Biomedical subjects

Wilhelm Bloch

Publications and source records attributed to Wilhelm Bloch.

70 records · Page 4Linked to original sources

PubMed2003

Reduced length-dependent cross-bridge recruitment in skinned fiber preparations of human failing myocardium.

A depressed activity of myosin ATPase has been described in human failing myocardium. Since alterations in cross-bridge kinetics may affect both systolic and diastolic cardiac function, the present study simultaneously investigated Ca(2+)-dependent tension and actomyosin ATPase activity (MYO) in triton X-skinned fiber preparations of human non-failing (donor hearts, n=8) and failing (dilated cardiomyopathy, n=11) left ventricular myocardium at increasing sarcomeric length (1.9 and 2.1 microm, alpha-actinin staining). The MYO/tension ratio was analyzed as a parameter characterizing myofibrillar energetics. At a sarcomere length of 1.9 microm, the Ca(2+) sensitivity of tension was significantly increased in human failing compared to non-failing myocardium. In human non-failing myocardium, maximal Ca(2+)-activated tension [1.9 microm vs. 2.1 microm, 23.7 (1.9) vs. 28.3 (1.9) mN/mm(2)] and the Ca(2+) sensitivity of tension [EC(50)Ca(2+ )(pCa): 5.67 (0.06) vs. 7.07 (0.11)] were increased by increasing sarcomere length. This was accompanied by an enhancement in Ca(2+)-dependent MYO [+72 (11) vs. +101 (9) microM ADP/s] as well as an increase in the Ca(2+)-sensitivity of MYO [EC(50)Ca(2+ )(pCa): 5.84 (0.08) vs. 6.86 (0.08)]. In human failing myocardium, only Ca(2+) sensitivity of tension (but not of MYO) increased. Tension cost was increased in failing vs. non-failing tissue [1.9 microm: 4.18 (0.06) vs. 3.53 (0.06) (mN.s)/(mm(2). microM ADP); 2.1 microm: 4.28 (0.13) vs. 3.52 (0.05) (mN.s)/(mm(2). microM ADP)]. We concluded that, in human failing myocardium, the length-dependent force generation may be blunted due to an already increased Ca(2+) affinity of troponin C as well as an impairment of length-dependent cross-bridge recruitment.

Adult↗

PubMed2003

N-acetylcysteine prevents reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery: results of a randomized, double-blind, placebo-controlled clinical trial.

OBJECTIVE: Reactive oxygen species have been shown to contribute to myocardial stress in patients undergoing cardiac surgery, as demonstrated by myocardial 8-iso-prostaglandin-F(2)alpha and nitrotyrosine formation. We hypothesized that the reactive oxygen species scavenger N-acetylcysteine attenuates reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery. METHODS: Forty patients undergoing coronary artery surgery (mean age +/- SD, 66 +/- 9 years; 9 women and 31 men) were randomized to receive either N-acetylcysteine (100 mg/kg into cardiopulmonary bypass prime followed by infusion at 20 mg.kg(-1).h(-1), n = 20) or placebo (n = 20). Patients and clinical staff were blinded to group assignment. Transmural left ventricular biopsy specimens collected before and at the end of cardiopulmonary bypass were subjected to immunocytochemical staining against 8-iso-prostaglandin-F(2)alpha (primary measure) as an indicator for reactive oxygen species-mediated lipid peroxidation and nitrotyrosine (coprimary measure) as a marker for peroxynitrite-mediated tissue injury. Cardiomyocyte staining was quantitatively determined by using densitometry (in gray units). Global left ventricular function was measured on the basis of fractional area of contraction by using transesophageal echocardiography. RESULTS: Patient characteristics in both groups were comparable. The change in left ventricular cardiomyocyte staining (end of cardiopulmonary bypass--before cardiopulmonary bypass) differed significantly between groups for both primary measures: 8-iso-prostaglandin-F(2)alpha, -1.8 +/- 7.5 gray units (mean +/- SD, N-acetylcysteine group) versus 5.0 +/- 4.1 gray units (placebo group; 95% confidence interval, 2.6-11.0, P =.003); nitrotyrosine, -6.4 +/- 10.0 gray units (N-acetylcysteine group) versus 9.2 +/- 8.4 gray units (placebo group; 95% confidence interval, 9.4-21.7, P <.001). Hemodynamics and clinical outcomes were comparable in both groups. CONCLUSIONS: Reactive oxygen species scavenging with N-acetylcysteine attenuates myocardial oxidative stress in the hearts of patients subjected to cardiopulmonary bypass and cardioplegic arrest.

