Appreciating the links between heart failure and depression

Depression and heart failure frequently occur together, symptoms overlap and the prognosis is worsened. Both conditions share biopsychosocial risk factors and are accompanied by behavioural/lifestyle, neurohormonal, inflammatory and autonomic changes that are implicated aetiologically. Depression has been conceptualized as a decompensated response to allostatic overload, wherein adaptive psychological, behavioural and physiological responses to chronic and/or severe stress, become unsustainable. Heart failure can similarly be viewed as a decompensated response to circulatory overload, wherein adaptive functional (neurohormonal effects on circulation, inotropic effects on heart) and structural (myocardial remodelling) changes, become unsustainable. It has been argued that the disengaged state of depression can initially be protective, limiting an individual's exposure to external challenges, such that full recovery is often possible. In contrast, heart failure, once past a tipping-point, can progress relentlessly. Here, we consider the bidirectional interactions between depression and heart failure. Targeted treatment of depression in the context of heart failure may improve quality of life, yet overall benefits on mortality remain elusive. However, effective treatment of heart failure typically enhances function and improves key psychological and behavioural determinants of low mood. Prospectively, research that examines the mechanistic associations between depression and heart failure offers fresh opportunity to optimize personalized management in the advent of newer interventions for both conditions.

Cardio-Oncology: a medical specialty in constant growth and evolution. the 10-year experience of the first cardio-oncology service in the United Kingdom

Introduction

Survivorship has increased significantly in cancer patients with the advent of novel therapies. However, this improvement has been at the cost of higher rates of cardiotoxicity. Cardiovascular disease has become the main cause of death or cancer therapy interruption in many of these patients. The need for specialist services to deal with these emerging problems has led to global development of many Cardio-Oncology services.

Objectives

To describe how a Cardio-Oncology service has grown and evolved over a 10 year period in response to the constantly changing oncological landscape.

Methods and results

Prospective, single center, study of cancer patients referred to our service from February 2011 to December 2021. 1499 patients were referred to the service. Mean age was 60 years (SD: 15) and 60% were female. CV risk factors including hypertension (32%), dyslipidaemia (12%) and diabetes (6%) were common.

The most frequent primary tumour location was breast (427 patients, 28%), followed by haematological (151, 10%) and gastrointestinal tract (114, 8%). The average number of referrals per month increased 6 fold from 2011, from 3.3 patients per month to 21 patients in 2021. In the last 5 years there was a 10 fold increase in the number of outpatient consultations from 189 consultations in 2016 to 1988 consultations in 2021.

The most frequent reason for referral was pre-treatment assessment (39%), followed by cancer therapy related cardiac dysfunction (CTRCD) (33%) and other acute cancer therapy related CV diseases (CTR-CVDs) (22%). From 2011 to 2017 CTRCD was the main CTR-CVD due to anthracycline and trastuzumab. This ratio changed in 2018 when other CTR-CVDs became the most frequent referral reason following pre-treatment assessment. Patients referred to our service were or had been, mostly under medical therapy alone or in combination with surgery or radiotherapy (1058 patients, 70%), anthracyclines being the predominant treatment (435 patients, 40%). Targeted therapies and immune check point inhibitors became more popular in the last two years (2020–2021). A multivariable logistic regression model was built to assess the relation between the medical treatment and the prevalence of CTRCD vs other CTR-CVDs. Anthracyclines and HER2 therapy are independently associated with a higher prevalence of CTRCD while tyrosine kinase inhibitors and immune checkpoint inhibitors increase the risk of other CTR-CVDs e.g. hypertension, arrhythmias and myocarditis.

Conclusions

Cardio-Oncology has rapidly evolved from its origin as a subspecialty of heart failure medicine, to a diverse medical specialty that encompasses many different domains of cardiology. Future cardio-oncology services should reflect this and be dynamic, collaborating with cardiac sub-specialities as necessary. Provision of cardio-oncology services requires a considerable knowledge and understanding of the ever growing and changing oncology therapies.

Funding Acknowledgement

Type of funding sources: None.

Nemvaleukin alfa monotherapy and in combination with pembrolizumab in patients (pts) with advanced solid tumors: ARTISTRY-1

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Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds to the intermediate-affinity interleukin-2 (IL-2) receptor (IL-2R) to preferentially activate antitumor CD8+ T cells and natural killer (NK) cells with minimal expansion of immunosuppressive regulatory T cells. It is sterically occluded from binding to the high-affinity IL-2R, leveraging antitumor effects of the IL-2 pathway but mitigating toxicity associated with preferential binding of IL-2 to the high-affinity IL-2R. Methods: ARTISTRY-1 (NCT02799095) is a 3-part, first-in-human, phase 1/2 study of IV nemvaleukin alone and in combination with pembrolizumab in pts with advanced solid tumors. Parts A (dose escalation to 10 µg/kg/day), B (monotherapy in pts with melanoma or renal cell carcinoma [RCC]), and C (combination) included nemvaleukin 3 or 6 µg/kg/day ´ 5 and pembrolizumab every 21 days. Investigator-assessed antitumor activity (confirmed responses as per RECIST v1.1) and safety are reported as of 29 October 2021. Results: In Part A (N = 46), nemvaleukin recommended phase 2 dose was 6 µg/kg/day IV; maximum tolerated dose not reached. One pt had dose-limiting toxicity (grade 4 acute kidney injury) at 10 µg/kg. Pts in Parts B and C were heavily pretreated (1–9 prior lines of therapy, including prior checkpoint inhibitor therapy). Durable antitumor activity was observed for nemvaleukin monotherapy, including in RCC (objective response rate [ORR], 18.2% [4/22]) and in melanoma (ORR, 8.7% [4/46]), with 2 partial responses (1 unconfirmed) in 30 pts with cutaneous melanoma (ORR, 6.7%) and 2 PRs (1 unconfirmed) in 6 pts with mucosal melanoma (ORR, 33.3%). Durable antitumor activity was also observed for combination therapy (ORR, 16.1% [22/137]; disease control rate [DCR], 59.9%), including in platinum-resistant ovarian cancer (PROC; ORR, 28.6% [4/14]; DCR, 71.4%), with 2 complete responses and 2 PRs (1 unconfirmed) in 14 pts. Forty-three pts remain on therapy. The most frequent grade 3/4 treatment-related adverse events in Parts B and C, respectively, were anemia (9%, 10%), neutropenia (34%, 9%), and decreased neutrophil count (12%, 9%). Safety was consistent with previous reports. In pharmacodynamic studies, nemvaleukin monotherapy induced robust expansion of CD8+ T and NK cells, with minimal effect on regulatory T cells. Conclusions: ARTISTRY-1 showed proof of principle for preferential expansion of CD8+ T cells and NK cells by nemvaleukin. Nemvaleukin was generally well tolerated and demonstrated promising efficacy. Durable responses were observed with monotherapy and combination therapy in heavily pretreated pts across a range of tumors, warranting further investigation. The US FDA granted nemvaleukin Fast Track designation for treatment of mucosal melanoma and PROC, and Orphan Drug designation for mucosal melanoma. Clinical trial information: NCT02799095.

Nemvaleukin alfa combination therapy for gastrointestinal (GI) cancers: Preclinical evidence and clinical data from the ARTISTRY-1 trial

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Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8+ T and NK cells, with minimal expansion of regulatory T cells. Inherently active, nemvaleukin neither requires metabolic/proteolytic conversion nor degrades into native IL-2. Preclinical characterization confirmed receptor selectivity and antitumor activity of nemvaleukin alone and with checkpoint inhibitors (CPIs) and informed dose selection for the first-in-human study ARTISTRY-1; other combination regimens are ongoing evaluation. In ARTISTRY-1, responses with nemvaleukin in combination with pembrolizumab were observed in a variety of tumors, including GI. In addition to the clinical outcomes of these patients (pts), we describe preclinical evaluation of nemvaleukin with tyrosine kinase inhibitors (TKIs)—a drug class indicated for some GI cancers. Methods: Pts with GI cancers who had progressed on prior therapy were enrolled into cohorts of mixed tumor types in ARTISTRY-1 (NCT02799095) and received IV nemvaleukin (3 µg/kg) and pembrolizumab (200 mg). Outcomes presented include antitumor activity and safety as of August 2021. Combinations of nemvaleukin with TKIs were evaluated in mouse tumor models, including colorectal adenocarcinoma (MC38). Results: Clinically, 26 pts with GI cancer (colon/colorectal, n = 14; esophageal, n = 5; hepatocellular, n = 3; pancreatic, n = 3; gastric, n = 1) received nemvaleukin + pembrolizumab (median 3 cycles [range: 1-24]). Median age was 55 y (range: 26-82), ECOG performance status was 0 (n = 6) or 1 (n = 20), and median prior lines of therapy was 3 (range: 1-6). Four pts had a partial response, 2 with esophageal, 1 with MSI-H colorectal, and 1 with pancreatic cancer, with target lesion decreases of 37% to 63%. Six pts had stable disease. Two responders remain on treatment (> 36 and > 80 wks for colorectal and esophageal cancer, respectively). Frequent (> 25%) nemvaleukin-related adverse events (AEs) among all pts receiving nemvaleukin combination (n = 156) were chills (58%), pyrexia (53%), nausea (29%), and fatigue (29%). Grade ≥3 nemvaleukin-related AEs (≥8%) were reported in 48%, including anemia (12%), neutrophil count decreased (10%), and neutropenia (8%). In mice, the combination of the mouse ortholog of nemvaleukin with VEGF TKIs showed improved antitumor activity and survival, along with increased immune activation and angiogenesis blockade in the tumor microenvironment compared with any compound alone. Conclusions: Emerging clinical data show responses in GI tumors may be achieved with nemvaleukin/pembrolizumab with manageable safety. Preclinical evidence of antitumor activity of nemvaleukin with CPIs or TKIs warrants further exploration of nemvaleukin in new combinations for pts with GI cancers. Clinical trial information: NCT02799095.

