Evidence for an exclusive association of matrix metalloproteinase-9 with dysfunctional high-density lipoprotein: A novel finding

Elevated interleukin 8 and matrix metalloproteinase 9 levels are associated with myocardial pathology in users of anabolic-androgenic steroids

AIMS

In the current paper, we aim to explore the effect of both current and former long-term anabolic-androgenic steroid (AAS) use on regulation of systemic inflammatory markers and mediators of extracellular matrix (ECM) remodelling and their association with hormones and echocardiographic myocardial pathology in weightlifters.

METHODS AND RESULTS

In a cross-sectional study, 93 weightlifting AAS users, of whom 62 were current and 31 were past users, with at least 1-year cumulative AAS use (mean 11 ± 7 accumulated years of AAS use), were compared with 54 non-using weightlifting controls (WLCs) using clinical interview, blood pressure measurements, and echocardiography. Serum levels of interleukin (IL)-6, IL-8, tumour necrosis factor (TNF), interferon (IFN)-γ, growth differentiation factor (GDF)-15, and matrix metalloproteinase (MMP)-9, sex hormones, and lipids were analysed. It was found that serum levels of IL-8, GDF-15, and MMP-9 were significantly increased in current AAS users compared with former users and WLCs. Matrix metalloproteinase 9, but not IL-8, correlated consistently with sex hormone levels, and sex hormone levels correlated consistently with mean wall thickness, in current users. Moreover, HDL cholesterol was significantly lower in current vs. former AAS users and significantly inversely correlated with MMP-9 in current users. Further, in current users, MMP-9 and IL-8 correlated with markers of myocardial strain, and MMP-9 also correlated with indices of cardiac mass, which was not seen in former users. Mediation analyses suggested that MMP-9 could partly explain hormone-induced alterations in markers of myocardial damage in current users.

CONCLUSION

Long-term AAS is associated with increased levels of markers of inflammation and ECM remodelling, which seems to have a hormone-dependent (MMP-9) and a hormone-independent (IL-8) association with markers of myocardial dysfunction.

Identification and validation of four hub genes involved in the plaque deterioration of atherosclerosis

In recent years, intense research has been conducted to explore the diagnostic value of mRNA expression differences in atherosclerosis (AS). Nevertheless, because various technology platforms are applied and sample sizes are small, the results are inconsistent among the studies. We conducted a comprehensive analysis of a total of 161 tissue samples from 4 published studies after evaluating 230 datasets from the Gene Expression Omnibus and ArrayExpress. Adopting the newly published robust rank aggregation approach, combined with Kyoto Encyclopedia of Genes and Genomes pathway analysis, Gene Ontology functional enrichment analysis, and protein-protein interaction network construction, we identified four significantly upregulated genes (CCL4, CCL18, MMP9 and SPP1) for diagnosing AS, even in the advanced stage. Then, we performed gene set enrichment analysis to identify the pathways that were most affected by altered mRNA expression in atherosclerotic plaques. We found that four hub genes cooperatively targeted lipid metabolism and inflammatory immune-related pathways and validated their high expression levels in ruptured plaques by qRT-PCR, western blot analysis and immunohistochemical staining. In summary, our study showed that these genes can be used as interventional targets for plaque progression, and the results suggested we should focus on small changes in these key indicators in the clinical setting.

Adverse effects on macrophage lipid transport and survival by high density lipoprotein from patients with coronary heart disease

High density lipoprotein (HDL)-macrophage interactions have the potential to modulate macrophage function in a beneficial way to prevent the development of lipid-loaded foam cell formation in atherosclerosis. Although HDL is atheroprotective, it can become dysfunctional in chronic inflammatory conditions and increase cardiovascular risk. Here, we examined the effect of dysfunctional-HDL from patients with coronary artery disease, on macrophage function in comparison to functional-HDL from controls. Exposure of macrophages to dysfunctional-HDL for 24 h resulted significant increase in cellular oxidative stress, cholesterol, and cytotoxicity. It also stimulated mitochondrial membrane depolarization, DNA damage, apoptosis, and cleavage of poly (ADP-ribose) polymerase, which are characteristics of proapoptotic pathways. In contrast, functional-HDL treatment maintained cholesterol homeostasis, essential membrane potential, DNA integrity, and cell survival. These results demonstrate that HDL from coronary artery disease (CAD) patient promotes proatherogenic effects that in turn trigger macrophage apoptosis, an important feature in atherogenesis and thereby providing new insight in our understanding of the atherogenic mechanisms.

