The Complex Interplay of Inflammation, Metabolism, Epigenetics, and Sex in Calcific Disease of the Aortic Valve

The N6-methyladenosine demethylase ALKBH5 is a novel epigenetic regulator of aortic valve calcification

AIMS

Calcific aortic valve disease (CAVD) is a common heart valve disease with significant clinical consequences. The mechanisms that drive the pathogenesis of CAVD remain to be fully elucidated. N6-methyladenosine (m6A), the most prevalent RNA epigenetic regulator, has recently been implicated in cardiovascular disease, but its role in CAVD has yet to be investigated. In this study, we investigated the potential function of m6A modification in CAVD.

METHODS AND RESULTS

Using clinical samples from CAVD patients in combination with human valve interstitial cell (hVIC) calcification model, we screened the expression of m6A modulators and discovered that alkB homolog 5, RNA demethylase (ALKBH5), a key m6A demethylase, was significantly down-regulated in calcified hVICs and human aortic valves. Consistently, increased m6A levels were seen in calcified hVICs, and treatment with 3-deazaadenosine (DAA), an inhibitor of m6A modification, significantly reduced hVIC osteogenic differentiation and calcification. In addition, we showed that silencing of ALKBH5 expression increased global m6A levels and accelerated hVIC osteogenic differentiation and calcification, whereas overexpression of ALKBH5 resulted in the opposite effect. We demonstrated that ALKBH5 directly modulate m6A levels of TGFBR2 and its mRNA stability, leading to altered TGFBR2 expression and SMAD2 signalling in hVICs. We further showed that inhibition of TGFBR2 or knockdown of SMAD2 attenuated ALKBH5 knockdown-induced hVIC osteogenic differentiation and calcification. The expression of the m6A reader protein YTH N6-methyladenosine RNA binding protein F1 (YTHDF1) was up-regulated during the process of hVIC calcification. Intriguingly, we revealed that the ALKBH5 silencing-induced increased hVIC osteogenic differentiation and calcification were abolished after knockdown of YTHDF1. These data suggest a potential role YTHDF1 in aortic valve calcification.

CONCLUSION

This study showed that ALKBH5 attenuated aortic valve calcification through the TGFBR2/SMAD2 signalling pathway via direct m6A modification of TGFBR2.

Biomarkers of Inflammation and Association with Cardiovascular Magnetic Resonance Imaging for Risk Stratification and Outcome in Patients with Severe Aortic Stenosis

Background: Inflammatory indices have been proposed as simple and routinely obtainable markers of systemic inflammation in cardiac disease. This study investigated whether the neutrophil-to-lymphocyte ratio (NLR), the monocyte-to-lymphocyte ratio (MLR), and the pan-immune inflammation value (PIV) serve as biomarkers for risk stratification and outcomes measures in patients with severe aortic stenosis (AS) following valve replacement (AVR). Methods: In this retrospective analysis (January 2017-June 2022), patients with AS underwent pre-procedural cardiovascular magnetic resonance (CMR) imaging and were assigned a treatment strategy by a multidisciplinary Heart Team: (1) transcatheter AVR, (2) surgical AVR, or (3) no valvular intervention. Kaplan-Meier estimates and regression analyses were used to demonstrate associations between the NLR, MLR, and PIV with myocardial fibrosis-assessed by late gadolinium enhancement (LGE) and extracellular volume (ECV) on CMR-and a combined endpoint of heart failure hospitalizations and all-cause mortality. Results: A total of 356 patients (median age: 80 years, 50% male) were followed for a median of 40 months, during which 162 (46%) reached the combined endpoint. Linear regression identified C-reactive protein, but not the presence of LGE or elevated ECV, as the only independent predictor of all three inflammatory indices (p for all <0.001). After multivariable adjustment for clinical (EuroSCORE II), laboratory (baseline N-terminal prohormone of brain natriuretic peptide [NT-proBNP] and C-reactive protein), and imaging parameters (AV mean pressure gradient, right ventricular ejection fraction, and ECV), the above-the-upper-quartile NLR (adjusted hazard ratio [aHR]: 1.45, 95%-confidence interval [CI]: 1.01-1.92, p = 0.042), MLR (aHR: 1.48, 95%-CI: 1.05-2.09, p = 0.025), and PIV (aHR: 1.56, 95%-CI: 1.11-2.21, p = 0.011) remained significantly associated with adverse outcomes. Following AVR, the median NLR (3.5 to 3.4) and PIV (460 to 376) showed a significant post-procedural decline compared to baseline (p ≤ 0.019 for both). Conclusions: Inflammatory indices are readily available biomarkers independently associated with adverse outcomes in severe AS following AVR. However, no significant relationship was observed between the NLR, MLR, PIV, and myocardial fibrosis on CMR.

