Role of the NO-GC/cGMP signaling pathway in platelet biomechanics

Cyclic guanosine monophosphate (cGMP) is a second messenger produced by the NO-sensitive guanylyl cyclase (NO-GC). The NO-GC/cGMP pathway in platelets has been extensively studied. However, its role in regulating the biomechanical properties of platelets has not yet been addressed and remains unknown. We therefore investigated the stiffness of living platelets after treatment with the NO-GC stimulator riociguat or the NO-GC activator cinaciguat using scanning ion conductance microscopy (SICM). Stimulation of human and murine platelets with cGMP-modulating drugs decreased cellular stiffness and downregulated P-selectin, a marker for platelet activation. We also quantified changes in platelet shape using deep learning-based platelet morphometry, finding that platelets become more circular upon treatment with cGMP-modulating drugs. To test for clinical applicability of NO-GC stimulators in the context of increased thrombogenicity risk, we investigated the effect of riociguat on platelets from human immunodeficiency virus (HIV)-positive patients taking abacavir sulfate (ABC)-containing regimens. Our results corroborate a functional role of the NO-GC/cGMP pathway in platelet biomechanics, indicating that biomechanical properties such as stiffness or shape could be used as novel biomarkers in clinical research.

The phosphodiesterase 2A controls lymphatic junctional maturation via cGMP-dependent notch signaling

The molecular mechanisms by which lymphatic vessels induce cell contact inhibition are not understood. Here, we identify the cGMP-dependent phosphodiesterase 2A (PDE2A) as a selective regulator of lymphatic but not of blood endothelial contact inhibition. Conditional deletion of Pde2a in mouse embryos reveals severe lymphatic dysplasia, whereas blood vessel architecture remains unaltered. In the absence of PDE2A, human lymphatic endothelial cells fail to induce mature junctions and cell cycle arrest, whereas cGMP levels, but not cAMP levels, are increased. Loss of PDE2A-mediated cGMP hydrolysis leads to the activation of p38 signaling and downregulation of NOTCH signaling. However, DLL4-induced NOTCH activation restores junctional maturation and contact inhibition in PDE2A-deficient human lymphatic endothelial cells. In postnatal mouse mesenteries, PDE2A is specifically enriched in collecting lymphatic valves, and loss of Pde2a results in the formation of abnormal valves. Our data demonstrate that PDE2A selectively finetunes a crosstalk of cGMP, p38, and NOTCH signaling during lymphatic vessel maturation.

Antiplatelet drugs do not protect from platelet-leukocyte aggregation in coronary artery disease

BACKGROUND

Despite advances in cardiovascular medicine, coronary artery disease (CAD) remains a leading cause of mortality. Among the pathophysiological features of this condition, platelet-leukocyte aggregates (PLAs) require further attention, either as diagnostic/prognostic disease markers or as potential interventional targets.

OBJECTIVES

In this study, we characterized PLAs in patients with CAD. Primarily, we investigated the association of PLA levels with CAD diagnosis. In addition, the basal levels of platelet activation and degranulation were assessed in patients with CAD and controls, and their correlation with PLA levels was analyzed. Finally, the effect of antiplatelet treatments on circulating PLA numbers, basal platelet activation, and degranulation was studied in patients with CAD.

METHODS

Participants were recruited at the Department of Cardiology of the University Heart and Vascular Centre Hamburg Eppendorf. Among patients admitted with severe chest pain, the diagnosis of CAD was made angiographically, and patients without CAD were used as controls. PLAs, platelet activation, and platelet degranulation were assessed by flow cytometry.

RESULTS

Circulating PLAs and basal platelet degranulation levels were significantly higher in patients with CAD than in controls. Surprisingly, there was no significant correlation between PLA levels and platelet degranulation (or any other measured parameter). In addition, patients with CAD on antiplatelet therapy did not display lower PLA or platelet degranulation levels compared with those in controls.

CONCLUSION

Overall, these data suggest a mechanism of PLA formation that is independent of platelet activation or degranulation and highlights the inefficiency of current antiplatelet treatments for the prevention of basal platelet degranulation and PLA formation.

Repetitive Antigen Responses of LDL-Reactive CD4+ T Cells Induce Tr1 Cell-Mediated Immune Tolerance

BACKGROUND

Inflammation triggered by the deposition of LDL (low-density lipoprotein) in the arterial wall leads to the development of atherosclerosis. Regulatory T (Treg) cells inhibit vascular inflammation through the induction of immune tolerance toward LDL-related antigens. However, tolerogenic mechanisms that promote the generation of LDL-specific Treg cells in vivo remain unclear.

METHODS

We identified LDL-specific T cells by activation-induced marker expression and analyzed expression profiles and suppressive functions of TCR (T-cell antigen receptor)-transgenic T cells upon repetitive transfer into antigen-transgenic mice via flow cytometry.

RESULTS

We investigated the naturally occurring Treg-cell response against human LDL in standard chow diet-fed mice that are transgenic for human ApoB100 (apolipoprotein B100). We found that IL (interleukin)-10 expression in LDL-specific T cells from spleen increases with age, albeit LDL-specific populations do not enlarge in older mice. To investigate the generation of IL-10-producing LDL-specific T cells, we transferred naive CD4+ T cells recognizing human ApoB100 from TCR-transgenic mice into human ApoB100-transgenic mice. Adoptive transfer of human ApoB100-specific T cells induced immune tolerance in recipient mice and effectively inhibited activation of subsequently transferred naive T cells of the same specificity in vivo. Moreover, repetitive transfers increased the population of Treg type 1 cells that suppress ApoB100-specific responses via IL-10. In a translational approach, LDL-specific Treg type 1 cells from blood of healthy donors suppressed the activation of monocytic THP-1 cells in an IL-10-dependent manner.

CONCLUSIONS

We show that repetitive transfer of naive ApoB100-specific T cells and recurrent LDL-specific T-cell stimulation induces Treg type 1 cell-mediated immune tolerance against LDL in vivo. Our results provide insight into the generation of autoantigen-specific anti-inflammatory T cells under tolerogenic conditions.

Targeting NETs using dual-active DNase1 variants

Background

Neutrophil Extracellular Traps (NETs) are key mediators of immunothrombotic mechanisms and defective clearance of NETs from the circulation underlies an array of thrombotic, inflammatory, infectious, and autoimmune diseases. Efficient NET degradation depends on the combined activity of two distinct DNases, DNase1 and DNase1-like 3 (DNase1L3) that preferentially digest double-stranded DNA (dsDNA) and chromatin, respectively.

Methods

Here, we engineered a dual-active DNase with combined DNase1 and DNase1L3 activities and characterized the enzyme for its NET degrading potential in vitro. Furthermore, we produced a mouse model with transgenic expression of the dual-active DNase and analyzed body fluids of these animals for DNase1 and DNase 1L3 activities. We systematically substituted 20 amino acid stretches in DNase1 that were not conserved among DNase1 and DNase1L3 with homologous DNase1L3 sequences.

