Thomas Baltus

Differential and additive effects of platelet-derived chemokines on monocyte arrest on inflamed endothelium under flow conditions.

Platelet‐derived chemokines, such as regulated on activation, normal T expressed and secreted (RANTES; CC chemokine ligand 5), platelet factor 4 [PF4; CXC chemokine ligand 4 (CXCL4)], and epithelial neutrophil‐activating protein 78 (ENA‐78; CXCL5), or precursors, such as β‐thromboglobulin, which can be processed to neutrophil‐activating protein‐2 (NAP‐2; CXCL7), may play an important role in monocyte recruitment during atherogenesis. Platelets can deposit chemokines on inflamed endothelium; however, little is known about differential or additive effects of platelet chemokines on monocyte arrest. Here, we demonstrate that preincubation of activated human microvascular endothelial cells (HMVECs) with RANTES, PF4, or NAP‐2 but not ENA‐78 dose‐dependently increased surface immobilization and subsequent monocyte arrest in flow. RANTES was the most potent and efficient arrest chemokine. Pretreatment of HMVECs with β‐thromboglobulin enhanced monocyte arrest in the presence of cathepsin G generating NAP‐2. Combined pretreatment of HMVECs with RANTES and PF4 at suboptimal concentrations synergistically increased arrest, and preincubation with chondroitinase ABC abrogated RANTES‐ and PF4‐induced monocyte arrest. This was associated with reduced expression of chondroitin sulfate, RANTES, and PF4 on the HMVEC surface. Perfusion of HMVECs with platelets known to deposit RANTES and PF4 on the endothelial surface enhanced monocyte arrest, which was inhibited by Met‐RANTES, chondroitinase, or a blocking antibody to PF4 but not to ENA‐78. The relevance of platelet‐derived chemokines was confirmed in adhesion assays with activated whole blood, where Met‐RANTES and to a lesser extent, antibodies to PF4 and NAP‐2 inhibited arrest of CD14‐positive monocytes. Thus, multiple platelet‐derived chemokines and processable precursors, which can be presented by specific endothelial proteoglycans, may contribute and cooperate differentially to induce monocyte recruitment.

Involvement of JAM-A in Mononuclear Cell Recruitment on Inflamed or Atherosclerotic Endothelium: Inhibition by Soluble JAM-A

Objective—The junctional adhesion molecule (JAM)-A on endothelium contributes to the inflammatory recruitment of mononuclear cells involving engagement of its integrin receptor lymphocyte function-associated antigen (LFA)-1. It is unknown whether these functions can be inhibited by soluble forms of JAM-A, whether JAM-A is expressed on atherosclerotic endothelium, and whether it participates in atherogenic recruitment of mononuclear cells. Methods and Results—Adhesion assays revealed that LFA-1–mediated binding of mononuclear cells to intercellular adhesion molecule (ICAM)-1 or cytokine-costimulated endothelium was dose-dependently inhibited by soluble JAM-A.Fc (sJAM-A.Fc). Similarly, sJAM-A.Fc reduced stromal cell-derived factor (SDF)-1&agr;–triggered transendothelial chemotaxis of activated T cells and their SDF-1&agr;–triggered arrest on cytokine-costimulated endothelium under flow conditions. Immunofluorescence analysis revealed an upregulation of JAM-A on early atherosclerotic endothelium of carotid arteries from apolipoprotein E-deficient (apoE−/−) mice fed an atherogenic diet. In ex vivo perfusion assays, pretreatment of mononuclear cells with sJAM-A.Fc inhibited their very late antigen (VLA)-4–independent accumulation on atherosclerotic endothelium of these arteries. Conclusions—Soluble forms of JAM-A can be effectively applied to inhibit distinct steps of mononuclear cell recruitment on inflamed or atherosclerotic endothelium. In conjunction with its expression on atherosclerotic endothelium, this suggests a functional contribution of JAM-A to atherogenesis.

The Effect of Xenon Anesthesia on the Size of Experimental Myocardial Infarction

BACKGROUND:Volatile anesthetics protect the myocardium from ischemia reperfusion damage. Our hypothesis for this study was that xenon reduces the size of myocardial infarction similar in extent to the reduction associated with ischemic preconditioning. METHODS:Thirty-six pigs weighing 30–35 kg were anesthetized with thiopental and then randomized into four groups: control (myocardial ischemia only), ischemic preconditioning (five 5-min episodes of intermittent myocardial ischemia), xenon preconditioning (three 10-min exposures to xenon 70% followed by myocardial ischemia), and xenon anesthesia (xenon 70%, continued before and after myocardial ischemia). Myocardial ischemia was induced by placing a tourniquet around the left anterior descending coronary artery for 60 min followed by 2 h of reperfusion. Myocardial infarct size and the area at risk for myocardial infarction were measured by Evans Blue and triphenyl tetrazolium chloride staining, respectively. RESULTS:Mean (sd) myocardial infarct size was reduced from 64% ± 9% of the area at risk in the control group to 19% ± 12% with ischemic preconditioning (P < 0.001), and to 50% ± 9% with xenon anesthesia (P < 0.05 versus control, P < 0.001 versus ischemic preconditioning). Myocardial infarct size was not reduced with xenon preconditioning compared with the control group (59% ± 11%, P = 0.41). CONCLUSION:Myocardial infarct size was reduced by ischemic preconditioning but less so by xenon anesthesia. Brief, intermittent exposure to xenon before myocardial ischemia did not reduce myocardial infarct size.

