P-selectin expression in myocardium of children undergoing cardiopulmonary bypass

The gut microbiome and cardiac surgery an unusual symphony

The relationship between the gut microbiome and various organ systems has gained interest throughout the scientific community in recent times. The understanding of these complex relationships has greatly improved with clinical benefits now being seen. Cardiopulmonary bypass (CPB) is a form of extracorporeal circulation that provides circulatory and respiratory support during cardiac surgery. This physiological support facilitates a still and bloodless field facilitating operations on the heart to be performed. Through various mechanisms CPB results in a systemic inflammatory response syndrome (SIRS). This response can vary from mild hypotension to multiple organ failure. It remains difficult to predict the degree to which a patient will experience SIRS post-operatively. The relationship between the composition of the gut microbiome and inflammatory processes associated with disease has been seen across several fields including gastroenterology, neurology, psychiatry and cardiology. To date, minimal research has been undertaken to examine the impact the gut microbiome has on outcomes following cardiac surgery. This review paper explores the pathophysiology behind the SIRS response associated with CPB for cardiac surgery and the hypothesis that a correlation exists between a patients gut microbiome composition and the degree of inflammatory response experienced following cardiac surgery.

Prediction of Potential Biomarkers in Early-Stage Nasopharyngeal Carcinoma Based on Platelet RNA Sequencing

Early diagnosis is essential for the treatment and prevention of nasopharyngeal cancer. However, there is a lack of effective biological indicators for nasopharyngeal carcinoma (NPC). Therefore, we explored the potential biomarkers in tumour-educated blood platelet (TEP) RNA in early NPC. Platelets were isolated from blood plasma and their RNA was extracted. High-throughput sequenced data from a total of 33 plasma samples were analysed using DESeq2 to identify the differentially expressed genes (DEGs). Subsequently, the DEGs were subjected to principal component analysis (PCA), gene ontology (GO) analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis; and Cytoscape, TargetScan, and miRanda software were used for inferring the competing endogenous RNA network. We identified 19 long non-coding (lnc) RNAs (DElncRNAs) and 248 mRNAs (DEmRNAs) that were differentially expressed in the TEP RNA. In addition, SELP gene mRNA and lncRNAs AC092135.3, AC012358.2, AL021807.1, AP001972.5, and GPX1 were found to be down-regulated DEmRNA and DElncRNAs in the early stage of NPC. Bioinformatic analysis showed that these DEmRNAs and DElncRNAs may be involved in regulating the pathogenesis of NPC. Our research may provide new insights for exploring the biological mechanisms of NPC and early diagnosis using potential biomarkers.

Sera From Children After Cardiopulmonary Bypass Reduces Permeability of Capillary Endothelial Cell Barriers

OBJECTIVES

Children undergoing cardiopulmonary bypass develop clinically impactful capillary leak of unclear etiology. A widely held hypothesis that exposure of circulating cells to the cardiopulmonary bypass circuit induces the release of inflammatory mediators that act to disrupt intercellular junctions of capillary endothelial cells inducing paracellular capillary leak either directly or through new gene expression.

DESIGN

Cohort study.

SETTING

Tertiary pediatric hospital.

PATIENTS

Twenty children undergoing surgery with cardiopulmonary bypass for congenital heart disease. Serum was collected before cardiopulmonary bypass, 2 hours after cardiopulmonary bypass, and 18 hours after cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We analyzed the effects of 10% patient sera on the "function, structure, and gene expression" of cultured human dermal and pulmonary microvascular endothelial cells. Changes in barrier "function" were measured using transendothelial electrical resistance. Associations between changes in transendothelial electrical resistance and subject characteristics were analyzed using linear mixed effects model with area under the resistance curve as outcome. Changes in junctional "structure" were assessed by analyzing the organization of the endothelial cell junctional proteins claudin-5 and VE-cadherin using immunofluorescence microscopy. Changes in inflammatory "gene expression" were measured using real-time quantitative reverse transcription-polymerase chain reaction. All serum samples induced a transient, 120-minute increase in transendothelial electrical resistance followed by persistent loss of barrier function. Unexpectedly, sera collected postcardiopulmonary bypass-induced significantly less loss of barrier function in both dermal and pulmonary capillary endothelial cell compared with precardiopulmonary bypass sera. Consistent with the transendothelial electrical resistance results, claudin-5 and vascular endothelial-cadherin junctional staining showed less disruption in cultures treated with postcardiopulmonary bypass sera. Expression of genes commonly associated with inflammation was largely unaffected by patient sera.

