Inhibition of cyclooxygenase with indomethacin phenethylamide reduces atherosclerosis in apoE-null mice

Identification of immune cell infiltration and diagnostic biomarkers in unstable atherosclerotic plaques by integrated bioinformatics analysis and machine learning

Objective

The decreased stability of atherosclerotic plaques increases the risk of ischemic stroke. However, the specific characteristics of dysregulated immune cells and effective diagnostic biomarkers associated with stability in atherosclerotic plaques are poorly characterized. This research aims to investigate the role of immune cells and explore diagnostic biomarkers in the formation of unstable plaques for the sake of gaining new insights into the underlying molecular mechanisms and providing new perspectives for disease detection and therapy.

Method

Using the CIBERSORT method, 22 types of immune cells between stable and unstable carotid atherosclerotic plaques from RNA-sequencing and microarray data in the public GEO database were quantitated. Differentially expressed genes (DEGs) were further calculated and were analyzed for enrichment of GO Biological Process and KEGG pathways. Important cell types and hub genes were screened using machine learning methods including least absolute shrinkage and selection operator (LASSO) regression and random forest. Single-cell RNA sequencing and clinical samples were further used to validate critical cell types and hub genes. Finally, the DGIdb database of gene–drug interaction data was utilized to find possible therapeutic medicines and show how pharmaceuticals, genes, and immune cells interacted.

Results

A significant difference in immune cell infiltration was observed between unstable and stable plaques. The proportions of M0, M1, and M2 macrophages were significantly higher and that of CD8⁺ T cells and NK cells were significantly lower in unstable plaques than that in stable plaques. With respect to DEGs, antigen presentation genes (CD74, B2M, and HLA-DRA), inflammation-related genes (MMP9, CTSL, and IFI30), and fatty acid-binding proteins (CD36 and APOE) were elevated in unstable plaques, while the expression of smooth muscle contraction genes (TAGLN, ACAT2, MYH10, and MYH11) was decreased in unstable plaques. M1 macrophages had the highest instability score and contributed to atherosclerotic plaque instability. CD68, PAM, and IGFBP6 genes were identified as the effective diagnostic markers of unstable plaques, which were validated by validation datasets and clinical samples. In addition, insulin, nivolumab, indomethacin, and α-mangostin were predicted to be potential therapeutic agents for unstable plaques.

Conclusion

M1 macrophages is an important cause of unstable plaque formation, and CD68, PAM, and IGFBP6 could be used as diagnostic markers to identify unstable plaques effectively.

Cardio-renal safety of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used therapeutic class in clinical medicine. These are sub-divided based on their selectivity for inhibition of cyclooxygenase (COX) isoforms (COX-1 and COX-2) into: (1) non-selective (ns-NSAIDs), and (2) selective NSAIDs (s-NSAIDs) with preferential inhibition of COX-2 isozyme. The safety and pathophysiology of NSAIDs on the renal and cardiovascular systems have continued to evolve over the years following short- and long-term treatment in both preclinical models and humans. This review summarizes major learnings on cardiac and renal complications associated with pharmaceutical inhibition of COX-1 and COX-2 with focus on preclinical to clinical translatability of cardio-renal data.

Celecoxib for the treatment of atherosclerosis

INTRODUCTION

It is widely accepted that inflammation plays a pivotal role in the progression of atherosclerosis. Anti-inflammatory drugs and especially selective cyclooxygenase-2 (COX-2) inhibitors have attracted a keen interest.

AREAS COVERED

In the present drug evaluation article, the authors elucidate the role of celecoxib, a selective COX-2 inhibitor, in the treatment of atherosclerosis. They discuss the atherogenic properties of the COX-2 enzyme. In addition, they address the studies that support an atheroprotective role of celecoxib. Moreover, they provide a review of the literature on the role of COX-2 inhibitors in increasing the rate of major adverse cardiovascular events. Finally, they discuss the emerging evidence that supports celecoxib as an adjuvant or neo-adjuvant therapy to percutaneous coronary intervention (PCI).

EXPERT OPINION

Several studies have demonstrated a beneficial effect of celecoxib on the progression of atherosclerosis. Nevertheless, this evidence is mainly derived from preliminary data, while a substantial number of clinical studies have raised concerns regarding the cardiovascular safety of COX-2 inhibitors. Interestingly, recent clinical studies have supported the advantages of short-term celecoxib administration in patients undergoing PCI. However, many more large scale clinical trials are required to assess the long-term safety and efficacy of celecoxib administration in patients with cardiovascular disease.

