Phosphorylation of USP20 on Ser334 by IRAK1 promotes IL-1ß-evoked signaling in vascular smooth muscle cells and vascular inflammation.

Reversible lysine-63 (K63) polyubiquitination regulates proinflammatory signaling in vascular smooth muscle cells (SMCs) and plays an integral role in atherosclerosis. Ubiquitin-specific peptidase 20 (USP20) reduces NFκB activation triggered by proinflammatory stimuli, and USP20 activity attenuates atherosclerosis in mice. The association of USP20 with its substrates triggers deubiquitinase activity; this association is regulated by phosphorylation of USP20 on Ser334 (mouse) or Ser333 (human). USP20 Ser333 phosphorylation was greater in SMCs of atherosclerotic segments of human arteries as compared with nonatherosclerotic segments. To determine whether USP20 Ser334 phosphorylation regulates proinflammatory signaling, we created USP20-S334A mice using CRISPR/Cas9-mediated gene editing. USP20-S334A mice developed ∼50% less neointimal hyperplasia than congenic WT mice after carotid endothelial denudation. WT carotid SMCs showed substantial phosphorylation of USP20 Ser334, and WT carotids demonstrated greater NFκB activation, VCAM-1 expression, and SMC proliferation than USP20-S334A carotids. Concordantly, USP20-S334A primary SMCs in vitro proliferated and migrated less than WT SMCs in response to IL-1ß. An active site ubiquitin probe bound to USP20-S334A and USP20-WT equivalently, but USP20-S334A associated more avidly with TRAF6 than USP20-WT. IL-1ß induced less K63-linked polyubiquitination of TRAF6 and less downstream NFκB activity in USP20-S334A than in WT SMCs. Using in vitro phosphorylation with purified IRAK1 and siRNA-mediated gene silencing of IRAK1 in SMCs, we identified IRAK1 as a novel kinase for IL-1ß-induced USP20 Ser334 phosphorylation. Our findings reveal novel mechanisms regulating IL-1ß-induced proinflammatory signaling: by phosphorylating USP20 Ser334, IRAK1 diminishes the association of USP20 with TRAF6 and thus augments NFκB activation, SMC inflammation, and neointimal hyperplasia.

International Consensus Statement on Obstructive Sleep Apnea.

BACKGROUND: Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA). METHODS: Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus. RESULTS: The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated. CONCLUSION: This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Drebrin attenuates atherosclerosis by limiting smooth muscle cell transdifferentiation.

AIMS: The F-actin-binding protein Drebrin inhibits smooth muscle cell (SMC) migration, proliferation, and pro-inflammatory signalling. Therefore, we tested the hypothesis that Drebrin constrains atherosclerosis. METHODS AND RESULTS: SM22-Cre+/Dbnflox/flox/Ldlr-/- (SMC-Dbn-/-/Ldlr-/-) and control mice (SM22-Cre+/Ldlr-/-, Dbnflox/flox/Ldlr-/-, and Ldlr-/-) were fed a western diet for 14-20 weeks. Brachiocephalic arteries of SMC-Dbn -/-/Ldlr-/- mice exhibited 1.5- or 1.8-fold greater cross-sectional lesion area than control mice at 14 or 20 weeks, respectively. Aortic atherosclerotic lesion surface area was 1.2-fold greater in SMC-Dbn-/-/Ldlr-/- mice. SMC-Dbn-/-/Ldlr-/- lesions comprised necrotic cores that were two-fold greater in size than those of control mice. Consistent with their bigger necrotic core size, lesions in SMC-Dbn-/- arteries also showed more transdifferentiation of SMCs to macrophage-like cells: 1.5- to 2.5-fold greater, assessed with BODIPY or with CD68, respectively. In vitro data were concordant: Dbn-/- SMCs had 1.7-fold higher levels of KLF4 and transdifferentiated to macrophage-like cells more readily than Dbnflox/flox SMCs upon cholesterol loading, as evidenced by greater up-regulation of CD68 and galectin-3. Adenovirally mediated Drebrin rescue produced equivalent levels of macrophage-like transdifferentiation in Dbn-/- and Dbnflox/flox SMCs. During early atherogenesis, SMC-Dbn-/-/Ldlr-/- aortas demonstrated 1.6-fold higher levels of reactive oxygen species than control mouse aortas. The 1.8-fold higher levels of Nox1 in Dbn-/- SMCs were reduced to WT levels with KLF4 silencing. Inhibition of Nox1 chemically or with siRNA produced equivalent levels of macrophage-like transdifferentiation in Dbn-/- and Dbnflox/flox SMCs. CONCLUSION: We conclude that SMC Drebrin limits atherosclerosis by constraining SMC Nox1 activity and SMC transdifferentiation to macrophage-like cells.