Results

We found that the ability of DNase1L3 to degrade chromatin is embedded into three discrete areas of the enzyme's core body, not the C-terminal domain as suggested by the state-of-the-art. Further, combined transfer of the aforementioned areas of DNase1L3 to DNase1 generated a dual-active DNase1 enzyme with additional chromatin degrading activity. The dual-active DNase1 mutant was superior to native DNase1 and DNase1L3 in degrading dsDNA and chromatin, respectively. Transgenic expression of the dual-active DNase1 mutant in hepatocytes of mice lacking endogenous DNases revealed that the engineered enzyme was stable in the circulation, released into serum and filtered to the bile but not into the urine.

Conclusion

Therefore, the dual-active DNase1 mutant is a promising tool for neutralization of DNA and NETs with potential therapeutic applications for interference with thromboinflammatory disease states.

Intrinsic coagulation pathway-mediated thrombin generation in mouse whole blood

Calibrated Automated Thrombography (CAT) is a versatile and sensitive method for analyzing coagulation reactions culminating in thrombin generation (TG). Here, we present a CAT method for analyzing TG in murine whole blood by adapting the CAT assay used for measuring TG in human plasma. The diagnostically used artificial and physiologic factor XII (FXII) contact activators kaolin, ellagic acid and polyphosphate (polyP) stimulated TG in murine blood in a dose-dependent manner resulting in a gradual increase in endogenous thrombin potential and peak thrombin, with shortened lag times and times to peak. The activated FXII inhibitor rHA-Infestin-4 and direct oral anticoagulants (DOACs) interfered with TG triggered by kaolin, ellagic acid and polyP and TG was completely attenuated in blood of FXII- (F12 -/-) and FXI-deficient (F11 -/-) mice. Moreover, reconstitution of blood from F12 -/- mice with human FXII restored impaired contact-stimulated TG. HEK293 cell-purified polyP also initiated FXII-driven TG in mouse whole blood and addition of the selective inhibitor PPX_Δ12 ablated natural polyP-stimulated TG. In conclusion, the data provide a method for analysis of contact activation-mediated TG in murine whole blood. As the FXII-driven intrinsic pathway of coagulation has emerged as novel target for antithrombotic agents that are validated in mouse thrombosis and bleeding models, our novel assay could expedite therapeutic drug development.

Clinical Correlates of Cardiac Conduction in Bipolar Disorder

Introduction

Patients with bipolar disorder (BD) have an increased risk for cardiovascular morbimortality. Clinical risk factors, specifically for arrhythmias and sudden cardiac death remain understudied.

Objectives

This study was conducted to assess differences in cardiac conduction among BD patients.

Methods

We included patients with BD in a cross-sectional design, confirmed by structured interview, age 18 through 80. Clinical characteristics were obtained using a structured questionnaire or medical records review. ECG intervals duration and morphology were manually assessed by cardiologists and compared among clinical subgroups using Chi-square, Mann-Whitney, and Kruskall-Wallis tests. Exploratory multivariable linear and logistic regression models were fitted to adjust for potential confounders.

Results

We included 117 patients (60.7% women, 76.9% bipolar I, 50% history of psychosis, 22.6% suicide attempts). We found a significantly longer QTc interval in BD patients with hypertension (difference: 9.5 ms, p=0.006), obesity (difference: 25 ms, p=0.001), and metabolic syndrome (difference: 13 ms, p=0.007). Hypertension remained a significant predictor of longer QTc after adjusting for age, gender, and antipsychotic use (estimate 17.718, p=0.018). We observed a significantly shorter PR interval in women (difference: 6 ms, p=0.029), early age of onset (difference 6 ms, p=0.025), non-users of lithium (difference 4 ms, p=0.002), and early trauma (difference 4 ms, p=0.038). Finally, we identified significant correlations between symptom severity, blood glucose and PR interval (r=0.298, p=0.001; r=0.278, p=0.003; respectively).

Conclusions

Patients with BD and hypertension may have an increased risk for QTc prolongation. Careful cardiovascular monitoring may be warranted.

Disclosure

No significant relationships.

The Role of Base Excision Repair in Major Depressive Disorder and Bipolar Disorder

Introduction

In vivo and in vitro studies suggest that inflammation and oxidative damage may contribute to the pathogenesis of major depressive disorder (MDD) and bipolar disorder (BD). Imbalance between DNA damage and repair is an emerging research area examining pathophysiological mechanisms of these major mood disorders.

Objectives

This systematic review sought to examine current evidence on the association between mood disorders and deficits in base excision repair (BER), the primary repair mechanism for repair of oxidation-induced DNA lesions.

Methods

We conducted a comprehensive literature search of Ovid MEDLINE® Epub Ahead of Print, Ovid MEDLINE® In-Process & Other Non-Indexed Citations, Ovid MEDLINE® Daily, EMBASE (1947), and PsycINFO for studies investigating the alterations in base excision repair in patients with MDD or BD.

Results

A total of 1,364 records were identified. 1,352 records remained after duplicates were removed. 24 records were selected for full-text screening and a remaining 12 articles were included in the qualitative synthesis. SNPs (Single Nucleotide Polymorphisms) of several BER genes have been shown to be associated with MDD and BD. However, it was difficult to draw conclusions from BER gene expression studies due to conflicting findings and the small number of studies.

Conclusions

Future studies comparing DNA repair during the manic or depressive episode to remission will give us a better insight regarding the role of DNA repair in mood disorders. These alterations might be utilized as diagnostic and prognostic biomarkers as well as measuring treatment response.

Disclosure

No significant relationships.

Liver damage promotes pro-inflammatory T-cell responses against apolipoprotein B-100

OBJECTIVES

Liver-derived apolipoprotein B-100 (ApoB100) is an autoantigen that is recognized by atherogenic CD4⁺ T cells in cardiovascular disease (CVD). CVD is a major mortality risk for patients with chronic inflammatory liver diseases. However, the impact of liver damage for ApoB100-specific T-cell responses is unknown.

METHODS

We identified ApoB100-specific T cells in blood from healthy controls, nonalcoholic fatty liver disease (NAFLD) patients, and CVD patients by activation-induced marker expression and analyzed their differentiation pattern in correlation to the lipid profile and liver damage parameters in a cross-sectional study. To assess the induction of extrahepatic ApoB100-specific T cells upon transient liver damage in vivo, we performed hydrodynamic tail vein injections with diphtheria toxin A (DTA)-encoding plasmid in human ApoB100-transgenic mice.

RESULTS

Utilizing immunodominant ApoB100-derived peptides, we found increased ApoB100-specific T-cell populations in NAFLD and CVD patients compared to healthy controls. In a peptide-specific manner, ApoB100 reactivity in healthy controls was accompanied by expression of the regulatory T (Treg)-cell transcription factor FOXP3. In contrast, FOXP3 expression decreased, whereas expression of pro-inflammatory cytokine interleukin (IL)-17A increased in ApoB100-specific T cells from NAFLD and CVD patients. Dyslipidemia and liver damage parameters in blood correlated with reduced FOXP3 expression and elevated IL-17A production in ApoB100-specific T-cell populations, respectively. Moreover, DTA-mediated transient liver damage in human ApoB100-transgenic mice accumulated IL-17a-expressing ApoB100-specific T cells in the periphery.

CONCLUSION

Our results show that liver damage promotes pro-inflammatory ApoB100-specific T-cell populations, thereby providing a cellular mechanism for the increased CVD risk in liver disease patients.

