Angiotensin Inhibition Decreases Progression of Advanced Atherosclerosis and Stabilizes Established Atherosclerotic Plaques

A novel mouse model of coronary stenosis mimicking Kawasaki disease induced by Lactobacillus casei cell wall extract

Kawasaki disease (KD), a febrile systemic vasculitis in infants associated with coronary aneurysm, is a major cause of cardiac sequelae such as myocardial infarction (MI) and sudden death. These events are caused by coronary stenosis due to intimal proliferation or thrombotic formation; however, histological evaluation is limited to autopsy cases of human KD. We therefore investigated the histological features of coronary artery (CA) stenosis in mice induced by Lactobacillus casei cell wall extract (LCWE). LCWE-induced coronary inflammation gradually progressed in a time-dependent manner and expanded to all layers of the vessel wall over 28 days. In addition, frequent elastin degradation was observed and abundant α-smooth muscle actin (SMA)-positive vascular smooth muscle cells (VSMCs) infiltrated into the intima. Furthermore, most VSMCs were positive for proliferating cell nuclear antigen (PCNA) following staining, suggesting that VSMCs likely exhibited a proliferative phenotype. In conclusion, we show a novel mouse model of coronary stenosis induced by LCWE that is characterized by coronary stenosis with severe coronary vasculitis and elastin degradation. In addition, VSMC proliferation plays an important role in the formation of coronary stenosis. This model is an appropriate model of KD coronary stenosis.

Relation Between Renin-Angiotensin System Blockers and Survival Following Isolated Aortic Valve Replacement for Aortic Stenosis

Renin-angiotensin system blockers (RASb) improve cardiac remodeling, but their clinical utility after surgical aortic valve replacement (SAVR) for aortic stenosis (AS) is unclear. We aimed to assess the impact of RASb on short- and long-term survival following isolated SAVR for severe AS. From January 2005 to January 2014, 508 consecutive patients had isolated SAVR for severe AS. Patients with RASb (n = 286; 53%) were more often female (p = 0.039), hypertensive (p < 0.0001), and diabetic (p = 0.004), with higher body mass index (p < 0.0001) and EuroSCORE II (p = 0.025), and lower mean aortic pressure gradient (p = 0.011). The 30-day mortality was similar in both groups (RASb: 3% vs no RASb: 5.8%, p = 0.13), but lower under angiotensin receptor blockers (ARB) than angiotensin-converting enzyme inhibitors (ACEi; 0.7% vs 5.6%, p = 0.017). Patients under RASb had a better 8-year survival than those without RASb (83 ± 3% vs 52 ± 5%, p < 0.0001), confirmed in a propensity score-matched pairs analysis (82 ± 4% vs 50 ± 7%, p < 0.0001). Regarding different types of RASb, patients under ARB had lower mortality than those under ACEi (87 ± 3% vs 79 ± 4%, p = 0.028). In multivariate analysis, the use of RASb was associated with improved survival (hazard ratio = 0.31, 95% confidence interval 0.20 to 0.47, p < 0.0001), with lower mortality under ARB than under ACEi (hazard ratio = 0.39, 95% confidence interval 0.18 to 0.85, p = 0.018). In this observational study, the use of RASb was associated with improved long-term outcome after isolated SAVR for severe AS. A randomized clinical trial is mandatory.

Increased Plasma Cathepsin S at the Time of Percutaneous Transluminal Angioplasty is Associated with 6-Months’ Restenosis of the Femoropopliteal Artery

