Uptake of propranolol, a cardiovascular pharmaceutical, from water into fish plasma and its effects on growth and organ biometry

Pharmaceuticals in the environment (PIE) are of importance since these compounds are designed to affect biological receptors/enzymes that are often conserved across vertebrate families. Across-species extrapolation of these therapeutic targets suggests potential for impacting amphibia and fish in the aquatic environment. Due to the scarcity of relevant ecotoxicological data, the long-tem impact of PIE remains a research question. Efficient use of mammalian data has been proposed to better understand and predict the potential for a given pharmaceutical to impact the environment. Using a model cardiovascular pharmaceutical (propranolol, a non-specific beta(1)/beta(2)-adrenergic antagonist), the hypothesis that mammalian data can be used to predict toxicity in fish was tested. Rainbow trout (Oncorhynchus mykiss (Walbaum)) have beta-adrenergic signalling mechanisms analogous to human cardiovascular receptors that respond to pharmacological doses of agonists and antagonists. Trout absorbed propranolol from water such that after 40 days of exposure, the linear relationship was [plasma] - 0.59[water] (n - 31, r - 0.96). Growth rate was affected only at very high aqueous concentrations (10-day (growth)NOEC - 1.0 and (growth)LOEC - 10 mg/l). Growth recovered with time (40-day (growth)NOEC - 10 mg/l), suggesting possible adaptation to the pharmaceutical, although the internal plasma concentration in trout exposed to 10mg propranolol/l of water was higher than the mammalian therapeutic plasma concentration. Additional endpoints suggested subtle changes of liver and heart size at much lower concentrations may have occurred, although these were not concentration-related. There was, however, a dose-dependent effect upon overall body condition. The trout plasma concentrations at these effective aqueous concentrations fell within the range of mammalian effective plasma concentrations, supporting the potential for developing 'read-across' from mammalian pharmacology safety data to fish ecotoxicology. Despite these effects at relatively high concentrations, propranolol is not expected to pose a risk to fish at the concentrations considered to be present in the aquatic environment.

Negative regulation of endogenous protein kinase Calpha on the dynamic change of carbachol-induced intracellular calcium response in different melanoma cells

Regulations of intracellular protein kinase C (PKC) on carbachol (CCh)-induced intracellular calcium ([Ca(2+)]i) responses were investigated in different stages of melanoma cells. We found that CCh (1 mM) significantly increased [Ca(2+)]i with 6-, 4-, 4-, and 25-folds intensities in WM793B, 451Lu, SK-MEL-5, and A2058 melanoma cells, respectively. Pretreatment of phorbol 12, 13-dibutyrate (PDBu, 2 microM), an activator of intracellular PKC, significantly suppressed CCh-induced peak reactions in WM793B, SK-MEL-5, and A2058 cells. RT-PCR data showed that mRNA levels of PKCalpha were 12-, 4-, 6-, and 0.9-folds higher in above four melanoma cells. Short interfering RNA (siRNA) targeting to PKCalpha in WM793B cells enhanced CCh-induced peak calcium reactions. Present data indicated that CCh-induced [Ca(2+)]i responses were dynamically changed in different stages of melanoma progression. Moreover, intracellular PKCalpha activated by exogenous agonist and expressed through endogenous gene transcription negatively regulated CCh-induced calcium responses. The functional analysis on the relationship between CCh-induced calcium response and endogenous PKCalpha expression might be helpful to predict the development of melanoma.

Relationship between anti-fibrotic effect of Panax notoginseng saponins and serum cytokines in rat hepatic fibrosis

The aim of this study was to investigate the relationship between anti-fibrotic effect of Panax notoginseng saponins (PNS) and serum cytokines in rat hepatic fibrosis. Hepatic fibrosis induced by carbon tetrachloride (CCl(4)) was studied in animal models using SD rats. Liver index, serum alanine amino transferase (ALT), aspartate amino transferase (AST), transforming growth factor-beta1 (TGF-beta1), tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-10 (IL-10) were measured, respectively. Liver index and the degree of liver fibrosis were also determined. Our results showed that the levels of ALT, AST and liver index in PNS-treated group were markedly lower than those in model group. PNS therapy also significantly attenuated the degree of hepatic fibrosis, collagen area and collagen area percent in liver tissue. Furthermore, the levels of serum TGF-beta1, TNF-alpha and IL-6 were strikingly reduced in PNS-treated group compared with model group while the production of IL-10 was up-regulated. These findings demonstrate that PNS has certain therapeutic effects on hepatic fibrosis probably by immunoregulating the imbalance between pro-fibrotic and anti-fibrotic cytokines.

Spermine improves recognition memory deficit in a rodent model of Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder associated with motor and cognitive impairment. Intrastriatal administration of quinolinic acid (QA) causes neurodegeneration, glial proliferation and cognitive impairment in animals, which are similar to these seen in human HD. Since polyamines improve memory in cognitive tasks, we now tested if the post-training intrastriatal administration of spermine, an agonist of the polyamine site at the NMDA receptor, reverses the deficits in the object recognition task induced by QA. Bilateral striatal injections of QA (180 or 360 nmol/site) caused object recognition impairment, neuronal death and reactive astrogliosis. A single injection of spermine (0.1 and 1 nmol/site), 5 days after QA injection, reversed QA-induced impairment of object recognition task. Spermine (0.1 nmol/site) also inhibited QA-induced reactive astrogliosis measured by a semi-quantitative determination of GFAP immunolabelling, but did not alter neuronal death, measured by a semi-quantitative determination of fluoro-Jade C staining. These results suggest that polyamine binding sites may be considered a novel therapeutic target to prevent reactive astrogliosis and mnemonic deficits in HD.

The role of carbonic anhydrase 9 in regulating extracellular and intracellular ph in three-dimensional tumor cell growths

We have studied the role of carbonic anhydrase 9 (CA9), a cancer-associated extracellular isoform of the enzyme carbonic anhydrase in multicellular spheroid growths (radius of approximately 300 microm) of human colon carcinoma HCT116 cells. Spheroids were transfected with CA9 (or empty vector) and imaged confocally (using fluorescent dyes) for both intracellular pH (pH(i)) and pH in the restricted extracellular spaces (pH(e)). With no CA9 expression, spheroids developed very low pH(i) (approximately 6.3) and reduced pH(e) (approximately 6.9) at their core, associated with a diminishing gradient of acidity extending out to the periphery. With CA9 expression, core intracellular acidity was less prominent (pH(i) = approximately 6.6), whereas extracellular acidity was enhanced (pH(e) = approximately 6.6), so that radial pH(i) gradients were smaller and radial pH(e) gradients were larger. These effects were reversed by eliminating CA9 activity with membrane-impermeant CA inhibitors. The observation that CA9 activity reversibly reduces pH(e) indicates the enzyme is facilitating CO(2) excretion from cells (by converting vented CO(2) to extracellular H(+)), rather than facilitating membrane H(+) transport (such as H(+) associated with metabolically generated lactic acid). This latter process requires titration of exported H(+) ions with extracellular HCO(3)(-), which would reduce rather than increase extracellular acidity. In a multicellular structure, the net effect of CA9 on pH(e) will depend on the cellular CO(2)/lactic acid emission ratio (set by local oxygenation and membrane HCO(3)(-) uptake). Our results suggest that CO(2)-producing tumors may express CA9 to facilitate CO(2) excretion, thus raising pH(i) and reducing pH(e), which promotes tumor proliferation and survival. The results suggest a possible basis for attenuating tumor development through inhibiting CA9 activity.

