HDAC class I inhibitor, Mocetinostat, reverses cardiac fibrosis in heart failure and diminishes CD90+ cardiac myofibroblast activation.

BACKGROUND: Interstitial fibrosis and fibrotic scar formation contribute to cardiac remodeling and loss of cardiac function in myocardial infarction (MI) and heart failure. Recent studies showed that histone deacetylase (HDAC) inhibitors retard fibrosis formation in acute MI settings. However, it is unknown whether HDAC inhibition can reverse cardiac fibrosis in ischemic heart failure. In addition, specific HDAC isoforms involved in cardiac fibrosis and myofibroblast activation are not well defined. Thus, the purpose of this study is to determine the effects of selective class I HDAC inhibition on cardiac fibroblasts activation and cardiac fibrosis in a congestive heart failure (CHF) model secondary to MI. METHODS: MI was created by left anterior descending (LAD) coronary artery occlusion. Class I HDACs were selectively inhibited via Mocetinostat in CD90+ fibroblasts isolated from atrial and ventricular heart tissue in vitro. In vivo, Class I HDACs were inhibited in 3 weeks post MI rats by injecting Mocetinostat for the duration of 3 weeks. Cardiac function and heart tissue were analyzed at 6 weeks post MI. RESULTS: In sham hearts, HDAC1 and HDAC2 displayed differential expression patterns where HDAC1 mainly expressed in cardiac fibroblast and HDAC2 in cardiomyocytes. On the other hand, we showed that HDAC1 and 2 were upregulated in CHF hearts, and were found to co-localize with CD90+ cardiac fibroblasts. In vivo treatment of CHF animals with Mocetinostat improved left ventricle end diastolic pressure and dp/dt max and decreased the total collagen amount. In vitro treatment of CD90+ cells with Mocetinostat reversed myofibroblast phenotype as indicated by a decrease in α-Smooth muscle actin (α-SMA), Collagen III, and Matrix metalloproteinase-2 (MMP2). Furthermore, Mocetinostat increased E-cadherin, induced ß-catenin localization to the membrane, and reduced Akt/GSK3ß signaling in atrial cardiac fibroblasts. In addition, Mocetinostat treatment of atrial CD90+ cells upregulated cleaved-Caspase3 and activated the p53/p21 axis. CONCLUSIONS: Taken together, our results demonstrate upregulation of HDAC1 and 2 in CHF. In addition, HDAC inhibition reverses interstitial fibrosis in CHF. Possible anti-fibrotic actions of HDAC inhibition include reversal of myofibroblast activation and induction of cell cycle arrest/apoptosis.

BACE1 levels are elevated in congestive heart failure.

Cardiovascular (CV) diseases are known to have a negative impact on the brain and neurocognition, and contribute to the development of vascular dementia and neurodegenerative diseases such as Alzheimer's disease (AD). Among CV diseases, congestive heart failure (CHF) after myocardial infarction (MI) is a condition where the ability of the left ventricle to eject blood to the circulation is impaired. As a consequence, CHF triggers inflammation and results in reduced cerebral blood flow which are considered among the risk factors for development of AD. However, biochemical alterations in the brain following MI and CHF remain unknown. To address this issue, we investigated microglia activation; levels of BACE1, the key rate-limiting enzyme involved in the pathogenesis of AD; and VEGF levels in the hippocampus and cortex following MI. We created MI by the ligation of the left anterior descending coronary artery in Sprague-Dawley male rats and collected brains either 3 days after MI (AMI) or 21 days after MI (CHF). We investigated microglia activation in AMI and CHF brains by immunohistochemistry and immunoblotting using macrophage/microglia marker Ionized calcium binding adaptor molecule 1 (Iba-1), and observed activated morphology of microglia in the cortex of rats in both AMI and CHF. We also showed the levels of BACE1 were increased in the cortex and hippocampus of CHF rats. To determine whether hypoxia occurs in the CHF brain, we assessed levels of VEGF in the hippocampus and cortex. Western blotting analysis showed up-regulation of VEGF in the hippocampus of CHF brains. These results suggest that neuroinflammation takes place secondary to myocardial infarction. In addition, CHF-induced hypoxia might play a role in the elevation of BACE1 and VEGF levels.

Increased CSF-BACE1 activity associated with decreased hippocampus volume in Alzheimer's disease.

The enzyme ß-secretase (BACE1) is essentially involved in the production of cerebral amyloidogenic pathology in Alzheimer's disease (AD). The measurement of BACE1 activity in cerebrospinal fluid (CSF) has been reported, which may render CSF measurement of BACE1 a potential biomarker candidate of AD. In order to investigate whether BACE1 protein activity is correlated with regional brain atrophy in AD, we investigated the association between CSF levels of BACE1 and MRI-assessed hippocampus volume in patients with AD (n = 30). An increase in CSF-BACE1 activity was associated with decreased left and right hippocampus volume corrected for global head volume in the AD patients. Boot-strapped regression analysis showed that increased CSF levels of BACE1 activity were associated with increased CSF concentration of total tau but not amyloid-ß1-42 in AD. White matter hyperintensities did not influence the results. BACE1 activity and protein levels were significantly increased in AD compared to 19 elderly healthy controls. Thus, the CSF biomarker candidate of BACE1 activity was associated with hippocampus atrophy in AD in a robust manner and may reflect neurotoxic amyloid-ß-related processes.

Molecular modeling, synthesis, and activity studies of novel biaryl and fused-ring BACE1 inhibitors.

A series of transition state analogues of beta-secretases 1 and 2 (BACE1, 2) inhibitors containing fused-ring or biaryl moieties were designed computationally to probe the S2 pocket, synthesized, and tested for BACE1 and BACE2 inhibitory activity. It has been shown that unlike the biaryl analogs, the fused-ring moiety is successfully accommodated in the BACE1 binding site resulting in the ligands with excellent inhibitory activity. Ligand 5b reduced 65% of Abeta40 production in N2a cells stably transfected with Swedish human APP.

Pax6 guides a relay of pioneer longitudinal axons in the embryonic mouse forebrain.

We have characterized a system of early neurons that establish the first two major longitudinal tracts in the embryonic mouse forebrain. Axon tracers and antibody labels were used to map the axon projections in the thalamus from embryonic days 9.0-12, revealing several distinct neuron populations that contributed to the first tracts. Each of the early axon populations first grew independently, pioneering a short segment of new tract. However, each axon population soon merged with other axons to form one of only two shared longitudinal tracts, both descending: the tract of the postoptic commissure (TPOC), and, in parallel, the stria medullaris. Thus, the forebrain longitudinal tracts are pioneered by a relay of axons, with distinct axon populations pioneering successive segments of these pathways. The extensive merging of tracts suggests that axon-axon interactions are a major guidance mechanism for longitudinal axons. Several axon populations express tyrosine hydroxylase, identifying the TPOC as a major pathway for forebrain dopaminergic projections. To start a genetic analysis of pioneer axon guidance, we have identified the transcription factor Pax6 as critical for tract formation. In Pax6 mutants, both longitudinal tracts failed to form due to errors by every population of early longitudinal axons. Taken together, these results have identified potentially important interactions between series of pioneer axons and the Pax6 gene as a general regulator of longitudinal tract formation in the forebrain.