NDP52 Protects Against Myocardial Infarction-Provoked Cardiac Anomalies Through Promoting Autophagosome-Lysosome Fusion via Recruiting TBK1 and RAB7

CALCOCO2 prevents AngII-induced atrial remodeling by regulating the interaction between mitophagy and mitochondrial stress

BACKGROUND

The biological functions of mitochondrial complexes are closely related to the development of atrial fibrillation (AF). Calcium binding and coiled-coil domain 2 (CALCOCO2) is a novel and specific receptor for mitophagy; however, its function in AF remains unknown. Therefore, this study aimed to investigate the role and molecular mechanisms of CALCOCO2 in AF, especially its regulatory mechanism in mitophagy and mitochondrial stress.

METHODS

Mice and HL-1 cells were treated with AngII to establish in vitro and in vivo AF models. Additionally, we examined the effect of CALCOCO2 or DAP3 Binding Cell Death Enhancer 1 (DELE1) overexpression on mitophagy and mitochondrial stress in AF models. To investigate the role of mitophagy in the regulatory effects of CALCOCO2 in AF, HL-1 cells were treated with chloroquine, a mitophagy inhibitor. Moreover, mitochondrial parameters were examined using specific fluorescent probes, transmission electron microscopy, western blotting, immunohistochemistry, and confocal microscopy.

RESULTS

AngII severely impaired the normal morphology and function of mitochondria; inhibited mitophagy; promoted atrial mitochondrial stress, fibrosis, and oxidative stress; and accelerated the progression of atrial remodeling in atrial myocytes. However, CALCOCO2 overexpression reversed/ameliorated these AF-induced changes. Additionally, CALCOCO2 overexpression restored mitochondrial homeostasis in atrial muscle by activating mitophagy and ameliorating mitochondrial stress. Mechanistically, DELE1 overexpression increased mitochondrial reactive oxygen species level and the expression of mitochondrial stress proteins (HRI, eIF2α, and ATF4) even in CALCOCO2-expressing in vitro AF models..

CONCLUSIONS

CALCOCO2 may serve as a potential target for AF therapy to prevent or reverse the progression of atrial remodeling by regulating mitophagy and DELE1-mediated mitochondrial stress.

Cardiomyocyte-specific Tbk1 deletion aggravated chronic doxorubicin cardiotoxicity via inhibition of mitophagy

Doxorubicin (Dox) use is limited by Dox-induced cardiotoxicity. TANK-blinding kinase 1 (TBK1) is an important kinase involved in the regulation of mitophagy, but the role of TBK1 in cardiomyocytes in chronic Dox-induced cardiomyopathy remains unclear. Cardiomyocyte-specific Tbk1 knockout (Tbk1CKO) mice received Dox (6 mg/kg, injected intraperitoneally) once a week for 4 times, and cardiac assessment was performed 4 weeks after the final Dox injection. Adenoviruses encoding Tbk1 or containing shRNA targeting Tbk1, or a TBK1 phosphorylation inhibitor were used for overexpression or knockdown of Tbk1, or inhibit phosphorylation of TBK1 in isolated primary cardiomyocytes. Our results revealed that moderate Dox challenge decreased TBK1 phosphorylation (with no effect on TBK1 protein levels), resulting in compromised myocardial function, obvious mortality and overt interstitial fibrosis, and the effects were accentuated by Tbk1 deletion. Dox provoked mitochondrial membrane potential collapse and oxidative stress, the effects of which were exacerbated and mitigated by Tbk1 knockdown, specific inhibition of phosphorylation and overexpression, respectively. However, Tbk1 （Ser172A） overexpression did not alleviate these effects. Further scrutiny revealed that TBK1 exerted protective effects on mitochondria via SQSTM1/P62-mediated mitophagy. Tbk1 overexpression mediated cardioprotective effects on Dox-induced cardiotoxicity were cancelled off by Sqstm1/P62 knockdown. Moreover, TBK1-mitophagy-mitochondria cascade was confirmed in heart tissues from dilated cardiomyopathy patients. Taken together, our findings denoted a pivotal role of TBK1 in Dox-induced mitochondrial injury and cardiotoxicity possibly through its phosphorylation and SQSTM1/P62-mediated mitophagy.

