Dynamin-Related Protein 1 Inhibition Attenuates Cardiovascular Calcification in the Presence of Oxidative Stress

Transcriptomic analysis reveals molecular characterization and immune landscape of PANoptosis-related genes in atherosclerosis

BACKGROUND

Atherosclerosis is a chronic inflammatory disease characterized by abnormal lipid deposition in the arteries. Programmed cell death is involved in the inflammatory response of atherosclerosis, but PANoptosis, as a new form of programmed cell death, is still unclear in atherosclerosis. This study explored the key PANoptosis-related genes involved in atherosclerosis and their potential mechanisms through bioinformatics analysis.

METHODS

We evaluated differentially expressed genes (DEGs) and immune infiltration landscape in atherosclerosis using microarray datasets and bioinformatics analysis. By intersecting PANoptosis-related genes from the GeneCards database with DEGs, we obtained a set of PANoptosis-related genes in atherosclerosis (PANoDEGs). Functional enrichment analysis of PANoDEGs was performed and protein-protein interaction (PPI) network of PANoDEGs was established. The machine learning algorithms were used to identify the key PANoDEGs closely linked to atherosclerosis. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic potency of key PANoDEGs. CIBERSORT was used to analyze the immune infiltration patterns in atherosclerosis, and the Spearman method was used to study the relationship between key PANoDEGs and immune infiltration abundance. The single gene enrichment analysis of key PANoDEGs was investigated by GSEA. The transcription factors and target miRNAs of key PANoDEGs were predicted by Cytoscape and online database, respectively. The expression of key PANoDEGs was validated through animal and cell experiments.

RESULTS

PANoDEGs in atherosclerosis were significantly enriched in apoptotic process, pyroptosis, necroptosis, cytosolic DNA-sensing pathway, NOD-like receptor signaling pathway, lipid and atherosclerosis. Four key PANoDEGs (ZBP1, SNHG6, DNM1L, and AIM2) were found to be closely related to atherosclerosis. The ROC curve analysis demonstrated that the key PANoDEGs had a strong diagnostic potential in distinguishing atherosclerotic samples from control samples. Immune cell infiltration analysis revealed that the proportion of initial B cells, plasma cells, CD4 memory resting T cells, and M1 macrophages was significantly higher in atherosclerotic tissues compared to normal tissues. Spearman analysis showed that key PANoDEGs showed strong correlations with immune cells such as T cells, macrophages, plasma cells, and mast cells. The regulatory networks of the four key PANoDEGs were established. The expression of key PANoDEGs was verified in further cell and animal experiments.

CONCLUSIONS

This study evaluated the expression changes of PANoptosis-related genes in atherosclerosis, providing a reference direction for the study of PANoptosis in atherosclerosis and offering potential new avenues for further understanding the pathogenesis and treatment strategies of atherosclerosis.

Efferocytosis by macrophages in physiological and pathological conditions: regulatory pathways and molecular mechanisms

Efferocytosis is defined as the highly effective phagocytic removal of apoptotic cells (ACs) by professional or non-professional phagocytes. Tissue-resident professional phagocytes ("efferocytes"), such as macrophages, have high phagocytic capacity and are crucial to resolve inflammation and aid in homeostasis. Recently, numerous exciting discoveries have revealed divergent (and even diametrically opposite) findings regarding metabolic immune reprogramming associated with efferocytosis by macrophages. In this review, we highlight the key metabolites involved in the three phases of efferocytosis and immune reprogramming of macrophages under physiological and pathological conditions. The next decade is expected to yield further breakthroughs in the regulatory pathways and molecular mechanisms connecting immunological outcomes to metabolic cues as well as avenues for "personalized" therapeutic intervention.

Oxidized phospholipid POVPC contributes to vascular calcification by triggering ferroptosis of vascular smooth muscle cells

Vascular calcification is an actively regulated biological process resembling bone formation, and osteogenic differentiation of vascular smooth muscle cells (VSMCs) plays a crucial role in this process. 1-Palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC), an oxidized phospholipid, is found in atherosclerotic plaques and has been shown to induce oxidative stress. However, the effects of POVPC on osteogenic differentiation and calcification of VSMCs have yet to be studied. In the present study, we investigated the role of POVPC in vascular calcification using in vitro and ex vivo models. POVPC increased mineralization of VSMCs and arterial rings, as shown by alizarin red staining. In addition, POVPC treatment increased expression of osteogenic markers Runx2 and BMP2, indicating that POVPC promotes osteogenic transition of VSMCs. Moreover, POVPC increased oxidative stress and impaired mitochondria function of VSMCs, as shown by increased ROS levels, impairment of mitochondrial membrane potential, and decreased ATP levels. Notably, ferroptosis triggered by POVPC was confirmed by increased levels of intracellular ROS, lipid ROS, and MDA, which were decreased by ferrostatin-1, a ferroptosis inhibitor. Furthermore, ferrostatin-1 attenuated POVPC-induced calcification of VSMCs. Taken together, our study for the first time demonstrates that POVPC promotes vascular calcification via activation of VSMC ferroptosis. Reducing the levels of POVPC or inhibiting ferroptosis might provide a novel strategy to treat vascular calcification.

[Ketone Body Metabolism and Renal Diseases]

A ketogenic diet limits energy supply from glucose and stimulates lipolysis, lipid oxidation, and ketogenesis, resulting in elevated levels of ketone bodies in the bloodstream. Ketone bodies are synthesized in the mitochondrial matrix of liver cells and β-hydroxybutyric acid (BHB) is the most abundant type of ketone body. Herein, we reviewed published findings on the metabolism of ketone bodies and the role of BHB in renal diseases. Through blood circulation, ketone bodies reach metabolically active tissues and provides an alternative source of energy. BHB, being a signaling molecule, mediates various types of cellular signal transduction and participates in the development and progression of many diseases. BHB also has protective and therapeutic effects on a variety of renal diseases. BHB improves the prognosis of renal diseases, such as diabetic kidney disease, chronic kidney disease, acute kidney injury, and polycystic kidney disease, through its antioxidant, anti-inflammatory, and stress response mechanisms. Previous studies have focused on the role of ketone bodies in regulating inflammation and oxidative stress in immune cells. Investigations into the effect of elevated levels of ketone bodies on the metabolism of renal podocytes and tubular cells remain inconclusive. Further research is needed to investigate the effect of BHB on podocyte damage and podocyte senescence in renal diseases.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) drives angiotensin II-induced vascular remodeling through regulating mitochondrial fragmentation

BACKGROUND

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a novel instigator for mitochondrial dysfunction, and plays an important role in the pathogenesis of cardiovascular diseases. However, the role and mechanism of DNA-PKcs in angiotensin II (Ang II)-induced vascular remodeling remains obscure.

METHODS

Rat aortic smooth muscle cells (SMC) and VSMC-specific DNA-PKcs knockout (DNA-PKcsΔVSMC) mice were employed to examine the role of DNA-PKcs in vascular remodeling and the underlying mechanisms. Blood pressure of mice was monitored using the tail-cuff and telemetry methods. The role of DNA-PKcs in vascular function was evaluated using vascular relaxation assessment.

RESULTS

In the tunica media of remodeled mouse thoracic aortas, and renal arteries from hypertensive patients, elevated DNA-PKcs expression was observed along with its cytoplasmic translocation from nucleus, suggesting a role for DNA-PKcs in vascular remodeling. We then infused wild-type (DNA-PKcsfl/fl) and DNA-PKcsΔVSMC mice with Ang II for 14 days to establish vascular remodeling, and demonstrated that DNA-PKcsΔVSMC mice displayed attenuated vascular remodeling through inhibition of dedifferentiation of VSMCs. Moreover, deletion of DNA-PKcs in VSMCs alleviated Ang II-induced vasodilation dysfunction and hypertension. Mechanistic investigations denoted that Ang II-evoked rises in cytoplasmic DNA-PKcs interacted with dynamin-related protein 1 (Drp1) at its TQ motif to phosphorylate Drp1S616, subsequently promoting mitochondrial fragmentation and dysfunction, as well as reactive oxygen species (ROS) production. Treatment of irbesartan, an Ang II type 1 receptor (AT1R) blocker, downregulated DNA-PKcs expression in VSMCs and aortic tissues following Ang II administration.

