Das Archaeon Nitrososphaera viennensis

Unkown heroes in the global nitrogen cycle – Nitrososphaera viennensis Ammonia oxidizing archaea exist everywhere in Nature, but have only been discovered about 10 years ago. Today they are recognized as one of the most abundant microbial guilds, in particular because they constitute up to 30% of the marine picoplankton in the oceans and are found in high numbers in soils. The global nitrogen cycle is heavily impacted due to intensified agricultural practice. Important steps therein, like nitrification, are exclusively performed by microorganisms. Therefore, it has become increasingly important to investigate ammonia oxidizing archaea, who participate in this step. Since these archaea are difficult to cultivate, their wide distribution and importance has only been recently recognized with the help of molecular techniques. Now, first isolates, like the type strain Nitrososphaera viennensis, which was isolated from a garden soil in Vienna allow their closer investigation. This might eventually help to find measures for the mitigation of nitrogen and greenhouse gas emissions from soils.     

Prasugrel suppresses development of lithium-induced nephrogenic diabetes insipidus in mice

Previously, we localized ADP-activated P2Y₁₂ receptor (R) in rodent kidney and showed that its blockade by clopidogrel bisulfate (CLPD) attenuates lithium (Li)-induced nephrogenic diabetes insipidus (NDI). Here, we evaluated the effect of prasugrel (PRSG) administration on Li-induced NDI in mice. Both CLPD and PRSG belong to the thienopyridine class of ADP receptor antagonists. Groups of age-matched adult male B6D2 mice (N = 5/group) were fed either regular rodent chow (CNT), or with added LiCl (40 mmol/kg chow) or PRSG in drinking water (10 mg/kg bw/day) or a combination of LiCl and PRSG for 14 days and then euthanized. Water intake and urine output were determined and blood and kidney tissues were collected and analyzed. PRSG administration completely suppressed Li-induced polydipsia and polyuria and significantly prevented Li-induced decreases in AQP2 protein abundance in renal cortex and medulla. However, PRSG either alone or in combination with Li did not have a significant effect on the protein abundances of NKCC2 or NCC in the cortex and/or medulla. Immunofluorescence microscopy revealed that PRSG administration prevented Li-induced alterations in cellular disposition of AQP2 protein in medullary collecting ducts. Serum Li, Na, and osmolality were not affected by the administration of PRSG. Similar to CLPD, PRSG administration had no effect on Li-induced increase in urinary Na excretion. However, unlike CLPD, PRSG did not augment Li-induced increase in urinary arginine vasopressin (AVP) excretion. Taken together, these data suggest that the pharmacological inhibition of P2Y₁₂-R by the thienopyridine group of drugs may potentially offer therapeutic benefits in Li-induced NDI.     

Roles of Aquaporins in Root Responses to Irrigation

Due to current environmental issues concerning the use of water for irrigation, the improvement of crop water-use efficiency and a reduction in water consumption has become a priority. New irrigation methods that reduce water use, while still maintaining production have been developed. To optimise these techniques knowledge of above- and below-ground plant physiological responses is necessary. During growth, plant roots are exposed to cycles of wetting and drying in normal rain-fed and irrigation situations. This review concentrates on the below-ground aspects, in particular the water permeability of roots. Significant research has been conducted on the root anatomy and hydraulic conductivity of desert plants subjected to wetting and drying. Major intrinsic proteins (MIPs), most of which show aquaporin (water-channel) activity are likely to be involved in balancing the water relations of the plants during water deficit. However, many MIPs seem to allow permeation of other small neutral solutes and some may allow permeation of ions under certain conditions. The ability of the plant to rapidly respond to rewetting may be important in maintaining productivity. It has been suggested that aquaporins may be involved in this rapid response. The down-regulation of the aquaporins during dry conditions can also limit water loss to the soil, and intrinsic sensitivity of aquaporins to water potential is shown here to be very strong in some cases (NOD26). However, the response of aquaporins in various plant species to water deficits has been quite varied. Another component of aquaporin regulation in response to various stresses (hypoxia/anoxia, salinity and chilling) may be related to redistribution of flow to more favourable regions of the soil. Some irrigation techniques may be triggering these responses. Diurnal fluctuations of root hydraulic conductance that is related to aquaporin expression seem to match the expected transpirational demands of the shoot, and it remains to be seen if shoot-to-root signalling may be important in regulation of root aquaporins. If so, canopy management typical of horticultural crops may impact on root hydraulic conductance. An understanding of the regulation of aquaporins may assist in the development of improved resistance to water stress and greater efficiency of water use by taking into account where and when roots best absorb water.     

Insulin induces monocytic CXCL8 secretion by the mitogenic signalling pathway

Oral glucose uptake alters the function of immune cells and an elevation of systemic CXCL8 was described. Monocytes secrete high amounts of CXCL8 and therefore it was analyzed whether glucose or insulin upregulate monocytic CXCL8 release. Incubation of monocytes with insulin for 2h induced CXCL8 mRNA and secretion whereas glucose had no effect. Inhibition of the phosphatidylinositol 3-kinase by wortmannin or the mammalian target of rapamycin by rapamycin did not influence insulin-mediated CXCL8 induction. In contrast, blockage of the ERK-specific MAP kinase MEK with PD98059, that prevents phosphorylation of ERK1/ERK2, abrogated insulin-induced CXCL8 release in primary monocytes. To investigate the in vivo effect of oral glucose uptake, monocytes of healthy probands were isolated in the fasted state and 2h after glucose ingestion and CXCL8 mRNA and protein were increased in the latter. CXCL8 was also higher when determined in the cell lysate of leukocytes 2h after glucose uptake whereas plasma CXCL8 levels were significantly reduced. In summary, these data indicate that oral glucose uptake in insulin-sensitive adults is associated with elevated monocytic and reduced systemic CXCL8.     