Current issues in oncology drug development, with a focus on Phase II trials

In this commentary we discuss several challenges that are of current relevance to the design of clinical trials in oncology. We argue that the compartmentalization of trials into the three standard phases, with non overlapping aims, is not necessary and in fact may slow the clinical development of agents. Combined Phase I/II trials and/or Phase I trials that at minimum collect efficacy data and more optimally include a preliminary measure of efficacy in dosing determination should be more widely utilized. Similarly, we posit that randomized Phase II trials should be used more frequently, as opposed to the traditional historical single arm Phase II trial that usually does not have a valid comparison group. The use of non binary endpoints is a simple modification that can improve the efficiency of early phase trials. The heterogeneity in scientific goals and contexts in early phase oncology trials is considerable, and the potential to improve the design to match these goals is great. We review these and other issues in the context of 5 manuscripts related to Phase II trials published in this volume. Our overall premise is that the potential benefits associated with the oncology clinical trial community moving away from the one size fits all paradigm of trial design are great, and that more flexible and efficient designs tailored to match the goals of each study are currently available and being used successfully.

Application of a library of artificial receptors formed by the self-organization of N-lipidated peptides immobilized on cellulose in studying the effects of the incorporation of a fluorine atom

A library of artificial receptors formed by the self-organization of N-lipidated peptides attached to cellulose via m-aminophenylamino-1,3,5-triazine was used for docking pairs of small colorless N-phenylpiperazines with and without a fluorine atom in the phenyl ring. The interactions of guests with the receptors were visualized by using competitive adsorption-desorption of an appropriate reporter dye. Several library members demonstrated attributes characteristic of the detection of alterations in the guest structure caused by the substitution of one hydrogen atom with fluorine. Analysis of the binding pattern of N-phenylpiperazine derivatives showed two characteristic bonding patterns: one with stronger binding of fluorinated analogues and weaker binding of native phenyl substituted analogues by the most of the receptors studied and another one with stronger binding of native hydrogen substituted compounds and respectively weaker binding of fluorinated analogues of guest molecules by receptors with tryptophan inside the binding pocket.

Metabolism of fluoroorganic compounds in microorganisms: impacts for the environment and the production of fine chemicals

Incorporation of fluorine into an organic compound can favourably alter its physicochemical properties with respect to biological activity, stability and lipophilicity. Accordingly, this element is found in many pharmaceutical and industrial chemicals. Organofluorine compounds are accepted as substrates by many enzymes, and the interactions of microorganisms with these compounds are of relevance to the environment and the fine chemicals industry. On the one hand, the microbial transformation of organofluorines can lead to the generation of toxic compounds that are of environmental concern, yet similar biotransformations can yield difficult-to-synthesise products and intermediates, in particular derivatives of biologically active secondary metabolites. In this paper, we review the historical and recent developments of organofluorine biotransformation in microorganisms and highlight the possibility of using microbes as models of fluorinated drug metabolism in mammals.

Collation, assessment and analysis of literature in vitro data on hERG receptor blocking potency for subsequent modeling of drugs' cardiotoxic properties

The assessment of the torsadogenic potency of a new chemical entity is a crucial issue during lead optimization and the drug development process. It is required by the regulatory agencies during the registration process. In recent years, there has been a considerable interest in developing in silico models, which allow prediction of drug-hERG channel interaction at the early stage of a drug development process. The main mechanism underlying an acquired QT syndrome and a potentially fatal arrhythmia called torsades de pointes is the inhibition of potassium channel encoded by hERG (the human ether-a-go-go-related gene). The concentration producing half-maximal block of the hERG potassium current (IC(50)) is a surrogate marker for proarrhythmic properties of compounds and is considered a test for cardiac safety of drugs or drug candidates. The IC(50) values, obtained from data collected during electrophysiological studies, are highly dependent on experimental conditions (i.e. model, temperature, voltage protocol). For the in silico models' quality and performance, the data quality and consistency is a crucial issue. Therefore the main objective of our work was to collect and assess the hERG IC(50) data available in accessible scientific literature to provide a high-quality data set for further studies.

Urinary NGAL marks cystic disease in HIV-associated nephropathy

Nephrosis and a rapid decline in kidney function characterize HIV-associated nephropathy (HIVAN). Histologically, HIVAN is a collapsing focal segmental glomerulosclerosis with prominent tubular damage. We explored the expression of neutrophil gelatinase-associated lipocalin (NGAL), a marker of tubular injury, to determine whether this protein has the potential to aid in the noninvasive diagnosis of HIVAN. We found that expression of urinary NGAL was much higher in patients with biopsy-proven HIVAN than in HIV-positive and HIV-negative patients with other forms of chronic kidney disease. In the HIV-transgenic mouse model of HIVAN, NGAL mRNA was abundant in dilated, microcystic segments of the nephron. In contrast, urinary NGAL did not correlate with proteinuria in human or in mouse models. These data show that marked upregulation of NGAL accompanies HIVAN and support further study of uNGAL levels in large cohorts to aid in the noninvasive diagnosis of HIVAN and screen for HIVAN-related tubular damage.

Lansoprazole, a proton pump inhibitor, mediates anti-inflammatory effect in gastric mucosal cells through the induction of heme oxygenase-1 via activation of NF-E2-related factor 2 and oxidation of kelch-like ECH-associating protein 1

Induction of heme oxygenase-1 (HO-1) expression has been associated with cytoprotective and anti-inflammatory actions of lansoprazole, a proton pump inhibitor, but the underlying molecular mechanisms remain largely unresolved. In this study, we investigate the role of transcriptional NF-E2-related factor 2 (Nrf2), its phosphorylation/activation, and oxidation of Kelch-like ECH-associating protein 1 (Keap1) in lansoprazole-induced HO-1 up-regulation using cultured gastric epithelial cells (rat gastric mucosal cell line, RGM-1). HO-1 expression of RGM-1 cells was markedly enhanced in a time- and dose-dependent manner by the treatment with lansoprazole, and this up-regulation of HO-1 contributed to the inhibition of chemokine production from stimulated RGM-1 cells. Transfection of Nrf2-siRNA suppressed the lansoprazole-induced HO-1. An electrophoretic mobility shift assay showed increases in the nuclear translocation and stress-response elements (StRE) binding activity of Nrf2 proteins in RGM-1 cells treated with lansoprazole. Furthermore, in RGM-1 cells transfected with HO-1 enhancer luciferase reporter plasmid containing mutant StRE, lansoprazole-induced HO-1 reporter gene activity was diminished. Lansoprazole promoted the phosphorylation of extracellular signal-regulated kinase (ERK), and lansoprazole-induced HO-1 up-regulation was suppressed by U0126, an ERK-specific inhibitor. Phosphorylated Nrf2 protein was detected in the phosphoprotein fraction purified by a Pro-Q Diamond Phosphoprotein Enrichment kit. Finally, an oxidative form of the Keap1 protein was detected in lansoprazole-treated RGM-1 cells by analyzing S-oxidized proteins using biotinylated cysteine as a molecular probe. These results indicate that lansoprazole up-regulates HO-1 expression in rat gastric epithelial cells, and the up-regulated HO-1 contributes to the anti-inflammatory effects of the drug. Phosphorylation of ERK and Nrf2, activation and nuclear translocation of Nrf2, and oxidation of Keap1 are all involved in the lansoprazole-induced HO-1 up-regulation.

