Review: Maternal and placental antioxidant response to preeclampsia – Impact on vasoactive eicosanoids

The abnormally developed placenta is believed to be the pathophysiological cause of preeclampsia (PE). The resulting malperfusion of the placenta in PE can be associated with fluctuations in oxygen levels, leading to oxidative stress. How then do the placenta and the circulatory system of the mother adapt and respond to the increased oxidative challenge associated with PE? Many antioxidant systems have been shown to be upregulated or downregulated in the placenta and/or the maternal circulation during PE. Such altered antioxidant response can lead to increased lipid peroxidation. Oxidation of arachidonoyl residues in phospholipids generates bioactive lipids such as F₂-isoprostanes, which are known vasoconstrictors. The consequences of changes in antioxidant status can also affect signal transduction and enzymatic pathways related to eicosanoid synthesis.     

Local inflammatory events induced by Bothrops atrox snake venom and the release of distinct classes of inflammatory mediators

Bothrops atrox is responsible for most accidents involving snakes in the Brazilian Amazon and its venom induces serious systemic and local effects. The local effects are not neutralized effectively by commercial antivenoms, resulting in serious sequelae in individuals bitten by this species. This study investigates the local inflammatory events induced in mice by B. atrox venom (BaV), such as vascular permeability, leukocyte influx and the release of important inflammatory mediators such as cytokines, eicosanoids and the chemokine CCL-2, at the injection site. The effect of BaV on cyclooxygenase (COX-1 and COX-2) expression was also investigated. The results showed that intraperitoneal (i.p.) injection of BaV promoted a rapid and significant increase in vascular permeability, which reached a peak 1 h after venom administration. Furthermore, BaV caused leukocyte infiltration into the peritoneal cavity between 1 and 8 h after i.p. injection, with mononuclear leukocytes (MNs) predominating in the first 4 h, and polymorphonuclear leukocytes (PMNs) in the last 4 h. Increased protein expression of COX-2, but not of COX-1, was detected in leukocytes recruited in the first and fourth hours after injection of BaV. The venom caused the release of eicosanoids PGD₂, PGE₂, TXA₂ and LTB₄, cytokines TNF-α, IL-6, IL-10 and IL-12p70, but not IFN-γ, and chemokine CCL-2 at different times. The results show that BaV is able to induce an early increase in vascular permeability and a leukocyte influx to the injection site consisting mainly of MNs initially and PMNs during the later stages. These phenomena are associated with the production of cytokines, the chemokine CCL-2 and eicosanoids derived from COX-1 and COX-2.     

Eicosanoide und Phospholipasen

Summary Prostaglandins, thromboxanes, and leukotrienes have been implicated to play an important role in physiology as well as in a growing list of pathophysiologic conditions. These oxidation products of 8.11.14.-eicosatrienoic-,5.8.11.14.-eicosatetraenoic-, and 5.8.11.14.17.-pentaenoic acids have been collectively designated eicosanoids. Many clinically important diseases are associated with altered eicosanoid biosynthesis. Furthermore, a series of hormones are known to induce acutely formation of eicosanoids, suggesting a crucial role in a multitude of tissue responses including phenomena such as secretion, platelet aggregation, chemotaxis, and smooth muscle contraction. The major precursor for the eicosanoids seems to be 5.8.11.14.-eicosatetraneoic acid or arachidonic acid. Virtually all of arachidonic acid however is present in esterified form in complex glycerolipids. Since cyclooxygenase and the lipoxygenases utilize arachidonic acid in its free form, a set of acylhydrolases is required to liberate arachidonic acid from membrane lipids before eicosanoid formation can occur. It became only recently apparent that a minor acidic phospholipid, phosphatidylinositol, comprising only 5%–10% of the phospholipid mass in mammalian cells, plays an important role in arachidonic acid metabolism. Phosphatidylinositol — after phosphorylation to phosphatidylinositolphosphate and phosphatidylinositolbisphosphate — appears to be hydrolyzed by specific phospholipases C generating 1-stearoyl-2-arachidonoyl-diglyceride. Diglyceride serves as substrate for diglyceride lipase to form monoglyceride and free fatty acid. Alternatively diglyceride is phosphorylated by diglyceride kinase yielding phosphatidic acid, which is believed to be reincorporated into phosphatidylinositol. In addition to phosphatidylinositol phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid may contribute to arachidonic acid release. These phospholipids are substrates for phospholipases A₂ generating free arachidonic acid and the respective lysophospholipid. Understanding of the biochemistry of arachidonic acid liberation may be critical in developing strategies of pharmacological intervention in a variety of pathological conditions.