FBXL4 protects against HFpEF through Drp1-Mediated regulation of mitochondrial dynamics and the downstream SERCA2a

AIMS

Heart failure with preserved ejection fraction (HFpEF) is a devastating health issue although limited knowledge is available for its pathogenesis and therapeutics. Given the perceived involvement of mitochondrial dysfunction in HFpEF, this study was designed to examine the role of mitochondrial dynamics in the etiology of HFpEF.

METHOD AND RESULTS

Adult mice were placed on a high fat diet plus l-NAME in drinking water ('two-hit' challenge to mimic obesity and hypertension) for 15 consecutive weeks. Mass spectrometry revealed pronounced changes in mitochondrial fission protein Drp1 and E3 ligase FBXL4 in 'two-hit' mouse hearts. Transfection of FBXL4 rescued against HFpEF-compromised diastolic function, cardiac geometry, and mitochondrial integrity without affecting systolic performance, in conjunction with altered mitochondrial dynamics and integrity (hyperactivation of Drp1 and unchecked fission). Mass spectrometry and co-IP analyses unveiled an interaction between FBXL4 and Drp1 to foster ubiquitination and degradation of Drp1. Truncated mutants of FBXL4 (Delta-Fbox) disengaged interaction between FBXL4 and Drp1. Metabolomic and proteomics findings identified deranged fatty acid and glucose metabolism in HFpEF patients and mice. A cellular model was established with concurrent exposure of high glucose and palmitic acid as a 'double-damage' insult to mimic diastolic anomalies in HFpEF. Transfection of FBXL4 mitigated 'double-damage'-induced cardiomyocyte diastolic dysfunction and mitochondrial injury, the effects were abolished and mimicked by Drp1 knock-in and knock-out, respectively. HFpEF downregulated sarco(endo)plasmic reticulum (SR) Ca2+ uptake protein SERCA2a while upregulating phospholamban, RYR1, IP3R1, IP3R3 and Na+-Ca2+ exchanger with unaltered SR Ca2+ load. FBXL4 ablated 'two-hit' or 'double-damage'-induced changes in SERCA2a, phospholamban and mitochondrial injury.

CONCLUSION

FBXL4 rescued against HFpEF-induced cardiac remodeling, diastolic dysfunction, and mitochondrial injury through reverting hyperactivation of Drp1-mediated mitochondrial fission, underscoring the therapeutic promises of FBXL4 in HFpEF.

TRIM27 Promotes Endothelial Progenitor Cell Apoptosis in Patients with In-Stent Restenosis by Ubiquitinating TBK1

Approximately 2-10% in-stent restenosis (ISR) may occur following percutaneous coronary intervention (PCI) despite the use of modern drug-eluting stents (DES); thus, our study aimed to explore the effects of tripartite motif-containing (TRIM) 27 on ISR and the underlying mechanism. For this purpose, a total of 42 patients undergoing coronary angiography who had prior coronary angiography with DES implantation were recruited. Endothelial progenitor cells (EPCs) markers (defined as CD34 and vascular endothelial growth factoreceptor-2 (VEGFR-2)) in peripheral blood were measured to asses the circulating EPC level. The TRIM family-related gene expressions were detected by reverse transcription-quantitative polymerase chain reaction. Results suggested that ISR patients had reduced CD34+VEGFR-2+ and increased apoptosis rate of EPCs, along with upregulated TRIM27 and TRIM37 and downregulated TRIM28. TRIM27 promoted and TBK1 inhibited the apoptosis rate of EPCs. Mechanically, TRIM27 interacted with TBK1 to ubiquitinate TBK1 in in vitro study. In summary, TRIM27 promoted the progression of ISR in patients after PCI by ubiquitinating TBK1, which might provide novel ideas for the clinical treatment of ISR.