Background: We tested the hypothesis that increased levels of cathepsin S and decreased levels of cystatin C in plasma at the time of percutaneous transluminal angioplasty (PTA) are associated with the occurrence of 6-months’ restenosis of the femoropopliteal artery (FPA). Methods: 20 patients with restenosis and 24 matched patients with patent FPA after a 6-months follow-up were in - cluded in this study. They all exhibited disabling claudication or critical limb ischemia and had undergone technically successful PTA. They were all receiving statins and ACE in hi - bitors (or angiotensin II receptor antagonist) before the PTA and the therapy did not change throughout the observational period. Plasma concentrations of C-reactive protein were < 10 mg/L and of creatinine within the reference range at the time of the PTA. Plasma concentration and activity of cathepsin S, together with its potent inhibitor cystatin C, were measured the day before and the day after the PTA. Results: The increased plasma concentration and activity of cathepsin S at the time of PTA was associated with the occurrence of 6-months’ restenosis of FPA, independently of established risk factors (lesion complexity, infrapopliteal run-off vessels, type of PTA, age, gender, smoking, diabetes, lipids) and of cystatin C. Plasma cystatin C concentration was not associated with restenosis and did not correlate with cathepsin S activity and concentration in the plasma. Conclusion: Increased level of plasma cathepsin S at the time of PTA is associated with 6-months’ restenosis of PTA, independently of established risk factors.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.

Losartan attenuates the coronary perivasculitis through its local and systemic anti-inflammatory properties in a murine model of Kawasaki disease

BACKGROUND

Kawasaki disease is a common systemic vasculitis that leads to coronary artery lesions. Besides its antihypertensive effects, losartan can modulate inflammation in cardiovascular disease. We examined whether losartan can attenuate coronary inflammation in a murine model of Kawasaki disease.

METHODS AND RESULTS

Five-wk-old C57/BL6J male mice were intraperitoneally injected with Lactobacillus casei cell wall extract to induce coronary inflammation and divided into four groups: placebo, intravenous immunoglobulin (IVIG), losartan, and IVIG+losartan. After 2 wk, mice were harvested. The coronary perivasculitis was significantly attenuated by losartan but not by IVIG alone, and further dramatic attenuation by IVIG+losartan was observed. The frequency of Lactobacillus casei cell wall extract-induced myocarditis (80%) was markedly lowered by losartan (22%) and IVIG+losartan (0%). Furthermore, interleukin (IL)-6 mRNA was markedly attenuated by IVIG+losartan. Serum levels of IL-6, TNF-α, MCP-1, and IL-10 after Lactobacillus casei cell wall extract injection were slightly decreased by IVIG or losartan. Moreover, IL-1β, IL-10, and MCP-1 levels were significantly decreased by IVIG+losartan.

CONCLUSION

The addition of losartan to IVIG strongly attenuated the severity of coronary perivasculitis and the incidence of myocarditis, along with suppressing systemic/local cytokines as well as the activated macrophage infiltration. Therefore, losartan may be a potentially useful additive drug for the acute phase of Kawasaki disease to minimize coronary artery lesions.

Running Exercise and Angiotensin II Type I Receptor Blocker Telmisartan Are Equally Effective in Preventing Angiotensin II-Mediated Vulnerable Atherosclerotic Lesions

INTRODUCTION

The present study was conducted to directly compare the efficacy of running exercise and telmisartan treatment on angiotensin (Ang) II-mediated atherosclerosis and plaque vulnerability.

MATERIALS AND METHODS

Apolipoprotein E-deficient (ApoE^-/-) mice with Ang II-mediated atherosclerosis (2-kidney, 1-clip [2K1C] renovascular hypertension model) were randomized into 3 groups: treadmill running exercise (RUN), telmisartan treatment (TEL), and sedentary untreated controls (SED) for 5 weeks. Atherosclerosis was assessed using histological and immunohistochemical analyses. Gene expression was determined by real-time reverse transcription polymerase chain reaction.

RESULTS

TEL but not RUN mice significantly decreased (50%) atherosclerotic lesion size compared to SED. RUN and TEL promoted plaque stabilization to a similar degree in ApoE^-/- 2K1C mice. However, plaque composition and vascular inflammatory markers were differently affected: RUN decreased plaque macrophage infiltration (35%), whereas TEL reduced lipid core size (88%); RUN significantly increased aortic peroxisome proliferator-activated receptor (PPAR)-α, -δ, and -γ expression, whereas TEL significantly modulated T-helper 1/T-helper 2 (Th1/Th2) aortic response toward an anti-inflammatory state (decreased aortic interleukin [IL] 2 to IL-10 and IL-2 to IL-13 expression ratios). Plaque smooth muscle cell content was similarly increased (128% and 141%, respectively). Aortic AT1 and AT2 receptor expression as well as aortic CD11c/CD206 and IL-1β/IL-1ra expression ratios were not significantly modulated by either RUN or TEL.

