Pulsed electric fields stimulate microglial transmitter release of VEGF, IL-8 and GLP-1 and activate endothelial cells through paracrine signaling.

As action potentials propagate along an axon, pulsed extracellular electric fields (E-fields) are induced. We investigated the role of E-fields in activating microglia cells and affecting capillary function and found that E-fields control human microglia secretions in concert with purinergic factors. We generated E-fields by applying transcranial pulsed electromagnetic fields (T-PEMF) identical to those appearing outside neurons as action potentials propagate. T-PEMF alone enhanced mRNA synthesis for VEGF, IL-8, IL-6 and the proglucagon gene as well as the PC1/3 enzyme that cleaves the proglucagon protein to glucagon and GLP-1 proteins. We found that T-PEMF enhanced secretion from microglia of VEGF, IL-8 and GLP-1 proteins having angiogenic and proliferative profiles. Interestingly, T-PEMF and purinergic transmitters together enhanced secretions confirming synergy between their actions. ATP also induced nitric oxide (NO) syntheses in distinct locations in the nucleus and the mRNA synthesis for the responsible iNOS was reduced by T-PEMF. When the microglia-secretory fluid was added to brain endothelial cells we saw vivid Ca2+ signaling and enhanced transcription of mRNA for IL-8 and VEGF. Our previous work shows that applying T-PEMF to the human brain provides up to 60% remission for patients with refractory depressions within 8 weeks and improvements for Parkinson patients. Thus, physiological E-fields activate microglia, work synergistically with neurotransmitters, and cause paracrine secretions which cause activation of capillaries. Application of these E-Fields is effective for treating refractory depressions and appear promising for treating neurodegenerative brain diseases.

Finasteride interferes with prostaglandin-induced CatSper signalling in human sperm.

Ca2+ signalling controls human sperm functions necessary for successful fertilization. Multiple endocrine-disrupting chemicals have been found to activate the CatSper Ca2+ channel and thereby interfering with Ca2+ signalling in human sperm. Finasteride is prescribed to men in the fertile age to treat hair loss and its use has been associated with impaired male fertility. Due to the structural relatedness of finasteride to the endogenous CatSper ligand progesterone, this study aimed to investigate whether finasteride affects human sperm in a progestogen-like manner. The effect of finasteride on Ca2+ signalling via CatSper in human sperm was investigated in cell suspensions by single-cell imaging. Additionally, effects on sperm penetration into viscous medium and acrosome reaction were assessed. Finasteride alone caused a minor transient rise in the intracellular, free Ca2+ concentration ([Ca2+]i) at physiologically relevant concentrations. Ca2+ signals induced by PGE1 were inhibited by finasteride displaying mixed type of inhibition consistent with multiple binding sites. Finasteride did not interfere with progesterone-induced Ca2+ signalling and no effect on acrosome reaction or sperm viability was found. Finasteride significantly decreased PGE1-induced penetration into viscous medium but in concentrations above what is measured in blood and seminal fluids during regular finasteride administration. In conclusion, the use of finasteride may affect Ca2+ signalling in human sperm through an interaction with the PGE1-binding site, but to which extend it alters the chances of a successful fertilization needs further investigation. It remains to be investigated whether finasteride administration may give rise to side effects by interfering with prostaglandin signalling elsewhere in the human body.

The Calcium-Sensing Receptor Is Essential for Calcium and Bicarbonate Sensitivity in Human Spermatozoa.

