Effects and mechanisms of the myocardial microenvironment on cardiomyocyte proliferation and regeneration.

The adult mammalian cardiomyocyte has a limited capacity for self-renewal, which leads to the irreversible heart dysfunction and poses a significant threat to myocardial infarction patients. In the past decades, research efforts have been predominantly concentrated on the cardiomyocyte proliferation and heart regeneration. However, the heart is a complex organ that comprises not only cardiomyocytes but also numerous noncardiomyocyte cells, all playing integral roles in maintaining cardiac function. In addition, cardiomyocytes are exposed to a dynamically changing physical environment that includes oxygen saturation and mechanical forces. Recently, a growing number of studies on myocardial microenvironment in cardiomyocyte proliferation and heart regeneration is ongoing. In this review, we provide an overview of recent advances in myocardial microenvironment, which plays an important role in cardiomyocyte proliferation and heart regeneration.

Single-cell RNA sequencing identifies interferon-inducible monocytes/macrophages as a cellular target for mitigating the progression of abdominal aortic aneurysm and rupture risk.

AIMS: Abdominal aortic aneurysm (AAA) represents a life-threatening condition characterized by medial layer degeneration of the abdominal aorta. Nevertheless, knowledge regarding changes in regulators associated with aortic status remains incomplete. A thorough understanding of cell types and signalling pathways involved in the development and progression of AAAs is essential for the development of medical therapy. METHODS AND RESULTS: We harvested specimens of the abdominal aorta with different pathological features in Angiotensin II (AngII)-infused ApoE-/- mice, conducted scRNA-seq, and identified a unique population of interferon-inducible monocytes/macrophages (IFNICs), which were amply found in the AAAs. Gene set variation analysis revealed that activation of the cytosolic DNA sensing cGAS-STING and JAK-STAT pathways promoted the secretion of type I interferons in monocytes/macrophages and differentiated them into IFNICs. We generated myeloid cell-specific deletion of Sting1 (Lyz2-Cre+/-; Sting1flox/flox) mice and performed bone marrow transplantation and found that myeloid cell-specific deletion of Sting1 or Ifnar1 significantly reduced the incidence of AAA, aortic rupture rate, and diameter of the abdominal aorta. Mechanistically, the activated pyroptosis- and inflammation-related signalling pathways, regulated by IRF7 in IFNICs, play critical roles in the developing AAAs. CONCLUSION: IFNICs are a unique monocyte/macrophage subset implicated in the development of AAAs and aortic rupture.

Single-cell sequencing reveals the impact of endothelial cell PIEZO1 expression on thoracic aortic aneurysm.

INTRODUCTION: Thoracic aortic aneurysm (TAA) is a severe vascular disease that threatens human life, characterized by focal dilatation of the entire aortic wall, with a diameter 1.5 times larger than normal. PIEZO1, a mechanosensitive cationic channel, monitors mechanical stimulations in the environment, transduces mechanical signals into electrical signals, and converts them into biological signals to activate intracellular signaling pathways. However, the role of PIEZO1 in TAA is still unclear. METHODS: We analyzed a single-cell database to investigate the expression level of PIEZO1 in TAA. We constructed a conditional knockout mouse model of Piezo1 and used the PIEZO1 agonist Yoda1 to intervene in the TAA model mice established by co-administration of BAPN and ANG-II. Finally, we explored the effect of Yoda1 on TAA in vitro. RESULTS AND DISCUSSION: We observed decreased PIEZO1 expression in TAA at both RNA and protein levels. Single-cell sequencing identified a specific reduction in Piezo1 expression in endothelial cells. Administration of PIEZO1 agonist Yoda1 prevented the formation of TAA. In PIEZO1 endothelial cell conditional knockout mice, Yoda1 inhibited TAA formation by interfering with PIEZO1. In vivo and in vitro experiments demonstrated that the effect of Yoda1 on endothelial cells involved macrophage infiltration, extracellular matrix degradation, and neovascularization. This study highlights the role of PIEZO1 in TAA and its potential as a therapeutic target, providing opportunities for clinical translation.

