Feasibility and Outcomes of a Cardiovascular Medicine Inclusive Extracorporeal Membrane Oxygenation (ECMO) Service.

Background: There has been a significant increase in the utilization of venoarterial extracorporeal membrane oxygenation (VA-ECMO) in recent years. Cardiothoracic surgery teams have historically led VA-ECMO care teams, with little data available on alternative care models. Methods: We performed a retrospective review of a cardiovascular medicine inclusive VA-ECMO service, analyzing patients treated with peripheral VA-ECMO at a large quaternary care center from 2018 to 2022. The primary outcome was death while on VA-ECMO or within 24 hours of decannulation. Univariate and multivariate analyses were used to identify predictors of the primary outcome. Results: Two hundred forty-four patients were included in the analysis (median age 61 years; 28.7% female), of whom 91.8% were cannulated by interventional cardiologists, and 84.4% were managed by a cardiology service comprised of interventional cardiologists, cardiac intensivists or advanced heart failure cardiologists. Indications for VA-ECMO included acute myocardial infarction (34.8%), decompensated heart failure (30.3%), and refractory cardiac arrest (10.2%). VA-ECMO was utilized during cardiopulmonary resuscitation in 26.6% of cases, 48% of which were peri-procedural arrest. Of the patients, 46% survived to decannulation, the majority of whom were decannulated percutaneously in the cardiac catheterization laboratory. There was no difference in survival following cannulation by a cardiac surgeon vs interventional cardiologist (50% vs 45%; P = .90). Complications included arterial injury (3.7%), compartment syndrome (4.1%), cannulation site infection (1.2%), stroke (14.8%), acute kidney injury (52.5%), access site bleeding (16%) and need for blood transfusion (83.2%). Elevated baseline lactate (odds ratio [OR], 1.13 per unit increase) and sequential organ failure assessment score (OR, 1.27 per unit increase) were independently associated with the primary outcome. Conversely, an elevated baseline survival after VA ECMO score (OR, 0.92 per unit increase) and 8-hour serum lactate clearance (OR, 0.98 per % increase) were independently associated with survival. Conclusions: The use of a cardiovascular medicine inclusive ECMO service is feasible and may be practical in select centers as indications for VA-ECMO expand.

Determining the Affinity and Kinetics of Small Molecule Inhibitors of Galectin-1 Using Surface Plasmon Resonance.

The beta-galactoside-binding mammalian lectin galectin-1 can bind, via its carbohydrate recognition domain (CRD), to various cell surface glycoproteins and has been implicated in a range of cancers. As a consequence of binding to sugar residues on cell surface receptors, it has been shown to have a pleiotropic effect across many cell types and mechanisms, resulting in immune system modulation and cancer progression. As a result, it has started to become a therapeutic target for both small and large molecules. In previous studies, we used fluorescence polarization (FP) assays to determine KD values to screen and triage small molecule glycomimetics that bind to the galectin-1 CRD. In this study, surface plasmon resonance (SPR) was used to compare human and mouse galectin-1 affinity measures with FP, as SPR has not been applied for compound screening against this galectin. Binding affinities for a selection of mono- and di-saccharides covering a 1000-fold range correlated well between FP and SPR assay formats for both human and mouse galectin-1. It was shown that slower dissociation drove the increased affinity at human galectin-1, whilst faster association was responsible for the effects in mouse galectin-1. This study demonstrates that SPR is a sound alternative to FP for early drug discovery screening and determining affinity estimates. Consequently, it also allows association and dissociation constants to be measured in a high-throughput manner for small molecule galectin-1 inhibitors.

Rapid Acute Coronary Syndrome Evaluation Over One Hour With High-Sensitivity Cardiac Troponin I: A United States-Based Stepped-Wedge, Randomized Trial.