CONTEXT: The calcium-sensing receptor (CaSR) is essential to maintain a stable calcium concentration in serum. Spermatozoa are exposed to immense changes in concentrations of CaSR ligands such as calcium, magnesium, and spermine during epididymal maturation, in the ejaculate, and in the female reproductive environment. However, the role of CaSR in human spermatozoa is unknown. OBJECTIVE: This work aimed to investigate the role of CaSR in human spermatozoa. METHODS: We identified CaSR in human spermatozoa and characterized the response to CaSR agonists on intracellular calcium, acrosome reaction, and 3',5'-cyclic adenosine 5'-monophosphate (cAMP) in spermatozoa from men with either loss-of-function or gain-of-function mutations in CASR and healthy donors. RESULTS: CaSR is expressed in human spermatozoa and is essential for sensing extracellular free ionized calcium (Ca2+) and Mg2+. Activators of CaSR augmented the effect of sperm-activating signals such as the response to HCO3- and the acrosome reaction, whereas spermatozoa from men with a loss-of-function mutation in CASR had a diminished response to HCO3-, lower progesterone-mediated calcium influx, and were less likely to undergo the acrosome reaction in response to progesterone or Ca2+. CaSR activation increased cAMP through soluble adenylyl cyclase (sAC) activity and increased calcium influx through CatSper. Moreover, external Ca2+ or Mg2+ was indispensable for HCO3- activation of sAC. Two male patients with a CASR loss-of-function mutation in exon 3 presented with normal sperm counts and motility, whereas a patient with a loss-of-function mutation in exon 7 had low sperm count, motility, and morphology. CONCLUSION: CaSR is important for the sensing of Ca2+, Mg2+, and HCO3- in spermatozoa, and loss-of-function may impair male sperm function.

Transcranial low-frequency pulsating electromagnetic fields (T-PEMF) as post-concussion syndrome treatment.

BACKGROUND: Treatment options for the subgroup of people who develop long-lasting symptoms following mild traumatic brain injury are limited. Transcranial pulsating low-frequency electromagnetic stimulation (T-PEMF) in other patient groups has shown promising results in several studies with proposed neuroprotective and anti-inflammatory effects. OBJECTIVE: The present pilot study was conducted to access feasibility and tolerability of T-PEMF in treating post-concussion syndrome. METHODS: Seven patients with post-concussion syndrome received 5 weeks of daily 30 minutes T-PEMF treatment with evaluation after 2 and 5 weeks and 3 months after ending treatment. RESULTS: Compliance was high as all subject completed the full treatment. Two patients however experienced a worsening of their concussion symptoms during the course of treatment. The remaining patients had some discomfort in relation to treatment, mainly headache, but passing and less for each treatment. The majority (n = 5) had a reduction in symptoms overall, up to 61% (2%-61%) based on the Rivermead Post-Concussion Symptoms Questionnaire. CONCLUSION: Further studies on T-PEMF as a treatment option for post-concussion syndrome are warranted.

GLP-1 inhibits VEGFA-mediated signaling in isolated human endothelial cells and VEGFA-induced dilation of rat mesenteric arteries.

We investigated the acute effects of glucagon-like peptide-1 (GLP-1), GLP-1(1-36), and GLP-1(7-36) on vascular endothelial growth factor-A (VEGFA)-induced endothelium-dependent signaling and vasodilation. Our hypothesis was that GLP-1 released from intestinal l-cells modulates processes related to PLCγ activation, Src, and endothelial NOS (eNOS) signaling, thereby controlling endothelial vessel tone. By using RT-PCR analysis, we found mRNA for the GLP-1 receptor (GLP-1R) in human dermal microvascular endothelial cells (HDMEC), human retinal microvascular endothelial cells, and rat arteries. In isolated rat mesenteric resistance arteries precontracted with the thromboxane analog U46619 to 80-90% of maximum contraction, VEGFA (25 ng/ml) caused a small and gradual relaxation (28.9 ± 3.9%). Pretreatment of arteries with either GLP-1(1-36) (500 nM) or GLP-1(7-36) (1 nM) abolished the VEGFA-induced relaxation. VEGFA-induced relaxations were also inhibited in endothelial-denuded arteries and in arteries pretreated with the nitric oxide synthase (NOS) inhibitor, Nω-nitro-l-arginine methyl ester (100 µM). In vivo studies on male Wistar rats also revealed that GLP-1(7-36) inhibited VEGFA-induced vasodilation of the same arteries. In isolated endothelial cells, GLP-1(1-36) and GLP-1(7-36) caused a reduction in VEGFA-induced phosphorylation of PLCγ. Ca2+ imaging of endothelial cells and rat mesenteric resistance arteries using fura-2, revealed that both GLP-1 analogs caused a reduction in VEGFA-induced Ca2+ signaling. GLP-1(1-36) also reduced VEGFA-induced eNOS phosphorylation in HDMEC. In conclusion, GLP-1 reduced relaxation induced by VEGFA in resistance arteries by inhibiting VEGFR2-mediated Ca2+ signaling and endothelial NO synthesis. GLP-1, on its own, also induced phosphorylation of Src and ERK1/2 that can lead to proliferation and is implicated in vessel permeability.

