[show abstract][hide abstract] ABSTRACT: CD40 ligand (CD40L) is involved in the vascular infiltration of immune cells and pathogenesis of atherosclerosis. Additionally, T cell CD40L release causes platelet, dendritic cell and monocyte activation in thrombosis. However, the role of CD40L in angiotensin II (ATII)-driven vascular dysfunction and hypertension remains incompletely understood. We tested the hypothesis that CD40L contributes to ATII-driven vascular inflammation by promoting platelet-leukocyte activation, vascular infiltration of immune cells and by amplifying oxidative stress. C57BL/6 and CD40L(-/-) mice were infused with ATII (1 mg/kg/day for 7 days) using osmotic minipumps. Vascular function was recorded by isometric tension studies, and reactive oxygen species (ROS) were monitored in blood and heart by optical methods. Western blot, immunohistochemistry, FACS analysis and real-time RT-PCR were used to analyze immune cell distribution, pro-inflammatory cytokines, NAPDH oxidase subunits, T cell transcription factors and other genes of interest. ATII-treated CD40L(-/-) mice showed improved endothelial function, suppression of blood platelet-monocyte interaction (FACS), platelet thrombin generation (calibrated automated thrombography) and coagulation (bleeding time), as well as decreased oxidative stress in the aorta, heart and blood compared to wild-type mice. Moreover, ATII-treated CD40L(-/-) mice displayed decreased levels of TH1 cytokines released by splenic CD4(+) T cells (ELISA) and lower expression levels of NOX-2, T-bet and P-selectin as well as diminished immune cell infiltration in aortic tissue compared to controls. Our results demonstrate that many ATII-induced effects on vascular dysfunction, such as vascular inflammation, oxidative stress and a pro-thrombotic state, are mediated at least in part via CD40L.
Archiv für Kreislaufforschung 11/2013; 108(6):386. · 7.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aims: Oxidative stress is involved in the development of cardiovascular disease. There is growing body of evidence for a crosstalk between different enzymatic sources of oxidative stress. With the present study we sought to determine the underlying crosstalk mechanisms, the role of the mitochondrial permeability transition pore (mPTP) and its link to endothelial dysfunction. Results: NADPH oxidase (Nox) activation (oxidative burst and translocation of cytosolic Nox subunits) was observed in response to mitochondrial reactive oxygen species (mtROS) formation in human leukocytes. In vitro, mtROS-induced Nox activation was prevented by inhibitors of the mPTP, protein kinase C, tyrosine kinase cSrc, Nox itself or an intracellular calcium chelator and was absent in leukocytes with p47phox deficiency (regulates Nox2) or with cyclophilin D deficiency (regulates mPTP). In contrast, the crosstalk in leukocytes was amplified by mitochondrial manganese superoxide dismutase deficiency (MnSOD+/-). In vivo, increases in blood pressure, degree of endothelial dysfunction, endothelial nitric oxide synthase (eNOS) dysregulation/uncoupling (e.g. eNOS S-glutathionylation) or Nox activity, p47phox phosphorylation in response to angiotensin-II in vivo treatment or the aging process were more pronounced in MnSOD+/- mice as compared to untreated controls and improved by mPTP inhibition by cyclophilin D deficiency or sanglifehrin A therapy. Innovation: These results provide new mechanistic insight to what extent mtROS trigger Nox activation in phagocytes and cardiovascular tissue leading to endothelial dysfunction. Conclusions: Our data show that mtROS trigger the activation of phagocytic and cardiovascular NADPH oxidases, which may have fundamental implications for immune cell activation and development of angiotensin-II-induced hypertension.
[show abstract][hide abstract] ABSTRACT: OBJECTIVE: Immune cells contribute to angiotensin II (ATII)-induced vascular dysfunction and inflammation. Interferon-γ (IFN-γ), an inflammatory cytokine exclusively produced by immune cells, seems to be involved in ATII-driven cardiovascular injury, but the actions and cellular source of IFN-γ remain incompletely understood.Approach and Results-IFN-γ(-/-) and Tbx21(-/-) mice were partially protected from ATII-induced (1 mg/kg per day of ATII, infused subcutaneously by miniosmotic pumps) vascular endothelial and smooth muscle dysfunction, whereas mice overexpressing IFN-γ showed constitutive vascular dysfunction. Absence of T-box expressed in T cells, the IFN-γ transcription factor encoded by Tbx21, reduced vascular superoxide and peroxynitrite formation and attenuated expression of nicotinamid adenosin dinucleotid phosphate oxidase subunits as well as inducible NO synthase, monocyte chemoattractant protein 1, and interleukin 12 in aortas of ATII-infused mice. Compared with controls, IFN-γ(-/-) and Tbx21(-/-) mice were characterized by reduced ATII-mediated vascular recruitment of both NK1.1(+) NK-cells as the major producers of IFN-γ and CD11b(+)Gr-1(low) interleukin-12 secreting monocytes. Selective depletion and adoptive transfer experiments identified NK-cells as essential contributors to vascular dysfunction and showed that T-box expressed in T cells(+)LysM(+) myelomonocytic cells were required for NK-cell recruitment into vascular tissue and local IFN-γ production. CONCLUSIONS: We provide first evidence that NK-cells play an essential role in ATII-induced vascular dysfunction. In addition, we disclose the T-box expressed in T cells-IFN-γ pathway and mutual monocyte-NK-cell activation as potential therapeutic targets in cardiovascular disease.