Direct interaction between Nrf2 and p21(Cip1/WAF1) upregulates the Nrf2-mediated antioxidant response

In response to oxidative stress, Nrf2 and p21(Cip1/WAF1) are both upregulated to protect cells from oxidative damage. Nrf2 is constantly ubiquitinated by a Keap1 dimer that interacts with a weak-binding (29)DLG motif and a strong-binding (79)ETGE motif in Nrf2, resulting in degradation of Nrf2. Modification of the redox-sensitive cysteine residues on Keap1 disrupts the Keap1-(29)DLG binding, leading to diminished Nrf2 ubiquitination and activation of the antioxidant response. However, the underlying mechanism by which p21 protects cells from oxidative damage remains unclear. Here we present molecular and genetic evidence suggesting that the antioxidant function of p21 is mediated through activation of Nrf2 by stabilizing the Nrf2 protein. The (154)KRR motif in p21 directly interacts with the (29)DLG and (79)ETGE motifs in Nrf2 and thus competes with Keap1 for Nrf2 binding, compromising ubiquitination of Nrf2. Furthermore, the physiological significance of our findings was demonstrated in vivo using p21-deficient mice.

Sphingosine 1-phosphate receptor signaling

The sphingosine 1-phosphate (S1P) receptor signaling system is a productive model system. A hydrophobic zwitterionic lysophospholipid ligand with difficult physical properties interacts with five high-affinity G protein-coupled receptors to generate multiple downstream signals. These signals modulate homeostasis and pathology on a steep agonist concentration-response curve. Ligand presence is essential for vascular development and endothelial integrity, while acute increases in ligand concentrations result in cardiac death. Understanding this integrated biochemical system has exemplified the impact of both genetics and chemistry. Developing specific tools with defined biochemical properties for the reversible modulation of signals in real time has been essential to complement insights gained from genetic approaches that may be irreversible and compensated. Despite its knife-edge between life and death, this system, based in part on receptor subtype-selectivity and in part on differential attenuation of deleterious signals, now appears to be on the cusp of meaningful therapy for multiple sclerosis.

Hydrogen sulfide-induced hypometabolism prevents renal ischemia/reperfusion injury

Hydrogen sulfide (H(2)S) can induce a hypometabolic, hibernation-like state in mammals when given in subtoxic concentrations. Pharmacologically reducing the demand for oxygen is a promising strategy to minimize unavoidable hypoxia-induced injury such as ischemia/reperfusion injury during renal transplantation. Here we show that H(2)S reduces metabolism in vivo, ex vivo, and in vitro. Furthermore, we demonstrate the beneficial effects of H(2)S-induced hypometabolism in a model of bilateral renal ischemia/reperfusion injury using three different treatment strategies. The results demonstrate striking protective effects on survival, renal function, apoptosis, and inflammation. A hypometabolic state induced by H(2)S might have therapeutic potential to protect kidneys that suffer from hypoxia.

Biomarkers in clinical drug development

The primary purpose of this Commentary is to complement the description of biomarkers given in this issue in the Pharmaceutical Research and Manufacturers of America report by Lathia et al. I offer several examples of the use of biomarkers that highlight their value in drug development and regulatory decision making.

Attenuation of ischemia-induced rat brain injury by 2-(-2-benzofuranyl)-2-imidazoline, a high selectivity ligand for imidazoline I(2) receptors

OBJECTIVE

The aim of this study was to determine whether 2-(2-benzofuranyl)-2-imidazoline, an imidazoline I(2) receptor ligand, could protect against cell death from brain injury and improve the functional outcome after focal cerebral ischemia in rats.

METHODS

Transient focal ischemia was induced by suture occlusion of the middle cerebral artery. Rats were intraperitoneally treated with a vehicle, 2-(2-benzofuranyl)-2-imidazoline or idazoxan immediately after focal ischemia. Infarct volume was assessed by 2,3,5-triphenyltrazolium chloride staining and neurobehavioral deficits were monitored. The volume of cell death in the penumbra after ischemia was determined by immunostaining using anti-cleaved caspase-3 antibody and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL).

RESULTS

Both 2-(2-benzofuranyl)-2-imidazoline and idazoxan significantly improved the neurological score compared with the vehicle at 24 hours after focal ischemia. Treatment with 2-(2-benzofuranyl)-2-imidazoline or idazoxan also significantly reduced infarct volume and the number of both caspase-3- and TUNEL-positive cells in the penumbra compared with vehicle-treated rats (p<0.01 and p<0.05, respectively).

CONCLUSION

The results suggest the neuroprotective role of 2-(2-benzofuranyl)-2-imidazoline and idazoxan in focal cerebral ischemia, and may therefore represent useful targets for developing new treatments for stroke.

Calcitonin gene-related peptide selectively relaxes contractile responses to endothelin-1 in rat mesenteric resistance arteries

We tested the hypothesis that endothelin-1 (ET-1) modulates sensory-motor nervous arterial relaxation by prejunctional and postjunctional mechanisms. Isolated rat mesenteric resistance arteries were investigated with immunohistochemistry, wire-myography, and pharmacological tools. ET(A)- and ET(B)-receptors could be visualized on the endothelium and smooth muscle and on periarterial fibers containing calcitonin gene-related peptide (CGRP). Arterial contractile responses to ET-1 (0.25-16 nM) were not modified by blockade of ET(B)-receptors, NO-synthase, and cyclooxygenase or desensitization of transient receptor potential cation channel, subfamily V, member 1 (TRPV1) with capsaicin. ET-1 reversed relaxing responses to CGRP in depolarized arteries. This effect was inhibited by ET(A)-antagonists. It was not selective because ET-1 also reversed relaxing responses to Na-nitroprusside (SNP) and because phenylephrine (PHE; 0.25-16 microM) similarly reversed relaxing responses to CGRP or SNP. Conversely, contractile responses to ET-1 were, compared with PHE, hypersensitive to the relaxing effects of the TRPV1-agonist capsaicin and to exogenous CGRP, but not to acetylcholine, forskolin, pinacidil, or SNP. In conclusion, ET-1 does not stimulate sensory-motor nervous arterial relaxation, but ET(A)-mediated arterial contractions are selectively sensitive to relaxation by the sensory neurotransmitter CGRP. This does not involve NO, cAMP, or ATP-sensitive K(+) channels.

