Oxidized HDL, as a Novel Biomarker for Calcific Aortic Valve Disease, Promotes the Calcification of Aortic Valve Interstitial Cells

Atherosclerosis Calcification: Focus on Lipoproteins

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipids in the vessel wall, leading to the formation of an atheroma and eventually to the development of vascular calcification (VC). Lipoproteins play a central role in the development of atherosclerosis and VC. Both low- and very low-density lipoproteins (LDL and VLDL) and lipoprotein (a) (Lp(a)) stimulate, while high-density lipoproteins (HDL) reduce VC. Apolipoproteins, the protein component of lipoproteins, influence the development of VC in multiple ways. Apolipoprotein AI (apoAI), the main protein component of HDL, has anti-calcific properties, while apoB and apoCIII, the main protein components of LDL and VLDL, respectively, promote VC. The role of lipoproteins in VC is also related to their metabolism and modifications. Oxidized LDL (OxLDL) are more pro-calcific than native LDL. Oxidation also converts HDL from anti- to pro-calcific. Additionally, enzymes such as autotaxin (ATX) and proprotein convertase subtilisin/kexin type 9 (PCSK9), involved in lipoprotein metabolism, have a stimulatory role in VC. In summary, a better understanding of the mechanisms by which lipoproteins and apolipoproteins contribute to VC will be crucial in the development of effective preventive and therapeutic strategies for VC and its associated cardiovascular disease.

Sepsis-Induced Coagulopathy Phenotype Induced by Oxidized High-Density Lipoprotein Associated with Increased Mortality in Septic-Shock Patients

Sepsis syndrome is a highly lethal uncontrolled response to an infection, which is characterized by sepsis-induced coagulopathy (SIC). High-density lipoprotein (HDL) exhibits antithrombotic activity, regulating coagulation in vascular endothelial cells. Sepsis induces the release of several proinflammatory molecules, including reactive oxygen species, which lead to an increase in oxidative stress in blood vessels. Thus, circulating lipoproteins, such as HDL, are oxidized to oxHDL, which promotes hemostatic dysfunction, acquiring prothrombotic properties linked to the severity of organ failure in septic-shock patients (SSP). However, a rigorous and comprehensive investigation demonstrating that oxHDL is associated with a coagulopathy-associated deleterious outcome of SSP, has not been reported. Thus, we investigated the participation of plasma oxHDL in coagulopathy-associated sepsis pathogenesis and elucidated the underlying molecular mechanism. A prospective study was conducted on 42 patients admitted to intensive care units, (26 SSP and 16 non-SSP) and 39 healthy volunteers. We found that an increased plasma oxHDL level in SSP was associated with a prothrombotic phenotype, increased mortality and elevated risk of death, which predicts mortality in SSP. The underlying mechanism indicates that oxHDL triggers an endothelial protein expression reprogramming of coagulation factors and procoagulant adhesion proteins, to produce a prothrombotic environment, mainly mediated by the endothelial LOX-1 receptor. Our study demonstrates that an increased plasma oxHDL level is associated with coagulopathy in SSP through a mechanism involving the endothelial LOX-1 receptor and endothelial protein expression regulation. Therefore, the plasma oxHDL level plays a role in the molecular mechanism associated with increased mortality in SSP.

Role of follistatin-like 1 levels and functions in calcific aortic stenosis

Background

Calcific aortic valve disease (CAVD) is a progressive disease resulting in severe calcific aortic stenosis (AS), and there is increasing interest in the discovery of novel biomarkers to identify patients with potential future calcific AS at an early stage. This study aimed to determine whether follistatin-like 1 (FSTL1) is associated with calcific AS events and its exact role in aortic valve calcification.

Methods

A prospective observational cohort study involving 656 patients was performed to investigate the relationship between serum FSTL1 and calcific AS incidence during a follow-up of 5 years. Furthermore, we detected FSTL1 levels in valvular interstitial cells (VICs) from calcified valves and explored the effects of FSTL1 on VIC osteogenic differentiation in vitro as well as the signaling pathways involved.