The PDGF-BB-SOX7 axis-modulated IL-33 in pericytes and stromal cells promotes metastasis through tumour-associated macrophages.

Signalling molecules and pathways that mediate crosstalk between various tumour cellular compartments in cancer metastasis remain largely unknown. We report a mechanism of the interaction between perivascular cells and tumour-associated macrophages (TAMs) in promoting metastasis through the IL-33-ST2-dependent pathway in xenograft mouse models of cancer. IL-33 is the highest upregulated gene through activation of SOX7 transcription factor in PDGF-BB-stimulated pericytes. Gain- and loss-of-function experiments validate that IL-33 promotes metastasis through recruitment of TAMs. Pharmacological inhibition of the IL-33-ST2 signalling by a soluble ST2 significantly inhibits TAMs and metastasis. Genetic deletion of host IL-33 in mice also blocks PDGF-BB-induced TAM recruitment and metastasis. These findings shed light on the role of tumour stroma in promoting metastasis and have therapeutic implications for cancer therapy.

The Diagnostic Apathia Scale predicts a dose-remission relationship of T-PEMF in treatment-resistant depression.

OBJECTIVE: The aim of this study was to evaluate the predictive validity of the apathy subsyndrome in patients with therapy-resistant depression in the dose-remission study with transcranial pulsating electromagnetic fields (T-PEMF). METHODS: The apathy subsyndrome consists of the symptoms of fatigue, concentration and memory problems, lack of interests, difficulties in making decisions, and sleep problems. We evaluated 65 patients with therapy-resistant depression. In total, 34 of these patients received placebo T-PEMF in the afternoon and active T-PEMF in the morning, that is, one daily dose. The remaining 31 patients received active T-PEMF twice daily. Duration of treatment was 8 weeks in both groups. The Hamilton Depression Scale (HAM-D17) and the Bech-Rafaelsen Melancholia Scale (MES) were used to measure remission. We also focused on the Diagnostic Apathia Scale, which is based on a mixture of items from the MINI and the HAM-D17/MES. RESULTS: In patients without apathy, the remission rate after T-PEMF was 83.9% versus 58.8% in patients with apathy (p≤0.05). In patients without apathy receiving one active dose daily 94.4% remitted versus 50% for patients with apathy (p≤0.05). In patients without apathy who received two active doses 69.9% remitted versus 66.7% for patients with apathy (p≤0.05). CONCLUSION: Taking the baseline diagnosis of the apathy syndrome into consideration, we found that in patients without apathy one daily dose of T-PEMF is sufficient, but in patients with apathy two daily doses are necessary. Including the apathy syndrome as predictor in future studies would seem to be clinically relevant.

Dose-remission of pulsating electromagnetic fields as augmentation in therapy-resistant depression: a randomized, double-blind controlled study.

OBJECTIVE: To evaluate to what extent a twice daily dose of Transcranial Pulsating ElectroMagnetic Fields (T-PEMF) was superior to once daily in patients with treatment-resistant depression as to obtaining symptom remission after 8 weeks of augmentation therapy. METHODS: A self-treatment set-up of the T-PEMF device was used allowing self-administration by patients in own homes. All patients were treated for 30 min per T-PEMF session. The antidepressant medication the patients were receiving at baseline remained unchanged during the trial. The patients were randomised to either one T-PEMF dose (active dose in the morning and sham in the afternoon) or two T-PEMF doses (active dose both morning and afternoon) in a double-blind procedure. A score of 7 or less on the Hamilton Depression Scale (HAM-D17) was the criterion of remission. RESULTS: In total 34 patients received active T-PEMF once a day and 31 patients twice daily. After 5 weeks of therapy remission was obtained in 26.5% and 32.3% on one dose and two doses of T-PEMF, respectively. After 8 weeks the rate of remission was 73.5% and 67.7%, respectively. The side effects as measured by the Udvalget for Kliniske Undersøgelser scale showed a better toleration of the antidepresssive medication in both treatment groups, which was reflected by the WHO-5 well-being scale with increased scores in both groups of patients. CONCLUSION: The high remission rate obtained by the T-PEMF augmentation was not a dose effect (one versus two daily T-PEMF sessions) but was explained by the extension of the treatment period from 5 to 8 weeks.