Acetylcysteine↗

PubMed2003

Cardioplegic arrest induces apoptosis signal-pathway in myocardial endothelial cells and cardiac myocytes.

OBJECTIVE: Myocardial ischemia-reperfusion is associated with free radical-mediated injury and may be involved in cardiac apoptosis. The purpose of our study was to investigate (1) if cardioplegia-induced ischemia-reperfusion initiates cardiac apoptosis signal pathway, and (2) if this is mediated by free radicals. METHODS: We subjected 13 pigs (56+/-10 kg) to 1 h of cold crystalloid cardioplegic arrest (CA) on cardiopulmonary bypass (CPB), and collected five transmural LV biopsies: prior to CPB (baseline), at 60 min CA, at 15 and 30 min reperfusion on CPB, and at 120 min post CPB. Two additional pigs were subjected to CPB but not CA and two further pigs were neither subjected to CPB nor CA and served as sham-operated time controls. LV specimens were cut at 7 microm and immunocytochemically stained against active caspase-3 and 85 kDa poly(ADP-ribose) polymerase (PARP) as apoptosis signal-pathway key enzymes, nitrotyrosine as indicator for peroxynitrite (ONOO(-))-mediated tissue injury, and 8-iso-prostaglandin-F(2)alpha as indicator for oxygen free radical-mediated lipid peroxidation. Specimen were assessed using a scale of 0 (negative) to 3 (highly positive), and cardiomyocytes were quantitatively investigated using TV densitometry. RESULTS: At 60 min CA, caspase-3 was increased by 9.2+/-3.7 gray units and remained on this level until 2 h post CPB (P</=0.003 vs. baseline); nitrotyrosine increased over time to reach a maximum of +8.5+/-8.1 gray units at 120 min post CPB (P=0.016); and there was a trend for increased 8-iso-prostaglandin-F(2)alpha at 60 min CA (+3.6+/-4.7 gray units; P=0.089). At 60 min CA, 92% of the hearts showed active caspase-3, only 42% demonstrated nitrotyrosine formation, and 58% exhibited 8-iso-prostaglandin-F(2)alpha. At 120 min post CPB, most hearts positive for caspase-3 were also positive for nitrotyrosine (83%), and 8-iso-prostaglandin-F(2)alpha (75%), but no heart showed PARP cleavage. Hearts subjected to CPB but not CA as well as time controls remained negative for all variables. CONCLUSIONS: Our data show that CA initiates apoptosis signal-pathway in myocardial endothelium and myocytes; however, this did not result in apoptotic cell death as we did not find PARP cleavage. Further, the data suggest that CA-induced apoptosis signal pathway activation is not mediated by free radicals as caspase-3 activation preceded both nitrotyrosine and 8-iso-prostaglandin-F(2)alpha formation.

Animals↗

PubMed2003

Localization of the neuropeptide galanin in nerve fibers and epithelial keratinocytes of the rat molar gingiva.

Knowledge of the histochemical substrates of cellular and neurovascular connections in the gingiva is essential in order to understand the initial mechanisms of inflammation in the periodontium. Since the localization of the neuroendocrine peptide galanin in the gingiva is still unclear, we used immunohistochemical, in situ hybridization and immunoblot techniques to assess the localization of galanin in the gingiva of rat molars. Galanin-immunoreactive nerve fibers were located around blood vessels in the lamina propria, beneath the epithelium, in the epithelial-proprial junction and in the basal layer of the epithelium. Galanin was highly expressed in the suprabasal keratinocytes of the gingival epithelium. The localization of galanin in gingival nerve fibers and the expression of galanin in keratinocytes of the gingival epithelium indicate that galanin may be a possible regulator of different cellular functions in the gingiva.

Animals↗

PubMed2003

Nitrotyrosine and 8-isoprostane formation indicate free radical-mediated injury in hearts of patients subjected to cardioplegia.

