Short-term inhibition of DPP-4 enhances endothelial regeneration after acute arterial injury via enhanced recruitment of circulating progenitor cells

Background

Endothelial injuries regularly occur in atherosclerosis and during interventional therapies of the arterial occlusive disease. Disturbances in the endothelial integrity can lead to insufficient blood supply and bear the risk of thrombus formation and acute vascular occlusion. At present, effective therapeutics to restore endothelial integrity are barely available.We analyzed the effect of pharmacological DPP-4-inhibition by Sitagliptin on endogenous progenitor cell-based endothelial regeneration via the SDF-1α/CXCR4-axis after acute endothelial damage in a mouse model of carotid injury.

Methods and Results

Induction of a defined endothelial injury was performed in the carotid artery of C57Bl/6 mice which led to a local upregulation of SDF-1α expression. Animals were treated with placebo, Sitagliptin or Sitagliptin + AMD3100. Using mass spectrometry we could prove that Sitagliptin prevented cleavage of the chemokine SDF-1α. Accordingly, increased SDF-1α concentrations enhanced recruitment of systemically applied and endogenous circulating CXCR4 + progenitor cells to the site of vascular injury followed by a significantly accelerated reendothelialization as compared to placebo-treated animals. Improved endothelial recovery, as well as recruitment of circulating CXCR4 + progenitor cells (CD133 +, Flk1 +), was reversed by CXCR4-antagonization through AMD3100. In addition, short-term Sitagliptin treatment did not significantly promote neointimal or medial hyperplasia.

Conclusion

Sitagliptin can accelerate endothelial regeneration after acute endothelial injury. DPP-4 inhibitors prevent degradation of the chemokine SDF-1α and thus improve the recruitment of regenerative circulating CXCR4 + progenitor cells which mediate local endothelial cell proliferation without adversely affecting vessel wall architecture.     

Predictive validity of the Depression Coping Self-Efficacy Scale (DCSES)

The Depression Coping Self-Efficacy Scale (DCSES) was developed to measure depressed individuals' confidence in their ability to follow treatment recommendations. The purpose of this study was to evaluate the validity of the DCSES as a unidimensional measure of depression coping self-efficacy. Data were collected from depressed psychiatric inpatients at admission and discharge (n = 99), and 6-8 weeks post-discharge (n = 75). Exploratory factor analysis yielded a single factor solution accounting for 48.8% of the variance with an eigenvalue of 12.7. DCSES scores at discharge were related to self-reported levels of functional impairment (FI), depression symptom distress, and suicidal ideation (SI), and predicted rehospitalization 6-8 weeks later. Patients with lower DCSES scores at discharge showed less improvement in depression coping self-efficacy from admission to discharge.     

Cl-IB-MECA [2-chloro-N6-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide] reduces ischemia/reperfusion injury in mice by activating the A3 adenosine receptor

We used pharmacological agents and genetic methods to determine whether the potent A(3) adenosine receptor (AR) agonist 2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide (Cl-IB-MECA) protects against myocardial ischemia/reperfusion injury in mice via the A(3)AR or via interactions with other AR subtypes. Pretreating wild-type (WT) mice with Cl-IB-MECA reduced myocardial infarct size induced by 30 min of coronary occlusion and 24 h of reperfusion at doses (30 and 100 mug/kg) that concomitantly reduced blood pressure and stimulated systemic histamine release. The A(3)AR-selective antagonist MRS 1523 [3-propyl-6-ethyl-5[(ethylthio)carbonyl]-2-phenyl-4-propyl-3-pyridine-carboxylate], but not the A(2A)AR antagonist ZM 241385 [4-{2-7-amino-2-(2-furyl)[1,2,4]triazolo-[2,3-a][1,3,5]triazin-5-ylamino]ethyl}phenol], blocked the reduction in infarct size provided by Cl-IB-MECA, suggesting a mechanism involving the A(3)AR. To further examine the selectivity of Cl-IB-MECA, we assessed its cardioprotective effectiveness in A(3)AR gene "knock-out" (A(3)KO) mice. Cl-IB-MECA did not reduce myocardial infarct size in A(3)KO mice in vivo and did not protect isolated perfused hearts obtained from A(3)KO mice from injury induced by global ischemia and reperfusion. Additional studies using WT mice treated with compound 48/80 [condensation product of p-methoxyphenethyl methylamine with formaldehyde] to deplete mast cell contents excluded the possibility that Cl-IB-MECA was cardioprotective by releasing mediators from mast cells. These data demonstrate that Cl-IB-MECA protects against myocardial ischemia/reperfusion injury in mice principally by activating the A(3)AR.     