ARTISTRY-1: Nemvaleukin alfa monotherapy and in combination with pembrolizumab in patients (pts) with advanced solid tumors

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Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel, engineered cytokine that selectively binds the intermediate-affinity interleukin-2 (IL-2) receptor complex to preferentially activate CD8+ T cells and natural killer cells with minimal expansion of regulatory T cells, designed to leverage antitumor effects of the IL-2 pathwaywhile mitigating potential toxicity that would limit use. Methods: ARTISTRY-1 (NCT02799095) is a phase 1/2 study. Parts A (dose escalation 0.1-10 µg/kg) and B (6 µg/kg [recommended phase 2 dose]) are monotherapy; pts receive intravenous nemvaleukin for 5 days every 14 or 21 days. In Part C, pts receive nemvaleukin (3 or 6 µg/kg) every 21 days in combination with pembrolizumab (200 mg on day 1). We present safety and antitumor activity (RECIST v1.1, iRECIST) data as of 12/02/2020. Results: In Part A, 39 pts received nemvaleukin. No dose-limiting toxicities were observed; maximum tolerated dose was not reached. Part B enrolled immune checkpoint inhibitor–pretreated pts into melanoma or renal cell carcinoma (RCC) cohorts. 18 pts with melanoma enrolled; 10 were evaluable, 2 (both with metastatic mucosal melanoma) achieved a partial response (PR; 1 unconfirmed). 24 pts with RCC enrolled; 1 of 16 evaluable pts achieved a PR (awaiting confirmation). 12 pts in each cohort continue on study. In Parts A and B, treatment-related adverse events in ≥40% included chills (74.4% and 52.4%, respectively) and pyrexia (74.4% and 47.6%, respectively). In Part C (83 evaluable pts), 12 objective responses (OR) were observed; an additional 5 pts had stable disease (SD) >6 months (1 pt with breast cancer, 2 with ovarian cancer, and 2 with non-small-cell lung cancer). Nemvaleukin did not demonstrate any additive toxicity to that already established with pembrolizumab alone. OR data are summarized in the table. Conclusions: Nemvaleukin was generally well tolerated and demonstrated antitumor activity as monotherapy and in combination with pembrolizumab. Pharmacodynamic studies to identify biomarkers are ongoing. Future research of monotherapy and combination therapy with nemvaleukin is warranted. Clinical trial information: NCT02799095. [Table: see text]

Failure of Perception of Hypocapnia: Physiological and Clinical Implications

Hyperventilation causes hypocapnia and respiratory alkalosis and thereby predisposes to coronary vasoconstriction and cardiac arrhythmia. Diagnostic methods for use between episodes have not been established.

In this study of 100 patients and 25 control subjects the resting end-tidal PCO2 (Pet CO2) levels and the results of a forced hyperventilation test did not show a significant difference between the groups. However the patients hyperventilated more profoundly in response to emotional stimulation, and were less aware of inappropriate breathing and hypocapnia.

It is suggested that these differences should be accommodated in cardiac rehabilitation.

Is Chronic Fatigue Syndrome Synonymous with Effort Syndrome?

Chronic fatigue syndrome (CFS), including myalgic encephalomyelitis (ME) and postviral syndrome (PVS), is a term used today to describe a condition of incapacity for making and sustaining effort, associated with a wide range of symptoms. None of the reviews of CFS has provided a proper consideration of the effort syndrome caused by chronic habitual hyperventilation. In 100 consecutive patients, whose CFS had been attributed to ME or PVS, the time course of their illness and the respiratory psychophysiological studies were characteristic of chronic habitual hyperventilation in 93. It is suggested that the labels ‘CFS’, ‘ME’ or TVS' should be withheld until chronic habitual hyperventilation - for which conventional rehabilitation is available - has been definitively excluded.

The Impact of Cardiac Radiation Dosimetry on Survival After Radiation Therapy for Non-Small Cell Lung Cancer

PURPOSE

The heart receives high radiation doses during radiation therapy of advanced-stage lung cancer. We have explored associations between overall survival, cardiac radiation doses, and electrocardiographic (ECG) changes in patients treated in IDEAL-CRT, a trial of isotoxically escalated concurrent chemoradiation delivering tumor doses of 63 to 73 Gy.

METHODS AND MATERIALS

Dosimetric and survival data were analyzed for 78 patients. The whole heart, pericardium, AV node, and walls of left and right atria (LA/RA-Wall) and ventricles (LV/RV-Wall) were outlined on radiation therapy planning scans, and differential dose-volume histograms (dDVHs) were calculated. For each structure, dDVHs were approximated using the average dDVH and the 10 highest-ranked structure-specific principal components (PCs). ECGs at baseline and 6 months after radiation therapy were analyzed for 53 patients, dichotomizing patients according to presence or absence of "any ECG change" (conduction or ischemic/pericarditis-like change). All-cause death rate (DR) was analyzed from the start of treatment using Cox regression.

RESULTS

38% of patients had ECG changes at 6 months. On univariable analysis, higher scores for LA-Wall-PC6, Heart-PC6, "any ECG change," and larger planning target volume (PTV) were significantly associated with higher DR (P=.003, .009, .029, and .037, respectively). Heart-PC6 and LA-Wall-PC6 represent larger volumes of whole heart and left atrial wall receiving 63 to 69 Gy. Cardiac doses ≥63 Gy were concentrated in the LA-Wall, and consequently Heart-PC6 was highly correlated with LA-Wall-PC6. "Any ECG change," LA-Wall-PC6 scores, and PTV size were retained in the multivariable model.

CONCLUSIONS

We found associations between higher DR and conduction or ischemic/pericarditis-like changes on ECG at 6 months, and between higher DR and higher Heart-PC6 or LA-Wall-PC6 scores, which are closely related to heart or left atrial wall volumes receiving 63 to 69 Gy in this small cohort of patients.

Endosulfatases SULF1 and SULF2 limit Chlamydia muridarum infection

The first step in attachment of Chlamydia to host cells is thought to involve reversible binding to host heparan sulfate proteoglycans (HSPGs), polymers of variably sulfated repeating disaccharide units coupled to diverse protein backbones. However, the key determinants of HSPG structure that are involved in Chlamydia binding are incompletely defined. A previous genome-wide Drosophila RNAi screen suggested that the level of HSPG 6-O sulfation rather than the identity of the proteoglycan backbone maybe a critical determinant for binding. Here, we tested in mammalian cells whether SULF1 or SULF2, human endosulfatases, which remove 6-O sulfates from HSPGs, modulate Chlamydia infection. Ectopic expression of SULF1 or SULF2 in HeLa cells, which decreases cell surface HSPG sulfation, diminished C. muridarum binding and decreased vacuole formation. ShRNA depletion of endogenous SULF2 in a cell line that primarily expresses SULF2 augmented binding and increased vacuole formation. C. muridarum infection of diverse cell lines resulted indownregulation of SULF2 mRNA. In a murine model of acute pneumonia, mice genetically deficient in both endosulfatases or in SULF2 alone demonstrated increased susceptibility to C. muridarum lung infection. Collectively, these studies demonstrate that the level of HSPG 6-O sulfation is a critical determinant of C. muridarum infection in vivo and that 6-O endosulfatases are previously unappreciated modulators of microbial pathogenesis.