A Thromboxane A2 Receptor-Driven COX-2-Dependent Feedback Loop That Affects Endothelial Homeostasis and Angiogenesis

BACKGROUND

TP (thromboxane A₂ receptor) plays an eminent role in the pathophysiology of endothelial dysfunction and cardiovascular disease. Moreover, its expression is reported to increase in the intimal layer of blood vessels of cardiovascular high-risk individuals. Yet it is unknown, whether TP upregulation per se has the potential to affect the homeostasis of the vascular endothelium.

METHODS

We combined global transcriptome analysis, lipid mediator profiling, functional cell analyses, and in vivo angiogenesis assays to study the effects of endothelial TP overexpression or knockdown/knockout on the angiogenic capacity of endothelial cells in vitro and in vivo.

RESULTS

Here we report that endothelial TP expression induces COX-2 (cyclooxygenase-2) in a G_i/o- and G_q/11-dependent manner, thereby promoting its own activation via the auto/paracrine release of TP agonists, such as PGH₂ (prostaglandin H₂) or prostaglandin F₂ but not TxA₂ (thromboxane A₂). TP overexpression induces endothelial cell tension and aberrant cell morphology, affects focal adhesion dynamics, and inhibits the angiogenic capacity of human endothelial cells in vitro and in vivo, whereas TP knockdown or endothelial-specific TP knockout exerts opposing effects. Consequently, this TP-dependent feedback loop is disrupted by pharmacological TP or COX-2 inhibition and by genetic reconstitution of PGH₂-metabolizing prostacyclin synthase even in the absence of functional prostacyclin receptor expression.

CONCLUSIONS

Our work uncovers a TP-driven COX-2-dependent feedback loop and important effector mechanisms that directly link TP upregulation to angiostatic TP signaling in endothelial cells. By these previously unrecognized mechanisms, pathological endothelial upregulation of the TP could directly foster endothelial dysfunction, microvascular rarefaction, and systemic hypertension even in the absence of exogenous sources of TP agonists.

Disturbed lipid and amino acid metabolisms in COVID-19 patients

The Coronavirus disease 2019 (COVID-19) pandemic is overwhelming the healthcare systems. Identification of systemic reactions underlying COVID-19 will lead to new biomarkers and therapeutic targets for monitoring and early intervention in this viral infection. We performed targeted metabolomics covering up to 630 metabolites within several key metabolic pathways in plasma samples of 20 hospitalized COVID-19 patients and 37 matched controls. Plasma metabolic signatures specifically differentiated severe COVID-19 from control patients. The identified metabolic signatures indicated distinct alterations in both lipid and amino acid metabolisms in COVID-19 compared to control patient plasma. Systems biology-based analyses identified sphingolipid, tryptophan, tyrosine, glutamine, arginine, and arachidonic acid metabolism as mostly impacted pathways in COVID-19 patients. Notably, gamma-aminobutyric acid (GABA) was significantly reduced in COVID-19 patients and GABA plasma levels allowed for stratification of COVID-19 patients with high sensitivity and specificity. The data reveal large metabolic disturbances in COVID-19 patients and suggest use of GABA as potential biomarker and therapeutic target for the infection.

Mutations in EPHB4 cause human venous valve aplasia

Venous valve (VV) failure causes chronic venous insufficiency, but the molecular regulation of valve development is poorly understood. A primary lymphatic anomaly, caused by mutations in the receptor tyrosine kinase EPHB4, was recently described, with these patients also presenting with venous insufficiency. Whether the venous anomalies are the result of an effect on VVs is not known. VV formation requires complex "organization" of valve-forming endothelial cells, including their reorientation perpendicular to the direction of blood flow. Using quantitative ultrasound, we identified substantial VV aplasia and deep venous reflux in patients with mutations in EPHB4. We used a GFP reporter in mice to study expression of its ligand, ephrinB2, and analyzed developmental phenotypes after conditional deletion of floxed Ephb4 and Efnb2 alleles. EphB4 and ephrinB2 expression patterns were dynamically regulated around organizing valve-forming cells. Efnb2 deletion disrupted the normal endothelial expression patterns of the gap junction proteins connexin37 and connexin43 (both required for normal valve development) around reorientating valve-forming cells and produced deficient valve-forming cell elongation, reorientation, polarity, and proliferation. Ephb4 was also required for valve-forming cell organization and subsequent growth of the valve leaflets. These results uncover a potentially novel cause of primary human VV aplasia.

EVL regulates VEGF receptor-2 internalization and signaling in developmental angiogenesis

Endothelial tip cells are essential for VEGF‐induced angiogenesis, but underlying mechanisms are elusive. The Ena/VASP protein family, consisting of EVL, VASP, and Mena, plays a pivotal role in axon guidance. Given that axonal growth cones and endothelial tip cells share many common features, from the morphological to the molecular level, we investigated the role of Ena/VASP proteins in angiogenesis. EVL and VASP, but not Mena, are expressed in endothelial cells of the postnatal mouse retina. Global deletion of EVL (but not VASP) compromises the radial sprouting of the vascular plexus in mice. Similarly, endothelial‐specific EVL deletion compromises the radial sprouting of the vascular plexus and reduces the endothelial tip cell density and filopodia formation. Gene sets involved in blood vessel development and angiogenesis are down‐regulated in EVL‐deficient P5‐retinal endothelial cells. Consistently, EVL deletion impairs VEGF‐induced endothelial cell proliferation and sprouting, and reduces the internalization and phosphorylation of VEGF receptor 2 and its downstream signaling via the MAPK/ERK pathway. Together, we show that endothelial EVL regulates sprouting angiogenesis via VEGF receptor‐2 internalization and signaling.

EphrinB2-EphB4 signalling provides Rho-mediated homeostatic control of lymphatic endothelial cell junction integrity

Endothelial integrity is vital for homeostasis and adjusted to tissue demands. Although fluid uptake by lymphatic capillaries is a critical attribute of the lymphatic vasculature, the barrier function of collecting lymphatic vessels is also important by ensuring efficient fluid drainage as well as lymph node delivery of antigens and immune cells. Here, we identified the transmembrane ligand EphrinB2 and its receptor EphB4 as critical homeostatic regulators of collecting lymphatic vessel integrity. Conditional gene deletion in mice revealed that EphrinB2/EphB4 signalling is dispensable for blood endothelial barrier function, but required for stabilization of lymphatic endothelial cell (LEC) junctions in different organs of juvenile and adult mice. Studies in primary human LECs further showed that basal EphrinB2/EphB4 signalling controls junctional localisation of the tight junction protein CLDN5 and junction stability via Rac1/Rho-mediated regulation of cytoskeletal contractility. EphrinB2/EphB4 signalling therefore provides a potential therapeutic target to selectively modulate lymphatic vessel permeability and function.

Lymph vessels are thin walled tubes that, similar to blood vessels, carry white blood cells, fluids and waste. Unlike veins and arteries, however, lymph vessels do not carry red blood cells and their main function is to remove excess fluid from tissues. The cells that line vessels in the body are called endothelial cells, and they are tightly linked together by proteins to control what goes into and comes out of the vessels. The chemical, physical and mechanical signals that control the junctions between endothelial cells are often the same in different vessel types, but their effects can vary.

