Heart failure with preserved ejection fraction (HFpEF) is a common, morbid, and mortal syndrome for which there are no evidence-based therapies. Here, we report that concomitant metabolic and hypertensive stress in mice elicited by a combination of high fat diet (HFD) and constitutive nitric oxide (NO) synthase inhibition by N[w]-nitro-l-arginine methyl ester (L-NAME) recapitulates the numerous systemic and cardiovascular features of human HFpEF. One of the unfolded protein response (UPR) effectors, the spliced form of X-box binding protein 1 (Xbp1s), was reduced in the myocardium of both experimental and human HFpEF. Mechanistically, the decrease in Xbp1s resulted from increased inducible NO synthase (iNOS) activity and S-nitrosylation of endonuclease inositol-requiring protein 1α (IRE1α), culminating in defective Xbp1 splicing. Pharmacological or genetic suppression of iNOS, or cardiomyocyte-restricted overexpression of Xbp1s, each ameliorated the HFpEF phenotype. We have unveiled iNOS-driven dysregulation of IRE1α-Xbp1s as a crucial mechanism of cardiomyocyte dysfunction in HFpEF.

Altering chromatin structure through histone posttranslational modifications has emerged as a key driver of transcriptional responses in cells. Modulation of these transcriptional responses by pharmacological inhibition of class I histone deacetylases (HDACs), a group of chromatin remodeling enzymes, has been successful in blocking the growth of some cancer cell types. These inhibitors also attenuate the pathogenesis of pathological cardiac remodeling by blunting and even reversing pathological hypertrophy. The mechanistic target of rapamycin (mTOR) is a critical sensor and regulator of cell growth that as part of mTOR complex I (mTORC1) drives changes in protein synthesis and metabolism in both pathological and physiological hypertrophy. Here, we demonstrated through pharmacological and genetic methods that inhibition of class I HDACs suppressed pathological cardiac hypertrophy through inhibition of mTOR activity. Mice genetically silenced for HDAC1 and HDAC2 had a reduced hypertrophic response to TAC and showed reduced mTOR activity. We determined that the abundance of tuberous sclerosis complex 2 (TSC2), an mTOR inhibitor, was increased through a transcriptional mechanism in cardiomyocytes when class I HDACs were inhibited. In neonatal rat cardiomyocytes, loss of TSC2 abolished HDAC-dependent inhibition of mTOR activity, and increased expression of TSC2 was sufficient to reduce hypertrophy in response to phenylephrine. These findings point to mTOR and TSC2-dependent control of mTOR as critical components of the mechanism by which HDAC inhibitors blunt pathological cardiac growth. These results also suggest a strategy to modulate mTOR activity and facilitate the translational exploitation of HDAC inhibitors in heart disease.

Background & Aims Dietary intake of the natural omega-3 fatty acid docosahexaenoic acid (DHA) has been implicated in protecting patients with viral hepatitis B or C from developing hepatocellular carcinoma (HCC). Little is known about the effects of DHA on established solid tumors. Herein, we describe a low-density lipoprotein (LDL)-based nanoparticle that acts as a transporter for unesterified DHA (LDL–DHA) and demonstrates selective cytotoxicity towards HCC cells. We investigated the ability of LDL–DHA to reduce growth of orthotopic hepatomas in rats. Methods ACI rats were given intrahepatic injections of rat hepatoma cells (H4IIE); 24 tumor-bearing rats (mean tumor diameter, ~1 cm) were subject to a single hepatic artery injection of LDL nanoparticles (2 mg/kg) loaded with DHA (LDL–DHA), triolein (LDL–TO) or sham surgery controls. Tumor growth was measured by magnetic resonance imaging and other methods; tumor, liver and serum samples were collected and assessed by histochemical, immunofluorescence, biochemical and immunoblot analyses. Results Three days after administration of LDL–TO or sham surgery, the control rats had large, highly vascularized tumors that contained proliferating cells. However, rats given LDL–DHA had smaller, pale tumors that were devoid of vascular supply and greater than 80% of the tumor tissue was necrotic. Four to 6 days after injection of LDL–DHA, the tumors were 3-fold smaller than those of control rats. The liver tissue that surrounded the tumors showed no histologic or biochemical evidence of injury. Injection of LDL–DHA into the hepatic artery of rats selectively deregulated redox reactions in tumor tissues by: increasing levels of reactive oxygen species and lipid peroxidation, depleting and oxidizing glutathione and nicotinamide adenine dinucleotide phosphate, and significantly downregulating the antioxidant enzyme glutathione peroxidase-4. Remarkably, the redox balance in the surrounding liver was not disrupted. Conclusion LDL–DHA nanoparticle selectively kills hepatoma cells and reduces growth of orthotopic liver tumors in rats. It induces tumor-specific necrosis by selectively disrupting redox balance within the cancer cell.