TNFR1 mediates TNF-α-induced tumour lymphangiogenesis and metastasis by modulating VEGF-C-VEGFR3 signalling.

Inflammation and lymphangiogenesis are two cohesively coupled processes that promote tumour growth and invasion. Here we report that TNF-α markedly promotes tumour lymphangiogenesis and lymphatic metastasis. The TNF-α-TNFR1 signalling pathway directly stimulates lymphatic endothelial cell activity through a VEGFR3-independent mechanism. However, VEGFR3-induced lymphatic endothelial cell tips are a prerequisite for lymphatic vessel growth in vivo, and a VEGFR3 blockade completely ablates TNF-α-induced lymphangiogenesis. Moreover, TNF-α-TNFR1-activated inflammatory macrophages produce high levels of VEGF-C to coordinately activate VEGFR3. Genetic deletion of TNFR1 (Tnfr1(-/-)) in mice or depletion of tumour-associated macrophages (TAMs) virtually eliminates TNF-α-induced lymphangiogenesis and lymphatic metastasis. Gain-of-function experiments show that reconstitution of Tnfr1(+/+) macrophages in Tnfr1(-/-) mice largely restores tumour lymphangiogenesis and lymphatic metastasis. These findings shed mechanistic light on the intimate interplay between inflammation and lymphangiogenesis in cancer metastasis, and propose therapeutic intervention of lymphatic metastasis by targeting the TNF-α-TNFR1 pathway.

IL-17A potentiates TNFα-induced secretion from human endothelial cells and alters barrier functions controlling neutrophils rights of passage.

Interleukin-17A (IL-17A) is an important pro-inflammatory cytokine that regulates leukocyte mobilization and recruitment. To better understand how IL-17A controls leukocyte trafficking across capillaries in the peripheral blood circulation, we used primary human dermal microvascular endothelial cells (HDMEC) to investigate their secretory potential and barrier function when activated with IL-17A and TNFα. Activation by TNFα and IL-17A causes phosphorylation of p38 as well as IκBα whereby NFκB subsequently becomes phosphorylated, a mechanism that initiates transcription of adhesion molecules such as E-selectin. Members of the neutrophil-specific GRO-family chemokines were significantly up-regulated upon IL-17A stimulation on the mRNA and protein level, whereas all tested non-neutrophil-specific chemokines remained unchanged in comparison. Moreover, a striking synergistic effect in the induction of granulocyte colony-stimulating factors (G-CSF) was elicited when IL-17A was used in combination with TNFα, and IL-17A was able to significantly augment the levels of TNFα-induced E-selectin and ICAM-1. In accordance with this observation, IL-17A was able to markedly increase TNFα-induced neutrophil adherence to HDMEC monolayers in an in vitro adhesion assay. Using a trans-well migration assay with an HDMEC monolayer as a barrier, we here show that pre-stimulating the endothelial cells with TNFα and IL-17A together enhances the rate of neutrophil transmigration compared to TNFα or IL-17A alone. These results show that IL-17A and TNFα act in cooperation to facilitate neutrophil migration across the endothelial cell barrier. In addition, the synergistic actions of IL-17A with TNFα to secrete G-CSF appear to be important for mobilizing neutrophils from the bone marrow to the blood stream.

IL-27 inhibits lymphatic endothelial cell proliferation by STAT1-regulated gene expression.

OBJECTIVE: IL-27 belongs to the IL-12 family of cytokines and is recognized for its role in Th cell differentiation and as an inhibitor of tumor angiogenesis. The purpose of this study was to investigate the effect of IL-27 on proliferation of lymphatic endothelial cells to gain insight into the interplay between the immune system and development of the lymphatic system. METHODS: IL-27-stimulated signal transduction in human dermal lymphatic endothelial cells was measured by western blotting and synthesis of CXCL10 and CXCL11 by use of RT-PCR and ELISA. Proliferation was measured using MTT and BrdU kits and the role of STAT1 and chemokines was determined by use of siRNA and recombinant proteins. RESULTS: Stimulation of lymphatic endothelial cell cultures with IL-27 induced JAK dependent phosphorylation of STAT1 and STAT3 and inhibited lymphatic endothelial cell proliferation and migration. Expression of CXCL10 and CXCL11, both STAT1 target genes, was profoundly up-regulated upon IL-27 stimulation, and recombinant CXCL10 and CXCL11 inhibited FGF-2-induced proliferation in vitro. siRNA targeting of STAT1 almost completely abrogated CXCL10 and CXCL11 expression as well as the proliferative effect of IL-27. CONCLUSIONS: IL-27 function as an anti-lymphangiogenic regulator in vitro by up-regulating chemokines and interfering with the mitogenic effect of growth factors through STAT1 activation.

