Alexy Tran-Dinh

High-Density Lipoproteins Limit Neutrophil-Induced Damage to the Blood–Brain Barrier in Vitro

Breakdown of the blood–brain barrier (BBB) is a key step associated with ischemic stroke and its increased permeability causes extravasation of plasma proteins and circulating leukocytes. Polymorphonuclear neutrophil (PMN) proteases may participate in BBB breakdown. We investigated the role of PMNs in ischemic conditions by testing their effects on a model of BBB in vitro, under oxygen-glucose deprivation (OGD) to mimic ischemia, supplemented or not with high-density lipoproteins (HDLs) to assess their potential protective effects. Human cerebral endothelial cells cultured on transwells were incubated for 4 hours under OGD conditions with or without PMNs and supplemented or not with HDLs or alpha-1 antitrypsin (AAT, an elastase inhibitor). The integrity of the BBB was then assessed and the effect of HDLs on PMN-induced proteolysis of extracellular matrix proteins was evaluated. The release of myeloperoxidase and matrix metalloproteinase 9 (MMP-9) by PMNs was quantified. Polymorphonuclear neutrophils significantly increased BBB permeability under OGD conditions via proteolysis of extracellular matrix proteins. This was associated with PMN degranulation. Addition of HDLs or AAT limited the proteolysis and associated increased permeability by inhibiting PMN activation. Our results suggest a deleterious, elastase-mediated role of activated PMNs under OGD conditions leading to BBB disruption that could be inhibited by HDLs.

Pseudomonas aeruginosa Post-Operative Peritonitis: Clinical Features, Risk Factors, and Prognosis

BACKGROUND Postoperative peritonitis (PP) is associated with a high rate of multi-drug-resistant micro-organisms. The role of Pseudomonas aeruginosa in this condition has never been assessed. We evaluated the risk factors and prognosis for PP caused by P. aeruginosa. METHODS Patients hospitalized in the intensive care unit (ICU) after re-operation for PP were identified prospectively. Analyses were performed retrospectively. Specific risk factors were investigated by comparing P. aeruginosa PP with PP having other causes. The main outcome endpoint was death in the hospital. RESULTS We found 55 P. aeruginosa PP among the 349 cases of PP (16%) in the ICU over 14 years. Factors associated with the presence of P. aeruginosa in peritoneal fluid culture were Acute Physiology and Chronic Health Evaluation (APACHE) II score (odds ratio [OR] 1.1; 95% confidence interval [CI] 1.02-1.09; p=0.004) and respiratory failure (OR 2.3; 95% CI 1.26-4.16; p=0.006). These criteria performed poorly in predicting P. aeruginosa PP. Such infections were associated with a higher hospital mortality rate, but not after adjustment for the severity score. Adequate antibiotic therapy comprising two antibiotics effective against P. aeruginosa was associated with a lower mortality rate for P. aeruginosa PP in the ICU. CONCLUSION The prevalence of P. aeruginosa PP is not high. Risk factors do not allow accurate prediction of the infection. Our data suggest two drugs effective against P. aeruginosa should be considered for treating these infections.

Detection of Apoptotic Cells in a Rabbit Model with Atherosclerosis-Like Lesions Using the Positron Emission Tomography Radiotracer [18F]ML-10.

[18F]ML-10 (2-(5-fluoro-pentyl)-2-methylmalonic acid) is a positron emission tomography (PET) radiotracer that accumulates in cells presenting apoptosis-specific membrane alterations. The aim of this study was to test whether [18F]ML-10 allows for the detection of apoptotic cells located in atherosclerotic plaques in rabbits. Atherosclerotic plaques were induced in the aortas of five rabbits, and five additional rabbits were used as controls. Activity in the aortas was quantified in vivo and ex vivo. The localization of [18F]ML-10 to the aortic wall was identified by autoradiography. Average target to background ratios measured in vivo by PET were higher in the aortas of atherosclerotic rabbits compared with those of control rabbits (2.00 ± 0.52 vs 1.22 ± 0.30; p < .05). Differences in [18F]ML-10 uptake between atherosclerotic and control aortas were confirmed ex vivo by PET and gamma counting (23.9 ± 11.2 vs 1.1 ± 2.4 counts/pixel; p <.05; 3.6 ± 2.0 vs 0.05 ± 0.05 % of injected activity/g; p < .05, respectively). Strong correlation was observed between the accumulation of [18F]ML-10 in aortic segments as detected by autoradiography and the number of apoptotic cells on corresponding histologic sections (r2 = .75; p < .05). In this study, we found that atherosclerotic plaques rich in apoptotic cells can be detected with [18F]ML-10 and PET.