STUDY OBJECTIVE: The real-world effectiveness and safety of a 0/1-hour accelerated protocol using high-sensitivity cardiac troponin (hs-cTn) to exclude myocardial infarction (MI) compared to routine care in the United States is uncertain. The objective was to compare a 0/1-hour accelerated protocol for evaluation of MI to a 0/3-hour standard care protocol. METHODS: The RACE-IT trial was a stepped-wedge, randomized trial across 9 emergency departments (EDs) that enrolled 32,609 patients evaluated for possible MI from July 2020 through April 2021. Patients undergoing high-sensitivity cardiac troponin I testing with concentrations less than or equal to 99th percentile were included. Patients who had MI excluded by the 0/1-hour protocol could be discharged from the ED. Patients in the standard care protocol had 0- and 3-hour troponin testing and application of a modified HEART score to be eligible for discharge. The primary endpoint was the proportion of patients discharged from the ED without 30-day death or MI. RESULTS: There were 13,505 and 19,104 patients evaluated in the standard care and accelerated protocol groups, respectively, of whom 19,152 (58.7%) were discharged directly from the ED. There was no significant difference in safe discharges between standard care and the accelerated protocol (59.5% vs 57.8%; adjusted odds ratio (aOR)=1.05, 95% confidence interval [CI] 0.95 to 1.16). At 30 days, there were 90 deaths or MIs with 38 (0.4%) in the standard care group and 52 (0.4%) in the accelerated protocol group (aOR=0.84, 95% CI 0.43 to 1.68). CONCLUSION: A 0/1-hour accelerated protocol using high-sensitivity cardiac troponin I did not lead to more safe ED discharges compared with standard care.

An augmented reality and high-speed optical tracking system for laparoscopic surgery.

While minimally invasive laparoscopic surgery can help reduce blood loss, reduce hospital time, and shorten recovery time compared to open surgery, it has the disadvantages of limited field of view and difficulty in locating subsurface targets. Our proposed solution applies an augmented reality (AR) system to overlay pre-operative images, such as those from magnetic resonance imaging (MRI), onto the target organ in the user's real-world environment. Our system can provide critical information regarding the location of subsurface lesions to guide surgical procedures in real time. An infrared motion tracking camera system was employed to obtain real-time position data of the patient and surgical instruments. To perform hologram registration, fiducial markers were used to track and map virtual coordinates to the real world. In this study, phantom models of each organ were constructed to test the reliability and accuracy of the AR-guided laparoscopic system. Root mean square error (RMSE) was used to evaluate the targeting accuracy of the laparoscopic interventional procedure. Our results demonstrated a registration error of 2.42 ± 0.79 mm and a procedural targeting error of 4.17 ± 1.63 mm using our AR-guided laparoscopic system that will be further refined for potential clinical procedures.

Is rapid acute coronary syndrome evaluation with high-sensitivity cardiac troponin less costly? An economic evaluation.

Objective: Protocols to evaluate for myocardial infarction (MI) using high-sensitivity cardiac troponin (hs-cTn) have the potential to drive costs upward due to the added sensitivity. We performed an economic evaluation of an accelerated protocol (AP) to evaluate for MI using hs-cTn to identify changes in costs of treatment and length of stay compared with conventional testing. Methods: We performed a planned secondary economic analysis of a large, cluster randomized trial across nine emergency departments (EDs) from July 2020 to April 2021. Patients were included if they were 18 years or older with clinical suspicion for MI. In the AP, patients could be discharged without further testing at 0 h if they had a hs-cTnI < 4 ng/L and at 1 h if the initial value were 4 ng/L and the 1-h value ≤7 ng/L. Patients in the standard of care (SC) protocol used conventional cTn testing at 0 and 3 h. The primary outcome was the total cost of treatment, and the secondary outcome was ED length of stay. Results: Among 32,450 included patients, an AP had no significant differences in cost (+$89, CI: -$714, $893 hospital cost, +$362, CI: -$414, $1138 health system cost) or ED length of stay (+46, CI: -28, 120 min) compared with the SC protocol. In lower acuity, free-standing EDs, patients under the AP experienced shorter length of stay (-37 min, CI: -62, 12 min) and reduced health system cost (-$112, CI: -$250, $25). Conclusion: Overall, the implementation of AP using hs-cTn does not result in higher costs.

