Hasan Mahmud

The vitamin D receptor activator paricalcitol prevents fibrosis and diastolic dysfunction in a murine model of pressure overload

BACKGROUND Activation of the vitamin D-vitamin D receptor (VDR) axis has been shown to reduce blood pressure and left ventricular (LV) hypertrophy. Besides cardiac hypertrophy, cardiac fibrosis is a key element of adverse cardiac remodeling. We hypothesized that activation of the VDR by paricalcitol would prevent fibrosis and LV diastolic dysfunction in an established murine model of cardiac remodeling. METHODS Mice were subjected to transverse aortic constriction (TAC) to induce cardiac hypertrophy. Mice were treated with paricalcitol, losartan, or a combination of both for a period of four consecutive weeks. RESULTS The fixed aortic constriction caused similar increase in blood pressure, both in untreated and paricalcitol- or losartan-treated mice. TAC significantly increased LV weight compared to sham operated animals (10.2±0.7 vs. 6.9±0.3 mg/mm, p<0.05). Administration of either paricalcitol (10.5±0.7), losartan (10.8±0.4), or a combination of both (9.2±0.6) did not reduce LV weight. Fibrosis was significantly increased in mice undergoing TAC (5.9±1.0 vs. sham 2.4±0.8%, p<0.05). Treatment with losartan and paricalcitol reduced fibrosis (paricalcitol 1.6±0.3% and losartan 2.9±0.6%, both p<0.05 vs. TAC). This reduction in fibrosis in paricalcitol treated mice was associated with improved indices of LV contraction and relaxation, e.g. dPdtmax and dPdtmin and lower LV end diastolic pressure, and relaxation constant Tau. Also, treatment with paricalcitol and losartan reduced mRNA expression of ANP, fibronectin, collagen III and TIMP-1. DISCUSSION Treatment with the selective VDR activator paricalcitol reduces myocardial fibrosis and preserves diastolic LV function due to pressure overload in a mouse model. This is associated with a reduced percentage of fibrosis and a decreased expression of ANP and several other tissue markers.

The Plk1 Inhibitor BI 2536 Temporarily Arrests Primary Cardiac Fibroblasts in Mitosis and Generates Aneuploidy In Vitro

BI 2536 is a new anti-mitotic drug that targets polo-like kinase 1 (Plk1) and is currently under clinical development for cancer therapy. The effect of this drug on cancer cells has been extensively investigated, but information about the effects on primary dividing cells and differentiated non-dividing cells is scarce. We have investigated the effects of this drug on primary neonatal rat cardiac fibroblasts and on differentiated cardiomyocytes and explored the possibility to use this drug to enrich differentiated cell populations in vitro. BI 2536 had a profound effect on cardiac fibroblast proliferation in vitro and arrested these cells in mitosis with an IC50 of about 43 nM. Similar results were observed with primary human cells (HUVEC, IC50  = 30 nM), whereas the cancer cell line HeLa was more sensitive (IC50 of 9 nM). Further analysis revealed that prolonged mitotic arrest resulted in cell death for about 40% of cardiac fibroblasts. The remaining cells showed an interphase morphology with mostly multi- and micro-nucleated nuclei. This indicates that a significant number of primary fibroblasts are able to escape BI 2536 induced mitotic arrest and apparently become aneuploid. No effects were observed on cardiomyocytes and hypertrophic response (growth) upon endothelin-1 and phenylephrine stimulation was normal in the presence of BI 2536. This indicates that BI 2536 has no adverse effects on terminally differentiated cells and still allows proliferation independent growth induction in these cells. In conclusion, cardiomyocytes could be enriched using BI 2536, but the formation of aneuploidy in proliferating cells most likely limits this in vitro application and does not allow its use in putative cell based therapies.

Genome-wide association study on plasma levels of midregional-proadrenomedullin and C-terminal-pro-endothelin-1.