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases.

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Ncf1 knockout in smooth muscle cells exacerbates angiotensin II-induced aortic aneurysm and dissection by activating the STING pathway.

AIMS: Aortic aneurysm and dissection (AAD) is caused by the progressive loss of aortic smooth muscle cells (SMCs) and is associated with a high mortality rate. Identifying the mechanisms underlying SMC apoptosis is crucial for preventing AAD. Neutrophil cytoplasmic factor 1 (Ncf1) is essential in reactive oxygen species production and SMC apoptosis; Ncf1 absence leads to autoimmune diseases and chronic inflammation. Here, the role of Ncf1 in angiotensin II (Ang II)-induced AAD was investigated. METHODS AND RESULTS: Ncf1 expression increased in injured SMCs. Bioinformatic analysis identified Ncf1 as a mediator of AAD-associated SMC damage. Ncf1 expression is positively correlated with DNA replication and repair in SMCs of AAD aortas. AAD incidence increased in Ang II-challenged Sm22CreNcf1fl mice. Transcriptomics showed that Ncf1 knockout activated the stimulator of interferon genes (STING) and cell death pathways. The effects of Ncf1 on SMC death and the STING pathway in vitro were examined. Ncf1 regulated the hydrogen peroxide-mediated activation of the STING pathway and inhibited SMC apoptosis. Mechanistically, Ncf1 knockout promoted the ubiquitination of nuclear factor erythroid 2-related factor 2 (NRF2), thereby inhibiting the negative regulatory effect of NRF2 on the stability of STING mRNA and ultimately promoting STING expression. Additionally, the pharmacological inhibition of STING activation prevented AAD progression. CONCLUSION: Ncf1 deficiency in SMCs exacerbated Ang II-induced AAD by promoting NRF2 ubiquitination and degradation and activating the STING pathway. These data suggest that Ncf1 may be a potential therapeutic target for AAD treatment.

Targeted depletion of PD-1-expressing cells induces immune tolerance through peripheral clonal deletion.

Thymic negative selection of the T cell receptor (TCR) repertoire is essential for establishing self-tolerance and acquired allograft tolerance following organ transplantation. However, it is unclear whether and how peripheral clonal deletion of alloreactive T cells induces transplantation tolerance. Here, we establish that programmed cell death protein 1 (PD-1) is a hallmark of alloreactive T cells and is associated with clonal expansion after alloantigen encounter. Moreover, we found that diphtheria toxin receptor (DTR)-mediated ablation of PD-1+ cells reshaped the TCR repertoire through peripheral clonal deletion of alloreactive T cells and promoted tolerance in mouse transplantation models. In addition, by using PD-1-specific depleting antibodies, we found that antibody-mediated depletion of PD-1+ cells prevented heart transplant rejection and the development of experimental autoimmune encephalomyelitis (EAE) in humanized PD-1 mice. Thus, these data suggest that PD-1 is an attractive target for peripheral clonal deletion and induction of immune tolerance.

Outcomes of Heart Transplantation From Donation After Circulatory Death: An Up-to-date Systematic Meta-analysis.

BACKGROUND: Donation after circulatory death (DCD) heart transplantation (HTx) significantly expands the donor pool and reduces waitlist mortality. However, high-level evidence-based data on its safety and effectiveness are lacking. This meta-analysis aimed to compare the outcomes between DCD and donation after brain death (DBD) HTxs. METHODS: Databases, including MEDLINE, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials, were systematically searched for randomized controlled trials and observational studies reporting the outcomes of DCD and DBD HTxs published from 2014 onward. The data were pooled using random-effects models. Risk ratios (RRs) with 95% confidence intervals (CIs) were used as the summary measures for categorical outcomes and mean differences were used for continuous outcomes. RESULTS: Twelve eligible studies were included in the meta-analysis. DCD HTx was associated with lower 1-y mortality rate (DCD 8.13% versus DBD 10.24%; RR = 0.75; 95% CI, 0.59-0.96; P  = 0.02) and 5-y mortality rate (DCD 14.61% versus DBD 20.57%; RR = 0.72; 95% CI, 0.54-0.97; P  = 0.03) compared with DBD HTx. CONCLUSIONS: Using the current DCD criteria, HTx emerges as a promising alternative to DBD transplantation. The safety and feasibility of DCD hearts deserve further exploration and investigation.

