Effects of interleukin-1, -2, -4, -6, interferon-gamma and granulocyte/macrophage colony stimulating factor on human vascular endothelial cells

Changes in aqueous and vitreous inflammatory cytokine levels in nonproliferative diabetic retinopathy: systematic review and meta-analysis

OBJECTIVE

Diabetic retinopathy is a complication of diabetes mellitus with the potential for significant patient morbidity. Although changes to intraocular inflammatory cytokines are integral to disease pathogenesis, studies have been inconsistent about which exact cytokines are associated with diabetic retinopathy. We aimed to quantitatively summarize proangiogenic and proinflammatory cytokines in nonproliferative diabetic retinopathy (NPDR), given its frequency among those with diabetes mellitus.

METHODS

A systematic literature search without year limitation to February 21, 2022, identified 59 studies assessing vitreous or aqueous cytokine levels in NPDR, encompassing 1378 eyes with NPDR and 1288 eyes from nondiabetic controls. Effect sizes were generated as standardized mean differences (SMD) of cytokine concentrations between patients with NPDR and controls.

RESULTS

Concentrations (SMD, 95% confidence interval, and p value) of aqueous interleukin-6 (IL-6) (2.58, 1.17‒3.99; p = 0.0003), IL-8 (1.56, 0.39‒2.74; p = 0.009), IL-17 (13.55, 7.50‒19.59; p < 0.001), transforming growth factor beta (TGF-β) (2.44, 1.02‒3.85; p = 0.0007) and vascular endothelial growth factor (VEGF) (1.35, 0.76‒1.93; p < 0.00001), and vitreous VEGF (1.49, 0.60‒2.37; p = 0.001) were significantly higher in patients with NPDR when compared with those of healthy controls.

CONCLUSIONS

These cytokines may serve as disease markers of the biochemical alterations seen in NPDR and may guide interventions, as we move into an era of more targeted therapeutics.

Association between Systemic Factors and Vitreous Fluid Cytokines in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a vision-threatening complication of diabetes mellitus (DM). Systemic and intraocular factors are intricately related to PDR, and vitreous fluid (VF) cytokines are representative intraocular biomarkers. However, the associations between systemic factors and VF cytokines and their influence on PDR pathology are unclear. This study aimed to examine the correlation between systemic factors and VF cytokines and analyze their contributions to the pathology of PDR using multivariate analyses. We conducted a retrospective observational study on 26 PDR eyes of 25 patients with type 2 DM, and 30 eyes of 30 patients with idiopathic macular hole or epiretinal membrane as controls. Fifteen systemic and laboratory tests including blood pressure (BP) and body mass index (BMI), and 27 cytokines in VF were analyzed. BP and BMI correlated positively with VF levels of IL-6 and IP-10 in PDR patients, while no significant correlation was found between systemic factors and VF cytokines in controls. MCP-1 and VEGF-A in VF separately clustered with different systemic factors in controls, but these cytokines lost the property similarity with systemic factors and acquired property similarity with each other in PDR. Systemic factors contributed to only 10.4%, whereas VF cytokines contributed to 42.3% out of 52.7% variance of the whole PDR dataset. Our results suggest that intraocular factors play a major role in the pathology of PDR, whereas systemic factors may have limited effects, and that BP and BMI control in PDR could be useful interventions to improve intraocular immune condition.

Promotion of angiogenesis in vitro by Astragalus polysaccharide via activation of TLR4 signaling pathway

During the implantation of functional tissue-engineered constructs for treating bone defects, a functional vascular network is critical for the survival of the construct. One strategy to achieve rapid angiogenesis for this application is the co-culture of outgrowth endothelial cells (OECs) and primary human osteoblasts (POBs) within a scaffold prior to implantation. In the present study, we aim to investigate whether Astragalus polysaccharide (APS) promotes angiogenesis or vascularization via the TLR4 signaling pathway in a co-culture of OECs and POBs. The co-cultures were treated with various concentrations of APS for 24 h and, subsequently, another 7 days, followed by CD31 staining and analysis of micro-vessel-formation areas using software. Additionally, APS (0.4 mg/ml for 24 h) was added to monocultures of OECs or POBs for evaluating proliferation, apoptosis, angiogenesis, osteogenesis, TLR4 signaling pathway, and inflammatory cytokine release. We found that APS promoted angiogenesis in the co-culture at the optimal concentration of 0.4 mg/ml. TLR4 activation by APS up-regulated the expression level of TLR4/MyD88 and enhanced angiogenesis and osteogenesis in monocultures of OECs and POBs. The levels of E-selectin adhesion molecules, three cytokines (IL-6, TNF-α, and IFN-γ), and VEGF and PDGF-BB, which can induce angiogenesis, increased significantly (p < .05) following APS treatment. Therefore, APS appears to promote angiogenesis and ossification in the co-culture system via the TLR4 signaling pathway. PRACTICAL APPLICATIONS: This study demonstrates that APS may promote angiogenesis and osteocyte proliferation in OEC and POB co-culture systems through the MyD88-dependent TLR4 signaling pathway. APS might represent a potential therapeutic strategy in tissue-engineered bone implantation for the treatment of large bone defects; additionally, it has the advantage of safety, as it exhibits low or no side effects. In the future, it is expected to be used in vitro for the construction of tissue-engineered bone and in vivo after implantation in patients with bone defects for promoting rapid vascularization and ossification of tissue-engineered bone and early fusion with the recipient's bone. In addition, as a food additive, Astragalus membranaceus can be used as a tonic material in patients recovering from a fracture for promoting blood-vessel formation at the fracture site and fracture recovery. Combining traditional Chinese medicine with tissue engineering can provide further strategies for promoting the development of regenerative medicine.

The interplay of oxidative stress and ARMS2-HTRA1 genetic risk in neovascular AMD

Age-related macular degeneration (AMD) is the leading cause of vision loss in adults over 60 years old globally. There are two forms of advanced AMD: “dry” and “wet”. Dry AMD is characterized by geographic atrophy of the retinal pigment epithelium and overlying photoreceptors in the macular region; whereas wet AMD is characterized by vascular penetrance from the choroid into the retina, known as choroidal neovascularization (CNV). Both phenotypes eventually lead to loss of central vision. The pathogenesis of AMD involves the interplay of genetic polymorphisms and environmental risk factors, many of which elevate retinal oxidative stress. Excess reactive oxygen species react with cellular macromolecules, forming oxidation-modified byproducts that elicit chronic inflammation and promote CNV. Additionally, genome-wide association studies have identified several genetic variants in the age-related maculopathy susceptibility 2/high-temperature requirement A serine peptidase 1 (ARMS2-HTRA1) locus associated with the progression of late-stage AMD, especially the wet subtype. In this review, we will focus on the interplay of oxidative stress and HTRA1 in drusen deposition, chronic inflammation, and chronic angiogenesis. We aim to present a multifactorial model of wet AMD progression, supporting HTRA1 as a novel therapeutic target upstream of vascular endothelial growth factor (VEGF), the conventional target in AMD therapeutics. By inhibiting HTRA1’s proteolytic activity, we can reduce pro-angiogenic signaling and prevent proteolytic breakdown of the blood-retina barrier. The anti-HTRA1 approach offers a promising alternative treatment option to wet AMD, complementary to anti-VEGF therapy.

