Myocardial glutathione metabolic status in fat-fed rabbits.

Short-term fat feeding could exert adverse cardiac effects by altering myocardial glutathione-related antioxidant defenses. We have here assessed total glutathione (TG), the activities of glutathione reductase (GSSG-Red), γ-glutamylcysteine synthetase (γ-GCS), γ-glutamyl transpeptidase (γ-GT) and glutathione peroxidase (GSH-Px), fluorescent damage products of lipid peroxidation (FDPL), thiobarbituric acid-reactive substances (TBARS), H2O2, and ATP in the aerobically perfused hearts of control rabbits and of rabbits fed a fat-enriched diet for 18 days. Such biochemical parameters, myocardial hemodynamics and infarct size were assessed in the perfused hearts of other control and fat-fed rabbits subjected to 60 min global ischemia plus 30 min reperfusion. Compared to controls, a reduced activity of GSSG-Red and γ-GT associated with decreased TG content was detected in the aerobically perfused hearts of fat-fed rabbits, which also showed insignificant γ-GCS activation, GSH-Px depressed activity, FDPL, TBARS and H2O2 burden, and unaltered ATP content. Ischemia-reperfusion decreased the myocardial levels of TG, ATP, and γ-GCS activity and augmented those of FDPL, TBARS, and H2O2 especially in the fat-fed rabbits, without significant changes in myocardial GSSG-Red, γ-GT, and GSH-Px activities. Ischemia-reperfusion induced greater hemodynamic dysfunction and infarct size in the hearts of fat-fed rabbits than in those of controls. Thus, short-term fat feeding and hyperlipidemia alter glutathione metabolic status of the rabbit myocardium, inducing a GSSG-Red- and γ-GT-related decrement of myocardial glutathione content, which, together with GSH-Px dysfunction, may favor tissue oxidative stress and render the myocardium more susceptible to ischemia-reperfusion injury.

Prediction of carotid plaques in hypertensive patients by risk factors, left ventricular hypertrophy, and epicardial adipose tissue thickness.

Hypertension and other risk factors (RFs) predispose to carotid plaques (CPs). An association between left ventricular hypertrophy (LVH) or epicardial adipose tissue (EAT) and CPs has also been reported. The aim of the study was to evaluate whether the assessment of LVH and EAT thickness, beyond RFs, would be of additive value in predicting CPs in hypertensive subjects. We studied 548 hypertensive patients aged ≥ 50 years without carotid bruit. LVH and CPs were evaluated and defined according to standard criteria. EAT was measured by echocardiography above the free wall of the right ventricle at end diastole. The presence of LVH and EAT thickness above the median value (3.9 mm) together significantly increased prevalence of CPs in subjects with 0-1 risk factor, but not in those with ≥ 2 RFs who showed high prevalence of CPs independently of LVH and/or EAT. Receiver operating characteristic curve analysis showed that the addition of LVH and higher EAT thickness together significantly improved prediction of CPs in patients with 0-1 risk factor. Indeed, the area under the curve improved from 0.63 (0.56-0.69) to 0.73 (0.67-0.79), which was significantly higher (p < 0.05). In patients with ≥ 2 RFs, the addition of LVH and EAT did not significantly improve prediction of CPs. This study shows that the presence of LVH and higher EAT thickness together improves prediction of CPs in hypertensive patients with 0-1 risk factor and that those with ≥ 2 RFs show high prevalence of CPs independently of LVH and/or EAT.

Ambulatory Resistant Hypertension and Risk of Heart Failure in the Elderly.

(1) Background: The aim of the study was to assess the risk of heart failure (HF) in elderly treated hypertensive patients with white coat uncontrolled hypertension (WUCH), ambulatory nonresistant hypertension (ANRH) and ambulatory resistant hypertension (ARH), when compared to those with controlled hypertension (CH). (2) We studied 745 treated hypertensive subjects older than 65 years. CH was defined as clinic blood pressure (BP) < 140/90 mmHg and 24-h BP < 130/80 mmHg; WUCH was defined as clinic BP ≥ 140/90 mmHg and 24-h BP < 130/80 mmHg; ANRH was defined as 24-h BP ≥ 130/80 mmHg in patients receiving ≤2 antihypertensive drugs; ARH was defined as 24-h BP ≥ 130/80 mmHg in patients receiving ≥3 antihypertensive drugs. (3) Results: 153 patients had CH, 153 had WUCH, 307 had ANRH and 132 (18%) had ARH. During the follow-up (8.4 ± 4.8 years), 82 HF events occurred. After adjustment for various covariates, when compared to CH, the hazard ratio (95% confidence interval) for HF was 1.30 (0.51-3.32), 2.14 (1.03-4.43) and 3.52 (1.56-7.96) in WUCH, ANRH and ARH, respectively. (4) Conclusions: among elderly treated hypertensive patients, those with ARH are at a considerably higher risk of developing HF when compared to CH.

