Are plasma VEGF and its soluble receptor sFlt-1 atherogenic risk factors? Cross-sectional data from the SAPHIR study.

AIMS: Vascular endothelial growth factor (VEGF) is a potent hypoxia-regulated angiogenic factor. Its soluble receptor soluble (s)Flt-1 binds VEGF with high affinity inhibiting the angiogenic function of VEGF. The role of circulating VEGF in atherosclerosis is unclear. METHODS AND RESULTS: In 909 healthy subjects (511 male, 398 female) from the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) we determined fasting plasma VEGF and sFlt-1 concentration, cardiovascular risk factors and carotid atherosclerosis. VEGF levels were lower and sFlt-1 levels higher in men than in women. VEGF and sFlt-1 showed a positive correlation. In the entire population VEGF correlated positively with age, BMI, insulin resistance, white blood cell and platelet count, C-reactive protein (CRP) and carotid intima media thickness (IMT). After adjustment for age, VEGF showed a weak positive correlation with BMI, liver enzymes, CRP and platelet count in males. In females VEGF correlated negatively with LDL-cholesterol and positively with insulin resistance and platelet count. After adjustment for age, no significant correlation with carotid atherosclerosis could be detected. CONCLUSION: Plasma VEGF and sFlt-1 are only weakly correlated with cardiovascular risk factors, suggesting that circulating VEGF levels do have only a minor impact on the development of atherosclerosis.

Antithrombin and near-fatal exertional heat stroke.

Heat waves result in excess deaths, excess emergency department visits, and intensive care unit admissions for heat stroke. We describe the clinical features and 3-month outcome of a patient with near-fatal heat stroke, admitted to our intensive care unit in July, 2001. After heavily working for hours at a construction site during a heat wave, the 28-year-old male presented with 41.4 degrees C body temperature and multiorgan failure, consisting of neurological impairment, rhabdomyolysis, acute renal failure, disseminated intravascular coagulation, and acute respiratory distress syndrome (ARDS). In the first week there was no evidence of infection. Treatment included cooling, aggressive volume resuscitation, administration of antithrombin-III concentrates and steroids. The patient survived and recovered normal neurological, renal, respiratory and haematological function, and no disability persisted. This case illustrates survival and complete recovery after multiorgan failure in heat stroke with vigorous intensive care. Treatment with antithrombin and steroids and may well have contributed to the favourable outcome. Correction of reduced antithrombin III levels to supranormal by therapeutic administration of antithrombin III concentrate in disseminated intravascular coagulation of heat stroke was not associated with any bleeding complications.

The role of immune activation in endotoxin-induced atherogenesis.

Some infectious agents may contribute to atherosclerosis by maintaining a heightened state of inflammatory response. Although the risk for atherosclerosis was associated with elevated plasma levels of endotoxin, it is difficult to firmly establish what place endotoxin assumes in the etiology of this disease. As the ability for endotoxin to promote disease may depend on its ability to initiate an inflammatory response, it may be controlled by additional regulatory factors. We measured plasma levels of endotoxin and serum levels of neopterin and soluble interleukin-2 receptor in a random population of 402 men and women, 50-79 years old at the 1990 baseline evaluation (Bruneck Study). End point of the prospective survey was incident (early) atherosclerosis in the carotid arteries as assessed with duplex ultrasound. Subjects with high endotoxin levels (90th percentile) in combination with low neopterin or soluble interleukin-2 receptor levels (below median) did not differ from those with low endotoxin in their risk of incident atherosclerosis. The risk associated with high endotoxin, however, was markedly elevated in subjects with high (above median) neopterin or soluble interleukin-2 receptor levels. The study provides epidemiological evidence that the atherogenic potential of endotoxemia is affected by concomitant immune activation.

Overexpression of p27(Kip1) by doxycycline-regulated adenoviral vectors inhibits endothelial cell proliferation and migration and impairs angiogenesis.

