Atherosclerosis licenses for an exceeding immune response in COVID-19 disease

Background

COVID-19 is characterized by emergency hematopoiesis with a dysregulated myeloid compartment, comprising proinflammatory and immunosuppressive immune cells. Preexisting cardiovascular disease (CVD) is a major risk factor for severe and fatal COVID-19 outcomes. Individuals with atherosclerosis are known to have a proinflammatory immune cell phenotype. However, the mechanisms of how CVD causes worse outcomes during SARS-Cov2 infection remain unknown.

Purpose

To investigate the mechanisms of how immune cells link atherosclerosis to worse COVID-19 outcomes

Methods

Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) derived from hospitalized SARS-Cov2 infected patients in an uncomplicated phase of the disease not requiring intensive-care treatment with (n=5) and without (n=6) preexisting atherosclerosis was performed.

Results

Baseline characteristics between the two groups were similar (atherosclerosis vs. no atherosclerosis: mean age 75 vs. 70 years, oxygen requirement 2.2 vs. 3.2 l/min, CRP 10.7 vs. 6.6 mg/dl, IL-6 61.6 vs. 60.6 pg/ml, all p>0.05). In accordance with previous COVID-19 scRNA-seq studies, we found low-density neutrophils, immature neutrophils, neutrophil like plasmablasts and mostly classical monocytes in the myeloid compartment. Low-density neutrophils from patients with atherosclerosis demonstrated an increased expression of proinflammatory (IL18R1 fold change (fc) = 3.3, IL18RAP fc=1.9, HMGB2 fc=1.8, S100A12 fc=1.7, TLR2 fc=1.5, S100A9 fc=1.4 C3AR1 fc=1.8, TLR4 fc= 1.4, all adjusted p-values <1.3x10^–98) and immunosuppressive genes (IL1R2 fc=2.6, ARG1 fc=1.7, ANXA1 fc= 1.6, all adjusted p-values <4.1x10^–67). Interestingly, we found an enrichment of proinflammatory COVID-19 specific neutrophil like plasmablasts in patients with atherosclerosis (p=0.049) with an increased expression of inflammatory genes (S100A12 fc=2.5, S100A9 fc=2.5, S100A8 fc=1.8, HMGB2 fc=2.8, IL18R1 fc=3.9 S100A10 fc=2, all adjusted p-values <1.1x10^–54). In accordance, monocytes from patients with atherosclerosis showed an enrichment of inflammatory (S100A9 fc=1.6, NEAT1 fc=1.8, C3AR1 fc= 1.5, TLR2 fc= 1.5, IL13RA1 q=1.3, CCR2 fc=1.2, all p-values <1.3x10^–60) and immunomodulatory genes (IL1R2 fc=3.5, CD163 fc=2.2, all adjusted p-values <2.7x10^–87).

Conclusions

Our data show for the first time that patients with atherosclerosis have a dysregulated myeloid immune response already in the uncomplicated phase of SARS-CoV-2 infection. Upregulated genes and cell populations found in this study have previously been associated with severe COVID-19. Therefore, the enhanced inflammatory response may contribute to the worse outcome of patients with CVD and might be addressed by antiinflammatory drugs. Further efforts are needed to understand how atherosclerosis may control chromatin accessibility to predispose for an enhanced inflammatory response.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): German Heart Foundation

Human, mouse scRNA-seq and flow cytometry data in ischemic heart failure models predict immune cell activation signatures with altered endothelial cell cross talk

 

Chronic ischemic Heart Failure (HF) with reduced ejection fraction is marked by adverse remodelling and sustained inflammation. The effects of monocytes and T cells in early state immune responses after myocardial infarction are known, to date their role in progression and maintenance of chronic HF remains elusive.

Single cell RNA sequencing of peripheral immune cells from healthy and HF donors revealed a significant increase of the antigen presentation (i.e. HLA-DRB5) and co-stimulatory molecules (i.e. ICAM-1) on monocytes, while the elevation of the T effector memory population in HF patients shows enhanced T cell activation. Subsequent flow cytometry validation in 55 healthy and 110 HF patients confirmed that HF derived monocytes have elevated levels of HLA-DRB5 predicts increased ICAM-1 and TREM-1 (p&lt;0.0001 for both), indicating enhanced T cell activation capacity. In addition, the activated fraction of both CD4+ and CD8+ T cells, including central memory, effector memory and TEMRA cells, is significantly enriched in the HF patients (p&lt;0.0001 for both) with reduction of the naïve T cells. T cell receptor (TCR) sequencing of age matched healthy and HF donors showed an increase in the relative TCR clonality in HF patients, indicating an expansion of the circulating T cells.

ScRNA-seq murine myocardial infarction (MI) time course data (day (d) 0/1/3/7/14/28/48 post-MI), found a progressive increase in Th17 cells and activated CD8+ T cells in the cardiac tissue at d48 (2.8x-, and 2.7x-fold, respectively) relative to d0. The T cell imbalance was marked by loss of immunosuppressive markers such as Lef1 (p=2e-30) in T cell clusters primarily populated by d48 relative to d0.

Mechanistically the downstream effects of the immune cell activation were analysed in the serum of HF patients, where increased levels of sICAM-1, IL-6 and TNFRI levels (1.75x-, 5.30x-, 2.63x-fold, respectively) could be detected. Furthermore, treatment of endothelial cells with the conditioning media from HF-immune cells induced capability to adhere with monocytes in a co-culture system but also decreased the checkpoint inhibitor molecule PD-L1, a known blocker of autoreactive T cells.

These data link HF with enhanced monocyte and T cell activation as well as T cell clonal expansion, along with increased T cell numbers in mouse hearts post-MI. These data suggest HF is may drive impaired resolution of inflammation in cardiac tissue and facilitate adverse remodelling and cardiac damage. Further studies will assess the specific role of chronic monocyte and T cell activation in the progression of heart failure.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): DFG -Deutsche ForschungsgemeinschaftDZHK -Deutsches Zentrum für Herzkreislauferkrankungen

Chronic ischemic heart failure in humans is associated with changes in expression of antigen processing HLA types and activation of T-cells

Background

Sustained pathological inflammation is a hallmark of chronic ischemic heart failure (HF). The short term response to myocardial ischemia has found a protective phenotype for T regulatory cells, yet the extent and consequence of prolonged T-cell activation in chronic ischemic heart failure is unclear.

