Collagen matricryptin promotes cardiac function by mediating scar formation.

AIMS: A peptide mimetic of a collagen-derived matricryptin (p1159) was shown to reduce left ventricular (LV) dilation and fibrosis after 7 days delivery in a mouse model of myocardial infarction (MI). This suggested p1159 long-term treatment post-MI could have beneficial effects and reduce/prevent adverse LV remodeling. This study aimed to test the potential of p1159 to reduce adverse cardiac remodeling in a chronic MI model and to elucidate p1159 mode-of-action. MATERIALS AND METHODS: Using a permanent occlusion MI rodent model, animals received p1159 or vehicle solution up to 28 days. We assessed peptide treatment effects on scar composition and structure and on systolic function. To assess peptide effects on scar vascularization, a cohort of mice were injected with Griffonia simplicifolia isolectin-B4. To investigate p1159 mode-of-action, LV fibroblasts from naïve animals were treated with increasing doses of p1159. KEY FINDINGS: Matricryptin p1159 significantly improved systolic function post-MI (2-fold greater EF compared to controls) by reducing left ventricular dilation and inducing the formation of a compliant and organized infarct scar, which promoted LV contractility and preserved the structural integrity of the heart. Specifically, infarcted scars from p1159-treated animals displayed collagen fibers aligned parallel to the epicardium, to resist circumferential stretching, with reduced levels of cross-linking, and improved tissue perfusion. In addition, we found that p1159 increases cardiac fibroblast migration by activating RhoA pathways via the membrane receptor integrin α4. SIGNIFICANCE: Our data indicate p1159 treatment reduced adverse LV remodeling post-MI by modulating the deposition, arrangement, and perfusion of the fibrotic scar.

Dopamine receptor D3 agonist (Pramipexole) reduces morphine-induced cardiac fibrosis.

Morphine is routinely used for pain management in heart failure patients. However, extended morphine exposure associates with major adverse cardiovascular events. Reports link the dopamine receptor D2-family with morphine-induced nociception modulation. This study first assessed whether morphine induces cardiac remodeling in healthy mice, then whether DRD3 agonist (DRD3ag, D2-family member) adjunct therapy prevents morphine-induced cardiac remodeling. Mice received morphine (2 mg/kg/day i. p.) for 7 days (D7) and were either euthanized at D7 or kept 7 more days without morphine (i.e. withdrawal period, D8-D14): G1, morphine; G2, morphine/DRD3ag; G3, morphine + withdrawal; G4, morphine/DRD3ag + withdrawal; G5, morphine + withdrawal/DRD3ag. A separate cohort of animals were used as naïve tissues. We evaluated functional and molecular parameters of cardiac remodeling. Although we did not observe significant differences in systolic function, morphine induced both interstitial fibrosis and cardiomyocyte hypertrophy. Interestingly, DRD3ag abolished these effects. Compared to naïve tissues, collagen 1 increased after withdrawal in G3 and G4 and collagen 3 increased in G1-G4 but at higher levels in G1 and G2. Only G5 did not show collagen differences compared to naïve, suggesting DRD3ag treatment during withdrawal may be beneficial and prevent morphine-induced fibrosis. Smad2/3 phosphorylation increased during withdrawal, indicating a likely upstream pathway for the observed morphine-induced fibrosis. Overall, our data suggest that DRD3ag adjunct therapy decreases morphine-induced adverse cardiac remodeling.

Age- and sex-dependent differences in extracellular matrix metabolism associate with cardiac functional and structural changes.

