The Antioxidative Effects of Flavones in Hypertensive Disease

Hypertension is the leading remediable risk factor for cardiovascular morbidity and mortality in the United States. Excess dietary salt consumption, which is a catalyst of hypertension, initiates an inflammatory cascade via activation of antigen-presenting cells (APCs). This pro-inflammatory response is driven primarily by sodium ions (Na+) transporting into APCs by the epithelial sodium channel (ENaC) and subsequent NADPH oxidase activation, leading to high levels of oxidative stress. Oxidative stress, a well-known catalyst for hypertension-related illness development, disturbs redox homeostasis, which ultimately promotes lipid peroxidation, isolevuglandin production and an inflammatory response. Natural medicinal compounds derived from organic materials that are characterized by their anti-inflammatory, anti-oxidative, and anti-mutagenic properties have recently gained traction amongst the pharmacology community due to their therapeutic effects. Flavonoids, a natural phenolic compound, have these therapeutic benefits and can potentially serve as anti-hypertensives. Flavones are a type of flavonoid that have increased anti-inflammatory effects that may allow them to act as therapeutic agents for hypertension, including diosmetin, which is able to induce significant arterial vasodilation in several different animal models. This review will focus on the activity of flavones to illuminate potential preventative and potential therapeutic mechanisms against hypertension.

Rosetta FlexPepDock to predict peptide-MHC binding: An approach for non-canonical amino acids

Computation methods that predict the binding of peptides to MHC-I are important tools for screening and identifying immunogenic antigens and have the potential to accelerate vaccine and drug development. However, most available tools are sequence-based and optimized only for peptides containing the twenty canonical amino acids. This omits a large number of peptides containing non-canonical amino acids (NCAA), or residues that undergo varied post-translational modifications such as glycosylation or phosphorylation. These modifications fundamentally alter peptide immunogenicity. Similarly, existing structure-based methods are biased towards canonical peptide backbone structures, which may or may not be preserved when NCAAs are present. Rosetta FlexPepDock ab-initio is a structure-based computational protocol able to evaluate peptide-receptor interaction where no prior information of the peptide backbone is known. We benchmarked FlexPepDock ab-initio for docking canonical peptides to MHC-I, and illustrate for the first time the method's ability to accurately model MHC-I bound epitopes containing NCAAs. FlexPepDock ab-initio protocol was able to recapitulate near-native structures (≤1.5Å) in the top lowest-energy models for 20 out of 25 cases in our initial benchmark. Using known experimental binding affinities of twenty peptides derived from an influenza-derived peptide, we showed that FlexPepDock protocol is able to predict relative binding affinity as Rosetta energies correlate well with experimental values (r = 0.59, p = 0.006). ROC analysis revealed 80% true positive and a 40% false positive rate, with a prediction power of 93%. Finally, we demonstrate the protocol's ability to accurately recapitulate HLA-A*02:01 bound phosphopeptide backbone structures and relative binding affinity changes, the theoretical structure of the lymphocytic choriomeningitis derived glycosylated peptide GP392 bound to MHC-I H-2Db, and isolevuglandin-adducted peptides. The ability to use non-canonical amino acids in the Rosetta FlexPepDock protocol may provide useful insight into critical amino acid positions where the post-translational modification modulates immunologic responses.

Abstract 148: Blockade of the Serotonin 2B Receptor Prevents Pulmonary Vascular Stiffening and Remodeling in a Mouse Model of Familial Pulmonary Arterial Hypertension

Objective: Pulmonary arterial hypertension (PAH) is a fatal disease of the pulmonary vasculature. In humans, familial PAH is caused by mutations in the bone morphogenetic protein receptor 2 gene (BMPR2). Serotonin signaling through the 2B receptor (5HT2BR) is also important in the pathogenesis of PAH, making 5HT2BR antagonism a potential target for PAH therapeutics. This study evaluates the hypothesis that antagonism of 5HT2BR will prevent PAH in a genetic mouse model and the pulmonary vascular stiffening and remodeling that is considered the underlying cause.