Methods and results

Single cell RNA sequencing of circulating immune cells (n=181,712 cells) from healthy (n=8) and heart failure donors (n=8) revealed a relative increase in the proportion of activated T cells in heart failure patients relative to healthy controls. T cell activation molecules of the HLA-DR series genes on antigen presenting cells were found to be strongly associated with heart failure patients in the sequencing data, with decreases in antigen processing genes (HLA-DM series) in heart failure patients. Validation via flow cytometry in 27 healthy controls and 43 heart failure patients showed relative decreases of greater than 30% for HLA-DM to HLA-DRB molecule ratios in HF patients (p=0.0082), suggesting an aberrant antigen presentation to T cells linked to autoimmunity in heart failure patients. Additionally, costimulatory molecules such as ICAM-1 (p=0.004) and activation markers like TREM-1 (p=0.04) were elevated in circulating monocytes cells, which may potentiate T cell activation. Correspondingly, a significant and striking decrease in CD4+ and CD8+ naïve T cells along with increases in combined effector memory and TEMRA cells could be evidenced in heart failure patients. Levels of the T-cell homing marker CCR5 were elevated in patients with heart failure. To gain additional insights into potential functional consequences in the heart, supernatants from 3h LPS stimulated immune cells (peripheral blood mononuclear cells or T cells) were applied to various vascular cell types (endothelial cells, pericytes) and with cardiac organoids for 48h. Apoptosis was increased more than 3 fold following incubation with media derived from peripheral blood cells of HF patients, suggesting that immune cells from heart failure patients can directly and indirectly impair cardiovascular cells.

Conclusion

Heart failure is marked by sustained increases in relative proportions of effector T cell and TEMRA populations and homing markers suggesting these cells may undergo extravasation to tissues and deteriorate inflamed myocardium - hastening heart failure progression, worsening prognosis. Further research is required to assess how these cells may migrate to myocardial tissues and what interventions could be useful for blocking myocardial damage.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): DZHK, DGK, SFB

[Culture conditions for gametes and embryos: Which culture medium? Which impact on newborn?]

Many studies have examined the impact of cell/embryo culture media on the development of human embryo during IVF process, but few studies have followed up and compared the effects of these culture media on the developmental outcome of children conceived by IVF. As recurrent experimental evidence from animal studies suggests potential long-term effects of embryo culture media on the health outcome of IVF-conceived children, more studies are needed to clarify the role of the culture media and mechanisms underlying such effects. In human, however, the effects of culture media are difficult to pinpoint due to complications stem from both the influence of maternal nutrition during the gestational period and the parental genetic. Based on a simple review of the literature integrating animal experimentations and human clinic studies, we suggest that the composition of culture medium should be considered beyond the character of unique or sequential medium, corresponding to "let embryo choose" or "back to nature" respectively. Instead, we suggest that the main components of embryo culture media should be considered from the point of view of metabolic consequences and potential epigenetic effects. Given that energetic metabolites can regulate epigenetic machinery, we hypothesize that metabolic abnormalities linked to morphological abnormalities could reveal epigenetic defects in embryos.

[Extracorporeal CO2 Elimination (ECCO2R) for Hypercapnic Respiratory Failure: From Pathophysiology to Clinical Application]

Extracorporeal CO₂ removal (ECCO₂R) is becoming an increasingly established treatment option for patients with acute severe hypercapnic respiratory failure. Technically, pumpless arterio-venous systems using the natural arterio-venous pressure gradient and also pump-driven veno-venous systems are available. Here, veno-venous ECCO₂R has become the preferred technique, as settings for arterio-venous ECCO₂R are restricted and side effects are more common with arterio-venous ECCO₂R. Using veno-venous ECCO₂R with blood flow rates up to 450 ml/min 60 to 80 ml CO₂ can be removed per minute corresponding to 20 to 30 % of the total amount of CO₂ production. However, in case of very severe hypercapnic respiratory failure with severe respiratory acidosis (pH 7.1 or less) blood flow rates of around 1000 ml/min are required for compensating severe respiratory acidosis corresponding to the elimination of 50 to 60 % of the total amount of CO₂ production. Relevant side effects include the activation of blood coagulation and associated bleeding complications. Two recent case-control studies in severely exacerbated COPD patients could demonstrate that intubation rates can be reduced by the application of ECCO₂R, but this was associated with non-ignorable side effects. Therefore, randomized controlled trials are urgently needed to more precisely establish the risks and benefits of ECCO₂R when aimed at avoiding intubation.

[Role of the vascular wall in the pathophysiology of the acute coronary syndrome]

The endothelium is of important significance in the development of the acute coronary syndrome. As an endo-/paracrine organ, the endothelium plays a key role in the regulation of the vascular homeostasis. The endothelial integrity and above all the bioavailability of nitric oxide (NO) are essential for the correct function of the endothelium. Cardiac risk factors may lead to an endothelial dysfunction with a consecutive imbalance of the vascular homeostasis. In an inflammatory or prothrombotic state the endothelium shows a number of abnormalities such as oxidative stress, expression of cell adhesion molecules, activation of cell signal-systems (renin-angiotensin-system, CD40/CD40L-system) and especially the loss of NO. The inflammatory cascades lead to coronary atherosclerosis over years or, more instantly, to the acute coronary syndrome caused by endothelial erosion or the rupture of an instable plaque. The knowledge of the pathophysiological processes in the arterial wall during the acute coronary syndrome may lead to the identification of high risk patients and the development of more targeted therapies.

