Oxidized low-density lipoprotein associates with cardiovascular disease by a vicious cycle of atherosclerosis and inflammation: A systematic review and meta-analysis

Paraoxonase 1: evolution of the enzyme and of its role in protecting against atherosclerosis

PURPOSE OF REVIEW

To review the discoveries which led to the concept that serum paraoxonase 1 (PON1) is inversely related to atherosclerotic cardiovascular disease (ASCVD) incidence, how this association came to be regarded as causal and how such a role might have evolved.

RECENT FINDINGS

Animal models suggest a causal link between PON1 present on HDL and atherosclerosis. Serum PON1 activity predicts ASCVD with a similar reliability to HDL cholesterol, but at the extremes of high and low HDL cholesterol, there is discordance with PON1 being potentially more accurate. The paraoxonase gene family has its origins in the earliest life forms. Its greatest hydrolytic activity is towards lactones and organophosphates, both of which can be generated in the natural environment. It is active towards a wide range of substrates and thus its conservation may have resulted from improved survival of species facing a variety of evolutionary challenges.

SUMMARY

Protection against ASCVD is likely to be the consequence of some promiscuous activity of PON1, but nonetheless has the potential for exploitation to improve risk prediction and prevention of ASCVD.

Crosstalk between Inflammation and Atherosclerosis in Rheumatoid Arthritis and Systemic Lupus Erythematosus: Is There a Common Basis?

Cardiovascular disease is the leading cause of morbidity and mortality in patients with rheumatoid arthritis and systemic lupus erythematosus. Traditional cardiovascular risk factors, although present in lupus and rheumatoid arthritis, do not explain such a high burden of early cardiovascular disease in the context of these systemic connective tissue diseases. Over the past few years, our understanding of the pathophysiology of atherosclerosis has changed from it being a lipid-centric to an inflammation-centric process. In this review, we examine the pathogenesis of atherosclerosis in systemic lupus erythematosus and rheumatoid arthritis, the two most common systemic connective tissue diseases, and consider them as emblematic models of the effect of chronic inflammation on the human body. We explore the roles of the inflammasome, cells of the innate and acquired immune system, neutrophils, macrophages, lymphocytes, chemokines and soluble pro-inflammatory cytokines in rheumatoid arthritis and systemic lupus erythematosus, and the roles of certain autoantigens and autoantibodies, such as oxidized low-density lipoprotein and beta2-glycoprotein, which may play a pathogenetic role in atherosclerosis progression.

Metabolite-derived damage-associated molecular patterns in immunological diseases

Damage-associated molecular patterns (DAMPs) are typically derived from the endogenous elements of necrosis cells and can trigger inflammatory responses by activating DAMPs-sensing receptors on immune cells. Failure to clear DAMPs may lead to persistent inflammation, thereby contributing to the pathogenesis of immunological diseases. This review focuses on a newly recognized class of DAMPs derived from lipid, glucose, nucleotide, and amino acid metabolic pathways, which are then termed as metabolite-derived DAMPs. This review summarizes the reported molecular mechanisms of these metabolite-derived DAMPs in exacerbating inflammation responses, which may attribute to the pathology of certain types of immunological diseases. Additionally, this review also highlights both direct and indirect clinical interventions that have been explored to mitigate the pathological effects of these DAMPs. By summarizing our current understanding of metabolite-derived DAMPs, this review aims to inspire future thoughts and endeavors on targeted medicinal interventions and the development of therapies for immunological diseases.

Bioactive fractions from Allium humile alleviate the risk of high fat diet induced atherosclerosis in albino Wistar rats by inhibiting protein kinase C

Atherosclerosis is a global concern that worsens with age, and plants that are effective medicinal herbs can give a viable alternative. PKC is a key factor in cardiovascular and other disorders; targeting it can reduce the risk of these diseases. We evaluated Allium humile for PKC inhibition and therapeutic efficacy against atherosclerosis. Soxhlet extraction was done to obtain extracts (hexane, ethyl acetate, methanol, ethanol and aqueous) and then tested for DPPH radical scavenging and PKC inhibitory activity. The methanolic extract was more active than the other extracts, so it was subjected to column chromatography, and seventeen fractions were obtained. Only 11, 12, and 15 showed good activity against PKC. Wistar rats were divided into six groups and each group received high fat diet for 30 days. Then the three potent fractions (10 mg/kg) were administered for 15 days along with high fat diet. Fraction II had the highest effectiveness (P < 0.0001) in decreasing lipid levels, lipid peroxidation, reducing IL-6 and TNF-α expression, and raising nitric oxide. This also demonstrated a decrease in PKC activity, as well as a decrease in the formation of the lipoidal layer in the aorta wall and rupture of the intima and media as validated by histological analysis. The two compounds, phytol acetate and cyanidin 3-(6″-o-malonyllaminaribioside) were characterised in fraction II by NMR and HRMS and cyanidin 3-(6″-o-malonyllaminaribioside) inhibited PKC more efficiently. Thus, Allium humile has strong anti-atherogenic activity as well as the ability to inhibit PKC both in vitro and in vivo.

Vitamin A, D, E, and K as Matrix Metalloproteinase-2/9 Regulators That Affect Expression and Enzymatic Activity

Fat-soluble vitamins (vitamin A, D, E, and K) assume a pivotal role in maintaining human homeostasis by virtue of their enzymatic functions. The daily inclusion of these vitamins is imperative to the upkeep of various physiological processes including vision, bone health, immunity, and protection against oxidative stress. Current research highlights fat-soluble vitamins as potential therapeutics for human diseases, especially cancer. Fat-soluble vitamins exert their therapeutic effects through multiple pathways, including regulation of matrix metalloproteinases' (MMPs) expression and enzymatic activity. As MMPs have been reported to be involved in the pathology of various diseases, such as cancers, cardiovascular diseases, and neurological disorders, regulating the expression and/or activity of MMPs could be considered as a potent therapeutic strategy. Here, we summarize the properties of fat-soluble vitamins and their potential as promising candidates capable of effectively modulating MMPs through multiple pathways to treat human diseases.