CONCLUSIONS

Contrary to the hypothesis, sera taken from children after cardiopulmonary bypass induces less capillary barrier disruption relative to sera taken from children before cardiopulmonary bypass, and none of the sera induced significant changes in expression of inflammatory genes.

Endothelial Cell Adhesion Molecules and Cardiopulmonary Bypass

Endothelial cell activation and the cell surface expression of adhesion molecules are considered to be crucial steps in the systemic inflammatory response to cardiopulmonary bypass. Endothelial cell adhesion molecules mediate the process of leukocyte adhesion to the endothelium and their subsequent transmigration and degranulation in the subendothelial tissues. The levels of soluble endothelial adhesion molecules in plasma have been used to draw conclusions regarding the cell surface expression of these molecules; the limitations of such studies are discussed. Inhibition of cell adhesion molecules may prevent the inflammatory condition caused by cardiopulmonary bypass and reperfusion injury. Further studies are needed to define the role of endothelial cell adhesion molecules in this inflammatory response.

P-Selectin Expressed by a Human SELP Transgene Is Atherogenic in Apolipoprotein E-Deficient Mice

OBJECTIVE

During inflammation, P-selectin expressed on activated endothelial cells and platelets mediates rolling adhesion of leukocytes. Atherosclerosis-prone mice crossed with P-selectin-deficient (Selp(-/-)) mice develop smaller lesions. Cytokines, such as tumor necrosis factor-α, increase Selp transcripts and augment atherosclerosis in mice. However, they decrease SELP transcripts in humans, challenging assumptions that human P-selectin is atherogenic. We used mice expressing a human SELP transgene to examine the atherogenic role of P-selectin.

APPROACH AND RESULTS

We crossed apolipoprotein E-deficient (Apoe(-/-)) mice with Selp(-/-) mice or transgenic mice expressing the entire human SELP gene (TgSELP(+/-)). Aortas developed larger, macrophage-rich atheromas in Apoe(-/-)Selp(-/-)TgSELP(+/-) mice than in Apoe(-/-)Selp(-/-) mice after 8 or 16 weeks on a Western diet. Confocal microscopy of Apoe(-/-)Selp(-/-)TgSELP(+/-) aortas revealed staining for human P-selectin in endothelial cells overlying atheromas but not in lesional macrophages. We also observed staining for human P-selectin in aortic endothelial cells of 3- to 4-week-old Apoe(-/-)Selp(-/-)TgSELP(+/-) weanlings before atheromas developed. Furthermore, human SELP transcripts were ≈3-fold higher in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) weanlings than in Selp(+/-)TgSELP(+/-) weanlings, whereas murine Selp and Sele transcripts were equivalent in weanlings of both genotypes. Human SELP transcripts in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) mice remained nearly constant during 16 weeks on a Western diet, whereas murine Selp and Sele transcripts progressively increased. Bone marrow transplantation in Apoe(-/-)Selp(-/-) and Apoe(-/-)Selp(-/-)TgSELP(+/-) mice demonstrated that both platelets and endothelial cells must express human P-selectin to promote atherogenesis.

CONCLUSIONS

P-selectin expressed by human SELP is atherogenic in Apoe(-/-) mice, suggesting that P-selectin contributes to atherogenesis in humans.

