Induction of endothelial cell decay-accelerating factor by vascular endothelial growth factor: a mechanism for cytoprotection against complement-mediated injury during inflammatory angiogenesis

Regulatory mechanisms of neutrophil migration from the circulation to the airspace

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

Mutations in an Innate Immunity Pathway Are Associated with Poor Overall Survival Outcomes and Hypoxic Signaling in Cancer

Complement-mediated cytotoxicity may act as a selective pressure for tumor overexpression of complement regulators. We hypothesize that the same selective pressure could lead to complement alterations at the genetic level. We find that, when analyzed as a pathway, mutations in complement genes occur at a relatively high frequency and are associated with changes in overall survival across a number of cancer types. Analysis of pathways expressed in patients with complement mutations that are associated with poor overall survival reveals crosstalk between complement and hypoxia in colorectal cancer. The importance of this crosstalk is highlighted by two key findings: hypoxic signaling is increased in tumors harboring complement mutations, and hypoxic tumor cells are resistant to complement-mediated cytotoxicity due, in part, to hypoxia-induced expression of complement regulator CD55. The range of strategies employed by tumors to dysregulate the complement system testifies to the importance of this pathway in tumor progression.

CD55 upregulation in astrocytes by statins as potential therapy for AQP4-IgG seropositive neuromyelitis optica

Background

Neuromyelitis optica spectrum disorder (herein called NMO) is an inflammatory demyelinating disease that can be initiated by binding of immunoglobulin G autoantibodies (AQP4-IgG) to aquaporin-4 on astrocytes, causing complement-dependent cytotoxicity (CDC) and downstream inflammation. The increased NMO pathology in rodents deficient in complement regulator protein CD59 following passive transfer of AQP4-IgG has suggested the potential therapeutic utility of increasing the expression of complement regulator proteins.

Methods

A cell-based ELISA was developed to screen for pharmacological upregulators of endogenous CD55 and CD59 in a human astrocyte cell line. A statin identified from the screen was characterized in cell culture models and rodents for its action on complement regulator protein expression and its efficacy in models of seropositive NMO.

Results

Screening of ~ 11,500 approved and investigational drugs and nutraceuticals identified transcriptional upregulators of CD55 but not of CD59. Several statins, including atorvastatin, simvastatin, lovastatin, and fluvastatin, increased CD55 protein expression in astrocytes, including primary cultures, by three- to four-fold at 24 h, conferring significant protection against AQP4-IgG-induced CDC. Mechanistic studies revealed that CD55 upregulation involves inhibition of the geranylgeranyl transferase pathway rather than inhibition of cholesterol biosynthesis. Oral atorvastatin at 10–20 mg/kg/day for 3 days strongly increased CD55 immunofluorescence in mouse brain and spinal cord and reduced NMO pathology following intracerebral AQP4-IgG injection.

Conclusion

Atorvastatin or other statins may thus have therapeutic benefit in AQP4-IgG seropositive NMO by increasing CD55 expression, in addition to their previously described anti-inflammatory and immunomodulatory actions.

The Role of Angiogenesis in Haemophilic Arthropathy: Where Do We Stand and Where Are We Going?

Haemophilia is an inherited bleeding disorder that can lead to degenerative joint arthropathy due to recurrent bleeding episodes affecting the musculoskeletal system of the patient. The cause of bleeding can be either traumatic or spontaneous. The pathogenesis of haemophilic arthropathy is unclear as many factors like iron, inflammatory cytokines, and angiogenic factors contribute to this process. Blood into joints can deteriorate the bone to such an extent that the patient experiences pain, reduction of the range of movement, and deformity of the joint, conditions that could have a great impact on quality of life. Over the years, management of haemophilic arthropathy has changed. Nowadays, early diagnosis with high resolution imaging like magnetic resonance imaging along with application of prophylaxis regimens can reduce the extent of damage to the joints. However, not all haemophilia patients have access to these interventions as cost may be prohibitive for some of them. The need for new, easy, and cost-effective strategies with the ability to identify early changes could be beneficial and could make a difference in the management of haemophilic arthropathy. Understanding the mechanism of processes like angiogenesis in the mechanism of developing arthropathy could be innovative for these patients and could help in the detection of new early diagnostic and therapeutic markers.

Cytoprotective pathways in the vascular endothelium. Do they represent a viable therapeutic target?

The vascular endothelium is a critical interface, which separates the organs from the blood and its contents. The endothelium has a wide variety of functions and maintenance of endothelial homeostasis is a multi-dimensional active process, disruption of which has potentially deleterious consequences if not reversed. Vascular injury predisposes to endothelial apoptosis, dysfunction and development of atherosclerosis. Endothelial dysfunction is an end-point, a central feature of which is increased ROS generation, a reduction in endothelial nitric oxide synthase and increased nitric oxide consumption. A dysfunctional endothelium is a common feature of diseases including rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus and chronic renal impairment. The endothelium is endowed with a variety of constitutive and inducible mechanisms that act to minimise injury and facilitate repair. Endothelial cytoprotection can be enhanced by exogenous factors such as vascular endothelial growth factor, prostacyclin and laminar shear stress. Target genes include endothelial nitric oxide synthase, heme oxygenase-1, A20 and anti-apoptotic members of the B cell lymphoma protein-2 family. In light of the importance of endothelial function, and the link between its disruption and the risk of atherothrombosis, interest has focused on therapeutic conditioning and reversal of endothelial dysfunction. A detailed understanding of cytoprotective signalling pathways, their regulation and target genes is now required to identify novel therapeutic targets. The ultimate aim is to add vasculoprotection to current therapeutic strategies for systemic inflammatory diseases, in an attempt to reduce vascular injury and prevent or retard atherogenesis.

Phenotypic expansion of DGKE-associated diseases

Atypical hemolytic uremic syndrome (aHUS) is usually characterized by uncontrolled complement activation. The recent discovery of loss-of-function mutations in DGKE in patients with aHUS and normal complement levels challenged this observation. DGKE, encoding diacylglycerol kinase-ε, has not been implicated in the complement cascade but hypothetically leads to a prothrombotic state. The discovery of this novel mechanism has potential implications for the treatment of infants with aHUS, who are increasingly treated with complement blocking agents. In this study, we used homozygosity mapping and whole-exome sequencing to identify a novel truncating mutation in DGKE (p.K101X) in a consanguineous family with patients affected by thrombotic microangiopathy characterized by significant serum complement activation and consumption of the complement fraction C3. Aggressive plasma infusion therapy controlled systemic symptoms and prevented renal failure, suggesting that this treatment can significantly affect the natural history of this aggressive disease. Our study expands the clinical phenotypes associated with mutations in DGKE and challenges the benefits of complement blockade treatment in such patients. Mechanistic studies of DGKE and aHUS are, therefore, essential to the design of appropriate therapeutic strategies in patients with DGKE mutations.