Endothelin-1 (ET-1) and adrenomedullin (ADM) are circulating vasoactive peptides involved in vascular homeostasis and endothelial function. Elevated levels of plasma ET-1 and ADM, and their biologically stable surrogates, C-terminal-pro-endothelin-1 (CT-pro-ET-1) and midregional proadrenomedullin (MR-pro-ADM), are predictors of cardiac death and heart failure. We studied the association of common genetic variation with MR-pro-ADM and CT-pro-ET-1 by genome-wide association analyses in 3444 participants of European ancestry. We performed follow-up genotyping of single nucleotide polymorphisms (SNPs) that showed suggestive or significant association in the discovery stage in additional 3230 participants. The minor variants in KLKB1 (rs4253238) and F12 (rs2731672), both part of the kallikrein-kinin system, were associated with higher MR-pro-ADM (P=4.46E-52 and P=5.90E-24, respectively) and higher CT-pro-ET-1 levels (P=1.23E-122 and P=1.26E-67, respectively). Epistasis analyses showed a significant interaction between the sentinel SNP of F12 and KLKB1 for both traits. In addition, a variant near the ADM gene (rs2957692) was associated with MR-pro-ADM (P=1.05E-12) and a variant in EDN-1 (rs5370) was associated with CT-pro-ET-1 (P=1.49E-27). The total phenotypic variation explained by the genetic variants was 7.2% for MR-pro-ADM and 14.6% for CT-pro-ET-1. KLKB1 encodes plasma kallikrein, a proteolytic enzyme known to cleave high-molecular-weight kininogen to bradykinin and prorenin to renin. We cloned the precursors of ADM and ET-1 and demonstrated that purified plasma kallikrein can cleave these recombinant proteins into multiple smaller peptides. The discovery of genetic variants in the kallikrein-kinin system and in the genes encoding pre-pro-ET-1 and pre-pro-ADM provides novel insights into the (co-)regulation of these vasoactive peptides in the vascular system.

Insights in dynamic kinome reprogramming as a consequence of MEK inhibition in MLL-rearranged AML

Single kinase-targeted cancer therapies often failed prolonged responses because cancer cells bypass through alternative routes. In this study, high-throughput kinomic and proteomic approaches enabled to identify aberrant activity profiles in mixed lineage leukemia (MLL)-rearranged acute myeloid leukemia (AML) that defined druggable targets. This approach revealed impaired activity of proteins belonging to the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathway. Pharmacological druggable MAPK pathway targets tested in primary MLL-rearranged AML included MAPKK1/2 (MEK), cyclic AMP-responsive element-binding protein (CREB) and MAPK8/9 (JNK). MEK inhibition showed to severely decrease MLL-rearranged AML cell survival without showing cytotoxicity in normal controls, whereas inhibition of CREB and JNK failed to exhibit MLL selectivity. Exploring the working mechanism of MEK inhibition, we assessed proteome activity in response to MEK inhibition in THP-1. MAPK1/3 (Erk) phosphorylation was instantly decreased in concurrence with a sustained Akt/mammalian target of rapamycin (mTOR) phosphorylation that enabled a subpopulation of cells to survive MEK inhibition. After exhaustion of MEK inhibition the AML cells recovered via increased activity of vascular endothelial growth factor receptor-2 (VEGFR-2) and Erk proteins to resume their proliferative state. Combined MEK and VEGFR-2 inhibition strengthened the reduction in MLL-rearranged AML cell survival by blocking the Akt/mTOR and MAPK pathways simultaneously. The generation of insights in cancerous altered activity profiles and alternative escape mechanisms upon targeted therapy allows the rational design of novel combination strategies.

Suicidal erythrocyte death, eryptosis, as a novel mechanism in heart failure-associated anaemia

