The Na+/H+ antiporter SALT OVERLY SENSITIVE 1 regulates salt compensation of circadian rhythms by stabilizing GIGANTEA in Arabidopsis.

The circadian clock is a timekeeping, homeostatic system that temporally coordinates all major cellular processes. The function of the circadian clock is compensated in the face of variable environmental conditions ranging from normal to stress-inducing conditions. Salinity is a critical environmental factor affecting plant growth, and plants have evolved the SALT OVERLY SENSITIVE (SOS) pathway to acquire halotolerance. However, the regulatory systems for clock compensation under salinity are unclear. Here, we show that the plasma membrane Na+/H+ antiporter SOS1 specifically functions as a salt-specific circadian clock regulator via GIGANTEA (GI) in Arabidopsis thaliana. SOS1 directly interacts with GI in a salt-dependent manner and stabilizes this protein to sustain a proper clock period under salinity conditions. SOS1 function in circadian clock regulation requires the salt-mediated secondary messengers cytosolic free calcium and reactive oxygen species, pointing to a distinct regulatory role for SOS1 in addition to its function as a transporter to maintain Na+ homeostasis. Our results demonstrate that SOS1 maintains homeostasis of the salt response under high or daily fluctuating salt levels. These findings highlight the genetic capacity of the circadian clock to maintain timekeeping activity over a broad range of salinity levels.

The E3 ubiquitin ligase COP1 regulates salt tolerance via GIGANTEA degradation in roots.

Excess soil salinity significantly impairs plant growth and development. Our previous reports demonstrated that the core circadian clock oscillator GIGANTEA (GI) negatively regulates salt stress tolerance by sequestering the SALT OVERLY SENSITIVE (SOS) 2 kinase, an essential component of the SOS pathway. Salt stress induces calcium-dependent cytoplasmic GI degradation, resulting in activation of the SOS pathway; however, the precise molecular mechanism governing GI degradation during salt stress remains enigmatic. Here, we demonstrate that salt-induced calcium signals promote the cytoplasmic partitioning of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), leading to the 26S proteasome-dependent degradation of GI exclusively in the roots. Salt stress-induced calcium signals accelerate the cytoplasmic localization of COP1 in the root cells, which targets GI for 26S proteasomal degradation. Align with this, the interaction between COP1 and GI is only observed in the roots, not the shoots, under salt-stress conditions. Notably, the gi-201 cop1-4 double mutant shows an enhanced tolerance to salt stress similar to gi-201, indicating that GI is epistatic to COP1 under salt-stress conditions. Taken together, our study provides critical insights into the molecular mechanisms governing the COP1-mediated proteasomal degradation of GI for salt stress tolerance, raising new possibilities for developing salt-tolerant crops.

Microplastic ingestion induces energy loss on the copepod Tigriopus koreanus.

In marine environments, exposure to microplastics threaten various organisms. A large portion of MPs may be bioavailable to copepods, and ingesting MPs has been reported to induce various adverse effects, including increased mortality, developmental retardation, and decreased reproduction. Adverse effects of MPs on these important processes of copepods may be induced by the obstructive effects of the ingested MPs on energy acquisition. However, few studies have explored the biological effects of MPs on copepods in terms of energy budgets. Therefore, we analyzed ATP (adenosine triphosphate) levels, enzyme activities, swimming distances, and excretion rates in marine copepods (Tigriopus koreanus) that have ingested polystyrene microplastics. Our results indicate that the ingestion of MPs may prevent adequate acquisition of nourishment and lead the copepods into a vicious circle in the respect to energetic burden. Our study provides biochemical evidence for a reduction in the energy budget of copepods due to MPs ingestion. Further, this study increases our understanding of the risks of microplastics, by providing advanced evidences of their effects on marine primary consumer.

Skeletal Muscle-Specific Bis Depletion Leads to Muscle Dysfunction and Early Death Accompanied by Impairment in Protein Quality Control.