The endothelial cells of both blood and lymph vessels have two interacting proteins on their membrane known as EphrinB2 and its receptor, EphB4. When these two proteins interact, the EphB4 receptor becomes activated, which leads to changes in the junctions that link endothelial cells together. Frye et al. examined the role of EphrinB2 and EphB4 in the lymphatic system of mice. When either EphrinB2 or EphB4 are genetically removed in newborn or adult mice, lymph vessels become disrupted, but no significant effect is observed on blood vessels. The reason for the different responses in blood and lymph vessels is unknown.

The results further showed that lymphatic endothelial cells need EphB4 and EphrinB2 to be constantly interacting to maintain the integrity of the lymph vessels. Further examination of human endothelial cells grown in the laboratory revealed that this constant signalling controls the internal protein scaffold that determines a cell’s shape and integrity. Changes in the internal scaffold affect the organization of the junctions that link neighboring lymphatic endothelial cells together.

The loss of signalling between EphrinB2 and EphB4 in lymph vessels reflects the increase in vessel leakage seen in response to bacterial infections and in some genetic conditions such as lymphoedema. Finding ways to control the signalling between these two proteins could help treat these conditions by developing drugs that improve endothelial cell integrity in lymph vessels.

The Importance of Mechanical Forces for in vitro Endothelial Cell Biology

Blood and lymphatic vessels are lined by endothelial cells which constantly interact with their luminal and abluminal extracellular environments. These interactions confer physical forces on the endothelium, such as shear stress, stretch and stiffness, to mediate biological responses. These physical forces are often altered during disease, driving abnormal endothelial cell behavior and pathology. Therefore, it is critical that we understand the mechanisms by which endothelial cells respond to physical forces. Traditionally, endothelial cells in culture are grown in the absence of flow on stiff substrates such as plastic or glass. These cells are not subjected to the physical forces that endothelial cells endure in vivo, thus the results of these experiments often do not mimic those observed in the body. The field of vascular biology now realize that an intricate analysis of endothelial signaling mechanisms requires complex in vitro systems to mimic in vivo conditions. Here, we will review what is known about the mechanical forces that guide endothelial cell behavior and then discuss the advancements in endothelial cell culture models designed to better mimic the in vivo vascular microenvironment. A wider application of these technologies will provide more biologically relevant information from cultured cells which will be reproducible to conditions found in the body.

Vascular Endothelial Receptor Tyrosine Phosphatase: Identification of Novel Substrates Related to Junctions and a Ternary Complex with EPHB4 and TIE2

Vascular endothelial protein tyrosine phosphatase (VE-PTP, PTPRB) is a receptor type phosphatase that is crucial for the regulation of endothelial junctions and blood vessel development. We and others have shown recently that VE-PTP regulates vascular integrity by dephosphorylating substrates that are key players in endothelial junction stability, such as the angiopoietin receptor TIE2, the endothelial adherens junction protein VE-cadherin and the vascular endothelial growth factor receptor VEGFR2. Here, we have systematically searched for novel substrates of VE-PTP in endothelial cells by utilizing two approaches. First, we studied changes in the endothelial phosphoproteome on exposing cells to a highly VE-PTP-specific phosphatase inhibitor followed by affinity isolation and mass-spectrometric analysis of phosphorylated proteins by phosphotyrosine-specific antibodies. Second, we used a substrate trapping mutant of VE-PTP to pull down phosphorylated substrates in combination with SILAC-based quantitative mass spectrometry measurements. We identified a set of substrate candidates of VE-PTP, of which a remarkably large fraction (29%) is related to cell junctions. Several of those were found in both screens and displayed very high connectivity in predicted functional interaction networks. The receptor protein tyrosine kinase EPHB4 was the most prominently phosphorylated protein on VE-PTP inhibition among those VE-PTP targets that were identified by both proteomic approaches. Further analysis revealed that EPHB4 forms a ternary complex with VE-PTP and TIE2 in endothelial cells. VE-PTP controls the phosphorylation of each of these two tyrosine kinase receptors. Despite their simultaneous presence in a ternary complex, stimulating each of the receptors with their own specific ligand did not cross-activate the respective partner receptor. Our systematic approach has led to the identification of novel substrates of VE-PTP, of which many are relevant for the control of cellular junctions further promoting the importance of VE-PTP as a key player of junctional signaling.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program

Tissue and vessel wall stiffening alters endothelial cell properties and contributes to vascular dysfunction. However, whether extracellular matrix (ECM) stiffness impacts vascular development is not known. Here we show that matrix stiffness controls lymphatic vascular morphogenesis. Atomic force microscopy measurements in mouse embryos reveal that venous lymphatic endothelial cell (LEC) progenitors experience a decrease in substrate stiffness upon migration out of the cardinal vein, which induces a GATA2-dependent transcriptional program required to form the first lymphatic vessels. Transcriptome analysis shows that LECs grown on a soft matrix exhibit increased GATA2 expression and a GATA2-dependent upregulation of genes involved in cell migration and lymphangiogenesis, including VEGFR3. Analyses of mouse models demonstrate a cell-autonomous function of GATA2 in regulating LEC responsiveness to VEGF-C and in controlling LEC migration and sprouting in vivo. Our study thus uncovers a mechanism by which ECM stiffness dictates the migratory behavior of LECs during early lymphatic development.

Heterogeneity in VEGFR3 levels drives lymphatic vessel hyperplasia through cell-autonomous and non-cell-autonomous mechanisms

Incomplete delivery to the target cells is an obstacle for successful gene therapy approaches. Here we show unexpected effects of incomplete targeting, by demonstrating how heterogeneous inhibition of a growth promoting signaling pathway promotes tissue hyperplasia. We studied the function of the lymphangiogenic VEGFR3 receptor during embryonic and post-natal development. Inducible genetic deletion of Vegfr3 in lymphatic endothelial cells (LECs) leads to selection of non-targeted VEGFR3⁺ cells at vessel tips, indicating an indispensable cell-autonomous function in migrating tip cells. Although Vegfr3 deletion results in lymphatic hypoplasia in mouse embryos, incomplete deletion during post-natal development instead causes excessive lymphangiogenesis. Analysis of mosaically targeted endothelium shows that VEGFR3⁻ LECs non-cell-autonomously drive abnormal vessel anastomosis and hyperplasia by inducing proliferation of non-targeted VEGFR3⁺ LECs through cell-contact-dependent reduction of Notch signaling. Heterogeneity in VEGFR3 levels thus drives vessel hyperplasia, which has implications for the understanding of mechanisms of developmental and pathological tissue growth.

VEGF-C is a key regulator of lymphatic development. Here, Zhang et al. show that while complete loss of its receptor VEGFR3 results in vessel hypoplasia, mosaic loss of VEGFR3 leads to hyperplasia through induction of cell proliferation in neighboringnon-targeted cells, uncovering cell- and non-cell-autonomous roles for VEGFR3 during lymphatic vessel growth.

Interfering with VE-PTP stabilizes endothelial junctions in vivo via Tie-2 in the absence of VE-cadherin

Inhibition of VE-PTP counters vascular leakage in inflammation via TIE-2, even in the absence of VE-cadherin.