Evidence for the Involvement of Matrix-Degrading Metalloproteinases (MMPs) in Atherosclerosis

Atherosclerosis leads to blockage of arteries, culminating in myocardial infarction, and stroke. The involvement of matrix-degrading metalloproteinases (MMPs) in atherosclerosis is established and many studies have highlighted the importance of various MMPs in this process. MMPs were first implicated in atherosclerosis due to their ability to degrade extracellular matrix components, which can lead to increased plaque instability. However, more recent work has highlighted a multitude of roles for MMPs in addition to breakdown of extracellular matrix proteins. MMPs are now known to be involved in various stages of plaque progression: from initial macrophage infiltration to plaque rupture. This chapter summarizes the development and progression of atherosclerotic plaques and the contribution of MMPs. We provide data from human studies showing the effect of MMP polymorphisms and the expression of MMPs in both the atherosclerotic plaque and within plasma. We also discuss work in animal models of atherosclerosis that show the effect of gain or loss of function of MMPs. Together, the data provided from these studies illustrate that MMPs are ideal targets as both biomarkers and potential drug therapies for atherosclerosis.

High-density lipoprotein from subjects with coronary artery disease promotes macrophage foam cell formation: role of scavenger receptor CD36 and ERK/MAPK signaling

Although high-density lipoprotein is atheroprotective, it can become dysfunctional in chronic inflammatory conditions and increase cardiovascular risk. We previously demonstrated that HDL from subjects with documented coronary artery disease is dysfunctional and is pro-oxidant/proinflammatory in macrophages. Here we examined the influence of dysfunctional/proinflammatory HDL (piHDL) on lipid accumulation in human macrophages, in comparison to functional HDL (nHDL). Exposure of macrophages to piHDL, in contrast to nHDL, resulted in oxidative stress and marked uptake of lipids from piHDL, leading to the formation of foam cell phenotype as noted by oil red O staining with concomitant increase in total cellular cholesterol content. Using western blotting, we identified that piHDL profoundly upregulated the expression of scavenger receptor CD36 and suppressed the expression of ABCG1 and SRB1 in macrophages, thereby facilitating cholesterol influx capacity of macrophages. We then identified that CD36 did not act alone, indeed it was activated in macrophages along with ERK/MAPK, in response to piHDL, which in turn led to lipid accumulation as well as proinflammatory response via activation of NFkB and subsequent release of proinflammatory markers-TNF-ά and MMP-9. These effects were confirmed using pharmacological inhibitors for either CD36 or ERK/MAPK. Furthermore, piHDL treatment moderately activated PPAR-γ and Nrf2, the known regulators of CD36 in macrophages, suggesting that the two forms of HDL differentially regulate CD36 expression. Taken together, the results demonstrate that a novel CD36-ERK/MAPK-dependent mechanism is involved in macrophage lipid accumulation by piHDL, there by revealing the importance of functional deficiency in HDL and its potential link to atherogenesis.

Ethnicity and coronary artery disease: the role of high-density lipoprotein - a change in paradigm

Cardiovascular disease (CVD) is the number one killer of men and women across ethnic groups in the USA. Health disparities in CVD, especially coronary artery disease (CAD), are well documented in the diverse American population. Despite efforts taken toward reducing cardiovascular health disparities, there are still gaps in its diagnosis and management. Current risk assessment guidelines consider high high-density lipoprotein (HDL) levels a protective factor against CAD, although its significance across races remains poorly understood. Recent clinical trials focused on increasing HDL levels have been disappointing. In this article, the authors have explored the role of HDL in CAD, have analyzed its significance across gender and ethnic groups and have challenged the broad application of widely used HDL level cutoffs in CAD risk assessment tools across these vulnerable groups. The current evidence suggests a paradigm change from HDL quantity to quality and function in future CVD risk research. This may better explain why some ethnic minority groups with a seemingly more benign lipid profile experience a higher CAD burden.