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

Diabetic retinopathy is one of the leading causes of visual impairment and morbidity worldwide, being the number one cause of blindness in people between 27 and 75 years old. It is estimated that ~191 million people will be diagnosed with this microvascular complication by 2030. Its pathogenesis is due to alterations in the retinal microvasculature as a result of a high concentration of glucose in the blood for a long time which generates numerous molecular changes like oxidative stress. Therefore, this narrative review aims to approach various biomarkers associated with the development of diabetic retinopathy. Focusing on the molecules showing promise as detection tools, among them we consider markers of oxidative stress (TAC, LPO, MDA, 4-HNE, SOD, GPx, and catalase), inflammation (IL-6, IL-1ß, IL-8, IL-10, IL-17A, TNF-α, and MMPs), apoptosis (NF-kB, cyt-c, and caspases), and recently those that have to do with epigenetic modifications, their measurement in different biological matrices obtained from the eye, including importance, obtaining process, handling, and storage of these matrices in order to have the ability to detect the disease in its early stages.

Comprehensive expression patterns of inflammatory cytokines in aqueous humor of patients with neovascular age-related macular degeneration

Neovascular age-related macular degeneration (nAMD) is a complex and multi-factorial disease, and low-grade inflammation is associated with pathogenesis of nAMD. Aqueous humor could reflect intraocular immune environments in various eye diseases. The research so far used aqueous humor samples and revealed that inflammation is involved in pathophysiology of nAMD, although immunological roles of cytokines were evaluated inadequately with aspect to individual effects. Here we used 27 kinds of cytokines covering general immunologic reactions, examined specific expression patterns of cytokines, and assessed relationships between inflammation and pathophysiology of nAMD by multivariate analyses. In nAMD eyes, principal component analysis showed that IL-7, MCP-1, MIP-1β and VEGF had high principal component loadings of over 0.6 in the first principal component constituting 32.6% of all variability of the data. In exploratory factor analysis, IL-6, MCP-1 and MIP-1β had high factor loadings (FL) of over 0.5 in Factor 1 constituting 32.6% of all variability, while VEGF had FL of over 1.0 in Factor 3 constituting 10.7% of all variability. In hierarchical cluster analysis, MCP-1 and VEGF were located in the cluster of first proximate mutual distance to central retinal thickness. These data could suggest that low-grade inflammation is a principal contributor in nAMD.

Aqueous Humor Mediator and Cytokine Aberrations in Diabetic Retinopathy and Diabetic Macular Edema: A Systematic Review and Meta-Analysis

Purpose

To evaluate the relationship between the aqueous humor levels of VEGF, TNF-α, IL-10, IL-6, IL-12, MCP-1, and IP-10 with DR/DME.

Methods

PubMed, Web of Science, Embase, China National Knowledge Infrastructure (CNKI), and Wanfang databases were searched up to October 2018. Systematic review and meta-analysis were conducted.

Results

18 studies comprising 362 cases with DR (100 with DME) and 620 controls without DR were included in this meta-analysis. There was a significant association between VEGF levels in the aqueous humor and DR (standardized mean difference (SMD) 1.94 (95% CI 1.05-2.83)) and DME (1.07 (0.71, 1.42)). Furthermore, a significant correlation was observed between levels of IL-6 and DR (3.53 (0.37, 6.69)), and similarly correlation with DME (1.26 (0.30, 2.21)). The relationship between MCP-1 and DR and DME was significant, in which the SMD was (0.49 (0.09, 0.89)) and (1.49 (0.78, 2.20)), respectively. However, IL-12, IP-10, and TNF-α had no correlation with DR and DME, whereas there was a significant relationship between IL-8 and DME (1.68 (0.97, 2.40)).

Conclusion

Elevated levels of VEGF, IL-6, and MCP-1 in the aqueous humor were associated with the risk for the presence of DR, and levels of VEGF, IL-6, IL-8, and MCP-1 were associated with the risk of DME. Furthermore, these biomarkers may be used as potential predictors or therapeutic targets for DR/DME.

Induction and characterization of anti-tumor endothelium immunity elicited by ValloVax therapeutic cancer vaccine

ValloVax is a placental endothelium derived vaccine which induces tissue-nonspecific antitumor immunity by blocking tumor angiogesis. To elucidate mechanisms of action, we showed that production of ValloVax, which involves treating placental endothelial cells with IFN-gamma, results in upregulation of HLA and costimulatory molecules. It was shown that in mixed lymphocyte reaction, ValloVax induces Type I cytokines and allo-proliferative responses. Plasma from ValloVax immunized mice was capable of killing in vitro tumor-like endothelium but not control endothelium. Using defined antigens associated with tumor endothelial cells, specific molecular entities were identified as being targeted by ValloVax induced antibodies. Binding of predominantly IgG antibodies to ValloVax cells was confirmed by flow cytometry. Further suggesting direct killing of tumor endothelial cells was expression of TUNEL positive cells, as well as, reduction in tumor oxygenation. Supporting a role for antibody mediated responses, cell depletion experiments suggested a predominant role of B cells in maintaining an intact anti-tumor endothelial response. Adoptive transfer experiments suggested that infusion of CD3+ T cells from immunized mice was sufficient to transfer tumor protection. Generation of memory T cells selective to tumor endothelial specific markers was observed. Functional confirmation of memory responses was observed in tumor rechallenge experiments. Furthermore, we observed that both PD-1 or CTLA-4 blockade augmented antitumor effects of ValloVax. These data suggest a T cell induced B cell mediated anti-tumor endothelial response and set the framework clinical trials through elucidation of mechanism of action.

Intraocular inflammatory cytokines in patients with neovascular age-related macular degeneration before and after initiation of intravitreal injection of anti-VEGF inhibitor

Age-related macular degeneration (AMD) is a cause of blindness in people older than 50 years. Accumulating evidence indicates the involvement of systemic and local inflammation in the pathogenesis and progression of AMD. Aflibercept is an anti-vascular endothelial growth factor (VEGF) inhibitor, and intravitreal injection of aflibercept (IVA) is the approved treatments of neovascular AMD (nAMD), but the effect on inflammatory response remains unclear. The aim of our study was to investigate the profiles of inflammatory cytokines in the aqueous humor of nAMD patients before and after initiation of IVA. In nAMD patients, IP-10 level was significantly higher and IL-6 level was significantly lower compared with those of cataract patients as controls. Logistic regression analysis identified IP-10 as a positive factor and IL-6 a negative factor associated with the pathogenesis of nAMD. In addition, IP-10 level correlated positively with the mean thickness of macula in the central 1-mm diameter circle. After initiation of IVA, IP-10 level was further elevated, and correlated negatively with VEGF level. These data suggest that IP-10 plays a critical role as an antiangiogenic factor and at the same time an inflammatory factor in the pathogenesis and pathophysiology of nAMD eyes at onset and after IVA initiation.