Integrated proteomics reveals autophagy landscape and an autophagy receptor controlling PKA-RI complex homeostasis in neurons.

Autophagy is a conserved, catabolic process essential for maintaining cellular homeostasis. Malfunctional autophagy contributes to neurodevelopmental and neurodegenerative diseases. However, the exact role and targets of autophagy in human neurons remain elusive. Here we report a systematic investigation of neuronal autophagy targets through integrated proteomics. Deep proteomic profiling of multiple autophagy-deficient lines of human induced neurons, mouse brains, and brain LC3-interactome reveals roles of neuronal autophagy in targeting proteins of multiple cellular organelles/pathways, including endoplasmic reticulum (ER), mitochondria, endosome, Golgi apparatus, synaptic vesicle (SV) for degradation. By combining phosphoproteomics and functional analysis in human and mouse neurons, we uncovered a function of neuronal autophagy in controlling cAMP-PKA and c-FOS-mediated neuronal activity through selective degradation of the protein kinase A - cAMP-binding regulatory (R)-subunit I (PKA-RI) complex. Lack of AKAP11 causes accumulation of the PKA-RI complex in the soma and neurites, demonstrating a constant clearance of PKA-RI complex through AKAP11-mediated degradation in neurons. Our study thus reveals the landscape of autophagy degradation in human neurons and identifies a physiological function of autophagy in controlling homeostasis of PKA-RI complex and specific PKA activity in neurons.

Evaluating the affinity and kinetics of small molecule glycomimetics for human and mouse galectin-3 using surface plasmon resonance.

Galectin-3 is a beta-galactoside-binding mammalian lectin that is one of a 15-member galectin family that can bind several cell surface glycoproteins via its carbohydrate recognition domain (CRD). As a result, it can influence a range of cellular processes including cell activation, adhesion and apoptosis. Galectin-3 has been implicated in various diseases, including fibrotic disorders and cancer, and is now being therapeutically targeted by both small and large molecules. Historically, the screening and triaging of small molecule glycomimetics that bind to the galectin-3 CRD has been completed in fluorescence polarisation (FP) assays to determine KD values. Surface plasmon resonance (SPR) has not been widely used for compound screening and in this study it was used to compare human and mouse galectin-3 affinity measures between FP and SPR, as well as investigate compound kinetics. The KD estimates for a set of compounds selected from mono- and di-saccharides with affinities across a 550-fold range, correlated well between FP and SPR assay formats for both human and mouse galectin-3. Increases in affinity for compounds binding to human galectin-3 were driven by changes in both kon and koff whilst for mouse galectin-3 this was primarily due to kon. The reduction in affinity observed between human to mouse galectin-3 was also comparable between assay formats. SPR has been shown to be a viable alternative to FP for early drug discovery screening and determining KD values. In addition, it can also provide early kinetic characterisation of small molecule galectin-3 glycomimetics with robust kon and koff values generated in a high throughput manner.

Sjögren-related cardiomyopathy presenting with cardiogenic shock.

Previous reports have described non-ischaemic cardiomyopathy related to a variety of autoimmune diseases. However, very few case reports describe Sjögren disease as a contributing factor to cardiomyopathy. We report the case of a 69-year-old woman with a history of Sjögren disease who presented with cardiogenic shock. Laboratory testing and cardiac MRI revealing apical septal late gadolinium enhancement were consistent with an autoimmune aetiology. After ruling out ischaemic, infectious and other possible causes, the patient's clinical presentation was thought to be related to underlying Sjögren disease. She was treated with intravenous steroids and evidence-based heart failure therapy, but she eventually died after having declined heart transplantation. Given the rarity of Sjögren disease, no diagnostic criteria or standard treatment has been established for cardiomyopathy related to this disease. Diagnosis should be considered in patients who show evidence of autoimmune processes after other possible causes are ruled out.