Lysine acetylation and its role in the pathophysiology of acute pancreatitis

Acute pancreatitis (AP) represents a severe inflammatory condition of the exocrine pancreas, precipitating systemic organ dysfunction and potential failure. The global prevalence of acute pancreatitis is on an ascending trajectory. The condition carries a significant mortality rate during acute episodes. This underscores the imperative to elucidate the etiopathogenic pathways of acute pancreatitis, enhance comprehension of the disease's intricacies, and identify precise molecular targets coupled with efficacious therapeutic interventions. The pathobiology of acute pancreatitis encompasses not only the ectopic activation of trypsinogen but also extends to disturbances in calcium homeostasis, mitochondrial impairment, autophagic disruption, and endoplasmic reticulum stress responses. Notably, the realm of epigenetic regulation has garnered extensive attention and rigorous investigation in acute pancreatitis research over recent years. One of these modifications, lysine acetylation, is a reversible post-translational modification of proteins that affects enzyme activity, DNA binding, and protein stability by changing the charge on lysine residues and altering protein structure. Numerous studies have revealed the importance of acetylation modification in acute pancreatitis, and that it is a favorable target for the design of new drugs for this disease. This review centers on lysine acetylation, examining the strides made in acute pancreatitis research with a focus on the contributory role of acetylomic alterations in the pathophysiological landscape of acute pancreatitis, thereby aiming to delineate novel therapeutic targets and advance the development of more efficacious treatment modalities.

Pathological Mechanism and Treatment of Calcified Aortic Stenosis

Calcified aortic stenosis (AS) is one of the most common valvular heart diseases worldwide, characterized by progressive fibrocalcific remodeling and thickening of the leaflets, which ultimately leads to obstruction of blood flow. Its pathobiology is an active and complicated process, involving endothelial cell dysfunction, lipoprotein deposition and oxidation, chronic inflammation, phenotypic transformation of valve interstitial cells, neovascularization, and intravalvular hemorrhage. To date, no targeted drug has been proven to slow down or prevent disease progression. Aortic valve replacement is still the optimal treatment of AS. This article reviews the etiology, diagnosis, and management of calcified aortic stenosis and proposes novel potential therapeutic targets.

Focusing on the Native Matrix Proteins in Calcific Aortic Valve Stenosis

Calcific aortic valve stenosis (CAVS) is a widespread valvular heart disease affecting people in aging societies, primarily characterized by fibrosis, inflammation, and progressive calcification, leading to valve orifice stenosis. Understanding the factors associated with CAVS onset and progression is crucial to develop effective future pharmaceutical therapies. In CAVS, native extracellular matrix proteins modifications, play a significant role in calcification in vitro and in vivo. This work aimed to review the evidence on the alterations of structural native extracellular matrix proteins involved in calcification development during CAVS and highlight its link to deregulated biomechanical function.

The Emerging Role of Raman Spectroscopy as an Omics Approach for Metabolic Profiling and Biomarker Detection toward Precision Medicine

Omics technologies have rapidly evolved with the unprecedented potential to shape precision medicine. Novel omics approaches are imperative toallow rapid and accurate data collection and integration with clinical information and enable a new era of healthcare. In this comprehensive review, we highlight the utility of Raman spectroscopy (RS) as an emerging omics technology for clinically relevant applications using clinically significant samples and models. We discuss the use of RS both as a label-free approach for probing the intrinsic metabolites of biological materials, and as a labeled approach where signal from Raman reporters conjugated to nanoparticles (NPs) serve as an indirect measure for tracking protein biomarkers in vivo and for high throughout proteomics. We summarize the use of machine learning algorithms for processing RS data to allow accurate detection and evaluation of treatment response specifically focusing on cancer, cardiac, gastrointestinal, and neurodegenerative diseases. We also highlight the integration of RS with established omics approaches for holistic diagnostic information. Further, we elaborate on metal-free NPs that leverage the biological Raman-silent region overcoming the challenges of traditional metal NPs. We conclude the review with an outlook on future directions that will ultimately allow the adaptation of RS as a clinical approach and revolutionize precision medicine.