Opiate-Induced Dopamine Release Is Modulated by Severity of Alcohol Dependence: An [18F]Fallypride Positron Emission Tomography Study

BACKGROUND Preclinical data implicate the reinforcing effects of alcohol to be mediated by interaction between the opioid and dopamine systems of the brain. Specifically, alcohol-induced release of β-endorphins stimulates μ-opioid receptors (MORs), which is believed to cause dopamine release in the brain reward system. Individual differences in opioid or dopamine neurotransmission have been suggested to be responsible for enhanced liability to abuse alcohol. In the present study, a single dose of the MOR agonist remifentanil was administered in detoxified alcohol-dependent patients and healthy control subjects to mimic the β-endorphin-releasing properties of ethanol and to assess the effects of direct MOR stimulation on dopamine release in the mesolimbic reward system. METHODS Availability of D(2/3) receptors was assessed before and after single-dose administration of the MOR agonist remifentanil in 11 detoxified alcohol-dependent patients and 11 healthy control subjects with positron emission tomography with the radiotracer [(18)F]fallypride. Severity of dependence as assessed with the Alcohol Use Disorders Identification Test was compared with remifentanil-induced percentage change in [(18)F]fallypride binding (Δ%BP(ND)). RESULTS The [(18)F]fallypride binding potentials (BP(ND)s) were significantly reduced in the ventral striatum, dorsal putamen, and amygdala after remifentanil application in both patients and control subjects. In the patient group, ventral striatum Δ%BP(ND) was correlated with the Alcohol Use Disorders Identification Test score. CONCLUSIONS The data provide evidence for a MOR-mediated interaction between the opioid and the dopamine system, supporting the assumption that one way by which alcohol unfolds its rewarding effects is via a MOR-(γ-aminobutyric acid)-dopamine pathway. No difference in dopamine release was found between patients and control subjects, but evidence for a patient-specific association between sensitivity to MOR stimulation and severity of alcohol dependence was found.

The Effect of Xenon on Isoflurane Protection Against Experimental Myocardial Infarction

OBJECTIVES To investigate if the protective effects of xenon and isoflurane against myocardial ischemia-reperfusion damage would be additive. DESIGN A prospective, randomized laboratory investigation. SETTING An animal laboratory of a university hospital. PARTICIPANTS Thirty-six pigs (female German landrace). INTERVENTIONS In an open-chest preparation with thiopental anesthesia, the left anterior descending artery was occluded to produce ischemia for 60 minutes. One hour previously, ischemic preconditioning, isoflurane (0.55 minimum alveolar concentration [MAC]) alone, or isoflurane together with xenon (0.55 MAC each) were started in the respective groups. A fourth (control) group received no protective intervention. Myocardial ischemia was followed by 2 hours of reperfusion. MEASUREMENTS AND MAIN RESULTS Hearts were excised and stained (Evans Blue/TTC) to measure infarct size as related to the area at risk. Myocardial infarct size was reduced (means +/- standard deviation) from 64% +/- 9% of the area at risk in the control group to 19% +/- 12% with ischemic preconditioning to 46% +/- 12% with isoflurane and to 39% +/- 13% with isoflurane and xenon. All intervention groups were significantly different from the control (p < 0.05), and both anesthetic groups were significantly different from ischemic preconditioning (p < 0.05). CONCLUSION Combined isoflurane/xenon anesthesia reduced infarct size but not more than isoflurane alone. Ischemic preconditioning was more effective than the anesthetics.

The basic residue cluster 55KKWVR59 in CCL5 is required for in vivo biologic function

Chemokine function in vivo depends on the presentation by structures of the extracellular matrix or on endothelial surfaces. CCL5 contains two clusters of basic amino acid residues ((44)RKNR(47) and (55)KKWVR(59)) implicated in presentation of the protein. While (44)RKNR(47) has been shown to moderate CCL5 binding to glycosaminoglycans (GAGs), no direct role for the basic residues in the so called 50s loop ((55)KKWVR(59)) as a presentation structure has been published to date. In ex vivo studies both regions were found to be necessary for direct tissue binding suggesting a role for (55)KKWVR(59). In vitroT lymphocyte and monocyte induced firm adhesion under flow, as well as leukocyte recruitment to the peritoneal cavity in vivo was reduced in the 50s mutant. The binding of the 50s mutant to endothelial cells was significantly reduced as compared to the wild type protein demonstrated by ELISA. The 50s mutant had little impact on GAG binding in vitro. These data suggest that functional CCL5 presentation is mediated through both the 40s as well as the 50s loop with differential functions of the two loops of clusters of basic residues.

Changes in D2/D3-receptor availability in detoxified patients with alcohol addiction compared to healthy subjects - a PET study with [18F]fallypride

This journal supplement has title: Abstracts from the XXVII CINP Congress, Hong Kong, 6–10 June 2010Abstract from the XXVII CINP Congress, 6-10 June 2010, Hong KongAbstract from the XXVII CINP Congress, 6-10 June 2010, Hong Kong