Experimental support for the "E pathway hypothesis" of coupled transmembrane e- and H+ transfer in dihemic quinol:fumarate reductase

Reconciliation of apparently contradictory experimental results obtained on the quinol:fumarate reductase, a diheme-containing respiratory membrane protein complex from Wolinella succinogenes, was previously obtained by the proposal of the so-called "E pathway hypothesis." According to this hypothesis, transmembrane electron transfer via the heme groups is strictly coupled to cotransfer of protons via a transiently established pathway thought to contain the side chain of residue Glu-C180 as the most prominent component. Here we demonstrate that, after replacement of Glu-C180 with Gln or Ile by site-directed mutagenesis, the resulting mutants are unable to grow on fumarate, and the membrane-bound variant enzymes lack quinol oxidation activity. Upon solubilization, however, the purified enzymes display approximately 1/10 of the specific quinol oxidation activity of the wild-type enzyme and unchanged quinol Michaelis constants, K(m). The refined x-ray crystal structures at 2.19 A and 2.76 A resolution, respectively, rule out major structural changes to account for these experimental observations. Changes in the oxidation-reduction heme midpoint potential allow the conclusion that deprotonation of Glu-C180 in the wild-type enzyme facilitates the reoxidation of the reduced high-potential heme. Comparison of solvent isotope effects indicates that a rate-limiting proton transfer step in the wild-type enzyme is lost in the Glu-C180 --> Gln variant. The results provide experimental evidence for the validity of the E pathway hypothesis and for a crucial functional role of Glu-C180.     

Diabetes enhances vasoreactivity to calcium entry blockers

Equipotent concentrations of diltiazem and verapamil relaxed coronary resistance vessels in isovolumically-perfused rat hearts. In diabetic hearts, the vasodilator response to diltiazem, and to a lesser extent verapamil, was significantly augmented. The addition of both calcium entry blockers also produced greater relaxation in precontracted isolated thoracic aorta of diabetic animals suggesting that diabetes increases the sensitivity of calcium entry blockers in two separate vessel types.     

Intervention research in highly unstable environments

This article highlights issues and presents strategies for conducting intervention research in highly unstable environments such as schools, critical care units, and long‐term care facilities. The authors draw on their own experiences to discuss the challenges that may be encountered in highly unstable settings. The concept of validity provides a framework for understanding the value of addressing the many methodological issues that can emerge in settings characterized by instability. We explain unstable environments by elaborating on knowable elements that contribute to instability. Strategies are provided for improving success of intervention research in unstable settings by carrying out an environmental assessment prior to beginning a study. © 2008 Wiley Periodicals, Inc. Res Nurs Health 32:110–121, 2009     

mRNA-transfected Dendritic Cells Expressing Polypeptides That Link MHC-I Presentation to Constitutive TLR4 Activation Confer Tumor Immunity

