Tyrosine B10 Inhibits Stabilization of Bound Carbon Monoxide and Oxygen in Soybean Leghemoglobin

Detailed comparisons of the carbon monoxide FTIR spectra and ligand-binding properties of a library of E7, E11, and B10 mutants indicate significant differences in the role of electrostatic interactions in the distal pockets of wild-type sperm whale myoglobin and soybean leghemoglobin. In myoglobin, strong hydrogen bonds from several closely related conformations of the distal histidine (HisE7) side chain preferentially stabilize bound oxygen. In leghemoglobin, the imidazole side chain of HisE7 is confined to a single conformation, which only weakly hydrogen bonds to bound ligands. The phenol side chain of TyrB10 appears to “fix” the position of HisE7, probably by donating a hydrogen bond to the Nä atom of the imidazole side chain. The proximal pocket of leghemoglobin is designed to favor strong coordination bonds between the heme iron and axial ligands. Thus, high oxygen affinity in leghemoglobin is established by a favorable staggered geometry of the proximal histidine. The interaction between HisE7 and TyrB10 prevents overstabilization of bound oxygen. If hydrogen bonding from HisE7 were as strong as it is in mammalian myoglobin, the resultant ultrahigh affinity of leghemoglobin would prevent oxygen transport in root nodules

Immunohistochemical Localization of AT1a, AT1b, and AT2 Angiotensin II Receptor Subtypes in the Rat Adrenal, Pituitary, and Brain with a Perspective Commentary

Angiotensin II increases blood pressure and stimulates thirst and sodium appetite in the brain. It also stimulates secretion of aldosterone from the adrenal zona glomerulosa and epinephrine from the adrenal medulla. The rat has 3 subtypes of angiotensin II receptors: AT1a, AT1b, and AT2. mRNAs for all three subtypes occur in the adrenal and brain. To immunohistochemically differentiate these receptor subtypes, rabbits were immunized with C-terminal fragments of these subtypes to generate receptor subtype-specific antibodies. Immunofluorescence revealed AT1a and AT2 receptors in adrenal zona glomerulosa and medulla. AT1b immunofluorescence was present in the zona glomerulosa, but not the medulla. Ultrastructural immunogold labeling for the AT1a receptor in glomerulosa and medullary cells localized it to plasma membrane, endocytic vesicles, multivesicular bodies, and the nucleus. AT1b and AT2, but not AT1a, immunofluorescence was observed in the anterior pituitary. Stellate cells were AT1b positive while ovoid cells were AT2 positive. In the brain, neurons were AT1a, AT1b, and AT2 positive, but glia was only AT1b positive. Highest levels of AT1a, AT1b, and AT2 receptor immunofluorescence were in the subfornical organ, median eminence, area postrema, paraventricular nucleus, and solitary tract nucleus. These studies complement those employing different techniques to characterize Ang II receptors

Use of Mesenchymal Stem Cells for Therapy of Cardiac Disease

Despite substantial clinical advances over the past 65 years, cardiovascular disease remains the leading cause of death in America. The past 15 years has witnessed major basic and translational interest in the use of stem and/or precursor cells as a therapeutic agent for chronically injured organs. Among the cell types under investigation, adult mesenchymal stem cells (MSCs) are widely studied and in early stage clinical studies show promise for repair and regeneration of cardiac tissues. The ability of MSCs to differentiate into mesoderm and non-mesoderm derived tissues, their immunomodulatory effects, their availability and their key role in maintaining and replenishing endogenous stem cell niches have rendered them one of the most heavily investigated and clinically tested type of stem cell. Accumulating data from preclinical and early phase clinical trials document their safety when delivered as either autologous or allogeneic forms in a range of cardiovascular diseases, but also importantly define parameters of clinical efficacy that justify further investigation in larger clinical trials. Here, we review the biology of MSCs, their interaction with endogenous molecular and cellular pathways, and their modulation of immune responses. Additionally, we discuss factors that enhance their proliferative and regenerative ability and factors that may hinder their effectiveness in the clinical setting

The impact of patient sex on the response to intramyocardial mesenchymal stem cell administration in patients with non-ischaemic dilated cardiomyopathy

Abstract Aims Sex differences impact the occurrence, presentation, prognosis, and response to therapy in heart disease. Particularly, the phenotypic presentation of patients with non-ischaemic dilated cardiomyopathy (NIDCM) differs between men and women. However, whether the response to mesenchymal stem cell (MSC) therapy is influenced by sex remains unknown. We hypothesize that males and females with NIDCM respond similarly to MSC therapy. Methods and results Male (n = 24) and female (n = 10) patients from the POSEIDON-DCM trial who received MSCs via transendocardial injections were evaluated over 12 months. Endothelial function was measured at baseline and 3 months post-transendocardial stem cell injection (TESI). At baseline, ejection fraction (EF) was lower (P = 0.004) and end-diastolic volume (EDV; P = 0.0002) and end-systolic volume (ESV; P = 0.0002) were higher in males vs. females. In contrast, baseline demographic characteristics, Minnesota Living with Heart Failure Questionnaire (MLHFQ), and 6-min walk test (6MWT) were similar between groups. EF improved in males by 6.2 units (P = 0.04) and in females by 8.6 units (P = 0.04; males vs. females, P = 0.57). EDV and ESV were unchanged over time. The MLHFQ score, New York Heart Association (NYHA) class, endothelial progenitor cell-colony forming units, and serum tumour necrosis factor alpha improved similarly in both groups. Conclusion Despite major differences in phenotypic presentation of NIDCM in males and females, this study is the first of its kind to demonstrate that MSC therapy improves a variety of parameters in NIDCM irrespective of patient sex. These findings have important clinical and pathophysiologic implications regarding the impact of sex on responses to cell-based therapy for NIDCM