Treatment of Obstructive Sleep Apnea: Choosing the Best Positive Airway Pressure Device.

Positive airway pressure (PAP) remains primary therapy for most patients with obstructive sleep apnea (OSA). CPAP, APAP, and BPAP are all reasonable therapies that can be used for patients with uncomplicated OSA across the spectrum of disease severity. BPAP should be considered for patients who are nonadherent to CPAP or APAP therapy because of pressure intolerance. Several additional factors should be considered when choosing the type of PAP device for a given patient, including associated symptoms and comorbid medical problems, cost, access to online data management and patient portals, and the portability for the device for patients who travel frequently.

Study design considerations for sleep-disordered breathing devices.

None: In recent years, sleep-disordered breathing (SDB) has been recognized as a prevalent but under-diagnosed condition in adults and has prompted the need for new and better diagnostic and therapeutic options. To facilitate the development and availability of innovative, safe and effective SDB medical device technologies for patients in the United States, the US Food and Drug Administration collaborated with six SDB-related professional societies and a consumer advocacy organization to convene a public workshop focused on clinical investigations of SDB devices. Sleep medicine experts discussed appropriate definitions of terms used in the diagnosis and treatment of SDB, the use of home sleep testing versus polysomnography, clinical trial design issues in studying SDB devices, and current and future trends in digital health technologies for diagnosis and monitoring SDB. The panel's breadth of clinical expertise and experience across medical specialties provided useful and important insights regarding clinical trial designs for SDB devices.

Reducing COPD Readmissions: Strategies for the Pulmonologist to Improve Outcomes.

Hospitalizations for patients with acute exacerbations of COPD are associated with several adverse patient outcomes as well as with significant health-care costs. Despite many interventions targeted at reducing readmissions following an initial hospitalization, there are few strategies that have been consistently associated with reductions in this outcome. Despite the lack of consensus as to the best strategies to deploy to reduce readmissions related to acute exacerbations of COPD, efforts must continue to focus on determining the best approaches for this population. These tactics will need to be cost-effective for payers while not being cost-prohibitive for providers. In addition, these interventions will need to be relatively easy to institute while not being overbearing for patients or providers. Larger systems with their greater financial resources will likely find success with technology and data-driven comprehensive programs; independent hospitals and practices are more likely to succeed with less resource-intensive interventions such as early postdischarge follow-up, coaching, action plans, self-management education, and pulmonary rehabilitation. Choosing the right interventions that will utilize financial and human resources in a cost-effective manner, while tailoring the approaches to meet the needs of a specific patient group, will be of key importance.

A Sleep Medicine Curriculum for Pulmonary and Pulmonary/Critical Care Fellowship Programs: A Multisociety Expert Panel Report.

BACKGROUND: Pulmonary medicine specialists find themselves responsible for the diagnosis and management of patients with sleep disorders. Despite the increasing prevalence of many of these conditions, many sleep medicine fellowship training slots go unfilled, leading to a growing gap between the volume of patients seeking care for sleep abnormalities and the number of physicians formally trained to manage them. To address this need, we convened a multisociety panel to develop a list of curricular recommendations related to sleep medicine for pulmonary fellowship training programs. METHODS: Surveys of pulmonary and pulmonary/critical care fellowship program directors and recent graduates of these programs were performed to assess the current state of sleep medicine education in pulmonary training, as well as the current scope of practice of pulmonary specialists. These data were used to inform a modified Delphi process focused on developing curricular recommendations relevant to sleep medicine. RESULTS: Surveys confirmed that pulmonary medicine specialists are often responsible for the diagnosis and treatment of a number of sleep conditions, including several that are not traditionally considered related to respiratory medicine. Through five rounds of voting, the panel crafted a list of 52 curricular competencies relevant to sleep medicine for recommended inclusion in pulmonary training programs. CONCLUSIONS: Practicing pulmonary specialists require a broad knowledge of sleep medicine to provide appropriate care to patients they will be expected to manage. Training program directors may use the list of competencies as a framework to ensure adequate mastery of important content by graduating fellows.

