Dermatochirurgie bei Kindern: Gegenwärtiger Stand zu Indikation, Anästhesie, Analgesie und potentiellen perioperativen Komplikationen.

HINTERGRUND: Anders als Erwachsene benötigen Kinder bei dermatochirurgischen Eingriffen besondere Aufmerksamkeit; die Anwendung verschiedener Analgetika, Anästhetika oder Sedativa erfordert eine gründliche Kenntnis von Pharmakokinetik und -dynamik der Medikamente. Außerdem können Medikamente zur Sedierung/Allgemeinanästhesie bei operierten Kindern zu Anästhesie- oder Analgesie-bedingten Komplikationen einschließlich Störungen der geistigen Entwicklung führen. ZIEL: Auf Basis unserer klinischen Erfahrung und einer Literaturübersicht stellen wir die gängigsten in der pädiatrischen Dermatochirurgie verwendeten Analgetika, Anästhetika und Sedativa dar und diskutieren Risiken und Komplikationen nach dermatochirurgischen Eingriffen. ERGEBNISSE: Topische Anästhetika können bei Kindern für oberflächliche dermatologische Eingriffe oder vor einer Infiltrationsanästhesie eingesetzt werden. Die Berechnung der empfohlenen Maximaldosen auf Basis des Körpergewichts ist erforderlich, um eine Überdosierung von Lokalanästhetika zu vermeiden. Die Allgemeinanästhesie gilt bei der Dermatochirurgie als sicher und hat eine geringe Nebenwirkungsrate. Allerdings ist bei Kindern im ersten Lebensjahr aufgrund potentieller langfristiger neurologischer Nebenwirkungen Vorsicht angebracht. NSAR und Opioide spielen bei der Analgesie von Kindern eine bedeutende Rolle. SCHLUSSFOLGERUNGEN: Dieser Artikel gibt eine Übersicht über die derzeit verfügbaren Daten zu Analgesie, Anästhesie und Komplikationen, die im Rahmen der pädiatrischen Dermatochirurgie auftreten können. Diese Daten können dabei helfen, die Sicherheit und Qualität der Versorgung zu optimieren und die Beratung der Eltern zu verbessern.

Dermatologic surgery in children: an update on indication, anesthesia, analgesia and potential perioperative complications.

BACKGROUND: Children undergoing dermatosurgical procedures require, unlike adults, particular attention; the administration of various analgesics, anesthetics or sedatives requires a thorough knowledge of drug pharmacokinetics and pharmacodynamics. Furthermore, there are concerns that drugs used for sedation/general anesthesia may result in anesthetic/analgesic complications in children undergoing surgery, with a risk of impaired mental development. OBJECTIVES: Based on our clinical experience and a literature review, we illustrate the most commonly used analgesic, anesthetic and sedative drugs in pediatric dermatosurgery, and identify risk factors and complications following dermatosurgical procedures. RESULTS: Topical anesthetics can be used in children for superficial dermatologic procedures or prior to infiltration anesthesia. Maximum recommended doses based on body weight should be calculated in order to avoid overdosage of local anesthetics. General anesthesia in dermatosurgery is considered safe and has a low rate of side effects. However, caution is advised in children under the age of one due to potential long-term neurological side-effects. NSAIDs and opioids play a significant role in analgesia for children. CONCLUSIONS: This article reviews currently available data on analgesia, anesthesia and complications that may arise in pediatric dermatosurgery. These data may be useful in optimizing the safety and quality of care and in improving parent counseling.

Role of the Purinergic Receptor P2XR4 After Blunt Chest Trauma in Cigarette Smoke-Exposed Mice.

