Potent antimalarial 4-pyridones with improved physico-chemical properties

Antimalarial 4-pyridones are a novel class of inhibitors of the plasmodial mitochondrial electron transport chain targeting Cytochrome bc1 (complex III). In general, the most potent 4-pyridones are lipophilic molecules with poor solubility in aqueous media and low oral bioavailability in pre-clinical species from the solid dosage form. The strategy of introducing polar hydroxymethyl groups has enabled us to maintain the high levels of antimalarial potency observed for other more lipophilic analogues whilst improving the solubility and the oral bioavailability in pre-clinical species.     

P2Y purinergic regulation of the glycine neurotransmitter transporters

The sodium- and chloride-coupled glycine neurotransmitter transporters (GLYTs) control the availability of glycine at glycine-mediated synapses. The mainly glial GLYT1 is the key regulator of the glycine levels in glycinergic and glutamatergic pathways, whereas the neuronal GLYT2 is involved in the recycling of synaptic glycine from the inhibitory synaptic cleft. In this study, we report that stimulation of P2Y purinergic receptors with 2-methylthioadenosine 5'-diphosphate in rat brainstem/spinal cord primary neuronal cultures and adult rat synaptosomes leads to the inhibition of GLYT2 and the stimulation of GLYT1 by a paracrine regulation. These effects are mainly mediated by the ADP-preferring subtypes P2Y(1) and P2Y(13) because the effects are partially reversed by the specific antagonists N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate and pyridoxal-5'-phosphate-6-azo(2-chloro-5-nitrophenyl)-2,4-disulfonate and are totally blocked by suramin. P2Y(12) receptor is additionally involved in GLYT1 stimulation. Using pharmacological approaches and siRNA-mediated protein knockdown methodology, we elucidate the molecular mechanisms of GLYT regulation. Modulation takes place through a signaling cascade involving phospholipase C activation, inositol 1,4,5-trisphosphate production, intracellular Ca(2+) mobilization, protein kinase C stimulation, nitric oxide formation, cyclic guanosine monophosphate production, and protein kinase G-I (PKG-I) activation. GLYT1 and GLYT2 are differentially sensitive to NO/cGMP/PKG-I both in brain-derived preparations and in heterologous systems expressing the recombinant transporters and P2Y(1) receptor. Sensitivity to 2-methylthioadenosine 5'-diphosphate by GLYT1 and GLYT2 was abolished by small interfering RNA (siRNA)-mediated knockdown of nitric-oxide synthase. Our data may help define the role of GLYTs in nociception and pain sensitization.     

Subcellular localization and role of lipin-1 in human macrophages

The lipins have been described as metabolic enzymes that regulate lipid biosynthesis and also signaling processes by controlling the cellular concentration of bioactive lipids, phosphatidic acid, and diacylgycerol. In the present work we have studied the subcellular localization and role of lipin-1 in human monocyte-derived macrophages. Human macrophages express lipin-1 isoforms α and β. A transfected lipin-1α-enhanced GFP construct associates with membranes of cellular organelles that can be stained with Nile Red. Colocalization experiments with lipid droplet (LD)-specific proteins such as adipophilin/adipose differentiation-related protein/perilipin 2 or TIP47/perilipin 3 show that both proteins colocalize with lipin-1α in the same cellular structures. Reduction of the expression levels of lipin-1 by small interfering RNA technology does not impair triacylglycerol biosynthesis but reduces the size of LDs formed in response to oleic acid. In agreement with these data, peritoneal macrophages from animals that carry a mutation in the Lpin-1 gene (fld animals) also produce less and smaller LDs in response to oleic acid. Mass spectrometry determinations demonstrate that the fatty acid composition of triacylglycerol in isolated LDs from lipin-1-deficient cells differs from that of control cells. Moreover, activation of cytosolic group IVA phospholipase A(2)α, a proinflammatory enzyme that is also involved in LD biogenesis, is also compromised in lipin-1-deficient cells. Collectively, these data suggest that lipin-1 associates with LDs and regulates the activation of cytosolic group IVA phospholipase A(2)α in human monocyte-derived macrophages.     