A Novel Three-Dimensional-Printed Ultrasound-Guided Hip Arthrocentesis Model.

When evaluating patients with hip pain, clinicians may be trained to both evaluate for a hip effusion and perform ultrasound-guided arthrocentesis to evaluate the etiology of the effusion. We present a novel 3-dimensional-printed hip arthrocentesis model, which can be used to train clinicians to perform both tasks under ultrasound guidance. Our model uses a combination of a 3-dimensional-printed hip joint, as well as readily available materials such as an infant Ambu (Ballerup, Denmark) bag, syringe, intravenous line kit, and silicone. We present our experience so that others may use and adapt our model for their training purposes.

ST-Segment Elevation Myocardial Infarction and Out-of-Hospital Cardiac Arrest: Contemporary Management From the Multicenter START Registry.

BACKGROUND: Recent studies suggest that primary percutaneous coronary intervention (PCI) and targeted temperature management (TTM) improve outcome in ST-segment elevation myocardial infarction (STEMI) complicated by out-of-hospital cardiac arrest (OHCA). The objective of this study was to evaluate a contemporary series of patients with STEMI and OHCA to characterize treatment approaches and predictors of neurologic outcome. METHODS: From January 2009 through November 2012, a total of 239 patients who underwent emergent coronary angiography at 10 medical centers across the United States were enrolled. All patients suffered OHCA with STEMI on either the prehospital or post-resuscitation electrocardiogram. Neurologic outcome was assessed using the cerebral performance category (CPC) score. Predictors of neurologic outcome were determined using multivariate logistic regression analysis. The primary endpoint was in-hospital survival with good neurologic function (CPC score 1 or 2). RESULTS: Mean age was 60 ± 13 years, 72% were male, and the majority of patients had a history of cardiovascular event. Initial rhythm was ventricular fibrillation in 72%. At hospital presentation, 76% of patients were intubated, 37% were in cardiogenic shock, and 33% were receiving vasopressors. Primary PCI was performed in 74%, with an average door-to-balloon time of 95 ± 77 minutes, and TTM was used in 51%. Forty-four percent of patients had full neurologic recovery (CPC score 1) and 55% had good neurologic function. Overall in-hospital survival rate was 66%. Independent predictors of in-hospital survival with good neurologic function were: receiving bystander cardiopulmonary resuscitation, location of arrest, receiving drug-eluting stents, and not experiencing a recurrent cardiac arrest. CONCLUSIONS: Short-term survival for patients with STEMI and OHCA undergoing emergent coronary angiography and revascularization with TTM in this contemporary, multicenter registry was high and neurologic outcome was good in more than half of patients.

Molecular recognition of ubiquitin and Lys63-linked diubiquitin by STAM2 UIM-SH3 dual domain: the effect of its linker length and flexibility.

Multidomain proteins represent a broad spectrum of the protein landscape and are involved in various interactions. They could be considered as modular building blocks assembled in distinct fashion and connected by linkers of varying lengths and sequences. Due to their intrinsic flexibility, these linkers provide proteins a subtle way to modulate interactions and explore a wide range of conformational space. In the present study, we are seeking to understand the effect of the flexibility and dynamics of the linker involved in the STAM2 UIM-SH3 dual domain protein with respect to molecular recognition. We have engineered several constructs of UIM-SH3 with different length linkers or domain deletion. By means of SAXS and NMR experiments, we have shown that the modification of the linker modifies the flexibility and the dynamics of UIM-SH3. Indeed, the global tumbling of both the UIM and SH3 domain is different but not independent from each other while the length of the linker has an impact on the ps-ns time scale dynamics of the respective domains. Finally, the modification of the flexibility and dynamics of the linker has a drastic effect on the interaction of UIM-SH3 with Lys63-linked diubiquitin with a roughly eight-time weaker dissociation constant.

Optimal TR-band weaning strategy while minimizing vascular access site complications.

