MMP-9 inhibition by ACE inhibitor reduces oxidized LDL-mediated foam-cell formation

The Role of MMP-9 and MMP-9 Inhibition in Different Types of Thyroid Carcinoma

Matrix metalloproteinase-9 (MMP-9), one of the most investigated and studied biomarkers of the MMPs family, is a zinc-dependent proteolytic metalloenzyme whose primary function is degrading the extracellular matrix (ECM). It has been proved that MMP-9 expression elevates in multiple pathological conditions, including thyroid carcinoma. MMP-9 has a detectable higher level in malignant or metastatic thyroid tumor tissues than in normal or benign tissues and acts as an additional marker to distinguish different tumor stages because of its close correlations with clinical features, such as lymph node metastasis, TNM stage, tumor size and so on. Natural and non-natural MMP-9 inhibitors suppress its expression, block the progression of diseases, and play a role in therapy consequently. MMP-9 inhibitory molecules also assist in treating thyroid tumors by suppressing the proliferation, invasion, migration, metastasis, viability, adhesion, motility, epithelial-mesenchymal transition (EMT), and other risk factors of different thyroid cancer cells. In a word, discovering and designing MMP-9 inhibitors provide great therapeutic effects and promising clinical values in various types of thyroid carcinoma.

Brain-Derived Neurotrophic Factor Precursor Contributes to a Proinflammatory Program in Monocytes/Macrophages After Acute Myocardial Infarction

Background The imbalance of monocyte/macrophage polarization toward the preferential proinflammatory phenotype and a lack of normal inflammation resolution are present in acute myocardial infarction (AMI). Our previous study showed that upregulation of brain-derived neurotrophic factor precursor (proBDNF) in M2-like monocytes may contribute to the proinflammatory response in the Stanford type-A acute aortic dissection. The present study aimed to investigate the role of proBDNF signaling in monocytes/macrophages in the progress of AMI. Methods and Results We observed the upregulation of proBDNF in the proinflammatory monocytes of patients with AMI. The upregulation of proBDNF was also observed in the circulating proinflammatory Ly6C^high monocytes and cardiac F4/80⁺CD86⁺ macrophages 3 days after AMI in a mice model. To neutralize proBDNF, the mice subjected to AMI were injected intraperitoneally with a monoclonal anti-proBDNF antibody. Echocardiography, 2,3,5-triphenyltetrazolium chloride staining, and positron emission tomography/computed tomography results demonstrate that monoclonal anti-proBDNF antibody treatment further impaired cardiac functions, increased infarct size, and exacerbated the proinflammatory state. Moreover, the level of proinflammatory Ly6C^high in the blood and F4/80⁺CD86⁺ in the heart was further increased in monoclonal anti-proBDNF antibody mice. RNA sequencing revealed that matrix metalloprotease-9 protein level was dramatically increased, along with the activated proinflammatory-related cytokines. Matrix metalloprotease-9 inhibitor treatment attenuated the deteriorated effect of monoclonal anti-proBDNF antibody on cardiac function and infarct areas. Conclusions Our study shows that endogenous proBDNF in monocytes/macrophages may exert protective roles in cardiac remodeling after AMI by regulating matrix metalloprotease-9 activity.

The immunomodulatory effects of antihypertensive therapy: A review

Hypertension remains the leading preventable risk factor for stroke and coronary artery disease, significantly contributing to all-cause global mortality and predisposing patients to renal and heart failure, as well as peripheral vascular disease. Due to the widespread usage of antihypertensive drugs, global mean blood pressure has remained unchanged or even slightly decreased over the past four decades. However, considering the broad spectrum of mechanisms involved in the action of antihypertensive drugs and the prevalence of their target receptors on immune cells, possible immunomodulatory effects which may exert beneficial effects of lowering blood pressure but also potentially alter immune function should be considered. In this review, we attempt to assess the consequences to immune system function of administering the five most commonly prescribed groups of antihypertensive drugs and to explain the mechanisms behind those interactions. Finally, we show potential gaps in our understanding of the effects of antihypertensive drugs on patient health. With regard to the widespread use of these drugs in the adult population worldwide, the discussed results may be of vital importance to evidence-based decision-making in daily clinical practice.