Prognostic Impact of 24-Hour Pulse Pressure Components in Treated Hypertensive Patients Older Than 65 Years.

(1) Background: The aim of this study was to assess the prognostic impact of 24-hour pulse pressure (PP), elastic PP (elPP) and stiffening PP (stPP) in elderly treated hypertensive patients; (2) Methods: In this retrospective study, we evaluated 745 treated hypertensive subjects older than 65 years who underwent ambulatory blood pressure monitoring to assess 24-hour PP and 24-hour elPP and stPP, as calculated by a mathematical model. The association of these PP components with a combined endpoint of cardiovascular events was investigated; (3) Results: The 24-hour PP, elPP and stPP were 59 ± 12.5, 47.5 ± 9.5 and 11.5 ± 6.5 mmHg, respectively. During the follow-up (mean 8.4 years), 284 events occurred, including coronary events, stroke, heart failure hospitalization and peripheral revascularization. In the univariate Cox regression analysis, 24-hour PP, elPP and stPP were associated with the combined outcome. After the adjustment for covariates, per one standard deviation increase, 24-hour PP had a borderline association with risk (hazard ratio (HR) 1.16, 95% confidence interval (CI) 1.00-1.34), 24-hour elPP remained associated with cardiovascular events (HR 1.20, 95% CI 1.05-1.36) and 24-hour stPP lost its significance. (4) Conclusions: 24-hour elPP is a predictor of cardiovascular events in elderly treated hypertensive patients.

Prognostic value of non-resistant and resistant masked uncontrolled hypertension detected by ambulatory blood pressure monitoring.

Masked uncontrolled hypertension (MUCH) is at higher cardiovascular risk than controlled hypertension (CH). In previous studies, patients with MUCH were considered as a unique group though those receiving ≤2 drugs could be defined as having nonresistant MUCH (NRMUCH) and those receiving ≥3 drugs as having resistant MUCH (RMUCH). The aim of this study was to assess the prognostic value of NRMUCH and RMUCH detected by ambulatory blood pressure (BP) monitoring. Cardiovascular risk was evaluated in 738 treated hypertensive patients with normal clinic BP. Patients were classified as having CH or MUCH if daytime BP < or ≥ 135/85 mmHg, respectively, regardless of nighttime BP, or CH or MUCH if 24-h BP < or ≥ 130/80 mmHg, respectively, regardless of daytime or nighttime BP. By daytime or 24-h BP, the authors detected 523 (71%), 178 (24%), and 37 (5%) or 463 (63%), 231 (31%), and 44 (6%) patients with CH, NRMUCH, and RMUCH, respectively. During the follow-up (median 10 years), 148 events occurred. After adjustment for covariates, compared to CH, the hazard ratio (HR), 95% confidence interval (CI), for cardiovascular events was 1.81, 1.27-2.57, and 2.99, 1.73-5.16, in NRMUCH and RMUCH defined by daytime BP, respectively, and 1.58, 1.12-2.23, and 2.21, 1.27-3.82, in NRMUCH and RMUCH defined by 24-h BP, respectively. If RMUCH was compared with NRMUCH, the risk tended to be higher in RMUCH but did not attain statistical significance (P = .08 and P = .23 by daytime and 24-h BP thresholds, respectively). In conclusion, both NRMUCH and RMUCH are at increased cardiovascular risk than CH.

Prediction of Masked Uncontrolled Hypertension Detected by Ambulatory Blood Pressure Monitoring.

The aim of this study was to provide prediction models for masked uncontrolled hypertension (MUCH) detected by ambulatory blood pressure (BP) monitoring in an Italian population. We studied 738 treated hypertensive patients with normal clinic BPs classified as having controlled hypertension (CH) or MUCH if their daytime BP was < or ≥135/85 mmHg regardless of nighttime BP, respectively, or CH or MUCH if their 24-h BP was < or ≥130/80 mmHg regardless of daytime or nighttime BP, respectively. We detected 215 (29%) and 275 (37%) patients with MUCH using daytime and 24-h BP thresholds, respectively. Multivariate logistic regression analysis showed that males, those with a smoking habit, left ventricular hypertrophy (LVH), and a clinic systolic BP between 130−139 mmHg and/or clinic diastolic BP between 85−89 mmHg were associated with MUCH. The area under the receiver operating characteristic curve showed good accuracy at 0.78 (95% CI 0.75−0.81, p < 0.0001) and 0.77 (95% CI 0.73−0.80, p < 0.0001) for MUCH defined by daytime and 24 h BP, respectively. Internal validation suggested a good predictive performance of the models. Males, those with a smoking habit, LVH, and high-normal clinic BP are indicators of MUCH and models including these factors provide good diagnostic accuracy in identifying this ambulatory BP phenotype.