Replacing the Promoter of the Murine Gene Encoding P-selectin with the Human Promoter Confers Human-like Basal and Inducible Expression in Mice

In humans and mice, megakaryocytes/platelets and endothelial cells constitutively synthesize P-selectin and mobilize it to the plasma membrane to mediate leukocyte rolling during inflammation. TNF-α, interleukin 1β, and LPS markedly increase P-selectin mRNA in mice but decrease P-selectin mRNA in humans. Transgenic mice bearing the entire human SELP gene recapitulate basal and inducible expression of human P-selectin and reveal human-specific differences in P-selectin function. Differences in the human SELP and murine Selp promoters account for divergent expression in vitro, but their significance in vivo is not known. Here we generated knockin mice that replace the 1.4-kb proximal Selp promoter with the corresponding SELP sequence (Selp(KI)). Selp(KI) (/) (KI) mice constitutively expressed more P-selectin on platelets and more P-selectin mRNA in tissues but only slightly increased P-selectin mRNA after injection of TNF-α or LPS. Consistent with higher basal expression, leukocytes rolled more slowly on P-selectin in trauma-stimulated venules of Selp(KI) (/) (KI) mice. However, TNF-α did not further reduce P-selectin-dependent rolling velocities. Blunted up-regulation of P-selectin mRNA during contact hypersensitivity reduced P-selectin-dependent inflammation in Selp(KI) (/-) mice. Higher basal P-selectin in Selp(KI) (/) (KI) mice compensated for this defect. Therefore, divergent sequences in a short promoter mediate most of the functionally significant differences in expression of human and murine P-selectin in vivo.

Directing stem cell trafficking via GPS

The success of stem-cell-based regenerative therapeutics critically hinges on delivering relevant stem/progenitor cells to sites of tissue injury. To achieve adequate parenchymal infiltration following intravascular administration, it is first necessary that circulating cells bind to target tissue endothelium with sufficient strength to overcome the prevailing forces of hemodynamic shear. The principal mediators of these shear-resistant binding interactions consist of a family of C-type lectins known as "selectins" that bind discrete sialofucosylated glycans on their respective ligands. One member of this family, E-selectin, is an endothelial molecule that is inducibly expressed on postcapillary venules at all sites of tissue injury, but is also constitutively expressed on the luminal surface of bone marrow and dermal microvascular endothelium. Most stem/progenitor cells express high levels of CD44, and, in particular, human hematopoietic stem cells express a specialized sialofucosylated glycoform of CD44 known as "hematopoietic cell E-/L-selectin ligand" (HCELL) that functions as a potent E-selectin ligand. This chapter describes a method called "glycosyltransferase-programmed stereosubstitution" (GPS) for custom-modifying CD44 glycans to create HCELL on the surface of living cells that natively lack HCELL. Ex vivo glycan engineering of HCELL via GPS licenses trafficking of infused cells to endothelial beds that express E-selectin, thereby enabling efficient vascular delivery of stem/progenitor cells to sites where they are needed.

Differential regulation of human and murine P-selectin expression and function in vivo

Basal and inducible expression of human P-selectin in transgenic mice differs from that of murine P-selectin, resulting in distinct functions.

Leukocytes roll on P-selectin after its mobilization from secretory granules to the surfaces of platelets and endothelial cells. Tumor necrosis factor (TNF), IL-1β, and lipopolysaccharide increase synthesis of P-selectin in murine but not in human endothelial cells. To explore the physiological significance of this difference in gene regulation, we made transgenic mice bearing the human Selp gene and crossed them with mice lacking murine P-selectin (Selp^−/−). The transgenic mice constitutively expressed human P-selectin in platelets, endothelial cells, and macrophages. P-selectin mediated comparable neutrophil migration into the inflamed peritoneum of transgenic and wild-type (WT) mice. Leukocytes rolled similarly on human or murine P-selectin on activated murine platelets and in venules of the cremaster muscle subjected to trauma. However, TNF increased murine P-selectin in venules, slowing rolling and increasing adhesion, whereas it decreased human P-selectin, accelerating rolling and decreasing adhesion. Both P- and E-selectin mediated basal rolling in the skin of WT mice, but E-selectin dominated rolling in transgenic mice. During contact hypersensitivity, murine P-selectin messenger (m) RNA was up-regulated and P-selectin was essential for leukocyte recruitment. However, human P-selectin mRNA was down-regulated and P-selectin contributed much less to leukocyte recruitment. These findings reveal functionally significant differences in basal and inducible expression of human and murine P-selectin in vivo.