CONCLUSION

Our data revealed that cytoplasmic DNA-PKcs in VSMCs accelerated Ang II-induced vascular remodeling by interacting with Drp1 at its TQ motif and phosphorylating Drp1S616 to provoke mitochondrial fragmentation. Maneuvers targeting DNA-PKcs might be a valuable therapeutic option for the treatment of vascular remodeling and hypertension.

Role of Mitochondrial Dynamics in Heart Diseases

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases.

The Complex Relationship between Hypoxia Signaling, Mitochondrial Dysfunction and Inflammation in Calcific Aortic Valve Disease: Insights from the Molecular Mechanisms to Therapeutic Approaches

Calcific aortic valve stenosis (CAVS) is among the most common causes of cardiovascular mortality in an aging population worldwide. The pathomechanisms of CAVS are such a complex and multifactorial process that researchers are still making progress to understand its physiopathology as well as the complex players involved in CAVS pathogenesis. Currently, there is no successful and effective treatment to prevent or slow down the disease. Surgical and transcatheter valve replacement represents the only option available for treating CAVS. Insufficient oxygen availability (hypoxia) has a critical role in the pathogenesis of almost all CVDs. This process is orchestrated by the hallmark transcription factor, hypoxia-inducible factor 1 alpha subunit (HIF-1α), which plays a pivotal role in regulating various target hypoxic genes and metabolic adaptations. Recent studies have shown a great deal of interest in understanding the contribution of HIF-1α in the pathogenesis of CAVS. However, it is deeply intertwined with other major contributors, including sustained inflammation and mitochondrial impairments, which are attributed primarily to CAVS. The present review aims to cover the latest understanding of the complex interplay effect of hypoxia signaling pathways, mitochondrial dysfunction, and inflammation in CAVS. We propose further hypotheses and interconnections on the complexity of these impacts in a perspective of better understanding the pathophysiology. These interplays will be examined considering recent studies that shall help us better dissect the molecular mechanism to enable the design and development of potential future therapeutic approaches that can prevent or slow down CAVS processes.

Mitochondria spatially and temporally modulate VSMC phenotypes via interacting with cytoskeleton in cardiovascular diseases

Cardiovascular diseases caused by atherosclerosis (AS) seriously endanger human health, which is closely related to vascular smooth muscle cell (VSMC) phenotypes. VSMC phenotypic transformation is marked by the alteration of phenotypic marker expression and cellular behaviour. Intriguingly, the mitochondrial metabolism and dynamics altered during VSMC phenotypic transformation. Firstly, this review combs VSMC mitochondrial metabolism in three aspects: mitochondrial ROS generation, mutated mitochondrial DNA (mtDNA) and calcium metabolism respectively. Secondly, we summarized the role of mitochondrial dynamics in regulating VSMC phenotypes. We further emphasized the association between mitochondria and cytoskelton via presenting cytoskeletal support during mitochondrial dynamics process, and discussed its impact on their respective dynamics. Finally, considering that both mitochondria and cytoskeleton are mechano-sensitive organelles, we demonstrated their direct and indirect interaction under extracellular mechanical stimuli through several mechano-sensitive signaling pathways. We additionally discussed related researches in other cell types in order to inspire deeper thinking and reasonable speculation of potential regulatory mechanism in VSMC phenotypic transformation.

Mitochondrial Dysfunction in the Cardio-Renal Axis

Cardiovascular disease (CVD) frequently complicates chronic kidney disease (CKD). The risk of all-cause mortality increases from 20% to 500% in patients who suffer both conditions; this is referred to as the so-called cardio-renal syndrome (CRS). Preclinical studies have described the key role of mitochondrial dysfunction in cardiovascular and renal diseases, suggesting that maintaining mitochondrial homeostasis is a promising therapeutic strategy for CRS. In this review, we explore the malfunction of mitochondrial homeostasis (mitochondrial biogenesis, dynamics, oxidative stress, and mitophagy) and how it contributes to the development and progression of the main vascular pathologies that could be affected by kidney injury and vice versa, and how this knowledge may guide the development of novel therapeutic strategies in CRS.

The Complex Interplay between Imbalanced Mitochondrial Dynamics and Metabolic Disorders in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a global burden, with an increasing number of people affected and increasing treatment costs. The advances in research and guidelines improve the management of blood glucose and related diseases, but T2DM and its complications are still a big challenge in clinical practice. T2DM is a metabolic disorder in which insulin signaling is impaired from reaching its effectors. Mitochondria are the "powerhouses" that not only generate the energy as adenosine triphosphate (ATP) using pyruvate supplied from glucose, free fatty acid (FFA), and amino acids (AA) but also regulate multiple cellular processes such as calcium homeostasis, redox balance, and apoptosis. Mitochondrial dysfunction leads to various diseases, including cardiovascular diseases, metabolic disorders, and cancer. The mitochondria are highly dynamic in adjusting their functions according to cellular conditions. The shape, morphology, distribution, and number of mitochondria reflect their function through various processes, collectively known as mitochondrial dynamics, including mitochondrial fusion, fission, biogenesis, transport, and mitophagy. These processes determine the overall mitochondrial health and vitality. More evidence supports the idea that dysregulated mitochondrial dynamics play essential roles in the pathophysiology of insulin resistance, obesity, and T2DM, as well as imbalanced mitochondrial dynamics found in T2DM. This review updates and discusses mitochondrial dynamics and the complex interactions between it and metabolic disorders.

Panax quinquefolius saponin inhibits vascular smooth muscle cell calcification via activation of nuclear factor-erythroid 2-related factor 2

BACKGROUND

Panax quinquefolius saponin (PQS) is the main active component of Panax quinquefolius. Emerging evidence suggests that PQS exerts beneficial effects against cardiovascular diseases. However, the role and mechanism of PQS in vascular calcification are not unclear. The present study investigated the effects of PQS on the calcification of vascular smooth muscle cell (VSMCs).

METHODS

The present study used calcification medium containing 3 mM inorganic phosphate (Pi) to induce rat VSMCs calcification. We investigated the effects of PQS on VSMCs calcification using alizarin red staining and alkaline phosphatase (ALP) activity assays. The intracellular reactive oxygen species (ROS) levels and the transcriptional activity of nuclear factor-erythroid 2-related factor 2 (Nrf2) were determined. The mRNA and protein expression levels of Nrf2, the antioxidant gene heme oxygenase-1 (HO-1), osteogenic markers, including runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 (BMP2), and Kelch-like ECH-associated protein 1 (Keap1) were also measured.

RESULTS

Treatment with Pi significantly increased intracellular calcium deposition and ALP activity, which were suppressed by PQS in a concentration-dependent manner. During VSMCs calcification, PQS inhibited the mRNA and protein expression of Runx2 and BMP2. PQS treatment reduced intracellular ROS production and significantly upregulated Nrf2 transcriptional activity and the expression of Nrf2 and its target antioxidant gene HO-1. PQS suppressed the Pi-induced protein expression of Keap1, which is an endogenous inhibitor of Nrf2. Keap1 siRNA treatment induced Nrf2 expression and downregulated Runx2 expression in the presence of Pi and PQS.

CONCLUSION

Taken together, these findings suggest that PQS could effectively inhibit VSMCs calcification by ameliorating oxidative stress and regulating osteogenic genes via the promotion of Nrf2 expression.

Prosthetic vascular grafts engineered to combat calcification: Progress and future directions

Calcification in prosthetic vascular conduits is a major challenge in cardiac and vascular surgery that compromises the long-term performance of these devices. Significant research efforts have been made to understand the etiology of calcification in the cardiovascular system and to combat calcification in various cardiovascular devices. Novel biomaterial design and tissue engineering strategies have shown promise in preventing or delaying calcification in prosthetic vascular grafts. In this review, we highlight recent advancements in the development of acellular prosthetic vascular grafts with preclinical success in attenuating calcification through advanced biomaterial design. We also discuss the mechanisms of action involved in the designs that will contribute to the further understanding of cardiovascular calcification. Lastly, recent insights into the etiology of vascular calcification will guide the design of future prosthetic vascular grafts with greater potential for translational success.