Curcumin and cardiovascular diseases: Focus on cellular targets and cascades

Cardiovascular diseases (CVDs) are one of the leading causes of the most considerable mortality globally, and it has been tried to find the molecular mechanisms and design new drugs that triggered the molecular target. Curcumin is the main ingredient of Curcuma longa (turmeric) that has been used in traditional medicine for treating several diseases for years. Numerous investigations have indicated the beneficial effect of Curcumin in modulating multiple signaling pathways involved in oxidative stress, inflammation, apoptosis, and proliferation. The cardiovascular protective effects of Curcumin against CVDs have been indicated in several studies. In the current review study, we provided novel information on Curcumin's protective effects against various CVDs and potential molecular signaling targets of Curcumin. Nonetheless, more studies should be performed to discover the exact molecular target of Curcumin against CVDs.

LDL receptors, caveolae and cholesterol in endothelial dysfunction: oxLDLs accomplices or victims?

Oxidized LDLs (oxLDLs) and oxysterols play a key role in endothelial dysfunction and the development of atherosclerosis. The loss of vascular endothelium function negatively impacts vasomotion, cell growth, adhesiveness and barrier functions. While for some of these disturbances, a reasonable explanation can be provided from a mechanistic standpoint, for many others, the molecular mediators that are involved are unknown. Caveolae, specific plasma membrane domains, have recently emerged as targets and mediators of oxLDL-induced endothelial dysfunction. Caveolae and their associated protein caveolin-1 (Cav-1) are involved in oxLDLs/LDLs transcytosis, mainly through the scavenger receptor class B type 1 (SR-B1 or SCARB1). In contrast, oxLDLs endocytosis is mediated by the lectin-like oxidized LDL receptor 1 (LOX-1), whose activity depends on an intact caveolae system. In addition, LOX-1 regulates the expression of Cav-1 and vice versa. On the other hand, oxLDLs may affect cholesterol plasma membrane content/distribution thus influencing caveolae architecture, Cav-1 localization and the associated signalling. Overall, the evidence indicate that caveolae have both active and passive roles in oxLDL-induced endothelial cell dysfunction. First, as mediators of lipid uptake and transfer in the subendothelial space and, later, as targets of changes in composition/dynamics of plasma membrane lipids resulting from increased levels of circulating oxLDLs. Gaining a better understanding of how oxLDLs interact with endothelial cells and modulate caveolae-mediated signalling pathways, leading to endothelial dysfunction, is crucial to find new targets for intervention to tackle atherosclerosis and the related clinical entities. LINKED ARTICLES: This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.

DUSP1 Is a Potential Marker of Chronic Inflammation in Arabs with Cardiovascular Diseases

Background

Cardiovascular disease (CVD) risks persist in patients despite the use of conventional treatments. This might be due to chronic inflammation as reflected in epidemiological studies associating circulating low-grade inflammatory markers with CVD recurrent events. Here, we explored this potential link by assessing plasma dual-specificity phosphatase 1 (DUSP1) levels and comparing them to high-sensitivity CRP (hsCRP) and oxidized low-density lipoprotein (oxLDL) levels and their associations to conventional CVD risk factors in confirmed CVD patients.

Methods

Human adults with reported CVD (n = 207) and controls (n = 70) living in Kuwait were used in this study. Anthropometric and classical biochemical parameters were determined. Plasma levels of DUSP1, oxLDL, and hsCRP were measured using human enzyme-linked immunosorbent assay kits.

Results

DUSP1 and hsCRP plasma levels and their least square means were higher in CVD cases, while oxLDL plasma levels were lower (p < 0.05). Multivariate logistic regression analysis showed that DUSP1 and hsCRP are independently associated with CVD in the studied population, as reflected by 2-fold and 1.5-fold increased risks with increased levels of DUSP1 and hsCRP, respectively. In our study, DUSP1 levels were found to be associated with CVD despite statin treatment and diabetes status (p < 0.05), whereas hsCRP mainly correlated with obesity markers.

Conclusions

Circulating DUSP1 might be a predictor of chronic subclinical inflammation and residual risk in CVD patients, whereas our data suggest that the association between hsCRP and CVD is largely accounted for adiposity risk factors.

