Popeye domain containing1 (Popdc1), also named Bves, is an evolutionary conserved membrane protein. Despite its high expression level in the heart little is known about its membrane localization and ...cardiac functions. The study examined the hypothesis that Popdc1 might be associated with the caveolae and play a role in myocardial ischemia tolerance. To address these issues, we analyzed hearts and cardiomyocytes of wild type and Popdc1-null mice. Immunoconfocal microscopy revealed co-localization of Popdc1 with caveolin3 in the sarcolemma, intercalated discs and T-tubules and with costameric vinculin. Popdc1 was co-immunoprecipitated with caveolin3 from cardiomyocytes and from transfected COS7 cells and was co-sedimented with caveolin3 in equilibrium density gradients. Caveolae disruption by methyl-β-cyclodextrin or by ischemia/reperfusion (I/R) abolished the cellular co-localization of Popdc1 with caveolin3 and modified their density co-sedimentation. The caveolin3-rich fractions of Popdc1-null hearts redistributed to fractions of lower buoyant density. Electron microscopy showed a statistically significant 70% reduction in caveolae number and a 12% increase in the average diameter of the remaining caveolae in the mutant hearts. In accordance with these changes, Popdc1-null cardiomyocytes displayed impaired Ca(+2)i transients, increased vulnerability to oxidative stress and no pharmacologic preconditioning. In addition, induction of I/R injury to Langendorff-perfused hearts indicated a significantly lower functional recovery in the mutant compared with wild type hearts while their infarct size was larger. No improvement in functional recovery was observed in Popdc1-null hearts following ischemic preconditioning. The results indicate that Popdc1 is a caveolae-associated protein important for the preservation of caveolae structural and functional integrity and for heart protection.
Summary
The histone deacetylase inhibitor (HDACI) butyroyloxymethyl diethylphosphate (AN-7) has been shown to synergize doxorubicin (Dox) anticancer activity while attenuating its cardiotoxicity. In ...this study we further explored the selectivity of AN-7’s action in several cancer and normal cells treated with anticancer agents. The cells studied were murine mammary 4T1, human breast T47D and glioblastoma U251 cancer cell lines, neonatal rat cardiomyocytes, cardiofibroblasts and astrocytes, and immortalized cardiomyocyte H9C2 cells. Cell death, ROS production and changes in protein expression were measured and in vivo effects were evaluated in Balb-c mice. AN-7 synergized Dox and anti-HER2 cytotoxicity against mammary carcinoma cells with combination indices of 0.74 and 0.79, respectively, while it protected cardiomyocytes against their toxicity. Additionally AN-7 protected astrocytes from Dox-cytoxicity. Cell-type specific changes in the expression of proteins controlling survival, angiogenesis and inflammation by AN-7 or AN-7+Dox were observed. In mice, the protective effect of AN-7 against Dox cardiotoxicity was associated with a reduction in inflammatory factors. In summary, AN-7 augmented the anticancer activity of Dox and anti-HER2 and attenuated their toxicity against normal cells. AN-7 modulation of c-Myc, thrombospondin-1, lo-FGF-2 and other proteins were cell type specific. The effects of AN-7, Dox and their combination were preserved in vivo indicating the potential benefit of combining AN-7 and Dox for clinical use.
