Inflammation leads through PGE/EP3 signaling to HDAC5/MEF2-dependent transcription in cardiac myocytes

RNA sequencing of formalin fixed paraffin-embedded heart tissue provides transcriptomic information about chemotherapy-induced cardiotoxicity

Gene expression of formalin-fixed paraffin-embedded (FFPE) tissue may serve for molecular studies on cardiovascular diseases. Chemotherapeutics, such as doxorubicin (DOX) may cause heart injury, but the mechanisms of these side effects of DOX are not well understood. This study aimed to investigate whether DOX-induced gene expression in archival FFPE heart tissue in experimental rats would correlate with the gene expression in fresh-frozen heart tissue by applying RNA sequencing technology. The results showed RNA from FFPE samples was degraded, resulting in a lower number of uniquely mapped reads. However, DOX-induced differentially expressed genes in FFPE were related to molecular mechanisms of DOX-induced cardiotoxicity, such as inflammation, calcium binding, endothelial dysfunction, senescence, and cardiac hypertrophy signaling. Our data suggest that, despite the limitations, RNA sequencing of archival FFPE heart tissue supports utilizing FFPE tissues from retrospective studies on cardiovascular disorders, including DOX-induced cardiotoxicity.

The roles of COX-2 in protozoan infection

Protozoan diseases cause great harm in animal husbandry and require human-provided medical treatment. Protozoan infection can induce changes in cyclooxygenase-2 (COX-2) expression. The role played by COX-2 in the response to protozoan infection is complex. COX-2 induces and regulates inflammation by promoting the synthesis of different prostaglandins (PGs), which exhibit a variety of biological activities and participate in pathophysiological processes in the body in a variety of ways. This review explains the roles played by COX-2 in protozoan infection and analyzes the effects of COX-2-related drugs in protozoan diseases.

Evidence for reciprocal network interactions between injured hearts and cancer

Heart failure (HF) and cancer are responsible for 50% of all deaths in middle-aged people. These diseases are tightly linked, which is supported by recent epidemiological studies and case control studies, demonstrating that HF patients have a higher risk to develop cancer such as lung and breast cancer. For HF patients, a one-size-fits-all clinical management strategy is not effective and patient management represents a major economical and clinical burden. Anti-cancer treatments-mediated cardiotoxicity, leading to HF have been extensively studied. However, recent studies showed that even before the initiation of cancer therapy, cancer patients presented impairments in the cardiovascular functions and exercise capacity. Thus, the optimal cardioprotective and surveillance strategies should be applied to cancer patients with pre-existing HF. Recently, preclinical studies addressed the hypothesis that there is bilateral interaction between cardiac injury and cancer development. Understanding of molecular mechanisms of HF-cancer interaction can define the profiles of bilateral signaling networks, and identify the disease-specific biomarkers and possibly therapeutic targets. Here we discuss the shared pathological events, and some treatments of cancer- and HF-mediated risk incidence. Finally, we address the evidences on bilateral connection between cardiac injury (HF and early cardiac remodeling) and cancer through secreted factors (secretoms).

Chronic isoprenaline/phenylephrine vs. exclusive isoprenaline stimulation in mice: critical contribution of alpha1-adrenoceptors to early cardiac stress responses

Hyperactivity of the sympathetic nervous system is a major driver of cardiac remodeling, exerting its effects through both α-, and β-adrenoceptors (α-, β-ARs). As the relative contribution of subtype α₁-AR to cardiac stress responses remains poorly investigated, we subjected mice to either subcutaneous perfusion with the β-AR agonist isoprenaline (ISO, 30 mg/kg × day) or to a combination of ISO and the stable α₁-AR agonist phenylephrine (ISO/PE, 30 mg/kg × day each). Telemetry analysis revealed similar hemodynamic responses under both ISO and ISO/PE treatment i.e., permanently increased heart rates and only transient decreases in mean blood pressure during the first 24 h. Echocardiography and single cell analysis after 1 week of exposure showed that ISO/PE-, but not ISO-treated animals established α₁-AR-mediated inotropic responsiveness to acute adrenergic stimulation. Morphologically, additional PE perfusion limited concentric cardiomyocyte growth and enhanced cardiac collagen deposition during 7 days of treatment. Time-course analysis demonstrated a diverging development in transcriptional patterns at day 4 of treatment i.e., increased expression of selected marker genes Xirp2, Nppa, Tgfb1, Col1a1, Postn under chronic ISO/PE treatment which was either less pronounced or absent in the ISO group. Transcriptome analyses at day 4 via RNA sequencing demonstrated that additional PE treatment caused a marked upregulation of genes allocated to extracellular matrix and fiber organization along with a more pronounced downregulation of genes involved in metabolic processes, muscle adaptation and cardiac electrophysiology. Consistently, transcriptome changes under ISO/PE challenge more effectively recapitulated early transcriptional alterations in pressure overload-induced experimental heart failure and in human hypertrophic cardiomyopathy.