Die Rolle der Gefäßwand in der Pathophysiologie des akuten Koronarsyndroms

Das Endothel ist in der Entstehung des akuten Koronarsyndroms von entscheidender Bedeutung. Als endo-/parakrines Organ nimmt das Endothel eine Schlüsselfunktion in der Regulation der vaskulären Homöostase ein. Die endotheliale Integrität und vor allem die Bioverfügbarkeit von Stickstoffmonoxid (NO) sind essenziell für die korrekte Funktion des Endothels. Kardiale Risikofaktoren können eine Endotheldysfunktion mit einem resultierenden Ungleichgewicht der vaskulären Homöostase verursachen. Im inflammatorischen oder prothrombotischen Zustand zeigt das Endothel oxidativen Stress, vermehrte Expression von Zelladhäsionsmolekülen, eine Aktivierung von Zell-Signalsystemen (Renin-Angiotensin-System, CD40/CD40L-System) und insbesondere einen NO-Verlust. Diese entzündungsbedingten Kaskaden führen oft über Jahre zur Koronarsklerose oder binnen kurzer Zeit zum akuten Koronarsyndrom, das durch Endothelerosion oder die Ruptur einer instabilen Plaque ausgelöst wird. Durch die Kenntnis der pathophysiologischen Vorgänge in der Gefäßwand beim akuten Koronarsyndrom lassen sich sowohl Hochrisikopatienten identifizieren als auch gezielte therapeutische Maßnahmen entwickeln.

Abnormal ion content, hydration and granule expansion of the secretory granules from cystic fibrosis airway glandular cells

The absence or decreased expression of cystic fibrosis transmembrane conductance regulator (CFTR) induces increased Na(+) absorption and hyperabsorption of the airway surface liquid (ASL) resulting in a dehydrated and hyperviscous ASL. Although the implication of abnormal airway submucosal gland function has been suggested, the ion and water content in the Cystic Fibrosis (CF) glandular secretory granules, before exocytosis, is unknown. We analyzed, in non-CF and CF human airway glandular cell lines (MM-39 and KM4, respectively), the ion content in the secretory granules by electron probe X-ray microanalysis and the water content by quantitative dark field imaging on freeze-dried cryosections. We demonstrated that the ion content (Na(+), Mg(2+), P, S and Cl(-)) is significantly higher and the water content significantly lower in secretory granules from the CF cell line compared to the non-CF cell line. Using videomicroscopy, we observed that the secretory granule expansion was deficient in CF glandular cells. Transfection of CF cells with CFTR cDNA or inhibition of non-CF cells with CFTR(inh)-172, respectively restored or decreased the water content and granule expansion, in parallel with changes in ion content. We hypothesize that the decreased water and increased ion content in glandular secretory granules may contribute to the dehydration and increased viscosity of the ASL in CF.

Defective remethylation of homocysteine is related to decreased synthesis of coenzymes B2 in thyroidectomized rats

We investigated the influence of hypothyroidism on homocysteine metabolism in rats, focusing on a hypothetical deficient synthesis of FAD by riboflavin kinases. Animals were allocated in control group (n = 7), thyroidectomized rats (n = 6), rats with diet deficient in vitamin B2, B9, B12, choline and methionine (n = 7), thyroidectomized rats with deficient diet (n = 9). Homocysteine was decreased in operated rats (2.6 +/- 1.01 vs. 4.05 +/- 1.0 mumol/L, P = 0.02) and increased in deficient diet rats (29.56 +/- 4.52 vs. 4.05 +/- 1.0 micromol/L, P = 0.001), when compared to control group. Erythrocyte-Glutathione-Reductase-Activation-Coefficient (index of FAD deficiency) was increased in thyroidectomized or deficient diet rats (P = 0.004 for both). Methylenetetrahydrofolate-reductase and methionine-synthase activities were decreased in thyroidectomized rats but not in those subjected to deficient diet. Cystathionine-beta-synthase was increased only in operated rats. Taken together, these results showed a defective re-methylation in surgical hypothyroidism, which was due in part to a defective synthesis of vitamin B2 coenzymes. This defective pathway was overcompensated by the increased Cystathionine-beta-synthase activity.

P-selectin in arterial thrombosis

P-selectin is a transmembrane protein present in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells. Following activation, it is rapidly translocated to the cell surface. P-selectin expression in platelets has been shown to be elevated in disorders associated with arterial thrombosis such as coronary artery disease, acute myocardial infarction, stroke, and peripheral artery disease. P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells as well as interactions of platelets with leukocytes. Platelet P-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes to form platelet-leukocyte aggregates. Furthermore, this interaction of P-selectin with PSGL-1 induces the upregulation of tissue factor, several cytokines in leukocytes and the production of procoagulant microparticles, thereby contributing to a prothrombotic state. P-selectin is also involved in platelet-platelet interactions, i. e. platelet aggregation which is a major factor in arterial thrombosis. P-selectin interacts with platelet sulfatides, thereby stabilizing initial platelet aggregates formed by GPIIb/IIIa-fibrinogen bridges. Inhibtion of the P-selectin-sulfatide interaction leads to a reversal of platelet aggregation. Thus, P-selectin plays a significant role in platelet aggregation and platelet- leukocyte interactions, both important mechanisms in the development of arterial thrombosis.

Sulfatides: targets for anti-phospholipid antibodies

BACKGROUND

Sulfatides are sulfated glycosphingolipids expressed on the surface of erythrocytes, leukocytes, and platelets. Sulfatides interact with several cell adhesion molecules involved in hemostasis. Beta2-glycoprotein I is an anionic phospholipid-binding plasma protein, and the phospholipid-bound form is the target for most anti-phospholipid antibodies that are associated with recurrent thrombosis, miscarriages, and neurological symptoms. In this study, we examined whether beta2-glycoprotein I forms a complex with sulfatides and thereby becomes a target for anti-phospholipid antibodies.

METHODS AND RESULTS

Beta2-glycoprotein I binds to surface-bound sulfatides but not to other glycolipids, such as ceramide, cerebrosides, sphingomyelin, or ganglioside. At a sulfatide coating density of 1 microg/well, beta2-glycoprotein I reaches half-maximal binding at 2.5 microg/mL, and the binding is saturated at 10 microg/mL. The binding of beta2-glycoprotein I also depends on the coating density of sulfatides in the well. At a constant beta2-glycoprotein I concentration of 5 microg/mL, maximal binding of beta2-glycoprotein I is observed at a coating density of 1 mug/well. The serum from 14 patients with anti-cardiolipin antibodies, a subset of anti-phospholipid antibodies, bound to sulfatide-bound beta2-glycoprotein I and previous absorption on cardiolipin-coated surfaces decreased the immunoreactivity toward sulfatide-beta2-glycoprotein I complex by >50% in 12 of 14 patients. Furthermore, immunoaffinity-purified anti-cardiolipin antibodies from 4 of 5 patients reacted with sulfatide-bound beta2-glycoprotein I.

