Lipoxin A-induced inhibition of human natural killer cell cytotoxicity: studies on stereospecificity of inhibition and mode of action

Human leukocyte-derived lipoxin A (LXA; 5S,-6R,15S-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid) inhibits the cytotoxic activity of human natural killer (NK) cells. LXA and three of its isomers were prepared by total organic synthesis and assayed for activity with human NK cells. Dose-response studies showed that biologically derived LXA and synthetic LXA were equally effective in inhibiting NK cell cytotoxicity. 6S-LXA, with its 6S-OH group in an (S) configuration, proved to be approximately half as potent as LXA. In contrast, 6S-11-trans-LXA and 11-trans-LXA displayed virtually no inhibitory activities. The methyl esters of both LXA and 6S-LXA proved to be more potent than their corresponding free acids. Thus, LXA inhibition of NK cells displays clear-cut stereochemistry. In the absence of putative inhibitors, NK cells bind to their targets to form conjugates. This event is followed by polarization of the NK Golgi apparatus, which moves towards the plasma membrane that is in contact with the target cell. However, in the presence of either the methyl ester or free acid of LXA, the Golgi apparati of NK cells bound to their targets were randomly oriented. In contrast, neither 6S-11-trans-LXA nor the potent NK inhibitor prostaglandin E2 affected the polarization. Furthermore, although prostaglandin E2 resulted in a decrease in NK-target cell binding efficiency, LXA and its isomers failed to affect conjugate formation. Together these results indicate that LXA-induced inhibition of NK cytotoxicity does not act on NK cell binding but may block cytotoxicity by disrupting "signals" involved in the specific orientation of the Golgi. Thus, this latter event may appear to be important in cytotoxicity.     

The action of lipoxin-A on glomerular microcirculatory dynamics in the rat

Intrarenal administration of 750 ng/kg/min of LX-A in euvolemic rats resulted in significant increases in single nephron GFR (38.4 +/- 1.7 to 45.5 +/- 3.0 nl/min) and plasma flow rate (95 +/- 6 to 127 +/- 9 nl/min). The latter was due to a dramatic fall in afferent arteriolar resistance. Mean transcapillary hydraulic pressure difference increased from 33 +/- 1 to 43 +/- 3 mmHg (p less than 0.05) and the glomerular capillary ultrafiltration coefficient fell from 0.060 +/- 0.013 to 0.033 +/- 0.005 nl/(s X mmHg) (p less than 0.05). These responses to LXA in the renal microcirculation are in sharp contrast to those previously observed for the leukotrienes, and thus may represent the first example of counterregulatory (constrictor/dilator) vascular interactions within the lipoxygenase pathways.     

Identification of a novel 7-cis-11-trans-lipoxin A4 generated by human neutrophils: total synthesis, spasmogenic activities and comparison with other geometric isomers of lipoxins A4 and B4

Addition of (15S)-hydroxy-5,8,11-cis-13-trans-eicosatetraenoic acid (15-HETE) and the ionophore A23187 (2.5 microM) to human neutrophils led to the formation of both lipoxin A4 and lipoxin B4 as well as a novel 5,6,15-trihydroxyeicosatetraenoic acid. The new compound was identified using an improved isolation and detection system and its basic structure was determined by physical methods. On the basis of biosynthetic considerations, geometric isomers of lipoxin A4 and lipoxin B4 were prepared by total synthesis. Comparison of these synthetic materials with the neutrophil-derived product showed that the new compound is (5S,6R,15S)-trihydroxy-9,11,13-trans-7-cis-eicosatetraenoic acid or the 7-cis-11-trans-isomer of LXA4 (7-cis-11-trans-LXA4). LXA4, 11-trans-LXA4, 7-cis-LXA4 and 7-cis-11-trans-LXA4 all evoked dose-dependent (0.1-10 microM) contractions of the guinea pig lung strip, whereas 6-cis-LXB4 and 6-cis-8-trans-LXB4 relaxed this preparation. LXA4 and 7-cis-LXA4 were approx. 10-times more potent than the compounds with 11-trans geometry. However, all four double-bond isomers of LXA4 caused contractions which, based upon pharmacological evidence, appeared to involve specific activation of the same site as cysteinyl-containing leukotrienes. In conclusion, 7-cis-11-trans-LXA4 was isolated and identified as a novel biologically active eicosanoid formed by human neutrophils.     

Action of novel eicosanoids lipoxin A and B on human natural killer cell cytotoxicity: effects on intracellular cAMP and target cell binding

Lipoxin A (5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic acid) and lipoxin B (5D,14,15-trihydroxy-6,8,10,12-eicosatetraenoic acid), two newly isolated compounds derived from the oxygenation of arachidonic acid in human leukocytes, inhibit the cytotoxic activity of human natural killer (NK) cells. Dose-response studies showed that both lipoxin A and lipoxin B inhibit, at submicromolar concentrations (ID50 10(-7) M), NK cell activity assayed against K562 target cells. Prostaglandin E2 (PGE2) also inhibited cytotoxicity, whereas both 15-HETE (5(S)-hydroxy-5,8,11,13-eicosatetraenoic acid) and leukotriene B4 (synthetic and biologically derived) were ineffective. PGE2 stimulated a time- and dose-dependent increase in intracellular cAMP, which was accompanied by a decrease in NK target cell binding. Lipoxin A and lipoxin B did not elevate intracellular cAMP, nor did they inhibit target cell binding. Together these findings suggest that lipoxin A and lipoxin B abrogate NK cell cytotoxicity at a step distal to target effector cell recognition. In contrast, PGE2 appears to exert its effect, at least in part, on cytotoxicity indirectly by decreasing the binding between target and effector cells (in vitro). Moreover, they suggest that novel oxygenated derivatives of arachidonic acid (i.e., lipoxin A, lipoxin B) may regulate the activities of NK cells.     