OBJECTIVE: Myocardial ischemia and reperfusion induced by cardioplegic arrest subjects the heart to free radical-mediated stress. The purpose of our study was to investigate the effect of cardioplegia-induced ischemia and reperfusion on myocardial formation and distribution of (1) nitrotyrosine as an indicator for peroxynitrite-mediated tissue injury resulting from increased nitric oxide release and (2) 8-isoprostane as an indicator for oxygen-derived free radical-mediated lipid peroxidation. METHODS: In 10 patients undergoing coronary artery operations (64 +/- 6 [mean +/- SD] years, 3 women and 7 men) subjected to cardiopulmonary bypass and intermittent cold blood cardioplegia, we collected transmural left ventricular biopsy specimens before and at the end of cardiopulmonary bypass. Specimens were cut at 10 micro m and subjected to immunocytochemical staining against the nitric oxide-producing enzyme constitutive nitric oxide synthase, cyclic guanosine monophosphate (intracellular second messenger of nitric oxide), nitrotyrosine, and 8-isoprostane by using polyclonal antibodies. For global left ventricular function determination, we measured the fractional area of contraction using transesophageal echocardiography. RESULTS: Nitric oxide synthase activity in cardiac myocytes increased from 34 +/- 10 gray units before cardiopulmonary bypass to 47 +/- 12 gray units at the end of bypass (P =.015), and all hearts showed increased cyclic guanosine monophosphate content in both myocytes and endothelial cells at the end of bypass. The number of nitrotyrosine-positive capillaries increased from 36 +/- 29/mm(2) before bypass to 82 +/- 47/mm(2) at the end of bypass (P =.012), and 8-isoprostane-positive capillaries increased from 92 +/- 72/mm(2) before bypass to 209 +/- 108/mm(2) at the end of bypass (P =.005). The fractional area of contraction was 53% +/- 12% before bypass and 56% +/- 12% after bypass (P =.47) but was slightly decreased to 45% +/- 14% at 4 hours after bypass (P =.121). CONCLUSIONS: Our data show that cardioplegia-induced myocardial ischemia and reperfusion is associated with nitrotyrosine and 8-isoprostane formation mainly in the coronary endothelium, indicating injury mediated by both peroxynitrite and oxygen-derived free radicals. Because nitric oxide synthase activation was accompanied with increased cyclic guanosine monophosphate, these data suggest that direct effects of nitric oxide on cardiac myocytes, as well as nitric oxide-mediated coronary endothelial injury, might contribute to injury associated with cardioplegia and cardiopulmonary bypass.

Coronary Vessels↗

PubMed2003

Targeting of platelet integrin alphaIIbbeta3 determines systemic reaction and bleeding in murine thrombocytopenia regulated by activating and inhibitory FcgammaR.

Previous work on cellular destruction induced by several clinically relevant anti-platelet IgG antibodies suggested antigen-specific mechanisms in the development of immune thrombocytopenia in mice. mAb directed against mouse platelet GPIbalpha and integrin alpha(IIb)beta(3) were highly pathogenic, and mediated their effects via different Fc-dependent (alpha(IIb)beta(3)) and Fc-independent (GPIbalpha) pathways, indicating that clearance of IgG-bound platelets is only one event in the pathogenesis of murine thrombocytopenia. Here, we demonstrate that in addition to thrombocytopenia, targeting of platelet integrin alpha(IIb)beta(3) results in acute systemic reaction and bleeding that is regulated by activating IgG Fc receptors (FcgammaR) and the inhibitory FcgammaRII. As shown by electron microscopy, anti-alpha(IIb)beta(3) IgG mediated initial loss of alpha(IIb)beta(3) integrin from platelet surfaces followed by rapid accumulation of alpha(IIb)beta(3) antibody-containing immune complex (IC)-like structures in spleen and liver in vivo. In FcRgamma chain deficiency, mice resisted bleeding, but not platelet destruction, while genetic ablation of FcgammaRII resulted in uncontrolled systemic reaction and severe hemorrhage leading to enhanced mortality. Together, these results provide evidence that IC formation and engagement of FcgammaR on effector cells determines the alpha(IIb)beta(3)-specific part of the platelet pathology of the systemic reaction and bleeding in murine thrombocytopenia.

Animals↗

PubMed2002

Nitric oxide pathways in human bladder carcinoma. The distribution of nitric oxide synthases, soluble guanylyl cyclase, cyclic guanosine monophosphate, and nitrotyrosine.