INTRODUCTION: The purpose of the study is to develop an optimal TR-Band weaning strategy while minimizing vascular access site complications of hematoma or radial artery occlusion (RAO). METHODS: The trial was a randomized, prospective, single center study of 129 patients who underwent cardiac catheterization via the radial artery. Group A was an accelerated protocol in which weaning was initiated 20 min after sheath removal. Group B was an adjusted protocol, in which weaning was dependent on the amount of anti-platelet or anti-coagulation used. All patients underwent radial artery ultrasound to demonstrate arterial patency. RESULTS: Baseline characteristics were similar in both groups, and PCI was performed in 36.7% of patients in Group A and 37.7% of patients in Group B. RAO occurred in 7.7% of patients overall, with no statistical difference between groups (Group A 5% versus Group B 10.1%, p-value = 0.337). Hematoma formation >5 cm in diameter occurred in 4.6% of patients in the overall cohort, without statistical difference between groups (Group A 5% versus Group B 4.3%, p-value = 1). The TR-Band duration was significantly shorter in Group A compared to Group B (112.9 ±â€¯50.7 versus 130.7 ±â€¯51.1 in minutes, respectively, p-value = 0.013). CONCLUSION: We have demonstrated an accelerated weaning protocol is simple to utilize for nursing staff without increased vascular site complications of RAO or hematoma formation.

Further validation of the hybrid algorithm for CTO PCI; difficult lesions, same success.

OBJECTIVES: To evaluate the success rates and outcome of the hybrid algorithm for chronic total occlusion (CTO) percutaneous coronary intervention (PCI) by a single operator in two different clinical settings. METHODS: We compared 279 consecutive CTO PCIs performed by a single, high-volume operator using the hybrid algorithm in two different clinical settings. Data were collected through the PROGRESS CTO Registry. We compared 145 interventions performed in a community program (cohort A) with 134 interventions performed in a referral center (cohort B). RESULTS: Patient in cohort B had more complex lesions with higher J-CTO (3.0 vs. 3.41; p<0.001) and Progress CTO (1.5 vs.1.8, P=0.003) scores, more moderate to severe tortuosity (38% vs. 64%; p<0.001), longer total occlusion length (25 vs. 40mm; p<0.001) and higher prevalence of prior failed CTO PCI attempts (15% vs. 35%; p=0.001). Both technical (95% vs. 91%; p=0.266) and procedural (94% vs. 88%; p=0.088) success rates were similar between the two cohorts despite significantly different lesion complexity. Overall major adverse cardiovascular events were higher in cohort B (1.4% vs. 7.8%; p=0.012) without any significant difference in mortality (0.7% vs. 2.3%, p=0.351). CONCLUSIONS: In spite of higher lesion complexity in the setting of a quaternary-care referral center, use of the hybrid algorithm for CTO PCI enabled similarly high technical and procedural success rates as compared with those previously achieved by the same operator in a community-based program at the expense of a higher rate of MACE.

Time-resolved neutron scattering provides new insight into protein substrate processing by a AAA+ unfoldase.

We present a combination of small-angle neutron scattering, deuterium labelling and contrast variation, temperature activation and fluorescence spectroscopy as a novel approach to obtain time-resolved, structural data individually from macromolecular complexes and their substrates during active biochemical reactions. The approach allowed us to monitor the mechanical unfolding of a green fluorescent protein model substrate by the archaeal AAA+ PAN unfoldase on the sub-minute time scale. Concomitant with the unfolding of its substrate, the PAN complex underwent an energy-dependent transition from a relaxed to a contracted conformation, followed by a slower expansion to its initial state at the end of the reaction. The results support a model in which AAA ATPases unfold their substrates in a reversible power stroke mechanism involving several subunits and demonstrate the general utility of this time-resolved approach for studying the structural molecular kinetics of multiple protein remodelling complexes and their substrates on the sub-minute time scale.

SAXS/SANS on Supercharged Proteins Reveals Residue-Specific Modifications of the Hydration Shell.