Doing It Better for Less: Incorporating OSA Management Into Alternative Payment Models.

As the cost of health care continues to escalate, payers are adapting by moving away from models based on traditional fee-for-service reimbursement to models focused on rewarding care delivery that reduces costs and improves quality. These alternative payment models (APMs) are being introduced by government and commercial payers and will likely become the norm over time. Recent changes in sleep medicine related to advances in technology and approaches by payers for the management of OSA make this an appropriate time to incorporate the delivery of sleep medicine services into APMs. For OSA, the approaches that should lead to success include the appropriate use of home sleep apnea testing and automatic positive airway pressure; lower cost providers to manage less complex patients; evolving technologies including cloud-based positive airway pressure adherence monitoring, telemedicine, and Internet-based coaching to improve adherence with treatments; data analytics to better identify high-risk populations and to more appropriately allocate resources; and appropriate referrals of more complex cases to sleep specialists for management. All of these approaches should improve the value of care for payers, providers, and patients while allowing sleep specialists to more appropriately allocate their efforts to overseeing APM program development and administration and allowing them to focus on the management of more complicated patients.

USP20 (Ubiquitin-Specific Protease 20) Inhibits TNF (Tumor Necrosis Factor)-Triggered Smooth Muscle Cell Inflammation and Attenuates Atherosclerosis.

Objective- Signaling that activates NFκB (nuclear factor κB) in smooth muscle cells (SMCs) is integral to atherosclerosis and involves reversible ubiquitination that activates proteins downstream of proatherogenic receptors. Deubiquitination of these proteins is mediated by USP20 (ubiquitin-specific protease 20), among other deubiquitinases. We sought to determine whether USP20 activity in SMCs decreases atherosclerosis. Approach and Results- To address this question, we used male Ldlr-/- mice without (control) or with SMC-specific expression of murine USP20 (SMC-USP20-transgenic) or its dominant-negative (DN; C154S/H643Q) mutant (SMC-DN-USP20-transgenic). Before the appearance of intimal macrophages, NFκB activation in aortic medial SMCs was greater in SMC-DN-USP20-transgenic than in control mice. After 16 weeks on a Western diet, SMC-DN-USP20-transgenic mice had 46% greater brachiocephalic artery atheroma area than control mice. Congruently, aortic atherosclerosis assessed en face was 21% greater than control in SMC-DN-USP20-transgenic mice and 13% less than control in SMC-USP20-transgenic mice. In response to TNF (tumor necrosis factor), SMCs from SMC-DN-USP20-transgenic mice showed ≈3-fold greater NFκB activation than control SMCs. Silencing USP20 in SMCs with siRNA (small interfering RNA) augmented NFκB activation by ≈50% in response to either TNF or IL-1ß (interleukin-1ß). Coimmunoprecipitation experiments revealed that USP20 associates with several components of the TNFR1 (TNF receptor-1) signaling pathway, including RIPK1 (receptor-interacting protein kinase 1), a critical checkpoint in TNF-induced NFκB activation and inflammation. TNF evoked ≈2-fold more RIPK1 ubiquitination in SMC-DN-USP20-transgenic than in control SMCs, and RIPK1 was deubiquitinated by purified USP20 in vitro. Conclusions- USP20 attenuates TNF- and IL-1ß-evoked atherogenic signaling in SMCs, by deubiquitinating RIPK1, among other signaling intermediates.

Drebrin regulates angiotensin II-induced aortic remodelling.