BACKGROUND: Nitric oxide (NO) is produced by a group of synthase enzymes (NOS). By means of different pathways, NO exerts several functions in benign and malignant human bladder tissues. The current paper describes the NO/guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) and the NO/oxidative pathways in human bladder tissues. METHODS: Bladder carcinoma tissues were collected from 18 patients by transurethral resection procedures. Normal benign vesical tissue specimens from a further eight patients with benign diseases served as controls. Immunohistochemistry was conducted for localization of sGC, cGMP, and nitrotyrosine in benign and malignant vesical tissues, evaluating two-three tissue sections per patient. RESULTS: Positive immunolabeling for sGC and cGMP was detected in vascular endothelial cells of normal and malignant vesical tissues. Those signals were most intense in bladder carcinoma tissues. Immunolabeling for sGC and cGMP was also detected in normal urothelial cells. In bladder carcinoma cells, a heterogeneous immunolabeling for sGC and cGMP was seen, with a wide spectrum of signal intensity. Positive immunostaining for sGC and cGMP was also observed in stromal round cells in benign and malignant bladder tissues. Immunolabeling for nitrotyrosine was mainly observed in endothelial cells, with a much stronger immunolabeling in bladder carcinoma tissues compared to normal benign controls. A weak immunolabeling for nitrotyrosine was also observed in bladder carcinoma cells. Normal urothelial cells did not show such nitrotyrosine expression. CONCLUSIONS: The current report provides evidences that NO play several roles through different pathways in benign and malignant vesical tissues. The influences generated by NO molecules can be divided into cGMP-mediated effects (those resulting from the NO/sGC/cGMP pathway) and non-cGMP-mediated effects (those resulting from the NO/oxidative pathway). Increased angiogenesis is a cGMP-mediated effect, while nitrotyrosine production is a non cGMP-mediated oxidative effect. Such an NO/oxidative pathway is observed more often in bladder carcinoma.

Aged↗

PubMed2002

In vitro activation of extracellular signal-regulated kinase1/2 in the inner ear of guinea pigs.

Growth factors such as vascular endothelial growth factor (VEGF) exert their proliferative properties partly through activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK1/2). Although both VEGF and inactive ERK could be detected in the inner ear of guinea pigs, under normal conditions activated ERK (phospho-ERK) was found only sparely. Cochleae of adult guinea pigs were removed, incubated with VEGF in a carbogen-gased organ-bath for 5, 15, 30 and 60 min (n=6 in each group), fixed with PFA 4%, embedded in paraffin and sectioned, followed by immunohistochemical staining to inactive and active ERK. Whereas inactive ERK was found in all cochleae, in sensory and supporting cells of the apex activated ERK was strongly detected after 5-min VEGF-incubation. After 15 min all Corti-organs showed clear staining corresponding to activated ERK, which decreased again after 30 min. Faint staining in endothelial cells of the spring-coil-vessels and in the spiral ganglion cells was found after 30 min and was increased after 60 min, while the staining in the Corti-organs vanished. Addition of the MEK-inhibitor PD 98059 to the organ-bath led to diminished phospho-ERK1/2 immunostaining. These findings provide evidence for a VEGF-dependent phosphorylation of ERK1/2 in the cochlea. Activated ERK1/2 is thought to support axonal outgrowth, enhancement of cell survival and to regulate the turnover of the NO/cGMP-pathway.

Animals↗

PubMed2002

Cellular cardiomyoplasty improves survival after myocardial injury.

BACKGROUND: Cellular cardiomyoplasty is discussed as an alternative therapeutic approach to heart failure. To date, however, the functional characteristics of the transplanted cells, their contribution to heart function, and most importantly, the potential therapeutic benefit of this treatment remain unclear. METHODS AND RESULTS: Murine ventricular cardiomyocytes (E12.5-E15.5) labeled with enhanced green fluorescent protein (EGFP) were transplanted into the cryoinjured left ventricular walls of 2-month-old male mice. Ultrastructural analysis of the cryoinfarction showed a complete loss of cardiomyocytes within 2 days and fibrotic healing within 7 days after injury. Two weeks after operation, EGFP-positive cardiomyocytes were engrafted throughout the wall of the lesioned myocardium. Morphological studies showed differentiation and formation of intercellular contacts. Furthermore, electrophysiological experiments on isolated EGFP-positive cardiomyocytes showed time-dependent differentiation with postnatal ventricular action potentials and intact beta-adrenergic modulation. These findings were corroborated by Western blotting, in which accelerated differentiation of the transplanted cells was detected on the basis of a switch in troponin I isoforms. When contractility was tested in muscle strips and heart function was assessed by use of echocardiography, a significant improvement of force generation and heart function was seen. These findings were supported by a clear improvement of survival of mice in the cardiomyoplasty group when a large group of animals was analyzed (n=153). CONCLUSIONS: Transplanted embryonic cardiomyocytes engraft and display accelerated differentiation and intact cellular excitability. The present study demonstrates, as a proof of principle, that cellular cardiomyoplasty improves heart function and increases survival on myocardial injury.