The Drp1-Mediated Mitochondrial Fission Protein Interactome as an Emerging Core Player in Mitochondrial Dynamics and Cardiovascular Disease Therapy

Mitochondria, the membrane-bound cell organelles that supply most of the energy needed for cell function, are highly regulated, dynamic organelles bearing the ability to alter both form and functionality rapidly to maintain normal physiological events and challenge stress to the cell. This amazingly vibrant movement and distribution of mitochondria within cells is controlled by the highly coordinated interplay between mitochondrial dynamic processes and fission and fusion events, as well as mitochondrial quality-control processes, mainly mitochondrial autophagy (also known as mitophagy). Fusion connects and unites neighboring depolarized mitochondria to derive a healthy and distinct mitochondrion. In contrast, fission segregates damaged mitochondria from intact and healthy counterparts and is followed by selective clearance of the damaged mitochondria via mitochondrial specific autophagy, i.e., mitophagy. Hence, the mitochondrial processes encompass all coordinated events of fusion, fission, mitophagy, and biogenesis for sustaining mitochondrial homeostasis. Accumulated evidence strongly suggests that mitochondrial impairment has already emerged as a core player in the pathogenesis, progression, and development of various human diseases, including cardiovascular ailments, the leading causes of death globally, which take an estimated 17.9 million lives each year. The crucial factor governing the fission process is the recruitment of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, from the cytosol to the outer mitochondrial membrane in a guanosine triphosphate (GTP)-dependent manner, where it is oligomerized and self-assembles into spiral structures. In this review, we first aim to describe the structural elements, functionality, and regulatory mechanisms of the key mitochondrial fission protein, Drp1, and other mitochondrial fission adaptor proteins, including mitochondrial fission 1 (Fis1), mitochondrial fission factor (Mff), mitochondrial dynamics 49 (Mid49), and mitochondrial dynamics 51 (Mid51). The core area of the review focuses on the recent advances in understanding the role of the Drp1-mediated mitochondrial fission adaptor protein interactome to unravel the missing links of mitochondrial fission events. Lastly, we discuss the promising mitochondria-targeted therapeutic approaches that involve fission, as well as current evidence on Drp1-mediated fission protein interactions and their critical roles in the pathogeneses of cardiovascular diseases (CVDs).

An integrated analysis of Dynamin 1 Like: A new potential prognostic indicator in hepatocellular carcinoma

Dynamin 1 Like (DNM1L), a member of dynamin superfamily capable of mediating mitochondrial outer membrane division, plays a key role in the progression of different types of tumors. However, the prognostic value, clinical significance of DNM1L and its specific mechanism involved in tumorigenesis of hepatocellular carcinoma (HCC) have not been investigated clearly. In this study, we found that the expression of DNM1L were significantly higher in HCC tissues than adjacent/normal liver tissues based on multiple data sets obtained from TCGA, GEO and ONCOMINE database, also its protein expression form Drp1 is significantly higher in HCC tissues than adjacent tissues, and is related to the degree of differentiation. Kaplan-Meier curves suggested that high DNM1L expression prominently correlated with poorer overall survival, progression-free survival, relapse-free survival and disease-specific survival. Multivariate analysis showed that higher DNM1L expression was independent prognostic factors of shorter overall survival and disease-free survival. Kyoto Encyclopedia of Genes and Genomes and Gene set enrichment analysis analysis combined with validation experiments revealed the regulatory role of DNM1L on key molecules in the metabolism of xenobiotics by cytochrome p450 pathway, and DNM1L may also affects invasion and metastasis capability of HCC by mediating extracellular matrix -receptor interaction pathway. Moreover, analysis showed that higher DNM1L, CYP2C9, CYP3A4, CYP1A2 expression were associated with the resistance to sorafenib therapy. TIMER and CIBERSORT analysis indicated that the increase of DNM1L expression may affect the infiltration of immune cells in the tumor microenvironment. Taken together, the above results indicated that DNM1L could be able to serve as a promising independent predictor and therapeutic target for HCC patients.

Mitochondrial dynamics in vascular remodeling and target-organ damage

Vascular remodeling is the pathological basis for the development of many cardiovascular diseases. The mechanisms underlying endothelial cell dysfunction, smooth muscle cell phenotypic switching, fibroblast activation, and inflammatory macrophage differentiation during vascular remodeling remain elusive. Mitochondria are highly dynamic organelles. Recent studies showed that mitochondrial fusion and fission play crucial roles in vascular remodeling and that the delicate balance of fusion-fission may be more important than individual processes. In addition, vascular remodeling may also lead to target-organ damage by interfering with the blood supply to major body organs such as the heart, brain, and kidney. The protective effect of mitochondrial dynamics modulators on target-organs has been demonstrated in numerous studies, but whether they can be used for the treatment of related cardiovascular diseases needs to be verified in future clinical studies. Herein, we summarize recent advances regarding mitochondrial dynamics in multiple cells involved in vascular remodeling and associated target-organ damage.

Comprehensive Analysis of Mitochondrial Dynamics Alterations in Heart Diseases

The most common alterations affecting mitochondria, and associated with cardiac pathological conditions, implicate a long list of defects. They include impairments of the mitochondrial electron transport chain activity, which is a crucial element for energy formation, and that determines the depletion of ATP generation and supply to metabolic switches, enhanced ROS generation, inflammation, as well as the dysregulation of the intracellular calcium homeostasis. All these signatures significantly concur in the impairment of cardiac electrical characteristics, loss of myocyte contractility and cardiomyocyte damage found in cardiac diseases. Mitochondrial dynamics, one of the quality control mechanisms at the basis of mitochondrial fitness, also result in being dysregulated, but the use of this knowledge for translational and therapeutic purposes is still in its infancy. In this review we tried to understand why this is, by summarizing methods, current opinions and molecular details underlying mitochondrial dynamics in cardiac diseases.

p53 Regulates Mitochondrial Dynamics in Vascular Smooth Muscle Cell Calcification

Arterial calcification is an important characteristic of cardiovascular disease. It has key parallels with skeletal mineralization; however, the underlying cellular mechanisms responsible are not fully understood. Mitochondrial dynamics regulate both bone and vascular function. In this study, we therefore examined mitochondrial function in vascular smooth muscle cell (VSMC) calcification. Phosphate (Pi)-induced VSMC calcification was associated with elongated mitochondria (1.6-fold increase, p < 0.001), increased mitochondrial reactive oxygen species (ROS) production (1.83-fold increase, p < 0.001) and reduced mitophagy (9.6-fold decrease, p < 0.01). An increase in protein expression of optic atrophy protein 1 (OPA1; 2.1-fold increase, p < 0.05) and a converse decrease in expression of dynamin-related protein 1 (DRP1; 1.5-fold decrease, p < 0.05), two crucial proteins required for the mitochondrial fusion and fission process, respectively, were noted. Furthermore, the phosphorylation of DRP1 Ser637 was increased in the cytoplasm of calcified VSMCs (5.50-fold increase), suppressing mitochondrial translocation of DRP1. Additionally, calcified VSMCs showed enhanced expression of p53 (2.5-fold increase, p < 0.05) and β-galactosidase activity (1.8-fold increase, p < 0.001), the cellular senescence markers. siRNA-mediated p53 knockdown reduced calcium deposition (8.1-fold decrease, p < 0.01), mitochondrial length (3.0-fold decrease, p < 0.001) and β-galactosidase activity (2.6-fold decrease, p < 0.001), with concomitant mitophagy induction (3.1-fold increase, p < 0.05). Reduced OPA1 (4.1-fold decrease, p < 0.05) and increased DRP1 protein expression (2.6-fold increase, p < 0.05) with decreased phosphorylation of DRP1 Ser637 (3.20-fold decrease, p < 0.001) was also observed upon p53 knockdown in calcifying VSMCs. In summary, we demonstrate that VSMC calcification promotes notable mitochondrial elongation and cellular senescence via DRP1 phosphorylation. Furthermore, our work indicates that p53-induced mitochondrial fusion underpins cellular senescence by reducing mitochondrial function.