Pathophysiology of cyclooxygenases in cardiovascular homeostasis

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandin H(2) (PGH(2)), which is subsequently converted to the prostanoids PGE(2), PGI(2), PGF(2alpha), and thromboxane A(2). COX has 2 distinct membrane-anchored isoenzymes: COX-1 and COX-2. COX-1 is constitutively expressed in most normal tissues; COX-2 is highly induced by proinflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include conventional nonselective nonsteroidal anti-inflammatory drugs and selective nonsteroidal anti-inflammatory drugs, such as COX-2 inhibitors. The adverse effects of COX inhibitors on the cardiovascular system have been addressed in the last few years. In general, COX inhibitors have many effects, but those most important to the cardiovascular system can be direct (through the effects of prostanoids) and indirect (through alterations in fluid dynamics). Despite reports of detrimental human cardiovascular events associated with COX inhibitors, short, long, and lifetime preclinical toxicology studies in rodents and nonrodents have failed to identify these risks. This article focuses on the expression and function of COX enzymes in normal and pathologic conditions of the cardiovascular system and discusses the cardiovascular pathophysiologic complications associated with COX inhibition.

Hyperhomocysteinemia induced by methionine supplementation does not independently cause atherosclerosis in C57BL/6J mice

A causal relationship between diet-induced hyperhomocysteinemia (HHcy) and accelerated atherosclerosis has been established in apolipoprotein E-deficient (apoE(-/-)) mice. However, it is not known whether the proatherogenic effect of HHcy in apoE(-/-) mice is independent of hyperlipidemia and/or deficiency of apoE. In this study, a comprehensive dietary approach using C57BL/6J mice was used to investigate whether HHcy is an independent risk factor for accelerated atherosclerosis or dependent on additional dietary factors that increase plasma lipids and/or inflammation. C57BL/6J mice at 4 wk of age were divided into 6 dietary groups: chow diet (C), chow diet + methionine (C+M), western-type diet (W), western-type diet + methionine (W+M), atherogenic diet (A), or atherogenic diet + methionine (A+M). After 2, 10, 20, or 40 wk on the diets, mice were sacrificed, and the levels of total plasma homocysteine, cysteine, and glutathione, as well as total plasma cholesterol and triglycerides were analyzed. Aortic root sections were examined for atherosclerotic lesions. HHcy was induced in all groups supplemented with methionine, compared to diet-matched control groups. Plasma total cholesterol was significantly increased in mice fed the W or A diet. However, the W diet increased LDL/IDL and HDL levels, while the A diet significantly elevated plasma VLDL and LDL/IDL levels without increasing HDL. No differences in plasma total cholesterol levels or lipid profiles were observed between methionine-supplemented groups and the diet-matched control groups. Early atherosclerotic lesions containing macrophage foam cells were only observed in mice fed the A or A + M diet. Furthermore, lesion size was significantly larger in the A + M group compared to the A group at 10 and 20 wk; however, mature lesions were never observed even after 40 wk on these diets. The presence of lymphocytes, increased hyaluronan staining, and the expression of endoplasmic reticulum (ER) stress markers were also increased in atherosclerotic lesions from the A + M group. Taken together, these results suggest that HHcy does not independently cause atherosclerosis in C57BL/6J mice even in the presence of increased total plasma lipids induced by the W diet. However, HHcy can accelerate atherosclerotic lesion development under dietary conditions that increase plasma VLDL levels and/or inflammation.

Contribution of cyclooxygenase-1 to thromboxane formation, platelet-vessel wall interactions and atherosclerosis in the ApoE null mouse

OBJECTIVE

Prostaglandin and thromboxane (TXA(2)) generation is increased in atherosclerosis. Studies with selective inhibitors attribute the enhanced prostacyclin (PGI(2)) generation to both cyclooxygenase-1 (COX-1) and COX-2 whereas the increased TXA(2) generation reflects platelet COX-1 expression. However, TXA(2) formation remains elevated in patients with cardiovascular disease on doses of aspirin that fully suppress platelet COX-1, suggesting other tissue sources for TXA(2) formation. Disruption of the thromboxane receptor gene suppresses the development of atherosclerosis. Notwithstanding this, the role of COX-1 in atherosclerosis is unclear, as it is widely distributed and contributes to a number of products, including those that potentially contribute to the resolution of inflammation.

METHODS AND RESULTS

We examined the role of COX-1 on prostaglandin generation, development of atherosclerosis and platelet-vessel wall interactions in the apoE(-/-) murine model by disrupting the COX-1 gene. ApoE(-/-)/COX-1(+/+), ApoE(-/-)/COX-1(+/-) and ApoE(-/-)/COX-1(-/-), were administered a 1% cholesterol diet for 8 weeks. Stable urinary metabolites of PGI(2) and TXA(2), which were markedly increased in the ApoE(-/-)/COX-1(+/+) were reduced by disruption of COX-1. Deletion of one or both copies of the COX-1 gene suppressed lesion formation. Assessment of platelet-vessel wall interactions by intravital microscopy showed a significant decrease in firm adhesion of platelets in the apoE/COX-1 double knockout (DKO).