Low Levels of Low-Density Lipoprotein-C Associated With Proprotein Convertase Subtilisin Kexin 9 Inhibition Do Not Increase the Risk of Hemorrhagic Transformation

Background and Purpose— Low levels of low-density lipoprotein-cholesterol (LDL-C) are suspected to be associated with a risk of hemorrhagic transformation after ischemic stroke. We assessed the risk of hemorrhagic transformation after cerebral ischemia/reperfusion in mice with low levels of LDL-C resulting from proprotein convertase subtilisin kexin 9 (PCSK9) deficiency. Methods— PCSK9−/− and PCSK9+/+ mice were fed with a high-fat/high-cholesterol (21%/0.15%) diet for 1 month. Plasma lipids were measured using colorimetric assays. PCSK9−/− and PCSK9+/+ mice (n=15 per group) were subjected to a 4-hour intraluminal occlusion of the middle cerebral artery followed by 20 hours of reperfusion. Spontaneous hemorrhagic transformation was assessed by quantification of hemoglobin in ischemic tissue. In vitro, a cell model of blood–brain barrier was used to test endothelial barrier integrity in response to decreasing concentrations of LDL-C from 1 to 0.25g/L in ischemia/reperfusion conditions. Results— PCSK9−/− mice had lower LDL-C, high-density lipoprotein-cholesterol, and total cholesterol levels than PCSK9+/+ mice before and after 1 month on the high-fat/high-cholesterol diet. Hemoglobin concentration in ischemic cerebral tissue was not different between PCSK9−/− and PCSK9+/+ mice (31.5 [18.9–60.1] and 32.8 [14.7–69.9] ng/mg protein, respectively; P=0.81). Infarct volume was also similar in both groups (P=0.66). Incubation of human cerebral endothelial cells with decreasing concentrations of LDL-C under ischemia/reperfusion conditions did not alter blood–brain barrier permeability. Conclusions— Low levels of LDL-C did not increase the risk of hemorrhagic transformation after cerebral ischemia/reperfusion in mice. Our observations suggest that PCSK9 inhibition, leading to LDL-C lowering, should not increase hemorrhagic complications after acute ischemic stroke.

A hemorrhagic transformation model of mechanical stroke therapy with acute hyperglycemia in mice

Clinical benefit for mechanical thrombectomy (MT) in stroke was recently demonstrated in multiple large prospective studies. Acute hyperglycemia (HG) is an important risk factor of poor outcome in stroke patients, including those that underwent MT. The aim of this therapy is to achieve a complete reperfusion in a short time, given that reperfusion damage is dependent on the duration of ischemia. Here, we investigated the effects of acute HG in a mouse model of ischemic stroke induced by middle cerebral artery occlusion (MCAO). Hyperglycemic (intraperitoneal [ip] injection of glucose) and control (ip saline injection) 10‐week male C57BL6 mice were subjected to MCAO (30, 90, and 180 min) followed by reperfusion obtained by withdrawal of the monofilament. Infarct volume, hemorrhagic transformation (HT), neutrophil infiltration, and neurological scores were assessed at 24 hr by performing vital staining, ELISA immunofluorescence, and behavioral test, respectively. Glucose injection led to transient HG (blood glucose = 250–390 mg/dL) that significantly increased infarct volume, HT, and worsened neurological outcome. In addition, we report that HG promoted blood‐brain barrier disruption as shown by hemoglobin accumulation in the brain parenchyma and tended to increase neutrophil extravasation within the infarcted area. Acute HG increased neurovascular damage for all MCAO durations tested. HTs were observed as early as 90 min after ischemia under hyperglycemic conditions. This model mimics MT ischemia/reperfusion and allows the exploration of brain injury in hyperglycemic conditions.

Evaluation of Cardiac Index and Extravascular Lung Water After Single-Lung Transplantation Using the Transpulmonary Thermodilution Technique by the PiCCO2 Device

OBJECTIVES First evaluation of the transpulmonary thermodilution technique by the PiCCO2 device to assess cardiac index and pulmonary edema during the postoperative course after single-lung transplantation. DESIGN Prospective observational study. SETTINGS Intensive care unit, university hospital (single center). PARTICIPANTS Single-lung transplant patients. INTERVENTIONS The authors compared cardiac index measured by PiCCO2 and pulmonary artery catheter and assessed pulmonary edema using extravascular lung water index and pulmonary vascular permeability index measured by PiCCO2. MEASUREMENTS AND MAIN RESULTS A Bland-Altman method was used to compare cardiac index measured by PiCCO2 and pulmonary artery catheter. Extravascular lung water index and pulmonary vascular permeability index were compared according to the PaO2/FiO2 ratio with a threshold value of 150 mmHg. Ten single-lung transplant patients were included. Cardiac index measured by PiCCO2 and pulmonary artery catheter were 3.3 L/min/m2 (2.9-3.6) and 2.5 L/min/m2 (2.2-3.0). Bias for cardiac index was 0.71 L/min/m2 (-0.03; 1.44) and limit of agreements were -0.03 and 1.44 L/min/m2. Extravascular lung water index was 12 mL/kg (11-16) and pulmonary vascular permeability index was 2.3 (2.0-3.1), consistent with pulmonary edema. Extravascular lung water index was higher in the group of PaO2/FiO2 ratio ≤150 mmHg compared with the group of PaO2/FiO2 ratio >150 mmHg (17 v 12 mL/kg, p = 0.04), whereas pulmonary vascular permeability index only tended to be higher (3.1 v 2.1, p = 0.06). CONCLUSION PiCCO2 device systematically overestimated cardiac index compared with pulmonary artery catheter. However, it might be useful to assess pulmonary edema in acute respiratory failure after single-lung transplantation.