Arteriosclerosis Thrombosis and Vascular Biology 03/2013; · 6.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dipeptidyl peptidase-4 (DPP-4) inhibitors are a novel class of drugs for the treatment of hyperglycaemia. Preliminary evidence suggests that their antioxidant and anti-inflammatory effects may have beneficial effects on the cardiovascular complications of diabetes. In the present study, we investigate in an experimental sepsis model whether linagliptin exerts pleiotropic vascular effects independent of its glucose-lowering properties.
Linagliptin (83 mg/kg chow for 7days) was administered in a rat model of lipopolysaccharide (LPS) (10 mg/kg, single i.p. dose/24 h)-induced sepsis. Vascular relaxation, reactive oxygen species (ROS) formation, expression of NADPH oxidase subunits and proinflammatory markers, and white blood cell infiltration in the vasculature were determined. Oxidative burst and adhesion of isolated human neutrophils to endothelial cells were measured in the presence of different DPP-4 inhibitors, and their direct vasodilatory effects (isometric tension in isolated aortic rings) were compared. In vivo linagliptin treatment ameliorated LPS-induced endothelial dysfunction and was associated with reduced formation of vascular, cardiac, and blood ROS, aortic expression of inflammatory genes and NADPH oxidase subunits in addition to reduced aortic infiltration with inflammatory cells. Linagliptin was the most potent inhibitor of oxidative burst in isolated activated human neutrophils and it suppressed their adhesion to activated endothelial cells. Of the inhibitors tested, linagliptin and alogliptin had the most pronounced direct vasodilatory potency.
Linagliptin demonstrated pleiotropic vasodilatory, antioxidant, and anti-inflammatory properties independent of its glucose-lowering properties. These pleiotropic properties are generally not shared by other DPP-4 inhibitors and might translate into cardiovascular benefits in diabetic patients.
Cardiovascular research 07/2012; 96(1):140-9. · 5.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: AimsIsosorbide-5-mononitrate (ISMN) is one of the most frequently used compounds in the treatment of coronary artery disease predominantly in the USA. However, ISMN was reported to induce endothelial dysfunction, which was corrected by vitamin C pointing to a crucial role of reactive oxygen species (ROS) in causing this phenomenon. We sought to elucidate the mechanism how ISMN causes endothelial dysfunction and oxidative stress in vascular tissue.Methods and resultsMale Wistar rats (n= 69 in total) were treated with ISMN (75 mg/kg/day) or placebo for 7 days. Endothelin (ET) expression was determined by immunohistochemistry in aortic sections. Isosorbide-5-mononitrate infusion caused significant endothelial dysfunction but no tolerance to ISMN itself, whereas ROS formation and nicotinamide adenine dinucleotidephosphate (NADPH) oxidase activity in the aorta, heart, and whole blood were increased. Isosorbide-5-mononitrate up-regulated the expression of NADPH subunits and caused uncoupling of the endothelial nitric oxide synthase (eNOS) likely due to a down-regulation of the tetrahydrobiopterin-synthesizing enzyme GTP-cyclohydrolase-1 and to S-glutathionylation of eNOS. The adverse effects of ISMN were improved in gp91phox knockout mice and normalized by bosentan in vivo/ex vivo treatment and suppressed by apocynin. In addition, a strong increase in the expression of ET within the endothelial cell layer and the adventitia was observed.Conclusion
Chronic treatment with ISMN causes endothelial dysfunction and oxidative stress, predominantly by an ET-dependent activation of the vascular and phagocytic NADPH oxidase activity and NOS uncoupling. These findings may explain at least in part results from a retrospective analysis indicating increased mortality in post-infarct patients in response to long-term treatment with mononitrates.
European Heart Journal 05/2012; · 14.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Angiotensin II (ATII), a potent vasoconstrictor, causes hypertension, promotes infiltration of myelomonocytic cells into the vessel wall, and stimulates both vascular and inflammatory cell NADPH oxidases. The predominant source of reactive oxygen species, eg, vascular (endothelial, smooth muscle, adventitial) versus phagocytic NADPH oxidase, and the role of myelomonocytic cells in mediating arterial hypertension have not been defined yet. METHODS AND RESULTS: Angiotensin II (1 mg · kg(-1) · d(-1) for 7 days) increased the number of both CD11b(+)Gr-1(low)F4/80(+) macrophages and CD11b(+)Gr-1(high)F4/80(-) neutrophils in mouse aorta (verified by flow cytometry). Selective ablation of lysozyme M-positive (LysM(+)) myelomonocytic cells by low-dose diphtheria toxin in mice with inducible expression of the diphtheria toxin receptor (LysM(iDTR) mice) reduced the number of monocytes in the circulation and limited ATII-induced infiltration of these cells into the vascular wall, whereas the number of neutrophils was not reduced. Depletion of LysM(+) cells attenuated ATII-induced blood pressure increase (measured by radiotelemetry) and vascular endothelial and smooth muscle dysfunction (assessed by aortic ring relaxation studies) and reduced vascular superoxide formation (measured by chemiluminescence, cytochrome c assay, and oxidative fluorescence microtopography) and the expression of NADPH oxidase subunits gp91(phox) and p67(phox) (assessed by Western blot and mRNA reverse-transcription polymerase chain reaction). Adoptive transfer of wild-type CD11b(+)Gr-1(+) monocytes into depleted LysM(iDTR) mice reestablished ATII-induced vascular dysfunction, oxidative stress, and arterial hypertension, whereas transfer of CD11b(+)Gr-1(+) neutrophils or monocytes from gp91(phox) or ATII receptor type 1 knockout mice did not. CONCLUSIONS- Infiltrating monocytes with a proinflammatory phenotype and macrophages rather than neutrophils appear to be essential for ATII-induced vascular dysfunction and arterial hypertension.