AIMS Suicidal death of erythrocytes (eryptosis) is characterized by cell shrinkage and exposure of phosphatidylserine (PS) residues at the cell surface. Excessive eryptosis may lead to anaemia. We aimed to study the role of eryptosis in heart failure (HF)-associated anaemia. METHODS AND RESULTS We measured eryptosis in rodent models of HF. Typical measures of eryptosis including PS-exposure, increased intracellular Ca(2+) levels, and decreased cell volume were determined by flow cytometry. Transgenic REN2 rats displayed mild anaemia which was associated with a two-fold increase in erythrocyte PS-exposure when compared with Sprague Dawley (SD) control rats (P < 0.01). Upon stimulation with eryptotic triggers such as oxidative stress, hyperosmotic shock and energy depletion, eryptosis was more prominent in REN2 as shown by increased PS-exposure, cytosolic Ca(2+) influx, and cell shrinkage (P < 0.05 vs. SD). Increasing cytosolic Ca(2+) levels resulted in a stronger increase in PS-exposure in REN2 erythrocytes (P < 0.01 vs. SD). Accordingly, inhibition of Ca(2+) entry blunted the increased PS-exposure upon oxidative stress. The REN2 rats had significantly higher reticulocytes (REN2: 10.6 ± 2.3%; SD: 5.4 ± 0.1%; P < 0.05) and erythrocyte turnover was increased, indicated by increased clearance of eryptotic erythrocytes. Eryptosis was also increased in a rat model of hypertensive cardiac remodelling (uninephrectomized rats implanted with deoxycorticosterone acetate pellets), in mice after transverse aortic constriction, as well as in a small proof-of-concept study in human HF patients. CONCLUSION Eryptosis is increased during HF development and could contribute to HF-associated anaemia. Eryptosis may therefore become a novel target for therapy in HF-associated anaemia.

Plasma renin and outcome in the community: data from PREVEND

AIMS The renin-angiotensin system plays a central role in patients with established cardiovascular (CV) disease, but the prognostic effect of plasma renin in the community is unclear. METHODS AND RESULTS The relationship between plasma renin concentration and CV events was studied in 6228 subjects who were enrolled in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) study, and who were not using antihypertensive medication. Plasma renin concentration was measured using a direct automated immunochemiluminescent assay. The mean (± SD) age was 47(± 12) years, 49% were male; the mean follow-up was 10.5 years. The median (Q1-Q3) plasma renin was 17.6 (10.9-27.2) µIU/mL, and plasma aldosterone was 119 (93-153) ng/L. The primary outcome was a composite of fatal (n = 27) and non-fatal (n = 408) CV events. Adjusted for age and sex each doubling of plasma renin was associated with a hazard ratio (HR) for the primary outcome of 1.22 (95% CI: 1.04-1.43; P= 0.015). In a multivariable model, plasma renin showed a positive correlation with heart rate and male sex and a negative correlation with blood pressure, urinary sodium, glucose, and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) (adjusted R(2): 0.167, P< 0.001). After adjustment for covariates associated with plasma renin, the HR for reaching the primary outcome was 1.28 (95% CI: 1.09-1.49, P= 0.002). Plasma renin was associated with CV events regardless of blood pressure, but in subjects using antihypertensive medication this association was absent. CONCLUSION Plasma renin concentration is associated with an increased risk for CV events in a community-based cohort not on antihypertensive medication.

Regulation of the (pro)renin–renin receptor in cardiac remodelling

The (pro)renin–renin receptor [(P)RR] was discovered as an important novel component of the renin–angiotensin system (RAS). The functional significance of (P)RR is widely studied in renal and vascular pathologies and has sparked interest for a potential role in cardiovascular disease. To investigate the role of (P)RR in cardiac pathophysiology, we aimed to assess (P)RR regulation in adverse cardiac remodelling of the failing heart. In particular, we evaluated the expression of (P)RR in different models of heart failure and across different species. Significantly increased levels of (P)RR mRNA were found in post‐myocardial infarcted (MI) hearts of rats (1.6‐fold, P < 0.05) and mice (5‐fold, P < 0.01), as well as in transgenic rats with overexpression of the mouse renin gene (Ren2) (2.2‐fold, P < 0.01). Moreover, we observed a strong increase of (P)RR expression in hearts of dilated cardiomyopathy (DCM) patients (5.3‐fold, P < 0.001). Because none of the tested commercially available antibodies appeared to detect endogenous (P)RR, a (P)RR‐specific polyclonal antibody was generated to study (P)RR protein levels. (P)RR protein levels were significantly increased in the post‐MI rat heart (1.4‐fold, P < 0.05) as compared to controls. Most interestingly in DCM patients, a significant 8.7‐fold (P < 0.05) increase was observed. Thus, protein expression paralleled gene expression. These results demonstrate that (P)RR expression is strongly up‐regulated both in rodent models of heart failure and in the failing human heart, hinting to a potential role for (P)RR in cardiac pathophysiology.