CONCLUSIONS

These results show that not only anionic phospholipids, as commonly known, but also sulfatides are targets for most anti-phospholipid antibodies. We therefore postulate that interactions of these antibodies with sulfatides may contribute to some of the clinical symptoms of the anti-phospholipid antibody syndrome.

Role for sulfatides in platelet aggregation

BACKGROUND

Sulfatides are sulfated glycosphingolipids present on the surface of oligodendrocytes, renal tubular cells, and certain tumor cells. They appear to be involved in nerve conduction and cell adhesion, but their precise physiological function is not known.

METHODS AND RESULTS

Here, we show a novel role for sulfatides as a major ligand for P-selectin in platelet adhesion and aggregation. Sulfatides are expressed on the platelet surface, and platelets expressing sulfatides adhere to P-selectin. Both sulfatide micelles and sulfatide-binding recombinant malaria circumsporozoite protein (MCSP) inhibit this adhesion. In parallel, platelets and CHO cells expressing P-selectin adhere to sulfatides, and anti-P-selectin antibodies inhibit this adhesion. Furthermore, both anti-P-selectin antibodies and sulfatide antagonist MCSP significantly reverse platelet aggregation induced by ADP, collagen, or thrombin receptor-activating peptide, suggesting that sulfatide-P-selectin interactions are necessary for the formation of stable platelet aggregates.

CONCLUSIONS

These results show that sulfatide interactions with P-selectin are important in platelet adhesion and platelet aggregation. The sulfatide interactions with P-selectin stabilize platelet aggregates, representing a new mechanism of platelet aggregation that may play a significant role in hemostasis and thrombosis.

Influence of culture conditions on the alpha 1,2-fucosyltransferase and MUC gene expression of a transformed cell line MM-39 derived from human tracheal gland cells

Human tracheal glands cells (HTGC) in culture are able to respond to adrenergic, cholinergic and purinergic agonists by increasing their serous and mucin secretions. These secretagogues are also able to maintain an optimal responsiveness of serous cells to stimulation when they are regularly and briefly delivered to the cells, making the HTGC a suitable model to study the serous secretion (Merten, in press). Our interest has been focused on the effects of cholinergic and purinergic secretagogues associated to histamine, on the mucous function of the transformed human tracheal gland cell line MM-39, which has a mixed, both serous and mucous, phenotype. When the cells were exposed to short stimulation every 2 days for 3 weeks with 10 or 100 microM carbachol, UTP and histamine, modifications of their mucous phenotype were observed. The expression of MUC genes appeared dependent on the culture conditions. Transcripts of MUC1, MUC4, and MUC5B genes were observed when the cells were regularly exposed to the mixture of secretagogues at a concentration of 10 microM, in contrast to the unstimulated expression of MUC1 and MUC4 in control cells. MUC1, MUC4, MUC7, MUC6 and MUC11 transcripts were observed when the cells were regularly exposed to the mixture of secretagogues at a concentration of 100 microM. These culture conditions were also able to induce an alpha 1,2-fucosyltransferase activity absent in the MM-39 cells cultivated with standard conditions. There was no marked effect on the alpha 2,3-sialyltransferase activity although the expression pattern of the sialyltransferase genes was reduced to the unique presence of ST3Gal III. In conclusion, MM-39 cells exposed to repeated stimulation by secretagogues at different concentrations express different sero-mucous phenotypes.

Cholesterol sulfate: a new adhesive molecule for platelets

BACKGROUND

Cholesterol 3-sulfate is present on a variety of cells and in human LDL, and it has been found in atherosclerotic lesions of human aorta. Its precise biological role has not yet been described.

METHODS AND RESULTS

In this study, we investigated the interaction of platelets with cholesterol sulfate. Platelets adhered in a concentration-dependent and saturable manner to cholesterol sulfate but did not adhere to cholesterol, cholesterol acetate, estrone sulfate, or dehydroepiandrosterone sulfate, suggesting that the specificity of this interaction is determined not only by the cholesterol moiety but also by the sulfate group. This adhesion did not increase after platelet activation, and it was not cation-dependent. Soluble cholesterol sulfate inhibited adhesion in a concentration-dependent manner. However, antibodies against glycoprotein Ib, glycoprotein IIb/IIIa, CD36, P-selectin, von Willebrand factor, or thrombospondin had no significant effect on platelet adhesion to cholesterol sulfate. Perfusion of whole blood in a parallel-plate flow chamber resulted in the rapid and progressive adhesion of platelets to cholesterol sulfate but not to cholesterol acetate or estrone sulfate.

CONCLUSIONS

Cholesterol sulfate supports platelet adhesion and may be one of the factors determining the prothrombotic potential of atherosclerotic lesions.

A new role for P-selectin in shear-induced platelet aggregation

BACKGROUND

P-selectin, expressed on platelets on activation, mediates rolling of platelets on endothelial cells, but its role in shear-induced platelet aggregation is not known.

METHODS AND RESULTS

Platelets were exposed to either a single pulse (30 seconds) or 3 pulses (10 seconds) of high shear stress (150 to 200 dynes/cm(2)) each followed by low shear stress (10 dynes/cm(2)) for 4.5 minutes or 90 seconds, respectively, at 37 degrees C to resemble more closely in vivo conditions such as those in stenotic arteries. Under these conditions, platelet aggregation was significantly increased compared with low or high shear stress alone. Monoclonal anti-P-selectin antibodies inhibited shear-induced platelet aggregation, especially when induced by the combination of high and low shear stress, by approximately 70% and had an additive effect on the inhibition by abciximab (anti-glycoprotein (GP) IIb/IIIa antibody). However, anti-P-selectin antibody inhibited shear-induced platelet aggregation only at 37 degrees C, not at 22 degrees C, whereas abciximab inhibited shear-induced platelet aggregation at both 22 degrees C and 37 degrees C. This differential effect of anti-P-selectin antibody is explained by the finding that shear-induced P-selectin expression on platelets was observed mainly at 37 degrees C.

