Dynamics of Vascular Protective and Immune Supportive Sphingosine-1-Phosphate During Cardiac Surgery

Introduction

Sphingosine-1-phosphate (S1P) is a signaling lipid and crucial in vascular protection and immune response. S1P mediated processes involve regulation of the endothelial barrier, blood pressure and S1P is the only known inducer of lymphocyte migration. Low levels of circulatory S1P correlate with severe systemic inflammatory syndromes such as sepsis and shock states, which are associated with endothelial barrier breakdown and immunosuppression. We investigated whether S1P levels are affected by sterile inflammation induced by cardiac surgery.

Materials and Methods

In this prospective observational study we included 46 cardiac surgery patients, with cardiopulmonary bypass (CPB, n=31) and without CPB (off-pump, n=15). Serum-S1P, S1P-sources and carriers, von-Willebrand factor (vWF), C-reactive protein (CRP), procalcitonin (PCT) and interleukin-6 (IL-6) were measured at baseline, post-surgery and at day 1 (POD 1) and day 4 (POD 4) after surgical stimulus.

Results

Median S1P levels at baseline were 0.77 nmol/mL (IQR 0.61-0.99) and dropped significantly post-surgery. S1P was lowest post-surgery with median levels of 0.37 nmol/mL (IQR 0.31-0.47) after CPB and 0.46 nmol/mL (IQR 0.36-0.51) after off-pump procedures (P<0.001). The decrease of S1P was independent of surgical technique and observed in all individuals. In patients, in which S1P levels did not recover to preoperative baseline ICU stay was longer and postoperative inflammation was more severe. S1P levels are associated with its sources and carriers and vWF, as a more specific endothelial injury marker, in different phases of the postoperative course. Determination of S1P levels during surgery suggested that also the anticoagulative effect of heparin might influence systemic S1P.

Discussion

In summary, serum-S1P levels are disrupted by major cardiac surgery. Low S1P levels post-surgery may play a role as a new marker for severity of cardiac surgery induced inflammation. Due to well-known protective effects of S1P, low S1P levels may further contribute to the observed prolonged ICU stay and worse clinical status. Moreover, we cannot exclude a potential inhibitory effect on circulating S1P levels by heparin anticoagulation during surgery, which would be a new pro-inflammatory pleiotropic effect of high dose heparin in patients undergoing cardiac surgery.

Anti-inflammatory HDL effects are impaired in atrial fibrillation

High-density lipoprotein (HDL), best known for cholesterol transport, also has anti-inflammatory effects. Previous studies suggest involvement of myeloperoxidase (MPO) in modification of HDL. HDL bound Sphingosine-1-phosphate (S1P) has been implied to be an essential protein regarding beneficial HDL effects. In this study, we analyzed anti-inflammatory HDL properties in patients with atrial fibrillation (AF), a disease involving atrial inflammation, compared to non-AF controls and whether anti-inflammatory properties improve upon catheter ablation. Additionally, association with serum concentrations of MPO and S1P were assessed. We isolated HDL from 25 AF patients, 13 non-AF individuals and 14 AF patients at follow-up (FU) after catheter ablation. S1P was measured in a cohort of 141 AF and 21 FU patients. Following preincubation with HDL from either group, bovine aortic endothelial cells were stimulated using tumor necrosis factor α and expression of pro-inflammatory genes intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), E-selectin (SELE) and P-selectin (SELP) was assessed using qPCR. Concentrations of circulating protein of these genes as well as MPO and S1P were measured in serum samples. Compared to non-AF individuals HDL from AF patients suppressed gene expression of the pro-inflammatory adhesion molecules ICAM1, VCAM1, SELE and SELP 27%, 18%, 21% and 57% less, respectively (p < 0.05 for all except SELE p = 0.06). In FU patients, the anti-inflammatory HDL activity was improved (suppression of ICAM1 + 22%, VCAM1 + 10%, SELE + 38% and SELP + 75%, p < 0.05 for all except VCAM1 p = 0.08). AF patients using angiotensin converting enzyme inhibitors or angiotensin receptor blockers had better anti-inflammatory HDL properties than non-users (gene expression suppression at least 28% more, p < 0.05 for all except ICAM1 p = 0.051). Circulating protein concentrations were not correlated with in vitro gene-expression, but circulating P-selectin was generally elevated in AF and FU patients compared to non-AF patients. MPO plasma concentration was positively associated with gene-expression of ICAM1, VCAM1 and SELP (r² > 0.4, p < 0.05). Serum concentrations of S1P were increased in FU patients {1.201 µM [1.077–1.543]} compared to AF patients {0.953 µM [0.807–1.135], p < 0.01} but not correlated with ICAM1, VCAM1 and SELP gene expression. We conclude that the anti-inflammatory activity of HDL is impaired in AF patients, which might promote AF progression and AF-associated complications.

Increased Sphingosine-1-Phosphate Serum Concentrations in Subjects with Periodontitis: A Matter of Inflammation

Purpose

Periodontitis is an inflammatory disease of the oral cavity with an alarmingly high prevalence within the adult population. The signaling lipid sphingosine-1-phosphate (S1P) plays a crucial role in inflammatory and immunomodulatory responses. In addition to cardiovascular disease, sepsis and tumor entities, S1P has been recently identified as both mediator and biomarker in osteoporosis. We hypothesized that S1P may play a role in periodontitis as an inflammation-prone bone destructive disorder. The goal of our study was to evaluate associations between periodontitis and S1P serum concentrations in the Study of Health in Pomerania (SHIP)-Trend cohort. In addition, we investigated the expression of S1P metabolizing enzymes in inflamed gingival tissue.

Patients and Methods

We analyzed data from 3371 participants (51.6% women) of the SHIP-Trend cohort. Periodontal parameters and baseline characteristics were assessed. Serum S1P was measured by liquid chromatography tandem mass spectrometry. The expression of S1P metabolizing enzymes was determined by immunofluorescence staining of human gingival tissue.

Results

S1P serum concentrations were significantly increased in subjects with both moderate and severe periodontitis, assessed as probing depth and clinical attachment loss. In contrast, no significant association of S1P was seen with caries variables (number and percentage of decayed or filled surfaces). S1P concentrations significantly increased with increasing high-sensitivity C-reactive protein (hs-CRP) levels. Interestingly, inflamed compared to normal human gingival tissue exhibited elevated expression levels of the S1P-generating enzyme sphingosine kinase 1 (SphK1).

Conclusion

We report an intriguingly significant association of various periodontal parameters with serum levels of the inflammatory lipid mediator S1P. Our data point towards a key role of S1P during periodontitis pathology. Modulation of local S1P levels or its signaling properties may represent a potential future therapeutic strategy to prevent or to retard periodontitis progression and possibly reduce periodontitis-related tooth loss.

Sphingosine-1-Phosphate, Motor Severity, and Progression in Parkinson's Disease (MARK-PD)

BACKGROUND

Treatment with sphingosine-1-phosphate (S1P) agonists confers neuroprotective effects in animal models of Parkinson's disease (PD).

OBJECTIVES

We assessed the association of serum S1P levels with motor and cognitive symptoms in patients with PD.

METHODS

S1P concentrations were analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) in serum of 196 PD patients and in 196 age- and sex-matched controls. Motor (Unified Parkinson's disease rating scale III [UPDRS III], Hoehn and Yahr) and cognitive (Montreal Cognitive Assessment [MoCA]) function were assessed at baseline. Follow-up data was available from 64 patients (median [interquartile range], 513 [381-677] days).

RESULTS

S1P levels were lower in PD patients compared with controls, that is 1.75 (1.38-2.07) and 1.90 (1.59-2.18) μmol/L, respectively (P = 0.001). In PD patients, lower S1P concentrations were associated with higher UPDRS III scores and Hoehn and Yahr stage. In the follow-up cohort, S1P concentrations below the median were associated with faster motor decline (hazard ratio: 4.78 [95% CI, 1.98, 11.50]), but not with cognitive worsening.