Association of clinic and ambulatory blood pressure with new-onset atrial fibrillation: A meta-analysis of observational studies.

The aim of this study was to perform a meta-analysis of studies evaluating the association of clinic and daytime, nighttime, and 24-h blood pressure with the occurrence of new-onset atrial fibrillation. We conducted a literature search through PubMed, Web of science, and Cochrane Library for articles evaluating the occurrence of new-onset atrial fibrillation in relation to the above-mentioned blood pressure parameters and reporting adjusted hazard ratio and 95% confidence interval. We identified five studies. The pooled population consisted of 7224 patients who experienced 444 cases of atrial fibrillation. The overall adjusted hazard ratio (95% confidence interval) was 1.05 (0.98-1.13), 1.19 (1.11-1.27), 1.18 (1.11-1.26), and 1.23 (1.14-1.32), per 10-mmHg increment in clinic, daytime, nighttime, and 24-h systolic blood pressure, respectively. The degree of heterogeneity of the hazard ratio estimates across the studies (Q and I-squared statistics) were minimal. The results of this meta-analysis strongly suggest that ambulatory systolic blood pressure prospectively predicts incident atrial fibrillation better than does clinic systolic blood pressure and that daytime, nighttime, and 24-h systolic blood pressure are similarly associated with future atrial fibrillation.

Inhibitory activity of salicylic acid on lipoxygenase-dependent lipid peroxidation.

BACKGROUND: Since iron is essential for lipoxygenase activity and salicylic acid (SA) can interact with the metal, possible lipoxygenase inhibition by SA was investigated. METHODS: Kinetic spectrophotometric evaluation of enzymatic lipid peroxidation catalyzed by soybean lipoxygenase (SLO), rabbit reticulocyte 15-lipoxygenase (RR15-LOX), porcine leukocyte 12-lipoxygenase (PL12-LOX) and human recombinant 5-lipoxygenase (HR5-LOX) with and without SA. RESULTS: SA inhibited linoleic, arachidonic and docosahexaenoic acid or human lipoprotein peroxidation catalyzed by SLO with IC50 of, respectively, 107, 153, 47 and 108 microM. Using the same substrates, SA inhibited RR15-LOX with IC50 of, respectively, 49, 63, 27 and 51 microM. Further, arachidonic acid peroxidation catalyzed by PL12-LOX and HR5-LOX was inhibited by SA with IC50 of 101 and 168 microM, respectively. Enzymatic inhibition was complete, reversible and non-competitive. Conceivably due to its lower hydrophobicity, aspirin was less effective, indicating acetylation-independent enzyme inhibition. SA and aspirin were ineffective peroxyl radical scavengers but readily reduced Fe3+, i.e. FeCl3, to Fe2+, suggesting their capacity to reduce Fe3+ at the enzyme active site. Indeed, similar to the catecholic redox inhibitor nordihydroguaiaretic acid, SA inhibited with the same efficiency both ferric and the native ferrous SLO form, indicating that these compounds reduce the active ferric enzyme leading to its inactivation. GENERAL SIGNIFICANCE: SA can inhibit lipoxygenase-catalyzed lipid peroxidation at therapeutic concentrations, suggesting its possible inhibitory activity against enzymatic lipid peroxidation in the clinical setting.

Prognostic Value of Masked Uncontrolled Hypertension Defined by Different Ambulatory Blood Pressure Criteria.

