Arash Haghikia

MicroRNA-146a is a therapeutic target and biomarker for peripartum cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a life-threatening pregnancy-associated cardiomyopathy in previously healthy women. Although PPCM is driven in part by the 16-kDa N-terminal prolactin fragment (16K PRL), the underlying molecular mechanisms are poorly understood. We found that 16K PRL induced microRNA-146a (miR-146a) expression in ECs, which attenuated angiogenesis through downregulation of NRAS. 16K PRL stimulated the release of miR-146a-loaded exosomes from ECs. The exosomes were absorbed by cardiomyocytes, increasing miR-146a levels, which resulted in a subsequent decrease in metabolic activity and decreased expression of Erbb4, Notch1, and Irak1. Mice with cardiomyocyte-restricted Stat3 knockout (CKO mice) exhibited a PPCM-like phenotype and displayed increased cardiac miR-146a expression with coincident downregulation of Erbb4, Nras, Notch1, and Irak1. Blocking miR-146a with locked nucleic acids or antago-miRs attenuated PPCM in CKO mice without interrupting full-length prolactin signaling, as indicated by normal nursing activities. Finally, miR-146a was elevated in the plasma and hearts of PPCM patients, but not in patients with dilated cardiomyopathy. These results demonstrate that miR-146a is a downstream-mediator of 16K PRL that could potentially serve as a biomarker and therapeutic target for PPCM.

Peripartum cardiomyopathy: current management and future perspectives

Pregnancy is associated with marked physiological changes challenging the cardiovascular system. Among the more severe pregnancy associated cardiovascular complications, peripartum cardiomyopathy (PPCM) is a potentially life-threatening heart disease emerging towards the end of pregnancy or in the first postpartal months in previously healthy women. A major challenge is to distinguish the peripartum discomforts in healthy women (fatigue, shortness of breath, and oedema) from the pathological symptoms of PPCM. Moreover, pregnancy-related pathologies such as preeclampsia, myocarditis, or underlying genetic disease show overlapping symptoms with PPCM. Difficulties in diagnosis and the discrimination from other pathological conditions in pregnancy may explain why PPCM is still underestimated. Additionally, underlying pathophysiologies are poorly understood, biomarkers are scarce and treatment options in general limited. Experience in long-term prognosis and management including subsequent pregnancies is just beginning to emerge. This review focuses on novel aspects of physiological and pathophysiological changes of the maternal cardiovascular system by comparing normal conditions, hypertensive complications, genetic aspects, and infectious disease in PPCM-pregnancies. It also presents clinical and basic science data on the current state of knowledge on PPCM and brings them in context thereby highlighting promising new insights in diagnostic tools and therapeutic approaches and management.

Signal transducer and activator of transcription 3-mediated regulation of miR-199a-5p links cardiomyocyte and endothelial cell function in the heart: a key role for ubiquitin-conjugating enzymes.

AIMS Mice with a cardiomyocyte (CM)-restricted knockout of signal transducer and activator of transcription 3 (STAT3-KO) develop spontaneous heart failure. We investigated the impact of STAT3-mediated regulation of microRNAs for pathophysiological alterations in the heart. METHODS AND RESULTS MicroRNAchip and qRT-PCR analysis revealed elevated cardiac expression of miR-199a in STAT3-KO mice. Lentiviral shRNA-mediated STAT3-knock-down in neonatal rat CMs markedly increased miR-199a promoter activity and miR-199a levels indicative of a suppressive effect of STAT3 on miR-199a transcription. Up-regulated miR-199a in CM by pre-miR-199a transfection (pre-miR-199a-CM) reduced expression of components of the ubiquitin-proteasome system (UPS), i.e. the ubiquitin-conjugating enzymes Ube2g1 (mRNA and protein) and Ube2i (protein). Pre-miR-199a-CM or CM with siRNA-mediated down-regulation of Ube2i and Ube2g1 (siRNA-Ube2i/2g1-CM) displayed massive down-regulation of α- and β-myosin heavy chain expression associated with disrupted sarcomere structures. In addition, protein arginine methyltransferase I (PRMT-I) expression and asymmetric dimethylarginine (ADMA) synthesis were increased in pre-miR-199a-CM or in siRNA-Ube2i/2g1-CM. Increased ADMA in cell culture supernatant (SN) from pre-miR-199a-CM or siRNA-Ube2i/2g1-CM lowered nitric oxide (NO) bioavailability of rat cardiac endothelial cells while lowering ADMA concentration in CM SNs by the PRMT inhibitor arginine methyltransferase inhibitor 1 (AMI-1) (100 µM) improved NO bioavailability. In STAT3-KO hearts Ube2i and Ube2g1 expression were markedly reduced. Human terminal failing hearts harbouring low STAT3 protein levels displayed increased miR-199a levels and decreased Ube2g1 expression. CONCLUSION This study identifies a novel pathophysiological circuit in the heart between reduced STAT3 protein levels, increased miR-199a expression, and subsequent impairment of the UPS that disrupts CM sarcomere structure and impairs via the release of ADMA endothelial cell function.

