17 beta-Estradiol inhibits angiotensin II activation of area postrema neurons

It is well established that the area postrema, as a circumventricular organ, is susceptible to modulation by circulating hormones and peptides. Furthermore, activation of the area postrema has been shown to modulate central neurons involved in the regulation of cardiovascular function and blood pressure. In particular, the vasoactive peptide angiotensin II (ANG II) has been shown to inhibit baroreflex regulation of heart rate and increase sympathetic outflow and blood pressure via activation of area postrema neurons. Estrogen is thought to protect against hypertension in both humans and animal models and has been shown in a number of systems to alter the effects of ANG II. The purpose of the present study was to determine the effects of estrogen on ANG II activation of area postrema neurons. In this study, the effects of ANG II and KCl on fura 2-measured cytosolic Ca2+ concentration ([Ca2+]i) responses in cultured area postrema neurons in the presence and absence of 12-h exposure to 100 nM 17 beta-estradiol (E2) were evaluated. In neurons incubated in control vehicle media, 50 nM ANG II increased [Ca2+]i by 92 +/- 12%. In neurons preincubated with 100 nM E2, ANG II increased [Ca2+]i by only 68 +/- 11%, for a total inhibition of the ANG II-evoked response of 24%. Coapplication of the estrogen receptor antagonist ICI-182,780 did not inhibit the effects of E2. In the same cells in which the effects of E2 on ANG II-evoked responses were tested, the effects of incubation in E on the depolarization-induced increased [Ca2+2]i due to 60 mM KCl were also tested. Incubation of the cells with 100 nM E increased the KCl-evoked [Ca2+2]i response, and this response was blocked by ICI-182,780. These results suggest that in the area postrema, estrogen may utilize multiple pathways to modulate neural activity and responses to ANG II.     

Salicylic acid reverses phorbol 12-myristate-13-acetate (PMA)- and tumor necrosis factor alpha (TNFalpha)-induced insulin receptor substrate 1 (IRS1) serine 307 phosphorylation and insulin resistance in human embryonic kidney 293 (HEK293) cells

Salicylates, including aspirin, have been shown to improve insulin sensitivity both in human and animal models. Although it has been suggested that salicylates sensitize insulin action by inhibiting IkappaB kinase beta (IKKbeta), the detailed mechanisms remain unclear. Protein kinase C isoforms and tumor necrosis factor alpha (TNFalpha) signaling pathways are well described mediators of insulin resistance; they are implicated in the activation of IKKbeta and the subsequent inhibition of proximal insulin signaling via insulin receptor substrate 1 (IRS1) and Akt. This study investigated the effect of salicylic acid on phorbol 12-myristate 13-acetate (PMA)- and TNFalpha-induced insulin resistance in a human embryonic kidney 293 (HEK293) cell line stably expressing recombinant human IRS1. The results showed that both PMA and TNFalpha inhibited insulin-induced Akt phosphorylation and promoted IRS1 phosphorylation on Ser-307. Salicylic acid pretreatment completely reversed the effects of PMA and TNFalpha on both Akt and IRS1. Whereas PMA activated protein kinase C isoforms and IKKbeta, TNFalpha activated neither. On the other hand, both PMA and TNFalpha activated the c-Jun N-terminal kinase (JNK), which has been reported to directly phosphorylate IRS1 Ser-307. SP600125, a JNK inhibitor, prevented PMA and TNFalpha-induced IRS1 Ser-307 phosphorylation. Finally, salicylic acid inhibited JNK activation induced by both PMA and TNFalpha. Taken together, these observations suggest that salicylic acid can reverse the inhibitory effects of TNFalpha on insulin signaling via an IKKbeta-independent mechanism(s), potentially involving the inhibition of JNK activation. The role of JNK in salicylic acid-mediated insulin sensitization, however, requires further validation because the JNK inhibitor SP600125 appears to have other nonspecific activity in addition to inhibiting JNK activity.     

