Low-intensity pulsed ultrasound improves myocardial ischaemia‒reperfusion injury via migrasome-mediated mitocytosis.

During myocardial ischaemia‒reperfusion injury (MIRI), the accumulation of damaged mitochondria could pose serious threats to the heart. The migrasomes, newly discovered mitocytosis-mediating organelles, selectively remove damaged mitochondria to provide mitochondrial quality control. Here, we utilised low-intensity pulsed ultrasound (LIPUS) on MIRI mice model and demonstrated that LIPUS reduced the infarcted area and improved cardiac dysfunction. Additionally, we found that LIPUS alleviated MIRI-induced mitochondrial dysfunction. We provided new evidence that LIPUS mechanical stimulation facilitated damaged mitochondrial excretion via migrasome-dependent mitocytosis. Inhibition the formation of migrasomes abolished the protective effect of LIPUS on MIRI. Mechanistically, LIPUS induced the formation of migrasomes by evoking the RhoA/Myosin II/F-actin pathway. Meanwhile, F-actin activated YAP nuclear translocation to transcriptionally activate the mitochondrial motor protein KIF5B and Drp1, which are indispensable for LIPUS-induced mitocytosis. These results revealed that LIPUS activates mitocytosis, a migrasome-dependent mitochondrial quality control mechanism, to protect against MIRI, underlining LIPUS as a safe and potentially non-invasive treatment for MIRI.

Low-intensity pulsed ultrasound protects from inflammatory dilated cardiomyopathy through inciting extracellular vesicles.

AIMS: CD4+ T cells are activated during inflammatory dilated cardiomyopathy (iDCM) development to induce immunogenic responses that damage the myocardium. Low-intensity pulsed ultrasound (LIPUS), a novel physiotherapy for cardiovascular diseases, has recently been shown to modulate inflammatory responses. However, its efficacy in iDCM remains unknown. Here, we investigated whether LIPUS could improve the severity of iDCM by orchestrating immune responses and explored its therapeutic mechanisms. METHODS AND RESULTS: In iDCM mice, LIPUS treatment reduced cardiac remodelling and dysfunction. Additionally, CD4+ T cell inflammatory responses were suppressed. LIPUS increased Treg cells while decreasing Th17 cells. LIPUS mechanically stimulates endothelial cells, resulting in increased secretion of extracellular vesicles (EVs), which are taken up by CD4+ T cells and alter their differentiation and metabolic patterns. Moreover, EVs selectively loaded with microRNA (miR)-99a are responsible for the therapeutic effects of LIPUS. The hnRNPA2B1 translocation from the nucleus to the cytoplasm and binding to caveolin-1 and miR-99a confirmed the upstream mechanism of miR-99a transport. This complex is loaded into EVs and taken up by CD4+ T cells, which further suppress mTOR and TRIB2 expression to modulate cellular differentiation. CONCLUSION: Our findings revealed that LIPUS uses an EV-dependent molecular mechanism to protect against iDCM progression. Therefore, LIPUS is a promising new treatment option for iDCM.

A promising frontier: targeting NETs for stroke treatment breakthroughs.

Stroke is a prevalent global acute cerebrovascular condition, with ischaemic stroke being the most frequently occurring type. After a stroke, neutrophils accumulate in the brain and subsequently generate and release neutrophil extracellular traps (NETs). The accumulation of NETs exacerbates the impairment of the blood‒brain barrier (BBB), hampers neovascularization, induces notable neurological deficits, worsens the prognosis of stroke patients, and can facilitate the occurrence of t-PA-induced cerebral haemorrhage subsequent to ischaemic stroke. Alternative approaches to pharmacological thrombolysis or endovascular thrombectomy are being explored, and targeting NETs is a promising treatment that warrants further investigation.

Platelet factor 4 promotes deep venous thrombosis by regulating the formation of neutrophil extracellular traps.

The presence of neutrophil extracellular traps (NETs) in thrombotic diseases has been extensively studied. The exact mechanism of NET formation in deep venous thrombosis (DVT) has not been largely studied. This study is aimed to explore the role of NETs and their interaction with platelet factor 4 (PF4) in DVT. In plasma samples from 51 healthy volunteers and 52 DVT patients, NET markers and PF4 were measured using enzyme-linked immunosorbent assays (ELISA). NET generation in blood samples from healthy subjects and DVT patients was analyzed by confocal microscopy and flow cytometry. The plasma levels of NETs were significantly elevated in DVT patients, and neutrophils from patients showed a stronger ability to generate NETs after treatment. PF4 was upregulated in plasma samples from DVT patients and mediated NET formation. NETs enhanced procoagulant (PCA) via tissue factor and activating platelets to induce procoagulant activity. In addition, we established an inferior vena cava ligation (IVC) model to examine the role of NETs in thrombogenicity in DVT. In conclusion, NET formation was mediated by PF4 and enhance the procoagulant activity in DVT.

