Hidehiro Kaneko

Regulatory Role of Dendritic Cells in Postinfarction Healing and Left Ventricular Remodeling

Background— Inflammation and immune responses are integral components in the healing process after myocardial infarction. We previously reported dendritic cell (DC) infiltration in the infarcted heart; however, the precise contribution of DC in postinfarction healing is unclear. Methods and Results— Bone marrow cells from CD11c-diphtheria toxin receptor/green fluorescent protein transgenic mice were transplanted into lethally irradiated wild-type recipient mice. After reconstitution of bone marrow–derived cells, the recipient mice were treated with either diphtheria toxin (DC ablation) or vehicle (control), and myocardial infarction was created by left coronary ligation. CD11c+ green fluorescent protein–positive DCs expressing CD11b and major histocompatibility complex class II were recruited into the heart, peaking on day 7 after myocardial infarction in the control group. Mice with DC ablation for 7 days showed deteriorated left ventricular function and remodeling. The DC-ablated group demonstrated enhanced and sustained expression of inflammatory cytokines such as interleukin-1&bgr;, interleukin-18, and tumor necrosis factor-&agr;, prolonged extracellular matrix degradation associated with a high level of matrix metalloproteinase-9 activity, and diminished expression level of interleukin-10 and endothelial cell proliferation after myocardial infarction compared with the control group. In vivo analyses revealed that DC-ablated infarcts had enhanced monocyte/macrophage recruitment. Among these cells, marked infiltration of proinflammatory Ly6Chigh monocytes and F4/80+ CD206− M1 macrophages and, conversely, impaired recruitment of anti-inflammatory Ly6Clow monocytes and F4/80+ CD206+ M2 macrophages in the infarcted myocardium were identified in the DC-ablated group compared with the control group. Conclusions— These results suggest that the DC is a potent immunoprotective regulator during the postinfarction healing process via its control of monocyte/macrophage homeostasis.

C-Reactive Protein Overexpression Exacerbates Pressure Overload–Induced Cardiac Remodeling Through Enhanced Inflammatory Response

Serum C-reactive protein (CRP) elevation predicts the development of heart failure in patients with hypertension. CRP activates macrophages and enhances oxidative stress. We hypothesize that CRP itself has a pathogenic role in the development of pressure overload–induced cardiac remodeling. Transgenic mice with human CRP overexpression (CRPtg) and nontransgenic littermates (CON) were subjected to transverse aortic constriction (TAC/CRPtg and TAC/CON) or sham operation (Sham/CRPtg and Sham/CON). One week after operation, in TAC/CRPtg, myocardial mRNA levels of interleukin (IL)-6, CD68, glutathione peroxidase-3 (GPx3), 47-kDa &agr;-subunit of nicotinamide adenine dinucleotide phosphate oxidase (p47phox), and collagen-I, the number of infiltrating Mac-2–positive macrophages, nuclear localization of phosphorylated NF-&kgr;B/p65 (p-p65) in cardiomyocytes, nuclear NF-&kgr;B-DNA-binding activity, and reactive oxygen species (ROS) content were increased compared to those in TAC/CON. Cardiac fibrosis was more prominent in TAC/CRPtg compared to TAC/CON. Four weeks after operation, heart and lung weights, cardiomyocyte cross-sectional area, and the extent of cardiac fibrosis were greater in TAC/CON than in Sham/CON, and these differences were further augmented in TAC/CRPtg compared to TAC/CON. Left ventricular (LV) fractional shortening was less and LV end-diastolic pressure was higher in TAC/CRPtg than in TAC/CON. Myocardial mRNA levels of angiotensin type 1 receptor, atrial natriuretic factor, IL-6, GPx3, p47phox, collagen-I, and transforming growth factor (TGF)-&bgr;1, the protein level of TGF-&bgr;1, and the numbers of Mac-2–positive macrophages and p-p65–positive cells were higher in TAC/CRPtg than in TAC/CON. In conclusion, CRP itself may have a pathogenic role in the development of pressure overload–induced cardiac remodeling, possibly through enhanced inflammation and oxidative stress.