Assessment of biomarkers using multiplex assays in aqueous humor of patients with diabetic retinopathy

Background

With the high prevalence of type 2 diabetes, diabetic retinopathy (DR) has become a leading health problem worldwide. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. The purpose of this study was to assess the levels of immune and inflammatory biomarkers in the aqueous humor of patients with different severities of DR and to analyze the correlations between Interleukin-6 (IL-6) and these biomarkers, and between IL-6 and the severity of the disease.

Methods

Aqueous humor samples were obtained from 51 non-diabetic patients and 151 diabetic patients. Levels of 45 different cytokines, chemokines, and growth factors were measured using a multiplex bead immunoassay.

Results

IL-6, IL-8, Inducible Protein-10 (IP-10), leukemia inhibitory factor (LIF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF)-A were significantly higher (p < 0.05) in the aqueous humor of the DR patients compared to the non-diabetic patients, while the concentrations of IL-1α, IL-4, IL-9, IL-21, IL-23, IL-27, IL-31, RANTES, interferon-α, growth regulated oncogene (GRO), and tumor necrosis factor (TNF)-α were significantly lower (p < 0.05) in the DR patients. The IL-6 levels increased as the severity of DR increased. In addition, the IL-6 level positively correlated with the IL-8, HGF and LIF levels, while negatively with the IL-31and GRO levels.

Conclusions

These findings suggest that inflammation and immune response may contribute to the pathogenesis of DR, and these biomarkers may potentially be new therapeutic targets for DR.

MCPIP1 contributes to clear cell renal cell carcinomas development

Monocyte Chemoattractant protein-induced protein 1 (MCPIP1), also known as Regnase-1, is encoded by the ZC3H12a gene, and it mediates inflammatory processes by regulating the stability of transcripts coding for proinflammatory cytokines and controlling activity of transcription factors, such as NF-κB and AP1. We found that MCPIP1 transcript and protein levels are strongly downregulated in clear cell renal cell carcinoma (ccRCC) samples, which were derived from patients surgically treated for renal cancer compared to surrounded normal tissues. Using Caki-1 cells as a model, we analyzed the role of MCPIP1 in cancer development. We showed that MCPIP1 expression depends on the proteasome activity; however, hypoxia and hypoxia inducible factor 2 alfa (HIF2α) are key factors lowering MCPIP1 expression. Furthermore, we found that MCPIP1 negatively regulates HIF1α and HIF2α levels and in the case of the last one, the mechanism is based on the regulation of the half time of transcript coding for HIF2α. Enhanced expression of MCPIP1 in Caki-1 cells results in a downregulation of transcripts encoding VEGFA, GLUT1, and IL-6. Furthermore, MCPIP1 decreases the activity of mTOR and protein kinase B (Akt) in normoxic conditions. Taken together, MCPIP1 contributes to the ccRCC development.

Idiopathic Choroidal Neovascularization: Intraocular Inflammatory Cytokines and the Effect of Intravitreal Ranibizumab Treatment

Idiopathic choroidal neovascularization (ICNV) is a disorder that primarily affecting patients younger than 50 years and can cause severe loss of vision. Choroidal abnormalities, especially choroidal inflammation, have been thought to be involved in the pathophysiology of ICNV. However, the exact pathogenesis of ICNV remains unclear. The aim of our study was investigate the levels of 27 inflammatory cytokines in the aqueous humor of eyes with ICNV, and to determine the effect of intravitreal injection of ranibizumab (IVR) on cytokine levels. Significantly higher levels of IL-2, IL-10, IL-15, IL-17, basic FGF, and GM-CSF were observed in patients with ICNV compared with controls. However, only IL-17 levels were significantly higher in patients with ICNV compared with controls after adjusting for axial length. Furthermore, there were significant correlations between the levels of IL-10, IL-17, GM-CSF, and VEGF and the lesion area. Significant changes in visual acuity and central retinal thickness were observed after IVR. Besides VEGF, IVR also significantly reduced the levels of IL-2, IL-10, basic FGF, and IL-12, however, the IL-6 levels were significantly increased. Our results suggest that there may be an involvement of IL-17-related inflammatory processes in the etiology of ICNV.

Association of Haemostatic and Inflammatory Biomarkers with Nephropathy in Type 1 Diabetes Mellitus

This study aimed at investigating the association between haemostatic biomarkers, proinflammatory, and anti-inflammatory cytokines with chronic kidney disease in type 1 diabetic patients. Patients were divided into two groups: with nephropathy (albuminuria ≥ 30 mg/g and/or GFR < 60 mL/min/1.73 m(2)), n = 65; and without nephropathy (albuminuria < 30 mg/g and GFR ≥ 60 mL/min/1.73 m(2)), n = 60. INF-γ, IL-6, IL-10, and TNF-α plasma levels were determined by flow cytometry. VWF, ADAMTS13 antigen, and D-Dimer plasma levels were determined by enzyme-linked immunosorbent assay and ADAMTS13 activity was assessed by fluorescence resonance energy transfer assay. Elevated levels of INF-γ, VWF, ADAMTS13 antigen, D-Dimer, and reduced ADAMTS13 activity/antigen ratio were observed in patients with nephropathy as compared to those without nephropathy (P = 0.001, P < 0.001, P < 0.001, P < 0.001, and P < 0.001, resp.). Cytokines and haemostatic biomarkers remained associated with nephropathy after adjustments (use of statin, acetylsalicylic acid, angiotensin converting enzyme inhibitor, and angiotensin antagonist). INF-γ, TNF-α, and IL-10 significantly correlated with haemostatic biomarkers. Inflammatory and hypercoagulability status are associated with nephropathy in type 1 diabetes mellitus and an interrelationship between them may play an important role in pathogenesis of diabetic nephropathy.

