Extracellular vesicles (EVs) are nanosized lipid bilayer-delimited particles released from cells that mediate intercellular communications and play a pivotal role in various physiological and pathological processes. Subtypes of EVs may include plasma membrane ectosomes or microvesicles and endosomal origin exosomes, although functional distinctions remain unclear. EVs carry cargo proteins, nucleic acids (RNA and DNA), lipids, and metabolites. By presenting or transferring this cargo to recipient cells, EVs can trigger cellular responses. We summarize contemporary understanding of EV biogenesis, composition, and function, with an emphasis on the role of EVs in the cardiovascular system. In addition, we outline the functional relevance of EVs in cardiovascular pathophysiology, further highlighting their potential for diagnostic and therapeutic applications.

There is a growing awareness that both thick-filament and classical thin-filament regulations play central roles in modulating muscle contraction. Myosin ATPase assays have demonstrated that under relaxed conditions, myosin may reside either in a high-energy-consuming disordered-relaxed (DRX) state available for binding actin to generate force or in an energy-sparing super-relaxed (SRX) state unavailable for actin binding. X-ray diffraction studies have shown that the majority of myosin heads are in a quasi-helically ordered OFF state in a resting muscle and that this helical ordering is lost when myosin heads are turned ON for contraction. It has been assumed that myosin heads in SRX and DRX states are equivalent to the OFF and ON states, respectively, and the terms have been used interchangeably. In this study, we use X-ray diffraction and ATP turnover assays to track the structural and biochemical transitions of myosin heads, respectively, induced with either omecamtiv mecarbil (OM) or piperine in relaxed porcine myocardium. We find that while OM and piperine induce dramatic shifts of myosin heads from the OFF to the ON state, there are no appreciable changes in the population of myosin heads in the SRX and DRX states in both unloaded and loaded preparations. Our results show that biochemically defined SRX and DRX can be decoupled from structurally defined OFF and ON states. In summary, while SRX/DRX and OFF/ON transitions can be correlated in some cases, these two phenomena are measured using different approaches, reflect different properties of the thick filament, and should be investigated and interpreted separately.

Central obesity with cardiometabolic syndrome (CMS) is a major global contributor to human disease, and effective therapies are needed. Here, we show that cyclic GMP–selective phosphodiesterase 9A inhibition (PDE9-I) in both male and ovariectomized female mice suppresses preestablished severe diet-induced obesity/CMS with or without superimposed mild cardiac pressure load. PDE9-I reduces total body, inguinal, hepatic, and myocardial fat; stimulates mitochondrial activity in brown and white fat; and improves CMS, without significantly altering activity or food intake. PDE9 localized at mitochondria, and its inhibition in vitro stimulated lipolysis in a PPARα-dependent manner and increased mitochondrial respiration in both adipocytes and myocytes. PPARα upregulation was required to achieve the lipolytic, antiobesity, and metabolic effects of PDE9-I. All these PDE9-I–induced changes were not observed in obese/CMS nonovariectomized females, indicating a strong sexual dimorphism. We found that PPARα chromatin binding was reoriented away from fat metabolism–regulating genes when stimulated in the presence of coactivated estrogen receptor-α, and this may underlie the dimorphism. These findings have translational relevance given that PDE9-I is already being studied in humans for indications including heart failure, and efficacy against obesity/CMS would enhance its therapeutic utility.

Background: Heart failure with preserved ejection fraction (HFpEF) constitutes more than half of all HF but has few effective therapies. Recent human myocardial transcriptomics and metabolomics have identified major differences between HFpEF and controls. How this translates at the protein level is unknown. Methods and Results: Myocardial tissue from patients with HFpEF and nonfailing donor controls was analyzed by data‐dependent acquisition (n=10 HFpEF, n=10 controls) and data‐independent acquisition (n=44 HFpEF, n=5 controls) mass spectrometry‐based proteomics. Differential protein expression analysis, pathway overrepresentation, weighted coexpression network analysis, and machine learning were integrated with clinical characteristics and previously reported transcriptomics. Principal component analysis (data‐dependent acquisition‐mass spectrometry) found HFpEF separated into 2 subgroups: one similar to controls and the other disparate. Downregulated proteins in HFpEF versus controls were enriched in mitochondrial transport/organization, translation, and metabolism including oxidative phosphorylation. Proteins upregulated in HFpEF were related to immune activation, reactive oxygen species, and inflammatory response. Ingenuity pathway analysis predicted downregulation of protein translation, mitochondrial function, and glucose and fat metabolism in HFpEF. Expression of oxidative phosphorylation and metabolism genes (higher) versus proteins (lower) was discordant in HFpEF versus controls. Data‐independent acquisition‐mass spectrometry proteomics also yielded 2 HFpEF subgroups; the one most different from controls had a higher proportion of patients with severe obesity and exhibited lower proteins related to fuel metabolism, oxidative phosphorylation, and protein translation. Three modules of correlated proteins in HFpEF that correlated with left ventricular hypertrophy and right ventricular load related to (1) proteasome; (2) fuel metabolism; and (3) protein translation, oxidative phosphorylation, and sarcomere organization. Conclusions: Integrative proteomics, transcriptomics, and pathway analysis supports a defect in both metabolism and translation in HFpEF. Patients with HFpEF with more distinct proteomic signatures from control more often had severe obesity, supporting therapeutic efforts targeting metabolism and translation, particularly in this subgroup.

Background: Resuscitation from hemorrhagic shock (HS) by blood transfusion restores oxygen (O₂) delivery and provides hemodynamic stability. Current regulations allow red blood cells (RBCs) to be stored and used for up to 42 days. During storage, RBCs undergo many structural and functional changes. These storage lesions have been associated with adverse events and increased mortality after transfusion, increasing the need for improved RBC storage protocols. This study evaluates the efficacy of anaerobically stored RBCs to resuscitate rats from severe HS compared with conventionally stored RBCs. Methods and results: Rat RBCs were stored under anaerobic, anaerobic/hypercapnic, or conventional conditions for a period of 3 weeks. Hemorrhage was induced by controlled bleeding, shock was maintained for 30 min, and RBCs were transfused to restore and maintain blood pressure near the prhemorrhage level. All storage conditions met current regulatory 24-h posttransfusion recovery requirements. Transfusion of anaerobically stored RBCs required significantly less RBC volume to restore and maintain hemodynamics. Anaerobic or anaerobic/hypercapnic RBCs restored hemodynamics better than conventionally stored RBCs. Resuscitation with conventionally stored RBCs impaired indices of left ventricular cardiac function, increased hypoxic tissue staining and inflammatory markers, and affected organ function compared with anaerobically stored RBCs. Conclusions: Resuscitation from HS via transfusion of anaerobically stored RBCs recovered cardiac function, restored hemodynamic stability, and improved outcomes.