Results

During a median follow-up of 5 years, lower FSTL1 levels were associated with a significantly higher risk of calcific AS events (log rank test, P = 0.007). In addition, Cox multivariable regression analyses verified the predictive value of FSTL1 after adjusting for both demographic features and laboratory confounders. Consistent with our results for serum, a lower concentration of FSTL1 was observed in calcified human valves (n = 11) and mainly colocalized with VICs. Recombinant human FSTL1 (rhFSTL1) stimulation inhibited calcium deposition, alkaline phosphatase (ALP) activity, and osteogenic gene expression partly through the downregulation of the ERK1/2 pathway.

Conclusion

Taken together, this study provides a strong rationale to consider FSTL1 as a potential therapeutic target for calcific AS.

Contribution of Oxidative Stress (OS) in Calcific Aortic Valve Disease (CAVD): From Pathophysiology to Therapeutic Targets

Calcific aortic valve disease (CAVD) is a major cause of cardiovascular mortality and morbidity, with increased prevalence and incidence. The underlying mechanisms behind CAVD are complex, and are mainly illustrated by inflammation, mechanical stress (which induces prolonged aortic valve endothelial dysfunction), increased oxidative stress (OS) (which trigger fibrosis), and calcification of valve leaflets. To date, besides aortic valve replacement, there are no specific pharmacological treatments for CAVD. In this review, we describe the mechanisms behind aortic valvular disease, the involvement of OS as a fundamental element in disease progression with predilection in AS, and its two most frequent etiologies (calcific aortic valve disease and bicuspid aortic valve); moreover, we highlight the potential of OS as a future therapeutic target.

Oxidized high-density lipoprotein enhances endocrine disorders and ovarian damage in rats

Previous findings have highlighted the association between oxidized high‐density lipoprotein (ox‐HDL) and polycystic ovary syndrome (PCOS) development; however, the underlying mechanism remains unclear. Under such context, the present study aimed to investigate the mechanism underlying the involvement of ox‐HDL in PCOS in relation to the p65/micro‐RNA‐34a (miR‐34a)/FOS axis. PCOS rat models were established with the injection of dehydroepiandrosterone (6 mg/100 g body weight). Both PCOS‐modelled rats and granulosa cells (GCs) were received treatment with ox‐HDL in order to identify its role in PCOS. Next, apoptosis and viability of GCs were detected with the application of TdT‐mediated dUTP Nick‐End Labeling and flow cytometry and Cell counting kit‐8, respectively. A series of assays were performed to determine the interaction among ox‐HDL, p65, miR‐34a, FOS and nuclear factor‐κB (NF‐κB). The results revealed high expression of ox‐HDL in PCOS, and enhanced endocrine disorders and ovarian damage in rats. ox‐HDL promoted apoptosis of GCs and decreased its viability. ox‐HDL activated NF‐κB pathway and induced p65 phosphorylation to promote miR‐34a expression. miR‐34a targeted and inhibited FOS expression. In conclusion, our findings suggested that ox‐HDL promoted the activation of p65 and transcription of miR‐34a, which stimulated apoptosis of GCs and inhibited expression of FOS, resulting in the overall acceleration of PCOS development.