Bcl-2-interacting cell death suppressor (BIS), also called BAG3, plays a role in physiological functions such as anti-apoptosis, cell proliferation, autophagy, and senescence. Whole-body Bis-knockout (KO) mice exhibit early lethality accompanied by abnormalities in cardiac and skeletal muscles, suggesting the critical role of BIS in these muscles. In this study, we generated skeletal muscle-specific Bis-knockout (Bis-SMKO) mice for the first time. Bis-SMKO mice exhibit growth retardation, kyphosis, a lack of peripheral fat, and respiratory failure, ultimately leading to early death. Regenerating fibers and increased intensity in cleaved PARP1 immunostaining were observed in the diaphragm of Bis-SMKO mice, indicating considerable muscle degeneration. Through electron microscopy analysis, we observed myofibrillar disruption, degenerated mitochondria, and autophagic vacuoles in the Bis-SMKO diaphragm. Specifically, autophagy was impaired, and heat shock proteins (HSPs), such as HSPB5 and HSP70, and z-disk proteins, including filamin C and desmin, accumulated in Bis-SMKO skeletal muscles. We also found metabolic impairments, including decreased ATP levels and lactate dehydrogenase (LDH) and creatine kinase (CK) activities in the diaphragm of Bis-SMKO mice. Our findings highlight that BIS is critical for protein homeostasis and energy metabolism in skeletal muscles, suggesting that Bis-SMKO mice could be used as a therapeutic strategy for myopathies and to elucidate the molecular function of BIS in skeletal muscle physiology.

Quality Control in the Endoplasmic Reticulum: Crosstalk between ERAD and UPR pathways.

Endoplasmic reticulum (ER)-associated degradation (ERAD) and the unfolded protein response (UPR) are two key quality-control machineries in the cell. ERAD is responsible for the clearance of misfolded proteins in the ER for cytosolic proteasomal degradation, while UPR is activated in response to the accumulation of misfolded proteins. It has long been thought that ERAD is an integral part of UPR because expression of many ERAD genes is controlled by UPR; however, recent studies have suggested that ERAD has a direct role in controlling the protein turnover and abundance of IRE1α, the most conserved UPR sensor. Here, we review recent advances in our understanding of IRE1α activation and propose that UPR and ERAD engage in an intimate crosstalk to define folding capacity and maintain homeostasis in the ER.

Osteopontin mediates the formation of corpora amylacea-like structures from degenerating neurons in the CA1 region of the rat hippocampus after ischemia.

We previously demonstrated that osteopontin (OPN) is closely associated with calcium precipitation in response to ischemic brain insults. The present study was designed to elucidate the possible association between deposition of OPN and progressive neurodegeneration in the ischemic hippocampus. To address this, we analyzed the OPN deposits in the rat hippocampus after global cerebral ischemia in the chronic phase (4 to 12 weeks) after reperfusion using immunoelectron microscopy and correlative light and electron microscopy. We identified three different types of OPN deposits based on their morphological characteristics, numbered according to the order in which they evolved. Dark degenerative cells that retained cellular morphology were frequently observed in the pyramidal cell layer, and type I OPN deposits were degenerative mitochondria that accumulated among these cells. Type II deposits evolved into more complex amorphous structures with prominent OPN deposits within their periphery and within degenerative mitochondria-like structures. Finally, type III had large concentric laminated structures with irregularly shaped bodies in the center of the deposits. In all types, OPN expression was closely correlated with calcification, as confirmed by calcium fixation and Alizarin Red staining. Notably, type II and III deposits were highly reminiscent of corpora amylacea, glycoprotein-rich aggregates found in aged brains, or neurodegenerative disease, which was further confirmed by ubiquitin expression and periodic acid-Schiff staining. Overall, our data provide a novel link between ongoing neurodegeneration and the formation of corpora amylacea-like structures and calcium deposits in the ischemic hippocampus, suggesting that OPN may play an important role in such processes.

Metabolic discrimination of synovial fluid between rheumatoid arthritis and osteoarthritis using gas chromatography/time-of-flight mass spectrometry.