Glycosyltransferase-programmed stereosubstitution (GPS) to create HCELL: engineering a roadmap for cell migration

During evolution of the vertebrate cardiovascular system, the vast endothelial surface area associated with branching vascular networks mandated the development of molecular processes to efficiently and specifically recruit circulating sentinel host defense cells and tissue repair cells at localized sites of inflammation/tissue injury. The forces engendered by high-velocity blood flow commensurately required the evolution of specialized cell surface molecules capable of mediating shear-resistant endothelial adhesive interactions, thus literally capturing relevant cells from the blood stream onto the target endothelial surface and permitting subsequent extravasation. The principal effectors of these shear-resistant binding interactions comprise a family of C-type lectins known as 'selectins' that bind discrete sialofucosylated glycans on their respective ligands. This review explains the 'intelligent design' of requisite reagents to convert native CD44 into the sialofucosylated glycoform known as hematopoietic cell E-/L-selectin ligand (HCELL), the most potent E-selectin counter-receptor expressed on human cells, and will describe how ex vivo glycan engineering of HCELL expression may open the 'avenues' for the efficient vascular delivery of cells for a variety of cell therapies.

Pathology of coronary narrowing after arterial switch operation: autopsy findings in two patients who died within 3 months of surgical treatment and review of the literature

The arterial switch operation (ASO) has become the surgical treatment of choice for transposition of the great arteries (TGA). Myocardial ischemia owing to coronary complication remains the commonest cause of mortality and morbidity following ASO. The main clinical manifestations of coronary obstruction reported after a switch procedure are heart failure, arrhythmias, or sudden death. Coronary complications are responsible for about 50% of early death and for almost all late deaths. We describe pathologic and anatomic findings in two cases of late sudden death after an ASO. Critical intimal thickening and acute take-off of coronary trunks were the main pathological substrates of death. Histological examination revealed an obstructive coronary proliferation characterised by a concentric stratum of intimal smooth muscle cell hyperplasia with preserved tunica media. Pathogenetic assessment of intimal coronary lesions after an ASO should consider the role of endothelium and vascular parietal wall in the unavoidable response to injury caused by arterial reconstruction. Since a rapidly progressive proliferative disease is suspected, to explain coronary narrowing, understanding endothelial biology and improving surgical technique should help to prevent late coronary events.

Differential-display polymerase chain reaction identifies nicotinamide adenine dinucleotide-ubiquinone oxidoreductase as an ischemia/reperfusion-regulated gene in cardiomyocytes

OBJECTIVE

Cardiac ischemia/reperfusion-induced oxidative damage often occurs in mitochondria. We identified differentially expressed genes in the canine heart after global cardiac ischemia/reperfusion injury was induced during cardiopulmonary bypass (CPB).

METHODS

Differential-display polymerase chain reaction (ddPCR) was performed on cardiac tissue from canine hearts with or without global cardiac ischemia/reperfusion injury induced during CPB. Ischemia/reperfusion-associated mitochondrial injury was investigated at the protein level using various cardioplegic solutions and Western blot analysis.

RESULTS

A mitochondrial protein nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase gene was identified on ddPCR. The NADH:ubiquinone oxidoreductase gene was up-regulated in canine hearts after 60 min of global cardiac ischemia/reperfusion injury during CPB. Western blot analysis revealed that, after manipulation with different cardioplegic solutions, increased Bcl-2 expression and decreased cytochrome c expression were associated with cardiomyocytic apoptosis.

CONCLUSIONS

The NADH:ubiquinone oxidoreductase gene is up-regulated during global cardiac ischemia/reperfusion injury during CPB in canines. To our knowledge, involvement of this gene in global cardiac ischemia/reperfusion injury during CPB has not been described previously. The NADH:ubiquinone oxidoreductase gene may have a role in the regulation of molecular changes during the global cardiac ischemia/reperfusion injury during CPB, such as the up-regulation of Bcl-2, which might block release of cytochrome c from the mitochondria and prevent cardiomyocytic apoptosis.

Myocardial immediate early gene activation after cardiopulmonary bypass with cardiac ischemia-reperfusion

BACKGROUND

The inflammatory process after cardiopulmonary bypass is accompanied by alterations in gene expression for various inflammatory mediators.