Cilostazol ameliorates heart failure with preserved ejection fraction and diastolic dysfunction in obese and non-obese hypertensive mice

Cilostazol (Ciloz) a potent Type III phosphodiesterase inhibitor is effective against inflammation, insulin resistance and cardiomyopathy. However, the effect of Ciloz on obesity-associated left ventricular diastolic dysfunction has not been explored yet. Hence, we examined the effect of Ciloz on cardiac remodelling and dysfunction in non-obese and obese-insulin resistant mice infused with AngiotensinII (AngII). Male C57BL/6 J mice were initially subjected to 19 weeks of chow or high fat diet (HFD) regimen and thereafter animals were randomised for AngII (1500 ng/kg/min, s.c) infusion or saline and Ciloz (50 mg/kg, p.o) for another 1 week. Obese and non-obese mice infused with AngII exhibited significant diastolic dysfunction and features of heart failure with preserved ejection fraction (HFpEF) since a decrease in fractional shortening and no change in ejection fraction were observed when compared with respective controls. Administration of AngII and Ciloz in HFD fed mice significantly improved the left ventricular function compared with AngII infused HFD mice as evinced from the echocardiographic data. Further, Ciloz treatment significantly reduced cardiomyocyte area, interstitial and perivascular fibrosis; and collagen deposition. Moreover, Ciloz reduced the inflammatory milieu in the heart as evinced by decreased F4/80⁺ and CD68⁺ cells; IL-1β and IL-6 gene transcripts. Quantitative assessment of the expression levels revealed substantial upregulation of MMP-9 (pro- and mature-forms) and α-SMA in the left ventricle of AngII infused HFD-fed mice, which was considerably suppressed by Ciloz regimen. The beneficial effect of Ciloz was associated with the normalization in gene expression of hypertrophic and fibrotic markers. Likewise, Ciloz administration markedly reduced the AngII and HFD induced TGF-β1/SMAD3 and Akt/mTOR signalling. Additionally, AngII administered and HFD-fed mice showed increased glycolytic flux, which was considerably diminished by Ciloz treatment as indicated from suppressed PKM2, HK-2, PDK-2, HIF-1α mRNA and GLUT-1 protein expression. Taken together, Ciloz might be therapeutically exploited against AngII and obesity-associated diastolic dysfunction thereby preventing overt heart failure.

LOX-1 activation by oxLDL triggers an epithelial mesenchymal transition and promotes tumorigenic potential in prostate cancer cells

Obesity is related to an increased risk of developing prostate cancer with high malignancy stages or metastasis. Recent results demonstrated that LOX-1, a receptor associated with obesity and atherosclerosis, is overexpressed in advanced and metastatic prostate cancer. Furthermore, high levels of oxLDL, the main ligand for LOX-1, have been found in patients with advanced prostate cancer. However, the role of LOX-1 in prostate cancer has not been unraveled completely yet. Here, we show that LOX-1 is overexpressed in prostate cancer cells and its activation by oxLDL promotes an epithelial to mesenchymal transition, through of lowered expression of epithelial markers (E-cadherin and plakoglobin) and an increased expression of mesenchymal markers (vimentin, N-cadherin, snail, slug, MMP-2 and MMP-9). Consequently, LOX-1 activation by oxLDL promotes actin cytoskeleton restructuration and MMP-2 and MMP-9 activity inducing prostate cancer cell invasion and migration. Additionally, LOX-1 increased the tumorigenic potential of prostate cancer cells and its expression was necessary for tumor growth in nude mice. In conclusion, our results suggest that oxLDL/LOX-1 could be ones of mechanisms that explain why obese patients with prostate cancer have an accelerated tumor progression and a greater probability of developing metastasis.

Contribution of lectin-like oxidized low-density lipoprotein receptor-1 and LOX-1 modulating compounds to vascular diseases

The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major receptor for binding and uptake of oxidized low-density lipoprotein (oxLDL) in endothelial cells. LOX-1 is also expressed in macrophages, smooth muscle cells and platelets. Following internalization of oxLDL, LOX-1 initiates a vicious cycle from activation of pro-inflammatory signaling pathways, thus promoting an increased reactive oxygen species formation and secretion of pro-inflammatory cytokines. LOX-1 plays a pivotal role in the development of endothelial dysfunction, foam cell and advanced lesions formation as well as in myocardial ischemia. Furthermore, it is known that LOX-1 plays a pivotal role in mitochondrial DNA damage, vascular cell apoptosis, and autophagy. A large number of studies provide evidence of a LOX-1's role in endothelial dysfunction, hypertension, diabetes, and obesity. In addition, novel insights into LOX-1 ligands and the activated signaling pathways have been gained. Recent studies have shown an interaction of LOX-1 with microRNA's, thus providing novel tools to regulate LOX-1 function. Because LOX-1 is increased in atherosclerotic plaques and contributes to endothelial dysfunction, several compounds were tested in vivo and in vitro to modulate the LOX-1 expression in therapeutic approaches.