Congestive heart failure, a complex disease of heterogeneous etiology, involves alterations in the expression of multiple genes. The Popeye domain-containing (POPDC) family of three novel ...muscle-restricted genes (POPDC1-3) is evolutionarily conserved and developmentally regulated. In mice, POPDC1 has been shown to play an important role in skeletal and cardiac muscles subjected to injury or stress. However, it has never been explored in human hearts. In biopsies from non-failing and failing human hearts, we examined the cellular distribution of POPDC1 as well as the expression patterns of POPDC1-3 mRNAs. POPDC1 was visualized by immunohistochemistry and estimated by Western immunoblotting. The mRNA levels of POPDC1-3 and ß myosin heavy chain (MYHC7) were assessed using reverse transcription/quantitative polymerase chain reaction. POPDC1 was predominantly localized in the sarcolemma with an enhanced expression in the intercalated discs. In failing hearts, many cardiomyocytes appeared deformed and POPDC1 labeling was deranged. The three POPDC mRNAs were expressed in the four heart chambers with higher transcript levels in the ventricles compared to the atria. Heart failure concurred with reduced levels of POPDC1 mRNA and protein in the left ventricle. Correlation analyses of mRNA levels among the failing heart specimens indicated the coordinated regulation of POPDC1 with POPDC3 and of POPDC2 with MYHC7. It can be concluded that POPDC gene expression is modified in end-stage heart failure in humans in a manner suggesting regulatory and/or functional differences between the three family members and that POPDC1 is particularly susceptible to this condition.
Excessive collagen deposition is a common complication of myocardial infarction that causes progressive heart disease. Several pro-fibrotic cytokines and hormones, including aldosterone, control this ...process. Procollagen processing by procollagen C-proteinase(s) is critical for collagen deposition and is potentiated by procollagen C-proteinase enhancer proteins (PCPEs). We have shown previously that, in addition to stimulation of collagen I expression, aldosterone increases PCPE-1 expression in cultured heart fibroblasts. The present study was designed to examine whether aldosterone acts similarly in vivo. Rats underwent coronary artery ligation to induce myocardial infarction. They were then left either untreated (control) or treated with spironolactone (an aldosterone receptor antagonist) for 5 weeks when they were sacrificed and their hearts removed for analysis. In situ hybridization co-localized PCPE-1 and collagen I mRNAs to fibroblasts surrounding the scar region and adjacent blood vessels. The levels of both transcripts in the remodeling myocardium of untreated rats increased twofold as compared to sham-operated controls, an increase greatly reduced by spironolactone. Correspondingly, a 2–5 fold increase in PCPE-1 and collagen I was observed in the hearts of untreated rats as compared to both the spironolactone-treated and sham-operated controls. The results establish aldosterone as a physiological stimulator of PCPE-1 expression in the remodeling myocardium after infarction. Since PCPE-1 itself is a positive regulator of collagen deposition, this finding suggests PCPE-1 as a new potential target for intervention with cardiac fibrosis.
Three Popeye domain-containing (
Popdc 1–3) family-members are known in vertebrates. Their exact function is as yet unknown although involvement in cell adhesion has been suggested. We report herein ...sequencing of the rat
Popdc 1–3 cDNAs that show high homology to other vertebrate orthologs and are expressed primarily in the heart and skeletal muscles.
Popdc2 splice variants were identified, with
Popdc2C showing a distinctive age-dependent decline. In isolated cardiomyocytes,
Popdc genes were negatively regulated by serum, an effect that was reversed by EGFR-kinase inhibition, suggesting an EGFR-dependent modulation of
Popdc gene expression.
Adenosine protects the ischemic myocardium by coronary vasodilation and the depression of heart rate and contractility, improving myocardial energy balance. Adenosine effects on the myocardium are ...mediated predominantly by the type A1 receptors. Atrial natriuretic peptide (ANP), a vasodilator and regulator of blood volume, is secreted from either atrial or ventricular myocytes in response to cellular distention. In vivo, adenosine infusion has been shown to induce a rapid increase in plasma ANP, independent of blood pressure. We examined the possibility that adenosine enhances ANP-gene expression in cardiac myocytes. Administration of adenosine (10 microM) to cultured neonatal rat cardiomyocytes led to a 1.7-fold increase (p = 0.014, n = 9) in the abundance of ANP messenger RNA (mRNA) within 30 min, as measured by Northern blot hybridization. No such increase was obtained when adenosine was coadministered with 8-cyclopentyl-1,3dipropylxanthine (CPX, 10 microM), an adenosine A1-receptor antagonist. Our results point at adenosine as regulator of ANP mRNA level in cardiac myocytes.
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