Arno Beer

Monocyte migration : A novel effect and signaling pathways of catestatin

Several members of the neuropeptide family exert chemotactic actions on blood monocytes consistent with neurogenic inflammation. Furthermore, chromogranin A (CgA) containing Alzheimer plaques are characterized by extensive microglia activation and such activation induces neuronal damage. We therefore hypothesized that the catecholamine release inhibitory peptide catestatin (hCgA(352-372)) would induce directed monocyte migration. We demonstrate that catestatin dose-dependently stimulates chemotaxis of human peripheral blood monocytes, exhibiting its maximal effect at a concentration of 1 nM comparable to the established chemoattractant formylated peptide Met-Leu-Phe (fMLP). The naturally occurring catestatin variants differed in their chemotactic property insofar as that the Pro370Leu variant was even more potent than wild type, whereas the Gly364Ser variant was less effective. Specificity of this effect was shown by inhibition of catestatin-induced chemotaxis by a specific neutralizing antibody. In addition, catestatin mediated effect was blocked by dimethylsphingosine and treatment with endothelial differentiation gene (Edg)-1 and Edg-3 antisense RNA as well as by incubation with pertussis toxin and genistein indicating involvement of tyrosine kinase receptor-, G-protein- and sphingosine-1-phosphate signaling. Catestatin also stimulated Akt- and extracellular signal related kinase (ERK)-phosphorylation and catestatin-induced chemotaxis was blocked by blockers of phosphoinositide-3 (PI-3) kinase and nitric oxide as well as by inhibition of the mitogen-activated protein kinases (MAPK) system indicating involvement of these signal transduction pathways. In summary, our data indicate that catestatin induces monocyte chemotaxis by activation of a variety of signal transduction pathways suggesting a role of this peptide as an inflammatory cytokine.

The neuropeptide catestatin acts as a novel angiogenic cytokine via a basic fibroblast growth factor-dependent mechanism.

Rationale: The neuropeptide catestatin is an endogenous nicotinic cholinergic antagonist that acts as a pleiotropic hormone. Objective: Catestatin shares several functions with angiogenic factors. We therefore reasoned that catestatin induces growth of new blood vessels. Methods and Results: Catestatin induced migration, proliferation, and antiapoptosis in endothelial cells and exerted capillary tube formation in vitro in a Matrigel assay, and such effects were mediated via G protein, mitogen-activated protein kinase, and Akt. Catestatin-induced endothelial cell functions are further mediated by basic fibroblast growth factor, as shown by blockade of effects by a neutralizing fibroblast growth factor antibody. Furthermore, catestatin released basic fibroblast growth factor from endothelial cells and stimulated fibroblast growth factor signaling. In addition to its function on endothelial cells, catestatin also exerted effects on endothelial progenitor cells and vascular smooth muscle cells. In vivo, catestatin induced angiogenesis in the mouse cornea neovascularization assay and increased blood perfusion and number of capillaries in the hindlimb ischemia model. In addition to angiogenesis, catestatin increased density of arterioles/arteries and incorporation of endothelial progenitor cells in the hindlimb ischemia model, indicating induction of arteriogenesis and postnatal vasculogenesis. Conclusion: We conclude that catestatin acts as a novel angiogenic cytokine via a basic fibroblast growth factor–dependent mechanism.

Hypoxia up-regulates the angiogenic cytokine secretoneurin via an HIF-1α- and basic FGF-dependent pathway in muscle cells