INTRODUCTION: Rheumatoid arthritis (RA) and osteoarthritis (OA) are clinicopathologically different. OBJECTIVES: We aimed to assess the feasibility of metabolomics in differentiating the metabolite profiles of synovial fluid between RA and OA using gas chromatography/time-of-flight mass spectrometry. METHODS: We first compared the global metabolomic changes in the synovial fluid of 19 patients with RA and OA. Partial least squares-discriminant, hierarchical clustering, and univariate analyses were performed to distinguish metabolites of RA and OA. These findings were then validated using synovial fluid samples from another set of 15 patients with RA and OA. RESULTS: We identified 121 metabolites in the synovial fluid of the first 19 samples. The score plot of PLS-DA showed a clear separation between RA and OA. Twenty-eight crucial metabolites, including hypoxanthine, xanthine, adenosine, citrulline, histidine, and tryptophan, were identified to be capable of distinguishing RA metabolism from that of OA; these were found to be associated with purine and amino acid metabolism. CONCLUSION: Our results demonstrated that metabolite profiling of synovial fluid could clearly discriminate between RA and OA, suggesting that metabolomics may be a feasible tool to assist in the diagnosis and advance the comprehension of pathological processes for diseases.

Determinants of Exercise Capacity in Patients With Hypertrophic Cardiomyopathy.

BACKGROUND: Reduced exercise capacity reflects symptom severity and clinical outcomes in patients with hypertrophic cardiomyopathy (HCM). The present study aimed to identify factors that may affect exercise capacity in patients with HCM. METHODS: In 294 patients with HCM and preserved left ventricular (LV) ejection fraction, we compared peak oxygen consumption (peak VO2) evaluated by cardiopulmonary exercise testing as a representative parameter of exercise tolerance with clinical and laboratory data, including N-terminal pro-hormone of brain natriuretic peptide (NT-proBNP), diastolic parameters on echocardiography, and the grade of myocardial fibrosis on cardiac magnetic resonance imaging (CMR). RESULTS: Median peak VO2, was 29.0 mL/kg/min (interquartile range [IQR], 25.0-34.0). Age (estimated ß = -0.140, P < 0.001), female sex (ß = -5.362, P < 0.001), NT-proBNP (ß = -1.256, P < 0.001), and E/e' ratio on echocardiography (ß = -0.209, P = 0.019) were significantly associated with exercise capacity. Peak VO2 was not associated with the amount of myocardial fibrosis on CMR (mean of late gadolinium enhancement 12.25 ± 9.67%LV). CONCLUSION: Decreased exercise capacity was associated with age, female sex, increased NT-proBNP level, and E/e' ratio on echocardiography. Hemodynamic changes and increased filling pressure on echocardiography should be monitored in this population for improved outcomes.

Serum lipoprotein-derived fatty acids regulate hypoxia-inducible factor.

Oxygen regulates hypoxia-inducible factor (HIF) transcription factors to control cell metabolism, erythrogenesis, and angiogenesis. Whereas much has been elucidated about how oxygen regulates HIF, whether lipids affect HIF activity is un-known. Here, using cultured cells and two animal models, we demonstrate that lipoprotein-derived fatty acids are an independent regulator of HIF. Decreasing extracellular lipid supply inhibited HIF prolyl hydroxylation, leading to accumulation of the HIFα subunit of these heterodimeric transcription factors comparable with hypoxia with activation of downstream target genes. The addition of fatty acids to culture medium suppressed this signal, which required an intact mitochondrial respiratory chain. Mechanistically, fatty acids and oxygen are distinct signals integrated to control HIF activity. Finally, we observed lipid signaling to HIF and changes in target gene expression in developing zebrafish and adult mice, and this pathway operates in cancer cells from a range of tissues. This study identifies fatty acids as a physiological modulator of HIF, defining a mechanism for lipoprotein regulation that functions in parallel to oxygen.

Patient Perspectives and Preferences Regarding Gout and Gout Management: Impact on Adherence.