Formation of new blood vessels in the adult animal (i.e., angiogenesis) is an important event for tissue repair and for tumor growth and metastasis. Angiogenesis involves the migration and proliferation of endothelial cells. We have investigated the role of the growth suppressor p27(Kip1) (p27) on endothelial cell function in vitro and angiogenesis in vivo. We have generated Ad-TetON, a replication-deficient adenovirus that constitutively expresses the reverse tet-responsive transcriptional activator, and Ad-TRE-p27, which drives expression of p27 under the control of the tet response element. Western blot analysis demonstrated doxycycline-dependent overexpression of p27 in human umbilical vein endothelial cells (HUVECs) coinfected with Ad-TetON and Ad-TRE-p27, which resulted in a marked inhibition of DNA replication and cell migration in vitro. Inducible overexpression of p27 in cultured HUVECs inhibited the formation of tubelike structures and, when applied in a murine model of hind limb ischemia, reduced hind limb blood flow recovery and capillary density. These findings thus underscore a novel role of p27 in regulating endothelial cell migration in vitro and angiogenesis in vivo, suggesting a novel anti-angiogenic therapy based on inducible p27 overexpression.

Reversal of experimental diabetic neuropathy by VEGF gene transfer.

The pathogenetic basis for diabetic neuropathy has been enigmatic. Using two different animal models of diabetes, we have investigated the hypothesis that experimental diabetic neuropathy results from destruction of the vasa nervorum and can be reversed by administration of an angiogenic growth factor. Nerve blood flow, as measured by laser Doppler imaging or direct detection of a locally administered fluorescent lectin analogue, was markedly attenuated in rats with streptozotocin-induced diabetes, consistent with a profound reduction in the number of vessels observed. A severe peripheral neuropathy developed in parallel, characterized by significant slowing of motor and sensory nerve conduction velocities, compared with nondiabetic control animals. In contrast, 4 weeks after intramuscular gene transfer of plasmid DNA encoding VEGF-1 or VEGF-2, vascularity and blood flow in the nerves of treated animals were similar to those of nondiabetic control rats; constitutive overexpression of both transgenes resulted in restoration of large and small fiber peripheral nerve function. Similar experiments performed in a rabbit model of alloxan-induced diabetes produced comparable results. These findings support the notion that diabetic neuropathy results from microvascular ischemia involving the vasa nervorum and suggest the feasibility of a novel treatment strategy for patients in whom peripheral neuropathy constitutes a secondary complication of diabetes.

Plasma-induced endothelial activation associated with incident atherosclerosis: prospective results from the Bruneck Study.

BACKGROUND: Whether systemic inflammation is an epiphenomenon of atherosclerosis or whether it is part of the atherosclerosis causal pathway requires further study. DESIGN: As part of a prospective population survey on the course and aetiology of atherosclerosis, we investigated the effects of plasma on the endothelial monolayers inducing activation for leukocyte transmigration. METHODS: An age- and sex-stratified random sample of inhabitants of Bruneck (Italy) with and without atherosclerotic disease aged 50-69 years was selected. Carotid arteries were evaluated by duplex sonography at baseline (1990). Carotid arteries were re-evaluated for the development of new plaques 5 years later (1995). Frozen plasma samples from baseline were available for a random sample of 152 men. Monolayers of endothelial cells cultured in micropore filter insets were pre-treated with plasma, then normal human neutrophils were added to the endothelial cells and subsequent transmigration through the monolayers and micropore filters was measured. RESULTS: The endothelial monolayers were activated for transmigration of leukocytes more potently by plasma from participants with carotid artery plaques than participants without it. Increased endothelial activation with plasma at baseline was associated with the development of new atherosclerotic lesions during a period of 5 years. CONCLUSIONS: Plasma from individuals with prevalent atherosclerosis of the carotid arteries activates the endothelium for leukocyte transmigration, suggesting the presence of systemic pro-inflammatory mediators. In an epidemiological survey, follow-up data on new lesion formation after 5 years indicated that plasma-mediated endothelium activation for interaction with leukocytes precedes the development of atherosclerotic lesions.

LST1: a gene with extensive alternative splicing and immunomodulatory function.