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Abkürzungen AA Arachidonsäure - CDP-DG Cytidindiphosphodiglycerid - DG Diglycerid - DPI Phosphatidylinositoldiphosphat - FA freie Fettsäure - GSH Glutathion - HETE Hydroxyeicosatetraensäure - HPETE Hydroperoxyeicosatetraensäure - MDA Malondialdehyd - MG Monoglycerid - MI Myoinositol - Lyso-PA Lysophosphatidsäure - Lyso-PC Lysophosphatidylcholin - Lyso-Pl Lysophosphatidylinositol - LT Leukotrien - PA Phosphatidsäure - PC Phosphatidylcholin - PG Prostaglandin - Pl Phosphatidylinositol - THETE Tetrahydroxyeicosatetraensäure - TX Thromboxan Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft (HA-1083/2-2) und dem Forschungsrat Rauchen und Gesundheit (Hamburg) unterstütztHerrn Professor Hans Neurath zum 75. Geburtstag gewidmet     

The Aetiology of Diabetic Neuropathy: the Combined Roles of Metabolic and Vascular Defects

A combination of metabolic and vascular defects have been implicated in the pathogenesis of diabetic neuropathy. Animal studies have demonstrated that a reduction in nerve blood flow may be an important early defect and that vasodilators can prevent or ameliorate nerve dysfunction. The potential factors contributing to nerve ischaemia include structural defects in the endoneurial microvasculature together with rheological abnormalities, abnormalities in vasoactive agents which regulate nerve blood flow including nitric oxide and the eicosanoids, and alterations in tone of the autonomic innervation of the nerve vasculature. The principle metabolic defects which have been implicated include disruption of the polyol pathway, altered lipid metabolism, advanced glycosylated end-product formation, increased oxidative stress, and diabetes-induced defects in growth factors. The demonstration that activation of the polyol pathway in experimental diabetes may affect nerve blood flow, and conversely that vasoactive agents appear to be important in regulating some aspects of nerve metabolism, has highlighted the interdependence of the metabolic and vascular defects in the pathogenesis of this condition. Thus, selective intervention aimed at a key defect early in this cascade may subsequently correct a number of later abnormalities offering therapeutic hope in this chronic debilitating complication.     

Effect of manoalide on human 5-lipoxygenase activity

The marine natural product manoalide (MLD) has been described to inactivate phospholipase A₂(PLA₂) from several sources as well as to inhibit synthesis of eicosanoids in human polymorphonuclear leukocytes (HPMNL). MLD also reduces chemically-induced inflammation in vivo. In this investigation we have examined the effect of MLD on A23187-induced generation of leukotriene B₄ (LTB₄) and thromboxane B₂ (TXB₂) in HPMNL as well as 5-lipoxygenase (5-LO) activity from HPMNL sonicated preparations. In the intact cell system, MLD inhibited with similar potency biosynthesis of LTB₄ and TXB₂ (IC₅₀ 1.7 and 1.4 M, respectively). In order to discern if inhibition of 5-LO is involved in the effect of MLD, we examined the action of this compound on 5-LO activity from 10,000×g and 100,000×g supernatants of sonicated HPMNL homogenates. The enzymatic activity was not affected at concentrations of MLD up to 50 M. These data indicate that MLD is not a direct inhibitor of 5-LO activity from HPMNL and support the hypothesis that its antiinflammatory action could be related with a reduction of eicosanoid biosynthesis via inhibition of PLA₂.accepted by I. Ahnfelt-Rønne     

Dietary fat, fatty acids and breast cancer

Results from some, but not all, epidemiological studies, and experimental investigations using animal models indicate that the level of fat in the diet, and more importantly the nature of the constituent fatty acids, influence both breast cancer risk and the progression of the established disease. High-fat diets rich in polyunsaturated omega-6 fatty acids stimulate mammary carcinogenesis and tumor progression; the long-chain omega-3 fatty acids present at high concentration in some fish oils exert inhibitory effects. Prominent among the biochemical mechanisms involved is the regulation of eicosanoid biosynthesis from dietary linoleic acid; both prostaglandins resulting from cyclooxygenase activity, and the leukotrienes and hydroxy-fatty acids produced under the influence of the lipoxygenases are involved in mammary carcinogenesis, tumor cell growth and apoptosis, angiogenesis, invasion and metastasis. A shift towards the typical high-fat Western diet, rich in omega-6 and poor in omega-3 fatty acids, may be a major factor in the increasing breast cancer incidence and mortality rates in Japanese women. Moreover, the results of the preclinical studies, together with supporting epidemiological data, suggest that a nutritional intervention comprising dietary omega-3 fatty acid supplementation and, in populations consuming a high fat diet a reduction in total fat and omega-6 fatty acid intake, may have a place not only in breast cancer prevention, but also as an adjunct to the surgical treatment of the breast cancer patient.     