Pro-Calcifying Role of Enzymatically Modified LDL (eLDL) in Aortic Valve Sclerosis via Induction of IL-6 and IL-33

One of the contributors to atherogenesis is enzymatically modified LDL (eLDL). eLDL was detected in all stages of aortic valve sclerosis and was demonstrated to trigger the activation of p38 mitogen-activated protein kinase (p38 MAPK), which has been identified as a pro-inflammatory protein in atherosclerosis. In this study, we investigated the influence of eLDL on IL-6 and IL-33 induction, and also the impact of eLDL on calcification in aortic valve stenosis (AS). eLDL upregulated phosphate-induced calcification in valvular interstitial cells (VICs)/myofibroblasts isolated from diseased aortic valves, as demonstrated by alizarin red staining. Functional studies demonstrated activation of p38 MAPK as well as an altered gene expression of osteogenic genes known to be involved in vascular calcification. In parallel with the activation of p38 MAPK, eLDL also induced upregulation of the cytokines IL-6 and IL-33. The results suggest a pro-calcifying role of eLDL in AS via induction of IL-6 and IL-33.

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.

Complement Cross Talks With H-K-ATPase to Upregulate Runx2 in Human Aortic Valve Interstitial Cells

INTRODUCTION

Calcific aortic valve disease (CAVD) is a slowly progressive fibro-calcific valve leaflet disorder. The underlying pathophysiology is complex and not yet well understood. Complement is known to play a role in the pathogenesis of CAVD by upregulating Runx2 to induce profibrogenic change in human aortic valve interstitial cells (AVICs). Furthermore, H-K-ATPase has independently been shown to induce tissue calcification. Therefore, we hypothesized that complement cross talks with H-K-ATPase to upregulate Runx2 in human AVICs.

MATERIALS AND METHODS

Human AVICs were isolated from normal and calcified aortic valves. Cells were treated with a variation of complement, H-K-ATPase, or ERK1/2 inhibitors. H-K-ATPase and its association with complement in AVICs were investigated by reverse transcriptase-polymerase chain reaction, immunofluorescence, and Western blot.

RESULTS

Calcified human AVICs expressed significantly higher H-K-ATPase level than normal human AVICs. Presence of complement C3 with H-K-ATPase is found in AVICs after complement treatment. Complement induced both H-K-ATPase and Runx2 expression in AVICs, which was associated with increased phosphorylation of ERK1/2 and its downstream molecule p-70 S6. Pharmacological inhibition of either H-K-ATPase or Erk1/2 abolished complement-induced Runx2 expression.

CONCLUSIONS

These findings indicate that complement cross talks with H-K-ATPase to upregulate Runx2 in human AVICs by activation of ERK1/2 signaling pathways. The study revealed the potential role of H-K-ATPase in the pathogenesis of CAVD and therapeutically targeting either complement system or H-K-ATPase may limit the development of CAVD.

Global burden of calcific aortic valve disease and attributable risk factors from 1990 to 2019

Background

Calcific aortic valve disease (CAVD) was highly prevalent among developed countries and caused numerous deaths. Based on the Global Burden of Disease 2019, this study was designed to present comprehensive epidemiological information, attributable risks, and relevant factors.

Methods

All data were available online via the Global Health Data Exchange (GHDx). In this study, we analyzed the global incidence, prevalence, deaths, and disability-adjusted life years (DALYs) of CAVD across different regions from 1990 to 2019. We applied the estimated annual percentage changes (EAPCs) to evaluate the change trends and their attributable risks. In addition, we explored several relevant factors.

