Increased monoamine oxidase activity and imidazoline binding sites in insulin-resistant adipocytes from obese Zucker rats.

BACKGROUND: Despite overt insulin resistance, adipocytes of genetically obese Zucker rats accumulate the excess of calorie intake in the form of lipids. AIM: To investigate whether factors can replace or reinforce insulin lipogenic action by exploring glucose uptake activation by hydrogen peroxide, since it is produced by monoamine oxidase (MAO) and semicarbazide-sensitive amine oxidase (SSAO) in adipocytes. METHODS: 3H-2-deoxyglucose uptake (2-DG) was determined in adipocytes from obese and lean rats in response to insulin or MAO and SSAO substrates such as tyramine and benzylamine. 14C-tyramine oxidation and binding of imidazolinic radioligands [3H-Idazoxan, 3H-(2-benzofuranyl)-2-imidazoline] were studied in adipocytes, the liver, and muscle. The influence of in vivo administration of tyramine + vanadium on glucose handling was assessed in lean and obese rats. RESULTS: 2-DG uptake and lipogenesis stimulation by insulin were dampened in adipocytes from obese rats, when compared to their lean littermates. Tyramine and benzylamine activation of hexose uptake was vanadate-dependent and was also limited, while MAO was increased and SSAO decreased. These changes were adipocyte-specific and accompanied by a greater number of imidazoline I2 binding sites in the obese rat, when compared to the lean. In vitro, tyramine precluded the binding to I2 sites, while in vivo, its administration together with vanadium lowered fasting plasma levels of glucose and triacylglycerols in obese rats. CONCLUSION: The adipocytes from obese Zucker rats exhibit increased MAO activity and imidazoline binding site number. However, probably as a consequence of SSAO down-regulation, the glucose transport stimulation by tyramine is decreased as much as that of insulin in these insulin-resistant adipocytes. The adipocyte amine oxidases deserve more studies with respect to their putative contribution to the management of glucose and lipid handling.

High doses of catecholamines activate glucose transport in human adipocytes independently from adrenoceptor stimulation or vanadium addition.

BACKGROUND: When combined with vanadium salts, catecholamines strongly activate glucose uptake in rat and mouse adipocytes. AIM: To test whether catecholamines activate glucose transport in human adipocytes. METHODS: The uptake of 2-deoxyglucose (2-DG) was measured in adipocytes isolated from pieces of abdominal subcutaneous tissue removed from women undergoing reconstructive surgery. Pharmacological approaches with amine oxidase inhibitors, adrenoreceptor agonists and antioxidants were performed to unravel the mechanisms of action of noradrenaline or adrenaline (also named epinephrine). RESULTS: In human adipocytes, 45-min incubation with 100 µmol/L adrenaline or noradrenaline activated 2-DG uptake up to more than one-third of the maximal response to insulin. This stimulation was not reproduced with millimolar doses of dopamine or serotonin and was not enhanced by addition of vanadate to the incubation medium. Among various natural amines and adrenergic agonists tested, no other molecule was more efficient than adrenaline and noradrenaline in stimulating 2-DG uptake. The effect of the catecholamines was not impaired by pargyline and semicarbazide, contrarily to that of benzylamine or methylamine, which are recognized substrates of semicarbazide-sensitive amine oxidase. Hydrogen peroxide at 1 mmol/L activated hexose uptake but not pyrocatechol or benzoquinone, and only the former was potentiated by vanadate. Catalase and the phosphoinositide 3-kinase inhibitor wortmannin inhibited adrenaline-induced activation of 2-DG uptake. CONCLUSION: High doses of catecholamines exert insulin-like actions on glucose transport in human adipocytes. At submillimolar doses, vanadium did not enhance this catecholamine activation of glucose transport. Consequently, this dismantles our previous suggestion to combine the metal ion with catecholamines to improve the benefit/risk ratio of vanadium-based antidiabetic approaches.

Mitotic Acetylation of Microtubules Promotes Centrosomal PLK1 Recruitment and Is Required to Maintain Bipolar Spindle Homeostasis.