CONCLUSION

Running exercise and telmisartan treatment are equally effective in preventing Ang II-mediated plaque vulnerability but through distinct cellular and molecular mechanisms. Our findings further support the use of exercise training and selective AT1 receptor blocker therapies for atherosclerotic cardiovascular disease prevention.

Atherosclerosis following renal injury is ameliorated by pioglitazone and losartan via macrophage phenotype

OBJECTIVE

Chronic kidney disease (CKD) amplifies atherosclerosis, which involves renin-angiotensin system (RAS) regulation of macrophages. RAS influences peroxisome proliferator-activated receptor-γ (PPARγ), a modulator of atherogenic functions of macrophages, however, little is known about its effects in CKD. We examined the impact of combined therapy with a PPARγ agonist and angiotensin receptor blocker on atherogenesis in a murine uninephrectomy model.

METHODS

Apolipoprotein E knockout mice underwent uninephrectomy (UNx) and treatment with pioglitazone (UNx + Pio), losartan (UNx + Los), or both (UNx + Pio/Los) for 10 weeks. Extent and characteristics of atherosclerotic lesions and macrophage phenotypes were assessed; RAW264.7 and primary peritoneal mouse cells were used to examine pioglitazone and losartan effects on macrophage phenotype and inflammatory response.

RESULTS

UNx significantly increased atherosclerosis. Pioglitazone and losartan each significantly reduced the atherosclerotic burden by 29.6% and 33.5%, respectively; although the benefit was dramatically augmented by combination treatment which lessened atherosclerosis by 55.7%. Assessment of plaques revealed significantly greater macrophage area in UNx + Pio/Los (80.7 ± 11.4% vs. 50.3 ± 4.2% in UNx + Pio and 57.2 ± 6.5% in UNx + Los) with more apoptotic cells. The expanded macrophage-rich lesions of UNx + Pio/Los had more alternatively activated, Ym-1 and arginine 1-positive M2 phenotypes (Ym-1: 33.6 ± 8.2%, p < 0.05 vs. 12.0 ± 1.1% in UNx; arginase 1: 27.8 ± 0.9%, p < 0.05 vs. 11.8 ± 1.3% in UNx). In vitro, pioglitazone alone and together with losartan was more effective than losartan alone in dampening lipopolysaccharide-induced cytokine production, suppressing M1 phenotypic change while enhancing M2 phenotypic change.

CONCLUSION

Combination of pioglitazone and losartan is more effective in reducing renal injury-induced atherosclerosis than either treatment alone. This benefit reflects mitigation in macrophage cytokine production, enhanced apoptosis, and a shift toward an anti-inflammatory phenotype.

Cysteine cathepsins and their potential in clinical therapy and biomarker discovery

Since their discovery, cysteine cathepsins were generally considered to be involved mainly in the nonspecific bulk protein degradation that takes place within the lysosomes. However, it has become clear that their proteolytical activity can also influence various specific pathological processes such as cancer, arthritis, and atherosclerosis. Furthermore, their localization was found not to be limited strictly to the lysosomes. In the light of those findings, it is not surprising that cysteine cathepsins are currently considered as highly relevant clinical targets. Moreover, recent development of proteomic-based methods for identification of novel physiological substrates of proteases provides a major opportunity also in the field of cysteine cathepsins. In this review, we will therefore present cysteine cathepsin roles in disease progression and discuss their potential relevance as prognostic and diagnostic biomarkers.