CONCLUSIONS

These results indicate that pulsatile shear stress, which resembles flow conditions in stenotic arteries, induces significantly more platelet aggregation at 37 degrees C than monophasic shear stress. Under these conditions, we show a novel role for P-selectin in platelet aggregation distinct from that of GP IIb/IIIa, which may be of importance in the initiation of thrombosis associated with atherosclerotic lesions.

P-selectin expression on platelets determines size and stability of platelet aggregates

BACKGROUND

P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells. After platelet activation, P-selectin is translocated from intracellular granules to the external membrane, whereas fibrinogen aggregates platelets by bridging glycoprotein (GP) IIb/IIIa between adjacent platelets.

METHODS AND RESULTS

In this study, we define a novel role for P-selectin in platelet aggregation. Expression of P-selectin on the platelet surface correlated strongly with the mean platelet aggregate size. Inhibition of P-selectin binding to its ligand by either monoclonal anti-P-selectin antibodies directed against the lectin domain or soluble human P-selectin reversed platelet aggregation even when added up to 5 minutes after activation; however, fibrinogen binding to platelets was not affected. This deaggregating effect significantly reduced the maximal size and number of platelet aggregates. When added 1 minute after platelet activation, anti-P-selectin antibody achieved 95% to 100% of the deaggregating effect of EDTA, whereas the anti-GP IIb/IIIa antibody abciximab had no effect. Monoclonal antibodies against known P-selectin ligands, such as P-selectin GP ligand-1 (PSGL-1) or GP Ib, had no effect on platelet aggregation, suggesting a different ligand for P-selectin in platelet aggregate stabilization. In kinetic studies, P-selectin was maximally expressed 10 minutes after platelet activation, whereas maximal activation of GP IIb/IIIa occurred within the first 10 seconds, suggesting that P-selectin operates after fibrinogen binding to activated GP IIb/IIIa.

CONCLUSIONS

These results indicate that P-selectin interaction with a ligand, different from PSGL-1 or GP Ib, stabilizes initial GP IIb/IIIa-fibrinogen interactions, allowing the formation of large stable platelet aggregates.

Histidylated polylysine as a synthetic vector for gene transfer into immortalized cystic fibrosis airway surface and airway gland serous cells

BACKGROUND

We recently designed a cationic polymer called histidylated polylysine made of polylysine partially substituted with histidyl residues which become protonated at slightly acidic pH. This polymer is thought to induce the leakage of acidic vesicles containing plasmid/histidylated polylysine complexes.

METHODS

and results Here, we have analyzed the ability of histidylated polylysine to transfer reporter or CFTR genes into immortalized cystic fibrosis airway surface epithelial cells (sigmaCFTE29o- cells) and airway gland serous cells (CF-KM4 cells) which are both important targets for cystic fibrosis gene therapy. The luciferase reporter gene expression measured after gene transfer with histidylated polylysine into both cell lines was quite high and similar to that obtained with commercially available vectors. In addition, the level of expression was not dependent on the presence of a membrane disrupting agent such as chloroquine. Histidylated complexes were present in slightly acidic non-lysosomal cellular compartments as shown by a cytological approach using biotinylated plasmid, lysosome-specific antibodies and confocal microscopy. Histidylated complexes appeared to be of small size when prepared at low ionic strength and formed aggregates upon increasing the ionic strength. However, aggregate formation was prevented by the addition of 10% fetal bovine serum. Gene transfer efficiency varied with the size of the complexes and decreased when small particles were used.

CONCLUSIONS

These results suggest that histidylated polylysine may be an efficient non-viral vector for gene transfer into cystic fibrosis airway surface epithelial cells and airway gland serous cells.

Efficient gene transfer into human normal and cystic fibrosis tracheal gland serous cells with synthetic vectors

Submucosal gland serous cells are believed to play a major role in the physiopathology of cystic fibrosis (CF) and may represent an important target for CF gene therapy. We have studied the efficiency of reporter gene transfer into immortalized normal (MM-39) and CF (CF-KM4) human airway epithelial gland serous cells using various synthetic vectors: glycosylated polylysines (glycofectins), polyethylenimine (PEI) (25 and 800 kD), lipofectin, and lipofectAMINE. In both cell lines, a high luciferase activity was achieved with various glycofectins, with PEI 25 kD, and with lipofectAMINE. After three transfections applied daily using alpha-glycosylated polylysine, 20% of the cells were transfected. At 24 h after CF transmembrane conductance regulator (CFTR) gene transfer into CF-KM4 cells using alpha-glycosylated polylysine, the immunolocalization of CFTR was analyzed by laser scanning confocal microscopy and the transgenic CFTR was detected by an intense labeling of the plasma membrane. The presence of membrane lectins, i. e., cell surface receptors binding oligosaccharides, was also examined on MM-39 and CF-KM4 cells by assessing the binding and uptake of fluorescein-labeled neoglycoproteins and fluorescein-labeled glycoplexes (glycofectins complexed to plasmid DNA). Among all the neoglycoproteins and glycoplexes tested, those bearing alpha-mannosylated derivatives were most efficiently taken up by both normal and CF gland serous cells. However, alpha-mannosylated polylysine was quite inefficient for gene transfer, indicating that the efficiency of gene transfer is determined both by the uptake of the complexes and also by their intracellular trafficking. Moreover, our results show that an efficient in vitro gene transfer was achieved in human airway gland serous cells with the same synthetic vectors described to efficiently transfect human airway surface epithelial cells.