Synergistic Role of NK Cells and Monocytes in Promoting Atherogenesis in Severe COVID-19 Patients

Clinical data demonstrate an increased predisposition to cardiovascular disease (CVD) following severe COVID-19 infection. This may be driven by a dysregulated immune response associated with severe disease. Monocytes and vascular tissue resident macrophages play a critical role in atherosclerosis, the main pathology leading to ischemic CVD. Natural killer (NK) cells are a heterogenous group of cells that are critical during viral pathogenesis and are known to be dysregulated during severe COVID-19 infection. Their role in atherosclerotic cardiovascular disease has recently been described. However, the contribution of their altered phenotypes to atherogenesis following severe COVID-19 infection is unknown. We demonstrate for the first time that during and after severe COVID-19, circulating proinflammatory monocytes and activated NK cells act synergistically to increase uptake of oxidized low-density lipoprotein (Ox-LDL) into vascular tissue with subsequent foam cell generation leading to atherogenesis despite recovery from acute infection. Our data provide new insights, revealing the roles of monocytes/macrophages, and NK cells in COVID-19-related atherogenesis.

Association of oxidized ApoB and oxidized ApoA-I with high-risk coronary plaque features in cardiovascular disease

BACKGROUND

Oxidized apolipoprotein B (oxLDL) and oxidized ApoA-I (oxHDL) are proatherogenic. Their prognostic value for assessing high-risk plaques by coronary computed tomography angiography (CCTA) is missing.

METHODS

In a prospective, observational study, 306 participants with cardiovascular disease (CVD) had extensive lipoprotein profiling. Proteomics analysis was performed on isolated oxHDL, and atherosclerotic plaque assessment was accomplished by quantitative CCTA.

RESULTS

Patients were predominantly White, overweight men (58.5%) on statin therapy (43.5%). Increase in LDL-C, ApoB, small dense LDL-C (P < 0.001 for all), triglycerides (P = 0.03), and lower HDL function were observed in the high oxLDL group. High oxLDL associated with necrotic burden (NB; β = 0.20; P < 0.0001) and fibrofatty burden (FFB; β = 0.15; P = 0.001) after multivariate adjustment. Low oxHDL had a significant reverse association with these plaque characteristics. Plasma oxHDL levels better predicted NB and FFB after adjustment (OR, 2.22; 95% CI, 1.27-3.88, and OR, 2.80; 95% CI, 1.71-4.58) compared with oxLDL and HDL-C. Interestingly, oxHDL associated with fibrous burden (FB) change over 3.3 years (β = 0.535; P = 0.033) when compared with oxLDL. Combined Met136 mono-oxidation and Trp132 dioxidation of HDL showed evident association with coronary artery calcium score (r = 0.786; P < 0.001) and FB (r = 0.539; P = 0.012) in high oxHDL, whereas Met136 mono-oxidation significantly associated with vulnerable plaque in low oxHDL.

CONCLUSION

Our findings suggest that the investigated oxidized lipids are associated with high-risk coronary plaque features and progression over time in patients with CVD.

TRIAL REGISTRATION

CLINICALTRIALS

gov NCT01621594.

FUNDING

National Heart, Lung, and Blood Institute at the NIH Intramural Research Program.

Targeting abnormal lipid metabolism of T cells for systemic lupus erythematosus treatment

Systemic lupus erythematosus (SLE) is an autoimmune disease in which the immune system attacks its own tissues and organs. However, the causes of SLE remain unknown. Dyslipidemia is a common symptom observed in SLE patients and animal models and is closely correlated to disease activity. Lipid metabolic reprogramming has been considered as a hallmark of the dysfunction of T cells in patients with SLE, therefore, manipulating lipid metabolism provides a potential therapeutic target for treating SLE. A better understanding of the underlying mechanisms for the metabolic events of immune cells under pathological conditions is crucial for tuning immunometabolism to manage autoimmune diseases such as SLE. In this review, we aim to summarize the cross-link between lipid metabolism and the function of T cells as well as the underlying mechanisms, and provide light on the novel therapeutic strategies of active compounds from herbals for the treatment of SLE by targeting lipid metabolism in immune cells.

Proteomic Exploration of Paraoxonase 1 Function in Health and Disease

High-density lipoprotein (HDL) exhibits cardio- and neuro-protective properties, which are thought to be promoted by paraoxonase 1 (PON1), a hydrolytic enzyme associated with an HDL subfraction also enriched with an anticoagulant protein (PROS1) and amyloid beta-transport protein clusterin (CLU, APOJ). Reduced levels of PON1 activity, characterized biochemically by elevated levels of homocysteine (Hcy)-thiolactone, oxidized lipids, and proteins modified by these metabolites in humans and mice, are associated with pathological abnormalities affecting the cardiovascular system (atherothrombosis) and the central nervous system (cognitive impairment, Alzheimer's disease). The molecular bases of these abnormalities have been largely unknown. Proteomic and metabolic studies over the past decade have significantly contributed to our understanding of PON1 function and the mechanisms by which PON1 deficiency can lead to disease. Recent studies discussed in this review highlight the involvement of dysregulated proteostasis in the pro-oxidative, pro-atherothrombotic, and pro-amyloidogenic phenotypes associated with low PON1 activity.