Recent advances in understanding the biochemical and molecular mechanism of diabetic nephropathy

Diabetic nephropathy (DN) is a chronic disease characterized by proteinuria, glomerular hypertrophy, decreased glomerular filtration and renal fibrosis with loss of renal function. DN is the leading cause of end-stage renal disease, accounting for millions of deaths worldwide. Hyperglycemia is the driving force for the development of diabetic nephropathy. The exact cause of diabetic nephropathy is unknown, but various postulated mechanisms are: hyperglycemia (causing hyperfiltration and renal injury), advanced glycosylation products, activation of cytokines. In this review article, we have discussed a number of diabetes-induced metabolites such as glucose, advanced glycation end products, protein kinase C and oxidative stress and other related factors that are implicated in the pathophysiology of the DN. An understanding of the biochemical and molecular changes especially early in the DN may lead to new and effective therapies towards prevention and amelioration of DN.

Aspirin downregulates angiotensin type 1 receptor transcription implications in capillary formation from endothelial cells

Aspirin [acetyl salicylic acid (ASA)] inhibits nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and reactive oxygen species generation, a pathway that underlies formation of new capillaries (angiogenesis). Angiotensin II (Ang II) participates in angiogenesis by activating type 1 receptor (AT1R). We examined if ASA would inhibit AT1R transcription, which requires NADPH oxidase, and thereby new capillary formation. Human umbilical vein endothelial cells were cultured in Matrigel and treated with Ang II with and without ASA. Expression of AT1R and NADPH oxidase was measured by quantitative polymerase chain reaction. Ang II in low concentrations induced AT1R messenger RNA and new capillary formation. ASA and its salicylic acid (SA) moiety both suppressed Ang II-mediated AT1R and vascular endothelial growth factor expression and the subsequent new capillary formation. Of note, the AT1R blocker losartan prevented new capillary formation. ASA and SA also suppressed NADPH oxidase (p22, p47, p67, and gp91 messenger RNA) expression. These observations suggest that ASA can inhibit Ang II-induced capillary formation in part via blocking NADPH oxidase and AT1R transcription. Because SA moiety had similar effect as ASA on AT1R expression, we suggest that the effect of ASA on new capillary formation is mediated by its SA moiety.

Cysteinyl cathepsins: multifunctional enzymes in cardiovascular disease

Until recently, the role of lysosomal cysteine protease cathepsins in intracellular protein degradation was believed to be mainly restricted to scavenging. However, recent studies have revealed nontraditional roles for cysteine protease cathepsins in the extracellular space during the development and progression of cardiovascular disease. Although the precise mechanisms are unknown, data from animal studies suggest that members of the cathepsin family, like other extracellular proteases, contribute to extracellular matrix protein remodeling and interstitial matrix degradation, as well as to cell signaling and cell apoptosis in heart disease. Inflammatory cytokines and hormones regulate the expression and secretion of cathepsins in cultured cardiovascular cells and macrophages. Serum levels of cathepsins L, S, and K and their endogenous inhibitor cystatin C may be useful predictive biomarkers in patients with coronary artery disease and cardiac disease. Furthermore, in vivo pharmacological intervention with a synthetic cathepsin inhibitor and cardiovascular drugs (including statins and angiotensin II type 1 receptor antagonists) has the potential for pharmacologic targeting of cathepsins in cardiovascular disease. This review focuses on cathepsin biology (structure, synthesis, processing, activation, secretion, activity regulation, and function) and the involvement of cysteinyl cathepsins in the pathogenesis of several heart and vessel diseases, especially with respect to their potential application as diagnostic and prognostic markers and drug targets to prevent inappropriate proteolysis in cardiovascular disease.

Macrophage polarization by angiotensin II-type 1 receptor aggravates renal injury-acceleration of atherosclerosis

OBJECTIVE

Angiotensin II is a major determinant of atherosclerosis. Although macrophages are the most abundant cells in atherosclerotic plaques and express angiotensin II type 1 receptor (AT1), the pathophysiologic role of macrophage AT1 in atherogenesis remains uncertain. We examined the contribution of macrophage AT1 to accelerated atherosclerosis in an angiotensin II-responsive setting induced by uninephrectomy (UNx).