Filarial excretory-secretory products induce human monocytes to produce lymphangiogenic mediators

The nematodes Wuchereria bancrofti and Brugia spp. infect over 120 million people worldwide, causing lymphedema, elephantiasis and hydrocele, collectively known as lymphatic filariasis. Most infected individuals appear to be asymptomatic, but many exhibit sub-clinical manifestations including the lymphangiectasia that likely contributes to the development of lymphedema and elephantiasis. As adult worm excretory-secretory products (ES) do not directly activate lymphatic endothelial cells (LEC), we investigated the role of monocyte/macrophage-derived soluble factors in the development of filarial lymphatic pathology. We analyzed the production of IL-8, IL-6 and VEGF-A by peripheral blood mononuclear cells (PBMC) from naïve donors following stimulation with filarial ES products. ES-stimulated PBMCs produced significantly more IL-8, IL-6 and VEGF-A compared to cells cultured in medium alone; CD14(+) monocytes appear to be the primary producers of IL-8 and VEGF-A, but not IL-6. Furthermore, IL-8, IL-6 and VEGF-A induced in vitro tubule formation in LEC Matrigel cultures. Matrigel plugs supplemented with IL-8, IL-6, VEGF-A, or with supernatants from ES-stimulated PBMCs and implanted in vivo stimulated lymphangiogenesis. Collectively, these data support the hypothesis that monocytes/macrophages exposed to filarial ES products may modulate lymphatic function through the secretion of soluble factors that stimulate the vessel growth associated with the pathogenesis of filarial disease.

A functional perspective of nitazoxanide as a potential anticancer drug

Cancer is a group of diseases characterized by uncontrolled cell proliferation, evasion of cell death and the ability to invade and disrupt vital tissue function. The classic model of carcinogenesis describes successive clonal expansion driven by the accumulation of mutations that eliminate restraints on proliferation and cell survival. It has been proposed that during cancer's development, the loose-knit colonies of only partially differentiated cells display some unicellular/prokaryotic behavior reminiscent of robust ancient life forms. The seeming "regression" of cancer cells involves changes within metabolic machinery and survival strategies. This atavist change in physiology enables cancer cells to behave as selfish "neo-endo-parasites" that exploit the tumor stromal cells in order to extract nutrients from the surrounding microenvironment. In this framework, it is conceivable that anti-parasitic compounds might serve as promising anticancer drugs. Nitazoxanide (NTZ), a thiazolide compound, has shown antimicrobial properties against anaerobic bacteria, as well as against helminths and protozoa. NTZ has also been successfully used to promote Hepatitis C virus (HCV) elimination by improving interferon signaling and promoting autophagy. More compelling however are the potential anti-cancer properties that have been observed. NTZ seems to be able to interfere with crucial metabolic and pro-death signaling such as drug detoxification, unfolded protein response (UPR), autophagy, anti-cytokine activities and c-Myc inhibition. In this article, we review the ability of NTZ to interfere with integrated survival mechanisms of cancer cells and propose that this compound might be a potent addition to the current chemotherapeutic strategy against cancer.

Anti-VEGF therapy reduces intestinal inflammation in Endoglin heterozygous mice subjected to experimental colitis

Chronic intestinal inflammation is associated with pathological angiogenesis that further amplifies the inflammatory response. Vascular endothelial growth factor (VEGF), is a major angiogenic cytokine that has been implicated in chronic colitis and inflammatory bowel diseases. Endoglin (CD105), a transforming growth factor-β superfamily co-receptor expressed on endothelial and some myeloid cells, is a modulator of angiogenesis involved in wound healing and potentially in resolution of inflammation. We showed previously that Endoglin heterozygous (Eng (+/-)) mice subjected to dextran sodium sulfate developed severe colitis, abnormal colonic vessels and high tissue VEGF. We therefore tested in the current study if treatment with a monoclonal antibody to VEGF could ameliorate chronic colitis in Eng (+/-) mice. Tissue inflammation and microvessel density (MVD) were quantified on histological slides. Colonic wall thickness, microvascular hemodynamics and targeted MAdCAM-1(+) inflamed vessels were assessed in vivo by ultrasound. Mediators of angiogenesis and inflammation were measured by Milliplex and ELISA assays. Colitic Eng (+/-) mice showed an increase in intestinal inflammation, MVD, colonic wall thickness, microvascular hemodynamics and the number of MAdCAM-1(+) microvessels relative to colitic Eng (+/+) mice; these parameters were all attenuated by anti-VEGF treatment. Of all factors up-regulated in the inflamed gut, granulocyte colony-stimulating factor (G-CSF) and amphiregulin were further increased in colitic Eng (+/-) versus Eng (+/+) mice. Anti-VEGF therapy decreased tissue VEGF and inflammation-induced endoglin, IL-1β and G-CSF in colitic Eng (+/-) mice. Our results suggest that endoglin modulates intestinal angiogenic and inflammatory responses in colitis. Furthermore, contrast-enhanced ultrasound provides an excellent non-invasive imaging modality to monitor gut angiogenesis, inflammation and responses to anti-angiogenic treatment.

Interleukin-6: an angiogenic target in solid tumours

During the past decade, incorporating anti-angiogenic agents into the therapeutic management of a myriad of malignancies has in certain cases made a significant impact on survival. However, the development of resistance to these drugs is inevitable and swift disease progression on their cessation often ensues. Hence, there is a drive to devise strategies that aim to enhance response to anti-angiogenic therapies by combining them with other targeted agents that facilitate evasion from resistance. The pleiotropic cytokine, interleukin-6 (IL-6), exerts pro-angiogenic effects in the tumour microenvironment of several solid malignancies and there is emerging evidence that reveals significant relationships between IL-6 signalling and treatment failure with antibodies directed against vascular endothelial growth factor (VEGF). This review summarises the role of IL-6 in pivotal angiogenic processes and preclinical/clinical research to support the future introduction of anti-IL-6 therapies to be utilised either in combination with other anti-angiogenic drugs or as a salvage therapy for patients with diseases that become refractory to these approaches.

Differences in aqueous concentrations of cytokines in macular edema secondary to branch and central retinal vein occlusion

PURPOSE

This study investigates the differential aqueous concentrations of interleukin 6, 8, 1β (IL-6, IL-8, IL-1β, respectively), serum amyloid A (SAA), transforming growth factor (TGF)-β, basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) in eyes with macular edema as a result of a branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO).

PRINCIPAL FINDINGS

Significantly higher concentrations of IL-6, IL-8, IL-1β, TGF-β, bFGF, SAA, and VEGF were found in the aqueous humor of CRVO and BRVO patients than in the aqueous humor of control patients. A significant correlation was observed between the concentration of bFGF and the inner central macular thickness (CMT) of BRVO patients (r = 0.688; P = 0.02). A significant correlation was observed between the concentration of SAA and both the full and outer CMT of the ischemic group (r = 0.545 and 0.683, respectively; P = 0.04 and 0.01, respectively). In the non-ischemic group, the level of IL-6 was significantly associated with inner CMT (r = 0.560; P = 0.03). The full and outer CMT was significantly reduced in CRVO patients when compared with BRVO patients (P = 0.02 and 0.02, respectively) after injection of intravitreal bevacizumab (IVB) at 4 weeks.