Age-related remodeling of the heart causes structural and functional changes in the left ventricle (LV) that are associated with a high index of morbidities and mortality worldwide. Some cardiac pathologies in the elderly population vary between genders revealing that cardiac remodeling during aging may be sex-dependent. Herein, we analyzed the effects of cardiac aging in male and female C57Bl/6 mice in four age groups, 3, 6, 12, and 18 month old (n = 6-12 animals/sex/age), to elucidate which age-related characteristics of LV remodeling are sex-specific. We focused particularly in parameters associated with age-dependent remodeling of the LV extracellular matrix (ECM) that are involved in collagen metabolism. LV function and anatomical structure were assessed both by conventional echocardiography and speckle tracking echocardiography (STE). We then measured ECM proteins that directly affect LV contractility and remodeling. All data were analyzed across ages and between sexes and were directly linked to LV functional changes. Echocardiography confirmed an age-dependent decrease in chamber volumes and LV internal diameters, indicative of concentric remodeling. As in humans, animals displayed preserved ejection fraction with age. Notably, changes to chamber dimensions and volumes were temporally distinct between sexes. Complementary to the traditional echocardiography, STE revealed that circumferential strain rate declined in 18 month old females, compared to younger animals, but not in males, suggesting STE as an earlier indicator for changes in cardiac function between sexes. Age-dependent collagen deposition and expression in the endocardium did not differ between sexes; however, other factors involved in collagen metabolism were sex-specific. Specifically, while decorin, osteopontin, Cthrc1, and Ddr1 expression were age-dependent but sex-independent, periostin, lysyl oxidase, and Mrc2 displayed age-dependent and sex-specific differences. Moreover, our data also suggest that with age males and females have distinct TGFß signaling pathways. Overall, our results give evidence of sex-specific molecular changes during physiological cardiac remodeling that associate with age-dependent structural and functional dysfunction. These data highlight the importance of including sex-differences analysis when studying cardiac aging.

High Fat Diet Dysregulates Hypothalamic-Pituitary Axis Gene Expression Levels which are Differentially Rescued by EPA and DHA Ethyl Esters.

SCOPE: Dietary fat composition can modulate gene expression in peripheral tissues in obesity. Observations of the dysregulation of growth hormone (GH) in obesity indicate that these effects extend to the hypothalamic-pituitary (H-P) axis. The authors thus determine whether specific high fat (HF) diets influence the levels of Gh and other key gene transcripts in the H-P axis. METHODS AND RESULTS: C57BL/6 mice are fed a lean control diet or a HF diet in the absence or presence of OA, EPA, or DHA ethyl esters. Comparative studies are conducted with menhaden fish oil. The HF diet lowered pituitary Gh mRNA and protein levels, and cell culture studies reveal that elevated insulin and glucose can reduce Gh transcripts. Supplementation of the HF diet with OA, EPA, DHA, or menhaden fish oil do not improve pituitary Gh levels. The HF diet also impaired the levels of additional genes in the pituitary and hypothalamus, which are selectively rescued with EPA or DHA ethyl esters. The effects of EPA and DHA are more robust relative to fish oil. CONCLUSION: A HF diet can affect H-P axis transcription, which can be mitigated in some genes by EPA and DHA, but not fish oil in most cases.

Mechanisms of cardioprotection via modulation of the immune response.

Both morbidity and mortality as a result of cardiovascular disease remain significant worldwide and account for approximately 31% of annual deaths in the US. Current research is focused on novel therapeutic strategies to protect the heart during and after ischemic events and from subsequent adverse myocardial remodeling. After cardiac insult, the immune system is activated and plays an essential role in the beginning, development, and resolution of the healing cascade. Uncontrolled inflammatory responses can cause chronic disease and exacerbate progression to heart failure and therefore, constitute a major area of focus of cardiac therapies. In the present overview, we share novel insights and promising therapeutic cardioprotective strategies that target the immune response.

Soluble guanylyl cyclase-activated cyclic GMP-dependent protein kinase inhibits arterial smooth muscle cell migration independent of VASP-serine 239 phosphorylation.