Arterial remodeling: the role of mitochondrial metabolism in vascular smooth muscle cells

Arterial remodeling is a common pathological basis of cardiovascular diseases such as atherosclerosis, vascular restenosis, hypertension, pulmonary hypertension, aortic dissection, and aneurysm. Vascular smooth muscle cells (VSMCs) are not only the main cellular components in the middle layer of the arterial wall but also the main cells involved in arterial remodeling. Dedifferentiated VSMCs lose their contractile properties and are converted to a synthetic, secretory, proliferative, and migratory phenotype, playing key roles in the pathogenesis of arterial remodeling. As mitochondria are the main site of biological oxidation and energy transformation in eukaryotic cells, mitochondrial numbers and function are very important in maintaining the metabolic processes in VSMCs. Mitochondrial dysfunction and oxidative stress are novel triggers of the phenotypic transformation of VSMCs, leading to the onset and development of arterial remodeling. Therefore, pharmacological measures that alleviate mitochondrial dysfunction reverse arterial remodeling by ameliorating VSMCs metabolic dysfunction and phenotypic transformation, providing new options for the treatment of cardiovascular diseases related to arterial remodeling. This review summarizes the relationship between mitochondrial dysfunction and cardiovascular diseases associated with arterial remodeling and then discusses the potential mechanism by which mitochondrial dysfunction participates in pathological arterial remodeling. Furthermore, maintaining or improving mitochondrial function may be a new intervention strategy to prevent the progression of arterial remodeling.

Role of Collagen in Vascular Calcification

ABSTRACT

Vascular calcification is a pathological process characterized by ectopic calcification of the vascular wall. Medial calcifications are most often associated with kidney disease, diabetes, hypertension, and advanced age. Intimal calcifications are associated with atherosclerosis. Collagen can regulate mineralization by binding to apatite minerals and promoting their deposition, binding to collagen receptors to initiate signal transduction, and inducing cell transdifferentiation. In the process of vascular calcification, type I collagen is not only the scaffold for mineral deposition but also a signal entity, guiding the distribution, aggregation, and nucleation of vesicles and promoting the transformation of vascular smooth muscle cells into osteochondral-like cells. In recent years, collagen has been shown to affect vascular calcification through collagen disc-domain receptors, matrix vesicles, and transdifferentiation of vascular smooth muscle cells.

The role of mitochondrial fission in cardiovascular health and disease

Mitochondria are organelles involved in the regulation of various important cellular processes, ranging from ATP generation to immune activation. A healthy mitochondrial network is essential for cardiovascular function and adaptation to pathological stressors. Mitochondria undergo fission or fusion in response to various environmental cues, and these dynamic changes are vital for mitochondrial function and health. In particular, mitochondrial fission is closely coordinated with the cell cycle and is linked to changes in mitochondrial respiration and membrane permeability. Another key function of fission is the segregation of damaged mitochondrial components for degradation by mitochondrial autophagy (mitophagy). Mitochondrial fission is induced by the large GTPase dynamin-related protein 1 (DRP1) and is subject to sophisticated regulation. Activation requires various post-translational modifications of DRP1, actin polymerization and the involvement of other organelles such as the endoplasmic reticulum, Golgi apparatus and lysosomes. A decrease in mitochondrial fusion can also shift the balance towards mitochondrial fission. Although mitochondrial fission is necessary for cellular homeostasis, this process is often aberrantly activated in cardiovascular disease. Indeed, strong evidence exists that abnormal mitochondrial fission directly contributes to disease development. In this Review, we compare the physiological and pathophysiological roles of mitochondrial fission and discuss the therapeutic potential of preventing excessive mitochondrial fission in the heart and vasculature.

Phenotypic plasticity of vascular smooth muscle cells in vascular calcification: Role of mitochondria

Vascular calcification (VC) is an important hallmark of cardiovascular disease, the osteo-/chondrocyte phenotype differentiation of vascular smooth muscle cells (VSMCs) is the main cause of vascular calcification. Accumulating evidence shows that mitochondrial dysfunction may ultimately be more detrimental in the VSMCs calcification. Mitochondrial participate in essential cellular functions, including energy production, metabolism, redox homeostasis regulation, intracellular calcium homeostasis, apoptosis, and signal transduction. Mitochondrial dysfunction under pathological conditions results in mitochondrial reactive oxygen species (ROS) generation and metabolic disorders, which further lead to abnormal phenotypic differentiation of VSMCs. In this review, we summarize existing studies targeting mitochondria as a treatment for VC, and focus on VSMCs, highlighting recent progress in determining the roles of mitochondrial processes in regulating the phenotype transition of VSMCs, including mitochondrial biogenesis, mitochondrial dynamics, mitophagy, mitochondrial energy metabolism, and mitochondria/ER interactions. Along these lines, the impact of mitochondrial homeostasis on VC is discussed.

Swimming Exercise Alleviates Endothelial Mitochondrial Fragmentation via Inhibiting Dynamin-Related Protein-1 to Improve Vascular Function in Hypertension

BACKGROUND

Regular exercise has been recommended clinically for all individuals to protect against hypertension but the underlying mechanisms are not fully elucidated. We recently found a significant mitochondrial fragmentation in the vascular endothelium of hypertensive human subjects. In this study, we investigated whether exercise could restore endothelial mitochondrial dynamics and thus improve vascular function in hypertension.

METHODS

Vascular endothelial mitochondrial morphological alterations were examined in patients with hypertension and hypertensive animal models. Furthermore, swimming exercise-induced endothelial mitochondrial dynamics and vascular function changes were investigated in spontaneously hypertensive rats (SHRs).

RESULTS

Mitochondrial fragmentation with an elevated mitochondrial fission mediator Drp1 (dynamin-related protein-1) was observed in the mesenteric artery endothelium from hypertensive patients. A similar mitochondrial fragmentation with increased Drp1 expression were exhibited in the aortic endothelium of angiotensin II-induced hypertensive mice and SHRs. Interestingly, swimming exercise significantly reduced vascular Drp1 expression and alleviated endothelial mitochondrial fragmentation, thus improving blood pressure in SHRs. In cultured endothelial cells, angiotensin II exposure induced Drp1 upregulation, mitochondrial fragmentation and dysfunction, and reduced nitric oxide production, which was blunted by Drp1 genetic reduction or its inhibitor Mdivi-1. Mdivi-1 administration also ameliorated endothelial mitochondrial fragmentation, vascular dysfunction and blood pressure elevation in SHRs while swimming exercise plus Mdivi-1 treatment provided no additional benefits, suggesting that Drp1 inhibition may partially contribute to swimming exercise-conferred anti-hypertensive effects.

CONCLUSIONS

These findings suggest that swimming exercise alleviates endothelial mitochondrial fragmentation via inhibiting Drp1, which may contribute to exercise-induced improvement of vascular function and blood pressure in hypertension.

Identification of MMP9 as a Novel Biomarker to Mitochondrial Metabolism Disorder and Oxidative Stress in Calcific Aortic Valve Stenosis

Calcific aortic valve stenosis (CAVS) is the most common heart valve disorder among humans. To date, no effective method has been identified to prevent this disease. Herein, we aimed to identify novel diagnostic and mitochondria-related biomarkers of CAVS, based on two machine learning algorithms. We further explored their association with infiltrating immune cells and studied their potential function in CAVS. The GSE12644, GSE51472, and GSE83453 expression profiles were downloaded from the Gene Expression Omnibus (GEO) repository. The GSE12644 and GSE51472 datasets were integrated to identify differentially expressed genes (DEGs). GSE12644 contains 10 normal and 10 CAVS samples, whereas GSE51472 contains 5 normal and 10 CAVS samples. GO and KEGG assays of DEGs were conducted, and the correlation between matrix metalloproteinase 9 (MMP9) expression and immune cell infiltration was explored, using CIBERSORT. The LASSO regression model and SVM-RFE analysis were used to identify diagnostic genes. The expression of MMP9 in CAVS and non-CAVS samples was measured using RT-PCR, western blotting and immunohistochemistry. A series of functional experiments were performed to explore the potential role of MMP9 in mitochondrial metabolism and oxidative stress during CAVS progression. Twenty-two DEGs were identified, of which six genes (SCG2, PPBP, TREM1, CCL19, WIF1, and MMP9) were ultimately distinguished as diagnostic genes in CAVS. Of these, MMP9 was indicated as a mitochondria-related gene, the expression and diagnostic value of which were further confirmed in the GSE83453 dataset. Correlation analysis revealed a positive correlation between MMP9 and infiltrating immune cells. In our cohort, MMP9 expression was distinctly increased in CAVS samples, and its inhibition attenuated the calcification of valve interstitial cells (VICs) by suppressing mitochondrial damage and oxidative stress. Taken together, our findings suggest MMP9 as a novel mitochondrial dysfunction biomarker and therapeutic target for CAVS.