SIGNIFICANCE

Serum amyloid A as a major protein involved in the acute and chronic stages of inflammation, and IL-6 and bFGF were significantly associated with the extent of macular edema in patients with RVO. Besides VEGF, other inflammatory cytokines and angiogenesic factors may be associated with RVO. This finding may have implications for the medical treatment of RVO.

Increased IL-6 levels are not related to NF-κB or HIF-1α transcription factors activity in the vitreous of proliferative diabetic retinopathy

PURPOSE

The purpose was to assess the activity of nuclear factor (NF)-κB and hypoxia inducible factor (HIF)-1α transcription factors and the expression levels of inflammation markers [interleukin (IL)-6 and IL-8] in the vitreous of patients suffering from proliferative diabetic retinopathy (PDR) scheduled for elective vitreous surgery in a single academic-based retina practice in a prospective clinical study.

METHODS

Twenty-seven patients with PDR were enrolled in the study. The severity of retinopathy was classified (0, 1, 2, 3, 4) and the activity of neovascularization was graded (0, 1, 2, 3, 4) by the surgeon intraoperatively. Samples of the vitreous were collected during surgery, and the activity of NF-κB and HIF-1α transcription factors and the expression levels of IL-6 and IL-8 were measured.

RESULTS

The majority of samples fell into the retinopathy class 3 (n = 12) or 4 (n = 13). The level of IL-6 increased from 68.9 ± 46.8 pg/ml to 102.7 ± 94.1 pg/ml, and IL-8 increased from 165.1 ± 136.0 pg/ml to 521.0 ± 870.9 pg/ml (mean ± S.D., nonsignificant change: normality test followed with Mann-Whitney Rank Sum Test). According to the neovascularization activity, the samples fell into grade 1 (n = 7), 2 (n = 12) or 3 (n = 7). In IL-6, there was a statistically significant increase (P < .05) from grade 2 to 3: 58.6 ± 40.3 pg/ml and 158.4 ± 102.5 pg/ml, respectively (Kruskal-Wallis One-Way Analysis of Variance on Ranks followed with Dunn's Method). The level of IL-8 was as follows: in grade 1: 118.0 ± 62.4 pg/ml, in grade 2: 192.3 ± 127.1 pg/ml and in grade 3: 884.3 ± 1161.0 pg/ml (statistically nonsignificant change). There was a statistically significant linear regression between IL-6 and IL-8 (P < .001): IL-6 = 51.88 pg/ml + (0.092*IL-8), r = 0.772. Increased activity of the NF-κB and HIF-1α transcription factors was not observed.

CONCLUSION

Interleukin-6 is a candidate to indicate activity of neovascularization process in PDR. It might be a new molecular therapeutic target to regulate innate immunity response in vitreous.

The link between major histocompatibility complex antibodies and cell proliferation

Experimental evidence indicates that donor-specific antibodies targeting major histocompatibility complex classes I and II molecules can elicit the key features of transplant vasculopathy by acting on the graft vasculature in 3 ways: directly activating proliferative, prosurvival, and migratory signaling in the target endothelial and smooth muscle cells; increasing expression of mitogenic factors in vascular endothelial cells, creating a potential proliferative autocrine loop; and promoting recruitment of inflammatory cells that produce mitogenic factors and elicit chronic inflammation, proliferation, and fibrosis. Here, we review the experimental literature showing the complement and Fc-independent effects of major histocompatibility complex classes I and II antibodies on graft vascular cells that may directly contribute to the proliferative aspect of transplant vasculopathy.

Inflammatory and angiogenic factors in the aqueous humor and the relationship to diabetic retinopathy

PURPOSE

To determine the relationship between the aqueous concentrations of inflammatory and angiogenic factors and the severity of diabetic retinopathy and diabetic macular edema.

METHODS

Aqueous samples were obtained from 50 eyes of diabetic patients and 28 eyes of nondiabetic subjects. The aqueous levels of inflammatory factors, including IL-1β, TNF-α, MCP-1, IP-10, IL-8, IL-6, and VEGF were measured with multiplex bead array assays. The aqueous levels of cytokines were investigated according to the severity of diabetic retinopathy and diabetic macular edema measured by optical coherence tomography.

RESULTS

The aqueous levels of MCP-1, IP-10, IL-8, and VEGF were higher in eyes of diabetic patients than in eyes of nondiabetic subjects. The aqueous levels of MCP-1 and IP-10 were elevated in eyes with severe NPDR and PDR compared to eyes with less severe DR and eyes of nondiabetic subjects. There was a trend toward elevated IL-8 levels in eyes with severe NPDR compared to eyes of nondiabetic subjects. The aqueous levels of VEGF were markedly elevated in eyes with PDR that had not received PRP compared to eyes with severe NPDR. Eyes with PDR that had received PRP treatment showed higher MCP-1 and IP-10 levels than eyes with PDR that had not received PRP treatment. The aqueous levels of IL-6 were positively correlated with TMV and CSMT in eyes with DR.

CONCLUSIONS

Elevation of MCP-1, IP-10, and IL-8 levels in eyes with severe NPDR suggests that inflammatory change precedes the development of neovascularization in PDR. The positive correlation between the aqueous levels of IL-6 and macular thickness indicates that IL-6 may play a central role in the development of diabetic macular edema.

Chemokines and common variable immunodeficiency; possible contribution of the fractalkine system (CX3CL1/CX3CR1) to chronic inflammation

Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by defective immunoglobulin production and high frequency of bacterial infections, autoimmunity and manifestations of chronic inflammation. The chemokine Fractalkine (CX3CL1) and its receptor CX3CR1 is suggested to play an important role in the pathogenesis of several inflammatory disorders. We hypothesized that enhanced CX3CL1/CX3CR1 interaction could be involved in the chronic inflammation characterising subgroups of CVID. CVID patients were characterized by raised plasma levels of CX3CLl and enhanced expression of its corresponding receptor CX3CR1 on CD4(+) and CD8(+) T cells, including both CD45RA(+) and CD45RA(-) subsets. CX3CR1 expression was particularly enhanced in patients characterized by chronic inflammation in vivo. The high expression of the receptor in CVID patients was accompanied by enhanced chemotactic, adhesive, and other inflammatory cell responses to stimulation with CX3CL1. Our findings suggest that increased CX3CL1/CX3CR1 interaction could contribute to the inflammatory phenotype seen in subgroups of CVID patients.

Hematopoietic progenitor cells and interleukin-stimulated endothelium: expansion and differentiation of myeloid precursors

BACKGROUND

Cytokine-stimulated endothelial cells (EC) propagate hematopoietic progenitor cell (HPC) expansion. However, the effects on the functional capacities of cultured progenitors have not been evaluated. HPC were assessed by flow cytometry, colony and cobblestone assays and long-term cultures (LTC) after culturing in the supernatant of EC stimulated by IL-1beta, IL-3 or IL-6.