Vascular endothelial (VE)–protein tyrosine phosphatase (PTP) associates with VE-cadherin, thereby supporting its adhesive activity and endothelial junction integrity. VE-PTP also associates with Tie-2, dampening the tyrosine kinase activity of this receptor that can support stabilization of endothelial junctions. Here, we have analyzed how interference with VE-PTP affects the stability of endothelial junctions in vivo. Blocking VE-PTP by antibodies, a specific pharmacological inhibitor (AKB-9778), and gene ablation counteracted vascular leak induction by inflammatory mediators. In addition, leukocyte transmigration through the endothelial barrier was attenuated. Interference with Tie-2 expression in vivo reversed junction-stabilizing effects of AKB-9778 into junction-destabilizing effects. Furthermore, lack of Tie-2 was sufficient to weaken the vessel barrier. Mechanistically, inhibition of VE-PTP stabilized endothelial junctions via Tie-2, which triggered activation of Rap1, which then caused the dissolution of radial stress fibers via Rac1 and suppression of nonmuscle myosin II. Remarkably, VE-cadherin gene ablation did not abolish the junction-stabilizing effect of the VE-PTP inhibitor. Collectively, we conclude that inhibition of VE-PTP stabilizes challenged endothelial junctions in vivo via Tie-2 by a VE-cadherin–independent mechanism. In the absence of Tie-2, however, VE-PTP inhibition destabilizes endothelial barrier integrity in agreement with the VE-cadherin–supportive effect of VE-PTP.

Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature

Retinal and choroidal neovascularization (NV) and vascular leakage contribute to visual impairment in several common ocular diseases. The angiopoietin/TIE2 (ANG/TIE2) pathway maintains vascular integrity, and negative regulators of this pathway are potential therapeutic targets for these diseases. Here, we demonstrated that vascular endothelial-protein tyrosine phosphatase (VE-PTP), which negatively regulates TIE2 activation, is upregulated in hypoxic vascular endothelial cells, particularly in retinal NV. Intraocular injection of an anti-VE-PTP antibody previously shown to activate TIE2 suppressed ocular NV. Furthermore, a small-molecule inhibitor of VE-PTP catalytic activity (AKB-9778) activated TIE2, enhanced ANG1-induced TIE2 activation, and stimulated phosphorylation of signaling molecules in the TIE2 pathway, including AKT, eNOS, and ERK. In mouse models of neovascular age-related macular degeneration, AKB-9778 induced phosphorylation of TIE2 and strongly suppressed NV. Ischemia-induced retinal NV, which is relevant to diabetic retinopathy, was accentuated by the induction of ANG2 but inhibited by AKB-9778, even in the presence of high levels of ANG2. AKB-9778 also blocked VEGF-induced leakage from dermal and retinal vessels and prevented exudative retinal detachments in double-transgenic mice with high expression of VEGF in photoreceptors. These data support targeting VE-PTP to stabilize retinal and choroidal blood vessels and suggest that this strategy has potential for patients with a wide variety of retinal and choroidal vascular diseases.

Effects of racing on reticulocyte concentrations in Greyhounds

BACKGROUND

Greyhounds have several hematologic variables that are outside of the respective reference intervals of other dog breeds. In addition, increases in HCT, total protein and HGB concentration, and RBC and WBC counts occur immediately after exercise; these values return to resting values within a few hour after racing.

OBJECTIVE

This study evaluated the effects of exercise on the concentration of reticulocytes in circulating blood in racing Greyhounds. We hypothesized that reticulocyte numbers are significantly increased immediately after a race, and return to baseline within one to 2 h postrace.

METHODS

Fifty actively racing Greyhounds at the Wheeling Island Racetrack and Casino were included in the study. Samples were collected by jugular venipuncture one day prior to racing at the kennel (resting), immediately after racing, and one to 2 h after the race (recovery). Reticulocyte counts were determined with an IDEXX ProCyte Dx Hematology Analyzer (IDEXX Laboratories, Inc., Westbrook, ME, USA). Due to a nonparametric distribution, the results were statistically compared using the Friedman test.

RESULTS

Reticulocyte concentrations were significantly different among the 3 sample collection times (P < .0001). There was a significant increase in reticulocyte concentration immediately after racing (P < .001); one to 2 h after racing, the reticulocyte numbers decreased significantly (P < .001) to counts comparable to resting samples.

CONCLUSION

The increase in reticulocyte concentration is probably related to splenic contraction secondary to the release of catecholamines, although premature bone marrow release could also account for these changes. Thus, it is important to consider a Greyhound's activity and degree of excitement when interpreting selected hematologic data in a clinical setting.

Heparan sulfate expression in the neural crest is essential for mouse cardiogenesis

Impaired heparan sulfate (HS) synthesis in vertebrate development causes complex malformations due to the functional disruption of multiple HS-binding growth factors and morphogens. Here, we report developmental heart defects in mice bearing a targeted disruption of the HS-generating enzyme GlcNAc N-deacetylase/GlcN N-sulfotransferase 1 (NDST1), including ventricular septal defects (VSD), persistent truncus arteriosus (PTA), double outlet right ventricle (DORV), and retroesophageal right subclavian artery (RERSC). These defects closely resemble cardiac anomalies observed in mice made deficient in the cardiogenic regulator fibroblast growth factor 8 (FGF8). Consistent with this, we show that HS-dependent FGF8/FGF-receptor2C assembly and FGF8-dependent ERK-phosphorylation are strongly reduced in NDST1(-/-) embryonic cells and tissues. Moreover, WNT1-Cre/LoxP-mediated conditional targeting of NDST function in neural crest cells (NCCs) revealed that their impaired HS-dependent development contributes strongly to the observed cardiac defects. These findings raise the possibility that defects in HS biosynthesis may contribute to congenital heart defects in humans that represent the most common type of birth defect.

Haematological and biochemical values in North American Scottish deerhounds

OBJECTIVE

Sighthounds, including deerhounds, have unique physiological traits that result in laboratory test results that may lie outside reference intervals for the general dog population. Although reference intervals for most analytes are thought to be similar among sighthounds, breed-specific reference intervals are available mainly for greyhounds. The aim of this study was to establish reference intervals for haematology and serum biochemical profiles in deerhounds.

METHODS

Venous blood samples were collected from healthy deerhounds. Haematological and biochemical analytes were examined and reference intervals were established using the 5th and 95th percentiles.

RESULTS

The reference intervals obtained from 96 dogs for platelets, reticulocytes, total thyroxine, chloride, gamma glutamyl transferase, bilirubin and glucose were lower than the general dog population. Reference intervals for mean cell volume, potassium, urea, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and cholesterol were higher than the general dog population. Reference intervals for eosinophils and globulin were wider than that of the general population.

CLINICAL SIGNIFICANCE

These results confirm that differences in haematological and biochemical values exist in the deerhound. Some appear to be shared by all sighthounds but others may be unique to this breed.