Role of vascular endothelial growth factor-A in development of abdominal aortic aneurysm

AIMS Increased angiogenesis, chronic inflammation, and extracellular matrix degradation are the major pathological features of abdominal aortic aneurysm (AAA). We sought to elucidate the role of vascular endothelial growth factor (VEGF)-A, a potent angiogenic and proinflammatory factor, in the development of AAA. METHODS AND RESULTS Human AAA samples showed increased VEGF-A expression, neovascularization, and macrophage infiltration compared with normal aortic walls. AAA was induced in mice by periaortic application of CaCl(2). AAA mice were treated with soluble VEGF-A receptor (sFlt)-1 or phosphate-buffered saline and sacrificed 6 weeks after the operation. Treatment with sFlt-1 resulted in reduced aneurysm size, restored wavy structure of the elastic lamellae, reduced Mac-2(+) monocytes/macrophages, CD3(+) T-lymphocytes, and CD31(+) vessels, and attenuated matrix metalloproteinase (MMP)-2 and 9 activity in periaortic tissue of AAA. Increased aortic mRNA expression of monocyte chemotactic protein-1, tumour necrosis factor-α, and intercellular adhesion molecule-1 in AAA was attenuated by sFlt-1 treatment. CONCLUSION VEGF-A was overexpressed in the aortic wall of human and experimental AAA. Treatment with sFlt-1 inhibited AAA development in mice, in association with reduced neoangiogenesis, infiltration of inflammatory cells, MMP activity, and extracellular matrix degradation. These findings suggest a crucial role of VEGF-A in the development of AAA.

Tumor necrosis factor-α converting enzyme is a key mediator of abdominal aortic aneurysm development

OBJECTIVE Tumor necrosis factor (TNF)-α is known to be elevated in plasma and the aorta in abdominal aortic aneurysm (AAA) patients. We sought to clarify the role of TNF-α converting enzyme (Tace), which cleaves the transmembrane precursor of TNF-α, in AAA development. METHODS We obtained aortic sample of AAA during surgical operation to assess the histological features and protein expression of human AAA. AAA was induced in mice with temporal systemic deletion of Tace by the inducible Mx-1 Cre transgene (TaceMx1) and in wild-type littermates (CON) by periaortic application of CaCl(2) (AAA/TaceMx1, AAA/CON). RESULTS Tace expression was increased in human AAA samples as compared with normal aorta. Six weeks postoperatively, aortic diameter in AAA/TaceMx1 was decreased than in AAA/CON in association with attenuated TNF-α expression and extracellular matrix disruption. Increased activities of matrix metalloproteinase (MMP)-9 and MMP-2, numbers of Mac-2-positive macrophages, CD3-positive T lymphocytes and CD31-positive vessels in periaortic tissues, mRNA expression of CD68, monocyte chemotactic protein-1, TNF-α, vascular endothelial growth factor-A, p47 and glutathione peroxidases, and protein expression of phospho-c-Jun N-terminal kinase in AAA were all attenuated by Tace deletion. Protein expression of transforming growth factor (TGF)-β1 was upregulated by Tace deletion in sham-operated mice. TGF-β1 expression was further increased in AAA/TaceMx1. CONCLUSIONS Tace was overexpressed in the aortic wall in human and experimental AAA. Temporal systemic deletion of Tace prevented AAA development in association with attenuating inflammation, oxidative stress, neoangiogenesis and extracellular matrix disruption, suggesting a crucial role of Tace in AAA development.

Increased C-reactive protein expression exacerbates left ventricular dysfunction and remodeling after myocardial infarction.

