg(-1) of the PAT1 inhibitor, L-tryptophan, significantly decreased the absorption rate constant, k(a), and C(max), and increased T(max) of gaboxadol, whereas the area under the curve and clearance of gaboxadol were constant.

CONCLUSIONS AND IMPLICATIONS

The absorption of gaboxadol across the luminal membrane of the small intestinal enterocytes is probably mediated by PAT1. This knowledge is useful for reducing gaboxadol absorption rates in order to decrease peak plasma concentrations.

The C terminus of Na+,K+-ATPase controls Na+ affinity on both sides of the membrane through Arg935

The Na(+),K(+)-ATPase C terminus has a unique location between transmembrane segments, appearing to participate in a network of interactions. We have examined the functional consequences of amino acid substitutions in this region and deletions of the C terminus of varying lengths. Assays revealing separately the mutational effects on internally and externally facing Na(+) sites, as well as E(1)-E(2) conformational changes, have been applied. The results pinpoint the two terminal tyrosines, Tyr(1017) and Tyr(1018), as well as putative interaction partners, Arg(935) in the loop between transmembrane segments M8 and M9 and Lys(768) in transmembrane segment M5, as crucial to Na(+) activation of phosphorylation of E(1), a partial reaction reflecting Na(+) interaction on the cytoplasmic side of the membrane. Tyr(1017), Tyr(1018), and Arg(935) are furthermore indispensable to Na(+) interaction on the extracellular side of the membrane, as revealed by inability of high Na(+) concentrations to drive the transition from E(1)P to E(2)P backwards toward E(1)P and inhibit Na(+)-ATPase activity in mutants. Lys(768) is not important for Na(+) binding from the external side of the membrane but is involved in stabilization of the E(2) form. These data demonstrate that the C terminus controls Na(+) affinity on both sides of the membrane and suggest that Arg(935) constitutes an important link between the C terminus and the third Na(+) site, involving an arginine-pi stacking interaction between Arg(935) and the C-terminal tyrosines. Lys(768) may interact preferentially with the C terminus in E(1) and E(1)P forms and with the loop between transmembrane segments M6 and M7 in E(2) and E(2)P forms.

Optimization of Self-Microemulsifying Drug Delivery Systems (SMEDDS) Using a D-Optimal Design and the Desirability Function

D-optimal design and the desirability function were applied to optimize a self-microemulsifying drug delivery system (SMEDDS). The optimized key parameters were the following: 1) particle size of the dispersed emulsion, 2) solubility of the drug in the vehicle, and 3) the vehicle compatibility with the hard gelatin capsule. Three formulation variables, PEG200, a surfactant mixture, and an oil mixture, were included in the experimental design. The results of the mathematical analysis of the data demonstrated significant interactions among the formulation variables, and the desirability function was demonstrated to be a powerful tool to predict the optimal formulation for the explored system.

Differential age-related changes in mitochondrial DNA repair activities in mouse brain regions

Aging in the brain is characterized by increased susceptibility to neuronal loss and functional decline, and mitochondrial DNA (mtDNA) mutations are thought to play an important role in these processes. Due to the proximity of mtDNA to the main sites of mitochondrial free radical generation, oxidative stress is a major source of DNA mutations in mitochondria. The base excision repair (BER) pathway removes oxidative lesions from mtDNA, thereby constituting an important mechanism to avoid accumulation of mtDNA mutations. The complexity of the brain implies that exposure and defence against oxidative stress varies among brain regions and hence some regions may be particularly prone to accumulation of mtDNA damages. In the current study we investigated the efficiency of the BER pathway throughout the murine lifespan in mitochondria from cortex and hippocampus, regions that are central in mammalian cognition, and which are severely affected during aging and in neurodegenerative diseases. A regional specific regulation of mitochondrial DNA repair activities was observed with aging. In cortical mitochondria, DNA glycosylase activities peaked at middle-age followed by a significant drop at old age. However, only minor changes were observed in hippocampal mitochondria during the whole lifespan of the animals. Furthermore, DNA glycosylase activities were lower in hippocampal than in cortical mitochondria. Mitochondrial AP endonuclease activity increased in old animals in both brain regions. Our data suggest an important regional specific regulation of mitochondrial BER during aging.

Expression of ZNF652, a novel zinc finger protein, in vulvar carcinomas and its relation to prognosis

AIMS

To determine the levels of expression of ZNF652 and its relevance to prognosis in vulvar squamous cell carcinomas.

METHODS

22 cases of vulvar intraepithelial neoplasia (VIN) and tumours from 217 patients with vulvar squamous cell carcinomas were investigated for expression of ZNF652 using immunostaining methods. The effect of ZNF652 ectopic expression was determined in the vulvar carcinoma cell line SW954 by western and cell-based assays.