Tubulin post-translational modifications regulate microtubule properties and functions. Mitotic spindle microtubules are highly modified. While tubulin detyrosination promotes proper mitotic progression by recruiting specific microtubule-associated proteins motors, tubulin acetylation that occurs on specific microtubule subsets during mitosis is less well understood. Here, we show that siRNA-mediated depletion of the tubulin acetyltransferase ATAT1 in epithelial cells leads to a prolonged prometaphase arrest and the formation of monopolar spindles. This results from collapse of bipolar spindles, as previously described in cells deficient for the mitotic kinase PLK1. ATAT1-depleted mitotic cells have defective recruitment of PLK1 to centrosomes, defects in centrosome maturation and thus microtubule nucleation, as well as labile microtubule-kinetochore attachments. Spindle bipolarity could be restored, in the absence of ATAT1, by stabilizing microtubule plus-ends or by increasing PLK1 activity at centrosomes, demonstrating that the phenotype is not just a consequence of lack of K-fiber stability. We propose that microtubule acetylation of K-fibers is required for a recently evidenced cross talk between centrosomes and kinetochores.

PAK1 Regulates MEC-17 Acetyltransferase Activity and Microtubule Acetylation during Proplatelet Extension.

Mature megakaryocytes extend long processes called proplatelets from which platelets are released in the blood stream. The Rho GTPases Cdc42 and Rac as well as their downstream target, p21-activated kinase 2 (PAK2), have been demonstrated to be important for platelet formation. Here we address the role, during platelet formation, of PAK1, another target of the Rho GTPases. PAK1 decorates the bundled microtubules (MTs) of megakaryocyte proplatelets. Using a validated cell model which recapitulates proplatelet formation, elongation and platelet release, we show that lack of PAK1 activity increases the number of proplatelets but restrains their elongation. Moreover, in the absence of PAK1 activity, cells have hyperacetylated MTs and lose their MT network integrity. Using inhibitors of the tubulin deacetylase HDAC6, we demonstrate that abnormally high levels of MT acetylation are not sufficient to increase the number of proplatelets but cause loss of MT integrity. Taken together with our previous demonstration that MT acetylation is required for proplatelet formation, our data reveal that MT acetylation levels need to be tightly regulated during proplatelet formation. We identify PAK1 as a direct regulator of the MT acetylation levels during this process as we found that PAK1 phosphorylates the MT acetyltransferase MEC-17 and inhibits its activity.

The Canadian Core Cariology Curriculum: Outcomes of a national symposium.

Despite the efforts that have been made in dental education and clinical practice to adopt the evidence-informed, risk-based, nonsurgical caries management approach, the surgical treatment approach continues to prevail. There is an urgent need to understand resistance to such a paradigm shift and establish a coordinated evidence-based Cariology teaching approach in Canadian dental schools so trainees are equipped to implement caries management in their practice. To work towards this goal, a two-day interinstitutional symposium was organized in Montreal, QC, bringing together clinical and research experts in cariology and dental education from all 10 Canadian dental schools to develop a consensus on an evidence-informed Core Cariology Curriculum, and strategies for its implementation. Through consensus, participants produced the Core Cariology Curriculum for Canadian dental schools and articulated the challenges and solutions for its implementation. Future work will include working collaboratively on the curriculum integration and evaluation.

Vanadium-dependent activation of glucose transport in adipocytes by catecholamines is not mediated via adrenoceptor stimulation or monoamine oxidase activity.