Association between the neutrophil-to-lymphocyte ratio and in-hospital mortality in patients with chronic kidney disease and coronary artery disease in the intensive care unit.

BACKGROUND: The objective of this study was to investigate the correlation between neutrophil-to-lymphocyte ratios (NLR) and the risk of in-hospital death in patients admitted to the intensive care unit (ICU) with both chronic kidney disease (CKD) and coronary artery disease (CAD). METHODS: Data from the MIMIC-IV database, which includes a vast collection of more than 50,000 ICU admissions occurring between 2008 and 2019, was utilized in the study and eICU-CRD was conducted for external verification. The Boruta algorithm was employed for feature selection. Univariable and multivariable logistic regression analyses and multivariate restricted cubic spline regression were employed to scrutinize the association between NLR and in-hospital mortality. The receiver operating characteristic (ROC) curves were conducted to estimate the predictive ability of NLR. RESULTS: After carefully applying criteria to include and exclude participants, a total of 2254 patients with CKD and CAD were included in the research. The findings showed a median NLR of 7.3 (4.4, 12.1). The outcomes of multivariable logistic regression demonstrated that NLR significantly elevated the risk of in-hospital mortality (OR 2.122, 95% confidence interval [CI] 1.542-2.921, P < 0.001) after accounting for all relevant factors. Further insights from subgroup analyses unveiled that age and Sequential Organ Failure Assessment (SOFA) scores displayed an interactive effect in the correlation between NLR and in-hospital deaths. The NLR combined with traditional cardiovascular risk factors showed relatively great predictive value for in-hospital mortality (AUC 0.750). CONCLUSION: The findings of this research indicate that the NLR can be used as an indicator for predicting the likelihood of death during a patient's stay in the intensive care unit, particularly for individuals with both CAD and CKD. The results indicate that NLR may serve as a valuable tool for assessing and managing risks in this group at high risk. Further investigation is required to authenticate these findings and investigate the mechanisms that underlie the correlation between NLR and mortality in individuals with CAD and CKD.

MEK1/2-PKM2 Pathway Modulates the Immunometabolic Reprogramming of Proinflammatory Allograft-infiltrating Macrophages During Heart Transplant Rejection.

BACKGROUND: Emerging evidence has highlighted the role of macrophages in heart transplant rejection (HTR). However, the molecular signals modulating the immunometabolic phenotype of allograft-infiltrating macrophages (AIMs) during HTR remain unknown. METHODS: We analyzed single-cell RNA sequencing data from cardiac graft-infiltrating immunocytes to characterize the activation patterns and metabolic features of AIMs. We used flow cytometry to determine iNOS and PKM2 expression and MEK/ERK signaling activation levels in AIMs. We then generated macrophage-specific Mek1/2 knockout mice to determine the role of the MEK1/2-PKM2 pathway in the proinflammatory phenotype and glycolytic capacity of AIMs during HTR. RESULTS: Single-cell RNA sequencing analysis showed that AIMs had a significantly elevated proinflammatory and glycolytic phenotype. Flow cytometry analysis verified that iNOS and PKM2 expressions were significantly upregulated in AIMs. Moreover, MEK/ERK signaling was activated in AIMs and positively correlated with proinflammatory and glycolytic signatures. Macrophage-specific Mek1/2 deletion significantly protected chronic cardiac allograft rejection and inhibited the proinflammatory phenotype and glycolytic capacity of AIMs. Mek1/2 ablation also reduced the proinflammatory phenotype and glycolytic capacity of lipopolysaccharides + interferon-γ-stimulated macrophages. Mek1/2 ablation impaired nuclear translocation and PKM2 expression in macrophages. PKM2 overexpression partially restored the proinflammatory phenotype and glycolytic capacity of Mek1/2 -deficient macrophages. Moreover, trametinib, an Food and Drug Administration-approved MEK1/2 inhibitor, ameliorated chronic cardiac allograft rejection. CONCLUSIONS: These findings suggest that the MEK1/2-PKM2 pathway is essential for immunometabolic reprogramming of proinflammatory AIMs, implying that it may be a promising therapeutic target in clinical heart transplantation.