BACKGROUND: Patient-centered management is becoming increasingly important in gout, but there are limited studies exploring patients' perspectives and preferences. We aimed to investigate patients' perspectives and preferences regarding gout and gout management, and their impacts on adherence to urate lowering therapy (ULT). METHODS: A paper-based survey was performed in patients with gout seen at the rheumatology outpatient clinics of 16 tertiary hospitals. The survey included questions regarding demographics, comorbidities, gout attacks, current treatment and adherence, and patients' perspectives and preferences regarding gout and gout management. Multivariate regression analysis was performed to determine the factors associated with ULT adherence. RESULTS: Of 809 surveyed patients with gout, 755 (94.5%) were using ULT. Among those using ULT, 89.1% had ≥ 80% adherence to ULT. Majority of the patients knew management strategies to some extent (94.8%), perceived gout as a life-long disease (91.2%), and were making efforts toward practicing at least one lifestyle modification (89.2%). Most patients (71.9%) obtained information about gout management during their clinic visits. Approximately half of the patients (53.6%) preferred managing their disease with both ULT and lifestyle modification, 28.4% preferred ULT only, and 17.4% preferred lifestyle modification only. Adherence was better in patients with older age (odds ratio [OR], 1.03), those with better knowledge of gout management strategies (OR, 3.56), and those who had preference for ULT (OR, 2.07). CONCLUSION: Patients' perspectives and management preferences had high impacts on adherence to ULT in gout. Consideration of patients' perspectives and preferences is important for achieving the desired clinical outcome in gout.

A Golgi rhomboid protease Rbd2 recruits Cdc48 to cleave yeast SREBP.

Hypoxic growth of fungi requires sterol regulatory element-binding protein (SREBP) transcription factors, and human opportunistic fungal pathogens require SREBP activation for virulence. Proteolytic release of fission yeast SREBPs from the membrane in response to low oxygen requires the Golgi membrane-anchored Dsc E3 ligase complex. Using genetic interaction arrays, we identified Rbd2 as a rhomboid family protease required for SREBP proteolytic processing. Rbd2 is an active, Golgi-localized protease that cleaves the transmembrane segment of the TatA rhomboid model substrate. Epistasis analysis revealed that the Dsc E3 ligase acts on SREBP prior to cleavage by Rbd2. Using APEX2 proximity biotinylation, we demonstrated that Rbd2 binds the AAA-ATPase Cdc48 through a C-terminal SHP box. Interestingly, SREBP cleavage required Rbd2 binding of Cdc48, consistent with Cdc48 acting to recruit ubiquitinylated substrates. In support of this claim, overexpressing a Cdc48-binding mutant of Rbd2 bypassed the Cdc48 requirement for SREBP cleavage, demonstrating that Cdc48 likely plays a role in SREBP recognition. In the absence of functional Rbd2, SREBP precursor is degraded by the proteasome, indicating that Rbd2 activity controls the balance between SREBP activation and degradation.

Risk of non-Hodgkin's lymphoma and thyroid cancer in primary Sjögren's syndrome measured using the Korean Health Insurance Claims Database.

OBJECTIVES: The aim of this study was to evaluate the incidence and risk of non-Hodgkin's lymphoma (NHL) and thyroid cancer in patients with primary Sjögren's syndrome (pSS) using the Korean National Health Insurance Service (NHIS) claims database. METHODS: pSS was identified using the Korean NHIS medical claims database between 2007 and 2017. The case definition required more than one visit based on the SS diagnostic code and the registration system for rare and incurable diseases. We included all admissions with a primary diagnosis of lymphoma and thyroid cancer. RESULTS: The pSS incidence was 1.88 cases/100,000 inhabitants. Female patients had a higher incidence than male patients, with a female-to-male ratio of 7.65:1. Of those, we identified 18 (0.34%), 1 (0.02%) and 29 (0.56%) patients with NHL, Hodgkin's disease and thyroid cancer, respectively. For pSS, the standardised incidence ratios for NHL and thyroid cancer were 6.32 (95% confidence interval [CI] 4.09-9.38) and 1.23 (95% CI 0.88-1.68), respectively. Compared with the general population, female patients with pSS had a 6.95-fold higher risk of developing NHL, while the male patients did not. Patients with pSS did not have a higher risk of developing thyroid cancer. CONCLUSIONS: Although pSS is associated with a higher risk of developing NHL, the risk of NHL appears to have decreased compared with that in previous studies. Our study suggests that the risk of NHL or thyroid cancer with SS is not higher than that reported in previous studies.

Clinical implications of exercise-induced regional wall motion abnormalities in significant aortic regurgitation.