The gene of the leukocyte-specific transcript (LST1) is encoded within the TNF region of the human MHC. The LST1 gene is constitutively expressed in leukocytes and dendritic cells, and it is characterized by extensive alternative splicing. We identified 7 different LST1 splice variants in PBMC; thus, 14 LST1 splice variants (LST1/A-LST1/N) have been detected in various cell types. These isoforms code for transmembrane as well as soluble LST1 proteins characterized by two alternative open reading frames at their 3' end. We demonstrate the presence of the transmembrane variant LST1/C on the cell surface of the monocytic cell lines U937 and THP1. Recombinant expression of LST1/C permitted its profound inhibitory effect on lymphocyte proliferation to be observed. In contrast, the alternative transmembrane variant LST1/A, the extracellular domain of which shows no amino acid sequence homology to LST1/C exerted a weaker but similar inhibitory effect on PBMC. These data demonstrate the protein expression of LST1 on the cell surface of mononuclear cells, and they show an inhibitory effect on lymphocyte proliferation of two LST1 proteins although they have only a very short amino acid homology.

Favorable effect of VEGF gene transfer on ischemic peripheral neuropathy.

Ischemic peripheral neuropathy is a frequent, irreversible complication of lower extremity vascular insufficiency. We investigated whether ischemic peripheral neuropathy could be prevented and/or reversed by gene transfer of an endothelial cell mitogen designed to promote therapeutic angiogenesis. Intramuscular gene transfer of naked DNA encoding vascular endothelial growth factor (VEGF) simultaneously with induction of hindlimb ischemia in rabbits abrogated the substantial decrease in motor and sensory nerve parameters, and nerve function recovered promptly. When gene transfer was administered 10 days after induction of ischemia, nerve function was restored earlier and/or recovered faster than in untreated rabbits. These findings are due in part to enhanced hindlimb perfusion. In addition, however, the demonstration of functional VEGF receptor expression by Schwann cells indicates a direct effect of VEGF on neural integrity as well. These findings thus constitute a new paradigm for the treatment of ischemic peripheral neuropathy.

Association of endotoxemia with carotid atherosclerosis and cardiovascular disease: prospective results from the Bruneck Study.

OBJECTIVES: Focus of the current study was on the significance of bacterial endotoxin, which shows a variety of pro-atherogenic properties and may occur at high concentration in the circulation of infected subjects. BACKGROUND: The possibility of an infectious risk factor in atherogenesis and cardiovascular disease has stimulated research interest, but the nature of such process remains obscure. METHODS: We measured plasma endotoxin levels (LAL assay) in a random population of 516 men and women 50 to 79 years old at the 1990 baseline evaluation (Bruneck Study). End points of this prospective survey were incident (early) atherosclerosis in the carotid arteries as assessed with high-resolution Duplex ultrasound (five-year follow-up rate, 98%) and incident cardiovascular disease (follow-up rate, 100%). RESULTS: Median endotoxin concentration amounted to 14.3 pg/ml (range, 6.0 to 209.2 pg/ml). Subjects with levels beyond 50 pg/ml (90th percentile) faced a threefold risk of incident atherosclerosis (odds ratio [95% confidence interval] 2.9 [1.4-6.3]; p < 0.01). The risk associated with high endotoxin was most pronounced in subjects with chronic infections and in current and ex-smokers. Notably, smokers with low endotoxin levels and nonsmokers did not differ in their atherosclerosis risk, whereas smokers with high levels almost invariably developed new lesions. All findings emerged as independent of vascular risk factors. Similar results were obtained for incident cardiovascular disease. CONCLUSIONS: The current study yields first epidemiologic evidence that endotoxemia constitutes a strong risk factor of early atherogenesis in subjects with chronic or recurrent bacterial infections and a link in the association between cigarette smoking and atherosclerotic disease.

Mediator-dependent effects of pentoxifylline on endothelium for transmigration of neutrophils.