The lipidation by hepatocytes of human apolipoprotein A-I occurs by both ABCA1-dependent and -independent pathways

The pathways of hepatic intra- and peri-cellular lipidation of apolipoprotein A-I (apoA-I) were studied by infecting primary mouse hepatocytes from either apoA-I-deficient or ABCA1-deficient mice with a recombinant adenovirus expressing the human apoA-I (hapoA-I) cDNA (endo apoA-I) or incubating the hepatocytes with exogenously added hapoA-I (exo apoA-I) and examining the hapoA-I-containing lipoproteins formed. The cells, maintained in serum-free medium, were labeled with [(3)H]choline, and the cell medium was separated by fast protein liquid chromatography or immunoprecipitated to quantify labeled choline phospholipids specifically associated with hapoA-I. With the apoA-I-deficient hepatocytes, the high density lipoprotein fraction formed with endo apoA-I contained proportionally more phospholipids than that formed with exo apoA-I. However, the lipoprotein size and electrophoretic mobility and phospholipid profiles were similar for exo apoA-I and endo apoA-I. Taken together, these data demonstrate that a significant proportion of hapoA-I is secreted from hepatocytes in a phospholipidated state but that hapoA-I is also phospholipidated peri-cellularly. With primary hepatocytes from ABCA1-deficient mice, the expression and net secretion of adenoviral-generated endogenous apoA-I was unchanged compared with control mice, but (3)H-phospholipids associated with endo apoA-I and exo apoA-I decreased by 63 and 25%, respectively. The lipoprotein size and electrophoretic migration and their phospholipid profiles remained unchanged. In conclusion, we demonstrated that intracellular and peri-cellular lipidation of apoA-I represent distinct and additive pathways that may be regulated independently. Hepatocyte expression of ABCA1 is central to the lipidation of newly synthesized apoA-I but also contributes to the lipidation of exogenous apoA-I. However, a significant basal level of phospholipidation occurs in the absence of ABCA1.     

Escherichia coli YrbH is a D-arabinose 5-phosphate isomerase

A gene encoding for arabinose 5-phosphate isomerase (API), which catalyzes the interconversion of d-ribulose 5-phosphate (Ru5P) and d-arabinose 5-phosphate (A5P), has been identified from the genome of Escherichia coli K-12. API is the first enzyme in the biosynthesis of 3-deoxy-d-manno-octulosonate (KDO), a sugar moiety located in the lipopolysaccharide layer of most Gram-negative bacteria. The API gene yrbH is located next to the recently identified specific KDO 8-P phosphatase gene, yrbI. The 328-amino acid open reading frame yrbH was cloned, overexpressed, and characterized. The purified recombinant enzyme is a tetramer and is sensitive to inhibition by zinc cations. API has optimal activity at pH 8.4 and catalytic residues with estimated pKa values of 6.55 +/- 0.04 and 10.34 +/- 0.07. The enzyme is specific for A5P and Ru5P, with apparent Km values of 0.61 +/- 0.06 mm for A5P and 0.35 +/- 0.08 mm for Ru5P. The apparent kcat in the A5P to Ru5P direction is 157 +/- 4 s-1, and in the Ru5P to A5P direction it is 255 +/- 16 s-1. The value of Keq (Ru5P/A5P) is 0.50 +/- 0.06. Homology searches of the E. coli genome suggest yrbH may be one of multiple genes that encode proteins with API activity.     

Stanniocalcin 1 is an autocrine modulator of endothelial angiogenic responses to hepatocyte growth factor

Stanniocalcin 1 (STC1) is a secreted glycoprotein originally described as a hormone involved in calcium and phosphate homeostasis in bony fishes. We recently identified the mammalian homolog of this molecule to be highly up-regulated in an in vitro model of angiogenesis, as well as focally and intensely expressed at sites of pathological angiogenesis (e.g. tumor vasculature). In the present study, we report that STC1 is a selective modulator of hepatocyte growth factor (HGF)-induced endothelial migration and morphogenesis, but not proliferation. STC1 did not inhibit proliferative or migratory responses to vascular endothelial growth factor or basic fibroblast growth factor. The mechanism of STC1 inhibitory effects on HGF-induced endothelial migration seem to occur secondary to receptor activation because STC1 did not inhibit HGF-induced c-met receptor phosphorylation, but did block HGF-induced focal adhesion kinase activation. In the mouse femoral artery ligation model of angiogenesis, STC1 expression closely paralleled that of the endothelial marker CD31, and the peak level of STC1 expression occurred after an increase in HGF expression. We propose that STC1 may play a selective modulatory role in angiogenesis, possibly serving as a "stop signal" or stabilizing factor contributing to the maturation of newly formed blood vessels. HGF is a mesenchyme-derived pleiotropic factor with mitogenic, motogenic, and morphogenic activities on a number of different cell types. HGF effects are mediated through a specific tyrosine kinase, c-met, and aberrant HGF and c-met expression are frequently observed in a variety of tumors. Recent studies have shown HGF to be a potent growth factor implicated in wound healing, tissue regeneration, and angiogenesis.     