Interorgan communication with the liver: novel mechanisms and therapeutic targets.

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

The OX40-TRAF6 axis promotes CTLA-4 degradation to augment antitumor CD8+ T-cell immunity.

Immune checkpoint blockade (ICB), including anti-cytotoxic T-lymphocyte associated protein 4 (CTLA-4), benefits only a limited number of patients with cancer. Understanding the in-depth regulatory mechanism of CTLA-4 protein stability and its functional significance may help identify ICB resistance mechanisms and assist in the development of novel immunotherapeutic modalities to improve ICB efficacy. Here, we identified that TNF receptor-associated factor 6 (TRAF6) mediates Lys63-linked ubiquitination and subsequent lysosomal degradation of CTLA-4. Moreover, by using TRAF6-deficient mice and retroviral overexpression experiments, we demonstrated that TRAF6 promotes CTLA-4 degradation in a T-cell-intrinsic manner, which is dependent on the RING domain of TRAF6. This intrinsic regulatory mechanism contributes to CD8+ T-cell-mediated antitumor immunity in vivo. Additionally, by using an OX40 agonist, we demonstrated that the OX40-TRAF6 axis is responsible for CTLA-4 degradation, thereby controlling antitumor immunity in both tumor-bearing mice and patients with cancer. Overall, our findings demonstrate that the OX40-TRAF6 axis promotes CTLA-4 degradation and is a potential therapeutic target for the improvement of T-cell-based immunotherapies.

Assessing causality between second-hand smoking and potentially associated diseases in multiple systems: A two-sample Mendelian randomization study.

INTRODUCTION: The global disease burden may be exacerbated by exposure to passive smoking (SHS), with the workplace being a primary location for such exposure. Numerous epidemiological studies have identified SHS as a risk factor for diseases affecting various systems, including cardiovascular, respiratory, immune, endocrine, and nervous systems. The conventional observational study has certain methodological constraints which can be circumvented through a Mendelian randomization (MR) study. Our MR study intends to investigate the causal link between workplace exposure to SHS and the potential associated diseases. METHODS: Summary statistics data involving European participants was sourced from three databases: the UK Biobank, the FinnGen study, and the European Bioinformatics Institute. Genetic variants linked with exposure to SHS in the workplace were identified as instrumental variables. The MR was carried out using inverse variance weighted (IVW), MR-Egger, and weighted median methods. Sensitivity tests were also undertaken within the MR to evaluate the validity of the causality. RESULTS: According to the IVW model, genetically determined atrial fibrillation (AF) and stroke [P= 6.64E-04 and 5.68E-07, odds ratio = 2.030 and 2.494, 95% confidence interval = 1.350,3.051 and 1.743,3.569] were robustly associated with exposure to SHS in the workplace. Suggestive associations were found between workplace SHS and myocardial infarction (MI), asthma, and depression. CONCLUSIONS: The MR study demonstrates that exposure to SHS in the workplace is a significant risk factor for AF and stroke in European individuals. Whether workplace exposure to SHS influences other diseases and the causality between them requires further exploration. IMPLICATIONS: This study explored the causality between exposure to SHS in the workplace and potential associated diseases in multiple systems, including MI, AF, stroke, lung cancer, asthma, allergic disease, type 2 diabetes, and depression, using a MR study. The MR study can circumvent the methodological constraints of observational studies and establish a causal relationship. The two-sample MR analysis provides evidence supporting the causal association of frequent workplace SHS with AF and stroke. Individuals exposed to SHS in the workplace may also have a heightened risk of MI, asthma, and depression. However, whether SHS affects other diseases and the causality between them requires further investigation. To our knowledge, this is the first two-sample MR study to determine the causal relationship between SHS and potential diseases. As exposure to SHS in the workplace is a prevalent issue and may contribute to a global disease burden. The reduction of exposure following the introduction of smoke-free laws has led to a decrease in the admission rate for cardiac events and an improvement in health indicators. It is crucial to further advance smoke-free policies and their implementation.