Collaborative interplay between FGF-2 and VEGF-C promotes lymphangiogenesis and metastasis.

Interplay between various lymphangiogenic factors in promoting lymphangiogenesis and lymphatic metastasis remains poorly understood. Here we show that FGF-2 and VEGF-C, two lymphangiogenic factors, collaboratively promote angiogenesis and lymphangiogenesis in the tumor microenvironment, leading to widespread pulmonary and lymph-node metastases. Coimplantation of dual factors in the mouse cornea resulted in additive angiogenesis and lymphangiogenesis. At the molecular level, we showed that FGFR-1 expressed in lymphatic endothelial cells is a crucial receptor that mediates the FGF-2-induced lymphangiogenesis. Intriguingly, the VEGFR-3-mediated signaling was required for the lymphatic tip cell formation in both FGF-2- and VEGF-C-induced lymphangiogenesis. Consequently, a VEGFR-3-specific neutralizing antibody markedly inhibited FGF-2-induced lymphangiogenesis. Thus, the VEGFR-3-induced lymphatic endothelial cell tip cell formation is a prerequisite for FGF-2-stimulated lymphangiogenesis. In the tumor microenvironment, the reciprocal interplay between FGF-2 and VEGF-C collaboratively stimulated tumor growth, angiogenesis, intratumoral lymphangiogenesis, and metastasis. Thus, intervention and targeting of the FGF-2- and VEGF-C-induced angiogenic and lymphangiogenic synergism could be potentially important approaches for cancer therapy and prevention of metastasis.

Non-genomic effects of vitamin D in human spermatozoa.

The spectrum for vitamin D (VD) mediated effects has expanded in recent years. Activated VD (1,25(OH)(2)D(3)) binds to the VD receptor (VDR) and mediates non-genomic effects through the alternative ligand binding-pocket (VDR-ap) or regulates gene transcription through the genomic binding-pocket. VDR and VD-metabolizing enzymes are expressed in human testis, male reproductive tract and mature spermatozoa, and VD is considered important for male reproduction. Expression of the VD-inactivating enzyme CYP24A1 at the annulus of human spermatozoa distinguish normal and infertile men with high specificity, and CYP24A1 expression is positively correlated with all semen variables and suggested as a marker for both semen quality and VD responsiveness. Moreover, spermatozoa are transcriptionally silent and are therefore a unique model to study non-genomic effects. 1,25(OH)(2)D(3) induced a rapid increase in intracellular calcium concentration [Ca(2+)](i) in human spermatozoa. The [Ca(2+)](i) increase was abrogated by the non-genomic VDR antagonist 1ß,25(OH)(2)D(3), while the specific agonist for VDR-ap (JN) increased [Ca(2+)](i) with similar kinetics as 1,25(OH)(2)D(3). The rise in [Ca(2+)](i) originated as a Ca(2+)-release from intracellular stores since inhibition of phospholipase-C diminished the 1,25(OH)(2)D(3) mediated Ca(2+) response, while suspending spermatozoa in a nominally Ca(2+)-free medium did not affect the VD mediated Ca(2+) rise. The spatio-temporal kinetics of the VD-response differed from the progesterone-mediated increase in [Ca(2+)](i) as the VD-mediated Ca(2+) rise was not observed in the tail region and was independent of extracellular Ca(2+). A functional role of the VD-mediated Ca(2+) increase was supported by showing that 1,25(OH)(2)D(3) increased sperm motility and induced the acrosome reaction in vitro.

Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa.