RESULTS

EC incubation with IL-6 did not improve cell expansion in comparison to non-stimulated EC supernatant, while the HPCs' phenotype and functional capacities were retained. In contrast, IL-1beta and IL-3 stimulation resulted in a 10- and 100-fold increase in cell numbers with more than 90% of these cells being CD33(+). Plating efficiencies and LTC initiating cells were greatest in IL-6 supernatants, whereas the highest numbers of burst-forming units were observed using IL-3. IL-1beta supernatants diminished the number of 5-week cobblestone-areas, whereas the number of 2-week cobblestone areas remained equal to freshly isolated HPC. Fewer 2-week cobblestones and greater amounts of 5-week cobblestones were observed with IL-6 and IL-3. Expanded progenitors from all interleukin conditions were further matured into functional granulocytes.

CONCLUSION

IL-1beta and IL-3 stimulated endothelium induces proliferation and differentiation of myeloid precursors, while IL-6 treatment induced a benefit of HPC survival.

Synergistic antitumor response of interleukin 2 with melphalan in isolated limb perfusion in soft tissue sarcoma-bearing rats

The cytokine interleukin 2 (IL-2) is a mediator of immune cell activation with some antitumor activity, mainly in renal cell cancer and melanoma. We have previously shown that tumor necrosis factor (TNF)-alpha has strong synergistic antitumor activity in combination with chemotherapeutics in the isolated limb perfusion (ILP) setting based on a TNF-mediated enhanced tumor-selective uptake of the chemotherapeutic drug followed by a selective destruction of the tumor vasculature. IL-2 can cause vascular leakage and edema and for this reason we examined the antitumor activity of a combined treatment with IL-2 and melphalan in our well-established ILP in soft tissue sarcoma-bearing rats (BN175). ILP with either IL-2 or melphalan alone has no antitumor effect, but the combination of IL-2 and melphalan resulted in a strong synergistic tumor response, without any local or systemic toxicity. IL-2 enhanced significantly melphalan uptake in tumor tissue. No signs of significant vascular damage were detected to account for this observation, although the tumor sections of the IL-2- and IL-2 plus melphalan-treated animals revealed scattered extravasation of erythrocytes compared with the untreated animals. Clear differences were seen in the localization of ED-1 cells, with an even distribution in the sham, IL-2 and melphalan treatments, whereas in the IL-2 plus melphalan-treated tumors clustered ED-1 cells were found. Additionally, increased levels of TNF mRNA were found in tumors treated with IL-2 and IL-2 plus melphalan. These observations indicate a potentially important role for macrophages in the IL-2-based perfusion. The results in our study indicate that the novel combination of IL-2 and melphalan in ILP has synergistic antitumor activity and may be an alternative for ILP with TNF and melphalan.

The role of insulin and the adipocytokines in regulation of vascular endothelial function

Vascular integrity in the healthy endothelium is maintained through the release of a variety of paracrine factors such as NO (nitric oxide). Endothelial dysfunction, characterized by reduced NO bioavailability, is associated with obesity, insulin resistance and Type II diabetes. Insulin has been demonstrated to have direct effects on the endothelium to increase NO bioavailability. Therefore altered insulin signalling in the endothelium represents a candidate mechanism underlying the association between insulin resistance and endothelial dysfunction. In recent years, it has become apparent that insulin sensitivity is regulated by the adipocytokines, a group of bioactive proteins secreted by adipose tissue. Secretion of adipocytokines is altered in obese individuals and there is increasing evidence that the adipocytokines have direct effects on the vascular endothelium. A number of current antidiabetic strategies have been demonstrated to have beneficial effects on endothelial function and to alter adipocytokine concentrations in addition to their effects on glucose homoeostasis. In this review we will explore the notion that the association between insulin resistance and endothelial dysfunction is accounted for by adipocytokine action on the endothelium. In addition, we examine the effects of weight loss, exercise and antidiabetic drugs on adipocytokine availability and endothelial function.

Interleukin-6-induced JAK2/STAT3 signaling pathway in endothelial cells is suppressed by hemodynamic flow

Endothelial cells (ECs) are constantly exposed to shear stress, the action of which triggers signaling pathways and cellular responses. During inflammation, cytokines such as IL-6 increase in plasma. In this study, we examined the effects of steady flow on IL-6-induced endothelial responses. ECs exposed to IL-6 exhibited STAT3 activation via phosphorylation of Tyr705. However, when ECs were subjected to shear stress, shear force-dependent suppression of IL-6-induced STAT3 phosphorylation was observed. IL-6 treatment increased the phosphorylation of JAK2, an upstream activator of STAT3. Consistently, shear stress significantly reduced IL-6-induced JAK2 activation. Pretreatment of ECs with an inhibitor of MEK1 did not alter this suppression by shear stress, indicating that extracellular signal-regulated kinase (ERK1/2) was not involved. However, pretreatment of ECs with an endothelial nitric oxide synthase inhibitor (nitro-l-arginine methyl ester) attenuated this inhibitory effect of shear stress on STAT3 phosphorylation. Shear stress-treated ECs displayed decreased nuclear transmigration of STAT3 and reduced STAT3 binding to DNA. Intriguingly, ECs exposed to IL-6 entered the cell cycle, as evidenced by increasing G2/M phase, and shear stress to these ECs significantly reduced IL-6-induced cell cycle progression. STAT3-mediated IL-6-induced cell cycle was confirmed by the inhibition of the cell cycle in ECs infected with adenovirus carrying the inactive mutant of STAT3. Our study clearly shows that shear stress exerts its inhibitory regulation by suppressing the IL-6-induced JAK2/STAT3 signaling pathway and thus inhibits IL-6-induced EC proliferation. This shear force-dependent inhibition of IL-6-induced JAK2/STAT3 activation provides new insights into the vasoprotective effects of steady flow on ECs against cytokine-induced responses.

Guanylate-binding protein-1 expression is selectively induced by inflammatory cytokines and is an activation marker of endothelial cells during inflammatory diseases

During angiogenesis and inflammatory processes, endothelial cells acquire different activation phenotypes, whose identification may help in understanding the complex network of angiogenic and inflammatory interactions in vivo. To this goal we investigated the expression of the human guanylate-binding protein (GBP)-1 that is highly induced by inflammatory cytokines (ICs) and, therefore, may characterize IC-activated cells. Using a new rat monoclonal antibody raised against GBP-1, we show that GBP-1 is a cytoplasmic protein and that its expression in endothelial cells is selectively induced by interferon-gamma, interleukin-1alpha, interleukin-1beta, or tumor necrosis factor-alpha, but not by other cytokines, chemokines, or growth factors. Moreover, we found that GBP-1 expression is highly associated with vascular endothelial cells as confirmed by the simultaneous detection of GBP-1 and the endothelial cell-associated marker CD31 in a broad range of human tissues. Notably, GBP-1 expression was undetectable in the skin, but it was highly induced in vessels of skin diseases with a high-inflammatory component including psoriasis, adverse drug reactions, and Kaposi's sarcoma. These results indicate that GBP-1 is a novel cellular activation marker that characterizes the IC-activated phenotype of endothelial cells.

