Inhibition of HDAC activity result in the early recruitment of reparative CD45/CD11b/CD206 macrophages in the post-MI heart and correlates with improved ventricular function and remodeling. This work identifies a very promising therapeutic opportunity to manage macrophage phenotype and enhance resolution of inflammation in the post-MI heart.

Left ventricular (LV) remodeling, after myocardial infarction (MI), can result in LV dilation and LV pump dysfunction. Post-MI induction of matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, have been implicated as causing deleterious effects on LV and extracellular matrix remodeling in the MI region and within the initially unaffected remote zone. Histone deacetylases (HDACs) are a class of enzymes that affect the transcriptional regulation of genes during pathological conditions. We assessed the efficacy of both class I/IIb-and class I-selective HDAC inhibitors on MMP-2 and MMP-9 abundance and determined if treatment resulted in the attenuation of adverse LV and extracellular matrix remodeling and improved LV pump function post-MI. MI was surgically induced in MMP-9 promoter reporter mice and randomized for treatment with a class I/IIb HDAC inhibitor for 7 days post-MI. After MI, LV dilation, LV pump dysfunction, and activation of the MMP-9 gene promoter were significantly attenuated in mice treated with either the class I/IIb HDAC inhibitor tichostatin A or suberanilohydroxamic acid (voronistat) compared with MI-only mice. Immunohistological staining and zymographic levels of MMP-2 and MMP-9 were reduced with either tichostatin A or suberanilohydroxamic acid treatment. Class I HDAC activity was dramatically increased post-MI. Treatment with the selective class I HDAC inhibitor PD-106 reduced post-MI levels of both MMP-2 and MMP-9 and attenuated LV dilation and LV pump dysfunction post-MI, similar to class I/IIb HDAC inhibition. Taken together, these unique findings demonstrate that selective inhibition of class I HDACs may provide a novel therapeutic means to attenuate adverse LV remodeling post-MI. myocardial infarction; histone deacetylase; matrix metalloproteinases; transcriptional regulation; macrophages; LV remodeling THE HEALING RESPONSE within the myocardium after a myocardial infarction (MI) is complex and involves both temporal and regional changes, including inflammation, new tissue formation, and tissue remodeling (11). After coronary artery occlusion, there is an induction of bioactive peptides and cytokines, extracellular matrix (ECM) degradation, and subsequent recruitment of inflammatory cells to the site of injury (9,16,53). Alterations in the post-MI ECM architecture are largely attributed to changes in the expression of a number of matrix metalloproteases (MMPs) (50). Previous work has demonstrated that induction of MMP-2 gene expression can be detected by day 1 post-MI, reaches its maximum at 7 days, and then gradually decreases (43, 51). Activation of the MMP-9 promoter was detectable by 3 days, peaked by 7 days, and remained upregulated throughout the 28-day time course post-MI (43). The dramatic increases in both MMP-2 and MMP-9 have been proposed to contribute to the disruption of the cardiocyte-matrix interactive network, resulting in cardiocyte misalignment and slippage (53).MMP-9-null mice show attenuated left ventricular (LV) dilation and improved LV function compared w...

Background Hypertension (HTN), which is a major risk factor for cardiovascular morbidity and mortality, can drive pathologic remodeling of the macro- and microcirculation. Patterns of aortic pathology differ, however, suggesting regional heterogeneity of the pressure-sensitive protease systems triggering extracellular matrix remodeling in the thoracic (TA) and abdominal aortas (AA). This study tested the hypothesis that the expression of two major protease systems (matrix metalloproteinases [MMPs] and cathepsins) in the TA and AA would be differentially affected with HTN. Methods Normotensive (BPN3) mice at 14–16 weeks of age underwent implantation of osmotic infusion pumps for 28-day angiotensin II (AngII) delivery (1.46 mg/kg/day; BPN3+AngII; n = 8) to induce HTN. The TA and AA were harvested to determine levels of MMP-2, MMP-9, and membrane type 1-MMP, and cathepsins S, K, and L were evaluated in age-matched BPN3 (n = 8) control and BPH2 spontaneously hypertensive mice (non-AngII pathway; n = 7). Blood pressure was monitored via CODA tail cuff plethysmography (Kent Scientific Corporation, Torrington, Conn). Quantitative real-time polymerase chain reaction and immunoblotting/zymography were used to measure MMP and cathepsin messenger RNA expression and protein abundance, respectively. Target protease values were compared within each aortic region via analysis of variance. Results Following 28 days infusion, the BPN3+AngII mice had a 17% increase in systolic blood pressure, matching that of the BPH2 spontaneously hypertensive mice (both P < .05 vs BPN3). MMP-2 gene expression demonstrated an AngII-dependent increase in the TA (P < .05), but MMP-9 was not altered with HTN. Expression of tissue inhibitor of metalloproteinases-1 was markedly increased in TA of BPN3+AngII mice, but tissue inhibitor of metalloproteinases-2 demonstrated decreased expression in the AA of both hypertensive groups (P < .05). Only cathepsin K responded to AngII-induced HTN with significant elevation in the TA of those mice, but expression of cathepsin L and cystatin C was inhibited in AA of both hypertensive groups (P < .05). Apoptotic markers were not significantly elevated in any experimental group. Conclusions By using two different models of HTN, this study has identified pressure-dependent as well as AngII-dependent regional alterations in aortic gene expression of MMPs and cathepsins that may lead to differential remodeling responses in each of the aortic regions. Further studies will delineate mechanisms and may provide targeted therapies to attenuate down-stream aortic pathology based on demonstrated regional heterogeneity. Clinical Relevance Hypertension represents a primary risk factor for cardiovascular morbidity and mortality. Given the epidemiologic association with aortic aneurysms, interest has been generated regarding whether the hypertensive state creates an environment in the aortic media that is vulnerable to degenerative remodeling. This investigation has been initiated by exploring two major protease systems...

