Age-dependent requirement of AKAP150-anchored PKA and GluR2-lacking AMPA receptors in LTP

Association of PKA with the AMPA receptor GluR1 subunit via the A kinase anchor protein AKAP150 is crucial for GluR1 phosphorylation. Mutating the AKAP150 gene to specifically prevent PKA binding reduced PKA within postsynaptic densities (>70%). It abolished hippocampal LTP in 7-12 but not 4-week-old mice. Inhibitors of PKA and of GluR2-lacking AMPA receptors blocked single tetanus LTP in hippocampal slices of 8 but not 4-week-old WT mice. Inhibitors of GluR2-lacking AMPA receptors also prevented LTP in 2 but not 3-week-old mice. Other studies demonstrate that GluR1 homomeric AMPA receptors are the main GluR2-lacking AMPA receptors in adult hippocampus and require PKA for their functional postsynaptic expression during potentiation. AKAP150-anchored PKA might thus critically contribute to LTP in adult hippocampus in part by phosphorylating GluR1 to foster postsynaptic accumulation of homomeric GluR1 AMPA receptors during initial LTP in 8-week-old mice.     

Defining the mode, energetics and specificity with which a macrocyclic hexaoxazole binds to human telomeric G-quadruplex DNA

Oxazole-containing macrocycles represent a promising class of anticancer agents that target G-quadruplex DNA. We report the results of spectroscopic studies aimed at defining the mode, energetics and specificity with which a hexaoxazole-containing macrocycle (HXDV) binds to the intramolecular quadruplex formed by the human telomeric DNA model oligonucleotide d(T2AG3)4 in the presence of potassium ions. HXDV binds solely to the quadruplex nucleic acid form, but not to the duplex or triplex form. HXDV binds d(T2AG3)4 with a stoichiometry of two drug molecules per quadruplex, with these binding reactions being coupled to the destacking of adenine residues from the terminal G-tetrads. HXDV binding to d(T2AG3)4 does not alter the length of the quadruplex. These collective observations are indicative of a nonintercalative 'terminal capping' mode of interaction in which one HXDV molecule binds to each end of the quadruplex. The binding of HXDV to d(T2AG3)4 is entropy driven, with this entropic driving force reflecting contributions from favorable drug-induced alterations in the configurational entropy of the host quadruplex as well as in net hydration. The 'terminal capping' mode of binding revealed by our studies may prove to be a general feature of the interactions between oxazole-containing macrocyclic ligands (including telomestatin) and intramolecular DNA quadruplexes.     

Tumor necrosis factor-alpha reduces argininosuccinate synthase expression and nitric oxide production in aortic endothelial cells

Endothelial dysfunction associated with elevated serum levels of TNF-alpha observed in diabetes, obesity, and congenital heart disease results, in part, from the impaired production of endothelial nitric oxide (NO). Cellular NO production depends absolutely on the availability of arginine, substrate of endothelial nitric oxide synthase (eNOS). In this report, evidence is provided demonstrating that treatment with TNF-alpha (10 ng/ml) suppresses not only eNOS expression but also the availability of arginine via the coordinate suppression of argininosuccinate synthase (AS) expression in aortic endothelial cells. Western blot and real-time RT-PCR demonstrated a significant and dose-dependent reduction of AS protein and mRNA when treated with TNF-alpha with a corresponding decrease in NO production. Reporter gene analysis demonstrated that TNF-alpha suppresses the AS proximal promoter, and EMSA analysis showed reduced binding to three essential Sp1 elements. Inhibitor studies suggested that the repression of AS expression by TNF-alpha may be mediated, in part, via the NF-kappaB signaling pathway. These findings demonstrate that TNF-alpha coordinately downregulates eNOS and AS expression, resulting in a severely impaired citrulline-NO cycle. The downregulation of AS by TNF-alpha is an added insult to endothelial function because of its important role in NO production and in endothelial viability.     

Bradykinin B1 antagonists: biphenyl SAR studies in the cyclopropanecarboxamide series

SAR study of the biphenyl region of cyclopropanecarboxamide derived bradykinin B(1) antagonists was examined. Incorporation of a pyridine in place of the proximal phenyl ring and chlorination of the distal phenyl ring proved to be well tolerated and provided compounds with improved pharmacokinetic profiles, CNS penetration, and enhanced receptor occupancy.     

Endothelial nitric oxide production is tightly coupled to the citrulline–NO cycle

Nitric oxide (NO) is an important vasorelaxant produced along with L-citrulline from L-arginine in a reaction catalyzed by endothelial nitric oxide synthase (eNOS). Previous studies suggested that the recycling of L-citrulline to L-arginine is essential for NO production in endothelial cells. However, there is no direct evidence demonstrating the degree to which the recycling of L-citrulline to L-arginine is coupled to NO production. We hypothesized that the amount of NO formed would be significantly higher than the amount of L-citrulline formed due to the efficiency of L-citrulline recycling via the citrulline-NO cycle. To test this hypothesis, endothelial cells were incubated with [14C]-L-arginine and stimulated by various agents to produce NO. The extent of NO and [14C]-L-citrulline formation were simultaneously determined. NO production exceeded apparent L-citrulline formation of the order of 8 to 1, under both basal and stimulated conditions. As further support, alpha-methyl-DL-aspartate, an inhibitor of argininosuccinate synthase (AS), a component of the citrulline-NO cycle, inhibited NO production in a dose-dependent manner. The results of this study provide evidence for the essential and efficient coupling of L-citrulline recycling, via the citrulline-NO cycle, to endothelial NO production.     