Purpose of review To provide an overview, highlighting recent findings, of a major mechanism of gene regulation and its relevance to the pathophysiology of heart failure. Recent findings The syndrome of heart failure is a complex and highly prevalent condition, one in which the heart undergoes substantial structural remodeling. Triggered by a wide range of disease-related cues, heart failure pathophysiology is governed by both genetic and epigenetic events. Epigenetic mechanisms, such as chromatin/DNA modifications and non-coding RNAs, have emerged as molecular transducers of environmental stimuli to control gene expression. Here, we emphasize metabolic milieu, aging, and hemodynamic stress as they impact the epigenetic landscape of the myocardium. Summary Recent studies in multiple fields, including cancer, stem cells, development, and cardiovascular biology, have uncovered biochemical ties linking epigenetic machinery and cellular energetics and mitochondrial function. Elucidation of these connections will afford molecular insights into long-established epidemiological observations. With time, exploitation of the epigenetic machinery therapeutically may emerge with clinical relevance.

Background: Polycystin-1 (PC1) is a transmembrane protein originally identified in autosomal dominant polycystic kidney disease where it regulates the calcium-permeant cation channel polycystin-2. Autosomal dominant polycystic kidney disease patients develop renal failure, hypertension, left ventricular hypertrophy, and diastolic dysfunction, among other cardiovascular disorders. These individuals harbor PC1 loss-of-function mutations in their cardiomyocytes, but the functional consequences are unknown. PC1 is ubiquitously expressed, and its experimental ablation in cardiomyocyte-specific knockout mice reduces contractile function. Here, we set out to determine the pathophysiological role of PC1 in cardiomyocytes. Methods: Wild-type and cardiomyocyte-specific PC1 knockout mice were analyzed by echocardiography. Excitation-contraction coupling was assessed in isolated cardiomyocytes and human embryonic stem cell-derived cardiomyocytes, and functional consequences were explored in heterologous expression systems. Protein-protein interactions were analyzed biochemically and by means of ab initio calculations. Results: PC1 ablation reduced action potential duration in cardiomyocytes, decreased Ca 2+ transients, and myocyte contractility. PC1-deficient cardiomyocytes manifested a reduction in sarcoendoplasmic reticulum Ca 2+ stores attributable to a reduced action potential duration and sarcoendoplasmic reticulum Ca 2+ ATPase (SERCA) activity. An increase in outward K + currents decreased action potential duration in cardiomyocytes lacking PC1. Overexpression of full-length PC1 in HEK293 cells significantly reduced the current density of heterologously expressed Kv4.3, Kv1.5 and Kv2.1 potassium channels. PC1 C terminus inhibited Kv4.3 currents to the same degree as full-length PC1. Additionally, PC1 coimmunoprecipitated with Kv4.3, and a modeled PC1 C-terminal structure suggested the existence of 2 docking sites for PC1 within the N terminus of Kv4.3, supporting a physical interaction. Finally, a naturally occurring human mutant PC1 R4228X manifested no suppressive effects on Kv4.3 channel activity. Conclusions: Our findings uncover a role for PC1 in regulating multiple Kv channels, governing membrane repolarization and alterations in SERCA activity that reduce cardiomyocyte contractility.

Background Recent studies have shown that low density lipoproteins reconstituted with the natural omega 3 fatty acid docosahexaenoic acid (LDL-DHA) is selectively cytotoxic to liver cancer cells over normal hepatocytes. To date, little is known about the subcellular events which transpire following LDL-DHA treatment. Methods Herein, murine noncancer and cancer liver cells, TIB-73 and TIB-75 respectively, were investigated utilizing confocal microscopy, flow cytometry and viability assays to demonstrate differential actions of LDL-DHA nanoparticles in normal versus malignant cells. Results Our studies first showed that basal levels of oxidative stress are significantly higher in the malignant TIB-75 cells compared to the normal TIB-73 cells. As such, upon entry of LDL-DHA into the malignant TIB-75 cells, DHA is rapidly oxidized precipitating global and lysosomal lipid peroxidation along with increased lysosomal permeability. This leakage of lysosomal contents and lipid peroxidation products trigger subsequent mitochondrial dysfunction and nuclear injury. The cascade of LDL-DHA mediated lipid peroxidation and organelle damage was partially reversed by the administration of the antioxidant, N-acetylcysteine, or the iron-chelator, deferoxamine. LDL-DHA treatment in the normal TIB-73 cells was well tolerated and did not elicit any cell or organelle injury. Conclusion These studies have shown that LDL-DHA is selectively cytotoxic to liver cancer cells and that increased levels of ROS and iron catalyzed reactions promote the peroxidation of DHA which lead to organelle dysfunction and ultimately the demise of the cancer cell. General significance LDL-DHA selectively disrupts lysosomal, mitochondrial and nuclear function in cancer cells as a novel pathway for eliminating cancer cells.

Long non-coding RNAs (lncRNAs) comprise the most representative transcriptional units of the mammalian genome, and they’re associated with organ development that can be associated with the emergence of diseases, such as cardiovascular diseases. Thus, we used bioinformatic approaches, machine learning algorithms and statistical techniques to define lncRNAs involved in mammalian cardiac development. We used a single-cell transcriptome dataset generated from 4 embryonic and 4 postnatal stages. Our study identified 8 distinct cell types, novel marker transcripts (coding/lncRNAs) and also, differential expression and functional enrichment analysis reveal cardiomyocyte subpopulations associated with cardiac function; meanwhile modular co-expression analysis reveals cell-specific functional insights for lncRNAs during myocardial development, including a potential association with key genes related to disease and the “fetal gene program”. Our results evidence the role of particular lncRNAs in heart development, and highlights the usage of co-expression modular approaches in the cell-type functional definition.