Biology subjects

Merryman, W. D.

Publications and source records attributed to Merryman, W. D..

6 recordsLinked to original sources

bioRxiv2020

Genetic ablation of serotonin receptor 2B improves aortic valve hemodynamics in a high-cholesterol diet mouse model

Calcific aortic valve disease (CAVD) is a deadly disease that is rising in prevalence due to population aging. While the disease is complex and poorly understood, one well-documented driver of valvulopathy is serotonin agonism. Both serotonin overexpression, as seen with carcinoid tumors and drug-related agonism, such as with Fenfluramine use, are linked with various diseases of the valves. Thus, the objective of this study was to determine if genetic ablation or pharmacological antagonism of the 5-HT2B serotonin receptor (gene: Htr2b) could improve the hemodynamic and histological progression of calcific aortic valve disease. Htr2b mutant mice were crossed with Notch1+/- mice, an established small animal model of CAVD, to determine if genetic ablation affects CAVD progression. To assess the effect of pharmacological inhibition on CAVD progression, Notch1+/- mice were treated with the 5-HT2B receptor antagonist SB204741. Mice were analyzed using echocardiography, histology, immunofluorescence, and real-time quantitative polymerase chain reaction. Htr2b mutant mice showed lower aortic valve peak velocity and mean pressure gradient - classical hemodynamic indicators of aortic valve stenosis - without concurrent left ventricle change. 5-HT2B receptor antagonism, however, did not affect hemodynamic progression. Leaflet thickness, collagen density, and CAVD-associated transcriptional markers were not significantly different in any group. This study reveals that genetic ablation of Htr2b attenuates hemodynamic development of CAVD in the Notch1+/- mice, but pharmacological antagonism may require high doses or long-term treatment to slow progression.

pharmacology and toxicology↗

bioRxiv2020

Cell Programmed Nutrient Partitioning in the Tumor Microenvironment

The tumor microenvironment (TME) includes transformed cancer and infiltrating immune cells1,2. Cancer cells can consume large quantities of glucose through Warburg metabolism3,4 that can be visualized with positron emission tomography (PET). While infiltrating immune cells also rely on glucose, disruptions to metabolism can contribute to tumor immunological evasion5-9. How immune cell metabolism is programmed or restrained by competition with cancer cells for nutrients, remains uncertain. Here we used PET tracers to measure the accessibility of glucose and glutamine to cell subsets in the TME. Surprisingly, myeloid cells including macrophages were the greatest consumers of intra-tumoral glucose, followed by T cells and cancer cells. Cancer cells, in contrast, had the highest glutamine uptake. This distinct nutrient partitioning was programmed through selective mTORC1 signaling and glucose or glutamine-related gene expression. Inhibition of glutamine uptake enhanced glucose uptake across tumor resident cell types and shifted macrophage phenotype, demonstrating glucose is not limiting in the TME. Thus, cancer cells are not the only cells in tumors which exhibit high glucose uptake in vivo and instead preferentially utilize glutamine over other cell types. We observe that intrinsic cellular programs can play a major role in the use of some nutrients. Together, these data argue cell selective partitioning of glucose and glutamine can be exploited to develop therapies and imaging strategies to alter the metabolic programs of specific cell populations in the TME.

cancer biology↗

bioRxiv2020

Macrophages Promote Aortic Valve Cell Calcification Through STAT3 Splicing

ObjectiveMacrophages have been described in calcific aortic valve disease, but it is unclear if they promote or counteract calcification. We aimed to determine how macrophages are involved in calcification using the Notch1+/- model of calcific aortic valve disease. Approach and ResultsMacrophages in wild-type and Notch1+/- murine aortic valves were characterized by flow cytometry. Macrophages in Notch1+/- aortic valves had increased expression of MHCII. We then used bone marrow transplants to test if differences in Notch1+/- macrophages drive disease. Notch1+/- mice had increased valve thickness, macrophage infiltration, and M1-like macrophage polarization regardless of transplanted bone marrow genotype. In vitro approaches confirm that Notch1+/- aortic valve cells promote macrophage invasion as quantified by migration index and M1-like polarization quantified by Ly6C and CCR2 positivity regardless of macrophage genotype. Finally, we found that macrophage interaction with aortic valve cells promotes osteogenic, but not dystrophic, calcification by decreasing abundance of the STAT3{beta} isoform. ConclusionsThis study reveals that Notch1+/- aortic valve disease involves increased macrophage recruitment and polarization driven by altered aortic valve cell secretion, and that increased macrophage recruitment promotes osteogenic calcification through STAT3 splicing changes. Further investigation of STAT3 and macrophage-driven inflammation as therapeutic targets in calcific aortic valve disease is warranted. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/919001v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@3ee95org.highwire.dtl.DTLVardef@24ae93org.highwire.dtl.DTLVardef@41497corg.highwire.dtl.DTLVardef@3f6c05_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2019