METHODS AND RESULTS

AT1(-/-) or AT1(+/+) marrow from apolipoprotein E deficient (apoE(-/-)) mice was transplanted into recipient apoE(-/-) mice with subsequent UNx or sham operation: apoE(-/-)/AT1(+/+)→apoE(-/-)+sham; apoE(-/-)/AT1(+/+) →apoE(-/-)+UNx; apoE(-/-)/AT1(-/-)→apoE(-/-)+sham; apoE(-/-)/AT1(-/-)→apoE(-/-)+UNx. No differences in body weight, blood pressure, lipid profile, and serum creatinine were observed between the 2 UNx groups. ApoE(-/-)/AT1(+/+) →apoE(-/-)+UNx had significantly more atherosclerosis (16907±21473 versus 116071±8180 μm(2), P<0.05). By contrast, loss of macrophage AT1 which reduced local AT1 expression, prevented any effect of UNx on atherosclerosis (77174±9947 versus 75714±11333 μm(2), P=NS). Although UNx did not affect total macrophage content in the atheroma, lesions in apoE(-/-)/AT1(-/-)→apoE(-/-)+UNx had fewer classically activated macrophage phenotype (M1) and more alternatively activated phenotype (M2). Further, UNx did not affect plaque necrosis or apoptosis in apoE(-/-)/AT1(-/-)→apoE(-/-) whereas it significantly increased both (by 2- and 6-fold, respectively) in apoE(-/-)/AT1(+/+) →apoE(-/-) mice. Instead, apoE(-/-)/AT1(-/-)→apoE(-/-) had 5-fold-increase in macrophage-associated apoptotic bodies, indicating enhanced efferocytosis. In vitro studies confirmed blunted susceptibility to apoptosis, especially in M2 macrophages, and a more efficient phagocytic function of AT1(-/-) macrophages versus AT1(+/+).

CONCLUSIONS

AT1 receptor of bone marrow-derived macrophages worsens the extent and complexity of renal injury-induced atherosclerosis by shifting the macrophage phenotype to more M1 and less M2 through mechanisms that include increased apoptosis and impaired efferocytosis.

PPARγ and chronic kidney disease

Peroxisome proliferator-activated receptor-γ (PPARγ) agonists, exemplified by the thiazolidinediones (TZDs), have been used extensively for their beneficial effects to improve insulin sensitivity and lipid metabolism in type 2 diabetic patients. PPARγ receptors are part of the steroid hormone nuclear receptor family and, when activated by agonist binding, can affect numerous target genes expressing PPAR response elements. Results from experimental studies and a limited number of studies in humans suggest that PPARγ agonists have manifold effects beyond those on dysmetabolic syndrome. These potentially beneficial actions are mediated via renal parenchymal and infiltrating cells and modulate fibrotic, inflammatory, immune, proliferative, reactive oxygen and mitochondrial injury pathways. Thus, the potential benefits of TZDs in chronic kidney disease impact numerous pathogenic pathways. This review will focus on evidence of the effects of TZDs in nondiabetic chronic kidney disease in experimental and human disease settings.

Vasculoprotective effects of rosiglitazone through modulating renin-angiotensin system in vivo and vitro

Background

The peroxisome proliferator-activated receptor-γ (PPARγ) agonist rosiglitazone has been suggested to exert cardiovascular protection through the improvement of lipid metabolism, anti-inflammation, anti-proliferation etc. However, whether renin-angiotensin system (RAS) is involved in the vascular protective effects of PPARγ agonists is not fully understood. The present study aimed to investigate the effects of the renin-angiotensin system in vascular protection mediated by PPARγ agonists.

Objective

To investigate the actions of the renin-angiotensin system in vascular protection mediated by activation of PPARγ in vivo and in vitro.

Methods

Rats were fed a regular diet (n = 8), a cholesterol-rich diet plus methylthiouracil (80 mg/Kg/day, n = 10), a cholesterol-rich diet plus methylthiouracil and rosiglitazone (4 mg/kg/day, n = 10). The rosiglitazone treatment was started from one month after the start of cholesterol-rich diet plus methylthiouracil, and lasted five months. Cultured vascular smooth muscle cells (VSMCs) were pretreated with 1 μmol/L angiotensin II (ANG II) for 6 h and randomly divided into the control group; the ANG II group (1 μmol/L ANG II); the groups respectively treated with different concentration rosiglitazone (20, 30, 50) μmol/L for 12 h; the groups treated with 30 μmol/L rosiglitazone for (6, 12, 24) h. Morphology changes of the aortic tissues were observed by hematoxylin and eosin stain. The VSMC growth was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Angiotensin II and expression of angiotensin receptors were determined by radioimmunoassay, reverse transcription polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry.