Transforming growth factor-beta1 decreases cardiac muscle L-type Ca2+ current and charge movement by acting on the Cav1.2 mRNA

Transforming growth factors-beta (TGF-betas) are essential to the structural remodeling seen in cardiac disease and development; however, little is known about potential electrophysiological effects. We hypothesized that chronic exposure (6-48 h) of primary cultured neonatal rat cardiomyocytes to the type 1 TGF-beta (TGF-beta1, 5 ng/ml) may affect voltage-dependent Ca(2+) channels. Thus we investigated T- (I(CaT)) and L-type (I(CaL)) Ca(2+) currents, as well as dihydropyridine-sensitive charge movement using the whole cell patch-clamp technique and quantified Ca(V)1.2 mRNA levels by real-time PCR assay. In ventricular myocytes, TGF-beta1 did not exert significant electrophysiological effects. However, in atrial myocytes, TGF-beta1 reduced both I(CaL) and charge movement (55% at 24-48 h) without significantly altering I(CaT), cell membrane capacitance, or channel kinetics (voltage dependence of activation and inactivation, as well as the activation and inactivation rates). Reductions of I(CaL) and charge movement were explained by concomitant effects on the maximal values of L-channels conductance (G(max)) and charge movement (Q(max)). Thus TGF-beta1 selectively reduces the number of functional L-channels on the surface of the plasma membrane in atrial but not ventricular myocytes. The TGF-beta1-induced I(CaL) reduction was unaffected by supplementing intracellular recording solutions with okadaic acid (2 microM) or cAMP (100 microM), two compounds that promote L-channel phosphorylation. This suggests that the decreased number of functional L-channels cannot be explained by a possible regulation in the L-channels phosphorylation state. Instead, we found that TGF-beta1 decreases the expression levels of atrial Ca(V)1.2 mRNA (70%). Thus TGF-beta1 downregulates atrial L-channel expression and may be therefore contributing to the in vivo cardiac electrical remodeling.     

Inactivation of the nodH gene in Sinorhizobium sp. BR816 enhances symbiosis with Phaseolus vulgaris L

Sulfate modification on Rhizobium Nod factor signaling molecules is not a prerequisite for successful symbiosis with the common bean (Phaseolus vulgaris L.). However, many bean-nodulating rhizobia, including the broad host strain Sinorhizobium sp. BR816, produce sulfated Nod factors. Here, we show that the nodH gene, encoding a sulfotransferase, is responsible for the transfer of sulfate to the Nod factor backbone in Sinorhizobium sp. BR816, as was shown for other rhizobia. Interestingly, inactivation of nodH enables inoculated bean plants to fix significantly more nitrogen under different experimental setups. Our studies show that nodH in the wild-type strain is still expressed during the later stages of symbiosis. This is the first report on enhanced nitrogen fixation by blocking Nod factor sulfation.     

Genomic basis of symbiovar mimosae in Rhizobium etli

Background

Symbiosis genes (nod and nif) involved in nodulation and nitrogen fixation in legumes are plasmid-borne in Rhizobium. Rhizobial symbiotic variants (symbiovars) with distinct host specificity would depend on the type of symbiosis plasmid. In Rhizobium etli or in Rhizobium phaseoli, symbiovar phaseoli strains have the capacity to form nodules in Phaseolus vulgaris while symbiovar mimosae confers a broad host range including different mimosa trees.

Results

We report on the genome of R. etli symbiovar mimosae strain Mim1 and its comparison to that from R. etli symbiovar phaseoli strain CFN42. Differences were found in plasmids especially in the symbiosis plasmid, not only in nod gene sequences but in nod gene content. Differences in Nod factors deduced from the presence of nod genes, in secretion systems or ACC-deaminase could help explain the distinct host specificity. Genes involved in P. vulgaris exudate uptake were not found in symbiovar mimosae but hup genes (involved in hydrogen uptake) were found. Plasmid pRetCFN42a was partially contained in Mim1 and a plasmid (pRetMim1c) was found only in Mim1. Chromids were well conserved.

Conclusions

The genomic differences between the two symbiovars, mimosae and phaseoli may explain different host specificity. With the genomic analysis presented, the term symbiovar is validated. Furthermore, our data support that the generalist symbiovar mimosae may be older than the specialist symbiovar phaseoli.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-575) contains supplementary material, which is available to authorized users.     

Steroid 5α-reductase in adult rat brain after neonatal testosterone administration

Testosterone (T) plays an important role in developing brain, dictating sex-specific behavior and physiology. 3α,5α-Reduced neurosteroids also regulate reproductive behavior. The key enzyme in the biosynthesis of these neurosteroids is 5α-reductase (5α-R), expressed as two isozymes, 5α-R1 and 5α-R2. In this study, T and sesame oil (vehicle) were administered during postnatal sexual differentiation of the central nervous system (CNS) and mRNA levels of 5α-R isozymes, were measured using quantitative RT-PCR in prefrontal cortex of male and female rats with different androgenic status at adulthood. Our results indicate that T concentrations during postnatal sexual differentiation of the rat CNS, among other sex-dependent factors, influence brain levels of 5α-R isozymes in adulthood and the pattern of their regulation by androgen hormones.