A role of inflammaging in aortic aneurysm: new insights from bioinformatics analysis.

Introduction: Aortic aneurysms (AA) are prevalent worldwide with a notable absence of drug therapies. Thus, identifying potential drug targets is of utmost importance. AA often presents in the elderly, coupled with consistently raised serum inflammatory markers. Given that ageing and inflammation are pivotal processes linked to the evolution of AA, we have identified key genes involved in the inflammaging process of AA development through various bioinformatics methods, thereby providing potential molecular targets for further investigation. Methods: The transcriptome data of AA was procured from the datasets GSE140947, GSE7084, and GSE47472, sourced from the NCBI GEO database, whilst gene data of ageing and inflammation were obtained from the GeneCards Database. To identify key genes, differentially expressed analysis using the "Limma" package and WGCNA were implemented. Protein-protein intersection (PPI) analysis and machine learning (ML) algorithms were employed for the screening of potential biomarkers, followed by an assessment of the diagnostic value. Following the acquisition of the hub inflammaging and AA-related differentially expressed genes (IADEGs), the TFs-mRNAs-miRNAs regulatory network was established. The CIBERSORT algorithm was utilized to investigate immune cell infiltration in AA. The correlation of hub IADEGs with infiltrating immunocytes was also evaluated. Lastly, wet laboratory experiments were carried out to confirm the expression of hub IADEGs. Results: 342 and 715 AA-related DEGs (ADEGs) recognized from GSE140947 and GSE7084 datasets were procured by intersecting the results of "Limma" and WGCNA analyses. After 83 IADEGs were obtained, PPI analysis and ML algorithms pinpointed 7 and 5 hub IADEGs candidates respectively, and 6 of them demonstrated a high diagnostic value. Immune cell infiltration outcomes unveiled immune dysregulation in AA. In the wet laboratory experiments, 3 hub IADEGs, including BLNK, HLA-DRA, and HLA-DQB1, finally exhibited an expression trend in line with the bioinformatics analysis result. Discussion: Our research identified three genes - BLNK, HLA-DRA, and HLA-DQB1- that play a significant role in promoting the development of AA through inflammaging, providing novel insights into the future understanding and therapeutic intervention of AA.

MTHFD2 ablation in T cells protects against heart transplant rejection by perturbing IRF4/PD-1 pathway through the metabolic-epigenetic nexus.