BACKGROUND: The vitamin D receptor (VDR) is expressed in human spermatozoa, and VDR-knockout mice and vitamin D (VD) deficiency in rodents results in impaired fertility, low sperm counts and a low number of motile spermatozoa. We investigated the role of activated VD (1,25(OH)(2)D(3)) in human spermatozoa and whether VD serum levels are associated with semen quality. METHODS: Cross-sectional association study of semen quality and VD serum level in 300 men from the general population, and in vitro studies on spermatozoa from 40 men to investigate the effects of VD on intracellular calcium, sperm motility and acrosome reaction. All men delivered samples for routine semen analysis and blood for measurements of follicle stimulating hormone, Inhibin B, 25-hydroxy-VD, albumin, alkaline phosphatase, calcium and parathyroid hormone (PTH). RESULTS: In the association study, 44% were VD insufficient (<50 nM), and VD was inversely correlated with PTH (P < 0.0005). VD serum levels correlated positively with sperm motility and progressive motility (P < 0.05), and men with VD deficiency (<25 nM) had a lower proportion of motile (P = 0.027), progressive motile (P = 0.035) and morphologically normal spermatozoa (P = 0.044) compared with men with high VD levels (>75 nM). 1,25(OH)(2)D(3) increased intracellular calcium concentration in human spermatozoa through VDR-mediated calcium release from an intracellular calcium storage, increased sperm motility and induced the acrosome reaction in vitro. CONCLUSIONS: 1,25(OH)(2)D(3) increased intracellular calcium concentration, sperm motility and induced the acrosome reaction in mature spermatozoa, and VD serum levels were positively associated with sperm motility, suggesting a role for VD in human sperm function.

VEGFR1-mediated pericyte ablation links VEGF and PlGF to cancer-associated retinopathy.

VEGF coordinates complex regulation of cellular regeneration and interactions between endothelial and perivascular cells; dysfunction of the VEGF signaling system leads to retinopathy. Here, we show that systemic delivery of VEGF and placental growth factor (PlGF) by protein implantation, tumors, and adenoviral vectors ablates pericytes from the mature retinal vasculature through the VEGF receptor 1 (VEGFR1)-mediated signaling pathway, leading to increased vascular leakage. In contrast, we demonstrate VEGF receptor 2 (VEGFR2) is primarily expressed in nonvascular photoreceptors and ganglion cells. Moreover, blockade of VEGFR1 but not VEGFR2 significantly restores pericyte saturation in mature retinal vessels. Our findings link VEGF and PlGF to cancer-associated retinopathy, reveal the molecular mechanisms of VEGFR1 ligand-mediated retinopathy, and define VEGFR1 as an important target of antiangiogenic therapy for treatment of retinopathy.

IL-20 activates human lymphatic endothelial cells causing cell signalling and tube formation.

IL-20 is an arteriogenic cytokine that remodels collateral networks in vivo, and plays a role in cellular organization. Here, we investigate its role in lymphangiogenesis using a lymphatic endothelial cell line, hTERT-HDLEC, which expresses the lymphatic markers LYVE-1 and podoplanin. Upon stimulation of hTERT-HDLEC with IL-20, we found an increase in the intracellular free calcium concentration, in Akt and eNOS phosphorylations as well as in perinuclear NO production. We found that eNOS phosphorylation and NO synthesis are highly dependent on the PI3K/Akt signalling pathway. We also found an IL-20 induced phosphorylation of Erk1/2 and mTOR, and using the MEK inhibitor PD98059 and mTOR complex inhibitor rapamycin we demonstrated the importance of these signalling pathways in IL-20-mediated proliferation. IL-20 triggered actin polymerization and morphological changes resulting in elongated cell structures, and in matrigels, IL-20 caused tube formations of hTERT-HDLEC in a PI3K- and mTOR dependent way. In a sprouting assay we found that IL-20 caused cell migration within 24 h at a rate comparable to VEGF-C, and this migration could be inhibited by wortmannin and rapamycin. These data show that IL-20 activates cell signalling resulting in lymphangiogenic processes including migration, proliferation and tube formation. Thus, IL-20 is a cytokine that has the potential of activating or modulating the formation of lymphatic vessels.

IL-20 is an arteriogenic cytokine that remodels collateral networks and improves functions of ischemic hind limbs.