Sulf-2, a heparan sulfate endosulfatase, promotes human lung carcinogenesis

Heparan sulfate (HS) proteoglycans (HSPGs) bind to multiple growth factors/morphogens and regulate their signaling. 6-O-sulfation (6S) of glucosamine within HS chains is critical for many of these ligand interactions. Sulf-1 and Sulf-2, which are extracellular neutral-pH sulfatases, provide a novel post-synthetic mechanism for regulation of HSPG function by removing 6S from intact HS chains. The Sulfs can thereby modulate several signaling pathways, including the promotion of Wnt signaling. We found induction of SULF2 transcripts and Sulf-2 protein in human lung adenocarcinoma and squamous cell carcinoma, the two major classes of non-small-cell lung carcinomas (NSCLCs). We confirmed widespread Sulf-2 protein expression in tumor cells of 10/10 surgical specimens of human lung squamous carcinomas. We studied five Sulf-2(+) NSCLC cell lines, including two, which were derived by cigarette-smoke transformation of bronchial epithelial cells. shRNA-mediated Sulf-2 knockdown in these lines caused an increase in 6S on their cell surface and in parallel reversed their transformed phenotype in vitro, eliminated autocrine Wnt signaling and strongly blunted xenograft tumor formation in nude mice. Conversely, forced Sulf-2 expression in non-malignant bronchial epithelial cells produced a partially transformed phenotype. Our findings support an essential role for Sulf-2 in lung cancer, the leading cancer killer.

Dobutamine-induced hyperaemia inversely correlates with coronary artery stenosis severity and highlights dissociation between myocardial blood flow and oxygen consumption

OBJECTIVES

To compare the relationship between dobutamine myocardial blood flow (MBF), rate-pressure product (RPP) and stenosis severity in patients with coronary artery disease (CAD).

METHODS

27 patients with single-vessel CAD were allocated to three groups based on stenosis severity: group 1, 50-69% (n = 9); group 2, 70-89% (n = 9); and group 3, >or= 90% (n = 9). Nine normal volunteers served as controls. Resting and dobutamine MBF were measured by positron emission tomography in the territory subtended by the stenosis (Isc) and remote myocardium (Rem). Mean left ventricular MBF was used for controls.

RESULTS

In group 1, mean dobutamine MBF-Isc (2.48 (SD 0.48 ml/min/g)) and dobutamine MBF-Rem (2.70 (0.50) ml/min/g, NS) were comparable. In groups 2 and 3, dobutamine MBF-Isc (1.91 (0.44) and 1.22 (0.21) ml/min/g) was significantly lower than dobutamine MBF-Rem (2.27 (0.28) and 1.98 (0.25) ml/min/g, p < 0.02 and p < 0.005, respectively). An inverse relation between dobutamine MBF and stenosis severity existed both in Isc (r = 0.79, p < 0.001) and in Rem territories (r = 0.71, p < 0.001). For any given RPP, dobutamine MBF was greater in controls than in Rem (p < 0.05), which in turn was greater than in Isc (p < 0.05).

CONCLUSION

Dobutamine MBF inversely correlated with stenosis severity and achieved significant flow heterogeneity for coronary stenoses > 70%. Dobutamine MBF and RPP were dissociated in both Isc and Rem segments in patients compared with controls.

Physiological insights into Shechita

The Government recently announced that it intends to reject a recommendation by the Farm Animal Welfare Council that all animals should be stunned before slaughter (see VR, April 10, p 446). In this Viewpoint article, Dr Stuart Rosen discusses physiological aspects of Shechita, the Jewish method of religious animal slaughter. He outlines the religious context and describes the act of Shechita. He discusses the scientific literature on the behavioural responses to Shechita as well as neurophysiological studies relevant to the assessment of pain, and concludes that Shechita is a painless and humane method of animal slaughter.

Sulphated endothelial ligands for L-selectin in lymphocyte homing and inflammation

Lymphocytes from the blood home to secondary lymphoid tissues through a process of tethering, rolling, firm adhesion and transmigration. Tethering and rolling of lymphocytes is mediated by the interaction of L-selectin on lymphocytes with sulphated ligands expressed by the specialized endothelial cells of high endothelial venules (HEVs). The sulphate-dependent monoclonal antibody MECA79 stains HEVs in peripheral lymph nodes and recognizes the complex of HEV ligands for L-selectin termed peripheral node addressin. High endothelial cell GlcNAc-6-sulphotransferase/L-selectin ligand sulphotransferase is a HEV-expressed sulphotransferase that contributes to the formation of the MECA79 epitope and L-selectin ligands on lymph node HEVs. MECA79-reactive vessels are also common at sites of chronic inflammation, suggesting mechanistic parallels between lymphocyte homing and inflammatory trafficking.

Central neural contribution to the perception of chest pain in cardiac syndrome X

OBJECTIVE

To investigate the central neural contribution to chest pain perception in cardiac syndrome X (angina-like pain, ECG changes during stress, angiographically normal coronary arteriogram).

SUBJECTS

Eight syndrome X patients and eight healthy volunteers.

METHODS

Dobutamine stress using echocardiography to assess myocardial function, and positron emission tomography to measure changes in regional cerebral blood flow, as an index of neuronal activity.

RESULTS

During similar doses of dobutamine, syndrome X patients and controls showed comparable regional cerebral blood flow changes in the hypothalamus, thalami, right orbito-frontal cortex, and anterior temporal poles, associated with the sensation of a fast or powerful heart beat. In patients, but not controls, the stress also generated severe chest pain associated with increased activity in the right anterior insula/frontal operculum junction. There were ischaemia-like ECG changes in the syndrome X patients, but no left ventricular dysfunction on echocardiography. Activation of the right insula during chest pain clearly distinguished the syndrome X patients from a group of patients with known coronary disease.

CONCLUSIONS

Chest pain and ECG changes were not accompanied by demonstrable myocardial dysfunction in syndrome X patients, but altered central neural handling of afferent signals may contribute to the abnormal pain perception in these patients.

P-selectin mediates the adhesion of sickle erythrocytes to the endothelium

The adherence of sickle red blood cells (RBCs) to the vascular endothelium may contribute to painful vaso-occlusion in sickle cell disease. Sickle cell adherence involves several receptor-mediated processes and may be potentiated by the up-regulated expression of adhesion molecules on activated endothelial cells. Recent results showed that thrombin rapidly increases the adhesivity of endothelial cells for sickle erythrocytes. The current report presents the first evidence for the novel adhesion of normal and, to a greater extent, sickle RBCs to endothelial P-selectin. Studies of the possible interaction of erythrocytes with P-selectin revealed that either P-selectin blocking monoclonal antibodies or sialyl Lewis tetrasaccharide inhibits the enhanced adherence of normal and sickle cells to thrombin-treated endothelial cells. Both RBC types also adhere to immobilized recombinant P-selectin. Pretreating erythrocytes with sialidase reduces their adherence to activated endothelial cells and to immobilized recombinant P-selectin. Herein the first evidence is presented for the binding of normal or sickle erythrocytes to P-selectin. This novel finding suggests that P-selectin inhibition be considered as a potential approach to therapy for the treatment of painful vaso-occlusion in sickle cell disease.

Sulfation of L-selectin ligands by an HEV-restricted sulfotransferase regulates lymphocyte homing to lymph nodes

Lymphocytes home to lymph nodes, using L-selectin to bind specific ligands on high endothelial venules (HEV). In vitro studies implicate GlcNAc-6-sulfate as an essential posttranslational modification for ligand activity. Here, we show that genetic deletion of HEC-GlcNAc6ST, a sulfotransferase that is highly restricted to HEV, results in the loss of the binding of recombinant L-selectin to the luminal aspect of HEV, elimination of lymphocyte binding in vitro, and markedly reduced in vivo homing. Reactivity with MECA 79, an adhesion-blocking mAb that stains HEV in lymph nodes and vessels in chronic inflammatory sites, is also lost from the luminal aspects of HEV. These results establish a critical role for HEC-GlcNAc6ST in lymphocyte trafficking and suggest it as an important therapeutic target.

A potential role for annexin 1 as a physiologic mediator of glucocorticoid-induced L-selectin shedding from myeloid cells

Glucocorticoids can dampen inflammatory responses by inhibiting neutrophil recruitment to tissue sites. The detailed mechanism by which glucocorticoids exert this affect on neutrophils is unknown. L-selectin is a leukocyte cell surface receptor that is implicated in several steps of neutrophil recruitment. Recently, several studies have shown that systemic treatment of animals and humans with glucocorticoids induces decreased L-selectin expression on neutrophils, suggesting one mechanism by which inflammation may be negatively regulated. However, when neutrophils are treated in vitro with glucocorticoids, no effect on L-selectin expression is observed. Thus, the existence of an additional mediator is plausible. In this study, we investigate whether annexin 1 (ANX1), a recognized second messenger of glucocorticoids, could be such a mediator. We show that ANX1 induces a dose- and time-dependent decrease in L-selectin expression on both peripheral blood neutrophils and monocytes but has no effect on lymphocytes. The loss of L-selectin from neutrophils is due to shedding that is mediated by a cell surface metalloprotease ("sheddase"). Using cell shape and a beta(2) integrin activation epitope, we show that the ANX1-induced shedding of L-selectin appears to occur without overt cell activation. These data may provide the basis for further understanding of mechanisms involved in the down-regulation of inflammatory responses.