Results

From 1990 to 2019, the incidence cases, prevalence cases, CAVD-related deaths, and DALYs of CAVD gradually increased globally. However, the age-standardized death rate (ASDR) was relatively stable, and the age-standardized DALYs rate gradually declined during the past 30 years. Males and elderly individuals were more likely to suffer from CAVD. High systolic blood pressure (SBP) was the predominant attributable risk of disease burden that presented a global downward trend (death: EAPC = -0.68, 95% CI -0.77~-0.59, P < 0.001; DALYs: EAPC = -0.99, 95% CI -1.09 to -0.89, P < 0.001). Alcohol consumption (R = 0.79, P < 0.001), smoking prevalence (R = 0.75, P < 0.001), and calcium (R = 0.72, P < 0.001) showed a positive correlation with the age-standardized incidence rate (ASIR), whereas classic monsoon region (R = -0.68, P < 0.001) and mean temperature (R = -0.7, P < 0.001) showed a negative correlation with age-standardized incidence rate (ASIR). Besides, medical and healthcare resources presented a positive correlation with ASIR. Meanwhile, similar relationships were found in age-standardized prevalence rate (ASPR), ASDR, and age-standardized DALY rate (ASDALYR).

Conclusion

CAVD displays widely varied spatial distribution around the world, of which high SDI regions have the highest burdens. Age is a powerful factor and hypertension a predominant attributable risk factor. Moreover, controlling blood pressure, avoiding smoking, reducing alcohol consumption, and so on, could effectively reduce the burden of CAVD.

VLA4-Enhanced Allogeneic Endothelial Progenitor Cell-Based Therapy Preserves the Aortic Valve Function in a Mouse Model of Dyslipidemia and Diabetes

The number and function of endothelial progenitor cells (EPCs) are reduced in diabetes, contributing to deteriorated vascular repair and the occurrence of cardiovascular complications. Here, we present the results of treating early diabetic dyslipidemic mice or dyslipidemic with disease-matched EPCs modified to overexpress VLA4 (VLA4-EPCs) as compared with the treatment of EPCs transfected with GFP (GFP-EPCs) as well as EPCs from healthy animals. Organ imaging of injected PKH26-stained cells showed little pulmonary first-pass effects and distribution in highly vascularized organs, with splenic removal from circulation, mostly in non-diabetic animals. Plasma measurements showed pronounced dyslipidemia in all animals and glycaemia indicative of diabetes in streptozotocin-injected animals. Echocardiographic measurements performed 3 days after the treatment showed significantly improved aortic valve function in animals treated with VLA4-overexpressing EPCs compared with GFP-EPCs, and similar results in the groups treated with healthy EPCs and VLA4-EPCs. Immunohistochemical analyses revealed active inflammation and remodelling in all groups but different profiles, with higher MMP9 and lower P-selectin levels in GFP-EPCs, treated animals. In conclusion, our experiments show that genetically modified allogeneic EPCs might be a safe treatment option, with bioavailability in the desired target compartments and the ability to preserve aortic valve function in dyslipidemia and diabetes.

Profiling Genome-Wide DNA Methylation Patterns in Human Aortic and Mitral Valves

Cardiac valves exhibit highly complex structures and specialized functions that include dynamic interactions between cells, extracellular matrix (ECM) and their hemodynamic environment. Valvular gene expression is tightly regulated by a variety of mechanisms including epigenetic factors such as histone modifications, RNA-based mechanisms and DNA methylation. To date, methylation fingerprints of non-diseased human aortic and mitral valves have not been studied. In this work we analyzed the differential methylation profiles of 12 non-diseased aortic and mitral valve tissue samples (in matched pairs). Analysis of methylation data [reduced representation bisulfite sequencing (RRBS)] of 16,101 promoters genome-wide revealed 584 differentially methylated (DM) promoters, of which 13 were reported in endothelial mesenchymal trans-differentiation (EMT), 37 in aortic and mitral valve disease and 7 in ECM remodeling. Both functional classification as well as network analysis showed that the genes associated with the DM promoters were enriched for WNT-, Cadherin-, Endothelin-, PDGF-, HIF-1 and VEGF- signaling implicated in valvular physiology and pathophysiology. Additional enrichment was detected for TGFB-, NOTCH- and Integrin- signaling involved in EMT as well as ECM remodeling. This data provides the first insight into differential regulation of human aortic and mitral valve tissue and identifies candidate genes linked to DM promoters. Our work will improve the understanding of valve biology, valve tissue engineering approaches and contributes to the identification of relevant drug targets.