A versatile multidimensional protein purification system with full internet remote control based on a standard HPLC system

The standard Akta Explorer high-performance liquid chromatography (HPLC) system has limitations for the automation of multidimensional protein purification. Here, we describe simple modifications that allow for automated multidimensional purification protocols to extend the possibilities of the Akta three-dimensional purification kit in terms of column number, flexibility of volumes stocked for re-injection of samples, and available choice of buffers. These modifications do not preclude the use of standard one-dimensional purification protocols. Additionally, we demonstrate a technology for encrypted full remote control of the machine over the Internet by cost-effective use of standard asymmetric digital subscriber line (ADSL) that enables direct remote interaction with the machine without preventing local control. A 4-column purification scheme, including equilibration and cleaning in place (CIP) procedures, was implemented on such a system. It significantly increased reproducibility and shortened processing time by 85%, as compared with manual operation, thus allowing for automated protein purification overnight.

The guardian recruits cops: the p53-p21 axis delegates prosurvival duties to the Keap1-Nrf2 stress pathway

In this issue of Molecular Cell, Zhang and colleagues (Chen et al., 2009) report their identification of p21 as a positive regulator of Nrf2, which extends p53 prosurvival functions through recruitment of a master stress-response regulator.

The novel nicotinic receptor antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB), inhibits nicotine-evoked [(3)H]norepinephrine overflow from rat hippocampal slices

Smoking is a significant health concern and strongly correlated with clinical depression. Depression is associated with decreased extracellular NE concentrations in brain. Smokers may be self-medicating and alleviating their depression through nicotine stimulated norepinephrine (NE) release. Several antidepressants inhibit NE transporter (NET) function, thereby augmenting extracellular NE concentrations. Antidepressants, such as bupropion, also inhibit nicotinic receptor (nAChR) function. The current study determined if a recently discovered novel nAChR antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB), inhibits nicotine-evoked NE release from superfused rat hippocampal slices. Previous studies determined that bPiDDB potently (IC(50)=2 nM) inhibits nicotine-evoked striatal [(3)H]dopamine (DA) release in vitro, nicotine-evoked DA release in nucleus accumbens in vivo, and nicotine self-administration in rats. In the current study, nicotine stimulated [(3)H]NE release from rat hippocampal slices (EC(50)=50 microM). bPiDDB inhibited (IC(50)=430 nM; I(max)=90%) [(3)H]NE release evoked by 30 microM nicotine. For comparison, the nonselective nAChR antagonist, mecamylamine, and the alpha7 antagonist, methyllycaconitine, also inhibited nicotine-evoked [(3)H]NE release (IC(50)=31 and 275 nM, respectively; I(max)=91% and 72%, respectively). Inhibition by bPiDDB and mecamylamine was not overcome by increasing nicotine concentrations; Schild regression slope was different from unity, consistent with allosteric inhibition. Thus, bPiDDB was 200-fold more potent inhibiting nAChRs mediating nicotine-evoked [(3)H]DA release from striatum than those mediating nicotine-evoked [(3)H]NE release from hippocampus.

A novel fluorescent alpha-conotoxin for the study of alpha7 nicotinic acetylcholine receptors

Homomeric alpha7 nicotinic acetylcholine receptors are a well-established, pharmacologically distinct subtype. The more recently identified alpha9 subunit can also form functional homopentamers as well as alpha9alpha10 heteropentamers. Current fluorescent probes for alpha7 nicotinic ACh receptors are derived from alpha-bungarotoxin (alpha-BgTx). However, alpha-BgTx also binds to alpha9* and alpha1* receptors which are coexpressed with alpha7 in multiple tissues. We used an analog of alpha-conotoxin ArIB to develop a highly selective fluorescent probe for alpha7 receptors. This fluorescent alpha-conotoxin, Cy3-ArIB[V11L;V16A], blocked ACh-evoked alpha7 currents in Xenopus laevis oocytes with an IC(50) value of 2.0 nM. Observed rates of blockade were minute-scale with recovery from blockade even slower. Unlike FITC-conjugated alpha-BgTx, Cy3-ArIB[V11L;V16A] did not block alpha9alpha10 or alpha1beta1deltaepsilon receptors. In competition binding assays, Cy3-ArIB[V11L;V16A] potently displaced [(125)I]-alpha-BgTx binding to mouse hippocampal membranes with a K(i) value of 21 nM. Application of Cy3-ArIB[V11L;V16A] resulted in specific punctate labeling of KXalpha7R1 cells but not KXalpha3beta2R4, KXalpha3beta4R2, or KXalpha4beta2R2 cells. This labeling could be abolished by pre-treatment with alpha-cobratoxin. Thus, Cy3-ArIB[V11L;V16A] is a novel and selective fluorescent probe for alpha7 receptors.

Induction of transglutaminase 2 by a liver X receptor/retinoic acid receptor alpha pathway increases the clearance of apoptotic cells by human macrophages

RATIONALE

Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are involved in the control of cholesterol homeostasis and inflammatory response. Human monocytes and macrophages express high levels of these receptors and are appropriate cells to study the response to LXR agonists.

OBJECTIVE

The purpose of this study was to identify new LXR targets in human primary monocytes and macrophages and the consequences of their activation.

METHODS AND RESULTS

We show that LXR agonists significantly increase the mRNA and protein levels of the retinoic acid receptor (RAR)alpha in primary monocytes and macrophages. LXR agonists promote RARalpha gene transcription through binding to a specific LXR response element on RARalpha gene promoter. Preincubation of monocytes or macrophages with LXR agonists before RARalpha agonist treatment enhances synergistically the expression of several RARalpha target genes. One of these genes encodes transglutaminase (TGM)2, a key factor required for macrophage phagocytosis. Accordingly, the combination of LXR and RARalpha agonists at concentrations found in human atherosclerotic plaques markedly enhances the capabilities of macrophages to engulf apoptotic cells in a TGM2-dependent manner.

CONCLUSIONS

These results indicate an important role for LXRs in the control of phagocytosis through an RARalpha-TGM2-dependent mechanism. A combination of LXR/RARalpha agonists that may operate in atherosclerosis could also constitute a promising strategy to improve the clearance of apoptotic cells by macrophages in other pathological situations.

X11alpha haploinsufficiency enhances Abeta amyloid deposition in Alzheimer's disease transgenic mice

The neuronal adaptor protein X11alpha/mint-1/APBA-1 binds to the cytoplasmic domain of the amyloid precursor protein (APP) to modulate its trafficking and metabolism. We investigated the consequences of reducing X11alpha in a mouse model of Alzheimer's disease (AD). We crossed hAPPswe/PS-1DeltaE9 transgenic (AD tg) mice with X11alpha heterozygous knockout mice in which X11alpha expression is reduced by approximately 50%. The APP C-terminal fragments C99 and C83, as well as soluble Abeta40 and Abeta42, were increased significantly in brain of X11alpha haploinsufficient mice. Abeta/amyloid plaque burden also increased significantly in the hippocampus and cortex of one year old AD tg/X11alpha (+/-) mice compared to AD tg mice. In contrast, the levels of sAPPalpha and sAPPbeta were not altered significantly in AD tg/X11alpha (+/-) mice. The increased neuropathological indices of AD in mice expressing reduced X11alpha suggest a normal suppressor role for X11alpha on CNS Abeta/amyloid deposition.