Polymerized Liposome Assemblies: Bifunctional Macromolecular Selectin Inhibitors Mimicking Physiological Selectin Ligands

Monomeric sialyl Lewis(X) (sLe(x)) and sLe(x)-like oligosaccharides are minimal structures capable of supporting selectin binding in vitro. However, their weak binding interactions do not correlate with the high-affinity binding interactions witnessed in vivo. The polyvalent display of carbohydrate groups found on cell surface glycoprotein structures may contribute to the enhanced binding strength of selectin-mediated adhesion. Detailed biochemical analyses of physiological selectin ligands have revealed a complicated composition of molecules that bind to the selectins in vivo and suggest that there are other requirements for tight binding beyond simple carbohydrate multimerization. In an effort to mimic the high-affinity binding, polyvalent scaffolds that contain multicomponent displays of selectin-binding ligands have been synthesized. Here, we demonstrate that the presentation of additional anionic functional groups in the form of sulfate esters, on a polymerized liposome surface containing a multimeric array of sLe(x)-like oligosaccharides, generates a highly potent, bifunctional macromolecular assembly. This assembly inhibits L-, E-, and P-selectin binding to GlyCAM-1, a physiological ligand better than sLe(x)-like liposomes without additional anionic charge. These multivalent arrays are 4 orders of magnitude better than the monovalent carbohydrate. Liposomes displaying 3'-sulfo Lewis(X)-like oligosaccharides, on the other hand, show slight loss of binding with introduction of additional anionic functional groups for E- and P-selectin and negligible change for L-selectin. The ability to rapidly and systematically vary the composition of these assemblies is a distinguishing feature of this methodology and may be applied to the study of other systems where composite binding determinants are important for high-affinity binding.

Chromosomal localization and genomic organization for the galactose/ N-acetylgalactosamine/N-acetylglucosamine 6-O-sulfotransferase gene family

The galactose/N-acetylgalactosamine/N-acetylglucosamine 6-O-sulfotransferases (GSTs) are a family of Golgi-resident enzymes that transfer sulfate from 3'phosphoadenosine 5'phospho-sulfate to the 6-hydroxyl group of galactose, N-acetylgalactosamine, or N-acetylglucosamine in nascent glycoproteins. These sulfation modifications are functionally important in settings as diverse as cartilage structure and lymphocyte homing. To date six members of this gene family have been described in human and in mouse. We have determined the chromosomal localization of these genes as well as their genomic organization. While the broadly expressed enzymes implicated in proteoglycan biosynthesis are located on different chromosomes, the highly tissue specific enzymes GST-3 and 4 are encoded by genes located both in band q23.1--23.2 on chromosome 16. In the mouse, both genes reside in the syntenic region 8E1 on chromosome 8. This cross-species conserved clustering is suggestive of related functional roles for these genes. The human GST4 locus actually contains two highly similar open reading frames (ORF) that are 50 kb apart and encode two highly similar enzyme isoforms termed GST-4 alpha and GST-4 beta. All genes except GST0 (chondroitin 6-O-sulfotransferase) contain intron-less ORFs. With one exception these are fused directly to sequences encoding the 3' untranslated regions (UTR) of the respective mature mRNAs. The 5' UTRs of these mRNAs are usually encoded by a number of short exons 5' of the respective ORF. 5'UTRs of the same enzyme expressed in different cell types are sometimes derived from different exons located upstream of the ORF. The genomic organization of the GSTs resembles that of certain glycosyltransferase gene families.

Sulfation of N-acetylglucosamine by chondroitin 6-sulfotransferase 2 (GST-5)

Based on sequence homology with a previously cloned human GlcNAc 6-O-sulfotransferase, we have identified an open reading frame (ORF) encoding a novel member of the Gal/GalNAc/GlcNAc 6-O-sulfotransferase (GST) family termed GST-5 on the human X chromosome (band Xp11). GST-5 has recently been characterized as a novel GalNAc 6-O-sulfotransferase termed chondroitin 6-sulfotransferase-2 (Kitagawa, H., Fujita, M., Itio, N., and Sugahara K. (2000) J. Biol. Chem. 275, 21075-21080). We have coexpressed a human GST-5 cDNA with a GlyCAM-1/IgG fusion protein in COS-7 cells and observed four-fold enhanced [(35)S]sulfate incorporation into this mucin acceptor. All mucin-associated [(35)S]sulfate was incorporated as GlcNAc-6-sulfate or Galbeta1-->4GlcNAc-6-sulfate. GST-5 was also expressed in soluble epitope-tagged form and found to catalyze 6-O-sulfation of GlcNAc residues in synthetic acceptor structures. In particular, GST-5 was found to catalyze 6-O-sulfation of beta-benzyl GlcNAc but not alpha- or beta-benzyl GalNAc. In the mouse genome we have found a homologous ORF that predicts a novel murine GlcNAc 6-O-sulfotransferase with 88% identity to the human enzyme. This gene was mapped to mouse chromosome X at band XA3.1-3.2. GST-5 is the newest member of an emerging family of carbohydrate 6-O-sulfotransferases that includes chondroitin 6-sulfotransferase (GST-0), keratan-sulfate galactose 6-O-sulfotransferase (GST-1), the ubiquitously expressed GlcNAc 6-O-sulfotransferase (GST-2), high endothelial cell GlcNAc 6-O-sulfotransferase (GST-3), and intestinal GlcNAc 6-O-sulfotransferase (GST-4).

Persistent but reversible coronary microvascular dysfunction after bypass grafting

The effect of coronary artery bypass grafting (CABG) on absolute myocardial blood flow (MBF) has not been investigated previously. MBF (ml. min(-1). g(-1)) was measured at rest and during hyperemia (0.56 mg/kg iv dipyridamole) using H(2)(15)O and positron emission tomography in eight patients with three-vessel disease before surgery and 1 and 6 mo after full revascularization. Baseline MBF was 0.87 +/- 0.12 preoperatively and 1.04 +/- 0.14 and 0.95 +/- 0.13 at 1 and 6 mo after CABG, respectively (P < 0.05, 6 mo vs. preoperatively). Hyperemic MBF was 1.36 +/- 0.28 preoperatively and increased to 1.98 +/- 0.50 and 2.45 +/- 0.64 at 1 and 6 mo after CABG, respectively (P < 0.01, 6 mo vs. preoperatively). Coronary vasodilator reserve (hyperemic/baseline MBF) increased from 1.59 +/- 0.40 preoperatively to 1.93 +/- 0.13 and 2.57 +/- 0.49 at 1 and 6 mo, respectively (P < 0.05, 6 mo vs. preoperatively). Minimal (dipyridamole) coronary resistance (mmHg. min. g(-1). ml(-1)) fell progressively from 59.37 +/- 14.56 before surgery to a nadir of 35. 76 +/- 10.12 at 6 mo after CABG (P < 0.01 vs. preoperatively). The results of the present study confirm that CABG improves coronary vasodilator reserve progressively as a result of reduction in minimal coronary resistance. These data suggest persistent microvascular dysfunction that recovers slowly after surgery.

Minimal sulfated carbohydrates for recognition by L-selectin and the MECA-79 antibody

Sulfated forms of sialyl-Le(X) containing Gal-6-SO(4) or GlcNAc-6-SO(4) have been implicated as potential recognition determinants on high endothelial venule ligands for L-selectin. The optimal configuration of sulfate esters on the N-acetyllactosamine (Galbeta1-->4GlcNAc) core of sulfosialyl-Le(X), however, remains unsettled. Using a panel of sulfated lactose (Galbeta1-->4Glc) neoglycolipids as substrates in direct binding assays, we found that 6',6-disulfolactose was the preferred structure for L-selectin, although significant binding to 6'- and 6-sulfolactose was observed as well. Binding was EDTA-sensitive and blocked by L-selectin-specific monoclonal antibodies. Surprisingly, 6', 6-disulfolactose was poorly recognized by MECA-79, a carbohydrate- and sulfate-dependent monoclonal antibody that binds competitively to L-selectin ligands. Instead, MECA-79 bound preferentially to 6-sulfolactose. The difference in preferred substrates between L-selectin and MECA-79 may explain the variable activity of MECA-79 as an inhibitor of lymphocyte adhesion to high endothelial venules in lymphoid organs. Our results suggest that both Gal-6-SO(4) and GlcNAc-6-SO(4) may contribute to L-selectin recognition, either as components of sulfosialyl-Le(X) capping groups or in internal structures. By contrast, only GlcNAc-6-SO(4) appears to contribute to MECA-79 binding.