Development of substituted Benzo[c]quinolizinium compounds as novel activators of the cystic fibrosis chloride channel

Chloride channels play an important role in the physiology and pathophysiology of epithelia, but their pharmacology is still poorly developed. We have chemically synthesized a series of substituted benzo[c]quinolizinium (MPB) compounds. Among them, 6-hydroxy-7-chlorobenzo[c]quinolizinium (MPB-27) and 6-hydroxy-10-chlorobenzo[c]quinolizinium (MPB-07), which we show to be potent and selective activators of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. We examined the effect of MPB compounds on the activity of CFTR channels in a variety of established epithelial and nonepithelial cell systems. Using the iodide efflux technique, we show that MPB compounds activate CFTR chloride channels in Chinese hamster ovary (CHO) cells stably expressing CFTR but not in CHO cells lacking CFTR. Single and whole cell patch clamp recordings from CHO cells confirm that CFTR is the only channel activated by the drugs. Ussing chamber experiments reveal that the apical addition of MPB to human nasal epithelial cells produces a large increase of the short circuit current. This current can be totally inhibited by glibenclamide. Whole cell experiments performed on native respiratory cells isolated from wild type and CF null mice also show that MPB compounds specifically activate CFTR channels. The activation of CFTR by MPB compounds was glibenclamide-sensitive and 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid-insensitive. In the human tracheal gland cell line MM39, MPB drugs activate CFTR channels and stimulate the secretion of the antibacterial secretory leukoproteinase inhibitor. In submandibular acinar cells, MPB compounds slightly stimulate CFTR-mediated submandibular mucin secretion without changing intracellular cAMP and ATP levels. Similarly, in CHO cells MPB compounds have no effect on the intracellular levels of cAMP and ATP or on the activity of various protein phosphatases (PP1, PP2A, PP2C, or alkaline phosphatase). Our results provide evidence that substituted benzo[c]quinolizinium compounds are a novel family of activators of CFTR and of CFTR-mediated protein secretion and therefore represent a new tool to study CFTR-mediated chloride and secretory functions in epithelial tissues.

Platelet microparticles promote platelet interaction with subendothelial matrix in a glycoprotein IIb/IIIa-dependent mechanism

BACKGROUND

Platelets, on activation, release vesicular particles called platelet microparticles. Despite their procoagulant activity, their functional role in platelet-vessel wall interactions is not known.

METHODS AND RESULTS

We examined the binding of microparticles to vessel wall components in vitro and in vivo. Microparticles bound to fibrinogen-, fibronectin-, and collagen-coated surfaces. Compared with activated platelets, we observed minimal binding of microparticles to vitronectin and von Willebrand factor. The glycoprotein IIb/IIIa (GP IIb/IIIa) inhibitors abciximab and eptifibatide (Integrilin) inhibited the binding to fibrinogen and fibronectin but had minimal effect on binding to collagen. Furthermore, monoclonal antibodies to GP Ib or anionic phospholipid-binding proteins (beta2-glycoprotein I or annexin V) had no effect in these interactions. Microparticles did not bind to monolayers of resting or stimulated human umbilical vein endothelial cells (HUVECs), even in the presence of fibrinogen or von Willebrand factor. However, under similar conditions, microparticles bound to extracellular matrix produced by cultured HUVECs. Abciximab inhibited this interaction by approximately 50%. In a rabbit model of arterial endothelial injury, the infusion of 51Cr-labeled microparticles resulted in a 3- to 5-fold increase of microparticle adhesion to the injured site compared with the uninjured site (P<0.05%). Furthermore, activated platelets bound to surface-immobilized microparticles in a GP IIb/IIIa-dependent mechanism. This binding increased in the presence of fibrinogen by approximately 30%.

CONCLUSIONS

Platelet microparticles bind to subendothelial matrix in vitro and in vivo and can act as a substrate for further platelet binding. This interaction may play a significant role in platelet adhesion to the site of endothelial injury.

Altered cytokine production by cystic fibrosis tracheal gland serous cells

Human submucosal tracheal glands are now believed to play a major role in the physiopathology of cystic fibrosis (CF). We successfully developed techniques for culturing human tracheal gland serous cells from normal individuals (HTGS cells) and from CF patients (CF-HTGS cells) and have shown that the cultured cells have retained most of their in vivo epithelial and secretory characteristics. In order to determine to what extent the serous cells may participate in the lung defense against infection, we examined the effects of the lipopolysaccharide (LPS) of Pseudomonas aeruginosa on HTGS and CF-HTGS cells, with special reference to tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and IL-8 secretion. HTGS cells showed a daily basal secretion of IL-6 (1.68 +/- 0.14 ng/10(6) cells) and IL-8 (9.6 +/- 1.3 ng/10(6) cells) and no constitutive secretion of TNF-alpha. Treatment with P. aeruginosa LPS resulted in a significant increase in the basal production of IL-6 (increase of 200% +/- 12%) and IL-8 (525% +/- 40%) as well as a rapid production of TNF-alpha (250 +/- 38 pg/10(6) cells). The LPS-induced secretion of IL-6 and IL-8, but not that of TNF-alpha, was inhibited by glucocorticoids. CF-HTGS cells showed a much higher basal secretion of IL-6 (13.2 +/- 0.5 ng/10(6) cells) and IL-8 (45.6 +/- 7.2 ng/10(6) cells) than normal cells. Treatment with the LPS of P. aeruginosa induced increased production of IL-6 (increase of 100% +/- 8%) and IL-8 (55% +/- 18%) but did not induce the secretion of TNF-alpha. Neither intracellular TNF-alpha nor TNF-alpha transcripts were found in CF-HTGS cells, whereas they were found in normal HTGS cells. In addition, dexamethasone was found to stimulate IL-6 and IL-8 secretion (in the presence or absence of LPS) but did not induce any secretion of TNF-alpha. All these data indicate that HTGS cells are responsive to P. aeruginosa LPS, which results in an increased secretion of IL-6, IL-8, and TNF-alpha, the secretion of which appeared to be impaired in CF-HTGS cells.

Defective ATP-dependent mucin secretion by cystic fibrosis pancreatic epithelial cells

The response of confluent monolayers of normal and cystic fibrosis (CF) pancreatic epithelial cells to stimulation by extracellular ATP and ATP analogues was investigated in terms of mucin secretion. Mucin secretion was measured as release of M1 antigens by a direct sandwich enzyme immunoassay. Extracellular ATP provoked rapid (< or = 15 min) and strong mucin secretion (+ 480 +/- 35%) by the normal pancreatic cell lines but was not able to induce mucin secretion by the CF cell lines. The order of efficacy of nucleotide agonists with ATP > ADP > AMP > adenosine was that of typical P2-purinergic receptors. ATP induced a rapid and transient intracellular [Ca2+] mobilization in both normal and CF pancreatic epithelial cells. This work demonstrated that CFTR seemed to mediate ATP-dependent mucin secretion.