Comprehensive biomarker analysis and final efficacy results of sorafenib in the BATTLE trial

PURPOSE

To report the clinical efficacy of sorafenib and to evaluate biomarkers associated with sorafenib clinical benefit in the BATTLE (Biomarker-Integrated Approaches of Targeted Therapy for Lung Cancer Elimination) program.

PATIENTS AND METHODS

Patients with previously treated non-small cell lung cancer (NSCLC) received sorafenib until progression or unacceptable toxicity. Eight-week disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) were assessed. Prespecified biomarkers included K-RAS, EGFR, and B-RAF mutations, and EGFR gene copy number. Gene expression profiles from NSCLC cell lines and patient tumor biopsies with wild-type EGFR were used to develop a sorafenib sensitivity signature (SSS).

RESULTS

A total of 105 patients were eligible and randomized to receive sorafenib. Among 98 patients evaluable for eight-week DCR, the observed DCR was 58.2%. The median PFS and OS were 2.83 [95% confidence interval (CI), 2.04-3.58] and 8.48 months (95% CI, 5.78-10.97), respectively. Eight-week DCR was higher in patients with wild-type EGFR than patients with EGFR mutation (P = 0.012), and in patients with EGFR gene copy number gain (FISH-positive) versus patients FISH-negative (P = 0.048). In wild-type EGFR tumors, the SSS was associated with improved PFS (median PFS 3.61 months in high SSS vs. 1.84 months in low SSS; P = 0.026) but not with eight-week DCR. Increased expression of fibroblast growth factor-1, NF-κB, and hypoxia pathways were identified potential drivers of sorafenib resistance.

CONCLUSION

Sorafenib demonstrates clinical activity in NSCLC, especially with wild-type EGFR. SSS was associated with improved PFS. These data identify subgroups that may derive clinical benefit from sorafenib and merit investigation in future trials.

Cytoprotective signaling and gene expression in endothelial cells and macrophages-lessons for atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the medium and large arteries driven in large part by the accumulation of oxidized low-density lipoproteins and other debris at sites rendered susceptible because of the geometry of the arterial tree. As lesions develop, they acquire a pathologic microcirculation that perpetuates lesion progression, both by providing a means for further monocyte and T-lymphocyte recruitment into the arterial wall and by the physical and chemical stresses caused by micro-hemorrhage. This review summarizes work performed in our department investigating the roles of signaling pathways, alone and in combination, that lead to specific programs of gene expression in the atherosclerotic environment. Focusing particularly on cytoprotective responses that might be enhanced therapeutically, the work has encompassed the anti-inflammatory effects of arterial laminar shear stress, mechanisms of induction of membrane inhibitors that prevent complement-mediated injury, homeostatic macrophage responses to hemorrhage, and the transcriptional mechanisms that control the stability, survival, and quiescence of endothelial monolayers. Lastly, while the field has been dominated by investigation into the mechanisms of DNA transcription, we consider the importance of parallel post-transcriptional regulatory mechanisms for fine-tuning functional gene expression repertoires.

[Chinese herbal medicine Xiayuxue Decoction inhibits liver angiogenesis in rats with carbon tetrachloride-induced liver fibrosis]

OBJECTIVE

To evaluate the effects of Xiayuxue Decoction, a compound traditional Chinese medicine, on liver angiogenesis in rats with carbon tetrachloride (CCl(4))-induced liver fibrosis.

METHODS

Liver cirrhosis was induced by intraperitoneal injection of 50% CCl(4)-olive oil solution at the dose of 1 mL/kg body weight, twice per week for 9 consecutive weeks. After 3- and 6-week injection, 6 rats in the normal group and 6 rats in the model group were randomly sacrificed for dynamic observation. The survival rats of model group were randomly divided into model group (n=15) and Xiayuxue Decoction group (n=11). Six normal rats were used as a normal control. Xiayuxue Decoction was administered orally starting from the 7th week for 3 weeks. At the end of the ninth week, animals were sacrificed and liver tissues were harvested to measure histological changes, activities of matrix metalloproteinase-2 (MMP-2) and MMP-9 and protein expressions of platelet endothelial cell adhesion molecule-1 (CD31), von Willebrand factor (vWF), vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor-2 (VEGFR2), complement decay-accelerating factor (DAF) and α-smooth muscle actin (α-SMA) in the liver tissues.

RESULTS

Compared with the normal group, liver injury, fatty degeneration and collagen deposition were evidently observed in the model group and protein expressions of CD31, vWF, VEGF, VEGFR2, DAF and α-SMA were gradually increased. In addition, the activities of MMP-2 and MMP-9 in liver tissues were enhanced in the model group (P<0.01). Compared with 9-week model group, liver injury, fatty degeneration and collagen deposition were markedly inhibited by Xiayuxue Decoction; protein expressions of CD31, vWF, VEGF, VEGFR2,α-SMA and DAF and activities of MMP-2 and MMP-9 in the liver tissues were decreased in the Xiayuxue Decoction group (P<0.01).

CONCLUSION

The angiogenesis is evident and aggravating gradually during the progression of liver cirrhosis induced by CCl(4). Xiayuxue Decoction inhibits the angiogenesis by decreasing the activities of MMP-2 and MMP-9, inhibiting the activation of hepatic stellate cells, and damaging the new vessel integrality.

Complement-mediated injury and protection of endothelium: lessons from atypical haemolytic uraemic syndrome

The complement system provides a vital defence against invading pathogens. As an intrinsic system it is always 'on', in a state of constant, low level activation. This activation is principally mediated through the deposition of C3b on to pathogenic surfaces and host tissues. C3b is generated by spontaneous 'tick over' and formal activation of the alternative pathway, and by activation of the classical and lectin pathways. If the deposited C3b is not appropriately regulated, there is progression to terminal pathway complement activation via the C5 convertases, generating the potent anaphylotoxin C5a and the membrane attack complex C5b-9. Unsurprisingly, these highly active components have the potential to cause injury to bystander host tissue, including the vascular endothelium. As such, complement activation on endothelium is normally tightly controlled by a large number of fluid-phase and membrane bound inhibitors, in an attempt to ensure that propagation of complement activation is appropriately restricted to invading pathogens and altered 'self', e.g. apoptotic and necrotic cells. The kidney is increasingly recognised as a site at particular risk from complement-mediated endothelial injury. Both genetic and acquired defects which impact on complement regulation predispose to this susceptibility. The thrombotic microangiopathy, haemolytic uraemic syndrome (HUS), will be used to illustrate the mechanisms by which the endothelial cell injury occurs. Finally, the underlying rationale for current and future potential therapeutic interventions in HUS and also the opportunities for enhancing endothelial defence to prevent relapsing disease through increased complement cytoprotective strategies will be summarised.