FOXO3/Rab7-Mediated Lipophagy and Its Role in Zn-Induced Lipid Metabolism in Yellow Catfish (Pelteobagrus fulvidraco)

Lipophagy is a selective autophagy that regulates lipid metabolism and reduces hepatic lipid deposition. However, the underlying mechanism has not been understood in fish. In this study, we used micronutrient zinc (Zn) as a regulator of autophagy and lipid metabolism and found that Ras-related protein 7 (rab7) was involved in Zn-induced lipophagy in hepatocytes of yellow catfish Pelteobagrus pelteobagrus. We then characterized the rab7 promoter and identified binding sites for a series of transcription factors, including Forkhead box O3 (FOXO3). Site mutation experiments showed that the -1358/-1369 bp FOXO3 binding site was responsible for Zn-induced transcriptional activation of rab7. Further studies showed that inhibition of rab7 significantly inhibited Zn-induced lipid degradation by lipophagy. Moreover, rab7 inhibitor also mitigated the Zn-induced increase of cpt1α and acadm expression. Our results suggested that Zn exerts its lipid-lowering effect partly through rab7-mediated lipophagy and FA β-oxidation in hepatocytes. Overall, our findings provide novel insights into the FOXO3/rab7 axis in lipophagy regulation and enhance the understanding of lipid metabolism by micronutrient Zn, which may help to reduce excessive lipid accumulation in fish.

NDP52 SUMOylation contributes to low-dose X-rays-induced cardiac hypertrophy through PINK1/Parkin-mediated mitophagy via MUL1/SUMO2 signalling

Radiation-induced heart damage caused by low-dose X-rays has a significant impact on tumour patients' prognosis, with cardiac hypertrophy being the most severe noncarcinogenic adverse effect. Our previous study demonstrated that mitophagy activation promoted cardiac hypertrophy, but the underlying mechanisms remained unclear. In the present study, PARL-IN-1 enhanced excessive hypertrophy of cardiomyocytes and exacerbated mitochondrial damage. Isobaric tags for relative and absolute quantification-based quantitative proteomics identified NDP52 as a crucial target mediating cardiac hypertrophy induced by low-dose X-rays. SUMOylation proteomics revealed that the SUMO E3 ligase MUL1 facilitated NDP52 SUMOylation through SUMO2. Co-IP coupled with LC-MS/MS identified a critical lysine residue at position 262 of NDP52 as the key site for SUMO2-mediated SUMOylation of NDP52. The point mutation plasmid NDP52K262R inhibited mitophagy under MUL1 overexpression, as evidenced by inhibition of LC3 interaction with NDP52, PINK1 and LAMP2A. A mitochondrial dissociation study revealed that NDP52K262R inhibited PINK1 targeting to endosomes early endosomal marker (EEA1), late/lysosome endosomal marker (LAMP2A) and recycling endosomal marker (RAB11), and laser confocal microscopy confirmed that NDP52K262R impaired the recruitment of mitochondria to the autophagic pathway through EEA1/RAB11 and ATG3, ATG5, ATG16L1 and STX17, but did not affect mitochondrial delivery to lysosomes via LAMP2A for degradation. In conclusion, our findings suggest that MUL1-mediated SUMOylation of NDP52 plays a crucial role in regulating mitophagy in the context of low-dose X-ray-induced cardiac hypertrophy. Two hundred sixty-second lysine of NDP52 is identified as a key SUMOylation site for low-dose X-ray promoting mitophagy activation and cardiac hypertrophy. Collectively, this study provides novel implications for the development of therapeutic strategies aimed at preventing the progression of cardiac hypertrophy induced by low-dose X-rays.