Water molecules in the immediate vicinity of biomacromolecules, including proteins, constitute a hydration layer characterized by physicochemical properties different from those of bulk water and play a vital role in the activity and stability of these structures, as well as in intermolecular interactions. Previous studies using solution scattering, crystallography, and molecular dynamics simulations have provided valuable information about the properties of these hydration shells, including modifications in density and ionic concentration. Small-angle scattering of x-rays (SAXS) and neutrons (SANS) are particularly useful and complementary techniques to study biomacromolecular hydration shells due to their sensitivity to electronic and nuclear scattering-length density fluctuations, respectively. Although several sophisticated SAXS/SANS programs have been developed recently, the impact of physicochemical surface properties on the hydration layer remains controversial, and systematic experimental data from individual biomacromolecular systems are scarce. Here, we address the impact of physicochemical surface properties on the hydration shell by a systematic SAXS/SANS study using three mutants of a single protein, green fluorescent protein (GFP), with highly variable net charge (+36, -6, and -29). The combined analysis of our data shows that the hydration shell is locally denser in the vicinity of acidic surface residues, whereas basic and hydrophilic/hydrophobic residues only mildly modify its density. Moreover, the data demonstrate that the density modifications result from the combined effect of residue-specific recruitment of ions from the bulk in combination with water structural rearrangements in their vicinity. Finally, we find that the specific surface-charge distributions of the different GFP mutants modulate the conformational space of flexible parts of the protein.

Uniqueness of models from small-angle scattering data: the impact of a hydration shell and complementary NMR restraints.

Small-angle scattering (SAS) has witnessed a breathtaking renaissance and expansion over the past 15 years regarding the determination of biomacromolecular structures in solution. While important issues such as sample quality, good experimental practice and guidelines for data analysis, interpretation, presentation, publication and deposition are increasingly being recognized, crucial topics such as the uniqueness, precision and accuracy of the structural models obtained by SAS are still only poorly understood and addressed. The present article provides an overview of recent developments in these fields with a focus on the influence of complementary NMR restraints and of a hydration shell on the uniqueness of biomacromolecular models. As a first topic, the impact of incorporating NMR orientational restraints in addition to SAS distance restraints is discussed using a quantitative visual representation that illustrates how the possible conformational space of a two-body system is reduced as a function of the available data. As a second topic, the impact of a hydration shell on modelling parameters of a two-body system is illustrated, in particular on its inter-body distance. Finally, practical recommendations are provided to take both effects into account and promising future perspectives of SAS approaches are discussed.

Distinct binding properties of TIAR RRMs and linker region.

The RNA-binding protein TIAR is an mRNA-binding protein that acts as a translational repressor, particularly important under conditions of cellular stress. It binds to target mRNA and DNA via its RNA recognition motif (RRM) domains and is involved in both splicing regulation and translational repression via the formation of "stress granules." TIAR has also been shown to bind ssDNA and play a role in the regulation of transcription. Here we show, using surface plasmon resonance and nuclear magnetic resonance spectroscopy, specific roles of individual TIAR domains for high-affinity binding to RNA and DNA targets. We confirm that RRM2 of TIAR is the major RNA- and DNA-binding domain. However, the strong nanomolar affinity binding to U-rich RNA and T-rich DNA depends on the presence of the six amino acid residues found in the linker region C-terminal to RRM2. On its own, RRM1 shows preferred binding to DNA over RNA. We further characterize the interaction between RRM2 with the C-terminal extension and an AU-rich target RNA sequence using NMR spectroscopy to identify the amino acid residues involved in binding. We demonstrate that TIAR RRM2, together with its C-terminal extension, is the major contributor for the high-affinity (nM) interactions of TIAR with target RNA sequences.

Current status of preventive cardiology training among United States cardiology fellowships and comparison to training guidelines.