Prokineticin 1 signaling and gene regulation in early human pregnancy

Prokineticin 1 (PROK1) is a recently described protein with a wide range of functions including tissue-specific angiogenesis, modulation of inflammatory responses, and regulation of hematopoiesis. The objective of this study was to investigate the role of PROK1 and prokineticin receptor 1 (PROKR1) in human endometrium during early pregnancy. PROK1 and PROKR1 expression is significantly elevated in first-trimester decidua, compared with nonpregnant endometrium. Expression of PROK1 and PROKR1 was localized in glandular epithelial and various cellular compartments within the stroma. To investigate the signaling pathways and target genes activated by PROK1, we generated an endometrial epithelial cell line stably expressing PROKR1 (Ishikawa PROKR1 cells). PROK1-PROKR1 interaction induced inositol phosphate mobilization and sequential phosphorylation of c-Src, epidermal growth factor receptor, and ERK 1/2. Gene microarray analysis on RNA extracted from Ishikawa PROKR1 cells treated with 40 nm PROK1 for 8 h revealed 49 genes to be differentially regulated. A number of these genes, including cyclooxygenase (COX)-2, leukemia inhibitory factor, IL-6, IL-8, and IL-11 are regulated in the endometrium during implantation and early pregnancy. We subsequently investigated the effect of PROK1 on expression of COX-2 in Ishikawa PROKR1 cells and first-trimester decidua. COX-2 mRNA and protein expression, and prostaglandin synthesis, were elevated in response to treatment with PROK1. Moreover, expression of COX-2 by PROK1 was dependent on activation of the Gq-phospholipase C-beta-cSrc-epidermal growth factor receptor-MAPK/ERK kinase pathway. These data demonstrate that PROK1 and PROKR1 expression is elevated in human decidua during early pregnancy and that PROK1-PROKR1 interaction regulates expression of a host of implantation-related genes.

A Protein Kinase Cε-Anti-apoptotic Kinase Signaling Complex Protects Human Vascular Endothelial Cells against Apoptosis through Induction of Bcl-2

Endothelial cell apoptosis is associated with vascular injury and predisposes to atherogenesis. Endothelial cells express anti-apoptotic genes including Bcl-2, Bcl-XL and survivin, which also contribute to angiogenesis and vascular remodeling. We report a central role for protein kinase Cepsilon (PKCepsilon) in the regulation of Bcl-2 expression and cytoprotection of human vascular endothelium against apoptosis. Using myristoylated inhibitory peptides, a predominant role for PKCepsilon in vascular endothelial growth factor-mediated endothelial resistance to apoptosis was revealed. Immunoblotting of endothelial cells infected with an adenovirus expressing a constitutively active form of PKCepsilon (Adv-PKCepsilon-CA) or control Adv-beta-galactosidase demonstrated a 3-fold, PKCepsilon-dependent increase in Bcl-2 expression, with no significant change in Bcl-XL, Bad, Bak, or Bax. The induction of Bcl-2 inhibited apoptosis induced by serum starvation or etoposide, and PKCepsilon activation attenuated etoposide-induced caspase-3 cleavage. The functional role of Bcl-2 was confirmed with Bcl-2 antagonist HA-14-1. Inhibition of phosphoinositide 3-kinase attenuated vascular endothelial growth factor-induced protection against apoptosis, and this was rescued by overexpression of constitutively active PKCepsilon, suggesting PKCepsilon acts downstream of phosphoinositide 3-kinase. Co-immunoprecipitation studies demonstrated a physical interaction between PKCepsilon and Akt, which resulted in formation of a signaling complex, leading to optimal induction of Bcl-2. This study reveals a pivotal role for PKCepsilon in endothelial cell cytoprotection against apoptosis. We demonstrate that PKCepsilon forms a signaling complex and acts co-operatively with Akt to protect human vascular endothelial cells against apoptosis through induction of the anti-apoptotic protein Bcl-2 and inhibition of caspase-3 cleavage.

Vascular endothelial growth factor receptor-2: structure, function, intracellular signalling and therapeutic inhibition

Vascular endothelial growth factors (VEGFs) regulate vascular development, angiogenesis and lymphangiogenesis by binding to a number of receptors. VEGFR-1 is required for the recruitment of haematopoietic stem cells and the migration of monocytes and macrophages, VEGFR-2 regulates vascular endothelial function and VEGFR-3 regulates lymphatic endothelial cell function. Over the last decade, considerable progress has been made in delineating the VEGFR-2 specific intracellular signalling cascades leading to proliferation, migration, survival and increased permeability, each of which contributes to the angiogenic response. Furthermore, therapeutic inhibition of VEGFR-2 action is now having an impact in the clinic for the treatment of a number of diseases.

Rat liver sinusoidal endothelial cells survive without exogenous VEGF in 3D perfused co-cultures with hepatocytes

Liver sinusoidal endothelial cells (SECs) are generally refractory to extended in vitro culture. In an attempt to recreate some features of the complex set of cues arising from the liver parenchyma, we cocultured adult rat liver SECs, identified by the expression of the marker SE-1, with primary adult rat hepatocytes in a 3D culture system that provides controlled microscale perfusion through the tissue mass. The culture was established in a medium containing serum and VEGF, and these factors were then removed to assess whether cells with the SE-1 phenotype could be supported by the local microenvironment in vitro. Rats expressing enhanced green fluorescent protein (EGFP) in all liver cells were used for isolation of the SE-1-positive cells added to cocultures. By the 13th day of culture, EGFP-expressing cells had largely disappeared from 2D control cultures but exhibited moderate proliferation in 3D perfused cultures. SE-1-positive cells were present in 3D cocultures after 13 days, and these cultures also contained Kupffer cells, stellate cells, and CD31-expressing endothelial cells. Global transcriptional profiling did not reveal profound changes between 2D and 3D cultures in expression of most canonical angiogenic factors but suggested changes in several pathways related to endothelial cell function.