Expression of angiogenic cytokines like vascular endothelial growth factor is enhanced by hypoxia. We tested the hypothesis that decreased oxygen levels up‐regulate the angiogenic factor sec‐retoneurin. In vivo, muscle cells of mouse ischemic hind limbs showed increased secretoneurin expression, and inhibition of secretoneurin by a neutralizing antibody impaired the angiogenic response in this ischemia model. In a mouse soft tissue model of hypoxia, secretoneurin was increased in subcutaneous muscle fibers. In vitro, secretoneurin mRNA and protein were up‐regulated in L6 myoblast cells after exposure to low oxygen levels. The hypoxia‐depen‐dent regulation of secretoneurin was tissue specific and was not observed in endothelial cells, vascular smooth muscle cells, or AtT20 pituitary tumor cells. The hypoxia‐dependent induction of secretoneurin in L6 myoblasts is regulated by hypoxia‐inducible factor‐la, since inhibition of this factor using si‐RNA inhibited up‐regulation of secretoneurin. Induction of secretoneurin by hypoxia was dependent on basic fibroblast growth factor in vivo and in vitro, and inhibition of this regulation by heparinase suggests an involvement of low‐affinity basic fibroblast growth factor binding sites. In summary, our data show that the angiogenic cytokine secretoneurin is up‐regulated by hypoxia in muscle cells by hypoxia‐inducible factor‐1α‐ and basic fibroblast growth factor‐dependent mechanisms.—Egger, M., Schgoer, W., Beer, A. G. E., Jeschke, J., Leierer, J., Theurl, M., Frauscher, S., Tepper, O. M., Niederwanger, A., Ritsch, A., Kearney, M., Wanschitz, J., Gurtner, G. C., Fischer‐Colbrie, R., Weiss, G., Piza‐Katzer, H., Losordo, D. W., Patsch, J. R., Schratzberger, P., Kirchmair, R. Hypoxia up‐regulates the angiogenic cytokine secretoneurin via an HIF‐1α‐ and basic FGF‐dependent pathway in muscle cells. FASEB J. 21, 2906–2917 (2007)

The Angiogenic Factor Secretoneurin Induces Coronary Angiogenesis in a Model of Myocardial Infarction by Stimulation of Vascular Endothelial Growth Factor Signaling in Endothelial Cells

Background—Secretoneurin is a neuropeptide located in nerve fibers along blood vessels, is upregulated by hypoxia, and induces angiogenesis. We tested the hypothesis that secretoneurin gene therapy exerts beneficial effects in a rat model of myocardial infarction and evaluated the mechanism of action on coronary endothelial cells. Methods and Results—In vivo secretoneurin improved left ventricular function, inhibited remodeling, and reduced scar formation. In the infarct border zone, secretoneurin induced coronary angiogenesis, as shown by increased density of capillaries and arteries. In vitro secretoneurin induced capillary tubes, stimulated proliferation, inhibited apoptosis, and activated Akt and extracellular signal-regulated kinase in coronary endothelial cells. Effects were abrogated by a vascular endothelial growth factor (VEGF) antibody, and secretoneurin stimulated VEGF receptors in these cells. Secretoneurin furthermore increased binding of VEGF to endothelial cells, and binding was blocked by heparinase, indicating that secretoneurin stimulates binding of VEGF to heparan sulfate proteoglycan binding sites. Additionally, secretoneurin increased binding of VEGF to its coreceptor neuropilin-1. In endothelial cells, secretoneurin also stimulated fibroblast growth factor receptor-3 and insulin-like growth factor-1 receptor, and in coronary vascular smooth muscle cells, we observed stimulation of VEGF receptor-1 and fibroblast growth factor receptor-3. Exposure of cardiac myocytes to hypoxia and ischemic heart after myocardial infarction revealed increased secretoneurin messenger RNA and protein. Conclusions—Our data show that secretoneurin acts as an endogenous stimulator of VEGF signaling in coronary endothelial cells by enhancing binding of VEGF to low-affinity binding sites and neuropilin-1 and stimulates further growth factor receptors like fibroblast growth factor receptor-3. Our in vivo findings indicate that secretoneurin may be a promising therapeutic tool in ischemic heart disease.