Neutrophil extracellular traps mediated by platelet microvesicles promote thrombosis and brain injury in acute ischemic stroke.

AIMS: Neutrophil extracellular traps (NETs) have been implicated in thrombotic diseases. There is no definitive explanation for how NETs form during acute ischemic strokes (AIS). The purpose of our study was to investigate the potential mechanism and role of NETs formation in the AIS process. METHODS: As well as 45 healthy subjects, 45 patients with AIS had ELISA tests performed to detect NET markers. Expression of high-mobility group box 1 (HMGB1) on platelet microvesicles (PMVs) was analyzed by flow cytometry in healthy subjects and AIS patients' blood samples. We established middle cerebral artery occlusion (MCAO) mice model to elucidate the interaction between PMPs and NETs. RESULTS: A significant elevation in NET markers was found in patient plasma in AIS patients, and neutrophils generated more NETs from patients' neutrophils. HMGB1 expression was upregulated on PMVs from AIS patients and induced NET formation. NETs enhanced Procoagulant activity (PCA) through tissue factor and via platelet activation. Targeting lactadherin in genetical and in pharmacology could regulate the formation of NETs in MCAO model. CONCLUSIONS: NETs mediated by PMVs derived HMGB1 exacerbate thrombosis and brain injury in AIS. Video Abstract.

Neutrophil extracellular traps contribute to coagulopathy after traumatic brain injury.

Coagulopathy contributes to the majority of deaths and disabilities associated with traumatic brain injury (TBI). Whether neutrophil extracellular traps (NETs) contribute to an abnormal coagulation state in the acute phase of TBI remains unknown. Our objectives were to demonstrate the definitive role of NETs in coagulopathy in TBI. We detected NET markers in 128 TBI patients and 34 healthy individuals. Neutrophil-platelet aggregates were detected in blood samples from TBI patients and healthy individuals using flow cytometry and staining for CD41 and CD66b. Endothelial cells were incubated with isolated NETs and we detected the expression of vascular endothelial cadherin, syndecan-1, thrombomodulin, von Willebrand factor, phosphatidylserine, and tissue factor. In addition, we established a TBI mouse model to determine the potential role of NETs in TBI-associated coagulopathy. NET generation was mediated by high mobility group box 1 (HMGB1) from activated platelets and contributed to procoagulant activity in TBI. Furthermore, coculture experiments indicated that NETs damaged the endothelial barrier and caused these cells to assume a procoagulant phenotype. Moreover, the administration of DNase I before or after brain trauma markedly reduced coagulopathy and improved the survival and clinical outcome of mice with TBI.

Histone Lactylation Boosts Reparative Gene Activation Post-Myocardial Infarction.

BACKGROUND: Inflammation resolution and cardiac repair initiation after myocardial infarction (MI) require timely activation of reparative signals. Histone lactylation confers macrophage homeostatic gene expression signatures via transcriptional regulation. However, the role of histone lactylation in the repair response post-MI remains unclear. We aimed to investigate whether histone lactylation induces reparative gene expression in monocytes early and remotely post-MI. METHODS: Single-cell transcriptome data indicated that reparative genes were activated early and remotely in bone marrow and circulating monocytes before cardiac recruitment. Western blotting and immunofluorescence staining revealed increases in histone lactylation levels, including the previously identified histone H3K18 lactylation in monocyte-macrophages early post-MI. Through joint CUT&Tag and RNA-sequencing analyses, we identified Lrg1, Vegf-a, and IL-10 as histone H3K18 lactylation target genes. The increased modification and expression levels of these target genes post-MI were verified by chromatin immunoprecipitation-qPCR and reverse transcription-qPCR. RESULTS: We demonstrated that histone lactylation regulates the anti-inflammatory and pro-angiogenic dual activities of monocyte-macrophages by facilitating reparative gene transcription and confirmed that histone lactylation favors a reparative environment and improves cardiac function post-MI. Furthermore, we explored the potential positive role of monocyte histone lactylation in reperfused MI. Mechanistically, we provided new evidence that monocytes undergo metabolic reprogramming in the early stage of MI and demonstrated that dysregulated glycolysis and MCT1 (monocarboxylate transporter 1)-mediated lactate transport promote histone lactylation. Finally, we revealed the catalytic effect of IL (interleukin)-1ß-dependent GCN5 (general control non-depressible 5) recruitment on histone H3K18 lactylation and elucidated its potential role as an upstream regulatory element in the regulation of monocyte histone lactylation and downstream reparative gene expression post-MI. CONCLUSIONS: Histone lactylation promotes early remote activation of the reparative transcriptional response in monocytes, which is essential for the establishment of immune homeostasis and timely activation of the cardiac repair process post-MI.