Recently, we have developed a novel genetic platform for improving dendritic cell (DC) induction of peptide-specific CD8 T cells, based on membrane-anchored β₂-microglobulin (β₂m) linked to a selected antigenic peptide at its N-terminus and to the cytosolic domain of toll-like receptor (TLR)4 C-terminally. In vitro transcribed mRNA transfection of antigen presenting cells resulted in polypeptides that efficiently coupled peptide presentation to cellular activation. In the present study, we evaluated the immunogenicity of such constructs in mRNA-transfected immature murine bone marrow-derived DCs. We show that the encoded peptide β₂m-TLR4 products were expressed at the cell surface up to 72 hours and stimulated the maturation of DCs. In vivo, these DCs prompted efficient peptide-specific T-cell activation and target cell killing which were superior to those induced by peptide-loaded, LPS-stimulated DCs. This superiority was also evident in the ability to protect mice from tumor progression following the administration of B16F10.9 melanoma cells and to inhibit the development of pre-established B16F10.9 tumors. Our results provide evidence that the products of two recombinant genes encoding for peptide-hβ₂m-TLR4 and peptide-hβ₂m-K^b expressed from exogenous mRNA can cooperate to couple Major Histocompatibility Complex (MHC-I) peptide presentation to TLR-mediated signaling, offering a safe, economical and highly versatile genetic platform for a novel category of CTL-inducing vaccines.     

High prevalence of thymic tissue in adults with human immunodeficiency virus-1 infection.

The thymus in adults infected with the HIV-1 is generally thought to be inactive, both because of age-related involution and viral destruction. We have revisited the question of thymic function in adults, using chest-computed tomography (CT) to measure thymic tissue in HIV-1-seropositive (n = 99) or HIV-1-seronegative (n = 32) subjects, and correlating these results with the level of circulating CD4(+) and CD8(+) T cells that are phenotypically described as naive thymic emigrants. Abundant thymic tissue was detectable in many (47/99) HIV-1-seropositive adults, aged 20-59. Independent of age, radiographic demonstration of thymic tissue was significantly associated with both a higher CD4(+) T cell count (P = 0.02) and a higher percentage and absolute number of circulating naive (CD45RA+CD62L+) CD4(+) T cells (P < 0.04). The prevalence of an abundant thymus was especially high in younger HIV-1-seropositive adults (</= 39 yr) with CD4 counts in the range 300-500 cells/microl and in older subjects (> 40 yr) regardless of CD4 count (P = 0.03). These studies suggest that the thymus is functional in some but not all adults with HIV-1 disease.     

Effect of Wegener's granulomatosis on work disability,need for medical care,and quality of life in patients younger than 40 years at diagnosis

Objectives

To evaluate the effects of Wegener's granulomatosis (WG) on employment status, work disability, and need for medical care of 60 consecutive WG patients aged ≤40 years at diagnosis.

Methods

Sixty WG patients (26 male, 34 female) with a median age of 36 years (range 17–48 years) and a median duration of disease of 39 months (range 0–228 months) completed self‐administered questionnaires on hospitalization, medical care, and employment status plus the Medical Outcomes Study‐Short Form‐36 (SF‐36) estimating their health‐related quality of life.

Results

Thirty‐two of the 60 patients reported full‐ or part‐time employment more than 3 years after diagnosis. Only 14 of the 51 patients employed at diagnosis (27%) were currently receiving a permanent work disability pension due to WG. Two additional patients had lost work because of WG. Women who were employed at diagnosis had a nearly 3‐fold higher risk of losing their jobs compared with men (P = 0.0006). There were no differences with regard to age at diagnosis, disease duration, disease severity, or education level between employed and unemployed patients. Employed patients had missed a median of 14 workdays (range 0–18 days) due to WG within the past 12 months. More than half of all patients (33 of 60) had been hospitalized during the previous 12 months because of WG. Ninety‐three percent of all patients had visited their physician once or more per month, more than half of them at least once per week, regardless of employment status, severity of disease, or type of current medication. Unemployed WG patients experienced significant reductions in social and physical function and in their perceived degree of general health as assessed by the SF‐36.

Conclusions

Twenty‐seven percent of WG patients younger than age 40 who were employed at diagnosis received permanent work disability within a disease duration of 39 months. Unemployment is followed by a considerable reduction in disease‐related quality of life compared with employed patients, independent of severity and extent of disease. Furthermore, because patients were followed closely by an interdisciplinary team, a high rate of hospitalization and frequent visits to physicians resulted.