Lipoproteins and fatty acids in chronic kidney disease: molecular and metabolic alterations

Chronic kidney disease (CKD) induces modifications in lipid and lipoprotein metabolism and homeostasis. These modifications can promote, modulate and/or accelerate CKD and secondary cardiovascular disease (CVD). Lipid and lipoprotein abnormalities - involving triglyceride-rich lipoproteins, LDL and/or HDL - not only involve changes in concentration but also changes in molecular structure, including protein composition, incorporation of small molecules and post-translational modifications. These alterations modify the function of lipoproteins and can trigger pro-inflammatory and pro-atherogenic processes, as well as oxidative stress. Serum fatty acid levels are also often altered in patients with CKD and lead to changes in fatty acid metabolism - a key process in intracellular energy production - that induce mitochondrial dysfunction and cellular damage. These fatty acid changes might not only have a negative impact on the heart, but also contribute to the progression of kidney damage. The presence of these lipoprotein alterations within a biological environment characterized by increased inflammation and oxidative stress, as well as the competing risk of non-atherosclerotic cardiovascular death as kidney function declines, has important therapeutic implications. Additional research is needed to clarify the pathophysiological link between lipid and lipoprotein modifications, and kidney dysfunction, as well as the genesis and/or progression of CVD in patients with kidney disease.

Oxidized High-Density Lipoprotein Shows a Stepwise Increase as Fibrosis Progresses in Patients with Nonalcoholic Fatty Liver Disease

Patients with nonalcoholic fatty liver disease (NAFLD) show dyslipidemia and a high risk for coronary heart disease (CHD). However, conventional atherosclerotic lipids are found at low levels in NAFLD patients with advanced fibrosis, in whom the risk for CHD is extremely high. The aim of the present study was to evaluate the levels of oxidized high-density lipoprotein (oxHDL), an emerging atherosclerotic biomarker, in patients with NAFLD. A total of 32 non-NAFLD subjects and 106 patients with NAFLD were enrolled. The fibrosis grades were stratified using non-invasive methods, including the Fibrosis-4 index and NAFLD fibrosis score. Total cholesterol and low-density lipoprotein (LDL)-cholesterol levels were significantly low in patients with advanced liver fibrosis. In contrast, oxHDL levels were high in NAFLD patients and showed a stepwise increase as fibrosis progressed. These oxHDL levels were independent of the HDL cholesterol levels, and statin use did not influence the oxHDL levels. Obese patients showed no increase in oxHDL levels, whereas patients with a low handgrip strength showed high oxHDL levels in NAFLD with advanced fibrosis. In conclusion, oxHDL is a potential biomarker for assessing the status of patients with NAFLD, including CHD and metabolic/nutritional disturbance, and particular cases with advanced liver fibrosis.

Extracellular Matrix in Calcific Aortic Valve Disease: Architecture, Dynamic and Perspectives

Calcific Aortic Valve Disease (CAVD) is the most common valvular heart disease in developed countries and in the ageing population. It is strongly correlated to median age, affecting up to 13% of the population over the age of 65. Pathophysiological analysis indicates CAVD as a result of an active and degenerative disease, starting with sclerosis and chronic inflammation and then leaflet calcification, which ultimately can account for aortic stenosis. Although CAVD has been firstly recognized as a passive event mostly resulting from a degenerative aging process, much evidences suggests that calcification arises from different active processes, involving both aortic valve-resident cells (valve endothelial cells, valve interstitial cells, mesenchymal stem cells, innate immunity cells) and circulating cells (circulating mesenchymal cells, immunity cells). Moreover, a role for the cell-derived "matrix vesicles" and extracellular matrix (ECM) components has also been recognized. The aim of this work is to review the cellular and molecular alterations occurring in aortic valve during CAVD pathogenesis, focusing on the role of ECM in the natural course of the disease.