Neutrophil extracellular traps: A novel therapeutic target for intracranial hemorrhage.

Neutrophil extracellular traps (NETs) are known to play a role in various diseases affecting coagulation. As of now, it is unclear whether NETs are present in hematoma samples collected from patients who have suffered an intracranial hemorrhage (ICH). The objective of this was to determine whether NETs are present in circulation and hematoma samples from ICH patients and to evaluate the procoagulant activity (PCA) of NETs during the ICH process. The expression of NET markers in samples from 78 ICH patients and 35 healthy donners was detected by ELISA and flow cytometry. Immunostaining for neutrophil markers (neutrophil CD66b) and NET markers (citrullinated histone H3 [H3Cit] and extracellular DNA) was performed on hematoma samples obtained from ICH patients undergoing intracranial hematoma evacuation. Our findings suggest that plasma and hematoma samples from patients with ICH showed high levels of NETs. Furthermore, using DNase I to target NETs enhanced ex vivo hematoma lysis. In conclusion, NETs play an important role in the ICH process and may be a novel therapeutic target for treatment of ICH patients.

Extracellular vesicle-packaged mitochondrial disturbing miRNA exacerbates cardiac injury during acute myocardial infarction.

Mounting evidence suggests that extracellular vesicles (EVs) are effective communicators in biological signalling in cardiac physiology and pathology. However, the role of EVs in cardiac injury, particularly in ischemic myocardial scenarios, has not been fully elucidated. Here, we report that acute myocardial infarction (AMI)-induced EVs can impair cardiomyocyte survival and exacerbate cardiac injury. EV-encapsulated miR-503, which is enriched during the early phase of AMI, is a critical molecule that mediates myocardial injury. Functional studies revealed that miR-503 promoted cardiomyocyte death by directly binding to peroxisome proliferator-activated receptor gamma coactivator-1ß (PGC-1ß) and a mitochondrial deacetylase, sirtuin 3 (SIRT3), thereby triggering mitochondrial metabolic dysfunction and cardiomyocyte death. Mechanistically, we identified endothelial cells as the primary source of miR-503 in EVs after AMI. Hypoxia induced rapid H3K4 methylation of the promoter of the methyltransferase-like 3 gene (METTL3) and resulted in its overexpression. METTL3 overexpression evokes N6-methyladenosine (m6 A)-dependent miR-503 biogenesis in endothelial cells. In summary, this study highlights a novel endogenous mechanism wherein EVs aggravate myocardial injury during the onset of AMI via endothelial cell-secreted miR-503 shuttling.

Circulating Exosomes Control CD4+ T Cell Immunometabolic Functions via the Transfer of miR-142 as a Novel Mediator in Myocarditis.

CD4+ T cells undergo immunometabolic activation to mount an immunogenic response during experimental autoimmune myocarditis (EAM). Exosomes are considered key messengers mediating multiple T cell functions in autoimmune responses. However, the role of circulating exosomes in EAM immunopathogenesis and CD4+ T cell dysfunction remains elusive. Our objective was to elucidate the mechanism of action for circulating exosomes in EAM pathogenesis. We found that serum exosomes harvested from EAM mice induced CD4+ T cell immunometabolic dysfunction. Treatment with the exosome inhibitor GW4869 protected mice from developing EAM, underlying that exosomes are indispensable for the pathogenesis of EAM. Furthermore, by transfer of EAM exosomes, we confirmed that circulating exosomes initiate the T cell pathological immune response, driving the EAM pathological process. Mechanistically, EAM-circulating exosomes selectively loaded abundant microRNA (miR)-142. We confirmed methyl-CpG binding domain protein 2 (MBD2) and suppressor of cytokine signaling 1 (SOCS1) as functional target genes of miR-142. The miR-142/MBD2/MYC and miR-142/SOCS1 communication axes are critical to exosome-mediated immunometabolic turbulence. Moreover, the in vivo injection of the miR-142 inhibitor alleviated cardiac injury in EAM mice. This effect was abrogated by pretreatment with EAM exosomes. Collectively, our results indicate a newly endogenous mechanism whereby circulating exosomes regulate CD4+ T cell immunometabolic dysfunction and EAM pathogenesis via cargo miR-142.

Circular RNA circSnx5 Controls Immunogenicity of Dendritic Cells through the miR-544/SOCS1 Axis and PU.1 Activity Regulation.