Cholesterol-dependent changes of glycosaminoglycan pattern in human aorta

Glycosaminoglycans are regular constituents of the arterial wall and essential for its structure and function. The arteriosclerosis-dependent changes of glycosaminoglycans were investigated, the degree of arteriosclerosis was monitored by the cholesterol content of the tissue. Histological characterization was achieved by electron microscopy. Total glycosaminoglycans were isolated from 33 delipidated segments of human aorta thoracica after exhaustive proteolytic digestion, and fractionated into the individual glycosaminoglycans by a multistep purification procedure. Chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), and hyaluronate (HA) were identified and quantified by chemical and enzymatic analysis. The concentration of total and individual glycosaminoglycans, expressed as mg/g delipidated dry weight of tissue, decreased significantly with increasing cholesterol content of tissue (p = 0.0005-0.005). The extent of decrease differed between the individual glycosaminoglycans as indicated by a shift in the CS/DS:HA:HS ratio from 47:32:21 in low cholesterol aortic segments to 59:29:12 in cholesterol-rich specimens. Determination of the relative molecular masses (Mr) revealed 58 kDa for CS/DS and 92 kDa for HS with a (statistically not significant) increase of the molecular mass of CS/DS and a decrease of HS with increasing cholesterol content. The copolymeric CS/DS glycosaminoglycans were disintegrated enzymatically into CS and DS containing fragments. A significantly higher relative DS content (p = 0.01) was found in cholesterol-rich arterial tissue (32.5%) as compared with low cholesterol tissue samples (28.8%). Cell culture experiments revealed that human arterial HS is able to inhibit the proliferation of cultured human arterial smooth muscle cells. The HS concentration required for a 30% inhibition of smooth muscle cell proliferation was in the same order as the tissue concentration of HS. This confirms the function of HS as an endogenous inhibitor of cell division and its impact for the development of atherosclerosis.

Intracellular free Ca2+ dynamic changes to histamine are reduced in cystic fibrosis human tracheal gland cells

This study documents a difference between cystic fibrosis human (CF-HTG) and normal human (HTG) tracheal gland cells: the ability of histamine to induce an increase of intracellular free calcium concentration [Ca2+]i was abnormally reduced in CF-HTG cells. The magnitude of the [Ca2+]i peak rise in response to histamine is smaller in CF-HTG cells than in HTG cells, and the percentage of CF-HTG cells that increase [Ca2+]i is decreased compared with HTG cells. In contrast to histamine, the human neutrophil elastase (HNE) stimulation of both CF-HTG and HTG cells generated [Ca2+]i asynchronous oscillations and the magnitude of the peak [Ca2+]i response as well as the percentage of responding cells were similar for both groups. By videomicroscopy observations, the secretory response (exocytosis of secretion granules) of CF-HTG cells occurred with HNE, but not with histamine, thus suggesting that [Ca2+]i asynchronous oscillations may be linked to the exocytosis process in human tracheal gland cells.

Fibrinogen promotes monocyte adhesion via a protein kinase C dependent mechanism

The accumulation of blood monocytes at sites of predilection of the vessel wall is an early cellular event of atherogenesis. Proteins of the vessel wall may facilitate monocyte adhesion and thus promote their recruitment. It has been shown that the relative content of extracellular fibrinogen increases during lesion development, and this study investigated the contribution of immobilized fibrinogen to monocyte adhesion and the underlying mechanism. Freshly isolated human blood monocytes were cultivated in serum-free RPMI 1640 in tissue culture wells precoated with albumin, fibrinogen, or fibrin. After 16 h the plates were washed and adherent cells enumerated. Immobilized fibrinogen enhanced monocyte adhesion more than 1.9-fold compared to immobilized albumin or fibrin (P < 0.05). Concomitant addition of the protein kinase C (PKC) inhibitors staurosporine or H7 suppressed monocyte adherence to immobilized fibrinogen but exerted no significant effect upon adhesion to any other surface tested. Stimulation of monocytes using phorbol myristate acetate resulted in increased binding of monocytes on fibrinogen but not on bovine serum albumin. When PKC activity was reduced through prolonged incubation with PMA for 16 h, a significant reduction of monocyte adhesion on fibrinogen was observed. Peptides containing RGD sequences, which have been demonstrated to be ligands for certain integrins, did not inhibit monocyte adhesion. The data suggest that fibrinogen promotes monocyte adhesion in vitro by a PKC-dependent mechanism. PKC appears to be important not only for the initial cell adhesion but also for sustained binding of monocytes to fibrinogen.

Asynchronous dynamic changes of intracellular free Ca2+ and possible exocytosis in human tracheal gland cells induced by neutrophil elastase

Measurements of the intracellular free calcium concentration [Ca2+]i in single cells of the human tracheal gland cell line MM 39 demonstrate dynamic changes in [Ca2+]i after their exposure to human neutrophil elastase (HNE). A heterogeneity in [Ca2+]i responses measured cell to cell in monolayer culture is evident: cells generate an initial [Ca2+]i peak rise with or without a delayed time (up to 180 sec) followed either by a rapid return to baseline, asynchronous oscillations or a sustained plateau phase. From basal concentration of 85 +/- 15 nM, HNE (1 microM) produces a [Ca2+]i increase of 91 +/- 66 nM in about 50% of responding cells. At lower concentrations of HNE (0.1 microM, 0.01 microM), the [Ca2+]i rise remains similar, but only 30-40% of the cells are responding. Pretreatment of cells with the recombinant elafin protein, a specific elastase inhibitor, reduces both the [Ca2+]i response to HNE and the number of responding cells. Electron microscopy observations reveal an increased number of secretory granules located beneath the cell plasma membrane after HNE treatment. These results suggest that intracellular [Ca2+]i changes may be associated to the HNE-induced exocytosis in human tracheal gland cells. These findings could have implications with regard to the pathogenesis of increased mucus secretion in human airway diseases.