Distinct role of mitochondrial function and protein kinase C in intimal and medial calcification in vitro

Introduction

Vascular calcification (VC) is a major risk factor for cardiovascular morbidity and mortality. Depending on the location of mineral deposition within the arterial wall, VC is classified as intimal and medial calcification. Using in vitro mineralization assays, we developed protocols triggering both types of calcification in vascular smooth muscle cells (SMCs) following diverging molecular pathways.

Materials and methods and results

Human coronary artery SMCs were cultured in osteogenic medium (OM) or high calcium phosphate medium (CaP) to induce a mineralized extracellular matrix. OM induces osteoblast-like differentiation of SMCs–a key process in intimal calcification during atherosclerotic plaque remodeling. CaP mimics hyperphosphatemia, associated with chronic kidney disease–a risk factor for medial calcification. Transcriptomic analysis revealed distinct gene expression profiles of OM and CaP-calcifying SMCs. OM and CaP-treated SMCs shared 107 differentially regulated genes related to SMC contraction and metabolism. Real-time extracellular efflux analysis demonstrated decreased mitochondrial respiration and glycolysis in CaP-treated SMCs compared to increased mitochondrial respiration without altered glycolysis in OM-treated SMCs. Subsequent kinome and in silico drug repurposing analysis (Connectivity Map) suggested a distinct role of protein kinase C (PKC). In vitro validation experiments demonstrated that the PKC activators prostratin and ingenol reduced calcification triggered by OM and promoted calcification triggered by CaP.

Conclusion

Our direct comparison results of two in vitro calcification models strengthen previous observations of distinct intracellular mechanisms that trigger OM and CaP-induced SMC calcification in vitro. We found a differential role of PKC in OM and CaP-calcified SMCs providing new potential cellular and molecular targets for pharmacological intervention in VC. Our data suggest that the field should limit the generalization of results found in in vitro studies using different calcification protocols.

Molecular Imaging and Quantification of Smooth Muscle Cell and Aortic Tissue Calcification In Vitro and Ex Vivo with a Fluorescent Hydroxyapatite-Specific Probe

Vessel calcification is characterized by the precipitation of hydroxyapatite (HAP) in the vasculature. Currently, no causal therapy exists to reduce or prevent vessel calcification. Studying the underlying pathways within vascular smooth muscle cells and testing pharmacological intervention is a major challenge in the vascular research field. This study aims to establish a rapid and efficient working protocol for specific HAP detection in cells and tissue using the synthetic bisphosphonate fluorescence dye OsteoSense™. This protocol facilitates especially early quantification of the fluorescence signal and permits co-staining with other markers of interest, enabling smaller experimental set-ups with lesser primary cells consumption and fast workflows. The fluorescence-based detection of vascular calcification with OsteoSense™ combines a high specificity with improved sensitivity. Therefore, this methodology can improve research of the pathogenesis of vascular calcification, especially for testing the therapeutic benefit of inhibitors in the case of in vitro and ex vivo settings.

Downregulation of HDAC9 by the ketone metabolite β-hydroxybutyrate suppresses vascular calcification

Vascular calcification is an actively regulated process resembling bone formation and contributes to the cardiovascular morbidity and mortality of chronic kidney disease (CKD). However, effective therapy for vascular calcification is still lacking. The ketone body β-hydroxybutyrate (BHB) has been demonstrated to have health-promoting effects including anti-inflammation and cardiovascular protective effects. However, whether BHB protects against vascular calcification in CKD remains unclear. In this study, Alizarin Red staining and calcium content assay showed that BHB reduced calcification of vascular smooth muscle cells (VSMCs) and arterial rings. Of note, compared with CKD patients without thoracic calcification, serum BHB levels were lower in CKD patients with thoracic calcification. Supplementation with 1,3-butanediol (1,3-B), the precursor of BHB, attenuated aortic calcification in CKD rats and VitD3-overloaded mice. Furthermore, RNA-Seq analysis revealed that BHB downregulated HDAC9, which was further confirmed by RT-qPCR and western blot analysis. Both pharmacological inhibition and knockdown of HDAC9 attenuated calcification of human VSMCs, while overexpression of HDAC9 exacerbated calcification of VSMCs and aortic rings, indicating that HDAC9 promotes vascular calcification under CKD conditions. Of note, BHB treatment antagonized HDAC9-induced vascular calcification. In addition, HDAC9 overexpression activated NF-κB signaling pathway and inhibition of NF-κB attenuated HDAC9-induced VSMC calcification, suggesting that HDAC9 promotes vascular calcification via activation of NF-κB. In conclusion, our study demonstrates that BHB supplementation inhibits vascular calcification in CKD via modulation of the HDAC9-dependent NF-κB signaling pathway. Moreover, we unveil a crucial mechanistic role of HDAC9 in vascular calcification under CKD conditions, thus nutritional intervention or pharmacological approaches to enhance BHB levels could act as promising therapeutic strategies to target HDAC9 for the treatment of vascular calcification in CKD. This article is protected by copyright. All rights reserved.

The mechanistic pathways of oxidative stress in aortic stenosis and clinical implications

Despite the elucidation of the pathways behind the development of aortic stenosis (AS), there remains no effective medical treatment to slow or reverse its progress. Instead, the gold standard of care in severe or symptomatic AS is replacement of the aortic valve. Oxidative stress is implicated, both directly as well as indirectly, in lipid infiltration, inflammation and fibro-calcification, all of which are key processes underlying the pathophysiology of degenerative AS. This culminates in the breakdown of the extracellular matrix, differentiation of the valvular interstitial cells into an osteogenic phenotype, and finally, calcium deposition as well as thickening of the aortic valve. Oxidative stress is thus a promising and potential therapeutic target for the treatment of AS. Several studies focusing on the mitigation of oxidative stress in the context of AS have shown some success in animal and in vitro models, however similar benefits have yet to be seen in clinical trials. Statin therapy, once thought to be the key to the treatment of AS, has yielded disappointing results, however newer lipid lowering therapies may hold some promise. Other potential therapies, such as manipulation of microRNAs, blockade of the renin-angiotensin-aldosterone system and the use of dipeptidylpeptidase-4 inhibitors will also be reviewed.

PTP1B Inhibition Improves Mitochondrial Dynamics to Alleviate Calcific Aortic Valve Disease Via Regulating OPA1 Homeostasis

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Increased PTP1B was observed in the human calcified aortic valve leaflets and VIC osteogenesis, which indicated a novel association of PTP1B with aortic valve calcification.

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MSI-1436, a specific pharmacological PTP1B inhibitor, attenuated osteogenic and myofibrogenic differentiation of VICs, which coincided with preventing aortic valve fibrocalcific disease in a diet-induced mouse model of CAVD.

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Treatment of CAVD with PTP1B inhibitor mitigated the disorder of aortic jet velocity and mean gradient in vivo.

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PTP1B inhibition preserved the mitochondrial biogenesis and function in VIC osteogenesis via regulating OPA1 homeostasis.

There are currently no pharmacological therapies for calcific aortic valve disease (CAVD). Here, we evaluated the role of protein tyrosine phosphatase 1B (PTP1B) inhibition in CAVD. Up-regulation of PTP1B was critically involved in calcified human aortic valve, and PTP1B inhibition had beneficial effects in preventing fibrocalcific response in valvular interstitial cells and LDLR^−/− mice. In addition, we reported a novel function of PTP1B in regulating mitochondrial homeostasis by interacting with the OPA1 isoform transition in valvular interstitial cell osteogenesis. Thus, these findings have identified PTP1B as a potential target for preventing aortic valve calcification in patients with CAVD.

Models and Techniques to Study Aortic Valve Calcification in Vitro, ex Vivo and in Vivo. An Overview

Aortic valve stenosis secondary to aortic valve calcification is the most common valve disease in the Western world. Calcification is a result of pathological proliferation and osteogenic differentiation of resident valve interstitial cells. To develop non-surgical treatments, the molecular and cellular mechanisms of pathological calcification must be revealed. In the current overview, we present methods for evaluation of calcification in different ex vivo, in vitro and in vivo situations including imaging in patients. The latter include echocardiography, scanning with computed tomography and magnetic resonance imaging. Particular emphasis is on translational studies of calcific aortic valve stenosis with a special focus on cell culture using human primary cell cultures. Such models are widely used and suitable for screening of drugs against calcification. Animal models are presented, but there is no animal model that faithfully mimics human calcific aortic valve disease. A model of experimentally induced calcification in whole porcine aortic valve leaflets ex vivo is also included. Finally, miscellaneous methods and aspects of aortic valve calcification, such as, for instance, biomarkers are presented.