Complement insufficiency limits efficacy in a xenograft model of hyperacute rejection for cancer therapy

Hyperacute rejection (HAR) is a rapid immunological response to an organ xenotransplant caused by recognition of endothelial galactose(alpha1,3)galactose (alphaGal) epitopes and complement-mediated cell lysis by host anti-alphaGal antibody ('natural antibody'). The alphaGal epitope is synthesised by a galactosyl transferase ((alpha1,3)GT) which humans lack. Because human cells transduced with (alpha1,3)GT are sensitised to natural antibody/complement-mediated lysis in human serum, delivery of (alpha1,3)GT to tumour vasculature in patients is a potential therapeutic strategy, by mimicking the pathophysiology of organ rejection. We therefore sought to develop an animal model of HAR for cancer therapy. Nude/(alpha1,3)GT knock-out mice allowed the growth of human tumour xenografts and the use of ecotropic retrovirus producer cells to generate expression of alphaGal on tumour vasculature. Lysis of alphaGal-positive murine endothelial cells with rabbit complement in conjunction with murine anti-alphaGal antibody in vitro was used to define the conditions necessary for HAR. However, tumour growth retardation and destruction of alphaGal-positive tumour endothelium were minimal after their administration, despite sera retaining post hoc cytolytic activity with fresh complement. The major limitation of this experimental system, of relevance to other therapeutic approaches, results from the use of a xenograft, in which additional xenoreactivities lead to complement insufficiency. Development of a tractable preclinical model in which to evaluate HAR for cancer therapy requires a syngeneic experimental system.

Cross-talk between the complement system and endothelial cells in physiologic conditions and in vascular diseases

The endothelial layer represents a continuous physical barrier that controls coagulation and allows selective passage of soluble molecules and circulating cells across the vessel wall into the tissue. The functional activity of the endothelial cells may be influenced by their interaction with components of the complement system. In this review we shall discuss the complex interplay that can be established between the endothelium and complement proteins or activation products. Endothelial cells may also secrete several complement components which contribute to the circulating pool. This process can be regulated by cytokines and other pro-inflammatory stimuli. In addition, complement activation products stimulate endothelial cells to acquire a pro-inflammatory and pro-coagulant status. Expression of regulatory molecules on the cell surface provides protection against an undesired attack by complement activation products. Unrestricted complement activation under pathological conditions may lead to structural and functional changes of the endothelium resulting in vascular disease.

Cell-surface density of complement restriction factors (CD46, CD55, and CD59): oral squamous cell carcinoma versus other solid tumors

OBJECTIVE

Complement restriction factors (CD46, membrane cofactor; CD55, decay accelerating factor; and CD59, protectin) are overexpressed on tumor cells, and they enable tumor cells to escape from complement-dependent and antibody-mediated killing. Cell-surface density of complement restriction factors (CRFs) on oral squamous cell carcinoma (OSCC) is compared with that found on other solid tumors (breast, pancreas, colon carcinomas, and melanoma) to understand the significance of their diversity.

STUDY DESIGN

The cell-surface expression of CRFs on tumor cells was confirmed with confocal laser scan fluorescent microscopy. Cell suspension enzyme-linked immunosorbent assay (cs-ELISA), which measures the density of cell-surface antigens, was utilized to study CRFs on the cell surface of tumor cells (OSCC, 2 cell lines; breast, 5 cell lines; pancreas, 3 cell lines; colon, 3 cell lines; and melanoma, 9 cell lines).

RESULTS

Confocal laser scan fluorescent microscopy confirmed the expression of CD46, CD55, and CD59 on the cell surface of OSCC cell lines SCC12 and SCC71. The relative densities of cell-surface expression obtained from cs-ELISAs of CRFs on OSCCs are as follows: CD59 > CD55 > CD46. The relative densities of the 3 CRFs in breast and pancreatic carcinomas were similar to those found in OSCCs, whereas the profile of CRFs in melanoma (CD59 > CD55 < CD46) and colon cancer (CD46 > CD55 > CD59) were different.

CONCLUSIONS

These findings indicate diverse strategies adopted by tumor types to resist antibody-mediated complement-dependent cytotoxicity; possibly the factors (exogenous and endogenous) in their respective microenvironments may play a role in the diversity.

Molecular cloning and characterization of novel splicing variants of human decay-accelerating factor

Decay-accelerating factor (DAF) is one of the complement regulatory proteins. Two isoforms of DAF have been identified in humans. In this study, we isolated novel cDNAs encoding five isoforms of DAF from the human lung, which were generated by insertion of new exonic sequences. RT-PCR revealed that all isoforms were expressed in almost all tissues tested, although the expression patterns and levels differed among the tissues. Transfection of isoform vDAF1, 2, and 3 cDNAs into CHO cells showed that these molecules are soluble forms secreted after glycosylation. Isoform vDAF4 and vDAF5 cDNAs included a part of and the entire intron 7 sequence, respectively, and the transfection of vDAF4 cDNA produced a large, glycosylated, membrane-bound form. These results suggest that more than seven isoforms of human DAF are involved in the regulation of complement activation under physiological conditions through their specific structures and localization.

Inhibition of decay-accelerating factor (CD55) attenuates prostate cancer growth and survival in vivo

Decay-accelerating factor (CD55) is a member of membrane-bound complement-regulatory proteins. CD55 expression correlates with poor survival in patients with colorectal cancer and has been implicated in the survival and tumorigenesis of blood-borne malignancies. Histologic analysis of clinical specimens from patients with advanced prostate cancer revealed an increase in CD55 expression in prostate tumor epithelial cells. CD55 was shown to be functionally active and to inhibit complement-mediated lysis in PC-3 and DU145 cells. The percentage of lysis was correlative with the CD55 expression profile observed in these prostate cancer cell lines. These data suggest that CD55 is an important regulator of prostate cancer cell survival. As a result, we have hypothesized that CD55 expression on prostate cancer cells promotes cell survival and contributes to the metastatic potential of prostate cancer cells. To determine the role of CD55 in prostate cancer tumorigenesis and metastasis, we generated PC-3(Luc) prostate cancer cells with CD55 siRNA-targeted disruption. We found that PC-3(Luc)/CD55 siRNA constructs in SCID mice resulted in a significant attenuation of overall tumor burden. Further investigation into the mechanisms of CD55-mediated tumor cell/microenvironment interaction is necessary to understand the role of CD55 in tumor cell survival and metastatic lesion formation.