We previously reported serum C-reactive protein (CRP) elevation after acute myocardial infarction (MI) to be associated with adverse outcomes including cardiac rupture, left ventricular (LV) remodeling, and cardiac death. Experimental studies have indicated that CRP per se has various biological actions including proinflammatory and proapoptotic effects, suggesting a pathogenic role of CRP in the post-MI remodeling process. We tested the hypothesis that increased CRP expression would exacerbate adverse LV remodeling after MI via deleterious effects of CRP. Transgenic mice with human CRP expression (CRP-Tg) and their transgene-negative littermates (control) underwent left coronary artery ligation. There was no apparent difference in phenotypic features between CRP-Tg and control mice before MI. Although mortality and infarct size were similar in the two groups, CRP-Tg mice showed more LV dilation and worse LV function with more prominent cardiomyocyte hypertrophy and fibrosis in the noninfarcted regions after MI than controls. Histological evaluation conducted 1 wk post-MI revealed a higher rate of apoptosis and more macrophage infiltration in the border zones of infarcted hearts from CRP-Tg mice in relation to increased monocyte chemotactic protein (MCP)-1 expression and matrix metalloproteinase (MMP)-9 activity. Increased CRP expression exacerbates LV dysfunction and promotes adverse LV remodeling after MI in mice. The deleterious effect of CRP on post-MI LV remodeling may be associated with increased apoptotic rates, macrophage infiltration, MCP-1 expression, and MMP-9 activity in the border zone.

Prognostic Significance of Acute Kidney Injury After Reperfused ST-Elevation Myocardial Infarction: Synergistic Acceleration of Renal Dysfunction and Left Ventricular Remodeling

BACKGROUND Acute kidney injury (AKI) after myocardial infarction is associated with poor clinical outcome. However, mechanisms of the adverse effect of AKI on clinical outcome after reperfused ST-elevation myocardial infarction (STEMI) have not been fully elucidated. METHODS AND RESULTS We examined 141 consecutive patients with reperfused first anterior STEMI. AKI was defined as an increase in serum creatinine of >or=0.3mg/dL within 48hours after admission. Patients with AKI had higher incidence of in-hospital cardiac death (P=.0004) and major adverse cardiac events (MACE, P=.020) during a mean of 39+/-40 (range, 1 to 96) months than those without, in association with adverse left ventricular (LV) remodeling. White blood cell count on admission and peak C-reactive protein were higher in patients with than those without AKI. Plasma norepinephrine on admission, interleukin-6, brain natriuretic peptide, and malondialdehyde-modified low-density lipoprotein 2 weeks after STEMI were higher in patients with AKI than those without AKI. Cox proportional hazards model analysis revealed AKI was an independent predictor of MACE (hazard ratio=2.38, P=.019). CONCLUSIONS AKI was a strong predictor of MACE in association with adverse LV remodeling. Enhanced inflammatory response, oxidative stress, and neurohormonal activation may synergistically accelerate renal dysfunction and LV remodeling after STEMI.

Role of Ischemic Preconditioning and Inflammatory Response in the Development of Malignant Ventricular Arrhythmias After Reperfused ST-Elevation Myocardial Infarction

BACKGROUND Sustained ventricular tachycardia and ventricular fibrillation (VT/VF) are major complications of ST-elevation myocardial infarction (STEMI), even in the era of reperfusion therapy. We sought to clarify the determinants of VT/VF after reperfused STEMI. METHODS AND RESULTS Consecutive STEMI patients treated with primary percutaneous coronary intervention (n=457) were divided into 2 groups by the presence or absence of VT/VF during hospitalization. Serum C-reactive protein (CRP) level and peripheral white blood cell (WBC) count were serially measured. VT/VF was observed in 54 patients (12%). Prior infarction was more common and preinfarction angina was less in patients with VT/VF than those without. Peak CRP level (P < .0001), WBC count on admission (P=.008), and maximum WBC count (P=.0014) were higher in patients with VT/VF than those without. VT/VF, especially VT/VF later than 48 hours after onset, was associated with greater left ventricular (LV) dimension during convalescence. Kaplan-Meier curves and log-rank test revealed VT/VF to be a significant determinant of long-term major adverse cardiac events. Multivariate analysis revealed that prior infarction, absence of preinfarction angina, and peak CRP >or=10mg/dL were independent determinants of VT/VF. CONCLUSIONS Lack of ischemic preconditioning, enhanced inflammatory response, and subsequent LV dysfunction are related to the development of VT/VF after STEMI.