Curcumin Alleviates oxLDL Induced MMP-9 and EMMPRIN Expression through the Inhibition of NF-κB and MAPK Pathways in Macrophages

Rupture of vulnerable atherosclerotic plaques is the leading cause of acute myocardial infarction (AMI) and unstable angina pectoris (UA). However, it still lacks an effective therapy to stabilize the vulnerable atherosclerotic plaques. Numerous reports have shown that upregulation of MMP-9 (matrix metalloproteinase-9) and EMMPRIN (extracellular matrix metalloproteinase inducer) in macrophages is involved in the progression and development of vulnerable plaques. Here we evaluated the impact of curcumin on the expression of MMP-9 and EMMPRIN in macrophages. Macrophages were pretreated with curcumin or specific inhibitors (p38 MAPK inhibitor, NF-κB p65 inhibitor) for 1 h, then cells were cultured with oxLDL for indicated time. Real-time PCR and Western blot analysis were used to evaluate the expression of mRNA and proteins. Translocation of NF-κB p65 was detected by using laser confocal microscopy. Here we showed that curcumin attenuated the MMP-9 and EMMPRIN expression in oxLDL stimulated macrophages. Further studies revealed that curcumin inhibited oxLDL induced NF-κB activation and p38 MAPK phosphorylation. These findings illustrated that curcumin can inhibit the expression of EMMPRIN and MMP-9 in oxLDL stimulated macrophages through down regulation of NF-κB and p38 MAPK signaling pathways, which might be the molecular mechanism for the anti-atherosclerotic effect of curcumin.

Morphological features of coronary plaques in WHHLMI rabbits (Oryctolagus cuniculus), an animal model for familial hypercholesterolemia

In order to examine their suitability for studies on coronary atherosclerosis, we evaluated the features of coronary atherosclerotic plaques in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits, a spontaneous animal model for coronary atherosclerosis and myocardial infarction. Coronary segments of the hearts of 187 WHHLMI rabbits (10–29 months old) were sectioned serially and stained histopathologically and immunohistologically. Progression of coronary lesions was prominent in rabbits that had died suddenly. The degree of coronary lesions of females was higher than that of males. Various types of atherosclerotic lesions were observed in the coronary arteries, such as plaques with a large lipid core covered by a thin fibrous cap, fatty streaks, early and advanced fibroatheromas, fibrous lesions, and advanced lesions with calcium accumulation and the vasa vasorum. In rabbits that had died suddenly, the frequencies of fibroatheromas or advanced lesions were higher than those of rabbits euthanized. Matrix metalloproteinase (MMP)-positive macrophages were detected in gaps among endothelial cells at the plaque surface, beneath the fibrous cap of thin-capped fibroatheromas, and at the bottom of the intimal plaques in which the tunica media was attenuated. Immunohistological results suggest that MMP-positive macrophages are involved in the initiation, progression, and destabilization of coronary plaques, in addition to vascular remodeling, even in WHHLMI rabbits. In conclusion, coronary lesions in WHHLMI rabbits resemble human atherosclerotic lesions, and thus, the WHHLMI rabbit is a suitable animal model for studies on human coronary plaques.

High serum level of matrix metalloproteinase 9 and promoter polymorphism - 1562 C:T as a new risk factor for metabolic syndrome

The altered matrix metalloproteinases (MMPs) have been suggested in the pathophysiology of metabolic syndrome (MetS). Genetic variants in the promoter region of MMP1 and MMP9 genes may modulate an individual's susceptibility to MetS. The aim of this study was to determine the frequency of MMP1 -519 A:G and MMP9 -1562 C:T polymorphisms and the correlation with serum levels of MMP1 and MMP9 in MetS susceptibility. On the basis of anthropometric profile and laboratory investigations, 180 confirmed MetS patients and 190 unrelated healthy controls of similar ethnicity were genotyped for MMP1 -519 A:G and MMP9-1562 C:T polymorphisms by using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. In addition, serum levels of MMP1 and MMP9 were quantified by ELISA. We found that the serum level of MMP9 was significantly higher in MetS patients. Variant genotype TT of MMP9 -1562 demonstrated increased risk (odds ratio [OR]=3.70, p=0.015) of MetS. Similarly, variant allele T (OR=1.77, p=0.002) and combined genotype CT+TT (OR=1.81, p=0.057) also showed a significantly higher risk. The CT and TT genotypes of MMP9 -1562 polymorphism contributed to high serum levels of MMP9 in MetS patients. However, no such association was observed with the MMP1 serum level and -519 A:G polymorphism. Our results suggest that a higher serum level of MMP9 in the presence of MMP9 polymorphism -1562 C:T might be a risk factor for the development of MetS. The MMP9 enzyme activity might be a significant indicator in the screening of MetS patients.