METHODS

To analyze differential gene expression after myocardial ischemia-reperfusion, subtraction hybridization was used to discover induction of TIS7/PC4, an immediate early gene heretofore not observed in the heart. This prompted characterization of the related immediate early genes c-fos and c-jun, by Northern analysis and in situ hybridization in human and lamb myocardium subjected to cardiopulmonary bypass with myocardial ischemia. For comparison, we analyzed expression of inducible nitric oxide synthase (iNOS), which requires cytokine-activation, resulting in a "delayed" response.

RESULTS

In ischemic-reperfused myocardium at endcardiopulmonary bypass, c-fos, c-jun, and TIS7/PC4 were induced, whereas iNOS transcripts were undetectable. Expression patterns of c-fos and c-jun by in situ hybridization were markedly different; myocardial c-fos expression was diffuse and homogeneous, whereas c-jun expression was patchy with areas of intense focal localization.

CONCLUSIONS

Cardiopulmonary bypass with myocardial ischemia rapidly induces the immediate early genes TIS7/PC4 (discovered by subtraction hybridization), and c-fos and c-jun (precursors to the transcriptional regulator AP-1). Immediate early genes presumably contribute to activation of inflammatory mediators after cardiopulmonary bypass and differences in their tissue expression patterns, as observed for c-fos and c-jun, presumably modulate their effect upon downstream gene activation.

Plasma-soluble E-selectin after cardiopulmonary bypass in children: is it a marker of the postoperative course?

OBJECTIVE

To investigate the relationship and possible role of soluble adhesion molecule E-selectin in the postoperative course in children undergoing cardiopulmonary bypass (CPB).

DESIGN

Prospective cohort study.

SETTING

Pediatric intensive care unit of a university hospital.

PARTICIPANTS

Thirteen children who were candidates for cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serial blood samples of 13 CPB patients were collected from the arterial catheter or from the bypass circuits preoperatively; on initiation of CPB; on termination of CPB; and 1, 2, 4, 8, 12, 18, 24, and 48 hours postoperatively. Plasma was recovered immediately, aliquoted, and frozen at -70 degrees C until use. Circulating soluble selectin molecules were measured with a sandwich enzyme-linked immunosorbent assay technique. There were significant changes in plasma levels of soluble E-selectins in patients after CPB, and these levels were associated with patient characteristics, operative variables, and postoperative course. Soluble E-selectin correlated significantly with inotropic support and the use of anti-inflammatory drugs. There was a significant association between the development of postoperative sepsis and soluble E-selectin levels. No correlation was found between soluble E-selectins and duration of CPB, aortic cross-clamping, or hemodynamic variables, including heart rate and mean systemic arterial pressure.

CONCLUSION

These results suggest a relationship between CPB-induced mediators and early and late clinical effects. Although the mechanism for the increase of soluble E-selectin remains to be elucidated, the upregulation of soluble E-selectin indicates neutrophil activation, and its inhibition may represent a target for reducing the inflammatory response associated with CPB.

Divergent Inducible Expression of P-Selectin and E-Selectin in Mice and Primates

We used in vitro and in vivo approaches to examine whether tumor necrosis factor- (TNF-) and oncostatin M (OSM), cytokines that bind to distinct classes of receptors, differentially regulate expression of P- and E-selectin in murine and primate endothelial cells. In human umbilical vein endothelial cells, TNF- rapidly increased mRNA for E-selectin but not P-selectin. OSM elicited little or no change in mRNA for E-selectin, but induced a delayed and prolonged increase in P-selectin mRNA. TNF- and OSM did not cooperate to further enhance P- or E-selectin mRNA. Intravenous infusion of Escherichia coli, which markedly elevates plasma lipopolysaccharide and TNF-, increased mRNA for E-selectin but not P-selectin in baboons. In murine bEnd.3 endothelioma cells, TNF- and OSM individually and cooperatively increased mRNA and protein for both P- and E-selectin. Intravenous injection of these cytokines also individually and cooperatively increased mRNA for P- and E-selectin in mice. We conclude that the murine P- and E-selectin genes respond to both TNF- and OSM, whereas the primate P- and E-selectin genes have much more specialized responses. Such differences should be considered when extrapolating the functions of P- and E-selectin in murine models of inflammation to humans.