Carbohydrate sulfotransferases in lymphocyte homing

Sulfation is a critical modification in many instances of biological recognition. Early work in lymphocyte homing indicated that the endothelial ligands for L-selectin depended upon sulfation modifications. Subsequent studies showed that the two specific modifications, Gal-6-SO4 and GlcNAc-6-SO4, were present on actual biological ligands. Recently, a family of carbohydrate sulfotransferases capable of generating these modifications has been identified at the molecular level. Reconstitution experiments implicate members of this family as critical participants in lymphocyte homing.

Breathlessness in humans activates insular cortex

Dyspnea (shortness of breath, breathlessness) is a major and disabling symptom of heart and lung disease. The representation of dyspnea in the cerebral cortex is unknown. In the first study designed to explore the central neural structures underlying perception of dyspnea, we evoked the perception of severe 'air hunger' in healthy subjects by restraining ventilation below spontaneous levels while holding arterial oxygen and carbon dioxide levels constant. PET revealed that air hunger activated the insular cortex. The insula is a limbic structure also activated by visceral stimuli, temperature, taste, nausea and pain. Like dyspnea, such perceptions underlie behaviors essential to homeostasis and survival.

The brain-heart axis in the perception of cardiac pain: the elusive link between ischaemia and pain

Angina pectoris is a common symptom and one that can have profound implications for the patient. However, it correlates poorly with the extent of myocardial ischaemia and with prognosis. In order to understand more fully the heterogeneity of the experience of chest pain, we have adopted the technique of functional neuroimaging, where positron emission tomography is used to measure regional cerebral blood flow as an index of regional neuronal activation, during myocardial ischaemia in patients with coronary artery disease. We have been able to delineate those brain areas that are involved in the perception of angina: the hypothalamus, periaquaductal grey, thalami and bilaterally the prefrontal cortex and in the left the inferior anterocaudal cingulate cortex. By studying patients with silent myocardial ischaemia, we have established that the silence is not merely a matter of impaired afferent signalling resulting from autonomic neuropathy, but that it is associated with a failure of transmission of signals from the thalamus to the frontal cortex. At the other end of the spectrum, we have studied patients with syndrome X, a condition of chest pain with ischaemic-like stress electrocardiography (ECG) but entirely normal coronary angiogram; (on the basis of our own and other data we consider an ischaemic aetiology to be most unlikely in this condition). In syndrome X, distinct patterns of cerebral activation were found with characteristic activation of the right anterior insula at its junction with the frontal operculum. In conclusion, we present a unified view of the cerebral handling of afferent signals from the heart throughout this spectrum of experience of chest pain, a view that accounts for the clinical features of the patients studied.

Vascular endothelial junction-associated molecule, a novel member of the immunoglobulin superfamily, is localized to intercellular boundaries of endothelial cells

During the process of lymphocyte homing to secondary lymphoid organs, such as lymph nodes and tonsils, lymphocytes interact with and cross a specialized microvasculature, known as high endothelial venules. There is a great deal of information available about the first steps in the homing cascade, but molecular understanding of lymphocyte transmigration through the intercellular junctions of high endothelial venules is lacking. In analyzing expressed sequence tags from a cDNA library prepared from human tonsillar high endothelial cells, we have identified a cDNA encoding a novel member of the immunoglobulin superfamily. The protein, which we have termed VE-JAM ("vascular endothelial junction-associated molecule"), contains two extracellular immunoglobulin-like domains, a transmembrane domain, and a relatively short cytoplasmic tail. VE-JAM is prominently expressed on high endothelial venules but is also present on the endothelia of other vessels. Strikingly, it is highly localized to the intercellular boundaries of high endothelial cells. VE-JAM is most homologous to a recently identified molecule known as Junctional Adhesion Molecule, which is concentrated at the intercellular boundaries of both epithelial and endothelial cells. Because the Junctional Adhesion Molecule has been strongly implicated in the processes of neutrophil and monocyte transendothelial migration, an analogous function of VE-JAM during lymphocyte homing is plausible.

Identification of endoglycan, a member of the CD34/podocalyxin family of sialomucins

CD34 and podocalyxin are structurally related sialomucins, which are expressed in multiple tissues including vascular endothelium and hematopoietic progenitors. These glycoproteins have been proposed to be involved in processes as diverse as glomerular filtration, inhibition of stem cell differentiation, and leukocyte-endothelial adhesion. Using homologies present in the cytoplasmic tails of these proteins, we have identified a novel member of this family, which we designate endoglycan. This protein shares a similar overall domain structure with the other family members including a sialomucin domain, but also possesses an extremely acidic amino-terminal region. In addition, endoglycan contains several potential glycosaminoglycan attachment sites and is modified with chondroitin sulfate. Endoglycan mRNA and protein were detected in both endothelial cells and CD34(+) bone marrow cells. Thus, CD34, podocalyxin, and endoglycan comprise a family of sialomucins sharing both structural similarity and sequence homology, which are expressed by both endothelium and multipotent hematopoietic progenitors. While the members of this family may perform overlapping functions at these sites, the unique structural features of endoglycan suggest distinct functions for this molecule.

Measurement of myocardial blood flow with positron emission tomography before and after transmyocardial laser revascularization

BACKGROUND

Transmyocardial laser revascularization (TMLR) has been proposed for treatment of refractory angina. It has been hypothesized that transmural left ventricular channels created by laser improve myocardial blood flow (MBF) in the treated zones. We aimed to assess the effect of TMLR on MBF and coronary vasodilator reserve (CVR).

METHODS AND RESULTS

We measured MBF by means of PET with (15)O-labeled water in 7 patients with refractory angina, Canadian Cardiovascular Society (CCS) class 3.6+/-0.5, on 3 occasions: before and at 7.5+/-2.8 weeks (FU-1) and 34.6+/-4.7 weeks (FU-2) after TMLR performed with a synchronized, high-powered CO(2) laser. In each study, MBF was measured at rest and during maximal intravenous dobutamine. CVR was computed as dobutamine divided by resting MBF. After TMLR, CCS class was 2.2+/-1.7 at FU-1 and 2.4+/-1 at FU-2 (P=0.04 versus pre-TMLR). Resting MBF in both lasered and nonlasered regions was unchanged after TMLR. Dobutamine MBF at baseline was 1.45+/-0.52 and 1.55+/-0.52 mL. min(-1). g(-1) in lasered and nonlasered regions, respectively (P=NS). At FU-1, dobutamine MBF in nonlasered regions had increased significantly to 1.89+/-0.82 mL x min(-1) x g(-1) (P<0.05) and was higher than in lasered regions (1.51+/-0.61 mL x min(-1) x g(-1); P<0.05 versus nonlasered). At FU-2, dobutamine MBF in nonlasered regions was still higher than in lasered regions (1.56+/-0.54 versus 1.21+/-0.44 mL x min(-1) x g(-1); P<0.01). CVR was comparable in nonlasered and lasered regions at baseline and FU-1, whereas it was higher in nonlasered regions at FU-2 (1.86+/-0.67 versus 1.53+/-0.72 mL x min(-1) x g(-1); P<0.05).

CONCLUSIONS

TMLR has been shown to reduce angina in severely diseased patients. The results of our study do not support the hypothesis that the symptomatic benefit of TMLR can be ascribed to improved myocardial perfusion or CVR in lasered areas.

Effect of alpha1-adrenoceptor blockade on coronary vasodilator reserve in cardiac syndrome X

We sought to test the response of the coronary microcirculation to alpha-adrenoceptor blockade in patients with syndrome X (angina, ischemia-like stress electrocardiogram, and a normal coronary arteriogram). The response of the microcirculation was assessed by quantification of coronary vasodilator reserve (the ratio of hyperemic to resting myocardial blood flow). We investigated 28 patients with syndrome X [18 women, age 54.4 (7.6) years]. Myocardial blood flow was measured at rest and after dipyridamole by using positron emission tomography with H(2)15O. The measurements were made before and after treatment for 10 days with doxazosin (1 mg o.d. for 3 days, followed by 2 mg o.d. for 7 days) or a matched placebo, similarly administered. Patients were randomized to alpha1-blockade or to placebo in double-blind fashion. No significant differences were demonstrable between syndrome X patients treated with doxazosin and those receiving placebo, with respect to resting myocardial blood flow, myocardial blood flow after dipyridamole, or coronary vasodilator reserve (the ratio of the latter two). In addition, no relations were demonstrable among myocardial blood flow, coronary vasodilator reserve, development of chest pain after dipyridamole, or development of ischemia-like ECG changes. Doxazosin had no effect on the perception of chest pain after dipyridamole. No differences were found between the effects of alpha1-blockade with doxazosin or those of placebo with respect to myocardial blood flow in syndrome X. The values obtained for myocardial blood flow and coronary vasodilator reserve for the patients were within the normal range. The data do not support the case for alpha1-mediated vasoconstriction having an etiologic role in the chest pain of syndrome X.

