Charalambos Tsagogiorgas

Effects of positive end-expiratory pressure on respiratory function and hemodynamics in patients with acute respiratory failure with and without intra-abdominal hypertension: a pilot study

IntroductionTo investigate the effects of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) with normal intra-abdominal pressure (IAP < 12 mmHg) and with intra-abdominal hypertension (IAH, defined as IAP ≥ 12 mmHg) during lung protective ventilation and a decremental PEEP, a prospective, observational clinical pilot study was performed.MethodsTwenty patients with ALI/ARDS with normal IAP or IAH treated in the surgical intensive care unit in a university hospital were studied. The mean IAP in patients with IAH and normal IAP was 16 ± 3 mmHg and 8 ± 3 mmHg, respectively (P < 0.001). At different PEEP levels (5, 10, 15, 20 cmH2O) we measured respiratory mechanics, partitioned into its lung and chest wall components, alveolar recruitment, gas-exchange, hemodynamics, extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI).ResultsWe found that ALI/ARDS patients with IAH, as compared to those with normal IAP, were characterized by: a) no differences in gas-exchange, respiratory mechanics, partitioned into its lung and chest wall components, as well as hemodynamics and EVLWI/ITBVI; b) decreased elastance of the respiratory system and the lung, but no differences in alveolar recruitment and oxygenation or hemodynamics, when PEEP was increased at 10 and 15cmH2O; c) at higher levels of PEEP, EVLWI was lower in ALI/ARDS patients with IAH as compared with those with normal IAP.ConclusionsIAH, within the limits of IAP measured in the present study, does not affect interpretation of respiratory mechanics, alveolar recruitment and hemodynamics.

Quantitative Renal Perfusion Measurements in a Rat Model of Acute Kidney Injury at 3T: Testing Inter- and Intramethodical Significance of ASL and DCE-MRI

Objectives To establish arterial spin labelling (ASL) for quantitative renal perfusion measurements in a rat model at 3 Tesla and to test the diagnostic significance of ASL and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in a model of acute kidney injury (AKI). Material and Methods ASL and DCE-MRI were consecutively employed on six Lewis rats, five of which had a unilateral ischaemic AKI. All measurements in this study were performed on a 3 Tesla MR scanner using a FAIR True-FISP approach and a TWIST sequence for ASL and DCE-MRI, respectively. Perfusion maps were calculated for both methods and the cortical perfusion of healthy and diseased kidneys was inter- and intramethodically compared using a region-of-interest based analysis. Results/Significance Both methods produce significantly different values for the healthy and the diseased kidneys (P<0.01). The mean difference was 147±47 ml/100 g/min and 141±46 ml/100 g/min for ASL and DCE-MRI, respectively. ASL measurements yielded a mean cortical perfusion of 416±124 ml/100 g/min for the healthy and 316±102 ml/100 g/min for the diseased kidneys. The DCE-MRI values were systematically higher and the mean cortical renal blood flow (RBF) was found to be 542±85 ml/100 g/min (healthy) and 407±119 ml/100 g/min (AKI). Conclusion Both methods are equally able to detect abnormal perfusion in diseased (AKI) kidneys. This shows that ASL is a capable alternative to DCE-MRI regarding the detection of abnormal renal blood flow. Regarding absolute perfusion values, nontrivial differences and variations remain when comparing the two methods.

N-octanoyl-Dopamine Is an Agonist at the Capsaicin Receptor TRPV1 and Mitigates Is Chemia-Induced Acute Kidney Injury in Rat

Since stimulation of transient receptor potential channels of the vanilloid receptor subtype 1 (TRPV1) mitigates acute kidney injury (AKI) and endogenous N-acyl dopamine derivatives are able to activate TRPV1, we tested if synthetic N-octanoyl-dopamine (NOD) activates TRPV1 and if it improves AKI. These properties of NOD and its intrinsic anti-inflammatory character were compared with those of dopamine (DA). TRPV1 activation and anti-inflammatory properties of NOD and DA were tested using primary cell cultures in vitro. The influence of NOD and DA on AKI was tested in a prospective, randomized, controlled animal study with 42 inbred male Lewis rats (LEW, RT1), treated intravenously with equimolar concentrations of DA or NOD one hour before the onset of warm ischemia and immediately before clamp release. NOD, but not DA, activates TRPV1 channels in isolated dorsal root ganglion neurons (DRG) that innervate several tissues including kidney. In TNFα stimulated proximal tubular epithelial cells, inhibition of NFκB and subsequent inhibition of VCAM1 expression by NOD was significantly stronger than by DA. NOD improved renal function compared to DA and saline controls. Histology revealed protective effects of NOD on tubular epithelium at day 5 and a reduced number of monocytes in renal tissue of DA and NOD treated rats. Our data demonstrate that NOD but not DA activates TRPV1 and that NOD has superior anti-inflammatory properties in vitro. Although NOD mitigates deterioration in renal function after AKI, further studies are required to assess to what extend this is causally related to TRPV1 activation and/or desensitization.