Both acute and chronic lung injury are associated with up-regulation of the pulmonary expression of the purinergic receptors P2XR4 and P2XR7. Genetic deletion or blockade of P2XR7 attenuated pulmonary hyperinflammation, but simultaneous P2XR4 up-regulation compensated for P2XR7 deletion. Therefore, we tested the hypothesis whether genetic P2XR4 deletion would attenuate the pulmonary inflammatory response and thereby improve organ function after blunt chest trauma in mice with and without pretraumatic cigarette smoke (CS) exposure.After 3 weeks to 4 weeks of exposure to CS, anesthetized wildtype or P2XR4 mice (n = 32) underwent a blast wave-induced blunt chest trauma followed by 4 h of lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline support to maintain mean arterial pressure >55 mm Hg. Hemodynamics, lung mechanics, gas exchange, and acid-base status were measured together with blood and tissue cytokine and chemokine concentrations, heme oxygenase-1, B-cell lymphoma-extra large (Bcl-xL), endogenous nuclear factor-κB inhibitor (IκBα) expression, nitrotyrosine formation, purinergic receptor expression, and histological scoring.Despite a significant increase in the histopathology score in both CS-exposed groups, neither CS exposure nor P2XR4 deletion had any significant effect on post-traumatic pulmonary function and inflammatory response. However, P2XR4 deletion was associated with attenuated impairment of glucose homeostasis and acid-base-status after CS exposure and chest trauma.In conclusion, genetic P2XR4 deletion failed to attenuate the acute post-traumatic pulmonary inflammatory response. The improved glucose homeostasis and acid-base-status after CS exposure in the P2XR4 group was possibly due to less alveolar hypoxia-induced right ventricular remodeling resulting in preserved liver metabolic capacity.

The Role of Cystathionine-γ-Lyase In Blunt Chest Trauma in Cigarette Smoke Exposed Mice.

Pretraumatic cigarette smoke (CS) exposure aggravates posttraumatic acute lung injury (ALI). Cystathionine-γ-lyase (CSE) protects against ALI and CS exposure-induced chronic obstructive lung disease (COPD). Therefore, we tested the hypothesis whether genetic CSE knockout (CSE) would aggravate posttraumatic ALI after CS exposure. After 3 to 4 weeks of CS exposure, anesthetized wild-type (WT) and CSE mice underwent blunt chest trauma, surgical instrumentation and 4 h of lung-protective mechanical ventilation. We measured hemodynamics, lung mechanics, gas exchange, metabolism, and acid-base status together with blood and tissue cytokine and chemokine levels, tissue expression of mediator proteins, parameters of oxidative and nitrosative stress, and histology. CSE mice without CS exposure showed higher cytokine and chemokine levels, and this was further enhanced by CS exposure, particularly in males. CS exposure in WT mice aggravated posttraumatic alveolar membrane thickening, dystelectasis, and inflammatory cell accumulation, which was associated with higher thoracopulmonary compliance. Pretraumatic CS exposure in CSE mice produced a similar response, except for less alveolar membrane thickening, most likely due to lung hyperinflation. CS-exposed WT mice showed the most pronounced metabolic acidosis, while CS exposure in CSE mice resulted in the lowest blood glucose levels. Urinary output and anesthesia rate were highest in male CS-exposed CSE animals. In conclusion, in murine acute-on-chronic pulmonary disease, CSE knockout aggravated posttraumatic inflammation, which was further worsened upon pretraumatic CS exposure, and this effect was particularly pronounced in males. Hence, maintaining CSE expression is critically important for stress adaptation during ALI and CS-induced COPD, most likely in a gender-dependent manner.

Association of Kidney Tissue Barrier Disrupture and Renal Dysfunction in Resuscitated Murine Septic Shock.

Septic shock-related kidney failure is characterized by almost normal morphological appearance upon pathological examination. Endothelial barrier disrupture has been suggested to be of crucial importance for septic shock-induced organ dysfunction. Therefore, in murine resuscitated cecal ligation and puncture (CLP)-induced septic shock, we tested the hypothesis whether there is a direct relationship between the kidney endothelial barrier injury and renal dysfunction. Anesthetized mice underwent CLP, and 15 h later, were anesthetized again and surgically instrumented for a 5-h period of intensive care comprising lung-protective mechanical ventilation, fluid resuscitation, continuous i.v. norepinephrine to maintain target hemodynamics, and measurement of creatinine clearance (CrCl). Animals were stratified according to low or high CrCl. Nitrotyrosine formation, expression of the inducible isoform of the nitric oxide synthase, and blood cytokine (tumor necrosis factor, interleukin-6, interleukin-10) and chemokine (monocyte chemoattractant protein-1, keratinocyte-derived chemokine) levels were significantly higher in animals with low CrCl. When plotted against CrCl and neutrophil gelatinase-associated lipocalin levels, extravascular albumin accumulation, and tissue expression of the vascular endothelial growth factor and angiopoietin-1 showed significant mathematical relationships related to kidney (dys)function. Preservation of the constitutive expression of the hydrogen sulfide producing enzyme cystathione-γ-lyase was associated with maintenance of organ function. The direct quantitative relation between microvascular leakage and kidney (dys)function may provide a missing link between near-normal tissue morphology and septic shock-related renal failure, thus further highlighting the important role of vascular integrity in septic shock-related renal failure.