BACKGROUND: Significant aortic regurgitation (AR) is sometimes accompanied by regional wall motion abnormalities (RWMA) during exercise stress echocardiography. The aim of this study was to estimate the association between RWMA after exercise and in the presence of significant AR in patients with coronary artery disease (CAD) or volume overload and to predict the eventual need for aortic valve replacement (AVR). METHODS AND RESULTS: We retrospectively reviewed 182 patients with significant AR who underwent exercise echocardiography. In addition, we investigated patients with AR who underwent coronary angiography (CAG) or coronary computed tomography angiography (CCTA) and were diagnosed with CAD. The presence of RWMA after exercise was defined as newly developed RWMA after exercise and included all changes in wall motion. Patients were divided into two groups according to the presence of RWMA after exercise: the RWMA group (n = 42) and non-RWMA group (n = 140). In the RWMA group, 31 patients (73.8%) underwent coronary artery evaluation by CAG or CCTA. Only two patients in the RWMA group were diagnosed with current CAD and underwent percutaneous coronary intervention. Patients with RWMA were older (61.6 ± 10.8 vs 52.0 ± 13.7 years, P < .001), had more severe AR (54.8% vs 32.9%), and underwent AVR more frequently (40.5% vs 14.3%, P = .001) than patients without RWMA. METs (odds ratio [OR], 0.796; P = .019), difference between rest and postexercise left ventricular end-diastolic volume (OR, 0.967; P = .001), and the difference between pre- and postexercise left ventricular end-systolic volume (OR, 1.113; P < .001) were identified as independent factors associated with RWMA after exercise according to multivariable logistic regression analysis. The majority of wall motion changes were seen in the lateral and inferior segments, and the locations of wall motion changes were relatively consistent with the direction of the AR jet. The relationship between RWMA after exercise and time to AVR was investigated by simple linear regression (hazard ratio [HR], 3.402; P < .001). After adjusting for baseline parameters of diastolic blood pressure, left ventricular end-systolic dimension (LVESD), aorta size, deceleration time, and METs, the presence of RWMA after exercise was not predictive of time to AVR (HR, 1.106; P = .81). On the other hand, without forcible entry of RWMA after exercise, LVESD (HR, 1.119; P < .001) and METs (HR, 0.828; P = .006) independently predicted the eventual need for AVR as an outcome. CONCLUSION: The degree of change in wall motion from rest to exercise in those with significant AR was not correlated with CAD, but was correlated with the severity of volume overload and exercise-induced preload changes, as well as the direction of the AR jet. In addition, RWMA after exercise had no role in predicting the need for AVR.

Mild Ischemic Mitral Regurgitation: Is Revascularization Enough for Every Patient?

BACKGROUND: The progress of mild ischemic mitral regurgitation (MR) after isolated coronary artery bypass is not clear. We aimed to determine the proportion of patients with mild ischemic MR undergoing isolated coronary artery bypass grafting (CABG) presenting with regression of or persistent MR one year after CABG and to identify the significantly different echocardiographic variables between regressing and persistent MR. METHODS: Sixty-three patients with preoperative mild ischemic MR were categorized into an MR- regression or an MR-persistence group one year after isolated CABG. The echocardiographic indices, indicating mitral leaflet configuration and remodeling of the left ventricle (LV), were measured before and one year after the surgery. RESULTS: One year after CABG, MR regressed in 60% (38/63) and persisted in 40% (25/63) of the patients. The left ventricular diameter, volume, and sphericity and anteroposterior diameter of the mitral annulus improved only in the MR-regression group, while the ejection fraction improved in both groups (47.7% ± 12.4% from 40.1% ± 11.3%, P < .001 in the regression group and 43.2% ± 14.0% from 39.3% ± 11.6%, P = .035 in the persistence group). A >15% decrease in the LV end-systolic volume was noted more frequently in the MR-regression group (60.5% versus 30%, P = .027). The leaflet angle did not show asymmetry or significant changes in both groups. CONCLUSIONS: Isolated CABG improved mild MR in most patients with mild ischemic MR. These patients showed greater reverse remodeling after revascularization than the patients with persistent MR after isolated CABG. Additional tests, which can predict LV reverse remodeling, are needed to predict persistent MR.

Higher serum uric acid is associated with higher lumbar spine bone mineral density in male health-screening examinees: a cross-sectional study.