BACKGROUND: Benzylamine and methylamine activate glucose uptake in adipocytes. For tyramine, this effect has even been extended to cardiomyocytes. AIM: To investigate the effects of catecholamines and other amines on glucose uptake. METHODS: A screening compared 25 biogenic amines on 2-deoxyglucose (2-DG) uptake activation in rat adipocytes. Pharmacological approaches and transgenic mouse models were then used to decipher the mode of action of several hits. RESULTS: In rat adipocytes, insulin stimulation of 2-DG uptake was reproduced with catecholamines. 100 µmol/L or 1 mmol/L adrenaline, noradrenaline, dopamine and deoxyepinephrine, maximally activated hexose transport only when sodium orthovanadate was added at 100 µmol/L. Such activation was similar to that already reported for benzylamine, methylamine and tyramine, well-recognized substrates of semicarbazide-sensitive amine oxidase (SSAO) and monoamine oxidase (MAO). Several, but not all, tested agonists of ß-adrenoreceptors (ß-ARs) also activated glucose transport while α-AR agonists were inactive. Lack of blockade by α- and ß-AR antagonists indicated that catecholamine-induced 2-DG uptake was not mediated by AR stimulation. Adipocytes from mice lacking ß1-, ß2- and ß3-ARs (triple KO) also responded to millimolar doses of adrenaline or noradrenaline by activating hexose transport in the presence of 100 µmol/L vanadate. The MAO blocker pargyline, and SSAO inhibitors did not block the effects of adrenaline or noradrenaline plus vanadate, which were blunted by antioxidants. CONCLUSION: Catecholamines exert unexpected insulin-like actions in adipocytes when combined with vanadium. For limiting insulin resistance by activating glucose consumption at least in fat stores, we propose that catecholamine derivatives combined with vanadium can generate novel complexes that may have low toxicity and promising anti-diabetic properties.

Kaleidoscope-based multi-view infrared system.

Multi-view snapshot systems are used for a wide range of applications in all the spectral ranges. In this Letter, we present the study and the realization of an optical system using a kaleidoscope in the long wavelength infrared (LWIR), compatible with uncooled infrared detectors such as microbolometers. The optical system has a high numerical aperture and a wide field of view, and it uses a single focal plane array. Here, we establish the advantages of this technology on other design strategies and its design rules for every subset of the optical architecture, and we present the results of a first demonstrator.

In utero exposure to nicotine abolishes the postnatal response of the cardiac sodium current to isoproterenol in newborn rabbit atrium.

BACKGROUND: In utero exposure to tobacco smoke is associated with sudden infant death syndrome (SIDS) and cardiac arrhythmias in newborns. The arrhythmogenic mechanisms seem linked to alterations of the cardiac sodium current (INa). We previously reported that in utero exposure to nicotine delays the postnatal development of the heart sinoatrial node in rabbits and altered expression of the sodium channels NaV1.5 and NaV1.1 in the atrium surrounding it. These channels react differently to sympathetic stimulation. OBJECTIVE: The purpose of this study was to test whether nicotine altered the response of INa to stimulation by the ß-adrenoreceptor agonist isoproterenol in atrial myocytes. Our hypothesis is that changes in the sympathetic response of sinoatrial node peripheral cells may create a substrate for arrhythmia. METHODS: Using the patch-clamp technique we measured the effect of nicotine on the response of INa to adrenergic stimulation in isolated cardiomyocytes. RESULTS: Isoproterenol increased INa by 50% in newborn sham rabbits but had no effect in newborn rabbits exposed to nicotine in utero. Our data also show that nicotine increases the late sodium current, an effect that may promote QT prolongation. CONCLUSION: We provide the first evidence linking fetal exposure to nicotine to long-term alterations of INa response to isoproterenol. These changes may impair INa adaptation to sympathetic tone and prevent awakening from sleep apnea, thus leading to arrhythmias that could potentially be involved in SIDS. Our data also raise concerns about the use of nicotine replacement therapies for pregnant women.

Nuclear import of Xenopus egg extract components into cultured cells for reprogramming purposes: a case study on goldfish fin cells.