Exposure to 100% Oxygen Abolishes the Impairment of Fracture Healing after Thoracic Trauma.

In polytrauma patients a thoracic trauma is one of the most critical injuries and an important trigger of post-traumatic inflammation. About 50% of patients with thoracic trauma are additionally affected by bone fractures. The risk for fracture malunion is considerably increased in such patients, the pathomechanisms being poorly understood. Thoracic trauma causes regional alveolar hypoxia and, subsequently, hypoxemia, which in turn triggers local and systemic inflammation. Therefore, we aimed to unravel the role of oxygen in impaired bone regeneration after thoracic trauma. We hypothesized that short-term breathing of 100% oxygen in the early post-traumatic phase ameliorates inflammation and improves bone regeneration. Mice underwent a femur osteotomy alone or combined with blunt chest trauma 100% oxygen was administered immediately after trauma for two separate 3 hour intervals. Arterial blood gas tensions, microcirculatory perfusion and oxygenation were assessed at 3, 9 and 24 hours after injury. Inflammatory cytokines and markers of oxidative/nitrosative stress were measured in plasma, lung and fracture hematoma. Bone healing was assessed on day 7, 14 and 21. Thoracic trauma induced pulmonary and systemic inflammation and impaired bone healing. Short-term exposure to 100% oxygen in the acute post-traumatic phase significantly attenuated systemic and local inflammatory responses and improved fracture healing without provoking toxic side effects, suggesting that hyperoxia could induce anti-inflammatory and pro-regenerative effects after severe injury. These results suggest that breathing of 100% oxygen in the acute post-traumatic phase might reduce the risk of poorly healing fractures in severely injured patients.

Blunt Chest Trauma in Mice after Cigarette Smoke-Exposure: Effects of Mechanical Ventilation with 100% O2.

Cigarette smoking (CS) aggravates post-traumatic acute lung injury and increases ventilator-induced lung injury due to more severe tissue inflammation and apoptosis. Hyper-inflammation after chest trauma is due to the physical damage, the drop in alveolar PO2, and the consecutive hypoxemia and tissue hypoxia. Therefore, we tested the hypotheses that 1) CS exposure prior to blunt chest trauma causes more severe post-traumatic inflammation and thereby aggravates lung injury, and that 2) hyperoxia may attenuate this effect. Immediately after blast wave-induced blunt chest trauma, mice (n=32) with or without 3-4 weeks of CS exposure underwent 4 hours of pressure-controlled, thoraco-pulmonary compliance-titrated, lung-protective mechanical ventilation with air or 100% O2. Hemodynamics, lung mechanics, gas exchange, and acid-base status were measured together with blood and tissue cytokine and chemokine concentrations, heme oxygenase-1 (HO-1), activated caspase-3, and hypoxia-inducible factor 1-α (HIF-1α) expression, nuclear factor-κB (NF-κB) activation, nitrotyrosine formation, purinergic receptor 2X4 (P2XR4) and 2X7 (P2XR7) expression, and histological scoring. CS exposure prior to chest trauma lead to higher pulmonary compliance and lower PaO2 and Horovitz-index, associated with increased tissue IL-18 and blood MCP-1 concentrations, a 2-4-fold higher inflammatory cell infiltration, and more pronounced alveolar membrane thickening. This effect coincided with increased activated caspase-3, nitrotyrosine, P2XR4, and P2XR7 expression, NF-κB activation, and reduced HIF-1α expression. Hyperoxia did not further affect lung mechanics, gas exchange, pulmonary and systemic cytokine and chemokine concentrations, or histological scoring, except for some patchy alveolar edema in CS exposed mice. However, hyperoxia attenuated tissue HIF-1α, nitrotyrosine, P2XR7, and P2XR4 expression, while it increased HO-1 formation in CS exposed mice. Overall, CS exposure aggravated post-traumatic inflammation, nitrosative stress and thereby organ dysfunction and injury; short-term, lung-protective, hyperoxic mechanical ventilation have no major beneficial effect despite attenuation of nitrosative stress, possibly due to compensation of by regional alveolar hypoxia and/or consecutive hypoxemia, resulting in down-regulation of HIF-1α expression.

Physiological and immune-biological characterization of a long-term murine model of blunt chest trauma.