CONCLUSIONS

Our observations reveal an association of S1P with PD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association of lipid levels with motor and cognitive function and decline in advanced Parkinson's disease in the Mark-PD study

OBJECTIVES

In prospective cohort studies different blood lipid fractions have been identified as risk factors of Parkinson's disease (PD). However, data relating lipoproteins to disease phenotypes and progression in advanced PD patients are sparse. Therefore, we assessed the most common lipoproteins in a case-control design and evaluated their associations with motor and cognitive function and decline in PD patients.

METHODS

Triglycerides, LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and lipoprotein a (Lp(a)) were analyzed in 294 PD patients of the MARK-PD study cohort and 588 controls matched for age, sex and cardiovascular risk factors. In PD patients, motor (MDS-UPDRS III, Hoehn-Yahr stage) and cognitive function (MoCA) were examined. In a sub-cohort (n = 98 patients), baseline lipid levels were correlated with motor and cognitive disease progression during a follow-up period of 523 ± 199 days.

RESULTS

At baseline, HDL-C levels were lower in PD patients compared to matched controls after adjustment. We observed a very weak association of Lp(a) levels with UDPRS III scores. In cross-sectional analyses, no other lipid fraction revealed a significant and consistent association with motor or cognitive function. During follow-up, no lipid fraction level was associated with motor or cognitive progression.

CONCLUSION

In advanced PD, there is no strong and consistent association of lipid levels with motor or cognitive function and decline.

Zinc Gluconate Induces Potentially Cancer Chemopreventive Activity in Barrett's Esophagus: A Phase 1 Pilot Study

BACKGROUND

Chemopreventive effects of zinc for esophageal cancer have been well documented in animal models. This prospective study explores if a similar, potentially chemopreventive action can be seen in Barrett's esophagus (BE) in humans.

AIMS

To determine if molecular evidence can be obtained potentially indicating zinc's chemopreventive action in Barrett's metaplasia.

METHODS

Patients with a prior BE diagnosis were placed on oral zinc gluconate (14 days of 26.4 mg zinc BID) or a sodium gluconate placebo, prior to their surveillance endoscopy procedure. Biopsies of Barrett's mucosa were then obtained for miRNA and mRNA microarrays, or protein analyses.

RESULTS

Zinc-induced mRNA changes were observed for a large number of transcripts. These included downregulation of transcripts encoding proinflammatory proteins (IL32, IL1β, IL15, IL7R, IL2R, IL15R, IL3R), upregulation of anti-inflammatory mediators (IL1RA), downregulation of transcripts mediating epithelial-to-mesenchymal transition (EMT) (LIF, MYB, LYN, MTA1, SRC, SNAIL1, and TWIST1), and upregulation of transcripts that oppose EMT (BMP7, MTSS1, TRIB3, GRHL1). miRNA arrays showed significant upregulation of seven miRs with tumor suppressor activity (-125b-5P, -132-3P, -548z, -551a, -504, -518, and -34a-5P). Of proteins analyzed by Western blot, increased expression of the pro-apoptotic protein, BAX, and the tight junctional protein, CLAUDIN-7, along with decreased expression of BCL-2 and VEGF-R2 were noteworthy.

CONCLUSIONS

When these mRNA, miRNA, and protein molecular data are considered collectively, a cancer chemopreventive action by zinc in Barrett's metaplasia may be possible for this precancerous esophageal tissue. These results and the extensive prior animal model studies argue for a future prospective clinical trial for this safe, easily-administered, and inexpensive micronutrient, that could determine if a chemopreventive action truly exists.

Determinants of Serum- and Plasma Sphingosine-1-Phosphate Concentrations in a Healthy Study Group

Introduction  To correctly interpret plasma- or serum-sphingosine-1-phosphate (S1P) concentrations measured in clinical studies it is critical to understand all major determinants in healthy controls.

Methods  Serum- and plasma-S1P from 174 healthy blood donors was measured by liquid chromatography-tandem mass spectrometry and correlated to clinical laboratory data. Selected plasma samples, 10 with high and 10 with low S1P concentrations, were fractionated into very low-density lipoprotein (VLDL)-, low density lipoprotein (LDL)-, high density lipoprotein (HDL)-, and lipoprotein-free fractions. S1P was then measured in each fraction to determine its distribution.

Results  The mean S1P concentration in serum (1.04 ± 0.24 nmol/mL) was found 39% higher compared with plasma (0.75 ± 0.16 nmol/mL) and overall was not different between men and women. Only when stratified for age and gender, older women were found to exhibit higher circulatory S1P levels than men. In plasma, S1P levels correlate to red blood cell (RBC) counts but not to platelet counts. Conversely, serum-S1P correlates to platelet counts but not to RBC counts. In addition, eosinophil counts are strongly associated with serum-S1P concentrations. Both serum- and plasma-S1P correlate to total cholesterol but not to HDL-C. The distribution of S1P between VLDL-, LDL-, HDL-, and lipoprotein-free fractions is independent of total plasma-S1P concentrations. S1P concentrations in HDL but not in LDL are highly variable.

Conclusion  These data indicate S1P concentrations in plasma and serum to be differentially associated with cell counts and S1P carrier proteins. Besides platelets, eosinophil counts are identified as a novel determinant for serum-S1P concentrations further suggesting a role for S1P in eosinophil pathologies.

Loss of sphingosine 1-phosphate (S1P) in septic shock is predominantly caused by decreased levels of high-density lipoproteins (HDL)

Background

Sphingosine 1-phosphate (S1P) is a signaling lipid essential in regulating processes involved in sepsis pathophysiology, including endothelial permeability and vascular tone. Serum S1P is progressively reduced in sepsis patients with increasing severity. S1P function depends on binding to its carriers: serum albumin (SA) and high-density lipoproteins (HDL). The aim of this single-center prospective observational study was to determine the contribution of SA- and HDL-associated S1P (SA-S1P and HDL-S1P) to sepsis-induced S1P depletion in plasma with regard to identify future strategies to supplement vasoprotective S1P.

Methods

Sequential precipitation of lipoproteins was performed with plasma samples obtained from 100 ICU patients: surgical trauma (n = 20), sepsis (n = 63), and septic shock (n = 17) together with healthy controls (n = 7). Resultant fractions with HDL and SA were analyzed by liquid chromatography coupled to triple-quadrupole mass spectrometry (LC-MS/MS) for their S1P content.

Results

Plasma S1P levels significantly decreased with sepsis severity and showed a strong negative correlation with increased organ failure, quantified by the Sequential Organ Failure Assessment (SOFA) score (rho - 0.59, P < 0.001). In controls, total plasma S1P levels were 208 μg/L (187-216 μg/L). In trauma patients, we observed an early loss of SA-S1P (- 70%) with a concurrent increase of HDL-S1P (+ 20%), resulting in unaltered total plasma S1P with 210 μg/L (143-257 μg/L). The decrease of plasma S1P levels with increasing SOFA score in sepsis patients with 180.2 μg/L (123.3-253.0 μg/L) and in septic shock patients with 99.5 μg/L (80.2-127.2 μg/L) was mainly dependent on equivalent reductions of HDL and not SA as carrier protein. Thus, HDL-S1P contributed most to total plasma S1P in patients and progressively dropped with increasing SOFA score.

Conclusions

Reduced plasma S1P was associated with sepsis-induced organ failure. A constant plasma S1P level during the acute phase after surgery was maintained with increased HDL-S1P and decreased SA-S1P, suggesting the redistribution of plasma S1P from SA to HDL. The decrease of plasma S1P levels in patients with increasing sepsis severity was mainly caused by decreasing HDL and HDL-S1P. Therefore, strategies to reconstitute HDL-S1P rather than SA-S1P should be considered for sepsis patients.