We evaluated preventive cardiology education in United States cardiology fellowship programs and their adherence to Core Cardiovascular Training Symposium training guidelines, which recommend 1 month of training, faculty with expertise, and clinical experience in cardiac rehabilitation, lipid disorder management, and diabetes management as a part of the prevention curricula. We sent an anonymous survey to United States cardiology program directors and their chief fellow. The survey assessed the program curricula, rotation structure, faculty expertise, obstacles, and recommended improvements. The results revealed that 24% of surveyed programs met the Core Cardiovascular Training Symposium guidelines with a dedicated 1-month rotation in preventive cardiology, 24% had no formalized training in preventive cardiology, and 30% had no faculty with expertise in preventive cardiology, which correlated with fewer rotations in prevention than those with specialized faculty (p = 0.009). Fellows rotated though the following experiences (% of programs): cardiac rehabilitation, 71%; lipid management, 37%; hypertension, 15%; diabetes, 7%; weight management/obesity, 6%; cardiac nutrition, 6%; and smoking cessation, 5%. The program directors cited "lack of time" as the greatest obstacle to providing preventive cardiology training and the chief fellows reported "lack of a developed curriculum" (p = 0.01). The most recommended improvement was for the American College of Cardiology to develop a web-based curriculum/module. In conclusion, most surveyed United States cardiology training programs currently do not adhere to basic preventive cardiovascular medicine Core Cardiovascular Training Symposium recommendations. Additional attention to developing curricular content and structure, including the creation of an American College of Cardiology on-line knowledge module might improve fellowship training in preventive cardiology.

Different modes of interaction by TIAR and HuR with target RNA and DNA.

TIAR and HuR are mRNA-binding proteins that play important roles in the regulation of translation. They both possess three RNA recognition motifs (RRMs) and bind to AU-rich elements (AREs), with seemingly overlapping specificity. Here we show using SPR that TIAR and HuR bind to both U-rich and AU-rich RNA in the nanomolar range, with higher overall affinity for U-rich RNA. However, the higher affinity for U-rich sequences is mainly due to faster association with U-rich RNA, which we propose is a reflection of the higher probability of association. Differences between TIAR and HuR are observed in their modes of binding to RNA. TIAR is able to bind deoxy-oligonucleotides with nanomolar affinity, whereas HuR affinity is reduced to a micromolar level. Studies with U-rich DNA reveal that TIAR binding depends less on the 2'-hydroxyl group of RNA than HuR binding. Finally we show that SAXS data, recorded for the first two domains of TIAR in complex with RNA, are more consistent with a flexible, elongated shape and not the compact shape that the first two domains of Hu proteins adopt upon binding to RNA. We thus propose that these triple-RRM proteins, which compete for the same binding sites in cells, interact with their targets in fundamentally different ways.

Transgenic expression of matrix metalloproteinase-9 modulates collagen deposition in a mouse model of atherosclerosis.

Matrix metalloproteinase-9 (MMP-9) has been proposed to be an important modulator of atherosclerotic plaque vulnerability. We generated a transgenic (tg) model expressing human proMMP-9 in macrophages, using the scavenger receptor enhancer/promoter A. This model was crossed into the double Apoe/Timp-1 knockout background. After 16 weeks of a high-fat diet, there were no significant changes in plaque size in the proximal aortas between the four groups of the study population (Apoe(-/-), Apoe(-/-)/MMP-9tg, Apoe(-/-)/Timp-1(-/-), and Apoe(-/-)/MMP-9tg/Timp-1(-/-)), and, in the Timp-1 knockout background, MMP-9 transgenic mice and control littermates had similar micro-aneurysm formation. However, lesions in Apoe(-/-)/MMP-9tg/Timp-1(-/-) mice contained significantly more collagen compared to the three other groups (P<0.005). Culture supernatants from elicited Apoe(-/-)/MMP-9tg/Timp-1(-/-) macrophages contained higher levels of active TGF-beta than the three other groups (P<0.05), suggesting that augmented collagen deposition resulted from an increase in TGF-beta activation due to transgenic MMP-9 in the Timp-1(-/-) background. This study indicates that, in human atherosclerosis, increased MMP-9 activity could up-regulate collagen deposition, possibly through TGF-beta activation.