Contraction of guinea pig inferior vena cava by eicosanoids

Summary Guinea pig inferior vena cava contracted in response to leukotriene (LT)C₄, LTD₄, LTE₄ U46619, phenylephrine, histamine, and KCl. Although LTC₄, LTD₄, and U46619 were the most potent agonists, active tension generated by these eicosanoids was only about half that of histamine or KCl. LTE₄ and phenylephrine were marginally active. Biochemical analysis showed vena cava able to convert about 23% LTC₄ to LTD₄ and LTE₄ in 45 min. Pretreatment with acivicin prevented this by abrogating conversion of LTC₄ to LTD₄. A subthreshold concentration of LTE₄ reduced responses to LTC₄ and LTD₄. LY171883 and WY-48252 competitively antagonized LTD₄-induced contractions of vena cava. In contrast, these antagonists blocked contractions to LTC₄ in a biphasic manner. Lower segments of the LTC₄ concentration-response curves were less affected than the upper portion suggesting the possibility of 2 LTC₄ receptor subtypes. Our results indicate that LTE₄ is a weak or partial agonist in this tissue and furthermore they suggest a lack of high affinity receptors for LTE₄ favoring LTC₄ and LTD₄. Indomethacin did not influence contractions to the leukotrienes or histamine. However, the response to U46619 was greatly enhanced suggesting release of a vasodilator prostaglandin as part of the overall response of the vena cava to the thromboxane A2 mimetic.Presented in part at a meeting of the American Society for Pharmacology and Experimental Therapeutics, Salt Lake City, Utah Correspondence to: J. H. Fleisch at the above address     

Xenogeneic ex vivo hemoperfusion of rhesus monkey livers with human blood

Abstract In order to copy the clinical situation of concordant xenotransplantation, Rhesus Monkey livers were hemoperfused with human blood. Changes of immunological (TNFα, IL-1β, IL-2, IL-2R, IL-6, IFNy, TXB2, 6kPGF1α, sICAM-1, SELAM-1, sHLA-I-Ag) and pathophysiological (GOT, GPT, LDH, CK) parameters were followed. Our experiment proves that all phenomena start in the first hour of xenogeneic blood circulation. Xenogeneic rejection in our concordant system is surprisingly severe. Preformed natural antibodies only cannot be the reason of such a damage [5, 6]. We think that beside other important immunological mechanisms, humoral mediators play a considerable role at the beginning of a xenogeneic rejection.     

Contemporary clinical usage of LC/MS: analysis of biologically important carboxylic acids

OBJECTIVES: This review summarizes the current role of LC/MS in the diagnosis and screening of clinical conditions involving the analysis of biologically important carboxylic acids. DESIGN AND METHODS: Carboxylic acids are divided into six logical categories of acid size and function. Details of chromatographic separation methods and modes of mass spectrometer operation are described for each category. RESULTS: The use of LC/MS in clinical applications such as the diagnosis of inherited and acquired metabolic disorders, gastrointestinal disorders, cancer and diabetes and therapeutic drug monitoring is discussed. CONCLUSIONS: The mild conditions, speed and sensitivity advantages of LC/MS analysis, over alternatives, are highlighted. The sensitivity and specificity afforded by the combination of tertiary and quaternary ammonium derivatives and tandem mass spectrometry for the analysis of carboxylic acids is emphasized. Potential for a greater range of LC/MS carboxylic analyses, including stereoisomeric intermediates, is predicted.     

Improving microdialysis extraction efficiency of lipophilic eicosanoids

Microdialysis recovery of the lipophilic analytes prostaglandin B₂, leukotriene B₄ and C₄ was studied in vitro. Relative recovery (RR) through different commercially-available microdialysis probes for prostaglandin B₂ and leukotrienes was examined using different flow rates. The enhancing effect at different concentrations of binding agents such as , β, γ-cyclodextrins (, β, γ-CD) on the microdialysis RR for different eicosanoids was evaluated. Small organic molecules such as ethanol, propylene glycol and dimethyl sulfoxide (DMSO) were studied in terms of their effect on enhancing RR. Inclusion of arachidonic acid in either the perfusion fluid or the sample medium caused the microdialysis RR for these hydrophobic analytes to be increased.