Presence of MRP8 and MRP14 in pancreatic cell lines: differential expression and localization in CFPAC-1 cells

A complex of two calcium binding proteins, MRP8 [also called cystic fibrosis (CF) antigen] and MRP14, proteins known to be expressed in cells of myeloid origin, has been shown to be present in higher amounts in the serum of CF patients and heterozygotes compared with normal subjects. We demonstrated here for the first time, by dot-blot analysis and immunocytochemistry, the expression and the presence of these S100 calcium binding proteins in the pancreatic cell lines CAPAN-1 and CFPAC-1, the latter provided from a patient with CF. Moreover, using immunocytochemical methods, we showed that the localization of MRP8 and MRP14 on the plasma membrane seems to be restricted to the cells expressing a cystic fibrosis transmembrane conductance regulator (CFTR) wild-type protein such as CAPAN-1 cells and CFPAC-1 cells transfected with a plasmid containing the nonmutated CFTR gene (CFPAC-PLJ-CFTR-6 cells). In CFPAC-1 cells, immunoreactivity remains in the cytoplasm throughout the stationary phase. We also showed an increased level of the mRNAs of the two proteins in the CFPAC-1 cells compared with those transfected with the nonmutated CFTR. The demonstration of a difference in the cellular localization of these two proteins and in their mRNA levels in the cell line of CF origin leads us to assume the existence of a possible correlation in the expression of the MRPs with that of the CFTR protein.

Trypsinogen expression by two human pancreatic cell lines CFPAC-1 and CAPAN-1. Modulation during spontaneous and induced cell growth

We previously demonstrated that two human pancreatic adenocarcinoma cell lines, CFPAC-1 (established from a patient with cystic fibrosis) and CAPAN-1, were able to secrete trypsinogens 1 and 2 specifically. In order to analyze the relation of trypsin secretion to differentiation and cell growth, we undertook a comparative study of immunoreactive trypsin 1 (IRT) secretion by the two cell lines during cell growth in the presence and in the absence of various differentiating agents: sodium butyrate (NaBut), dimethylsulfoxide (DMSO), and dexamethasone (DX). In the presence of NaBut, IRT levels in the supernatants of both cell lines were slightly increased, whereas the cellular growth of both cell lines decreased significantly. In the presence of DX, IRT levels in cell culture conditioned media immediately and dramatically decreased, but the cell growth of neither cell line was affected by DX. An important increase in IRT levels was observed when CFPAC-1 cells and CAPAN-1 cells were grown in the presence of DMSO, but for both cell lines the cellular growth decreased in the presence of DMSO. Our data show that neither the IRT secretion level nor the differentiation state of these cell lines correlates with cellular growth, and suggests that the expression of pancreatic proteases by these two tumor cell lines could be either related to a common stem cell with this potential or to a possible acinar origin of pancreatic cancer, as recently proposed by others.

Increased coexpression of CFTR and S100 calcium binding proteins MRP8 and MRP14 mRNAs in cystic fibrosis human tracheal gland cells

We have demonstrated for the first time, by Northern analysis, the presence of the S-100 calcium binding proteins MRP8 (also called "cystic fibrosis protein") and MRP14 mRNAs in cultured human tracheal gland cells, obtained from normal and cystic fibrosis (CF) patients. A significant increase of these mRNAs in cells of CF origin (as well as that of CFTR mRNA) is shown. These results allow us to assume a potential pretranslational regulation of MRP8 and MRP14 gene expression related to the presence of a mutated CFTR gene.

Possible regulation of CFTR-chloride channels by membrane-bound phosphatases in pancreatic duct cells

We have studied CFTR-Cl- channels in non-CF CAPAN-1 and in CFTR-transfected CFPAC-PLJ-CFTR-6 epithelial cells from human pancreas. Theophylline and IBMX induced the opening of cell-attached CFTR-Cl- channels. Theophylline, IBMX and the alkaline phosphatase (AP) inhibitor levamisole enhanced the activity of excised channels and reduced by 70-75% the apical membrane-associated APs activity. Okadaic acid had no effect on APs and channel activities. A polyclonal anti-alkaline phosphatase antibody (which detected apical APs) reduced APs activity and activated quiescent excised chloride channels. These results suggest that CFTR channels may be regulated by membrane-bound phosphatases.

Characterization of trypsinogens 1 and 2 in two human pancreatic adenocarcinoma cell lines; CFPAC-1 and CAPAN-1

Proteins with trypsin-like immunoreactivity (first detected by a specific immunoenzymatic assay) were isolated from CAPAN-1 and CFPAC-1 cell culture-conditioned media by chromatography on an immunoadsorbent prepared with a polyclonal antibody directed against trypsin 1. The adsorbed proteins were devoid of free trypsin activity but trypsin activity was present after enterokinase activation demonstrating that the immunoreactive trypsin present in cell supernatants corresponds to trypsinogens. When characterised by Western blotting using a monoclonal antibody directed against human trypsin 1 two protein bands corresponding to trypsinogen 1 (23 kDa) and trypsinogen 2 (25 kDa) gave a positive reaction. These results demonstrate the presence of trypsinogens 1 and 2 in CAPAN-1 and CFPAC-1 cells and in their culture-conditioned media.

Culture and characterization of human tracheal gland cells

In order to study the composition and regulation of human tracheal gland (HTG) cell secretion, we cultured HTG cells isolated by enzymatic digestion from tracheal mucosa obtained 30 to 60 min after death. On microscopic observation, isolated cells were mainly composed of secretory glandular cells. Maximal HTG cell growth was observed when cells were cultured on type I collagen in the presence of 2% Ultroser G. Under these conditions, 3 to 6 HTG cell passages, corresponding to 20 to 30 population doublings, could be achieved. Lysozyme and bronchial inhibitor (Brl), two secretory protein markers specific to the serous HTG cells, were released in the culture medium, maximal secretion being observed 7 days after the cells had reached confluency. At that time, Brl could be detected, with an immunoperoxidase technique, in about 90% of the cells in culture, suggesting that most cells in culture were serous cells. Using transmission electron microscopy, after in situ fixation, HTG cells exhibited an epithelioid appearance at confluency. Using the biotin-streptavidin gold technique, we identified Brl in cytoplasmic vesicles and in small, immature electron-dense secretory granules. In high cell density cultures, we observed dome formation, suggesting active ion transport mechanisms in HTG cell culture. At confluency, a dose-dependent increase of Brl secretion was induced by phenylephrine, isoproterenol, and carbochol. These results suggest that HTG cell culture provides a useful tool to study the biochemistry and regulation of human tracheobronchial gland cell secretion.