RESULTS

High levels of ZNF652 nuclear expression were observed in 5 (100%) of VIN I, 6 (75%) of VIN II and 109 (50.2%) of the vulvar carcinomas, whereas low levels were seen in 2 (25%) VIN II, 9 (100%) of VIN III and 108 (49.8%) of the vulvar carcinomas. High levels of ZNF652 expression in the vulvar carcinomas were significantly correlated to high expression of EphA2. However, when correcting for multiple testing this correlation was lost. No association was identified between ZNF652 expression and p16, p21, p27, p53, cyclin A, D1, D3, E, EphrinA-1 and human papillomavirus. Variations in levels of ZNF652 were not related to prognosis. Low levels of ZNF652 protein were identified in the vulvar carcinoma cell line SW954. Furthermore, SW954 cells ectopically expressing ZNF652 showed reduced cell proliferation and the ability to form colonies on plastic.

CONCLUSIONS

ZNF652 protein expression is reduced in 25% of VIN II, 100% of VIN III and approximately 50% of the cases of vulvar squamous cell carcinoma, and may be an early event in the pathogenesis of vulvar squamous cell carcinoma. Variations in the levels of ZNF652 were not related to patient's prognosis.

Expression of EphA2 and EphrinA-1 in vulvar carcinomas and its relation to prognosis

AIMS

To examine the expression of EphA2 and EphrinA-1 in vulvar squamous cell carcinomas and investigate their prognostic relevance.

METHODS

Tumours from 224 patients with vulvar squamous cell carcinomas were investigated for expression of EphA2 and EphrinA-1 using single and double immunostaining methods.

RESULTS

High expression (strong/moderate staining intensity) of EphA2 and EphrinA-1 was observed in 114 (51%) and 126 (56%) vulvar carcinomas, respectively. In the three cases tested using the double immunostaining method, colocalisation of EphA2 and EphrinA-1 proteins was identified in the same neoplastic cells. High EphA2 expression was significantly correlated to high expression of EphrinA-1 (p<0.01) and cyclin A (p<0.01), large tumour size (p = 0.03), deep invasion (p<0.01) and higher FIGO stage (p = 0.05). A correlation between high EphrinA-1 expression and high levels of cyclin A (p<0.01) and p21 (p<0.01), deep invasion (p<0.01) and higher FIGO stage (p = 0.01) was also seen. In univariate analysis, high expression of EphrinA-1 was associated with poor survival (p = 0.03). However, in the multivariate analysis neither EphrinA-1 nor EphA2 were significantly correlated to survival.

CONCLUSIONS

EphA2 and EphrinA-1 were overexpressed in 51% and 56% of the vulvar squamous cell carcinomas, respectively, and high levels of EphA2 and EphrinA-1 proteins were associated with deep tumour invasion and high FIGO stage. However, EphA2 and EphrinA-1 were not independently associated with clinical outcome in vulvar carcinomas.

Molecular markers for lymph node involvement in locally advanced cervical carcinomas

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Background: Lymph node involvement is the first indication of cervical cancer spread and a strong prognostic factor. The aims of the present study were to identify genes associated with lymph node involvement. Methods: The nodal status and tumor volume were determined from MR images in 48 patients with FIGO stage 2a to 4a at the time of diagnosis. cDNA microarray technique was used to identify genes that differed in expression between node positive and negative tumors. Biopsies enriched for carcinoma tissue were co-hybridized with a common reference sample in a dye-swap design. Quantitative real time PCR (qRT PCR) and immunohistochemistry were used to validate microarray results and determine protein expression of selected genes. Results: Pathologic lymph nodes were seen in 29 patients and normal nodes in 19. We identified 16 genes with higher and 15 with lower expression in node positive tumors as compared to the negative ones. QRT PCR data of 4 genes were consistent with these findings. CKS2, MRPS23, MRPL11, LSM3 and PDK2 were upregulated in node positive tumors suggesting high proliferation activity and oxygen consumption. MSN, KLF3 and TBX3 were downregulated. CKS2, MRPS23, MRPL11, PDK2, LSM3, TBX3, KLF3 and MSN were significantly related to progression free survival in univariate analysis. Protein expression, determined for CKS2 and MSN, was significantly correlated to survival, consistent with these results. In multivariate analysis including only gene variables, MRPL11, PDK2 and TBX3 were significant. Including also clinical and MRI variables, tumor volume, KLF3 and TBX3 were significant. NEK1, CSTA, ANX4 and DDOST were upregulated indicating activated DNA damage repair (NEK1) and resistance to apoptosis (CSTA, ANX4, DDOST). NTN4 and HYAL1, which are involved in cell-matrix interactions, were downregulated, suggesting mechanisms for increased cell migration and invasive growth. Conclusions: Our findings are consistent with known phenotypic characteristics of node positive cervical tumors, such as hypoxia and high lactate content. They point to molecular mechanisms for development of hypoxia, deregulation of glucose metabolism, activation of survival strategies and interactions between carcinoma cells and tumor stroma that may promote metastasis formation.

No significant financial relationships to disclose.

Markers of apoptosis in stage IB squamous cervical carcinoma

AIMS

To examine the prognostic relevance of the expression of the Bcl-2, Bcl-xL, and Bax proteins in stage IB squamous cervical carcinoma (SCC).