Cutting edge: Endothelial-specific gene ablation of CD99L2 impairs leukocyte extravasation in vivo

CD99-like 2 (CD99L2) is a membrane protein with moderate sequence homology to CD99, which initiates cell aggregation of transfected cells and that is strongly expressed on endothelial cells, neutrophils, and lymphocytes. We showed recently that Abs against CD99L2 inhibit neutrophil, but not T lymphocyte, recruitment into inflamed tissues. In this study, we have generated conditional gene-deficient mice for CD99L2 and show by analyzing them in various inflammation models several results. First, gene ablation of CD99L2 impairs neutrophil recruitment into inflamed cremaster and peritoneum. Second, despite the strong expression of CD99L2 on peripheral neutrophils, only gene ablation on endothelial cells but not on myeloid cells affects neutrophil extravasation. Third, in contrast to our previous Ab-based results, recruitment of activated T cells into inflamed skin was impaired in mice lacking CD99L2 on endothelial cells. We conclude that CD99L2 is an essential endothelial Ag for leukocyte extravasation, which does not require homophilic interactions with CD99L2 on leukocytes.

Dissociation of VE-PTP from VE-cadherin is required for leukocyte extravasation and for VEGF-induced vascular permeability in vivo

Artificially stabilizing contacts between VE-cadherin and VE-PTP reduce vascular permeability and leukocyte extravasation in vivo.

We have recently shown that vascular endothelial protein tyrosine phosphatase (VE-PTP), an endothelial membrane protein, associates with VE-cadherin and is required for optimal VE-cadherin function and endothelial cell contact integrity. The dissociation of VE-PTP from VE-cadherin is triggered by vascular endothelial growth factor (VEGF) and by the binding of leukocytes to endothelial cells in vitro, suggesting that this dissociation is a prerequisite for the destabilization of endothelial cell contacts. Here, we show that VE-cadherin/VE-PTP dissociation also occurs in vivo in response to LPS stimulation of the lung or systemic VEGF stimulation. To show that this dissociation is indeed necessary in vivo for leukocyte extravasation and VEGF-induced vascular permeability, we generated knock-in mice expressing the fusion proteins VE-cadherin-FK 506 binding protein and VE-PTP-FRB* under the control of the endogenous VE-cadherin promoter, thus replacing endogenous VE-cadherin. The additional domains in both fusion proteins allow the heterodimeric complex to be stabilized by a chemical compound (rapalog). We found that intravenous application of the rapalog strongly inhibited VEGF-induced (skin) and LPS-induced (lung) vascular permeability and inhibited neutrophil extravasation in the IL-1β inflamed cremaster and the LPS-inflamed lung. We conclude that the dissociation of VE-PTP from VE-cadherin is indeed required in vivo for the opening of endothelial cell contacts during induction of vascular permeability and leukocyte extravasation.

SS06-01 - Are we getting the most out of combination therapy in the short-term and long-term treatment of mania?

The extensive research into the treatment of bipolar disorder over the last 20 years means that we, as clinicians, have never been in a better position to treat patients with bipolar disorder. Yet despite the availability of modern, evidence-based treatment guidelines, bipolar disorder remains an everyday treatment challenge. Newly diagnosed patients requiring treatment for the first time are not always adequately controlled with single-agent therapy and, similarly, combination therapy is also frequently necessary as maintenance treatment. But with this recognition comes the new challenge of identifying when monotherapy is not enough, which agents to combine, when and for how long? How do we know?

Joined by an internationally respected faculty, Professor Siegfried Kasper chairs a discussion to help answer some of the key questions facing clinicians today:

What response can be anticipated from recommended first-line monotherapies for acute mania?

How do we know whether the response we observe when we prescribe a first-line treatment in a manic patient is adequate?

To what extent can a partial non-response to monotherapy be improved by the addition of a second agent?

What's the benefit of maintaining combination treatment once patients are stable and how long should I continue?

Does adding an antipsychotic to a mood stabiliser increase the risk of adverse events, in the short term or in the long term?

Drawing on latest guideline recommendations, recent clinical research, case studies and their extensive clinical experience, the panel will debate these interesting questions and shed light on how we can optimize both acute and maintenance treatment in this patient group.

Although the design of maintenance studies in bipolar disorder has significantly evolved in recent years, individual study designs continue to differ in important ways, with important implications. What may appear to be small differences between study designs, such as the type of most recent episode experienced by the patients or the stabilisation criteria used in the trial, can have big implications for study outcome. It is thus becoming increasingly important to be able to evaluate the results of trials within the context of the design and determine what they mean for treatment practice. Our panel will therefore also discuss the extent to which the design of bipolar maintenance studies can influence the results achieved and share their views on what this means for treatment now, and in the future.

Are we, and more importantly our patients, getting the most out of combination therapy for bipolar mania? Come and debate the issues with the panel, share your views and see what can be achieved.

Mitochondrial haplotypes and the New Zealand origin of clonal European Potamopyrgus, an invasive aquatic snail

The small aquatic snail Potamopyrgus antipodarum is an important invading species in Europe, Australia and North America. European populations are generally believed to derive from accidental introductions from New Zealand, probably dating back to the mid-19th century. We have employed mitochondrial DNA sequences to test the proposed New Zealand origin of European Potamopyrgus, and to learn more about its genealogical history. Using a 481-bp region of the 16S ribosomal RNA gene, we identified 17 distinct haplotypes among 65 snails from New Zealand. In marked contrast, only two haplotypes were found across all European samples, which cover a large geographical area. Importantly, these two haplotypes are shared with snails from the North Island of New Zealand. Due to sampling limitations we cannot rule out a South Island origin for one of the haplotypes, but our results clearly demonstrate the New Zealand origin of European populations. The marked divergence among the two European haplotypes implies the successful colonization by two distinct mitochondrial lineages, which is consistent with previous data based on nuclear markers.

The impact of antidepressant discontinuation versus antidepressant continuation on 1-year risk for relapse of bipolar depression: a retrospective chart review

BACKGROUND

Current treatment guidelines recommend discontinuation of an antidepressant within 3 to 6 months after remission of depression in patients with bipolar illness. Yet few studies directly compare the impact of antidepressant discontinuation versus antidepressant continuation on the risk for depressive relapse in patients with bipolar disorder who have been successfully treated for a depressive episode.

METHOD

In a retrospective chart review, patients with DSM-IV bipolar disorder who were treated for an index episode of depression by adding antidepressant medication to ongoing mood stabilizer medications were identified. The risk of depressive relapse in 25 subjects who stopped antidepressant medications after improvement was compared with the risk of depressive relapse in 19 subjects who continued antidepressants after improvement.

RESULTS

Termination of antidepressant medication significantly increased the risk of a depressive relapse. Antidepressant continuation was not significantly associated with an increased risk of mania.

CONCLUSION

While this study may have been limited by the retrospective nature of the chart review, nonrandomized assignment of treatment, and reliance on unstructured progress notes, it suggests that antidepressant discontinuation may increase the risk of depressive relapse in some patients with bipolar disorder. Further research is needed to clarify whether maintenance antidepressant treatment may be warranted in some patients with bipolar disorder, especially in those with frequent recurrent depressive episodes.