Divergent Inducible Expression of P-Selectin and E-Selectin in Mice and Primates

We used in vitro and in vivo approaches to examine whether tumor necrosis factor- (TNF-) and oncostatin M (OSM), cytokines that bind to distinct classes of receptors, differentially regulate expression of P- and E-selectin in murine and primate endothelial cells. In human umbilical vein endothelial cells, TNF- rapidly increased mRNA for E-selectin but not P-selectin. OSM elicited little or no change in mRNA for E-selectin, but induced a delayed and prolonged increase in P-selectin mRNA. TNF- and OSM did not cooperate to further enhance P- or E-selectin mRNA. Intravenous infusion of Escherichia coli, which markedly elevates plasma lipopolysaccharide and TNF-, increased mRNA for E-selectin but not P-selectin in baboons. In murine bEnd.3 endothelioma cells, TNF- and OSM individually and cooperatively increased mRNA and protein for both P- and E-selectin. Intravenous injection of these cytokines also individually and cooperatively increased mRNA for P- and E-selectin in mice. We conclude that the murine P- and E-selectin genes respond to both TNF- and OSM, whereas the primate P- and E-selectin genes have much more specialized responses. Such differences should be considered when extrapolating the functions of P- and E-selectin in murine models of inflammation to humans.

Tumor necrosis factor-alpha- or lipopolysaccharide-induced expression of the murine P-selectin gene in endothelial cells involves novel kappaB sites and a variant activating transcription factor/cAMP response element

Tumor necrosis factor-alpha (TNF-alpha) or lipopolysaccharide (LPS) increases expression of the P-selectin gene in murine, but not in human, endothelial cells. These mediators augment expression of a reporter gene driven by the murine, but not the human, P-selectin promoter in transfected endothelial cells. The regions from -593 to -474 and from -229 to -13 in the murine P-selectin promoter are required for TNF-alpha or LPS to stimulate reporter gene expression. Within these regions, we identified two tandem kappaB elements, a reverse-oriented kappaB site and a variant activating transcription factor/cAMP response element (ATF/CRE), that participate in TNF-alpha- or LPS-induced expression. The tandem kappaB elements bound to NF-kappaB heterodimers and p65 homodimers, the reverse-oriented kappaB site bound to p65 homodimers, and the variant ATF/CRE bound to nuclear proteins that included activating transcription factor-2. Mutations in each individual element eliminated binding to nuclear proteins and decreased by 20-60% the TNF-alpha- or LPS-induced expression of a reporter gene driven by the murine P-selectin promoter in transfected endothelial cells. Simultaneous mutations of all elements further decreased, but did not abolish, induced expression. Co-overexpression of p50 and p65 enhanced murine P-selectin promoter activity in a kappaB site-dependent manner. These data indicate that the kappaB sites and the variant ATF/CRE are required for TNF-alpha or LPS to optimally induce expression of the murine P-selectin gene. The presence of these elements in the murine, but not the human, P-selectin gene may explain in part why TNF-alpha or LPS stimulates transcription of P-selectin in a species-specific manner.

Comparison of promoters for the murine and human P-selectin genes suggests species-specific and conserved mechanisms for transcriptional regulation in endothelial cells

P-selectin, an adhesion receptor for leukocytes, is constitutively expressed in megakaryocytes and endothelial cells. Tumor necrosis factor-alpha (TNF-alpha) or lipopolysaccharide (LPS) increases synthesis of P-selectin in murine but not in human endothelial cells. To identify potential species-specific and conserved mechanisms for regulation of expression of P-selectin, we cloned the 5'-flanking region of the murine P-selectin gene and compared its features with those previously reported for the human gene. The murine and human genes shared conserved Stat-like, Hox, Ets, GATA, and GT-IIC elements. In the murine gene, a conserved GATA element bound to GATA-2 and functioned as a positive regulatory element, whereas a conserved Ets element bound to GA-binding protein and functioned as a negative regulatory element. Significantly, the murine P-selectin gene had several features not found in the human gene. These included an insertion from -987 to -649 that contained tandem GATA and tandem AP1-like sequences, which resembled enhancers in beta-globin locus control regions. Both tandem elements bound specifically to nuclear proteins. The murine gene lacked the unique kappaB site specific for p50 or p52 homodimers found in the human gene. Instead, it contained two tandem kappaB elements and a variant activating transcription factor/cAMP response element site, which closely resembled sites in the E-selectin gene that are required for TNF-alpha- or LPS-inducible expression. TNF-alpha or LPS augmented expression of a reporter gene driven by the murine, but not the human, P-selectin promoter in transfected endothelial cells. Deletional analysis of the murine 5'-flanking region revealed several sequences that were required for either constitutive or inducible expression. These data suggest that both species-specific and conserved mechanisms regulate transcription of the human and murine P-selectin genes.