Dendritic cells (DCs) can orchestrate either immunogenic or tolerogenic responses to relay information on the functional state. Emerging studies indicate that circular RNAs (circRNAs) are involved in immunity; however, it remains unclear whether they govern DC development and function at the transcriptional level. In this study, we identified a central role for a novel circRNA, circSnx5, in modulating DC-driven immunity and tolerance. Ectopic circSnx5 suppresses DC activation and promotes the development of tolerogenic functions of DCs, while circSnx5 knockdown promotes their activation and inflammatory phenotype. Mechanistically, circSnx5 can act as a miR-544 sponge to attenuate miRNA-mediated target depression on suppressor of cytokine signaling 1 (SOCS1) and inhibit nuclear translocation of PU.1, regulating DC activation and function. Furthermore, the main splicing factors (SFs) were identified in DCs, of which heterogeneous nuclear ribonucleoprotein (hnRNP) C was essential for circSnx5 generation. Moreover, our data demonstrated that vaccination with circSnx5-conditioned DCs prolonged cardiac allograft survival in mice and alleviated experimental autoimmune myocarditis. Taken together, our results revealed circSnx5 as a key modulator to fine-tune DC function, suggesting that circSnx5 may serve as a potential therapeutic avenue for immune-related diseases.

Metabolic reprogramming orchestrates CD4+ T-cell immunological status and restores cardiac dysfunction in autoimmune induced-dilated cardiomyopathy mice.

Cellular autoimmune responses, especially those mediated by T-cells, play vital roles in the immunopathogenesis of dilated cardiomyopathy (DCM). Metabolic reprogramming directly controls T-cell function, imprinting distinct functional fates. However, its contribution to T-cell dysfunction and the immunopathogenesis of DCM is unknown. Here, we found that in DCM patients, CD4+ T-cells exhibited immune dysfunction and glycolytic metabolic reprogramming based on extracellular acidification and oxygen consumption rates. Similar results were observed in splenic and cardiac CD4+ T-cells from autoimmune-induced DCM mice. In vitro, the glycolysis inhibitor 2-deoxy-d-glucose (2-DG) reversed T-cell dysfunction; thus, heightened metabolic activity directly controls CD4+ T-cell immunological status. Adoptive transfer of CD4+ T-cells from DCM mice to normal recipients induced cardiac remodeling and cardiac T-cell dysfunction. Strikingly, these effects were abolished by preconditioning cells with 2-DG, indicating that CD4+ T-cell dysfunction partially induced by metabolic reprogramming contributes to cardiac remodeling. Moreover, the microRNA let-7i modulated the metabolism and function of T-cells from DCM mice by directly targeting Myc. Collectively, our results show that metabolic reprogramming occurs in T-cells of autoimmune-induced DCM mice and patients. Further, our findings highlight that glycolytic metabolism is a critical contributor to T-cell dysfunction and DCM immunopathogenesis. Our data position the modulation of the metabolism as a central integrator for T-cell function, representing a promising strategy against autoimmune-mediated DCM progression.

Protosappanin A protects against experimental autoimmune myocarditis, and induces metabolically reprogrammed tolerogenic DCs.

Autoimmune myocarditis is an immune-mediated myocardial injury that evolves into dilated cardiomyopathy (DCM). Protosappanin A (PrA), an immunosuppressive compound, induces immune tolerance in cardiac transplantation. However, whether PrA confers protective immunosuppression on experimental autoimmune myocarditis (EAM) is unknown. In this study, PrA treatment remarkably suppressed cardiac inflammatory cell infiltration and ameliorated cardiac remodeling in EAM mice. Additionally, PrA treatment reduced splenic T cells response, and induced expansion of immunosuppressive regulatory T cells (Tregs). Meanwhile, PrA induced the splenic dendritic cells (DCs) into a tolerogenic state with reduced co-stimulatory molecules, increased the production of tolerogenic cytokines in vivo. PrA also reprogrammed the metabolism of splenic DCs to a more glycolytic phenotype. To further investigate the effect of PrA on the functional and metabolic phenotype of DCs, the compound was added into the in vitro culture of MyHC-α-loaded DCs. These cells switched to a tolerogenic state and a metabolic profile similar to that found in cells during in ex vivo experiments. Treatment with glycolytic inhibitor 2-DG significantly reversed PrA-mediated DC tolerogenic properties, suggesting that glycolysis is indispensable for PrA-conditioned DCs to maintain their tolerogenic properties. Notably, PrA-conditioned DC vaccinations dampened EAM progress, and promoted Tregs expansion. Similarly, tolerogenic and metabolic patterns were also observed in PrA-modified human DC. In conclusion, PrA endows DC with a tolerogenic profile via glycolytic reprogramming, thereby inducing expansion of immunosuppressive Tregs, and preventing EAM progress. Our results suggested that PrA may confer immunosuppressive and protective effects on EAM by metabolically reprogramming DCs, which could contribute to the development of a new potential immunotherapy for the treatment of EAM and immune-related disorders.