Aims: The actin-binding protein Drebrin is up-regulated in response to arterial injury and reduces smooth muscle cell (SMC) migration and proliferation through its interaction with the actin cytoskeleton. We, therefore, tested the hypothesis that SMC Drebrin inhibits angiotensin II-induced remodelling of the proximal aorta. Methods and results: Angiotensin II was administered via osmotic minipumps at 1000 ng/kg/min continuously for 28 days in SM22-Cre+/Dbnflox/flox (SMC-Dbn-/-) and control mice. Blood pressure responses to angiotensin II were assessed by telemetry. After angiotensin II infusion, we assessed remodelling in the proximal ascending aorta by echocardiography and planimetry of histological cross sections. Although the degree of hypertension was equivalent in SMC-Dbn-/- and control mice, SMC-Dbn-/- mice nonetheless exhibited 60% more proximal aortic medial thickening and two-fold more outward aortic remodelling than control mice in response to angiotensin II. Proximal aortas demonstrated greater cellular proliferation and matrix deposition in SMC-Dbn-/- mice than in control mice, as evidenced by a higher prevalence of proliferating cell nuclear antigen-positive nuclei and higher levels of collagen I. Compared with control mouse aortas, SMC-Dbn-/- aortas demonstrated greater angiotensin II-induced NADPH oxidase activation and inflammation, evidenced by higher levels of Ser-536-phosphorylated NFκB p65 subunits and higher levels of vascular cell adhesion molecule-1, matrix metalloproteinase-9, and adventitial macrophages. Conclusions: We conclude that SMC Drebrin deficiency augments angiotensin II-induced inflammation and adverse aortic remodelling.

Regulation of inflammation by ß-arrestins: Not just receptor tales.

The ubiquitously expressed, multifunctional scaffolding proteins ß-arrestin1 and ß-arrestin2 each affect inflammatory signaling in a variety of cell lines. In addition to binding the carboxyl-terminal tails of innumerable 7-transmembrane receptors, ß-arrestins scaffold untold numbers of other plasma membrane and cytoplasmic proteins. Consequently, the effects of ß-arrestins on inflammatory signaling are diverse, and context-specific. This review highlights the roles of ß-arrestins in regulating canonical activation of the pro-inflammatory transcription factor NFκB.

Treatment of Obstructive Sleep Apnea: Choosing the Best Positive Airway Pressure Device.

Positive airway pressure (PAP) remains primary therapy for most patients with obstructive sleep apnea (OSA). CPAP, APAP, and BPAP are all reasonable therapies that can be used for patients with uncomplicated OSA across the spectrum of disease severity. BPAP should be considered for patients who are nonadherent to CPAP or APAP therapy because of pressure intolerance. Several additional factors should be considered when choosing the type of PAP device for a given patient, including associated symptoms and comorbid medical problems, cost, access to online data management and patient portals, and the portability for the device for patients who travel frequently.

Interleukin-9 mediates chronic kidney disease-dependent vein graft disease: a role for mast cells.

AIMS: Chronic kidney disease (CKD) is a powerful independent risk factor for cardiovascular events, including vein graft failure. Because CKD impairs the clearance of small proteins, we tested the hypothesis that CKD exacerbates vein graft disease by elevating serum levels of critical cytokines that promote vein graft neointimal hyperplasia. METHODS AND RESULTS: We modelled CKD in C57BL/6 mice with 5/6ths nephrectomy, which reduced glomerular filtration rate by 60%, and we modelled vein grafting with inferior-vena-cava-to-carotid interposition grafting. CKD increased vein graft neointimal hyperplasia four-fold, decreased vein graft re-endothelialization two-fold, and increased serum levels of interleukin-9 (IL-9) five-fold. By quantitative immunofluorescence and histochemical staining, vein grafts from CKD mice demonstrated a ∼two-fold higher prevalence of mast cells, and a six-fold higher prevalence of activated mast cells. Concordantly, vein grafts from CKD mice showed higher levels of TNF and NFκB activation, as judged by phosphorylation of NFκB p65 on Ser536 and by expression of VCAM-1. Arteriovenous fistula veins from humans with CKD also showed up-regulation of mast cells and IL-9. Treating CKD mice with IL-9-neutralizing IgG reduced vein graft neointimal area four-fold, increased vein graft re-endothelialization ∼two-fold, and reduced vein graft total and activated mast cell levels two- and four-fold, respectively. Treating CKD mice with the mast cell stabilizer cromolyn reduced neointimal hyperplasia and increased re-endothelialization in vein grafts. In vitro, IL-9 promoted endothelial cell apoptosis but had no effect on smooth muscle cell proliferation. CONCLUSION: CKD aggravates vein graft disease through mechanisms involving IL-9 and mast cell activation.