BACKGROUND: Masked uncontrolled hypertension (MUCH), that is, nonhypertensive clinic but high out-of-office blood pressure (BP) in treated patients is at increased cardiovascular risk than controlled hypertension (CH), that is, nonhypertensive clinic and out-of-office BP. Using ambulatory BP, MUCH can be defined as daytime and/or nighttime and/or 24-hour BP above thresholds. It is unclear whether different definitions of MUCH have similar prognostic information. This study assessed the prognostic value of MUCH defined by different ambulatory BP criteria. METHODS: Cardiovascular events were evaluated in 738 treated hypertensive patients with nonhypertensive clinic BP. Among them, participants were classified as having CH or daytime MUCH (BP ≥135/85 mm Hg) regardless of nighttime BP (group 1), nighttime MUCH (BP ≥120/70 mm Hg) regardless of daytime BP (group 2), 24-hour MUCH (BP ≥130/80 mm Hg) regardless of daytime or nighttime BP (group 3), daytime MUCH only (group 4), nighttime MUCH only (group 5), and daytime + nighttime MUCH (group 6). RESULTS: We detected 215 (29%), 357 (48.5%), 275 (37%), 42 (5.5%),184 (25%) and 173 (23.5%) patients with MUCH from group 1 to 6, respectively. During the follow-up (10 ± 5 years), 148 events occurred in patients with CH and MUCH. After adjustment for covariates, compared with patients with CH, the adjusted hazard ratio (95% confidence interval) for cardiovascular events was 2.01 (1.45-2.79), 1.53 (1.09-2.15), 1.69 (1.22-2.34), 1.52 (0.80-2.91), 1.15 (0.74-1.80), and 2.29 (1.53-3.42) from group 1 to 6, respectively. CONCLUSIONS: The prognostic impact of MUCH defined according to various ambulatory BP definitions may be different.

Prognostic value of average real variability of systolic blood pressure in elderly treated hypertensive patients.

OBJECTIVE: The independent prognostic significance of ambulatory blood pressure variability in the elderly is incompletely clear. We investigated the prognostic value of average real variability of 24-hour blood pressure in elderly treated hypertensive patients. METHODS: The occurrence of a combined end-point including stroke, coronary events, heart failure requiring hospitalization and peripheral revascularization was evaluated in 757 elderly treated hypertensive patients. According to tertiles of average real variability of 24-hour systolic blood pressure patients were classified as having low (≤8.66 mmHg; n = 252), medium (8.67-10.05 mmHg; n = 252) or high (>10.05 mmHg; n = 253) average real variability. RESULTS: During the follow-up (6.9 ± 3.4 years, range 0.4-12.9 years), 195 events occurred. The event rate of the population was 3.74 per 100 patient-years. After adjustment for age, sex, previous events, diabetes, estimated glomerular filtration rate, left ventricular hypertrophy, left atrial enlargement, asymptomatic left ventricular systolic dysfunction at baseline, 24-hour systolic blood pressure, non-dipping and dipping with high morning surge of blood pressure, patients with high average real variability were at higher cardiovascular risk than those with low average real variability (hazard ratio 1.64, 95% confidence interval 1.12-2.40). CONCLUSIONS: In elderly treated hypertensive patients, high average real variability of 24-hour systolic blood pressure is associated with higher cardiovascular risk independently of other risk markers, average 24-hour systolic blood pressure and circadian blood pressure changes.

Prognostic value of morning surge of blood pressure in middle-aged treated hypertensive patients.

We investigated the prognostic value of morning surge (MS) of blood pressure (BP) in middle-aged treated hypertensive patients. The occurrence of a composite end point (coronary events, stroke, and heart failure requiring hospitalization) was evaluated in 1073 middle-aged treated hypertensive patients (mean age 49 years). Patients with preawakening MS of BP above the 90th percentile (27/20.5 mm Hg for systolic/diastolic BP) were defined as having high MS of BP. During the follow-up (mean 10.9 years), 131 cardiovascular events occurred. After adjustment for various covariates, including known risk markers and ambulatory BP parameters, patients with high MS of systolic BP (hazard ratio 1.81, 95% confidence interval 1.10-2.96) and those with high MS of diastolic BP (hazard ratio 1.98, 95% confidence interval 1.19-3.28) were at higher cardiovascular risk than those with normal MS. In middle-aged treated hypertensive patients, high MS of systolic and diastolic BP is independently associated with increased cardiovascular risk.

Suppression of RAGE as a basis of simvastatin-dependent plaque stabilization in type 2 diabetes.