BACKGROUND: One-carbon metabolism supports the activation, proliferation, and function of multiple immune cells. However, researchers have not clearly determined whether and how one-carbon metabolic enzymes contribute to heart transplant rejection. METHODS: We investigated the dynamic metabolic adaptation in grafts during heart transplant rejection by conducting transcriptomics, metabolomics and single-cell RNA sequencing studies of cardiac tissue from human and mouse heart transplant recipients. We also assessed the expression of the one-carbon metabolic enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) in cardiac grafts by immunofluorescence and flow cytometry assays. Then we constructed a murine heart transplant model with T cell-specific Mthfd2 knockout mice, analyzed T cells function by flow cytometry assays and enzyme-linked immunospot assays, and studied the mechanism by Cleavage Under Targets and Tagmentation assays. Finally, we studied the effect of a pharmacological inhibitor of MTHFD2 in humanized skin transplant model. RESULTS: We revealed that the one-carbon metabolism enzyme MTHFD2 was a hallmark of alloreactive T cells and was linked to T cell proliferation and function after exposure to alloantigen. And, Mthfd2 ablation prevented murine heart transplant rejection. Mechanistically, we found Mthfd2 ablation affected the interferon regulatory factor 4/programmed death-1 pathway through a metabolic-epigenetic mechanism involving H3K4me3. Furthermore, we found that inhibiting MTHFD2 attenuated human allograft rejection in a humanized skin transplant model. CONCLUSIONS: These data show that the one-carbon metabolic enzyme MTHFD2 serves as a metabolic checkpoint of alloreactive T cells and suggest that it may be a potential therapeutic target for heart transplant rejection.

Exploring the genetic association of allergic diseases with cardiovascular diseases: a bidirectional Mendelian randomization study.

Background: In observational and experimental studies, allergic diseases (AD) have been reported to be associated with some types of cardiovascular diseases (CVD), as both share common pathophysiological processes involving inflammation and metabolic disorders. However, the direction of the causal association between them remains unclear. This Mendelian randomization (MR) study aims to examine the bidirectional causality between AD and CVD. Methods: We utilized publicly available genome-wide association study (GWAS) summary statistics data from European participants in the UK Biobank and the IEU Open GWAS database. Genetic variants associated with AD, asthma, and CVD were identified and used as instrumental variables to investigate the genetically causal association between them. MR analyses were performed using various analytical methods, including inverse variance weighted-fixed effects (IVW-FE), inverse variance weighted-multiplicative random effects (IVW-RE), MR-Egger, weighted median, weighted mode, and maximum likelihood. Sensitivity tests were conducted to assess the validity of the causality. Results: The MR analysis with the IVW method revealed a genetically predicted association between AD and essential hypertension [odds ratio (OR)=0.9987, 95% confidence interval (CI): 0.9976-0.9998, P=0.024], as well as between asthma and atrial fibrillation (OR=1.001, 95% CI: 1.0004-1.0017, P=6.43E-05). In the reverse MR analyses, heart failure was associated with allergic diseases (OR=0.0045, 95% CI: 1.1890E-04 - 0.1695, P=0.004), while atherosclerosis (OR=8.7371E-08, 95% CI: 1.8794E-14 - 4.0617E-01, P=0.038) and aortic aneurysm and dissection (OR=1.7367E-07, 95% CI: 3.8390E-14 - 7.8567E-01, P=0.046) might be protective factors of asthma. However, after a Bonferroni correction, only the association between asthma and atrial fibrillation remained robust. Conclusion: The MR study revealed that asthma is a predominant risk of atrial fibrillation in European individuals, consistent with most experimental and observational studies. Whether AD affects other CVD and the causality between them needs further investigation.

MicroRNA let-7a mediates posttranscriptional inhibition of Nr4A1 and exacerbates cardiac allograft rejection.