Decay-accelerating factor (CD55): a versatile acting molecule in human malignancies

The decay-accelerating factor (DAF, CD55) physiologically serves as an inhibitor of the complement system. Moreover, DAF is broadly expressed in malignant tumors. Here, DAF seems to dispose of several different functions reaching far beyond its immunological role, e.g., promotion of tumorigenesis, decrease of complement mediated tumor cell lysis, autocrine loops for cell rescue and evasion of apoptosis, neoangiogenesis, invasiveness, cell motility, and metastasis via oncogenic tyrosine kinase pathway activation, and specific seven-span transmembrane receptors (CD97) binding. Furthermore, DAF has already been included in diagnostic or therapeutic studies. Thereby, studies applying monoclonal anti-DAF antibodies and anti-DAF vaccination for a targeted therapy have been enrolled recently.

Cyclooxygenase-2 induction and prostacyclin release by protease-activated receptors in endothelial cells require cooperation between mitogen-activated protein kinase and NF-kappaB pathways

The functional significance of protease-activated receptors (PARs) in endothelial cells is largely undefined, and the intracellular consequences of their activation are poorly understood. Here, we show that the serine protease thrombin, a PAR-1-selective peptide (TFLLRN), and SLIGKV (PAR-2-selective peptide) induce cyclooxygenase-2 (COX-2) protein and mRNA expression in human endothelial cells without modifying COX-1 expression. COX-2 induction was accompanied by sustained production of 6-keto-PGF1alpha, the stable hydrolysis product of prostacyclin, and this was inhibited by indomethacin and the COX-2-selective inhibitor NS398. PAR-1 and PAR-2 stimulation rapidly activated both ERK1/2 and p38MAPK, and pharmacological blockade of MEK with either PD98059 or U0126 or of p38MAPK by SB203580 or SB202190 strongly inhibited thrombin- and SLIGKV-induced COX-2 expression and 6-keto-PGF1alpha formation. Thrombin and peptide agonists of PAR-1 and PAR-2 increased luciferase activity in human umbilical vein endothelial cells infected with an NF-kappaB-dependent luciferase reporter adenovirus, and this, as well as PAR-induced 6-keto-PGF1alpha synthesis, was inhibited by co-infection with adenovirus encoding wild-type or mutated (Y42F) IkappaBalpha. Thrombin- and SLIGKV-induced COX-2 expression and 6-keto-PGF1alpha generation were markedly attenuated by the NF-kappaB inhibitor PG490 and partially inhibited by the proteasome pathway inhibitor MG-132. Activation of PAR-1 or PAR-2 promoted nuclear translocation and phosphorylation of p65-NF-kappaB, and thrombin-induced but not PAR-2-induced p65-NF-kappaB phosphorylation was reduced by inhibition of MEK or p38MAPK. Activation of PAR-4 by AYPGKF increased phosphorylation of ERK1/2 and p38MAPK without modifying NF-kappaB activation or COX-2 induction. Our data show that PAR-1 and PAR-2, but not PAR-4, are coupled with COX-2 expression and sustained endothelial production of vasculoprotective prostacyclin by mechanisms that depend on ERK1/2, p38MAPK, and IkappaBalpha-dependent NF-kappaB activation.

Statin-induced expression of CD59 on vascular endothelium in hypoxia: a potential mechanism for the anti-inflammatory actions of statins in rheumatoid arthritis

Hypoxia, which leads to dysfunctional cell metabolism, and complement activation both play central roles in the pathogenesis of rheumatoid arthritis (RA). Recent studies have reported that mice deficient for the complement-inhibitory protein CD59 show enhanced susceptibility to antigen-induced arthritis and reported that statins have anti-inflammatory effects in RA. We hypothesized that the anti-inflammatory effect of statins in RA relates in part to their ability to increase CD59 expression in hypoxic conditions and therefore to reduce complement activation. Flow-cytometric analysis showed that CD59 expression on endothelial cells (EC) was unaffected by atorvastatin in normoxia (21% O2), whereas in hypoxic conditions (1% O2) an up to threefold dose-dependent increase in CD59 expression was seen. This effect of hypoxia was confirmed by treatment of EC with chemical mimetics of hypoxia. The upregulation of CD59 protein expression in hypoxia was associated with an increase in steady-state mRNA. L-Mevalonate and geranylgeraniol reversed the response, confirming a role for inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase and geranylgeranylation. Likewise, inhibition by NG-monomethyl-L-arginine and NG-nitro-L-arginine methyl ester confirmed that CD59 upregulation in hypoxia was nitric oxide dependent. The expression of another complement-inhibitory protein, decay-accelerating factor (DAF), is known to be increased by atorvastatin in normoxia; this response was also significantly enhanced under hypoxic conditions. The upregulation of CD59 and DAF by atorvastatin in hypoxia prevented the deposition of C3, C9 and cell lysis that follows exposure of reoxygenated EC to serum. This cytoprotective effect was abrogated by inhibitory anti-CD59 and anti-DAF mAbs. The modulation of EC CD59 and DAF by statins under hypoxic conditions therefore inhibits both early and late complement activation and may contribute to the anti-inflammatory effects of statins in RA.

Membrane complement regulatory proteins

A number of proteins anchored on the cell surface function to protect host tissues from bystander injury when complement is activated. In humans, they include decay-accelerating factor (DAF, CD55), membrane cofactor protein (MCP, CD46), complement receptor 1 (CR1, CD35) and CD59. Although disease conditions directly attributable to abnormal function of these proteins are relatively rare, it has become evident from recent studies using animal models that membrane complement regulatory proteins are important modulators of tissue injury in many autoimmune and inflammatory disease settings. Evidence is also emerging to support a role of these proteins in regulating cellular immunity. In this article, we highlight recent advances on the in vivo biology of membrane complement regulatory proteins and discuss their relevance in human disease pathogenesis and therapeutics.

Effect of IL-4 on altered expression of complement activation regulators in rat pancreatic cells during severe acute pancreatitis

AIM: To investigate the effect of IL-4 on the altered expression of complement activation regulators in pancreas and pancreatic necrosis during experimental severe acute pancreatitis (SAP).

METHODS: SAP model of rats was established by retrograde injection of 5% sodium taurocholate (1 mL/kg) into the pancreatic duct. We immunohistochemically assayed the expression of three complement activation regulators: decay accelerating factor (DAF; CD55), 20 ku homologous restriction factor (HRF20; CD59) and membrane cofactor protein (MCP; CD46), in the pancreatic acinar cells of rats at 0, 3, 6, 12, and 24 h after the induction of SAP model. Meanwhile the levels of amylase and lipase were determined, and morphological examination was performed. Then, 61 rats were randomly divided into three groups. Group A (n = 21) received no treatment after the SAP model was established; group B (n = 20) was given IL-4 (8 µg/animal) intraperitoneally 0.5 h before the SAP model was established; group C (n = 20) was given IL-4 (8 µg/animal) intraperitoneally 0.5 h after the SAP model was established. Plasma amylase and lipase, extent of pancreatic necrosis and expression of complement activation regulators were investigated 6 h after the induction of SAP model.