Coronary artery disease (CAD) accounts for over half of all cardiovascular disease-related deaths. Uncontrolled arterial smooth muscle (ASM) cell migration is a major component of CAD pathogenesis and efforts aimed at attenuating its progression are clinically essential. Cyclic nucleotide signaling has long been studied for its growth-mitigating properties in the setting of CAD and other vascular disorders. Heme-containing soluble guanylyl cyclase (sGC) synthesizes cyclic guanosine monophosphate (cGMP) and maintains vascular homeostasis predominantly through cGMP-dependent protein kinase (PKG) signaling. Considering that reactive oxygen species (ROS) can interfere with appropriate sGC signaling by oxidizing the cyclase heme moiety and so are associated with several CVD pathologies, the current study was designed to test the hypothesis that heme-independent sGC activation by BAY 60-2770 (BAY60) maintains cGMP levels despite heme oxidation and inhibits ASM cell migration through phosphorylation of the PKG target and actin-binding vasodilator-stimulated phosphoprotein (VASP). First, using the heme oxidant ODQ, cGMP content was potentiated in the presence of BAY60. Using a rat model of arterial growth, BAY60 significantly reduced neointima formation and luminal narrowing compared to vehicle (VEH)-treated controls. In rat ASM cells BAY60 significantly attenuated cell migration, reduced G:F actin, and increased PKG activity and VASP Ser239 phosphorylation (pVASP·S239) compared to VEH controls. Site-directed mutagenesis was then used to generate overexpressing full-length wild type VASP (FL-VASP/WT), VASP Ser239 phosphorylation-mimetic (FL-VASP/239D) and VASP Ser239 phosphorylation-resistant (FL-VASP/239A) ASM cell mutants. Surprisingly, FL-VASP/239D negated the inhibitory effects of FL-VASP/WT and FL-VASP/239A cells on migration. Furthermore, when FL-VASP mutants were treated with BAY60, only the FL-VASP/239D group showed reduced migration compared to its VEH controls. Intriguingly, FL-VASP/239D abrogated the stimulatory effects of FL-VASP/WT and FL-VASP/239A cells on PKG activity. In turn, pharmacologic blockade of PKG in the presence of BAY60 reversed the inhibitory effect of BAY60 on naïve ASM cell migration. Taken together, we demonstrate for the first time that BAY60 inhibits ASM cell migration through cGMP/PKG/VASP signaling yet through mechanisms independent of pVASP·S239 and that FL-VASP overexpression regulates PKG activity in rat ASM cells. These findings implicate BAY60 as a potential pharmacotherapeutic agent against aberrant ASM growth disorders such as CAD and also establish a unique mechanism through which VASP controls PKG activity.

AMP-activated protein kinase inhibits vascular smooth muscle cell proliferation and migration and vascular remodeling following injury.

Vascular smooth muscle cell (VSMC) activation promotes a synthetic phenotype that underlies many vessel growth disorders. In this regard it has been suggested that the metabolic sensor adenosine 5'-monophosphate-activated protein kinase (AMPK) has significant antigrowth and antimetastatic properties and may serve as a viable therapeutic target. In the current study we hypothesized that AMPK reduces neointima formation following balloon injury and that this occurs through reduction in VSMC proliferation and migration. Data reveal that local or systemic dosing with the AMPK agonist 5-aminoimidazole-4-carboxamide-1-ß-d-ribofuranoside (AICAR) significantly increased AMPK activity in vivo and inhibited neointima formation in rat carotid arteries 2 wk after injury. In primary VSMCs, AICAR inhibited migration and induced cytostatic growth arrest through increased protein phosphatase 2A-mediated inhibition of mitosis-promoting cyclin B. AICAR also significantly enhanced AMPK-specific T278 phosphorylation of the actin anticapping vasodilator-activated serum phosphoprotein, increased G- to F-actin ratios and stress fiber formation, and abrogated PDGF-stimulated S397 autophosphorylation of focal adhesion kinase, promigratory cytoplasmic accumulation of paxillin, and extracellular matrix proteolysis by matrix metalloproteinase-9. Together, these results provide compelling evidence that AMPK serves to inhibit vascular smooth muscle migration and proliferation through regulation of cytoskeletal/focal adhesion/ECM stability, increasing our knowledge of this important metabolic regulator and providing support for its continued investigation in the treatment of vascular growth disorders.