The biochemistry of disease: desperately seeking syzygy

The elucidation of the precise molecular structure and dynamics of biological processes is the great work of biochemistry. From this, insights into the changes leading to process dysfunction or disease are derived, as well as the possible approaches to restore healthy function. Translating this information into effective and safe treatments for disease requires a coordinated interdisciplinary effort, a fusion of creativity and practicality, and a healthy dose of luck. Using several reviews in this volume as springboards, I discuss the broader issues of drug development, highlighting some recent successes and future directions. Such occurrences inspire awe but remain too rare for comfort.

Rescue of impaired fracture healing in COX-2-/- mice via activation of prostaglandin E2 receptor subtype 4

Although the essential role of cyclooxygenase (COX)-2 in fracture healing is known, the targeted genes and molecular pathways remain unclear. Using prostaglandin E2 receptor (EP)2 and EP4 agonists, we examined the effects of EP receptor activation in compensation for the lack of COX-2 during fracture healing. In a fracture-healing model, COX-2(-/-) mice showed delayed initiation and impaired endochondral bone repair, accompanied by a severe angiogenesis deficiency. The EP4 agonist markedly improved the impaired healing in COX-2(-/-) mice, as evidenced by restoration of bony callus formation on day 14, a near complete reversal of bone formation, and an approximately 70% improvement of angiogenesis in the COX-2(-/-) callus. In comparison, the EP2 agonist only marginally enhanced bone formation in COX-2(-/-) mice. To determine the differential roles of EP2 and EP4 receptors on COX-2-mediated fracture repair, the effects of selective EP agonists on chondrogenesis were examined in E11.5 long-term limb bud micromass cultures. Only the EP4 agonist significantly increased cartilage nodule formation similar to that observed during prostaglandin E2 treatment. The prostaglandin E2/EP4 agonist also stimulated MMP-9 expression in bone marrow stromal cell cultures. The EP4 agonist further restored the reduction of MMP-9 expression in the COX-2(-/-) fracture callus. Taken together, our studies demonstrate that EP2 and EP4 have differential functions during endochondral bone repair. Activation of EP4, but not EP2 rescued impaired bone fracture healing in COX-2(-/-) mice.

Experimental manipulations blunt time-induced changes in brain monoamine levels and completely reverse stress, but not Pb+/-stress-related modifications to these trajectories

This study sought to further understand how environmental conditions influence the outcomes of early developmental insults. It compared changes in monoamine levels in frontal cortex, nucleus accumbens and striatum of male and female Long-Evans rat offspring subjected to maternal Pb exposure (0, 50 or 150ppm in drinking water from 2 months pre-breeding until pup weaning)+/-prenatal (PS) (restraint on GD16-17) or PS+offspring stress (OS; three variable stress challenges to young adults) determined at 2 months of age and at 6 months of age in littermates subsequently exposed either to experimental manipulations (EM: daily handling and performance on an operant fixed interval (FI) schedule of food reward), or to no experience (NEM; time alone). Time alone (NEM conditions), even in normal (control) animals, modified the trajectory of neurochemical changes between 2 and 6 months across brain regions and monoamines. EM significantly modified the NEM trajectories, and except NE and striatal DA, which increased, blunted the changes in monoamine levels that occurred over time alone. Pb+/-stress modified the trajectory of monoamine changes in both EM and NEM conditions, but these predominated under NEM conditions. Stress-associated modifications, occurring mainly with NEM OS groups, were fully reversed by EM procedures, while reversals of Pb+/-stress-associated modifications occurred primarily in nucleus accumbens, a region critical to mediation of FI response rates. These results extend the known environmental conditions that modify developmental Pb+/-stress insults, which is critical to ultimately understanding whether early insults lead to adaptive or maladaptive behavior and to devising behavioral therapeutic strategies. That time alone and a set of EM conditions typically used as outcome measures in intervention studies can themselves invoke neurochemical changes, moreover, has significant implications for experimental design of such studies.

Comparative metabolite profiling of the insecticide thiamethoxam in plant and cell suspension culture of tomato

The metabolism of thiamethoxam [(EZ)-3-(2-chloro-1,3-thiazol-5-yl-methyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene (nitro) amine] was investigated in whole plant, callus, and heterotrophic cell suspension culture of aseptically and field grown tomato (Lycopersicon esculentum Mill.) plants. The structure of the metabolites was elucidated by chromatographic (HPLC) and spectroscopic (IR, NMR, and MS) methods. Thiamethoxam metabolism proceeded by the formation of a urea derivative, a nitroso product, and nitro guanidine. Both urea and nitro guanidine metabolites further degraded in plants, and a mechanism has been proposed. In the plant, organ-specific differences in thiamethoxam metabolism were observed. Only one metabolite was formed in whole plant against four in callus and eight metabolites in cell suspension culture under aseptic conditions. Out of six metabolites of thiamethoxam in tomato fruits in field conditions, five were similar to those formed in the cell suspension culture. In the cell suspension culture, thiamethoxam degraded to maximum metabolites within 72 h, whereas in plants, such extensive conversion could only be observed after 10 days.

Redox-regulated chaperones

Redox regulation of stress proteins, such as molecular chaperones, guarantees an immediate response to oxidative stress conditions. This review focuses on the two major classes of redox-regulated chaperones, Hsp33 in bacteria and typical 2-Cys peroxiredoxins in eukaryotes. Both proteins employ redox-sensitive cysteines, whose oxidation status directly controls their affinity for unfolding proteins and therefore their chaperone function. We will first discuss Hsp33, whose oxidative stress-induced disulfide bond formation triggers the partial unfolding of the chaperone, which, in turn, leads to the exposure of a high-affinity binding site for unfolded proteins. This rapid mode of activation makes Hsp33 essential for protecting bacteria against severe oxidative stress conditions, such as hypochlorite (i.e., bleach) treatment, which leads to widespread protein unfolding and aggregation. We will compare Hsp33 to the highly abundant eukaryotic typical 2-Cys peroxiredoxin, whose oxidative stress-induced sulfinic acid formation turns the peroxidase into a molecular chaperone in vitro and presumably in vivo. These examples illustrate how proteins use reversible cysteine modifications to rapidly adjust to oxidative stress conditions and demonstrate that redox regulation plays a vital role in protecting organisms against reactive oxygen species-mediated cell death.