Erythropoietin and granulocyte colony-stimulating factor increase plasminogen activator inhibitor-1 release in HUVEC culture

Recombinant human erythropoietin (rHuEPO) is considered to be a mitogenic and chemotactic agent in cultured endothelial cells (ECs). The effect of recombinant granulocyte-macrophage (rGM-CSF) and granulocyte (rG-CSF) colony-stimulating factors on the proliferation of human umbilical vein endothelial cells (HUVECs) has been controversial.

METHODS

HUVEC proliferation and the release of endothelial markers in HUVEC culture stimulated by rHuEPO, rGM-CSF and G-CSF were measured.

RESULTS

We found the dose-dependent stimulating effect of rHuEPO and rGM-CSF on HUVEC proliferation, but we did not achieve this with rG-CSF. rHuEPO like rG-CSF was an effective agent in stimulating the plasminogen activator inhibitor (PAI)-1 release from HUVECs to a cultured medium, while rGM-CSF failed.

CONCLUSION

We suggest that rHuEPO showed prothrombotic changes in HUVEC culture. Our results support the idea of suspected rHuEPO direct prothrombotic role in haemodialysed patients treated with rHuEPO.

Activation of endothelium by immunotherapy with interleukin-2 in patients with malignant disorders

Treatment with intravenous recombinant human interleukin-2 (rh IL-2) is frequently accompanied by the capillary leak syndrome and disturbances of the coagulation system. Although the exact mechanisms are still not fully understood, the involvement of the endothelium is proven. This investigation aimed to elucidate more precisely the role of the endothelium in the generation of IL-2-based side-effects. In nine tumour patients receiving intravenous rh IL-2, parameters characterizing endothelial cell activation as well as activation of the coagulation system were evaluated. A significant increase of the circulating endothelial leucocyte adhesion molecule-1 (cELAM-1) and the vasoconstrictor peptide endothelin-1 (ET-1) was observed (P<0.05), indicating activation of endothelial cells. The simultaneous increase of tissue-plasminogen activator and plasminogen activator inhibitor type-1 during therapy (P<0.05) corroborated this observation. A decrease in platelet count parallelled by an increase of fibrin degradation products, the prolongation of partial thromboplastin time, and the decrease of fibrinogen (P<0.05) suggested the development of disseminated intravascular coagulation (DIC), induced by activated endothelium and intensified by transient hepatic failure. We concluded that activation of the endothelium mediated by IL-2 was accompanied by a loss of endothelial integrity and capillary leak. The activated endothelium can trigger DIC via activation of the coagulation cascade. The increased ET-1 might act as an endogenous counter-regulator of the disadvantageous haemodynamic side-effects induced by IL-2.

Differential signaling pathways in platelet-activating factor-induced proliferation and interleukin-6 production by rat vascular smooth muscle cells

Vascular smooth muscle cells (SMCs) can be induced to proliferate in response to several cytokines and growth factors, including interleukin (IL)-6. Platelet-activating factor (PAF) also has been shown to induce SMC proliferation. Because PAF can stimulate IL-6 production in monocytes, macrophages, and endothelial cells, our study was undertaken to determine whether PAF could induce IL-6 production by SMCs and to define the underlying signaling pathways. Exposure of rat aortic SMCs to picomolar concentrations of PAF resulted in enhanced production of IL-6. The effect was concentration dependent, selective for the active form of PAF, and mediated by specific PAF receptors. Pretreatment of the cells with Bordatella pertussis toxin (PTX) prevented the effect of PAF, suggesting the involvement of alpha i-type subunits of G proteins in the signal-transduction pathway. PAF-dependent IL-6 production was also prevented by inhibition of tyrosine kinases with genistein or erbstatin. Inhibition of eicosanoid production by blocking either phospholipase A2 or cyclooxygenase also abrogated the effect of PAF on IL-6 production. Moreover, inhibition of Ca2+-calmodulin activity with W7 or blocking of calcium channels with verapamil or nifedipine prevented PAF-mediated enhancement of IL-6 production. Whereas PAF-induced signal-transduction pathways leading to IL-6 production and SMC proliferation were partially common, they appeared to diverge downstream of PLA2 activation: inhibition of cyclooxygenase had no effect on proliferation, whereas augmentation of cyclic adenosine monophosphate (cAMP) levels or activation of protein kinase A inhibited proliferation, in contrast to IL-6 production. Our findings suggest a role for PAF in modulating vascular function by stimulating local production of IL-6 by SMCs and promoting their proliferation. The two effects are, however, associated with partially divergent signaling pathways and may not be causally related.

Interleukin 6 gene-transfected mouse mammary adenocarcinoma: tumour cell growth and metastatic potential

Cells from the spontaneous metastatic TSA mammary adenocarcinoma of BALB/C mouse were transfected with the murine (interleukin-6) IL6 gene. The clone (TSA-IL6) secreting the largest amount of IL6 displayed an in vitro increased growth rate compared with that of TSA cells transfected with the neomycin resistance gene only (TSA-neo). TSA-IL6 cell colonies consisted mainly of fusiform cells and TSA-neo colonies of polygonal cells. When subcutaneously (s.c.) injected in syngeneic mice, TSA-IL6 cells gave rise to tumours that grew significantly slower than TSA-neo cell tumours. Microscopically, TSA-IL6 tumours displayed a fascicular pattern of growth, associated with a very scanty macrophage infiltrate. S.c. TSA-IL6 tumours were significantly less metastatic than TSA-neo tumours. By contrast, following intravenous (i.v.) challenge, TSA-IL6 cells produced 5-7 times more lung metastases than TSA-neo cells. The i.v. TSA-IL6 cell lung metastases showed a marked macrophage infiltrate and a rich vascularization. The high in vitro TSA-IL6 cell growth rate is attributable to the IL6-induced production of growth factors, some of which possess heparin-binding properties, such as amphiregulin. The differences in vascularization and macrophage infiltrate may underlie the observed differences between s.c. TSA-IL6 tumour growth with low spontaneous metastatic potential and the widespread growth of i.v. metastasis.

