Martina Wendel

Anticancer Actions of Omega-3 Fatty Acids - Current State and Future Perspectives

Omega-3 fatty acids (omega3-FA) were shown to attenuate growth and induce apoptosis in a variety of human cancer cell lines derived from colonic, pancreatic, prostate, and breast cancer. In addition, recent findings indicate that omega3-FA act synergistically with chemotherapeutic agents and may also be used to enhance tumour radiosensitivity. The mechanisms underlying the anti-tumour effects of omega3-FA are complex. Incorporation of omega3-FA in biological membranes alters the profile of lipid mediators generated during inflammatory reactions. Furthermore, omega3-FA act as ligands of nuclear peroxisome proliferator-activated receptors that attenuate transcription of NF-kappaB-dependent genes. Thereby, the cyclooxygenase-2/prostaglandin E(2)-dependent production of pro-angiogenic vascular endothelial growth factor and levels of anti-apoptotic bcl-2 and bcl-X(L) are decreased. Eicosanoid-independent pro-apoptotic pathways include enhanced lipid peroxidation, modulation of mitochondrial calcium homeostasis and enhanced production of reactive oxygen species as well as activation of p53. This review article will give a comprehensive overview over the pleiotropic actions of omega3-FA and will discuss the potential of omega3-FA and derivatives like conjugated eicosapentaenoic acid as important nutritional adjuvant therapeutics in the management of various human cancer diseases and the impact of nutritional omega-3 FA on cancer prevention.

Distribution of Endothelin Receptor Subtypes ETA and ETB in the Rat Kidney

The endothelin (ET) receptor system is markedly involved in the regulation of renal function under both physiological and pathophysiological conditions. The present study determined the detailed cellular localization of both ET receptor subtypes, ETA and ETB, in the vascular and tubular system of the rat kidney by immunofluorescence microscopy. In the vascular system we observed both ETA and ETB receptors in the media of interlobular arteries and afferent and efferent arterioles. In interlobar and arcuate arteries, only ETA receptors were present on vascular smooth muscle cells. ETB receptor immunoreactivity was sparse on endothelial cells of renal arteries, whereas there was strong labeling of peritubular and glomerular capillaries as well as vasa recta endothelium. ETA receptors were evident on glomerular mesangial cells and pericytes of descending vasa recta bundles. In the renal tubular system, ETB receptors were located in epithelial cells of proximal tubules and inner medullary collecting ducts, whereas ETA receptors were found in distal tubules and cortical collecting ducts. Distribution of ETA and ETB receptors in the vascular and tubular system of the rat kidney reported in the present study supports the concept that both ET receptor subtypes cooperate in mediating renal cortical vasoconstriction but exert differential and partially antagonistic effects on renal medullary function. (J Histochem Cytochem 54:1193-1203, 2006)

Imaging of the three-dimensional alveolar structure and the alveolar mechanics of a ventilated and perfused isolated rabbit lung with Fourier domain optical coherence tomography

In this feasibility study, Fourier domain optical coherence tomography (FDOCT) is used for visualizing the 3-D structure of fixated lung parenchyma and to capture real-time cross sectional images of the subpleural alveolar mechanics in a ventilated and perfused isolated rabbit lung. The compact and modular setup of the FDOCT system allows us to image the first 500 microm of subpleural lung parenchyma with a 3-D resolution of 16 x 16 x 8 microm (in air). During mechanical ventilation, real-time cross sectional FDOCT images visualize the inflation and deflation of alveoli and alveolar sacks (acini) in successive images of end-inspiratory and end-expiratory phase. The FDOCT imaging shows the relation of local alveolar mechanics to the setting of tidal volume (VT), peak airway pressure, and positive end-expiratory pressure (PEEP). Application of PEEP leads to persistent recruitment of alveoli and acini in the end-expiratory phase, compared to ventilation without PEEP where alveolar collapse and reinflation are observed. The imaging of alveolar mechanics by FDOCT will help to determine the amount of mechanical stress put on the alveolar walls during tidal ventilation, which is a key factor in understanding the development of ventilator induced lung injury (VILI).

Mitochondrial function and dysfunction in sepsis.