In the present study, we investigated the effects of the anti-inflammatory drug pentoxifylline (PTX) on activation of endothelial cells for enhanced adhesion and transmigration of neutrophils by lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF), interleukin-1 (IL-1) and granulocyte colony-stimulating factor (G-CSF). To evaluate the mechanism by which PTX exerts its effect, human umbilical vein endothelial cells (HUVEC) were pretreated with theophylline, 2'-O-dibutyryl-3', 5'-cyclic adenosine monophosphate (db cAMP), and 3-isobutyl-1-methylxanthine, respectively, prior to stimulation. Pretreatment of HUVEC with PTX significantly antagonized TNF-, IL-1-, and G-CSF-activated transmigration of neutrophils. Additive stimulatory effects of PTX were seen with LPS. With the exception of theophylline, all other test cAMP-raising agents stimulated transmigration in similar fashion to PTX. Upon stimulation with TNF or LPS, HUVEC produced IL-8 and PTX affected this process in opposing fashions, with inhibition of the effects of TNF and augmentation of those of LPS. These results demonstrate that PTX differentially affects mediator-induced activation of HUVEC. The present IL-8 dependent and cAMP-regulated augmentation of LPS-induced stimulation of transmigration is the first description of an additive effect of PTX with a pro-inflammatory agent.

Secretoneurin and neurogenic inflammation.

AIM: Review of evidence that the 33-amino-acid polypeptide secretoneurin, which is generated by proteolytic cleavage of secretogranin II, plays a role in neurogenic inflammation. METHODS: Survey of the literature using a MEDLINE search database. RESULTS: Secretoneurin is synthesized in spinal ganglia, transported through the dorsal roots and stored in the axon terminals of primary afferent neurons. Investigations using capsaicin suggest that secretoneurin functions as an excitatory transmitter. Secretoneurin specifically activates various cell functions including the chemotactic migration of monocytes, eosinophils, fibroblasts, smooth muscle cells, and endothelial cells, which suggests that the peptide may modulate inflammatory reactions. Secretoneurin receptors have been functionally characterized. They are G-proteins linked and effects are abrogated by inhibition of protein kinase C. CONCLUSION: With actions as diverse as those seen with other mediators such as tachykinins, secretoneurin may be considered another sensory neuropeptide with modulatory potential in neurogenic inflammation.

Association of high plasma antioxidant capacity with new lesion formation in carotid atherosclerosis: a prospective study.

BACKGROUND: In atherosclerosis, both reductions and elevations in plasma levels of antioxidants have been reported. This study investigated total antioxidant capacity of plasma from subjects with atherosclerotic disease. MATERIALS AND METHODS: The study population consisted of 48 men with or without carotid atherosclerosis. At baseline (1990) carotid arteries were evaluated by duplex sonography and plasma samples were obtained for testing antioxidant capacity by two different test systems. One assay system used neutrophils from healthy volunteers as a source of oxygen free radicals activating the non-fluorescent dichlorofluorescin diacetate in the presence of antioxidant containing plasma from study subjects. In the other test system, total plasma antioxidants were detected colorimetrically by using 2,2'-azino-di-(3-ethylbenzthiazoline sulphonate), metmyoglobin and superoxide in the presence of plasma. Carotid arteries were re-evaluated for the development of new plaques 5 years later (1995). RESULTS: Increased baseline total antioxidant capacity of plasma was significantly associated with the development of new atherosclerotic lesions during a period of 5 years. CONCLUSIONS: Endogenous antioxidant capacity of plasma is increased in patients with active atherosclerotic disease. As scavenging of oxygen free radicals is thought to protect from atherogenesis, elevated antioxidative capacity may represent an adaptive mechanism.

Release of chemoattractants for human monocytes from endothelial cells by interaction with neutrophils.

OBJECTIVE: The release of monocyte chemoattractant protein-1 (MCP-1) in the vessel wall may lead to accumulation of monocytes in the subendothelial space. The role of neutrophils (PMNL) in the initiation of this process is unknown. We tested whether PMNL are able to induce the production and release of MCP-1 in endothelial cells. METHODS: PMNL were allowed to interact with human umbilical vein endothelial cell (HUVEC) monolayers in culture. Culture media were collected and assessed for chemotactic activity on mononuclear leukocytes (MNC) or purified monocytes in a modified Boyden chamber assay. Additionally, MCP-1 levels in supernatants were quantified by ELISA. RESULTS: Media from unstimulated HUVEC culture supernatants induced a slight increase (1.2-fold) of MNC and purified monocyte chemotaxis, which was significantly augmented by addition of PMNL for 1 h (1.4-fold; P < 0.05). The increase in chemotaxis was time- and dose-dependent and could be blocked by an anti-MCP-1 monoclonal antibody. Media obtained after coculture of PMNL and HUVEC for 1-5 h contained increased amounts of MCP-1 as measured by ELISA; addition of cycloheximide abolished this response. CONCLUSIONS: Interaction of PMNL with endothelium induces the release of functionally active MCP-1 suggesting that in the vascular wall, PMNL may play a role in the recruitment of MNC.