Factors controlling the reactivity of hydrogen sulfide with hemeproteins

Hemoglobin I (HbI) from the clam Lucina pectinata is an intriguing hemeprotein that binds and transports H(2)S to sulfide-oxidizing chemoautotrophic bacteria to maintain a symbiotic relationship and to protect the mollusk from H(2)S toxicity. Single point mutations at E7, B10, and E11 were introduced into the HbI heme pocket to define the reactivity of sulfide with hemeproteins. The functional and structural properties of mutant and wild-type recombinant proteins were first evaluated using the well-known ferrous CO and O(2) derivatives. The effects of these mutations on the ferric environment were then studied in the metaquo and hydrogen sulfide derivatives. The results obtained with the ferrous HbI mutants show that all the E7 substitutions and the PheB10Tyr mutation influence directly CO and O(2) binding and stability while the B10 and E11 substitutions induce distal structural rearrangements that affect ligand entry and escape indirectly. For the metaquo-GlnE7His, -PheB10Val, -PheB10Leu, and -E11 variants, two individual distal structures are suggested, one of which is associated with H-bonding interactions between the E7 residues and the bound water. Similar H-bonding interactions are invoked for these HbI-H(2)S mutant derivatives and the rHbI, altering in turn sulfide reactivity within these protein samples. This is evident in the resonance Raman spectra of these HbI-H(2)S complexes, which show reduction of heme iron as judged by the appearance of the nu(4) oxidation state marker at 1356 cm(-1), indicative of heme-Fe(II) species. This reduction process depends strongly on distal mutations showing faster reduction for those HbI mutants exhibiting the strongest H-bonding interactions. Overall, the results presented here show that (a) H(2)S association is regulated by external kinetic barriers, (b) H(2)S release is controlled by two competing reactions involving simple sulfide dissociation and heme reduction, (c) at high H(2)S concentrations, reduction of the ferric center dominates, and (d) reduction of the heme is also enhanced in those HbI mutants having polar distal environments.

Limiting transport steps and novel interactions of Connexin-43 along the secretory pathway

Connexins are four-transmembrane-domain proteins expressed in all vertebrates which form permeable gap junction channels that connect cells. Here, we analysed Connexin-43 (Cx43) transport to the plasma membrane and studied the effects of small GTPases acting along the secretory pathway. We show that both GTP- and GDP-restricted Sar1 prevents exit of Cx43 from the endoplasmic reticulum (ER), but only GTP-restricted Sar1 arrests Cx43 in COP II-coated ER exit sites and accumulates 14-3-3 proteins in the ER fraction. FRET-FLIM data confirm that already in ER exit sites Cx43 exists in oligomeric form, suggesting an in vivo role for 14-3-3 in Cx43 oligomerization. Exit of Cx43 from the ER can be blocked by other factors—such as expression of the β subunit of the COP I coat or p50/dynamitin that acts on the microtubule-based dynein motor complex. GTP-restricted Arf1 blocks Cx43 in the Golgi. Lastly, we show that GTP-restricted Arf6 removes Cx43 gap junction plaques from the cell–cell interface and targets them to degradation. These data provide a molecular explanation of how small GTPases act to regulate Cx43 transport through the secretory pathway, facilitating or abolishing cell–cell communication through gap junctions.

Coupling reactions of catechins with natural aldehydes and allyl alcohols and radical scavenging activities of the triglyceride-soluble products

Hydrophobic catechin derivatives were produced by heating with natural aldehydes or allyl alcohols. (+)-Catechin or (-)-epigallocatechin-3-O-gallate was heated with trans-2-hexenal, citral, (+)-citronellal, geraniol, or phytol. Although each reaction generated complex mixtures of products, 11 compounds were isolated and characterized by spectroscopic methods. The unsaturated aldehydes were found to attach to the flavan A-ring. Besides C-C linkage between aldehyde and the C-8 and/or C-6 of the catechin A-ring, formation of ether linkages between unsaturated carbons of the aldehydes and phenolic hydroxyl groups was observed. The allyl alcohols, geraniol and phytols, reacted at the galloyl group as well as the A-ring. After partitioning between triglyceride and water, the lipid layer of the reaction products showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. In contrast, epigallocatechin-3-O-gallate was not transferred to the lipid layer.

Incorporating physiological and biochemical mechanisms into pharmacokinetic-pharmacodynamic models: a conceptual framework

The aim of this conceptual framework paper is to contribute to the further development of the modelling of effects of drugs or toxic agents by an approach which is based on the underlying physiology and pathology of the biological processes. In general, modelling of data has the purpose (1) to describe experimental data, (2a) to reduce the amount of data resulting from an experiment, e.g. a clinical trial and (2b) to obtain the most relevant parameters, (3) to test hypotheses and (4) to make predictions within the boundaries of experimental conditions, e.g. range of doses tested (interpolation) and out of the boundaries of the experimental conditions, e.g. to extrapolate from animal data to the situation in man. Describing the drug/xenobiotic-target interaction and the chain of biological events following the interaction is the first step to build a biologically based model. This is an approach to represent the underlying biological mechanisms in qualitative and also quantitative terms, thus being inherently connected in many aspects to systems biology. As the systems biology models may contain variables in the order of hundreds connected with differential equations, it is obvious that it is in most cases not possible to assign values to the variables resulting from experimental data. Reduction techniques may be used to create a manageable model which, however, captures the biologically meaningful events in qualitative and quantitative terms. Until now, some success has been obtained by applying empirical pharmacokinetic/pharmacodynamic models which describe direct and indirect relationships between the xenobiotic molecule and the effect, including tolerance. Some of the models may have physiological components built in the structure of the model and use parameter estimates from published data. In recent years, some progress toward semi-mechanistic models has been made, examples being chemotherapy-induced myelosuppression and glucose-endogenous insulin-antidiabetic drug interactions. We see a way forward by employing approaches to bridge the gap between systems biology and physiologically based kinetic and dynamic models. To be useful for decision making, the 'bridging' model should have a well founded mechanistic basis, but being reduced to the extent that its parameters can be deduced from experimental data, however capturing the biological/clinical essential details so that meaningful predictions and extrapolations can be made.

Salivary acetaldehyde increase due to alcohol-containing mouthwash use: a risk factor for oral cancer

Increasing evidence suggests that acetaldehyde, the first and genotoxic metabolite of ethanol, mediates the carcinogenicity of alcoholic beverages. Ethanol is also contained in a number of ready-to-use mouthwashes typically between 5 and 27% vol. An increased risk of oral cancer has been discussed for users of such mouthwashes; however, epidemiological evidence had remained inconclusive. This study is the first to investigate acetaldehyde levels in saliva after use of alcohol-containing mouthwashes. Ready-to-use mouthwashes and mouthrinses (n = 13) were rinsed in the mouth by healthy, nonsmoking volunteers (n = 4) as intended by the manufacturers (20 ml for 30 sec). Saliva was collected at 0.5, 2, 5 and 10 min after mouthwash use and analyzed using headspace gas chromatography. The acetaldehyde content in the saliva was 41 +/- 15 microM, range 9-85 microM (0.5 min), 52 +/- 14 microM, range 11-105 microM (2 min), 32 +/- 7 microM, range 9-67 microM (5 min) and 15 +/- 7 microM, range 0-37 microM (10 min). The contents were significantly above endogenous levels and corresponding to concentrations normally found after alcoholic beverage consumption. A twice-daily use of alcohol-containing mouthwashes leads to a systemic acetaldehyde exposure of 0.26 microg/kg bodyweight/day on average, which corresponds to a lifetime cancer risk of 3E-6. The margin of exposure was calculated to be 217,604, which would be seen as a low public health concern. However, the local acetaldehyde contents in the saliva are reaching concentrations associated with DNA adduct formation and sister chromatid exchange in vitro, so that concerns for local carcinogenic effects in the oral cavity remain.