CONCLUSION

COX-1 contributes to the enhanced formation of both PGI(2) and TXA(2) in atherosclerosis, and to the development of the disease. Non-platelet sources of COX-1 and TXA(2) that are inaccessible to standard doses of aspirin may contribute to the development of atherosclerosis.

The select cyclooxygenase-2 inhibitor celecoxib reduced the extent of atherosclerosis in apo E-/- mice

Many investigators have suggested that immune activation may trigger the atherosclerotic process. The benefits of aspirin in preventing myocardial infarction have been attributed, in part, to its anti-inflammatory effects. Several reports have documented that cyclooxygenase (COX)-2 is up-regulated in human and mouse atherosclerotic lesions. To clarify the role of COX-2 in atherosclerosis, we conducted a study to test whether the COX-2 inhibitor, celecoxib, prevents the development and progression of the atherosclerotic process. We have used the apo E-/- mouse, a relevant animal model of atherosclerosis that develops fibrofatty lesions similar to human atherosclerosis. Treatment of 4-wk old apo E-/- mice with a standard rodent no. 5020 diet supplemented with 900 ppm of celecoxib for 16 wk led to an 81% reduction in lesion size. The mean lesion area per section (mean +/- SD) of proximal aorta from the apo E-/- mice fed the diet with celecoxib (33,991 +/- 7863 microm2, P < 0.001) was significantly less than that of the untreated apo E-/- mice (183,401 +/- 36,212 microm2). There were no lesions detected in the C57B1/6 mice. Immunohistochemistry of the ileum revealed that there was 80% reduction in staining for intercellular adhesion molecule and 60% reduction in staining for vascular cell adhesion molecule in the celecoxib treated mice. The protective effect of celecoxib was not maintained when the mice were switched after feeding the celecoxib-supplemented diet to the control 5020 diet for an additional 10 wk. These findings demonstrate that selective inhibition of the COX-2 enzyme with celecoxib prevented the development of atherosclerotic lesions in the proximal aortas from apo E-/- mice. One of the possible mechanisms is reduction in expression of the endothelial cell adhesion cell molecules intercellular adhesion molecule and vascular cell adhesion molecule, which plays a key role in the recruitment of inflammatory cells during the early stages of atherogenesis.

Drug-induced immunomodulation to affect the development and progression of atherosclerosis: a new opportunity?

Inflammation and cytokine pathways are crucial for the development and progression of atherosclerotic lesions. In this review, the hypothesis that immunomodulatory drugs provide a possible therapeutic modality for cardiovascular disease is evaluated. Therefore, after a short overview of the specific inflammatory pathways involved in atherosclerosis, literature on the effect of several immunomodulatory drugs, such as nonsteroidal anti-inflammatory drugs, specific cyclooxygenase inhibitors and immunosuppressive drugs, used currently in the prevention of rejection after organ transplant, on the development and progression of atherosclerosis is reviewed. In addition, the pleiotropic immunomodulatory effect of two established cardiovascular drugs (angiotensin-converting enzyme inhibitors and statins) is discussed.

Aging associated with mild dyslipidemia reveals that COX-2 preserves dilation despite endothelial dysfunction

The endothelial function declines with age, and dyslipidemia (DL) has been shown to hasten this process by favoring the generation of reactive oxygen species (ROS). Cyclooxygenase-2 (COX-2) can be induced by ROS, but its contribution to the regulation of the endothelial function is unknown. Since COX-2 inhibitors may be deleterious to the cardiovascular system, we hypothesized that DL leads to ROS-dependent endothelial damage and a protective upregulation of COX-2. Dilations to acetylcholine (ACh) of renal arteries isolated from 3-, 6-, and 12-mo-old wild-type (WT) and DL mice expressing the human ApoB-100 were recorded with or without COX inhibitors and the antioxidant N-acetyl-l-cystein (NAC). Nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) were inhibited using N(omega)-nitro-l-arginine (l-NNA) and a depolarizing solution, respectively. In WT mice, the dilation to ACh declined at 12 mo but was insensitive to COX-1/2 inhibition alone or with NAC. DL led to an early endothelial dysfunction at 6 mo, normalized, however, by NAC. At 12 mo, vascular sensitivity to ACh was further reduced by DL. At this age, selective COX-2 inhibition reduced the dilation, whereas addition of NAC improved it. In 3- and 6-mo-old WT mice, l-NNA significantly reduced the dilation, whereas it limited the dilation only in 3-mo-old DL mice. EDHF-dependent dilation remains identical in both groups. These data suggest that COX-2 activity confers endothelium-dependent vasodilatory function in aged DL mice in the face of a pro-oxidative environment. Upregulation of this pathway compensates for the early loss of the contribution of NO in DL mice.