Animals↗

PubMed2002

Immunohistochemical expression of VEGF and VEGF receptors in nasal polyps as compared to normal turbinate mucosa.

The factors involved in the development of chronic inflammation and edema in nasal polyps remain to be clarified. The expression of vascular endothelial growth factor (VEGF) has been described in plasma cells, suggesting that plasma cells may play a major role in the development of edema in nasal polyps through the production of VEGF. We performed immunohistochemical analysis using specific antibodies to VEGF and to the known VEGF receptors, VEGFR-1 and VEGFR-2, on paraffin sections of human nasal polyps ( n=11) and controls of human mucosa of the normal middle turbinates ( n=6). In normal turbinate mucosa, sporadic immunostaining for VEGF was observed throughout the endothelial cells of the small veins and arteries. VEGFR-1 and VEGFR-2 expression was faint in the healthy turbinates. In nasal polyp tissues, strong immunostaining for VEGF was found in the endothelium of blood vessels and in the infiltrating perivascular inflammatory cells. Fibroblasts also stained for VEGF. Strong immunolabeling to VEGFR-1 was evident in the vascular endothelium, whereas weak to moderate VEGFR-1-staining was generally confined to scattered mononuclear round cells. Mononuclear round cells and the endothelium of capillaries revealed immunoreactivity to VEGFR-2. These findings support a role for VEGF and its receptors, VEGFR-1 and VEGFR-2, in the development and perpetuation of edema and angiogenesis in nasal polyps.

Endothelial Growth Factors↗

PubMed2002

Cellular cardiomyoplasty in a transgenic mouse model.

BACKGROUND: Recent progress in the cardiotypic differentiation of embryonic and somatic stem cells opens novel prospects for the treatment of cardiovascular disorders. The aim of the present study was to develop a novel surgical approach that allows standardized cellular cardiomyoplasty in mouse with low-perioperative mortality. METHODS: Reproducible transmural lesions were generated by cryoinjury followed by intramural injection of embryonic cardiomyocytes using a newly designed holding device and vital dye staining. This approach was validated with a transgenic mouse model, in which the live reporter gene-enhanced green fluorescent protein (EGFP) is under control of a cardiac-specific promoter. RESULTS: The perioperative mortality was 10%. The engrafted EGFP-positive cardiomyocytes could be identified in a high percentage (72.2%, n=36) of operated animals. CONCLUSIONS: This novel approach enables reliable cellular replacement therapy in mouse and greatly facilitates the analysis of its molecular, cellular, and functional efficacy.

Animals↗

PubMed2002

Increased Ca2+-sensitivity of myofibrillar tension in heart failure and its functional implication.

In human failing myocardium, an increased Ca2+-sensitivity of myofilament tension development has been described in Triton X skinned cardiac myocytes compared to cardiomyocytes obtained from non-failing human donor hearts. The present study aimed to investigate whether there are functional implications of the increased Ca2+-sensitivity in heart failure and whether alterations of myofilament function are already obvious at earlier stages of heart failure, such as in cardiac hypertrophy or whether alterations of the intracellular Ca2+-homeostasis are able to induce alterations in myofilament function. Ca2+-activated tension development was measured in Triton X-skinned fibers from human failing and non-failing myocardium. Ca2+-sensitivity of myofilament tension development was significantly shifted to the left in human failing myocardium. Plots of diastolic free Ca2+ versus diastolic tension development showed that in a range of similar diastolic Ca2+-concentrations, diastolic tension was significantly enhanced in the failing hearts. The Ca2+/tension relationship was shifted to the right in Triton X-skinned fiber preparations from transgenic renin overexpressing rats (TG(mREN2)27), shown to have concentric hypertrophy. In addition, the Ca2+/tension relationship was unchanged in phospholamban knock-out mice with an increased systolic Ca2+ (and enhanced diastolic Ca2+-load). It is concluded that the increased Ca2+-sensitivity of myofilament tension observed in single cardiomyocytes from failing human myocardium may be a phenomenon also present in multicellular preparations and may contribute to the diastolic dysfunction observed in human heart failure. Alterations of myofilament function occur at very early stages of heart failure and may be species dependent, or dependent on intracellular free Ca2+-levels.

Animals↗

PubMed2002

Role of cardiopulmonary bypass and cardioplegic arrest in the regulation of cardiac nitric oxide synthase activity.