BACKGROUND: Acute allograft rejection remains a major obstacle after heart transplantation, and CD4+ T cells play a crucial role in allograft rejection. Upregulation of Nr4A1 could regulate CD4+ T-cell function and alleviate allograft rejection. However, the regulatory mechanism of Nr4A1 in allograft rejection remains elusive. METHODS: BALB/c mouse hearts were transplanted into WT C57BL/6 mice, and dynamic detection of the changes in Nr4A1 expression revealed that Nr4A1 was regulated posttranscriptionally after heart transplantation. Potential upstream miRNAs of Nr4A1 were screened, and the transfection of cells with these miRNA mimics/inhibitors and dual-luciferase reporter experiments were performed to clarify the regulatory mechanism of miRNAs on Nr4A1 expression. The miRNA agomiR/antagomiR was applied in vivo to validate the role of the corresponding miRNA in heart transplantation. Finally, Nr4A1 knockout mice and an adoptive T-cell cotransfer model were used to confirm the specific effects of miRNA. RESULTS: The expression of Nr4A1 protein (rather than mRNA) exhibited a trend of initially increasing and then decreasing rapidly, and this phenomenon could not be reversed by lysosomal or proteasomal inhibitors. The miRNA let-7a directly binds to the Nr4A1 3'UTR and posttranscriptionally regulates Nr4A1 expression. The let-7a antagomiR prolonged allograft survival and regulated CD4+ T-cell function by upregulating Nr4A1 protein expression in CD4+ T cells. CONCLUSIONS: This study confirmed that let-7a is a potential target for interfering with Nr4A1 expression in CD4+ T cells and preventing the pathological progression of cardiac allograft rejection.

Immune Regulation of the Liver Through the PCSK9/CD36 Pathway During Heart Transplant Rejection.

BACKGROUND: PCSK9 (proprotein convertase subtilisin/kexin 9), which is mainly secreted by the liver, is not only a therapeutic target for hyperlipidemia and cardiovascular disease, but also has been implicated in the immune regulation of infections and tumors. However, the role of PCSK9 and the liver in heart transplant rejection (HTR) and the underlying mechanisms remain unclear. METHODS: We assessed serum PCSK9 expression in both murine and human recipients during HTR and investigated the effect of PCSK9 ablation on HTR by using global knockout mice and a neutralizing antibody. Moreover, we performed multiorgan histological and transcriptome analyses, and multiomics and single-cell RNA-sequencing studies of the liver during HTR, as well. We further used hepatocyte-specific Pcsk9 knockout mice to investigate whether the liver regulated HTR through PCSK9. Last, we explored the regulatory effect of the PCSK9/CD36 pathway on the phenotype and function of macrophages in vitro and in vivo. RESULTS: Here, we report that murine and human recipients have high serum PCSK9 levels during HTR. PCSK9 ablation prolonged cardiac allograft survival and attenuated the infiltration of inflammatory cells in the graft and the expansion of alloreactive T cells in the spleen. Next, we demonstrated that PCSK9 was mainly produced and significantly upregulated in the recipient liver, which also showed a series of signaling changes, including changes in the TNF-α (tumor necrosis factor α) and IFN-γ (interferon γ) signaling pathways and the bile acid and fatty acid metabolism pathways. We found mechanistically that TNF-α and IFN-γ synergistically promoted PCSK9 expression in hepatocytes through the transcription factor SREBP2 (sterol regulatory element binding protein 2). Moreover, in vitro and in vivo studies indicated that PCSK9 inhibited CD36 expression and fatty acid uptake by macrophages and strengthened the proinflammatory phenotype, which facilitated their ability to promote proliferation and IFN-γ production by donor-reactive T cells. Last, we found that the protective effect of PCSK9 ablation against HTR is dependent on the CD36 pathway in the recipient. CONCLUSIONS: This study reveals a novel mechanism for immune regulation by the liver through the PCSK9/CD36 pathway during HTR, which influences the phenotype and function of macrophages and suggests that the modulation of this pathway may be a potential therapeutic target to prevent HTR.

Lysosomal-associated protein transmembrane 5 ameliorates non-alcoholic steatohepatitis by promoting the degradation of CDC42 in mice.

Non-alcoholic steatohepatitis (NASH) has received great attention due to its high incidence. Here, we show that lysosomal-associated protein transmembrane 5 (LAPTM5) is associated with NASH progression through extensive bioinformatical analysis. The protein level of LAPTM5 bears a negative correlation with NAS score. Moreover, LAPTM5 degradation is mediated through its ubiquitination modification by the E3 ubquitin ligase NEDD4L. Discovered by experiments conducted on male mice, hepatocyte-specific depletion of Laptm5 exacerbates mouse NASH symptoms. In contrast, Laptm5 overexpression in hepatocytes exerts diametrically opposite effects. Mechanistically, LAPTM5 interacts with CDC42 and promotes its degradation through a lysosome-dependent manner under the stimulation of palmitic acid, thus inhibiting activation of the mitogen-activated protein kinase signaling pathway. Finally, adenovirus-mediated hepatic Laptm5 overexpression ameliorates aforementioned symptoms in NASH models.