RESULTS: Three complement activation regulators were all expressed in pancreatic acinar cells. MCP was not found on the basolateral surface as reported. Contrary to the gradually increasing plasma level of amylase and lipase, expression of complement activation regulators decreased after SAP model was set up. At the same time, the severity of pancreatic necrosis was enhanced. A strong negative correlation was found between the expression of MCP, DAF, CD59 in pancreatic acinar cells and the severity of pancreatic necrosis (r = –0.748, –0.827, –0.723; P<0.01). In the second series of experiments, no matter when the treatment of IL-4 was given (before or after the induction of SAP model), the serum level of amylase or lipase was decreased and the extent of pancreatic necrosis was ameliorated significantly. Compared to SAP control group, the expression of DAF and CD59 in pancreas was reinforced when IL-4 was given before the induction of SAP model (P<0.01, P<0.05), but the expression of MCP was not influenced (P>0.05). The expression of DAF was enhanced, when IL-4 was given after the induction of SAP model (P<0.05), but the expression of CD59 and MCP did not change (P>0.05).

CONCLUSION: Complement activation regulators may participate in the pathogenesis of pancreatic inflammation. Downregulation of complement activation regulators expression may be one of the causes of pancreatic necrosis. IL-4 treatment may control SAP aggravation by enhancing expression of DAF and CD59 in pancreas and decreasing pancreatic necrosis. Moreover, DAF and CD59 may play an important role in the regulation of complement activation regulators during SAP.

Hypoxia and angiogenesis in rheumatoid arthritis

PURPOSE OF REVIEW

Angiogenesis is a prominent feature of rheumatoid synovitis. Although new blood vessels deliver oxygen to the augmented inflammatory cell mass, the neovascular network is dysfunctional and fails to restore tissue oxygen homeostasis, so that the rheumatoid joint remains a markedly hypoxic environment. The purpose of this review is to discuss the role of hypoxia and angiogenesis in the pathogenesis of rheumatoid arthritis.

RECENT FINDINGS

Vascular pathologic change, in the form of angiogenesis, is important in the perpetuation of rheumatoid arthritis and, in the form of endothelial dysfunction, contributes to associated cardiovascular comorbidity. Recent data suggest that tumor necrosis factor-alpha blockade may modify the vascular pathologic changes in rheumatoid arthritis. Angiogenesis is a prominent feature of rheumatoid synovitis. Emerging evidence based on ultrasonographic vascular imaging and angiogenic biomarkers implicates angiogenesis in the active phase of erosive disease. Many factors contribute to the profoundly hypoxic environment that can arise within the joint affected by rheumatoid arthritis. At a cellular level, hypoxia is detected by a mechanism that regulates cytoplasmic concentrations of hypoxia-inducible factor-1alpha. After translocation to the nucleus, hypoxia-inducible factor-1alpha binds its partner hypoxia-inducible factor-1beta to form a heterodimeric, functional transcription factor, hypoxia-inducible factor-1, which activates a gene program associated with angiogenesis, glycolysis, and adaptation to pH.

SUMMARY

Despite the luxuriant vasculature associated with rheumatoid arthritis synovitis, the joint affected by rheumatoid arthritis is hypoxic. Repetitive cycles of hypoxia and reoxygenation together with oxidants produced by phagocytic cells promote chronic oxidative stress within the microenvironment of the affected joint, leading to the generation of reactive oxygen species with the potential to contribute to tissue damage.

A role for proteinase-activated receptor 2 and PKC-epsilon in thrombin-mediated induction of decay-accelerating factor on human endothelial cells

Thrombin, an important mediator of thrombosis and inflammation, may also enhance vascular cytoprotection. Thus thrombin induces expression of the complement-inhibitory protein decay-accelerating factor (DAF) in human umbilical vein endothelial cells (HUVECs), thus increasing protection against complement-mediated injury. Using PKC isozyme-specific peptide antagonists and adenoviral constructs, we have shown in the present study that PKC-epsilon is the primary isozyme involved in DAF induction by thrombin. Experiments with proteinase-activated receptor-1 (PAR1) and PAR2 activating peptides (APs) showed that DAF expression induced by PAR1-AP was PKC-alpha-dependent; in contrast, PAR2-AP induction of DAF required activation of PKC-epsilon. PAR1-AP and PAR2-AP in combination exerted an additive effect on DAF protein expression, which was equivalent to that observed with thrombin alone. These data implied a specific role for PAR2 in DAF induction, which was supported by the observation that upregulation of endothelial cell (EC) PAR2-enhanced DAF induction by thrombin. ERK1/2, p38, and JNK MAPK were also involved in thrombin-induced DAF upregulation, with evidence of interdependence between ERK1/2 and JNK. A role for transactivation of PAR2 by PAR1 was suggested by partial inhibition of thrombin-induced DAF expression by the PAR1 signaling antagonists BMS-200261 and SCH79797, whereas inhibition of thrombin-induced cleavage of PAR1 by specific MAbs or hirudin completely abrogated the response. Together, these data imply that the predominant pathway for thrombin-induced DAF expression involves transactivation of PAR2 by PAR1 and signaling via PKC-epsilon/MAPK. This may represent an important, novel pathway for endothelial cytoprotection during inflammation and angiogenesis and suggests that PAR2 may play a central role in some thrombin-induced responses.

Constitutive and inducible expression and regulation of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF), which was originally discovered as vascular permeability factor, is critical to human cancer angiogenesis through its potent functions as a stimulator of endothelial cell survival, mitogenesis, migration, differentiation and self-assembly, as well as vascular permeability, immunosuppression and mobilization of endothelial progenitor cells from the bone marrow into the peripheral circulation. Genetic alterations and a chaotic tumor microenvironment, such as hypoxia, acidosis, free radicals, and cytokines, are clearly attributed to numerous abnormalities in the expression and signaling of VEGF and its receptors. These perturbations confer a tremendous survival and growth advantage to vascular endothelial cells as manifested by exuberant tumor angiogenesis and a consequent malignant phenotype. Understanding the regulatory mechanisms of both inducible and constitutive VEGF expression will be crucial in designing effective therapeutic strategies targeting VEGF to control tumor growth and metastasis. In this review, molecular regulation of VEGF expression in tumor cells is discussed.