Proteolytic processing of chemokines: implications in physiological and pathological conditions

Chemokines are small, secreted proteins that orchestrate the migration of cells, which are involved in immune defence, immune surveillance and haematopoiesis. However, chemokines are also implicated in the pathology of various inflammatory diseases, cancers and HIV. The chemokine system is considerably large and has a redundancy in the repertoire of its inflammatory mediators. Therefore, strict regulation of chemokine activity is crucial. Chemokines are the substrate for various proteases including the serine protease CD26/dipeptidyl-peptidase IV and matrix metalloproteinases. Regulation by proteolytic cleavage controls and fine-tunes chemokine function by either enhancing or reducing its chemotactic activity or receptor selectivity. Often chemokines and the proteases that regulate them are produced in the same microenvironment and expression of both may be simultaneously induced by a common stimulus enabling the rapid regulation of chemokine activity. The overall impact of cleaved chemokines in cellular responses is very complex. In this review, we will give an overview on chemokine modification and the respective chemokine modifying proteases. Furthermore, we will summarize the emerging literature describing the consequences in inflammation, haematopoiesis, cancer and HIV infection upon proteolytic chemokine processing.     

Evidence for CALM in directing VAMP2 trafficking

Clathrin assembly lymphoid myeloid leukemia protein (CALM) is a clathrin assembly protein with a domain structure similar to the neuron-specific assembly protein AP180. We have previously found that CALM is expressed in neurons and present in synapses. We now report that CALM has a neuron-related function: it facilitates the endocytosis of the synaptic vesicle protein VAMP2 from the plasma membrane. Overexpression of CALM leads to the reduction of cell surface VAMP2, whereas knockdown of CALM by RNA interference results in the accumulation of surface VAMP2. The AP180 N-terminal homology (ANTH) domain of CALM is required for its effect on VAMP2 trafficking, and the ANTH domain itself acts as a dominant-negative mutant. Thus, our results reveal a role for CALM in directing VAMP2 trafficking during endocytosis.     

Combinatorial synthesis of anilinoanthraquinone derivatives and evaluation as non-nucleotide-derived P2Y2 receptor antagonists

A library of anilinoanthraquinone derivatives was synthesized by parallel Ullmann coupling reaction of bromaminic acid with aniline derivatives in solution using a compact parallel synthesizer. The products were purified by HPLC and evaluated as antagonists at mouse and human P2Y2 receptors. 4-Phenylamino-substituted 1-amino-2-sulfoanthraquinones, for example, 1-amino-4-(2-methoxyphenyl)-2-sulfoanthraquinone (PSB-716), were potent P2Y2 antagonists with IC50 values in the low micromolar range.     

Extracellular NAD induces a rise in [Ca]i in activated human monocytes via engagement of P2Y1 and P2Y11 receptors

Extracellular nicotinamide adenine dinucleotide (NAD⁺) is known to increase the intracellular calcium concentration [Ca²⁺]_i in different cell types and by various mechanisms. Here we show that NAD⁺ triggers a transient rise in [Ca²⁺]_i in human monocytes activated with lipopolysaccharide (LPS), which is caused by a release of Ca²⁺ from IP₃-responsive intracellular stores and an influx of extracellular Ca²⁺. By the use of P2 receptor-selective agonists and antagonists we demonstrate that P2 receptors play a role in the NAD⁺-induced calcium response in activated monocytes. Of the two subclasses of P2 receptors (P2X and P2Y) the P2Y receptors were considered the most likely candidates, since they share calcium signaling properties with NAD⁺. The identification of P2Y₁ and P2Y₁₁ as receptor subtypes responsible for the NAD⁺-triggered increase in [Ca²⁺]_i was supported by several lines of evidence. First, specific P2Y₁ and P2Y₁₁ receptor antagonists inhibited the NAD⁺-induced increase in [Ca²⁺]_i. Second, NAD⁺ was shown to potently induce calcium signals in cells transfected with either subtype, whereas untransfected cells were unresponsive. Third, NAD⁺ caused an increase in [cAMP]_i, prevented by the P2Y₁₁ receptor-specific antagonist NF157.     

Adiponectin upregulates monocytic activin A but systemic levels are not altered in obesity or type 2 diabetes

Adiponectin is an adipocyte-derived protein with atheroprotective and immunoregulatory function. Adiponectin and activin A reduce foam cell formation and adiponectin activates the p38 MAPK pathway that is well described to induce activin A. Therefore, it was analyzed whether adiponectin alters activin A in primary human monocytes. Adiponectin dose- and time-dependently induced activin A in the supernatant, and the maximal amount was observed after 12 h of incubation. Adiponectin-stimulated release of activin A was blocked by a p38 MAPK inhibitor. Metformin and pioglitazone are drugs frequently used to treat diabetic patients and metformin slightly reduced monocytic activin A release whereas pioglitazone had no effect. Type 2 diabetes is associated with elevated inflammatory systemic cytokines but activin A serum levels were similar in slim probands, overweight controls and type 2 diabetic patients. Furthermore, activin A did not correlate to systemic adiponectin, body mass index, waist to hip ratio or C-reactive protein. These findings indicate that adiponectin upregulates monocytic activin A release via the p38 MAPK pathway, and this may in part explain the immunoregulatory and antiatherosclerotic effects of this adipokine.