Ecklonia cava extracts decrease hypertension-related vascular calcification by modulating PGC-1α and SOD2

Vascular calcification (VC) is induced by a decrease in sirtuin 3 (SIRT3) and superoxide dismutase (SOD)2 and increases mitochondrial reactive oxygen species (mtROS), eventually leading to mitochondrial dysfunction and phenotype alterations in vascular smooth muscle cells (VSMCs) into osteoblast-like cells in hypertension. Ecklonia cava extract (ECE) is known to increase peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) and SOD2. In this study, we evaluated the effect of ECE on decreasing VC by increasing PGC-1α which increased SOD2 activity and decreased mtROS in an in vitro VSMC model of treating serums from Wistar Kyoto (WKY), spontaneous hypertensive rats (SHRs), and ECE-treated SHRs. Furthermore, the decreasing effect of ECE on VC was evaluated with an in vivo SHR model. PGC-1α expression, SIRT3 expression, and SOD2 activity were decreased by the serum from the SHRs and increased by the serum from the ECE-treated SHRs in the VSMCs. PGC-1α silencing eliminated those increases. mtROS generation and mitochondrial DNA (mtDNA) damage increased in the SHRs but decreased with ECE. Mitochondrial fission increased in the SHRs but decreased by ECE. Mitochondrial fusion, mitophagy, and mitochondrial biogenesis were decreased in the SHRs but increased by ECE. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and calcium deposition in the medial layer of the aorta increased in the SHRs but decreased with ECE. Therefore, ECE decreases VC via the upregulation of PGC-1α and SIRT3, which increases SOD2 activity. Activated SOD2 decreases mtDNA damage and mtROS generation, which sequentially decreases NADPH oxidase activity and changes the mitochondrial dynamics, thereby decreasing VC.

Cell death regulation by MAMs: from molecular mechanisms to therapeutic implications in cardiovascular diseases

The endoplasmic reticulum (ER) and mitochondria are interconnected intracellular organelles with vital roles in the regulation of cell signaling and function. While the ER participates in a number of biological processes including lipid biosynthesis, Ca²⁺ storage and protein folding and processing, mitochondria are highly dynamic organelles governing ATP synthesis, free radical production, innate immunity and apoptosis. Interplay between the ER and mitochondria plays a crucial role in regulating energy metabolism and cell fate control under stress. The mitochondria-associated membranes (MAMs) denote physical contact sites between ER and mitochondria that mediate bidirectional communications between the two organelles. Although Ca²⁺ transport from ER to mitochondria is vital for mitochondrial homeostasis and energy metabolism, unrestrained Ca²⁺ transfer may result in mitochondrial Ca²⁺ overload, mitochondrial damage and cell death. Here we summarize the roles of MAMs in cell physiology and its impact in pathological conditions with a focus on cardiovascular disease. The possibility of manipulating ER-mitochondria contacts as potential therapeutic approaches is also discussed.

Current Understanding of the Pivotal Role of Mitochondrial Dynamics in Cardiovascular Diseases and Senescence

The heart is dependent on ATP production in mitochondria, which is closely associated with cardiovascular disease because of the oxidative stress produced by mitochondria. Mitochondria are highly dynamic organelles that constantly change their morphology to elongated (fusion) or small and spherical (fission). These mitochondrial dynamics are regulated by various small GTPases, Drp1, Fis1, Mitofusin, and Opa1. Mitochondrial fission and fusion are essential to maintain a balance between mitochondrial biogenesis and mitochondrial turnover. Recent studies have demonstrated that mitochondrial dynamics play a crucial role in the development of cardiovascular diseases and senescence. Disruptions in mitochondrial dynamics affect mitochondrial dysfunction and cardiomyocyte survival leading to cardiac ischemia/reperfusion injury, cardiomyopathy, and heart failure. Mitochondrial dynamics and reactive oxygen species production have been associated with endothelial dysfunction, which in turn causes the development of atherosclerosis, hypertension, and even pulmonary hypertension, including pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Here, we review the association between cardiovascular diseases and mitochondrial dynamics, which may represent a potential therapeutic target.

Endothelial cell-derived tetrahydrobiopterin prevents aortic valve calcification

AIMS

Tetrahydrobiopterin (BH4) is a critical determinant of the biological function of endothelial nitric oxide synthase. The present study was to investigate the role of valvular endothelial cell (VEC)-derived BH4 in aortic valve calcification.

METHODS AND RESULTS

Plasma and aortic valve BH4 concentrations and the BH4:BH2 ratio were significantly lower in calcific aortic valve disease patients than in controls. There was a significant decrease of the two key enzymes of BH4 biosynthesis, guanosine 5'-triphosphate cyclohydrolase I (GCH1) and dihydrofolate reductase (DHFR), in calcified aortic valves compared with the normal ones. Endothelial cell-specific deficiency of Gch1 in Apoe-/- (Apoe-/-Gch1fl/flTie2Cre) mice showed a marked increase in transvalvular peak jet velocity, calcium deposition, runt-related transcription factor 2 (Runx2), dihydroethidium (DHE), and 3-nitrotyrosine (3-NT) levels in aortic valve leaflets compared with Apoe-/-Gch1fl/fl mice after a 24-week western diet (WD) challenge. Oxidized LDL (ox-LDL) induced osteoblastic differentiation of valvular interstitial cells (VICs) co-cultured with either si-GCH1- or si-DHFR-transfected VECs, while the effects could be abolished by BH4 supplementation. Deficiency of BH4 in VECs caused peroxynitrite formation increase and 3-NT protein increase under ox-LDL stimulation in VICs. SIN-1, the peroxynitrite generator, significantly up-regulated alkaline phosphatase (ALP) and Runx2 expression in VICs via tyrosine nitration of dynamin-related protein 1 (DRP1) at Y628. Finally, folic acid (FA) significantly attenuated aortic valve calcification in WD-fed Apoe-/- mice through increasing DHFR and salvaging BH4 biosynthesis.

CONCLUSION

The reduction in endothelial-dependent BH4 levels promoted peroxynitrite formation, which subsequently resulted in DRP1 tyrosine nitration and osteoblastic differentiation of VICs, thereby leading to aortic valve calcification. Supplementation of FA in diet attenuated hypercholesterolaemia-induced aortic valve calcification by salvaging BH4 bioavailability.

Iron promotes Slc7a11-deficient valvular interstitial cell osteogenic differentiation: A possible mechanism by which ferroptosis participates in intraleaflet hemorrhage-induced calcification

Calcific aortic valve disease (CAVD) is the most frequent pathogeny of aortic valve replacement in developed countries. Iron deposits are found in the intraleaflet hemorrhage (IH) areas of calcific aortic valves. Ferroptosis is a form of regulated cell death that involves metabolic dysfunction resulting from iron overload-dependent excessive lipid peroxidation. In this study, histological analysis showed that ferroptosis occurs in the IH areas of calcific aortic valves. We also demonstrated that Slc7a11 is expressed at low levels in OM-treated valvular interstitial cells (VICs) and IH areas and that low Slc7a11 expression is associated with calcification in CAVD. However, iron overload treatment did not promote VIC calcification under osteogenic conditions in vitro. Using lentiviral transfection to knockdown Slc7a11 in VICs, we found that the degree of iron overload-induced ferroptosis was positively increased in vitro. Finally, we also found that Slc7a11 knockdown promoted the osteogenic differentiation of VICs in vitro. In summary, this study reports a novel mechanism linking ferroptosis and CAVD development in which iron may promote Slc7a11-deficient VIC osteogenic differentiation by aggravating ferroptosis in vitro, thereby accelerating the progression of aortic valve calcification.