Serum vascular markers and vascular imaging in assessment of rheumatoid arthritis disease activity and response to therapy

Vascular pathology, in the form of angiogenesis, is important in the perpetuation of rheumatoid arthritis (RA) and, in the form of endothelial dysfunction, contributes to associated cardiovascular co-morbidity. Emerging evidence suggests that TNFalpha blockade may modify vascular pathology in RA. Serum concentrations of vascular endothelial growth factor (VEGF), a potent endothelial cell-specific growth factor that is up-regulated by pro-inflammatory cytokines and by hypoxia, are elevated in RA and correlate with disease activity. Serum levels of VEGF at first presentation in RA predict radiographic progression of the disease over the subsequent year. Power Doppler ultrasonography is a sensitive method for demonstrating the presence of blood flow in small vessels and the vascular signal correlates with histopathological quantification of the vascular density of synovial tissue. Recent data indicate that high-frequency ultrasound and power Doppler are sensitive tools for evaluation of disease activity and assessment of response to therapy. Power Doppler imaging may also have the potential to predict those patients most at risk of accelerated joint destruction. However, much work has yet to be done to standardize the use of these imaging technologies.

Angiogenesis as an immunopharmacologic target in inflammation and cancer

Many pathological processes including wound healing, chronic inflammation and cancer require angiogenesis, i.e., the formation of new vasculature in the lesions. Accumulating evidence indicates that angiogenesis is crucial for both chronic inflammation and the growth of malignant tumors with the participation of diverse cytokines, chemokines and growth factors. It is nevertheless believed that differences exist in angiogenesis between cancer and chronic inflammatory diseases. The aim of this review is to outline the characteristics of angiogenesis in chronic inflammation and cancer. A better understanding of the angiogenic processes may facilitate the design of more effective therapies for chronic inflammation and cancer.

Decay-accelerating factor induction on vascular endothelium by vascular endothelial growth factor (VEGF) is mediated via a VEGF receptor-2 (VEGF-R2)- and protein kinase C-alpha/epsilon (PKCalpha/epsilon)-dependent cytoprotective signaling pathway and is inhibited by cyclosporin A

Decay-accelerating factor (DAF), a membrane-bound complement regulatory protein, is up-regulated on endothelial cells (ECs) following treatment with vascular endothelial growth factor (VEGF), providing enhanced protection from complement-mediated injury. We explored the signaling pathways involved in this response. Incubation of human umbilical vein ECs with VEGF induced a 3-fold increase in DAF expression. Inhibition by flk-1 kinase inhibitor SU1498 and failure of placental growth factor (PlGF) to up-regulate DAF confirmed the role of VEGF-R2. The response was also blocked by pretreatment with phospholipase C-gamma (PLCgamma) inhibitor U71322 and protein kinase C (PKC) antagonist GF109203X. In contrast, no effect was seen with nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA). Use of PKC agonists and isozyme-specific pseudosubstrate peptide antagonists suggested a role for PKCalpha and -epsilon in VEGF-mediated DAF up-regulation. This was confirmed by transfection of ECs with PKCalpha and -epsilon dominant-negative constructs, which in combination completely abrogated induction of DAF by VEGF. In contrast, LY290042, a phosphoinositide 3-kinase (PI3K) inhibitor, significantly augmented DAF expression, suggesting a negative regulatory role for phosphoinositide 3-kinase. The widely used immunosuppressive drug cyclosporin A (CsA) inhibited DAF induction by VEGF in a dose-dependent manner. The VEGF-induced DAF expression was functionally effective, significantly reducing complement-mediated EC lysis, and this cytoprotective effect was reversed by CsA. These data provide evidence for a VEGF-R2-, phospholipase C-gamma-, and PKCalpha/epsilon-mediated cytoprotective pathway in ECs. This may represent an important mechanism for the maintenance of vascular integrity during chronic inflammation involving complement activation. Moreover, inhibition of this pathway by CsA may play a role in CsA-mediated vascular injury.

C-Reactive Protein Upregulates Complement-Inhibitory Factors in Endothelial Cells

BACKGROUND

Because complement-mediated vascular injury participates in atherosclerosis and C-reactive protein (CRP) can activate the complement cascade, we sought to determine whether CRP affects the expression of the protective complement-inhibitory factors on the cell surface of endothelial cells (ECs).

METHODS AND RESULTS

Human coronary artery or human saphenous vein ECs were incubated with CRP (0 to 100 microg/mL, 0 to 72 hours), and the expression of the complement-inhibitory proteins decay-accelerating factor (DAF), membrane cofactor protein (CD46), and CD59 were measured by flow cytometry. Incubation with CRP resulted in a significant increase in the expression of all 3 proteins. CRP-induced upregulation of DAF required increased steady-state mRNA and de novo protein synthesis. The increased expression of complement-inhibitory proteins was functionally effective, resulting in significant reduction of complement-mediated lysis of antibody-coated human saphenous vein ECs.

CONCLUSIONS

These observations provide evidence for a possible protective role for CRP in atherogenesis.

Bifunctional role for VEGF-induced heme oxygenase-1 in vivo: induction of angiogenesis and inhibition of leukocytic infiltration

Heme-oxygenases (HOs) catalyze the conversion of heme into carbon monoxide and biliverdin. HO-1 is induced during hypoxia, ischemia/reperfusion, and inflammation, providing cytoprotection and inhibiting leukocyte migration to inflammatory sites. Although in vitro studies have suggested an additional role for HO-1 in angiogenesis, the relevance of this in vivo remains unknown. We investigated the involvement of HO-1 in angiogenesis in vitro and in vivo. Vascular endothelial growth factor (VEGF) induced prolonged HO-1 expression and activity in human endothelial cells and HO-1 inhibition abrogated VEGF-driven angiogenesis. Two murine models of angiogenesis were used: (1) angiogenesis initiated by addition of VEGF to Matrigel and (2) a lipopolysaccharide (LPS)–induced model of inflammatory angiogenesis in which angiogenesis is secondary to leukocyte invasion. Pharmacologic inhibition of HO-1 induced marked leukocytic infiltration that enhanced VEGF-induced angiogenesis. However, in the presence of an anti-CD18 monoclonal antibody (mAb) to block leukocyte migration, VEGF-induced angiogenesis was significantly inhibited by HO-1 antagonists. Furthermore, in the LPS-induced model of inflammatory angiogenesis, induction of HO-1 with cobalt protoporphyrin significantly inhibited leukocyte invasion into LPS-conditioned Matrigel and thus prevented the subsequent angiogenesis. We therefore propose that during chronic inflammation HO-1 has 2 roles: first, an anti-inflammatory action inhibiting leukocyte infiltration; and second, promotion of VEGF-driven noninflammatory angiogenesis that facilitates tissue repair.