Decreased levels of beta-endorphin in circulating mononuclear leukocytes from patients with acute myocardial infarction.

Lymphocytes can be activated to produce and release opioid peptides. We investigated the levels of immunoreactive beta-endorphin in peripheral blood mononuclear cells from 11 patients with acute myocardial infarction. The concentrations of beta-endorphin in mononuclear leukocytes of 30.2 +/- 6.9 pg/10(6) cells on admission were in the normal range of 20-40 pg/10(6) cells and decreased significantly to 6.9 +/- 1.9 pg/10(6) cells after 48 h (p < 0.05). Decreased levels of mononuclear leukocyte-associated beta-endorphin in acute myocardial infarction may be due to the release of endogenous opioid after stimulation by stress and acute-phase reactants and play a role in inflammation and pain.

Effect of inhibitors of Na+/H+-exchange and gastric H+/K+ ATPase on cell volume, intracellular pH and migration of human polymorphonuclear leucocytes.

1. Stimulation of chemotaxis of human polymorphonuclear leucocytes (PMNs) with the chemoattractive peptide fMLP (N-formyl-Met-Leu-Phe) is paralleled by profound morphological and metabolic alterations like changes of intracellular pH (pHi) and cell shape. The present study was performed to investigate the interrelation of cell volume (CV) regulatory ion transport, pHi and migration of fMLP stimulated PMNs. 2. Addition of fMLP to PMNs stimulated directed migration in Boyden chamber assays and was accompanied by rapid initial intracellular acidification and cell swelling. 3. Inhibition of the Na+/H+ exchanger suppressed fMLP stimulated cell migration, accelerated the intracellular acidification and inhibited the fMLP-induced cell swelling. 4. Step omission of extracellular Na+ caused intracellular acidification, which was accelerated by subsequent addition of gastric H+/K+ ATPase inhibitor SCH 28080, or by omission of extracellular K+ ions. In addition Na+ removal caused cell swelling, which was further enhanced by fMLP. 5. H+/K+ATPase inhibitors omeprazole and SCH 28080 inhibited stimulated migration and blunted the fMLP-induced increase in CV. 6. Increasing extracellular osmolarity by addition of mannitol to the extracellular solution caused cell shrinkage followed by regulatory volume increase, partially due to activation of the Na+/H+ exchanger. In fMLP-stimulated cells the CV increase was counteracted by simultaneous addition of mannitol. Under these conditions the fMLP stimulated migration was inhibited. 7. The antibacterial activity of PMNs was not modified by Hoe 694 or omeprazole. 8. Western analysis with a monoclonal anti gastric H+/K+ ATPase beta-subunit antibody detected a glycosylated 35 kD core protein in lysates of mouse and human gastric mucosa as well as in human PMNs. 9. The results indicate that fMLP leads to cell swelling of PMNs due to activation of the Na+/H+ exchanger and a K+-dependent H+-extruding mechanism, presumably an H+/K+ ATPase. Inhibition of these ion transporters suppresses the increase in CV and precludes PMNs from stimulated migration.

Similar involvement of VIP receptor type I and type II in lymphocyte chemotaxis.