Blunt chest trauma causes pulmonary and systemic inflammation. It is still a matter of debate whether the long-term course of this inflammatory response is associated with persistent impairment of lung function. We hypothesized that an increase of inflammatory biomarkers may still be present at later time points after blunt chest trauma, eventually, despite normalized lung mechanics and gas exchange. Anesthetized spontaneously breathing male C57BL/6J mice underwent a blast wave-induced blunt chest trauma or sham procedure. Twelve and 24 h later, blood gases and lung mechanics were measured, together with blood, bronchoalveolar lavage (BAL), and tissue cytokine concentrations (multiplex cytokine kit); heme oxygenase 1 (HO-1), activated caspase-3, Bcl-xL, and Bax expression (Western blotting); nuclear factor-κB activation (electrophoretic mobility shift assay); nitrotyrosine formation; and purinergic (P2XR4 and P2XR7) receptor expression (immunohistochemistry). Histological damage was assessed by hematoxylin and eosin and periodic acid-Schiff staining. High-resolution respirometry allowed assessing mitochondrial respiration in diaphragm biopsies. Chest trauma significantly increased tissue and BAL cytokine levels, associated with a significant increase in HO-1, purinergic receptor expression, and tissue nitrotyrosine formation. In contrast, lung mechanics, gas exchange, and histological damage did not show any significant difference between sham and trauma groups. Activation of the immune response remains present at later time points after murine blunt chest trauma. Discordance of the increased local inflammatory response and preserved pulmonary function may be explained by a dissociation of the immune response and lung function, such as previously suggested after experimental sepsis.

Shedding of APP limits its synaptogenic activity and cell adhesion properties.

The amyloid precursor protein (APP) plays a central role in Alzheimer's disease (AD) and has essential synapse promoting functions. Synaptogenic activity as well as cell adhesion properties of APP presumably depend on trans-cellular dimerization via its extracellular domain. Since neuronal APP is extensively processed by secretases, it raises the question if APP shedding affects its cell adhesion and synaptogenic properties. We show that inhibition of APP shedding using cleavage deficient forms of APP or a dominant negative α-secretase strongly enhanced its cell adhesion and synaptogenic activity suggesting that synapse promoting function of APP is tightly regulated by α-secretase mediated processing, similar to other trans-cellular synaptic adhesion molecules.

Amyloid precursor protein dimerization and synaptogenic function depend on copper binding to the growth factor-like domain.

Accumulating evidence suggests that the copper-binding amyloid precursor protein (APP) has an essential synaptic function. APP synaptogenic function depends on trans-directed dimerization of the extracellular E1 domain encompassing a growth factor-like domain (GFLD) and a copper-binding domain (CuBD). Here we report the 1.75 Å crystal structure of the GFLD in complex with a copper ion bound with high affinity to an extended hairpin loop at the dimerization interface. In coimmunoprecipitation assays copper binding promotes APP interaction, whereas mutations in the copper-binding sites of either the GFLD or CuBD result in a drastic reduction in APP cis-orientated dimerization. We show that copper is essential and sufficient to induce trans-directed dimerization of purified APP. Furthermore, a mixed culture assay of primary neurons with HEK293 cells expressing different APP mutants revealed that APP potently promotes synaptogenesis depending on copper binding to the GFLD. Together, these findings demonstrate that copper binding to the GFLD of APP is required for APP cis-/trans-directed dimerization and APP synaptogenic function. Thus, neuronal activity or disease-associated changes in copper homeostasis likely go along with altered APP synaptic function.

Effects of glycemic control on glucose utilization and mitochondrial respiration during resuscitated murine septic shock.