Enhancing tissue repair in annulus fibrosus defects of the intervertebral disc: analysis of a bio‐integrative annulus implant in an in‐vivo ovine model

Annulus fibrosus repair techniques for the intervertebral disc (IVD) address the unsolved problem of reherniation after IVD herniation and might facilitate the development of nucleus pulposus replacement techniques for IVD diseases. This study investigates the suitability of a bio‐integrative annulus implant.Standardized box defects were applied to the annulus L3/4 and L4/5 of 16 sheep, followed by randomized insertion of the textile polyglycolic acid/polyvinylidene fluoride annulus implant in one of the defects. Explantation was conducted after 2, 6 and 12 weeks, followed by provocative pressure testing and histological analysis. At 2 weeks’ follow‐up, all specimens of the control defect group demonstrated uncontained herniated nucleus pulposus tissue in the annulus defects. For the treated specimens, the annulus implant consistently provided an effective barrier for herniating nucleus pulposus tissue, with no implant dislocation at all time‐points. After 2 weeks, a homogeneous cell infiltration of the annulus implant was observed, leading to a progressive directional matrix build‐up. Repair tissue thickness was significantly stronger with the annulus implant at all follow‐ups (p < 0.01). No pronounced foreign body reaction and no difference in the amount of supra‐annular scar tissue over the defect sites were observed. The implantation procedure inflicted annulus damage adjacent to the defect. At later time‐points, however, no difference in comparison with the control defect group was evident. The investigated biointegrative annulus implant showed promising results with regard to biointegration, enhancement of repair tissue and function as a mechanical barrier in an ovine model.

Dopamine and Lipophilic Derivates Protect Cardiomyocytes against Cold Preservation Injury

Donor heart allografts are extremely susceptible to prolonged static cold storage. Because donor treatment with low-dose dopamine improves clinical outcome after heart transplantation, we tested the hypothesis that dopamine and its lipophilic derivate, N-octanoyl dopamine (NOD), protect cardiomyocytes from cold storage injury. Neonatal rat cardiomyocytes were treated with dopamine or NOD or left untreated and subsequently subjected to static cold storage (8–12 hours). Dopamine- and NOD-treated cardiomyocytes displayed a better viability compared with untreated cells after hypothermia. In untreated cardiomyocytes, cell damage was reflected by lactate dehydrogenase (LDH) release and a decrease in intracellular ATP. NOD was approximately 20-fold more potent than dopamine. Similarly to cardiomyocytes in vitro, rat hearts perfused with NOD before explantation showed significantly lower LDH release after static cold storage. ATP regeneration and spontaneous contractions after cold storage and rewarming only occurred in treated cardiomyocytes. Hypothermia severely attenuated isoprenaline-induced cAMP formation in control but not in dopamine- or NOD-treated cells. Esterified derivates of NOD with redox potential and lipophilic side chains reduced cell damage during cold storage similarly to NOD. In contrast to dopamine, neither NOD nor its derivates induced a significant β-adrenoceptor–mediated elevation of cellular cAMP levels. The β1-adrenoceptor antagonist atenolol and D1/D2 receptor antagonist fluphenazine had no impact on the protective effect of NOD or dopamine. We conclude that dopamine as well as NOD treatment mitigates cold preservation injury to cardiomyocytes. The beneficial effects are independent of β-adrenoceptor or dopaminergic receptor stimulation but correlate with redox potential and lipophilic properties.