Precise tuning of cortical contractility regulates cell shape during cytokinesis

The mechanical properties of the cellular cortex regulate shape changes during cell division, cell migration and tissue morphogenesis. During cell division, contractile force generated by the molecular motor myosin II (MII) at the equatorial cortex drives cleavage furrow ingression. Cleavage furrow ingression in turn increases stresses at the polar cortex, where contractility must be regulated to maintain cell shape during cytokinesis. How polar cortex contractility controls cell shape is poorly understood. We show a balance between MII paralogs allows a fine-tuning of cortex tension at the polar cortex to maintain cell shape during cytokinesis, with MIIA driving cleavage furrow ingression and bleb formation, and MIIB serving as a stabilizing motor and mediating completion of cytokinesis. As the majority of non-muscle contractile systems are cortical, this tuning mechanism will likely be applicable to numerous processes driven by MII contractility.

cell biology↗

bioRxiv2019

CADHERIN-11 BLOCKADE REDUCES INFLAMMATION DRIVEN FIBROTIC REMODELING AND IMPROVES OUTCOMES AFTER MYOCARDIAL INFARCTION

BackgroundOver one million Americans experience myocardial infarction (MI) every year, and the resulting scar and subsequent cardiac fibrosis contribute to heart failure and death. A specialized cell-cell adhesion protein, cadherin-11 (CDH11), contributes to inflammation and fibrosis in rheumatoid arthritis, pulmonary fibrosis, and aortic valve calcification but has not yet been studied in the context of cardiac remodeling after MI. We hypothesized that targeting CDH11 function after MI would reduce inflammation-driven fibrotic remodeling and infarct expansion to improve functional outcomes in mice. MethodsMI was induced by ligation of the left anterior descending artery in transgenic mice with reduced or ablated CDH11, wild type mice receiving bone marrow transplants from Cdh11 transgenic animals, and wild type mice treated with a functional blocking antibody against CDH11 (SYN0012). Cardiac function was measured by echocardiography, expression of cell populations was quantified by flow cytometry, and tissue remodeling by altered histological assessment and transcription of inflammatory and pro-angiogenic genes by qPCR. Co-culture was used to assess interactions between cardiac fibroblasts and macrophages. ResultsMI increased transcription of Cdh11 in non-cardiomyocyte cells. Mice with deletion of Cdh11 and wild type mice receiving bone marrow transplants from Cdh11 transgenic animals had improved cardiac function and dimensions after MI. Animals given SYN0012 had improved cardiac function, reduced tissue remodeling, and altered transcription of inflammatory and proangiogenic genes. Targeting CDH11 also reduced the number of bone marrow-derived myeloid cells and increased pro-angiogenic cells in the heart three days after MI, consistent with a decrease in transcription and expression of IL-6 in the infarct region. Cardiac fibroblast and macrophage interactions led to an increase in IL-6 secretion that was reduced with SYN0012 treatment in vitro. ConclusionsOur findings suggest that CDH11-expressing cells contribute to inflammation-driven fibrotic remodeling after MI, and that targeting CDH11 with a blocking antibody improves cardiac function after MI. This improvement is likely mediated by altered recruitment of bone marrow-derived cells, thereby limiting the macrophage-induced expression of IL-6 by fibroblasts and promoting vascularization.

molecular biology↗

bioRxiv2018

Focal adhesion kinase regulates early steps of myofibrillogenesis in cardiomyocytes

Forces generated by myofibrils within cardiomyocytes must be balanced by adhesion to the substrate and to other cardiomyocytes for proper heart function. Loss of this force balance results in cardiomyopathies that ultimately cause heart failure. How this force balance is first established during the assembly of myofibrils is poorly understood. Using human induced pluripotent stem cell derived cardiomyocytes, we show coupling of focal adhesions to myofibrils during early steps of de novo myofibrillogenesis is essential for myofibril maturation. We also establish a key role for Focal adhesion kinase (FAK), a known regulator of adhesion dynamics in non-muscle cells, in regulating focal adhesion dynamics in cardiomyocytes. Specifically, FAK inhibition increased the stability of vinculin in focal adhesions, allowing greater substrate coupling of assembling myofibrils. Furthermore, this coupling is critical for regulating myofibril tension and viscosity. Taken together, our findings uncover a fundamental mechanism regulating the maturation of myofibrils in human cardiomyocytes.

cell biology↗