Localized two-dimensional shift correlated MR spectroscopy of human brain

A two-dimensional (2D) chemical shift correlated MR spectroscopic (COSY) sequence integrated into a new volume localization technique (90 degrees -180 degrees -90 degrees ) is proposed for whole-body MR spectroscopy (MRS). Using the product operator formalism, a theoretical calculation of the volume localization as well as the coherence transfer efficiencies in 2D MRS is presented. Phantom model solutions were used to test and optimize the efficiency of the proposed sequence. A combination of different MRI transmit/receive RF coils was used: a head MRI coil and a 3" surface coil receive combined with a body coil transmit. The J cross-peaks due to N-acetyl aspartate (NAA), glutamate/glutamine (Glx), myo-inositol (mI), creatine (Cr), choline (Ch), aspartate (Asp), gamma-aminobutyrate (GABA), taurine (Tau), glutathione (GSH), threonine (Thr), and macromolecules (MM) were identified. The cross-peak intensities excited by the proposed 2D sequence were asymmetric with respect to the diagonal peaks. Localized COSY (L-COSY) spectra of cerebral prefrontal and occipital gray/white matter regions in 15 healthy controls are presented. Magn Reson Med 46:58-67, 2001.

Expression of human beta-defensin-1 promotes differentiation of keratinocytes

Epithelial cells have been shown to express the antibiotic peptides human beta-defensins-1 and 2. While beta-defensin-2 is known to be up-regulated by bacterial factors and proinflammatory mediators, the expression of beta-defensin-1 does not appear to be affected by these mediators. To determine the regulation and function of beta-defensin-1 we analyzed its expression upon stimulation of inflammatory mediators in vitro and ex vivo. In immortalized human cell lines (HaCaT) and nasal polyps beta-defensin-1 was not induced upon incubation with bacteria or proinflammatory mediators, suggesting that the inertness of beta-defensin-1 expression levels is not the result of the shortcoming of HaCaT cells. As proliferation and regeneration play an important role at sites of inflammation, we examined the expression level of beta-defensin-1 in relation to the differentiation and proliferation of HaCaT cells. beta-defensin-1 mRNA levels remained low during proliferation but were highly induced upon differentiation. In contrast, beta-defensin-2 expression was unaffected under these conditions. To examine the function of beta-defensin-1 in cellular proliferation and differentiation processes beta-defensin-1 was overexpressed in keratinocytes. Protein expression analysis of the differentiation marker keratin 10 revealed that its expression is highly induced in the presence of increased concentrations of beta-defensin-1. Hence our data indicate that high expression of beta-defensin-1 promotes cell differentiation processes of keratinocytes.

Expression of human alpha-defensin 5 (HD5) mRNA in nasal and bronchial epithelial cells

BACKGROUND/AIMS

Human defensins are antibiotic peptides expressed in myeloid and epithelial cells. Human alpha-defensin 5 (HD5) has been detected in Paneth cell granules in the crypts of Lieberkühn and has recently been identified in the female reproductive tract. The aim of this study was to investigate the presence of HD5 mRNA in nasal and bronchial epithelial cells.

METHODS/RESULTS

Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) analysis showed that HD5 mRNA was expressed infrequently and to varying degrees in bronchial and nasal epithelial cells. In situ hybridisation resulted in a positive signal in the epithelial layer of nasal polyps. HD5 mRNA was locally restricted to a specific area of epithelial cells and also occurred in submucosal glands.

CONCLUSIONS

HD5 mRNA expression in nasal and bronchial epithelial cells is rare and seemed to be locally induced. The results indicate that HD5 might play a role in innate defence in nasal and bronchial epithelia.

Differential expression of human alpha- and beta-defensins mRNA in gastrointestinal epithelia

BACKGROUND

While defensins have received great attention for their role in bronchial innate immune defence, little is known about the expression levels of the four human epithelial defensins (HD5, HD6, hBD1 and hBD2) in the digestive tract. In this study we quantified the alpha- and beta-defensins mRNA in biopsies obtained from the gastrointestinal mucosa and identified the cells expressing the beta-defensin hBD1 mRNA in ileal mucosa.

MATERIAL AND METHODS

Biopsies from human stomach (corpus and antrum), duodenum, jejunum, ileum and colon were analysed for their expression of alpha- and beta-defensins. The mRNA of defensins was quantified by semiquantitative reverse transcription-polymerase chain reaction. Cells expressing beta-defensin hBD1 mRNA were identified by in situ hybridization with 35S-labelled RNA probes in tissue sections of human ileum.

RESULTS

The hBD1 mRNA was expressed at low levels with little variability throughout the gastrointestinal tract and was detected in all epithelial cells of ileal mucosa. HD5 and HD6 mRNA expression was restricted to the intestine and displayed high interindividual variability. The highest expression levels were observed in jejunum and ileum. Biopsies obtained from duodenum displayed low levels or no expression of HD5 and HD6. The expression level increased considerably in a biopsy obtained from a patient with acute coeliac sprue. In contrast, low levels were observed in a biopsy from a patient with coeliac sprue in remission.

CONCLUSIONS

The expression levels of hBD1, HD5 and HD6 throughout the gastrointestinal tract are tissue and peptide specific and these defensins are expressed with high interindividual variability.

Gabapentin in the acute treatment of refractory bipolar disorder

BACKGROUND

Gabapentin, a new anti-epileptic agent, has been anecdotally reported to be effective in the treatment of mania. We systematically assessed the response rate in bipolar patients being treated adjunctively with gabapentin for manic symptoms, depressive symptoms, or rapid cycling not responsive to standard treatments.

METHOD

Twenty-eight bipolar patients experiencing manic (n = 18), depressive (n = 5), or rapid-cycling (n = 5) symptoms inadequately responsive to at least one mood stabilizer were treated in an open fashion with adjunctive gabapentin. Illness response was assessed using the Clinical Global Impression Scale modified for bipolar disorder (CGI-BP). A 'positive response' was operationalized as a CGI response of much or very much improved.

RESULTS

Fourteen of the 18 (78%) treated for hypomania or mania had a positive response to a dosage range of 600-3,600 mg/day. Patients with hypomania responded fastest, with a positive response achieved in 12.7 +/- 7.2 days. Patients with classic mania had a mean time to positive response of 25 +/- 12 days, and in patients with mixed mania it was 31.8 +/- 20.9 days. All of the five patients treated for depression had a positive response within 21 +/- 13.9 days. Only one of five patients with rapid cycling had a positive response. Gabapentin was well tolerated by all patients, with the most common side-effect being sedation.

CONCLUSIONS

Gabapentin appears to have acute anti-manic and anti-depressant properties as an adjunctive agent for refractory bipolar illness. Prospective double-blind studies are needed to further delineate its acute efficacy when used as monotherapy and its prophylactic efficacy as monotherapy or in conjuction with other mood stabilizers.

Epithelial defensins impair adenoviral infection: implication for adenovirus-mediated gene therapy

Epithelial cells have been to participate actively in host defense by producing small cationic peptides called defensins. To investigate the biological activity of epithelial defensins in more detail, we expressed two defensins, hBD-1 and HD-5, in eukaryotic cell lines. Defensins were localized in the cytoplasm and in cell culture medium and exhibited strong microbicidal activity toward Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Moreover, our data indicate that the presence of defensins protected the cells from adenoviral infection. The presence of HD-5 or hBD-1 reduced the infectivity of Av1CF2 three- to fivefold. These results imply that defensins must be considered a serious obstacle whenever adenovirus is used to deliver genes to epithelial cells.