Complement protein C1q promotes macrophage anti-inflammatory M2-like polarization during the clearance of atherogenic lipoproteins

OBJECTIVE

Innate immune protein C1q plays a dual role in the chronic inflammatory disease of atherosclerosis. Complement activation via C1q exacerbates pathology in the atherosclerotic lesion in later stages of the disease. However, in early stages of disease C1q is protective. We hypothesize that complement-independent activities of C1q are involved in reprogramming macrophage inflammatory polarization.

METHODS

The influence of C1q on macrophage inflammatory responses during clearance of oxLDL was examined. Changes in cytokines at the gene and protein level were measured by quantitative PCR and ELISA assay.

RESULTS

C1q modulated cytokine expression in Raw264.7 macrophages during ingestion of oxLDL. Levels of pro-inflammatory cytokines IL-1β and IL-6 were downregulated by C1q, whereas levels of the anti-inflammatory cytokine IL-10 were increased. In addition, data from an NFκB-luciferase gene reporter assay suggest that C1q suppresses activation of NFκB during lipoprotein clearance in macrophages, providing one mechanism by which C1q downregulates pro-inflammatory cytokine production.

CONCLUSIONS

C1q-polarization of macrophages toward an anti-inflammatory (M2-like) phenotype may be important in dampening inflammation in the early atherosclerotic lesion. Further investigation of molecular pathways targeted by C1q may provide novel therapeutic targets for this disease.

Plaque-stabilizing effect of angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker in a rabbit plaque model

AIM

Previous studies have revealed that blockade of the renin angiotensin system attenuates plaque vulnerability and reduces cardiovascular events; however, few studies have compared the effects of an angiotensin-converting enzyme inhibitor (ACEI) with an angiotensin receptor blocker (ARB) and evaluated combination therapy. The objective of this study was to compare the efficacy and mechanisms of plaque stabilization by ACEI or ARB and to determine the effects of combination therapy.

METHODS

Twenty-eight male Japanese white rabbits were fed a high-cholesterol diet after balloon injury of the carotid arteries, then separated into ACEI (n= 7; imidapril 0.5 mg/kg/day), ARB (n= 7; TA606 4.5 mg/kg/day), combination (n= 7; imidapril 0.5 mg/kg/day+TA606 4.5 mg/kg/day), and vehicle (n= 7) groups.

RESULTS

No difference in plaque volume was identified among the 4 groups. ACEI or ARB increased the thickness of the fibrous cap, collagen content and the number of smooth muscle cells in the intima (% smooth muscle cell in intima: ACEI, 36.3%; ARB, 36.4%; vehicle, 14.9%), and reduced the accumulation of macrophages (% macrophages in intima: ACEI, 20.1%; ARB, 24.0%; vehicle, 37.9%), suggesting the plaque-stabilizing effects of each drug. ACEI reduced matrix metalloproteinase (MMP)-9 expression and gelatinolytic activity in the intima. While ARB did not change gelatinolytic activity, accumulation ot T cell in the intima was suppressed. Combination therapy did not show additive effects.

CONCLUSION

These results suggest that ACEIs and ARBs have similar, but not additive, plaque-stabilizing effects. Each agent showed specific effects, with ACEIs decreasing gelatinolytic activity and ARBs suppressing T cell accumulation.

Atherogenic effects of TNF-α and IL-6 via up-regulation of scavenger receptors

Patients with chronic inflammatory disorders such as rheumatoid arthritis (RA) have a high risk of developing cardiovascular disease. We evaluated the effects of TNF-α and IL-6 on foam cell formation, a pivotal process in atherogenesis. Accumulation of intracellular oxidized LDL (oxLDL) was induced when THP-1/macrophages were stimulated with TNF-α or IL-6. TNF-α induced the expressions of scavenger receptors SR-A and LOX-1, and IL-6 induced SR-A expression. Inhibition of the NF-κB signaling markedly decreased TNF-α-induced foam cell formation and SR-A expression. Serum from RA patients, but not healthy subjects, induced foam cell formation, which was partially reversed by either IL-6 or TNF-α blockade in conjunction with inhibiting the induction of scavenger receptors. The present study clearly showed that in patients with chronic inflammation mediated by TNF-α and IL-6, these cytokines are directly implicated in atherosclerotic plaque formation.