Results

After 6 months, lipid deposition, VSMC proliferation and migration toward intima were observed in aortic tissues in the rats on a cholesterol-rich diet plus methylthiouracil, while these pathological changes induced by the cholesterol-rich diet were significantly suppressed by rosiglitazone. In addition, VSMC proliferation induced by ANG II was markedly inhibited by rosiglitazone. Rosiglitazone markedly down-regulated expression of angiotensin type 1 receptor (AT₁R) and up-regulated expression of angiotensin type 2 receptor (AT₂R) in the aortic tissues and ANG II-treated VSMCs.

Conclusions

The present study demonstrated that PPARγ agonist rosiglitazone suppressed ANG II-induced VSMC proliferation in vitro and early atherosclerotic formation evoked by cholesterol-rich diet in vivo. These vasculoprotective effects of rosiglitazone were mediated at least partially by reduction in local tissue ANG II concentration, down-regulation of AT₁R expression and up-regulation of AT₂R expression both at the mRNA and protein levels.

Oral activated charcoal adsorbent (AST-120) ameliorates extent and instability of atherosclerosis accelerated by kidney disease in apolipoprotein E-deficient mice

BACKGROUND

Accelerated atherosclerosis and increased cardiovascular events are not only more common in chronic kidney disease (CKD) but are more resistant to therapeutic interventions effective in the general population. The oral charcoal adsorbent, AST-120, currently used to delay start of dialysis, reduces circulating and tissue uremic toxins, which may contribute to vasculopathy, including atherosclerosis. We, therefore, investigated whether AST-120 affects CKD-induced atherosclerosis.

METHODS

Apolipoprotein E-deficient mice, a model of atherosclerosis, underwent uninephrectomy, subtotal nephrectomy or sham operation at 8 weeks of age and were treated with AST-120 after renal ablation. Atherosclerosis and its characteristics were assessed at 25 weeks of age.

RESULTS

Uninephrectomy and subtotal nephrectomised mice had significantly increased acceleration of atherosclerosis. AST-120 treatment dramatically reduced the atherosclerotic burden in mice with kidney damage, while there was no beneficial effect in sham-operated mice. The benefit was independent of blood pressure, serum total cholesterol or creatinine clearance. AST-120 significantly decreased necrotic areas and lessened aortic deposition of the uremic toxin indoxyl sulfate without affecting lesional macrophage or collagen content. Furthermore, AST-120 lessened aortic expression of monocyte chemoattractant protein-1, tumor necrosis factor-α and interleukin-1β messenger RNA.

CONCLUSIONS

AST-120 lessens the extent of atherosclerosis induced by kidney injury and alters lesion characteristics in apolipoprotein E-deficient mice, resulting in plaques with a more stable phenotype with less necrosis and reduced inflammation.

AT1 blockade attenuates atherosclerotic plaque destabilization accompanied by the suppression of cathepsin S activity in apoE-deficient mice

Although it has been suggested that the renin-angiotensin (RA) system and cathepsins contribute to the development and vulnerability of atherosclerotic plaque, the interaction of the RA system and cathepsins is unclear. Thus, we investigated the effects of an angiotensin II type 1 receptor (AT1) antagonist, olmesartan, on the levels of cathepsins in brachiocephalic atherosclerotic plaque and plaque stabilization in apolipoprotein E (apoE)-deficient mice receiving a high-fat diet. Under a high fat diet, treatment with olmesartan (3 mg/kg per day) maintained collagen and elastin at high levels and attenuated the plaque development and cathepsin S (Cat S) level in the atherosclerotic plaque of apoE-deficient mice. The administration of olmesartan suppressed the accumulation of macrophages in plaque. Immunoreactivities of Cat S and AT1 were observed in macrophages. The amount of Cat S mRNA and the macrophage-mediated collagenolytic and elastolytic activities in cultured macrophages were increased by exposure to angiotensin II (Ang II), and these effects were diminished by olmesartan and the NADPH-oxidase inhibitor apocynin. These results suggested that Cat S derived from macrophages is involved in the mechanisms of atherosclerotic plaque vulnerability, and AT1 blocker maintained the plaque stabilization alongside the suppression of Cat S and macrophage activities.