ApoC-III is a novel inducer of calcification in human aortic valves

Calcific aortic valve disease (CAVD) occurs when subpopulations of valve cells undergo specific differentiation pathways, promoting tissue fibrosis and calcification. Lipoprotein particles carry oxidized lipids that promote valvular disease, but low-density lipoprotein-lowering therapies have failed in clinical trials, and there are currently no pharmacological interventions available for this disease. Apolipoproteins are known promoters of atherosclerosis, but whether they possess pathogenic properties in CAVD is less clear. To search for a possible link, we assessed 12 apolipoproteins in nonfibrotic/noncalcific and fibrotic/calcific aortic valve tissues by proteomics and immunohistochemistry to understand if they were enriched in calcified areas. Eight apolipoproteins (apoA-I, apoA-II, apoA-IV, apoB, apoC-III, apoD, apoL-I, and apoM) were enriched in the calcific versus nonfibrotic/noncalcific tissues. Apo(a), apoB, apoC-III, apoE, and apoJ localized within the disease-prone fibrosa and colocalized with calcific regions as detected by immunohistochemistry. Circulating apoC-III on lipoprotein(a) is a potential biomarker of aortic stenosis incidence and progression, but whether apoC-III also induces aortic valve calcification is unknown. We found that apoC-III was increased in fibrotic and calcific tissues and observed within the calcification-prone fibrosa layer as well as around calcification. In addition, we showed that apoC-III induced calcification in primary human valvular cell cultures via a mitochondrial dysfunction/inflammation-mediated pathway. This study provides a first assessment of a broad array of apolipoproteins in CAVD tissues, demonstrates that specific apolipoproteins associate with valvular calcification, and implicates apoC-III as an active and modifiable driver of CAVD beyond its potential role as a biomarker.

Association of carbamylated high-density lipoprotein with coronary artery disease in type 2 diabetes mellitus: carbamylated high-density lipoprotein of patients promotes monocyte adhesion

BACKGROUND

Increasing evidence showed that carbamylated lipoprotein accelerated atherosclerosis. However, whether such modification of high-density lipoprotein (HDL) particles alters in type 2 diabetes mellitus (T2DM) patients and facilitates vascular complications remains unclear. We aimed to investigate the alteration of the carbamylation in HDL among T2DM patients and clarify its potential role in atherogenesis.

METHODS

A total of 148 consecutive T2DM patients undergoning angiography and 40 age- and gender-matched control subjects were included. HDL was isolated from plasma samples, and the concentration of HDL carbamyl-lysine (HDL-CBL) was measured. Furthermore, the HDL from subjects and in-vitro carbamylated HDL (C-HDL) was incubated with endothelial cells and monocyte to endothelial cell adhesion. Adhesion molecule expression and signaling pathway were detected.

RESULTS

Compared with the control group, the HDL-CBL level was remarkably increased in T2DM patients (6.13 ± 1.94 vs 12.00 ± 4.06 (ng/mg), P < 0.001). Of note, HDL-CBL demonstrated a more significant increase in T2DM patients with coronary artery disease (CAD) (n = 102) than those without CAD (n = 46) (12.75 ± 3.82 vs. 10.35 ± 4.11(ng/mg), P = 0.001). Multivariate logistic regression analysis demonstrated that higher HDL-CBL level was independently associated with a higher prevalence of CAD in diabetic patients after adjusting for established cofounders (adjusted odds ratio 1.174, 95% confidence Interval 1.045-1.319, p = 0.017). HDL from diabetic patients with CAD enhanced greater monocyte adhesion than that from the non-CAD or the control group (P < 0.001). Such pro-atherogenic capacity of diabetic HDL positively correlated with HDL-CBL level. Furthermore, in-vitro incubation of carbamylated HDL (C-HDL) with endothelial promoted monocyte to endothelial cell adhesion, induced upregulation of cell adhesion molecules expression, and activated NF-κB/p65 signaling in endothelial cells. Inhibiting carbamylation of HDL or NF-κB activation attenuated the monocyte to endothelial cell adhesion and cell surface adhesion molecules expression.

CONCLUSIONS

Our study identified elevated carbamylation modification of HDL from T2DM patients, especially in those with concomitant CAD. We also evidenced that C-HDL enhanced monocyte to endothelial cell adhesion, indicating a potential pro-atherogenic role of C-HDL in atherosclerosis among T2DM patients. Trial registration https://register.clinicaltrials.gov , NCT04390711 Registered on 14 May 2020; Retrospectively registered.