Soil Organic Phosphorus Transformations During Pedogenesis

Abstract Long-term changes in soil phosphorus influence ecosystem development and lead to a decline in the productivity of forests in undisturbed landscapes. Much of the soil phosphorus occurs in a series of organic compounds that differ in their availability to organisms, but changes in the relative abundance of these compounds during pedogenesis remain unknown. We used alkaline extraction and solution phosphorus-31 nuclear magnetic resonance spectroscopy to assess the chemical nature of soil organic phosphorus along a 120,000-year post-glacial chronosequence at Franz Josef, New Zealand. Inositol phosphates, DNA, phospholipids, and phosphonates accumulated rapidly during the first 500 years of soil development characterized by nitrogen limitation of biological productivity, but then declined slowly to low concentrations in older soils characterized by intense phosphorus limitation. However, the relative contribution of the various compounds to the total organic phosphorus varied along the sequence in dramatic and surprising ways. The proportion of inositol hexakisphosphate, conventionally considered to be relatively recalcitrant in the environment, declined markedly in older soils, apparently due to a corresponding decline in amorphous metal oxides, which weather to crystalline forms during pedogenesis. In contrast, the proportion of DNA, considered relatively bioavailable in soil, increased continually throughout the sequence, due apparently to incorporation within organic structures that provide protection from biological attack. The changes in soil organic phosphorus coincided with marked shifts in plant and microbial communities, suggesting that differences in the forms and bioavailability of soil organic phosphorus have ecological significance. Overall, the results strengthen our understanding of phosphorus transformations during pedogenesis and provide important insight into factors regulating the composition of soil organic phosphorus.     

SLC5A8 gene, a transporter of butyrate: a gut flora metabolite, is frequently methylated in African American colon adenomas

Background

Colon cancer is one of the leading causes of cancer related deaths. Its impact on African Americans (AAs) is higher than in the general population both in the incidence and mortality from the disease. Colon cancer aggressiveness in AAs as well as non-frequent check-ups and follow up in this population have been proposed as ways to explain the observed discrepancies. These facts made the detection of early carcinogenesis markers in this population a priority.

Materials and Methods

Here, we analyzed 50 colon adenomas from AA patients for both microsatellite instability (MSI) and the methylation status of SLC5A8 gene. This gene''s product is involved in the transport of butyrate that has anti-proliferative properties through its effects on histone acetylation and gene expression. A proteomic analysis to check the expressed histones in adenoma and normal tissues was also performed.

Results

The analyzed samples displayed 82% (n = 41) methylation level of SLC5A8 gene in adenomas. The MSI-H (high) adenoma were about 18% (n = 9) while the rest were mostly MSS (microsatellite stable) with few MSI-L (Low). No association was found between SLC5A8 methylation and the MSI status. Also, there was no association between SLC5A8 methylation and the sex and age of the patients. However, there were more right sided adenomas with SLC5A8 methylation than the left sided ones. The proteomic analysis revealed distinct histone expression profiles between normal and adenoma tissues.

Conclusion

SLC5A8 is highly methylated in AA colon adenomas which points to its potential use as a marker for early detection. The MSI rate is similar to that found in colon cancer tumors in AAs. These findings suggest that both processes stem from the same epigenetic and genetic events occurring at an early stage in colon carcinogenesis in AAs.     

Sesiid Moths Reduce Germination,Seedling Growth,and Survivorship in Pentaclethra macroloba (Mimosoideae), a Locally Dominant Lowland Neotropical Tree1

Monodominant forests are a widespread feature of the humid and wet lowland tropics, but little is known about their origins or factors mediating their persistence. Nonetheless, escape from significant vertebrate and invertebrate seed predation plays a prominent role in most hypotheses. The seeds of Pentaclethra macroloba (Fabaceae: Mimosoideae) have long been thought to be virtually immune to predation, contributing to its local dominance in the canopy of some Mesoamerican forests. Here, we describe herbivory by the larvae of Carmenta surinamensis (Lepidoptera: Sesiidae) on the seeds of P. macroloba, and report the results of studies designed to clarify how this interaction influences germination, seedling growth, and mortality. To this end, we collected P. macroloba seeds at 30‐d intervals for 5 mo along a rain forest transect in Costa Rica. The seeds were monitored in a shade house for 30 d. Adult moths were reared from 43.6 percent of seeds, and significantly affected germination and mortality, and all measures of growth (number of leaves, seedling height, seed and seedling mass at 30 d, and 30‐d change in seed and seedling mass). Based on these observations, we conclude that seed boring by C. surinamensis is a potentially important factor influencing population dynamics in P. macroloba, and warrants further investigation for its prospective role in regulating local abundance in this locally dominant and ecologically significant tree.