BACKGROUND: This study aims to test the hypothesis whether lowering glycemia improves mitochondrial function and thereby attenuates apoptotic cell death during resuscitated murine septic shock. METHODS: Immediately and 6 h after cecal ligation and puncture (CLP), mice randomly received either vehicle or the anti-diabetic drug EMD008 (100 µg · g(-1)). At 15 h post CLP, mice were anesthetized, mechanically ventilated, instrumented and rendered normo- or hyperglycemic (target glycemia 100 ± 20 and 180 ± 50 mg · dL(-1), respectively) by infusing stable, non-radioactive isotope-labeled (13)C6-glucose. Target hemodynamics was achieved by colloid fluid resuscitation and continuous i.v. noradrenaline, and mechanical ventilation was titrated according to blood gases and pulmonary compliance measurements. Gluconeogenesis and glucose oxidation were derived from blood and expiratory glucose and (13)CO2 isotope enrichments, respectively; mathematical modeling allowed analyzing isotope data for glucose uptake as a function of glycemia. Postmortem liver tissue was analyzed for HO-1, AMPK, caspase-3, and Bax (western blotting) expression as well as for mitochondrial respiratory activity (high-resolution respirometry). RESULTS: Hyperglycemia lowered mitochondrial respiratory capacity; EMD008 treatment was associated with increased mitochondrial respiration. Hyperglycemia decreased AMPK phosphorylation, and EMD008 attenuated both this effect as well as the expression of activated caspase-3 and Bax. During hyperglycemia EMD008 increased HO-1 expression. During hyperglycemia, maximal mitochondrial oxidative phosphorylation rate was directly related to HO-1 expression, while it was unrelated to AMPK activation. According to the mathematical modeling, EMD008 increased the slope of glucose uptake plotted as a function of glycemia. CONCLUSIONS: During resuscitated, polymicrobial, murine septic shock, glycemic control either by reducing glucose infusion rates or EMD008 improved glucose uptake and thereby liver tissue mitochondrial respiratory activity. EMD008 effects were more pronounced during hyperglycemia and coincided with attenuated markers of apoptosis. The effects of glucose control were at least in part due to the up-regulation of HO-1 and activation of AMPK.

Adrenomedullin binding improves catecholamine responsiveness and kidney function in resuscitated murine septic shock.

PURPOSE: Adrenomedullin (ADM) has been referred to as a double-edged sword during septic shock: On one hand, ADM supplementation improved organ perfusion and function, attenuated systemic inflammation, and ultimately reduced tissue apoptosis and mortality. On the other hand, ADM overproduction can cause circulatory collapse and organ failure due to impaired vasoconstrictor response and reduced myocardial contractility. Since most of these data originate from un-resuscitated shock models, we tested the hypothesis whether the newly developed anti-ADM antibody HAM1101 may improve catecholamine responsiveness and thus attenuate organ dysfunction during resuscitated murine, cecal ligation and puncture (CLP)-induced septic shock. METHODS: Immediately after CLP, mice randomly received vehicle (phosphate-buffered saline, n = 11) or HAM1101 (n = 9; 2 µg·g(-1)). Fifteen hours after CLP, animals were anesthetized, mechanically ventilated, instrumented, and resuscitated with hydroxyethylstarch and continuous i.v. norepinephrine to achieve normotensive hemodynamics (mean arterial pressure > 50 to 60 mmHg). RESULTS: HAM1101 pretreatment reduced the norepinephrine infusion rates required to achieve hemodynamic targets, increased urine flow, improved creatinine clearance, and lowered neutrophil gelatinase-associated lipocalin blood levels, which coincided with reduced expression of the inducible nitric oxide synthase and formation of peroxynitrite (nitrotyrosine immunostaining) in the kidney and aorta, ultimately resulting in attenuated systemic inflammation and tissue apoptosis. CONCLUSIONS: During resuscitated murine septic shock, early ADM binding with HAM1101 improved catecholamine responsiveness, blunted the shock-related impairment of energy metabolism, reduced nitrosative stress, and attenuated systemic inflammatory response, which was ultimately associated with reduced kidney dysfunction and organ injury.

Temperature and cell-type dependency of sulfide effects on mitochondrial respiration.

Previous studies suggest that sulfide-induced inhibition of cytochrome c oxidase (cCox) and, consequently, the metabolic and toxic effects of sulfide are less pronounced at low body temperature. Because the temperature-dependent effects of sulfide on the inflammatory response are still a matter of debate, we investigated the impact of varying temperature on the cCox excess capacity and the mitochondrial sulfide oxidation by the sulfide-ubiquinone oxidoreductase in macrophage-derived cell lines (AMJ2-C11 and RAW 264.7). Using an oxygraph chamber, the inhibition of mitochondrial respiration was measured by stepwise titrations with sulfide and the nonmetabolizable cCox inhibitor sodium azide at 25°C and 37°C. Using the latter of the two inhibitors, the excess capacity of the cCox was obtained. Furthermore, we quantified the capacity of these cells to withstand sulfide inhibition by measuring the amount required to inhibit respiration by 50% and 90% and the viability of the cells after 24-h exposure to 100 ppm of hydrogen sulfide. At low titration rates, the AMJ2-C11 cells, but not the RAW 264.7 cells, increased their capacity to withstand exogenously added sulfide. This effect was even greater at 25°C than at 37°C. Furthermore, only the AMJ2-C11 cells remained viable after sulfide exposure for 24 h. In contrast, only in the RAW 264.7 cells that an increase in cCox excess capacity was found at low temperatures. In macrophage-derived cell lines, both the excess capacity of cCox and the efficiency of sulfide elimination may increase at low temperatures. These properties may modify the effects of sulfide in immune cells and, potentially, the inflammatory response during sulfide exposure at different body temperatures.