Semifluorinated alkanes - A new class of excipients suitable for pulmonary drug delivery

INTRODUCTION Semifluorinated alkanes (SFAs) are considered as diblock molecules with fluorocarbon and hydrocarbon segments. Unlike Perfluorocarbons (PFCs), SFAs have the potential to dissolve several lipophilic or water-insoluble substances. This makes them possibly suitable as new excipients for inhalative liquid drug carrier systems. PURPOSE The aim of the study was to compare physico-chemical properties of different SFAs and then to test their respective effects in healthy rabbit lungs after nebulisation. METHODS Physico-chemical properties of four different SFAs, i.e. Perfluorobutylpentane (F4H5), Perfluorohexylhexane (F6H6), Perfluorohexyloctane (F6H8) and Perfluorohexyldodecane (F6H12) were measured. Based on these results, aerosol characteristics of two potential candidates suitable as excipients for pulmonary drug delivery, i.e. F6H8 and F4H5, were determined by laser light diffraction. Tracheotomised and ventilated New Zealand White rabbits were nebulised with either a high- or a low dose of SFAs (F6H8(low/high) and F4H5(low/high)) or saline (NaCl). Ventilated healthy animals served as controls (Sham). Arterial blood gases, lung mechanics, heart rate and blood pressure were recorded prior to nebulisation and in 30 min intervals during the 6-h study period. RESULTS Out of the four SFAs studied initially, no satisfactory behaviour as a solvent has to be expected because of low lipophilicity for F6H6. Output rate during aerosolisation was very low for F6H12. F6H8 and F4H5 presented comparable aerosolisation characteristics and lipophilicity and were therefore tested in the in vivo model. Aerosol therapy, either SFAs or saline, impaired paO2/FiO2 ratio, dynamic lung compliance and respiratory mechanics in all groups, except for F4H5(low) group which behaved like the control group (Sham). F4H5(low) had no adverse effects on gas exchange or pulmonary mechanics. CONCLUSIONS Perfluorobutylpentane (F4H5) in a low-dose application may be suitable as a new inhalable excipient in SFA-based pulmonary drug delivery systems for lipophilic or water-insoluble substances.

Open lung approach with low tidal volume mechanical ventilation attenuates lung injury in rats with massive brain damage.

IntroductionThe ideal ventilation strategy for patients with massive brain damage requires better elucidation. We hypothesized that in the presence of massive brain injury, a ventilation strategy using low (6 milliliters per kilogram ideal body weight) tidal volume (VT) ventilation with open lung positive end-expiratory pressure (LVT/OLPEEP) set according to the minimal static elastance of the respiratory system, attenuates the impact of massive brain damage on gas-exchange, respiratory mechanics, lung histology and whole genome alterations compared with high (12 milliliters per kilogram ideal body weight) VT and low positive end-expiratory pressure ventilation (HVT/LPEEP).MethodsIn total, 28 adult male Wistar rats were randomly assigned to one of four groups: 1) no brain damage (NBD) with LVT/OLPEEP; 2) NBD with HVT/LPEEP; 3) brain damage (BD) with LVT/OLPEEP; and 4) BD with HVT/LPEEP. All animals were mechanically ventilated for six hours. Brain damage was induced by an inflated balloon catheter into the epidural space. Hemodynamics was recorded and blood gas analysis was performed hourly. At the end of the experiment, respiratory system mechanics and lung histology were analyzed. Genome wide gene expression profiling and subsequent confirmatory quantitative polymerase chain reaction (qPCR) for selected genes were performed.ResultsIn NBD, both LVT/OLPEEP and HVT/LPEEP did not affect arterial blood gases, as well as whole genome expression changes and real-time qPCR. In BD, LVT/OLPEEP, compared to HVT/LPEEP, improved oxygenation, reduced lung damage according to histology, genome analysis and real-time qPCR with decreased interleukin 6 (IL-6), cytokine-induced neutrophil chemoattractant 1 (CINC)-1 and angiopoietin-4 expressions. LVT/OLPEEP compared to HVT/LPEEP improved overall survival.ConclusionsIn BD, LVT/OLPEEP minimizes lung morpho-functional changes and inflammation compared to HVT/LPEEP.

N-Octanoyl Dopamine Inhibits the Expression of a Subset of κB Regulated Genes: Potential Role of p65 Ser276 Phosphorylation