Reprogramming of cultured cells using Xenopus egg extract involves controlling four major steps: plasma membrane permeabilization, egg factors import into the nucleus, membrane resealing, and cell proliferation. Using propidium iodide to assess plasma membrane permeability, we established that 90% of the cultured fin cells were permeabilized by digitonin without any cell losses. We showed that egg extract at metaphase II stage was essential to maintain nuclear import function in the permeabilized cells, as assessed with a fusion GFP protein carrying the nuclear import signal NLS. Moreover, the Xenopus-egg-specific Lamin B3 was detected in 87% of the cell nuclei, suggesting that other egg extract reprogramming factors of similar size could successfully enter the nucleus. Lamin B3 labelling was maintained in most cells recovered 24 h after membrane resealing with calcium, and cells successfully resumed cell cycle in culture. In contrast, permeabilized cells that were not treated with egg extract failed to proliferate in culture and died, implying that egg extract provided factor essential to the survival of those cells. To conclude, fish fin cells were successfully primed for treatment with reprogramming factors, and egg extract was shown to play a major role in their survival and recovery after permeabilization.

Microtubule polyglutamylation and acetylation drive microtubule dynamics critical for platelet formation.

BACKGROUND: Upon maturation in the bone marrow, polyploid megakaryocytes elongate very long and thin cytoplasmic branches called proplatelets. Proplatelets enter the sinusoids blood vessels in which platelets are ultimately released. Microtubule dynamics, bundling, sliding, and coiling, drive these dramatic morphological changes whose regulation remains poorly understood. Microtubule properties are defined by tubulin isotype composition and post-translational modification patterns. It remains unknown whether microtubule post-translational modifications occur in proplatelets and if so, whether they contribute to platelet formation. RESULTS: Here, we show that in proplatelets from mouse megakaryocytes, microtubules are both acetylated and polyglutamylated. To bypass the difficulties of working with differentiating megakaryocytes, we used a cell model that allowed us to test the functions of these modifications. First, we show that α2bß3integrin signaling in D723H cells is sufficient to induce ß1tubulin expression and recapitulate the specific microtubule behaviors observed during proplatelet elongation and platelet release. Using this model, we found that microtubule acetylation and polyglutamylation occur with different spatio-temporal patterns. We demonstrate that microtubule acetylation, polyglutamylation, and ß1tubulin expression are mandatory for proplatelet-like elongation, swelling formation, and cytoplast severing. We discuss the functional importance of polyglutamylation of ß1tubulin-containing microtubules for their efficient bundling and coiling during platelet formation. CONCLUSIONS: We characterized and validated a powerful cell model to address microtubule behavior in mature megakaryocytes, which allowed us to demonstrate the functional importance of microtubule acetylation and polyglutamylation for platelet release. Furthermore, we bring evidence of a link between the expression of a specific tubulin isotype, the occurrence of microtubule post-translational modifications, and the acquisition of specific microtubule behaviors. Thus, our findings could widen the current view of the regulation of microtubule behavior in cells such as osteoclasts, spermatozoa, and neurons, which express distinct tubulin isotypes and display specific microtubule activities during differentiation.

A novel three base-pair deletion in domain two of the cardiac sodium channel causes Brugada syndrome.

INTRODUCTION: Mutations within SCN5A are found in a significant proportion (15-30%) of Brugada syndrome (BrS) cases and impair sodium transport across excitable cardiac cells that mediate ventricular contractions. Genetic testing offers a means to clinically assess and manage affected individuals and their family members. METHODS AND RESULTS: The proband at age 44 years old exhibited a syncopal event during exercise, and presented later with a spontaneous type-I BrS pattern on 12­lead resting electrocardiogram (ECG). Mutational analysis performed across all SCN5A exons revealed a unique three base-pair deletion p.M741_T742delinsI (c.2223_2225delGAC), in a heterozygous state in the proband and 2 siblings. This mutation was not seen in a cohort of 105 ethnicity-matched controls or in public genome databases. Patch clamp electrophysiology study conducted in TSA201 cells showed an abolishment of sodium current (INa). The proband, and several relatives, also harboured a known SCN5A variant, p.R1193Q (c.3578G>A). CONCLUSION: Our study has demonstrated the deleterious effect of a novel SCN5A mutation p.M741_T742delinsI (c.2223_2225delGAC). The findings highlight the complex effects of gender and age in phenotype manifestation. It also offers insights into improving the long-term management of BrS, and the utility of cascade genetic screening for risk stratification.

Initiation of DNA replication requires actin dynamics and formin activity.