Age at SARS-CoV-2 infection and psychological and physical recovery among Chinese health care workers with severe COVID-19 at 28 months after discharge: A cohort study.

Background: No prior study had reported the psychological and physical recovery of patients with COVID-19 2~3 years after discharge from the hospital. Moreover, it is not clear whether there is any difference in the health status of the patients with COVID-19 of different ages after discharge from the hospital. Methods: Embedding in the "Rehabilitation Care Project for Medical Staff Infected with COVID-19" in China, this study included 271 health care workers (HCWs) with severe COVID-19. Their status of health-related quality of life, persistent symptoms, functional fitness and immune function at 28 months after discharge were followed, and compared according to tertiles of age at SARS-CoV-2 infection (group of younger (≤ 33 years); medium (34-42 years); and older (≥43 years)). Multivariate linear regression and multivariable adjusted logistic regression models were applied in investigating the associations of age at SARS-CoV-2 infection and outcomes. Results: At 28 months after discharge, 76% of the HCWs with severe COVID-19 had symptom of fatigue/weakness; 18.7% of the HCWs with severe COVID-19 did not fully recover their functional fitness; the decrease of CD3+ T cells, CD8+ T cells and the increase of natural killer cells accounted for 6.6, 6.6, and 5.5%, respectively. Compared with the HCWs with severe COVID-19 in younger group, HCWs with severe COVID-19 in older group had lower scores regarding physical functioning, role physical, bodily pain and role emotional; HCWs with severe COVID-19 in older group had higher risk of cough, joint pain, hearing loss and sleep disorder; HCWs with severe COVID-19 in older group scored lower on flexibility test. The variance of relative numbers of CD3+ T cells, CD8+ T cells and natural killer cells among HCWs with severe COVID-19 of different age groups were significant. Conclusions: This study demonstrated that older HCWs with severe COVID-19 recovered slower than those with younger age regarding health-related quality of life, persistent symptoms, functional fitness and immune function at 28 months after discharge. Effective exercise interventions regarding flexibility should be performed timely to speed their rehabilitation, especially among those with older age.

Aortic Dissection Research in China: Analysis of Studies Funded by the National Natural Science Foundation of China.

OBJECTIVE: The National Natural Science Foundation of China (NSFC) has made great progress in promoting the development of aortic dissection research in recent years. This study aimed to examine the development and research status of aortic dissection research in China so as to provide references for future research. METHODS: The NSFC projects data from 2008 to 2019 were collected from the Internet-based Science Information System and other websites utilized as search engines. The publications and citations were retrieved by Google Scholar, and the impact factors were checked by the InCite Journal Citation Reports database. The investigator's degree and department were identified from the institutional faculty profiles. RESULTS: A total of 250 grant funds totaling 124.3 million Yuan and resulting in 747 publications were analyzed. The funds in economically developed and densely populated areas were more than those in underdeveloped and sparsely populated areas. There was no significant difference in the amount of funding per grant between different departments' investigators. However, the funding output ratios of the grants for cardiologists were higher than those for basic science investigators. The amount of funding for clinical researchers and basic scientific researchers in aortic dissection was also similar. Clinical researchers were better in terms of the funding output ratio. CONCLUSION: These results suggest that the medical and scientific research level of aortic dissection in China has been greatly improved. However, there are still some problems that urgently need to be solved, such as the unreasonable regional allocation of medical and scientific research resources, and the slow transition from basic science to clinical practice.