Trihydroxytetraenes: A novel series of compounds formed from arachidonic acid in human leukocytes

Addition of 15L-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) to human leukocytes led to the formation of a novel series of compounds containing four conjugated double bonds. The yield of tetraenes was increased approx. 100-fold when ionophore A23187 (5 μM) was added simultaneously with 15-HPETE. The structure of the major tetraene was established by physical methods as well as by chemical degradation and found to be 5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic acid.     

Native drivers of fish life history traits are lost during the invasion process

Rapid adaptation to global change can counter vulnerability of species to population declines and extinction. Theoretically, under such circumstances both genetic variation and phenotypic plasticity can maintain population fitness, but empirical support for this is currently limited. Here, we aim to characterize the role of environmental and genetic diversity, and their prior evolutionary history (via haplogroup profiles) in shaping patterns of life history traits during biological invasion. Data were derived from both genetic and life history traits including a morphological analysis of 29 native and invasive populations of topmouth gudgeon Pseudorasbora parva coupled with climatic variables from each location. General additive models were constructed to explain distribution of somatic growth rate (SGR) data across native and invasive ranges, with model selection performed using Akaike's information criteria. Genetic and environmental drivers that structured the life history of populations in their native range were less influential in their invasive populations. For some vertebrates at least, fitness‐related trait shifts do not seem to be dependent on the level of genetic diversity or haplogroup makeup of the initial introduced propagule, nor of the availability of local environmental conditions being similar to those experienced in their native range. As long as local conditions are not beyond the species physiological threshold, its local establishment and invasive potential are likely to be determined by local drivers, such as density‐dependent effects linked to resource availability or to local biotic resistance.     

Tick survey and detection of Crimean-Congo hemorrhagic fever virus in tick species from a non-endemic area, South Marmara region, Turkey

Crimean-Congo hemorrhagic fever (CCHF) is an increasing health concern in Turkey since 2002. There were also some recent human cases from the South Marmara region of Turkey; thus, a tick survey was performed, and possible vector tick species for the CCHF virus were determined in the region. A total of 740 adult ticks were collected from infested livestock from five locations: Çanakkale-Biga, Bursa-Orhaneli, Bursa-Keles, Bal?kesir and Bilecik. Total of 11 tick species from the genera Hyalomma, Rhipicephalus, Dermacentor, Ixodes and Haemaphysalis were identified. Rhipicephalus ticks were dominant in the region; the most frequently observed tick species was R. turanicus, (53.1 %), and only 15.4 % of the identified ticks were H. marginatum. The occurrence of H. rufipes infestation in the region fort he first time. A total of 73 pools of adult ticks were tested with both an antigen-detecting ELISA and RT real-time PCR (RT rt PCR). The presence of the CCHF virus was demonstrated in 9 (12.3 %) of the tested tick pools. Although seven of the tick pools were positive for the CCHF virus with both of the methods, one pool was positive only with RT rt PCR and the other pool was only positive with the ELISA. Positive results were obtained from ticks collected from cattle, sheep and goats from two locations, Bursa-Orhaneli and Bilecik. The CCHF virus was detected in R. turanicus (n = 3), R. bursa (n = 2), H. marginatum (n = 2) and D. marginatus (n = 2) ticks. The results of this study confirm the presence of the CCHF virus and present preliminary data on the vector tick species in the southern Marmara region of Turkey.     

A Novel Anti-Inflammatory and Pro-Resolving Role for Resolvin D1 in Acute Cigarette Smoke-Induced Lung Inflammation

Introduction

Cigarette smoke is a profound pro-inflammatory stimulus that contributes to acute lung injuries and to chronic lung disease including COPD (emphysema and chronic bronchitis). Until recently, it was assumed that resolution of inflammation was a passive process that occurred once the inflammatory stimulus was removed. It is now recognized that resolution of inflammation is a bioactive process, mediated by specialized lipid mediators, and that normal homeostasis is maintained by a balance between pro-inflammatory and pro-resolving pathways. These novel small lipid mediators, including the resolvins, protectins and maresins, are bioactive products mainly derived from dietary omega-3 and omega-6 polyunsaturated fatty acids (PUFA). We hypothesize that resolvin D1 (RvD1) has potent anti-inflammatory and pro-resolving effects in a model of cigarette smoke-induced lung inflammation.

Methods

Primary human lung fibroblasts, small airway epithelial cells and blood monocytes were treated with IL-1β or cigarette smoke extract in combination with RvD1 in vitro, production of pro-inflammatory mediators was measured. Mice were exposed to dilute mainstream cigarette smoke and treated with RvD1 either concurrently with smoke or after smoking cessation. The effects on lung inflammation and lung macrophage populations were assessed.

Results

RvD1 suppressed production of pro-inflammatory mediators by primary human cells in a dose-dependent manner. Treatment of mice with RvD1 concurrently with cigarette smoke exposure significantly reduced neutrophilic lung inflammation and production of pro-inflammatory cytokines, while upregulating the anti-inflammatory cytokine IL-10. RvD1 promoted differentiation of alternatively activated (M2) macrophages and neutrophil efferocytosis. RvD1 also accelerated the resolution of lung inflammation when given after the final smoke exposure.

Conclusions

RvD1 has potent anti-inflammatory and pro-resolving effects in cells and mice exposed to cigarette smoke. Resolvins have strong potential as a novel therapeutic approach to resolve lung injury caused by smoke and pulmonary toxicants.     

A global review and meta-analysis of applications of the freshwater Fish Invasiveness Screening Kit

Reviews in Fish Biology and Fisheries - The freshwater Fish Invasiveness Screening Kit (FISK) has been applied in 35 risk assessment areas in 45 countries across the six inhabited continents (11...