Potent anti-inflammatory properties of HDL in vascular smooth muscle cells mediated by HDL-S1P and their impairment in coronary artery disease due to lower HDL-S1P: a new aspect of HDL dysfunction and its therapy

Dysfunctional HDL is associated with coronary artery disease (CAD), but its effect on inflammation in vascular smooth muscle cells (VSMCs) in atherosclerosis is unknown. We investigated the effect of healthy human HDL and CAD-HDL on TNF-α-driven inflammation in VSMCs and examined whether HDL-associated sphingosine-1-phosphate (HDL-S1P) could modulate inflammation with the aim of designing novel HDL-based anti-inflammatory strategies. Healthy human HDL, human CAD-HDL, and mouse HDL were isolated by ultracentrifugation, S1P was measured by liquid chromatography-tandem mass spectrometry, and TNF-α-induced inflammation was characterized by gene expression and analysis of NF-κB-dependent signaling. Mechanisms of S1P interference with TNF-α were assessed by S1P receptor antagonists, mouse knockouts, and short interfering RNA. We observed that healthy HDL potently inhibited the induction of TNF-α-stimulated inflammatory genes, such as iNOS (inducible NO synthase) and MMP9 (matrix metalloproteinase 9), a process that was entirely dependent on HDL-S1P, as evidenced by loss-of-function using S1P-less HDL and mimicked by genuine S1P. Inhibition was based on suppression of TNF-α-activated Akt signaling resulting in reduced IkBαSer32 and p65Ser534 NF-κB phosphorylation based on a persistent phosphatase and tensin homolog activation by S1P through the S1P receptor 2. Intriguingly, S1P suppressed inflammation even hours after initial TNF-α stimulation. The anti-inflammatory effect of healthy HDL correlated with HDL-S1P content and was superior to that of CAD-HDL featuring lower HDL-S1P. Nevertheless, therapeutic loading of HDL with S1P completely restored the anti-inflammatory capacity of CAD-HDL and greatly boosted that of both healthy and CAD-HDL. Suppression of inflammation by HDL-S1P defines a novel pathophysiologic characteristic that distinguishes functional from dysfunctional HDL. The anti-inflammatory HDL function can be boosted by S1P-loading and exploited by S1P receptor-targeting to prevent and even turn off ongoing inflammation.-Keul, P., Polzin, A., Kaiser, K., Gräler, M., Dannenberg, L., Daum, G., Heusch, G., Levkau, B. Potent anti-inflammatory properties of HDL in vascular smooth muscle cells mediated by HDL-S1P and their impairment in coronary artery disease due to lower HDL-S1P: a new aspect of HDL dysfunction and its therapy.

Feasibility Study of a Novel Thoraco-abdominal Aortic Hybrid Device (SPIDER-graft) in a Translational Pig Model

BACKGROUND

The hybrid SPIDER-graft consists of a proximal descending aortic stent graft and a conventional six branched Dacron graft for open abdominal aortic repair. Technical feasibility with regard to avoiding thoracotomy and extracorporeal circulation (ECC) during thoraco-abdominal aortic hybrid repair and peri-procedural safety of this novel device are unknown.

MATERIAL AND METHODS

This was a feasibility and safety study in domestic pigs (75-85 kg). The abdominal aorta including iliac bifurcation, left renal artery, and visceral arteries were exposed via retroperitoneal access. The right iliac branch was first temporarily anastomosed end to side to the distal aorta via partial clamping. During inflow reduction and infra-coeliac cross-clamping, the coeliac trunk (CT) was divided and the proximal stent graft portion of the SPIDER-graft was deployed into the descending aorta via the CT ostium. Retrograde visceral and antegrade aorto-iliac blood flow was maintained via the iliac side branch. The visceral, renal, and iliac arteries were sequentially anastomosed, finally replacing the first iliac end to side anastomosis. Technical success, blood flow, periods of ischaemia, and peri-procedural complications were evaluated after intra-operative completion angiography and post-operative computed tomography angiography.

RESULTS

Six animals underwent successful thoracic stent graft deployment and distal open reconstruction without peri-operative death. The median thoracic graft implantation time was 4.5 min, and the median ischaemia times before reperfusion were 10 min for the CT, 8 min for the superior mesenteric artery, 13 min for the right renal artery, and 22 min for the left renal artery. Angiography demonstrated appropriate graft implantation and blood flow measurements confirmed sufficient blood flow through all side branches.

CONCLUSION

In this translational pig model, thoraco-abdominal hybrid repair using the novel SPIDER-graft was successful in avoiding thoracotomy and ECC. Technical feasibility and safety appear promising, but need to be reassessed in humans.

Data on subgroup specific baseline characteristics and serum sphingosine-1-phosphate concentrations in the Study of Health in Pomerania

In this data article, we provide subgroup specific baseline characteristics and serum sphingosine-1-phosphate (S1P) concentrations for healthy individuals within the Study of Health in Pomerania (SHIP)-TREND cohort. After exclusion of subjects with cardiovascular disease, diabetes mellitus, hypertension, metabolic syndrome, elevated liver enzymes and/or chronic kidney disease stadium III or IV, four subgroups were defined according to different limits for body mass index (BMI), alterations in blood lipid levels and smoking status. Tables show respective clinical and laboratory parameters stratified by gender. Serum S1P concentrations are also stratified by age groups. The data presented herein is related to the research article entitled "Reference intervals for serum sphingosine-1-phosphate in the population-based Study of Health in Pomerania" (E. Moritz, D. Wegner, S. Groß, M. Bahls, M. Dörr, S.B. Felix, T. Ittermann, S. Oswald, M. Nauck, N. Friedrich, R.H. Böger, G. Daum, E. Schwedhelm, B.H. Rauch, Clin Chim Acta. 468 (2017) 25-31) [1].

Reference intervals for serum sphingosine-1-phosphate in the population-based Study of Health in Pomerania

BACKGROUND

The bioactive signaling lipid sphingosine-1-phosphate (S1P) is a potential biomarker for cardiovascular disease (CVD). To date, no reference intervals for S1P have been defined. This study aims to establish a reference range for serum S1P in healthy individuals.

METHODS

We determined reference intervals for S1P levels according to gender and age in a sample of 1339 healthy participants of the Study of Health in Pomerania (SHIP)-TREND cohort after exclusion of subjects with CVD, diabetes mellitus, hypertension, metabolic syndrome, elevated liver enzymes, chronic kidney disease stadium III or IV, or body mass index (BMI)>30kg/m². Serum S1P was measured by liquid chromatography-tandem mass spectrometry.

RESULTS

The median age of the participants was 41 (25th; 75th percentile 32; 51) years, 65% were women. The median serum concentration of S1P was 0.804 (0.694; 0.920) μmol/L. No association with gender and age was observed. The overall reference interval was 0.534-1.242μmol/L (2.5th; 97.5th percentile). Further exclusion of smokers, individuals with BMI>25kg/m² or elevated lipid levels did not significantly affect median S1P concentrations.

CONCLUSIONS

This study provides reference intervals for serum S1P in healthy individuals. Total serum S1P concentrations vary irrespectively of age, gender, BMI or smoking status.

Evaluation of 68 Ga-Glutamate Carboxypeptidase II Ligand Positron Emission Tomography for Clinical Molecular Imaging of Atherosclerotic Plaque Neovascularization

Objective—

Intraplaque neovascularization contributes to the progression and rupture of atherosclerotic lesions. Glutamate carboxypeptidase II (GCPII) is strongly expressed by endothelial cells of tumor neovasculature and plays a major role in hypoxia-induced neovascularization in rodent models of benign diseases. We hypothesized that GCPII expression may play a role in intraplaque neovascularization and may represent a target for imaging of atherosclerotic lesions. The aim of this study was to determine frequency, pattern, and clinical correlates of vessel wall uptake of a 68 Ga-GCPII ligand for positron emission tomographic imaging.