METHODS

In total, 220 patients who underwent radical hysterectomy and bilateral lymphadenectomy at the Norwegian Radium Hospital for stage IB SCC between 1987 and 1993 were studied. Immunohistochemistry using monoclonal antibodies against Bcl-2, Bcl-xL, and Bax was used to examine protein expression. Ten patients who underwent hysterectomy for uterine prolapse served as controls.

RESULTS

Cytoplasmic expression of Bcl-2, Bcl-xL, and Bax was low (< 5% positive cells) in 159 of 220 (73%), 193 of 220 (87%), and 39 of 220 (18%) tumours, respectively, and high (> or = 5% positive cells) in 61 of 220 (27%), 27 of 220 (13%), and 181 of 220 (82%) tumours, respectively. In univariate analysis, all classic clinicopathological parameters but none of the investigated proteins were associated with prognosis. In multivariate analysis, only deep stromal invasion was independently related to survival.

CONCLUSION

Bcl-2, Bcl-xL, and Bax were not independently associated with prognosis in stage IB SCC.

TP53 mutations in early-stage ovarian carcinoma, relation to long-term survival

We conducted the present study to evaluate the frequency and prognostic importance on long-term survival of TP53 mutations and TP53 protein accumulation in a cohort of 178 patients with early-stage ovarian carcinomas. TP53 mutations scored as aberrant temporal temperature gradient gel electrophoresis pattern from all exons were observed in 39.9% of the tumours. Full screening of exons 5–8, followed by sequencing, was successful in 135 cases, and 48 mutations altering the protein were detected in 39 cases (28.9%). TP53 mutations were slightly less common in the Federation of Gynecologists and Obstetricians stage IA than in IB/IC (P=0.05). No significant correlations with histological type, grade of differentiation, DNA ploidy status or age at diagnosis were found. TP53 protein accumulation analysed by immunohistochemistry was found in 32.6% of all tumours, and was a poor predictor of TP53 mutations with 56.4% sensitivity, 77.1% specificity, 50% positive predictive value and 81.3% negative predictive value. Neither TP53 mutations nor TP53 protein accumulation influenced the prognosis significantly in this group of patients.

Comparison of two intervention programmes in young female players in European handball - with and without ankle disc

INTRODUCTION

The prevention of injuries in all sports calls for a structured plan. The plan consists, as earlier described, of four steps. We have previously presented studies incorporating all four steps. The studies have shown that it is possible to prevent most injuries in young female players in European handball by applying a training programme combining the use of an ankle disc with functional strength training. In the previous studies we were not able to discriminate whether the preventive effect was due to the functional strength training or the training with the ankle disc. The aim of this study was to compare a programme with ankle disc and functional strength training with a programme with functional strength training only.

METHODS

Twenty handball teams were asked to participate, and 16 of 20 handball teams agreed to participate. The teams were cluster randomised to either the programme with or without an ankle disc.

RESULTS

The group using the programme without the ankle disc had a significantly higher number of traumatic injuries (16 vs. 6). The incidences of traumatic injuries in the ankle disc group were 2.4 (95% CI 0.7; 6.2) injuries per 1000 h of match and 0.2 (95% CI 0.02; 0.7) injuries per 1000 h of practice. In the group without ankle disc the incidences were 6.9 (95% CI 3.3; 12.7) injuries per 1000 h of match and 0.6 (95% CI 0.2; 1.3) injuries per 1000 h of practice. A significantly higher multivariate odds ratio (4.8) was found in the group not using the ankle disc. In addition the group using the ankle disc had significantly fewer moderate and major injuries.

CONCLUSION

By adding ankle disc training to a training programme with functional strength training, it is possible to reduce the number of injuries significantly, especially the number of moderate and major injuries.

Deregulation of D-type cyclins in uterine cancers. Cyclin D1/D3 is differentially expressed in cervical cancer

BACKGROUND

We have previously found cyclin D1 to be overexpressed in 45% of corpus cancers, but in only 3% of cervical cancers. To see whether and how D-type cyclins contribute to the neoplastic phenotype in uterine cancers, aberrant expression and association between cyclins D1 and D3 proteins were studied.

MATERIALS AND METHODS

Expression of cyclin D3 was investigated by immunohistochemistry in 51 patients with primary cancer of the corpus and 73 cases of primary cervical carcinomas. Amplification of the cyclin D1 and D3 genes was investigated by fluorescence in situ hybridisation (FISH).

RESULTS

We found high/moderate levels of cyclin D3 in 53.5% of cervical cancers and 55% of corpus cancers. High/moderate expression of cyclin D1 and D3 was associated in the corpus cancers, but not in cervical cancers. The accumulation of cyclin D3 but not D1 protein could, in some cases, be explained by increased gene dosage since extra copies of chromosome 6 were found.

CONCLUSION

This study demonstrates that in cervical cancers cyclin D3 may compensate for low levels of cyclin D1, whereas in corpus cancers both isoforms may contribute to the neoplastic phenotype.