A Proteasome Inhibitor, an Antioxidant, or a Salicylate, but not a Glucocorticoid, Blocks Constitutive and Cytokine-Inducible Expression of P-Selectin in Human Endothelial Cells

Proteasome inhibitors, antioxidants, salicylates, or glucocorticoids block the cytokine-induced expression of the endothelial cell adhesion molecules E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1. These pharmacological agents have been assumed to inhibit the expression of adhesion molecules primarily by blocking activation of the transcription factor NF-κB. We found that the proteasome inhibitor ALLN, the antioxidant PDTC, or sodium salicylate, but not the glucocorticoid dexamethasone, inhibited both the constitutive and the interleukin-4– or oncostatin M–induced expression of the adhesion molecule P-selectin in human endothelial cells. ALLN, PDTC, or sodium salicylate decreased P-selectin expression without a detectable requirement for inhibition of NF-κB activation or for an intact κB element in the P-selectin gene. These results extend the potential anti-inflammatory utility of such drugs to inhibition of P-selectin expression and suggest that they have important actions that do not involve the NF-κB system.

A Proteasome Inhibitor, an Antioxidant, or a Salicylate, but not a Glucocorticoid, Blocks Constitutive and Cytokine-Inducible Expression of P-Selectin in Human Endothelial Cells

Proteasome inhibitors, antioxidants, salicylates, or glucocorticoids block the cytokine-induced expression of the endothelial cell adhesion molecules E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1. These pharmacological agents have been assumed to inhibit the expression of adhesion molecules primarily by blocking activation of the transcription factor NF-κB. We found that the proteasome inhibitor ALLN, the antioxidant PDTC, or sodium salicylate, but not the glucocorticoid dexamethasone, inhibited both the constitutive and the interleukin-4– or oncostatin M–induced expression of the adhesion molecule P-selectin in human endothelial cells. ALLN, PDTC, or sodium salicylate decreased P-selectin expression without a detectable requirement for inhibition of NF-κB activation or for an intact κB element in the P-selectin gene. These results extend the potential anti-inflammatory utility of such drugs to inhibition of P-selectin expression and suggest that they have important actions that do not involve the NF-κB system.

Selectin-carbohydrate interactions during inflammation and metastasis

L-, E-, and P-selectin are membrane-anchored, C-type lectins that initiate tethering and rolling of flowing leukocytes on endothelial cells, platelets, or other leukocytes during inflammation. The selectins bind to sialylated, fucosylated, or, in some cases, sulfated glycans on glycoproteins, glycolipids, or proteoglycans. However, they bind with relatively high affinity or avidity to only a few, appropriately modified glycoproteins on leukocytes or endothelial cells. One leukocyte mucin, PSGL-1, tethers flowing leukocytes to P-selectin on activated platelets or endothelial cells, and also helps tether leukocytes to L-selectin on other leukocytes. The physiologic expression of the selectins is tightly controlled to limit the inflammatory response. But dysregulated expression of the selectins may contribute to inflammatory and thrombotic disorders, and perhaps to tumor metastases.