Cloning and characterization of a mammalian N-acetylglucosamine-6-sulfotransferase that is highly restricted to intestinal tissue

Using the sequences of a galactose 6-O-sulfotransferase and an N-acetylglucosamine 6-O-sulfotransferase as probes in an EST approach, we have identified a highly related cDNA in human and an apparent orthologue in mouse. The cDNAs predict type II transmembrane proteins that constitute new members of the Gal/GalNAc/GlcNAc 6-O-sulfotransferase (GST) family. Members of this family have previously been implicated in the sulfation of GAG chains within proteoglycans and the sulfation of O-linked chains within sialomucin ligands for l-selectin. Expression of the newly identified cDNA in COS cells led to the addition of sulfate to C-6 of GlcNAc in an acceptor glycoprotein. The tissue expression of transcripts corresponding to the cDNA was highly restricted to the small intestine and colon in humans. Based on these characteristics, the novel sulfotransferase is designated I-GlcNAc6ST for intestinal GlcNAc 6-O-sulfotransferase.

Painful stimulation suppresses joint inflammation by inducing shedding of L-selectin from neutrophils

Although the inflammatory response is essential for protecting tissues from injury and infection, unrestrained inflammation can cause chronic inflammatory diseases such as arthritis, colitis and asthma. Physiological mechanisms that downregulate inflammation are poorly understood. Potent control might be achieved by regulating early stages in the inflammatory response, such as accumulation of neutrophils at the site of injury, where these cells release chemical mediators that promote inflammatory processes including plasma extravasation, bacteriocide and proteolysis. To access an inflammatory site, neutrophils must first adhere to the vascular endothelium in a process mediated in part by the leukocyte adhesion molecule L-selectin. This adhesion is prevented when L-selectin is shed from the neutrophil membrane. Although shedding of L-selectin is recognized as a potentially important mechanism for regulating neutrophils, its physiological function has not been demonstrated. Shedding of L-selectin may mediate endogenous downregulation of inflammation by limiting neutrophil accumulation at inflammatory sites. Here we show that activation of nociceptive neurons induces shedding of L-selectin from circulating neutrophils in vivo and that this shedding suppresses an ongoing inflammatory response by inhibiting neutrophil accumulation. These findings indicate a previously unknown mechanism for endogenous feedback control of inflammation. Failure of this mechanism could contribute to the etiology of chronic inflammatory disease.

Fractalkine, a CX3C chemokine, is expressed by dendritic cells and is up-regulated upon dendritic cell maturation

The lone CX3C chemokine, fractalkine (FK), is expressed in a membrane-bound form on activated endothelial cells and mediates attachment and firm adhesion of T cells, monocytes and NK cells. We now show that FK is associated with dendritic cells (DC) in epidermis and lymphoid organs. In normal human skin, dual-color fluorescence microscopy co-localized FK expression with Langerhans cells expressing CD1a. In tonsil, FK-positive DC expressed CD83, a marker for mature DC. Human and murine cultured DC up-regulated FK mRNA expression with maturation. Furthermore, CD40 ligation, but not TNF-alpha or lipopolysaccharide treatment, of activated, migratory DC that had migrated from skin explants resulted in a 2.5-fold increase of surface expression of FK without significant alterations of expression of CD80, CD86, CD54 or MHC class II. Since FK mediates adhesion of T cells to activated endothelial cells, the increased expression of FK during DC maturation (and particularly by CD40 ligation) may play a role in the ability of T cells and mature DC to form conjugates and engage in cell-cell communication.

Separate oligosaccharide determinants mediate interactions of the low-molecular-weight salivary mucin with neutrophils and bacteria

The low-molecular-weight human salivary mucin (MG2) coats oral surfaces, where it is in a prime location for governing cell adhesion. Since oligosaccharides form many of the interactive facets on mucin molecules, we examined MG2 glycosylation as it relates to the molecule's adhesive functions. Our previous study of MG2 oligosaccharide structures showed that the termini predominantly carry T, sialyl-T, Lewisx (Lex), sialyl Lex (sLex), lactosamine, and sialyl lactosamine determinants [Prakobphol, A., et al. (1998) Biochemistry 37, 4916-4927]. In addition, we showed that sLex determinants confer L-selectin ligand activity to this molecule. Here we studied adhesive interactions between MG2 and cells that traffic in the oral cavity: neutrophils and bacteria. Under flow conditions, neutrophils tethered to MG2-coated surfaces at forces between 1.25 and 2 dyn/cm2, i.e., comparable to the shear stress generated at the tooth surface by salivary flow ( approximately 0.8 dyn/cm2). MG2 was also found in association with neutrophils isolated from the oral cavity, evidence that the cells interact with this mucin in vivo. Since MG2 serves as an adhesion receptor for bacteria, the MG2 saccharides that serve this function were also identified. Seven of 18 oral bacteria strains that were tested adhered to MG2. Importantly, six of these seven strains adhered via T antigen, sialyl-T antigen, and/or lactosamine sequences. No adherence to Lex and sLex epitopes was detected in all the strains that were tested. Together, these results suggest that distinct subsets of MG2 saccharides function as ligands for neutrophil L-selectin and receptors for bacterial adhesion, a finding with interesting implications for both oral health and mucin function.

Sulfotransferases of two specificities function in the reconstitution of high endothelial cell ligands for L-selectin

L-selectin, a lectin-like receptor, mediates rolling of lymphocytes on high endothelial venules (HEVs) in secondary lymphoid organs by interacting with HEV ligands. These ligands consist of a complex of sialomucins, candidates for which are glycosylation- dependent cell adhesion molecule 1 (GlyCAM-1), CD34, and podocalyxin. The ligands must be sialylated, fucosylated, and sulfated for optimal recognition by L-selectin. Our previous structural characterization of GlyCAM-1 has demonstrated two sulfation modifications, Gal-6-sulfate and GlcNAc-6-sulfate in the context of sialyl Lewis x. We now report the cloning of a Gal-6-sulfotransferase and a GlcNAc-6-sulfotransferase, which can modify GlyCAM-1 and CD34. The Gal-6-sulfotransferase shows a wide tissue distribution. In contrast, the GlcNAc-6-sulfotransferase is highly restricted to HEVs, as revealed by Northern analysis and in situ hybridization. Expression of either enzyme in Chinese hamster ovary cells, along with CD34 and fucosyltransferase VII, results in ligand activity, as detected by binding of an L-selectin/IgM chimera. When coexpressed, the two sulfotransferases synergize to produce strongly enhanced chimera binding.

Parametric polar maps of regional myocardial beta-adrenoceptor density

Quantification of myocardial beta-adrenoceptor density (Bmax) is of interest in cardiac diseases in which altered function of the sympathetic nervous system is thought to play a pathophysiological role. PET provides an unrivaled means of taking regional measurements of cardiac microcirculatory function, tissue metabolism and autonomic nervous system activity. Measurements in small regional areas may be biased because of increased noise levels. This study examined the parametric polar map approach for the regional quantification of Bmax.

METHODS

Dynamic PET with parametric polar map imaging was performed in 10 healthy volunteers and 4 patients with hypertrophic cardiomyopathy using (S)-[11C]-(4-(3-tertiarybutylamino-2-hydroxypropoxy)-benzidimaz ole-2)-on hydrochloride (CGP)-12177 and a double-injection protocol. Time-activity curves were corrected for partial volume, spill-over and wall motion effects. The mean Bmax of the left ventricle was calculated in two ways. First, the average time-activity curve of all segments, having the highest achievable signal-to-noise ratio, was used to calculate Bmax(mTAC) (the myocardial beta-adrenoceptor density of the left ventricle calculated using the average time-activity curve). The bias in Bmax(mTAC) introduced by noise is minimal. Second, an estimate of whole-heart receptor density was calculated using the polar map method by averaging the values of Bmax obtained for 576 individual segments. In these calculations, three different filters (3 x 5, 3 x 9 and 3 x 13 segments) were used to smooth the time-activity curves before calculating Bmax. Mean values of whole-left-ventricular receptor density obtained by averaging regional values using the different filters (Bmax(PMF1/2/3)) were compared with Bmax(mTAC) to assess bias introduced by the polar map approach. Segments with a calculated Bmax outside the range 0.1-50 pmol/g were considered unreliable and were excluded from the analysis.