Growth hormone secretagogues and growth hormone releasing peptides act as orthosteric super-agonists but not allosteric regulators for activation of the G protein Galpha(o1) by the Ghrelin receptor

Some growth hormone secretagogues act as agonists at the ghrelin receptor and have been described as "ago-allosteric" ligands because of an ability to also modulate the maximum efficacy and potency of ghrelin (Holst et al., 2005). In membranes prepared from cells coexpressing the human ghrelin receptor and the G protein Galpha(o1), N-[1(R)-1, 2-dihydro-1-ethanesulfonylspiro-3H-indole-3,4'-piperidin)-1'-yl]carbonyl-2-(phenylmethoxy)-ethyl-2-amino-2-methylpropanamide (MK-677), growth hormone-releasing peptide 6 (GHRP-6), and the 2(R)-hydroxypropyl derivative of 3-amino-3-methyl-N-(2,3,4,5-tetrahydro-2-oxo-1-([2'-(1H-tetrazol-5-yl) (1,1'-biphenyl)-4-yl]methyl)-1H-1-benzazepin-3(R)-yl)-butanamide (L-692,585) each functioned as direct agonists, and each displayed higher efficacy than ghrelin. The effect of multiple, fixed concentrations of each of these ligands on the function and concentration-dependence of ghrelin and the effect of multiple, fixed concentrations of ghrelin on the action of MK-677, GHRP-6, and L-692,585 was analyzed globally according to a modified version of an operational model of allosterism that accounts for allosteric modulation of affinity, efficacy, and allosteric agonism. Each of the data sets was best fit by a model of simple competition between a partial and a full agonist. Both positive and negative allosteric modulators are anticipated to alter the kinetics of binding of an orthosteric agonist. However, none of the proposed ago-allosteric regulators tested had any effect on the dissociation kinetics of (125)I-[His]-ghrelin, and GHRP-6 and MK-677 were able to fully displace (125)I-[His]-ghrelin from the receptor. At least in the system tested, each of the ligands acted in a simple competitive fashion with ghrelin as demonstrated by analysis according to a model whereby ghrelin is a partial agonist with respect to each of the synthetic agonists tested.

Chemokine signaling in embryonic cell migration: a fisheye view

Chemokines and their receptors were discovered about twenty years ago as mediators of leukocyte traffic. Over the past decade, functional studies of these molecules have revealed their importance for cell migration processes during embryogenesis, which, in addition to providing mechanistic insights into embryonic development, could complement information about chemokine function in the immune system. Here, we review the roles of the chemokine stromal cell-derived factor 1 (SDF-1/CXCL12) and its receptor CXCR4 during zebrafish and mouse embryonic development, and discuss their function in regulating the interactions of cells with their extracellular environment, in directing their migration, and in maintaining their location.

Imaging the function of P-glycoprotein with radiotracers: pharmacokinetics and in vivo applications

P-glycoprotein (P-gp), an efflux transporter, controls the pharmacokinetics of various compounds under physiological conditions. P-gp-mediated drug efflux has been suggested as playing a role in various disorders, including multidrug-resistant cancer and medication-refractory epilepsy. However, P-gp inhibition has had, to date, little or no clinically significant effect in multidrug-resistant cancer. To enhance our understanding of its in vivo function under pathophysiological conditions, substrates of P-gp have been radiolabeled and imaged using single-photon emission computed tomography (SPECT) and positron emission tomography (PET). To accurately quantify P-gp function, a radiolabeled P-gp substrate should be selective for P-gp, produce a large signal after P-gp blockade, and generate few radiometabolites that enter the target tissue. Furthermore, quantification of P-gp function via imaging requires pharmacological inhibition of P-gp, which requires knowledge of P-gp density at the target site. By meeting these criteria, imaging can elucidate the function of P-gp in various disorders and improve the efficacy of treatments.

Lipopolysaccharide directly alters renal tubule transport through distinct TLR4-dependent pathways in basolateral and apical membranes

Bacterial infection of the kidney is associated with renal tubule dysfunction and dysregulation of systemic electrolyte balance. Whether bacterial molecules directly affect renal tubule transport is unknown. We examined the effects of LPS on HCO3(-) absorption in the isolated rat and mouse medullary thick ascending limb (MTAL). LPS decreased HCO3(-) absorption when added to bath or lumen. The MEK/ERK inhibitor U0126 eliminated inhibition by bath LPS but had no effect on inhibition by lumen LPS. Conversely, the mammalian target of rapamycin (mTOR) inhibitor rapamycin eliminated inhibition by lumen LPS but had no effect on inhibition by bath LPS. Inhibiting basolateral Na(+)/H(+) exchange with amiloride eliminated inhibition of HCO3(-) absorption by lumen but not bath LPS. Confocal immunofluorescence showed expression of TLR4 in basolateral and apical membrane domains. Inhibition of HCO3(-) absorption by bath and lumen LPS was eliminated in MTALs from TLR4(-/-) mice. Thus LPS inhibits HCO3(-) absorption through distinct TLR4-dependent pathways in basolateral and apical membranes. These results establish that bacterial molecules can directly impair the transport function of renal tubules, identifying a new mechanism contributing to tubule dysfunction during bacterial infection. The LPS-induced reduction in luminal acidification may contribute to Gram-negative pathogenicity by promoting bacterial adherence and growth and impairing correction of infection-induced systemic acid-base disorders.

Antiviral effect of epigallocatechin gallate on enterovirus 71

Oxidative stress is known to be a determinant of a host's susceptibility to pathogens. Natural compounds with antioxidant activity may provide a preventive measure against infection. Tea polyphenols were evaluated for their ability to inhibit enterovirus 71 (EV71) replication in Vero cell culture. Among the polyphenolic compounds tested, epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG) potently inhibited replication of EV71. EGCG and GCG reduced the titer of infectious progeny virus by 95%. Quantitative RT-PCR analysis also revealed that EGCG suppressed replication of genomic RNA. It was accompanied by an increased cytoprotective effect. EGCG and GCG caused 5-fold increase in the viability of EV71-infected cells. The viral inhibitory effect correlated well with the antioxidant capacity of polyphenol. Mechanistically, EV71 infection led to increased oxidative stress, as shown by increased dichlorofluorescein and MitoSOX Red fluorescence. Upon EGCG treatment, reactive oxygen species (ROS) generation was significantly reduced. Consistent with this, EV71 replication was enhanced in glucose-6-phosphate dehydrogenase deficient cells, and such enhancement was largely reversed by EGCG. These findings suggest that EGCG may suppress viral replication via modulation of cellular redox milieu.