Nuclear actin regulates transcriptional programmes in a manner dependent on its levels and polymerisation state. This dynamics is determined by the balance of nucleocytoplasmic shuttling, formin- and redox-dependent filament polymerisation. Here, using Xenopus egg extracts and human somatic cells, we show that actin dynamics and formins are essential for DNA replication. In proliferating cells, formin inhibition abolishes nuclear transport and initiation of DNA replication, as well as general transcription. In replicating nuclei from transcriptionally silent Xenopus egg extracts, we identified numerous actin regulators, and disruption of actin dynamics abrogates nuclear transport, preventing NLS (nuclear localisation signal)-cargo release from RanGTP-importin complexes. Nuclear formin activity is further required to promote loading of cyclin-dependent kinase (CDK) and proliferating cell nuclear antigen (PCNA) onto chromatin, as well as initiation and elongation of DNA replication. Therefore, actin dynamics and formins control DNA replication by multiple direct and indirect mechanisms.

Early gametogenesis in the Pacific oyster: new insights using stem cell and mitotic markers.

While our knowledge of bivalve gametogenesis has progressed in recent times, more molecular markers are needed in order to develop tissue imaging. Here, we identified stem cell and mitotic markers to further characterize oyster early gametogenesis, mainly through immunofluorescence microscopy. Intense alkaline phosphatase activity, a non-specific marker for stem cells, was detected on the outer edge of the gonad ducts at the post-spawning stage, suggesting an abundance of undifferentiated cells very early during the sexual cycle. This observation was confirmed using an antibody against Sox2, a transcription factor specific for stem or germline cells, which labeled cells in the gonad duct inner mass and ciliated epithelium early during the initial oyster sexual cycle. Moreover, Vasa, a cytoplasmic marker for germline cells, was also detected in the gonad acini and duct cells, thus confirming that germline cells were abundant early on. In addition, the binding of the minichromosome maintenance MCM6 protein to chromatin indicated the gonad acini and duct cells were engaged in the cell cycle. DNA replication was indeed confirmed by an abundant in vivo incorporation of BrdU into the duct cell chromatin. Finally, proliferation of acini and duct cells was demonstrated by the chromatin-bound Ser10-phosphorylated histone H3, a mitotic marker. The markers for the cell cycle and mitosis used here thus indicate that acini and duct cells were already actively dividing early during the oyster sexual cycle. In addition, together with the stem cell markers, these data reveal that the epithelium delimiting the duct outer edge contains a dynamic population of undifferentiated cells.

In-utero exposure to nicotine alters the development of the rabbit cardiac conduction system and provides a potential mechanism for sudden infant death syndrome.

In-utero exposure to tobacco smoke remains the highest risk factor for sudden infant death syndrome (SIDS). To alleviate the risks, nicotine replacement therapies are often prescribed to women who wish to quit smoking during their pregnancy. Cardiac arrhythmias is considered the final outcome leading to sudden death. Our goal in this study was to determine if exposing rabbit fetus to nicotine altered the cardiac conduction system of newborn kittens in a manner susceptible to cause SIDS. Using neuronal markers and a series of immunohistological and electrophysiological techniques we found that nicotine delayed the development of the cardiac pacemaker center (sinoatrial node) and decreased its innervation. At the molecular level, nicotine favored the expression of cardiac sodium channels with biophysical properties that will tend to slow heart rate and diminish electrical conduction. Our results show that alterations of the cardiac sodium current may contribute to the bradycardia, conduction disturbances and other cardiac arrhythmias often associated to SIDS and raise awareness on the use of replacement therapy during pregnancy.

Heterogeneity in sarcoma cell lines reveals enhanced motility of tetraploid versus diploid cells.