C-X-C Motif Chemokine Receptor 3 Splice Variants Differentially Activate Beta-Arrestins to Regulate Downstream Signaling Pathways.

Biased agonism, the ability of different ligands for the same receptor to selectively activate some signaling pathways while blocking others, is now an established paradigm for G protein-coupled receptor signaling. One group of receptors in which endogenous bias is critical is the chemokine system, consisting of over 50 ligands and 20 receptors that bind one another with significant promiscuity. We have previously demonstrated that ligands for the same receptor can cause biased signaling responses. The goal of this study was to identify mechanisms that could underlie biased signaling between different receptor splice variants. The C-X-C motif chemokine receptor 3 (CXCR3) has two splice variants, CXCR3A and CXCR3B, which differ by 51 amino acids at its N-terminus. Consistent with an earlier study, we found that C-X-C motif chemokine ligands 4, 9, 10, and 11 all activated G αi at CXCR3A, while at CXCR3B these ligands demonstrated no measurable G αi or G αs activity. ß-arrestin (ßarr) was recruited at a reduced level to CXCR3B relative to CXCR3A, which was also associated with differences in ßarr2 conformation. ßarr2 recruitment to CXCR3A was attenuated by both G protein receptor kinase (GRK) 2/3 and GRK5/6 knockdown, while only GRK2/3 knockdown blunted recruitment to CXCR3B. Extracellular regulated kinase 1/2 phosphorylation downstream from CXCR3A and CXCR3B was increased and decreased, respectively, by ßarr1/2 knockout. The splice variants also differentially activated transcriptional reporters. These findings demonstrate that differential splicing of CXCR3 results in biased responses associated with distinct patterns of ßarr conformation and recruitment. Differential splicing may serve as a common mechanism for generating biased signaling and provides insights into how chemokine receptor signaling can be modulated post-transcriptionally.

The Actin-Binding Protein Drebrin Inhibits Neointimal Hyperplasia.

OBJECTIVE: Vascular smooth muscle cell (SMC) migration is regulated by cytoskeletal remodeling as well as by certain transient receptor potential (TRP) channels, nonselective cation channels that modulate calcium influx. Proper function of multiple subfamily C TRP (TRPC) channels requires the scaffolding protein Homer 1, which associates with the actin-binding protein Drebrin. We found that SMC Drebrin expression is upregulated in atherosclerosis and in response to injury and investigated whether Drebrin inhibits SMC activation, either through regulation of TRP channel function via Homer or through a direct effect on the actin cytoskeleton. APPROACH AND RESULTS: Wild-type (WT) and congenic Dbn(-/+) mice were subjected to wire-mediated carotid endothelial denudation. Subsequent neointimal hyperplasia was 2.4±0.3-fold greater in Dbn(-/+) than in WT mice. Levels of globular actin were equivalent in Dbn(-/+) and WT SMCs, but there was a 2.4±0.5-fold decrease in filamentous actin in Dbn(-/+) SMCs compared with WT. Filamentous actin was restored to WT levels in Dbn(-/+) SMCs by adenoviral-mediated rescue expression of Drebrin. Compared with WT SMCs, Dbn(-/+) SMCs exhibited increased TRP channel activity in response to platelet-derived growth factor, increased migration assessed in Boyden chambers, and increased proliferation. Enhanced TRP channel activity and migration in Dbn(-/+) SMCs were normalized to WT levels by rescue expression of not only WT Drebrin but also a mutant Drebrin isoform that binds actin but fails to bind Homer. CONCLUSIONS: Drebrin reduces SMC activation through its interaction with the actin cytoskeleton but independently of its interaction with Homer scaffolds.