STAT3 and cardiac remodeling

Multiple in vitro and in vivo studies showed that the signal transducer and activator of transcription 3 (STAT3) protein is involved in cardiomyocyte protection and hypertrophy and via paracrine pathways impacts on the non-myocyte compartment, i.e., the vasculature and the extracellular matrix. In this regard, STAT3 interacts with a broad range of cellular and molecular mechanisms that direct remodeling processes in cardiac physiology (exercise, pregnancy) and pathophysiology (pressure overload, ischemia/reperfusion, myocardial infarction, and cardiotoxic agents). STAT3 is constitutively activated by a multitude of factors including cytokines, growth factors, neurohormones, mechanical load, and ischemia. It acts as a signaling molecule, a transcription factor and according to latest observations as a mitochondrial protein involved in energy production. In this review, we provide an overview on STAT3 signaling and summarize the current understanding of the role of STAT3 for different aspects of cardiac remodeling obtained from numerous experimental and clinical studies. Finally, we highlight and critically discuss STAT3 signaling as a possible target for future therapeutic approaches in the setting of cardiac remodeling.

Prevention of liver cancer cachexia-induced cardiac wasting and heart failure

AIMS Symptoms of cancer cachexia (CC) include fatigue, shortness of breath, and impaired exercise capacity, which are also hallmark symptoms of heart failure (HF). Herein, we evaluate the effects of drugs commonly used to treat HF (bisoprolol, imidapril, spironolactone) on development of cardiac wasting, HF, and death in the rat hepatoma CC model (AH-130). METHODS AND RESULTS Tumour-bearing rats showed a progressive loss of body weight and left-ventricular (LV) mass that was associated with a progressive deterioration in cardiac function. Strikingly, bisoprolol and spironolactone significantly reduced wasting of LV mass, attenuated cardiac dysfunction, and improved survival. In contrast, imidapril had no beneficial effect. Several key anabolic and catabolic pathways were dysregulated in the cachectic hearts and, in addition, we found enhanced fibrosis that was corrected by treatment with spironolactone. Finally, we found cardiac wasting and fibrotic remodelling in patients who died as a result of CC. In living cancer patients, with and without cachexia, serum levels of brain natriuretic peptide and aldosterone were elevated. CONCLUSION Systemic effects of tumours lead not only to CC but also to cardiac wasting, associated with LV-dysfunction, fibrotic remodelling, and increased mortality. These adverse effects of the tumour on the heart and on survival can be mitigated by treatment with either the β-blocker bisoprolol or the aldosterone antagonist spironolactone. We suggest that clinical trials employing these agents be considered to attempt to limit this devastating complication of cancer.

Risk for ventricular fibrillation in peripartum cardiomyopathy with severely reduced left ventricular function—value of the wearable cardioverter/defibrillator

The true incidence of life‐threatening ventricular tachyarrhythmic events and the risk of sudden cardiac death in the early stage of peripartum cardiomyopathy (PPCM) are still unknown. We aimed to assess the usefulness of the wearable cardioverter/defibrillator (WCD) to bridge a potential risk for life‐threatening arrhythmic events in patients with early PPCM, severely reduced left ventricular ejection fraction (LVEF) and symptoms of heart failure.

Cytokine-activated NK cells inhibit PMN apoptosis and preserve their functional capacity

Natural killer (NK) cells and polymorphonuclear cells (PMNs) play a critical role in the first line of defense against microorganisms. Upon host infection, PMNs phagocytose invading pathogens with subsequent killing by oxidative or nonoxidative mechanisms. NK cells are known to have immunoregulatory effects on T cells, B cells, dendritic cells (DCs), and monocytes through secretion of various soluble products and cell-cell contact. However, their impact on PMN survival and function is not well known. We found that soluble factors derived from cytokine-activated NK cells delay PMN apoptosis and preserve their ability to perform phagocytosis and produce reactive oxygen species (ROS). The expression patterns of CD11b and CD62L on PMNs differed according to the cytokine combination used for NK-cell stimulation. Irrespective of the NK-cell treatment, however, PMN survival was prolonged with sustained functional capacity. We found that interferon gamma, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha produced by NK cells upon stimulation with cytokines played a crucial role in NK cell-mediated effects on PMNs. Our study demonstrates that soluble factors derived from cytokine-activated NK cells send survival signals to PMNs, which would promote their accumulation and function at the site of inflammation in vivo.

Molecular Imaging of the Chemokine Receptor CXCR4 After Acute Myocardial Infarction.