Changes in cardiac gene expression contribute to the progression of heart failure by affecting cardiomyocyte growth, function, and survival. The Na+ -Ca2+ exchanger gene (Ncx1) is upregulated in hypertrophy and is often found elevated in end-stage heart failure. Studies have shown that the change in its expression contributes to contractile dysfunction. Several transcriptional pathways mediate Ncx1 expression in pathological cardiac remodeling. Both α-adrenergic receptor (α-AR) and β-adrenergic receptor (β-AR) signaling can play a role in the regulation of calcium homeostasis in the cardiomyocyte, but chronic activation in periods of cardiac stress contributes to heart failure by mechanisms which include Ncx1 upregulation. Our studies have even demonstrated that NCX1 can directly act as a regulator of “activity-dependent signal transduction” mediating changes in its own expression. Finally, we present evidence that histone deacetylases (HDACs) and histone acetyltransferases (HATs) act as master regulators of Ncx1 expression. We show that many of the transcription factors regulating Ncx1 expression are important in cardiac development and also in the regulation of many other genes in the so-called fetal gene program, which are activated by pathological stimuli. Importantly, studies have revealed that the transcriptional network regulating Ncx1 expression is also mediating many of the other changes in genetic remodeling contributing to the development of cardiac dysfunction and revealed potential therapeutic targets for the treatment of hypertrophy and failure.

Background: Following a myocardial infarction (MI) the extracellular matrix (ECM) undergoes massive remodeling to prevent rupture and maintain cardiac output. Large increases in matrix metalloproteinase-9 (MMP-9) are associated with adverse ECM remodeling. We found that treatment with an HDAC inhibitor repressed post-MI upregulation of MMP-9. Significant sources of MMP-9 in the post-MI LV are M1 macrophages. Both phenotypes (M1 and M2) can contribute to MMP expression, but this is dependant on the phase of ECM remodeling. We hypothesize that HDAC inhibition regulates the post-MI expression of MMP-9 by mediating the M1 to M2 macrophage polarization. Methods: CD1 and MMP-9 β-gal reporter mice were induced with MI by LAD ligation then administered HDAC inhibitors: trichostatin A (TSA; class I and IIb), PD106 (class I), or Tubastatin A (HDAC 6) until termination at 5 or 7 days post-MI. Heart function evaluated by echocardiogram and cells or tissue by immunohistochemistry and immunoblotting. Results: The post-MI change in LV end-diastolic volume (49±9%) is significantly lower and ejection fraction (-44±8%) is improved with treatment of TSA vs. control (69±12%; -59±6%) respectively [n=28]. Immunohistochemical analysis revealed that infiltrating macrophages express MMP-9 at 5 and 7 days post-MI. HDAC inhibition decreases this expression and did so without reducing presence of macrophages within infarct. Immunoblotting shows that expression of all class I HDACs are increased following MI; however, in cultured macrophages only HDAC2 and HDAC3 are increased. TSA and PD106, inhibit control levels and lipopolysacharide (LPS) stimulated upregulation of MMP-9 in cultured RAW264.7 and bone marrow derived macrophages. Immunofluorescence revealed that treatment with PD106, Tub A, and TSA leads to M1 to M2 morphology specific polarization and maintenance of anti-inflammatory, M2, phenotype even with LPS stimulation in culture. However, only PD106 and TSA reduced MMP-9 expression in cultured macrophages. Conclusions: Macrophage mediated secretion of MMP-9 contributes to adverse ECM remodeling and loss of LV function post-MI. Class I HDAC inhibition promotes both M2 macrophage polarization and attenuates adverse remodeling by reducing MMP-9 expression.