Explore the source record for details and available documents.

Coronary Artery Bypass↗

PubMed2002

Beta2 integrins are required for skin homing of primed T cells but not for priming naive T cells.

Beta2 integrins are of critical importance for leukocyte extravasation through vascular endothelia and for T cell activation. To elucidate the role of beta2 integrins in T cell-mediated immune responses, allergic contact dermatitis (ACD), irritant dermatitis, and delayed-type hypersensitivity (DTH) were assessed in mice lacking the beta2 integrin subunit, CD18. ACD and DTH responses, but not edema formation, were severely suppressed in CD18(-/-) mice. Extravasation of CD18(-/-) T cells into eczematous skin lesions was greatly impaired, whereas migration of Langerhans cell precursors and dendritic cells was normal in CD18(-/-) mice. CD18(-/-)lymph nodes (LNs) contained an abnormal population of CD3(-)CD44(high) lymphocytes and showed evidence of widespread T cell activation. T cells from regional LNs of sensitized CD18(-/-) mice proliferated in response to hapten challenge, and subcutaneous injection of sensitized syngeneic LN cells directly into ears of hapten-challenged naive recipients restored the defective ACD in CD18(-/-) mice, suggesting that CD18 is not required for priming of naive T cells but is indispensable for T cell extravasation. Thus, a dysfunction of T cells, in addition to granulocytes, may contribute to the pathophysiology of leukocyte adhesion deficiency type I, which arises from mutations in the human CD18 gene.

Animals↗

PubMed2002

A crucial role of beta 1 integrins for keratinocyte migration in vitro and during cutaneous wound repair.

Integrins are ubiquitous transmembrane receptors that play crucial roles in cell-cell and cell-matrix interactions. In this study, we have determined the effects of the loss of beta 1 integrins in keratinocytes in vitro and during cutaneous wound repair. Flow cytometry of cultured beta 1-deficient keratinocytes confirmed the absence of beta 1 integrins and showed downregulation of alpha 6 beta 4 but not of alpha v integrins. beta 1-null keratinocytes were characterised by poor adhesion to various substrates, by a reduced proliferation rate and by a strongly impaired migratory capacity. In vivo, the loss of beta 1 integrins in keratinocytes caused a severe defect in wound healing. beta 1-null keratinocytes showed impaired migration and were more densely packed in the hyperproliferative epithelium. Surprisingly, their proliferation rate was not reduced in early wounds and even increased in late wounds. The failure in re-epithelialisation resulted in a prolonged inflammatory response, leading to dramatic alterations in the expression of important wound-regulated genes. Ultimately, beta 1-deficient epidermis did cover the wound bed, but the epithelial architecture was abnormal. These findings demonstrate a crucial role of beta 1 integrins in keratinocyte migration and wound re-epithelialisation. Movies available on-line

Animals↗

PubMedDate not supplied

Endostatin down-regulates soluble guanylate cyclase (sGC) in endothelial cells in vivo: influence of endostatin on vascular endothelial growth factor (VEGF) signaling.

Endostatin was suggested to be an antiangiogenic agent with the potential for clinical use in cancer therapy. Unfortunately, up to now no antiangiogenic effect was seen in clinical trials using this substance. The lack of response might be caused by an incomplete understanding of endostatin signaling. Endostatin is known to influence the vascular endothelial growth factor (VEGF) signaling pathway. It has been reported to bind to the VEGF receptor KDR directly and to decrease the phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177 via the protein phosphatase 2A (PP2A). But so far no details of endostatin signaling with regard to NO downstream effectors have been revealed. In the present work the authors demonstrate that endostatin down-regulates the protein level of soluble guanylate cyclase (sGC) in endothelial cells of newly formed blood vessels in 5 day-old wounds (control: 62.5 +/- 33 vessels/mm2, endostatin: 9.2 +/- 3.2 vessels/mm2). This was confirmed in experiments with endothelial tubes of embryoid bodies and endothelial cells derived from embryonic stem cells (eESCs; control: 126 +/- 20, endostatin: 58 +/- 10). The decrease of sGC protein levels in response to endostatin was abolished after preincubation with the PP2A inhibitor okadaic acid. No alterations of sGC mRNA levels could be found under endostatin treatment in eESC. The authors conclude that endostatin affects VEGF signaling in endothelial cells by a post-transcriptional PP2A-dependent down-regulation of sGC protein levels.

Angiogenesis Inhibitors↗