Insights Into the Role of Mitochondria in Vascular Calcification

Vascular calcification (VC) is a growing burden in aging societies worldwide, and with a significant increase in all-cause mortality and atherosclerotic plaque rupture, it is frequently found in patients with aging, diabetes, atherosclerosis, or chronic kidney disease. However, the mechanism of VC is still not yet fully understood, and there are still no effective therapies for VC. Regarding energy metabolism factories, mitochondria play a crucial role in maintaining vascular physiology. Discoveries in past decades signifying the role of mitochondrial homeostasis in normal physiology and pathological conditions led to tremendous advances in the field of VC. Therapies targeting basic mitochondrial processes, such as energy metabolism, damage in mitochondrial DNA, or free-radical generation, hold great promise. The remarkably unexplored field of the mitochondrial process has the potential to shed light on several VC-related diseases. This review focuses on current knowledge of mitochondrial dysfunction, dynamics anomalies, oxidative stress, and how it may relate to VC onset and progression and discusses the main challenges and prerequisites for their therapeutic applications.

[Bax inhibitor 1 inhibits vascular calcification in mice by activating optic atrophy 1 expression]

OBJECTIVE

To investigate the effects of Bax inhibitor 1 (BI- 1) and optic atrophy protein 1 (OPA1) on vascular calcification (VC).

METHODS

Mouse models of VC were established in ApoE-deficient (ApoE-/-) diabetic mice by high-fat diet feeding for 12 weeks followed by intraperitoneal injections with Nε-carboxymethyl-lysine for 16 weeks. ApoE-/- mice (control group), ApoE-/- diabetic mice (VC group), ApoE-/- diabetic mice with BI-1 overexpression (VC + BI-1TG group), and ApoE-/- diabetic mice with BI-1 overexpression and OPA1 knockout (VC+BI-1TG+OPA1-/- group) were obtained for examination of the degree of aortic calcification using von Kossa staining. The changes in calcium content in the aorta were analyzed using ELISA. The expressions of Runt-related transcription factor 2 (RUNX2) and bone morphogenetic protein 2 (BMP-2) were detected using immunohistochemistry, and the expression of cleaved caspase-3 was determined using Western blotting. Cultured mouse aortic smooth muscle cells were treated with 10 mmol/L β-glycerophosphate for 14 days to induce calcification, and the changes in BI-1 and OPA1 protein expressions were examined using Western blotting and cell apoptosis was detected using TUNEL staining.

RESULTS

ApoE-/- mice with VC showed significantly decreased expressions of BI-1 and OPA1 proteins in the aorta (P=0.0044) with obviously increased calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 (P= 0.0041). Overexpression of BI-1 significantly promoted OPA1 protein expression and reduced calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 (P=0.0006). OPA1 knockdown significantly increased calcium deposition and expressions of RUNX2, BMP-2 and cleaved caspase-3 in the aorta (P=0.0007).

CONCLUSION

BI-1 inhibits VC possibly by promoting the expression of OPA1, reducing calcium deposition and inhibiting osteogenic differentiation and apoptosis of the vascular smooth muscle cells.

Lipoprotein(a) Induces Vesicular Cardiovascular Calcification Revealed With Single-Extracellular Vesicle Analysis

Lipoprotein(a) (Lp[a]) blood levels >50 mg/dL is a major cardiovascular disease risk factor in humans. Lp(a) associates with increased cardiovascular calcification, a critical pathology with no clinically available drug therapies. The mechanisms through which Lp(a) increases cardiovascular calcification risk remain undefined. We hypothesized that Lp(a) promotes the release of calcifying extracellular vesicles (EVs) that contribute to formation of microcalcification in cardiovascular tissues. Here, we show Lp(a) increased calcification in both primary human smooth muscle cells (SMCs) and valvular interstitial cells (VICs), potentially through inflammation-related mechanisms that were suppressed with E06 antibody that neutralizes pro-inflammatory oxidized phospholipids. Incubating human SMCs and VICs with Lp(a) altered the composition of EVs, increasing CD29⁺/tetraspanin⁻ microvesicle release, demonstrated with a tailored single-EV microarray assay that can distinguish multivesicular body-derived exosomes and plasma membrane budded microvesicles at a single-vesicle level. Lp(a) stimulation led to release of SMC and VIC EVs that readily calcified in acellular 3D-collagen hydrogels mimicking formation of ectopic microcalcification occurring in extracellular matrix of human atherosclerotic arteries and stenotic aortic valves. Our study mechanistically demonstrates that Lp(a) partially mediates cardiovascular calcification formation via inducing the release of calcifying EVs. Additionally, we provide a customized method to assess calcifying EVs at a single-vesicle level that can be more broadly applied to assist in quantitatively differentiating exosome and microvesicle EV subpopulations.

Dynamin-related protein 1 inhibition reduces hepatic PCSK9 secretion

AIMS

Proteostasis maintains protein homeostasis and participates in regulating critical cardiometabolic disease risk factors including proprotein convertase subtilisin/kexin type 9 (PCSK9). Endoplasmic reticulum (ER) remodeling through release and incorporation of trafficking vesicles mediates protein secretion and degradation. We hypothesized that ER remodeling that drives mitochondrial fission participates in cardiometabolic proteostasis.

METHODS AND RESULTS

We used in vitro and in vivo hepatocyte inhibition of a protein involved in mitochondrial fission, dynamin-related protein 1 (DRP1). Here, we show that DRP1 promotes remodeling of select ER microdomains by tethering vesicles at ER. A DRP1 inhibitor, mitochondrial division inhibitor 1 (mdivi-1) reduced ER localization of a DRP1 receptor, mitochondrial fission factor, suppressing ER remodeling-driven mitochondrial fission, autophagy, and increased mitochondrial calcium buffering and PCSK9 proteasomal degradation. DRP1 inhibition by CRISPR/Cas9 deletion or mdivi-1 alone or in combination with statin incubation in human hepatocytes and hepatocyte-specific Drp1-deficiency in mice reduced PCSK9 secretion (-78.5%). In HepG2 cells, mdivi-1 increased low-density lipoprotein receptor via c-Jun transcription and reduced PCSK9 mRNA levels via suppressed sterol regulatory binding protein-1c. Additionally, mdivi-1 reduced macrophage burden, oxidative stress, and advanced calcified atherosclerotic plaque in aortic roots of diabetic Apoe-deficient mice and inflammatory cytokine production in human macrophages.

CONCLUSIONS

We propose a novel tethering function of DRP1 beyond its established fission function, with DRP1-mediated ER remodeling likely contributing to ER constriction of mitochondria that drives mitochondrial fission. We report that DRP1-driven remodeling of select ER micro-domains may critically regulate hepatic proteostasis and identify mdivi-1 as a novel small molecule PCSK9 inhibitor.

Autophagy up-regulated by MEK/ERK promotes the repair of DNA damage caused by aflatoxin B1

Aflatoxin B1 (AFB1), a kind of mycotoxin, exerts its cytotoxicity by increasing the oxidative damage of target organs, especially the liver. In vivo and in vitro experiments were carried out to elucidate the toxic mechanism of AFB1. The results of MTT, cloning-formation, flow cytometry, immunocytochemistry, Reverse transcription PCR (RT-PCR) and western blot showed that AFB1 activated NOX2 gp91 phox, inhibited proliferation and migration, and blocked cell cycle at G0/G1 period of HHL-5 cells. Autophagy promoted the repair of NOX2-dependent DNA damage. NOX2/gp91 phox mainly activates MEK/ERK pathway and then up-regulates autophagy. In vivo experiments have shown that AFB1 (0.75 mg/kg daily orally, 4 weeks) had no significant changes in the size and shape of the liver in mice. However, these treatments lead to structural abnormalities of hepatocytes and DNA damage. In summary, AFB1 caused intracellular oxidative stress and DNA damage, NOX2/gp91-phox activates the MEK/ERK pathway, and upregulated autophagy to promote the repair of DNA damage. We concluded that by increasing the level of autophagy, the ability of anti-AFB1 toxicity of liver can be increased.