Background and Purpose Catechol containing compounds have anti-inflammatory properties, yet for catecholamines these properties are modest. Since we have previously demonstrated that the synthetic dopamine derivative N-octanoyl dopamine (NOD) has superior anti-inflammatory properties compared to dopamine, we tested NOD in more detail and sought to elucidate the molecular entities and underlying mechanism by which NOD down-regulates inflammation. Experimental Approach Genome wide gene expression profiling of human umbilical vein endothelial cells (HUVECs) was performed after stimulation with TNF-α or in the combination with NOD. Confirmation of these differences, NFκB activation and the molecular entities that were required for the anti-inflammatory properties were assessed in subsequent experiments. Key Results Down regulation of inflammatory genes by NOD occurred predominantly for κB regulated genes, however not all κB regulated genes were affected. These findings were explained by inhibition of RelA phosphorylation at Ser276. Leukocyte adherence to TNF-α stimulated HUVECs was inhibited by NOD and was reflected by a diminished expression of adhesion molecules on HUVECs. NOD induced HO-1 expression, but this was not required for inhibition of NFκB. The anti-inflammatory effect of NOD seems to involve the redox active catechol structure, although the redox active para-dihydroxy benzene containing compounds also displayed anti-inflammatory effects, provided that they were sufficiently hydrophobic. Conclusions and Implications The present study highlighted important mechanisms and molecular entities by which dihydroxy benzene compounds exert their potential anti-inflammatory action. Since NOD does not have hemodynamic properties, NOD seems to be a promising candidate drug for the treatment of inflammatory diseases.

Improvement of oxygen supply by an artificial carrier in combination with normobaric oxygenation decreases the volume of tissue hypoxia and tissue damage from transient focal cerebral ischemia

Tissue hypoxia may play an important role in the development of ischemic brain damage. In the present study we investigated in a rat model of transient focal brain ischemia the neuroprotective effects of increasing the blood oxygen transport capacity by applying a semifluorinated alkane (SFA)-containing emulsion together with normobaric hyperoxygenation (NBO). The spread of tissue hypoxia was studied using pimonidazole given prior to filament-induced middle cerebral artery occlusion (MCAO, 2 h). Treatment consisted of intravenous injection of saline or the SFA-containing emulsion (0.5 or 1.0 ml/100g body weight; [SFA(0.5) or SFA(1.0)]) either upon establishing MCAO (early treatment) or after filament removal (delayed treatment). After injection NBO was administered for 8 h (early treatment) or 6 h (delayed treatment). Experiments were terminated 8 or 24 h after MCAO. In serial brain sections tissue hypoxia and irreversible cell damage were quantitatively determined. Furthermore, we studied hypoxia-related gene expression (VEGF, flt-1). Early treatment significantly (p<0.05) reduced the volumes of tissue damage (8 h after MCAO: SFA(1.0), 57±34 mm³; controls, 217±70 mm³; 24 h after MCAO: SFA(1.0), 189±82 mm³; controls, 317±60 mm³) and of P-Add immunoreactivity (8 h after MCAO: SFA(1.0), 261±37 mm³; controls, 339±26 mm³; 24h after MCAO: SFA(1.0), 274±47 mm³; controls, 364±46 mm³). Delayed treatment was comparably successful. The volume of the hypoxic penumbra was not decreased by the treatment. Similarly, VEGF and flt-1 mRNA levels did not differ between the experimental groups. From these data we conclude that increasing the blood oxygen transport capacity in the plasma compartment provides a neuroprotective effect by alleviating the severity of hypoxia to a level sufficient to prevent cells from transition into irreversible damage.

N-Octanoyl Dopamine for Donor Treatment in a Brain-death Model of Kidney and Heart Transplantation.

Background This study investigated the potential use of N-octanoyl dopamine (NOD) in donor management to ameliorate the damage caused by brain death and ischemia-reperfusion injury in a rat model of kidney and heart transplantation. Methods Brain-dead Fisher rats were treated for 6 hours with either saline or saline plus NOD. Orthotopic kidney and heterotopic heart transplantation were performed in different Lewis recipient rats. The right donor kidneys were stored for biochemical analysis. Blood samples were taken from the donor and on several days after transplantation from the recipient. All grafts were harvested after 7 days. Results There was no effect on donor heart rate and blood pressure under NOD treatment. The release of lactate dehydrogenase (LDH) during brain death was reduced in the NOD group. The right kidneys from NOD-preconditioned animals revealed diminished expression of the proinflammatory cell adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1). Nevertheless, there was no difference in renal infiltration with ED1 (CD68) or major histocompatibility complex (MHC) class II–positive cells. Recipients receiving a renal allograft from NOD-treated donors had a significantly better renal function at day 1 after transplantation. Banff-grading after 7 days showed significantly reduced scores for tubulitis and vasculitis in the grafts of these recipients. In the heart allograft recipients, lower plasma LDH levels were observed. Conclusions Donor preconditioning with NOD leads to better graft function and reduced acute rejection in untreated renal allograft recipients without displaying adverse effects on heart allografts.