OBJECTIVE: Receptor for advanced glycation end products (AGEs) (RAGE) plays a central role in the process of plaque rupture in diabetic patients. Recently, it has been reported that RAGE may be downregulated by improving glycemic control. In contrast, despite being well known that RAGE may be induced in human vessels in a glucose-independent fashion, also by myeloperoxidase (MPO)-dependent AGE generation, no data exist regarding the possibility of a pharmacological modulation of glucose-independent RAGE generation. Thus, the aim of this study was to characterize the effect of simvastatin on the expression of RAGE and RAGE-dependent plaque-destabilizing genes in human atherosclerotic plaques. METHODS AND RESULTS: Seventy type 2 diabetic patients with asymptomatic carotid artery stenosis (>70%) were randomized to American Heart Association (AHA) step 1 diet plus simvastatin (40 mg/d) or AHA step 1 diet alone for 4 months before endarterectomy. Plaque expression of MPO, AGEs, RAGE, NF-kappaB, COX-2, mPGES-1, matrix metalloproteinase (MMP)-2 and MMP-9, lipid and oxidized LDL (oxLDL) content, procollagen 1, and interstitial collagen was analyzed by immunohistochemistry and Western blot; zymography was used to detect MMP activity. Plaques from the simvastatin group had less (P<0.0001) immunoreactivity for MPO, AGEs, RAGE, p65, COX-2, mPGES-1, MMP-2, and MMP-9, lipids and oxLDL; reduced (P<0.0001) gelatinolytic activity; increased (P<0.0001) procollagen 1 and collagen content; and fewer (P<0.0001) macrophages, T-lymphocytes, and HLA-DR+ cells. Of interest, RAGE inhibition by simvastatin, observed not only in plaque sections but also in plaque-derived macrophages, was reverted by addition of AGEs in vitro. CONCLUSIONS: This study supports the hypothesis that simvastatin inhibits plaque RAGE expression by decreasing MPO-dependent AGE generation. This effect in turn might contribute to plaque stabilization by inhibiting the biosynthesis of PGE2-dependent MMPs, responsible for plaque rupture.

Association between 5-lipoxygenase expression and plaque instability in humans.

OBJECTIVE: The participation of 5-lipoxygenase (5-LO) in the development of atherosclerosis has been suggested by recent studies. However, a role for 5-LO as a modulator of atherosclerotic plaque instability has not been previously reported in humans. Thus, the aims of this study was to analyze the expression of 5-LO in human carotid plaques and to investigate the mechanism by which this enzyme could lead to plaque instability and rupture. METHODS AND RESULTS: We obtained atherosclerotic plaques from 60 patients undergoing carotid endarterectomy. We divided the plaques into symptomatic and symptomatic according to clinical evidence of plaque instability. Clinical evidence of plaque instability was provided by the assessment of recent ischemic symptoms attributable to the stenosis and by the presence of ipsilateral cerebral lesion(s) determined by computed tomography. Plaques were analyzed for CD68+ macrophages, CD3+ T cells, alpha-actin+ smooth muscle cells, 5-LO, cyclooxygenase 2, matrix metalloproteinase (MMP)-2, and MMP-9 by immunohistochemical, immunoblotting, and densitometric analyses. MMP activity was assessed by zymography. Leukotriene (LT) B4 and collagen were quantified by ELISA and Sirius red polarization, respectively. The percentage of macrophage-rich and T-cell-rich areas was larger in symptomatic compared with asymptomatic patients (25+/-6% versus 8+/-4%, P<0.0001, and 74+/-17 versus 18+/-4 cell/mm2, P<0.003). 5-LO expression was higher in symptomatic compared with asymptomatic plaques (24+/-4% versus 6+/-3%, P<0.0001) and was associated with increased MMP-2 and MMP-9 expression (27+/-4% versus 7+/-3%, P<0.0001, and 29+/-5% versus 8+/-2%, P<0.0001) and activity and with decreased collagen content (6.9+/-2.4% versus 17.8+/-3.1%, P<0.01). Immunofluorescence showed that 5-LO and MMPs colocalize in activated macrophages. Notably, higher 5-LO in symptomatic plaques correlated with increased LTB4 production (18.15+/-3.56 versus 11.27+/-3.04 ng/g tissue, P<0.0001). CONCLUSIONS: The expression of 5-LO is elevated in symptomatic compared with asymptomatic plaques and is associated with acute ischemic syndromes, possibly through the generation of LTB4, subsequent MMP biosynthesis, and plaque rupture.

Association between prostaglandin E receptor subtype EP4 overexpression and unstable phenotype in atherosclerotic plaques in human.