Mechanism of diastolic stiffening of the failing myocardium and its prevention by angiotensin receptor and calcium channel blockers

OBJECTIVE

To investigate the mechanism responsible for the increased cardiac stiffness associated with hypertensive heart failure in Dahl salt-sensitive (DS) rats and the effects of treatment with the combination of a calcium channel blocker [azelnidipine (AZE)] and angiotensin II type 1 receptor blocker [olmesartan (OLM)].

METHODS

DS rats fed a high-salt diet from 7 weeks of age were treated (or not) from 12 to 19 weeks of age with the vasodilator hydralazine, OLM plus AZE, or the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin. Rats fed a low-salt diet served as controls.

RESULTS

Treatment with OLM plus AZE attenuated changes in the expression of collagen isoforms and a decrease in the ratio of elastin to collagen in the left ventricle and prevented the increase in myocardial stiffness and diastolic dysfunction in DS rats in a manner independent of the hypotensive effect of these drugs. Such treatment also inhibited the expression and activation of elastolytic proteases (including cathepsins S and K and metalloproteinases-2, -9, and -12), NADPH oxidase-dependent superoxide production, and inflammatory changes in the failing myocardium. All these effects were mimicked by treatment with apocynin.

CONCLUSIONS

The changes in collagen isoform expression and the decrease in the elastin to collagen ratio in the failing myocardium likely account for the increase in diastolic stiffness in this model of hypertensive heart failure. Administration of angiotensin receptor and calcium channel blockers prevented these changes in a manner independent of the hypotensive effect of these drugs by inhibiting the increase in elastolytic activity induced by activation of NADPH oxidase.

Neointimal-specific induction of apoptosis by losartan results in regression of vascular lesion in rat aorta

We previously reported that initiating treatment with the angiotensin II receptor antagonist losartan, prior to and immediately after balloon injury, attenuates neointimal hyperplasia via induction of smooth muscle cell (SMC) apoptosis in the aorta of spontaneously hypertensive rats (SHR). The present study examines whether losartan can induce regression of an established neointima. Balloon angioplasty was performed in the aorta of 1 1 week-old SHR. Five weeks were allowed for neointima formation before rats received placebo or losartan (30 mg/kg/day) for 1 to 4 weeks. Blood pressure was measured by tail cuff plethysmography. Losartan significantly reduced blood pressure (16%) versus placebo within 2 weeks of treatment. In situ labeling with terminal deoxynucleotidyl transferase among neointimal SMC was transiently increased with losartan (10-fold at 2 weeks; P=0.004) in correlation with internucleosomal fragmentation of vascular DNA. Accordingly, losartan reversed neointimal hyperplasia by 43% (P=0.002) and 61% (P=0.007) at weeks 2 and 4, respectively, and neointimal mass by 63% (P<0.001) and 75% (P<0.001) at weeks 2 and 4, respectively, as compared to pre-treatment values. No change in aortic medial hyperplasia or mass was observed during losartan treatment. Taken together, endothelial denudation rendered the underlying media resistant to drug-induced remodeling, while losartan treatment induced vascular lesion regression by inducing apoptosis selectively in neointimal SMC, an effect that may contribute to the reduction of cardiovascular complications in hypertension.