Up-regulation of heme oxygenase-1 by celastrol alleviates oxidative stress and vascular calcification in chronic kidney disease

Vascular calcification is very commonly observed in patients with chronic kidney disease (CKD), but there is no efficient therapy available. Oxidative stress plays critical roles in the progression of vascular calcification. Celastrol (Cel), a natural constituent derived from Chinese herbals, exhibits anti-oxidative stress activity. Here, we investigated the effect of celastrol on vascular calcification using vascular smooth muscle cells (VSMCs), arterial rings and CKD rats. Alizarin red staining and gene expression analysis showed that Cel dose-dependently inhibited rat VSMC calcification and osteogenic differentiation. Similarly, ex vivo study revealed that Cel inhibited calcification of rat and human arterial rings. In addition, micro-computed tomography, alizarin red staining and calcium content analysis confirmed that Cel inhibited aortic calcification in CKD rats. Interestingly, Cel treatment increased the mRNA and protein levels of heme oxygenase-1 (HMOX-1), and reduced the levels of reactive oxygen species (ROS) in VSMCs. Furthermore, both pharmacological inhibition of HMOX-1 and knockdown of HMOX-1 by siRNA independently counteracted the inhibitory effect of Cel on vascular calcification. Moreover, knockdown of HMOX-1 prevented Cel treatment-mediated reduction in ROS levels. Finally, Cel treatment reduced Vitamin D3-induced aortic calcification in mice and this effect was blocked by HMOX-1 inhibitor ZnPP9. Collectively, our results suggest that up-regulation of HMOX-1 is required for the inhibitory effect of Cel on vascular calcification. Modulation of HMOX-1 may provide a novel strategy for the treatment of vascular calcification in CKD.

Trimethylamine -N-oxide induces osteogenic responses in human aortic valve interstitial cells in vitro and aggravates aortic valve lesions in mice

AIMS

Recent studies have shown that the choline-derived metabolite trimethylamine N-oxide (TMAO) is a biomarker that promotes cardiovascular disease through the induction of inflammation and stress. Inflammatory responses and stress are involved in the progression of calcified aortic valve disease (CAVD). Here, we examined whether TMAO induces the osteogenic differentiation of aortic valve interstitial cells (AVICs) through endoplasmic reticulum (ER) and mitochondrial stress pathways in vitro and in vivo.

METHODS AND RESULTS

Plasma TMAO levels were higher in patients with CAVD (n = 69) than in humans without CAVD (n = 263), as examined by liquid chromatography-tandem mass spectrometry. Western blot and staining probes showed that TMAO- induced an osteogenic response in human AVICs. Moreover, TMAO promoted ER stress, mitochondrial stress and NF-κB activation in vitro. Notably, the TMAO- mediated effects were reversed by the use of ER stress, mitochondrial stress and NF-κB activation inhibitors and siRNA. Mice treated with supplemental choline in a high fat diet had markedly increased TMAO levels and aortic valve thicknesses, which were reduced by 3,3-dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) treatment.

CONCLUSIONS

Choline-derived TMAO promotes osteogenic differentiation through ER and mitochondrial stress pathways in vitro and aortic valve lesions in vivo.

TRANSLATIONAL PERSPECTIVE

Trimethylamine-N-oxide (TMAO), a gut microbiota-generated metabolite, is associated with cardiovascular diseases. Here, we show that patients with calcified aortic valve disease (CAVD) have elevated circulating TMAO levels. TMAO induces osteogenic responses in human aortic valve interstitial cells via endoplasmic reticulum-mitochondrial stress in vitro and aggravates aortic valve lesions in mice. This may provide clues to the pathogenesis of CAVD and attractive potential targets for the prevention, diagnosis and treatment of this disease.

Mitochondria Homeostasis and Vascular Medial Calcification

Vascular calcification occurs highly prevalent, which commonly predicts adverse cardiovascular events. The pathogenesis of calcification, a complicated and multifactorial process, is incompletely characterized. Accumulating evidence shows that mitochondrial dysfunction may ultimately be more detrimental in the vascular smooth muscle cells (VSMCs) calcification. This review summarizes the role of mitochondrial dysfunction and metabolic reprogramming in vascular calcification, and indicates that metabolic regulation may be a therapeutic target in vascular calcification.

Label-Free Multiphoton Microscopy for the Detection and Monitoring of Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is the most common valvular heart disease. CAVD results in a considerable socio-economic burden, especially considering the aging population in Europe and North America. The only treatment standard is surgical valve replacement as early diagnostic, mitigation, and drug strategies remain underdeveloped. Novel diagnostic techniques and biomarkers for early detection and monitoring of CAVD progression are thus a pressing need. Additionally, non-destructive tools are required for longitudinal in vitro and in vivo assessment of CAVD initiation and progression that can be translated into clinical practice in the future. Multiphoton microscopy (MPM) facilitates label-free and non-destructive imaging to obtain quantitative, optical biomarkers that have been shown to correlate with key events during CAVD progression. MPM can also be used to obtain spatiotemporal readouts of metabolic changes that occur in the cells. While cellular metabolism has been extensively explored for various cardiovascular disorders like atherosclerosis, hypertension, and heart failure, and has shown potential in elucidating key pathophysiological processes in heart valve diseases, it has yet to gain traction in the study of CAVD. Furthermore, MPM also provides structural, functional, and metabolic readouts that have the potential to correlate with key pathophysiological events in CAVD progression. This review outlines the applicability of MPM and its derived quantitative metrics for the detection and monitoring of early CAVD progression. The review will further focus on the MPM-detectable metabolic biomarkers that correlate with key biological events during valve pathogenesis and their potential role in assessing CAVD pathophysiology.

Lactate accelerates vascular calcification through NR4A1-regulated mitochondrial fission and BNIP3-related mitophagy

Arterial media calcification is related to mitochondrial dysfunction. Protective mitophagy delays the progression of vascular calcification. We previously reported that lactate accelerates osteoblastic phenotype transition of VSMC through BNIP3-mediated mitophagy suppression. In this study, we investigated the specific links between lactate, mitochondrial homeostasis, and vascular calcification. Ex vivo, alizarin S red and von Kossa staining in addition to measurement of calcium content, RUNX2, and BMP-2 protein levels revealed that lactate accelerated arterial media calcification. We demonstrated that lactate induced mitochondrial fission and apoptosis in aortas, whereas mitophagy was suppressed. In VSMCs, lactate increased NR4A1 expression, leading to activation of DNA-PKcs and p53. Lactate induced Drp1 migration to the mitochondria and enhanced mitochondrial fission through NR4A1. Western blot analysis of LC3-II and p62 and mRFP-GFP-LC3 adenovirus detection showed that NR4A1 knockdown was involved in enhanced autophagy flux. Furthermore, NR4A1 inhibited BNIP3-related mitophagy, which was confirmed by TOMM20 and BNIP3 protein levels, and LC3-II co-localization with TOMM20. The excessive fission and deficient mitophagy damaged mitochondrial structure and impaired respiratory function, determined by mPTP opening rate, mitochondrial membrane potential, mitochondrial morphology under TEM, ATP production, and OCR, which was reversed by NR4A1 silencing. Mechanistically, lactate enhanced fission but halted mitophagy via activation of the NR4A1/DNA-PKcs/p53 pathway, evoking apoptosis, finally accelerating osteoblastic phenotype transition of VSMC and calcium deposition. This study suggests that the NR4A1/DNA-PKcs/p53 pathway is involved in the mechanism by which lactate accelerates vascular calcification, partly through excessive Drp-mediated mitochondrial fission and BNIP3-related mitophagy deficiency.

Reduced Levels of Drp1 Protect against Development of Retinal Vascular Lesions in Diabetic Retinopathy

High glucose (HG)-induced Drp1 overexpression contributes to mitochondrial dysfunction and promotes apoptosis in retinal endothelial cells. However, it is unknown whether inhibiting Drp1 overexpression protects against the development of retinal vascular cell loss in diabetes. To investigate whether reduced Drp1 level is protective against diabetes-induced retinal vascular lesions, four groups of mice: wild type (WT) control mice, streptozotocin (STZ)-induced diabetic mice, Drp1^+/− mice, and STZ-induced diabetic Drp1^+/− mice were examined after 16 weeks of diabetes. Western Blot analysis indicated a significant increase in Drp1 expression in the diabetic retinas compared to those of WT mice; retinas of diabetic Drp1^+/− mice showed reduced Drp1 level compared to those of diabetic mice. A significant increase in the number of acellular capillaries (AC) and pericyte loss (PL) was observed in the retinas of diabetic mice compared to those of the WT control mice. Importantly, a significant decrease in the number of AC and PL was observed in retinas of diabetic Drp1^+/− mice compared to those of diabetic mice concomitant with increased expression of pro-apoptotic genes, Bax, cleaved PARP, and increased cleaved caspase-3 activity. Preventing diabetes-induced Drp1 overexpression may have protective effects against the development of vascular lesions, characteristic of diabetic retinopathy.