OBJECTIVE: We recently demonstrated that inducible cyclooxygenase/PGE synthase-1 (COX-2/mPGES-1) are overexpressed in symptomatic plaques in association with PGE2-dependent metalloproteinase (matrix metalloproteinase [MMP]) biosynthesis and plaque rupture. However, it is not known which of the 4 PGE2 receptors (EP1-4) mediates macrophage metalloproteinase generation. The aim of this study was to characterize EP1-4 expression in plaques from symptomatic and asymptomatic patients undergoing carotid endarterectomy and correlate it with the extent of inflammatory infiltration, COX-2/mPGES-1 and MMP expression and clinical features of patients' presentation. METHODS AND RESULTS: Plaques were analyzed for COX-2, mPGES-1, EP1-4, MMP-2, and MMP-9 by immunohistochemistry, reverse-transcription polymerase chain reaction and Western blot; zymography was used to detect MMP activity. We observed strong EP4 immunoreactivity, only very weak staining for EP2, and no expression of EP1 and EP3 in atherosclerotic plaques. EP4 was more abundant in MMP-rich symptomatic lesions, whereas EP2 was no different between symptomatic and asymptomatic plaques. Finally, MMP induction by PGE2 in vitro was inhibited by the EP4 antagonist L-161 982, but not by its inactive analog L-161 983 or by the EP2 antagonist AH6809. CONCLUSIONS: This study shows that EP4 overexpression is associated with enhanced inflammatory reaction in atherosclerotic plaques. This effect might contribute to plaque destabilization by inducing culprit metalloproteinase expression.

Preprocedural level of soluble CD40L is predictive of enhanced inflammatory response and restenosis after coronary angioplasty.

BACKGROUND: Inflammation plays a pathogenic role in the development of restenosis after percutaneous transluminal coronary angioplasty (PTCA). CD40-CD40L interaction is involved in the pathogenesis of atherosclerosis; however, its role in the pathophysiology of restenosis is still unclear. We tested the hypothesis that soluble CD40L (sCD40L) may be involved in the process of restenosis and that it exerts its effect by triggering a complex group of inflammatory reactions on endothelial and mononuclear cells. METHODS AND RESULTS: We studied 70 patients who underwent PTCA and who had repeated angiograms at 6-month follow-up. Plasma sCD40L was measured before and 1, 5, 15, and 180 days after PTCA, whereas plasma soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, E-selectin, and monocyte chemoattractant protein (MCP)-1 were measured before and 24 hours after PTCA. Furthermore, the release of adhesion molecules and MCP-1 and the ability to repair an injury in endothelial cells, as well as the generation of O2- in monocytes, were analyzed in vitro after stimulation with serum from patients or healthy control subjects. Restenosis occurred in 18 patients (26%). Restenotic patients had preprocedural sCD40L significantly higher than patients with favorable outcomes (2.13+/-0.3 versus 0.87+/-0.12 ng/mL, P<0.0001). Elevated sCD40L at baseline was significantly correlated with adhesion molecules and MCP-1 generation after PTCA and with lumen loss at 6-month follow-up. Furthermore, high sCD40L was directly associated in vitro with adhesion molecules and MCP-1 generation and impaired migration in endothelial cells and with enhanced O2- generation in monocytes. CONCLUSIONS: We conclude that increased sCD40L is associated with late restenosis after PTCA. This may provide an important biochemical link between restenosis and aspirin-insensitive platelet activation. These results provide a rationale for studies with new antiplatelet treatments in patients who underwent PTCA.

Blockade of the angiotensin II type 1 receptor stabilizes atherosclerotic plaques in humans by inhibiting prostaglandin E2-dependent matrix metalloproteinase activity.

BACKGROUND: Clinical trials have demonstrated that agents that inhibit the angiotensin II pathway confer benefit beyond the reduction of blood pressure alone. However, the molecular mechanism underlying this effect has yet to be investigated. Recently, we have demonstrated enhanced expression of inducible cyclooxygenase (COX) and prostaglandin (PG)E2-dependent synthase (COX-2/mPGES-1) in human symptomatic plaques and provided evidence that it is associated with metalloproteinase (MMP)-induced plaque rupture. Thus, the aim of this study was to characterize the effect of the angiotensin II type 1 (AT1) receptor antagonist irbesartan on the inflammatory infiltration and expression of COX-2/mPGES-1 and MMPs in human carotid plaques. METHODS AND RESULTS: Seventy patients with symptomatic carotid artery stenosis were randomized to irbesartan (300 mg/d) or chlorthalidone (50 mg/d) for 4 months before endarterectomy. Plaques were subjected to analysis of COX-1, COX-2, mPGES-1, MMP-2, and MMP-9, angiotensin II, AT(1), AT2, and collagen content by immunocytochemistry, Western blot, and reverse-transcriptase polymerase chain reaction, whereas zymography was used to detect MMP activity. Immunohistochemistry was also used to identify CD68+ macrophages, CD3+ T lymphocytes, smooth muscle cells (SMCs), and HLA-DR+ inflammatory cells. Plaques from the irbesartan group had fewer (P<0.0001) macrophages, T lymphocytes, and HLA-DR+ cells; less (P<0.0001) immunoreactivity for COX-2/mPGES-1 and MMPs; reduced (P<0.0001) gelatinolytic activity; and increased (P<0.0001) collagen content. It is worth noting that COX-2/mPGES-1 inhibition was observed after incubation in vitro with irbesartan but not with the selective AT2 blockade PD123,319. CONCLUSIONS: This study demonstrates that irbesartan decreases inflammation and inhibits COX-2/mPGES-1 expression in plaque macrophages, and this effect may in turn contribute to plaque stabilization by inhibition of MMP-induced plaque rupture.