Prevention of aortic elastic lamina defects by losartan in apolipoprotein(E)-deficient mouse

1. In a previous study, we identified prevalent internal elastic lamina (IEL) defects in the aorta of hyperlipidaemic apolipoprotein E (ApoE)-deficient mice that are thought to provide a structural basis for the development of atherosclerosis and intimal thickening. In the present study, we examined the effects of losartan, an angiotensin AT1 receptor antagonist, on the development of IEL defects. 2. Male 18-week-old ApoE-deficient mice (maintained on a normal diet) were treated with losartan (3 or 30 mg/kg per day) for 10 weeks via the drinking water. The IEL defects were quantified histologically by measuring the continuity of the IEL within the inner curvature of the aortic arch. 3. In untreated animals, there was an age-dependent increase in IEL defects from 7.2 ± 2.1% at 18 weeks to 13.8 ± 4.0% at 28 weeks. Treatment with the high dose of losartan significantly prevented the development of IEL defects (4.7 ± 1.3% at 28 weeks; P < 0.05 vs untreated). This effect was independent of changes in blood pressure or plasma lipid levels. Using quantitative real-time polymerase chain reaction, we found that the effects of losartan were not associated with changes in levels of matrix metalloproteinase (MMP)-2 and MMP-9, tissue inhibitor of matrix metalloproteinase-1 or inflammatory markers in the aorta. 4. The results suggest that the renin-angiotensin system may contribute to the development of aortic IEL defects in a blood pressure-independent manner.

Attenuation of inflammation and expansive remodeling by Valsartan alone or in combination with Simvastatin in high-risk coronary atherosclerotic plaques

AIMS

We investigated the role of Valsartan (V) alone or in combination with Simvastatin (S) on coronary atherosclerosis and vascular remodeling, and tested the hypothesis that V or V/S attenuate the pro-inflammatory effect of low endothelial shear stress (ESS).

METHODS

Twenty-four diabetic, hyperlipidemic swine were allocated into Early (n=12) and Late (n=12) groups. In each group animals were treated with Placebo (n=4), V (n=4) and V/S (n=4) and followed for 8 weeks in the Early group and 30 weeks in the Late group. Blood pressure, serum cholesterol and glucose were similar across the treatment subgroups. ESS was calculated in plaque-free subsegments of interest (n=109) in the Late group at week 23. Coronary arteries of this group were harvested at week 30, and the subsegments of interest were identified, and analyzed histopathologically.

RESULTS

V alone or with S reduced the severity of inflammation in high-risk plaques. Both regimens attenuated the severity of enzymatic degradation of the arterial wall, reducing the severity of expansive remodeling. V alone or with S attenuated the pro-inflammatory effect of low ESS.

CONCLUSIONS

V alone or with S exerts a beneficial effect of reducing and stabilizing high-risk plaque characteristics independent of a blood pressure- and lipid-lowering effect.

Superoxide-dependent cathepsin activation is associated with hypertensive myocardial remodeling and represents a target for angiotensin II type 1 receptor blocker treatment

The elastolytic activity of cathepsins in the myocardium is implicated in hypertensive heart failure (HF). Given that reactive oxygen species are also implicated in protease activation associated with cardiac remodeling, we examined the role of the reactive oxygen species-induced cathepsin activation system in cardiac remodeling during the development of hypertensive HF. Dahl salt-sensitive hypertensive rats maintained on a high-salt diet were treated with vehicle, the cathepsin inhibitor E64d, or the angiotensin receptor blocker olmesartan from 12 to 19 weeks of age. Cathepsin expression and activity were increased in the left ventricle of HF rats; olmesartan inhibited these effects, restored the balance between elastin and collagen in the left ventricle, and suppressed degradation of the elastic lamina of coronary arteries of HF rats. Furthermore, olmesartan inhibited up-regulation of NADPH oxidase subunits and activity as well as superoxide generation. These effects of olmesartan were mimicked by E64d and were accompanied by amelioration of cardiac fibrosis. Finally, olmesartan and apocynin reduced angiotensin II-induced increases in cathepsin mRNA and protein levels in cultured rat neonatal cardiac myocytes. These data suggest that cathepsins likely trigger and promote cardiac remodeling and that blocking the angiotensin II type 1 receptor attenuates cathepsin expression and activity by inhibiting the production of superoxide by NADPH oxidase, thereby attenuating cardiac remodeling and dysfunction.