Methods: Rosa26-Bmpr2 R899X mice on an FVB/N background express the patient-derived R899X mutation in BMPR2 in all tissues when induced with doxycycline. 10-14 week old BMPR2 mutant mice were fed doxycycline in a high-fat diet for 6 weeks. After 2 weeks, osmotic pumps containing either the 5HT2BR antagonist SB204741 (1 mg/kg/day) or DMSO/water vehicle were implanted. Right ventricular systolic pressure (RVSP) was measured via a venous jugular catheter under anesthesia, and the mice euthanized. Lungs were collected and prepared for histology, gene expression analysis, and atomic force microscopy (AFM, Bioscope Catalyst). Immortalized pulmonary microvascular smooth muscle cells (SMCs) with a BMPR2 mutation were assessed for long-term changes in cytoskeletal contractility using a free floating collagen gel assay.

Data: BMPR2 R899X mice treated with SB204741 failed to develop elevated RVSP. Histologic analysis revealed that SB204741 reduced both the total number of inflammatory cells in the lung as well as the muscularization of peripheral pulmonary arterioles. Microarray analysis revealed that 5HT2BR antagonism primarily changed the expression contractility-associated genes. Measurements of pulmonary arteriole elastic modulus with AFM show significantly increased vessel wall stiffness in BMPR2 R899X arterioles that is also normalized with SB204741 treatment. Taken together, these data suggest that 5HT2BR antagonism prevents the vascular stiffening and remodeling that causes PAH.

Matrigel Mattress: A Method for the Generation of Single Contracting Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

RATIONALE

The lack of measurable single-cell contractility of human-induced pluripotent stem cell-derived cardiac myocytes (hiPSC-CMs) currently limits the utility of hiPSC-CMs for evaluating contractile performance for both basic research and drug discovery.

OBJECTIVE

To develop a culture method that rapidly generates contracting single hiPSC-CMs and allows quantification of cell shortening with standard equipment used for studying adult CMs.

METHODS AND RESULTS

Single hiPSC-CMs were cultured for 5 to 7 days on a 0.4- to 0.8-mm thick mattress of undiluted Matrigel (mattress hiPSC-CMs) and compared with hiPSC-CMs maintained on a control substrate (<0.1-mm thick 1:60 diluted Matrigel, control hiPSC-CMs). Compared with control hiPSC-CMs, mattress hiPSC-CMs had more rod-shape morphology and significantly increased sarcomere length. Contractile parameters of mattress hiPSC-CMs measured with video-based edge detection were comparable with those of freshly isolated adult rabbit ventricular CMs. Morphological and contractile properties of mattress hiPSC-CMs were consistent across cryopreserved hiPSC-CMs generated independently at another institution. Unlike control hiPSC-CMs, mattress hiPSC-CMs display robust contractile responses to positive inotropic agents, such as myofilament calcium sensitizers. Mattress hiPSC-CMs exhibit molecular changes that include increased expression of the maturation marker cardiac troponin I and significantly increased action potential upstroke velocity because of a 2-fold increase in sodium current (INa).

CONCLUSIONS

The Matrigel mattress method enables the rapid generation of robustly contracting hiPSC-CMs and enhances maturation. This new method allows quantification of contractile performance at the single-cell level, which should be valuable to disease modeling, drug discovery, and preclinical cardiotoxicity testing.

A template for non-religious-based discussions against euthanasia

We submit this manuscript as part of the ongoing conversation in society at large about physician-assisted death (PAD) and euthanasia. This outlines an approach used by lay healthcare professionals in arguing against PAD/euthanasia during a 1-hour debate conducted on a secular medical school campus. We have included the elements chosen for the "con" side of the argument (i.e., against PAD) by the medical students and attending physician. The goal of this manuscript is to provide a focused and pithy template upon which to build an approach that honors the dignity of life in all circumstances. Lay summary: The discussion over physician assisted death and euthanasia remains ongoing in secular academic medical institutions across the United States and much of the western world. These debates have incentivized efforts to develop a framework for arguments against Euthanasia that will find traction in an environment generally hostile to religion and religious thought. In this essay, we present arguments given by the "con" side in a student-led debate over physician assisted death and euthanasia at Vanderbilt University with the hope that they will provide a foundation for future discussions promoting truth and life without alienating our secular colleagues.