Approach and Results—

Data from 150 patients undergoing 68 Ga-GCPII ligand positron emission tomography were evaluated. Tracer uptake in various arterial segments was analyzed and was compared with calcified plaque burden, cardiovascular risk factors, and immunohistochemistry of carotid specimens. Focal arterial uptake of 68 Ga-GCPII ligand was identified at 5776 sites in 99.3% of patients. The prevalence of uptake sites was highest in the thoracic aorta; 18.4% of lesions with tracer uptake were colocalized with calcified plaque. High injected dose ( P =0.0005) and obesity ( P =0.007) were significantly associated with 68 Ga-GCPII ligand accumulation, but other cardiovascular risk factors showed no association. The number of 68 Ga-GCPII ligand uptake sites was significantly associated with overweight condition ( P =0.0154). Immunohistochemistry did not show GCPII expression. Autoradiographic blocking studies indicated nonspecific tracer binding.

Conclusions—

68 Ga-GCPII ligand positron emission tomography does not identify vascular lesions associated with atherosclerotic risk. Foci of tracer accumulation are likely caused by nonspecific tracer binding and are in part noise-related. Taken together, GCPII may not be a priority target for imaging of atherosclerotic lesions.

Gender differences in patients with carotid stenosis

Abstract. This overview analyses gender differences in prevalence, epidemiology, risk factors and therapy in patients with carotid stenosis in a systematic review. Ischemic stroke is a leading cause of death in Western society, where about 20% of cases are triggered by a carotid stenosis or occlusion, which occurs more frequently in men than in women. The stroke-protective effect of carotid endarterectomy is greater in men. Men have lower peri-procedural stroke and death rates. Particularly men with carotid stenosis and a life expectancy of at least 5 years benefit from surgical treatment. Also, the recurrence rate of ipsilateral stroke 5 years after initial surgery is lower in men than in women. It is not yet fully clarified whether there are significant gender differences regarding the outcome after endovascular versus surgical treatment. Gender differences in the outcome of carotid artery repair may be caused by biological, anatomical (smaller vessel diameter in women) or hormonal differences as well as a protracted development of atherosclerotic changes in women and different plaque morphology. Moreover, women are on average older at the time of surgery and their surgical treatment is often delayed. To reduce the risk of stroke and to improve treatment outcome especially for women, further research on gender differences and their causes is mandatory and promising.

Open repair of an aortic aneurysm in a patient with Loeys-Dietz syndrome using Gore hybrid vascular branch grafts

A 44-year-old woman with Loeys-Dietz syndrome (transforming growth factor-β [TGFBR2] gene mutation) presented with a retrograde type B dissection. She developed rapid expansion of the thoracoabdominal aortic false lumen aneurysm. The patient was successfully treated with open thoracoabdominal repair using Gore Hybrid Vascular Grafts (W. L. Gore and Assoc, Flagstaff, Ariz) for revascularization of the celiac trunk, the superior mesenteric artery, and both renal arteries. Follow-up imaging documented patency for all visceral branches. The described off-label use for sutureless revascularization might be a fast, simple, and reliable solution for revascularization during open thoracoabdominal repair. Furthermore, anastomotic aneurysm in patients with connective tissue disease might be prevented by sutureless anastomosis.

Release of sphingosine-1-phosphate from human platelets is dependent on thromboxane formation

BACKGROUND

Platelets release the immune-modulating lipid sphingosine-1-phosphate (S1P). However, the mechanisms of platelet S1P secretion are not fully understood.

OBJECTIVES

The present study investigates the function of thromboxane (TX) for platelet S1P secretion during platelet activation and the consequences for monocyte chemotaxis.

METHODS

S1P was detected using thin-layer chromatography in [(3)H]sphingosine-labeled platelets and by mass spectrometry. Monocyte migration was measured in modified Boyden chamber chemotaxis assays.

RESULTS

Release of S1P from platelets was stimulated with protease-activated receptor-1-activating peptide (PAR-1-AP, 100 μM). Acetylsalicylic acid (ASA) and two structurally unrelated reversible cyclooxygenase inhibitors diclofenac and ibuprofen suppressed S1P release. Oral ASA (500-mg single dose or 100 mg over 3 days) attenuated S1P release from platelets in healthy human volunteers ex vivo. This was paralleled by inhibition of TX formation. S1P release was increased by the TX receptor (TP) agonist U-46619, and inhibited by the TP antagonist ramatroban and by inhibitors of ABC-transport. Furthermore, thrombin-induced release of S1P was attenuated in platelets from TP-deficient mice. Supernatants from PAR-1-AP-stimulated human platelets increased the chemotactic capacity of human peripheral monocytes in a S1P-dependent manner via S1P receptors-1 and -3. These effects were inhibited by ASA-pretreatment of platelets.

CONCLUSIONS

TX synthesis and TP activation mediate S1P release after thrombin receptor activation. Inhibition of this pathway may contribute to the anti-inflammatory actions of ASA, for example by affecting activity of monocytes at sites of vascular injury.

VASP phosphorylation at serine239 regulates the effects of NO on smooth muscle cell invasion and contraction of collagen

Nitric oxide triggers cGMP-dependent kinase-mediated phosphorylation of the actin regulator vasodilator-stimulated phosphoprotein (VASP) at residue serine239. The function of this phosphorylation for smooth muscle cell (SMC) adhesion, spreading, matrix contraction, and invasion is not well understood. We reconstituted VASP deficient SMC with wild-type VASP (wt-VASP) or VASP mutants that mimic "locked" serine239 phosphorylation (S239D-VASP) or "blocked" serine239 phosphorylation (S239A-VASP). Collagen gel contraction was reduced in S239D-VASP compared to S239A-VASP and wt-VASP expressing cells and nitric oxide (NO) stimulation decreased gel contraction of wt-VASP reconstituted SMC. Invasion of collagen was enhanced in S239D-VASP and NO-stimulated wild-type SMCs compared to S239A-VASP expressing cells. Expression of S239D-VASP impaired SMC attachment to collagen, reduced the number of membrane protrusions, and caused cell rounding compared to expression of S239A-VASP. Treatment of wt-VASP reconstituted SMCs with NO exerted similar effects as expression of S239D-VASP. As unstimulated cells were spreading on collagen S239A-VASP and wt-VASP localized to actin fibers whereas S239D-VASP was enriched in the cytosol. NO interferes with SMC invasion and contraction of collagen matrices. This requires phosphorylation of VASP on serine239, which reduces VASP binding to actin fibers. These findings support the conclusion that VASP phosphorylation at serine239 regulates cytoskeleton remodeling.

Sphingosine 1-phosphate: a regulator of arterial lesions

Sphingosine-1 phosphate (S1P) is a bioactive sphingolipid that is critical in the development of blood vessels, and in the adult regulates vascular functions including vascular tone, endothelial integrity, and angiogenesis. Further, S1P may regulate arterial lesions in disease and after injury by controlling leukocyte recruitment and smooth muscle cell functions.