The receptor RAGE as a progression factor amplifying arachidonate-dependent inflammatory and proteolytic response in human atherosclerotic plaques: role of glycemic control.

BACKGROUND: RAGE (receptor for advanced glycation end products [AGEs]) plays a role in diabetic atherosclerosis. Recently, we have demonstrated enhanced expression of cyclooxygenase-2 and PGE synthase-1 (COX-2/mPGES-1) in human symptomatic plaques, and provided evidence that it is associated with metalloproteinase (MMP)-induced plaque rupture. However, the specific transmembrane signaling pathway(s) influencing plaque COX-2/mPGES-1 expression is unknown. The aim of this study was to characterize RAGE expression in human plaques and to correlate it with the inflammatory infiltration, COX-2/mPGES-1 and MMP expression, and with clinical evidence of diabetes. METHODS AND RESULTS: Plaques obtained from 60 patients undergoing carotid endarterectomy were divided into diabetic and nondiabetic according to clinical evidence of type 2 diabetes. Plaques were subjected to analysis of RAGE, NF-kappaB, COX-2/mPGES-1, MMP-2 and MMP-9, lipid and oxidized LDL (oxLDL) content, and collagen content by immunohistochemistry and Western blot, whereas zymography was used to detect MMP activity. Immunohistochemistry was used to identify CD68+ macrophages, CD3+ T-lymphocytes, smooth muscle cells (SMCs), and HLA-DR+ inflammatory cells. Diabetic plaques had more (P<0.0001) macrophages, T-lymphocytes, and HLA-DR+ cells, more (P<0.0001) immunoreactivity for RAGE, activated NF-kappaB, COX-2/mPGES-1, and MMPs, increased (P<0.0001) gelatinolytic activity, reduced (P<0.0001) collagen content, and increased (P<0.0001) lipid and oxLDL content. Interestingly, RAGE, COX-2/mPGES-1, and MMP expression was linearly correlated with plasma level of HbA1c. CONCLUSIONS: In conclusion, this study demonstrates in humans that RAGE overexpression is associated with enhanced inflammatory reaction and COX-2/mPGES-1 expression in diabetic plaque macrophages, and this effect may contribute to plaque destabilization by inducing culprit metalloproteinase expression.

Balance between PGD synthase and PGE synthase is a major determinant of atherosclerotic plaque instability in humans.

OBJECTIVE: Inducible cyclooxygenase (COX-2) catalyzes the first step in prostanoid biosynthesis and is considered a proinflammatory enzyme. COX-2 and type 1 inducible PGE synthase (mPGES-1) have a role in metalloproteinase (MMP) release leading to plaque rupture. In contrast, lipocalin-type PGD synthase (L-PGDS) has been shown to exert antiinflammatory actions. Thus, in this study we investigated whether a shift from a PGDS-oriented to a PGES-oriented profile in arachidonate metabolism leads to inflammatory activation in rupture-prone plaque macrophages. METHODS AND RESULTS: Atherosclerotic plaques were obtained from 60 patients who underwent carotid endarterectomy, symptomatic (n=30) and asymptomatic (n=30) according to evidence of recent transient ischemic attack or stroke. Plaques were analyzed for COX-2, mPGES-1, L-PGDS, PPARgamma, IkappaBalpha, NF-kappaB, and MMP-9 by immunocytochemistry, Western blot, reverse-transcriptase polymerase chain reaction, enzyme immunoassay, and zymography. Prostaglandin E2 (PGE2) pathway was significantly prevalent in symptomatic plaques, whereas PGD2 pathway was overexpressed in asymptomatic ones, associated with NF-kappaB inactivation and MMP-9 suppression. In vitro COX-2 inhibition in monocytes was associated with reduced MMP-9 release only when PGD2 pathway overcame PGE2 pathway. CONCLUSIONS: These results suggest that COX-2 may have proinflammatory and antiinflammatory properties as a function of expression of downstream PGH2 isomerases, and that the switch from L-PGDS to mPGES-1 in plaque macrophages is associated with cerebral ischemic syndromes, possibly through MMP-induced plaque rupture.

Increased expression of transforming growth factor-beta1 as a stabilizing factor in human atherosclerotic plaques.