RGS3L allows for an M2 muscarinic receptor-mediated RhoA-dependent inotropy in cardiomyocytes

The role and outcome of the muscarinic M₂ acetylcholine receptor (M₂R) signaling in healthy and diseased cardiomyocytes is still a matter of debate. Here, we report that the long isoform of the regulator of G protein signaling 3 (RGS3L) functions as a switch in the muscarinic signaling, most likely of the M₂R, in primary cardiomyocytes. High levels of RGS3L, as found in heart failure, redirect the G_i-mediated Rac1 activation into a G_i-mediated RhoA/ROCK activation. Functionally, this switch resulted in a reduced production of reactive oxygen species (- 50%) in cardiomyocytes and an inotropic response (+ 18%) in transduced engineered heart tissues. Importantly, we could show that an adeno-associated virus 9-mediated overexpression of RGS3L in rats in vivo, increased the contractility of ventricular strips by maximally about twofold. Mechanistically, we demonstrate that this switch is mediated by a complex formation of RGS3L with the GTPase-activating protein p190RhoGAP, which balances the activity of RhoA and Rac1 by altering its substrate preference in cardiomyocytes. Enhancement of this complex formation could open new possibilities in the regulation of the contractility of the diseased heart.

Mechanisms and consequences of dysregulation of the Tiam family of Rac activators in disease

The Tiam family proteins - Tiam1 and Tiam2/STEF - are Rac1-specific Guanine Nucleotide Exchange Factors (GEFs) with important functions in epithelial, neuronal, immune and other cell types. Tiam GEFs regulate cellular migration, proliferation and survival, mainly through activating and directing Rac1 signalling. Dysregulation of the Tiam GEFs is significantly associated with human diseases including cancer, immunological and neurological disorders. Uncovering the mechanisms and consequences of dysregulation is therefore imperative to improving the diagnosis and treatment of diseases. Here we compare and contrast the subcellular localisation and function of Tiam1 and Tiam2/STEF, and review the evidence for their dysregulation in disease.

Common mechanistic pathways in cancer and heart failure. A scientific roadmap on behalf of the Translational Research Committee of the Heart Failure Association (HFA) of the European Society of Cardiology (ESC)

The co-occurrence of cancer and heart failure (HF) represents a significant clinical drawback as each disease interferes with the treatment of the other. In addition to shared risk factors, a growing body of experimental and clinical evidence reveals numerous commonalities in the biology underlying both pathologies. Inflammation emerges as a common hallmark for both diseases as it contributes to the initiation and progression of both HF and cancer. Under stress, malignant and cardiac cells change their metabolic preferences to survive, which makes these metabolic derangements a great basis to develop intersection strategies and therapies to combat both diseases. Furthermore, genetic predisposition and clonal haematopoiesis are common drivers for both conditions and they hold great clinical relevance in the context of personalized medicine. Additionally, altered angiogenesis is a common hallmark for failing hearts and tumours and represents a promising substrate to target in both diseases. Cardiac cells and malignant cells interact with their surrounding environment called stroma. This interaction mediates the progression of the two pathologies and understanding the structure and function of each stromal component may pave the way for innovative therapeutic strategies and improved outcomes in patients. The interdisciplinary collaboration between cardiologists and oncologists is essential to establish unified guidelines. To this aim, pre-clinical models that mimic the human situation, where both pathologies coexist, are needed to understand all the aspects of the bidirectional relationship between cancer and HF. Finally, adequately powered clinical studies, including patients from all ages, and men and women, with proper adjudication of both cancer and cardiovascular endpoints, are essential to accurately study these two pathologies at the same time.

The microRNA miR-134-5p induces calcium deposition by inhibiting histone deacetylase 5 in vascular smooth muscle cells

Calcium deposition in vascular smooth muscle cells (VSMCs) is a form of ectopic ossification in blood vessels. It can result in rigidity of the vasculature and an increase in cardiac events. Here, we report that the microRNA miR‐134‐5p potentiates inorganic phosphate (Pi)‐induced calcium deposition in VSMCs by inhibiting histone deacetylase 5 (HDAC5). Using miRNA microarray analysis of Pi‐treated rat VSMCs, we first selected miR‐134‐5p for further evaluation. Quantitative RT‐PCR confirmed that miR‐134‐5p was increased in Pi‐treated A10 cells, a rat VSMC line. Transfection of miR‐134‐5p mimic potentiated the Pi‐induced increase in calcium contents. miR‐134‐5p increased the amounts of bone runt‐related transcription factor 2 (RUNX2) protein and bone morphogenic protein 2 (BMP2) mRNA in the presence of Pi but decreased the expression of osteoprotegerin (OPG). Bioinformatic analysis showed that the HDAC5 3′untranslated region (3′UTR) was one of the targets of miR‐134‐5p. The luciferase construct containing the 3′UTR of HDAC5 was down‐regulated by miR‐134‐5p mimic in a dose‐dependent manner in VSMCs. Overexpression of HDAC5 mitigated the calcium deposition induced by miR‐134‐5p. Our results suggest that a Pi‐induced increase of miR‐134‐5p may cause vascular calcification through repression of HDAC5.

