Atsushi Anzai

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.

Temporal dynamics of cardiac immune cell accumulation following acute myocardial infarction

Acute myocardial infarction (MI) causes sterile inflammation, which is characterized by recruitment and activation of innate and adaptive immune system cells. Here we delineate the temporal dynamics of immune cell accumulation following MI by flow cytometry. Neutrophils increased immediately to a peak at 3 days post-MI. Macrophages were numerically the predominant cells infiltrating the infarcted myocardium, increasing in number over the first week post-MI. Macrophages are functionally heterogeneous, whereby the first responders exhibit high expression levels of proinflammatory mediators, while the late responders express high levels of the anti-inflammatory cytokine IL-10; these macrophages can be classified into M1 and M2 macrophages, respectively, based on surface-marker expression. M1 macrophages dominated at 1-3 days post-MI, whereas M2 macrophages represented the predominant macrophage subset after 5 days. The M2 macrophages expressed high levels of reparative genes in addition to proinflammatory genes to the same levels as in M1 macrophages. The predominant subset of dendritic cells (DCs) was myeloid DC, which peaked in number on day 7. Th1 and regulatory T cells were the predominant subsets of CD4(+) T cells, whereas Th2 and Th17 cells were minor populations. CD8(+) T cells, γδT cells, B cells, natural killer (NK) cells and NKT cells peaked on day 7 post-MI. Timely reperfusion reduced the total number of leukocytes accumulated in the post-MI period, shifting the peak of innate immune response towards earlier and blunting the wave of adaptive immune response. In conclusion, these results provide important knowledge necessary for developing successful immunomodulatory therapies.

Deleterious Effect of the IL-23/IL-17A Axis and γδT Cells on Left Ventricular Remodeling After Myocardial Infarction

Background Left ventricular (LV) remodeling leads to chronic heart failure and is a main determinant of morbidity and mortality after myocardial infarction (MI). At the present time, therapeutic options to prevent LV remodeling are limited. Methods and Results We created a large MI by permanent ligation of the coronary artery and identified a potential link between the interleukin (IL)–23/IL-17A axis and γδT cells that affects late-stage LV remodeling after MI. Despite the finsinf that infarct size 24 hours after surgery was similar to that in wild-type mice, a deficiency in IL-23, IL-17A, or γδT cells improved survival after 7 days, limiting infarct expansion and fibrosis in noninfarcted myocardium and alleviating LV dilatation and systolic dysfunction on day 28 post-MI. M1 macrophages and neutrophils were the major cellular source of IL-23, whereas >90% of IL-17A-producing T cells in infarcted heart were CD4− TCRγδ+ (γδT) cells. Toll-like receptor signaling and IL-1β worked in concert with IL-23 to drive expansion and IL-17A production in cardiac γδT cells, whereas the sphingosine-1-phosphate receptor and CCL20/CCR6 signaling pathways mediated γδT cell recruitment into infarcted heart. IL-17A was not involved in the acute inflammatory response, but it functioned specifically in the late remodeling stages by promoting sustained infiltration of neutrophils and macrophages, stimulating macrophages to produce proinflammatory cytokines, aggravating cardiomyocyte death, and enhancing fibroblast proliferation and profibrotic gene expression. Conclusions The IL-23/IL-17A immune axis and γδT cells are potentially promising therapeutic targets after MI to prevent progression to end-stage dilated cardiomyopathy.

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.

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.

Obesity accelerates T cell senescence in murine visceral adipose tissue

Chronic inflammation in visceral adipose tissue (VAT) precipitates the development of cardiometabolic disorders. Although changes in T cell function associated with visceral obesity are thought to affect chronic VAT inflammation, the specific features of these changes remain elusive. Here, we have determined that a high-fat diet (HFD) caused a preferential increase and accumulation of CD44hiCD62LloCD4+ T cells that constitutively express PD-1 and CD153 in a B cell-dependent manner in VAT. These cells possessed characteristics of cellular senescence and showed a strong activation of Spp1 (encoding osteopontin [OPN]) in VAT. Upon T cell receptor stimulation, these T cells also produced large amounts of OPN in a PD-1-resistant manner in vitro. The features of CD153+PD-1+CD44hiCD4+ T cells were highly reminiscent of senescence-associated CD4+ T cells that normally increase with age. Adoptive transfer of CD153+PD-1+CD44hiCD4+ T cells from HFD-fed WT, but not Spp1-deficient, mice into the VAT of lean mice fed a normal diet recapitulated the essential features of VAT inflammation and insulin resistance. Our results demonstrate that a distinct CD153+PD-1+CD44hiCD4+ T cell population that accumulates in the VAT of HFD-fed obese mice causes VAT inflammation by producing large amounts of OPN. This finding suggests a link between visceral adiposity and immune aging.

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.

Adventitial CXCL1/G-CSF expression in response to acute aortic dissection triggers local neutrophil recruitment and activation leading to aortic rupture

Rationale: In-hospital outcomes are generally acceptable in patients with type B dissection; however, some patients present with undesirable complications, such as aortic expansion and rupture. Excessive inflammation is an independent predictor of adverse clinical outcomes. Objective: We have investigated the underlying mechanisms of catastrophic complications after acute aortic dissection (AAD) in mice. Methods and Results: When angiotensin II was administered in lysyl oxidase inhibitor–preconditioned mice, AAD emerged within 24 hours. The dissection was initiated at the proximal site of the descending thoracic aorta and propagated distally into an abdominal site. Dissection of the aorta caused dilatation, and ≈70% of the mice died of aortic rupture. AAD triggered CXCL1 and granulocyte-colony stimulating factor expression in the tunica adventitia of the dissected aorta, leading to elevation of circulating CXCL1/granulocyte-colony stimulating factor levels. Bone marrow CXCL12 was reduced. These chemokine changes facilitated neutrophil egress from bone marrow and infiltration into the aortic adventitia. Interference of CXCL1 function using an anti-CXCR2 antibody reduced neutrophil accumulation and limited aortic rupture post AAD. The tunica adventitia of the expanded dissected aorta demonstrated high levels of interleukin-6 (IL-6) expression. Neutrophils were the major sources of IL-6, and CXCR2 neutralization significantly reduced local and systemic levels of IL-6. Furthermore, disruption of IL-6 effectively suppressed dilatation and rupture of the dissected aorta without any influence on the incidence of AAD and neutrophil mobilization. Conclusions: Adventitial CXCL1/granulocyte-colony stimulating factor expression in response to AAD triggers local neutrophil recruitment and activation. This leads to adventitial inflammation via IL-6 and results in aortic expansion and rupture.

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.