Genetic determinants of responsiveness to mesenchymal stem cell injections in non-ischemic dilated cardiomyopathy

Non-ischemic dilated cardiomyopathy (NIDCM) responds variably to intramyocardial injection of mesenchymal stem cells (MSCs). We hypothesized that NIDCM genotype may influence responsiveness to MSC therapy and performed genotyping on all patients in the POSEIDON-DCM trial. POSEIDON-DCM patients (n = 34) underwent genetic sequence analysis and deletion/duplication testing. The results were classified as positive for pathological variants (PV+; n = 8), negative for any variants (V−; n = 6), or as variants of uncertain significance (VUS; n = 20). All outcomes of therapy were analysed for each category of genetic results. The 3 groups were indistinguishable at baseline with regard to ejection fraction (EF), demographics, medication use, or functional parameters. V− patients had an increase in EF at 12 months: +13.6% (IQR = +7.8%; +20.5%; p = 0.002), compared with VUS (+6.5%; IQR = +0.9%, +11.1%; p = 0.005) and PV+(−5.9%; IQR = −12.7%, +1.0; p = 0.2; p = 0.01 between groups). Six-minute walk distance improved in V- patients, but not in VUS and PV+. V− patients improved MLHFQ, compared to the other 2 groups, which did not improve over time. EPCCFUs increased by 9.7 ± 1.9 in V− (p = 0.009) compared to VUS and PV+ patients. V− patients had one-year survival (100%) compared with VUS (85%) and PV+ (40%; p = 0.015 log-rank). Similarly, MACE rates were lower in V− (0%) than PV+ (61.9%) or VUS (42.2%; p = 0.021 log-rank). Our findings support the concept that the genetic profile of NIDCM patients plays a role in responsiveness to MSC therapy, with V− patients more likely to benefit and the converse for PV+. This observation emphasizes the need for further genetic studies, because of important implications for the management of NIDCM syndromes

Randomized Comparison of Allogeneic Versus Autologous Mesenchymal Stem Cells for Nonischemic Dilated Cardiomyopathy

BACKGROUND: While human mesenchymal stem cells (hMSCs) have been tested in ischemic cardiomyopathy, few studies exist in chronic non-ischemic dilated cardiomyopathy (NIDCM). OBJECTIVES: The POSEIDON-DCM trial is a randomized comparison of safety and efficacy of autologous (auto) vs. allogeneic (allo) bone marrow-derived hMSCs in NIDCM. METHODS: Thirty-seven patients were randomized to either allo- or auto-hMSCs in a 1:1 ratio. Patients were recruited between December 2011 and July 2015 at the University of Miami Hospital. Patients (age: 55.8 ± 11.2; 32% female) received hMSCs (100 million) by transendocardial stem cell injection (TESI) in ten left ventricular sites by NOGA Catheter. Treated patients were evaluated at baseline, 30 days, 3-, 6-, and 12-months for safety: serious adverse events (SAE), and efficacy endpoints: Ejection Fraction (EF), Minnesota Living with Heart Failure Questionnaire (MLHFQ), Six Minute Walk Test (6MWT), MACE, and immune-biomarkers. This trial is registered with ClinicalTrials.gov, #NCT01392625. RESULTS: There were no 30-day treatment-emergent (TE)-SAEs. 12-month SAE incidence was 28.2% (95% CI: 12.8, 55.1) in allo, and 63.5% (95% CI: 40.8, 85.7; p=0.1004) in auto. One allo-group patient developed an elevated donor specific cPRA. EF increased in allo by 8.0 units (95% Cl: 2.8, 13.2; p=0.004), and in auto: 5.4 units (95% Cl: −1.4, 12.1; p=0.116, allo vs. auto p=0.4887). 6MWT increased for allo: 37.0 meters (95% Cl: 2.0 to 72.0; p=0.04), but not auto: 7.3 meters (95% Cl: −47.8, 33.3; p=0.71, auto vs. allo p=0.0168). MLHFQ score decreased in allo (p=0.0022), and auto (p=0.463; p=0.172). The MACE rate was lower in allo vs. auto (p=0.0186). Tumor necrosis factor alpha (TNF-α) decreased (p=0.0001 for each), to a greater extent in allo vs. auto at six-months (p=0.05). CONCLUSION: These findings demonstrate safety and support greater, clinically meaningful efficacy of allo-hMSC vs. auto-hMSC in NIDCM patients. Pivotal trials of allo-hMSCs are warranted based on these results