ZusammenfassungDie Mitochondrien sind die quantitative bedeutsamste ATP-Quelle von Zellen. Durch die pathophysiologischen Vorgänge, die im Verlauf der Abwehr von eindringenden Miroorganismen in Gang gesetzt werden, kommt es zu einer Beeinrächtigung von Funktion und Struktur der Mitochondrien. Insbesondere das hochreaktive Peroxynitrit, das aus der Reaktion von Stickstoffmonoxid und Superoxid-Anionen entsteht, schädigt die mitochondrialen Lipide, Proteine und Nukleinsäuren. Der starke oxidative Stress induziert DNA-Strangbrüche, die unter Aktivierung der Poly(ADP-Ribose)-Polymerase repariert werden. Dieser Prozess verbraucht große Mengen an Nicotinamid-Dinucleotid (NAD+), wodurch es zur zellulären NAD+-Verarmung kommt. Dies beeinträchtigt die Einschleusung von Elektronen in die Atmungskette und verstärkt die Inflammation. Neue therapeutische Strategien, die auf eine Abschwächung der Wirtsreaktion auf eindringende Mikroorganismen oder auf eine Modulation intrazellulärer Signalkaskaden, die zu oxidativem Stress führen, abzielen, konnten in experimentellen Studien die mitochondriale Funktion und letztlich auch die Organfunktion verbessern.SummaryMitochondria are the key source of cellular ATP and their structure and function are markedly affected by pathophysiologic processes associated with the hosts response to invading pathogens. In particular, the highly reactive compound peroxynitrite, generated by the reaction of nitric oxide and superoxide anions, inhibits mitochondrial enzymes and damages lipids, proteins, and nucleic acids. Enhanced oxidative stress induces DNA strand breaks that are repaired by activation of poly(ADP-ribose)polymerase (PARP). This process consumes large amounts of nicotinamide adenine dinucleotide (NAD+) leading to cellular NAD+ depletion that impairs flux of reducing equivalents into the respiratory chain and also further promotes inflammation. In experimental studies, novel therapeutic strategies that aim to ameliorate the hosts pathogen response or to modulate intracellular signaling events related to oxidative stress protected mitochondrial function and preserved cellular respiration ultimately leading to improved organ function.

Effects of advanced glycation end products‐inductor glyoxal and hydrogen peroxide as oxidative stress factors on rat retinal organ cultures and neuroprotection by UK‐14,304

Retinal ganglion cell degeneration is supposed to be mediated by reactive oxygen species (ROS) and advanced glycation end products (AGEs). The alpha2‐adrenergic agonist, 5‐bromo‐N‐(4,5‐dihydro‐1H‐imidazol‐2‐yl)‐6‐quinoxalinamine (brimonidine; UK‐14,304), is said to exert a neuroprotective effect. To investigate these mechanisms in detail, we exposed rat whole mounts to glyoxal or H2O2 and treated them with either UK‐14,304 alone or additionally with the phosphatidylinositide 3 kinase (PI3) kinase inhibitor, 2‐(4‐Morpholinyl)‐8‐phenyl‐4H‐1‐benzopyran‐4‐one (Ly 294002). The accumulation of Nε‐[carboxymethyl] lysine (CML) was assessed immunohistochemically and changes in intracellular pH (pHi), mitochondrial transmembrane potential (MTMP) and ROS production in cell bodies of multipolar ganglion cell layer were studied by intravital fluorescence microscopy and confocal laser scanning microscopy. Ultrastructural changes in mitochondria of multipolar ganglion cell layer cell bodies were determined by transmission electron microscopy. We found that glyoxal and H2O2 increased accumulation of CML‐modified proteins and ROS production and decreased pHi and MTMP in cell bodies of multipolar ganglion cell layer. UK‐14,304 could prevent production of ROS, accumulation of CML‐modified proteins, ameliorate acidification, preserve MTMP and attenuate ultrastructural damages of ganglion cell mitochondria. Ly 294002 reversed the UK‐14,304‐mediated attenuation of CML and ROS production. We conclude that the protective effects of UK‐14,304 seem partly to be mediated by PI3 kinase‐dependent pathways.

Muscular ETB Receptors Develop Postnatally and Are Differentially Distributed in Specific Segments of the Rat Vasculature

The endothelin/endothelin-receptor system is a key player in the regulation of vascular tone in mammals. We raised and characterized an antiserum against rat ETB receptor and investigated the distribution of ETB receptors in different vascular beds during postnatal development (day 0 through day 28) and in the adult rat. We report the tissue-specific and age-dependent presence of vasoconstrictor ETB receptors. At the time of birth, vascular smooth muscle cells from all tissues examined did not exhibit ETB receptor immunoreactivity. The occurrence of ETB receptor immunoreactivity in the postnatal development was time dependent and started in small coronary and meningeal arteries at day 5, followed by small mesenteric arteries as well as brachial artery and vein at day 14. At day 21, ETB receptors were present in the media of muscular segments of pulmonary artery, large coronary arteries, and intracerebral arterioles. At day 28, ETB receptor immunoreactivity was evident in interlobular renal arteries, vas afferens, and efferens. Large renal arteries, mesenteric artery, and elastic segments of pulmonary arteries, as well as coronary and mesenteric veins, did not exhibit ETB receptor immunoreactivity. These data demonstrate the age-dependent and tissue-specific presence of ETB receptors, mainly on arterial smooth muscle cells in the vascular system of the rat.

Common-path Fourier domain optical coherence tomography of irradiated human skin and ventilated isolated rabbit lungs

A compact common path Fourier domain optical coherence tomography (FD-OCT) system based on a broadband superluminescence diode is used for biomedical imaging. The epidermal thickening of human skin after exposure to ultraviolet radiation is measured to proof the feasibility of FD-OCT for future substitution of invasive biopsies in a long term study on natural UV skin protection. The FD-OCT system is also used for imaging lung parenchyma. FD-OCT images of a formalin fixated lung show the same alveolar structure as scanning electron microscopy images. In the ventilated and blood-free perfused isolated rabbit lung FD-OCT is used for real-time cross-sectional image capture of alveolar mechanics throughout tidal ventilation. The alveolar mechanics changing from alternating recruitment-derecruitment at zero positive end-expiratory pressure (PEEP) to persistent recruitment after applying a PEEP of 5 cm H2O is observed in the OCT images.