Soft tissue sarcomas with complex genomics are very heterogeneous tumors lacking simple prognosis markers or targeted therapies. Overexpression of a subset of mitotic genes from a signature called CINSARC is of bad prognosis, but the significance of this signature remains elusive. Here we precisely measure the cell cycle and mitosis duration of sarcoma cell lines and we found that the mitotic gene products overexpression does not reflect variation in the time spent during mitosis or G2/M. We also found that the CINSARC cell lines, we studied, are composed of a mixture of aneuploid, diploid, and tetraploid cells that are highly motile in vitro. After sorting diploid and tetraploid cells, we showed that the tetraploid cell clones do not possess a proliferative advantage, but are strikingly more motile and invasive than their diploid counterparts. This is correlated with higher levels of mitotic proteins overexpression. Owing that mitotic proteins are almost systematically degraded at the end of mitosis, we propose that it is the abnormal activity of the mitotic proteins during interphase that boosts the sarcoma cells migratory properties by affecting their cytoskeleton. To test this hypothesis, we designed a screen for mitotic or cytoskeleton protein inhibitors affecting the sarcoma cell migration potential independently of cytotoxic activities. We found that inhibition of several mitotic kinases drastically impairs the CINSARC cell invasive and migratory properties. This finding could provide a handle by which to selectively inhibit the most invasive cells.

P-cadherin promotes collective cell migration via a Cdc42-mediated increase in mechanical forces.

Collective cell migration (CCM) is essential for organism development, wound healing, and metastatic transition, the primary cause of cancer-related death, and it involves cell-cell adhesion molecules of the cadherin family. Increased P-cadherin expression levels are correlated with tumor aggressiveness in carcinoma and aggressive sarcoma; however, how P-cadherin promotes tumor malignancy remains unknown. Here, using integrated cell biology and biophysical approaches, we determined that P-cadherin specifically induces polarization and CCM through an increase in the strength and anisotropy of mechanical forces. We show that this mechanical regulation is mediated by the P-cadherin/ß-PIX/Cdc42 axis; P-cadherin specifically activates Cdc42 through ß-PIX, which is specifically recruited at cell-cell contacts upon CCM. This mechanism of cell polarization and migration is absent in cells expressing E- or R-cadherin. Thus, we identify a specific role of P-cadherin through ß-PIX-mediated Cdc42 activation in the regulation of cell polarity and force anisotropy that drives CCM.

Whole-genome duplication increases tumor cell sensitivity to MPS1 inhibition.

Several lines of evidence indicate that whole-genome duplication resulting in tetraploidy facilitates carcinogenesis by providing an intermediate and metastable state more prone to generate oncogenic aneuploidy. Here, we report a novel strategy to preferentially kill tetraploid cells based on the abrogation of the spindle assembly checkpoint (SAC) via the targeting of TTK protein kinase (better known as monopolar spindle 1, MPS1). The pharmacological inhibition as well as the knockdown of MPS1 kills more efficiently tetraploid cells than their diploid counterparts. By using time-lapse videomicroscopy, we show that tetraploid cells do not survive the aborted mitosis due to SAC abrogation upon MPS1 depletion. On the contrary diploid cells are able to survive up to at least two more cell cycles upon the same treatment. This effect might reflect the enhanced difficulty of cells with whole-genome doubling to tolerate a further increase in ploidy and/or an elevated level of chromosome instability in the absence of SAC functions. We further show that MPS1-inhibited tetraploid cells promote mitotic catastrophe executed by the intrinsic pathway of apoptosis, as indicated by the loss of mitochondrial potential, the release of the pro-apoptotic cytochrome c from mitochondria, and the activation of caspases. Altogether, our results suggest that MPS1 inhibition could be used as a therapeutic strategy for targeting tetraploid cancer cells.

A Brugada syndrome proband with compound heterozygote SCN5A mutations identified from a Chinese family in Singapore.