Metalloproteinases in metabolic syndrome

Experimental and clinical evidence supports the concept that metalloproteinases (MMPs), beyond different physiologic functions, also play a role in the development and rupture of the atherosclerotic plaque. Interest in MMPs has been rapidly increasing during the last years, especially as they have been proposed as biomarkers of vulnerable plaques. Different components of the metabolic syndrome (MS) have been identified as possible stimulus for the synthesis and activity of MMPs, like pro-inflammatory and pro-oxidant state, hyperglycemia, hypertension and dyslipidemia. On the other hand, anti-inflammatory cytokines like adiponectin are inversely associated with MMPs. Among the several MMPs studied, collagenases (MMP-1 and MMP-8) and gelatinases (MMP-2 and MMP-9) are the most associated with MS. Our aim was to summarize and discuss the relation between different components of the MS on MMPs, as well as the effect of the cluster of the metabolic alterations itself. It also highlights the necessity of further studies, in both animals and humans, to elucidate the function of novel MMPs identified, as well as the role of the known enzymes in different steps of metabolic diseases. Understanding the mechanisms of MS impact on MMPs and vice versa is an interesting area of research that will positively enhance our understanding of the complexity of MS and atherosclerosis.

THE AUTODIGESTION HYPOTHESIS AND RECEPTOR CLEAVAGE IN DIABETES AND HYPERTENSION

One of the key features of cardiovascular complications, such as hypertension or diabetes, is that they often appear at the same time in the same individual together with other forms of co-morbidities. While clinically a recognized phenomenon, no molecular mechanism for such co-morbidities has received universal acceptance. We propose a new hypothesis that provides a molecular basis for co-morbidities in hypertension due to unchecked proteolytic activity and receptor destruction. Testing of the hypothesis in the spontaneously hypertensive rat reveals an unchecked matrix metalloproteinase and serine protease activity in plasma and on several cardiovascular and parenchymal cells. The elevated proteolytic activity causes extracellular cleavage of multiple receptor types, such that cleavage of one receptor type leads to loss of the function carried out by this receptor. Proteolytic cleavage of the extracellular domain of the β(2) adrenergic receptor in arteries and arterioles causes vasoconstriction and elevation of the central blood pressure while cleavage of the extracellular domain of the insulin receptor leads to insulin resistance and lack of transmembrane glucose transport. A diverse set of cell dysfunctions in the spontaneously hypertensive rat are accompanied by cleavage of the membrane receptors that are involved in these functions. Chronic inhibition of the unchecked protease activity in the spontaneously hypertensive rat serves to restore the extracellular receptor density and alleviates the corresponding cell dysfunctions. The mild unchecked proteolytic activity in the spontaneously hypertensive rat points towards a chronic autodigestion process as a contributor to the end organ injury encountered in this rat strain. The presence of various soluble receptors, which consist of extracellular fragments of membrane receptors, in the plasma of hypertensive and diabetic patients suggest that the autodigestion process may also be present in man.

Atherosclerosis in chronic kidney disease: the role of macrophages

Patients with chronic kidney disease (CKD) are at increased risk of atherosclerotic cardiovascular disease and loss of renal parenchyma accelerates atherosclerosis in animal models. Macrophages are central to atherogenesis because they regulate cholesterol traffic and inflammation in the arterial wall. CKD influences macrophage behavior at multiple levels, rendering them proatherogenic. Even at normal creatinine levels, macrophages from uninephrectomized Apoe(-/-) mice are enriched in cholesterol owing to downregulation of cholesterol transporter ATP-binding cassette subfamily A member 1 levels and activation of nuclear factor κB, which leads to impaired cholesterol efflux. Interestingly, treatment with an angiotensin-II-receptor blocker (ARB) improves these effects. Moreover, atherosclerotic aortas from Apoe(-/-) mice transplanted into renal-ablated normocholesterolemic recipients show plaque progression and increased macrophage content instead of the substantial regression seen in recipient mice with intact kidneys. ARBs reduce atherosclerosis development in mice with partial renal ablation. These results, combined with the clinical benefits of angiotensin-converting-enzyme (ACE) inhibitors and ARBs in patients with CKD, suggest an important role for the angiotensin system in the enhanced susceptibility to atherosclerosis seen across the spectrum of CKD. The role of macrophages could explain why these therapies may be effective in end-stage renal disease, one of the few conditions in which statins show no clinical benefit.