Cyclic AMP represses pathological MEF2 activation by myocyte-specific hypo-phosphorylation of HDAC5

Class IIa histone deacetylases (HDACs) critically regulate cardiac function through the repression of the activity of myocyte enhancer factor 2 (MEF2)-dependent gene programs. Protein kinase D (PKD) and Ca²⁺/Calmodulin-dependent kinase II (CaMKII) activate MEF2 by phosphorylating distinct HDAC isoforms and thereby creating 14-3-3 binding sites for nucleo-cytoplasmic shuttling. Recently, it has been shown that this process is counteracted by cyclic AMP (cAMP)-dependent signaling. Here, we investigated the specific mechanisms of how cAMP-dependent signaling regulates distinct HDAC isoforms and determined their relative contributions to the protection from pathological MEF2 activation. We found that cAMP is sufficient to induce nuclear retention and to blunt phosphorylation of the 14-3-3 binding sites of HDAC5 (Ser259/498) and HDAC9 (Ser218/448) but not HDAC4 (Ser246/467/632). These regulatory events could be observed only in cardiomyocytes and myocyte-like cells but not in non-myocytes, pointing to an indirect myocyte-specific mode of action. Consistent with one previous report, we found that blunted phosphorylation of HDAC5 and HDAC9 was mediated by protein kinase A (PKA)-dependent inhibition of PKD. However, we show by the use of neonatal cardiomyocytes derived from genetic HDAC mouse models that endogenous HDAC5 but not HDAC9 contributes specifically to the repression of endogenous MEF2 activity. HDAC4 contributed significantly to the repression of MEF2 activity but based on the mechanistic findings of this study combined with previous results we attribute this to PKA-dependent proteolysis of HDAC4. Consistently, cAMP-induced repression of agonist-driven cellular hypertrophy was blunted in cardiomyocytes deficient for both HDAC5 and HDAC4. In conclusion, cAMP inhibits MEF2 through both nuclear accumulation of hypo-phosphorylated HDAC5 and through a distinct HDAC4-dependent mechanism.

Nuclear receptor corepressor 1 represses cardiac hypertrophy

The function of nuclear receptor corepressor 1 (NCoR1) in cardiomyocytes is unclear, and its physiological and pathological implications are unknown. Here, we found that cardiomyocyte‐specific NCoR1 knockout (CMNKO) mice manifested cardiac hypertrophy at baseline and had more severe cardiac hypertrophy and dysfunction after pressure overload. Knockdown of NCoR1 exacerbated whereas overexpression mitigated phenylephrine‐induced cardiomyocyte hypertrophy. Mechanistic studies revealed that myocyte enhancer factor 2a (MEF2a) and MEF2d mediated the effects of NCoR1 on cardiomyocyte hypertrophy. The receptor interaction domains (RIDs) of NCoR1 interacted with MEF2a to repress its transcriptional activity. Furthermore, NCoR1 formed a complex with MEF2a and class IIa histone deacetylases (HDACs) to suppress hypertrophy‐related genes. Finally, overexpression of RIDs of NCoR1 in the heart attenuated cardiac hypertrophy and dysfunction induced by pressure overload. In conclusion, NCoR1 cooperates with MEF2 and HDACs to repress cardiac hypertrophy. Targeting NCoR1 and the MEF2/HDACs complex may be an attractive therapeutic strategy to tackle pathological cardiac hypertrophy.

cAMP guided his way: a life for G protein-mediated signal transduction and molecular pharmacology-tribute to Karl H. Jakobs

Karl H. Jakobs, former editor-in-chief of Naunyn-Schmiedeberg's Archives of Pharmacology and renowned molecular pharmacologist, passed away in April 2018. In this article, his scientific achievements regarding G protein-mediated signal transduction and regulation of canonical pathways are summarized. Particularly, the discovery of inhibitory G proteins for adenylyl cyclase, methods for the analysis of receptor-G protein interactions, GTP supply by nucleoside diphosphate kinases, mechanisms in phospholipase C and phospholipase D activity regulation, as well as the development of the concept of sphingosine-1-phosphate as extra- and intracellular messenger will presented. His seminal scientific and methodological contributions are put in a general and timely perspective to display and honor his outstanding input to the current knowledge in molecular pharmacology.