High-mobility group box 1 protein blockade suppresses development of abdominal aortic aneurysm

BACKGROUND Abdominal aortic aneurysm (AAA) expansion is characterized by chronic inflammatory cell infiltration and extracellular matrix degradation. High-mobility group box 1 protein (HMGB1) is one of the damage-associated molecular pattern molecules derived from injured/necrotic and activated inflammatory cells. We investigated the expression of HMGB1 in human AAA and mouse experimental AAA. Then, we evaluated the effect of HMGB1 blockade on AAA formation in the mouse model. METHODS AND RESULTS Human AAA samples showed increased HMGB1 expression compared with normal aortic wall. In a mouse CaCl(2)-induced AAA model, the expression of HMGB1 was increased compared with that in sham, and was positively correlated with matrix metalloproteinase (MMP)-2 and MMP-9 activity. We administered neutralizing anti-HMGB1 antibody (AAA/anti-H) or control antibody (AAA/C) to AAA mice subcutaneously every 3 days for 6 weeks. Treatment with neutralizing anti-HMGB1 antibody suppressed AAA formation, and attenuated elastin fragmentation. HMGB1 blockade markedly reduced the number of macrophages and MMP-2 and MMP-9 activity in aneurysmal tissue. The mRNA level of tumor necrosis factor-α and CD68 in the aorta was reduced in AAA/anti-H compared with AAA/C. CONCLUSIONS Elevation of HMGB1 level in aneurysmal tissue was observed in human AAA and mouse experimental AAA. HMGB1 blockade in a mouse AAA model reduced AAA progression, in association with reduced infiltration of macrophages and MMPs activity. These findings suggest a significant role for HMGB1 in the pathogenesis of AAA.

Impact of chronic kidney disease on postinfarction inflammation, oxidative stress, and left ventricular remodeling.

BACKGROUND Patients with chronic kidney disease (CKD) have poor clinical outcomes after myocardial infarction (MI). However, the precise mechanisms are unclear. We sought to determine the prognostic significance of CKD in patients with MI in relation to left ventricular (LV) remodeling. METHODS AND RESULTS We examined 120 consecutive patients with a reperfused first anterior ST-elevation MI. Patients were divided into 2 groups according to the presence or absence of CKD, defined as estimated glomerular filtration rates <60 mL x min x 1.73 m2. Patients with CKD had a higher incidence of in-hospital cardiac death and readmission for heart failure during follow-up, in association with a greater LV volume and lower LV ejection fraction 2 weeks after MI compared with those without CKD. Cox proportional hazards model analysis revealed that CKD was an independent predictor of major adverse cardiac events (hazard ratio=3.13, P=.001). Plasma interleukin-6 on admission, and peak serum C-reactive protein, and malondialdehyde-modified low-density lipoprotein levels during convalescence, were higher in patients with CKD than in those without. CONCLUSIONS Patients with CKD had poorer clinical outcomes and accelerated infarct expansion in association with enhanced inflammation and oxidative stress, as compared with non-CKD patients, suggesting a major impact of CKD in the development of LV remodeling after MI.

Interaction between renal function and percutaneous edge-to-edge mitral valve repair using MitraClip

BACKGROUND MitraClip (MC; Abbott Vascular, Menlo Park, CA, USA) is a treatment option for mitral regurgitation. Renal dysfunction is closely associated with cardiovascular disease. However, the influence of renal function in MC remains not fully understood. In this study, we aimed to clarify the association between renal function and MC. METHODS AND RESULTS We examined 206 consecutive patients who underwent MC and divided patients into 3 groups according to estimated glomerular filtration rate (eGFR), normal eGFR (≥60mL/min/1.73m2) (n=70), mild chronic kidney disease (CKD) (30-59mL/min/1.73m2) (n=106), and severe CKD (<30mL/min/1.73m2) (n=30). N-terminal pro-B type natriuretic peptide (NT-pro BNP) levels increased with decreasing eGFR. Kaplan-Meier curves revealed that the long-term survival rate significantly decreased with eGFR. After adjustment with the covariates, severe CKD was still associated with mortality. Improved renal function was observed in 30% and associated with baseline lower NT-pro BNP levels. Patients with improved renal function had higher chronic phase survival rate. CONCLUSION Renal dysfunction is common in MC patients and the survival rate decreased with eGFR in association with increased NT-pro BNP levels. MC may improve renal function in approximately 30% of MC patients. Improved renal function is associated with lower NT-pro BNP levels and results in satisfactory prognosis. These results implies a close association between renal function and MC treatment.