Successful therapeutic angiogenesis for the treatment of ischemic disorders relies on selection of optimal proangiogenic or arteriogenic agents that are able to promote establishment of functional collateral networks. Here, we show that IL-20, a pleiotropic inflammatory cytokine, displays an imperative effect on vascular remodeling. Stimulation of both large and microvascular endothelial cells with IL-20 leads to activation of receptor-dependent multiple intracellular signaling components, including increased phosphorylation levels of JAK2/STAT5, Erk1/2, and Akt; activation of small GTP-binding proteins Rac and Rho; and intracellular release of calcium. Surprisingly, IL-20 significantly promotes endothelial cell tube formation without affecting their proliferation and motility. These findings suggest that the vascular function of IL-20 involves endothelial cell organization, vessel maturation, and remodeling. Consistent with this notion, delivery of IL-20 to the ischemic muscle tissue significantly improves arteriogenesis and blood perfusion in a rat hind-limb model. Our findings provide mechanistic insights on vascular functions of IL-20 and define therapeutic implication of this cytokine for the treatment of ischemic disorders.

Nerve growth factor activates aorta endothelial cells causing PI3K/Akt- and ERK-dependent migration.

Nerve growth factor (NGF) is a well-known neurotrophin. We determined whether NGF can activate endothelial cell migration and signalling that underlie angiogenic processes. We showed that aorta endothelial cells express mRNA for both the receptor tyrosine kinase TrkA and the p75 neurotrophin receptor (p75NTR) that associates with TrkA when signalling occurs. Pig aortic endothelial cells migrated when exposed to an NGF gradient, due to the simultaneous activation of the phosphatidylinositol 3-kinase and extracellular signal-regulated kinase signalling pathways. Furthermore, morphological changes were found in migrating cells: they appear with elongated structures with a smaller cell volume than control cells. Our data show that NGF is an activator of endothelial cells and suggest that NGF plays a role in mediating angiogenesis.

PDGF-BB induces intratumoral lymphangiogenesis and promotes lymphatic metastasis.

Cancer metastases are commonly found in the lymphatic system. Like tumor blood angiogenesis, stimulation of tumor lymphangiogenesis may require the interplay of several tumor-derived growth factors. Here we report that members of the PDGF family act as lymphangiogenic factors. In vitro, PDGF-BB stimulated MAP kinase activity and cell motility of isolated lymphatic endothelial cells. In vivo, PDGF-BB potently induced growth of lymphatic vessels. Expression of PDGF-BB in murine fibrosarcoma cells induced tumor lymphangiogenesis, leading to enhanced metastasis in lymph nodes. These data demonstrate that PDGF-BB is an important growth factor contributing to lymphatic metastasis. Thus, blockage of PDGF-induced lymphangiogenesis may provide a novel approach for prevention and treatment of lymphatic metastasis.

Small GTP-binding protein Rac is an essential mediator of vascular endothelial growth factor-induced endothelial fenestrations and vascular permeability.

BACKGROUND: Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) induces both angiogenesis and vascular permeability. Although its angiogenic activity has been well characterized, the signaling pathways of VEGF-induced permeability remain poorly understood. METHODS AND RESULTS: Using the mouse corneal micropocket assay, Miles assay, and a combination of cytochemical, electron microscopic, and biochemical assays, we demonstrate that VEGF-induced vascular leakage partly can be separated from its angiogenic activity. VEGF but not FGF-2 induced capillaries with a highly fenestrated endothelium, a feature linked with increased vascular permeability. A cell-permeable Rac antagonist (TAT-RacN17) converted VEGF-induced, leaky vascular plexuses into well-defined vascular networks. In addition, this Rac mutant blocked formation of VEGF-induced endothelial fenestrations and vascular permeability but only partially inhibited angiogenesis. Studies on endothelial cell cultures further revealed that VEGF stimulated phosphorylation of VEGF receptor-2 (VEGFR-2), leading to activation of Rac as well as increased phosphorylation of phospholipase Cgamma (PLCgamma), protein kinase B (Akt), endothelial nitric oxide synthase (eNOS), and extracellular regulated kinase (Erk1/2). We further found that phosphatidylinositol-3-OH kinase (PI3K) acted upstream of Rac and Akt-eNOS in VEGF/VEGFR-2 signaling. CONCLUSIONS: Our findings indicate that the small GTP-binding protein Rac is a key component in mediation of VEGF-induced vascular permeability but less so in neovascularization. This may have conceptual implications for applying Rac antagonists in treatment and prevention of VEGF-induced vascular leakage and edema in connection with ischemic disorders.