Bone health has been associated with oxidative stress and antioxidants have received interest to this end. Serum uric acid (SUA), an end product of purine metabolism in humans, has recently shown antioxidant properties regarding bone health, but there are conflicting results. The aim of this study was to investigate the relationship between SUA levels and lumbar spine bone mineral density (BMD) in clinically apparently healthy males aged 40-60 years. We performed a cross-sectional study of 6588 Korean males who completed a health-screening program from January 2011 to December 2014. Of the study participants, the mean age was 48.2 ± 10.7 years. Multiple regression analyses resulted in a significant positive association with lumbar spine BMD across SUA quintiles in a dose-response manner after adjusting for various confounding factors (p = 0.013); for each 1 mg/dl increase of SUA, BMD rose by 0.0054 g/cm2 (p = 0.004). Stratified analyses revealed that this association between SUA and lumbar spine BMD was consistently observed across all clinically relevant subgroups. The present study demonstrated a positive association in males between SUA and lumbar spine BMD, suggesting that SUA could have a profitable effect on bone metabolism.

Serial Changes of Transmitral and Transtricuspid Pressure Gradients After Simultaneous Mitral and Tricuspid Ring Annuloplasty.

BACKGROUND: Although flexible-ring annuloplasty is more inclined to increase the transmitral gradient over time, its effect on the tricuspid annulus is unknown. This study was conducted to evaluate serial changes in mean pressure gradient (mPG) across tricuspid and mitral valves after simultaneous dual implantation of flexible bands. METHODS: Seventy-one (71) patients (median age, 61.6 years; IQR: 50.8-69.0 years) underwent simultaneous mitral/tricuspid annuloplasties using St. Jude Tailor rings. Serial mPGs across mitral and tricuspid valves were evaluated at three postoperative time points: predischarge, 3 years, and 5 years. To gauge the effects and clinical outcomes of prophylactic intervention, patients were categorised as tricuspid regurgitation (TR)≥moderate or TR

Characterization of protein complexes of the endoplasmic reticulum-associated degradation E3 ubiquitin ligase Hrd1.

Hrd1 is the core structural component of a large endoplasmic reticulum membrane-embedded protein complex that coordinates the destruction of folding-defective proteins in the early secretory pathway. Defining the composition, dynamics, and ultimately, the structure of the Hrd1 complex is a crucial step in understanding the molecular basis of glycoprotein quality control but has been hampered by the lack of suitable techniques to interrogate this complex under native conditions. In this study we used genome editing to generate clonal HEK293 (Hrd1.KI) cells harboring a homozygous insertion of a small tandem affinity tag knocked into the endogenous Hrd1 locus. We found that steady-state levels of tagged Hrd1 in these cells are indistinguishable from those of Hrd1 in unmodified cells and that the tagged variant is functional in supporting the degradation of well characterized luminal and membrane substrates. Analysis of detergent-solubilized Hrd1.KI cells indicates that the composition and stoichiometry of Hrd1 complexes are strongly influenced by Hrd1 expression levels. Analysis of affinity-captured Hrd1 complexes from these cells by size-exclusion chromatography, immunodepletion, and absolute quantification mass spectrometry identified two major high-molecular-mass complexes with distinct sets of interacting proteins and variable stoichiometries, suggesting a hitherto unrecognized heterogeneity in the functional units of Hrd1-mediated protein degradation.

The altered right frontoparietal network functional connectivity in migraine and the modulation effect of treatment.

Aims This study aims to investigate the resting-state functional connectivity (rs-fc) of the right frontoparietal network (rFPN) between migraineurs and healthy controls (HCs) in order to determine how the rFPN rs-fc can be modulated by effective treatment. Methods One hundred patients and 46 matched HCs were recruited. Migraineurs were randomized to verum acupuncture, sham acupuncture, and waiting list groups. Resting-state functional magnetic resonance imaging data were collected before and after longitudinal treatments. Independent component analysis was applied in the data analysis. Results We found that migraineurs showed decreased rs-fc between the rFPN and bilateral precuneus compared with HCs. After treatments (real and sham), rFPN rs-fc with the precuneus was significantly reduced. This reduction was associated with headache intensity relief. In order to explore the role of the precuneus in acupuncture modulation, we performed a seed-based rs-fc analysis using the precuneus as a seed and found that the precuneus rs-fc with the bilateral rostral anterior cingulate cortex/medial prefrontal cortex, ventral striatum, and dorsolateral prefrontal cortex was significantly enhanced after treatment. Conclusion Our results suggest that migraineurs are associated with abnormal rFPN rs-fc. An effective treatment, such as acupuncture, may relieve symptoms by strengthening the cognitive adaptation/coping process. Elucidation of the adaptation/coping mechanisms may open up a new window for migraine management.