Endothelial cell injury in cardiovascular surgery: the systemic inflammatory response

Many of the components currently used to perform cardiovascular operations lead to systemic insults that result from cardiopulmonary bypass circuit-induced contact activation, circulatory shock, and resuscitation, and a syndrome similar to endotoxemia. Experimental observations have demonstrated that these events have profound effects on activating endothelial cells to recruit neutrophils from the circulation. Once adherent to the endothelium, neutrophils release cytotoxic proteases and oxygen-derived free radicals, which are responsible for much of the end-organ damage seen after cardiovascular operations. Recently the cellular and molecular mechanisms of endothelial cell activation have become increasingly understood. It is conceivable that once the molecular mechanisms of endothelial cell activation are better defined, therapies will be developed allowing the selective or collective inhibition of vascular endothelial activation during the perioperative period.

Endothelial cell injury in cardiovascular surgery: ischemia-reperfusion

Myocardial ischemia and reperfusion is a common occurrence in cardiovascular surgery patients. Acute ischemia results in a spectrum of derangements, which range from transient reversible stunning of the myocardium to severe irreversible abnormalities such as infarction. Many of these abnormalities are accentuated upon reperfusion with oxygenated blood. Recently, the endothelium has been shown to play a key role in the injury suffered after ischemia and reperfusion. When rendered hypoxic and then reoxygenated, endothelial cells become activated to express proinflammatory properties that include the induction of leukocyte-adhesion molecules, procoagulant factors and vasoconstrictive agents that increase vasomotor tone. These changes may contribute to the no-reflow phenomenon by promoting endothelial edema, neutrophil and platelet plugging, microthrombosis, and enhanced vasomotor tone. An increased understanding of the role that hypoxic endothelial cell activation plays in myocardial dysfunction after ischemia/reperfusion may allow therapies to be designed to further attenuate this response.

Endothelial cell injury in cardiovascular surgery

In the last decade the endothelium has been shown to play a major role in regulating membrane permeability, lipid transport, vasomotor tone, coagulation, inflammation, and vascular wall structure. These critical endothelial cell functions are extremely sensitive to injury in the form of hypoxia, exposure to cytokines, endotoxin, cholesterol, nicotine, surgical manipulation, or hemodynamic shear stress. In response to injury endothelial cells become activated, tipping the balance of endothelial-derived factors to disrupt barrier function, and enhance vasoconstriction, coagulation, leukocyte adhesion, and smooth muscle cell proliferation. Although these responses likely exist as protective mechanisms, if the stimuli are severe the responses may become excessive, resulting in damaged tissue, impaired organ function, and an abnormal fibroproliferative response. Recent discoveries in the field of vascular biology have led to an expanded understanding of many of the complications of cardiovascular operations. Because of the wide impact endothelial cell dysfunction has on patients with cardiovascular disease, issues pertaining to endothelial biology are in the forefront of research that will affect the current and future practice of cardiothoracic surgery.

Interleukin 4 or oncostatin M induces a prolonged increase in P-selectin mRNA and protein in human endothelial cells

During acute inflammation, P-selectin is transiently mobilized from Weibel-Palade bodies to the surface of histamine-activated endothelial cells, where it mediates rolling adhesion of neutrophils under hydrodynamic flow. During chronic or allergic inflammation, sustained expression of P-selectin on the endothelial cell surface has been observed. We found that the cytokines interleukin 4 (IL-4) or oncostatin M (OSM) induced a five- to ninefold increase in P-selectin messenger RNA (mRNA) in human umbilical vein endothelial cells (HUVEC) that persisted as long as 72 h. IL-4 elevated P-selectin mRNA by increasing its transcription rate rather than by prolonging its already long half-life. Stimulation of P-selectin transcription by IL-4 or OSM required new protein synthesis and tyrosine phosphorylation of cellular proteins. Tumor necrosis factor alpha, IL-1 beta, lipopolysaccharide, or IL-3 did not increase P-selectin mRNA in HUVEC, and did not augment the IL-4-induced increase in P-selectin transcripts. IL-4 or OSM increased P-selectin protein on the cell surface as well as in Weibel-Palade bodies. Under flow conditions, neutrophils rolled on P-selectin expressed by IL-4-treated HUVEC, and even more neutrophils rolled on P-selectin after IL-4-treated HUVEC were stimulated with histamine. These data demonstrate that IL-4 or OSM stimulates endothelial cells to synthesize more P-selectin over prolonged periods. The increased expression of P-selectin may facilitate the emigration of leukocytes into sites of chronic or allergic inflammation.