Identification of mitophagy-related genes with potential clinical utility in myocardial infarction at transcriptional level

Background

Myocardial infarction (MI) ranks among the most prevalent cardiovascular diseases. Insufficient blood flow to the coronary arteries always leads to ischemic necrosis of the cardiac muscle. However, the mechanism of myocardial injury after MI remains unclear. This article aims to explore the potential common genes between mitophagy and MI and to construct a suitable prediction model.

Methods

Two Gene Expression Omnibus (GEO) datasets (GSE62646 and GSE59867) were used to screen the differential expression genes in peripheral blood. SVM, RF, and LASSO algorithm were employed to find MI and mitophagy-related genes. Moreover, DT, KNN, RF, SVM and LR were conducted to build the binary models, and screened the best model to further external validation (GSE61144) and internal validation (10-fold cross validation and Bootstrap), respectively. The performance of various machine learning models was compared. In addition, immune cell infiltration correlation analysis was conducted with MCP-Counter and CIBERSORT.

Results

We finally identified ATG5, TOMM20, MFN2 transcriptionally differed between MI and stable coronary artery diseases. Both internal and external validation supported that these three genes could accurately predict MI withAUC = 0.914 and 0.930 by logistic regression, respectively. Additionally, functional analysis suggested that monocytes and neutrophils might be involved in mitochondrial autophagy after myocardial infarction.

Conclusion

The data showed that the transcritional levels of ATG5, TOMM20 and MFN2 in patients with MI were significantly different from the control group, which might be helpful to further accurately diagnose diseases and have potential application value in clinical practice.

TBK1-medicated DRP1 phosphorylation orchestrates mitochondrial dynamics and autophagy activation in osteoarthritis

Mitochondrial dynamics, including mitochondrial fission and fusion, are critical for maintaining mitochondrial functions. Evidence shows that TANK-binding kinase 1 (TBK1) regulates mitochondrial fusion and fission and then mitophagy. Since a previous study demonstrates a strong correlation between mitophagy and osteoarthritis (OA), we herein investigated the potential role of TBK1 in OA process and mitochondrial functions. We demonstrated a strong correlation between TBK1 and OA, evidenced by significantly downregulated expression of TBK1 in cartilage tissue samples of OA patients and in the chondrocytes of aged mice, as well as TNF-α-stimulated phosphorylation of TBK1 in primary mouse chondrocytes. TBK1 overexpression significantly attenuated TNF-α-induced apoptosis and abnormal mitochondrial function in primary mouse chondrocytes. Furthermore, TBK1 overexpression induced remodeling of mitochondrial morphology by directly phosphorylating dynamin-related protein 1 (DRP1) at Ser637, abolishing the fission of DRP1 and preventing its fragmentation function. Moreover, TBK1 recruitment and DRP1 phosphorylation at Ser637 was necessary for engulfing damaged mitochondria by autophagosomal membranes during mitophagy. Moreover, we demonstrated that APMK/ULK1 signaling contributed to TBK1 activation. In OA mouse models established by surgical destabilization of the medial meniscus, intraarticular injection of lentivirus-TBK1 significantly ameliorated cartilage degradation via regulation of autophagy and alleviation of cell apoptosis. In conclusion, our results suggest that the TBK1/DRP1 pathway is involved in OA and pharmacological targeting of the TBK1-DRP1 cascade provides prospective therapeutic benefits for the treatment of OA.