Assessment of reverse remodeling predicted by myocardial deformation on tissue tracking in patients with severe aortic stenosis: a cardiovascular magnetic resonance imaging study.

BACKGROUND: The technique of tissue tracking with balanced steady-state free precession cine sequences was introduced, and allowed myocardial strain to be derived directly, offering advantages over traditional myocardial tagging. The aim of this study was to evaluate the correlation between reverse remodeling as an outcome and left ventricular strain using cardiovascular magnetic resonance imaging (CMR) tissue tracking, and to evaluate prediction of reverse remodeling by myocardial deformation in patients with severe aortic stenosis (AS). METHODS: We enrolled 63 patients with severe AS and normal left ventricular (LV) systolic function (ejection fraction > 60%), who underwent both CMR and transthoracic echocardiography (Echo) before surgical aortic valve replacement (AVR). CMR at 1.5 T, including non and post-contrast T1 mapping for extracellular volume (ECV), was carried out to define the amount of myocardial fibrosis. Cardiac Performance Analysis software was used to derive myocardial deformation as strain parameters from three short-axis cine views (basal, mid and apical levels) and apical 2, 3, and 4 chamber views. The primary outcome was reverse remodeling, as evaluated by regression of left ventricular mass index (LVMI). RESULTS: Median follow-up was 28.8 months (interquartile range 11.3-38.3 months). As evaluated by LVMI between baseline and follow-up, mass regression was significantly improved after AVR (baseline 145.9 ± 37.0 [g/m2] vs. follow-up 97.7 ± 22.2[g/m2], p < 0.001). Statistically significant Pearson's correlations with LVMI regression were observed for longitudinal global strain (r = -0.461, p < 0.001), radial strain (r = 0.391, p = 0.002), and circumferential strain (r = -0.334, p = 0.009). A simple linear regression analysis showed that all strain parameters could predict the amount of LVMI regression (P < 0.05), as well as non-contrast T1 value (beta = -0.314, p < 0.001) and ECV (beta = -2.546, p = 0.038). However, ECV had the lowest predictive power (multiple r2 = 0.071). Multiple regression analysis showed strain could independently predict the amount of LVMI regression and the longitudinal global strain (beta = -3.335, p < 0.001). CONCLUSION: Longitudinal global strain measured by CMR tissue tracking as a technique was correlated with reverse remodeling as LVMI regression and was predictive of this outcome. As a simple and practical method, tissue tracking is promising to assess strain and predict reverse remodeling in severe AS, especially in patients with suboptimal Echo image quality.

Proximity-dependent biotin labelling in yeast using the engineered ascorbate peroxidase APEX2.

The engineered ascorbate peroxidase (APEX2) has been effectively employed in mammalian cells to identify protein-protein interactions. APEX2 fused to a protein of interest covalently tags nearby proteins with biotin-phenol (BP) when H2O2 is added to the cell culture medium. Subsequent affinity purification of biotinylated proteins allows for identification by MS. BP labelling occurs in 1 min, providing temporal control of labelling. The APEX2 tool enables proteomic mapping of subcellular compartments as well as identification of dynamic protein complexes, and has emerged as a new methodology for proteomic analysis. Despite these advantages, a related APEX2 approach has not been developed for yeast. Here we report methods to enable APEX2-mediated biotin labelling in yeast. Our work demonstrated that high osmolarity and disruption of cell wall integrity permits live-cell biotin labelling in Schizosaccharomyces pombe and Saccharomyces cerevisiae respectively. Under these conditions, APEX2 permitted targeted and proximity-dependent labelling of proteins. The methods described herein set the stage for large-scale proteomic studies in yeast. With modifications, the method is also expected to be effective in other organisms with cell walls, such as bacteria and plants.