Regulation of arterial lesions in mice depends on differential smooth muscle cell migration: a role for sphingosine-1-phosphate receptors

The response of mice arteries to injury varies significantly between strains. FVB mice develop large neointimas after injury, whereas very small lesions form in C57BL/6 mice. After injury, platelet interaction with the denuded artery and early smooth muscle (SMC) replication are identical in both strains; however, the migration of SMCs differs significantly. FVB cells readily move into the developing neointima, whereas only the occasional C57BL/6 cells migrate. Injured arteries showed no difference in matrix metalloproteinases (MMP-2 and MMP-9) and plasminogen activator activities. In vitro, sphingosine-1-phosphate (S1P) in combination with platelet-derived growth factor (PDGF) stimulates migration of FVB cells but inhibits migration of C57BL/6 SMCs. Both SMCs migrate equally well to PDGF alone. One explanation is that the SMCs express different S1P receptors. Real-time polymerase chain reaction shows that FVB cells express higher levels of S1P receptor-1 (S1P(1)) compared with C57BL/6 cells, which express higher levels of S1P receptor-2 (S1P(2)). In addition, the migration of C57BL/6 cells can be increased by inhibiting S1P(2), whereas inhibiting S1P(1) expression slows the migration of FVB cells. Taken together these studies suggest that expression of S1P receptors vary within inbred mouse strains and that S1P is critical for SMC migration and lesion formation after injury.

Sphingosine 1-phosphate receptor 2 negatively regulates neointimal formation in mouse arteries

Neointimal lesion formation was induced in sphingosine 1-phosphate (S1P) receptor 2 (S1P2)-null and wild-type mice by ligation of the left carotid artery. After 28 days, large neointimal lesions developed in S1P2-null but not in wild-type arteries. This was accompanied with a significant increase in both medial and intimal smooth muscle cell (SMC) replication between days 4 to 28, with only minimal replication in wild-type arteries. S1P2-null SMCs showed a significant increase in migration when stimulated with S1P alone and together with platelet-derived growth factor, whereas both wild-type and null SMCs migrated equally well to platelet-derived growth factor. S1P increased Rho activation in wild-type but not in S1P2-null SMCs, and inhibition of Rho activity promoted S1P-induced SMC migration. Plasma S1P levels were similar and did not change after surgery. These results suggest that activation of S1P2 normally acts to suppress SMC growth in arteries and that S1P is a regulator of neointimal development.

Dynamics of neutral lipid storage and mobilization in yeast

We make use of the yeast Saccharomyces cerevisiae as a flexible experimental system to investigate coordinate pathways of neutral lipid synthesis, storage and mobilization with special emphasis on the role of different organelles in these processes. Recently, a number of new gene products involved in triacylglycerol (TAG) and steryl ester (STE) metabolism were identified in our laboratory and by other groups. STE are synthesized by the two STE synthases Are1p and Are2p, whereas TAG are formed mainly through the action of the two TAG synthases Dga1p and Lro1p with minor contributions of Are1p and Are2p. Once formed, TAG and STE are stored in so-called lipid particles. A dga1Deltalro1Deltaare1Deltaare2Delta quadruple mutant which lacks neutral lipid synthesis and is consequently devoid of lipid particles turned out to be a valuable tool for studying the physiological role of storage lipids and lipid particles. Mobilization of neutral lipid depots occurs through catalysis of TAG lipases and STE hydrolases. Three TAG lipases named Tgl3p, Tgl4p and Tgl5p, and three STE hydrolases named Tgl1p, Yeh1p and Yeh2p were recently identified at the molecular level. Although these hydrolases exhibit overlapping function within the enzyme families, they are specific for TAG and STE, respectively. With the exception of Dga1p, whose activity is partially localized to lipid particles, TAG and STE forming enzymes are restricted to the endoplasmic reticulum. TAG lipases and STE hydrolases are components of lipid particles with the exception of Yeh2p, which is plasma membrane located. Thus, neutral lipid metabolism is not only regulated at the enzyme level but also by the distribution of the components to organelles. The fact that neutral lipid homeostasis is linked to a number of cell biological processes confirms the important role of this class of lipids as cellular modulators or effectors.

The life cycle of neutral lipids: synthesis, storage and degradation

Triacylglycerols (TAGs), steryl esters (SEs) and wax esters (WEs) form the group of neutral lipids. Whereas TAGs are present in all types of cell, the occurrence of SEs in prokaryotes is questionable, and the presence of WEs as storage molecules is restricted to plants and a few bacteria. Here, we summarize recent knowledge on the formation, storage and degradation of TAGs and SEs in various cell types. We describe the biochemical pathways involved in TAG and SE synthesis and discuss the subcellular compartmentation of these processes. Recently, several novel enzymes governing the metabolism of storage lipids have been identified and characterized. Regulatory aspects of neutral lipid storage are just beginning to be understood. Finally, we describe consequences of defects in neutral lipid metabolism. Since severe diseases like atherosclerosis, obesity and type 2 diabetes are caused by lipid accumulation, mechanisms underlying neutral lipid synthesis, depot formation and mobilization are of major interest for curing such diseases that are increasingly associated with modern civilization.

Formation and mobilization of neutral lipids in the yeast Saccharomyces cerevisiae

Since energy storage is a basic metabolic process, the synthesis of neutral lipids occurs in all kingdoms of life. The yeast Saccharomyces cerevisiae, widely accepted as a model eukaryotic cell, contains two classes of neutral lipids, namely STEs (steryl esters) and TAGs (triacylglycerols). TAGs are synthesized through two pathways governed by the acyl-CoA diacylglycerol acyltransferase Dga1p and the phospholipid diacylglycerol acyltransferase Lro1p. STEs are formed by two STE synthases Are1p and Are2p, two enzymes with overlapping function, which also catalyse TAG formation, although to a minor extent. Neutral lipids are stored in the so-called lipid particles and can be utilized for membrane formation under conditions of lipid depletion. For this purpose, storage lipids have to be mobilized by TAG lipases and STE hydrolases. A TAG lipase named Tgl3p was identified as a major yeast TAG hydrolytic enzyme in lipid particles. Recently, a new family of hydrolases was detected which is required for STE mobilization in S. cerevisiae. These enzymes, named Yeh1p, Yeh2p and Tgl1p, are paralogues of the mammalian acid lipase family. The role of these proteins in biosynthesis and mobilization of TAG and STE, and the regulation of these processes will be discussed in this minireview.

Phospholipids: synthesis, sorting, subcellular traffic - the yeast approach

Most of the enzymes and genes required for lipid biosynthesis and degradation in the budding yeast Saccharomyces cerevisiae have now been identified and the global mechanisms that regulate their activity are being established. Synthesis of phospholipids is restricted to specific subcellular compartments, and the lipids migrate from their site of formation to their final destination. In addition to synthesis, remodelling and degradation of phospholipids controls the content of the lipid portion of cellular membranes, while highly specific phospholipases catalyse the release of lipid-based second messengers. In this review, we describe the current understanding of the organization and regulation of phospholipid metabolism in yeast, and discuss the mechanisms that have been proposed for intracellular lipid transport.

Arterial injury repair in nonhuman primates-the role of PDGF receptor-beta

BACKGROUND

This study documents the time course of the response to injury of the saphenous artery in baboons and the role of the platelet-derived growth factor-beta. Fundamental differences with the well-characterized rat arterial injury model have been found.

MATERIALS AND METHODS

Thirty-eight baboons received a unilateral balloon injury to the saphenous artery and were treated with a chimeric blocking antibody to PDGFR-beta or vehicle control for 7, 14, or 28 days. The arteries were evaluated morphologically and for cell proliferation.

RESULTS

Both medial and intimal smooth muscle cell proliferation were elevated 7 days after injury and were back close to baseline at 14 days. Unlike the rat, blockade of PDGFR-beta inhibited medial proliferation over 80% at 7 and 14 days, while intimal proliferation was only inhibited at 14 days (>95%). Also, unlike the rat, the baboon arterial media, as well as the intima, increased in size by 14 days after injury. Blockade of PDGFR-beta completely inhibited both intimal and medial growth at 14 days, but there was less of an effect on intimal growth at 28 days.