Ethyl pyruvate for the treatment of acetaminophen intoxication: alternative to N-acetylcysteine?

N-acetylcysteine is the classical antidote for acetaminophen overdose-induced hepatotoxicity, but its efficacy is limited by the need for early and only temporary treatment. Therefore, Yang and colleagues tested the hypothesis of whether ethyl pyruvate--another anti-inflammatory and antioxidant compound, which they had previously shown to protect against liver injury of various other etiologies--may allow circumventing these limitations. While ethyl pyruvate improved liver regeneration when administered early and during a limited period only, the opposite response was present both after delayed as well as prolonged treatment. The authors concluded that prolonged anti-inflammatory treatment is detrimental after acetaminophen intoxication-induced liver damage. On the one hand, this research paper confirms the need for biomarkers to monitor organ recovery after acetaminophen. On the other hand, this paper adds to the ongoing discussion on the usefulness of ethyl pyruvate as a resuscitation fluid in the critically ill.

Inhaled hydrogen sulfide induces suspended animation, but does not alter the inflammatory response after blunt chest trauma.

The treatment of acute lung injury and septic complications after blunt chest trauma remains a challenge. Inhaled hydrogen sulfide (H2S) may cause a hibernation-like metabolic state, which refers to an attenuated systemic inflammatory response. Therefore, we tested the hypothesis that inhaled H2S-induced suspended animation may attenuate the inflammation after pulmonary contusion. Male Sprague-Dawley rats were subjected to blunt chest trauma (blast wave) or sham procedure and subsequently exposed to a continuous flow of H2S (100 ppm) or control gas for 6 h. Body temperature and activity were measured by an implanted transmitter. At 6, 24, or 48 h after trauma, animals were killed, and the cellular contents of bronchoalveolar lavage (BAL) as well as cytokine concentrations in BAL, plasma, and culture supernatants of blood mononuclear cells, Kupffer cells, splenic macrophages, and splenocytes were determined. Hydrogen sulfide inhalation caused a significant reduction in body temperature and activity. The trauma-induced increase in alveolar macrophage counts was abrogated 48 h after trauma when animals received H2S, whereas the trauma-induced increase in neutrophil counts was unaltered. Furthermore, H2S inhalation partially attenuated the mediator release in BAL and culture supernatants of Kupffer cells as well as splenic cells; it altered plasma cytokine concentrations but did not affect the trauma-induced changes in mononuclear cell culture supernatants. These findings indicate that inhaled H2S induced a reduced metabolic expenditure and partially attenuated inflammation after trauma. Nevertheless, in contrast to hypoxic- or pathogen-induced lung injury, H2S treatment appears to have no protective effect after blunt chest trauma.

APP dimer formation is initiated in the endoplasmic reticulum and differs between APP isoforms.

The amyloid precursor protein (APP) is part of a larger gene family, which has been found to form homo- or heterotypic complexes with its homologues, whereby the exact molecular mechanism and origin of dimer formation remains elusive. In order to assess the cellular location of dimerization, we have generated a cell culture model system in CHO-K1 cells, stably expressing human APP, harboring dilysine-based organelle sorting motifs [KKAA-endoplasmic reticulum (ER); KKFF-Golgi], accomplishing retention within early secretory compartments. We show that APP exists as disulfide-bonded dimers upon ER retention after it was isolated from cells, and analyzed by SDS-polyacrylamide gel electrophoresis under non-reducing conditions. In contrast, strong denaturing and reducing conditions, or deletion of the E1 domain, resulted in the disappearance of those dimers. Thus we provide first evidence that a fraction of APP can associate via intermolecular disulfide bonds, likely generated between cysteines located in the extracellular E1 domain. We particularly visualize APP dimerization itself and identified the ER as subcellular compartment of its origin using biochemical or split GFP approaches. Interestingly, we also found that minor amounts of SDS-resistant APP dimers were located to the cell surface, revealing that once generated in the oxidative environment of the ER, dimers remained stably associated during transport. In addition, we show that APP isoforms encompassing the Kunitz-type protease inhibitor (KPI) domain exhibit a strongly reduced ability to form cis-directed dimers in the ER, whereas trans-mediated cell aggregation of Drosophila Schneider S2-cells was isoform independent. Thus, suggesting that steric properties of KPI-APP might be the cause for weaker cis-interaction in the ER, compared to APP695. Finally, we provide evidence that APP/APLP1 heterointeractions are likewise initiated in the ER.