SUMOylation targeting mitophagy in cardiovascular diseases

Small ubiquitin-like modifier (SUMO) plays a key regulatory role in cardiovascular diseases, such as cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. As a multifunctional posttranslational modification molecule in eukaryotic cells, SUMOylation is essentially associated with the regulation of mitochondrial dynamics, especially mitophagy, which is involved in the progression and development of cardiovascular diseases. SUMOylation targeting mitochondrial-associated proteins is admittedly considered to regulate mitophagy activation and mitochondrial functions and dynamics, including mitochondrial fusion and fission. SUMOylation triggers mitochondrial fusion to promote mitochondrial dysfunction by modifying Fis1, OPA1, MFN1/2, and DRP1. The interaction between SUMO and DRP1 induces SUMOylation and inhibits lysosomal degradation of DRP1, which is further involved in the regulation of mitochondrial fission. Both SUMOylation and deSUMOylation contribute to the initiation and activation of mitophagy by regulating the conjugation of MFN1/2 SERCA2a, HIF1α, and PINK1. SUMOylation mediated by the SUMO molecule has attracted much attention due to its dual roles in the development of cardiovascular diseases. In this review, we systemically summarize the current understanding underlying the expression, regulation, and structure of SUMO molecules; explore the biochemical functions of SUMOylation in the initiation and activation of mitophagy; discuss the biological roles and mechanisms of SUMOylation in cardiovascular diseases; and further provide a wider explanation of SUMOylation and deSUMOylation research to provide a possible therapeutic strategy for cardiovascular diseases. Considering the precise functions and exact mechanisms of SUMOylation in mitochondrial dysfunction and mitophagy will provide evidence for future experimental research and may serve as an effective approach in the development of novel therapeutic strategies for cardiovascular diseases. Regulation and effect of SUMOylation in cardiovascular diseases via mitophagy. SUMOylation is involved in multiple cardiovascular diseases, including cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. Since it is expressed in multiple cells associated with cardiovascular disease, SUMOylation can be regulated by numerous ligases, including the SENP family proteins PIAS1, PIASy/4, UBC9, and MAPL. SUMOylation regulates the activation and degradation of PINK1, SERCA2a, PPARγ, ERK5, and DRP1 to mediate mitochondrial dynamics, especially mitophagy activation. Mitophagy activation regulated by SUMOylation further promotes or inhibits ventricular diastolic dysfunction, perfusion injury, ventricular remodelling and ventricular noncompaction, which contribute to the development of cardiovascular diseases.

Programmed Cell Death: Complex Regulatory Networks in Cardiovascular Disease

Abnormalities in programmed cell death (PCD) signaling cascades can be observed in the development and progression of various cardiovascular diseases, such as apoptosis, necrosis, pyroptosis, ferroptosis, and cell death associated with autophagy. Aberrant activation of PCD pathways is a common feature leading to excessive cardiac remodeling and heart failure, involved in the pathogenesis of various cardiovascular diseases. Conversely, timely activation of PCD remodels cardiac structure and function after injury in a spatially or temporally restricted manner and corrects cardiac development similarly. As many cardiovascular diseases exhibit abnormalities in PCD pathways, drugs that can inhibit or modulate PCD may be critical in future therapeutic strategies. In this review, we briefly describe the process of various types of PCD and their roles in the occurrence and development of cardiovascular diseases. We also discuss the interplay between different cell death signaling cascades and summarize pharmaceutical agents targeting key players in cell death signaling pathways that have progressed to clinical trials. Ultimately a better understanding of PCD involved in cardiovascular diseases may lead to new avenues for therapy.

Molecular Signaling to Preserve Mitochondrial Integrity against Ischemic Stress in the Heart: Rescue or Remove Mitochondria in Danger

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide, and ischemic heart disease is the most common cause of heart failure (HF). The heart is a high-energy demanding organ, and myocardial energy reserves are limited. Mitochondria are the powerhouses of the cell, but under stress conditions, they become damaged, release necrotic and apoptotic factors, and contribute to cell death. Loss of cardiomyocytes plays a significant role in ischemic heart disease. In response to stress, protective signaling pathways are activated to limit mitochondrial deterioration and protect the heart. To prevent mitochondrial death pathways, damaged mitochondria are removed by mitochondrial autophagy (mitophagy). Mitochondrial quality control mediated by mitophagy is functionally linked to mitochondrial dynamics. This review provides a current understanding of the signaling mechanisms by which the integrity of mitochondria is preserved in the heart against ischemic stress.