CONCLUSION

Blockade of PDGFR-beta may be a clinical approach to inhibit intimal hyperplasia in humans, but this study raises concerns about the long-term efficacy of this treatment.

Vasodilator-stimulated phosphoprotein regulates proliferation and growth inhibition by nitric oxide in vascular smooth muscle cells

OBJECTIVE

Vasodilator-stimulated phosphoprotein (VASP) was identified as a substrate for cGMP-dependent protein kinase (PKG) and cAMP-dependent protein kinase (PKA). It is preferentially phosphorylated at serine239 by PKG, whereas serine157 is a preferred phosphorylation site for PKA. In addition, serine157 is phosphorylated by PKC in response to serum. We have investigated the effects of VASP and VASP phosphorylation at serine157 and serine239 on smooth muscle cell (SMC) proliferation and nitric oxide (NO)-mediated growth inhibition.

METHODS AND RESULTS

Aortic SMCs derived from VASP-deficient mice were transduced with retroviral vectors encoding either wild-type VASP or VASP mutants (S157A-VASP and S239A-VASP), in which serine157 and serine239, respectively, were replaced by a nonphosphorylatable amino acid, alanine. Expression of wt-VASP and S239A-VASP significantly increased proliferation, whereas expression of S157A-VASP was inhibitory. Expression of S239A-VASP rendered SMCs less sensitive to growth inhibition by the NO donor, S-nitroso-n-acetylpenicillamine, when compared with cells expressing wt-VASP. Similar effects were observed in cultured rat SMCs in which wt-VASP, S157A-VASP, and S239A-VASP were expressed.

CONCLUSIONS

Our data suggest that VASP phosphorylation at serine157 is required for the growth-stimulatory effect of VASP in SMCs, whereas VASP phosphorylation at serine239 is involved in the growth inhibitory effects of NO on SMCs.

Interleukin-1beta inhibits PDGF-BB-induced migration by cooperating with PDGF-BB to induce cyclooxygenase-2 expression in baboon aortic smooth muscle cells

OBJECTIVE

Smooth muscle cell (SMC) migration from the media into the intima is pivotal for intimal formation after vascular injury. Platelet-derived growth factor (PDGF)-BB is a potent chemoattractant for SMCs in vitro and in vivo. We investigated whether interleukin (IL)-1beta affects migration in response to PDGF-BB. Our data suggest that IL-1beta is inhibitory and that this effect is mediated by cyclooxygenase (COX)-2. We further addressed the role of the mitogen-activated protein kinase p38, which is activated by PDGF-BB and by IL-1beta.

METHODS

Baboon aortic SMCs were prepared with the explant method. Migration was measured in a Boyden chamber assay through filters coated with monomeric collagen. COX2 expression and phosphorylation of p38 MAPK were analyzed by Western blotting.

RESULTS

PDGF-BB (10 ng/mL) stimulates migration 3.8-fold, and IL-1beta (0.1 ng/mL) reduces this response by 40%. The inhibitory effect of IL-1beta is abolished by the COX inhibitor, indomethacin (10 micromol/L), the specific COX2 inhibitor, NS398 (10 micromol/L), and the p38 MAPK inhibitor SB203580 (3 micromol/L). We found that IL-1beta and PDGF-BB synergize to stimulate COX2 expression. We further demonstrated that p38 MAPK is activated by IL-1beta and PDGF with different kinetics and that p38 MAPK is required for maximal COX2 expression in response to IL-1beta plus PDGF-BB.

CONCLUSION

IL-1beta inhibits PDGF-BB-induced migration by cooperating with PDGF-BB to induce COX2 through activation of p38 MAPK. Whether this effect of IL-1beta modulates intimal growth after vascular injury remains to be elucidated.

Vasodilator-stimulated phosphoprotein is a substrate for protein kinase C

Vasodilator-stimulated phosphoprotein (VASP), an actin binding protein localized to areas of focal contacts, is a substrate for the cyclic adenosine monophosphate/cyclic guanosine monophosphate (cAMP/cGMP)-dependent protein kinases (PKA, PKG). In this study, we show that serum stimulation of vascular smooth muscle cells (SMCs) induces VASP phosphorylation on Ser157, in a mechanism not dependent on PKA or PKG. We tested the possibility that protein kinase C (PKC), a regulator of cytoskeletal function, is involved. PKC inhibition or down-regulation prevented serum-induced phosphorylation of VASP at Ser157 in rat vascular SMCs. Additionally, recombinant PKCalpha directly phosphorylated Ser157 on VASP. In summary, our data support the hypothesis that PKC phosphorylates VASP and mediates serum-induced VASP regulation.

Concomitant blockade of platelet-derived growth factor receptors alpha and beta induces intimal atrophy in baboon PTFE grafts

OBJECTIVE

Although current treatments for restenosis attempt to prevent the development of intimal hyperplasia, an alternative strategy is to induce intimal atrophy after restenosis has developed. Because platelet-derived growth factor (PDGF) is a smooth muscle cell growth and survival factor, we tested the hypothesis that complete blockade of PDGF by using antibodies against PDGF receptors alpha and beta would cause intimal atrophy in a baboon vascular graft model.

METHODS

We administered chimeric antibodies against PDGF receptor alpha or PDGF receptor beta, either separately or together, to baboons with bilateral prosthetic aortoiliac grafts, the intimas of which had reached maximal size before treatment was begun. High blood flow, which we have previously shown to cause intimal atrophy, was induced through one graft to serve as a positive control. After 2 weeks, the intima lining the grafts was assessed for cross-sectional area, cell proliferation, and apoptosis by standard morphologic and immunohistochemical techniques.

RESULTS

Blocking both PDGF receptors simultaneously reduced the cross-sectional area of the normal-flow graft intima by 44% (P <.05 vs control), whereas treatment with the individual antibodies did not significantly alter intimal area. Blockade of both receptors also inhibited smooth muscle cell proliferation by 66% (P <.05 vs control), whereas neither antibody alone altered proliferation. In contrast, all treatments increased smooth muscle cell apoptosis threefold to fivefold.

CONCLUSIONS

These data suggest that simultaneous inhibition of cell proliferation and stimulation of cell death by the administration of antibodies to both PDGF receptor alpha and receptor beta is required for intimal atrophy in this baboon graft model. In addition, these data provide an in vivo model for the pharmacologic induction of intimal atrophy and introduce a novel clinical approach to treat intimal hyperplasia. Clinical relevance This study introduces the concept of pharmacologic induction of intimal atrophy. Intimal hyperplasia plagues all forms of arterial reconstruction. Currently, the only effective treatment of these restenotic lesions is balloon angioplasty or operative revision. An alternative approach to patients with clinically significant intimal hyperplasia might be to stimulate intimal regression by modulating growth and survival factors required for intimal maintenance. Although PDGF is known to be critical in intimal formation, the results of this study suggest that PDGF is also critical for intimal maintenance. Inhibition of the PDGF system may prove to be a clinically applicable approach for inducing intimal atrophy.