RESULTS

The differences between the two methods of calculating Bmax were small (7.8%, 4.8% and 3.2%, with the three filters, respectively). Reliable results were obtained in >95% of the segments and in 9 volunteers and all 4 patients.

CONCLUSION

When using PET for the quantification of beta-adrenoceptor density, the regional variation in Bmax can be reliably assessed using the parametric polar map approach.

GlyCAM-1 supports leukocyte rolling in flow: evidence for a greater dynamic stability of L-selectin rolling of lymphocytes than of neutrophils

L-selectin plays a major role in leukocyte traffic through lymph node high endothelial venules (HEV). We have investigated the role of GlyCAM-1, a major L-selectin ligand produced by HEV, in mediating leukocyte rolling under in vitro flow conditions. Purified GlyCAM-1 was found to support tethering and rolling in physiological shear flow of both human and murine L-selectin expressing leukocytes at an efficiency comparable to the HEV-derived L-selectin ligands termed peripheral node addressin (PNAd). Major dynamic differences between L-selectin rolling of peripheral blood T lymphocytes and neutrophils expressing similar L-selectin level were observed on GlyCAM-1. Lymphocytes established slower and more shear resistant rolling than neutrophils and could roll on GlyCAM-1 at shear stresses lower than the threshold values required for L-selectin-mediated neutrophil rolling. Notably, high stability of L-selectin rolling of lymphocytes requires intact cellular energy, although initial lymphocyte tethering to L-selectin ligands is energy-independent. By contrast, L-selectin mediated rolling of neutrophils is insensitive to energy depletion. The distinct dynamic behavior and energy-dependence of L-selectin rolling in different leukocytes suggest that L-selectin adhesiveness in shear flow is regulated in a cell-type specific manner. The greater stability of L-selectin rolling of lymphocytes on surface-adsorbed GlyCAM-1 may contribute to their selective recruitment at peripheral lymph nodes.

A high endothelial cell-derived chemokine induces rapid, efficient, and subset-selective arrest of rolling T lymphocytes on a reconstituted endothelial substrate

The homing of lymphocytes to secondary lymphoid organs is thought to involve the action of chemokines. Secondary lymphoid-tissue chemokine (SLC), a high endothelial venule (HEV)-associated chemokine, has emerged as a candidate for participating in this process. We now show that immobilized SLC strongly induces beta2 integrin-mediated binding of T lymphocytes of naive phenotype and B lymphocytes to ICAM-1 under static conditions. This effect is not mediated by beta2 integrin affinity modulation, because SLC does not elicit a beta2 integrin activation epitope (mAb24) on naive T lymphocytes. In a parallel plate flow chamber, lymphocytes rolling via L-selectin are rapidly arrested through beta2 integrins in a pertussis toxin-sensitive manner on a substrate consisting of L-selectin ligands (peripheral lymph node addressins) together with ICAM-1 and SLC. Naive T lymphocytes are arrested on the HEV substrate with sixfold higher efficiency than memory cells. Neutrophils roll, but are not arrested by SLC, whereas they respond to immobilized IL-8 with rapid arrest. Thus, our artificial HEV system recapitulates critical features of lymphocyte interactions with HEV in vivo. These observations strongly point to the participation of SLC in homing of lymphocytes to secondary lymphoid organs.

Normal values for left ventricular volumes obtained using gated PET

BACKGROUND

Accurate assessment of left ventricular (LV) volumes provides important insights into myocardial function, being particularly important for diseases of the heart in which there is progressive dilatation of the LV, such as remodeling after myocardial infarction. We have recently validated a method for measuring LV volumes using gated positron emission tomography (PET) with oxygen-15 labeled carbon monoxide (C15O). The present study was performed to establish normal values for LV volumes, in absolute units, using this technique.

METHODS

Forty subjects [21 males and 19 females; age 49 +/- 13 years (mean +/- SD), range 24-80; body surface area (BSA) range 1.50-2.18 m2] were studied. End diastolic (EDV) and end systolic volumes (ESV) were calculated by determining the edge of the end diastolic and end systolic blood pool images (obtained using PET with C15O) and summing the volume of the voxels comprising the blood pool.

RESULTS

For the overall study population, EDV was 109 +/- 20 ml and ESV 37 +/- 12 ml. When stratified according to gender, these values were: in males, EDV was 117 +/- 18 ml and ESV 42 +/- 18 ml; in females, EDV was 100 +/- 19 ml and ESV 32 +/- 8 ml. The differences between gender groups (EDV: p = 0.0027, ESV: p = 0.0029) were eliminated when volumes were corrected for BSA.

CONCLUSIONS

These data will form a database of normal values for comparison with pathological conditions of the heart. PET quantification of LV volumes offers a means of measurement of function using an imaging modality that can also assess regional myocardial perfusion and metabolism during the same study session.

Pitfalls in the economic evaluation of thrombolysis in myocardial infarction. The impact of national differences in the cost of thrombolytics and of differences in the efficacy across patient subgroups

BACKGROUND

The economic evaluation of the results of the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Artery (GUSTO) trial found that recombinant tissue plasminogen activator is more cost-effective than streptokinase for the treatment of acute myocardial infarction.

AIM

We evaluated the impact on a cost effectiveness analysis, of the differences in the cost of thrombolytics among countries and of differences in efficacy across patient subgroups.

METHODS

We considered the crude costs of streptokinase and recombinant tissue plasminogen activator in Germany, Italy, the United Kingdom, and the United States of America, and the 30-day mortality found in the GUSTO trial. We calculated the incremental costs for each life saved when streptokinase is substituted by recombinant tissue plasminogen activator. We also calculated the incremental costs for each life saved for two protocols implying a selective use of streptokinase and recombinant tissue plasminogen activator (age-selective protocol: recombinant tissue plasminogen activator in patients < or = 75 years, streptokinase in older patients; site-selective protocol: recombinant tissue plasminogen activator in anterior acute myocardial infarction, streptokinase in non-anterior acute myocardial infarction).

RESULTS

The incremental costs for each life saved when streptokinase is substituted by recombinant tissue plasminogen activator in all GUSTO patients vary greatly among countries: the incremental costs for each life saved are 31%, 45%, and 97% higher in Germany, Italy, and the United States of America compared to the United Kingdom. The use of a site-selective protocol implies a halved cost-effectiveness ratio compared to the use of recombinant tissue plasminogen activator in all cases of acute myocardial infarction.

CONCLUSIONS

(1) The cost-efficacy of recombinant tissue plasminogen activator vs streptokinase in acute myocardial infarction varies greatly among countries due to differences in the cost of drugs. (2) A selective use of thrombolytics for some sites of infarction is more cost-effective than the exclusive use of recombinant tissue plasminogen activator.

Identification of an N-acetylglucosamine-6-0-sulfotransferase activity specific to lymphoid tissue: an enzyme with a possible role in lymphocyte homing

BACKGROUND

The leukocyte adhesion molecule L-selection participates in the initial attachment of blood-borne lymphocytes to high endothelial venules (HEVs) during lymphocyte homing to secondary lymphoid organs, and contributes to leukocyte adhesion and extravasation in HEV-like vessels at sites of chronic inflammation. The L-selection ligands on lymph mode HEVs are mucin-like glycoproteins adorned with the unusual sulfated carbohydrate epitope, 6-sulfo sialyl Lewis x. Sulfation of this epitope on the N-acetylglucosamine (GlcNAc) residue confers high-avidity L-selection binding, and is thought to be restricted in the vasculature to sites of sustained lymphocyte recruitment. The GlcNAc-6-0 sulfotransferase that installs the sulfate ester may be a key modulator of lymphocyte recruitment to secondary lymphoid organs and sites of chronic inflammation and is therefore a potential target for anti-inflammatory therapy.

RESULTS

A GlcNAc-6-0-sulfotransferase activity was identified within porcine lymph nodes and characterized using a rapid, sensitive, and quantitative assay. We synthesized two unnatural oligosaccharide substrates, GlcNAc beta 1-->6Gal alpha-R and Gal beta 1-->4GlcNAc beta 1-->6Gal alpha-R, that incorporate structural motifs from the native L-selection ligands into an unnatural C-glycosyl hydrocarbon scaffold. The sulfotransferase incorporated greater than tenfold more sulfate into the disaccharide than the trisaccharide, indicating a requirement for a terminal GlcNAc. Activity across tissues was highly restricted to the HEVs within peripheral lymph node.