Gene Therapy With the Angiogenic Cytokine Secretoneurin Induces Therapeutic Angiogenesis by a Nitric Oxide–Dependent Mechanism

Rationale: The neuropeptide secretoneurin induces angiogenesis and postnatal vasculogenesis and is upregulated by hypoxia in skeletal muscle cells. Objective: We sought to investigate the effects of secretoneurin on therapeutic angiogenesis. Methods and Results: We generated a secretoneurin gene therapy vector. In the mouse hindlimb ischemia model secretoneurin gene therapy by intramuscular plasmid injection significantly increased secretoneurin content of injected muscles, improved functional parameters, reduced tissue necrosis, and restored blood perfusion. Increased muscular density of capillaries and arterioles/arteries demonstrates the capability of secretoneurin gene therapy to induce therapeutic angiogenesis and arteriogenesis. Furthermore, recruitment of endothelial progenitor cells was enhanced by secretoneurin gene therapy consistent with induction of postnatal vasculogenesis. Additionally, secretoneurin was able to activate nitric oxide synthase in endothelial cells and inhibition of nitric oxide inhibited secretoneurin-induced effects on chemotaxis and capillary tube formation in vitro. In vivo, secretoneurin induced nitric oxide production and inhibition of nitric oxide attenuated secretoneurin-induced effects on blood perfusion, angiogenesis, arteriogenesis, and vasculogenesis. Secretoneurin also induced upregulation of basic fibroblast growth factor and platelet-derived growth factor-B in endothelial cells. Conclusions: In summary, our data indicate that gene therapy with secretoneurin induces therapeutic angiogenesis, arteriogenesis, and vasculogenesis in the hindlimb ischemia model by a nitric oxide–dependent mechanism.

Secretoneurin, substance P and neuropeptide Y in the oxygen-induced retinopathy in C57Bl/6N mice

In this study, we investigated whether the proangiogenic neuropeptides secretoneurin (SN), substance P (SP), and neuropeptide Y (NPY) contribute to the development of abnormal neovascularization in the oxygen-induced retinopathy (OIR) model in mice. By exposing litters of C57Bl/6N mice to 75% oxygen from postnatal day 7 (P7) until postnatal day 11 (P11) and then returning them to normoxic conditions, retinal ischemia and subsequent neovascularization on the retinal surface were induced. Retinae were dissected on P9, P11, P12-P14, P16 and P20, and the concentrations of SN, SP, NPY and VEGF determined by radioimmunoassay or ELISA. The levels of SN and SP increased in controls from P9 until P16 and from P9 until P14, respectively, whereas the levels of NPY were high at P9 and decreased thereafter until P20, suggesting that NPY may participate in the development of the retina. However, dipeptidyl peptidase IV (DPPIV) and the NPY-Y2 receptor were not detectable in the immature retina indicating that NPY is not involved in the physiological vascularization in the retina. Compared to controls, OIR had no effect on the levels of SN, whereas levels of both SP and NPY slightly decreased during hyperoxia. Normalization of the levels of SP, and to a more pronounced extent of NPY, was significantly delayed during relative hypoxia. This clearly indicates that these three neuropeptides are not involved in the pathogenesis of neovascularization in OIR. Moreover, since there were no differences in the expression of two vessel markers in the retina of NPY knockout mice versus controls at P14, NPY is also not involved in the delayed development of the intermediate and deep vascular plexus in the retina in this animal model.

Treatment Strategies of Adult Primary Focal Segmental Glomerulosclerosis: A Systematic Review Focusing on the Last Two Decades

Adult primary focal segmental glomerulosclerosis (FSGS) remains a therapeutic challenge for the treating physician. With the advent of novel immunosuppressive measures, our arsenal of therapeutic options increased considerably. The aim of this review was to summarize reports published over the last two decades which reported on treatment outcome. Most reports included patients with a steroid-resistant (SR) disease course, yet the cohort with the highest unmet need, since persistent nephrotic range proteinuria is associated with a poor renal prognosis and portends a high risk of developing end-stage renal disease. While in first-line treatment, steroid treatment remains the recommended standard with an overall remission rate of 50% and higher, optimal treatment strategies for steroid-dependent/multirelapsing (SD/MR) and SR patients have to be defined. In both entities, calcineurin inhibitors showed good efficacy, while mycophenolate mofetil was less effective in SR cases compared to those with SD/MR. The same was true for rituximab, a monoclonal antibody targeting B-cells. In resistant cases, addition of extracorporeal treatment options or treatment with alkylating agents may be considered. To shape the future for treatment of FSGS, international collaborations to conduct larger clinical trials are needed to identify potential novel efficacious immunosuppressive or immunomodulatory therapies.

