Deficiency of GATA3-Positive Macrophages Improves Cardiac Function Following Myocardial Infarction or Pressure Overload Hypertrophy.

BACKGROUND: Macrophages are highly plastic cells that play an important role in the pathogenesis of cardiovascular disease. OBJECTIVES: This study investigated the role of GATA3-positive macrophages in modulating cardiac function after myocardial infarction (MI) or in response to pressure overload hypertrophy. METHODS: Myeloid-specific GATA3-deficient (mGATA3KO) mice were generated, MI or pressure overload was induced, and cardiac function was determined by echocardiography. GATA3-sufficient Cre mice were used as a control. Immunohistochemical staining, flow cytometry, MILLIPLEX Mouse Cytokine/Chemokine Assay, cultured macrophages, quantitative real-time polymerase chain reaction, and western blot were used to determine the role of GATA3 in macrophages. RESULTS: GATA3-positive macrophages rapidly accumulated in the infarcted region of the myocardium after acute MI. Deficiency of GATA3-positive macrophages led to a significant improvement of cardiac function in response to acute MI or pressure overload hypertrophy compared with the control mice. This improvement was associated with the presence of a large number of proinflammatory Ly6Chi monocytes/macrophages and fewer reparative Ly6Clo macrophages in the myocardium of mGATA3KO mice compared with control mice. Analysis of serum proteins from the 2 mouse genotypes revealed no major changes in the profile of serum growth factors and cytokines between the 2 mice genotypes before and after MI. GATA3 was found to be specifically and transiently induced by interleukin 4 in cultured macrophages through activity of the proximal promoter, whereas the distal promoter remained silent. In addition, the absence of GATA3 in macrophages markedly attenuated arginase-1 expression in cultured macrophages. CONCLUSIONS: We demonstrated that the presence of GATA3-positive macrophages adversely affects remodeling of the myocardium in response to ischemia or pressure overload, whereas the absence of these macrophages led to a significant improvement in cardiac function. Targeting of signaling pathways that lead to the expression of GATA3 in macrophages may have favorable cardiac outcomes.

Bone Marrow-Derived Tenascin-C Attenuates Cardiac Hypertrophy by Controlling Inflammation.

BACKGROUND: Tenascin-C (TNC) is a highly conserved matricellular protein with a distinct expression pattern during development and disease. Remodeling of the left ventricle (LV) in response to pressure overload leads to the re-expression of the fetal gene program. OBJECTIVES: The aim of this study was to investigate the function of TNC in cardiac hypertrophy in response to pressure overload. METHODS: Pressure overload was induced in TNC knockout and wild-type mice by constricting their abdominal aorta or by infusion of angiotensin II. Echocardiography, immunostaining, flow cytometry, quantitative real-time polymerase chain reaction, and reciprocal bone marrow transplantation were used to evaluate the effect of TNC deficiency. RESULTS: Echocardiographic analysis of pressure overloaded hearts revealed that all LV parameters (LV end-diastolic and -systolic dimensions, ejection fraction, and fractional shortening) deteriorated in TNC-deficient mice compared with their wild-type counterparts. Cardiomyocyte size and collagen accumulation were significantly greater in the absence of TNC. Mechanistically, TNC deficiency promoted rapid accumulation of the CCR2+/Ly6Chi monocyte/macrophage subset into the myocardium in response to pressure overload. Further, echocardiographic and immunohistochemical analyses of recipient hearts showed that expression of TNC in the bone marrow, but not the myocardium, protected the myocardium against excessive remodeling of the pressure-overloaded heart. CONCLUSIONS: TNC deficiency further impaired cardiac function in response to pressure overload and exacerbated fibrosis by enhancing inflammation. In addition, expression of TNC in the bone marrow, but not the myocardium, protected the myocardium against excessive remodeling in response to mild pressure overload.

Smooth and Rough Biotypes of Arcanobacterium haemolyticum Can Be Genetically Distinguished at the Arcanolysin Locus.

Arcanobacterium haemolyticum is a Gram-positive, ß-hemolytic emerging human pathogen that is classified into smooth or rough biotypes. This bacterial species is also a rare pathogen of animals. Smooth biotypes possess smooth colony edges, are moderate to strong in ß-hemolysis, and predominately cause wound infections. In contrast, rough biotypes possess rough and irregular colony edges, have weak to no ß-hemolytic activity, and predominately cause pharyngitis. Using horse erythrocytes we confirmed that smooth isolates are generally more hemolytic than rough isolates. A hemolysin from A. haemolyticum, arcanolysin (aln/ALN), was recently discovered and is a member of the cholesterol-dependent cytolysin (CDC) family. PCR amplification of aln from all 36 smooth A. haemolyticum isolates yielded the expected 2.0 kb product. While 21 rough isolates yielded the 2.0 kb product, 16 isolates had a 3.2 kb product. The extra 1.2 kb segment was 99% identical to IS911 (insertion sequence) from Corynebacterium diphtheriae. PCR amplification and sequence analysis of the upstream region of aln revealed ~40 nucleotide polymorphisms among 73 clinical isolates from Finland, Denmark, Germany and United States (Nebraska). Remarkably, multi-sequence alignments of the aln upstream region demonstrated that ~90% of the isolates phylogenetically clustered as either smooths or roughs. Differential restriction enzyme analysis of the aln upstream region also demonstrated that the aln upstream region of most (~75%) smooth isolates was cleaved with ClaI while this region in most (~86%) rough isolates was cleaved with XcmI. We conclude that the aln upstream region can be used to genetically distinguish between smooth and rough biotypes of this important emerging pathogen.