In yeast sterol biosynthesis the 3-keto reductase protein (Erg27p) is required for oxidosqualene cyclase (Erg7p) activity

In Saccharomyces cerevisiae, the 3-keto reductase (Erg27p) encoded by ERG27 gene is one of the key enzymes involved in the C-4 demethylation of the sterol intermediate, 4,4-dimethylzymosterol. The oxidosqualene cyclase (Erg7p) encoded by the ERG7 gene converts oxidosqualene to lanosterol, the first cyclic component of sterol biosynthesis. In a previous study, we found that erg27 strains grown on cholesterol- or ergosterol-supplemented media did not accumulate lanosterol or 3-ketosterols but rather squalene, oxidosqualene, and dioxidosqualene intermediates normally observed in ERG7 (oxidosqualene cyclase) mutants. These results suggested a possible interaction between these two enzymes. In this study, we present evidence that Erg27p interacts with Erg7p, facilitating the association of Erg7p with lipid particles (LPs) and preventing digestion of Erg7p both in the endoplasmic reticulum (ER) and LPs. We demonstrate that Erg27p is required for oxidosqualene cyclase (Erg7p) activity in LPs, and that Erg27p co-immunoprecipitates with Erg7p in LPs but not in microsomal fractions. While Erg27p is essentially a component of the ER, it can also be detected in LPs. In erg27 strains, a truncated Erg7p mislocalizes to microsomes. Restoration of Erg7p enzyme activity and LPs localization was achieved in an erg27 strain transformed with a plasmid containing a wild-type ERG27 allele. We suggest that the physical interaction of Erg27p with Erg7p is an essential regulatory tool in yeast sterol biosynthesis.

Protein tyrosine phosphatase RQ is a phosphatidylinositol phosphatase that can regulate cell survival and proliferation

Protein tyrosine phosphatase RQ (PTPRQ) was initially identified as a protein tyrosine phosphatase (PTPase)-like protein that is upregulated in a model of renal injury. Here we present evidence that, like PTEN, the biologically important enzymatic activity of PTPRQ is as a phosphatidylinositol phosphatase (PIPase). The PIPase specificity of PTPRQ is broader than that of PTEN and depends on different amino acid residues in the catalytic domain. In vitro, the recombinant catalytic domain of PTPRQ has low PTPase activity against tyrosine-phosphorylated peptide and protein substrates but can dephosphorylate a broad range of phosphatidylinositol phosphates, including phosphatidylinositol 3,4,5-trisphosphate and most phosphatidylinositol monophosphates and diphosphates. Phosphate can be hydrolyzed from the D3 and D5 positions in the inositol ring. PTPRQ does not have either of the basic amino acids in the catalytic domain that are important for the PIPase activity of PTEN or the sequence motifs that are characteristic of type II phosphatidylinositol 5-phosphatases. Instead, the PIPase activity depends on the WPE sequence present in the catalytic cleft of PTPRQ, and in the "inactive" D2 domains of many dual-domain PTPases, in place of the WPD motif present in standard active PTPases. Overexpression of PTPRQ in cultured cells inhibits proliferation and induces apoptosis. An E2171D mutation that retains or increases PTPase activity but eliminates PIPase activity, eliminates the inhibitory effects on proliferation and apoptosis. These results indicate that PTPRQ represents a subtype of the PTPases whose biological activities result from its PIPase activity rather than its PTPase activity.

Triacylglycerol biosynthesis in yeast

Triacylglycerol (TAG) is the major storage component for fatty acids, and thus for energy, in eukaryotic cells. In this mini-review, we describe recent progress that has been made with the yeast Saccharomyces cerevisiae in understanding formation of TAG and its cell biological role. Formation of TAG involves the synthesis of phosphatidic acid (PA) and diacylglycerol (DAG), two key intermediates of lipid metabolism. De novo formation of PA in yeast as in other types of cells can occur either through the glycerol-3-phosphate- or dihydroxyacetone phosphate-pathways-each named after its respective precursor. PA, formed in two steps of acylation, is converted to DAG by phosphatidate phosphatase. Acylation of DAG to yield TAG is catalyzed mainly by the two yeast proteins Dga1p and Lro1p, which utilize acyl-CoA or phosphatidylcholine, respectively, as acyl donors. In addition, minor alternative routes of DAG acylation appear to exist. Endoplasmic reticulum and lipid particles (LP), the TAG storage compartment in yeast, are the major sites of TAG synthesis. The interplay of these organelles, formation of LP, and enzymatic properties of enzymes catalyzing the synthesis of PA, DAG, and TAG in yeast are discussed in this communication.

Blockade of the epidermal growth factor receptor decreases intimal hyperplasia in balloon-injured rat carotid artery

HYPOTHESIS

Arterial intimal hyperplasia is induced by injury and is frequently the cause of luminal narrowing after vascular reconstruction. Smooth muscle cells (SMC) respond to injury by proliferating and migrating into the intima. This process is regulated by thrombin, endothelin, and angiotensin II, all ligands of G protein-coupled receptors. Signal transduction from these receptors in cultured cells depends in part on transactivation of epidermal growth factor receptor (EGFR). We hypothesize that EGFR has a substantial role in activation of SMC in vivo and development of intimal hyperplasia.

METHODS

Intimal hyperplasia was induced in rat carotid arteries by passage of a balloon catheter. Animals were given a monoclonal blocking antibody to rat EGFR, matched mouse immunoglobulin G (IgG) control antibody, or saline solution.

RESULTS

Blocking EGFR antibody inhibited medial SMC proliferation, as determined by 5-bromo-2'-deoxyuridine labeling at 2 days (IgG control, 8.0% +/- 2.0%; anti-EGFR, 3.2% +/- 0.8%) and intimal hyperplasia at 14 days (intimal area: IgG control, 0.07 +/- 0.01 mm(2); anti-EGFR, 0.04 +/- 0.01 mm(2)).

CONCLUSION

Activation of EGFR is important for early induction of SMC proliferation and subsequent intimal thickening.

Interleukin-1beta inhibits expression of p21(WAF1/CIP1) and p27(KIP1) and enhances proliferation in response to platelet-derived growth factor-BB in smooth muscle cells

OBJECTIVE

Intimal growth depends on smooth muscle cell (SMC) migration and proliferation and is regulated by thrombotic and inflammatory responses to vascular injury. Platelet-derived growth factor (PDGF)-BB and interleukin (IL)-1beta have been shown to contribute to intimal hyperplasia and lesion progression in atherosclerosis. Mitogenic effects of IL-1 on SMCs have been reported and have been attributed to the expression of PDGF-A chain. In some, but not all, studies, IL-1beta was found to cooperate with growth factors, including PDGF, in stimulating proliferation. The molecular basis for such cooperative effects is unknown and is the subject of the present study.

METHODS AND RESULTS

We demonstrate that in baboon aortic SMCs, IL-1beta enhances the proliferation induced by PDGF-BB independently of PDGF-A signaling. IL-1beta increases the phosphorylation of retinoblastoma protein, a pivotal step in the G(1)-to-S transition in the cell cycle. Analysis of expression levels of cyclins and cyclin-dependent kinase (CDK) inhibitors suggests that IL-1beta stimulates CDKs by downregulating p21 and p27. Consistent with this hypothesis is the finding that CDK2 activity, induced by PDGF-BB, is enhanced 2.3+/-0.2-fold in the presence of IL-1beta.

CONCLUSIONS

Our data suggest that IL-1beta may promote SMC proliferation after vascular injury and in atherogenesis by suppression of PDGF-BB-induced p21 and p27.

Screening for drug and alcohol abuse among older adults using a modified version of the CAGE

This study examined the sensitivity, specificity, and receiver operating characteristics (ROC) curves of a modified version of the CAGE, a screening measure used in the detection of older alcohol- and drug-abusing individuals. In a retrospective review of clinical records of 976 patients screened by a geriatric substance abuse program, the authors examined patients' responses on a modified version of the CAGE that included queries regarding drug use. The CAGE was administered to individuals age 50 or over draw from three diagnostic groups: alcohol abuse/dependence, drug abuse/dependence, and normal controls. Analysis of variance and discriminant function analyses revealed that the modified CAGE was able to discriminate both alcohol and drug abusers from controls. Analyses examining test sensitivity, specificity, and ROC curves revealed the CAGE to demonstrate excellent sensitivity but poor specificity. Omitting the "cut down'' item from the CAGE significantly improved specificity with only a modest drop in sensitivity. Given the ease of administration and sensitivity to both alcohol and drug abuse, these data suggest that the modified CAGE is well suited as a screening instrument for geriatric drug and alcohol abuse.