Lamotrigine for the treatment of bipolar disorder: a clinical case series

BACKGROUND

Recently, a number of new agents have become available to treat bipolar disorder, however many patients may not respond fully even when used in combination. Early reports in epilepsy studies suggested mood-related effects of lamotrigine treatment, as have preliminary reports in bipolar patients.

METHODS

Seventeen patients meeting DSM-IV criteria for bipolar I (n = 9) or bipolar II (n = 8) disorder displaying affective symptoms and a past history of inadequate response or tolerability to at least two standard mood stabilizing agents were recruited through the Stanley Foundation Bipolar Network and treated with the new anticonvulsant lamotrigine in an add-on, open-label study. Response to therapy was assessed using the Clinical Global Impression Scale modified for bipolar disorder.

RESULTS

The mean dose of lamotrigine was 187+/-157 mg/day (range 50-600 mg/day) for a mean duration of 159+/-109 days (range 14-455 days). Eleven (65%) patients were rated as very much or much improved. Lamotrigine was well tolerated, and may have mood stabilizing and antidepressant properties in some patients with bipolar disorder.

LIMITATIONS

The study is hypothesis generating because it was uncontrolled and open. Controlled studies are warranted.

CONCLUSIONS

This preliminary report supports clinical improvement for both mood cycling and depression in patients with bipolar disorder treated with lamotrigine.

Olanzapine in treatment-resistant bipolar disorder

BACKGROUND

We evaluated the response to olanzapine in 14 consecutive patients with bipolar I disorder who were inadequately responsive to standard psychotropic agents.

METHODS

Fourteen patients with bipolar I disorder by DSM-IV criteria experiencing persistent affective symptoms inadequately responsive to at least one standard mood stabilizer were treated with open-label olanzapine by one of the authors. Response was assessed with the Clinical Global Impression Scale modified for use in bipolar disorder (CGI-BP).

RESULTS

The 14 patients received olanzapine at a mean (SD dosage of 14.1+/-7.2 (range 5-30) mg/day for a mean+/-SD of 101.4+/-56.3 (range 30-217) days of treatment. Of the 14 patients, 8 (57%) displayed much or very much overall improvement in their illness. In general, olanzapine was well tolerated. The most common side effects were sedation, tremor, dry mouth, and appetite stimulation with weight gain.

LIMITATIONS

Data were obtained nonblindly and without a randomized control group, and olanzapine was added to ongoing psychotropic regimens.

CONCLUSION

Olanzapine may have antimanic and mood-stabilizing effects in some patients with bipolar disorder, and is generally well tolerated. Controlled studies of olanzapine in bipolar disorder appear warranted.

Rational polypharmacy in the bipolar affective disorders

Bipolar affective illness represents a syndrome not readily treated by single agents. Approximately 50% of patients are inadequately responsive to lithium and the majority of patients require supplemental antidepressants, antimanic, antipsychotic or hypnotic medications. These traditional adjunctive medications are associated with potential problems. Antidepressants may precipitate mania (at a rate about double that of placebo) or cause cycle acceleration. Neuroleptics may be associated with either more profound or longer depressive phases, and clearly increase the risk of tardive dyskinesia, to which bipolar patients appear particularly predisposed. Moreover, there are subgroups of patients who are known to be poorly responsive to lithium. These include patients with rapid cycling, dysphoric mania, co-morbid drug or alcohol abuse, a pattern of depression-mania-well interval (D-M-I as opposed to the M-D-I pattern), and patients without a family history of bipolar illness in first-degree relatives. There is increasing recognition that the anticonvulsants carbamazepine and valproate are effective alternatives or adjuncts to lithium in the acute and long-term treatment of bipolar illness. Ideally, one would want to assess whether patients who were unresponsive to lithium were responsive to an anticonvulsant alone prior to utilizing lithium in addition to anticonvulsant combination therapy. However, from the clinical perspective, it is often more expedient to use an anticonvulsant adjunctively to lithium to assess the efficacy of this combination and establish mood stabilization. When lithium is not discontinued, the increased morbidity during lithium withdrawal also would not occur and would not confound the evaluation of the new agent. We suggest the initial use of acute adjuncts to lithium with the anticonvulsants carbamazepine or valproate (instead of neuroleptics) so that their efficacy can be assessed in the individual's acute episode, with the likelihood of a positive response in longer-term prophylaxis. Hypnotic benzodiazepines with anticonvulsant properties, such as clonazepam or lorazepam, are often used to help to induce sleep in escalating bipolar patients, and may be useful adjuncts as well. Patients who were inadequately responsive to either carbamazepine or valproate alone may be responsive to the anticonvulsant combination. In a similar fashion, one can also utilize several mood-stabilizing drugs (lithium and an anticonvulsant such as carbamazepine or valproate) in the treatment of depressive breakthroughs, and then augment this combination (if necessary) with a catecholamine-active antidepressant such as bupropion or a serotonin-selective reuptake inhibitor (SSRI) such as fluoxetine, paroxetine, sertraline or if necessary a monoamine oxidase inhibitor (MAOI). Once the patient has responded to a combination of drugs, it becomes problematic to decide whether the last agent added was the crucial ingredient in helping the patient achieve remission or that remission might have occurred with this agent alone. A conservative approach would have merit in patients who are finally stabilized on complex polypharmacy regimens only after many years of sequential trials; in this instance, the potential risk of re-exacerbating the illness with a taper of one of the drugs in the regimen. Rational polypharmacy should thus be implemented with careful delineation of the prior course of illness (typically using life chart methodology) and targeted treatment outcomes titrated against side effects, using sequential clinical trials in individual patients who have not adequately responded to monotherapy. In this fashion, it is hoped that pharmacodynamic differences among agents can be maximized and pharmacokinetic and side effects minimized.

Single arterial puncture vs arterial cannula for arterial gas analysis after exercise. Change in arterial oxygen tension over time

In an attempt to find the least invasive, safest, easiest, and cheapest method of obtaining resting and exercise samples of arterial blood, a comparison was made between samples from an arterial needle puncture and an arterial cannula. This study demonstrated that samples of arterial blood may be obtained by radial arterial puncture both at rest and during exercise in practically all cases without morbidity. Samples from arterial needle puncture provide the same results as those from arterial cannulas. In the very rare patient in whom arterial puncture during maximal exercise is unsuccessful, the arterial oxygen pressure (PaO2) measured at 10 seconds after exercise correlates very well with the PaO2 at maximal exercise, and the 15-second value correlates nearly as well. Arterial cannulas are needed in the infrequent case when arterial puncture is not accomplished during maximal exercise and the 10-second or 15-second PaO2 decreases from the resting value. In this instance, determination of the exact extent of the hypoxemia requires an exercise sample obtained by cannula; however, the decrease in PaO2 obtained by arterial needle puncture at 10 or 15 seconds will be all that is needed many times to make a clinical decision. Values obtained at 20 seconds after maximal exercise reflect less of the exercise measurement and cannot be used; however, all episodes of significant hypoxemia (PaO2 less than 60 mm Hg) were captured by the analysis at 20 seconds after exercise.