Sustained stimulation of vasopressin and oxytocin release by ATP and phenylephrine requires recruitment of desensitization-resistant P2X purinergic receptors

Coexposure of hypothalamo-neurohypophyseal system explants to ATP and phenylephrine [PE; an alpha1-adrenergic receptor (alpha1-AR) agonist] induces an extended elevation in vasopressin and oxytocin (VP/OT) release. New evidence is presented that this extended response is mediated by recruitment of desensitization-resistant ionotropic purinergic receptor subtypes (P2X-Rs): 1) Antagonists of the P2X2/3 and P2X7-Rs truncated the sustained VP/OT release induced by ATP+PE but did not alter the transient response to ATP alone. 2) The P2X2/3 and P2X7-R antagonists did not alter either ATP or ATP+PE-induced increases in [Ca(2+)](i). 3) P2X2/3 and P2X7-R agonists failed to elevate [Ca(2+)](i), while ATP-gamma-S, an agonist for P2X2-Rs increased [Ca(2+)](i) and induced a transient increase in VP/OT release. 4) A P2Y1-R antagonist did not prevent initiation of the synergistic, sustained stimulation of VP/OT release by ATP+PE but did reduce its duration. Thus, the desensitization-resistant P2X2/3 and P2X7-R subtypes are required for the sustained, synergistic hormone response to ATP+PE, while P2X2-Rs are responsible for the initial activation of Ca(2+)-influx by ATP and ATP stimulation of VP/OT release. Immunohistochemistry, coimmunoprecipitation, and Western blot analysis confirmed the presence of P2X2 and P2X3, P2X2/3, and P2X7-R protein, respectively in SON. These findings support the hypothesis that concurrent activation of P2X2-R and alpha1-AR induces calcium-driven recruitment of P2X2/3 and 7-Rs, allowing sustained activation of a homeostatic circuit. Recruitment of these receptors may provide sustained release of VP during dehydration and may be important for preventing hemorrhagic and septic shock.

The Differential Gene Expression Pattern of Mycobacterium tuberculosis in Response to Capreomycin and PA-824 versus First-Line TB Drugs Reveals Stress- and PE/PPE-Related Drug Targets

Tuberculosis is a leading infectious disease causing millions of deaths each year. How to eradicate mycobacterial persistence has become a central research focus for developing next-generation TB drugs. Yet, the knowledge in this area is fundamentally limited and only a few drugs, notably capreomycin and PA-824, have been shown to be active against non-replicating persistent TB bacilli. In this study, we performed a new bioinformatics analysis on microarray-based gene expression data obtained from the public domain to explore genes that were differentially induced by drugs between the group of capreomycin and PA-824 and the group of mainly the first-line TB drugs. Our study has identified 42 genes specifically induced by capreomycin and PA-824. Many of these genes are related to stress responses. In terms of the distribution of identified genes in a specific category relative to the whole genome, only the categories of PE/PPE and conserved hypotheticals have statistical significance. Six among the 42 genes identified in this study are on the list of the top 100 persistence targets selected by the TB Structural Genomics Consortium. Further biological elucidation of their roles in mycobacterial persistence is warranted.

IL-10 suppresses calcium-mediated costimulation of receptor activator NF-kappa B signaling during human osteoclast differentiation by inhibiting TREM-2 expression

Induction of effective osteoclastogenesis by RANK (receptor activator of NF-kappaB) requires costimulation by ITAM-coupled receptors. In humans, the TREM-2 (triggering receptor expressed on myeloid cells 2) ITAM-coupled receptor plays a key role in bone remodeling, as patients with TREM-2 mutations exhibit defective osteoclastogenesis and bone lesions. We have identified a new rapidly induced costimulatory pathway for RANK signaling that is dependent on TREM-2 and mediated by calcium signaling. TREM-2-dependent calcium signals are required for RANK-mediated activation of calcium/calmodulin-dependent protein kinase (CaMK)II and downstream MEK and ERK MAPKs that are important for osteoclastogenesis. IL-10 inhibited RANK-induced osteoclastogenesis and selectively inhibited calcium signaling downstream of RANK by inhibiting transcription of TREM-2. Down-regulation of TREM-2 expression resulted in diminished RANKL-induced activation of the CaMK-MEK-ERK pathway and decreased expression of the master regulator of osteoclastogenesis NFATc1. These findings provide a new mechanism of inhibition of human osteoclast differentiation. The results also yield insights into crosstalk between ITAM-coupled receptors and heterologous receptors such as RANK, and they identify a mechanism by which IL-10 can suppress cellular responses to TNFR family members.

Nitrosyl hydride (HNO) as an O2 analogue: long-lived HNO adducts of ferrous globins

Nitrosyl hydride, HNO or nitroxyl, is the one-electron reduced and protonated form of nitric oxide. HNO is isoelectronic to singlet O(2), and we have previously reported that deoxymyoglobin traps free HNO to form a stable adduct. In this report, we demonstrate that oxygen-binding hemoglobins from human, soy, and clam also trap HNO to form adducts which are stable over a period of weeks. The same species can be formed in higher yields by careful reduction of the ferrous nitrosyl adducts of the proteins. Like the analogous O(2)-Fe(II) adducts, the HNO adducts are diamagnetic, but with a characteristic HNO resonance in (1)H NMR at ca. 15 ppm that splits into doublets for H(15)NO adducts. The (1)H and (15)N NMR resonances, obtained by HSQC experiments, are shown to differentiate subunits and isoforms of proteins within mixtures. An apparent difference in the reduction rates of the NO adducts of the two subunits of human hemoglobin allows assignment of two distinct nitrosyl hydride peaks by a combination of UV-vis, NMR, and EPR analysis. The two peaks of the HNO-hHb adduct have a persistent 3:1 ratio during trapping reactions, demonstrating a kinetic difference between HNO binding at the two subunits. These results show NMR characterization of ferrous HNO adducts as a unique tool sensitive to structural changes within the oxygen-binding cavity, which may be of use in defining modes of oxygen binding in other heme proteins and enzymes.

Structural-thermodynamic relationships of interactions in the N-terminal ATP-binding domain of Hsp90

Despite its importance as a target in anti-cancer therapeutics and the numerous rational-based inhibitor design efforts aimed at it, there are only limited data available on structural-thermodynamic relationships of interactions of the N-terminal ATP-binding domain of Hsp90 (N-Hsp90). Here, we redress this by presenting an investigation of binding of nucleotides and ansamycin compounds to this domain. Interactions of nucleotides with N-Hsp90 are relatively weak (>10 microM) and are strongly enthalpy driven over the temperature range 10-25 degrees C. Geldanamycin (GA) and its analogues 17-AAG [17-(allylamino)-17-demethoxy-GA] and 17-DMAG (17-N,N-dimethylaminoethylamino-17-demethoxy-GA) bind more strongly and have a dominant favourable enthalpic contribution over the temperature range investigated. We investigated the temperature dependence of the enthalpic contribution to binding. We found that while the ansamycin compounds have the commonly observed negative value, the nucleotides show a negligible or even a positive DeltaC(p) of binding. These data represent the first observation of a single binding site for which interactions with different ligands result in both negative and positive DeltaC(p) values. By addressing the likely impact of the potential contributions from protein-ligand interactions, we are able to attribute the anomalous DeltaC(p) for the nucleotides largely to a change in the conformation of the domain structure and local motion in the lid region of N-Hsp90 with the concomitant exposure of hydrophobic amino acid side chains.