Platelet-activating factor stimulates interleukin-6 production by human endothelial cells and synergizes with tumor necrosis factor for enhanced production of granulocyte-macrophage colony stimulating factor

The interaction between human endothelial cells (EC) and leukocytes during inflammation is in part mediated through the release of soluble factors. Since platelet-activating factor (PAF) is a potent mediator of inflammatory responses, we investigated the potential of PAF to modulate IL-6 and GM-CSF production by EC. Exposure of these cells to PAF resulted in a concentration-dependent increase in IL-6 production, with a maximum at 10(-10) M PAF. Sequential incubation of EC with PAF and TNF alpha resulted in a synergistic increase of IL-6 production. This effect was specific for PAF since it was prevented by preincubation with the PAF receptor antagonist, WEB 2086. Northern blot analysis revealed enhanced IL-6 mRNA expression in PAF-treated EC. However, the synergy observed in protein synthesis between PAF and TNF alpha was not reflected in IL-6 mRNA accumulation, suggesting a post-translational modulation. Pretreatment of EC with the protein synthesis inhibitor cycloheximide before their exposure to PAF resulted, after washout of the cycloheximide, in a markedly augmented production of IL-6, suggesting a synergy between augmented IL-6 mRNA accumulation by PAF and IL-6 mRNA superinduction by cycloheximide. GM-CSF production by EC was also stimulated by the combined effects of PAF and TNF alpha, but PAF alone did not affect GM-CSF production. Taken together, our data suggest that PAF can stimulate EC to synthesize cytokines, including IL-6 and GM-CSF, which may contribute to local and, possibly, systemic responses during inflammation.

Molecular mimicry of human cytokine and cytokine response pathway genes by KSHV

Four virus proteins similar to two human macrophage inflammatory protein (MIP) chemokines, interleukin-6 (IL-6), and interferon regulatory factor (IRF) are encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome. vIL-6 was functional in B9 proliferation assays and primarily expressed in KSHV-infected hematopoietic cells rather than KS lesions. HIV-1 transmission studies showed that vMIP-I is similar to human MIP chemokines in its ability to inhibit replication of HIV-1 strains dependent on the CCR5 co-receptor. These viral genes may form part of the response to host defenses contributing to virus-induced neoplasia and may have relevance to KSHV and HIV-I interactions.

ET-1 induces IL-6 gene expression in human umbilical vein endothelial cells: synergistic effect of IL-1

Endothelins are a family of potent vasoactive peptides that have also been implicated in inflammation. To examine the consequence of endothelin stimulation on cytokine production, we explored the effect of endothelin-1 (ET-1) on interleukin-6 (IL-6) gene expression. ET-1 augmented the production of IL-6 in human umbilical vein endothelial cells (HUVEC) by 2- to 5-fold and synergized with IL-1 to induce a 150-fold increase in IL-6 secretion, compared with spontaneous production. The peak of IL-6 production was in the presence of 100 pM ET-1 after 12 h of stimulation. ET-1 augmented IL-6 mRNA expression at the optimal concentration of 100 pM, in the presence of 1 ng/ml of IL-1. ET-1-induced IL-6 mRNA expression was significant within 4 h of stimulation and persisted for 18 h. Similarly, the ETB receptor-specific agonist, IRL-1620, also augmented IL-6 mRNA expression and IL-6 protein production in HUVEC. Our results suggest that endothelin may play a role at the vascular inflammatory site by modulating cytokine production through ETB receptor activation in endothelial cells of human origin.

Granulocyte macrophage colony stimulating factor produced in lesioned peripheral nerves induces the up-regulation of cell surface expression of MAC-2 by macrophages and Schwann cells

Peripheral nerve injury is followed by Wallerian degeneration which is characterized by cellular and molecular events that turn the degenerating nerve into a tissue that supports nerve regeneration. One of these is the removal, by phagocytosis, of myelin that contains molecules which inhibit regeneration. We have recently documented that the scavenger macrophage and Schwann cells express the galactose-specific lectin MAC-2 which is significant to myelin phagocytosis. In the present study we provide evidence for a mechanism leading to the augmented expression of cell surface MAC-2. Nerve lesion causes noneuronal cells, primarily fibroblasts, to produce the cytokine granulocyte macrophage-colony stimulating factor (GM-CSF). In turn, GM-CSF induces Schwann cells and macrophages to up-regulate surface expression of MAC-2. The proposed mechanism is based on the following novel observations. GM-CSF mRNA was detected by PCR in in vitro and in vivo degenerating nerves, but not in intact nerves. The GM-CSF molecule was detected by ELISA in medium conditioned by in vitro and in vivo degenerating peripheral nerves as of the 4th h after injury. GM-CSF activity was demonstrated by two independent bioassays, and repressed by activity blocking antibodies. Significant levels of GM-CSF were produced by nerve derived fibroblasts, but neither by Schwann cells nor by nerve derived macrophages. Mouse rGM-CSF enhanced MAC-2 production in nerve explants, and up-regulated cell surface expression of MAC-2 by Schwann cells and macrophages. Interleukin-1 beta up-regulated GM-CSF production thus suggesting that injury induced GM-CSF production may be mediated by interleukin-1 beta. Our findings highlight the fact that fibroblasts, by producing GM-CSF and thereby affecting macrophage and Schwann function, play a significant role in the cascade of molecular events and cellular interactions of Wallerian degeneration.

Adhesion-independent synergy of monocytes and endothelial cells in cytokine production: regulation of IL-6 and GM-CSF production by PAF

Co-Cultures of monocytes (MO) and endothelial cells (EC) were studied for their capacity to synergize in the production of interleukin-6 (IL-6) and granulocyte-macrophage colony-stimulating factor (GM–CSF), two cytokines potentially important in vascular physiopathology. Resting monocytes produced detectable amounts of IL-6 but no GM–CSF, whereas confluent EC produced significant quantities of GM–CSF, but minimal IL-6. In co-cultures without stimuli, additive synthesis of both cytokines was observed. When EC were pretreated, however, with either PAF, TNF or both stimuli, before addition of MO, synergistic production of IL-6 was observed. In contrast, GM–CSF production was not enhanced by coculture of monocytes with activated EC. When either cell population was fixed with paraformaldehyde or killed by freeze-thawing before addition to the co-culture, cytokine levels reverted to those produced by the unaffected population alone. On the other hand, separating the two cell populations by a cell-impermeable membrane in transwell cultures did not affect the synergistic production of the cytokines. Taken together, our data suggest that EC and MO can synergize in response to stimuli by producing IL-6 and that this synergy is dependent on the integrity of both cell populations, but independent of cell-cell contact.

Angiogenesis inhibition: a review

In this review we discuss the concept of anti-angiogenesis, which is the inhibition of neovascularization. Anti-angiogenic agents are viewed from the standpoint of their effect on various elements of the angiogenic process, including induction of vascular discontinuity, endothelial cell movement, endothelial cell proliferation, and three-dimensional restructuring of patent vessels. An effort is made to place the many different approaches to anti-angiogenesis research into a comprehensible structure, in order to identify problems of evaluation and interpretation, thereby providing a clearer basis for determining promising and needed directions for further investigation.