Parental vitamin D deficiency during pregnancy is associated with increased blood pressure in offspring via Panx1 hypermethylation

Vitamin D deficiency is one of the most common nutritional deficiencies worldwide. Maternal vitamin D deficiency is associated with increased susceptibility to hypertension in offspring, but the reasons for this remain unknown. The aim of this study was to determine if parental vitamin D deficiency leads to altered DNA methylation in offspring that may relate to hypertension. Male and female Sprague-Dawley rats were fed a standard or vitamin D-depleted diet. After 10 wk, nonsibling rats were mated. The conceived pups received standard chow. We observed an increased systolic and diastolic blood pressure in the offspring from depleted parents (F1-depl). Genome-wide methylation analyses in offspring identified hypermethylation of the promoter region of the Pannexin-1 (Panx1) gene in F1-depl rats. Panx1 encodes a hemichannel known to be involved in endothelial-dependent relaxation, and we demonstrated that in F1-depl rats the increase in blood pressure was associated with impaired endothelial relaxation of the large vessels, suggesting an underlying biological mechanism of increased blood pressure in children from parents with vitamin deficiency. Parental vitamin D deficiency is associated with epigenetic changes and increased blood pressure levels in offspring.

Cardiac Function and Architecture Are Maintained in a Model of Cardiorestricted Overexpression of the Prorenin-Renin Receptor

The (pro)renin-renin receptor, (P)RR has been claimed to be a novel element of the renin-angiotensin system (RAS). The function of (P)RR has been widely studied in renal and vascular pathology but the cardio-specific function of (P)RR has not been studied in detail. We therefore generated a transgenic mouse (Tg) with cardio-restricted (P)RR overexpression driven by the alpha-MHC promotor. The mRNA expression of (P)RR was ∼170-fold higher (P<0.001) and protein expression ∼5-fold higher (P<0.001) in hearts of Tg mice as compared to non-transgenic (wild type, Wt) littermates. This level of overexpression was not associated with spontaneous cardiac morphological or functional abnormalities in Tg mice. To assess whether (P)RR could play a role in cardiac hypertrophy, we infused ISO for 28 days, but this caused an equal degree of cardiac hypertrophy and fibrosis in Wt and Tg mice. In addition, ischemia-reperfusion injury was performed in Langendorff perfused isolated mouse hearts. We did not observe differences in parameters of cardiac function or damage between Wt and Tg mouse hearts under these conditions. Finally, we explored whether the hypoxia sensing response would be modulated by (P)RR using HeLa cells with and without (P)RR overexpression. We did not establish any effect of (P)RR on expression of genes associated with the hypoxic response. These results demonstrate that cardio-specific overexpression of (P)RR does not provoke phenotypical differences in the heart, and does not affect the hearts’ response to stress and injury. It is concluded that increased myocardial (P)RR expression is unlikely to have a major role in pathological cardiac remodeling.

Recognition of Recurrent Protein Expression Patterns in Pediatric Acute Myeloid Leukemia Identified New Therapeutic Targets

Heterogeneity in the genetic landscape of pediatric acute myeloid leukemia (AML) makes personalized medicine challenging. As genetic events are mediated by the expression and function of proteins, recognition of recurrent protein patterns could enable classification of pediatric AML patients and could reveal crucial protein dependencies. This could help to rationally select combinations of therapeutic targets. To determine whether protein expression levels could be clustered into functionally relevant groups, custom reverse-phase protein arrays were performed on pediatric AML (n = 95) and CD34+ normal bone marrow (n = 10) clinical specimens using 194 validated antibodies. To analyze proteins in the context of other proteins, all proteins were assembled into 31 protein functional groups (PFG). For each PFG, an optimal number of protein clusters was defined that represented distinct transition states. Block clustering analysis revealed strong correlations between various protein clusters and identified the existence of 12 protein constellations stratifying patients into 8 protein signatures. Signatures were correlated with therapeutic outcome, as well as certain laboratory and demographic characteristics. Comparison of acute lymphoblastic leukemia specimens from the same array and AML pediatric patient specimens demonstrated disease-specific signatures, but also identified the existence of shared constellations, suggesting joint protein deregulation between the diseases. Implication: Recognition of altered proteins in particular signatures suggests rational combinations of targets that could facilitate stratified targeted therapy. Mol Cancer Res; 16(8); 1275–86. ©2018 AACR. See related article by Hoff et al., p. 1263