BACKGROUND AND PURPOSE: Transforming growth factor-beta (TGF-beta) is a growth factor/cytokine involved in vascular remodeling and atherogenesis. Recent studies in apolipoprotein E-deficient mice have demonstrated a pivotal role of TGF-beta in the maintenance of the balance between inflammation and fibrosis in atherosclerotic plaques. Furthermore, inhibition of TGF-beta signaling has been shown to accelerate plaque formation and its progression toward an unstable phenotype in mice. However, if this mechanism is operative also in humans is still unknown. The aim of this study was to characterize the expression of TGF-beta1 in human carotid plaque and to correlate it with the extent of inflammatory infiltration and collagen content with the clinical signs of plaque instability. METHODS: Plaques were obtained from patients undergoing carotid endoarterectomy and divided into symptomatic and asymptomatic according to clinical evidence of recent transient ischemic attack or stroke. Plaques were analyzed for TGF-beta1 expression by Immunocytochemistry, Western, and Northern blotting analysis. Immunocytochemistry was used to identify CD68+ macrophages, CD3 T lymphocytes, HLA-DR+ cells, and alpha-smooth muscle cells. Procollagen and interstitial collagen content were analyzed by immunohistochemistry and Sirius Red staining, respectively. RESULTS: Plaque TGF-beta1 mRNA was increased up to 3-fold in asymptomatic as compared with symptomatic plaques. Plaques from asymptomatic group had fewer (P<0.0001) macrophages and T lymphocytes compared with symptomatic plaques. TGF-beta1 gene was transcriptionally active as demonstrated by increased (P<0.0001) TGF-beta1 protein expression in asymptomatic plaques. Immunohistochemistry showed that TGF-beta was mainly expressed in plaque shoulder and was associated with a comparable increase (P<0.0001) in plaque procollagen and collagen content. CONCLUSIONS: In conclusion, this study demonstrates the higher expression of TGF-beta1 in human asymptomatic lesions and provides evidence that TGF-beta1 may play an important role in the process of plaque stabilization.

A polymorphism in the cyclooxygenase 2 gene as an inherited protective factor against myocardial infarction and stroke.

CONTEXT: Myocardial infarction (MI) and ischemic stroke are thought to be caused by matrix digestion by metalloproteinases (MMPs) leading to rupture of atherosclerotic plaques. Production of macrophage MMP-2 and MMP-9 is induced by cyclooxygenase 2 (COX-2) and prostaglandin E(2) synthesis. Although COX-2 expression may be genetically determined, the relation between COX-2 polymorphisms and the risk of MI and stroke is unclear. OBJECTIVE: To investigate the relationship between the -765G-->C polymorphism of the COX-2 gene and clinically evident plaque rupture. DESIGN, SETTING, AND PARTICIPANTS: Prospective, matched case-control study conducted between March 2002 and October 2003 among 864 patients with first MI or atherothrombotic ischemic stroke and 864 hospitalized controls. The groups were matched for age, sex, body mass index, smoking, hypertension, hypercholesterolemia, and diabetes. The -765G-->C variant of the COX-2 gene was genotyped by restriction endonuclease digestion of polymerase chain reaction products. MAIN OUTCOME MEASURES: Presence of the -765G-->C polymorphism of the COX-2 gene; COX-2, MMP-2, and MMP-9 expression and activity in plaques and in peripheral monocytes; urinary 6-keto PGF1alpha (marker of endothelial prostacyclin); and endothelium-dependent and -independent forearm blood flow vasodilation. RESULTS: The prevalence of -765GC was 2.41 times higher among controls than among cases (43.3% vs 17.9%; P<.001). The prevalence of -765CC homozygosity was 5.81 times higher (6.4% vs 1.1%; P =.04). Among participants carrying the -765GC and -765CC genotypes, the prevalence ratios for MI or stroke were 0.48 (95% CI, 0.36-0.68) and 0.33 (95% CI, 0.24-0.55), respectively. Expression of COX-2 and MMPs was significantly lower in atherosclerotic plaques from participants carrying the -765C allele, while the -765G-->C polymorphism did not affect endothelial prostacyclin biosynthesis or endothelium-dependent vasodilation in vivo. In subgroup analyses (n = 224 cases), serum high-sensitivity C-reactive protein was significantly lower in patients carrying the -765C allele (mean [SD], 0.78 [0.1] vs 2.56 [0.4] mg/L; P =.04). CONCLUSIONS: We found that the -765G-->C polymorphism of the COX-2 gene is associated with a decreased risk of MI and stroke. Detection of this genotype may be useful for predicting genetic risk of MI and stroke.