Decay-accelerating factor induction by tumour necrosis factor-alpha, through a phosphatidylinositol-3 kinase and protein kinase C-dependent pathway, protects murine vascular endothelial cells against complement deposition

We have shown that human endothelial cells (EC) are protected against complement-mediated injury by the inducible expression of decay-accelerating factor (DAF). To understand further the importance of DAF regulation, we characterized EC DAF expression on murine EC in vitro and in vivo using a model of glomerulonephritis. Flow cytometry using the monoclonal antibody (mAb) Riko-3 [binds transmembrane- and glycosylphosphatidylinositol (GPI)-anchored DAF], mAb Riko-4 (binds GPI-anchored DAF) and reverse transcription-polymerase chain reaction (RT-PCR), demonstrated that murine EC DAF is GPI-anchored. Tumour necrosis factor-alpha (TNF-alpha) increased EC DAF expression, detectable at 6 hr and maximal at 24-48 hr poststimulation. DAF upregulation required increased steady-state DAF mRNA and protein synthesis. In contrast, no increased expression of the murine complement receptor-related protein-Y (Crry) was seen with TNF-alpha. DAF upregulation was mediated via a protein kinase C (PKC)alpha, phosphoinositide-3 kinase (PI-3 kinase), p38 mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-kappaB)-dependent pathway. The increased DAF was functionally relevant, resulting in a marked reduction in C3 deposition following complement activation. In a nephrotoxic nephritis model, DAF expression on glomerular capillaries was significantly increased 2 hr after the induction of disease. The demonstration of DAF upregulation above constitutive levels suggests that this may be important in the maintenance of vascular integrity during inflammation, when the risk of complement-mediated injury is increased. The mouse represents a suitable model for the study of novel therapeutic approaches by which vascular endothelium may be conditioned against complement-mediated injury.

Statin-induced expression of decay-accelerating factor protects vascular endothelium against complement-mediated injury

Complement-mediated vascular injury is important in the pathophysiology of atherosclerosis and myocardial infarction. Because recent evidence shows that statins have beneficial effects on endothelial cell (EC) function independent of lipid lowering, we explored the hypothesis that statins modulate vascular EC resistance to complement through the upregulation of complement-inhibitory proteins. Human umbilical vein and aortic ECs were treated with atorvastatin or simvastatin, and decay-accelerating factor (DAF), membrane cofactor protein, and CD59 expression was measured by flow cytometry. A dose-dependent increase in DAF expression of up to 4-fold was seen 24 to 48 hours after treatment. Statin-induced upregulation of DAF required increased steady-state mRNA and de novo protein synthesis. L-Mevalonate and geranylgeranyl pyrophosphate reversed the effect, confirming the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibition and suggesting that constitutive DAF expression is negatively regulated by geranylgeranylation. Neither farnesyl pyrophosphate nor squalene inhibited statin-induced DAF expression, suggesting that the effect is independent of cholesterol lowering. Statin-induced DAF upregulation was mediated by the activation of protein kinase Calpha and inhibition of RhoA and was independent of phosphatidylinositol-3 kinase and NO activity. The increased DAF expression was functionally effective, resulting in significant reduction of C3 deposition and complement-mediated lysis of antibody-coated ECs. These observations provide evidence for a novel cytoprotective action of statins on vascular endothelium that is independent of the effect on lipids and results in enhanced protection against complement-mediated injury. Modulation of complement regulatory protein expression may contribute to the early beneficial effects of statins in reducing the morbidity and mortality associated with atherosclerosis.

Angiogenesis and chemokines in rheumatoid arthritis and other systemic inflammatory rheumatic diseases

Angiogenesis, the formation of new vessels, is important in the pathogenesis of rheumatoid arthritis (RA) and other inflammatory diseases. Chemotactic cytokines termed chemokines mediate the ingress of leukocytes, including neutrophils and monocytes into the inflamed synovium. In this review, authors discuss the role of the most important angiogenic factors and angiogenesis inhibitors, as well as relevant chemokines and chemokine receptors involved in chronic inflammatory rheumatic diseases. RA was chosen as a prototype to discuss these issues, as the majority of studies on the role of angiogenesis and chemokines in inflammatory diseases were carried out in arthritis. However, other systemic inflammatory (autoimmune) diseases including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), mixed connective tissue disease (MCTD), polymyositis/dermatomyositis (PM/DM) and systemic vasculites are also discussed in this context. As a number of chemokines may also play a role in neovascularization, this issue is also described here. Apart from discussing the pathogenic role of angiogenesis and chemokines, authors also review the regulation of angiogenesis and chemokine production by other inflammatory mediators, as well as the important relevance of neovascularization and chemokines for antirheumatic intervention.

bFGF and VEGF synergistically enhance endothelial cytoprotection via decay-accelerating factor induction

The complement-regulatory protein decay-accelerating factor (DAF) can be upregulated on endothelial cells (EC) by protein kinase C (PKC)-dependent and -independent pathways. We hypothesized that basic fibroblast growth factor (bFGF) might induce EC DAF expression, providing a cytoprotective mechanism for angiogenic neovessels against complement-mediated injury. Incubation of umbilical vein, aortic, and dermal EC with bFGF or vascular endothelial growth factor (VEGF) significantly increased DAF expression. Growth factor-induced EC proliferation was inhibited by PKC antagonists. In contrast, although PKC antagonists inhibited VEGF-induced DAF expression, bFGF-induced DAF was unaffected. Investigation of mitogen-activated kinase (MAPK) pathways also revealed differences, with bFGF-induced DAF dependent on p44/42 and p38 MAPK and VEGF requiring activation of p38 MAPK alone. Upregulation of DAF by bFGF was functionally relevant, reducing C3 deposition on EC after complement activation by 60% and resulting in marked reduction in complement-mediated EC lysis. bFGF and VEGF were synergistic in terms of DAF expression, resulting in enhanced cytoprotection. These observations reveal parallel PKC-dependent and -independent pathways regulating complement activation during angiogenesis. Further elucidation of these pathways may provide important insights into innate cytoprotective mechanisms in endothelium.