Effects of vasoactive intestinal peptide (VIP) on T cell migration are mediated by structurally distinct types I (VIPR1) and II (VIPR2) G protein-associated receptors. The two receptor types were proposed to transduce opposite effects on human T cells, since cytokine-induced chemotaxis of VIPR1-bearing HuT 78 human T cells, in contrast to T cells that express VIPR2, was inhibited by VIP. We studied chemotactic effects of VIP and related agonists with different affinities for VIP- and peptide histidine-isoleucine (PHI)-related receptors. All, VIP, secretin (SEC), a specific ligand for VIPR1, helodermin (HEL), an activator of helodermin-preferring VIPR2, as well as PHI, stimulated chemotaxis into micropore filters of both normal human peripheral blood T and B cells. Involvement of VIPRs was supported by inhibition of VIP-related agonist-induced migration of T and B cells with a VIPR antagonist. Peripheral blood lymphocyte (PBL) chemotaxis to VIP, SEC, HEL and PHI was reduced by inhibition of tyrosine kinase and pertussis or cholera toxin, whereas inhibition of protein kinase C only affected SEC-induced chemotaxis of PBL significantly. VIP-related agonists induced deactivation of migration at high concentrations. Findings in PBL suggest that VIPR1 activation can stimulate normal T and B cell chemotaxis. Different signaling mechanisms may be involved in mediating chemotactic activation of VIPRs and PHIRs, which may allow further exploration of receptor-dependent mechanisms and signaling pathways of VIP as mediator of PBL functions.

Secretoneurin, a novel neuropeptide, is a potent chemoattractant for human eosinophils.

Secretoneurin (SN), a 33-amino acid neuropeptide, is derived from secretogranin II that is released from sensory afferent C-fibers by capsaicin. Described functions of secretoneurin include chemotaxis of monocytes and endothelial cells, and inhibition of endothelial cell proliferation. Inhibition of monocyte chemotaxis by staurosporine indicated involvement of specific signaling pathways. We have tested effects of SN, substance P (SP), and interleukin-8 (IL-8) on eosinophil migration in modified Boyden chambers including signaling mechanisms of neuropeptide and cytokine stimulation of human eosinophils. Experiments showed SN as eosinophil chemoattractant comparable in its potency to IL-8. Checkerboard analysis, usage of a specific anti-SN-antibody, and receptor desensitization experiments confirmed the chemotactic activity. Preincubation of the cells with effective concentrations of staurosporine or tyrphostin-23 showed no effect, whereas treatment with wortmannin (WTN) or 3-isobutyl-1-methylxantin (IBMX) completely blocked SN-induced migration. Additionally, experiments ruled out tyrphostin-23- and WTN-sensitive signaling pathways for SP-induced chemotaxis of eosinophils. We conclude that SN-stimulated human eosinophil chemotaxis is mediated via a unique and specific signal transduction pathway that involves activation of phosphodiesterases and WTN-sensitive enzymes, ie, phospholipase D and phosphatidylinositol-3-kinase. In contrast, we report that activation of the latter and tyrosine kinases is required for SP-induced chemotaxis of eosinophils.

Induction of arachidonic acid metabolite release by human fibroblasts in proliferative vitreoretinopathy.

Proliferative vitreoretinopathy is a severe ocular disorder characterized by unwanted proliferation of cells and excessive production of fibrous tissue, which leads to the formation of cellular membranes on the surface of the retina and in the vitreous. Proliferative vitreoretinopathy is the most common cause of failure in retinal reattachment surgery, approximately occurring in one out of ten operated eyes. Proliferation of retinal pigment epithelial cells and fibroblasts is a cornerstone in the pathogenesis of proliferative vitreoretinopathy. An in vitro-proliferation assay showed previously that intraocular fluid from patients with proliferative vitreoretinopathy is potently effective in stimulating proliferation of human fibroblasts. Here we show that exposure of human fibroblasts to vitreous fluids from patients with proliferative vitreoretinopathy causes a rapid and sustained increase in arachidonic acid metabolite release as measured by competitive enzyme-immunoassay. The findings implicate prostaglandin E2 as a contributor to enhanced intraocular fibrosis in proliferative vitreoretinopathy. As prostaglandin E2 is a mediator of continuous aqueous-blood retinal barrier breakdown in this severe disease, cycclooxygenase inhibitors such as acetylsalicylic acid, which was successfully used in this study for blocking the effect of intraocular fluid, may be useful agents in targeting the progression of intraocular fibrosis.