OBJECTIVES An assay for molecular imaging of myocardial CXCR4 expression was evaluated, in order to obtain mechanistic insights noninvasively based on quantitative positron emission tomography (PET). BACKGROUND The chemokine receptor CXCR4 has emerged as a therapeutic target after acute myocardial infarction (AMI), because of its role in inflammatory and progenitor cell recruitment. METHODS PET with the specific CXCR4 ligand, gallium-68 ((68)Ga)-pentixafor, was performed in mice (n = 53) and compared with ex vivo autoradiography, immunohistochemistry, and left ventricular flow cytometry. In addition, 12 patients were imaged at 2 to 8 days after AMI. RESULTS In mice, (68)Ga-pentixafor identified regional CXCR4 upregulation in the infarct region, peaking at 3 days (infarct/remote [I/R] ratio 1.5 ± 0.2 at 3 days vs. 1.2 ± 0.3 at 7 days; p = 0.03), corresponding to a flow cytometry-based peak of CD45+ leukocytes and immunohistochemical detection of CD68+ macrophages and Ly6G+ granulocytes. Blockade with the CXCR4 antagonist AMD3100 abolished the signal. No specific uptake was found in sham-operated or control animals. Long-term treatment with oral enalapril attenuated the CXCR4 signal (I/R 1.2 ± 0.2 at 3 days and 1.0 ± 0.0.1 at 7 days; p = 0.01 vs. untreated). Patients showed variable degrees of CXCR4 upregulation in the infarct region. No single clinical parameter allowed for prediction of CXCR4 signal strength. At multivariate analysis, a combination of infarct size and time after reperfusion predicted the CXCR4 infarct signal (rmultiple = 0.73; p = 0.03). Infarct signal in the myocardium was paralleled by elevated pentixafor uptake in bone marrow (r = 0.61; p = 0.04), which highlighted systemic interactions. CONCLUSIONS Targeted PET imaging with (68)Ga-pentixafor identifies the global and regional CXCR4 expression pattern in myocardium and systemic organs. CXCR4 upregulation after AMI coincides with inflammatory cell infiltration, but shows interindividual variability in patients. This may have implications for the response to CXCR4- or other inflammation-targeted therapy, and for subsequent ventricular remodeling.

STAT3, a key regulator of cell-to-cell communication in the heart

The signal transducer and activator of transcription 3 (STAT3) is fundamental for physiological homeostasis and stress-induced remodelling of the heart as deregulated STAT3 circuits are sufficient to induce dilated and peripartum cardiomyopathy and adverse remodelling after myocardial infarction. STAT3 activity depends on multiple post-translational modifications (phosphorylation, acetylation, and dimerization). It is regulated by multiple receptor systems, which are coupled to positive and negative feedback loops to ensure physiological and beneficial action. Its intracellular functions are diverse as it acts as a signalling protein, a transcription factor but also participates in mitochondria energy production and protection. STAT3 modulates proliferation, differentiation, survival, oxidative stress, and/or metabolism in cardiomyocytes, fibroblasts, endothelial cells, progenitor cells, and various inflammatory cells. By regulating the secretome of these cardiac cells, STAT3 influences a broad range of intercellular communication systems. It thereby impacts on the communication between cardiomyocytes, the plasticity of the cardiac microenvironment, the vasculature, the extracellular matrix, and the inflammation in response to physiological and pathophysiological stress. Here, we sum up current knowledge on STAT3-mediated intra- and intercellular communication within the heterogeneous cellular network of the myocardium to co-ordinate complex biological processes and discuss STAT3-dependent targets as novel therapeutic concepts to treat various forms of heart disease.

Bromocriptine for the treatment of peripartum cardiomyopathy: a multicentre randomized study

Abstract Aims An anti-angiogenic cleaved prolactin fragment is considered causal for peripartum cardiomyopathy (PPCM). Experimental and first clinical observations suggested beneficial effects of the prolactin release inhibitor bromocriptine in PPCM. Methods and results In this multicentre trial, 63 PPCM patients with left ventricular ejection fraction (LVEF) ≤35% were randomly assigned to short-term (1W: bromocriptine, 2.5 mg, 7 days) or long-term bromocriptine treatment (8W: 5 mg for 2 weeks followed by 2.5 mg for 6 weeks) in addition to standard heart failure therapy. Primary end point was LVEF change (delta) from baseline to 6 months assessed by magnetic resonance imaging. Bromocriptine was well tolerated. Left ventricular ejection fraction increased from 28 ± 10% to 49 ± 12% with a delta-LVEF of + 21 ± 11% in the 1W-group, and from 27 ± 10% to 51 ± 10% with a delta-LVEF of + 24 ± 11% in the 8W-group (delta-LVEF: P = 0.381). Full-recovery (LVEF ≥ 50%) was present in 52% of the 1W- and in 68% of the 8W-group with no differences in secondary end points between both groups (hospitalizations for heart failure: 1W: 9.7% vs. 8W: 6.5%, P = 0.651). The risk within the 8W-group to fail full-recovery after 6 months tended to be lower. No patient in the study needed heart transplantation, LV assist device or died. Conclusion Bromocriptine treatment was associated with high rate of full LV-recovery and low morbidity and mortality in PPCM patients compared with other PPCM cohorts not treated with bromocriptine. No significant differences were observed between 1W and 8W treatment suggesting that 1-week addition of bromocriptine to standard heart failure treatment is already beneficial with a trend for better full-recovery in the 8W group. Clinical trial registration ClinicalTrials.gov, study number: NCT00998556.