AIMS: Brugada syndrome (BrS) is a rare heritable ventricular arrhythmia. Genetic defects in SCN5A, a gene that encodes the α-subunit of the sodium ion channel Nav1.5, are present in 15-30% of BrS cases. SCN5A remains by far, the highest yielding gene for BrS. We studied a young male who presented with syncope at age 11. This proband was screened for possible disease causing SCN5A mutations. The inheritance pattern was also examined amongst his first-degree family members. METHODS AND RESULTS: The proband had a baseline electrocardiogram that showed Type 2 BrS changes, which escalated to a characteristic Type I BrS pattern during a treadmill test before polymorphic ventricular tachycardia onset at a cycle length of 250 ms. Mutational analysis across all 29 exons in SCN5A of the proband and first-degree relatives of the family revealed that the proband inherited a compound heterozygote mutation in SCN5A, specifically p.A226V and p.R1629X from each parent. To further elucidate the functional changes arising through these mutations, patch-clamp electrophysiology was performed in TSA201 cells expressing the mutated SCN5A channels. The p.A226V mutation significantly reduced peak sodium current (INa) to 24% of wild type (WT) whereas the p.R1629X mutation abolished the current. To mimic the functional state in our proband, functional expression of the compound variants A226V + R1629X resulted in overall peak INa of only 13% of WT (P < 0.01). CONCLUSION: Our study is the first to report a SCN5A compound heterozygote in a Singaporean Chinese family. Only the proband carrying both mutations displayed the BrS phenotype, thus providing insights into the expression and penetrance of BrS in an Asian setting.

Prolongation of action potential duration and QT interval during epilepsy linked to increased contribution of neuronal sodium channels to cardiac late Na+ current: potential mechanism for sudden death in epilepsy.

BACKGROUND: Arrhythmias associated with QT prolongation on the ECG often lead to sudden unexpected death in epilepsy. The mechanism causing a prolongation of the QT interval during epilepsy remains unknown. Based on observations showing an upregulation of neuronal sodium channels in the brain during epilepsy, we tested the hypothesis that a similar phenomenon occurs in the heart and contributes to QT prolongation by altering cardiac sodium current properties (INa). METHODS AND RESULTS: We used the patch clamp technique to assess the effects of epilepsy on the cardiac action potential and INa in rat ventricular myocytes. Consistent with QT prolongation, epileptic rats had longer ventricular action potential durations attributable to a sustained component of INa (INaL). The increase in INaL was because of a larger contribution of neuronal Na channels characterized by their high sensitivity to tetrodotoxin. As in the brain, epilepsy was associated with an enhanced expression of the neuronal isoform NaV1.1 in cardiomyocyte. Epilepsy was also associated with a lower INa activation threshold resulting in increased cell excitability. CONCLUSIONS: This is the first study correlating increased expression of neuronal sodium channels within the heart to epilepsy-related cardiac arrhythmias. This represents a new paradigm in our understanding of cardiac complications related to epilepsy.

New testosterone derivatives as semi-synthetic anticancer agents against prostate cancer: synthesis and preliminary biological evaluation.

Prostate cancer (PC) is a major health issue in the world. Treatments of localized PC are quite efficient and usually involve surgery, radiotherapy and/or hormonal therapy. Metastatic PC is however rarely curable to this day. Treatments of metastatic PC involve radiotherapy, chemotherapy and hormonal treatment such as orchiectomy, antiandrogens and luteinizing hormone-releasing hormone agonists. The suppression of tumor growth by hormonal treatment is efficient but overtime resistance still occurs and the disease progresses. Thus, more urgently than ever there is a need for discovery of new treatment options for castration-resistant PC (CRPC). Hence, we designed and tested a series of amide derivatives located at position 7α of testosterone as prospective "natural" or "semisynthetic" anticancer agents against CRPC with the goal of discovering therapeutic alternatives for the disease. This manuscript describes an efficient path towards the target molecules that are made in only 6 or 7 chemical steps from testosterone in good overall yields. This strategy can be used to make several compounds of interest that present higher biological activity than the classic antiandrogen; cyproterone acetate (3). The best testosterone-7α-amide was the N-2-pyridylethylamide (25) which was as active as the antiandrogen cyproterone acetate (3) on androgen-dependent LNCaP cells and 2.7 times more active on androgen-independent PC3 prostate cancer cells. The results obtained show the synthetic feasibility and the potential for future development of this unique class of semi-synthetic anticancer agents that offer the premise of new treatment modalities for patients afflicted with CRPC.