Expression of a recombinant full-length LRP1B receptor in human non-small cell lung cancer cells confirms the postulated growth-suppressing function of this large LDL receptor family member

Low-density lipoprotein (LDL) receptor-related protein 1B (LRP1B), a member of the LDL receptor family, is frequently inactivated in multiple malignancies including lung cancer. LRP1B is therefore considered as a putative tumor suppressor. Due to its large size (4599 amino acids), until now only minireceptors or receptor fragments have been successfully cloned. To assess the effect of LRP1B on the proliferation of non-small cell lung cancer cells, we constructed and expressed a transfection vector containing the 13.800 bp full-length murine Lrp1b cDNA using a PCR-based cloning strategy. Expression of LRP1B was analyzed by quantitative RT-PCR (qRT-PCR) using primers specific for human LRP1B or mouse Lrp1b. Effective expression of the full length receptor was demonstrated by the appearance of a single 600 kDa band on Western Blots of HEK 293 cells. Overexpression of Lrp1b in non-small cell lung cancer cells with low or absent endogenous LRP1B expression significantly reduced cellular proliferation compared to empty vector-transfected control cells. Conversely, in Calu-1 cells, which express higher endogenous levels of the receptor, siRNA-mediated LRP1B knockdown significantly enhanced cellular proliferation. Taken together, these findings demonstrate that, consistent with the postulated tumor suppressor function, overexpression of full-length Lrp1b leads to impaired cellular proliferation, while LRP1B knockdown has the opposite effect. The recombinant Lrp1b construct represents a valuable tool to unravel the largely unknown physiological role of LRP1B and its potential functions in cancer pathogenesis.

Regression of left atrial diameter after kidney transplantation is associated with prolonged survival: an observational study

Renal transplantation reduces the dramatically elevated risk of cardiovascular death in dialysis patients. We previously showed that left atrial diameter before transplantation predicts cardiovascular and overall mortality. Now, we investigated the association of changes in cardiac morphology after transplantation and mortality. We retrospectively analyzed data from the Austrian transplant repository using multivariable Cox and competing risk models and multivariable logistic regression for the prediction of changes in cardiac morphology. We identified 414 patients with a median follow‐up of 8 years and observed a significant progression of mean diameter of left atrium (LA), right atrium and right ventricle and a significant regression of left ventricle. Complete case analysis of 243 patients with a regression of initially enlarged LA diameter had a significantly lower risk of adjusted overall and cardiovascular mortality; hazard ratio (HR 0.45, 95% CI 0.30–0.69, P < 0.001, 124 deaths), and HR of 0.43 [95% CI 0.21–0.92, P = 0.029, 48 cardiovascular (CV) deaths], respectively. Only age at transplantation was significantly associated with regression of LA (OR 0.75, 95% CI 0.60–0.93, P = 0.007). Patients with regression of LA after kidney transplantation exhibited a lower overall and CV mortality risk. Besides age, peritoneal dialysis and antihypertensive therapy were mediators of LA regression.

The novel angiogenic cytokine secretoneurin promotes angiogenesis, arteriogenesis and vasculogenesis in the mouse hind-limb ischemia model

Secretoneurin (SN) represents a sensory, inflammatory neuropeptide which was recently demonstrated to act as an angiogenic and vasculogenic cytokine in vitro and in vivo. The present study was conducted to test the hypothesis that SN may be implicated in reparative angiogenesis. Furthermore, we challenged the healing potential of SN applied as a newly generated SN gene therapy vector in the setting of limb ischemia.