Leukocyte antibacterial functions are not impaired by perfluorocarbon exposure in vitro

Application of liquid, aerosolized, and vaporized perfluorocarbons (PFC) in acute lung injury has shown anti-inflammatory effects. Although this may be beneficial in states of pulmonary hyperinflammation, it also could increase susceptibility to nosocomial lung infection. We hypothesized that PFC impair cellular host defense and therefore investigated in an in vitro model the influence of perfluorohexane (PFH) on crucial mechanisms of bacterial elimination in human neutrophils and monocytes. Using scanning and transmission electron microscopy, we could show membrane-bound and ingested PFH particles that morphologically did not alter adherence and phagocytosis of Escherichia coli or leukocyte viability. The amount of adherent and phagocytosed bacteria as determined by flow cytometry was not influenced in cells only pretreated with PFH for 1 and 4 h. When PFH was present during E. coli challenge, bacterial adherence was decreased in polymorphonuclear neutrophils, but respective intracellular uptake was not impaired and was even significantly promoted in monocytes. Overall, E. coli-induced respiratory burst capacity was not reduced by PFH. Our findings provide evidence that key functions of innate host defense are not compromised by PFH treatment in vitro.

Pathomechanismen des Organversagens

ZusammenfassungEntzündungsmediatoren sowie vermehrt gebildete reaktive Sauerstoff- und Stickstoffverbindungen führen zu zellulären Sauerstoffverwertungsstörungen im Rahmen der Sepsis. Insbesondere das hochreaktive Peroxynitrit schädigt Lipide, Proteine und Nukleinsäuren irreversibel und hemmt Enzymkomplexe der Atmungskette. Hierdurch werden der zelluläre Funktionsstoffwechsel und in der Folge die Organfunktionen beeinträchtigt. Die Reparatur geschädigter Desoxyribonukleinsäure (DNA) durch die Poly(adenosindiphosphat)ribose-Polymerase verbraucht große Mengen Nicotinamid-Adenin-Dinukleotid (NAD+), wodurch es zur zellulären NAD+-Verarmung kommt und die proinflammatorischen Reaktion weiter unterhalten wird. Die vorliegende Übersichtsarbeit fasst wesentliche Aspekte dieses pathophysiologischen Geschehens zusammen und stellt neue therapeutische Strategien vor, die experimentell effektiv sind und das Potenzial der klinischen Anwendung in sich tragen.AbstractProinflammatory mediators as well as increased formation of reactive oxygen and nitrogen species impair cellular respiration during sepsis. In particular, the highly reactive peroxynitrite irreversibly damages lipids, proteins and nucleic acids and also inhibits enzyme complexes of the respiratory chain. In this way cellular metabolic functions and subsequently organ functions are also impaired. Repair of DNA by poly(ADP-ribose)polymerase consumes large amounts of nicotinamide adenine dinucleotide (NAD+) which leads to cellular NAD+ depletion further promoting inflammation. This article summarizes central aspects of the pathophysiology of mitochondrial dysfunction during sepsis and gives an overview about newly developed strategies which proved effective in experimental studies and may have a potential clinical application in the future.Proinflammatory mediators as well as increased formation of reactive oxygen and nitrogen species impair cellular respiration during sepsis. In particular, the highly reactive peroxynitrite irreversibly damages lipids, proteins and nucleic acids and also inhibits enzyme complexes of the respiratory chain. In this way cellular metabolic functions and subsequently organ functions are also impaired. Repair of DNA by poly(ADP-ribose)polymerase consumes large amounts of nicotinamide adenine dinucleotide (NAD+) which leads to cellular NAD+ depletion further promoting inflammation. This article summarizes central aspects of the pathophysiology of mitochondrial dysfunction during sepsis and gives an overview about newly developed strategies which proved effective in experimental studies and may have a potential clinical application in the future.

INFLAMMATORY-ACTIVATED MICROVASCULAR ENDOTHELIAL CELLS REGULATE INTERLEUKIN-8 AND MONOCYTE CHEMOATTRACTANT PROTEIN-1 EXPRESSION OF A549 CELLS IN A PARACRINE FASHION

Increased levels of interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1 have been found in bronchoalveolar lavage fluid of acute respiratory distress syndrome (ARDS) patients. The authors investigated whether inflammatory-activated microvascular pulmonary endothelial cells (HMVECL) regulate expression of IL-8 and MCP-1 in the alveolar epithelial cell line A549 and studied the effects of hypoxia (5% O2) and hyperoxia (85% O2). The authors observed significant up-regulation of IL-8 and MCP-1 expression in A549 cells that was independent from the IL-1 receptor pathway but was modified by oxygen tension. These data show that the pulmonary microvascular endothelium is able to regulate epithelial cell chemokine expression in a paracrine fashion.