Novel drug designing approach for dual inhibitors as anti-inflammatory agents: implication of pyridine template

Compounds incorporating thiophene moiety, a pi excess five membered heterocycle, have attracted a great deal of research interest, owing to the therapeutic utility of the template as useful drug molecular scaffolding. We report the synthesis and pharmacological evaluation of thiophenes substituted with 4-methanesulfonyl benzoyl moiety at the fifth position of the ring, as possible anti-inflammatory lead candidates. The aryl sulfonyl methyl thiophene analogs AP29, AP82, and AP37, when screened for anti-inflammatory activity in carrageenin induced rat paw edema, an acute in vivo model, exhibited moderate to good activity at a dose level of 100 mg/kg body weight P.o compared to Ibuprofen. In a five day formalin induced rat paw edema, a chronic in vivo anti-inflammatory model, candidates AP29, AP82, and AP37 inhibited the disease progression by 53%, 34%, and 65%, respectively on the fifth day, at a dose level of 100 mg/kg body weight P.o compared to Rofecoxib, Ibuprofen, and Dexamethasone at therapeutic doses which gave a protection of 53.8%, 81.5%, and 81.5%, respectively. The replacement of the 4-methanesulfonyl benzoyl moiety in AP82 with the pyridine template, 3,5-dimethyl-4-methoxy-2-pyridyl function, gave rise to AP84, which was less active in the acute model, but gave 54% and 75% protection both during the first day and fifth day, respectively, in the chronic model. A dual mechanism of action is proposed for AP84, a non-steroidal drug which has exhibited remarkable activity when compared to the steroid dexamethasone. These results open up new avenues in designing novel anti-inflammatory drugs as dual inhibitors with the incorporation of a pyridine template as part of the pharmacophore.     

Tracking the acetate threshold using DO-transient control during medium and high cell density cultivation of recombinant Escherichia coli in complex media

DO-transient nutrient controllers use the dissolved oxygen signal to attempt acetate threshold tracking during fed-batch cultivation of recombinant E. coli. Here we apply DO-transient control to the production of Jembrana disease virus protein in complex Super Luria medium and compare performance against a high-limit pH-stat controller. For induction at medium cell density (harvest between 31 and 32.5 g dcw L) a total productivity of 0.27 g L h was achieved as compared to 0.24 g L h with the high-limit pH-stat. For induction at high cell density (harvest at 60 g dcw L), decreased productivity (0.12 g L h) was attributed to the effect of acetate accumulation on recombinant protein formation and a concomitant lowering of the critical growth rate. Our results suggest that complex media provides a difficult environment for the application of acetate threshold tracking DO-transient control because of difficulties in re-oxidizing acetate, and apparent localized production of acetate below the production threshold (as detected by the DO-transient controller as SPOUR(crit)). Configuring the DO-transient controller to avoid aggressive threshold probing is suggested as a means to improve performance and reduce acetate accumulation in complex media.     

Improper chromosome synapsis is associated with elongated RAD51 structures in the maize<Emphasis Type="Italic"> desynaptic2</Emphasis> mutant

The RecA homolog, RAD51, performs a central role in catalyzing the DNA strand exchange event of meiotic recombination. During meiosis, RAD51 complexes develop on pairing chromosomes and then most disappear upon synapsis. In the maize meiotic mutant desynaptic2 (dsy2), homologous chromosome pairing and recombination are reduced by ~70% in male meiosis. Fluorescent in situ hybridization studies demonstrate that a normal telomere bouquet develops but the pairing of a representative gene locus is still only 25%. Chromosome synapsis is aberrant as exemplified by unsynapsed regions of the chromosomes. In the mutant, we observed unusual RAD51 structures during chromosome pairing. Instead of spherical single and double RAD51 structures, we saw long thin filaments that extended along or around a single chromosome or stretched between two widely separated chromosomes. Mapping with simple sequence repeat (SSR) markers places the dsy2 gene to near the centromere on chromosome 5, therefore it is not an allele of rad51. Thus, the normal dsy2 gene product is required for both homologous chromosome synapsis and proper RAD51 filament behavior when chromosomes pair. Edited by: P. Moens