Structural aspects and physiological consequences of APP/APLP trans-dimerization.

The amyloid precursor protein (APP) is one of the key proteins in Alzheimer's disease (AD), as it is the precursor of amyloid ß (Aß) peptides accumulating in amyloid plaques. The processing of APP and the pathogenic features of especially Aß oligomers have been analyzed in detail. Remarkably, there is accumulating evidence from cell biological and structural studies suggesting that APP and its mammalian homologs, the amyloid precursor-like proteins (APLP1 and APLP2), participate under physiological conditions via trans-cellular dimerization in synaptogenesis. This offers the possibility that loss of synapses in AD might be partially explained by dysfunction of APP/APLPs cell adhesion properties. In this review, structural characteristics of APP trans-cellular interaction will be placed critically in context with its putative physiological functions focusing on cell adhesion and synaptogenesis.

Cardiopulmonary, histologic, and inflammatory effects of intravenous Na2S after blunt chest trauma-induced lung contusion in mice.

BACKGROUND: When used as a pretreatment, hydrogen sulfide (H2S) either attenuated or aggravated lung injury. Therefore, we tested the hypothesis whether posttreatment intravenous Na2S (sulfide) may attenuate lung injury. METHODS: After blast wave blunt chest trauma or sham procedure, anesthetized and instrumented mice received continuous intravenous sulfide or vehicle while being kept at 37°C or 32°C core temperature. After 4 hours of pressure-controlled, thoracopulmonary compliance-titrated, lung-protective mechanical ventilation, blood and tissue were harvested for cytokine concentrations, heme oxygenase-1, IκBα, Bcl-Xl, and pBad expression (western blotting), nuclear factor-κB activation (electrophoretic mobility shift assay), and activated caspase-3, cystathionine-ß synthase and cystathionine-γ lyase (immunohistochemistry). RESULTS: Hypothermia caused marked bradycardia and metabolic acidosis unaltered by sulfide. Chest trauma impaired thoracopulmonary compliance and arterial Po2, again without sulfide effect. Cytokine levels showed inconsistent response. Sulfide increased nuclear factor-κB activation during normothermia, but this effect was blunted during hypothermia. While histologic lung injury was variable, both sulfide and hypothermia attenuated the trauma-related increase in heme oxygenase-1 expression and activated caspase-3 staining, which coincided with increased Bad phosphorylation and Bcl-Xl expression. Sulfide and hypothermia also attenuated the trauma-induced cystathionine-ß synthase and cystathionine-γ lyase expression. CONCLUSIONS: Posttreatment sulfide infusion after blunt chest trauma did not affect the impaired lung mechanics and gas exchange but attenuated stress protein expression and apoptotic cell death. This protective effect was amplified by moderate hypothermia. The simultaneous reduction in cystathionine-ß synthase and cystathionine-γ lyase expression supports the role of H2S-generating enzymes as an adaptive response during stress states.

Of mice and men (and sheep, swine etc.): the intriguing hemodynamic and metabolic effects of hydrogen sulfide (H2S).

Whether the hydrogen sulfide (H2S)-induced metabolic depression observed in awake rodents exists in larger species is controversial. Therefore, Derwall and colleagues exposed anesthetized and ventilated sheep to incremental H2S concentrations by means of an extracorporeal membrane oxygenator. H2S caused pulmonary vasoconstriction and metabolic acidosis at the highest concentration studied. Oxygen uptake and carbon dioxide production remained in the physiological range. The authors concluded that, beyond the effect of temperature, H2S hardly modifies metabolism at all. Since the highest H2S concentration caused toxic side effects (possibly due to an inhibition of mitochondrial respiration), the therapeutic use of inhaled H2S should be cautioned.