CONCLUSIONS

The restricted expression of the GlcNAc-6-0-sulfotransferase activity to lymph node HEVs strongly suggestions a role in the biosynthesis of L-selection ligands. In addition, similar sulfated epitopes are known to be expressed on HEV-like vessels of chronically inflamed tissues; indicating that this sulfotransferase may also contribute to inflammatory lymphocyte recruitment. We identified a concise disaccharide motif, GlcNAc beta 1-->6Gal alpha-R, that preserved both recognition and specificity determinants for the GlcNAc-6-0-sulfotransferase. The absence of activity on the trisaccharide Gal beta 1-->6Gal alpha-R indicates a requirement for a substrate with a terminal GlcNAc residue, suggesting that sulfation precedes further biosynthetic assembly of L-selection ligands.

Measurement of myocardial blood flow with oxygen-15 labelled water: comparison of different administration protocols

Positron emission tomography (PET) in conjunction with C15O2 or H215O can be used to measure myocardial blood flow (MBF) and tissue fraction (TF), i.e. the fraction of the tissue mass in the volume of the region of interest. However, with C15O2 inhalation, the tissue fraction in the septum is overestimated. Bolus injection of H215O together with arterial cannulation gives very precise results but is invasive. The purpose of this study was to develop a method which circumvents these problems. A four-parameter model with parameters for MBF, TF and spill-over fractions from both left and right ventricular cavities was developed. This method was compared with a three-parameter model (no right ventricular cavity spill-over) in both septal and non-septal regions of interest for three different administration protocols: bolus injection of H215O, infusion of H215O and inhalation of C15O2. It was found that MBF can be measured with intravenous administration of H215O without the requirement for arterial cannulation. The four-parameter protocol with bolus injection was stable in clinical studies. The four-parameter model proved essential for the septum, where it gave highly significantly better fits than did the three-parameter model (P<0.00003 in each of 15 subjects). Administration of H215O together with this four-parameter model also circumvented the problem of overestimation of TF in the septum seen with C15O2 inhalation. In addition, the radiation dose of H215O protocols is lower than that of C15O2 inhalation. Using a left atrial input curve instead of a left ventricular cavity input curve gave the same mean MBF and TF.

Identification of podocalyxin-like protein as a high endothelial venule ligand for L-selectin: parallels to CD34

The leukocyte adhesion molecule, L-selectin, mediates the recruitment of lymphocytes to secondary lymphoid organs via interactions with specific ligands presented on high endothelial venules (HEV). Although the HEV-derived ligands for L-selectin are still incompletely defined, they share a common sialomucin-like structure which is thought to present clustered oligosaccharides to the lectin domain of L-selectin. Podocalyxin-like protein (PCLP) is a transmembrane sialomucin that is similar in structure to the well-characterized L-selectin ligand CD34. PCLP has been shown previously to be expressed on the foot processes of podocytes in the kidney glomerulus as well as on vascular endothelium at some sites. We have determined that PCLP is present on HEV, where it binds to both recombinant L-selectin and the HEV-specific monoclonal antibody MECA-79. Furthermore, purified HEV-derived PCLP is able to support the tethering and rolling of lymphocytes under physiological flow conditions in vitro. These results suggest a novel function for PCLP as an adhesion molecule and allow the definition of conserved structural features in PCLP and CD34, which may be important for L-selectin ligand function.

Human low-molecular-weight salivary mucin expresses the sialyl lewisx determinant and has L-selectin ligand activity

Previously we showed that the low-molecular-weight mucin (MG2, encoded by MUC7), a major component of human submandibular/sublingual saliva, is a bacterial receptor that coats the tooth surface. Here we tested the hypothesis that the structure of its carbohydrate residues contains important information about its function. Purified MG2 (Mr 120 000) was digested with trypsin, and the resulting Mr 90 000 fragment, which carried primarily O-linked oligosaccharides, was subjected to reductive beta-elimination. The released oligosaccharides were characterized by using nuclear magnetic resonance spectroscopy and mass spectrometry. Of the 41 different structures we detected, the most prominent included NeuAcalpha2-->3Galbeta1-->3GalNAc-ol (sialyl-T antigen), Galbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-->6(Galbeta1 -->3)GalNAc-ol [type 2 core with Lewisx (Lex) determinant], and NeuAcalpha2-->3Galbeta1-->4(Fucalpha1-->3)GlcNAcbet a1-->6(Galbeta1--> 3) GalNAc-ol [type 2 core with sialyl Lex (sLex) determinant]. We also detected di-, tri-, and pentasaccharides with one sulfate group. Lex, sLex, and related sulfated structures are ligands for selectins, adhesion molecules that mediate leukocyte trafficking. Therefore, we investigated whether MG2 was a selectin ligand. In an enzyme-linked immunosorbent assay, L-selectin chimeras interacted with immobilized MG2 in a Ca2+-dependent manner. L-Selectin chimeras also bound to MG2 immobilized on nitrocellulose. Together, these results suggest that the saccharides that MG2 carries could specify some of its important functions, which may include mediating leukocyte interactions in the oral cavity.

Regional myocardial blood flow redistribution as a cause of postprandial angina pectoris

BACKGROUND

Postprandial angina pectoris has been recognized for more than two centuries and can be identified in up to 10% of patients with chronic ischemic heart disease. Redistribution of myocardial blood flow, from a region supplied by a severely stenotic coronary artery to those supplied by less diseased or normal vessels, is a potential mechanism of postprandial angina.

METHODS AND RESULTS

To test this hypothesis, we have determined the effects of a standard liquid meal on whole heart and regional myocardial blood flow, measured by means of dynamic positron emission tomography (PET) with 15O-labeled water in 14 patients with a reproducible history of postprandial angina and 7 matched control subjects. The standard liquid meal precipitated angina pectoris in all patients. Baseline whole heart blood flow was similar and increased normally after the meal in patients (0.97+/-0.14 to 1.14+/-0.25 mL.min(-1).g(-1), P<.04) as in control subjects (0.92+/-0.12 to 1.02+/-0.13 mL.min(-1).g(-1), P<.02). In contrast, the coefficient of variation of blood flow increased significantly after the standard liquid meal in patients (34+/-9%, P<.05 versus baseline) but not in control subjects (17+/-7%, P=NS versus baseline). In patients, analysis of regional myocardial blood flow demonstrated decreased myocardial blood flow in territories supplied by stenotic arteries (1.01+/-0.35 to 0.76+/-0.27 mL.min(-1).g(-1), P<.03), but there was an increase in blood flow in territories supplied by normal arteries (0.89+/-0.16 to 1.34+/-0.25 mL.min(-1).g(-1), P<.001) after the meal.

CONCLUSIONS

The standard liquid meal induced angina pectoris in patients with coronary artery disease. Although whole heart blood flow increased appropriately for the greater cardiac work, there was a redistribution of regional blood flow from territories supplied by severely stenosed coronary arteries to those supplied by less diseased or normal arteries. This redistribution may be the cause of myocardial ischemia in postprandial angina.

Affinity and kinetic analysis of L-selectin (CD62L) binding to glycosylation-dependent cell-adhesion molecule-1

The selectin family of cell adhesion molecules mediates the tethering and rolling of leukocytes on blood vessel endothelium. It has been postulated that the molecular basis of this highly dynamic adhesion is the low affinity and rapid kinetics of selectin interactions. However, affinity and kinetic analyses of monomeric selectins binding their natural ligands have not previously been reported. Leukocyte selectin (L-selectin, CD62L) binds preferentially to O-linked carbohydrates present on a small number of mucin-like glycoproteins, such as glycosylation-dependent cell adhesion molecule-1 (GlyCAM-1), expressed in high endothelial venules. GlyCAM-1 is a soluble secreted protein which, following binding to CD62L, stimulates beta2-integrin-mediated adhesion of lymphocytes. Using surface plasmon resonance, we show that a soluble monomeric form of CD62L binds to purified immobilized GlyCAM-1 with a dissociation constant (Kd) of 108 microM. CD62L dissociates from GlyCAM-1 with a very fast dissociation rate constant (>/=10 s-1) which agrees well with the reported dissociation rate constant of CD62L-mediated leukocyte tethers. The calculated association rate constant is >/=10(5) M-1 s-1. At concentrations just above its mean serum level (approximately 1.5 microg/ml or approximately 30 nM), GlyCAM-1 binds multivalently to immobilized CD62L. It follows that soluble GlyCAM-1 may cross-link CD62L when it binds to cells, suggesting a mechanism for signal transduction.