EGFR transactivation in the regulation of SMC function

Vascular smooth muscle cells (SMCs) are the principal cellular component of the normal artery and intimal lesions that develop in response to arterial injury. Several growth factors and their receptors participate in SMC activation, including the tyrosine kinase receptors for platelet-derived growth factor (PDGF) and basic fibroblast growth factor as well as the G-protein-coupled receptors (GPCRs) for thrombin and angiotensin II. During the last couple of years, it has become evident that GPCRs transactivate receptor tyrosine kinases, particularly the epidermal growth factor receptor (EGFR). The EGFR is not well characterized in terms of its role in vascular biology, but recent findings indicate that GPCRs induce EGFR transactivation in cultured vascular SMCs, perhaps by intracellular and extracellular pathways. Studies from our laboratory as well as two other groups have demonstrated that EGFR transactivation by different GPCR agonists and in different cell types, including SMCs, is mediated by heparin-binding EGF-like growth factor (HB-EGF). HB-EGF-dependent EGFR activation is blocked by heparin, a growth inhibitor of SMCs in vitro and in vivo. These data suggest that the EGFR may be important in the regulation of SMC function. The complexity of the GPCR-EGFR crosstalk, involving several different cell surface molecules and an inside-out signaling step, may provide novel targets for the control of SMC growth and intimal hyperplasia in the arterial injury response.

The roles of phosphatidylinositol 3-kinase and protein kinase Czeta for thrombopoietin-induced mitogen-activated protein kinase activation in primary murine megakaryocytes

Thrombopoietin (TPO) stimulates a network of intracellular signaling pathways that displays extensive cross-talk. We have demonstrated previously that the ERK/mitogen-activated protein kinase pathway is important for TPO-induced endomitosis in primary megakaryocytes (MKs). One known pathway by which TPO induces ERK activation is through the association of Shc with the penultimate phosphotyrosine within the TPO receptor, Mpl. However, several investigators found that the membrane-proximal half of the cytoplasmic domain of Mpl is sufficient to activate ERK in vitro and support base-line megakaryopoiesis in vivo. Using BaF3 cells expressing a truncated Mpl (T69Mpl) as a tool to identify non-Shc/Ras-dependent signaling pathways, we describe here novel mechanisms of TPO-induced ERK activation mediated, in part, by phosphoinositide 3-kinase (PI3K). Similar to cells expressing full-length receptor, PI3K was activated by its incorporation into a complex with IRS2 or Gab2. Furthermore, the MEK-phosphorylating activity of protein kinase Czeta (PKCzeta) was also enhanced after TPO stimulation of T69Mpl, contributing to ERK activity. PKCzeta and PI3K also contribute to TPO-induced ERK activation in MKs, confirming their physiological relevance. Like in BaF3 cells, a TPO-induced signaling complex containing p85PI3K is detectable in MKs expressing T61Mpl and is probably responsible for PI3K activation. These data demonstrate a novel role of PI3K and PKCzeta in steady-state megakaryopoiesis.

Roles of phosphatidylethanolamine and of its several biosynthetic pathways in Saccharomyces cerevisiae

Three different pathways lead to the synthesis of phosphatidylethanolamine (PtdEtn) in yeast, one of which is localized to the inner mitochondrial membrane. To study the contribution of each of these pathways, we constructed a series of deletion mutants in which different combinations of the pathways are blocked. Analysis of their growth phenotypes revealed that a minimal level of PtdEtn is essential for growth. On fermentable carbon sources such as glucose, endogenous ethanolaminephosphate provided by sphingolipid catabolism is sufficient to allow synthesis of the essential amount of PtdEtn through the cytidyldiphosphate (CDP)-ethanolamine pathway. On nonfermentable carbon sources, however, a higher level of PtdEtn is required for growth, and the amounts of PtdEtn produced through the CDP-ethanolamine pathway and by extramitochondrial phosphatidylserine decarboxylase 2 are not sufficient to maintain growth unless the action of the former pathway is enhanced by supplementing the growth medium with ethanolamine. Thus, in the absence of such supplementation, production of PtdEtn by mitochondrial phosphatidylserine decarboxylase 1 becomes essential. In psd1Delta strains or cho1Delta strains (defective in phosphatidylserine synthesis), which contain decreased amounts of PtdEtn, the growth rate on nonfermentable carbon sources correlates with the content of PtdEtn in mitochondria, suggesting that import of PtdEtn into this organelle becomes growth limiting. Although morphological and biochemical analysis revealed no obvious defects of PtdEtn-depleted mitochondria, the mutants exhibited an enhanced formation of respiration-deficient cells. Synthesis of glycosylphosphatidylinositol-anchored proteins is also impaired in PtdEtn-depleted cells, as demonstrated by delayed maturation of Gas1p. Carboxypeptidase Y and invertase, on the other hand, were processed with wild-type kinetics. Thus, PtdEtn depletion does not affect protein secretion in general, suggesting that high levels of nonbilayer-forming lipids such as PtdEtn are not essential for membrane vesicle fusion processes in vivo.

A subfraction of the yeast endoplasmic reticulum associates with the plasma membrane and has a high capacity to synthesize lipids

Large parts of the endoplasmic reticulum of the yeast, Saccharomyces cerevisiae, are located close to intracellular organelles, i.e. mitochondria and the plasma membrane, as shown by fluorescence and electron microscopy. Here we report the isolation and characterization of the subfraction of the endoplasmic reticulum that is closely associated with the plasma membrane. This plasma membrane associated membrane (PAM) is characterized by its high capacity to synthesize phosphatidylserine and phosphatidylinositol. As such, PAM is reminiscent of MAM, a mitochondria associated membrane fraction of the yeast [Gaigg, B., Simbeni, R., Hrastnik, C., Paltauf, F. & Daum, G. (1995) Biochim. Biophys. Acta 1234, 214-220], although the specific activity of phosphatidylserine synthase and phosphatidylinositol synthase in PAM exceeds several-fold the activity in MAM and also in the bulk endoplasmic reticulum. In addition, several enzymes involved in ergosterol biosynthesis, namely squalene synthase (Erg9p), squalene epoxidase (Erg1p) and steroldelta24-methyltransferase (Erg6p), are highly enriched in PAM. A possible role of PAM in the supply of lipids to the plasma membrane is discussed.

Regulation of the Saccharomyces cerevisiae DPP1-encoded diacylglycerol pyrophosphate phosphatase by zinc

The DPP1 gene, encoding diacylglycerol pyrophosphate (DGPP) phosphatase from Saccharomyces cerevisiae, has recently been identified as a zinc-regulated gene, and it contains a putative zinc-responsive element (UAS(ZRE)) in its promoter. In this work we examined the hypothesis that expression of DGPP phosphatase was regulated by zinc availability. The deprivation of zinc from the growth medium resulted in a time- and dose-dependent induction of beta-galactosidase activity driven by a P(DPP1)-lacZ reporter gene. This regulation was dependent on the UAS(ZRE) in the DPP1 promoter and was mediated by the Zap1p transcriptional activator. Induction of the DGPP phosphatase protein and activity by zinc deprivation was demonstrated by immunoblot analysis and measurement of the dephosphorylation of DGPP. The regulation pattern of DGPP phosphatase in mutants defective in plasma membrane (Zrt1p and Zrt2p) and vacuolar membrane (Zrt3p) zinc transporters indicated that enzyme expression was sensitive to the cytoplasmic levels of zinc. DGPP phosphatase activity was inhibited by zinc by a mechanism that involved formation of DGPP-zinc complexes. Studies with well characterized subcellular fractions and by indirect immunofluorescence microscopy revealed that the DGPP phosphatase enzyme was localized to the vacuolar membrane.